Under normal conditions all of the gold protecting the base metal should
dissolve into the solder.

For ENIG, the gold plating process produces a thin layer of gold that is
entirely dissolved. The solder connection is to the nickel.

Many connectors have electroplated gold that can be much thicker than the
ENIG process we see on bare boards. Check the data sheet.
Then, consider the requirements in J-STD-001, with the knowledge that gold
makes it brittle. I've seen white papers that suggest degradation begins
about 2%, though there is a consensus that it should not exceed 4%.

There are threads in the archives discussing the condition.


-----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,