Hi Ramon,

A good reflow oven is designed in such a way that there's very little
mixing with ambient air, depending of course on the amount of nitrogen
that's going in.  With cryogenic nitrogen you should be able to achieve
levels below 100 ppm O2 in the reflow zone.
If the nitrogen sole purpose is to open up the process window then this
may be of lesser importance, but to prevent oxidation and keep
solderability of OSP boards it's the ppm-level of O2 that can (according
to literature) make the difference between succes and failure.
And 0.5% is a lot of ppm's !!

Daan Terstegge
Thales Communications
Unclassified mail
Personal Website: http://www.smtinfo.net

>>> [log in to unmask] 03/10/04 01:57pm >>>
        Dave:
                For wave soldering and reflow oven  the 99.5 % would be
more
than necessary. Ambient air which is about 40 percent O2 is all around
the
machine and very quickly will mix with the injected N2. If it was for
a
close chamber such as it is used on semiconductor fabs, then it would
make a
difference if O2 was not desirable in a particular process. Your
decision
should be based on what is more economical.
        Regards,
        Ramon

> -----Original Message-----
> From: Dave Hillman [SMTP:[log in to unmask]]
> Sent: Tuesday, March 09, 2004 1:00 PM
> To:   [log in to unmask]
> Subject:      [TN] Nitrogen Purity Question/Survey
>
> Hi folks! Question for those folks using nitrogen for an inert
atmosphere
> in their reflow processes or as a blanket gas on their wave solder
> processes. Cryogenic nitrogen is typically 99.998% purity (in terms
of O2
> content). On-site nitrogen generation equipment can deliver N2 gas
ranging
> from 99.5% to 99.99% purity (again, in terms of O2 content). What
gas
> purity level are you using in your processes and do you have a
rationale
> for selecting that purity level?  The reason for the question is that
I am
> involved in an exercise of comparing on-site nitrogen generation
versus
> cryogenic nitrogen supplies.
>
> Thanks in advance for you assistance.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
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