Fabrication Of Flat Micro Heat Pipe Based On Electroforming

LED is widely cited in lighting, display and other fields, which has energy-saving, environmental protection, long life and other characteristics, it has broad application prospects. However, LED junction temperature and thermal resistance constrainted its development. As the junction temperature rises, the luminous efficiency of LED chips will drop, so to solve the LED junction temperature and the thermal resistance is the bottleneck of its development. Micro heat pipe, which has the advantage of highly efficient heat transfer, good average temperature performance and low thermal resistance, provides the basis for the development of that problem. Because of the micro heat pipe has the advantage of highly efficient heat transfer, good average temperature performance and low thermal resistance, it will not only be able to solve the high-power LED thermal problems, but also to solve the high heat flux cooling problem of electronic chip cooling field.In this paper, we designed the silicon-copper micro heat pipe which was manufactured by growing copper micro-channel directly on the silicon substrate using electroforming method. We got silicon-copper micro heat pipe by sealing with copper plate and vacuum infusion refrigerants. The overall size of the silicon-copper micro heat pipe is 45 × 16 × 3 mm3, the work cross-sectional area of micro heat pipe is 9 × 35 mm2. Silicon-copper micro heat pipe which was manufactured by this method is no interface, no thermal glue and adhesives, no larger thermal interface resistance between the silicon substrate and the micro heat pipe. So the overall thermal resistance of the device is small. And its heat transfer capacity is not suddenly dump due to the glue dries. Therefore, the heat transfer capacity, reliability and life of the device is improved.In this paper, we founded that, in the production of silicon-copper micro heat pipe, after the way in the use of brazing sealing micro heat pipe, micro heat pipe can be deformed, even copper micro heat pipe lifted from the silicon substrate, since the thermal expansion coefficient of silicon and copper in an order of magnitude difference. In this paper, we use two methods to solve this problem, the first one was that the use of silicone adhesive sealant sealing micro heat pipe. The second was that changing the micro-channel copper heat pipe inside the structure, linear micro-channel will be changed back to the font of the micro channel.In this paper, we tested the heat transfer performance of two structures of silicon - copper micro heat pipe. We can got the test results from the fifth chapter, the equivalent thermal conductivity of the linear structure of the micro heat pipe is k1=1.06×103W / (m·K), the equivalent thermal conductivity of the back-shaped structure of the micro heat pipe is k2=1.30×103W/(m·K). Obtained from the test results heat transfer performance of back to the font structure of silicon-copper micro heat pipe is better than micro heat pipe of linear structure. Compared to the thermal conductivity of copper (0.4×103W　/　(m·K)), silicon-copper micro heat pipe has good heat transfer properties.In this paper, we use electroforming copper column to deposit microstructures of copper column in the silicon channel of silicon-glass micro heat pipe. It can improve the silicon channel capillary traction in the horizontal and vertical flow direction, thereby increasing the heat transport capability of silicon-glass micro heat pipe, therefore, this method can improve silicon-glass heat transfer performance micro heat pipe. Therefore, this method can improve the heat transfer performance of the silicon-glass micro heat pipe. From the test results in the Chapter V we can got that heat transfer performance of silicon-glass micro heat pipe after electroforming microstructure is significantly improved. This method differs from the general surface modification method, electroformed micro structure is not easily detached, and it has high reliability.