Study On Heat Transfer Performance Of Vapor Chamber Module With Multiple Chips

With the increasingly severe energy crisis,the development of alternative fuel vehicles has become an inevitable trend.Insulated Gate Bipolar Transistor(IGBT),as the key part of the Power Control Units(PCUs)in alternative fuel vehicles,should exhibit explosive growth in the next twenty years.With the increasing of output power,the heat flux in IGBT chip will reach 500W/cm~2,and thus cooling will be the major problem in IGBT modules.Many existing cooling methods for IGBT modules suffer from the problems including insufficient heat transfer capability,low space utilization rate,complex structures,or prohibitively high cost.Because of the extremely high thermal conductivity and good thermal homogeneity,vapor chamber has been recognized as one of the most promising cooling approaches.This work leveraged the ceramic heating element to simulate the IGBT chip and freewheeling diode chip(FWD)in IGBT modules,and integrated the chip and vapor chamber.According to different heat flux in chips,two experimental systems including the uniform chip power case and non-uniform chip power case have been built.The number of chips and their arrangements were changed to study the heat transfer performance.The main contents are as follows:In the experiments of chips with equal power,four arrangements were designed according the number of chips.The total heating power was set from 10W to 80W,and the total heating power was remained the same in each arrangement.The heat transfer performance of vapor chamber has been analyzed.In general,with the increasing of heating power,1-dimensional,spreading,and total thermal resistances firstly decrease and then rise for both single-chip and double-chip modules;For triple-chip and four-chip modules,these three thermal resistances firstly increase and then decrease with the heating power,and finally go stable.Furthermore,heat transfer limit of the vapor chamber was not found even under the maximum heating power in the experiments.Thermal spreading resistance dominates the total thermal resistance.Under the same value of heating power,the more the chips,the lower the thermal spreading resistance of the module.For single-chip,double-chip and triple-chip modules,the thermal spreading resistance is higher than the 1-dimensional resistance,but its proportion becomes lower with the increasing chips.For four-chip module,the1-dimensional resistance is higher than thermal spreading resistance.In the experiment with non-uniform chip power,the simulated powers of IGBT and FWD chips were 83.3W and 10.7W,respectively.By changing the horizontal distance between FWD chips on the vapor chamber surface,denoted as s1,and both horizontal distance and vertical distance between the FWD chip and IGBT chip,denoted as s2 and s3,respectively,a three-factor and four-level orthogonal experiment was designed.The optimal combination was obtained with the range analysis.Under this combination,the heat transfer properties of multi-heat-source modules for vapor chamber and copper plate were compared,and results show that the total thermal resistance of multi-heat-source module decreases with the s1,s2,and s3.s3 has the largest impact on the heat transfer property of vapor chamber multi-heat-source module,s2 the second,and s1 the smallest.Both the self-thermal resistance and the coupled thermal resistance of each chip in vapor chamber module are lower than those in the copper plate module.Besides.The vapor chamber module has higher speed of response and better thermal homogeneity.In the IGBT module,replacing the pure copper plate with vapor chamber can enhance the heat transfer capability of the module to some extent.