Wrist straps and work surface mats are some of the most common devices used to remove static charges. Wrist straps drain charges from operators and a properly grounded mat will provide path-to-ground for for exposed ESD susceptible devices . However, what if the static charge in question is on something that cannot be grounded – an insulator or isolated conductor? All electronic products consist of conductors and insulators. And insulators and isolated conductors can be items used at the workstation such as hand tools, packaging materials, or fixtures.
The ESD Association’s ANSI/ESD S20.20 requires insulators/isolated conductors that charge to:
- 125 volts or more be kept 1 inch or more away from ESD sensitive items.
- 1000 volts or more be kept 12 inches or more away from ESD sensitive items.
How are insulators/isolated conductors that cannot meet these requirements controlled?
There are 3 options available for handling insulators/isolated conductors in an EPA:
- Move the insulators/isolated conductors beyond the 1 inch and 12 inch requirements from ANSI/ESD S20.20 2014
- Replace the non-ESD version of insulators/isolated conductors with an ESD protective version of insulators/isolated conductors.
- Use air ionization to neutralize charges on insulators/isolated conductors.
Most every ESD workstation will have some insulators/isolated conductors that cannot be removed or replaced and could be addressed with ionization. These insulators/isolated conductors that cannot be removed are called: process-required. Common process necessary insulators/isolated conductors include product housings, screens, specialized components, or unique sub-assemblies. The charged ions created by an ionizer will:
- neutralize charges on process required insulators
- neutralize charges on non- essential insulators
- neutralize isolated conductors
- minimize triboelectric charging
The maximize discharge time for neutralizing 1,000 volts to 100 volts is user definable per ANSI/ESD S20.20. A good starting point for most standard ESD susceptible items is <7 seconds. But, the faster, the better.
Content courtesy of Desco
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