Lum Wee Mei,

It has already been suggested that you are not allowing enough time for the
conformal coating's solvents to evaporate prior to the outer surface of the
coating reaching it's tack free cure. While extending your time between
coating and curing will help you should also try processing at lower temps
and slower conveyor speed to eliminate outgassing. Lower cure temperature
will slow the curing process and slower conveyor speed will ensure that you
still reach the desired cure to the product upon output from the cure oven.

Sincerely,

Brian Stumm
Manufacturer of curing ovens


>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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ETS, LLC - West                      ETS, Inc. - East
3939 N. Freya St.                    PO Box 47887
Spokane, WA 99207                    Plymouth, MN 55447
509-483-0900 (voice)                 612-553-0051 (voice)
509-483-0331 (fax)                   612-553-0246 (fax)
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