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

Abstract

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 Cu3Sn solder joints in electronic packaging was conducted systematically. For forming full Cu3Sn solder joints, 260°C, 1N, 5h was determined as the optimal parameter combination. At 260°C and 1N, planar Cu6Sn5 was first precipitated at Cu-Sn interface, which was followed by the formation of planar Cu3Sn. Until the total consumption of residual Sn, the Cu6Sn5 continued to grow with a transition from the planar shape to scallop-like shape, while the Cu3Sn 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 Cu3Sn and Cu6Sn5, the Cu3Sn continued to grow at the expense of Cu6Sn5 until full Cu3Sn 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 Cu3Sn 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 Cu3Sn solder joints when the loading rate was varied.