Three element gas flow sensor integrated with low

Three element gas flow sensor integrated with low temperature cofired ceramic module (Trójelementowy czujnik przepływu zintegrowany z modułem z niskotemperaturowej ceramiki współwypalanej (LTCC)) mgr inż. DOMINIK JURKÓW, mgr inż. KAROL MALECHA, prof. dr hab. inż. LESZEK GOLONKA

Wrocław University of Technology, Faculty of Microsystem Electronics and Photonics The LTCC (Low Temperature Cofired Ceramics) has been developed for last three decades. At the beginning the technique was mainly used to manufacture ceramic MCM-C (Multi Chip Modules) [1]. However, LTCC has good both electrical and mechanical properties, because of it the technology was applied in sensors and microsystems applications. Recently Low Temperature Cofired Ceramics are used to fabricate various devices e. g. microwave band-pass filter, miniaturized strip antenna [2], chemical sensor, cantilever structures [3]. In addition LTCC enables fabrication of various fluidic devices such as chambers, [4,5], fluid mixers [6], biosensors [7], enzymatic microreactors [8] and microflow analyzers [9]. The first LTCC thermal-based flow sensor was presented in [10]. The device consisted of thick-film resistor placed between two thick-film thermistors. The bridge was electrically heated with the resistor and the bridge temperature on both its sides was measured with thermistors.Gas flow velocity affected temperature differences between thermistors, therefore base on thermistors temperature measurements gas flow velocity was calculated. However, electrical components were not electrically isolated from fluid in the channel and temperature differences were relatively small. The device with isolated bridge was presented in [11], the sensor consisted of one thick-film thermistor placed on a bridge. The temperature of thermistor, which was electrically heated, depended on gas flow velocity. On base of temperature measurement gas flow rate was calculated. However, the fluid velocity measurements highly depended on fluid temperature. Next LTCC fluid flow sensor, which combines advantages of structures presented in [10,11], is presented in the paper. The structure geometry was designed based on CFD (Computational Fluid Dynamics) modeling of gas flow. The sensor consists of first and second bridges with screen printed passive components. Thermistor and thermistor with resistor were screen-printed on the first and second bridge, respectively. The flow is calculated on the base of temperature difference measurements between two thermistors. The temperature is measured with the first thermistor and the flow velocity is calculated with second thermistor. The numerical simulation of gas flow velocity, measuring circuit, sensor’s calibration process, and sensor’s technology are described in the paper.

tween thermistors depend on gas flow velocity. The gas flow rate is calculated based on thermistors temperature measurements. The gas flow sensor geometry was designed on grounds of CFD simulations results. Moreover, the fluid flow condition and thermal properties were estimated using FEM (Finite Element Method) implemented in ANSYS® software. Numerical Simulations were done for two-dimensional steady, laminar, compressible flow. As a fluid model air was used. All properties of materials employed in the FEM analysis are shown in Tabl. 1. The analysis was made for different fluid flow rates. Exemplary results of the fluid particles trajectories, temperature distribution and dependence between the fluid’s pressure drop and flow rate inside the LTCC-based sensor are presented in Fig. 2 and 3a, respectively.

Tabl. 1. Material properties used in FEM analysis Tab. 1. Właściwości materiałów użytych w symulacji metodą elementów skończonych Parameter

Viscosity [Pas]

Density [kg m-3]

LTCC [12]

-

3100

Air

5.6 • 10-6

1.2

Thermal conductivity [W m-1 K-1]

Specific heat [J kg-1K-1]

3

450

0.025

1005

The pressure drop inside the flow sensnor varied from 4.2 Pa to 185 Pa (for minimal and maximal flow rates equal to 3 ml/s and 37 ml/s, respectively. The pressure drop increased with growth of the gas flow velocity. The temperature difference between thermistors varied between 14.3K and 1.7 K for flow rates equal to 3 ml/s and 37 ml/s, respectively. Obtained results of the numerical simulations showed that presented device can be succefully applied as a flow sensor.

Design of the flow sensor

The sensor working principle with marked fluid velocity direction (FD), small (SM) and large bridge (LM), gas channel (CH), fluid connection (FC) is shown in Fig. 1. A gas temperature is measured with thermistor placed on the small bridge. Large bridge is electrically heated with resistor, which temperature is measured with thermistor on LB. Temperature differences beELEKTRONIKA 12/2009

Fig. 1. Working principle Rys. 1. Zasada działania

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Fig. 2. Fluid particles trajectories [m/s] in the vicinity of the bridges (Q = 3 ml/s) Rys. 2. Trajektoria przepływu cząsteczek płynu w okolicy mostka (Q = 3 ml/s)

a)

one bottom and one top bridge layer (SM - small bridge, LM large bridge, T1 - first thermistor, T2 - second thermistor, R1 resistor, MM - conductive path. Electrical connections, resistor and thermistors were screen-printed with PdAg DP6146 (DuPont), CF021 (DuPont) and NTC-2114 (ESL) compositions, respectively. Electrical properties of the applied thickfilm passive components are well-known and were described in [13,14]. LTCC green tapes were cut with Nd-YAG laser to obtain designed shapes. The top, bottom and top bridge with the bottom bridge layers were separately bonded with thermocompression method (at pressure 20 MPa, at temperature 70°C for 10 min). This lamination technique enables good bonding quality. However, it strongly affects a geometry of the LTCC spatial structures. Therefore, the top and the bottom channel layers were joined with the top and the bottom part using Cold Chemical Lamination (CCL) [11,15], which is chemical based method. A film of special solvent (DuPont thinner DP4553) is screen-printed on one of the ceramics layer surface, then next tape is placed on dissolved surface and pressed with rubber roll with hand pressure. Solvent dissolves the surface and enables to carry out lamination process at room temperature and at very low pressure. Then next tape is applied on dissolved surface and pressed with rubber roll with hand pressure. The process is repeated until all tapes are joined. The technique enables good bonding quality without any deformation of channel geometry. In last step CCL prebonded parts (top with top channel and bottom with bottom layers) are laminated with thermo-compressed bridge layers. a)

b)

c)

d)

e)

f)

b)

Fig. 3. Basic simulations, a) temperature distribution [K] inside the flow sensor (Q = 3 ml/s), b) pressure drop [Pa] inside the flow sensor vs. flow velocity Rys. 3. Podstawowe symulacje, a) rozkład temperatury [K] wewnątrz kanału (Q = 3 ml/s), b) spadek ciśnienia [Pa] wewnątrz kanału w funkcji przepływu

Technology

Sensor was obtained with LTCC technology. The technique is based on shaping, stacking, laminating and sintering green ceramic sheets. The device design is presented in Fig. 4. The bottom, lower channel, lower bridge, top bridge, ) top channel and top layers are shown in Fig. 4a, 4b, 4c, 4d, 4e, 4f, respectively. The gas flow sensor consists of four bottom and four top layers (FC - fluid connection), two bottom and two top channel layers (CH - gas channel, EC - electrical connection),

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Fig. 4. Sensor design: a) bottom layer, b) lower channel layer, c) lower bridge layer, d) top bridge layer, e) top channel layer, f) top layer Rys. 4. Projekt czujnika: a) spód, b) kanał pod mostkiem, c) dolny mostek, d) górny mostek, e) kanał nad mostkiem, f) wierzch

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a) Fig. 6. Calibration circuit block diagram Rys. 6. Schemat układu kalibracyjnego a)

b)

Fig. 5. Final device: a) top view, b) cross-section of the test CCL channel structure Rys. 5. Gotowy czujnik: a) widok od góry, b) przekrój poprzeczny komory testowej, struktury połączonej za pomocą niskotemperaturowej laminacji chemicznej

b)

They were bonded together using CCL. Next, LTCC module was sintered in Nabertherm furnace in temperature cycle recommended by DuPont. Final sintered device and cross-section of the CCL test channel structure are presented in Fig. 5a and 5b, respectively.

Results

Four flow sensor test structures were taken into account. Applied calibration circuit block diagram is presented in Fig. 6. It consists of an air compressor with gas valve, reference gas flow sensor (Honeywell AWM5101) and calibrated LTCC sensor. A value of air pressure is set with the gas valve and measured with a manometer. The sensors output signal was measured as a difference of temperature between two thermistors versus a resistor heating power. Dependence between measured temperature difference vs. gas flow rate for three power levels (1.3, 0.8 and 0.6 W) is presented in Fig. 7a. The output signal and the sensitivity were increased for higher power level. Temperature differences between two thermistors for gas flow rate equal to 3 ml/s were 17, 14 and 5.5K, for heating power 1.3, 0.8 and 0.6 W, respectively. Heating power of 0.8 W provides much higher output signal than in case 0.6 W and a little bit lower output signal in comparison with 1.3 W. However, heating power of 0.8 W was chosen because of significantly lower power consumption level. Afterwards all four sensors were calibrated. Normalized calibration curve with marked standard deviations and compared with simulation are presented in Fig. 7b. The normalization is given by equation (1):

where: Sout - normalized output signal, ∆Ti - i-th temperature difference between thermistors [K], ∆Tmax - max. temperature difference [K]. ELEKTRONIKA 12/2009

Fig. 7. Results: a) differences in temperatures vs. flow rate, b) normalized output signal vs. flow rate Rys. 7. Wyniki: a) zmiana różnicy temperatur w funkcji prędkości przepływu, b) znormalizowana odpowiedź czujnika w funkcji wartości przepływu (pomiar i symulacja)

Basic sensors parameters are presented in Tab. 1. LTCC gas flow sensor exhibits low working and dropout pressures and fairly enough sensitivity. Measuring range is limited by precision of gas valve and reference sensor. Maximum relative error is affected by measuring hysteresis. Sensors repeatability depends on measuring hysteresis and not enough accurate temperature measurement. Tabl. 2. Sensor parameters Tab. 2. Parametry czujnika

Sensitivity [%/ml]

Measuring range [ml/s] Max. relative error [%]

2.7

Error of sensor’s [%]

2.5 - 36 Working pressure [kPa] 6

8.2

< 10

Conclusion

• New construction of the LTCC gas flow sensor was presented in the paper. • The gas flow sensor geometry was designed on the grounds of FEM simulations. • The gas flow rate was calculated on the base of thermal principle. • Two thermistors enabled reduction of the gas temperature influence on measured value of the flow rate.

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• Measuring sensitivity and range were increased and extended in comparison with data presented by earlier researches. • Pressure drop was decreased significantly and linearity was improved. In further investigations: • repeatability of thermistors electrical properties will be increased by using precise screen-printer (AUREL VS1520A), • analyze of sensor’s output signal versus gas flow rate for different gases will be examined.

[6]

References

[11]

The authors wish to thank the Polish Ministry of Science and Higher Education (grant no. R02 017 02) for financial support. [1]

Golonka L.: Technology and applications of Low Temperature Cofired Ceramic (LTCC) based sensors and microsystems. Bulletin of the Polish Academy of Science, vol. 54, 2006, pp. 221- 231. Baker M., Lanagan C., Randall Semouchkina E., Semouchkina G., Rajab K., Eitel R.: Integration concepts for the fabrication of LTCC structures. Int. J. Appl. Ceram. Technol., vol. 2, 2005, pp. 514-520. Thelemann T., Thust H., Hintz M.: Using LTCC for microsystems. Microelectronics International, vol. 19, 2002, pp. 19-23. Briol H., Maeder T., Jacq C., Ryser P.: 3D structuration of LTCC for sensor micro-fluidic applications European Microelectronic and Packaging Symposium, June 2004, pp. 366-371. Briol H., Maeder T., Jacq C., Straessler S., Ryser P.: Fabrication of Low Temperature Cofired Ceramics microfluidic devices using sacrifical carbon layers. Int. J. Appl. Ceram. Technol., vol. 2, 2005, pp. 364-373.

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Kamiński S., Rebenklau L., Uhlemann J., Wolter K.: Mixer with microchannels in LTCC technology. Electron Technology - Internet Journal, vol. 9, 2006 pp. 1-3. Achmann S., Hammerle M., Kita J., Moss R.: Miniaturized Low Temperature Cofired Ceramics (LTCC) biosensor for amperometric gas sensing. Sensors and Actuators B, vol. 135, 2008, pp. 89-95. Malecha K., Pijanowska D., Golonka L., Torbicz W.: LTCC enzymatic microreactor. Journal of Microelectronics and Electronics Packaging, vol 4, no. 2, 2007, pp. 51-56. Martinez-Cisneros C., Ibanez-Garcia N., Valdes F., Alonso J.: LTCC microflow analyzers with monolithic integration of thermal control. Sensors and actuators A, vol. 138, 2007, pp. 63-70. Gongora-Rubio M., Solá-Laguna L. M., Moffett P. J., SantiagoAvilés J. J.: The utilisation of low temperature co-fired ceramic (LTCC-ML) technology for meso-scale EMS, a simple thermistor based flow sensor. Sensors and Actuators A, vol. 73, 1999, 73, 215-221. Jurków D., Golonka L.: Novel cold chemical lamination bonding technique - a simple LTCC thermistor-based flow sensor. Journal of the European Ceramic Society, (in press). Zawada T.: Simultaneus estimation of heat transfer coefficient and thermal conductivity with application to microelectronics materials. Microelectronics Journal, vol. 37, 2006, pp. 340-352. Jurków D., Malecha K., Golonka L.: Investigation of LTCC thermistor properties. Proceedings of the XXXII International Microelectronics and Packaging Conference IMAPS Poland Chapter, Pultusk (Poland), 2008. Jurków D., Golonka L.: Cold Chemical Lamination - New Bonding Method of Green Tapes. Proceedings of the XXXII International Microelectronics and Packaging Conference IMAPS Poland Chapter, Pultusk (Poland), 2008. Jurków D., Roguszczak H., Golonka L.: Cold chemical lamination of ceramic green tapes. Journal of the European Ceramic Society, vol. 29, 2009, pp. 703-709.

Two phase reliability analysis of quantum circuits in a block based approach (Dwuetapowa analiza niezawodnościowa obwodów kwantowych z wykorzystaniem metody blokowej) OANA BONCALO, ALEXANDRU AMARICAI University Politehnica of Timisoara, Timisoara, Romania

Much interest has been given to quantum computing during the last decade, yielding both theoretical developments and physical implementations - for different technologies [5]. Although significant improvements have been made, reliability is still an issue, as quantum computers are plagued by high error rates (typical for the associated technologies). Therefore, developing, assessing and validating solutions for improving fault tolerance, is an important research area. VHDL-based simulated fault injection (SFI) proved advantageous for classical circuits reliability analysis [8]. The SFI techniques are attractive for quantum circuits especially due to the high costs and low availability of quantum circuits. Furthermore, VHDL techniques such as saboteurs and mutants, offer a comprehensive and flexible approach to quantum fault modeling [2,3]. The goal is to use them in order to study a wide range of noise scenarios and to derive relevant results from the campaigns pursued, with minimum coding effort. An important drawback to this approach is the cost of simulating

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quantum circuits, which tends to grow exponentially in computational resources (memory and time) needed with the number of qubits. Hence, it limits the size of the quantum circuit that can be analyzed with SFI. We address this problem by splitting our analysis in two phases. During the first phase, simulated fault injection is applied for the basic blocks yielding reliability estimates. The second phase molds together the SFI outcomes within a reliability block to estimate the reliability of the original circuit as a whole. This creates incentive for an accurate noise modeling, with reasonable simulation cost. The paper is organized as follows: first a brief overview of quantum noise models is given in Section 2; Section 3 is dedicated to a brief presentation of simulation based approaches to quantum reliability analysis, with special emphasis being given to VHDL simulated fault injection techniques. Next the proposed approach for assessing quantum circuits is presented. Section 4 offers a case study for serial block decomELEKTRONIKA 12/2009