Dave,
Thanks for the feedback. I did get some specifics on IPC-4552 proposed
recommendations from the committee co-chair that we're going to put in
our requirements.
Regards,
Rick Thompson
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of
[log in to unmask]
Sent: Thursday, January 31, 2002 6:37 AM
To: [log in to unmask]
Subject: Re: [TN] ENIG Thickness Standard?
Good Morning TechNet! Rick, I have a very different perspective on ENIG
than Peter so here is some food for thought. There is a specification
for ENIG - IPC-4552 - which is in final ballot and should be release in
the March/May timeframe. I recommend getting a copy. It's my opinion
that the specification is quite useful considering there is no other
specification available for industry use. The ASTM B488 specification is
not a workable solution for electronics applications. There was a great
deal of committee discussion on the electroless nickel plating
thickness. The nickel thickness is very much viewed as application
specific, for example, RF designers desire minimal thickness (30-50
uinches) as opposed to connecting applications which use 200 uinches.
Rockwell Collins is successfully using 2-5 uninches for the immersion
gold thickness and 50-150 uinches for the electroless nickel thickness
in avionics applications and we intend on using the IPC-4552
specification in our documentation. Additionally, 50 uinches of
electroless nickel is very adequate as a diffusion barrier as both the
nickel/copper and nickel/gold phase diagrams demonstrate a wide range of
immiscibility The only instances I have seen a 50 uinch electroless
nickel thickness not be adequate was for pwbs which were subjected to
repetitive thermal excursions (e.g. lots of rework, or 4 reflow passes).
Using an immersion gold thickness of 6 uinches will not guarantee you
solderability - the 4552 committee demonstrated that (by conducting
testing) that 2 uinches of immersion gold can be steam conditioned and
still provide expected solderability coverage. Teaming with your ENIG
vendor, understanding their plating process control practices and
requiring some level of solderability testing is the best way of
insuring solderability. Good Luck.
Dave Hillman
Rockwell Collins
[log in to unmask]
[log in to unmask]@ipc.org> on 01/30/2002 09:03:53 PM
Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please
respond
to [log in to unmask]
Sent by: TechNet <[log in to unmask]>
To: [log in to unmask]
cc:
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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