Abstract
Sn–9Zn and Sn–8Zn–3Bi solder balls were bonded to Cu or electroless Au/Ni(P) pads, and the effect of aging on jointreliability, including impactreliability, was investigated. For the purpose of quantitatively evaluating the impact toughness of the solder joints, a test similar to the classic Charpy impact test was performed. The interfacial compounds formed in the solder/Cu joint during soldering were Cu–Zn intermetallic compounds (IMCs), not Cu–Sn IMCs. One of the Cu–Zn IMCs, γ–Cu5Zn8, thickenedremarkably with aging, and eventually its morphology changed from layer-type into discontinuous. The rapid growth of the ³–Cu5Zn8 and void formation at the bond interface led to the significant degradation of the jointreliability due to a ductile-to-brittle transition of the joint. Meanwhile, the compound formed in the solder/Au/Ni(P) joint during soldering was a Au–Zn IMC, above which Zn redeposited during aging. Both the dissolution and diffusion of Ni into the solders were extremely slow, which contributes to negligible void formation at the bond interface. As aresult, the solder bumps on the Au/Ni(P) pads were able to mauntaun the high joint strength and impact toughness even after prolonged aging.
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Date, M., Tu, K.N., Shoji, T. et al. Interfacialreactions and impactreliability of Sn–Zn solder joints on Cu or electroless Au/Ni(P) bond-pads. Journal of Materials Research 19, 2887–2896 (2004). https://doi.org/10.1557/JMR.2004.0371
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DOI: https://doi.org/10.1557/JMR.2004.0371