| With the development of integrated circuit processing technology,the integration and power of chips is getting higher and higher,but the size is getting smaller and smaller,resulting in increasingly high heat flux is difficult to disperse.Microwave Monolithic Integrated Circuit(MMIC)is an essential chip of phased array antennas.The heat flux of military amplifier MMIC has reached to 500W/cm2 or more currently.If the heat is difficult to dissipate,the performance and reliability of radars will be seriously affected.LTCC,whose thermal conductivity is only 2~5W/ m·K,is a kind of excellent packaging material for RF multi-chip.Its poor heat dissipation performance become one of the main factors restricting its packaging density.In this paper,simulation and experimental study of microchannels based on LTCC base will be conducted.There are five key issues in the study: processing technology and experiment for LTCC microchannel,the heat transfer characteristics of LTCC microchannel,the heat transfer characteristics of silver holes,the study on topological structure and heat transfer characteristics of microchannels used to power amplifier,thermal deformation analysis of antenna array.Specific work includes:(1)This paper will introduce the characteristics of LTCC package at first.Then design the experimental model and processing molding according to the process steps of integrated sintering the LTCC.Experiments were carried out by using the processed LTCC test piece to study the heat transfer capacity of the LTCC microchannels with silver holes.Experiment and simulation results were compared to analysis.Finally,according to the theory of thermal resistance,the general formula for calculating the total heat resistance of microchannels with heat through holes is deduced.(2)The effects of various parameters on the heat transfer performance of the LTCC substrate with no heat through holes were studied.The parameters including the thermal conductivity of the substrate,the aspect ratio of height and width,the inlet flow velocity,the hydraulic diameter,channel height,wall thickness.The heat transfer characteristics of circular shape,square shape and long strip shape are studied in detail.Compared with the three kinds of silver hole heat dissipation,it is found that the circular hole has the best heat dissipation effect.Then,the heat transfer characteristics of the four microchannel ribs are studied in the case of circular hole.The heat transfer coefficient of PA chip maximum temperature,inlet and outletpressure drop and hot window fluid-solid coupling surface under four schemes are studied emphatically.(3)The heat transfer characteristics of LTCC substrate microchannel for multi-power amplifier array are studied.According to the LTCC process,the channel path of the two-way parallel flow channel and the unidirectional parallel flow channel is designed.Then,the simulation results of the two flow paths are analyzed respectively.The parameters of the analysis are: the maximum temperature of the highest and lowest PA chip,the maximum temperature difference of different PA chips,the maximum temperature difference of LTCC substrate,the standard deviation of substrate temperature,Import and export pressure drop.The results show that the two-way parallel flow path can meet the cooling requirement of 16 × 16 power amplifier array with heat flux density of 100W/cm2.(4)According to the temperature field distribution of the subarray in the case of bidirectional parallel flow path,the thermal deformation and thermal stress of the subarray plane are analyzed,which is in the safe range. |
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