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Subject:
From:
Steve Gregory <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steve Gregory <[log in to unmask]>
Date:
Fri, 15 Mar 2013 14:13:39 -0400
Content-Type:
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Hi again,

Still trying to understand why the different ranges of the recommended 
levels of added tin between all the formulas to bring the tin level back to 
63%.

I'm really confused why the AIM formula says we only need 14, but all the 
other formulas are up around 37 - 39 pounds...

Can somebody please help this confused soul?

Steve

-----Original Message----- 
From: Steve Gregory
Sent: Friday, March 15, 2013 10:33 AM
To: [log in to unmask]
Subject: Re: [TN] Low Tin Levels in wave solder pot...

Hi Dave,

I've got the handbook and I'm trying to make sense of the calculations:

Case 1: Solder pot mass constant. (i.e., solder is removed and replaced by
new solder/tin)

            Mp (Sn%d - Sn%c)
Mt_a= ------------------------
               (Sn%a - Sn%c)

Case 2: Solder pot mass increases with added solder or tin

          Mp (Sn%d - Sn%c)
Mt_a= ------------------------
               (Sn%a - Sn%d)

And if I do this above, I get 39.75 lbs

Mt_a = The mass of tin to be added to the solder pot.
Mp    = The mass of solder pot (prior to addition).
Sn%d = The tin content desired in the solder pot (% by weight)
Sn%c = The tin content currently in the solder pot (% by weight)
Sn%a = The tin content in solder or tin bar used for addition (e.g. 100 for
pure tin bar)

So if I do case 1 above with a 500 lb pot, I get 37.16 lbs with an existing
tin content of 60.25% and want to bring it up to 63%,  and I will have to
remove the same amount of solder before I add the tin if I want to stay at
500 lbs, right?

Steve

-----Original Message----- 
From: David D. Hillman
Sent: Friday, March 15, 2013 7:38 AM
To: [log in to unmask]
Subject: Re: [TN] Low Tin Levels in wave solder pot...

Hi team - and just an additional comment. The IPC JSTD-001 Handbook has a
complete explanation and lists both formulas in section 5.3.7 Tin
Depletion with much better detail than what was on either the Kester or
AIM weblinks. Yu-Shan Han's explanation/differentiation is contained in
the 001 Handbook section.

Dave Hillman
Rockwell Collins
[log in to unmask]




From:   Yu-Shan Han <[log in to unmask]>
To:     <[log in to unmask]>
Date:   03/14/2013 10:27 PM
Subject:        Re: [TN] Low Tin Levels in wave solder pot...
Sent by:        TechNet <[log in to unmask]>



Hi Steve, Your equation and Kester's formula are exactly the same, just
different arrangements.  Use your equation you should also get 37.16  lb,
not 39.86. The AIM calculations assume that you have to first remove some
solder to make room for the addition (in this case, approximately 15.8
lb),  Since the pot volume stays the same, 13.75 lb tin is all you need,
and 2.05 ib bar solder to top off the pot. Yu-Shan Han

> Date: Thu, 14 Mar 2013 18:56:54 -0400
> From: [log in to unmask]
> Subject: [TN] Low Tin Levels in wave solder pot...
> To: [log in to unmask]
>
> Hi All,
>
> I know this is an old question, and I forgot exactly how to determine
how much tin you should add to a wave solder pot when the tin gets low.
The existing wave solder machine at my new employer that they have now has
a 500-lb pot, and the last analysis that was done had the solder at:
60.25% Sn / 39.61% Pb, everything else was within limits. Obviously the
tin content needs to be corrected.
>
> I talked to my old buddy Ed Popielarski about this and he referenced me
to a link from Kester that has the calculation at this link at the bottom
of the page. According to this formula, I need to add around 37.16 lbs of
tin to the pot:
>
> http://www.galco.com/techdoc/kstr/14-6337-0027_td.pdf
>
> Then AIM solder has this calculation at the bottom of the page at this
link. This one says I?ll need to add around 14 lbs. of tin:
>
> http://www.advprecision.com/pdf/Solder_Pot_Maintenance.pdf
>
> And Indium offered this formula to my boss (it?s a cut and paste from a
email that he forwarded to me), which I?m having a hard time following
(but I can be dense sometimes), I don?t see how they came up with the
39.86 lb figure:
>
> I did a quick calculation. If you have a 500 lb. pot and the tin level
is at 60.25%, you want to add 39.86 lbs. of tin to bring it back to 63%.
>
> Here is the equation I always use: let assume you need to add X:
>
> (500*0.6025 + X)÷(500+X) = 0.63
>
> X=39.86
>
> So I wonder why the discrepancies between the solder mfg formulas? The
tin content that they say I should add ranges from around 14 ? 40 lbs. Can
anybody help refresh this old geezers mind?
>
> Steve
>
>
>
>
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