Long-term product reliability is a concern for any production manager responsible for the plastic-encapsulated microcircuits (PEMs) going on printed circuit boards used in military, aerospace or medical applications. Similar concern for reliability is exercised in manufacturing some commercial products, especially where competition is intense and a word-of-mouth reputation for field failures can be harmful. It is widely understood that images of internal anomalies made by acoustic micro imaging can be used to evaluate component reliability before assembly, and thus help to predict product reliability in the field. Typically the required quantity of a given component is imaged, and evaluation of each image is performed according to one of the limited number of existing standards. One of the functions of Sonoscan's laboratory division, known as SonoLab, is the screening of large and small lots of components. The components involved may be lead-frame-based or substrate-based PEMs, ceramic IC packages, various types of flip chips, ceramic chip capacitors, or other types. This article discusses PEMs.
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