A failure mode occasionally observed in multilayer ceramic capacitors (MLCC) is degradation of insulation resistance as the capacitor ages under temperature and electrical stress. The dielectric in MLCC can have a heterogeneous appearance when examined by optical microscope or SEM. This makes it difficult to identify features that could explain the root cause of failure or that could be used in devising inspection criteria for lot acceptance. Conventional cross sectioning in an epoxy mount leaves the sample unsuitable for examination in highvacuum equipment such as field emission scanning electron microscopy or Auger Electron Spectroscopy (AES) because epoxy outgasses and badly contaminates the high vacuum system. A novel twostep potting technique for sample preparation and inspection was developed to meet these challenges. This technique enabled us to perform electricallymonitored cross sectioning in combination with thermal inspection (infrared microscopy). Once a shorting site was identified, the sample was easily removed from the epoxy mount, allowing examination of the actual location of the short circuit in the field emission SEM (necessary to avoid sample charging). By precisely identifying the defect site, the chemistry of the defect could then be determined using electron spectroscopy and materials identification techniques1, 2, 3.

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