Hi Richard,

We use to use the Wondermask W here, but when we switched to a closed-loop
DI water treatment system for our inline cleaner we switched over to the
Wondermask WSOL because it's supposed to be less harmful to closed-loop
water treatment systems. It doesn't slump very much either, in fact we have
to thin it out a little sometimes to avoid getting it too thick which
increases cure times and sometimes causes us to have to run the boards
twice through the cleaner to fully remove it.

Steve

On Tue, Dec 9, 2014 at 7:47 AM, Stadem, Richard D. <
[log in to unmask]> wrote:

> Hi, Dave
> I use a temporary solder maskant that works quite well for that specific
> application. The product I eventually ended up using is Techspray
> Wondermask "W". But I want to let you know that this particular maskant
> does have an issue of separation. However, we found that if properly
> stirred prior to application it was the best-performing maskant on the
> market in terms of both toughness and its ability to completely wash away.
> The separation, if it does occur, is easily visible inside the ketchup
> bottle that the material comes in. The material is a light blue color, and
> the separated portion produces very dark blue streaks. This particular
> maskant is a de-ammoniated maskant, which is what you would want for that
> application. I have found that the highly ammoniated maskants will cause
> some etching of inks and even to metal surfaces.
> If the material is not mixed, the result is a very crumbly maskant that is
> not robust at all, and also does not wash off easily.
> We decided to thoroughly train our operators and go with this product only
> because it was so much better than others if it was properly mixed. It is
> very easy to mix, simply unscrew the ketchup bottle cover and mix with a
> popsicle stick or tongue depresser, screw the cover back on and dispense.
> The fact that we have to do that to get a better product is a depressing
> subject, eh?
> It cures to a very hard and tough finish in just 15-20 minutes in a 105
> deg. C. oven and will easily hold the BGA in place through reflow.
> It will also allow you to achieve a more columnar or elongated solder
> connection, which is inherently more reliabile. Printed paste should be
> used for that application to ensure all balls are making contact with the
> molten solder and ensures a pad-to-pad connection.
> The Wondermask "W" is also thick enough to be able to apply without
> excessive slumping, which was a problem with some of the other maskants we
> evaluated.
> Hope this helps you.
> dean
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
> Sent: Tuesday, December 09, 2014 7:42 AM
> To: [log in to unmask]
> Subject: [TN] BGA Reflow Issue
>
> Hi gang - looking for an adhesive suggestion. I have an assembly in which
> a heavy BGA was accidently located on process side one (bottom) so that
> when we reflow process side two (top) the BGA is doing its best to fall off.
> Unfortunately I can't reverse my process order for a couple of reasons so
> I am looking for a temporary fix until I can get the assembly revised. I
> was thinking of using some type of adhesive to temporarily hold the BGA in
> place during reflow - tack down the corners sort of action. Does anyone
> have any adhesive (ideally temporary, water washable/removable) suggestions
> I can investigate?
>
> TIA
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
>
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