IMC Layer Growth in Cu/Sn-58Bi with Varying Reaction Times

Abstract

The increasing use of electronic devices has led to a rise in electronic waste, particularly from components such as Printed Circuit Boards (PCBs), which often contain lead-based solder. Lead (Pb) poses significant environmental and health hazards. To address this issue, this study investigates the use of lead-free Sn-58Bi solder as a safer alternative. The research focuses on analyzing the interfacial reaction between Sn-58Bi solder and a Cu substrate, particularly the influence of reflow time on the formation of intermetallic compounds (IMCs) and their morphology. The Cu substrates were first cut to the desired dimensions and combined with Sn-58Bi solder balls using the interfacial reaction couple method. Samples were coated with flux and arranged in a solder ball/substrate/solder ball configuration inside a test tube, then subjected to reflow soldering at 220 °C for 15, 30, 45, and 60 minutes. Post-reaction, the specimens were mounted, ground, and examined using Optical Microscopy to observe IMC layer formation. Further characterization was performed using SEM-EDS and XRD to identify the phases and morphologies formed. The results confirmed the formation of Cu₆Sn₅ and Cu₃Sn phases at the solder-substrate interface, with the IMC layer thickness increasing with longer reflow durations.