LED electrostatic failure principle and detection method

With the increasing competition in the LED industry, LED quality has received unprecedented attention. During the manufacture, transportation, assembly and use of LEDs, production equipment, materials, and operators are likely to cause electrostatic (ESD) damage to the LEDs, leading to premature LED leakage current increase, light attenuation, and even dead lights. Static electricity has a very important impact on LED quality. The antistatic index of LED is not only simply reflecting its antistatic strength. The antistatic ability of LED has a great relationship with its leakage value and overall reliability, and it is a comprehensive reflection of overall quality and reliability. Because of the high anti-static LED, its optical and electrical properties will be good.

LED electrostatic failure principle and detection method

LED electrostatic failure principle:

Due to the different levels of static electricity in the environment, a certain amount of electrostatic charges having opposite polarities are accumulated at both ends of the PN junction of the LED chip by electrostatic induction or direct transfer to form different degrees of electrostatic voltage. When the electrostatic voltage exceeds the maximum withstand value of the LED, the electrostatic charge will discharge between the two electrodes of the LED chip in a very short time (nanoseconds), thereby generating heat. The conductive layer inside the LED chip and the PN junction light-emitting layer form a high temperature of 1400 ° C or higher, and the high temperature causes local melting into small holes, thereby causing leakage, darkening, dead light, short circuit, and the like of the LED.

LEDs that are damaged by static electricity often cause dead lights and electric leakage. Slight electrostatic damage, LED generally has no abnormalities, but at this time, the LED has a certain hidden danger, when it is subject to secondary electrostatic damage, then there will be a chance of dark, deadlights, leakage. Through case analysis and summary, when the LED chip is subjected to slight, undetected electrostatic damage, it is necessary to scan the electron microscope to enlarge it to more than 10,000 times for further diagnosis to prevent a higher probability of failure.

Antistatic index depends on the LED chip, but the LED lamp is more susceptible to electrostatic damage.

The anti-static index of the LED lamp bead depends on the LED light-emitting chip itself, which is basically independent of the encapsulation material's expected packaging process, or the influence factor is small and very subtle; the LED lamp is more susceptible to electrostatic damage, which is separated from the two pins. The relationship, the distance between the two electrodes of the bare chip of the LED chip is very small, generally, less than one hundred micrometers and the LED pin is about two millimeters. When the electrostatic charge is to be transferred, the larger the spacing, the easier to form a large potential difference, that is, high voltage. Therefore, it is often more prone to electrostatic damage accidents after being sealed into LED lights.

The good antistatic index is a comprehensive reflection of the comprehensive performance of LED

The antistatic index of LED is not only simply reflecting its antistatic strength. Anyone who knows the design and manufacture of LED chips knows that the antistatic ability of LED chips has a lot to do with its leakage value and overall reliability. A comprehensive performance of comprehensive quality and reliability, because LEDs with high antistatic ability, its optical characteristics, and electrical characteristics will be good.

The antistatic index of LEDs not only means that it can be applied to various products and various environments, but also the reliable performance of LED comprehensive performance. According to different brands of LED anti-static indicators, LED anti-static of international LED manufacturers are generally better, and some anti-static products of B, miscellaneous and Korean chips are still very low. The antistatic ability of LED is the core embodiment of LED reliability. Even if the brightness and electrical properties of the LED are good, once the antistatic index is low, it is easy to die due to electrostatic damage.

Companies familiar with LED manufacturing are well aware that the quality of products in China's LED industry is uneven. Different quality LEDs have far different stability, which makes many LED users confused and even suffer. Among them, the quality accidents such as dark, deadlights and electric leakage caused by low antistatic of LEDs are the most costly. In particular, there are some low-quality sub-products and Korean companies that have low quality, even if they are Large-scale products, intermediate sellers often occur with the sub-filling phenomenon, many companies face huge risks. Industry experts believe that LED packaging companies only need to use LED chips with higher static resistance and better packaging process, the products are sure to be reliable and stable.

Detection method:

Many companies evaluate the antistatic properties of LEDs by "trying a batch to see the consequences". In fact, this is an evaluation method with the long cycle, large error, high cost and high risk.

Electrostatic breakdown of LEDs is a very complicated process. In the antistatic test of LED, static electricity must be directly applied to the two pins of the LED. The discharge waveform of the instrument has strict standard regulations. Among them, both human body mode and mechanical mode are used to measure the antistatic ability of the measured object.

Human body mode: When static electricity is applied to the measured object, a 330-ohm resistor is applied in series. This is to simulate the charge transfer when the person is in contact with the device. The contact between the human and the object is usually also 330 ohms, so it is called the human body mode.

Mechanical mode: Static electricity is directly applied to the device under test. The simulation tool mechanically transfers the electrostatic charge directly to the device, so it is called mechanical mode.

The internal electrostatic charge storage energy and discharge waveform of the two test instruments are also somewhat different. The results of the human body model test are generally 8-10 times that of the mechanical mode. The LED industry, and now many companies use indicators of the human body model.

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