Thermal Stress Reliability Study on Substrates for High Temperature, Silicon Carbide Power Electronic Modules

Abstract

The goal of this study is to investigate packaging techniques for extreme environment (i.e., −50 °C to 250 °C) power electronics. Areas of interest include substrate materials and baseplate/heat spreader materials. Multiple substrate technologies are evaluated, including direct bond copper (DBC), direct bond aluminum (DBA), and active metal braze (AMB) substrates. When possible, varying thicknesses of ceramic and metal layers are included to determine if that parameter affects reliability. Within each material and thickness sample lot, different layout geometries and overall sizes are tested, again to determine if that specific parameter has an impact on reliability. In a power electronics application, these substrates are required to be attached to a baseplate/heat spreader for mechanical support and to improve thermal performance. Therefore, a smaller sample size of substrate materials was also tested for reliability when soldered to a metal matrix composite (MMC) baseplate. To evaluate the reliability of said materials, several inspection methods are utilized, comprising of scanning acoustic microscopy (SAM), optical microscopy, florescent penetrant inspection, cross section analysis, and optical profilometery. This paper will present the results of thermal stress studies on each of the materials under varying conditions. The conditions include: thermal dwell conditions of 250 °C in excess of 1000 hours and thermal cycling from −50 °C to 250 °C in excess of 1000 cycles. Current results will be presented and discussed.