Can a process essential insulator directly contact the ESDS item?
Yes, if the requirements are met. Per ANSI/ESD S20.20-2021 Section 8.3.1 – “Insulators”:
“For any process essential insulators located less than or equal to 25 mm from an unprotected ESDS item, the voltage on the surface of the insulator shall be less than 125 volts when measured with a non-contact electrostatic voltmeter. When using an electrostatic field meter, the reading shall be less than 125 volts when measured at the meter’s stipulated measuring distance.”
Hello,
When the standard calls for “The Organization’s ESD program shall include a plan for handling insulators…”, what is exactly the expectation? Is it to have an initial qualification by measuring an initial status and also by having a compliance verification in time (with a frequence) to make sure the insulators are within the rule?
Thank you very much!
Depends on what the insulator is… most typically bare PCB’s or CCA’s could be considered a process required insulator in which case, based on your risk assessment, you may need to take additional precautions such as ionization.
See this statement from the forward of S20.20:
B. Process essential insulators in the environment cannot lose their electrostatic charge by attachment to ground. Ionization systems provide neutralization of charge on these process
essential insulators (circuit board materials and some device packages are examples of necessary insulators). Assessment of the ESD hazard created by electrostatic charge on the
process essential insulators in the workplace is required to ensure that appropriate actions are
implemented, commensurate with the risk to ESDS items.
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For almost any ESD control item or item defined in ANSI/ESD S20.20 there is a qualification and complinace verification that needs to be done. In the case of insulators, there should be an intial qualificaiton where the insulators should be handled as they would in the process to observe what the maximum voltage could be generated.
There should be ongoing compliance verificaiton done where the insulators are measured as they are found. If there is some handling during the process, they could be handled before they are measured. They should not be artifically charged before a compliance verificaiton measurment.
How often this is done is up to the ESD coordinator. ANSI/ESD S20.20 requires that time frame to be defined but does not require any specific time frame.
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Thank you very much!