Influence of shear height on shear strength to tin-lead solder ball bonding

摘要

The crack generation energy U, and the crack progress energy U{sub}2 of eutectic Sn-37 mass%Pb solder ball and Sn-36 mass%Pb-2 mass%Ag one were surveyed by the shear test. Both balls were bonded at various reflow cooling rates (10-200 K/min). The shear test was carried out under the condition of two kinds of the shear height, Z = 0 μm and Z = 200 μm, U{sub}1 and U{sub}2 were calculated by multiplying the shear strength by the shear distance. Though U{sub}2 was independent on the cooling rate, the ball composition and the shear height, U{sub}1 changed depending on these parameters. Only U{sub}1 of Sn-36 mass%Pb-2 mass%Ag ball bonding cooled at 200 K/min dropped sharply though U{sub}1 of both ball bonding was almost the same and increased with the faster cooling rates in case of Z = 0 μm. U{sub}1 of Sn-36 mass%Pb-2 mass%Ag ball bonding was higher than that of the eutectic ball at each cooling rate as a result of the shear test at Z = 200 μm. The needle shape Ag{sub}3Sn intermetallic compound in Sn-36 mass%Pb-2 mass%Ag ball and near the interface contributed mainly to the lower U, at Z = 0 μm because Ni{sub}3Sn{sub}4 reaction layer formed at 200 K/min was thin. The higher U{sub}1 at Z = 200 μm was due to the fine lamellar structure (Sn phase/Pb phase) in Sn-36 mass%Pb-2 mass%Ag ball. The shear property of the same ball depended on the shear height in the present study.