JP2007113654A - Fine hollow structure diaphragm and its application element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diaphragm capable of generating a large displacement without complicating its structure and to structure an element of a microactuator having a large displacement by using the diaphragm. <P>SOLUTION: A large deflection is generated and a large displacement is obtained by making a flexible part of a minute diaphragm in a fine hollow structured shape. By making the shape of the fine hollow structure annular, or a fine double hollow structured shape comprising the fine hollow structure at the center and an annular fine hollow structure surrounding the fine hollow structure at the center, the displacement of the fine diaphragm can be enhanced. By structuring the flexible part of the fine hollow structure by a metallic glass film, an elastic deformation range can be made large, and the diaphragm can be manufactured without complicating the process too much. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a micro-diaphragm having a micro-hollow structure in a flexible part and its applied element.

  A flat disk-shaped diaphragm is a fluid actuator that produces deflection as an output displacement of the deflection generated in the disk by the pressure of the fluid, or a piezoelectric element that causes the disk to bend and change the volume inside the disk to change the volume. The pump is often used for a pump for pushing out or a valve having an elastic support element in a sealed structure.

  In recent years, with the development of micromachining, there has been a demand for a microdiaphragm having higher performance with a microscopic dimension. An ordinary diaphragm having a flat disk shape cannot obtain a large amount of displacement due to deflection due to an in-plane pulling force of the disk. For this reason, it has been difficult to increase the output displacement of the actuator, increase the discharge amount of the pump, or increase the stroke of the valve body of the valve using such a diaphragm.

Therefore, as a method for increasing the amount of displacement due to bending, a diaphragm in which an axisymmetric waveform is formed on a flat disk has been proposed (Non-Patent Document 1). However, in order to form a waveform on a micro-diaphragm, for example, a micro-fabrication technique as shown in Patent Document 1 is used, so that the number of steps is complicated and it is difficult to obtain a high yield. There is a problem that the structure of the diaphragm manufactured by the method becomes complicated.
JP-A-5-1669 I. Chakraborty, WG Tan, DP Bame, and T. K, Tang, MEMS Micro-valve applications, Sensors aaaand Actuators, Vol. 83, pp. 188-193, (2000)

  The present invention solves the problems of the conventional diaphragm described above, and provides a diaphragm capable of generating a large amount of displacement without complicating the structure. By using this diaphragm, a large output displacement is caused by the pressure of the fluid. It is intended to make it possible to obtain a large discharge amount as a fluid actuator that can obtain a fluid, a pump that pushes out fluid by driving a piezoelectric element, etc., and a large stroke of a valve body of a valve as a valve .

  The present inventor has found that, as a method of increasing the amount of bending of the micro-diaphragm, a large deflection can be generated by making the flexible portion into a micro hollow structure (so-called dome shape). As the shape of the fine hollow structure, the plan view is formed in a circular axisymmetric structure, and it has been found that the amount of deflection can be further increased by forming an annular structure having a bulge in the circular peripheral portion. Moreover, it discovered that it was preferable to form such a fine hollow structure shape with a metallic glass. Further, it has been found that a large displacement can be obtained by using such a micro diaphragm for a fluid actuator, and the present invention has been made.

  The micro-diaphragm of the present invention is characterized in that a flexible portion having a micro hollow structure is formed on a substrate.

  It was found that a large amount of displacement can be generated without complicating the structure by making the flexible portion into the shape of a fine hollow structure.

  In the present invention, the flexible portion can be formed into an annular fine hollow structure. Here, the shape of the annular fine hollow structure is a shape in which the flexible portion of the diaphragm having a circular plane is formed in an annular shape along the circumference. In addition, the flexible part may be formed into a fine double hollow structure formed of a central fine hollow structure and an annular fine hollow structure surrounding the central fine hollow structure. Furthermore, the flexible part may be formed into a fine multiple hollow structure formed of a central fine hollow structure and a plurality of annular fine hollow structures surrounding the central fine hollow structure. However, the micro-diaphragm of the present invention does not require a very complicated multiple structure.

  It was found that such a relatively simple fine hollow structure shape can generate a large amount of displacement as a diaphragm.

  It is desirable to form such a flexible portion having the shape of the fine hollow structure by using metallic glass. By constructing the micro hollow structure of the flexible part with a film of metallic glass, the elastic deformation range can be increased compared to a crystalline metal alloy film, and a larger displacement can be obtained as a diaphragm. all right.

  In addition, a fluid actuator can be configured by driving the microdiaphragm of the present invention with a fluid pressure.

  According to the present invention, it is possible to generate a large amount of displacement by making the flexible portion of the micro diaphragm a micro hollow structure. Such a fine hollow structure can be formed without making the manufacturing process complicated by using metallic glass. Further, by using the micro-diaphragm of the present invention for a fluid actuator, a fluid actuator capable of obtaining a large output displacement, a fluid pump capable of obtaining a large discharge amount, or a valve capable of obtaining a large stroke of a valve body can be configured.

  Next, further details of the present invention will be described by describing embodiments of the present invention.

  1 to 3 are diagrams schematically showing an embodiment of the shape of a fine hollow structure used for the flexible part of the diaphragm of the present invention, and FIG. 2 shows an annular fine hollow structure shape, and FIG. 3 shows a double fine hollow structure shape. In each figure, (a) is a schematic plan view, and (b) is a schematic cross-sectional view. is there.

  In FIG. 1, a single fine hollow structure shape 11 of a flexible portion of a diaphragm 10 is formed on a flat substrate 12. In FIG. 2, an annular fine hollow structure shape 13 is formed on the flat substrate 12 along the circumference of the flexible portion of the diaphragm 10. Further, in FIG. 3, an annular fine hollow structure shape 13 and a fine hollow structure 14 at the center along the circumference of the flexible portion of the diaphragm 10 are formed on the flat substrate 12.

  Such a fine hollow structure shape can be manufactured without using a complicated process by using, for example, metallic glass and using the method described in JP-A-2004-58261.

  First, a sacrificial layer is formed on a substrate such as silicon. Next, a thin film layer of metallic glass that is softened by heat is formed thereon and the sacrificial layer is covered. However, the portion of the sacrificial layer that becomes an opening with respect to the hollow portion formed by removing the sacrificial layer is left uncovered with a thin film. Subsequently, the sacrificial layer is removed by etching, and a hollow portion is formed between the substrate and the thin film layer. A portion of the sacrificial layer left without being covered with the thin film is used as an opening, and the sacrificial layer is removed by etching through the opening. The opening is closed by forming a film for closing the opening, for example, and forms an enclosed portion of the closed space. If the thin film formation for closing the opening is performed by sputtering using a rare gas having a predetermined pressure, the rare gas can be included in the closed space as it is.

  By heating the microplanar structure formed with the encapsulating portion containing the gas in this way, softening the metallic glass thin film, and lowering the atmospheric pressure outside the closed space containing the gas, By inflating and deforming, a micro hollow three-dimensional structure in which the inner packet part expands and is three-dimensionalized is formed.

  By heating the metallic glass thin film to the supercooled liquid region between the glass transition point and the crystallization temperature and utilizing the viscous flow in this region, the shape of the fine hollow structure can be formed by the expansion and deformation of the thin film. it can. As the metallic glass for forming such a thin film, Zr-based metallic glass (such as Zr-Cu-Al) and Pd-based metallic glass (such as Pd-Cu-Si) can be used, and other metallic glasses. For example, a thin film of metallic glass of each group such as Cu group, Fe group, and Au group can be used. The film forming conditions for obtaining a high-quality metallic glass thin film suitable for the object of the present invention are described in detail in the Journal of Precision Engineering, Vol. 67, 1708-1713 (2001).

  As the sacrificial layer used here, any sacrificial layer can be used as long as the sacrificial layer can be selectively removed by etching, and a metal such as chromium, silicon oxide, glass, resist, or the like can be used.

  Instead of the sacrificial layer, a gas generating agent capable of generating gas by heat treatment can be used. That is, a fine planar structure in which a gas generating agent pattern is formed on a substrate, a thin film layer that is then softened by heat is formed thereon, and the gas generating agent is covered with the thin film layer. Can be used to form a fine hollow structure. When a gas generating agent is used, it is not necessary to remove by etching after forming a thin film as in the case where a sacrificial layer is provided, so that the manufacturing process is simplified and a relatively high pressure can be obtained. . As the gas to be enclosed in the hollow portion for expanding the thin film to form a fine hollow structure, a non-corrosive gas such as nitrogen gas or rare gas is preferable. As already described, a rare gas such as argon used for sputtering during film formation can be enclosed and used as it is. When the thin film is heated and expanded and molded, the pressure value of the gas to be sealed may be any pressure value necessary for the expansion of the film with respect to the outside when the thin film is heated and expanded and molded.

  The single fine hollow structure shown in FIG. 1 can be manufactured using the above technique. The annular fine hollow structure in FIG. 2 is provided with a sacrificial layer at the position of the central flexible portion, and a disk-shaped metal glass thin film is formed thereon, and the sacrificial layer of the disk-shaped metal glass thin film is formed. After the portion that hits the outside is expanded by the above-described technique, it can be manufactured by removing the sacrificial layer. The double fine hollow structure in FIG. 3 is provided with a sacrificial layer at the position of an annular plane portion between the central fine hollow structure and the annular fine hollow structure surrounding the fine hollow structure. A plate-shaped metallic glass thin film is formed, and after the outer and inner portions of the sacrificial layer of the disk-shaped metallic glass thin film are expanded by the above technique, the sacrificial layer is removed.

  In the present invention, as a mold (so-called mold) for molding a thin film that is softened by heating, various planar substrates such as silicon that have been etched in a predetermined shape by a microfabrication technique can be used. By using this mold, it is possible to manufacture various shapes of the fine hollow structure. For example, in the annular fine hollow structure shown in FIG. 2, a disk-shaped metallic glass thin film is arranged by concentrically arranging such molds having a disk-shaped surface smaller than the disk. By suppressing the expansion in the vicinity of the center of the metal glass thin film, the vicinity of the center of the disk-shaped metal glass thin film is not expanded and deformed, and the portion near the outer periphery is expanded in a dome shape. In addition, the shape of the double fine hollow structure shown in FIG. 3 is such that these molds are arranged concentrically with respect to a disk-shaped metallic glass thin film, and the expansion of the part where the molds are arranged is suppressed. It can be formed by expanding the outside like a dome.

  Next, for the flexible part of the diaphragm according to the embodiment of the present invention, the deflection of the central part when a uniform pressure with in-plane stress equal to or less than the allowable stress is applied perpendicularly to the surface is calculated using the finite element method. Asked. The diaphragm diameter was 2 mm, and the plate thickness was 1 μm. The material constants were set to 57.9 GPa for the longitudinal elastic modulus, 0.41 for the Poisson's ratio, and 1.1 GPa for the allowable stress of the thin metal glass. Under this condition, the circular micro hollow structure-shaped diaphragm shown in FIG. 2 has a diameter of 2 mm, and the circular micro hollow structure has a width of 0.45 mm, 0.50 mm, and 0.55 mm from the outer periphery to the inside. The thickness is 15% of the width, and the amount of displacement up to an allowable stress of 1.1 GPa is obtained. The diaphragm has a flat disk-shaped flexible part and has a square wave cross section with a height of 18 μm in 9 cycles in the diameter direction. It was compared with a diaphragm having a flexible part with an axisymmetric waveform. The amount of displacement up to this allowable stress is the maximum amount of displacement, which is a parameter for evaluating the diaphragm.

  As a result, when the width of the annular micro hollow structure is 0.50 mm, the deflection is 193 μm and 3.0 times compared to 65 μm in the case of a flat disk, and 0.85 times the deflection of 226 μm in the case of an axisymmetric waveform As a result, it was found that a large deflection was obtained compared to the conventional case, and that the deflection was only 15% smaller than that of the complex axisymmetric wave shape. The result is shown in FIG.

  For comparison, FIG. 5 shows a result of obtaining a displacement amount up to an allowable stress of 1.1 GPa for a diaphragm having a flat disk-shaped flexible portion. In addition, FIG. 6 shows the result of obtaining the displacement amount up to the allowable stress of 1.1 GPa in the same manner for a diaphragm having an axisymmetric wave-shaped flexible part having a square wave cross section with a height of 18 μm in 9 cycles in the diameter direction. .

  Furthermore, based on the shape of this annular micro hollow structure, the initial height of the central part is 0.2 mm to prevent interference during bending, and an annular micro hollow structure having a width of 0.3 mm and a height of 45 μm is provided on the outer periphery. FIG. 7 shows the result of obtaining the displacement amount up to the permissible stress of 1.1 GPa for the diaphragm having the flexible portion of the double fine hollow structure. In this case, 137 μm was obtained as the maximum displacement up to the allowable stress.

  As shown in FIG. 8, three double fine hollow structure-shaped diaphragms 10 were arranged at the apex positions of regular triangles each having a side of 2.5 mm, and a unit was formed between flat plates 81 and 82. . By laminating 30 units, it was confirmed that a maximum displacement of 4.1 mm, a radius of curvature of 7 mm or less, a maximum bending angle of 90 °, a large displacement and a large bending angle were obtained.

  According to the present invention, it is possible to construct a micro-diaphragm that can obtain a higher displacement than in the past, and it is possible to manufacture the micro-diaphragm of the present invention without increasing the number of steps. For this reason, the microdiaphragm of the present invention has great applicability in various industrial fields including micromachining.

BRIEF DESCRIPTION OF THE DRAWINGS It is the figure which showed typically one Embodiment about the single fine hollow structure shape used for the flexible part of the diaphragm of this invention, Comprising: (a) is the schematic top view, (b) is the figure It is typical sectional drawing. It is the figure which showed typically one Embodiment about the annular | circular shaped fine hollow structure shape used for the flexible part of the diaphragm of this invention, Comprising: (a) is the schematic top view, (b) is the model FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is the figure which showed typically one Embodiment about the double fine hollow structure shape used for the flexible part of the diaphragm of this invention, Comprising: (a) is the schematic top view, (b) is the model FIG. In the embodiment of the present invention, the deflection of the central portion when a uniform pressure with an in-plane stress equal to or lower than an allowable stress is applied perpendicularly to the surface with respect to the diaphragm flexible portion having the shape of the annular fine hollow structure. FIG. For comparison with the diaphragm of the embodiment of the present invention, the result of obtaining the displacement amount up to the allowable stress for the diaphragm having the flat disk-shaped flexible portion is shown. For comparison with the diaphragm of the embodiment of the present invention, the amount of displacement up to the allowable stress is obtained for a diaphragm having an axially symmetric wave-shaped flexible section having a square wave cross section with a height of 18 μm in nine cycles in the radial direction. It is a figure which shows the result. In the embodiment of the present invention, the deflection of the center portion when a uniform pressure with an in-plane stress equal to or less than an allowable stress is applied to the diaphragm flexible portion having a double fine hollow structure shape in a direction perpendicular to the surface. FIG. It is a figure which shows the actuator element which has arrange | positioned three diaphragms of a double fine hollow structure shape in the vertex position of the regular triangle whose one side is 2.5 mm.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Diaphragm, 11 ... Single fine hollow structure shape, 12 ... Planar board | substrate, 13 ... Annular fine hollow structure shape, 14 ... Fine hollow structure body of center part, 81, 82 ... Point plane board.

Claims (6)

  A micro-diaphragm characterized in that a flexible portion having a shape of a micro hollow structure is formed on a substrate.   2. The micro diaphragm according to claim 1, wherein the flexible portion has an annular micro hollow structure shape.   The said flexible part is a fine double hollow structure shape which consists of an annular fine hollow structure surrounding the fine hollow structure in the center and the fine hollow structure in the center. Small diaphragm.   The flexible section has a fine multiple hollow structure shape including a central fine hollow structure and a plurality of annular fine hollow structures surrounding the central fine hollow structure. 1. The micro diaphragm according to 1.   The micro diaphragm according to any one of claims 1 to 4, wherein the flexible portion having the shape of the fine hollow structure is formed of metal glass.   A fluid microactuator for driving the microdiaphragm according to any one of claims 1 to 5 by pressure of fluid.

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