Research On Key Techniques For Polymer Micro Hot Embossing

Micro hot embossing now is becoming the most important technology as its advantages such as low cost, rapid fabrication, high efficiency and excellent flexibility. Supported by the National Nature and Science program'Research on fabrication on conductive polymer via hot embossing'(No.50905162), this article gives out the research on fabrication on polymer and conductive polymer via micro hot embossing. Actively to solve the current problems about the development on hot embossing, the process models are established for both large deformation of embossing process and small deformation of demolding process. The effects of both the geometry parameters and technological parameters are investigated, also some experiments are taken out to verify the simulation results and model theory. A new method of fabricating micro structures on conductive polymer is expounded, the variations of conductive polymer property under the impacts of shearing are indicated.In chapter 1, the background and significance of the hot embossing on polymer and conductive polymer are introduced, include the current research, development trend, advantages and disadvantages. Then the study of this dissertation is proposed.In chapter 2, based on the polymer rheological mechanism, the property of viscoelastic model is introduced. The process of polymer micro hot embossing is separated into two parts, one is about the large deformation of embossing and the other is about the small deformation of cooling and demolding. The thermo-mechanical finite deformation theory and Power-Low model are used for the two processes. The model parameters of PMMA are given out.In chapter 3, the simulation model is established to investigate the impacts of geometry parameters and technological parameters on embossing process such as the flow behavior, filling efficiency and the stress concentration. The closed mold structures are used to analyse the limitation of the flow behavior. Also the differences of isothermal hot embossing and non-isothermal hot embossing on the polymer forming profile are proposed.In chapter 4, the principles of the stress distribution during the demolding process are developed. A simulation method is given out to verify the stress concentration due to the effects of demolding velocity and angle. The stress mainly accumulates at two parts, one at the transition corner between the mold cavity and the embossed polymer pattern, the other at the contact region where the moving mold cavity edge contacting with the replicated pattern profile during the demolding process.In chapter 5, a small pressure device is designed for experiments; the orthogonal method is used to optimize the embossing process. Also the simulation results are compared with experiments to demonstrate the simulation model.In chapter 6, the research on conductive polymer micro hot embossing technology is indicated. The PMMA is used as the substrate of conductive polymer film. Also under the shearing effect, the variations of conductive polymer property under the impacts of shearing are indicated.In chapter 7, the study and conclusions of the dissertation have been summarized and the further research works have been forecast.