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Tin Whiskers — Fact Or Fiction? 459

Posted by timothy
from the shave-before-dates dept.
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?"
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Tin Whiskers — Fact Or Fiction?

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  • by LM741N (258038) on Sunday June 15, 2008 @03:51PM (#23802667)
    grow whiskers. That would be a major bummer. But then lead would be pretty heavy.
  • by Anonymous Coward on Sunday June 15, 2008 @03:55PM (#23802719)

    My cat gets through tins of Whiskas extremely rapidly. Perhaps scientists can interview him.

  • lead free solder (Score:5, Informative)

    by Ethanol-fueled (1125189) on Sunday June 15, 2008 @03:57PM (#23802745) Homepage Journal
    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.
    • Re:lead free solder (Score:5, Informative)

      by Sponge Bath (413667) on Sunday June 15, 2008 @04:11PM (#23802877)

      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.

      • Re: (Score:3, Informative)

        by celtic_hackr (579828)
        A company that makes systems for trains use lead free solder, and I've not seen these problems. But they also coat the boards and solder joints with a sealant. This removes oxidation and any possible tin growth problem. You'd better hope these work, because the boards are used on freight trains.
        • Re:lead free solder (Score:4, Informative)

          by Anonymous Coward on Monday June 16, 2008 @08:11AM (#23808703)
          No sealant or coating has been shows to have the slightest effect on tin whiskers. They grow from below and are atomically sharp; thus they poke right through surface oxidation, confirmal coatings, or whatever.

          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: (Score:3, Informative)

      by gweihir (88907)
      Indeed. I have switched my soldering to this type of solder some time ago, and the results look a bit like you do not know what you are doing. It is not quite that bad though. Apart from that, my impression is that the joints are more durable.
      • Re:lead free solder (Score:5, Informative)

        by mrmeval (662166) <mrmeval@gmail.cGINSBERGom minus poet> on Sunday June 15, 2008 @08:35PM (#23804765) Journal

        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]
  • Exception (Score:5, Informative)

    by pipatron (966506) <pipatron@gmail.com> on Sunday June 15, 2008 @03:57PM (#23802747) Homepage

    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: (Score:3, Informative)

      by Anonymous Coward
      In the electronics manufacturing lines I deal with, they have some Pb-Free and some non Pb-Free lines. So the article's concern about safety critical devices is incorrect.

      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.

    • You forgot... (Score:3, Informative)

      by msauve (701917)
      the exemption for military electronics.

      RoHS may b e good for plebes, but the ruling class can't risk losing control.
      • As TFA points out, the military folks must buy their components from somewhere, and the parts suppliers are shipping tin-coated components...

        So even if they get to use leaded solder, they can get whiskers on their components...

  • Does it matter? (Score:4, Insightful)

    by NerveGas (168686) on Sunday June 15, 2008 @04:00PM (#23802765)
    Cars, televisions, players, music, computers... are there really any electronics intended to last 30 years any more?
    • Re: (Score:3, Insightful)

      by Anonymous Coward
      I know of $100M electronic devices orbiting 23,500 miles out in space which would indeed live 30 years if the tin whiskers don't kill them first.
    • Re:Does it matter? (Score:4, Interesting)

      by plasticsquirrel (637166) on Sunday June 15, 2008 @07:13PM (#23804287)

      Cars, televisions, players, music, computers... are there really any electronics intended to last 30 years any more?
      Electric guitars and some guitar vacuum tube amps are the only electronics I know of that are still made to last decades and be serviced easily. A $2000 Marshall amp, for example, needs to be able to be serviced if a capacitor goes bad, or if the transformer blows out.

      Many vintage amps from the 1950's just need a few capacitors replaced, and they will work perfectly, 50-year old vacuum tubes and all.
      • Re:Does it matter? (Score:5, Interesting)

        by cayenne8 (626475) on Sunday June 15, 2008 @07:54PM (#23804551) Homepage Journal
        "Many vintage amps from the 1950's just need a few capacitors replaced, and they will work perfectly, 50-year old vacuum tubes and all."

        Yup...back to a day when people AND companies took pride in their engineering and craftsmanship.

        I know now why some of those old McIntosh tube amps from the 60's still sell for $1200 and up. Things built back then were built like tanks.....and meant to last.

        Sad you no longer see that in today's disposable society. Strange that in this day or people trying so hard to be "green", that these same people don't demand that companies built products with such quality that they will last and not have to be replaced every other year.

        • Re:Does it matter? (Score:5, Insightful)

          by squiggleslash (241428) on Sunday June 15, 2008 @09:57PM (#23805313) Homepage Journal

          There really aren't that many consumer electronics items from the 1950s and 1960s in general use, even when they're compatible with "current" standards. The exception are a few items, like those you mention, that were expensive then and are expensive now. There were hundreds - possible thousands - of millions of radios and TVs made during that time, for example. These are 100% electronic items, unlikely to have failed due to mechanical problems (wear and tear), nor incompatible (in practice) with current standards and systems. Where are they now?

          There are items made today that will still be in use in 40 years time, but the number is small, and as with the previous example, they'll be the obscure, highly priced, built-by-craftsmen objects. The "decline in quality" meme is a myth. If it's built in a factory, for the mass market, it isn't - and never has been - in the manufacturer's best interests to make it last for more than a decade. Exceptions exist - but they'll always exist. And, to be honest, there's a remarkable amount of stuff hitting landfills these days not because it fails to function as designed, but because it's obsolete. I suspect the number of 8088-based PCs that could still be working if their owners hadn't put them in the trash would probably number in the tens of millions. And that was hardly an industry where quality was considered a priority.

  • by Linker3000 (626634) on Sunday June 15, 2008 @04:07PM (#23802851) Journal
    Imagine a ...er, no..

    I blame Mic..hang on..

    The RIA...Uh..

    In Soviet Ru...Damn..

    SCO probably...fu..

    Does solder run Lin...um...

    Bah!
  • NASA Are Worried (Score:5, Informative)

    by Ganty (1223066) on Sunday June 15, 2008 @04:09PM (#23802863)
    Well, NASA Goddard are worried about the situation and they have done extensive studies on the subject:

    http://nepp.nasa.gov/WHISKER/ [nasa.gov]

    Ganty
  • by zejackal (186296) on Sunday June 15, 2008 @04:10PM (#23802871)
    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.
    • by AllergicToMilk (653529) on Sunday June 15, 2008 @04:27PM (#23803033)
      This, of course, is not always what happens. The whiskers, being very fine, don't have much current carrying capacity so they are quite likely to just vaporize. Nevertheless, there is risk.
      • by veranikon (202025) <westbywest@nOsPAM.gmail.com> on Sunday June 15, 2008 @05:17PM (#23803415)
        It takes *very little* current to short a FET gate, i.e. microamps or less. Indeed, compare the geometry of these whiskers to the tracks etched on silicon. Not every bit of metal exposed on a PCB will carry current large enough to fuse these whiskers before they cause disruption. Furthermore, chip-scale assembly techniques likes BGA will give you plenty of areas with large blobs of solder within convenient whisker distance of each other.

        As referenced in another comment, NASA Goddard Space Flight Center does indeed seem pretty concerned:
        http://nepp.nasa.gov/WHISKER/ [nasa.gov]
      • Re: (Score:3, Informative)

        by budgenator (254554)
        The ionized tin arc bridge is quite capable of conducting all of the available current. If your lucky it's a high impeadance low current signal line that shorts out instead of a 200 amp power feed. If the first happens your equipment glitches, if the second the Li-ion battery explodes in your pocket or worse.
    • Re: (Score:3, Interesting)

      by hughk (248126)
      Avionics & military electronics were excluded from the no-lead rule in the EU. Automotive not, so it could still me that your ABS fails safe (but not very safe on a wet road).
    • by plusser (685253) on Sunday June 15, 2008 @05:34PM (#23803585)
      As far as I am aware (and bearing in mind that I am a component engineer in the aerospace industry working equipment that is fitted to both Boeing and Airbus aircraft) there are currently NO LEAD FREE SOLDERS approved for use on critical applications on commercial jet aircraft. The Aerospace is currently out of scope of the RoHS directive as aircraft are not on open sale to the domestic consumer.

      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.
  • by Stiletto (12066) on Sunday June 15, 2008 @04:15PM (#23802929)

    Look at it from the manufacturer's point of view. There's a chance that any piece of consumer electronics is now going to wear out and die even faster, causing people to buy replacements more frequently. Sounds like a great deal for the manufacturer with no downside. They don't have to pay to dispose of these things properly. And no, chucking your old electronics in the trash is not the proper way of disposing of them, unless you like cadmium, mercury, hexavalent chromium, and brominated flame retardants seeping into your drinking water.

    Make manufacturers bear the ENTIRE cost of properly and safely disposing of their products, and overnight we'd have cleaner, greener, more long-lasting and durable products.
    • by Chineseyes (691744) on Sunday June 15, 2008 @04:50PM (#23803217)
      Make manufacturers bear the ENTIRE cost of properly and safely disposing of their products, and overnight we'd have cleaner, greener, more long-lasting and durable products.

      Very idealistic of you but manufacturers will NEVER bear the cost, it will be passed on to the consumer who will then bitch and moan to their government representation that they are being gouged. The manufacturers will then play the victim, "It's the big bad government restricting our ability to provide you with cheap goods". Now Mr. John Q. Politician is stuck in a real crap hole because the next election is coming up soon and his constituents are angry at him because they are paying what they perceive is too much for certain goods. Also the manufacturers lobby who funded his last campaign are threatening to fund his competition who has promised to rescind any laws that keep the manufacturers from doing business as usual. To compound John Q. Politician's problems the manufacturers are saying they will have to move their factories to more friendly territory in Asia so they can continue to stay competitive providing cheap goods. This would cause thousands of jobs to be lost among Mr John Q. Politicians constituency and many thousands more job losses among the constituency of his colleagues who will refuse to endorse him if he goes against a bill that will hurt their own chances of re-election.

      Now he is facing pressure from his constituency, lobbyists, and even his own colleagues.

      What do you suppose Mr. Politician does? Stick to his guns and fight the good fight? Hell no he doesn't. He votes to rescind any law that forces the manufacturers to bear any costs that will be pushed onto consumers. Why? because if he doesn't he will be voted out of office and the guy who takes his office will do what he refused to.

      Is it right? No. Do I agree with it? No. But thats the way it is.
      • Re: (Score:3, Insightful)

        by The Man (684)
        Dunno about him but I'm happy to bear the cost. Figure out the cheapest way to recycle or dispose of these things properly, then add that to the price and let me put it in the bin with the rest of my rubbish (or a separate one as with other recyclables). That system is simple and convenient and it provides the correct incentives. What we have now is a system in which it is often illegal to dispose of something but no alternative is available and, where one is, I have no pricing information to determine w
      • by Vellmont (569020) on Sunday June 15, 2008 @06:32PM (#23804003)

        Very idealistic of you but manufacturers will NEVER bear the cost, it will be passed on to the consumer who will then bitch and moan to their government representation that they are being gouged.

        It worked for catalytic converters, (and as a result unleaded gas). It's worked for low-sulphur diesel. It's worked for air bags. All of those examples likely cause higher prices for consumers that are passed on from manufacturers. I recall auto makers making these exact same arguments against airbags, and nowadays people are afraid of any used car without them. I don't recall any politicians being thrown out of office for making these requirements.

        I'm sure there were some naysayers, there always are. The trick is you just have to sell it to the public. Not everyone is a dumbass that only cares about saving a few pennies on electronics.

        Right now it's a pain in the ass to get rid of electronics. A lot of garbage collectors won't take them. Cities sometimes do, but you have to bring them to a special collection place, often many miles away and open odd hours. Put something in the legislation that anyone that sells electronics has to also take them for recycling. In Minnesota (and likely other states) we already do this for motor oil.
      • Re: (Score:3, Insightful)

        by ekhben (628371)

        ... but manufacturers will NEVER bear the cost, it will be passed on to the consumer ...

        Not holding the manufacturers responsible merely keeps the cost hidden, it doesn't get rid of it.

  • According to the web (Score:5, Informative)

    by Midnight Thunder (17205) on Sunday June 15, 2008 @04:16PM (#23802939) Homepage Journal
    Tin Whiskers appear real:

        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]
  • Fact (Score:5, Interesting)

    by Telecommando (513768) on Sunday June 15, 2008 @04:23PM (#23802999)
    Years ago I used to work on GE radio equipment. GE radios (Master II series) had tin-plated resonant cavities in their receivers. Tin whiskers were seldom a problem in the mobile radios as vehicle vibration tended to keep the whiskers knocked off. But in base stations the whiskers would grow along the lines of current until they shorted out the coils within the cavities.

    The symptoms were always the same. The radio would be working fine one minute and be stone-deaf the next. Sometimes just opening the cabinet door would be enough to dislodge the whiskers and remove the short. But it always returned a few days or weeks later. We got to the point where whenever we were sent out to fix a deaf base, our first repair technique was to take a large screwdriver and rap the cavities with the handle a couple of times, hard. We got some funny looks from the customers but they were happy to be back on the air.

    GE finally admitted that the plating was the problem and shipped us a bunch of cavities with a different alloy to use as replacements. They never would tell us what the difference was. Curious, we disassembled some of the old cavities and shook out tiny metal slivers that were finer than a human hair. Some were up to a centimeter in length.

    All of the radios we had problems with were less than five years old at the time.

    On a somewhat unrelated note, a friend of mine works for a company building avionics. They're still using Lead/Tin/Silver solder for US military contracts. He thinks they know something the rest of us don't.

  • by Mike1024 (184871) on Sunday June 15, 2008 @04:27PM (#23803035)

    Robert Cringley wrote this up this some time ago, but it seems that the world has not been taking notice.
    Of Cringely? Well, of course not.
  • by billcopc (196330) <vrillco@yahoo.com> on Sunday June 15, 2008 @04:31PM (#23803067) Homepage
    I understand the rationale for getting rid of lead in various products due to its toxicity, but is the amount of lead in solder really dangerous ? It seems like it would be such a small quantity, and perhaps more importantly it's sealed away in some plastic or steel enclosure... it's not like I go around licking motherboards all day long, and quite frankly if your kid wants to lick lead solder and you let him, brain damage might be an improvement!
  • by plasmacutter (901737) on Sunday June 15, 2008 @04:54PM (#23803239)
    I'm sorry but I don't see the danger to life and limb these politicians do in the tiny dimples of lead alloy solder which are enclosed in numerous tough outer casings.

    Have there been any studies comparing this "health risk" to your average city's smog layer?

    Lead has its place in society. It's not as if lead based solder is being used to paint walls or as inlay in children's toys.
  • by nurb432 (527695) on Sunday June 15, 2008 @05:06PM (#23803321) Homepage Journal
    If your computer has a limited life expectancy, then you have to buy a new one at some point. So why would they 'fix' the problem ?
  • by Stavr0 (35032) on Sunday June 15, 2008 @05:11PM (#23803365) Homepage Journal
    I've had several equipment fail, not because of tin whiskers, but because of crappy capacitors that leaked and/or burst.
  • Ice spikes (Score:3, Insightful)

    by Fry-kun (619632) on Sunday June 15, 2008 @05:23PM (#23803483)
    What's interesting is, nobody seems to draw a parallel between spikes that appear when clear water is frozen and tin whiskers.
    Something very similar happens - as the temperature goes down, spikes/whiskers appear. It only happens in pure or near-pure water. And it's a well established fact (although not well understood until recently).

    This is too much of a coincidence to not investigate it.
    • Re: (Score:3, Informative)

      by shbazjinkens (776313)

      What's interesting is, nobody seems to draw a parallel between spikes that appear when clear water is frozen and tin whiskers.

      Yeah, they do. NASA shows here [nasa.gov] a parallel between salt whiskers and tin whiskers. They're both crystalline structures, just like ice. I imagine lots of other crystals probably do the same thing, judging by macro-scale crystal growths in rock appearing as spikes.

  • by Jeffrey Baker (6191) on Sunday June 15, 2008 @05:34PM (#23803577)
    The problem of tin whiskers is real but the consequences ascribed to them by Cringley are not. A printed circuit board like the one in your computer or TV is made of fiberglass and copper layered in a sandwich. In the early days of electronics the copper was plated with tin to prevent corrosion, but scientists discovered that pure tin tends to form hairlike growths, causing the circuits to fail. Adding lead to the tin prevented the growths, and had other desirable properties, so the tin/lead alloy became a universal standard.

    More recently we got something called "the restriction of the use of certain hazardous substances in electrical and electronic equipment" or RoHS. RoHS prohibits the sale of materials containing more than 1% lead in the EU. (Old-style electronic assemblies use 37% lead solder.) RoHS came into force in 2006 but research into lead-free electronics began decades ago. Initially researchers tried pure tin plating, which lead to tin whiskers. Some products marketed in the late 90's even failed from this problem. But researchers did not throw up their hands in despair. RoHS has led to innovations in metallurgy to the extent that a circuit board designer can now choose from half a dozen different alloys. Today only 2% of printed circuit boards use tin plating.

      Some of these new alloys use gold or silver finishes over copper. These are completely immune to tin whiskers. The most popular new system eliminated the plating step, attaching components directly to the bare copper using chemicals called Organic Solderability Preservatives. OSP leads to stronger and more durable assemblies than even the old tin/lead process.

      The whining we see today on the subject of RoHS mirrors almost perfectly the doomsaying seen when California began regulating automobile emissions. There was at that time a tremendous amount of yelling about how the catalytic converter spelled the end of civilization as we know it, and only a moron would take the lead out of gasoline. But soon afterwards we saw the introduction of clean, efficient, powerful cars by Honda. Honda was even able to meet California emissions standards without using catalytic converters or even fuel injection. Their brand of engineering eventually trickled down to even the most benighted American car maker, and California emissions standards are now in force in every industrialized nation.

    I would expect to see the same thing with RoHS. We have only just entered the initial stage of complaining. The tin/lead dinosaurs with backwards-looking engineering departments face an existential crisis. In other design houses the challenge of lead-free assembly is being embraced as a competitive advantage. Those who can adapt to RoHS will thrive and those who cannot will clearly suffer.

    Cringley brags about a 1966 Thunderbird with a 428 cu. in. motor, a car so heavy, so polluting, and so slow by modern standards that it would be impounded by CARB and laughed off a drag strip by a base model minivan. As time goes on I think Cringley's views on the metallurgy of printed circuit boards will seem as antique at that T-Bird.
    • It occurs to me that this debate has lots of comparisons with the current minor furor over the rise of multiple CPUs. Many in the programming industry are despairing because we are being forced to design software that runs on multiple CPUs at once, rather than just getting more CPU speed. And again, it's due to externally imposed constraints. In the automobile industry, the catalytic converter was that constraint, in the lead electronics debate, the RoHS is that external constraint.

      In the programming worl
    • Re: (Score:3, Informative)

      by SydShamino (547793)

      The most popular new system eliminated the plating step, attaching components directly to the bare copper using chemicals called Organic Solderability Preservatives. OSP leads to stronger and more durable assemblies than even the old tin/lead process.

      The problem we ran into with OSP was that it wears off in less than a year. Sure, the boards can be shipped back to the vendor, cleaned off, and coated with a new layer, but that's expensive. We found that OSP-coated boards had a lower shelf life, and tended to show intermittent failures during in-circuit test because of poor electrical contact on the test bed probes.

      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

    • 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 failur
  • by Moof123 (1292134) on Sunday June 15, 2008 @06:32PM (#23804001)
    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.
  • Pb was in the GLASS! (Score:3, Informative)

    by Gim Tom (716904) on Sunday June 15, 2008 @07:25PM (#23804387)
    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!).
  • by wcl3 (1308145) on Sunday June 15, 2008 @07:30PM (#23804447) Homepage
    Yes, "newer alloys" are better. Tin whiskers can appear before your eyes. I've recently seen a whisker grow between two tin plated component leads while I watched (under a high power microscope). While I use new CuAgSn solders, many of the "RoHsS complant" parts I buy use pure tin finishes on the leads and there are no other finishes available yet. Classic Tin/Lead solders producted joints that were easy to visually inspect - the shape and surface texture of a good joint were fairly unique. Modern non-leaded solders produce a variety of lumpy grey results even when carefully applied. Aiding an abetting the RoHS issues are the use of fluxes that are easily cleaned without CFCs. Old school rosin based fluxes worked well and left beautiful joints - but were nearly impossible to clearn off without CFC based solvents.
  • Uggh (Score:3, Funny)

    by Anonymous Coward on Sunday June 15, 2008 @10:16PM (#23805415)
    I guard my rosin core solder like it's gold. I cannot stand the lead free solder.

    What made me laugh one night was when I was at the local DC401 group and we were assembling the RGB light kits. A few of the guys had vented soldering stations and warned to "wash you hands" after handling leaded solder.

    It was then that I brought up that if you lived in any area that was built up from the 19th century, more than likely your water distribution was via lead pipe. Not to mention the environmental lead you're exposed to every day.

    The hand washing is probably a good idea, and not inhaling the fumes might be helpful.

    But hell, I've been soldering stuff with lead based solder for many years. Maybe it explains why I'm so deranged.

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