Micro-USAL technique for the manufacture of high quality microstructures in brittle materials

In the paper, microultrasonic assisted lapping (USAL) is proposed as a flexible alternative to micro-system technologies for the manufacture of high surface quality microstructures in brittle materials. The authors first introduce the background and principles of micro-USAL of microstructures, analyze obstacles in implementing and using this technique, and configure a micro-path-controlled USAL test-rig with the integration of on-line AE (acoustic emission) monitoring system. They then discuss the effectiveness of automatic tool–workpiece contact detection and tool wear compensation using AE-based feedback, of which both are important for a stable micro-USAL. They also identify the influence of the AEʹs positional dependence which was recognized by the authors for the first time. The AEʹs positional dependence was identified to be inherently attributed to the ultrasonic generator and, under certain conditions, it caused a misjudgment of AE-based feedback. In the paper, they also demonstrate the highly flexible capability of the new micro-USAL in generating microstructures of various geometrical patterns through a number of machining experiments, as well as its current limitations in achievable concave feature sizes, aspect ratios and surface roughness. Also in the paper, the authors finally discuss, in detail, micro-USALed surface properties, effects of process parameters and lapping media, and the newly proposed chemo-mechanical way to improve the micro-USALed surfaces with the achieved minimum roughness of Ra 7 nm.