A high-density, super-high-aspect-ratio microprobe array realized by high-frequency vibration assisted inverse micro w-EDM

This study is focused on the fabrication of a high-density, super-high-aspect-ratio microprobe array using high-frequency vibration assisted inverse micro w-EDM (wire electric discharge machining). An inverse micro w-EDM design in which a brass wire ϕ20 μm in diameter is located beneath the workpiece for bottom-up machining is devised. The wire is triggered to a high-frequency oscillation by a piezoelectric actuator thereby changing the flow regime of dielectric fluid and quickly sending out debris from the narrow spark-gap. The debris is rapidly removed via gravity decreasing debris concentration around the wire-electrode thereby reducing the probability of discharge-shorting and heat-accumulation. Combining magnetic force design and micro wire vibration-inhibition, wire-wriggling and wire-swaying are readily minimized. Three kinds of high-density, super-high-aspect-ratio microprobe arrays comprising: (1) straight-type, (2) wave-type, and (3) spanning-type are verified successfully. Studies show that each probe has highly consistent dimensional and form accuracy with aspect-ratio realized at104:1. Experimental results also demonstrate that processing time 'with' a high-frequency vibration assistance of 1.6 KHz is about 75-80% that of the time 'without' high-frequency vibration, validating inverse micro w-EDM with high-frequency vibration assistance enhancing machining efficiency of microstructure arrays. Additionally, the following aspects are evaluated in detail: wire-tension control, discharge energy, corner path designs, wire-running speed, vibration assistance effect, vibrational frequency, and side-erosion.