The Effects of Filler Shape, Type, and Size on the Properties of Encapsulation Molding Components

Fillers are essential in the encapsulation molding compound. For three fillers of crystal, spherical, and fused silica, the effects of their size, type, and shape on the viscosity, flow spiral length, thermal conductivity, and coefficient of thermal expansion (CTE) of the compound were explored in this study. The results show that fillers with a larger particle size have a smaller viscosity and flow better; spherical fillers are better than the polygonal ones in this respect. In contrast, both thermal conductivity and CTE increase as the filler particle size increases; the values of these two properties of crystal silica are about twice those of fused silica; the thermal conductivity of polygonal silica is larger than that of spherical silica. On the other hand, the dependence of CTE on the filler shape is insignificant, but is significant to the filler type. The degree of curing of the compound with polygonal silica is also higher than that with either spherical or crystal silica. Namely, curing is affected by both filler type and shape, and can be tuned accordingly to suit specific needs.