Behavior of Different Ultrasonically Bonded Aluminum Heavy Wires in the Shear Test

Abstract

Shear tests are known to be quick tests for heavy wire bonds to evaluate the interconnect quality. The challenge is to interpret the results of such shear tests, in terms of shear strength and the shear code defined by the German Welding Society (DVS). In this study, we aim to get a better understanding of the shear process by studying the material behavior through the shear test of heavy wire bonds. We took two different aluminum wire materials, Al H11 and AlMg0.5, and ultrasonic bonded them on 99.95% copper sheets, resulting in a good bond quality according to the DVS standard. We performed shear tests on these samples, stopping them shortly before final failure. We investigated the resulting deformed state by cross-sections and further instrumental indentation patterns in the middle of the wedge. The indentation hardness patterns revealed that Al H11 and AlMg0.5 behave significantly differently in terms of hardening under deformation. Our experiments show that the different material behavior has an influence on the failure path of the shear tests. We conclude, when comparing different materials by means of shear test results, that the outcome is influenced by the different hardening behavior.