Interface fracture mechanics evaluation by correlation of experiment and simulation

Abstract

Interface fracture mechanics is one of the main focuses of electronics reliability research. Determination of fracture mechanical properties of interface cracks is a substantial task for design for reliability comcept. Without experimental determined fracture mechanical parameters such as the critical energy release rate a reliability forecast based on simulation results cannot be given. In fracture mechanics testing often a correct measurement of the crack tip location is needed for the calculation of the energy release rate. The authors present a combined simulative and experimental method for crack tip location determination of typical interface specimens. The specimens are loaded in a newly designed testing apparatus, the Mixed Mode Chisel (MMC) setup, and images of the crack tip at the interface are taken at different load states during the testing procedure. Then images are analyzed by image correlation techniques (DAC, deformation analysis by correlation) and cra ck tip displacement fields are determined. In the next analysis step the displacement fields are compared to fields from finite element analysis of the same specimen geometry with boundary conditions similar to the experimental setup. The point of the best matching of the experimental and simulative field is the actual crack tip location. If finite-element data or analytical solution for the crack tip displacement field is available the method can be applied for a variety of different interface samples

Advanced mixed-mode bending test: A rapid, inexpensive and accurate method for fracture-mechanical interface characterisation

“…However, if the crack does not gape, which is very often the case near mode-II loading, or if higher accuracy is needed, then greyscale correla tion based methods can be applied [39]. Figure 13b pinpoints the crack tip at the crossing of the two measured displacement curves: The frames are taken at different times during the load ing and then analysed afterwards to assign a crack length to each point on the force-displacement curve [6]. Even higher accu racy is achieved by using a correlation technique for the crack tip fields (see figure l3c): A simulated crack tip displacement field (inset) is compared numerically to the experimentally ob- tained one.…”

“…Even higher accu racy is achieved by using a correlation technique for the crack tip fields (see figure l3c): A simulated crack tip displacement field (inset) is compared numerically to the experimentally ob- tained one. The crack tip is found where the correlation integral peaks [6]. Care has been taken that this greyscale-based method can also be applied to the AMB-test stand.…”

“…Four-point bending tests were effectuated [2,3] as well as chisel bending tests [4,5] using a specific clamping mechanism. Mixed-mode bending specimens were tested by [6] in a standard testing machine or by [7] integrated within a DMA. Other papers consider Brasil-nut specimen testing [8] or button shear tests [9,10].…”

Establishing the critical fracture properties of the die backside-to-molding compound interface

“…The finite element model is built using the specimen's geometry including the crack length characterizing the local geometry in crack tip vicinity. For crack length measurements see [10]. The load situation of the experiment determines the model's boundary conditions including the prescribed load displacement.…”