Basic ideas and technical approaches to electrostatic protection
Electrostatic discharge can cause damage to the device, but by taking proper and appropriate ESD protection and control measures to establish an ESD system, the ESD can be eliminated or controlled to minimize damage to components. There are two basic ideas for electrostatic protection and control of sensitive devices:
1. (1) Prevent the accumulation of static electricity in places where grounding may occur, and take certain measures to avoid or reduce the occurrence of electrostatic discharge, or adopt the method of “leaking while generating side” to eliminate the accumulation of electric charge. The charge is controlled to the extent that it does not cause harm.
1. (2) Accumulate the accumulated charge quickly and reliably.
2.1 Process Control Method
Designed to produce as little static charge as possible during the production process. To this end, measures are taken from the aspects of process flow, material selection, equipment installation and operation management to control the generation and accumulation of static electricity, and to suppress the electrostatic potential and electrostatic discharge capability so as not to exceed the degree of damage. As in the semiconductor manufacturing process, the resistivity of the deionized water for rinsing must be controlled after the shallow junction forming process of the high speed device is completed. Although the higher the resistivity, the better the cleaning effect, but the higher the resistivity, the higher the static electricity generated on the chip. Therefore, it is generally controlled at a level slightly higher than 8 MΩ, and cannot be 16-17 MΩ for the initial process. In addition, in the choice of materials, the packaging materials should use anti-static materials, try to avoid untreated polymer materials.
2.2 Leakage method
It is designed to eliminate static electricity through leakage. Usually, electrostatic grounding is the leakage of electric charge to the earth; there is also a method of increasing the electrical conductivity of the object to cause the ground to leak along the surface or inside of the object, such as adding an electrostatic agent or increasing the humidity. The most common is the anti-static wrist strap worn by the staff and the static grounding post.
2.3 Electrostatic shielding method
According to the principle of electrostatic shielding, it can be divided into two types: internal field shielding and external field shielding. The specific measure is to isolate the charged body from other objects with a grounded screen cover, so that the electric field of the charged body will not affect other surrounding objects (inside field shielding); sometimes the shielded cover is used to surround the isolated object, so that It is protected from external electric fields (outfield shielding). For example, a GaAs device package uses a metal case or a metal film.
2.4 Compound Neutralization Method
It aims to eliminate the static charge by means of complex neutralization. The use of a grounding eliminator to produce a complex with a charged ion on the charged body to achieve neutralization. Generally speaking, when the charged body is an insulator, since the electric charge cannot flow on the insulator, the grounding method cannot be used to leak the electric charge. In this case, an antistatic eliminator must be used to generate the dissimilar ion to neutralize. This method is used to eliminate the electrostatic charge generated on the conveyor belt.
2.5 Clean measures
Designed to avoid intermittent discharges. To this end, the surface of the charged body and surrounding objects should be kept as smooth and clean as possible to reduce the possibility of intermittent discharge.