Research On Welding Technology Of Ultra-thin T2 Copper/6061 Aluminum Alloy By Using Pulsed Laser

Copper has been widely used due to its good thermal conductivity,electrical conductivity,ductility and corrosion resistance,but its cost is high.While the electrical and thermal conductivity of aluminum is close to that of copper and the cost of fraud is low,aluminum is often used in the industry to replace part of copper to reduce production costs.Copper and aluminum vary greatly in physical and chemical properties,so welding between copper and aluminum is difficult.In the thin,medium and thick plates,the methods commonly used in copper-aluminum welding are continuous laser welding,friction stir welding and brazing.The research direction of this subject is the application of ultra-thin copper-aluminum composite structure in 3C electronic products.The method is not applicable,only nanosecond fiber laser welding is suitable for the welding of ultra-thin difficult-to-weld materials.Welding by nanosecond pulsed fiber laser is an emerging welding method.Compared with other common welding methods,its main advantages are as: pulse width is nanosecond,welding heat affected area is very small,so the weldment deformation is very small;solder joint size can be flexibly adjusted,and solder joint size can be very small.The repetition rate laser beam output with good repeatability is high.This type of welding is currently in the application stage,and there are few detailed studies at home and abroad,especially in the field of ultra-thin heterogeneous hard-to-weld materials.The objective of this project is to study the process window of nano-pulse fiber laser welding with thicknesses of 0.1mm copper and aluminum dissimilar materials,the weld forming mechanism,the electrical and mechanical properties of copperaluminum composite structure and the fracture mechanism of joints.This paper analyzes the pulse waveforms corresponding to the eight pulse widths and the single pulse energy,60 ns is the most suitable for nanosecond pulse welding,then uses different process parameters to pre-experiment the 0.1 mm thick copper aluminum plate.The formal process of round spot welding and the well-formed joints are: power is 75-90 W,welding speed is 30-40 mm/s,frequency is 210 KHz,line spacing is 0.03-0.06 mm.According to the weld surface and cross-sectional shape,the influence of different laser process parameters on the formation of solder joints was analyzed.The 150 W pulse laser has a spot diameter of 0.05 mm,and the minimum laser average power density of the ultra-thin copper plate can be 3.6x106 W/cm2.The welding mechanism is similar to the laser deep-welding welding mechanism.The law of the interaction between the nanosecond laser and the metal material is used to derive the theoretical weld process of the ultra-thin and difficult-to-weld dissimilar materials.Then,the specific morphology of the weld at 90 W and 120 W is observed by electron microscope and the elemental energy spectrum analysis is performed to obtain the nanosecond pulse.The welding process and forming mechanism of the ultra-thin and difficult-to-weld dissimilar materials under laser action.Then,through the high-speed camera,the welding process with the line spacing of 0.03 mm and 0.06 mm respectively is obtained,and the power is moderately increased to increase the line spacing,which can effectively suppress the heat accumulation effect.Finally,the specimen was subjected to shear test,and the maximum shear force of the joint was 123.987 N,and the average shear force was 111.012 N,which was 70% of the maximum shear force of the copper base material.Under the action of shearing force,the position of the joint is mostly concentrated in the first few lasers and the action of the material,and the fracture mode is plastic fracture.The copper-copper joint and the copper-aluminum joint were tested by a semiconductor measuring instrument respectively,and the copper-aluminum joint had a slight decrease in electrical conductivity compared to the copper-copper joint,but its electrical conductivity was still between the conductor and the semiconductor,which proved it is feasible to apply the 0.1mm thick aluminum partial copper composite structure to the internal and external components of 3C electronic products.