JPH0529740A - Electrolytic copper foil for printed circuit board - Google Patents

Abstract

PURPOSE:To eliminate warpage due to a crystalline distortion by a wide electrolytic copper foil having uniform thickness distribution and to enhance a connecting strength with an insulating board with predetermined surface roughness by forming gloss copper-plated layers on both surfaces of the foil in such a manner that the thickness, surface roughness of the plated layer provided on one surface of the foil fall in special ranges. CONSTITUTION:A ratio of a thickness of a gloss copper-plated layer 2 provided on one surface of an electrolytic copper foil 1 to that of the layer provided on the other surface is desirably 50-150%. The surface of the layer 2 of the foil 1 for a first printed circuit board is roughed to 0.2-5mum of roughness, one or more thin film 3 selected from a group consisting of a zinc layer, a zinc alloy layer, a nickel layer and a nickel alloy layer is provided at the side of the roughed surface at least to be connected to the insulating board, and the surface of the thin film is chromated. Further, the roughed surface or the chromated surface 4 connected to the insulating board of the copper foil for a second printed circuit board is coated with silane coupling agent 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic copper foil for printed wiring boards.

[0002]

2. Description of the Related Art A printed wiring board is a supercomputer.
From printed circuit boards to toys, they are widely used in circuits of various electric devices, and thin printed wiring boards are desired in view of demands for resource saving, material cost reduction, and miniaturization and high performance of electronic devices. As a method for thinning a printed wiring board, there is a method of thinning a copper foil portion (which later constitutes a circuit) of an original plate for manufacturing a printed wiring board or a method of thinning an insulating substrate joined to the copper foil.

However, when the copper foil itself is made thin, there are drawbacks that the current carrying capacity of the formed electric circuit becomes small and the strength of the circuit itself is lowered, and the handling of the copper foil becomes difficult. And the manufacturing cost of the printed wiring board becomes high.

Further, in the original plate having two or more layers of copper foil, if the insulating substrate is made thin, the distance between the opposing copper foils becomes short, so that when the printed wiring board is produced from this original plate, the insulation resistance between the circuits is reduced. Decrease, the electrical signal is disturbed,
There is a drawback that the quality of the printed wiring board is deteriorated because an electrical short circuit easily occurs.

Further, an electrolytic copper foil having a roughened surface is generally used as an original plate of a printed wiring board, and fine irregularities on the surface are eroded into an insulating substrate to bond with a substrate resin. Is increasing.

However, in such an electrolytic copper foil for a printed wiring board, for example, as shown in FIG. 3, the unevenness 8 on the surface of the electrolytic copper foil 1 bites into the insulating substrate 10,
Since the effective thickness (L1) of the board becomes thin, there is a drawback that the quality of the printed wiring board deteriorates as in the case where the insulating board is made thin.

Therefore, in order to reduce the thickness of the printed wiring board, the printed wiring board can have a sufficient thickness as a circuit conductor and can maintain a high bonding strength with the insulating substrate.
An electrolytic copper foil for printed wiring boards having a sufficiently small surface roughness is required.

By the way, as a copper foil having a sufficiently small surface roughness, a rolled copper foil can be mentioned first. A rolled copper foil with a smooth surface can be easily obtained, and the surface roughness is a standard rolled copper foil of 35 μm with a thickness of 0.5-4 μm.
It is about m (Rz value). In order to increase the bonding strength with the insulating substrate, the rolled copper foil may be electroplated on the surface of the rolled copper foil 11 to form irregularities 9 for roughening treatment, as shown in FIG. Alternatively, the surface can be etched and roughened (see Japanese Patent Publication No. 61-54592).

However, it is difficult to manufacture a rolled copper foil having a uniform thickness in the width direction, and this tendency is
The thinner the foil and the wider it becomes more difficult.
Therefore, unlike electrolytic copper foil, which has a wide width, which is advantageous for improving the productivity of printed wiring boards, and has a uniform foil thickness distribution even in thin foils, rolled copper foil provides a stable wide foil thickness with a uniform foil thickness distribution. However, there is a drawback that the production cost is higher than that of the electrolytic copper foil.

On the other hand, the electrolytic copper foil has a thickness of 40
Since it is manufactured with a high current density of 150 A / dm ² ,
As shown in FIG. 3, the unevenness 8 on the plated surface became rough, and it was difficult to obtain a copper foil having a smooth surface. A method of adding a brightening agent such as thiourea to a plating bath is known as a method for obtaining an electrolytic copper foil having a smooth surface roughness (Rz is about 0.5 μm) similar to that of rolled copper foil. In this method, since the operating current density is as small as ¹ to 5 A / dm ² , there is a drawback that the productivity of the copper foil is significantly reduced, and the brightening agent increases the electrode potential, so-called polarization, While reducing the surface roughness, the copper crystals that make up the foil are distorted, which causes the internal stress to accumulate and the foil to warp.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to easily produce a foil having a wide width and a uniform foil thickness distribution by an electrolysis method, and to prevent warping due to crystal strain, An object of the present invention is to provide an electrolytic copper foil for printed wiring boards, which is a copper foil having a sufficiently small roughness and which can enhance the bonding strength with an insulating substrate.

[0012]

The first aspect of the present invention is an electrolytic copper foil for a printed wiring board having a bright copper plating layer on both sides of the electrolytic copper foil.

A second aspect of the present invention is that the surface of the bright copper plating layer of the first electrolytic copper foil for printed wiring board has a roughness of 0.2 to 5 μm.
Roughened, and at least one of the roughened surfaces to be joined to the insulating substrate is one or more thin layers selected from the group consisting of a zinc layer, a zinc alloy layer, a nickel layer and a nickel alloy layer. And the surface of the thin layer is chromate-treated, which is an electrolytic copper foil for a printed wiring board.

The third aspect of the present invention is to provide a roughened surface or chrome which is to be joined to the insulating substrate of the second electrolytic copper foil for printed wiring board.
The electrolytic copper foil for printed wiring boards has a silane coupling agent applied to its treated surface.

The present invention will be described in detail below. The electrolytic copper foil used in the present invention is not particularly limited as long as it is a copper foil manufactured by an electrolytic method. Among them, JIS B 0601
It is preferable that the surface roughness (hereinafter, referred to as surface roughness) indicated by the Rz value specified in 1 is 8 μm or less, and if the surface roughness is small, the glossy copper plating layer described later can be thinned. The foil productivity can be improved.

The bright copper plating layer used in the present invention includes:
There is no particular limitation as long as it can reduce the surface roughness of the electrolytic copper foil, and for example, it can be formed on the electrolytic copper foil surface using a known bright copper plating method.

As the bright copper plating bath, a known bright copper plating bath, for example, a commercially available bright copper plating bath for decoration can be used, and a known electrolytic bath to which a brightening agent such as thiourea or molasses is added. May be used.

As the counter electrode, for example, a phosphorus-containing copper, lead, a lead alloy, a titanium electrode coated with a platinum group metal or an oxide of a platinum group metal, and the like can be used. Among them, a phosphorus-containing copper electrode is preferable. .

The temperature of the plating bath is preferably 15 to 40 ° C. When the temperature of the plating bath is higher than 40 ° C, the additive may be consumed much, and the glossiness of the obtained plated surface may be insufficient.
The plated surface may have insufficient gloss.

The current density is preferably 0.5 to 20 A / dm ² . When the current density exceeds 20 A / dm ² , the plated surface may have insufficient gloss, and when the current density is less than 0.5 A / dm ² , the obtained plated surface has insufficient gloss. In some cases, productivity will decrease.

The surface roughness of the bright copper plating layer thus obtained is preferably 0.2 to 5 μm. The thickness of the bright copper plating layer needs to be thick when the surface of the electrolytic copper foil used is rough, and can be thin when the surface is small. For example, in order to obtain a bright copper plating layer having a surface roughness within the above range, when the surface roughness of the electrolytic copper foil exceeds 4 μm and is 8 μm or less, the thickness of the bright copper plating layer is 10 to 20 μm. Is preferable, and when the surface roughness of the electrolytic copper foil is 4 μm or less, the thickness of the bright copper plating layer is preferably 6 to 12 μm.

The bright copper plating may be carried out simultaneously on the front and back of the electrolytic copper foil or separately on each side. The ratio of the thickness of the bright copper plating layer on one surface of the electrolytic copper foil to the thickness of the bright copper plating layer on the other surface is 50 to 150.
% Is preferred. When the plating stress is tensile stress, when the ratio is less than 50%, the foil may warp with the thin bright copper plating layer side swelling, and when it exceeds 150%, the thick bright copper plating layer may be warped. The foil may warp with the sides dented. Also,
The opposite is true when the plating stress is a compressive stress.

The electrolytic copper foil for a printed wiring board according to the present invention is provided with bright copper plating layers on both sides of the electrolytic copper foil so as to have the above-mentioned predetermined thicknesses, so that the both bright copper plating layers have respective internal stresses. Since it cancels, it prevents curling.

As the bright copper plating layer used in the present invention,
It is preferable that the surface is roughened in order to further increase the bonding strength with the insulating substrate or another layer to be bonded to the layer later. The bright copper plating layer whose surface is roughened is, for example,
As shown in FIG. 2, the unevenness 6 of the bright copper plating layer 2 is made into a finer unevenness 7.

As a roughening treatment method, a foil on which a bright copper plating layer is formed is subjected to an etching treatment on the surface of the bright copper plating layer in an electrolytic solution by using alternating current, direct current or a combination thereof (Japanese Patent Publication No. 61-54592). (See Japanese Patent Laid-Open Publication) and an electrolytic solution, at a high current density near the limiting current density, one or more metal thin layers selected from the group consisting of copper, copper alloys, zinc and zinc alloys are used as bright copper plating layers. Method of electrodeposition on the surface (UK Patent GB203246A, JP-A-63-8969)
No. 8) is preferable.

As the bath used for the etching roughening treatment,
A hydrochloric acid bath and a sulfuric acid bath are preferable, but among them, the hydrochloric acid bath can form a treated surface having a small surface roughness,
It is more preferable because the bonding strength with the insulating substrate or another layer bonded to this treated surface can be increased.

The conditions for the etching roughening treatment include, for example, the following conditions. Conditions when using hydrochloric acid bath Composition of hydrochloric acid: 10 to 100 g / l Conditions Counter electrode: Stainless steel plate or titanium electrode coated with platinum group metal or its oxide Bath temperature:・ ・ 30 to 80 ℃ Frequency ・ ・ ・ ・ ・ ・ 20 to 100Hz Current density ・ ・ ・ 10 to 40A / dm ² Treatment time ・ ・ ・ 10 to 60 seconds

When the hydrochloric acid concentration is less than 10 g / l, the roughening may be too deep, and when it exceeds 100 g / l, the roughening may not be sufficiently performed. When the current density is less than 10 A / dm ² , roughening may not be sufficiently performed, and when the current density exceeds 40 A / dm ² , roughening may be too deep. The treatment time can be appropriately adjusted so as to obtain a desired roughness.

Condition bath composition when using a sulfuric acid bath : Sulfuric acid : 30 to 150 g / l, or hydrochloric acid added to this: 5 to 20 g / l Conditions: Counter electrode: stainless steel plate, platinum group metal or titanium electrodes coated with the oxide, lead or lead alloy electrode bath temperature · · · · · 30 to 80 ° C. current density ··· 10~70A / dm ² (DC) processing time ... 10 ~ 60 seconds

When the current density exceeds 70 A / dm ² , a surface on which powder easily falls may be obtained, and 10 A / dm ² may be obtained.
When it is less than dm ² , roughening may not be sufficiently performed. Further, when the bath is a mixed acid bath of sulfuric acid and hydrochloric acid, it may be sufficient to immerse it.

In the method of electrodepositing a thin layer of a metal having a rough surface on the surface of a bright copper plating layer, the metal to be electrodeposited is
For example, copper, a copper-zinc alloy, a copper-nickel alloy, a copper-tin alloy, a zinc-nickel alloy, etc. can be mentioned, and two or more thin layers of these metals may be provided in combination. In practical use, it is more preferable that a normal copper layer for fixing the roughened layer is provided on the roughened copper thin layer, and further the roughened copper-
A thin layer of nickel alloy is provided.

The plating conditions for forming a thin layer of copper or a copper-nickel alloy include, for example, the following conditions.

Copper plating conditions Bath composition Metallic copper: 3 to 8 g / l Sulfuric acid: 20 to 70 g / l Arsenic: 50 to 300 ppm Conditions Counter electrode: Titanium electrode, lead or lead alloy electrode coated with platinum group metal or its oxide Bath temperature ・ ・ ・ 10-35 ℃ Current density ・ ・ ・ 2-25A / dm ² (DC) Treatment time ・ ・ ・5-40 seconds

When the current density is less than 2 A / dm ² ,
In some cases, roughening may not be sufficient, and when it exceeds 25 A / dm ² , roughening may be too large or powder may easily fall off.

As the conditions for further plating a thin copper layer and the copper-nickel alloy plating conditions on the roughened thin layer of copper electrodeposited under such conditions, the following conditions can be mentioned, for example. .

Copper plating conditions for the second layer Bath composition Metallic copper: 40-80 g / l Sulfuric acid: 20-150 g / l Conditions Counter electrode: Platinum group metal or its Titanium electrode coated with oxide, lead or lead alloy electrode Bath temperature ・ ・ ・ 30-70 ℃ Current density ・ ・ ・ 1-25A / dm ² (DC) Treatment time ・ ・ ・ 5-40 seconds

The second thin copper layer prevents the first roughened copper thin layer from falling off.

Copper-Nickel Alloy Plating Conditions Bath Composition Nickel Sulfate ... 10-30 g / l Copper Sulfate ... 0.2-6 g / l Ammonium Sulfate ... 20-80 g / l Boric acid: Adjust the pH to 1.5 to 3.5 with 3 to 20 g / l sulfuric acid Conditions Counter electrode: A titanium electrode coated with a platinum group metal or its oxide, lead or Lead alloy electrode Bath temperature ・ ・ ・ 15-35 ℃ Current density ・ ・ ・ 1-25A / dm ² (DC) Treatment time ・ ・ ・ 5-40 seconds

When the current density under the copper-nickel alloy plating condition is less than 1 A / dm ² , roughening may not be sufficient, and when it exceeds 25 A / dm ² , roughening may be too large. is there.

As described above, the roughening treatment with a small roughness can be performed only by the above-mentioned first layer copper plating, but the second layer ordinary copper plating is further applied, and the above-mentioned copper If nickel alloy plating is applied, the roughening particles that have been electrodeposited on the surface of the bright copper plating layer can be further fixed under the copper plating conditions for the first layer described above, and then finer roughening particles can be electrodeposited. This is preferable because the bonding strength with the insulating substrate and other layers can be further increased.

Further, as the electrolytic copper foil for a printed wiring board of the present invention, more preferable is a zinc layer on at least the side of the surface of the roughened copper plating layer thus roughened, which is to be joined to the insulating substrate, It has one or more thin layers selected from the group consisting of a zinc alloy layer, a nickel layer and a nickel alloy layer, and the surface of the thin layer is chromated.

The method for forming the thin layer and the method for chromating the surface of the thin layer are described in, for example, JP-A-60.
The method described in JP-A-86894 can be adopted.

As the zinc alloy, for example, Zn-W, Z
n-V, Zn-Tl, Zn-Sn, Zn-Se, Zn-
Sb, Zn-Pt, Zn-Pb, Zn-Ni, Zn-M
o, Zn-Mn, Zn-In, Zn-Fe, Zn-G
e, Zn-Ga, Zn-Cu, Zn-Cr, Zn-C
o, Zn-Cd, Zn-Au, Zn-Ag, etc. can be mentioned. Among them, Zn-Cu is preferable.

As the nickel alloy, for example, Ni-
P, Ni-W, Ni-Co, Ni-Mo, Ni-Pd,
Ni-Sn, Ni-Zn, Ni-Cu, Ni-Mn, N
Examples thereof include i-Fe and Ni-Mn-Zn.
Among them, Ni-P is preferable. The thickness of the thin layer is
It is preferably 0.0005 to 0.002 μm.

The chromate treatment in the present invention is a treatment for adhering chromium oxide and its hydrate, or a mixture of zinc or its oxide and chromium oxide and its hydrate to the surface of the thin layer. Say.

The amount of the chromium oxide and its hydrate, or the mixture of zinc or its oxide and chromium oxide, and its hydrate, deposited in an amount of 0.01 to 0.
2 mg / dm ² is preferred.

The method for forming the thin layer and the method for chromating the surface of the thin layer are described in, for example, JP-A-60.
The method described in JP-A-86894 can be adopted.

As an electrolytic copper foil for a printed wiring board of the present invention, as shown in FIG. 1, both surfaces of an electrolytic copper foil 1 are provided with a bright copper plating layer 2 having a roughened surface, and an insulating substrate is further provided. The roughened surface to be joined is provided with a thin layer 3, and the chrome coupling surface 5 of the thin layer 3 is coated with a silane coupling agent 5 to obtain various properties such as rust resistance, heat resistance and hydrochloric acid resistance. It is particularly preferable because it can be improved.

Examples of the silane coupling agent used in the present invention include the following formula (I): YRSiX ₃ (I) (wherein, X is independently a hydrolyzable group, and R is an alkyl group. Group, and Y represents an organic functional group capable of binding to the organic matrix polymer).

Of these, X is preferably a chlorine atom, an alkoxy group or an alkoxyalkoxy group, and Y is preferable.
Is a vinyl group, an epoxy group, a glycidoxy group, a methacryloxy group, an amino group, an N- (2-aminoethyl) amino group, or a silane coupling agent in which YR is a vinyl group.

Specific examples thereof include vinyl tris (2-
Methoxyethoxy) silane, 3-glycidoxypropyltrimethoxysilane, N- (2-aminoethyl) -3-
Aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, etc. can be mentioned.

The silane coupling agent is 0.001 to 5
% Aqueous solution is preferably used. When the concentration of the silane coupling agent in this aqueous solution is less than 0.001%,
The effect of the above-mentioned silane coupling agent cannot be expected, and 5%
When it exceeds, it is difficult to dissolve the silane coupling agent, and it is not possible to expect a corresponding improvement in the effect.

The silane coupling agent used in the present invention is
A compound (YRSi (O) having a silanol group as shown in the following reaction formula is hydrolyzed by the aqueous solution, water in the air or water adsorbed on the surface of the hydrated chromium oxide layer.
H) ₃ ) is generated. YRSiX ₃ + 3H ₂ O → YRSi (OH) ₃ + 3HX (wherein X, Y and R are the same as above)

In this compound having a silanol group, --S
The silanol group represented by i (OH) ₃ is bonded to the roughened surface of the bright copper plating layer or the surface of the chromium hydrate oxide or the chromium hydrate oxide-dispersed zinc layer, and at the same time, --Y
The organic functional group capable of binding to the organic matrix polymer shown in (3) binds to the resin of the substrate when the electrolytic copper foil for printed wiring board of the present invention is joined to the resin substrate.

[0055]

EXAMPLES The present invention will be described more specifically below with reference to examples. Example 1 On both surfaces of an electrolytic copper foil having a surface roughness of 3.9 μm and a thickness of 18 μm on the rough surface side, a plating bath having the following composition was used and bright copper plating having a thickness of 8.5 μm on one surface was performed under the following conditions. went. The surface roughness (Rz value) of the obtained bright copper plating was 0.6 μm. Next, this was washed with water and dried to prepare an electrolytic copper foil for a printed wiring board having a thickness of 35 μm.

Conditions for bright copper plating Plating bath composition Metallic copper 55 g / l Sulfuric acid 55 g / l Chlorine (sodium chloride)・ ・ ・ 90 ppm Bright copper plating additive for decoration ・ ・ Nippon Shering Co., Ltd. Caparaside 210 Mecap agent ・ ・ ・ ・ 5 m / l Brightener A ・ ・ ・ ・0.5 m / l

Plating conditions Counter electrode: Liquid temperature of phosphorus-containing copper plate: 27 ° C Current density: 6 A / dm ²

With respect to the obtained electrolytic copper foil for printed wiring board, the peeling strength shown below was measured, and the degree of warpage was evaluated according to the following criteria. The results are shown in Table 1.

Peeling strength After the electrolytic copper foil for printed wiring board and the FR-4 resin substrate were press-bonded, the load when peeling the foil from the resin substrate was measured.

Evaluation Criteria for Curling ◯: There was no curling of the foil. △ ・ ・ ・ ・ When a 10 cm square foil was placed on a horizontal plate, the edge was lifted by 5 to 20 mm. × ・ ・ ・ ・ The foil curled and curled up when left unattended.

Example 2 The electrolytic copper foil for a printed wiring board obtained in the same manner as in Example 1 was subjected to etching roughening treatment under the following conditions using an aqueous solution containing 60 g / l of hydrochloric acid as a bath.

Etching roughening treatment conditions Counter electrode --- Phosphorus-containing copper plate liquid temperature --- 60 ° C. current --- AC (50 Hz) current density --- 6 A / dm ² processing time: 120 seconds

When the surface roughness (Rz value) of the roughened bright copper-plated surface was measured, it was 0.6 μm, but it was observed by an electron microscope. Further, fine irregularities were formed. This is because the Rz value is measured using a stylus having a diameter of 2 μm, and therefore the fine unevenness formed by the roughening treatment cannot be accurately reflected as it is. FIG. 5 shows an electron micrograph of the bright copper-plated surface before the roughening treatment, and FIG. 6 shows an electron micrograph of the bright copper-plated surface after the roughening treatment (magnification:
800 times).

The electrolytic copper foil for a printed wiring board thus obtained was evaluated for peeling strength and degree of warp in the same manner as in Example 1, and further observed for powder falling. The results are shown in Table 1.

Example 3 11 g / l of zinc sulfate heptahydrate was formed on the surface of the electrolytic copper foil for printed wiring board obtained in the same manner as in Example 2 to be joined to the resin substrate.
An aqueous solution containing 40 g / l of sodium hydroxide was used as a bath, and galvanization was performed under the following conditions, followed by immediate washing with water.

Zinc plating conditions Counter electrode: Stainless plate liquid temperature: Room temperature current density: 0.43 A / dm ² Treatment time: 1.6 Second

Next, the zinc-plated surface of this copper foil was treated with an aqueous solution containing 4.75 g / l of chromium trioxide (pH 11.3;
Using sodium hydroxide) as a bath, chromate treatment was performed under the following conditions, followed by washing with water and drying. With respect to the obtained copper foil, the peel strength and the degree of warpage were evaluated in the same manner as in Example 2, and the presence or absence of powder drop was observed. The results are shown in Table 1.

Example 4 An epoxy-based silane coupling agent (3-glycidoxypropyltrimethoxysilane) was formed on the surface of the electrolytic copper foil for printed wiring board obtained in the same manner as in Example 3 to be bonded to the substrate.
After applying 1% aqueous solution of and squeezing with a soft rubber piece,
Heat dried. With respect to the obtained copper foil, the peel strength and the degree of warpage were evaluated in the same manner as in Example 2,
The presence or absence of powder drop was observed. The results are shown in Table 1.

Example 5 Hydrochloric acid 6 used in the etching roughening treatment in Example 4
An aqueous solution containing 120 g / l of sulfuric acid was used in place of the aqueous solution containing 0 g / l, and the bright copper plating layer was subjected to etching roughening treatment under the following conditions.

Etching roughening treatment conditions Counter electrode: Lead plate liquid temperature: 60 ° C Current: DC current density: 30 A / dm ² Processing time: 20 seconds

When the surface roughness (Rz value) of the roughened bright copper-plated surface was measured, it was almost the same as 0.8 μm, but when observed by an electron microscope, it was found that the rough copper-plated uneven surface was Further, finer unevenness was formed.

A copper foil was prepared in the same manner as in Example 4 except that the bright copper plating layer was roughened as described above, and the peel strength and the degree of warpage were evaluated. Was observed. The results are shown in Table 1.

Example 6 Instead of the etching roughening treatment performed in Example 4, three plating layers were provided under the following conditions to roughen the bright copper plating layer.

[0074]

[0075]

[0076]

When the surface roughness (Rz value) of the roughened bright copper-plated surface was measured, it did not change to 0.6 μm, but when observed with an electron microscope, the uneven surface of the bright copper-plated surface was Further, fine irregularities were formed.

A copper foil was prepared in the same manner as in Example 4 except that the bright copper plating layer was roughened as described above, and the peel strength and the degree of warpage were evaluated. Was observed. The results are shown in Table 1.

Comparative Example 1 An electrolytic copper foil having a surface roughness on the rough surface side of 3 μm and a thickness of 35 μm was subjected to etching roughening treatment in the same manner as in Example 5.
The surface roughness (Rz value) of the roughened electrolytic copper foil was measured and found to be 3.5 μm. The degree of warpage of the obtained copper foil was evaluated. The results are shown in Table 2.

Comparative Example 2 One side of an electrolytic copper foil was plated with bright copper having a thickness of 17 μm. The surface roughness (Rz value) of the bright copper plating was measured and found to be 0.6 μm. An electrolytic copper foil for a printed wiring board was produced in the same manner as in Example 1 except that one side was plated with bright copper. The degree of warpage of the obtained copper foil was evaluated. The results are shown in Table 2.

Comparative Example 3 A copper foil having a thickness of 35 μm was produced only by the bright copper plating of Example 1. The surface roughness (Rz value) of the bright copper plating was 0.3 μm. The degree of warpage of the obtained copper foil was evaluated. The results are shown in Table 2.

[0082]

[Table 1]

[0083]

[Table 2]

Evaluation (1) As shown in Table 1, the electrolytic copper foils for printed wiring boards of Examples 1 to 6 have bright copper plating layers on both sides of the electrolytic copper foils, so that they do not warp and , The surface roughness is small.

(2) As shown in Example 2, the surface of the bright copper plating layer was roughened by etching, and the peel strength was 0.7 kg / cm ^2. The bonding strength between the foil and the insulating substrate was improved more than that of the untreated material (0.3 kg / cm ² ), and as shown in Example 3, a thin zinc layer was formed on the surface of the bright copper plating layer subjected to the etching roughening treatment. The film provided with the chromate treatment on its surface had a peeling strength of 0.9 kg / cm ² , and the bonding strength with the insulating substrate was further improved. Further, the zinc thin layer and the chromate treatment of the surface thereof can improve the rust preventive power and heat resistance of the copper foil.

Further, as shown in Example 4, the chrome-treated surface was treated with a silane coupling agent, and the peel strength was 1.3 kg / cm ^2, and it was further bonded to an insulating substrate. Strength improved.

(3) As shown in Example 4, the surface of the bright copper plating layer was roughened by etching in a hydrochloric acid bath, and the surface was roughened by etching in a sulfuric acid bath (Example 5).
Compared with, the surface roughness of the etched surface is small and the peel strength is large.

Example 4 Surface roughness: 0.6 μm, Peel strength:
1.3 kg / cm ² Example 5: Surface roughness: 0.8 μm, Peel strength:
1.1kg / cm ² In contrast,

(4) As shown in Table 2, in Comparative Example 1, the surface of the electrolytic copper foil was directly roughened without performing bright copper plating, so that the surface roughness did not decrease and the Rz value I couldn't get a small copper foil.

(5) In Comparative Example 2, since bright copper plating was applied to only one side of the electrolytic copper foil, the copper foil was greatly warped and could not be used. Further, in Comparative Example 3, since a copper foil having a thickness of 35 μm was produced only by bright current copper plating having a low current density, the copper foil was warped.

[0091]

EFFECTS OF THE INVENTION According to the present invention, a foil having a wide width and a uniform foil thickness distribution can be easily manufactured by an electrolysis method, there is no warpage due to electrodeposition strain, and the surface roughness is small. Therefore, a fine pattern circuit can be formed, and moreover, the bonding strength with the insulating substrate can be increased.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating an electrolytic copper foil for a printed wiring board according to the present invention.

FIG. 2 is a cross-sectional view illustrating a fine concavo-convex shape after roughening the surface of a bright copper plating layer.

FIG. 3 is a cross-sectional view illustrating an original plate obtained by joining an electrolytic copper foil for a conventional printed wiring board having a roughened surface of an electrolytic copper foil to an insulating substrate.

FIG. 4 is a cross-sectional view illustrating an original plate in which an electrolytic copper foil for a conventional printed wiring board in which a surface of a rolled copper foil is roughened and an insulating substrate are joined together.

FIG. 5 is an electron micrograph of a bright copper-plated surface before roughening treatment.

FIG. 6 shows an electron micrograph of a bright copper-plated surface after roughening treatment.

[Explanation of symbols]

1 ... Electrolytic copper foil 2 ... Bright copper plating layer 3 ... Thin layer 4 ... Chromate processing 5: Silane coupling agent 6 ... Asperity of bright copper plating layer 7 ... Finer irregularities formed on the irregularities 6 8 ... Asperities formed on the surface of electrolytic copper foil 9 ... Asperities formed on the surface of rolled copper foil 10 ... Insulating substrate 11 ... Rolled copper foil L1 ... ・ Effective thickness of substrate

Claims (5)

[Claims] 1. An electrolytic copper foil for a printed wiring board, which has bright copper plating layers on both sides of the electrolytic copper foil. 2. The printed wiring board according to claim 1, wherein the thickness of the bright copper plating layer on one surface of the electrolytic copper foil is 50 to 150% of the thickness of the bright copper plating layer on the other surface. Electrolytic copper foil for use. 3. The surface of the bright copper plating layer has a roughness of 0.2 to
The electrolytic copper foil for a printed wiring board according to claim 1, which has been roughened to a thickness of 5 μm. 4. One or more thin layers selected from the group consisting of a zinc layer, a zinc alloy layer, a nickel layer and a nickel alloy layer on at least the side of the roughened surface that is to be joined to the insulating substrate. The electrolytic copper foil for a printed wiring board according to claim 3, wherein the surface of the thin layer is chromate-treated. 5. The electrolytic copper foil for a printed wiring board according to claim 4, wherein a silane coupling agent is applied to a chromate-treated surface of the electrolytic copper foil for a printed wiring board which is joined to the insulating substrate.