Skima FEMTOST Institute December 21 st 2015 Accelerated Lifetime Tests and Failure Analysis of an Electrothermally Actuated MEMS valve firstnamelastnamefemtostfr FEMTOST Institute ID: 830392
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Slide1
ICM conference 2015
Haithem
Skima
FEMTO-ST Institute
December 21
st
, 2015
Accelerated Lifetime Tests and Failure Analysis of an Electro-thermally Actuated MEMS valve
firstname.lastname@femto-st.fr
FEMTO-ST Institute,
Besançon
– France
Haithem
Skima
,
Kamal
Medjaher
,
Noureddine
Zerhouni
, Christophe
Varnier
,
Eugen
Dedu
and Julien Bourgeois
Slide2Outline
H.
Skima
, K.
Medjaher
, N.
Zerhouni
,
C.
Varnier, E. Dedu, J. Bourgeois, ICM Conference, December 20-23,
2015Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion and future work
Slide3Micro-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.
Others
MOEMS
RF MEMS
Micro actuators
Micro sensors
Bio MEMS
Categories of MEMS
Applications
Automotive
Aerospace
Biomedical
Optical
Fluidic
Communication technologies
Introduction
Introduction
Motivation Accelerated lifetime tests Results
Conclusion
Slide4Introduction
Mechanical, electrical and material based failures mechanisms
Failure mechanisms related to manufacturing or to utilization
Mechanical
Electrical
Material
Delamination, Fracture, Fatigue, Creep, Stiction, Plastic-deformation, Adhesion
Degradation of dielectrics, Electrostatic discharge ESD
Electro-migration, Electrical short Circuit, Electrical
stiction
Stiction,
Contamination
Related to utilization
Related to manufacturing
Stiction, Delamination, Fatigue, Creep,
Fracture, Adhesion, ESD,
Electro-migration,
Electrical
short circuit
Stiction, Contamination, Fracture,
Electrical
short circuit
Influence factors
:
temperature, humidity, vibration, noise, dust,
shocks
,
overcharges
…
[
H. R.
Shea
2007
,
M. McMahon et al. 2012
,
J. Ruan et al. 2009
, R.
Mûller-Fiedler
et al. 2002]
[
M. MATMAT 2010
]
Introduction
Motivation Accelerated lifetime tests Results
Conclusion
Slide5Introduction
Stiction in electro-thermal actuator
[
M.
Dardalhon
2003
]
Micro-actuator finger fracture
[ B.
Charlot
2001]
Contamination in a comb-drive
[Tanner et al. 2000
]
Stiction
of the finger on the substrate
[Tanner et al. 2000]
Examples of failure mechanisms in MEMS
Introduction
Motivation Accelerated lifetime tests Results
Conclusion
Slide6Prognostics & Health Management: PHM
Motivation
MEMS
Reliability issues
L
oss of performance
Faults
(Non achieved functions)
Risk of accidents
Reliability
Availability
Security
cost
Introduction
Motivation
Accelerated lifetime tests Results
Conclusion
Accelerated lifetime tests performing
Health assessment and state estimation
Time to failure prediction
Decision making
Degradation model definition
MEMS
Slide7Accelerated lifetime tests
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.
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
Slide8Accelerated lifetime tests
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
Movable membrane
Fluid connection ports
Common port
Normally closed
Normally open
Normally open
Common port
Normally closed
Scanning Electron Microscope (SEM) pictures (FEMTO-ST)
Anchorage
Anchorage
ᶿ
l
Hot arms
Shuttle
Direction of movement
Maximum actuation voltage: 12V
Current consumption can reach 1A
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
Slide9Computer
Arduino
Voltage suppliers
NI card
Camera
Light source
MEMS
Experimental platform - (FEMTO-ST
)
Accelerated lifetime tests
Experimental setup
PT100 RTD
Input and output of air
Metal plate
Electronic card
MEMS
Pins
Support
1- Experimental platform
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
2
- Setup in the SEM
Slide10Accelerated lifetime tests
NI card
Camera
Arduino card
Voltage supplier
Light source
Pressure regulator
Air filter
MEMS
PT100
Air supply
Temperature measurement
Supply
Image acquisition
Air flow
Electronic card
Global synoptic of the experimental platform
Processing and storage of data
Experimental setup
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
1- Experimental platform
Slide11Accelerated lifetime tests
Direction of motion
Movable Membrane
Direction of motion
Guppy Pro F-031
with
100
fps
Matlab Image-
processing
algorithm
Time
response
–
parameters
identification
MEMS are supplied with a square signal of
8V
magnitude and a frequency equal to 1Hz.
This voltage is not too high to not bring up prematurely degradation and not to low to obtain enough displacement
The current consumption of a new MEMS at 8V is about 0.55A and the displacement is about 65µm
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
Slide12Accelerated lifetime tests
Movable membrane
Experimental setup
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
2
- Setup in the SEM
Electrical connections
MEMS
Slide13Accelerated lifetime tests
Tests
Tests consist in cycling MEMS valves and changing at each time the operating condition:
Unfiltered air – Experimental platform
Without air – in the SEM
Filtered air – Experimental platform
Unfiltered air
Without air
Filtered 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.
Cycling one MEMS valve inside the SEM without air
The displacement of the membrane is calculated by using the SEM images.
Cycling four MEMS valves with filtered air
Experiments remained running for more than three months
Measurements were collected after approximately 90000 cycles.
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
Slide14Results
Unfiltered air
SEM image showing contamination at the normally closed fluid port
Image taking by the camera showing a damaged membrane
Video showing the degraded state of the membrane and its small displacement
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
Test
Initial displacement
Performed cycles
Displacement at the end
of the test
Membrane state
Without air
65 µm
800000
50 µm
good
This test has been stopped since we can not use the SEM for long
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
Slide15Good surface state of the membrane
For the
electrothermally
actuators, a failure is defined as the point at which the displacement decreases by 20%
[Conant et al 1998]
Results
F
iltered 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
Faulty MEMS
Degradation at the actuator
New MEMS
MEMS at the end cycling
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
After 12 million cycles, the displacement is about 15 µm (23% of the initial displacement)
Slide16Results
Test
Initial displacement
Performed cycles
Displacement at the end
of the test
Membrane state
Unfiltered air
65 µm
1 million
10 µm
degraded
Without air65 µm
800000
50 µmgood
filtered air65 µm
12
million
15 µm
good
The variation of the displacement depends on the degradation
Introduction
Motivation
Accelerated lifetime tests
Results
Conclusion
0
2
4
6
8
10
12
0
50
100
150
MEMS-1
Voltage (V)
Displacement (µm)
MEMS-1 EOL
MEMS-1 cycle0
0
2
4
6
8
10
12
0
20
40
60
80
MEMS-2
Voltage (V)
Displacement (µm)
MEMS-2 EOL
MEMS-2 cycle0
Slide17Conclusion
Two experimental setup designed to perform accelerated lifetime tests to an electro-thermally 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
Perform
new tests by changing input
parameters such as supply
voltage and operating
frequency to
see their impact on the MEMS
degradationAnalyze 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
Conclusion
Future works
Introduction
Motivation
Accelerated lifetime tests Results
Conclusion
Slide18Thank you for your attention
H.
Skima
, K.
Medjaher
, N.
Zerhouni
,
C.
Varnier
, E.
Dedu
, J. Bourgeois,
ICM Conference, December 20-23,
2015