Study Of Heat Transfer Enhancement On Micro-electronics Based On Electrohydrodynamics

With the dramatical development of electronic technology,the application of microelectronic devices is spreading across various fields.The thermal management of electronic devices has always been of paramount importance.With the size of the device shrinking,the dissipation space becomes more and more confined and the power density becomes more and more larger making hotspot cooling challenged.As a relatively new type of cooling technology,the ionic wind heat dissipation method based on electrohydrodynamic(EHD)exhibits great potential for cooling applications of microelectronic devices due to its advantages,including compact structure,no mechanical parts,quietness,and easy integration.Researchers have conducted a lot of efforts to study the factors influencing the ionic wind generator performance(e.g.electrode structure,operating conditions,ionization environment,electrode polarity and other aspects)which has made great progress on performance improvement.However,in a confined space,the research on the enhancement of heat transfer for the existence of non-uniform heat flux density is still limited.Based on the analysis above,this thesis takes microelectronic devices with local hotspots as the research object to build a multi-physics numerical model of coupling electric field,flow field and temperature field.The electrode structure,parameters and arrangements are optimized to enhance the hotspots heat dissipation.The feasibility of ionic wind for effectively removing the hotspot is examined,and the electrode design schemes for single hotspot and multiple hotspots are proposed.The physical mechanisms behind the performance improvement are revealed.The result shows that for single hotspot cooling,partial ground pattern is better,while the entire grounding is more suitable for multiple hotspots cooling.The layout of the electrodes plays an important role in improving the cooling performance.Three effects,including impingement just on the hotspot,barrier effect between multiple discharge electrodes,and the entrance effect on the discharge electrode should be comprehensive considered to enhance the single hotspot cooling.However,it is not suitable for multiple hotspots.Hence,a concept of "Intensified Electrode Pair" is proposed,which can effectively enhance heat transfer of multiple hotspots in confined space.To further improve the hotspot cooling capacity of ionic wind,a new hotspot cooling structure that integrates ion wind and porous medium heat sink is proposed.The influence of electrode geometry and porous media parameters are examined,and then the optimized structure is proposed.The electrode geometries include needle-to-plate,needle-to-mesh and needle-to-ring configuration.The porous medium parameters include geometric parameters,porosity,permeability and the quadratic drag factor.The results show that needle-to-ring configuration has obvious advantages to achieve the best heat transfer performance with lower power consumption.The volume of the porous medium has an optimal value to reach the strongest heat transfer performance.The porous medium with higher porosity,larger permeability and smaller quadratic drag factor should be chosen to improve the overall heat transfer performance.The porous fins heat sink can further improve the hotspot cooling.It can meet the heat transfer demand of 90 kW/m2 at an operating potential of 10 kV with the optimized structure.