| The technology of wave soldering by electromagnetic force driving tin liquid has the characteristics of low cost and high reliability.Selective wave soldering equipment with metal electromagnetic flow control technology as the core can realize stable spray of liquid column and precise control of wave peak height by controlling the input current or magnetic field,so as to ensure the reliability and effectiveness of welding.In this paper,the electromagnetic theory and fluid theory are combined,and the COMSOL Multiphysics multi-physics coupling simulation software is used to obtain the most suitable wave crest for welding,and the electromagnetic-magnetic-fluid coupling numerical simulation of the wave crest generator,the core structure of the wave soldering equipment,is carried out.,respectively analyzed the influence of valve body flow channel shape and size combination and nozzle shape and size combination on each physical field,and processed the optimal structure combination for experimental research.During the simulation process,the material parameters required for the simulation are obtained through experimental measurement or by looking for relevant literature.The SN63 A type electrode with a melting point of 183°C is used as the solder,and the density,viscosity and conductivity of the solder are measured at a temperature of230°C.The magnetic field strength of the sintered Nd Fe B permanent magnet at room temperature is 4.5685 T.Secondly,based on the COMSOL Multiphysics simulation software,an orthogonal simulation method was established,which comprehensively considered the energy utilization rate,the height of the wave crest and the flow state of the melt,and set the shape and three-dimensional size of the runner model of the valve body and the nozzle.Using the load transfer coupling method and taking the outlet pressure value as the evaluation basis,the shape and size of the flow channel of the valve body and the nozzle are simulated respectively,and the influence of the structure size of the valve body and the nozzle on the peak height and flow state is analyzed.The results show that the conical flow channel with length L of 38 mm,width D of 6mm and height H of 61 mm as the peak generator has the highest energy efficiency and lower cost.Generally,the nozzle aperture used by wave soldering machines is 3-6mm.The nozzle structure selected by simulation in this paper is a cylindrical runner nozzle with a height of 16 mm and a nozzle aperture of 3 mm.Experiments show that due to the influence of temperature and distance,the magnetic field strength in the tin melting tank is only 3.6 T,and the other input conditions remain unchanged.After combining the optimal valve body and nozzle,multi-field coupling analysis is carried out to obtain the average value of the simulated nozzle outlet.The speed is 0.7 m/s.In the experimental study,according to the electromagnetic induction principle,the three-dimensional structure of the peak generator is combined,the valve body is designed as the main body,the valve cover and the Teflon insulating housing three Part,the internal shape of the Teflon insulating housing is the conical flow path obtained by the simulation analysis,and the main body,the body and the valve cover portion still need to be plated to Toflon.Secondly,based on parameter measurement experiment,the magnetic field force of the permanent magnet is set to 3.6 T,the current value of 70 A and the tin liquid temperature 230 °C are performed,respectively,the original and the optimized valve body combined with the nozzle were carried out,then the results were analyzed.The results show that the maximum peak height produced by the optimized pre-peak generating device is 28 mm,and the annex is 0.2 mm.Only the maximum wave height is 33 mm when the nozzle is optimized,and the exit speed is0.3 m/s,and the optimized rear device is generated.The maximum wave height is 42 mm,and the exit speed is 0.6 m/s,that is,the exit speed is increased by about 67%.The optimized structure simulation exit speed is 0.7 m/s,the experimental results are more than 14%,and the error is 14%,and the error is within the allowable range,the parameter setting of the simulation model will be reasonable,the simplification process is reasonable,and the experimental device is accurate It demonstrates the feasibility of simulation structure.The experiment was obtained at the input current 50 A,the magnetic field strength of 3.6 T,the temperature of 240°C,obtained 0-9 mm adjustable stable liquid column,with respect to general welding wave height 0.25-4.3mm,and the experimental result is high to satisfy most soldering scenes. |
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