ESD Systems - Questions And Answers

1) Is static dissipative range 10^5 to 10^9 ohms the norm or up to 10^11 ohm. How effective is 10^11 or 10^12 in ESD control?

2) How to evaluate static dissipative material based on volume resistivity (ohms, surface resistivity and surface resistance? Why is it so much different?

3) How to evaluate (and choose) the performance of ESD brushes use to clean foreign material on ESDS devices? - Anonymous,

By definition, the static dissipative range is from 1x10^4 ohms to 1x10^11 ohms. Depending on the application, 1x10^11 ohms surface resistivity is adequate for some packaging materials, but not for say work surface or floor materials. Volume resistivity, surface resistivity and surface resistance are three different measurement techniques and properties of a material. The ESD Association realizes this may be confusing to some folks and has started the trend to use just surface resistance in its electrical constraints where appropriate. Hardly any material is truly homogeneous unless it is a pure element such as copper. Therefore inconsistencies in surface and volume measurements may occur from lab to lab for the same material. Typically, surface resistivity is one magnitude higher than surface resistance. For multi-layered materials, volume resistivity may vary depending on the placement of the conductive buried layer and or thickness of the filler materials. ESD brushes come in many sizes, shapes and hardness, all serving different applications.

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