[Elecraft] Anti Static Mats

[Fred Townsend]

Don, if you mean by ‘developed’ a charge is generated then no, the triboelectric effect doesn’t work that way. See http://en.wikipedia.org/wiki/Triboelectric_effect.

If you mean the previously, developed by friction on the body, charge is transferred then yes, but then in only in a very limited way. A RC of 47 ohms and 1500 pf is often used to model the human body. The charge transferred will be in proportion to the surface capacity of the touched object. Small objects tend to have a very small surface capacity so little or no charge is transferred.

Back to the subject at hand. What part do the antistatic mats play? The argument Alan seems to make is there is an optimal resistance for the anti-static mat and that is critical to maintain the mat within that range. To that I say the Emperor has no clothes.

There are really two issues here. 
1.	How do I prevent static from being developed in the first place?
2.	How is a developed charge going to hurt my component?

With regard to mats, just about any soft rubber mat will not react to the triboelectric effect so it is passes item 1 above. Hard rubber, plastic or other dielectric materials such as Formica or Varathane tabletops are questionable.

With regard to item 2) components are damaged when either their dielectric limits or their current carrying capacity are exceeded. By definition antistatic mats do not build up a charge so exceeding dielectric limits seems improvable and so that brings us down to exceeding current limits. 
The argument has been made that when a high voltage charge it is discharged through the mat that the discharge must not be too fast nor too slow. It must be just right. To Goldilocks and her followers I say no it’s not so. I think a proof here is beyond the scope of this forum. However, an examination of the human body model (47 ohms and 1500 pf) will easily lead to that proof.  

For those still not convinced I offer this except from the first TI data sheet I picked up. It states: “ESD Protection Exceeds JESD 22”. Yes there is a manufacture’s requirement for antistatic endurance. If they don’t exceed JESD22, then special packaging and markings are required. You’ll know to take extra special precautions when you see the labels.

73
Fred, AE6QL 



-----Original Message-----
>From: Don Wilhelm <w3fpr at embarqmail.com>
>Sent: Apr 7, 2014 10:37 PM
>To: elecraft at mailman.qth.net
>Subject: Re: [Elecraft] Anti Static Mats
>
>When one touches it, a charge is developed - then when it comes in 
>contact with a fully conducting surface, damage can occur.  If instead 
>you are working on a proper anti-static mat, the charge from your body 
>and the part is dissipated slowly, no damage will be done and everything 
>will be at the same potential.
>
>73,
>Don W3FPR
>
>On 4/8/2014 12:47 AM, Fred Townsend wrote:
>> That would mean the part was charged. How would that happen?
>>
>>