Effects of Cooling Rate and Cu/Ni-P/Au UBM on Microstructure and Tensile properties of Sn-Ag-xSb Lead-Free Solder Joints.

• Main Authors: Li-Wen Sung, 宋立文
• Other Authors: Hwa-Teng Lee
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/32256b

碩士 === 國立成功大學 === 機械工程學系碩博士班 === 92 === 　　This study is to discuss the effect of Sb additions (0~3.86 wt%) as well as the cooling rate(slowly cooling, 1.68℃/sec、fast cooling, 5.03℃/sec) upon the microstructure ad the interfacial metallic compound variations of Sn-Ag solder joints combined with Cu/Ni-P/Au UBM and Cu substrates. The Single Lap specimens and high temperature storage at 150℃ are also performed to evaluate the shear strength and thermal resistance of solder joints. 　　The experimental results show that melting points of Sn-Ag-xSb solders increased with the addition of Sb. When the amounts of Sb is lower than 3.86%, Sb will solve into beta-Sn matrix, and the microstructures is composed of the eutectic phase of beta-Sn with Ag3Sn dispersion surrounding primary beta-Sn. When Sb is reached to 3.86%, the laminar-like Sn4Sb3 compounds are dispersed in beta-Sn matrix. Ag3Sn compounds and beta-Sn dendrite will become finer by fast cooling of the solder joints. Meanwhile the finer fibrous Ag3Sn will be bound into interfacial surface to suppress the growth rate of IMC layer. Sb additions reduce the coarseness of the Ag3Sn at high temperature, however, this effect is not evident as the amount of Sb reaches 3.86%. 　　The shear strength of Sn3.5Ag solder joints combined with Cu substrates decreased by increasing the thermal storage time at 150℃. But this did not occur by the results of the Sn-Ag solder joints with Sb addition. Shear strength of whole solder joints combined with Cu/Ni-P/Au UBM on the contrary increased after thermal storage for 600 hours. In Sn-Ag-xSb solder, fast cooling by specimen of low Sb addition has the same effect on strength performance as that by more Sb addition. The shear strength of Sn-3.15Ag-2.18Sb solder joints combined with Cu/Ni-P/Au UBM under fast cooling is 61.4 MPa, and Sn-2.92Ag-3.86Sb solder joints under slowly cooling is 64.7 MPa. Fracture observation reveals that all the specimen fractured at solder joints matrix. Fractographical observation show that the fracture dimples become finer as the duration of thermal storage increased. The adhesion strength of solder joints also increased as dimple size decreased. Evaluation on based this study show that, the Sn-3.15Ag-2.18Sb solder joints combined with Cu/Ni-P/Au UBM under fast cooling has a better reliability and performance among the all.