Analysis of fatigue life on solder joints of Compliant Wafer Level Packaging with MEMS air-gap

Based on current Compliant Wafer Level Package structure, a novel compliant structure with embedded MEMS air-gap is designed, Then, taking DDR DRAM chip as research object, 3D finite element model is established by ANSYS software with designed bump structure. Analysis on stress-strain response of key fatigue failure solder joints under thermal loading condition is carried out. The thermal fatigue life of solder joints is estimated by Soloman low cycle thermal fatigue life expression. The results show that, the key position of fatigue failure locates at the furthest solder joints from the central point of the chip. Compared with other rigid bump structures and traditional compliant bump structure, thermal fatigue life of solder joints is enhanced significantly by adopting the embedded MEMS air-gap.