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.”