Ag₃Sn IMC cluster suppression and heat transfer mechanism enhancement by controlling Sn content in Pb-based solder alloys

Abstract

Lead-based solder alloys remain widely used in power electronics due to their excellent wettability, high-temperature tolerance, and long-term mechanical stability. However, the formation of intermetallic compounds (IMCs), particularly Ag₃Sn, can adversely affect joint reliability by promoting brittleness and thermal fatigue. This study investigates the thermal behavior and heat dissipation characteristics of three PbSnAg solder compositions: PbSnAg-1 (medium Sn%), PbSnAg-2 (high Sn%), and PbSnAg-3 (low Sn%), using Differential Scanning Calorimetry (DSC) analysis. DSC results revealed that PbSnAg-2, with the highest Sn content, exhibited the narrowest melting range and lowest melting peak, indicating uniform phase transformation and reduced Ag₃Sn formation compared to PbSnAg-1 and PbSnAg-3. Thermal conductivity analysis further validated these trends, with PbSnAg-2 exhibiting the highest thermal conductivity at 206.6 W/m·K, approximately 73% and 66% higher than PbSnAg-1 and PbSnAg-3, respectively. These enhancements are attributed to improved Ag dispersion and suppressed IMC clustering, facilitated by higher Sn reactivity. Based on this experimental evidence, we can infer that the Sn content in the solder composition plays a crucial role in defining the melting behavior, IMC evolution, and heat dissipation efficiency. PbSnAg-2 demonstrates superior thermal stability, reduced IMC formation, and significantly enhanced thermal conductivity, making it a reliable choice for thermally demanding power electronic applications.