HP rp8400 Site Preparation Guide, Second Edition - HP rp8400 Server Series - Page 41

Electrostatic Discharge (ESD) Prevention, <TABLE>, Static Protection Measures, Table 2-1

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Electrical and Environmental Guidelines Environmental Elements Although this problem is relatively rare, it may be an issue within your computer room. Since metallic contamination can cause permanent or intermittent failures on your electronic equipment, Hewlett-Packard strongly recommends that your site be evaluated for metallic particulate contamination before installation of electronic equipment. Electrostatic Discharge (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 lists charge levels based on personnel activities and humidity levels. 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 25

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Chapter 2
Electrical and Environmental Guidelines
Environmental Elements
25
Although this problem is relatively rare, it may be an issue within your computer room. Since metallic
contamination can cause permanent or intermittent failures on your electronic equipment, Hewlett-Packard
strongly recommends that your site be evaluated for metallic particulate contamination before installation of
electronic equipment.
Electrostatic Discharge (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 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 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