Microstructure and melting property of Sn-2.5Ag-0.7Cu-XGe solder

The 3 composition Sn-2.5Ag-0.7Cu-XGe leadfree solders were studied by scanning electron microscope and differential scanning calorimetry equipments.The result indicates that the microstructure is cobblestone-like pro-eutectic grain and scattered long narrow piece and small pellet eutectic mixture.With 0.5% or 1.0% element Ge, the microstructure morphology does not change. But the intermetallic compounds of Ag₃Sn and Cu₆Sn₅ tend to be fine, and their dispersion tends to be well-distributed, and Ag₃Sn phase tends to be fine needle from long narrow piece.By adding element Ge, the temperatures of the melting beginning, the melting peak and the melting finish all reduce correspondingly.And in the melting curve, the endothermic peak changes is narrow, and the melting finish part is long, but the melting temperature zone varies a little.