Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1995-08-07
1997-10-14
Dean, Ralph H.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
156329, 156330, 428413, 428447, 4284735, 428901, C08G 6948, C09J 700, C09J16300, C09J18304
Patent
active
056773935
DESCRIPTION:
BRIEF SUMMARY
FIELD OF TECHNOLOGY
This invention relates to heat-resistant film adhesives for use in fabrication of printed circuit boards and, more particularly, to novel heat-resistant film adhesives containing polyimides with silicone units soluble in organic solvents and epoxy resins for use in printed circuit boards.
To be more specific, this invention relates to heat-resistant film adhesives which are useful for special applications such as fabrication of multilayer printed circuit boards by lamination of patterned layers, formation of composites of different circuit materials and bonding of a base material to another and hence relates to heat-resistant adhesives in the form of films which can fill the uneven surface of a patterned layer and exhibit high adhesive strength and good heat resistance and, in particular, good heat resistance at soldering temperature after moisture absorption.
BACKGROUND TECHNOLOGY
Base materials which have been used for printed circuit boards include phenolic resin-impregnated paper, epoxy resin-impregnated glass fibers and laminates of polyimide or poly(ethylene terephthalate) films and metal foils.
In recent years, a decrease in the wiring area in printed circuit boards in the fields of electric and electronic equipment and precision equipment has created a rising demand for multilayer printed circuit boards. A variety of adhesives and adhesive films are used in fabrication of multilayer printed circuit boards by lamination of patterned layers and in formation of composites from different circuit materials.
Known examples of such adhesives are prepregs prepared by impregnating woven glass fibers with epoxy resins or bismaleimide resins. However, they have presented problems such as insufficient flexibility and poor dimensional stability.
A number of proposals have been made for using adhesives based on acrylonitrile-butadiene rubber/phenolic resin, phenolic resin/butyral Koho Nos. Hei 4-29,393 (1992), Hei 4-36,366 (1992) and Hei 4-41,581 (1992)!. These adhesives, however, are not sufficient in chemical and heat resistance and deteriorate markedly under heat. Moreover, they are not satisfactory in heat resistance at soldering temperature after moisture absorption and also in processibility on account of such defects as generation of smears during drilling of through-holes.
Polyimide-based adhesives with excellent heat resistance have been proposed in recent years and adhesives based on thermoplastic polyimides are disclosed, for example, in U.S. Pat. No. 4,543,295. However, bonding of base materials such as copper foils and polyimide films with the aforementioned polyimides requires heat contact bonding at a temperature of 250.degree. C. or more for development of satisfactory adhesive strength and this makes it difficult to put them to practical use.
Adhesives based on polyimides from diaminopolysiloxanes and aromatic tetracarboxylic acids are proposed for heat contact bonding at low of this kind alone, however, suffered from such shortcomings as insufficient adhesive strength and poor reliability.
Film adhesives composed of polyamideimides and epoxy resins are disclosed as polyimide-based adhesives of high adhesive strength for the manufacture of copper-clad films for flexible printed circuit boards in Japan Kokai Tokkyo Koho No. Sho 52-91,082 When films such as those set forth above, are used to bond patterned layers with uneven surfaces in the fabrication of multilayer printed circuit boards, they are not able to fill the gap between the patterned layers satisfactorily nor do they develop sufficient heat resistance to withstand dipping in a soldering bath.
In consequence, either for use in fabrication of multilayer printed circuit boards or for use in film overlay, a demand has grown for adhesives which can be used in heat contact bonding at a low temperature of 250 .degree. C. or less and yet perform well in such properties as adhesive strength, chemical resistance, heat resistance, heat resistance at soldering temperature after moisture absorption and dimensional stability d
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Nakajima Kenji
Ohkubo Misao
Ohmori Fumihiro
Shimose Makoto
Wada Keiichirou
Dean Ralph H.
Nippon Steel Chemical Co. Ltd.
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