A study on optimization of process parameters, microstructure evolution and fracture behavior for full Cu<inf>3</inf>Sn 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 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.