Study On Sintering Process And Properties Of Composite Micro-Nano-Cu@Ag Solder Paste

Third-generation semiconductors and their power devices SiC,GaN,fieldeffect devices,schottky diodes,etc,have been widely used in automotive electronics,high-speed locomotives,energy development and transmission,aerospace industry,Marine exploration and other fields,and to high-density,highpower,multi-functional direction.However,due to the performance,cost,environmental protection and other factors of electrode extraction chip,its packaging material can not meet its work requirements.Therefore,the research and development of a new lead-free solder is urgent,it can be used for high temperature power equipment packaging,can be connected at low temperature,at high temperature use.In order to improve the performance and cost of nano silver or copper solder paste,the method of mixing micro-nanoparticles in solder paste was introduced.Cu@Ag core-shell particles with different particle sizes were prepared by liquid phase reduction method.The particle sizes of Cu@Ag core-shell particles on 50,5 and 20 micron copper particles are 30-70 nm,3-5 ?m and 15-25 ?m,respectively.The core-shell particles were mechanically mixed at a mass ratio of 5:3:2 and mixed evenly with the organic solvent echinol.The composite mirconano Cu@Ag solder paste was prepared by 80:20 mechanical stirring and ultrasonic dispersion method.The street micro-structure morphology of composite micro-nano Cu@Ag solder paste connecting analog chip and copper substrate was observed,and its internal structure morphology was studied and compared with the expected structure morphology in the design process of the solder paste.Moreover,the effects of sintering temperature,holding time and bonding pressure on the microstructure and morphology of the joints under different process conditions were carefully analyzed.The results show that the solder paste can successfully connect the analog chip to the copper substrate,and by observing the morphology of the internal microstructures of the joints,it can be found that the internal microstructures of the joints are distributed among the large particles embedded in the small particles,which is the same as the expected microstructures.The change of internal structure under different sintering temperature,holding time and connecting pressure was studied.With the increase of sintering temperature,the density increased continuously,but when the temperature reached 300 ?,the increase became gentle.With the increase of holding time,the density increased continuously,but with the increase of sintering temperature,the density increased gradually.After more than 30 minutes,the voids begin to increase and the porosity increases slightly.With the increase of the connecting pressure,the density increases continuously.However,when the pressure increases to 10 MPa,it is found that the thickness of the sintered layer decreases to about 10 ?m,and that the copper substrate has obvious plastic deformation.The influences of sintering temperature,holding time and joint pressure on its mechanical properties were analyzed under different technological conditions.The shear strength of the joint and its fracture mechanism were studied in detail,and the influence mechanism of the shear strength of the composite core-shell particle solder paste under different technological conditions was deeply analyzed.Through the result of the test,with the increase of sintering temperature,the shear strength increases gradually,but when the temperature reaches 300 ?,the shear strength increases gradually smooth.With the extension of the holding time,the shear strength gradually increased,but when the holding time was extended to 30 min,the shear strength decreased slightly.The shear strength increases with the increase of connection pressure.After the high-temperature aging test and the temperature cycling test respectively,it can be found that after the hightemperature aging test,the shear strength of the joint increases slightly in the first 24-96 h,and gradually decreases after 96 h.However,after the temperature cycling test,it was found that the shear strength of the joint did not change significantly at first and then gradually decreased with the increase of the number of cycles.When the number of cycles was 200,the shear strength was only 2.3 MPa.It is found in different reliability tests that the influence of temperature cycle on the reliability is more significant.