Research on the Key Processes of Large-Area Silver Sintering for SiC Power Modules
Guiqin Chang, Di An, Erping Deng, Xiang Li, Haihui Luo, Yongzhang Huang
Abstract
In this article, an alternative process method was proposed for the large-area silver sintering joint in silicon carbide (SiC) power modules, with integrated drying process. This proposed method significantly simplified the production process of large-area sintering. As a typical application, SiC power modules (1200 V/17 m<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula>, eight chips in parallel) were packaged using the method, achieving a reliable connection between ceramic substrates (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50\times 60$ </tex-math></inline-formula> mm2) and heat sinks. The advantages of the proposed large-area silver sintering have been verified through the assessments of mechanical properties, thermal resistance, and thermal shock reliability. Results indicate that adjusting the silver paste printing thickness can accommodate the warpage of active metal brazing (AMB) substrates. Optimizing the drying temperature and heating rate allows for a structurally uniform and dense large-area sintered silver layer, even with single printing and integrated drying processes. The sintered joint has a porosity of 2%–3%, with no apparent delamination defects. Compared to traditional solder SnSb5, the average shear strength of the silver sintering connection layer has increased by 95%. Under thermal shock conditions (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 60~^{\circ }$ </tex-math></inline-formula>C to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$+ 150~^{\circ }$ </tex-math></inline-formula>C), the silver sintering layer demonstrates excellent reliability, with only a 2% degradation of the connection layer after 1000 cycles. Furthermore, compared to traditional solder (SnSb5), the total thermal resistance of power modules is reduced by 10.3%, effectively enhancing the heat dissipation capacity of the SiC module. In summary, this study identified and resolved key process issues in large-area sintering, providing significant guidance for the packaging of high-power density and high-reliability SiC modules.