Transcript Document

Development of Air-Coupled
Ultrasound transducer for
nondestructive evaluation
Xuefeng Wang1, Ying Fan1, Wei-Cheng Tian1, Hyon-Jin Kwon2, Stacey
Kennerly1, Glenn Claydon1, and Andrew May1
1. GE Global Research Center, Niskayuna, New York, USA
2. GE Sensing, Fremont, California, USA
MEMS 2008, Tucson, AZ, USA, January 13-17, 2008
Teacher ： Cheng-Hsien Liu
Reporter：Chien Thanh Nguyen
Date：2008.6.11
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Outline
Introduction
Ultrasound inspection
Transducer Design and Fabrication
Ultrasound transducer Function
Test Result
Conclusion
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Introduction
Nondestructive Evaluation Method
Nondestructive
Evaluation method
Radiographic
method
Thermographic
method
Electromagnetic
method
Optical
method
Ultrasonic
method
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Ultrasound inspection
Fig. Example of ultrasound Inspection
Fig. Defect exist inside sample
 Ultrasound inspection can be used to investigate the property
of material, the thickness, defect, …
 Can be apply for many field such as: composites in aircraft
structure, wood materials, food and pharmacy…
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Ultrasound inspection
immersion
Fig. Linear ultrasound inspection techniques
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Coupling media
 Constant coupling during
entire inspection for reliable
testing
 Suitable acoustic matching
for acoustic energy transfer
 No influence on the properties
of the testing object
 Not toxic or corrosive
 Wets both the surface of the
transducer and of the sample
(suitable viscosity)
 Can easily be removed after
inspection
Can not apply for many field
Piezoelectric
material
Capacitive
micromachined
ultrasound
transducers
(CMUTs)
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Ultrasound
transducer
Coupling
layer
PME5230 Final Presentation
Transducer Design
A schematic of a cross-sectional view
of an air-coupled CMUT.
A microscope image (top view) of arrayed
cells on a CMUT device.
A prototype CMUT device packaged
on a printed circuit board
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Transducer Fabrication
(a) Etch Si substrate
(b) Grow and pattern SiO2
(c) Bond to SOI (silicon-oninsulator) wafer
(d) Remove SOI handle wafer
(e) Open substrate contact window and
ion implantation
(f) Remove SiO2
(g) Form metal electrodes
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Ultrasound transducer Function
Transmitter
Receiver
- DC bias voltage is applied
between the membrane and
substrate
- DC bias voltage is applied
between the membrane and
substrate
V
- Driving voltage AC is
superimposed on the DC bias
V
- Impacting ultrasound pressure
causes the membrane to vibrate
Ultrasound can function both as a transmitter and a receiver
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Test Result
Fig. A block diagram of the CMUT acoustic test
setup
Fig. Ultrasound signal obtained by CMUT
receiver in a transmission test. A loop gain of 51 dB was calculated from the received and
the input signal
 AC Receiver Magnitude/ AC drive Transmitter Magnitude
 Best set of commercial transducer: -65 dB loop gian.
14 dB lower than CMUTs reported here
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Test Result
 DC bias and AC operating voltages were applied to two CMUT devices
 Scanning laser-Doppler vibrometer: inspect the membrane vibration
 Patterned SiO2 insulation layers showed consistent and synchronized
cell vibration for a long period of time
 Un-patterned blanket oxide showed out-of-phase membrane vibration
The unsynchronized membrane vibration was due to charging of the
SiO2 insulation layer
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Conclusions
Ultrasound inspection method face tremendous challenges
when implemented in ambient air without liquid coupling.
Capacitive micromachined ultrasound transducers for aircoupled non-contact non-destructive evaluation has been
developed to gain higher transduction efficiency.
The developed devices have large gaps and patterned
dielectric insulation layers to ensure high transduction
efficiency without dielectric breakdown or charging failures.
Acoustic transmission test, paired transducers showed a 51dB loop gain, higher than commercial air-coupled
ultrasound transducers.
CMUT may be used widely for air inspection
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Reference
1) http://en.wikipedia.org/wiki/Ultrasonic_testing
2) Nonlinear acoustic interaction on contact interfaces and its use
for nondestructive testing
D. Donskoy*, A. Sutin, A. Ekimov
3) Air-coupled ultrasound inspection of various materials
R. Stoessel *, N. Krohn, K. Pfleiderer, G. Busse
4) Air-coupled Ultrasound Inspection as a New Nondestructive
Testing Tool for Quality Assurance.
Von der Fakultat maschinenbau der University Stuttgart
5) Fabricating Capacitive Micromachined Ultrasonic
Transducers With Wafer-Bonding Technology
Yongli Huang, A. Sanli Ergun, Edward Hæggström, Mohammed H.
Badi, and B. T. Khuri-Yakub
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Thank you for your attention!
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