1. Appearance inspection
Chip size and shape
High-quality LED chips have high dimensional accuracy and regular shape. For example, for common square chips, the error of their side length is usually within a very small range (such as within ±0.1mm). If the chip size is uneven or the shape is irregular, it may be a manifestation of poor process control during the manufacturing process, which will affect the performance and reliability of the chip.
Surface finish
The surface of a high-quality chip should be smooth, without obvious scratches, cracks or particle impurities. The chip surface can be observed through a high-power microscope. If there are defects on the surface, it may cause local current concentration, poor heat dissipation and other problems during the operation of the chip, thereby reducing the performance and life of the chip.
2. Electrical performance test
Forward voltage (VF)
Measure the forward voltage of the chip at a certain forward current. For a good quality LED chip, its forward voltage value is relatively stable and within the specified range. For example, for a certain model of LED chip, when its rated forward current is 20mA, the forward voltage should be between 3.0-3.4V. If the forward voltage deviates too much from this range, it may indicate that there is a problem with the internal structure or material of the chip.
Reverse leakage current (IR)
When a reverse voltage is applied to the chip, its reverse leakage current is measured. For a good LED chip, the reverse leakage current should be very small under the specified reverse voltage, usually at the nanoampere (nA) level. If the reverse leakage current is too large, it means that the PN junction of the chip may be defective, which will affect the chip’s antistatic ability and stability.
Luminous intensity (IV) characteristics
The IV curve is drawn by testing the luminous intensity of the chip at different forward currents. The IV curve of a high-quality chip should have good linearity, and the luminous intensity can increase steadily within a certain current range. If the curve fluctuates abnormally or deviates from the normal trend, it may mean that the carrier recombination efficiency inside the chip is unstable.
3. Reliability test
High temperature aging test
Put the chip in a high temperature environment (such as 85°C or higher), work continuously for a certain period of time (such as 1000 hours or longer), and then test its electrical and optical properties. After high-temperature aging, the parameters of good quality chips such as forward voltage and luminous intensity change less. If the performance of the chip drops significantly after high-temperature aging, it means that its stability in a high temperature environment is poor and its reliability is low.
Humidity sensitivity test
Place the chip in a humidity-controlled environment (such as relative humidity above 85%), and after a certain period of testing, check the performance of the chip. For reliable quality chips, there should be no problems such as short circuit, leakage, or serious decline in luminous performance in a high humidity environment.
Electrostatic discharge (ESD) resistance test
Use special ESD test equipment to apply different levels of electrostatic discharge pulses to the chip, and then detect whether the chip is damaged and whether the performance is affected. A good LED chip should have high ESD resistance and be able to maintain normal operation without being damaged under a certain level of electrostatic discharge.
Supplier evaluation
Check the customer evaluation and market reputation of the supplier. If a supplier can continuously provide LED chips with stable quality and good performance, and has a good reputation in the industry, then the quality of the chips it provides is more likely to be reliable.
Post time: Mar-08-2025
