Removal and Replacement Preliminaries
Maintenance and Service Guide 4–7

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.

Tabl e 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 2 6,500 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