Wednesday, December 29, 2010
Weak current College】 【LED lights for the latest protection technology (2)】.
<br> <br> Four, LED by electrostatic protection <br> <br> All materials are made of atoms, Atomic electrons and protons are in. When the substance or lost email, it becomes negatively or positively charged, the charge accumulation on .the surface of the material we termed the object with the static electricity. Charge accumulation is usually due to material contact separation, can also be caused by friction, known as the frictional electrification. There are many factors that affect the accumulation of electric charges, including .the contact pressure, friction and separation speed, etc. Electrostatic charge will continue to accumulate, if not relief channel, this number will reach very high until the cause of action to stop the charge, charge was venting or achieve sufficient strength can penetrate the surrounding .material media. Dielectric breakdown, electrostatic charge will soon be balanced, the fast and the charge is called electrostatic discharge. Due to the very small resistors on rapid discharge voltage, current will discharge, may be more than 20 amps, if such a discharge through .electrostatic sensitive components, such as the current design will be the only on-voltage is 3V more and current is 20mA LEDs causing serious injuries. <br> 1. Why do you want to raise awareness of electrostatic protection <br> <br> 70 .in this century, the former generation ago many static electricity problems are because people do not have static electricity protection awareness, even now many people doubt the electrostatic discharge will cause damage to electronic products. This is because the majority of electrostatic discharge damage occurred in a .person's feelings, because the human perception of electrostatic discharge voltage is approximately 3KV, and many electronic components in several hundred volts or even dozens of Volt is damaged, typically electronic devices were after electrostatic discharge damage has no clear boundaries, the component installed on the device ., then you can start testing, resulting in a lot of questions, the analysis is also very difficult. In particular, potential damage, even if the use of precision instruments is also difficult to measure its performance changes significantly. But in recent experiments confirmed that .the potential damage after a certain time, the reliability of electronic products decreased significantly. Electrostatic damage is really true and false. <br> <br> 2. electrostatic damage to electronic products which forms? <br> <br> The basic physical characteristics .of static electricity to attract or exclusion, and the Earth has a potential difference, produces the discharge current. These three characteristics can influence has three components: <br> ①. electrostatic adsorption dust, reducing component insulation resistance (shortened life expectancy). < .br> ②. electrostatic discharge damage component damage cannot work (completely destroyed). <br> ③. electrostatic discharge electric or thermal currents, so that the components were injured (potential injury). <br> The more common ③ situation, is also .very difficult to discover. <br> <br> 3. electrostatic damage to electronic products which are the characteristics? <br> <br> (1). the hidden <br> The human body cannot be directly perceived electrostatic unless electrostatic discharge electrostatic .discharge occurred, but the human body does not necessarily have an electric shock sensations, this is because the human perception of electrostatic discharge voltage 2-3KV, electrostatic has hidden. <br> (2). the potential <br> Some electronic components from .electrostatic damage after the performance is not obvious, but many cumulative discharge will give devices caused due to the risk. Therefore static damage to the device has the potential. <br> (3). the randomness <br> Static electricity generation and randomness. .Its damage also has randomness. <br> (4). the complexity <br> <br> Electrostatic discharge damage failure analysis work, electronic products, fine, tiny structural characteristics and time consuming, laborious and expensive, requiring a higher technical and often .require the use of scanning electron microscopy, high-precision instruments. Even so, some electrostatic damage phenomenon can and other causes of injury, the distinction between mistake of electrostatic damage failure as other failure. This damage to the electrostatic discharge did not fully understand, .often due to premature failure or failure of unknown circumstances, thereby unwittingly obscures the real cause of the failure. Therefore, static analysis on damage of electronic components with complexity. <br> <br> 4. how to control ESD? <br> < .br> From the preceding analysis that electrostatic separation due to contact with objects, or no contact with induction, etc., can be said: at any time, anywhere, will generate static electricity. To completely eliminate anti-static almost impossible, but you .can take a number of measures to control ESD does not cause harm. <br> 5. how to control the human body static electricity (human body static electricity protection)? <br> <br> The human body is the most prevalent source of .static electricity. For static electricity, the human body is a conductor, so you can take a grounding on the human body. <br> <br> (1). the use of anti-static floor / anti-static shoes / socks ( .static import from feet to the ground) <br> By anti-electrostatic of ground, mats, rugs, personnel to wear an antistatic footwear, a combination of grounding. <br> (2). the wear an antistatic wrist strap and grounding ( .static import from hand to Earth) <br> By hand to discharge static electricity of the human body. It consists of static elastic belt, campaign buttons, spring soft line. protection resistance and plugs or Chuck. Elastic belt for inner layer with antistatic yarns .woven, knitted outer with ordinary yarn. <br> <br> 6, anti-static shoes and wrist strap use human security issues <br> <br> Only from the perspective of anti-static, total body Earth resistance as small as possible ., but the minimum value subject to security restrictions, the body must have a certain value of resistance, so that in case of a metal equipment or appliance and power frequency power shorted by the resistance to flow through the operation of the human body to limit the .current. The minimum value should not be less than 105 Ω, maximum of 109 Ω. <br> <br> 7, anti-static shoes and wrist strap use should pay attention to what issues? <br> ⑴, use the wrist strap .when you do not allow disconnected operation, or you will lose ground. A variety of wrist strap use main question is open, sometimes temporary, sometimes long break, the lost ground. <br> ⑵, wrist strap buckle is not tight cause human skin .contact with wrist strapResistance gets bigger <br> ⑶, some wristband a resistance is the strap itself, when touched the ground which resistance significantly reduce, may therefore lead to the risk of electric shock to the human body. <br> ⑷, some claiming .to be wireless wrist strap, the effect is far better than cable. <br> ⑸, anti-static shoes in wear should be anti-static socks / insoles and antistatic ground work to make the human body with electrostatic Guide to Earth, any part .of the resistance is too large or disconnect may cause the body to bring harm. So in important sectors should have human resistance tester at any time to detect human body wearing shoes / socks / insoles and and the human body, the total resistance to static leakage .. <br> ⑹ wristband application specialist outlets and link of grounding line and cannot be caught in a desktop or table's metal body, because these metal body on the ground of resistance can be quite large. <br> ⑺ should always check the wristband a .resistance <br> <br> 5. LED workshop of static electricity protection <br> <br> Workshop workspace using anti-static products such as appliances, over time, the resistance is likely to more than 109, in order to achieve the purpose .of anti-static, recommendations, mainly the creation of the following four basic conditions, is to ensure that the implementation of the measures human protection; the second is to ensure that the production equipment of electrostatic protection; third, to bring production plant and the .surrounding environment reach the anti-static requirements; 4 is the perfect system to develop practices that build a strong internal audit inspection system to ensure that the system be implemented, focus on employee static awareness training; development of static electricity protection supplies technical standards that guarantee .the quality of protection products. In the monitoring and control tools, add the workspace to monitor temperature and humidity, temperature and humidity; daily record monthly measurement of static pressure; staff anti-static clothing, hat after every wash once detected a surface resistance and .friction voltage; anti-static radio mat annual detection surface resistance at a time. Shop door set human integrated resistance Tester; monthly ion fan balance voltage and electrostatic dissipation. production process note taking appropriate preventive measures, the following information only: <br> < .br> To prevent static electricity generation: Assembly personnel action is required to wear anti-static clothing (such as anti-static clothing, hats, shoes, refers to the set or gloves, etc.) must be able rapidly to its surface or internal .electrostatic dissipative: Assembly operations personnel to wear an antistatic wrist strap. (Wrist strap must be connected to ground system) can provide a shield protection from electrostatic discharge or sudden shock: electric field <br> ① Assembly bench (bench) need to use anti .-static grounding pad, and radio. <br> ② costumes LED use anti-static cartridge. <br> ③ Cutter, soldering iron, Tin stove (or automatically reflow equipment) shall be grounded. <br> <br> Jobs, as .far as possible avoid directly touch the pins of the led, access as possible contact with colloidal portion. Grounding measures have to be completely prevent electrostatic, bench, soldering iron, cutter, Tin stove (or automatically reflow equipment) of the Earth, you must .use coarse wire into the soil, the wire does not end on big iron, buried in the ground surface 1 m, the Earth wire is connected with the main line, the operations staff wear antistatic ring if a PIN, the PIN is also required on .buried ground wire. Semi-finished products, finished products testing equipment are grounded. <br> <br> LED packaging bags and semi-finished goods packing materials to use anti-static sponge or packaging. <br> <br>.