Note: Descriptions are shown in the official language in which they were submitted.
PCl`/US90/02139 .
WO 90/1~668
- 2ll3i4Qg ~`
,~
j .
APPARATUS~ AND METHOD FOR FABRICATING
PR INTED C IRCUIT BOARDS . `
Related A ~lications
This application is a continuation in-part of
5 Application Serial No. 2~4,3~0, filed July 1, 1988
entitled "Solderable Printed Circuits Formed Without
Plating". The applications are commonly assigned. The
parent application is incorporated by refe~ence.
Field of the Invention
The present in~ention relates ~o a method and
apparatus for trsnsmitting unifonmly applied pressure ~o
a patterned relea~e media to obtain a composite havin~ a
conduc~or, graphlcs and/or coating unifonmly honded to a
substrate. This invention particularly relates to
15 formation of a printed circuit board. :
Background of the Invention '.
The art araa has been directed to forming
oircuit boaxds by techniques other than transferring a :.
conductor to a ~ubstrate u~ed to form the circuit board.
20 The art area h~s b~en concerned principally with
lamination of multilayered circuit boards.
For ~xample, United Sta~es Patent No. 4,029,845
: relates to a thermosetting r~s~n in which heat and .:
pr~sure are u~ed to form a composite circuit board. The
25 r~ference only discloses forming the base board and does
not teach forming printed circuit elemen~ on that
base~oard.~ The reference refers t~ a~ addi~i~e proces`s
for manufacturing a prin~ed circui~ board wi~hout
explanation of ~h~t ~aching.
United S~ate~ P~tent No. 4,180,608 te~che~ heat
~nd pre~sure used to form a~composite printed circuit
boArd. However, the reference u~e~ a carrier layer for
I
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WO90/12668 PCT/US90/02139
.
3~8'~ 2
. resin but not a printed circuit as in the present
I invention. A lamination i5 formed as taught in the art.
j As examples of methods and appa~atus for
molding structural parts, U.S. Patent No. 4,148,597
! 5 teaches an appara~us comprising a rigid container, pads
i of silicone rubber in the container used to exert
i pressure on the part to be formed and an expandable
I diaphragm which controls the pressure exerted on the part
to be molded. The patent teaches such a method and
10 apparatus useful to form complex-shaped parts from fiber
reinforced plastic composi*e material.
U.S. Patent No. 4,243,368 also-teaches a method
and apparatus for making plastic articles from plastic
particles utilizing heat and pressure applied using a
15 flexible diaphragm to apply even fluid pressure. In
operation, a layer of plas~ic particles is spread to a
depth substantially equal to or slightly greater than
that of 8 cavity formed on top of a platen~ An air
release means, which can be a wire cloth or screen, is
20 located over th~ particles during compression.
; U.S.~Patent No. 4,670,084 ~eaches an apparatus
for applying decorative images to members wherein sheets
containing the images are overlaid on the members and
maintained in pressurized engagement while the sheets and
25 the memb~rs are heated. Vacuum is used to maintain the
pressuriz~d engagement. ~:
U.S. Patent No. 4,636,275 teaches n
integrated ~circuit package fabrica~ed~by a~sembling à
s~ack co~pri~ing a plu~all~y of thin flat epoxy glass
l ` 30 layers, adhesive layer~ between those layers and:a
cavity. ~ conductor is not belng tran~erred to:a
~ substrate. The:stack is covered with an ela~ic ~ladder
: ~ and is laminated:~y forcing fluld~:into the bladder at a
~ ~ .
: ~
,. ~
~ ! ,.
~' ~
PCT/US9~/02139
WO90/126~8
~ ~ 2~
; tempera~ure and pressure which causes the bladder to
`:` "'t ~ push against the surfaces of the cavity. This dams the
;~ adhesive fr~m flowing into the bonding pads.
The preceding references are all incorporated
5 by reference.
~ This invention overcomes disad~antages f~und in
:~ the prior art which relates to laminating conductor to
subs~rates, particularly those substrates which have
: complex shapes.
10 ~
This invention relates to a unifonm pressure
transmittin~ apparatus ~or uniformly laminating a
. conductor to an at least two-dimensional substrate
surface comprising (a) a first platen means having a
15 first cavity means, the first cavity means subs~antially
confining a mold which is a mirror Lmage of the at least
two-dimensional substra~e surface, (b) a ~econd platen
means con~aining a second cavity means which
substantially confines ~hP thickness of the substrate,
20 (c) pressuri2ation means for compressing a conductor
positioned on the ~ubstrate surface using the first
platen means, and (d) laminating ~eans to ~ond the
conductor to the substrate surf ace .
This invention al50 relates to a uniform
25 pressure transmitting apparatus for uniformly laminating
a printed circuit to an at least two-dim~nsional
~ubstrate fiurface composed of a polyaryIsulfone polymer
comprising (a) a ~irst platen means having a firs!t cavity
means, the fir~t cavity means ~ubstantially confin-ng a
~ 30 mold which is a mirror image of the at least two-
;1 dimensional substrate surface, (b) a ~econd pla~en means
;`"1 containing a ~econd ca~ity means dimensioned to confine a
~ substantial po~tion of ~he thickness of ~he subs~rate
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WO90~1~66~ PCT/US90/02139
!
2~314~
composed of polyarylsulfone pol~ner, (c) pressurization
means for compressing a prin~ed circuit positioned on the
j substrate surface using the first ca~ity means, and (d)
., laminating means to bond the printed circuit to the
S substrate surface to form a circuit board.
This invention further relates to a method for
t uniformly laminating a conductor to an at least two-
! dimensional substrate surface comprising inserting a
substantial portion of the thickness of the substrate in
10 a cavity means of a platen means, positioning a conductor
on the at least two-dimensional substrate surface,
applying a uniform pressure to the conductor and the
substrate surface using another platen means con~aining
another cavity means which substantially conf ines a mold
15 which is a mirror image of the at least two-dimensional
substrate surface, and laminating the conductor ~o the
substrate surface.
This invention also further relates to a method
for unifor~tly l~minating a printed circuit to an at least
~ 20 two-dimensional substrate surface comprising inserting a
; substantial portion of the thickness of a substrate
composed of polyarylsulfone polymer in a cavity means of
~; a p}aten msans, positioning a printed circuit on ~he at
least two-dimensional substrate surface, applying a
25 uniform pressure to the positioned printed circuit and
the sùbstrate ~urface using another plàten means
:~ containing another cavity means which substantially~ ,;
eonfine~ a.mold which is a mirror image of ~he at least
~wo-dimensi~nal su~stra~e surface, and:laminating the
30 printed circuit to the substrate surface to form a
i printed ci~cuit. . ~
~: ~ :
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1 ~
; WO~0/126~8 PCT/U~90/02139
:.'
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2~ 31 d. ~S
Brief Descripti ~ in~s
, This invention will now be described using
1 drawings which depict certain embodiments of the present
:1 invent.ion. The drawings are exemplary only; they are not
5 considered to limit the invention:
j Fig. 1 shows a schematic depiction of the
uniform pressure apparatus of ~he present invention;
.' Fig. 2 shows a printed circuit on a substratei
Figs. 3A and 3B show applicants' earlier press
10 and transfer method with Fig. 3B further showing use of
pins to obtain registration of conductor on the
substrate;
~ ig. 4 shows results of adhesion tests
performed on a conducti~e surface adhered to a substra~e
15 prepared using the earlier press and ~ethod of Figs. 3A
and 3B;
Fig. 5~shows the press and transfer method of
this inventi~n; and
! Fig- 6 shows the results of adhesion tests
20 performed on a composite prepared according to the press
and method of Fig. 5.
Detailed Description of~the Invention
: This invention rèlates to a method and
apparatus for uni~ormly applying pressure to at least one
25 side of a su}:)~;trate or circuit board to laminate a
conductor or printed circuit on it. ~he conductor can
include a circuit alone or combined with other
compo~e~s,lfor example, adhesive, soldex mask, graph1cs
ànd~or transfer media.
~ LaminatLnq Conductor To Substrate
:A release:surface carrying at least a circuit
covered by adheslve is contacted with a substrate such
that the :circuit is ad~acen~the substrate surface
:: ~
. WO90/12668 PCT/US90/02139
. .
2~ &8 6
separated therefrom by adhesive. Sufficient heat and
~ pressure are applied to form a composite structure,
;~ using the apparatus in Fig. 3 or Fig.,5, whereby the
'~ adhesive is reacted. Thus, the circuit is transferred
', S from the release surface and bonded to the substrate
surf ace . In some cases, only parti~l curing and/or
reaction need be obtained. The release surface is then
separated from the composite structure.
The release surface and the s~bs~rate surface
10 axe contacted at a temperature of from about 100C to
about 230C and preferably 140C to l9~0~C. The surfaces
are contacted at a pxessure of from about 200 psi to
about 1,200 psi and preferably 500 psi to 700 psi`but not
so great as to cause distortion of components. A
lS pressure of 60Q psi is preferred. Optionally, the
substrate may be preheated to avoid distortion. Pressure
can be applied for about 0025 to 5 minutes, preferably 3
minutes.
In another embodiment, when the composite is
20 formed, they are subjected to sufficient pressure during
lamination to cause some compaction of the printed
; circuit. This causes further densification of the
printed circuit, improving its conduc~ive qualities. It
has~been noted that such compaction does not result in
~`~ 25 smearin~ of~the. electric circuit. Thus, the fine edges
achieved in printing the electric circuit are
maintained. Preferably, compaction of 25 ~o 40~ of
origlnal printed elec~ric pathway thick;ness is lobtailned.
This~ invention overcomes many deficien~ie~s in
30 printed circuitry fabricatiQn ln terms of simplici~y,
ease of operation, functi`onal utilization and
. performance. ~;
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WO 90/12668 PCltUS90/û2139
...
7 20~ ~ 4~ ~
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Substrate_Surf ace
The substrate may he any known dielectric, that
is, insulating or non-conducting substrate. The related
application referred to abova provides a detailed list of
5 suitable substr~tes which ~an be used in this in~ention.
' Suitable substrates include those fabricated from
t thermoset and thermoplastic materials and their mixtures.
; Preferred substra~es will he taugh~ below. They can have
two or three dimensional surfaces.
1~ Thermoplastics, in general, exhibit a more
complex range of chemical, thermal, and mechanical
behavior than traditional thenmoset printed circuit board `-
laminates. This makes material selection for printed
circuit uses even more critical. Current resin systems
15 typically exhibit one or two desired characteristics but
in general lack overall property balance to make them
good printed circuit support candidates. Resin
deficiencies be~ome readily apparent during assembly
operations where substrat~ warpage, bubbling, dimensional
~` 20 instability and printed circuit del~mination are common
.
occurrences.
To address this need, applican~s use
.engineering resins called pol~arylsulfone resins. These
;~` resins offer a highly desirable property balance for .
` 25 circuit board u~efi where excellent dimensional stability,
warp resis~ance and~bondin~ of circuit and substrate are
requirements.
Polyarylsulfone resins are characterized byl'
inherently high he~-t-dis~rtion temperature~, ex¢ellent
30 dimen~ional ~tability, ~reep resistance, low loss ~C
¦ dielectric properties, and high mechanical strength.
:
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~. : :
:
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~,, .,~. :
}
~ WO90/1X668 PCT/US90/0213~
., .
2 ~ 14'~f~ 8
i Ty$fical Pro~ferties of PolyarYlsulfone Resins
ProPerty Units Typical PropertY ~`
~ Tensile Strength psi 13,400
;~ Elongati~n to Break % 2.2
5 Tensile Modulus psi 892,000
Flexural Strengtb psi 13,300
Heat Deflection
Temperature C 215
Density gm/cc 1.55
10 AC Dielectrics
Dielectric Constant
60 Hz -- 3.86
1 KH~ -- 3.85
Dissipation Factor
15 60 Hz -- 0.0042
1 KHZ -_ O,0035
~ielectric Strength
lt8" specimen ~Volts/mil 398 550
Volllme re~istivity at 50C meg ohm-cm 0.41 x 10
Iniection Moldinq
Polyarylsul~one resins are easily processed
utilizing standard injection~molding machinery and
`~ practice. ~Prior to molding, resins should be dried to
obtain optimum performance in;a dehumidified hopper drier
25 or circulating~air oven. ~tilizà~ion of a hopper drier
is preferredl~with an~inlet air temperature in the~l49
163C range~and ~an outlet temperature not less than
; 135C. When tray drying is utllized, pqlle~s shouldl~e
' spread into a ~ayer 1-2~ in depth. It is impo~tant~in
30 all cases;that~the pellets reach~and maintain a~minimum
tempera~tu~re of 135C~for 3-4 hours. Drled~resin should
be molded promptly~and~handled~ carefully to preclude
moisture~rea~sorption.
.~1 WO 90/1266~ PCr/lJS90/02139
2~3~48~ ~
. , The rheological characteristics of
L po~yarylsulfone resins provide excellent flow for filling
. ~ thin and intricate wall sections typirally encountered in :~
`'~ printed wiring boaxds, chip carriers, and related ~.
5 devices. The resins process readily at stock
temperatures in the 360-382C ran~es (wave soldering
grade). Mold temperatures of 110-157C are used
typically with the resin for wave solderabl~ mo~din~s.
Clean polyarylsulf one resin scrap may be reground and
10 utilized in fabrication, provided it is properly dried
and kept free of contamination.
Polyarylsulfone produces warp-free moldings
that are dimensionally stable both prior to and following
the transfer process. Transfexred circuitry exhibits
15 tenacious adhesion to the resin as transferred,.and
maintains its adhesion following wave soldering.
Additives which may be used with the
thermoplastic and/or thermosetting resin for making the
printed circuit board, include reinforcing and/or non-
20 reinforcing fillers such as wollastonite, asbestos, talc,
alumina, clay, mica, glass beads, fumed silica, gypsum
and the like; and reinforcement fîbers such as aræmid,
boxon, carbon, graphite, and glass. Glass fiber is the
most widely used reinforcement in the form of chopped or
25 milled strands, ribbon, yarnj filaments, or woven mats.
Mixtures of reinforcing and non~reinforcing fillers may
be used, such as a mixture of glass f ibers and talc or
p ~ w~llastonite. These reinforcing agents are used in
-amounts of from about 10 t~ a~out B~ weigh~ percent,
. 30 whereas the non-reinforcing fillers are used in amounts
~"1 of up to 50 weight percent~. Other additiYes include
I . ~ stabili~ers, pigmen~s, flame retardants, plasticizers,
I processing aids, coupling~agents, lubricants, mold
:~
,~
~:
: WO90~ 68 ~CT/US~0/0~139
2 ~ o
' release agents, and the like. These additives are used
i in amounts which achieve the desired resu.t.
.~ Polyarvlsulfone
: ~ Polyarylsulfone is the preferred thermoplastic
5 polymer substrate of ~he invention. It is an amorpho~1s
thermoplastic polymer containing units of the formula:
2 ~ . n~
and/or
'~
wherein R55 is independently hydrogen, Cl to C6 alkyl to
:` C4 to C~ cycloalkyl, X' is independently
: R56 ; . ~ :
: R
wherein Rs6 and ~57 are independently:hydrogen or Cl~to~ :
:; Cg alkyl,:~or ~
` WOgOJ12~68 PCT/VS90/02~39
, . . . .
11
2~4~3
wherein Rs8 and Rsg are independently hydrogen or Cl to
, C8 alkyl, and a1 is an integer of 3 to 8; -S-, -O-, or
, a is an in~eger of 0 to 4 and n is independently an
integer o 1 to 3 and wherein the ratio of unit (I) to
S the sum of units (II) and/or (III~ is greater than 1.
The units ~re attached to each other by an -O- bond.
,i A pre~erred polymer of this inven~ion contains
units of the formula:
: . anZ
~50~
Another preferred polyarylsulfone of this
10 invention contains units of the formula:
So~ . and
C~
~'1~
C~
~: :
These units are attached to each other by an -O- bond
. ~ :
The polyarylsulfone may be random or may have
an ordered structure. The p~lyarylsulfones of this
: invention have a reduced viscosity of from about ~.4 to
15 greate;r,th~an 2.5, as measured in N-me~hylpyrolidolne, or
o~her suitable soIvent, at:25C.
`
Lamlnatin~ Appa3atus
: '; Fig. l ~hows an:~apparatus for uniformly
~ applying~pressure to laminate a~conductor or printed
1 ~
t
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:; .
WO90/126~8 Pi-~T/US90/~2139
~ 8~ 12
circuit to a substrate. The apparatus comprises heated
, platens 10 and 11, which may be differently disposed.
:I Each of the platens has a cavity 12 and 13, respectively. :`
! The platens are heated in a conventional manner which is
5 not shown. Platen.ll contains a mold ~4 which is
confined in the cavity 13. Nold 14 c~n be made o~
silicone rubber and is the mirror imaye of substrate 15
t located in cavity 12 in platen 10. The mold can be made
of other conventional high ~emperature elastomeric
10 materials known in the art. The exposed s-lrface of mold ;
14. preferably lies in the plane of the exposed suxface of
platen 11. The mold and substrate can be retained in
their respective cavities using any conventional' means.
The surface of the substrate 15 can be two or three
15 dimensional.
The mold is located so that during compression,
movement lateral to the normal direc~ion of compression
of the platens is avoided to the extent that uniform
;~ pressure is applied across the surface of the su~strate,
~:~ 20 that 1s, the mol~ is substantially confined. A portion
of the substrste should project beyond the upper surface
of platen 10 ~o facilitate uniform transfer and to
compensate for any misalignment of platens. Only as much
of board as; neces~sary need project:so that the board
~ ~ 25 cannot distor:t ~r move laterally during compression. :~
: : :Thus the cavity subs:tantially confines:the board. :~
Also shown, are registration pins 16 and
~ attendant openings on the opposling~platen~ whlich facil'i-
:~ tate all~ning the opposin~ or upper mold with the sub-30 stratè :15.~ Conventional press~lrization means which cause : ~
platen mo~ement and compression~is used~but not ~hown. ::
: : :~
~ WO90/12668 PCT/~S90/02139
: 2031~
i 13
,.
In operation, the p1atens are spre~d apart with
:~ the platen 11 containing the`silicone rubber mold 14. A
plastic substrate 15 is inserted into cavity 12 in platen
10. Thereafter a release or transfer paper 17, carrying
5 a printed circuit and adhesive, is placed over the
j substrate 15. Conventi~nal pressurization means causes
'. at least one platen to move toward the o~her. The
alignment o~ the platens is facilitaked utilizing
registration pins 16 on one platen which mates with a
10 complementary apature on the opposing platen. Lamination
occurs Bt conventional temperatures and pressures by
heating the platens utilizing conventional heating means
(not shown). Thereafter, the printed cixcuit, which is
completely or partially laminated to the su~strate, is
15 removed as a product and the release or transfer paper
removed.
The b sic components carried by the release or
transfer medium or paper are the conduc~or and adhesive.
There are preferably more components. They include in
~0 the order ~pplied to the release paper before transfer:
; graphics or legending, solder mask, printed circuit and
a~hesive. The first-mentioned component is informational
or educationzl legends for the circui~ ~oard. This
transfer medium facilitates manufacture of the circuit
2~ board in an expeditious manner. Howe~er, one or more
componcnts can be applied to the circuit board
separately. For example, the legending can be applied
directl~y to,~he board or multiple trànsfers !of circui~s
can be-~one to the ~ame circuit board.
~ ~ 30 This apparatus has the advantage of uniformly
'~ applying pres~ure across ~he entire surface of the
ubstrate, whether it~is~two-dimensional or ~hree-
dimensional ~in shape. That: is, the: surface upon whlch
' .
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W090/12668 PCT/US9~/02139
~3~8~ 14
" the printed circuit is applied can be fla~ or three-
dimensional. The confinement of the silicone rubber mold
, 14 in the cavity 13 restricts movement of the mold in the
"~ ca~ity and is a factor in promo~ing the uniform pressure
; 5 and superior lamin~tion of the printed circuit across the
~ surface of the su~strate. The cavity 12 further
-~ promotes the uniform application of pressure because the
substrate is substantially confined in the cavity 12
which precludes its movement, especially laterial
lO movement, and distortion of the upper surface of the
substrate when pressure is applied to its upper surface.
These cavities are critical to obtain the superior
!`~ lamination of printed circuit to substrate and overcomes
earlier disadvantages.
Intended Vse
The transfer of circuitry can be made to take
place over planar or three~dimensional substrates ~o the
extent the surface is "developable". For example, a
three-dimensional circuit can be transferred to an
20 injection molded substrate.
Uses for the process are aimed at such three-
dimensional type devices in high volume where the speed
of th~ printing process for the circuit and the
efficiency of ~he use of injection molded subs~rate can
25 be utilized cost-effecti~ely.
Specifically, planar or shallow three~
~ime~sional circuit boards can be efficiently produced
using the process. Also; with~some processlmodification,
a series o~ molded-plastic ch~ip carriers can be tooled
30 and produced. These plastic chip carriers utilize a pre-
molded thermoplastic substrate and a transfer process to
~apply the conductors, which are ~ubsequently plated, to
¦ accomoda~e wire bonding and sol~ering operations.
t
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W~90/12S68 PCT/US90/02139
2 ~ 3 ~
.~ These chip carriers are manufactured from the
:~ same resin system that is used in the circuit boards; and
when they are used together, there is no thermal mismatch
-~ between ~he chip carrier and the circuit board.
An automotive use includes molding a circuitry
to the inside roof portion of an automobile having dome
ht circuitry.
Examples
The invention will now be described with
10 examples of the teachings set forth above. These
examples are exemplary and not exclusive. They are not
considered limiting. Concentrations are percent by
wei~ht unless otherwise indicated.
Examele l :~:
The following ingredients in percent by weight
are blended together at room kemperature:
(I) 1.81 percent polyhydroxyethex known as Phenoxy
PKFE,
(II) 2.75 percent 3,4 epoxy cyclohexyl methyl 3,4
; 20 epoxy cyc~lohexyl carboxylate known as epoxy
ERL-4221, and
(III) 8.47 percent diethylene glycol monobutyl ether
acetate known as butyl Carbitol acetate.
To this mixture is added the following
25 ingredients: : :
~IV) 82.62 percent of~silver powder from Metz
` Metallurgical Co. known as ~ETZ EG200ED; and
(V) 4.,35 percent of silver flak~e al!so fromiMetz
Metallurgical Co. ~own ~s METZ 50S.
~, 30 ~ More particul:arly, the phenoxy resin is
dissolved in diethylene glycol monobutyl ether acetate
~ ~ith agitation~. The epoxy resin i9 added to thi mixture
:~i while agitation is ~ontinued. Then, silver powder is
~,
~: ~ ~ :
WO90/12668 PCT/US90/02139
.
~3~" 16
added to the mixture under continued agitation until it ::
is dispersed to a Hegman grind of six. Then, the silver
flake is added until it is also dispersed to a grind of
six or better. The viscosity of the mixture is 35,000
cps as determined with a BrooksfiPld RVT Viscometer at
24C using a number six spindle at ~Orpm. The 2.5/20rpm
viscosity ratio is 4. The conductive metal and binder
~ are mixed together until completely homogenized to form
! an ink.
This conductive ink is screen printed (U.S.
Sieve s-ize 230), using conventional techniques, onto VNS
Supermat release paper (obtained from S.D. Warren Co.~ :
Westbrook, Maine) to a thickness of approximately l mil
after drying. .
The printed paper is dried in a forced
convection o~en at 96C for ten minutes.
Separately, an adhesive containing the
following ingredients i~ prepared:
TRAD~E NAME CHEMICAL ~NAME NEW (WT.%)
PHENOXY PKFE POLYHYDROXY ETHER l8.99
RESIMENE 2040 MELAMINE FORMALDEHYDE 0.95
25.BVTYL CARBITOL DIETHYLENE GLYCOL MONO 75.96
ACETATE B~TYL ETHER ACETATE
BLACK SAPL NIGROSINE BL~CK 0.19
30 BENZOIC ACID BENZOIC ACID 0.05
CABOSIL SILICA 3.86~ `
Makinq The Adhesive
;-~ The polyhydroxyether or phenoxy re~in is
35 dissol~ed in the diethylene g~ycol monobutyl ~ther
¦ : acetate using high speed mixing until all the resin
.j
I
":,~
. WO90/12~68 PCT/U~90/02139
.,~
_.... !
17 2~3~
particles are dissolved. The melamine foxmaldehyde
.. resin is then added. The nigrosine black a~d benzoic :~
acid are mixed together and then added with high shear
-~ agitation. The high surface area silica is then added
S with high shear mixing. The entrained air is removed
with ~acuum. The viscosity of the adhesive composition
measured with an ~VT Viscometer at 24C using a number
six spindle at 20 rpm is 35,000 cps with a 2.5/20rpm
viscosity ratio of 4.
The prepared adhesive is screen printed in
registration on top of the conductor surface of the
printed circuit which is already dried. Then, the
adhesive coated circuit.is placed in a forced convection
oven at 96C for 10 minutes until the adhesive coat is
15 dry but not fully cured.
~ substrate is molded from a composition
; containing 78 weight percent of a polymer containing the
. following unit:
~>o~ ~~ ~~
: having a reduced viscosity of 0.61 dlig as measured in N-
20 methyl pyrrolidinone (0.~ gJ100 ml) at 25C. The composi-
tion also contains 12 weight percent mica and 10 weight
percent of chopped glass fi~ers obtained from Owens Corning.
The substrate composition is injection molded
using conventional conditions. A~6:in. x 6 in. plaque which
25 is ~.06 ln. thick is molded. The melt temperature is 377C:,
~j and the mold tempera~ure is 151C. :The in~ection speed is
35mm/sec, ~and the in~ection ~olding~pressure is 1~0 bars:for
. ,~ .
~ .~ : ~ . 7 sec.
:. ' : '
:' ~: :
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WO90/12668 PCT/US90~02139
:`
'2~ 18
` The substrate sheet is vapor polished with ~.
methylene chloride for about one second.
;j The substrate is placed in a compression platen
:~ press as shown in Figures 3 and 5 with the release paper
5 containing the conductor (1.0-1.2 mils dry film thickness)
and the adhesive printed in the registration (0.6-0.8 mils
dry f.ilm thickness). Then it is molded at 600 psi for 3
m.inutes at 177C after the release paper is stripped away.
The circuit board îs then cured in an ~ven at
10 150C for 30 minutes. After cure, the board can be :.
soldered with a hand soldering iron or in a wave solder
machine set at 246C with a carrier speed of 6 ft/min. The
electrical resistance of a square serpentine pattern was
measured with a milliohm meter. Consistent values in the
15 range of 5-10 milliohms/mil s~uare are obtained.
Comparative tests are conducted using an earlier
press shown in Figures 3~ and 3B an~ a press according to
the teachings of this invention shown in Figure 5. In each
test, a substrate ha~ing a two-dimensional surface is placed
20 on or in a platen. The thickness which protrudes is 20
mils. The release or transfer paper with printed circuit
and adhesive components is placed on it. The board and
transfer medium are compressed by closing ~he platens.
Lamination is achieved using a pressure of 600 psi, a
25 temperature of 177~C and a time of three minutes. Then,
the release paper is removed, and the circui~ized ~ubstrate
is cured at 150C for thirty minutes. After cure, the board
~i can be soldered with a hand soldering iron or in`a wave
s-older ma~hine ~et at 246C with a carrier speed of 6 ft/mm.
s 30 ~or bond:strength determination, copper wires
~' (.05/inh diameter) are ~oldered onto 1/4 inch diameter
~pads of the circuit board. After cooling, the wires ar~
i
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; WQ9~/126~8 PCT/US90/0213~
:`
, 203~,8~'
19
pulled from the boards clamped onto the base ~f a
Chatillon tensile tester Model UTSM. The wires are
hooked onto the end of a AMETE~ ACCU Force Gage II. The
~¦ circuit board is then lowered at the #l setting of the
j 5 Chattilon tester, and the maximum force is measured to
break the bond between the wire and the lt4 inch pad on a
~ 1/16 inch substrate board. The sample obtained using
! the prior art press showed the non-uniform adhesion tes~
i results of Figure 4. Those obtained using the process of
10 this invention showed the uniform results of Figure 6.
Figure 4 shows an average tensile s~rength of
25.06 lbs. or in other words 510.4 psi with 13~ of the
failures in the substrate. However, Figure S shows an
average tensile strength 48.1 lbs. or 980.6 psi with 91
15 of failures in the substrate.
While these results are very impressive, ei~ch
figure shows the test results at different locations on a
circuit board like that of Figure 2. Each of the sixteen
cixcuits were tested. The tensile strength measurement
20 for the sdhesion bond of each circuit isi shown with the
bond strength detexmination for the soldered wire shown
in the upper right hand corner. Failur~s are designated
"P" or "S" to ind1cate plug (plastic board) or snap
(circuit interface) failures, respectively. In Figure 4,
25 the earlier technique shows the least bond strength about
the perimeter of the circuit board. However, Figure 5
according to this invention shows superior, uniform bond
si~reng~h all over the circuit board c~mpared to the ~'
results of Figure 4-tests.
~m~
Example 1 is repeated except that both i~ides of
he circui~ board are laminated with a printed circuit.
:: J~ ~
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WO90/12668 PCT/US~0/02139
2~ ` 20
Example 3
Example 1 is repeated except that the surface
~ of the circuit board upon which circuitry is applied is
3 three dimensional
Although the invention has been described in
, conjunction with specific embodiments, it is evident that
j many alte~natives and ~ariations will be apparent to
those skilled in the art in light of the foregoing
description. This may include optionally pla~ing the
10 printed circuit even though the circuit is solderable
without this treatment. This may also include reversin~
the platen arrangPment so ~hat the substrate is above
the platen housing the mold. Also the alig~ment pins can
be attached to ei~her platen. Further, both sides of
15 the substrate may be processed. Accordingly, the :~
invention is intended to embrace all of the alternatives
and variations that fall within the spirit and scope of
the appended claims.
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