Determination of Biaxial Bending Strength of Thin Silicon Dies by the PoEF Test

The easy-to-use point-load on elastic foundation (PoEF) test with biaxial bending stress state, similar to a conventional ball-on-ring test, is studied for determining the thin silicon die strength, which may feature geometric and contact nonlinearities. The feasibility of this test method with a linear theory is evaluated by a nonlinear finite element method (NFEM) with taking into account geometric and contact nonlinearities. The results show that the geometric nonlinearity would cause significant errors of strength calculation of using the linear theory for thin dies in this test. The NFEM results, more accurate than theoretical formulation, are proposed for calculating the strength of thin dies. As a result, the geometric nonlinearity has to be taken into account for this PoEF test, when the thin silicon dies are tested for bending strength data.