Aluminum foil as anti-static foil?

[profdc9]

This is something I've been wondering about for awhile.

Sometimes I have circuit boards I want to store or transport that I don't have antistatic bags large enough to hold.  Since, from what I understand, the purpose of antistatic bags is to conduct an electric discharge around the interior of the bag, I thought that aluminum foil might substitute in a pinch.  I know it isn't ideal because aluminum foil pierces easily, but it's available on large rolls very cheaply.  I did not find a consensus on this issue when querying the hive mind of the internet.  But, for example, wrapping the item in aluminum foil and then bubblewrap around that for mechanical protection, seems like it might be an acceptable substitute.

Any opinions on this?

[fourfathom]

I have no authoritative proof, but I use Al foil for this very purpose.  The only issue I see is that you need to have the seams in good contact, but with a simple folding of the edges I'm pretty sure that you have a better antistatic enclosure than one of those lightly-metalized plastic zip-bags.  I have used Al foil to shield radio devices and it is quite effective.

[Miyuki]

I know in the old days of DIP packages and when they were low density and you needed huge amounts of them.
They were commonly stored on sheets of styrofoam rolled in aluminum foil and ICs just stuck to it (piercing foil with legs)

[ajb]

Even 'conductive' ESD packaging materials have significantly higher resistivity than aluminum, so the way that discharges occur through these materials will differ.  A more resistive material will allow a slower discharge, resulting in lower currents, which may be beneficial.  On the other hand, a more conductive material maintains a lower potential difference across it when a given current flows.  Hypothetically, if all pins of a device are in contact with something really conductive, like aluminum foil, then probably won't be much of an issue.  But if some pins are NOT in contact, and a discharge is applied, then it's possible that the higher conductivity will allow a more rapid discharge through the device than an otherwise equivalent 'conductive' ESD material would and therefore more likely to result in damage to the device.  In practice the details probably matter quite a bit.  Since aluminum foil does pierce easily and also has no elasticity it seems very easy to end up losing contact between the foil and the device with vibration/jostling, it certainly seems like a poor substitute for a proper ESD shielding bag.  But it's also probably better than nothing as long as you're careful about wrapping it.

[james_s]

Make sure the board doesn't have any onboard batteries, aluminum is a whole lot more conductive than those ESD bags, and the lithium and NiCd memory backup batteries used on some boards can produce a lot of current into a short.

[rsjsouza]

Just like others, I have used aluminium foil for decades for the smaller CMOS CD4000/SN74 logic devices and, in later years, for processors and memory - foam and anti-static material were almost non-existent back then.

For larger boards it works the same and all aforementioned cautions apply - especially how easily it can be teared.

Also, put yourself, the paper and the device at the same potential before you wrap it or touch anything - since the foil has very little resistance (unlike a static dissipative or conductive material), any difference will quickly cause a severe current flow to/from the board pins.

Obviously that, if you have to do such transportation often, consider buying the bags. Search for anti static bags motherboard for the larger ones.

[ChristofferB]

I am pretty sure I have seen 1960's MIL spec ESD sensitive parts wrapped in thin lead foil, which would be very similar to aluminium foil (unless you're packing sandwiches!). I don't recall the source for this though.

Edit: Pretty sure it was 1N23 microwave diodes.