Study On Glass Fiber Reinforced SU-8 Micro Molding Technology

SU-8 is a negative photoresist that can pattern high aspect ratio microstructures at a low cost.It has broad application prospects in the field of non-silicon MEMS.While there are multiple advantages of prototyping microstructures with SU-8 by lithography,SU-8 has lower modulus of elasticity and breaking strength,compared to inorganic materials.Using high-strength reinforcing material composites is one of the most common improving method of this type of materials.However,there are not many studies on the improvement of mechanical properties reported.What's more,the existence of the reinforcing materials often affects the lithography ability of thick photo resist.Therefore,it is of great significance to carry out innovative research on the SU-8 photo resist composite modification technology to expand its application in the MEMS field.The main research contents and results of this thesis are as follows:1.Based on a systematic summary of the studies of SU-8 composite modification,and previous work of our research team in the field of SU-8applied technology,micro glass fiber reinforced SU-8 was proposed.This research is intended to develop a modification technology that can effectively improve the mechanical strength of SU-8 microstructure without significantly affecting its photolithography molding ability of thick films,so that it will gain superior mechanical properties while maintain the low-cost manufacturing.Thus this new material can better meet the design and manufacturing requirements of non-silicon MEMS devices.2.Aiming at the research ideas of using micro glass fiber as a reinforcing material,this research firstly demonstrates its novelty through comparison with domestic and foreign research schemes.Secondly,this research demonstrates the advanced nature of the micro glass fiber.Lastly,this research demonstrates the feasibility from the aspect of microfabrication.3.Aiming at the research project of micro glass fiber reinforced SU-8,based on the finite element analysis method,a simplified approximate model was established.Using ANSYS software as the circumstance of finite element analysis,the simulation analysis of the strengthening effect of glass fiber fabrics on the mechanical properties of SU-8 thick-film material is presented.Factors such as cell definitions,boundary conditions,and load application methods were analyzed.The calculation results show that the glass fiber composite can significantly improve the mechanical strength of the SU-8 composite material.The higher the proportion of reinforcing material is,the more significant the strengthening effects.The tensile strength increases almost linearly with the glass fiber content.This model validates the principle of glass fiber composite rationality.In addition,the error sources of the calculation results of the composite material's elastic modulus are also analyzed.4.The composite precursor preparation procedure of spin coating SU-8 photo resist-fiberglass fabric stamping-prebaking-spin coating SU-8photo resist again,was developed.Through repeated experiments on exposure / development process,we mastered glass fiber / SU-8 composite precursor photolithography process parameters.A controlled etching method by hydrofluoric acid for revealing glass fiber was proposed and developed.The selective etching of revealing glass fibers after photolithography was successfully achieved.The combination of the two procedures has achieved the overall patterning of the glass fiber / SU-8composite microstructure,which is equivalent to the direct photolithography of glass fiber / SU-8 composite materials.5.Glass fiber / SU-8 composite samples are developed by direct photolithography technology of glass fiber / SU-8 composite material.Microscope images showed that the microstructure of glass fiber fabrics /SU-8 thick film formed well.The Dynamic Mechanical Analysis(DMA)was used to test the mechanical properties.The results are compared with the pure SU-8 samples.The results show that for a single-layer composite sample of SU-8 with a thickness of 120 ?m,the tensile strength increases by about 35% and the breaking strength increases by 199%,which verifies the rationality and feasibility of innovative research assumptions.In summary,this research has mastered key technologies such as composite precursor preparation,thick film lithography,and selective etching of glass fiber fabrics through a systematic study of glass fiber / SU-8 composite microstructure lithography patterning technology.The goal of improving the mechanical strength of the SU-8 microstructure through glass fiber reinforcing,while maintaining the advantages of direct molding has been achieved.This has opened up a new technical route for the SU-8microstructure modification.