HP Integrity rx1600 Site Preparation Guide, Second Edition - HP Integrity rx16 - Page 30

Electrostatic Discharge ESD Prevention, Acoustics

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General Site Preparation Guidelines Environmental Elements 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 3-1 Effect of Humidity on ESD Charge Levels Personnel Activitya Humidityb and 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. Acoustics Computer equipment and air conditioning blowers cause computer rooms to be noisy. Ambient noise level in a computer room can be reduced as follows: • Dropped ceiling-Cover with a commercial grade of fire-resistant, acoustic rated, fiberglass ceiling tile. • Sound deadening-Cover the walls with curtains or other sound deadening material. • Removable partitions-Use foam rubber models for most effectiveness. 30 Chapter 3

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General Site Preparation Guidelines
Environmental Elements
Chapter 3
30
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
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.
Acoustics
Computer equipment and air conditioning blowers cause computer rooms to be noisy. Ambient noise level in a
computer room can be reduced as follows:
•
Dropped ceiling—Cover with a commercial grade of fire-resistant, acoustic rated, fiberglass ceiling tile.
•
Sound deadening—Cover the walls with curtains or other sound deadening material.
•
Removable partitions—Use foam rubber models for most effectiveness.
Table 3-1
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