Electrostatic in SMT workshop
Marking specification for ESD protection
1、 Electrostatic knowledge
The so-called static electricity is a kind of static charge or non-flowing charge (the flowing charge forms the current). When the charge is gathered on an object or surface, static electricity is formed, and the charge is divided into positive charge and negative charge, that is to say, there are two kinds of electrostatic phenomena, namely, positive static electricity and negative static electricity. When the positive charge gathers on an object, it forms positive static electricity. When the negative charge gathers on a certain object, it forms negative static electricity. However, whether it is positive or negative static electricity when the electrostatic object contacts the zero potential object (grounding object) or the object with a potential difference, the charge transfer will occur, which is the phenomenon of spark discharge that we see every day.
For example, in northern winter, the weather is dry, the human body is easy to carry static electricity when contacting other people or metal conductors, the discharge phenomenon will appear. People will have a sense of electric shock and sparks can be seen at night. This is the reason why chemical fiber clothing rubs against the human body and brings positive static electricity to the human body. (if we have basic physics knowledge, we know that rubber rod rubs with fur, rubber rod is negatively charged, fur is positively charged).
2、 Generation of static electricity
Static electricity is not static electricity, but electricity temporarily staying somewhere. When people stand up on the carpet or sofa, the human body voltage can also be more than 10000 volts, and the static electricity of the rubber and plastic film industry can be as high as 100000 volts.
Any two objects of different materials contact and then separate can produce static electricity, and the common method of generating static electricity is friction electricity. The better the insulation of the material, the more likely to generate static electricity. Because air is also made up of atoms, it can be said that static electricity can be generated at any time and anywhere in people's lives.
It is almost impossible to eliminate static electricity completely, but some measures can be taken to control static electricity so that it does not cause harm.
When two different objects touch each other and rub against each other, the electrons of one object are transferred to the other and are positively charged because of the lack of electrons, while the other is negatively charged with some residual electrons, and the object is charged with static electricity.
3、 Harm of static electricity
A lot of it comes from electrostatic hazards.
The second major hazard of static electricity is the possibility of an explosion of some flammable objects ignited by electrostatic sparks.
The generation of static electricity in industrial production is inevitable, and its harm can be attributed to the following two mechanisms
The first is the harm caused by electrostatic discharge (ESD)
(1) Cause the malfunction or misoperation of electronic equipment and cause electromagnetic interference.
(2) Breakdown of integrated circuits and precision electronic components, or promote the aging of components, reduce the yield of production.
(3) High voltage electrostatic discharge causes electric shock and endangers personal safety.
(4) It is easy to cause explosion and fire in the production place with many inflammable and explosive materials, dust, and oil mist.
Second, the harm caused by electrostatic attraction (ESA)
(1) Electronic industry: adsorption of dust, resulting in integrated circuit and semiconductor components pollution, greatly reducing the yield.
(2) Film and plastic industry: uneven winding of film or film; dust contamination of film and CD plastic disc, affecting quality.
(3) Papermaking and printing industry: uneven paper winding, inaccurate overprint, serious dirt absorption, and even paper bonding, affecting production.
(4) Textile industry: causes the root silk to float, entangles the flower to break the end, the yarn tangles and so on harm.
4、 Methods to eliminate static electricity
Use of anti-static equipment: static bracelet, electrostatic gloves, electrostatic clothing, electrostatic cap, electrostatic table pad, electrostatic floor
Increase humidity: wash hands frequently, take a bath frequently and change clothes frequently, which can effectively eliminate the static electricity accumulated on the human body surface. Workshop humidity control.
Grounding: to keep the human body connected with the earth, the static electricity of human body can be introduced into the earth
Use antistatic materials: static rubber basin, static material box, static trolley
Discharge static electricity: holding the metal door frame can discharge the static electricity from the body at any time when the friction generates static electricity,