Note: Descriptions are shown in the official language in which they were submitted.
2~7~85
P~T 90 2~3
19.03.1990/fi 1030Z
BASF Lacke und Farben Aktieng~ell~chaft, ~nster
queously develo~able, neqative-workinq,
electrophoretically depositable and
~hotocurable coatinq aq~nt, and also
its u~e to produce conductor tracks
The present invention relates to an aqueously
developable, negative-working, electrophoretically
depositable and photocurable coating agent which contains
A) 35 to 85 4 by weight of at least one ethylenically
unsaturated, water-d~isper~3ible or watar-~oluble
polymer,
B) 0 to 60 % by weight of at least one ethylenically
un~aturated monomer,
C) 1 to 10 % by weight o~ at least one photoinitiator,
D) 0 to 10 % by weight of auxiliaries and additives,
and
~) possibly an organic solvent
disparsed in water, the ~um of the proportions by waight
o~ the components A to D always being 100 % by weight.
The prosent invention al~o relates to the u~e of
~aid coating agentR ~or producing conductor tracks.
Printed clrcuit boards have acquired a Yary great
2S significance in tha production of electronia equipment.
The conventional printed circuit boards are based on
2~7~
glass-fiber/epoxy laminate3 or other laminate~. The
function of said printed circuit boards is primarily that
of a flat two-dimensional base and connecting element for
khe individual electroni~ components such a~, for ex-
S ample, c~pacitors, transistors and resistors. In order to
~onnect the printed circuit board electrically and
mechanically to the remainder o~ the apparatus, other
electrical and structural elements are neces~ary.
Such two-dLmensio~al printed circuit board~ ~re
produced, for example, by depoRiting a photocurable
resist film electrophoretically on a copper-clad layer
and exposing through a mask. Then the printed circuit
pattern i8 developed by ~tripping o~f the unexposed
place~ in the case of negative-working photoresist
material~ or the exposed places in the case of posi-
tive-working photore~ist materials. The copper areas laid
bare are then removed by treatment with an acid etching
solution. The printed circuit i~ then obtained by remov-
ing the remaining resist layer.
Such a process ~or producing the two-dimensional
printed circuit board~ using negative-working, aqueou~ly
developable, electrophoretically depo~itable and photo-
curable resist matarial~ i8 described, for example, in
EP-B-176 ~56. Tho re~i~t material used ~s an aqueous
solution or emulsion of a prefarably ~aturated polymer
having carrier groups, an acid or base to neutralize the
carrier groups, a photoinitlator and an unsaturated,
cros~linkin~ monomer. A~ example~ of suitable pol~mer~,
mentlon i~ made of linear acrylate polymars, vinyl
2 ~ 3 ~
-- 3 --
polymer~, epoxy resins, polyurethanes and polyesters.
If the photoresist ma~erials are deposited
anodically, problems ari~e due to the fact that the
copper, which i~ connected a~ anode, i~ partially oxi-
dized to Cu (II) ions. These copper ions diffuse into thedeposited resist film and form with the carboxyl groups,
thio group~ etc., complexe~ which Lmpair the developabil-
ity of the resist material~ and re~ult in re6idual layers
on the substrate. Thi~ effect occurs to an increa~ing
extent wi~h incr~a~ing deposition voltage of the resist
material and results in appreciable problems, in par-
ticular, in the vicinity of the so-called break-off
voltage of the material to be deposited.
In the process described in the German Laid-Open
Application DOS 3 715 412, this problem is s~lved by
adding a chelating reagent for ~opper ion~ to the photo-
resist materials. In addition, these photoreslst mater
lals described in German Laid-Open Application
DOS 3 715 412 contain a water-soluble or water-disper~-
ible polymerizable un~aturated resin having an acid
nu~ber of 20 to 300, an unsaturation equivalent of 150
to 300 an~ al~o a number-average molecular weight of not
less than 300, po~sibly an unsaturated monomeric compound
and a water-insoluble photopolymerization initiator. As
axamples of unsaturated resin~, mention is made, inter
alia, of reactlon products of linear acrylates containing
carboxyl groups with un~aturated compounds containing
glycidyl group~, and al~o o~ reaction product~ o~ linear
acrylates containing hydroxyl group~ with un~a~urated
2~7~
-- 4 --
compounds containing i~ocyanate groups.
The photore~i~t material~ described in German
Laid-Open Application DOS 3 715 412 have, however, the
disadvantage that the deposition voltages achievable for
S obtaining sufficiently high dry film thicknesses (~30 ~m)
have very low value~ owing to the low breaX-off voltages
of these material~. As a result of this, the~e materials
exhibit only a very poor throwing power.
A further development of the conventional printed
circuit boards is the 2~- and 3-dLmensional printed
circuit boards. Such printed circuit board~ are thermo-
plastic parts which are produc2d by the in~ection molding
method and which are selectively metallized. Functionally
they combine: printed circuit board, plug connector, chip
carrier and also mechanical and structural elements.
Since the shape of the part, the cutouts, the holes e~c.
reside in the precision in~ection-molding tool, the
accuracy and reproducibility ~rom one part to another i~
excellent.
To ensure a uniform coating of 3-dimQnsional
moldings with the photore~ist material, i.e. a uniform
coating of raarwardly and internally situa~ed surfaces
such as, for sxample, of throughholes, a high deposition
voltage ~in general from 2S0 to 300 V, depending on
molding) o~ the photore~ist materials i8 nece~sary since
it i~ only in this way that a goad throwing power can be
achie~ed. In order to be able to work with such high
deposition voltages, the photoresi~t materials usad mu~t
have a break-o~f voltage o~ at lea~t 300 to 350 V,
2 ~
-- 5 --
depending on molding.
Finally, US-PS 4,04û,925 discloses anodically
depositable, photocura~le coating ~aterials based on
unsaturated linear or branched acrylate polymers having
5an average molecular weight of 170 to 100,000. The
coating materials described therain result in coatings
having high hardne~s and good solvent reslstance. How-
ever, any use or suitability of said coating ma~erials as
photoresi~t material i~ not described in ~S-PS 4,040,925.
10Furthermore, US-PS 4,039,414 discloseR cathodic-
ally depo~itable, photocurable coating materials ba~ed on
unsaturated linear or hranched acrylate polymers having
an average molecular weight o~ 170 to 100,000. ~ny use or
suitability of the~e coating materials as photoresist
15material i9 likewlse not describ~ed.
It i~ consequently the ob~ect o~ the pre~ent
invention to provide aqueously developable, negative-
working, electrophoretically depositable and photocurable
photore~iRt m~terials whlch have as high 8 brea}c-off
20voltage as pos~ible o~ at lea~t 300 ~o 35û V, depending
on molding, and al~o a good throwing power perfonnance.
Furthermo~e, said photoresist materials must cure as
rapidly aB possible and have a good and rapid strip-
pability and developability with, at the ~ame time, good
25re~istance to the etching and electroplating bath~
normally used .
Surpri3ingly, this o}~ect is achie-lred by an
aqueou~ly developabl~, negative-working,
alectrophoretically depositable and photocurable coating
- 6 - 2~
agent which contains
A) 35 to 85 ~ by weight of at least one ethylenically
un~aturated, water-dispersible or water-~oluble
polymer,
B) 0 to 60 ~ by weight of at least one ethylenically
un~aturated monomer,
C) 1 to 10 % by weight of at least one photoinitiator,
D) 0 to lO ~ by weight of auxiliarie6 and additives,
and
E) pos3ibly an organic solvent
dispersed in water, the 8um of the proportions by weisht
of ~he component~ A to D always being 100 ~ by weight,
wherein the polymer A has a double-bond equivalent of
1,500 to 10,000, and al~o a content of anion- or cation-
forming group~ o~ 0.5 to 5.0 milliequivalents/g and can
be prepared by
I. radical copolymerizatlon o~
a1) 5 to 30 % by weight of at least one monomer
containing at lea~t two ethylenically
uns~turated, polymerizable double bonds per
molecule and having a number-average molecular
weight of <400,
a2.) _ 5_to--3~-~-b~ we~ght--~--~t--le~st--D~e~~F~la~-
ally un~aturated, copolymeriz ~ monomer
~5 containing at leAst one ani~n-~ r ca~on-for~-
ing group and/or at ~ as't one functional group,
a3) 40 to 80 ~ ~b~e~ght of at lea~t one furthar
ethyl~n~cally unsaturated copol~merizable
~m~onome~ n~ -cont~in~n~r~~n~ n---~r~ tion-~ -
2 ~ 7 ~
6~L
__ ------- 7
a2) 5 to 30 % by weight of at least one ethylenic-
ally unsaturated, copolymerizable monomer
containing at least one anion- or cation-form-
ing group and/or at lea~t one functional qroup,
a3) ~0 to 80 % by weight of at lea~t one further
ethylenically un~aturated copolymerizable
monomer not contain.ing an anion- or cation-
~EPL~CEM~NT PAG~
2 ~
-- 7 --
forming group, except vinylaromatic
hydrocarbons, and
a4) 0 to 50 ~ by weight of at least one vinylaro
matic hydrocarhon, the sum of the proportions
by weight of the component3 a~ to a~ alway~
being 100 ~ by wsight
in a fir~t stage,
II. in the event that the copolymer obtained in the
fir~t ~taga does not contai.n either anion- or
cation-forming group~
at least partial reactlon of the ~unctional group~
o~ the copolymer obtained with
a~) 2 to 85 ~ by welght, based on the weight o~ tha
sum of the component~ a1 to a~, oE at lea~t one
lS compound which aontains at least one anion- or
cation-~orming group and also a group capable
of reac-ting with the ;Eunctional group~ of the
copolym~r and has a number-average molecular
weight of ~300, or
III. ~ubsequant reaction, or reaction occurlng prior to
the reaction of the copolymer with aS), with
a~) 2 to 20 % by weight, based on the wei~ht of the
~um of the components a~ to a~, of at least ona
compound which contain~ at lea~t one ethyleni-
cally un~aturated double bond and also a group
capabla of reacting with the anion- or cation~
~orming groups of tha component a2 or a5 and~or
the unctional groups o~ ~he copolymer and has
REPLACEMENT PA&~
/ 7~
a number-average molecular weight of ~00
and
IV. at leaYt partial neutralization o~ the anion- or
cation-forming groups of the copolymer obtained.
5~he pre~ent invention relates, in addition, to a
method of producing a printed circuit in which said
coating a~ents according to the invention are electropho-
retically deposited on the copper surface and a polymer
image i8 produced by irradiation and AlsO development. In
addition, the pre~ent invention relate~ to tha u~e of
said coating agents as photoresist material and for
producing 2-, 2~- and 3-dimen~ional conductor track~.
It is gurpri8inq and W218 not ~oreseeable that
~aid coating materials exhibit high break-off voltages of
15at least ~00 to 350 V, depending on the molding to be
coated and a good throwlng power. per~ormanca and at the
same time cure very rapidly and also exhibit a good and
rapid strippability and developability. With ~aid coating
agents according to the invention, it i9 pos~ible
20 .. ........., in particular, 2~- and 3-dimensional, but also
~. .....
REPL~C~M~NT PAGE
2 ~ ;J3
-- 8 ~
rv~--C~-lea_t part~ ne~ralization of the-ani~n- ur
cation-forming groups of the copolymer obtained.
The pre~ent invention relates, in addition, to a
method of producing a printed circuit in which said
coating agent~ according to the invention are electropho-
retically deposited on the copper surface and a polymer
Lmage i8 produced by irradiation and al~o development. In
addltion, the present invention relates to the u~e of
said coating agents a~ photoresist ma~erial and for
producing 2-, 2~- and 3-dlmensional conductor track~.
It iR surpri~ing and w~` not foreseeable that
said coatin~ material~ exhibit high break-off voltages of
at lea~k 300 to 350 V, depending on the molding to be
coa~ed and a good throwing power performa\ce and at the
same time cure very rapidly and also exhibit a~ ood and
rapid strippabllity and developability. Wlth said ~o\ating
agents according to the inventlon, it i~ po~sibl ~to
pro~ucs~ icular, 2~- nd ~-~men~lonal, but also
2-dimansional conductor tracks by means o~ a slmple and
economical mathod. ~ a re~ult of the high break-off
voltage of the coating agents, it is possible to work
with rel~tively high deposltion voltages which are
important for achi2ving uniform coating thiGknessQs aven
on surfaces ~acing away from the electrode and in C8Vi-
tie~. Neverthales~, thesa required depo~ition voltagesare, however, su~iciently remote from the break-of~
voltage, ae a reRult o~ which problem~ dua to an oxi-
dation o~ tha copper ions are largely avoided in tha case
of anodic depoRition.
9 2~g~
The compounds suitable for preparing the un-
~aturated polymer are now commented on in greater detail
below.
The polymerizable unsaturated resin A u~ed
according to the in~ention can be prepared by fir~t
preparing a copolymer by radical solution polymeri~ation
of the monomer~ a, to a~ at, in general, 70 to 200C,
preferably 100 to 150C.
Examples of suitable monomers a1 having at lea6t
two ethylenically unsaturated, polymerizable double bonds
per molecula and a number-average molecular weight of
le~s than 400 are csmpounds of the general formula
R O O R (I)
CH2 ~ C-C-X-(CH2)n X-C-C - CH2
where
15 d~H~b
X ~ , NR' or 5, where R' = H, alkyl, aryl,
n = 2 ~ 12,
\ X-(C)m-X- (I~)
\R2
whera
R1, R2 = H, -CHa, -CH2-CHa, -CH2-CH- ~ ,
whese X - O, NR' or S, where R' - ~ aryl,
. . .
m - 1-2
~7~
9~
,_
- `~
where ~ ~ ~ or C~33; X =~ O, N~%~ or S, where ~' - B, alkyl,
arylî n - 2 to 12,
H2C ~ C-C-X-~ I )m-X-C-C ~ C~2 (II)
where Rl, R2 ~ ~, -CE13 ~ -CEl2-cE~3 ~ -CE~2-CE~- ~ CH3 ) 2;
S R ~ H or C~3; X ~ O, NR ' or S
where R ' - ~, alkyl, aryl; m 5~
REPLACE~IEN~ P~G13
2~73~2
-- 10 --
R O O R
CH ~ C- l-x-CH2-CH2-S-cH2-cH2 X ~ 2 ( III )
where X = I NR ~ or S; where R ' - H, alkyl, aryl;
R ~ H or CH3
CH I U X CH ~C~12-X-~-C - Ctl2 ~ IV)
5 where X ~ O, NR~ or S; R~ - H, alkyl, aryl;
R - H or CH3
H2C -- C-C-X-CH2-CH-CH2-X-C-C - C~2 (V)
where X ~ O, NR' or S, where .R'! a ~ alkyl, aryl~
~ ~ H or CEI3
CH2 ~ C - C-X-R-O-~-O-R-X-C-C CH2 lVI)
where R ~ alkyl, ar~rl,
X ~ O, NR ' or S, where R ~ a ~ ~ alkyl, aryl; ~ H or CH3
REPL~CE~IENT PAGE
2~17~
- 10~-
where X = O, NR' or S, where R' = H, alkyl, aryl, /
-X-CH2 ~ CH2~X- / (IV)
where X = O, MR' or S, where R' f H, alkyl, aryl,
OH/ (V)
-X~C~2~zH C~2
where X ~ I NR' ~ where R' = H, alkyl, aryl~
/ -X-R-O-C-O-R-X- (VI)
O
wh~e ~ - al~cyl, aryl,
. X-~-N, NR' ~r ~, wh~ R~ kyl, nryl.
Ex~ples of such compounds are hexanediol di-
acrylate, hexanediol dimethacrylate, glycol diacrylate,
glycol dimethacrylata, butanediol diacrylate, butanediol
dimethacrylate, trimethylolpropane triacrylate and
trimethylolpropane trimethacrylate. Furthermore, divinyl
compound8 ~uCh ag, for example, divinylbanzene are also
~uitable as component al. O course, mixture8 of multi-
functional monomers may al~o be used.
2~7~
-- 11
The component a1 may also be a reaction product
of a carboxylic acid having a polymerizable, olefinically
unsaturated double bond and a glycidyl acrylate and/or
glycidyl methacrylate. The component al may furthermore
be a polycar~oxylic acid esterified with an unsatura~ed
alcohol containing a polymerizable double bon~ or an
unsaturated monocarboxylic acid esterified with an
unsaturated alcohol containing a polymerizable double
bond.
Furthermore, the reaction product of two moles of
acrylic or methacrylic acid with one mole of bi~phenol-A
or bi~phenol-F diglycidyl ether i8 al~o ~uitable as
component al. Oxyalkylated blsphenol A or bisphanol-F
di(meth)acrylate may also be used a~ component al.
React~on product~ o a polyisocyanate with
alcohol~ or amines containing un~aturated pol~merizable
double bonds can al~o be usad a~ component a1. As an
example of thl~, mention may ba made of the reaction
product of one mole of hexa~ethylene diisocyanate and two
moles of allyl alcohol.
Preferred component~ al are compound~ containing
at le~st two methacryloyl group~ per molecule.
~ he component a1 i~ u~ed in amounts of 5 to 30 %
by weight, pre~erably 10 to 20 % by wei~ht, ba~ed on the
total weight of the ~um o~ the components ~1 to a~.
M~nomers which contain an anion- or cation-form-
ing group ara prefer~bly use~ a8 component a2.
Examples of ~luitable monomer~ a2 which contain an
anion-form~ng group ara monomer~ containing carboxyl
- 12 - 2~7~
groups such a~, for example, acrylic, methacrylic,
maleic, fumaric, crotonic, isocrotonic and dimethyl-
acrylic acid, and al80 mono(mPth)acryloyloxyethyl
succinate, mono(meth)acryloyloxyethyl phthalate and
reaction pxoducts of phthalic anhydride or ~uccinic
anhydride with hydro~yalkyl (meth~acrylate/~-caprolactone
adducts ~uch a~, for example, the product obtainable
commercially under the tradename TONE M100 from the Union
Carbide Company. Derivatives of phosphoric and ~ulfuric
acid such a~, for example, the monopho~phate of hydroxy-
alkyl (meth)acryla~e and the monosulfate of hydroxyalkyl
(meth)acrylate. Preferably, acrylic and methacrylic acid
are u~ed.
Furthermore, monomer~ which are able to form
cations such a~, for example, a quaternary ammonium
group, ~ulfonium group or sulfoxclnium group, are sui~able
as component a2. Preferably, monomer~ containinq amino
groups are used a~ cation-forming monomers a2. Examples
of suitable monomers a2 containing amino groups are N,N-
dimethylaminoethyl ~math)acrylate, N,N-dimethylamino-
propyl (meth)acrylata, N-2-tert-butylaminoethyl (meth)-
acrylate,. N,N-dimethylaminopropyl (meth)acrylamide and
p-dimethylamino~tyrene.
Monomers which, although they do not contain an
anion- or cation-forming group, contain another func-
tional group ~uch as, for example a hydroxyl, epoxy or
i~ocyanate group, may, however, also bo u~ed as
component a2.
Examples of suitable monomers a2 containing
2 ~
- 13 -
hydroxyl group~ are hydroxyalkyl esters of ~ unsatu-
rated carboxylic acids containing primary or secondary
hydroxyl groups and also mixtures of ~aid esters contain-
ing primary and secondary hydroxyl groups. Examples of
~uitable hydroxyalkyl e~ter~ of ~,~-unsaturated car-
boxylic acids containing primary hydroxyl group~ are
hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxy-
butyl aerylate, hydroxyamyl aerylate, hydroxyhexyl
acrylate, hydroxyoctyl acrylate and the correspondinq
methacrylate~. A~ example~ of usable hydroxyalkyl esters
containing ~ ~econdary hydroxyl group mention may be made
of 2-hydroxypropyl acrylat~, 2-hydroxybutyl acrylate,
3-hydroxybutyl aerylate and the corresponding
methacrylates.
Of course, the eorresponding esters o~ other ~
un~atura~ed earboxylie acid~ ~3uch as, for example,
crotonic aeid and i~oerotonia aeid may also be used in
each ea~e.
AdvAntageously, the eomponent az may ba at least
par~ly a reae~ion product of one mole of hydroxyethyl
aerylate and~or hydroxyethyl methacrylate and, on aver-
age, two mole~ o~ c-eaprolactone.
A reaetion produet of aerylic aeid and/or meth-
aerylie aeid with the glycidyl ester of a earboxylie acld
2S having a tertiary ~-carbon atom may al~o be used at least
partly as component a2. Glyeidyl esters of extensi~ely
branehQd monoearboxylie aeids are available under the
tradename Cardura. Aerylie aeid or methaerylie acid may
be reaeted with the glyeidyl ester of a earboxylle aeid
2 ~ 2
- 14 _
containing a tertiary ~-carbon atom before, during or
after the polymerization reaction.
Examples of suitable monomer~ containing epoxy
groups are glycidyl esters of unsaturated carboxylic
acids and/or glycidyl ethers of unsaturated compounds
~uch a~, for example, glycidyl (meth)acrylate, glycidyl
fumarates and maleates, glycidyl vinyl phthalate,
glycidyl allyl phthalate and glycidyl allyl malonate.
Examples of suitable monomer~ con~aining i~ocya-
nate groups are ~inyl isocyanate, m-isopropenylbenzyl
i~ocyanate, ~ dimethylbenzyl isocyanate and isocya-
natoalkyl e~ters of ~ unsaturated carboxylic acids of
the general formula
R 0
1 11
CH2 G C-C-0-X-NC0,
where R = H, CH3, C2~5 ~
and X = (CH2)~, where n = 1-12.
It i~ also pos~ible to use adducts of, for
example, isophorone dii~ocyanate on hydroxyal~yl (meth)-
acrylates- ~uch as, for example, hydroxyethyl
methacrylate.
The component a2 is u~ed in an amount of 5 to 30 ~
by weight, preferably 10 to 20 % by weight, based on the
total weight of the 8~m of the componsnts a~ to a~.
Th~ component a3 is used in an amount of 40 to
80 ~ by waight, prefarably 40 to 60 ~ by weight, based on
the total weight of the sum of tha components a~ to a~.
2~71~$~2
_ 15 -
Examples of suitable compound6 a3are hydroxyalkyl esters,
alkoxyalkyl esters, aryloxyalkyl esters, alkyl es~ers and
amide~ of ~ un-~aturated carboxylic acids and ~imilar
monomer~.
Thu~, for example, alkyl esters ~uch as ~ for
example, methyl acrylate, ethyl acrylate, propyl ac-
rylata, butyl acrylate, iYopropyl acrylate, i~obutyl
acrylate, pentyl acrylate, isoamyl acrylate, hexyl
acrylate, 2-ethylhexyl acrylate, octyl acrylate,
3,5,5-trimethylhexyl acrylate, decyl acrylate, dodecyl
acrylate, hexadecyl acrylate, octadecyl acrylate,
octadecenyl acrylate, pentyl methacrylate, isoamyl
methacrylate, hexyl methacrylate, 2-ethylhexyl meth-
acrylate, octyl methacrylate, 3,5,5-trimethylhexyl
methacrylate, decyl methacrylate, dodecyl methacrylate,
hexadecyl methacrylate, octadecyl methacrylate, methyl
methacrylate, ethyl methacryla~.e, propyl me~hacrylate,
i~opropyl methacrylate, butyl methaclylate, cyclohexyl
acrylate, cyclohexyl methacrylate, and also the
corresponding esters of maleic, fumaric, crotonic and
isocrotonic acid may ba u~ed.
However, monomers containing hydroxyl groups such
a~, for example, the compounds already cit~d in the
descr~ption of tha component a2 may al~o be used as
component a3.
AlXoxyalkyl and aryloxyalkyl esters o~
un~aturated carboxylic acids, ~or example butoxyethyl
acrylate and methac~ylate, phenoxyethyl acrylate and
methacrylate, ~cryloni~rile and .methacrylonitrilQ are
2 ~ g l~
- 16 -
also suitable a~ component a3.
The component a4 used in an amount of 0 to 50 %
by weight, based on the total weight of the 0um of the
components a1 to a~, is a monovinyl aromatic compound.
Preferably it contains 8 to 9 carbon atoms per molecule.
Example~ of suitable compound~ are ~tyrene, vinyltolu-
enes, ~-methyl~tyrene, chlorostyrenes, o-, m- or p-
methylstyrene, 2,5-dlmethylstyrene, p-methoxystyrene, p-
ter~-butylstyrene, p-acetamidostyrene and m-vinylphenol.
Preferably, vinyltoluenes and al~o, in particular,
styrene are used.
The polymerization reaction is carried out using
polymerization initiators and po~sibly polymerization
regulators.
Sultable free-radical initiator~ are organic
pe.roxide~ such as, ~or example, dibenzoyl peroxide,
dlcumyl peroxide, t-butylcumyl peroxide, t-amylcumyl
peroxide, cumol hydroperoxide, di-tart-butyl peroxide,
tert-butyl hydroperoxide, 2,2-di-tert-butyl peroxibutana,
text-amyl perbenzoate, 1,3-bis(tert-butylperoxii~o-
propyl)-benzene, ~iisopropylbenzene monohydroperoxide and
diacyl perox~des YUCh a8, for example, diacetyl peroxide,
peroxiketals such as, for example, 2,2-di-~tert-amyl-
peroxy)propane and ethyl-3;3-di-(tert-amylperoxy)buty-
2S rate, tharmolabile, highly substituted ethane deriv-
ative~, for example based on silyl-sub~tituted ethane
derivative~ and ba~ed on benzopinacol. Furthermor0,
aliphatic azo compound~ such as, for example, a~obis-
cyclohexanenitrile may also be u~ed.
2 0 7 ~ ~ 8 r~
- 17 -
In most cases, the amount of initiator amounts to
0.1 to 5 ~ by weight, ba~ed on the amount of monomer to
be processed, but it may pos~ibly be even higher. The
initiator dissolved in ~ome of the solvent used for the
polymerizatLDn i~ gradually added durinq the polymeriz-
ation reaction. Prefarably, the feeding-in of initiator
la~ts about 1 ~o 2 hours longer than the feeding-in of
monomer in order also to achieve a good action during the
postpolymerization phase in this way. If initiators
having only a low decomposition rate under the existing
reaction condLtions are u~ed, it is also po~sible to
intxoduce the initiator completely or in part.
Preferably, the reaction i8 carried out in the
presence of polymeri2ation regulators in order to be able
to control the molecular weights or the molecular weight
distribution better in thi~ way. Suitable regulators are
pre~erabl.y mercapto compounds, melrcaptoethanol being used
with particular preference. Other possible regulators
are, for example, alkylmercap~ans such as, for example,
t-dodecylmercaptan, octylmercaptan, phenylmercapthn,
octyldecyLmercap~an, butylmarcaptan, thiocarboxylic acid~
such as,~ for instance, thioacetic acid or thiolactic
acid. In the ca~e o~ anhydride-functional comonomer~,
care 3hould ba taken to ensure that the regulator does
not react, or can only react in small amounts, with the
cyclic anhydride groups. In this case, t-dodecylmercaptan
is praferably u~ed. These regulators are used in an
amount of up to 2 ~ by weight, based on the amount o~
monomer to be proce~ed. Pre~arably, they are dis~olved
2 ~
- lB ~
in one of the monomer feeds and added with ~he
monomers .
The polymerization i5 carriad out in an organic
solvent. Examples of ~uitable solvents are alcohol~ such
as, for example, isobutanol, n-hexanol, 2-ethylhexanol,
i800ctyl alcohol, isononyl alcohol, isodecyl alcohol,
i~otridecyl alcohol, cyclohexanol, methylcyclohexanol,
benzyl alcohol, methylben~yl alcohol, tetrahydrofur~uryl
alcohol, di~cetone alcohol, 2,6-dLmethyl-4-heptanol,
4-methyl-2-pentanol, tridecanol; glycol~ and glycol
derivatives ~uch as, for example, ethylene glycol, 1,2-
propylene glycol, 1,3-butylene glycol, 1,4-butanediol,
hexylene glycol, 2-ethyl-1,3-hexanediol, diothylene
glycol, triethylene glycol, dipropylene glycol, methyl
dlglycol, ethyl diglycol, butyl cliglycol, hexyl diglycol,
tripropylene glycol methyl ether, methoxytriglycol, ethyl
glycol acetate, butyl glycol acetate, ethyl diglycol
acetate, ethylene glycol diacetate; substituted aromatics
uch a~, for example, xylene, toluene, Solvent Naphtha~,
hea~y benzole, various solveRso~ typas~ various Shellsol~
types and Dea~ol~, and also aliphatic and cycloaliphatic
hydrocarbons such as, for example, various white spirits,
mineral terpentine oil, tetralin and decalin. Praferably,
inert solvents such as aromatic and aliphatic hydro-
carbon~, e~ters or ethers ar~ usad.
The copolymers 80 obtained are now modifi~d fur-
ther. If thay do not contain either anion- or cation-
forming groups, the copolymer is reacted with com-
pounds aS. Sui~able as component a~ ara compound~ having
~7~ 3
-- 19 --
a number-average molecular weight of <300 which contain
at least one anion- or cation-forming group and al50 a
group capable of reacting with the functional groups of
~he compon~nt a2.
In this connection it i8 po~sible to introduce
~aid anion- or cation-forming group~ by reactlng the
copolymer obtained in the first ~tage with the com-
ponent a~ and then modifying the product obtained further
by reaction with the component a6. However, the copolymer
obtained in the first stage may first be reacted with the
component a~ and the product obtained then modified
further by reaction with the component a5.
The componant a, is used in amounts of 2 to 85 ~
by weight, preferably 5 to 50 ~ by weight, basad on tha
weight of the sum of the components al to a~.
If the copolymer obtained in the first stage of
the method contains, Eor exa~lple, hydro~yl groups,
carboxylic acid anhydride~ such a~3, for example, succinlc
anhydride, maleic anhydride, dodecenylsuccinic anhydride,
hexahydrophthalic anhydride, tetrahy~rophthalic anhydride
and phthallc anhydride which react with the copolymer to
form half~eeters are proferably u~ed as component a~. The
copolymer 80 obtained is then modified further with ~he
component a~ to introduce the ethylenically unsaturated
double bonds.
If the copolymer obtained in the first stage of
the method contain~, for example, epoxy groups, it i~
first advantageously reacted wlth ethylenically
unsaturated compounds containing carboxyl groups a~
2 ~ ?
_ 20 --
component a~. The hydroxyl grollp produced in thi~ reaction
can be reacted by adding carboxylic acid anhydrides a~
component a5 and the desired acid value of the polymer A
can be ad~usted in this way. Examples of suitable
monomers containing carboxyl group~ and also of suitable
carboxylic acid anhydrides are the compounds already
cited.
Cation-forming group~ may be introduced, for
example, by aminolysi~.
The double bond are introduced into the poly-
mer A by reaction with the component a6. If the copolymer
obtained in the first stage already contains anion- or
cation-forming groups, said copolymer obtained in the
first stage i~ reacted directly with the componant aa.
The component a8 iB used :Ln an amount of 2 to 20 ~
by weight, preferably 2 to 10 ~ by weight, based on the
weight of the sum of the components al to a~.
Suitable a~ component a6 are compounds which
contain, in addition to a group capable of reacting with
the anion~ or cation-forming grQups of the component a2
or A~ and/or the functional groups of the copolymer, at
least one e~hylenically un~aturated double bond and which
have a number-average molecular wei~ht of ~300.
If the copolymer propared contains csrboxyl
~5 groups, monomers containing hydroxyl group~ or epoxy
groups, for example, may be used as component a~.
Examples of suitable monomers contalning epoxy
group~ and hydroxyl groups aro tha compounds already
cited.
2 1~ 7 ~ & ~ r J
- 21 -
The addition reaction o~ component a~ with the
acrylate copolymer obtained can be carried out ea~ily
under reaction conditions known per se. Depending on the
type of reaction (carboxy/epoxy; carboxy/hydroxy), the
reaction is carried out at B0 to 150C. A ~uitable
catalyst such a~, for example, tertiary amines ~
triphenylphosphine, trialkyl phosphite and chromium~III)
octoate may or may not also be concomitantly used.
In thi~ connection, the cataly~t is normally used
in an amount of 0.01 to 0.5 % by weight, ba~ed on the
weight of the 8um of tha component~ al to a6.
The component a~ ls advantageously reacted with
the acrylate copolymar in the presence o~ a polymeriz-
ation inhibltor or in the presence o~ ~uitable stablli~-
ers in order to prevent a the~nal polymerizstion, andconsequently a gelation o~ the ~ystem, during the reac~
tion in this way. Ex~mples of suitable polymerization
lnhibitors or stabilizers are hy~oquinona, methylhydro-
quinone, hydroquinone monomethyl ether, benzophenone,
~terically hindered phenols such a~, ~or example, 2,6-di-
tert-butyl-Q-cresol, phenothiazine, nitroben2ene etc.
Said inhibitors or stabilizers are normally used in
amount~ of 0.001 to 0.5 ~ by weight, preerably 0.01 to
0.1 ~ by weig~t, alway~ based on the weight of the ~um of
the componsnt~ a~ to a~.
The component a~ is normally reacted with the
acrylate copolymer un~er inertization, for exampla by
working in a n~trogen/air atmosphere (mixing ratlo 3 2 1 ) .
~ ha un~aturated polymer ~ prepared ~n thi~ way
.... . ~
~7~
- 22 -
ha~ 8 double~bond equivalent of 1,500 to 10,0~0, prefer~
ably of 2,000 to 5,000. In this connection, the double-
bond equivalent is the weight of the polymer A in g which
contains 1 mole of ethylenically unsaturated double
bonds. The number-average molecular weight of the un-
saturated polymer A i~ normally from 1,000 to 10,000,
preferably from 2,000 to 5,000. Usually ~aid unsaturated
resins A have a dispersity of from 2 to 15. To achieve
water ~olubility or water dispersibility, said un~aturat-
ed resin~ A contain 0.5 to 5.0 milliequivalent3, prafer-
ably 1.25 to 2.32 milliequivalents, of anion- or
cation-forming groups per 1 g of resin. ~hese groups are
converted into the charged group~ by at least partial
reaction with a base or acid. The degree of neutraliz-
ation of these group~ is in general from 10 to 80 ~,
preferably from 30 to 40 %.
Pre~erred re~ins A are copolymer~ containing
car~oxyl groups whi~h have an acid ~alue of from 50 to
200 mg KO~/g, prefer~bly from 70 to 130 mg ROH~g.
To neutralize the car~oxyl group, tertiary amine~
such a~, for example, triethylamine, alkali-metal hydrox-
ide~ ~uch as ~odium and potas~ium hydroxide etc. are
norm~lly uRed. ~hese may be used individually or as
mixtures o~ two or more base~.
Suitable for neutrnlizing basic groups are lactic
acid, acetic acid, formic acid, pho~phoric acid and the
like.
The unsaturated resin A i~ used in the coatlng
agants in an amount of 35 to 85 % by weight, preferably
2~7~8~
- 23 -
60 to 85 ~ by weight, always based on the wei~ht of the
~um of the components A to D.
Advantageously, the coating agents contain, in
addition to the ethylenically unsaturated polymer A, at
lea~t one monomeric, ethylenically unsaturated com-
pound B. Preferably, compounds containing at least two
ethylenically unsaturated double bond~ per molecule are
u~ed a~ componant B. The coating agent normally contains
Raid compound B in amounts of 0 to 60 % by weight,
preferably 10 to 35 % by weight, ba~ed on the waight of
the aum of the components A to D.
Examples of suitable monomeric compounds B are
di- and poly~meth)acrylate~ ~uch a~, for exampls, 1,3-
propanediol di(meth)acrylate, 1,2-propanediol di(meth)-
acrylate, 1,3-butanediol di(meth)acrylate~ 1,4-butanediol
di(meth)acrylate, 2-butene-1,4-diol di(meth)acrylate,
butylene glycol di(meth)acrylate, pentanediol di(meth)-
acryla~e~, hexanediol di(meth)acrylate~, ethylene glycol
di(meth~acrylate, diethylene glycol di(meth)acryla~e,
tri- and tetraethylene glycol di(meth)acrylate, dipropyl-
ene glycol di(meth)acrylate, tripropylene glycol di-
(meth)acrylate, hexamethylene glycol di(meth)acrylate,
1,4~cyclohaxanediol di(meth)acrylate, 2,2-dimethyl-1,3-
propanediel di~meth)acrylata, l,9-nonanediol di(meth)-
2S acrylate~ decamethylene glycol di(meth)acrylate, 2,2,4-
trLmethyl-1,3-pentanediol di(meth)acrylate, trimethylol-
ethane tri(math)acrylate, trimethylolethane di(meth)-
acrylate, trimethylolpropane di(meth)acxylata, trimethyl-
olpropane tri~meth)acrylate, glycerol tr~(meth)acrylate,
2 ~
- 24 ~
glycerol di(meth)acrylate, polyoxypropyl trimethylol-
propane tri(meth)acrylste, pentaerythritol di(meth)-
acrylate, pentaerythritol tri(meth)acrylate, penta-
erythritol tetra(meth)acrylate, 1,2,4-butanetriol
S tri(meth~acrylate, 1,~,4-butanetriol di(meth)acrylate,
and also compounds such a~, for example, alkyl (meth)-
acrylate, crotyl (meth)acrylate, athoxyethoxyethyl
acrylate, butoxyethyl acrylate, phenoxyethyl acrylate, N-
vinylpyrrolidone, i~obornyl acrylate, vinyltoluanes,
~tyrene, multifunctional (meth)acrylamides etc.
Preferably used a8 compound B are hexanediol
diacrylate, trimethylolpropane triacrylate, pentaeryth-
ritol triacrylate, pentaerythritol tetraacrylate and the
triacrylate of oxalkylated trimathylolpropane.
To accelerate the curing, the coa~ing agents
accosdlng to the invention contain, a8 component C, 1 to
10 ~ by weight, preferably 2 to 7 ~ by weight, based on
the woight of the Rum o~ the cc)mponents A to D, of at
least one photoinltiator. Normally, initiators with a
ketona base, for example, acetophenone, benzophenone,
diethoxyacetophenone, m-chloroacetophenone,
propioph~none, ben~oin, benzil, benzildimethyl katal,
anthraquinone, thioxanthone and thioxanthone derlvative~,
and also mixture~ of various initiator~. Further suitable
photoinitiators are described in EP-A-176 356.
The aqueous coating agents according to the
lnven~ion may or may not furthermore contain solvents in
order to improve the flowability of the resin component.
Example~ o~ solvents normally used for thiB purpose are
2 ~ 7 ~ ~ $ r~
_ 25 -
hydrophilic solvent~ such as isopropanol, n-butanol,
t-butanol, methoxyethanol, ethoxyethanol, butoxyethanol,
diethylene glycoll methyl ether, dioxane and tetrahydro-
furan. The aqueous coating agents may or may not also
contain hydrophobic ~olvents ~uch as, for example,
toluene, xylene and other aromatic hydrocarbons and al80
methyl ethyl ketone and methyli~obutyl ketone, ethyl
acetate, butyl acetate and 2-ethylhexyl alcohol. The
amount of the organic solvent u~d as component E is in
general from 0 to 30 % by weight, pref~rably from 0 to
5 ~ by weight, based on the weight of the sum of the
components A to D.
Finally, the coating agents according to the
in~ention may or may not also contain 0 to 10 % by
weight, pre~erably from 0 to 2 ~ by we~ght, based on the
weight of the sum of the components A to D, of further
auxiliaries and additive~. For example, dyestuffs,
levelling agent~, matting agentl3, complexing agent~ for
copper ions and the like may be added to the coating
agant~
To produce a printed circuit, the aqueou~ coating
agent 18 first deposited elactrophoretically on the
copper surface. The bath concentration (as a solid~
contant) i~ normally 3 to 25 4 by weight, preferably 10
to 20 ~ by weight. The bath temperature is in general
from 15 to 40C, preferably from 25 to 30C. ~ copper-
clad su~strate made of insulating material i~ immersed in
this coatinq bath ad~usted in thi~ way and connected to
a direct current voltage source. In this connection,
2~7~
_ 26 -
depending on the coating material u~ed, said copper-clad
~ub3trate is connected as anode or cathode. The deposi-
tion voltage i~ in general from 50 to 500 V, the deposi-
tion time in general from 30 s to 5 min. The dry film
layer ~hickneYs of the film obtained i in general
between 10 and 35 ~m.
In this connection, the choice of the depo~ition
voltage and the deposition time depend~ not only on the
~ize ratio of anode to cathods, their di~tance from one
another, the flow condition~ in ~he depo~ition vessel,
the bath temperature and the bath ~olid, but on the
desired layer thickness of the resi~t film and also on
the geometry of the substrate to be coated. If ~hree-
dimensional molding~ are to be coated with a uniform
layer thickness exploiting the so-called throwing power,
i.e. if rearward and internally situated surfAce~ are
al~o to be coated, this requires higher depo~ition
voltages and longer deposition times than if only 2-
di~ensional molding~ are to be coated. In particular, it
i~ therefora necessary for the production of 2~- and 3-
dimensional printed circuit ~oard~ to work with as high
deposition voltage~ as po~sible in order to guarantee in
this way a good throwing power performance and, conse
quently, a uniform layer thicknQ~s development over the
entire coating Yur~ace, ~or example also in drilled
hole~, recesses and at places which are ~urther removed
from the counterelectrode. Normally, deposition voltages
of 25D to 500 V, preferably 300 to 4S0 V are employed in
these cases. At the ~me tLme, however, it must be borne
2 ~ J
- 27 -
in mind that the deposition voltage should, if pos~ible,
be at least 50 V below the break-off voltage, since if
work is carried out in the vicinity of the break-off
voltage, the oxidation of copper to copper~II) ions
occurs to an increased extent during the anodic deposi-
tion. The copper(II) ions then diffuse into the depo~ited
re~ist film and fonm complexes with the carboxyl groups,
thio groups etc. which, on the one hand, impair the
developability of the r~sist ma erials and, on the other
hand, re~ult in residual layer~ on the substrate.
Aftar the electrophoretic coating, the coated
product i~ removed from the electrolytic Lmmersion bath
and washed with water or with ultrafiltrate. Then the
moisture contained in the deposited film is normally
removed by heating to 50 to 150~C for a time of 3 to
30 min.
A maAk which i8 as~entlally compo~ed o~
radiation-opaque and radLation-t:ransparent area~ i8 now
laid on the uncured, photocurable coating film obtained.
The irradiation i8 then carried out through ~aid mask.
The expo~ure may, however, also be carried out without
a mask by a computer-controlled laser beam.
The radiation used in the expo~ure according to
the invention varien a~ a function of the absorption of
~5 the photopolymerization initiator. Normally, the wave-
leng~h of the radiation i8 in the range from 200 to
600 nm. Suitable radiation sources are, for example,
carbon arcs, mercury vapor lamps, tungsten lamp~, argon
and xenon glow di~charge lamp~, photographic ~loodlamps
2 0 7 ~ ~ u rJ
- 28
and fluorescent tubes containing ultraviolet-emitting
phosphor , and also exlmer, argon, xenon, fluoride and
crypton-fluoride laser~. Of these radiation source~, in
particular, mercury vapor lamp8 and metal halide lamp8,
and al~o laser~ in the case of 3-dLmensional conductor
tracks, are particularly preferred.
Th~ expo~ure time is as a rule dependent on the
nature of the radlation-~ensitive resin used and also on
other factors such as the thickness of the electrodepo-
~ited polymer layer and the cho~en photoinitiator, thenatur~ of the radiation source and its distance from th~
film. The particular irradiation time can readily be
determined by routine expariments. In order to be able to
cura tha films as economically as possible, as ~hort
curing rates aB possible should be realized.
After the irradiation, those parts of the film
are removed which have not been af~ected by the radi-
atlon. For this purposq, the f:Llm is developed with an
agueous solvent. If the radiation-polymerizable resin
2 0 COntainB acidic groups, weaX alkaline aqueous solut~ons
which affect water solubility of the unexposed parts by
neutrali~ing the acidic groups in tho film layer are u~ed
as development solution. Examples o~ ~uch de~elopment
~olutions are aqueou~, very dilute sodium hydroxide or
pota~sium hydroxide solution, aqueous sodium or potassium
hydrogencarbonate solutions, sodium or potas~ium ~ar-
bonate solutions, agueous ammonia or disodium hydrogen-
phosphate solutions. I~, on the other hand, the radi-
ation-polymerizable resin contalna basic groups, weakly
2 ~
- 29 -
acidic, aqueous solution~ such a~, for example, agueous
acetic acid, lactic acid, glycolic acid or p-toluene-
~ulfonic acid are used as development solutions.
The further proce3s step then depends on whether
- as i~ usual in ~he case of conventional printed circuit
boards - the conductor tracks are produced by etching
away excess copper or whether they are built up by
electroplating.
The printed circuit boards can be produced by
removing, by means of an etch trea~ment with iron(III)
chlorid~ solution or ammonium perchlorate solution ~ the
proportion of the copper foil on the sub~trate laid bare
on the subs~rate by the development treatment. Then the
film on the circuit pattern cured by means of radiation
i8 removed with a strongex solvent than the solvsnt u3ed
in the development, in which proc:ess a printed circuit ifi
produced on the substrate. A similar solvent a~ in the
case of tha development may, however, al~o be used, but
only under more severe condition~.
For this so-called stripping operation, concen-
trated ~odium hydroxide or potas~ium hydroxide solution,
for example, can be ussd in the case of resins containing
acidic group~ or concentrated acid~ such as, for example,
sulfuric acid can be use~ in the case of re~in~ contain~
ing basic groups.
Another po~sibility of producing the printed
circuit boards i~ to electrodeposit, after davelopment,
-Eurther copper on the copper area~ laid bara until a
layer thickne~s o~ the copper layer of 30 to 35 ~m i~
2 ~ 8 ~
- 3~ -
reached. At these places where the copper layer i~
reinforced, the conductor tracks are later situated. Then
the polymerizad film i~ removed - a~ de~cribed above - by
treatment with a ~tronger solvent or with a sLmilar
solvent to that used for development, but under more
severe conditions. The metal laid bare is then - as also
dascribed above - etched away. This method has the
advantage that at first only a very ~hin copper layer of
0.5 to 5 ~m which solely ensures that the substrate i8
c~ated with a conductive layer and can consequently be
electrophoretically coated with the resist ma~erial has
to be deposited. In addition, in this method appreciably
le~s copper ha~ to be etched away, which is a ~urther
cr~cial advantsge.
The invention will now be explained in more
detail below on the basi~ of exemplary embodiments. In
these, all percentages and partl3 are by weight, unless
expressly stated otherwise.
1 Preparation of the polymer component A
The polymers A were prsparQd in a reactor with
nitrogan feed, stirrer ~nd dispensing devices. ~he
monomer composltion of the polymers is specified in
Tabla 1.
All the polymers are prepared in ~yleno contain-
~5 ing 50 ~ polymeriæation ~olid at a pol~merization temper-
ature of llO^C with nitrogen feed. In all cases azoiso-
valeronitrile is usad as initiator in an amount of 4 ~,
based on the weight of the monomer~. Mercaptoethanol in
an amount of 1 %, ba~ed on the weight o~ the monomers, is
2 ~ 7 ~ 3
- 31 -
used in all ca~es a~ regulator. At the same tLme, the
regulator i8 added together with the monomer over a time
of 4 h. The initiator is added in the form of a 10 ~-
strength solution in xylene via a separate feed over a
tLme of 4.5 h. The temperatur~ is then held at 110C
until the theo~etical 301id of 50 ~ (20 min, 180~C) i8
reached (approximately 3-4 h~.
The ~ub~equent modification of the polmer Db-
tained with glycidyl methacrylate as component a~ i5
carried out in an atmo~phere of air at a temperature of
90C in the presence of 0.1 ~ chromium octoate aB
catalyst, and 0.1 ~ 2,6-di-tert-hutyl-p-cresol and 0.05 ~
phenothiazine aa polymerization inhibitors, all the
percentages being based on the weight of the monomers
used, including glycidyl methacI~late. At the same time,
~he reaction is carried out unl:il the theoretical acid
value i8 reached. Then the xylene i~ distilled off until
a solid~ content of 70 ~ i8 reach~d (1 h, 130nC).
Example 1
The 70 %-strength solution of polymer Al is
partially neutrali2ed with dimethylethanolamine. The
degree o~ neutralization ~NG) i~ specified in Table 1.
Then the other con~tituents of the coating agent (mono-
mer B, photoinitiator C) are added and ubsequently
converted into a di~persion ~y ~lowly addinq distilled
water while ~tirring. The composition o~ the resultant
aqueou~ coating agent 1 i~ shown in ~a~le 2.
Tha aqueous coating agent 1 was then stirred to
evaporato the readily volatile ~Qlvent components such
2~7~
- 32 -
as, for example, the xylene by continuou~ly ~tirring in
the dark at 30C for 7 days before the depo~itions and
tests were carriad out.
The resist film~ are deposited at 25C bath
S temperature in a 3 1 ve~sel and with 2.5 1 of bath
liquid. For this purpose, purified and degreased copper
laminates (Lmmersed hrea ~30 cm2) are connected as anode
and coated.
A ~tainles~-steel sheet (Lmmersed area 70 cm2~
Lmmer~ed in the bath liquid serve~ as counterelectrode.
At the same time, the depo~ition conditions are 80 chosen
that resi~t films with a dry film layer thickne~s o~
approximately 30 ~m result. The xequired depo~ition data
are likewise specified in Table 2.
The coated laminates are then dried for 20 min at
80~C in 8 circulating alr oven. After storage at room
temperature for 24 h, 1he reslst films axe cured after
being partly covered with a commercial mask by irradi-
ation by means of a mercury vapor medium-pressure la~p
(lamp power 80 W/cm~. In this operation, the distance
between lamp and coatad substr~te i8 25 cm. The lamp is
arranged perpendicularly with re~pect to the direction of
conveyanc2. The rate of advance of the conveyor belt is
regulated to values from 1 to ~O m~min. The maximum rate
o advance which ensures that the cured films e~hibit no
changes of any kind in the sur~ace in the development
bath is shown in Table 3.
The coa~ings obtained are ~hen sub~ected to ~he
ollowing te~t~s
- 33 ~ $
1. Devalopability:
After development, the unexposed part~ of the
resist film are removed by Lmmersing the coated copper
laminate in a 2 %-strength ~odium carbonate solution. In
thi~ opera~ion the sodium carbon~te solution i8 at 20nC
and i~ stirred at 200 rev~lutions/min. The immersion time
required to strip the unexposed parts is specified in
Table 3.
2. Resistance_to copper-platinq baths:
To test the resistance of the resist film~ to
copper-plating baths, the exposed copper laminates are
immer~ed for 1 h at room temperature in an aqueous
solution which contain~ 20 % sulfuric acid and 2 % copper
sulfate. Then the surface of ~he resis~ films iB asse~ed
lS (iØ ~ no change of any kind ln the resist surface)~ The
te~t re~ults ara shown in Table 3.
3. Strippabilit~
The cured parts of the resist ~ilm are remo~ed by
immersing the developed coppex laminate~ in a 3 %-
strength sodium hydroxide solution. In this proces~ the
sodium hydroxide ~olution i8 at 20nC and is ~tirred at
200 revolutions/min. The immersion time required to strip
the expo~ed parts is specified $n Table 3.
Example 2
~n aqueou~ coating aqent 2 which dif~er~ from the
aqueou~ coating agent 1 only in that the solution of the
polymer A2 i8 now used instead o~ the solution o~ the
polymer ~1, iB prepared analogou~ly to Example 1. The
compo~ition of ~aid coating agant 2 i8 ~hown in ~able 2.
2~7~
- 34 ~
The deposi~ion of ~aid aqueous coating agent 2 and al80
the curing and testing of the resultant coating are
carried out analogously to Example 1. The re~ults are
shown in Tables 2 and 3.
S Comparison Example~ 1 ~o 4
Variou~ aqueous coating agent~ Vl to V4 which
dif~er from the aqueous coating agent 1 only in that the
solutions of the polymers V1 to V4 are now used instaad
of the solution of ~he polymer Al, are prepared
analogously to Example 1. The compo~ition of said coating
agent~ Vl to V4 i~ shown in Table 2.
The deposltion of ~aid aqueou~ coating agents Yl
to V4 and al80 the curing and testing of the resultant
coatings are carried out analogou~ly to Example 1. The
ra~ults are shown in Tables 2 and 3.
Example 3
An agueou~ coating agent 3 wh~ch di~faru from the
aqueous coating agent 2 only in that 5 % trimethylol-
propane triacrylate iB used inst;ead of 3 % trimethylol-
propane triacrylate, in all cases based on the totalwaight of the aqueous coating agent, i~ prepared
analogou~ly to Example 2.
The depo~ition of ~ald aqueous coat~ng agant 3
and al~o the curing and testing of the reRultant coating
25 iB carr~ed out analogously to Example 2. The deposition
data and te~t results are shown in Table 4.
Comparison Ex~E~les V$ to V7
Aqueou~ coat:Lng agents V5 to V7 which differ from
the aqueou~ coating agent~ V2 to V4 only in that ~hey now
2~7~
- 35 -
contain 5 % trimethylolpropane triacrylate instead of 3 ~
trLmethylolpropane triacrylate, in all ca~e~ ba~ed on the
total weight of the aqueous coating agent, are prepared
analogously to Comparison Examples 2 to 4.
S The deposition of said aqueous coating agent~ V5
~o V7 and also the curing and testing of the resultant
coatings i~ carried out analogously to Example 1. The
deposition data and test results are shown in Table 4.
2 ~ ,'3
o o o
O O ~D O
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I ~ ~ ~ ,, CO ~ o
I
. ~
o o
8
_. I
1 0 0
0 1 u~ In o o ~ ,~
II C~ O O O ~--I I N ` `
? I o o o
o ~ ~ o
o I o o I o o c~
o o o
o o U~ o
;3 ~ I I C~ o ~` o ~ O U~
~ N 1~ ~ ~ N
00 _- "" I ,_",_., _ ~
pl I O O O
P~ O O ~ O
~1 I O C S~ O ~ ~ U~
~--I--- --- - - --- - - -- - ----
O
eo I
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U
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U ~ U o
,q I ?~ ~ ~ m x ~ ~ N N m
I O ~ Q ~ m
X ~ W u~ a
2 0 ~ d
- 37 _
Exelanatory notes to Table 1:
~ Acid value of the polymer before neutralization
2) Determined by means of gel permeation chromatography
against a polystyrene standard
3~ DetermLned at 23C with the ICI plate-and-cone
viscometer with a 45 %-strength solution of the
polymex in isobutanol
4) Weight of the polymer in g which contain~ 1 mole of
methacryloyl groups.
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- 39 -
Explanatory notes to Table 2:
The ~olid content of partially neutralized polymer A
in the bath is specified in %, i.e. without ~olvent.
At the same time, the percentage is based on the
total weigh~ of the aqueou~ coating agent.
Z) Content in %, based on the total weight of the
aqueou~ coa~ing agent.
3) Daposition voltage
4) Depos~tion time
Q 5) The break-of~ voltage~ which i8 often also described
as breakdown voltage, is the upper limit of the bath
voltage or deposition voltage. At this or higher
voltage~ one or more of the ~eollowing e~fect~ occur~
Increase in bath temperature, higher current flow,
lS gas evolution at the electrodes and film defec~s.
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- 42 -
Summary of the te t re~ults for_Examples 1 to 3 and also
for Compari~on Examples Vl to V7
Comparison Example V2 shows that the break-off
voltag0 can ~e lncreased by incorporating hexanediol
dimeth~crylate in the polymer. A disadvantage i8, how-
ever, that the incorporation of hexanediol dimethacrylate
increase3 the curing time dra~tically as a re~ult of
which the achievable conveyance rate of 10 m/min drops to
1 m/min. A curing of this system under economically
favorable conditions is therefore not po~ible. In
addi~ion, a d1sadvantagQ is that, despite the high acid
value of the coating agent, the stripping time with 3 ~-
strength sodium hydroxide solution cannot be reduced to
economical times.
Although the coating agent of Comparison Ex-
ample 1 exhibits a break-off voltage of 300 V ~o that an
adequate throwing power can be achieved with thi~ coating
agent, the other properties of the coating agent are
completely inadequate for u~e as photoresist material.
Thus, despita a relatively low double-bond equivalent a~d
a consequently high double-bond density, only a rate of
ad~ance of 1 m/min can be set to achieve an adequate
curing. A disadvantage is, in sddition, that, despita the
high acid value of the coating agent, the ~trippinq time
with 3 ~-s~rength sodium hydroxide solution cannot be
reduced to economical times of les3 than 10 min.
The coating agents o Comparison Examples 3, 4,
6 and 7 have break-of voltages which are much too low
for practical applications.
~ ,3
- 43
The coating agents of Examples 1 and 2, on the
other hand, ara remarkable for high break-off voltages of
450 and 400 V respectively with, at the same tLme, good
cura~ility, developability and strippability.
The comparison of Examples 2 and 3, and also of
Comparison Examples V2 to V4 and V5 to V7 shows the
effect of the monomer component B. The advantage of an
increa ed break-off voltage in the case of the coating
agents according to the invention emerges particularly
clearly with fairly hi~h amounts of component B, as is
shown by the comparison of Example 3 with Comparison
Examples V5 to V7.
Example 4
A glas~-fiber reinforced epoxy resin laminate
provided with a 3 to 5 ~m thick copper layer and normally
used for producing printed circuit boards is coated
electrophore ically with the aqueous coatin~ agent 2. The
deposition conditions ares
~epo~ition voltage 325 V
Depo~ition time 120 s
~ath temp~rature 25 9 C
Anode/cathode distancQ 10 cm
Laminata to cathode area ratio 2s1
Re~ultant dry film layer thickness 25 ~m
Adhering bath material was rinsed o with ully
demineralized water. The coated laminate i~ then dried
~or 10 min at 80~C in a circulatlng air oven. ~ter
2 0 7 ~ ~ ~g ~
- ~4 -
covering with a commercial photomask, the coating i8
cured by irradiation by means of a mercury medium-pres-
~ure lamp (radiation powsr 100 J/cm2, measured at the
resist surface). Then the unexposed parts of the resi t
film are stripped in a suitable spray chamber by treat-
ment with 3 ~-strength sodium hydro~en carbonate solu-
tlon. The edges of the material left are then smooth and
steep. ~he copper areas laid bare are then reinforced in
a commercial electroplating bath to a layer thickness of
30 ~m without damage to the resis~ layer occurring in the
process. The exposed parts of the resist film are then
removed in a suitable ~pray chamber by treatment for
5 minutes wit~ 3 %-strength sodium hydroxide solution.
The conductor track~ reinforced by electroplating are
then obtained by diffarential etching with a commercial
etching ~olution based on sulfuri.c acid.
