Capacitive sensor

Abstract

According to the present invention, a first detection electrode (21) is provided on an insulating layer (10). A second detection electrode (22) is provided on the insulating layer (10) at a distance from the first detection electrode (21), while forming an electrostatic capacitance together with the first detection electrode (21). A protective layer (50) covers the first detection electrode (21) and the second detection electrode (22), while having a thickness d that satisfies 1 μm ≤ d ≤ 10 μm. The protective layer (50) is formed of zirconia or alumina.

Description

Technical Field

[0001] The present invention relates to a capacitive sensor.

Background Art

[0002] According to Japanese Unexamined Patent Application Publication No. 2009-210503 (Patent Document 1), a liquid level sensor is disclosed. The liquid level sensor has a substrate made of polyimide and a plurality of electrodes made of Ag. The liquid level is calculated based on the magnitude of the capacitance between the electrodes.

[0003] According to Japanese Unexamined Patent Application Publication No. 2008-111669 (Patent Document 2), a liquid property sensor for detecting the property of a liquid whose relative permittivity changes depending on the property is disclosed. The liquid property sensor has a semiconductor substrate, a first and a second electrode arranged at a predetermined interval on the same plane of the semiconductor substrate, and a protective film formed on the semiconductor substrate so as to cover the surface of the semiconductor substrate on which the first and second electrodes are formed and having resistance to the liquid. The protective film is arranged so as to be exposed to the liquid, and the capacitance value corresponding to the relative permittivity of the liquid is detected by the first and second electrodes. According to the above publication, it is preferable that the protective film is formed to have a film thickness of 10 μm or less. The reason is that when the film thickness of the protective film becomes thick, the electric field acting between the first and second electrodes hardly reaches the liquid near the surface of the protective film, and the detection sensitivity decreases. Also according to the above publication, it is preferable that the protective film is formed of either a silicon oxide film or a silicon nitride film. The reason is that these films have good resistance to liquids such as gasoline, alcohol, and oil, which are the liquids to be detected in the above liquid property sensor, and can be easily formed using ordinary semiconductor manufacturing techniques.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to the technology of the above-mentioned Japanese Patent Application Laid-Open No. 2009-210503, a configuration for protecting an electrode from a liquid whose liquid level is detected is not disclosed. Without such a configuration, it is difficult to ensure corrosion resistance and chemical resistance. Specifically, when a cleaning process is performed on the sensor, there is a concern that the electrode may be damaged due to peeling or the like. Further, since the electrode can be a source of metal contamination into the liquid, the sensor may not be suitable for applications that avoid metal contamination, such as for semiconductor processes and medical use.

[0006] According to the technology of the above-mentioned Japanese Patent Application Laid-Open No. 2008-111669, a silicon oxide film or a silicon nitride film is used as a configuration for protecting the electrode. These materials have a relatively low relative dielectric constant. As a result, the magnitude of the detected capacitance tends to be small. Therefore, the sensor sensitivity tends to be low.

[0007] The present invention has been made to solve the above problems, and an object thereof is to provide a capacitance type sensor capable of performing high-sensitivity detection while ensuring corrosion resistance and chemical resistance.

Means for Solving the Problems

[0008] A capacitance-type sensor according to one aspect is a capacitance-type sensor that utilizes a change in capacitance. The capacitance-type sensor includes an insulating layer, a first detection electrode, a second detection electrode, and a protective layer. The first detection electrode is provided on the insulating layer. The second detection electrode is provided on the insulating layer and separated from the first detection electrode, and forms the capacitance together with the first detection electrode. The protective layer covers the first detection electrode and the second detection electrode, has a thickness d satisfying 1 μm ≤ d ≤ 10 μm, and is made of zirconia or alumina.

[0009] Preferably, the protective layer is made of zirconia.

[0010] The protective layer has a relative permittivity ε, and preferably ε / d ≥ 1 is satisfied.

[0011] Preferably, the minimum distance between the first detection electrode and the second detection electrode is 100 μm or less. The minimum distance is a dimension on at least one straight line, and preferably, the dimensions of each of the first detection electrode and the second detection electrode are 100 μm or less at least on the at least one straight line.

[0012] The capacitance-type sensor may further include a heater for heating the protective layer.

[0013] The capacitance-type sensor may be a liquid detection sensor.

[0014] The capacitance-type sensor may be a liquid level sensor.

[0015] The capacitance-type sensor may be a dew condensation sensor.

Advantages of the Invention

[0016] According to the capacitance type sensor, first, a protective layer covering the first detection electrode and the second detection electrode is made of zirconia or alumina. Thereby, the corrosion resistance and chemical resistance of the capacitance type sensor are enhanced. Second, the thickness d of the protective layer satisfies 1 μm ≤ d ≤ 10 μm. Thereby, while ensuring the above-described corrosion resistance and chemical resistance, a significant decrease in the sensitivity of the capacitance type sensor due to the provision of the protective layer is avoided. From the above, detection with high sensitivity can be performed while ensuring corrosion resistance and chemical resistance.

[0017] When the protective layer is made of zirconia, the relative permittivity of the protective layer becomes relatively high. Thereby, a decrease in the sensitivity of the capacitance type sensor due to the provision of the protective layer is more sufficiently avoided.

[0018] When ε / d ≥ 1 is satisfied, the capacitance per unit area formed through the protective layer becomes large. Thereby, it becomes easier to sufficiently ensure the sensitivity of the capacitance type sensor.

[0019] When the capacitance type sensor includes a heater for heating the protective layer, the liquid adhering to the protective layer can be removed by heating. Thereby, the sensitivity for newly detecting the liquid can be quickly ensured.

[0020] According to the liquid detection sensor, a liquid can be detected with high sensitivity while ensuring corrosion resistance and chemical resistance.

[0021] According to the liquid level sensor, the liquid level can be detected with high sensitivity while ensuring corrosion resistance and chemical resistance.

[0022] According to the dew condensation sensor, dew condensation can be detected with high sensitivity while ensuring corrosion resistance and chemical resistance.

[0023] The object, features, aspects, and advantages of the present invention will become clearer from the following detailed description and the accompanying drawings.

Brief Description of the Drawings

[0024]

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Embodiments for Carrying Out the Invention

[0025] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0026] <Embodiment 1> (Configuration) Each of FIGS. 1 and 2 is a front view and a rear view schematically showing the configuration of a detection system 500 having a liquid level sensor 101 (a capacitance type sensor as a liquid detection sensor) according to the present embodiment. FIG. 3 is a schematic partial cross-sectional view taken along line III-III of FIGS. 1 and 2. FIG. 4 is a schematic partial cross-sectional view taken along line IV-IV of FIGS. 1 and 2. FIG. 5 is a schematic partial cross-sectional view taken along line V-V of FIGS. 1 and 2. In FIGS. 1 and 2, an example of the liquid level PL of the liquid LQ to be detected by the liquid level sensor 101 is shown by a virtual line. Further, the liquid LQ is shown in FIG. 5. Also, an XYZ orthogonal coordinate system is shown to make the drawings easier to view. In the present embodiment, the direction Z corresponds to vertically upward. Also, the origin in the Z direction corresponds to the zero position of the liquid level PL.

[0027] The detection system 500 includes a liquid level sensor 101 and a measuring instrument 200. The liquid level sensor 101 is a capacitance type sensor that performs detection using a change in capacitance. The liquid level sensor 101 includes an insulating layer 10, a first detection electrode 21, a second detection electrode 22, and a protective layer 50. Further, the liquid level sensor 101 may include a first pad electrode 31, a second pad electrode 32, a first via electrode 41, and a second via electrode 42.

[0028] The insulating layer 10 is preferably made of a ceramic insulator, and more preferably made of the same material as the protective layer 50. The thickness of the insulating layer 10 is, for example, about 1 mm.

[0029] As shown in FIGS. 3 to 5, the first detection electrode 21 is provided on one surface of the insulating layer 10. The second detection electrode 22 is provided on the insulating layer 10 away from the first detection electrode 21. The second detection electrode 22 forms a capacitance together with the first detection electrode 21.

[0030] Define the minimum distance between the first detection electrode 21 and the second detection electrode 22 as the electrode interval S (Figure 1). The electrode interval S is preferably 20 μm or more and 100 μm or less. The minimum interval S is a dimension on at least one straight line ML. Define the dimensions of the first detection electrode 21 and the second detection electrode 22 on at least one straight line ML as the electrode width L1 and the electrode width L2, respectively. Each of the electrode width L1 and the electrode width L2 is preferably 20 μm or more and 100 μm or less. In the following, the electrode width L1 and the electrode width L2 may be collectively referred to as the electrode width L. As shown in Figure 1, the first detection electrode 21 and the second detection electrode 22 may form a line-and-space pattern. The first detection electrode 21 and the second detection electrode 22 are preferably made of a high melting point metal that is difficult to oxidize, for example, platinum, tungsten, or cobalt. The thickness of the first detection electrode 21 and the second detection electrode 22 is, for example, about 5 μm.

[0031] The protective layer 50 covers the first detection electrode 21 and the second detection electrode 22. Specifically, the protective layer 50 has a surface SF and a surface facing the first detection electrode 21 and the second detection electrode 22, which is opposite to the surface SF. The protective layer 50 has a thickness d that satisfies 1 μm ≤ d ≤ 10 μm, and preferably has a thickness d that satisfies 1 μm ≤ d ≤ 5 μm. The protective layer 50 is made of zirconia or alumina, and preferably made of zirconia. The protective layer 50 has a relative dielectric constant ε, and preferably, ε ≥ 10 is satisfied. For example, by using zirconia, ε of about 30 can be obtained, and by using alumina, ε of about 10 can be obtained. Preferably, ε / d ≥ 1 is satisfied.

[0032] The first pad electrode 31 is provided on the surface of the insulating layer 10 opposite to the one surface. The second pad electrode 32 is provided on the surface of the insulating layer 10 opposite to the one surface, separated from the first pad electrode 31. The first via electrode 41 penetrates the insulating layer 10 and has one end connected to the first detection electrode 21 and the other end connected to the first pad electrode 31. The second via electrode 42 penetrates the insulating layer 10 and has one end connected to the second detection electrode 22 and the other end connected to the second pad electrode 32.

[0033] The measuring instrument 200 has a function of measuring capacitance. The measuring instrument 200 is electrically connected to the first pad electrode 31 and the second pad electrode 32. Thereby, the measuring instrument 200 can measure the capacitance formed by the first detection electrode 21 and the second detection electrode 22.

[0034] In the liquid detection method using the liquid level sensor 101, the following plurality of steps are performed. First, a step of detecting the capacitance of the liquid level sensor 101 is performed. Next, a step of detecting the liquid LQ, specifically, a step of detecting the liquid level PL of the liquid LQ, is performed based on the capacitance detected in the step of detecting the capacitance.

[0035] FIG. 6 is a circuit diagram showing an approximate equivalent circuit corresponding to FIG. 5. FIG. 7 is a graph showing an example of the relationship between the liquid level PL and the measured value of the capacitance of the liquid level sensor 101. The result of FIG. 7 is such that each of the first detection electrode 21 and yo the second detection electrode 22 has a width of 3 mm, a thickness of 0.5 mm, and a length of 30 mm in each of the X direction, the Y direction, and the Z direction, and the liquid LQ has a conductivity of 1 mS / m.

[0036] Referring to FIGS. 5 and 6, the configuration in which the liquid LQ and the first detection electrode 21 face each other via the protective layer 50 forms the capacitance C1. Similarly, the configuration in which the liquid LQ and the second detection electrode 22 face each other via the protective layer 50 forms the capacitance C2. Since the capacitance C measured by the measuring instrument approximately corresponds to the capacitance constituted by the series connection of the capacitance C1 and the capacitance C2, C = C1 × C2 / (C1 + C2) is calculated by. As shown in FIG. 1, when the configuration of the second detection electrode 22 is the same as that of the first detection electrode 21, C2 = C1. In this case, the above formula becomes C = C1 / 2 which can be rewritten as. The measured value of the capacitance C is approximately proportional to the liquid level PL as shown in FIG. 6. Therefore, by grasping in advance the relationship between the liquid level PL and the measured value of the capacitance C as shown in FIG. 7, it becomes possible to detect the liquid level using the measured value of the liquid level sensor 101.

[0037] Here, since the capacitance C is approximated by the capacitance formed via the protective layer 50, it is approximately proportional to the product of the relative permittivity and the thickness of the protective layer 50, that is, ε / d. In order to detect the change rate of the capacitance C with high precision, it is preferable that the magnitude of the capacitance C is relatively large. Therefore, it is preferable that ε / d is relatively large, and specifically, it is preferable that ε / d ≧ 1 is satisfied.

[0038] (Manufacturing method) FIG. 8 is a partial cross-sectional view schematically showing one step in the manufacturing method of the liquid level sensor 101 in the present embodiment.

[0039] Referring to FIGS. 3 and 8, a laminate including a green sheet 10G to be the insulating layer 10, a paste layer 21G to be the first detection electrode 21, a paste layer 22G to be the second detection electrode 22, a paste layer 31G to be the first pad electrode 31, a paste layer 32G to be the second pad electrode 32, a paste layer 41G to be the first via electrode 41, and a paste layer 42G to be the second via electrode 42 is prepared. Each paste layer can be formed by printing a paste containing metal powder and ceramic powder onto the green sheet 10G. Note that the green sheet 10G may be constituted by a single layer, or may be constituted by laminating a plurality of green sheets.

[0040] On the above laminate, a green sheet 50G to be the protective layer 50 is pressure-bonded as shown by the arrow (FIG. 8). This pressure-bonding is preferably performed together with heating.

[0041] Next, the laminate with the green sheet 50G pressure-bonded as described above is fired. Thereby, the liquid level sensor 101 is obtained.

[0042] (Example) Table 1 below shows the experimental results for Examples A1 to A4 of the liquid level sensor 101 described above and Comparative Examples B1 and B2 thereof.

[0043]

Table 1

[0044] In the lower part of the above table, the sensitivities when measuring the liquid levels of a liquid with a conductivity of 1 mS / cm and a liquid with a conductivity of 0.01 mS / cm using each of these liquid level sensors are shown. As can be seen from these results, in the case of Examples A1 to A3 where the protective layer 50 is made of zirconia and its thickness d is 10 μm or less, compared with the case of Comparative Example B1 where the protective layer 50 is made of glass, and the case of Comparative Example B2 where the thickness d of the protective layer 50 is 20 μm which is greater than 10 μm, high sensitivity was obtained. Also, in the case of Example A4 where the protective layer 50 is made of alumina and its thickness d is 10 μm or less, specifically 3 μm, high sensitivity was obtained compared with the cases of Comparative Example B1 and Comparative Example B2.

[0045] In the above experiment, the first detection electrode 21 and the second detection electrode 22 were each a pair of line patterns having a width of 100 μm, and these line patterns were separated by a space having a width of 100 μm. In other words, in FIG. 1, dimensions of L = S = 100 μm were adopted. Also, each of the first detection electrode 21 and the second detection electrode 22 had an area of 13 square mm and a thickness of 3 μm.

[0046] Table 2 below shows the experimental results for further Examples A5 to A8 having the same protective layer 50 as Example A1, together with the experimental results of Example A1.

[0047]

Table 2

[0048] Examples A1 to A7 having an electrode interval S of 100 μm or less had higher sensitivity than Example A8 having an electrode interval S of 150 μm. Also, Examples A1 to A7 having an electrode width L of 100 μm or less had higher sensitivity than Example A8 having an electrode width L of 150 μm.

[0049] (Summary of effects) According to this embodiment, first, the protective layer 50 covering the first detection electrode 21 and the second detection electrode 22 is made of zirconia or alumina. Thereby, the corrosion resistance and chemical resistance of the liquid level sensor 101 are enhanced.

[0050] Second, the thickness d of the protective layer 50 satisfies 1 μm ≤ d ≤ 10 μm. Thereby, while ensuring the above-described corrosion resistance and chemical resistance, a significant decrease in the sensitivity of the liquid level sensor 101 due to the provision of the protective layer 50 is avoided.

[0051] From the above, detection with high sensitivity can be performed while ensuring corrosion resistance and chemical resistance. Specifically, the liquid level can be detected with high sensitivity.

[0052] The protective layer 50 is preferably made of zirconia. Thereby, the relative permittivity ε of the protective layer 50 becomes a high value of about 30. Thereby, a decrease in the sensitivity of the liquid level sensor 101 due to the provision of the protective layer 50 is more sufficiently avoided.

[0053] It is preferable that ε / d ≥ 1 is satisfied. Thereby, the capacitance per unit area formed through the protective layer 50 increases. Thereby, it becomes easier to sufficiently ensure the sensitivity of the liquid level sensor 101.

[0054] When the electrode interval S is 100 μm or less, higher sensitivity can be obtained. When the electrode interval S is 20 μm or more, a desired electrode interval can be formed relatively easily by the multilayer ceramic technology.

[0055] When the electrode width L is 100 μm or less, higher sensitivity can be obtained. When the electrode width L is 20 μm or more, a desired electrode width can be formed relatively easily by the multilayer ceramic technology.

[0056] The insulating layer 10 and the protective layer 50 are preferably both made of a ceramic insulator, and more preferably made of the same material. Thereby, the difference in shrinkage rate in the firing process for manufacturing the liquid level sensor 101 is suppressed. Therefore, even if the thickness d of the protective layer 50 is relatively small, a protective layer 50 without pinholes can be obtained. Therefore, while sufficiently obtaining the effect of improving corrosion resistance and chemical resistance by the protective layer 50, the thickness d can be reduced.

[0057] The portion that becomes the protective layer 50 is preferably formed by pressure bonding of the green sheet 50G (FIG. 8). Thereby, even if the thickness d of the protective layer 50 is relatively small, a protective layer 50 without pinholes can be obtained as compared with the case where the portion is formed by applying a ceramic paste.

[0058] The first detection electrode 21 and the second detection electrode 22 are preferably made of a high melting point metal, for example, platinum, tungsten, or cobalt. Thereby, volatilization and melting of the electrodes in the firing process for manufacturing the liquid level sensor 101 can be avoided.

[0059] <Embodiment 2> FIG. 9 is a cross-sectional view schematically showing the configuration of the dew condensation sensor 102 (capacitive sensor as a liquid detection sensor) in the present embodiment. Each of FIGS. 10 to 12 is a schematic partial cross-sectional view taken along line X-X, line XI-XI, and line XII-XII of FIG. 9.

[0060] In the detection system 500 (FIGS. 1 and 2), by using the dew condensation sensor 102 instead of the liquid level sensor 101, dew condensation on the protective layer 50 can be detected. The first detection electrode 21 and the second detection electrode 22 for the dew condensation sensor 102 preferably have a comb shape as shown in FIG. 10. Thereby, the detection sensitivity of dew condensation is enhanced.

[0061] Referring to FIG. 10, similar to the case of FIG. 1 (Embodiment 1), the minimum distance between the first detection electrode 21 and the second detection electrode 22 is defined as the electrode distance S (FIG. 10). The electrode distance S is preferably 20 μm or more and 100 μm or less. Similar to the case of FIG. 1 (Embodiment 1), the electrode distance S (FIG. 10) is a dimension on at least one straight line ML, and the dimensions of the first detection electrode 21 and the second detection electrode 22 on at least one straight line ML are defined as the electrode width L1 and the electrode width L2, respectively. Each of the electrode width L1 and the electrode width L2 is preferably 20 μm or more and 100 μm or less. Note that, similar to Embodiment 1, in this embodiment as well, the electrode width L1 and the electrode width L2 may be collectively referred to as the electrode width L.

[0062] The dew condensation sensor 102 preferably has a heater 60 for heating the protective layer 50. Heat generation is obtained by passing an electric current through the heater 60. By heating the protective layer 50 in this way, the liquid adhering to the surface SF can be removed by evaporation. Therefore, when a large amount of liquid adheres to the surface SF due to cleaning or long-term use, etc., by removing it using the heater 60, a state where the occurrence of dew condensation can be detected again can be quickly obtained.

[0063] The heater 60 is preferably embedded inside the dew condensation sensor 102, and more preferably embedded inside the insulating layer 10. In that case, the dew condensation sensor 102 may have a pad electrode 71, a pad electrode 72, a via electrode 81, and a via electrode 82 in order to enable electrical connection to the heater 60. One end (the upper end in FIG. 9) of the via electrode 81 and one end (the upper end in FIG. 9) of the via electrode 82 are each connected to one end and the other end of the heater 60. The other end (the lower end in FIG. 9) of the via electrode 81 and the other end (the lower end in FIG. 9) of the via electrode 82 are each connected to the pad electrode 71 and the pad electrode 72. With this configuration, by applying a voltage between the pad electrode 71 and the pad electrode 72, the heater 60 can be heated.

[0064] Incidentally, the heater 60 and the related configurations described above may be applied to other capacitance sensors such as the liquid level sensor 101 (Embodiment 1).

[0065] Regarding the configurations other than the above, since they are substantially the same as the configuration of the liquid level sensor 101 (Embodiment 1), the same reference numerals are given to the same or corresponding elements, and the description thereof will not be repeated.

[0066] Table 3 below shows the experimental results for Example D1 of the dew condensation sensor 102 described above and its Comparative Example E1.

[0067]

Table 3

[0068] In the lower part of the above table, the change in capacitance when steam is blown from a steam generation source separated by 50 mm to each of these dew condensation sensors is shown. As can be seen from this result, in the case of Example D1 where the thickness d of the protective layer 50 is 5 μm, the occurrence of dew condensation due to the blowing of steam and the disappearance of dew condensation due to the stoppage of the blowing of steam could be detected as changes in capacitance. On the other hand, in the case of Comparative Example E1 where the thickness d of the protective layer 50 is 20 μm, the change in capacitance due to the blowing of steam could not be detected.

[0069] Table 4 below shows the experimental results for further Examples D2 to D4 and Comparative Example E2 having the same protective layer 50 as in Example D1, together with the experimental results of Example D 1.

[0070]

Table 4

[0071] Incidentally, in the above table, the measured value change (pF / mm 2) is the amount of change in capacitance per unit area of the effective portion EF (FIG. 10) of the dew condensation sensor 102. The effective portion EF is the portion of the dew condensation sensor 102 (FIG. 10) that substantially contributes to the capacitance in a plan view (FIG. 10). Specifically, the effective portion EF is the portion other than the outer peripheral portion that does not substantially contribute to the capacitance in a plan view (FIG. 10).

[0072] In Examples D1 to D4 having an electrode interval S of 100 μm or less, a change in the measured value due to dew condensation could be detected. On the other hand, in Comparative Example E2 having an electrode interval S of 150 μm, a change in the measured value due to dew condensation could not be detected. The reason is considered to be that since the size of the droplets generated by dew condensation was smaller than less than 150 μm, in Comparative Example E2, the droplets were not positioned so as to straddle between the first detection electrode 21 and the second detection electrode 22 in a plan view (FIG. 10). Therefore, when the capacitance type sensor is a dew condensation sensor as in the present embodiment, it is particularly desirable that the electrode interval S be 100 μm or less.

[0073] In each of Examples D1 to D4, assuming that the electrode width L is made excessive while maintaining the electrode interval S, it is considered that the change in the measured value becomes small.

[0074] According to the present embodiment, dew condensation can be detected with high sensitivity while ensuring corrosion resistance and chemical resistance. Note that the configuration of the protective layer 50 in the examples shown in Table 3 above is an example, and instead of this, the configuration of the protective layer 50 described in Embodiment 1 may be applied. The preferred configuration of the protective layer 50 is substantially the same in the case of the present embodiment as in the case of Embodiment 1.

[0075] When the electrode interval S is 100 μm or less, dew condensation can be detected more reliably. When the electrode interval S is 20 μm or more, a desired electrode interval can be formed relatively easily by the multilayer ceramic technology.

[0076] When the electrode width L is 100 μm or less, it is possible to avoid a small change in the measured value due to an excessive electrode width L. When the electrode width L is 20 μm or more, a desired electrode width can be relatively easily ensured by the multilayer ceramic technology.

[0077] As described above, when a fine dimension of 100 μm or less is used in relation to the first detection electrode 21 and the second detection electrode 22, it is particularly difficult to ensure corrosion resistance and chemical resistance by the protective layer 50 while preventing the protective layer 50 from significantly inhibiting the detection of dew condensation. According to the present embodiment, this can be achieved.

[0078] When the heater 60 is provided, the liquid adhering to the surface SF of the protective layer 50 can be removed by heating. Thereby, it is possible to promptly ensure the sensitivity for newly detecting the liquid.

[0079] In the above, as an application of the capacitance type sensor, the applications for detecting the liquid level and dew condensation have been described in detail. However, the capacitance type sensor may be applied to other applications. The above-described embodiments and modified examples may be freely combined with each other. Although the present invention has been described in detail, the above description is illustrative in all aspects and the present invention is not limited thereto. It is understood that innumerable modified examples not illustrated can be assumed without departing from the scope of the present invention.

Description of Reference Numerals

[0080] 10: Insulating layer 21: First detection electrode 22: Second detection electrode 31: First pad electrode 32: Second pad electrode 41: First via electrode 42: Second via electrode 50: Protective layer 60: Heater 71: Pad electrode 72: Pad electrode 81: Via electrode 82: Via electrode 101: Liquid level sensor (capacitive sensor as a liquid detection sensor) 102: Dew sensor (capacitive sensor as a liquid detection sensor) 200: Measuring instrument 500: Detection system LQ: Liquid PL: Liquid level SF: Surface

Claims

1. A capacitance-type sensor that utilizes a change in capacitance, an insulating layer, a first detection electrode provided on the insulating layer, a second detection electrode provided on the insulating layer away from the first detection electrode and forming the capacitance together with the first detection electrode, a protective layer that covers the first detection electrode and the second detection electrode and has a thickness d satisfying 1 μm ≤ d ≤ 10 μm and is a fired body made of zirconia or alumina, and is provided with the capacitance is formed by the liquid on the protective layer facing each of the first detection electrode and the second detection electrode through the protective layer. A capacitance-type sensor.

2. The capacitance-type sensor according to claim 1, wherein the protective layer is made of zirconia.

3. The capacitance-type sensor according to claim 1 or 2, wherein the protective layer has a relative dielectric constant ε and ε / d ≥ 1 is satisfied.

4. The capacitance-type sensor according to any one of claims 1 to 3, wherein the minimum distance between the first detection electrode and the second detection electrode is 100 μm or less.

5. The capacitance-type sensor according to claim 4, wherein the minimum distance is a dimension on at least one straight line, and the dimensions of each of the first detection electrode and the second detection electrode are 100 μm or less at least on the at least one straight line.

6. The capacitance-type sensor according to any one of claims 1 to 5, further comprising a heater for heating the protective layer.

7. The capacitance-type sensor according to any one of claims 1 to 6, wherein the capacitance-type sensor is a liquid detection sensor.

8. The capacitance-type sensor according to any one of claims 1 to 7, wherein the capacitance-type sensor is a liquid level sensor.

9. The capacitance-type sensor according to any one of claims 1 to 7, wherein the capacitance-type sensor is a dew condensation sensor that detects the occurrence of dew condensation.

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