Use of ESD symbols

#1

Hello,

Do I need to have my facility ESD certified in order to use the ESD symbols on my products, or can I apply the symbols to my products if they are tested against ESD test methods?

Thank you in advance!

#2

The symbols that are in ANSI/ESD S8.1 are for general use. They are meant to be caution and warning symbols. They are free to use. The need to be used properly as they denote sensitive materials inside packaging or indicate ESD control items.

#3

Hi JohnK,

I’m Ryan, Related to ESD grounding and Electric equipment grounding system, i have some concerns that need your advice:

  1. Do we need to separate completely GND of electric equipment and GND of ESD?
  2. Impedance spec between GND of electric equipment and GND of ESD?
  3. Do we have the rule/ specification for that?

image
image1495×832 221 KB

#4

Hi Ryan,

In response to your questions, ESD ground and the equipment grounding conductor can be the same. It depends on the local electrical codes if it is allowed or not. If the ESD technical elements are connected to the equipment grounding conductor, then from the groundable point of the ESD control item to the common ground point to the equipment grounding conductor is 2 ohms. In reality, this means just use wires without any added resistance.
If a separate ESD ground is established, then check with the local electric code for the maximum resistance between them. In the US, the maximum resistance between any grounding system is less than 25 ohms.

#5

Hi JohnK,

Thanks for your reply to my query.
I just have a concern that if we do not separate completely GND of electrical equipment and ESD system. When happen leakage current from electrical equipment will have dangerous to human because the impedance between GND & ESD is very small (ex: 1 ohm or 2 ohm). I mean for better we could separate completely, the impedance between GND and ESD system should be Kilo ohm or Mega ohm. For my understanding, the rule when design the Factory they must be layout 2 system far from each other (the far distance has, the high impedance is).

Please give me advice. Great thanks

#6

While it is true the impedence is small, the resistance in the wrist strap or ESD control equipment will cause the current to flow in the equipment grounding conductor. Even if there if the resistor is not present in the wrist strap system, the skin contact resistance is still very high compared to the ground connection.

There are some countries that do not allow human direct connection to ground and that may cause a separate grounding system for ESD. If you separate the ESD ground and equipment ground by a large resistance, then if there is a fault which caused the equipment grounding conductor to have a voltage, there could be a potential deference between the two grounding systems. This could be an unsafe condition and why the two systems should be bonded together.