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It is my understanding that the “Plan” is the organization’s scope within that “Program” that conforms to their own internal requirements while evolving with changes to technical elements as time goes by.
ESD and Static Control Questions
Answered by the experts at Ground Zero Electrostatics
Q: What is Static Electricity?
A: Static Electricity can be defined as an electrical charge at rest. ESD is the transfer of static charges between bodies or objects at different electrical potentials. This may be caused by either direct contact or by induction of an electrostatic field. Static Charges are generated when two materials are rubbed together. This term is called Triboelectric Generation or Tribocharging
Factors that Influence Tribocharging:
- Intimacy of Contact Speed of Separation
- Conductivity of Materials
- Triboelectric Series Position
- Relative Humidity
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Q: I’m having a hard time understanding the difference between an ESD Control “Program” and an ESD Control Program “Plan”… Can someone explain what is required? Do I need two documents, one “Program” and one “Plan”, do I need to develop a single ESD document? I’m not sure what the difference between a program and a plan is.
A: It is my understanding that the program is ANSI/ESD S20.20-2007’s way of providing requirements to establish, implement, and maintain an ESD program.
Q: May I know the standard test procedures and parameters (ie: surface resistivity/surface to or person to ground resistance, decay time or any other parameter if applicable) and recommended values for confirming the worthiness of the following ESD items?
- ALL ESD PACKAGING ITEM
- ESD FLOOR AND WORK SURFACES
- ESD CLOTHINGS
- ESD FOOT WEARS
- ESD HANDLING ITEM viz., BRUSHES / BINS / PCB RACKS
A: Please consult your copy of ANSI/ESD S20.20-1999 from the ESDA at http://www.esda.org/. It has specific documents for different technical elements. For example, S1.1 for wrist straps, 2.1 for garments, 3.2 for ionization, 4.1 for worksurfaces-resistive characterization, 4.2 for worksurfaces- charge dissipation, 5.1 for Human Body Model, 5.2 for Machine Model, 5.3 for Charged Device Model, 6.1 for grounding, 7.1 for resistive characterization of materials-flooring materials, 8.1 for symbols-ESD awareness, 9.1 for footwear-resistive characterization, 10.1 automated handling, s11.11 surface resistance of static dissipative planar materials, 11.12 for EDS items-volume resistance of…, 11.2 for Triboelectric charge accumulation testing, 11.31 for bags, 12.1 for seating, 13.1 for electrical potential from soldering/desoldering hand tools, STM 97.1 for floor materials and footwear-resistance measurement in combination with a person, and STM 97.2 for floor materials and footwear-voltage measurement on a person just to name a few.
I could spend a lot of time digging up actual values for these specific items that we provide, but I haven’t put anything like that together all in one place. I will work on that and perhaps we can post that info all in one place. But keep in mind. We do not determine the parameters, we merely work to comply with them.
Q: What should be the Minimum ESD earth resistance and voltage?
A: RTG and PTP resistance needs to be between 2.5e4 and 1e06 Ω for conductive and from 1e06 to 1e09 Ω per ANSI/ESD S20.20-1999 via ANSI/ESD S7.1-2005 or the combination of a person wearing ESD footwear and standing on an ESD floor should have a resistance to ground of < 3.5e7 Ω per ANSI/ESD STM97.1.
That’s the resistance part of your question. What should the voltage be? That’s up to you. Go to your design engineers and find out what the most sensitive electronic device is and design a floor that creates no more than ½ of that voltage threshold. At minimum, no ESD flooring system in combination with ESD footwear should create more than 100V per ANSI/ESD STM97.2. I like a floor that generates less than +/- 15 volts. I have more to learn about this testing as I have recently acquired the equipment necessary to measure Body Voltage Tests on all floorings that I install and/or test.
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