Question of the Day 02/03/06

Hello,

I am a manufacturing engineer from Connecticut. We are setting up an assembly line where ESD protection is needed for the components that will be handled. Our line will have benches and various equipment. There will be many people working in the cell and I am concerned how to ensure that everything will be at the same electrical potential. I am not familiar with ESD protection so I am looking for help.

I reviewed the materials on your website and I found them useful. It seems that an epoxy floor system would best meet my needs. I saw the illustration regarding bonding the floor to beam structure for earth ground but I did not see how equipment would be bonded to the floor. I will need to bond workbenches to the floor. How is this done?

Do you strictly sell the materials or do you also perform installations. I would be interested in having someone install a floor system. Can you recommend someone if this is something you do not do.

Regards,

Dan

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Answers

Hi Dan,

 

Thanks for taking the time to visit our site! 

 

Your right on track with using the ElectraGuard ESD Epoxy flooring.  The ElectraGuard can indeed be grounded to a column (if convenient) however I prefer to ground it to an AC electrical bldg ground as in http://ultrastat2000.com/electraguard_grounding.html.  The ElectraGuard flooring has  a bit of resistance built into it for safety reasons (I.E. in case an errant electrician happens to touch a hot wire;) so I wouldn't recommend grounding your bench (s) and equipment directly to the floor.  I recommend that they too are attached to the electrical ground system of the building.  In the case of the bench this can be the center screw of AC electrical face plate (fully compliant). The benches can be permanently mounted to the ElectraGuard / Concrete substrate using standard concrete fasteners.

The metal equipment framework typically get it's ground from the ac electrical system (via the power cord). In the case of non powered metal equipment (like conveyors) attach a cable from the framework directly to AC electrical ground.  I like to test the resistance of the metal framework of the equipment to AC electrical ground just to be sure it is indeed grounding via power cable.  FYI, the ESD Association has shied away from having us ground to copper ground rods that are not attached to the ground system in the building (like I used to do in the military).  Independent ground rods can be at a different potential very easily so it's bad juju;)

 

The potential or your esd system will vary somewhat for safety reasons and for controlling the discharge of static in a timely manor.  Sometimes discharging too quickly get's you into more trouble than not discharging at all.

 

EOS ESD S2020 (the holy grail) recommends that the flooring system be in the conductive range (resistance to ground <1.0E06.  They will let a static dissipative floor slide by for now (1.0E06 to 1.0E09).  However conventional industry wisdom (as well as the ESD Association are recommending (more and more) that the range falls below 1.0E06.  It will be mandatory in a year or two (in my opinion).

 

Each operator is to wear heel grounders (with 1 meg safety resistors).

 

They also recommend that table tops or bench matting fall in the static dissipative (>1.0E06, <1.0E09) range.  If you are using table top mats (and not esd laminated bench tops) and want to ALWAYS be fully compliant, use a trilayer or dual layer bench mat material (like our and UltraComfort, UltraTough  or ElectraTherm ESD rubber matting.  The materials work great with constant monitors too negating the need to test the bench top material and wrist straps (saves a lot of logging). I'd stay away from humidity dependant bench matting (we clearly define the material's need for humidity on our site's bench mat menu).  Humidity dependant materials are slightly less money but not worth the headaches.  Seems the humidity (hence mat conductivity) drops drastically in esd audit situations!

 

As you know along with the operators wearing heel grounders they are usually attached to ground with wrist straps (here again with each strap having a 1 meg safety resistor built in).  It's important to have the GROUND for these wrist straps and the mat (or bench laminate) all at the same potential.  Common point ground blocks like our 113 AS makes this grounding requirement fully compliant with the "grail."

 

Along with supplying materials we often provide installation of the flooring, equipment mats etc.  Upon completion we provide certification of flooring, benches, chairs and more all tested to the latest industry standards.  Our ESD product certifications are typically good for a year and really help keep the ISO boys happy.

 

Please let me know if you have any further questions, never hesitate to email me (or contact me on my cell) and thanks again for taking the time to visit!

 

 

Ernie C.

Engineering Services
United ESD Incorporated
POB 19252, 4878 Lakeview Cir
Co City, CO 81019
United States of America
Direct: 719. 676. 3928

Cell: 719 331 0656
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http://ultrastat2000.com
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