Development of high-reliability epoxy molding compounds for surface-mount devices

The authors have researched and developed new epoxy molding compounds for surface mount devices. In the compound design, physical properties were established by examining the mechanism of cracking with thermal stress generated during soldering. In the compound development, conventional resin systems were reviewed to obtain significant improvements of the physical properties. As a result, low water absorption, low thermal expansion, and high strength were attained by adopting the biphenyl epoxy resin which has very low melt viscosity and high filler loading capability compared with conventional ortho-cresol-novolak epoxy resin. For the phenolic hardener, it is found that low flexural modulus, high adhesion, and low moisture absorption are attained by adopting an aromatic and alicyclic structure instead of a methyl chain in the frame of the conventional phenol novolak.<>