Electrostatic Discharge (ESD) Explained
Electrostatic Discharge (ESD) occurs when a circuit is created that allows electrons to rush from a statically charged body to another with an unequal charge. The electricity is released with a spark. The charge follows the path of least resistance, so it can occur between an electrical circuit ground, such as a doorknob or a computer chassis, and a charged body, such as a human hand. ESD can damage sensitive computer equipment. While ESD is the primary electrical danger to computer equipment, Electromagnetic Interference (EMI) can also cause problems with microcomputer circuitry. EMI occurs when a magnetic field builds up around one electrical circuit and interferes with the signal being carried on an adjacent circuit.
Charges as low as 10 volts can damage or destroys sensitive electronic circuits. This is why ESD is such an enemy of integrated circuits. Static charges can build up on both conductors and insulators, as well as in the human body. When you work with computer equipment, you must take steps to protect against ESD. Anti-static bags that are used for shipping components that actually conduct electricity, so keep them away from equipment that is powered on.
ESD Prevention Measures
You can protect against ESD in your work environment by:
• Eliminating unnecessary activities that create static charges.
• Removing unnecessary materials that are known charge generators.
• Using anti-static vacuums for cleaning computer components (such as chassis, power supplies, and fans).
• Using anti-static materials.
• Grounding conductive materials.
• Using anti-static bags to store computer components that are particularly sensitive to ESD.
• Using an air ionizer, which releases negative ions into the air. They attract positively charged particles and from neutrally charged particles.
• Humidifying the air to speed up static discharge from insulators. When the air is extremely dry, more static is likely. A humidity rate of 50 to 60 percent is best.
• And, grounding yourself before touching electronic equipment. To avoid a static shock, touch a grounded object made of a dissipative material. A dissipative material is a conductor, but with high resistance. It loses its electrical charges slowly, so when you touch it, the electron flow is spread over time and you do not feel a shock.
Some people who work on computer equipment never use a single piece of ESD safety equipment. They discharge themselves by touching an unpainted metal part of the computer case before touching any components. In other instances, the company policy might require that you use a properly equipped ESD-free work area. The minimum equipment in this case would be a grounded wrist strap. Other ESD-protection equipment includes leg strap, grounded mat to cover the work surface, and grounded floor mats to stand on.