Abstract

We describe an approach to characterize the initiation toughness of silicon/glass anodic bonds based on the universal stress state that exists at the most common site of fracture initiation: the silicon/glass interface corner. The approach consists of a rigorous mechanics-based framework to assess the initiation toughness of anodic bonds; it can be used to rank bond toughness as a function of processing parameters and to facilitate the design of reliable bonds. By initiation toughness, we mean the resistance of anodic bonded interfaces to crack initiation under mechanical and/or thermal loading. The framework is universal in that it is independent of the bond size (area), and it is possible to discriminate between different failure modes via the initiation toughness. In order to validate the approach we designed and fabricated relatively simple anodic bond test specimens and carried out a mechanical test program to characterize bond toughness. We find that while failure stresses vary significantly with bond area, the inferred toughness is invariant with respect to bond area.

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