ESD Systems - Questions And Answers

We are subcontractors for the assembly of electronic boards. We assemble both SMD components on Philips automatic machines and conventional components.We are considering to lay antistatic carpeting in the factory area.I am confused and am sure that you can help me. Do the standards require a conductive flooring or a static dissipative one? I understand that the difference between them is the static dissipative carpeting has a higher resistance than the conductive one. Can you please give your expert advice? - Anthony Galea, MSC (Malta) Ltd, San Gwann, Malta

For applications where ESD control is needed for semiconductor/electronics manufacturing/assembling such as your plant, there are a few standards to look at. The ANSI/ESD S20.20 recommends that the floor be less than 1x10^9 ohms and references ANSI/ESD S7.1. S20.20 also recommends that the combined flooring and footwear resistance be less than 35x10^6 ohms referencing a different standard, ESD STM 97.1. Yet another standard, ESD STM 97.2, recommends that the Body Voltage Generation (BVG) be less than 100 volts when walking on an ESD Floor. Which standard or recommendation you adopt is up to you and your control program. I'd make sure the flooring is uniformly conductive in a resistance range that is less than 1x10^9 per ANSI/ESD S7.1 and generates less than 100 volts on a mobile person wearing quality foot wear. Our Statproof® Floor care program meets both these standards recommended constraints as listed in ANSI/ESD S20.20.

Also note that in the ESD Control industry, electrical resistances from 1x10^4 - 1x10^9 ohms is considered within the dissipative range. Some possible drawbacks of a conductive flooring (< 1x10^4 ohms) are: one - safety (if direct contact to floor with a live wire may endanger the operator under high voltage) and two - possible rapid discharge via a CDM occurrence, i.e., if a charged device or person came in direct contact with a very conductive surface (floor) an ESD event may occur.

Related Categories:

If you have found this Q/A useful, please rate it based on its helpfulness.