Investigation of the Influence of Shear Height in the Wire Bond Shear Test

Heavy wire bonds are particularly important in power electronics. With the wide range of wire and substrate materials used, the need for a well understood qualification test is obvious. The shear test is a widely used and accepted part of the qualification of heavy wire bonds. In the DVS 2811 standard, the shear height is specified as one tenth of the wire diameter. The influence of this shear height on the shear force and the shear code we investigate in this work. For this purpose, both materials we shear crosswise in their raw wire form in a range of 5 to 60 µm shear height to obtain the shear strength of the pure wire materials. Furthermore, we perform shear tests on Al H11 and AlMg0.5 heavy wire bonds in the range of 5 to 60 µm for the shear height. The results show that for the shear tests results of wire bonds, the maximum shear force does not change significantly with shear height. However, the shear code, or more precisely the residual wedge area in comparison to the area of the wedge does change with shear height. This is in contrast to the crosswise shear test of the pure wire material where the shear height does influence the maximum shear force. The results raise the question of whether one tenth of the diameter is the correct shear height or whether there should be a range of shear heights to be tested. Understanding the influence of shear height on the shear test result could improve the reliability of heavy wire bonds.