Ultra-precision Machining of Micro-step Pillar Array Using a Straight-Edge Milling Tool

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ORIGINAL ARTICLE

Ultra‑precision Machining of Micro‑step Pillar Array Using a Straight‑Edge Milling Tool Kui Liu1   · Hu Wu1 · Rui Huang1 · Nicholas Yew Jin Tan2 Received: 14 June 2020 / Revised: 17 August 2020 / Accepted: 3 September 2020 © International Society for Nanomanufacturing and Tianjin University and Springer Nature Singapore Pte Ltd. 2020

Abstract Ultra-precision machining has been well known as a very precise and effective way to prototype and fabricate different types of components with microstructures. In this paper, an ultra-precision micro-milling method has been presented to produce a micro-step pillar array as an embossing mold for semiconductor application. Theoretical analysis on machining mechanics indicates that work material property, machining strategy, and cutting tool geometry largely affect machining distortion on the machined microstructure. Experimental investigation has been conducted on micromachining of the micro-step pillar array using different types of cutting tools and work materials. Experimental results demonstrate that the material property, cutting tool edge radius, and cutting force play a significant role in the machined micro-structure accuracy and surface finish, while grain boundary of brass has no significant effect on the micro-milling performance. The best outcome among the tests done is achieved when using brass as work material and cutting with a straight-edge single crystalline diamond tool. The main reasons to achieve this outcome are based on: the brass material having a higher elastic modulus and the diamond tool having a smaller cutting edge radius, which contributes to better machinability of brass. One micro-step pillar array has been successfully obtained with very precise feature and dimensional accuracy using brass work material and single-crystal diamond tool. It is believed that the outcomes of this study would largely benefit the research community and end-users. Keywords  Single-crystalline diamond · Ultra-precision · Milling · Micro-step pillar · Brass

1 Introduction Since the 1760s, humans have experienced a lot of unprecedented technology development using precise tools and manufacturing methods to achieve continuously increasing accuracy from millimeter to micron, to nanometer, and to angstrom levels [1]. In last couple of decades, remarkable advances have been achieved in ultra- and high- precision manufacturing, where the fabricated shape could successfully reach nanometer-level dimensional accuracy and atomic-level surface roughness [2]. The trend of product miniaturization has been driving to a mass and volume reduction largely, which can significantly increase the convenience and value of products [3]. * Kui Liu [email protected]‑star.edu.sg 1



Singapore Institute of Manufacturing Technology, 73 Nanyang Drive, Singapore 637662, Singapore



National University of Singapore, 21 Lower Kent Ridge Road, Singapore 119077, Singapore

2

There are rapidly increasing demands on high-accuracy miniaturized components from various industry sectors,