Dynamic scanning method to clarify the mechanism of WLCSP package reliability issue

This study proposes a brand new method for identifying the mechanism that obtains when various current densities are individually applied to the architecture of WLCSP. A multi-steps current-destroying method was applied to clarify the effect of current density and the failure mechanism, both the environments and testing qualifications for these packages are becoming increasingly demanding. Failure mechanisms assumed to have been eliminated, or at least to have been alleviated to some extent in new package technology designs, are once again challenges to their process integrity and reliability. Because of dynamic loading induced by mechanical vibration and impact shock negatively impacting reliability for CSP package, analytical models and simulations of some mechanisms were developed. This work examines the reliability of a wafer-level chip-scale package (WLCSP) subjected to various accelerated current stressing conditions under a fixed ambient temperature of 125°C. A reasonable correlation was obtained between mean-time-to-failure (MTTF) of the WLCSP test vehicle and the average current density carried by a solder joint was obtained.