How big of a deal is the "electrostatic sensitive device" warning?

Discussion in 'General Electronics Chat' started by Ingeniir, Jul 16, 2011.

  1. Ingeniir

    Thread Starter New Member

    Jun 29, 2011
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    The solid state relays that I ordered from digikey arrived with a caution sticker that reads "Electrostatic sensitive devices, do not open or handle except at a static-free workstation". I'm inclined to just ignore it because I think most household desks are pretty static-free, but I wanted to check. Should I worry about this? How sensitive are the solid state relays to static electricity, are they easily damaged?
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    OMG, did you look at the package to read that? YOU CAN'T DO THAT WITH MOS CIRCUITRY. Just looking at electronic parts can result in a nuclear disaster! Just look at what's going on in Japan. It wasn't an earthquake, someone opened a bag containing 4001's!

    On CARPETING! What were they thinking?

    OK, on a serious note, "in the industry" components are only handled on anti-static mats, sheets of rubber that are somewhat conductive and connected to a good earth ground. Anyone handling parts is also grounded with a wrist strap and wire to ground. Wrist straps have a lot of resistance in them so they bleed static but don't endanger the person if they touch a live wire. Everything gets retested yearly, straps and writs bands daily.

    That's "proper procedure" per the QA department. In reality, in engineering I do not wear a strap when working protos (I do so when handling any production material). I would rather learn early on if I have something particularly sensitive (so I can remove it from my design).

    It has been over 10 years since I saw a repeatable failure I could definitely say was due to static, and in that case it was a 4000 series chip bare die being wire bonded pad by pad. They showed a 75%+ failure rate till I had the operation wire Vss and Vdd first, so the protection diodes were active.

    Those diodes are everywhere and are quite effective.
     
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  3. MrChips

    Moderator

    Oct 2, 2009
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    How important is this warning? Very important!

    But don't be paranoid... it is better to be informed.

    The rules you apply will differ depending on if you are an amateur or professional, working in winter or summer, on a cheap 20-cent BJT or a $500 development system board.
    HP has done extensive studies on how hidden undetected ESD at the component handling stage can escalate from a $1 cost to $1000 repair once the device is in the field.

    The bottom line is if you are in manufacturing, you apply ESD protection at all times.
    If you are hobbyist, take precautions when ESD is particularly high in winter times and ESD generating environments, carpet, soft chairs etc. Just pulling off masking tape off a plastic bag can generate huge ESD or even using that solder sucker.

    Be informed.
     
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  4. Wendy

    Moderator

    Mar 24, 2008
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    I don't follow procedure either, but don't minimize the risks. I've had 2N2222A NPN transistors blown from lack of static control at my former job. Took me a while to figure out what was happening. With the possible exception of power diodes, there is no part that can not be zapped with static.

    Walking wounded is always a problem. If a part gets zapped it can take a while to fail.

    ElectroStatic Discharge

    If your home has any static zaps, any at all, then you need to care. You may not be able to feel the static zap (AKA ESD event) that takes out a part, and you may not be able to tell the part is going to fail in a couple of weeks. If you throw sparks at all on door knobs or anywhere else it is a definite indicator there is a problem.
     
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  5. someonesdad

    Senior Member

    Jul 7, 2009
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    Many non-engineering/technical folks will often ignore the warnings. This is somewhat understandable because often the electrostatic discharges that damage something won't be felt by an individual. Your experiences will likely change once you work in industry, however. Antistatic behaviors are commonly seen and run the gamut of an engineer/tech working at a bench on a static mat with a grounded wrist strap to production workers having to put on special static gear and not being allowed to enter e.g. a production clean room area without being tested on special measurement equipment. This makes sense when thousands of expensive electrical devices are being worked on at one time and the failure costs are high.

    I didn't really internalize it until I had seen the SEM/surface analysis work done on some thin film devices of ours that we believe had been damaged by static discharges -- at least no other hypothesis fit the facts.

    I believe I've come across the data MrChips alludes to -- the corporate head of reliability engineering at HP (can't remember his name now, but I still remember his face -- and he was quite a nice guy) would often travel and give seminars on reliability and failure analysis and the common statistic bandied about was that a component costing a few cents that got damaged in the factory could result in ultimate repair costs or lost business costs later that were many orders of magnitude higher. It wasn't specific to just ESD damage, as there are many failure modes of electronic devices (electromigration in IC metallization used to be a big one back then).

    Now that I just occasionally work on hobby projects at home, I never use any static protection. However, just before I open a static sensitive bag, I'll ground myself on an instrument just to be safe. This casual approach has worked OK for the occasional projects I work on.
     
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  6. creakndale

    Active Member

    Mar 13, 2009
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  7. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Are you saying the 2N2222A is particularly ESD sensitive? I had a drive board stop working. I troubleshot the problem to a 2N2222A and replaced it. I did not observe any antistatic protection measures. I have not tested it yet (this was months ago) - still sitting on a shelf. What are the chances I jacked up the new one while installing it? I did it on a wood bench in a plasic chair on carpet.
     
  8. Adjuster

    Well-Known Member

    Dec 26, 2010
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    No, BJTs like 2N2222 have only moderate sensitivity to static. If you read Bill's post carefully you will see that he is pointing out that it is unwise to be complacent, because static damage does not only affect the more sensitive items like MOS devices. Almost any semiconductor device can be damaged by static if the discharge is sufficiently energetic.

    Static discharges can sometimes be quite intense, for instance when someone with synthetic soled shoes walks on a dry carpet, when the body can easily get up to tens of kV. Personally I would not recommend a plastic chair for doing electronics - a wooden one might be better. A lot of the risk can be avoided by using a wrist strap, which of course must incorporate a high resistance to avoid increasing your shock risk should you happen to touch something live. A static mat for your bench is another possible precaution.

    Having said that, it's anyone's guess why your 2N2222 packed up.
     
  9. hspalm

    Active Member

    Feb 17, 2010
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    I'm glad I don't care for ESD in my home lab. I spend enough time untangling oscilloscope-, soldering-, power supply- and multimeter leads, if I had a wrist strap connected to my work desk I would go insane. The layers of components and gadgets would hide any anti static mat, but I guess it wouldn't affect its purpose.
     
  10. Wendy

    Moderator

    Mar 24, 2008
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    Yeah, but the first time you handled a $50 component and it got zapped I suspect you would change your attitude. A common thread is complacency, myself included, but there is a difference between being casual and not caring at all. If you have enough money on the line it is a really good idea to understand the basics.

    Most of the newer tools sold for electronics are ESD rated. This is a good thing. The mat is important, but just as if not more important is the wrist strap. ESD control is a method, a system, to prevent damaging expensive parts.

    My current project, a digital clock, I bought a handful of CD4026 CMOS chips, cost 54¢ each. One of them didn't work, I'm pretty sure it was ESD damage. I threw the part away and grabbed another, as I bought spares just for something like this. 54¢ is pocket change, but at my job our products are worth thousands of dollars and a failure of what we make could cost a young man or woman their life. I and my company take ESD control considerably more serious there. I've been known to remind my fellow operators why it is important. I also have a kid who is talking about joining the military, it is also personal.

    The parts person for Collin's Radio at that time was an old man. I suspect he was middle aged when they were making radios from tube (AKA valves). They hadn't gotten serious about ESD control at that point, so why would he care? I kept having failures of units I repaired after a couple of hours, the walking wounded syndrome.
     
    Last edited: Jul 17, 2011
  11. #12

    Expert

    Nov 30, 2010
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    We've had some fun ridiculing the vendors for shipping things like GE MOVs with static warnings on them. Best to check here instead of letting the idiots in the shipping department make you crazy.
     
  12. MrChips

    Moderator

    Oct 2, 2009
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    I think some folks are still missing the point. Complacency may be the word to describe such attitude.

    ESD is not just about damaged components that immediately fail to function. ESD may cause undetectable damage what HP calls the "walking wounded" component that then fails later when the instrument is in the field. The cost of failure at that stage could be astronomical. (Think... multimillion dollar satellite up in space.)

    Here are some notes from HP on ESD:

    http://www.hp.woodshot.com/hprfhelp/4_downld/lit/other/ana004r.pdf

    http://www.hparchive.com/Bench_Briefs/HP-Bench-Briefs-1983-03-05.pdf

    Someonesdad, maybe it was Dick Moss at HP.
     
    Last edited: Jul 17, 2011
  13. hspalm

    Active Member

    Feb 17, 2010
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    Just to make it clear; I understand the importance of ESD protection and safety, and I would never be as dumb to ignore those guidelines in a professional setting, or if I were working on other peoples stuff. I always remove any static by touching the water mixer in the sink or other grounded shied before I handle sensitive devices (at least ICs that are not dispensable). I would use my anti static wrist-wrap if I were working on other peoples stuff, it's just that I almost never work on other peoples stuff, but I know where it is at least :)
     
  14. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    When you buy ESD bags in bulk they come with the protection warning already printed on them. You can ship 3mm nuts and bolts and mica washers in those bags if you like... ;)
     
  15. radiohead

    Active Member

    May 28, 2009
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