Design And Experimental Research Of Laser Melt Jet Welding System

With the increasing number and decreasing size of pins on the chip,the modern electronic manufacturing industry put forward higher requirements on the material and equipment technology of soldering.At present,the lead-free solder has some disadvantages such as high melting point,poor wettability and quite complex species to chose.The traditional reflow and manual soldering method hold many defects for it's complex procedure and low efficiency,and the solder joints formed by such traditional method using lead-free solder are of poor quality.To solve the above problems,this paper designs a kind of laser solder jet equipment,which used to improve the welding quality and efficiency.It meets the needs of modern electronic manufacturing industry,and promotes the development of the industry.The main research contents are as follows:The paper select the material and diameter of the solder ball used for analysis,and determine the influencing factors of it's physical parameters.Through theoretical analysis on the heating process of solder ball,the paper concludes the laser energy absorption rate of solder ball and find out the heat dissipation process which caused by thermal radiation and heat conduction;analysis the factors such as surface tension,Van der Waals force,parameters of nozzle,working pressure of nitrogen and diameter of the solder ball,and concludes their influencing characteristics on the average velocity of molten solder ball just when it separating from the nozzle;determine the factors influencing the maximum spreading diameter of the molten solder ball,and concludes the conditions when the molten solder ball breakup and splash.On the basis of theoretical analysis,then the paper simulates the solder ball heating process,molten solder ball jetting process,and at last solder joint forming process by using the finite element method and software based on it.In this step,the paper analysis the influencing characteristics of the parameters of nozzle,the wetting angle between molten solder ball and nozzle,the gas working pressure,the gas working time,the laser output power and the temperature of molten solder ball,at last concludes a set of parameters with which the system working well.Then according to the parameter settings,the paper determine the type and structure of parts and electronic components of the laser jet welding system.These conclusions provide a basis for the whole system design and subsequent experimental research.The paper carried out the whole structure design of the laser jet welding system,and then built the machine and establish the experimental platform.The experiments investigate the influence of motor speed on the success rate and stability of the solder ball transmission process,and determine the optimal speed of motor is at 0.25r/s.Then on the basis of simulation and theoretical analysis,the paper test the whole system and obtain the optimal parameter settings which the laser output power at 90 W,laser output time at 20 ms,working gas pressure at 5500 Pa,gas working time at 6.2ms,nozzle diameter at 0.5mm,solder ball diameter at 0.76 mm,under these parameter settings,the solder ball joints formed by the system are of high quality.By using the optimal parameter settings obtained above,the paper conducts the single factor experiment,concludes the influencing factors on solder ball transmission process and molted solder ball jetting process and the factors' influence characteristics on these process.