Stock material or miscellaneous articles – Composite – Of metal
Patent
1988-02-05
1989-11-28
Herbert, Thomas J.
Stock material or miscellaneous articles
Composite
Of metal
4284735, 428901, 528125, 528176, 528185, 564430, B32B 1508, B32B 2706
Patent
active
048837180
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to flexible copper-clad circuit substrates and particularly related to the flexible copper-clad circuit substrates which are excellent in high-temperature stability and high-temperature adhesion.
BACKGROUND OF THE INVENTION
The flexible copper-clad circuit substrates which are used for printed circuit substrates of electronic instruments recently have a serious problem of increase in heat generation accompanied by rise up of package density and wiring pattern density. Thus an important subject is to improve high-temperature stability of the substrates. High-temperature resin which substitutes conventional epoxy resin, includes heat-stable epoxy, polyamide imide, polybenzimidazole, silicone, and polyimide resin. These resins, however, are not always satisfactory to the peel strength to copper foil. Among these resins, polyimide in particular is excellent in high-temperature stability and electrical characteristics, and has increasingly been interested as the materials for electrical insulation. Polyimide, however, has poor bonding strength to metals and requires adhesives to bond the copper foil when polyimide is used for the base film of copper-clad circuit substrates. In spite of good high-temperature stability, insufficient thermal stability of the adhesives inhibits the full utilization of essential high-temperature stability of polyimide. Therefore, polyimide is extensively required which is excellent in high-temperature stability and adhesive strength to metals.
The object of this invention is to provide the high-temperature stable and flexible copper-clad circuit substrates which cause no reduction of adhesive strength during and after use at high temperatures and require no adhesives.
DETAILED DESCRIPTION OF THE INVENTION
The inventors studied hard to solve these problems and achieved the invention by finding the fact that polyimide prepared from particular diamine and tetracarboxylic acid dianhydride was flowable at high temperatures as well as excellent in high temperature stability and bonding strength to the copper foil.
High temperature flowable polyimide in this invention means polyimide which has melt viscosity of 5.times.10.sup.5 poises and less at 400.degree. C. and shear rate of 10.sup.3 l/second by the flow tester of the Society of Polymer Science model (Shimadzu Seisakusho CFT-500) with a nozzle of 0.1 cm in diameter and 1 cm in length. Polyimide in this category is prepared from the following diamine and tetracarboxylic acid dianhydride.
Polyimide and/or its polyamic acid precursor for use in this invention are not restricted in particular on the method of their preparation. They can normally be prepared by polymerizing various diamine with tetracarboxylic acid dianhydride in organic solvents.
Diamine for use in this method includes 3,3'-diaminobenzophenone, 1,3-bis(3-aminophenoxy)benzene, 4,4'-bis(3-aminophenoxy)-biphenyl, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexfluoropropane, bis[4-(3aminophenoxy)-phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]ketone and bis[4-(3-amino-phenoxy)phenyl]sulfone. These are used singly or in mixtures of the two or more.
Tetracarboxylic acid dianhydride to be reacted with diamine has the following formula(I): ##STR1## (where R is a tetra-valent radical selected from the group consisting of aliphatic radical having 2 and more carbons, cycloaliphatic radical, monoaromatic radical, condensed polyaromatic radical, and non condensed polyaromatic radical wherein aromatic radicals are mutually connected with a bond or a crosslinking function).
The dianhydride includes, for example, ethylene tetracarboxylic dianhydride, cyclopentane tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 2,2'3,3'-biphenyl tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)
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Kawashima Saburo
Ohta Masahiro
Oikawa Hideaki
Snobe Yoshiho
Tamai Shoji
Herbert Thomas J.
Mitsui Toatsu Chemicals Inc.
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