Note: Descriptions are shown in the official language in which they were submitted.
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METAL AND ELECTRONIC DEVICE COATING PROCESS FOR MARINE USE AND
OTHER ENVIRONMENTS
RELATED APPLICATIONS
The present invention relates, in part, to U.S. Patent Application Number
12/104,080 filed on 04/16/2008 and U.S. Patent Application Number 12/104,152
filed on
04/16/2008, the contents of which are incorporated herein by reference in
their entirety
and the benefit of which is hereby claimed under 35 U.S.C. 120.
BACKGROUND
Conformal coatings, e.g., those with high electrical resistivity and moisture
resistance, are commonly used to protect components in commercial devices
employed in
the consumer, automotive, military, medical, and aerospace industries, for
example. A
variety of methods exist for applying such coatings. For example, chemical
vapor
deposition at low pressure can produce a thin, even conformal (also called
conformational)
coating on various surfaces. There is a need for improved methods for applying
conformal
coatings to expand their applications. Moreover, new coating compositions with
characteristics that will improve effectiveness in certain applications are
also needed. For
example, coatings with greater durability and greater heat transfer properties
are
particularly sought.
BRIEF SUMMARY OF THE INVENTION
Applicants have discovered, in part, ultra-thin, conformal polymer coatings
that
resist moisture penetration, and methods and apparatus for applying such
coatings to
objects. Ultra-thin, conformal polymer coatings that resist moisture
penetration can be
applied directly to a broad range of objects, including, in particular, "off-
the-shelf"
electronic equipment. Accordingly, some aspects of the disclosure include
compositions,
methods and apparatus for coating objects. In other aspects, conformal coating
compounds
are disclosed, such as Parylene compounds, that are capable of forming an
ultra-thin,
conformal coating on an object. In other aspects, coating compositions are
disclosed that
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comprise a conformal coating compound capable of forming an ultra-thin,
conformal
coating and an additive(s), such as a thermally conductive material (e.g.,
boron nitride), for
modifying any one of a number of properties of the conformal coating,
including, for
example, electrical resistivity, thermal conductivity, light transmittance,
hardness, and
durability. In other aspects, the disclosure includes "off-the-shelf"
electronic equipment,
such as cell phones and mp3 players, having ultra-thin, conformal coatings
that resist
moisture penetration (e.g., waterproof coatings). Methods and apparatus useful
for
applying an ultra-thin, conformal coating on a surface of an object by vapor
deposition are
also disclosed. In other aspects, multi-stage heating apparatus for vapor
deposition of
ultra-thin, conformal polymer coatings are disclosed. The objects to be coated
by the
coating compositions and methods disclosed herein include electronics
equipment, such as
cell phones, radios, circuit boards and speakers; equipment used in ocean and
space
exploration; hazardous waste transportation equipment; medical instruments;
paper
products; and textiles. Any solid surface of an object can be coated,
including plastics,
metals, woods, paper and textiles. Biomedical devices (e.g., hearing aids,
cochlear ear
implant, prosthesis, etc), automotive, electromechanical, artwork (paintings,
wood, water
colors, chalk, ink, charcoal), military systems components, ammunition, guns,
weapons and
similar objects may be coated using the methods and coating compositions
disclosed
herein.
According to some aspects, coating compositions are provided that comprise a
conformal coating compound and a thermally conductive material. In some
embodiments,
the thermally conductive material is dispersed in polymers of the conformal
coating
compound. In some embodiments, the coating composition is a solid (e.g., a
conformal
coating) having a hardness of about R80 to about R95. In some embodiments, the
coating
composition is a gaseous mixture comprising monomers of the conformal coating
compound in a gaseous phase. In certain embodiments, the gaseous mixture
comprises
solid particles of the thermally conductive material.
In some embodiments, the conformal coating compound is a Parylene compound
optionally selected from the group consisting of. Parylene D, Parylene C,
Parylene N and
Parylene HT compounds. In some embodiments, the coating composition comprises
two
or more different Parylene compounds. In some embodiments, the coating
composition
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comprises two or more Parylene compounds of different purity levels. In some
embodiments, the coating composition has a thermal conductivity that is 5-10%
greater
than the Parylene compound alone. In some embodiments, the coating composition
has a
thermal conductivity that exceeds a level which is 10% greater than the
Parylene compound
alone. In some embodiments, the coating composition has a thermal conductivity
that is up
to about 5% greater than the Parylene compound alone.
In some embodiments, the thermally conductive material is a ceramic. In some
embodiments, the thermally conductive material is selected from the group
consisting of:
aluminum nitride, aluminum oxide, and boron nitride. In some embodiments, the
thermally
conductive material has a volume resistivity of greater than 1010 ohms* cm. In
some
embodiments, the mass of the thermally conductive material in the coating
composition is
up to about 3% (or more) of the total mass of the conformal coating compound
and the
thermally conductive material in the coating composition. In some embodiments,
the mass
of the thermally conductive material in the coating composition is up to about
1% of the
total mass of the conformal coating compound and the thermally conductive
material in the
coating composition.
In some aspects, a conformal coating is provided that is on at least a portion
of a
surface of an object. In some embodiments, the conformal coating comprises any
of the
foregoing coating compositions.
In some embodiments, the conformal coating is on at least a portion of a
surface of
an object that is an electronic device. The electronic device may optionally
be selected
from a communication device, a speaker, a cell phone, an audio player, a
camera, a video
player, a remote control device, a global positioning system, a computer
component, a
radar display, a depth finder, a fish finder, an emergency position-indicating
radio beacon
(EPIRB), an emergency locator transmitter (ELT), and a personal locator beacon
(PLB).
In some embodiments, the conformal coating is on at least a portion of a
surface of
an object selected from the group consisting of a paper product; a textile
product; an
artwork; a circuit board; an ocean exploration device; a space exploration
device; a
hazardous waste transportation device; an automotive device, a
electromechanical device; a
military systems component; ammunition; a gun; a weapon; a medical instrument;
and a
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biomedical device, wherein the biomedical device is optionally selected from
the group
consisting of a hearing aid, a cochlear ear implant, and a prosthesis.
In some embodiments, the conformal coating is on at least a portion of a
surface of
an object, wherein the surface is a plastic, a metal, a wood, a paper or a
textile. In certain
embodiments, the surface is an external surface of the object. In certain
other
embodiments, the surface is an internal surface of the object.
In some aspects, an object is provided that comprises a conformal coating on
at least
a portion of a surface. In some embodiments, the conformal coating on the
surface of the
object comprises any of the foregoing coating compositions.
In some embodiments, the object is an electronic device, optionally selected
from a
communication device, a speaker, a cell phone, an audio player, a camera, a
video player, a
remote control device, a global positioning system, a computer component, a
radar display,
a depth finder, a fish finder, an emergency position-indicating radio beacon
(EPIRB), an
emergency locator transmitter (ELT), and a personal locator beacon (PLB).
In some embodiments, the object is selected from the group consisting of a
paper
product; a textile product; an artwork; a circuit board; an ocean exploration
device; a space
exploration device; a hazardous waste transportation device; an automotive
device, a
electromechanical device; a military systems component; ammunition; a gun; a
weapon; a
medical instrument; and a biomedical device, wherein the biomedical device is
optionally
selected from the group consisting of a hearing aid, a cochlear ear implant,
and a
prosthesis.
In some embodiments, the surface of the object is a plastic, a metal, a wood,
a paper
or a textile. In certain embodiments, the object is coated on an external
surface. In certain
other embodiments, the object is coated on an internal surface. In some
embodiments, the
surface is substantially covered with the conformal coating. A substantially
covered
surface may be one that is completely covered or sufficiently covered to
protect the
underlying surface of the object from contact with a substance (e.g., water)
against which
protection is desired.
In some aspects, methods of applying a conformal coating to an object are
provided.
In some embodiments, the methods comprise:
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A) heating a conformal coating compound to form gaseous monomers of the
conformal coating compound,
B) combining a thermally conductive material with the gaseous monomers,
thereby forming a gaseous mixture, and
5 C) contacting an object with the gaseous mixture, under conditions where a
conformal coating comprising the conformal coating compound and the thermally
conductive material is formed on at least a portion of a surface of the
object, thereby
applying a conformal coating to the object.
In some embodiments of the methods, the conformal coating compound is a
Parylene compound optionally selected from the group consisting of. Parylene
D, Parylene
C, Parylene N and Parylene HT compounds.
In some embodiments of the methods, the thermally conductive material is a
ceramic. In other embodiments, the thermally conductive material is selected
from the
group consisting of. aluminum nitride, aluminum oxide, and boron nitride. In
certain
embodiments, the thermally conductive material is in a solid particle form. In
specific
embodiments, the solid particles are about 1.8 micron to about 2.5 micron.
In some embodiments, the methods comprise:
A) heating a Parylene compound to a temperature of about 125 to about 200
degrees C to form a gaseous Parylene compound, wherein the heating of the
Parylene
compound is performed in two or more heating stages,
B) heating the gaseous Parylene compound to a temperature of about 650 to
about 700 degrees C to cleave the gaseous Parylene compound, thereby forming
Parylene
monomers,
C) contacting an object with the Parylene monomers, under conditions where a
conformal coating, comprising a Parylene polymer, is formed on at least a
portion of
surface of the object, thereby applying a coating to the object.
In some embodiments of the methods, step A comprises heating the Parylene
compound to a temperature of about 125 to about 180 degrees C, and heating the
Parylene
compound to a temperature of about 200 to about 220 degrees C.
In some embodiments of the methods, heating of the gaseous Parylene compound
is
performed in two or more stages. In some embodiments, step B comprises heating
the
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gaseous Parylene compound to a temperature of about 680 degrees C, and heating
the
gaseous Parylene compound to a temperature of at least about 700 degrees C.
In some embodiments, the Parylene compound is selected from a group consisting
of Parylene D, Parylene C, Parylene N and Parylene HT compounds.
In some embodiments, the methods further comprise contacting the object with
gaseous silane prior to step C, under conditions wherein the silane activates
the surface of
the object. In some embodiments, the silane is one or more silanes selected
from the group
consisting of Silquest A- 174, Silquest 111 and Silquest A- 174 (NT).
In some embodiments of the foregoing methods, the object is at a temperature
of
about 5 degrees to about 30 degrees C during step C. In some embodiments, the
conformal
coating, which is applied to the surface, is about 100 Angstrom to about 3.0
millimeters.
In some embodiments, the conformal coating, which is applied to the surface,
is about
0.0025 mm to about 0.050 mm thick.
In some embodiments of the foregoing methods, the object is an electronic
device,
optionally selected from a communication device, a speaker, a cell phone, an
audio player,
a camera, a video player, a remote control device, a global positioning
system, a computer
component, a radar display, a depth finder, a fish finder, an emergency
position-indicating
radio beacon (EPIRB), an emergency locator transmitter (ELT), and a personal
locator
beacon (PLB).
In some embodiments of the foregoing methods, the object is selected from the
group consisting of a paper product; a textile product; an artwork; a circuit
board; an ocean
exploration device; a space exploration device; a hazardous waste
transportation device; an
automotive device, a electromechanical device; a military systems component;
ammunition;
a gun; a weapon; a medical instrument; and a biomedical device, wherein the
biomedical
device is optionally selected from the group consisting of a hearing aid, a
cochlear ear
implant, and a prosthesis.
In some embodiments of the foregoing methods, the surface is a plastic, a
metal, a
wood, a paper and a textile.
In some aspects, an object is provided having a coating applied to at least a
portion
of a surface (external or internal) by any of the foregoing methods.
In some aspects, an apparatus for applying a conformal coating to an object is
provided.
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In some embodiments, the apparatus comprises: a vaporization chamber,
comprising at least
two temperature zones; a pyrolysis chamber that is operably linked to the
vaporization
chamber; and a vacuum chamber that is operably linked to the pyrolysis
chamber. In some
embodiments, the apparatus further comprises a connection that operably links
the pyrolysis
chamber and the vacuum chamber, wherein the connection is capable of
transmitting a gas
between the pyrolysis chamber and the vacuum chamber and wherein the
connection
comprises a T-port. In some embodiments, the T-port is operably linked with a
means for
injecting a thermally conductive material into a gas that is transmitted
through the connection
from the pyrolysis chamber to the vacuum chamber. In some embodiments, a
vacuum
produced in the vacuum chamber draws the thermally conductive material through
the T-port
into the connection comprising the gas.
In some embodiments, the vacuum chamber comprises a deposition chamber
operably
linked to the pyrolysis chamber and a vacuum generating component. In some
embodiments,
the vacuum generating component (vacuum means) comprises one or more vacuum
pumps.
In some embodiments, the vaporization chamber has two temperature zones. In
some
embodiments, the vaporization chamber is a tubular furnace.
In some embodiments, the pyrolysis chamber has a plurality of temperature
zones.
In some embodiments, the pyrolysis chamber has two temperature zones. In some
embodiments, the pyrolysis chamber is a tubular furnace.
BRIEF DESCRIPTION OF DRAWINGS
Further advantages of the present invention may be understood by referring to
the
following descriptions taken in conjunction with the accompanying drawings, in
which:
Fig. IA-E are diagrams of the chemical structures of varieties of Parylene and
Silquest . Fig. 1A is a diagram of Parylene N. Fig. lB is a diagram of
Parylene C. Figure
1 C is a diagram of Parylene D. Figure I D is a diagram of Parylene HT .
Figure 1 E is a
diagram of Silquest A-174 silane (also known as Silquest A-174 (NT)).
Fig. 2A is a schematic diagram of one embodiment of the apparatus for chemical
vapor deposition of Parylene.
Fig. 2B is a schematic diagram of one embodiment of an apparatus to apply
a coating of Parylene and powder.
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Fig. 3A-C are schematic diagrams of three embodiments of the Parylene-coated
objects. Fig. 3A depicts an object coated with separate layers of Parylene and
boron
nitride, where the boron nitride layer is closest to the object. Fig. 3B
depicts an object
coated with separate layers of Parylene and boron nitride, where the Parylene
layer is
closest to the object. Fig. 3C depicts an object coated with a layer of
Parylene inter-
dispersed with boron nitride.
DETAILED DESCRIPTION
The disclosure, in some aspects, provides compositions, methods and apparatus
for
coating objects with conformal polymers. In some aspects, conformal coating
compounds
(e.g., Parylene) are provided that are capable of forming an ultra-thin,
conformal coating on
an object. In other aspects, coating compositions are provided that comprise a
conformal
coating compounds (e.g., Parylene) and an additive (one or more additives),
e.g. a
thermally conductive material, for modifying any one of a number of properties
of the
coating, including, for example, electrical resistivity, thermal conductivity,
light
transmittance, hardness, and durability. In other aspects, objects, such as
electronic
devices, are provided that have ultra-thin, conformal coatings which resist
moisture
penetration (e.g., waterproof coatings). Also provided are methods and
apparatus useful for
applying an ultra-thin, conformal coating on at least a portion of a surface
of an object by
vapor deposition. In certain aspects, multi-stage heating apparatus are
provided which are
useful for vapor deposition of ultra-thin, conformal polymer coatings.
A particularly important discovery disclosed herein is that conformal coatings
may
be applied directly to "pre-assembled" or "off-the-shelf' devices, such as
consumer
electronics devices. Thus, it is possible with the methods and compositions
disclosed
herein to apply conformal coatings to all or a portion of the external
surfaces of "pre-
assembled" or "off-the-shelf" devices (e.g., creating a hermetic or nearly
hermetic seal) and
thereby protecting internal components of the devices from environment
insults, such as
moisture penetration and oxidation. Accordingly, using the methods disclosed
herein,
certain objects, e.g., electronic devices (equipment), do not have to be
disassembled, coated
and then reassembled, but rather, may be coated in its "off-the-shelf' state.
The methods
disclosed herein may apply a conformal coating, e.g., comprising a Parylene
compound,
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both to a circuit board inside an electronic device as well as the outside
surface of the
electronic device (e.g., in one process). Thus, the methods may be used to a
particular
advantage with "off-the-shelf" electronics equipment. The methods disclosed
herein may
also be very useful to improve the ease and efficiency by which many other
objects are
conformally coated.
Objects suitable for conformal coating with the compositions and methods
disclosed
herein include, but are not limited to, electronics equipment, cameras,
circuit boards,
computer chips, paper, textiles, batteries, speakers, solid fuel, medical
devices, hazardous
waste transportation equipment, hazardous waste, medical instruments,
equipment used in
ocean and space exploration, space suits, and so on. In some embodiments, the
object is an
electronic device, optionally selected from a communication device, a speaker,
a cell
phone, an audio player, a camera, a video player, a remote control device, a
global
positioning system, a computer component, a radar display, a depth finder, a
fish finder, an
emergency position-indicating radio beacon (EPIRB), an emergency locator
transmitter
(ELT), and a personal locator beacon (PLB).
In some embodiments, the objects are those which are incompatible with
submersion in water, including but not limited to, off-the-shelf electronics
components,
such as laptop computers, cameras, radios, cell phones, paper, textiles,
batteries, speakers,
solid fuel, medical devices, paper, space suits and others disclosed herein or
known in the
art. In other embodiments, the objects may be ones that are degraded upon
submersion in
water, such as but not limited to, metal screws and other hardware, paper
products and
textiles. In other embodiments, the objects may be those which require
flexibility to be
functional, such as audio speakers. In further embodiments, the objects may be
those which
are desired to be protected from oxygen, such as but not limited to, fuel
cells, weapons
cartridges and ammunition. In further embodiments, the objects may be those
which must
be isolated from the environment, such as hazardous waste products. In further
embodiments, the objects may be those which require protection from chemical
exposure,
such as but not limited to, hazardous waste transportation equipment.
The coatings may be applied to objects having a variety of surface materials,
include for example ceramics, polymers, plastics, metals, frozen liquids, and
so on. In
some embodiments, the object to be coated may be one that generates or
consumes heat
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and/or requires a rugged coating. In some embodiments, the object may generate
heat or
absorb heat, such as cold packs, frozen liquids and gases and heat pumps. In
some
embodiments, the object may be expected to be subjected to harsh physical
impact during
its lifetime. In some aspects, methods are provided in the disclosure which
may be used to
5 coat such objects and surfaces.
The conformal coatings disclosed herein may be applied to a broad range of
devices
used in the consumer electronics, commercial marine, recreational boating,
military
(aerospace and defense), industrial and medical industries, as well as others.
In some
instances, the conformal coatings are specifically designed to "seal" devices.
Such coatings
10 are useful, for example to protect devices commonly used in marine and
hazardous
environments against operational malfunction caused by exposure to moisture,
immersion
in water, dust, effects of high wind and chemicals. The coatings may enhance
the
survivability and sustainability of operational equipment and high value
specialty products
susceptible to corrosion and degradation.
In some embodiments, the conformal coating may be on the inside and outside
surface of the object, and in particular, the conformal coating on the outside
of the object
may be continuous with the conformal coating on the inside of the object.
In some instances where pretreatment with a compound, e.g., an organic
compound,
such as silane, is desired, any object that has a solid surface which can be
exposed to the
pretreatment compound (e.g., in its vapor phase) are suitable. Accordingly,
one embodiment
provides objects coated with at least one conformal coating compound having
been pretreated
with a silane, such as Silquest , where the uncoated objects may be
incompatible with
immersion in water. Uncoated objects that are incompatible with immersion in
water may be
those which partially or totally lose functionality after immersion in water.
In preferred
embodiments, the objects may be those which when uncoated become at least
partially non-
functional after immersion in water and subsequent drying, including but not
limited to, off-
the-shelf electronics components, such as laptop computers, radios and cell
phones.
Objects coated with at least a conformal coating compound (and optionally
pretreated
with silane) may have a conformal coating on the outside of the object, as
well on the inside of
the object if there are gaps in the outer surface of the object that allow the
conformal coating
compound gases (optionally and/or the silane gases) admission to the inside of
the object. In a
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preferred embodiment, the outside conformal coating is continuous with the
inside conformal
coating.
The coated objects may be particularly suited for the use in the harsh
environmental
conditions encountered by the military. In some embodiments, the coated object
may meet
the applicable requirements of military specifications MIL PRF-38534, the
general
performance requirements for hybrid microcircuits, Multi-Chip Modules (MCM)
and
similar devices. In some embodiments, the coated object may meet the
applicable
requirement of military specifications MIL-PRF-38535, the general performance
requirements for integrated circuits or microcircuits. In some embodiments, a
coated object
may meet the applicable requirements of both military specifications MIL-PRF-
38534 and
MIL-PRF-38535.
Another embodiment includes objects coated with Parylene and boron nitride
compositions (e.g., by methods disclosed herein). The objects to be coated by
this method
include any object that has a solid surface capable of being of contacted with
gaseous
Parylene monomers and boron nitride under conditions suitable for forming a
conformal
coating, which comprises Parylene polymers and boron nitride, on at least a
portion of the
surface of the object. Such objects include, but are not limited to,
electronics equipment,
circuit boards, paper, textiles, batteries, speakers, solid fuel, medical
devices, hazardous
waste transportation equipment, hazardous waste, equipment used in ocean and
space
exploration, space suits, and others disclosed herein and/or known in the art.
In some
embodiments, the object may be one which generates heat or consumes heat, such
as, but
not limited to, computers, drill equipment for deep hole drilling, exposed
electronics on oil
rigs. In other embodiments, the object may be one that requires a particularly
rugged
coating.
Objects coated with at least a conformal coating compound and thermally
conductive material, e.g., boron nitride, may have a conformal coating on the
outside of the
object, as well on the inside of the object if there are gaps in the outer
surface of the object
that allow a gaseous mixture comprising the conformal coating compound and the
thermally conductive material (e.g., boron nitride powder particles) admission
to the inside
of the object. In a preferred embodiment, the outside conformal coating is
continuous with
the inside conformal coating. For example, an electronics device such as a
cell phone may
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have a conformal coat on the circuit boards and battery within the device as
well as on the
keyboard and screen of the cell phone.
In some embodiments, the Parylene and the boron nitride may be inter-dispersed
within the coating 8' on the object 7'. Fig. 3C. In some embodiments, the
inter-dispersion
of the Parylene and the boron nitride may be on the molecular level. In some
embodiments, the coating of inter-dispersed Parylene and boron nitride may
about 0.0025
mm to about 0.050 mm. In other embodiments,. the inter-dispersed Parylene and
boron
nitride coat may be less that about 2.0 mm.
In other embodiments, at least one conformal coating, such as a Parylene
conformal
coating, and the boron nitride are found in separate layers on the object.
Conformal
coatings of interest include, but are not limited to, polynaphtahlene (1-4-
napthalene),
diamine (0-tolidine), polytetrafluoroethylene (Teflon ), polyimides. In
preferred
embodiments, the polymer coating may be Parylene C. In other embodiments,
other forms
of Parylene may be used, including but not limited to, Parylene N, Parylene D
and Parylene
HT . In preferred embodiments, the layers of boron nitride and polymer coating
may be
about 0.05 mm thick each. In other preferred embodiments, each layer may
contain
essentially the polymer coating or essentially boron nitride. In some
embodiments, the
boron nitrate layer 2' may be closer to the object 1' than the Parylene layer
3'. Fig. 3A. In
other embodiments, the Parylene layer 5' may be closer to the object 4' than
the boron
nitride 6'. Fig. 3B.
Conformal Compositions/Coatings
According to some aspects, coating compositions, comprising a conformal
coating
compound and a thermally conductive material are provided. As used herein, a
"conformal
coating compound" is a compound (e.g., a partially purified compound. 'a
purified
compound, a synthetic compound, an isolated natural compound) that is capable
of forming
an ultra-thin, pin-hole free, polymeric coating on a surface that conforms to
the geometry
of that surface. Such coatings are referred to herein as "conformal coatings".
A conformal
coating compound may equivalently be referred to as a "conformational coating
compound". Conformal coating compounds may be applied as a coating to the
surface of
an object by a variety of methods, including for example chemical vapor
deposition. For
RECTIFIED SHEET (RULE 91)
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example, vapor phase monomers of conformal coating compounds may be contacted
with
the surface of an object under conditions where the monomers condense, adsorb
to the
surface and, concomitantly, polymerize together to form a pin-hole free
conformal coating
on the surface. The thickness of the coatings may range from about 10
angstroms up to 50
microns or more depending on the application. For example, a coating may have
a
thickness of up to 3 millimeters. In some embodiments, the coating has a
thickness of
about 0.0025 mm to about 0.050 mm. The conformal coatings may be electrical
insulators
(e.g., volume resistivity greater than 1010 ohms*cm). Alternatively or
additionally, the
conformal polymers may have a hardness of about R70 to about R90. (Rockwell
Hardness
Scale). The conformal coatings may also be hydrophobic, depending on the
application.
Conformal coating compounds may exist in a variety of forms including
monomeric and
polymeric (e.g., dimeric, multimeric) forms and phase states (e.g., gaseous,
solid).
A particularly useful conformal coating compound is a Parylene compound.
Parylene is the generic name for members of a unique series of compounds. The
basic
member of the series, called Parylene N, is poly-para-xylylene, a compound
manufactured
from di-p-xylylene ([2,2]paracyclophane). Parylene N is a completely linear,
highly
crystalline material. Parylene C, a second commercially available member of
the series, is
produced from the same monomer modified only by the substitution of a chlorine
atom for
one of the aromatic hydrogens. Parylene D, a third member of the series, is
produced from
the same monomer modified by the substitution of the chlorine atom for two of
the
aromatic hydrogens. Parylene D is similar in properties to Parylene C with the
added
ability to withstand higher use temperatures. In some embodiments, the
Parylene may be
one derived from poly-para-xylylene by the substitution of various chemical
moieties. In
preferred embodiments, the Parylene may be capable of forming linear, highly
crystalline
material. Other Parylene molecules, e.g., derivatives and analogs of the
foregoing, may
also be used. In some embodiments, Parylene compounds provided by a commercial
source, e.g., Specialty Coating Systems (SCS), Inc., may be used.
Conformal coating compounds may also include, but are not limited to,
polynaphtahlene (1,4-napthalene), diamine (0-tolidine),
polytetrafluoroethylene (Teflon ),
and polyimides. These polymers may be applied by standard techniques, as will
be well
known to those of ordinary skill in the art.
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14
Conformal coatings comprising Parylene may be thermally insulating, and do not
readily allow the coated object to release heat into the environment. This
characteristic of
Parylene may be problematic for objects such as electronics equipment that
generate heat,
which, if not dissipated, can lead to early failure of the equipment. Some
Parylene based
conformal coatings disclosed herein include thermally conductive materials
that facilitate
heat dissipation from the coated object. As compared to a Parylene alone
coating, such
conformal coatings are useful to coat objects that require heat dissipation,
either by
releasing heat or absorbing heat. The Parylene-based conformal coating
compositions
disclosed herein also may have increased hardness compared to a coating of
Parylene
alone. Therefore, the Parylene-based coating compositions may also be useful
to coat
objects that require a rugged protective coat, such as those that will be
subjected to harsh
physical impact during their lifetime.
Thus according to some aspects of the disclosure, conformal coating compounds
may be combined with other additive(s) to obtain coating compositions having
one or
more improved performance properties compared with the conformal coating
compound
alone. For example, coating compositions which have improved heat transfer
capabilities
may be produced. As used herein, a "thermally conductive material" is a
material that is
capable of combining with a conformal coating compound to form a coating
composition
having a thermal conductivity greater than the thermal conductivity of the
conformal
coating compound alone. The thermally conductive materials disclosed herein
typically
have higher thermal conductivity compared with conformal coating compounds
themselves.
Exemplary thermally conductive materials have a thermal conductivity of at
least 1, at least
5, at least 10, at least 15, or at least 20 W/(m*K). The skilled artisan will
appreciate that
there are a variety of methods for measuring thermal conductivity, including
for example
the testing methods set forth in the following standards: IEEE Standard 98-
2002, "Standard
for the Preparation of Test Procedures for the Thermal Evaluation of Solid
Electrical
Insulating Materials", ISBN 0-7381-3277-2; ASTM Standard D5470-06, "Standard
Test
Method for Thermal Transmission Properties of Thermally Conductive Electrical
Insulation
Materials"; ASTM Standard E1225-04, "Standard Test Method for Thermal
Conductivity
of Solids by Means of the Guarded-Comparative-Longitudinal Heat Flow
Technique";
ASTM Standard D5930-01, "Standard Test Method for Thermal Conductivity of
Plastics by
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Means of a Transient Line-Source Technique"; and ISO 22007-2:2008 "Plastics --
Determination of thermal conductivity and thermal diffusivity -- Part 2:
Transient plane
heat source (hot disc) method". Exemplary thermally conductive materials
include various
ceramic materials, including for example silicon dioxide and silicon nitride.
Thermally
5 conductive materials may also be selected from the group consisting of.
aluminum nitride,
aluminum oxide, and boron nitride. Other thermally conductive materials
include for
example titania (Ti02). Still others will be apparent to the skilled artisan.
In some
embodiments, the coating composition comprises a conformal coating compound
and
lanthanum hexaboride (LaB6). In some embodiments, the coating composition
comprises a
10 conformal coating compound and silica (Si02).
In some aspects, coating compositions that comprise a Parylene compound, as a
conformal coating compound, and a thermally conductive material have greater
thermal
conductivity than the Parylene compound alone, and in some cases about 10%
greater than
the thermal conductivity of the Parylene compound alone. In some embodiments,
the
15 thermal conductivity of such coating compositions is about 5-10% greater
than the Parylene
compound alone. Alternatively or additionally, the coating compositions may
have a
greater hardness than the Parylene alone and particularly greater than about
10% hardness
than the Parylene alone.
An exemplary thermally conductive material is boron nitride. Boron nitride
(BN) is
a binary chemical compound, consisting of equal numbers of boron and nitrogen
atoms. Its
empirical formula is therefore BN. Boron nitride is isoelectronic with carbon
and, like
carbon, boron nitrides exists as various polymorphic forms, one of which is
analogous to
diamond and one analogous to graphite. The diamond-like polymorph is one of
the hardest
materials known and the graphite-like polymorph is a useful lubricant. In
addition, both of
these polymorphs exhibit radar-absorptive properties. (Silberberg, Martin S.
Chemistry:
The Molecular Nature of Matter and Change, Fifth Edition. New York: McGraw-
Hill,
2009. p. 483.) Accordingly, in some aspects, the disclosure provides coating
compositions
which may contain a Parylene compound and boron nitride. In these
compositions, the
Parylene compound and boron nitride may be inter-dispersed (e.g., boron
nitride particles
may be dispersed among Parylene polymers). While any Parylene compound may be
used
in these compositions, Parylene D, Parylene C, Parylene N and Parylene HT
compounds
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may be preferred, and Parylene C compound may be particularly preferred. In
these
compositions, the boron nitride may have a hexagonal plate structure. In some
embodiments, the weight of boron nitride to the total weight of Parylene
compound and
boron nitride may be less then about 80%. In some embodiments, the weight of
boron
nitride may be up to about 1%, up to about 2%, up to about 3%, up to about 5%,
up to
about 10%, or up to about 20% of the total weight of the Parylene compound and
boron
nitride.
In some embodiments, a coating composition may consist essentially of Parylene
and boron nitride. In other embodiments, a coating composition consists of
Parylene and
boron nitride. In some embodiments, the Parylene and boron nitride comprise at
least
about 50%, at least about 70%, at least about 90%, at least about 95%, at
least about
99%, or at least about 99.9% of the composition.
In some embodiments coatings on an object comprising Parylene and boron
nitride,
the boron nitride may be inter-dispersed in Parylene in the coating (dispersed
in a polymer of
Parylene compounds). While any Parylene may be used in these objects, Parylene
C,
Parylene N, Parylene D and Parylene HT may be preferred, and Parylene C
particularly
preferred. In some embodiments, the coating may be about 0.0025 mm to about
0.050 mm
thick.
While in some embodiments, this Parylene-boron nitride coating composition may
contain Parylene C, in other embodiments, it may contain Parylene D, Parylene
N or
Parylene HT . Figs. 1 A, 1 B, 1 C and 1 D. In some embodiments, the Parylene
may be
derived from Parylene N, or poly-para-xylylene, by the substitution of various
chemical
moieties. In preferred embodiments, the Parylene forms a completely linear,
highly
crystalline material. In some embodiments, the boron nitride may have a
hexagonal plate
structure. In some embodiments, the Parylene and boron nitride form separate
layers
within the Parylene composition. In some embodiments, the Parylene composition
may
have strong covalent bonds within the Parylene and boron nitride layers. In
other
embodiments, the Parylene composition may have weak Van der Waals forces
between the
Parylene and boron nitride layers.
In some embodiments, a Parylene composition may have greater thermal
conductivity than Parylene alone, e.g., as measured in (cal/sec)/cm2/C. In
specific
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17
embodiments, a Parylene-boron nitride composition may have greater than about
10%,
greater than about 30%, or greater than about 50% thermal conductivity than
the Parylene
alone. In other embodiments, a Parylene composition may have greater hardness
than
Parylene alone as defined by Rockwell hardness test. E.L. Tobolski & A. Fee,
Macroindentation Hardness Testing ASM Handbook. Volume 8: Mechanical Testing
and
Evaluation, 203-211 (ASM International, 2000). In specific embodiments, the
Parylene-
boron nitride composition may have greater than about 10%, greater than about
30%,
greater than about 50% or greater than about 90% hardness than the Parylene
alone. The
relative amounts of Parylene and boron nitride in the Parylene-boron nitride
composition
may determine the thermal conductivity and hardness of the composition. In
some
embodiments, the weight of boron nitride in the total weight of Parylene and
boron nitride
in the composition will be less than about 5%, less than about 10%, less than
about 20%,
less than about 40%, less than about 60%, or less than about 80%. In some
embodiments,
the weight of boron nitride in the total weight of Parylene and boron nitride
in the
composition will be up to about 1%, up to about 2%, up to about 3%, or up to
about 4%.
In some cases, objects may require prior treatment to make the surfaces of the
object
more amenable to the adherence of a conformal coating, such as by applying a
silane. Pre-
treatment methods may entail immersing the object in a solution comprising a
suitable
compound, including for example an organic compound, such as silane, then
removing the
object from the silane-solution and allowing the object to dry. Such
pretreatments can
improve surface bonding of conformal coating compounds and upgrade (improve)
mechanical and electrical properties.
In cases where an object may be destroyed by submersion in a solution, e.g.,
electronics devices, an alternative pretreatment method may be used which
includes coating
the object with silane. For example, silane may be applied in a vapor phase to
an object to
be coated with a conformal coating comprising a Parylene compound. This may
allow
some objects, e.g., those that are incompatible with immersion but that
require surface
pretreatment with silane, to be coated with Parylene.
In another aspect, the disclosure includes objects with at least one coat of a
conformal coating compound and at least one coat of boron nitride. In some
embodiments,
the conformal coating compound may be polynaphtahlene, diamine,
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18
polytetratluoroethylene, polyimides. Parylene C, Parylene N, Parylene D or
Parylene HT ,
and may be preferably Parylene C. In some embodiments, the boron nitride coat
may be
closer to the object than the polymer coat, while in other embodiments, the
polymer coat
may be closer to the object than the boron nitride coat. In some embodiments,
the coatings
of boron nitride and polymer may be at least about 0.05 mm thick each.
Conformal Coating Apparatus
Apparatus useful for applying an ultra-thin, conformal coating on a surface of
an
object by vapor deposition are also disclosed. In other aspects, multi-stage
heating
apparatus for vapor deposition of ultra-thin, conformal polymer coatings are
disclosed.
In some aspects, the disclosure provides an apparatus to apply a conformal
coating
comprising Parylene, which includes a vaporization chamber with a plurality of
(two or
more) temperature zones that is operably linked to a pyrolysis chamber that is
operably
linked to a vacuum chamber. In some embodiments, the vacuum chamber may
include a
deposition chamber that is operably linked to the pyrolysis chamber and a
vacuum means,
and the vacuum means may be one or more vacuum pumps. In some embodiments, the
vaporization chamber may have a plurality of temperature zones, preferably two
temperature zones. In other embodiments, the pyrolysis chamber may have a
plurality of
temperature zones, preferably two temperature zones. In some embodiments, the
vaporization chamber and/or the pyrolysis chamber may be a tubular furnace.
Other apparatus for chemical vapor deposition of conformal coating compounds
onto objects are known in the art. See for example, United States Patent
Numbers
4,945,856, 5,078,091, 5,268,033, 5,488,833, 5,534,068, 5,536,319, 5,536,321,
5,536,322,
5,538,758, 5,556,473, 5,641,358, 5,709,753, 6,406,544, 6,737,224, and
6,406,544, all of
which are incorporated by reference herein.
In another aspect, the disclosure provides an apparatus to apply a conformal
coating
comprising a conformal coating compound and a thermally conductive material,
which may
include a vaporization chamber that is operably linked to a pyrolysis chamber
that is
operably linked to a vacuum chamber, wherein a connection comprising a T-port
operably
links the pyrolysis chamber to the vacuum chamber. In some embodiments, the
connection
operably linking the pyrolysis chamber and the vacuum chamber may be a means
for
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19
transmitting gas from the pyrolysis chamber to the vacuum chamber. In other
embodiments, the T-port may be operably connected to a means for injecting
solid particles
(e.g., a powder) or another gas into the gas transmitted through the
connection. In some
embodiments, the vacuum chamber may contain a deposition chamber operably
linked to the
pyrolysis chamber and a vacuum means, where the vacuum means may be one or
more
vacuum pumps.
One embodiment is an apparatus for the chemical vapor deposition of Parylene
which may comprise an improved vaporization chamber and/or pyrolysis chamber.
While
this apparatus may be particularly useful for the chemical vapor deposition of
Parylene, is
may also be used to vapor deposit other conformal coating compound, including
but not
limited to, polynaphtahlene (1,4-napthalene), diamine (0-tolidine),
polytetrafluoroethylene
(Teflon`), polyimides, and others that will be well-known to those in the art.
In some
embodiments, the apparatus comprises a vaporization chamber and/or a pyrolysis
chamber
with a plurality of temperature zones. While not limiting the operation of the
apparatus, it
is thought that by allowing different temperature set points within each
chamber, the rate of
heating of Parylene is improved. The multi-zoned vaporization and pyrolysis
chambers
may allow the Parylene to be uniformly cleaved into a monomer, and allow
better control
of the final thickness of the Parylene coat on the object. The Parylene may
remain a
monomer longer in the deposition chamber so that it can be better spread
throughout the
deposition chamber.
Fig. 2A shows a Parylene coating apparatus. The vaporization chamber 1 may
have
two temperature zones 10 and 11. The pyrolysis chamber 3 also may have two
temperature
zones 12 and 13. The vaporization chamber 1 may be operably linked to the
pyrolysis
chamber 3 by a component 2 that may be capable of communicating gas from the
vaporization
chamber 1 to the pyrolysis chamber 3. The pyrolysis chamber 3 may be operably
linked to the
vacuum chamber 14, which may comprise a deposition chamber 6 and may be
operably linked
to a vacuum means 9 by a component 8 which may be capable of pulling a vacuum
on the
deposition chamber 6. The component 5 operably linking the pyrolysis chamber 3
to the
vacuum chamber 14 may be capable of communicating gas from the pyrolysis
chamber 3 to
the vacuum chamber 14, and also may include a,valve 4 that is capable of
regulating the flow
of gas from the pyrolysis chamber 3 to the vacuum system 14.
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The vaporization chamber 1 may be any furnace/heating system that is capable
of
heating a solid to about 150 to about 200 degrees C. In preferred embodiments,
the
vaporization chamber is capable of heating a gas to 1200 degrees C. In some
embodiments,
the vaporization chamber 1 may be capable of containing gases. The
vaporization chamber 1
5 may also be capable of generating zones within its heating chamber that are
different
temperatures. Finally, the vaporization chamber 1 may be capable of
maintaining a high
vacuum. In preferred embodiments, the vaporization chamber may support a
vacuum of at
least about 0.1 Ton.
The vaporization chamber 1 may be operably linked to the pyrolysis chamber 3
by
10 many components that will be well known to those of ordinary skill in the
art. The operable
connection between the vaporization chamber 1 and pyrolysis chamber 3 may be,
in some
embodiments, a connection that allows gas to pass from the vaporization
chamber 1 to the
pyrolysis chamber. In some embodiments, this component 2 may be a glass tube,
a retort, or a
metal tube, among others. In other embodiments, this component 2 may also
contain valves,
15 temperature sensors, other sensors, and other conventional components, as
will be well know
to those in the art.
The pyrolysis chamber 3 may be any furnace/heating system that is capable of
heating
a gas to about 650 to about 700 degrees C. In some embodiments, the pyrolysis
chamber 3
may be capable of containing gases. In some embodiments, the pyrolysis chamber
3 may be
20 capable of generating zones within its heating chamber that are different
temperatures.
Finally, in some embodiments, the pyrolysis chamber 3 may be capable of
maintain a high
vacuum. In preferred embodiments, the vaporization chamber may support a
vacuum of at
least about 0.1 Torr.
The vaporization chamber and the pyrolysis chamber, preferably, may be
furnaces
capable of generating two or more temperature zones within their chamber. In a
preferred
embodiment, the furnace has two temperature zones. In some embodiments, the
temperature
zones are situated in the furnace chamber such that a gas will move
sequentially through the
temperature zones before exiting the furnace. Preferably, the furnace may have
a maximum
temperature of 1200 degrees C. In a preferred embodiment, the furnace is a
tubular furnace. In
other embodiments, the furnace may have a glass retort. The specific
parameters of one
embodiment of a two zoned furnace suitable to be used as the vaporization
chamber and/or the
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21
pyrolysis chamber may be found in Example 2.
The pyrolysis chamber 3 may be operably linked to the vacuum system 14 by many
components that will be well known to those of ordinary skill in the art. The
operable
connection between the pyrolysis chamber 3 and the vacuum system 14 may be, in
some
embodiments, a connection that allows gas to pass from the pyrolysis chamber 3
to the
vacuum system 14. In some embodiments, this component 5 may be a glass tube, a
retort, or a
metal tube, among others. In other embodiments, this component 5 may contain
valves,
temperature sensors, other sensors, and other conventional components, as will
be well know
to those in the art. In a preferred embodiment, component 5 may contain one or
more valves 4
by which the flow of gas through the component 5 may be regulated.
The vacuum system 14 may contain a deposition chamber 6 which may be operably
connected 8 to a vacuum means 9. In some embodiments, the operable connector 8
may be
capable of holding a vacuum up to at least about 0.05 Torr, and preferably at
least about 1 x
104 Torr. In other embodiments, the vacuum means 9 may be one or more vacuum
pumps,
which may be capable of pulling a vacuum on the deposition chamber of at least
about 0.05
Torr, and preferably at least about 1 x 10-4 Ton. In some embodiments, the
deposition
chamber 6 may be of sufficient size to contain the object to be coated 7. In
other
embodiments, the deposition chamber 6 may be capable of holding a vacuum of at
least about
0.05 Tort, and preferably at least about 1 x 104 Torr range.
Another embodiment disclosed herein is an apparatus useful for the chemical
vapor
deposition of the Parylene and boron nitride composition which contains a
means to inject
a powder into the chemical vapor prior to deposition. Fig. 2B shows a coating
apparatus
according to one embodiment. The vaporization chamber 15 may be operably
linked to
the pyrolysis chamber 17 by a component 16 that may be capable of
communicating gas
from the vaporization chamber 15 to the pyrolysis chamber 17. The pyrolysis
chamber 17
may be operably linked to the vacuum chamber 25, which may comprise a
deposition
chamber 21 and may be operably linked to a vacuum means 24 by a component 23
which
may be capable of pulling a vacuum on the deposition chamber 21. The component
19
operably linking the pyrolysis chamber 17 to the vacuum chamber 25 may be
capable of
communicating gas from the pyrolysis chamber 17 to the vacuum chamber 25, and
also
may include a valve 18 that is capable of regulating the flow of gas from the
pyrolysis
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chamber 17 to the vacuum system 25. Component 19 may also have a T-port 20,
also
called a "tee nipple." In some embodiments, the T-port may be operably
connected to a
means for injecting a powder into the gas transmitted through component 19. In
some
embodiments, the means for injecting a power includes, but is not limited to,
ovens, power
coat equipment and compressed air. In a preferred embodiment, the means for
injecting a
power includes a power container operably linked to an electronic valve, which
is operably
linked to the T-port.
The vaporization chamber 15 may be any furnace/heating system that is capable
of
heating a solid to about 150 to about 200 degrees C. In some embodiments, the
vaporization chamber 15 may be capable of containing gases. Finally, the
vaporization
chamber 15 may be capable of maintaining a high vacuum.
The vaporization chamber 15 may be operably linked to the pyrolysis chamber 17
by many components that will be well known to those of ordinary skill in the
art. The
operable connection between the vaporization chamber 15 and pyrolysis chamber
17 may
be, in some embodiments, a connection that allows gas to pass from the
vaporization
chamber 15 to the pyrolysis chamber. In some embodiments, this component 16
may be a
glass tube, a retort, or a metal tube, among others. In other embodiments,
this component
16 may also contain valves, temperature sensors, other sensors, and other
conventional
components, as will be well know to those in the art.
The pyrolysis chamber 17 may be any furnace/heating system that is capable of
heating a gas to about 650 to about 700 degrees C. In some embodiments, the
pyrolysis
chamber 17 may be capable of containing gases. Finally, in some embodiments,
the
pyrolysis chamber 17 may be capable of maintaining a high vacuum, preferably
at least 0.1
Torr.
The pyrolysis chamber 17 may be operably linked to the vacuum system 25 by
many components that will be well known to those of ordinary skill in the art.
The
operable connection between the pyrolysis chamber 17 and the vacuum system 25
may be,
in some embodiments, a connection that allows gas to pass from the pyrolysis
chamber 17
to the vacuum system 25. In some embodiments, this component 19 may be a glass
tube, a
retort, or a metal tube, among others. In other embodiments, this component 19
may
contain valves, temperature sensors, other sensors, and other conventional
components, as
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23
will be well know to those in the art. In a preferred embodiment, component 19
may
contain one or more valves 4 by which the flow of gas through the component 19
may be
regulated.
The vacuum system 25 may contain a deposition chamber 21 which may be
operably connected by component 23 to a vacuum means 24. In some embodiments,
the
connector 8 may be capable of holding a vacuum up to at least about 0.05 Ton.
In other
embodiments, the vacuum means 24 may be one or more vacuum pumps, which may be
capable of pulling a vacuum on the deposition chamber of at least about 0.05
Ton. In some
embodiments, the deposition chamber 21 may be of sufficient size to contain
the object to
be coated 22. In other embodiments, the deposition chamber 21 may be capable
of holding
a vacuum of at least about 0.05 Torr.
Conformal Coating Methods
Methods for applying an ultra-thin, conformal coating on a surface of an
object by
vapor deposition are also disclosed. In some aspects, multi-stage heating
methods for
vapor deposition of ultra-thin, conformal coatings are disclosed. In other
aspects, methods
for vapor deposition of ultra-thin, conformal coatings comprising additives,
such as
thermally conductive materials, are disclosed.
The conformal coating deposition process disclosed herein may preferably be
carried out in a closed system under negative pressure. For example, Parylene
compounds
are deposited from a vapor phase at a low pressure, e.g., of around 0.1 Ton,
to form
conformal coatings. In this example, a first step is vaporization of solid
Parylene dimers at
approximately 150 degrees C in a vaporization chamber. A second step is a
quantitative
cleavage (pyrolysis) of the dimer at the two methylene-methylene bonds, e.g.,
at about 680
degrees C, in a pyrolysis chamber to yield the stable monomer diradical, para-
xylylene.
Finally, the monomer in gas form enters a room temperature deposition chamber
where it
adsorbs and polymerizes on the object to be coated. The closed system
preferably has
separate chambers for the vaporization, pyrolysis and deposition of the
Parylene, with the
chambers being connected with the appropriate plumbing or tubular connections.
The conformal coating compound may be provided for use in the methods in a
variety of forms and purities levels. In some embodiments, the conformal
coating
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compound is provided at a purity level of about 90%, about 92.5%, about 95%,
about 96%,
about 97%, about 98%, about 98.5%, about 99%, about 99.5%, about 99.9%, or up
to about
100% purity. In some embodiments, the conformal coating compound is provided
as a
blend of conformal coating compounds (e.g., of the same type, e.g., Parylene
C) from
different sources and/or of different purity levels. In some embodiments, the
conformal
coating compound is provided as a blend of conformal coating compounds of
multiple
types (e.g., Parylene C, Parylene N, Parylene D, Parylene HT .).
According to other aspects, methods of applying a conformal coating to an
object
involve heating a Parylene compound to a temperature of about 125 to about 200
degrees C
to form a gaseous Parylene compound, wherein the heating of the Parylene
compound is
performed in two or more heating stages, heating the gaseous Parylene compound
to a
temperature of about 650 to about 700 degrees C to cleave the gaseous Parylene
compound,
thereby forming Parylene monomers, and contacting an object with the Parylene
monomers, under conditions where a conformal coating, comprising a Parylene
polymer, is
formed on at least a portion of surface of the object, thereby applying a
coating to the
object. In some embodiments, the Parylene compound is heated to a temperature
of about
125 to about 180 degrees C, and then heated to a temperature of about 200 to
about 220
degrees C. In some embodiments, the gaseous Parylene compound is heated in two
or
more stages. For example, the gaseous Parylene compound may be heated to a
temperature
of about 680 degrees C, and then to a temperature of at least about 700
degrees C.
In some cases, the methods may be useful for applying a uniform, thin layer of
a
conformal coating comprising Parylene within a vacuum chamber at 25 degrees C
using
standard chemical vapor deposition practices, and may be applied in
thicknesses ranging,
e.g., from 0.01 to 3.0 millimeters, depending on the item coated. The item
once coated
may be weatherproof and water resistant, and may withstand exposure to extreme
weather
conditions and exposure to most chemicals. Any solid surface may be coated,
including
plastics, metals, woods, paper and textiles. Sample applications are disclosed
herein
include, but are not limited to: electronics equipment, such as cell phones,
radios; circuit
boards and speakers; equipment used in ocean and space exploration, or oil rig
operations;
hazardous waste transportation equipment; medical instruments; paper products;
and
textiles.
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In some embodiments, the length of time that the object may be contacted with
the
gaseous Parylene monomers may be varied to control the final thickness of the
Parylene
coat on the object. In various embodiments, the final thickness of the
Parylene coating may
be between about 100 Angstrom to about 3.0 millimeters. In some embodiments,
the final
5 thickness of the Parylene coating may be between about 0.5 millimeters to
about 3.0
millimeters. In some embodiments, the final thickness of the Parylene coating
may be
between about 0.0025 millimeters to about 0.050 millimeters. Preferably, a
deposition time
from about 2 hours to about 18 hours (e.g., 5 hours) may be used to achieve a
Parylene coat
thickness of about 0.002 inches (0.050 mm), depending on the temperature of
the
10 deposition chamber. The choice of final thickness of Parylene coating may
depend to some
degree on the object to be coated and the final use of the object. Thinner
final coats may be
desirable for objects that require some movement to be functional, such as
power buttons.
Thicker coatings may be desirable for objects that will be submerged in water.
The adhesion of certain coating compositions, e.g., those comprising Parylene
15 compounds, to a wide variety of objects can be improved by pre-treating the
surface of the
object to be coated with an organic compound, such as silane, prior to
applying the
conformal coating. Silane treatment forms radicals on the surface of the
object to which
Parylene can bond. Two silanes, vinyl trichlorosilane in either xylene,
isopropanyl alcohol,
or Freon, and gamma-methacryloxypropyltrimethoxy silane (Silquest A- 174
silane or
20 Silquest A-174 (NT) silane) in a methanol-water solvent have been used for
this purpose.
However, electronics components cannot tolerate electrical paths that are
developed either
by direct contact with a liquid that allows conduction of electricity, nor are
they compatible
with the ion residue often left after the evaporation of water or the liquid
in which it was
immersed. Even if there is no immediate growth, dendritic conductors may grow
later on,
25 due to the voltage between conductors on the electronics component. These
short circuits
caused by the conductive fluids and dendrites can drain batteries and allow
high currents to
flow in areas in which they were not intended, and result in unintended
circuit operation or
failure. Often, it is best if sometimes the components of electronic
equipment, such as
circuit boards, must be silane and Parylene coated separately, and then
assembled into a
finished product.
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26
In some aspects, the disclosure provides methods to coat objects with silanes
such
as Silquest saline. In some embodiments, the methods may involve: (A.)
vaporizing
silane by heating it to its evaporation point to form gaseous silane; and (B.)
contacting at
least a portion of a surface of an object to be coated (e.g., a surface
intended to be coated
with a conformal coating, e.g., comprising Parylene) with the gaseous silane
of Step A. In
some embodiments, the silane may be Silquest A-174, Silquest 111 or Silquest
A-174
(NT), and may be preferably Silquest A-174. In some embodiments, in Step A,
the silane
may be vaporized in a 50:50 solution with water. In some embodiments, in Step
A, the
silane may be vaporized at 80 degrees C for about 2 hours
In some aspects, the disclosure provides methods for applying a pretreatment
with
silane and a Parylene coating compound to at least a portion of a surface of
an object. The
methods may include: (A.) vaporizing Parylene dimer by heating it to 150-200
degrees C to
form gaseous Parylene dimers; (B.) cleaving gaseous Parylene dimers to gaseous
Parylene
monomers by heating gaseous Parylene dimers to 650 to 700 degrees C; (C.)
vaporizing
silane by heating it to its evaporation point to form gaseous silane; (D.)
contacting the
object to be coated with Parylene with the gaseous silane of Step C; and (E.)
contacting the
object to be coated with Parylene with the gaseous Parylene monomers of Step B
for
sufficient time to deposit coat of Parylene of a final thickness. In some
embodiments, the
Parylene may be selected from a group consisting of Parylene D, Parylene C,
Parylene N,
Parylene HT, and a Parylene derived from Parylene N, and may preferably be
Parylene C.
In some embodiments, the silane may be Silquest , Silquest A-174, Silquest
111 or
Silquest A-174 (NT), and may preferably be Silquest A-174.
In some embodiments, in Step A, the Parylene dimer may be vaporized by heating
in two or more stages, and preferably in two stages of about 170 degrees C,
and about 200
degrees C to about 220 degrees C. In some embodiments, in Step B, the Parylene
dimer
may be cleaved by heating in two or more stages, and preferably in two stages
of about 680
degrees C and to more than about 700 degrees C. In some embodiments, in Step
C, the
silane may be vaporized in a 50:50 solution with water. In other embodiments,
in Step C
the silane may be vaporized at 80 degrees C for about 2 hours. In some
embodiments, the
final thickness of the Parylene coat may be from about 100 Angstrom to about
3.0 mm.
Methods that comprise pre-treating the objects with a silane compound may
include
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the following steps:
A. vaporizing a Parylene dimer form by heating to 150-200 degrees C to form
gaseous Parylene dieters;
B. cleaving gaseous Parylene dimers to gaseous Parylene monomers by heating
gaseous Parylene dimers to about 650 to about 700 degrees C;
C. vaporizing silane by heating it to its evaporation point to form gaseous
silane;
D. contacting an object to be coated with gaseous silane; and
E. contacting the object to be coated with gaseous Parylene monomers for
sufficient time to deposit a coat of Parylene of a final thickness. Steps A, B
and E may be
performed by any manner that is currently in use for the coating of objects
with Parylene, as
will be well-known to those of ordinary skill in the art. Further, any of the
steps may be
performed in an order different that than the one presented. For example, Step
D may be
performed prior to Step A. Further, some steps may be performed simultaneously
with other
steps: for example, Step D may be performed simultaneously with Step A. In
preferred
embodiments, Parylene C may be used. See Fig. I B. In other embodiments, other
forms of
Parylene may be used, including but not limited to, Parylene N, Parylene D and
Parylene HT .
See Figs. 1 A, 1 B and 1 D. In some embodiments, the Parylene may be derived
from Parylene
N, or poly-para-xylylene, by the substitution of various chemical moieties. In
preferred
embodiments, the Parylene may form completely linear, highly crystalline
material. In the
Examples section, an embodiment of the method is set forth with a more
detailed description
on how the method may be performed.
In some embodiments, Step A, vaporizing Parylene dimer form by heating to 150-
200
degrees C to form gaseous Parylene dimers, may be performed in a furnace
chamber. In
preferred embodiments, the Parylene dimer is heated in stages to the desired
150-200 degrees
C. In some embodiments, this staged heating of the Parylene dimer takes place
in a furnace
chamber that is multi-zoned, allowing for different temperature set points in
different zones
of the furnace chamber. While not limiting the method of action of this staged
heating
procedure, it is thought that the method allows the Parylene to be uniformly
"cracked" as a
monomer and allow better control of the thickness of the final Parylene
coating on the object,
as it will remain a monomer longer in the deposition chamber so that it can
spread throughout
the deposition chamber. In some embodiments, the Parylene dimer may be
vaporized by
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heating in 2 stages, 3 stages, 4 stages, or more than 4 stages. In some
embodiments, the
temperatures of the stages are about 170 degrees C, and about 200 to about 220
degrees C.
While not limited the a particular theory, the inventors believe in the first
stage of
vaporization, the Parylene will be vaporized, and in the second stage the
vapor will be
preheated to that when it enters the Pyrolization chamber, it will be cleaved
into a monomer
at a higher rare.
In some embodiments, Step B, cleaving gaseous Parylene dimers to gaseous
Parylene
monomers by heating gaseous Parylene dimers to 650 to 700 degrees C, may be
performed in a
furnace chamber. In preferred embodiments, the gaseous Parylene dimer is
heated in stages to
the desired 650 to 700 degrees C. In some embodiments, this staged heating of
the gaseous
Parylene dimer takes place in a furnace chamber that is multi-zoned, allowing
for different
temperature set points in different zones of the furnace chamber. In some
embodiments, the
Parylene dimer is cleaved to monomers by heating in 2 stages, 3 stages, 4
stages, or more than
4 stages. In some embodiments, the temperatures of the stages are about 680
degrees C and
more than about 700 degrees C. While not limited to a particular theory, it is
thought that in
the first stage of heating, the gaseous Parylene dimers will be cleaved into a
monomers, and in
the second state of heating, the gaseous monomers will be heated further to
above about 700
degrees C to assure that the gaseous monomers are in the deposition chamber
longer so as to
fill it more evenly.
The methods may utilize a step in which gaseous silane (Fig. 1 E) may be
brought into
contact with the object to be coated (Step D). This step is particularly
advantageous to aid the
Parylene coating hydrophilic surfaces of objects. In some embodiments,
Silquest silane,
Silquest A-174 (NT) silane, or Silquest A-174 silane is used throughout the
method to coat
objects with a Parylene compound. In one embodiment, the object may be
contacted with the
gaseous silane in a vacuum chamber.
In Step C, the silane may be vaporized by heating it to its evaporation point.
In
preferred embodiments, this step may be performed prior to contacting the
object to be
pretreated with the gaseous silane. In one embodiment, this step may be
preformed by placing
the silane into a crucible, inserting the crucible into a T' thermocouple onto
a hot place in the
vacuum chamber containing the object to be coated. The amount of silane poured
into the
crucible may depend on the number and size of objects in the vacuum chamber.
In various
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embodiments, the amount of silane vaporized may range from about 10 to about
100 ml, or in
some cases more. In one embodiment, the hot plate may heat the silane to its
evaporation point.
In other embodiments, other methods to heat the silane to its evaporation
point may be used, as
will be well-known to those of ordinary skill in the art. In another
embodiment, a mixture of
silane with distilled water may be vaporized. In one embodiment, a 50/50 mix
of silane and
distilled water is heated until the silane is vaporized, which may be at about
80 degrees C for
about 2 hours.
While in some embodiments, the object may be pretreated with silane and then
Parylene in the same vacuum chamber, in other embodiments, the two coatings
may be applied
in different chambers, and/or at different times. In a preferred embodiment,
once the exposure
of the object to the evaporated silane is complete, the chamber may be put
under a vacuum,
and the Parylene deposition may start as soon as a suitable vacuum is reached.
It may be
preferable to completely exhaust the silane vapor from the chamber before
introducing the
gaseous Parylene monomers. The period of time between the application of the
silane
pretreatment and the Parylene coating may be, in various embodiments, from
about 0 minutes
to about 120 minutes. The temperature of the evaporation point of silane is
about 80 degrees C.
While not limiting the mechanism of action of the silane, it is thought that
the vaporized silane
pretreats the object, increasing the ability of the surface to accept the
Parylene monomer gas by
causing the surface to have free radical sites to which the Parylene monomers
will bond.
In Step D, the object to be coated may be contacted with gaseous silane. In
preferred
embodiments, this contacting may be done in the same deposition chamber that
will later be
used to contact the gaseous Parylene monomers to the object. In some
embodiments, the
object is contacted with the gaseous silane for a time of about 2 hours.
In Step E, the object to be coated may be contacted with gaseous Parylene
monomers
for sufficient time to deposit coat of Parylene. In preferred embodiments,
this step may be
performed in a deposition chamber, and particularly preferably in the same
deposition chamber
in which the object was contacted with silane. In other preferred embodiments,
the deposition
chamber and the objects to be coated may be at room temperature. In some
embodiments, the
deposition temperature may be about 5 to about 30 degrees C, preferably about
20 to about 25
degrees C. In some embodiments, the deposition chamber may be refrigerated to
speed up the
deposition process.
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Another embodiment provides a method to treat objects with silane. This method
contains the following steps:
A. vaporizing silane by heating it to its evaporation point to form gaseous
silane; and
B. contacting an object to be coated with gaseous silane.
5 In Step A, the silane may be vaporized by heating it to its evaporation
point. In some
embodiments, Silquest , Silquest A-174, Silquest 111 or Silquest 174(NT) is
the silane
throughout the method. In preferred embodiments, this step may be performed
prior to
contacting the object to be pretreated with the gaseous silane. In one
embodiment, this step
may be performed by placing thesilane into a crucible, inserting the crucible
into a 2"
10 thermocouple onto a hot place in the vacuum chamber containing the object
to be coated the
amount of silane poured into the crucible may depend on the number and size of
items in the
vacuum chamber. In various embodiments, the amount of silane vaporized may
range from
about 10 to about 100 ml, or in some cases more. In one embodiment, the hot
plate may heat
the silane to its evaporation point. In other embodiments, other methods to
heat the silane to its
15 evaporation point may be used, as will be well known to those, of ordinary
skill in the art. In
another embodiment, a mixture of silane with distilled water may be vaporized.
In one
embodiment, a 50/50 mix of silane and distilled water may be heated until the
silane is
vaporized, which may be at about 80 degrees C for about 2 hours.
In Step B, the object to be coated may be contacted with gaseous silane. In
some
20 embodiments, the object is contacted with the gaseous silane for a time of
about 2 hours.
Methods for applying coatings that comprise a conformal coating compound and a
thermally conductive material are also provided. In some embodiments, the
methods
involve heating a conformal coating compound to form gaseous monomers of the
conformal coating compound; combining a thermally conductive material with the
gaseous
25 monomers, thereby forming a gaseous mixture, and contacting an object with
the gaseous
mixture, under conditions where a conformal coating comprising the conformal
coating
compound and the thermally conductive material is formed on at least a portion
of a surface
of the object, thereby applying a conformal coating to the object.
As used herein a "gaseous mixture" is a mixture that comprises at least one
30 constituent in a vapor (gaseous) phase and at least one other constituent
which may or may
not be in a vapor phase. For example, a gaseous mixture may comprise a
conformal
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31
coating compound in a vapor phase and a solid phase compound (e.g., a powder
particle)
suspended in the conformal coating compound vapors. Similarly, a gaseous
mixture may
comprise a conformal coating compound in a vapor phase and a liquid phase
compound
(e.g., a nebulized liquid) suspended in the conformal coating compound vapors.
In
addition, a gaseous mixture may comprise multiple vapor phase constituents
(e.g., a
plurality of different vapor phase conformal coating compounds). It is to be
understood,
that gaseous mixtures may include any number of combinations of constituents
of the same
and/or different phases. In some embodiments, the gaseous mixture comprises at
least one
vapor phase conformal coating compound (e.g., Parylene) and at least one
thermally
conductive material. In some embodiments, a thermally conductive material in a
gaseous
mixture is in a solid phase (e.g., a powder particles). In some embodiments, a
thermally
conductive material in a gaseous mixture is in a liquid phase. In still other
embodiments, a
thermally conductive material in a gaseous mixture is in a gaseous phase.
The coating methods disclosed herein may be used on products used in the
commercial marine, recreational boating, military (aerospace and defense),
industrial and
medical industries, as well as others disclosed herein and known in the art.
In some cases,
the coating process may specifically be designed to "seal" a device. Thus, the
coating
methods may be useful to protects devices commonly used in marine and
hazardous
environments against operational malfunction caused by exposure to moisture,
immersion
in water, dust, effects of high wind and chemicals. The coating may enhance
the
survivability and sustainability of operational equipment and high value
specialty products
susceptible to corrosion and degradation.
In another aspect, the disclosure provides a method to apply a conformal
coating
comprising a Parylene compound and boron nitride to at least a portion of a
surface of an
object, which may have: (A.) vaporizing Parylene dimers by heating them to
about 150 to
about 200 degrees C to form gaseous Parylene dieters; (B.) cleaving gaseous
Parylene
dimers to gaseous Parylene monomers by heating gaseous Parylene dimers to
about 650 to
about 700 degrees C; (C.) injecting boron nitride into the gaseous Parylene
monomers of
Step B; and (D.) contacting the object to be coated with Parylene with the
gaseous Parylene
monomers and boron nitride of Step C for sufficient time to deposit coat of
Parylene and
boron nitride of a final thickness. While any Parylene may be used in this
method, Parylene
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D, Parylene C, Parylene N and Parylene HT may be preferred, and Parylene C
may be
particularly preferred. In some preferred embodiments, the boron nitride may
be injected
into the gaseous Parylene monomers as a powder, preferably between about 18
micron and
about 25 micron. In other embodiments, Step D may take place at about 5
degrees to about
30 degrees C. In some embodiments, the final thickness of the coat may be
between about
100 Angstrom to about 3.0 millimeters. In some embodiments, the method may
have an
additional Step E in which the object to be coated may be contacted with a
silane
composition until the object is coated with silane.
In some embodiments, the method applies a uniform, thin layer of a conformal
coating comprising a Parylene compound and boron nitride within a vacuum
chamber at 25
degrees C using standard chemical vapor deposition practices in thicknesses
ranging from
0.01 to 3.0 millimeters, depending on the item coated. The item once coated is
weatherproof and water resistant, and can withstand exposure to extreme
weather
conditions and exposure to most chemicals. Any solid surface can be coated,
including
plastics, metals, woods, paper and textiles. Sample applications include, but
are not limited
to: electronics equipment, such as cell phones, radios, circuit boards and
speakers;
equipment used in ocean and space exploration; hazardous waste transportation
equipment;
medical instruments; paper products; and textiles.
Thus, methods for coating objects with a composition of Parylene and boron
nitrite
may include the following several steps: A. vaporizing Parylene dimer form by
heating to
150-200 degrees C to form gaseous Parylene dimers; B. cleaving gaseous
Parylene dimers to
gaseous Parylene monomers by heating gaseous Parylene dimers to 650 to 700
degrees C;
C. injecting boron nitride into the gaseous Parylene monomers of Step B; and
contacting
the object to be coated with gaseous Parylene monomers and boron nitride for
sufficient
time to deposit coat of Parylene of a final thickness.
Steps A and B of the method to coat objects with Parylene and boron nitride
may
be performed by any manner that is currently in use for the vapor coating of
objects with
Parylene, as will be well known to those of ordinary skill in the art.
Further, the steps may
be performed in an order different than the one presented. In preferred
embodiments,
Parylene C is used. In other embodiments, other forms of Parylene may be used,
including
but not limited to, Parylene N, Parylene D and Parylene HT . In some
embodiments, the
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Parylene may be derived from Parylene N, or poly-para-xylylene, by the
substitution of
various chemical moieties. In preferred embodiments, the Parylene forms a
completely
linear, highly crystalline material. In the examples section, one embodiment
of the
method is set forth with a more detailed description on how the method may be
performed.
In some embodiments, Step A, vaporizing Parylene dimer form by heating to 150-
200 degrees C to form gaseous Parylene dimers, may be performed in a furnace
chamber.
In some embodiments, Step B, cleaving gaseous Parylene dimers to gaseous
Parylene
monomers by heating gaseous Parylene dimers to 650 to 700 degrees C, may be
performed
in a furnace chamber. In some embodiments, Step C, injecting boron nitride
into the
gaseous Parylene monomers of Step B, may be performed after Step B. In some
embodiments, the boron nitride may be injected into the gaseous Parylene
monomer as a
powder. One embodiment of this step is described in the Example. In some
embodiments,
the boron nitride powder may be at least about 500 grit. In some embodiments,
the boron
nitrate powder is between about 1.8 micron and about 2.5 micron.
In Step D, the object to be coated may be contacted with gaseous Parylene
monomers and boron nitride for sufficient time to deposit a coat of Parylene
and boron
nitride on the object. In some embodiments, this step may be performed in a
deposition
chamber. In other embodiments, the deposition chamber and the objects to be
coated may
be at room temperature, from about 5 degrees C to about 30 degrees C, or most
preferably
from about 20 degrees C to about 25 degrees C. In some embodiments, the length
of time
that the object may be contacted with the gaseous Parylene monomers and boron
nitride
may be varied to control the final thickness of the Parylene-boron nitride
coat on the
object. In various embodiments, the final thickness of the Parylene-boron
nitride coating
may be between about 100 Angstrom to about 3.0 millimeters. In some
embodiments,
Parylene is deposited from about 8 hours to about 18 hours to obtain a coat
thickness of
about 0.05 mm. In some embodiments, Parylene is deposited from about 5 hours
to about
18 hours to obtain a coat thickness of about 0.05 mm. In preferred
embodiments, the final
thickness of the Parylene coating may be between about 0.5 millimeters to
about 3.0
millimeters. The choice of final thickness of Parylene coating depends to some
degree on
the object to be coated and the final use of the object. Thinner final coats
may be
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desirable for objects that require some movement to be functional, such as
power buttons.
Thicker coatings may be desirable for objects that will be submerged in water.
In some embodiments, the method may have the additional step E of contacting
the
object to be coated with a silane composition until the object is pretreated
with silane. In
preferred embodiments, this step may be performed prior to Step D. In some
embodiments, the silane composition may be in solution when the object is
contacted with
it. In other embodiments, the silane composition may be in a gas when the
object is
contacted with it. In some embodiments, the silane composition may be Silquest
A- 174
silane (Fig. 1E). This step is particularly advantageous to aid the Parylene
coating
hydrophilic surfaces of objects.
EXAMPLES
Example 1: Method and apparatus used to coat an object with Parylene.
This embodiment uses Parylene C.
Coating Process
The apparatus consists of two sections: (1) a furnace/heating section; and (2)
a
vacuum section. The furnace section is made up of two furnaces which are
connected by glass
tubes referred to as retorts. The furnace and vacuum sections are connected by
valves that
allow gas flow between the furnace and vacuum sections.
The furnace portion of the equipment was fabricated by Mellen Furnace Co.
(Concord,
NH. See Example 2. The vacuum portion was fabricated by Laco Technologies Inc.
(Salt Lake
City, UT).
The process to coat items with Parylene is as follows:
(1) First Furnace Chamber. Parylene C in Dimer form (two molecule form) in an
amount sufficient to coat the item is placed in the furnace chamber. The items
are coated in a
thickness ranging from 0.01 to 3.0 mms. The Parylene C is placed in a
stainless steel "boat" (a
standard container made out of metal or glass) that is inserted into the
furnace through a
vacuum secured opening of the tube (the boat is pushed with a rod into the
furnace). The
opening is sealed after inserting the Parylene C. The furnace is then brought
to 150-200
degrees C to create an environment in which the solid Parylene C becomes a
gas. The gas is
held in the first furnace chamber until two valves open. The first of two
valves will not open
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until the cold traps in the vacuum section are filled with liquid nitrogen
(LN2) and the traps
are "cold". The LN2 is purchased from a local supply house. The LN2 is placed
into a one
gallon container at the supplier. The LN2 is poured from the container into
the "trap." The
second valve is variable and is opened when the gas is pulled from the first
furnace by
5 vacuum.
(2) Second Furnace Chamber. The Parylene C gas moves to the second furnace
which
is a temperature of 650 to 700 degrees C. The heat in this furnace causes the
Parylene C gas
to separate into individual molecules (monomers). The gas in monomer form is
then pulled
by vacuum into the deposition chamber.
10 (3) Vacuum Chamber. The vacuum portion of the machine consists of a
deposition
chamber with two vacuum pumps. The first vacuum pump is a "roughing" pump
which pulls
down the initial vacuum. The initial pressure is in the 1 x 10"3 Torr range.
The second stage
pump then pulls down to the final pressure in the 1 x 10-4 Torr range. The
vacuum pumps are
protected by liquid nitrogen traps that protect the pumps from the
solidification of the
15 monomer gas by condensing the gas on the cold trap surface.
The items to be coated are set on shelves in the deposition chamber prior to
starting the
coating process. The devices to be coated are masked (with workmanlike
methods) in those
areas on and within the device that are not to be coated. The masking is done
in areas where
electrical or mechanical connectivity must remain. The material is coated onto
the item at
20 room temperature (75 degrees Fahrenheit).
Inside the vacuum chamber there is a crucible of Silquest A- 174 silane
(Momentive
Performance Materials Inc., Wilton, CT) that is poured into a ceramic
crucible. The crucible is
inserted into a 2 inch, thermocouple onto a hot plate in the vacuum chamber.
The amount of
Silquest A-174 silane poured depends on the amount of items in the chamber,
but is between
25 10-100 ml. The plate heats the Silquest A-174 silane to an evaporation
point such that it
coats the entire area inside the chamber, included any objects within the
chamber.
Once the Silquest vapor is evacuated from the deposition chamber, the monomer
gas
is pulled by the lower vacuum in the vacuum chamber. When the gas is pulled
into the
chamber it is deflected so that it sprays within the entire area of the
chamber. The items are
30 coated as the monomer gas cools. The gas cools from 600 degrees C to 25
degrees C and
hardens on the device within the chamber. During that cooling process, the
monomers deposit
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on the surface of the item to be coated creating a polymer three dimensional
chain that is
uniform and pin hole free. The deposition equipment controls the coating rate
and ultimate
thickness. The required thickness of a Parylene coating is, determined by time
exposed to the
monomer gas. The thickness can range from hundreds of angstroms to several
millimeters.
Example 2: A zoned furnace that may be used in the apparatus to apply a
coating of Parylene.
This furnace assembly was fabricated by the Mellen Company, Inc., Concord NH.
One
Mellen Model TV 12,
Single or two zoned - solid tubular furnace is capable of operation at
temperatures up
to 1200 degrees C in air. The furnace utilizes the Mellen standard Series 12V
heating elements
(exposed Fe-Cr-Al windings within a special designed holder). The furnace has
an energy
efficient ceramic fiber insulation package alone with 2" long vestibules. The
thermocouples
are placed at the center of each zone. A ten-foot long power cable for each
zone is provided to
facilitate connection to the power source. A furnace is designed for
horizontal or vertical
operation and has the following specifications:
Table 1:
MODEL: TV 12-3x32-1/2Z
Maximum Temperature 1200 de rees C
Nominal Bore I.D. 3 inches
Heated Len h of Furnace 32 inches
Furnace Outer Diameter Shell (a rox) 10 -12 inches
Overall Furnace Len h a rox.) 36.25 inches
No, of Furnace Zones 1 or 2 zones
Voltage (Nominal, 1 phase, 50/60 Hz.) 208 volts
Total Power 6,400 watts
Mellen Series PS205 Power Supply/Temperature Controller
One (1) Mellen Model PS205-208-(2)25-S, two zone, digital temperature
controllers
and solid state relay. The MELLEN Series PS205 consists of the following:
a.) Two (2) digital temperature controller calibrated for a Type "S"
thermocouples
featuring 126 segments & 31 programs.
b.) One (1) solid state relay.
c.) One (1) General Electric or equal circuit breaker, two pole, with
appropriate-sized
amperage rating.
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d.) One (1) Mellen cabinet to house the above components.
e.) Two (2) Type "S" thermocouples including 10 it of compensated thermocouple
extension wire, terminal boards, etc., per zone.
f.) All necessary wiring, terminal boards, interconnections, etc., to make a
completely
workable system.
Over-temperature Protection for Power Supply/Temperature Controller
One (1) over-temperature (O.T.) alarm utilizing an independent digitally
indicating,
digital set-point "hi-limit alarm" controller. The O.T. Alarm package is
furnished, with an
appropriate thermocouple, TIC extension wire, and sufficient mechanical power
contactor(s)
to interrupt power to the furnace in the event of an over temperature
condition at the location
of the over-temperature sensor. The O.T. alarm option is mounted in the main
temperature
controller enclosure.
Retort Model: RTA -2.5 x32-OBE
One (1) Mellen Model RTA-2.5-32-OBE, round, Hi-Purity Alumina (actual system
has a Quartz retort) retort to be used with the furnace described above. The
retort working
diameter is approximately 2.5 inches I.D. by 32 inches. The retort has an O.D.
of
approximately 2.75" inches and is 48" inches long & contains the necessary
stainless steel
flange/seal assemblies, & heat shields to permit gas tight operation.
Feedthroughs are
provided in the cover plates of the retort for gas in/out and temperature
measurement. The
retort is capable of operating with different types of atmospheres.
Example 3: Method and apparatus used to coat an object with Parylene and Boron
nitride.
This embodiment uses Parylene C.
Coating Process
The apparatus will consist of two sections: (1) a furnace/heating section; and
(2) a
vacuum section. The furnace section will be made up of two furnaces which are
connected
by glass tubes referred to as retorts. The furnace and vacuum sections will be
connected by
valves that allow gas flow between the furnace and vacuum sections.
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38
The furnace portion of the equipment was fabricated by Mellen Furnace Co.
(Concord, NH. The vacuum portion was fabricated by Laco Technologies Inc.
(Salt Lake
City, UT).
The process to coat items with Parylene and boron nitride will be is as
follows:
(1) First Furnace Chamber. Parylene C in Dimer form (two molecule form) in an
amount sufficient to coat the item is placed in the furnace chamber. The items
are coated
in a thickness ranging from 0.01 to 3.0 mms. The Parylene C is placed in a
stainless steel
"boat" (a standard container made out of metal or glass) that is inserted into
the furnace
through a vacuum secured opening of the tube (the boat is pushed with a rod
into the
furnace). The opening is sealed after inserting the Parylene C. The furnace is
then brought
to 150-200 degrees C to create an environment in which the solid Parylene C
becomes a
gas. The gas is held in the first furnace chamber until two valves open. The
first of two
valves will not open until the cold traps in the vacuum section are filled
with liquid
nitrogen (LN2) and the traps are "cold". The LN2 is purchased from a local
supply house.
The LN2 is placed into a one gallon container at the supplier. The LN2 is
poured from the
container into the "trap." The second valve is variable and is opened when the
gas is pulled
from the first furnace by vacuum.
(2) Second Furnace. Chamber. The Parylene C gas will move to the second
furnace
which is a temperature of 650 to 700 degrees C. The heat in this furnace will
cause the
Parylene C gas to separate into individual molecules (monomers). The gas in
monomer
form is then pulled by vacuum into the deposition chamber.
Boron nitride in powder form is placed in a KF 16 tube that is connected to a
KF
connection tube that has a "T" KF16 port. This K1716 tube is partially filled
with a
"charge" of boron nitride powder (minimum of 500 grit). The KF16 tube is
capped. After
the coating process is initiated, the boron is injected into the coating
"stream." The boron
flows as a powder and will become entrapped with the deposition of the coating
process.
The K1716 tube is attached to the retort perpendicular to the flow of the
monomer
gas just before it enters the deposition chamber. There is a valve that is
opened which
allows the boron nitride to flow into the gas. The gas will bind with the
monomer and is
deposited on the items to be coated. This process is similar to powder
coating. The
process may be repeated to increase the amount of boron nitride inserted into
the coating on
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39
the items. While not limiting the characteristics of the boron
nitride/Parylene coating, it is
thought that boron nitride improves the hardness of the coat and supplies a
method to better
allow the heat to escape the coated object, such as an electronic device. The
boron nitride
is inserted into the Parylene as a dust.
(3) Vacuum Chamber. The vacuum portion of the machine will consist of a
deposition chamber with two vacuum pumps. The first vacuum pump is a
"roughing"
pump which pulls down the initial vacuum. The initial vacuum is in the 1 x 10-
3 Ton
range. The second stage pump then will pull down to the final vacuum in the 1
x 10-4 Ton
range. The vacuum pumps are protected by Liquid Nitrogen traps that protect
the pumps
from the solidification of the monomer gas by condensing the gas on the cold
trap surface.
The items to be coated are set on shelves in the deposition chamber prior to
starting
the coating process. The devices to be coated are masked (with workmanlike
methods) in
those areas on and within the device that are not to be coated. The masking is
done in areas
where electrical or mechanical connectivity must remain. The material is
coated onto the
item at room temperature (75 degrees Fahrenheit).
Inside the vacuum chamber there is a crucible of Silquest A- 174 silane that
is
poured into a ceramic crucible. The crucible is inserted into a 2 inch
thermocouple onto a
hot plate in the vacuum chamber. The amount of Silquest A- 174 silane poured
depends
on the amount of items in the chamber, e.g., between 10-100 ml. The plate will
heat the
Silquest A- 174 silane to an evaporation point such that it coats the entire
area inside the
chamber, included any objects within the chamber.
The monomer gas is pulled by the lower vacuum in the vacuum chamber. When the
gas is pulled into the chamber it is deflected so that it sprays within the
entire area of the
chamber. The items are coated as the monomer gas cools. The gas will cool from
600
degrees C to 25 degrees C and will harden on the device within the chamber.
During that
cooling process, the monomers deposit on the surface of the item to be coated
will create a
polymer three dimensional chain that is uniform and pin hole free. The
deposition
equipment will control the coating rate and ultimate thickness. The required
thickness of a
Parylene coating is determined by time exposed to the monomer gas. The
thickness can
range from hundreds of angstroms to several millimeters.
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While several aspects and embodiments of the invention have been described, it
should be apparent, however, that various modifications, alterations and
adaptations to
those embodiments may occur to persons skilled in the art with the attainment
of some or
all of the advantages of the present invention. For example, in some
embodiments of the
5 present invention disclosed herein, a single component may be replaced by
multiple
components, and multiple components may be replaced by a single component, to
perform
a given function or functions. Except where such substitution would not be
operative to
practice embodiments of the present invention, such substitution is within the
scope of the
present invention. The disclosed embodiments are therefore intended to include
all such
10 modifications, alterations and adaptations without departing from the scope
and spirit of the
present invention as defined by the appended claims. Preferred features of
each aspect and
embodiment of the invention are as for each of the other aspects and
embodiments mutatis
mutandis.
It is to be further understood that the figures and descriptions of the
present
15 disclosure have been simplified to illustrate elements that are relevant
for a clear
understanding of the present disclosure, while eliminating, for purposes of
clarity, other
elements, e.g., components of a conventional conformal coating method or
apparatus. For
example, certain conformal coating systems may include additional components,
e.g.,
deposition chambers, valves, vacuum pumps, that are not described herein.
Those of
20 ordinary skill in the art will recognize, however, that these and other
elements may be
desirable in a typical conformal coating system. However, because such
elements are well
known in the art and because they do not facilitate a better understanding of
the present
disclosure, a discussion of such elements is not provided herein.
Also, in the claims appended hereto, any element expressed as a means for
25 performing a specified function is to encompass any way of performing that
function
including, for example, a combination of elements that perform that function.
Furthermore
an invention, as defined by means-plus-function claims, resides in the fact
that the
functionalities provided by the various recited means are combined and brought
together
in a manner as defined by the appended claims. Therefore, any means that can
provide
30 such functionalities may be considered equivalents to the means shown
herein.
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For the purposes of this specification, unless otherwise indicated, all
numbers
expressing quantities of ingredients, time, temperature, thickness of coats,
and other
properties or parameters used in the specification are to be understood as
being modified
in all instances by the term "about." Accordingly, unless otherwise indicated,
it should be
understood that the numerical parameters set forth in the following
specification and
attached claims are approximations. At the very least, and not as an attempt
to limit the
application of the doctrine of equivalents to the scope of the claims,
numerical parameters
should be read in light of the number of reported significant digits and the
application of
ordinary rounding techniques.
Additionally, while the numerical ranges and parameters setting forth the
broad
scope of the invention are approximations as discussed above, the numerical
values set
forth in the Examples section are reported as precisely as possible. It should
be understood,
however, that such numerical values inherently contains certain errors
resulting from the
measurement equipment and/or measurement technique.
Any patent, publication, or other disclosure material, in whole or in part,
that is said
to be incorporated by reference herein is incorporated herein only to the
extent that the
incorporated material does not conflict with the existing definitions,
statements, or other
disclosure material set forth in this disclosure. As such, and to the extent
necessary, the
disclosure as explicitly set forth herein supersedes any conflicting material
incorporated
herein by reference. Any material, or portion thereof, that is said to be
incorporated by
reference herein, but which conflicts with existing definitions, statements or
other
disclosure material set forth herein will only be incorporated to the extent
that no conflict
arises between the incorporated material and the existing disclosure material.
