Just a word of caution: You might also do an analysis on the "other"
chemistry in the solder pot. Over time other chemicals build up in the mix
(such as flux residues, and chemicals from melted "pookie" masking
materials, or other incidental elements) which can affect not only the
consistency of the solder, but the long term effects of the solder
junctions. Personal opinion is that most people think these "extra
chemicals" are burnt off/fumed out as the solder pot temperatures reach
around 500 degrees F. However, there are residuals that can exist at these
temperatures. The best (albeit somewhat costly) policy is to periodically
replace the solder in the pot, based on the build up of the "other"
chemistry and the changes in SnPb mix that you've stated below.
Lou does have a good point about the analysis process. It is sometimes hard
to get down to the 0.01% level.
And, my thanks to Ed Szpruch for begging the question: "What about the other
stuff?"
Dale Ritzen, CQA
Quality Manager
Austin Manufacturing Services
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Louis Hart
Sent: Wednesday, December 03, 2003 8:25 AM
To: [log in to unmask]
Subject: Re: [TN] SnPb Solder pot composition.
Yordan, I'll leave others to comment on solder joint quality and
reliability. How are the composition analyses done? I'd bet the
measurements are not truly good to 0.01%. I asked a big solder manufacturer
for measurement quality data 2 or 3 years ago, and did not get a good
answer. Lou Hart
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Yordan Venev
Sent: Wednesday, December 03, 2003 7:58 AM
To: [log in to unmask]
Subject: [TN] SnPb Solder pot composition.
We have made a composition analysis of our solder wave solder pot and
discovered a deviation of the SnPB content. The Sn percentage had gone up to
65.45% and the Pb content down to 34.54%. I suppose there will be a (small)
change in the constitutional behaviour of the alloy - some bigger range of
the liquid-to-solid stage. Except this, what should we be aware of in
practice in regards to solder joint quality and reliability? We continue to
maintain the pot temperature at 250 deg C (482 deg F).
Any inputs will be appreciated!
Best regards,
Yordan Venev
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