Basic Research On Method Of Laser Transmission Micro Welding Of Thermoplastics Based On Binary Optical Technology

More and more people are highlighting laser transmission welding of thermoplastics because of so many advantages, such as excellent welding quality, easy to control, available for micro-welding and so on. But the most advanced technologies of laser transmission welding of thermoplastics are generally in foreign countries, although the domestic people are convinced of the importance to this technology, but there are less substantive researches. And studying laser transmission micro welding of thermoplastics has great significance to solve the problem of connecting plastics in micro-device and micro-device packaging, as well as how to complete welding with high efficiency when there is a complex two-dimensional weld.A new method of laser transmission micro welding of thermoplastics based on binary optical technology is proposed in this paper.First of all, the process system of laser micro welding of thermoplastics is studied, the mathematical model of laser beam and micro welding system are established. The plastic materials and welding absorbent of process system are studied.Secondly, the theory and scalar mathematical models of diffraction optical element (DOE) are established, and as the basis for the establishment of diffraction mathematical model.In succession, the traditional GS algorithm is modified to apply to fresnel diffraction model; The DOE is designed by using the modified GS algorithm, diffraction results are simulated, and because the initial value has great impact to the results calculated by GS algorithm, three typical initial values containing IFT Phase, Constant Phase, Random Phase are selected to simulate and calculate. The results indicate that use of IFT Phase as the initial value can get higher diffractive efficiency and smaller Sum of Square Error (SSE); The target image is encoded, the influences to the calculation results are analyzed when add amplitude freedom and phase freedom to the target image respectively and simultaneously. The results indicate that add appropriate amplitude freedom and phase freedom to the target image simultaneously can improve the diffraction effects; The DOE is designed when the target image is complex, the good results prove the correctness of the procedure.At the end of paper, the DOE is designed and fabricated to the Nd: YAG laser. The diffraction experiment results indicate that the shape of laser beam spot after diffraction is almost as same as the shape of target image. This research lays a solid foundation of research on method of laser transmission micro welding of thermoplastics based on binary optical technology.