From: Rob Borenstein
Subject: Re: ASSY: Low Tin Level in Wave Solder

Greetings Techneters,

Could someone please explain the adverse effects of having a solder pot
slightly skewed from the eutectic point, as is the case with Steve's pot-2?
Do we get bridging, insufficient barrel fill, cold solder joints? Has anyone
correlated an increase in wave fallout to solder pot metallurgy?

Thanks in advance,


 Date: 03 Jan 97 16:32:11 -0500
 From: "Aric Parr" <[log in to unmask]>
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 Subject: Re: ASSY: Low Tin Level in Wave Solder
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      Tin oxidizes faster than lead. This means that dross has a higher tin
      content than the solder in the pot.

      In a previous job, with a very high dross machine, we regularly added
      tin to the bath.

      Have the dross production and dross composition from that machine
      checked and compare it with that of the other machines. The tin is
      probably coming from the dross.

      High antimony alloys were used to reduce this differential. I notice
      that you are using an antimony free alloy.


 ______________________________ Reply Separator
 _________________________________
 Subject: ASSY: Low Tin Level in Wave Solder
 Author:  [log in to unmask] at internet
 Date:    1/3/97 3:41 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  (   )
                (   )   ) /
                 \ (   (_/
                  \_)


Robert Borenstein                          Phone:(416) 448-5607
Dept 110, Celestica                        Fax:  (416) 448-4736
Process Engineering            Internet: [log in to unmask]

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