Flexible laminate printed-circuit board and methods of making sa

Stock material or miscellaneous articles – Composite – Of polyimide

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428209, 428901, 428458, 427 96, 156228, 156233, B32B 300, B32B 2700, B32B 3100, B05D 512

Patent

active

048392324

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a flexible laminate for printed-circuit board comprising a metal-clad polyimide sheet having excellent heat resistance, electrical properties and mechanical properties, as well as methods of making the same.


BACKGROUND ART

Flexible laminate for printed-circuit boards are materials for the fabrication of printed circuits having flexibility, and their use is increasing in recent years, for example, because the cases for containing printed circuits are being reduced in size. Conventionally, such flexible laminate for printed-circuit boards have been made by bonding a polyimide film to copper foil with the aid of an adhesive. In such boards, the polyimide film has satisfactorily good heat resistance, electrical properties and mechanical properties, but the adhesive has inadequate properties. For this reason, they have had the disadvantage that the good properties of the polyimide film are not fully utilized.
Accordingly, attempts have been made in the prior art to form a flexible laminate for printed-circuit board comprising a metal-clad polyimide sheet, without the aid of an adhesive. Some examples are disclosed in U.S. Pat. No. 3,179,634, Japanese Patent Laid-Open Nos. 129862/'74, 190091/'83 and 190092/'83, and the like. However, a flexible laminate for printed-circuit board having a combination of adequate heat resistance, adhesion strength and flexibility has not yet been provided.


DISCLOSURE OF THE INVENTION

The present invention has been made in view of the above-described problems, and it is an object thereof to provide a flexible laminate for printed-circuit board comprising a metal-clad polyimide sheet having a combination of excellent heat resistance, electrical properties, and mechanical properties such as adhesion strength, flexibility, etc., as well as methods of making the same.
The present invention is concerned with a method of making a flexible laminate for printed-circuit board which comprises the steps of mixing a symmetrical aromatic meta-substituted primary diamine with a symmetrical aromatic para-substituted primary diamine in an equivalent weight ratio of 10-60:90-40, reacting the resulting mixture with an aromatic tetracarboxylic acid anhydride to form a polyamic acid as a polyimide precursor, coating a metal foil directly with the resulting organic solvent solution of said polyamic acid, and then heating the coated metal foil to dehydrate said polyamic acid; a method of making a flexible laminate for printed-circuit board which comprises the steps of reacting a symmetrical aromatic meta-substituted primary diamine with an aromatic tetracarboxylic acid anhydride to form a polyamic acid (A), reacting a symmetrical aromatic para-substituted primary diamine with an aromatic tetracarboxylic acid anhydride to form a polyamic acid (B), mixing the resulting organic solvent solution of said polyamic acid (A) with the resulting organic solvent solution of said polyamic acid (B) in an equivalent weight ratio of 10-60:90-40, coating a metal foil directly with the resulting mixture, and then heating the coated metal foil to dehydrate said polyamic acids; and flexible laminate for printed-circuit boards made by these methods.


BEST MODE FOR CARRYING OUT THE INVENTION

A flexible laminate for printed-circuit board having more excellent properties is obtained when the aforesaid step of heating the coated metal foil to dehydrate said polyamic acid(s) is carried out in an atmosphere of an inert gas. A flexible laminate for printed-circuit board can be relatively simply and economically made by coating a metal foil directly with the resulting organic solvent solution of the polyamic acid(s), drying the resulting laminate to a substantially tack-free state, rolling up the laminate, and then heating the rolled laminate in an atmosphere of an inert gas to dehydrate the polyamic acid(s).
The symmetrical aromatic meta-substituted primary diamines (hereinafter referred to briefly as m-diamines) useful in the present invention can be represented by the general f

REFERENCES:
patent: 3179634 (1965-04-01), Edwards
patent: 3666709 (1972-05-01), Suzuki et al.
patent: 4411952 (1983-10-01), Sasaki et al.
patent: 4508766 (1985-04-01), Inaike et al.
patent: 4528833 (1985-07-01), Inaike et al.
patent: 4690999 (1987-09-01), Numata et al.
Chemical Abstracts 104:187094q.
Chemical Abstracts 104:111010p.

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