CA1042734A - Fabrication of printed circuit boards - Google Patents
Fabrication of printed circuit boardsInfo
- Publication number
- CA1042734A CA1042734A CA163,581A CA163581A CA1042734A CA 1042734 A CA1042734 A CA 1042734A CA 163581 A CA163581 A CA 163581A CA 1042734 A CA1042734 A CA 1042734A
- Authority
- CA
- Canada
- Prior art keywords
- substrate
- hydrocarbon
- polymer
- circuit board
- hydrocarbon polymer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
Abstract of the Disclosure The invention is directed to a printed circuit board comprising a substrate having a hydrocarbon polymer surface where the hydrocarbon polymer is based upon an elastomeric com-ponent of a conjugated diene polymer such as a polybutadiene, and a thermosetting component such as a phenolic, and where a metal coating is directly bonded by additive plating, including electroless deposition, to at least a portion of the hydrocarbon polymer. Such circuit boards are characterized by a superior bond between the metal coating and the hydrocarbon polymer and one preparational method involves metalizing the hydrocarbon polymer either in an uncured or partially cured state, and thereafter completing the cure of the hydrocarbon polymer to produce a bond between the polymer and the metal coating of su-perior strength.
Description
104Z739t T`~l; ;nve~lti(~ r~lat~s t;~ ~rlnted circlit boards havin~
a substr~te ~ilth a lydrocarbon ~olynler sllrface and a m~tal coat-ing direct]y bon(ie~l to at lea~t a nort-ion of sllCh hydrocarbon ~olymer. `lore r-articular1y, it relates to a ~rinted circu3t board where th~ hydrocarbon nol~rner is based, in ~art, u~on a ~, con~ugated diene nolymel; where the m~t~l coating is electro-lessly de~os;ted on the hy~rocarbon ~olymer; and where the bond strength or adheslon between tho hydrocarbon ~olymer and metal coating is extremely hl~.r,h~
As known, printed circuit boards have become an im-~ort~nt comrnercial form of` circuits for the electronic industry.
In ~eneral, they com~rise a metal coating in a particular design representin~ a circuit or circuits attached either directly or indirectly, for exam~le, by adhesives, to the surface or sur-faces of an electrically nonconductive substrate. Often, the ~ substrate is rigid as in reinforced epoxies, although it can - also be flexible as in polyester films. Several important ad-vantages have resulted from the use of printed circuit boards.
These include dimensional reproducibility of both the circuit elements and their physical separation which are ~articularly important with higher frequencies and with miniature circuits.
Also, several boards can he combined to form multilayer ~rinted circuit boards in compact form.
~ hile these printed circuit boards have been very use-ful, they have not been entirely satisfactory. With the use of higher frequencies and miniature circuits, the electrical prop-erties of the substrate are of increased im~ortance to the per-` formance of the circuit. In many applications, such ~roperties as dielectric constant, surface conductivity and dissipation power factor must be fairly low as well as constant over wide - temperature changes. Xowever, with multilayer printed circuit boards, an excessive dissipation ~ower factor often causes -tf~M;)erature c`;.,n ~ ir tl(-~ cn-lf` r~erl or ~uried sll~)strrlt~s wl~ich resultr ;n c~ltln~f-~; in t'ae ci~ t c!!<lr~ctcristLc-;.
In addi~iorl, and llerila?3 Or even ~ mol-e seriolls nature, the metu1 coaJ~in~ `tli~h f`o~m3 t~,e circu-it on the boar~l fre4uently senarate~ rrom the underl~Jing su~)3trat~ naLIt;cularly w~len the metal coacinf~ is ar-pl;e(t by ad(~i~ivc ola~ing techni~ues. This delaminat-;on of the met~l c~oa-t-in~; from t'~e su~strate of the ; board tyr-ical]y occllrs during ttle boa-d manu~acture and often during soldering at; elevated tenneratures. This results either in destruetiorl of the board or undesirable eleetr;cal ~roperties for the board. Consequently, this delamination has substantially preeluded employment o~ additive nlating techniques in the prep-aration of printed cireuit boards. The development, therefore, of a nrinted eircuit board prepared by additive plating teeh-niques havin~; a substrate with desirable eleetrical Dronerties and with high resistance to delamination ~rom the added metal eoating is partieularly desirable.
Briefly, the present invention is direeted to an arti-ele of manufaeture and more partieularly to a printed eireuit board having a substrate eharaeterized by a surfaee of a hydro-carbon polymer based, in part, upon a eonjugated diene polymer and a metal eoating direetly bonded by additive plating to at least a portion of the hydroearbon po]ymer surfaee. The resu]-tant printed eireuit board eom~only exhibits both desirable eleetrieal properties and a high resistanee to delamination of the metal eoating ~rom the substrate. Generally, these printed eireuit boards are produeed by first forming on the substrate, a surfaee layer or coating of an unsaturated hydroearbon polymer based, in ~art, u~on the conjugated diene polymer fo]lowed by etching and sensitizing part or all of the hydroearbon polymer surface, and finally electrolessly depositing a coating of metal on the sensitized surfaee. This proeedure results in bonding the metal eoating direetly to the hydroearbon nolymer. Moreover,
a substr~te ~ilth a lydrocarbon ~olynler sllrface and a m~tal coat-ing direct]y bon(ie~l to at lea~t a nort-ion of sllCh hydrocarbon ~olymer. `lore r-articular1y, it relates to a ~rinted circu3t board where th~ hydrocarbon nol~rner is based, in ~art, u~on a ~, con~ugated diene nolymel; where the m~t~l coating is electro-lessly de~os;ted on the hy~rocarbon ~olymer; and where the bond strength or adheslon between tho hydrocarbon ~olymer and metal coating is extremely hl~.r,h~
As known, printed circuit boards have become an im-~ort~nt comrnercial form of` circuits for the electronic industry.
In ~eneral, they com~rise a metal coating in a particular design representin~ a circuit or circuits attached either directly or indirectly, for exam~le, by adhesives, to the surface or sur-faces of an electrically nonconductive substrate. Often, the ~ substrate is rigid as in reinforced epoxies, although it can - also be flexible as in polyester films. Several important ad-vantages have resulted from the use of printed circuit boards.
These include dimensional reproducibility of both the circuit elements and their physical separation which are ~articularly important with higher frequencies and with miniature circuits.
Also, several boards can he combined to form multilayer ~rinted circuit boards in compact form.
~ hile these printed circuit boards have been very use-ful, they have not been entirely satisfactory. With the use of higher frequencies and miniature circuits, the electrical prop-erties of the substrate are of increased im~ortance to the per-` formance of the circuit. In many applications, such ~roperties as dielectric constant, surface conductivity and dissipation power factor must be fairly low as well as constant over wide - temperature changes. Xowever, with multilayer printed circuit boards, an excessive dissipation ~ower factor often causes -tf~M;)erature c`;.,n ~ ir tl(-~ cn-lf` r~erl or ~uried sll~)strrlt~s wl~ich resultr ;n c~ltln~f-~; in t'ae ci~ t c!!<lr~ctcristLc-;.
In addi~iorl, and llerila?3 Or even ~ mol-e seriolls nature, the metu1 coaJ~in~ `tli~h f`o~m3 t~,e circu-it on the boar~l fre4uently senarate~ rrom the underl~Jing su~)3trat~ naLIt;cularly w~len the metal coacinf~ is ar-pl;e(t by ad(~i~ivc ola~ing techni~ues. This delaminat-;on of the met~l c~oa-t-in~; from t'~e su~strate of the ; board tyr-ical]y occllrs during ttle boa-d manu~acture and often during soldering at; elevated tenneratures. This results either in destruetiorl of the board or undesirable eleetr;cal ~roperties for the board. Consequently, this delamination has substantially preeluded employment o~ additive nlating techniques in the prep-aration of printed cireuit boards. The development, therefore, of a nrinted eircuit board prepared by additive plating teeh-niques havin~; a substrate with desirable eleetrical Dronerties and with high resistance to delamination ~rom the added metal eoating is partieularly desirable.
Briefly, the present invention is direeted to an arti-ele of manufaeture and more partieularly to a printed eireuit board having a substrate eharaeterized by a surfaee of a hydro-carbon polymer based, in part, upon a eonjugated diene polymer and a metal eoating direetly bonded by additive plating to at least a portion of the hydroearbon po]ymer surfaee. The resu]-tant printed eireuit board eom~only exhibits both desirable eleetrieal properties and a high resistanee to delamination of the metal eoating ~rom the substrate. Generally, these printed eireuit boards are produeed by first forming on the substrate, a surfaee layer or coating of an unsaturated hydroearbon polymer based, in ~art, u~on the conjugated diene polymer fo]lowed by etching and sensitizing part or all of the hydroearbon polymer surface, and finally electrolessly depositing a coating of metal on the sensitized surfaee. This proeedure results in bonding the metal eoating direetly to the hydroearbon nolymer. Moreover,
-2-;, 104;~73~
the borld s~; ~)r-oiu(~ed ; h;!~hly resistant to del.am;nation or ser-ar.tion ~f th~ m~ .~l. coat:ini~ rrom t~-~e hyclroc~rbon ~olyrrler, . n~rticu~ y under al)r)l:Lcs-t;:Lon of he<ll. .,uGh as occllrs dur.l.ng solderl.ng and thus a].lows em~loyrnerlt o~ addlti~e !)lat;ng tech-niques for circuit board !nanuf`acture.
The printed ci.r(~u:it ~)oard of this invent;.on com~rises essentially, a sllbstr~.lte charnct;erized by a surrace Or a hydro-carbon nol.ymer hased, in ~)u~t, u~on a conjugated diene polymer and a mets] coating dirt-ctl.y bonded hy al(iitive Dlating to at . 10 least a portion of the hylrocarbon ~olymer surrace. The prlnted circuit board is in the form com~!only utili7ed i.n the industry and can have one or more apertures extending part or all of the distance between generally oorposite, external surfaces of the , .
. substrate. The desired polymeric hydrocarbon is ~resent on at least one of the surfaces of the board substrate and advantageous- .
ly on all surraces associated with the formation of circuit ele-. ments.
~; Commonly, the entire substrate is composed of the hydro-carbon polymer and advantageously has reinforcing or core members - 20 such as layers of paper, glass fillers of glass or other rela-: tively inert materlals contained within the hydrocarbon polymer.
While in some instances these reinforcing members are pretreated to improve bonding with the hydrocarbon polymer, as illustrated by the pretreatment of paper with a phenol-formaldehyde resin, it ` is preferred according to this invention to incorporate such thermosetting material directly into the hydrocarbon polymer . prior to application of the hydrocarbon polymer, preferably as a coating, to the reinforcing core material. Accordingly, as em-ployed herein, the hydrocarbon polymer, forming at least the sur-face of the substrate, is composed of a thermosetting component in addition to the elastomeric component based upon the conju-gated diene polymer. Thus, this hydrocarbon polymer composed of . the thermosetting and eiastomeric components can be readily . --3--iO~'~7;~4 !i.7-ci'ly, . ~ ,0 V'.''~ r~ rl! ~{)l~e .llter~ uco c~ n()1-:or~l~ v(;~ tre~lte~ n.~ er, ntlenol:i.cs~
e~oxies, I)olye~;t.e~ , o ccr.Ar;.c. to ."olm rein:force~ substr~tes parti.clll.ar]~ sui.t;~ le !'or m(~tc~ inr by ~Id(~3t~ve ~)lati.n~- tech-niques invol.vin~ :ir~ an e~ectroless metl~ der-os;tion.
~ioreoverJ those re.i.r~i'olce(~ substrnt.e~ coatcd with the hydro-carbon ~olymer ultLIn.ale]y resll!.t in the r~roducti()n Or r)r.intcd circuit boards havin~r exce'l.lent el.ectrical. ~ro~erties and hi~h resistance to both delamination of tl~e hy~rocarbon pol.ymer fror the reinforcing core and delamination of the me-tal coati.ng from the hydrocarbon nolymer.
The elnstomeric component Or the hydrocarbon ~olyme}
is essentially coml~osed oi' a conjusated diene polymer based u~on diene monomers having from 4 to 6 carbon atoms such as bu-tadiene or isoprene. Such diene polymers may be em~loyed solely as homopolymers of such diene monomers, for example, as polybuta-diene or polyisoprene, or may be employed in combination or poly-merized with various other unsaturated polymerizable monomers including, for example, acry]onitrile or styrene or various com-binations thereof. Preferably, the elastomeric component is a copolymer or terpolymer of these various polymerizable monomers, and suitable copolymer examples include copolymers of butadiene-acrylonitrile, butadiene-styrene, iso~rene-styrene, or isoprene-' acrylonitrile, and suitable examples of terPolymers include iso-prene-acrylonitrile-styrene or butadiene-acrylonitrile-styrene.
:~:. Of these various polymers, however, a copolymer or butadiene-acrylonitrile is particularly preferred as the elastomeric com-: ponent of the hydrocarbon polymer used in the formation of the substrate according to this invention.
~he polymers of the above general class which can be utilized according to this invention as the elastomer or elas-tomeric component of the hydrocarbon polymer, generally include those products available commercially which are classified as ~4-104273~
cld.t(j~ler.;; ;~ich ar~ s~ on 1 ~liene ~n(,no.~er G~ r~om a~,out 4 to ~Iboul 6 c<lr~)on at~m~; and w~l;.ch are re~ y solvent 301u-bilized fol coatlrlg anr?li(~tJi.orls. ~`or examl)le~ ho~lopolymers sllch as nolybutcl(l;.ene cln ;nclude the com~er-cially avail.a~le ~R syn-thetic rubher~. Si.r~ rly, th~ ~ol~tso~rene can be eith~r a nat-ur~ or synthetic rub~.!er av~1lal-le under such trade names as `JR~or IR~ubbers. Th.e connlymerc em~loyable, such as butadiene-acry-].oni.trlle cor~olymer, inc:lude those co~ol~Jmers av~i]ab].e as ~R~
rubbers or nitrile rub~ers which generally have an acrylonitrile : 10 content of from about 1~ to 50 weight percent ACI'yl on:itrile and are ty~ical3y prepared by catalytic emulsion polymerization. A
parti.cularly prererred butadiene-acrJlonitrile co~olymer, for ex-ample, has an ~crylonitrile content o~ ~rom about 25 to 40 weight percent, a specific gravity of 0.9~ and a .~looney plasticity of 68 to ~5.
~..
Suitable copolymers of butadiene-styrene for employment ~ as the elastomeric component are available as the SBR, Buna-S or GR-S~synthetic rubbers of commerce, which are typical]y a poly-merization product of about 3 parts butadiene and a~out 1 part 20 styrene. Other copolymers of butadiene-styrene which are also particularly suitable for use as the elastomeric component of the hydrocarbon polymer include both liquid and solid forms of '. random, graft, or block copolymers, and can include those poly-. mers having polar end groups such as hydroxy terminated or car-boxy terminated Polymers. The liquid forms of these copolymers are particularly advantageous because when cornbined with a liq-uid or solvent solubilized thermosetting component, the resulting liqui.d hydrocarbon polymer is readily applied to the reinforcing core material utilizing conventional coating techniques. In general, liquid po~ymers of this type have a number average molecular weight of about 500 to 5, ooo and a styrene content of about O to 50 mole percent and are characterized by a vinyl or ~r~ 5-~ .
104Z73~
! J~ t~ rl OI~J`~)OIIt L~ nerCer1t OL' the ~;otal llnS~tl.lr~l t,iOn. ~ e COr`l`~'S~Ond; n~r '301 i(~ CO~O1YrtIer9 COm~r1~3e hiD;her molec~ r ~iie~i~rt oro(lucts, or ~rti.a~.ly c~oss-li.nkec3 ~roduct;, or block co~o1ymers as ~ene~ully i~ str~te~ in [~nited States Patent; ~,To. 3,~(~-;,76~ ti.ll another su;table co~olymer of but~cilerle-st~rene is a co~o]-JIner which has a vinyl or 1,~. unsatl1r~lt;t)n helow 5(~ ercent. Ynrt:iclllar nolymers of th;s class are il]ustrated in United States ~atent No. 3,265,765 as block co~olymers o~ a n~n-el.astomeric ~o]ymer b~ock and an elastomeric ~olymer block, for example, a styrene ~olymer block and a butadiene polymer block. Advantageously, the~e ~olymers are high molecular weight block co~olymers with a general formul.a . of A-B, A-B-A, A-B-A-B-A, and the like, wherein "A" is a non-elastomeric polymer having an average mol.ecular weight of 2,0no to 100,000 and a glass transition temperature above about Z5 C.
The elastomeric polymer block "Bl' is characterized as having an average molecular we;ght between about 2~,000 to 1,000,000 and a glass transition temperature below about 10 C. Normally, these block copolymers are linear and contain less than about 50 weigh-t `. 20 percent, but at least above about 10 weight percent of the sty-;~ rene polymer, and more than 50 weight percent of the butadiene .:- polymer.
. The copolymer of butadiene-styrene when used as the elastomeric comp~nent of the hydrocarbon polymer may also com-prise various blends of different specific butadiene-styrene co-polymers. For example~ a blend of the above described butadiene-styrene co~olymers where one copolymer has a high vinyl or 1,2 olefinic unsaturation above about 50 percent, and the other co-polymer below 50 percent, i~ particularly sui.table as the elas-tomeric component of the hydrocarbon polymer.
When terpolymers are desired as the elastomeric compo-nent of the hydrocarbon polymer, they may generally be obtained commercially; for example, a terpolymer of butadiene-acryloni-' :' ' , . .:
,. ,:
~ ~04'~73~
trlIe-~t~;rene is rea(Ii.l;, oht~in~'-)le as 1~ co~merc:L~Il h~ resins, w~l~h normtllIy cont~lln ~ut~dlerl w;t~ln t;he rnn~e nr f`rom ahout ', to l!O ~eirrht ~)eYc~nt acr~lolI-t.trlIe wit~-lin the r~ln~le o~ from :: a~o~l1; '~, to 3() ~/e;~ht l~erc~nt, t~n~ ~:tyrene within the r-ange of fron, ahout 3~ to ~ e;~ht ~rcent;. Y~riI.e not techni~a~ly a terr~olymer, l~hysl.c~l. a(l!n;.tllres ot` butarliene-acrylonitrile-sty-rene may also be emnl-)ye(l, f`or ~xam~le, an aclmixture of a co-. ~ol.rmer of butadiene-st~rene resin ~nd a co~ol~mer of butadiene-: acryl.onitrile. The ter~olymer3 of iso~rene, acrylonitrile and styrene are a].so ~vai:lahl.e commercial.1.y, an~ tyoically comprise ~ a ter~o~ymer containi~g isoprene within the ran~e from ahout 5 ~ to l~o wei~ht nercent; acrylonltrile within the range of from about 5 to 30 weight percent; and styrene within the ran~e of from about 30 to 90 weight percent.
.
The thermoset or thermosetting comP~nent employed to-gether with the elastomer or elastomeric component to rorm the hy-drocarbon polymer can generally include any of those resinous ma-` terials conventionally employed for electrical ap~lication which . form infusible, thermoset resins under appropriate curing condi-tions and which are compatible with the elastomeric componentO
: Suitable thermosets include the aminoplasts, for exam~le, the I thermosetting resins prepared by the polycondensation of formal-dehyde with an aliphatic alcohol, for example, butanol, and a ni-. trogen compound such as urea or a tria7.ine such as melamine. Oth-er thermosetting resins which may also be successfully employed include epoxy resins or ~henolic resins prepared by the conven-` tional reaction of phenols with aldehydes such as formaldehyde, acetaldehyde, or furfuryl alcohol, which are heat curable to an infusible thermoset. Of the various thermosets which may be em-nloyed as the thermosetting component, however, the phenolics ,~
are particularly preferred, and especial].y the pheno].-formaldehyde ~-~: reaction products. A tynical exam~le of a preferred phenol-formaldehyde resin, com~rises the reaction product of about 1 mol ~ of phenol and from about LO to about 105 mols of formaldehyde with :. -7~
~04'Z734 a more 1imite-1 r~ln~e Or f'rom ~ t 1.~ to ~?~nut ~.3 mols of - rorm~llde;ly(iie ferle~ ly beir,r ~ref'crred.
In ~re!~)ri.tl- t;he `~y(~roc~lrbnn ~olymer accor(3:ini- to t'~is invention ror anr~iccltl.nrl, ~artlcula~ a3 a coat;.np to the re-inforci.n~r corn ma-teri~1 Or the substr~te, for ex~lrn~].e, a phen-olic treatecl paper 1amirlate, the elast()mer~c com~onent )nd the thermosetti.ng co~TIr~onent can be ~dmixed in wl(1el~y varie(3 r)ror)or-tions. Tlle ~artic?.llar r~ro~-ortion r~osen i.n any Lnstance wi~ be a runction Or the s-necif';.c elastomer and thermoset em~loyecl, as . 10 wel~ as the ~articlllar electrical or nhysica] ~roperties ulti-mate]y desired fcr the printed circuit board. Tynicall-J~ how-ever, the pro~ortion of the elastomer to the thermoset in the hydrocarbon polymer can range from about 15 weight parts of elas-tomer to 1 weight ~art thermoset, to 1 weight part elastomer to 2 weight parts of thermoset. Generally, however, & more limited '~ proportion is usua]ly pref'erred, partieularly to maximize the bondi.ng of the hydrocarbon polymer to the reinforcing eore and especially to achieve greater adhesion of the metal coating to the hydroearbon polymer. For example, when nreparing a partieu-'~. 20 larly desirable hydrocarbon polymer according to this invention ~ where the elastomeric component comprises a butadiene-aeryloni-: ~. trile copolymer and the thermoset component comnrises a phenolie ' resin of phenol-formaldehyde, the proportinn of the elastomer to the thermoset is~referably maintained within the range of `; . from about 1 to 10 weight parts elastomer to about 1 weight ~art thermoset with a range of from about 6 to 9 weight parts elas-tomer per 1 weight part of the thermoset being especially pre-'~ ferred particularly to maximize bonding of the metal coating to the hydroearbon pol.ymer.
The hydrocarbon polymer ean contain other materials in addition to the elastomeric and thermosetting components and sueh materials typically include curing agents, rubber accelerators, anti-tack components and cross-linking agents. The euring agents ~0~ 3~
UC'Cel~'r`l~tOr'' ~I.`'? e~r~ v~rl ro cu-~ th~ elasto~eric or t'-~rrno~ ttirl~ ~o!-~ons~lt: to ~ o~ ri~-id st~te. '~oY~ever, be-ccl~lse the tl-le-m(~;~t;tirl c(jmronent e~ ved accord-lng to this ln-vention is ~ner.~ eat ctlru~)le, such curin~r or accel~r~t1ng agent,s arc~ t~rnicnll~ us~(l sol~ ror tht~ elasto~eric co~ onent.
L'he eArticlllar cllring~ or ac~elerat;inr~ l~ent er~r)]oye(l can be widely varied anc~ r!ost o," t;he cu~in~ .lnd accclel,tlng a~ronts con-ventionall y emnl o,~ed ~or the curin~:, of ru~ ery elas-tomers May be $ ' suitably utilized. Gener~llly, the ~articular curing ac~-ent se-lected will de~en~l ur~on the elastomer-;c comr~onent em~loyed and ; the tem~erature range or series of temnerature ran~es selected to effect the cure. Suit~ble curing agents include or~anic ~er-oxides such as those llsted in irk-Othmer, Encyclopedia Or Chemical Techno]o~y, Vol. 11~ and particularly those with activa-tion temperatures of 30 to 50~ C. or sulf'ur containing vulcan-izers which are comr~lonly employed to harden natural or synthetic elastomers. Irradiation techni~ues conventionally em~loyed to initiate free radical formations may also be employed alone or in combination with curing agents to effect the desired curing.
The quantity of curing agent or accelerator emI~]oyed in the hydrocarbon polymer may vary but typically those quantities con-ventionally employed in the curing of rubbery e]astomers may be satisfactorily used. For example, when utilizing curing agents such as sulfur-containing vulcanizers such as te-tramethylthiuram disulfide or 4-4 ~ -dithiodimorpholine, suitab'le amounts range ~' from about 1 to 10 weight parts of vulcanizer per hundred weight ` parts of elastomer.
The cross-linking agents which may be suitably added to the hydrocarbon polymers to increase the thermoset character-istics can include thosc monomers conventionally employed ascross-linking multifunctiona] monorners. F`or example, poly-functional isocyanates illustrated by the addition product formed from the reaction of toluene diisocyanate and "
_9_ ~, :
10~ 34 trimethylolpropane may suitably be employed. The anti-tack components are added to provide easier mechanical handling of the elastomer during preparation of the hydrocarbon polymer and especially to provide anti-blocking properties to the hydro-carbon polymer prior and subsequent to metalization. Particu-larly suitable anti-tack components include mica, soapstone, alkaline-earth silicates such as magnesium silicate and talc.
In preparing the circuit board according to this in-vention, several different preparational procedures may be em-ployed. For example, where the hydrocarbon polymer is employedsolely as the substrate without any reinforcing core material, the hydrocarbon polymer may simply be cured or partially cured to a relatively rigid state and thereafter metalized to add the desired metal coating. However, when the preferred boards are prepared with a substrate comprising a reinforcing core coated ~` with the hydrocarbon polymer, the basic procedure involves ap-plying the hydrocarbon polymer as a coating to the core material, curing or partially curing the hydrocarbon polymer, metalizing ` ` such polymer and thereafter completing, if necessary, the curing of the hydrocarbon polymer so as to effectively bond the metal coating to the hydrocarbon polymer as well as to effectively bond the reinforcing core material to the hydrocarbon polymer.
In preparing the hydrocarbon polymer for application as a coating, the selected elastomeric component and thermosetting component may simply be physically admixed and then applied to the reinforcing core materials utilizing conventional coating techniques. Such reinforcing core materials can include any of the material conventionally employed in printed circuit boards, including, for example, phenolic resins, epoxies, and polyesters which may contain further reinforcing materials such as glass in fiber or mat form, cotton, asbestos, or cellulose, for example, a laminate of phenolic treated paper. Preferably, the hydrocar-bon polymer is applied to the reinforcing core as a coating in ,AI -1 O-" . :
~04Z7391 1 L~ l f`or~m I or~ c~ n. (~ ner~ r,~ t ~ on the l-r~t~ clll .lr ~la ,t;~r~-e~ ~in~ tlfr-losot co~r~)nents emr~]~-yerl as well as t;`~e ~t:i.cular rclrl~orcirl~ co~c material llt;l;zed, ttle therno,ett~nlr l3nd el.~st~-~rne-r;.c co-nnonents wi.t~in the hydroc-lrbon no]yr1le~ e~cln be ~o'~ .e~ n v~lr;~ a~lueous or oY~ nic colven-ts either be~ore or a~'ter s~lml~ lch o-'`'AniC` solvent can in-clu e, for e~nmr-le, l;etones, al(1eh~de., or est;el-s ~`nich `nave vo~atilities sui.tr~ e f`or coat;n~ at el.:tive].y low tem~eratures.
The nartieular sol.vent SyS t,ent emnloyed ror the nylrocarbon poly-mer can vary, bllt general.ly a comhination of dirferent sol.vents are selected so as -to ~rovide suitable disso1.ving or susnending I
of the elastomer and thermosetting com~onent; a desirable drying time during the coa-ting of the reinforcing core; and a solubiliz-ing attack or dissolvin~-g Or the reinforcing eore material to pro-f vide ~hysical anchorinr of the hydrocarbon ~olymer to the corematerial. For example, when em~loyinr a hylrocarbon polymer formed from an elastomer such as a butadiene-acrr]-onitrile co-: ~olymer and a thermoset such as a phenol-formaldehyde resin, a suitable solvent system comprises an admixture of an alkanol such as methanol, ketones such as methy].-isobutyl ketone and methyl-ethyl ketone, and an ester sueh as n-butyl aeetate.
, With the hydroearbon polymer solubilized in liquid : form, it can be readily applied to the reinforcing core material utilizlng such eonventional eoating teehniques as roller, doctor blade, or curtain coatin~. Thereafter~ the polymer is dried to remove the volatil.e solvents, leaving the hydrocarbon polymer on : the eore ready for curing and metalizing by additive plating.
The hydroearbon polymer eoating so annlied to the eured material.
ean vary in thiekness with the partieular thiekness or amount of 30 polymer in any instanee being dependent u~on such variables as the partieular hydrocarbon ~olymer employed, the reinforcing core material utilized as well. as the physical or eleetrical pro~erties ultimately desired for the final eireuit boar~
1042739, ~ `V~r~ fr~ ~`'n~ clr~)orl~o~lym~r ~r a ~ t~ n~-~c~ nitrl.l.~ co~ol~,~rler as the elasto~neric comnonent and a ~)tle~ol-forrn~ h~lde ~e<;;n ~s the ti~erlnosettin comr)onent, t~le `~y(lrocclr~-on T~o~yrrler i.s a~ ;e-l to the reinforcing core in an amount ;ufriclellt; to ~l~o~luce s coating ufte:r sol.vent ren!oval and after either rllll or r)art:ial cllr~.n~r, hAvin~; a dry t~ickness ran~rin~r from a~)ou'; 0.] to .5 In;ls with fro~ 0 to 1.75 rnils usual]y beinr nreft~rre(~ i.n ~.lo;t instances.
~ fter the y,-lroccr'.o~ olymcr :i: a~olie(l to the re-n inforcin~ core and dricd to remove the solvents, the nolymer is cured prior to metnli~atlon. This curing can be cGnducted so as to completely cure the hydrocarbon polymer rrior to the metaliza-tion or conducted so as to effect only a ~artial cure prior to metalization with the remaining cure being completed subse~luent to the metali.zati.on. Generally, the Preferred procedure, ~ar-ticul&rly to maximize bonding between the metal coating and - hydrocarbon polymer, involves conducting the cure in at least two steps with a partial cure being effected beforc metaliza-tion and the cure being completed subsequent to metalization or partial metalization. The particular temperature range selected to effect the cure wil] vary depending upon the particular hy-drocarbon polymer and especiall.y the elastomeric component em-ployed, the number of heat curing steps, and the particular cur-ing agent, if any, employed within the hydrocarbon polymer. : -Usually, however, a temperature ranging from about 80 C. to . about 190 C. may be employed for any heat curing .~tep with a : more limited range of from about 100 C. to 160 C. generally being preferred. The duration of the cure is a function of the :~
~articular hydrocarbon ~olymer, its thickness, the number of curing steps em~oyed, and the particular curing temperature Ty~ically, however, when the curing is effected in one or two heating steps with ternperatures ranging from about 100 C. to ;
-, 104273~
~()c~,., tile t~to-l ~ nl t~ o~ t~le c~ o e ~3rt t ~)f~er - met~ ing m~ly r lnl e fro~n ().!,~ to ~, ~lollrs.
~ ft~r ti~c IJ~r~ r~on ~ol.ymer i cured or nartial~y cllred, t~lç metal c~ting ~s ~I-sr)l:;ed by metr,~i~.ing th~ ~ubstrate util;zin~; ad(iitiv~ r-~ating tec'-ln;clles. E~asicall~, thi~. lr)volve3 first etcl:lingr and s(r~sLtiz!.n;r the hydrocclrbon nolymer surface, electroles.~ly de~)o3i.t:ing the met~l. coatin~ followed, lr desire(i, by electrol.ytlc de~o~it.ion of ai'ditionl1 met;il. A~vantageou~ly, the etching is c~lrr:ied out wlth strong, acids such as sul:furic or phos~ho:ri( with su~.)stances such as sodium dichromate. The severity of the etch is somewhat dependent on the extent of cure of the nydroc~rbon polymeric surface of the substrate. The sen-sitizing stel~ is carried out according to conventional practice - with reducing agents such as stannous chloride followed by pal-ladium chlori~e or other catal-yst. It is understood that partial masking of the hydrocarbon ~olymer surface can be carried out before the etching or sensitizing step to limit the modification of the polymer surface where only insulating and not circuit ~: properties are required.
2~ A metal coating is then applied to the sensitized sur-.~ face by electroless deposition techniques. This usually results . in a thin coating with a thickness and continuity sufficient to conduct electricity with the thickness ranging up to about 1 `. mil which minimizes subse~,uent metal removal during the formation of circuit elementsO The metal applied in the electroless depo-sition is conventionally and conveniently nickel, copper, cobalt, gold or various alloys thereof, or other metal selected both for ease of application and performance in the final circuit board.
Usually, the metal is a transition metal with an atomic number of about 21 to 79 such as nickel, copper, gold, silver, cobalt, and the like. Preferably, the metal is nickel or co~per.
When tne metal coating is applied by electroless depo-sition over the entire hydrocarbon surface, the metal coating ~oa~Z73~
~ er t~ ft~ )e ~ ti.l!ly ~-kc~ i the r~r!!1;nir~r~lr~
e~ctror~lat~ t;o !~i ovi~l~ a ~';.rl~ll a~l i;tional met.i~ Jer r~ cir-C~l;t ouro~-~es. Tbe met~ll s~lect~-l ror this ad~]it.on~il metal er rn~y a~so i,e any ~1~ tht' a')OV~` grOUn 0I transLt;orl metals r~d ~)r~ferl~l)ly i coo~t, silv~r ~r lol~i. rl`he mask and the r)or-tion~ of tlle electroless m(t~ yer underl~ing the mask i; then removed by kno~n chernlcul etch;ng tt)chniques lelv;n~ the metal coating on t;he hy(lrocsrhon su~face o~ the boar(i in the desired circuit confi~llrrition.
]0 The fo1lowing exam~?les illustrate some of the embodi-ments of this invention. It is to be undeI;tood that these are for illustrati~e purooses on~y and do not purport to be wholly definitive to conditiors or sco~e.
~xample I
A hydrocarbon substrate was prepared by coating an etched, thermoset-hydrocarbon laminate with a toluene solution containing about 5 weight percent of a styrene-butadiene block copolymer based on approximately 23-25 weight percent styrene.
The solution also contained a~proximately 6 pph of benzoyl per-oxide to provide later cure.
The coated ~roduct was baked at about lOQ C. for ap-proximately 4~ minutes to provide solvent removal and ~artial cure of the hydrocarbon coating. The board was then treated with an etchant composed of about 69 weight percent of 96% sul-furic acid, 25 wei~ht percent of ~5% phosphoric acid, 2 weight percent of sodium dichromate (dihydrate) and about 5. o weight `~
percent water. Treatment was carried out at about 55 c. for about 1-2 minutes. After being rinsed, the board was treated ; with a solution of 10 weight percent of stannous chloride, rinsed ; 30 with water, and immersed in a HCl solution of palladium chloride (about lg./l.).
A thin nicke] coating was a~plied to the rinsed, sen-sitized surface using a nickel chloride solution with a ~04~73~
`r!y~ o~ te r(`d;,Cirli- '3,'~('tl~ tle t~li(`l'llCS.; ':,'.'a sufiicient tc, ren(i~r l.ae sllri- c~ conùllctlv~ to ~n ~ trical curr~nt.
~ u~se(!l~rltly~ co);~r l,:as el~ctr~lat~d to a thickn~ss of a~ roxir~at~ly 1 in;l. r[`',c resllltant metal coatingr nl~te ~as then he~ted at a ,;)rox i:!lately l()o" c . ror a~)ou t; L~, minutt s to re-;rove water and cornt)l(-~tt t;`l~ curlng cycle.
A -)0 o~el strengt~l test wa~; c~r~ie~ out on a ~a~ple Or the metal coa-te~, the~rloset board using A ~ee] rate of ahout 2 inches r?er !~inute on one inch (~idt~ amples. Values of ',-6 `~ 10 lb~s. ~er inch were oLtained.
~xanl~le II
Additional sam~les of a metal coated board Nere pre-pared using the techniques o~ ~xam~le I. The coating solutions contained from 2 1/2 to 1() weight percent o~ the butadiene-sty-rene ~)o]ymer in toluene with the curing ag,ent bein~ in a concen-tration Or about 6 pph. Samples of the dip coated laminate after being coated with e]ectroless metal were then plated with copper to varying thicknesses. The resultant sam~le~ were then sub-jected to dip-solder resistance tests at 500 F. in which the sample was im~ersed in solder and the degree of blistering and destruction of the metal bond to the hydrocarbon surface was de-termined. In the test, it -~,Jas found that samples prepared from polymer concentrations of 2 1/2 to 5 weight percent produced products which passed the dip-solder test for at least 60 seconds~
In these tests, the thickness of copper ~late on the various samples that passed the 60 second dip-solder test, ranged ~rom o.o56 mils to 0.15 mils.
Example III
A hydrocarbon laminate was fabricated from layers of phenol-formaldehyde treated paper which had been saturated with a graft copolymer of po]yautadiene and styrene. The copolymer was based on a butaoiene content of approximately 60 mole per-cent, a 1,2 unsaturation in the polybutadiene of about 60-70 104'~734 ~ rcel!t, ~In~i corlt~,ine(i erl or~J~Ilc l~erlY~ cetsly,l. f~aoric~ltll,rl ()f t''!e l~lr~irlat,~ W~l'; c~ilr~ie~ olt ~ith cur~in~ of tle eolymerlc ~-iy-~-~rocl7borl t- r~rovl(le ~1 t~lerilo-~t; llmlna~.
rrhe 1 `1~1;n11~;f` `iltl~; Cleclne'~ wlth arl all~ul;n~- solution and t~en t;rca~.ed wlt~ r-, e~ nt ,oluti~n cont,;;ning n~-ollt ~ Je:ight l~ercènt o~ ~)f~ clC;d~ G'' wei!rht ~crcent of '15,~ nhos!)horic acid, 4 weigh-t r~ercent o~ so~l;urn dichr~,mate (diil~dr~e) and weight ~-ercent of ~ tr. Treatment wns carried out at a;~out ]75 F. with vigoroil-l agit;ation for about l5-20 minutes. The board was then rinse(i, imrnersed in a 5,~ Na~E solution at about 110 F. for n few minutes, rinsed again, and then se~sitiæed in the manner descrihed in Exam-c)le I.
After being sensitized, the board was rinsed and c~ tcd with a thin layer of nickel applied from the solution described in Example I. An electroplated coating of copper was then a~-plied and the resultant board was baked at about 200 F. for about 4~ minute~.
A 90 peel test was carried out on a sample of the board. Values of 3-4 lbs. per inch were obtained as measured at the rate of 2 inches ~er minute.
Example IV
A circuit board was prepared utilizing a hydrocarbon polymer with an elastomer component and a thermoset component according to the following procedure. The hydrocarbon polymer ~; was prepared by dissolving 96.25 weight parts of NBR rubber con-taining about ~.75 weight parts talc and about ~7.5 weight ~arts of a butadiene-acrylonitrile copolymer having an acrylonitrile content of about 25 to 40 weight percent, a specific gravity of 0.99 and a Mooney ~lasticity of from 6~ to ~5 in about 725 weight parts of methyl ethy] ketone with agitation. To the resultant solution were added with mixing about 1?.5 weight parts of a phenolic resin comprising the reaction Product of 1 mol phenol and from about 1.2 to 1.3 mols formaldehyde .:`
`: :
`: :
~ 0~ 734 dissolved in P!.5 ~e~ht parts methyl ethyl ketone. The solubilized hy~rocarbon ro]ymer was transferred to a ~ip tank and a ~henolic treated l)a~er laminate (5 inches square and 1 inch th ck) was coated on both sides by immersion into the hy-drocarbon nolymer solution for a ~eriod Or about 10 minutes.
The coated laminate was thereafter dried at llQ C. for about 30 minutes to re~ove solvent. The hydrocarbon polymer coating was then cured by heating the coated laminate first at 110 C.
for 10 ~inutes, then from 110 C. to 150 c. for 30 minutes and finally at 150 c. for 30 minutes. The cured hydrocarbon polymer coating had a thickness of approximately 1. 5 mils.
The resultant substrate comprising the cured hydrocar-bon polymer coated over the reinforcing core of the r~henolic treated laminate was then metalized according to the following procedure. After detergent washing, the substrate was etched by treatment with an aqueous chromic solution for about 5 min-utes at about 25~ c. After removing from the etching solution and water rinsingJ the substrate was contacted with a 5 percent sodium hydroxide solution and then water rinsed. Thereafter, the substrate polymer surface was sensitized by treatment with aqueous stannous chloride solution (10 weight percent stannous chloride) followed by water washing after which the polymer sur-face was treated with an aqueous hydrochloric acid, palladium chloride solution (about 1 gram PdCl per leter). A nickel coat-ing was then applied to the sensitized hydrocarbon polymer sur-face of the substrate by treatment with a nickel chloride soluti;on in the presence of a reducing agent. The nickel coating so de-posited was sufficient to render the surface electrically con- -ductive. Thereafter, a copper coating of approximately 1 mil thickness was electroplated onto the nickel coating and the re-sultant copper coated substrate was cleaned and dried to obtain the desired circuit board of a metal coated substrate. In the board so produced, the circuit is represented by the m-atal 104'~;34 C D ~l t i r~ ~ ~ . I f t, ! l (~ c i ~ i t i ~ D ~' Df ~I D~Y~tic~ r~ d~sit~;n, t~len conv~nt,ion/~l m.~ o(~t,~ r~ a' ~r~/iously discllssed r,1ay be .
en~r)~o,~ to ~,r~J(I~ t~ ,irc~ dl~3i~n.
'I'he ctr~rl"t~l or ~ tl~,Lc,ll of the cop,)er met~l co~tin~, bonded to the ~Iydroc~lrt)or~ ~lymer ~va~ evaluate(~ by conducting a '~0 ~)eel strength t~st on the boar(3 accor(lingr to the f'ollowing rocedllre: A st;r;t~ of c~ ,roximately 1/2 inch wldth and an~roxi-mately l~ inches lon~ was cut on the sur~'ace of the substrate~
and a ta~ rormc~ at or~e end ot` the strir) by separating the me-t~1 coatinp; from the hydrocarbon polymer. While maintaining the substrate at 25 C., the tab WAS then pulled vertically upward at an angle Or 90 at ~1 rate of 2 inches per minute and the force required to separate the metal coating from the hydrocarbon polymer was measured as the 90 peel strength. A peel strength - Or aDproximately 20 lbs. per inch width of the strip was ob-'" tained for the substrate prepared according to the procedures of this Example.
Example V
A circuit board was prepared utilizing a hydrocarbon polymer with an elastomer component and a thermoset component ~;; according to the following procedure. The hydrocarbon polymer was prepared by dissolvingr 96.25 weight parts of NBR rubber con-taining 8.75 weight parts talc and 8705 weight parts Or the buta-diene-acrylonitrile copolymer as described in ExamDle IV in about 350 parts by weight of methyl ethyl ketone with agitation. To - the resultant solution were added with mixing about 22.8 weight parts of the phenolic resin described in Example IV dissolved in ' ~ methanol (55 percent solids). About 1.28 weight parts of tetra-'~ methylthiuram disulfide and 1.28 weight parts of l~,4~ dithio-d~morpholine were mixed with 31 weight parts Or methyl isobutyl ketone and 103 weight parts of n-butyl acetate and the resulting -~ mixture added to the solubilized hydrocarbon polymer. A glass-reinforced epoxy resin panel (5 inches square and l/4 inch thick) .' ~ .
104'~734 W;l'' C')~l t,~`'! 0'1 ~`lt,~ wlt,ll t'le ~J'~oc ~ on ~o1,1mer b~,r roller coat.Ln,;. llle co~ n1~ t~ ; t`~lc~r~ .t't~r ~.~r:ie~l cl t ?5 0 C . rOr ahout ~'`in;nut.~s t~ r~ ov~ .,o1v r-~t. The `.~;~rdrocar~on ro1,ymer ~,c.~in~ c~ tt~en n,~r~,ic?].ly curc(l ~y heat,i~, the colt~l 1.ami.nate at 15(~`) c. ror ~J(~ nlirllltc; t o foI m a eo] :,ymQr cost:int- hllv:lng; a th:icknes; oi ~ ~)out ~.5 mils.
The res~1.t~nt sub.t,~sa'G~ cornr)ri~,;.n~ the ~artia].1,y cured hydrocarbon no'lymcr coat,e(~ over the reinforcin~i; core Or t'ne g1ass reinforced e~oxy re~:in nanel wa~ then metal:l7.ed accordir-lg to the rrocedure o,t' ~xam~1e IV -to ultimately produce a co~)per coating about n.l mil. thickness. The conner electro~la-ting was then stopned and the copper plated substr2te was heated at 150 C0 for 60 minutes to comolete curing of the hydrocarbon r)olymer.
Thereafter, the electroplating ~.vas continued to increase the cop~er coating to about l mil. thicknes~ to form the desired circuit board of a metal coated substrate. In the board so produced, the circuit is represented by the metal coating~ If the circuit is to be of a -particular design, then conventional masking ~rocedures as previously discussed may be employed to ~roduce the desired design.
The 90 peel strengtn Or the circuit board was evalu-ated according to the procedure of Example IV to give a value Or about 20 pounds per inch. The circuit board was also evalu-ated for dip solder resistance according to the procedure Or Example II and results in excess of 20 seconds were obtained.
Exam~le VI
A circuit board was Drepared utilizing a hydrocarbon polymer with an elastomer component and a thermoset com~onent according to the following procedure. The hydrocarbon polymer was prepared by dissolving 82.5 weight parts of NBR rubber con-taining 7.5 weight parts talc and 75 weight parts of the buta-diene-acrylonitrile copolymer described in ~xample IV in about 323 weight parts of' methy1 ethyl ketone with agit~tion. To the - ..... ~. . .
104'~739L
re;~;lt;lnt ~ ti~n ~lere af! Ic~ w;th rni~ini!~ ar)out llr~ weight ~arts cr t~le ohenollc re:in (le crlbed in L~anl~le TV di.solve(l in meth-anol (',' ~ercent 901~ Abollt 1.l ~!ei ht narts Or tetramethyl-t;,1uram ~lisu~lf`i(~e ancl l.l wei~t narts Or ~4 '-ditaiodimorpho-line were mixed with ~o'. weitht n~rts o methy] isobutyl ketone and '~'~ wei~uht nart of n-~ltyl acetate and the reslllting mixture added to the soll~)ili%ed h~dr(car~)on !ol~m~r. A r~] as -rein~orced enox~ rec~in ~anel (C. inches ~quare ar~d 1/ll inch tnick) 1Na~s coated on both si~les with the hrtlrocarbon ~olymer by roller coat-ing. The coated laminnte was therea~ter driel at ~5 C. forabout 60 minutes to remove solvent to form a i)olymer coating thickness of about 1.5 mils. The hydrocarbon ~olymer coating was then partially cured by heatinc~r the coatèd laminate at 150 C. for 60 minutes.
The resultant substrate corn~rising the partial]y cured -~ hydrocarbon ~olymer coated over the reinforcing core of the glass reinforced epoxy resin panel was then metalized according to the procedure of Example IV to ultimately produce a co~per coating about 0.1 mil. thickness. The cor)per electroplating was then stopped and the copper ~lated substrate was heated at 150 C. for 60 minutes to complete curing of the hydrocarbon polymer.
Thereafter, the electrop]ating was continued to increase the co~per coating to about 1 mil. thickness to form the desired circuit board o~ a metal coated substrate. In the board so :.
produced, the circuit is represented by the metal coating. If the circuit is to be of a particular design, then conventional masking procedures as previously discussed may be employed to produce the desired design.
The 90 peel strength of the circuit board was evalu-ated according to the procedure of Example IV to give a value of from 10 to 18 pounds per inch. The circuit board was also evalu-ated for dip solder resistance according to the procedure of Example II and results in excess of 20 seconds were obtainedO
1()4'~73~
x~ r A ci.rc lit ~or~r~ r(~ rt~l t~til 1 ~ In~ a yIroearhon r~ ~ol~er Of ~ all e~ 't;Or~t'r C()!~r)Ol~t?!lt an l ~ ermo3et coln~onent ac-co~ g to ~h~ ,c~llow;n~ r-rocedure. l`he lIydroc~Jrborl ~olymer ~as nreoclrel l)y dis .)lvin~ .'5 \~ r~t )art of ~3R rub~er contain-~ Ing ~.75 wei?~t nart~ t~lc ar!(l S'~7~5 ~veis;ht r)arts of the buta-; diene-acry]onitriIe cooolYmer descLi~)e(l ;n ~Y~aI-~r)lè IV in about 350 narts by wei~rr~It Or ~etlIy~ et'~yl ~eton~, 31 wei~rht ~art~ of methyl isobutyl I.etone and 1~3 ~arts of n-butyl acetate Nith agitat~on. To the resultant ;olution were added with mixing about 22.~ weight parts o~ the n!lenolic resin described in Ex-ample IV dissolved in met~lanol (55 S~ercent solids) and then about 1.28 weight parts of tetramethylthiuram disulfide and 1.2 weight parts of 4,4~-dithiodimor~holine ~ere added to the solu-bilized hydrocarbon polymer. A glass-reinforced e~oxy resin laminate (5 inches square and 1/4 inch thick) as coated on both sides with the hydrocarbon polymer ~y roller coating. The coated laminate was thereafter dried at 25 C. for about 120 minvtes to remove solvent to form a polymer coat;ng thickness of about 1.5 mils. The hydrocarbon ~olymer coating was then par-tially cured by heating the coated laminate at 150 C. for about 60 minutes.
The resultant substrate com~rising the partially cured hydrocarbon polymer coated over the reinforcing core of the glass reinforced epoxy resin panel was then metaliz~d according to the procedure of E~ample IV to ultimately produce a copper coating about 0.1 mil. thickness. The copper electro~lating was then stor~ped and the copper plated substrate was heated to complete curing of the hydrocarbon polymer at 107 C. for 35 minutes, 107 to 121 C. for 15 minutes, 121 C. for 45 minutes, 121 C.
to 135 c. for 20 minutes and 135 c. for 60 minutes. There-after, the electroplating was continued to increase the copper coating to about 1 mil~ thickness to form the desired circuit . , ' ~ 0~7;~
boa~d ol` a met~l coller~ hstr~lte. Tn the bo~rd so nroduced, t`rre C ~ l'C~li t i.3 rt'r-rC ~;ente(.l l)y t'rle ;net-~l c~a~-inir~ the cir-cult is to be of ~I r~lrticll1ar ~le;iyrl, then c~nventiona] masking ~rocedlir3c. ~ revi(~ ly disc~ls~e~ may be ~ )loyed tr~ r~roduce the ~er1ir~ iesl~rl.
The ?0~ ~eel strenrth (!r the ci.~cuit bon~d was evalu-ated accordin~ t~ tne r-eoc~-lure Or ~xamr~le IV to ~ive a val.ue Or : about ,~ ounds r?er lnch. ~.lhe circuit boa-d was also eval.uated ror dip solder resistance accordinr; to the nrocedure of ~xamn].e II and reslllts in excess of 20 seconrl3 were obtained.
~xamnle VIII
A circuit board was r,repared util.i~ing a hydrocarbon ; polymer of an elastomer com~onent and a thermoset coml~onent ac-cordi1-~g to the followin~ procedure. The hydrocarbon polymer was prepared by dissolving 5i~ weight parts Or NBR rubber contain-ing 5 weight parts talc and 50 weight parts of the butadiene-acrylonitril.e copolymer described in Example IV in about 270 parts by weight of methyl ethyl ketone with agitation. To the . resultant solution were added with mixing about 91 ~eight parts of the phenolic resin described in Ev.am?le IV dissolved in methanol (55 percent solids). About 0.73 weight parts of tetra-` methylthiuram disulfide and 0.73 weight parts of 4,41-dithio-dimorpholine were mixed with 1~ weight parts of methyl isobutyl ketone and 59 weight parts of n-butyl acetate and the resulting mixture added to the solubilized hydrocarbon polymer. A glass-reinforced epoxy resin panel (5 inches square and 1/4 inch ~ thick) was coated on both sides with the hydrocarbon polymer by : roller coating. The coated laminate was thereafter dried at 25 C. for about 60 minutes to remove solvent to form a polymer coating thickness of about 1.5 mils. The hydrocarbon polymer coating was then partially cured by heating the coated laminate at 150 C. for 60 minutes.
0~ ~7 ~
at ~ st,~ate co s,r;sirl,~ t,`ae !~asti~'!ly cured r~ 'I,y~!t,r ~ ,t, ! (jv~ f`3 cil~lr c~r~ Or t'~ ~,lass rl~;`o~ce(3 er~oxy rt~ ina~ tren Irlet~lize~' ~ccordin~ to the r)~oc~ur~ of' ~xrlio'le T~ to liltimatel,l i,roducc ~ col)per cc~t,-irlr~ of al~out ~.l mi'l. tllicknel,s. T~ co,-ner electron]~tlrlg was ~`, t~len sto)oed ~Inl the c~-r)l~er r~ t~(3 ~u~str.~tc ~ . he te(~ at 150~
C. ror 6~ rn;nute; to (~ornolete curirl,~ of the hydroc~rbon nolymer.
There~t`ter~ t~e electr(~rl~tlnir ~as contLnued to Lnc~eAse the co~-ner coating to fl!out 1 mll. ttlicklle(-,s to rorm t~le de~-lred circu,it board of a met~)l coated sllbstrate. In the board 90 ~-roduc~d, -the circuit is represente~1 by the metnl coat;in~r. Ir the circuit is to be of a particul,ar desi(~n, then conventional mnsking proce-dures as previously discussed may be en~rlo~ed to produce the desir~,d design.
The 90 peel strengtl o~ the circuit boa~d was evalu-ated according~ to the procedure of Exam~le IV to give a value of about 12 to l~ pounds ~er inch. The circuit board was also evaluated for di~ solder resistance according to the ~rocedure of Example II and results in excess of l0 to 20 seconds were obtained.
Exarnple IX
A circuit board was prePared utilizing a hydrocarbon polymer of an elastomer component and a thermoset component ac-cording to the following procedure. The hydrocarbon polymer was prepared by dissolving 96.?5 we;ght parts of NBR rubber contain-ing 8.75 weight parts talc and 87.5 weic,ht parts of the buta-' diene-acrylonitrile copolymer described in Example IV in about 35Q parts by weight of methyl ethyl ketone with agitation. To , the resultant solution were added with mixing about 22.8 weight parts of the phenolic resin described in ~xample IV dissolved in methanol t55 percent solids~. About 1.28 weight parts of tetra-methylthiuram dis-ulfide and 1.28 weight parts of l~,4l-dithiodi-morpholine were mixed with 31 weight parts of methyl isobutyl -~3~
' '' ' 1~4'~7;3~
e ~nd l~`3 :t~ ,t ~ t~ ' n~ ty' c,ce-t~lt~- ln(' th~ res-lltinr .-~ixtl,re c~ t~ t'.~. ;;olu~ l `rl~J(lrocer~ n ~ol~Jmer. A nheno--` C t r` e .l t, ~ r) ~ r ~ l i na t, ~ ` '; s~ r~ It~ irl~h. t~l:ick) was cocl~e(t on t)oth ;:i~le: wit~l t;hc ~iroc~r~on r)ol~Jmer- by rol.lrr COatirl~. Th~ COfite'l F~ rlnt,(,' `N.~`: t~-orci~`t~r (3rie~ to rernove ;~
vent to ~`orln 1 r~o~lvmer~ ('otJ~ `' t~li.Ckrit`..'~ ot` nt)out 1.~l-) m:ils.
The r~.ydrocarborl r1olymer coati.r~ ;a~ th~?n r)a~tially cure(l by heating the co~lte~d l.ami.na~e ~It ~5C` C. f`or ()0 :n:inutes.
The re:lll-tc~nt substr-~1te coi!~-rising the -oartially cured hydrocarbon ~lol~fmer coate(1 over the relnro,ci-~g coL-e of tne ~neno]ic treatèd l)ar)er laminate was then metallzed according to : the procedllre Or E.xample IV to ultillately produce a conr)er coat-ing about 0.1 mil. thickness. The copper electroplating was then stonped and the co~per plated substrate was heated at 150 C. for ~0 minutes to complete curing of the hydrocarbon polymer.
Thereafter, the electroDlating was continued to increase the ~`` co~per coating to about 1 mil. thickness to form the desl.red ~ circuit board of a metal coated substrate. In the board so produced, the circuit is represented by the metal coating. If the circuit is to be of a particular design, then conventional ` ~ masking procedures as previously discussed ma~y be employed to . produce the desired design.
The 90 peel strength of the circuit board was evalu-.. ated according to the procedure of Exam~le IV to give a value of from 14 to 17 pounds ~er inch. The circuit board was also evaluated for dip solder resistance according to the procedure Or Example II and results in excess of .~0 seconds were obtained.
_24 .. ~
the borld s~; ~)r-oiu(~ed ; h;!~hly resistant to del.am;nation or ser-ar.tion ~f th~ m~ .~l. coat:ini~ rrom t~-~e hyclroc~rbon ~olyrrler, . n~rticu~ y under al)r)l:Lcs-t;:Lon of he<ll. .,uGh as occllrs dur.l.ng solderl.ng and thus a].lows em~loyrnerlt o~ addlti~e !)lat;ng tech-niques for circuit board !nanuf`acture.
The printed ci.r(~u:it ~)oard of this invent;.on com~rises essentially, a sllbstr~.lte charnct;erized by a surrace Or a hydro-carbon nol.ymer hased, in ~)u~t, u~on a conjugated diene polymer and a mets] coating dirt-ctl.y bonded hy al(iitive Dlating to at . 10 least a portion of the hylrocarbon ~olymer surrace. The prlnted circuit board is in the form com~!only utili7ed i.n the industry and can have one or more apertures extending part or all of the distance between generally oorposite, external surfaces of the , .
. substrate. The desired polymeric hydrocarbon is ~resent on at least one of the surfaces of the board substrate and advantageous- .
ly on all surraces associated with the formation of circuit ele-. ments.
~; Commonly, the entire substrate is composed of the hydro-carbon polymer and advantageously has reinforcing or core members - 20 such as layers of paper, glass fillers of glass or other rela-: tively inert materlals contained within the hydrocarbon polymer.
While in some instances these reinforcing members are pretreated to improve bonding with the hydrocarbon polymer, as illustrated by the pretreatment of paper with a phenol-formaldehyde resin, it ` is preferred according to this invention to incorporate such thermosetting material directly into the hydrocarbon polymer . prior to application of the hydrocarbon polymer, preferably as a coating, to the reinforcing core material. Accordingly, as em-ployed herein, the hydrocarbon polymer, forming at least the sur-face of the substrate, is composed of a thermosetting component in addition to the elastomeric component based upon the conju-gated diene polymer. Thus, this hydrocarbon polymer composed of . the thermosetting and eiastomeric components can be readily . --3--iO~'~7;~4 !i.7-ci'ly, . ~ ,0 V'.''~ r~ rl! ~{)l~e .llter~ uco c~ n()1-:or~l~ v(;~ tre~lte~ n.~ er, ntlenol:i.cs~
e~oxies, I)olye~;t.e~ , o ccr.Ar;.c. to ."olm rein:force~ substr~tes parti.clll.ar]~ sui.t;~ le !'or m(~tc~ inr by ~Id(~3t~ve ~)lati.n~- tech-niques invol.vin~ :ir~ an e~ectroless metl~ der-os;tion.
~ioreoverJ those re.i.r~i'olce(~ substrnt.e~ coatcd with the hydro-carbon ~olymer ultLIn.ale]y resll!.t in the r~roducti()n Or r)r.intcd circuit boards havin~r exce'l.lent el.ectrical. ~ro~erties and hi~h resistance to both delamination of tl~e hy~rocarbon pol.ymer fror the reinforcing core and delamination of the me-tal coati.ng from the hydrocarbon nolymer.
The elnstomeric component Or the hydrocarbon ~olyme}
is essentially coml~osed oi' a conjusated diene polymer based u~on diene monomers having from 4 to 6 carbon atoms such as bu-tadiene or isoprene. Such diene polymers may be em~loyed solely as homopolymers of such diene monomers, for example, as polybuta-diene or polyisoprene, or may be employed in combination or poly-merized with various other unsaturated polymerizable monomers including, for example, acry]onitrile or styrene or various com-binations thereof. Preferably, the elastomeric component is a copolymer or terpolymer of these various polymerizable monomers, and suitable copolymer examples include copolymers of butadiene-acrylonitrile, butadiene-styrene, iso~rene-styrene, or isoprene-' acrylonitrile, and suitable examples of terPolymers include iso-prene-acrylonitrile-styrene or butadiene-acrylonitrile-styrene.
:~:. Of these various polymers, however, a copolymer or butadiene-acrylonitrile is particularly preferred as the elastomeric com-: ponent of the hydrocarbon polymer used in the formation of the substrate according to this invention.
~he polymers of the above general class which can be utilized according to this invention as the elastomer or elas-tomeric component of the hydrocarbon polymer, generally include those products available commercially which are classified as ~4-104273~
cld.t(j~ler.;; ;~ich ar~ s~ on 1 ~liene ~n(,no.~er G~ r~om a~,out 4 to ~Iboul 6 c<lr~)on at~m~; and w~l;.ch are re~ y solvent 301u-bilized fol coatlrlg anr?li(~tJi.orls. ~`or examl)le~ ho~lopolymers sllch as nolybutcl(l;.ene cln ;nclude the com~er-cially avail.a~le ~R syn-thetic rubher~. Si.r~ rly, th~ ~ol~tso~rene can be eith~r a nat-ur~ or synthetic rub~.!er av~1lal-le under such trade names as `JR~or IR~ubbers. Th.e connlymerc em~loyable, such as butadiene-acry-].oni.trlle cor~olymer, inc:lude those co~ol~Jmers av~i]ab].e as ~R~
rubbers or nitrile rub~ers which generally have an acrylonitrile : 10 content of from about 1~ to 50 weight percent ACI'yl on:itrile and are ty~ical3y prepared by catalytic emulsion polymerization. A
parti.cularly prererred butadiene-acrJlonitrile co~olymer, for ex-ample, has an ~crylonitrile content o~ ~rom about 25 to 40 weight percent, a specific gravity of 0.9~ and a .~looney plasticity of 68 to ~5.
~..
Suitable copolymers of butadiene-styrene for employment ~ as the elastomeric component are available as the SBR, Buna-S or GR-S~synthetic rubbers of commerce, which are typical]y a poly-merization product of about 3 parts butadiene and a~out 1 part 20 styrene. Other copolymers of butadiene-styrene which are also particularly suitable for use as the elastomeric component of the hydrocarbon polymer include both liquid and solid forms of '. random, graft, or block copolymers, and can include those poly-. mers having polar end groups such as hydroxy terminated or car-boxy terminated Polymers. The liquid forms of these copolymers are particularly advantageous because when cornbined with a liq-uid or solvent solubilized thermosetting component, the resulting liqui.d hydrocarbon polymer is readily applied to the reinforcing core material utilizing conventional coating techniques. In general, liquid po~ymers of this type have a number average molecular weight of about 500 to 5, ooo and a styrene content of about O to 50 mole percent and are characterized by a vinyl or ~r~ 5-~ .
104Z73~
! J~ t~ rl OI~J`~)OIIt L~ nerCer1t OL' the ~;otal llnS~tl.lr~l t,iOn. ~ e COr`l`~'S~Ond; n~r '301 i(~ CO~O1YrtIer9 COm~r1~3e hiD;her molec~ r ~iie~i~rt oro(lucts, or ~rti.a~.ly c~oss-li.nkec3 ~roduct;, or block co~o1ymers as ~ene~ully i~ str~te~ in [~nited States Patent; ~,To. 3,~(~-;,76~ ti.ll another su;table co~olymer of but~cilerle-st~rene is a co~o]-JIner which has a vinyl or 1,~. unsatl1r~lt;t)n helow 5(~ ercent. Ynrt:iclllar nolymers of th;s class are il]ustrated in United States ~atent No. 3,265,765 as block co~olymers o~ a n~n-el.astomeric ~o]ymer b~ock and an elastomeric ~olymer block, for example, a styrene ~olymer block and a butadiene polymer block. Advantageously, the~e ~olymers are high molecular weight block co~olymers with a general formul.a . of A-B, A-B-A, A-B-A-B-A, and the like, wherein "A" is a non-elastomeric polymer having an average mol.ecular weight of 2,0no to 100,000 and a glass transition temperature above about Z5 C.
The elastomeric polymer block "Bl' is characterized as having an average molecular we;ght between about 2~,000 to 1,000,000 and a glass transition temperature below about 10 C. Normally, these block copolymers are linear and contain less than about 50 weigh-t `. 20 percent, but at least above about 10 weight percent of the sty-;~ rene polymer, and more than 50 weight percent of the butadiene .:- polymer.
. The copolymer of butadiene-styrene when used as the elastomeric comp~nent of the hydrocarbon polymer may also com-prise various blends of different specific butadiene-styrene co-polymers. For example~ a blend of the above described butadiene-styrene co~olymers where one copolymer has a high vinyl or 1,2 olefinic unsaturation above about 50 percent, and the other co-polymer below 50 percent, i~ particularly sui.table as the elas-tomeric component of the hydrocarbon polymer.
When terpolymers are desired as the elastomeric compo-nent of the hydrocarbon polymer, they may generally be obtained commercially; for example, a terpolymer of butadiene-acryloni-' :' ' , . .:
,. ,:
~ ~04'~73~
trlIe-~t~;rene is rea(Ii.l;, oht~in~'-)le as 1~ co~merc:L~Il h~ resins, w~l~h normtllIy cont~lln ~ut~dlerl w;t~ln t;he rnn~e nr f`rom ahout ', to l!O ~eirrht ~)eYc~nt acr~lolI-t.trlIe wit~-lin the r~ln~le o~ from :: a~o~l1; '~, to 3() ~/e;~ht l~erc~nt, t~n~ ~:tyrene within the r-ange of fron, ahout 3~ to ~ e;~ht ~rcent;. Y~riI.e not techni~a~ly a terr~olymer, l~hysl.c~l. a(l!n;.tllres ot` butarliene-acrylonitrile-sty-rene may also be emnl-)ye(l, f`or ~xam~le, an aclmixture of a co-. ~ol.rmer of butadiene-st~rene resin ~nd a co~ol~mer of butadiene-: acryl.onitrile. The ter~olymer3 of iso~rene, acrylonitrile and styrene are a].so ~vai:lahl.e commercial.1.y, an~ tyoically comprise ~ a ter~o~ymer containi~g isoprene within the ran~e from ahout 5 ~ to l~o wei~ht nercent; acrylonltrile within the range of from about 5 to 30 weight percent; and styrene within the ran~e of from about 30 to 90 weight percent.
.
The thermoset or thermosetting comP~nent employed to-gether with the elastomer or elastomeric component to rorm the hy-drocarbon polymer can generally include any of those resinous ma-` terials conventionally employed for electrical ap~lication which . form infusible, thermoset resins under appropriate curing condi-tions and which are compatible with the elastomeric componentO
: Suitable thermosets include the aminoplasts, for exam~le, the I thermosetting resins prepared by the polycondensation of formal-dehyde with an aliphatic alcohol, for example, butanol, and a ni-. trogen compound such as urea or a tria7.ine such as melamine. Oth-er thermosetting resins which may also be successfully employed include epoxy resins or ~henolic resins prepared by the conven-` tional reaction of phenols with aldehydes such as formaldehyde, acetaldehyde, or furfuryl alcohol, which are heat curable to an infusible thermoset. Of the various thermosets which may be em-nloyed as the thermosetting component, however, the phenolics ,~
are particularly preferred, and especial].y the pheno].-formaldehyde ~-~: reaction products. A tynical exam~le of a preferred phenol-formaldehyde resin, com~rises the reaction product of about 1 mol ~ of phenol and from about LO to about 105 mols of formaldehyde with :. -7~
~04'Z734 a more 1imite-1 r~ln~e Or f'rom ~ t 1.~ to ~?~nut ~.3 mols of - rorm~llde;ly(iie ferle~ ly beir,r ~ref'crred.
In ~re!~)ri.tl- t;he `~y(~roc~lrbnn ~olymer accor(3:ini- to t'~is invention ror anr~iccltl.nrl, ~artlcula~ a3 a coat;.np to the re-inforci.n~r corn ma-teri~1 Or the substr~te, for ex~lrn~].e, a phen-olic treatecl paper 1amirlate, the elast()mer~c com~onent )nd the thermosetti.ng co~TIr~onent can be ~dmixed in wl(1el~y varie(3 r)ror)or-tions. Tlle ~artic?.llar r~ro~-ortion r~osen i.n any Lnstance wi~ be a runction Or the s-necif';.c elastomer and thermoset em~loyecl, as . 10 wel~ as the ~articlllar electrical or nhysica] ~roperties ulti-mate]y desired fcr the printed circuit board. Tynicall-J~ how-ever, the pro~ortion of the elastomer to the thermoset in the hydrocarbon polymer can range from about 15 weight parts of elas-tomer to 1 weight ~art thermoset, to 1 weight part elastomer to 2 weight parts of thermoset. Generally, however, & more limited '~ proportion is usua]ly pref'erred, partieularly to maximize the bondi.ng of the hydrocarbon polymer to the reinforcing eore and especially to achieve greater adhesion of the metal coating to the hydroearbon polymer. For example, when nreparing a partieu-'~. 20 larly desirable hydrocarbon polymer according to this invention ~ where the elastomeric component comprises a butadiene-aeryloni-: ~. trile copolymer and the thermoset component comnrises a phenolie ' resin of phenol-formaldehyde, the proportinn of the elastomer to the thermoset is~referably maintained within the range of `; . from about 1 to 10 weight parts elastomer to about 1 weight ~art thermoset with a range of from about 6 to 9 weight parts elas-tomer per 1 weight part of the thermoset being especially pre-'~ ferred particularly to maximize bonding of the metal coating to the hydroearbon pol.ymer.
The hydrocarbon polymer ean contain other materials in addition to the elastomeric and thermosetting components and sueh materials typically include curing agents, rubber accelerators, anti-tack components and cross-linking agents. The euring agents ~0~ 3~
UC'Cel~'r`l~tOr'' ~I.`'? e~r~ v~rl ro cu-~ th~ elasto~eric or t'-~rrno~ ttirl~ ~o!-~ons~lt: to ~ o~ ri~-id st~te. '~oY~ever, be-ccl~lse the tl-le-m(~;~t;tirl c(jmronent e~ ved accord-lng to this ln-vention is ~ner.~ eat ctlru~)le, such curin~r or accel~r~t1ng agent,s arc~ t~rnicnll~ us~(l sol~ ror tht~ elasto~eric co~ onent.
L'he eArticlllar cllring~ or ac~elerat;inr~ l~ent er~r)]oye(l can be widely varied anc~ r!ost o," t;he cu~in~ .lnd accclel,tlng a~ronts con-ventionall y emnl o,~ed ~or the curin~:, of ru~ ery elas-tomers May be $ ' suitably utilized. Gener~llly, the ~articular curing ac~-ent se-lected will de~en~l ur~on the elastomer-;c comr~onent em~loyed and ; the tem~erature range or series of temnerature ran~es selected to effect the cure. Suit~ble curing agents include or~anic ~er-oxides such as those llsted in irk-Othmer, Encyclopedia Or Chemical Techno]o~y, Vol. 11~ and particularly those with activa-tion temperatures of 30 to 50~ C. or sulf'ur containing vulcan-izers which are comr~lonly employed to harden natural or synthetic elastomers. Irradiation techni~ues conventionally em~loyed to initiate free radical formations may also be employed alone or in combination with curing agents to effect the desired curing.
The quantity of curing agent or accelerator emI~]oyed in the hydrocarbon polymer may vary but typically those quantities con-ventionally employed in the curing of rubbery e]astomers may be satisfactorily used. For example, when utilizing curing agents such as sulfur-containing vulcanizers such as te-tramethylthiuram disulfide or 4-4 ~ -dithiodimorpholine, suitab'le amounts range ~' from about 1 to 10 weight parts of vulcanizer per hundred weight ` parts of elastomer.
The cross-linking agents which may be suitably added to the hydrocarbon polymers to increase the thermoset character-istics can include thosc monomers conventionally employed ascross-linking multifunctiona] monorners. F`or example, poly-functional isocyanates illustrated by the addition product formed from the reaction of toluene diisocyanate and "
_9_ ~, :
10~ 34 trimethylolpropane may suitably be employed. The anti-tack components are added to provide easier mechanical handling of the elastomer during preparation of the hydrocarbon polymer and especially to provide anti-blocking properties to the hydro-carbon polymer prior and subsequent to metalization. Particu-larly suitable anti-tack components include mica, soapstone, alkaline-earth silicates such as magnesium silicate and talc.
In preparing the circuit board according to this in-vention, several different preparational procedures may be em-ployed. For example, where the hydrocarbon polymer is employedsolely as the substrate without any reinforcing core material, the hydrocarbon polymer may simply be cured or partially cured to a relatively rigid state and thereafter metalized to add the desired metal coating. However, when the preferred boards are prepared with a substrate comprising a reinforcing core coated ~` with the hydrocarbon polymer, the basic procedure involves ap-plying the hydrocarbon polymer as a coating to the core material, curing or partially curing the hydrocarbon polymer, metalizing ` ` such polymer and thereafter completing, if necessary, the curing of the hydrocarbon polymer so as to effectively bond the metal coating to the hydrocarbon polymer as well as to effectively bond the reinforcing core material to the hydrocarbon polymer.
In preparing the hydrocarbon polymer for application as a coating, the selected elastomeric component and thermosetting component may simply be physically admixed and then applied to the reinforcing core materials utilizing conventional coating techniques. Such reinforcing core materials can include any of the material conventionally employed in printed circuit boards, including, for example, phenolic resins, epoxies, and polyesters which may contain further reinforcing materials such as glass in fiber or mat form, cotton, asbestos, or cellulose, for example, a laminate of phenolic treated paper. Preferably, the hydrocar-bon polymer is applied to the reinforcing core as a coating in ,AI -1 O-" . :
~04Z7391 1 L~ l f`or~m I or~ c~ n. (~ ner~ r,~ t ~ on the l-r~t~ clll .lr ~la ,t;~r~-e~ ~in~ tlfr-losot co~r~)nents emr~]~-yerl as well as t;`~e ~t:i.cular rclrl~orcirl~ co~c material llt;l;zed, ttle therno,ett~nlr l3nd el.~st~-~rne-r;.c co-nnonents wi.t~in the hydroc-lrbon no]yr1le~ e~cln be ~o'~ .e~ n v~lr;~ a~lueous or oY~ nic colven-ts either be~ore or a~'ter s~lml~ lch o-'`'AniC` solvent can in-clu e, for e~nmr-le, l;etones, al(1eh~de., or est;el-s ~`nich `nave vo~atilities sui.tr~ e f`or coat;n~ at el.:tive].y low tem~eratures.
The nartieular sol.vent SyS t,ent emnloyed ror the nylrocarbon poly-mer can vary, bllt general.ly a comhination of dirferent sol.vents are selected so as -to ~rovide suitable disso1.ving or susnending I
of the elastomer and thermosetting com~onent; a desirable drying time during the coa-ting of the reinforcing core; and a solubiliz-ing attack or dissolvin~-g Or the reinforcing eore material to pro-f vide ~hysical anchorinr of the hydrocarbon ~olymer to the corematerial. For example, when em~loyinr a hylrocarbon polymer formed from an elastomer such as a butadiene-acrr]-onitrile co-: ~olymer and a thermoset such as a phenol-formaldehyde resin, a suitable solvent system comprises an admixture of an alkanol such as methanol, ketones such as methy].-isobutyl ketone and methyl-ethyl ketone, and an ester sueh as n-butyl aeetate.
, With the hydroearbon polymer solubilized in liquid : form, it can be readily applied to the reinforcing core material utilizlng such eonventional eoating teehniques as roller, doctor blade, or curtain coatin~. Thereafter~ the polymer is dried to remove the volatil.e solvents, leaving the hydrocarbon polymer on : the eore ready for curing and metalizing by additive plating.
The hydroearbon polymer eoating so annlied to the eured material.
ean vary in thiekness with the partieular thiekness or amount of 30 polymer in any instanee being dependent u~on such variables as the partieular hydrocarbon ~olymer employed, the reinforcing core material utilized as well. as the physical or eleetrical pro~erties ultimately desired for the final eireuit boar~
1042739, ~ `V~r~ fr~ ~`'n~ clr~)orl~o~lym~r ~r a ~ t~ n~-~c~ nitrl.l.~ co~ol~,~rler as the elasto~neric comnonent and a ~)tle~ol-forrn~ h~lde ~e<;;n ~s the ti~erlnosettin comr)onent, t~le `~y(lrocclr~-on T~o~yrrler i.s a~ ;e-l to the reinforcing core in an amount ;ufriclellt; to ~l~o~luce s coating ufte:r sol.vent ren!oval and after either rllll or r)art:ial cllr~.n~r, hAvin~; a dry t~ickness ran~rin~r from a~)ou'; 0.] to .5 In;ls with fro~ 0 to 1.75 rnils usual]y beinr nreft~rre(~ i.n ~.lo;t instances.
~ fter the y,-lroccr'.o~ olymcr :i: a~olie(l to the re-n inforcin~ core and dricd to remove the solvents, the nolymer is cured prior to metnli~atlon. This curing can be cGnducted so as to completely cure the hydrocarbon polymer rrior to the metaliza-tion or conducted so as to effect only a ~artial cure prior to metalization with the remaining cure being completed subse~luent to the metali.zati.on. Generally, the Preferred procedure, ~ar-ticul&rly to maximize bonding between the metal coating and - hydrocarbon polymer, involves conducting the cure in at least two steps with a partial cure being effected beforc metaliza-tion and the cure being completed subsequent to metalization or partial metalization. The particular temperature range selected to effect the cure wil] vary depending upon the particular hy-drocarbon polymer and especiall.y the elastomeric component em-ployed, the number of heat curing steps, and the particular cur-ing agent, if any, employed within the hydrocarbon polymer. : -Usually, however, a temperature ranging from about 80 C. to . about 190 C. may be employed for any heat curing .~tep with a : more limited range of from about 100 C. to 160 C. generally being preferred. The duration of the cure is a function of the :~
~articular hydrocarbon ~olymer, its thickness, the number of curing steps em~oyed, and the particular curing temperature Ty~ically, however, when the curing is effected in one or two heating steps with ternperatures ranging from about 100 C. to ;
-, 104273~
~()c~,., tile t~to-l ~ nl t~ o~ t~le c~ o e ~3rt t ~)f~er - met~ ing m~ly r lnl e fro~n ().!,~ to ~, ~lollrs.
~ ft~r ti~c IJ~r~ r~on ~ol.ymer i cured or nartial~y cllred, t~lç metal c~ting ~s ~I-sr)l:;ed by metr,~i~.ing th~ ~ubstrate util;zin~; ad(iitiv~ r-~ating tec'-ln;clles. E~asicall~, thi~. lr)volve3 first etcl:lingr and s(r~sLtiz!.n;r the hydrocclrbon nolymer surface, electroles.~ly de~)o3i.t:ing the met~l. coatin~ followed, lr desire(i, by electrol.ytlc de~o~it.ion of ai'ditionl1 met;il. A~vantageou~ly, the etching is c~lrr:ied out wlth strong, acids such as sul:furic or phos~ho:ri( with su~.)stances such as sodium dichromate. The severity of the etch is somewhat dependent on the extent of cure of the nydroc~rbon polymeric surface of the substrate. The sen-sitizing stel~ is carried out according to conventional practice - with reducing agents such as stannous chloride followed by pal-ladium chlori~e or other catal-yst. It is understood that partial masking of the hydrocarbon ~olymer surface can be carried out before the etching or sensitizing step to limit the modification of the polymer surface where only insulating and not circuit ~: properties are required.
2~ A metal coating is then applied to the sensitized sur-.~ face by electroless deposition techniques. This usually results . in a thin coating with a thickness and continuity sufficient to conduct electricity with the thickness ranging up to about 1 `. mil which minimizes subse~,uent metal removal during the formation of circuit elementsO The metal applied in the electroless depo-sition is conventionally and conveniently nickel, copper, cobalt, gold or various alloys thereof, or other metal selected both for ease of application and performance in the final circuit board.
Usually, the metal is a transition metal with an atomic number of about 21 to 79 such as nickel, copper, gold, silver, cobalt, and the like. Preferably, the metal is nickel or co~per.
When tne metal coating is applied by electroless depo-sition over the entire hydrocarbon surface, the metal coating ~oa~Z73~
~ er t~ ft~ )e ~ ti.l!ly ~-kc~ i the r~r!!1;nir~r~lr~
e~ctror~lat~ t;o !~i ovi~l~ a ~';.rl~ll a~l i;tional met.i~ Jer r~ cir-C~l;t ouro~-~es. Tbe met~ll s~lect~-l ror this ad~]it.on~il metal er rn~y a~so i,e any ~1~ tht' a')OV~` grOUn 0I transLt;orl metals r~d ~)r~ferl~l)ly i coo~t, silv~r ~r lol~i. rl`he mask and the r)or-tion~ of tlle electroless m(t~ yer underl~ing the mask i; then removed by kno~n chernlcul etch;ng tt)chniques lelv;n~ the metal coating on t;he hy(lrocsrhon su~face o~ the boar(i in the desired circuit confi~llrrition.
]0 The fo1lowing exam~?les illustrate some of the embodi-ments of this invention. It is to be undeI;tood that these are for illustrati~e purooses on~y and do not purport to be wholly definitive to conditiors or sco~e.
~xample I
A hydrocarbon substrate was prepared by coating an etched, thermoset-hydrocarbon laminate with a toluene solution containing about 5 weight percent of a styrene-butadiene block copolymer based on approximately 23-25 weight percent styrene.
The solution also contained a~proximately 6 pph of benzoyl per-oxide to provide later cure.
The coated ~roduct was baked at about lOQ C. for ap-proximately 4~ minutes to provide solvent removal and ~artial cure of the hydrocarbon coating. The board was then treated with an etchant composed of about 69 weight percent of 96% sul-furic acid, 25 wei~ht percent of ~5% phosphoric acid, 2 weight percent of sodium dichromate (dihydrate) and about 5. o weight `~
percent water. Treatment was carried out at about 55 c. for about 1-2 minutes. After being rinsed, the board was treated ; with a solution of 10 weight percent of stannous chloride, rinsed ; 30 with water, and immersed in a HCl solution of palladium chloride (about lg./l.).
A thin nicke] coating was a~plied to the rinsed, sen-sitized surface using a nickel chloride solution with a ~04~73~
`r!y~ o~ te r(`d;,Cirli- '3,'~('tl~ tle t~li(`l'llCS.; ':,'.'a sufiicient tc, ren(i~r l.ae sllri- c~ conùllctlv~ to ~n ~ trical curr~nt.
~ u~se(!l~rltly~ co);~r l,:as el~ctr~lat~d to a thickn~ss of a~ roxir~at~ly 1 in;l. r[`',c resllltant metal coatingr nl~te ~as then he~ted at a ,;)rox i:!lately l()o" c . ror a~)ou t; L~, minutt s to re-;rove water and cornt)l(-~tt t;`l~ curlng cycle.
A -)0 o~el strengt~l test wa~; c~r~ie~ out on a ~a~ple Or the metal coa-te~, the~rloset board using A ~ee] rate of ahout 2 inches r?er !~inute on one inch (~idt~ amples. Values of ',-6 `~ 10 lb~s. ~er inch were oLtained.
~xanl~le II
Additional sam~les of a metal coated board Nere pre-pared using the techniques o~ ~xam~le I. The coating solutions contained from 2 1/2 to 1() weight percent o~ the butadiene-sty-rene ~)o]ymer in toluene with the curing ag,ent bein~ in a concen-tration Or about 6 pph. Samples of the dip coated laminate after being coated with e]ectroless metal were then plated with copper to varying thicknesses. The resultant sam~le~ were then sub-jected to dip-solder resistance tests at 500 F. in which the sample was im~ersed in solder and the degree of blistering and destruction of the metal bond to the hydrocarbon surface was de-termined. In the test, it -~,Jas found that samples prepared from polymer concentrations of 2 1/2 to 5 weight percent produced products which passed the dip-solder test for at least 60 seconds~
In these tests, the thickness of copper ~late on the various samples that passed the 60 second dip-solder test, ranged ~rom o.o56 mils to 0.15 mils.
Example III
A hydrocarbon laminate was fabricated from layers of phenol-formaldehyde treated paper which had been saturated with a graft copolymer of po]yautadiene and styrene. The copolymer was based on a butaoiene content of approximately 60 mole per-cent, a 1,2 unsaturation in the polybutadiene of about 60-70 104'~734 ~ rcel!t, ~In~i corlt~,ine(i erl or~J~Ilc l~erlY~ cetsly,l. f~aoric~ltll,rl ()f t''!e l~lr~irlat,~ W~l'; c~ilr~ie~ olt ~ith cur~in~ of tle eolymerlc ~-iy-~-~rocl7borl t- r~rovl(le ~1 t~lerilo-~t; llmlna~.
rrhe 1 `1~1;n11~;f` `iltl~; Cleclne'~ wlth arl all~ul;n~- solution and t~en t;rca~.ed wlt~ r-, e~ nt ,oluti~n cont,;;ning n~-ollt ~ Je:ight l~ercènt o~ ~)f~ clC;d~ G'' wei!rht ~crcent of '15,~ nhos!)horic acid, 4 weigh-t r~ercent o~ so~l;urn dichr~,mate (diil~dr~e) and weight ~-ercent of ~ tr. Treatment wns carried out at a;~out ]75 F. with vigoroil-l agit;ation for about l5-20 minutes. The board was then rinse(i, imrnersed in a 5,~ Na~E solution at about 110 F. for n few minutes, rinsed again, and then se~sitiæed in the manner descrihed in Exam-c)le I.
After being sensitized, the board was rinsed and c~ tcd with a thin layer of nickel applied from the solution described in Example I. An electroplated coating of copper was then a~-plied and the resultant board was baked at about 200 F. for about 4~ minute~.
A 90 peel test was carried out on a sample of the board. Values of 3-4 lbs. per inch were obtained as measured at the rate of 2 inches ~er minute.
Example IV
A circuit board was prepared utilizing a hydrocarbon polymer with an elastomer component and a thermoset component according to the following procedure. The hydrocarbon polymer ~; was prepared by dissolving 96.25 weight parts of NBR rubber con-taining about ~.75 weight parts talc and about ~7.5 weight ~arts of a butadiene-acrylonitrile copolymer having an acrylonitrile content of about 25 to 40 weight percent, a specific gravity of 0.99 and a Mooney ~lasticity of from 6~ to ~5 in about 725 weight parts of methyl ethy] ketone with agitation. To the resultant solution were added with mixing about 1?.5 weight parts of a phenolic resin comprising the reaction Product of 1 mol phenol and from about 1.2 to 1.3 mols formaldehyde .:`
`: :
`: :
~ 0~ 734 dissolved in P!.5 ~e~ht parts methyl ethyl ketone. The solubilized hy~rocarbon ro]ymer was transferred to a ~ip tank and a ~henolic treated l)a~er laminate (5 inches square and 1 inch th ck) was coated on both sides by immersion into the hy-drocarbon nolymer solution for a ~eriod Or about 10 minutes.
The coated laminate was thereafter dried at llQ C. for about 30 minutes to re~ove solvent. The hydrocarbon polymer coating was then cured by heating the coated laminate first at 110 C.
for 10 ~inutes, then from 110 C. to 150 c. for 30 minutes and finally at 150 c. for 30 minutes. The cured hydrocarbon polymer coating had a thickness of approximately 1. 5 mils.
The resultant substrate comprising the cured hydrocar-bon polymer coated over the reinforcing core of the r~henolic treated laminate was then metalized according to the following procedure. After detergent washing, the substrate was etched by treatment with an aqueous chromic solution for about 5 min-utes at about 25~ c. After removing from the etching solution and water rinsingJ the substrate was contacted with a 5 percent sodium hydroxide solution and then water rinsed. Thereafter, the substrate polymer surface was sensitized by treatment with aqueous stannous chloride solution (10 weight percent stannous chloride) followed by water washing after which the polymer sur-face was treated with an aqueous hydrochloric acid, palladium chloride solution (about 1 gram PdCl per leter). A nickel coat-ing was then applied to the sensitized hydrocarbon polymer sur-face of the substrate by treatment with a nickel chloride soluti;on in the presence of a reducing agent. The nickel coating so de-posited was sufficient to render the surface electrically con- -ductive. Thereafter, a copper coating of approximately 1 mil thickness was electroplated onto the nickel coating and the re-sultant copper coated substrate was cleaned and dried to obtain the desired circuit board of a metal coated substrate. In the board so produced, the circuit is represented by the m-atal 104'~;34 C D ~l t i r~ ~ ~ . I f t, ! l (~ c i ~ i t i ~ D ~' Df ~I D~Y~tic~ r~ d~sit~;n, t~len conv~nt,ion/~l m.~ o(~t,~ r~ a' ~r~/iously discllssed r,1ay be .
en~r)~o,~ to ~,r~J(I~ t~ ,irc~ dl~3i~n.
'I'he ctr~rl"t~l or ~ tl~,Lc,ll of the cop,)er met~l co~tin~, bonded to the ~Iydroc~lrt)or~ ~lymer ~va~ evaluate(~ by conducting a '~0 ~)eel strength t~st on the boar(3 accor(lingr to the f'ollowing rocedllre: A st;r;t~ of c~ ,roximately 1/2 inch wldth and an~roxi-mately l~ inches lon~ was cut on the sur~'ace of the substrate~
and a ta~ rormc~ at or~e end ot` the strir) by separating the me-t~1 coatinp; from the hydrocarbon polymer. While maintaining the substrate at 25 C., the tab WAS then pulled vertically upward at an angle Or 90 at ~1 rate of 2 inches per minute and the force required to separate the metal coating from the hydrocarbon polymer was measured as the 90 peel strength. A peel strength - Or aDproximately 20 lbs. per inch width of the strip was ob-'" tained for the substrate prepared according to the procedures of this Example.
Example V
A circuit board was prepared utilizing a hydrocarbon polymer with an elastomer component and a thermoset component ~;; according to the following procedure. The hydrocarbon polymer was prepared by dissolvingr 96.25 weight parts of NBR rubber con-taining 8.75 weight parts talc and 8705 weight parts Or the buta-diene-acrylonitrile copolymer as described in ExamDle IV in about 350 parts by weight of methyl ethyl ketone with agitation. To - the resultant solution were added with mixing about 22.8 weight parts of the phenolic resin described in Example IV dissolved in ' ~ methanol (55 percent solids). About 1.28 weight parts of tetra-'~ methylthiuram disulfide and 1.28 weight parts of l~,4~ dithio-d~morpholine were mixed with 31 weight parts Or methyl isobutyl ketone and 103 weight parts of n-butyl acetate and the resulting -~ mixture added to the solubilized hydrocarbon polymer. A glass-reinforced epoxy resin panel (5 inches square and l/4 inch thick) .' ~ .
104'~734 W;l'' C')~l t,~`'! 0'1 ~`lt,~ wlt,ll t'le ~J'~oc ~ on ~o1,1mer b~,r roller coat.Ln,;. llle co~ n1~ t~ ; t`~lc~r~ .t't~r ~.~r:ie~l cl t ?5 0 C . rOr ahout ~'`in;nut.~s t~ r~ ov~ .,o1v r-~t. The `.~;~rdrocar~on ro1,ymer ~,c.~in~ c~ tt~en n,~r~,ic?].ly curc(l ~y heat,i~, the colt~l 1.ami.nate at 15(~`) c. ror ~J(~ nlirllltc; t o foI m a eo] :,ymQr cost:int- hllv:lng; a th:icknes; oi ~ ~)out ~.5 mils.
The res~1.t~nt sub.t,~sa'G~ cornr)ri~,;.n~ the ~artia].1,y cured hydrocarbon no'lymcr coat,e(~ over the reinforcin~i; core Or t'ne g1ass reinforced e~oxy re~:in nanel wa~ then metal:l7.ed accordir-lg to the rrocedure o,t' ~xam~1e IV -to ultimately produce a co~)per coating about n.l mil. thickness. The conner electro~la-ting was then stopned and the copper plated substr2te was heated at 150 C0 for 60 minutes to comolete curing of the hydrocarbon r)olymer.
Thereafter, the electroplating ~.vas continued to increase the cop~er coating to about l mil. thicknes~ to form the desired circuit board of a metal coated substrate. In the board so produced, the circuit is represented by the metal coating~ If the circuit is to be of a -particular design, then conventional masking ~rocedures as previously discussed may be employed to ~roduce the desired design.
The 90 peel strengtn Or the circuit board was evalu-ated according to the procedure of Example IV to give a value Or about 20 pounds per inch. The circuit board was also evalu-ated for dip solder resistance according to the procedure Or Example II and results in excess of 20 seconds were obtained.
Exam~le VI
A circuit board was Drepared utilizing a hydrocarbon polymer with an elastomer component and a thermoset com~onent according to the following procedure. The hydrocarbon polymer was prepared by dissolving 82.5 weight parts of NBR rubber con-taining 7.5 weight parts talc and 75 weight parts of the buta-diene-acrylonitrile copolymer described in ~xample IV in about 323 weight parts of' methy1 ethyl ketone with agit~tion. To the - ..... ~. . .
104'~739L
re;~;lt;lnt ~ ti~n ~lere af! Ic~ w;th rni~ini!~ ar)out llr~ weight ~arts cr t~le ohenollc re:in (le crlbed in L~anl~le TV di.solve(l in meth-anol (',' ~ercent 901~ Abollt 1.l ~!ei ht narts Or tetramethyl-t;,1uram ~lisu~lf`i(~e ancl l.l wei~t narts Or ~4 '-ditaiodimorpho-line were mixed with ~o'. weitht n~rts o methy] isobutyl ketone and '~'~ wei~uht nart of n-~ltyl acetate and the reslllting mixture added to the soll~)ili%ed h~dr(car~)on !ol~m~r. A r~] as -rein~orced enox~ rec~in ~anel (C. inches ~quare ar~d 1/ll inch tnick) 1Na~s coated on both si~les with the hrtlrocarbon ~olymer by roller coat-ing. The coated laminnte was therea~ter driel at ~5 C. forabout 60 minutes to remove solvent to form a i)olymer coating thickness of about 1.5 mils. The hydrocarbon ~olymer coating was then partially cured by heatinc~r the coatèd laminate at 150 C. for 60 minutes.
The resultant substrate corn~rising the partial]y cured -~ hydrocarbon ~olymer coated over the reinforcing core of the glass reinforced epoxy resin panel was then metalized according to the procedure of Example IV to ultimately produce a co~per coating about 0.1 mil. thickness. The cor)per electroplating was then stopped and the copper ~lated substrate was heated at 150 C. for 60 minutes to complete curing of the hydrocarbon polymer.
Thereafter, the electrop]ating was continued to increase the co~per coating to about 1 mil. thickness to form the desired circuit board o~ a metal coated substrate. In the board so :.
produced, the circuit is represented by the metal coating. If the circuit is to be of a particular design, then conventional masking procedures as previously discussed may be employed to produce the desired design.
The 90 peel strength of the circuit board was evalu-ated according to the procedure of Example IV to give a value of from 10 to 18 pounds per inch. The circuit board was also evalu-ated for dip solder resistance according to the procedure of Example II and results in excess of 20 seconds were obtainedO
1()4'~73~
x~ r A ci.rc lit ~or~r~ r(~ rt~l t~til 1 ~ In~ a yIroearhon r~ ~ol~er Of ~ all e~ 't;Or~t'r C()!~r)Ol~t?!lt an l ~ ermo3et coln~onent ac-co~ g to ~h~ ,c~llow;n~ r-rocedure. l`he lIydroc~Jrborl ~olymer ~as nreoclrel l)y dis .)lvin~ .'5 \~ r~t )art of ~3R rub~er contain-~ Ing ~.75 wei?~t nart~ t~lc ar!(l S'~7~5 ~veis;ht r)arts of the buta-; diene-acry]onitriIe cooolYmer descLi~)e(l ;n ~Y~aI-~r)lè IV in about 350 narts by wei~rr~It Or ~etlIy~ et'~yl ~eton~, 31 wei~rht ~art~ of methyl isobutyl I.etone and 1~3 ~arts of n-butyl acetate Nith agitat~on. To the resultant ;olution were added with mixing about 22.~ weight parts o~ the n!lenolic resin described in Ex-ample IV dissolved in met~lanol (55 S~ercent solids) and then about 1.28 weight parts of tetramethylthiuram disulfide and 1.2 weight parts of 4,4~-dithiodimor~holine ~ere added to the solu-bilized hydrocarbon polymer. A glass-reinforced e~oxy resin laminate (5 inches square and 1/4 inch thick) as coated on both sides with the hydrocarbon polymer ~y roller coating. The coated laminate was thereafter dried at 25 C. for about 120 minvtes to remove solvent to form a polymer coat;ng thickness of about 1.5 mils. The hydrocarbon ~olymer coating was then par-tially cured by heating the coated laminate at 150 C. for about 60 minutes.
The resultant substrate com~rising the partially cured hydrocarbon polymer coated over the reinforcing core of the glass reinforced epoxy resin panel was then metaliz~d according to the procedure of E~ample IV to ultimately produce a copper coating about 0.1 mil. thickness. The copper electro~lating was then stor~ped and the copper plated substrate was heated to complete curing of the hydrocarbon polymer at 107 C. for 35 minutes, 107 to 121 C. for 15 minutes, 121 C. for 45 minutes, 121 C.
to 135 c. for 20 minutes and 135 c. for 60 minutes. There-after, the electroplating was continued to increase the copper coating to about 1 mil~ thickness to form the desired circuit . , ' ~ 0~7;~
boa~d ol` a met~l coller~ hstr~lte. Tn the bo~rd so nroduced, t`rre C ~ l'C~li t i.3 rt'r-rC ~;ente(.l l)y t'rle ;net-~l c~a~-inir~ the cir-cult is to be of ~I r~lrticll1ar ~le;iyrl, then c~nventiona] masking ~rocedlir3c. ~ revi(~ ly disc~ls~e~ may be ~ )loyed tr~ r~roduce the ~er1ir~ iesl~rl.
The ?0~ ~eel strenrth (!r the ci.~cuit bon~d was evalu-ated accordin~ t~ tne r-eoc~-lure Or ~xamr~le IV to ~ive a val.ue Or : about ,~ ounds r?er lnch. ~.lhe circuit boa-d was also eval.uated ror dip solder resistance accordinr; to the nrocedure of ~xamn].e II and reslllts in excess of 20 seconrl3 were obtained.
~xamnle VIII
A circuit board was r,repared util.i~ing a hydrocarbon ; polymer of an elastomer com~onent and a thermoset coml~onent ac-cordi1-~g to the followin~ procedure. The hydrocarbon polymer was prepared by dissolving 5i~ weight parts Or NBR rubber contain-ing 5 weight parts talc and 50 weight parts of the butadiene-acrylonitril.e copolymer described in Example IV in about 270 parts by weight of methyl ethyl ketone with agitation. To the . resultant solution were added with mixing about 91 ~eight parts of the phenolic resin described in Ev.am?le IV dissolved in methanol (55 percent solids). About 0.73 weight parts of tetra-` methylthiuram disulfide and 0.73 weight parts of 4,41-dithio-dimorpholine were mixed with 1~ weight parts of methyl isobutyl ketone and 59 weight parts of n-butyl acetate and the resulting mixture added to the solubilized hydrocarbon polymer. A glass-reinforced epoxy resin panel (5 inches square and 1/4 inch ~ thick) was coated on both sides with the hydrocarbon polymer by : roller coating. The coated laminate was thereafter dried at 25 C. for about 60 minutes to remove solvent to form a polymer coating thickness of about 1.5 mils. The hydrocarbon polymer coating was then partially cured by heating the coated laminate at 150 C. for 60 minutes.
0~ ~7 ~
at ~ st,~ate co s,r;sirl,~ t,`ae !~asti~'!ly cured r~ 'I,y~!t,r ~ ,t, ! (jv~ f`3 cil~lr c~r~ Or t'~ ~,lass rl~;`o~ce(3 er~oxy rt~ ina~ tren Irlet~lize~' ~ccordin~ to the r)~oc~ur~ of' ~xrlio'le T~ to liltimatel,l i,roducc ~ col)per cc~t,-irlr~ of al~out ~.l mi'l. tllicknel,s. T~ co,-ner electron]~tlrlg was ~`, t~len sto)oed ~Inl the c~-r)l~er r~ t~(3 ~u~str.~tc ~ . he te(~ at 150~
C. ror 6~ rn;nute; to (~ornolete curirl,~ of the hydroc~rbon nolymer.
There~t`ter~ t~e electr(~rl~tlnir ~as contLnued to Lnc~eAse the co~-ner coating to fl!out 1 mll. ttlicklle(-,s to rorm t~le de~-lred circu,it board of a met~)l coated sllbstrate. In the board 90 ~-roduc~d, -the circuit is represente~1 by the metnl coat;in~r. Ir the circuit is to be of a particul,ar desi(~n, then conventional mnsking proce-dures as previously discussed may be en~rlo~ed to produce the desir~,d design.
The 90 peel strengtl o~ the circuit boa~d was evalu-ated according~ to the procedure of Exam~le IV to give a value of about 12 to l~ pounds ~er inch. The circuit board was also evaluated for di~ solder resistance according to the ~rocedure of Example II and results in excess of l0 to 20 seconds were obtained.
Exarnple IX
A circuit board was prePared utilizing a hydrocarbon polymer of an elastomer component and a thermoset component ac-cording to the following procedure. The hydrocarbon polymer was prepared by dissolving 96.?5 we;ght parts of NBR rubber contain-ing 8.75 weight parts talc and 87.5 weic,ht parts of the buta-' diene-acrylonitrile copolymer described in Example IV in about 35Q parts by weight of methyl ethyl ketone with agitation. To , the resultant solution were added with mixing about 22.8 weight parts of the phenolic resin described in ~xample IV dissolved in methanol t55 percent solids~. About 1.28 weight parts of tetra-methylthiuram dis-ulfide and 1.28 weight parts of l~,4l-dithiodi-morpholine were mixed with 31 weight parts of methyl isobutyl -~3~
' '' ' 1~4'~7;3~
e ~nd l~`3 :t~ ,t ~ t~ ' n~ ty' c,ce-t~lt~- ln(' th~ res-lltinr .-~ixtl,re c~ t~ t'.~. ;;olu~ l `rl~J(lrocer~ n ~ol~Jmer. A nheno--` C t r` e .l t, ~ r) ~ r ~ l i na t, ~ ` '; s~ r~ It~ irl~h. t~l:ick) was cocl~e(t on t)oth ;:i~le: wit~l t;hc ~iroc~r~on r)ol~Jmer- by rol.lrr COatirl~. Th~ COfite'l F~ rlnt,(,' `N.~`: t~-orci~`t~r (3rie~ to rernove ;~
vent to ~`orln 1 r~o~lvmer~ ('otJ~ `' t~li.Ckrit`..'~ ot` nt)out 1.~l-) m:ils.
The r~.ydrocarborl r1olymer coati.r~ ;a~ th~?n r)a~tially cure(l by heating the co~lte~d l.ami.na~e ~It ~5C` C. f`or ()0 :n:inutes.
The re:lll-tc~nt substr-~1te coi!~-rising the -oartially cured hydrocarbon ~lol~fmer coate(1 over the relnro,ci-~g coL-e of tne ~neno]ic treatèd l)ar)er laminate was then metallzed according to : the procedllre Or E.xample IV to ultillately produce a conr)er coat-ing about 0.1 mil. thickness. The copper electroplating was then stonped and the co~per plated substrate was heated at 150 C. for ~0 minutes to complete curing of the hydrocarbon polymer.
Thereafter, the electroDlating was continued to increase the ~`` co~per coating to about 1 mil. thickness to form the desl.red ~ circuit board of a metal coated substrate. In the board so produced, the circuit is represented by the metal coating. If the circuit is to be of a particular design, then conventional ` ~ masking procedures as previously discussed ma~y be employed to . produce the desired design.
The 90 peel strength of the circuit board was evalu-.. ated according to the procedure of Exam~le IV to give a value of from 14 to 17 pounds ~er inch. The circuit board was also evaluated for dip solder resistance according to the procedure Or Example II and results in excess of .~0 seconds were obtained.
_24 .. ~
Claims (6)
1. A printed circuit board comprising a hydrocarbon substrate of a butadiene-acrylonitrile copolymer and a phenol-formaldehyde resin where the copolymer and resin are present in a ratio of from about 6:1 to about 9:1 parts by weight, respectively, and where the phenol-formaldehyde resin contains formaldehyde and phenol in a mol ratio of from about 1:1 to about 1.5:1, respectively, and an electroless metal deposit bonded to at least a portion of the substrate.
2. The circuit board of claim 1 wherein the butadiene-acrylonitrile copolymer contains from about 18 to 50 weight percent of acrylonitrile.
3. The circuit board of claim 2 wherein the phenol-formaldehyde resin contains formaldehyde and phenol in a mol ratio of from about 1.2:1 to about 1.3:1, respectively.
4. The circuit board of claim 2 wherein the sub-strate contains a reinforcing core which is coated with the substrate.
5. A method of preparing, by electroless plating, a printed circuit board having high adhesion between the deposited metal coating and the insulating substrate which comprises the steps of (1) coating a reinforcing core with a hydrocarbon substrate of a butadiene-acrylonitrile copolymer and a phenol formaldehyde resin where the copolymer and resin are present in a ratio of from about 6:1 to about 9:1 parts by weight respectively, (2) at least partially curing the hydrocarbon substrate, and (3) metalizing by electroless plating, the partially cured substrate to add the metal coating, said metalizing comprising the steps of (1) etching, (2) sensitizing, and (3) electrolessly depositing an electrically conductive metal layer on the sensitized, hydrocarbon sub-strate and thereafter electroplating to completely form the desired metal coating whereby the circuit board thus prepared has the reinforcing core coated with the substrate and the metal coating is bonded to at least a portion of the surface of the substrate.
6. The method of claim 5 wherein the hydrocarbon substrate is cured in two steps which comprises partially curing the hydrocarbon substrate prior to etching and complet-ing the curing subsequent to the addition of the metal coating by electroplating with both the partial and complete curing being effected by heating at a temperature of from about 80°C.
to about 160°C.
to about 160°C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA163,581A CA1042734A (en) | 1973-02-13 | 1973-02-13 | Fabrication of printed circuit boards |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA163,581A CA1042734A (en) | 1973-02-13 | 1973-02-13 | Fabrication of printed circuit boards |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1042734A true CA1042734A (en) | 1978-11-21 |
Family
ID=4095818
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA163,581A Expired CA1042734A (en) | 1973-02-13 | 1973-02-13 | Fabrication of printed circuit boards |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1042734A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4876178A (en) * | 1981-05-11 | 1989-10-24 | Sierracin Corporation | Electroconductive film system for aircraft windows |
-
1973
- 1973-02-13 CA CA163,581A patent/CA1042734A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4876178A (en) * | 1981-05-11 | 1989-10-24 | Sierracin Corporation | Electroconductive film system for aircraft windows |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US3737339A (en) | Fabrication of printed circuit boards | |
| CA1262778A (en) | Method for producing circuit boards with deposited metal patterns and circuit boards produced thereby | |
| TWI780176B (en) | Copper clad laminate and print circuit board comprising the same | |
| US20150030824A1 (en) | Circuit materials, circuits laminates, and method of manufacture thereof | |
| US4654262A (en) | Polyolefin resin surface preparation | |
| US4804575A (en) | Multilayer printed wiring boards | |
| US4954185A (en) | Method of applying adherent coating on copper | |
| GB2057351A (en) | Laminated blanks | |
| US3267007A (en) | Bonding metal deposits to electrically non-conductive material | |
| US3770571A (en) | Fabrication of printed circuit boards | |
| CA1042734A (en) | Fabrication of printed circuit boards | |
| KR20020067627A (en) | Thermosetting epoxy resin composition, its formed article and multilayer printed circuit board | |
| Abu-Isa | Metal plating of polymeric surfaces | |
| US3681474A (en) | Electrical substrates | |
| US5419946A (en) | Adhesive for printed wiring board and production thereof | |
| US4774279A (en) | Adherent coating for copper | |
| JP4556260B2 (en) | Additive insulation film for printed wiring boards | |
| WO2003018213A2 (en) | Silanated copper foils, method of making, and use thereof | |
| CA2046882A1 (en) | Electroless plating method | |
| JP2001102758A (en) | Printed wiring board, insulation resin sheet used therefor and manufacturing method of insulation resin sheet | |
| JP4556261B2 (en) | Additive adhesive for printed wiring boards | |
| JPS5844709B2 (en) | Resin composition for printed wiring boards | |
| EP0473069B1 (en) | Electroless plating of materials having electrophilic polarity | |
| JP3536937B2 (en) | Additive method adhesive for printed wiring board and method for manufacturing wiring board using the adhesive | |
| JPH03255185A (en) | Adhesive for printed wiring board made by the additive process |