JPH043674B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Conventionally, flexible printed wiring boards have been made of polyester films or polyimide films laminated with copper foil via an adhesive. However, especially in flexible printed wiring boards using polyimide film, the characteristics of the flexible printed wiring board are determined by the heat resistance, moisture absorption, and flammability of the adhesive, and the inherent superiority of polyimide film is The situation is that the heat resistance is not fully demonstrated.

In order to improve the above-mentioned drawbacks, attempts have been made to apply polyimide varnish or polyamic acid varnish directly to the copper foil and then heat treat it, but the results were not satisfactory, with curling and insufficient bending durability. It has not been done.

The present invention provides a flexible printed wiring board with excellent heat resistance and flame retardancy by not using an adhesive.

That is, the present invention is a heat-resistant resin varnish containing a Pd salt soluble in an aprotic solvent on a green film produced by casting a heat-resistant resin varnish (A) on a carrier and in which the solvent is not completely blown off. The present invention relates to a method for manufacturing a flexible printed wiring board, characterized in that a circuit is formed by casting a flexible resin varnish (B), heating it, and then etching the Pd salt-containing resin layer.

The heat-resistant resin used in the present invention is preferably one having an amic acid structure which is an imide group or a precursor of an imide group, and examples thereof include polyimide, polyamideimide, polyetherimide, etc., or polyamide which is a precursor of these. Although acids can be used, polyimide or its precursor polyamic acid is particularly desirable.

The heat-resistant resin varnishes (A) and (B) may be the same or different, but it is desirable that the heat-resistant resin varnish (B) is polyamic acid.

As a Pd salt soluble in aprotic polar solvents,
Li ₂ PdCl ₄ , Pd(S(CH ₃ ) ₂ ) ₂ Cl ₂ , Pd(S
(CH ₂ CH ₃ ) ₂ ) ₂ Cl ₂ , Na ₂ PdCl ₄ , PdCl ₂ and the like are exemplified, but Li ₂ PdCl ₄ and Pd(S(CH ₃ ) ₂ ) ₂ Cl ₂ are preferable.
The concentration of Pd salt is appropriately determined depending on the required conductivity, but it is usually sufficient for the Pd concentration to be 10% by weight or less, further 5% by weight or less, based on the solid content.

It is desirable that the green film produced by casting heat-resistant resin varnishes (A) and (B) and then heating and drying is dry to the touch.

The thickness of each layer of the film produced from the heat-resistant resin varnishes (A) and (B) can be freely adjusted depending on the purpose and use, but is usually preferably about 1 to 50 microns.

The composite film produced by the above method is heat-treated to remove residual solvent and to close the ring, either with the carrier attached or after being peeled off from the carrier. Perform heat treatment. The temperature of the heat treatment may be at least the temperature at which ring closure of the polyamic acid occurs, but
A temperature of 200°C or higher is desirable, and a temperature of 300°C or higher is even more desirable.

The circuit formation method is to laminate etching resist on both sides of a composite polyimide film obtained by heat treatment, draw a circuit on the Pd-containing layer side by irradiating it with ultraviolet rays, etching it with an acid such as hydrochloric acid, and then applying hydrazine or hydrazine. A circuit is formed by etching with alkali or dry etching.
Leave a Pd-containing layer.

The flexible printed wiring board obtained by the method of the present invention may be further subjected to electroless plating or electroplating to improve its conductivity.

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 A polyamic acid dimethylacetamide varnish with a resin content of 15% obtained from pyromellitic dianhydride and diaminodiphenyl ether was cast onto a glass plate using an applicator, and then dried at 100°C for 15 minutes. and got a green film.

20% resin obtained from benzophenonetetracarboxylic dianhydride and diaminodiphenyl ether
A varnish obtained by mixing Pd(S(CH ₃ ) ₂ ) Cl ₂ in dimethylacetamide varnish of polyamic acid at a Pd concentration of 5% by weight was cast onto the green film, and then heated at 100°C. , dried for 15 minutes.

The obtained composite film was removed from the glass plate, fixed on a metal frame, and heat treated at 200°C for 30 minutes and at 300°C for 30 minutes to obtain a composite polyimide film.

After laminating etching resist on both sides of the composite polyimide film, a photomask was placed on the Pd-containing layer side, and the film was exposed to ultraviolet light and developed.
A flexible printed wiring board was obtained by etching with an aqueous hydrochloric acid solution and further etching with an aqueous hydrazine solution to form a circuit.

The volume resistivity of the circuit part of the obtained flexible printed wiring board was less than 10 ⁵ Ωcm, and the soldering heat resistance was
300℃ or more, and the folding durability according to the MIT method is
It was over 500 times.

Comparative Example 1 The green film obtained in Example 1 was peeled off from a glass plate, fixed on a metal frame, and heat treated at 200°C for 30 minutes to obtain a polyimide film.

This film is laminated with copper foil using an epoxy adhesive, and then etched to form a circuit.The resulting flexible printed wiring board has a soldering heat resistance of 300°C or less, and a folding resistance of 200 times or less. It was hot.

Example 2 A polyamic acid dimethylacetamide varnish with a resin content of 15% obtained from pyromellitic dianhydride and diaminodiphenyl ether was cast onto a glass plate using an applicator, and then dried at 100°C for 15 minutes. and got a green film.

20% resin obtained from benzophenonetetracarboxylic dianhydride and diaminodiphenyl ether
A varnish obtained by mixing Li ₂ PdCl ₄ in dimethylacetamide varnish of polyamic acid at a Pd concentration of 5% by weight was cast onto the green film and dried at 100° C. for 15 minutes.

The obtained composite film was removed from the glass plate, fixed on a metal frame, and heat treated at 200°C for 30 minutes and at 300°C for 30 minutes to obtain a composite polyimide film.

After laminating etching resist on both sides of the composite polyimide film, a photomask was placed on the Pd-containing layer side, irradiated with ultraviolet rays, and then developed. A flexible printed wiring board was obtained by etching using an argon ion beam and forming a circuit.

The volume resistivity of the circuit part of the obtained flexible printed wiring board was 5.0×10 ⁶ Ωcm, and the soldering heat resistance was
300℃ or more, and the folding durability according to the MIT method is
It was over 500 times.

Example 3 P- of polyimide with a resin content of 10% obtained from pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, and diaminodiphenyl ether
Chlorphenol varnish was cast onto a glass plate using an applicator, and then dried at 100°C for 30 minutes to obtain a green film.

In dimethylacetamide varnish of polyamic acid with a resin content of 20% obtained from benzophenone tetracarboxylic dianhydride and diaminodiphenyl ketone.
A varnish obtained by mixing Pd(S(CH ₃ ) ₂ ) ₂ Cl ₂ to a Pd concentration of 5% by weight was cast onto the green film and dried at 100° C. for 15 minutes.

The obtained composite film was removed from the glass plate, fixed on a metal frame, and heat treated at 200°C for 30 minutes and at 300°C for 30 minutes to obtain a composite polyimide film.

After laminating etching resist on both sides of the composite polyimide film, a photomask was placed on the Pd-containing layer side, irradiated with ultraviolet rays, and then developed. A flexible printed wiring board was obtained by etching with an aqueous hydrochloric acid solution and then etching with an aqueous hydrazine solution to form a circuit.

The volume resistivity of the circuit part of the obtained flexible printed wiring board was 4.2×10 ⁷ Ωcm, and the soldering heat resistance was
300℃ or more, and the folding durability according to the MIT method is
It was over 500 times.

Example 4 A polyamic acid dimethylacetamide varnish containing pyromellitic dianhydride and diaminodiphenyl ether with a resin content of 15% was cast onto a glass plate using an applicator, and then dried at 100°C for 15 minutes. I got a green film.

Add Li ₂ PdCl ₄ to dimethylacetamide varnish of polyamic acid with a resin content of 20% obtained from pyromellitic dianhydride and diaminodiphenyl carbinol.
After casting a varnish obtained by mixing the Pd concentration to 5% by weight on the green film,
It was dried at 100°C for 15 minutes.

The obtained composite film was removed from the glass plate, fixed on a metal frame, and heat treated at 200°C for 30 minutes and at 300°C for 30 minutes to obtain a composite polyimide film.

After laminating etching resist on both sides of the composite polyimide film, a photomask was placed on the Pd-containing layer side, irradiated with ultraviolet rays, and then developed. After etching with hydrochloric acid aqueous solution, further KOH
A flexible printed wiring board was obtained by etching using an aqueous solution and forming a circuit.

The volume resistivity of the circuit part of the obtained flexible printed wiring board was 5.2 × 10 ¹¹ Ωcm, the soldering heat resistance was 300°C or higher, and the folding durability according to the MIT method was 5.2 × 10 11 Ωcm.
It was over 500 times.

Claims (1)

[Claims] 1. A Pd salt soluble in an aprotonic polar solvent is placed on a green film produced by casting a heat-resistant resin varnish (A) on a carrier and on which the solvent has not been completely blown off. A method for producing a flexible printed wiring board, characterized in that a circuit is formed by casting a heat-resistant resin varnish (B) containing the Pd salt, heating it, and then etching the Pd salt-containing resin layer. 2. The method for producing a flexible printed wiring board according to claim 1, wherein the heat-resistant resin varnishes (A) and (B) are polyamic acid varnishes. 3. The method for producing a flexible printed wiring board according to claim 1, wherein the heat-resistant resin varnish (A) is a polyimide varnish. 4 Pd salts soluble in aprotic polar solvents
The method for producing a flexible printed wiring board according to claim 1, 2 or 3, characterized in that the material is Li ₂ PdCl ₄ or Pd(S(CH ₃ ) ₂ ) ₂ Cl ₂ .