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November 1998

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Tue, 17 Nov 1998 13:42:27 -0600
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Everything that's been said is right. I just wanted to talk to inert atmosphere as in using
nitrogen. Nearly all dross is eliminated using "the gas" and an extra large solder pot.

I bring this up because it has been an interesting experience working with my first Seho wave
soldering machine (model 2135). What a beast at 24' in length and 5 conveyor systems. At
first, I thought it was overkill. I probably still do in light of the demise of tin/lead
solder in the near future.

The machine uses a fairly tightly controlled tunnel in which nitrogen is injected as it is
directly into the solder pot (about 2 tons of it). Also, it is introduced to an ultrasonic
spray fluxer (possibly ideal for VOC free no-cleans).

Solder joints look good, though I only saw a few examples without proper profiling. Getting
back to dross reduction, the method used (blanket and direct injection into the solder pot)
really prevents dross - and that is easily understandable as no oxygen is present to form,
what else, oxides of tin and/or lead.

This is not an endorsement for this machine. It is a simple statement backing up what already
has been said. Minimize molten solder contact with oxygen (lower temperatures and pump speeds)
or shift to neutral as nitrogen (not as an after thought).

Earl Moon

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