Hi Gordon -
The JSTD-001 does use the word "shall" when referring to solder purity
maintenance requirements. The specifications states"....and machine
soldering shall be analyzed, replaced or replenished at a frequency to
ensure compliance to ...Table 5.1 or equivalent documented data..".
The copper levels do not always reach a steady state - I have seen
both extremes, one wave solder machine that needed changed every 7
months and one solder machine that was never dumped! The amount of
metallic contaminates that build up in the solder pot is dependent on
the type and quantity of assemblies you are running. Having too much
copper in your solder joints will lead to degradation of the solder
joint properties. The JSTD-001 gives you the ability to run your
process the way you want to without unnecessarily adding costs out of
routine. Check out "Solder Mechanics - A State Of the Art" by Frear,
Jones, Kinsman, ISBN0-87339-166-7, it has some good information on
copper influence.
Dave Hillman
Rockwell Collins
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Subject: Solder pot to allow removal of copper
Author: [log in to unmask] at ccmgw1
Date: 2/3/97 3:14 PM
Bob Mesick offered to design and get built a solder pot into which
solder which had become laden with copper could be transferred so as to
allow the copper-tin IMC to rise to the surface so that it could be
scooped out. If such a pot were to be built, then it seems to me that
it would be good to have something a little better than a ladle to
transfer the solder from pot 1 to pot 2 and back again. How about
including a pump with heated transfer line?
I am curious about the need for such a machine. First, how many
operations are there that keep the wave solder machine running so
consistently that it can't be "shut down" (i.e., not operated, so that
the solder can be allowed to sit just above its liquidus temperature)
for a day every so often?
Second, why does the copper have to be removed? Apart from the fact
that J-STD-001 sets a limit on the copper in Table 5-1, the worst that
can be said for the presence of the copper in the solder is that it
makes it look kind of funny. If ignored, the copper level in the
solder does not continue to rise but reaches a steady state, since
fresh solder must continue to be added to the pot. Excess copper in
the solder is not a defect per Table 11-1, and in this standard,
"'must' and 'shall' are used to emphasize characteristics that must be
considered during the development of the process control program"
(Para. 1.5). The way I read this sentence, if the process control
program has determined that copper in solder is not worth controlling,
it doesn't have to be.
Gordon Davy
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