Chapter 2.1 Electrostatic Discharge Information - Compaq Concerto Maintenance And Service Manual

Chapter 2 - Service Preliminaries
INTRODUCTION
This chapter provides general service information for the computer and
FlexConnect.
Adherence to the procedures and precautions described in this chapter is
essential for proper service.

Chapter 2.1 ELECTROSTATIC DISCHARGE INFORMATION

A sudden discharge of static electricity from a finger or other conductor
can destroy static-sensitive devices or micro circuitry. 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 2-1 shows how different activities generate static electricity and at
different electrostatic voltage levels.
Table 2-1. Typical Electrostatic Voltages
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Event
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Walking across carpet
Walking across vinyl floor
Motions of bench worker
Removing DIPS from plastic tubes
Removing DIPS from vinyl trays
Removing DIPS from Styrofoam
Removing bubble pack from PCBs
Packing PCBs in foam-lined box
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NOTE: 700 volts can degrade a product.
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Preventing Electrostatic Damage to Equipment
Many electronic components are sensitive to ESD.
structure determine the degree of sensitivity. The following proper
Relative Humidity
10% 40%
35,000V 15,000V
12,000V 5,000V
6,000V 800V
2,000V 700V
11,500V 4,000V
14,500V 5,000V
26,000V 20,000V
21,000V 11,000V
Circuitry design and
55%
7,500V
3,000V
400V
400V
2,000V
3,500V
7,000V
5,000V