This paper presents a new methodology for the mechanical characterisation of solders used in integrated circuit (IC) packages. The methodology is formulated on the basis of package-level solder joints (BGA packages) to properly account for the effects of microstructure and intermetallic compound distribution. The methodology is implemented on the lead-free Sn-3.5Ag solder. In the indentation tests, the lead-free solder is found to be sensitive to the applied strain rates as well as the thermal cycling conditions. Finite element analyses, together with the experimental results are used to extract the elastic modulus and the elastic-plastic constitutive relations. The methodology has shown that the extracted properties are in good agreement with other publications.

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