"Tin Whiskers" a Growing Electronic Concern
Thu Oct 11, 2007 11:23PM EDT
See Comments (10)
Tin whiskers: They sound so cute, so harmless. How could something called "tin whiskers" be one of the most serious problems that will face computing over the next few years? Here's how.
Tin whiskers are tiny filaments of tin, a component of solder, which form on electronics components and cause short circuiting when they bridge from one wire to another. The whiskers form spontaneously and over time, and no one has yet figured out exactly why they grow. And that's the problem... because as electronic components get smaller and smaller, whiskers become a bigger concern. The bridging and short-circuiting effect is simply much easier since components are closer together and the whiskers have less distance they have to cross to cause short the circuit. That's a close-up picture (courtesy Wikipedia) of the whiskers in action (click the pic for a better look).
Tin whiskers are an even bigger problem now because the alternative to tin solder isn't a pretty one: lead. Lead is not as susceptible to the whisker effect, but now that lead has been widely outlawed (in Europe it was phased out in 2006), we're seeing the problem far more than before. That will only get worse as lead is completely eliminated in the U.S.
The solution? For now, nothing. There's no known alternative to lead or tin solder, and since the problem takes months or years to crop up, the issue is largely being ignored. That could change in a couple of years, when failure rates begin to skyrocket with no advance warning. Is your computer crashing for no apparent reason? This might be why.
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7 Posted by djbrazier59 on Thu Sep 3, 2009 3:44PM EDT Report Abuse
Would a non-conductive coating like plastic stop the growth of tin whiskers?
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8 Posted by brianwrx on Thu Sep 3, 2009 3:13PM EDT Report Abuse
I wouldn't say that tin whiskers are being ignored. Any company that is selling a world class product is well aware of the risks of tin lead and other compromises imposed by the RoHS legislation. Proper testing is being done to ensure that there is enough spacing between pins or "wires" to prevent a problematic shorts or that mechanical forces are not promoting whisker growth. I would be worried about cheap toys and gadgets though. Small or cheap companies likely don't have the resources to properly design and test RoHS products. RoHS is interesting in general. It is supposed to be good for the environment, but if you look at solder in electronics, the net effect is a loss for the environment. Tin solder must be heated an additional 40C than lead solder which means more energy is being used to produce RoHS electronics. Also, that lead is being replaced with other elements such as Silver which is not banned under RoHs and are just as harmful to animals. Lastly, the number 1 user of lead in consumer products is the battery industry and they are exempt from RoHS requirements. Batteries introduce 85-90% of lead in new products each year. By comparison, electronics are only responsible for 0.5% of lead introduced in products (before RoHS). RoHS was well intentioned but a failed piece of legislation.
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9 Posted by retired_navy_doc on Thu Sep 3, 2009 8:36PM EDT Report Abuse
Couldn't they use aluminum?
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10 Posted by auricman on Thu Sep 3, 2009 2:59PM EDT Report Abuse
Tin alloyed with bismuith, copper and silver have all been developed as alternatives for tin/lead. All have drawbacks and "none" are whisker "free". BTW, not even tinlead is 100% whisker free. Reduced smaller and once they develope they tend not to continue to grow. The most effective means of control is in design and processing. Stress in the deposit and design of conponets are a huge contributing factor in whisker growth rate. certainly, time, temperature and humidity are other major factors
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6 Posted by piearesquared2001 on Thu Sep 3, 2009 8:11PM EDT Report Abuse
Interestingly enough, any chemist with or without a background in crystallography can tell you why tin whiskers form. The Wiki article actually covers it, but in complex terms and with a lot of hand-waving. When you heat a substance, you are causing the molecules and atoms to vibrate faster. If you heat a solid substance enough, the attractions between the molecules break down, forming a liquid. This is pretty obvious, right? Well some of those molecules and atoms when heated enough become free-floating, IE a gas. Now, the inside of a computer is hot - but not hot enough, as a general rule - to spontaneously sublimate (go from solid to gas) every atom in every component. That said, a -few- atoms and molecules do get knocked loose all the time. They "float" around until they find a surface to "land" on. Like sugar crystals in a jar with a string, they begin to accumulate on the available surface (substrate) in re-formed solid state (crystals). Why they grow "straight" as opposed to dendrite-like would take another long explanation that would bore most readers to tears. This is a horribly simplistic explanation of a particularly complex process. The Wikipedia article does a good job of explaining the problem and a few of the proposed solutions. To be blunt, though, entropic forces are constantly at work in any system of any complexity. The more complex and detailed a system, the more entropy can and will play hob with the components. Perhaps our best bet is not to attempt to circumvent the inevitable, but to embrace it and create recyclable micro components.