Lum Wee,

You ask what could be the problem:
If Conformal Coating is subjected to elevated temperature (subjective as to
what is elevated temperature), before fully curing, the solvents remaining
in the coating can try to rapidly outgas and create bubbles. Extended room
temperature time for curing may solve the problem, your process may or may
not have time for full cure before entering temperatures generated by other
curing ovens, testing of high wattage components, temperature cycle or
temperature testing. Have experienced this problem in my production lines.
Semper Fi
Tom

> ----------
> From:         Lum Wee Mei[SMTP:[log in to unmask]]
> Sent:         Monday, August 31, 1998 8:26 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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