TWI419575B - Thermal sound generating device and preparation method thereof - Google Patents

Description

Thermal sound generating device and preparation method thereof

The invention relates to a thermal sound generating device and a preparation method thereof, in particular to a metal-based thermal sound generating device and a preparation method thereof.

The sounding device generally consists of a signal input device and a sounding component, and a signal is input through the signal input device to the sounding component to emit a sound. The thermoacoustic device is one of the sounding devices, which is a sounding device based on the principle of thermoacoustic effect. The prior art thermoacoustic device uses a metal material having a lower heat capacity as a sounding element.

HDArnold and IBCrandall disclose in the document "The thermophone as a precision source of sound", Phys. Rev. 10, p22-38 (1917) a simple thermoacoustic device comprising a platinum sheet as a sounding element, a clamp disposed at both ends of the platinum sheet for holding the platinum sheet to be suspended, and a signal input device electrically connected to the platinum sheet. The thermoacoustic device realizes sound generation by introducing an alternating current into the platinum sheet. The platinum sheet has a thin thickness and a thickness value of 0.7 μm, so that the platinum sheet has a small heat capacity per area, so that when an alternating current passes through the platinum sheet, the inside thereof is generated. Heat is quickly transferred to the surrounding air by heat exchange, which causes the surrounding air molecules to move and emit sound waves.

However, in the prior thermal sounding device, due to the limitation of the metal preparation process, it is difficult to form a metal sheet which can be suspended and has a smaller thickness, so that the heat capacity per unit area of the metal piece cannot be made small, thereby The low intensity of the previous thermal sounding device limits its practical application.

In view of the above, it is necessary to provide a thermo-acoustic device having a high vocal intensity and a method of preparing the same.

A thermal sounding device comprising: a signal input device; and a sound emitting element, the sound emitting element comprising a metal film, wherein the metal film is electrically connected to the signal input device; wherein the sound emitting element further comprises a substrate and a plurality of microstructures disposed on the substrate, the metal film is disposed on the plurality of microstructures and supported by the plurality of microstructures, and the metal film is suspended relative to the substrate, and the signal input device inputs a signal to The metal film emits sound waves by heating the surrounding gas medium through the metal film.

A method for preparing a thermo-acoustic device, comprising: providing a substrate having a surface; forming a plurality of microstructures on a surface of the substrate; forming a sacrificial layer on a surface of the substrate to fill the plurality a gap between the microstructures; forming a metal film on the surface of the sacrificial layer; heating the sacrificial layer until the sacrificial layer is completely decomposed to form a sounding element; providing a signal input device to enable the signal input device Electrically connected to the metal film to form a thermo-acoustic device.

Compared with the prior art, in the thermal sound generating device, the metal film is suspended by the plurality of microstructures and the surface of the substrate, so that the metal film and the surrounding The air or other gaseous medium can be subjected to sufficient heat exchange; at the same time, the metal film having a smaller thickness and a smaller heat capacity per unit area can be prepared by the preparation method of the present invention, so that the thermoacoustic device of the present invention has a higher temperature. The intensity of the sound.

10,20‧‧‧Thermal sounding device

12,22‧‧‧Signal input device

14,24‧‧‧Acoustic components

15,25‧‧‧Metal film

16,26‧‧‧ base

162,262‧‧‧ surface

17,27‧‧‧Microstructure

18, 28‧‧‧ electrodes

19,29‧‧‧Wire

1 is a schematic structural view of a thermo-acoustic device according to a first embodiment of the present invention.

2 is a flow chart of a method for preparing a thermoacoustic device according to a first embodiment of the present invention.

3 is a schematic structural view of a thermo-acoustic device according to a second embodiment of the present invention.

Hereinafter, a thermoacoustic sounding device and a method of manufacturing the same according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1 , a first embodiment of the present invention provides a thermo-acoustic device 10 . The thermo-acoustic device 10 includes a signal input device 12 , a sound emitting element 14 , and at least two electrodes 18 .

The sounding element 14 includes a substrate 16, a plurality of microstructures 17, and a metal film 15. The substrate 16 has a surface 162. The microstructure 17 is disposed on the surface 162 of the substrate 16. The metal film 15 is disposed on the surface. The plurality of microstructures 17 are disposed by the plurality of microstructures 17 and the surface 162 of the substrate 16 are suspended. The at least two electrodes 18 are spaced apart and electrically connected to the metal film 15. The at least two electrodes 18 are electrically connected to the two ends of the signal input device 12 via external wires 19 for inputting the electrical signals in the signal input device 12 into the sound emitting element 14.

The substrate 16 mainly functions to support the microstructure 17 and the metal film 15, and the shape thereof is not limited, and any object having a certain shape can be used as the substrate in the embodiment. 16. In this embodiment, the plurality of microstructures 17 are a plurality of micro protrusions of the substrate 16 itself, and the metal film 15 is directly disposed on the plurality of protrusions, and the plurality of protrusions and the substrate 16 are The surface 162 is suspended. The material of the substrate 16 is not limited. In this embodiment, the material of the substrate 16 is a rigid or flexible insulating material, such as diamond, glass, quartz plastic or resin. Preferably, the material of the substrate 16 should have better materials. The heat insulating property prevents the heat generated by the metal film 15 from being excessively absorbed by the substrate 16, so that the purpose of heating the surrounding gas medium and sounding cannot be achieved.

The contact area of the metal film 15 with each of the microstructures 17 should be less than 1 square micrometer, so that the metal film 15 has a large contact area with ambient air or other external gas or liquid medium as much as possible, and has as large as possible. The heat dissipation area can further improve the sounding effect of the sounding device 10 to some extent. Meanwhile, the shortest distance between the two contact positions of the microstructure 17 and the metal film 15 should be less than 1 micrometer to ensure that the metal film 15 is uniformly supported by the microstructure 17, and Will deform under the influence of gravity. Since the metal film 15 is supported by the substrate 16 and the microstructure 17, the metal film 15 can withstand high-intensity signal input without being deformed, thereby having a high vocal intensity.

The material of the metal film 15 is a material having low heat capacity or good ductility, and may be iron, nickel, cobalt, platinum, copper, silver, gold, palladium, aluminum, ruthenium, copper or lead. Since the metal film 15 is supported by the substrate 16 and the plurality of microstructures 17, the thickness of the metal film 15 can be extremely thin and is not easily deformed during operation. In the embodiment, the thickness of the metal film 15 can be less than 0.7 μm. At the same time, since the heat capacity per unit area is related to the type of the material itself, it is also related to the thickness of the material, that is, the metal film 15 formed of the same material, the larger the thickness, the larger the heat capacity per unit area, and the smaller the thickness. The smaller the heat capacity per unit area, the smaller the heat capacity per unit area of the metal film 15 having a smaller thickness, the smaller the heat capacity per unit area can be less than 2 x 10 ^-4 joules per square centimeter Kelvin. The sound emission frequency of the metal film 15 is closely related to the heat capacity per unit area, that is, the larger the heat capacity per unit area of the metal film 15, the narrower the sound frequency range and the lower the sound intensity; on the contrary, the smaller the heat capacity per unit area, The wider the audible frequency range, the higher the vocal intensity. It can be seen that the sound emitting element 14 having the metal film 15 having a small thickness in the sounding device 10 of the present embodiment has a wide sounding frequency range and a high sounding intensity.

The at least two electrodes 18 are formed of a conductive material, and the specific shape structure thereof is not limited. In particular, the at least two electrodes 18 may be selected as layers, rods, blocks or other shapes. The material of the at least two electrodes 18 may be selected from a metal, a conductive paste, a metallic carbon nanotube, an indium tin oxide (ITO), or the like. In this embodiment, the electrode 18 is two rod-shaped metal electrodes, and the electrode 18 is used to realize electrical connection between the signal input device 12 and the sound emitting element 14. The electrode 18 is fixedly disposed on the surface of the metal film 15 . Specifically, the at least two electrodes 18 can be fixed to the metal film 15 through a conductive adhesive and can be electrically connected. The conductive adhesive can be silver glue. . Preferably, the length of the electrode 18 in this embodiment is equal to the width of the metal film 15, so that the audio signal is conducted into the entire metal film 15. In addition, the at least two electrodes 18 are optional components of the thermoacoustic device 10. Since the metal film 15 is electrically conductive, the signal input device 12 can also be directly electrically connected to the metal film, thereby further audio. The electrical signal is directly input to the sound emitting element 14.

The signal input device 12 can be electrically connected to the metal film 15 directly through a wire or an electrode lead or the like, or can be electrically connected to the metal film 15 through the electrode 18 indirectly. It is only necessary to ensure that the signal input device 12 can input an electrical signal to the metal film 15 can. Any manner of achieving electrical connection between the signal input device 12 and the metal film 15 is within the scope of the present invention.

The signal input by the signal input device 12 includes an audio signal and the like. The signal input device 12 is electrically connected to the electrode 18 via a wire 19, and a signal is input into the sounding element 14 through the electrode 18.

When the sound emitting device 10 is in use, since the metal film 15 has a small thickness, a small heat capacity, and a large heat dissipating surface, the metal film 15 can rapidly rise and fall after the signal is input, and the periodicity is generated. The temperature changes and exchanges heat with the surrounding gas medium rapidly, so that the surrounding gas medium rapidly expands and contracts, which makes the human ear perceive the sound, and the sound frequency is wide, which can reach 20 Hz to 100,000 Hz. The vocal intensity can exceed 60 decibels per watt of sound pressure level, and the sounding effect is better. Therefore, in the embodiment, the sounding device 10 has a wide range of applications. In addition, since the metal film 15 in the embodiment is supported by the substrate 16 and the plurality of microstructures 17, it is not easily deformed or damaged, and can withstand high-intensity signal input, and has a long service life.

Referring to FIG. 2, the present invention provides a method for fabricating the sounding device of the first embodiment, which specifically includes the following steps: Step 1: providing a substrate having a surface; and Step 2, forming a plurality of surfaces on the surface of the substrate The microstructure is characterized in that a plurality of micro protrusions are etched on the surface of the substrate by an etching process to form a plurality of microstructures, such as photolithography, electron beam etching or ion beam etching.

Step 3, forming a sacrificial layer on the surface of the substrate to fill a gap between the plurality of microstructures; the material of the sacrificial layer is an organic material having a lower decomposition temperature, and the decomposition temperature is lower than the substrate and The melting point of the metal film in the sounding device is preferably an organic material which can be completely decomposed below 450 ° C, such as acrylic resin or nitrocellulose. This embodiment is an acrylic resin. The thickness of the sacrificial layer is not limited.

The preparation method of the sacrificial layer specifically includes: firstly, providing an organic polymer solution composed of a polymer, a plasticizer, a solvent and a cosolvent according to a certain proportion. The polymer includes polyisobutyl methacrylate and acrylic B-72 resin, the plasticizer may be dibutyl phthalate, and the solvent includes ethyl acetate and butyl acetate, the co-solvent Including anhydrous ethanol and n-butanol, the specific configuration of the polymer solution in this embodiment is shown in Table 1; secondly, the polymer solution is uniformly applied to the substrate by manual coating or spin coating. The surface is allowed to stand for a while to form a sacrificial layer. In addition, in the preparation method, in order to reduce the surface tension of the solid, it is advantageous for the polymer solution to spread and spread on the specific surface, or the uneven substrate may have a smooth surface, and the polymer may be further coated. The substrate is wetted with water or water solution for 1 minute to 10 minutes before the solution.

Table 1 Polymer solution group distribution ratio

Step 4, forming a metal film on the surface of the sacrificial layer; the material of the metal film is a metal material having low heat capacity or good ductility, such as iron, nickel, cobalt, silver, copper, gold, palladium, aluminum,铍, indium, platinum or lead, the specific preparation method of the metal film is physical vapor deposition method such as vacuum evaporation method or magnetron sputtering method. By this method, a metal film having a small thickness can be formed on the surface of the sacrificial layer, and the metal film can be prevented from being directly formed on the substrate and integrated with the substrate.

Step 5, heating the sacrificial layer until the sacrificial layer is completely decomposed to form the sounding element; heating the sacrificial layer between the substrate and the metal film until the sacrificial layer is completely decomposed, and the sacrificial layer is decomposed In the thinning of the thickness of the sacrificial layer, the metal film formed on the surface of the sacrificial layer is gradually lowered by the action of gravity, so that the metal film is in contact with the microstructure of the substrate. Since the decomposition temperature of the sacrificial layer is lower than the melting point of the metal film and the substrate, when the sacrificial layer is completely decomposed The metal film and the substrate are not melted, and the phenomenon of bonding to each other due to melting does not occur. Therefore, after the sacrificial layer is removed, the surface of the metal film and the substrate will be suspended by the plurality of microstructures, so that the metal film has a larger contact area with air or other external gas or liquid medium.

Further, the step further includes providing at least two electrodes which are bonded and fixed to the surface of the sound emitting element, that is, the metal film, by a conductive adhesive.

In step six, a signal input device is provided to electrically connect the signal input device to the sound emitting element to form a thermal sound generating device.

In this step, the signal input device may be an audio input device such as an MP3 or a radio, or a power amplifier, etc., which may directly connect the signal input device to the metal film through a wire, or indirectly input the signal into the device. Electrical connection is made to the metal film by at least two electrodes, and the signal input device and the electrode are connected by wires.

In this embodiment, the preparation method forms a plurality of microstructures on the surface of the substrate, and then forms a sacrificial layer to fill the gap between the plurality of microstructures, and deposits a thin thickness on the surface of the sacrificial layer. The metal film is then removed by heating to obtain the sounding element. It can be seen that, in the whole process, the sacrificial layer can be removed by heating, so that the metal film can be self-supported through the plurality of microstructures and the surface portion of the substrate is suspended, so that the self-supporting system does not need to be By supporting a support, it is also possible to maintain its own specific shape without damage. That is, the metal film portion is supported by the plurality of microstructures, partially suspended from the support, and the partially suspended metal film can be formed in situ, so-called In-situ formation means that the relative displacement of the metal film to the substrate and the plurality of microstructures is small during the implementation of the dangling arrangement, and the relative position thereof is approximately fixed. Therefore, the formation process does not easily cause damage to the metal film having a relatively small thickness due to a change in the relative position of the substrate and the plurality of microstructures, and the metal film may be suspended at the same time. It can be seen that the preparation method of the present invention allows a metal film having a relatively thin thickness to be partially suspended by a plurality of microstructures. The metal film of the same material has a smaller thickness than the metal film having a larger thickness, a smaller heat capacity per unit area, a wider sounding frequency range, and a higher sounding intensity. The plurality of microstructures provide a plurality of supports for the metal film, so that the sounding device is not easily broken during use, and at the same time, the surface of the substrate and the metal film are suspended, thereby ensuring that the metal film has the largest possible heat dissipation. The area has an ideal sounding effect.

Referring to FIG. 3, a second embodiment of the present invention provides a thermo-acoustic device 20 including a signal input device 22, a sounding element 24, and at least two electrodes 28.

The sounding element 24 includes a substrate 26, a plurality of microstructures 27, and a metal film 25. The substrate 26 has a surface 262. The microstructures 27 are disposed on the surface 262 of the substrate 26. The metal film 25 is disposed on the surface. The plurality of microstructures 27 are disposed by the plurality of microstructures 27 and the substrate 26 are suspended. The at least two electrodes 28 are spaced apart and electrically connected to the metal film 25. The at least two electrodes 28 are electrically connected to the two ends of the signal input device 22 via external wires 29 for inputting the electrical signals in the signal input device 22 into the sound emitting element 24.

The structure of the present embodiment is substantially the same as that of the thermo-acoustic device 10 of the first embodiment described above, except that the microstructures 27 of the present embodiment are particles, and the metal film 25 is disposed on the plurality of particles.

The particles are uniformly dispersed on the surface 262 of the substrate 26, the particles having a diameter of less than 1 micron. The material of the particles is not limited and may be a hard material such as diamond, glass or quartz. Preferably, the material of the plurality of particles should have better thermal insulation properties, so that the heat generated by the metal film 25 is prevented from being excessively absorbed by the plurality of particles, and the purpose of heating the surrounding gaseous medium and sounding is not achieved. Further, the surface 262 of the substrate 26 may be provided with an adhesive layer for bonding and fixing the plurality of particles. The type of the adhesive to be selected for the adhesive layer is not limited, and it is only necessary to ensure that the plurality of particles in the embodiment are uniformly fixed to the surface 262 of the base 26.

Referring to FIG. 4, the present invention provides a method for fabricating the sound generating device according to the second embodiment, which specifically includes the following steps: Step 1: providing a substrate having a surface; and Step 2, forming a plurality of surfaces on the surface of the substrate a microstructure; step 3, forming a sacrificial layer on the surface of the substrate to fill a gap between the plurality of microstructures; and step 4, forming a metal film on the surface of the sacrificial layer; and step 5, heating the sacrificial layer Until the sacrificial layer is completely decomposed to form the sound emitting element; and in step 6, a signal input device is provided to electrically connect the signal input device to the sound generating element to form a thermo-acoustic device.

The preparation method of the sounding device of the embodiment is basically the same as the preparation method of the sounding device of the first embodiment, and the difference is that the steps of the method for preparing the sounding device of the embodiment The plural microstructures formed by the two are particles. Specifically, first, an adhesive layer is coated on the surface of the substrate; secondly, a plurality of particles are provided, and the plurality of particles are uniformly dispersed on the surface of the adhesive layer, so that the plurality of particles are fixed to the substrate The surface, thereby forming a plurality of microstructures.

The thermal sound generating device and the preparation method thereof provided by the embodiments of the present invention have the following advantages: since the metal film in the thermal sound generating device is supported by the substrate and the plurality of microstructures, the thickness of the metal film can withstand even if the thickness is small. Higher signal input without deformation, so as to have higher vocal intensity; the metal film prepared by the preparation method of the invention may have a thickness of less than 0.7 micron, and the smaller the thickness, the smaller the heat capacity per unit area, the invention The heat capacity per unit area can be less than 2×10 ^-4 joules per square centimeter Kelvin, and the sound frequency of the metal film is closely related to the heat capacity per unit area. The smaller the heat capacity per unit area, the wider the sound frequency range and the higher the sound wave intensity. Therefore, the sounding device of the present invention has a wide range of sounding frequencies and a high sounding intensity; the preparation method of the present invention can make the prepared metal film and the surface of the substrate be suspended, so that the contact area between the metal film and the surrounding medium is large, and the work is performed. The metal film can rapidly exchange heat with the surrounding medium and rapidly expand and contract the surrounding medium, thereby giving the human ear a feeling. It sounds.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application of the present invention. Equivalent modifications or variations made by persons skilled in the art in light of the spirit of the invention are intended to be included within the scope of the following claims.

10‧‧‧Thermal sounding device

12‧‧‧Signal input device

14‧‧‧ Sounding components

15‧‧‧Metal film

16‧‧‧Base

162‧‧‧ surface

17‧‧‧Microstructure

18‧‧‧ electrodes

19‧‧‧Wire

Claims (25)

A thermoacoustic device comprising: a signal input device; and a sound emitting element comprising a metal film, wherein the metal film is electrically connected to the signal input device; and the improvement is that the sound emitting device further comprises a a substrate and a plurality of microstructures disposed on the substrate, the metal film is disposed on the plurality of microstructures and supported by the plurality of microstructures, and the metal film is suspended relative to the substrate portion, the signal input device inputs The electric signal is given to the metal film, and the surrounding gas medium is heated by the metal film to emit sound waves. The thermal sound generating device of claim 1, wherein the metal film has a heat capacity per unit area of less than 2 x 10 ^-4 joules per square centimeter Kelvin. The thermoacoustic device according to claim 1, wherein the material of the metal film is iron, nickel, cobalt, platinum, copper, silver, gold, palladium, platinum, rhodium, indium, aluminum or lead. The thermal sound generating device of claim 1, wherein the metal film has a thickness of less than 0.7 μm. The thermal sound generating device of claim 1, wherein a contact area of the microstructure with the metal film is less than 1 square micrometer. The thermal sound generating device of claim 5, wherein a shortest distance between two adjacent microstructures and a contact position of the metal film is less than 1 micrometer. The thermal sound generating device of claim 1, wherein the substrate has a surface, and the microstructure is uniformly disposed on a surface of the substrate. The thermoacoustic device of claim 7, wherein the microstructure is a particle. The thermal sounding device of claim 8, wherein the sound emitting element further comprises an adhesive layer disposed on the surface of the substrate for bonding and fixing the particles. The thermal sound generating device of claim 8, wherein the material of the particles is a heat insulating material comprising diamond, glass, quartz, plastic or resin. The thermal sound generating device of claim 7, wherein the microstructure is a protrusion formed by roughening the surface of the substrate. The thermal sounding device of claim 1, wherein the microstructured material is an insulating material. The thermo-acoustic device according to claim 1, wherein the thermo-acoustic device further comprises at least two electrodes spaced apart from each other and electrically connected to the metal film. The thermal sound generating device of claim 12, wherein the at least two electrodes are further electrically connected to both ends of the signal input device by wires. A thermal sound generating device comprising: a signal input device; and a sound emitting element, the sound emitting element further comprising: a substrate having a surface; a plurality of microstructures disposed on the surface of the substrate; and a metal film, the metal The film is disposed at a distance from the substrate through the plurality of microstructures. The metal film is electrically connected to the signal input device, and the signal input device inputs a signal to the metal film, and the surrounding gas medium is heated by the metal film to emit sound. A method for preparing a thermoacoustic device, comprising the steps of: providing a substrate having a surface; forming a plurality of microstructures on a surface of the substrate, wherein the plurality of microstructures have a gap therebetween; and a surface of the substrate Forming a sacrificial layer filling a gap between the plurality of microstructures; forming a metal film on a surface of the sacrificial layer; heating the sacrificial layer until the sacrificial layer is completely decomposed to form a sounding element; A signal input device electrically connects the signal input device to the metal film to form a thermo-acoustic device. The method of producing a thermoacoustic device according to claim 16, wherein the microstructure is a particle. The method of producing a thermoacoustic device according to claim 17, wherein an adhesive layer is formed on the surface of the substrate before the particles are formed. The method for producing a thermoacoustic device according to claim 16, wherein the microstructure is a protrusion of the substrate itself. The method of producing a thermoacoustic device according to claim 19, wherein the protrusion is formed by an etching process. The method for producing a thermoacoustic device according to claim 16, wherein the method of forming the metal film is a magnetron sputtering method or an evaporation method. The method for preparing a thermal sound generating device according to claim 16, wherein the method for forming a sacrificial layer comprises the steps of: providing an organic polymer solution, the organic polymer solution being polymerized according to a certain ratio Materials, plasticizers, solvents and solubilizers The composition of the agent; the organic polymer solution is applied to the surface of the substrate by a manual coating method or a spin coating method. The method for producing a thermoacoustic device according to claim 22, wherein before the applying the organic polymer solution to the surface of the substrate, the method further comprises: wetting the substrate with a solution of water or water; The surface is 1 minute to 10 minutes. The method for producing a thermoacoustic device according to claim 16, wherein the material of the sacrificial layer is an organic material having a low decomposition temperature. The method for producing a thermo-acoustic device according to claim 24, wherein the low decomposition temperature organic material is acrylic resin or nitrocellulose.