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 A degrees C, while the non-isothermal aging was performed within the temperature range from -40 to +150 A degrees 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.