The ESD Journal received the following email
with ESD prevention People grounding
Flooring system and conductive shoes (a microsoft
powerpoint presentation) attached. Please take a look at this
I read your document "Static
in the Call Center" in the ESD Journal..
I am not very surprised about electrostatic shocks in area were
no precaution to eliminate Static Electricity is applicate.
So in my opinion and by experince the basic rule is :
No charge, no discharge.
And in my job were we handled very sensitive components (HBM sensitivity
< 100 V), it is some time difficult to solve the problem.
But to protect people it is only necessary to maintain level of
charge at about 2 KV (usualy people feel ESD when the potentiel
of charge, before the ESD, is about 3 500 V).
So I think it is only necessary to create a path to the ground.
This path can have a resistance to ground Rtg with a resistance
compatible with the level of charge acceptable and security of
I propose :
10 Ex 7 < Rtg < 10 ex 8
I dont well now how are designed the head set people are wearing.
But I think it is possible to create a path to ground with the
use a dissipative material to manufacture the head set and coonnect
this material to an electrical ground. This solution seems to
me equivalent to the well known Wrist Strap.
In that case I think the control of Relative Humidity at about
55 % can be sufficient (it si certainly more expensive).
The choice of materials of chairs can also reduce the risk, We
use chairs with a materials which generate potential on body of
about 20 000 V for HR 20 %, we change of materials and the charge
become lower 1 to 2 KV and discharge were not felt by people.
But conductive chairs are not necessary for this application.
The use of conductive chairs need conductive flooring system........
I should be very interrested by your opinion on my comments and
PS I joined a document I present in LONDON last year about the
choice of flooring system
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