Simulation Of Parallel GAP Resistance Welding Of Solar Cell And Interconnector And Optimization Of Process Parameters

Space solar cells are the main components of spacecrafts to supply the energy.Their service life in complex space environment has always been an important qualification to measure the performance of solar cells.At present,parallel gap micro-resistance welding technology is mainly used to connect the interconnector and solar cell.However,due to the influence of interconnector material and thickness,electrode morphology and size,welding voltage,welding time and other parameters,the contact state and temperature distribution of the interface in parallel gap resistance welding process are complex,the quality consistency of the joint is poor,and the performance of the joint will affect the service life of solar cells.Therefore,it is necessary to carry out simulation and experimental research on parallel gap micro-resistance welding process of interconnector and solar cell,to determine the optimal strategy of interconnector material and parameters of parallel gap resistance welding,so as to improve the quality of the joint.Aiming at the quality problem of parallel gap resistance welding between solar cell and interconnector,on the basis of synthesizing the latest research progress at home and abroad,silver plated molybden?m composite interconnector was prepared in this paper.The electrical performance and surface morphology of the interconnector and their effects on welding process were analysed.The finite element simulation model of parallel gap micro-resistance welding for solar cell and interconnect was established.The evolution laws of stress distribution,current density distribution and temperature field distribution between different interfaces during the welding process were obtained,and the simulation result was verified by experiments.On this basis,the influences of the process parameters,such as welding voltage,welding time and electrode gap,and the material property and thickness of the interconnector on the joint temperature field were analysed,which can provide reference for the selection of process parameters and the design of interconnector for parallel gap resistance welding of solar cell and interconnector.The main research contents and conclusions are as follows:(1)Material preparation and performance evaluation of interconnectorDouble-sided silver-plated molybden?m interconnector was prepared by electron beam evaporation.The coating thickness,surface morphology,bulk resistance,contact resistance and their effects on welding process were analyzed.The results show that the thickness of the coating is precisely controlled and the surface is smooth.The contact between the coating and the substrate is close.The quality of the prepared sample meets the welding requirements.(2)Simulation modeling of parallel gap resistance welding process of solar cell and interconnectorA finite element simulation model for parallel gap resistance welding of solar cell interconnects is established.The simulation results show that the maxim?m temperature of the battery-interconnect interface is 890 C,which is less than the melting point of the welding piece,so the connection mechanism is solid-state connection,the temperature at the end of the electrode is higher than the temperature of the welding piece,the heat flows from the electrode to the welding piece,and the gap size of the electrode will affect the current density distribution and heat transfer state in the welding process,thus affecting the welding quality.The simulation results are validated by establishing an on-line infrared temperature measurement experimental system.The deviation between the experimental results and the simulation results is less than 6%,which is in good agreement.(3)Study on the effect of process parameters on welding performanceBased on the finite element simulation results,the influence of welding voltage,welding time and electrode clearance on welding quality was explored by combining infrared temperature measurement experiment and 45 degree tensile shear experiment.The results show that when the welding voltage is 0.8V,the welding time is 50 ms and the gap between the electrodes is 0.2mm,the joint strength is the highest,and the critical optimal temperature of the interface between the electrodes and interconnector is 900.2?.When the temperature is higher or lower,the joint strength decreases.(4)Study on the effect of interconnector on welding performanceThrough finite element comparative analysis,combined with metallographic experiment and SEM/EDS test,the influence of the substrate's material and thickness of the composite interconnector on welding quality was investigated.The results show that at the same welding parameters,silver-plated Kovar interconnector have higher temperature and more element diffusion on the welding interface than silver-plated Mo interconnector,silver-plated Mo interconnector with 15 ?m substrate thickness have higher temperature and more element diffusion on the welding interface than silver-plated Mo interconnector with 25 ?m substrate thickness.Considering the weldability,the substrate material with high resistivity and small thickness should be selected.