1. Generation of static electricity

1. Friction: In daily life, static electricity can be generated when any two objects of different materials come into contact and then separate. The most common way to generate static electricity is by friction. The better the insulation of the material, the easier it is to use friction to generate electricity. In addition, static electricity can also be generated when any two objects of different materials come into contact and then separate.

2. Induction: For conductive materials, since electrons can flow freely on their surface, if they are placed in an electric field, positive and negative electrons will be transferred due to like charges repelling each other and opposite charges attracting each other.

3. Conduction: For conductive materials, since electrons can flow freely on its surface, if it comes into contact with a charged object, charge transfer will occur.

2. The impact of static electricity on the electronics industry

The circuits of integrated circuit components are reduced, the withstand voltage is reduced, and the circuit area is reduced, which weakens the device's ability to withstand electrostatic shock. The electrostatic electric field and electrostatic current have become the fatal killers of these high-density components. At the same time, the widespread use of a large number of high-insulation materials such as plastic products has greatly increased the chances of generating static electricity. In daily life, such as walking, air flow, and transportation, static electricity can be generated. People generally believe that only CMOS chips are sensitive to static electricity. In fact, highly integrated components and circuits are very sensitive.

A. The impact of static electricity on electronic components:

1. Static electricity attracts dust, changes the impedance between circuits, and affects the function and life of the product;
2. The insulation or conductor of the component is destroyed by the electric field or current, making the component inoperable (complete destruction);
3. Due to the heat generated by the instantaneous electric field or current, the components are damaged, but they can still work and their life span is shortened.

B. Characteristics of electrostatic damage:

1. Concealment The human body cannot directly sense static electricity unless static electricity discharge occurs. However, when static electricity discharge occurs, the human body may not feel an electric shock. This is because the static electricity discharge voltage perceived by the human body is 2-3KV;

2. Latent performance: Some electronic components do not show significant performance degradation after being damaged by static electricity. However, multiple cumulative discharges can cause internal damage to the components and create hidden dangers. They also increase the sensitivity of the components to static electricity. There is no way to recover from the problems that have occurred.

3. Randomness Under what circumstances will electronic components be damaged by static electricity? It can be said that all processes from the production of a component to its damage are threatened by static electricity, and the generation of static electricity is also random. Since the generation and discharge of static electricity occur instantly, it is difficult to predict and protect;

4. Complex electrostatic discharge damage sub-board work is time-consuming, troublesome and expensive due to the delicate and tiny structural characteristics of electronic products. It requires more complex technology and often requires the use of precision instruments such as scanning electron microscopes. Even so, some electrostatic damage phenomena are difficult to distinguish from damage caused by other reasons, which makes people mistakenly regard electrostatic damage failure as other failures. This is because before the electrostatic discharge damage is fully understood, it is often attributed to early failure or failure of unknown circumstances, thus unconsciously covering up the real cause of the failure;

5. Severity: On the surface, ESD problems only affect users of finished products, but in fact they also affect manufacturers at all levels, such as warranty costs, repairs, and company reputation.

3. Three types of ESD

1. Human body type refers to the friction between the body and clothes when the human body moves, which generates triboelectric charges. When people hold ESD-sensitive devices without first pulling the charges to the ground, the triboelectric charges will move to the ESD-sensitive devices and cause damage;

2. The charging type of microelectronic devices refers to these ESD-sensitive devices, especially plastic parts, which will generate friction charges during the automated production process. These friction charges are discharged very quickly to the highly conductive and firmly grounded surface through low-resistance lines, thus causing damage; or the metal parts of the ESD-sensitive devices are charged by induction and cause damage;

3. Field-sensing type means that there is a strong electric field around, which may come from plastic materials or human clothes, and electrons will be transferred across the oxide layer. If the potential difference exceeds the dielectric constant of the oxide layer, an arc will be generated on the side to destroy the oxide layer, resulting in a short circuit.

4. Electrostatic protection

1. Grounding
Grounding is to discharge static electricity directly to the earth through a wire connection. It is a direct and effective anti-static measure. For conductors, grounding methods are usually used, such as wearing an anti-static wrist strap and grounding the work surface.

Grounding is implemented by:

1) The human body is grounded through a wrist strap;
2) The human body is grounded through anti-static shoes (or shoelaces) and anti-static floors;
3) Grounding of the work surface;
4) Test instruments, tool clamps, and soldering irons are grounded;
5) Anti-static floor, grounding mat;
6) Anti-static transport vehicles, boxes, and racks should be grounded as much as possible;
7) Anti-static chair is grounded.

2. Electrostatic shielding
Electrostatic sensitive components will be exposed to static electricity during storage or transportation. Electrostatic shielding can reduce the impact of external static electricity on electronic components. The usual method is to use static shielding bags and anti-static turnover boxes as protection. In addition, anti-static clothing has a certain shielding effect on human clothing.

3. Ion neutralization
Insulators are often prone to generating static electricity. The grounding method is ineffective in eliminating static electricity on insulators. The commonly used method is ion neutralization (partially using shielding), that is, using ion fans in the working environment to provide a working area with equal potential.
Therefore, among anti-static materials and anti-static facilities, products are derived from these three methods and can be divided into anti-static instruments, grounding system anti-static products, shielding anti-static packaging, transportation and storage anti-static materials, neutralization static elimination equipment, and other anti-static products.

A. Anti-static instrument
1. Wrist strap/foot strap/anti-static shoes comprehensive tester is also called human body comprehensive tester - Purpose: used to test whether wrist straps, foot straps, and anti-static shoes meet the requirements;
2. When testing foot straps and anti-static shoes, you need to add a metal plate and a wire connected to the instrument;
3. Anti-static ion fan detector - Purpose: Regularly test and calibrate the balance and decay time of the ion fan to ensure that the ion fan works within the normal indicator range;
4. Static Electric Field Detector is also called Static Electric Tester or Static Electric Voltage Meter - Purpose: To measure the static electric field to reflect the existence of static electric field, and read the value in the form of voltage to test the static electric intensity of the environment. Generally, it is difficult to truly reflect the actual situation due to the influence of the environment and the instantaneous characteristics of static electric field;
5. Electrostatic shielding bag tester - Purpose: used to detect the shielding effect of electrostatic shielding bags;
6. Surface resistance meter - Purpose: used to measure the surface resistance and volume resistance of materials.

B. Grounding anti-static products

1. Anti-static wrist strap: widely used in various operating stations. There are many types of wrist straps. It is recommended to use a wrist strap equipped with a 1 megohm resistor. The length of the line should have a certain margin.
2. Anti-static watches: Other anti-static measures are needed to achieve better anti-static effects (such as adding an ion fan, wearing anti-static heel straps, etc.). It is recommended not to wear anti-static watches in large quantities;
3. Anti-static foot straps/anti-static shoes: After using anti-static floor in the factory, anti-static shoelaces or anti-static shoes should be worn. It is recommended that the workshop mainly wear anti-static shoes to reduce the introduction of dust. The effect will be better if the operator wears an anti-static wrist strap;
4. Anti-static mat: used for laying on the surface of each workbench. Each mat should be connected to the anti-static ground reliably after being connected with a 1 megohm resistor.
5. Anti-static floor: Anti-static floor is divided into: PVC floor, polyurethane floor, raised floor;
6. Antistatic wax and antistatic paint: Antistatic wax can be used on various floor surfaces to increase antistatic function and make the floor brighter and cleaner. Antistatic paint can be used on various floor surfaces and can also be applied to various shelves, turnover boxes and other containers.

C. Shielding anti-static packaging, transportation and storage materials

1. Anti-static turnover boxes and anti-static component boxes: used for turnover, transportation and storage of single boards and components in workshops;
2. Anti-static shielding bags: used for packaging, transportation and storage of single boards and components, with a certain moisture-proof effect;
3. Anti-static tape: used for various packaging boxes, etc.;
4. Anti-static IC material strips and IC trays: used for storage and transportation of IC components in the production workshop. It is prohibited to store IC in the open air before use; or to unpack and transport it;
5. Anti-static shelves, trolleys and workbenches: Anti-static shelves and trolleys are widely used for the turnover and transportation of single boards and components in electronic assembly workshops.Anti-static shelves and workbenches should be connected to the anti-static floor, and the anti-static mat on the trolley should have a metal chain in contact with the anti-static floor;
6. Anti-static work clothes and work shoes: In processing workshops with electrostatic sensitive components and certain cleanliness requirements, employees should generally be strictly required to wear anti-static work clothes and work shoes;
7. Anti-static finger cots: If employees at the operating station need to frequently hold workpieces or static-sensitive components, it is necessary to wear anti-static finger cots.

D. Neutralization equipment

1. Ion blower: According to the placement method, it can be divided into desktop, horizontal and hanging types. According to the number of holes, it can be divided into single-head ion blower, double-head ion blower, three-head ion blower, four-head ion blower and five-head ion blower. There are also ion blowers suitable for harsh environments and those that require large-scale and rapid static elimination. Desktop ion blowers, horizontal ion blowers and single-head ion blowers can be placed on the workbench or installed in a hanging manner. Double-head, three-head, four-head and five-head ion blowers are all hanging ion blowers. Ion blowers only need to be plugged into a 220V power supply to use, and the air volume can be adjusted. Except for ion blowers, due to the limitation of air volume, ion blowers are suitable for eliminating static electricity in places where the residual voltage of static electricity is relatively high. The dust removal function is inferior to other static elimination equipment.

2. Ion air gun: divided into ordinary ion air gun, plastic gun body ion air gun, large head ion air gun, high-precision ion air gun (suitable for clean rooms with high requirements). Ion air guns are generally hand-held, and can eliminate static electricity and remove dust at the same time. External compressed air is required, and the air source must not contain water and oil (generally, air compressors are equipped with oil and water filtering devices. If not, they can be purchased at hardware stores, ranging from 30 to 100 yuan each);

3. Ion air nozzle: There are ordinary ion air nozzles and induction ion air nozzles (automatically sensing objects and blowing air), which are generally fixedly installed on the assembly line for use;

4. Ion wind snake: Similar to the ion wind nozzle, the difference is that it has a base, the wind pipe can be folded, and the blowing direction can be changed at will;

5. Ion wind rod: According to the material, there are copper rods (ion copper rods, ion wind copper rods), aluminum alloy rods (ion aluminum rods, ion wind aluminum rods, ion wind curtains), according to the ion generation method, there are ionization type and induction type. Copper rods generally have ions, and aluminum alloy rods are generally induction type. The length is generally customized according to needs. There are wind-carrying and wind-free types, and they are generally installed on equipment for use;

6. Anti-static net: It is generally installed at the air inlet on the top of the workshop. It is better to install it in the clean room. It can cover the entire room and the size can be customized as required.