Silicon substrate LED technology status, application and trend outlook
In the past 10 years, the LED industry has developed by leaps and bounds. The performance of LED light source devices has risen step by step and the cost has been decreasing. Most of the light source fields have been replaced by LEDs. As the fourth generation of light source, LED has been widely used in indoor and outdoor lighting, automotive lighting, LCD backlighting, landscape lighting, mobile lighting and other fields. With the upgrading of people's consumption concept, in some special lighting fields, high-quality light sources have gradually become competitive. The characteristics of the high-quality light source are: small illumination angle, uniform spot and high illumination. Silicon-based LEDs have received much attention in the high-quality light source market due to their single-sided light output, good directionality, and good light quality.
So, what is the current silicon substrate LED technology, market status and future development trends?
Growing GaN materials on silicon substrates faces two major technical challenges. First, up to ~17% lattice mismatch between silicon substrate and GaN makes the internal dislocation density of GaN material high, affecting luminous efficiency; second, up to ~54% heat loss between silicon substrate and GaN. The GaN film is easily cracked after being grown at a high temperature to room temperature, which affects the production yield. Therefore, the growth of the buffer layer between the silicon substrate and the GaN thin film is extremely important, and the buffer layer serves to reduce the dislocation density inside the GaN and to alleviate the GaN crack. To a large extent, the technical level of the buffer layer determines the internal quantum efficiency and production yield of the LED, which is the focus and difficulty of the silicon substrate LED. Up to now, after the investment in research and development by the industry and academic circles, this technical difficulty has been basically overcome.
The silicon substrate strongly absorbs visible light, so the GaN film must be transferred to another substrate. Before the transfer, a high-reflectivity mirror is inserted between the GaN film and the other substrate, so that the light emitted by the GaN is not lined. Bottom absorption. The LED structure after substrate transfer is known in the industry as a thin film chip. Thin film chip current diffusion, heat conduction and spot uniformity are superior to traditional formal structure chips.
The technical performance is mainly as follows: the substrate material cost is low; the device has good heat dissipation and long life; the packaging process is simple, and it is easy to realize automatic production; it can be used for large-scale epitaxy, improve production efficiency, and reduce overall cost.
The silicon substrate LED technology chip produced by Jingneng Optoelectronics has the following four advantages:
(1) Having original technical property rights: products can be sold to the international market and are not subject to international patent restrictions;
(2) It has excellent performance: the device has good heat dissipation, good antistatic performance, long service life and high current density;
(3) The device packaging process is simple: the chip is an upper and lower electrode, a single-lead vertical structure, simplifies the packaging process, and saves packaging cost;
(4) It has obvious characteristics and advantages in terms of direction light and light quality.
Packaging technology features based on Si substrate chip characteristics:
1: In combination with the gold substrate tin plating process of the Si substrate chip, the gold-tin eutectic process is adopted in the package can solve the heat dissipation bottleneck from the chip to the substrate;
2: Using aluminum oxide and aluminum nitride ceramic substrate to push the chip to higher power;
3: Using the single-sided illumination and directional light intensity of the Si substrate chip, the technology of coating the phosphor on the wafer sheet was successfully developed, and the white light chip was realized. The white light chip is packaged into a lamp bead, which has good color consistency and uniform spot, and is very suitable for the mobile lighting market;
4: Since the Si substrate has light absorbing characteristics, in order to solve this problem, a special white glue is placed around the chip to increase the brightness;
5: According to different chip sizes, design different lenses to maximize the brightness performance of the product;
6: Developed a new generation of fluorescent diaphragm technology that optimizes product spot, color zone hit rate and cost reduction.