In recent years, LED packaging products continue to innovate, COB packaging with its excellent light quality, excellent heat dissipation performance and low cost and ease of use, more and more favored by the market. However, the structural design, material selection and packaging process of COB package will affect the performance and life, COB package has been a hot research spot in recent years, especially the high optical density COB package. The functions of COB package and conventional SMD LED package are basically the same, mainly including:
1. Mechanical protection to improve reliability;
2. Strengthen heat dissipation to reduce chip junction temperature and ensure LED performance;
3. Optical control, optimize the beam distribution, improve the light efficiency.
The choice of LED packaging method, material, structure and process is mainly determined by the chip structure, photoelectric/mechanical characteristics, specific application and cost. After more than 40 years of development, LED packaging has experienced scaffolding (Lamp LED), SMD LED(SMD LED), Power LED(Power LED), integrated COB (Chip on Board) and other development stages. With the popularity of LED lighting, the application market is further expanded, in the replacement of traditional lamps, especially high-end traditional light sources, such as: Gold halide lamps, automotive lights and other markets, LED packaging optical, thermal, electrical and mechanical structure put forward new and higher requirements, at this stage the conventional SMD package can not meet, it not only requires high power input and high optical density output, the light effect, light distribution Angle requirements are particularly strict. In order to effectively increase the power, increase the optical density, reduce the thermal resistance of the package and improve the optical efficiency, we must adopt a new technical idea to carry out the package design.
According to the above market demand, high power, high optical density, small luminous surface COB products have been produced, in order to meet the above performance requirements, the chip of such products is relatively dense and the power density is large, therefore, chip heat dissipation is a key problem that must be solved by high power and high optical density COB packaging. It mainly includes chip layout, packaging material selection (substrate material, thermal interface material) and process, and heat sink design. The thermal resistance of 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). The chip includes formal chip, vertical chip and flip chip. The role of the cooling 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 cooling substrate materials include silicon, metals (such as aluminum, copper), ceramics (such as Al2O3, AlN, SiC) and composite materials.
