Dumb Question:

 What Is "Hyper-corrosion"?

Bob K.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Friday, May 25, 2012 9:29 AM
To: [log in to unmask]
Subject: Re: [TN] Phosphorus content in Electroless Nickel

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]> Sent by: TechNet
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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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