Whisker growth on SnAgCu–xPr solders in electronic packaging

The addition of rare earth Pr into Sn3.8Ag0.7Cu solder results in the formation of PrSn 3 phase, which can induce the whiskers growth. After several hours’ exposure at room temperature in air, different morphologies of whiskers appear in the regions of PrSn 3 intermetallic compounds. The Pr content and storage time are the main parameters for affecting the whiskers growth at ambient temperature. The oxidation mechanism of PrSn 3 phase was used to explain the whiskers growth, the compressive stress is proposed as the driving force for whisker growth.