Static electricity in the manufacture of electronic products
It appeared in many of our daily working situation, such as:
(1) The activity of the human body, static electricity generated by friction, contact and separation between people and clothes, shoes, socks, etc. is one of the main static power sources in the manufacture of electronic products. Static electricity in the human body is the main cause of hard (soft) breakdown of the device. The electrostatic voltage generated by human activities is about 0.5-2KV. In addition, the humidity of the air has a great influence on the electrostatic voltage, and it is increased by one order of magnitude in a dry environment. Table 2 shows the relationship between relative humidity and human body activity.
When the human body is charged and touched to the ground wire, a discharge phenomenon will occur, and the human body will produce different degrees of electric shock response. The degree of reaction is called the electric shock sensitivity. Table 3 shows the shock sensitivity of the human body during different static voltage discharges.
(2) When the chemical fiber or cotton overalls are rubbed against the work surface and the seat, an electrostatic voltage of 6000V or more can be generated on the surface of the garment, and the human body is charged. When contact with the device, it will cause discharge and easily damage the device.
(3) The insulation resistance of the rubber or plastic sole is as high as 1013 Ω. When it rubs against the ground, it generates static electricity and charges the human body.
(4) When the resin, paint film, and plastic film packaged device are transported in a package, the surface of the device and the packaging material can generate an electrostatic voltage of several hundred volts to discharge the sensitive device.
(5) Various packaging, cartridges, and turnovers made of polymer materials such as PP (polypropylene), PE (polyethylene), PS (polyvinylidene), PVR (polyurethane), PVC, polyester, and resin. Boxes, PCB racks, etc. may generate 1-3.5KV electrostatic voltage due to friction and shock, and discharge sensitive parts.
(6) Ordinary work surface, generated by friction to generate static electricity.
(7) The insulation resistance of concrete, waxed polished floor, rubber sheet and other insulating floors is high, and the static charge on the human body is not easy to leak.