U.S. patent application number 09/838228 was filed with the patent office on 2002-12-05 for method of producing a roughening-treated copper foil.
Invention is credited to Endo, Yasuhiro.
Application Number | 20020182433 09/838228 |
Document ID | / |
Family ID | 26590764 |
Filed Date | 2002-12-05 |
United States Patent
Application |
20020182433 |
Kind Code |
A1 |
Endo, Yasuhiro |
December 5, 2002 |
METHOD OF PRODUCING A ROUGHENING-TREATED COPPER FOIL
Abstract
A roughening-treated copper foil, comprising (A) a copper foil,
(B) a composite metal layer, which is formed on a bonding surface
of the copper foil and comprises (I) copper, (II) at least one
metal selected from the group consisting of tungsten and molybdenum
and (III) at least one metal selected from the group consisting of
nickel, cobalt, iron and zinc, and (C) a roughened layer comprising
copper, which is formed on the composite metal layer.
Inventors: |
Endo, Yasuhiro;
(Shimodate-shi, JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
26590764 |
Appl. No.: |
09/838228 |
Filed: |
April 20, 2001 |
Current U.S.
Class: |
428/606 ;
205/111; 205/182; 428/607 |
Current CPC
Class: |
Y10T 428/12438 20150115;
H05K 3/384 20130101; C25D 5/605 20200801; Y10T 428/12431 20150115;
H05K 2203/0307 20130101; H05K 2203/0723 20130101; C25D 3/58
20130101; H05K 2201/0355 20130101; C25D 5/10 20130101 |
Class at
Publication: |
428/606 ;
428/607; 205/111; 205/182 |
International
Class: |
B21C 037/00; C25D
003/38; C25D 005/10 |
Claims
What is claimed is,
1. A roughening-treated copper foil, comprising (A) a copper foil,
(B) a composite metal layer, which is formed on a bonding surface
of the copper foil and comprises (I) copper, (II) at least one
metal selected from the group consisting of tungsten and molybdenum
and (III) at least one metal selected from the group consisting of
nickel, cobalt, iron and zinc, and (C) a roughened layer comprising
copper, which is formed on the composite metal layer.
2. The roughening-treated copper foil of claim 1, wherein the
composite metal layer comprises 5,000 to 10,000 .mu.g/dm.sup.2 of
copper, 10 to 1,000 .mu.g/dm.sup.2 of at least one metal selected
from the group consisting of tungsten and molybdenum and 10 to
1,000 .mu.g/dm.sup.2 of at least one metal selected from the group
consisting of nickel, cobalt, iron and zinc, all in coating
amount.
3. The roughening-treated copper foil of claim 1, wherein the
roughened layer comprises 30,000 to 300,000 .mu.g/dm.sup.2 of
copper in coating amount.
4. The roughening-treated copper foil of claim 2, wherein the
roughened layer comprises 30,000 to 300,000 .mu.g/dm.sup.2 of
copper in coating amount.
5. A method of producing a roughening-treated copper foil,
comprising treating a copper foil as a cathode by electrolysis in a
plating bath containing (i) copper ions, (ii) metal ions of at
least one metal selected from the group consisting of tungsten and
molybdenum and (iii) metal ions of at least one metal selected from
the group consisting of nickel, cobalt, iron and zinc, at a current
density lower than a limiting current density of the plating bath,
to form on the copper foil a composite metal layer comprising (I)
copper, (II) at least one metal selected from the group consisting
of tungsten and molybdenum and (III) at least one metal selected
from the group consisting of nickel, cobalt, iron and zinc; and
forming a roughened layer comprising copper on the composite metal
layer by carrying out electrolysis in a plating bath containing
copper ions at a current density not lower than a limiting current
density of the plating bath to form a dendritic copper
electrodeposition layer and then carrying out subsequent
electrolysis at a current density lower than the limiting current
density of plating bath to form nodular copper.
6. The method of claim 5, wherein the plating bath containing (i)
copper ions, (ii) metal ions of at least one metal selected from
the group consisting of tungsten and molybdenum and (iii) metal
ions of at least one metal selected from the group consisting of
nickel, cobalt, iron and zinc is pH 1.5 to 5.0.
Description
BACKGROUND OF THE INVENTION
[0001] (a) Field of the Invention
[0002] The present invention relates to a roughening-treated copper
foil useful for printed wiring boards or the like and to the
production thereof, particularly, to a roughening-treated copper
foil, which is useful for printed wiring boards due to its
excellent adhesive strength to resin base materials of high Tg's,
such as FR-5, and to a method suitable for the production
thereof.
[0003] (b) Description of the Related Art
[0004] Copper foil for printed wiring boards generally has a
bonding surface, which is previously roughened by some means to
give higher adhesive strength on lamination onto resin base
materials. For electrolytic copper foil, plating methods are mainly
used as the roughening treatment. Japanese Patent Application
Examined Publication No. 53-39376 (1978) discloses an example of
the plating methods. According to the method, first a dendritic
copper electrodeposition layer is formed on at least one bonding
surface of a copper foil as a cathode by the so-called burning
plating in an acidic copper plating bath at a current of the
limiting current density or higher, then a smooth copper
electrodeposition layer is formed on the dendritic copper
electrodeposition layer at a current of a current density lower
than the limiting current density (covering plating) to change the
dendritic copper into nodular copper and to increase the adhesive
strength by the nodular copper. After the formation of the nodular
copper by the electrolysis treatment, the surface of the copper
foil has a larger specific surface than before the electrolysis
treatment, and the nodular copper works as an anchor, improving the
adhesive strength between resin base materials and the copper foil.
When nodular copper is formed on electrolytic copper foil, which
generally has a surface (mat surface) rougher than the other
surface (shiny surface), current is mainly centered to convexes,
and the formation of the nodular copper is centered on the extreme
ends of the convexes.
[0005] The recent spread of note type personal computers and pocket
telephones has increased the use of glass-epoxy printed wiring
boards produced by using as resin base materials FR-5 materials
having high Tg's. As compared with conventional FR-4 materials,
epoxy resins having high Tg's are more resistive to heat but have
lower adhesive strength to copper foil. A means of enhancing the
adhesive strength of copper foil to resin base materials is to
increase the roughness of the bonding surface of copper foil.
However, increasing the surface roughness tends to cause the
so-called copper powder-falling off that is the falling of nodular
copper even with small abrasion force and the so-called residual
copper that is nodular copper left in resin base materials after
the etching step in the production of printed circuits.
[0006] Japanese Patent Application Examined Publication No.
54-38053 (1979) discloses an improved method of forming a roughened
surface by carrying out electrolysis treatment at an approximate
limiting current density in an acidic copper plating bath to which
a specific amount of at least one metal selected from arsenic,
antimony, bismuth, selenium and tellurium is added. The addition of
a very small amount of arsenic, antimony, bismuth, selenium or
tellurium permits the formation of minute projections, but cannot
solve the problem centering to the convexes on the copper foil.
Further, using copper foil containing arsenic, antimony, bismuth,
selenium or tellurium, which are poisons or deadly poisons, in
printed wiring boards causes the problem of environmental pollution
on discarding etching waste liquors or the printed wiring
boards.
[0007] Addition of benzoquinoline to an acidic copper plating bath
(Japanese Patent Application Examined Publication No. 56-41196
(1981)) or addition of molybdenum (Japanese Patent Application
Examined Publication No. 62-56677 (1987)) are also proposed, but
cannot improve adhesive strength sufficiently.
[0008] Japanese patent Application Unexamined Publication No.
8-236930 (1996) discloses a method for solving the problem, wherein
electrolysis is carried out at approximate limiting current density
in an acidic copper plating bath containing metal ions of at least
one metal selected from chromium and tungsten and metal ions of at
least one metal selected from vanadium, nickel, iron, cobalt, zinc,
germanium and molybdenum, to form a roughening-treated layer
containing the metals added. Japanese Patent Application Unexamined
Publication No. 11-256389 (1999) discloses a method of carrying out
electrolysis at approximate limiting current density in an acidic
copper plating bath containing molybdenum ions and metal ions of at
least one metal selected from iron, cobalt, nickel and tungsten, to
form a layer of burnt deposits (a layer formed by burning plating)
containing the metals added.
[0009] These methods, however, also cause the phenomena of copper
powder-falling off and residual copper because nodular copper is
formed exclusively on the extreme ends of the convexes on copper
foil.
SUMMARY OF THE INVENTION
[0010] An object of the present invention is to solve the problems
in the prior arts. That is, an object of the present invention is
to provide a roughening-treated copper foil, which is suitable for
printed wiring boards due to its high adhesive strength to resin
base materials, by treating the bonding surface of copper foil by
electrolysis so as to form nodular copper not only on the convexes
on the bonding surface but also on the concaves thereon without
increasing the surface roughness.
[0011] Another object of the present invention is to provide a
method suitable for producing the roughening-treated copper
foil.
[0012] Accordingly, the present invention provides a
roughening-treated copper foil, comprising
[0013] (A) a copper foil,
[0014] (B) a composite metal layer, which is formed on a bonding
surface of the copper foil and comprises (I) copper, (II) at least
one metal selected from the group consisting of tungsten and
molybdenum and (III) at least one metal selected from the group
consisting of nickel, cobalt, iron and zinc, and
[0015] (C) a roughened layer comprising copper, which is formed on
the composite metal layer.
[0016] Herein, the terms "the bonding surface of a copper foil"
mean a surface of a copper foil, which faces an adherent when the
copper foil is bonded to the adherent.
[0017] The present invention further provides a method of producing
a roughening-treated copper foil, comprising
[0018] treating a copper foil as a cathode by electrolysis in a
plating bath containing (i) copper ions, (ii) metal ions of at
least one metal selected from the group consisting of tungsten and
molybdenum and (iii) metal ions of at least one metal selected from
the group consisting of nickel, cobalt, iron and zinc, at a current
density lower than a limiting current density of the plating bath,
to form on the copper foil a composite metal layer comprising (I)
copper, (II) at least one metal selected from the group consisting
of tungsten and molybdenum and (III) at least one metal selected
from the group consisting of nickel, cobalt, iron and zinc; and
[0019] forming a roughened layer comprising copper on the composite
metal layer by carrying out electrolysis in a plating bath
containing copper ions at a current density not lower than a
limiting current density of the plating bath to form a dendritic
copper electrodeposition layer, and then carrying out subsequent
electrolysis at a current density lower than the limiting current
density of the plating bath to form nodular copper. Herein, the
terms "the limiting current density of the plating bath" mean a
current density at which generation of hydrogen accompanies the
cathode reaction for the deposition of the metals or metal
compounds.
BRIEF DESCRIPTION OF THE DRAWING
[0020] FIG. 1 is a scanning electron microscope photograph showing
the roughened surface of the roughening-treated copper foil
obtained in Example 1.
[0021] FIG. 2 is a scanning electron microscope photograph showing
the roughened surface of the roughening-treated copper foil
obtained in Comparative Example 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] A preferred example of the copper foil (raw copper foil) to
be used in the present invention is electrolytic copper foil. It is
also possible to use other ones, such as rolled copper foil or
plastic film coated with copper film by, for example, vacuum
plating. There is no particular limitation in the thickness of the
copper foil and the roughness and form of the surfaces of the
copper foil. The copper foil may have one or two bonding
surfaces.
[0023] The bonding surface of the copper foil is coated with a
composite metal layer, which comprises (I) preferably 5,000 to
10,000 .mu.g/dm.sup.2 of copper, (II) preferably 10 to 1,000
.mu.g/dm.sup.2, more preferably 100 to 1,000 .mu.g/dm.sup.2 of at
least one metal selected from the group consisting of tungsten and
molybdenum and (III) preferably 10 to 1,000 .mu.g/dm.sup.2, more
preferably 10 to 300 .mu.g/dm.sup.2 of at least one metal selected
from the group consisting of nickel, cobalt, iron and zinc, all in
coating amount.
[0024] If the coating amount of the at least one metal selected
from the group consisting of nickel, cobalt, iron and zinc is less
than 10 .mu.g/dm.sup.2, the formation of the nodular copper by the
plating may not extend to the concaves on the copper foil, but be
centered to the convexes, and if more than 1,000 .mu.g/dm.sup.2,
etching the plated layer may require very long time to remove
unnecessary copper to form copper circuits. The coating amount of
the at least one metal selected from the group consisting of
nickel, cobalt, iron and zinc depends on the composition of the
plating bath and the treating conditions, which may be selected
from those described later.
[0025] If the coating amount of copper in the composite metal layer
is less than 5,000 .mu.g/dm.sup.2, the nodular copper may not be
formed on the entire concaves, and if more than 10,000
.mu.g/dm.sup.2, the formation of the nodular copper on the entire
concaves may be less effective and the production cost may
increase. If the coating amount of the at least one metal selected
from the group consisting of tungsten and molybdenum in the
composite metal layer is less than 10 .mu.g/dm.sup.2, nodular
copper may not be formed on the entire concaves, and if more than
1,000 .mu.g/dm.sup.2, the nodular copper may not grow large. The
composite metal layer is preferably 0.05 to 0.15 .mu.m thick, more
preferably 0.07 to 0.12 .mu.m thick.
[0026] According to the present invention, the composite metal
layer is formed by treating the bonding surface of a copper foil as
a cathode by electrolysis in a plating bath containing (i) copper
ions, (ii) metal ions of at least one metal selected from the group
consisting of tungsten and molybdenum and (iii) metal ions of at
least one metal selected from the group consisting of nickel,
cobalt, iron and zinc, at a current density lower than the limiting
current density of the plating bath. The bonding surface of the
copper foil is preferably subjected to pickling and degreasing
prior to the electrolysis.
[0027] The sources of the metal ions in the plating bath are
water-soluble metal salts. The following is a non-limitative but
preferred range of the composition of the bath.
[0028] copper ion source--copper sulfate pentahydrate: 10-100
g/l
[0029] tungsten ion source--sodium tungstate dehydrate: 0.01-20
g/l
[0030] molybdenum ion source--sodium molybdate dehydrate: 0.5-20
g/l
[0031] nickel ion source--nickel sulfate hexahydrate
[0032] cobalt ion source--cobalt sulfate heptahydrate
[0033] iron ion source--ferrous sulfate heptahydrate
[0034] zinc ion source--zinc sulfate heptahydrate
[0035] the total of nickel sulfate hexahydrate, cobalt sulfate
heptahydrate, ferrous sulfate heptahydrate and zinc sulfate
heptahydrate: 10-100 g/l
[0036] So far as the current density is lower than the limiting
current density of the plating bath, the electrolysis conditions
are not limited, and are generally selected from the following
ranges.
[0037] current density: 1-10 A/dm.sup.2
[0038] electrolysis treatment period: 1-30 sec.
[0039] bath temperature: 10-60.degree. C.
[0040] The preferred pH of the plating bath ranges from 1.5 to 5.0.
If the pH is lower than 1.5, the preferred ranges of the coating
amounts of the at least one metal selected from the group
consisting of tungsten and molybdenum and the at least one metal
selected from the group consisting of nickel, cobalt, iron and zinc
in the composite layer may be narrowed, so that the formation of
nodular copper by the plating does not extend to the concaves on
the copper foil but be centered on the convexes. If the pH is
higher than 5.0, it may take a very long time to dissolve the metal
ions of at least one metal selected from tungsten and molybdenum,
lowering the productivity. The pH more preferably ranges from 2.0
to 4.0.
[0041] By forming the composite metal layer, fine particles are
formed on the convexes on the copper foil, but cannot give
sufficient adhesive strength as they are or even after coated with
copper by burning plating or covering plating. To improve adhesive
strength, a roughened layer comprising copper is formed on the
composite metal layer by using both burning plating and covering
plating to deposit nodular copper further on the concaves on the
copper foil.
[0042] That is, the copper foil treated under the above-described
conditions is washed with water, and then a roughened layer
comprising copper is formed on the composite metal layer by
carrying out burning plating whereby a dendritic copper
electrodeposition layer is formed by electrolysis in a plating bath
containing copper ions at a current density not lower than the
limiting current density of the plating bath, followed by covering
plating whereby nodular copper is formed by electrolysis at a
current density lower than the limiting current density of the
plating bath.
[0043] The coating amount of copper in the roughened layer
comprising copper is preferably 30,000 to 300,000 .mu.g/dm.sup.2.
If it is less than 30,000 .mu.g/dm.sup.2, copper nodules may be too
small to give sufficient adhesive strength, and if more than
300,000 .mu.g/dm.sup.2, adhesive strength may be sufficient, but
the production cost will be problematically high. More preferred
coating amount is 100,000 to 200,000 .mu.g/dm.sup.2. The combined
step of burning plating/covering plating may be repeated to form
the roughened layer comprising copper.
[0044] In cases where the roughened layer comprising copper is
formed by using a common sulfuric acid-acidic copper sulfate bath,
preferred but non-limitative examples of the composition of the
bath and electrolysis conditions are as follows.
[0045] copper ion source--copper sulfate pentahydrate: 20-300
g/l
[0046] sulfuric acid: 10-200 g/l
[0047] current density: burning plating (not lower than limiting
current density of the plating bath)--10-200 A/dm.sup.2; covering
plating (lower than limiting current density or the plating
bath)--1-20 A/dm.sup.2
[0048] electrolysis treatment period: burning plating--1-10
seconds; covering plating--40-100 seconds
[0049] bath temperature: 20-60.degree. C.
[0050] On the copper foil coated with the roughened layer
comprising copper, it is preferable to form other layers commonly
formed on copper foil, for example, a rust preventing layer, such
as a chromate layer, a zinc layer, a copper-zinc alloy layer, a
zinc alloy layer, a nickel-molybdenum-cobalt layer or an
indium-zinc layer, a coupling agent treatment layer, or an adhesive
resin layer, such as a phenolic resin, epoxy resin or polyimide
resin layer, according to demands. The roughening-treated copper
foil coated with the above-described layers is laminated onto a
resin base material with heat and pressure, to form a copper-clad
laminate for printed wiring boards.
[0051] Hereinafter the present invention will be described in more
detail referring to Examples and Comparative Examples, which,
however, do not limit the scope of the present invention.
EXAMPLES 1 TO 8 AND COMPARATIVE EXAMPLES 1 TO 8
Example 1
[0052] (1) A 35 .mu.m thick electrolytic copper foil (surface
roughness Ra of mat surface: 0.9 .mu.m as measured according to JIS
B 0601) was subjected to pickling for 20 seconds by using a 10%
sulfuric acid solution.
[0053] (2) The copper foil was then washed with water, and the mat
surface (bonding surface) of the copper foil was treated by
electrolysis at a current density of 6 A/dm.sup.2 for 4 seconds in
a plating bath, which contained 50 g/l of copper sulfate
pentahydrate, 2 g/l of sodium molybdate dehydrate and 50 g/l of
nickel sulfate hexahydrate and was adjusted to pH 3.0 and to a bath
temperature of 30.degree. C., to form on the bonding surface of the
copper foil a composite metal layer containing copper molybdenum
and nickel. The coating amounts of the metals in the composite
metal layer were measured by an ICP (inductively coupled plasma
luminescent) analyzer to be 7,900 .mu.g/dm.sup.2 of copper, 178
.mu.g/dm.sup.2 of molybdenum and 145 .mu.g/dm.sup.2 of nickel.
After the treatment, the treated surface had a surface roughness Ra
of 0.9 .mu.m.
[0054] (3) The copper foil was then washed with water, and the
surface of the composite metal layer was treated by {circle over
(1)} electrolysis at a current density of 30 A/dm.sup.2 (not lower
than the limiting current density) for 3 seconds followed by
{circle over (2)} electrolysis at 5 A/dm.sup.2 (lower than the
limiting current density) for 80 seconds both in a plating bath
containing 130 g/l of copper sulfate pentahydrate and 100 g/l of
sulfuric acid and adjusted to a bath temperature of 30.degree. C.,
to form a roughened layer comprising copper. The roughened layer
comprising copper had a coating amount of copper of 150,000
.mu.g/dm.sup.2 and a surface roughness Ra of 1.4 .mu.m. On the
roughening-treated electrolytic copper foil was observed nodular
copper formed all over the irregularities on the copper foil. FIG.
1 shows a scanning electron microscope photograph (magnification:
2000, object angle: 45.degree.) of the roughened surface.
[0055] (4) The copper foil was then washed with water, and dipped
for 10 seconds in an aqueous solution of 3.5 g/l of sodium
bichromate dihydrate adjusted to pH 4.2 and a bath temperature of
28.degree. C., to form a rust preventing layer.
[0056] (5) The copper foil was then washed with water, dipped for
10 seconds in an aqueous solution of 0.1 wt %
3-glycidoxypropyltrimethoxysil- ane, and then immediately dried at
80.degree. C., to form a silane coupling agent treatment layer.
form on the bonding surface of the copper foil a composite metal
layer containing copper, molybdenum, cobalt and iron. The coating
amounts of the metals in the composite metal layer were measured by
an ICP (inductively coupled plasma luminescent) analyzer to be
7,900 .mu.g/dm.sup.2 of copper, 180 .mu.g/dm.sup.2 of molybdenum,
12 .mu.g/dm.sup.2 of cobalt and 50 .mu.g/dm.sup.2 of iron. After
the treatment, the treated surface had a surface roughness Ra of
0.9 .mu.m. Subsequently, a roughened layer comprising copper was
formed in the same manner as in Example 1. The roughened layer
comprising copper had a coating amount of copper of 150,000
.mu.g/dm.sup.2 and a surface roughness Ra of 1.5 .mu.m. On the
roughening-treated electrolytic copper foil was observed nodular
copper formed all over the irregularities on the copper foil.
[0057] After the treatments (4) and (5) of Example 1 were carried
out, the measurement of adhesive strength and tests for residual
copper and powder falling were carried out in the same manner as in
Example 1 (6), and the results are listed in Table 1.
Example 3
[0058] After the same electrolytic copper foil as that used in
Example 1 was pickled and washed with water in the same manner as
in Example 1, the mat surface (bonding surface) of the copper foil
was treated by electrolysis at a current density of 7 A/dm.sup.2
for 4 seconds in a plating bath, which contained 50 g/l of copper
sulfate pentahydrate, 2 g/l of sodium molybdate dehydrate and 50
g/l of zinc sulfate heptahydrate and was adjusted to pH 2.5 and to
a bath temperature of 30.degree. C., to form on the bonding surface
of the copper foil a composite metal layer containing copper,
molybdenum and zinc. The coating amounts of the metals in the
composite metal layer were measured by an ICP (inductively coupled
plasma luminescent) analyzer to be 9,200 .mu.g/dm.sup.2 of copper,
230 .mu.g/dm.sup.2 of molybdenum and 159 .mu.g/dm.sup.2 of m. On
the roughening-treated electrolytic copper foil was observed
nodular copper formed all over the irregularities on the copper
foil.
[0059] After the treatments (4) and (5) of Example 1 were carried
out, the measurement of adhesive strength and tests for residual
copper and powder falling were carried out in the same manner as in
Example 1 (6), and the results are listed in Table 1.
Example 5
[0060] After the same electrolytic copper foil as that used in
Example 1 was pickled and washed with water in the same manner as
in Example 1, the mat surface (bonding surface) of the copper foil
was treated by electrolysis at a current density of 6 A/dm.sup.2
for 4 seconds in a plating bath, which contained 50 g/l of copper
sulfate pentahydrate, 10 g/l of sodium tungstate dihydrate, 30 g/l
of cobalt sulfate heptahydrate and 30 g/l of ferrous sulfate
heptahydrate and was adjusted to pH 2.0 and to a bath temperature
of 30.degree. C., to form on the bonding surface of the copper foil
a composite metal layer containing copper, tungsten, cobalt and
iron. The coating amounts of the metals in the composite metal
layer were measured by an ICP (inductively coupled plasma
luminescent) analyzer to be 7,900 .mu.g/dm.sup.2 of copper, 200
.mu.g/dm.sup.2 of tungsten, 12 .mu.g/dm.sup.2 of cobalt and 50
.mu.g/dm.sup.2 of iron. After the treatment, the treated surface
had a surface roughness Ra of 0.9 .mu.m. Subsequently, a roughened
layer comprising copper was formed in the same manner as in Example
1. The roughened layer had a surface roughness Ra of 1.5 .mu.m. On
the roughening-treated electrolytic copper foil was observed
nodular copper formed all over the irregularities on the copper
foil.
[0061] After the treatments (4) and (5) of Example 1 were carried
out, the measurement of adhesive strength and tests for residual
copper and powder falling were carried out in the same manner as in
Example 1 (6), and the results are listed in Table 1.
Example 6
[0062] After the same electrolytic copper foil as that used in
Example 1 was pickled and washed with water in the same manner as
in Example 1, the mat surface (bonding surface) of the copper foil
was treated by electrolysis at a current density of 7 A/dm.sup.2
for 4 seconds in a plating bath, which contained 50 g/l of copper
sulfate pentahydrate, 1 g/l of sodium tungstate dihydrate, 2 g/l of
sodium molybdate dihydrate and 50 g/l of zinc sulfate heptahydrate
and was adjusted to pH 2.5 and to a bath temperature of 30.degree.
C., to form on the bonding surface of the copper foil a composite
metal layer containing copper, tungsten, molybdenum and zinc. The
coating amounts of the metals in the composite metal layer were
measured by an ICP (inductively coupled plasma luminescent)
analyzer to be 9,200 .mu.g/dm.sup.2 of copper, 50 .mu.g/dm.sup.2 of
tungsten, 180 .mu.g/dm.sup.2 of molybdenum and 160 .mu.g/dm.sup.2
of zinc. After the treatment, the treated surface had a surface
roughness Ra of 0.9 .mu.m. Subsequently, a roughened layer
comprising copper was formed in the same manner as in Example 1.
The roughened layer comprising copper had a surface roughness Ra of
1.4 .mu.m. On the roughening-treated electrolytic copper foil was
observed nodular copper formed all over the irregularities on the
copper foil.
[0063] After the treatments (4) and (5) of Example 1 were carried
out, the measurement of adhesive strength and tests for residual
copper and powder falling were carried out in the same manner as in
Example 1 (6), and the results are listed in Table 1.
Example 7
[0064] The same treatments as in Example 4 were repeated except
that a 18 .mu.m thick rolled copper foil (surface roughness Ra: 0.1
.mu.m) was used, to form a composite metal layer containing copper,
tungsten and nickel. The coating amounts of the metals in the
composite metal layer were 7,900 .mu.g/dm.sup.2 of copper, 145
.mu.g/dm.sup.2 of tungsten and 128 .mu.g/dm.sup.2 of nickel. After
the treatment, the treated surface had a surface roughness Ra of
0.1 .mu.m. Subsequently, a roughened layer comprising copper was
formed in the same manner as in Example 1. The roughened layer
comprising copper had a surface roughness Ra of 0.5 .mu.m.
[0065] After the treatments (4) and (5) of Example 1 were carried
out, the measurement of adhesive strength and tests for residual
copper and powder falling were carried out in the same manner as in
Example 1 (6), and the results are listed in Table 1.
Example 8
[0066] The same treatments as in Example 4 were repeated except
that a 12 .mu.m thick electrolytic copper foil (surface roughness
Ra of the mat surface: 0.2 .mu.m) was used, to form a composite
metal layer containing copper, tungsten and nickel. The coating
amounts of the metals in the composite metal layer were 7,900
.mu.g/dm.sup.2 of copper, 150 .mu.g/dm.sup.2 of tungsten and 135
.mu.g/dm.sup.2 of nickel. After the treatment, the treated surface
had a surface roughness Ra of 0.2 .mu.m. Subsequently, a roughened
layer comprising copper was formed in the same manner as in Example
1. The roughened layer comprising copper had a surface roughness Ra
of 0.6 .mu.m.
[0067] After the treatments (4) and (5) of Example 1 were carried
out, the measurement of adhesive strength and tests for residual
copper and powder falling were carried out in the same manner as in
Example 1 (6), and the results are listed in Table 1.
Comparative Example 1
[0068] The same treatments as in Example 1 were repeated except
that the step (3) for forming a roughened layer by using a with
water and then treated by electrolysis at a current density of 5
A/dm.sup.2 (lower than the limiting current density) for 80 seconds
by using a plating bath, which contained 130 g/l of copper sulfate
pentahydrate and 100 g/l of sulfuric acid and was adjusted to a
bath temperature of 30.degree. C., to form a smooth copper layer
(covering plating). The smooth copper layer had a coating amount of
copper of 132,000 .mu.g/dm.sup.2 and a surface roughness Ra of 1.1
.mu.m.
[0069] After the treatments (4) and (5) of Example 1 were carried
out, the measurement of adhesive strength and tests for residual
copper and powder falling were carried out in the same manner as in
Example 1 (6), and the results are listed in Table 1.
Comparative Example 5
[0070] The same electrolytic copper foil as that used in Example 1
was pickled and washed with water in the same manner as in Example
1. Without forming a composite metal layer, the mat surface
(bonding surface) of the copper foil was then treated in a plating
bath of a bath temperature of 30.degree. C. containing 130 g/l of
copper sulfate pentahydrate and 100 g/l of sulfuric acid by {circle
over (1)} electrolysis at a current density of 30 A/dm.sup.2 (not
lower than the limiting current density) for 3 seconds and {circle
over (2)} electrolysis at a current density of 5 A/dm.sup.2 (lower
than the limiting current density) for 80 seconds, to form a
roughened layer comprising copper. The roughened layer comprising
copper had a coating amount of copper of 150,000 .mu.g/dm.sup.2 and
a surface roughness Ra of 1.8 .mu.m. On the roughening-treated
electrolytic copper foil was observed the formation of nodular
copper centered on the convexes on the irregular surface of the
copper foil. FIG. 2 shows a scanning electron microscope photograph
(magnification: 2000, object angle: 45.degree.) of the roughened
surface.
[0071] After the treatments (4) and (5) of Example 1 were carried
out, the measurement of adhesive strength and tests for residual
copper and powder falling were carried out in the same manner as in
Example 1 (6), and the results are listed in Table 1.
Comparative Example 6
[0072] The same rolled copper foil as that used in Example 7 was
pickled and washed with water in the same manner as in Example 1.
Without forming a composite metal layer, the mat surface (bonding
surface) of the copper foil was then treated in a plating bath of a
bath temperature of 30.degree. C. containing 130 g/l of copper
sulfate pentahydrate and 100 g/l of sulfuric acid by {circle over
(1)} electrolysis at a current density of 30 A/dm.sup.2 (not lower
than the limiting current density) for 3 seconds and {circle over
(2)} electrolysis at a current density of 5 A/dm.sup.2 (lower than
the limiting current density) for 80 seconds, to form a roughened
layer comprising copper. The roughened layer comprising copper had
a coating amount of copper of 150,000 .mu.g/dm.sup.2 and a surface
roughness Ra of 0.8 .mu.m.
[0073] After the treatments (4) and (5) of Example 1 were carried
out, the measurement of adhesive strength and tests for residual
copper and powder falling were carried out in the same manner as in
Example 1 (6), and the results are listed in Table 1.
Comparative Example 7
[0074] The same electrolytic copper foil as that used in Example 8
was pickled and washed with water in the same manner as in Example
1. Without forming a composite metal layer, the mat surface
(bonding surface) of the copper foil was then treated in a plating
bath of a bath temperature of 30.degree. C. containing 130 g/l of
copper sulfate pentahydrate and 100 g/l of sulfuric acid by {circle
over (1)} electrolysis at a current density of 30 A/dm.sup.2 (not
lower than the limiting current density) for 3 seconds and {circle
over (2)} electrolysis at a current density of 5 A/dm.sup.2 (lower
than the limiting current density)
1 TABLE 1 Adhesive strength kN/m Residual copper Powder-falling
Example 1 2.0 No No Example 2 1.9 No No Example 3 1.9 No No Example
4 2.0 No No Example 5 2.1 No No Example 6 1.9 No No Example 7 1.0
No No Example 8 0.9 No No Comp. 0.9 No Countless particles Example
1 of about 0.1 .mu.m in diameter Comp. 0.9 No Countless particles
Example 2 of about 0.1 .mu.m in diameter Comp. 1.0 No Countless
particles Example 3 of about 0.1 .mu.m in diameter Comp. 1.3 No No
Example 4 Comp. 1.6 15 particles of 10 .mu.m 23 particles of 2-10
Example 5 or less in diameter .mu.m in diameter Comp. 0.5 8
particles of 10 .mu.m 15 particles of 2-10 Example 6 or less in
diameter .mu.m in diameter Comp. 0.5 7 particles of 10 .mu.m 18
particles of 2-10 Example 7 or less in diameter .mu.m in diameter
Comp. 1.7 2 particles of 10 .mu.m 3 particles of 2-10 Example 8 or
less in diameter .mu.m in diameter
[0075] As apparent from comparison of FIG. 1 with FIG. 2, unlike
the roughening-treated copper foil obtained in Comparative Example
5 on which nodular copper was locally electrodeposited on the
convexes on the copper foil surface,
* * * * *