Conformity Magazine - December 2007 - (Page 18) ESD Open Forum Grounding ESD Wax Tiles Provided by the ESD Association Q: A: I am in the process of restructuring a 1,600 square foot production line so that employees will work while standing. I am going to lay down an ESD wax on our regular vinyl tile. What is the proper method of grounding ESD wax tiles? How many waxed tiles must be grounded per square feet? It is unlikely that you will actually be able to ground a floor that is only treated with wax. Generally, the wax is not sufficiently conductive to allow peripheral grounding but relies upon the very large surface area to act as a capacitive sink. The floor must be cleaned very well and rinsed completely. The pH of the final rinse and the floor must be close to a neutral level (7) and most certainly must not measure as a base level (8 or more). Most waxes and other surface treatments react chemically with a base level pH and this will probably hurt the electrical performance of the coating. After the thorough cleaning, it may be necessary to install copper foil tape strips to the floor. The tape strips should be about 12 inches onto the floor and go up the wall several inches. The separation between strips is difficult to determine but a starting point might be three (3) feet. Bond the strips across the wall with a strip of tape. Attach the copper strip network to ground. The recommended ground connection point is to the equipment-grounding conductor, which is the third wire electrical ground in a North American electrical system. If electrical outlets are available, terminate a connection from the tape with a wire to the center screw of the outlet or to a metal electrical box or conduit. All of these points are electrically common to the equipment-grounding conductor in a properly wired electrical system (the electrical system needs to be verified by a licensed electrician). Apply the wax over the floor following the manufacturer’s instructions. After thorough drying or curing as appropriate, measure the electrical properties of the floor. The measurements are made using the procedures established in ANSI/ESD S7.1 – Floor Materials, Characterization of Materials. Two measurements are generally made on a new floor installation or, in this case, a new wax application. Pointto-point and resistance to ground measurements are made in this test method standard. The electrodes are 2.5 inches in 18 Conformity DeCember 2007 diameter, have a conductive rubber or aluminum foil contact face and weigh 5 pounds. The measurement instrument is a high voltage ohmmeter (megger) that makes the resistance measurement at 10 volts and 100 volts. Place one electrode on the floor and set the other electrode three (3) feet away. Connect the leads from the megger to the electrodes. Select 10 volts and activate the instrument. If the measured value is less than or equal to 1 x 106 ohms, record the value. If the measured value is greater than 1 x 106 ohms, switch the megger measurement output to 100 volts, activate the meter and record the measurement. The pointto-point measurements are used to evaluate the coating or wax uniformity across the surface. Repeat the measurements
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