Views:157 Author:Site Editor Publish Time: 2017-04-27 Origin:Site
Electrostatic discharge (ESD) has been around since the beginning of time. However, this natural phenomenon has only become an issue with the widespread use of solid-state electronics. Since the beginning, electrostatic discharge (ESD) already exists. However, this natural phenomenon is only a widely used problem in solid-state electronics.
Sources of ESD
All materials (insulators and conductors) are the source of ESD. They are concentrated in the so-called triboelectric series, which define materials related to positive or negative charges. Positive charges are mainly concentrated on human skin or animal fur. Synthetic materials such as polystyrene foam or plastic cups, negative charge are more common. The amount of static charge accumulated on any item depends on its ability to store charge. For example, the human body can store a charge equal to 250 picofarads. This is associated with the stored charge, which can be as high as 25,000 V.
How does ESD damage electronic circuitry?
ESD is a tiny lightning version. As the current dissipates through the object, it seeks a low impedance path to balance the potential. In most cases, the ESD current will move to the ground through the metal chassis of the device. However, it is well known that current will travel on each available path. In some cases, there may be a path between the PN junctions in the integrated circuit to reach the ground. This current will burn the visible holes in the integrated circuit and show thermal damage in the surrounding area. An ESD event does not interrupt device operation. However, repetitive events can worsen the internal components of the device over time.
How does ESD occur?
ESD can occur in various forms. The most common is through human contact with sensitive equipment. The human touch is only sensitive to more than 4000V ESD levels.
The most recent survey found that during normal working days, the human body and its clothes can be stored between 500V and 2,500V static electricity. This is much higher than the level of damage to the circuit but below the human perception threshold. Other sources of ESD damage to the equipment include:
• Eliminate electronic devices or handle printed circuit boards without using static wrist straps;
• Place synthetic materials (ie plastic, foamed polystyrene, etc.) on or near electronic equipment; and
• Rapid movement of air near the electronic equipment (including the use of compressed air to blow the printed circuit board, blow the fan on the electronic device, or use an electronic device near the air handling system).
In all these cases, accumulation of static electricity costs may occur, but you may never know. In addition, charged objects do not have to be associated with ESD events to occur.
How do you measure electrostatic voltage?
One of the most effective ways to identify potential ESD problems is to use an electrostatic voltmeter for measurement. The meter will effectively measure up to 30,000V of electrostatic voltage on all conductors and insulators. It will also show whether the charge is negative or positive. This may help you determine the source of static buildup.
How can you prevent ESD?
You can not completely eliminate ESD from any website. However, experience has shown that the following criteria are helpful:
• Keep all synthetic materials at least 4 inches from the electronics.
• When cleaning the printed circuit board, use a ionizing air nozzle marked as non-static.
• When troubleshooting an electronic device, always wear an electrostatic wrist strap and secure it to the frame of the device. In addition, wristbands are worn when handling printed circuit boards.
• Deal with carpets and flooring with compounds that reduce static electricity costs.
• Use an electrostatic mat if necessary.
Ensure that the grounding system of the device has a low impedance to prevent the ESD current from dissipating into the ground reference.
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