Combined Electromigration and Strain Accelerated Failure Test Development for Al Wire Bonds and Reliability Analysis of Grid-Tied Solar Inverter

Abstract

The advancement of power electronic technologies has led to a decrease in the size of the power electronic module. This decrease in size coupled with power module loading trending upwards of 1kA results in significantly higher power densities for the electrical systems than in the past. Elevated power densities pose reliability concerns for new-age electronic systems. Electromigration is a phenomenon that can occur at elevated temperature and current density in conductive materials, both of which are results of elevated power densities. This study is being conducted to develop a lifetime estimation model for a grid-tied solar inverter at various power loads and design a testing methodology to observe the combined effects of electromigration and mechanical strain on aluminum wire bonds. In this study, the use conditions for a grid-tied solar inverter were employed to define a set of accelerated electromigration testing procedures for wire bonds at elevated ambient temperatures and current densities. The data provided by accelerated testing allowed for extrapolation of solar inverter lifetime estimation using Black’s Law for electromigration in metallic interconnects. Lifetime estimation calculations were then used to optimize the solar inverter design to lengthen the estimated inverter lifetime. Examination of these lifetime estimation models provided the foundation for exploration into other modes of failure in wire bonds related to electromigration. This exploration led to the development of a novel testing setup to observe the combined effects of electromigration and mechanical strain on wire bonds.