Relatively little solder is actually virgin, that is to say never used
before. But there is such a thing as virgin grade. This is metal that has
been smelted/refined back to a known high purity standard. Some suppliers
also claim to remove non metal impurities - oxides ,sulphides and stuff.

The effects of individual impurities are well documented in all soldering
text books and in IPC standards. Usually your supplier will have reference
data also.

If you were in an ideal world your solder would be 100% pure metals exactly
on the eutectic composition. In the real world this can not be the case and
you have therefore departed from the ideal in someway. Any impurities
present will cause the solder to behave in a less than ideal way. In use
further impurities will leech from the work and the solder will go further
from ideal.
The point of a high purity solder is therefore two fold:
1) to reduce unknown variables
2) to keep the solder as close to ideal for as long as possible.
This implies that the purest solder is the best solder, and this is true but
there is a law of diminishing returns in solders as elsewhere.

However your enquiry focussed on tin content. The solder could be virgin
grade and still have a low tin content. It is not unusual to have different
analyses results from different labs. This may reflect poor technique on
sample taking or at the lab. (although most solder suppliers for obvious
economic reasons usually know exactly what they are supplying)

When evaluating samples like this best practice would be to send two each
samples of the same material to each lab. This would enable you to see how
accurate the lab is.

Best practise on sampling is to run machine up to temp and take sample
directly from the wave after it had been running for some time - say mid
late morning from 8am start. Use a clean dry stainless steel ladle and
decant immediately into a dry mould which will chill the sample solid
straight away. This ensures no segregation of constituents to give false
lows/highs and that the sample you are sending is representative of the pot
contents. Again vendors have instructions on this and some even supply
sampling kits.

Hope this helps.


Regards

Mike Fenner

Applications Engineer, European Operations
Indium Corporation
 T: + 44 1908 580 400
M: + 44 7810 526 317
 F: + 44 1908 580 411
 E: [log in to unmask]
W: www.indium.com
Leadfree: www.Pb-Free.com



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Paul Truit
Sent: Friday, March 14, 2003 4:05 PM
To: [log in to unmask]
Subject: [TN] Solder analysis for 63/37


I have an issue I'd like to hear from this forum.  I have recently had a
sales call from "solder company B" wanting to sell me solder.  When
asked which solder company I use "solder company A"  I am warned about
the possibility of not receiving virgin grade metals.  Suggests that I
have an analysis performed to verify.  I allowed "company B" to perform
the analysis but I also sent a sample out to "company A" for the same
test.  The results came back not agreeing. One said my solder is fine in
regard to tin content (62.78%) the other said it was bad (60.8%)  The
skeptic in me doesn't want to believe either of them right now.

Purchasing loves to "shop" for the best price on solder.

Can someone tell me about this virgin grade versus reclaimed solder?  Is
this a marketing idea? What defects would I see from the "inferior" one?
How do I know if my solder was from "reclaimed" metal?  Isn't tin tin
and lead lead?  Is there an unbiased source to send a solder sample to
so I can really know what is in my solder pot?
--
Paul Truit, Mfg. Eng.
RBB Systems, Inc.
4265C E. Lincolnway
Wooster, OH  44691
Ph. (330) 567-2906 ext 514
Fax (330) 263-5324
Email: [log in to unmask]

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