Lifetime Prediction of a SiC Power Module by Micron/Submicron Ag Sinter Joining Based on Fatigue, Creep and Thermal Prop
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https://doi.org/10.1007/s11664-020-08410-5 Ó 2020 The Minerals, Metals & Materials Society
TMS2020 MICROELECTRONIC PACKAGING, INTERCONNECT, AND PB-FREE SOLDER
Lifetime Prediction of a SiC Power Module by Micron/Submicron Ag Sinter Joining Based on Fatigue, Creep and Thermal Properties from Room Temperature to High Temperature CHUANTONG CHEN ,1,2 CHANYANG CHOE,1 DONGJIN KIM,1 and KATSUAKI SUGANUMA1 1.—Flexible 3D Collaborative Research Institute, Osaka University, Ibaraki-shi, Osaka 567-0047, Japan. 2.—e-mail: [email protected]
Ag sinter joining technology has gained increasing attention for its excellent thermal and mechanical properties, especially for high-temperature applications. This study focuses on the lifetime prediction of a SiC power module by Ag sinter joining based on mechanical properties including tensile, fatigue, and creep properties from room temperature to 200°C, as well as thermal properties including thermal conduction and the coefficient of thermal expansion. These mechanical properties and thermal properties of sintered Ag paste were evaluated in the study and the results show that mechanical properties of sintered Ag largely depend on the test temperature. The sintered Ag paste tends to soften at high temperature, and the fracture changed from nearly brittle to totally ductile with the testing temperature increase. From the S–N curve, the fatigue is close to the Morrow equation but not the Coffin– Manson law at room temperature. The finite element simulation of the lifetime based on Morrow’s equation for the sintered Ag layer shows that there has a crack occurrence with one fourth the side length after 10,000 cycles from 40°C to 200°C but the crack extension area is less than one tenth of the sintered Ag layer. This study will add to the understanding of the high temperature properties and high temperature reliability as well as the lifetime of Ag sinter joining in high-temperature applications. Key words: Ag sinter joining, mechanical properties, fracture behaviors, Morrow’s equation, lifetime, finite element simulation
INTRODUCTION Wide-bandgap (WBG) power semiconductors such as SiC (silicon carbide) and GaN (gallium nitride) possess better physical and electrical properties than a Si semiconductor. WBG results in high breakdown voltage so that devices can be operated at high voltages, and excellent thermal stability enables devices based on WBG materials to operate at high temperatures higher than 250°C.1–3 In order
(Received April 19, 2020; accepted August 11, 2020)
to maximize the performance of WBG devices, die attach material for high temperature (> 250°C) is required in power modules. Currently, Pb-based solder and Au-based solder with a high melting point greater than 250°C, is applied to the hightemperature operation. However, Pb is not good for the environment and human health, and Au-based solder has a high cost. Meanwhile, both solder materials inevitably generate an intermetallic compound (IMC) layer at the bonding interface, which was considered for rel
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