20 ms·

Tin whiskers: What happens when they spontaneously erupt? (2018)

200 points by forgotthepasswd 5y ago

deleted 5y ago
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mmastrac 5y ago
After seeing the articles on ice spikes, I wonder if this is somehow a related phenomenon.
- thanatos519 5y ago
  Indeed. Maybe they are also related to bone spurs!
- jerf 5y ago
  Remind me more of this, only in slow-mo: https://www.nature.com/articles/nature.2015.16771 https://www.nature.com/articles/nature.2015.16771
dmitrygr 5y ago
Use lead solder, like NASA does: easier to use, and no whisker issues. Just wash your hands afterwards
- mmastrac 5y ago
  Better to solve these issues long-term. Lead's external costs in full product lifecycles are just too high.
  - iancmceachern 5y ago
    Yeah, and we're not allowed to even put it in products anymore by law (RoHs, reach, etc)
  - dmitrygr 5y ago
    As you read in TFA, there is no known solution, nor even a known cause for whiskers
    - mmastrac 5y ago
      No known cause or solution _yet_
      - adrian_b 5y ago
        It is extremely unlikely to ever find any solution to the tin whiskers problem, other than alloying tin with toxic elements, i.e. either lead or antimony. The reliability problem could be solved only by replacing soldering with another method of making electrical connections during PCB assembly, e.g. thermal/ultrasonic welding of copper on copper, metal deposition in vacuum etc. While replacing soldering is possible, any known alternative method would hugely increase the price for the assembly of electronic equipment. Soldering is not used because it is a good method for making electrical connections, but because it is extremely cheap, allowing many thousands of connections to be made simultaneously, during a pass of a PCB through a reflow oven, or over a soldering wave.
        Animats 5y ago
        The reliability problem could be solved only by replacing soldering with another method of making electrical connections during PCB assembly, e.g. thermal/ultrasonic welding of copper on copper, metal deposition in vacuum etc. There's been some interest in laser welding for PCB assembly. But most modern components are not designed with the pins out where you can get at them with a laser beam. Laser welding is commonly used to weld the connections in automotive battery packs, so it does work.
        Animats 5y ago
        If you can get the parts you need in SSOP or TSSOP packaging, with the pins visible from straight down, laser brazing might work. Brazing is done at higher temperatures than soldering, but with a laser, you can apply the heat to just the area of interest, and hopefully not cook the ICs. Laser soldering already exists, and there are laser cutters, so adapting one for laser brazing ought to be possible. The advantage of brazing is that you can use many more materials, most of which don't contain either tin or lead. Low-cost aluminum brazing rod or wire might work. Working temp around 700C. This is going to take careful heat management. Worth a try for aerospace applications.
- Steltek 5y ago
  On the contrary, I am not NASA. I'm not even a consumer electronics company. I'm a hobbyist at home, soldering things at my desk or table. Lead-free is the least of my problems when building something and I don't believe "just wash your hands" is sufficient for cleaning my workspace (or kitchen table?) of possible lead contamination.
  - JaggedNZ 5y ago
    Fellow hobbyist here. Actually your biggest health risk is industrial asthma from flux fumes. I know professionals who have spent a good fraction of there lives soldering with no lead poisoning issues. Lead needs to be consumed or inhaled for it to be an issue. The guy I meet who did have lead poisoning, large bore rifle shooting coach, from spending to much time at the “wrong end” of the rifle range. Lots of lead dust there.
  - alar44 5y ago
    It definitely is enough. I don't know where the myth that looking at lead kills you started, but unless you are eating it or breathing it in (soldering is not hot enough to vaporize lead) there's nothing to worry about.
    - throwaway0a5e 5y ago
      >I don't know where the myth that looking at lead kills you started For a large subset of western society it's highly fashionable to give a lot of shits about health and safety. I'm not saying this is a bad thing to care about but let's be honest here, when you treat abstract concepts like a minor religious deity there's some baggage that comes with that. Let the feedback loops run their course for a decade or three and combine that with the fact that it's very easy to be scared of things you're not familiar with and you get the current situation. This is why people go crazy over a long forgotten package of asbestos shingles sitting on some shelf in the maintenance department's storeroom or think you're gonna get black lung from using an antique coal stove a couple times a year. Their belief system tells them to go crazy and they don't have the experience to know they don't need to.
- Flozzin 5y ago
  I wouldn't recommend this. If you do use lead soldering, make sure you don't breathe in any fumes.
  - the-dude 5y ago
    The boiling point of lead is 1749 °C (3180 °F).
    - xmodem 5y ago
      The boiling point of water is 100 °C, and yet my shower seems to produce an awful lot of steam despite not being anywhere close to that.
      - deleted 5y ago
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      - at_a_remove 5y ago
        You have confused steam with small water droplets, akin to what emerges from an ultrasonic mister. If it were steam, you would be shrieking and then dead.
        B1FF_PSUVM 5y ago
        Good point. Also, steam is invisible. What we see - e.g. from a boiling kettle - is condensation.
        deathanatos 5y ago
        But it's still water, and it's still moving up and about of its own accord in the local air which is the point. That it isn't technically steam doesn't disprove the point the person you're responding to is trying to make… The commenter's point isn't that the lead has technically been boiled, it's that, if we analogize to "steam" in a shower, I don't have to reach water's boiling point before I'm breathing in water. Does that translate to lead: i.e., even if I'm below lead's boiling point, could I be nonetheless breathing in lead vapor, or something like that? (I don't know the answer here, which would push me towards lead-free solder. I.e., I don't know if the precautions I'd take with lead would actually suffice.)
- adrian_b 5y ago
  Besides lead, there is a second element which greatly reduces the risk of tin whiskers, when alloyed to tin: antimony. However the proposals of replacing the tin-lead alloys withe tin-antimony alloys have been rejected due to the fear that antimony is also toxic. While antimony in high doses is indeed quite toxic, it is less dangerous as a pollutant than lead, because it does not have the same tendency for very long time accumulation in animal bodies and such a strong effect on the nervous system.
RicoElectrico 5y ago
> No one has been able to eliminate whiskering, as the phenomenon is not yet fully understood. It's the kind of stuff we should be embarrassed not to understand. I get that understanding living things can be tricky due to complexity and issues with controlling conditions, but a lump of metal? Whatever we find out will at least save us money in damaged devices, and hopefully drive some progress in metallurgy as well. We had an era in semiconductor manufacturing when despite the relative simplicity the process was not understood/controlled fully, which took the toll on yield. E.g. CMOS was super fussy due to difficulties in creating gate oxide - impurities in air like halogens made the yield seasonal [1]. But now I assume that if any problems arise, they're due to bona-fide complexity. [1] https://news.ycombinator.com/item?id=28178612 https://news.ycombinator.com/item?id=28178612
- deleted 5y ago
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- semi-extrinsic 5y ago
  A lot of the challenge here AFAIK is that the process needs to be understood at the molecular level, where we measure time in picoseconds (10^-12), while this process takes something like 10^6 seconds. The disparity is an absolutely astronomical factor of 10^18.
- robomartin 5y ago
  > It's the kind of stuff we should be embarrassed not to understand. We understand it. Onset is stochastic. Mitigation is impossible given current regulations in consumer-land. Read my longer comment for further details. EDIT: What I mean by "we understand it" is that we know that lead-free solder chemistry leads to tin whisker growth. When I was taking a deep dive into this many years back, the researchers I was working with at NASA told me "Growth onset can be 0 days to 3 years after manufacturing. Your guess is as good as mine.". And, BTW, you can have growth start in a few days in one corner of the PCB and a few months later elsewhere. It's a complex relationship of materials properties. We know that tin whisker growth in lead-free solder is as much of a reality as gravity is between two celestial bodies. In other words, it will happen. We simply have no way to predict when or how quickly they will grow. It might just be too complex to compute/predict given the variables involved.
prutschman 5y ago
Could potting prevent this, or can the whiskers "push through" epoxy?
- dr_orpheus 5y ago
  Yes? In my experience (some spacecraft electronics stuff) this is also on the list of things where we think conformal coating/potting helps prevent tin whiskers. But there are still instances where Tin whiskers have grown and pushed through conformal coating on a PCB. Edit: Go look at the more detailed response from robomartin
- robomartin 5y ago
  No. Can't prevent it. Yes, they can push through epoxy or buckle under it (which isn't a solution). Read my longer answer for details. These things are a nightmare.
- jccooper 5y ago
  Yes; satellite boards tend to have conformal coatings, it helps but it's not a complete solution. (The coatings also help avoid shorts from junk floating around, and launch vibration.) Because of the inherent unreliability and difficulty in replacement, they also try really hard to avoid lead-free solder requirements.
robomartin 5y ago
I have dealt with the tin whisker problem in the context of aerospace applications (both space-borne and terrestrial flight), including extensive consulting with subject matter experts from NASA. The bottom line is quite simple: Tin whisker growth onset is a stochastic process. We cannot predict when it will start and we cannot prevent it. Once they start growing it is almost impossible to contain them. They will poke through conformal coatings such as parylene and arathane. If they don't, they will buckle (coil-up) under the coating. While buckling sounds like a desirable outcome, this could lead to shorting of adjacent contacts in todays fine pitch integrated circuits and components. Growth rate can be in the order of 10 mm per year. This means that adjacent leads of something as mundane as a SOIC-16 package can be shorted by a tin whisker in 28 days or less. The take away is: There's nothing we can do about tin whiskers that is 100% guaranteed to prevent growth or slow it down by a non-trivial amount. The only path that prevents their growth is to use lead-based solder. This is why, as an example, we would do such things as send out BGA's with RoHS compliant solder balls to be re-balled with leaded solder. Time for a bit of a rant: All my work in this area led me to look at the RoHS initiative as yet another example of something that, while well intentioned, it will likely have precisely the opposite effect from what was intended. The fact that lead-free solder is susceptible to tin whisker growth means that 100% of all consumer electronic products are ticking time bombs when it comes to failures. This means that all kinds of consumer, commercial and industrial electronic products will fail over time in ways we might not be able to explain. The reason for this is that nobody does deep forensics when products fail. There is no reporting from the likes of Apple, Samsung, LG, Visio, Sony and myriad other manufacturers on failure rates and causes. In fact, they might not even have this data as consumer, commercial and industrial users simply replace the devices as they fail and move on. In other words, it is likely RoHS has caused --or will cause-- massively more garbage in landfills. As a simple data point, my 40 year old HP-41 calculator still works perfectly fine. It is impossible to imagine a RoHS-compliant calculator not ending up in a landfill way earlier than 40 years. There was a bit of a movement to roll back RoHS around the time it was being enacted. Going up against many nations and politicians using "save the planet" to get elected proved impossible for those who rightly brought-up that the transition to lead-free solder required far more research before we fully understood the potential consequences. It wasn't about not wanting to go lead-free, it was about making the move when the science and math indicated that it would not create the massive problem we now likely have on our hands. The data on electronics waste due to tin whiskers is probably impossible to find. It might not even exist. Which is a tragedy. If you want to learn more about this, here are a couple of good links: https://nepp.nasa.gov/whisker./background/index.htm https://nepp.nasa.gov/whisker./background/index.htm https://nepp.nasa.gov/whisker/reference/tech_papers/kadesch2001-article-dangers-of-tin-whiskers-and-conformal-coat-study.pdf https://nepp.nasa.gov/whisker/reference/tech_papers/kadesch2... https://www.google.com/search?q=tin+whisker&hl=en&tbm=isch https://www.google.com/search?q=tin+whisker&hl=en&tbm=isch https://web.calce.umd.edu/tin-whiskers/ https://web.calce.umd.edu/tin-whiskers/
FpUser 5y ago
Accepting RoHS was in my opinion one of the most idiotic environmental initiatives that was rammed through without much thinking about long term cost / benefit analysis.
- hulitu 5y ago
  A repaired device is one less device sold new. At the end what matters is money.
Damogran6 5y ago
State of Colorado Datacenters got them. The response to them were weird...if any machine were in any of the affected areas, they were persona non grata...they could never leave those datacenters as functional server. It DID lever some money for an awesome off-site backup datacenter...which was eventually our only datacenter for 'reasons'. In our case, I think one of the datacenter's raised floors got carpeted (don't judge, it predated me, I was equally baffled) and a grounding issue caused a voltage drift causing the tin to migrate...
- walrus01 5y ago
  raised floors in general are a nightmare for grounding/bonding/differences in potential between racks, the steel floor structure, the building, and electrical conduits. there's a reason why almost nobody builds them new from a clean-sheet-of-paper design anymore for serious datacenter applications or ISP/telecom purposes, which are racks/cabinet on concrete slab and everything overhead now. it's much easier to ground/bond everything together using some very fat copper cables run along ladder rack overhead, and bond all the racks to that.
  - pomian 5y ago
    Raised floors where a great way to create laminar flow for clean rooms. I suspect that as with manufacturing, the "clean" space is inside the computers now.
tejohnso 5y ago
This is very surprising to me. I had no idea that certain conductors had some kind of (stochastic, according to robomartin) built-in time delayed short circuit mechanism that will, without question, manifest itself given enough time. Like some kind of natural electronics prank.
- voakbasda 5y ago
  If you were feeling particularly cynical, you might wonder whether this phenomenon has been incorporated into shipping products, such manufacturers would be assured that their goods would fail shortly after the warranty expired.
  - robomartin 5y ago
    > assured that their goods would fail shortly after the warranty expired I have seen a number of similar comments on this thread. Manufacturers were dragged kicking and screaming --they were forced, through legislation-- to switch to lead-free solder. Nobody --nobody-- in manufacturing wanted this. This idea that going lead-free was a conspiracy by manufacturers to have their products fail more often is completely false. One of the most well-known episodes of mass failures due to tin whiskers happened when the Swatch Group (watch manufacturer) converted to lead-free solder. They had so many failures that they ended-up requesting an exception from RoHS [0]. As I said in another comment. The problem with RoHS as it pertains to tin whisker failures is that we will likely never know what percentage of failing consumer, commercial and industrial products end-up in the landfill because of the forced and premature transition to this lead-free solder. If one studies that history of the transition it is easy to see it includes many companies clamoring for years of additional studies before making the change. We went into it by force in 2006 without having had full data on potential issues. At the time I was manufacturing expensive FPGA-based real time image processing boards. I made the decision to stop shipping product to Europe. My decision was based on a very simple reality: I still had to honor a years-long warranty in Europe and could not include any clause stating that we could not be responsible for a government-mandated technology known to have serious problems that could lead to failures at any time, even very early on. Companies were forced through mandate and given absolutely no immunity from the very real tin whisker problem. I did not ship a product into Europe for two or three years. We were busy enough everywhere else, so I did not care one bit. We actually had European customers who needed the hardware buy through a US-based path and then hand carry into the EU through whatever means. Not my problem. [0] https://hlinstruments.com/RoHS_articles/A-1018_Swatch.pdf https://hlinstruments.com/RoHS_articles/A-1018_Swatch.pdf
1970-01-01 5y ago
Much more info here: https://nepp.nasa.gov/whisker/ https://nepp.nasa.gov/whisker/
ChuckMcM 5y ago
It really is an amazing phenomena. Effectively atoms of tin are moving from the tin out to the end of the whisker. We spent a week talking about whiskering(sp?) in my materials science class at USC because it was such a big deal in the EE world. Prior to that class my world view was that only electrons could travel through metal, only to find that metal can travel through metal too! Locally at NASA Ames they had an experiment where they had a bunch of different assemblies being exposed to various conditions (high electric fields, non-ionizing radiation, etc) and one of the things they were measuring was the production of whiskers and other changes in material properties (strength, toughness, Etc.). Always amazing what we know and what we don't know about what we know.
- zdragnar 5y ago
  > that metal can travel through metal too! I recommend watching clips of mercury amalgamations forming (nile red has some great videos on youtube). There is something about it that is both disturbing and beautiful to me.
  - cjameskeller 5y ago
    That was a welcome rabbit hole. Thank you!
  - pontifier 5y ago
    My current theory of whisker formation is single atom mercury impurities causing local mobility at the base of a whisker.
- rootusrootus 5y ago
  > Effectively atoms of tin are moving from the tin out to the end of the whisker. Don't tin whiskers get built from the base up, though? So the tip was the first thing built, and just gets pushed farther away.
jwilk 5y ago
> as fast as 15 nanometer per second to 1 mm per year That doesn't sound right. 15 nm/s is ~47 cm/year.
- greggsy 5y ago
  I don’t think it’s a steady growth rate.
- coryrc 5y ago
  They break off if they get too long and will run out of material at some point.
atesti 5y ago
Does anybody from Germany know where I can still buy leaded solder? Unfortunately I forgot to order a lifetime supply while it was still available
- tinco 5y ago
  When did that happen? I bought a spool just over a year ago and the sales person didn't bat an eye. This was in The Netherlands, if we don't have the same law then maybe there's your answer?
- askvictor 5y ago
  Is every package coming into Germany screened for Lead? Could you not just order some from another country?
- q-big 5y ago
  > Does anybody from Germany know where I can still buy leaded solder? I ordered on ebay, sold by a vendor from another EU country that cares less about the regulations.
- detaro 5y ago
  It's trivial to find online shops selling it, even if the large hobby-electronics suppliers have generally stopped stocking it. RS, TME, eleshop, ... all have it.

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mmastrac 5y ago

After seeing the articles on ice spikes, I wonder if this is somehow a related phenomenon.

thanatos519 5y ago
Indeed. Maybe they are also related to bone spurs!
jerf 5y ago
Remind me more of this, only in slow-mo: https://www.nature.com/articles/nature.2015.16771 https://www.nature.com/articles/nature.2015.16771

dmitrygr 5y ago

Use lead solder, like NASA does: easier to use, and no whisker issues. Just wash your hands afterwards

mmastrac 5y ago
Better to solve these issues long-term. Lead's external costs in full product lifecycles are just too high.
- iancmceachern 5y ago
  Yeah, and we're not allowed to even put it in products anymore by law (RoHs, reach, etc)
- dmitrygr 5y ago
  As you read in TFA, there is no known solution, nor even a known cause for whiskers
  - mmastrac 5y ago
    No known cause or solution _yet_
    - adrian_b 5y ago
      It is extremely unlikely to ever find any solution to the tin whiskers problem, other than alloying tin with toxic elements, i.e. either lead or antimony. The reliability problem could be solved only by replacing soldering with another method of making electrical connections during PCB assembly, e.g. thermal/ultrasonic welding of copper on copper, metal deposition in vacuum etc. While replacing soldering is possible, any known alternative method would hugely increase the price for the assembly of electronic equipment. Soldering is not used because it is a good method for making electrical connections, but because it is extremely cheap, allowing many thousands of connections to be made simultaneously, during a pass of a PCB through a reflow oven, or over a soldering wave.
      - Animats 5y ago
        The reliability problem could be solved only by replacing soldering with another method of making electrical connections during PCB assembly, e.g. thermal/ultrasonic welding of copper on copper, metal deposition in vacuum etc. There's been some interest in laser welding for PCB assembly. But most modern components are not designed with the pins out where you can get at them with a laser beam. Laser welding is commonly used to weld the connections in automotive battery packs, so it does work.
        Animats 5y ago
        If you can get the parts you need in SSOP or TSSOP packaging, with the pins visible from straight down, laser brazing might work. Brazing is done at higher temperatures than soldering, but with a laser, you can apply the heat to just the area of interest, and hopefully not cook the ICs. Laser soldering already exists, and there are laser cutters, so adapting one for laser brazing ought to be possible. The advantage of brazing is that you can use many more materials, most of which don't contain either tin or lead. Low-cost aluminum brazing rod or wire might work. Working temp around 700C. This is going to take careful heat management. Worth a try for aerospace applications.
Steltek 5y ago
On the contrary, I am not NASA. I'm not even a consumer electronics company. I'm a hobbyist at home, soldering things at my desk or table. Lead-free is the least of my problems when building something and I don't believe "just wash your hands" is sufficient for cleaning my workspace (or kitchen table?) of possible lead contamination.
- JaggedNZ 5y ago
  Fellow hobbyist here. Actually your biggest health risk is industrial asthma from flux fumes. I know professionals who have spent a good fraction of there lives soldering with no lead poisoning issues. Lead needs to be consumed or inhaled for it to be an issue. The guy I meet who did have lead poisoning, large bore rifle shooting coach, from spending to much time at the “wrong end” of the rifle range. Lots of lead dust there.
- alar44 5y ago
  It definitely is enough. I don't know where the myth that looking at lead kills you started, but unless you are eating it or breathing it in (soldering is not hot enough to vaporize lead) there's nothing to worry about.
  - throwaway0a5e 5y ago
    >I don't know where the myth that looking at lead kills you started For a large subset of western society it's highly fashionable to give a lot of shits about health and safety. I'm not saying this is a bad thing to care about but let's be honest here, when you treat abstract concepts like a minor religious deity there's some baggage that comes with that. Let the feedback loops run their course for a decade or three and combine that with the fact that it's very easy to be scared of things you're not familiar with and you get the current situation. This is why people go crazy over a long forgotten package of asbestos shingles sitting on some shelf in the maintenance department's storeroom or think you're gonna get black lung from using an antique coal stove a couple times a year. Their belief system tells them to go crazy and they don't have the experience to know they don't need to.
Flozzin 5y ago
I wouldn't recommend this. If you do use lead soldering, make sure you don't breathe in any fumes.
- the-dude 5y ago
  The boiling point of lead is 1749 °C (3180 °F).
  - xmodem 5y ago
    The boiling point of water is 100 °C, and yet my shower seems to produce an awful lot of steam despite not being anywhere close to that.
    - deleted 5y ago
      [deleted]
    - at_a_remove 5y ago
      You have confused steam with small water droplets, akin to what emerges from an ultrasonic mister. If it were steam, you would be shrieking and then dead.
      - B1FF_PSUVM 5y ago
        Good point. Also, steam is invisible. What we see - e.g. from a boiling kettle - is condensation.
      - deathanatos 5y ago
        But it's still water, and it's still moving up and about of its own accord in the local air which is the point. That it isn't technically steam doesn't disprove the point the person you're responding to is trying to make… The commenter's point isn't that the lead has technically been boiled, it's that, if we analogize to "steam" in a shower, I don't have to reach water's boiling point before I'm breathing in water. Does that translate to lead: i.e., even if I'm below lead's boiling point, could I be nonetheless breathing in lead vapor, or something like that? (I don't know the answer here, which would push me towards lead-free solder. I.e., I don't know if the precautions I'd take with lead would actually suffice.)
adrian_b 5y ago
Besides lead, there is a second element which greatly reduces the risk of tin whiskers, when alloyed to tin: antimony. However the proposals of replacing the tin-lead alloys withe tin-antimony alloys have been rejected due to the fear that antimony is also toxic. While antimony in high doses is indeed quite toxic, it is less dangerous as a pollutant than lead, because it does not have the same tendency for very long time accumulation in animal bodies and such a strong effect on the nervous system.

RicoElectrico 5y ago

> No one has been able to eliminate whiskering, as the phenomenon is not yet fully understood. It's the kind of stuff we should be embarrassed not to understand. I get that understanding living things can be tricky due to complexity and issues with controlling conditions, but a lump of metal? Whatever we find out will at least save us money in damaged devices, and hopefully drive some progress in metallurgy as well. We had an era in semiconductor manufacturing when despite the relative simplicity the process was not understood/controlled fully, which took the toll on yield. E.g. CMOS was super fussy due to difficulties in creating gate oxide - impurities in air like halogens made the yield seasonal [1]. But now I assume that if any problems arise, they're due to bona-fide complexity. [1] https://news.ycombinator.com/item?id=28178612 https://news.ycombinator.com/item?id=28178612

deleted 5y ago
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semi-extrinsic 5y ago
A lot of the challenge here AFAIK is that the process needs to be understood at the molecular level, where we measure time in picoseconds (10^-12), while this process takes something like 10^6 seconds. The disparity is an absolutely astronomical factor of 10^18.
robomartin 5y ago
> It's the kind of stuff we should be embarrassed not to understand. We understand it. Onset is stochastic. Mitigation is impossible given current regulations in consumer-land. Read my longer comment for further details. EDIT: What I mean by "we understand it" is that we know that lead-free solder chemistry leads to tin whisker growth. When I was taking a deep dive into this many years back, the researchers I was working with at NASA told me "Growth onset can be 0 days to 3 years after manufacturing. Your guess is as good as mine.". And, BTW, you can have growth start in a few days in one corner of the PCB and a few months later elsewhere. It's a complex relationship of materials properties. We know that tin whisker growth in lead-free solder is as much of a reality as gravity is between two celestial bodies. In other words, it will happen. We simply have no way to predict when or how quickly they will grow. It might just be too complex to compute/predict given the variables involved.

prutschman 5y ago

Could potting prevent this, or can the whiskers "push through" epoxy?

dr_orpheus 5y ago
Yes? In my experience (some spacecraft electronics stuff) this is also on the list of things where we think conformal coating/potting helps prevent tin whiskers. But there are still instances where Tin whiskers have grown and pushed through conformal coating on a PCB. Edit: Go look at the more detailed response from robomartin
robomartin 5y ago
No. Can't prevent it. Yes, they can push through epoxy or buckle under it (which isn't a solution). Read my longer answer for details. These things are a nightmare.
jccooper 5y ago
Yes; satellite boards tend to have conformal coatings, it helps but it's not a complete solution. (The coatings also help avoid shorts from junk floating around, and launch vibration.) Because of the inherent unreliability and difficulty in replacement, they also try really hard to avoid lead-free solder requirements.

robomartin 5y ago

I have dealt with the tin whisker problem in the context of aerospace applications (both space-borne and terrestrial flight), including extensive consulting with subject matter experts from NASA. The bottom line is quite simple: Tin whisker growth onset is a stochastic process. We cannot predict when it will start and we cannot prevent it. Once they start growing it is almost impossible to contain them. They will poke through conformal coatings such as parylene and arathane. If they don't, they will buckle (coil-up) under the coating. While buckling sounds like a desirable outcome, this could lead to shorting of adjacent contacts in todays fine pitch integrated circuits and components. Growth rate can be in the order of 10 mm per year. This means that adjacent leads of something as mundane as a SOIC-16 package can be shorted by a tin whisker in 28 days or less. The take away is: There's nothing we can do about tin whiskers that is 100% guaranteed to prevent growth or slow it down by a non-trivial amount. The only path that prevents their growth is to use lead-based solder. This is why, as an example, we would do such things as send out BGA's with RoHS compliant solder balls to be re-balled with leaded solder. Time for a bit of a rant: All my work in this area led me to look at the RoHS initiative as yet another example of something that, while well intentioned, it will likely have precisely the opposite effect from what was intended. The fact that lead-free solder is susceptible to tin whisker growth means that 100% of all consumer electronic products are ticking time bombs when it comes to failures. This means that all kinds of consumer, commercial and industrial electronic products will fail over time in ways we might not be able to explain. The reason for this is that nobody does deep forensics when products fail. There is no reporting from the likes of Apple, Samsung, LG, Visio, Sony and myriad other manufacturers on failure rates and causes. In fact, they might not even have this data as consumer, commercial and industrial users simply replace the devices as they fail and move on. In other words, it is likely RoHS has caused --or will cause-- massively more garbage in landfills. As a simple data point, my 40 year old HP-41 calculator still works perfectly fine. It is impossible to imagine a RoHS-compliant calculator not ending up in a landfill way earlier than 40 years. There was a bit of a movement to roll back RoHS around the time it was being enacted. Going up against many nations and politicians using "save the planet" to get elected proved impossible for those who rightly brought-up that the transition to lead-free solder required far more research before we fully understood the potential consequences. It wasn't about not wanting to go lead-free, it was about making the move when the science and math indicated that it would not create the massive problem we now likely have on our hands. The data on electronics waste due to tin whiskers is probably impossible to find. It might not even exist. Which is a tragedy. If you want to learn more about this, here are a couple of good links: https://nepp.nasa.gov/whisker./background/index.htm https://nepp.nasa.gov/whisker./background/index.htm https://nepp.nasa.gov/whisker/reference/tech_papers/kadesch2001-article-dangers-of-tin-whiskers-and-conformal-coat-study.pdf https://nepp.nasa.gov/whisker/reference/tech_papers/kadesch2... https://www.google.com/search?q=tin+whisker&hl=en&tbm=isch https://www.google.com/search?q=tin+whisker&hl=en&tbm=isch https://web.calce.umd.edu/tin-whiskers/ https://web.calce.umd.edu/tin-whiskers/

FpUser 5y ago

Accepting RoHS was in my opinion one of the most idiotic environmental initiatives that was rammed through without much thinking about long term cost / benefit analysis.

hulitu 5y ago
A repaired device is one less device sold new. At the end what matters is money.

Damogran6 5y ago

State of Colorado Datacenters got them. The response to them were weird...if any machine were in any of the affected areas, they were persona non grata...they could never leave those datacenters as functional server. It DID lever some money for an awesome off-site backup datacenter...which was eventually our only datacenter for 'reasons'. In our case, I think one of the datacenter's raised floors got carpeted (don't judge, it predated me, I was equally baffled) and a grounding issue caused a voltage drift causing the tin to migrate...

walrus01 5y ago
raised floors in general are a nightmare for grounding/bonding/differences in potential between racks, the steel floor structure, the building, and electrical conduits. there's a reason why almost nobody builds them new from a clean-sheet-of-paper design anymore for serious datacenter applications or ISP/telecom purposes, which are racks/cabinet on concrete slab and everything overhead now. it's much easier to ground/bond everything together using some very fat copper cables run along ladder rack overhead, and bond all the racks to that.
- pomian 5y ago
  Raised floors where a great way to create laminar flow for clean rooms. I suspect that as with manufacturing, the "clean" space is inside the computers now.

tejohnso 5y ago

This is very surprising to me. I had no idea that certain conductors had some kind of (stochastic, according to robomartin) built-in time delayed short circuit mechanism that will, without question, manifest itself given enough time. Like some kind of natural electronics prank.

voakbasda 5y ago
If you were feeling particularly cynical, you might wonder whether this phenomenon has been incorporated into shipping products, such manufacturers would be assured that their goods would fail shortly after the warranty expired.
- robomartin 5y ago
  > assured that their goods would fail shortly after the warranty expired I have seen a number of similar comments on this thread. Manufacturers were dragged kicking and screaming --they were forced, through legislation-- to switch to lead-free solder. Nobody --nobody-- in manufacturing wanted this. This idea that going lead-free was a conspiracy by manufacturers to have their products fail more often is completely false. One of the most well-known episodes of mass failures due to tin whiskers happened when the Swatch Group (watch manufacturer) converted to lead-free solder. They had so many failures that they ended-up requesting an exception from RoHS [0]. As I said in another comment. The problem with RoHS as it pertains to tin whisker failures is that we will likely never know what percentage of failing consumer, commercial and industrial products end-up in the landfill because of the forced and premature transition to this lead-free solder. If one studies that history of the transition it is easy to see it includes many companies clamoring for years of additional studies before making the change. We went into it by force in 2006 without having had full data on potential issues. At the time I was manufacturing expensive FPGA-based real time image processing boards. I made the decision to stop shipping product to Europe. My decision was based on a very simple reality: I still had to honor a years-long warranty in Europe and could not include any clause stating that we could not be responsible for a government-mandated technology known to have serious problems that could lead to failures at any time, even very early on. Companies were forced through mandate and given absolutely no immunity from the very real tin whisker problem. I did not ship a product into Europe for two or three years. We were busy enough everywhere else, so I did not care one bit. We actually had European customers who needed the hardware buy through a US-based path and then hand carry into the EU through whatever means. Not my problem. [0] https://hlinstruments.com/RoHS_articles/A-1018_Swatch.pdf https://hlinstruments.com/RoHS_articles/A-1018_Swatch.pdf

1970-01-01 5y ago

Much more info here: https://nepp.nasa.gov/whisker/ https://nepp.nasa.gov/whisker/

ChuckMcM 5y ago

It really is an amazing phenomena. Effectively atoms of tin are moving from the tin out to the end of the whisker. We spent a week talking about whiskering(sp?) in my materials science class at USC because it was such a big deal in the EE world. Prior to that class my world view was that only electrons could travel through metal, only to find that metal can travel through metal too! Locally at NASA Ames they had an experiment where they had a bunch of different assemblies being exposed to various conditions (high electric fields, non-ionizing radiation, etc) and one of the things they were measuring was the production of whiskers and other changes in material properties (strength, toughness, Etc.). Always amazing what we know and what we don't know about what we know.

zdragnar 5y ago
> that metal can travel through metal too! I recommend watching clips of mercury amalgamations forming (nile red has some great videos on youtube). There is something about it that is both disturbing and beautiful to me.
- cjameskeller 5y ago
  That was a welcome rabbit hole. Thank you!
- pontifier 5y ago
  My current theory of whisker formation is single atom mercury impurities causing local mobility at the base of a whisker.
rootusrootus 5y ago
> Effectively atoms of tin are moving from the tin out to the end of the whisker. Don't tin whiskers get built from the base up, though? So the tip was the first thing built, and just gets pushed farther away.

jwilk 5y ago

> as fast as 15 nanometer per second to 1 mm per year That doesn't sound right. 15 nm/s is ~47 cm/year.

greggsy 5y ago
I don’t think it’s a steady growth rate.
coryrc 5y ago
They break off if they get too long and will run out of material at some point.

atesti 5y ago

Does anybody from Germany know where I can still buy leaded solder? Unfortunately I forgot to order a lifetime supply while it was still available

tinco 5y ago
When did that happen? I bought a spool just over a year ago and the sales person didn't bat an eye. This was in The Netherlands, if we don't have the same law then maybe there's your answer?
askvictor 5y ago
Is every package coming into Germany screened for Lead? Could you not just order some from another country?
q-big 5y ago
> Does anybody from Germany know where I can still buy leaded solder? I ordered on ebay, sold by a vendor from another EU country that cares less about the regulations.
detaro 5y ago
It's trivial to find online shops selling it, even if the large hobby-electronics suppliers have generally stopped stocking it. RS, TME, eleshop, ... all have it.