Hi Brian,

Here at Heraeus we also produce Nitrogen Reflow ovens that go to very low
purity levels with very little N2 consumption.  (a shameless plug for my
company =-)  To answer your question they will be able to reach whatever
purity level their gas is spec'ed at as long as they are willing to pay for
it in total nitrogen consumption.

Simply put, the spec residual oxygen level will be dependent on the
internal (relative) positive pressure of the gas inside the process
chamber.  Specific formulas for consumption depend on oven design so it is
best to use empirical data - i.e. run experiments.  But if they crank up
the internal pressure they will be able to reach those levels but they will
have to pay for it, and prices of Nitrogen in Asia are quite expensive.

On another note, your customer will also have fluctuating levels of
residual oxygen along the length (and width for that matter) of the process
chamber.  This situation depends on your configuration for feeding nitrogen
into the process chamber.  So, if your customer has concerns about
reliability of a steady residual oxygen level throughout the entire process
chamber this could be a problem.  Our reflow oven has a patented system
that solves that problem - but that's another story (ok, that was the final
shameless plug).

Hope this helps

Doug Bennett
Sales Engineer
Heraeus Amersil, Inc.
Atlanta, Georgia
770-623-5630 ext 4225


At 04:48 PM 4/27/98 -0700, you wrote:
>Dear Technet,
>
>My company builds reflow ovens that are capable of processing in a Nitrogen
>(N2) atmosphere. We are getting ready to send an N2 machine to a customer in
>Asia. While preparing for the installation our customer found that his
>source N2 has 25 - 30 PPM of Oxygen (O2). At our factory we have source N2
>that is 99.999% pure or has 1-3 PPM of O2. With this source purity level we
>are able to acheive less than 20 PPM of O2 in the process cavity. With this
>in mind what purity level should our Asian customer be able to acheive with
>his source of 25 - 30 PPM?
>
>Is there a relationship between source N2 and process cavity purity levels
>at constant flow rates? Does it have something to do with the expansion
>rates of these gases during heating?
>
>Thanks in advance for all replies.
>
>Brian Stumm
>
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