Pressure Sensor Element

Abstract

To provide a sensor element that is appropriate for miniaturization.SOLUTION: A pressure sensor element comprises a metal plate, an insulating film provided on one surface of the metal plate, or a first surface, so as to form a coated region where the first surface is coated and an exposed region where 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.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pressure sensor element having a pressure detection circuit. [Background technology]

[0002] A known pressure sensor has a pressure detection circuit formed on the outer bottom surface of a cylindrical metal member with a bottom called a stem, via an insulating film. This type of pressure sensor is used by fixing the stem to the end of a pipe using a crimping member or the like, and has good durability even in high-temperature and high-pressure environments (see Patent Document 1, etc.).

[0003] However, conventional pressure sensors that use a bottomed cylindrical stem have limitations in the dimensions that the stem can be formed to with high precision, and they require fixing using a crimping member or the like, posing challenges in terms of miniaturization.

[0004] On the other hand, pressure sensor elements that do not use stems have also been proposed. However, these pressure sensor elements also require a metal base to be clamped and fixed using a frame such as an outer frame, and therefore the overall size of the sensor including the fixing member poses challenges in terms of miniaturization (see Patent Document 2, etc.). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2001-324402 A [Patent Document 1] Japanese Patent Application Publication No. 6-137979 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and provides a sensor element suitable for miniaturization. [Means for solving the problem]

[0007] In order to achieve the above object, the pressure sensor element according to the present invention comprises: A metal plate; an insulating film provided on a first surface, which is one surface of the metal plate, so as to form a covering region where the first surface is covered and an exposed region where the first surface is exposed; and a pressure detection circuit formed in the insulating film so as to be insulated from the first surface by the insulating film.

[0008] In the pressure sensor element according to the present invention, an insulating film is formed on a metal plate, and a pressure detection circuit is formed on the insulating film, so that the pressure sensor element including the substrate and the detection circuit can be made smaller than when a stem is used. In addition, by providing an exposed area where the first surface of the metal plate is exposed, in such a pressure sensor element, it is possible to perform current processing such as resistance welding on the metal plate from the first surface of the metal plate. Therefore, in such a pressure sensor element, it is possible to easily fix it to a housing or the like by welding or the like without using a frame such as an outer frame, and the shape of the entire unit can be made smaller.

[0009] Also, for example, a second surface of the metal plate opposite to the first surface may have a weld portion that is welded to a housing.

[0010] The pressure sensor is fixed to the housing by the welded joint, so it can be made smaller than conventional pressure sensor elements that are fixed by members such as an outer frame. In addition, since it is fixed by welding, it has good durability in high-temperature environments. In addition, since the welded joint is on the second surface, no fixing member is placed on the outer periphery of the metal plate, which is also advantageous for miniaturization.

[0011] For example, at least a portion of the weld overlaps the exposed region when viewed from a direction perpendicular to the first surface.

[0012] In such a pressure sensor element, the welded portion on the second surface can be formed by contacting an electrode for electric current processing with the first surface close to the welded portion, and therefore, the welded portion of such a pressure sensor element can be formed with good accuracy.

[0013] Also, for example, the exposed region may be continuous in the circumferential direction so as to surround a portion of the covered region in which the pressure detection circuit is formed.

[0014] In such a pressure sensor element, the welded portion on the second surface can be formed by contacting an electrode for current processing with the first surface close to the welded portion. Therefore, in such a pressure sensor element, the welded portion can be formed with high precision so as to surround the pressure-receiving area of ​​the second surface that corresponds to the opposite side of the first surface to the portion where the pressure detection circuit is formed.

[0015] Also, for example, a recessed portion recessed towards the first surface may be formed on a second surface, which is a surface of the metal plate opposite to the first surface.

[0016] Such a pressure sensor element can increase the sensitivity of the sensor.

[0017] Also, for example, a convex portion protruding toward the opposite side to the first surface side may be formed on a second surface, which is a surface of the metal plate opposite to the first surface side, The welded portion may be formed on the protruding portion.

[0018] Also, for example, a sloped surface that slopes from a center side toward an outer periphery side toward the first surface side may be formed on a second surface, which is a surface of the metal plate opposite to the first surface, The weld may be formed on the inclined surface.

[0019] In addition, for example, in the pressure sensor element according to the present invention, the metal plate may include an outer peripheral portion having a smaller thickness than a central portion, A step portion may be formed on a second surface of the metal plate opposite to the first surface, the step portion being stepped from a center side to the outer circumferential edge portion, The welded portion may be formed at the stepped portion.

[0020] In such a pressure sensor element, the welded portion can be formed with high precision. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a pressure sensor element and its surrounding area according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a top view of the pressure sensor element shown in FIG. 1 as viewed from above. [Diagram 3] FIG. 3 is a schematic cross-sectional view of the pressure sensor element shown in FIG. [Figure 4] FIG. 4 is a conceptual diagram showing a process for welding the pressure sensor shown in FIG. 2 to a housing. [Diagram 5] FIG. 5 is a top view of the pressure sensor element according to the second embodiment of the present invention. [Figure 6] FIG. 6 is a schematic cross-sectional view of a pressure sensor element according to a third embodiment of the present invention. [Figure 7] FIG. 7 is a schematic cross-sectional view of a pressure sensor element according to a fourth embodiment of the present invention. [Figure 8] FIG. 8 is a schematic cross-sectional view of a pressure sensor element according to a fifth embodiment of the present invention. [Figure 9] FIG. 9 is a schematic cross-sectional view of a pressure sensor element according to a sixth embodiment of the present invention. [Figure 10] FIG. 10 is a graph showing the dependency of the maximum stress generated in the metal plate of the pressure sensor element on the shape of the metal plate. [Figure 11] FIG. 11 is a graph showing the dependency of the resistance change of the strain gauge of the pressure sensor element on the shape of the metal plate. [Figure 12] FIG. 12 is a graph showing the film thickness dependency of the electrical resistance of the insulating film in the pressure sensor element. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, the present invention will be described based on the embodiments shown in the drawings.

[0023] First embodiment 1 is a schematic cross-sectional view of a pressure sensor unit 60 including a pressure sensor element 10 according to a first embodiment of the present invention. In addition to the pressure sensor element 10, the pressure sensor unit 60 includes a housing 50, a printed circuit board 52, a connector 54, a cover member 55, and the like.

[0024] 1, the pressure sensor element 10 is fixed to an end surface of a housing 50. The housing 50 is cylindrical, and a flow path 50a is formed inside the housing 50. The flow path 50a is airtightly connected to a pressure chamber filled with a fluid to be measured.

[0025] Examples of materials for the housing 50 include, but are not limited to, metal materials such as stainless steel, ceramics such as silicon carbide, and semiconductor materials such as silicon.

[0026] 1, the metal plate 20 of the pressure sensor element 10 seals an end of a flow path 50a of a housing 50. As a result, a pressure-receiving area 24a that receives pressure from a fluid is formed on a second surface 24, which is the lower surface of the metal plate 20.

[0027] A printed circuit board 52 is fixed to an end face of the housing 50. The printed circuit board 52 is disposed on the outer periphery 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 by wire bonding or the like.

[0028] A cover member 55 that covers the pressure sensor element 10 and the printed circuit board 52 is provided on an 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.

[0029] The cover member 55 is provided with a connector 54 for connecting the pressure sensor unit 60 to an external control unit, power source, etc. Power, control signals, etc. are sent 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, a detection signal detected by the pressure sensor element 10 and a signal calculated by the printed circuit board 52 using the detection signal are sent to the outside via the connector 54.

[0030] 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 those shown in Fig. 1, and can be appropriately changed depending on the measurement target of the pressure sensor element 10. For example, the housing 50 included in the pressure sensor unit 60 may also serve as part of the piping. Also, a connector portion for connecting to the outside may be formed on the printed circuit board 52 of the pressure sensor unit 60, and the cover member 55 may be omitted.

[0031] Fig. 2 is a top view of the pressure sensor element 10 included in the pressure sensor unit 60 shown in Fig. 1, and Fig. 3 is a schematic cross-sectional view of the pressure sensor element 10. As shown in Fig. 3, the pressure sensor element 10 has a metal plate 20, an insulating film 30 provided on a first surface 22 which is one surface of the metal plate 20, and a pressure detection circuit 40 formed on the insulating film 30.

[0032] 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 defined as the Z-axis direction, and directions perpendicular to the Z-axis direction and perpendicular to each other are defined as the X-axis direction and the Y-axis direction. The first surface 22 of the metal plate 20 corresponds to the upper surface of the metal plate 20 (the surface on the positive side of the Z-axis).

[0033] 2 and 3, the metal plate 20 has a disk-like outer shape, but the shape of the metal plate 20 is not limited to this and may be an elliptical plate, a rectangular plate, or other shape. Details of the shape of the metal plate 20 will be described later.

[0034] The material of the metal plate 20 is not particularly limited as long as it is a material that generates an appropriate elastic deformation in response to pressure, and examples of the material include elemental metals such as Fe, nickel, and aluminum, and alloys containing these metals, such as stainless steel, steel materials such as chromium steel and carbon steel, and nickel alloys such as Invar and Kovar. The metal plate 20 is preferably made of a conductive material.

[0035] 3, the insulating film 30 formed on the first surface 22 of the metal plate 20 covers only a portion of the first surface 22, and does not cover the entire first surface 22. That is, the first surface 22 of the metal plate 20 has a covered region 22a that is covered by the insulating film 30 and an exposed region 22b where the first surface 22 is exposed.

[0036] 3, the insulating film 30 is provided in a central portion close to the center 20a on the first surface 22. Therefore, the central portion of the first surface 22 forms a covered region 22a located under the insulating film 30.

[0037] 2 and 3, the exposed region 22b exposed from the insulating film 30 is formed in a portion of the first surface 22 close to the outer periphery 20b of the metal plate 20. As shown in Fig. 2, the exposed region 22b of the pressure sensor element 10 is continuous in the circumferential direction so as to surround the portion of the covered region 22a where the pressure detection circuit 40 is formed.

[0038] The exposed region 22b may be continuous along the outer periphery 20b of the first surface 22 and may surround the entire covered region 22a, but instead, a part of the covered region 22a may be formed outside the exposed region 22b. The exposed region 22b may be formed discontinuously in the circumferential direction.

[0039] 3, the pressure detection circuit 40 is formed on the surface on the positive side of the insulating film 30 in the Z-axis direction.

[0040] 2, the pressure detection circuit 40 has a strain gauge 41 that detects the strain of the metal plate 20, an electrode section 42 to which a wiring section 51 is connected to a printed circuit board 52 shown in Fig. 1, and the like. The pressure detection circuit 40 may have, for example, a Wheatstone bridge circuit that detects the strain of the metal plate 20 by a resistance change or the like, but the pressure detection circuit 40 is not limited to this.

[0041] Examples of the material of the insulating film 30 include, but are not limited to, silicon oxide, silicon nitride, alumina, etc. The insulating film 30 is formed on the first surface 22 of the metal plate 20 by, for example, a sputtering method, a vacuum deposition method, a CVD method, a sol-gel method, etc. When forming the insulating film 30 on the first surface 22 of the metal plate 20, a mask is applied to the exposed region 22b, or a part of the insulating film 30 is removed after its formation, thereby forming the covered region 22a and the exposed region 22b on the first surface 22.

[0042] The pressure detection circuit 40 is formed by, for example, performing microfabrication using semiconductor processing techniques such as laser processing and screen printing on a functional film made of a semiconductor such as silicon or a metal with good conductivity. The functional film constituting the detection circuit is formed on the insulating film 30 formed on the first surface 22 by a sputtering method, a vacuum deposition method, a CVD method, a sol-gel method, or the like. As a patterning method for forming the pressure detection circuit 40 from the functional film, a photopatterning method, which is a semiconductor processing technique, can be used.

[0043] The pressure sensor element 10 shown in Figures 2 and 3 is fixed to the upper end surface 50b of the housing 50 as shown in Figure 1. Figure 4 shows an example of a process for fixing the pressure sensor element 10 to the housing 50. As shown in Figure 4, the pressure sensor element 10 can be fixed to the housing 50 by resistance welding.

[0044] 4, an exposed region 22b where the metal plate 20 is exposed is formed on the first surface 22 of the pressure sensor element 10. Moreover, on the second surface 24, which is the surface of the metal plate 20 opposite to the first surface 22, the insulating film 30 is not formed, and the metal surface is exposed.

[0045] When fixing the pressure sensor element 10 to the housing 50, first, the pressure sensor element 10 is placed in the housing 50 so that the second surface 24 of the pressure sensor element 10 contacts the upper end surface 50b of the housing 50. Next, an electrode for resistance welding is brought into contact with the exposed area 22b of 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, thereby fixing the second surface 24 and the upper end surface 50b by welding, as shown in Fig. 4. As a result, a welded portion that is welded to the housing is formed on the second surface 24 of the metal plate 20.

[0046] In this way, since an exposed area 22b exposed from the insulating film 30 is formed on the first surface 22 of the pressure sensor element 10, by contacting an electrode from the first surface 22 to the metal plate 20, the second surface 24 and the upper end surface 50b of the housing 50 can be easily fixed by resistance welding.

[0047] 4, at least a portion of the welded portion 24b overlaps with the exposed region 22b when viewed from a direction perpendicular to the first surface 22 (the positive direction of the Z axis). This makes it possible to bring an electrode 70 into contact with the first surface 22 directly above the portion where the welded portion 24b will be formed, thereby performing electric current processing.

[0048] 2, since the exposed region 22b is circumferentially continuous on the first surface 22, the welded portion 24b formed on the second surface 24 can be easily formed in a shape that is circumferentially continuous on the second surface 24 and the upper end surface 50b. That is, in the pressure sensor element 10, 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, as shown in FIG.

[0049] As shown in FIGS. 1 and 4, 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.

[0050] As described above, the pressure sensor element 10 can be fixed to the upper end surface 50b of the housing 50 by resistance welding, for example, as shown in Fig. 4, so that the welding speed is fast and the welding process can be easily automated. In addition, the pressure sensor element 10 does not require a jig 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.

[0051] In addition, in the pressure sensor element 10, by fixing the metal plate 20 using resistance welding, distortion caused by heat during fixing can be suppressed compared to when the metal plate 20 is fixed by other welding methods. Note that the welded portion 24b that fixes the metal plate 20 to the upper end surface 50b of the housing 50 is not limited to that formed by resistance welding. For example, the metal plate 20 may be fixed to the housing 50 by a welded portion formed by electron beam welding, ultrasonic welding, seam welding, friction welding, laser welding, or the like.

[0052] In addition, in the pressure sensor element 10 in which the metal plate 20 is fixed to the housing 50 by welding, even if a slight gap is formed between the second surface 24 and the upper end surface 50b before welding, the gap is sealed by the welded portion 24b. Therefore, from this point of view, the pressure sensor element 10 having the welded portion 24b has good productivity.

[0053] Second embodiment 5 is a plan view of the pressure sensor element 110 according to the second embodiment as viewed from above. The pressure sensor element 110 according to the second embodiment is similar to the pressure sensor element 10 according to the first embodiment (see FIG. 2) except that the shape of the insulating film 130 is different. In the explanation of the pressure sensor element 110, only the differences from the pressure sensor element 10 will be explained, and the explanation of the commonalities with the pressure sensor element 10 will be omitted.

[0054] 5, the insulating film 130 of the pressure sensor element 110 has a cross shape. In this way, it is sufficient for the insulating film 130 to insulate the pressure detection circuit 40 from the metal plate 20, and the shape of the insulating film 130 is not limited to a circular shape like the insulating film 30 shown in FIG.

[0055] The shapes of the covered region 122a and the exposed region 122b formed on the first surface 122 of the metal plate 20 also change in accordance with the shape of the insulating film 130. The pressure sensor element 110 according to the second embodiment also has the same effects as the pressure sensor element 10 according to the first embodiment.

[0056] Third embodiment 6 is a schematic cross-sectional view of a pressure sensor element 210 according to the third embodiment. The pressure sensor element 210 according to the third embodiment is similar to the pressure sensor element 10 according to the first embodiment (see FIG. 2) except that the shape of the second surface 224 of the metal plate 220 is different. In the explanation of the pressure sensor element 210, only the differences from the pressure sensor element 10 will be explained, and the explanation of the commonalities with the pressure sensor element 10 will be omitted.

[0057] 6, a recess 224c recessed toward the first surface 22 is formed on the second surface 224 of the metal plate 220 of the pressure sensor element 210. The recess 224c has a curved shape in which the thickness of the metal plate 220 decreases toward the center 20a.

[0058] The recessed portion 224c is formed in a pressure-receiving portion (see FIG. 1) of the second surface 224 that faces the flow path 50a of the housing 50. A flat portion that forms a welded portion to be welded to the housing 50 is formed on the outer periphery of the recessed portion 224c in the second surface 224.

[0059] 6, a recess 224c is formed on the second surface 224 of the pressure sensor element 210, and the thickness of the metal plate 220 in the pressure-receiving portion is thin. Therefore, the pressure sensor element 210 can increase the strain of the metal plate 220 associated with a unit pressure change, thereby increasing the sensitivity of the sensor.

[0060] The recessed portion 224c may be configured with a curved surface as shown in Fig. 6, but may also be configured with a flat bottom surface and a slanted surface inclined relative to the bottom surface or a wall surface perpendicular to the bottom surface. In addition, the pressure sensor element 210 according to the third embodiment has the same effects as the pressure sensor element 10 according to the first embodiment.

[0061] Fourth embodiment 7 is a schematic cross-sectional view of a pressure sensor element 310 according to the fourth embodiment. The pressure sensor element 310 according to the fourth embodiment is similar to the pressure sensor element 10 according to the first embodiment (see FIG. 2) except for the shape of the metal plate 320. In the explanation of the pressure sensor element 310, only the differences from the pressure sensor element 10 will be explained, and the explanation of the commonalities with the pressure sensor element 10 will be omitted.

[0062] 7, the metal plate 320 of the pressure sensor element 310 includes an outer peripheral edge portion 328 that is thinner than the center 20a side. A step portion 324f that is stepped from the pressure-receiving region 24a on the center 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, a welded portion (see FIG. 1) for welding the metal plate 320 to the housing 50 is formed in the step portion 324f.

[0063] In the pressure sensor element 310, a welded portion can be formed accurately and reliably by welding a stepped portion (not shown) with which the stepped portion 324f engages to a housing 50 (see FIG. 1) having an upper end surface 50b. In addition, the pressure sensor element 310 according to the fourth embodiment has the same effects as the pressure sensor element 10 according to the first embodiment.

[0064] Fifth embodiment 8 is a schematic cross-sectional view of a pressure sensor element 410 according to the fifth embodiment. The pressure sensor element 410 according to the fifth embodiment is similar to the pressure sensor element 10 according to the first embodiment (see FIG. 2) except that the shape of the second surface 424 of the metal plate 420 is different. In the description of the pressure sensor element 410, only the differences from the pressure sensor element 10 will be described, and the description of the commonalities with the pressure sensor element 10 will be omitted.

[0065] 8, an inclined surface 424e is formed on the second surface 424 of the metal plate 420 of the pressure sensor element 410, inclining from the center 20a toward the outer periphery 20b toward the first surface 22 (the positive Z-axis direction). The inclined surface 424e is formed so as to surround the flat pressure-receiving area 24a disposed in the center 20a portion of the second surface 424. The inclined surface 424e is continuous in a ring shape along the outer periphery of the second surface 424. In the pressure sensor element 410, a welded portion (see FIG. 1) for welding the metal plate 420 to the housing 50 is formed on the inclined surface 424e.

[0066] In such a pressure sensor element 410, the inclined surface 424e is in contact with and welded to a corner (see FIG. 1) between the upper end surface 50a of the housing 50 and the flow passage 50a, thereby forming a welded joint with high precision and reliability. In addition, the pressure sensor element 410 according to the fifth embodiment has the same effects as the pressure sensor element 10 according to the first embodiment.

[0067] Sixth embodiment 9 is a schematic cross-sectional view of a pressure sensor element 510 according to the sixth embodiment. The pressure sensor element 510 according to the sixth embodiment is similar to the pressure sensor element 10 according to the first embodiment (see FIG. 2) except that the shape of the metal plate 520 is different. In the explanation of the pressure sensor element 510, only the differences from the pressure sensor element 10 will be explained, and the explanation of the commonalities with the pressure sensor element 10 will be omitted.

[0068] 9, a convex portion 524d is formed on the second surface 524 of the metal plate 520 of the pressure sensor element 510, protruding toward the Z-axis negative direction side, which is the opposite side to the first surface 522 side. The convex portion 524d is formed so as to surround a flat pressure-receiving area 24a disposed around the center 20a of the second surface 524. The convex portion 524d is continuous in a ring shape along the outer periphery 20b of the second surface 524. In the pressure sensor element 510, a welded portion (see FIG. 1) for welding the metal plate 520 to the housing 50 is formed on the convex portion 524d.

[0069] In such a pressure sensor element 510, the protrusion 524d is welded to the upper end surface 50b (see FIG. 1) of the housing 50 in contact with the housing 50, so that a weld is formed accurately and reliably. The protrusion 524d can be formed, for example, by pressing a flat metal plate 20 as shown in FIG. 3, and in this case, a recess 522d corresponding to the protrusion 524d of the second surface 524 is formed in the first surface 522. Such a recess 522d functions as a mark or guide for contacting the welding electrode 70 as shown in FIG. 4. In addition, the pressure sensor element 510 according to the sixth embodiment has the same effects as the pressure sensor element 10 according to the first embodiment.

[0070] Working Example The pressure sensor element according to the present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0071] FIG. 10 shows a calculation of the plate thickness T1 dependency of the maximum stress generated in the metal plate 20 when a predetermined pressure (30 MPa) is applied to the second surface 24 of the metal plate 20 of the pressure sensor element 10 shown in FIG.

[0072] In the embodiment, the diameter D1 (see FIG. 3) of the metal plate 20 was 6 mm, and a model with both ends fixed was used as the mechanical model. The plate thickness T1 (see FIG. 3) was changed between 3.6 and 10 mm. The material of the metal plate 20 was assumed to be SUS316L.

[0073] 10 showing the calculation results, it can be seen that the thinner the thickness of the metal plate 20, the larger the maximum stress generated in the metal plate 20. It can also be seen from Fig. 10 that by setting the thickness T1 of the metal plate 20 to 1 mm or more, the maximum stress generated in the metal plate 20 becomes equal to or less than 175 MPa, which is the yield strength of SUS316L.

[0074] FIG. 11 shows a calculation of the dependency of the resistance change occurring in the strain gauge 41 shown in FIG. 2 on the plate thickness T1 when a predetermined pressure is applied to the pressure sensor element 10 shown in FIG.

[0075] The pressure detection circuit 40 using the strain gauge 41 used in the embodiment was assumed to be a circuit capable of detecting a resistance change of 4Ω or more with appropriate accuracy when the resistance change occurs in the strain gauge 41 with an initial resistance of 1 KΩ. The plate thickness T1 (see FIG. 3) was changed between 3.6 and 10 mm.

[0076] 11, which shows the calculation results, it can be seen that the greater the plate thickness T1 of the metal plate 20, the smaller the resistance change amount. It can also be seen from Fig. 11 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 4 Ω or more, which is the resistance change amount that can be appropriately detected by the assumed circuit.

[0077] 10 and 11, it can be seen that a small pressure sensor element 10 having suitable durability and resolution can be realized by setting the thickness T1 of the metal plate 20 shown in FIG. 1 to 1 mm to 2 mm. Furthermore, by setting the metal plate 20 to such a thickness, it is possible to make the overall thickness of the pressure sensor element 10 thinner than, for example, 6 mm. Such a pressure sensor element 10 can be manufactured by a process in a standard semiconductor factory, and therefore has good productivity.

[0078] FIG. 12 shows a calculation of the film thickness dependency of the electrical resistance of the insulating film 30 formed in the pressure sensor element 10 shown in FIG. 3. The material of the insulating film 30 was assumed to be SiO2, and the film formation method was assumed to be a vapor phase method. From FIG. 12, it can be seen that by setting the film thickness of the insulating film 30 to 4000 nm, the resistance of the insulating film 30 can be set to 1 GΩ, which is sufficient to properly insulate the pressure detection circuit 40 from the metal plate 20, and this is preferable. The thickness of the pressure detection circuit 40 formed from the functional film is not particularly limited, but is preferably about 0.05 to 1 μm. [Explanation of symbols]

[0079] 10, 110, 210, 310, 410, 510...Pressure sensor element 20, 220, 420, 520...metal plate 20a…Central 20b…Outer circumference 22, 122, 522...first surface 22a, 122a...Covering area 22b, 122b...Exposed area 24, 224, 424, 524...second surface 24a…Pressure receiving area 24b…Welded section 30, 130...insulating film 40...Pressure detection circuit 41...Strain gauge 42...Electrode section 50…Housing 50a...flow path 50b…Top end surface 51...Wiring section 52...Printed circuit board 54…Connector 55…Cover member 60...Pressure sensor unit 70...Welding electrodes 224c…Recessed part 324f…Step 328...Outer edge 424e…Slanted surface 522d…Concave 524d…Convex part

Claims

1. a metal plate that seals an end of a fluid flow path of a cylindrical housing formed therein; an insulating film provided on a first surface, which is one surface of the metal plate, so as to form a covering region where the first surface is covered and an exposed region where the first surface is exposed; a pressure detection circuit formed in the insulating film so as to be insulated from the first surface by the insulating film; a second surface of the metal plate opposite to the first surface has a welded portion that is directly welded to a flat surface of the housing that is in contact with the periphery of the end of the flow path to seal the end surface of the housing and that forms a pressure-receiving area on the second surface that receives pressure from the fluid; The metal plate includes an outer peripheral edge portion having a smaller thickness than a central portion, A step portion is formed on the second surface of the metal plate, the step portion being stepped from a center side to the outer circumferential edge portion, The step portion is formed continuously along an outer periphery of the metal plate, The welded portion is formed on the stepped portion of the pressure sensor element.

2. The pressure sensor element according to claim 1 , wherein at least a portion of the weld overlaps the exposed region when viewed from a direction perpendicular to the first surface.

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

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

5. 5. The pressure sensor element according to claim 1, wherein a second surface of the metal plate opposite to the first surface is formed with a recess that is recessed toward the first surface.

Images