Test methods for characterizing the local plastic deformability of bonding wires

Different methods for characterizing the local plastic deformability of small Al bonding wire samples were presented including Vickers and spherical indentation as well as micro compression testing for two different sample orientations. The results were compared to reference data derived from tensile testing of macroscopic wire specimens and to the Al grain microstructure as characterized by the Electron Backscatter Diffraction (EBSD) method. A close correlation between tensile wire strength, hardness data and grain size was found. This relationship can be used to evaluate local changes in the wire material properties due to the influence of process steps or application conditions. In addition, the potential and high accuracy of the newly developed micro compression test was demonstrated. Stress-strain curves derived from micro compression testing agreed well with the reference data in most cases. In so far, the micro compression test can be used as a tool to quantify the local mechanical behaviour of processed bonding wires and bonded interconnects.