Hi Folks!
    I tend to agree with Dave.  The moisture in the potatoes is
most likely causing the dross and not pushing any existing
dross to the surface.  I have seen instances where a fairly
significant amount of dross was circulating up through the
solder wave and forming inclusions in the solder joints.  The
cause was an area of turbulence on the solder surface
adjacent to the impeller shaft.  As that turbulence caused
small pieces of dross to submerge, the down draft of the
impeller sometimes caught those pieces and circulated them
through the solder chimney and nozzles. 

Jon Moore
TRW
Marshall , IL

>>> ddhillma <[log in to unmask]> 12/13/96
09:46am >>>
     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
     [log in to unmask]
     


______________________________ Reply Separator
_________________________________
Subject: Assy: Cleaning solder pot
Author:  [log in to unmask] at ccmgw1
Date:    12/13/96 2:16 AM


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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