Research On A High Performance Positioning Stage With Floating Stator

High performance XY platform is one of the core modules of microelectronic manufacturing equipment.In IC packaging,with the reduction of chip size and increase of productivity,it needs higher acceleration and higher precision motion,this proposes a big challenge for XY platform design.The typical characters of the XY platform motion in semiconductor packaging device are high acceleration and frequent switch between stop and star,due to this,unavoidable vibration of base and entire machine is generated,furthermore,the vibration becomes more serious with the increase of acceleration.While the traditional structure of linear stage whose motor's stator is fixed on base is incapable to suppress this vibration then results in degeneration of the end accuracy.In order to get rid of this problem,this paper proposes a linear stage with floating stator,in which the stator can move on the base comparative to the conventional fixed structure.In the proposed structure,the reactive force is released by the motion of stator,so the vibration is suppressed.First of all,the mathematical model of single axis linear stage with floating stator is developed.With that,the application requirements of high accuracy for end-effector positioning and low vibration for base are converted into mathematical functions of stator mass,damping and spring coefficients.Then the integrated design problem is formulated by employing the settling time of stator motion,the maximize moving distance of stator and the vibration transmissibility as objective functions and taking stator mass,damping and spring coefficients as optimal variables.Differential Evolution algorithm is used to solve the optimization problem.Secondly,the parallel model of 2-DOF platform decoupled through guide is constructed by involving the optimized variables.In order to avoid undesired deformation of critical elements as high inertia force imposed,finite element method is used to analyze and modify the whole stage.After that,the optimized model is obtained.Then the prototype of 2-DOF stage is set up and its real model is obtained by system identification.Thirdly,in proposed floating stator stage,the critical factors influencing performance on negative direction include floating stator,time delay of physical system in rapid responding system,nonlinear friction and uncertainty.In order to get rid of them,two control strategies are designed: gain scheduling controller and robust controller based on disturbance observer.By comparing the performance of real stage under two controllers,it is found that the gain scheduling controller has higher robustness and faster tuning ability than the disturbance observer controller.In addition,the performance of gain scheduling controller is stable even in complicate motion which is unreachable for disturbance observer.Finally,a number of experiments are implemented on proposed stage,including required wire bonding motion for positioning accuracy test and vibration suppression test.The super performance of proposed stage and gain scheduling controller are strongly validated by numerous experiments results.