Process for roughening surface of epoxy resin

Epoxy resin is pretreated with an organic solvent such as furfuryl alcohol, methyl alcohol, ethyl alcohol, n-propyl alcohol, iso-propyl alcohol, formic acid, acetic acid, propionic acid, butyric acid, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, acetone, diethyl ketone, dipropyl ketone, methylethyl ketone, diisopropyl ketone, methylpropyl ketone, ethylpropyl ketone, acetonitrile and nitromethane as a pretreating solution, and the pretreated resin is then etched with an etching solution containing hydrogen peroxide or a persulfate and sulfuric acid, or the resin is pretreated with an organic solvent containing furfuryl alcohol, methyl alcohol, ethyl alcohol, n-propyl alcohol or isopropyl alcohol, and formamide or ethylene glycol, 1,2-propylene glycol or glycerine, and the pretreated resin is etched with an etching solution containing hydrogen peroxide and sulfuric acid to roughen the surface of the resin. A good adhesiveness is obtained between the surface of the resin and a film of metal when the resin is coated with a metal.

This invention relates to a process for roughening a surface of epoxy 
resin. 
Epoxy resin has excellent electrical and mechanical properties, and is 
widely used in various applications. Among the applications, it has been 
so far highly desired to form a metallic film having a high adhesiveness 
on the surface of shaped articles of the epoxy resin. 
Generally, a metallic film is formed on a surface of resin by vapor 
deposition, electroless plating, a combination of electroless plating and 
electrolytic plating, etc. When a metallic film is formed according to any 
one of these procedures, it is necessary to roughen the surface of resin 
before forming the metallic film to provide a high adhesiveness between 
the resin and the metallic film. 
The following procedures have been so far available for roughening the 
surface of resin: (1) a procedure for physically roughening the surface of 
resin, (2) a procedure for roughening the surface of resin by a mixed 
solution of chromic acid and sulfuric acid, etc. However, in the case of 
procedure (1), a treating cost is high, and in many cases there is such a 
disadvantage that the physical properties of resin are deteriorated by the 
treatment. In the case of procedure (2), there are such disadvantages as 
pollution of working environment by chromic acid and complication of a 
facility for treating a waste effluent, etc. Thus, any of these procedures 
is not always satisfactory. 
As a result of extensive studies to overcome these disadvantages of the 
prior art procedures for roughening the surface of resin, the present 
inventors have found that the surface of epoxy resin can be roughened by 
pretreating the epoxy resin with some organic solvent at first, and then 
etching the pretreated epoxy resin with a solution containing hydrogen 
peroxide, or a persulfate, and sulfuric acid. The present inventors have 
also found that, when a film of metal, etc. is formed on the resulting 
epoxy resin having the roughened surface, a high adhesiveness can be 
obtained between the resin and the film. 
The present invention provides a process for roughening a surface of epoxy 
resin, which comprises pretreating an epoxy resin with (1) an organic 
solvent comprising at least one compound selected from the group 
consisting of: 
(a) a compound represented by the general formula, R.sub.1 --OH, wherein 
R.sub.1 is an alkyl group or furfuryl group, 
(b) a compound represented by the general formula, 
##STR1## 
wherein R.sub.2 is a hydrogen atom, or an alkyl group, R.sub.3 is an alkyl 
group, an alkoxyl group, or a hydroxyl group, and when R.sub.2 is a 
hydrogen atom, R.sub.3 is an alkoxyl group or a hydroxyl group, and 
(c) a compound represented by the general formula, CH.sub.3 --X, wherein X 
is a nitrile group, or a nitro group, or 
(2) an organic solvent comprising: 
(a) a compound represented by the general formula, R.sub.1 --OH, wherein 
R.sub.1 has the same meaning as defined above, and 
(d) at least one compound selected from the group consisting of formamide 
and a polyhydric alcohol (the organic solvent will be hereinafter referred 
to as "pretreating solution"), and then etching the resulting pretreated 
epoxy resin with a solution containing hydrogen peroxide and sulfuric acid 
(the solution will be hereinafter referred to as "etching solution"). 
The present invention furthermore provides a process for roughening a 
surface of epoxy resin, which comprises pretreating an epoxy resin with an 
organic solvent comprising at least one compound selected from the group 
consisting of: 
(a) a compound represented by the general formula, R.sub.1 --OH, wherein 
R.sub.1 is an alkyl group or furfuryl group, 
(b) a compound represented by the general formula, 
##STR2## 
wherein R.sub.2 is a hydrogen atom, or an alkyl group, R.sub.3 is an alkyl 
group, an alkoxyl group, or a hydroxyl group, and when R.sub.2 is a 
hydrogen atom, R.sub.3 is an alkoxyl group or a hydroxyl group, and 
(c) a compound represented by the general formula, CH.sub.3 --X, wherein X 
is a nitrile group, or a nitro group, then etching the resulting 
pretreated epoxy resin with a solution containing a persulfate and 
sulfuric acid (the solution will be hereinafter referred to as "etching 
solution"). 
The epoxy resin used in the present invention is the well known epoxy 
resin, and means polymeric compounds containing at least two epoxy groups 
in one molecule, and synthetic resins formed by ring-opening reaction of 
the epoxy groups of the compounds. 
The epoxy resin is not only single, but also includes modified epoxy resin. 
The modified epoxy resin must contain at least 25% by weight of epoxy 
resin. 
Shaped articles of the epoxy resin to be used in the present invention can 
be made in any manner, so long as the shaped articles have exposed 
surfaces of the epoxy resin. 
The shaped articles of the epoxy resin to be used in the present invention 
will be illustrated below in detail, but are not restricted thereto. The 
shaped articles of the epoxy resin to be used in the present invention are 
such glass-epoxy resin boards shaped by compression molding, injection 
molding, casting molding, extrusion molding, lamination molding, etc. 
Furthermore, they include shaped articles prepared by coating the epoxy 
resin on surfaces of various synthetic resin, metal, glass, ceramics, 
etc., and curing the resin. 
The shaped articles of the epoxy resin contain glass fibers, paper, 
synthetic fibers, carbon black, alumina powders, silica powders, wax, etc. 
as filler, pigment, mold release agent, reinforcing agent, etc., or can be 
used together with phenol resin, urea resin, melamine resin, etc. or 
modified epoxy resin with silicone, ester resins, etc. can be also used. 
The pretreating solution used in the present invention comprises an organic 
solvent of at least one of organic compounds (a), (b) and (c), or an 
organic solvent comprising the compound (a) and at least one of the 
compounds (d). When R.sub.1, R.sub.2, and R.sub.3 of the compounds (a), 
and (b) are alkyl groups, it is preferable that the alkyl groups have not 
more than three carbon atoms. When R.sub.3 of the compound (b) is an 
alkoxyl group, it is preferable that the alkoxyl group has not more than 
three carbon atoms. 
Examples of an organic solvent are furfuryl alcohol, methyl alcohol, ethyl 
alcohol, n-propyl alcohol, iso-propyl alcohol, formic acid, acetic acid, 
propionic acid, butyric acid, methyl formate, ethyl formate, propyl 
formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, 
ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 
propyl butyrate, acetone, diethyl ketone, dipropyl ketone, methylethyl 
ketone, diisopropyl ketone, methyl propyl ketone, ethyl propyl ketone, 
acetonitrile and nitromethane. 
Preferable examples of the organic compounds are methyl alcohol, ethyl 
alcohol, n-propyl alcohol, furfuryl alcohol, formic acid, acetic acid, 
methyl formate, ethyl formate, acetone, methylethyl ketone, acetonitrile, 
nitromethane, etc. 
As to the polyhydric alcohol of the organic compounds (d), polyhydric 
alcohols having 2 to 3 carbon atoms are preferable. Preferable examples of 
the compounds (d) are formamide, ethylene glycol, 1,2-propylene glycol, 
glycerine, etc. 
A mixing ratio of the compound (a) to the compound (d) is 1:0.1 to 10 by 
volume. A mixing ratio of the compound (a) to the compound (d) of 1:less 
than 0.1 by volume is not preferable, since a substantial effect as the 
pretreating solution based on the mixture of the compounds (a) and (d) is 
lost. A mixing ratio of the compound (a) to the compound (d) of 1:more 
than 10 by volume is also not preferable, since the effect as the 
pretreating solution is reduced. 
It is possible to use the organic compounds as such as the pretreating 
solution, but is also possible to use them in mixture of water. When the 
organic compounds are used in mixture with water, the concentration of the 
organic compounds in the aqueous solution is not particularly restricted, 
but usually is at least 15% by volume. Too low a concentration of the 
organic compound is not preferable, since the effect of pretreatment with 
the pretreating solution is reduced. 
When an aqueous solution containing hydrogen peroxide and sulfuric acid is 
used as the etching solution of the present invention, usually a 
concentration of hydrogen peroxide is at least 1 W/V % (where the 
expression "W/V %" indicates grams of hydrogen peroxide in 100 ml of its 
aqueous solution, and will be hereafter applied to designation of the 
concentration), and a concentration of sulfuric acid is at least 30% by 
volume. Preferable concentration of hydrogen peroxide is 7 to 20 W/V % and 
that of sulfuric acid is 40 to 70% by volume. 
When an aqueous solution containing a persulfate and sulfuric acid is used 
as the etching solution of the present invention, usually a concentration 
of persulfate is at least 1 W/V % (the expression "W/V %" indicates grams 
of persulfate in 100 ml of its aqueous solution, and will be hereafter 
applied to designation of the concentration), and a concentration of 
sulfuric acid is at least 30% by volume. Preferable concentration of 
persulfate is 10 to 50 W/V %, and that of sulfuric acid is 30 to 70% by 
volume. Examples of the persulfate are ammonium persulfate, sodium 
persulfate, potassium persulfate, etc. Preferable example of the 
persulfate is ammonium persulfate. 
In the present invention, the pretreatment is carried out by dipping the 
epoxy resin in said pretreating solution, or by contacting the epoxy resin 
with vapors of said pretreating solution, or by spraying said pretreating 
solution onto the epoxy resin. 
Temperature of the pretreating solution and the pretreating time are not 
particularly restricted, and are appropriately selected in view of the 
kind of the pretreating solution and other pretreating conditions, but 
usually the pretreating temperature is in a range of 20.degree. C to a 
boiling point of the pretreating solution, and the pretreating time is in 
a range of 3 to 60 minutes. 
When the pretreating is carried out insufficiently, the surface of epoxy 
resin is not fully roughened even after the etching with the etching 
solution, and a peeling strength of a film becomes low when a film of 
metal, etc. is formed on the resin. When the pretreatment is carried out 
excessively to the contrary, the surface of the resin is so roughened that 
a finished surface of the film becomes poor. 
The epoxy resin pretreated with the pretreating solution is preferably 
washed with water before the etching with the etching solution. 
In the present invention, the pretreated epoxy resin is etched by dipping 
the epoxy resin into the etching solution, or by spraying the etching 
solution onto the resin. Temperature of the etching solution and treating 
time are not particularly restricted, and are appropriately selected in 
view of the kind of the pretreating solution and other conditions. 
Usually, the etching temperature is 30.degree. to 80.degree. C, and the 
etching time is 3 to 60 minutes. 
When the etching is carried out insufficiently, the surface of epoxy resin 
is not much roughened, and consequently a peeling strength of a film of 
metal, etc. becomes low. When the etching is carried out excessively to 
the contrary, a finished surface of the film becomes poor. 
The epoxy resin whose surface has been roughened according to the present 
invention is then passed through steps of bonding, coating, plating, after 
sensitizing by use of an aqueous tin chloride solution and the like, and 
then the sensitized surface of the epoxy resin is activated by means of 
palladium chloride and the like. The epoxy resin whose surface has been 
roughened according to the present invention is particularly suitable as 
materials on which films of metal are formed by vacuum vapor deposition, 
electroless plating or a combination of electroless plating and 
electrolytic plating. 
According to the present invention, a good workability can be obtained in 
the pretreating when the pretreating is carried out with the pretreating 
solution of (a), (b) or (c), and when the pretreatment is carried out with 
the pretreating solution comprising the compound (a) and at least one of 
the compound (d), and the etching is carried out with an etching solution 
of hydrogen peroxide and sulfuric acid, the surface of epoxy resin can be 
very finely roughened, and thus the roughened surface of epoxy resin is 
hardly damaged by scratching. When the roughed surface of epoxy resin is 
coated with metal, etc., a smooth coating surface can be obtained, even if 
the coating film is thin, and a uniform peeling strength of the film can 
be obtained. That is, a metal-coated board having a good peeling strength 
can be obtained according to the present invention. 
To remove the fouling of the shaped articles, it is preferable to wash the 
shaped article with a neutral detergent or water before the pretreating. 
To remove the pretreating solution before the etching, it is preferable to 
wash the shaped article with water, and to remove the etching solution 
after the etching it is preferable to wash the shaped article with water. 
Furthermore, no etching solution containing chromic acid and sulfuric acid 
as in the prior art is used in the present invention for roughening the 
surface of epoxy resin, and thus the present invention provides a process 
with a good improvement of the working environment or a good prevention of 
environmental pollution. 
Now, the present invention will be described in detail, referring to 
Examples, but will not be, of course, limited to these Examples. 
In Examples % is percent by weight, unless otherwise specified. The peeling 
strength and surface hardness in Examples were measured according to 
JIS-C-6481, and pencil scratching test of JIS-K-5400, respectively.

EXAMPLE 1 
A glass-epoxy resin board (trade-mark GEP-130, board prepared by 
impregnating glass fiber fabrics as a substrate with epoxy resin, followed 
by lamination molding, a product made by Mitsubishi Gas-Chemical Co., 
Ltd., Japan, size: 40 .times. 100 .times. 1.6 mm) was sufficiently washed 
with a neutral detergent, and then with water. Then, the board was dipped 
in methanol as a pretreating solution at 40.degree. C for 30 minutes, and 
then washed with water. Then, the board was dipped in an etching solution 
consisting of 400 ml of 35% H.sub.2 O.sub.2, 500 ml of 98% H.sub.2 
SO.sub.4 and 100 ml of H.sub.2 O at 40.degree. C for 30 minutes, and 
washed with water, thereby roughening the surface of the board. 
Then, the board with the roughened surface was dipped in an aqueous 
solution of tin chloride sensitizer consisting of 15 g of SnCl.sub.2 
.multidot.2H.sub.2 O, 20 ml of 35% HCl, and 980 ml of H.sub.2 O at 
20.degree. C for 5 minutes, then washed with water, dipped into an aqueous 
solution of palladium chloride activator consisting of 0.25 g of 
PdCl.sub.2, 5 ml of 35% HCl and 995 ml of H.sub.2 O at 20.degree. C for 3 
minutes, and washed with water. 
Then, the board was dipped in an electroless plating solution (Copper Mix 
328 made by Shiprey Co. USA, consisting of 100 ml of solution A, 100 ml of 
solution B and 800 ml of H.sub.2 O) at 30.degree. C for 20 minutes, 
thereby coating the board with metal. 
Then, the metal-coated board was electroplated in a copper sulfate plating 
solution containing 210 g/l of CuSO.sub.4 .multidot.5H.sub.2 O, 60 g/l of 
98% H.sub.2 SO.sub.4, 0.012 g/l of 35% HCl, 0.01 g/l of dextrin, and 0.01 
g/l of urea under 3.5 A for 90 minutes, washed with water, and dried at 
120.degree. C for 1 hour, whereby the metal-coated board was obtained. 
Peeling strength of the metal coating film was 2.0 kg/cm. 
EXAMPLE 2 
Surface of the same glass-epoxy resin board as used in Example 1 was 
roughened in the same manner as in Example 1, except that acetonitrile was 
used as the pretreating solution in place of the methanol. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 1, thereby obtaining a metal-coated board. 
Peeling strength of the metal coating film was 1.5 kg/cm. 
EXAMPLE 3 
The same glass-epoxy resin board as used in Example 1 was sufficiently 
washed with a neutral detergent, washed with water, dipped in acetonitrile 
as the pretreating solution at 40.degree. C for 30 minutes, and then 
washed with water. Then, the board was dipped in an etching solution 
consisting of 300 g of (NH.sub.4).sub.2 S.sub.2 O.sub.8, 500 ml of 98% 
H.sub.2 SO.sub.4 and 500 ml of H.sub.2 O at 40.degree. C for 30 minutes, 
and washed with water, thereby roughening the surface of the board. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 1, thereby obtaining a metal-coated board. 
Peeling strength of the metal coating film was 1.5 kg/cm. 
EXAMPLE 4 
Surface of the same glass-epoxy resin board was roughened in the same 
manner as in Example 1, except that an aqueous 85% formic acid solution 
was used as the pretreating solution in place of methanol. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 1, thereby obtaining a metal-coated board. 
Peeling strength of the metal coating film was 1.3 kg/cm. 
EXAMPLE 5 
Surface of the same glass-epoxy resin board as used in Example 1 was 
roughened in the same manner as in Example 1, except that an aqueous 50% 
furfuryl alcohol solution was used as the pretreating solution in place of 
methanol. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 1, thereby obtaining a metal-coated board. 
Peeling strength of the metal coating film was 0.8 kg/cm. 
EXAMPLE 6 
Surface of the same glass-epoxy resin board as used in Example 1 was 
roughened in the same manner as in Example 1, except that an aqueous 80% 
acetone solution was used as the pretreating solution in place of 
methanol. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 1, thereby obtaining a metal-coated board. 
Peeling strength of the metal coating film was 1.4 kg/cm. 
EXAMPLE 7 
Surface of the same glass-epoxy resin board as used in Example 3 was 
roughened in the same manner as in Example 3, except that methyl ethyl 
ketone was used as the pretreating solution in place of acetonitrile. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 1, thereby obtaining a metal-coated board. 
Peeling strength of the metal coating film was 1.6 kg/cm. 
EXAMPLE 8 
The same glass-epoxy resin board as used in Example 1 was sufficiently 
washed with a neutral detergent, washed with water, brought into contact 
with vapors of ethyl formate at 60.degree. C for 10 minutes, and then 
washed with water. Then, the board was dipped in an etching solution 
consisting of 400 ml of 35% H.sub.2 O.sub.2, 500 ml of 98% H.sub.2 
SO.sub.4, and 100 ml of H.sub.2 O at 40.degree. C for 30 minutes, and 
washed with water, thereby roughening the surface of the board. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 1, thereby obtaining a metal-coated board. 
Peeling strength of the metal coating film was 1.4 kg/cm. 
EXAMPLE 9 
The same glass-epoxy resin board as used in Example 1 was sufficiently 
washed with a neutral detergent, washed with water, brought into contact 
with vapors of methyl formate at 40.degree. C for 10 minutes, and then 
washed with water. Then, the board was dipped into an etching solution 
consisting of 300 g of (NH.sub.4).sub.2 S.sub.2 O.sub.8, 500 ml of 98% 
H.sub.2 SO.sub.4 and 500 ml of H.sub.2 O at 40.degree. C for 30 minutes, 
and washed with water, thereby roughening the surface of the board. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 1, thereby obtaining a metal-coated board. 
Peeling strength of the metal coating film was 1.1 kg/cm. 
EXAMPLE 10 
The same glass-epoxy resin board as used in Example 1 was sufficiently 
washed with a neutral detergent, washed with water, and sprayed with 
ethanol at 40.degree. C for 15 minutes through a spray nozzle, and washed 
with water. The board was then sprayed with an etching solution consisting 
of 400 ml of 35% H.sub.2 O.sub.2, 500 ml of 98% H.sub.2 SO.sub.4 and 100 
ml of H.sub.2 O at 40.degree. C for 15 minutes, and washed with water, 
thereby roughening the surface of the board. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 1, thereby obtaining a metal-coated board. 
Peeling strength of the metal coating film was 0.7 kg/cm. 
EXAMPLE 11 
Surface of the same glass-epoxy resin board as used in Example 1 was 
roughened in the same manner as in Example 10, except that nitromethane 
was used as the pretreating solution in place of methanol. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 1, thereby obtaining a metal-coated board. 
Peeling strength of the metal coating film was 1.0 kg/cm. 
EXAMPLE 12 
The same glass-epoxy resin board as used in Example 1 was sufficiently 
washed with a neutral detergent, washed with water, and sprayed with an 
aqueous 80% acetic acid solution at 40.degree. C for 15 minutes through a 
spray nozzle, and washed with water. Then, the board was sprayed with an 
etching solution consisting of 400 g of (NH.sub.4).sub.2 S.sub.2 O.sub.8, 
500 ml of 98% H.sub.2 SO.sub.4 and 500 ml of H.sub.2 O at 40.degree. C for 
15 minutes, and washed with water, thereby roughening the surface of the 
board. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 1, thereby obtaining a metal-coated board. 
Peeling strength of the metal coating film was 1.2 kg/cm. 
EXAMPLE 13 
The same glass-epoxy resin board as used in Example 1 was sufficiently 
washed with a neutral detergent, washed with water, dipped in an aqueous 
solution consisting of 50% by volume of furfuryl alcohol, 30% by volume of 
formamide, and 20% by volume of water at 60.degree. C for 15 minutes, and 
washed with water. Then, the board was dipped in the same etching solution 
as used in Example 1 and washed with water in the same manner as in 
Example 1, thereby roughening the surface of the board. 
Then, the board was dipped into the same aqueous solution of tin chloride 
sensitizer as used in Example 1, washed with water, dipped into the same 
electroless plating solution as used in Example 1 in the same manner as in 
Example 1, thereby coating the board with metal. 
Then, the resulting metal-coated board was electro-plated in the same 
copper sulfate plating solution as used in Example 1 under 3.5 A for 60 
minutes, washed with water, and dried at 120.degree. C for 1 hour, thereby 
obtaining a metal-coated board. 
The resulting metal-coated board had a smooth metal-coated surface, and 
peeling strength of the metal coating film was 1.8 kg/cm on average. 
Surface hardness of the glass-epoxy resin board with the roughened surface 
before the plating was 4 H. 
EXAMPLE 14 
Surface of the same glass-epoxy resin board as used in Example 13 was 
roughened in the same manner as in Example 13, except that an aqueous 
solution consisting of 30% by volume of furfuryl alcohol and 70% by volume 
of glycerin was used as the pretreating solution in place of the furfuryl 
alcohol-formamide solution. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 13, thereby obtaining a metal-coated board. 
The resulting metal-coated board had a smooth metal-coated surface, and 
peeling strength of the metal coating film was 1.5 kg/cm on average. 
Surface hardness of the glass-epoxy resin board with the roughened surface 
before the plating was 4 H. 
EXAMPLE 15 
Surface of the same glass-epoxy resin board as used in Example 13 was 
roughened in the same manner as in Example 13, except that a solution 
consisting of 50% by volume of methanol and 50% by volume of ethylene 
glycol was used as the pretreating solution in place of the furfuryl 
alcohol-formamide solution. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 13, thereby obtaining a metal-coated board. 
The resulting metal-coated board had a smooth metal-coated surface, and 
peeling strength of the metal coating film was 2.3 kg/cm on average. 
Surface hardness of the glass-epoxy resin board with the roughened surface 
before the plating was 4 H. 
EXAMPLE 16 
Surface of the same glass-epoxy resin board as used in Example 13 was 
roughened in the same manner as in Example 13, except that a solution 
consisting of 80% by volume of methanol and 20% by volume of glycerin was 
used as the pretreating solution in place of the furfuryl 
alcohol-formamide solution. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 13, thereby obtaining a metal-coated board. 
The resulting metal-coated board had a smooth metal-coated surface, and 
peeling strength of the metal coating film was 2.1 kg/cm on average. 
Surface hardness of the glass-epoxy resin board with the roughened surface 
before the plating was 4 H. 
EXAMPLE 17 
Surface of the same glass-epoxy resin board as used in Example 13 was 
roughened in the same manner as in Example 13, except that a solution 
consisting of 70% by volume of methanol and 30% by volume of propylene 
glycol was used as the pretreating solution in place of the furfuryl 
alcohol-formamide solution. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 13, thereby obtaining a metal-coated board. 
The resulting metal-coated board had smooth metal-coated surface and 
peeling strength of the metal coating film was 2.0 kg/cm on average, and 
surface hardness of the glass-epoxy resin board with the roughened surface 
before the plating was 4 H. 
EXAMPLE 18 
The same glass-epoxy resin board as used in Example 1 was sufficiently 
washed with a neutral detergent, washed with water, sprayed with a 
solution consisting of 90% by volume of ethanol and 10% by volume of 
formamide at 40.degree. C for 60 minutes through a spray nozzle, and 
washed with water. Then, the board was sprayed with an etching solution 
consisting of 400 ml of 35% H.sub.2 O.sub.2, 500 ml of 98% H.sub.2 
SO.sub.4, and 100 ml of water at 40.degree. C for 30 minutes through a 
spray and washed with water, thereby roughening the surface of the board. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 13, thereby obtaining a metal-coated board. 
The resulting metal-coated board had a smooth metal-coated surface, and 
peeling strength of the metal coating film was 1.3 kg/cm on average. 
Surface hardness of the glass-epoxy resin board with the roughened surface 
before the plating was 4 H. 
EXAMPLE 19 
Surface of the same glass-epoxy resin board as used in Example 18 was 
roughened in the same manner as in Example 18, except that a solution 
consisting of 60% by volume of ethanol and 40% by volume of ethylene 
glycol was used as the pretreating solution in place of the 
ethanol-formamide solution. 
The resulting board with the roughned surface was further treated in the 
same manner as in Example 13, thereby obtaining a metal-coated board. 
The resulting metal-coated board had a smooth metal-coated surface, and 
peeling strength of the metal coating film was 1.2 kg/cm on average. 
Surface hardness of the glass-epoxy resin board with the roughened surface 
before the plating was 4 H. 
EXAMPLE 20 
Surface of the same glass-epoxy resin board as used in Example 18 was 
roughened in the same manner as in Example 18, except that n-propyl 
alcohol used as the pretreating solution in place of the ethanol-formamide 
solution. 
The resulting board with the roughened surface was further treated in the 
same manner as in Example 13, thereby obtaining a metal-coated board. 
The resulting metal-coated board had a smooth metal-coated surface, and 
peeling strength of the metal coating film was 0.8 kg/cm on average, and 
surface hardness of the glass-epoxy resin board with the roughened surface 
before the plating was H.