For a starter, here is an answer on this China subject that I gave to a
similar, slightly broader question on long term (chemical) stability of
solders and fluxes in electronic assemblies recently. It's good for a
perspective if nothing else. Hope it helps:
--
Hmm, the answer to your question is a very long time, many decades for tin
/lead solders. We know that from the life cycles of existing soldered
assemblies, and other applications for tin and lead containing items. The
alloys are stable and any degradation through temperature cycling results in
a kind of work hardening which can lead to fractures under stress, but aside
from lack of functionality nothing else happens. With no temperature
extremes/cycling I would venture to say the life of a solder joint is
probably centuries. The earliest soldered assemblies are still around OK,
(Roman helmets that sort of stuff.)
So far as leaching is concerned, or at least chemical attack from
ingredients, the fluxes are defined as non corrosive by IPC for the
applications they are in. A no clean flux is little different in this
respect than its RMA predecessors and again we can point to decades of use.
The worst conditions we can point to are probably those pertaining to
landfill, end of life in other words. Here the studies show that leaded
solders are stable, the US EPA did a study on environmental impact of leaded
solders/electronics >15 years ago and you should be able to find that OK. If
its OK in damp ground with acids etc from landfill its must be OK in
ordinary air.
Turning to lead free, the situation is not so clear, first there are a
number of novel alloys involved so not so much history, secondly
environmental impact studies on SAC alloys for example show they can leach
into ground water from landfill, unlike leaded ones.
Looking at the nearest thing to SACs, we get the tin/silvers, these have
been used in the automotive and defence industries for about 50 years with
no indications of unreliability, so for the purposes of this study we can
say they are stable and we go back to the fluxes. They meet the same
standards as leaded so no change.
For documentation on this: as said the US EPA study, the British NPL has
done some reliability studies and these are free to download. One of the
biggest repositories of knowledge on line for solders is
http://www.boulder.nist.gov/div853/lead%20free/props01.html
and I would look there first for authoritative references.
--
Regards
Mike Fenner
Indium Corporation
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of kwood716
Sent: Thursday, February 22, 2007 10:50 PM
To: [log in to unmask]
Subject: [TN] China / Solder Longevity
Hi all,
I have been asked to place a label on a product that is being sold in China
that
states how long, under normal circumstances, the solder joints, or solder I
guess, will last.
Anyone have experience with this issue?
The material used is 63/37 no clean solder.
_____
Saturn PCB Design, Inc.
Kenneth J. Wood CID
2737 Bishop Lane
Deltona, Fl 32725
Phone: 407-340-2668
email: <mailto:[log in to unmask]> [log in to unmask]
www.saturnpcb.com <http://www.saturnpcb.com/>
***This email, its content and any files transmitted with it are intended solely for the addressee(s) and may be legally privileged and/or confidential. If you are not the intended recipient please delete and contact the sender by return and delete the material from any computer. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited.
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