Effect of filler content on tensile properties of underfill material for flip chip bonding

The effects of the filler content and temperature on tensile properties of underfill were investigated using underfill materials which are composed of bisphenol F-type epoxy resin and spheroidal SiO2 filler. Young´s modulus of underfill increased and fracture strain decreased with increasing the SiO2 filler content. The effects of the SiO2 filler content on Young´s modulus and fracture strain were relatively large. However, the effect on tensile strength was negligible. Tensile strength was strongly affected by the strength of matrix resin itself. When the temperature was above Tg, Young´s modulus decreased and fracture strain increased remarkably. Fracture mainly occurred in matrix resin below Tg and in the interface between matrix resin and filler above Tg.