Air conductivity is the ability of air to conduct (pass) an electric current under the influence of an electric field.
Air ions are molecular clusters of about 10 molecules (water, impurities, etc.) bound by polarisation forces to a singly charged oxygen or nitrogen molecule.
Antistatic is a minimal generation or retention of a ‘static’ charge. It usually refers to the property of a material that inhibits triboelectric charging. Note: A material’s antistatic characteristic is not necessarily co-relatable with its resistively or resistance.
Auxiliary ground is a separate supplemental grounding conductor for uses other than general equipment grounding.
Bonding is the permanent joining of metallic parts to form an electrically conductive path that will assure electrical continuity and the capacity to safely conduct any current likely to be imposed.
Breakaway force is the force required to disconnect the ground cord from the cuff.
When an electronic device is exposed to an ESD event it may have caused a metal melt, junction failure or oxide breakdown, permanently damaging its circuitry and resulting in catastrophic failure. Such failure can usually be detected when the device is tested before shipping. If the ESD event occurs after the test the damage will go undetected until the device fails in operation.
Charge decay is the decrease and/or neutralisation of a net electrostatic charge.
Charge induction is the displacement of charge in an isolated conductor when placed in an electric field (for example, from a charged body). Note: Momentary grounding of such a conductor would result in its gaining a net charge.
A charged plate monitor (CPM) is an instrument used to measure the charge neutralisation properties of ionisation equipment.
A common connection point is a device or location (less than 1 ohm within itself) where the conductors of two or more ESD technical elements are connected in order to bring the ungrounded ESD technical elements to the same electrical potential through equipotential bonding.
Common point ground is a grounded device or location where the conductors of one or more ESD control items are bonded.
Compliance verification is the periodic testing done to indicate that the performance has not changed from initial baseline values to exceed selected limits.
Compliance verification equipment is an instrument or collection of instruments that provide a periodic indication or measurement to verify the performance of ESD test equipment and materials. Measurements may or may not be repeatable or accurate. Compliance verification equipment is typically used for indications of pass or fail.
A component is an active or passive item such as a resistor, diode, transistor, integrated circuit, or hybrid circuit.
Component failure is a condition in which a tested component does not meet one or more specified static or dynamic data sheet parameters.
Conductive flooring material is a floor material that has a resistance to ground of less than 1.0 x 106 ohms. The term ‘conductive’ or ‘conductivity’ does not guarantee low charge generation. To prevent static charge and ESD damage to static sensitive components, flooring materials must measure in the required resistance range and either be used in conjunction with ESD footwear/heel straps or be low charge generating.
A conductive material is a material that has either a surface resistance of less than 1 x 104 ohms or a volume resistance of less than 1 x 104 ohms or a surface resistivity less than 1 x 105 ohms/square or a volume resistivity less than 1 x 104 ohm-cm.
Note: “conductive flooring material” is not the same as “conductive material.”
The term “conductive” refers to the ability of a material to conduct a charge to ground; low resistance (i.e. less than 1 meg-ohm (10^(6)) – the closer to 1 meg-ohm, the slower the discharge.)
A conductor is a material with low electrical resistance that will effectively attract and transport an electrical charge to ground.
Examples of conductors are carbon, copper, aluminium and water. Practical examples of conductors are a lightning rod and a copper wire.
Conductivity is the ratio of the current per unit area (current density) to the electric field in a material. Conductivity is expressed in units of siemens/meter. In non-technical usage, conductivity is the ability to conduct current.
Also known as Conductive Correx®, Conductive Corriplast® protects the item inside the packaging from static charges. Conductive Corriplast® is a robust ESD Safe material – made from a corrugated plastic board – that is perfect for use in cleanroom, medical and laboratory applications and / or where static protection is also required. The Polypropylene / Ethylene copolymers used in the material provide a level of durability that makes it particularly suitable when longevity and re-usability is also a concern. Corriplast® packaging comes in all types of forms including tote boxes, tote divisions and layer pads.
The main benefits of Corriplast® is that it can be fabricated to create custom sized totes, containers and packaging that offers strength and performance approaching that of moulded plastic options. Corriplast® packaging has a resistance to moisture and dust, an enhanced lifespan, greater load bearing capacity and it is easy to clean.
Corona is the production of positive and negative ions by a very localised high electric field. The field is normally established by applying a high voltage to a conductor in the shape of a sharp point or wire.
A carbon based coating applied to corrugated cardboard which is then used for anti-static packaging solutions. Corstat packaging comes in all sorts of forms, including bins, boxes, totes, dividers, and other inserts. It is known as the ESD industry standard for conductive packaging.
The Corstat coated cardboard provides a “Faraday cage” that channels static around the outside of the packaging, protecting the static sensitive items within. Many blue-chip and multi-national electronics manufacturers typically use Corstat for its performance, reliability, and cost-effectiveness. Corstat packaging, manufactured from coated cardboard, is also an environmentally friendly anti-static bag alternative.
Decay time is the time required for an electrostatic potential to be reduced to a given percentage (usually 10%) of its initial value.
A device is the product being processed by AHE (e.g., an integrated circuit [IC] or a printed circuit [PC] board).
Dielectric is an insulating material that can sustain an electric field with little current flow.
Dielectric strength is the maximum electric field that a dielectric can sustain.
A discharge current is the current produced by causing a stored charge to flow out of a component into a conductor from an ESD simulator.
The discharge time is the time necessary for the voltage (due to electrostatic charge) to decay from an initial value to some arbitrarily chosen final value.
Dissipative materials is a material that has a surface resistance greater than or equal to 1 x 10E4 ohms but less than 1 x 10E11 ohms or a volume greater than or equal to 1 x 10E4 ohms but less than 1 x 10E11 ohms.
“ESD” is the abbreviation for electrostatic discharge.
Electrostatic discharge (ESD) is an uncontrolled surge of “static” between objects with different potentials. It is the rapid, spontaneous transfer of electrostatic charge induced by a high electrostatic field. Details of such processes, such as the rate of the charge transfer, are described in specific electrostatic discharge models. ESD events occur when people walk across various forms of flooring, then touch or approach static-sensitive components or devices.
“EPA” is the abbreviation for electrostatic protected area.
An EPA (Electrostatic Protected Area) is a static-safe handling area where static-sensitive electronic components are handled, requiring special ESD protection. An example on an EPA could be a bench, a room or any other designated area and should not have and ‘static field’ greater than 100v maximum.
Electronics manufacturing and handling facilities have designated EPAs, where static-control measures are in place and stringently enforced – including the use of special ESD footwear – following protocols outlined in ANSI/ESD S20.20.
An electrostatic discharge protective worksurface is a worksurface that dissipates electrostatic charge from materials placed on the surface or from the surface itself.
Electrostatic discharge sensitivity (ESDS) is the ESD level that causes component failure.
An electrostatic discharge shield is a barrier or enclosure that limits the passage of current and attenuates an electromagnetic field resulting from an electrostatic discharge.
Electrostatic discharge susceptible item is an electrical or electronic piece part, device, component, assembly, or equipment item that has some level of electrostatic discharge susceptibility.
An electrostatic field is an attractive or repulsive force in space due to the presence of electric charge.
Electrostatic potential is the voltage difference between a point and an agreed upon reference.
The term “equipotential” refers to having the same electrical potential; of uniform electrical potential throughout.
An ESD event is the occurrence of a single electrostatic discharge from any source. Examples of source include ESD simulators, humans and other charged objects. ESD events far below the human threshold for perception—static charges humans cannot see, hear, or feel—can damage static-sensitive components/devices and cause product failure, disruption or financial loss. In work environments, most ESD events are caused by the static generated when people walk, called walking body voltage.
Electrostatic damage to static-sensitive electronic components/devices can occur at any point from manufacture to field service. Damage results from handing the devices in uncontrolled surroundings or when poor ESD control practices are used. Generally damage is classified as either a catastrophic failure or a latent defect.
Catastrophic Failure: When a static-sensitive component/device is exposed to an ESD event it may have caused a metal melt, junction failure or oxide breakdown, permanently damaging its circuitry and resulting in failure. Such failure can usually be detected when the device is tested before shipping. If the ESD event occurs after the test the damage will go undetected until the device fails in operation.
Latent Damage: A latent defect is much more difficult to identify. A device may be partially degraded yet continue to perform its intended function. However, the operating life of the component/device maybe reduced dramatically. This could cause premature systems failure which could prove extremely hazardous and very costly.
The ESD Susceptibility Symbol, consists of a triangle, a reaching hand, and a slash through the reaching hand. The triangle means “caution” and the slash through the reaching hand means “Don’t touch.” Because of its broad usage, the hand in the triangle has become associated with ESD and the symbol literally translates to “ESD sensitive device, don’t touch.”
The ESD Susceptibility Symbol is applied directly to integrated circuits, boards, and assemblies that are static sensitive. It indicates that handling or use of this item may result in damage from ESD if proper precautions are not taken. If desired, the sensitivity level of the item may be added to the label
The ESD Protective Symbol, consists of the reaching hand in the triangle. An arc around the triangle replaces the slash. This “umbrella” means protection. The symbol indicates ESD protective material. It is applied to ESD furniture, mats, chairs, wrist straps, garments, packaging, and other items that provide ESD protection. It also may be used on equipment such as hand tools, conveyor belts, or automated handlers that is specially designed or modified to provide ESD control
The ESD grounding system selected for use in a facility or situation that best suits the application: a) AC equipment ground; b) auxiliary ground; c) equipotential bonding.
Electrical resistance describes the capacity of a material to stop, or resist, the flow of electricity. Resistance tests are typically used to predict how quickly or slowly an ESD flooring material will transport static charges to ground; this is measured in ohms (Ω).
Electrification time refers to the time for the resistance measuring instrument to stabilise at the value of the upper resistance range verification fixture.
A faraday cage is a conductive barrier against ESD that attenuates a stationary electric field. e.g. Metallised Shielding Bag, Conductive Box etc.
Field induced charging is a charging method using electrostatic induction.
In electrical terminology, the term “ground” refers to a conductive connection; representing “zero electrical potential”. It is the safe point of discharge of unwanted static electricity.
When something is grounded, it’s neutral; it has no charge. Connecting a conductive floor to ground ensures that static charges will be diverted to Earth through the conductive flooring system. Examples of typical grounds include: electrical conduit, building steel, copper bus bars and steel rods buried in the Earth.
A groundable point is a designated connection location or assembly used on an electrostatic discharge protective material or device that is intended to accommodate an electrical connection from the floor material to an appropriate ground.
The term “grounded” refers to being connected to Earth or some other conducting body that serves in place of the Earth.
Ionisation is the process by which a neutral atom or molecule acquires a positive or negative charge.
An ioniser is a specialised device which is designed to generate positive and/or negative air ions. Ionisers help to remove static charge on objects and surfaces by passing an electrical charge to molecules in the air. The primary function of an ioniser is to neutralise electrostatic charges on “process-essential” insulators and isolated (non-grounded) conductors. For more information, see our guide on ionisers in ESD control.
An isolated conductor is a non-grounded conductor. Examples of isolated conductors include: Conductive traces or printed circuit board components not in contact with ESD work-surface.
The property of “insulation” refers to a material’s ability to store as opposed to conduct electrical current.
An insulator is the opposite of a conductor. It does not allow the free flow of electrons, therefore it will more than likely cause problems to prevent a path to Earth, hold a ‘static’ field etc. Examples of insulative materials include: plastic, glass, wood and rubber.
The term “insulative material” refers to a material having a surface or volume resistivity ≥ 1 x 10E11 ohms.
An insulator is a material with high electrical resistance. It will not conduct a charge to ground. Examples of insulators are plastic, rubber, vinyl, glass and wood. A practical example of an insulator is the rubber or vinyl casings around common electrical wires.
The term “latent failure” refers to a malfunction that occurs following a period of normal operation.
Latent failure, otherwise known as a latent defect, is much more difficult to identify. A device may be partially degraded yet continue to perform its intended function. However, the operating life of the device maybe reduced dramatically. This could cause premature systems failure which could prove extremely hazardous and very costly.
The term “low charge generation” replaces the older, less descriptive term “antistatic” (or anti-static). Low charge generation is a property that refers to the propensity of a material (or flooring material) to inhibit static charges.
Low charge generation should not be confused with conductivity or grounding. A low charge-generating floor may or may not be electrically groundable. Likewise, a grounded floor may generate enough static to cause a damaging ESD event.
This is why ESD floors should be evaluated for both conductivity (electrical resistance) and charge generation.
The term “neutralise” refers to eliminating an electrostatic field by recombing positive and negative charges, either by conducting the charge to ground or by introducing an equal opposite charge.
Offset voltage refers to the observed voltage on the isolated conductive plate of a charged plate monitor that has been placed in an ionised environment.
Ohm is a unit of resistance. Symbolised by the Greek capital letter omega (Ω). It is defined as the resistance, at 0o C, of a uniform column of mercury weighing 14.451 grams. One ohm is the value of resistance through which a potential difference of one volt will maintain a current of one ampere.
For pulsed ionisers, the maximum value of the peak offset voltage for each polarity, as the ioniser cycles between positive and negative ion outputs.
Potential difference causes ESD when there is a static voltage difference between two items/objects: i.e. flooring, articles of clothing, shelving, conveyers, work surfaces, people.
The path to ground is an electrical link between a static-dissipative and conductive material and the Earth.
Point-to-point resistance is the resistance in ohms measured between two electrodes placed on any surface.
A process-essential insulator is necessary to build or assemble the finished product. When grounding of these is not possible, choosing a method to neutralise electrostatic charge is necessary. This can be achieved with ionisation. Examples of a process-essential insulator include: product plastic housing or PC board substrate.
Resistance range refers to a user-specified upper and lower resistance values which define the user-acceptable resistance values of a wrist strap or wrist strap system.
Resistance to ground is the resistance in ohms measured between a single electrode placed on a surface and ground.
Resistance to groundable point is the resistance in ohms measured between a single electrode placed on a surface and a groundable point.
Static electricity is a stationary electrical charge/ field, typically produced by friction, which causes sparks, crackling or the attraction of dust or hair.
All items are made of small atoms. These atoms are made up of even smaller items called protons, neutrons and electrons. The protons are charged positive, the neutrons have no charge and the electrons are charged negative. Under normal conditions, there are the same amount of protons and electrons giving atoms no charge.
However, these electrons can move. When separating or rubbing together materials, electrons can move from atom to atom or from one material to another (triboelectric charges). This can mean that atoms can hold a positive or negative charge. (Dependant on movement and direction of electrons). If the material in question is an insulator, this charge can be held and not move. This is called static electricity.
The rapid movement or decay of these charges can cause expensive problems, whether it is huge and dangerous charges such as lightening or simply an annoying (and sometimes painful) “electric shock” when touching a filling cabinet or when getting out of a car. (These charges are normally on you!).
These charges can be a huge problem for small sensitive electronic devices. Some devices can be damaged or destroyed by as little as 10 volts. Charges on your body simply by walking or even sitting at your chair can be in excess of 5000 volts (human body material). This is because of items of clothing rubbing together or as simple as shoes separating from the ground.
When items are insulators such as carpets, charges are much higher – imagine the damage this could cause. This is why it is important that insulators should be avoided and all possible static electricity generators (such as you) should (must) be grounded to eliminate any build up of charges.
An example of static generation is when people walk across a floor, the friction between the soles of their shoes and the surface of the floor generates static—also called walking body voltage.
Static dissipative refers to increased resistance, which protects better against an ESD i.e. between 1 meg-ohm (10^6) and 1000 meg-ohm (10^9). Static dissipative materials allow any static charge to be dispersed. Charge transfers from static dissipative materials are slower than from conductive materials and are significantly faster than from insulators.
Products such as ESD clothing and ESD bench matting are typically made from static dissipative materials, or often a combination of other materials i.e. conductive.
Surface resistance is the resistance of a surface measured by a concentric ring electrode test method defined in 61340-5-1 and IEC 61340-2-3: 2000.
It is the ratio of DC voltage to the current flowing between two electrodes of specified configuration that contact the same side of a material. This measurement is expressed in ohms.
A static decay test is a procedure in which an item is first charged to a specified voltage, then allowed to dissipate to a specified voltage while measuring the duration of the discharge.
Not to be confused with surface resistance, surface resistivity is a measurement of a material’s inherent electrical resistance. For electric current flowing across a surface, the ratio of DC voltage drop per unit length to the surface current per unit width.
In effect, the surface resistivity is the resistance between two opposite sides of a square and is independent of the size of the square or its dimensional units.
To test a material’s electrical resistance, a surface resistivity meter can be used. Surface resistivity measurements are expressed in ohms/square.
Tribocharge, otherwise known as triboelectric charge or tribocharging, is the generation of electrostatic charges by the rubbing or separating of surfaces. The molecules in the two materials interact, forming an electrical bond. Separating the materials creates friction. This frictional force draws electrons away from one material and deposits an excess of electrons on the other, leaving a positive or negative electrical charge on both materials.
The amount of charge created by triboelectric generation is affected by the area of contact, the speed of separation, relative humidity, the chemistry of the materials, surface work function, and other factors.
An electrostatic charge may also be created on the material in other ways, such as by induction, ion bombardment, or contact with another charged object. However, triboelectric charging is the most common.
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