The purpose and general principle of anti-static
The fundamental purpose of anti-static is to prevent the hazards caused or possible due to the mechanical and discharge effects of static electricity during the manufacturing and use of electronic components, components, and equipment, or to limit these hazards to * To a small extent to ensure that the design performance and use performance of components, components and equipment will not be damaged due to electrostatic effects.
We all know that the main form of electrostatic hazards in the electronics industry is the sudden failure and potential failure of components caused by electrostatic discharge, which in turn causes the performance of the whole machine to decline or fail. Therefore, the main purpose of anti-static and static control should be to control electrostatic discharge, that is, to prevent the occurrence of electrostatic discharge or reduce the energy of electrostatic discharge below the damage threshold of all sensitive devices. In principle, anti-static should be carried out from two aspects: controlling the generation of static electricity and controlling the dissipation of static electricity. Controlling the generation of static electricity mainly controls the process and the selection of materials in the process; controlling the dissipation of static electricity is mainly to quickly and safely discharge static electricity. Discharge and neutralize; the result of the combined effect of the two makes it possible that the static electricity level does not exceed the safety limit and achieve the purpose of anti-static.
When an object has a certain amount of net positive or net negative charge, it can be said to have static electricity. Static electricity is a relative term, because in many cases, static electricity will gradually decrease after a period of time. The length of this period of time is related to the resistance of the object. The two extreme examples in practical applications are plastic and metal.
Generally speaking, the resistance of plastic is very high, so plastic can keep static electricity for a long time. The resistance of the metal is very low, and the grounded metal is charged with static electricity for a very short time. Static electricity is usually expressed in volts. Although 220V AC power is dangerous, 100kV static electricity is very common. The voltage in an object is determined by two factors: the charge of the object and the capacitance of the object. It can be expressed by a simple relational expression, that is, Q=CV, where Q represents the amount of electricity, V represents the voltage, and C represents the capacitance of the object.
If the charge of an object is given, the lower the capacitance, the higher the voltage, and vice versa. Plastics generally have very low capacitance, so a very high voltage can be generated with a small amount of electricity. On the contrary, the capacitance of metal is very high, so more electricity only produces lower voltage. This is the reason why people pay more attention to the static electricity problem caused by the use of plastics in practical applications. High voltages can attract dust, cause electric shocks to operators, or change the properties of objects.
There are two main types of static electricity: body static electricity and surface static electricity. Bulk static refers to the electric charge distributed inside an object. Surface charge refers to the charge on the outer surface of the object*.
In practical applications, static electricity problems are basically related to surface static electricity. Although there is no way to neutralize body static electricity, body static electricity rarely causes problems. Generally, the effect of bulk static electricity is very small compared to surface static electricity.