LED electrostatic problems and solutions
1. Static electricity is an electrostatic charge that is excessive or insufficient on the surface of an object. It is a kind of electric energy. Anti-static solution
Static electricity is the result of a loss of balance between positive and negative charges in a localized range, and static electricity is formed by electron or ion transfer.
2. Static electricity is the relatively static charge of an object.
Static characteristics
High potential: up to tens of thousands to hundreds of thousands of volts, often operating hundreds of thousands and thousands of volts. Low battery: The electrostatic current is mostly microampere (mA). Short duration of action: microseconds. Affected by the environment: especially humidity, humidity rise, static electricity decline.
Electrostatic generation
Contact, friction, rushing, piezoelectric, temperature difference, freezing, electrolysis
Electrostatic hazard
Electrostatic discharge (ESD) causes breakdown of the PN junction of the LED, which is the main method of electrostatic hazard in the LED device packaging and application assembly industry. Electrostatic damage has the following characteristics:
1. Concealment: The human body cannot directly sense static electricity. Even if electrostatic discharge occurs, the human body may not have the feeling of electric shock. This is because the human body senses the electrostatic discharge voltage to be 2-3KV. In most cases, it is through testing or practical application that the LED device has been damaged by static electricity.
2. Latency: Electrostatic discharge may cause sudden or ineffective LED failure. Sudden failure causes permanent failure of the LED: short circuit. Potential failures can degrade the performance parameters of LEDs, such as increased leakage current. There is no cure for the hidden dangers of GaN-based LEDs after electrostatic damage.
3. Complexity: In the case of electrostatic discharge, the discharge power source is a space charge, so its stored energy is limited. Unlike the external power supply, it has the ability to sustain discharge, so it can only provide a short-lived partial blow. Wear energy. Although the energy of electrostatic discharge is small, the discharge waveform is complicated and it is troublesome to control. In addition, the LED is extremely fine, and the failure analysis is difficult, which makes it easy for people to mistake the electrostatic damage failure as other failures. Before the electrostatic discharge damage is not fully recognized, it is often attributed to early failure or unclear failure, thus unconsciously concealing The real reason for failure.
4. Severity: ESD potential failure only causes some parameters to deteriorate. If it does not exceed the qualified range, it means that the damaged LED may pass the final test without any notice, resulting in early failure, which is manufactured at various levels. For business, the result is the most detrimental. ESD occurs very rapidly with extremely high intensity. When the discharge current flows through the PN junction of the LED, the Joule heat generated causes the local medium between the two poles of the chip PN to melt, causing a short circuit or leakage of the PN junction.
Antistatic area design principle: It suppresses the accumulation of static charge and the generation of static voltage. Such as equipment, instruments, tooling does not use plastic, plexiglass, ordinary plastic bags.
1. Safely, quickly and effectively eliminate the static charge that has been generated. Use a corded anti-static wrist anti-static chair, car, and box.
2. Ground Anti-static floor, (anti-static terrazzo, anti-static floor) 105 ~ 1010, laying ground wire network.
3. Work station ESD protection materials should be used for countertops, work chairs and stools.
4. The human body wears anti-static clothing, shoes, wrists, etc. (1M).
5. Grounding
a. The anti-static working area must have a safe and reliable anti-static grounding device with a ground resistance of less than 4. The anti-static ground wire must not be connected to the power supply neutral line, and should not be shared with the lightning protection ground wire. When using the three-phase five-wire power supply, the ground wire can be used as an anti-static ground wire.
b. Work surface, floor mat, seat, stool and other ESD protection measures should be connected to the ground through the current limiting resistor. The wrist strap should be connected to the ground through the grounding point of the top surface of the workbench. Connected in series.
c. Anti-static working area grounding system, including current limiting resistor and connecting terminal should be connected reliably and have a certain current carrying capacity. The current limiting resistor should be selected to ensure that the leakage current does not exceed 5 mA and the lower limit is taken as 1 M Ω.
6. When the humidity is less than 60%, an anti-static operating system must be built.
7. Ionizers In the event that the static charge cannot be effectively vented, the ionizer can be used to prevent and accumulate charge on neutralizing components and other objects by positive and negative ions in the air. The ionization capacity is greater than 250V/s.
8. Humidification The humidifier can keep the humid air flowing and prevent the accumulation of static charge. This method is not suitable; the site that has harmful effects after humidification.
9. Packaging Electrostatic sensitive devices should be protected packaging; static sensitive device packaging equipment must use anti-static storage box, anti-static plastic bag.
10. Transportation and storage SSDs must be placed in anti-static containers (boxes, bags) and used with anti-static vehicles (cars). The warehouse needs to meet the requirements of the anti-static operating system. The SSD must be placed in an anti-static container. Keep away from static electricity, electromagnetic fields or the location of the radiation field during storage and transportation.
11, SSD components should be classified and put, static sensitive symbols symbol in accordance with GJB1649 regulations. E. Measurement method and timeliness of antistatic materials 1. Friction electrification method: cotton cloth 120 times/min 20 times. 2, resistivity measurement method, less than 1010W is better. 3, attenuation constant RC red plastic bag and red foam aging period of six months, can not be exposed to the sun, black anti-static box for 5 years, with IC plastic tube, also time-sensitive. F, problems in the production system site
LED assembly static static protection minimum requirements
surroundings
When the humidity of the air is controlled, less than 60%, the anti-static operating system must be strengthened.
The countertop anti-static tablecloth is well grounded and the effectiveness is checked regularly.
2. Machine, equipment, tools
Good grounding wire for machine, equipment and tools. (Cannot be shared with the static electricity ground of the human body to prevent electric shocks from machine, equipment and tools)
3. human body
The body is equipped with a rope anti-static wrist, well grounded, and tested daily for effective performance.
Check that the electrostatic wrist is in good contact with the human skin, and the grounding end is in good contact with the ground wire.
4. other
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 constant current test should not be too high, so as to prevent the LED from being damaged by the impact of the negative feedback pulse voltage.
5. Avoid and reduce material buildup and friction