Desco Europe ESD - Questions And Answers

I need to prove to a customer what the ESD effects are to a computer system. -Anonymous, Mardi, Australia

Most certainly ESD is a concern for any electronic device or equipment, especially an open computer. Preventing electrostatic discharge the components inside your computer are extremely sensitive to static electricity, also known as electrostatic discharge (ESD). ESD can permanently damage electrostatic discharge sensitive components in the computer. Prevent ESD damage by following ESD guidelines every time you open the computer case. Before opening the computer case, follow these guidelines: Turn off the computer power. Wear a grounding wrist strap (available at most electronics stores) and attach it to a bare metal part of the computer. The drive is sensitive to ESD. Take standard precautions before it is installed in the system. CAUTIONS: An electrostatic discharge (ESD) can damage disk drives, add-in boards, and other components. This system can withstand normal levels of environmental ESD while hot-swapping SCSI hard-disk drives. EOS/ESD Considerations All electronic components can be damaged by ESD (Electrostatic Discharge) or EOS (Electrical Overstress) throughout their life cycle. Whenever there is movement static charge is produced: Static charge is always present, ESD caused by the rapid flow of charge between two objects, Voltages as low as 200v can damage devices, we feel ESD at > 3000v, we hear it at > 6000v, we see it at > 8000v. ESD/EOS Control Will: Reduce charge generation, Reduce potential differences between objects (Grounding), Neutralize charges (ionizers), Remove field effects. Eliminating charge generation or charge transfer at the workstation is accomplished by grounding operators and equipment. The following is a list of prevention techniques: Personal grounding. The purpose of the wrist strap is to drain off the operator's static charge. A wrist strap or ESD cuff is kept in constant contact with bare skin and has a cable for attaching it to the ESD ground. The wrist strap cord has a current- limiting resistor for personnel safety. Wrist straps must be tested frequently to assure that they are undamaged and operating correctly. When a wrist strap is impractical, there are special heel straps or shoes that can be used. These items are effective only when used in conjunction with a dissipative floor. ESD protective clothing/smocks. Even though you are using a wrist strap, street clothing must not come in close contact with components or computer boards since the various materials in clothing can generate high static charges. ESD protective smocks are recommended to serve as a barrier/shield between the electrostatic field and the sensitive components. Dissipative table mat. The mat should provide a controlled discharge of static voltages and must be grounded. The surface resistance is designed such that sliding a computer board across the mat's surface will not generate more than 100 volts. ESD chairs. Chairs can be charged by the physical movement of the chair and your feet on the floor. The chair should be conductive with conductive wheels, or the frame should be grounded with a drag chain to the flooring. ESD protective floor or mat. The floor or mat dissipates the static charge of personnel approaching the work bench. Special conductive tile or floor treatment can be used if mats are not practical or cause a safety hazard. Air Ionizer. An ionizer can provide (some) protection when you cannot remove all static generators from the manufacturing process. Examples are plastic packaging for connectors and fixtures for soldering. The ionizer produces an ionized air stream to neutralize static charges over a short period of time. Electrostatic Field Meter. This device is used to measure how much electrostatic potential (voltage) exists in a given area.Charge Plate Analyzer. This device is used to evaluate ionization systems by how rapidly they neutralize the applied charge.Static Awareness Labels. Parts which are ESD sensitive need to be identified to warn people that they must be opened only at ESD controlled workstations. WHAT CAN I DO TO PREVENT ESD WHILE TRANSPORTING PRODUCTS? Areas of susceptibility to ESD damage exist during transportation or movement of components and circuit boards. This can include integrated circuits that are shipped to your factory; the movement of integrated circuits to the assembly line; the movement of assembled board products through test; and the packaging material that is used to ship your product in. ESD protection for components and circuit boards during transportation can be accomplished by using available electrostatic shielding packages and enclosures. Antistatic or dissipative packaging for shipment. "Antistatic" a property of the material that resists charge generation whereas "dissipative" controls the rate of discharge. Generally it is acknowledged that dissipative is a better solution than antistatic but is more expensive. Integrated circuits typically are shipped in antistatic tubes to eliminate the possibility of charge generation, while hard drives are shipped in dissipative bags that minimize charge generation and control charge dissipation. For components that are extremely sensitive, neither antistatic, dissipative, nor a combination will be sufficient. Instead, an electrostatic shielding bag would be the best choice. This would be a nickel or an aluminum metallized bag that is a more expensive solution. Electrostatic shielding totes or containers for movement within the factory. For boards or subassemblies that are susceptible to ESD damage, totes that are made out of ruggedized plastic can be used for safe transportation. For these totes or containers to be effective for ESD protection,, they must completely enclose the product and be conductive. There are many vendors of ESD-protective equipment and materials who are willing to audit your facilities, recommend appropriate procedures, and assist in their implementation. You should consult with such a firm to determine your exact requirements.

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