Using High Speed Shear and Cold Ball Pull to Characterize Lead Free Solder Alloys and Predict Board Level Drop Test Performance

In recent years, coincidental with the increased use of LF solders, manufacturers of portable electronics devices such as cell phones have become increasingly aware of this issue. Increased emphasis has been placed on fine pitch array packages including flip chip (FC) and chip scale package (CSP) interconnects and their ability to withstand mechanical impact type events. An interconnect as defined herein is the solder bump and under bump metallurgy (UBM) structure combined, since both can have a significant effect on the mechanical strength of the overall interconnect structure. Various forms of mechanical impact tests have been designed to gauge the robustness of CSP interconnects to withstand mechanical impacts. Board level drop test (BLDT) is now in wide use as a standard reliability test requirement for many cell phone manufacturers. High speed shear (HSS) and high speed cold ball pull (HSCBP) are shown to be valuable tools in simulating/gauging BLDT performance. Samples are tested with HSS/HSCBP and then drop tested. Qualitative correlation between the HSS/HSCBP and drop tests is shown.