A study on optimization of process parameters, microstructure evolution and fracture behavior for full Cu3Sn solder joints in electronic packaging

For understanding full IMCs solder joints comprehensively, the widely used Cu-Sn system was adopted as the research object. A study on optimization of process parameters, microstructure evolution and fracture behavior for full Cu
₃
Sn solder joints in electronic packaging was conducted systematically. For forming full Cu
₃
Sn solder joints, 260°C, 1N, 5h was determined as the optimal parameter combination. At 260°C and 1N, planar Cu
₆
Sn
₅
was first precipitated at Cu-Sn interface, which was followed by the formation of planar Cu
₃
Sn. Until the total consumption of residual Sn, the Cu
₆
Sn
₅
continued to grow with a transition from the planar shape to scallop-like shape, while the Cu
₃
Sn continued to grow with a round-trip change from the planar shape to wave-like shape. After the formation of full IMCs solder joints including Cu
₃
Sn and Cu
₆
Sn
₅
, the Cu
₃
Sn continued to grow at the expense of Cu
₆
Sn
₅
until full Cu
₃
Sn solder joints were obtained by 300min. When the loading rate was 0.001mm/s, 0.01mm/s and 0.1mm/s respectively, the shear strength of full Cu
₃
Sn solder joints was 46.1MPa, 50MPa and 60.5MPa correspondingly. Through analysis of fracture surface, we found that different microscopic fracture mechanisms led to different strength of full Cu
₃
Sn solder joints when the loading rate was varied.