Clean room static control
1. Basic principles of static control
(1) Determine the static control level
(2) Minimize the generation of static charge
(3) The method of venting and neutralization accelerates the dissipation of static charge and prevents the accumulation of static electricity
(4) Protect the product from ESD damage
2. Determine the level of static control
(1) Classification of electrostatic susceptibility of components, components and equipment
Level 1: easily damaged by 0-1999V electrostatic voltage
Level 2: easily damaged by 2000-3999V electrostatic voltage
Level 3: easily damaged by 4000-5999V electrostatic voltage
If the sensitive static voltage is greater than 16000V, it is not necessary to take anti-static measures.
(2) Classification of electrostatic protection work area
Class A: Allow the electrostatic potential to the ground to not exceed ±100V
Class B: Allow the electrostatic potential to the ground to not exceed ±1000V
In the actual project, the electrostatic potential does not exceed 3 levels of the electrostatic sensitive voltage of the corresponding components, components and equipment such as 100V, 500V, and 1000V.
3. Minimize the generation of static charge as much as possible
This is the first step in the trilogy of static control. In this clean working environment, the best measures are:
(1) Try to use equipment with similar properties to reduce electrostatic charge generated during the contact friction separation process;
(2) Try to use static conductive or static dissipative materials to reduce the accumulation of static charges during the process of contact friction and separation;
(3) Try to use a production process that reduces electrostatic charge generated by contact friction separation.
4. Release and neutralization
This is the first step in the three-step process of controlling static electricity. The usual measures in the clean room of microelectronics production are grounding, using conductive or dissipative materials to discharge static charges, and ionizing dissipators to neutralize static charges.
(1) Grounding
The clean room should be equipped with an independent electrostatic grounding system (including ground grounding metal mesh support system, production line workstation grounding support system), so that the metal shells of all equipment in the room, metal supports for mobile equipment, anti-static equipment, etc., can safely and effectively discharge static charges. Put it on the ground. The staff’s charged electricity is grounded through a wrist strap, and is discharged to the ground through an anti-static shoe or heel strap and then through an anti-static ground. Ground, walls, ceilings, partitions, etc. are hard grounded, while equipment shells, mobile equipment (cars, chairs, shelves, etc.), workbenches, etc. are soft grounded.
(2) Ionized Xiao Electric
Components and PCBs produced and assembled in clean rooms, production lines, and workstations are always unavoidable that there are some insulated conductors and insulating dielectric materials (such as most ordinary plastics) that cannot be grounded. In some environments, ionizing eliminators are often used to locally dissipate the static charges on these objects, and more often by means of air ionization to neutralize the static charges on the insulating medium and isolated conductors.
(3) Static electricity and static dissipative materials
Static electricity conductive materials and static dissipative materials are also very good static charge discharge materials due to their static electricity conductivity, and are safer than metal conductor discharges. They are usually used as floors, walls, workbenches, and turnover containers. , Tweezers, brushes and other anti-static equipment.
5. Prevent ESD and protect products
This is the last step in the trilogy of controlling static electricity. In the clean room of microelectronics production, in order to prevent ESD from occurring on electrostatic sensitive components or components, PCBs, one method is to provide suitable grounding or shunts for components and components to "dissipate" the static electricity that exists on the product. Charge; another method is to use appropriate packaging methods and materials to handle the packaging and transportation of electrostatic sensitive devices. These materials can effectively shield the intrusion of electric charges into the product and reduce the static charge generated by the movement of the product in the packaging box.
Internationally, semiconductors, flat liquid crystal displays, and optoelectronics have developed rapidly, with higher and higher integration levels, thinner chip wire diameters, and higher and higher requirements for anti-static. The American ESD Association has begun to revise the ANS ESD S 20.20-1999 electrostatic discharge control program, and has made some amendments to the SSD electrostatic susceptibility classification.
This gives component users a warning, no matter when personnel or equipment is making equipment, tell you the environmental control requirements that can be needed. If the allowable voltage in the EPA area reaches 25V, I am afraid that our existing anti-static equipment, equipment, tools and engineering will have to go through hard work.