JPH04193956A - Method for etching polyimide resin - Google Patents

Abstract

PURPOSE:To improve workability and work environment by exerting etching to the surface of a polyimide resin by using an etchant consisting of a strongly oxidizing salt. CONSTITUTION:In a plating treatment exerted at the time of applying electroless plating to a polyimide resin, etching is applied to the polyimide resin by using an etchant consisting of a strongly oxidizing salt to make it hydrophilic. By this method, etching treatment can be applied safely under superior work environment to the polyimide resin which is difficult to etch with superior workability without adversely affecting a human body, and further, the adhesive strength of the electroless plating film activated after the above treatment can be improved. As a result, a copper polyimide substrate prepared by applying the above plating film can sufficiently withstand practical use as a substrate for packaging for FPC and TAB.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for etching polyimide resin in a plating pretreatment method performed when forming electroless plating on polyimide resin.

(Prior technology) Polyimide resin has excellent heat resistance and mechanical, electrical, and chemical properties that are equal to or better than other plastic materials, so it is used in electrical equipment, etc. Widely used as a material. Therefore, flexible printed circuits (FPC) and automatic tape bonding (T
AB) Mounting etc. are manufactured by photo-etching a copper polyimide substrate on which an upper body coating of this polyimide film is formed.
Copper polyimide substrates, which are the raw material for C and TAB, have been manufactured using a lamination method in which a polyimide resin film and copper foil are bonded together using an adhesive.

However, when using this lamination method, the thermal properties of the adhesive used are not suitable and the heat resistance is not sufficient, so the copper foil may peel off from the resin part due to the thermal shock that occurs during bonding, or the adhesive may Due to the low chemical resistance of the copper film, ion adsorption may occur during etching of the copper film, resulting in poor insulation of the circuit if the gaps between the circuits formed are particularly narrow.

In order to overcome this drawback, a method of directly forming a metal coating layer on polyimide resin without using an adhesive is being considered. This method has already been used for other plastic materials, and involves etching the plastic surface with a solution consisting of a variety of materials, forming a hydrophilic etching film on the surface, and then etching palladium (Pd). Silver (A
The surface of the material is catalytically activated using a special metal catalyst such as g), and then electroless plating is applied to the surface. In this case, homogeneous catalyst activation is performed at an appropriate thickness on the polyimide resin surface that has been made hydrophilic by etching, and as a result, the electroless plating film is adhered to the polyimide resin surface with a certain level of high adhesion strength. This is an important requirement for manufacturing FPCs and TABs.

Methods for etching the polyimide resin surface include reducing agents such as hydrazine, amine compounds such as ethylenesibumine, alkaline solutions such as aqueous solutions of alkali metal hydroxides,
A method is known in which water-soluble alcohols such as ethyl alcohol are used alone or in a mixture of two or more. However, when etching is performed using these chemicals, the working environment is generally extremely poor and the toxicity to the human body is also high.

Therefore, when etching the surface of a polyimide resin with good workability and without adversely affecting the human body, and then performing electroless plating after a subsequent activation treatment, a plated film with excellent adhesion can be obtained. The reality is that an etching method capable of forming a uniformly hydrophilic chemical film has not yet been established.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned circumstances, and its purpose is to perform etching treatment on the surface of polyimide resin with good workability and without adversely affecting the human body. The object of the present invention is to provide a method for etching polyimide resin that can make the surface uniformly hydrophilic.

(Means for Solving the Problems) As a result of intensive studies to achieve the above object, the present inventors have found that salts with strong oxidizing properties such as permanganate or hypochlorite, especially salts such as these When etching the surface of a polyimide resin using an alkali metal salt of an acid as an etching solution, it is possible to form a uniform hydrophilic etching film layer on the resin surface with good working environment and without harmful effects on the human body. It has been found that an electroless plating layer with high adhesion can be applied to the resin surface.

That is, the present invention is characterized in that the surface of the polyimide resin is etched using an etching solution consisting of a strongly oxidizing salt such as an aqueous permanganate solution or a hypochlorite solution.

(Function) According to the present invention, the permanganate aqueous solution or hypochlorite solution used as the etching solution itself has a strong oxidizing effect, and in the case of the hypochlorite solution, the etching Although thermal decomposition sometimes occurs at high temperatures, the hypochlorous acid liberated by thermal decomposition also has strong oxidizing properties, so when etching the polyimide resin surface with these etching solutions, avoid the strong oxidizing action. The thickness of the polyimide resin surface is 0,0 by
A uniform and highly hydrophilic etching chemical layer of about 1 to 0.1 μm is formed. Therefore, catalyst metals such as Pd and ACI are finely and homogeneously adsorbed in the etched layer by the subsequent catalyst activation treatment, and these serve as the core during the subsequent electroless plating treatment. By combining with metal atoms, it is possible to form a uniformly plated metal layer on the surface of the polyimide resin.

In the present invention, when an aqueous solution of permanganate is used as an etching solution for the surface of a polyimide resin, the concentration of permanganate in the etching solution is preferably 0.1 m01/u or more.

This is because if the concentration of permanganate is less than 0.1 mol/Ω, the etching ability is too low, leading to an increase in etching time and early deterioration of the solution.

The upper limit of the permanganate concentration is determined by the saturation concentration of the permanganate used, and since this saturation concentration differs depending on the type of permanganate, it cannot be determined unconditionally.

The etching temperature and time are appropriately set according to the concentration of permanganate so that there is no excess or deficiency in etching.

When etching is performed at a high concentration of permanganate or at a high temperature, the etching time is shortened, but even so, sometimes excessive etching tends to cause unevenness of the plating film during plating. When carrying out this process, it is recommended to determine suitable conditions in advance through preliminary experiments, since the adhesion of the plating film may be reduced due to insufficient etching, and productivity may be reduced due to long-term processing.

For example, when using an aqueous solution of potassium permanganate 0.3 m01/I, the solution temperature is 40 to 50°C and the etching time is 5
Appropriate treatment conditions are approximately 10 minutes. The permanganate used is preferably potassium permanganate or sodium permanganate. Other permanganates can be used, but are less economical.

Further, when a hypochlorite solution is used as the etching solution, it is desirable that the effective chlorine concentration in the solution is 3% or more. When the effective chlorine concentration is less than 3%, the etching ability is significantly reduced, which tends to increase the etching time and cause premature deterioration of the solution.

When using a hypochlorite solution as the etching solution, the etching temperature and time also depend on the available chlorine concentration in the etching solution and cannot be definitively determined, but hypochlorite solutions are easily decomposed by heat, so The temperature is 2
It is desirable to maintain the temperature below 0°C.

The hypochlorite used is preferably potassium hypochlorite or sodium hypochlorite. When other hypochlorite salts are used as the etching solution, it is not a good idea because it becomes an aqueous solution and the etching ability is significantly reduced.

The polyimide resin whose surface has been subjected to the etching treatment according to the present invention in this way is subjected to an activation treatment according to a conventional method, and then subjected to an electroless plating treatment to form a uniform plated metal film with high adhesion strength. I can do it.

In this case, the activation treatment may be carried out by employing the well-known catalyzing method or acmolating method, which is usually used in this type of electroless plating treatment. The plating may be carried out under known plating conditions by applying a copper plating solution used in

(Example) Next, examples of the present invention will be described.

Example 1 One side of a 30 x 30 cIn polyimide resin film made by Toshi DuPont Co., Ltd., XAPTPN 200, was sealed and immersed in a 0.3 mol/ll potassium permanganate aqueous solution at 50°C for 5 minutes, and then washed with water. ,
2 using Okuno Pharmaceutical Co., Ltd. 0PC-80 Catalyst M
Catalyzing was performed at 5° C. for 5 minutes, and after washing with water, acceleration was performed at 25° C. for 7 minutes using an 0PC-555 accelerator manufactured by Okuno Pharmaceutical Co., Ltd., and this was thoroughly washed with water.

After the above pretreatment process, the seal applied to one side was removed, and electroless copper plating was performed under the conditions shown below.

CLISO4・5820: 10g/IEDTA
-2Na: 30g/137%HCHO:
5m4! /1 Dipyridyl: 10■/I PEG #1000: 0.5 g/l! Plating conditions> Temperature: 65°C Stirring: Air Time = 5 minutes pH: 12.5 The thickness of the obtained electroless plating film was 0.2 μm,
The plating film had no defects such as blistering, peeling, and unevenness, and had a good appearance.

After that, the substrate was further subjected to electrolytic copper plating to form a copper film with a thickness of 35 μm, and the adhesion strength of the plating film was measured by the method specified in JIS C-6481, and the value was 1.0 kg/an. Obtained. This value is FP
This sufficiently satisfies the adhesion strength value of the metal coating layer required for substrates for C and TAB mounting.

Example 2 Electroless plating of copper was carried out in the same manner as in Example 1, except that polyimide resin was etched using a 0.1 mol/u potassium permanganate aqueous solution at a temperature of 70°C for 10 minutes. Ta. The thickness of the electroless plated film obtained was 0.2 μm, and the plated film had no defects such as swelling, peeling, or unevenness, and had a good appearance.

After that, the substrate was further subjected to electroless plating to form a copper film with a thickness of 35 μm, and the adhesion strength of the plating film was measured by the method specified in JIS C-6481, and the value was 1.1 kg/CXn. Obtained. This value is F
This sufficiently satisfies the adhesion strength value of the metal coating layer required for PC and TAB mounting substrates.

Example 3 Electroless plating of copper was carried out in the same manner as in Example 1, except that polyimide resin was etched using a 1.0...01/p sodium permanganate aqueous solution at a temperature of 30°C for 10 minutes. I did it.

The thickness of the obtained electroless plating film was 062 μm,
The plating film had no defects such as blistering, peeling, or unevenness, and had a good appearance.

Thereafter, the substrate was further subjected to electrolytic copper plating to form a copper film with a thickness of 35 μm, and the adhesion strength of the plating film was measured by the method specified in JIS C-6481, and the value was 1.1 kg/an. Obtained. This value is FP
This sufficiently satisfies the adhesion strength value of the metal coating layer required for substrates for C and TAB mounting.

Comparative Example 1 Electroless plating of copper was performed in the same manner as in Example 1, except that polyimide resin was etched using a 0.05 mol/ρ potassium permanganate aqueous solution at a solution temperature of 70°C for 1 hour. As a result, defects due to blistering had occurred in a portion of the electroless copper plating obtained.

Example 4 Polyimide resin was etched using a sodium hypochlorite solution containing 5% available chlorine at a temperature of 5°C.
Electroless plating of copper was carried out in the same manner as in Example 1, except that the plating was carried out for a minute.

The thickness of the obtained electroless plating film was 0.2 μm,
The plating film had no defects such as blistering, peeling, and unevenness, and had a good appearance.

After that, the substrate was further subjected to electrolytic copper plating to form a copper film with a thickness of 35 μm, and the adhesion strength of the plating film was measured by the method specified in ISC-6481, and the value was 1.1 kg/cxn. Obtained. This value is FP
This sufficiently satisfies the adhesion strength value of the metal coating layer required for substrates for C and TAB mounting.

Example 5 Polyimide resin was etched using a potassium hypochlorite solution containing 6% available chlorine at a temperature of 10°C.
Electroless plating of copper was performed in the same manner as in Example 1 except that the plating was performed for 0 minutes.

The thickness of the obtained electroless plating film was 0.2 μm,
The plating film had no defects such as blistering, peeling, and unevenness, and had a good appearance.

Thereafter, the substrate was further subjected to electrolytic copper plating to form a copper film with a thickness of 35 μm, and the adhesion strength of the plating film was measured according to the method specified in JIS C-6481, and the value was 1.0 kg/can. was gotten. This value sufficiently satisfies the adhesion strength value of the metal coating layer required for a board for FPC'i'TAB mounting.

Example 6 Polyimide resin was etched using a sodium hypochlorite solution containing 3% available chlorine at a temperature of 5°C.
Electroless plating of copper was performed in the same manner as in Example 1 except that the plating was performed for 0 minutes.

The thickness of the obtained electroless plating film was 0.2 μm,
The plating film had no defects such as blistering, peeling, and unevenness, and had a good appearance.

Thereafter, the substrate was further subjected to electrolytic copper plating to form a copper film with a thickness of 35 μm, and the adhesion strength of the plating film was measured by the method specified in JIS C-6481, and the value was 1.1 kg/an. Obtained. This value is FP
This sufficiently satisfies the adhesion strength value of the metal coating layer required for substrates for C and TAB mounting.

Comparative Example 2 Electroless plating of copper was performed in the same manner as in Example 1, except that polyimide resin was etched using a sodium hypochlorite solution containing 2% available chlorine at a solution temperature of 5°C for 1 hour. As a result, defects due to blistering had occurred in a portion of the electroless copper plating obtained.

(Effects of the Invention) As described above, according to the present invention, it has been difficult to perform etching treatment with good workability and without adversely affecting the human body in the pretreatment performed when performing electroless plating treatment. Etching can be carried out safely in a good working environment on polyimide resin, and the adhesion strength of the electroless plating film applied after subsequent activation treatment is also high, so the copper polyimide substrate obtained by etching can be It is possible to obtain a board that can be used in practical use as a mounting board for FPC or TAB, and its effects are great.

Patent applicant: Sumitomo Metal Mining Co., Ltd.

Claims (5)

[Claims] (1) A method for etching a polyimide resin, which is characterized in that the surface of the polyimide resin is made hydrophilic by etching it with an etching solution made of a salt having strong oxidizing properties. (2) The method for etching a polyimide resin according to claim 1, wherein the etching solution made of a strongly oxidizing salt is an aqueous solution containing 0.1 mol/l or more of permanganate. (3) The method for etching polyimide resin according to claim 2, wherein the permanganate is sodium permanganate or potassium permanganate. (4) The method for etching polyimide resin according to claim 1, wherein the etching solution made of a salt having strong oxidizing properties is a hypochlorite solution containing 3% or more of available chlorine. (5) The method for etching polyimide resin according to claim 4, wherein the hypochlorite is sodium hypochlorite or potassium hypochlorite.