JPH07109936B2 - Method for manufacturing copper foil for printed circuit - 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 circuit having improved bonding characteristics, and more specifically, a bonding surface of a basic copper foil with an insulating substrate for improving bonding with the insulating substrate. Further, the present invention relates to a method for producing a copper foil for a printed circuit, which comprises coating a copper-arsenic alloy layer and a zinc-iron alloy layer on the copper-arsenic alloy layer, followed by chromate treatment.

[0002]

2. Description of the Related Art Printed circuits are widely used in circuits of various electronic devices such as radios, televisions, telephone exchanges and computers. In particular, recently, in response to the demand for miniaturized and highly integrated printed circuits, a printed circuit board in which a copper foil is bonded to a resin insulating substrate has been proposed, but copper ions diffuse into the resin layer. Since it enters, brown spots often occur on the joint surface between the copper foil and the resin layer of the substrate,
This not only deteriorates the appearance of the circuit, but also weakens the electrical insulation of the insulating substrate.

Further, in the recent process of manufacturing a printed circuit board,
The number of high temperature treatment processes is increasing. Therefore, the bonding strength between the copper foil and the resin layer is reduced due to heat deterioration, which is a serious problem in practical use. As a method for solving such a problem, the following method has been proposed.

In US Pat. No. 3,585,010, indium, zinc, tin, nickel, cobalt, brass (copper-zinc alloy) is formed on the surface of a copper foil bonded to an insulating substrate.
Alternatively, a method of electrodepositing bronze (copper-tin alloy) with a thickness of 4 × 10 ⁻⁶ inch or more is described.

However, in the method of plating brass, there is no practical method except when using a cyanide bath, and the cyanide bath has not only a problem in the working environment but also a pollution problem. is doing.

When zinc plating is etched with an acidic etching solution, the etching solution corrodes the copper foil and the resin layer, causing a so-called undercut phenomenon.

[0007] Korean Patent Publication No. 84-1643 discloses a method of coating a copper foil surface bonded to an insulating substrate with nickel containing 0.02 to 15% by weight of phosphorus.

However, this method is uneconomical because nickel is coated using an electrolytic solution of 50 ° C. or higher, and it is very difficult to control the phosphorus content within the above range. is there.

The publication of Korean Patent Publication No. 83-2611 describes a method of coating a tin layer on both sides or one side of a copper foil and coating a zinc-vanadium alloy layer on the tin layer. .

However, tin has the disadvantage that it is almost impossible to etch with a solution of ammonium persulfate, which is one of the etching solutions usually used in the technology of printed circuits.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to maintain a good adhesive force even after high temperature heat treatment or chemical treatment,
An object of the present invention is to provide a copper foil that has good etching properties without causing an undercut phenomenon of a circuit with any etching solution and that suppresses diffusion of copper ions into an insulating resin layer.

[0012]

In order to solve the above problems, according to the present invention, a copper-arsenic alloy layer and a copper-arsenic alloy layer are formed on the surface of a basic copper foil for bonding a printed circuit copper foil to a resin insulating substrate. Was coated with a zinc-iron alloy layer and chromated.

Then, a method for producing a copper foil for a printed circuit is described in a)
The surface of the basic copper foil to be adhered to the insulating substrate is roughened, and b) 50 to 70 g / l of copper sulfate is added to the roughened surface.
(Liter), arsenic compound 1-3 g / l and sulfuric acid 50-
The first plating solution composed of 70 g / l was used and the solution temperature was 20
A copper-arsenic alloy layer is coated by electrodeposition at ˜35 ° C. with a pulsed current for 5-10 seconds, and c) 10-20 g / zinc sulfate on the copper-arsenic alloy layer.
1, pH 1 to 5 g / l iron sulfate and pH 3 composed of sulfuric acid
Use the second plating solution of No. 5 and pulse current at room temperature for 3 to 8
After coating the zinc-iron alloy layer by electrodeposition for sec, d) electrolysis was performed to perform chromate treatment with a solution containing 5 g / l of sodium dichromate.

When the copper-arsenic alloy is coated by the above manufacturing method, the current density of the peak current phase is 10 to 20 amp / min.
Run between 8~10msec as dm ^2, it was decided to run between 10~60msec the current density in the phase of the base bottom current as 3~8amp / dm ^2.

When the zinc-iron alloy is coated by the above manufacturing method, the current density of the peak current phase is 8-10 amp / d.
Run between 8~10msec as m ^2, and the performing inter 10~60msec the current density of the base bottom current phase as 4~7amp / dm ^2.

[0016]

[Operation] A copper-arsenic alloy layer is formed on the surface of a printed circuit copper foil with a first plating solution, and then a zinc-iron alloy layer is formed with a second plating solution. Finally, a rust preventive treatment is applied by chromate treatment. When such a copper foil is bonded to the resin-made insulating substrate, it is possible to prevent erosion between the copper foil and the resin layer during etching and prevent an undercut phenomenon from occurring. Further, it becomes possible to suppress the diffusion of copper ions into the resin layer.

[0017]

EXAMPLES Examples of the present invention will be described in detail below. The copper foil for a printed circuit of the present invention provided to achieve the above-mentioned object has a copper-arsenic alloy layer electrodeposited on a surface to be bonded to an insulating substrate by using a pulse current, Zinc-
It is manufactured by electrodeposition of the iron alloy layer and then chromate treatment.

More specifically, the copper foil for a printed circuit according to the present invention is a copper foil for a basic copper layer (hereinafter referred to as "basic copper foil"), which is roughened by a usual method. , A copper-arsenic alloy layer is electrodeposited using a first plating solution having a copper sulfate concentration of 50 to 70 g / l, an arsenic compound of 1 to 3 g / l, and a sulfuric acid concentration of 50 to 70 g / l, washed with water, and then zinc sulfate. Concentration 1
PH 3 with 0-20 g / l and iron sulfate concentration 1-5 g / l
It is manufactured by electrodeposition of a zinc-iron alloy using the second plating solution of Nos. 5 to 5, and then performing anticorrosion treatment in a chromate treatment solution having a sodium dichromate concentration of 5 g / l.

As the above-mentioned basic copper foil, any one can be used as long as it is used for a usual copper foil for printed circuits, but an electrolytic copper foil or a rolled copper foil is preferable.

The roughening treatment for improving the bonding strength of the alloy layer to the surface of the basic copper foil is etching by pickling, but it is described in US Pat. No. 3,220,897 or 3,293,910. It is suitable to carry out by electrodeposition described in the above publication.

[0021] The copper - arsenic alloy layer, maintaining the first plating liquid having a temperature of 20 to 35 ° C., a current density 10~20amp / dm ² of the peak current phase of the current, the current density of the current of the base bottom current phase 3～8Amp / utilizing pulse current conditions dm ^2, but is coated with wear between conductive 5～10Sec, the execution time of the peak current density and 8～10Msec, based bottom current density execution time for Is suitable for 10 to 60 msec. If not formed fine particles becomes denser peak current density and less than 10 amp/dm ^2, is formed powder if it exceeds 20amp / dm ² with poor adhesion occurs. And
Density of the base bottom current can be adjusted to account for processing time. In the first plating solution, the arsenic compound is preferably in the form of a water-soluble salt, and arsenic binds to copper to form an alloy, which suppresses diffusion of copper ions during heat treatment. Further, if the sulfuric acid concentration is higher or lower than the above range, the electrical conductivity and the electrodeposition uniformity of the first plating solution will deteriorate.

The zinc-iron alloy layer is formed by using the second plating solution at room temperature, and the current density of the peak current phase is 8 to 10 am.
p / dm ^2, the current base bottom current phase current density 4~7amp / d
The electrodeposition is performed for 3 to 8 seconds using a pulse current under the condition of m ² and the execution time at the peak current density is 8 to 10 seconds.
and msec, based bottom current density execution time for the 10~60msec
It is preferable that

In the second plating solution, if the zinc sulfate concentration is less than 10 g / l, bath management is difficult, and 20 g / l
There is no special problem when exceeding, but continuous operation is uneconomical due to liquid loss.

If the concentration of iron sulfate is less than 1 g / l, it is difficult to prevent the undercut phenomenon, and if it exceeds 5 g / l, the electrodeposition uniformity and etching property of the alloy deteriorate.

When the pH of the second plating solution becomes 5 or more, hydroxide is formed and it becomes difficult to control the concentration.
There are many chemical losses. The pH of the second plating solution is preferably adjusted using sulfuric acid. The zinc-iron alloy exhibits the effect of suppressing the diffusion of copper ions, and the iron has the effect of suppressing the elution of zinc during chemical treatment.

For the chromate treatment, an electrolytic method is used, and a solution having a sodium dichromate concentration of 5 g / l is used.
It is preferable to carry out the process at a potential of about 30 V at room temperature until gas is generated. Also, it takes about 5 seconds until gas is generated under the above conditions. The generated gas forms a coating of chromium hydroxide, chromium oxide, or the like on the surface of the copper foil, and prevents the surface from being oxidized during work, transportation, or storage.

Specific examples of embodiments and comparative examples of the present invention will be shown below, but the present invention is not limited to the following embodiments and can be freely modified within the scope of the invention.

(Embodiment example) Copper sulfate pentahydrate 70 g / l, arsenous acid 5 g / l and sulfuric acid 5
A solution composed of 0 g / l was used as an electrolytic solution, and a roughened copper foil having a thickness of 35 μm was used as a cathode. The electrolyte temperature to 30 ° C., the peak current density 10 amp/dm ^2, group bottom <br/> current density 5 at Amp/dm ² pulsed current 5 minutes electrodeposition to copper - coated arsenic alloy layer. At that time, the peak current density 10
execution time for # 038 / dm ² was set to 10 msec, the execution time of the basal current density 5 amp/dm ² was 20 msec.

Then, after washing with deionized water, a pH composed of 10 g / l of zinc sulfate, 2 g / l of iron sulfate and sulfuric acid.
5 solution kept at 30 ° C. and an electrolytic solution, between 8msec peak current density 10 amp/dm ² and group bottom current density 4 amp/dm ²
At that time, electrodeposition was performed for a total treatment time of 5 sec including 20 msec to coat the zinc-iron alloy. Then, it was washed with deionized water, a solution of sodium dichromate 5 g / l was kept at 25 ° C., and chromate treatment was carried out at a potential of 30 V for 5 seconds.

Comparative Example A solution having a pH of 5 containing 10 g / l of zinc sulfate was kept at 30 ° C. and used as an electrolytic solution, and a roughened copper foil having a thickness of 35 μm was used as a cathode. 5 seconds at a current density of 5 amp / dm ² .
After performing electrodeposition and washing with deionized water, chromate treatment was performed under the same conditions as in the above-described embodiment.

After bonding the copper foils obtained in the above-described embodiment examples and comparative examples to a glass fiber-epoxy fiber insulating substrate, the adhesive strength was measured. 630 with hot air at 210 ℃
After heat treatment for minutes, the adhesive strength was measured. Furthermore, 5N
The reduction rate (%) of the adhesive strength after the immersion treatment with the HCl solution for 1 hour was measured. The measurement results are shown in FIG.

[0032]

As described above, according to the present invention, the adhesive force between the copper foil and the resin layer is good even after the high temperature treatment or the chemical treatment, so that the etching solution is eroded between the copper foil and the resin layer. This has the effect of preventing the undercut phenomenon and suppressing the diffusion of copper ions into the resin layer.

[Brief description of drawings]

FIG. 1 is a diagram comparing the adhesive strengths of an embodiment example and a comparative example.

Claims (3)

[Claims] 1. A surface of a basic copper foil to be adhered to an insulating substrate is roughened, and b) 50 to 70 g of copper sulfate is added to the roughened surface.
1, arsenic compound 1-3 g / l and sulfuric acid 50-70 g / l
Using the first plating solution composed of the above, the electrodeposition of copper is performed by electroplating for 5 to 10 seconds with a pulse current at a liquid temperature of 20 to 35 ° C.
C) covering the arsenic alloy layer, and c) 10-20 g / zinc sulfate on the copper-arsenic alloy layer.
1, pH 1 to 5 g / l iron sulfate and pH 3 composed of sulfuric acid
Use the second plating solution of No. 5 and pulse current at room temperature for 3 to 8
After coating the zinc-iron alloy layer by electrodeposition for sec, d) a method for producing a copper foil for a printed circuit, characterized by performing a chromate treatment with a solution containing 5 g / l of sodium dichromate by an electrolytic method. . 2. When coating a copper-arsenic alloy, the current density of the peak current phase is 8 to 10 ms when the current density is 10 to 20 amp / dm ² .
Run between ec, 3~8amp the current density in the phase of the base bottom current /
The method for producing a copper foil for a printed circuit according to claim 1, wherein the dm ² is performed for 10 to 60 msec. 3. When coating a zinc-iron alloy, the current density of the peak current phase is 8-10 amp / dm ² and 8-10 msec.
Run while, 4～7Amp the current density of the base bottom current phase / dm ²
The method for producing a copper foil for a printed circuit according to claim 1, wherein the step is performed for 10 to 60 msec.