Mr. Anderson (Sorry, I could not help myself),
I'm in total agreement with my colleagues. Get some aluminum bread pans
and very slowly empty the solder pot contents into the pans. Depending
upon the size of the solder pot, this could take up to 8 hours (trust
me). Wear plenty of safety equipment. From my personal experience, we
found little to no aluminum in the solder after it was drained. Using
the bottom drain can be done, but it will require 2-3 people to
coordinate the effort to perform this operation safely. If you don't
have good people who can work together, then scoop it out into the pans.
If you are converting to a Lead Free solder, there are a few things to
remember. First, the solder pot will degrade if it is not finished with
a protective coating due to the high tin content of Lead Free solder
alloys. There is a great picture of a solder pot and its fixtures
(website: http://www.twi.co.uk/j32k/unprotected/band_1/elec_nl3.html) of
what could happen if you use a tin lead solder pot with Lead Free
solders.
Keep in mind that you have to keep the Tin Lead (SnPb) bar stock away
from the Lead Free solder pot. At my facility, where we have a SnCu wave
soldering capability, we keep the SnPb solder labelled and away from the
wave solder machine when we are building Lead Free hardware. On a 800
pound solder pot, 2 bars of Tin Lead (SnPb)solder can contaminate the
solder pot sufficiently to above the 0.1% UCL defined by the RoHS
Directive.
Which leads to another point. To assure that you have no Lead (Pb)
residue in the pot, you may have to fill the pot with pure Tin (Sn) to
purge the pot of any remaining Lead (Pb). I have heard that some solder
manufacturers will do this as a service but I have not investigated it.
Most folks I know are getting new solder pots for their wave solder
systems and are installing the Lead Free Solder in the new pot. With a
few heavy duty carts and a good electrician, you can make this a quick
modular switch between Tin Lead Wave Soldering and Lead Free Wave
Soldering.
Hope this helps.
Good Luck.
Lee Whiteman
Senior Manufacturing Engineer
American Competitiveness Institute
E-Mail: [log in to unmask]
Ph: (610) 362-1200 x208
Fax: (610) 362-1290
This message is for informational purposes only and does not supersede,
modify, or create any agreements with ACI. Information contained in this
message does not bind ACI or its affiliates to any commitment, either
express or implied, unless ratified in writing by an authorized
representative.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Anderson, Greg (GE
Infrastructure)
Sent: Wednesday, April 13, 2005 3:27 PM
To: [log in to unmask]
Subject: [TN] Wave Solder Pot Draining Best Practices
TechNet:
We are going to drain and clean a wave solder pot in preparation for
conversion to lead-free solder.
We have not completely purged a wave solder pot in some time, and the
people in the know have moved on.
Does anyone have "best practices" recommendations for draining and
handling the solder (other than BE VERY CAREFUL ! ) ?
Greg Anderson
GE Fanuc Automation
Charlottesville, VA
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