Electrostatic Discharge; Relative Humidity - Compaq Presario 7360 Maintenance And Service Manual

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REMOVAL & REPLACEMENT

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
The table below shows the different amounts of static electricity generated by different activities .
Event
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
NOTE: 700 volts can degrade a product!
Preventing Electrostatic Damage to Equipment
Many electronic components are sensitive to ESD. Circuitry design and structure determine the degree of
sensitivity. The following proper packaging and grounding precautions are necessary to prevent damage:
Protect all electrostatic parts and assemblies with conductive or approved containers
or packaging.
Keep electrostatic sensitive parts in their containers until they arrive at static-free
stations.
Place items on a grounded surface before removing them from their container.
Always be properly grounded when touching a sensitive component or assembly.
Place reusable electrostatic-sensitive parts from assemblies in protective packaging
or conductive foam.
Use transporters and conveyors made of antistatic belts and metal roller bushings. Mechanized
equipment used for moving materials must be wired to ground and proper materials selected to avoid
static charging. When grounding is not possible, use an ionizer to dissipate electric charges.
Preventing Damage to Drives
To prevent static damage to hard drives, use the following precautions:
Handle drives gently, using static-guarding techniques.
Store drives in the original shipping containers.
Avoid dropping drives from any height onto any surface.
Handle drives on surfaces that have at least one inch of shock-proof foam.
Always place drives PCB assembly side down on the foam.
Grounding Methods
The method for grounding must include a wrist strap or a foot strap at a grounded workstation. When
seated, wear a wrist strap connected to a grounded system. When standing, use footstraps and a
grounded floor mat.
Method
Voltages
Grounding Workstations
To prevent static damage at the workstation, use the following precautions:
Cover the workstation with approved static-dissipative material. Provide a wrist strap
connected to the work surface and properly grounded tools and equipment.
Use static-dissipative mats, heel straps, or air ionizers to give added protection.
Handle electrostatic sensitive components, parts, and assemblies by the case or PCB
laminate. Handle them only at static-free workstations.
Avoid contact with pins, leads, or circuitry.
Turn off power and input signals before inserting and removing connectors or test
equipment.
Use fixtures made of static-safe materials when fixtures must directly contact
dissipative surfaces.
Keep work area free of nonconductive materials such as ordinary plastic assembly
aids and Styrofoam.
Use field service tools, such as cutters, screwdrivers, and vacuums, that are
conductive.
Use a portable field service kit with a static dissipative vinyl pouch that folds out of a
work mat. Also use a wrist strap and a ground cord for the work surface. Ground the
cord to the chassis of the equipment undergoing test or repair.
Grounding Equipment
Use the following equipment to prevent static electricity damage to the equipment:
Wrist Straps are flexible straps with a minimum of 1 megohm ±10% resistance to the ground cords. To
provide proper ground, a strap must be worn snug against the skin. On grounded mats without banana-
plug connectors, connect a wrist strap with alligator clips.
Heelstraps/Toestraps/Bootstraps can be used at standing workstations and are compatible with most
types of boots and shoes. On conductive floors or dissipative floor mats, use them on both feet with a
minimum of 1 megohm resistance between operator and ground. To be effective, the conductive strips
must be worn in contact with the skin.
Recommended Materials and Equipment
Other materials and equipment that are recommended for use in preventing static electricity include:
Antistatic tape
Antistatic smocks, aprons, or sleeve protectors
Conductive bins, and other assembly or soldering aids
Conductive foam
Conductive tabletop workstations with ground cord of 1 megohm of resistance
Static dissipative table or floor mats with hard tie to ground
Field service kits
Static awareness labels
Wrist straps and footwear straps providing 1 megohm ±10% resistance
Material handling packages
Conductive plastic bags
Conductive plastic tubes
Conductive tote boxes
Metal tote boxes
Opaque shielding bags
Transparent metallized shielding bags
Transparent shielding tubes
Maintenance and Service Guide
Compaq Presario 7300 Series Computers
Removal &
Replacement
(Return to Service
Static-Shielding Protection Levels
Antistatic Plastic
1,500
Troubleshooting
Jumper & Switch
Information
Considerations)
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
Carbon-Loaded
Plastic
7,500
Illustrated Parts Catalog

Relative Humidity

40%
15,000 V
5,000 V
800 V
700 V
4,000 V
5,000 V
20,000 V
11,000 V
Metallized Laminate
15,000
Specifications
55%
7,500 V
3,000 V
400 V
400 V
2,000 V
3,500 V
7,000 V
5,000 V