The Journal of the Acoustical Society of Korea (한국음향학회지)

The Acoustical Society of Korea (한국음향학회)
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Fabrication and Evaluation of a VHF Focusing Ultrasonic Transducer Made of PVDF Piezoelectric Film

PVDF 압전막을 이용한 초고주파 집속 초음파 트랜스듀서의 제작 및 특성 평가

  • Received : 2011.03.05
  • Accepted : 2011.05.06
  • Published : 2011.05.31
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Abstract

In order to obtain high resolution images, a focusing ultrasonic transducer operated in very high frequency (VHF) range was fabricated and its characteristics were evaluated. A 9-${\mu}m$ thick PVDF film with only one metalized surface for electric ground was adhered to a CCP (Copper-clad polyimide) film by using epoxy. It was pressed by a metal ball to form a concave surface and its rear side was filled with the epoxy. The radius of curvature and the f-number of the fabricated transducer are 7.5 mm and 1.7, respectively. The pulse-echo measurement results from a target located at the focal point showed that the frequency bandwidth was 35.0 MHz and the insertion loss near the peak frequency of approximately 40 MHz was about 60 dB. Those values agreed well with the simulation results by the KLM equivalent circuit analysis including the effect of the epoxy bonding layer. When the image of thin copper lines by the 35 MHz transducer of the UBM (Ultrasonic Backscattering Microscope) system was compared with the image by the transducer fabricated in this study, the fabricated transducer was observed that the axial resolution was improved although the lateral resolution was degraded.

높은 분해능의 영상을 얻는데 사용하기 위하여 초고주파 대역에서 동작하는 집속 초음파 트랜스듀서를 제작하고 그 특성을 평가하였다. 그 트랜스듀서는 한쪽 면에만 접지용 전극이 있는 두께 9 ${\mu}m$의 PVDF 압전막의 다른 쪽 면에 CCP (Copper Clad Polyimide)막을 에폭시로 접착한 후, 금속구로 압착함에 의해 구각형을 형성시키고, 그 뒷면에 에폭시를 채워 몰딩 시키는 방법에 의해 만들어졌다. 제작된 곡률반경 7.5 mm, f-number 1.7의 트랜스듀서는 초점에 있는 표적에 대한 펄스에 코 측정결과 35.0 MHz의 대역폭을 가지며, 약 40 MHz인 피크주파수 부근에서의 삽입손실은 약 60 dB 을 나타내었는데, 그 측정결과는 에폭시 접착층의 두께를 고려한 KLM 등가회로 해석에 의한 시뮬레이션 결과와 유사한 것이었다. 나아가, 그 트랜스듀서에 의해 얻어진 가는 구리선 표적에 대한 영상을 35 MHz 트랜스듀서를 장착한 UBM (Ultrasonic Backscattering Microscope) 장치에 의한 영상과 비교한 결과, 측방향 분해능은 떨어지나 축방향 분해능은 다소 향상됨을 알 수 있었다.

Keywords

Acknowledgement

Supported by : 부경대학교

References

  1. C. Passmann and H. Ermert, "A 100-MHz ultrasound imaging system for dermatologic and ophthalmologic diagnostics", IEEE Trans. on UFFC, vol. 43, no. 4, pp. 545-552, 1996. https://doi.org/10.1109/58.503714
  2. G. S. Kino, Acoustic waves -devices, imaging, & analog signal processing-, Prentice-Hall Inc., Englewood Cliffs, 1987.
  3. T. A. Ritter, T. R. Shrout, R. Tutwiler, and K. K. Shung, "A 30-MHz piezo-composite ultrasound array for medical imaging applications", IEEE Trans. on UFFC, vol. 49, no. 2, pp. 217-230, 2002. https://doi.org/10.1109/58.985706
  4. M. Robert. G. Molingou, K. Snook, J. Cannata, and K. K. Shung, "Fabrication of focused poly (vinylidene fluoridetrifluoroethylene) P (VDF-TrFE) copolymer 40-50 MHz ultrasound transducers on curved surfaces", Journal of Applied Physics, vol. 96, no. 1, pp. 252-256, 2004. https://doi.org/10.1063/1.1760233
  5. J. A. Ketterling, F. L. Lizzi, O. Aristizabal, and D. H. Turbull. "Design and fabrication of a 40-MHz annular array transducer", IEEE Trans. on UFFC, vol. 52, no. 4, pp. 672- 681, 2005. https://doi.org/10.1109/TUFFC.2005.1428050
  6. A. Denoyer, F. Ossant, B. Arbeille, F. Fetissof, F. Patat, L. Pourcelot, and P. J. Pisella, "Very-high-frequency ultrasound corneal imaging as a new tool for early diagnosis of ocular surface toxicity in rabbits treated with a preserved glaucoma drug", Ophthalmic Res., vol. 40, pp. 298-308, 2008. https://doi.org/10.1159/000134928
  7. F. S. Foster, C. J. Pavlin, G. R. Lockwood, L. K. Ryan, K. A. Harasiewicz, L. R. Berube, and A. M. Rauth, "Principles and applications of ultrasound backscatter microscopy", IEEE Trans. on UFFC, vol. 40, no. 5, pp. 608-617, 1993. https://doi.org/10.1109/58.238115
  8. F. S. Foster, C. J. Pavlin, K. A. Harasiewicz, D. A. Christopher, and D. H. Turnbull, "Advanced in ultrasound biomicroscopy", Ultrasound in Med. & Bilo., vol. 26, no. 1, pp. 1-27, 2000. https://doi.org/10.1016/S0301-5629(99)00096-4
  9. http://www.capolabs.com/index.htm
  10. R. Krimholtz, D.A. Leedom, and G.L. Matthaei, "New equivalent circuit for elementary piezoelectric transducers", Electron. Lett., vol. 6, pp. 398-399, 1970. https://doi.org/10.1049/el:19700280
  11. S. Sherrit, S.P. Leary, B.P. Dolgin, and Y. Bar-Cohen "Comparison of the Mason and KLM equivalent circuits for piezoelectric resonators in the thickness mode", 1999 IEEE Ultrasonics Symposium, pp. 921-926, 1999.
  12. 양정화, 이경성, 강관석, 팽동국, 최민주, "초음파프로브의 결함이 B-모드 영상의 공간 분해능에 미치는 영향," 한국음향학회 2009년도 춘계학술발표대회 논문집, 제28권, 1(s)호, 176-179쪽, 2009.
  13. 최광윤, 하강렬, 김무준, 김정순, 양정화, 강관석, 최민주, "의료용 초음파프로브의 압전소자 결함이 과도음장과 B-모드 영상에 미치는 영향," 한국음향학회지, 제29권, 8호, 476-482쪽, 2010.

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