Effect of corrosion in acidic solution to the phase and microstructure of SN-CU solder

Abstract

The effect of corrosion to the phase and microstructure for solder Sn-Cu solder in 1.0 MHCl was studied. The corrosion tests were carried out by potentiodynamic polarization method meanwhile the scan rate used was fixed at 2.5 mV/s. In corrosion analysis, the concentration of 1.0 M HCl solution was the optimum concentration. The raw Sn-Cu wire was pressed and punched into pellet shape after the melting process. Next, the pellets were cold-mounted with epoxy resin and hardener. The ready-samples were sent to undergo first characterization by machine XRD and FESEM. For corrosion characterization, the pellets were connected to copper wire by soldering process and then processed by cold mounting method. After the corrosion analysis, the cold-mounted samples undergo XRD and FESEM to determine secondary characterization. The microstructural analysis showed two phase morphologies presented in first characterization, XRD and EDX confirmed the existence of β-Sn and Cu6Sn5 IMCs on the samples. Three regions of Sn-Cu solder were examined during the corrosion analysis and recorded as primary activation, passivation and transpassive regions. Regarding to the second characterization of Sn-Cu solder, the presence of corrosion products such as SnCl2, SnO and SnO2 were revealed in the analysis, apart from the β-Sn and Cu6Sn5 IMCs. The existence of SnO and SnO2 were used to protect the solder from corrosion attack meanwhile the SnCl2 acted as aggressive element which initiated the corrosion process.