At  8:16 AM 3/7/97 -0500, Sheila Smith wrote:
>Technetters:
>
>I am soliciting opinions on conformal coating of PBW-mounted connectors.
>Our manufacturing folks refuse to conformal coat within 1/8" of any board
>mount connectors.  They contend the conformal coating will wick up the pins
>and get on the contact areas, regardless of the type of conformal coating
>used or the method of application.  The connectors are not sealed.  These
>boards have to pass salt fog & humidity testing and I don't like the idea of
>having bare areas, especially at the interface where the connector meets the
>board.  Does anyone have any experience with this?  Thanks in advance for
>your help!
>
>S. Smith, Tracor Aerospace Electronics Systems
>
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        Since the back of the connectors is not sealed, there is little you
can do to prevent the coating material from wicking up the pins.  Some of
the stuff is very low viscosity with great wetting strength and will move
through the very thin spaces with alacrity.
        We use two different techniques, with the first being preferred
since it has the highest success rate and we do all our stuff (except
Parylene) by hand.
1. Dam the rear of the connector with a Cabosil (or any other acceptable
thickening agent) loaded version of your coating material. Cure that before
applying the final coating.
2. Mate the connector with a sealed dummy connector before coating. Note:
has lots of pitfalls and sometimes doesn't work at all, ie, the stuff still
wets out onto some pins.

        Good Luck,
        Howard Feldmesser
        The Johns Hopkins University Applied Physics Laboratory


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