A modified single lap shear test configuration, based on the Iosipescu geometry, is proposed for determination of the constitutive properties of solder alloys. An auxiliary device (extension unit) is introduced to improve the accuracy of measurement. The extension unit is attached directly to the specimen and it converts shear displacements to axial displacements, which are subsequently captured by a high-resolution extensometer. With aid of the extension unit, shear deformations are measured without compensating machine and grip compliance. The specimen configuration includes geometrical constraints at the solder/substrate interfaces in most electronic assemblies. Consequently, the results represent pseudo-continuum properties that take account for grain constraints at the solder/pad interface. They are properties that are more realistic for continuum mechanics based stress studies such as an FEM analysis.

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