Our pwb suppliers provide our large  boards with the peelable soldermask
applied to the ground plane which needs protection from the wavesolder
bath.   But let me add a few words of caution....

Peelable soldermask is typically thermoplastic and therefore if there is
any direct contact with any part of the conveying system through the reflow
oven, you will run the risk of making a "peelable" adhesive bond between
your board and the reflow oven.  We've seen assemblies get knocked off of
the rails in the hotter zones of the oven and have to be scrapped.

We have experienced considerable problems with our center board supports
and at this point no longer allow our new designs to use this type of maskant.

Kapton tape (3M#5419)is our current masking material, if the assembly
cannot live without it.

Another problem we have experienced with peelable is that if it is
overheated, it can permanently bond to the board.  Our blue maskant
actually turns a very dark blue/black when overheated.

If anyone has any solutions to this problem, I'd love to hear them, but
I've posted this over the Technet before without any positive responses.

Regards,

Phil Bavaro


At 06:40 PM 7/24/98 -0400, Michael Blackburn wrote:

>We have a number of boards that we hand apply a peelable solder mask in
>areas where components are added after wave soldering. Recently, I saw a
>board that had a screened peelable solder mask that had been applied by
>the board vendor. Does anyone have any experience with using this type
>of mask? I've checked with one of our vendors and although he doesn't
>use peelable mask, he has seen such a product and is willing to run some
>samples. Any feedback would be greatly appreciated!
>
>
>Mike Blackburn
>Sr. Designer
>Novar Controls Corp.
>Copley, OH 44321
>(330) 670-1010, Ext. 5584
>
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Phil Bavaro
Senior Manufacturing Engineer
Process Engineering, CCA Technical Support
Qualcomm Incorporated
(619) 658-2542
(619) 658-1584 (fax)
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