Manufacturing concerns of the electronic industry regarding intermetallic compound formation during the soldering stage

The intermetallic compound (IMC) formed at the interface between the solder and substrate is an inevitable result of the soldering process. It is an indication of good metallurgical bonding. But if it grows too thick, either during soldering or subsequent solid stage aging, it can have a deleterious effect on the strength of a joint or on the subsequent solderability of a component. Most of the literature studies have concentrated on the IMC growth during the solid stage aging. A few papers addressed the IMC formation during the molten stage, but most of these studies were in a temperature and time domain not applicable to the manufacturing soldering process. In this study, we examined the growth mechanism of the Cu₆Sn₅ IMC in the molten stage between 100Sn, 96.5Sn-3.5Ag, and 63Sn-37Pb solders on electroplated copper, which mimics the printed-wiring boards, and on rolled OFHC copper sheet, which simulates the component leads and electrical connectors