Effects of surface absorption of Ge on Sn2.5Ag0.7Cu/Cu interfacial reaction and wettability

The evolution of wetting property and interfacial morphology of Sn2.5Ag0.7Cu solder was investigated before and after adding active elements.The spreading areas of solder with different contents of Ge were measured, and the morphology of the compound was analyzed with SEM.The relationship between tension on the solid-liquid interface and the absorption amount of active elements on the same place during soldering and its effect on wetting properties were studied.The results showed that when the Ge content in solder was 0.5%, its absorption on the interface quickly raised, the forward-growing tendency of the compound was strong, and the spreading area was the largest.When the Ge content in solder was 1.0%, the absorption remained obvious but the wetting performance was weakened, and the thickness of the compound was relatively thinner.This phenomenon indicates that Ge can reduce the tension on the soldering interface within a certain range.In addition, when the absorption was relatively large, the diffusion between Cu and solder can be restrained and the growth of the compound can be hindered.