High power and high optical density COB
In recent years, LED packaging products have continued to introduce new products. COB packaging has become more and more popular in the market for its excellent light and color quality, excellent heat dissipation performance, low cost and ease of use. However, the structural design, material selection, and packaging process of COB packaging will affect the performance and lifespan. COB packaging has been a research hotspot in recent years, especially for high optical density COB packaging. The functions of the COB package and the conventional SMD LED package are basically the same, including: 1. Mechanical protection to improve reliability; 2. Strengthen heat dissipation to reduce the chip junction temperature and ensure LED performance; 3. Optical control, optimize the beam distribution, and improve Light efficiency.
The selection of LED packaging methods, materials, structures and processes is mainly determined by factors such as chip structure, optoelectronic/mechanical characteristics, specific applications, and cost. After more than 40 years of development, LED packaging has successively gone through the development stages of bracket type (Lamp LED), chip type (SMD LED), power LED (Power LED), integrated COB (Chip on Board) and so on. With the popularization of LED lighting and the further expansion of the application market, replacing traditional lamps, especially high-end traditional light sources, such as metal halide lamps, automotive lamps and other markets, has proposed the optical, thermal, electrical and mechanical structures of LED packaging. The new and higher requirements cannot be met by conventional SMD packaging solutions at this stage. It not only requires high power input and high optical density output, but also strict requirements on the light output effect and the light distribution angle. In order to effectively increase the power, increase the optical density, reduce the thermal resistance of the package, and improve the light output efficiency, it is necessary to adopt a brand-new technical idea to carry out the package design.
According to the above market demand, COB products with high power, high optical density and small light-emitting surface have been produced one after another. In order to meet the above performance requirements, such products have relatively dense chips and high power density. Therefore, chip heat dissipation is a must for high-power and high-light-density COB packaging. The key issue. Mainly include chip layout, packaging material selection (substrate material, thermal interface material) and process, heat sink design, etc. The thermal resistance of the COB package mainly includes the internal thermal resistance and the interface thermal resistance of the material (the thermal resistance of the chip itself, the heat dissipation substrate and the heat sink structure). Chips include formal chip, vertical chip and flip chip. The role of the heat dissipation substrate is to absorb the heat generated by the chip and conduct it to the heat sink to achieve heat exchange with the outside world. Commonly used heat dissipation substrate materials include silicon, metals (such as aluminum, copper), ceramics (such as Al2O3, AlN, SiC) and composite materials.
