Growth kinetics of Ag₃Sn in silicon solar cells with a sintered Ag metallization layer

The interfacial reactions and growth kinetics of intermetallic compounds at the solder/sintered Ag metallization interface in silicon solar cells were investigated during solid-state aging. Three common solders (Sn₃₇Pb, Sn₃₆Pb₂Ag, and Sn₃Ag_0.5Cu) were used to conduct several experiments testing the quality of the solder joints in this study. Accelerated tests were performed to determine the long-term reliability of the solder joints. The storage temperatures were 100, 120, 150, and 180±1 C for various aging durations. The results showed that the sintered Ag electrode gradually transformed into an Ag₃Sn intermetallic compound (IMC), and the growth kinetics of Ag₃Sn remained a diffusion-controlled process during isothermal aging. The formation of Ag ₃Sn increased the series resistances (R_S) of the cell modules because Ag₃Sn had a higher electrical resistivity than sintered Ag did. In addition, the results revealed that Sn₃Ag _0.5Cu PV ribbon effectively slowed down the growth kinetics of Ag₃Sn. The apparent activation energies for Ag₃Sn at Sn₃₇Pb/sintered Ag, Sn₃₆Pb₂Ag/sintered Ag, and Sn₃Ag_0.5Cu/sintered Ag interfaces were calculated to be 104, 108, and 121 KJ/mole, respectively. These kinetics data were established for the first time for the solder alloys commonly used in PV module assembly industry.