Research On Interface Thermal Resistance Of Cryogenic Packaging For Infrared Focal Plane Assembly

The development trend of the third-generation infrared focal plane detectors is of large format,small pixels,high integration,multi-band,light weight,low cost and low power consumption.To fulfill the requirement of reducing the power consumption of cooling infrared focal plane detectors,we in this thesis carries out research on the interface thermal resistance of cryogenic packaging to reduce the temperature difference of the interface and to improve the refrigeration utilization efficiency of infrared assembly.A structure function analysis method is proposed to extract thermal resistance information by samples' comparison.A cryogenic T3 Ster thermal transient test system is built,and four kinds of thermal interface materials are studied of indium,graphene,silver paste,DW-3 glue.The influence is investigated of temperature,thickness of the thermal interface material and its internal pores on the interface thermal resistance.Simulation of the temperature filed is also conducted with Flo EFD software for packaged infrared focal plane assembly,and comparison is made with the experimental results for verifying the accuracy of the measurement of the interface thermal resistance.Analysis is also performed of the apparent thermal resistance and apparent thermal conductivity for two-stage thermoelectric cooler at different temperatures.The major research activities and innovation as well are as follows:1.A sample structure function analysis method is proposed based on T3 ster thermal transient test.By reasonable design of the sample structure and comparative analysis of the structure function curves of different sample structures,the target thermal resistance information is obtained;based on this analysis method,the thermal resistance and thermal conductivity are obtained for the sample at normal atmospheric temperature,with the absolute value of the relative error being less than 30.0%.A cryogenic T3 ster thermal transient test system is set up,using the modified liquid nitrogen Dewar and Dewar temperature controller instead of T3 ster dry temperature controller,which can be used for the measurement of thermal resistance-related parameters from 93 K to room temperature;The thermal resistance and thermal conductivity are obtained from the sample at cryogenic,with the absolute value of the relative error being less than 20.0%.2.The cryogenic T3 Ster thermal transient test system is used to measure the interface thermal resistance of aluminum alloy samples based on indium flakes,graphene flakes and DW-3 glue,silver paste colloidal thermal interface materials at cryogenic.The influence is investigated of temperature,thickness of the thermal interface material and its internal pores on the interface thermal resistance,and for which empirical formulas are established.It is found that as the temperature increases,the interface thermal resistance decreases and gradually stabilizes;for silver paste and DW-3 glue,the interface thermal resistance has a linear relationship with the thickness,and when the thickness reaches a certain value,the bulk thermal resistance of the thermal interface material occupies a dominant role,while the pores inside the thermal interface material reduce the thermal conductivity,resulting in an increase to the bulk thermal resistance,which in turn increases the interface thermal resistance between aluminum alloy samples.3.The temperature field is simulated using Flo EFD software for the packaged infrared focal plane assembly,the results show that the temperature of the lead substrate decreases with the increase of the input current,while the temperature difference increases between the lead substrate and the package bottom,and the trend gets gradually slow-down.The importance is verified of the interface thermal resistance in the reduction of the cooling power consumption in the packaged infrared focal plane assembly.The experimental verification is conducted of the temperature field of the infrared focal plane assembly,and the experimental and the simulated temperatures of the lead substrate,the bottom surface of the package,and the heat sink manifest good consistencies.4.The non-operating-state apparent thermal conductivity and apparent thermal resistance of the two-stage thermoelectric cooler are measured,with the thermoelectric cooler working curve and T3 ster thermal transient test method,and the apparent thermal resistances take the values of 0.442,0.603,0.649 K/W,respectively,at temperatures of 233.1,249.8,298.0 K.It shows as the temperature increases an increase trend of the apparent thermal resistance of the two-stage thermoelectric cooler.