Static electricity is formed by an imbalance of electrons caused by separation and contact of materials. Dependent on the area and speed of separation and contact, relative humidity and some other factors, the amount of the static charge will vary. For instance, when someone walks across a floor, static electricity can be generated from their shoes contacting and separating from the surface of the floor. The transfer of the charge generates a shock which is referred to as "electrostatic discharge" (ESD).
To some extent, most materials are subject to the creation of static electricity and ESD. What varies is the amount of the charge and discharge.
Types of ESD
Three types of ESD exist:
Direct ESD to an object – The most common occurrence, this type is caused by directly touching an object after generating a static charge.
ESD from an object – Moving parts within a device can automatically create the charge and then discharge upon contact
Field-induced ESD – Grounding an object within an electrostatic field will cause ESD.
Categories of ESD Damage
Catastrophic – complete breakdown of an object
Latent Defect – partial degrading of an object that will downgrade productivity and longevity
Combating ESD
We can't eliminate generation or discharge of static in a working environment, therefore the best solution is to neutralize the charges when they occur. Proper grounding and use of anti-static mats neutralizes the ESD.
Anti-Static Mats
Anti-static mats have a high electrical resistance. They allow ESD to flow across the surface at a slow rate which neutralizes the ESD. By neutralizing the ESD, damage to delicate electronic devices such as circuit boards is prevented by moving the charge to the grounded mat. Mats can be used both on the table or work station and on the floor. Depending on the sensitivity of the items being handled, more anti-static protection may be needed.
The mats often offer more than just ESD protection. Many anti-static floor mats are cushions for preventing fatigue from standing. Mats are manufactured from rubber or vinyl, materials that resist electrical charges. When placed on the floor of the work station, the mat stays in place thereby alleviating accidents due to slippery floors. The worker wears a band, most commonly around the wrist, that has a wire connected to ground in order to safely handle electronic components. When choosing anti-static mats for a manufacturing or shipping floor, consider the product being handled and the level of ESD that can damage it.
Note: An ungrounded anti-static mat will retain the ESD and transfer the charge to the next object that comes in contact with it.
