LED chip is a solid state semiconductor device. The heart of LED is a semiconductor chip. One end of the chip is attached to a bracket, one end is a negative pole, and the other end is connected to the positive pole of the power supply, so that the entire chip is encapsulated by epoxy resin. What are the technical problems of LED chip for high-power LED lamp beads? In particular, the main technical difficulties faced by high-power LED chips are as follows:

1. Low luminous efficiency

Although the luminous efficiency of white LED packaged by various manufacturers has reached more than 100lm/w, compared with small LED chips, its luminous efficiency is still very low. Due to the large size of LED chips, when light propagates inside the device, the distance of light passing through the device is longer than that of the chip with small size, which leads to a higher probability of light absorption by device materials. A large amount of light is limited inside the device and cannot be emitted, leading to a lower luminous efficiency.

2. Uneven current diffusion

For high-power LED chips, large current drive is required (generally 350mA). In order to obtain uniform current diffusion, a reasonable electrode structure should be designed to make the current evenly distributed on the P-type layer. Due to the large chip size, high-power LED chips are difficult to obtain uniform current diffusion on the P-type layer, resulting in current accumulation under the electrode, causing current crowding effect. Due to the current accumulation effect, that is, the current is mainly concentrated in the area directly below the electrode, the lateral expansion is relatively small, and the current distribution is very uneven, resulting in excessive local current density.

3. Unstable photoelectric characteristics

Due to the low light output efficiency of high-power LED chip devices, a large amount of light is absorbed inside the devices. These absorbed light is converted into heat energy inside the devices, causing the rise of LED chip junction temperature. The rise of junction temperature will not only cause light degradation, which seriously affects the life of LED chips, but also cause the blue light peak of the chips to shift to the long wavelength direction (i.e., red shift), As a result, the emission wavelength of the chip does not match the excitation wavelength of the phosphor, which will also reduce the color rendering.

4. The light efficiency of industrialization research is far lower than the level of laboratory research and development

Although the laboratory research and development of the international mainstream LED chip manufacturers has reached a high level, the research level of industrialization is still low. The main reason for this is that industrialization should not only take into account the cost requirements, but also take into account the complexity of the production process and the chip yield.