Influence Of Reflow Time On IMC Formation At SAC305 Solder And Cu Substrate Interface

Abstract

Soldering plays a critical role in electronic packaging by connecting components using metal alloys. In this study, the solder joint is made from lead-free SAC305 solder (96.5 wt% Sn–3 wt% Ag–0.5 wt% Cu) on a Cu substrate, with an intermetallic compound (IMC) layer forming at their interface. The IMC layer, essential for ensuring a strong metallurgical bond, can negatively affect joint reliability if it becomes too thick, as it tends to be brittle. Therefore, this research aims to analyze the effect of reflow time on IMC layer formation at the SAC305/Cu interface. The experimental method includes several steps: preparing the Cu substrate by cutting and cleaning, then assembling specimens using the interfacial reaction couple technique with a 1:3 ratio of Cu substrate to SAC305 solder. Flux is applied to both sides of the substrate, and the setup is placed in a reaction tube, wrapped in aluminium foil, and reflowed in a furnace at 290°C for varying times (10, 30, 50, and 70 minutes). Characterization is performed using optical microscopy, SEM-EDS, and XRD. Results show the formation of Cu₆Sn₅ and Cu₃Sn IMC phases at the interface, with the IMC layer's thickness increasing with longer reflow times, affecting the overall joint quality.