Gas sensor

Abstract

Heat conduction from the heater to the substrate can be suppressed.SOLUTION: The gas sensor 10 includes a gas sensor element 20 containing a ceramic material and a substrate 30. The gas sensor element 20 has a heater 26. The gas sensor element 20 and the substrate 30 are connected to each other through the connection portion 40, and the entire gas sensor element 20 is separated from the substrate 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to gas sensors. [Background technology]

[0002] Patent Document 1 discloses a gas sensor. This gas sensor includes a substrate and a heater disposed on the substrate with a first insulating layer interposed therebetween. The gas sensor further includes a gas inlet passage disposed on the heater with a second insulating layer interposed therebetween for introducing a gas to be measured, a lower electrode disposed on the gas inlet passage, a solid electrolyte layer disposed on the lower electrode, and an upper electrode disposed on the surface of the solid electrolyte layer facing the lower electrode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 014033 Summary of the Invention [Problem to be solved by the invention]

[0004] In the gas sensor of Patent Document 1, a heater is disposed on the substrate, and therefore the substrate is heated by the heat from the heater, which may cause the temperature of the sensor to rise. As a result, the environment in which such a gas sensor can be used is limited. The present disclosure has been made in view of the above-described circumstances, and aims to provide a gas sensor that can suppress heat conduction from a heater to a substrate. The present disclosure can be realized in the following aspects. [Means for solving the problem]

[0005] The gas sensor of the present disclosure comprises: a gas sensor element including a ceramic material; A substrate; A gas sensor comprising: the gas sensor element has a heater; The gas sensor element and the substrate are connected via a connecting portion, and at least a portion of the gas sensor element is spaced apart from the substrate. [Effects of the Invention]

[0006] The present disclosure can provide a gas sensor that can suppress heat conduction from a heater to a substrate. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a side cross-sectional view of a gas sensor according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a plan view of the gas sensor of FIG. [Figure 3] FIG. 2 is a side cross-sectional view of the gas sensor element of FIG. [Figure 4] FIG. 2 is a bottom view of the gas sensor element of FIG. [Figure 5] FIG. 2 is a side cross-sectional view of the substrate of FIG. [Figure 6] FIG. 2 is a plan view of the substrate of FIG. [Figure 7] FIG. 4 is a side cross-sectional view of a gas sensor according to a second embodiment of the present disclosure. [Figure 8] FIG. 8 is a plan view of the gas sensor of FIG. 7. [Figure 9] FIG. 10 is a cross-sectional side view of a gas sensor according to a third embodiment of the present disclosure. [Figure 10] FIG. 10 is a plan view of the gas sensor of FIG. 9. [Figure 11] FIG. 10 is a side cross-sectional view of a gas sensor according to a fourth embodiment of the present disclosure. [Figure 12] FIG. 12 is a plan view of the gas sensor of FIG. [Figure 13] FIG. 10 is a side cross-sectional view of a gas sensor according to a fifth embodiment of the present disclosure. [Figure 14] FIG. 10 is a side cross-sectional view of a gas sensor according to a sixth embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0008] In the following, embodiments of the present disclosure are listed and illustrated. [1] A gas sensor element including a ceramic material; A substrate; A gas sensor comprising: the gas sensor element has a heater; The gas sensor comprises a connecting portion that connects the gas sensor element and the substrate, and at least a portion of the gas sensor element is spaced apart from the substrate.

[0009] According to the gas sensor of the above item [1], the gas sensor element having the heater is separated from the substrate via the connecting portion, so that the conduction of heat generated by the heater to the substrate can be suppressed.

[0010] [2] The gas sensor according to [1], wherein the connecting portion is at least one selected from the group consisting of a conductive bump and a conductive wire.

[0011] According to the gas sensor of the above item [2], the connecting portion can support the gas sensor element relative to the substrate while ensuring electrical continuity between the substrate and the gas sensor element.

[0012] [3] The substrate has a frame and a membrane, the membrane is fixed to the frame so as to cover the cavity surrounded by the frame, The gas sensor according to [1] or [2], wherein the gas sensor element is disposed on a surface of the membrane opposite to the cavity.

[0013] According to the gas sensor of the above item [3], the cavity provided in the substrate can further suppress the conduction of heat generated by the heater to the substrate.

[0014] [4] The gas sensor according to any one of [1] to [3], wherein the gas sensor element has a solid electrolyte body made of zirconia and an electrode mainly composed of a metal formed on the surface of the solid electrolyte body.

[0015] According to the gas sensor of the above item [4], the zirconia gas sensor element can be driven well by heating with the heater.

[0016] First Embodiment 1. Configuration of the gas sensor 10 A gas sensor 10 according to a first embodiment of the present invention will be described below with reference to FIGS. 1 to 6. The gas sensor 10 according to the first embodiment shown in FIG. 1 is an example of a gas sensor according to the present disclosure. In the following description, for convenience of explanation, the up-down direction shown in FIG. 1 is defined as the up-down direction, but it does not have to coincide with the up-down direction in the actual arrangement of the gas sensor 10. The up-down direction corresponds to the thickness direction of the substrate 30.

[0017] 1 and 2, the gas sensor 10 includes a gas sensor element 20 and a substrate 30. The gas sensor element 20 includes a ceramic material. The gas sensor 10 measures the concentration of a measurement target gas, such as oxygen.

[0018] 1-1. Configuration of the substrate 30 The substrate 30 shown in FIGS. 5 and 6 is, for example, a MEMS (Micro Electro Mechanical Systems) chip. FIG. 5 is a diagram showing a cross section taken along line BB in FIG. 6. The substrate 30 has a frame 31 and a membrane 32. The frame 31 is, for example, in the shape of a rectangular ring. A rectangular parallelepiped cavity 31A is formed inside the frame 31. The membrane 32 is fixed to the upper surface of the frame 31. The membrane 32 is a plate-like member that is quadrangular (for example, square) in plan view. The membrane 32 covers the cavity 31A surrounded by the frame 31 from above. The frame 31 and the membrane 32 form a diaphragm structure in which the central portion of the membrane 32 serves as a diaphragm film.

[0019] Specifically, as shown in Fig. 1, the substrate 30 has a semiconductor substrate 33A and insulating layers 33B-33F. The substrate 30 further has a pair of signal leads 34, a pair of signal pads 35, a pair of signal electrodes 36 (see Fig. 6), a pair of heater leads 37, a pair of heater pads 38, and a pair of heater electrodes 39 (see Fig. 6). Note that Fig. 1 is a cross section taken along line AA in Fig. 2, and shows one signal lead 34, one signal pad 35, one signal electrode 36, one heater lead 37, one heater pad 38, and one heater electrode 39.

[0020] The material of the semiconductor substrate 33A includes, for example, silicon (Si). An opening 33G is formed in the semiconductor substrate 33A so as to penetrate the substrate so as to open to both the top and bottom surfaces. The opening 33G has, for example, a rectangular shape in a plan view. A portion of the insulating layer 33B is exposed in the opening 33G.

[0021] The insulating layers 33B-33F may be made of any material, as long as they have sufficient insulating properties. The insulating layers 33B-33E are stacked on the upper surface of the semiconductor substrate 33A. From the upper surface of the semiconductor substrate 33A, the insulating layer 33B, the insulating layer 33C, the insulating layer 33D, and the insulating layer 33E are stacked in this order. The insulating layers 33B and 33D are formed of, for example, silicon oxide (SiO2). The insulating layer 33B is formed by, for example, thermal oxidation (such as thermal oxidation of a silicon substrate). The insulating layers 33C and 33E are made of, for example, silicon nitride (Si3N4). The insulating layers 33C and 33E are formed by, for example, low-pressure CVD. The insulating layer 33D is formed by, for example, plasma CVD using TEOS (Si(OC2H5)4) as a liquid source. The insulating layer 33D is formed by, for example, two film deposition processes, one of which sandwiches the process of forming the pair of signal leads 34 and the pair of signal pads 35.

[0022] The insulating layer 33F is laminated on the lower surface of the semiconductor substrate 33A. The material of the insulating layer 33F contains, for example, silicon oxide (SiO2). The insulating layer 33F is formed by, for example, thermal oxidation (thermal oxidation of a silicon substrate, etc.).

[0023] The pair of signal leads 34 and the pair of heater leads 37 are embedded in the insulating layer 33D. The pair of signal leads 34 and the pair of heater leads 37 extend horizontally from the outside to the inside of the insulating layer 33D when viewed from the top-bottom direction.

[0024] The signal lead 34 is connected to the signal pad 35 and the signal electrode 36. The signal lead 34 is a conductive path for extracting an electric signal such as a current from the gas sensor element 20 that measures the gas concentration. The signal lead 34 has a two-layer structure, for example, a layer containing titanium (Ti) and a layer containing platinum (Pt) formed thereon.

[0025] A signal pad 35 is connected to one end (outer end) of the signal lead 34. The signal pad 35 has a two-layer structure, for example, a layer containing chromium (Cr) and a layer containing gold (Au) formed thereon. Wiring (not shown) for supplying power from an external circuit is connected to the signal pad 35. The signal pad 35 is formed at a position that overlaps the semiconductor substrate 33A (frame body 31) in the vertical direction.

[0026] A signal electrode 36 is connected to the other end (inner end) of the signal lead 34. The material of the signal electrode 36 contains, for example, gold (Au). The signal electrode 36 is disposed in a hole 30A formed on the upper surface side of the substrate 30. The hole 30A penetrates the insulating layers 33D and 33E, and the other end of the signal lead 34 is exposed at the bottom. The thickness of the signal electrode 36 is, for example, the same as the thickness of the insulating layer 33D. A connection part 40, which will be described later, is connected to the signal electrode 36.

[0027] The heater lead 37 is connected to the heater pad 38 and the heater electrode 39. The heater lead 37 is a conductive path for passing a current to the heater 26 of the gas sensor element 20, which will be described later. The heater lead 37 has a two-layer structure, for example, a layer containing titanium (Ti) and a layer containing platinum (Pt) formed thereon.

[0028] A heater pad 38 is connected to one end (outer end) of the heater lead 37. The heater pad 38 has a two-layer structure, for example, a layer containing chromium (Cr) and a layer containing gold (Au) formed thereon. Wiring (not shown) for supplying power from an external circuit is connected to the heater pad 38. The heater pad 38 is formed at a position that overlaps the semiconductor substrate 33A (frame 31) in the vertical direction.

[0029] A heater electrode 39 is connected to the other end (inner end) of the heater lead 37. The material of the heater electrode 39 contains, for example, gold (Au). The heater electrode 39 is disposed in a hole 30B formed on the upper surface side of the substrate 30. The hole 30B penetrates the insulating layers 33D and 33E, and the other end of the heater lead 37 is exposed at the bottom. The thickness of the heater electrode 39 is, for example, the same as the thickness of the insulating layer 33D. A connection part 40, which will be described later, is connected to the heater electrode 39.

[0030] The pair of signal pads 35 and the pair of heater pads 38 are positioned in rotational symmetry around the center (center of gravity) C of the gas sensor 10 (specifically, the gas sensor element 20 and the substrate 30) when viewed from above in the thickness direction (vertical direction) of the substrate 30. As shown in Fig. 6, the pair of signal electrodes 36 and the pair of heater electrodes 39 are positioned in rotational symmetry around the center (center of gravity) C of the gas sensor 10 (specifically, the gas sensor element 20 and the substrate 30) when viewed from above in the thickness direction (vertical direction) of the substrate 30.

[0031] The frame 31 is composed of a semiconductor substrate 33A and an insulating layer 33F. The membrane 32 is composed of an inner portion (excluding the portion vertically overlapping with the frame 31) of the portion composed of insulating layers 33B-33E, a pair of signal electrodes 36, and a pair of heater electrodes 39.

[0032] 1-2. Configuration of the gas sensor element 20 3 and 4, the gas sensor element 20 includes a solid electrolyte body 21, a detection electrode 22, a reference electrode 23, insulating layers 24 and 25, a heater 26, a pair of element-side pads 27, and a pair of element-side electrodes 28. The gas sensor element 20 has, for example, a quadrangular (square) plate shape in plan view.

[0033] The solid electrolyte body 21 contains a material that is activated by heating to a high temperature and exhibits ion conductivity. The solid electrolyte body 21 is preferably made of zirconia (ZrO2). The solid electrolyte body 21 contains, for example, stabilized zirconia. The stabilized zirconia is, for example, yttria-stabilized zirconia (YSZ). The solid electrolyte body 21 has, for example, a quadrangular (e.g., square) plate shape in plan view. The solid electrolyte body 21 is, for example, not a layer formed by sputtering, but a bulk ceramic (ceramic sintered body) formed by sintering a ceramic material. The solid electrolyte body 21 has better detection accuracy than a structure formed by sputtering.

[0034] The detection electrode 22 and the reference electrode 23 are electrodes mainly composed of metal and formed on the surface of the solid electrolyte body 21. The detection electrode 22 is laminated on one surface (upper surface) of the solid electrolyte body 21. The material of the detection electrode 22 contains, for example, platinum (Pt). The detection electrode 22 is, for example, a porous body. The reference electrode 23 is laminated on the other surface (lower surface) of the solid electrolyte body 21. The material of the reference electrode 23 contains, for example, platinum (Pt). The reference electrode 23 is, for example, a porous body. The solid electrolyte body 21 is sandwiched between the detection electrode 22 and the reference electrode 23.

[0035] The detection electrode 22 is exposed to a gas to be measured (detection gas). A reference gas (oxygen, etc.) of a predetermined concentration is introduced into the reference electrode 23. The structure for introducing the gas to be measured into the detection electrode 22 and the structure for introducing the reference gas into the reference electrode 23 are not shown in the figure.

[0036] The insulating layers 24 and 25 are laminated on the other surface (lower surface) of the solid electrolyte body 21 and one surface (lower surface) of the reference electrode 23. The insulating layer 24 and the insulating layer 25 are laminated in this order from top to bottom. The material of the insulating layers 24 and 25 contains aluminum oxide (Al2O3). When viewed from above and below, the insulating layers 24 and 25 overlap the solid electrolyte body 21.

[0037] The heater 26 is embedded in the insulating layer 25. The heater 26 has, for example, a strip shape. When viewed from above and below, the heater 26 has, for example, a rectangular spiral shape or a serpentine shape (meandering shape). The heater 26 is made of a material containing, for example, platinum (Pt). The heater 26 generates heat for activating the solid electrolyte body 21 when energized.

[0038] 4, the pair of element-side pads 27 and the pair of element-side electrodes 28 are arranged, for example, at the four corners of the lower surface of the insulating layer 25. The pair of element-side pads 27 and the pair of element-side electrodes 28 have a two-layer structure, for example, a layer containing gold (Au) and a layer formed thereunder containing platinum (Pt). When the pair of element-side pads 27 and the pair of element-side electrodes 28 have a two-layer structure, it is preferable that the material of the upper layer is the same as the material of the connection part 40, which will be described later.

[0039] One of the element-side pads 27 is a pad for extracting a signal obtained from the detection electrode 22. Although not shown, the element-side pad 27 is electrically connected to the detection electrode 22 via a through-hole formed in the gas sensor element 20 (insulating layers 24, 25, etc.).

[0040] The other element-side pad 27 is a pad for extracting a signal obtained from the reference electrode 23. Although not shown, the other element-side pad 27 is electrically connected to the reference electrode 23 via a through-hole formed in the gas sensor element 20 (insulating layers 24, 25, etc.).

[0041] The pair of element-side electrodes 28 are electrodes for passing current through the heater 26. One of the element-side electrodes 28 is connected to one end of the heater 26. The other element-side electrode 28 is connected to the other end of the heater 26. Conduction between the pair of element-side electrodes 28 and the heater 26 is ensured via through holes formed in the gas sensor element 20 (insulating layers 24, 25, etc.).

[0042] The gas sensor element 20 is formed, for example, by a sheet molding process or a printing process. For example, the gas sensor element 20 can be formed by preparing a sheet formed from a ceramic raw material that forms the base of the solid electrolyte body 21, a sheet that forms the base of the insulating layers 24 and 25, etc., printing various electrodes on the sheets, and then sintering the sheets.

[0043] The gas sensor element 20 outputs a signal (voltage signal) based on the difference between the concentration of the measurement gas to which the detection electrode 22 is exposed and the concentration of the reference gas introduced into the reference electrode 23. For example, when the measurement gas is oxygen, the solid electrolyte body 21 can be made ion-conductive by maintaining it at a high temperature, and oxygen ions are conducted from the reference electrode 23 side, where the oxygen concentration is high, to the detection electrode 22 side, generating a current. Because the oxygen ions have a negative charge, an electromotive force is generated between the two electrodes 22, 23.

[0044] The operating temperature of the gas sensor element 20 (the surface temperature of the solid electrolyte body 21 when heated by the heater 26) is preferably 550° C. to 800° C., more preferably 600° C. to 750° C., and even more preferably 650° C. to 700° C. The surface temperature of the frame body 31 (semiconductor substrate 33A) when the gas sensor element 20 is operated is preferably room temperature (e.g., 25° C.) to 50° C.

[0045] 1-3. Support structure of the gas sensor element 20 by the substrate 30 As shown in Fig. 1, the gas sensor element 20 is disposed on the surface (upper surface) of the membrane 32 opposite to the cavity 31A. The gas sensor 10 further includes four connection portions 40 (two connection portions 40 appear in Fig. 1). The gas sensor element 20 and the substrate 30 are connected via the connection portions 40, and the entire gas sensor element 20, except for the portions in contact with the connection portions 40, faces the substrate 30 while being spaced apart from it. A space exists between the gas sensor element 20 and the substrate 30.

[0046] Each of the pair of connection portions 40 is disposed between the signal electrode 36 of the substrate 30 and the element-side pad 27 of the gas sensor element 20. The connection portion 40 is connected to the signal electrode 36 and the element-side pad 27. The connection portion 40 is inserted into the hole 30A in which the signal electrode 36 is disposed. A part of the connection portion 40 may protrude onto the insulating layer 33E.

[0047] The other pair of connecting portions 40 are respectively disposed between the heater electrode 39 of the substrate 30 and the element-side electrode 28 of the gas sensor element 20. The connecting portions 40 are connected to the heater electrode 39 and the element-side electrode 28. The connecting portions 40 are inserted into the holes 30B in which the heater electrodes 39 are disposed. Parts of the connecting portions 40 may protrude onto the insulating layer 33E.

[0048] The connection portions 40 are conductive bumps. The material of the connection portions 40 includes, for example, precious metals and base metals. The material of the connection portions 40 is preferably gold (Au), nickel (Ni), or metallic glass. The material of the connection portions 40 is preferably the same as the material of the pair of element-side pads 27 and the material of the pair of element-side electrodes 28. If the pair of element-side pads 27 and the pair of element-side electrodes 28 have a two-layer structure, the material of the connection portions 40 is preferably the same as the material of the layer on the connection portion 40 side.

[0049] The gas sensor 10 shown in FIGS. 1 and 2 is fabricated by fabricating the gas sensor element 20 shown in FIGS. 3 and 4 and the substrate 30 shown in FIGS. 5 and 6, respectively, and then connecting the gas sensor element 20 to the substrate 30 via the connecting portion 40.

[0050] 2. Effects of the First Embodiment The gas sensor 10 of the first embodiment includes a gas sensor element 20 containing a ceramic material, and a substrate 30. The gas sensor element 20 has a heater 26. The gas sensor element 20 and the substrate 30 are connected via a connecting portion 40, and the entire gas sensor element 20 is spaced apart from the substrate 30.

[0051] According to this gas sensor 10, the gas sensor element 20 having the heater 26 is separated from the substrate 30 via the connection portion 40, thereby suppressing the conduction of heat generated by the heater 26 to the substrate 30. Therefore, the gas sensor 10 operates at a relatively low temperature on the substrate 30 side, making it applicable to a wide range of applications, including medical and industrial applications. For example, the gas sensor 10 can be easily placed near the human body and used because the substrate 30 side can be kept at a relatively low temperature. Furthermore, the gas sensor 10 tends to eliminate the need for packaging that takes thermal insulation into consideration, thereby suppressing an increase in size.

[0052] In the gas sensor 10 of the first embodiment, the connecting portions 40 are conductive bumps. According to this gas sensor 10, the connecting portions 40 can support the gas sensor element 20 on the substrate 30 while ensuring electrical continuity between the substrate 30 and the gas sensor element 20.

[0053] In the gas sensor 10 of the first embodiment, the substrate 30 has a frame 31 and a membrane 32. The membrane 32 is fixed to the frame 31 so as to cover a cavity 31A surrounded by the frame 31. The gas sensor element 20 is disposed on the surface of the membrane 32 opposite to the cavity 31A. In this gas sensor 10, the cavity 31A is provided in the substrate 30, so that the conduction of heat generated by the heater 26 to the substrate 30 can be further suppressed.

[0054] In the gas sensor 10 of the first embodiment, the gas sensor element 20 includes a solid electrolyte body 21 made of zirconia, and a detection electrode 22 and a reference electrode 23, each of which is mainly made of metal and formed on the surface of the solid electrolyte body 21. According to this gas sensor 10, the zirconia-type gas sensor element 20 can be effectively driven by heating with a heater 26.

[0055] Second Embodiment A second embodiment of the present disclosure will be described below with reference to FIGS. 7 and 8. The gas sensor of the second embodiment differs from the first embodiment in the configuration of the substrate, but is otherwise the same. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. Note that FIG. 7 is a view showing a cross section taken along CC in FIG. 8.

[0056] The gas sensor 210 of the second embodiment includes a gas sensor element 20 and a substrate 230. The substrate 230 has a frame 31, a membrane 32, and a rim portion 231B. The rim portion 231B is formed inside the frame 31 (inside the cavity 31A). The rim portion 231B has a rectangular ring shape. A rectangular ring-shaped groove portion 231C is formed between the frame 31 and the rim portion 231B. The frame 31 and the rim portion 231B are connected by four connecting portions 231D arranged around the center C of the substrate 230. The rim portion 231B and the connecting portions 231D are formed by a part of the semiconductor substrate 233A and a part of the insulating layer 233F.

[0057] With this configuration, the rim portion 231B can increase the strength of the connection portion between the substrate 230 and the connection portion 40. Heat generated in the gas sensor element 20 is transferred to the rim portion 231B via the connection portion 40, but the presence of the groove portion 231C can suppress the transfer of heat from the rim portion 231B to the frame body 31.

[0058] <Third embodiment> A third embodiment of the present disclosure will be described below with reference to FIGS. 9 and 10. The gas sensor of the third embodiment differs from the first embodiment in the configuration of the connection portion, but is otherwise the same as the first embodiment. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. Note that FIG. 9 is a view showing a cross section taken along line DD in FIG. 10.

[0059] The gas sensor 310 of the third embodiment includes a gas sensor element 20, a substrate 30, and four connecting portions 340. The connecting portions 340 are conductive wires. The connecting portions 340 are made of a material such as gold (Au), copper (Cu), or aluminum (Al). The gas sensor element 20 is supported on the substrate 30 by the four connecting portions 340.

[0060] One pair of connecting portions 340 is connected to the signal electrode 36 of the substrate 30 and the element-side pad 27 of the gas sensor element 20, respectively. The other pair of connecting portions 340 is connected to the heater electrode 39 of the substrate 30 and the element-side electrode 28 of the gas sensor element 20, respectively.

[0061] Even with this configuration, the gas sensor element 20 having the heater 26 is separated from the substrate 30 via the connection portion 340. This makes it possible to suppress the conduction of heat generated by the heater 26 to the substrate 30. Furthermore, since the connection portion 340 is connected to the membrane 32 (the portion above the cavity 31A) in the substrate 30, thermal insulation with respect to the bottom side of the substrate 30 (the side opposite to the gas sensor element 20) can be improved.

[0062] <Fourth embodiment> A fourth embodiment of the present disclosure will be described below with reference to FIGS. 11 and 12. The gas sensor of the fourth embodiment differs from the first embodiment in the configuration of the substrate and the connection portion, but is otherwise the same. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. Note that FIG. 11 is a view showing an E-E cross section of FIG. 12.

[0063] The gas sensor 410 of the fourth embodiment includes a gas sensor element 20, a substrate 430, and four connecting portions 440. The connecting portions 440 are conductive wires. The connecting portions 440 may be made of a material such as gold (Au), copper (Cu), or aluminum (Al). The gas sensor element 20 is supported on the substrate 430 by the four connecting portions 440.

[0064] One pair of connecting portions 440 is connected to the signal electrode 36 of the substrate 30 and the element-side pad 27 of the gas sensor element 20, respectively. The other pair of connecting portions 440 is connected to the heater electrode 39 of the substrate 30 and the element-side electrode 28 of the gas sensor element 20, respectively.

[0065] The substrate 430 has a frame 31, a membrane 32, and a rim portion 431B. The rim portion 431B is formed inside the frame 31 (inside the cavity 31A). The rim portion 431B is rectangular annular. A rectangular annular groove 431C is formed between the frame 31 and the rim portion 431B. The frame 31 and the rim portion 431B are connected by four connecting portions 431D arranged around the center C of the substrate 430. The rim portion 431B and the connecting portions 431D are formed by a portion of the semiconductor substrate 433A and a portion of the insulating layer 433F.

[0066] Even with this configuration, the gas sensor element 20 having the heater 26 is separated from the substrate 430 via the connection portion 440. This makes it possible to suppress the conduction of heat generated by the heater 26 to the substrate 430. Furthermore, the rim portion 431B increases the strength of the connection portion between the substrate 430 and the connection portion 440. Heat generated by the gas sensor element 20 is conducted to the rim portion 431B via the connection portion 440, but the presence of the groove portion 431C makes it possible to suppress the conduction of heat from the rim portion 431B to the frame body 31.

[0067] Fifth Embodiment A fifth embodiment of the present disclosure will be described below with reference to Fig. 13. The gas sensor of the fifth embodiment differs from the first embodiment in the configuration of the substrate and the connection portion, but is otherwise the same as the first embodiment. Note that the same components as the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0068] The gas sensor 510 of the fifth embodiment includes the gas sensor element 20, a substrate 530, and four connection portions 540.

[0069] The substrate 530 is a resin substrate (glass epoxy substrate) in which reinforcing fibers are impregnated with resin. The substrate 530 is a rectangular (square, etc.) plate in plan view. A pair of wires 534 and a pair of wires 537 are provided on the substrate 530. Note that one of the wires 534 and one of the wires 537 are shown in FIG. 13. The wires 534 and 537 are made of a material containing metal. The wire 534 is a conductive path for extracting an electric signal such as a current from the gas sensor element 20 that measures the gas concentration. The wire 537 is a conductive path for passing a current to the heater 26 of the gas sensor element 20.

[0070] The connecting portions 540 are conductive wires. The material of the connecting portions 540 includes, for example, gold (Au), copper (Cu), aluminum (Al), etc. The gas sensor element 20 is supported on the substrate 30 by the four connecting portions 540.

[0071] One pair of connecting portions 540 is connected to the wiring 534 of the substrate 530 and the element-side pad 27 of the gas sensor element 20, respectively. The other pair of connecting portions 540 is connected to the wiring 537 of the substrate 530 and the element-side electrode 28 of the gas sensor element 20, respectively.

[0072] Even with this configuration, the gas sensor element 20 having the heater 26 is spaced apart from the substrate 530 via the connecting portion 540. Therefore, conduction of heat generated by the heater 26 to the substrate 530 can be suppressed.

[0073] Sixth Embodiment A sixth embodiment of the present disclosure will be described below with reference to Fig. 14. The gas sensor of the sixth embodiment differs from the first embodiment in the configuration of the substrate and the connection portion, but is otherwise the same as the first embodiment. Note that the same components as the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0074] The gas sensor 610 of the sixth embodiment includes the gas sensor element 20, a housing 650, and four connection portions 640.

[0075] The housing 650 is a member that forms the outer shell of the gas sensor 610. The material of the housing 650 contains a resin (glass epoxy) in which reinforcing fibers are impregnated with resin. The housing 650 has a substrate 630. The substrate 630 forms, for example, a side wall of the housing 650.

[0076] The substrate 630 is a resin substrate (glass epoxy substrate) in which reinforcing fibers are impregnated with resin. The substrate 630 is, for example, a quadrangular (square or other) plate. A pair of wires 634 and a pair of wires 637 are provided on the substrate 630. Note that one of the wires 634 and one of the wires 637 are shown in FIG. 14. The wires 634 and 637 are made of a material containing metal. The wire 634 is a conductive path for supplying a current to the gas sensor element 20 to measure the gas concentration. The wire 637 is a conductive path for supplying a current to the heater 26 of the gas sensor element 20.

[0077] The connecting portions 640 are conductive wires. The material of the connecting portions 640 includes, for example, gold (Au), copper (Cu), aluminum (Al), etc. The gas sensor element 20 is supported on the substrate 630 (housing 650) by the four connecting portions 640.

[0078] One pair of connecting portions 640 is connected to the wiring 634 of the substrate 630 and the element-side pad 27 of the gas sensor element 20, respectively. The other pair of connecting portions 640 is connected to the wiring 637 of the substrate 630 and the element-side electrode 28 of the gas sensor element 20, respectively.

[0079] In this configuration, the housing 650 can have a wiring function. In addition, the gas sensor element 20 having the heater 26 is separated from the substrate 630 (housing 650) via the connection portion 640. Therefore, it is possible to suppress the conduction of heat generated by the heater 26 to the substrate 630 (housing 650).

[0080] <Other embodiments> The present disclosure is not limited to the embodiments described above and in the drawings. For example, any combination of features of the above-described or following embodiments is possible within a range that does not contradict. Furthermore, any feature of the above-described or following embodiments may be omitted unless explicitly stated as essential. Furthermore, the above-described embodiment may be modified as follows.

[0081] In the first to sixth embodiments, the entire gas sensor element 20 is separated from the substrate 30. However, the gas sensor element 20 may be partially separated from the substrate 30. That is, the gas sensor element 20 may be partially in contact with the substrate 30.

[0082] In the first to sixth embodiments, a cavity is formed inside the frame, but the cavity does not have to be formed, that is, the opening 33G does not have to be formed in the semiconductor substrate 33A.

[0083] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0084] 10: Gas sensor 20: Gas sensor element 21: Solid electrolyte body 22: Sensing electrode 23: Reference electrode 24,25: Insulating layer 26: Heater 27: Element side pad 28: Element side electrode 30: Circuit board 30A: Hole 30B: Hole 31: Frame 31A: Cavity 32: Membrane 33A: Semiconductor substrate 33B-33F: Insulating layer 33G: Opening 34: Signal lead 35: Signal pad 36: Signal electrode 37: Heater lead 38: Heating pad 39: Heater electrode 40: Connection 210: Gas sensor 230: Circuit board 231B: Rim 231C: Groove 231D: Connecting part 233A: Semiconductor substrate 233F: Insulating layer 310: Gas sensor 340: Connection 410: Gas sensor 430: Circuit board 431B: Rim 431C: Groove 431D: Connection part 433A: Semiconductor substrate 433F: Insulating layer 440: Connection 510: Gas sensor 530: Circuit board 534,537: Wiring 540: Connection 610: Gas sensor 630: Circuit board 634,637: Wiring 640: Connection 650: Case C: Center (center of gravity)

Claims

1. a gas sensor element including a ceramic material; A substrate; A gas sensor comprising: the gas sensor element has a heater; The gas sensor comprises a connecting portion that connects the gas sensor element and the substrate, and at least a portion of the gas sensor element is spaced apart from the substrate.

2. 2. The gas sensor according to claim 1, wherein the connecting portion is at least one selected from the group consisting of a conductive bump and a conductive wire.

3. the substrate has a frame and a membrane, the membrane is fixed to the frame so as to cover the cavity surrounded by the frame, 3. The gas sensor according to claim 1, wherein the gas sensor element is disposed on a surface of the membrane opposite to the cavity.

4. 3. The gas sensor according to claim 1, wherein the gas sensor element comprises a solid electrolyte body made of zirconia and an electrode mainly made of metal formed on a surface of the solid electrolyte body.

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