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March 2013

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From:
Mike Fenner <[log in to unmask]>
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Date:
Thu, 14 Mar 2013 10:38:36 +0000
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HI Steve
It's fairly simple to at least approximate what you've got to do to get an
in spec alloy. It's just a matter of percentages.
Assuming you do have a 1800 lb pot and 200 lb of lead free alloy, and the
alloy is SAC305. 
.
At 0.5% cu, 200 Lb of SAC will give you 1lb of copper. In a 1800 lb pot that
will be 1/1800x100= 0.06% Cu
.
Same sums for tin and silver.
.
Then look at what you want to end up with.(0.63 x 1800 minus 186 of Sn you
already have = add 948 lb Sn and 666 lb Pb. Fortuitously that's around 1600
pounds of 60/40.
.
You would need to pump the machine for several hours to get an homogenous
mix and then re-analyse.
Given that the 200 lb is an estimate it may be advisable to count the amount
of alloy you are adding so you can redo the sums as you go/required, leaving
room for a correction.

Anyway you get the idea I hope.

Regards 
 
Mike Fenner 
Bonding Services & Products
M: +44 [0] 7810 526 317 
T: +44 [0] 1865 522 663

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Thursday, March 14, 2013 12:21 AM
To: [log in to unmask]
Subject: [TN] Extra Lead Free solder in wave solder pot...

Hi all!

My new employer has purchased a used Vitronics-Soltec 6622 wave solder
machine that supposedly still has 100-200 lbs. of lead free solder in the
pot because they were told that it was difficult to remove. My new employer
is intending for this wave to be run as a leaded machine.

So, what do you think about leaving that residual lead free solder in the
pot and just filling it up with 63/37? I haven't seen the machine yet (I've
yet to get to Boise), and I've never seen the inside of a empty -6622 wave
solder pot, so I don't know why it would be difficult to empty the pot
completely. I've always been able to get all of the solder out of all the
pots that I have ever emptied. Does it have immersion heaters that are
mounted in some sort of structure at the bottom of the pot that prevents all
of the solder from being removed?

I've been told that a sample of the solder that was left in the pot has been
sent to AIM solder for analysis, so we'll know exactly what it is. I know
that most lead free solders are mostly tin, so would it be just a matter of
adding extra lead to the pot to bring everything into compliance? 

I definitely plan on getting the solder analyzed once the pot is filled and
before any product is run, but I want to know if this is a bad idea? I don't
want to load up the pot with solder and learn later that the pot is
contaminated and has to be drained. Sorry for all the questions but I have
never taken a wave that has been run as a lead-free machine and then be
converted to a leaded machine...plus I'm not yet as familiar with the pot
and heater configuration of the Soltec-6622 machine as I would like to be. 

If it was the other way around (leaded ----> Lead-free) I wouldn't even be
thinking about it, NO WAY!

Steve

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