Hi Tom,

I had the same problem before on ENIG finished boards. In my case it was the entire lot not only two boards that went purple. I do not remember the details but it had something to do with reaction between the Nickel/Gold chemistry and the silk screen ink. If your boards have ENIG finish, get the board supplier to do the silk screen after the gold plating. Also, request your boards' supplier to contact the ENIG chemistry supplier to address this issue.

Good luck.

Sherif,

--------------
>
> From: "Tom Parkinson - Quality System Manager - WinTronics, Inc."              <[log in to unmask]>
> Date: 2003/01/29 Wed PM 03:28:40 EST
> To: [log in to unmask]
> Subject: [TN] Silk Screen Goes Purple
>
> Purple?!
>
> We just finished running a batch of 15 PCBs through reflow and noticed
> on 2 of them, the silk screen changed from white to a very even shade of
> semi-dark purple.  The change was uniform across the entire board.  The
> boards were not the first or last ones through the reflow, no changes
> were made to the profile.
>
> Contacted the PCB house and they said they have never seen anything like
> it.
>
> Any ideas??
>
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