The harm of static electricity to the assembly of electronic equipment- Rio Tinto brand
Date: 2010/1/11 18:46
The harm caused by static electricity to the assembly of electronic equipment Hits: 3096 Published: 2009-01-18
First, electrostatic hazards can be divided into two categories: one is the adsorption of floating dust caused by electrostatic attraction; the other is the dielectric breakdown caused by electrostatic discharge.
During the manufacturing process of semiconductor components, due to the large amount of quartz and high-molecular appliances and materials used, its insulation is very high, and some unavoidable friction during use can cause its surface charges to continuously accumulate, The potential is getting higher and higher. Due to the mechanical effect of static electricity, in this case, it is easy to cause the floating dust in the workplace to be adsorbed on the chip surface, and small dust adsorption may affect the good performance of the semiconductor device.
2. Electrostatic discharge and dielectric breakdown
The starting and discharging power source of electrostatic discharge is space charge, so its stored energy is limited, so it can only provide transient breakdown energy. Although the energy of electrostatic discharge is small, its discharge waveform is very complicated and it is more troublesome to control. Soft breakdown of semiconductor devices is related to it.
The breakdown of components caused by static electricity is the main way of electrostatic hazards in electronic equipment, and it is the most common and severe hazard in the manufacture of electronic equipment.
Electrostatic discharge can cause hard or soft breakdown of the device. Hard breakdown is a permanent failure of the device, such as the output and input of the device open or short. Soft breakdown can degrade the performance of the device and reduce its index parameters and cause hidden troubles. Because the soft breakdown can make the circuit change from time to time (caused by the decrease of the index parameters), and it is not easy to find, it causes a lot of trouble for the whole machine to run and find the fault. When the soft breakdown occurs, the equipment can still work with "illness", the performance has not changed fundamentally, it is likely to pass the factory inspection, but it may cause another failure at any time. Multiple soft breakdowns can cause hard breakdowns and make electronic equipment operate abnormally.
The human body also generates static electricity. The human body's electrostatic discharge may cause the human body to be shocked and reduce work efficiency, and may cause secondary accidents (ie, device damage), so it should be paid sufficient attention.
In military training, the human body forms static electricity because the human body converts the consumed mechanical energy into electrical energy during activities. The human body is an electrostatic conductor. When the body is insulated from the ground (for example, the sole of the shoe being worn is an insulating material), the body forms a capacitance with the ground to store the charge. Its charging voltage is generally ≤50kV. When the charge accumulates to a certain level, it will discharge to form a spark once the conditions are mature, the instantaneous discharge voltage can reach thousands of kilovolts, and the discharge power can reach several thousand kilowatts.
When the human body is charged and discharged, the human body will have different degrees of reflection. This reflection is called the shock sensitivity. When the human body is subjected to electrostatic shock, although no major physical obstacles will occur, it may affect people's work efficiency, or cause mental stress and secondary damage.
Second, the anti-static of electronic equipment that should be paid attention to
Due to the rapid development of electronic equipment, small-scale and highly integrated devices have been mass-produced, which has led to smaller and smaller wire spacings, thinner insulation films, and lower breakdown voltages. However, the electrostatic voltage generated by electronic equipment in the process of production, transportation, storage, and transfer far exceeds its breakdown voltage threshold, which may cause breakdown or failure of the device, affect the technical indicators of the equipment, and reduce its reliability. .
The prevention of static electricity is mainly to suppress the generation of static electricity, accelerate the leakage of static electricity, and perform static neutralization. When a person wears non-conductive shoes, charges can be generated and accumulated due to walking and other activities, and can reach a potential of the kilovolt level. When two different objects come into contact with each other, a charge movement occurs at the interface, and positive and negative charges are arranged oppositely to form an electric double layer. If the objects are separated, an equal amount of charge of different polarity will be generated on each of the two objects. The principle to prevent this kind of static electricity is: Exclude as much as possible the main factors that generate static electricity (object characteristics, surface state, charging history, contact area and pressure, separation speed, etc.); make the objects in contact with each other in the charged sequence Position as close as possible; make the contact area and pressure between objects small, the temperature should be low, the number of contacts should be small, the separation speed should be small, and the contact status should not change sharply. Powder, liquid, and gas can generate static electricity due to friction during transportation. Therefore, measures such as limiting the flow rate, reducing the bending of the pipeline, increasing the diameter, and avoiding vibration should be adopted.