Rupture Life of CSP Solder Joints with Sn-Ag Lead-Free Solders under Thermal Cycle Condition.

概要

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A thermal fatigue life evaluation was performed for 0.5 mm pitch CSP solder joints with several Sn-Ag lead-free solders. Comparing the average of fatigue life, the experimental result showed Sn-3.5Ag>Sn-3.5Ag-0.76Cu>Sn-37Pb>Sn-1.9Ag-0.52Cu-7.6Bi. A crack grew in solder near a joint interface in the joints with Sn-3.5Ag and Sn-37Pb. However, a crack growth occurred at a interface between Cu-Sn-Ni compound and a pad or solder in the joints with Sn-3.5Ag-0.76Cu and Sn-1.9Ag-0.52Cu-7.6Bi. When the interfacial cracking was a dominant rupture mode, the fatigue life of each test piece scattered widely. The reliability of a prediction for thermal fatigue life decreases in the case of solder joints which rupture at a joint interface.
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