Modified Advanced Grounding of an ESD Flooring System
The purpose of this document is to specify a procedure necessary to ground an ESD Flooring System (ESD Technical Element) while satisfying requirements set forth in ANSI/ESD S6.1-2005 per ANSI/ESD S20.20-2007. JESD625-A will be referenced and satisfied as well.
AC Equipment Ground is the preferred ground when available (per ANSI/ESD S6.1-2005 5.1.1). “The equipment grounding conductor electrically bonds the AC equipment ground to the ground bus at the main service equipment panel of the facility. AC equipment within the EPA (ESD Protected Area) and all of the ESD technical elements (ESD Flooring System) will be at or near the same electrical potential when this system is used.” 5.1.2 Auxiliary Ground; “Some facilities require the use of a separate or supplemental ground system. When this is the case, the auxiliary ground shall be bonded to the AC equipment ground when possible .” This will prevent “significantly different electrical potentials.” Per 6.3.2, if both grounding systems are present, the resistance between the AC and the auxiliary ground shall be <25 ohms. The following measurement shall be conducted by connecting the ohmmeter between the AC equipment ground and any auxiliary ground. The measurement probes shall be placed to include the resistance of all the interconnecting and securing devices.
Earth and equipment ESD grounds (per JEDEC Standard No. 625-A Page 13); “Equipment ground should be used instead of earth ground. When both equipment and earth grounds are used at the same ESD protective workstation they shall be bonded together at some point in the ground system.” The document then goes on to reference ANSI/ESD S6.1-2005.
Isolated Ground Receptacles; Per ANSI/ESD S6.1-2005 5.3.2, “Isolated ground receptacles should not be used to derive an ESD ground. The use of an isolated ground for ESD purposes may compromise the function of the isolated ground system.” These receptacles are typically designated by an orange body with a green triangle on the face of the receptacle as well.
Grounding of ESD technical elements such as ESD flooring are accomplished at Ground Zero ElectroStatics, Inc. with a combination of Copper Grounding Tape and GZ Grounding Plates. Each method provides a ground point which bonds the ESD Technical Element to AC Equipment Ground (and Auxiliary Ground if used).
The Ground Zero ElectroStatics ESD Flooring Sales Representative can assist the client on the quantity of copper tape (typically 108’ rolls of ½” width, though ¼”, 1”, and 2” widths are available upon request) and GZ Ground Plates needed for a given ESD Flooring System. One roll of copper tape and 2 ESD Ground Plates are the specified minimum grounding material for the first 500 square feet of installation with a minimum of 2 ground points within that area.
For GZ Ground Plate requirements:
Sq Ft up to 5,000 Sq Ft : (2) Ground Plates for the 1st 500 Sq Ft and add (1) Ground Plate for every 500 Sq Ft after.
5,000 Sq Ft to 10,000 Sq Ft : (2) Ground Plates for the 1st 500 Sq Ft and (1) Ground Plate for every 1,000 Sq Ft after.
Above 10,000 Sq Ft : (2) Ground Plates for the 1st 500 Sq Ft and (1) Ground Plate for every 2,000 Sq Ft after.
For GZ Copper Grounding Tape requirements:
1 Sq Ft up to 5,000 Sq Ft: 1 Roll of Copper Tape for every 1000 Sq Ft.
5,000 Sq Ft and above: 1 Roll of Copper Tape for every 2000 Sq Ft.
In figure 1 of page 3, the lines in the diagram represent an ESD flooring system that has been equally partitioned with copper tape to create a grid of approximately equal spacing. This is the most effective way to neutralize ESD charge potential and is the most efficient use of the copper tape.
For example, a room that is 50 ft long by 20 feet wide will allow a 50 ft. run of tape down the middle of the floor along the x-axis (running horizontal) and two 20-ft. runs along the y-axis (running vertical) equidistant or about 16’ 8” apart. This will utilize about 90’ of a 108’ roll of copper and leave about 18’ of tape to terminate the grid to Electrical or Machine Ground or Building Ground.
One roll of Copper tape 108’ x ½” can provide an adequate grid for up to 1000 sq ft of flooring. As in Figure 1, two ground points can be derived from the copper grid system to AC Equipment Ground.
This tape is conductive to less than 0.1Ω surface and volume resistance as the adhesive backing of the tape is very conductive as well. After the flooring system has been prepped, profiled, patched, floated, anchor coated, etc, this tape can be applied directly to the flooring system and should lie just beneath the final ESD floor coating but underneath a ground plane coating for Epoxy systems using such a coating or under conductive adhesives used for resilient ESD tile or ESD roll goods.