ESD Systems - Questions And Answers

Hello, I'm doing research at school and I need an answer to a question, I hope you can help. The static bags that electronic parts come, what are they made of and is the bag at a positive or a negative condition. Thanks - Benjamin, MF High, FL

There are several types of static bags; shielding (metal-in, metal-out, moisture vapor barrier), antistatic and conductive. The most commonly used "static" or ESD bag is a shielding bag, which has all three properties listed above . A shielding bag has a layer of metal, usually aluminum (Al) (similar to Aluminum foil), that provides "shielding" of a Faraday cage affect. An ESD shielding bag has several properties: MECHANICAL (mechanically holds items within)ELECTRICAL SHIELDING: (Faraday cage) to minimize an electrical current (voltage discharge) or ElectroStatic Discharge (ESD) from penetrating the film thereby "protecting" the contents from being hit with an ESD. ANTISTATIC: Non-tribocharging, or prohibits the generation of charge through contact and separation, i.e., when the object moves around within the bag. An example would be when you walk along the floor, i.e., on a carpet, and then touch a metal object, i.e., a door knob, and feel a "zap" from a spark generated from triboelectric generation (walking along the carpet). CONDUCTIVE: A material is said to be conductive when it allows charge flow or electrical charge on the surface can travel to a lower or higher potential, e.g., when you connect the surface to a grounded (zero potential) point. It is good to have a conductive material in ESD (from 100,000 Ohms to 10,000,000,000 Ohms). Anything over 100,000,000,000 in considered insulative, and anything under conductive. A typical shielding bag is composed of: polyester (0.0005 inches thick) aluminum on polyester (10 - 25 Angstroms, 1 Angstrom = 1x10^-10 meters) polyethylene. (0.0025 inches)

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