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Nitrogen in the Reflow Oven

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Nitrogen in the Reflow Oven | 8 October, 2013

I'm looking for evidence to support, or disprove, the use of Nitrogen in the reflow oven. I've heard many arguments on both sides. I have my own personal opinion. But I'm looking for scientific studies or white papers, specifically addressing the benefits of the use of nitrogen.

Has anybody seen anything? (I'd prefer to find papers NOT written by Nitrogen or Reflow Oven Manufacturers)

Thanks in advance!

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Nitrogen in the Reflow Oven | 8 October, 2013

Here's something from Indium that I had saved...


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Nitrogen in the Reflow Oven | 8 October, 2013

Thanks Phil!

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Nitrogen in the Reflow Oven | 11 October, 2013

I think the critical item is that you are soldering in a reduced oxy environment, lowering the rate of ongoing oxidation. Heat accelerates oxidation, lack of oxygen (of course) slows it down.

The 10 Nitrogen soldering "myths" seem to be more like "10 things that perople don't really understand about Low oxygen soldering."

No dis-respect intended for either Phil S or Indium.


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Nitrogen in the Reflow Oven | 14 October, 2013

Thanks 'hege for the info. Have you seen a reduction in solder defects after switching from Air Reflow to N2 Reflow?

I'm curious, because in my experience of over 20 years, working at five different companies, (Jabil being one of them), I've never used N2 in the reflow until I landed at my present company. I haven't had any solder issues that I could attribute to oxidation in the reflow.

I'm certainly trying to keep an open mind, but I'm having a hard time trying to see a cost justification of reflow soldering in an N2 environment for my product.

I could understand if we were manufacturing complex, safety, aerospace, or medical assemblies. But with my automotive "peanut butter and jelly" assemblies, I just don't see the Bang for the Buck.

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Nitrogen in the Reflow Oven | 14 October, 2013

We do in fact see a reduction in soldering defects, most especially wetting issues for both parts and PWBs, tombstones, billboards, etc...

As a CM we see all kinds of customer furnished material, some of it not in the greatest condition. Our best preventative and mitigator of potential defects has been the relatively inert environment of the Nitrogen reflow.

I can run the same setup side by side with questionable parts, put one set through normal reflow oven, and the other through the Nitrogen. Without fail the N02 board will have WAY less solderability defects.

In our philosophy, better to prevent rework whenever possible. This is a path by which we feel like we have a good chance of success, even with possibly marginal parts. For that reason we maintain multiple N02 Lines, and will add more as time goes on.

ROI chasing Solder Defects related to oxidation during reflow might be too far out for consideration, I agree, but since removal of oxides is part of (all)our process, prevention and retardation of oxidation would be of some help too. We are pro-active that way. Lucky for me.

Added side benefit, lead free solder actually start to look shiny, closer to good old Sn63.


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Nitrogen in the Reflow Oven | 15 October, 2013

Another benefit to low O2 levels with Pb Free is increased mobility of the alloy during soldering. It is an effective mobility enhancement in reflow as in wave soldering.

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Nitrogen in the Reflow Oven | 16 October, 2013

Thanks guys.

I can see the benefit as a CM, when you have no control over the Parts/PCBs that come in the back door. In my previous job at a CM I did often have product coming in the back door that did appear to have exceeded its shelf life, and having an N2 process to help deal with oxidized parts/PCBs would have been beneficial.

As far as mobility, I don't have issues with wetting, and my part placement has been pretty accurate, so I don't really have a need to depend on mobility of solder to properly wet or to "pull" parts back on pad that have been misplaced.

I do appreciate all of the assistance. It has helped to affirm my beliefs that Nitrogen in the Reflow, though may be beneficial in some applications, isn't a necessity as long as proper design/process rules are followed, and the assemblies being manufactured don't require an extremely narrow process window.

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Nitrogen in the Reflow Oven | 16 October, 2013

Your 3rd paragraph hits it on the head, Frazz. Especially with regards to the narrow process window.

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