JP3292774B2 - Copper foil for printed wiring board and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper foil for a printed wiring board and a method for producing the same, and more particularly, to improving heat resistance, chemical resistance and adhesion to a substrate for a printed wiring board without using arsenic. The present invention relates to a copper foil for a printed wiring board and a method for manufacturing the same.

[0002]

2. Description of the Related Art When a printed wiring board is made, a copper foil and a base material such as a glass epoxy impregnated base material are bonded by heat compression or the like, and an unnecessary portion of the copper foil for forming a conductive circuit is made of acid or alkali. Removal is performed with an etchant.

Conventionally, on the side of the copper foil to be bonded to the substrate, a granular copper layer is provided by electrodeposition in order to increase the bonding strength.
Further, so-called burn plating is performed with a copper plating solution to which arsenic is added in order to increase the adhesion to the base material.
Further, in order to improve various problems occurring after the formation of the conductor circuit, a rust preventive layer is formed thereon by zinc or zinc alloy plating, chromate treatment, and silane coupling agent treatment. The characteristics improved by these rust prevention treatments include heat resistance, chemical resistance, moisture resistance, and adhesion to a substrate.

Japanese Patent Publication No. Sho 61-52240 discloses that it is effective to provide a zinc-tin-copper alloy layer on a copper foil as a treatment for improving heat resistance.

However, at this time, as described above, a treatment containing arsenic harmful to the human body is indispensable. On the other hand, in JP-B-58-56758 in which the hydrochloric acid resistance is improved, the thickness of the zinc-tin-copper alloy layer is sufficient, but the heat resistance is not improved because arsenic is not added.

As described above, many processes have been proposed to satisfy various characteristics of a printed wiring board. However, in order to satisfy all of these required characteristics, it is necessary to add arsenic to burnt plating. Has become.

[0007] As the heat resistance standard of the printed wiring board, the UL standard requires that the peel strength after heat treatment at 177 ° C for 10 days is 0.36 kgf / cm or more. In order to satisfy this standard, it is not enough to strengthen the adhesive by roughening treatment alone, and it can be achieved by adding the thickness effect of the rust preventive layer. However, in the case where the zinc-tin-copper alloy layer described above is formed, if a considerable amount or more is electrodeposited in order to meet UL standards, the layer containing arsenic serving as an underlayer plays an important role. When arsenic is not contained, the thicker the rust preventive layer, the lower the hydrochloric acid resistance. An undercut occurs during etching or pickling during the production of a printed wiring board, causing circuit peeling. However, the harmfulness of arsenic is known, and there is an environmental problem due to the stability at the time of handling in the manufacturing process or the drainage of the processing solution and the etching solution.

When arsenic is not contained, hydrochloric acid resistance can be improved by reducing the thickness of the zinc or zinc alloy layer, but in such a case, heat resistance cannot be satisfied.

Thus, without using arsenic, heat resistance,
A copper foil for a printed wiring board satisfying each property such as chemical resistance, especially hydrochloric acid resistance and adhesion to a printed wiring board base material has not been obtained.

[0010]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and provides a copper foil for a printed wiring board which does not contain arsenic and has remarkably excellent heat resistance, hydrochloric acid resistance and adhesion to a substrate. It is to provide a manufacturing method thereof.

[0011]

The above object of the present invention is achieved by the following copper foil.

That is, the copper foil for a printed wiring board according to the present invention comprises an arsenic-free copper-zinc-tin layer on a granular copper layer provided on the side of the copper foil bonded to the printed wiring board base material. Alternatively, it has a ternary alloy layer of copper-zinc-nickel, has a chromate rust preventive layer on the alloy layer, and further has a rust preventive layer containing a silane coupling agent and a hexavalent chromium compound on the chromate layer. Is provided.

FIG. 1 is a schematic sectional view showing the structure of a copper foil for a printed wiring board according to the present invention. In the figure, 1 is a copper foil, 2 is a copper-zinc-tin alloy layer (copper-zinc-nickel layer), 3 is a chromate layer, and 4 is a silane coupling agent and a rust-preventive layer of hexavalent chromium.

A granular copper layer (not shown) is provided on the side of the copper foil 1 shown in FIG. The reason for providing such a granular copper layer is to improve the adhesion between the copper foil and the base material. The copper foil used here may be either an electrolytic copper foil or a rolled copper foil. Also,
The surface to be adhered to the printed wiring board substrate may be a rough surface or a glossy surface of the electrolytic copper foil.

A ternary alloy layer 2 made of a copper-zinc-tin alloy or copper-zinc-nickel is provided on the granular copper layer. This is because the provision of such a ternary alloy layer 2 improves both the heat resistance and the hydrochloric acid resistance of the copper foil.

On this ternary alloy layer 2, a chromate layer 3 is provided. Further, on the chromate layer, there is provided a rust-preventive layer 4 of a silane coupling agent and hexavalent chromium, and the rust-preventive layer 4 is joined to a substrate for a printed wiring board.

Such a copper foil for a printed wiring board can be obtained by the following manufacturing method. That is, the method for producing a copper foil for a printed wiring board of the present invention comprises the steps of: electrodepositing granular copper containing no arsenic on the adhesive surface side of the copper foil with the substrate for a printed wiring board; Zinc-tin plating or zinc-
Nickel plating, chromate treatment, 0.5
Silane coupling agent of 0.1 to 10 g / l and 0.1 to 2 g / l
After performing the rust-proof treatment with a mixed solution containing a hexavalent chromium l, and performing heat treatment at 180 to 260 ° C..

In the present invention, granular copper is electrodeposited on the side of the surface of the copper foil to be bonded to the substrate for a printed wiring board, and the surface is roughened to improve the adhesion between the copper foil and the substrate. Electrodeposition of granular copper on copper foil is usually performed by a two-stage plating process. In the first stage plating, fine-structured granular copper is electrodeposited on the copper foil, and in the second stage, the fine-structured granular copper is dropped off. To prevent this, Kabuse smooth plating is performed. Here, the burnt plating containing arsenic is not performed as in the conventional case.

Next, according to the present invention, the granular copper is roughened by electrodeposition and then subjected to zinc-tin plating or zinc-nickel plating to form a zinc-tin alloy layer or a zinc-tin alloy layer.
A nickel alloy layer is formed. It is desirable that the content of tin or nickel in this alloy layer be 1 to 15% by weight.

An example of the basic composition of the electrolytic solution when applying such zinc-tin plating or zinc-nickel plating is shown below, taking tin as an example. (Zn-Sn alloy plating) Zinc pyrophosphate 12-25 g / l Potassium stannate 1-10 g / l Potassium pyrophosphate 50-300 g / l pH 9-12 Liquid temperature Room temperature

The alloy composition can be changed depending on the tin / zinc concentration ratio. It is necessary to adjust the concentration of tin so that the electrodeposition ratio becomes 1 to 15% by weight, and if it is too high, blackening occurs in alkali etching. Further, the composition can be adjusted depending on the current density.
At 10 A / dm ² , the higher the current density, the higher the ratio of zinc to zinc. The electrolysis time is set to 1 to 8 seconds, and the total electrodeposition amount of zinc-tin is adjusted to improve the heat resistance to a required level.
That is, the heat resistance can be increased in proportion to the thickness of the alloy layer. However, when the amount of zinc increases, corrosion due to dezincification of the alloy layer easily occurs, and the hydrochloric acid resistance decreases. Therefore, the thickness of the alloy layer must be selected in consideration of these two characteristics. In the present invention, the range that satisfies the UL standard and is effective in hydrochloric acid resistance is a zinc-tin alloy or a zinc-nickel alloy in the range of 150 to 700 mg / m ² .

In the present invention, the zinc-tin alloy layer or the zinc-nickel alloy layer thus formed is subjected to a chromate treatment in order to obtain a sufficient rust-preventive effect.

This chromate treatment is performed by electrolytic chromate. An example of the processing conditions is shown below. Chromic acid 0.2-5 g / l pH 9-13 Current density 0.1-3 A / dm ²

In this case, the pH is adjusted to an alkaline condition for the treatment, but the same effect can be obtained even if the treatment is performed under an acidic condition. The electrolysis time is 1 to 8 seconds, but the effect of time on the effect is small. However, the chromate treatment of a zinc alloy generally makes it difficult to completely form an effective chromate layer (coating) as compared to the chromate treatment on a zinc-only layer. Therefore, a mixed solution containing a silane coupling agent and hexavalent chromium is applied on this chromate layer (coating) to form a rust preventive layer.

As the silane coupling agent used in the present invention, compounds such as aminoalkylsilane, epoxyalkylsilane, methacryloxyalkylsilane, and mercaptoalkylsilane can be used.

An example of a liquid composition having an effect on hydrochloric acid resistance in the present invention is shown below. Silane coupling agent 0.5 to 10 g / l Chromic acid 0.1 to 2 g / l pH 2 to 12

The mixed solution having such a composition is applied by spraying. The hexavalent chromium in the rust preventive layer (coating) formed thereby reinforces the defects of the incompletely pretreated chromate layer (coating), and the silane coupling agent chemically bonded to the hexavalent chromium forms a base. Strengthens adhesion to materials and reduces undercuts caused by hydrochloric acid used for etching and pickling.

In the present invention, a heat treatment is performed next. By this heat treatment, the bonding between the silane coupling agent and the chromate layer (coating) or the dehydration condensation of the silane coupling agents proceed sufficiently, and an appropriate rust-preventive layer (coating) is formed.

Further, this heat treatment changes the zinc-tin alloy or the zinc-nickel alloy into a ternary alloy of copper-zinc-tin or copper-zinc-nickel. The appearance color at this time has changed to brass.

The heating temperature needs to be in an appropriate temperature range in view of the balance between the formation of the ternary alloy and the strengthening of the bonding of the rust preventive layer (coating). The temperature and time in the heating range where the surface temperature of the rustproof surface of the copper foil is 180 to 260 ° C are effective. When the temperature is out of this range, for example, when the temperature is low, a ternary alloy is not formed, the effect on dezincification is not sufficiently obtained, and a rust prevention layer containing a chromate layer or a silane coupling agent and hexavalent chromium. However, no effective coating is formed. Conversely, when the temperature is high, the chromate layer and the rust-preventive layer are also decomposed, losing the rust-preventive effect and failing to provide an effect on hydrochloric acid resistance.

[0031]

EXAMPLES Hereinafter, the present invention will be specifically described based on examples and the like.

Example 1 A surface roughening treatment (formation of a granular copper layer) for increasing the adhesion strength was performed on the side of the surface of the 35 μm-thick electrolytic copper foil to be bonded to the substrate for a printed wiring board. The surface roughening treatment was performed by the following one-step processing and two-step processing.

(Single-step processing conditions) Cu 12 g / l H ₂ SO ₄ 180 g / l Liquid temperature 30 ° C. Current density 30 A / dm ² Electrolysis time 4 seconds

In order to prevent the electrodeposited copper of the fine structure formed by the one-step treatment from falling off, a two-step treatment was performed as a flattened plating.

(Two-step treatment conditions) Cu 70 g / l H ₂ SO ₄ 180 g / l Liquid temperature 48 ° C. Current density 32 A / dm ² Electrolysis time 4 seconds

Rust prevention treatment was sequentially performed on the electrodeposited copper (cob-treated surface) by the first and second steps under the following conditions.

(Zinc-tin plating bath composition) Zinc 6 g / l Tin 1 g / l Potassium pyrophosphate 100 g / l pH 10.5

(Plating conditions) Solution temperature 25 ° C. Current density 6 A / dm ² Electrolysis time 2 seconds

Under these conditions, zinc-tin alloy plating was carried out, and immediately after washing with water, the surface was subjected to a chromate treatment under the following conditions.

(Chromate treatment conditions) CrO ₃ 1 g / l pH 12.0 Current density 1.5 A / dm ² Electrolysis time 4 seconds

Immediately after the chromate treatment, the mixture was washed with water, and a mixed solution of a silane coupling agent and chromic acid was applied by a shower. The composition of this treatment liquid is as follows.

(Silane Coupling Agent-Chromic Acid Solution Composition) Silane Coupling Agent 5 g / l CrO ₃ 0.6 g / l pH 5.0

The copper foil coated with this treatment solution was heated and ternary alloyed without washing. The heating time was 4 seconds, and the heating zone temperature was adjusted so that the temperature of the copper foil surface at this time was 220 ° C. The temperature of the copper foil surface was measured using an irreversible discoloration indicating tape.

The obtained copper foil was adhered to a glass epoxy-impregnated base material (FR-4 base material), and was subjected to hydrochloric acid resistance (deterioration rate).
UL heat resistance was measured. Table 1 shows the results.

The evaluation was performed as follows. Hydrochloric acid resistance: A 0.2 mm wide circuit was immersed in 18% hydrochloric acid for 1 hour, the peeling strength was measured, and the deterioration rate was determined. Heat resistance: The peel strength after heating a 10 mm wide circuit at 177 ° C. for 10 days was measured.

Example 2 A copper foil was produced in the same manner as in Example 1 except that the electrolysis time of the zinc-tin alloy was 4 seconds, the thickness of the alloy layer was increased, and the other conditions were the same as in Example 1. Table 1 shows the evaluation results.

Example 3 A copper foil was produced in the same manner as in Example 1 except that the electrolysis time of the zinc-tin alloy was 6 seconds, the thickness of the alloy layer was further increased, and the other conditions were the same as in Example 1. Table 1 shows the evaluation results.

Example 4 Zinc-nickel alloy plating was performed using nickel instead of tin. The composition of the plating solution was the same as that of Example 1 except that potassium stannate was replaced with nickel sulfate, and other processing conditions were the same as in Example 1 to produce a copper foil. Table 1 shows the evaluation results.

Comparative Example 1 A copper foil was produced under the same conditions as in Example 2 except that tin was removed from the zinc-tin alloy plating solution and zinc plating was performed. Table 1 shows the evaluation results at this time.

Comparative Example 2 A copper foil was produced under the same conditions as in Example 2 except that the treatment with the silane coupling agent and the chromic acid mixed solution was changed to the treatment with only the silane coupling agent. Table 1 shows the evaluation results.

Comparative Example 3 A copper foil was produced in the same manner as in Example 2 except that the heating temperature was 150 ° C. on the surface of the copper foil. Table 1 shows the evaluation results.
Shown in

Comparative Example 4 A copper foil was produced in the same manner as in Example 2 except that the heating temperature was 280 ° C. on the surface of the copper foil. Table 1 shows the evaluation results.
Shown in

[0053]

[Table 1]

As shown in Table 1, Examples 1 to 4 are excellent in hydrochloric acid resistance and sufficiently satisfy the UL standard in heat resistance.

As shown in Examples 1 to 3, UL heat resistance can be improved by increasing the thickness of the zinc-tin alloy layer.

On the other hand, as shown in Comparative Examples 1 to 4, zinc-tin alloy plating,
The rust preventive treatment of the mixed solution of the silane coupling agent and the chromic acid and the heating ternary alloying have the respective effects, but sufficient properties cannot be obtained by themselves, and these treatments are performed as in Examples 1 to 4. The composite exhibits a synergistic effect and can provide a copper foil for a printed wiring board having extremely excellent performance.

Comparative Example 5 In order to compare the effects when arsenic was contained, the following copper foil was prepared. That is, arsenic-containing copper plating was performed on the copper foil subjected to the surface roughening treatment (formation of the granular copper layer) used in Example 1 under the following conditions.

Cu 8 g / l Arsenic 1 g / l H ₂ SO ₄ 80 g / l Liquid temperature 25 ° C. Current density 8 A / dm ² Electrolysis time 4 seconds

Further, zinc plating, chromate treatment, and silane coupling agent treatment were sequentially performed on the arsenic-containing copper layer, and the drying temperature was set to 130 ° C. at the copper foil surface temperature to produce an arsenic-containing copper foil. Table 2 shows the evaluation results of the copper foil. Table 2 also shows the evaluation results of Example 2 for reference.
Shown in

Comparative Example 6 An arsenic-free copper foil was produced in the same manner as in Comparative Example 5 except that the arsenic-containing copper plating of Comparative Example 5 was not performed. Table 2 shows the evaluation results of the copper foil.

[0061]

[Table 2]

From the results shown in Table 2, it can be seen that when arsenic is contained as in Comparative Example 5, even when other conditions have no effect on hydrochloric acid resistance, the resistance to hydrochloric acid is higher than that when Comparative Example 6 does not contain arsenic. Is improved by about 20%, and the peel strength is also improved. As described above, arsenic is harmful to the human body.

Further, in Example 2, the hydrochloric acid resistance is remarkably superior to that of Comparative Example 5 even though it does not contain arsenic. .

Further, in Example 2, the UL heat resistance and the peel strength were higher than those of the arsenic-containing copper foil of Comparative Example 5, and the adhesion to the substrate was also improved.

[0065]

As described above, the copper foil of the present invention
It has good heat resistance, chemical resistance, especially hydrochloric acid resistance, and also has excellent adhesiveness to substrates for printed wiring boards. Therefore, the copper foil of the present invention is suitably used as a copper foil for printed wiring boards.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a configuration of a copper foil for a printed wiring board of the present invention.

[Explanation of symbols]

1: Copper foil, 2: Copper-zinc-tin alloy layer (copper-zinc-nickel layer), 3: Chromate layer, 4: Rust prevention layer containing silane coupling agent and hexavalent chromium.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H05K 3/00-3/38 C25D 7/06

Claims (3)

(57) [Claims] An arsenic-free ternary alloy layer of copper-zinc-tin or copper-zinc-nickel is provided on a granular copper layer provided on the side of an adhesive surface of a copper foil to a substrate for a printed wiring board. Having a chromate rust preventive layer on the alloy layer, and further provided with a rust preventive layer containing a silane coupling agent and a hexavalent chromium compound on the chromate layer. Copper foil for wiring boards. 2. An arsenic-free granular copper is electrodeposited on a bonding surface side of a copper foil with a substrate for a printed wiring board to perform a roughening treatment.
Zinc then - mixed solution of nickel-plated, comprising further chromate treatment, hexavalent chromium Sila <br/> coupling agent and 0.1-2 g / l of 0.5 to 10 g / l - tin-plated or zinc in after performing the anti-rust treatment, 180~260 ℃
A method for producing a copper foil for a printed wiring board, wherein the heat treatment is performed in step (a). 3. When the pH of the mixed solution is in the range of 2-12.
3. The printed wiring board according to claim 2, wherein
Production method of copper foil for use.