Static Electricity and Shipping Electronics in Styrofoam 2

[docbuild]

Hello,

Not sure what forum to post this in, so I'm going to ask this here. I know that static electricity damages electronics, however electronics (computer monitors, flat-screen TVs, etc) are packed in styrofoam. Why are the electronics not damaged by the static generated by the styrofoam, during shipping?

I'm asking, because I'm preparing to ship a prototype electronic device (garage-built) for air-shipment, and the device case will be packed in styrofoam (see details below). I don't know much about static-electricity dynamics, so I'm just checking to make sure the styrofoam won't "zap" or otherwise damage my device during shipment.

In case it's important, there are the full shipping container details:
[ol 1]
[li]Device is a small appliance (like a printer), that has static-sensitive components.[/li]
[li]Device is disassembled, and the parts are placed in molded cavities in an anti-static pink foam block (a block of pick-foam).[/li]
[li]The above (pink foam and device) is inside a sealed plastic case.[/li]
[li]Plastic case is then placed in a styrofoam box (with form-fitting styrofoam top); some paper cushioning material is between the gaps of the plastic case and styrofoam box[/li]
[li]Styrofoam box is then put into a corrugated cardboard shipping box; some paper cushioning material is between the gaps of the plastic case and styrofoam box[/li]
[/ol]

Does the above look static-safe?

Thanks in advance!

 

[IRstuff]

They're supposed to be wrapped in anti-static BAGS. Pink foam and pink poly are verboten in our facilities.

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[docbuild]

They're supposed to be wrapped in anti-static BAGS

That super-thin clear bag (that's wrapping the monitor/TV/etc) is an anti-static bag? So assuming there's no holes in the bag, it forms a "shield" from the static?

 

[IRstuff]

Most completely assembled products are relatively robust against ESD, since the only entry points are the connectors, and the interfaces there are designed to withstand touch ESD.

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[itsmoked]

As IR sez properly designed products and devices are not susceptible to static zapping. Usually only input pins have high impedance making them most susceptible. But knowing this product designers add componentry to handle static zaps to those pins exposed to the outside of the product or use predesigned components that have built-in static protection.

You won't typically zap a board, even not enclosed, IF, you handle its edges and avoid touching circuitry.

But bare circuit boards are much more susceptible because anywhere you touch could be connected to unprotected logic inputs.

Now as for Styrofoam you should do everything in your power to avoid using that environmental nightmare. Just about nothing is worse than that crap. Being incompressible it gobbles up dumpster and garbage space. It rapidly fills landfills up. It crumbles easily and is blown on the wind away from landfills and away from your garbage truck down your street. There is probably nothing you could use to pack ANYTHING that would generate more static electricity, often making unpacking more difficult. Use formed cardboard or even recyclable bubble-wrap. Use cornstarch peanuts, use inflated bags, use anything but Styrofoam peanuts or worse brick or molded Styrofoam.

I often don't buy products if I know I'm going to be saddled with the hassle of Styrofoam blocks or peanuts, knowing the company I'm buying from doesn't care about our environment also makes me balk.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[zappedagain]

google "pink vs black foam".

Z

 

[docbuild]

Now as for Styrofoam you should do everything in your power to avoid using that environmental nightmare.

The styrofoam I'm using is reused from something else, so I'm not generating new waste.

The sensitive electronics are packed in grey, sealed, anti-static bags. So I think the electronic components should be safe from static, even though the anti-static bags are surrounded by anti-static pink foam.

Thanks everyone!

 

[IRstuff]

"The styrofoam I'm using is reused from something else, so I'm not generating new waste."

But, you've passed the problem onto someone else

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I can do absolutely anything. I'm an expert!

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[docbuild]

Hmmm... Good point. I'll look into molded cardboard.

 

[IRstuff]

The environment says "Thanks!"

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[itsmoked]

If this is just a one-off, recycled SF is a lot better than otherwise.

If it's unprotected boards in the grey bags you may still be asking for it because the handler can get charged up and eventually end up touching the unbagged board.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[docbuild]

If it's unprotected boards in the grey bags you may still be asking for it because the handler can get charged up and eventually end up touching the unbagged board.

Should I tell the handler to "ground" himself before opening the bag then?

 

[IRstuff]

Our general rule is that any handling should be done by a person with a well-grounded wrist strap. While ESD packaging generally provides adequate protection, there's always some risk that someone with an extremely high charge could zap the bag and punch a hole through the protective coating. Given the usually high sunk cost of a finished board, scrimping on ESD protection is just not that prudent.

Handlers should not just "ground" themselves, as that runs the risk of getting electrocuted. ESD wriststraps have series resistors that prevent electrical shock, but are sufficiently low resistance to quickly dissipate ESD charges.

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[itsmoked]

Should I tell the handler to "ground" himself before opening the bag then?

If the humidity is over 65% don't worry about it.

If lower than that and sans a wrist-strap they can use a 'thoughtful' approach.

Essentially touch bare metal. Then without walking turn and extract the stuff from the shipping box while keeping their hand always on the anti-static bag. Then once extracted and all the SFoam is away from the bagged board they touch bare metal again. This safely sheds all charge generated by triboelectric action contained on the bag and person. Then they can carry the bagged board around all they want as long as they touch metal with the other hand before setting the board down or opening it. The method takes some conscious thought but works well if the technique is properly applied.

If you ever watch EEs handing boards to each other you'll always see them touch hands or fingers before handing over boards. This keeps them and the board -even charged- at the same potential so there's never any current driving potential available.

Keith Cress
kcress -

http://www.flaminsystems.com