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Acoustic sealing of silicon MEMS microspeakers by the means of polymer films

A. HOUDOUIN1, I. SHAHOSSEINI2, N. YAAKOUBI1, E. LEFEUVRE2, E. MARTINCIC2, Y. AUREGAN1, S. DURAND1

Affiliation

  1. LUNAM Université, LAUM (Laboratoire d'acoustique de l'université du Maine), UMR CNRS 6613, Avenue Olivier Messiaen, F-72085 Le Mans, France
  2. Institut d'Electronique Fondamentale (IEF), Univ. Paris Sud – UMR CNRS 8622, 91405 Orsay, France

Abstract

We present here a silicon MEMS microspeaker with an acoustic leakage reduction polymer sealing. The silicon MEMS microspeakeris formed by a silicon emissive surface suspended by thin silicon suspension beams. The high rigidity of the acoustic emissive surface is obtained thanks to the design of stiffeners located on its backside. Its displacement is obtained by an electrodynamic actuator, i.e. a micromachined planar coil manufactured onto the emissive surface and placed in the near vicinity of a permanent magnet. Out of plane displacements up to ±400 µm are possible without failure of the structure and 80 dBSPL at 10 cm were obtained. The performances of silicon microspeakerscan be further improved by an optimized sealing between the static part and the emissive surface. The sealing requires high mechanical compliance and low mass to limit its impact on the microspeaker's characteristics. A thin polymer (PolyDiMethylSiloxane or dry resist film) seal has been designed with finite elements modelling. We demonstrate that the stiffness added by the seal can be reduced by a factor 10 compared to the same material seal with no forming. A fabrication process with a dedicated homemade vacuum forming set-up is presented..

Keywords

: MEMS, Microspeaker, Acoustic leakage, FEM, Polymer, PDMS, Seal, Dry resist film.

Submitted at: April 17, 2013
Accepted at: June 12, 2013

Citation

A. HOUDOUIN, I. SHAHOSSEINI, N. YAAKOUBI, E. LEFEUVRE, E. MARTINCIC, Y. AUREGAN, S. DURAND, Acoustic sealing of silicon MEMS microspeakers by the means of polymer films, Journal of Optoelectronics and Advanced Materials Vol. 15, Iss. 5-6, pp. 463-470 (2013)