CA2031488A1

CA2031488A1 - Apparatus and method for fabricating printed circuit boards

Info

Publication number: CA2031488A1
Application number: CA 2031488
Authority: CA
Inventors: George A. Salensky; Thomas S. Thoman
Original assignee: Individual
Current assignee: BP Corp North America Inc
Priority date: 1989-04-27
Filing date: 1990-04-17
Publication date: 1990-10-28
Also published as: JPH03506003A; WO1990012668A1; EP0424505A1

Abstract

This invention relates to an apparatus and a process for uniformly laminating a conductor (18) to a substrate (15). The conductor can be a printed circuit; the substrate can be any dielectric.
The apparatus comprises two platens (10, 11) containing cavities (12, 13). One of the cavities (13) contains a mold (14) which is the mirror image of a substrate surface. The other cavity (12) substantially contains the substrate (15). It can have two-dimensional or three-dimensional surfaces to which the printed circuit is laminated. The product results in a superior lamination of the printed circuit across the surface of the substrate.

Description

PCl`/US90/02139 .
WO 90/1~668 - 2ll3i4Qg ~`

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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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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 ~ ~ .
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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 !

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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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; WO~0/126~8 PCT/U~90/02139 :.' .. .
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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 ...

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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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~ WO90/1X668 PCT/US90/0213~
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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 :~
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: 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 , . . . .

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
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Another preferred polyarylsulfone of this 10 invention contains units of the formula:

So~ . and C~
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C~
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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.
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Lamlnatin~ Appa3atus : '; Fig. l ~hows an:~apparatus for uniformly ~ applying~pressure to laminate a~conductor or printed 1 ~
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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. ::

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~ 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.

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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 ~, ~: ~ ~ :

.

~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

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. WO90/12~68 PCT/U~90/02139 .,~
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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~

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; WQ9~/126~8 PCT/US90/0213~
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, 203~,8~' 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.
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Example 1 is repeated except that both i~ides of he circui~ board are laminated with a printed circuit.

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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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Claims

21

1. A uniform pressure transmitting apparatus for uniformly laminating a conductor to an at least two-dimensional substrate surface comprising (a) a first platen means having a first cavity means, the first cavity means substantially confining a mold which is a mirror image of the at least two-dimensional substrate surface, (b) a second platen means containing a second cavity means which substantially confines the thickness of the substrate, (c) pressurization means for compressing a conductor positioned on the substrate surface using the first platen means, and (d) laminating means to bond the conductor to the substrate surface.

2. The apparatus according to claim 1, wherein the substrate is three-dimensional.

3. The apparatus according to claim 1, wherein the mold is a silicone rubber mold.

4. The apparatus according to claim 1, wherein the substrate is plastic.

5. The apparatus according to claim 4, wherein the plastic is a thermosplastic.

6. The apparatus according to claim 4, wherein the plastic is a polyarylsulfone polymer.

7. The apparatus according to claim 1, wherein a platen contains registration pins.

8. The apparatus according to claim 7, wherein the first platen contains registration pins.

9. The apparatus of claim 1, wherein the conductor is a printed circuit.

10. A uniform pressure transmitting apparatus for uniformly laminating a printed circuit to an at least two-dimensional substrate surface composed of a polyarylsulfone polymer comprising (a) a first platen means having a first cavity means, the first cavity means substantially confining a mold which is a mirror image of the at least two-dimensional substrate surface, (b) a second platen means containing a second cavity means dimensioned to confine a substantial portion of the thickness of the substrate composed of polyarylsulfone polymer, (c) pressurization means for compressing a printed circuit positioned on the substrate surface using the first cavity means, and (d) laminating means to bond the printed circuit to the substrate surface to form a circuit board.

11. A method for uniformly laminating a conductor to an at least two-dimensional substrate surface comprising inserting a substantial portion of the thickness of the substrate in 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 containing another cavity means which substantially confines a mold which is a mirror image of the at least two-dimensional substrate surface, and laminating the conductor to the substrate surface.

12. The process according to claim 11, wherein the substrate surface is three-dimensional.

13. The method according to claim 11, further comprising laminating utilizing a conventional heating source.

14. The method according to claim 11, wherein the mold is a silicone rubber mold.

15. The method according to claim 11, wherein the substrate is plastic.

16. The method according to claim 15, wherein the plastic is a thermoplastic.

17. The method according to claim 15, wherein the plastic is a polyarylsulfone polymer.

18. The method according to claim 11, wherein one of the platens contains registration pins.

19. The method according to claim 11, wherein the substrate is preheated.

20. The method according to claim 11, wherein the conductor is a printed circuit.

21. The method according to claim 11, wherein lamination occurs between 100°C and 230°C.

22. The method according to claim 21, wherein lamination occurs between 140°C and 190°C.

23. The method according to claim 11, wherein the pressure is between 500 psi and 700 psi.

24. A method for uniformly laminating a printed circuit to an at least 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 platen means, positioning a printed circuit on the at least two-dimensional substrate surface, applying a uniform pressure to the positioned printed circuit and the substrate surface using another platen means containing another cavity means which substantially confines a mold which is a mirror image of the at least two-dimensional substrate surface, and laminating the printed circuit to the substrate surface to form a printed circuit.