Mark,

It is possible, as the density of the dross (SnCu) is greater than the
molten solder.  However, I have heard that lowering the pot temp and letting
it sit idle, can cause the "dross" to float, so you can skim.



Tom Braswell
Manufacturing Engineer
Fawn Electronics
6441 East NC 97
Elm City, NC 27822
Ph: (252) 977-8745
Fx: (252) 977-3477
Email: [log in to unmask]





-----Original Message-----
From: Leadfree [mailto:[log in to unmask]]On Behalf Of Boyd, Mark
Sent: Monday, March 07, 2005 10:58 AM
To: [log in to unmask]
Subject: [LF] Lead-Free Dross in Wave Solder systems


During the IPC conference in 2004, a couple class instructors mentioned that
dross formation in some types of lead-free wave solder system could form
dross that had a density greater than the molten solder - and would
therefore sink to the bottom of the pot, making dross skimming unmanageable.

My solder reps assure me that this is not the case in SAC solder, but that
there may be some intermetallics that would sink.

Has anyone encountered this?

     Thanks,
     Mark

          M Boyd
          Pelco Engineering
          www.pelco.com


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