Study On Device Performance And Reliability Based On Nano Copper Package

With the development of the third generation of semiconductors,the industry has higher requirements for the switching frequency,voltage and power of power devices,which also means that the packaging of power devices in the future needs to withstand higher operating temperatures and greater power density.Nano-copper materials benefit from their excellent thermoelectric properties and the low-temperature sintering characteristics of nano-materials.Researches on the application of nano-copper in power device packaging has great practical prospects and value.This paper studied the interconnection process and reliability of nano-copper sintered devices.In the first aspect,this paper optimized the parameters of the interconnection process from four angles:sintering temperature,sintering atmosphere,interconnection interface and sintering pressure,and proposed a set of interconnection processes for nano-copper sintered devices.In the relevant tests,there are mainly the following findings.(1)When the sintering temperature is increased from 240?to 300?,the sintering degree of the nano-copper particles and the reaction rate of the organic carrier in the solder paste will be improved.When the sintering temperature is 300?,on the premise of avoiding high temperature damage to the device,it can achieve effective chip interconnection and obtain better solder layer density.(2)The participation of H₂ in the sintering process can have a good reduction effect on copper oxide,but as the concentration increases,the porosity of the solder layer also gradually increases.When the sintering atmosphere is 15%H₂ and 85%Ar,the best sintering quality can be obtained.(3)The choice of interconnection interface is the premise of whether the device can be interconnected.Ni,Cu and Ag can make the device successfully interconnected.When the interconnection interface is Cu,the shear strength of the device reaches the maximum,which is 12.03MPa.(4)In the range of 0-0.52MPa,the increase in sintering pressure helps to reduce the porosity generated during the sintering process of the solder layer,and a tight connection will be formed inside the device.When only 0.52MPa is applied during the sintering process,the sintered quality of the device prepared at this time is the best,and the shear strength can reach 11.5MPa.At the sintering temperature of 300?,the sintering atmosphere was 15%H₂ and 85%Ar,the interconnection interface was Cu,the sintering pressure was 0.52MPa,and the application stage was the sintering stage.The feasibility of the interconnection process.-In the second aspect,the reliability test of the nano-copper sintered device prepared by this process was conducted in this paper.The reliability test cycle was 1000 cycles,and the duration of each cycle was 1h.During the temperature shock test,the thermal resistance of the device will decrease in 0-200 cycles,and gradually increase in 200-1000 cycles.Combined with finite element simulation and porosity test,it is found that the change of thermal resistance is related to the porosity in the solder layer.At the beginning of the reliability test,the sintering residual stress in the welding layer was released,and the quality of the internal structure of the welding layer was improved.After that,temperature shock generated new stress in the welding layer,and the quality of the joint declined.In the reliability test of the pores in the solder layer,stress concentration occured in the surrounding area.As the test period increases,the pore volume grew.The position of the initial pores in the weld layer also had different effects on the distribution of stress.When the pores are at the edge,their impact on the surrounding weld layer is greater than the pores in the center.