First, micro reasons
According to the theory of atomic physics, the substance is in an electrical equilibrium state when it is electrically neutral. Due to the contact of different atomic atoms, the electrons are lost and lost, causing the material to lose its electrical balance and generate static electricity.
Matter is composed of molecules, which are composed of atoms, which have negatively charged electrons and a positively charged composition. Under normal conditions, the number of protons of an atom is the same as the number of electrons, positive and negative, so it shows an uncharged phenomenon. But protons are electrons that surround the nucleus. Once they are out of orbit, they leave the original nucleus and invade other atoms. The atom has a positive charge due to the lack of electron numbers. It is called a cation. The atom is negatively charged by increasing the number of electrons. Phenomenon, called anion.
The reason for the imbalance of electron distribution is that the electrons are out of orbit by external force. This external force contains various energies (such as kinetic energy, potential energy, thermal energy, chemical energy, etc.). In daily life, any two objects of different materials are in contact with each other. Separation can generate static electricity.
Second, the macro reasons
1. Frictional heat between objects, triggering electron transfer.
2. Contact and separation between objects produces electron transfer.
3. Electromagnetic induction causes an imbalance in the surface charge of the object.
4. The combined effect of friction and electromagnetic induction.
When two different objects are in contact with each other, one object is positively charged due to loss of some electronic bands, while the other is negatively charged due to some residual electrons. If the charge is difficult to neutralize during the separation process, the charge will accumulate and cause the object to be electrostatically charged. Therefore, when the object comes into contact with other objects, it will be electrostatically charged. Insulation coatings and thermal insulation materials are usually a kind of "contact separation" when a plastic film is peeled off from an object. The static electricity generated by undressing in daily life is also "contact separation".
Solids, liquids, and even gases are electrostatically charged by contact separation. This is because the gas is also composed of molecules and atoms. When the air flows, the molecules and atoms also "contact and separate" and electrify.
We all know that friction starts and rarely hears about electricity. In essence, triboelectric charging is a process of contact and separation that causes a positive and negative charge imbalance. Friction is a process of constant contact and separation. Therefore, the triboelectric charging is essentially the contact separation electrification. In daily life, all kinds of objects may generate static electricity due to movement or friction.
Another common type of electrification is induction. When a charged object approaches an uncharged object, negative and positive charges are induced at the two ends of the uncharged conductor, respectively.
Static power supply in the manufacture of electronic products
(1) The activity of the human body, static electricity generated by friction, contact and separation between people and clothes, shoes, socks, etc. is one of the main static power sources in the manufacture of electronic products. Static electricity in the human body is the main cause of hard (soft) breakdown of the device. The electrostatic voltage generated by human activities is about 0.5-2KV. In addition, the air humidity has a great influence on the electrostatic voltage, and if it is in the dry environment, it is increased by one order of magnitude.
(2) When the chemical fiber or cotton overalls are rubbed against the work surface and the seat, an electrostatic voltage of 6000V or more can be generated on the surface of the garment, and the human body is charged. When contact with the device, it will cause discharge and easily damage the device.
(3) The insulation resistance of the rubber or plastic sole is as high as 1013 Ω. When it rubs against the ground, it generates static electricity and charges the human body.
(4) When the resin, paint film, and plastic film packaged device are transported in a package, the surface of the device and the packaging material can generate an electrostatic voltage of several hundred volts to discharge the sensitive device.
(5) Various packaging, cartridges, and turnovers made of polymer materials such as PP (polypropylene), PE (polyethylene), PS (polyvinylidene), PVR (polyurethane), PVC, polyester, and resin. Boxes, PCB racks, etc. may generate 1-3.5KV electrostatic voltage due to friction and shock, and discharge sensitive devices.
(6) Ordinary work surface, which is electrostatically generated by friction.
(7) The insulation resistance of concrete, waxed polished floor, rubber sheet and other insulating floors is high, and the static charge on the human body is not easy to leak.
(8) Electronic production equipment and tools: High-voltage transformers and circuits in equipment such as soldering irons, wave soldering machines, reflow soldering furnaces, placement machines, commissioning and inspections all induce static electricity on the equipment. If the device is not properly vented, it will cause the sensitive device to fail during the manufacturing process. The hot air circulating in the oven and the box friction, and the CO2 vapor in the CO2 cryostat cooling box can generate a large amount of static charge.
(9) Air flows, and friction between air and other objects generates static electricity.
