Design Of Motion Positioning Platform And High-precision Positioning For Mini/Micro LED Transfer

Mini/Micro LEDs are reduced in size to the micron level by filmforming and miniaturization technology,and can form independent pixels on the driving circuit boar by using independent encapsulation technology,the density of light emission on the display panel is greatly increased.Mini/Micro LED displays are expected to become a popular display screen after LCD and OLED displays due to their high resolution,high brightness,low power consumption,and quick response.In the production process of Mini/Micro LED displays,thousands of micro-sized Mini/Micro LEDs need to be transferred from the source substrate to the driving panel through a motion positioning platform,and the motion positioning accuracy determines the yield of Mini/Micro LED displays manufacturing.The currently used “mechanical structure support + linear motor drive”motion positioning platform has low positioning accuracy due to the inherent friction of the mechanical structure and the interference of various external uncertainties during operation.It can only achieve large-scale production of Mini LEDs.However,for the mass production of Micro LEDs with a size of less than 50μm,greater challenges are posed to the positioning accuracy of the motion platform。Therefore,in order to improve the positioning accuracy of the motion positioning platform,this paper conducts the following research from the perspectives of mechanical structure and control strategy:(1)Based on the shortcomings of existing Mini/Micro LED chips mass transfer method with slowly transfer efficiency and low transfer accuracy,the laser lift-off motion positioning platform is proposed,the overall structure and working principle of the laser lift-off motion positioning platform are introduced,the performance indicators of the laser lift-off motion positioning platform are analyzed,and the key components of the motion positioning platform(permanent magnet synchronous linear motor,motion control system)are effectively selected.(2)Considering the performance index of the motion positioning platform,the main structural dimensions of the permanent magnet synchronous linear motor are designed,the magnetic field characteristics of the motor are analyzed by analytical method,and the no-load and load characteristics of the motor are studied by Maxwell finite element simulation to explore the causes of thrust fluctuations.Analyze cogging and end forces to determine key structural parameters that affect thrust fluctuations and optimize motor structures.Finally,the auxiliary pole structure is used to suppress the cogging force and end force of the motor to reduce the thrust fluctuation.(3)Because the motion positioning platform is susceptible to nonlinear interference from uncertain factors such as friction and load changes during operation,a sliding mode control system is built on the basis of space vector control,and the uncertainty disturbance is estimated by introducing nonlinear expansion observer,and the estimated value is compensated to the sliding mode controller,the robust performance of the system is improved,the tracking error of the system is reduced,and the position tracking performance and anti-interference ability are better.(4)Based on the selection of key components,a prototype of the principle of motion positioning platform is built,and the performance test and analysis of motion positioning platform is carried out.Through the positioning accuracy measurement experiment and the dynamic response experiment of the system position loop and velocity loop,the superiority of the designed motion positioning platform structure and control strategy is verified.