Analysis of 5-DOF Error Motion on a Precision Rotary Stage

Abstract

High precision rotary stages (HPRS) in semiconductors, displays and many other fields require accuracy to perform their functions properly. In particular, the axis of rotation error in an HPRS system can be significant; i.e., the spindle error motion of an aligner, wire bonder and inspector machine, which results in poorly manufactured goods. To evaluate and improve the performance of such precision rotary stages, parasitic movements on the other five degrees of freedom (5-DOF) of the rotary stage must be measured and analyzed. In this paper, we measure the three translations and two tilt error motions of two types of rotary stages with high precision capacitive sensors. To obtain the error motion from raw measurement data, we have eliminated the thermal drift and misalignment that can happen at assembly, such as a centering error by mathematical algorithm. After remove thermal drift and centering error, must separate roundness error to get error motion. To obtain the radial error motion of radial direction, we have used Donaldson’s reversal technique. The axial components of the spindle tilt error motion can be obtained from the axial direction outputs of sensors by the Estler face motion reversal technique. Furthermore, we have developed two kinds of precision rotary stages. It is low speed stage that is drive by stepping motor with worm gear. Other stage is direct drive motor that use air-bearing with frameless motor. Also, standard cylinder and sensor mounting jig are developed for the simple reversal technique.