How many kinds of ESD anti-static products
Anti-static products are divided into four categories: human body static protection, anti-static consumables, static detectors and static elimination instruments.
1. Basic ideas for general ESD protection
(1) From the aspect of component design, the electrostatic protection is designed into LED devices, such as high-power LEDs. The designer designs electrostatic protection diodes on the flip-chip silicon wafers carrying GaN-based LED chips. At this time, the silicon wafers not only act as GaN The carrier substrate also plays a role of ESD protection, so that the device ESDS packaged with this chip can reach several thousand volts. Its advantage is to directly improve the anti-ESD ability of the device, simplify the electrostatic protection measures in the process of packaging production and device installation; the disadvantage is that it increases the cost, increases the volume, the chip production process is complex and requires professional production equipment. It is suitable for high-value LED devices.
(2) From the aspect of production process, there are two ways of electrostatic protection;
① Eliminate the materials and processes that generate static electricity. Through the selection of materials, the path of static electricity generation is eliminated or reduced, and the generation and accumulation of static discharge is eliminated from the source. It is one of the effective basic methods of static electricity protection.
② Drain or neutralize to prevent electrostatic discharge. Because all the ways to generate static electricity cannot be completely eliminated, we need to safely discharge or neutralize the static electricity that will occur to prevent the occurrence of static discharge.
2. ESD electrostatic protection grounding technology
Grounding is to directly discharge static electricity to the ground through a wire connection. This is a more direct and effective method of anti-static measures. The effect of most electrostatic protection systems depends on the quality of the grounding wire. Electrostatic grounding technology is the main link in the electrostatic discharge process. The quality of the system grounding will directly affect the discharge capacity of the charge. The ground wire must be able to accept or provide a large amount of charge. The ideal ground wire should be a good conductor, that is, no potential drop occurs when the current flows through the ground wire, and the potential of all points on the ground wire is the same. The static ground wire in the work area should be a dedicated ground wire for static electricity, and cannot be shared with other ground wires. Anti-static grounding is one of the important indicators in plant infrastructure projects.
3. ESD electrostatic protection operating system
When operating electrostatic sensitive devices, an anti-static table mat made of materials with electrostatic conductivity and electrostatic dissipation functions should be laid on the workbench. Make all terminals, tools, instruments, and human bodies in contact with the device reach a consistent potential, and ground the static electricity to quickly discharge.
4. Anti-static system for human body
The human body anti-static system is mainly composed of anti-static wrist straps, anti-static work clothes, footwear, etc., and when necessary, it needs to be supplemented with anti-static work caps, gloves, foot covers and other items. This kind of integral anti-static system has the functions of static discharge, neutralization and shielding. The anti-static wrist strap is made of electrostatic conductive material, which can directly conduct static electricity away from the human body through direct contact with the skin. Therefore, the wrist strap must be in good contact with the skin when using it, so that the instantaneous electrostatic voltage on the skin is less than 100V. The anti-static work chair uses electrostatic conductive fabric as the fabric. They do not generate static electricity in contact with people, and can quickly discharge the static electricity of the human body, leading to the earth, and playing a role of static electricity protection.
5. ESD protection during production
The production process of LED from chip to packaging application is more complicated. As far as anti-static is concerned, it is a comprehensive treatment process. It should penetrate into all links of production, and according to the process requirements of each production link, different countermeasures should be proposed to achieve the Effective electrostatic protection of the device. Process requirements for fixing a single device (such as die bonder, bonding station, test equipment, wave soldering equipment, etc.):
(1) Each device should be well grounded;
(2) It is necessary to install anti-static mats around each area;
(3) The operator wears anti-static clothing, hat, wrist strap, etc.;
(4) If necessary, set up ion fans at key parts of static protection.
6. Ion fan
Insulators are often prone to static electricity. Grounding methods cannot eliminate the static electricity on the insulators. The effect of ions is usually used to neutralize the static electricity on these insulating materials. Ion blower is a device that blows out ionized airflow. It is used to neutralize any charge accumulated on insulating materials and provide an equipotential working area.
7. Other precautions for ESD protection
(1) When testing GaN-based LEDs, in addition to the grounding of the tester, it is also necessary to understand the test circuit of the tester, especially the open circuit voltage of the power supply for constant current test.
(2) The table shows the static electricity of the human body in several states. It is not difficult to see that under the same conditions, the increase in humidity (moisture in the air) reduces the electrostatic potential U, that is, the risk of ESD is reduced, but it still exists. Therefore, static protection measures cannot be relaxed, and good working habits should be maintained.
(3) Packaging is the next link before the product leaves the factory. The quality of the packaging technology directly affects whether the product reaches the user's hand or not. The packaging should be an anti-static shielding bag, which is used for the packaging, transportation and storage of the device and has a certain moisture-proof effect.