Weak current College】 【anti-static knowledge (5)】.

<br> 51, asked: our design and production of switching power supply, the internal circuit is the product by EPOM a main PCB (double panel), welding surface on the underside, with 1 mm thick aluminum housing cover (only section shielding, .ventilation slots, etc.), open the rear full. My question is, which is a combination of ESD bag? packaging <br> A: the exact details depends on you to protect sensitive equipment and has a running program. You are also adjustable .level, reference standards, when MIL-STD-1686 electrostatic discharge voltage is greater than 0 - 1999V, damage extremely sensitive component is classified as having electrostatic discharge-sensitive parts. <br> For level device, you should use the electrostatic discharge system made .of electrostatic discharge bag, strictly in accordance with the electronic and MIL-B-81705C mechanical property requirements, which also have rosion of internal characteristics. In addition to some of its protective packaging, ESD bag can be used for electrostatic discharge protection, so switching .power supply you can normally use. <br> <br> 52. q: my company's portion of the business is manufacturing financial and health care, blank plastic cards. These cards through heating and extruded into thin slices, 10 tablets each time. Each .formation process is as follows: a PVC core material (usually 0.66 mm) in two PVC cover plate. Then the two stainless steel Transport Board. 10 PVC plate and transfer plate sandwich over two-tier 6.35 mm thick rubber sheet, and then put the .two standard plate on the outside. One card is placed in layer press roller, nine cards with heating for half an hour. But in each card separately when it encountered the electrostatic problems. Stainless steel transfer plate and shock, I was a foot away from .the card by electrostatic discharge arc of electrical shock. On the factory floor, antistatic mat and operation workers wear anti-electrostatic gloves, Transport Board still have some vibration. Indeed, they touch the new stainless steel plate, subjected to electric shock is very weak .. Each card may need to enable workers to electric shocks on nine occasions. I think that static is laminated, due to the heat and pressure PVC plate between the mutual friction. Part of the static charge from plastic card transfer to the plate, thus the .electrostatic conductive to operatives. I don't know whether through stainless steel transfer plate soon will the static charge from the surface of the clear plastic cards. I guess the net charge on the card is negative, then I can charge through to produce some intermediate .plate, stainless steel transport charges from the surface of the card, and then make the nutty or reduce it to clear? <br> A: your problem seems to be due to the heat electrochemically heating and compression process charge accumulation or separate card when the .friction electric. Your say (card) looks like a large capacitance, when you produce multilayer alternate conductive and insulating (or very high resistance) of the substance, in essence, multilayer formation of conductive material has been alternately. Therefore, you are in a .foot away from the to electrostatic discharge "arc", the electric field between the cards must have been great, usually ranging from 300000V, in atmospheric pressure as 760 mmHg, temperature 25 degrees are likely to reach 600000V. Best of all at the same point .grounding plate, operatives are in the same point on the Earth. This will decrease the action between workers and steel great potential difference. But you still need further measurement of electric field, in separate cards, use the electric meter, see generated electrostatic charge has .a grounding effect. If you really like this, you need to use the card further to compressed air ions and PVC core material in the charge. <br> <br> 53. q: I use air freshener anion. Every time I touch the .front (metal parts), it will emit a little fresher. May I ask how to solve this problem? <br> Answer: you are using air freshener adopts high-voltage Corona to launch freshener ion. Metal part might be the transmitter or eccentric .plate. If the Board is not grounded, you will be "shocked" or have a current flows from the body. High-voltage transmission line will keep you from electrical shock. Recommends the adoption of the following methods to resolve this problem: <br .> <br> Do not touch the metal parts check circuit, convinced that the metal parts have the power to get together and <br> <br> In metal parts on the front cover of a insulated objects (gridding) so that the body away .from the metal part (you need to check the use effect is affected) <br> <br> Reconnect the freshener tank location, use the human body is not easy to touch, and warning signs. <br> <br> Check the polarity .of the power to, try look polarity reversed <br> <br> Ensure that the correct tank earthing <br> <br> 54. q: anti-static wrist tester with the public, we have received from the bench. When anti- .static wrist in public places, they can be received when the role of the Earth? <br> A:. In fact, compared with the power to establish the public for the purposes of grounding, it is best to take and touches the Earth to .reduce electronic noise, depending on the equipment of several factors (electronic), power and might be feasible. <br> <br> 55,: electronic components made of antistatic bag is made from what material do? it work in positive polarity or negative .sexual conditions? <br> A: there are several types of electrostatic bag: shielding (in-line metal, metal, vapor shield), antistatic and conductive. Most of the usual "static" or electrostatic discharge shielding bag is a bag with these .three characteristics. Shielding bags have a layer of metal, usually aluminium (aluminium foil similar), a Faraday cage effect "shield". Electrostatic discharge shielding bag has the following characteristics: <br> <br> Mechanical (internal mechanical parts) <br .> <br> Electronic shield: (Faraday cage) so that the current (voltage discharge electricity) or electrostatic discharge through the diaphragm. It can protect its internal from electrostatic discharge <br> Electrical interference. <br> <br> Antistatic: non .-friction charging, or through contact with and separation from static, that is, when a body in motion around electrostatic bag. When walking on the floor, touch metal objects, such as doorHandle, will feel the electrostatic spark discharge attacks (walking on the .carpet). <br> <br> Conductivity: allows you to charge mobile or surface charge can be moved to a lower or higher potential, that is, when you will connect to the receive location on the surface (zero voltage). It is .best to use a static discharge characteristics of conductive materials (105-1010), more than 1011 insulation excellent materials and any conductive material is inappropriate use of difference. <br> <br> Typical shielding bag consists of: <br>? <br .> Polyester (0.0127 mm thick) <br> Aluminium polyester materials deposition (10-25 El, 1 Angstrom = 10-10 m) <br> Polyethylene (0.0635 mm) <br> <br> 56. q: in winter, 17 .from computer - 20 feet away from electrostatic discharge occurs so that it restarts. Have you heard? (for related data to prove in the distance of ESD damage equipment?) how to solve this problem? <br> A: A, activities of people .often with large amounts of static electricity, can shop anti-static discharge electrostatic floor and wear shoes to be resolved. <br> B, conductive surface can give fast access to high energy electrical discharge, may be provided in each conductive surface anti-static .floor mats and sprayed with tear coated and reliable grounding. <br> C, dry environment, will further increase the risk of electrostatic discharge, on the main part of the control of the humidity or air ion beams. <br> <br> Product .solution: using electrostatic dissipation resistance and better of anti-static floor finishing agent, or to all vulnerable to interference areas for coating protection. It is recommended that you use good antistatic properties of zinc floor finishing agent, and anti-static shoes (such as .electrostatic discharge system dedicated model 24802 anti-static shoes). These two products will drastically reduce friction shock to electrostatic charge, in the process may be one of the more important factors. For all non-typical loss application surface anti-static material, loss .material replaces all conductive surface (104) or is covered with a loss of materials, conductive surface using type T2 or model L floor cushion material. Ensure that all conductive surface and operations staff (anti-static shoes, anti-static wrist, etc) .are grounded. On conductive surface with high resistance of the material, so that the static discharge can make the transfer of energy, at the same time can reduce or eliminate electromagnetic interference. <br> <br> 57. q: in wafer fabrication process ., the circuit chip <br> A: first of all need make semiconductor material smallest of exposure time, so that it reached a very high energy electron pulses. Highly integrated microcircuits of wafer like other chips, be sensitive to receive high energy pulses. Metal .gaskets can smaller point not to touch. But if the conductor on one of the micro-liner and of discharge at two points transfer current or potential difference exists, in the vicinity of semiconductor materials may get corrupted. We know, but the application logic and .electrostatic discharge-sensitive semiconductor material (for some), when combined, can cause a decrease in the number of products or low quality, thereby reducing the production efficiency. <br> <br> 58. q: different models of ESD flooring differ between .the mat (ie rubber, vinyl, 3 laminate, polypropylene fibers, laminated insulation plate, etc.) Which they can be used in the environment, the price? <br> A: select the pad material, the following factors: <br> .First of all to clear, whether the wire on the mat, whether or not to use it for bad chemical environment, fall strength, is used for floor or worktable? internal parameters pad resistance? well, as long as the consideration of these factors, .then things become very simple. How much are you going to draw a table, or want to shop, how many square feet of mat? is permanent or temporary? mica and glass fiber reinforced plastic can be used as permanent coverings or as automotive cushion material .. Rubber mat with good heat resistance and chemical resistance, vinyl and more effective. You need anti-fatigue material or not need? you need and electronic parts with very good floor mat appliances? or do you want to split the floor mat as needed? .Finally, what colour do you want? if you clear these issues, you would have the right to make a choice. <br> <br> 59. q: If you have a truck with a printed circuit plug-in support, and where .no electrostatic discharge of the garage. But you still must wear an antistatic wrist and e pliers to banana plug. The following two points work? or is both didn't work? <br> A, anti-static wrist cables connected to the computer .the same truck assembly bracket shelf, ensure that in carrying out the operation, so that you and the truck shelf in the same potentials. <br> B, in anti-static wrist cable ends, e pliers received a grounding box, and then hand .on a shelf, computer Assembly frame for equipotential, begin checking the jigs. <br> 2. use e pliers? if there are any harm? <br> A: when the circuit Assembly stage work, anti-static wrist received and with the .enclosures for similar vehicles in the rack will have certain advantages. However, it must be in strict accordance with the following requirements to do: assembling sets must be conductive ("1011) also desired conductive, rack and the connection to the whole body, anti .-static wrist next to the body of the connection point and the circuit. Because the integrity of the contact resistance, grounding, friction electrification and static induction problems, not through the hands of the car body grounding. Non-conductive parts of the body may .also have electric field (wheels, car, etc.), so if you happened to handling electrostatic discharge-sensitive parts before you let it go, it may in part on the side of the body conducting the charge distribution imbalances caused by. <br .> The static wrist on e pliers received public pick up location (CPG) is harmless. Before use, you should start with both mechanical and electronic to check the connection quality is good or bad, sure e pliers and public sites have received good electrical lap ., disconnect power (mechanical integrity) greater than or equal to 1 lb, less than 5 pounds of force as a whole. <br> <br> <br>.