What are the main methods for handling static electricity in the electronics manufacturing industry?
As the technology level of the electronics industry continues to improve, product requirements for static electricity are getting higher and higher. Recently, a hot topic of discussion among Chinese people is that Huawei has been banned by the US ZF. In fact, Huawei had high requirements for product layout many years ago. Professionals develop the Kirin series of smart devices, Kunpeng series service CPUs for data centers; AI chipset series SoCs for artificial intelligence scenarios; chips for connection, etc. It can be seen from this that to make a high-quality product, it is necessary to Be prepared in advance, and the same is true for electrostatic protection. Do n’t wait until customers come to the factory to find out that this is not possible. Rectification is needed there. People who are sensible will be okay. They will give you the opportunity to rectify. Speak out in person, but directly PK off, not up to standard in electrostatic protection, and customers who have lost the opportunity to take orders are not a few, unfortunately!
What are the main methods for handling static electricity in the electronics manufacturing industry?
Before solving the problem, you must understand the static electricity and its hazards, so that you can do more effective electrostatic protection measures!
A. Generation and harm of static electricity
Static electricity is the product of electrons moving (including polarization and conduction) inside or between materials. Two different materials are in contact with each other. The distance between them is less than a certain distance, such as 10-25cm. Due to the tunneling effect, the electrons in the two materials pass through the interface and exchange with each other. When the exchange reaches equilibrium, a certain potential difference will occur between the materials, and equal amounts of positive and negative charges appear on both sides of the interface. If the two materials after contact are separated, the two materials will be charged with equal and negative charges respectively, which is the basic principle of static electricity generation.
There are three main ways to generate static electricity: triboelectric charging, conductive charging, and induction charging.
a. Friction electrification: Because objects of different materials are separated after contact, due to the different atomic nuclei's ability to bind electrons, when two different materials are in contact or rubbed, the peripheral electrons will be transferred to the party with the larger ability to bind, resulting in a A material is positively charged and another material is negatively charged.
b. Conductive charging: Because a conductor can move electrons freely on its surface. When in contact with a charged body, electrons will be transferred from the charge, which will cause the charge balance between the two, thereby forming an electrostatic phenomenon.
c. Inductive charging: refers to the induction of nearby electric fields. For a conductor, electrons move freely on the surface of a conductive material. If the conductor is placed in another electrostatic field, the same-type charges repel each other and the opposite-type charges attract each other. Transfer will occur, and the conductor will become charged due to the imbalance of the positive and negative charges caused by the induction of the electrostatic field.
From the basic principles and methods of static electricity generation, it can be seen that in the entire manufacturing process of general electronic products, many processes may generate static electricity. In the electronics manufacturing process, static electricity may be generated by operators, work surfaces, tools, components, and packaging. As long as static electricity exists, there must be an ESD (Electro-Static Discharge) process, which is mainly caused by instantaneous discharge The noise generated by the induction of the circuit and the discharge current cause the reference ground potential such as the product ground and signal ground potential to fluctuate and fluctuate, thereby causing interference to the normal operation of the circuit.
Static electricity hazards have different characteristics from general lightning protection or electromagnetic interference:
a. Concealment: The general electrostatic discharge is not perceived by the human body, but the components are damaged unknowingly.
b. Potentiality and accumulation: Some components have only shown some performance parameter degradation after being damaged by electrostatic discharge, but have not yet failed. It may cause failure under continuous use, so static electricity has potential damage to the device.
c. Randomness: Electrostatic discharge damage of electronic components may occur at any step, step, and contact with any relevant charged human body (or object) from processing to manufacturing to use and maintenance. It has strong randomness. .
d. Complexity: Some electrostatic damages are also difficult to distinguish from damages caused by other reasons, causing people to mistake electrostatic damage failures as other failures, thus making wrong judgments.
For the assembly of electronic products, the harm of static electricity seriously affects the quality, yield and reliability of the product. It is necessary to carry out system anti-static measures in the clean room for electronic product assembly to reduce the degree of electrostatic harm in the production process. low.
B. Static electricity protection
Good electrostatic protection usually requires following three basic principles:
(A) reduce or prevent the chance of electrostatic charge buildup;
(B) Establish a safe static discharge path;
(C) Introduce necessary and effective static monitoring equipment for system static monitoring.
B.1 Good grounding system
To reduce or prevent the chance of electrostatic charge accumulation and the foundation of a safe electrostatic discharge path, a good electrostatic grounding system is required. Electrostatic grounding refers to passing an object with static electricity or an object that may generate static electricity (non-insulator) through a conductive body Form an electrical circuit with the earth, so that it is at the same potential level as the earth. The purpose is to speed up the flow and leakage of static electricity, so that the electrostatic charge of the charged material can be effectively and smoothly discharged to avoid static electricity accumulation.