In message  <[log in to unmask]> [log in to unmask] writes:
> We have an application where we need to apply temporary solder mask prior
> to a high temp bake in preperation for wave solder. These are polyimid
> boards and we bake them at 125C for 12 hours prior to wave solder. We try
> to wave solder them as soon as they cool to ambient so applying mask after
> bake is out of the question.
>
> We have two different masks we currently use that are water-soluble.
> Neither one comes off very well in the water wash and one of them leaves a
> residue/stain due to the high temp bake.
>
> Do any of you have a source for a temporary solder mask that can hold up to
> this temp/time and still be removed easily without residue (preferably with
> water)?

I think one of the problems here is that many of the water soluable solder
masks need to be re-saturated before they start dissolving. When you have baked
them at over 100C for a long time, there is no residual moisture left in the
mask, so the re-saturating process takes a long(er) time. You could try
increasing the water temperature, water pressure or immersion time to get
better removal. Perhaps a pre-soak? A different kind a mask chemistry might
also be tried - a couple of names which haven't been mentioned in this thread
are worth contacting in this regard, Tech Spray and Dymax.

Peter
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Peter Swanson                                              Oxfordshire, England
INTERTRONICS
[log in to unmask]                  http://www.intertronics.co.uk

Suppliers of materials and consumables to the electronics & related industries
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