Methods for Implementing Anti-static Layout in Production Workshops
The hazards of static electricity are obvious, and more and more manufacturers are now implementing various levels of anti-static measures and projects. However, it is important to recognize that a complete and effective anti-static project must be tailored to the specific circumstances of different enterprises and different work objects. Anti-static measures should be systematic and comprehensive; otherwise, they may be counterproductive or even cause destructive backlash. Below, we discuss specific anti-static methods for workshops.
I. Anti-static Work Area
1. Floor Material: The floor should be made of static-conductive materials, such as anti-static raised flooring or anti-static mats laid on ordinary flooring, and effectively grounded. Direct use of wooden floors or laying wool, hemp, synthetic fiber carpets, and ordinary floor coverings is prohibited.
2. Grounding: a. The anti-static system must have an independent and reliable grounding device. The grounding resistance should generally be less than 10Ω, and the installation and testing methods should comply with the requirements of GBJ 97. b. The anti-static grounding wire must not be connected to the power supply neutral wire and must not be shared with the lightning protection grounding wire. c. A three-phase five-wire power supply system should be used, with the earth wire serving as the anti-static ground wire (but the neutral and ground wires must not be mixed).
d. The cross-sectional area of the main grounding conductor should be no less than 100 mm²; the cross-sectional area of the branch conductors should be no less than 6 mm²; the grounding wires for equipment and workbenches should use multi-strand plastic-coated conductors with a cross-sectional area of no less than 1.25 mm², and the grounding wire color should preferably be yellow-green.
e. The main grounding conductor should be connected by brazing.
f. The connection terminals of anti-static equipment should ensure reliable contact and easy installation and removal; various clamp-type connectors, such as snap-fit connectors and plug sockets, are permitted.
g. Workplaces with high requirements for grounding resistance should install a grounding system monitoring and alarm device, such as our company's SL-038A grounding system monitoring and alarm device, which can monitor the contact between the ground wire and the earth at any time.
3. Ceiling materials: Anti-static materials should be selected. Generally, gypsum board products are permitted, but ordinary plastic products are prohibited. 4. Wall Coverings: Antistatic wallpaper should be used. Generally, gypsum board or lime paint is permitted, but ordinary wallpaper and plastic wallpaper are prohibited.
5. Humidity Control: a. The relative humidity of the antistatic work area should ideally be no less than 50%. b. Humidifiers may be used to increase humidity, provided they do not cause harmful effects on the products. c. The humidity in computer rooms should comply with the relevant provisions of GB 2887, and similar computer rooms should also comply with this provision.
6. Area Boundaries: The boundaries of the antistatic work area should be clearly marked, and warning signs should be displayed in prominent locations. Warning signs should comply with GJB1649. An ionized air bath should be installed at the entrance of the work area.
7. Static Electricity Sources: Products that easily generate static charges are prohibited from use or contact within the antistatic work area. These include painted or varnished work surfaces, ordinary plastic laminate surfaces, ordinary vinyl and resin-surfaced flooring, plastic and ordinary linoleum, and polished and waxed wood flooring. General vinyl resin work clothes, hats, shoes; general polyester, synthetic fiber and nylon fabrics; plastic and general rubber-soled shoes; operating tools and equipment; general plastic boxes, racks, bottles, trays and paper products; general foam and general mobile tools; compressors, spraying equipment, evaporation equipment, etc.
II. Application and Management of Antistatic Products in Production Sites
1. Grounding
Grounding involves connecting antistatic products or other equipment to a ground wire. An "independent" ground wire is established using buried grounding. The resistance between the ground wire and the earth should be <10Ω. Its function is to discharge any charge that may accumulate on conductors. For static electricity accumulated on conductors (such as the human body), grounding is usually used to conduct it away.
Grounding is implemented through the following methods:
① Grounding the human body through a wrist strap.
② Grounding the human body through antistatic shoes (or shoelaces) and antistatic flooring.
③ Grounding the workbench surface.
④ Grounding testing instruments, tool holders, and soldering irons.
⑤ Grounding antistatic flooring and mats.
⑥ Grounding of anti-static transport carts, boxes, and racks whenever possible.
⑦ Grounding of anti-static chairs.
2. Anti-static Safety Workbench: ① Consists of a workbench, anti-static mat, wrist strap connector, and grounding wire. If necessary, anti-static equipment, such as an ionizer produced by our company, should also be provided. ② The anti-static mat should have at least two wrist strap connectors, one for operators and one for technicians/inspectors. ③ Plastic boxes, rubber, cardboard, glass, and other easily static-generating items are not allowed to be piled on the anti-static safety workbench. Drawings and documents should be placed in anti-static document bags.
3. Static Electricity Elimination Equipment: An ionizer should be placed on the product assembly workbench where static electricity is easily generated. Blowing the ionizer onto the products can quickly eliminate static electricity generated at any time.
4. Anti-static Wrist Straps: Personnel directly handling static-sensitive devices must wear anti-static wrist straps. The wrist strap should have good contact with the skin, and the wrist strap system's resistance to ground should be within the range of 750KΩ-10.5MΩ. Antistatic wrist straps should be regularly tested for damage using a wrist strap tester. Our company's wrist strap tester can be used. Companies with the resources or higher requirements should ideally use an online wrist strap monitoring device, as this connects the wrist strap to a ground wire, allowing for real-time detection of wrist strap damage and proper worker wearing.
5. Antistatic Clothing: Personnel entering antistatic work areas and those handling static-sensitive devices must wear antistatic work clothes, especially in dry environments with relative humidity below 50% (such as winter). The fabric of the work clothes should comply with relevant national standards.
6. Antistatic Shoes: Personnel entering antistatic work areas should wear antistatic shoes. Those wearing ordinary shoes should use conductive shoe straps, antistatic shoe covers, or heel straps. Antistatic shoes should be regularly tested for their antistatic performance using a human body comprehensive tester. Our company's SL-031 human body comprehensive tester can be used.
7. Antistatic Socks: Many companies neglect the importance of antistatic socks, which is incorrect. When wearing anti-static shoes, it's best to wear anti-static socks. If anti-static socks are unavailable, cotton socks can be worn, but nylon socks should be avoided. Nylon socks have poor conductivity and will prevent static electricity from being conducted to the anti-static shoes. Sometimes, when testing a pair of qualified anti-static shoes with a human body comprehensive tester, the resistance is found to be too high; this is because nylon socks are worn.
8. Anti-static capacitors: Component storage bags, turnover boxes, PCB loading and unloading racks, etc., in the production area should have anti-static protection. Metal and ordinary containers are not allowed. If necessary, containers used for storing components should be grounded.
9. Conveyor belts and drive shafts used on the production line should be equipped with anti-static grounded brushes and support rods. Static elimination equipment, such as ion fans and ion bars produced by our company, can be used on the surface of the conveyor belt.
10. Assembly fixtures, testing fixtures, welding tools, and various instruments used in the production area should all have good grounding wires.
11. Human Body Comprehensive Tester: A human body comprehensive tester should be installed at the entrance of the production area. Every person entering the production area must undergo an anti-static test and pass it before entering. Our company's human body comprehensive tester can test the overall resistance of anti-static shoes, wrist straps, and the human body.