Three-Point Bending Strength and Failure of Window Glass Substrate by Considering Edge Stress Distribution

The window glass substrates have been generally used in optical semiconductor and micro-electrical-mechanical system packages. The determination of bending strength of such glass substrates is essential for ensuring good yield rate and reliability of those packages. For evaluating the dicing effect on the bending strength of window glass substrate, the typical 3PB test is adopted in this study. One of paradoxes is that the test specimens are generally plate-like, rather than beam-like, but a beam stress theory is commonly used for calculating strength from experimentally obtained maximum load in the 3PB test. Therefore, the other goal of this study is to determine the free-edge stress of the test specimen using finite element analysis during the 3PB test, if failure initiation of the test specimen starts at the free edge. The test results will be presented in terms of bending strength for edge (frontside) control and non-edge (backside) control cases, associated the failure modes. And precise edge-stress calculation will be discussed in detailed through finite element analysis with various models, including non-contact and contact models with both displacement and force boundary conditions.