Quasi in situ study about growth kinetics of Ag3Sn at the interface of eutectic SnPb/electroplated Ag soder joint in the long-term satellite

Abstract

The interfacial reaction and the growth kinetics of intermetallic compounds between 63Sn37Pb (wt.%) solder and the electroplated silver layer during the solid-state aging were studied in this paper. To measure the growth kinetics of Ag3Sn, the product of the interfacial reaction, more accurately, we used the quasi in situ method. And three same joints between solar cells and solder were annealed at 100°C, 120°C and 150°C for various aging durations. The results showed that the electroplated Ag layer gradually transformed into scalloped Ag3Sn, and the growth kinetics of Ag3Sn was a diffusion-controlled process during isothermal aging. Through measuring the thickness of Ag3Sn during the isothermal storage, the activation energy for IMC at eutectic SnPb solder/electroplated Ag layer interface was calculated and the result was 106 kJ/mole. On the basis of the growth kinetics, a correspondence between long-term thermal recycle and isothermal aging was presented. And the relation could be used to replace the long-term thermal recycle with accelerated annealing experiment, which would have a significant meaning for testing the reliability of low earth orbit satellites' solar cells.