ESD Systems - Questions And Answers

Thanks for your advice on the subject described in question 1223, is there another way for getting rid of a charge in an object such as a memory module. For example for field work, would it not be possible to remove the charge of the memory module in a safe way by for example a special mat with and extra large resistance between the mat and ground.

I am quite certain that adding to the resister value in the ground cord will not slow down the ESD event when the charged memory module comes in contact with a grounded surface. Preventing or neutralizing the charge from the memory module would be preferable.However, increasing the surface resistance of the surface contacted will slow the discharge. ESD Handbook TR20.20 paragraph 5.3.1.7 Electrical Considerations "[RTG is] The most important functional consideration for worksurfaces. This establishes the resistance of the primary path to ground for items, placed on the surface. When worksurface materials are being selected, consideration should be given to possible Charged Device Model(CDM) damage to ESD sensitive products. If CDM damage is a concern then setting a lower resistance limit for the worksurface should be considered.Typically, the lower limit for these types of worksurfaces is 1 X10^6 ohms."ESD Handbook TR20.20 section 2.5.3 "The transfer of charge from a static dissipative material will generally take longer than from a conductive material of equivalent size." This cannot be achieved by using a highly conductive metal surface with a 1 Megohm resistor in the ground.Two possible solutions: 1) Increase the RTT (Resistance Point to Point of the worksurface material. 2) If the grounded surface the charged memory modules are coming into contact with is the operator's hand, consider using Static Dissipative Gloves. Once again, increasing the surface resistance would slow down the speed of the discharge.

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