Adhesive sheet with base for flexible printed wiring boards, production method therefor, multilayer flexible printed wiring board and flex-rigid printed wiring board
An adhesive sheet with a base for flexible printed wiring boards is provided, which has advantages of easiness of machining, excellent moldability, high rigidity and preventing the fall of resin dust particles during machining of a multilayer flexible printed wiring board or a flex-rigid printed wiring board. This adhesive sheet is used for bonding of a flexible printed wiring board made of a polyimide resin, and comprises a woven or nonwoven fabric as the base and a resin composition. The resin composition contains, as essential components, (a) an epoxy resin having two or more of epoxy groups in one molecule; (b) a polycarbodiimide resin dispersible in a solvent, in which the epoxy resin (a) is also dispersible, and having a number average molecular weight of 2000 or more and less than 10000; and (c) an imidazole curing agent. A weight ratio of the component (a) and the component (b) is in a range of 80:20 to 20:80.
1 . An adhesive sheet with a base, which is used for bonding of a flexible printed wiring board made of a polyimide resin, and comprises a woven fabric or a nonwoven fabric as the base and a resin composition,
wherein said resin composition contains, as essential components,
(a) an epoxy resin having two or more of epoxy groups in a molecule;
(b) a polycarbodiimide resin dispersible in a solvent, in which said epoxy resin of the component (a) is also dispersible, and having a number average molecular weight of 2000 or more and less than 10000;
(c) an imidazole curing agent, and
a weight ratio of the component (a) and the component (b) is in a range of 80:20 to 20:80.
2 . The adhesive sheet as set forth in claim 1 , wherein said woven fabric is a glass cloth.
3 . The adhesive sheet as set forth in claim 1 , wherein said nonwoven fabric is a glass nonwoven fabric or an organic fiber nonwoven fabric.
4 . A multilayer flexible printed wiring board comprising a flexible printed wiring board made of a polyimide resin, and an outer-layer flexible substrate bonded to the flexible printed wiring board by use of the adhesive sheet as set forth in claims 1 .
5 . A flex-rigid printed wiring board comprising a flexible printed wiring board made of a polyimide resin, and an outer-layer laminate bonded to the flexible printed wiring board by use of the adhesive sheet as set forth in claims 1 .
6 . A method of producing an adhesive sheet with a base, which is used for bonding of a flexible printed wiring board made of a polyimde resin, the method comprising the steps of:
preparing a varnish by dispersing a resin composition into a solvent, said resin composition containing, as essential components, (a) an epoxy resin having two or more of epoxy groups in a molecule; (b) a polycarbodiimide resin dispersible in a solvent, in which said epoxy resin of the component (a) is also dispersible, and having a number average molecular weight of 2000 or more and less than 10000; and (c) an imidazole curing agent;
impregnating said varnish into a woven fabric or a nonwoven fabric as the base; and drying a resultant product.
7 . A multilayer flexible printed wiring board comprising a flexible printed wiring board made of a polyimide resin, and an outer-layer flexible substrate bonded to the flexible printed wiring board by use of the adhesive sheet as set forth in claim 2 .
8 . A multilayer flexible printed wiring board comprising a flexible printed wiring board made of a polyimide resin, and an outer-layer flexible substrate bonded to the flexible printed wiring board by use of the adhesive sheet as set forth in claim 3 .
9 . A flex-rigid printed wiring board comprising a flexible printed wiring board made of a polyimide resin, and an outer-layer laminate bonded to the flexible printed wiring board by use of the adhesive sheet as set forth in claim 2 .
10 . A flex-rigid printed wiring board comprising a flexible printed wiring board made of a polyimide resin, and an outer-layer laminate bonded to the flexible printed wiring board by use of the adhesive sheet as set forth in claim 3 .