Research On Active Manufacturing Of DIW Microchannel Heat Sink With High Heat Dissipation Performance

The development of electronic components with high integration,lightweight,and miniaturization has put forward higher heat dissipation requirements for heat sinks.Unidirectional porous copper material with high specific surface area,superior thermodynamic properties,and high fluid flow permeability has become a new type of microchannel heat sink material.However,the size and position of the pores inside the unidirectional porous copper prepared by the traditional process are uncontrollable,and the pore connectivity is poor.Therefore,it is urgent to find a new unidirectional porous copper preparation process.In this paper,the direct ink writing(DIW)process of the unidirectional copper was proposed,the influence of DIW process parameters on the forming quality of the printed blank was studied,the influence of the thermal treatment process on the density of the printed samples was explored,and the unidirectional porous copper with microchannel aspect ratio was optimized by simulation.Combined with DIW and heat treatment,the microchannel structure was prepared and its heat dissipation performance was tested.The main results are as follows:(1)Based on the comparison of different metal 3D printing processes,a method for the rapid preparation of the unidirectional porous copper was proposed based on layer-by-layer stacking of microfilaments by DIW extrusion ink,and the preparation procedures for DIW unidirectional porous copper were designed,which can realize the controllable preparation and active manufacturing of the pore parameters of the unidirectional porous copper structure with high pore connectivity.(2)The pneumatic DIW printing device was self-made to print unidirectional porous copper.Solvent volatile copper paste was prepared with the volume ratio of copper powder to binder of 7:3,and the method of screw stirring thickening and simple centrifugal defoaming was proposed.The results show that the inner diameter of the printing needle cannot be less than 15 times the inner diameter of the copper particle.The effects of printing speed,extrusion pressure,printing height,and printing filament spacing on printing quality were investigated.The density of copper paste was determined to be 3.6g/cm~3,and the matching relationship between printing speed and extrusion pressure under different printing needles was obtained.When the printing layer height is set at 80%of the diameter of the printing needle,the printing layer height can be accurately controlled and the close bonding between the layers can be ensured.The solid layer printing filament spacing is determined to be 90%of the diameter of the printing filament.(3)A thermogravimetric analysis experiment was carried out on the ink,and a multi-temperature segmenting debinding process was set for the binder,dispersant and surfactant in the ink.The effects of sintering temperature,heating rate and holding time on the forming quality of the printed parts were studied.The results showed that the highest density copper printed parts could be obtained when the sintering temperature was 1100℃,the heating rate was 5℃/min and the holding time was 6h.The relative density of copper printed parts reached87.2%and the shrinkage rate was about 33%.In addition,the problem of oxidation during debinding and sintering was solved by changing the protective atmosphere to a mixture of argon and hydrogen(concentration ratio of argon to hydrogen:95:5)at a flow rate of100ml/min.(4)Based on the common water-cooled heat sink,a new directional porous copper embedded microchannel heat sink is designed and manufactured by using active manufacturing procedures.The heat dissipation simulation of microchannels with different aspect ratios(aspect ratios are 3,1.5,1.2,and 0.9)is carried out.Considering the cooling effect and pressure drop,the radiator can achieve a better cooling effect and an appropriate pressure drop when the aspect ratio is set at 1.5,so it is selected as the target component of active manufacturing.The optimum height to width ratio oriented porous copper material was prepared by the optimum printing process and heat treatment process.The pore size of the material was uniform and had a regular distribution,and the pore connectivity reached 100%.(5)A test platform for heat dissipation performance was built.The optimal aspect ratio oriented porous copper material was embedded into a water-cooled heat sink,and the heat dissipation performance was tested at different flow rates.The heat transfer characteristics of the new directional porous copper microchannel heat sink are demonstrated through experiments and simulations.That is,the cooling effect of the heat sink increases with the increase in flow velocity,but the increase in flow velocity leads to an increase in internal pressure and the deterioration of liquid flow effect,which is the main reason for the slowdown of the cooling range.When the flow rate increased from 0.1m/s to 0.2m/s,the cooling effect of the CPU packaging temperature increased by 6.1%.However,when the flow rate continued to increase,the cooling effect slowed down until the 0.8 m/s and the CPU packaging temperature decreased to 50.3℃.