Anti-static technical requirements and anti-static process
(1) Basic requirements
① Floor materials
a. It is prohibited to directly use wooden floors or lay wool, linen, chemical fiber carpets and ordinary floor leather.
b. The floor should be made of electrostatic conductive materials, such as anti-static raised floors or anti-static mats on ordinary floors, and effectively grounded.
c. It is allowed to use terrazzo floors that have been specially treated, such as laying ground wire mesh in advance, carburizing or spraying antistatic agents on the floor.
② Humidity control
a. The relative humidity of the anti-static work area should not be less than 50%.
b. Under the premise of not causing harmful effects on the product, it is allowed to use humidification equipment to spray agents or water to increase the humidity of the environment.
(2) Technical requirements for electrostatic grounding
Electrostatic grounding technology is the main link in the electrostatic leakage process. The quality of the system grounding will directly affect the charge release ability.
① Ground wire
The ground wire refers to a material that can accept or provide a large amount of charge, such as the earth, equipment base, casing, etc. The ideal ground wire should be a good conductor, that is, when current flows through the ground wire, no potential drop occurs, and the potential of each point on the ground wire is the same. The ground wire should be laid to each position. The material can be a 3mm thick and about 25mm wide copper strip or a copper core soft wire with a cross-sectional area greater than 4mm~6mm, so that the static charge of electrostatic equipment and human body can be leaked smoothly. Anti-static grounding is one of the important indicators in factory infrastructure projects. The static ground in the work area should be set as a dedicated static ground and must not be shared with other ground wires.
② Grounding resistance is the contact resistance between the grounding body and the earth. It is a standard for the quality of grounding. The maximum value of the static charging current I in general industrial production is 10-4A. The safety voltage is U=100V, so the grounding resistance R≤U/I = 10^6Ω.
(3) Static control method: Static control should take different measures according to different situations and different positions.
① Anti-static technology for fixed positions
An anti-static leakage process should be used for fixed positions. An anti-static control position becomes an anti-static point, and a production line constitutes a safe operation area. A safe operation area includes: a. Grounding busbar; b. Anti-static floor mat; c. Anti-static table mat; d. Anti-static wrist strap; e. Anti-static tools (such as electric soldering iron, etc.). The above five must be well grounded to be effective.
② Anti-static technology for mobile positions
Mobile positions are divided into three types: fully mobile, semi-mobile, and fixed when mobile. Mobile positions can use the electrostatic leakage method and the composite neutralization method to cross-use, and the process control method can be supplemented with a complete process plan (such as anti-static packaging and transfer vehicles for items when picking materials, etc.).
③ Process requirements for fixed single equipment:
a. The equipment should be well grounded;
b. Anti-static floor mats should be laid around necessary equipment;
c. The operator should wear anti-static clothing, hats, wrist straps, etc.
(4) Anti-static requirements for each major link in the production process
①Main links in production
The main links in production are: device procurement → factory inspection → aging screening → bulk warehouse management → material collection → material preparation → batching → installation → commissioning → high temperature aging → inspection → packaging → finished product storage → transportation → to users. Anti-static safety points should be placed according to different production links.
②General requirements for anti-static safety areas
a. The entrances and exits of the anti-static safety area should be clearly marked as warnings, and anti-static shoe covers should be provided at the entrance to allow outsiders without anti-static protection measures to enter the work area safely.
b. The room temperature in the safety area should be controlled between 150°C and 200°C, and the relative humidity should be between 50% and 70%. It is strictly forbidden to operate electrostatic sensitive devices in an environment with a humidity of less than 30%.
c. High-voltage operations should be avoided in the anti-static working area.
d. Anti-static facilities in the safety area must not be moved or dismantled at will, and the working surface in the safety area must be well conductive.
e. Non-productive items (such as newspapers, books, food, handbags, etc.) are prohibited from being placed on the work surface in the operation area.
f. Drawings and materials used in the operation area must be placed in anti-static plastic bags to prevent the generation of static electricity when reading. Workers in the electrostatic safety area must wear anti-static work clothes and anti-static shoes.
g. Personnel in non-working areas are not allowed to enter without permission. Those who are allowed to enter must release static electricity at the entrance and wear anti-static clothing, shoes or shoe covers and other anti-static items. When entering, they must not touch the components, components and product terminals at will.
③Protection requirements for electrostatic sensitive devices in transportation, storage and custody
a. Electrostatic sensitive devices should be handled with care during transportation and should not be handled roughly to avoid damage to the device or peeling of the packaging.
b. All pins of electrostatic sensitive devices should be at the same potential during transportation.
c. The relative humidity in the warehouse where electrostatic sensitive devices are stored shall not be lower than 30% to 40%. The original packaging should be kept during the storage of electrostatic sensitive devices. If the original packaging needs to be replaced, it is necessary to use anti-static containers. Non-anti-static equipment must not be used to package or hold electrostatic sensitive devices.
d. Anti-static containers must have obvious anti-static labels. Anti-static signs should be posted in obvious locations in the warehouse where electrostatic sensitive devices are stored as a warning.