The debate about lead free solders seem to be nearly as politically charged as that about anthropogenic global warming and a casualty seems to be useful data.
I've read plenty of comments to the effect that lead-free is less reliable in the long term (vibration seems to be a key weakness AIUI - maybe also thermal cycling) which presumably explains the exemptions for certain categories, yet I've also seen some studies that claim it can out-perform lead containing solders.
Is there any real hard and fast information out there that one can rely on ?
Eeyore wrote in news: snipped-for-privacy@hotmail.com:
If it were better than lead solders there would not be any exemptions needed, every thing would be required to be lead free. Critical (Mil, Aero, etc)equipment gets an exemption though...
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It is really application and chip package specific, and even makes a big difference on where the chip is mounted on the board. It also makes a big difference on the various lead finishes, process steps and how they are done, and which of the common 23 lead-free mixes you use. Would you believe ENIG finishes can even cause issues with lead-free?
Personally, if you look there is a consortium lead by Boeing, of areospace industries, who have been doing a lot of testing on the subject, and ended up settling on just 1 or 2 alloys that perform the best in the early phases, to pick out which ones to run thru the gauntlet- with control subject of regular leaded solder.
If you do searches on key documents/terms listed within these, you will find more than you ever wanted to know:
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- a whole list of documents
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Another key term to search for is Thomas Woodrow, who has dedicated years attempting to unravel this puzzle for best practices.
When looking at these presentations, it is important to look hard into the nitty gritty of the source references, or you will easily end up with the wrong conclusions. Things like a good number of the tests were done with immersion silver, and ENIG (gold) and other board finishes can have a big impact on the results of the test. ENIG has it's own issues, such as a big increase in what is becomming known as "black pad" failures when lead-free solders are used with it. As I recall, it had something to do with the ENIG process steps, which vary from board house to board house.
In the second one, several working groups have found the failure shown in page 33 of the document( pdf page 33), where you can see cracks running all through the BGA ball, and a rather clear separation off the pad. Caused by temperature cycling, and failures in less than 150 thermal cycles!
Tin Whiskers Theory and Mitigation Practices Guideline:
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"The amount of damage required for a BGA to fail on an assembly was used to predict lifetimes for other BGAs, at other locations, on the same board. They tested: Sn3.9Ag0.6 for reflow soldering, Sn3.4Ag1.0Cu3.3Bi for reflow, Sn0.7Cu0.05Ni for wave, and
63Sn37Pb for reflow and wave. The surprising part is that BGAs using tin/lead will outlast SAC BGAs by a factor of 20x. Thus, SAC BGAs in high-reliability electronics could be problematic in high-vibration environments. ... There has been no other transition to affect all aspects of our industry as fundamentally as lead-free. Predicting reliability will prevent future disasters, and that's the best reason to glean information from all approaches. There's still so much we need to know."
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----- Original Message ----- From: "Eeyore" Newsgroups: sci.electronics.design,sci.electronics.repair Sent: Tuesday, July 24, 2007 3:42 PM Subject: So what's the truth about lead-free solder ?
Follow the derogations/exemptions. Military , aerospace & medical do have derogation from WEEE and RoSH, but can anyone nail down precisely why they are exempted. The suggestion from the following would be they are maverics putting themselves in an awkward position regarding spares etc.
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"... Much equipment manufactured before the application of RoHS will suffer premature obsolescence, as component parts which have been modified to meet the RoHS requirement may not be compatible. Businesses supplying sectors such as defence, medical, instrumentation and control, currently have a derogation from the regulation in Europe. But this poses problems for the future availability of lead-free components. This issue has product lifetime implications for public sector purchases as well as business implications to those supplying export markets where RoHS standards do not yet apply. ..."
The real conspiracy would be if it could be shown what manufacturing industries deliberately went with lead-free knowing that their products would fail due to that and not component failure, knowing they would sell more product. The engineers I have talked to in UK industry are genuinly unaware of in-service problems in electronic products, due to their enforced lead-free soldering. But the ones I know are in scientific/technical kit and instrumentation production so not subjected to vibrational environments. Do automotive electronics have a derogation ? as that would be an area that would soon show up lead-free solder problems.
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
I'm not sure that I would find this "surprising", having seen the general performance of lead-free from a service angle, for several years now. At the end of the day, like several other technologies we have been forced to ditch as a result of dubious science and conclusions, lead-based soldering was a mature, proven, and above all *reliable* way to construct electronic equipment.
If Boeing Corporation are really leading research into the performance of this hateful material, then I hope that it is with a view to reinforcing the avionics industry's opinion that this stuff has no right to up be in the sky, and responsible for getting 450 people safely to their destination. If they are researching with the intention of determining the best compromise alloy to use in place of conventional solder, then I believe that is indeed a worrying development ...
It would be interesting to know from someone directly involved in avionics or avionics service, how many in-service equipment failures are currently as a result of bad joints, and what sorts of levels of failures are being recorded in the vibration tests that must be being done on evaluation sample pieces, constructed with lead-free.
Bullshit. Lead based solder alloys are superior in damn near all electronic realms, and there is no configuration where they would not be other than high end commercial and military applications, and they certainly do not include Tin.
RoHS is a Euro-ploy to boost the Euro-dollar, and there is no health problem surrounding lead alloyed solders.
It is all bullshit, and it was all bullshit when it was started.
We already had regulations in place for such matters for DECADES.
Whilst I don't disagree with you, where's the hard comparative data ?
I only wish it was just the EU.
FYI, the idea(l) behind RoHS is to encourage recycling by removing elements that would be troublesome otherwise.
Personally, I can think of no good reason to attempt to 'recycle' old printed circuit boards. For example it appears to be both uneconomic and likely energy wasteful too.
Considering the fact that we have 5 decade old circuit cards still operating perfectly, and that we already know what alloys containing Tin which is not bound by Lead do over time and temperature cycling, I do not think that precise numerical analysis is even needed on such a profoundly lopsided issue.
If one (read a business) had an incinerator for refuse, which is common in the US, one could very easily have enough heat energy "left over" to reflow, and "Smack and Gather" soldered assemblies after they reach reflow temperatures.
It would not take long to gather a ton of "solder".
A ton is a ton is a ton, and gathering several grams from each assembly one has for salvage makes the planet more "green", because reprocessing lead, and lead alloys is far easier and less costly than mining it.
Whilst I agree with you, bureacrats tend not to be very receptive to anecdotal comment. And make no mistake, the bureacrats are the ones in control of this.
I have just this minute finished repairing a Panasonic DAB / FM radio which was dying as soon as it was switched on, with a "F76 Pdet" error in the display. I took this to be "power detect", which seemed reasonable, given the symptoms. When I took the main board out to have a look at the underside, I found the power supply section riddled with poor and 'cracked-right-round' lead-free solder joints ( the board actually has "PbF" silk-screened on it ). The poor joints were particularly well defined on the main free-air cooled regulator transistor, which is obviously subject to thermal cycling.
I reworked all the joints with lead-free, as that is what the RoHS legislation legally charges me to do as a commercial repair outfit, but boy, the temptation was strong to just reach for the leaded solder, and do the job 'properly' ...
What was the chipcode dates on that DAB ? No more than 2 years old no doubt.
If you had not repaired it than also no doubt it would have ended in landfill taking with it ,perhaps not lead, but antimony, bismuth, tin, copper, barium , phthalates etc
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
On a sunny day (Wed, 25 Jul 2007 12:28:58 +0100) it happened "N Cook" wrote in :
Actually, in the long ago past when I had the TV repair shop, I had exactly the same problem on old tube connectors in PCBs and also on inductiors, and old Philips K8 connectors, some after 2 years too I think. With leaded solder. This is also also an issue of better connections, some that allow some movement, like WIRES for example... I mean use flexible wires to connect the hot components to a PCB. That defeats the idea of PCB perhaps. But I only wanted to point out that that thermal effect is also present in leaded solder. It could be worse in leadfree, but you'd have to test in the same setup. He *could* have resoldered one with 60/40 and when it comes back in 2 years see which ones gave way ;-)
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