Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT...
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Transcript of Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT...
![Page 1: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/1.jpg)
Gy. Bognár1, P. Fürjes2, V. Székely1, M. Rencz3
TRANSIENT THERMAL CHARACTERISATION OF HOT
PLATES
&of MEMS MOEMS
200
4
3MicReD Ltd., Budapest, Hungary
1BUTE, Budapest, Hungary
2KFKI-MFA Research Institute for Technical Physics and Materials Science, Hungary
![Page 2: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/2.jpg)
The physical structure to be characterised thermally: an integrated gas sensor• Thermally isolated heater and • sensing resistor filament (Pt)• 100m x 100m x 1m• Encapsulated by reduced
stress silicon rich silicon-nitride (LPCVD)
• Selective dissolution ofelectrochemically formedporous silicon (60-80m)
• Mechanical support under the hotplate
100m
Mechanical support
Thermal operation needs thermal characterisation
![Page 3: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/3.jpg)
Reasons of thermal characterisation
• To check the maximal operation speed of the sensor device (strongly influenced by the thermal isolation of the membrane structure)
• To check how to reach maximal temperature elevation with minimal heating power (e.g.: for explosion-proof detection of combustible gases)
100-600C achieved with 10-25mW
• To detect the differences in the thermal behaviour of hotplates with and without mechanical support
![Page 4: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/4.jpg)
Outline• Presentation of the following studies:
– Simulation:• Structure without mechanical support: steady-state,
transient
– Measurement – thermal transient• Structure with mechanical support• Structure without mechanical support
• Comparison by means of – Time-constant spectra– Structure functions– Simple compact model created
• Conclusions
![Page 5: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/5.jpg)
The simulation
• Simulated by the SUNRED program (without mechanical support)
• FD model, solved by SUccessive Network REDuction
The simulation results were verified by thermal transient measurements using the T3Ster equipment and related analysis software
The model:
![Page 6: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/6.jpg)
The simulationTransient result
Time evaluation of temperature is not to scale
The 1µs .. 1s time range was covered on a logarithmic time-scale
![Page 7: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/7.jpg)
The simulationTransient result
The 1µs .. 1s time range was covered on a logarithmic time-scale
![Page 8: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/8.jpg)
Max. temperature elevation is 227oC @ 8.5mW
The simulationSteady-state result (figure is not to scale)
![Page 9: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/9.jpg)
Steady-state resultThe simulation
Uniform temperature distribution on the hotplate
![Page 10: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/10.jpg)
Verification by measurements
• The resistor of the hotplate was used both as a heater and a temperature sensor– Sensitivity of the sensor was identified by a
calibration process• The thermal response was recorded by T3Ster
using the 4 wire method:
Idrive Isense
DUT
Umeas ~ T
Force: Sense:
![Page 11: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/11.jpg)
Verification by measurements
Simulated8.5mW
Measured8.5mW
Structure without mechanical support
Steady state values agree well
![Page 12: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/12.jpg)
Verification by measurements
Simulated
Measured
Structure without mechanical support
The dominant time constants are in a good agreement
2.24 ms1.10 ms
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time [s]
Tem
pera
ture
[C
]
Simulated8.5mW
Measured8.5mW
Measured6.5mW
(with support)
Verification by measurements
![Page 14: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/14.jpg)
Verification by measurements
Simulated woMeasured w
Measured wo
The dominant time constant is only slightly influenced by the mechanical support
![Page 15: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/15.jpg)
• Foster type network model of the structure is constructed from the time constant spectra
• Equivalent Cauer type network model corresponds to the real physical structure
Structure functions
![Page 16: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/16.jpg)
• The discrete RC model network in the Cauer canonic form now corresponds to the physical structure, but
n
iiRR
1
n
iiCC
1
• This is called cumulative structure function
• it is very hard to interpret its “meaning”
• Its graphical representation helps:
Structure functions
![Page 17: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/17.jpg)
The cumulative structure function is the map of the heat-conduction path:
n
iiRR
1
n
iiCC
1
ambi
ent
heater
Structure functions
![Page 18: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/18.jpg)
Structure functions
Agrees well with the volume calculated from exact geometry
hotplate
27000 K/W40 nWs/K
![Page 19: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/19.jpg)
Structure functions
• The thermal capacitance ~ 40 nWs/K
• The thermal resistance ~ 27000 K/W
• The structure has only one dominant time constant
• The simplified thermal model constructed
hotplate
27000 K/W40 nWs/K
![Page 20: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/20.jpg)
Summary of transient characterisation
Power level
Thermal resistance
Thermal capacitance
Time constant
measured w support 8.5mW 27000 K/W 40 nWs/K 1.10ms
measured wo support 6.5mW 26000 K/W 40 nWs/K 1.12ms
simulated wo support 8.5mW 30000 K/W 40 nWs/K 2.24ms
Identified from the structure functions
![Page 21: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/21.jpg)
• The structures can be represented by one dominant time constant ( ~ 1.1ms)
• The time constants of the two structures are nearly the same
• The pillar support has small thermal capacitance and high resistance, so it hardly influences the thermal behavior of the hotplate
Summary of transient characterisation
![Page 22: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/22.jpg)
Summary• The response time of the heater was investigated
by time constant analysis, and the single dominant time constant of the structure was found in the range of milliseconds
• We identified and generated a reduced order (compact) thermal model of the structure
• The thermal properties (Rth, Cth, ) of the structures with and without support were nearly identical
• Consequently the dynamic behaviour was not deteriorated significantly by the mechanical support
![Page 23: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/23.jpg)
Acknowledgment
This work was partially supported
by the
• OTKA T033094 project of the Hungarian National Research Fund
• INFOTERM NKFP 2/018/2001 project of the Hungarian Government
and the
• SAFEGAS and the REASON FW5 Projects of the EU
![Page 24: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/24.jpg)
Measurements: temperature calibration
0
100
200
300
400
500
600
700
800
0 10 20 30
Power loss [mW]
Tem
per
atur
e [o
C]
calculated
measured
• Surface temperature was measured by resistance calibration technique
• Rth26.5K/mW (with mechanical support)
• heat conduction in the suspending beams,• conduction and convection in the surrounding gas,• radiation from the hot surfaces
![Page 25: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/25.jpg)
• The complex loci – Nyquist diagram – was calculated from the measured thermal impedance curves
• Slight transfer effect can be observed that is due to the heat transfer between different sections of the heating meander
Frequency domain behavior derived from measured transient curves
![Page 26: Gy. Bognár 1, P. Fürjes 2, V. Székely 1, M. Rencz 3 TRANSIENT THERMAL CHARACTERISATION OF HOT PLATES &of MEMS MOEMS 2004 3 MicReD Ltd., Budapest, Hungary.](https://reader033.fdocuments.us/reader033/viewer/2022052913/56649e435503460f94b36077/html5/thumbnails/26.jpg)
Measuredwithout support
Measuredwith support
Frequency domain behavior derived from measured transient curves