ltcc thermal gas viscometer heater module
TRANSCRIPT
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LTCC thermal gas viscometer-
Heater module
Thomas Maeder, Caroline Jacq, Giancarlo Corradini, SigfridSträssler, Hansu Birol and Peter Ryser
EPFL-LPM, Lausanne, Switzerland
lpm.epfl.ch
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Determination of gas viscosity
• Purpose: identification of gas mixtures
• Simple sensor principle: time relaxation
Viscous gas
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Determination of gas viscosity
• Purpose: identification of gas mixtures
• Simple sensor principle: time relaxation
Viscous gasThin gas
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Modular LTCC sensor
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Sensor principle
• Pressure differential generated by heating / cooling
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Sensor principle
• Pressure differential generated by heating / cooling
• Pressure measured by membrane sensor
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Sensor principle
• Pressure differential generated by heating / cooling
• Pressure measured by membrane sensor
• Pressure relaxation through meander
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Why LTCC (1) ?
• Ease of structuration
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Why LTCC (2) ?
• Integration of many functions
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Why LTCC (3) ?
• Microreactor & flowsensor
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Why LTCC (3) ?
• Microreactor & flowsensor
• Inclination sensor
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Why LTCC (3) ?
• Microreactor & flowsensor
• Inclination sensor
• Gas sensor (Golonka etal., 1998)
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Why LTCC (3) ?
• Microreactor & flowsensor
• Inclination sensor
• Gas sensor (Golonka etal., 1998)
• Flow sensor (Gongora etal., 2001)
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LTCC for membranes & meanders
• Small spacings
• Intricate layout
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LTCCsintering
Graphiteburnout
Cavities by graphite fugitive phase
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LTCCsintering
Graphiteburnout
Cavities by graphite fugitive phase
• Graphite burnsout shortlybefore LTCCdensifies.
• Spacing can becontrolled byheating rate.
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Heater module (1)
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Heater module (2)
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Heater module (2)
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Heater module (2)
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Results (1/3): thermal resistance
• Good correspondance with model
• Change = increase of air conductivity with temperature
• Some positive temperature drift at low power
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Results (2/3): lid temperature
• Fractional lid temperature rise (rel. to heating resistor)
• Air conductivity rises with increasing temperature.
• Lid (Al2O3) conductivity drops with increasing temp.
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Results (3/3): reference resistor
• Fractional reference resistor temperature rise
• Slight rise with increasing temperature, due toproportionally hotter lid
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Origin of thermal drift
• Thermal resistance vs. weighted reference (block+lid)
• No hysterisis with these boundary conditions
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Transient behaviour
• Very fast resistor response time (!1 s)
• Heating faster than cooling due to TCR
• Additional delayed response due to lid, etc.
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Thermal resistances
• Res. of base & heat sink compound: ca. 3% of total
• Average « parasitic » resistances: ca. 12%
• Lid + module: large resistances, slow equilibration
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Materials (& better alternatives)
0.026AirCavity
0.6Grease + Al2O3Heat sink comp.
0.2
60
Silicone glue
Sn-Ag-Cu solderJoints
24
150
Alumina 96%
Al, Al-SiLid
3
6
LTCC
LTCC+AgModule
Conductivity[W/m/K]
MaterialPart / layer
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Conclusions
• High thermal resistance (! 250"K/W)
• Average cavity !T @ 0.5"W: ca. +60K
• Generated pressure peak: ca. ±0.2"bar
• High speed (! 1s)
• Boundary conditions not yet optimal
• Improvement by using better materials
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Merci / Danke / Grazie / Hvala
THANK
YOU !