Hi Brian,

Assuming this is peelable type of wavesolder maskant, our experience has
shown that the temporary soldermasks are thermoplastic as far as reflow
oven resistance is concerned.

If it is processed through the oven with normal time exposure, then it will
come off after wavesolder in one piece, but obviously the warmer the better
because adhesion is typically the last property to develop after a cure cycle.

Now if you add large boards which require center board support mechanisms
to the situation, you have a formula for disaster, because the peelable
mask can foul up or tack itself to the mechanism and cause a jam inside the
reflow zones.

If this happens, then it is baked so hard (it turns dark in color) that it
is almost impossible to lift an edge and remove it, but unfortunately by
then the assembly is history anyways due to excessive time at reflow
temperatures.


Stick to the tape provided it meets ESD requirements or else design out the
requirement for masking.

Please let me know if anyone has any other solutions to this problem.

Phil
-----




At 08:59 AM 2/17/98 -0500, Brian L Guidi wrote:
>Hello Technetters,
>        With all this talk of "temporary soldermask" I was wondering, is
>there a "temporary soldermask" out there that will survive the hot air
>reflow process? If so, how is it applied/removed? Any information or
>guidance would be much appreciated.
>
>        Right now, we are limited to a special tape we use to mask before
>reflow.
>
>     Thanks in advance. Brian G.
>
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Phil Bavaro
Senior Manufacturing Engineer
Process Engineering, CCA Technical Support
Qualcomm Incorporated
(619) 658-2542
(619) 658-1584 (fax)
[log in to unmask]

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