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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

Nitrogen to use or not to use

Chuck Morehouse


Nitrogen to use or not to use | 16 December, 1999

Have any of you ever gone from using Nitrogen in your Reflow and Wave solder process to using only compressed air? No Clean users only please. I'd like to get away from Nitrogen if it makes sense.

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Mike Naddra


Re: Nitrogen to use or not to use | 16 December, 1999

At reflow an inert atmosphere is used to mitigate the occurance of oxidation, to me the decision weather to move from an inert atmosphere is based on several things ; PCB surface finish - are you using a HASL finish, OSP or another surface finish and what are the characteristics of that finish. What is the Solids content of the solder paste you are using. Does the board go through a duble sided reflow. My expierence has been that when using boards with a HASL surface finish and a solder paste with moderate solids content I can produce to IPC standards with an air atmosphere. FPY remain good and solder wetting looks good. I have found that when I am using an OSP and solder paste with low solids content that the inert atmosphere signifigantly improved my FPY and greatly improved my ppm solder defect rate. The inert atmosphere improved solder wetting , this was most evidant on the second side (my process is a double sided reflow). Inert atmosphere or air atmosphere - the decision really depends on the Product , Process and materials involved.

Regards, Mike

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Re: Nitrogen to use or not to use | 16 December, 1999

Hi, I am new on this, I want to ask you what is HASL finish, OSP, FPY, ppm. About to eliminate the Nitrogen in reflow soldering, a listen about one solder paste that no requires Nitrogen, the solder paste is called Indium, I don't know if this is true, can anyone give more information please.

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Re: Nitrogen to use or not to use | 17 December, 1999

Hi Chuck, let�s say it the other way round. We use noclean since I can�t even remember without nitrogen and all of our subcons do with no known problems. The processes are adapted to it and no complaints are heard up to now. That is related to our products and customer requirements. I know about the better wetting and prevention of reoxidation but I would consider it only if there were no other solution and there always was. The only case our products were soldered under nitrogen atmosphere by one subcon there were no noticable differences exept for more solderballs caused by wavesoldering. They said they knew the problem and were working on it. For rework I like to use nitrogen, it makes the things somewhat easier. I think you must find out for yourself.

Good luck


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Nancy V


Re: Nitrogen to use or not to use | 21 December, 1999


Go to the library on SMTnet and you will see Standard and Terms. Select that and you will be able to download the terms and definitions for SMT assembly. It is very useful. Of the terms you requested, only FPY is not there. I was curious about that one myself. HASL: Hot Air Solder Leveled OSP: Organic Solder Preservative (definition on list) ppm: parts per million

Hope that helps.


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