Microstructure Evolution of Cu/In/Cu Joints After Solid-Liquid Interdiffusion

In this study, we identified the morphologies and growth kinetics of IMC for the solid liquid interfacial reaction between In and Cu substrates. We chose Indium foil and copper substrates to form sandwich structures that were bonded at 200 °C for 10 min, while several samples were aged at 245 °C, 273 °C, and 287 °C for different hours. After aging, the Cu/ solder interfaces were examined by using scanning electron microscopy (SEM) to observe the microstructure of intermetallic compounds (IMCs) after interfacial reactions. Also, the energy dispersive x-ray spectroscopy (EDX) was used to identify the compositions of those IMCs. For the well-bonded interconnections, Cu2In and Cu7In_3 IMCs with high melting points can be formed that exhibit high thermal stability. Simultaneously, The wave-edged interfaces and Kirkendall voids were also found after aging at those temperatures. In this paper, we demonstrated systematically the transition of the Cu/In interfacial reaction at different temperatures and conducted a microstructure analysis of those different IMCs.