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SMT production line must prevent damage from static electricity(2)

2020-4-13 Frome:Dongguan Huaxian Electronic Technology Co., Ltd.
As the damage of electrostatic discharge to components cannot be ignored, some commonly used anti-static methods are introduced below.            
Set up electrostatic safe working area:            
The basic equipment in this area includes worktable, anti-static table pad, wrist strap joint and grounding wire, etc. it is necessary to maintain certain humidity on site. Please refer to the guidance issued by American National Standards Institute (ANSI) to establish this area.
Safety measures for personnel:
◆ All personnel shall conduct anti-static test before entering the electrostatic safe work area, and can enter the site only after passing the test.
◆ Workers must wear anti-static clothing and work shoes.
◆ Other people wearing ordinary shoes should use conductive shoelaces, anti-static shoelaces or heel straps.
◆ Personnel directly contacting electrostatic sensitive elements must wear anti-static wrist strap.
Safety measures for materials:
◆ There should be more than two wrist strap joints on the anti-static table mat, one for the operator and one for the technical or inspection personnel.
◆ Do not place anything with high electrostatic potential, such as plastic box, rubber, cardboard, glass, etc.
◆ All conductive materials of workbench must be grounded
Storage and transmission of static sensitive components and circuit boards:
In addition to making every effort to create an anti-static working environment, the storage or transmission mode of static sensitive components is also very important. The most common way to deal with these components is to use an electrostatic shield made of Faraday cage concept, or an anti-static bag.
These items are made of metal or good conductor, which will lead the current to the ground without any damage. The design of the car is based on the Faraday cage concept, so it is not afraid to walk under the lightning strike, nor to hit.
Electrostatic shielding cage or electrostatic shielding cover: it is made of metal or good conductor, and the cage body is connected with the earth. The static or non-static power supply is led to the frame of the shielding cage and connected to the ground wire, so as to prevent the static electricity from entering the cage.            
Anti static bag: the outer layer of this translucent heat sealed bag is made of wear-resistant metal coating, and the inner layer is made of insulating material to protect electrostatic sensitive elements from potential electrostatic hazards. Although these portable bags can' t be grounded like electrostatic shielding cages, the effect is the same as long as they are placed on a workbench with grounding wires.            
A circuit board is stored in the anti-static bag and warning signs are pasted.
Anti-static tube: it is especially suitable for the integrated circuit with many pins. It can be placed in the conductive plastic tube which is made according to the shape of components. It can prevent both static electricity and mechanical wear. Then put the components into the conductive box to ensure that they are not subject to electrostatic interference.            
Anti static should not be taken lightly. Although some seemingly solid components, such as bipolar transistors, are unlikely to be damaged by electrostatic discharge, it does not mean they are completely immune. There are some newly developed high-speed components that can' t even withstand a voltage as small as three volts.            
Some components made of metal oxide semiconductors, such as special resistors and capacitors, are not afraid of static electricity, but will still be damaged by electrostatic discharge.            
In any case, as long as we follow the correct guidelines, implement all anti-static measures, and use the anti-static nozzle made of anti-static materials, we can eliminate the electrostatic risk on the production line.

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