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From:
Dave Hillman <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 4 Dec 2003 13:40:12 -0600
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Oh bumbles! Its that complicated math that always messes me up! Wait,
weight percent is in metric right? That's my excuse - I am metrically
impaired! No wonder I lose more tin in my solder wave with an extra 4%!

Guess I better switch to Mt. Dew!

Dave


                                                                       
                      Doug Pauls                                       
                      <dopauls@rockwellc        To:       [log in to unmask]
                      ollins.com>               cc:                    
                      Sent by: TechNet          Subject:  Re: [TN] SnPb Solder pot composition
                      <[log in to unmask]>                                
                                                                       
                                                                       
                      12/04/2003 01:28                                 
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                      Please respond to                                
                      "TechNet E-Mail                                  
                      Forum."; Please                                  
                      respond to dopauls                               
                                                                       
                                                                       




Sasha,
Dave is a superior metallurgist.  We never knew just how superior he was
until he came up with an alloy that is 104%.  Dave, is it a company
proprietary process that produces this 64 Sn/40Pb alloy?

Four Diet Cokes and he is STILL not awake........

Doug Pauls




                      Dave Hillman
                      <ddhillma@rockwellc        To:       [log in to unmask]
                      ollins.com>                cc:
                      Sent by: TechNet           Subject:  Re: [TN] SnPb
Solder pot composition
                      <[log in to unmask]>


                      12/04/2003 01:12 PM
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Hi Sasha! The tin composition of your wave solder bath is preferentially
depleted because of two factors: a) Sn preferentially oxidizes in
comparison to Pb so the wave solder dross is has a much higher Sn
percentage than Pb percentage (this is the dominate loss mechanism); b)  If
you are using 64Sn/40Pb, you are using more tin in every solder joint than
lead and tin forms an intermetallic with the copper pwb pads whereas lead
does not. The JSTD-001 Handbook conveniently lists the Tin Depletion
replenishment formulas (page 62 in the 001 Handbook with amendment
revision).

Dave Hillman
Rockwell Collins
[log in to unmask]




                      Sasha Miladinovic
                      <sasha.miladinovic@AM        To:
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                      ERSHAM.COM>                  cc:
                      Sent by: TechNet             Subject:  Re: [TN] SnPb
Solder pot composition
                      <[log in to unmask]>


                      12/04/2003 12:17 PM
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                      Forum."; Please
                      respond to Sasha
                      Miladinovic






Ed,

I like Your declaration about "cold" joints... :) I had a minor war i a
earlier life with a Q-department about the definition.. :)

I'm not sure it any of us is right or wrong, but why would be Tin that
drops?
Isn't it density and temparature that is the governing factors in this
case?

Enyone outthere that can explain this? :)

*************************************************************************
Sasha Miladinovic - Production Engineering
Amersham Biosciences, PCB Production, Umeå
Tel:      +46 (0) 90 150 232
Fax:     +46 (0) 90 138 372
E-mail: [log in to unmask]
*************************************************************************





Ed Popielarski <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
2003-12-04 18:40
Please respond to "TechNet E-Mail Forum."; Please respond to Ed
Popielarski


        To:     [log in to unmask]
        cc:
        Subject:        Re: [TN] SnPb Solder pot composition


Yordan,

Deviation from 63/37 can cause increased solder shorts in a wave soldering
machine. At 63/37 (eutectic) the melt point is minimum, and there is no
plasticus range. As you drift from there the melt point increases and the
plastic range increases. This is why hand solder is preferred at 60/40...
there IS plastic range and makes it easier to judge the joint as you
solder.
This is also the main cause of "frosty" joints (I hate to say "cold" since
it is a very inaccurate term).

Another thought to add to the mix is the accuracy of the lab. I recommend
using either Alpha Metals or Kester to do the analysis (Type C which is
the
"whole enchilada" variety) and perhaps to rule out other variables
discussed
in other's postings, take a few samples, from the static part of the pot,
from the wave after running at temperature, etc. If all the samples come
back relatively the same, then you are good to go, but if one or two stand
out, there could be something worth looking into.

Additionally, (yes, another variable) the tin  is usually the element that
drops, not the lead. This has me wondering as well. Why?

Have a safe and happy holiday!

Regards,

Ed Popielarski
QTA Machine
27291 Jardines
Mission Viejo, Ca. 92692

Phone:949-581-6601
Fax: 949-581-2448
Cel: 949-337-2578

WWW.QTA.NET

"Thank God for America...
before it's too late!"

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