Elimination of hidden dangers of static electricity
Static electricity is harmful to any electronic product, but being able to effectively prevent static electricity is the top priority of the electronics industry.
1. The harm of ESD to the chip
Computers are composed of boards, and today most boards are manufactured using MOS technology, and their circuits are quite sensitive to high voltages of static electricity. Electrostatic discharge (ESD) occurs when a person or object with static electricity touches these devices. When the static high voltage impacts the MOS circuit, the internal oxide film will be broken down and destroyed, causing the electrical components to be damaged on the spot or work abnormally. Of course, devices that have been exposed to electrostatic discharge will not fail immediately, which is why most people do not pay attention to ESD. In fact, in daily life where static electricity is ubiquitous, practice has proved that the static electricity that people can feel is at least 3.5kV, while the static electricity that can hear sounds must be above 4.5kV, and the flash static electricity on the sweater must be above 5kV.
In addition to the above-mentioned ESD directly damages the device, ESD can also induce a lock-in effect (or parasitic thyristor effect) in the MOS circuit. As a result, the internal current of the MOS increases greatly and the internal logic function fails, causing the so-called lock-in effect. Once the MOS circuit is in the locked state, as long as the power supply is not cut off, the circuit will deadlock forever. Over time, it may burn out the circuit or degrade the circuit performance. For example, when the computer is abnormal (the mouse cannot be moved, the printer alarms) when the printer connector is plugged and unplugged when the power is on, the first remedy is to shut down immediately.
For this international organization, the corresponding standards have been specially formulated to classify electrical faults caused by ESD into the following types:
1. Operation ESD failure
The person operating the computer is charged with static electricity. When he touches the exterior of the computer such as the keyboard, mouse, and reset button, the following computer failures may be caused by ESD: the computer restarts, pauses, crashes, and other abnormal conditions. If you install certain software, you need to replace the hardware.
2. Maintain ESD failure
The person operating the computer is charged with static electricity, and he touched the conductive metal part inside the case. For example, touching the internal boards and cards with your hands will cause the above failures.
3. Overhaul ESD faults
The person operating the computer is charged with static electricity, and he touches the computer’s CPU, board, etc. The ESD that occurs will cause damage to the parts.
2. Measures to eliminate ESD
1. Properly ground
Computers nowadays generally have a ground wire. The ground wire is connected to the AC power line and the ground wire at the same time with two small capacitors. The grounding state is not good. For more sensitive people, as long as you touch the metal of the chassis, you will feel an electric shock ( Only 110V, the current is very small). The chip's ability to withstand voltage is much less than 110V, so if the computer equipment (such as the host, printer, display, etc.) is not all grounded, the printer port and display card will be damaged. Nowadays, many low-quality wiring boards look like three-wire systems, and their internal ground wires are not connected at all. Users should pay special attention when purchasing them.
2. Chip and board carrier packaging
Manufacturers generally attach great importance to ESD, and computer accessories will use anti-static packaging bags before they leave the factory. Packaging materials with good insulation properties are prone to ESD, such as bubble plastic bags, foam plastics, etc. These materials are not suitable for packaging computer accessories.
3. Operation or maintenance personnel's own electrostatic treatment
As a computer operator, you must always keep in mind the hazards of ESD, try to avoid touching the internal board of the computer, if you must touch the internal circuit, you must also add a grounding ring on your finger.
4. Electrostatic treatment in the workplace
Conditional workplaces should use anti-static floor (note: walking on all kinds of carpets is prone to high-voltage static electricity, and if the indoor humidity is too low, it is also easy to generate static electricity), and the ideal humidity should be 40%-60%.
5. Mount the chip on the board to improve ESD resistance
A single chip has low ESD resistance, if the chip is mounted on a board, it has a higher ESD resistance. This is the truth if the pins of the easily damaged CMOS chip are short-circuited and then transported away.
6. Measuring instruments and electric soldering irons also need to be grounded when working
7. Improve the quality of the device itself
In order to protect the computer port from ESD damage, the most effective way is to improve the internal quality of the device product. At present, some high-quality boards have adopted overvoltage and overcurrent protection devices on the I/O ports. A series of test standards have been specially formulated internationally for the design and manufacture of new devices. For example, MAXIM has many industrial serial port devices with ±15kV ESD protection, it must pass such as human body model, IEC 1000-4-2 contact discharge, IEC 1000-4-2 air gap discharge and IEC1000-4-4 electrical fast transient Change/burst discharge test, and these tests should be carried out many times under normal operation, shutdown mode and power-off state respectively.
Recovery CD can help you restore the system to the factory state
1. Put the Recovery CD into the optical drive.
2. Start up, press F2 to enter [BIOS Setup].
3. Select [Startup Configuration], and then press Enter.
4. Use【←】【→】key to change【1st device in Boot Device Sequence】to【CD-ROM】
5. Press the ESC key to return to the main screen, then press ESC (then Enter) to save the modified value and restart the system.
6. After the CD-ROM drive starts, the A: prompt appears. Type "Recovery" and press Enter.
7. Note: The keyboard language is: English, then press Enter.
8. Press the A key to accept the copyright agreement.
9. Press the Y key to continue.
10. Press the Y key again to confirm to continue. At this time, the computer is doing disk copying work. After the copy is completed, the computer automatically restarts. Remember: You cannot take out the RECOVERYCD at this time. The computer also needs to copy some software from the RECOVERY CD.
11. The computer will automatically eject the CD after the system recovery is complete.
12. Press the space bar twice to start the system. At this time, the computer's internal software and various settings have been restored to the factory state.
※ Important note: Using RECOVERYCD to restore the system will delete all data on the original hard disk, please use it with caution. Please make sure that you have made a data backup before performing this operation.