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  • EEVblog #247 – Anti Static Bag Myth Revisted

    Posted on February 25th, 2012 EEVblog 30 comments


    Element 14 shipped Dave some chips in just “anti-static” packaging, instead of proper “static shielding” bags. So he decided to revisit the anti-static bag myth he mentioned in episode #3, but this time doing some static measurements and actually trying to kill a chip.

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    • Luciano

      Could you run the same test with your µCurrent adapter? (During normal operation the contacts of the switches are exposed to static electricity).

    • Pablo

      Mmmm… I wouldn’t fool around with that spark generator near expensive test equipment. Many years ago I killed a poor Casio calculator with one of those, and I still regret it.

    • Simon

      Thanks, that was good stuff to know.

      It would be interesting to see how the performancce of a “silver” bag degrades when it gets crumpled or mistreated. I have a lot of these bags flying around here and I’d love to have an idea about the point where it stops protecting its content.

      Bye,
      Simon

    • Olivier

      What about the last few seconds of the video. The LED is blinking again.
      Is this a new IC or is this the supposedly zapped one?

      • http://www.eevblog.com EEVblog

        Read the text overlay on the video, it’s a new chip. The old one didn’t magically start working again.

    • Jay Ts

      Does anyone know a good source (USA, hopefully) for small metallic anti-static bags? Ideally, I would like a package of 100 2×3″ ziploc bags or something similar.

      Now some comments about the video:

      Dave, this was really good. You showed products that had been improperly shipped, which shows that there are people functioning in a professional capacity who need to learn this stuff, not just beginners! It is so good that you are helping by making this video.

      I think many people assume that as long as they don’t see or feel a spark, everything is ok — especially if the device “still works” afterwards. You showed hundreds of volts being generated by seemingly-safe things. Smaller discharges may not kill a device, but keep in mind the absolute maximum ratings specs on datasheets. The manufacturer typically says that anything over that can “damage” the device, which I assume means it may not function the same afterwards. It may fail completely, or still “work” but differently, or even out of spec.

      After you showed tests with the pink plastic bag, I was hoping you would compare it to a plain (clear) plastic bag. I wonder if the limited protection provided by the pink plastic bag is caused by anything more than the effect of the electrical insulating property of the plastic.

      How about a video sometime showing how to protect inputs to a circuit, using MOV or TVS devices, or other methods? I would love to see you test them with your spark generator to see how well input protection devices (and surge suppressors, too) actually work.

    • Mike

      Just a comment not so much about the test but on element14.
      I’m wondering about that package marked mcp4912.
      Did you really buy them from element 14?
      When I look at their site they are asking $3.78 in single quantities.
      When I look at microchip direct they are asking only $1.83 each in single quantities. Depending on how many you bought the free shipping from element14 doesn’t even compensate if you bought 10.
      element14 $37.80 for 10 delivered
      microchip direct $32.48 for 10 delivered
      if you bought 20 the difference is even greater as the 14.18 delivery from microchip is spread more.
      at 25 and over the difference starts at 20 dollars for 25 pieces.
      While advertising free delivery is great marketing you have to realise that it’s not free but built into the price of their parts.
      Unless of course you do buy only 1 part at a time. But who does that?

      • http://www.eevblog.com EEVblog

        I only bought 3.
        I’m in Australia, so shipping is usually a BIG deal, so Element 14 andRS are very attractive with their free postage.

    • siliconmix

      great video .it doesn’t apply to me .because i live in wales and it’s very damp

      • Jay Ts

        Is high humidity actually a “cure” for ESD dangers, or is that another myth? I have never read or seen any definitive discussion of that, or any actual tests.

        I like to think that because I run humidifiers in the winter to keep my RH above 50%, that I am “probably safe”. But I also have a nagging feeling that I am probably wrong. :)

        I would love to see a test showing ambient relative humidity vs. ESD voltage, as measured by a meter like the one Dave is using in the video (the new model is at http://www.trifield.com/content/surface-dc-voltmeter/). It is about $300, so I’m not able to get one right away. :(

        • Jay Ts

          Well, I found this: http://www.esda.org/fundamentalsP1.html

          In short, no matter what your humidity, you still need to be careful about ESD.

          “Poly bag picked up from bench
          [10-25% RH:] 20,000V
          [65-90% RH:] 1,200V”

          Raising the humidity may really help, but it is not by itself a solution. I’m happy that I’m reducing my ESD voltages by about 90%, but I will now go shop for some ESD-safe tools and supplies. ;-)

          • http://www.eevblog.com EEVblog

            Good link, thanks.

    • Agent24

      Farnell are strange, I don’t think half the people who work there packing the components know what they’re doing.

      I’ve had DIP IC *SOCKETS* put into tubes and sealed into the silver shielding bags.

      I’ve had capacitors put into the pink bags

      I’ve had JFETS put in PLAIN PLASTIC.

      Recently I had some pushbuttons switches stuck into foam and wrapped in so much tape it wasn’t funny.

      Most of the time they get it right, but sometimes it makes me wonder…

    • Drone

      c

    • MikrySoft

      Thats nothing, I bought couple ATMega328s in DIPs pushed in styrofoam…

    • http://ilord.it Chief

      Excellent post Dave. I always wondered how much of an urban myth the whole static threat is to components. It’s nice to be able to see real measured figures and also zapped chips. I have recently seen hardware as a standalone board in a device which has a nvram device to store settings, after testing and prog. prior to site delivery everything worked fine. I have recently seen one of these loose it’s config after arriving on site, I was putting this down to static build up due to transportation. Now I’m totally convinced this is the case. Also I would think that people forget the fact that static in itself is not an issue. I suspect that the major issue occurs with the sudden surge of current that occurs due to the pd between two objects, this is why “anti static” mats are so effective, they safely dissipate the charge in a controlled manner. Keep up the good work Dave. What do you reckon on my theory about the cards I mentioned, is this a likely real world case?

      • Rafael

        Working for an IC manufacturer, I’ve seen a small share of pre-programmed flash memory devices being “re-programmed” during transportation or handling. However, it was hard to find a singular reason. Most where a combination of the main factors: cut bags, bad handling during board assembly and inappropriate packaging (as pointed by Dave).
        Regarding the device zapping alone (not reprogramming), the most interesting I’ve seen was due to zero-ohm path to ground: the bench was grounded with a metal cover and all parts eventually put there were zapped – the operator’s hands and/or the bag both had a high potential, but shorting everything to ground actually zapped them.
        Therefore your suspicion is correct: the sudden surge of current is what ultimately zaps the parts.

        • http://ilord.it Chief

          I think the low Z may well be the issue in this case, the device in question is an interface card for a touchscreen. The card is connected to a PC via USB in a standalone kiosk. Although I have not measured, it’s clear that there is a grounding/shielding lug connected to the board from the USB connection I would think to the ground plain on the board.
          The PC is then earthed via mains supply as most due to exposed extraneous conductive parts. (BOOM) straight to ground ironically before power up.

    • Kandos

      Just received a small shipment from e14 and glad to report all semiconductors in tubes & ESD shielded bags.
      Another point worth mentioning is just because a chip works when fitted if no ESD precautions are taken, does not mean the chip is o.k there can be other damage caused which may shorten the chips lifespan or cause intermittent problems later on and such..

      • Agent24

        Exactly. And I think this is just what happens with people who don’t take the precautions.

        Because often nothing obvious happens *straight away* they assume that they aren’t doing anything wrong or that taking ESD precautions “doesn’t matter”

        If on occasion they do kill something they probably say it’s DOA and blame the shop.

    • Martin

      At 3:25 into the video mention is made of conductive bags (the black type)as being ok

      That is news to me as they were deemed as unacceptable for static protection over 20 years ago in the UK as you can simply pick up the bag and the charge is conducted through the wall of the bag directly into the device.

      • Michael Taylor

        I believe that the ‘black anti-static’ bags may be actually static dissipative, not static shielding. That is speculation on my part.

        But I’ve had Analog Devices send me very pricey samples using such black anti-static bags, so I would be surprised if they weren’t static dissipative.

        The only other thing I wanted to comment on is that while David was focused on total and instant (“catastrophic”) device failure, electrostatic discharge events often cause less obvious “latent” failures that don’t necessarily kill the device instantly, but may cause the device to fail in the near future (say the next time the device is power cycled).

    • Bill Clay

      Hey Dave, you should wear that lab coat more often. It looks cool! Maybe even change that “HAL” logo to “EEVblog.com”.

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    • Kerry Veenstra

      Thanks for this. In the US, ULINE has the static-shielding bags.

      http://www.uline.com/Grp_2/Static-Shielding-Bags

      They have both open-end and reclosable versions. When they say “With Print” and “No Print” they are referring to the yellow ink on the bag that identifies the bags’ shielding capability. The “No Print” versions are offered for decorative purposes.

    • https://plus.google.com/u/0/109920401953767744541/posts/p/pub Malcolm

      I know it is a long time since the blog was made but in my days when I was an apprentice antistatic was very serious problem, mostly before chips were buffered especially 4000 series chips.

      The issue was not necessarily instant failure but life expectancy would greatly reduce. So instead of lasting many years possibly lifetime it would fail in 6 months or a year.

      • http://www.eevblog.com EEVblog

        Yes, the old infant mortality issue can be a big one.