Removal And Replacement Preliminaries; Electrostatic Discharge; Generating Static - Compaq ArmadaStation Maintenance And Service Manual

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Chapter 4

Removal and Replacement Preliminaries

This chapter provides general service information for the Compaq ArmadaStation and
Armada MiniStation. 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 nor 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.

Generating Static

Table 4-1 shows how different activities generate static electricity and at different
electrostatic voltage levels.
Event
Walking across carpet
Walking across vinyl floor
Motions of bench worker
Removing DIPS from plastic tube
Removing DIPS from vinyl trays
Removing DIPS from Styrofoam
Removing bubble pack from PCBs
Packing PCBs in foam-lined box
NOTE: 700 volts can degrade a product.
Table 4-1
Typical Electrostatic Voltages
10%
35,000 V
12,000 V
6,000 V
2,000 V
11,500 V
14,500 V
26,000 V
21,000 V
Relative Humidity
40% 55%
15,000 V 7,500 V
5,000 V 3,000 V
800 V 400 V
700 V 400 V
4,000 V 2,000 V
5,000 V 3,500 V
20,000 V 7,000 V
11,000 V 5,000 V
Removal and Replacement Preliminaries 4-1