WO2004062318A1 - Membrane pour transducteurs acoustiques - Google Patents

Membrane pour transducteurs acoustiques Download PDF

Info

Publication number
WO2004062318A1
WO2004062318A1 PCT/EP2004/000011 EP2004000011W WO2004062318A1 WO 2004062318 A1 WO2004062318 A1 WO 2004062318A1 EP 2004000011 W EP2004000011 W EP 2004000011W WO 2004062318 A1 WO2004062318 A1 WO 2004062318A1
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WO
WIPO (PCT)
Prior art keywords
membrane
eptfe
basis weight
thickness
value
Prior art date
Application number
PCT/EP2004/000011
Other languages
German (de)
English (en)
Inventor
Charles Thomas Rosenmayer
Original Assignee
W. L. Gore & Associates Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by W. L. Gore & Associates Gmbh filed Critical W. L. Gore & Associates Gmbh
Publication of WO2004062318A1 publication Critical patent/WO2004062318A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R7/00—Diaphragms for electromechanical transducers; Cones
    • H04R7/02—Diaphragms for electromechanical transducers; Cones characterised by the construction
    • H04R7/04—Plane diaphragms
    • H04R7/06—Plane diaphragms comprising a plurality of sections or layers
    • H04R7/10—Plane diaphragms comprising a plurality of sections or layers comprising superposed layers in contact
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R19/00—Electrostatic transducers
    • H04R19/01—Electrostatic transducers characterised by the use of electrets
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R19/00—Electrostatic transducers
    • H04R19/01—Electrostatic transducers characterised by the use of electrets
    • H04R19/013—Electrostatic transducers characterised by the use of electrets for loudspeakers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R19/00—Electrostatic transducers
    • H04R19/01—Electrostatic transducers characterised by the use of electrets
    • H04R19/016—Electrostatic transducers characterised by the use of electrets for microphones
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2307/00—Details of diaphragms or cones for electromechanical transducers, their suspension or their manufacture covered by H04R7/00 or H04R31/003, not provided for in any of its subgroups
    • H04R2307/027—Diaphragms comprising metallic materials
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2307/00—Details of diaphragms or cones for electromechanical transducers, their suspension or their manufacture covered by H04R7/00 or H04R31/003, not provided for in any of its subgroups
    • H04R2307/029—Diaphragms comprising fibres

Definitions

  • the invention relates to a membrane for acoustic transducers, in particular for acoustic transducers of the so-called fiat panel technology, comprising a - in particular metal-coated - polymer membrane.
  • Acoustic transducers of Fiat panel technology can work according to two different principles.
  • the polymer membrane is first charged to a constant electrical potential.
  • the membrane is electrically biased by means of a direct voltage applied to the membrane in the range of typically 100 V to 400 V. This principle is typically used in home audio devices.
  • the membrane is permanently electrostatically charged from the outset, which eliminates the need for an electrical bias. This principle is typically used with microphones, but not with loudspeakers.
  • the biased or charged membrane is then subjected to an AC voltage in a capacitor in accordance with the acoustic signal to be generated in order to generate acoustic vibrations of the membrane (loudspeaker function), or an acoustic oscillation is converted into such an AC voltage by means of the membrane (microphone function).
  • Electrostatic membranes usually consist of metallized fluoroethylene poly mer- (FEP) films. However, due to their low tensile strength of typically less than 10 MPa, these membranes are only of limited suitability for use in loudspeakers, since the membrane area, load and vibration amplitude in loudspeaker membranes are comparatively large.
  • FEP metallized fluoroethylene poly mer-
  • Electrostatic membranes are also suitable for use in mobile electronic devices, in particular in mobile telecommunications terminals, since acoustic transducers in flat-panel technology can be implemented easily and space-saving on circuit boards.
  • the increasing miniaturization of electronic devices requires the development of new membranes for acoustic transducers for these purposes.
  • the object of the present invention is therefore to propose a membrane for acoustic transducers, which is particularly suitable for loudspeakers and / or for use in mobile telecommunication terminals.
  • the membrane according to the invention consists of polymeric, permanently electrostatically chargeable material, the term "permanent" not to be understood in the strict sense, but in such a way that the natural loss of voltage occurs very slowly, so that the electrostatic bias is not renewed during the service life of the membrane or in any case only necessary at longer intervals. Nevertheless, the membrane according to the invention can of course also be used for applications in which the membrane is continuously electrically biased by means of a DC voltage source.
  • the membrane according to the invention is distinguished by a special choice of material for the polymeric membrane material.
  • the decisive influencing factors in the choice of material are, on the one hand, the weight per unit area of the polymer Membrane material, which should be as low as possible, and on the other hand, the surface charge density of the membrane material, which should be as high as possible.
  • the thickness of the membrane is a critical factor for acoustic conversion, since a thicker membrane is slower and therefore has less favorable vibration properties than a correspondingly thinner membrane. In fact, it is not the material thickness but the basis weight of the material that is the critical factor for the vibration properties. A thick membrane made of a material with a low density can therefore have better acoustic properties than a membrane made of a thinner but much denser material. Therefore, a particularly critical factor for the present invention is the basis weight of the membrane material.
  • the acoustic properties of a transducer with an electrostatic membrane are the better, the higher the surface charge density of the electrostatically charged membrane. It is therefore desirable in connection with the present invention to use a membrane material with the highest possible maximum surface charge density.
  • the maximum achievable surface charge density is essentially a material-specific value that can be influenced only slightly by the type of electrostatic charging process.
  • the membrane according to the invention is characterized by a value which is referred to below as the El value ("electret inertia”) and which results from the ratio of the membrane basis weight M to the surface charge density ⁇ :
  • the El value is below about 22 mg / ⁇ C, in particular below about 20 mg / ⁇ C.
  • a fluoropolymer is preferably used as the polymeric membrane material because fluoropolymers are highly temperature-resistant. Temperatures above 80 ° C can occur over long periods of time in mobile telecommunication end devices. In cooperation with microelectronic components, temperatures of up to 250 ° C can be reached for a short time.
  • Stretched polytetrafluoroethylene (ePTFE) and HSF have proven to be particularly suitable materials. HSF is compressed ePTFE.
  • ePTFE While the maximum achievable area charge density of ePTFE is only about 75% of the maximum area charge density of FEP, ePTFE can be manufactured with a much lower basis weight than FEP.
  • HSF An even more suitable polymer material for the membrane is HSF.
  • HSF cannot be produced with such a low basis weight as ePTFE because it is compressed ePTFE. However, it can still be produced with a lower surface density than the conventional FEP and moreover has the particular surprising advantage that the maximum achievable surface charge density is more than twice the maximum achievable surface charge density of FEP.
  • ePTFE can be electrostatically pre-stressed with a surface charge density of approximately 700 ⁇ C / m 2
  • HSF with a surface charge density of approximately 2100 ⁇ C / m 2 .
  • the maximum achievable surface charge density of FEP is around 1000 ⁇ C / m 2 .
  • an El value of less than 22 mg / ⁇ C can therefore already be achieved with ePTFE films that have a basis weight of less than 15 g / m 2 .
  • Typical commercially available ePTFE membranes for example, have a basis weight of 8 g / m 2 with a membrane thickness of about 15 ⁇ m. With such a membrane, the El value is only 11.4 mg / ⁇ C.
  • the El value of the typically 12.5 ⁇ m thick FEP films with a basis weight of 27 g / m 2 is 27.2 mg / ⁇ C, that is to say 2.5 times the value.
  • the easiest way to determine the respective membrane thickness is from the weight per unit area and the experimentally determined material density.
  • the thickness of an ePTFE membrane can suitably be less than 30 ⁇ m.
  • ePTFE membranes with a basis weight between 5 g / m 2 and 10 g / m 2 can be manufactured without any problems and their use as an acoustic membrane is quite realistic.
  • the thickness of the membrane is then between approximately 9 ⁇ m and 19 ⁇ m.
  • ePTFE membranes can be realized with a basis weight of 2 g / m 2 or even 1 g / m 2 if necessary by adding any additives.
  • the thickness of the membrane is then only about 4 ⁇ m or 2 ⁇ m.
  • HSF membranes Due to the high maximum surface charge density of HSF, the corresponding El values of HSF membranes are much cheaper than the El values of conventional FEP membranes than the El values of ePTFE membranes.
  • An El value of about 22 mg / ⁇ C is already achieved, for example, with an HSF membrane that has a weight per unit area of 45 g / m 2. sitting. Such a membrane would have a thickness of approximately 21 ⁇ m.
  • HSF membranes only have a basis weight of 28 g / m 2 , so that the El value is only 13.2 mg / ⁇ C, ie less than half the El value of conventional FEP membranes , HSF membranes with a weight per unit area of between 10 g / m 2 and 30 g / m 2 can be produced without any problems in the current state of the art.
  • Such membranes have a thickness between approximately 5 ⁇ m and 15 ⁇ m.
  • HSF membranes have the particular advantage over ePTFE membranes that they have no pores and therefore no air passages, so that they are more suitable for acoustic transducers.
  • the membranes according to the invention can be integrated in a space-saving manner on a printed circuit board in an acoustic transducer. They are not only suitable for microphones, but due to their low basis weight and high tensile strength, they are also particularly suitable for loudspeakers, in particular also for large-area loudspeakers such as those used for. B. can be found in home audio systems. They are also particularly suitable for use as an ultrasonic transducer or for other pressure sensor and sound transmission applications.
  • FIG. 1 shows the process of electrostatically charging a membrane according to the invention
  • Figure 3 shows a membrane between two electrodes. Practical tests were carried out with the following three materials:
  • ePTFE membrane with a basis weight M 8 g / m 2 and a thickness of 15 ⁇ m
  • the aforementioned membranes were first vapor-deposited with a 20 nm thick gold layer and then electrostatically charged in a corona discharge process using a corona triode, as shown in FIG. 1.
  • the thickness of the metal coating is not critical since the metal coating only serves as a reference electrode. Electrons were transmitted from the corona electrode 1 through a grid electrode 2 onto the metal coating of the membrane substrate 3. In the experimental setup, the distance between the corona electrode 1 and the grid electrode 2 was 40 mm and the distance between the grid electrode 2 and the substrate 4 was 7 mm.
  • the gold coating 4 had a circular diameter of approximately 50 mm.
  • the voltage applied to the corona electrode 1 was - 11 kV and the voltage applied to the grid electrode was - 1.5 kV. The voltage was maintained for 60 s.
  • the surface tension of the samples charged in this way was then measured using a Kelvin probe.
  • the area charge density ⁇ can be determined from this using the following equation:
  • Tefzel T2 23 2.60 991 39 39.5 PFA T2 20 2.10 991 43 43.4
  • FIG. 2 shows a cross section through the acoustic transducer comprising the membrane 3 with an external metallic coating 4.
  • the membrane 3 is electrostatically charged and arranged at a distance from an electrode 6 by means of insulating spacers 5.
  • the electrode 6 and the metal coating 4 of the membrane 3 are connected to an electrical circuit 7 which is constructed in such a way that the acoustic transducer can be used as a microphone, loudspeaker, ultrasonic transducer or other pressure sensor or sound transmission device in accordance with its desired function.
  • Either the membrane 3 is vibrated supply offset by applying an alternating voltage between the metallic coating 4 and the electrode 6 (loudspeaker function). Or an oscillation of the membrane 3 due to sound pressure is converted in the opposite way into an alternating voltage (microphone function).
  • the electrode 6 can be part of a printed circuit board, not shown here. It has acoustic passage openings 8.
  • the metal coating 4 acting as an electrode does not necessarily have to be part of the membrane 3. It can also be spaced apart from the membrane 3. In this case, the membrane 3 is thus uncoated.
  • Figure 3 There is an uncoated membrane 3 between two electrodes 6, each of which is equipped with acoustic passages 8. The electrodes 6 are kept at a distance from the membrane 3 by means of insulating spacers 5.
  • the electrostatic bias of the membrane 3 can be carried out in a corona discharge process using a corona triode, after the membrane 3 has already been integrated into an acoustic transducer, as shown schematically in cross section in FIG.
  • One of the two electrodes 6 serves as a grid electrode and the other as a reference electrode of the corona triode.
  • the corona electrode (discharge electrode) itself is not shown in FIG. 3.
  • the two electrodes 6 are exposed to an alternating voltage with respect to the electrostatically charged membrane 3 (“push-pull configuration”) in order to set the membrane 3 in vibration in accordance with the acoustic signal to be generated.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)

Abstract

L'invention concerne une membrane polymère (3) pouvant être chargée électrostatiquement, conçue pour des transducteurs acoustiques. Cette membrane présente une valeur EI inférieure à 22 mg/νC, ladite valeur EI représentant le quotient de la masse surfacique du matériau constituant la membrane par la densité de charge en surface de la membrane chargée électrostatiquement. De préférence, les matériaux utilisés pour former ladite membrane polymère sont le polytétrafluoroéthylène expansé (ePTFE) ainsi que l'ePTFE comprimé (HSF).
PCT/EP2004/000011 2003-01-03 2004-01-02 Membrane pour transducteurs acoustiques WO2004062318A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE10300063.1 2003-01-03
DE2003100063 DE10300063A1 (de) 2003-01-03 2003-01-03 Membran für akustische Wandler

Publications (1)

Publication Number Publication Date
WO2004062318A1 true WO2004062318A1 (fr) 2004-07-22

Family

ID=32519602

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2004/000011 WO2004062318A1 (fr) 2003-01-03 2004-01-02 Membrane pour transducteurs acoustiques

Country Status (2)

Country Link
DE (1) DE10300063A1 (fr)
WO (1) WO2004062318A1 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102005035210B4 (de) * 2005-07-28 2007-09-06 Hidde, Axel R., Dr. Ing. Kabeldurchführung mit Membranventil
DE102006034224B3 (de) * 2005-07-28 2007-11-22 Hidde, Axel R., Dr. Kabeldurchführung mit Membranventil 2
WO2008011854A1 (fr) 2006-07-25 2008-01-31 Hidde Axel R Passage de câble avec soupape à membrane
EP2150075A3 (fr) * 2008-07-31 2010-04-14 HTC Corporation Dispositif électronique et son transducteur électro-acoustique
EP2182737A1 (fr) 2008-10-31 2010-05-05 HTC Corporation Dispositif électronique avec transducteur électro-acoustique à électret
CN102487468A (zh) * 2010-12-06 2012-06-06 洪爱琴 一种麦克风
US8369545B2 (en) 2008-12-31 2013-02-05 Htc Corporation Flexible luminescent electro-acoustic transducer and electronic device using the same
US8411882B2 (en) 2008-10-31 2013-04-02 Htc Corporation Electronic device with electret electro-acoustic transducer
CN106471821A (zh) * 2014-07-07 2017-03-01 W.L.戈尔及同仁股份有限公司 用于保护微‑电子‑机械系统的设备和方法

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE202005011301U1 (de) 2005-07-19 2005-09-22 Hidde, Axel R., Dr.-Ing. Kabeldurchführung mit Membranventil
GB0600014D0 (en) 2006-01-03 2006-02-08 Warwick Audio Technologies Ltd Electrostatic loudspeakers

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3711941A (en) * 1970-11-02 1973-01-23 Bell Telephone Labor Inc Fabrication of electret transducer elements using low energy electron beam
EP0587032A1 (fr) * 1992-09-11 1994-03-16 Centre Suisse D'electronique Et De Microtechnique S.A. Transducteur capacitif intégré
US6243474B1 (en) * 1996-04-18 2001-06-05 California Institute Of Technology Thin film electret microphone

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3711941A (en) * 1970-11-02 1973-01-23 Bell Telephone Labor Inc Fabrication of electret transducer elements using low energy electron beam
EP0587032A1 (fr) * 1992-09-11 1994-03-16 Centre Suisse D'electronique Et De Microtechnique S.A. Transducteur capacitif intégré
US6243474B1 (en) * 1996-04-18 2001-06-05 California Institute Of Technology Thin film electret microphone

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102006034224B3 (de) * 2005-07-28 2007-11-22 Hidde, Axel R., Dr. Kabeldurchführung mit Membranventil 2
DE102005035210B4 (de) * 2005-07-28 2007-09-06 Hidde, Axel R., Dr. Ing. Kabeldurchführung mit Membranventil
WO2008011854A1 (fr) 2006-07-25 2008-01-31 Hidde Axel R Passage de câble avec soupape à membrane
DE112007002229B4 (de) * 2006-07-25 2016-07-21 Axel R. Hidde Kabeldurchführung mit Membranventil 2
US8306247B2 (en) 2008-07-31 2012-11-06 Htc Corporation Electronic device and electro-acoustic transducer thereof
EP2150075A3 (fr) * 2008-07-31 2010-04-14 HTC Corporation Dispositif électronique et son transducteur électro-acoustique
EP2378791A1 (fr) 2008-07-31 2011-10-19 HTC Corporation Dispositif électronique et son transducteur électro-acoustique
EP2182737A1 (fr) 2008-10-31 2010-05-05 HTC Corporation Dispositif électronique avec transducteur électro-acoustique à électret
US8411882B2 (en) 2008-10-31 2013-04-02 Htc Corporation Electronic device with electret electro-acoustic transducer
EP2369855A3 (fr) * 2008-10-31 2012-04-04 HTC Corporation Dispositif électronique avec transducteur électro-acoustique à électret
US8369545B2 (en) 2008-12-31 2013-02-05 Htc Corporation Flexible luminescent electro-acoustic transducer and electronic device using the same
CN102487468A (zh) * 2010-12-06 2012-06-06 洪爱琴 一种麦克风
CN106471821A (zh) * 2014-07-07 2017-03-01 W.L.戈尔及同仁股份有限公司 用于保护微‑电子‑机械系统的设备和方法
EP3167623A1 (fr) * 2014-07-07 2017-05-17 W. L. Gore & Associates, Inc. Appareil et procédé pour protéger un système micro-électromécanique
CN106471821B (zh) * 2014-07-07 2022-01-11 W.L.戈尔及同仁股份有限公司 用于保护微-电子-机械系统的设备和方法
EP3167623B1 (fr) * 2014-07-07 2023-08-30 W. L. Gore & Associates, Inc. Appareil et procédé pour protéger un système micro-électromécanique

Also Published As

Publication number Publication date
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