Analysis on the Effects of Packaging Materials on Structural Thermal Stress in Stacked Chip Scale Package

SCSP (stacked chip scale package) attracts more and more attentions in advanced packages application with light weight, thin and small size, high reliability, low power and high storage capability. However, more and more physical and electrical issues are reported being caused by package induced thermal stress in SCSP recently. After the SCSP packaging failure modes caused by structural stress due to packaging structure design, materials and process flow are theoretically discussed, the effects of material factors, including glass transition temperature (Tg) of die attach film and curing temperature of mold compound, on package induced thermal stress are focused to be simulated and analyzed with finite element analysis (FEA). The simulations show that higher Tg of die attach film can effectively reduce peak-to-peak thermal stress of SCSP. and lower curing temperature of mold compound can obviously decrease both the maximum thermal stress and peak-to-peak thermal stress. In other word, high Tg of die attach film and low curing temperature of mold compound can greatly relieve the thermal stress conditions and are helpful to avoid chip crack failure and device failures caused by transconductance shift.