dear green,
good questions.  copper accumulates in the HAL solder pot much faster than
most realize.  the accepted level of copper by weight is .3
above this is not a drop dead zone, but above this level you will need to raise the
pot temperature to keep the higher concentration is solution.  as long as you maintain
a temperature the same or lower than the assembly temps, you should have no problem.

im sure by now you have seen the grainy condition resulting from too much copper
in solution at a given temp.   drossing the pot, as you mention is very effective in
reducing cu concentrations when done properly.  the key is good heaters and controls
that can maintain the transition temp for a sustained time.  for eutectic sn63, its
183c or 361f.  youll need a little more because of the copper. like 370f approx. but
you must let it rest at that temp for an hour.  collecting the tin coated cu dendrites
is like fishing for hair balls.  you'll find that the cu migrates to itself in clouds.
your recovery rate will vary or course depending on the quantity of product you run
daily.    the only other contaminant to keep track of is gold.  but, it takes a bunch
to create an issue.

hope this helps,
for specific info, contact me direct.

Mark Simmons, Vscore Central



Julie Dixon wrote:

> TechNet,
>
> We have sporadic problems with the copper level rising in our solder pot. We
> reduce the temp and dross each morning. Could you recommend a specific PM
> program to keep our SnPb clean? We believe per the certicates of analyses
> that
> our supplier gives us good product. Any other reasons it might rise?
>
> Thanks,
> Green
>
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