The
ESD Journal received the following email with ESD
prevention People grounding by
Flooring system and conductive shoes
(a microsoft powerpoint presentation) attached. Please take a look
at this interesting presentation
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 persons.
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 proposed solutions.
Best Regards
Michel DUBAN
PS I joined
a document I present in LONDON last year about the choice of flooring system
