Electronic – How to protect electronics from static electricity during shipping

antistaticesdstaticstatic-electricity

I have some electronics (EDIT: electronics are in enclosures, but with lots of wires coming out of the enclosures; the electronics are a part of a prototype) with ESD sensitive components I need to ship overseas (air freight). I'm using pick-foam (soft black foam) to create a form-fitting mold for the electronics. The shipping container is made from polypropylene. When I press the pick-foam into the polypropylene container, I can feel static building up. That means that jostling during the flight will generate static between the foam and the container.
Also, before the electronics are put into the pick-foam, they will be put into silvery ESD bags.
My questions are:

  1. Will putting the electronics in ESD bags be enough protection from static or static discharges?
  2. Is there something I can do to the shipping container to reduce static build-up? For example, can I coat the inside of the container with something?
    • 2a. (EDIT: I just learned they make pink anti-static pick-foam. I can switch to this, but is it worth the switch if my electronics are already in ESD bags?)
  3. If a customs official opens the ESD bags, how much static damage could they cause? Do you have a suggestion on reducing damage if they open the ESD bags?

Best Answer

Silvery anti-static bags are (should be) conductive, so they act as a Faraday's cage against ESD coming from outside the bag, i.e. they protect from the ESD events coming from outside the bag. If the electronics in the bag rubs against something inside the bag that can build-up static charges, the bag won't protect it.

Therefore you should ensure that whatever is inside the bag, especially if it could move and rub against the electronics, doesn't build up charges. For example, the foam you use, if it is in contact with the electronics inside the silvery bag, should either be somewhat conductive or static-dissipative, i.e. a material that doesn't allow charge to build up (that pink plastic that is sometimes used to wrap electronic circuitry and components is usually a static-dissipative material).

Dave Jones (Author of EEVblog) has made a couple of videos about anti-static stuff that you may find relevant: EEVblog #3, EEVblog #247 and EEVblog #250.

Regarding your 3rd point, probably you cannot do anything to protect your circuit. The circuit must self-protect itself, i.e. it should have enough protection circuitry built-in. This is because customs officers could do pretty anything to the thing they are inspecting, short of breaking them mechanically (they even could do that in some countries, if they suspect the thing may contain dangerous or illegal materials).

If you are unlucky enough, officers will reach for the circuit board and will examine it thoroughly holding it in their hands and handling it brashly (if they don't think it's dangerous, they won't lose time with careful handling). In a dry day and with the right combination of statics-generating surfaces your circuit could be well zapped to death, without suitable ESD protection built-in.

EDIT (prompted by a comment)

Just a simple example: you mention wires coming out of the enclosure. If those wires are directly connected to inputs or outputs of chips/components that are ESD-sensitive, those connection must be protected by adding ESD-protection circuitry on the board. A simple protection measure is to put backwards connected diodes from the pin to be protected to the power rails, maybe adding a current-limiting resistor in series. Something like this:

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There are more advanced strategies as well. There are even dedicated ICs whose only purpose is to protect the I/O pins of other chips/boards. You may be interested in these documents:

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