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Hi all, A colleague of mine had spoken with our soldering tin contractor about cleaning the solder pot. We had a theory that dross is floating beneath the surface but not at the bottom of the solder pot. The question was in how get them out. The contractors chemist had a theory which he had not tried himself but recommended it. He said: "Make somekind of skewer to attach four potatos in a row. The moisture in the potato will evaporate in the solder pot and make small bubbles which will push up the dross from the pot". We tried it and god(!!) what a reaction. We let them stay in the pot for about half an hour and sure got up some dross. WOW! The whole solderpot surface was covered by it. So now i'm wondering, does organic stuff like potato leave anything in the pot which will affect the quality in any way?? Has anyone tried anything similar? (probably not!) Dave, SIRguru any comments?

/Jan Merstrand

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Good Morning Jan!

Wow! Well I'm glad you tried it because I'm too chicken! The first rule they taught us in metallurgy school is that molten metal and water is a BAD combination. I would be a bit leery of the moisture in a potato initiating an explosion. Dross is typically oxides and other contaminates that are less dense than the solder alloy itself and so dross floats on the surface of a solder pot. Because of this density difference dross shouldn't be throughout your solder pot unless the wave pumping action pulls some around. Dross is also very abrasive so the wave solder equipment manufacturers don't want dross anywhere but at the top of the solder pot. There are chemical additives that can be used to "de-dross" a solder pot but I don't think they are potato based. My guess is that all the dross that accumulated in the half hour was generated because of the potatoes themselves. Sometimes dross sinks just below the surface of a solder pot because it's not pure dross - it contains small chunks of solder thus making it heavier. Maybe the TechNet chemists can help out.

Dave Hillman
Rockwell Collins
HYPERLINK mailto:ddhillma@cacd.rockwell.com ddhillma@cacd.rockwell.com