As co-chairman of the 4552 committee, I must take exception to your
comment" It does not contain a
lot of useful detail". For this specification extensive testing was
performed and data presented , paper appeared in the last issue of IPC
review as well as in the Orlando fall conference. The specification for
ENIG is 2 micro inches minimum Au at -4 sigma from the mean and 120 to
240 microinches for the nickel. As a point of note, I tested two days ago
samples from two of the five vendors that supplied samples for wetting
balance testing that were used to generate this specification. The samples
are now 14 months old (they have been lying around my office not protected)
and for the test we had them plated with 1 microinch of gold. THEY STILL
SOLDER AND PASS ALL WETTING BALANCE CRITERIA!!! The degree of porosity at 1
microinch is obviously greater than at 5 microinches however the protection
afforded the underlying nickel is still excellent, solderability testing
was with a ROL0 type flux per j-std 004.
It is intention of the 4552 committee to publish the total data set as a TR
report.
If anyone would like a copy of testing specifics or a copy of a specific
test data set - XRF , wetting balance, contact resistance , please feel
free to contact myself, George Milad -chairman of the committee or Tom
Newton at the IPC
Regards
Gerard O'Brien
Photocircuits Corp.
-----Original Message-----
From: [log in to unmask] [SMTP:[log in to unmask]]
Sent: Wednesday, January 30, 2002 10:04 PM
To: [log in to unmask]
Subject: Re: [TN] ENIG Thickness Standard?
Rick,
I went through this pain a while ago, and got a lot of tremendous help from
Ingemar Hernefjord in particular. I believe there is no released standard
for ENIG, though there is an empirical spec IPC-4552. It does not contain a
lot of useful detail, though. I specify 5 microinches (0.12 microns) of
Gold over minimum 235 microinches (6 microns) Nickel for my boards, after
reading a number of studies and failure reports. In fact I was recommended
to use 250 microinches of Nickel, but this would have made our boards too
thick. The thicker gold layer minimises porosity and therefore oxidation to
the underlying Nickel layer.
Older thinking was for around 100 to 120 microinches Nickel, but studies by
Eriksson and others concluded that with the growth of gold flashing through
the Nickel from one side and Cu/Ni intermetallics on the other side of the
plating, that a thicker Nickel layer would offer the boards a longer
solderability shelf life and greater solder joint reliability.
Hope this helps a bit. Certainly, I haven't experienced any problems with
soldering or mounting of components on boards to this spec.
Peter
Rick Thompson
<rthompson@VENTURAELECTR To: [log in to unmask]
ONICS.COM> cc: (bcc: DUNCAN
Peter/Asst Prin Engr/ST
Sent by: TechNet Aero/ST Group)
<[log in to unmask]> Subject: [TN] ENIG
Thickness Standard?
01/31/02 08:36 AM
Please respond to
"TechNet E-Mail Forum.";
Please respond to Rick
Thompson
Is there a standard for the plating thickness of the ENIG surface
finish? I've searched the archives and didn't find anything. Based on
a customer request we had increased the requirement for the electroless
nickel to 200u inches. A couple of our board vendors are telling me that
that is excessive and that anything over 100u inches is overkill. I've
seen references in the archives for anything from 120u inches to 200u
inches. What (if anything) is considered standard for this finish?
Thanks for your inputs.
Rick Thompson
Ventura Electronics Assembly
2655 Park Center Dr.
Simi Valley, CA 93065
+1 (805) 584-9858 x-304 voice
+1 (805) 584-1529 fax
[log in to unmask]
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