Static Electricity Technical Information
Basics of Static Control
Static electricity is readily identified in everyday life. Nuisance occurrences, shocks from the metal portion of a vehicle after sliding across fabric seats and the simple act of touching a door knob after walking across a carpet are examples. These ELECTROSTATIC DISCHARGES (ESD) occur because objects (your feet and the carpet) have been separated. Atoms near the surfaces of separation will transfer electrons to one another and as a result will either have a surplus of electrons, referred to as a negative charge or a deficiency in electrons, referred to as a positive charge. In addition, rubbing or sliding materials together will increase the amount of charge because a greater number of electrons will come in contact at the surface of the material. In this manner objects are commonly charged to 30,000 volts by walking or transferring materials along an assembly line.
Types of Materials
The two basic types of materials are conductors and insulators. All materials will fall within these categories in terms of static control. Insulators do not transfer electrons while conductors freely transfer electrons. However, both types of materials may hold a static charge. When a conductor is charged with surplus electrons it readily discharges when it comes close to another conductor with a different electrical potential. ESD is the spark we feel when we touch the car door after sliding across the fabric seat. The threshold of voltage that a person can feel is generally recognized as 3,000 volts. The voltages that may damage today’s sensitive electronics is much lower than what a person can feel. ESD is not a new phenomenon. In the past, any process which involved separation of materials caused static charges. It has not been until relatively recent times that it has been anything more than a nuisance for the electronics industry. The flammable gas/solvent industries as well as the explosives industry have been using LEGGE products for over 70 years to control potentially hazardous static discharges. The changing microelectronic industry has made ESD a special problem. As devices get smaller and more circuits are packed in modern microchips they have also become more susceptible to damage by ESD. Some devices may be damaged by a charge as low as 30 volts!
How Can Legge Systems Help You?
How can Legge help you control static electricity and prevent ELECTROSTATIC DISCHARGE from degrading your electronic devices or preventing fires or explosions? We manufacture a full line of static control products and can provide professional recommendations for your specific requirements.
Equal Potential will eliminate most problems with ESD. This involves grounding conductors and making non-conductors static dissipative and grounding them as well. The most common form of grounding involves the human body. The body is a conductor, but it is normally isolated from ground by clothing, shoes, etc.
Wrist Straps and Foot Grounders
Wrist straps and foot grounders, when used properly, drain static electricity to ground as it occurs, preventing static build up and the associated spark or ESD event from occurring. A person may be grounded with a wrist strap connected to ground or with a common point ground. Foot grounders will create a path to ground when worn on conductive or static dissipative surfaces.
Conductive and Static Dissipative Coatings
Conductive and Static Dissipative Coatings will allow objects that are normally insulators to be made conductive (or static dissipative). Coating normal flooring and work surfaces also facilitates the grounding of these surfaces. Generally, industries involving explosives or flammable solvents utilize conductive surfaces and items while the electronics industry employs static dissipative items and surfaces. Once the flooring and work surfaces have been made conductive or static dissipative a person may be grounded using foot grounders and connecting to ground via the conductive floor. Sprays, referred to as topical antistats, may be used to control static electricity and dust accumulation in localized areas for shorter periods of time. Static dissipative floor finishes may also be used on vinyl composition and other types of flooring – providing high gloss and cleanliness as well as static protection.