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Nitrogen used in selective soldering

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Nitrogen used in selective soldering | 22 January, 2015

I am curious to know how others are providing N2 for their lead free selective soldering process. If you are utilizing a nitrogen generator, is it a PSA type or Membrane type? I am trying to get a handle on nitrogen purity and what purity is necessary for lead free soldering.

At this point we are using a membrane N2 generator to 3 selective soldering stations but I fear we have severely overloaded the generator and degraded the purity of the N2. All responses are appreciated.

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Nitrogen used in selective soldering | 22 January, 2015

We are using a nitrogen generator (with a N2 storage tank) that feeds 1 selective solder machine. I do not know which type of generator it is.

The N2 generator has an oxygen analyzer on it. The selective solder manufacturer recommends a N2 purity (oxygen level) of <20ppm. We have found that our SS system works fine at purity levels up to 100ppm. Also, it is very important to be feeding the generator with clean, dry air. If the air is not dry, the generator has a much harder time getting the level down below 100ppm.

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Nitrogen used in selective soldering | 23 January, 2015

What are the continuing costs on the N2 generator? Is there replaceable media that needs to be monitored/replaced at regular intervals to maintain N2 generation?

We're currently using tank-supplied N2, but are just getting ready to fire up our selective solder for the first time. I know what the costs are to keep the tanks on hand and filled....wondering if a generator is a better option, and what kind of ROI I can get out of purchasing one. A quick Google search shows me that they ain't cheap :)

Thanks, ..rob

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Nitrogen used in selective soldering | 23 January, 2015

Per our selective solder provider, they recommend a PSA type generator to supply the needed 99.999% pure N2. The membrane type (which we have) does not provide the minimum (99.995%) purity necessary for lead free wave soldering. They happen to sell PSA type (of course) at approx. 18k per selective solder which will provide the purity @ 30 to 50 scfH @ 80 psi. I am told they are virtually maintenance free, depending quality of air from compressor.

I am bringing in a tank of 99.999% N2 as a comparison to hopefully prove out our need for high purity N2 and costs associated with it.

BTW, Rob, what is the cost of tank N2?

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Nitrogen used in selective soldering | 23 January, 2015

Our nitrogen generator and an air drying unit came with the selective solder machine when it was purchased new in 2008 as a package deal. We originally were feeding the system with air that was not properly dried. That lead to some maintenance costs on the drying unit. We are now properly drying the air (and filtering for oil) at the compressor end of our air system. The maintenance costs of the dryer unit have gone way down since then. We may not even need the dryer unit now but are leaving it on the front end of the generator.

As for the N2 generator, the hour meter shows it has run for 3619 hours. Over that time we have done nothing but feed electricity to it. When figuring out the ROI on N2 tanks, it is not only the cost of the tanks you need to consider. You also need to factor in a $$$ value for the time it takes someone to order/change out the tank for a new one. Then what happens if/when your tank runs out in the middle of running a job? All things to consider when using tanks that you don't have to mess with when you have a generator.

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Nitrogen used in selective soldering | 23 January, 2015


For the 300 cylinder (the largest Airgas sells), it's going to cost about $66/cylinder for the gas (plus delivery charges). They also charge a $99/year lease for the cylinder. Based on those costs, and a low-end N2 generator system that I found on-line, it's about a three year payback for the generator system. I do like, however, that the generator is on-demand, so, no tanks of N2 hanging around the shop.

We're just getting our SS up and running, so, I don't know the consumption rate yet, or have any guess as to how long a tank will last.

Of course, the ROI is not just the raw costs...but, since we're in start-up mode, it's the most important component at the moment :) Where can we put what money we have budgeted for capital equipment to the best use for the short term?

I think that an N2 generator may not be in my immediate future, but, it's definitely going on the wish list.


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Nitrogen used in selective soldering | 24 January, 2015

Liquid is significantly cheaper than compressed gas tanks if you are in continuous production.

Of course, it will eat your lunch if you're running things for a few days, then the machine sits idle for two weeks. It boils off whether you use it or not. But if you need a fair amount, liquid costs half to a third what compressed gas does. We've been running our selective off liquid nitrogen since 2012.

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