JPH08277485A - Production of copper foil for printed circuit - Google Patents

Abstract

PURPOSE: To obtain a heat-resistant coating layer having a sufficient adhesive strength to a substrate and not generating a dissolution residue at the time of forming a circuit by etching without using a toxic cyanide bath by using a pyrophosphoric acid-polyphosphoric acid bath to form a Cu-Zn alloy barrier film on a surface-roughened electrolytic copper foil. CONSTITUTION: A plating bath consisting of one kind selected from the alkali metal salts of pyrophosphoric acid and polyphosphoric acid, a copper salt, zinc and at least one kind selected from amino acids and their salts is used, and plating is conducted with the traveling speed of copper foil in the bath controlled to 500-3000m/hr, and the cathode current density to 6-15A/dm<2> . The bath composition is connected with the plating condition and not generally indicated. However, the current density is controlled to 10A/dm<2> , the current to 80A.s/dm<2> and the copper foil travel to 2000/hr. When the bath is kept at 30 deg.C, the bath preferably contains 0.30-1.50mol/l K4 P4 O7 , 0.10-0.20mol/l Cu<2+> , 0.04-0.10mol/l Zn<2+> and 0.05-0.10mol/l L-histidine hydrochloride, and the bath is kept at pH8-13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for producing a copper foil for a printed circuit, and more particularly to a method for providing a Cu-Zn alloy plating barrier layer on a roughened surface of an electrolytic copper foil. . More specifically, the present invention relates to an improvement in a method for forming a Cu-Zn alloy plating barrier layer, which is characterized in that the barrier layer is formed by a pyrophosphoric acid / polyphosphoric acid plating bath without using cyanide. The present invention relates to a manufacturing technology of a copper foil for a printed circuit.

[0002]

2. Description of the Related Art The following characteristics are required for the surface (roughened surface) of a copper foil for a printed circuit that is bonded to a resin base material that serves as a substrate: Sufficient adhesive strength with a substrate ( Peeling strength), it has a moderate solubility in an etching solution, and it does not leave a residue when forming a circuit. The adhesive interface is stable and the heating and chemicals involved in circuit formation, component lamination, and soldering. Maintain sufficient adhesive strength even after being treated and even when placed in the environment where the product is actually used. For example, when an epoxy resin, which is often used as a circuit board, is heated while being in direct contact with metallic copper, the resin deteriorates and deteriorates due to the catalytic action of copper, and the adhesive strength is significantly reduced. In order to prevent this, a heat resistant coating layer (barrier layer) made of a chemically stable component with respect to the resin is formed on the surface of the copper foil.

As the heat resistant coating layer, Zn, Cu-Z
Many materials such as n, Cu-Ni, and Cu-Co have been put to practical use. Among them, the copper foil coated with the heat-resistant coating layer made of Cu-10 to 30% Zn (brass) does not cause stains when laminated on a printed circuit board made of epoxy resin or the like, and has an adhesive strength after heating at high temperature. It is widely used because it has excellent characteristics such as less decrease in As a method of forming this Cu-Zn layer, there is a method of forming an Cu-Zn alloy layer by alloy plating using a cyan-based bath or by plating Zn on a copper foil and then heating and diffusing it. Cyan-based alloy plating has been mainly adopted for the purpose of control of the above and other reasons. Regarding the cyan alloy plating method and conditions and the properties of the foil to be produced, for example, Japanese Patent Publication No. 35-51711 and Japanese Patent Publication No. 54-6701.
And JP-A-3-122298, and others.

[0004]

However, these conventional cyan baths have a large safety and environmental burden, and wastewater treatment requires a high cost. Therefore, development of a non-cyan type Cu-Zn alloy plating bath for copper foil for printed circuits is strongly demanded.

Non-cyan-based Cu-Zn alloy plating baths have been widely studied in the decorative plating industry for the purpose of developing a golden color plating method. The important point is the search for a complexing agent for obtaining the equilibrium potential that enables the co-deposition of Cu and Zn, and the search for an additive that increases the overvoltage of the precipitation reaction of Cu. Currently, non-cyan baths that are attracting attention in the decorative plating industry and the like are glucoheptonic acid baths that use sodium glucoheptonate as a complexing agent, pyrophosphoric acid is a complexing agent, and L-histidine is added as an additive for improving precipitation overvoltage. There is a pyrophosphate bath. From these baths, golden smooth plated surfaces were obtained in the low cathode current density range. Pyrophosphate C
An example of the composition of the u-Zn alloy plating bath and plating conditions (Japanese Patent Publication No. 3-20478) is shown below. (Pyrophosphate Cu-Zn alloy plating bath composition) Potassium pyrophosphate: 180 g / l Sodium polyphosphate: 100 g / l Copper pyrophosphate: 12 g / l Zinc pyrophosphate: 2.5 g / l Quen Acid soda: 100 g / l Glycine: 2.0 g / l L-histidine hydrochloride: 2.0 g / l Potassium stannate: 1.0 g / l (plating conditions) Bath temperature: 35 ° C Cathode current density: 0.3-5 A / dm ² Agitation: Still bath pH: 10.8

These pyrophosphoric acid baths do not have the toxicity problem of cyanide baths. However, there were the following problems and problems with this pyrophosphoric acid bath: Only the actual results of static baths assuming bright decorative plating are known, and roll products such as copper foil are fed out to obtain a plating bath. The possibility and conditions for continuous plating to a uniform thickness while moving inside are unknown. In these pyrophosphoric acid baths, the current density that enables uniform and bright plating is 5 A / dm ² or less, preferably 2 A / dm ² or less, and a Cu-Zn alloy layer of the required thickness can be formed with high productivity in copper foil. Current density required to do 4-8A
It is smaller than / dm ² .

An object of the present invention is to form a Cu-Zn alloy plating barrier layer on a roughened surface of an electrolytic copper foil by a non-cyan bath, especially a pyrophosphoric acid type plating bath, for an electrolytic copper foil for a printed circuit. Is to establish the plating method and conditions.

[0008]

As mentioned above, the known pyrophosphate plating has a cathode current density of 5 A / dm without exception.
^{It is 2} or less, and is not intended for a copper foil that is continuously moving. The inventors of the present invention thoroughly examined the factors of the cathode current density, the moving speed of the copper foil, the amount of electricity supplied, and the bath composition. As a result, (1) at least 1 selected from alkali metal salts of pyrophosphoric acid and alkali metal salts of polyphosphoric acid.
, A (2) copper salt, (3) zinc salt, and (4) an amino acid and at least one selected from the salts thereof are used to increase the moving speed of the foil in the bath and increase the cathode current density. It was confirmed that a Cu-Zn alloy plating barrier layer having properties equivalent to those of the cyan bath Cu-Zn alloy plating was obtained by the method of significantly increasing the height. Based on this finding, the present invention performs Cu-Zn alloy plating while moving the electrolytic copper foil through a Cu-Zn alloy plating bath to form a Cu-Zn alloy plating barrier layer on the roughened surface of the electrolytic copper foil. A method for manufacturing a copper foil for a printed circuit, comprising the steps of:
At least one selected from (1) alkali metal salts of pyrophosphoric acid and alkali metal salts of polyphosphoric acid as an n alloy plating bath, (2) copper salts, (3) zinc salts, and (4) amino acids and salts thereof. A plating bath consisting of at least one selected from the following, the moving speed of the electrolytic copper foil in the plating bath is 500 m / hr to 3000 m / hr, and the cathode current density is 6 A / dm ^{2 to} 15 A / dm ² . A method for producing a copper foil for a printed circuit is provided.

[0009]

[Function] At least one selected from cyanide-free alkali metal salts of pyrophosphoric acid and alkali metal salts of polyphosphoric acid, typically potassium pyrophosphate, copper salts, typically copper sulfate, zinc salts. Cu using a plating bath typically consisting of zinc sulfate, amino acid and its salt, typically L-histidine hydrochloride to increase the moving speed of the foil in the bath and increase the cathode current density. In conclusion, the method of forming the Zn alloy plating barrier layer has the effect of keeping the equilibrium potential and precipitation overvoltage of Cu and Zn in a favorable relationship, and provides a homogeneous C
It is judged that the u-Zn alloy plating layer can be formed.

As the alkali metal salt of pyrophosphoric acid and the alkali metal salt of polyphosphoric acid used in the present invention, any of known ones can be used, and examples thereof include sodium salt and potassium salt thereof. Is potassium pyrophosphate. As the copper salt, any known one can be used,
Examples thereof include copper pyrophosphate, copper sulfate, copper phosphate, cupric citrate and the like. Any known zinc salt can be used, and examples thereof include zinc pyrophosphate, zinc sulfate, zinc phosphate, and zinc lactate. Any known amino acids and salts thereof can be used, and examples thereof include α-amino acids such as glycine, glutamic acid, aspartic acid, and histidine, or their hydrochlorides and sodium salts. Hereinafter, potassium pyrophosphate, copper sulfate, zinc sulfate, and L-histidine hydrochloride will be described as examples, but the present invention is not limited thereto.

The preferred composition of the pyrophosphoric acid plating bath used in the present invention is closely related to the plating conditions, so it is difficult to make a unique display. For example, the cathode current density: 10
A / dm ² , energization amount: 80 A · S / dm ² , moving speed of foil in plating bath: 2000 m / hr, plating bath temperature of 30 ° C., effective concentration range (Mol / l) of plating bath component
Is as follows (the optimum concentration range (Mol / l) is shown in parentheses). K ₄ P ₂ O ₇ : 0.30 to 1.50 (0.50 to 1.00) Cu ²⁺ : 0.10 to 0.30 (0.10 to 0.25) Zn ²⁺ : 0.04 to 0.10 (0.40 to 0.06) L-histidine hydrochloride: 0.005 to 0.03 (0.008) ~ 0.01
0) pH: 8.0 to 13 (8.0 to 11.5)

If the concentration of K ₄ P ₂ O ₇ is too high, the bath becomes unstable, for example, a fine suspension appears in the plating bath. K ₄ P
_If the concentration of ₂ O ₇ is too low, the solubilities of Cu and Zn decrease, and it becomes impossible to obtain a preferable stable bath composition. If the Cu ion concentration is too high, the color tone of the plated surface becomes reddish and the Zn content of the plated layer becomes low. When the concentration of Cu ions is too low, the amount of electrolytic deposition of Zn increases, and the color tone of the plated surface becomes bluish, and Cu-Z having the desired composition is obtained.
No n-alloy plating barrier layer is obtained. The Zn ion concentration is similarly determined so as to obtain a Cu—Zn alloy plating barrier layer having a desired composition and a desired finish of the plating surface. On the other hand, L-histidine hydrochloride is K ₄ P ₂
Similar to O ₇ , the metal ion complexing agent increases the stability of the bath and contributes to the change in the precipitation overvoltage of Cu and Zn.
It has a great influence on the smoothness of the u-Zn alloy plating layer. Excessive addition lowers the heat resistance of the Cu-Zn alloy plating barrier layer. On the other hand, if the addition amount is too small, the alloy composition becomes rich in copper, and the heat resistance also deteriorates. PH of plating bath
Affects the stability of the bath and the color tone of the electrolytically deposited Cu—Zn alloy plating layer. If the pH is too high, precipitated Cu-Z
A Cu—Zn alloy plating layer is inferior, for example, an oxide of Cu—Zn is observed in the n alloy plating layer. On the other hand, pH
If is too low, pyrophosphate decomposes.

Although the moving speed of the foil is determined in relation to other conditions, the plating bath having the optimum concentration shown above is used, the bath temperature: 45 ° C., the cathode current density: 10 A / dm ² , and the electrification electric current. Amount: 80 A · S / dm ² The moving speed of the foil that is effective under the conditions of 500 m / hr to 3000 m / hr, and the optimum value is 1000 m / hr to 2500 m / hr. A decrease in the moving speed of the copper foil causes powdery precipitation, and when the moving speed is too fast, copper-colored Cu-Zn alloy plating with a small Zn content is obtained, and the intended barrier layer cannot be obtained. Under such a condition that the foil moves at a high speed and the solution is stirred, high-speed plating with a higher current density than that described in the existing art is possible.

The current density is also selected in relation to the bath composition, the copper foil moving speed and the like. For example, the optimum concentration bath shown above, the bath temperature of 45 ° C., the foil speed of 2000 m / hr, and the amount of electricity supplied: Under the condition of 80 A · S / dm ² , the preferable cathode current density is 6 A / dm ^{2 to} 15 A / dm ² , and the optimum value is 10 A / dm ^{2 to} 13 A / dm ² . When the cathode current density is too high, the deposited Cu-Zn alloy plating becomes powdery deposition. Further, if it is too low, the copper content of the Cu is small and the Zn content is small.
-Zn alloy plating results and the intended barrier layer cannot be obtained.

The effect of the amount of electricity supplied is also affected by other conditions. The optimum concentration bath shown above, bath temperature: 45 ° C., foil moving speed: 2000 m / hr, cathode current density: 10 A / dm ²
The effective range is 60 A · S / dm ^{2 to} 130
A · S / dm ² , optimum value is 80 A · S / dm ^{2 to} 130
A · S / dm ² . When the amount of electricity supplied is insufficient, the coating becomes insufficient and the heat resistance of the barrier layer becomes low. If it is too high, the smoothness is impaired, resulting in a reddish Cu-Zn alloy plating.

Similarly, the plating bath temperature is the optimum concentration bath described above, the cathode current density is 10 A / dm ² , and the foil moving speed is 2000.
The effect is observed at 30 ° C to 55 ° C under the condition of m / hr, and the optimum value is 40 ° C to 50 ° C. At low temperature, powdery precipitation occurs,
At a high temperature, the Zn content decreases, resulting in copper-colored Cu-Zn alloy plating, and the intended barrier layer cannot be obtained.

[0017]

EXAMPLES Examples and comparative examples are presented below for the purpose of illustrating the present invention. All of the starting material foils were roughened surface roughened foils that were subjected to a surface roughening treatment to enhance the adhesiveness. The amount of electrolytic deposition, composition, color difference, and heat deterioration rate of adhesiveness were tested. The amount of surface electrodeposition was the weight before and after Cu-Zn alloy plating, and the composition was calculated from the Zn content and the plating weight obtained by analysis by completely dissolving a predetermined amount of copper foil. The color difference is
Using a color computer color difference meter manufactured by Suga Test Instruments Co., Ltd., a standard foil was used as a copper foil obtained by Cu-Zn alloy plating in a cyan bath, and a relative comparison value ΔE * (sensation of ΔE * value with this copper foil was obtained. 0-0.5: faintly, 0.5-
1.5: Slightly, 1.5-3.0: Conspicuous ... JI
S Z 8730) was obtained and compared. The heat deterioration rate of the adhesiveness is the normal state of the circuit board prepared by thermocompression bonding the roughened surface of the obtained copper foil and the substrate material (FR-4) with an epoxy adhesive and after heating at 180 ° C. × 48 hr. The peel strength was measured and determined. (Standard foil) Cu-Zn alloy plating amount: 22.0 mg / dm ² Zn content of Cu-Zn alloy plating layer: 20.0% Cu-Zn alloy plating surface color tone: △ E * = 0.0 Normal drawing after bonding to substrate Peel strength: 2.25 kg / cm After adhering to the substrate 180 ℃ × 48hr After heating Peel strength: 1.96 kg / cm Heat deterioration rate: 13.0%

(Example 1) A roughened surface roughened foil having a thickness of 35 μm was used as a cathode, a brass plate of Zn20% -Cu80% was used as an anode, and a bath composition: K ₄ P ₂ O ₇ : 1.0 Mol / l, C
u: 0.25 Mol / l, Zn: 0.06 Mol / l,
L-histidine hydrochloride: 0.01 Mol / l, pH:
Using a Cu-Zn pyrophosphate Cu plating bath of 9.9, temperature: 40 ° C., foil speed: 2000 m / hr, cathode current density: 10 A / dm ² , for 8 sec (electricity: 80 A · S / Dm ² ) plated. Immediately thereafter, it was washed with water, and the obtained surface was bath composition: CrO ₃ : 3.5 g
/ L, pH: 4.8, and a bath temperature of 50 ° C. Immediately thereafter, it was washed with water and dried to prepare an electrolytic copper foil for a printed circuit having a Cu-Zn alloy plating barrier layer. The composition, color tone (color difference) of the Cu—Zn alloy plating layer of the obtained foil,
The measurement results of normal peel strength after adhesion, peel strength after adhesion and heating, and heat deterioration rate are as follows: (Measurement results) Cu-Zn alloy plating amount: 22.1 mg / dm ² Cu-Zn alloy plating layer Zn content: 19.8% Cu-Zn alloy Plating surface color tone: △ E * = 0.3 Normal peel strength after bonding to substrate: 2.28 kg / cm 180 ℃ × 48hr after bonding to substrate: Peel strength after heating: 1.98 kg / cm Heat deterioration rate: 13.0%

(Example 2) A roughened surface roughened foil having a thickness of 35 μm was used as a cathode, a brass plate of Zn30% -Cu70% was used as an anode, and a bath composition: K ₄ P ₂ O ₇ : 1.0 Mol / l, C
u: 0.25 Mol / l, Zn: 0.06 Mol / l,
L-histidine hydrochloride: 0.01 Mol / l, pH:
Using a Cu-Zn pyrophosphate alloy plating bath of 9.9, temperature: 45 ° C., foil moving speed: 2000 m / hr, current density: 13 A / dm ² for 6.2 sec (the amount of electricity supplied: 80 A · S / dm ² ) was plated. Immediately thereafter, it was washed with water, and the obtained surface was bath composition: CrO ₃ : 3.5 g
/ L, pH: 4.8, and a bath temperature of 50 ° C. Immediately thereafter, it was washed with water and dried to prepare an electrolytic copper foil for a printed circuit having a Cu-Zn alloy plating barrier layer. The composition, color tone (color difference) of the Cu—Zn alloy plating layer of the obtained foil,
The measurement results of normal peel strength after adhesion, peel strength after adhesion and heating, and heat deterioration rate are as follows: (Measurement results) Cu-Zn alloy plating amount: 22.1 mg / dm ² Cu-Zn alloy plating layer Zn content: 20.1% Cu-Zn alloy Plating surface color tone: △ E * = 0.4 Normal peel strength after bonding to substrate: 2.28 kg / cm 180 ℃ × 48hr after bonding to substrate: Peel strength after heating: 1.97 kg / cm Heat deterioration rate: 13.8%

(Comparative Example 1) A roughened surface roughened foil having a thickness of 35 μm was used as a cathode, a brass plate of Zn20% -Cu80% was used as an anode, and a bath composition: K ₄ P ₂ O ₇ : 1.0 Mol / l, Cu :
0.25 Mol / l, Zn: 0.06 Mol / l, L-
Histidine hydrochloride: 0.01 Mol / l, pH: 11.
0, Cu-Zn pyrophosphate alloy plating bath, temperature: 45 ° C., foil speed: 0 m / hr, current density: 10 A
The plating was performed for 8 seconds under the condition of / dm ² . Immediately after that, an attempt was made to wash with water, but since the obtained surface was partially washed out by washing with black powdery electrodeposition, the subsequent treatment and characteristic measurement were not performed.

(Examples 3 to 13 and Comparative Examples 2 to 3) Table 1
Cu-Zn pyrophosphate alloy plating was performed under the bath composition and plating conditions shown in (1) and chromate treatment was performed in the same manner as above. Immediately thereafter, it was washed with water and dried to prepare an electrolytic copper foil for a printed circuit having a Cu-Zn alloy plating barrier layer. Table 1 shows the measurement results of the color tone (color difference) of the plated surface of the obtained foil, the normal peel strength after adhesion, the peel strength after adhesion and heating, and the heat deterioration rate.

[0022]

[Table 1]

[0023]

According to the present invention, it has not been possible until now.
A barrier layer can be produced by Cu-Zn alloy plating on the roughened surface of an electrolytic copper foil with a non-cyan bath, and work safety and drainage treatment cost are greatly improved.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshio Kawasumi, 3-17-35, Shinzonan, Toda City, Saitama Prefecture Within Japan Energy (72) Inventor Hiroo Tsuchiya 3--1735, Shinzonan, Toda City, Saitama Prefecture No. Stock Company Japan Energy

Claims (1)

[Claims] 1. A printing method comprising performing Cu—Zn alloy plating while moving the electrolytic copper foil through a Cu—Zn alloy plating bath to form a Cu—Zn alloy plating barrier layer on a roughened surface of the electrolytic copper foil. In the method for producing a copper foil for a circuit, as the Cu-Zn alloy plating bath, at least one selected from (1) an alkali metal salt of pyrophosphoric acid and an alkali metal salt of polyphosphoric acid, (2) a copper salt, ( 3) Using a plating bath comprising at least one selected from a zinc salt and (4) an amino acid and its salt, and setting a moving speed of the electrolytic copper foil in the plating bath to 500 m / hr to 3000 m / hr and a cathode current. method of manufacturing a printed circuit copper foil, characterized in that the density of ^{6A / dm 2 ~15A / dm 2} .