Electrostatic Solutions Ltd
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EPA equipment, surfaces and furniture
Equipment used in an EPA should conform to the requirements over the full range of operational atmospheric humidity conditions.
It is not necessary to use all the items specified - however if any item is used, it must conform to the specification given.
Working surfaces and storage racks, trolleys, carts
Any surfaces on which ESDS are placed must be connected to EPA ground, and have a point-to-point resistance between 104 Ω and 1010Ω, and resistance-to-ground between 7.5x105Ω and 109 Ω. It is permissible to "hard ground" (<104Ω ) surfaces when approved by the ESD Co-ordinator.
Surface to ground resistance values may be achieved by including discrete resistors in the ground path, or by the resistance of the material which is directly grounded.
Floors & footwear
Use of an EPA compliant floor is often to be recommended, particularly for new installations. However an EPA does not have to include a compliant floor for compliance with 61340-5-1:2007. If the EPA does not include a floor, ESD protective packaging should be used when moving sensitive devices between EPA workstations - as in any situation where ESDS are transported outside an EPA.
EPA floor surfaces must have a surface-to-EPA ground resistance of <109Ω. (N.B. A minimum resistance-to-ground may be required due to safety considerations). The personnel-to-ground resistance of a footwear-flooring combination (for grounding personnel) must be <3.5x107Ω . This may mean that in practice the floor resistane-to-ground must be around 107Ω. Many people have a minimum resistance of 7.5 x07Ω for safety reasons.
The resistance from the wearer's body to EPA ground (metal plate) should be between 5x104Ω and 108Ω (and at least 105Ω for each shoe)
If seats are used, the resistance to groundable point, from any area of the seat which may have contact with personnel, must be less than 1010Ω. It is advisable that at least two wheels or feet should provide a path to ground.
Compliant garments must be clearly marked and must completely cover all clothing in the arms & torso region. There must be electrical continuity between all parts. The point-point resistance over the outer surface must be less than 1012Ω. Decay of charge on the outer surface of the garment is no longer specified in 61340-5-1:2007.
Gloves and finger cots
No specification for these is given in 61340-5-1:2007.
Ionisers must bring the potential due to charge (of either polarity) on items to be brought from 1000V to less than 100V in less than 20 seconds. The ioniser offset voltage must be < +/- 50V.
Tools, machinery, dispensers and test equipment
No specification for tools is given in 61340-5-1:2007. However it is often good practice that tools should not have insulating handles and soldering irons should have grounded tips. Any non-insulating part of a tool should be grounded (resistance-to-ground less than 1012Ω. (Decay of charge to less than 10% of initial value within 2 sec. is good practice).
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Last modified: October 23, 2009
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