Research On Key Technologies Of Selective Laser Metallization On Polycarbonate Surface

With the rapid development of portable wearable electronic devices,light-emitting displays?LEDs?,microelectronics,bioelectronics,etc.,it becomes more and more urgent to develop a novel and advanced technology of selective metallization on the surface of dielectric materials.The selective metallization technology basing on laser rapid activation and electroless plating has such advantages as simple process,wide application range,low cost,high efficiency,and wide range of applicabale substrates.In this paper,spinel type compound X₂?OH?YO₄?X was one of transition metallic elements and with variable chemical valence;Y was one of the III_A or V_A main group elements in periodic table?was selected as laser active matter for the substitution of some precious metallic compounds?e.g.,palladium chloride and silver nitrate?.It had such obvious advantages as low cost and high selectivity.X-ray photoelectron spectroscopy?XPS?was used to investigate its interaction mechanism and change trend with three lasers?i.e.,1064 nm-wavelength nanosecond pulse fiber laser,continuous fiber laser,and355 nm-wavelength nanosecond pulse ultraviolet laser?.The results showed that,when the nanosecond pulse fiber laser was used,within the range of laser energy density of2.76-24.00 J/cm²,the reduction ratio of X²⁺to X⁺in laser-treated products increased first and then decreased with the laser energy density.For the continuous fiber laser,in the range of the laser power of 0.13-3.89 W,there was no stable change trend for the reduction of X²⁺to X⁺with the laser power.When X₂?OH?YO₄ was treated by the ultraviolet nanosecond pulse laser,with the increase of the laser energy density in the range of4.68²5.48 J/cm²,the X²⁺in the X₂?OH?YO₄ were more and more reduced to X⁺gradually.Finally,combining thermogravimetric analysis?TGA?with ultraviolet-visible absorption spectroscopy of X₂?OH?YO₄,it was preliminarily inferred that,in the above reduction process,the photothermal and photochemical reaction happened simultaneously.Comprehensively considering the reduction effect of X₂?OH?YO₄ under laser action,the influence on the surface morphology of polycarbonate?PC?,the price of the lasers,and the processing efficiency,the nanosecond pulse fiber laser was selected as the laser source for further investigating the copper electroless plating.The influence of laser energy density and electroless plating conditions on the electroless deposition rate and quality of copper layer were discussed in detail,and scanning electron microscopy?SEM?was used to observe the microstructure of the copper deposition layer.The results showed that the optimal experimental conditions for the selective metallization on the PC surface by nanosecond pulse fiber laser were as follows,laser energy density of 13.67 J/cm²,electroless plating conditions of pH=12.5¹3.0,temperature T=55⁶0?,and inert-gas argon stirring.Under these conditions,after 90 min electroless plating,the copper layer with excellent selectivity,the thickness of about 2.76?m,and the volume resistivity of about 3.85??·cm could be obtained.The adhesion strength between the deposited copper layer and PC substrate met the standard of 4B-5B after the test by the method B of American Society for Testing and Materials?ASTM?D3359-08.Therefore,this was a high-efficiency,low-cost,excellent-selectivity selective metallization technology with broad application prospects.