HP Compaq NX7300, Maintenance And Service Manual

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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