Wire sweep control with mold compound formulations [plastic packaging]

Twenty different epoxy compound formulations were evaluated to assess the moldability and the resulting wire sweep propensity in a manual gang-pot molding machine. Effects such as filler content, filler shape and size, hardener viscosity, catalyst level, resin type, and thixotropic index were considered. Results obtained on a 160-lead PQFP with wire lengths up to 160 mils helped reduce the selection down to 5 formulations, which were then tested in a fully automated gang-pot system in a production environment. Aside from wire sweep, effects on die pad shift was also considered. This paper will discuss the relationship between the compound formulations, moldability, wire sweep, and pad shift. Although results were obtained on a test die with 100 μm pad pitch, the information garnered should be extendible down to finer pitch