| Laser welding of dissimilar materials is a processing technology which uses laser beam for energy absorption,conversion and material melting to realize the direct combination between materials.This technology has the advantages of green environmental protection,high processing efficiency,no direct contact with the workpiece,simple operation and low cost.Based on the existing problems in flexible copper clad laminate manufacturing technology,this paper proposed a method of laser welding to realize the direct combination of copper foil and polymer.On the basis of single laser welding technology,combined with UV laser etching technology,laser shock flattening and imprinting technology,the combination of multiple technologies can ensure high bonding strength and further reduce the copper foil surface roughness,and then reduce the effect of current loss due to the skin effect.In this paper,the effects of copper foil surface roughness,preheating temperature,modification,flattening and imprinting on the experimental results were studied.The reasons for the change of bonding strength between copper foil and polymer were analyzed and discussed.The mechanisms of coarsening,modification,flattening,imprinting and high bonding strength were revealed.Firstly,the feasibility of laser welding of dissimilar materials(copper foil and polyethylene terephthalate)was tried by a single laser welding technology,which laid the foundation for its application in flexible printed circuit board.In this part,the influence of laser parameters(welding speed and laser power)on the bonding strength of copper foil and PET was carried out,and the optimal parameters were determined.On this basis,the copper foil surface was roughened,and the influence of surface roughness on the bonding strength of weldments was studied.The results showed that the bonding strength of roughened copper foil was 376.6% higher than that of original copper foil and PET.Finally,the preheating experiment was carried out to further improve the bonding strength between copper foil and PET,and the bonding strength of the weldment increased by 427.9% after preheating.Based on the experimental results,the reason for the improvement of welding strength was explained and the bonding mechanism was revealed.Secondly,in order to adapt to the development trend of thin,light,short and small electronic products,20 ?m thick copper foil and liquid crystal polymer(LCP)were used for welding experiment,and UV laser treatment technology was introduced to ensure high bonding strength and enhance the peel strength of copper foil and LCP.The results showed that the peel strength of copper foil and LCP can reach 682.78N/m under the ultimate bonding strength.This section proposed a laser integrated manufacturing method,which was easier to realize automation in the actual production process,and balanced the relationship between the copper foil surface roughness and the bonding strength of weldment.Finally,on the basis of the previous research,in order to further reduce the influence of skin effect in high-frequency and high-speed signal transmission,this part integrated laser shock(including laser shock flattening and laser shock imprinting)technology and laser welding technology,and studied the change law of copper foil in the process of laser processing.By laser flattening technology,the copper foil surface roughness was reduced from 40.6 nm to 7.8 nm,which was reduced by 80.8%.By laser shock imprinting technology,regular array nanostructures can be fabricated on the copper foil surface,the diameter of cylinder can reach 582.9 nm,which was close to the limit size of mold diameter of 600 nm,the imprinting effect was good.The high bonding strength of flattened and imprinted copper foil and LCP was achieved by laser welding technology.The mechanism of flattening,imprinting and welding was revealed by FSEM and AFM.There are 52 figures,8 tables and 100 references in this paper. |
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