Rick - as co-chairman of the 4552 committee that has recently wrote the new
ENIG spec (waiting for the IPC to release it), the recommended specification
is 2 microinches minimum at -4 sigma from the mean for the gold with 3-5
being typical. We presented a technical paper on the subject at the IPC
Orlando meeting in 2001, it was also published in the IPC review. As a point
of interest, part of the study was testing real time the shelf life of 1
microinch of Au (verified by a reference XRF unit costing $500,000+ so not
your typical PCB house XRF), I have recently tested parts at 2 years and
still producing excellent wetting forces and acceptable wetting times. May I
suggest you get a copy of the paper we presented and as soon as it is
released a copy of 4552.

Regards

Gerard O'Brien
Photocircuits Corporation
co-chairman of 4552


-----Original Message-----
From: Rick Thompson [mailto:[log in to unmask]]
Sent: Friday, January 03, 2003 12:29 PM
To: [log in to unmask]
Subject: [TN] 'Thin' Immersion Gold Finish?


We have an overseas board supplier that is supplying an immersion gold
finished board that is only 1-1.5 microinches of gold over 100 microinches
of nickel.  I believe this may be too thin a gold layer for adequate
protection of the nickel but don't have any objective evidence for this.
Can anybody give me any feedback or other information sources that might
support this?  IPC-2221 specifies approximately 3-9 microinches of gold
which is what we generally require, but I'm looking for additional objective
evidence for requiring thicker gold deposits.

Thanks in advance.

Rick Thompson

Sr. SMT Process Engineer
SMTEK International, Inc.
+1 (805) 532-2800
[log in to unmask]

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