Evaluation of manufacturing variables in the reliability of surface mount capacitors

The reliability of surface mount capacitors assembled under a variety of conditions has been evaluated in temperature cycling, vibration, altitude, and temperature-humidity-bias (THB) environments. Both initial assembly (vapor phase) and rework processes were used to assemble capacitors to alumina substrates, with the following variables: assembly thermal conditions, capacitor manufacturer, conformal coating materials, and number of assembly cycles. Failure rates were higher for the rework process than for the initial assembly process. The failures observed in environmental testing correlated well with earlier scanning laser acoustic microscopy (SLAM) testing on capacitors prior to assembly, and SLAM testing has been implemented as a screen for incoming capacitors.<
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