High-temperature wettability of indium on NiCu alloy for advanced thermal management

Indium has attracted significant attention in thermal management applications due to its low melting point, high thermal conductivity, and ductility. However, the wetting behavior between indium and nickel or its alloys, commonly used as bonding layers, is often suboptimal in soldering applications. This study investigates the high-temperature wetting behavior and intermetallic compound (IMC) growth between indium and NiCu alloy layers. NiCu alloy layers were successfully electroplated, ensuring uniform thickness and smooth surfaces. Nano-thick wetting layers of Cu, Ag, and Au were applied to improve wetting. The wetting behavior of indium on NiCu, Cu-coated NiCu, Ag-coated NiCu, and Au-coated NiCu was studied within a temperature range of 200°C–300°C. Contact angles and spreading diameters were measured, revealing a contact angle of 90° on the NiCu alloy. On the Au-coated NiCu surface, indium exhibited super-wetting properties with a contact angle of just 24.2°. Scanning electron microscopy characterized the IMC and precursor films at the interface. Indium showed reactive wetting on NiCu, and when an Au layer was applied, the IMC extended beyond the three-phase contact line. This study provides valuable insights for improving heat dissipation in high-power-density devices using indium.