Special properties of molding compound for surface mounting devices

An equation was developed for use in the design of a molding compound with increased resistance to the popcorn (package cracking) phenomenon. After evaluating many kinds of raw materials to achieve the goal, the authors chose two resin systems; one resin system is low glass transition temperature, Tg, while the other is high T/sub g/. High-density filling with silica helped improve the antipopcorn properties. It is concluded that low-Tg molding compounds have obvious advantages over high-Tg molding compounds in terms of the antipopcorn property. From this study, the authors recommend low-Tg molding compounds that have low-S, low-E, low-Df, and high- sigma properties to protect surface-mount devices from the popcorn phenomenon.<>