4–8
Maintenance and Service Guide
Removal and Replacement Preliminaries
Table 4-1 shows how humidity affects the electrostatic voltage
levels generated by different activities.
Table 4-2 lists the shielding protection provided by antistatic
bags and floor mats.
Table 4-1
Typical Electrostatic Voltage Levels
Relative Humidity
Event
10%
40%
55%
Walking across carpet
35,000 V
15,000 V
7,500 V
Walking across vinyl floor
12,000 V
5,000 V
3,000 V
Motions of bench worker
6,000 V
800 V
400 V
Removing DIPS from plastic tube
2,000 V
700 V
400 V
Removing DIPS from vinyl tray
11,500 V
4,000 V
2,000 V
Removing DIPS from Styrofoam
14,500 V
5,000 V
3,500 V
Removing bubble pack from PCB
26,500 V
20,000 V
7,000 V
Packing PCBs in foam-lined box
21,000 V
11,000 V
5,000 V
✎
A product can be degraded by as little as 700 V.
Table 4-2
Static-Shielding Materials
Material
Use
Voltage Protection Level
Antistatic plastic
Bags
1,500 V
Carbon-loaded plastic
Floor mats
7,500 V
Metallized laminate
Floor mats
5,000 V
Содержание Compaq nw8440
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