Analysis of LED chip life test process

Introduction

LED, as an electronic component, has been around for more than 40 years. However, for a long time, due to limitations of luminous efficiency and brightness, LEDs have only been used in indicators and other aspects. Until recent years, with technological breakthroughs and the emergence of high-brightness and high-efficiency LEDs, the application range of LEDs has been greatly expanded, and they can even be used as lighting sources. As the scope of LED applications continues to expand, it is increasingly important to improve the reliability and lifespan of LEDs. Take you to understand LED chips: technology, application and development.

In the actual production and research and development process of LED, life test is one of the important means to evaluate the reliability level of LED chips. Through the life test, the light output attenuation of the LED chip can be understood and its lifespan can be inferred. To this end, we need to determine the appropriate life test conditions and design the corresponding life test bench to improve the scientific nature of the life test and the accuracy of the results.

Determination of life test conditions

The conditions of the life test need to be determined based on the characteristics of the LED device and the actual situation. With the improvement of LED production technology, the traditional life test under normal rated stress can no longer objectively evaluate the life and reliability of the product. Therefore, we need to specify more stringent life test conditions. What is the difference between SMD LED display and COB LED display?

For example, for LED chips below 0.3×~0.3mm², we stipulate the following life test conditions:

The sampling quantity is 8 to 10 chips to make a ф5 single lamp device. The operating current is 1.5 times the rated value, which is 30mA. The environmental conditions are room temperature (25℃±5℃). There are three test periods: 96 hours, 1000 hours and 5000 hours. Although this kind of life test with increased electrical stress cannot represent the real life situation, it has great reference value. At the same time, by sampling epitaxial wafer production batches, the situation of the entire production batch can be represented. Let you understand the difference between CSP and COB LED chips.

Process and precautions

During the life test of LED chips, you need to pay attention to the following aspects:

Sample extraction method: Use a scientific sampling method, which should not only consider the representativeness of the sample, but also minimize the test cost. Photoelectric parameter testing method and device light distribution curve: The test samples are tested and screened for photoelectric parameters to ensure the accuracy of the test. The impact of resin deterioration on life test: Resin deterioration may affect the accuracy of life test results, and corresponding measures need to be taken to control it. The impact of packaging process on life test: Different packaging processes will affect the life test results. It is necessary to pay attention to the selection of appropriate packaging materials and process conditions.

Design of life test bench

In order to conduct large-scale LED life tests, we designed a dedicated life test bench. The test bench consists of a life test unit board, a bench and special power supply equipment, and can conduct multiple sets of LED life tests at the same time. We adopted constant current drive and series connection to ensure the accuracy and stability of the test. Through reasonable wiring and microcomputer timing control function, online operation can be realized, and the life test results can be monitored and recorded. What are the supporting equipment for LED display screens?

Conclusion

The life test of LED chips is an important means to evaluate the reliability of LEDs. Through the scientific life test process, the quality and reliability of LED products can be improved and the long-term stable operation of LED chips can be ensured. In the future R&D and production process, we will continue to optimize the life test conditions and methods to adapt to the development needs of the LED industry and contribute to the further development of LED technology.

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