Mutsuya Takahashi

Novel fabrication method for 3D microstructures using surface-activated bonding and its application to micro-mechanical parts

The purpose of this work is to demonstrate that a novel fabrication method for 3-D microstructures (FORMULA) is applicable to fabrication of micro mechanical parts with a large flexibility. This method is a kind of layer manufacturing method of thin films for metallic or dielectric microstructures using surface-activated bonding (SAB). The bonding interfaces of thin films are investigated by transmission electron microscope (TEM). Voids were observed at the interfaces of both pure aluminum films and Al-Cu alloy films. The ratio of void on the Al-Cu/Al-Cu interface is much larger than that of Al/Al interface, although the films have the same surface roughness of 3nm in Ra (average roughness). And approximately 10nm-thick amorphous intermediate layers were found at the interfaces. Furthermore, we have fabricated a micro gear of 900μm in diameter and 200μm in height, which is about ten times as large as our previous test pieces. Overhung structures such as a bridge structure and a cantilever were also fabricated without supporting layers beneath them.

High Performance Microcooler Fabricated by Multiple Stacking of Electroplated Metal Patterns

We present a high performance microcooler fabricated by multiple-stacking of electroplated metal patterns using surface-activated bonding (SAB). We demonstrated the potential of a microchannel liquid cooler for a high-power electronic device, which is 10 mm square and 0.6 mm high and consists of 800 microchannels in 10 stories of the structure by stacking 20 layers of 30 mum-thick electroplated nickel patterns. We experimentally showed that the cooling capacity was 85 W with only a hydraulic pressure drop of 0.1 MPa.