Hi folks - George beat me to the punch! Just to add to his good details -
the majority of the gold embrittlement cases you see published (and many
of others that are never published) are due to an incorrect soldering
process. The gold wants to dissolves at 100+ microinches per second but if
you don't use sufficient soldering heat, dwell time and solder volume, you
don't allow the gold to distribute itself equally throughout the solder
joint microstructure. There is also a good paper by the Agilent and Cal
Poly folks in the 2012 February issue of Journal of Electronic Materials
(JEM) on the how gold distributes itself in a solder joint when nickel
plating (just like what we have in ENIG) is present.  The Bader reference
George mentioned is a must for everyone's files.

Dave Hillman
Rockwell Collins
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Re: [TN] ENIG thickness






Victor,

If you go back to Wally Bader's paper that he published in The Welding
Journal when he was working for AT&T, which I refer to as "The Dissolution
Bible", you will see that gold dissolves in 450F SnPb solder at a rate of
117.9 microinches per second.  Therefore the gold on an ENIG plated
surface with 4 to 5 microinches of gold will be gone in 0.03 to 0.04
seconds.  I don't think you can realistically make the gold thick enough
so that it won't be totally consumed in a soldering process.

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 Victor Hernandez
Sent: Thursday, February 02, 2012 10:38 AM
To: [log in to unmask]
Subject: [TN] ENIG thickness

Fellow TechNetters:

   At what ENIG thickness will the gold not be totally consumed by the
soldering process on a connector lead, LF solder joint.   What happens
when the gold is not consumed.  Will the joint structure be compromised.
What about the IMC formation.  The SJ strength.

Victor,