Abstract
Adhesion strength evaluation of molding compounds is a critical issue in structural design and material selection of IC plastic packages. However, since conventional adhesion tests can only give apparent adhesion strengths which include the effect of residual stress, their results cannot be used for design. This paper proposes a new method which can experimentally separate residual stress from adhesion strength. In this method, three-point bending tests of ENF specimens are performed in two opposing directions. Residual stress can be canceled simply by averaging the apparent strengths for these two directions. The method's validity was studied by experiments and stress analyses of specimens composed of an IC molding compound and Fe-42Ni lead frame material. Adhesion strength was expressed in terms of the stress intensity factor of the interface crack, Ki. It was confirmed that constant strengths can be obtained independently of specimen dimensions.
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