| Along with the implementation of the comprehensive Prohibition law of worldindustry developed countries for containing Pb solder of the production and use onelectronic field the research and development of the lead-free solder has launchedvigorously. Sn-Ag-Cu solder has good mechanical properties and performance, so it isconsidered to be one of the most potential substitutes for Sn-Pb solder.The properties of Sn-Ag-Cu Lead-free solder have been researched a lot, but theuse of performance on the actual package structure is still on the way. In thisdissertation，shear creep behavior of Sn-3.0Ag-0.5Cu Lead-free solder alloy on the actualpackage structure of BGA was investigated. The main contents of this dissertation are asfollowing.Shear creep behaviors of Sn-3.0Ag-0.5Cu Lead-free solder BGA samples wereinvestigated at297K,313K,333K,353K and373K with the homemade precise creeptesting machine. At the preceding temperature and applied stress range, the stressexponent n was6.60, and the creep activation energy Q was57.216KJ/mol, and the creepconstitutive equation is determined. In discussing the creep deformation mechanism, itneeds to consider other factors, such as geometry constraints, terminal metal dissolutionupon soldering, interfacial IMCs and their dissolution. The creep properties of solderitself cannot be fully representative of the actual package structure’s creep properties.In the same experimental conditions, the influence of thermal aging on Shear creepbehaviors of Sn-3.0Ag-0.5Cu Lead-free solder BGA samples was also investigated. Theresults showed that the thermal aging had barely any effect on the creep index, but thecreep activation energy was significantly reduced. The reasons for those changes maybewere the thermal aging caused the intermetallic compounds (IMCs) thickness increase. |
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