Mechanical bending strength measurements, part of a quality screening process for ceramic substrate package designs, revealed a significant difference between two substrates that could not be attributed to constituent materials or structural thickness effects. Structural analysis was performed to generate a hypothesis that the metal vias were not structurally adhered to the ceramic holes and thus caused stress concentrations that reduced the bending strength of the substrates. In this detailed case study, the authors explain how they proved their hypothesis using FEA to calculate stress concentration factors, optical microscopy to examine fracture surfaces, and electron spectroscopy to determine chemical compositions. The successful outcome attests to the value of strength criteria as an investigative tool for the assessment of electronic package substrate quality.

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