LTCC gas flow sensor

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Cofired Ceramics (LTCC) gas flow sensor is developed. The sensor consists ... The gas flow sensor is made in the LTCC technology using DuPont 951 A2 tape.
LTCC GAS FLOW SENSOR Dominik JURKÓW, Henryk ROGUSZCZAK, Leszek GOLONKA Faculty of Microsystem Electronics and Photonics, Wybrzeze Wyspianskiego 27, 50 - 370 Wroclaw, Poland http://wemif.net/lmg/ TECHNOLOGY

INTRODUCTION 1. A new construction of the Low Temperature Cofired Ceramics (LTCC) gas flow sensor is developed. The sensor consists of a gas channel and a cavity with a moving turbine. The turbine and the axle are made separately. 2. The rotational speed of the moving turbine depends on the gas flow velocity. The speed of the turbine is calculated by the optical method. 3. The test structure cover is made of a transparent glass for the turbine movement observation.

The gas flow sensor is made in the LTCC technology using DuPont 951 A2 tape. The thickness of the tape is equal to 165 mm before firing. The sensor consists of two parts cofired separately: Part 1 - a main body of the sensor with the gas channel, the via for optical measurement and a chamber with the axle, Part 2 - the turbine. The turbine, the axle, the vias, the chamber and the gas channel are made in the green tapes using a Nd - YAG laser. The design of the turbine is shown below. The turbine and axle are made independently without sacrificial layer. The test device is made with the transparent glass cover. It allows on the observation of the turbine movement.

FINAL STRUCTURES

Part 1 Final structure

Part 2

Final structure

EXPERIMENTAL

Block diagram of the measure circuit

RESULTS

CONCLUSION 1. The rotational speed of the moving turbine depends on the gas flow velocity. The wings of the turbine cause generation of the light impulses with various frequency which are detected by the light detector. The gas flow is calculated on the base of the frequency measurements. 2. The rotational velocity of the turbine does not depend on the gas temperature. The device can work at high temperature. 3. Using of the microcontroller will allow on light impulses counting during accessible time. One second counting will decrease the hysteresis significantly.

Air flow measurements