HP Integrity rx8620 Site Preparation Guide, Fourth Edition - HP Integrity rx86 - Page 33

ESD Prevention

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General Site Preparation Guidelines Environmental Elements ESD Prevention 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 Table 2-1 Effect of Humidity on ESD Charge Levels Personnel Activitya Humidityband Charge Levels (voltages)c 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 a. Source: B.A. Unger, Electrostatic Discharge Failures of Semiconductor Devices (Bell Laboratories, 1981) 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. 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. Chapter 2 27

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Chapter 2
General Site Preparation Guidelines
Environmental Elements
27
ESD Prevention
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
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 2-1
Effect of Humidity on ESD Charge Levels
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