I. Terms and definitions
1. static electricity: the surface of the object excess or lack of static charge
2. electrostatic field: electrostatic field formed around it
3. electrostatic discharge: two objects with different electrostatic potential, due to direct contact or electrostatic field induction caused by the transfer of static charge between the two objects. The energy of the electrostatic field reaches a certain level, breaking through the medium between the discharge phenomenon is electrostatic discharge.
4. electrostatic sensitivity: components can withstand the electrostatic discharge voltage
5. electrostatic-sensitive devices: electrostatic discharge-sensitive devices
6. grounding: electrical connection to the object that can supply or receive a large number of charges, such as the earth, ships and so on.
7. Neutralization: the use of anisotropic charge to make static electricity disappear
8. anti-static work area: equipped with a variety of anti-static equipment and equipment, can limit the static potential, with clear regional boundaries and special markings suitable for static protection operations of the workplace
The two static electricity:
1. Friction: in daily life, any two different materials objects come into contact and then separate. Material objects in daily life, any two different objects in contact and then separated, you can generate static electricity, and the most common method of generating static electricity, is the friction of electricity. The better the insulation of the material, the easier it is to use friction electricity. In addition, any two different substances in contact with the object and then separated, can also produce static electricity;.
2. Induction: For conductive materials, because the electrons can flow freely on its surface, such as placing it in an electric field, due to the repulsion of the same sex, opposites attract, positive and negative electrons will be transferred.
3. Conduction: for conductive materials, because the electrons can flow freely on its surface, such as in contact with charged objects, charge transfer will occur.
Three, the impact of static electricity on the electronics industry
Integrated circuit components line shrinkage, voltage reduction, line area reduction, making the device resistance to electrostatic shock ability to weaken the electrostatic field (Static ElectricField) and electrostatic current (ESDcurrent) to become a fatal killer of these high-density components. At the same time a large number of plastic products and other highly insulating materials commonly used, resulting in a large increase in the opportunity to generate static electricity. Daily life such as walking, air flow, handling, etc. can generate static electricity. It is generally believed that only CMOS chips are sensitive to static electricity, but in fact, highly integrated components and circuits are very sensitive.
A. The impact of static electricity on electronic components
A) Static electricity adsorbs dust, changing the impedance between the lines, affecting the function and life of the product.
B) Because the electric field or current damage to the insulation or conductor of the component, so that the component can not work (complete destruction).
C) Injury to the device due to heat generated by an instantaneous electric field or current, but the device is still functional and has a damaged lifespan.
B, the characteristics of electrostatic damage:
1. hidden human body can not directly perceive static electricity, unless the occurrence of electrostatic discharge, but the occurrence of electrostatic discharge, the human body does not necessarily have the feeling. This is because the human body perceives the electrostatic discharge voltage of 2-3KV.
2. latent some electronic components are subject to electrostatic damage after the performance does not have a significant decline, but many times the cumulative discharge will cause internal injuries to the device and the formation of hidden problems, but also increase the device sensitivity to static electricity. Problems that have arisen and there is no way to cure.
3. Randomness of electronic components in what circumstances will be subjected to electrostatic damage? It can be said that, from the production of a component until it is damaged before all the processes are threatened by static electricity, and the generation of these static electricity also has a random nature. Because the generation and discharge of static electricity are instantaneous, and difficult to predict and protect.
4. Complexity of electrostatic discharge damage board work, due to electronic products, fine, small structural features and time-consuming, laborious, costly, requiring more complex technology often need to use precision instruments such as scanning electron microscope, even so some electrostatic damage phenomenon is difficult to distinguish from other causes of damage, so that people mistakenly take the failure of electrostatic discharge damage as other failures, which is the damage of the electrostatic discharge is not fully understood before, often attributed to the damage of electrostatic discharge, but also the damage of electrostatic discharge. This is the damage of electrostatic discharge is not fully recognized, often attributed to the early failure or failure of the situation is not clear, thus unconsciously cover up the real cause of failure.
5. The severity of the ESD problem on the surface only seems to affect the user of the finished product, but in fact also affects the manufacturer at all levels, such as: warranty, maintenance and the company's reputation and so on.
Four, ESD three types
1. human body type that is, when the human body activities between the body and clothing friction friction charge. When people hold ESD-sensitive devices without first tugging the charge to ground, the friction charge will move to the ESD-sensitive devices and cause damage.
2. Microelectronic devices charged type refers to these ESD-sensitive devices, especially for plastic parts, when in the automated production process, will produce friction charges, and these friction charges through the low-resistance lines very quickly to the highly conductive solid ground surface, thus causing damage; or through the induction of ESD-sensitive devices in the metal part of the charge and damage.
3. Field-sensitive type that there is a strong electric field around, which may come from plastic materials or human clothing, electronic conversion will occur across the oxide layer. If the potential difference exceeds the dielectric constant of the oxide layer, the side will produce an arc to destroy the oxide layer, the result is a short circuit.
4. There are other:? iliac J Jian3 ≡ Luang knock P Ting (4) Song Low Oryza P Ting be careful of the English Gracilar insults P Ting (12)? ∑ Skull P Ting?br> five, static protection
1. grounding
Grounding is directly over a line of electrostatic discharge to the earth, which is the most direct and effective anti-static measures, for the conductor is usually grounding methods, such as artificial anti-static wristbands and workstations grounding and so on.
Grounding is implemented through the following methods:
1) The human body through the wrist strap grounding.
2) The human body through the anti-static shoes (or shoelaces) and anti-static floor grounding.
3) The work surface is grounded.
4) Grounding of test instruments, tool holders, and soldering irons.
5) Anti-static floor, floor mats grounded.
6) Anti-static transfer car, box, rack as far as possible grounding.
7) Anti-static chair grounding.
2. electrostatic shielding
Static sensitive components in storage or transportation process will be exposed to static electricity in the region, with electrostatic shielding methods can weaken the external electrostatic impact on electronic components, the most common method is to use electrostatic shielding bags and anti-static crates as protection. In addition, anti-static clothing on human clothes have a certain shielding effect.
3. Ion Neutralization
Insulators are often easy to generate static electricity, the elimination of static electricity on the insulator, with the grounding method is ineffective, the method usually used is ion neutralization (part of the use of shielding), that is, the use of ionic fans and other in the work environment, to provide a potential work area.
Therefore, in the anti-static materials and anti-static facilities, are derived from these three ways of products can be divided into anti-static instrumentation, grounding system class anti-static products, shielding class anti-static packaging, transportation and storage of anti-static materials, neutralization of static elimination equipment, as well as other anti-static supplies.
A.Anti-static Instrument
1.Wrist strap/foot strap/anti-static shoes comprehensive detector-use: for the detection of wrist straps, foot straps, anti-static shoes are in line with the requirements.
2. When testing footbands and anti-static shoes, it is necessary to add a piece of metal plate and the wire connected to the meter.
3. De-static ionizing fan tester - purpose: regular ionizing fan balance and decay time for testing and calibration to ensure that the ionizing fan work in a safe range of indicators.
4. Static field detector - purpose: measurement of electrostatic field to reflect the presence of static electricity, readings in the form of voltage, used to test the environment of electrostatic strength. Generally affected by the environment and static electricity instantaneous characteristics, it is difficult to truly reflect the actual situation.
5. Static shielding bag tester - purpose: used to detect the shielding effect of static shielding bag.
6.Surface Resistance Measuring Instrument-use: used to measure the material surface resistance, volume resistance.
B. Grounding anti-static products
1. Anti-static wristbands: widely used in various operating stations, wristbands are many types, it is recommended that the general use of wristbands with 1 megohm resistance, the length of the line should be left a certain amount of margin.
2. anti-static watch: need other anti-static measures to remedy (such as: additional ion fan, wear anti-static heel strap, etc.) to achieve a better anti-static effect. It is recommended not to use a large number of ways to wear anti-static watch.
3. anti-static footwear / anti-static shoes: plant use of anti-static ground, should be equipped with anti-static shoe laces or wear anti-static shoes, it is recommended that the workshop to wear anti-static shoes based on the introduction of dust can be reduced. Operators and employees combined with anti-static wristbands will have a better effect.
4. Anti-static table mat: used to lay the surface of the workbench, the table mat string 1 megohm resistance and anti-static ground reliable connection.
5. anti-static flooring:
Anti-static flooring is divided into: PVC flooring, polyurethane flooring, movable floor.
Anti-static wax and anti-static paint: anti-static wax can be used for a variety of floor surfaces to increase the anti-static function and make the floor more bright and clean
Anti-static paint can be used for a variety of floor surfaces, but also can be coated in a variety of shelves, crates and other containers.
C. Shielding anti-static packaging, transportation and storage materials
1. Anti-static crates, anti-static component boxes: used for workshop veneer and parts of the turnover, transportation and storage.
2. Anti-static shielding bags: used for packaging, transportation and storage of veneer and components, with a certain moisture-proof effect.
3. Anti-static tape: used for various packaging boxes
4. Anti-static IC material strips and IC trays: used for the production of IC components in the workshop storage, handling. Prohibit the use of IC before the open storage; or unpacking transportation.
5. Anti-static shelves, carts and workstations: anti-static shelves, carts are widely used in electronic assembly workshop veneer, parts of the turnover, handling and so on. Anti-static shelves and benches to have anti-static ground connection, cart on the anti-static mat should have a metal chain and anti-static ground contact
6. anti-static work clothes and shoes: in the static-sensitive components, with a certain degree of cleanliness requirements of the processing plant, generally should be strictly required to wear anti-static work clothes and shoes
7. anti-static finger cuffs: such as the operation of workstations employees need to often hand Take the workpiece or static-sensitive components, it is necessary to wear anti-static finger cots.
D. Neutralization equipment
Ion blower, air gun
6, anti-static general process requirements
A, anti-static conventional process requirements:
1, the operator must wear a wired anti-static wrist
2, involved in the operation of static-sensitive devices on the table surface must be used to prevent static pad
3, ESD-sensitive type of workpiece or static-sensitive components, it is necessary to wear anti-static finger cushions. p>3, ESD-sensitive devices must be used with electrostatic shielding and anti-static equipment transfer.
4, ready to open, test static-sensitive devices must be carried out on the anti-static workbench, conditions can be equipped with an ion air generator to remove the charge in the air
5, assembly of soldering equipment and molding tooling equipment must be grounded, soldering tools using an endothermic soldering iron, grounding should be a good grounding, grounding resistance should be small
6, the power supply system must be modified with a transformer to isolate the power supply. Modified with a transformer for isolation, ground to be reliable, to prevent suspension of the ground, grounding resistance of less than 10 ohms
7, product testing, in the case of power supply, you can not arbitrarily plug and unplug the device must be switched off in the case of plugging and unplugging.
8, where ESD-sensitive devices should not be taken out of the original package too early, to be correct according to the operation, as far as possible not to touch the ESD-sensitive device legs.
9, with wave soldering, solder and transfer system must be grounded.
B, in the strict requirements of anti-static occasions, the following anti-static process requirements are often needed.
1, where ESD-sensitive machine for high and low temperature test or aging test, it must be the first workplace and high and low temperature box for static electricity level test, the potential can not exceed the safety value, otherwise, to eliminate static electricity processing.
2, welded printed circuit boards to be three defense processing, but also to use anti-static measures. Do not use general brushing, ultrasonic cleaning or
Spraying.
3, debugging, measurement, inspection of low-resistance instruments, equipment (such as signals, bridges, etc.) should be in the ESD-sensitive devices connected to the power supply,
Can be connected to the input of ESD-sensitive devices.
4, in the ESD-sensitive test equipment production line, should be strictly use electrostatic potential test to monitor the change of electrostatic potential, in order to take static elimination measures
time.
How to choose anti-static equipment (-)
There are many kinds of anti-static equipment, to choose reasonably in order to save money and can play a good anti-static effect?
One, the control of human static electricity
1. What is the most common source of static electricity?
2. To control human static electricity, the most effective measures?
3. People wear anti-static shoes and anti-static mats, anti-static composite rubber sheet or anti-static floor can play a good anti-static effect?
4. Why do people wear anti-static shoes in addition to anti-static overalls?
5. People wearing anti-static overalls can play a role in anti-static?
6. In order to better control the human body static electricity, what measures should be taken?
7. people wear wireless bracelets (also called wireless wristbands) can play an anti-static effect?
1. What is the most common source of static electricity?
People in activities such as walking, standing up and other activities will produce static electricity, the human body is the most common source of static electricity, so the human body is the most important static electricity protection.
2. To control the human body static electricity, the most effective measures?
To control human static electricity, the most effective measure is to let the human body and the earth are "connected" that is, "grounded". Therefore, people should wear anti-static shoes. To keep the human body connected to the earth, which requires the ground is also anti-static in order to be able to conduct the body's static electricity into the earth, so the ground can be used with anti-static mats, anti-static composite rubber sheet, and anti-static grounding line connected to the ground, such as sufficient funds, you can choose to use anti-static flooring, especially in the planning and design of plant rooms can be considered to choose to use anti-static flooring, if the plant has been set up and the equipment has also been installed And do not want to install anti-static equipment on these devices caused by production stoppages and so on when the impact of also choose both inexpensive and simple construction of anti-static mats, anti-static composite panels and so on.
3. People wear anti-static shoes and anti-static mats, anti-static composite rubber sheet or anti-static flooring can play a good anti-static effect?
People wear anti-static shoes and have anti-static mats, anti-static composite rubber sheet or anti-static activity flooring can not necessarily play a good anti-static effect. Usually people also wear socks and insoles, young people's feet are easy to sweat, these socks and insoles can also conductive static electricity, but in the middle-aged and elderly people in the dry season due to the dryness of the shoes, the socks and insoles can not conductive static electricity, and many manufacturers only require the staff to wear antistatic clothing and antistatic shoes, ignoring the socks and insoles of the adverse effects, so that this antistatic shoes and antistatic floor can not play the role of antistatic electricity. . Therefore, in the machine room or plant at the entrance to place the "human body integrated resistance detector", it can quickly and accurately detect those who wear unqualified anti-static shoes, socks and insoles.
4. Why do people wear anti-static shoes in addition to anti-static work clothes?
People in addition to wearing anti-static shoes but also wear anti-static overalls in order to better control the human body static electricity. Because clothing can also bring a high level of static electricity, especially nowadays most of the clothing is chemical fiber, can produce thousands of tens of thousands of volts of static electricity.
5. People wear anti-static work clothes can play a role in anti-static?
Not. Experiments have shown that people only wear anti-static work clothes such as not wearing anti-static shoes and no good anti-static ground, anti-static effect is very poor.
6. In order to better control the human body static electricity, what measures should be taken?
To have a perfect human body anti-static facilities and test these facilities are effective electrostatic measuring instruments.
7. people wear wireless wristbands can play a role in anti-static?
No. The theory of cordless wristbands is that they utilize the power of a device to prevent static electricity. Cordless wristbands theory is to use the principle of corona discharge to dissipate some of the static electricity, corona discharge is also known as the tip of the discharge, is a guide to the body itself charged, usually requires a voltage of more than 1500V, the tip of the part of it will be discharged into the air, so as to dissipate static electricity, but cordless wristbands to dissipate static electricity when the electrostatic voltage required is too high, is not suitable for the electronics industry, because how many electronic components can withstand the high voltage of 1500V. Above the high voltage it. So we do not recommend, do not sell, do not produce, do not use wireless wristbands.
Factory anti-static basic requirements
A, the basic principles of electrostatic protection
a, inhibit the accumulation of static charges; b, rapid, safe and effective elimination of static charges have been generated.
Two, anti-static work area site
1, ground materials a, prohibit the direct use of wooden floors or laying wool, linen, chemical fiber carpets and ordinary floor leather. b, should be selected by the static conductor material composition of the ground, such as anti-static activities on the floor or in the ordinary ground on the floor of the anti-static mats, and effectively grounded. c, allowing the use of terrazzo floor with special treatment, such as the prior c, allows the use of special treatment of terrazzo floor, such as prior to laying the ground network, carburizing or spraying antistatic agent on the ground.
2, grounding a, anti-static system must have an independent and reliable grounding device, grounding resistance should generally be less than 10 Ω, buried and testing methods should be consistent with the requirements of GBJ97. b, anti-static ground line shall not be connected to the power supply on the zero line, shall not be used with the lightning ground line ****. c, the use of three-phase, five-wire power supply, the earth can be used as an anti-static ground line (but the zero line, the ground line shall not be mixed). d, the grounding trunk line cross-sectional area should not be less than 100mm2; trunk line cross-sectional area should not be less than 6mm2; equipment and bench grounding line should be used cross-sectional area of not less than 1.25mm2 of the multi-stranded plastic conductor, grounding line color to the yellow-green line is preferred. e, the grounding of the trunk line should be used in the way of brazing. f, anti-static equipment connection terminals to ensure that contact is reliable, easy to install and dismantle, allowing the use of a variety of Clip connectors, such as E fish clips, plugs and so on.
3, ceiling materials ceiling materials should be selected antistatic material products, generally allowed to use gypsum board products, prohibit the use of ordinary plastic products.
4, wall coverings Wall coverings should be used antistatic wallpaper, generally allowed to use gypsum paint or lime paint wall, prohibit the use of ordinary
wallpaper and plastic wallpaper.
5, humidity control a, anti-static work area of the relative humidity of the environment to not less than 50% is appropriate. b, in the product does not cause harmful effects on the premise of allowing the use of humidification equipment spray preparation or water to increase the humidity of the environment. c, the humidity of the computer room should be in line with the relevant provisions of the GB2887, a similar computer room should be in line with the provisions of the. d, the computer room should be in line with the relevant provisions of the GB2887, similar computer room should be in line with the regulations.
6, regional boundaries anti-static work area should be marked regional boundaries, and in the obvious place to hang warning signs, warning signs should be consistent with the provisions of GJB1649, the entrance to the work area should be configured with ionized air bath equipment.
7, anti-static work area is prohibited to use and contact easy to generate static charge charge source (the following table).
Painted or painted surfaces, ordinary plastic veneer, ordinary vinyl and resin surface floor
Plastic and ordinary floor leather, polished and waxed wooden floors. Ordinary vinyl work clothes, hats, shoes
Ordinary polyester, synthetic fibers and nylon fabrics, plastic and ordinary rubber-soled shoes operating tools and equipment
Ordinary plastic boxes, shelves, bottles, trays, supplies and paper products, ordinary foam and general mobile tools, compressors, spray equipment, evaporation equipment, etc.
Three, anti-static facilities for electronic products
1. Safety bench a, static safety bench is the basic components of the anti-static work area, which consists of a workbench, anti-static table mat, wrist strap connector and earth line, etc. b, anti-static table mat should be no less than two wrist strap connector, one for the operator to use, and another for the technicians, inspectors, or other personnel to use. c, if necessary, the static safety workbench should be equipped with ionized wind static eliminator. d, static safety workbench is the most important part of the anti-static safety work area, the workbench should be equipped with ionized wind static eliminator. d, electrostatic safety workbench does not allow stacking plastic boxes (pieces), rubber, cardboard, glass and other easy to produce static debris, drawings and other information should be loaded into the anti-static bag.
2, anti-static wristbands direct contact with static-sensitive devices should wear anti-static wristbands, wristbands should have good contact with human skin, wristbands must be non-stimulating, non-allergic effects on the human body, the wristbands system should be 106~108Ω range of resistance to ground.
3, anti-static containers in the development and production of electronic equipment, all storage, turnover SSD containers (component bags, transfer boxes, printed circuit board racks, component storage boxes, etc.) should have electrostatic protection properties. Metal and ordinary plastic containers are not allowed. If necessary, the storage of components with the crate should be grounded.
4, ion wind electrostatic eliminator to eliminate static charges on the surface of the insulating material should use ion wind electrostatic eliminator.
5, anti-static work clothes a, into the anti-static work area or contact with SSD personnel should wear anti-static work clothes, anti-static work clothes fabrics should be in accordance with the provisions of GB12014. b, in the relative humidity greater than 50% of the environment, anti-static work clothes are allowed to choose cotton products.
6, anti-static work shoes into the anti-static work area or contact SSD personnel should wear anti-static work shoes, anti-static work shoes should be consistent with the relevant provisions of GB4385. Generally allowed to wear ordinary shoes, but should be used at the same time conductive shoe harness or heel strap.
7, anti-static car transfer SSD or SSD containing the whole, parts, should be used with anti-static properties of the transport vehicle.
7.