![]() This method improves the service life of inchworm piezoelectric actuators. This actuator adopts the spring servo differential clamping mechanism to realize effective disengagement and locking, which not only reduces the harsh requirements of the motor on machining accuracy, but also greatly improves the stability of the motor in the operation process and overcomes the performance degradation caused by wear in the existing mechanism. In this research, an advanced inchworm piezoelectric actuator is proposed, whose major clamping feet are linked with a pair of auxiliary clamping feet by a spring, and one of the guiders is designed to be movable. These two designs show that it is possible to enlarge the stroke of the inchworm mechanism by differential clamping of two pairs of clamping feet. This design also adopted a differential clamping mechanism. Its motor is capable of a 20 mm stroke and speed of 12 mm/s. DSM developed another design to realize long stroke by a specific linkage mechanism between two camping feet. To overcome these drawbacks, Marth and Waldbronn invented a piezoelectric actuator that is pushed by eight groups of piezoelectric legs. Therefore, these designs demonstrate common disadvantages like short stroke and short life span. Moreover, the output force of the actuator during operation is quite different from the locking force after power failure. After running for some time, with the wear of the clamping mechanism, the performance of the actuator will decline rapidly and fail. ![]() The deformation output of laminated piezoelectric ceramics is micron level, therefore, all the above mechanisms have high requirements for structural machining accuracy. ![]() In the existing research on inchworm actuators, the way to realize clamping and release mainly depends on the deformation of laminated piezoelectric ceramics or the deformation of mechanical amplification mechanism actuated by laminated piezoelectric ceramics. Inchworm actuators have high thrust and high resolution, and utilizing the inchworm principle increases the stroke by accumulating paces of the actuator and can obtain very high resolution within one pace. However, the reaction force is proportional to the weight of vibrating mass, so this type of actuator is suitable for small dimension applications. These actuators have a simple structure and compact size. The inertial actuators are pushed by the reaction force generated from an unsymmetrical mass vibration system, which is formed by either an unsymmetrical structure or voltage excitation. The non-resonance piezoelectric actuators avoid high-frequency resonance, so it is suitable for both open-loop and closed-loop motion systems.Īmong non-resonance piezoelectric actuators, there are two main classes, inertial actuators and inchworm actuators. Consequently, a motion system actuated by resonance actuators always needs closed-loop control. However, the control strategy of resonance systems is complex since both the mechanical actuator and its power source exhibits high nonlinearity. The resonance actuators are fast and compact. According to vibration state, they can be classified into resonance piezoelectric actuators and non-resonance piezoelectric actuators. This work provides a potential solution of piezoelectric motors for the wafer probe station.Īfter several decades of development, many piezoelectric actuators with different principles have been proposed. Due to characteristics like a fast response, high resolution, and long stroke, piezoelectric actuators have been applied in many areas, such as aeronautics and precision instrument. ![]() Consequently, the demand for high speed, long travel stroke, and high-resolution motion servo systems becomes urgent. As the die size on the wafer decreases and the wafer diameter increases, the number of dies on a wafer increases significantly. To realize high efficient tests of wafers with hundreds of dies, the motion servo system needs to be fast, stable, and precise within a long travel range. The wafer probe station is the key testing equipment for electrical performance measurement in the manufacturing process of integrated circuits.
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