Transcript icm15slidesx

ICM conference 2015
Accelerated Lifetime Tests and Failure Analysis
of an Electro-thermally Actuated MEMS valve
Haithem Skima, Kamal Medjaher, Noureddine Zerhouni, Christophe Varnier, Eugen Dedu
and Julien Bourgeois
[email protected]
Haithem Skima
FEMTO-ST Institute
Événement - date
FEMTO-ST Institute, Besançon – France
December 21st, 2015
Outline
o Introduction
o Motivation
o Accelerated lifetime tests
o Results
o Conclusion and future work
H. Skima, K. Medjaher, N. Zerhouni, C. Varnier, E. Dedu, J. Bourgeois, ICM Conference, December 20-23,
2/ 2015
18
Introduction
o
Micro-Electro-Mechanical Systems: MEMS
A MEMS is a micro-system that integrates mechanical components using electricity as
source of energy in order to perform measurement functions and / or operating in structure
having micrometric dimensions.
Micro
sensors
Bio MEMS
Micro
actuators
RF MEMS
MOEMS
Others
Categories of MEMS
o
Applications
Automotive
Aerospace
Introduction
Biomedical
Motivation
Optical
Fluidic
Accelerated lifetime tests
Communication technologies
Results
Conclusion
3/ 18
Introduction
o Mechanical, electrical and material based failures mechanisms
Mechanical
Electrical
Delamination, Fracture,
Fatigue, Creep, Stiction,
Plastic-deformation, Adhesion
Material
Degradation of dielectrics,
Electrostatic discharge ESD
Electro-migration, Electrical
short Circuit, Electrical stiction
Stiction, Contamination
[H. R. Shea 2007, M. McMahon et al. 2012, J. Ruan et al. 2009, R. Mûller-Fiedler et al. 2002]
o Failure mechanisms related to manufacturing or to utilization
Related to utilization
Related to manufacturing
Stiction, Delamination, Fatigue, Creep, Fracture,
Adhesion, ESD, Electro-migration, Electrical short
circuit
Stiction, Contamination, Fracture, Electrical
short circuit
[M. MATMAT 2010]
Influence factors: temperature, humidity, vibration, noise, dust, shocks, overcharges …
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
4/ 18
Introduction
o
Examples of failure mechanisms in MEMS

Stiction of the finger on the substrate

Stiction in electro-thermal actuator
[M. Dardalhon 2003]
[Tanner et al. 2000]

Micro-actuator finger fracture

Contamination in a comb-drive
[ B. Charlot 2001]
Introduction
Motivation
[Tanner et al. 2000]
Accelerated lifetime tests
Results
Conclusion
5/ 18
Motivation
MEMS
Reliability
issues
Loss of
performance
Faults
(Non achieved
functions)
Risk of
accidents
Prognostics & Health Management: PHM
MEMS
Accelerated
lifetime tests
performing
 Reliability
Introduction
Degradation
model
definition
 Availability
Motivation
Health
assessment and
state estimation
Time to failure
prediction
 cost
 Security
Accelerated lifetime tests
Decision
making
Results
Conclusion
6/ 18
Accelerated lifetime tests
o Definition
Accelerated lifetime test is an aging of a product that induces normal failures in a short
amount of time by applying stress levels much higher than normal ones (stress, strain,
temperatures, voltage, vibration rate, pressure, etc.). The main interest is to observe the
evolution over time to predict the life span.
Reliability results can then be obtained by analyzing the product’s response to such tests.
o Difficulty in MEMS failure analysis
‒ Structures of interest are not exposed for direct observation
‒ Structures that provide the stimulus for motion or actuation are obscured from view
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
7/ 18
Accelerated lifetime tests
o System description
Electrothermally actuated MEMS valve designed by DunAn Microstaq
company to control flow rates or pressure with high precision at ultra-fast time
response (<< 100 ms). It is currently being used in a number of applications
in air conditioning and refrigeration, hydraulic control and air pressure control
‒
‒
Electrical
connections
Maximum actuation
voltage:
Normally
closed 12V
Current consumption
can reach 1A
Shuttle
Anchorage
Movable
membrane
Direction of movement
Normally open
Common port
ᶿ
Anchorage
Hot arms
Fluid connection
ports
Normally closed
Normally open
Common port
Scanning Electron Microscope (SEM) pictures (FEMTO-ST)
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
8/ 18
Accelerated lifetime tests
o Experimental setup
1- Experimental platform
Input SEM
and output of air
2- Setup in the
Computer
Camera
PT100
RTD
Electronic
card
Metal
plate
Light source
Voltage suppliers
Support
MEMS
Arduino
Pins
NI card
MEMS
Experimental platform - (FEMTO-ST)
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
9/ 18
Accelerated lifetime tests
Processing and storage of data
o Experimental setup
1- Experimental platform
Image
acquisition
NI card
Camera
Arduino card
Light source
Voltage supplier
Electronic card
MEMS
PT100
Supply
Temperature
measurement
Air flow
Air filter
Air supply
Pressure regulator
Global synoptic of the experimental platform
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
10/ 18
Accelerated lifetime tests
Guppy Pro F-031
with 100 fps
MEMS are supplied with a square
signal of 8V magnitude and a
frequency equal to 1Hz.
Matlab Imageprocessing algorithm
This voltage is not too high to not
bring up prematurely degradation and
not to low to obtain enough
displacement
70
The current consumption of a new
MEMS at 8V is about 0.55A and the
displacement is about 65µm
60
50
Displacement (µm)
Time response –
parameters identification
Direction of
motion
Direction of
motion
40
30
20
10
0
Movable Membrane
0
0.1
Introduction
0.2
0.3
0.4
0.5
Time (s)
Motivation
0.6
0.7
0.8
0.9
1
Accelerated lifetime tests
Results
Conclusion
11/ 18
Accelerated lifetime tests
o Experimental setup
2- Setup in the SEM
Electrical connections
MEMS
Movable membrane
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
12/ 18
Accelerated lifetime tests
o Tests
Tests consist in cycling MEMS valves and changing at each time the operating condition:
a) Unfiltered air – Experimental platform
b) Without air – in the SEM
c) Filtered air – Experimental platform
Unfiltered air
Without air
• Cycling four MEMS valves with an
unfiltered air
• Experiments remained running for
more than one month
• Measurements were collected every
day, after 25000 cycles, and at each
measurement the displacement of the
membrane is calculated.
Introduction
•
•
Cycling one MEMS valve inside
the SEM without air
The
displacement
of
the
membrane is calculated by
using the SEM images.
Motivation
Accelerated lifetime tests
Filtered air
• Cycling four MEMS valves with
filtered air
• Experiments remained running for
more than three months
• Measurements were collected after
approximately 90000 cycles.
Results
Conclusion
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Results
o Unfiltered air
Video showing the degraded state
of the membrane and its small
displacement
o Without air
Test
Without air
Test
Initial
displacement
Unfiltered air
Initial
displacement
65 µm
SEM image showing contamination
at the normally closed fluid port
Image taking by the camera showing
a damaged membrane
65 µm
Performed
cycles
800000
Performed
cycles
Displacement at
the end of the test
1 million
10 µm
Displacement at
Membrane
the end of the test
state
50 µm
Membrane
state
degraded
good
This test has been stopped since we can not use the SEM for long
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
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Results
o Filtered air
‒ 8 million cycles (guaranteed by the manufacturer) performed without a significant
decrease of the displacement (less than 10% of displacement decrease) or membrane
degradation
‒ After 12 million cycles, the displacement is about 15 µm (23% of the initial displacement)
New MEMS
MEMS at the end cycling
‒ Good surface state of the membrane
Degradation at the actuator
‒ For the electrothermally actuators, a failure is defined as the point at which the
displacement decreases by 20% [Conant et al 1998]
Faulty MEMS
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
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Results
MEMS-2
MEMS-1
80
MEMS-1 EOL
MEMS-1 cycle0
Displacement (µm)
Displacement (µm)
150
100
50
0
0
2
4
6
Voltage (V)
8
10
12
MEMS-2 EOL
MEMS-2 cycle0
60
40
20
0
0
2
4
6
Voltage (V)
8
10
12
The variation of the displacement depends on the degradation
Test
Initial
displacement
Performed
cycles
Displacement at
the end of the test
Membrane
state
Unfiltered air
65 µm
1 million
10 µm
degraded
Without air
65 µm
800000
50 µm
good
filtered air
65 µm
12 million
15 µm
good
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
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Conclusion
o Conclusion
‒ Two experimental setup designed to perform accelerated lifetime tests to an electrothermally actuated MEMS valve
‒ Three accelerated lifetime tests performed
‒ Unfiltered air can cause the contamination at the actuator and the membrane, early failure
‒ Very small displacement of the membrane after 12 million cycles with good surface state
degradation at the actuator which is obscured from view
o Future works
‒ Perform new tests by changing input parameters such as supply voltage and operating
frequency to see their impact on the MEMS degradation
‒ Analyze data collected during tests in order to define a degradation model of the MEMS
‒ Implement Prognostics and Health Management approach to estimate MEMS health states
and predict their time to failure
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
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Thank you for your attention
H. Skima, K. Medjaher, N. Zerhouni, C. Varnier, E. Dedu, J. Bourgeois, ICM Conference, December 20-23,
18/2015
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