CA2020624A1

CA2020624A1 - Swelling agent for pretreatment of a synthetic resin prior to electroless metallization and improved method of making a circuit board using same

Info

Publication number: CA2020624A1
Application number: CA 2020624
Authority: CA
Inventors: Andrea Riedl; Detlef Tessmann; Burkhard Bressel
Original assignee: Individual
Current assignee: Bayer Pharma AG
Priority date: 1989-07-06
Filing date: 1990-07-06
Publication date: 1991-01-07
Also published as: JPH03204992A; DE3922477A1; EP0406678A1; DD296510A5

Abstract

ABSTRACT OF THE DISCLOSURE

The swelling agent composition for pretreating a synthetic resin substrate prior to electroless metallization contains a solvent system and includes at least one glycol ether characterized by the following formula I
R1-(OCH2?CH2)n-OR2 (I) wherein R1 and R2 are independently selected from the group consisting of alkyl groups and aryl groups and n = 1 to 8, especially diethyleneglycol dimethylether, triethyleneglycol dimethylether, tetraethyleneglycol dimethylether or diethyleneglycol diethylether. The process of completely metallizing a synthetic resin substrate includes pretreating the synthetic resin substrate with the swelling agent composition, etching the substrate in an oxidizing etching solution to form an oxidizing agent residue on the substrate, removing the oxidizing agent residue from the substrate, activating the surface of the substrate and electroless metallizing the surface of the substrate with, fro example, copper.

Description

BACKG~oU~D OF ~HE INVEN~'Io~T

Our invention relates t~ a swelling ag~nt ~ompositlon based on a solv~n~ sy~tem ~o~ pretreatmellt oE ~yn-th~tic resin ~r~or to electroless me~allization and a method of completely metallizing a substxate using this swelling a~en~ composition.

~ etallized s~nthe~ic resin substra~es a~e used in di~fe~ent areas o~ ~pplica~ioll. In one a~ea for ~arious reasons the direct metallization o~ fla~ or more complex-sh~p~d substrates ~o ~orm condu~tive stru~tures is desired, e.g. ci~-c~it ~oa~ds for the electronic industr~. Furthermore, it ~s ~re~uently necessar~ to protect eleotroni~ elements from emission and/or propayated electroma~netic ra~iation. ~o~ that a metal la~er is ~i~ilarl~
~pplied ~o a s~nthetic resin by e~c~ochemical ~eposition.
Additional a~eas of applica~ion are ~ound in maki~g de~ora~ive componen~s for the automobile in~us~xy an~ ~or plum~ing fi~tures.

In all the above-mentioned cases ~ very intlmate ~ombin~ti~n o the metal coa~ing with the syn~hetic resin substrate i~
desired. The required high adherence values, ~ox example a~

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me~su~ed in a peel test, must be maint~ined unde~ all circumstances, also in cases where there are thermal stresses(~hich can occur ln practlce on ~oldering ths circuit board).

In currént pra~tice circuit bcards are advantag~ously made acco~ding to the subtrac~ive ~echnique~ For this purpose epoxy ~es~n ~ubs~rates pro~ided wit~ a thin coppe~ layer on both xides, fre~uentl~ reinforced ~ lass fibex network and in many cas~
ho~ever also containing phenolic resin-soaked paper layer~, are used. ~he process ~or making circuit boards ac~ording ~o thi~
process ~omprises metallizing ~he holes ser~in~ ~or elec~xi~al ~`
connection of differen~ conduotion plane~ or for receiving electronic component connectox pins and the proce~ ep~
~onnected with it in¢luding ~ircuit board hole cleanin~, condltioning~ activatin~ and me~allizing.

~ subst~ntial di~d~ant~e oE the a~ove-mentioned proçe~s i~
th~t the re~uired etchin~ pro~es~ ~or making the con~uotiv~
st~ture on the ou~er sur~ace o~ ~e ci~cuit ~oa~ds i~ not economic~l, since the ~o~per going into ~olu~ion m~st be r~cov~red ~nd also there are substan~ial limitations o~ ~he ~1315 i.E~ 13 ~1 l S ~ ;~13 ~ 1 l S 5 5 ~ ~ n ~

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re~olu~ion (structure ~id~hs and dis~ances) vf the conduc-~or pa~tern produced on the outer surface o~ the circult boa~d~ This se~ond point c~n be explained by the consideraPl~ ~nderetching of t~e conduc~ing elements, since the entire coyper eoil portion lamina~ed on the subst~ate must be removed~ Fo~ -techniaal re~sons a lower limit of ~7 mic~ome.~ers Xor ~he copper Eoil thickn~ss is not ~o be e~ceeded. Thinner coppe~ ~o~ls h~ve not be pu~ down or deposi~ed in practice, since thi~ type o~ layered epoxy resin ~ubs~ate material~ a~e manufact.ured only with di~icult~ and are very e~pensi~e.

~ oxeo~er very high requi~emen~ are pl~ced on the consistency of the e~hlny process, when thirXQ~ ~opper laye~s must b~ remo~ed. ~o ~et around this limita~ion, ~he additive or ~emiadditive method can be us~d, in whi~h circuit board substra~es not layered wi~h copper are used to sta~t wi~h. This is ~lso true fo~ all co~plex shaped syn~he~ia re~in bodies, which mus~ ~e me~allized, since in tha~ ca~e no copper ~oll can be laminated on ~he body o~ the s~bstr~te during m~nu~actu~e, ~hich means for example in the case of pro~eating fram elect~om~gnetia radia~ion or in t~e making of molded bodies ha~in~ co~plio~d .
conductor pa~terns.

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This ~ype o~ me~hod o~ cirouit ~oard ~anufac~ure, whose con~ol ~pends on the adherent metalli~ation o ~he outer sur~ace of circuit board b~side~ on the ~ethodical circui~ boaxd hole m~talli~ation, are us~d to ~ certa~n extent with ~u~strat~
which hav~ an adhesive layer for the above~men~ioned adherent~

~ considerable disadvantage of ~hese materials, which has st~ongly inhibite~ the e~pansion of ~he a~ov~-men~ioned air~uik bvard man~fac~uring method, is that ~hen using an adhe~ive layex:
First, substra~es ~ith an adhesi~e layer are expensive and seaond there are considerable ~uali~ative requirements ~or the adhesive la~er in rela~ion to th~ ~onstancy o~ t~e adhesive properties bo~h f~om board ~o ~oaxd and in the microscopic region. MorePver the circuit boaxd produc~d has a oonsiderable mechanic~l sen~i~ivi~ which can easily lead to damayP. to ~he substrate material surface.

~ he a~herence of ~he ~dhesive film to the c~rcuit board substrate is fre~uently imperfec~, so ~hat ~n ord~rly assembly o~
the ~nti~e unit o~ s~bstr~el adhesi~e laye~/ ropper i~ not gu~ranteed in all cases.

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7,~2ll ~ hese disad~anta~es can be avo~ded when a direct metalliza~ion follo~ing a suitable pretre~tm~n~ o~ th~ circuit board s~bstrate i5 pexformed. These ~ype of proce~ses, whi~h for e~ample pxesuppo.s~ ~n o~idati~e decomposition of the resin sur~ace in a Cr(VI~- ~r permanya~ate ion containing solu~ion after a swelling step in an organia an~/or inorganic solven~, are k~own in themselves. If in conne~tion wi~h the o~idati~a attack on th~ synthe~ic resin sur~Ace a pretreatment-/adhesion-/m talliæation se~uence occur5 according to ~he usual pattern, a st~ng.Ly adherent metal laye~ is obtained, whi~h withs~and~ a t~ermal load (e.g. by ~ipping o~ the metallized substrat~ in a soldering bath a~ ~8RC for 10 sec) wi~hout damage, The above-de~cribed method however cannot ~e perfoxmed in practice, sin~e because of the oxida~ive attacX, which ~auses a roughening of the subs~ra~e, glass fibers of the reln~orcing materials of the substrate are exposed. This 1eads to two ~isad~nta~eous e~fects in the circuit board m~kin~ process, which are so serio~ that the process cannot be used:

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First, the adheren~e o~ the copper on the glass ~ibers exposed i~ ex~raordi~ri~y weak, so ~hat local defects oc~ur, which lead to ~erious di~ficultie~ with ver~ small conduo~or paths. ~mon~ other things protruding gl~ss ~ibers ~an cause unevenness problems in ~he transmis~ion o~ the conduc~or pat~rn.

In di~f~r~nt improvemen~s of the ~bove-described proces~
special substrates, e~peciall~ epoxy base~ resin material~, have been used to avoid the ~ ul~ie~ describ~d: ~ possible alternative is the use of the socalled resin-enriche~ laminate.
Th~se laminates include fillin~ material, x~sin systems, ad~antage~usl~ glass fiber/xesin systems, whose sur~aces have a higher proporti~n o~ resin mass relative to the total volume and th~s a greater resin thickness. In this case ~here i5 also a st~onger etching a~tack, whl~h does not expose glass ~ r~ in ~he deepest loca~ions in the substrate.

~ n ano~her v~iant of the ahove process reslns s~rongly cross~in~ed ln bonded ~ubstrate m~terials w~re us~, such as epoxy resin$ mixed with di~unctional or te~rafun~ional ~omponents. ~n this case ~he roughening by e~Ghing attaoX is ~educed and no ~l~ss fibers ar~ expo~ed ~y ~h~ et~hin~.

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In both cases disadvantages ~em~in since only oertain ~pecial substrates can be used in the last ~wo me~llod~ menti.oned above, so ~hat the application o~ ~hese processe~ are alear}y limi~ed. If resin-enriched ma~rial is used, in addition ~o the other disadvan~ag~s a strong ~oughening o~ ~he surfaces must be o~erved to pxoduce ~ su~fioient adherence. That has the followi~ disadvantage:

First a stron~ clea~age o~ ~h~ cir~Uit board su~faces assists ~h~ sliyht contamina~ion occur~in~ on the unme~allized or already exposed ~urfa~e~. This is very troubleso~e for example during ~he etching away of the c~pper du~ing pa~ rning of -the conduc~ln~ sur~ace. Bec~use ~f this contamination the sur~ace resi~tance value.s can be cleaxly i~paired. An additional disadvanta~e occu~s in high frequency appliGa~ion, when in this c~s~ ~rQn~ impedance fluctuations be~ween the individual c~nducto~s are produced in an unpredictable way by ~h~ skin effe~t.
.
Also an ~xtensive ro~ghening ~or ~ par~icul~ applica~ion, in which protec~ion ~rom elec~romagnetic radiatlQn is requ~red, is no~ desirable.

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SU~D~ARY OF TH~ INV~NTI~

It is ~n ob~ec~ of the present invention to provide a means Q~ avoidin~ the disadvanta~es o~ excessive s~PstrAte e~ching ln a method o~ making a cir~uit board, while a~ ~he same time providing a higher adherence o~ the coating laye~s on the substra~e and ~ uniform adhesive underlayer without impairing ~he re~ui~ed adhesive streng~h~

~ t i~ al~o an o~jec~ o~ ~e presen~ inven~ion to provide an improved swelling agent composition fo~ use in a method o~ makins a çir~uit board.

It is another object o~ ~h~ presen~ invention to provide an impxoved ~ethod a~ manuEacturing a clrcuit bo~rd.

~ hese objec~s are at~ained in an excellen~ manner, when th~
swelling agent composl~ion ~f claim 1 is used to tre~t th~
suPstrate p~ior ~o metalliza~ion. ~ddi~ional ~orms o~ the inventlon ~re des~ibed in the dependent claims.

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According to our inven~ion ~he swellin~ a~ent co~posl~ion used to pretxeat ~he ~ub~trate includes a ~lycol ether and a solvent system.

~ he g-ycol ether~ o~ ~he present in~ention advantageously are ~har~cte~iz~d by the following ~ormula I

R~ C~-CH2)n~~2 ~I) wh~ein n Y 1 to 8, pre~er~bly 1 to 4, and ~1 and ~ are equ~ or different and are alkyl or aryl ~roups. The preferred ~1 and ~2 groups o the inven~ion are methyl, ethyl, n-propyl or n-butyl.

~ he fol~owin~ glyaol ethers are parti~ularly outs~anding;
di~thyleneglycol dimethylether, ~riethyleneglycol dimethylether, ~e~ra~thyl~n~g~ycol dl~e~hylether and diethyleneglyc~l diethyle~her.

The ~ly~ol ethers of the invention ~re p~e~en~ in ef~ec~i~e amounta of from 0.1 to 100 percent b~ wei~ht, adv~ntag~ous~y in th~ am~unt of 20 to 70 perc~nt b~ weight, The swellîng agent ....
.. . ........................ - 1 0 T T ~ t`l 31~ 13 ~ l 15 ~r `~ 3 ~ T lZI: lZI T I ~ '3 --3 n r -- 2~ ,;7 compo5ition ~an he used in ~ide ~e~pera~ure xang~s, adv~nta~eousl~ howe~er ~rom room temperatur~ to the ~oiling t~mperature o~ the s~elling ~gent ether, The solve~t system includes water and various org~nic solvents. The organic sol~ents ca~ inclu~e ethylene glycol, di~et~ylformami~e and ethylene ylycol.

As synthe~ic resin for example epoxy resin ~n diffe~nt forms can be used. This includes th~ FR4- and FRS- epox~ r~si~
ma~erials known in cir~uit board ~e~hnology with and withvut mul~ifunc~ional additives such as phenol and c~esol~Nova lacquer and tetra~unctional ma~erials, bismaleictriazino resln and thermopl~s~ic substrates such as acryloni~xile/b~tadien~/~tyrene copolymerizate, polycarbonate and o~her cynthe~ic resin materials.

~ he e~ching step oc~urs in oxidizing solution. Commerci~l alkali p~xman~an~te solution, ch~omic ~cid ~olu~ion o~ ~hxomic sRlfUriC acid solution m~y b~ used, Alkali permanganate solution ~ntains ~dvantageously alkali salts o~ permangani~ acid, e.g. pot~ss~u~ or sodlum perm~nganate Z: T ' d ~ ~ 131 S ~ J 3 ~ ~15 ~- ~ 3 ~ S ~ 3 e~ ~ --3 n ~

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in a concen~ra~ion of from 30 g/l to the leve~ o~ a saturated ~olu~ion. The al~ali content i5 advantage~u~ly adjusted by addition o~ al~ali hy~roxide, e/~. sodium hydroxide or po~assium hydroxide in a concentra~ion o~ 10 to 200 ~tli~. The operatin~
~pera~re o~ thi~ etchln~ solution amoun~s ~dvantageou~ly ~ 40 ~o 9 OC .

~ hromia acid ~olukions c~ntai~ing chroml4 t~io~ide. in a con~en~ra~ion o~ ~rom ~00 ~o gO0 g~lite~ ~an ~e used ~t t~mpeXatures o~ f~m room te~peratu~e to ~0~.

Chromic sul~uric acid solutions have hee~ used as s~andard etching ~gents ~or acrylonitrile/hutadiene/~yrene copolymerization. For makin~ khe substrates accoxding to the inVention ~hey are u~ed in exactly ~his w~y.

Removal o~ ~he residual oxidiziny age ffl ~rom the resin sur~ace a~ter trea~ment occurs with an acl~ soluti~n of a reducin~ agent according ~o the typ~ of oxidizing agent used similar ~o ~e~allizing processes.

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T~e ~c~iva~ion occu~s in the st~ndard way as in ~hQ Xnow~
pxocesses. ~ono~ens ~n be used as colloidal a~ivators.

~ he sub~e~u~nt electroless metallizin~ ~an occur in a metallizing bath accor~l~y to ohoi~e of ~he manu~a~turer. copper, niok~l, silv~r, gold, pal~adium, zino or their alloy~ can be me~allized rom ~he appropria~e bath~ The ~lectroles& metallized layer ~hickness amoun~s to about ~.05 micrometers to ab~ut ~0 micr~m~ters and allows a s~bse~uent electroshemi~al me~alliz~tion of very ~hin to ~bitrarily ~hi~X layer~, A me~al layer ~e~uired ~or certain applioations i~ applie~
to ~ ~ir~ metal layer formed ~y elect~oles~ methods ~y a curr~n~less or ~le~roche~ical prooe~s~ A copper-, nickel-, co~alt-, zinc-, lead , gold-r palladium-, sil~er-, ~in~ laye~ or a la~er o~ ~heir alloys may be ~eposi~ed in this way~

~ he workpieces made accordin~ to ~he invention are ~sed fo~
di~erent process purposes: as ~old~d bodie~ h~in~ conduc~4r patterns in ~he electronics indust~ies/ al~o Eor e~ample a~
oircuit boards, chip oarrier~, hydrid oircuits, ~ock~t connectors and other applic,l~ions includin~ th~se invol~in~ ~rotec~i~n ~rom emitted or pxopa~ated eleGtromagnetic radiation.

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The subst~ate material made ac~ordiny to the lnventlon used ~or mak~ng ~ircui~ ~oar~s with the hol~s neçes~ary ~or the elect~onic aomponent pins or the electrical connection o~
dif~eren~ wires prior to metalliza~.ion can ~e processed usi~ an advantageous vaxia~ion o~ the semiad~itive o~ additive ~thod.

In the ~emiaddi~ive metho~ ~he ~nm~t~llized material is me~allized completely accordlng to the invention A~er the holes ar~ produced. ~ayer thic~nesses o~ ab~u~ 5 micrometer~ are produce~. Subse~ue~tly the struc~ure o~ ~he mol ded body having the ~onductor pat~ern i~ p~oduced acc~r~lng ~o a known ~echnique(e.g. print screen te~hnology or phot~pxoceses). Th~
~roces~ steps ar~ pex~ormed according to a known pa~e~n.

the ~dditive method the unmetallized ~at~ri~l under~oes ~h~ worXing sequence of struc~urin~ according ~o the known process a~er making the holeg. Subsequen~ly an e~ectroless metallization o~ the subst~ate occurs a~co~ding to ~he me~hod of the invention only at the places at which the i~ished blank should ha~e ~the later-~ormed conductor pattern. It i~ conceivabl~
also that the su~stra~e is pretrea~ed a~tex the holes ~ccording to the process o~ our invention and ~he me~allizati~n andJo~
ac~ivation occurs nex~ a~ter structu~ing with a g~l~ani~ xesi~t.

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An addi~ional altex~ative consi~ts in th~t the base material a~ter ~ormin~ the hole~ is me~allized with a metal layer thioXness suf~icient ~or ~ming the conductor pa~exn comple~ely ~o subse~uen~ly produce a ~tructure on it in ~le man~er o~ a known tenting technique.

Alt~rna~ively the ma~exi~l without hole~ can be first completely ~oated with a thin copper layer according to our lnvention. S~bs~quen~l~ the holes arq pr~uced and the known subtractive process coulcl be u~ed ~or making the condu~tor pa~tern.

The ~ollowing examples se~ve to illus~rate the inv~ntion~

~XAMPI,ES

Examplq_1 Epoxide resin/glass fiber laminates are made in the us~al wa~ by p~essing p~epregs u~er high p~essur~ and temperature, ~owever no copper foil is laminated on the outer layers in ~ont~ast ~ the ~on~ention~l process, ~ut on the prepre~s~ ~
fluo~opolymer foil is ~pplie~ to ~o~h sides ~o prevent s~icking to ~he press par~s.

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~ h~ ready lamina~e is me~llized until a copper layer o~ g micro~letexs is formed on 'ooth side~ in the ~ollowing p~oces~
6equence:
1. Swelling in a solution oF 45 pe~cent by ~olume ~im~thyl ~ormamide, 20 percent by volume die~hyleneglycol dime~hylethe~, o volume per~en~ ~thylene glycol, 25 ~olu~e perc~nt wa~er and 10 of NaOH/lit~r (10 min, 30~), ~ . Etc~in~ in a solution o~ 300 g CrO3/liter in wa~er(10 min 70c), 3. ~edu~ing adh~riny CrtVl)-ion qroups in a ~odium bi~ul~ite solution, 4. Cleanin~/condi~ioning in ~n alkali so~ing solution ~a~inq a catio~i~ soa~in~ a~en~, 5. ~leaning/con~itioning in an aaidia ~oaking solutinn with a cationic soaking a~ent, 6. Immersing in a 10 ml H25O~ solution per liter, 7. ~Gtivatin~ in an alkaline palladium aompl~iny solu~ion, . ~educin~ in a NaBH4 solution, 9. Electroless metallizing with ~opp~r to ~orm a 0.2 micrometer layer, and lo. El~ctro~hemical metallizing with ~opper ~o ~orm a 30 mic~o~e~er layer.

, .... . . - - 16 -~131 S ~ ;~ 3 ~ 1 l S " ;~13 :~1 I ~ l S ~ ~ ~ --3nr ,S~ 7 Generally there are rinsing or w~shing ~tep~ between the abo~e descri~ed pro~ess steps 1, 2, 3, 4, 5, 6 and/or 7, 8, ~ ~nd 10 .

A 1 cm strip was cu~ from ~he ~etallized material~ ~or adhesion ~estin~ and ~he ~dherenGe valu~ was measured in a peel test. Values of 1~ to 20 N/cm were the result o~ the peel testing on these samples produced by th~ above proc~s5.

E:X~MRI~ 2 ~ he process steps o~ example 1 ar~ repea~ed e~p~ a thermal shock is ~pplied ~ e test sample prior to peel tes~ing. Th~
met~llized subs~r~e ~s immerse~ completely in a solAering ba~h (SnP~) a~ 288C ~or lo sec and su~equently the peel test is per~oxm~d to measure the adherence. One obtains resul~s ~rom the pael test o~ ~rom 15 to 20 NJcm~

EXAMP~E 3 The process of example 1 i5 ~gain repea~ed ex~ept with diethylenegly~ol die~hylether instead o~ die~h~le~egl~col dimeth~le~he~ in the same concentration while maintaining th~
sa~e parameters in the ~welling s~ep ~nd ~he o~her process s~eps. One o~ains an adhe~ence ~lue of 1~ ~o 18 NJc~ in the peel ~es~
..... - - 17 :~: T ~ 1 3 1 ~ ~ 3 ~ 1 l S ~ ;~ 3 ~ I ~ 1 ~ ~ 3 ~ ~ n - .~ :::

EXAMPLE ~

The process s~eps ~ ex~mple 1 ar~ repeated with triethyleneglycol ~imekhylether. One obtains adh~r~nce value~ of 16 to ~ N/cm.

~ he p~ocess steps ~ example 1 are repeated with -~e~rae~h~leneyly~ol dimethyle~her~ One obtains an adherence value o~ 16 to ~ N/cm.

~ PLE 6 The pro~ess steps of example 1 a~e again rep~ated with an electroless metalliziny con~entrated copper ba~h instead of ~ilute copper b~th. ~er ~he cu~rentless me~ zing the substra~e is pxovided wi~h a 5 micromet~r thiak bubble-~ree ele~ole~sly deposi~ed copper l~er, which is ~u~thex xe~n~orced or thickened by metallizing ~rom ~n elea~rochemical ~ath.

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Epoxide resin/glass fiber Rrepregs are p~essed to~ether with a laminate made of epoxi~e ~e~in/~lass fiber ~omposite ~e~ials with interior l~yers s~ructured by ~he usual met~ods to for~
multila~er connec~ion~ f~r circ~t board appli~a~ion under pressure and high tempe~ature so that the prepregs ~re on ~he eXterior. On bo~h ~i~es of the resultin~ ~ompos~te su~tra~e fluoropol~mer ~o~l is ~pplie~.

The ~u~str~te is provided accordlng to a prede~ermlned patte~n wi~h differ~t sized holes (of 0.6 ko 1.2 mm diameter).

Subseguently ~he subst~te composit~ is m~talliz~d according to the process ~teps in E~ample 1. 0~ qou~se an e~hing clea~ing o~ the exposed sur~ace of the coppe~ interio~ layers in the hol~s i5 performed be~ween s~eps 5 and ~ with a sodium pexsul~ate-cont~ining cleaner. The ele~troche~ni~l coppe~ layer is built Up ~o a total thickn~$~ cf 5 micr~met2r. Subsequ~ntly a cond~c~o~ pa~tern is produ~ed by lamin~tirlg on a :Eilm, illuminatin~ ~he coated ci~cui~ bo~d ~d dev~lopm~nt wi~h the aid o~ a photoresis~. The sur~a~es appe~rin~ late~ With cop~er .... .. .
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therPon are etched from the copper underl~yer as ducts.
Su~e~uen~ly a~ter an ~cid cleaniny of the exposed ~opper surfaces an additional electroc~lemical copp~r metalliza~ion is perPormed until a final thi~kness o~ 35 micrometer~ ~esult~. The galvanie resi~t i~ then removed. The thin aopp~r surEaces are remov~d in an etching bath (e.~, CuCl~~etching solution) and the copper is p~ssivated.

One ob~ains ~ ciro~it board in a socalle~ GOpper m~thod with a minimal etchin~ a~ent consum~tion and with ne~ ihle underetching of the conductor paths.

EX~MP~E_.8 The same manu~acturin~ process is use~ a~ in Ex~mple 7 with ~he following dif~erence~:

Prior to patterning a copper laye~ o 35 micrometers is applied ~o all sides ~o ~over the en~ire sur~a~e. Su~seq~en~ly a ~nting ~ilm is laminated on the substrate, which shoul~ act a~
an etchiny ~esist. The film i5 illumina~qd ~nd develvp~d.
Subsequently the copper is etche~ away ~ro~ the exposed ~uxfa~e, the ~ilm is stri~ped ~nd ~h~ ~opper passiva~ed~

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one obtains a ~ircui~ ~o~d b~ copper engineerin~
te~hnology method~.

X~PL~_~

~ or an application in which integrated semi~nductor componen~s aXQ moun~e~ ~lr~tly on the ciraui~ b~ard a FR 5 substra~e lamina~ed on bo~h sides wi~h 3~ mlcromet~rs thick copper la~ is p~ep~ed by milling wi~h quadrila~er~l h41es ~o~
receiving the directly mounted componen~s. A surf~ce metalliza~ion o~ the enti~ ~ur~ace~ tin~lu~ing the copper coating and th~ holes) is per~orm~d with ~he help of the process s~ps accoxdin~ to example l after maXing ~he holes in the ~oard.
~o attain an intima~e ~ond wi~h the resin, the proces~ steps use a 600 g CrO3 per li~er solution instead o~ a 300 g ~rO3 pe~
liter solution. To pxevent tha oxide layer on the copper ~ur~ace ~rom pre~enting an adheren~ bon~ with the layer~, an etchin~ ;
~leaning in a so~ium pe~su~fate-~on~aininy solu~ion prior ~o imme~sion must be perform~d.

A good adherence of the wet chemically-me~allized coppe~
l~e~ on the resin sur~ace resul~, which is retained even a~ter ~he thermal shocX provided by sold~r.

- 21 ~

EXP~MPLE 1 0 ~ n in~egra~qd semicondu~o~ compo~ent is embedd~d in an epoxld~ resin-poured resin mass. A copper/ni~kel laye~ should be applied for pro~ec~ion from elec~roma~netic ~adi~ion.

,`
The process steps o~ exa~ple 1 ~xe pe~fo~med with the followinq di~erenGes:

Th~ hing solution o~ain~ in s~ep 2 contains 600 g CrO3~1iter in water. Only 10 mi~ometer~ copp~r a~e ~eposited by ele~ro~hemical reinforcement. Subseguently a~ter an activation an electrole~s coating with a Ni/P ~lloy occurs up t~
a tota~ thic~ness of ~0 micrometers.

~` One ob~ains a bubble-~ree ~dherent coa~ing.
' .
EXAM~

The substrate named in Example 10 a~ter the electroless deposi~ion o~ ~ ~hin ~opper ~oa~in~ and ~ub~equen~ a~ n with a 10 micrometer is coated with a 10 micrometer electroless . deposited Ni/P layer.

- on~ ob~alns a bubble-~ree adherent coating.

...... -- ~2 --.... .. .

' ~ ~" , :`, ' 2 ~ J t.l EXAMPLE 12.

The su~kr~te mentioned in example lU is directly coated with ~ 10 micrometer eleatrolessly deposited ~i/P layer.

One obtain~ a smooth bubble fxee and adheren~ la~er.

It will be unders~ood that ea~h o~ tlle elemen~ cribed above, or two or more to~ether, may also find a useful applicati~n in oth~r types of methods dl~ering ~rom the types des~ri~ed ~bove.

While the invention has been illustrated and des~ribed ~s e~bodied in a swelling a~ent composition ~or ~reatmQnt o~ a s~n~etic resin p~ior to ele~ less me~alli~ation and an improved me~hod o~ ~akiny a circui~ board uslng that ~welling agent composition, it i~ not inten~ed to he limited to ~he details shown, since v~ri~us modi~i~ations and ~tructur~l ch~n~es may be ma~e wi~hou~ ~eparting in any wa~ ~xom the ~pirit o~ ~he presen~ invention.

Z ~ 131~ 13 ~ I :~15 ~ ~13 ~ 115 ;~ 3 n 2 ~ 2 ~ ~ r J ~

W~thout ~lrther anal~sis, ~he ~oregoing will so ~ully reveal ~he gis~ of ~e p~esen~ in~tion ~ha~ o~hers aan, by appl~ing curre~nt ]cnDwledge, readily adapt it :~or various applications withou~ omi~ting ~eatures that~ from the standpoint o~ p~ior art ~ai~ly collst.i~u~e e~en~ial charac~e~istics of the generic or speci~i~ aspecl;s o~ this in~en~ion.
.
Wha~ is claimed is new and desired to be protec:ted ~y Le~ters Pa~erlt i3 set forth in ~he appended claims.

, ~ .......... ~ -- 2~ ~

S Z ~ ,_r ~1 3 1 _; - ~1 3 :~1 I .~1 1 S ~ 1 3 ~1 T ~ `= T ~- t r T ~ .

Claims

1. A swelling agent composition for pretreatment of a synthetic resin substrate prior to an electroless metallization containing a solvent system comprising a plurality of solvents and at least one glycol ether.

2. A swelling agent composition according to claim 1, wherein said glycol ether is characterized by the following formula I
R1-(OCH2?CH2)n-OR2 (I) wherein n + 1 to 8 and R1 and R2 are independently selected from the group consisting of alkyl groups and aryl groups.

3. A swelling agent composition according to claim 2, wherein n = 1 to 4.

4. A swelling agent composition according to claim 2, wherein said R1 and R2 groups are independently selected form the group consisting of methyl, ethyl, n-propyl and n-butyl.

5. A swelling agent composition according to claim 1, wherein said glycol ether is selected from the group consisting of diethyleneglycol dimethylether, triethyleneglycol diemethylether, tetraethyleneglycol dimethylether and diethyleneglycol diethylether.

6. A swelling agent composition according to claim 1, wherein said glycol ether is present in an effective amount of from 0.1 to 100 percent by weight.

7. A swelling agent composition according to claim 1, wherein said glycol ether is present in an effective amount of from 20 to 70 percent by weight.

8. A swelling agent composition according to claim 1, wherein said solvent system comprises water and at least one organic solvents.

9. A swelling agent composition according to claim 8, wherein said organic solvent comprises ethylene glycol.

10. A swelling agent composition according to claim 1, wherein said organic solvents include water, dimethylformamide and ethylene glycol.

11. Method of preparing an epoxide resin substrate for a completely covering metallization comprising treating said substrate prior to said metallization with a swelling agent composition according to claim 1.

12. Process of completely metallizing a synthetic resin substrate having a surface, comprising the steps of:
a. pretreating said synthetic resin substrate with a swelling agent composition according to claim 1, b. etching said substrate with an oxidizing etching solution to form an oxidizing agent residue on said substrate, c. removing said oxidizing agent residue form said substrate, d. activating the surface of the substrate, and e. electroless metallizing the surface of the substrate.

13. Process according to claim 12, wherein said synthetic resin substrate is multilayered and made of successively alternating copper and glass fiber-containing epoxide resin layers hardened under heat and pressure.

14. Process according to claim 12, wherein said metallizing proceeds from an electroless copper bath.

15. Process according to claim 12, wherein said pretreating occurs at a temperature of from about 20°C to a boiling temperature of said solvent system.

16. Process according to claim 12, wherein said oxidizing etching solution contains a species selected from the group consisting of permanganate ions and chromium VI compounds.

17. Process according to claim 16, wherein said permanganate ions are provided by an alkali permanganate solution.

18. Process according to claim 16, wherein said chromium VI
compound comprises chromium trioxide.

19. A completely metallized substrate made according to the process according to claim 12.

20. Method of making one of a circuit board, chip support, hydrid circuit, a multilayer laminated semifinished product provided with a copper inlay and a semifinished product having protection from electromagnetic radiation comprising using said completely metallized substrate of claim 19.