Hello Yordan,
There are few more things to consider...
I've seen that some of the replays U got, already have pin-pointed some of
the issues... There is actually nothing wrong with 65,45:34,54 ratio
First.... As Edward and Dale already said, it seems that the analyses is
not done with a professional approach and U are not aware of the
contamination level in the bath...
Secondly, there is a phenomenon in the solder bath that needs to be
considered when taking a sample...
The density of Pb and Sn are significantly different... And if I assume
that U have a large soldering pot and the frequency of use is low, U can
get phenomena where Pb and Sn separate partially meaning that the
composition on the top of the pot involves more Sn then on the bottom of
the bath where U get larger amount of Pb molecules...
Alloy needs to be disturbed to restore SnPb ratio evenly in the bath...
That's why U should let soldering wave pump around the solder for some
time before soldering and before taking a solder sample....
I assume that the sample is taken from the surface from the soldering bath
and that could explain the higher level of Sn in the result U got from
analysis...
If my assumptions are right, I would suggest that U repeat the sample
analysis and disturb the bath before taking a sample...
Then, send it to someone that would make a serious analysis....
And if the ratio still bothers U, U can simply restore it by adding pure
Lead or pure Tin... No advanced calculations needed here...
Ratio between Pb and Sn are generally not a problem that gives U
headache...
The contamination level is a bigger issue and this is more complicated to
fix and often involves production disturbance...
Regards,
Sasha
*************************************************************************
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]
*************************************************************************
Yordan Venev <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
2003-12-03 13:58
Please respond to "TechNet E-Mail Forum."; Please respond to Yordan Venev
To: [log in to unmask]
cc:
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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