Crowbar Loading-A New Test Technique to Characterize Interfacial Delamination

This paper presents a new test method called Crowbar Loading (CBL) to characterize interfaces between dissimilar materials. In this test, a cylindrical roller is sandwiched in the delaminating interfaces and acts as a fulcrum to facilitate crack propagation. Although the externally applied load is compressive on one side of the fulcrum, the fulcrum translates the applied external load into an opening-mode load at the crack tip. By varying the location of the roller, this work shows that a wide range of loads can be altered at the loading point. Numerical models were developed to determine the critical crack length from the experimentally measured compliance of the test sample and, thus to determine the critical strain energy release rate (Gc). The crack length, determined using compliance, is also validated through optical measurements. Copper-epoxy mold compound (Cu/EMC) bimaterial samples, commonly seen in microelectronic packages, were successfully characterized using the developed CBL test method. The results from the CBL test have been compared against the double-cantilever beam (DCB) test results.