Study On The Microchannel Heat Sink Of Metal Ceramic Composite Structure To Enhance Heat Dissipation

In recent years,the chip is widely used in many electronics equipment,and chip technology process is becoming more and more advanced,while the package density and the capacity of power electronics chip are becoming higher and higher.Here comes that the thermal value of electronic chip system has increased dramatically,and an era of high heat flux(100-1000W/cm~2)has arrived.As one of the workable methods to reduce heat flux density,the microchannel heat sinks develop rapidly.Research Institution of Micro/Nano Science and Technology(Shanghai Jiao Tong University)has put forward a kind of microchannel heat sink with metal-ceramic composite structure,which has comprehensive advantages such as small volume,high thermal mechanical stability,and good thermal performance.Based on moderate integration UV-LIGA technology,the cooling capacity of early samples has reached 200 W/cm~2,and further develops sharply,which shows high heat dissipation capacity and the potential of further development.To explore the possibility of further enhancing its various aspects,the paper systematically studies the reinforcement of heat dissipation and hot spot suppression in the multi-microchannel design instead of a single microchannel scheme with pin fin design;discusses the thermal influence of inclined pin fins;studies the effect of applying nanofluids on the heat dissipation capacity of this kind of heat sink.Based on the simulation analysis results,a variety of multi-microchannel heat sink samples are developed by moderate integration UV-LIGA technology and the test verification test is completed.The specific research progress is as follows:1.First analyzing the multi-channel design of the research status worldwide,combined with single channel and pin fin system research experience and technology accumulation,radial microchannel,wavy microchannel,veins microchannel,and cross microchannel design are presented after repeated arguments.Finite element models are established by CFD software,then typical design scheme of the port layout,the size of the channel,channel spacing,inlet and outlet position,and differential pressure changes are simulated on the heat dissipation capacity,combining with the knowledge of microfluidics and micro area of heat transfer mechanism analysis,which is suitable for metal-ceramic composite characteristics of microchannel heat sink design.The simulation results show that the smaller the radial microchannel,the lower the surface temperature of the chip,but the velocity of the diagonal region of the outlet is low,where cannot exchange heat efficiently.The fluctuation of the wavy flow has a significant effect on temperature reduction because it can destroy the boundary layer.Gradient scheme in veins microchannel is more appropriate,and small size channels are arranged in the center area to increase the solid liquid heat transfer area,while the large size entrance channels are arranged in the inlet and outlet in order to decrease the pressure drop.The difference between various styles of staggered microchannels is small.2.To test the simulation results above,some experiments have been carried out to verify design and improvement measures,based on moderate integration UV-LIGA technology,the test results show that the wavy microchannel has better heat dissipation.Under the power density of 50W/cm~2 and the flow rate of 50 ml/min,the highest surface temperature of the straight microchannel,big wavy microchannel and small wavy microchannel are 322.9 K,322.2 K and 321.8 K,and the simulation results are 324.8 K,323.8 K and 323.6 K.Although the test is better than that of the simulation experiment,they have the same trend.3.The simulation analysis of incline pin fin design has been carried out to evaluate the longitudinal disturbance effects on micro fluid heat capacity.The simulation results show that the incline pin fin has a slight enhancement to the heat dissipation capacity,but it is not significant.Considering the difficulty of fabricating the incline pin fins,it is not worth trying this design scheme.4.To study the application of nanofluids in metal-ceramic composite microchannel heat sinks,three kinds of typical nanofluids has been chosen,and simulation analysis and experimental verification are conducted.The results show that when the power density of 50 W/cm~2,and copper oxide particles volume fraction increases from 1%to 2%,the reduction of temperature is 0.99%.The simulation results of other two nanofluids are similar.Since the enhanced heat dissipation effect of the nanofluid is not significant,considering the possibility of microchannel blockages,it is not advisable to apply nanofluids in this system.