There are nice examples of the differences in BGA spheres soldered in
nitrogen and air in IPC 7095, if you need documentation to prove your
point. They are shown in section 9.6.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Wednesday, January 18, 2006 3:08 PM
To: [log in to unmask]
Subject: Re: [TN] Time to fish or cut bait
You can, but with a higher DPMO. Nitrogen reduces the ability to form
oxides that prevent wetting just prior and during reflow. Without it,
and especially at higher temperatures with alloys that are more
resistant to wetting than 63/37, the difference becomes greater,
especially on BGAs.
The price of the nitrogen option is usually not a great amount. I would
recommend buying it with the capability to do so.
You may need every weapon you can find in your arsenal to promote
wetting to the outer edges of the pads, and being able to get solder to
fully flow over the terminations using the Pb-free alloys.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Neil Maloney
Sent: Wednesday, January 18, 2006 2:32 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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