What is ESD?
Electrostatic discharge; when two objects come into contact creating a release of static energy. Everyday examples include: after tumble drying clothes or walking on a carpet then touching a metal door-handle.
For a discharge to occur two material need to rub together to build up the electro static charge. One of the materials is now positively charged and one is now negatively. The positively charge material now holds the electro static charge; when this meets a preferred material, the static is transferred and an ESD event occurs.
Why should we prevent an ESD event?
The heat from said event is extremely hot, we do not feel it as we are shocked but when this charge is released onto electronic devices the intense heat can melt tiny parts causing the device to fail. Occasionally the device continues to function through the damage as it is hard to detect but will significantly shorten the life of a device. This is known as Latent Defect.
Even an event as low as 10 Volts is enough to seriously damage components, so manufactures take special measures throughout the whole process to ensure events like these do not occur. Wrist straps, ESD control footwear and ESD floor mats are a few examples that will direct the charge into the ground instead of the device but nothing will compare to the durability and life expectancy of an ESD trolley or workbench.
Basic ESD events
Discharge to device: occurs when any charged conductor (including the user) discharges to an item. This directly transfers the electrostatic charge from the user to the sensitive device.
Discharge from the device: The transfer of a static charge from the device to the user. The static may build up on the device itself through handling or contact with surfaces. This is due to movement in packaging. Devices maybe more sensitive to damage when assembled by automated equipment due to their composition.
Field Induced Discharge: As on object becomes electrostatically charged it produces an electrostatic field, if a device is placed within this field a charge could be place on said device and cause damage.
Sources of Static Electricity?
MiniCircuits shows us in the table below a list of sources of static electricity from objects or processes. It is said that humidity does have some effect ESD; they recommend that humidity must be between 40 – 60% to have the least effect on ESD.
| OBJECT/PROCESS | MATERIAL/ACTIVITY |
| Work Surfaces | Waxed, painted or plastic surfaces |
| Floors | Waxed, Common Vinyl tiles, Sealed Concrete |
| Clothing | Common smocks, Non-Conductive Shoes, Synthetic Materials |
| Chairs | Vinyl, Fibre-glass, Finished Wood |
| Packaging | Common Plastic Bags, Foam, Trays, Tote Boxes |
| Assembly Area | Spray Cleanersm Heat Guns, Blowers, Plastic Tools |
How to detect static in the work area?
One tool commonly used is an electrostatic field meter which detects the presence and magnitude of static charges. Calibration to specific distances must occur frequently correctly and accurately. The user guide of each device will describe the correct operating procedures.
What is the best protection from ESD sensitive devices?
- Work Area
You must handle EDS sensitive devices at an anti-static workstation. This will prevent any damage of any sort.
Avoid bringing sources of static electricity into the static safe environment.
- Personnel
Static energy must be dispelled before the user works in a static free work area.
The use on an antistatic smock for each user is recommended.
Education and training on ESD as a preventative measure.
- Packing & Transportation
Devices are contained in a static protective bag or container at all times during transportation and storage.
Options for an Anti-static work area
- ESD workbench
Each workbench has a robust steel construction with an anti-static work top to prevent a static event. Common options for a top are: Neostat, a dual layer worktop with a dissipative top layer and conductive bottom layer. This guarantees a safe path for grounding, the work top constructed of rubber gives grip and stops small parts sliding.
Lamstat worktop; constructed of plastic laminate which is durable and resistant to solder, heat and largely resistant to chemicals.
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ESD matting
Antistatic/anti-fatigue matting provides a tough mat ideal for industrial applications. Easy to clean and provides grounding via a 10mm male stud fitted in the mat. Maximum performance is achievable when used with floor mat grounding cable and UK plug. Coupled with anti-fatigue properties increase productivity of the user.
Non-Conductive Switchboard matting ideal for use in front of switchboards and high voltage equipment.
Antistatic ribbed rubber matting constructed of natural rubber which is highly versatile: provides insulation as a mat from factory floors and may be used on the top of a workbench to increase slip resistance and protect small parts. -
Antistatic wrist strap
a primary type of grounding for the user. When worn correctly the strap keeps the user grounded. As all objects and the user are grounded a hazardous charge between them cannot occur. This applies to a person sitting on a chair that is not static safe, if they’re still wearing the wrist strap correctly they will be grounded.
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ESD Shelf Trolley
an efficient tool in all organisations but when coated in an anti-static material they are perfect for transporting parts and components in the electronics industry. Each truck removes the build-up and grounds the static charge absorbing it into the ground.
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ESDA