Hi Choong!

     Finally! Somebody else experienced the same problem I had a few years
ago...I thought I was going nuts back then. We were building VGA cards and the
same thing happened to us. Down around the gold fingers was where we had what
we started calling; "The purple plague".

     The vendor you spoke with was right, it does have something to do with
the gold plating chemicals. If I remember correctly, it was because the FAB
vendor didn't follow the proper process, or clean the PCB adequately when
doing the gold plating...I'm not sure of the precise problem, we were just
told that it had to do with something not being done right during the gold
plating.

     Whatever it is, it'll get darker with higher temperatures during reflow.
Once we found the problem, we tried cleaning the boards using Freon as well as
water, to see if by doing that it would eliminate the problem, but no luck.

     We were told back then that once the chemicals had soaked into the
laminate, that was it...you couldn't do anything to keep it from discoloring.
The bad thing about it is, it doesn't start to turn purple until the board
sees reflow temperatures, so you couldn't separate and purge the bad PCB's
before hand...so unless somebody else has figured out something else, these
boards are hosed...

     Supposedly though, it's nothing harmful, it just makes the boards
purple...

                           -Steve Gregory-

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