How do Anti-Static Bags work

[Tab]

How do they work and what are they made out of?

 

[Bowfinger]

They are made of electrically-conductive plastic that dissipates any static electric charges that start to form.

 

[ShawnD1]

simple statics
it's a rule in physics that when you have a conductor that completely surrounds something and that conductor has a charge, the inside of the conductor has 0 charge in it.

example, you have a large hollow copper sphere with a charge. the charge on the copper sphere itself may be extremely large but the charge inside of the of the hollow sphere will always be 0.

 

[Mark R]

They are usually metalised plastic - a conventional plastic bag with the inner surface coated with a very thin layer of aluminium.

Motherboards, which have integral batteries can be adversely affected by such packaging (the aluminium can discharge the battery - it's 'too' conductive') so a plastic with lower conductivity is used.

For components without batteries, aluminium foil is a cheap and readily available alternative to 'proper' antistatic packaging, although it is much more fragile.

 

[CTho9305]

Originally posted by: Mark R
They are usually metalised plastic - a conventional plastic bag with the inner surface coated with a very thin layer of aluminium.

Motherboards, which have integral batteries can be adversely affected by such packaging (the aluminium can discharge the battery - it's 'too' conductive') so a plastic with lower conductivity is used.

For components without batteries, aluminium foil is a cheap and readily available alternative to 'proper' antistatic packaging, although it is much more fragile.

So it is ok to store electronics in aluminum foil? I thought so but some people insist that the inside of static bags is nonconductive (which to me seems to defeat the purpose)

 

[Mark R]

Anti-static packaging is electrically conductive, but very poorly so - if you test it with a conventional DMM it will be out of range. Most commonly the material is polyethylene doped to make it slightly conductive. The shiny metallic looking bags usually use 2 layers of this, with a thin aluminium of other metal layer inbetween

Here's a link with lots of detail about different types of pacakging and how they differ:
http://www.staticcontrol.com/pdfs/P1%20Choosing%20the%20Right%20Static%20Bag.pdf

Al foil provides great protection for storage, but its very low resistance brings with it another problem. If a part has a static charge at one point, placing it onto the Al, could potentially result in a very high discharge current as the static is dissipated. That high current is potentially damaging. Use of high-resistance materials limits the discharge current to a safe level.

 

[Tab]

Originally posted by: ShawnD1
simple statics
it's a rule in physics that when you have a conductor that completely surrounds something and that conductor has a charge, the inside of the conductor has 0 charge in it.

example, you have a large hollow copper sphere with a charge. the charge on the copper sphere itself may be extremely large but the charge inside of the of the hollow sphere will always be 0.

So, when I put my stick of ram in my ESD Bag, the charge of the bag could be 2v and but the Ram would be 0?

 

[Peter]

If we're talking electrostatic discharges, the voltages will be more like 2000 volts than 2.

 

[CTho9305]

Originally posted by: Peter
If we're talking electrostatic discharges, the voltages will be more like 2000 volts than 2.

But yes, the voltage on the outside could be arbitrary, and inside there will be no charge.

 

[p5000]

I think what the guy is saying with the zero conductivity rule is also known as a Faraday Cage (so named after its discoverer?). His explanation is closest to the mark regarding the charge inside the sphere being theoretical zero (there will always be leakage).

If esd is a big problem for you as it is here in Arizona, then simply take more precautions like removing the pc boards from the bags while standing on a nonconductive mat.

 

[lovisaken]

Hello

Anti static bags is a bag used for electronic components or devices, which are prone to damaged caused by electrostatic discharge. Anti static bags are used to store and transfer electrostatic sensitive equipment.

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[John Connor]

OMG! Captain obvious.

 

[bryanl]

So it is ok to store electronics in aluminum foil? I thought so but some people insist that the inside of static bags is nonconductive (which to me seems to defeat the purpose)

It's OK if the electronics have no battery, including any internal one (Dallas clock chips contain lithium cells), and you first touch the ground of the electronics to the interior of the bag. Actually the insides of anti-static bags are always conductive (cannot typically be measured with an ordinary meter), but metal plated plastic ones are typically not static protective on the outside, unless explicitly labelled "metal out." The vast majority are only "metal in," meaning you should not set any electronics on top of them.