I have two suggestions.  One has already been suggested and that is to keep
the coated cards away from elevated temperatures as long as possible.  The
second suggestion is to thin the conformal coat which allows the entrapped
air to escape easier.  Jon

        ----------
        From:  Lum Wee Mei [SMTP:[log in to unmask]]
        Sent:  Monday, August 31, 1998 9:27 PM
        To:  [log in to unmask]
        Subject:  [TN] Bubbles from conformally coated board

        The test engineer came back to us to complain that bubbles are found
        along the edge of the power modules after going through the
temperature
        cycling tests. This problems are found on both coated boards. The
power
        modules are mounted completely flushed onto the board and subject to
        conformal coating using the diping method. The coated board undergo
QC
        to ensure all components are completely coated, inlcuding the edges
        around the modules.

        What could be the problem?

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