Abstract It is significant to attach power devices on low-cost copper (Cu) substrates by pressureless silver-sintering in air. The Cu surface in direct-bond-copper (DBC) substrates could have a wide range of surface roughness due to the various processing techniques. It is crucial to find out how the surface roughness influences the bonding strength of the sintered-silver (Ag) die-attachment. In this study, we did die-attach on Cu substrates with surface roughness Ra = 0.15–8.41 µm and Rz = 1.22–50.97 µm by pressureless sintering of nanosilver paste in air. When the surface roughness (Ra of 0.65 μm) is slightly larger than the silver nanoparticles (diameter of 0.6 μm), the high shear strength in excess of 50 MPa was achieved, likely due to both strong metallic bonds and mechanical interlock. This work could help to prepare DBC substrates with optimized surface roughness to accommodate the viscosity, the particle size, and the sintering shrinkage of the silver paste for well using the sintered-Ag die-attach technology.

中文翻译：

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如何在空气中确定用于坚固无压烧结银的铜基板的表面粗糙度

摘要 通过在空气中无压银烧结将功率器件附着在低成本的铜（Cu）基板上具有重要意义。由于各种加工技术，直接键合铜 (DBC) 基板中的 Cu 表面可能具有广泛的表面粗糙度。找出表面粗糙度如何影响烧结银 (Ag) 芯片连接的结合强度至关重要。在这项研究中，我们通过在空气中无压烧结纳米银浆，在表面粗糙度 Ra = 0.15–8.41 µm 和 Rz = 1.22–50.97 µm 的 Cu 基板上进行芯片贴装。当表面粗糙度（Ra 为 0.65 μm）略大于银纳米粒子（直径为 0.6 μm）时，实现了超过 50 MPa 的高剪切强度，这可能是由于强金属键和机械互锁。