Seek knowledge about static electricity, prevention and utilization of static electricity

Static electricity is an objective natural phenomenon that occurs in many ways, such as contact, friction, rushing, and so on. The basic process of its generation can be summarized as follows: contact charge transfer, galvanic layer formation, charge separation.

The static electricity on the equipment or the human body can reach up to tens of thousands of volts to hundreds of thousands of volts, and often reach hundreds to thousands of volts under normal operating conditions. Static electricity is the result of positive and negative charges losing their balance on a local scale. It is a kind of electrical energy that remains in the performance of objects, and has the characteristics of high potential, low charge, low current and short action time.

The main measures of electrostatic control are: leakage and dissipation of static electricity, electrostatic neutralization, electrostatic shielding and grounding, humidification, etc.

Component breakdown damage caused by electrostatic discharge is the most common and serious electrostatic hazard in the electronics industry, which is divided into hard breakdown and soft breakdown. Hard breakdown is a one-time breakdown, burn-out or permanent failure of the component dielectric; Soft breakdown is the result of deterioration of the device's performance or degradation of parameters.

In the process of transmission and storage of electrostatic sensitive components and printed circuit boards, anti-static loading boxes, component boxes, turnover boxes, turnover trays, etc. must be used. to prevent the hazards caused by the accumulation of static electricity. When packaging as a finished product, anti-static shielding bags, bags, boxes, baskets, etc. must be used to avoid electrostatic damage during transportation.

In the production process of electronic products, its components and components are often in contact, separation, and friction with equipment and tools, etc., and static electricity must be generated.

Friction and human static electricity are the two major sources of harm in the electronics and microelectronics industries, but the generation of static electricity is not the harm, the harm lies in the accumulation of static electricity and the resulting electrostatic charge discharge, charged objects, the formation of electrostatic field around it, will produce mechanical effects, discharge effects and electrostatic induction effects, so it must be controlled.

Due to the mechanical effect of static electricity, the floating dust particles in the air will be adsorbed on silicon wafers and other components, which will seriously affect the quality of electronic products, so anti-static measures must be taken for the purification space. The walls, ceilings and floors of the clean room should be made of anti-static dust-free materials, and a series of electrostatic protection measures should also be taken for operators, workpieces and appliances.

In order to understand the electrostatic activation in the production process, it is necessary to measure the electrostatic and related parameters to determine the influence of static electricity in the production process and to inspect the quality of electrostatic protection equipment and equipment.

The measurement of electrostatic electricity is mainly the measurement of electrostatic voltage, material resistance, grounding resistance, electrostatic shutdown period, electrostatic charge, electrostatic eliminator power dissipation performance, cloth charge surface density, etc.

Electrostatic protection work is a systematic project, any link of negligence or mistakes, will lead to the failure of electrostatic protection work, must be prevented from time to time, everyone to prevent.

Static electricity refers to the electric charge that is distributed on the surface or volume of a dielectric and is at rest on the surface of an insulating conductor. Electrostatic electricity is a common electrically charged phenomenon and is also common in industrial production. On the one hand, people use static electricity to carry out certain production activities, such as the application of static electricity for dust removal, painting, flocking, mineral processing and photocopying.

The prevention of static electricity should start from its main hazards: discharge sparks and the adsorption of static electricity. And the utilization of static electricity is mainly in:

According to the principle of charge homogeneity and different absorption, high-voltage electrostatic electricity generates electric field and electrostatic discharge.

Knowledge point 1: prevention of static electricity

OnePrinciple of prevention of static electricity:

The main hazard of static electricity is discharge sparks, such as when the oil tanker transports oil, because of the oscillating friction between the oil and the metal, it will produce the accumulation of static electricity, and the spark discharge will be caused to a certain extent, which is easy to detonate the fuel and cause accidents, so it is necessary to drag it to the ground with an iron chain to guide away the static electricity generated.

In addition, the adsorption of static electricity will cause deviations in the dyeing industry of the printing and dyeing industry, and attention should also be paid to prevent it.

Second, the main way to prevent static electricity:

1) Avoid static electricity. If possible, materials that are not prone to static electricity are used.

2) Avoid the accumulation of static electricity. To generate static electricity, try to guide away, such as increasing air humidity, grounding, etc.

Knowledge point 2; Utilization of static electricity

1. According to the nature of electrostatic energy to attract light and small objects and the principle of repulsion of the same charge and attraction of different charges, the main applications are: electrostatic copying, electrostatic dust removal, electrostatic painting, electrostatic flocking, electrostatic spraying, etc.

2. The electric field generated by high-voltage static electricity is used in the following applications: electrostatic preservation, electrostatic sterilization, crop seed treatment, etc.

3. Use ozone and aseptic disinfection generated by electrostatic discharge. Lightning is a large-scale electrostatic discharge phenomenon that occurs in nature, which can produce large amounts of ozone and synthesize nitrogen in the atmosphere into ammonia to provide plant nutrition.

Knowledge of electrostatic fields in high school physics

1. Coulomb's law

1) The content of the law: The interaction force between two stationary charges in a vacuum is proportional to the product of their charges, inversely proportional to the square of their distances, and the direction of the force is on their lines.

2) Expression: k = electrostatic force constant.

3) Applicable conditions: stationary point charge in a vacuum.

2. The law of conservation of electric charge

The charge is neither created nor destroyed, it can only be transferred from one object to another, or from one part of the object to another, and the total amount of charge remains the same during the transfer.

There are various mechanisms by which static electricity is generated. For example, there are contact energies, triboelectric energies, induction electrostatic energies, thermoelectric and piezoelectric energies, jet energies, and flow energies.

Static electricity in the plastics and paper industry is caused by contact and triboelectric conduct. When two materials are separated by pressure contact or friction contact, the molecules on the surface of one of the materials will break due to friction or extrusion because of the small energy of the electronic bonds, and the loss of part of the electrons will be positively charged, while the surface of the other material will be negatively charged due to the gain of electrons.

If one of the two interacting materials is electrically conductive, then electrons can be conducted to earth through the material, and static electricity will not be generated. Gain and loss of electronsFor insulators such as plastics and paper, an electrostatic region with a certain amount of energy is formed on the surface of some or all of them. Practice has proven that:

The tighter the contact between the two materials or the faster they separate, the greater the static electricity generated.

1. Causes of static electricity.

The main causes of static electricity are:

a) Internal characteristics of the substance.

1) Since different substances need different amounts of work to get electrons out of the original surface, electron transfer occurs on the contact surface when they are in close contact. Substances with small work of escape are prone to lose electrons and have a positive charge, while substances with large work of escape have a negative charge of electrons. The difference in the work of escaping from various substances is the basis for generating static electricity.

2) The generation of static electricity has a lot to do with the conductivity of the substance, and they are expressed in terms of resistivity. The lower the resistivity, the better the conductivity. Conclusions based on a large number of experimental data:

The resistivity is 1012Substances of cm are the most prone to static electricity, and greater than 1016cm or less than 109

Substances of cm are not prone to static electricity. Therefore, resistivity is the condition for static electricity to accumulate or not.

3) The dielectric constant of a substance is the main factor that determines the electrostatic capacitance, and it affects the result of electrostatic electricity together with the resistivity of the substance.

2) The role of external conditions.

1 Triboelectric Electricity.

In addition to friction, its main manifestations include tearing, peeling, stretching, impact, etc. In industrial production, such as crushing, screening, rolling, stirring, spraying, filtration, polishing and other processes, triboelectric will occur.

2 Attached to the charged.

The attachment of some polar ion or free electron to an object insulated from the earth can also make the object appear electrostatic.

3.Induction of electricity.

A charged object can also cause a different part of the surface of another conductor that is not connected to it to be charged by opposite polarity.

4.Polarization electrification.

In the electrostatic field, the molecules inside or on the surface of some substances can be polarized and charged, which is called electrostatic polarization, such as when an object with static electricity is contained in an insulating container, the outer wall of the container is also charged.

When static electricity is generated on a well-grounded conductor, it will quickly leak to the ground, but if it is an insulator or poorly grounded, the charge will accumulate more and more, forming a very high position. When a charged body is close to an uncharged or electrostatic potential object, if the potential difference reaches more than 300V, a discharge phenomenon will occur and a spark will occur.

Static electricity is a kind of electric charge that is at rest or does not flow (the flowing charge forms an electric current).

Static electricity is formed when the charge is gathered on an object or surface, and the charge is divided into two types: positive charge and negative charge, that is to say, the phenomenon of static electricity is also divided into two types, namely positive static electricity and negative static electricity.

When the positive charge is gathered on an object, it forms positive static electricity, and when the negative charge is gathered on an object, negative static electricity is formed, but whether it is positive static electricity or negative static electricity, when the electrostatic object touches a zero-potential object (grounded object) or an object with a potential difference, the charge transfer will occur, which is the spark discharge phenomenon we see every day. For example, the weather in the north is dry in winter, and the human body is prone to static electricity, and when it comes into contact with other people or metal conductors, it will cause discharge. People will have the pinprick feeling of electric shock, and sparks can be seen at night, which is the reason why chemical fiber clothes rub against the human body and bring positive static electricity.

Static electricity is not static electricity, it is electricity that temporarily stays somewhere on a macroscopic scale. When people stand up on the carpet or sofa, the human body voltage can also be higher than 10,000 volts, and the static electricity in the rubber and plastic film industry can be as high as more than 100,000 volts.

As the name suggests, electrons that cannot move freely along a conductor.

It's not that it can't. It's just that it's really not doing directional motion.

.Static electricity terms and definitions.

Static electricity: An excess or insufficient stationary charge on the surface of an object.

Electrostatic field: The electric field around which static electricity is formed.

Electrostatic discharge: The transfer of electrostatic charge between two objects with different electrostatic potentials due to direct contact or electrostatic field induction. When the energy of the electrostatic electric field reaches a certain level, it breaks through the medium and discharges the electrostatic discharge.