Research On The Critical Preparation Technologies Of DPC Ceramic Substrate With Embedded Microchannel

The reliability issue brought on by heat buildup is becoming increasingly apparent as chip power and package integration increase.The performance and sustained reliability of power devices are directly influenced by chip connectivity and heat dissipation,which depend on the packing substrate.Direct plated copper(DPC)ceramic substrate is the latest packaging substrate with high thermal conductivity,good heat dissipation performance,and three-dimensional stackability.DPC ceramic substrate can achieve high integration,high heat dissipation efficiency,and high-reliability packaging of power devices,which has found widespread use in semiconductor lighting(white LED),sterilization and disinfection(deep ultraviolet LED),laser and optical communication,power electronics,high-temperature sensors,thermoelectric coolers,microwave radio frequency,and other applications.Unfortunately,there is still room for improvement in the DPC ceramic substrate preparation process.One is to achieve defect-free filling of the through ceramic vias(TCV),which affects the interconnection reliability and heat resistance.The other is the poor electroplating rate of thick copper patterns,which substantially impacts manufacturing efficiency.Additionally,in order to improve heat dissipation for superpower devices,active heat dissipation technology(such as microfluid heat dissipation)must be integrated with the packaging substrate.However,the current microchannels were typically created by welding,which has high thermal resistance(increasing thermal interface)and low reliability.In light of this,together with the concept of"embedded cooling,"this work made the first proposal for the structure and preparation technique of the DPC ceramic substrate with embedded microchannel to address the issue of power device heat dissipation.We thoroughly investigated the critical technologies for preparing DPC ceramic substrates with embedded microchannels,including TCV filling,high-speed thick copper electroplating on the surface,and embedded microchannel structure preparation.Additionally,we used DPC ceramic substrates with embedded microchannels for power device packaging.The concrete research content includes:1)Structure and process design of DPC ceramic substrate with embedded microchannel:DPC ceramic substrate with embedded microchannel structure was first proposed and designed to meet the heat dissipation requirements of power devices,including TCV vertical electrical interconnection structure and embedded microchannel heat dissipation structure.The critical processes for preparing DPC ceramic substrate were analyzed detailly.The defect-free filling process of TCV with different aspect ratios and the high-speed electroplating process of the thick copper pattern was designed.Moreover,aiming at preparing a microchannel structure embedded in DPC ceramic substrate,the all-electroplating process,including a sacrificial layer process and the thick copper high-speed electroplating technology,was designed.2)TCV defect-free filling technology:In order to realize defect-free and efficient filling of TCV,flow field simulation of TCV in Haring cell,electrochemical analysis of additives,and TCV filling experiments were combined.The flow field distribution variation in TCV with different aspect ratios(ceramic substrate thickness/via diameter)was investigated deeply.The direct current electroplating formula was optimized to improve the TCV filling ability.The effect of the TCV aspect ratio and the interactions among the additives on TCV filling quality were explored.Furthermore,the additives’adsorption model and interaction mechanism in TCV with different aspect ratios were proposed,and the defect-free filling of TCV with multiple aspect ratios(6.25:1-3.17:1)was achieved.3)Thick copper pattern high-speed electroplating on the surface of DPC ceramic substrate:The flow field simulation of Haring cell,Hull cell experiments,electrochemical measurements,and pattern electroplating experiments were combined to improve the thick copper pattern preparation efficiency.The influence of pattern size on the flow field distribution was examined.The high-speed direct current copper electroplating formula was optimized,and the complex interactions among the additives affected by convection and cathode polarization were analyzed.The mechanism of synchronous improvement of pattern electroplating rate and coating quality was determined.An ultra-high electroplating rate of 152μm/h could be achieved under the current density of 8 ASD.The copper coating was dense,uniform,and mirror-bright without defects.4)Fabrication of DPC ceramic substrate with embedded microchannel and its application in heat dissipation of high-power devices:The preparation of DPC ceramic substrate with embedded microchannel was achieved by all-electroplating processes,which comprised of sacrificial layer process and high-speed copper electroplating process.Specifically,tin was selected as the sacrificial layer and was patterned electroplated to achieve the microchannel conformal structure.The column and cover plate of the microchannel was fabricated by the high-speed copper electroplating process,and the microchannel structure was obtained by etching tin.Moreover,the DPC ceramic substrate with embedded microchannel was applied to high-power chip packaging.By combining fluid-heat transfer simulation with heat transfer experiment,the DPC ceramic substrate with embedded microchannel presented excellent heat dissipation performance and realized heat dissipation with an ultra-high heat flux(673 W/cm~2).