Intermetallic growth study at Sn–3.0Ag–0.5Cu/Cu solder joint interface during different thermal conditions

The morphology and growth behaviors of intermetallic compounds (IMCs) of Sn–3.0Ag–0.5Cu/Cu solder joints were investigated during isothermal aging, thermal cycling and thermal shock. The Sn–3.0Ag–0.5Cu/Cu solder joints were isothermal aged at 150 °C, while the non-isothermal aging was performed within the temperature range from −40 to +150 °C. It was observed that the Cu₆Sn₅ layer initially formed between the copper substrate and solder, followed by the creation of a Cu₃Sn layer for aging times greater than 200 h or 200 thermal cycles. However, the Cu₃Sn could not be found in solder joints until thermal shock 800 cycles. The results showed that the initial scallop-like IMCs layer changed into a level duplex structure with the aging time (cycling numbers) increasing. The growth rate of Cu₆Sn₅ was lower than that of Cu₃Sn during isothermal aging. While for thermal cycling, it was Cu₆Sn₅ contributed more to the growth of IMCs than the Cu₃Sn. The value of the time exponent n under isothermal aging, thermal cycling and thermal shock were about 0.58, 0.64, 0.66 respectively.