高純度アルミニウムを利用した高耐熱パワーデバイス実装構造における信頼性評価

摘要

In this study we propose a new mounting structure for SiC power devices that operate at high tem-peratures and evaluate its reliability. In this new structure the stress relaxation function rests withthe circuit metal on the substrate rather than the joint layer, so high purity aluminum, which hassimilar characteristics to conventional solder, was chosen as the circuit metal. By conducting a Fi-nite-Element-Method analysis using the measured nonlinear material properties of aluminum, itwas possible to make a stress–strain evaluation of the structure. In order to investigate the practicalfatigue properties of aluminum we devised a mechanical test method which makes local strain con-centration of the chip joint appear, and this method enabled prediction of the thermal fatigue lifecycle of the structure. Moreover, a harsh Thermal Cycle Test of the chip mounting samples was con-ducted between –50 and 300 degrees Celsius, and a positive correlation was obtained between thepredictions and the test results.