Monday, February 7, 2011

Weak current College】 【anti-static knowledge (7)】.

<br> <br> 71. q: Wireless electrostatic discharge protection mean? <br> <br> A: the only applicable forced air corona discharge and ionization of measures can be widely used as "air ion generator." Electrostatic discharge system there .are several models to choose from, only cancel the discharge time, it depends on the charge-discharge rate, air flow speed and proximity up close to 2 seconds, the production period in urgent need of protection measures, but use a grounded wrist and ESD .floor mat, a second protection measures are also possible. <br> <br> 72. q: How can I tell if failure of the antistatic shielding bags, for example, the bag has a crease or small holes. <br> <br .> A: MIL-B-81705C standard file you can find all your answers, in particular, if an anti-static shielding bags (model III) meet any of the following conditions, it can be considered as invalid: <br> * Standard .electrostatic bags occurred MIL-B-81705C section in the details of the stratification. <br> * Electrostatic discharge electrostatic decay rate is more than 2 seconds. <br> * The attenuation of electromagnetic interference not to 10dB. <br> .* Small hole of diameter greater than 2mm. <br> * You cannot shield 30kV following electrostatic discharge event. <br> * Miles per square area on the surface resistance is greater than 1012, internal resistance per flat area is less than 105. < .br> In short, as the Faraday effect, if the shielding bags with creases or holes, so it still has a shielding effect. But will these electrostatic bag thrown away are more secure, this may take more test fee, proof of eligibility after just .replace it. <br> <br> 73, asked: <br> 1, used in the production of hard disk clean room class 100, its nominal humidity level? <br> 2, Pomalux is I know in electrostatic discharge security best only .a plastic material, but rather expensive, there are other similar materials? <br> 3, there is no common ion generator? if so, what vendors? how can we test its results are correct? <br> 4, electrostatic sensor reading why .would substantially change? (ie no repetitive or large jumps.) <br> <br> A: <br> 1: good's nominal humidity at 40% -55%. You need to minimize corrosion, while at the same time as much as .possible to strengthen the electrostatic discharge protection. There you can test the humidity of paper available for your convenience. <br> 2: static security good materials are vinyl, rubber, cardboard and polyethylene, etc., depending on your application. Electrostatic discharge safety .also means the loss characteristics of antistatic characteristics, and shielding characteristics, this also depends on your application. <br> 3 and 4: charge plate will analyze instrument is monitoring the corona discharge of air carrier ion generator preferred instrument. Moreover, electrostatic sensor each .measurement a smaller area, electrostatic charge in conductive or insulated surfaces do not have to be balanced. If a substance subjected to electric or friction electric stimulation, free electrons occurs imbalances. Balance is not always consistent, electrometer sensor and the measured surface distance also further .so that this balance changes. The measuring surface geometry structure can also lead to changes in the field, for example, a surface (like a pyramid-shaped) comparison of flat surfaces have a stronger field, because the charge always accumulate in body-art .Department <br> <br> 74, asked: <br> 1, conductive finger can reduce the load? loss of glove use conductive finger what benefits? <br> 2, we have many 3M961 ion generator, the zero-level stations in .good enough? <br> A: <br> 1: the advantages of electrically conductive finger set depends on the following issues: the specifications of the conductive finger? do you want to handle any questions? operators feel most comfortable? do you want to .work in clean room inside job or not?, loss of gloves and will have less conductive finger ("104 = electrostatic discharge may occur, but when you use a loss of gloves when there is no difference. Glove hands than a set of covered area .larger, if you are 12 or more occasions to wear gloves, wear gloves will be more effective. <br> 2: for zero-level stations, in any event, any particle tolerance cannot exceed 2.5 micron. The only way is to get an .ion generator for zero-level clean room to ensure clean indoor only part is a corona discharge emission source. You may know some with corona discharge emission source system, I'm not familiar with 961 units. If it is overhead or other "blower" .types of devices, so that it does not meet your standards. For 100-level, our overhead line is good, once you start to get ready. <br> <br> 75. q: Suppose our electrostatic discharge measures do very well, .but the following one thing not satisfactory: the staff of our company like the pink anti-static foam on computer motherboards, they felt that this would prevent the motherboard in ESD workstation produces sliding. Because they believe this will extend the life of the surface of .the workstation. However, I believe that this is not likely, because of the foam insulation. On the other hand, because the measurement, I bring an electrometer, placed in the things on this piece of foam (on the work surface) will consume .electric charge. So, this is acceptable? <br> <br> A: If pink foam not expendable and electrical connections to the land, then you're ready (General use). In fact this depends on your efforts to protect the product .from electrostatic discharge-sensitive. In order to measure up to the surface impedance of foam, you will need a megohm meter. At 10V and 100V two voltage measured at the surface resistance to 10 ^ 5-10 ^ 9, it is safe. < .br> You say you use the static electric field strength meter to measure, this is good, but this does not fully guarantee the foam is secure. You test this is only one characteristic of electrostatic Tester is discharge time. The most important thing is to .workSurface charge should be less than 100ms time eliminate clean. If you take a few seconds to clear out all charge, which will extend the charge relief time may give rise to an electrostatic discharge-sensitive parts subjected to electrostatic discharge. <br> There are .other materials to choose from, you can place your work in electrostatic discharge protection for workstations, and no sliding characteristics. Type T2 floor cushion material is in this case the best choice. <br> The following questions: <br> A, I will .protect sensitive components? <br> B, foam in the security level can be conductive losses? <br> C, foam in charge may release the pained in about 100ms? <br> D, foam necessary grounding it (if a conductive)? .<br> E, operators need to wear a set of static discharge wrist? <br> If you have agreed to the above questions, then you are using a number of security measures to prevent electrostatic discharge. <br> <br> 76. .q: my company in the bench trial, ESD footwear floor mat set and wrist. If the operator is being welded components and other can cause confusion or fever part, what other materials can be placed on the mat on the floor, without prejudice to the .electrostatic discharge performance? when space is limited, the operator does not have to move the floor mat? <br> A: Yes, your best choice is the glass fiber reinforced plastic (FRP) solder fillers, is a high-heat resistant solder electrostatic .discharge floor mat. This allows you to check your standard rubber or vinyl floor mats electrostatic discharge table, or you can order a larger glass solder packing, that is, with grounding cord of Workbench floor mat. Rubber cushions also has good heat-resistance characteristics .(although not as FRP good). Recommended type T2 or model L Workbench floor mat. <br> <br> 77. q: If we are using the wrist and floor mats, you also need to put on a heel grounding device? if .you use the heel grounding device, you need to use floor coating? <br> A: If the operations staff walking up and down, and close to sensitive components, you must use the heel grounding device. It will keep you in handling electrostatic discharge .-sensitive parts with security. If you transferred between workstation electrostatic discharge-sensitive products or components, the cart and the body should be grounded by the heel or shoes (human), drag the grounding wire (trolley). And with the proper ground floor .. In electrostatic discharge-sensitive area nearby introduced ground floor mats or antistatic floor coating is a very good idea, because these materials have excellent limits of antistatic characteristics of friction charging. If the staff must constantly move about, so in order to take full advantage .of safe ESD programme requires plankingwith layer of antistatic discharge of floor coatings and ESD shoes. <br> <br> 78. q: I work in a computer network, we know that mutual contacts of metal in the joints caused by oxidation, thus making .system cause problems. We are trying to take the best methods to troubleshoot it, some technical staff recommendations with rubber will clean the joints and other technical personnel claimed it would cause electrostatic discharge event, I ask that this be? <br> A: Yes ., the eraser can be on the metal surface, so the friction charging may generate electrostatic discharge phenomenon, although this is work Workshop cleaning joints of a universal approach. But when the scrub lap surface, as long as it is grounded in respect to the risk .of electrostatic discharge to minimize, or in your bare hands, using a conductive rubber and wear a wrist grounding it set. <br> The first thing to do is to pass on the most sensitive elements on each Board to estimate in order to determine its .sensitivity level (ESD sensitivity). This will tell you whether the Board is very sensitive to electrostatic discharge. If you do not need the sensitive, you may take a few simple prevention measures to avoid the potential danger of electrostatic discharge. <br> Testing .electrostatic discharge sensitivity is the best way is to find a piece of old circuit boards, use the eraser to clean solder joint, and then use the electrometer to measure the scrubbing process of electric field (measuring voltage). The first step you need to put .the electrometer zero, after two readings taken before and after. If you read into the numbers more than 50V, it is recommended that you use this method to clean lap. <br> Note that not all of the circuit board. Some boards may inline .some very sensitive to electrostatic discharge (0) components, or that is made up of different materials (such materials will have different frictional electrification priority) element, and so on. Eraser also have different friction up power sequencing / antistatic characteristics, so that each .circuit board should be regarded as an independent module. <br> <br> 79, asked: our production personnel protection measures including through electrostatic discharge clothes, if not in the front line of clothes clip to its level of shielding effectiveness, we have differences .. Overalls have no need to hold, in other words, if the work is not labelled, it will be screened? <br> A: on the overalls are good, the benefit is that protection of external non-conductive and non-grounding clothing .. Even overalls are not wearing a seat, it still has some protection, because the back and sleeves, working on both sides were in peacetime covering the clothes, not only is the front cover. While the earlier part of the body is the most sensitive .products easy to close / contact parts. <br> <br>.

1 comment:

  1. Great article! Pretty exhaustive description of the static system. I just wish you had touched more on anti static coating systems. Maybe you could do a follow-up post?