Anti-static knowledge
Static electricity is an objective natural phenomenon, which can be produced in many ways, such as contact, friction, rushing, and so on. The basic process of its production can be summarized as: contact → charge → transfer → formation of an even electric layer → charge separation. The static electricity on the equipment or the human body can reach tens of thousands of volts or even hundreds of thousands of volts, and it often reaches hundreds to thousands of volts under normal operating conditions. The human body can carry thousands of volts or even tens of thousands of volts of static electricity due to factors such as its own actions and contact-separation, friction or induction with other objects. Static electricity is the result of the loss of balance between positive and negative charges in a local area. It is a kind of electric energy, which is retained in objects, and has the characteristics of high potential, low power, small current and short action time. The main measures of static control include: static leakage and dissipation, static neutralization, static shielding and grounding, and humidification.
The breakdown of components caused by electrostatic discharge is the most common and most serious electrostatic hazard in the electronics industry. It is divided into hard breakdown and soft breakdown. Hard breakdown is a one-time cause of dielectric breakdown, burnout or long-term failure of components; soft breakdown is caused by deterioration of device performance or decreased parameter indexes.
The transfer and storage of electrostatic sensitive components and printed circuit boards between processes in the production process must use anti-static feeding boxes, component boxes, turnover boxes, turnover trays, etc. To prevent the accumulation of static electricity from causing harm. Electrostatic sensitive components and printed circuit boards must be packaged as finished products with anti-static shielding bags, packaging bags, packaging boxes, strips, baskets, etc., to avoid electrostatic damage during transportation.
In the production process of electronic products, the components and components of finished products often come into contact with, separate from equipment and tools, and generate static electricity due to friction. Anti-static cushions, turnover carts, maintenance kits, tools, work chairs (stools), etc. must be used, and Through proper grounding, static electricity can be discharged quickly.
Friction electrification and human body static electricity are the two major sources of hazards in the electronics and microelectronics industries, but the generation of static electricity is not the hazard. The hazard lies in the accumulation of static electricity and the resulting electrostatic charge discharge, so it must be controlled. An object with static electricity will form an electrostatic field around it, which will produce mechanical effects, discharge effects and electrostatic induction effects. Due to the mechanical effect of static electricity, floating dust particles in the air will be adsorbed on silicon chips and other electronic components, which will seriously affect the quality of electronic products. Therefore, anti-static measures must be taken to purify the working space.
The walls, ceilings and floors of the clean room should be made of anti-static and non-dust materials, and a series of electrostatic protection measures should be taken for operators, workpieces and appliances.
In order to understand the situation of static electricity in the production process, determine the degree of static electricity in the production process, and inspect the quality of electrostatic protection products and equipment, it is necessary to measure static electricity and related parameters. The measurement of static electricity mainly refers to the measurement of static voltage, material resistance, ground resistance, static off decay period, static electricity quantity, static elimination performance, cloth charge surface density, etc.
Electrostatic protection is a systematic project. Omissions or errors in any link will lead to the failure of electrostatic protection. It must be guarded from time to time, and everyone should guard against it.