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June 2004

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Subject:
From:
Graham Naisbitt <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 10 Jun 2004 10:59:26 +0100
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Lance

Are you sure this is happening on the leads of the components? If the answer
remains yes, then this would worry me.

The problem is de-wetting. The cause of which is often attributed to
silicone contamination from mould release agents, masking residues, staking
compounds or maybe adhesive residues. It is also conceivable that it is
present in the feed lines of a spray gun or nozzle, especially if it has
been used to apply a silicone coating for another application.

I assume that you are inspecting this under UV (Black) light? If so, then
please verify that you can observe this happening by coating under the light
source. If it is, then I am confident this is a silicone issue.

Otherwise, is this problem appearing on the vertical or horizontal surfaces?

If you can, maybe you could take a photo and post it to Steve's web site,
then we could all take a look - a picture is often worth a thousand
words...and therefore a darned site quicker!

Graham Naisbitt

> Hello again Techies;
>
> We are having issues with our conformal coating on some of our components.
> It pulls back from some of the components leads along the edges.
> We are wondering if this will make a difference in the protection of the
> board.
> We're using Humiseal Acrylic 1B31 and Humiseal Thinner 521 in a mixture.
> The conformal machine sprays a nice coating and then the coating starts to
> recede.  Sometimes this happens even when we paint the acrylic manually.
> Has anyone else ran into this problem, and what to do to overcome it?
>
> This is a good one for the end of the day.  I'll be waiting.
>
> Thanks again
>
>
>                       P.  Lance Mayes
>
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