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Tin Whiskers — Fact Or Fiction?
bLanark writes "Some time ago, most electronics were soldered with old-fashioned lead solder, which has been tried and tested for decades. In 2006, the EU banned lead in solder, and so most manufacturers switched to a lead-free solder. Most made the switch in advance, I guess due to shelf-life of products and ironing out problems working with the new material. Lead is added to solder as it melts at low temperature, but also, it prevents the solder from growing 'whiskers' — crystalline limbs of metal. The effect of whiskers on soldered equipment would include random short-circuits and strange RF-effects. Whiskers can grow fairly quickly and become quite long. Robert Cringley wrote this up this some time ago, but it seems that the world has not been taking notice. I guess cars (probably around 30 processors in a modern car) and almost every appliance would be liable to fail sooner than expected due to tin whiskers. Note that accelerated life-expectancy tests can't simulate the passing of time for whiskers to grow. I've googled, and there is plenty of research into the effects of tin whiskers. I should point out that the Wikipedia page linked to above states that tin whisker problems 'are negligible in modern alloys,' but can we trust Wikipedia? So: was the tin whisker problem overhyped, was it an initial problem that has been solved in the few years since lead-free solder came into use, or is it affecting anyone already?"
SnAgCu Rohs solder(with 3% silver and .05% copper) joints don't appear to whisker but they appear dimpled and shitty compared to the smooth, shiny joints of garden-variety tin/lead. At least in the electronics industry, your percenteges and mileage may vary.
One thing to remember is that safety control and monitoring products like fire alarms, but probably also car electronics, are excepted from the RoHS directive until at least 2012, possibly until 2018, but there's really no fixed date set yet. So yes, your DVD player might die, your car probably won't.
c++;
Well, NASA Goddard are worried about the situation and they have done extensive studies on the subject:
http://nepp.nasa.gov/WHISKER/
Ganty
Tin whiskers are, in fact a reality. They are a problem with pure tin specifically. The older tin-lead, and newer tin-vanadium alloys don't have the problem. However, many manufacturers still manufacture parts in a pure tin variety. The reason for all of this pure tin madness is that the EU passed strict anti-lead regulations and so the lead had to be removed from electronics. EU manufacturers immediately started using pure tin parts. In the US, many manufacturers followed suit, partly because pure tin parts were now more available than tin-lead (and at the time there was hardly any tin-vanadium), and partly because they wanted to maintain a good environmental image. Some manufacturers, having been burned by the whisker problem insisted on a better solution hence the tin-vanadium solders now available. The problem is there are a lot of electronics out there with pure tin parts in there. For example, I'm no fan of flying on Airbus aircraft manufactured in the late '90s and early 2000s (pure tin baby). The thing is, the hardware will work perfectly... until it doesn't, then an errant short will cause a malfunction and in the act, the tin whisker will vaporize. The only way you'll find the problem is with electron microscopy.
Any whiskering is far more likely to be a result of board contaminants than just the tin migrating. Modern solders are less forgiving of bad handling practices.Poor flux choice and board cleaning practices are normally to blame for many faults. Changes in board cleaning practices to eliminate various chemicals means that the industry has had to learn how to do things again.
So, while modern practices might be less forgiving, any faults are really just a result of poor processes.
Engineering is the art of compromise.
Tin Whiskers appear real:
http://nepp.nasa.gov/WHISKER/background/index.htm
http://www.calce.umd.edu/lead-free/tin-whiskers/
From what I can tell from these links there issue is still present in lead-free solder, and very much an issue in certain conditions. I have not seen any pages which indicate long-term solutions, though it would be interesting if someone can turn one up.
Another link:
http://www.national.com/analog/packaging/leadfree
Jumpstart the tartan drive.
The issue is more for some little Chinese kid who lives by scrapping our electronics. This means the lead is concentrated and gets into water and all sorts.
See my journal, I write things there
It's sealed away properly now, but unless people dispose of old equipment properly it ends up in a dump somewhere, and there's a risk that in a few decades it will end up contaminating groundwater. Obviously it's a hard risk to quantify, so I'll fence-sit as to whether this is a useful precaution or not.
More importantly, where in "the Wikipedia page linked to above" did it state "that tin whisker problems 'are negligible in modern alloys'"?
I saw nothing that said that in current version, and it hasn't been edited (minor or otherwise) since June 13th. I certainly cannot find that single-quoted statement.
I am all for scrutinizing Wiki pages, and not using unverifiable statements from them, but I will not support discrediting them on material that was not written on them in the first place.
You can hold down the "B" button for continuous firing.
Not likely as most modern tinfoil hat are actually made of aluminum foil available at grocery stores.
Or just follow the links to the original sources that the Wikipedia article cites.
I've had several equipment fail, not because of tin whiskers, but because of crappy capacitors that leaked and/or burst.
Zinc whiskers are also a problem - specifically if the raised floor in a datacenter is held up by older galvanized steel standards. i've actually got a client with this issue - you can see the whiskers on server motherboards with a flashlight held at an oblique angle.
symptoms included random server failures, power supplies and pdu's exploding (had one go off when i was in the room - NOT FUN)
they not only had the old standards, but the roof overhead was steel, soldered with a solder that also contained zinc.
...but is the amount of lead in solder really dangerous?
The risk is likely more to people repairing and building electronics than to the consumer. The last transmitter tech that I worked with was adamant about handwashing and always had a high wattage light positioned over solder work so that rising hot air would draw lead fumes up and away from his face.
People who hand load ammunition face a similar long term but real risk of lead exposure.
Three Squirrels
rickroll
GENERATION 24: The first time you see this, copy it into your sig on any forum and add 1 to the generation. Social exper
the exemption for military electronics.
RoHS may b e good for plebes, but the ruling class can't risk losing control.
"National Security is the chief cause of national insecurity." - Celine's First Law
The board was in the field in a T&M application for about 1 year. Root cause pointed to 2 factors. First the board had very poor (actually out of spec) via to pad alignment. The result was significantly increased voltage density between the offending 12V via and the ground plane. The second factor WAS RoHS compliant board prep and solder. Basically drilled and plated via holes are not 100% sealed (rough bits of fiberglass can still protude through the plating). The solder was one of these high Tin (97%) varieties, and we got dendrite growth (not the more common whisker growth) INSIDE the board along the fiberglass fibers between the via hole and the ground plane, creating a short from a ~30A power bus to ground. The board caught fire. Indications are that it creates a crappy short that repeatedly fries open, and regrows causing intermittents, then eventually enough heat for fire if the power supply can handle it. Higher power electronics with dendrite growth or tin whiskers may fail only briefly (or not at all) when a wimpy short occurs. Low power signal lines won't always have enough juice to overcome the short and may fully die on the very first short. Our safety/reliability group said dendrite growth is a known, but poorly talked about issue that is greatly exacerbated by the lack of lead, and greatly increased board densities today. To a previous post about melting points. Yes, Tin/Lead solder melts well below the melting point of either element in the alloy, at about 175-180C depending on the particulars. NASA literature indicates that conformal coating is ineffective against whisker growth. At a previous defense sub-component job we had to resort to getting many parts re-plated with a tin/lead finish over their matte tin finish to comply with contract requirements. Most commercial off the shelf parts (COTS) are no longer available with anything but matte Tin, or other RoHS finishes. Many vendors changed finishes without any notice, creating havoc in our stick room.
My car is 16 years old and still in pretty good shape. I guess it will last a few more years. So 20 years are not unrealistic for a car.
You can tell they don't use road salt where you live...
-1 Uncomfortable Truth
There is no such thing as "lead fumes" while soldering. Temperatures are NOT high enough to vaporize lead at all. Granted, some of the flux materials used in solder are not so good for you to breathe, but you will not inhale any lead while soldering. Wash your hands after soldering and your lead intake is practically zero.
The EU Lead regulations came about when the CRT was king and the glass screen in front of the CRT was made of heavily leaded GLASS -- yep similar to the heavily leaded glass "crystal" that some EU countries are so proud of for wine glasses! The amount of lead in the electronics was minimal compared to the lead in this glass, which was usually broken up and sent to the land fill. Of course the problem is going away pretty fast since the CRT is going away! LCD displays don't have or need the leaded glass -- they are not first cousins to an X-Ray tube! Oh, the single BIGGEST source of Lead getting into the environment is automobile batteries -- and no they don't have lead free versions of those (well they do, but the cadmium is worse!).
Ham no, but I live in a place where "seafood sticks" are made out of cows. Amazing what can can be done with tripe and boiled down prawn (shrimp) shells for flavour.
When soldering, I'm far more worried about that nasty flux than any imaginary lead vapors. Lead boils at 1600'C or so... definitely higher than my iron's tip.
-Billco, Fnarg.com
Anyway, at my company we've settled on immersion silver as our PCB finish of choice. (We've been through white tin and OSP, and dabbled in immersion gold, but the silver finish has been working well for 3-4 years.)
It doesn't hurt to be nice.
These are completely immune to tin whiskers.
I would be supprised if silver grew tin. Technicaly you are correct, Silver doesn't grow Tin whiskers.
Silver whiskers is a real problem in industrial locations where Florene is present. The circuit breakers, buss bars and other industrial power components are prone to growing Silver whiskers. Failures are the result of increased contact reistance causing failure from overheating and arc flash failures from arcs initiated from the short. Both are serious failures.
Refrence with photos, Of course:
http://nepp.nasa.gov/WHISKER/other_whisker/silver/index.htm
The truth shall set you free!
With Wikipedia I find it interesting to read the talk page when there is a contested article. If you're really interested in the subject matter, You can often learn significantly more with two knowledgeable people arguing about that topic.
ROHS has been a billion dollar expense to the electronics industry, and it is argued the solutions are causing more enviromental damage than the original problem which was based ONE scientific paper out of the USA which was since retracted.
Lead free is a huge pain.
All soldering processes run 20deg hotter, consuming more electricity and stressing components, especially MLS devices (Mousture absorbed by components turns to steam fracturing parts if you are not careful). Wetting is poorer. Tin whiskers is a problem the industry is still trying to fully understand.
All because some beurorats in the EU listened to one faulty research paper.
http://www.edn.com/article/CA6355639.html
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* JEDEC/IPC JP002 "Current Tin Whiskers Theory and Mitigation Practices Guideline" (http://www.jedec.org/DOWNLOAD/search/JP002.pdf)
* JEDEC JESD201 "Environmental Acceptance Requirements for Tin Whisker Susceptibility of Tin and Tin Alloy Surface Finishes" (http://www.jedec.org/Catalog/catalog.cfm)
Further work is ongoing within JEDEC, IPC, iNEMI, and other groups to further refine industry practices. See http://thor.inemi.org/webdownload/newsroom/Presentations/Sn_Whisker_Symposium_2008.pdf for one example of this.
I've eaten a fair amount of silver in my day, with no harm done. Hindus eat a lot of it too. And I've applied silver-based cream to burns (makes 'em heal faster). Westerners used to mark cattle by slipping a silver dime into a cut, that way you could check with your fingers to see if somebody had re-branded cattle they'd rustled from your spread.
Silver's a doddle. And there most certainly is plenty of documentation and research on lead leaching into ground water.