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<p>Understanding the aging mechanisms of materials is essential for improving the reliability of power modules in the field of power electronics. This study investigates the reliability of silver-sintered joints, focusing on the fatigue behavior of copper active-metal-brazed (AMB) substrates under thermal cycling with respect to the copper grain size ranging from 250 to 960&#xa0;µm. Analytical techniques, including confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD), were used to analyze the fatigue behavior of bare copper substrates. Silver joint reliability of sintered samples was evaluated by scanning acoustic microscopy (SAM), die shear testing, and cross-sectional microstructural observation. The findings indicate that thermal cycling induces thermo-mechanical stresses, resulting in localized plastic deformation, surface defects, and out-of-plane displacement of individual grains in the copper sheet, leading to surface roughening and crack formation in the silver layer. In terms of Ag joint reliability, a clear correlation to the copper grain size is revealed. Larger copper grains exhibit pronounced deformation, leading to high thickness variations in the adjacent silver layer, which critically affects the joint reliability. This research emphasizes that fine-grained copper substrates can enhance the reliability of the silver joints in power electronic applications.</p>

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Fatigue of metal-ceramic substrates through thermal cycling and its consequences for silver-sintered joint reliability

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年10月9日

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  • Tamira Stegmann,
  • Enrico Bruder,
  • Karsten Durst,
  • André Schwöbel

摘要

Understanding the aging mechanisms of materials is essential for improving the reliability of power modules in the field of power electronics. This study investigates the reliability of silver-sintered joints, focusing on the fatigue behavior of copper active-metal-brazed (AMB) substrates under thermal cycling with respect to the copper grain size ranging from 250 to 960 µm. Analytical techniques, including confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD), were used to analyze the fatigue behavior of bare copper substrates. Silver joint reliability of sintered samples was evaluated by scanning acoustic microscopy (SAM), die shear testing, and cross-sectional microstructural observation. The findings indicate that thermal cycling induces thermo-mechanical stresses, resulting in localized plastic deformation, surface defects, and out-of-plane displacement of individual grains in the copper sheet, leading to surface roughening and crack formation in the silver layer. In terms of Ag joint reliability, a clear correlation to the copper grain size is revealed. Larger copper grains exhibit pronounced deformation, leading to high thickness variations in the adjacent silver layer, which critically affects the joint reliability. This research emphasizes that fine-grained copper substrates can enhance the reliability of the silver joints in power electronic applications.