Lamp cooling research status LED cooling methods are mainly two: First, by improving the LED's internal packaging structure and packaging materials to reduce the internal thermal resistance; the second is to reduce the external thermal resistance to improve the external thermal efficiency package Thermal package mainly from Packaging structure and packaging materials to start, using low thermal resistance package structure and technology. The first choice of substrate, bonding materials and packaging materials such as thermal resistance is low; second structural design to be reasonable, the thermal conductivity between the material to match the material between the thermal connection is good, to avoid heat generated in the heat pipe bottleneck, To ensure that heat dissipates from the inside to the outside. In order to solve the problem of high-power LED package cooling, a variety of structures have been developed at home and abroad.
In 2001, Lumi-Leds developed an AlGaInN power flip chip structure in which heat is directly transferred from the solder layer to the Si substrate and to the metal base via the Si substrate and the bonding material. A thin film encapsulation structure was designed by magnetron sputtering. The heat sink and insulation layer of the interface electrode were fabricated directly on the metal radiator, which reduced the thermal resistance of the internal heat sink. Luo and so put forward a micro-pump structure, the role of water in the micro-pump into the LED bottom plate to absorb heat, and then back to the micro-water containers, through the fan cooling. This structure is cool, but more complex. After determining the package structure, the thermal resistance of the system can be further reduced by selecting different materials to improve the thermal conductivity of the system. At present, at home and abroad often for substrate materials, paste materials and packaging materials for merit. LED thermal substrate materials require high electrical insulation, high stability, high thermal conductivity and thermal expansion coefficient (CTE), flatness and high strength that match the chip. Commonly used substrate materials are silicon, metal (aluminum, copper, etc.), ceramics (AlO, AlN, SiC) and composite materials. At present, the main substrates are metal insulation board (IMS), metal core printed circuit board (MCPCB), ceramic substrate and metal matrix composite substrate (MMC). Bonding materials have a great impact on LED heat dissipation, commonly used adhesive materials are thermal plastic, conductive type silver paste and alloy solder.