Matsuo Kishi

Micro thermoelectric modules and their application to wristwatches as an energy source

Microthermoelectric (TE) coolers are currently used in high power electronic devices such as laser diodes to stabilize temperature. With the aim of miniaturizing this technology, we have developed a fabrication technique to create micro-TE modules with a cross-section element size of about 100 /spl mu/m/spl times/100 /spl mu/m and a height of several hundred mm. We have previously reported the cooling properties of a module fabricated by this technique. With the recent advances in micro-electric technology, which has decreased the energy consumption in an electric wristwatch to about 1 /spl mu/W, there has been increased discussion about utilizing these micro-TE modules to generate energy of several /spl mu/W to power a wristwatch. In response, we have developed a micro-TE module with an overall size of 2 /spl times/ 2 /spl times/ 1.3 mm consisting of more than 50 pairs of elements, and have succeeded in making and marketing a TE powered wristwatch. This paper presents the fabrication and the properties of the micro-TE module, as well as the TE powered wristwatch.

Low-Temperature Synthesis of Aluminium Nitride Film by HCD-Type Ion Plating

Aluminium nitride (AlN) thin films were deposited on glass substrates, using aluminium and nitrogen as source materials, by hollow cathode discharge (HCD)-type ion plating. The films were evaluated using X-ray diffraction, scanning electron microscopy, infrared transmission spectroscopy and Auger electron spectroscopy, and their densities were measured. The phase of the deposits changed from Al to Al+AlN and to AlN with an increase in nitrogen flow rate. The structure of the AlN films varied from a dense structure to columnar structure with a rise in nitrogen flow rate. The film with the dense structure had a density near the theoretical value. Oxygen caused by the attack of H2O in air was detected only on the surface of films with the dense structure, but throughout the inside of the films with the columnar structure.

Fabrication of a miniature thermoelectric module with elements composed of sintered Bi-Te compounds

A new manufacturing process of a /spl pi/-shaped miniature thermoelectric module composed of sintered Bi-Te compounds has been developed. The manufacturing process is suitable for mass production as it is comprised of simple technologies such as conventional photolithography technology, microbonding technology using the solder bump method and precise cutting technology using a dicing machine. A miniature module with the dimensions of 3 mm/spl times/3 mm/spl times/1.3 mm in which 102 elements (51 junctions) with the dimensions of 120 /spl mu/m/spl times/120 /spl mu/m in cross section parallel to the substrates and a height of 600 /spl mu/m were included was fabricated while developing the process. The maximum temperature difference /spl Delta/T/sub max/, and the heat absorption Q/sub max/ of the module were 61.3/spl deg/C and 0.36 W, respectively. This indicates that the performance of the module as a cooling device was equivalent to that of conventional modules. The specification for high voltage and low current input, a significant purpose in addition to the miniaturization of the module, was achieved because the maximum voltage V/sub max/ and current I/sub max/ were 6.7 V and 110 mA, respectively.

Effect of RF Bias on Low-Temperature Synthesis of Aluminium Nitride Film by Hollow Cathode Discharge-Type Ion Plating

The effects of RF bias potential on the synthesis of aluminium nitride (AlN) film on a glass substrate using the hollow cathode discharge (HCD) ion plating technique, and on some properties of the film were investigated. The deposits were characterized by X-ray diffraction and scanning electron microscopy. The AlN films prepared with application of RF bias potential were superior in flatness to those prepared without applying of RF bias potential, but excess RF bias voltage to the substrate caused the film to come off not just from the substrate, but also with peeling of the glass substrate surface. The Vickers microhardness of film consisting of AlN single phase was estimated to be about 2300 kg/mm2. The film density was increased by applying RF bias voltage, its value being close to the theoretical value.