The electronic packaging industry is gradually moving away from lead solder to lead-free solder, which is more environmentally friendly. However, there is still work to be done to ensure that lead-free solder meets the demands and requirements of the latest technology. The present study demonstrates the analysis of the microstructure formation of Cu6Sn5 and Cu3Sn intermetallic compound layers in Sn-10Cu/Cu solder joints. Therefore, the key objective of this research is to determine the growth rate and activation energy of the Cu6Sn5and Cu3Sn intermetallic compound layer ofthe Sn-10Cu/Cu solder joint. The investigation on the bulk solder microstructure which consists of Cu6Sn5and Cu3Sn intermetallic compound layer was carried out using Optical Microscope (OM), Scanning Electron Microscope (SEM) with EDX and ImageJ software. The IMC layer undergoes rapid growth with increasing aging temperature and duration and the two main IMC layers (Cu6Sn5and Cu3Sn) grew thicker. The growth kinetic solder joints for Sn-10Cu and Sn-0.7Cu are 22.44 kJ/mol and 31.20 kJ/mol, respectively. Hence, the findings from this study may offer useful information for the development of high-reliability solder joints in future applications.