Determination of mechanical properties of small test volumes using nanoindentation - a critical review

Material parameters that describe the mechanical behavior of small test volumes realistically are required if the thermo-mechanical properties of microelectronic or micromechanical components are to be determined. Today the smallest microelectronic solder joints consist of only a few crystals, some-times even just a single one, and/or intermetallic compound phases which, as a statistical ensemble, determine the mechanical properties of the joint on the continuum level in the following sense: The orientation of the crystals and of the phases characterizes the very local properties of the solder and, as a direct consequence after a ldquosuitablerdquo averaging procedure also those of the whole joint. Therefore, in order to acquire some first knowledge about the orientation of phases and its impact on material properties miniature experiments must be performed. These can be, for example, nanoindentation or miniature tensile tests, the latter of which involve very small test specimens with only a few grains, thus mimicking the mechanical behavior of the real microelectronic joint.