We compared the adhesive strength estimated by the stress-singularity-parameters approach with that measured by the shear debonding test of photoresist patterns on Cu substrates. This comparison shows that the stress-singularity-parameters approach is not capable of consistent estimation over a wide range of adherend sizes. We therefore developed a new method (based on the concept of energy release rate) for evaluating adhesive strength. The method is based on the finite element approach and places an "energy release element" (which mathematically represent the energy release due to debonding) between the interface of the photoresist and the Cu substrate. By using this method to calculate the shell debonding strength of a photoresist, we showed that the calculated strength agrees well with the shear-test-measured strength. We also found that the stress-singularity-parameters approach is only useful when strains are nearly elastic.
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