Novel underfill material with low coefficient of thermal expansione

The novel underfill material with low coefficient of thermal expansion was prepared by cyanate, epoxy, polyimide and silica filler. Rheological properties, curing behaviors, mechanical and thermal properties of the resultant materials were investigated by rheometer, DSC, FTIR, TMA and DMA, respectively. The results showed that the modification of cyanate resin and its copolymer with silica filler has high fluidity for capillary underfill application. With an increase in silica fillers loading, the coefficient of thermal expansion reduces from 68.2 to 19.5 ppm/°C at 70 wt% silica fillers at room temperature, while the glass transition temperature of cured material is greater than 230 °C. This indicates that the novel underfill material has good dimensional stability and thermal stability, which can be used for high density flip chip interconnection assembly.