To protect ultra-sensitive electronic circuitry, electronics manufacturing and handling facilities must adhere to more rigid standards than for other types of ESD flooring applications—such as call centers or 9-1-1 dispatch operations that need to protect data, hand-held devices, or networked computers.
Under ANSI/ESD S20.20-2014 guidelines, for use in electronics manufacturing and handling facilities, the floor—tested in combination with footwear—must generate no more than 100 volts of static. Without static-protective footwear—toe straps, heel straps, sole straps, or ESD shoes—every flooring material on the market will generate more than 100 volts.
To meet ESD standards for electronics manufacturing and handling operations, every person in the environment must wear some form of ESD footwear at all times. Footwear options depend in part upon the flooring material. With certain types of flooring, the options are limited.
* Because standards for telecommunications and other mission-critical applications are less stringent—the floor must generate no more than 500 volts of static—low charge-generating materials, like conductive rubber and static-dissipating carpet, will reliably protect these areas from static without the use of special ESD footwear (i.e., people wearing regular street shoes).
Why ESD Footwear?
As we walk, the contact and separation between the soles of our shoes and the floor generates a static charge. The charge stays in place, on our body, until we touch something or someone. In a rush of current, like a tiny lightning bolt, the static discharges to that person or object. This discharge—or static event—can damage or destroy sensitive electronics or electronic circuitry.
Footwear is the meeting point between the floor and a person walking on the floor. When a person walks on the floor, the conductive elements in ESD footwear form an electrical bond or bridge between his or her body and the carbon veins or particles in the ESD floor, drawing static away from the body and dissipating charges to ground.
ESD footwear comes in several forms: sole straps, heels straps, toe straps, and shoes. Benefits and performance vary; buyers should select footwear based on their needs, priorities, and test results.
Does it Matter Which Type of ESD Footwear People Use?
Yes, very much so. Static-protective toe and heel straps cover only a small surface on the soles of shoes. Depending upon the flooring material, less contact area between the protective footwear and the floor can make toe and heel straps less reliable than ESD sole straps or shoes.
Extremely hard surface floors like epoxy, with a base composition of charge-generating resins, need full sole contact. Sole straps or ESD shoes, needed to provide greater surface area contact, have a better chance of working with hard surface ESD flooring materials.
Static-Dissipative Carpet and Conductive (EC) Rubber
Softer, “low-static-generating” materials, like static-dissipative carpet and conductive (EC) rubber, have built-in fault-tolerance, so it matters less if the bond between the shoe sole and floor is periodically broken.
Conductive rubber and ESD carpet tile are low charge-generating materials, for two reasons:
- Carbon embedded during the manufacturing process is distributed evenly throughout the materials, including the surface, where it makes direct contact with shoe soles.
- The conductive elements in the floor bleed static away from shoe soles, decreasing charge generation.
- Both materials have low contact resistance—i.e., the contact area between shoe soles and these somewhat softer floor surfaces is large enough to prevent static generation.
- With conductive rubber, its resilience provides better contact, so more of the footwear or shoe sole comes into contact with the conductive veins in the rubber.
- With carpet, the fibers sweep static from the soles of shoes, much like brushes inside a copying machine sweep static from the paper, so it doesn’t cling to the machine as it moves through the copier.
With low charge-generating materials, any type of footwear will maintain a much lower threshold of static generation.
Conductive (EC) Rubber
On an extremely hard surface, any irregularity on the soles of shoes—the grip on athletic shoes, for example—prevents part of a sole from touching the floor. Rubber’s inherent resilience compensates for contact irregularities, so more of the foot—or shoe surface—comes into contact with the floor.
Due to its low contact resistance and distribution of carbon veins or chips across the surface of rubber tile, even with their small surface area, toe and heel straps can bond electrically to an EC rubber floor.
Bottom line: on an EC rubber floor, it’s perfectly fine to use any type of ESD footwear.
Conductive Carpet > 2.5 x 104 – < 1.0 x 106
Like any carpeting material, conductive carpet is extremely resilient with little to no contact resistance—feet almost sink into carpet, creating full contact with the floor across the sole of the shoe. The resistance of the conductive carpet is also extremely low—and resistance from tile to tile can vary by as much as 2 magnitudes—meaning a carpet that measures 105 in one area could test at a dangerously low 103 in another, posing risk of a harmful electrical shock.
Bottom line: Conductive carpet (e.g. any carpet potentially measuring < 1.0 x 106) is not advised for use in any area housing electrified equipment—with or without ESD shoes.
Static-Dissipative Carpet > 1.0 x 106 – < 1.0 x 109
Like EC Rubber, because of its low contact resistance and even distribution of carbon fibers, static-dissipative carpet will generate less than 100 volts—in use with any type of ESD footwear.
Bottom line: Any type of footwear can be used with static-dissipative carpet.
Conductive vinyl tile is a hard-surface flooring material, with high contact resistance. Comprised of a base material made from insulative PVC polymers, vinyl generates static—even if electrical resistance of the material is relatively low. For these reasons, vinyl should never be used without ESD footwear.
Conductive vinyl flooring has become the consensus choice for flooring in ESD-protected areas in electronics manufacturing. Long-lasting and relatively inexpensive, vinyl performs extremely well—as long as ESD footwear is worn by people walking on the floor or working in the space.
Due to the density of conductive particles on its surface, conductive vinyl tile makes reliable contact with any type of ESD footwear.
Bottom line: Conductive vinyl must be used in conjunction with ESD footwear—but any type of static-protective footwear will perform adequately.
Static-Dissipative Vinyl (SDT)
Static-dissipative vinyl composition vinyl tile—also called ESD VCT or SDT—is made from insulative composite materials, making it a static-generating material. SDT will not prevent static generation on people wearing standard footwear.
To achieve its static-control properties, SDT requires the application of multiple layers of a special static-dissipative floor wax or polish. The polish must be periodically tested for changing electrical resistance and refurbished as the properties diminish. Without regular testing, there is no way to know when the static-dissipative properties of the material have worn off.
Bottom line: Before purchasing SDT vinyl, determine whether or not regular resistance testing is feasible and/or if someone will monitor the application and reapplication of ESD finishes.
ESD epoxy is not conductive across 100% of the surface. Most of the surface composition of ESD epoxy is actually insulative, with only a small percentage containing conductive elements. Like vinyl, the majority of the material composition of ESD epoxy is hard and non-conductive. This is why epoxy floors generate significant static when people walk on them with regular footwear.
Epoxy will generate static on any portion of a shoe that is not covered with ESD toe and heel straps. To work properly, epoxy floors require reliable contact between their conductive particles and the conductive elements in ESD footwear. For optimal performance, ESD epoxy surfaces require compressive contact with the entire surface area of a conductive shoe sole—not just the heel or the toe.
Bottom Line: Sole straps or ESD shoes should be used with ESD epoxy.
ESD Flooring and Footwear in Electronics Manufacturing and Handling
No ESD flooring material can reduce charges to the minute voltage necessary to protect sensitive—and ultra-sensitive—electronics. For this reason, every electronics manufacturing and handling facility should mandate and enforce the use of ESD-protective footwear. When evaluating ESD flooring materials, it is absolutely imperative to account for the charge-generation potentials of the flooring in conjunction with the footwear to be worn in the space, and to choose the most compatible options.
Matrix: Static-protective Footwear/ESD Flooring Material
|Material||Any ESD footwear||Sole straps or shoes ONLY||Unsuitable for electronics applications|
|Static-dissipative Vinyl (VCT)||X||Requires full coverage ESD footwear|
* Some ESD coatings perform well with any type of ESD footwear while other coatings only meet ANSI/ESD S20.20-2014 with ESD shoes or full coverage ESD sole straps.
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- Keeping Architects Grounded
- The Need for Due Diligence in Specifying Static-Free Flooring
- Standard of Care for Specifying Floors in Mission-Critical Spaces
- Static-Control Footwear for Electronics Manufacturing and Handling Applications
- Understanding the Hidden Costs of ESD Flooring
With Staticworx ESD flooring, you never have to choose between performance and aesthetics. Our beautiful, high quality ESD carpet tile, vinyl, EC rubber tile and sheet goods, and ESD epoxy floors are as beautiful as they are functional.