| With the rapid development of semiconductor technology, high-power LEDs as the representative of electronic chips has been used widely. A great challenge in heat dissipation has been encountered which caused by the high degree of integration,miniaturization and GHz of chips. In order to solve the problem that the traditional cooling devices can’t meet the requirements of heat dissipation of high-power LED, an novel column cooling system is proposed in this paper, which possess an excellent heat transfer capabilities and flexible installation mode. The ploughing-extrusion method is proposed to process the structure of three-dimensional fin on the inner wall of the copper pipe. And then the structure of the composite wick could be acquired by sintering cooper powder on the surface of the three-dimensional fin structure. The influences of several parameters including sintering temperature, sintering time and the shape and size of the copper powder are analyzed on the forming mechanism of the composite sintering wick. The effects of input power, filling rate and the size of wick on the heat transfer performance of the column cooling device are investigated. The result indicates that composite wick column cooling system has a good start performance and better heat dissipation ability compared with the traditional heat sink and similar products of heat transfer in market. This paper mainly includes the following aspects:(1) A chipless processing method—ploughing-extrusion method is applied to process the structure of space fin micro-groove. The influence of three key processing parameters including the plowing depth, the interval of micro-grooves in the radial and axial direction on the morphology of three-dimensional trench wings were investigated. Results show that the best morphology of the three-dimensional trench wings can be acquired under the combination value of the plowing depth, the interval of the micro-groove in radial direction and axis direction are 0.4mm, 0.4mm and π/25 rad, respectively.(2) Based on the sintering theory of metal powder, the growth mechanism of sintering necks and the influence of sintering temperature, sintering time, the shape and size of the copper powder on the morphology structure of the sintered wick is analyzed. The study indicates that the sintered wick properties can be acquired the best level when the sintering temperature and the sintering time is 900℃ and 60 min, respectively. In this experiment, the performance of the sintered wick which sintered by the copper powder in particle shape is better than that of copper powder in spherical shape. In addition, the smaller the copper size, the richer of the porous structure of sintered wicks.(3) According to the special requirements of high-power LED in heat dissipation, the body structure of the column cooling device is designed, which consist of evaporator, condenser, composite wicks and working fluid. A reasonable machining process of the novel column cooling system is designed and each procedure including material selection, the processing of the main body, cleaning, welding and the filling of working fluid are analyzed, which could ensure that the samples manufactured can meet the testing requirements.(4) An experimental platform is constructed according to the shape and the dimension of the column cooling device to test the quick starting performance of the cooling apparatus in high temperature. A research on the heat dissipation performance of the column cooling device is took under different input power, filling rate and parameters(size and shape) of the copper powder. It is found that the cooling device has a good start performance in high temperature and it’s maximum heat load can be reach at 120 W. In addition, the heat diffusion capability of the device has a linear relationship with the length and the diameter of the composite wick and the size of cooper powders. Furthermore, a comparison in the heat transfer performance of the composite wick heat column, common heat sink, several trench wick heat column in single direction and the similar heat transfer products in market is conduced. Results proved that the composite wick heat column system has great advantages in heat transfer once again. Finally, the heat dissipation capabilities of the heat column under the simulated heat source and the real high-power LED source are compared, the results shows that the heat dissipation performance of the heat column system under the two different kinds of source is very similar and close. This phenomenon indicates that the experimental data acquired under the simulated heat source above is credible and reasonable, which can be a strong support for the heat column to solve the heat problem of high-power LEDs. |
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