Tin Whiskers — Fact Or Fiction? 459
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?"
lead free solder (Score:5, Informative)
Exception (Score:5, Informative)
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.
Re:Exception (Score:3, Informative)
Yes, once you convert a line, there's no going back. But you don't have to convert all your equipment at once. You can keep a mix for as long as you see the demand for plain old lead solder.
NASA Are Worried (Score:5, Informative)
http://nepp.nasa.gov/WHISKER/ [nasa.gov]
Ganty
Tin Whiskers are fact (Score:5, Informative)
Re:lead free solder (Score:5, Informative)
This makes it a bitch to visually detect bad solder joints also. Not only are they dimpled/mottled, the solder does not wick up onto leads like tin/lead. The leads just sort of mush down into the solder paste. Maybe this is less of a problem with the newer leadless packages, but for older SOIC packages it makes visual detection of defects more difficult.
Well here are a few facts... (Score:4, Informative)
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.
According to the web (Score:5, Informative)
http://nepp.nasa.gov/WHISKER/background/index.htm [nasa.gov]
http://www.calce.umd.edu/lead-free/tin-whiskers/ [umd.edu]
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 [national.com]
Re:Is lead truly that dangerous ? (Score:5, Informative)
Re:Is lead truly that dangerous ? (Score:5, Informative)
An attempt to discredit WP with lies, I say. (Score:4, Informative)
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 [wikipedia.org]. I certainly cannot find that single-quoted statement.
I am all for scrutinizing Wiki pages, and not using unverifiable statements [wikipedia.org] from them, but I will not support discrediting them on material that was not written on them in the first place.
Re:Well here are a few facts... (Score:5, Informative)
Re:Well here are a few facts... (Score:5, Informative)
Re:An attempt to discredit WP with lies, I say. (Score:2, Informative)
ROSH laws require less than 0.1% though... i think they need to rethink that on lead, if 1% lead stops whiskering, it's well worth it.
cadmium is also banned, and was the first metal to ever verify whiskering. chromate actually accelerates whiskering, so finding an additive that is better than lead might be hard.
Re:Will my tin foil hats (Score:1, Informative)
Re:If you don't trust wikipedia... (Score:2, Informative)
CRAPacitors failed way before tin whiskers (Score:4, Informative)
zinc whiskers (Score:2, Informative)
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.
Re:An attempt to discredit WP with lies, I say. (Score:5, Informative)
""Tin Whiskers" were a problem with early electronic solders which were coincidentally lead-free, and lead was initially added in part to eliminate them. These problems are negligible in modern alloys,[citation needed]"
the only metal I've heard of as being whisker free is lead, though, even gold silver and copper can whisker.
Re:Is lead truly that dangerous ? (Score:5, Informative)
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.
Re:Tin Whiskers are fact (Score:5, Informative)
Since 1994 the Aerospace and Military industry have been using commercial components to keep down costs as a result of the Perry Directive. This means that while the assemblies are manufactured using Tin Lead (Sn/Pb) solders, the components are now supplied with a Lead Free solder finish on the solderable terminations in order to comply with the RoHS requirements on commercial equipment. The problem is that different manufacturers have different finishes, and the suitability of that finish can very much depend on the design of the component (surface mount or through hole technology) and the design of the PCB to which it is attached (ground plane design), as well as the type of lead free solder that has been used.
In addition, some lead free solders (such as Tin Bismuth) which have lower melting points that traditional Tin/Lead, leading to poor solder joints if mixed with a tin/lead process.
To summarise, the problems that can be caused by using lead free solders are significant and there are more problems than just tin whiskering. The solution is knowledge of the problem and careful assessment of every component and processes used if the product is going to be used in a long life, high reliability product, irrespective of whether the product comes under the RoHS are not.
Re:Tin Whiskers are fact (Score:3, Informative)
Re:Useless without pictures. (Score:1, Informative)
Re:Well here are a few facts... (Score:2, Informative)
You forgot... (Score:3, Informative)
RoHS may b e good for plebes, but the ruling class can't risk losing control.
RoHS caused one of our boards to catch FIRE (Score:5, Informative)
Re:Does it matter? (Score:3, Informative)
You can tell they don't use road salt where you live...
Re:Is lead truly that dangerous ? (Score:3, Informative)
Pb was in the GLASS! (Score:3, Informative)
Re:lead free solder (Score:3, Informative)
Re:Well here are a few facts... (Score:3, Informative)
Re:An attempt to discredit WP with lies, I say. (Score:3, Informative)
Oh really?
http://nepp.nasa.gov/WHISKER/other_whisker/index.htm#pb [nasa.gov]
Re:Is lead truly that dangerous ? (Score:3, Informative)
Re:lead free solder (Score:5, Informative)
I've been seeing heat related issues, some component manufacturers have removed the lead but their parts do not hold up to the heat required for no-lead reflow and wave soldering. We're having parts not only fall out during testing but getting field failures back. This is for non-electrolytic capacitors a ceramic surface mount type and a through hole mylar type.
I've been seeing some units that were done with no-lead less than a year ago where parts are falling off the board. These were some of our early no-lead units so they'll just warranty them and replace the boards.
As to the tin whisker problem NASA has a lot of information on it.
http://nepp.nasa.gov/WHISKER/ [nasa.gov]
But I can't see where they're following their own advice if it means it's a 'show stopper'
http://www.nasaspaceflight.com/content/?cid=4537 [nasaspaceflight.com]
Re:Is lead truly that dangerous ? (Score:3, Informative)
Re:Tin Whiskers are fact (Score:3, Informative)
Re:Exception (Score:1, Informative)
Yes, once you convert a line, there's no going back. But you don't have to convert all your equipment at once. You can keep a mix for as long as you see the demand for plain old lead solder.
It was a feel good law that more and more idiots sucked up and didn't bother to fight.
Re:Ice spikes (Score:3, Informative)
Re:Well here are a few facts... (Score:4, Informative)
It's not just the solder that changed, it is also the "tinning" on all of the components, this is a huge change in the industry and we're basically throwing out decades of experience just to start learning all over again.
Rumors floating out of NASA/JSC a few years back were that they were pretty seriously concerned about the sea-change in industry since they get so much of their current componentry off the shelf, and they have documented cases of whisker induced failures. It's one thing when your iPod craps out, quite another when a GPS satellite goes off-line.
In the world of implantable medical devices (actually quite similar to space, since after a device is "launched" you really don't want to replace it for a stupid failure), there is also a lot of concern. Both of these fields can still use lead based solder, but they can no longer buy basic capacitors, and other components with the traditional lead alloy end-caps, and just the absence of lead in the caps can lead to whisker formation.
What the parent posted is a very macho statement from an industry that wants you to believe that they have a handle on the problem. Stop for a minute and think about all the mom & pop immigrant employing electronic sweatshops in the US - now think how most of those assembly plants are run in Costa Rica, Taiwan, and mainland China... how many of them are going to be educated enough to even begin to approach the kind of expertise required to avoid tin whiskers in lead free assemblies?
My take is that the electronics industry is laughing all the way to the bank, because they've taken another step on the road to manufacturing a disposable commodity. Nothing helps sales more than replacement business, and if everybody makes crap that dies within 5-10 years, you aren't going to be able to buy anything that lasts anymore.
My stereo amplifier from 1985 still works almost like the day I bought it, but with lead free connections inside, it would likely have a half-life on the order of just a few years, you never know when it's going to die, but die someday it will.Re:Reprinted from my blog (Score:3, Informative)
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.)
Re:Silver immune from tin wiskers (Score:3, Informative)
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 [nasa.gov]
Re:lead free solder (Score:3, Informative)
Re:I wouldn't go that far (Score:4, Informative)
Re:Well here are a few facts... (Score:3, Informative)
Re:You forgot... (Score:2, Informative)
That's a bit misleading. Basically all military systems are of electronic categories (e.g. control & monitoring systems) which would make them exempt if they were civilian also.
Vehicles and aircraft electronics for example are exempt until around 2018 regardless of them being military or civilian.
Re:Is lead truly that dangerous ? (Score:4, Informative)
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 [edn.com]
Re:Well here are a few facts... (Score:3, Informative)
Re:An attempt to discredit WP with lies, I say. (Score:3, Informative)
There are conformal coatings which can delay the effects of tin whiskering, but that's all they do. They do not prevent the tin whisker from forming.
There are many tests out there which test for strength of the connection. But very few test for whiskering. We need to be careful when discussing this subject. Oh, and one other thing: the new solder alloys are not compatible with the older tin plated parts. This issue has turned the market in to one great big experiment.
At the end of the day we don't really have much of a lead problem with electronics. Now, the RoHS folk have turned this relatively minor ecological problem in to a major headache for the general public. I hope you weren't expecting that pacemaker to last more than three years....
Re:lead free solder (Score:4, Informative)
What has been shown to have an effect is a bake/anneal after tin coating to form a stable Cu/Sn intermetallic layer; that basically preempts the low-temperature intermetallic recrystallization that is behind whisker growth.
Re:lead free solder (Score:3, Informative)
Re:Well here are a few facts... (Score:4, Informative)
Interestingly enough, there are lead-(and other hazardous substance)-containing parts that are considered RoHS by exemption. Usually, this is because there is no existing viable alternative. Of course, a battery is also likely to be recycled, since it has a cash value even as junk.
Tin Whiskers largely a non-issue now (Score:1, Informative)
* JEDEC/IPC JP002 "Current Tin Whiskers Theory and Mitigation Practices Guideline" (http://www.jedec.org/DOWNLOAD/search/JP002.pdf [jedec.org])
* JEDEC JESD201 "Environmental Acceptance Requirements for Tin Whisker Susceptibility of Tin and Tin Alloy Surface Finishes" (http://www.jedec.org/Catalog/catalog.cfm [jedec.org])
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 [inemi.org] for one example of this.
What? I've eaten silver... (Score:3, Informative)
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 [unca.edu] and research [doi.org] on lead leaching into ground water.