Basic idea of ESD electrostatic protection
Generally speaking, the basic idea of ESD electrostatic protection can be summarized into two aspects:
1. Component planning
In terms of component planning, electrostatic protection can be planned into LED equipment, such as high-power LEDs. The planner can plan an ESD protection diode on the silicon wafer that carries the GaN-based LED chip in an inverted manner. In this way, the silicon wafer not only serves as the carrying substrate for GaN, but also plays a role in ESD protection, making the equipment using this type of chip package ESD-resistant up to several thousand volts. The advantage of this method is that it can directly improve the equipment's resistance to ESD and simplify the ESD protection methods in the packaging and equipment installation processes. The disadvantage is the added cost, increased volume, complex chip production technology, and the need for specialized production equipment, making it suitable for high-value LED equipment.
2. Production technology
There are two ESD protection methods in production technology:
① Eliminate materials and processes that generate static electricity. By selecting materials, the path of electrostatic discharge can be eliminated or reduced from the source, which is one of the effective fundamental methods of ESD protection.
② Dissipate or neutralize static electricity to prevent electrostatic discharge. Since it is impossible to completely eliminate all paths that generate static electricity, it is necessary to safely dissipate or neutralize the static electricity that is about to occur to prevent electrostatic discharge.
In ESD electrostatic protection, grounding technology is a very important link. Grounding means directly discharging static electricity through a wire connection to the ground, which is the most direct and effective method in ESD protection. The effectiveness of most ESD protection systems depends on the quality of the grounding wire. Grounding technology is the primary link in electrostatic discharge technology, and the quality of the system's grounding will directly affect the discharge capability of the charge. The grounding wire should be able to withstand or provide a large amount of charge. The ideal grounding wire should be an excellent conductor, that is, the potential drop does not occur when the current flows through the grounding wire, and the potential at each point on the grounding wire is the same. The static grounding wire in the operating area should be a dedicated grounding wire and should not be shared with other wires. Anti-static grounding is one of the important goals in plant construction projects.
When operating static-sensitive equipment, an anti-static mat made of materials with static conductivity and static dissipation functions should be placed on the workbench to ensure that all terminals, objects, instruments, and human bodies that come into contact with the equipment reach a common potential and the static electricity can be quickly discharged through grounding.
The human body ESD protection system is mainly composed of anti-static wristbands, anti-static work clothes, shoes and socks, and when necessary, supplemented with anti-static work hats, gloves, and shoe covers. This comprehensive ESD protection system has the functions of static electricity dissipation, neutralization, and shielding. The anti-static wristband is made of static conductive materials and directly contacts the skin to directly discharge the static electricity of the human body. Therefore, it is necessary to have good contact with the skin when using the wristband to ensure that the instantaneous static voltage on the skin does not exceed 100V. The anti-static work chair is made of static conductive fabric, which does not generate static electricity when in contact with the human body, and can quickly discharge the static electricity carried by the human body, leading it to the ground, and plays a role in ESD protection.
In the production process of LED equipment from chip to packaging, ESD protection needs to penetrate into various links of production, and different countermeasures should be proposed according to the technical requirements of each production link to achieve effective ESD protection for the equipment. For the technical requirements of fixed individual devices (such as die bonders, wire bonders, test equipment, wave soldering equipment, etc.):
(1) The equipment should be well grounded;
(2) When necessary, anti-static mats should be placed around the equipment;
(3) Operators should wear anti-static clothing, hats, wristbands, etc.;
(4) When necessary, ion fans should be installed in key ESD protection areas.
An ion fan is a device that blows ionized airflow to neutralize any charge accumulated on insulating materials and provides a working area with an equipotential.
In ESD electrostatic protection, packaging is also a very important link. Anti-static shielding bags should be used for packaging, transportation, and storage of equipment, which have certain moisture-proof effects.
Finally, it should be noted that when testing GaN-based LEDs, in addition to grounding the tester, the tester's test circuit should also be understood, especially the open circuit voltage of the constant current test should not be too high to avoid the LED being affected by negative feedback pulse voltage and failing. In addition, under the same conditions, the increase in humidity (moisture in the air) reduces the static potential U, that is, the risk of ESD is reduced, but ESD protection methods should not be relaxed, and good work habits should be maintained.
Watt Smith
Collaborator & Editor
Hello! My name is Watt Smith working on Chipdatas. I write and share relevant articles on electronic components category.
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