JPH07216553A - Production of copper-coated polyimide substrate - Google Patents

Abstract

PURPOSE:To improve adhesion strength of a Cu-plating layer to the surface of a polyimide resin film by including a step of treating the film with an alkali metal oxide soln. after the film surface is etched in the process of Cu plating on the surface of the film. CONSTITUTION:After the surface of a polyimide resin film is cleaned, the surface is etched, to which a catalyst for electroless plating is added and activated. A plating layer of Ni, Co or alloy of them is formed by electroless plating on the surface activated with the catalyst. The electroless plating layer is activated by heating in an inert gas atmosphere and subjected to electroplating with Cu. In this process, after pretreatment of the polyimide resin film by etching, such a step is added that the film is treated with an alkali liquid containing 0.1-5 mol/l density of alkali metal hydroxide such as NaOH or KOH at 10-50 deg.C. Thus, adhesion property of the Cu electroplating film to the polyimide resin film is significantly improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a copper-clad polyimide substrate which is a material for a printed wiring board (PWB) such as a flexible printed wiring board (FPC) and a tape automatic bonding (TAB) tape.

[0002]

2. Description of the Related Art In recent years, further miniaturization and higher speed of electronic equipment have been demanded, and higher density has been demanded for printed wiring boards and the like used therein. For this reason, substrates having better heat resistance, flame resistance, dimensional stability, solvent resistance, electrical insulation, and mechanical strength are required as substrates for producing printed wiring boards and the like. ing.

One of those that most satisfy this requirement is a copper-clad polyimide substrate. This is one in which a copper layer is also provided on the surface of a polyimide resin film. As a method for coating copper on a polyimide resin film, a so-called laminating method in which a copper foil is attached using an adhesive, a sputtering method, an ion plating method, a vapor deposition method, an electroless plating method or the like is used to directly form a polyimide layer on a metal layer. There is a method to install it. Among these methods, the electroless plating method is drawing attention because of the reliability of the final product such as a printed wiring board produced by using a copper-clad polyimide substrate and the possibility of mass production at low cost. .

Generally, when a polyimide resin film is directly coated with copper by an electroless plating method, the surface of the polyimide resin film is subjected to an etching treatment, a catalyst for electroless plating is applied, and a catalyst activation treatment is performed. Perform electrolytic copper plating. However, when a wiring board or the like is manufactured using the copper-coated polyimide substrate obtained by this method, a situation occurs in which the wiring portion is separated from the polyimide resin film, especially when the wiring portion becomes fine.

Various methods have been proposed to solve this problem. For example, when forming a copper layer on a polyimide resin, a method of forming a metal layer of nickel or the like between the resin and the copper layer (Japanese Patent Laid-Open No. 286580/1988, US Pat. No. 5,246,546).
564) and a method of performing heat treatment in an inert atmosphere or in a vacuum (JP-A-4-59351, JP-A-4-236833, JP-A-4-254598, etc.).

[0006]

When a copper coating is provided on a polyimide resin film having a thickness of 50 μm or more by using such a method, the adhesion strength between the copper coating and the polyimide resin film is certainly improved, and it is practically used. A substrate that can withstand is created. However, if the thickness of the polyimide resin film is set to about 25 μm in order to satisfy the demand for higher density, the adhesion strength between the copper coating and the polyimide resin film is significantly reduced. The conditions for use under high temperature and high humidity conditions are 1.
Far from 0 kgf / cm or more, it is difficult to stably satisfy the JIS or JPCA standard value of 0.8 kgf / cm or more.

An object of the present invention is to provide a stable copper-coated polyimide resin film having an adhesion strength between the copper coating and the polyimide resin film of 1.0 kgf / cm or more even when the thickness of the polyimide resin film is about 25 μm. It is to provide a method for manufacturing.

[0008]

Means for Solving the Problems The method of the present invention for solving the above problems comprises a step of etching the surface of a polyimide resin film, a step of applying a catalyst for electroless plating, and an activation of the applied catalyst. Of the chemical treatment, nickel, cobalt or a step of electrolessly plating any of these metal alloys, a step of heat-treating the obtained object to be plated in an inert atmosphere, further electroless plating layer In a method for producing a copper-coated polyimide substrate basically composed of a step of electrolytic copper plating on the surface of the polyimide resin film, the surface of the polyimide resin film is subjected to etching treatment, and then the surface has a concentration of 0.1 to 5 mol / liter and a temperature of 10-50 ° C
It is treated with an alkaline solution.

As the alkaline solution which can be used in the present invention, sodium hydroxide solution or potassium hydroxide solution can be recommended.

[0010]

As a result of various investigations, the present inventors have found that after the surface of the polyimide resin film is subjected to an etching treatment, the surface is further treated with an alkali metal hydroxide solution to increase the adhesion strength. It is not clear why such a result is obtained. The present inventors consider as follows.

That is, generally, when a metal-coated polyimide resin is produced by an electroless plating method, a decomposition product generated by hydrolysis or cleavage of an imide bond at the interface between the metal layer and the polyimide resin film is generated. Remains. The thickness of the polyimide resin film is 25 μm
Although the reason is not clear, it is considered that the properties of the remaining decomposition products differ between before and after and before and after 50 μm. As a result, the adhesion strength varies depending on the thickness of the polyimide resin film even if the same manufacturing method is adopted.

The surface of the polyimide resin film after etching by the method of the present invention is treated with an alkaline solution because the alkaline solution dissolves the polyimide resin. That is, this is to dissolve the decomposition product layer on the surface of the polyimide resin film together with the polyimide resin and leave the minimum hydrophilic layer necessary for electroless plating on the surface of the polyimide resin film. Then, the catalyst for electroless plating is adsorbed on the hydrophilic layer to form a good electroless plated film.

The alkali metal hydroxide is not particularly limited, but sodium hydroxide or potassium hydroxide is preferable from the viewpoint of price and availability. When the concentration of the alkali metal hydroxide in the liquid is less than 0.1 mol / l, the decomposition product layer is not sufficiently dissolved, and when it is more than 5 mol / l, pinholes, skips, etc. Non-plating is likely to occur.

When the liquid temperature of the alkaline solution is lower than 10 ° C., the dissolution of the decomposition product layer is insufficient, and
When the temperature is higher than 0 ° C., non-plating such as pinholes and skips is likely to occur.

However, the optimum condition among these conditions is the type of the material polyimide resin film, the composition of the etching solution,
It should be selected for economic reasons such as altered layer thickness and productivity depending on conditions and is not particularly limited.

Incidentally, the etching treatment of the surface of the polyimide resin film carried out in the present invention, the catalyst applying treatment for electroless plating, the catalyst activation treatment, electroless plating of nickel, cobalt or an alloy of these metals. Since the treatment, the heat treatment in an inert atmosphere, and the treatment procedure in the electrolytic copper plating treatment are not different from those conventionally used, the description thereof will be omitted.

[0017]

EXAMPLES Next, examples of the present invention will be described.

Example 1 As a substrate material, Apical NPI-25 polyimide resin film manufactured by Kaneka Corporation is used.
Mask one side of the 20 × 20 cm test sample,
3 in an aqueous solution containing 25% hydrazine hydrate at 25 ° C
Soak for 0 seconds to make the surface hydrophilic, then wash with water, and then add 3 mol.
Soak for 0 seconds and wash with water. OPC-80 manufactured by Okuno Pharmaceutical Co., Ltd.
After applying the catalyst using Catalyst M, washing with water, activating the catalyst with OPC-555 accelerator manufactured by Okuno Seiyaku Co., Ltd., and washing with water, the substrate surface was subjected to electroless nickel plating under the conditions shown in Table 1. By this treatment, a nickel plating film could be formed on the substrate.

Table 1 NiCl ₂ .6H ₂ O 0.1 mol / l NaH ₂ PO ₂ .H ₂ O 0.1 mol / l Glycine 0.3 mol / l pH 7.0 Plating bath temperature 50 ° C. Plating time 75 Second

Next, this substrate was heated to 400 ° C. at a temperature rising rate of 9 ° C./min in a nitrogen gas atmosphere using a hot air circulation type heating furnace manufactured by Koyo Lindbergh, and kept at the same temperature for 1.5 hours. After that, heat treatment for cooling at a temperature decrease rate of 2.5 ° C./min was performed.

Thereafter, electrolytic copper plating treatment was performed under the conditions shown in Table 2. By this treatment, a 35 μm thick electrolytic copper plating film was formed on the substrate to obtain a copper-coated polyimide substrate.

Table 2 CuSO ₄ .5H ₂ O 100 g / liter H ₂ SO ₄ 150 g / liter Plating solution temperature 25 ° C. Plating time 90 minutes

A copper-clad polyimide substrate is cut in half, a resist is applied to one of the copper surfaces, masked and etched to give a polyimide resin film surface with a width of 10 m.
A strip-shaped copper layer having a length of m and a length of 100 mm was formed, and an end portion of the copper layer was peeled off in a direction perpendicular to the substrate to measure adhesion strength between the copper coating and the polyimide resin film. As a result, an adhesion strength of 1.5 kgf / cm (initial adhesion strength) was obtained. Then, the other copper-coated polyimide substrate was left in the atmosphere at 200 ° C. for 3 hours, and the adhesion strength between the copper coating and the polyimide resin film was measured in the same manner. As a result, the adhesion strength was 1.3 kgf / cm.

Example 2 A copper-coated polyimide substrate was obtained in the same manner as in Example 1 except that 1 mol / liter sodium hydroxide solution at 10 ° C. was used as the alkaline solution. Then, each adhesive strength was measured in the same manner as in Example 1. The value obtained is 200 kgf / cm at the initial adhesion strength of 200.
The adhesion strength after standing for 3 hours in the atmosphere at 1.1 ° C. was 1.1 kgf / cm.

Example 3 A copper-coated polyimide substrate was obtained in the same manner as in Example 1 except that the concentration of the alkaline solution was 5 mol / liter and the immersion time in the alkaline solution was 5 seconds. Then, each adhesive strength was measured in the same manner as in Example 1. The obtained value is the initial adhesion strength of 1.4 kgf / c.
Adhesion strength after leaving for 3 hours at 200 ° C in the atmosphere of 1.0kg
It was f / cm.

(Example 4) The concentration of the alkaline solution was set to 0.1.
Mol / l and the immersion time in the alkaline solution is 1
A copper-coated polyimide substrate was obtained in the same manner as in Example 1 except that the time was 20 seconds. Then, each adhesive strength was measured in the same manner as in Example 1. The obtained value is the initial adhesion strength of 1.4 k.
The adhesive strength was gf / cm, and the adhesion strength was 1.1 kgf / cm after standing at 200 ° C. in the atmosphere for 3 hours.

Example 5 A copper-coated polyimide substrate was obtained in the same manner as in Example 1 except that the concentration of the alkaline solution was 3 mol / liter and the immersion time in the alkaline solution was 10 seconds. Then, each adhesive strength was measured in the same manner as in Example 1. The obtained value is the initial adhesion strength of 1.4 kgf /
cm, adhesion strength 1.0k after standing in the air at 200 ° C for 3 hours
It was gf / cm.

(Example 6) The temperature of the alkaline solution was set to 50 ° C.
A copper-coated polyimide substrate was obtained in the same manner as in Example 1 except that the immersion time in the alkaline solution was 5 seconds. Then, each adhesive strength was measured in the same manner as in Example 1. The obtained value is 200 kgf / cm in initial adhesion strength, 200
The adhesive strength was 1.3 kgf / cm after standing for 3 hours in the atmosphere at ℃.

Example 7 A copper-coated polyimide substrate was obtained in the same manner as in Example 2 except that the concentration of the alkaline solution was 5 mol / liter and the immersion time in the alkaline solution was 10 seconds. Then, each adhesive strength was measured in the same manner as in Example 1. The obtained value is the initial adhesion strength of 1.4 kgf /
cm, adhesion strength 1.1k after standing in the atmosphere at 200 ° C for 3 hours
It was gf / cm.

(Embodiment 8) The concentration of the alkaline solution is set to 0.1.
Mol / l and the immersion time in the alkaline solution is 1
A copper-coated polyimide substrate was obtained in the same manner as in Example 2 except that the time was 80 seconds. Then, each adhesive strength was measured in the same manner as in Example 1. The obtained value is the initial adhesion strength of 1.4 k.
The adhesive strength was gf / cm, and the adhesion strength was 1.1 kgf / cm after standing at 200 ° C. in the atmosphere for 3 hours.

Example 9 A copper-coated polyimide substrate was obtained in the same manner as in Example 2 except that the concentration of the alkaline solution was 3 mol / liter and the immersion time in the alkaline solution was 20 seconds. Then, each adhesive strength was measured in the same manner as in Example 1. The obtained value is the initial adhesion strength of 1.4 kgf /
cm, adhesion strength 1.1k after standing in the atmosphere at 200 ° C for 3 hours
It was gf / cm.

(Example 10) The temperature of the alkaline solution was set to 50.
C. and a copper-coated polyimide substrate was obtained in the same manner as in Example 2 except that the immersion time in the alkaline solution was 5 seconds.
Then, each adhesive strength was measured in the same manner as in Example 1.
The obtained value is 20 kg for the initial adhesion strength of 1.4 kgf / cm.
Adhesion strength of 1.2 kgf / cm after standing at 0 ° C in the atmosphere for 3 hours
Met.

(Comparative Example 1) A copper-coated polyimide resin substrate was obtained in the same manner as in Example 1 except that the treatment with an alkaline solution was omitted. Then, the adhesion strength of this substrate was measured by the same method as in Example 1. As a result, initial adhesion strength 0.8k
The adhesive strength was gf / cm, and the adhesion strength was 0.7 kgf / cm after standing at 200 ° C. in the atmosphere for 3 hours.

Comparative Example 2 A copper-coated polyimide resin substrate was obtained in the same manner as in Example 1 except that the concentration of the alkaline solution was 6 mol / liter.

The obtained substrate was not suitable for practical use due to non-plating such as pinholes and skips.

Comparative Example 3 The concentration of the alkaline solution was 0.0
A copper-coated polyimide resin substrate was obtained in the same manner as in Example 1 except that the amount was 8 mol / liter. Then, in the same manner as in Example 1, the adhesion strength of this substrate was measured. The obtained adhesion strength was 0.8 kgf / cm.

(Comparative Example 4) The temperature of the alkaline solution was set to 60 ° C.
A copper-coated polyimide resin substrate was obtained in the same manner as in Example 1 except for the above.

The obtained substrate was not suitable for practical use due to non-plating such as pinholes and skips.

[0039]

According to the method of the present invention, a polyimide resin film having a thickness of 25 μm is 1.0 kgf / cm.
It is possible to manufacture a copper-coated polyimide resin film that can obtain the above adhesion strength, and to use it as a material for flexible printed wiring boards (FPC), printed wiring boards (PWB) such as tape automatic bonding (TAB) tapes, and the like. It will be possible.

Claims (2)

[Claims] 1. A step of etching the surface of a polyimide resin film, a step of applying a catalyst for electroless plating, and a step of activating the applied catalyst.
Electroless plating of nickel, cobalt or any of these metal alloys, heat treatment of the obtained object to be plated in an inert atmosphere, and electrolytic copper plating on the electroless plating layer In the method for producing a copper-clad polyimide substrate basically composed of steps, after the surface of the polyimide resin film is subjected to etching treatment, the surface is treated with an alkaline solution having a concentration of 0.1 to 5 mol / liter and a temperature of 10 to 50 ° C. A method for producing a copper-clad polyimide substrate, characterized by comprising: 2. The method according to claim 1, wherein a sodium hydroxide solution or a potassium hydroxide solution is used as the alkaline solution.