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Chapter 4
Removal and Replacement Preliminaries 4-1
Removal and Replacement
Preliminaries
This chapter provides general service information for the Compaq Armada 4100 and
4200 Families.
Adherence to the procedures and precautions described in this chapter is essential for
proper service.
4.1 Electrostatic Discharge
A sudden discharge of static electricity from a finger or other conductor can destroy
static-sensitive devices or microcircuitry. Often the spark is neither felt or heard, but
damage occurs. An electronic device exposed to electrostatic discharge (ESD) may not
be affected at all and will work perfectly throughout a normal cycle. Or it may function
normally for a while, then degrade in the internal layers, reducing its life expectancy.
Networks built into many integrated circuits provide some protection, but in many
cases, the discharge contains enough power to alter device parameters or melt silicon
junctions.
4.1.1 Generating Static
Table 4-1 shows how different activities generate static electricity and at different
electrostatic voltage levels.
Table 4-1
Typical Electrostatic Voltages
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 tubes 2,000 V 700 V 400 V
Removing DIPS from vinyl trays 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 PCBs 26,000 V 20,000 V 7,000 V
Packing PCBs in foam-lined box 21,000 V 11,000 V 5,000 V
NOTE:
700 volts can degrade a product.