Development of Biphenyl Epoxy Type Molding Compound for Surface Mount Devices

Shiro HONDA*, Masayuki TANAKA†, Yasushi SAWAMURA††, Atsuto TOKUNAGA††† and Keiji KAYABA†††

Chemicals Research Laboratories, Toray Industries, Inc.; 9-1, Oe-cho, Minato-ku, Nagoya-shi 455-8502 Japan
† Present address: Toray Research Center Inc.; 3-1-8, Nihonbashimuromachi, Chuou-ku, Tokyo 103-0022 Japan
†† Present address: Electronic Materials Technical Department, Toray Industries, Inc.; 1-1-1, Sonoyama, Ootsu-shi 520-8558 Japan
††† Electronic Materials Technical Department, Toray Industries, Inc.; 9-1, Oe-cho, Minato-ku, Nagoya-shi 455-8502 Japan

We developed and commercialized the biphenyl-type epoxy molding compound at the first time in 1989, which was suitable for surface mount devices. The biphenyl-type epoxy molding compound with low crosslinking density showed higher fracture toughness at high temperature than conventional cresol novolac-type epoxy molding compound. Furthermore, water absorption was reduced by increasing the silica content through the addition of small amount of micro spherical silica that gave good fluidity to the molding compound. As a result, the biphenyl-type epoxy molding compound made a significant improvement on resistance against cracks during re-flow soldering process.
We also developed and commercialized the halogen-free flame retardant epoxy molding compound in 1995. By decreasing content of flammable epoxy matrix resin in the compound and increasing aromatic group content in the epoxy matrix resin, the flame resistance of the epoxy molding compound without either halogenated flame retardant or antimony compound successfully passed the level of UL94, V-0. It also possessed excellent reliability, such as heat resistance, humidity resistance and re-flow soldering resistance, due to its low impurity and low water absorption.


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