Wednesday, January 5, 2011
Weak current College】 【anti-static and weak current of principle】.
ESD English ElectroStaticDischarge "electrostatic discharge" means. We all know, different material contacts, isolation or mutual friction to generate static electricity. For example in the production process of extrusion, cutting, handling, mixing and filtering as well as the life of walking, standing, clothes, etc., will generate static electricity. Visible, the static electricity in our daily life is everywhere, our body and surrounding it with a very high voltage, kV or even tens of thousands of volts. These static electricity may have little effect on the human body, but for some ESDS (electrostatic sensitive components), but direct makes it loses itself due to normal performance, or even a complete loss of functionality. This ESD protection is necessary.
Combined with the concept of ESD and work with some of the accumulated experience, and I'm from human, machine, process, material, ring the following five aspects to talk about ESD protection.
A few words on the person. The human body is a body high quiet power supplies, protection for electronic, with a shield and release the static electricity. Strictly speaking requirements for achieving the "heavily armed", namely: to wear anti-static electrical apparatus, anti-static masks, anti-static glove, finger, etc, to wear anti-static clothing, anti-static shoes, while wearing the overhand wristband to shield and guided walks. In short, try not to let the people of the exposed skin.
Second on the machine. The machine is also a high quiet power supplies, because machine mechanical parts, in particular motor, etc., easy to produce EMI (electromagnetic), protection for electronic machines, is very necessary. For protection for electronic machines, generally through the electromagnetic field of the elimination, high static parts of the screen, such as machine grounding. General degaussing borrowed is degaussing, the Elimination of charge using the ion fan.
Degaussing is very simple, it is not as described, we take a look at ion fan. Ion fan can produce a wealth of positive and negative ions, will these ions to high static objects, the objects will be in and static electricity. These ions are ion fan internal ions occurring components, air ionization. The ions occurring elements from low current, high voltage transformer to incentive air ionization. And transformers in turn contain current limiting resistors, which can strengthen the ionization of stability and safety. Role in the stainless steel ion launch round circuit on top of the high-voltage alternating current to launch a strong alternating electric field, the field will produce air ionization, pole-ion. When electromagnetic field cannot be eliminated or more difficult to eliminate, we use static device to shield the high electrostatic equipment or devices, such as high static parts, motor, we all know that the motor is easy to produce EMI, but also to operate the machine without motor, therefore, not against its shield. There are benches, power cable, computer keyboard, you can then use the static methods for ESD protection, available shielding products anti-static radio pad, antistatic film, anti-static curtain, anti static, anti-static electricity adhesive tape, etc. Finally, no matter what machine shield or degaussing effect how to connect to the machine ESD grounding wire is necessary.
III about material, i.e. the material. A sentence is absolute, if your product is sensitive to electrostatic discharge, so your line do not have high appear electrostatic materials, especially from the product closer to the regions as possible using anti-static material, such as element boxes, racks, bench, transport equipment, cleaning equipment, chemical reagents, finally even you use pen and notebook with anti-static pen and notebook, because when you use a pen, it is likely to come into contact with the product. Of course, if you, your product on electrostatic sensitivity is not very high, you can use at their discretion, but it is best to prove ESD test and see if it really can be assured.
Four on the ring, the work area of the environment. A good anti-static work environment for the production is very important that this environment is generally so to establish:
First of all, the establishment of ESD safe operating area, namely the EPA (ESDProtectionArea), preferably in the appropriate location on ESD protection warning signs, etc.
Secondly, the ESD safe working area of resettlement, anti-static floor systems, dust removal system, grounding system and air temperature and humidity to talk in three areas. Anti-static floor systems, most notably in the shop of ordinary floor and anti-static floor, the floor has an antistatic PVC flooring, anti-static epoxy resin floors, anti-static floor, requests must meet the standards of the International Association of anti-static, anti-static floor must also connect the ground wire and ESD. An anti-ESD working environment, it is critical that no dust, because the dust in the air in motion process collide with each other, will also have an ESD, if not dust, looking up the resulting ESD problem of kindness. In general we use dust removal system to solve the problem. First of all requires air dust filtration system, such as: air shower, air shower, shower goods, with dust pad, with dust cylinder, air filter, dust-free transfer window, clean room air shower transfer window, etc. Secondly, as far as possible the establishment of purification lights, clean room cleaning glass, clean room color steel plate smallpox, clean room color steel plate package corner, clean room color steel plate package column, etc. Selection of the above, the enterprise according to the product on ESD sensitivity, preferably using a professional advice. A sophisticated ESD protection work environment, establishing independent sound ESD grounding system is also very important. And, in the workplace, work surfaces, and other devices are connected to the ESD grounding system. In addition, a complete ESD working environment for temperature and humidity have certain requirements, from ESD protection perspective, the humidity higher the better, but the humidity is too high, will corrode equipment, so in General, 40%-60% humidity is ideal. Of course, the enterprise also according to the characteristics of their products, after all this work done more cumbersome. Also, establish ceilings, wall supply outlet, and frequently used dust on the clean room for purification, etc.
So, with this kind of work environmentWe think that the human body static electricity is not through electrostatic discharge clothes, shoes, or through the wrist strap, dissipative ESD grounding system and import the Earth. By controlling the air temperature and humidity environment of electrostatic dissipative through floor system and import the Earth.
Of course, on second thought, the front of the man, machine, material should belong to the environment protection, as long as the link's work well, then, a proper ESD protection work environment is established. With reasonable operational specifications, that is the correct way to essentially through.
5 about the law. Talk about the law, first clear the above four-point, in fact, the law is to establish a reasonable method and specification to ensure the effective implementation of the above four. In addition, you need to add is that when you have reason not explicitly ESD should be based on the production process, the design corresponding to ESD test, produce ESD carefully to find the cause of the issue. Ultimately it is necessary to establish appropriate ESD practice and disciplinary norms to regulate the production.
Of course, the ESD protection system established in the future, for staff, have to do is constantly testing the system to continuously find irregularities, and make the appropriate improvements to ensure the long-term and effective to maintain its role of ESD. Thus, the establishment of appropriate ESD functions, and constantly develop their professional skills, improve their ESD protection awareness is ESD protection indispensable part.
In recent years, with the rapid development of science and technology, extensive application of microelectronics technology and electromagnetic environment is increasingly complex, ESD is a growing problem, the issue has become more prominent, enterprises are increasingly attach importance to ESD protection.
How is the static electricity
Substances are molecules, molecules are made of atoms, Atomic are negatively charged electron and positively charged protons. Under normal circumstances, an atomic number of proton and electron number are the same, and negative balance, so it's not a live show. But electronic wrapping around the nucleus, is liable on the detachment track outside, leave the original Atomic infants and invade other Atomic B, A number of atoms due to lack of e-and with the positive phenomenon, known as cationic, B atomic number by increasing the e is negatively charged phenomenon, called anions.
Imbalance electronic distribution of reasons which are the electronic outside and away from the track, this external force contains a variety of energy (such as kinetic energy, potential energy, thermal energy, chemical energy ... And so on) in daily life, any two objects of different materials and separation after contact, you can generate static electricity.
When two different objects touching is making a loss of some objects, such as the electronic transfer of the charge to another object so that it with the positive and the other bodies have some remaining electronic objects and negatively charged. If in the process of separation is difficult to charge, charge in and will accumulate static electricity that makes an object with. Therefore objects with other objects after separation will be in contact with static electricity. Usually from one object split a piece of plastic film when it is a typical "contact separation" electrification, in everyday clothes produced electrostatic separation was also a form of "contact" electrification.
Solid, liquid or gas will contact separation but with static electricity. Why gas will generate static? because gas is composed of molecules, atoms, when the air flow is molecular and Atomic also occur "contact separation" and electrification. So in our surroundings and even our body will have different levels of static electricity, static electricity accumulated to a certain extent discharge occurs.
1. What is ESD?
ESD is the representative English ElectroStaticDischarge "electrostatic discharge" means. ESD is the formation of the century since the mid-to study the formation and decay of static electricity, static discharge model, electrostatic discharge effect, such as current thermal effects (sparks) (such as the ignition of explosive) and and electromagnetic effects (such as EMI), and other subjects. In recent years, with the rapid development of science and technology, extensive application of microelectronics technology and electromagnetic environment is increasingly complex, electrostatic discharge of electromagnetic field effects such as electromagnetic interference (EMI) and electromagnetic compatibility (EMC) issues are becoming more and more attention.
2. electrostatic ignition limits?
Electrostatic ignition potential of non-conductor about 30KV. National standards for the prevention of electrostatic accident general guidelines in section 5.2.3, electrostatic potential non-conductor than 15KV does not ignite ignition energy greater than minimum 0.2mJ of flammable gas. But in some cases, produce ignition limits also small, standard provisions about 5KV. Prevent human suffering from non-conductor electrical shock to electrostatic charging potential about 10KV.
3. electrostatic properties of parameters?
How many commonly used object charged electrostatic charge capacity and voltage and measurement materials such as plastic, rubber, anti-static floor (faces), carpets, etc., anti-static properties are usually used resistance, electrical resistivity, volume resistivity, surface resistivity, charge (or voltage) half-life, electrostatic capacitance, dielectric constant, etc. But the most commonly used the most reliable or resistance and resistivity.
4. electrostatic effects on the human body?
If the human body static electricity for more than 2-3kV, when human contact when grounding metal will generate static electric shocks, if the voltage is high, then the human psychological and physiological impact of.