By Dave Long

 

As electronic components become faster and more sensitive to electrical interference, the need for static control has grown exponentially, particularly into technology reliant spaces like banks, data centers, power plants, flight towers and mission-critical 911 call centers, where the loss or corruption of data can pose a security or safety threat. When most of us think static, we think nuisance – static cling or irritating static shocks. But for humans to feel these effects of static electricity, the discharge must be at least 3500 Volts. To put that into perspective, today’s sensitive computer parts can be damaged by a static discharge as low as 20 Volts.

Since static electricity is the result of friction between two materials, walking across a floor is the major source of static buildup. That’s why the cornerstone of any static-free environment is antistatic and conductive flooring. Fortunately, almost every conceivable floor covering material, including carpet, epoxy, vinyl and rubber, can be manufactured to provide some static dissipative or antistatic properties.

Before helping your customers select any type of static-free flooring, it is imperative to understand how the floor will interface with its particular environment and the people working in it. The first question a buyer or specifier should ask is this: Will the people who walk on this floor wear grounded heel straps and conductive shoes? If the answer is no – which it usually is – then the grounded floor must provide a combination of conductive elements and the capacity to prevent or inhibit static build-up.

To prevent static build-up, static-control floors must meet two basic requirements. They must not contribute to static generation and they must be ground-able after they are installed. Although these requirements seem basic, in practice they are anything but simple. For example, a 3.5 kV antistatic floor will not generate charges higher than 3500 Volts. However, this typical computer-grade antistatic floor is not ground-able and cannot come close to reducing charges to the minute thresholds necessary to protect today’s ultra-sensitive electronics.

Many static-protective or so-called ESD (electrostatic discharge) floors are incapable of providing both of these attributes. The fact that a vinyl tile is advertised as “conductive or ESD tile” does not necessarily mean that it will prevent static problems in a 911 call center or in a server room.

Certain excellent conductors – conductive vinyl, for instance – are comprised primarily of ordinary static-generating materials, such as polyvinyl chloride (PVC), with a small distribution of carbon or graphite particles. Although the embedded conductors enable the vinyl composition floor to be grounded, the floor fails to prevent static build-up.

	How ESD carpet works Static charges are ionized at the surface of the carpet and conducted directly to ground through a conductive thermoplastic backing and patented conductive adhesive system. Click here for a pdf of the "How Carpet Works" info sheet.

When that same server room is equipped with an ESD carpet tile, it is almost impossible to create a harmful amount of static charge – regardless of footwear. Intuitively, we would assume that conductive carpet would be less capable than conductive vinyl, but the opposite is usually true. Conductive carpet tiles contain thousands of grounded conductive fibers that sweep off static and safely discharge it to ground from shoes, much the same way small brushes eliminate static on high speed copiers as paper is fed into the collator. This does not mean that conductive vinyl is an inferior product. It means that conductive vinyl works best in applications, such as electronic manufacturing and assembly, where footwear and traffic are controlled and monitored.

Two layer conductive rubber provides static inhibiting properties similar to conductive carpet tiles. However, conductive rubber  achieves its performance characteristics from a completely different set of attributes than ESD carpet tiles: From physics we know whenever two dissimilar surfaces are rubbed together they generate static. The corollary is also true: Similar materials generate less static when they interact. The base compound used in tow layer conductive rubber flooring sufficiently resembles most shoe soles to the point that it will inhibit static generation when shoe soles rub against it. Unlike conductive vinyl, this type of ESD rubber is essentially a homogenous material with static-dissipative properties distributed across the surface and throughout the thickness of the tile. Like conductive carpet and vinyl, rubber can be grounded and has many of the same ergonomic properties as conductive carpet. Every static-control floor has its attributes and its drawbacks. Carpet, for example, despite its positive ergonomic and charge reduction properties, is inappropriate in certain applications. Some areas in electronics manufacturing are constantly wet or can become contaminated with splashes of lead solder or solvents. These areas are best handled with heavy-duty ESD flooring materials that can be easily cleaned and mopped. Conductive rubber, vinyl and quartz-filled conductive epoxy coatings are particularly suitable for these wet, messy areas. That does not mean that adjacent areas can’t be covered with ESD carpet tiles and broadloom carpeting, but it does mean that extra thought should go into the layout and design of the facility.

The advent of conductive release adhesive has greatly enabled interchangeability of various ESD flooring materials, such as conductive rubber and antistatic carpet. Before installing, it would be wise to ensure that ESD carpet tiles and conductive resilient tiles are modular and compatible with the same adhesive.

Finally, in choosing static-free flooring, buyers should consider the need for permanent static protection and also maintenance procedures and costs. The static-control properties of certain floors wear off, requiring periodic buffing or waxing to maintain performance. Certain SDT vinyl tiles are not even warranted unless the customer uses special antistatic floor finishes. Any carpet that requires a restoring agent, called an antistatic/stain blocker, should be carefully scrutinized. Before purchasing any ESD flooring, buyers must decide whether or not they’re prepared to pay the additional cost, which over time can be substantial, of maintaining the conductivity of their floor. They must also consider whether it’s prudent to install, in a mission critical areas like  flight control towers and power plants, a flooring material that requires periodic rejuvenation. After all, static is invisible. How would they know exactly when the static control properties had worn off?

Today, there are static control floors and styles to meet every flooring consideration and every budget. As with any specialty product, it’s easy to be confused by the technical jargon and complicated specifications. Before helping your customers make any decisions, it’s wise to identify reputable suppliers who offer a combination of flooring and static control knowledge. Finding a supplier with both skill sets will ensure that the ESD flooring your customer purchases will yield a lifetime of utility. You also help your customers guarantee that their mission-critical operations are safe from the hazards of random static discharge.

Dave Long has been solving static problems for government and  businesses worldwide since 1976. He can be reached at dave@Staticworx.com