Edgebond and Edgefill Induced Loading Effect on Large WLCSP Thermal Cycling Performance

Abstract

Various external load conditions affecting components on electronic devices and modules are constant factors, which need to be considered for the component long-term reliability. Recently, to enhance the high stress component thermo-mechanical cycling performance, various types and configuration using edgebond and edgefill technology are introduced and tested. These applications induce a multi-axis loading condition, which alter the degradation mechanism and failure location during thermal cycling, which need closer investigation. In this study, high stress 12x12mm² wafer level chip scale packages (WLCSP) were selected and subject to thermal cycling with full-edgebond, dot-edgebond and edgefill adhesive, which improves the characteristic lifecycle numbers base on the configurations, but altered the failure location due to different stress conditions. The -40 to 125^oC thermal cycling profile revealed localized degradation per configuration during thermal cycling, showed a shift of the crack propagation path, based on full-edgebond, dot-edgebond and edgefill adhesive sample conditions. Through these series of observation, the interconnect thermal cycling degradation mechanisms are able to be explained. The correlation between the stress condition and microstructure are  presented and discussed based on Electron backscattered diffraction (EBSD) analysis.