Abstract
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.
Highlights
In consumer electronics, IC chips are always protected by resin-type encapsulation molding compounds (EMCs) in which silica (SiO2 ) fillers are indispensable due to manufacturing and reliability needs
The variation of the flow spiral length versus D50 for polygonal fused silica fillers (F01 to F06) is depicted in Figure 1; the data standard deviation is denoted by σ
The result clearly indicates that, for polygonal fused silica fillers, the flow spiral length increased linearly as the filler size increased, indicating that EMC flows better by increasing the filler size. This trend was further evidenced by the results of EMC viscosity portrayed in Figure 2, which illustrates that for polygonal fused silica fillers, the EMC viscosity decreased as the filler size increased
Summary
IC chips are always protected by resin-type encapsulation molding compounds (EMCs) in which silica (SiO2 ) fillers are indispensable due to manufacturing and reliability needs. In this study, we examine experimentally the effects of filler shape (polygonal and spherical), type (fused and crystal), and size on the EMC properties relevant to manufacturing and package reliabilities, including the glass transition temperature (Tg), CTE, thermal conductivity, viscosity, and flow spiral length. The latter two properties are essential to curing, which can lead to residual stresses [11] or warpage [12], a critical issue for fan-out packages. Based on previous findings [8]
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