The polymer spin coating is critical in flexible electronic manufaction and micro-electro-mechanical system（MEMS）devices due to its simple operation, and uniformly coated layers. Some researchers focus on the effect...The polymer spin coating is critical in flexible electronic manufaction and micro-electro-mechanical system（MEMS）devices due to its simple operation, and uniformly coated layers. Some researchers focus on the effects of spin coating parameters such as wafer rotating speed, the viscosity of the coating liquid and solvent evaporation on final film thickness.In this work, the influence of substrate curvature on film thickness distribution is considered. A new parameter which represents the edge bead effect ratio（re） is proposed to investigate the influence factor of edge bead effect. Several operation parameters including the curvature of the substrate and the wafer-spin speed are taken into account to study the effects on the film thickness uniformity and edge-bead ratio. The morphologies and film thickness values of the spin-coated PDMS films under various substrate curvatures and coating speeds are measured with laser confocal microscopy. According to the results, both the convex and concave substrate will help to reduce the edge-bead effect significantly and thin film with better surface morphology can be obtained at high spin speed. Additionally, the relationship between the edge-bead ratio and the thin film thickness is like parabolic curve instead of linear dependence. This work may contribute to the mass production of flexible electronic devices.展开更多
Milling is one of the main methods for processing titanium alloy.At present,the complex process of milling is usually simulated by finite element method,which often has problems in mesh distortion and mesh reconstruct...Milling is one of the main methods for processing titanium alloy.At present,the complex process of milling is usually simulated by finite element method,which often has problems in mesh distortion and mesh reconstruction.Therefore,a meshless three-dimensional milling simulation model was established for TC4 titanium alloy using the smooth particle hydrodynamics(SPH)method.Firstly,the established SPH model was analyzed by the LS-DYNA software,and the stress distribution,temperature field,and cutting force during milling were studied under specific conditions.Subsequently,the cutting force was simulated under different cutting parameters and the effects of these parameters on the cutting force were determined.Finally,based on a series of cutting force experiments,the accuracy of the simulation model was verified.This study proves the feasibility of SPH method in the simulation of titanium alloy milling process and provides novel methods for investigating the processing mechanism and optimizing the processing technology of titanium alloys.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51605079 and 51475076)the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(Grant No.51621064)the China Postdoctoral Science Foundation(Grant No.2016M591424)
文摘The polymer spin coating is critical in flexible electronic manufaction and micro-electro-mechanical system（MEMS）devices due to its simple operation, and uniformly coated layers. Some researchers focus on the effects of spin coating parameters such as wafer rotating speed, the viscosity of the coating liquid and solvent evaporation on final film thickness.In this work, the influence of substrate curvature on film thickness distribution is considered. A new parameter which represents the edge bead effect ratio（re） is proposed to investigate the influence factor of edge bead effect. Several operation parameters including the curvature of the substrate and the wafer-spin speed are taken into account to study the effects on the film thickness uniformity and edge-bead ratio. The morphologies and film thickness values of the spin-coated PDMS films under various substrate curvatures and coating speeds are measured with laser confocal microscopy. According to the results, both the convex and concave substrate will help to reduce the edge-bead effect significantly and thin film with better surface morphology can be obtained at high spin speed. Additionally, the relationship between the edge-bead ratio and the thin film thickness is like parabolic curve instead of linear dependence. This work may contribute to the mass production of flexible electronic devices.
文摘Milling is one of the main methods for processing titanium alloy.At present,the complex process of milling is usually simulated by finite element method,which often has problems in mesh distortion and mesh reconstruction.Therefore,a meshless three-dimensional milling simulation model was established for TC4 titanium alloy using the smooth particle hydrodynamics(SPH)method.Firstly,the established SPH model was analyzed by the LS-DYNA software,and the stress distribution,temperature field,and cutting force during milling were studied under specific conditions.Subsequently,the cutting force was simulated under different cutting parameters and the effects of these parameters on the cutting force were determined.Finally,based on a series of cutting force experiments,the accuracy of the simulation model was verified.This study proves the feasibility of SPH method in the simulation of titanium alloy milling process and provides novel methods for investigating the processing mechanism and optimizing the processing technology of titanium alloys.
