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June 2005

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Subject:
From:
"Blair K. Hogg" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Blair K. Hogg
Date:
Thu, 16 Jun 2005 05:46:49 -0700
Content-Type:
text/plain
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text/plain (70 lines)
Is ENIG applied before or after soldermask? 

If after, wouldn't there only be a small area of Ni at the pad? Does this still have a significant effect?

Blair

>>> [log in to unmask] 06/15/05 06:24PM >>>
Hi, Martin
Werner has the numbers right. I put something on the forum a week or two
back with a little more detail. I will copy it to you directly offline
Thurs. a.m. It might help you.
Basically, at the high frequency/high impedance levels, the signals move
along the outside surface of the conductors due to the Hall effect (skin
effect) of electron/hole recombination. Therefore the conductance of the
different alloys becomes much more critical. During soldering of ENIG,
the gold is absorbed into the solder joint, and you have an underlying
conductor that is basically nickel.
With immersion silver the silver is absorbed into the solder joint, and
you now have a conductor that is essentially copper.
While nickel's conductance is only slightly worse than copper, the
addition of phosphorus needed in the plating process for ENIG brings
nickel's resistance much higher.
The signal loss of the nickel is approximately 10 times that of copper,
per centimeter. This becomes more important at frequencies above 1Ghz.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Wednesday, June 15, 2005 4:27 PM
To: [log in to unmask] 
Subject: Re: [TN] RF board finishes

Hi Martin,
The electrical performance of Ni is not as good as Cu: 90 micro-Ohm/cm
v.
1.67; 4.7 microDb/cm v. 0.6.
My recommendation is iAg.


Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com 



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