Lee,
Not sure which topic you are referring to, nitrogen use in the reflow
process or nitrogen storage of components, or both.
But most companies are going away from storage of components in nitrogen
boxes. Component solderability is not usually an issue anymore, and the
cost of having nitrogen boxes all over the factory leaking nitrogen 24/7
is a very spendy proposition.
Storage in a dry atmosphere is still needed, of course, to prevent
moisture damage for MSD's. But for this purpose dessicator boxes such as
McDry cabinets are a much better option than nitrogen, as they do not
need anything but a 110V outlet and use very little electricity. You can
move them readily, as no plumbing is necessary, you can verify the
moisture levels, etc. They actually dessicate parts and boards in a
short time, while nitrogen simply stops additional moisture absorption,
but takes much longer to purge a board or part of oxygen (moisture).
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee Whiteman
Sent: Wednesday, January 18, 2006 3:53 PM
To: [log in to unmask]
Subject: Re: [TN] Time to fish or cut bait
Neil,
I echo Dave Hillman's response, but with a few caveats.
Up to January, 2005, I thought that it was required to use Nitrogen with
Lead Free solders. Since then, having run hardware without Nitrogen and
with Nitrogen in our Demostration Factory, plus the work done on the
JG-PP / JCAA Lead Free Program, I feel that Nitrogen is not required but
a good option to have.
Controlling your inventory environment will reduce the probability of
hardware becoming oxidized which will lead to poor solderability. The
GIGO - garbage in garbage out - rule applies in this case. Hardware
thought to be acceptable with Tin Lead (SnPb) may not be acceptable for
Lead Free alloys because these alloys do not wet as well as Tin Lead
(SnPb). Of course you can use a really active solder flux to get the
alloy to wet better, but then your cleaning processes would have to
become more aggressive to remove the residues.
Nitrogen will reduce the amount of residues on the board and the solder
joints will look brighter. It will open that process window to solder
hardware which may be marginal. With Tin Lead (SnPb), using Nitrogen it
may be possible to solder marginal material (boards, components,
etc.)depending on how bad the material is. However, since most Lead Free
alloys do not wet as well as Tin Lead (SnPb), if you have marginal
material, Lead Free soldering may be more difficult.
If you don't have Nitrogen, you probably would have to control your
inventory tighter than for Tin Lead (SnPb). If you have Nitrogen, then
save it for emergencies and use it as required. A potential thought
would be to use a Nitrogen Generator but I don't know if there are any
available that can support a reflow oven or wave soldering system. I
heard some rumors that there are but I have no first hand knowledge.
Hope this helps.
Good luck.
Lee Whiteman
Senior Manufacturing Engineer
American Competitiveness Institute
E-Mail: [log in to unmask]
Ph: (610) 362-1200 x208
Fax: (610) 362-1290
This message is for informational purposes only and does not supersede,
modify, or create any agreements with ACI. Information contained in this
message does not bind ACI or its affiliates to any commitment, either
express or implied, unless ratified in writing by an authorized
representative.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Neil Maloney
Sent: Wednesday, January 18, 2006 3:32 PM
To: [log in to unmask]
Subject: [TN] Time to fish or cut bait
Greetings, Technet!
My company is making the transition from leaded to lead -free assembly
in the US (we have already converted our overseas facility) Now we are
in the throes of the N2 vs. air battle. Our overseas unit uses air
only without any problems (ENIG boards, 0602s to QFPs, no BGAs) In
the US we are looking to start designing BGA and flip-chip assemblies
with the same type ENIG and Entek boards. We are buying a new 10 zone
reflow oven, and battle begins. Do we start with nitrogen or not? Can a
small company make lead-free BGA assemblies without going to an N2
atmosphere?
Does air make the process window too small for BGA?
Our smallest PCB is about 8x12cm.
Thanks in advance
Neil Maloney, Manufacturing Engineer
Contemporary Control Systems, inc
2431 Curtiss St Downers Grove, IL 60515
(630) 963-7070 x132
[log in to unmask]
http://www.ccontrols.com <http://www.ccontrols.com/>
http://www.ctrlink.com <http://www.ctrlink.com/>
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