The cause of static electricity in the LED production p […]
The cause of static electricity in the LED production process
From a microscopic point of view, according to the theory of atomic physics, when the material is electrically neutral, the material is in an electric equilibrium state. Because of the gains and losses of electrons generated by the contact of different material electrons, the material loses its electric balance and generates an electrostatic phenomenon.
From the macro perspective, the reasons are: friction between objects heat, stimulate electron transfer;
Contact and separation of objects produce electron transfer; electromagnetic induction creates an unbalanced distribution of the surface charge of the object; the combined effect of friction and electromagnetic induction.
Electrostatic voltage is generated by the contact and separation of different kinds of substances. This effect is known as frictional electrification, and the voltage generated depends on the characteristics of the materials that rub against each other. As the LED product is in the actual production process, the main body is the direct contact and indirect contact between the human body and related components to generate static electricity. Therefore, according to the characteristics of the industry we can do some targeted static electricity prevention measures.
1. The basic idea of ESD electrostatic protection
(1) From the aspect of component design, design electrostatic protection into LED devices, such as high-power LEDs. Designers design electrostatic protection diodes on silicon wafers carrying GaN-based LED chips flipped. Then silicon chips not only serve as GaN. The carrier substrate also plays an ESD protection role, so that the device ESD packaged using this chip reaches several kV. Its advantages are direct anti-ESD capability of the company, and it also simplifies the electrostatic protection measures for package production and device installation. The disadvantages are increased costs, increased volume, complicated chip production processes, and special production facilities. The value of LED devices.
(2) From the production process, there are two ways to prevent static electricity; 1 to eliminate the static electricity generated materials and processes. Through the selection of materials, the path of static electricity generation does not exist or is reduced. Eliminating the generation and accumulation of electrostatic discharge from the source is one of the effective basic methods for electrostatic protection. 2 Vent or neutralize to prevent electrostatic discharge. Since all the ways to generate static electricity cannot be completely eliminated, we need to safely discharge or neutralize the static electricity that must occur to prevent the occurrence of electrostatic discharge.
2, esd electrostatic protective grounding technology
Grounding is the direct discharge of static electricity through a wire connection to the earth. This is the most direct and effective method for preventing static electricity. The effectiveness of most electrostatic protection systems depends on the quality of the grounding ground. Electrostatic grounding technology is the main link in the electrostatic discharge process. The quality of the system grounding will directly affect the charge release capability. 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 current drop occurs when the current flows through the ground wire, and the potentials of the ground wires are the same. The electrostatic ground wire in the work area should be a special electrostatic ground wire and must not be shared with other ground wires. Anti-static grounding is one of the important indicators in the infrastructure construction of a factory.
3. Esd ESD operating system
In the operation of the electrostatic sensitive device, an antistatic pad made of a material having static electricity and static electricity dissipating function should be laid on the work table. Bring all terminals, tools, instrumentation, and human bodies in contact with the device to a consistent potential and quickly discharge the electrostatic energy through grounding.
4. Human body anti-static system
The human body anti-static system is mainly composed of an anti-static wrist strap, anti-static overalls, footwear, etc. If necessary, it also needs to be supplemented with anti-static work caps, gloves, and foot covers. This overall anti-static system combines electrostatic discharge, neutralization, and shielding. The anti-static wrist strap is made of static conductive material, which directly contacts the skin and directs the body's static electricity away. Therefore, the wrist strap must be in good contact with the skin during application, and the instantaneous static voltage on the skin should be 100V. Anti-static work chairs use electrostatic conductive fabrics as the fabrics. They do not generate static electricity in contact with people, and they can discharge the static electricity from the body itself and discharge them quickly, leading to people's land and playing the role of electrostatic protection.
5. Esd electrostatic protection during production
The production process of LED from chip to package application (ying1 yong4) is more complicated. As far as anti-static electricity is concerned, it is a process of comprehensive management. It should penetrate into every link of production, and put forward different countermeasures according to the process requirements of various production processes. To achieve effective electrostatic protection of the device.
6. Ion fan
Insulators tend to be prone to static electricity, and static electricity on insulators cannot be eliminated by grounding. Ionic action is often used to neutralize static electricity on these insulating materials. An ion blower is a device that blows out ionized gas streams. It is used to neutralize any charge accumulated on the insulating material, providing an equipotential work area.
7. Esd electrostatic protection other precautions
(1) When testing GaN-based LEDs, besides grounding the tester, you must also understand the test circuit of the tester. In particular, the open-circuit voltage of the constant-current test must not be too high to prevent the LED from failing due to the negative feedback pulse voltage.
(2) The table shows the state of static electricity in several states of the human body. It is not difficult to see that under the same conditions, the humidity (air humidity) rises and the electrostatic potential U decreases, that is, the risk of ESD decreases, but it still exists. Therefore, static protection measures should not be relaxed and good work habits should be maintained.
(3) Packaging is the last link before the product leaves the factory. The quality of the packaging process directly affects whether the product reaches the user's hands whether it is a qualified product. The packaging should use anti-static shielding bags, which are used for packaging, transportation and storage of devices and have a certain moisture-proof effect.