Study On Preparation Technology Of Monodisperse Polymer Microspheres For Anisotropic Conductive Films

The research content of this paper is a part of the program "Research of Basic Set Material in Multi-layer Connecting Flexible High Welding Density Circuit " (No.00107), which is subsidized by The Education Ministry in 2000. The purpose of the research is to design and prepare monodisperse (coefficient of variation ?^ 0.05) polymer microspheres with micron size and different compose, structure, property through complete system research, and to develop a good technology for functionalizing the polymer microspheres surface and preparing anisotropic conductive films in later jobs.Firstly, polystyrene (PS) microspheres with different size were prepared by emulsion polymerization, suspension polymerization and dispersion polymerization. Three sorts of microspheres were compared in size, size distribution and polymerization dynamics, then dispersion polymerization was selected as experiment system. Secondly, the internal influence factors (stabilizer, co-stabilizer, monomer, initiator) and the external influence factors (the polarity of reaction media, reaction temperature, stirring rate) in dispersion polymerization, which affected size, size distribution, and polymerization dynamics, were investigated. On the basis of influence effects of all factors, monodisperse polystyrene microspheres in the size range of 1.0~ 10.0 u m were prepared in reaction conditions optimized in dispersion polymerization. Monodisperse polystyrene microspheres with micron size withdifferent size and size distribution can be designed to prepare by people. Finally, monodisperse polymethyl methacrylate (PMMA) microspheres with micron size were prepared in optimum conditions. Meanwhile the appearance and morphology, dispersion, technology stability and other properties of PS and PMMA homopolymer microspheres were characterized.In order to satisfy with the application of anisotropic conductive films, monodisperse polymer microspheres with micron size should be modified, such as the property of surface, heat-resistance, solvent-resistance etc. Adding the copolymerization monomer and crosslinked monomer in dispersion polymerization system, copolymer microspheres and crosslinked polymer microspheres with micron size with narrow size distribution were prepared. These kinds of functional polymer microspheres have better properties of heat-resistance and solvent-resistance.Due to applying large amount of solvent in dispersion polymerization, solvent problem have become an obstacle in extending this technology. In this paper, the feasibility of recycling solvent in dispersion polymerization was investigated. The results showed that the solvent in dispersion polymerization could recycle some times. The size of polymer microspheres and the coefficient of variation increased slightly with increasing the times of recycling solvent. If the coefficient of variation e of polymer microspheres increased beyond the applying range, the solvent must be purified.