Static electricity is the nemesis of any electronics production facility, striking quickly and silently and leaving a trail of burned-out or weakened circuits. Controlling the static charge is the challenge. It requires a unified regulation system designed from the floor up.
Many ESD-control problems, especially those involving mobile personnel, are resolved with the installation of an ESD-control flooring or floor coating that conducts the harmful static charges to ground. There is a broad selection of flooring products to help you find the path to static safety, but not all may be appropriate for your needs.
To be effective, flooring must be an integral part of an ESD-control system, said Charlie Bloss, Product Manager for Garland Floor. The total ESD-control system consists of a properly grounded floor, footwear and personnel.
Qualify ESD flooring materials by subjecting them to point-to-point and point-to-ground resistance tests, body-voltage decay tests, and body-voltage generation tests, said Mr. Bloss. Also examine footwear to determine the best type to use with your flooring choice.
A conductive floor will perform better than a static-dissipative floor when static-controlled footwear is used, said Bruce Lampert, Executive Vice President of United Technical Products. Conductive footwear offers additional static control, providing body-voltage results of less than 100 V.
On the other hand, insulative shoes can accumulate more than 4,000 V of static charge, pointed out Steve Fowler, President of ESD Flooring Systems. To understand the interaction of different footwear on either dissipative or conductive carpet, are, here are a few examples of the static charge that accumulates on personnel:
· ESD dissipative footwear: <50 V.· Neolite soles: 300 V to 1,000 V.
· Leather soles: 500 V.
· Suede soles: 1,000 V to 2,000 V.
· Rubber soles: 200 V to 2,000 V.
The combination of conductive floors and ESD footwear keeps the accumulative voltages on mobile personnel to a minimum, said Mr. Fowler. For best results, use footwear with a conductive sole in the kW range and a person-to-floor volume resistance in the MW range.
Nonelectrical Considerations
The most appropriate flooring selection must meet your requirements for durability, chemical resistance and maintenance, said Mr. Bloss. Durability indicates how long the floor will last in its intended environment. In part, it is determined by the types of vehicles and material-handling equipment that will be used on the floor.
Also consider life-cycle cost, wear and abrasion resistance, impact and indention resistance, and appearance, said John Schneider of Fritz Industries. For example, conductive or dissipative flooring may have excellent electrical features but the wear and indention resistance may be poor. Conversely, another type of floor material may have outstanding wear features and electrical characteristics but may be very expensive to install. Only you know the appropriate flooring traits for your operation.
Chemical resistance requirements are dictated by the solvents, fluxes, alcohols, acids and solders the flooring is exposed to. Maintenance is especially important if the floor will require special care such as waxing or finishing, because these needs add to the upkeep of the system. Consider how easily a damaged floor can be repaired, said Mr. Bloss.
Other factors to consider before purchasing ESD flooring are the building arrangements, such as a short-term lease; and the time required to retrofit an existing facility, said Jurgen Bahlo of Tek Stil Concepts. Installing a full-surface glued-down material might not be practical if your company isn’t staying in a location permanently. As an alternative, you could install a carpet roll material or a loose-laid vinyl, or use a self-stick, releasable adhesive with vinyl or carpet-roll material. These options allow you to take the material with you and reconfigure it as needed, added Mr. Bahlo.
After a few years, the effectiveness of the electrical properties can diminish with some flooring products, said Mr. Bahlo. A good material should have the same electrical properties regardless of the amount of use. Lower-quality materials will require ESD waxes after some time because the top layer has disappeared and the flooring no longer performs as intended.
The selection of any floor should be based on physical, aesthetic and cost benefits, said Mr. Fowler. Refer to Table 1 for help comparing the advantages and disadvantages of several flooring types.
Table 1
Flooring Material Advantages Disadvantages
Rubber/Vinyl Low installation cost Maintenance
Chemical resistant Outgassing
Clean-room suitable Affected by heavy traffic
Abrasion resistant
Epoxy Durable High initial cost
Seamless Installation
Clean-room suitable Solid colors do not hide dirt
Abrasion resistant
Chemical resistant
Withstands heavy traffic
Carpet Color coordination Clean-room limitation
Low noise Affected by heavy traffic
Low maintenance cost Affected by chemicals
Personnel comfort
Non-slip surface
Finishes, Sprays, Apply over existing floors Durability
Waxes Enhances existing ESD floors Improper application affects
Easy to apply performance
Low-cost application Clean-room limitations
Water soluble
Slippery
Humidity dependent
Affected by heavy traffic
COPING WITH ESD
Reader Interest
High Medium Low
Interest Interest Interest
285 286 287
Flooring/Floor Coatings
Antistatic Flooring Is
Slip-Resistant
Altro Walkway SD is an antistatic vinyl flooring that conforms to the slip-resistance static coefficient of friction requirements of the Americans with Disability Act and OSHA for both dry and wet floors. The material meets the requirements of ASTM E 648 for flame spread, and resists acids and alkalis. Surface-to-ground resistance is 8.57 x 106 W . Altro Floors, (800) 382-0333.
Carpet Offers Resistances
From 25 kW to >100 MW
Ten-Six™ is an ESD carpet with average point-to-point resistances of 1 MW per the requirements of ESD Association S-7.2; however, the product can be specified for resistances ranging from 25 kW to several hundred megaohms. Walking on the carpet with ESD-protective shoes meets maximum body-voltage requirements of AATCC 134. The nylon carpet is offered in roll, tile or mat versions and several colors. ESD Flooring Systems, (803) 574-6415
Rubber Flooring Generates
Noraplan Mega AL is a static-dissipative rubber floor covering with a random pattern of color flecks with a 3-D look. It is resistant to oil and grease and generates <20 V per AATCC 134. The covering is free of PVCs, asbestos and halogens. It is slip-resistant and needs no waxing. Eight colors are available. Freudenberg Building Systems, (800) 332-NORAChemically Resistant Flooring
Generates <15 V Body VoltageChemi-Cote ESD floor coating controls electrostatic discharges and resists chemicals. The uniformly dissipative surface eliminates arcing caused by static electricity. The coating keeps body-voltage generation to <15 V. Voltage decay is 5,000 V in <0.1 s @ 72° F and 12% RH throughout the coating. The coating can be applied over nonconducting floor surfaces, including concrete and existing static-control tiles. Garland Floor, (800) 321-2395.Flooring Reinstalls
In New Configurations
Sigaway® Electronic is a conductive dry adhesive system for installation with Datwyler ESD conductive sheet vinyl or tile flooring. The adhesive and flooring are placed over structurally sound and clean concrete, wood, epoxy, steel, asbestos- or vinyl-composition tile, and glue-down carpet. Seams may be heat welded. The flooring may be immediately subjected to foot or rolling traffic. The sheets or tiles also release from flooring, leaving no residue; and may be reinstalled in new configurations. Tek Stil Concepts, (609) 428-4464.
PVC Floor Tile
Never Needs Waxing
The 8410 Series of static-dissipative and the 8430 Series of conductive floor tiles are made from 100% PVC, resist abrasion, do not dry out and never require waxing. The dissipative and conductive tiles are available in brown, white, gray and blue. Static decay for the 8410 Series is <0.1 s and <0.03 s for the 8430 Series, per FTM 101B Method 4046. Static generation for the static-dissipative tile is <50 V with conductive footwear @ 20% RH, and <25 V for the conductive flooring. The 0.125"-thick tiles are available in standard 12" x 12" squares or optional 24" x 24" and 36" x 36" versions. 3M Electrical Specialties Division, (800) 665-7862Carpet Tiles Install
Over Any Flooring
CompuTile ESD Seriesä provides 1-MW surface-to-surface resistance. The carpet tile can be installed over any flooring, including VCT and VAT types, with Compu-Release, a conductive adhesive. Electrostatic propensity testing with static-dissipative footwear yields <15 V at 20% RH, per AATCC 134. United Technical Products, (800) 225-6052.Marble Tile Has
RTG of 2 x 105 W
The 600 Series Static Control Terrazzo Tile uses marble in a thermoset resin to provide a flexible stone tile that handles 3,000 psi. It accommodates industrial-weight machinery, roll carts and forklifts. The silver-based tile provides permanent flooring and has a resistance-to-ground of 2 x 105 W . It also meets the Americans with Disabilities Act for slip resistance. A conductive adhesive and grounding strip are provided with the system. It is available in 23 colors. Fritz Industries, (800) 955-1323.
Urethane Coating Is
Permanently Conductive
Elimstat UXM is a waterborne, urethane coating available in conductive and static- dissipative formulations. The coatings provide permanent electrical conductivity and are insensitive to humidity. Neither version contains carbon. The coatings are available with any range of conductivity. Walter G. Legge, (800) 345-3443.
Conductive Carpet
Has RTG of 106 W
AZO ESD Conductive Berber Carpet is made by double V-loop needling with olefin fibers blended with graphite staple fibers. It is available in roll and tile form, is nonraveling, and does not shed fibers. It has a resistance to ground of <1 x 106 W and a surface resistivity of 1 x 106 W /sq. The carpet is supplied in five standard colors as well as custom shades. Rolls are 78″ wide by 50’ long. Tiles are 20″ x 20″. Tek Stil Concepts, (609) 428-4464.Epoxy Flooring Installed
With Selected Thicknesses
The 3M 8900 ESD Epoxy Flooring System is a multilayer liquid epoxy system offered with electrical properties ranging from conductive to static dissipative. It is available in thicknesses ranging from 8 mils to 125 mils. The epoxy is resistant to chemicals used in the electronics industry and can be poured over new or old concrete floors. Colors include off-white, light gray, oyster gray, tower gray, sky blue and country blue. Typical resistance to ground at 30% RH ranges from 1 x 105 W at 10 mils thick to 6 x 108 W at 90 mils thick. 3M Electrical Specialties, (800) 665-7862.
Copyright 1996 Nelson Publishing Inc.
February 1996