Relaxation of metal salt coating conditions of Sn-Zn solder sheet with formic acid on Cu joint strength

In recent years, Sn-3Ag-0.5Cu solder has been widely used as a Pb-free solder material for mounting electronic components. The price of Pb-free solder materials has been increasing, and Sn-Zn solder is expected to have low-cost bonding processing. In previous studies, we have investigated the effect of metal salt coating by boiled formic acid on good Cu bonding using Sn-Zn solder. However, the use of boiled formic acid has been found to increase the health risk to workers, and even small differences in modification time have a large impact on the bondability. In this study, we investigated whether the use of room-temperature formic acid in Cu/Cu joints has the same effect on joint strength as the use of boiled formic acid. As a result, it was confirmed that the same effects could be obtained using room-temperature formic acid of 0.5～20 min modification conditions as boiled formic acid was used. The effect of the difference in modification time on the bondability was smaller than that of using boiled formic acid, and it was also confirmed that it is effective in simplifying the work.