Self-aligned machining and assembly of high aspect ratio microparts into silicon

A new technology is presented in this paper for the selfaligned machining and assembly of 3D microparts and their tools using a WEDG unit and a mini work table consisting of a metal plate or a silicon and metal plate combination. Machining and assembly was carried out in a modular way on a single, newly developed prototype of low-cost and the following fabrication examples are given: micropipe-macrocylinder combination, a simple microrotor module which is inserted and guided into a silicon substrate and some mechanical parts of a skeleton of a possible 3D electromagnetic micromotor (permalloy stator fabricated through a silicon block into a permalloy substrate and a permalloy rotor disk with shaft). The following machining techniques were used: wire electrodischarge grinding (WEDG) [ 11, micro electrodischarge machining (micro-EDM), reverse micro-EDM (RMEDM) and micro ultrasonic machining (microUSM). Ultrasonic vibration was also applied for the self-aligned assembly of (micro)parts. The WEDG/micro-USM processing combination is a novel development, it features the self-aligned "throughwafer" machining. With a metal plate connected at the wafer's backside, self-aligned machining and assembly was carried out on the silicon substrate indirectly. Examples (electromagnetic micro motor, etc) are given of 3D MEMS that could be fabricated in the future when these techniques are successfully combined with MEMS fabrication techniques.