Seguridad ESD y Precauciones Generales al Ensamblar una Computadora

ESD precautions

Electrostatic discharge (ESD) is a concern when handling computer components. Static charges can build up in the body just by walking across the room. It may not be apparent, but it is usually enough to damage computer components if they were to be touched. A static charge of 2000 volts is enough for a person to notice. This may have been experienced when walking across a room and touching a doorknob or other metal surface. A static charge of only 200 volts is sufficient to damage a computer component.

ESD is probably the greatest problem when a user unwraps newly purchased computer parts and components when preparing to assemble the computer. Always review the ESD precautions before beginning the assembly process. The following recommendations will help to prevent ESD related damage:

• Keep all computer parts in antistatic bags.
• Keep the humidity between 20 to 30 percent.
• Use grounded mats on workbenches.
• Use grounded floor mats in work areas.
• Use wrist straps when working on computer parts, except when working on monitors.
• Touch unpainted grounded metal parts of the computer frequently to lower the static energy of the body.

Remember that just because a discharge cannot be felt does not mean that it cannot harm a computer component. Components can sustain minor damage or be totally destroyed. Minor damage allows the component to function to some degree or may cause intermittent errors. This type of ESD damage is the most difficult to detect. When cases are closed properly they are designed to provide ESD protection for the components inside. The cases channel ESD away from sensitive components. ESD becomes a threat when the case is opened and the components inside are exposed. The same threat applies to the components when they are removed from the antistatic bags in which they are shipped.

The best way to protect against ESD is to use an antistatic mat, a grounding wrist strap, and antistatic bags. The grounding wrist strap is worn around the wrist and can be connected to the mat. The mat is then grounded to a wall outlet. The wrist strap can also be clipped to the metal frame of the computer case.

Overview of general safety issues

Computer assembly helps IT professionals learn about the inner workings of a computer. It also helps create the confidence needed to advance in the IT profession. Before beginning any assembly project, it is a good idea to review the following safety procedures:

• Keep the work area free of clutter and keep it clean.
• Keep food and drinks out of the work area.
• Avoid opening a computer monitor unless trained since it can store up to 25,000 volts.
• Remove all jewelry and watches.
• Make sure that the power is off and the power plug has been removed.
• Do not look into the laser beam that is found in computer related equipment.
• Make sure that a fire extinguisher and first aid kit are available.
• Cover sharp edges with tape when working inside the computer case.

There are safety concerns when leaving the computer plugged in while working inside of it. If the computer is plugged in, there may be an unequal electric potential between a person and the computer case. This potential difference may discharge through the person. There are 120 volts inside the case in North America and some parts of Asia. This value can be 220 volts or more in Europe and the rest of the world. By moving the machine when it is plugged into the power outlet, the technician might accidentally press the power button. This would create a live machine and a dangerous situation.

If the computer is plugged in and the power supply has a short to the ungrounded power line, there may be an energized chassis. This will create a lethal situation even if the computer is turned off. To remedy these concerns, the computer should be plugged into a power strip. The power strip should then be turned off, along with the machine and power supply on the back of the case. This removes the concern of live power. When the technician connects the wrist strap to the chassis, the ground connector in the power cord protects the equipment from electrostatic discharge (ESD), which is commonly referred to as static electricity.

The technician should also know where the main power or the circuit breakers are located in case of a fire or short. The importance of protecting the technician and the computer hardware cannot be overemphasized. The student lab safety agreement from Module 1, Information Technology Basics, can be consulted for more information. Recall that this is a contract that requires the technician to work in accordance with the safety procedures in this document.

Technicians are required to handle computer components, so it is best to take precautions to protect oneself and the computer hardware by following some basic safety procedures:

• Use an antistatic mat and grounding wrist strap.
• Use antistatic bags to store and move computer components. Do not put more than one component in each bag, because stacking them can cause some of the components to break or become loose.
• Do not remove or install components while the computer is on.
• Ground often to prevent static charges from building up by touching a piece of bare metal on the chassis or power supply.
• Work on a bare floor because carpets can build up static charges.
• Hold cards by the edges to avoid touching chips or the edge connectors on the expansion cards.
• Do not touch chips or expansion boards with a magnetized screwdriver.
• Turn off the computer before moving it. This is to protect the hard drive, which is always spinning when the computer is turned on.
• Keep installation/maintenance CDs and disks away from magnetic fields, heat, and cold.
• Do not place a circuit board of any kind onto a conductive surface, especially a metal foil. The lithium and nickel cadmium (Ni-Cad) batteries used on boards may short out.
• Do not use a pencil or metal-tipped instrument to change DIP switches or to touch components. The graphite in the pencil is conductive and could easily cause damage.
• Do not allow anyone who is not properly grounded to touch or hand off computer components. This is true even when working with a lab partner. When passing components, always touch hands first to neutralize any charges.