1、 Electrostatic hazards can be divided into two categories: one is the adsorption of floating dust caused by electrostatic attraction; The other is dielectric breakdown caused by electrostatic discharge.
1. Electrostatic adsorption
In the production and manufacturing process of semiconductor components, due to the use of a large number of tools and materials made of quartz and polymer materials, their insulation is very high. During the use process, some inevitable friction can lead to the continuous accumulation of surface charges, and the potential is getting higher and higher. Due to the mechanical effect of static electricity, in this case, it is easy to make the floating dust in the workplace adsorb on the chip surface, and even a small amount of dust adsorption may affect the good performance of semiconductor devices.
2. Electrostatic discharge and dielectric breakdown
The starting and discharging power supply of electrostatic discharge is space charge, so its stored energy is limited, so it can only provide temporary partial breakdown energy. Although the energy of electrostatic discharge is small, its discharge waveform is very complex and difficult to control. The soft breakdown of semiconductor devices is related to it.
The breakdown of components caused by static electricity is the main way of electrostatic hazards in electronic equipment, and is the most common and serious hazard in electronic equipment manufacturing.
The human body will also generate static electricity. Human body static electricity discharge may not only cause electric shock to the human body and reduce work efficiency, but also may cause secondary accidents (i.e. device damage). Therefore, enough attention should be paid.
When the human body is charged and discharged, the human body will have different degrees of reflection, which is called electric shock sensitivity. When the human body is shocked by static electricity, although no major physiological obstacle will occur, it may affect the work efficiency of people, or cause mental tension and secondary damage.
2、 Anti static of electronic equipment that should be paid attention to
With the rapid development of electronic equipment, devices with small size and high integration have been produced on a large scale, resulting in smaller and smaller wire spacing, thinner and thinner insulation film, and lower breakdown resistance voltage. However, the electrostatic voltage generated in the process of production, transportation, storage and transportation of electronic equipment far exceeds its breakdown voltage threshold, which may cause breakdown or failure of devices, affect the technical indicators of equipment and reduce its reliability.
The prevention of static electricity is mainly to inhibit the generation of static electricity, accelerate the leakage of static electricity, and neutralize static electricity. When people wear non-conductive shoes, electric charges will be generated and accumulated due to walking and other activities, and the potential can reach kilovolt level. When two different objects contact each other, charge movement will occur on their interfaces, and positive and negative charges will be arranged relatively to form a double electric layer. If the object is separated, the two objects will each produce an equal amount of charge with different polarity.
The principle to prevent such static electricity is to eliminate the main factors (object characteristics, surface state, electrification history, contact area and pressure, separation speed, etc.) that generate static electricity as much as possible; Make the positions of objects in contact with each other in the charged sequence as close as possible; The contact area and pressure between objects should be small, the temperature should be low, the contact times should be small, the separation speed should be small, and the contact state should not change dramatically. Powder, liquid and gas will generate static electricity due to friction during transportation. Therefore, measures such as limiting flow rate, reducing pipe bending, increasing diameter and avoiding vibration shall be taken.
In addition to inhibiting measures such as reducing speed, pressure, friction and contact frequency, selecting appropriate materials and shapes, and increasing conductivity, the following measures can also be taken for electrostatic protection: ① grounding. ② Overlap (or jumper) ③ Shielding. ④ Antistatic agents are used for insulators that can hardly leak static electricity to increase conductivity and make static electricity easy to leak. ⑤ Use spray, watering and other methods to improve the environmental humidity and inhibit the generation of static electricity. ⑥ Use static eliminator to neutralize static electricity. This is the most effective way to eliminate static electricity.
3、 Ways to eliminate static electricity in electronic equipment production
Anti static is mainly to prevent electrostatic discharge. To control electrostatic discharge, we should control the generation and elimination of static electricity. Controlling the generation of static electricity is mainly to control the technological process and the selection of materials in the technological process; The elimination of static electricity is mainly to accelerate the leakage and neutralization of static electricity. These two points work together to make the electrostatic voltage not exceed the safety threshold, so as to achieve the purpose of electrostatic protection.
Static electricity can cause harm to static sensitive devices, but it is controllable and can be eliminated.
1. Elimination of static electricity:
① Prevent the accumulation of static charges in places that may generate static electricity. Take certain measures to avoid or reduce the generation of electrostatic discharge. The method of generating while leaking can be used to eliminate the charge accumulation.
② The existing charge accumulation shall be eliminated quickly. When the insulating object is charged, the charge cannot flow and cannot leak, so the electrostatic eliminator can be used to generate foreign ions to neutralize the static charge. When the charged object is a conductor, a simple grounding leakage method shall be adopted to completely eliminate the charge.
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2. Electrostatic control: Electrostatic control technology is to take comprehensive measures to control electrostatic hazards within the allowable range when electrostatic charge accumulation is unavoidable.
① The purpose of the process control method is to minimize the generation of electrostatic charges in the production process. Preventive measures shall be taken in the process of material selection, equipment installation, operation management, etc. in the process flow to control the generation of static electricity and the accumulation of charges, inhibit the electrostatic potential and discharge energy, and minimize the harm.
② The leakage method aims to eliminate the static charge through leakage. Generally, electrostatic grounding is used to make charges leak to the ground, and the method of increasing the conductivity of objects is usually used to make electrostatic leakage.
③ The electrostatic shielding method uses a grounded shield to isolate the charged body from other objects, so that the electric field of the charged body will not affect other objects around. This shielding method is called internal field shielding. Sometimes, the isolated object is surrounded by a grounded shield to protect it from the influence of external electric field. This shielding method is called external field shielding.
④ The compound neutralization method and other methods can eliminate the static charge. Generally, the positive and negative ions generated by electrostatic eliminator: ion air gun, ion fan, ion air rod, ion nozzle, ion air drum are used to neutralize the charge of charged body, which may make the surface of charged object smooth and the surrounding environment cleaner, thus reducing the possibility of tip discharge.
