Note: Descriptions are shown in the official language in which they were submitted.
W~ 91/08~0 2 ~ u ~ PCr/US90/07468
-- 1 --
AUTODEPOSITION EMUISION FOR SELECTIVELY PROTECTING
METALLIC SURFACES
Technical Field
Generally, the invention relates to the technical
field of autodeposition emulsions and methods of
selectively coating matallic surfaces therewith,
especially those surfaces which are subjected to
etchant baths as the surfaces are being processed as
circuit traces for electronic circuit boards.
Backqround Art
In many instances, it is desirable to coat
metallic surfaces so as to protect the surfaces from
corrosive environments. For instance, automobile
underbodies are coated to protect them ~rom road salt
- compounds. Marine vessel parts are coated to protect
them from the marine air. In those instances, a
polymer coating is applied to the entire surface of
the substrate, or, in the alternative, a prepolymer
coating is applied to the substrate and then
polymerized~in to~o.
In addition, it is also desirable to selectively
protect certain areas of a metallic surface. One such
instance is the selective protection of metallic
surfaces being processed as circuit traces for
electronic circuit boards. In those instances, only
certain preselected areas of the metallic surface are
coated by a polymeric film.
Specifically, circuit traces can be made by using
either of two photoresist systems in a coating r
imaging ! developing and etching process. In the first
system, the substrates or metallic surfaces are coated
with a negative working photoresist which polymerizes
upon exposure to actinic radiation. In the second
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~V091/0~4~ PCT/US90/07468
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-- 2
system, the substrate or metallic surface is coated
with a positive acting photoresist which becomes
soluble in developer solution upon exposure to ac~inic
radiation.
Once either one of the resists have been applied
to the surface, the surface is then e~posed to actinic
radiation. When using the negative resist, the
surface is exposed to radiation through a photographic
negative bearing an image of the desired circuit. As
a result, the sections of the resist exposed by the
radiation become photopolymeri~ed and thus less
soluble in a developer solution. Then during the
development phase, those sections of resist which were
shielded from the radiation, and which thus remain
substantially unpolymerized, are dissolved away by
means of a suitable solvent that does not dissolve the
photopolymerized sections. This stage is known as
development because it develops an image of the
circuit by uncovering certain sections of the metallic
surface. A~ter development, the uncovered metal
surf~ce is etched to form a printed circuit. The
photopolymerized resi~t may then be ~tripped
chemically by means of a solvent, leaving a circuit
pattern formed from the unetched metal surface.
When using the positive resist, the coated surface
is exposed to radiation through a positive image of
the desired circuit. The exposed areas of the coating
are thus rendered more soluble and subsequently
removed in a developing solvent. As done when using
the negative resist, the metal surfaces left uncovered
during development are etched, thus leaving a positive
image of the desired circuit.
Photoresists have become important tools when
preparing circuit boards having plated through holes.
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W~l/08~0 ~ Ll ~ a PCTtUS90/07468
-- 3
Such holes are being increasingly used as circuit
boards are increasingly being made with two conductive
sides. The additional conductive surface increases
the boards' capabilities.
The above-described two sided boards are
conv~ntionally made ~rom a laminate consisting of
copper/epoxy/copper sheets. Each copper side of the
laminate has a circuit etchecl onto it. ~he two sides
are connected electrically, as required for the
particular circuits involved, by small apertures or
"through holes". Other terms used in the art are
"component holes" or i'vias." Through holes, as
initially drilled or otherwise formed, are not
electrically conductive because of the intervening
1~ insulating epoxy layer. Accordingly, the holes'
interiors must be coated with copper to electrically
connect the two copper sheets. This copper coating
can be applied by electroless copper deposition, thus
forming one type of plated through hole (PTH).
Another type of PTH includes those holes which have
copper electrolytically deposited thereon after the
initial electroless deposition of copper. See Norman
S. ~inarson, Printed Circuit Technoloqv (published by
Printed Circuit Technolo~y, 1977); Fisher, G.L.;
Sonnenberg, W., & Bernards, R.; "Electroplating of
High Aspect Ratio Holes "Printed Circuit Fabrication,
Vol. 12, No. 4 (~pril, 1989) pp.39-66; D'Ambrisi, J.J.
et al., "The Chemistry of Plating Small Diameter
Holes", Part II; Printed Circuit Fabrication, Vol. 12,
No. 8 (Aug., 1989) pp.30-42.
Some of the difficulties in making circuit boards
begin with those copper-coated holes. After the holes
are created and plated with copper, the laminate is
subjected to the etchant operations that tend to
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WO91/08~ PCT/US90/07468
~t~ i3 4 _
attack the copper coatings within the holes.
Accordingly, the art has deve:Loped various methods for
protecting the copper plated holes.
Two methods of protection include (1) paraffin
plugs for the holes and (2) tenting with dry and
liquid photoresist films. However, paraffin plugs are
difficult to handle because of problems in removing
the plugs when they are no longer needed. In
addition, while tenting has been used w'th greater
success, the problems attendant upon tenting also make
its use somewhat awkward.
Tenting works by protecting the plated holes with
a dry film comprising a photopolymerizable sheet. The
areas of the sheet whi~h cover and protect the holes
1~ are exposed to W radiation and polymerized. The
circ~it board is then later processed with the plated
holes remaining covered by the "tent". The tents are
then later removed by proper solvents.
As recognized by those skilled in the art, proper
photoimaging of the circuit requires that any
` protective photopolymerizable coverings used in the
; process be extremely thin. As a result, when using
tenting techniques, the polymerizable tents are thin.
Howevar, because of their thinness, these tents tend
to be weak and thus are subject to tearing, breaks or
"pinholes." Once those flaws form, solvents or
etchants can seep through and come in contact with the
copper deposited on the through holes' sides, thus
destroying the interconnect: between the two copper
sheets. The same problem occurs when the dry film is
laid down improperly, thus allowing etchant solutions
and developers to leak underneath the film.
In addition to film flaws, tenting results in the
formation of "annular rings" or shoulders on the
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WO9l/OB~0 ~ PCT/US90/07468
board's surface. These rings result from the
requirement that a tent's diameter must be larger than
the hole diameter in order to provide an attachment
point for the tent and to afford hole protection.
Their formation occurs during the etching process,
because, after etching, the tent has not only
protected the inner lining of the aperture, but has
also protected an annular portion of the metal surface
surrounding the aperture.
However, annular rings have become a problem as
the trend towards smaller circuit boards and higher
dansity circuits continues. For axample, as circuit
boards get smaller there will be less space available
for the rings on the boards' surfaces. Thus, there
will be less surface area onto which the tents can be
anchored. Moreover, as more and more circuit traces
are designed into the boards, large annular rings are
more and more becoming a hindrance to design around.
For example, there are some instances where multiple
fine line circuits are run parallel and one of the
circuit traces will require a connaction to the other
side of the board. In such an instance, a hole will
be required. However, i~ the annular ring for that
hole is too large, the other traces must be diverted
away from the hole to avoid a short-circuit. Thus, to
avoid designing around the ring, it would be ideal to
eliminate their presence altogether.
Further, it is generally recognized that the
current resin/photoactive functionality combinations
found in common photoresists are capable of resolving
smaller fe.atures. On the other hand, the current
liquid ancl dry film photoresists do not maximize those
capabilities in that to form finer features with a
good manufacturing yield it is generally recognized
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WO91/088qO PCT/US9~/07468
~ ~3 `` '3~ t ~ ~ - 6 -
that thinner films with fewer defects than those
provided by current liquid ancl dry film photoresist
application methods are needecl. However, other known
application methods, such as ]amination, roll coating,
flood screen printing, spraying, dip coating, curtain
coating, etc., fail as an appropriate application
method as the film thickness decreases below 1 mil.
For instance, in order to resolve features as small or
smaller than 4 mils, which is currently the state of
the art, it is preferable that the film thickness of
the protective covering used be 25~ or less o~ the
feature size being resolved. However, when attempting
to obtain thic~nesses less than 1 mil with those
methods, a significant number of defects begin to
appear in the coating that results.
One method that avoids the above problems is the
electrodeposition of a photoresist. For instance, a
photoresist coating is applied to the substrate by
applying an electric charge to the substrate, ~hich in
turn attracts a charged photoresist. See U. S.
Patents 4,632',900 to Demmer et al. and 3,954,587 to
Kokawa. Thus, in electrodeposition a thin film of
resist forms directly onto the surfaces of the plated
through holes and thus avoids the awkward tenting
process of laying the film down, the attendant annular
ring formation and the film flaw problem. However,
electrodeposition involves additional equipment and
time to construct the electrodeposition apparatus.
Electrodeposition also consumes electrical power and
requires charged resins. Even further, photoresist
compositions usually have optimal component ratios at
which the components should be applied to the surface.
However, by using electrodeposition, preferential
deposition of certain charged particles may alter the
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WO91/08~0 2 ~a ~ ~ ~ r. PCT/US90/07468
ratio of components actually deposited. Thus, a
method which has the advantages of electrodeposition
baths in that the substrate can be effectively coated
and protected, but which also avoids the problems
encountered when using electrodeposition methods would
be desirable.
Disclosure of Invention
- lO Thus, the general object of the invention is to
provide a method and emulsion which effectively coats
and selectively protects metallic surfaces by inducing
the deposition of a protective coating on the surface
by simply immersing the surface in an emulsion and
then selectively processing the coating so that only
certain portions of the surface remain coated. Such a
method comprises
(a) immersing the surface in an emulsion
comprising
(i) resin,
(ii) photoactive functionality,
(iii) acid,
(iv) oxidizing agent, and
(v) sur~actant,
wherein ~ (v) are present in amounts
and the surface is immersPd for a period
of time sufficient to induce a coating
of resin (i) and functionality (ii) on
said metallic surface;
(b) exposing said coating of resin (i) and
functionality (ii) to actinic radiation
in an image-wise fashion; and
(c) immersing said exposed coated surface
from (b) above in a developer to develop
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WO91/08840 PCT/US90/07468
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an image on said surface.
It is a particular object of the invention to
provide a method and emulsion capable of selectively
protecting a metallic surface being processed to make
electrical circuit traces, wherein the method
comprises
(a) immersing the surface in an emulsion
comprising
(i) resin,
(ii) photoactive functionality,
(iii) acid,
(iv) .oxidizing agent, and
(v) surfactant,
wherein (i)-(v) are present in amounts and
the surface is immersed for a period of time
sufficient to induce a coating of resin (i)
and functionality (ii) on said metallic
surface;
(b) exposing said coating of resin (i) and
functionality (ii) to actinic radiation in an
image-wise fashion;
(c) immersing said exposed coated surface from
(b) abovs in a developer solution to develop
an image on said surface;
~d) immersing the developed st~face from (c) in
an etchant bath to remove metallic surfaces
which were ttncovered during step ~c); and
(e) stripping any remainin~ coating in a solvent.
These and other objects will become apparent from
the following detailed description of the invention.
The emulsion described above can be defined as an
autodeposit:ion bath. These types of baths have been
described in the art and are termed as ~uch because
they deposit a coating on a metal surface by physical
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WO 91/08~0 ~ PCT/US90/07468
_ g _
contact, e.g. immersion. They do not require the
surface on the coating components in the bath to be
electrically charged. See U.S. patents 4,103,049 and
4/347,172 to Nishida et al. and U.S. Patent 4,366,195
to Hall. Briefly, autodeposition baths are water
based emulsions comprising resin, a surfactant and a
combination of an acid and an oxidizing agent. A11 of
those components are present in amounts sufficient to
induce the resin to coat a metal surface when immersed
in the bath. Further, such baths deposit coatings in
- such a manner that the coating grows in thickness with
timè. The art has described using such baths to coat ~~
- steel, aluminum, zinc and some copper surfaces.
Contrarv to previous autodeposition emulsions in
the art, the emulsion described herein contains
photoactive functionality and is used to deposit a
coating which can selectively protPct metal surfaces,
aspecially those surfaces which are being processed
for electrical circuit traces. As described above,
the emulsion comprises
(i) resin,
(ii) photoactive functionality,
(iii) acid,
(iv) oxidizing agent, and
(v) surfactant.
Resins which are suitable for the emulsion
include, but are not limited to, acid containing
polymers or copolymers of one of the following
monomers: styrene, butadiene, isoprene, vinylidene
chloride, methyl acrylate, ethyl acrylate, butyl
acrylate, methyl methacrylate, ethyl methacrylate,
butyl methacrylate, acrylonitrile, acrylic acid,
itanoic acid, methacrylic acid, vinyl alcohol, maleic
anhydride and vinyl acetate. Specific copolymers
. . . . . . . .
WO9l/08~40 PCT/US90/07468
~ ~ a - 1 O
include
butadiene/acrylonitrile/methacrylic acid
styrene/acrylic acid
styrene/butadiene/acrylic acid
styrene/butadiene/methacry~lic acid
styrene/butadiene/itaconic: acid
styrene/butadiene/maleic acid
styrene/butadiene/butylacrylate/acrylic acid
; styrene/butadiene/butylacrylate/methacrylic acid
styrene/butadiene/butylacrylate/itaconic acid
styrene/butadiene/butylacrylate/maleic acid
styrene/ethyl acrylate/methacryiic ~cid
styrene/maleic anhydride
styr~ne methacrylic acid, and
vinylidene chloride/methacrylic acid.
Resins comprising acid copolymers which have been
partially modified by compounds such as simple alkyl
alcohols, e.g. acid resins esterfied with butanol, may
also be used. Commercially available resins include
Joncryl~ 67 styrene/acrylic acid copolymer from
~ohnson Wax, Scripset~ 550 ~rom Monsanto and SMA 17352
from Sartomer, both styrene/maleic anhydride
copolymers partially esterfied with simple alkyl
alcohols.
Other suitable resins include novolak resins
derived from an aldehyde, such as formaldehyde, and a
phenolic compound, such as phenol or cresol. Suitable
examples include HT 9690, from Ciba-Geigy and HRJ
10805 from Schenectady, both cresol novolaks.
For the purposes of this invention, the
photoactive functionalities suitable for the emulsion
are those functionalities or compounds which are
positive or negative acting. As is well ~nown in the
art, a positive acting functionality is a
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WO91/~8~0 ;,~ PCT/U~90/0~468
-- 11 --
functionality or compound which becomas soluble in a
developer solution when exposed to actinic radiation.
A negative acting functionality is a functionality or
compound which polymerizes, and becomes less soluble,
when exposed to radiation. As discussed latsr below,
the photoactive functionality can be a functionality
or compound separate from the rasin, or the
functionality can be attached to the resin, e.g. a
copolymer product from an additional monomer.
Suitable positive acting photoactive
functionalities include, but are not limited to,
oxymethylene based monomers, o-nitrocarbinol esters,
o-nitrophenyl acetals and polyesters and end-capped
derivatives thereof, and benzo- and naphthoquinone
diazide sulphcnic estars. See U.S. Patent 4,632,900 to
Demmer et al. A preferred positive acting
functionality is a 4- or 5- sulfonic acid derivative
of an orthodiazonaphthoquinone, e.g. a 2-diazo-1-
naphthoquinone sulfonate ester. An especially
preferred functionality is the 2-diazo-1-
naphthoquinone-5-sulfonate triester of 2,3,4-
trihydroxybenzophenone. A co~mercially available
adduct is that known as THB~ 215 Diazoester from
International Photochemicals.
Another preferred positive acting functionality
is o-nitrocarbinol ester. This monomer may be
polymerized as a homopolymer to form the functionality
or, as in one embodiment of the invention, preferably
polymerized as part of a copolymer with an unsaturated
acid and the same or a different ester. Such
copolymers are formed using standard emulsion
polymerizat:ion techniquss described later below. If a
nitrocarbinol is used, suitable copolymers therefrom
should have a molecular weight of at least 500 and --^
, ~ ':': - , '' '.''~','.''," . '' : ' ''
WO91/08840 PCT/~S90/07~68
- 12 -
- c~ntain in the molecule at least 5% by weight, by
reference to the molecular weight, of aro~atic
carbocyclic or heterocyclic o-nitrocarbinol ester
groups of formula
r
CO
HC-R~
, ~ N2
~ A
--}5 ~
where ~ denotes an aromatic carbocyclic or
heterocyclic ring that may be substituted and has 5 to
14 members, and R4 denotes a hydrogen atom, an alXyl
group of from 1 to B carbon atoms, or an optionally
substituted aryl or aralkyl group, the optional
substituents on the groups A and R4 being alkyl or
alkoxy groups of from 1 to 8 carbon atoms, halo~en
atoms, nitro, amino, or carboxylic acid groups.
Suitable ring systems A may be mononuclear or
polynuclear, such as benzene, naphthalene, anthracene,
anthraquinone, phenanthrene, or pyridine rings.
Examples of suitable aromatic o-nitrocarbinols
upon which these o-nitrocarbinol ester groups are
based include o-nitrobenzyl alcohol, 2-nitroveratryl
alcohol, 6-nitroveratryl alcohol, 2-nitro-4-
aminobenzyl alcohol, 2-nitro-4-dimethylaminobenzyl
alcohol, 2-nitro-5-dimethylaminobenzyl alcohol, 2-
nitro-5-aminobenzyl alcohol, 2-nitro-4,6-
dimethoxybenzyl alcohol, 2,4-dinitrobenzyl alcohol, 3-
methyl-2,4-dinitrobenzyl alcohol, 2-nitro-4-
methylbenzyl alcohol, 2,4,6-trinitrobenzyl alcohol, 2-
nitrobenzhydrol, 2,2'-dinitrobenzhydrol, 2,4-dinitro-
- benzhydrol, 2,2',4,4'-tetranitrobenzhydrol, 2-nitro-
': , ', . .' . ' ' :, , ,'. .. '' ~. I . ' : ,
W~91/~X840 ~ 3~ 3 Q PCT/US9~/07~68
- 13 -
4-methylaminobenzyl alcohol, 2-nitro-3-hydroxymethyl
naphthalene, l-nitro-2-hydroxymethyl naphthalene, 1-
nitro-2-hydroxymethyl anthraquinone, 3-methoxy-4-
(2-nitratoethoxy)-6-nitrobenzyl alcohol and 2-nitro-
3-hydroxymethyl pyridine.
If desired, photosensitizers such as aromatic
ketones and thioxanthones may be included with the
positive acting functionalitiec;.
Suitable negative acting photoactive
functionalities include, but are not limited to, a
variety of photoprepolymers. Generically those
. . .
prepolymPrs include, but are not limited to acrylates.
~ore specifically, they include acrylic and
methacrylic acid esters of mono-, di-, and polyhydric
alcohols; and mono-, di-, and polyalkoxy acrylate and
methacrylate.
~lso suitable are mono-, di-, and poly- acrylates
or methacrylates which are derivatized from the
reaction of hydroxyl terminated acrylate or
methacrylate esters with mono-, di-, and
polyisocyanates, epoxides, and other hydroxy reactive
compounds. Speci~ic examples include:
ethylene glycol diacrylate
ethylene glycol dimethacrylate
propylene glycol diacrylate
propylene glycol dimethacrylate
trimethylolpropane triacrylate
trimethylolpropane ethoxylate triacrylate
trimethylolpropane propoxylate triacrylate
trimethylolpropane ethoxylate trimethacrylate
trimethylolpropane propoxylate trimethacrylate
bisphenol A diacrylate
phenoxyethyl methacrylate
`~ hexanediol diacrylate
..
.
- . : . . ~, ,.. ;
WO91/088~0 PCT/US90/07468
~ ~-3ig~ 14 -
neopentyl glycol diacrylate
neopentyl propoxylate diacrylate
pentaerythritol triacrylate
dipentaerythritol hydroxypentaacrylate
polyethylene glycol diacrylate
Trimethylolpropane ethoxylate triacrylate is
available as Photomer~ 4149 and 4155 from Henkel
Corporation. Other preferred negative acting
prepolymers include those known as Sartomer~ 454, 205,
and 399 from Sartomer Co.
When using the negative acting functionalities
described above, it is necessary to use a
photoinitiator. Thus hereinafter, unless described
otherwise, when the term "photoactive functionality"
is specifically used in regards to a negative acting
functionality, the term "photoactive functionality"
also includes a photoinitiator. Suitable
photoinitiators for initiating polymerization of the
negative acting photoprepolymers with W radiation
include, but are not limited to, b~nzoin ethers,
benzil ketones, and phenones and phenone derivatives.
Examples are:
acetophenone
9,10-anthraquinone
benzil
benzil dimethyl ketal
benzoin
benzoin tetrahydropyranyl ether
benzoin isobutyl ether
benzophenone
benzoyl cyclobutanone
4,4'-bis(dimethylamino)benzophenone
dibenzosuberone
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WO 91/0~0 ~ ;J ~ .3 PCT/US90/07468
- 15 -
dioctyl acetone
diethoxy acetophenone
methyl ethyl kPtone
methyl isobutyl ketone
thioxanthone
xanthone
A commercially available photoinitiator used in
the Examples below is Irgacure~ 651 from Ciba-Geigy.
As mentioned above, resin ~i) and the photoactive
functionality (ii) may be chemically separate
components in the bath or they may be chemically
bound. As also mentioned above, an embodiment in
which (i) and (ii) are bound can be prepared by
emulsion polymerizing a monomer containing the
photoactive functionality with another monomer to
produce a resin having the photoactive functionality
attached thereto, e.g. the nitrocarbinol ester co-
polymer. One embodiment is illustrated in Example 1.
Emulsion polymerization techniques, conditions
and polymerization initiators are those well known in
the art. Known techniques for the addition of
monomers in emulsion polymerization techniques include
continuous addition or sequential addition of monomer
in separa*e portions. Known surfactants suitabla for
emulsifying the monomers in aqueous solution include,
but are not limited to, 2,4,7,9-tetramethyl-5-decyn-
4,7-diol, 3,5-dimethyl-1-hexyn-3-ol, glycProl
monostearate, dipropylene glycol monostearate,
` 30 dipropylene glycol monolaurate, dipropylene glycol
monooleate, pentaerythritol monooleate, sodium dioctyl
sulfosuccinate, sorbitan monolaurate, sodium lauryl
ether sulfate, potassium xylene sulfonate, sodium
cumene sulfonate, ethylene glycol monostearate,
. : "~
: : ~ - . : ,
W091/08840 ~CT/US~0/0746B
~ J~ - 16 -
glycerol, nonyl ph~nol ethoxylate, polyoxyethylene
cetyl ether, N-octadecyl sulfosuccinamate,
polypropylene glycol monostea]ate, 3,6-dimethyl-4~
octyn-3,6-diol, dodecyl benzene sodium sulfonate, and
sodium lauryl sulfate. When emulsion polymerization
is used to prepare a bath, the surfactant used in the
polymerization reaction may also serve as surfactant
(v) of the emulsion.
Suitable polymerization initiators include free
radical generators such as p_roxy disulfates- and
persulfate-lron-bisulfate or metabisulfate systems.
Detailed techniques, methods and conditions for
emulsion polymerization are described in F. W.
Billm~yer, Textbook of Polymer Science (Wiley-
15 Interscience, New York; 2ed 1971); K. Bovey, et al.,
Emulsion Polymerization, (Interscience Publishers,
Inc.; New York l9S5); and G. M. Dekker, Kinetics and
~echanisms of Pol~merization, Vol. 1 (Ed. by G.E. Ham
1969)-
A preferred embodiment of the emulsion in which
resin (i) is not already prepared in emulsion form
can be prepared by direct emulsification of (i) and
(ii). In some instances, standard emulsion techniques
can be used. See U. S. 4,177,177 to Vanderhoff and
Xirk-Othner EncycloPedia of Chemical Technoloqy, 3rd
edition, Volume 8, "Emulsions - Preparation", pp. 919-
923. In other instances certain resins and
photoactive functionalities may require other emulsion
techniques. For instance one preferable technique is
a combination of phase inversion and comminution
techniques. Specifically, at room temperature, a
water-in-oil (w/o) emulsion is formed by preparing
resin (i) and photoactive functionality (ii) in
solution by mixing (i) and (ii) into organic solvents
.
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WO91/08~0 ~3 ~ CT/US9~/0746
- 17 -
such as ethyl acetate and then adding to that solution
a lesser amount of water, e.g. about fifty percent by
weight of the solution. The resulting w/o emulsion is
then inverted into an oil-in-water ~o/w) emulsion by
5 addition of well known surfactants such as sodium
alkyl benzene sulfonates, sodi~lm alkyl sulfates or
alky phenol ethoxylates in aqueous solution. In some
instances, subsecruent additions of surfactants may be
needed to complete the inversion. To stabilize the
10 resulting emulsion, the emulsion is comminuted by well
known homogenizer or, preferably, ultrasound
techniques. Any of the resins described above can be
used in this technique.
Another method for forming a mixture of (i) and
15 (ii) is illustrated in Examples 3-14. Specifically,
a resin latex can be prepared by the standard emulsion
~olymerization techniques described above for the
above-mentioned resins. The resulting latex contains
resin particles which would constitute resin (i~ of
20 the emulsion.
The specific latex for this embodiment is not
critical. However, latex particles are preferable to
use with certain photoactive functionalities because
they appear to emulsify the functionality component. r
25 In addition, as recognized by those skilled in the
art, they can provide acid functionalities to the
- coating so that when using an alkali ~eveloping
solution, the uncured coatings can be removed more
easily. Further, because the latices are generally
30 made with high molecular weight material, the latices
act as fillers to provide a more uniform coating. A
wide variety of latices is available and are made from
the monomers suitable for preparing resin (i).
Commerc:ially available latices include Darex~
., , . ~ , . .. . .
~VO91/08840 PCT/U~90/07468
i2 ~3 a ~ i9 ~3 i3 - 18 -
528L from the Organic Chemicals Division of W. R.
Grace & Co.-Conn. Acrysol~ ASE-75 from Rohm & Haas is
also suitable.
When using latices, a surfactant from the group
described earlier may be used to emulsify components
(i) and (ii) in order to assist the deposition
process. A commercially available surfactant used in
the Examples herein is Surfynol TG surfactant from Air
Products, Inc.
When using any of the above-described methods for
preparing the emulsion, the amounts of (i) and (ii)
should be sufficient so that the total solids content
of the emulsion is in the range of about 1 to 20% by
weight.
After the emulsion of (i) and (ii) is formed,
acid (iii) and oxidizing agent (iv) are then added to
the emulsion. The acid and oxidizing agent include
those known in the art of autodeposition. It is
thought that the acid and oxidant cause metal from
; 20 metallic surfaces to dissolve, thus cxeating metal
ions. Those metal ions are believed to destabilize
the emulsion near the metallic surface and cause the
resin particles in the emulsion to deposit thereon.
See U.S. Patent 4,177,180 to Hall. Examples of acids
include hydrochloric, hydrofluoric, phosphoric,
citric, sulfuric and acetic acids. An example of an
oxidizing agent is hydrogen peroxide. The acid should
be added in amounts so that the p~ of the resulting
emulsions is generally in the range of 1-5 and
preferably in the range of 1.7-3. In some instances,
metal halides such as cupric chloride and ferric
chloride can also be used as oxidizing agents. In
certain autodeposition baths, it may also be desirable
; to include a metal salt, such as a metal halide, in
. .
- : :~ - - - : ' , :.: ,~ . : :
, , , . ~ : . . . ~: . .
- . . : . , .. . .: :: , : ~ , . . , . . :
WO 91/0~0 ~ n PCT/US90/07468
-- 19 --
the bath even when another oxidizing agent is already
included, e.g. H202. For instance, in certain latex-
based emulsions, CuCl2 can be used in conjunction with
H202. In some instances, the addition of CuCl2 may
help induce autodeposition. See Examples 5 and 7-12.
In addition, when using the embodiment comprising
preformed resin latices, e.g. t:hose illustrated in
Examples 3-14, it was found that certain combinations
of acid and oxidizing agents were more suitable than
others for preparing suitable autodeposition
emulsions. Suitable combinations are illustrated in
the Examples beiow, but other combinations known in
the art of autodeposition may also be suitable.
The surfactant (v) used in the au~todeposition
emulsion can be any of those well known in the art.
They include those listed earlier in conjunction with
the emulsification t~chniques and are preferably added
in addition to those used when making the emulsions of
`~ the resin and photoactive functionality.
The amounts of the emulsion's components, other
than the acid, are tabulated below.
Emulsion Com~onent Percentaqe bY_Weight
Suitable Preferred
" resin 0.5-18.01.8-9.0
photoactive functionality 0.1-10.0 0.15-~.0
:
total surfactants 0.5-5.0 1-2
oxidizing agent 0.05-5.00.1-1.0
Other additives can also be included in the
, .
.
. . :,
.
. .
~YO9l/~8~0 P~T/US90/074S8
~ ~j3 C~ 3 ~
- 20 -
emulsion. The additives can be included as one oE the
original emulsion forming components or they can be
added after the emulsion has been formed, depPnding on
the additive used. Such additives include, but are
not limited to, coalescing agents, stabilizers,
pigments, flow aids and adhesion promoters.
Commercially available stabilizers for negative
photoactive functionalities include hydroquinone, p-
methoxyphenol, pyrogallol, 2,5-di-t-butyl-4-
methylphenol and phenothiazine. Available flow aidsinclude Modaflow~ from Monsanto and Lithene PL~ from
Rivertex. Available pigments and dyes include any oE
a wide variety, e.g. Neopen Blue 808~ from BASF.
Suitable coalescing agents are glycol ethers and
esters such as PM Acetate~ (propylene glycol
monomethyl ether acetate) from Eastman Chemical Co.
and Butyl Dipropasol~ (dipropylene glycol monobutyl
ether), Hexyl Carbitol~ (hexyloxyethoxy ethanol) and
UCAR~ ester E~P (ethyl 3-ethoxy propionate) fxom Union
Carbide.
To obtain a coating o]E (i) and (ii~ on a metallic
surface, standard autodeposition techniques are used.
For instance, the surface is immersed in the emulsion
iEor about 30 seconds to 15 minutes. After the surface
has been immersed for a period of time so that the
desired coating thickness has been obtained, the
coated surface is removed from the emulsion and
preferably rinsed and dried.
Subsequently, the coated metallic surface is
exposed to actinic radiation in an image-wise fashion.
; In instances where circuits are being mad~ and
positive act:ive functionalities are being used for
photoactive ~Eunctionality (ii), the coating is exposed
to radiation through an image bearing transparency
; ~ ..
. . .~ .. .. , - ., , . .: .,: ,'
- -;.: , ,. ,, ,- ~ , i.
, ~, : ;, . : .
- . , : . ~ .. . :, . .:. : -
- - ,., ,.~
WO91~08~ PCT/US90/07468
~ 3 L `;`1, ~
- 21 -
such that only the coating on the metal areas to be
protected from the etchant bath remain unexposed. If
negative acting functionalities are being used, the
image-bearing transparency used is such that the
coating on the metal areas to be protected from the
etchant bath are exposed to the radiation.
Radiation used in the present invention
preferably has a wavelength of 200-600 nm. ~uitable
sources of actinic radiation include carbon arcs,
mercury vapor arcs, fluorescent lamps with phosphors
emitting ultraviolet light, argon and xenon glow
lamps, tungsten lamps, and photographic flood lamps.
Of these, mercury vapor arcs, fluorescent sun lamps,
and metal halide lamps are most suitable. The time
required for the exposure will depend upon a variety
of factors which include for example, the individual
photoactive groups used in the emulsion, the
proportion of thesè groups in the emulsion, the type
of light source, and its distance from the
-~ 20 composition. Suitable times may be readily determined
by those familiar ~ith photoimaging techniques.
The developer used in the present process is
selected according to the nature of the resin and
photoactive functionality and photolysis products and
may be an aqueous or aqueous organic solution of a
base; or an organic solvent or mixture of solvents.
The use of a base to form a salt, and hence solubilize
the fractions of photoactive functionality or resin
remaining in the areas of coating which are to be
removed after irradiation, is preferred. Such basic
solutions ar~e, typically, 0.25-3.0% by weight sodium
or potassium hydroxide or carbonate. After
development of the image formed by the radiation,
certain areas of the metal surface remain coated,
.. , ~ , . . . .
. . . - : -: , , :
' ' ,, ~ i, . "
WO91/~8~40 PCT/US90/0746X
2 v ~ 22 -
while the other areas are uncovered. For instance, if
positive acting functionalities are used the areas of
coating which are exposed to radiation are removed to
uncover metal surface. On the other hand, when
S negative acting functionalities are used, the areas of
coating unexposed to radiation are removed. Thus, in
either instance, the image resulting from development
selectively coats and the imaged metal surface can be
left "as is" or further processed.
In one embodiment, the selectively coated surface
is coppe~ and can be further processed to prepare
electrical traces for circuit boards. As mentioned
above, the processing step taken would be to process
the copper s~rface in an etching solution. Etching
solutions that may ~e used to remove the uncovered
copper metal after development are known in the art
and may be varied according to the nature of the metal
surface. For example, with a copper surface, an
` acidic solution of ammonium persulfate, cupric
chloride or ferric chloride is usually used. Another
cupric chloride etching solution is basic aqueous
ammonium hydroxide/cupric chloride.
Other suitable surfaces are copper laminate
wherein a copper layer has been laminated onto a
reinforcing layer. Suitable reinforcing layers
include paper, epoxy, glass reinforced epoxy,
polyimide, polytetrafluorethylene and the like.
After etching a positive resist coated surface,
the coating covering the protected metal traces is
then exposed to actinic radiation to render the
coating soluble. Any exposed positive acting coating
is then removed with a stripping solution, usually
aqueous NaOH. Exposed negative acting coating is
generally removed by a warm (57F) spray of 3-5% by
. ~ . , . r, .
.' ' '', ,' , , ~ ' ' ~ ' ' '
' ' ' "~'~, '' ''' '''' ' ' '
'. ," ~ .
WV91/0~840 ~ 3~ PCT/US90/07468
- 23 -
weight aqueous sodium hydroxide.
As mentioned above, using the autodeposition
emulsion method is useful in protecting conductiv~
apertures or "through holes" in two sided circuit
boards. By using an autodeposition method, the
surfaces of the conductive metallic linings of these
apertures are covered and effectively protected from
the etching bath. Thus, the above emulsion provides
protection equal to that obtained by electro- ;^`
deposition, but it is more advantageous in that emf
inducing equipment is not needed nor is there a need
for an additional process step of connecting thë
~- metallic surface to an electrical current. Moreover,
resin (i) and functionality (ii) do not need to be
processed to contain a charge, nor is there the
pre~erential deposition which results from electro-
depositing such charged particles.
Further, in making circuit traces on boards
having plated through holes, the positive acting
system is sometimes preferable to a negative acting
system. For instance, when a negativeiimaging system
is employed to protect the lining of the holes, it is
difficult to fully irradiate and polymerize, and thus
render insoluble, the coating on the insid~ surfaces
of the apertures. Thus, it is possible that the
composition will not be fully resistant to the normal
development and etching processes, and the metal
lining in the aperture may be etched away, even though
this was not intended.
On the other hand, the use of a positive acting
functionality avoids the above described problem
because the positive phototool is designed to shield
the apertures from the actinic radiation. Thus,
because unirradiated areas of a positive resist
.... i
,
.
: - - . . : , ::
:. :- . ... ..
.. ..
. ~
WO9l/~X~0 PCT/US90/07468
2~.3 ~ d~ - 24
coating are insoluble and remain intact during and
after development, linings are protected from the
etching bath.
In order to further illust:rate the practice of
the present invention and the advantages thereof, the
~ollowing examples are provided. However, these
examples are in no way meant to be limitative, but
merely illustrative.
Modes for Carryinq Out the Invention
_
Example l
~Emulsion Polymerization of Photoactive Functionality)
;'~
A mixture of 16.6g of o-nitrobenzyl acryla~e,
5.3g of methyl methacrylate, and l.9g of acrylic acid
was prepared, with the resulting mixture being divided
into and added in five (5) equal portions to a mixture
composed of lOOg of distilled water and 0.5g of sodium
bisulfite. Each addition of monomer was preceded by
~he addition of 3.Oml of a 10% (by weight) aqueous
dodecyl benzene sodium sulfonate and follo~ed by the
addition of l.Oml of a 10% (by weight) aqueous sodium
persulfate. The reaction temperature was maintained
between 65-75C. The resulting latex contained 15.8%
total solids.
To 67.Qg of this latex emulsion was added 0.8g of
hydrofluoric acid, 16.7g of 30% hydrogen peroxide, and
enough distilled water to fill the mixture to lOOml.
A copper-covered, glass-reinforced epoxy laminate
submerged in the latex/acid/peroxide composition for
five (5) minutes exhibited a coating that, upon
removal from the composition, could not be removed by
vigorous rinsing with water. The coating was then
- .
: . . ............ , ... .~ :: . , . . :
~, , : :
: : -: . . .
WO 91/08840 ~ l~ J ~ r i ~ PCT/US90/07468
~ 25 ~
dried for 10 minutes at 90C.
The dried coating was covered with a silver
halide phototool and exposed for 12 minutes under a 1
kW high-pressure, mercury-xenon, W light source rich
in light of 3 65 nm. Following this exposure, the
coated substrate was immersed in 5.0% (by weight)
aqueous sodium hydroxide for 3() seconds, resulting in r
removal of coating that had been exposed to the W
light, and leaving a positive image of the phototool.
The photoimaged board was then immersed in a
hydrochloric acid/cupric etchant bath for five (5)
minutes. After removal, the areas of the substrate
that had been covered with the coating were protected
while the exposed copper had been etched away.
ExamDle 2
A mixture of 8.9g vinylidene chloride and 41.4g
O-nitrobenzyl acrylate was added dropwise (30 to 60
drops per minute~ into a resin kettle containing
120.0ml deionized water, lOOOml of 10~ by weight
aqueous sodium dodecylbenzene sulfonatP, l.Og sodium
bisulfite, and O.Olg ammonium iron(II) sulfate. The
kettle mixture was stirred mechanically.
Concurrently, a mixture of 30.Oml deionized water and
l.Og sodium persulfate was added dropwise ~5 to 10
drops per minute) to the kettle. Before, during, and
after the additions, the kettle temperature was
maintained at 42C. The stirring and heating
continued for one hour after both additions were
complete. The result was a latex emulsion containing
22.4~ total solids by weight.
44.6g of this emulsion were mixed with a solution
of 50.9ml deionized water, 1.2g of 85~ phosphoric
- . :
WO91/08~0 PCT/US90/07468
2 ~ ~ _L~ 26 -
acid, and 3.3g 30% hydrogen peroxide. A clean copper
laminate was immersed in the resulting autodeposition
bath for 5 minutes. The laminate was then removed
from the bath, rinsed, and dried at 9OC for 5
minutes. A 0.3mil coating was observed on the
laminate. This coating was then shielded with a
silver halide phototool and exposed to W light for 12
; minutes. Successful de~elopment of the coa~ing was
accomplished in 5-6 minutes, using 5~ NaOH. Etching
in a cupric chloride etchant resulted in copper traces
- having the image of the phototool.
Example 3
(Latex Emulsion o~ Photoactive Functionality)
Resin Latex: 50g Darex 528L styrene butadiene
methacrylic acid copolymer
Photoactive Functionality: 75g trimethylolpropane
triacrylate (TMPTA) and 2.5g Irgacure~
651 photoinitiator
Surfactant: lOg Surfynol TG
The components above were prepared in an emulsion
by first blending the above amounts of latex and
~5 surfactant in lOOml of water. Second, the photoactive
functionality components were added with subsequent
addition of lOOml of water and high speed blending for
3 to 5 minutes. The blended mixture was diluted to
- lOOOml with deionized (DI) water.
Example 4
To lOOml of the emulsion prepared in Example 3,
lg of hydrofluoric acid (HF) and lg of hydrogen
peroxide (H2O2) were added. A copper panel was
immersed in the resulting emulsion for lO minutes.
'' : : ' ~' . ., ,,, , , !
:' " " ' .. ' ': '`', . '":' '' ,.:: , i . ' ' ,'
: ' ' ' ' , :: ''~: : ' .:' ' ~ ' '' ': .'.` ' '`
'' . . . . ~ :. : ' '. - :
- ' ' ' ~ ' . . . "' ' ,','"' ' : .', ` .. , ': '- ' ,
:. . ' ': . .- .:'; '' ' : . .
WO91/08840 ~ Lr 3 ~ PCTtUS90/07468
- 27 -
Deposition of coating on the copper was observed.
Coatings from the emulsion were found to be
photoimagable and etch resista,nt.
Example 5
'
0.5g of cupric chloride ~CuCl2) was added to the
deposition bath prepared according to Example 4. A
0.2 mil coating was deposited after immersion of a
copper panel for 10 minutes followed by a water rinse.
The deposited coating was found to be photoimageable
and etch resistant.
::
ExamDle 6
3g phosphoric acid and lg H2O2 were added to lOOml
of the emulsion prepared according to Example 3. A
coating less than 0.1 mil was deposited on a copper
panel after the panel had been immersed for 10 minutes
and was found to be photoimageable and etch resistant.
Example 7
0.5g CuCl2 was added to the emulsion prepared
according to Example 6. A 0.15 mil coating was
deposited on a copper panel which had been immersed
for 10 minutes. The coating was both photoimageable
and etch resistant.
Example 8
Resin Latex: 25g Darex 528L
Photoactive Functionality: 38g Photomer 4149
ethoxylated TMPTA from Henkel Corporation and
1.75g Irgacure 651 photoinitiator
WO91/08840 PCT/~S90/~7468
2 ~
- 28 -
Surfactant: 5g Surfynol TG
The processing steps used t:o make the emulsion
according to Example 3 were usecl except the above was
diluted to a 500ml emulsion.
To lOOml of the emulsion prepared above, lg HCl,
lg H2O2 and 0.5g CuCl2 was added. A photoimageable and
atch resistant coating deposited on a copper panel
which had been immersed in the bath for 10 minutes.
Example 9
Resin Latex: 1.75g Darex 528L
Photoactive Functionality: l.9g TMPTA, 38g
Photomer 4155 and 1.75g Irgacure 651
pbotoinitiator
Surfactant: 5g Surfynol TG
The processing steps used to make an emulsion
described in to Example 3 were used except the above
was diluted to a 500ml emulsion.
To lOOml of the emulsion prepared above, 3.8g
citric acid, lg H2O2 and 0.5g CuCl2 were added.
copper panel was immersed in the resulting bath for 10
minutes, resulting in the deposition of a
photoimageable and etch resistant coating on the
panel.
Exam~le 10
An emulsion was prepared according to Example 9
except 38g of Photomer 4149 was used instead of
Photomer 4155. The components for the ~ath were
diluted to 500ml.
To lOOml of the emulsion prepared above, 3.8g
. - . . . . .
: ,. . . .
~YO91/08~0 ~ s'~l) PCT/US9010746B
~ 29 - ;
citric acid, lg H2O2 and 0.5g CuCl2 were added. A
copper panel was immersed in the resulting bath,
resulting in the deposition of a 0.40 mil thick
coating which was photoimageable and etch resistant.
s
- Example :Ll
An emulsion was prepared with the following
components:
Resin Latex: 25g Darex 528L
Photoactive Functionality: 38g dipentaerythritol
hydroxy pentaacrylate and 1.75g
Irgacure 651 photoinitiater
Surfactant: 5g Surfynol TG
The above components were mixed toyether
according to the steps described in Example 3, except
the above components were diluted to 500ml.
To lOOml of the emulsion prepared above, lg HCl,
lg H2O2 and 0.25g CuCl2 were added. A copper panel was
im~tersed in the resulting bath, resulting in a 0.2 mil
thick coating which was photoimageable and etch
resistant.
Example 12
An emulsion was prepared accordiny to Example 11,
except 38g of pentaerythritol triacrylate was added
instead of dipentaerythritol hydroxypentaacrylate.
The above components were diluted to 500ml.
To lOOml of the emulsion prepared above, lg HCl,
lg H2O2 and 0.25g CuCl2 were added. A copper panel was
immersed in the resulting bath, resulting in a 0.2 mil
thick coating which was photoimageable and etch
. .
WO91/0~40 PC~/US90/0746
~ ;.3~J - 30 -
resistant.
ExamPle 13
5 A liter of emulsion was prepared as follows: lOg
of Irgacure 651 was dissolved in 50g of Photomer 4149.
This was add~d to 375ml of Acrysol~ ASE-75 aqueous
acrylic emulsion (150g solids) made by Rohm & Haas
` Company, in a blender. Enough water was then added to
make 1 liter of solution. The resulting solids
content of this emulsion was 21%.
Deposition baths were prepared from the above-
described emulsion as follows:
a, 3g of 30% H2O2 was added to lOOmls of
t5 emulsion. A 10% phosphoric acid solution
was used to titrate this solution to a pH of
1.8.
- b. 150g of 30% H202 was added to 5 liters of
emulsion. Concentrated phosphoric acid was
used to titrate this bath to a pH of 1.8.
In lOOml of bath a., 117 X 1-1/2" copper coupohs were
immersed for 1, 3, 5 and 10 minutes. Deposition, as
measured by weighing, increased with time.
Approximately lmil of polymer was deposited in 1
minute at these conditions. Agitation was by mild
stirring. In the 5-liter bath b., 50 6" x 6" circuit
boards were coated sequentially for 2 minutes.
Coating thickness variad from 2 mils initially to 1
mil at the end. Agitation was accomplished by moving
the board back and forth gently. These boards were
then dried at 80C ~or 5-10 min., contact imaged at 80
mj and developed in 1% Na2CO3. All coatings were etch
resistant.
W~91/08~0 ~ Ja PCT/U~90/07~68
- 31 -
ExamPle 14
Emulsions were prepared as in Example 13 except
fox substituting hydrofluoric, sulfuric, or citric
S acid for the phosphoric acid. The pH was maintained
at 1.8 for all examples. The resulting emulsions were
all acceptable but the emulsion containing phosphoric
acid was preferred because it gave more polymer
deposition per unit amount of copper removed by the
microetchant. In other words, that emulsion was more
efficient.
,
Exam~le 15
(Emulsification of Resin and Photoactive Functionality)
A solution of 34g Ciba Geigy HT9690 novolak resin
and 6g International Photochemicals THBP-215 Diazo
Ester (2,3,4-trihydroxybenzophenone 2-diazo-1-
naphthoquinone-5-sulfonate, 54~ triester) in 60g ethyl
acetate and lOg PM Acetate from Eastman Chemical was
prepared. The solution was stirred while a mixture of
1.5g Polystep A16-22 surfactant from Stepan and lOOg
water was added drop-wise. A water-in-oil emulsion
resulted.
A mixture of 0.5g Triton X-100 nonionic
surfactant from Rohm and Haas and 20g water was then
dripped in resulting in an oil-in-water (o/w) emulsion
~efore sonicating the emulsion for 2 minutes at about
180W estimated intensity with a 50nics and Materials
500W cPll disrupter with a 3/4" high gain Q horn. The
low boiling ethyl acetate solvent was removed on a
rotary evaporator. The resulting o/w emulsion
contained 31.7% solids following concentration.
A deposition bath was then prepared by diluting
. , . . ~ . , :
,. ~ ., :., : - ':-: '~ ' - `~
W091/08~0 PCT/US90/07468
,J~s~`3~ 3 ~"3 32 -
the emulsion to 10% solids with water, acidifying to
pH 1.8 with phosphoric acid, and adding an amount of
hydrogen peroxide equal to 1% of the total bath
weight. A copper foil/epoxy glass laminate strip was
immersed into the bath for 1 minute, resulting in the
deposition of about 0.2-0.3 mil coating which was
dried and coalesced for 5 minutes at 80C. The
coating was imagewise exposed to W light for 30
seconds (about 40 mJ/cm2 on an EIT radiometer) and then
developed by immersion in 1% NaOH until the exposed
part~ of the coating completely developed away, i.e.
1-~ minutes. The patterned coating was sufficiently
resistant to e~ching in aqueous CuCl2/HCl so that the
pattern was etched into the underlying metal after
about 2 minutes in a spray etching system.
Example 16
An emulsion was prepared from a solution of ~5g
of Charkit PR-12 positive photoresist, a 2-diazo-1-
naphthoquinone-5-sulfonate ester of a t-butyl
phenol/formaldehyde resin and 25g of ethyl acetate
from Charkit. To the above solution was added 0.16g
Triton X-100, followed by dropwise addition of 25g
deionized (DI) water. A solution of 0.5g Polystep A
16-22 surfactant in 35g DI water was added dropwise,
followed hy 20g of DI water and a further solution of
0.6g Polystep A16-22 surfactant in 40g DI water. A
water-in-oil emulsion resulted. Addition of lg Triton
X-100 in 5g ethyl acetate resulted in an oil-in-water
emulsion. The emulsion was sonicated for 2 minutes at
about 180W estimated intensity with a Sonics and
Materials 500 cell disrupter with a 3/4 inch high gain
Q horn. The low boiling ethyl acetate was removed on
: . . : :. :: .,. ,.-, , ,,:: ~ :
WO91~08840 ~ PCT/US90/07468
- 33 -
a rotary evaporator. The solids content of the
emulsion was 17.5~. A deposition bath was prepared by
diluting the emulsion to 8.4% total solids with water,
adding an amount of phosphoric acid equal to 1% of the
total bath weight and hydrogen peroxide equal to 1% of
; the total bath weight. A copper foil/epoxy glass
laminate strip was immersed in the bath for 1 minute,
and the resulting coating rinsed and dried. The
coating was imagewise exposed through a positive
pattern to W light (90 mJ/cm2) and developed by
immersion in a 5:1 dilution of a positive photoresist~~ ~ ~~~ developer from MacDermid to give a coated pattern
corresponding to the positive pattern. After heating
at 150C for 3 minutes, the patterned coating was
sufficiently resistant to etching in a 10% CuClz/10%
HCl bath at 60C to etch the coating pattern into the
underlying metal.
Exam~le 17
2~
A solution of 76.5g HT 9690 novolak resin from
Ciba-Geigy, 51.0g HRJ 10805 novolak resin from
Schenectady Chemicals, 22.5g THBP-215 Diazo Ester from
International Photochemicals, l5g Hexyl Carbitol
(hexyloxy ethoxy ethanol) from Union Carbide, and 150g
ethyl acetate was prepared.
To the stirred solution at room temperature was
added dropwise, over 1.5 hours, a solution of 6.0g
Polystep A-I6-22 surfactant in 224g deionized water to
form a water in-oil emulsion. This step was followed
by addition over 0.5 hours of a solution of l.Og
Triton X-100 in 70g deionized water to invert the
emulsion to an oil-in-water (o/w) emulsion. The
resulting o/w emulsion was sonicated for 2 minutes at
about 180W e-;timated intensity with a Sonics and
Materials 500W cell disrupter with a 3/4" high gain Q
horn. The ethyl acetate was removed on a rotary
, . - , . ....... - . ., ~, ..... : . .
- : . . .
WO 91/~8840 PCI/US90/07468
~ r~ 3
-- 34 --
evaporator to give an emulsion containing 34 . ~%
solids. A deposition bath was prepared by diluting
the emulsion to 5% total solids with an aqueous
phosphoric acid solution of pH 1.8 and adding an
amount of hydrogen peroxide equal to 0.5% of the total
bath weight.
. A copper foil/epoxy glass laminate coupon was
immersed in the bath for 1 minute, rinsed, and dried
for 4 minutes at 100C to give a coalesced coating of
- 10 a thickness of 0.2 to 0.3 mil. The coating was
imagewise exposed to W light through a positive
pattern (9OmJ/cm2) and immersed in a developer solution
or 0.5~ aqueous sodium hydroxide. The exposed area of
the coating was developed to leave a coating
corresponding to the positive pattern. The copper
uncovered during developing was etched away with an
acidic cupric chloride spray. The remaining coating
was further exposed (without p~ttern) to W light (200
mJ/cm2) after which it was dissolved away by immersion
in 0.5~ aqueous sodium hydroxide to leave a copper
pattern on the epoxy glass laminate corresponding to
the imaging pattern.
Exam~le 18
2~
A solution of a negative acting formulation was
prepared with the following components:
280g SMA 17352 styrene/maleic anhydride copolymer
partially esterified with simple alkyl
alcohols, e.g. methyl, butyl and isobutyl
alc:ohol, from Sartomer Co.
lOOg Sartomer 454 ethoxylated trimethylolpropane
; ~: :. ..
- : .
- : . :
: : ` : ; :. ` . ~: :::: .: . . . ::
WV91/08840 PCT/US90/07468
-;J ~ r 9~ V
~ 35 ~
triacrylate
20g Irgacure 651 photoin:itiator from Ciba-Geigy
S 40g PM Acetate from Eastman Chemicals-
420g ethyl acetate
To 100g of the above solution was added 0.3g Triton X-
100 surfactant followed by 50g water, dropwise with
mechanical stirring to form a water-in-oil emulsion. ,~
A mixture of 0.9g Polystep A16-22 surfactant from
Stepan in 70g water was then added dropwise to invert
the emulsion to an oil-in-water (o/w) emulsion. The
- 15 resulting o/w emulsion was sonicated for 2 minutes
with a Sonics & Materials 500W disruptor using a 3/4"
high gain Q horn at an estimated 180W intensity level.
The ethyl acetate was then removed on a rotary
evaporator.
A deposition bath was then prepared by diluting
the emulsion to 10% solids with wa,ter, acidifying to
pH 1.8 with phosphoric acid, and adding an amount of
hydrogen peroxide equal to l~ of the total bath
weight. Immersion of a copper foil/epoxy glass
laminate strip in the bath for 20 seconds resulted in
about 0.8 mil of coating which was dried and coalesced
for 5 minutes at 80C. The coating was imagewise
exposed to W light for 90 seconds ~about 110 mJ/cm2 on
an EIT radiometer) and then developed by immersion in
0.5% NaOH until the exposed parts of the coating
completely developed away, i.e. in 1-2 minutes. The
patterned coating was sufficiently resistant to
aqueous CuCl2/HCl so that the pattern was etched into
~, the underlying metal after about 2 minutes in a spray
~'
.: , : - . - , . . . : ................. ..
'` . ~ ' . ' . . "' '.. '.' ' . ' .. ; , ! , ~ , .
:, ' ' . ' , ': . ": ''`' ~' .. : ' .. ' . :.' ` ': ' . ', ' . ' ' . `
WO9l/~8840 P~T/~90/07468
~ 36 -
etching system.
Example 19
A solution of a negative acting formulation was
prepared with the following components:
23.2g Scripset 550 styrene malelc anhydride
copolymer esterfied with simple alkyl
alcohols from Monsanto
7.4g Photomer 4155 ethyoxylated trimethylol
- propane triacrylate from Henkel
7.4g Sartomer 45~ ethyoxylated trimethylol
propane triacrylate from Sartomer
2.0g Irgacure 651 photoinitiator from Ciba-Geigy
4.0g PM Acetate from Eastman
93g ethyl acetate
To the above solution was added 0.3g Triton X~lO0
surfactant followed by 50g water, dropwise with
mechanical stirring to form a water-in-oil emulsion.
A mixture of O.9g Stepan Polystep A16-22 surfactant in
70g water was added dropwise to invert the emulsion
into an oil-in-water to/w3 emulsion. The resulting
o/w emulsion was sonicated for 2 minutes with a Sonics
& Materials 500W disruptor using a 3/4" high gain Q
horn at an estimated 180W intensity level. The ethyl
acetate was then removed on a rotary evaporator.
A deposition bath was then prepared by d~luting
the emulsion to 10% solids with water, acidifying to
pH 2.0 with phosphoric acid, and adding an amount of
hydrogen peroxide equal to 0.3~ of the total bath
weight. Immersion of a copper foil/epoxy glass
laminate str:ip in the bath for 30 seconds caused
.:. ., ,, ; .. : - ~. .
WO91/08~0 ~ PCT/US90/07468
- 37 -
deposition of about 0.4 mil of coating which was dried
and coalesced for 5 minutes at 80C. The coating was
imagewise exposed to W light for 3 minutes (about 220
mJ/cm2 on an EIT radiometer) ancl then developed by
immersion in 0.5% NaOH until thc exposed parts of the
coating completely developed away, i.e. in 1-2
minutes. The patterned coating was sufficiently
resistant to aqueous CuCl2/~Cl such that the pattern
was etched in~o the underlying metal after about 2
minutes in a spray etching system.
.. . . .. .
Example 20
A solution of a negative acting formulation was
prepared with the following components:
- 36.0g Joncryl 67 styrene/acrylic acid
copolymer from Johnson Wax
ll.Og Sartomer 205 triethylene glycol
dimethacrylate from Sartomer
4.0g Sartomer 399 dipentaerythritol hydroxy
pentaacrylate from Sartomer
2.0g Irgacure 651 from Ciba-Geigy
4.0g PM aCetatQ from Eastman Chemical
60.0g ethyl acetate
To the above solution was added 0.3g Triton X-l00
surfactant followed by 50g water, dropwise with
mechanical stirring to form a water-in-oil emulsion.
A mixture of 0.9g Polystep Al6-22 surfactant from
Stepan in 70g water was added dropwise to invert the
emulsion to form an oil-in-water (o/w) emulsion. The
o/w emulsion was sonicated for 2 minutes with a Sonics
& Materials 500W disruptor using a 3/4" high gain Q
- ~. .. : .:
WO91/08~0 P~T/US90/07468
f '3
- 38 -
horn at an estimated 180W intensity level. The ethyl
acetate was then removed on a rotary evaporator.
A deposition bath was then prepared by diluting
the emulsion to 10% solids with water, acidifying to
pH 2.0 with phosphoric acid, and adding an amount of
hydrogen peroxide equal to 0.3% of the total bath
weight. Immersion of a copper foil/epoxy glass
laminate strip in the bath for 2 minutes caused
deposition of about 1.0 mil of coating which was dried
and coalesced for 5 minutes at 80C. The coating was
imagewise exposed to W light for 1.5 minutes (about
110 mJ/cm2 on an EIT radiometer) and then developed by
immersion in 0.5% NaOH. The coating was developable
but was not as cleanly developed as that for the
coatings illustrated in Examples 18 and 19. As a
result, the etching was retarded in some areas of the
coated substrate in this example.
Example 21
20A solution of a negative acting formulation was
prepared with the following components:
28.0g Joncryl 67 from Johnson Wax
5.0g Sartomer 454 ethoxylated trimethylol
25propane triacrylate from Sartomer Co.
5.0g Photomer 4155 ethyoxylated trimethylol
propane triacrylate from Henkel
2.0 g Irgacure 651 from Ciba-Geigy
4.0g PM acetate from Eastman
60.0g ethyl acetate
To the above solution was added 0.3g Triton X-100
surfactant followed by 50g water, dropwise with
mechanical stirring to form a water-in-oil emulsion.
A mixture of 0.9g Stepan Polystep A16-22 surfactant in
. . ~, ~ .................. : . . :
,, :
: . ' , ',. ; . ~ .. ',.,. ' - . ' -. ' ~ :: ,
: .: . ~ : ' '.. : ,, : : ; : ~' ;
: ' : '. ., '' :.' , '.' ', :
W~91/08B4~ ~ ~'3-1t'~J~ P~T/US90/07468
- 39 -
70g water was added dropwise to invert the emulsion to
an oil-in-water (o/w) emulsion. The o/w emulsion was
sonicated for 2 minutes with a Sonics & Materials 500W
disruptor using a 3/4" high gain Q horn at an
estimated 180W intensity level. The ethyl acetate was
then removed on a rotary evaporator.
A deposition bath was prepared by diluting the
emulsion to lO~ solids with water, acidifying to pH
2.0 with phosphoric acid, and adding an amount of
hydrogen peroxide equal to 0.3% of the total bath
weight. Immersion of a copper foil/epoxy glass
laminate strip in the bath for 2 minutes caused
deposition of about 0.8 mil of coating which was dried
and coalesced for 5 minutes at 80C. The coating was
imagew~se exposed to W light for 3 minutes (about 220
mJ/cm2 on an EIT radiometer) and then developed in a 1%
Na2CO3 spray. The coating was developable but was not
as cleanly developed as that for the coatings
illustrated in Examples 18 and 19. As a result, the
etching was retarded in some areas of the coated
substrate in this example.
While the invention has been described with
preferred embodiments, it is to be understood that
variations and modifications may be resorted to as
will be apparent to those skilled in the art. Such
variations and modifications are to be considered
within the purview and the scope of the claims
appended hereto.
.
