Transducer production

Abstract

The present disclosure relates to a method of production of planar electroacoustic transducers. This method comprises providing a diaphragm substrate as the basis for multiple subsequently formed transducer and applying on or embedding in the diaphragm substrate at least one dynamic coil per transducer. The method further comprises forming a suspension around the at least one dynamic coil per transducer and laminating a cover layer on at least one side of the diaphragm substrate over the at least one dynamic coil per transducer and the suspension to form a diaphragm. The formed diaphragm is then mounted around the suspension on a frame.

Description

TRANSDUCER PRODUCTIONFIEUD

[0001] The present disclosure relates to methods of production of electroacoustic transducers. The most commonly known exemplary embodiments of such electro-acoustic transducers are loudspeakers and microphones, to which the present disclosure also relates. Furthermore, the present disclosure relates to a device, such as an electronic device like a TV or a mobile device, comprising at least one such transducer.BACKGROUND

[0002] The expression ‘electroacoustic transducer’ refers to transduction of energy, such as carried in an signal, in one of two ways: from an electrical signal to an acoustic signal (a loudspeaker) and / or from an acoustic signal to an electrical signal (a microphone). The signal may be defined in either a time or frequency domain. If expressed in the frequency domain, a signal may comprise multiple frequency bands. For example, a signal may comprise a bass frequency band of lower signal frequencies, a mid-range frequency band of intermediate frequencies and a treble frequency band of higher frequencies. Generally, several electroacoustic transducers are combined to cover a frequency range that spans multiple frequency bands.

[0003] Electroacoustic transducers acting as microphones generally operate on the principle of electromagnetic induction and include a dynamic coil that is attached to or embedded in a diaphragm and arranged in a static magnetic field. The diaphragm is excited to vibrate by acoustic waves and causes the dynamic coil to vibrate within a static magnetic field produced by a permanent magnet. Conversely, an electrical signal can be applied to the dynamic coil in order to generate an alternating magnetic field which interacts with the static magnetic field to excite motion in or of the diaphragm and thereby produce sound waves.

[0004] The diaphragm of conventional electroacoustic transducers emits or collects sound waves over its entire surface area while the dynamic coil is attached to a small part or even single point of the diaphragm. For example, in conventional loudspeakers, the diaphragm has the shape of an end-opened cone and the dynamic coil is attached to said conus on a perimeter at its smaller opened end, and in conventional microphones, the center of a circular diaphragm is attached to the dynamic coil.

[0005] The above traditional transducers have the disadvantage of placing restrictive and mutually incompatible requirements on the diaphragm in order to transduce signals faithfully. The diaphragm of conventional electroacoustic transducers must be:(a) infinitely stiff to propagate sound waves through the whole diaphragm;(b) strongly sound damping to avoid ringing or otherwise affecting the received or emitted sound waves; and(c) light in mass to reduce inertia of the diaphragm with respect to sound waves.

[0006] Since these requirements can’t easily be met in known composites, let alone in known pure materials, fidelity of transduction suffers in known electroacoustic transducers and / or is restricted to relatively narrow frequency bands. For example, materials with a high stiffness also naturally have relatively weak damping characteristic.

[0007] The developers of the present disclosure have previously developed improvements in the production of transducers, which are disclosed in publication WO-2021 / 194.339, which is acknowledged here as the closest prior art..

[0008] Transducers according to the prior art comprise a planar diaphragm, and at least one dynamic coil mechanically coupled to the diaphragm. The dynamic coil is connected to a controller for the dynamic coil to receive or provide electrical signals comprising sound information. In order to generate sound with the diaphragm or an electrical signal induced in the dynamic coil, at least one static magnetic field generator is provided. The present disclosure is aimed at production of such planar diaphragms.SUMMARY

[0009] To realize a planar or flat transducer with a more than just adequate quality, the present disclosure relates to a method of production of planar electroacoustic transducers, comprising:- providing a diaphragm substrate as the basis for multiple subsequently formed transducers;- applying on or embedding in the diaphragm substrate at least one dynamic coil per transducer;- forming a suspension around the at least one dynamic coil per transducer;- laminating a cover layer on at least one side of the diaphragm substrate over the at least one dynamic coil per transducer and the suspension to form a diaphragm;- mounting the diaphragm around the suspension on a frame.

[0010] Further, the forming of the suspension may comprise a step from a group, comprising at least one of cutting, die cutting, and embossing.[Oi l] The laminating of the cover layer may comprise: applying an assembly of an adhesive layer and a finish layer. Then, the adhesive layer may comprise an acryl layer, and the finish layer may comprise a BoPET or PET layer. Additionally or alternatively the method may further comprise removing the finish layer around the suspension, for mounting the diaphragm to the frame. Then, the removing of the finish layer may comprises a step from a group, comprising at least one of cutting, kiss cutting, die cutting, and embossing, and peeling the finish layer away in an area outside the suspension.

[0012] In an additional or alternative embodiment, the method may further comprise applying an adhesive under the cover layer from a group of adhesives, at least comprising glue and varnish.

[0013] In an additional or alternative embodiment, the method may further comprise singularizing each subsequently formed diaphragm prior to mounting the formed diaphragm onto the frame.

[0014] In an additional or alternative embodiment, the method may further comprise applying an adhesive on the cover layer from a group of adhesives, at least comprising glue and varnish, prior to mounting the formed diaphragm onto the frame.

[0015] In an additional or alternative embodiment, the applying on or embedding in the diaphragm substrate of at least one dynamic coil per transducer may comprise applying a layer of conductive material and forming a coil pattern by at least one step from a group, comprising ablation, laser ablation, kiss cutting, printing and 3D printing.

[0016] In an additional or alternative embodiment, the applying on or embedding in the diaphragm substrate of at least one dynamic coil per transducer comprises: applying a flexible printed circuits (FPC) forming the dynamic coil onto the diaphragm substrate.

[0017] Further, the present disclosure relates to a diaphragm of or for a transducer, comprising:- a diaphragm substrate;- at least one dynamic coil applied on or embedded in the diaphragm substrate;- a suspension formed around the at least one dynamic coil;- a cover layer laminated on at least one side of the diaphragm substrate over the at least one dynamic coil per transducer and the suspension.

[0018] In a potential embodiment, opposing dynamic coils are arranged in parallel on or in the diaphragm substrate, each covered by one cover layer.

[0019] In an additional or alternative embodiment, at least the diaphragm substrate may extend outside the suspension.

[0020] In an additional or alternative embodiment, the cover layer may comprise an assembly of an adhesive layer and a finish layer. Then, at least the adhesive layer may extend outside the suspension for mounting the diaphragm to a frame. Additionally or alternatively, the adhesive layer may comprise an acryl layer, and the finish layer may comprise a BoPET or PET layer.

[0021] Yet further, the present disclosure relates to atransducer comprising a diaphragm according to the disclosure, mounted on a frame, wherein the diaphragm is substantially planar.

[0022] Yet further, the present disclosure relates an apparatus from a group of electroacoustic transducer apparatuses at least comprising loudspeakers and microphones, with the apparatus comprising at least one aforementioned transducer and a connection to a controller.

[0023] Also, the present disclosure relates to an electronic device comprising the transducer in the aforementioned apparatus, and the controller.BRIEF DESCRIPTION OF THE DRAWING

[0024] The present disclosure is further clarified through the appended drawing, in which the same or similar elements, components and / or functional assemblies may be designated with the same or distinct reference signs, and wherein:

[0025] Figure 1 schematically depicts a cross section of a conventional electroacoustic transducer in the form of a loudspeaker for ease of reference;

[0026] Figure 2 schematically depicts an embodiment of an electroacoustic transducer according to the prior art disclosure in WO2021194339;

[0027] Figure 3 schematically depicts a perspective view of a prior art electroacoustic transducer with a planar diaphragm;

[0028] Figure 4 schematically depicts a top view of a diaphragm with multiple dynamic coils;

[0029] Figures 5 and 6 schematically depict embodiments of a suspension;

[0030] Figures 7A and 7B depict augmenting frontal and side views of an embodiment of the present disclosure;

[0031] Figures 8 and 9 exhibit improvement over a prior art configuration in figure 8 by a configuration according to the present disclosure in figure 9;

[0032] Figure 10 depicts an electronic device with therein implemented a transducer in accordance with the principles of the present disclosure;

[0033] Figures 11A and 1 IB depict an arrangement of two dynamic coils, one at either side of a diaphragm;

[0034] Figures 12A - 12D depict subsequent production steps, starting out from a basic embodiment in Figure 1 IB;

[0035] Figure 13A depicts an embodiment of a magnetic field shield or guide, and

[0036] Figure 13B depicts the magnetic field shield or guide of Figure 13A with an added frame;

[0037] Figure 14 depicts an installation assembled to embody a method of producing at last partially a transducer according to the present disclosure; and

[0038] Figure 15 depicts an installation assembled to embody a method of producing at last partially a transducer according to the present disclosure.DETAILED DESCRIPTION OF EMBODIMENTS

[0039] The following detailed description of the drawing is based on the example of a loudspeaker to illustrate the principles of the present disclosure in a coherent manner. However, the scope of protection of or for the present disclosure should not be understood to be limited to this particular application of the electroacoustic transducer, as limits on the scope of protection for the present disclosure are defined solely in the definitions thereof in the appended independent claims. The same as the embodiments in the below description, dependent claims involve preferred but not limiting features.

[0040] FIG. 1 shows a conventional electroacoustic transducer, in particular a loudspeaker, in cross section through a plane containing a central axis thereof. The illustrated conventional electroacoustic transducer has circular symmetry around its central axis. The conventional loudspeaker has a stiff diaphragm 2 in the form of an truncated cone which is suspended by a suspension 7 that is in turnatached to a chassis 6. A dynamic coil 3 is mechanically coupled to a cylindrical extension of the diaphragm 2 at the center of the diaphragm 2 and magnetically coupled to a permanent static field magnet 5, by being arranged in an opening of the static field magnet 5. Electrical signals are supplied or received from the dynamic coil 3 by conventional means (not illustrated). An alternating electrical signal may be supplied to the dynamic coil 3 to generate alternating magnetic fields which interact with the static field from the static field magnet 5 in order to convert the electrical signal to mechanical motion of the diaphragm 2, which results in an acoustic signal in a surrounding medium. Conversely, mechanical motion of the diaphragm 2 as a result of an acoustic signal moves the dynamic coil 3 within the static field and induces an electrical signal in the dynamic coil 2.

[0041] FIG. 2 shows an embodiment of an electroacoustic transducer 1 according to WO- 2021 / 194.339, with a diaphragm 2 having a central region 2.1 and an outer region 2.2. A dynamic coil 3 is mechanically coupled to the diaphragm 2. The dynamic coil 3 is arranged on or in at least a portion of the outer region 2.2 of the diaphragm 2. The diaphragm 2 is illustrated as an end-opened conus, such as in conventional loudspeakers, though the diaphragm 2 may have various forms or shapes, such as conical, hemispherical, spherical, planar, circular, oval, rectangular, lobed and combinations thereof, each with or without openings. Examples are presented in this disclosure.

[0042] The function of the dynamic coil 3 is moving the diaphragm 2 by creating an alternating magnetic field according to the supplied electrical signal. The mechanical coupling between the dynamic coil 3 and diaphragm 2 causes the diaphragm 2 to vibrate, thus producing sound waves. The dynamic coil 3 consists out of an electrical conductor in the form of a wire. The number of rotations of the dynamic coil 3 dependents on the density of the material of the diaphragm 2, the area of the diaphragm 2 and the density of the electrical conductor.

[0043] The electroacoustic transducer 1 of FIG. 2 further comprises a static field magnet 5, which may be a permanent magnet and / or an electromagnetic coil. In advantageous embodiments, the static field magnet 5 is a static field coil. The static field magnet 5 may be arranged at different positions, for example within or around the cone-shaped diaphragm which results in a thinner construction. The illustrated electroacoustic transducer 1 further comprises a chassis 6. However, the suspension 7 present in conventional electroacoustic transducers is made redundant.

[0044] The function of the static field magnet or coil 5 is to create a static magnetic field which opposes the magnetic field of the dynamic coil 3. The static field coil 5 consists out of an electrical conductor in the form of a wire. The properties of the static field coil 5 may be the same as the properties of the dynamic coil 3 but can also differ. It is further noted that the dynamic coil 3 and / or the static field coil 5 may exist out of multiple parts to limit inductance of said coils.

[0045] The electroacoustic transducer 1 of FIG. 2 is particularly suited to serve as a loudspeaker 8, though is not limited to this function. For example, it can - in principle - also function as a microphone. The illustrated example is deliberately presented in the form of a conventional loudspeaker to show implementation within existing systems. In this example, a conventional voicecoil arranged within an opening of the static field magnet 5 is replaced by the dynamic coil 3 arranged on or in at least a portion of the outer region 2.2 of a replacing diaphragm 2.

[0046] In the function of a loudspeaker with an open-ended cone shaped diaphragm 2, a dynamic coil 3, a static field magnet 5 and a chassis 6, diaphragm 2 is actuated by movement of the dynamic coil 3 relative to the static field magnet or coil 5. In FIG. 1, the dynamic coil 3 is arranged in a center region of the diaphragm 2, while in FIG. 2, the dynamic coil 3 is arranged on at least a portion of an outer region of the diaphragm 2. Because of the arrangement illustrated in FIG. 2, the dynamic coil 3 actuates the diaphragm 2 over at least a portion of its outer region, in contrast to the center region of the conventional loudspeaker of FIG. 1, in which the dynamic coil is mounted at a perimeter of the smaller open end of the diaphragm 2. The diaphragm 2 of FIG. 1 needs to be stiff, damping and low in mass to propagate sound waves through the diaphragm 2 faithfully. Moreover, a flexible suspension 7 is required. However, in FIG. 2, the diaphragm 2 need not be stiff to transfer force through the entire cone to obtain faithful sound production and no flexible suspension 7 is needed. Choice of materials is therefore increased, construction is simplified and quality of sound production is improved.

[0047] The above argument equally applies to an electroacoustic transducer 1 in the function of a microphone, in which sound waves through air impinge on diaphragm 2 and are collected rather than produced. A stiff diaphragm 2 is no longer required and thus no longer limiting design of electroacoustic transducers 1.

[0048] FIG. 3 shows another prior art embodiment of an electroacoustic transducer 1 wherein the diaphragm 2 is substantially planar. The substantially planar diaphragm 2 reduces a thickness of the electroacoustic transducer 1 compared to conventional electroacoustic transducers, such as illustrated in FIG. 1 and FIG. 2. A static field magnet 5 is provided and may be a permanent magnet and / or electromagnet.

[0049] The electroacoustic transducer 1 of FIG. 3 is particularly suited to serve as a microphone, or as a loudspeaker 8.

[0050] In an embodiment having a static field magnet 5 in the form of a static field coil 5, the coil 5 may be arranged parallel to the diaphragm 2, further contributing to the small dimensions of the resulting transducer 1. The static field coil 5 may advantageously be wound in a plane, such as in a spiral, and / or may be fixed in space relative to the dynamic coil 3.

[0051] Such a prior art embodiment constitutes an advantageously improved electroacoustic transducer 1 comprising two coils 3, 5, namely a dynamic coil 3 and a static field coil 5, that are positioned in a stacked manner with a small distance between the coils 3, 5. The dynamic coil 3 is incorporated in the diaphragm 2 and thus mechanically coupled to the diaphragm 2. The dynamic coil 3 acts as a receiving coil or a voice coil while the static field coil 5 produces a static magnetic field. An electrical audio signal applied to both coils 3, 5 via input or output terminal 4 creates interacting magnetic fields which cause the two coils 3, 5 to attract or repel each other according to the applied electrical signal. The mechanical coupling between the dynamic coil 3 and the diaphragm 2 forces thediaphragm 2 to start vibrating and hence produce sound waves according to the applied electrical signal. The use of two flat coils 3, 5 results in an even thinner electroacoustic transducer which may thus be integrated in various other systems more easily.

[0052] The electroacoustic transducer 1 of any embodiment may comprise at least one magnet or static field coil 5 configured to electromagnetically interact with the dynamic coil 3. Where multiple dynamic coils 3 are employed, as in FIG. 4, an equal number of static field coils 5 may be deployed or even be preferred. The multiple static field coils 5 are then preferably arranged in a similar geometry as the multiple dynamic coils 3, preferably in parallel thereto. The configuration with multiple dynamic coils 3 and / or multiple static field coils 5 is further addressed in relation to figure 4.

[0053] FIG. 10 shows an example of integration of the electroacoustic transducer 1 in an electronic device 10. In the shown embodiment, the electronic device 10 is a TV, in which a signal source is provided as a controller 11 internally for supplying electrical signals to transducer 1 in the form of a loudspeaker 8 which is provided at an outer surface of a housing of the electronic device 10, in order to emit sounds. Alternatively the device 10 could be a mobile device with a microphone and a processor forming the controller 11 to process electrical signal from and induced in the dynamic coil 3. The electronic device 10 comprises the controller 11, that may be connected to the electroacoustic transducer 1 via the above described input or output terminals 4 and is configured to provide or received electrical signals to or from the dynamic coil 3 and the static field coil 5. Both a TV and most mobile devices have a screen 17, sometimes a touch screen, but the present disclosure may equally relate to an electronic device without a screen 17.

[0054] The electronic device 10 has an advantage that it can be fully enclosed with respect to the environment also at the transducer 1 because the diaphragm of the electroacoustic transducer 1 mounted in the electronic device 10 seals an opening in the electronic device 10 in which the electroacoustic transducer 1 is mounted. This contrasts with conventional electroacoustic transducers, which maintain a connection between the external and internal environments of the electronic device. Examples of these are microphones and loudspeakers in mobile devices. This has the negative consequence of soiling, malfunctioning or blocking of the electronic device and / or the electroacoustic transducers thereof. The electronic device 10 with the electroacoustic transducer 1 is better sealed and may even be waterproof and / or gas proof.

[0055] Furthermore, electronic devices 10 may also be made smaller because less space is required for electroacoustic transducers 1 due to their reduced thickness compared to conventional electroacoustic transducers.

[0056] Finally, the electroacoustic transducer 1 may be used as a microphone and / or a loudspeaker 8 and may additionally be switched between those functions, for example by the controller 11, so that a separate microphone and a separate loudspeaker 8 are not needed and a single electroacoustic transducer 1 can be used to perform both functions.

[0057] FIG. 4 shows planar views of a diaphragm 2 with multiple dynamic coils 3. The multiple dynamic coils 3 are arranged on or in the diaphragm 2. Each dynamic coil 3 is preferably associated with an acoustic frequency band. This can be achieved, for example, by supplying or receiving electrical signals to each dynamic coil 3 separately, using a single controller 11 or multiple controllers 11. Each of the multiple dynamic coils 3 may be electrically connected to an input or output terminal 4 of the controller 11. Jointly, the multiple dynamic coils 3 may thus cover a selected acoustic frequency spectrum faithfully.

[0058] With multiple dynamic coils 3 on or in a single diaphragm 2, the electroacoustic transducer 1 may cover a wider frequency range. Furthermore, combinations of multiple electroacoustic transducers (one for each sub-divided acoustic frequency band), as is conventionally the case, may be avoided and a single electroacoustic transducer 1 may be employed to cover similar frequency bands with one device.

[0059] In FIG. 4, a circular diaphragm 6 is illustrated with three dynamic coils 3, labelled 3. 1, 3.2 and 3.3. The coils 3.1, 3.2, 3.3 are concentrically arranged and each is electrically connected to a separate input or output terminal 4, labelled 4.1, 4.2 and 4.3 corresponding to their respective coils 3.1, 3.2, 3.3. In the illustrated example, the dynamic coil 3. 1 may be a bass coil 3.1 , the dynamic coil 3.2 may be a mid-range coil 3.2 and the dynamic coil 3.3 may be a treble coil 3.3 so that the bass coil 3. 1, the midrange coil 3.2 and the treble coil 3.3 are arranged in order of acoustic frequency band with the treble coil 3.3 with the highest acoustic frequency band arranged nearest or at the central region of the diaphragm 2. As illustrated, the dynamic coils 3 are arranged over the diaphragm 2 at a radial offset or spacing with respect to each other.

[0060] As a loudspeaker, each input terminal 4. 1, 4.2, 4.3 receives its own audio supply from controller 11, which higher frequency signals are fdtered out according to the frequency band of each of the multiple dynamic coils 3.1, 3.2, 3.3. For the bass coil 3.3, the input terminal 4.3 supplies lower acoustic frequencies than the input terminal 4.2 to the mid-range coil 3.2. In turn, the input terminal 4.2 supplies lower acoustic frequencies to the mid-range coil 3.2 than the input terminal 4. 1 to the treble coil 3.1. Thus, the larger a dynamic coil 3.1, 3.2, 3.3, the lower the frequency band supplied to it. Though this arrangement is preferred, other orders and two or four or more dynamic coils 3 may be considered.

[0061] Splitting the dynamic coil 3 into multiple parts has the advantage that the center of the diaphragm 2 vibrates with frequencies in the entire sound spectrum while the outer part of the diaphragm 2 vibrates with lower parts of the sound spectrum. The frequencies which are produced by the different areas are limited by acoustic wavelength and size of the diaphragm 2, in this example the diameter of the circular diaphragm 2. When the wavelength is smaller than said diameter, waves start to travel through the surface of the diaphragm 2. This causes faults in the sound produced. The number of areas and corresponding diameters can be determined based on the wavelengths of different octaves. This produces a full-range loudspeaker 8 with faithful sound production.

[0062] Though the above advantages are explained with FIG. 4 interpreted as a loudspeaker 8, similar advantages are obtained with a microphone in which the dynamic coil 3 is split into multiple dynamic coils 3, each associated with an acoustic frequency band. The plurality of coils making up the dynamic coil 3 need not be arranged concentrically, and may be dispersed over an area of a diaphragm 2 having a large enough surface to accommodate such multiple dynamic coils 3.

[0063] In the above, FIG. 4 is disclosed as an embodiment having the diaphragm 2 with multiple dynamic coils 3. However, then such configurations may also relate to arrangements of multiple static field coils or magnets 5 that may be combined with corresponding diaphragms 2 and multiple dynamic coils 3.

[0064] FIG.11 shows an advantageous arrangement of two dynamic coils 3 on or in the diaphragm 2. As illustrated here, a first dynamic coil 3 is arranged on or in an upper side of the diaphragm 2 and a second dynamic coil 3 is arranged on or in a lower side of the diaphragm 2 opposite the upper side. The two dynamic coils 3 are illustrated at an exaggerated mutual spacing for clarity. Arranging the dynamic coils 3 in such a way increases contact between the dynamic coil 3 and the diaphragm 2 to improve fidelity and longevity of the electroacoustic transducer 1. The two dynamic coils 3 are mutually connected through or across the diaphragm 2, for example by electrical contact arranged through or perforating the diaphragm 2 at a via 22. The input or output terminal 4 and electrical ground may now be arranged at an outer perimeter of the diaphragm 2 without overlap with windings of the dynamic coils 3 (which may be the case in FIG.’s 3 and 4). This reduces distortion in the magnetic field and thus further enhances fidelity of the transducer 1. Moreover, the two dynamic coils 3 may be wound in the same direction (e.g. clockwise or anticlockwise) when viewing from one side of the diaphragm 2. In such arrangement, each the dynamic coil 3 strengthens a magnetic field (or is sensitive to an external magnetic field) of the other in a similar way. Alternatively or additionally, the two dynamic coils 3 may be arranged in parallel planes and / or be configured to follow a spatially offset yet identical path. This further improves sensitivity of the electroacoustic transducer 1 by the joint electromagnetic interaction of the two dynamic coils 3.

[0065] As shown in FIG. 11A and FIG. 1 IB (showing a cross sectional view of a diaphragm like the one in FIG. 11A in an assembled state), the first and second dynamic coils 3 are arranged at an offset along the thickness of the diaphragm relative to each other, in the shown embodiment: one coil 3 on the top and one opposing coil 3 on the bottom of the diaphragm 2. This offset may be employed instead of or in addition to a radial offset between the two opposing dynamic coils 3. The two dynamic coils 3 are electrically connected through the diaphragm 2 at a via 22, and may be configured to receive the same electroacoustic signal from a joint input or output terminal 4 arranged at an outer perimeter of the diaphragm 2. In this arrangement, leads running over the diaphragm or stationary terminals in potentially active areas of the diaphragm are avoided, thus further improving fidelity and power transmission of the electroacoustic transducer.

[0066] Though two dynamic coils 3 are illustrated in FIG. 11, this arrangement may be applied to multiple pairs of dynamic coils 3, for example as illustrated in FIG. 4. Contacts of each pair of dynamic coils 3 that perforate the diaphragm 2 at a centrally located via 22 may also be arranged radially offset rather than centrally. The dynamic coils 3 and / or lead for their input or output terminal(s) 4 or electrical ground(s) may be embedded in the diaphragm 2 at various depth positions. In a configuration according to FIG. 11, with one coil 3 on top of, and one coil 3 on the bottom of the diaphragm substrate 2, a via 22 may also be formed at a lateral edge of the coils 3 or of the diaphragm substrate, to enable same side connection of the coils 3 to the input or output terminal 4 and / or ground.

[0067] The diaphragm 2 may comprise a material layer having a thickness of 20 - 50 pm, and may be made of polyimide or PET or any other suitable material. To avoid short circuiting the diaphragm substrate 2 should be made of an electrically insulating material layer. The coil or coils 3 may comprise a copper conductor, or another layer of conductive material, having a thickness of for example 18 pm.

[0068] For a continuous production process, as set out in more detail below, the diaphragm substrate may be supplied on rolls. The coil material may be purchased patterns on rolls as flexible printed circuits (FPC). Alternatively, the coils may be formed by applying a layer of conductive material on the diaphragm 2, and cut out the coil pattern in each conductive layer using a laser (laser ablation). Laser ablation can also be performed before applying a coil 3 onto diaphragm 2. Furthermore, the pattern for the coils 3 may be formed by applying a layer of conductive material, and kiss cut the coil pattern in each conductive layer already laminated to the diaphragm 2. A kiss cut moves the conductive material sidewards and creates a separation between the coil paths, and can be suitably integrated into a continuous production process applying rollers to administer the kiss cut. It should also be considered that applying a coil 3 may be achieved through (3D) printing. Then, from a perspective of production speeds, using a form of screen printing may currently be preferred.

[0069] In FIG. 12A - 12D, results of subsequent processing steps are shown. To this end, a production line as shown in FIG. 14 may be used.

[0070] In FIG. 12A, the suspension 7 is formed, e.g. by applying a cut. Alternatively incisions may be applied, or the central diaphragm substrate may be embossed or die cut in a continuous process of subsequently manufacturing diaphragms om rolled off diaphragm substrate. In FIG. 12B, directly after forming the suspension 7 around coils 3, a cover layer is be laminated onto the assembly of FIG. 12A. In the embodiment of FIG. 12B, acryl layers 23 are formed on the top and bottom of the laminated substrate of FIG 12A, and also PET or BoPET layers 24 on the top and bottom of the acryl layers 23. The cover layer extends beyond the suspension 7. The acryl layers 23 may be flexible and sticky and have a thickness of about 60 - 130 pm. The (Bo)PET cover layers 24 may have a thickness of about 50 pm. The acryl layers 23 and the (Bo)PET layers 24 may be applied together in the form of a combined transfer tape, forming a cover layer also over the suspension 7. Then, as shown in FIG. 12C, the outermost (Bo)PET layers 24 may be cut at an edge of the suspension 7. Only the outermost(Bo)PET layers 24 are cut, so as to leave the acryl layers 23 across the suspension 7. The cut 25 may be applied using rollers, lasers, or any other suitable means, e.g. a die cut or a kiss cut. Subsequently, and as shown in FIG. 12D, portions of the outer (Bo)PET layers outside the suspension 7 are removed, for example by peeling. In case the acryl layers 23 and (Bo)PET layers 24 are applied in the form of a transfer tape, the outer portions of the outer (Bo)PET layers 24 may be peeled off. Exposing the underlying sticky and flexible acryl layers 23 is advantageous in that this facilitates mounting the resulting assembly onto a frame 20 on a magnetic field shield 12, which may require using additional adhesive (glue, varnish or the like). After then connecting the coils 3 to input or output terminal 4 and / or ground, the resulting transducer 1 is ready to be put to use.

[0071] Preferably, an automated process results in performing the above steps, as will be disclosed herein below.

[0072] FIGS. 5 and 6 show an advantageous suspension 7 for a diaphragm 2. The suspension is configured to improve acoustic insulation of the diaphragm 2 from attached structures. As illustrated in FIG. 5, the structure of the suspension 7 may be provided by arranging slits in a membrane 9 around the actual diaphragm 2 within which the dynamic coil 3 is arranged. The suspension 7 may thus be integral with the diaphragm 2. Alternatively, the suspension 7 of the illustrated embodiment may be provided as a distinct component. The slits are configured to reduce transfer of mechanical vibrations across the suspension 7 by defining a tortuous path of mechanical connectivity between components internally and externally coupled to the suspension 7 (e.g. the diaphragm 2 and the chassis 6).

[0073] As illustrated in FIGS. 5 and 6, the suspension 7 comprises inner angular slits 7.1, outer angular slits 7.2 and radial slits 7.3. Here, the terms angular and radial indicate directions relative to the center of a plane or space enclosed by the suspension 7 (e.g. the diaphragm 2), in which the dynamic coil 3 is arranged. The inner and outer angular slits 7.1, 7.2 partly overlap in angular direction but are spaced apart in radial direction. The radial slits 7.3 are connected to the inner angular slits 7. 1 and preferably protrude towards a radial dimension corresponding to the outer angular slits 7.3 and may protrude to a position between two outer angular slits 7.3. Though the angular slits 7.1, 7.2 are illustrated as concentric circle segments, other shapes are possible such as elliptical, linear and angled forms. The radial slits 7.3 may also be implemented with angular components. Various alternative arrangements of the slits 7.1, 7.2, 7.3 are thus conceivable.

[0074] The suspension 7 of FIGS. 5 and 6 thus provides mechanical integrity yet improves acoustic insulation of the plane or space enclosed by the suspension 7 (e.g. the diaphragm 2) and adjacent structures (e.g. the chassis 6 or the electronic device 10). The slits 7.1, 7.2, 7.3 may thus define the suspension 7, while the diaphragm 2 may in turn be delineated by the suspension 7. For example, the suspension 7 may be provided in a flat object, such as a face of an electronic device 10, and define the diaphragm 2 as the part enclosed by the suspension 7, e.g. as shown in FIG. 5. The slit structure defining the suspension 7 may thus be employed with known electroacoustic transducers as well as with the electroacoustic transducer 1.

[0075] The diaphragm 2 of any embodiment is preferably elastic in the acoustic frequency bands associated with the multiple dynamic coils 3. 1, 3.2, 3.3 or at least the frequency band of the dynamic coil 3 where only one dynamic coil 3 is present. Additionally or alternatively, the diaphragm 2 comprises at least one material from a group, the group comprising a rubber-like material, rubber, silicone, polyimide, polyamide, polyester resin and polycarbonate, preferably reinforced with carbon and / or glass fibers. The materials from this group possess sufficient flexibility to conform to local deformation due to impinging sound waves and / or to actuation by the one or multiple dynamic coil(s) 3. Additionally or alternatively, the diaphragm 2 is composed of a non-stiff material, preferably with a Young’s modulus between 0.1 gPa and 2.4 gPa. In tests of an electroacoustic transducer according to an embodiment, these materials and this range was found to provide effective transduction of electrical signals to acoustic signals.

[0076] FIG. 7 depicts an embodiment of the present disclosure in a frontal view in FIG. 7A and a side view in FIG. 7B. In this embodiment, the diaphragm 2 has a rectangular and more in particular a square circumference, and is mounted in a square chassis 6 via suspension 7. As shown in FIG. 7B, windings of dynamic field coil 3 are embedded in diaphragm 2, but may alternatively be arranged on a surface of diaphragm 2. Static field coil or magnet 5 is, in the view of FIG. 7B, arranged under the diaphragm 2. When an electric signal from controller 11 is fed through the dynamic coil 3, this generates an electromagnetic field, that interacts with the (electro)magnetic field of the static field coil or magnet 5. The dynamic field coil 3 and therewith the diaphragm 2 is thereby attracted to or repelled from the static field coil or magnet 5, and a back-and-forth movement of the diaphragm 2 creates sounds. Conversely, when air pressure waves forming the basis of sounds impinge on diaphragm 2 with the dynamic field coil 3 thereon or therein, the diaphragm is made to vibrate with the sounds, and currents are induced in the dynamic field coil 3 lying in the (electro)magnetic field of the static field coil or magnet 5.

[0077] From a perspective of minimizing thickness of the configuration of the transducer, a thickness of the static field coil or magnet (in a direction perpendicular to the diaphragm and also in the N-S direction of static coil or magnet 5) is preferably minimized. However, at the same time a sufficient magnetic field strength / flux is required from the static field coil or magnet 5 at the diaphragm or at least the dynamic coil 3 thereon or therein, which may be compromised if the static field coil or magnet 5 is too small. Increasing a width of the static field coil or magnet 5 (perpendicular to the N-S orientation) aggravates this concern. Therefore, any configuration with a very wide static field coil or magnet 5 and short N-S length is not very good. It’s commonly known that a relation exists between width and N-S length of a static field coil or magnet 5 that influences field strengths or flux to be generated by the static field coil or magnet 5. FIG. 8 depicts an exemplary view of magnetic field lines from a static field coil or magnet 5 set-up at the diaphragm 2 in a possible configuration.

[0078] In FIG. 9, a magnetic field shield 12 is additionally provided. The magnetic field shield 12 is arranged opposite the diaphragm 2, relative to the static field coil or magnet 5, so that the static fieldcoil or magnet 5 is placed between the diaphragm 2 and the magnetic field shield 12. The magnetic field shield 12 has dimensions that at least approximately the size and shape of the diaphragm 2. In the shown embodiment of FIG. 7B, the magnetic field shield 12 is even bigger than the diaphragm 2 and corresponds in size and form with the chassis 6 or circumscribes suspension 7.

[0079] FIG. 9 depicts the effects of providing the magnetic field shield 12. Magnetic field lines on the side of the magnetic field shield 12, opposite the side with the diaphragm 2, are suppressed, in that the magnetic field shield 12 acts as a conduit for magnetic field lines, and magnetic field lines on the side of the diaphragm have a higher density / flux. Moreover, the field lines are better homogenized in FIG. 9, than in FIG. 8 that represents a configuration without the magnetic field shield 12.

[0080] The magnetic field shield 12 can be considered to enhance field strength and flux, and to improve homogeneity of the field at the diaphragm 2. This is in particular realized under the following circumstances (to which the scope of the present disclosure is not necessarily limited).

[0081] The magnetic field shield 12 comprises a metal plate, in the embodiment shown in FIG. 7B and 9. Preferably, the magnetic field shield 12 is made from a ferromagnetic metal. Such a metal can be one of: iron, nickel, cobalt. Less common, but not excluded, would be the use of at least one of magnetite, gadolinium, awaruite and permalloy. Naturally, it’s well known to the skilled reader, that alloys of ferromagnetic materials also function for guiding magnetic fields. Therefore, the magnetic field shield could equally be referred to as a magnetic field guide.

[0082] The magnetic field shield is designed, in relation to a strength of the magnetic field from the static field coil or magnet 5, to approximate magnetic saturation of the magnetic field shield 12. Saturation is the state reached by the magnetic field shield when an increase in applied external magnetic field does not yield a further increase in the magnetization of the material. Especially in an embodiment with a plate shaped magnetic field shield 12, a circumferential shape and a thickness of the metal plate are configured to approximate magnetic saturation of the magnetic field shield.

[0083] Preferably, and in the embodiment of FIG. 7B and 9, the magnetic field shield 12 and the static field coil or magnet 5 are mechanically connected. In particular when ferromagnetic metals are used for the magnetic field shield 12, this improves magnetic coupling of the magnetic field from the static field coil or magnet 5 into the magnetic field shield 12.

[0084] In the embodiment of FIG. 13A, a magnetic field shield 12 is depicted. In the center thereof, a permanent magnet embodying the static magnetic coil or magnet 5 is arranged. The permanent magnet could be replaced by one or more than one static field coil. The magnet 5 may be fixed to the magnetic field shield 12. For magnetic decoupling magnet 5 may nevertheless be held at a distance with a gap in between magnet 5 and magnetic field shield 12.

[0085] When diaphragm 2 is vibrating, this is either caused by air pressure waives (sound) impinging on the diaphragm 2 with the dynamic coil 3 for generating electrical signals induced in dynamic coil 3 or by air pressure waves (sounds) generated by the diaphragm 2 vibrating as a result of currents introduced into dynamic field coil 3. Either way, the magnetic field shield 12 in the form of a squareplate comprises at least one air flow passage 16, so as not to hamper air pressure waves. In the embodiment of FIG. 13A, the air flow passages 16 extend radially, but these can extend circularly or even concentrically of spiraling. Four air passages 16 are arranged in the magnetic field shield 12, but a lower or higher number of air passages 16 may be provided. Evidently, there’s a relationship between a need for air passages and the amount thereof to maintain high quality sound generation / capture on the one hand, and on the other hand the mass and surface of ferromagnetic material to form an effective magnetic field shield 12. Also, when the magnetic field shield 12 has another circumferential form than square, like oval or rectangular or any other shape, other shapes of air passages 16 may be deployed than the one shown in FIG. 13 A. Preferably, a plurality of air flow passages is provided. If so, then these are preferably arranged in an at least approximately rotation symmetric fashion, relative to an axis running through a center of and at least locally perpendicular to the diaphragm, for similar considerations as those in play for arrangement of a plurality of magnets 5 or coils 13, 14.

[0086] FIG. 14 schematically shows a continuous production installation 30 to embody a process or method for manufacturing processing, starting from a sub-assembly according to FIG. 1 IB, comprising a polyimide or PET diaphragm 2 and coils 3. The polyimide or PET diaphragm 2 serves as a substrate or basis for the production of multiple transducers 1. Dynamic coils 3 are formed on or in the polyimide or PET diaphragm 2 and are applied on or embedded in the diaphragm 2, as is disclosed herein below. The installation 30 of FIG. 14 comprises a succession of specific embodiments of stations for performing the steps disclosed herein above in relation to FIG. 12A - 12D.

[0087] Installation 30 comprises first a die cut station 31. There, the suspension 7 is formed by applying cuts around coils 3. Both rollers of the die cut station 31 may comprise cutters, or one of the rollers may have cutters and the other roller provides a suitable base.

[0088] Directly after forming the suspension 7 around the coils 3 at die cut station 31, a further cover layer is laminated onto the resulting assembly of FIG. 12A. In the subsequent step at applicator station 32, acryl layers 23 are formed on the top and bottom of the laminated substrate of FIG 12A, and also PET or BoPET layers 24 on the top and bottom of the acryl layers 23. The acryl layers 23 and the (Bo)PET layers 24 are here applied at applicator station 32 together in the form of a combined transfer tape, forming a cover layer over the dynamic coils 3 and the suspensions 7 around the coils 3, and possibly beyond. The transfer tape forming the cover layer is supplied from a supply roll 33, and a protective sheet may be peeled from the acryl layer 23 for removal on discharge roll 34. Press rollers 35 are provided in the applicator station 32, to ensure bonding of the acryl layers 23 onto the coils 3 and base polyimide or PET diaphragm 2. If necessary an adhesive like glue or varnish or the like may also be added under the acryl layers 23.

[0089] Then, at kiss cut station 36 comprising opposing kiss cut rollers 37, the outermost (Bo)PET finish layers 24 may be cut at an edge of the suspension 7. Only the outermost (Bo)PET layers 24 are cut, so as to leave the acryl layers 23 extending over or across the suspension 7. In a specificembodiment only the (Bo)PET layer 24 on one side (upper or lower) of the laminate is kiss cut, for later bonding the underlying acryl layer 23 to the frame 20 that has been molded or 3D-printed onto a magnetic field shield 12 (on which at least one permanent magnet 5 may be arranged). For this reason the cover layer comprises the sticky and flexible acryl layers as adhesive layers and the (Bo)PET layers as finish layers.

[0090] Thereby, portions of the outer (Bo)PET layer 24 outside the suspension 7 may be removed and collected on (Bo)PET collection roll 38, thus peeling off the outer portions of the (Bo)PET layer 24 on one side of the resulting laminate. Exposing the underlying sticky and flexible acryl layers 23 is advantageous in that this facilitates, at mounting station 39, mounting the resulting assembly onto the frame 20 on the magnetic field shield 12. It is possible that adding additional adhesive (glue, varnish or the like) may be required to achieve a good bonding. Before mounting the diaphragm onto frame 20, the diaphragm may be cut free (singularized) from the continuously supplied polyimide or PET substrate, or the frame may be attached to thereafter cut the resulting transducer free.

[0091] In FIG. 15, an embodiment of an assembly 40 of stations is shown, for producing a basic form of a diaphragm according to FIG. 1 IB. After manufacturing the basic form of a transducer according to FIG. 1 IB, processing may continue with the steps according to FIG. 14, and the embodiments of FIG. 14 and FIG. 15 may be a single inter-related embodiment or separate embodiments.

[0092] In a configuration of the assembly 40 in FIG. 15, a PET sheet supply roll 41 introduces a PET sheet into die cut station 42. The PET sheet forms a diaphragm substrate 2 as the basis of a diaphragm to be formed. The die cut station 42 comprises opposing die cut rollers of which at least one comprises cutters to form via’s 22. One via 22 per transducer 1 is arranged centrally and another via 22 is arranged off-center with respect to the transducer to 1 be formed, so as to manufacture an embodiment of a basic transducer 1 as shown in FIG. 11. Numerous alternatives are available and known to the person skilled in the art to substitute die cutting the via’s or a single via through the diaphragm substrate 2, such as laser cutting, or the like.

[0093] At copper lamination station 43, copper sheets in layers are supplied from copper supply rolls 44, to be applied as continuous layers on top and bottom surfaces of the PET diaphragm 2. Adhesive, glue or varnish may be applied by applicators 45 on PET diaphragm substrate 2 before adding the copper sheets from the copper supply rolls 44. Opposing press rolls 46 are rotated to assemble the PET diaphragm 2 and copper sheets from copper supply rolls 44.

[0094] Further downstream, to the right in FIG. 15, two die cut stations 47 and 48 are provided, to respectively form one coil 3 on top of, and one coil 3 on the bottom of the PET diaphragm substrate 2, in the copper sheet layers formed there. Each die cut station 47, 48 comprises one roller with cutters and an opposing support roll. At embossing station 49, portions of spiral shaped copper patterns forming dynamic coils 3 are pressed through via’s 22 to connect the coils 3 at the center of the transducer 1 and allow single sided connection to the input or output terminal 4 and / or ground at the suspension 7.

[0095] The diaphragm 2 may comprise a material layer having a thickness of 20 - 50 pm, and may be made of polyimide instead of PET, or any other suitable material. The coils 3 may comprise a copper conductor, or another layer of conductive material, and may have a thickness of for example 18 pm.

[0096] For a continuous production process, the PET diaphragm 2 is supplied on rolls at PET sheet supply roll 41. The coil material may be purchased patterns on rolls as flexible printed circuits (FPC), instead of being die cut, or may be cut out of each continuous conductive (copper) layer using a laser (laser ablation), which may also be performed before applying a coil 3 onto diaphragm 2. Yet further, the pattern for the coils 3 may be formed by applying a kiss cut to form the coil pattern in each top- and bottom continuous conductive (copper) layer already laminated to the diaphragm 2. It should also be considered that applying a coil 3 may also alternatively be achieved through 3D printing or regular conductive track or PCB printing. Then, from a perspective of production speeds, using a form of screen printing may currently be preferred.

[0097] A microphone may comprise an electroacoustic transducer 1, where examples are illustrated in the figures and discussed herein above. Although a microphone could be referred as an acoustoelectric transducer, for the purpose of the present disclosure, herein all transducers for generating sound from electrical signals and vice versa are designated as ‘electroacoustic’ transducers. When a microphone comprises an electroacoustic transducer 1, the dynamic coil 3 is configured to receive an acoustic signal and transduce the acoustic signal into an electrical signal upon electromagnetic interaction with a static field magnet 5. The static field magnet 5 can be a permanent magnet or an electromagnet, such as the static field coil 5 of preferred embodiments of the disclosed electroacoustic transducer.

[0098] An electronic device 10 may comprise an electroacoustic transducer 1. When an electronic device 10 comprises an electroacoustic transducer 1, the electroacoustic transducer 1 can be configured to act as a loudspeaker 8 and / or microphone in distinct or similar frequency bands.

[0099] Diaphragm 2 is to be suspended on frame 20, opposite magnetic field shield 12 relative to frame 20. Also for suspending diaphragm 2 by frame 20, appendages and the like can be formed in the process of molding frame 20 onto magnetic field shield 12. Nevertheless, frames 20 may be manufactured separate from magnetic field shield 12 and be linked or attached to the magnetic field shield 12, but then there’s a risk of some deviation in dimensions and a risk of vibrations and noise being generated. Also when 3D printing the frame 20 on the shield 20 from printable material, the same or at least similar advantages can be achieved.

[0100] Though various features have been described with and illustrated in separate figures, it is understood that these features can be combined to obtain advantageous embodiments. For example, in any of the embodiments, a chassis may be provided with a static field magnet 5 and / or the static field magnet 5 may be at least one static field coil 5. Further, the dynamic coil 3 or the multiple dynamic coils 3, 3.1, 3.2, 3.3 may each be electrically connectable or connected to an input or output terminal 4, 4.1, 4.2, 4.3 of controller 11.

[0101] The present disclosure is not limited to the illustrated configurations and the scope of protection is defined and only limited by the appended claims, in more in particular only the independent claims.

Claims

CLAIMS1. A method of production of planar electroacoustic transducers, comprising:- providing a diaphragm substrate as the basis for multiple subsequently formed transducers;- applying on or embedding in the diaphragm substrate at least one dynamic coil per transducer;- forming a suspension around the at least one dynamic coil per transducer;- laminating a cover layer on at least one side of the diaphragm substrate over the at least one dynamic coil per transducer and the suspension to form a diaphragm;- mounting the diaphragm around the suspension on a frame.

2. The method of claim 1, wherein forming the suspension comprises a step from a group, comprising at least one of cutting, die cutting, and embossing.

3. The method of claim 1 or 2, wherein laminating the cover layer comprises applying an assembly of an adhesive layer and a finish layer.

4. The method of claim 3, wherein the adhesive layer comprises an acryl layer, and the finish layer comprises a BoPET or PET layer.

5. The method of claim 3 or 4, further comprising; removing the finish layer around the suspension, for mounting the diaphragm to the frame.

6. The method of claim 5, wherein removing the finish layer comprises a step from a group, comprising at least one of cutting, kiss cutting, die cutting, and embossing, and peeling the finish layer away in an area outside the suspension.

7. The method of any of the preceding claims, further comprising applying an adhesive under the cover layer from a group of adhesives, at least comprising glue and varnish.

8. The method of any of the preceding claims, further comprising: singularizing each subsequently formed diaphragm prior to mounting the formed diaphragm onto the frame.

9. The method of any of the preceding claims, further comprising applying an adhesive on the cover layer from a group of adhesives, at least comprising glue and varnish, prior to mounting the formed diaphragm onto the frame.

10. The method of any of the preceding clams, wherein the applying on or embedding in the diaphragm substrate of at least one dynamic coil per transducer comprises: applying a layer of conductive material and forming a coil pattern by at least one step from a group, comprising ablation, laser ablation, die cutting, and kiss cutting.

11. The method of any of the preceding clams, wherein the applying on or embedding in the diaphragm substrate of at least one dynamic coil per transducer comprises: applying a flexible printed circuits (FPC) forming the dynamic coil onto the diaphragm substrate, or printing or 3D printing the coil.

12. A diaphragm of or for a transducer, comprising:- a diaphragm substrate;- at least one dynamic coil applied on or embedded in the diaphragm substrate;- a suspension formed around the at least one dynamic coil;- a cover layer laminated on at least one side of the diaphragm substrate over the at least one dynamic coil per transducer and the suspension.

13. The diaphragm of claim 12, wherein opposing dynamic coils are arranged in parallel on or in the diaphragm substrate, each covered by one cover layer.

14. The diaphragm of claim 12 or 13, wherein at least the diaphragm substrate extends outside the suspension.

15. The diaphragm of claim 12, 13 or 14, wherein the cover layer comprises an assembly of an adhesive layer and a finish layer.

16. The diaphragm of claim 15, wherein at least the adhesive layer extends outside the suspension for mounting the diaphragm to a frame.

17. The diaphragm of claim 15 or 16, wherein the adhesive layer comprises an acryl layer, and the finish layer comprises a BoPET or PET layer18. A transducer comprising a diaphragm of any of the preceding claims 12 - 17, mounted on a frame, wherein the diaphragm is substantially planar.

19. Apparatus from a group of electroacoustic transducer apparatuses at least comprising loudspeakers and microphones, with the apparatus comprising at least one transducer according to claim 18 and an connection to a controller.

20. Electronic device comprising the transducer according to claim 18, and the controller.

Images