Laser-induced Electroless Copper Deposition On Modified Plastic Surface

Along with the electronic industry is moving toward a miniaturization,simplicity and low pollution, the traditional electroless copper plating process can nolonger meet the requirements. Laser is introduced into the electroless plating processcan not only simplify the process, but also can accomplish the task of completeselective electroless plating of copper without mask, in which the process is preciselycontrolled by computer.The most important step in the electroless plating process is activation.Traditional heavy metal activation process not only is comlicated and expensive, butalso cause pollution to enviroment. In this paper, focusing on a novel technologycalled laser induced electroless plating, efforts are made to the investigation of itsmechanism and the relevant experimental studies. This process can selectivelydeposit copper on surface of plastic matrix without Pd activation, which can bedescribed as follow: The surface of modified plastic was treated by the fiberlaser(wavelength1064nm) at first, then the sample was dipped into the5%NaOHsolution and cleaned with ultrasonic washer for10minutes, rinsed with distilledwater to clean. Finally, the irradiated sample was immersed in an electroless copperplating bath for2h and deposition of copper is achieved on the laser irradiation area.Through in-depth analysis of experiments, combined with XPS, SEM, surfaceroughness instrument, optical microscope and other experimental apparatus onexperimental samples, the following conclusions can be drawn:on the one hand, thelaser irradiation increased the surface roughness of plastic substrate which enhancedthe mechanical meshing between the Cu plating and substrate to improve the adhesivestrength; on the other hand, after laser irradiation, the surface of the modified plasticsubstrate containing copper oxide due to organometellic compound decoposition,which will serve as the catalytic center of the subsequent electroless copper platingBy changing the parameters of the laser power, pulse frequency, scanning speed,and scan spacing, we can research their effects on the topography, width and continuity of the line, and then determine the optimum conditions for laser surfacetreatment. At the same time, in order to optimize the selective electroless copperplating process, the influences of the complexing agent, bath additives, PH and thetemperature of solution on the deposition rate and plating properties were studied.Atlast,the comprehensive evaluation of the copper plating was given: the deposition areais confined in the laser treated portion resulting in well selective plating; Theresistivity of the Cu pattern is determined to be about2.02u·cm, which iscomparable to that of bulk Cu(1.67u·cm);the tape test results show that copperpattern has an excellent adherence with the plastics suface.