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Determine the ESD Requirements
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Determine the ESD Requirements
Static charges (voltage levels) occur when objects are separated or rubbed together. The voltage level of a
static charge is determined by the following factors:
• Types of materials
• Relative humidity
• Rate of change or separation
Effect of humidity on ESD charge levels
The table following lists charge levels based on personnel activities and humidity levels.
Static protection measures
Follow these precautions to minimize possible ESD-induced failures in the computer room:
• Maintain recommended humidity level and airflow rates in the computer room.
• Install conductive flooring (conductive adhesive must be used when laying tiles).
• Use conductive wax if waxed floors are necessary.
• Ensure that all equipment and flooring are properly grounded and are at the same ground potential.
• Use conductive tables and chairs.
• Use a grounded wrist strap (or other grounding method) when handling circuit boards.
• Store spare electronic modules in antistatic containers.
Table 5
Personnel activity
a
a. Source: B.A. Unger, Electrostatic Discharge Failures of Semiconductor Devices (Bell
Laboratories, 1981)
Humidity
b
and charge levels (voltages)
c
b. For the same relative humidity level, a high rate of airflow produces higher static charges
than a low airflow rate.
c. Some data in this table has been extrapolated.
26% 32% 40% 50%
Person walking across a linoleum floor 6,150 V 5,750 V 4,625 V 3,700 V
Person walking across a carpeted floor 18,450 V 17,250 V 13,875 V 11,100 V
Person getting up from a plastic chair 24,600 V 23,000 V 18,500 V 14,800 V