Hi Steve -
     
     One possible explanation for your one solder pot to be low in tin is 
     the amount of drossing and/or drossing conditions that it has seen 
     since your last analysis. You will lose tin content from your solder 
     pot as part of the de-drossing operations. Since solder is more tin 
     than lead (ie. 63 tin - 37 lead) and tin preferentially oxidizes 
     versus lead, its almost logical that your dross will impact your tin 
     content to some level. Some testing results we gathered on our dross 
     content (for another reason entirely than low tin) confirmed that this 
     could be one contributor. You should probably check out what method of 
     solder alloy analysis was used too - what is the typical measurement 
     error for the analysis method and could it impact the number you are 
     getting reported as a result. Then again if you were cooking potatoes 
     or getting rid of solder paste on your solder pot then lots of strange 
     interactions could happen!!!! Good Luck.
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: ASSY: Low Tin Level in Wave Solder
Author:  [log in to unmask] at ccmgw1
Date:    1/3/97 2:19 PM


     
Good Day Everyone!
     
     We just got our solder analysis back (it's from a lab that everyone uses) 
for our wave solder pots, and we have one wave solder pot that's low in Tin... 
61.4% to be exact. The recommendation is to add 4.3 lbs. of pure Tin for each 
100 lbs. of solder to return it to the nominal 63%.
     
     My question is; just how in tarnation did we get one wave solder pot low on
Tin? It don't make sense...we use the same bar solder in all our machines, we 
wave solder basically the same kinds of products in all of our machines. By that
I mean we don't have one line waving only gold plated boards all the time, or 
only OSP coated PCB's all the time, etc.. so what gives?
     
     This is the very first time that I've ever had a solder analysis come back 
and tell me to put pure Tin into the pot...this is weird. I've had nickel get a 
little high before, but that's about it. We've got three machines and all of the
analysis looks like this:
     
     
                Pot-1           Pot-2           Pot-3
     
Tin             62.4%           61.4%           62.7% 
Lead            Balance         Balance         Balance 
Antimony       <0.005%         <0.005%         <0.005% 
Copper          0.039%          0.048%          0.033% 
Gold            0.017%         <0.003%         <0.003% 
Silver         <0.001%         <0.001%          0.002% 
Aluminum       <0.001%         <0.001%         <0.001% 
Arsenic        <0.010%         <0.010%         <0.010% 
Bismuth         0.001%          0.001%         <0.001% 
Cadmium        <0.001%         <0.001%         <0.001% 
Indium         <0.005%         <0.005%         <0.005% 
Iron           <0.003%         <0.003%         <0.003% 
Nickel          0.006%          0.005%          0.004% 
Zinc           <0.001%         <0.001%         <0.001%
     
     
The analysis was conducted according to specifications in IPC-S-815B. As you can
see, Pot-2 is the "slacker" tin-wise. The only noticable difference that I can 
see between the other two is that the copper content is just a tad higher...does
that have anything to do with anything? Looking at the tin content on the other 
two pots, they're just barely above the limit which is 62.4%-63.6%...is my bar 
solder vendor starting to get tight with the Tin? Any light that anybody can 
shed on this would be 'preciated...
     
                   __\/__
               .  / ^  _ \  .
               |\| (o)(o) |/|
     #------.OOOo----oo----oOOO.-----#
     #          Steve Gregory        #
     #      SMT Process Engineer     #
     #  The SMT Centre Incorporated  #
     #   [log in to unmask]   #
     #________________Oooo.__________#
               .oooO  (   )
               (   )   ) /
                \ (   (_/
                 \_)
     
     
*************************************************************************** 
* TechNet mail list is provided as a service by IPC using SmartList v3.05 * 
*************************************************************************** 
* To unsubscribe from this list at any time, send a message to:           * 
* [log in to unmask] with <subject: unsubscribe> and no text.        * 
*************************************************************************** 
* If you are having a problem with the IPC TechNet forum please contact   * 
* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask]      * 
***************************************************************************
     

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************
* If you are having a problem with the IPC TechNet forum please contact   *
* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask]      *
***************************************************************************