A 200 degrees C fluxless process is developed to produce In-Cu joints. The fluxless feature is achieved by preventing indium oxidation during composite fabrication and the subsequent bonding process. Indium and copper are deposited on an object in high vacuum to inhibit indium oxidation. Copper interacts with indium to form a CuIn intermetallic that further protects the inner indium from oxidation. For the specific design of this study, the resulting joints consist of CuIn intermetallic grains surrounded by pure indium as revealed by scanning electron microscopy with energy dispersive X-ray analysis. Scanning acoustic microscope examination indicates that the joints are nearly void free. This technology enables versatile control of alloy composition, thus leading to several remelting temperatures and various physical properties. The CuIn compound was clearly identified in this study even though it was not shown in two published Cu-In phase diagrams.