Impurity-induced unusual microstructural evolution and mechanical property in Sn/Cu solder joints
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The use of functional additives in the electroplating process results in an impurity incorporation in the Cu plated layer. A high level of impurity residual has been recognized as a severe reliability problem to the Sn/Cu joints because voids are prone to form at the Sn/Cu interface in the thermal aging process. This study focuses on the effect of aging temperature on the formation and distribution of voids. Two electroplated Cu substrates and one rolled Cu foil were joined Sn balls to prepare the Sn/Cu joints for thermal aging in the range of 100–200 °C. The microstructural examination results indicated that the additive formula of polyethylene glycol (PEG) and Cl− resulted in massive void formation at the Sn/Cu interface, and the distribution of voids showed a strong dependence on the aging temperature. The strong temperature dependence of void distribution led to an unusual evolution of microstructure and shear strength in the Sn/Cu joints.
This work is supported by the Ministry of Science and Technology of Taiwan through Grant No. MOST-105-2221-E-005-087.
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