Soft-Acting, Noncontact Gripping Method for Ultrathin Wafers Using Distributed Bernoulli Principle

Abstract

The handling of ultrathin wafers ( $ thickness) is a challenging task since these are among the thinnest and most fragile materials. This paper provides a soft-acting and noncontact gripping technology for ultrathin wafer based on the distributed Bernoulli principle, and also proposes an experimental measurement method for evaluating the performance. A distributed Bernoulli gripper for ultrathin wafers is designed, and the characteristics of the gripper are studied via theoretical analysis and experiments. Three performance indices for evaluating the properties of the soft gripping: deformation, vibration, and stress are presented. Through measurement experiments, the effects of the key operational parameters consisting of air flow rate and gap height on the performance indices are investigated. Based on the experimental data, the appropriate parameters settings are obtained. The comparison to present grippers reveals that the proposed gripping technology is superior in soft gripping thin and fragile materials. This paper provides guidance for implementing the distributed Bernoulli principle in practical applications of soft-acting and noncontact gripping for thin and fragile materials. Note to Practitioners —This research of developing a new soft-acting and noncontact gripper was motivated by the problem of gripping of fragile workpieces like ultrathin wafers. The traditional contact handling method often leads to defective products including cracks, contact contamination, or mechanical wears, and the existing Bernoulli gripper has the shortcoming of resulting in large deformation as the impact of center negative pressure force, and the collision of wafer onto the gripper as the sharp lifting force curve. In this paper, we propose a soft-acting and noncontact gripper for ultrathin wafer based on the distributed Bernoulli principle. A systematic approach which consists of modeling, measurement, and evaluation is provided for the gripping techniques. We present three performance indices for evaluating the characteristics of soft gripping, and experimentally study the effect of supply flow rate and the gap height on the performance of deformation, vibration, and stress in the thin and fragile wafers. It is found that an optimal value exists. We then verify the merit in gripping ultrathin wafers softly with a small deformation or stress via comparison with two Bernoulli grippers and a combined gripper. The new gripper plays an important role in handling thin and fragile materials.