How to do electrostatic protection in SMT production
(1) The surface of the equipment and tools should have a good ground
According to the national standard, the method of laying earth wires and setting up static piles is used to ensure that the company's production site has an independent earth connection structure. Use an AC impedance meter to measure the impedance between the static grounding wire and the grounding pile and the ground to be less than 10 Ω, in order to meet the anti-static standard requirements. This method is also called hard grounding.
(2) Protect various work surfaces and floor mats by means of 1 MΩ resistance grounding
Including employees using electrostatic wristbands to protect the human body through a 1 MΩ resistance grounding method. The purpose of grounding through a 1 MΩ resistor is to ensure that less than 5 mA is discharged to ground. This method is also called soft grounding.
(3) Elimination method of conductor static electricity
If there is static electricity on the conductor, the static current can be returned to the ground in the form of connecting a ground wire, and care should be taken to prevent the leakage current from being too fast or too large, causing damage to the SSD device. The static voltage must be reduced to a safe range below 100 V within 1 s.
Generally, for operation safety, connect the object and the earth wire through a 1 MΩ current limiting resistor to limit the discharge current to less than 5 mA.
(4) Static elimination method of insulating objects
① Increasing the ambient humidity in the workplace, making it difficult for static charges to accumulate on the surface of the object. It can also increase the surface conductivity of non-conductor materials and accelerate the flow of charge of e799bee5baa6e997aee7ad94e78988e69d8331333363393731.
②Using active static elimination agent, often scrub the surface of objects and instruments to quickly remove the static charge on the surface of various objects.
③The ion wind nozzle is installed near the worktable and the chip head, which uses the high voltage to ionize the charge in the air and neutralize the electrostatic charge on the surface of the object, so as to achieve the purpose of eliminating static electricity, and has the characteristics of rapid and stable.
④Equipment that is prone to static charge can be shielded with an electrostatic shield and connected to a ground wire.