Intermetallic compound layer growth at the interface between Sn-Cu-Ni solder and Cu substrate

摘要

Phase analysis and growth kinetics of intermetallic compound (IMC) layers formed between low cost Sn-Cu-Ni solder for wave soldering and Cu substrate by solid state isothermal aging were examined at temperatures between 80 and 150 deg C for 0 to 60 days. The IMC layer was composed of two phases; Cu_6Sn_5 (also (Cu,Ni)_6Sn_5) adjacent to the solder, Cu_3Sn adjacent to the copper. The Cu_3Sn layer was absent at all time periods for the aging temperatures of 80 and 100 deg C. After isothermal aging at 120 deg C for 30 days and at 150 deg C for all time periods, the solder/Cu interface exhibited a duplex structure of CueSns and CuaSn intermetallics. From the EPMA analysis, a comparatively high Ni concentration is found between the Cu_6Sn_5 and Cu_3Sn layer. The Ni concentration in the (Cu,Ni)_6Sn_5 intermetallic was about 4.3 at. percent. The total IMC layer thickness was approximately 11.5 mu m after 60 days of aging at 150 deg C. The apparent activation energies for growth of total and Cu_6Sn_5 IMC layer were 76.17 and 66.35 kJ/mol, respectively.