Fabrication And Testing Of Miniaturized Phase Change Heat Sink For High Power Led

High power Light Emitting Diode (LED) is a new type of solid-state light source. There are a number of advantages compared to traditional light sources such as energy conservation, environmental friendly and long life time etc. With the development of LED light source to miniaturization and high power, traditional solid heat sink is difficult to meet cooling demand of high power LED due to spreading resistance, so thermal management has become one of the challenges for application of high power LED. In this paper, a kind of miniaturized phase change heat sink based on principle of phase change heat transfer is designed for high power LED packaging and its manufacturing technique is analysized. Boiling enhancement structures is formed in evaporation surface to improve boiling efficiency and it is proved that phase change heat sink possessed faster heat response performance and higher heat transfer performance than that of traditional solid heat sink by heat transfer testing. The research in the paper is mainly as follows:(1) Theory analysis and design of phase change heat sinkHigh power LED packaging structure based on phase change heat sink, which makes up of main body, end-cover, wick and refrigerant, is designed and its heat transfer principle is analysized. Thermal resistance model of solid and phase change heat sink with variable section are established respectively. It is found that spreading resistance of solid heat sink is greater than that of phase change heat sink and the most important factor to impact thermal resistance of phase change heat sink is boiling efficiency of evaporation surface by the theoretical analysis. Considering the materials, sealing method, refrigerant, wick, perfusion and vacuum, structure parameters of phase change heat sink are designed.(2) Forming method of boiling enhancement structures in evaporation surfaceBased on analysis of forming technology for boiling structure of outside tube and plane, forming method of 3D boiling enhancement structures in evaporation surface of phase change heat sink is designed. Spiral groove is processed by ploughing-extrusion (P-E) method, meanwhile, relationship between P-E speed, processing time and feed is analysized. Radial groove is formed by stamping method based on spiral grooves to obtain 3D enhancement structures which interconnect the radial and circumferential grooves in evaporation surface. Relationship among interferential length, feed angle, stamping depth and angle of stamping tool is analysized. (3) Finite numerical simulation of boiling enhancement structures forming3D finite element model of spiral P-E and radial stamping are established based on the analysis of theory of large rigid plastic deformation by the DEFORM-3D software. Groove plastic deformation, distribution rule of stress and force in the spiral and radial grooves process under different parameters are simulated. The results show that the spiral grooves are influenced by P-E depth and feed, and 3D boiling structures are affected by P-E depth, feed, stamping depth and feed angle together. Simulation results of groove are consistent with the experimental results.(4) Manufacturing of miniaturized phase change heat sink for high power LEDManufacturing technology of miniaturized phase change heat sink is analysized. Formation mechanism of 3D enhancement structure is researched and the processing parameters are optimized. Relationships of sintering temperature, sintering time of copper wick and porosity and withdrawing state are studied. The optimized parameters of sintering temperature and time are determined. At the same time, processing parameters of refrigerant injection, vacuum-pumping and welding, are investigated. Finnaly, miniaturized phase-change heat sinks for high power LED are obtained.(5) Performance testing and analysis of phase change heat sinkHeat response performance and temperature distribution are observed by the infrared test. It is found that the area of higher temperature of phase change heat sink is far larger than that of solid heat sink in the equivalent heating time. Heat transfer performances under different input power, refrigerants and inclination of phase change heat sink are tested. The results show that phase change heat sink is suitable for less than 10W LED heat dissipation and solid heat sink is only suitable for less than 3W.