ESD Mitigation - Floor mats or conductive floor?

[David Hartman]

Another thing that I have learned from all this: If you create a conductive surface that measures less than 10^6 ohms from any two points and is larger than 20 square feet (~1.86 square meters), this surface essentially becomes earth ground. Sinking large copper rod into the earth not required.

Yeah, Icy if you get to thinking about it, How far do you have to sink a ground rod for a ship at sea to become "grounded"? And where is my grounding rod for my TV, computer, stereo, et cetera? When you work on your TV, computer, et all do you strap to earth ground, or do you strap to chassis ground (most appliance manuals refer to strapping to chassis ground)? Isn't the point really to make sure that the equipment, devices, and you are at the same realive potential?

 

[Al Rosen]

Please don't say grounded chair. Wrist straps are $25 and I have a hard enough time keeping those on peoples' arms.
The first chair that came up on google is $286! And that assumes that it actually works through 3 or 4 layers of polyester clothing.

You can buy antistatic spray for the chairs. An ESD program never seems to end.

 

[Al Rosen]

Here's a recipe for homemade antistatic spray that you can use on fabric.

 

[Icy Mountain]

Dave and Al,
You've hit the nail on the head. This isn't about meeting a standard for me. It's about "assurance". Are you REASONABLY assured that you are not damaging your product with electro-static discharge? It IS a relative potential thing.

I have upgraded my $1,000 computer at home with a $100 additional hard disk drive, a better DVD-RW drive @$80 , a higher speed DVD reader @$40 , and faster video card with twice the memory @$40. I wrist strap myself to the computer chassis and then pull the cards or drives from their anti-static bags and plug 'em in. I've never damaged anything. Believe me, at those prices, I don't want to even come close.

At work, I need to have some specifications (i.e. data) to PROVE TO A TS AUDITOR that I am reasonably assured that I am not damaging anything. In God We Trust, all others submit data.

 

[Icy Mountain]

Here's a recipe for homemade antistatic spray that you can use on fabric.

Of course, at work, you need an MSDS for the fabric softener, ammonia, and probably the water, too. Now you're helping too much, Al.

 

[Jim Wynne]

Of course, at work, you need an MSDS for the... water, too. Now you're helping too much, Al.

Better have a look here, just to be safe: Dihydrous Monoxide FAQ

 

[Al Rosen]

Better have a look here, just to be safe: Dihydrous Monoxide FAQ

Jim, that's so old it's growing hair.

 

[Jim Wynne]

Jim, that's so old it's growing hair.

Well, it smelled OK to me.

 

[Icy Mountain]

Boy, oh, boy. Once you get your questions answered, things digress pretty rapidly around here.

 

[jeffrey_Chang]

Question:
Do we really need conductive floor mats?
Is it a correct assumption that product on the mat can be safely manipulated while wearing only heel straps on the floor mat? Painted floor? Epoxy floor?
Is it a correct assumption that product at earth ground can be safely manipulated while wearing only heel straps on a floor mat? Painted floor? Epoxy floor?

No, coductive flooring is not a must.
No, it is not a correct assumption that product on the mat can be safely manipulated while wearing only heel straps on the floor mat as it will also depend on the device sensitivity level.

There are bascially 3 principles to proper ESD control.
1. All conductors must be grounded.
2. All insulators must be isolated or neutralised.
3. Prevention. Example, through providing proper training to all concern.

Wearing heel straps only does not guarantee that the devices or products are protected from ESD events as there will still be charges generated and through what I've seen, the voltage could go as high as 70V to 90V and if your device or product sensitivity level is relatively lower, e.g. in some IC, the HBM level could be as low as 10 - 20 V, in this case, it will be a real concern.

I would suggest that you continue to put on your wrist strap even with ESD footwear on to give you the added assurance that if somehow or rather, your device or product becomes more sensitive to ESD.

Understanding and complying to ANSI/ESD S20.20 will definitely give you the added value to a well protected ESD safe workplace. It is definitely NOT just about getting a certificate.

thks.
jeffrey.