Abstract
A continuous layer of Ni3Sn4 compounds was formed at the Sn-37Pb solder/Ni interface in ball grid array solder joints after reflowing. Au0.5Ni0.5Sn4 compounds were formed between Sn-37Pb solder and Ni3Sn4 layer during thermal shock between -196 °C and 150 °C, and the solder/Ni interface exhibited a duplex structure of Au0.5Ni0.5Sn4 and Ni3Sn4 layers only after 300 cycles. The growth of Ni3Sn4 and Au0.5Ni0.5Sn4 under thermal shock was significantly enhanced by high thermal stresses generated from the thermal expansion mismatch between Sn-37Pb solder and Ni, and the extreme temperature change (ΔT = 346 °C). The fast growth and high stiffness of Ni3Sn4 and Au0.5Ni0.5Sn4, as well as the thermal expansion mismatch between Ni3Sn4 and Au0.5Ni0.5Sn4, and the extreme temperature change resulted in the brittle fracture of Sn-37Pb solder joints at the Ni3Sn4/Au0.5Ni0.5Sn4 interface under extreme temperature changes.
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