Electromagnetic miniature loudspeaker, its coil module, loudspeaker / coil module array and its fabrication method

Abstract

The present invention discloses a coil module, comprising: a vibration membrane suspended on an air cavity defined and supported by a first substrate; at least one planar coil embedded in the vibration membrane; and at least one soft magnetic body embedded in the vibration membrane and arranged around at least a portion of the contour of the planar coil; wherein most of the planar coil is located on a plane substantially the same as a plane on which a portion of the soft magnetic body is arranged. The present invention also discloses a micro speaker and a method for manufacturing the same.

Description

Technical Field

[0001] The present invention relates to a MEMS (micro-electromechanical system) electromagnetic micro-speaker, and in particular to an actuator module for the electromagnetic micro-speaker and a preparation method of the micro-speaker and the actuator thereof. Background Art

[0002] In smartphones, audio systems using traditional speakers consume nearly one-third of the battery power when used in hands-free mode. Developing micro speakers with high efficiency and high linearity has become an important task for engineers in this technical field. Micro-electromechanical systems (MEMS) technology provides the possibility of low-cost and high-precision manufacturing of micro speakers.

[0003] The inventor has disclosed a variety of MEMS electromagnetic speakers in the following documents:

[0004] 1. Chen, YC, Cheng, YT, A low-power milliwatt electromagnetic microspeaker using a PDMS membrane for hearing aids application, MEMS 2011, Cancun, Mexico, January 23-27, 2011, pp. 1213-1216.

[0005] 2. Jadhav, P. R., Cheng, Y. T., Fan, S. K., Liang, C. Y., A sub-MW electromagnetic microspeaker with bass enhancement using aparylene / graphene / parylene composite membrane, MEMS 2018, Belfast, Northern Ireland, January 21-25, 2018, pp. 620-623.

[0006] Reference 1 discloses a MEMS electromagnetic speaker having a polydimethylsiloxane (PDMS) film. The film is suspended on an air cavity supported by a silicon substrate. A Cu planar coil formed on the PDMS film is surrounded by a soft magnetic layer, which is a NiFe soft magnetic layer and is configured around a coil pattern. A coil module including a PDMS film, an air cavity, a coil, and a soft magnet is coupled to an acrylic substrate provided with a hard magnet, which is configured to be located directly below the Cu coil. In this way, a micro speaker is formed.

[0007] In reference 2, the PDMS membrane is replaced by a parylene / graphene / parylene composite film.

[0008] In addition, US2005 / 275497A1 also discloses a microfabricated system for magnetic field generation and focusing, and discloses a method for forming a planar microcoil on a Si substrate, the microcoil having a coil winding with a high aspect ratio and a variety of geometric shapes. The microcoil has a magnetic field enhancement ferromagnetic column rising above the plane of the microcoil, formed at a location of maximum magnetic field strength. The microcoil may also include a magnetic layer formed below the substrate and in contact with the column, the magnetic layer forming a substantially closed magnetic flux path. The substrate is thinned to be comparable to a thin film.

[0009] US2014 / 035708A1 discloses a magnetic actuator having a nanocomposite membrane. The magnetic actuator has a substrate and a membrane layer on the substrate. The membrane layer is composed of an elastic polymer material matrix and magnetic nanoparticles dispersed therein. The actuator also includes a magnetic field generator. The magnetic nanoparticles are arranged in a pattern corresponding to the magnetic field generator, and the magnetic field generator is arranged in a cavity between the substrate and the membrane layer.

[0010] WO2008 / 106928A2 discloses a method for producing membranes that can be electrically and / or magnetically activated, and a magnetic actuator having such a membrane. The method is to mix magnetic microparticles or nanoparticles with a matrix material in a flowable state and apply them to a substrate. A magnetic field is used to change the distribution of particles in the layer to obtain a distribution pattern of the magnetic substance. After curing, a magnetic actuator membrane is formed.

[0011] DE102014112531A1 discloses a method for manufacturing a loudspeaker film (Verfahren zur Herstellung einer Lautsprechermembran), comprising the following steps: A) providing a film; B) providing a flowing powder mixture (2) of plastic and magnetic material; C) applying the powder mixture (2) as a thick film (2) on the film (1); E) aligning magnetic powder particles of the magnetic material with a magnetic field and bonding the powder mixture (2) to the film (1). The patent also discloses a loudspeaker diaphragm made from the finished product.

[0012] WO2017 / 171757A1 discloses an electromagnetic haptic actuator integral with a multilayer substrate. The haptic actuator has an induction coil formed in a packaging substrate material, an elastic membrane above the coil, a magnet on the membrane, and a power plane for providing a drive signal to move the magnet toward and away from the coil. The packaging substrate material inside the coil is removed to form a cavity surrounded by the coil. The cavity portion at the center of the coil is filled with a soft magnetic material. Summary of the invention

[0013] The object of the present invention is to provide an electromagnetic microspeaker of small size which provides improved sound generation performance both in the high and low frequency ranges.

[0014] Another object of the present invention is to provide a new structure of an actuator module suitable for producing small-sized electromagnetic micro-speakers.

[0015] Another object of the present invention is to provide a novel diaphragm structure which is relatively thin and provides improved sound generation performance in both the high and low frequency ranges.

[0016] According to one aspect of the present invention, the present invention discloses a MEMS coil module. The coil module of the present invention comprises: a vibration membrane suspended on an air cavity defined and supported by a first substrate; at least one planar coil embedded in the vibration membrane; and at least one soft magnet embedded in the vibration membrane and arranged around at least a portion of the outline of the planar coil.

[0017] In some preferred embodiments of the present invention, the material of the first substrate is selected from silicon, rubber, plastic, polymer, resin, wood, ceramic, glass, paper and any combination thereof, preferably a silicon substrate. In a preferred embodiment, the planar coil is a metal coil or a metal alloy coil, such as a Cu coil, an Ag coil or an Al coil, preferably a Cu coil. In a preferred embodiment, the planar coil forms a planar pattern, and the soft magnetic body includes at least one strip arranged along a portion of the outer contour or inner contour of the planar pattern. The material of the soft magnetic body is not particularly limited, preferably selected from Fe, Co, Ni and their alloys, preferably a NiFe soft magnetic body.

[0018] In a preferred embodiment of the present invention, the vibration membrane is preferably selected from one of a PDMS membrane and a polyparaxylene / graphene / polyparaxylene composite membrane.

[0019] In the above embodiments, and in other embodiments, the planar coil includes at least one multilayer structure and / or the soft magnetic body includes at least one multilayer structure. In some of these embodiments, the majority of the planar coil is located on a plane substantially the same as the plane where a portion of the soft magnetic body is located. In some embodiments of the present invention, the planar coil includes a spiral structure, which includes at least one outer ring and an inner ring connected in series. In some such embodiments, the planar coil also includes at least one ring configured between the outer ring and the inner ring and connected to the outer ring and the inner ring. In such embodiments, the planar coil may also include a soft magnetic body configured between the two coil rings, wherein the pattern formed by the soft magnetic body may have a shape corresponding to an adjacent outer ring and / or inner ring.

[0020] In a plurality of preferred embodiments of the present invention, the planar coil comprises one or more circular rings connected in series and arranged in layers. In such an embodiment, the planar coil may further comprise a soft magnetic body disposed between two coil layers, wherein the pattern formed by the soft magnetic body may have a shape corresponding to the upper and / or lower coils thereof.

[0021] In a preferred embodiment of the present invention, the planar coil forms a coil pattern, whose outer contour has a circular, elliptical or polygonal shape, preferably a regular concentric polygon, such as a square, pentagon, hexagon, etc. In some of these embodiments, the coil pattern has an inner contour, and the shape of the inner contour corresponds to the shape of the outer contour.

[0022] In most embodiments of the present invention, the soft magnetic body is arranged in a material layer different from the material layer of the coil ring. In some of these embodiments, the majority of the planar coil is located on substantially the same plane as the plane in which a portion of the soft magnetic body is arranged.

[0023] In some preferred embodiments of the present invention, the coil module is provided in a MEMS structure, more preferably a CMOS structure.

[0024] In some embodiments of the present invention, two or more planar coils are provided and embedded in a vibrating membrane. The plurality of planar coils are driven by one or more drivers, and when driven by two or more drivers, each driver independently actuates the corresponding planar coil. In some preferred embodiments, a first planar coil is arranged in an area defined by a second planar coil, and the second planar coil can be arranged in an area defined by a third planar coil. The first and second planar coils can be concentric.

[0025] The coil module may further include a cover surrounding the vibrating membrane. The cover provides a vent to expose at least a portion of the planar coil. The vent may be opened at the top of the vibrating membrane, with its ventilation direction perpendicular to or inclined to the membrane plane. The vent may also be opened on one side of the vibrating membrane, with its ventilation direction parallel to or inclined to the membrane plane. In some embodiments of the present invention, two or more vents are provided on the cover.

[0026] The coil module may further be provided with a second ventilation hole on the air cavity to expose at least a portion of the air cavity. The ventilation direction of the ventilation hole may be perpendicular to or inclined to the membrane plane.

[0027] According to another aspect of the present invention, the present invention provides a micro speaker including a coil module as described above and a second substrate, the second substrate being coupled to the substrate of the coil module on the side of the air cavity opposite to the diaphragm to support the coil module and at least one hard magnet and define the air cavity. At least one hard magnet may be arranged at a position in the air cavity corresponding to at least one planar coil. In such an embodiment, the air cavity forms a resonant cavity. The second substrate is preferably provided with at least one opening.

[0028] According to a third aspect of the present invention, the present invention provides a micro-speaker, comprising a coil module as described above and a second substrate, the second substrate being coupled to the substrate of the coil module on the side of the air cavity opposite to the vibration membrane to support the coil module and define the air cavity. The cover surrounds the vibration membrane, and at least one hard magnet is provided on the cover, and the at least one hard magnet extends from a position corresponding to at least one planar coil to the space between the cover and the vibration membrane. In such an embodiment, the resonance cavity can be a chamber defined by the cover and the vibration membrane. The second substrate is preferably provided with at least one opening. In such an embodiment, the opening of the second substrate can be as wide as the air cavity. In such an embodiment, the opening of the second substrate is preferably formed as a vent.

[0029] In these embodiments, the hard magnet may form a ring shape. The diameter / length / width of the hard magnet may be greater than the diameter / length / width of the at least one planar coil.

[0030] According to a fourth aspect of the present invention, a coil module with or without a cover further comprises a waveguide located on the vibrating membrane. The waveguide is preferably formed in a cap shape and coupled to the second substrate to regulate the path of the micro-speaker to output sound. The cap may be made of metal, silicon or glass, preferably a silicon cap. The waveguide may provide at least one through hole for connecting the electrical contact to the planar coil. If the waveguide is a silicon cap, the through hole is preferably a through-silicon via (TSV). BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A cross-sectional view showing a first embodiment of a microspeaker according to the present invention.

[0032] Figure 2 Shown including Figure 1 A perspective view of a coil assembly of an embodiment.

[0033] Figure 3A A schematic diagram showing the positional relationship between the planar coil and the soft magnetic body constituting the coil module of the present invention is shown. Figure 3B and Figure 3C The formation Figure 3A Schematic diagram of the coil patterns of the two coil layers of the planar coil.

[0034] Figure 4 A cross-sectional view showing a portion of a coil module according to an embodiment of a microspeaker of the present invention.

[0035] Figure 5 A flow chart showing one embodiment of a method for preparing a micro-speaker of the present invention.

[0036] Figure 6 FIG. 4 is a cross-sectional view of a second embodiment of a micro-speaker according to the present invention.

[0037] Fig. 7A and Figure 7B The shapes and structural schematic diagrams of two waveguides suitable for the present invention are shown respectively.

[0038] Figure 8 FIG. 4 is a cross-sectional view of a third embodiment of a micro-speaker according to the present invention.

[0039] Fig. 9 FIG. 4 is a cross-sectional view of a fourth embodiment of a micro-speaker according to the present invention.

[0040] Figures 10A-10C are cross-sectional views of several possible combinations of multiple planar coils and multiple hard magnets used in some embodiments of the present invention.

[0041] Figures 11A-11B are plan views showing two possible combinations of multiple microspeakers used in some embodiments of the present invention.

[0042] Reference Mark List

[0043] 10. First substrate

[0044] 15 Air cavity

[0045] 20 Second substrate

[0046] 21 Pad

[0047] 25 Opening

[0048] 30 Vibrating membrane

[0049] 30A Ground Floor

[0050] 30B First dielectric layer

[0051] 31 Planar Coil

[0052] 31A, 31B coil layer

[0053] 33 First coil

[0054] 34 Second coil

[0055] 41 Soft magnets

[0056] 41A First soft magnetic layer

[0057] 41B Second soft magnetic layer

[0058] 42 Wire

[0059] 43 Ring Strip

[0060] 44 Ring Strip

[0061] 51 Hard magnet

[0062] 60 Cover

[0063] 61 Vents / Openings

[0064] 65 Waveguide

[0065] 66 Through Holes DETAILED DESCRIPTION

[0066] Several embodiments of the micro-speaker of the present invention will be described in detail below with reference to the accompanying drawings to demonstrate the design, features and effects of the present invention.

[0067] Figure 1 1 is a cross-sectional view of a first embodiment of a micro-speaker of the present invention. As shown in the figure, in the first embodiment, the micro-speaker has a diaphragm 30, the diaphragm 30 has a planar coil 31 and soft magnetic bodies 41, 41 embedded in the diaphragm 30; a first substrate 10 supporting the diaphragm 30 and defining an air cavity 15; a second substrate 20 covering a portion of the air cavity 15 and a hard magnetic body 51 supported by the second substrate 20. In addition, there is a cover 60 surrounding the assembly formed by the above-mentioned components. The cover 60 has a vent hole 61 to expose a portion of the assembly.

[0068] As shown, the coil 31 and the soft magnetic bodies 41, 41 are embedded in and form a part of the vibrating membrane 30. The soft magnetic bodies 41, 41 are arranged close to the outline of the planar coil 31, and the details will be described below. The assembly formed by the vibrating membrane 30, the coil 31 and the soft magnetic bodies 41, 41 is supported by the first substrate 10, so that the walls of the first substrate 10 and the vibrating membrane 30 define an air cavity 15, which functions as a resonance cavity when the vibrating membrane 30 vibrates. The combination of the vibrating membrane 30, the coil 31 and the soft magnetic bodies 41, 41 and the first substrate 10 forms a coil module.

[0069] Figure 1 Also shown is a second substrate 20 coupled to the first substrate 10 and supporting the coil module. The second substrate 20 also supports a hard magnet 51 disposed in the air cavity 15 at a position corresponding to the coil 31. More specifically, the hard magnet 51 is located directly below the planar coil 31, and its planar shape corresponds to the shape of the planar coil 31. An opening 25 is formed in the second substrate 20. When the second substrate 20 is coupled to the first substrate 10, the two substrates and the vibration membrane 30 together define an air cavity 15. The opening 25 in the second substrate 20 provides a ventilation hole for the air cavity 15. Figure 1 In the example of , the opening 25 is located below the core portion of the hard magnet 51, so the opening 25 is located at the center of the module. However, this design is not any technical limitation. The opening 25 can be formed at any position in the second substrate 20. In addition, the number of openings is not limited to one.

[0070] exist Figure 1In the example, a cover 60 is provided to surround the assembly formed by the coil module and the second substrate 20. The cover 60 has a vent 61 that exposes a portion of the vibrating membrane 30. More specifically, the vent 61 exposes a portion of the coil 31. However, the position and exhaust direction of the vent 61 are not technically limited. In other embodiments, the vent 61 may be provided at the top of the vibrating membrane 30, with its ventilation direction perpendicular to or inclined to the membrane plane. The vent 61 may also be opened on one side of the vibrating membrane 30, with its ventilation direction parallel to or inclined to the membrane plane. In addition, the number of vents 61 is not limited. Two or more vents may be provided on the cover 60. If more than one vent is provided, it may not be necessary to separate a group of two or more vents. Two or more holes may intersect to form an opening.

[0071] There is no particular limitation on the material of the cover 60. Any material that provides a good resonance effect can be applied to the cover 60. Preferred materials of the cover 60 include metal, plastic, ceramic, glass, etc., and are preferably metal, especially steel.

[0072] The coil module may further be provided with a second vent hole 25 on the air cavity 15 to expose at least a portion of the air cavity 15. The vent hole 25 may have a venting direction perpendicular to or inclined to the film plane. In a preferred embodiment of the present invention, the second vent hole 25 may be an opening 25 of the second substrate 20.

[0073] Figure 2 Shown including Figure 1 A perspective view of a microspeaker of an embodiment. Figure 2 supply Figure 1 A clearer view of the micro-speaker. As shown in the figure, the micro-speaker of the present invention has a coil module, which includes: a vibration membrane 30 suspended on an air cavity 15 defined and supported by a first substrate 10, at least one planar coil 31 embedded in the vibration membrane 30, at least one soft magnet 41, 41 embedded in the vibration membrane 30 and surrounding a portion of the contour of the at least one planar coil 31; the second substrate 20 is coupled to the first substrate 10 on the side of the air cavity 15 opposite to the vibration membrane 30; the second substrate 20 supports the coil module and at least one hard magnet 51, and defines the air cavity 15. Figure 1 In the example, at least one hard magnet 51 is disposed in the air cavity 15 at a position corresponding to the planar coil 31 .

[0074] However, in the present embodiment, the hard magnet 51 may also be arranged on the lower surface of the upper cover body of the cover 60 having an upper cover body and a side wall connected to the upper cover. The main body of the cover 60 is coupled to the second substrate to surround the vibration membrane 30. The space defined by the cover 60 and the vibration membrane 30 forms a resonance cavity. The second substrate 20 is also provided with at least one opening 25, the diameter of which may be the same as that of the planar coil 31. The opening 61 is formed on the cover 60 and serves as a vent. As described above, the number of the openings 61 is not limited to one.

[0075] exist Figure 2 As shown in FIG. 2 , a pad 21 is prepared on the bottom of the second substrate 20 , and a wire 42 electrically connects the pad 21 and the coil 31 .

[0076] In a preferred embodiment of the present invention, the first substrate 10 can be made of a material selected from silicon, rubber, plastic, polymer, resin, wood, ceramic, glass, paper and any combination thereof, and is preferably a silicon substrate. In a preferred embodiment of the present invention, the planar coil 31 can be a metal coil or a metal alloy coil. Suitable materials for the coil 31 include Cu, Ag or Al. The coil 31 is preferably a Cu coil. The material of the soft magnet 41 is not particularly limited, preferably one of Fe, Co, Ni and their alloys, preferably a NiFe soft magnet. In addition, the vibration membrane 30 is preferably selected from one of PDMS membrane and polyparaxylene / graphene / polyparaxylene composite membrane. The vibration membrane 30 is preferably a multilayer film, so it can be manufactured using CMOS technology. Suitable materials for the second substrate 20 can be silicon, rubber, plastic, polymer, resin, wood, ceramic, glass, paper and any combination thereof. The preferred material for the second substrate 20 is acrylic. As for the hard magnet 51, it can be made of any known magnetic material, such as Fe and Fe alloys.

[0077] In terms of manufacturing the micro speaker, it is preferred to prepare the coil module with a MEMS (micro-electromagnetic system) structure. The preferred process for the MEMS micro speaker is the CMOS process. Of course, this is not any technical limitation.

[0078] The coil 31 is preferably a planar coil, especially a MEMS planar coil, more preferably a MEMS planar coil with a CMOS structure. Although some materials used to produce micro-speakers are not standard SMOS materials, the CMOS process can be used to prepare the micro-speaker of the present invention with only minor necessary changes.

[0079] In a preferred embodiment of the present invention, the planar coil 31 forms a planar pattern. As in conventional technology, the planar coil can form a spiral pattern or a circle pattern. In the present invention, the soft magnetic body includes at least one strip arranged along a portion of the outer contour or inner contour of the planar pattern. The positional relationship between the planar coil 31 and the soft magnetic body 41 can be obtained from Figure 1 and Figure 2It can be seen in. Figure 3A An example is shown in which the coil 31 forms a circular pattern, and the soft magnetic body 41 includes two annular strips, a larger annular strip 44 surrounding the outer contour of the planar coil pattern 31 and a smaller annular strip 43 located within the inner contour of the planar coil pattern 31 .

[0080] If the planar coil 31 has a CMOS structure or a structure compatible with the CMOS structure, the planar coil 31 and / or the soft magnetic body 41 can form a multilayer structure. In some of such embodiments, most of the planar coil 31 can be located on a plane substantially the same as the plane on which a portion of the soft magnetic body 41 is disposed. An example of this feature is shown in Figure 4 , which is a cross-sectional view of a portion of a coil module of an embodiment of a micro-speaker of the present invention. Figure 4 As shown, the planar coil 31 has two coil layers 31A and 31B. Both are embedded in the multilayer vibration membrane 30. The multilayer vibration membrane 30 is composed of a bottom layer 30A, on which the coil layer 31A is formed. The first dielectric layer 30B is formed on the coil layer 31A, and the first soft magnetic layer 41A is formed on the first dielectric layer 30B. The first coil layer 31A and the first soft magnetic layer 41A are separated and insulated by the first dielectric layer 30B, and most of the planar coil 31 is located on the plane where the soft magnetic body 41 is located. This positional relationship also applies to the second coil layer 31B and the second soft magnetic layer 41B.

[0081] Although it is not intended to limit the scope of the present invention, the above structure is possible mainly because of the etching process used in preparing the multi-layer diaphragm. Figure 4 It can be seen that the etching process forms an undulating morphology of the dielectric layer, so most of the planar coil 31 is arranged on a plane that is substantially the same as the plane where the soft magnetic body 41 is located. For example, when forming the first coil layer 31A, a metal layer is first formed on the bottom layer 30A, and then the unnecessary part of the metal layer is etched away to form the first coil layer 31A. The first dielectric layer 30B is formed on the first coil layer 31A and on the bottom layer portion from which the metal layer has been removed. The first dielectric layer 30B thus forms a wavy morphology. Then, on the first dielectric layer 30B, the first soft magnetic body 41A is formed in an area where the first dielectric layer 30B is at a lower level. After the above process, most of the planar coil 31 will be arranged on a plane that is substantially the same as the plane where the soft magnetic body 41 is located.

[0082] As described above, the planar coil 31 may have a spiral structure including multiple layers. The structure preferably has at least one outer ring and an inner ring connected in series. In addition, the spiral structure may also have at least one ring disposed between the outer ring and the inner ring, and connected in series with the outer ring and the inner ring. In such an embodiment, the planar coil 31 may also include a soft magnetic body 41 disposed between the two coil rings. The pattern formed by the soft magnetic body 41 is preferably a shape corresponding to an adjacent outer ring and / or inner ring.

[0083] Another alternative is to make the planar coil 31 have one or more rings connected in series and arranged in layers. In such an embodiment, the planar coil 31 may also include a soft magnetic body 41 disposed between two coil layers. Similar to the spiral structure, the pattern formed by the soft magnetic body may have a shape corresponding to the upper and / or lower coils. An example of this embodiment is as follows Figure 3B As shown, the figure shows the coil pattern of two coil layers forming a multi-layer planar coil. The two coil layers are connected in series, and their outer and inner contours are surrounded by soft magnetic bodies 41.

[0084] As described above, the planar coil 31 forms a coil pattern. In some embodiments, the outer contour of the coil pattern can be a circular, elliptical or polygonal shape. If it is a polygon, it is preferably a regular concentric polygon. Suitable polygonal shapes include squares, pentagons, hexagons, etc. In some of these embodiments, the coil pattern has an inner contour. The shape of the inner contour can correspond to the shape of the outer contour. But it may also be different or not corresponding.

[0085] Figure 3C Another example is shown in which each coil layer is surrounded by a plurality of soft magnetic bodies 41 .

[0086] As described above, the micro-speaker of the present invention can be manufactured using CMOS technology. Figure 5 A flow chart showing an embodiment of a method for preparing a micro-speaker of the present invention is shown below. Figure 5 The process of the present invention is described.

[0087] like Figure 5As shown, the micro speaker can be prepared in the following steps: In step 501, an oxide layer is first deposited on the silicon chip as a mask layer for subsequent silicon KOH etching. Then in step 502, the back silicon is patterned using photolithography and RIE processes to form a circular area. Then in step 503, the substrate is etched in a KOH solution with IPA for a predetermined time to form a circular concave structure leaving a thin silicon layer on the top. In step 504, another RIE process is performed to remove the nitride layer on the front side, and in step 505, a Ti / Cu layer is sputtered on the front side of the substrate to plate Cu as an etch stop layer. Then in step 506, the substrate is placed in the KOH solution again to remove the remaining Si layer and form a circular oxide / Cu composite film. Then in step 507, PDMS is spin-coated on the film and cured, and then in step 508, a Ti / Cu layer is deposited as a seed / adhesion layer. In step 509, a series of alternating and repeated photolithography and electroplating processes are performed on the PDMS to form a Cu coil pattern layer and a NiFe soft magnetic pattern layer arranged on the PDMS film adjacent to the outline of the Cu coil pattern, and preferably a structure with a PDMS layer. In step 510, a protective layer is formed on the Cu coil / NiFe soft magnetic layer. Thereafter, in step 511, the resulting coil module is immersed in BOE and Cu etchant to remove the seed layer in the structure and the oxide / Cu barrier layer under the PDMS film. In step 512, the coil module is separated and then joined to an acrylic plate carrying a NdFeB magnet in step 513. In step 514, a soldering pad extending through the acrylic plate is provided and in step 515, an electrical connection is formed between the soldering pad and the electrode of the coil module. In step 516, the combined components are separated again. In step 517, a cover having a vent corresponding to the central area of ​​the membrane body is coupled to the acrylic plate. In this way, a structure such as Figure 1 Coil module shown.

[0088] In step 509 of the above method, a Cu coil pattern layer and a NiFe soft magnetic layer adjacent to the Cu coil pattern outline are formed on the PDMS film using an alternating and repeated photolithography and electroplating process. Due to the alternating and repeated photolithography and electroplating process, for example, a strip of soft magnetic material is formed after a layer of copper coil and a PDMS layer covering the copper coil layer are formed, and most of the formed soft magnetic layer will be located in a plane / level substantially the same as the plane where the coil layer is located, mainly because the coil material that may be just outside the outer outline of the coil pattern has been removed in the etching step. Figure 4 An example of a coil module produced in this way is shown. Figure 4 In the example shown in FIG. 4 , both the planar coil 31 and the soft magnetic body 41 are embedded in the vibration membrane 30 .

[0089] Figure 6Another embodiment of the present invention is shown, in which the MEMS microspeaker further comprises a waveguide 65. The waveguide regulates the path of the output sound of the microspeaker. Figure 6 In the example shown, the waveguide is a cap-shaped cover, preferably a silicon cap-shaped cover, coupled to the cover 60. The waveguide 65 applicable to the present invention includes any material, shape and form as long as the waveguide 65 can guide the sound generated by the micro speaker to one or more predetermined directions. Fig. 7A and Figure 7B Two examples of the shape and structure of the waveguide are shown respectively. Each example is characterized by the direction of the output sound, as shown by the arrows in the figures. Other materials besides silicon, such as metals, ceramics, glass, etc., can also be used to make the waveguide.

[0090] Figure 8 A third embodiment of the present invention is shown, in which a magnetic ring of a hard magnet 51 is attached to a package cover 60 and is located directly above the planar coil 31. In this structure, the sound of the speaker is emitted from the second substrate 20 side. In a preferred embodiment, the width (diameter) of the opening 25 of the second substrate 20 may be the same as the width of the air cavity 15. Fig. 9 In the fourth embodiment of the invention shown, no cover is used to cover the package. The waveguide 65 is preferably a cap-shaped cover with through holes 66, preferably through silicon vias (TSVs), provided therein for providing electrical connection to the top side of the speaker.

[0091] In some embodiments of the present invention, two or more planar coils are provided and embedded in a diaphragm.

[0092] Figures 10A-10C is a cross-sectional view and shows several possible combinations of multiple planar coils and multiple hard magnets used in some embodiments of the present invention. As shown in the figure, the coil module includes a small-sized membrane and a large-sized membrane. Fig. 10A An embodiment is shown in which the microspeaker comprises two hard magnets arranged in the same polarity sequence, Fig. 10B An embodiment showing a similar structure but with two hard magnets arranged in opposite polarity order is shown, while Fig. 10C It is shown that the micro speaker includes a hard magnet and a solid cylindrical magnet, and the polarity directions of the two are orthogonal.

[0093] In some embodiments of the present invention, a module consisting of two or more micro-speaker or coil modules may be provided and prepared in a single process.

[0094] Figures 11A-11B are plan views and illustrate two possible combinations of multiple micro-speakers used in some embodiments of the present invention. As shown in these figures, the multiple micro-speakers include at least one micro-speaker with a lower frequency bandwidth and one micro-speaker with a higher frequency bandwidth. Fig.11AIn the case of the 1 woofer, 1 midrange and 2 tweeters are formed in one coil module. Fig. 11B In the embodiment, two speakers are formed in the same membrane and respectively include a first coil 33 having a smaller size / diameter and a second coil 34 having a larger size / diameter and arranged outside the first coil 33. In a coil module having multiple coils, the materials for the multiple coils and / or multiple soft magnets can be applied to the substrate or membrane layer in one process step or in different process steps. The multiple coils can be formed in separate membranes or can share a vibrating membrane. The materials of the multiple coils and / or multiple soft magnets can be the same or different. Fig. 11B In the example of, the first coil 33 can provide a pad (not shown) for connecting a lead or wire in a direction perpendicular to the plane of the coil. Preferably, the pad can extend to form a lead that spans above or below the second coil 34 and terminates outside the second coil 34 to connect a lead or wire.

Claims

1. A micro speaker, comprising: A coil module, the coil module comprising: a diaphragm suspended in an air cavity defined and supported by the first substrate; at least one planar coil embedded in the diaphragm; and at least one soft magnet embedded in the diaphragm and arranged around at least a portion of the contour of the planar coil, wherein most of the planar coil is located on substantially the same plane as a plane on which a portion of the soft magnetic body is disposed, The micro speaker further comprises: a second substrate coupled to the substrate of the coil module at a side of the air cavity opposite to the vibration membrane to support the coil module and define the air cavity; a cover surrounding the diaphragm; and At least one hard magnet is attached to the cover, the at least one hard magnet extending from a position corresponding to the at least one planar coil into a space between the cover and the diaphragm. 2 . The microspeaker of claim 1 , wherein the second substrate is provided with at least one opening. 3 . The microspeaker of claim 2 , wherein the opening of the second substrate has the same width as the air cavity. 4 . The microspeaker of claim 1 , wherein the hard magnet is in a ring shape, and a diameter of the hard magnet is larger than a diameter of the at least one planar coil.

5. The microspeaker of claim 1, further comprising a waveguide located above the diaphragm. 6 . The microspeaker of claim 5 , wherein the waveguide is formed in a hat shape and is coupled to the second substrate to standardize a path for outputting sound from the microspeaker.

7. A microspeaker as claimed in claim 6, wherein the waveguide is a silicon cap.

8. The microspeaker of claim 5, wherein the waveguide provides at least one through hole for connecting an electrical contact to the planar coil. 9 . The microspeaker according to claim 1 , wherein the planar coil forms a planar pattern, and the soft magnetic body comprises at least one strip arranged along a portion of an outer contour or an inner contour of the planar pattern.

10. The microspeaker according to any one of claims 1 to 8, wherein the planar coil comprises at least one multi-layer structure and / or the soft magnetic body comprises at least one multi-layer structure.

11. The micro-speaker according to any one of claims 1 to 8, wherein the material of the first substrate is selected from silicon, rubber, plastic, polymer, resin, wood, ceramic, glass, paper or any combination thereof.

12. The microspeaker according to any one of claims 1 to 8, wherein the planar coil is a metal coil or a metal alloy coil selected from a Cu coil, an Ag coil or an Al coil.

13. The micro-speaker according to any one of claims 1 to 8, wherein the material of the soft magnetic body is selected from Fe, Co, Ni or alloys thereof. 14 . The microspeaker according to claim 1 , wherein the vibration membrane is selected from one of a PDMS membrane and a polyparaxylene / graphene / polyparaxylene composite membrane.

15. The micro-speaker according to any one of claims 1 to 8, wherein the planar coil is a spiral structure, and the spiral structure includes at least one outer ring and an inner ring connected in series. 16 . The microspeaker of claim 15 , wherein the planar coil further comprises at least one ring, the ring being disposed between the outer ring and the inner ring and connected to the outer ring and the inner ring.

17. The micro-speaker as claimed in claim 16, wherein the planar coil further comprises a soft magnetic body arranged between the outer ring and the inner ring, and a pattern formed by the soft magnetic body between the outer ring and the inner ring has a shape corresponding to the adjacent outer ring and / or inner ring.

18. The microspeaker according to any one of claims 1 to 8, wherein the planar coil comprises a plurality of circular rings connected in series and arranged in layers.

19. The micro-speaker of claim 18, wherein the planar coil further comprises a soft magnetic body disposed between two coil layers, wherein: The pattern formed by the soft magnetic material between the two coil layers has a shape corresponding to the upper and / or lower coil layers.

20. The microspeaker according to any one of claims 1 to 8, wherein the planar coil forms a coil pattern, the outer contour of which is circular, elliptical, square, pentagonal or hexagonal.

21. The microspeaker according to any one of claims 1 to 8, wherein the soft magnetic body is disposed in a material layer other than a material layer of the planar coil, and a majority of the planar coil is located on substantially the same plane as a plane on which a portion of the soft magnetic body is disposed.

22. The microspeaker according to any one of claims 1 to 8, wherein: The coil module includes a first planar coil and a second planar coil.

23. The microspeaker of claim 22, wherein the first planar coil and the second planar coil are driven by at least two independent drivers.

24. The microspeaker of claim 22, wherein the first planar coil is disposed within an area defined by the second planar coil.

25. The microspeaker of claim 24, wherein the first planar coil and the second planar coil are concentric.

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