Study On The Rheological And Mechanical Properties Of TiO₂ Nano-doped Tin Paste And The Design Of Key Parts Of Printing Machine

With the rapid development of microelectronics technology,microelectronics packaging technology has become the mainstream of electronic packaging technology,with high assembly density,electronic products small size,light weight,high reliability.Traditional screen printing technology has reached the limit of solder joint size and pin spacing,and cannot meet the requirements of 3D packaging.Solder paste printing technology is a new technology of non-contact solder paste distribution combined with ink-jet printing technology.Solder paste printing technology on the rheological properties of solder paste is still very lack of research,solder paste in the printing process is prone to plugging phenomenon,resulting in production can not be continuous,low efficiency.In addition,the development of solder paste printing technology has put forward higher requirements for the printing equipment,the existing solder paste printing equipment still has the problems of low life,easy to block,wearing parts,high price.Therefore,it is necessary and urgent to study the rheological properties,mechanical properties and the core structure and simulation of printing equipment of compound solder paste.In this paper,the influence of TiO₂ nanoparticles on the rheological properties and solder joint mechanical properties of printed solder paste was studied.In addition,the important parts of the printing device are studied,such as the nozzle and firing pin,and the design and simulation of the amplifying structure are carried out,and the following research results are obtained:1)Nano doping method was used to add TiO₂ nanoparticles on the basis of SAC105 solder paste.Mechanical properties,microstructure and rheological properties of the modified solder paste were studied by means of tensile machine,scanning electron microscope,rotating rheometer,viscometer and other equipment.It was found that the shear strength of TiO₂nanoparticle doped modified SAC105 paste welded joints reached up to 71.4MPa,which was65%higher than that of undoped SAC105 joints.This was attributed to the significant increase in shear strength due to the second phase strengthening of TiO₂ nanoparticles in solder joints.The creep test results showed that the deformation area of the creep compliance curve of the TiO₂ contents 1%SAC105 solder paste was about 50%smaller than that of the undoped SAC105 solder paste,indicating the potential of effectively inhibiting the swelling effect of the solder paste at the nozzle of the printing equipment.The study also found that adding TiO₂nanoparticles with a content of 0-2%could significantly adjust the paste viscosity value from98.3 Pa.s to 127.0 Pa.s with the thixotropic coefficient of 0.73-0.75 basically unchanged,providing a new method for coupling regulation of thixotropic coefficient and viscosity of printing solder paste,which has application prospect for the 3D printing and packaging industry of circuit board.2)Based on the theory of piezoelectric ceramics,the structure of printing equipment was designed and analyzed by Ansys Workbench simulation software.The main design parameters were given:Angle=6.10°,wall thickness=0.62mm,side thickness T=5.10mm,and shape width B=10.10mm.The theoretical amplification factor of diamond structure is 9.36 According to the statics analysis of Ansys Workbench,the amplification factor is 9.05,which is consistent with the calculated value.Aiming at the problem that nozzles are easy to be blocked and expensive,a new composite structure nozzle is proposed,which can effectively reduce the friction and increase the wear resistance of the nozzles in the process of printing by coating the nozzles with diamond-like vapor deposition technology.In this paper,the composite TiO₂-SAC105 solder paste was prepared by TiO₂ nano-doping method,which effectively regulated the rheological properties and microstructure of solder paste,and obtained the solder paste with good viscosity,thixotropic coefficient,creep and other rheological properties and high shear strength mechanical properties.The structure and main design parameters of printing equipment are given by means of technology and software simulation,and a new composite structure nozzle is proposed,which provides theoretical guidance and experimental basis for the application of printing technology in electronic packaging industry.