My opinion? For T3 applications it is difficult to justify the expense of nitrogen and probably for most T4. There is a visual difference, solder resists are not darkened for example, but generally you only notice on a side by side comparison. Possibly cleaning is simplified for similar reasons - a reduction in oxidative degradation of organics which in this case would be the flux. For sure with low or so called zero residue flux types, nitrogen is a process requirement. For some older no clean formulations there might be/have been some benefit. For Current no cleans pastes which leave around 50% (guide number) the presence or absence of oxygen above that amount of flux is not so significant. (Current lead free paste formulations and leaded products derived from them, are easily back in place on the "paste progress curve" after lagging from the Pb-free diversion). The downside of inerting apart from the material cost and extra process monitoring is that the surface tension of the solder can be effectively increased; this offsets any increase in spread, leading to an increase in probability of tombstoning. Not a good thing with lead free in particular as high tin alloys have a higher ST than Sn/Pb. There is any amount of papers on this topic available and I am sure your friendly paste supplier and wannabe supplier can send you their favourites. The savings can be very significant. Certainly you could at the very least use the published data to make a case to run a trial. In that you could run a series of test boards at increasing levels of oxygen to determine the max amount of oxygen permissible to maintain your desired quality levels. That would make sense anyway. The chances are high you would find approx 209,460PPM O2 is acceptable. :) Regards Mike -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Jim West Sent: Friday, May 02, 2014 6:50 PM To: [log in to unmask] Subject: [TN] Use of Nitrogen (reflow ovens) Good Friday all, Wondering how many out there, using both lead and lead-free solder, are using nitrogen with your reflow process? At a previous factory, we did not use nitrogen as part of our reflow process and where I'm working today, we use Nitrogen on all our lines. I had success without nitrogen and we are having success with nitrogen. At the APEX show, I spoke with at least one reflow oven manufacture about their oven and what they feel about the use of nitrogen and they pretty much said they are selling less ovens with nitrogen. To the point of 90%+ of their ovens are sold without the nitrogen option. As most know, nitrogen is very expensive and I would like to justify not using nitrogen in the future, but I have an uphill climb due to my parent company suggesting we use nitrogen based on a policy created over 7 years ago. Based on our product mix, I'm of the opinion we don't need nitrogen. What are your thoughts on using nitrogen with the reflow process? Has anyone gone through the process of eliminating the use of nitrogen and had success afterwards? Thanks, Jim ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________