ESD Bench Mat. How much coverage??

[diydidi]

Hi.
I have just finished building a new workbench. The top measuring 2000mm x 900mm.
I would like to purchase some ESD rubber matting for the work top. My question is, how much covering will be enough? These mats are expensive here in S. Africa. Is it a good thing to cover the whole top, or more practical to do only a section??

[Steve Conner]

You only need to cover the area on which you'll actually be handling static sensitive items. I just bought the nearest standard sized mat to my benchtop, and used the uncovered areas to pile my test equipment.

Don't forget the accessories like the wrist strap, cords and connectors.

[defaced]

Long these lines, is conductivity the primary characteristic of the mat? I have free access to sheet metal, and prefer something a little tougher than rubber, could that be used as a ESD bench covering?

[Steve Conner]

Yes, but too much conductivity can be bad for other reasons. I often work with boards on my bench while they're powered up, and even if they're not, some of them have backup batteries. If my bench were made of steel, things would get shorted and sparks would fly.

The rubber mats are just conductive enough to dissipate static and no more.

[defaced]

Point taken, thanks Steve.

[philbo]

Yeah, most ESD mats have a resistivity of 1 to 10 G-Ohms per square. It's enough to dissipate static, but won't short anything out & cause your parts to turn to smoke....

[olddawg]

I used to use a rollup mat on a carpeted bench. You don't always need an anti-static surface. At the time these mats were under $30 and came with a wrist strap and a cable that snapped onto the mat. I would just roll it out when I was working on something sensitive. You don't want to strap yourself to a metal surface! Yikes!

[philbo]

I used to use a rollup mat on a carpeted bench. You don't always need an anti-static surface. At the time these mats were under $30 and came with a wrist strap and a cable that snapped onto the mat. I would just roll it out when I was working on something sensitive. You don't want to strap yourself to a metal surface! Yikes!

Yep -- that would be a great way to get electrocuted! Though, generally, the wriststrap cords have a 1 M-Ohm resistor built in somewhere. That would still give you a good 'bite' if you touched the 110VAC hot line or anything higher...

[defaced]

How would one get electrocuted when strapped to a grounded metal surface? Isn't that what a chassis is.....

[Enzo]

Why yes, a chassis is a (usually) grounded metal surface. And if you stick one finger on B+ and the other wrist on that chassis, you just conducted 500v through your body. Many people like to repeat the one-hand rule of working on high voltage for this very reason. Most of us are not grounded or at least not well grounded when we work on things. Tying a metal strap to a wrist and grounding it is half a lethal circuit.

[52 Bill]

Back when I was in high school I would "work" in my dad's radio & tv shop, where some of the benches were those green all metal things that were grounded to the ac ground. Working on any of those transformerless 5 tube radios was a real fun time if you forgot to use the isolation transformer or the rubber isolation mats.

My bench is all wood.

[defaced]

Why yes, a chassis is a (usually) grounded metal surface. And if you stick one finger on B+ and the other wrist on that chassis, you just conducted 500v through your body. Many people like to repeat the one-hand rule of working on high voltage for this very reason. Most of us are not grounded or at least not well grounded when we work on things. Tying a metal strap to a wrist and grounding it is half a lethal circuit.

Thanks Enzo. I hadn't connected that dot yet (obviously).

[peterr88]

You only need to cover the area on which you'll actually be handling static sensitive items
http://www.centplay.com/affiliate/id_139/

[Enzo]

I agree, my static mat is a piece of masonite with the static foam surface glued on, and it is about the size of two computer keyboards.