Surface and subsurface characterisation in micro-milling of monocrystalline silicon

Abstract

This paper presents an experimental investigation on surface and subsurface characterisation of micro-machined single-crystal silicon with (100) orientation. Full immersion slot milling was conducted using solid cubic boron nitride (CBN) and diamond-coated fine grain tungsten carbide micro-end mills with a uniform tool diameter of 0.5 mm. The micro-machining experiments were carried out on an ultra-precision micro-machining centre. Formal design of experiments (DoE) techniques were applied to design and analysis of the machining process. Surface roughness, edge chipping formation and subsurface residual stress under varying machining conditions were characterised using white light interferometry, SEM and Raman microspectroscopy. Tens of nanometre-level surface roughness can be achieved under the certain machining conditions, and influences of variation of cutting parameters including cutting speeds, feedrate and axial depth of cut on surface roughness were analysed using analysis of variance (ANOVA) method. Raman microspectroscopy studies show that compressive subsurface residual stress and amorphous phase transformation were observed on most of the micro-machined subsurface, which provides evidence of ductile mode cutting. Surface and subsurface characterisation studies show that the primary material removal mode is ductile or partial ductile using lower feedrate for both tools, and diamond-coated tools can produce better surface quality. Silicon brain implants were fabricated with good dimensional accuracy and edge quality using the optimised machining conditions, which demonstrated that micro-milling is an effective process for fabrication of silicon components at a few tens to a few hundreds of micron scale.

Surface finish and subsurface damage distribution during diamond turning of silicon

“…The need to manufacture highly precise optical components with dimensions and accuracy in micro-nano scale is a rising research area. It is well accepted that micro-manufacturing has been a key facilitated technology in industries producing useful micro-electronic components and products [1][2]. Subsurface Damage, which was introduced to optical materials by fabrication processes, may bring about the decrease of output in optical, laser and infrared applications.…”

Investigation on the Tool Wear Suppression Mechanism in Non-Resonant Vibration-Assisted Micro Milling

“…The machining performance can be influenced by the tool edge radius when the uncut chip thickness is small enough. It has been reported that the ratio of uncut chip thickness to cutting edge radius is closely linked with the machining surface ploughing effect, effective rake angle, and specific cutting energy, which in turn impacts the cutting performance [4][5][6]. Moreover, when it refers to hard and brittle materials, low fracture toughness and often poor thermal conductivity make processing these materials a challenging task.…”

Kinematics and tool-workpiece separation analysis of vibration assisted milling

“…High-accuracy precision or micro components are increasingly in demand for various industries, such as biomedical engineering, MEMS, electro-optics, aerospace and communications [1][2][3][4][5]. Previously, non-conventional machining methods such as electrical discharge machining (EDM), electrochemical machining (ECM), laser machining, ion beam machining, and electro-beam machining, are adopted to machine hard and brittle materials.…”