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When to use Nitrogen in SMT Wave Soldering

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    This video is for electronics assemblers who currently or are considering using nitrogen during their processes. It includes details regarding when nitrogen should be used.
     
    Phil Zarrow: Dr. Lasky, you and I know that one of the ongoing issues in soldering and surface mount through hole has been the use of nitrogen. First of all, is it really needed? Does it add anything to the process? At the same time, the economics of it, it is an additional cost to the process. I seem to recall there was an episode in The Adventures of Patty and the Professor, where they encountered this issue.
     
    Dr. Ronald C. Lasky: You know Phil, this is one of the more comical stories in Patty and the Professor, and absolutely based on a true situation. Patty arrives at the facility. She's walking past a reflow oven, and she notices what look like stalactites hanging from the ceiling. What had happened is, the flux had condensed from the reflow oven, and dust had collected on that, and it was never cleaned. She asked her host about this, and he said that management had done a financial analysis, and it determined that cleaning did not pay financially, so they did not clean the facility at all, which was obvious. There was dust on the floor, and paper, and everything, but they didn't… Even the restrooms; they counted on the workers to do that. It was one of the more comical Patty and the Professor episodes.
     
    Phil Zarrow: Talk about a lack of industrial hygiene, if you will.
     
    Dr. Ronald C. Lasky: Right.
     
    Phil Zarrow: What about the nitrogen has a fold in this issue?
     
    Dr. Ronald C. Lasky: One of the things, Phil, in reflow, customers should be able to demand of their solder paste suppliers that nitrogen not be needed. If your solder paste supplier said, "Well, you probably should use nitrogen," you probably should be going to a different solder paste supplier, because modern solder paste shouldn't need nitrogen in the reflow process. But, wave soldering is a different animal. I found in most cases nitrogen really helps. There may be some cases where it's not needed, but nitrogen really helps. In this situation, what happened is management had just decided that they didn't want to pay for nitrogen any more, so they turned the nitrogen off in the wave solder process. I'll bet you can guess what happened.
     
    Phil Zarrow: Yes.
     
    Dr. Ronald C. Lasky: The first patch yield went from 95% to 80%. The lesson here is that you should never make a move like this without doing some sort of designed experiment, or something, to show that you could get successful yield without using nitrogen.
     
    Phil Zarrow: Where can we find the complete story of this?
     
    Dr. Ronald C. Lasky: The full story is chronicled in Patty and the Professor on page 33. If you don't have a copy of Patty and the Professor, you can download it on www.indium.com.
     
    Phil Zarrow: Pretty good. Dr. Lasky, thank you.

     

    Keywords: indium, Indium Corporation, Dr. Ron Lasky, ronlasky@aol.com, Phil Zarrow, itm@itmconsulting.org,  wave soldering, nitrogen, surface mount, reflow, solder paste

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