In the SMT process, electrostatic discharge will cause damage or failure of electronic components, with the improvement of IC integration and the gradual reduction of components, the impact of static electricity has become more serious.
According to statistics, among the factors that lead to the failure of electronic products, static electricity accounts for 8% to 33%, and the loss of electronic products caused by static electricity every year is as high as billions of dollars.
Therefore, in the SMT production, the implementation of electrostatic protection measures is very important, this article will be from the generation of static electricity to the protection of components and scenes, etc., detailed introduction of how to do electrostatic protection measures.
How is static electricity produced?
Electro Static Discharge (ESD) is a physical phenomenon that refers to the transfer of charge caused by the proximity or direct contact of objects with different electrostatic potentials. In charge transfer, there is a flow of charge that delivers enough electricity to offset the voltage.
The insignificant electrostatic phenomenon in life has a great impact on electronic components and electronic circuit boards, such as electrostatic breakdown may cause damage or failure of components, thereby affecting electronic products. So what are the common static electricity in SMT production?
Common principles of electrostatic generation
01 Friction power-on
When two different materials are rubbed against each other, one of them picks up an electric charge, forming a static charge.
02 Induction electrification
Under the action of electrostatic field, charge redistribution occurs on the object. For example, when an charged object is near an uncharged object, an electric potential difference is formed between the two, and this electric potential difference causes the charge to move on the uncharged object, resulting in a static charge on the uncharged object.
03 Capacitive electrification
Since the charged body with a certain charge is close to and separated from another object, the capacitance of the system will change, and the electrostatic potential on the charged body will change, forming static electricity.
Prevent static electricity from electronic components
Electrostatic sensitive electronic components generally have anti-static signs, and special attention should be paid to anti-static problems when the components with these signs are encountered in the production process.
Semiconductor integrated circuits are designed to take protective measures against electrostatic failure, which can provide electrostatic discharge design protection below 2000V for sensitive components, and can also increase protection resistance and embed diodes through circuit peripheral design to make it have stronger antistatic ability.
Forms of damage to electronic components
1, completely lost function
1) The electrical parameters of the device are seriously deteriorated and the original function is lost;
2) About 10% of the components damaged by static electricity.
2, intermittent loss of function
1) The performance is that the various electrical parameters of the device or product are still qualified, but its service life will be greatly shortened, its reliability will become worse, and it may completely fail in a subsequent damage;
2) About 90% of the components damaged by static electricity.
Common electrostatic damage scenarios
01 Placement element
When the component is placed on the patch board, due to the presence of electrostatic fields, the component may slip or deform from the placement position, resulting in defects or failures.
02 Electrostatic charge accumulation
Due to the metal shell and grounding device of SMT equipment, electrostatic charge will accumulate, and if the electrostatic charge is not released in time, it will cause damage to the component.
03 Pollution damage
Electrostatic charge can absorb impurities such as dust and oil, resulting in surface pollution of components or circuit boards, thus affecting their normal operation.
04 Adsorption damage
During handling, storage, or assembly, electrostatic charges can attach to components or other parts, causing them to fail to function properly or to be damaged.
Basic principles of electrostatic protection
Code of electrostatic protection
1. Use or install electrostatic sensitive components in electrostatic safe areas.
2. Use electrostatic shielding containers to transport and store electrostatic sensitive components or circuit boards.
3. Regularly check whether the installed electrostatic protection system is operating normally.
4. Ensure that suppliers understand and comply with the above three principles.
Electrostatic protection procedure
1, avoid electrostatic sensitive components and circuit boards and plastic products or tools together.
2, ensure that the work area ground and desk mat have enough conductive capacity, it is best to use conductive rubber desktop or use conductive tape to stick to the four sides of the table.
3, often check whether the grounding system is good, the ground cable must be correctly connected to the bus.
4, when using electronic tools or instruments, ensure that the tools or instruments used meet the requirements of electrostatic protection.
5, limit the use of plastic bags and foam boxes and other packaging materials, if you must use, but also to ensure that the packaging materials through conductive treatment or the use of metal materials made of packaging boxes.
6. Wear ESD clothes, shoes, ESD tools, gloves, and ESD bracelets.
7. Hire professionals trained in electrostatic protection to ensure that anti-static measures are correctly implemented.
8, regular electrostatic protection checks and tests to ensure the effectiveness of anti-static measures.
9, do not tie the overhand ring staff and guests close to the electrostatic protection workstation, once found violations, should immediately stop and report to the superior leadership.
10, if you find that there are problems or defects in the electrostatic protection system, you should immediately report to the superior leader or the person in charge of electrostatic protection, and take timely measures to improve and deal with, to ensure the effectiveness of the electrostatic protection system.
