Author Topic: EEVblog #247 - Anti Static Bag Myth Revisted  (Read 16499 times)

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Offline JohnS_AZ

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EEVblog #247 - Anti Static Bag Myth Revisted
« on: February 24, 2012, 05:20:40 am »
Excellent video Dave.

You probably couldn't kill the part in the tube because it would be quite difficult to get the current to flow through the chip. They you arranged the pink bag pretty much assured that you'd get some pin to pin current flow.
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Offline mikeselectricstuff

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #1 on: February 24, 2012, 10:00:51 am »
"The whole ESD industry is heavily researched "....by the people trying to sell you ESD products, some of which veer very close to 'snake oil' territory.

As regards Farnell, I call "nothing to see here" - as long as the packaging doesn't generate static, that's perfectly adequate for shipping packaging. There is no significant risk of them experiencing enough of a static hit in transit for shielding to be necessary.
If the devices are packed and unpacked in a static-free environment, and the packaging won't generate anything from movement during shipping, what static exposure do they need protecting from that isn't present as soon as you open the packaging?

People often seem to forget about the D in ESD - 10KV on a pin won't damage anything - it needs a sufficiently low-impedance path to create a high enough current to cause damage. This means to be at risk from a charged person, there needs to be a reasonable capacitive or resistive coupling from the device to ground for any discharge current to flow.

This is why static-safe products like bench mats are resistive and not highly conductive. In the past people used to use polystyrene with foil - this is actually worse than just polystyrene, as the foil provides a nice low-impedance path with a reasonable capaacitance to ground for the very fast (sub nS) risetimes of a spark discharge.

Due to the small pin size, capacitance from an individual device pin isn't likely to be enough - touching an assembled board carries a much higher risk due to the board area coupling to ground, although to counter that, the board offers some protection as many pins will have components or other pins connected to them to help dissipate any current flow.


 
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Offline Stephen Hill

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #2 on: February 24, 2012, 10:16:29 am »
I think it's simply a matter of risk management.

If I'm spending a couple of quid/dollars on a dozen jelly bean op amps or micro controllers, then I'll take the risk of not storing them in any type of anti-static bag or tube.

However, if I'm spending a fair chunk of money on a single IC, then I'm going to take extra care and store these in a static shielding bag and tube.

Cheers
Stephen
 

Offline metalphreak

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #3 on: February 24, 2012, 12:23:35 pm »
I once got a tube of 50x SOIC '795 shift regs from E14. They must not have had any static shielding bags long enough, so they cut a slit in the end of a bag, and inserted the tube with about 2-3cm sticking out. They all worked fine, and it's only about $10 worth of chips. I'm sure E14 would have gone to any length necessary to get replacements to me if they were not ok. The last time I bought some microchip SMD TQFP package chips they came in little plastic clip cases with ESD foam inside. Very well packed. RS-Components sent similar ones in folded pieces of foam shoved in a static bag.

When you start buying production run quantities of stuff you usually get good packaging. Vacuum sealed reels with moisture indicators and such.

Everything I've had shipped from MicroChipDirect has been professionally packaged regardless of quantity. 25 TQFP ICs came with a 140 capacity waffle tray in a static shield bag!

Offline im_a_human

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #4 on: February 24, 2012, 12:29:43 pm »
Theres alot of marketing bullS*** sourounding this. For example the static wrist strap testers costing more than 100 pounds is  extremely excessive when they could probably be built for 10 or twenty perhaps. The high cost and excess hype of anything antistatic or static sheilding dosent inspire confidence.
 

Offline firewalker

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #5 on: February 24, 2012, 12:32:01 pm »
A old article that popped in my mind when saw the mylar tape.

Scotch Tape Unleashes X-Ray Power.

http://www.nytimes.com/2008/10/28/science/28xray.html

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Offline G7PSK

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #6 on: February 24, 2012, 02:26:27 pm »
A old article that popped in my mind when saw the mylar tape.

Scotch Tape Unleashes X-Ray Power.

http://www.nytimes.com/2008/10/28/science/28xray.html

Alexander.

Should I wear lead gloves when wrapping parcels, or will health and safety ban the tape in order to save us.
 

Offline harnon

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #7 on: February 24, 2012, 03:28:49 pm »
A old article that popped in my mind when saw the mylar tape.

Scotch Tape Unleashes X-Ray Power.

http://www.nytimes.com/2008/10/28/science/28xray.html

Alexander.

Should I wear lead gloves when wrapping parcels, or will health and safety ban the tape in order to save us.

Quote
The phenomenon has been observed only when tape is unpeeled in a vacuum.
If your workplace is in vacuum (and you aren't an astronaut) there are probably other things more worrying than a few xrays :D
 

Offline wkb

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #8 on: February 24, 2012, 05:26:39 pm »
A old article that popped in my mind when saw the mylar tape.

Scotch Tape Unleashes X-Ray Power.

http://www.nytimes.com/2008/10/28/science/28xray.html

Alexander.

Should I wear lead gloves when wrapping parcels, or will health and safety ban the tape in order to save us.

They will ban the gloves first mate.  RoHS  8)
 

Offline Colfaxmingo

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #9 on: February 25, 2012, 12:22:40 am »
I still don't understand how when you put a static sensitive device on a PC board it becomes not static sensitive...I was wondering if anyone had any thing they could point me to that would help a young player out.
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Online IanB

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #10 on: February 25, 2012, 12:35:45 am »
I still don't understand how when you put a static sensitive device on a PC board it becomes not static sensitive...I was wondering if anyone had any thing they could point me to that would help a young player out.

Well, firstly it becomes "less static sensitive" rather than not static sensitive  :)

You can very easily destroy computer memory cards by unsafe handling even though all the chips are on a board. You can even destroy them when they are plugged into the PC main board  :o

But the answer to the question is that after a chip is soldered into a board there may be other components on the board that can conduct static charge away from the device. The IC gets damaged because some of its pins are input gates to FET devices and charge buildup on the pin will damage the insulation on the gate. If a path exists on the board to conduct charge away from the vulnerable pins then damage is less likely.
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Online EEVblog

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #11 on: February 25, 2012, 01:09:34 am »
"The whole ESD industry is heavily researched "....by the people trying to sell you ESD products, some of which veer very close to 'snake oil' territory.

As regards Farnell, I call "nothing to see here" - as long as the packaging doesn't generate static, that's perfectly adequate for shipping packaging. There is no significant risk of them experiencing enough of a static hit in transit for shielding to be necessary.
If the devices are packed and unpacked in a static-free environment, and the packaging won't generate anything from movement during shipping, what static exposure do they need protecting from that isn't present as soon as you open the packaging?

My apologies for exposing less than best-practice ESD packaing, and trying to teach people what the correct practice is  ::)
Next time I'll try and focus on and promote "good enough" instead, and throw in some "she'll be right mate" for good measure.

Dave.
 

Online Rerouter

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #12 on: February 25, 2012, 02:09:28 am »
now that scotch tape artical.. somehow i feel 2 weeks tops will be behind some snake oil product. "light your house with scotch tape" or something like that...
 

Offline Psi

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #13 on: February 25, 2012, 02:36:42 am »
well... peeling tape does produce xrays :)

Greek letter 'Psi' (not Pounds per Square Inch)
 

Offline SeanB

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #14 on: February 25, 2012, 06:12:28 am »
Anti static handling is good. I worked in an area where it was dry enough that static was a problem, but now live on the coast. Now I would have a problem trying to operate a Van de Graaf generator in any place other than a sealed room that has had an airconditioner running in it for at least 2 days, to drop the humidity low enough.  Dave would have the same problem if he moved further north to Brisbane or higher up.

I tried one day to kill a Pentium processor, wiring  a few pins to ground and arcing the output of an electric fence energiser across  a few of the others. After a few dozen flashes I put it back in the socket and powered it up. It still worked.
 

Offline PeteInTexas

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #15 on: February 25, 2012, 07:07:38 am »
Personally, I'm more worried about the trash.  So much packaging materials for such tiny things... :(
 

Offline im_a_human

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #16 on: February 26, 2012, 04:47:24 pm »
These packaging items are expensive and precious and should be used over again, anyway i challenge anyone to do a teardown of an antistatic wrist strap tester and see if it has a tenners worth of parts in it. I would do it but i cant afford one.  ;D
 

Offline G7PSK

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #17 on: February 26, 2012, 10:40:00 pm »
Having watched Dave's video on the anti-static bags I tried my own experiment. I put the lead from a piezoelectric source in side one of those grey metallic bags and held the outside of the bag the charge went straight through it into my fingers and in a dark room I could see the spark go through,it was not tracking around.  What I would like to be able to do is measure the current involved going through the bag does any one have any ideas on this as I don't think that a Fluke will withstand the voltages.
 

Online IanB

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #18 on: February 26, 2012, 11:57:25 pm »
Having watched Dave's video on the anti-static bags I tried my own experiment. I put the lead from a piezoelectric source in side one of those grey metallic bags and held the outside of the bag the charge went straight through it into my fingers and in a dark room I could see the spark go through,it was not tracking around.  What I would like to be able to do is measure the current involved going through the bag does any one have any ideas on this as I don't think that a Fluke will withstand the voltages.

With static discharges the important factor is not so much the current as the energy (measured in joules, or J). It is ultimately the energy in a discharge that measures its ability to do damage. The current could be quite high, but might last for only a microsecond. No ordinary meter can measure that.
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Offline bfritz

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #19 on: February 27, 2012, 04:03:48 am »
I think it's simply a matter of risk management.

If I'm spending a couple of quid/dollars on a dozen jelly bean op amps or micro controllers, then I'll take the risk of not storing them in any type of anti-static bag or tube.

However, if I'm spending a fair chunk of money on a single IC, then I'm going to take extra care and store these in a static shielding bag and tube.

Cheers
Stephen

This is perhaps an acceptable idea for a hobbyist, but not in a professional environment.  Places I have worked require ISO certifiactions to sell to the companies we do business with.  If the risk of damage to a component is only 0.01% because the wrong packaging is chosen, that is too high.  For example a common pcb may contain 100 semiconductors.  At a 0.01 failure rate, that means that on average every board will contain a damaged component!  This stuff is important and paid attention to in a real business environment, because not doing it right can cost you tons of money, in a hurry!  The cost to replace the damaged component is the least of the worry.  It is the cost of testing, troubleshooting to determine what is damaged, reworking the board to fix it, and then retesting to make sure you fixed it.

It's cheaper to do it right the first time!

Remember that in the receiving department of the typical board builder, the people unpacking the boxes aren't wearing wrist straps as they pull the bags from the boxes.  So yeah, companies really do need to get this right.
« Last Edit: February 27, 2012, 04:07:12 am by bfritz »
 

Online EEVblog

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #20 on: February 27, 2012, 04:12:53 am »
This is perhaps an acceptable idea for a hobbyist, but not in a professional environment.  Places I have worked require ISO certifiactions to sell to the companies we do business with.  If the risk of damage to a component is only 0.01% because the wrong packaging is chosen, that is too high.  For example a common pcb may contain 100 semiconductors.  At a 0.01 failure rate, that means that on average every board will contain a damaged component!  This stuff is important and paid attention to in a real business environment, because not doing it right can cost you tons of money, in a hurry!  The cost to replace the damaged component is the least of the worry.  It is the cost of testing, troubleshooting to determine what is damaged, reworking the board to fix it, and then retesting to make sure you fixed it.

I worked on a project once where it was an instant sackable offence to not take proper ESD precautions for everything in the lab. Entering the lab without your lab coat meant instant dismissal regardless of who you were.
Paranoid?
Well, when your entire $10M project schedule is tied up in few one-off prototype boards, you kinda take this stuff serious.
This was the same company that actually blacklisted Farnell for lack of ESD as I mentioned in the video, that was actually a real story.

Dave.
 

Offline G7PSK

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #21 on: February 27, 2012, 08:03:01 am »
Having watched Dave's video on the anti-static bags I tried my own experiment. I put the lead from a piezoelectric source in side one of those grey metallic bags and held the outside of the bag the charge went straight through it into my fingers and in a dark room I could see the spark go through,it was not tracking around.  What I would like to be able to do is measure the current involved going through the bag does any one have any ideas on this as I don't think that a Fluke will withstand the voltages.

With static discharges the important factor is not so much the current as the energy (measured in joules, or J). It is ultimately the energy in a discharge that measures its ability to do damage. The current could be quite high, but might last for only a microsecond. No ordinary meter can measure that.

OK how do I set about measuring the Jules involved, as I said when I tried a piezoelectric generator  from inside the bag it went straight through it . I used one of those pain be gone pens that generate an electric pulse when you click the button and I have often wondered how much power they produce.
 

Online IanB

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #22 on: February 27, 2012, 10:21:57 am »
OK how do I set about measuring the Jules involved, as I said when I tried a piezoelectric generator  from inside the bag it went straight through it . I used one of those pain be gone pens that generate an electric pulse when you click the button and I have often wondered how much power they produce.

You could connect the positive and negative wires from the piezo generator to a capacitor and measure how much the capacitor voltage increases with each press of the button. You could then use the capacitor formula to calculate how much energy was stored.
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Offline billclay

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #23 on: March 04, 2012, 05:00:50 pm »
Here is the ANSI/ESD Standard for the Protection of Electrostatic Discharge Susceptible Items.
It explains in more detail what Dave has shown us in the difference between low-charging/antistatic, dissipative/conductive, and static shielding materials.

http://www.esda.org/documents/ANSI-ESD_S541-2008.PDF
 

Offline G7PSK

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Re: EEVblog #247 - Anti Static Bag Myth Revisted
« Reply #24 on: March 08, 2012, 05:24:43 pm »
I recived a package today with ESD overkill, I had ordered a new trigger switch for an electric drill no speed control just plain 2 pole 1 way switch. It came in a grey anti static bag which was in turn inside an anti-static wrapping.
 


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