Dear ESD experts
in a screen production line, does the station where the film paper is removed from the panel and then be wiped using a special glass panel wipe cloth to remove dust particles requires neutralization via ionizers.
Awaiting your advice
Meriem,
The need for ionization would depend on the electric field strength on the panel after the film is removed and wipe is done and how far the panel is from the ESDS items. Per ANSI/ESD S20.20:
• 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.
• For any process essential insulators located more than 25 mm, but less than 300 mm from an unprotected ESDS item, the voltage on the surface of the insulator shall be less than 2000 volts when measured with a non-contact electrostatic voltmeter. When using an electrostatic field meter, the reading shall be less than 2000 volts when measured at the meter’s stipulated measuring distance.
Generally the process of removing the film and wiping the panel will generate thousands of volts and the only effective way to remove this charge in a timely way is ionization. Keep in mind that ionization itself will take some time to reduce the charge to an acceptable level. The amount of time any ionizer needs to remove the charge effectively should be measured as this can vary from ionizer to ionizer
Meriem,
Andy is correct in the requirements of S20.20. You must consider the work you are completing on the particular item and its proximity to other parts. If there are no ESD sensitive items within 12" of this operation than chances are there is no need for ionization. However, without know all of your and your customers standards you are required to meet this cannot be stated for sure.
Regards
Chris