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January 2006

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TechNet E-Mail Forum <[log in to unmask]>, Neil Maloney <[log in to unmask]>
Date:
Wed, 18 Jan 2006 16:52:45 -0500
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TechNet E-Mail Forum <[log in to unmask]>, Lee Whiteman <[log in to unmask]>
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Lee Whiteman <[log in to unmask]>
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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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