Reliability analysis of metal thermal interface materials for ultra-large size FCLGA package

During a ultra-size flip chip land grid array(FCLGA) package level temperature cycling(TC), we found that metal thermal interface material(TIM) had obviously degraded by ultrasonic scanning. TIM coverage decreased from the 90% initially to 20% at 1000 cycles. scanning electron microscope(SEM) image showed that the crack starts from the to TIM interface and propagates inside the TIM or near the intermetallic compound(IMC) of lid to TIM interface. The results of finite element analysis(FEA) shows a severe plastic strain at the corners and center of the die during the temperature change, which will lead to the crack initiation. Finally, five process parameters are analyzed by finite element method and response surface method, who have significant impact on TIM reliability.