Sounds like residual moisture or some other volatile in the board.

Bob Dube

-----Original Message-----
From: Stephen R. Gregory <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Wednesday, February 09, 2000 12:15 PM
Subject: [TN] Delamination


>Hi ya'll!
>
>We just finished building a lot of 48-boards through SMT. Out of that 48
>there was one board that we just discovered a big delamination blister on
the
>backside...it's about 1.5" wide and maybe 2.5 - 3" long. There was no
rework
>done on the board, and it was reflowed under the same profile in a
>Conceptronic HVA-70 that the rest of them were...and they don't exhibit any
>problems. There no sign of overheating at all around the blister, and the
>silkscreen is nice and bright white...we just have this big blister. What
>might cause that? The boards are polyimide. We didn't bake them, and they
>were real fresh boards date code was 0300. Like I said, it was the only
board
>that had a problem...the rest are fine.
>
>TIA
>
>-Steve Gregory-
>
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