Steve,

There has been a renewed interest in nitrogen at the reflow process.  Much
of this has been the increase in sandwich solder joints as seen with BGA
technology.  More oxides in the oven create greater flux activation and more
outgassing.  Some folks have done research that points towards a 180-200ppm
level in reflow to reduce BGA voiding.
Other than reduction in voiding, the effects of nitrogen are very much a
subject of discussion among production.  Some parts of questionable
solderability (perhaps old parts with quite a bit of oxidation) can benefit
from nitrogen.  Nitrogen is a good safety net for BGAs because when you look
at the area that the flux must clean on the ball and pad, the surface area
is probably 3 times greater than that of a QFP lead and pad.

If you are not getting into BGA technology, or some old no clean paste that
requires an inert atmosphere, then I am not sure if there will be a major
benefit- hence, breaching 180ppm would not be that much of a problem for
you.

Hope this helps.

Steve A

> -----Original Message-----
> From: Shoda, Steve [SMTP:[log in to unmask]]
> Sent: Friday,August 31,2001 9:51 AM
> To:   [log in to unmask]
> Subject:      [TN] Nitrogen Purity for SMT IR Reflow
>
> Our facility is considering changing from stored liquid nitrogen at
> 99.9999%
> purity to onsite generated at 99.5% purity (5000ppm impure).  Our reflow
> manufacturer recommends a maximum of 180ppm oxygen in the nitrogen
> environment.   What problems could occur if the 180ppm level is breached?
> What maximum impurity levels have been observed without any adverse
> effects?
>
> Thanks in advance for your inputs.
>
> Steve Shoda
> BAE SYSTEMS Controls
> Fort Wayne, IN
>
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