What is the acceptable body resistance range of a person to safely handle ESDS Devices? If not resistance, what is the acceptable voltage range of the person? What part of ANSI/ESD Standard does this fall into? Hope someone could help me with this. Just genuinely curious with this subject matter. Thank you!
That depends on a few things. First of all, you need to determine what is the sensitivity of the device you are going to handle. Let’s use the claim in ANSI/ESD S20.20 - 2021 of devices that are 100 volt HBM sensitive.
Now it depends on which system you used. A wrist strap system (including a garment system) or a footwear/flooring system.
For a wrist strap system, the maximum resistance to ground from a persons hands are listed at 3.5 x 10E7 ohms or 35 Megaohms. The information for this can be found in TR20.20. Since most, if not all, wrist straps systems have only a 1Megohm resistor, wrist straps systems meet this requirement.
For footwear/flooring systems it requires a two step process. First the total resistance from the hand to ground is less than 1x10E9 ohms. Then there is a body voltage test that must be done to ensure that a persons body voltage is less than 100 volts.
If you want to handle devices more sensitive, then the limits and requirements will change. For a typical wrist strap system, with a 1 Megohm resistor, the maximum body voltage is less than 10 volts. For footwear/flooring systems, the system resistance will be less than 1x10E9 ohms and the body voltage will be defined.
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Thank you for this, John. The system we are using is a Wrist Strap System. Given that the maximum resistance to ground from a person’s hands is 35Mohms, what is the minimum in this case?
There is no minimum resistance. The resistance in a typical wrist strap is to limit current that may flow through the body in case of a fault.
Hello again, John. As I was reviewing this forum post, I now want to ask for some clarification. You indicated this sentence:
For a typical wrist strap system, with a 1 Megohm resistor, the maximum body voltage is less than 10 volts.
I would like to ask what do you mean about this? Is it that if I use a 1MΩ resistor, the body voltage shouldn’t reach 10volts? Is this according to the HBM standard of 100V?
I am still a student and can’t afford to purchase the TR20.20. Perhaps, where can I be able to acquire a copy?
Maximum body voltage tracks linearly resistance to ground of a person. Multiple experiments have shown that at 35 Mohms the maximum voltage that is on a person is 100 volts. At 1 Mohm it is around 10 volts. It has nothing to do with a HBM which is applied to a device but the actual voltage measured on person.
As far as a copy of TR20.20, I cannot help you with that.