Integrated LTCC Gas Flow Sensor with Measuring

Integrated LTCC Gas Flow Sensor with Measuring Device Dominik JURKÓW, 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. An electronic device consists of a LED diode, a light-voltage converter, two voltage stabilizators integrated with LTCC substrate.

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 a gas channel, a 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 a sacrificial layer. The test device is made with the transparent glass cover. It allows on the observation of the turbine movement.

FINAL STRUCTURES The electronic elements are soldered to the LTCC substrate. A SMD elements are used

Part 1 Final structure

Final structure

EXPERIMENTAL

CONCLUSION

Block diagram of the measuring circuit

RESULTS Working range

Working pressure Max. pressure Output signal Frequency in working range Resolution Absolute error Relative error on the full scale Work temperature range Voltage supply range

Air flow measurements

Part 2

Sensor

Presented integrated LTCC sensor 7 – 25 ml/s (0.42 – 1,5 l/min) < 150 kPa

< 400 kPa

< 2 MPa 13280 pulses/l 124 – 332 Hz

< 2 MPa 24705 pulses/l 70 – 420 Hz

0.0865 ml/pulse ? 12 Hz 3.6%

? 14 Hz 3.3%

6 – 17 ml/s (0.36 – 1 l/min)

0.03 ml/pulse

10 – 75 0C

up to 7000C

6 – 35V, (max 1A)

No stabilizer were used

Sensor parameters

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 measuring circuit is based on the microcontroller. The solution permits to miniaturise size of the measuring circuit significantly. 3. The electronic device is succesfully integrated with the LTCC substrate. It is improving electrical parameters of the sensor.