Interfacial Effects of Surface Roughness and Topography on the Bond Strength of Silver-Sintered Joints on Copper Substrates

The increasing focus on renewable energy and electromobility is driving advancements in power electronics devices, with the industry increasingly utilizing wide-bandgap semiconductors and alternative interconnect technologies such as silver sintering to meet high-performance requirements. This study investigates the interfacial effects of surface roughness and topography on the bonding strength of silver-sintered joints on copper substrates, considering variations in silver particle size. Experimental analysis includes surface modifications, characterization using microscopy techniques, shear testing for bond strength evaluation, and assessment of joint porosity. The study demonstrates that surface roughness and topography significantly impact the bond strength, with surface blasting reducing bond strength and anisotropy effects being observed for ground surfaces. It is suggested that there are limitations on achievable bond strength due to increased surface roughness from mechanical treatment. Additionally, this work emphasizes the significance of surface topography in addition to surface roughness values such as Rₐ and examines the interaction between silver particle size and roughness at both the micron and submicron levels in terms of bond strength and porosity. Maximum bond strength is achieved at lower roughness levels (Rₐ < 1 µm) for submicron and micron particles in silver sintered joints. However, contrary to recent research, maximum bond strength of the micron-particle sintered material is achieved at a ratio 0.1 of Rₐ to particle diameter d, one order of magnitude lower than that of the submicron-particle sintered material. Therefore, achieving strong adhesion and bond strength in silver-sintered joints requires careful consideration of surface properties and particle size.