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Date: | Fri, 25 May 2012 08:29:24 -0500 |
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Hi folks! Just to add a couple of details to Geoge's good details. The
general rule of thumb is that the "low P" nickels have good solderability
but can be prone to "black pad" issues and the "high P" nickels have good
corrosion resistance but can be prone to solderability issues. The "mid P"
nickels are requested by many users/designers are a compromise for dealing
with those three attributes. And as George detailed, the P content isn't
the root cause of black pad - hypercorrosion of the nickel plating prior
to immersion gold deposition is the root cause and can be (but not always)
more prevalent with some "low P" nickel plating formulations. One thing to
keep in mind is that process control of a nickel plating chemistry is
critical to achieving the plating properties you are expecting - any of
these three types of nickel plating can be done incorrectly if due
diligence is not followed.
Dave
"Wenger, George M." <[log in to unmask]>
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05/24/2012 11:51 AM
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Re: [TN] Phosphorus content in Electroless Nickel
Frank,
2-5% is considered Low P
6-10% is considered Mid range P
11-14% is considered High P
Many of the boards we examined years ago that were fabricated with ENIG
had Mid range P. I'm not sure if I can find Zequm Mei's original ENIG
work but he first thought that P content was the cause of BP failures
since when he looked at fracture surface there was always high P content.
However, you can't look just at a fracture surface because there will
always be a high P content because at the interface you consume some Ni
during the IAu processing and then more again during soldering. So you
might have a Mid range P ENIG but at the fractured surface it may look
like High P. Since then there has been lots of information indicating
that P content isn't the root cause for BP. I think I have the final HP
paper on ENIG that Sequm was one of he authors and can send it if I find
it.
Regards,
George
George M. Wenger
Senior Principal Reliability / FMA Engineer
Andrew Corporation - Wireless Network Solutions
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 Office (732) 309-8964 Mobile
E-mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Frank Kimmey
Sent: Thursday, May 24, 2012 12:22 PM
To: [log in to unmask]
Subject: [TN] Phosphorus content in Electroless Nickel
I know this may be difficult to commit to but what would you consider an
acceptable percentage of Phosphorus in Electroless Nickel.
I am being asked to accept 7-10% and am not sure if this may lead towards
Solderability issues.
Feedback from Chemists, Board Fabricators or anyone with an opinion is
appreciated.
Thanks to a great group of minds,
FNK
Frank N Kimmey CID+
Manager - PCB Design
Powerwave Technologies Inc.
Mobile - 916-670-0645
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