Planar dynamic converter

Abstract

Membrane arrangement for a planar dynamic sound transducer with - a support frame (130, 250); and - a membrane (110) stretched on the support frame, onto which at least one electrically conductive conductor track (120) is applied by coating, wherein at least one end of the conductor track (120) applied by coating extends to a contact surface (200) of the membrane arrangement, wherein the contact surface (200) is part of the support frame (130, 250).

Description

[0001] The invention relates to a planar dynamic transducer, in particular a planar dynamic sound transducer. background

[0002] Planar dynamic transducers typically consist of a magnet array with several parallel magnet bars and a diaphragm, where the plane of the magnet array is parallel to the diaphragm plane. In sound reproduction mode, an electric current flows through a planar coil mounted directly on the diaphragm, generating a deflection force due to the magnetic field of the magnet array. This deflection force moves the diaphragm, thus producing sound. In sound recording mode, i.e., as a microphone, the sound excitation of the diaphragm induces a corresponding electric current in the coil. The basic, well-known design of a planar dynamic transducer is described in Fig. Figure 1 shows the assembly. It contains bar magnets 100a and 100b, each with a 180° alternating orientation of their magnetic poles, a supporting membrane film 110, a conductor structure 122 applied to it, contact surfaces 125 and 125a at the ends of the conductor structure, and a support frame 130 on which the membrane film 110 is fixed, for example, by adhesive bonding. The arrangement of the bar magnets shown generates a magnetic field that runs horizontally in the plane of the membrane film. When current flows through the conductor structure, the resulting magnetic field interacts with that of the bar magnets, generating a driving force acting perpendicular to the membrane plane. This deflects the membrane film, which is freely suspended in this area, and produces a variation in the pressure of the surrounding air, i.e., sound. By inverting this principle, sound waves can be converted into alternating electrical current.

[0003] In the prior art, various methods are used to produce the conductor structures on the carrier film. On the one hand, suitable material (thin wires, thin film, etc.) can be bonded to the carrier film by gluing, laminating, ultrasonic welding, etc., and the conductor structure can be created before or after this bonding step by cutting, punching, laser cutting, laser ablation, photolithography, or similar processes.

[0004] Alternatively, a conductive layer can be built up on the substrate material by means of a coating process, which, for example, has the desired path structure from the outset by local focusing of the coating (e.g. by aerosol or inkjet printing of metal particles) or by means of a shading mask, or the path structure is created by selective ablation using a laser or photolithography.

[0005] Electrically contacting these coated track structures is not trivial, as the resulting metallic layers are too thin and fragile to achieve a reliable and very low-resistance connection directly, for example, by soldering or bonding. In contrast to electrostatic or capacitive transducers, planar dynamic systems typically have a relatively low overall resistance, for example, in the range of 16 to 50 ohms, which means that contact resistances can have measurable negative effects. In the current state of the art, contacting is usually achieved by mechanically pressing a conductive part onto the coated track to create a solid base, for example, for a soldered connection.

[0006] US3674946A discloses an electrodynamic transducer in which the voice coil, in the form of one or more strip-shaped electrical conductors, is attached to the diaphragm (e.g., glued on). The conductor ends lie on the diaphragm and are electrically connected by means of two connecting wires. DE1234266B, DE1184803B, US4281223A, and US6097830A disclose similar solutions: a strip-shaped conductor is applied as a thin layer to a diaphragm for a planar transducer, with its ends serving as connection points and also lying on the diaphragm.

[0007] US5095357A, US6201286B1 and US2015 / 0021758 A1 describe the contacting of terminal pads by growing a conductive layer and the use of vias in semiconductor manufacturing.

[0008] Fig. Figure 2a shows, as an example, a cross-section in the area of ​​the contact surface 125 or 125a, the carrier film or membrane 110, the metal coating 120, the carrier frame 130, the pressed-on conductive part 140, the screw connection 150, 151 generating the contact pressure, and the connection of a connecting cable 170 via a soldered connection 160. With this design, however, the conductor track can be damaged or punctured by even the smallest irregularities.

[0009] Aluminum is a popular conductor material, but upon contact with oxygen, it immediately forms an oxide layer that is inherently insulating. This can impair the described contact by crimping. Furthermore, there is a risk that the contact pressure will decrease over time due to shocks, vibrations, material shrinkage and fatigue, etc., or that humidity or other substances will penetrate between the contact surfaces via capillary action, causing contamination or corrosion. In each of these cases, contact resistances arise, which reduce the efficiency of the transducer, potentially leading to complete failure due to interruption.

[0010] An alternative contacting option is to use an initially or permanently viscous, electrically conductive material, e.g. silver conductive adhesive, to connect the conductor track to other contacting structures, e.g. a printed circuit board or circuit board. Fig. Figure 2b shows an example of an additional circuit board 180 with copper cladding 181 and a soldered connection 160 attached to it. The connection to the metal coating 120 is made by means of a via 182, which is filled with a conductive adhesive 190. However, such conductive viscous materials generally have a lower conductivity than metals, which reduces the efficiency. In addition, the sometimes complex chemical composition of these materials can be problematic for the long-term stability of the electrical connection.

[0011] An additional challenge arises with configurations featuring multiple conductor structures. Here, not just one, but several conductors are present per bar magnet. Electrically, these conductors are connected in series, so the driving current flows through the same magnetic field multiple times, corresponding to several turns in a regular cylindrical coil. The factor "I" for the length in the formula F=B * I * i is multiplied, and thus so is the driving force "F". However, this comes at the cost of high system resistance and a significantly increased mass of the conductor structure. Fig. Figure 3 shows a planar coil with multiple conductor tracks 122 and the necessary external return lines 123, 124. These returns require additional space on the membrane, increase the system resistance, and make it more difficult to contact the conductor track ends 125, 125a. Summary of the invention

[0012] The present invention improves the second of the above-mentioned manufacturing methods, namely a coating process for membrane arrangements, as well as a membrane arrangement produced by coating.

[0013] One object of the present invention is to provide an improved membrane arrangement for planar dynamic transducers in which the conductor tracks are easier to connect or this connection is more robust and / or has improved conductivity.

[0014] According to the invention, this problem is solved by direct contacting, wherein at least one electrically conductive layer is applied to the membrane as a conductor track by coating and wherein at least one end of the conductor track extends to a contact surface of the membrane arrangement, which is part of the support frame.

[0015] A membrane arrangement according to the invention for planar dynamic sound transducers is specified in claim 1.

[0016] According to the invention, a membrane arrangement for planar dynamic sound transducers comprises a support frame and a membrane stretched on the support frame, onto which at least one electrically conductive conductor track is applied by coating, wherein at least one end of the conductor track applied by coating extends to a contact surface of the membrane arrangement, and wherein the contact surface is part of the support frame.

[0017] Further advantageous embodiments are described in claims 2-8.

[0018] Claim 9 relates to a planar dynamic sound transducer, such as can be used in headphones or microphones, with a diaphragm arrangement according to the invention.

[0019] Claim 10 relates to a method for manufacturing a membrane assembly for a planar dynamic transducer, comprising the steps of providing a support frame with at least one contact surface, attaching a membrane to the support frame with at least one contact surface, and coating the membrane attached to the support frame with an electrically conductive material such that at least one conductive track is formed, wherein the coating also extends to the at least one contact surface of the support frame. The conductive track is thereby electrically connected to the contact surface. Brief description of the drawings

[0020] Further details and advantageous embodiments are shown in the drawings. These show Fig. 1. the basic structure of planar dynamic transducers; Fig. 2 known contacting of a membrane arrangement by pressing on a contact surface or bonding with viscous conductive material; Fig. 3 known arrangements of multiple conductor tracks on a membrane; Fig. 4 the basic principle of direct contacting of conductor tracks applied by coating in various variants; Fig. 5 variants of direct contacting with through-hole plating of the carrier frame; Fig. 6 Direct contacting of conductor tracks applied by coating in various variants of the carrier frame; Fig. 7 Direct contacting according to the invention in multiple conductor structures with and without feedback; Fig. 8 the contact surface as the top layer of a multilayer circuit board; and Fig. 9 a deeper layer of the multilayer circuit board. Detailed description of the invention

[0021] Fig. Figure 4 illustrates the basic principle of direct contacting of conductive traces applied by coating in various configurations. During the layer build-up, the transducer's membrane film is coated with an electrically conductive material up to its edge and beyond, extending onto an adjacent electrically conductive surface. This surface must be divided into at least two electrically separated areas at the overall system level to prevent a short circuit between the at least two connection points.

[0022] The coating can be applied, for example, by physical or chemical vapor deposition processes, evaporation, sputtering, plasma coating, laser transfer, aerosol printing, inkjet printing, etc. Suitable conductive materials are known, e.g., gold, copper, or aluminum.

[0023] In the Fig. In the arrangement shown in Figure 4a, the support frame 130 has a conductive surface 200, e.g., a copper cladding. In this example, both extend beyond the edge of the membrane film 110. During the coating process, in which the conductive track 120 is created on the membrane 110, the membrane is already attached to the support frame 130. Simultaneously and through the same build-up process, a connection is also created between the conductive track 120 and the conductive surface of the contact area 200 by bringing the conductive coating of the membrane into direct contact with the conductive layer or contact area 200 in an area 210 referred to as the "direct contact zone". The connecting wire 170 can be connected to this via a solder joint 160. This allows the solder joint 160 of the connecting wire 170 to be spatially separated from the direct contact zone 210 of the applied conductive track 120.This is advantageous because it prevents damage to the sensitive applied conductor track 120 when soldering the connecting lead 170. Furthermore, the solder joint 160 is independent of the contacting of the coated membrane, making it possible to apply the solder joint 160 to the contact surface 200 before the coating process.

[0024] As in Fig. As shown in Figure 4b, the conductive layer of the contact surface 200 can alternatively be located above the membrane film 110. In this case, the contact surface is a component applied to the membrane, or part of such a component, whereas in most other described cases, the contact surface can be part of the support frame. In some examples, the membrane is applied to the conductive layer of the contact surface 200. As shown in Figure 4b, the conductive layer of the contact surface 200 can be applied to the membrane. Fig. As shown in Figure 4c, the contact surface 200 can also be located next to the membrane film 110. Any small gap between them can also be filled with the conductive coating material. In all these cases, the conductive coating 120 extends beyond the edge of the membrane onto the contact surface.

[0025] In Fig. In section 4d, the direct contact zone 210 is located in a perforation of the membrane film 110. This perforation can be, for example, a recess in the membrane film produced by cutting, punching, milling, etc. Other arrangements of these or similar elements are also possible while simultaneously utilizing the described basic principle of direct contacting.

[0026] Further variants of direct contacting with through-hole plating of the carrier frame are described in Fig. 5 shown. In the Fig. In the arrangement shown in 5a, the connection to the direct contact zone 210 of the coating 120 is made analogously to Fig. 4a, however, there is also a via 220 and a contact surface 230 attached to the underside of the carrier frame 130, onto which the solder connection 160 can then be placed.

[0027] In the Fig. In the arrangement shown in Figure 5b, the contact surface is the surface of a multilayer circuit board. This can be part of the support frame 130, but it doesn't have to be. In this example, the via 220 leads to a second layer or intermediate layer 230 of the multilayer circuit board, which leads to any other point in the support frame. There, another via 220a is located, via which another conductor structure 120a on the membrane is then contacted. In this way, for example, several conductor tracks on the membrane can be connected to form several turns of a single coil. In addition to the robust and low-impedance connection option, another advantage of this arrangement is that the conventionally necessary return connections on the membrane can be reduced in length or completely eliminated. Since these return connections normally run perpendicular to the magnetic field, no force is generated in them; they are merely for connection or...This is necessary for connecting further windings of the coil. Reducing or eliminating these windings increases the effectively usable area on the diaphragm and also reduces the diaphragm mass. For example, it is possible to cover the diaphragm with only straight conductor tracks that are connected to each other via contact surfaces on the support frame. This is shown in [reference missing]. Fig. 7b shown and described further below.

[0028] While in the examples described so far the contact surface 200 was arranged between the membrane film 110 and the support frame 130, other arrangements are also possible. In one example, Fig. In the variant shown in Figure 5c, the through-hole connection is created by first fixing the membrane film 110 to the support frame 130 and then inserting a suitable rivet 225 into a designated bore. The membrane film is locally recessed or pierced and secured by the collar of the rivet. On the underside of the support frame, the rivet connection is formed by deforming the rivet with a suitable tool. Suitable designs of the rivet and forming tool create a mechanically very stable electrical connection between the two sides of the support frame. During the subsequent application of the coating 120, the top side of the rivet, as the contact surface of the membrane assembly, is also coated, thus creating a stable electrical connection 210 between the rivet and the remaining coated surface 120. On the underside of the support frame, for example,A direct soldered connection 160 can be made to the connecting wire 170, or a conductive layer can be provided there, to which the rivet is connected by its forming through pressing. This then leads, for example, to other, spatially separated through-hole rivets or to a spatially separated soldered connection.

[0029] Rivets generally offer a simple, stable, and electrically conductive way to attach the membrane to the support frame. The rivets can be used as through-hole connections, but this is not mandatory.

[0030] Also Fig. Figure 6 shows different variants of the carrier frame with direct contact of conductive traces applied by coating. Fig. In Figure 6a, an additional outer support frame 250 is added as an example, and the membrane film 110 is guided over the outer edge of the (inner) support frame 130. The membrane film is fixed between these two parts, for example, by gluing or clamping 115. The controlled guidance of the membrane film 110 over the edge, as well as the selected thickness ratios of the inner support frame 130, the outer support frame 250, and the contact surface 200, ensures that the coating 120 is also flat in the transition area. This improves the bond between the coating 120 and the direct contact zone 210. Fig. The setup shown in 6b basically corresponds to that of Fig. 4a, however, the membrane film 110 is attached to the underside of the support frame 130. The coating 120 is applied to the top side of the film and extends over a chamfer 121 of the support frame to the direct contact 210 on the conductive surface 200. The chamfer 121 simplifies the coating process. In this variant, the application and delimitation of the membrane film 110 is simpler, as the coating 120 does not extend over the outer edge of the film.

[0031] Fig. Figure 7 shows direct contacting according to the invention in multiple conductor structures. Fig. 7a Four separate conductor structures 122 are applied in a meandering pattern to the membrane 110. Each conductor structure is connected at both ends by direct contact to an area of ​​the contact surface, the different areas of the contact surface being electrically separated from each other by breaks 201. The contact surfaces 200 can be the surface of a multilayer circuit board, which in turn can be part of the support frame 130. In a deeper layer of the multilayer circuit board, which is not in Fig. As shown in 7a, the individual conductor structures 122 can be selectively connected to each other, e.g. as in Fig. 5b.

[0032] In Fig. In 7b, four straight conductor structures 122 are applied to the membrane 110, and each conductor structure is connected at both ends to an area of ​​the contact surface via direct contact. However, in this case, the breaks 201 are arranged such that two adjacent conductor structures are connected to each other via common contact surfaces 200. Therefore, a multilayer circuit board is not necessary, so the contact surface 200 can be a single layer, e.g., copper lamination.

[0033] It is also possible to implement embodiments in which not all conductor tracks are as shown in the diagram. Fig. 7a and Fig. 7b shows that they are not connected serially, but are configured to form two or more individually controllable parallel branches, or are even individually controlled.

[0034] Fig. Figure 8 shows the layout of the contact surface of the [unclear text]. Fig. In the example shown in Figure 7a, the top layer of a multilayer circuit board can also serve directly as a support frame 130. The contact surface 200, e.g., copper cladding, is subdivided into sections by interruptions 201. Vias 220 connect the contact surface 200 to a deeper layer of the multilayer circuit board, which is in Fig.Figure 9 shows that this layer can, for example, be located on the underside of the carrier frame. In this example, each of the sub-areas contains a via 220 and is directly connected to one end of a conductor structure. The deeper layer of the multilayer circuit board connects two different vias to each other, thereby forming return paths 230. These connect the conductor structures to form a single coil. This reduces the number and length of return paths required on the membrane and simplifies the overall coating pattern. On such areas of the contact surface 200 that are connected to the ends of the coil, pads 205 are provided to which connecting leads 170, 170a can be soldered. The return connections 230 can, for example, be produced from a copper area by photolithography.Since such a copper conductor used for feedback is significantly thicker than the coating, the feedback can be implemented with virtually no resistance. Connecting the connecting leads is also straightforward and very stable. Furthermore, the space required on the membrane for conventional feedback leads is eliminated. It is also possible to design the membrane in which the contact surface 200 belongs to an electronic component mounted on the support frame, which then forms part of the membrane assembly.

[0035] The membrane arrangement according to the invention can be advantageously used for sound transducers, in particular for sound transducers in headphones, loudspeakers and microphones.

Claims

[1] Membrane arrangement for a planar dynamic sound transducer with - a support frame (130, 250); and - a membrane (110) stretched on the support frame, onto which at least one electrically conductive conductor track (120) is applied by coating, wherein at least one end of the conductor track (120) applied by coating extends to a contact surface (200) of the membrane arrangement, wherein the contact surface (200) is part of the support frame (130, 250). [2] Membrane arrangement according to claim 1, wherein both ends of the at least one electrically conductive conductor track (120) extend to two separate contact surfaces of the membrane arrangement. [3] Membrane arrangement according to claim 2, wherein several conductor tracks (122) running parallel to each other are applied to the membrane by coating and at least two of the conductor tracks (122) are electrically connected at both ends to contact surfaces (200) by the coating, and wherein an electrically conductive connection of the at least two conductor tracks (122) to a single flat coil is made by connecting the contact surfaces (200). [4] Membrane arrangement according to claim 3, wherein the contact surfaces (200) are located on the top layer of a multilayer circuit board and wherein at least two of the contact surfaces (200) are connected to each other on a lower layer of the circuit board. [5] Membrane arrangement according to one of claims 1-4, wherein the membrane (110) is attached to the contact surface (200), the membrane (110) is perforated in the attachment area, and the conductor track applied by coating extends through the perforation to the contact surface. [6] Membrane arrangement according to one of claims 1-4, wherein the conductive track applied by coating extends beyond the outer edge of the membrane onto the contact surface. [7] Membrane arrangement according to claim 6, wherein the contacting surface is located next to the membrane without overlap. [8] Membrane arrangement according to one of claims 1-7, wherein the contacting surface (200) is a first contacting surface which is connected by means of a through-hole (220) to a second contacting surface (230) which is connected to a connecting wire (170), wherein the first and second contacting surfaces are located on different sides of the support frame (130). [9] Planar dynamic sound transducer with a diaphragm arrangement according to one of claims 1-8. [10] Method for manufacturing a membrane assembly for a planar dynamic sound transducer comprising the steps - Providing a support frame (130) with at least one contact surface (200); - Attaching a membrane (110) to the support frame (130) which is provided with at least one contact surface (200); and - Coating the membrane (110) attached to the support frame (130) with an electrically conductive material (120), wherein the coating also extends to the at least one contact surface (200) of the support frame (130), so that the electrically conductive material (120) is electrically connected to the contact surface (200). [11] The method of claim 10, with the additional step - before coating the membrane (110), soldering a connecting lead (170) to the at least one contact surface (200).

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