How to Eliminate Static Electricity Hazards?
Static electricity is harmful to any electronic product, but effectively preventing it is a top priority in the electronics industry.
I. The Harm of ESD to Chips: Computers are composed of circuit boards, and today's boards are mostly manufactured using MOS technology. Their circuits are highly sensitive to high voltage electrostatic discharge (ESD). When a person or object carrying static electricity touches these devices, ESD occurs. When the high voltage of ESD impacts the MOS circuit, the internal oxide film is broken down and damaged, causing immediate damage or malfunction of the components. Of course, devices subjected to ESD usually do not immediately malfunction, which is why most people don't pay attention to ESD. In fact, static electricity is ubiquitous in daily life. Experience shows that the static electricity that people can feel is at least 3.5kV, the static electricity that can be heard is at least 4.5kV, and the static electricity that causes a flash on a sweater can reach over 5kV.
Besides directly damaging devices, ESD can also induce a latch-up effect (or parasitic silicon controlled rectifier effect) within MOS circuits. This results in a significant increase in internal current within the MOS, causing internal logic malfunction and the so-called latch-up effect. Once a MOS circuit is latched up, it will remain locked indefinitely as long as the power supply is not disconnected, potentially burning out the circuit or degrading its performance over time. For example, if a computer malfunctions (mouse not working, printer alarm) due to hot-plugging a printer connector, the first remedial measure is to immediately shut down the computer.
Therefore, international organizations have specifically developed corresponding standards, classifying ESD-induced electrical faults into the following categories:
1. ESD Faults During Operation: When a person operating the computer carries static electricity and touches the computer's exterior, such as the keyboard, mouse, or reset button, ESD may cause the following computer faults: computer restart, pause, or crash. These may require a reset or reinstallation of software, or even hardware replacement.
2. ESD Faults During Maintenance: When a person operating the computer carries static electricity and touches conductive metal parts inside the computer case, such as internal circuit boards or cards, the above faults may occur.
3. Troubleshooting ESD Faults: If a person operating a computer carries static electricity and touches the CPU, circuit boards, etc., ESD can cause damage to these components.
II. Measures to Eliminate ESD
1. Proper Grounding: Modern computers generally have a ground wire. This ground wire, along with the AC live wire and ground wire, connects to two small capacitors. Poor grounding can cause a slight electric shock (only 110V, very small current) to sensitive individuals just by touching the metal of the computer case. Chips can withstand voltages far less than 110V, so if computer equipment (such as the host, printer, monitor, etc.) is not fully grounded, the printer port and graphics card will be damaged. Many inferior power strips appear to be three-wire systems, but their internal ground wire is not connected at all; users should pay special attention when purchasing them.
2. Chip and Circuit Board Packaging: Manufacturers generally pay close attention to ESD, and computer accessories are packaged in anti-static bags before leaving the factory. Packaging materials with good insulation properties are prone to ESD generation, such as bubble wrap and foam plastic; these materials are unsuitable for packaging computer accessories.
3. Static Electricity Handling for Operators and Maintenance Personnel: Computer operators must always remember the dangers of ESD and avoid touching internal circuit boards as much as possible. If contact with internal circuitry is unavoidable, use a grounding ring on your fingers.
4. Static Electricity Management in the Workplace: Workplaces with the resources should use anti-static flooring (Note: Walking on carpets can easily generate high-voltage static electricity, and low indoor humidity can also easily generate static electricity). The ideal humidity level is 40%-60%.
5. Improving ESD Resistance by Mounting Chips on Circuit Boards: Individual chips have low ESD resistance, but mounting chips on circuit boards provides significantly higher ESD resistance. This is the principle behind short-circuiting the pins of easily damaged CMOS chips before transporting them.
6. Grounding is Also Required for Measuring Instruments and Soldering Irons During Operation.