Effect of thermal shock profile on solder joint of WLCSP

Wafer level Chip Scale Package (WLCSP) fulfills the demand for small, lightweight, and portable handheld electronic devices, and it´s one of the most advanced packaging concepts. When the WLCSP was assembled on board level, the solder joints are generally the critical issue for device´s reliability. Thermal shock (TS) was an effective way to test reliability of WLCSP for reducing the cost and time. Appropriate transfer time and dwell time in TS can enhance the efficiency of test and it´s necessary to study the influence of temperature profiles on reliability of WLCSP. In this investigation, the WLCSP with Sn-3.8Ag-0.7Cu solder joints were analyzed by finite element method in 3D model. The elastic-plastic-creep consititutive model was used and the thermal shock processes with different transfer and dwell time were studied. The Maximum stress, plastic strain, creep strain and inelastic strain energy density were illustrated in various temperature profiles. On the basis of analysis, the possible optimization suggestions on thermal shock temperature profiles were obtained.