People grounding by Flooring system & conductive shoes

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