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March 2007

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Subject:
From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Thu, 15 Mar 2007 10:51:49 -0500
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I have, and I have the data. Once I found pwbs with a very deep
orange-colored BGA pads and some not quite so orange, more of a very
light orange/copper color. These would be a single pad amongst others
that had a very uniform gold color. When we performed XRF and other lab
analysis at a metallurgical lab, the readings showed complete nickel
skips on the bright orange pads, and nickel plating less than the
standard 150 uinches (typically 30 to 70 uinches) on the light orange
pads.
The laboratory had seen the same experience with a different company,
but from the same board vendor. Since that time I have seen this two or
three times, and I knew immediately what it was.
Apparently the 150 uinches of nickel was deemed the minimum to prevent
copper from migrating to the surface (through the nickel). That is why
the standard ENIG finish is usually 150-180 uinches of nickel, with 2-7
uinches of gold to prevent the nickel from oxidizing. 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Thursday, March 15, 2007 9:30 AM
To: [log in to unmask]
Subject: Re: [TN] IPC ENIG SPECIFICATION

Too thin an Ni plating may have adhesion problems due to bleed-through
of Cu form the underlying Cu layer. But i do not know for sure, since i
have not run into it before.

Werner



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