Pressure sensor element

Abstract

The invention provides a sensor element suitable for miniaturization. This pressure sensor element is provided with: a metal plate; an insulating film provided so as to form, on a first surface, which is one surface of the metal plate, a covered region in which the first surface is covered and an exposed region in which the first surface is exposed; and a pressure detection circuit formed on the insulating film so as to be insulated from the first surface by the insulating film.

Description

[0001] This application is a divisional application of a patent application with an application date of August 28, 2020 and an application number of 202080061192.0 and an invention title of Pressure trans Sensor element Technical Field

[0002] The present invention relates to a pressure sensor element having a pressure detection circuit. Background Art

[0003] As a pressure sensor, there is known a sensor in which a pressure detection circuit is formed via an insulating film on the outer bottom surface of a bottomed cylindrical metal member called a stem. Such a pressure sensor is used by fixing the stem to the end of a pipe using a riveting member or the like, and can exhibit good durability even in a high-temperature and high-pressure environment (see Patent Document 1, etc.).

[0004] However, for existing pressure sensors using a bottomed cylindrical stem, there is a limit to the dimensions of the stem that can be formed with high precision. In addition, since it is necessary to use a riveting member or the like for fixing, there is a problem from the viewpoint of miniaturization.

[0005] On the other hand, a pressure sensor element that does not use a stem has also been proposed. However, such a pressure sensor element also requires a frame such as an outer frame to hold and fix the metal substrate, and thus there is also a problem from the viewpoint of miniaturization with respect to the size of the entire sensor including the fixing member (see Patent Document 2, etc.).

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-324402

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 6-137979 Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] In view of such circumstances, the present invention provides a sensor element suitable for miniaturization.

[0012] Technical Means for Solving the Problems

[0013] In order to achieve the above object, the pressure sensor element of the present invention has:

[0014] a metal plate;

[0015] ​An insulating film provided in such a manner that a covered region covering the first surface and an exposed region where the first surface is exposed are formed on the first surface which is one surface of the metal plate; and

[0016] A pressure detection circuit formed on the insulating film in such a manner as to be insulated from the first surface by the insulating film.

[0017] In the pressure sensor element of the present invention, an insulating film is formed on a metal plate, and a pressure detection circuit is formed on the insulating film. Therefore, compared with the case of using a socket, the pressure sensor element including a base material and a detection circuit can be miniaturized. In addition, by providing an exposed region where the first surface of the metal plate is exposed, in such a pressure sensor element, electric conduction processing such as resistance welding can be performed on the metal plate from the first surface of the metal plate. Therefore, in such a pressure sensor element, even without using a frame or the like, it can be easily fixed to a housing or the like by welding or the like, and the shape of the entire unit can be miniaturized.

[0018] In addition, for example, it may be that a second surface on the side opposite to the first surface of the metal plate has a welding portion welded to a housing.

[0019] The pressure sensor is fixed to the housing by the welding portion. Therefore, compared with an existing pressure sensor element fixed by a member such as a frame, it can be miniaturized. In addition, since the fixing is performed by welding, the durability in a high-temperature environment is also good. In addition, since there is a welding portion on the second surface, fixing members are not arranged on the outer periphery of the metal plate, which is also advantageous for miniaturization in this respect.

[0020] In addition, for example, it is characterized in that at least a part of the welding portion overlaps with the exposed region when viewed from a direction orthogonal to the first surface.

[0021] In such a pressure sensor element, an electrode used for electric conduction processing can be brought into contact with the first surface close to the welding portion to form the welding portion on the second surface. Therefore, the formation accuracy of the welding portion of such a pressure sensor element is good.

[0022] In addition, for example, it may be that the exposed region is continuous in the circumferential direction so as to surround a portion where the pressure detection circuit is formed in the covered region.

[0023] In such a pressure sensor element, an electrode used for electric conduction processing can be brought into contact with the first surface close to the welding portion to form the welding portion on the second surface. Therefore, such a pressure sensor element can form a welding portion with high precision so as to surround a pressure receiving region on the second surface corresponding to the side opposite to the first surface where the portion where the pressure detection circuit is formed is located.

[0024] Further, for example, a recessed portion that is recessed toward the first surface may be formed on a second surface of the metal plate, which is a surface opposite to the first surface.

[0025] Such a pressure sensor element can improve the sensitivity of the sensor.

[0026] Further, for example, a convex portion that protrudes toward the side opposite to the first surface side may be formed on a second surface of the metal plate, which is a surface opposite to the first surface.

[0027] Alternatively, the welding portion may be formed on the convex portion.

[0028] Further, for example, an inclined surface that slopes from the center side toward the outer peripheral side and toward the first surface side may be formed on a second surface of the metal plate, which is a surface opposite to the first surface.

[0029] Alternatively, the welding portion may be formed on the inclined surface.

[0030] Further, for example, in the pressure sensor element of the present invention, the metal plate may include an outer peripheral edge portion that is thinner than the center side.

[0031] Alternatively, a stepped portion that is stepped from the center side to the outer peripheral edge portion may be formed on a second surface of the metal plate, which is a surface opposite to the first surface.

[0032] Alternatively, the welding portion may be formed on the stepped portion.

[0033] Such a pressure sensor element can form the welding portion with high precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a schematic cross-sectional view showing a pressure sensor element and its peripheral portion according to a first embodiment of the present invention.

[0035] Figure 2 is a top view of the pressure sensor element shown Figure 1 as viewed from above.

[0036] Figure 3 is Figure 2 a schematic cross-sectional view of the pressure sensor element shown.

[0037] Figure 4 is a conceptual diagram showing a process of welding the pressure sensor shown Figure 2 to a housing.

[0038] Figure 5It is a top view of the pressure sensor element according to the second embodiment of the present invention as viewed from above.

[0039] Figure 6 It is a schematic cross-sectional view of the pressure sensor element according to the third embodiment of the present invention.

[0040] Figure 7 It is a schematic cross-sectional view of the pressure sensor element according to the fourth embodiment of the present invention.

[0041] Figure 8 It is a schematic cross-sectional view of the pressure sensor element according to the fifth embodiment of the present invention.

[0042] Figure 9 It is a schematic cross-sectional view of the pressure sensor element according to the sixth embodiment of the present invention.

[0043] Figure 10 It is a graph showing the dependence of the maximum stress generated in the metal plate of the pressure sensor element on the metal plate shape.

[0044] Figure 11 It is a graph showing the dependence of the change in the strain gauge resistance of the pressure sensor element on the metal plate shape.

[0045] Figure 12 It is a graph showing the dependence of the resistance of the insulating film of the pressure sensor element on the film thickness. Detailed Embodiments

[0046] Hereinafter, the present invention will be described based on the embodiments shown in the drawings.

[0047] First Embodiment

[0048] Figure 1 It is a schematic cross-sectional view of a pressure sensor unit 60 including a pressure sensor element 10 according to the first embodiment of the present invention. The pressure sensor unit 60 includes, in addition to the pressure sensor element 10, a housing 50, a printed circuit board 52, a connector 54, a cover member 55, and the like.

[0049] As Figure 1 shown, the pressure sensor element 10 is fixed to the end face of the housing 50. The housing 50 is cylindrical, and a flow path 50a is formed inside the housing 50. The flow path 50a communicates with a pressure chamber filled with a fluid to be measured in an airtight manner.

[0050] Examples of the material of the housing 50 include metal materials such as stainless steel, ceramics such as silicon carbide, and semiconductor materials such as silicon, but there is no particular limitation.

[0051] As Figure 1As shown, the metal plate 20 of the pressure sensor element 10 seals the end of the flow path 50a of the housing 50. Thus, a pressure-receiving area 24a that receives pressure from the fluid is formed on the second surface 24, which is the lower surface of the metal plate 20.

[0052] A printed circuit board 52 is fixed to the end face of the housing 50. The printed circuit board 52 is disposed on the outer peripheral side of the pressure sensor element 10. The printed circuit board 52 is electrically connected to the pressure detection circuit 40 of the pressure sensor element 10 via a wiring portion 51. The wiring portion 51 is formed of a bonding wire or the like.

[0053] A cover member 55 that covers the pressure sensor element 10 and the printed circuit board 52 is provided on the end face of the housing 50. The pressure sensor element 10 is accommodated in a space formed between the housing 50 and the cover member 55.

[0054] A connector 54 that connects the pressure sensor unit 60 to an external control unit, power supply, etc. is provided on the cover member 55. Electric power, control signals, etc. are transmitted to the pressure sensor element 10 and the printed circuit board 52 included in the pressure sensor unit 60 via the connector 54. In addition, the detection signal detected by the pressure sensor element 10 and the signal calculated on the printed circuit board 52 using the detection signal are transmitted to the outside via the connector 54.

[0055] In addition, the shapes of the housing 50, the cover member 55, and the connector 54 included in the pressure sensor unit 60 are not limited to Figure 1 the shapes shown, and can be appropriately changed according to the measurement object of the pressure sensor element 10. For example, the housing 50 included in the pressure sensor unit 60 can also serve as part of a pipe. In addition, a connector portion connected to the outside can be formed on the printed circuit board 52 of the pressure sensor unit 60, and the cover member 55 can also be omitted.

[0056] Figure 2 is a top view of the pressure sensor element 10 included in the pressure sensor unit 60 as viewed from above Figure 1 shown, Figure 3 is a schematic cross-sectional view of the pressure sensor element 10. As Figure 3 shown, the pressure sensor element 10 includes: a metal plate 20, an insulating film 30 provided on a first surface 22 that is one surface of the metal plate 20, and a pressure detection circuit 40 formed on the insulating film 30.

[0057] In addition, in the description of the pressure sensor element 10, the stacking direction of the metal plate 20, the insulating film 30, and the pressure detection circuit is set as the Z-axis direction, and the directions perpendicular to the Z-axis direction and perpendicular to each other are set as the X-axis direction and the Y-axis direction for description. The first surface 22 of the metal plate 20 corresponds to the upper surface (the surface on the positive Z-axis side) of the metal plate 20.

[0058] As Figure 2 and Figure 3 shown, the metal plate 20 has a circular plate-like outer shape, but the shape of the metal plate 20 is not limited thereto, and it may also be an elliptical plate-like shape, a rectangular plate-like shape, or other shapes. In addition, the details of the shape of the metal plate 20 will be described later.

[0059] The material of the metal plate 20 is not particularly limited as long as it is a material that produces appropriate elastic deformation according to pressure. Examples include single metals such as Fe, nickel, and aluminum, steel materials such as stainless steel, chrome steel, or carbon steel containing these metals, and alloys such as nickel alloys like invar or kovar alloy. Additionally, the metal plate 20 is preferably composed of a conductive material.

[0060] As Figure 3 shown, the insulating film 30 formed on the first surface 22 of the metal plate 20 only covers a part of the first surface 22 and does not cover the entire first surface 22. That is, on the first surface 22 of the metal plate 20, there are formed a covered area 22a covered by the insulating film 30 and an exposed area 22b where the first surface 22 is exposed.

[0061] As Figure 3 shown, the insulating film 30 is provided at the central portion of the first surface 22 close to the center 20a. Therefore, the central portion of the first surface 22 becomes the covered area 22a under the insulating film 30.

[0062] In contrast, as Figure 2 and Figure 3 shown, the exposed area 22b exposed from the insulating film 30 is formed in a part of the first surface 22 close to the outer periphery 20b of the metal plate 20. As Figure 2 shown, the exposed area 22b of the pressure sensor element 10 is continuous in the circumferential direction so as to surround the portion where the pressure detection circuit 40 is formed in the covered area 22a.

[0063] In addition, the exposed area 22b may also be continuous along the outer periphery 20b of the first surface 22 to surround the entire covered area 22a, but it may also be different from this case, where a part of the covered area 22a is formed outside the exposed area 22b. Additionally, the exposed area 22b may also be formed discontinuously in the circumferential direction.

[0064] As Figure 3 shown, the pressure detection circuit 40 is formed on the surface on the positive Z-axis side of the insulating film 30. Therefore, the pressure detection circuit 40 is insulated from the first surface 22 through the insulating film 30.

[0065] As Figure 2 shown, the pressure detection circuit 40 has: a strain gauge 41 that detects the strain of the metal plate 20, and a connection toFigure 1 The electrode portion 42 of the wiring portion 51 of the printed circuit board 52 shown, etc. The pressure detection circuit 40 may have, for example, a Wheatstone bridge circuit that detects the strain of the metal plate 20 through a change in resistance or the like, but the pressure detection circuit 40 is not limited thereto.

[0066] Examples of the material of the insulating film 30 include silicon oxide, silicon nitride, aluminum oxide, etc., but there is no particular limitation. The insulating film 30 is formed on the first surface 22 of the metal plate 20 by, for example, sputtering, vacuum evaporation, CVD method, sol-gel method, etc. In addition, when forming the insulating film 30 on the first surface 22 of the metal plate 20, a mask is applied to the exposed area 22b, or a part of it is removed after forming the insulating film 30, whereby the covering area 22a and the exposed area 22b can be formed on the first surface 22.

[0067] The pressure detection circuit 40 is formed as follows. For example, a functional film of a semiconductor such as silicon or a metal that is a good conductor is microfabricated by semiconductor processing techniques such as laser processing or screen printing. The functional film constituting the detection circuit is formed on the insulating film 30 formed on the first surface 22 by sputtering, vacuum evaporation, CVD method, sol-gel method, etc. As a patterning method for forming the pressure detection circuit 40 from the functional film, a photolithography patterning method or the like as a semiconductor processing technique can be adopted.

[0068] As Figure 1 shown, Figure 2 and Figure 3 shown, the pressure sensor element 10 is fixed to the upper end surface 50b of the housing 50. Figure 4 is a diagram showing an example of the process of fixing the pressure sensor element 10 to the housing 50. As Figure 4 shown, the pressure sensor element 10 can be fixed to the housing 50 by resistance welding.

[0069] As Figure 4 shown, an exposed area 22b where the metal plate 20 is exposed is formed on the first surface 22 of the pressure sensor element 10. In addition, an insulating film 30 is not formed on the second surface 24 of the metal plate 20, which is the surface opposite to the first surface 22, and the surface of the metal is exposed.

[0070] When fixing the pressure sensor element 10 to the housing 50, first, the pressure sensor element 10 is disposed on the housing 50 such that the second surface 24 of the pressure sensor element 10 contacts the upper end surface 50b of the housing 50. Then, an electrode for resistance welding is brought into contact with the exposed area 22b on the first surface 22 of the pressure sensor element 10, and electricity is passed between the second surface 24 and the upper end surface 50b, whereby, as Figure 4As shown, the second surface 24 and the upper end surface 50b are fixed by welding. Thus, a welded portion that is welded to the housing is formed on the second surface 24 of the metal plate 20.

[0071] As described above, an exposed area 22b that exposes from the insulating film 30 is formed on the first surface 22 of the pressure sensor element 10. Therefore, by bringing the electrode into contact with the first surface 22 and the metal plate 20, it is possible to easily fix the second surface 24 and the upper end surface 50b of the housing 50 by resistance welding.

[0072] In addition, as Figure 4 shown, when viewed from the direction (positive Z-axis direction) orthogonal to the first surface 22, at least a part of the welded portion 24b overlaps with the exposed area 22b. Thus, the electrode 70 can be brought into contact with the first surface 22 directly above the portion where the welded portion 24b is formed and energized for processing.

[0073] In addition, as Figure 2 shown, the exposed area 22b is continuous in the circumferential direction on the first surface 22. Thus, the welded portion 24b formed on the second surface 24 can also be easily formed into a shape that is continuous in the circumferential direction on the second surface 24 and the upper end surface 50b. That is, in the pressure sensor element 10, as Figure 4 shown, the gap between the second surface 24 of the metal plate 20 and the upper end surface 50b of the housing 50 is reliably sealed by the welded portion 24b formed with high precision.

[0074] As Figure 1 and Figure 4 shown, a pressure-receiving area 24a that faces the flow path 50a and receives the pressure of the fluid to be measured is formed in the portion of the second surface 24 surrounded by the welded portion 24b.

[0075] As described above, the pressure sensor element 10 can, for example, as Figure 4 shown, fix the second surface 24 of the metal plate 20 to the upper end surface 50b of the housing 50 by resistance welding. Therefore, the welding speed is fast and the automation of the welding process is easy. In addition, the pressure sensor element 10 does not require a fixture for fixing, and the shape of the metal plate 20 is simple. Therefore, the pressure sensor element 10 is suitable for miniaturization and has good productivity.

[0076] In addition, in the pressure sensor element 10, by using resistance welding to fix the metal plate 20, compared with the case of fixing the metal plate 20 by other welding methods, the strain generated in the metal plate 20 and the like due to the thermal influence during fixing can be suppressed. Further, the welding portion 24b that fixes the metal plate 20 and the upper end surface 50b of the housing 50 is not limited to being formed by resistance welding. For example, the metal plate 20 can also be fixed to the housing 50 by a welding portion formed by electron beam welding, ultrasonic welding, seam welding, friction welding, laser welding, or the like.

[0077] In addition, in the pressure sensor element 10 in which the metal plate 20 is fixed to the housing 50 by welding, even if some gaps are formed between the second surface 24 and the upper end surface 50b before welding, these gaps are sealed by the welding portion 24b. Therefore, from this perspective, the productivity of the pressure sensor element 10 having the welding portion 24b is good.

[0078] Second Embodiment

[0079] Figure 5 is a top view of the pressure sensor element 110 of the second embodiment as viewed from above. The pressure sensor element 110 of the second embodiment is the same as the pressure sensor element 10 of the first embodiment (refer to Figure 2 ) except for the different shape of the insulating film 130. In the description of the pressure sensor element 110, only the differences from the pressure sensor element 10 are described, and the common points with the pressure sensor element 10 are omitted.

[0080] As Figure 5 shown, the insulating film 130 of the pressure sensor element 110 has a cross shape. In this way, as long as the insulating film 130 can insulate the pressure detection circuit 40 from the metal plate 20, the shape of the insulating film 130 is not limited to the circular shape like the insulating film 30 shown in Figure 2 .

[0081] Corresponding to the shape of the insulating film 130, the shapes of the covering region 122a and the exposed region 122b formed on the first surface 122 of the metal plate 20 also change. The pressure sensor element 110 of the second embodiment also achieves the same effects as the pressure sensor element 10 of the first embodiment.

[0082] Third Embodiment

[0083] Figure 6 is a schematic cross-sectional view of the pressure sensor element 210 of the third embodiment. The pressure sensor element 210 of the third embodiment is the same as the pressure sensor element 10 of the first embodiment (refer to Figure 2)The same applies to the description of the pressure sensor element 210. Only the differences from the pressure sensor element 10 are described, and the common points with the pressure sensor element 10 are omitted.

[0084] As Figure 6 shown, on the second surface 224 of the metal plate 220 of the pressure sensor element 210, a recessed portion 224c that is recessed toward the first surface 22 is formed. The recessed portion 224c has a curved surface shape that faces the center 20a and the thickness of the metal plate 220 becomes thinner.

[0085] The recessed portion 224c is formed in the pressure-receiving portion (refer to Figure 1 ) of the second surface 224 that faces the flow path 50a of the housing 50. A flat portion for forming a welded portion welded to the housing 50 is formed on the outer periphery of the recessed portion 224c on the second surface 224.

[0086] In Figure 6 shown, a recessed portion 224c is formed on the second surface 224 of the pressure sensor element 210, and the thickness of the metal plate 220 of the pressure-receiving portion is thin. Therefore, the pressure sensor element 210 can increase the strain of the metal plate 220 accompanying a unit pressure change and improve the sensitivity of the sensor.

[0087] The recessed portion 224c may also be constituted by Figure 6 a curved surface as shown, or may be constituted by a flat bottom surface and an inclined surface inclined with respect to the bottom surface or a wall surface perpendicular to the bottom surface. In addition, the pressure sensor element 210 of the third embodiment achieves the same effects as the pressure sensor element 10 of the first embodiment.

[0088] Fourth Embodiment

[0089] Figure 7 is a schematic cross-sectional view of the pressure sensor element 310 of the fourth embodiment. The pressure sensor element 310 of the fourth embodiment is the same as the pressure sensor element 10 of the first embodiment (refer to Figure 2 ) except for the different shape of the metal plate 320. In the description of the pressure sensor element 310, only the differences from the pressure sensor element 10 are described, and the common points with the pressure sensor element 10 are omitted.

[0090] As Figure 7 shown, the metal plate 320 of the pressure sensor element 310 includes an outer peripheral edge portion 328 whose thickness is thinner than that on the central 20a side. A stepped portion 324f that is stepped from the pressure-receiving region 24a on the central 20a side to the outer peripheral edge portion 328 is formed on the second surface 324 of the metal plate 320. In the pressure sensor element 310, the welded portion (refer to Figure 1 ) for welding the metal plate 320 to the housing 50 is formed on the stepped portion 324f.

[0091] This pressure sensor element 310 is welded to a housing 50 having an upper end surface 50b (refer to Figure 1 ) by a stepped portion (not shown) that engages with the stepped portion 324f, thereby enabling the formation of a welded portion with high precision and reliability. In addition, the pressure sensor element 310 of the fourth embodiment achieves the same effects as the pressure sensor element 10 of the first embodiment.

[0092] Fifth Embodiment

[0093] Figure 8 FIG. is a schematic cross-sectional view of a pressure sensor element 410 of the fifth embodiment. The pressure sensor element 410 of the fifth embodiment is the same as the pressure sensor element 10 of the first embodiment (refer to Figure 2 ) except for the shape of the second surface 424 of the metal plate 420. In the description of the pressure sensor element 410, only the differences from the pressure sensor element 10 are described, and the common points with the pressure sensor element 10 are omitted.

[0094] As Figure 8 shown, on the second surface 424 of the metal plate 420 of the pressure sensor element 410, an inclined surface 424e is formed that slopes from the central 20a side toward the outer periphery 20b and toward the first surface 22 side (the +Z-axis direction side). The inclined surface 424e is formed so as to surround a flat pressure-receiving area 24a disposed in the central 20a portion of the second surface 424. In addition, the inclined surface 424e is continuously formed in a ring shape along the outer periphery of the second surface 424. In the pressure sensor element 410, the welded portion (refer to Figure 1 ) for welding the metal plate 420 to the housing 50 is formed on the inclined surface 424e.

[0095] This pressure sensor element 410 contacts and is welded to the upper end surface 50a of the housing 50 and the corner of the flow path 50a (refer to Figure 1 ) through the inclined surface 424e, thereby enabling the formation of a welded portion with high precision and reliability. In addition, the pressure sensor element 410 of the fifth embodiment achieves the same effects as the pressure sensor element 10 of the first embodiment.

[0096] Sixth Embodiment

[0097] Figure 9 FIG. is a schematic cross-sectional view of a pressure sensor element 510 of the sixth embodiment. The pressure sensor element 510 of the sixth embodiment is the same as the pressure sensor element 10 of the first embodiment (refer to Figure 2)The same applies hereinafter. In the description of the pressure sensor element 510, only the differences from the pressure sensor element 10 will be described, and the common points with the pressure sensor element 10 will be omitted.

[0098] As Figure 9 shown, on the second surface 524 of the metal plate 520 of the pressure sensor element 510, a convex portion 524d protruding toward the side opposite to the first surface 522 side, i.e., the negative Z-axis direction side, is formed. The convex portion 524d is formed so as to surround the flat pressure-receiving area 24a around the center 20a disposed on the second surface 524. In addition, the convex portion 524d is continuously formed in a ring shape along the outer periphery 20b of the second surface 524. In the pressure sensor element 510, the metal plate 520 is welded to the housing 50 at a welding portion (refer to Figure 1 ) formed on the convex portion 524d.

[0099] This pressure sensor element 510 contacts and is welded to the upper end surface 50b of the housing 50 (refer to Figure 1 ) through the convex portion 524d, thereby forming a welding portion with high precision and reliability. The convex portion 524d can be formed, for example, by stamping a flat metal plate 20 as shown in Figure 3 . In this case, a concave portion 522d corresponding to the convex portion 524d on the second surface 524 is formed on the first surface 522. Such a concave portion 522d functions as a mark or a guide for contacting the welding electrode 70 as shown in Figure 4 . In addition to this, the pressure sensor element 510 of the sixth embodiment achieves the same effects as the pressure sensor element 10 of the first embodiment.

[0100] Example

[0101] Hereinafter, examples will be shown to further describe the pressure sensor element of the present invention in detail. However, the present invention is not limited to these examples.

[0102] Figure 10 is a graph showing the dependence of the maximum stress generated in the metal plate 20 on the plate thickness T1 when a specified pressure (30 MPa) acts on the second surface 24 of the metal plate 20 of the pressure sensor element 10 as shown in Figure 3 .

[0103] In the example, the diameter D1 of the metal plate 20 (refer to Figure 3 ) was set to 6 mm, and a fixed-end model at both ends was used as the mechanical model. In addition, the plate thickness T1 (refer to Figure 3 ) was varied between 3.6 and 10 mm. As the material of the metal plate 20, SUS316L was assumed.

[0104] According to the calculation result Figure 10 It can be understood that the thinner the thickness of the metal plate 20 is, the greater the maximum stress generated in the metal plate 20 is. Figure 10 It can be understood that by setting the plate thickness T1 of the metal plate 20 to be 1 mm or more, the maximum stress generated in the metal plate 20 becomes equal to or less than 175 MPa, which is the proof strength of SUS316L.

[0105] Figure 11 is to Figure 3 When a predetermined pressure is applied to the pressure sensor element 10 as shown, the calculation is performed Figure 2 FIG. 4 is a graph showing the dependence of the resistance variation of the strain gauge 41 on the plate thickness T1.

[0106] As the pressure detection circuit 40 for the strain gauge 41 of the embodiment, a circuit capable of detecting the resistance change with appropriate accuracy when a resistance change of 4Ω or more occurs in the strain gauge 41 having an initial resistance of 1KΩ is assumed. Figure 3 ) varies between 3.6 and 10 mm.

[0107] According to the calculation result Figure 11 It can be understood that the greater the thickness T1 of the metal plate 20, the smaller the resistance change. Figure 11 It can be understood that by setting the plate thickness T1 of the metal plate 20 to 2 mm or less, the resistance change amount generated in the metal plate 20 becomes 4Ω or more, which is a resistance change amount that can be appropriately detected by an assumed circuit.

[0108] according to Figure 10 and Figure 11 It can be understood that by Figure 1 The thickness T1 of the metal plate 20 shown is set to 1 mm to 2 mm, and a small pressure sensor element 10 with appropriate durability and resolution can be realized. In addition, by setting the metal plate 20 to such a thickness, the thickness of the entire pressure sensor element 10 can be made thinner than 6 mm, for example. Such a pressure sensor element 10 can be manufactured by a process of a semiconductor factory of standard specifications, and therefore has good productivity.

[0109] Figure 12 It is calculated in Figure 3 The film thickness dependence of the resistance of the insulating film 30 of the pressure sensor element 10 is shown in FIG. The insulating film 30 is made of SiO2 and the film formation method is assumed to be a vapor phase method. Figure 12, preferably, by setting the film thickness of the insulating film 30 to 400 nm, the resistance of the insulating film 30 can be set to 1 GΩ, which can properly insulate the pressure detection circuit 40 from the metal plate 20. In addition, the thickness of the pressure detection circuit 40 formed of the functional film is not particularly limited, and is preferably about 0.05 to 1 μm.

[0110] Description of Reference Numerals

[0111] 10, 110, 210, 310, 410, 510... Pressure sensor element

[0112] 20, 220, 420, 520... Metal plate

[0113] 20a... Center

[0114] 20b... Periphery

[0115] 22, 122, 522... First surface

[0116] 22a, 122a... Covered area

[0117] 22b, 122b... Exposed area

[0118] 24, 224, 424, 524... Second surface

[0119] 24a... Compressed area

[0120] 24b... Welding part

[0121] 30, 130... Insulating film

[0122] 40... Pressure detection circuit

[0123] 41... Strain gauge

[0124] 42... Electrode part

[0125] 50... Housing

[0126] 50a... Flow path

[0127] 50b... Upper end face

[0128] 51... Wiring part

[0129] 52... Printed circuit board

[0130] 54... Connector

[0131] 55... Cover member

[0132] 60... Pressure sensor unit

[0133] 70... Welding electrode

[0134] 224c... Depression

[0135] 324f…Step portion

[0136] 328…Outer peripheral edge portion

[0137] 424e…Inclined surface

[0138] 522d…Recessed portion

[0139] 524d…Protruding portion.

Claims

1. A pressure sensor element, wherein, it has: a metal plate; an insulating film provided in such a manner as to form a covered area covering the first surface and an exposed area where the first surface is exposed on the first surface which is one surface of the metal plate; and a pressure detection circuit formed on the insulating film in a manner insulated from the first surface through the insulating film, a second surface which is a surface of the metal plate opposite to the first surface has a welding portion welded to a housing, when viewed from a direction orthogonal to the first surface, at least a part of the welding portion overlaps with the exposed area, the metal plate includes a peripheral edge portion thinner than the central side in thickness, on the second surface which is a surface of the metal plate opposite to the first surface, a stepped portion is formed which is stepped from the central side to the peripheral edge portion, the welding portion is formed on the stepped portion.

2. The pressure sensor element according to claim 1, wherein, the exposed area is continuous in the circumferential direction so as to surround a portion where the pressure detection circuit is formed in the covered area.

3. The pressure sensor element according to claim 2, wherein, the exposed area is continuous along the outer periphery of the first surface.

4. The pressure sensor element according to claim 1, wherein, the pressure detection circuit has a strain gauge for detecting strain of the metal plate.

5. The pressure sensor element according to claim 1, wherein, the second surface bears the pressure of fluid in a flow path extending in a direction orthogonal to the second surface.

6. The pressure sensor element according to claim 1, wherein, the plate thickness of the metal plate is 1 mm to 2 mm.

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