Sulfur detection sensor

Abstract

To provide a sulfidation detection sensor with which it is possible to accurately and easily detect a sulfidation degree.SOLUTION: A sulfidation detection sensor 10 comprises: an insulating substrate 1 of rectangular parallelepiped shape; a resistor 2 which is formed so as to be in close contact with the surface of the insulating substrate 1; a sulfidation detection conductor 3 which is formed so as to be in close contact with the surface of the resistor 2; a sulfide gas impermeable protective layer 4 which is formed so as to cover a portion of the sulfidation detection conductor 3; and a pair of electrodes 6 which is formed at both edges of the insulating substrate 1 and connected to the resistor 2 and the sulfidation detection conductor 3. The sulfidation detection conductor 3 is formed from a metal whose resistance value is lower than that of the resistor 2 and incudes an exposed part 3a that is exposed to the outside without being covered with the protective layer 4.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a sulfur detection sensor for detecting the cumulative amount of sulfur in a corrosive environment.

Background Art

[0002] Generally, as an internal electrode of an electronic component such as a chip resistor, an Ag (silver)-based electrode material with low specific resistance is used. However, when silver is exposed to sulfur gas, it becomes silver sulfide, and since silver sulfide is an insulator, there is a problem that the electronic component is disconnected. Therefore, in recent years, measures against sulfurization have been taken, such as adding Pd (palladium) or Au (gold) to Ag to form an electrode that is difficult to sulfurize, or making the structure such that sulfur gas hardly reaches the electrode.

[0003] However, even if such measures against sulfurization are taken for electronic components, it becomes difficult to completely prevent disconnection when the electronic components are exposed to sulfur gas for a long time or to high-concentration sulfur gas. Therefore, it is necessary to detect disconnection in advance and prevent the occurrence of a failure at an unexpected timing.

[0004] Therefore, conventionally, as described in Patent Document 1, a sulfur detection sensor has been proposed that can detect the degree of cumulative sulfurization of an electronic component and detect the risk before the electronic component fails due to sulfurization disconnection or the like. The sulfur detection sensor described in Patent Document 1 has a configuration in which a sulfur detection conductor mainly composed of Ag is formed on an insulating substrate, a transparent and sulfur gas-permeable protective film is formed so as to cover the sulfur detection conductor, and end face electrodes connected to the sulfur detection conductor are formed at both end portions of the insulating substrate.

[0005] After mounting the sulfurization detection sensor configured as described above on a circuit board together with other electronic components, when the circuit board is used in an atmosphere containing sulfurized gas, the sulfurized gas permeates the protective film of the sulfurization detection sensor and contacts the sulfurization detection conductor. Therefore, the color of the sulfurization detection conductor changes according to the concentration of the sulfurized gas and the elapsed time. Further, as the sulfurization progresses, the silver constituting the sulfurization detection conductor changes to silver sulfide, so the resistance value of the sulfurization detection sensor gradually increases and eventually the wire breaks. As a result, it becomes possible to detect the degree of sulfurization by visually observing the change in the color of the sulfurization detection body through the protective film, detecting the reflected light from the sulfurization detection body of the light irradiated on the upper surface of the sulfurization detection sensor, or detecting the change in the resistance value of the sulfurization detection body.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, since the change in the color of the sulfurization detection conductor due to sulfurized gas is subtle, it is difficult for an operator to accurately detect the degree of sulfurization by visual observation. Even if the degree of sulfurization is detected based on the reflected light from the sulfurization detection conductor, there is a problem that large-scale equipment for detection is separately required.

[0008] Further, when detecting the change in the resistance value of the sulfurization detection conductor, since the sulfurization detection conductor is a conductor mainly composed of Ag or the like with a low specific resistance, the change in the resistance value within the time until the sulfurization detection conductor is sulfurized and the wire breaks is extremely small, and it is difficult to accurately detect the degree of sulfurization based on the change in the resistance value of the sulfurization detection conductor during this period.

[0009] The present invention has been made in view of the above-described state of the prior art, and an object thereof is to provide a sulfurization detection sensor capable of accurately and easily detecting the degree of sulfurization.

Means for Solving the Problems

[0010] In order to achieve the above object, the sulfurization detection sensor of the present invention includes a rectangular parallelepiped-shaped insulating substrate, a resistor provided on the main surface of the insulating substrate, a sulfurization detection conductor provided on the resistor and sulfurized by sulfur gas, a sulfur gas non-permeable protective layer provided so as to cover a part of the sulfurization detection conductor, and a pair of electrode portions provided at both ends of the insulating substrate and connected to the resistor and the sulfurization detection conductor. The sulfurization detection conductor is made of a metal having a lower resistance value than the resistor and has an exposed portion that is not covered by the protective layer and is exposed to the outside.

[0011] In the sulfurization detection sensor configured as described above, conduction between the pair of electrode portions is always ensured by the resistor. When exposed to an atmosphere containing sulfur gas and sulfurization progresses, the sulfurization detection conductor provided on the resistor starts sulfurization from the exposed portion that is not covered by the protective layer and is exposed to the outside, and then sulfurizes into the inside covered by the protective layer. Therefore, the current path flowing between the pair of electrode portions changes according to the degree of sulfurization of the sulfurization detection conductor. Thereby, the resistance value of the resistor can be continuously changed in accordance with the degree of sulfurization of the sulfurization detection conductor, and the degree of sulfurization can be accurately and easily detected.

[0012] In the sulfurization detection sensor having the above configuration, the sulfurization detection conductor may be formed so as to cover the entire surface of the resistor. However, the resistor has an adjustment region that is not covered by the sulfurization detection conductor. When a trimming groove for resistance value adjustment is formed in this adjustment region and the adjustment region is covered by a part of the protective layer, not only can the initial resistance value of the resistor be increased by the trimming groove, but also a sulfurization detection sensor with good temperature characteristics (TCR) can be realized.

[0013] In addition, in the sulfur detection sensor with the above configuration, the sulfur detection conductor may be composed of a single material. However, if the sulfur detection conductor is composed of a first sulfur detection conductor and a second sulfur detection conductor made of different materials with different gas selectivities, and these first and second sulfur detection conductors each have an exposed portion, the degree of sulfurization can be reliably detected regardless of the type of sulfur gas contained in the use atmosphere.

[0014] That is, the reactivity of sulfur gas varies depending on the type of metal constituting the sulfur detection conductor. For example, silver (Ag) easily reacts with hydrogen sulfide (H2S) but has low reactivity with sulfur dioxide (SO2), and nickel (Ni) easily reacts with sulfur dioxide (SO2) but has low reactivity with hydrogen sulfide (H2S). Therefore, if one of the first sulfur detection conductor and the second sulfur detection conductor is made of Ag and the other is made of Ni, a multi-type sulfur detection sensor capable of corresponding to different types of sulfur gas can be realized. In addition, since copper (Cu) is a material that easily reacts with both hydrogen sulfide (H2S) and sulfur dioxide (SO2), a single copper (Cu) can also be a multi-type sulfur detection sensor. However, like the above-mentioned Ag material and Ni material, by combining materials with different gas selectivities and high reactivity with the target sulfur gas, the detection accuracy can be improved compared to the case where a sulfur detection body is formed of a single copper (Cu).

[0015] In this case, it is preferable that the resistor has an exposed area not covered by the first sulfur detection conductor and the second sulfur detection conductor, an intermediate protective layer is provided on this exposed area, and the exposed portions of the first sulfur detection conductor and the second sulfur detection conductor are arranged at positions sandwiching the intermediate protective layer.

[0016] In addition, in the sulfur detection sensor with the above configuration, the resistor and the sulfur detection conductor may be a metal glaze formed by thick film formation using screen printing or the like. However, if these resistor and sulfur detection conductor are metal films formed by thin film formation using sputtering or the like, the variation in the film thickness of the resistor and the sulfur detection conductor can be eliminated and the detection accuracy can be improved.

[0017] In this case, if the insulating substrate is made of an alumina substrate and the resistor is a Ni-Cr metal film formed on the surface of the alumina substrate by sputtering, the bonding strength with the alumina substrate is increased by Cr in the metal film, and the adhesion with a sulfurization detection conductor (Ag, Cu, Ni, etc.) is increased by Ni, which is preferable.

[0018] Further, in the sulfurization detection sensor having the above configuration, the protective layer is composed of an undercoat layer made of a glass material formed on the sulfurization detection conductor and an overcoat layer made of a resin material formed on the undercoat layer, and it is preferable that the electrode portion covers the end portion of the sulfurization detection conductor and is in close contact with the overcoat layer. With such a configuration, the adhesion between the electrode portion and the overcoat layer made of a resin material is improved, so that not only can the sulfurization of the end portion of the sulfurization detection conductor covered by the electrode portion be suppressed, but also an undercoat layer that does not permeate sulfurized gas is provided under the overcoat layer made of a resin material, thereby preventing the sulfurization detection conductor in the portion covered by the protective layer from reacting with the sulfurized gas that has permeated through the overcoat layer and being sulfurized.

Advantages of the Invention

[0019] According to the sulfurization detection sensor of the present invention, the degree of sulfurization can be accurately and easily detected.

Brief Description of the Drawings

[0020]

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Mode for Carrying Out the Invention

[0021] Hereinafter, embodiments of the invention will be described with reference to the drawings.

[0022] FIG. 1 is a plan view of a sulfur detection sensor according to the first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. As shown in FIGS. 1 and 2, the sulfur detection sensor 10 according to the first embodiment mainly includes a rectangular parallelepiped insulating substrate 1, a resistor 2 formed so as to be in close contact with the surface of the insulating substrate 1, a sulfur detection conductor 3 formed so as to be in close contact with the surface of the resistor 2, a protective layer 4 formed of a sulfur gas-impermeable material that covers a part of the sulfur detection conductor 3, a pair of back electrodes 5 formed at both longitudinal ends of the back surface of the insulating substrate 1, and a pair of electrode portions 6 formed at both longitudinal ends of the insulating substrate 1.

[0023] The insulating substrate 1 is obtained by dividing a large-sized substrate along vertical and horizontal dividing grooves and taking a large number of them. The large-sized substrate is an alumina substrate having alumina as a main component (purity 96%).

[0024] The resistor 2 is made of a Ni-Cr metal film formed on the surface of the insulating substrate (alumina substrate) 1 by thin film formation such as sputtering or vapor deposition. The resistor 2 is formed in a rectangular shape over the entire surface of the insulating substrate 1, and both ends of the resistor 2 are respectively connected to a pair of electrode portions 6.

[0025] The sulfur detection conductor 3 is made of a metal film such as Cu, Ag, or Ni formed on the surface of the resistor 2 by sputtering, vapor deposition, or the like. The resistance value of these metal films is sufficiently smaller than the resistance value of the metal film constituting the resistor 2 (for example, the resistor is several kΩ and the sulfur detection conductor is several tens of mΩ). The sulfur detection conductor 3 is formed in a rectangular shape over the entire surface of the resistor 2, and both ends of the sulfur detection conductor 3 are also connected to a pair of electrode portions 6, respectively.

[0026] The protective layer 4 is formed of an insulating material having a property of not permeating sulfur gas. For example, it has a two-layer structure in which an undercoat layer made of a glass material and an overcoat layer made of a resin material are laminated. The protective layer 4 is formed at two locations excluding the central portion and both ends of the sulfur detection conductor 3, and the central portion of the sulfur detection conductor 3 not covered by these protective layers 4 is an exposed portion 3a exposed to the outside.

[0027] The back electrode 5 is made of a metal film of Cr-Cu or Cr-Ni-Cu formed by sputtering on the back surface of the insulating substrate (alumina substrate) 1. The pair of back electrodes 5 are formed at both longitudinal ends on the back surface of the insulating substrate 1. Note that it is also possible to form a thick film instead of forming the back electrode 5 as a thin film. In that case, an Ag-based paste or a Cu-based paste may be screen-printed and dried and fired.

[0028] The electrode portion 6 is composed of an end face electrode 7 having a U-shaped cross section that conducts between the end of the sulfur detection conductor 3 exposed from the protective layer 4 and the back electrode 5, and an intermediate electrode 8 and an external electrode 9 sequentially formed so as to cover the end face electrode 7. The end face electrode 7 is formed by sputtering Ni / Cr on the end face of the insulating substrate 1. The intermediate electrode 8 is a Ni plating layer formed by electrolytic plating, and the external electrode 9 is a Sn plating layer formed by electrolytic plating.

[0029] Next, the manufacturing process of the sulfurization detection sensor 10 configured as described above will be described with reference to FIGS. 3 and 4. FIGS. 3(a) to (f) are plan views of a large-sized substrate used in this manufacturing process as seen from the surface, and FIGS. 4(a) to (f) are cross-sectional views corresponding to one chip along the central portion in the longitudinal direction of FIGS. 3(a) to (f), respectively.

[0030] First, as shown in FIGS. 3(a) and 4(a), a large-sized substrate 1A on which a large number of insulating substrates 1 are placed is prepared. The large-sized substrate 1A is previously provided with primary division grooves and secondary division grooves in a lattice pattern, and each square divided by both division grooves becomes a chip region for one unit. Although FIGS. 3 and 4 show a large-sized substrate 1A corresponding to one chip region as a representative, actually, the following steps described below are collectively performed on the large-sized substrate 1A corresponding to a large number of chip regions.

[0031] That is, after sputtering Ni-Cr on the surface of the large-sized substrate 1A, Cu or the like is sputtered thereon to form a two-layer metal film. Thereafter, by patterning these metal films into a rectangular shape by photolithography, a resistor 2 that adheres to the surface of the large-sized substrate 1A and a sulfurization detection conductor 3 that adheres to the surface of the resistor 2 are formed as shown in FIGS. 3(b) and 4(b).

[0032] Next, by sputtering Cr-Cu or Cr-Ni-Cu from above a mask on the back surface of the large-sized substrate 1A (mask sputtering), a back electrode 5 that faces the back surface of the large-sized substrate 1A at a predetermined interval is formed as shown in FIGS. 3(c) and 4(c).

[0033] Next, an SiO2 film is formed on the surface side of the large-sized substrate 1A by CVD (Chemical Vapor Deposition) method or sputtering, or a glass paste is screen-printed and then dried and fired to form an undercoat layer. Then, an epoxy resin or a phenolic resin is screen-printed from above the undercoat layer and then heat-cured to form an overcoat layer, thereby forming a protective layer 4 that covers portions other than both ends and the central portion of the sulfurization detection conductor 3 as shown in FIGS. 3(d) and 4(d).

[0034] Next, after the large-sized substrate 1A is first divided into strip-shaped substrates 1B along the first dividing groove, Ni / Cr is sputtered on the dividing surface of the strip-shaped substrate 1B, and as shown in FIGS. 3(e) and 4(e), end electrodes 7 that connect between the sulfurization detection conductor 3 and the back electrode 5 are formed at both ends of the strip-shaped substrate 1B. This end electrode 7 is connected not only to the end of the sulfurization detection conductor 3 exposed from the protective layer 4 but also to the end surface of the resistor 2 covered by the sulfurization detection conductor 3.

[0035] Next, after the strip-shaped substrate 1B is secondarily divided into a plurality of chip-shaped substrates 1C along the second dividing groove, electrolytic plating is performed on these chip-shaped substrates 1C, and an intermediate electrode 8 made of a Ni plating layer and an external electrode 9 made of a Sn plating layer are sequentially formed. As a result, as shown in FIGS. 3(f) and 4(f), electrode portions 6 composed of the end electrode 7, the intermediate electrode 8, and the external electrode 9 are formed at both ends of the chip-shaped substrate 1C, and the sulfurization detection sensor 10 shown in FIGS. 1 and 2 is completed.

[0036] FIG. 5 is an explanatory diagram showing a change in the current path when the sulfurization detection sensor 10 according to the present embodiment is arranged in a sulfur gas atmosphere, and FIG. 6 is an explanatory diagram showing the relationship between the elapsed time and the resistance value when the sulfurization detection sensor 10 is arranged in a sulfur gas atmosphere.

[0037] In the initial state before the sulfurization detection sensor 10 is exposed to sulfur gas, the entire surface of the resistor 2 is covered by the sulfurization detection conductor 3, and both ends of these resistor 2 and sulfurization detection conductor 3 are connected to a pair of electrode portions 6. Therefore, as shown by the arrow X1 in FIG. 5(a), the current flowing between the pair of electrode portions flows through the sulfurization detection conductor 3 having a significantly smaller resistance value than the resistor 2.

[0038] When this sulfurization detection sensor 10 is placed in an atmosphere containing hydrogen sulfide gas, the exposed portion 3a of the sulfurization detection conductor 3 that is exposed to the outside without being covered by the protective layer 4 comes into contact with the hydrogen sulfide gas. Therefore, sulfurization starts from the exposed portion 3a over time, and then sulfurization progresses into the inside of the sulfurization detection conductor 3 covered by the protective layer 4. As a result, as shown by the arrow X2 in Fig. 5(b), the current path becomes from one unsulfurized portion of the sulfurization detection conductor 3, through the resistor 2, to the other unsulfurized portion. Along with this, the resistance value between the pair of electrode portions changes as shown in Fig. 6. That is, the resistance value of the sulfurization detection sensor 10 rises with a gentle curve until the time point (T1) when the exposed portion 3a of the sulfurization detection conductor 3 is sulfurized. After that, as sulfurization progresses into the inside of the sulfurization detection conductor 3, it rises linearly, and reaches a constant value (the resistance value of the resistor 2) at the time point (T2) when the entire sulfurization detection conductor 3 is sulfurized. Thus, within the threshold value indicated by the symbol S in Fig. 6, since the resistance value of the resistor 2 changes continuously according to the degree of sulfurization of the sulfurization detection conductor 3, the degree of sulfurization can be detected accurately and easily.

[0039] As described above, in the sulfurization detection sensor 10 according to the first embodiment, conduction between the pair of electrode portions 6 is always ensured by the resistor 2 formed on the insulating substrate 1. When exposed to an atmosphere containing hydrogen sulfide gas and sulfurization progresses, the sulfurization detection conductor 3 provided on the resistor 2 starts sulfurization from the exposed portion 3a that is exposed to the outside without being covered by the protective layer 4, and then sulfurizes into the inside covered by the protective layer 4. Therefore, the current path flowing between the pair of electrode portions 6 changes according to the degree of sulfurization of the sulfurization detection conductor 3. Thereby, the resistance value of the resistor 2 can be continuously changed according to the degree of sulfurization of the sulfurization detection conductor 3, and the degree of sulfurization can be detected accurately and easily.

[0040] In addition, in the sulfur detection sensor 10 according to the first embodiment, since the resistor 2 and the sulfur detection conductor 3 are metal films formed by thin film formation using sputtering or the like, variations in the film thickness of the resistor 2 and the sulfur detection conductor 3 are eliminated, and the detection accuracy can be improved. Moreover, since the resistor 2 is a Ni-Cr metal film formed as a thin film on the surface of the insulating substrate (alumina substrate) 1, the bonding strength with the alumina substrate 1 can be increased by Cr in the metal film, and the adhesion with the sulfur detection conductor 3 made of Ag, Cu, Ni, etc. can be increased by Ni.

[0041] Note that Cr plays a role in improving the sulfur resistance of the metal film itself. However, if the Cr content in the metal film increases, it becomes mechanically brittle. Therefore, the Cr content in the Ni-Cr metal film is desirably within the range of 40 to 60 wt%. Also, the Ni-Cr metal film only needs to have a main component, and titanium (Ti), tungsten (W), etc. may be appropriately added for the purpose of lowering the temperature coefficient of resistance (TCR) as long as the above-described functions can be maintained.

[0042] FIG. 7 is a plan view of the sulfur detection sensor 20 according to the second embodiment of the present invention, and FIG. 8 is a cross-sectional view taken along line VIII-VIII of FIG. 7. Parts corresponding to FIGS. 1 and 2 are denoted by the same reference numerals.

[0043] As shown in FIGS. 7 and 8, the sulfur detection sensor 20 according to the second embodiment has an adjustment region 2a where the resistor 2 is not covered by the sulfur detection conductor 3. A trimming groove 21 for adjusting the resistance value is formed in this adjustment region 2a, and the adjustment region 2a is covered with a protective layer 4.

[0044] In the sulfur detection sensor 20 configured in this way, by forming the trimming groove 21 in the adjustment region 2a, the initial resistance value of the resistor 2 can be increased, and a sulfur detection sensor 20 with good temperature characteristics (TCR) can be realized. Note that the trimming groove 21 is not limited to the I-cut shape as shown, and may be other shapes such as an L-cut. Also, the number of trimming grooves 21 is not limited to two as shown, and may be appropriately increased or decreased.

[0045] FIG. 9 is a plan view of a sulfur detection sensor 30 according to a third embodiment of the present invention, FIG. 10 is a cross-sectional view taken along line X-X of FIG. 9, and parts corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals.

[0046] As shown in FIGS. 9 and 10, a protective layer 4 of the sulfur detection sensor 30 according to the third embodiment is constituted by an undercoat layer 31 made of a glass material formed on a sulfur detection conductor 3 and an overcoat layer 32 made of a resin material formed on the undercoat layer 31, and an electrode portion 6 covers an end portion of the sulfur detection conductor 3 and is in close contact with the overcoat layer 32.

[0047] In the sulfur detection sensor 30 configured as described above, since the protective layer 4 has an overcoat layer 32 made of a resin material, the adhesion between the overcoat layer 32 and the electrode portion 6 is improved, so that sulfurization of the end portion of the sulfur detection conductor 3 covered by the end face electrode 7 of the electrode portion 6 can be suppressed. However, since the resin material has the property of permeating gas, if the entire protective layer 4 is formed of the resin material, the sulfur detection conductor 3 located directly below the protective layer 4 may be sulfurized by the sulfur gas that has permeated through the protective layer 4. Therefore, by forming an undercoat layer 31 made of a glass material that does not permeate sulfur gas under the overcoat layer 32 made of a resin material, it is possible to prevent the sulfur detection conductor 3 located directly below the protective layer 4 from reacting with the sulfur gas that has permeated through the overcoat layer 32 and being sulfurized.

[0048] FIG. 11 is a plan view of a sulfur detection sensor 40 according to a fourth embodiment of the present invention, FIG. 12 is a cross-sectional view taken along line XII-XII of FIG. 11, and parts corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals.

[0049] As shown in FIGS. 11 and 12, in the sulfurization detection sensor 40 according to the fourth embodiment, the resistor 2 has an exposed region 2b at the central portion in the longitudinal direction, and the first sulfurization detection conductor 41 and the second sulfurization detection conductor 42 are formed at two positions on the resistor 2 sandwiching the exposed region 2b. These first sulfurization detection conductor 41 and second sulfurization detection conductor 42 are made of metal films of different materials formed by thin film formation such as sputtering or vapor deposition on the surface of the resistor 2. For example, the first sulfurization detection conductor 41 is a Ni metal film, and the second sulfurization detection conductor 42 is an Ag metal film.

[0050] A sulfur gas non-permeable protective layer 4A is formed at the central portion of the first sulfurization detection conductor 41, and the inner end portion of the first sulfurization detection conductor 41 is an exposed portion 41a that is exposed to the outside without being covered by the protective layer 4A. Similarly, a sulfur gas non-permeable protective layer 4A is also formed at the central portion of the second sulfurization detection conductor 42, and the inner end portion of the second sulfurization detection conductor 42 is an exposed portion 42a that is exposed to the outside without being covered by the protective layer 4A. Further, a sulfur gas non-permeable intermediate protective layer 4B is formed in the exposed region 2b of the resistor 2, and the exposed portion 41a of the first sulfurization detection conductor 41 and the exposed portion 42a of the second sulfurization detection conductor 42 are arranged at opposing positions sandwiching the intermediate protective layer 4B.

[0051] In the sulfurization detection sensor 40 configured as described above, the first sulfurization detection conductor 41 and the second sulfurization detection conductor 42 made of different materials with different gas selectivities are formed on the resistor 2, and since these first sulfurization detection conductor 41 and second sulfurization detection conductor 42 each have exposed portions 41a, 42a, it is possible to reliably detect the degree of sulfurization regardless of the type of sulfur gas contained in the use atmosphere.

[0052] That is, the reactivity of sulfurized gas varies depending on the type of metal constituting the sulfurization detection conductor. For example, silver (Ag) easily reacts with hydrogen sulfide (H2S), but has low reactivity with sulfur dioxide (SO2). Nickel (Ni) easily reacts with sulfur dioxide (SO2), but has low reactivity with hydrogen sulfide (H2S). Therefore, in a gas atmosphere containing sulfur dioxide, sulfurization starts from the exposed portion 41a of the first sulfurization detection conductor 41 made of Ni, and in a gas atmosphere of hydrogen sulfide, sulfurization starts from the exposed portion 42a of the second sulfurization detection conductor 42 made of Ag. Thus, a multi-type sulfurization detection sensor 40 capable of corresponding to different sulfurized gases can be realized.

[0053] Note that copper (Cu) is a material that easily reacts with both hydrogen sulfide (H2S) and sulfur dioxide (SO2). Therefore, even a single copper (Cu) can be a multi-type sulfurization detection sensor. However, like the above-mentioned Ag material and Ni material, by combining with materials having different gas selectivities from each other and high reactivity with the target sulfurized gas, the detection accuracy can be improved compared to the case where a sulfurization detection body is formed of a single copper (Cu).

[0054] Also, in the sulfurization detection sensor 40 according to the fourth embodiment, the resistor 2 has an exposed region 2b that is not covered by the first sulfurization detection conductor 41 and the second sulfurization detection conductor 42, and an intermediate protective layer 4B is formed so as to cover this exposed region 2b. Since the exposed portion 41a of the first sulfurization detection conductor 41 and the exposed portion 42a of the second sulfurization detection conductor 42 are arranged at opposing positions sandwiching the intermediate protective layer 4B, by sputtering Ni and Ag from above the mask on the surface of the resistor 2 (mask sputtering), the first sulfurization detection conductor 41 and the second sulfurization detection conductor 42 made of different materials can be easily formed.

[0055] In each of the above embodiments, the case where the resistor 2 and the sulfur detection conductor 3 (41, 42) are metal films formed by thin film formation using sputtering or the like has been described. However, it is also possible to configure these resistor and sulfur detection conductor with a metal glaze by thick film formation. For example, after screen printing an Ag-Pd (50%) paste and then drying and firing it, a resistor can be formed, or after screen printing a Cu paste or an Ag paste and then drying and firing it, a sulfur detection conductor may be formed.

Explanation of Reference Numerals

[0056] 1 Insulating substrate 1A Large-sized substrate 1B Strip-shaped substrate 1C Chip-shaped substrate 2 Resistor 2a Adjustment region 2b Exposed region 3 Sulfur detection conductor 3a Exposed portion 4, 4A Protective layer 4B Intermediate protective layer 5 Back electrode 6 Electrode portion 7 End face electrode 8 Intermediate electrode 9 External electrode 10, 20, 30, 40 Sulfur detection sensor 21 Trimming groove 31 Undercoat layer 32 Overcoat layer 41 First sulfur detection conductor 41a Exposed portion 42 Second sulfur detection conductor 42a Exposed portion

Claims

1. A rectangular parallelepiped-shaped insulating substrate, a resistor provided on the main surface of the insulating substrate, a sulfurization detection conductor provided on the resistor and sulfurized by sulfur gas, a sulfur gas non-permeable protective layer provided so as to cover a part of the sulfurization detection conductor, and a pair of electrode portions provided at both ends of the insulating substrate and connected to the resistor and the sulfurization detection conductor. The sulfurization detection conductor is made of a metal having a lower resistance value than the resistor, and has an exposed portion that is not covered by the protective layer and is exposed to the outside. A sulfurization detection sensor characterized by this.

2. In the sulfurization detection sensor according to claim 1, The resistor has an adjustment region that is not covered by the sulfurization detection conductor, a trimming groove for adjusting the resistance value is formed in the adjustment region, and the adjustment region is covered by a part of the protective layer. A sulfurization detection sensor characterized by this.

3. In the sulfurization detection sensor according to claim 1, The sulfurization detection conductor is composed of a first sulfurization detection conductor and a second sulfurization detection conductor made of different materials having different gas selectivities, and the first sulfurization detection conductor and the second sulfurization detection conductor each have the exposed portion. A sulfurization detection sensor characterized by this.

4. In the sulfurization detection sensor according to claim 3, The resistor has an exposed region that is not covered by the first sulfurization detection conductor and the second sulfurization detection conductor, an intermediate protective layer is provided on the exposed region, and the exposed portion of the first sulfurization detection conductor and the exposed portion of the second sulfurization detection conductor are arranged at positions sandwiching the intermediate protective layer. A sulfurization detection sensor characterized by this.

5. In the sulfurization detection sensor according to any one of claims 1 to 4, The resistor and the sulfurization detection conductor are each made of a metal film formed by thin film formation. A sulfurization detection sensor characterized by this.

6. In the sulfurization detection sensor according to claim 5, The insulating substrate is made of an alumina substrate, and the resistor is a Ni—Cr metal film formed on the surface of the alumina substrate by sputtering. A sulfurization detection sensor characterized by this.

7. In the sulfurization detection sensor according to any one of claims 1 to 6, The protective layer is composed of an undercoat layer made of a glass material formed on the sulfurization detection conductor and an overcoat layer made of a resin material formed on the undercoat layer, and the electrode portion covers an end portion of the sulfurization detection conductor and is in close contact with the overcoat layer. A sulfurization detection sensor characterized by this.

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