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April 2005

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Subject:
From:
"Morse, Carrie" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Morse, Carrie
Date:
Wed, 20 Apr 2005 09:05:58 -0400
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text/plain
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text/plain (60 lines)
What color did it turn?

We recently ran some ENIG boards and found the silkscreen turned a
pinkish purple color.  That color darkened with each successive thermal
excursion.  We have not done a cause and effect, but, we believe since
we've only seen it on ENIG boards that it's somehow related to the bare
board process and/or rework to plating that we were not informed of.

Anyone in the board fab arena have any ideas?

-Carrie

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Martin Butcher
Sent: Tuesday, April 19, 2005 6:29 PM
To: [log in to unmask]
Subject: [TN] PCB Silkscreen Discoloration

Hi All,

I have a question regarding the discoloration of the silk screen ink
after reflow.  What can cause it other than overheating during reflow?

Here is some background to this question.  We received a consigned kit,
processed it and shipped it about three months ago.  Our profile data
shows that the PCB did not reach peak temperatures above 216 deg C.  We
have run this product once prior with a peak temperature of 212 deg C
and with no reports of discoloration.

Our client has contacted their board shop concerning this and were told
by the board shop that the discoloration is due to overheating.  Are
there other variables that could account for this?

Regards,
Martin Butcher,
Process Engineer.

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