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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 1 PME5230 Final Presentation Outline Introduction Ultrasound inspection Transducer Design and Fabrication Ultrasound transducer Function Test Result Conclusion 2 PME5230 Final Presentation Introduction Nondestructive Evaluation Method Nondestructive Evaluation method Radiographic method Thermographic method Electromagnetic method Optical method Ultrasonic method 3 PME5230 Final Presentation 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… 4 PME5230 Final Presentation Ultrasound inspection immersion Fig. Linear ultrasound inspection techniques 5 PME5230 Final Presentation 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) 6 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 7 PME5230 Final Presentation 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 8 PME5230 Final Presentation 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 9 PME5230 Final Presentation 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 10 PME5230 Final Presentation 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 11 PME5230 Final Presentation 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 12 PME5230 Final Presentation 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 13 PME5230 Final Presentation Thank you for your attention! 14 PME5230 Final Presentation