Static electric fields (EF) develop naturally in the environment in many ways:
- The approach of storm clouds
- Through triboelectric charge separation on clothing
- Artificially generation association with technical processes or devices
Static electricity is generated when two materials are in contact with each other. And, as you’re probably already aware, materials are made up of electrically charged atoms. Universally there are equal quantities of negative electrical charge (electrons) and positive charge (protons); these generally are balanced at every location
However, when two materials come in contact, some of the charges redistribute by migrating from one material to another; this leaves a surplus of positive charge on one material and an equivalent of negative charge on the other. When the materials move apart, each goes along its own charge with it. One material will becomes charged positively and the other negatively. If the materials can conduct electricity away from the charges, it will dissipate and, in the end, come together. In this case, static electricity effects may be too small to be noticed.
If the charges are separated quicker than the material can dissipate them, the quantity of electrostatic charge builds up; eventually, a high voltage, and other effects of static electricity, may be noticed. Static electricity hazards or nuisances arise when charge separation occurs, leading to an accumulation of one sign of charge within some defined boundary.
However, static energy is found at all levels (from the simple spark by combing the hair, to the discharges in industrial machines, to lightning and its dangers of electrocution and fire). However, even a small amount of static electricity can be dangerous, especially in the presence of flammable or explosive products. Static electric charge is created on every occasion that two surfaces come in contact and separate, and at least one of the surfaces has a high resistance to electric current.
The effects of static electricity are accustomed to most people because people can sense, feel, hear, and even see the spark as the excess charge is neutralized when brought close to a large electrical conductor, When a statically-charged person or object touches an electrostatic discharge sensitive (ESDS) device, there is a possibility that the electrostatic charge could be drained through sensitive circuitry in the device. If the electrostatic discharge possesses sufficient energy, the damage could occur in the device due to localized overheating. Generally, devices with finer geometries are more susceptible to damage from ESD.
The ways in which ESD damage occurs include the following:
(a) Discharge to the devices
(b) Discharge from the devices
(c) Field-induced discharges
One of the most common occurs through human contact with sensitive devices. Human touch is only sensitive to ESD levels that exceed 4,000V and a recent investigation found the human body and its clothing capable of storing between 500V and 2,500V electrostatic during a normal workday. This is far above the level that damages circuits yet below the human perception threshold.
Other sources of ESD damage to equipment include:
• Troubleshooting electronic equipment or the handling of printed circuit boards without using an electrostatic wrist strap
• Placement of synthetic materials (i.e., plastic, Styrofoam, etc.) on or near electronic equipment
• Rapid movement of air near electronic equipment (including using compressed air to blow dirt off printed circuit boards, circulating fans blowing on electronic equipment, or using an electronic device close to an air handling system).
In all of these scenarios, the accumulation of static charges may occur, but you may never know. Furthermore, a charged object does not necessarily have to contact the item for an ESD shock to occur. Sometimes within buildings, we do not encounter lightning-like discharges; which defines the severity of the electrostatic shock. In the majority of these circumstances, is the quantity of electrical charge that is produced and stored on the human body. When someone reaches for a door handle and experiences an electric shock, it is the release of electrical energy developed on their body by actions or movement prior to touching the handle. The electrical shock that is experienced happens when the body loses its stored energy very fast in the form of a spark.
There is no suspicion or guess that static electricity is an insidious danger; it is, by nature, unpredictable and difficult to detect. With the correct approach, however, the risks presented by static can be quantified and controlled. For a hazard to occur, the following three elements must be present
• Generation of electrostatic charge
• Accumulation of charge
• Electrostatic discharge (ESD)
Feeling the discharge of static is as unpleasant as it is short-lived.
However, less than 100 volts is enough to potentially damage beyond repair an electronic component. That is why operators and technicians who work with ESD sensitive components or equipment are required to use appropriate protection when entering a designated ESD protected area or workstation.
One of the most prominent producers of ESD is the human body itself. Operators and workers move around work areas, surfaces of clothing rubbing against each other, generating static. The starting point of any ESD control systems is to start with grounding the operator.
To make sure an operator is grounded properly, personal ESD grounding products should be used. But to ensure the right products are used and used properly, a basic understanding of ESD is needed.
One of the most significant concepts in the field of static control is grounding. For example, attaching all electrically conductive and dissipative items in the workplace to ground allows built-up electrostatic charges to equalize with ground potential. A grounded conductor cannot hold a static charge.” To determine your specific ESD grounding requirements, you must first identify the areas where grounding is needed.
These areas can include:
- Manufacturing floors
- Packing and shipping centers
- Clean rooms
- Research and development labs
ESD grounding requirements are codified forms of static control as set out in the American National Standards Institute. To reach full compliance with your company’s ESD grounding requirements, you will almost certainly have to use grounding wrist straps, anti-static work mats, and earth bonding plugs. These are standard industry equipment used for controlling and dissipating static electricity.
The basic working principle of grounder is the use of conductivity of carbon (the black part) to bring electrons to the ground.
An ESD workspace