シリカ粒子充てんエポキシ樹脂の破壊じん性に及ぼす充てん材粒度分布の影響

Abstract

Epoxy resins used for encapsulating integrated circuit (IC) devices are filled with silica particles that have broadly distributed diameters, ranging in size from less than 1μm to about 100μm. Since the particles occupy 60 to 70% of the volume, they have a significant effect on the fracture properties of the resin. However, very little is known about the effect of particle-size distribution. In this study, the fracture toughness of silica particulate-filled epoxy resins, with eleven different particle-size distributions, was measured using the double torsion test. Polynomial regression analysis of the measured results was done on various definitions of mean particle diameters.It was found that the resin fracture toughness increases with increasing filler particle size. Scanning electron microscopy of the fracture surfaces indicates that a crack bypasses small particles less than about 5μm in diameter by propagating through the matrix around the particle, whereas it propagates through particles larger than about 30μm. The crack propagates along the particle/matrix interface for particle sizes in between these sizes. The best correlation with resin fracture toughness is obtained for the volume mean diameter of filler particles among various definitions of mean diameters. The effect of the volume mean diameter on crack propagation is explained in terms of filler particle distribution around the crack front.