Design and use of an array-based test structure to characterize mechanical stress effects caused by WLCSP solder bumps

This paper discusses a 2100-DUT-array based test structure approach for high-resolution characterization of spatial mechanical stress distributions that are attributable to wafer level chip scale package solder bumps. DUT cell layout requirements, array implementation, measurement approach, and some data analysis challenges are reviewed in detail. Several examples of solder bump induced mobility variation illustrate the value of these test structures.