HP nw8440 User Manual download pdf (Page 90)

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

1 2 ... 85 86 87 88 89 90 91 92 93 94 95 ... 236 237

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HP nw8440 User Manual Page 90