For those of you who have lead free solder... Tin Whiskers!

[s2000db]

I enclose a copy from ken Rockwells site, and I must admit I'd forgotten all about Tin Whiskers...


Tin Whiskers
Aha! A reader sent me some NASA documentation about how severe is the problem with tin whiskers. The part abotu whiskers starts around page 41.
Tin whiskers are what mysteriously grow out of electronic parts that don't have enough lead in them to stop the problem. When these grow, they start shorting out circuits and causing all sorts of intermittent and permanent weird problems.
Solder is the soft white metal that holds all the parts together on circuit boards. Military and space electronics require at least 3% lead in their solder for precisely this reason. Normal solder is 40% lead, but optional RoHS proposals (that's the little "10" in circles on Nikon lenses and other products) demand no lead.
Consumer products makers love the RoHS/no lead standards, because these whiskers ensure that consumer electronics made without lead will all die in about ten years, so no one will get away with using old products, and have to keep buying new ones.
10 years is a perfect target life: it's long enough that no one blames the makers for deliberately building this in, and long enough that the maker has no warranty or good will problems. "Hey, it was ten years old, what do you expect?" Hey, I have plenty of thirty-year old and older audio and video products working here just perfectly, thank you.
If we all have to replace everything after 10 years, that's a lot of TVs sold. I have a two Visio TVs, a crappy brand, that died on me at 1 year and four years.
Reading the NASA paper, it may be a lot less than 10 years. All AF lenses work with electronics; they have been loaded with circuit boards and microprocessors and memory since the 1980s. Lose a circuit, and even a lens becomes useless.
No one ever died when their lens died, but the news media, sponsored by car ads, certainly doesn't want anyone learning what caused the Toyota unintended acceleration (UA) problems. Toyotas, like most modern cars, are drive-by-wire. Your gas pedal is nothing more than an input to a computer. Cars haven't had gas pedals connected to throttle valves since the 1980s. Toyotas use a variable resistor to encode gas pedal position, and feed that to the computer that does some math, and then controls the fuel injection and air induction systems itself for optimum efficiency.
The unintended accelerations were caused when a tin whisker in the throttle pedal encoder shorted it to make it seem as if the pedal was pushed all the way down!
See page 16, fourth paragraph: "Destructive physical analysis of this pedal assembly found tin whiskers, one of which had formed the resistive partial short circuit between the pedal signal outputs. A second tin whisker of similar length was also found in this pedal assembly that had not caused an electrical short. If a resistive short between the potentiometer accelerator pedal signal outputs exists, the system may be vulnerable to a specific second fault condition that could theoretically lead to UA."
I didn't read the whole report, but you might want to. You can use your browser to highlight "whisker." This isn't just me venting, it's NASA and NHTSA, the National Highway and Traffic Safety Administration.
So what does this all mean? Use real solder, and the problems go away. Buy RoHS products or use lead-free solder or products in your designs, and people die — far more than from any tiny amount of lead used in electronics products. Car batteries still have a zillion times more lead in them than we're discussing in solder.
This RoHS baloney is a clever plan by electronics makers to render all electronics products as disposable. RoHS was invented in China, obviously to ensure a steady demand for new electronics products, and adopted in Europe. The rest of the world is still free from this baloney, although many of the products we buy have these problems. Lead-free tin solder is crap.
I compliment car makers. Japanese cameras are run by computers, and due to sloppy design make themselves more difficult to use than a computer. Everything in a car, from the lights and beepers and gauges to the engines, brakes and transmissions are controlled by computers, and the levers, pedals and buttons are only inputs to those computers, but at least car makers make all this look the same from the driver's point of view as any other car from decades ago.
Camera makers ought to take this cue and make cameras that just go, instead of throwing up reams of code between us and making the camera take a picture.
If women knew just how unsafe these tin whiskers were making their cars, we'd have a riot on our hands. The media has done a great job of keeping this quiet. Looking at who pays for media (look at the ads), and now I know why this has been kept so quiet.
Here's NASA's page with a lot more about these whiskers.

[rocker65]

Hi,
Thanks for the headsup.
This is important.
I am not at all surprised that that there has been no outcry in the totally controlled British press.
Has there been a vehicle recall.
In the USA they are usually quite hot about things like this.
Rgds

[AmDismal]

I need a tin foil helmet. No, wait...

[Pac67]

Its not just "tin whiskers" that seems to be the issue with lead free solders (although the safety example above makes a decent enough point if true!). They are less malleable too and with circuit boards, the lack of malleability of the connections can matter. Repeated thermal expansion and contraction can cause minute cracks in circuit boards. One manufacturer told me a few years ago that since the introduction of lead free solders, the failure (return) rate for some of their hifi kit had risen from 1% to 5% within the first year. I guess that they could look at making the PCBs thicker and other ways of limiting thermal stress, but it does seem that lead free solders, as well as being more difficult to work with (more chance of cold joints forming) are less reliable.

[Cable Monkey]

There is nothing going on there that can't be overcome by recognising and engineering around the potential issues. Noting an increased failure rate is natural. What will define the companies involved is how quickly they fix the design issues and roll it out across any other potential areas where it might manifest itself. That is the business of Quality Assurance, which should be a function of R&D and be essentially separate from the quality control function found during and immediately after manufacture. Most reputable companies will simply treat this a business as usual and sort the problems out. That does still leave the kit out there with these issues. That will be absorbed by the retailers in warranty and by the customer out of warranty. Recalls on electrical gear simply won't happen on the basis of potential early failure. It would need to be a significant safety issue such as exploding laptop supplies etc.

[i_should_coco]

This is old news and why military an aerospace applications are exempt...

[JPG]

This is old news and why military an aerospace applications are exempt...

Medical applications too, IIRC.

[Pac67]

There is nothing going on there that can't be overcome by recognising and engineering around the potential issues.

...like reverting to solder with lead in it?

[s2000db]

And lead solder sounds so much better, don't you think?

[stewartwen]

Graham Slee was raving about the use of lead free solder some years ago and the possibility of eqpt failure. He was of the opinion that the originators of the ROHS was the Chinese mfrs and wrote reams about it. He put a lot of it on his (old) website and really upset most of the marketing men in the industry, although the engineers undoubtedly agreed with him.
He found, by trial and error, the best lead free solder to use.
I have forgotten which type he uses, as a mfr he HAS to use lead free solder on all new eqpt. he builds. I think these regs are ridiculous!
I only use leaded solder as it is much more reliable and has greater longevity.
But there again I am not a manufacturer and dont have to comply with these stupid regulations.
S

[DMA]

The unintended accelerations were caused when a tin whisker in the throttle pedal encoder shorted it to make it seem as if the pedal was pushed all the way down!

I'll remember that one next time I have to do a speed awareness course.

[s2000db]

I'll remember that one next time I have to do a speed awareness course.

Yes, it was the tin whiskers officer.

[JPG]

There is nothing going on there that can't be overcome by recognising and engineering around the potential issues.

It appears that the only ways of avoiding tin whiskers are either not using tin at all or adding lead. Either are quicker, easier and cheaper than any alternative.

And as Coco says, it's not a new problem. Ever fixed an early-60s transistor radio by whacking it on the kitchen table? If so, you've probably removed some tin whiskers in the transistors.

http://www.vintage-radio.net/forum/s...ead.php?t=5058

[earlofsodbury]

Interesting. As noted, this should be solveable with research - the process of formation needs to be understood first, then something like a resin coating or post-soldering electroplating utitlised, maybe just different fluxes - not much point double-guessnig at this stage.

Where the quoted piece is wrong is devaluing RoHS - it covers a lot more lethal substances besides lead, but lead IS a large threat to human health: landfill site leachate contains dangerously high levels of lead from dumped electronics and that passes readily into the water table and thus to us. We can't go back to using lead for this purpose.

[Jazid]

The end of the (very cursorily) read basic info section contains this:

Suggestions for Reducing Risk of Tin Whisker Induced Failures:

The uncertainties associated with tin whisker growth make it extremely difficult to predict if/when tin whiskers may appear. The following list provides some suggestions for reducing the risk of tin whisker induced failures.



Avoid the use of PURE TIN plated components if possible. Utilization of procurement specifications that have clear restrictions against the use of pure tin plating is highly recommended. Most (but not all) of the commonly used military specifications currently have prohibitions against pure tin plating. Studies have shown that alloying tin with a second metal reduces the propensity for whisker growth. Alloys of tin and lead are generally considered to be acceptable where the alloy contains a minimum of 3% lead by weight. Although some experimenters have reported whisker growth from tin-lead alloys, such whiskers have also been reported to be dramatically smaller than those from pure tin plated surfaces and are believed to sufficiently small so as not to pose a significant risk for the geometries of today's microelectronics.

Given it's from near on ten years ago, and there is no mention of silver solder, I wonder if the alloying process is sufficient in silver/tin solder to reduce the whisker formation? Certainly there is nothing to suggest otherwise. I hope so as someone hereabouts recommended Cardas silver solder which I got from eBay, and it is a joy to use - MUCH easier than lead/tin solder - flows nicely and less dry joints as well.

[myles]

We (military) still use the 60/40 stuff. No tin whiskers accepted here!

[Jazid]

Proper waxed whiskers or nothing


Sent from my GT-I5800 using Tapatalk 2

[Muddy Funster]

I am not at all surprised that that there has been no outcry in the totally controlled British press.

Who's going to cry out, when the Daily Mail is one of the biggest news organs around?

If we objected to RoHS restrictions on the grounds of tin whiskers, we'd end up with a 'hi-fi gives you cancer!' campaign... or worse:

Asylum-seeking triode amplifiers in child-death shocker

Millions of cute Aryan British children face a painful death today because of imported foreign hi-fi from somewhere foreign like France, Germany or China. Slitty-eyed sausage-chomping cheese-eating surrender monkeys who used to respect our Empire are secretly planning to poison our kids with noxious lead solder fumes, while forcing them to listen to foreign music that will turn them homosexual.

According to medical experts, possible side effects of lead solder inhalation include learning difficulties, incomprehensible speech patterns, a propensity to set fire to farmyard animals, cancer of the saveloy, and death. While we at the Daily Bastard have previously tried to execute European bureaucrats for trying to straighten our bananas, RoHS (which may mean 'Royal order for Health & Safety') was in fact discovered by engineers at the Britishness department of University of Keeping Britain British, and has been approved by the Queen. Or, if you are reading this in the Daily Excess, Princess Di. Which takes the edge off the whole European thing.

We demand an end to this. Britain didn't win two world wars, one world cup, forge an Empire and send men to the moon by breathing in lead fumes. We put the Great into Great Britain by exporting little pieces of lead, one at a time at very high speeds, into the torsos of damn foreigners who dared to object to us attempting to keep Africa British. We invented electricity, good solid Victorian British electricity that powered steam trains and gas lights the way it always was and always was be.

In the good old days, Sir Winston Churchill would have put an end to such nonsense. OK, so until it got really unfashionable to do so (sometime around 1954, we believe) we were supporters of that jolly nice Mr Hitler, but despite that.... Churchill. Spitfires. That sort of thing.

No.