Sulfidation detection sensor

Abstract

To provide a sulfidation detection sensor capable of detecting a degree of sulfidation accurately.SOLUTION: A sulfidation detection sensor 1 comprises: a rectangular insulating substrate 2; a pair of surface electrodes 3 formed on both longitudinal end parts of a surface of the insulating substrate 2; a sulfidation detection conductor 4 connected to the pair of surface electrodes 3 via a resistor 5; a first insulating resin 6 that covers the entire sulfidation detection conductor 4 and is permeable to sulfide gas; and a second insulating resin 7 that covers an upper surface of the first insulating resin 6 and is non-permeable to the sulfide gas. The first insulating resin 6 has an exposed part 6a that is not covered by the second insulating resin 7.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Generally, Ag (silver)-based electrode materials with low resistivity are used as internal electrodes for electronic components such as chip resistors, but when silver is exposed to sulfur gas, it turns into silver sulfide, which has low electrical conductivity (increases resistivity), causing problems such as disconnection of electronic components. Therefore, in recent years, measures against sulfurization have been taken, such as adding Pd (palladium) or Au (gold) to Ag to form electrodes that are less susceptible to sulfurization, or designing electrodes so that sulfur gas cannot easily reach them.

[0003] However, even if such sulfuration countermeasures are taken for electronic components, if the electronic components are exposed to sulfurizing gas for a long period of time or to a high concentration of sulfurizing gas, it becomes difficult to completely prevent disconnection, so it becomes necessary to detect disconnection before it occurs and prevent failure from occurring at an unexpected time. Therefore, various sulfurization detection sensors have been proposed that detect the cumulative degree of sulfurization of electronic components and detect the risk before the electronic components break down due to sulfurization or the like.

[0004] For example, Patent Document 1 discloses a sulfide detection sensor in which a pair of electrodes are formed at both ends of the main surface of an insulating substrate, and a sulfide detection conductor mainly made of Ag and a resistor are formed and connected in series between the electrodes, and the sulfide detection conductor and resistor are covered with an insulating protective film that is impermeable to sulfide gas, with a portion of the sulfide detection conductor exposed from the side of the insulating protective film.

[0005] In the sulfur detection sensor configured as above, the sulfur detection conductor has an exposed portion exposed to the outside from the insulating protective film that is impermeable to sulfur gas when placed in an atmosphere containing sulfur gas. Then, the metals such as silver and copper that constitute the sulfur detection conductor are changed to silver sulfide or copper sulfide by sulfurization, and the resistance value of these sulfides increases to several MΩ or more, so that the current path flowing between the pair of front electrodes changes as the sulfurization progresses, and the resistance value of the entire product gradually increases accordingly. As a result, even if the proportion of the resistance value of the sulfur detection conductor in the resistance value of the entire product is reduced, it is possible to detect a sign of disconnection based on the continuous change in resistance value as the sulfurization progresses. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2022-154283 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the sulfur detection sensor described in the above Patent Document 1, the sulfur detection conductor is covered with a sulfur gas impermeable insulating protective film consisting of a two-layer structure of a glass layer and a resin layer except for the exposed part, so that the sulfurization of the sulfur detection conductor progresses from the exposed part to the inside covered with the insulating protective film, and a continuous change in resistance value accompanying the progress of sulfurization can be detected. However, since the sulfide sulfurized in reaction with sulfur gas increases in volume compared to the material before the reaction, when the sulfurization of the sulfur detection conductor progresses to the inside covered with the insulating protective film, the volume expansion of the sulfide sulfurized up to that point applies stress to the insulating protective film. As a result, cracks occur in the insulating protective film due to the stress accompanying the volume expansion of the sulfide, and when this crack progresses, sulfur gas penetrates into the inside of the product, resulting in a decrease in detection accuracy.

[0008] The present invention has been made in view of the above-mentioned state of the art, and an object of the present invention is to provide a sulfurization detection sensor capable of accurately detecting the degree of sulfurization. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, one embodiment of the present invention is a sulfide detection sensor comprising an insulating substrate having a rectangular parallelepiped shape, a pair of front electrodes formed at both ends in a first direction on a main surface of the insulating substrate with a predetermined distance therebetween, a sulfide detection conductor formed to be conductive to the pair of front electrodes, a first insulating resin permeable to sulfide gas formed to cover the entire sulfide detection conductor, and a second insulating resin impermeable to sulfide gas formed to cover an upper surface of the first insulating resin, wherein the first insulating resin has an exposed portion that is not covered by the second insulating resin. Effect of the Invention

[0010] According to the present invention, it is possible to provide a sulfide detection sensor capable of accurately detecting the degree of sulfidation. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a plan view of a sulfide detection sensor according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 2 is a cross-sectional view taken along line III-III in FIG. [Figure 4] 5A to 5C are plan views showing a manufacturing process of the chip resistor. [Diagram 5] 3A to 3C are cross-sectional views showing a manufacturing process of the chip resistor. [Figure 6] FIG. 4 is an explanatory diagram showing a current path caused by sulfurization in the sulfurization detection sensor. [Figure 7] FIG. 4 is an explanatory diagram showing the relationship between elapsed time and resistance value in the sulfide detection sensor. [Figure 8] FIG. 4 is a plan view of a sulfide detection sensor according to a second embodiment of the present invention. [Figure 9] FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. [Figure 10] FIG. 4 is an explanatory diagram showing the relationship between elapsed time and resistance value in the sulfide detection sensor. [Figure 11] FIG. 11 is a plan view of a sulfide detection sensor according to a third embodiment of the present invention. [Figure 12] FIG. 11 is a plan view of a sulfide detection sensor according to a fourth embodiment of the present invention. [Figure 13] FIG. 4 is an explanatory diagram showing a current path caused by sulfurization in the sulfurization detection sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] FIG. 1 is a plan view of a sulfide detection sensor according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, and FIG. 3 is a cross-sectional view taken along line III-III in FIG.

[0014] As shown in Fig. 1 to Fig. 3, the sulfide detection sensor 1 according to the first embodiment is mainly composed of an insulating substrate 2 having a rectangular parallelepiped shape, a pair of front electrodes 3 formed on both ends of the front surface of the insulating substrate 2 in the longitudinal direction, a sulfide detection conductor 4 formed between the pair of front electrodes 3, a pair of resistors 5 formed between the sulfide detection conductor 4 and one (left side in the figure) front electrode 3 and the other (right side in the figure) front electrode 3, a first insulating resin 6 covering the entire sulfide detection conductor 4 and a part of the pair of resistors 5, a second insulating resin 7 covering the entire upper surfaces of the first insulating resin 6 and the pair of resistors 5, a pair of back electrodes 8 formed on both ends of the rear surface of the insulating substrate 2 in the longitudinal direction, a pair of end electrodes 9 formed on both ends of the insulating substrate 2 in the longitudinal direction, and a pair of external electrodes 10 formed on the surfaces of the end electrodes 9. In the following description, the longitudinal direction of the insulating substrate 2 (left-right direction in Fig. 1) is the X-axis direction (first direction), and the lateral direction of the insulating substrate 2 (up-down direction in Fig. 1) is the Y-axis direction (second direction).

[0015] The insulating substrate 2 is obtained by dividing a large sheet-like substrate along vertical and horizontal dividing grooves into a number of pieces, and the large substrate is a ceramic substrate whose main component is alumina.

[0016] The pair of front electrodes 3 are formed by forming a thick film from an Ag-based paste or a Cu-based paste by screen printing and then drying and firing, or by forming a thin film of Cu or the like by sputtering and then patterning it. These front electrodes 3 are formed at both ends of the insulating substrate 2 in the longitudinal direction (X-axis direction) so as to face each other with a specified gap between them.

[0017] The sulfide detection conductor 4 is made by forming a thick film of a metal that is sulfurized by sulfide gas, for example, an Ag paste mainly composed of silver that is easily sulfurized or a Cu-based paste mainly composed of copper, by screen printing, and then drying and baking it, or by forming a thin film of Cu or the like by sputtering and patterning it. The sulfide detection conductor 4 is formed in a rectangular shape in the center of the insulating substrate 2, and both ends of the sulfide detection conductor 4 in the Y-axis direction are spaced from the side surfaces on the long sides of the insulating substrate 2.

[0018] The pair of resistors 5 are formed by forming a thick film of resistor paste such as ruthenium oxide by screen printing and then drying and baking, or by forming a thin film of NiCr or the like by sputtering and then patterning it. Both ends of one resistor 5 are connected to the front electrode 3 on the left side of the figure and the sulfide detection conductor 4, and both ends of the other resistor 5 are connected to the front electrode 3 on the right side of the figure and the sulfide detection conductor 4. In other words, the pair of resistors 5 are connected in series between the left and right surface electrodes 3 via the sulfide detection conductor 4.

[0019] The first insulating resin 6 is made of a porous resin material having sulfide gas permeability, such as a silicone resin having siloxane bonds. The first insulating resin 6 is formed by forming a thick film of a resin paste made of such a porous material by screen printing and then heating and curing it, and is formed in a rectangular shape so as to cover the upper surface of the sulfide detection conductor 4 including the connection portion with the resistor 5. One end of the first insulating resin 6 in the Y-axis direction (the lower end in FIG. 1) extends to a position coinciding with the side surface of the long side of the insulating substrate 2, and the other end of the first insulating resin 6 in the Y-axis direction (the upper end in FIG. 1) is spaced apart from the side surface of the long side of the insulating substrate 2.

[0020] The second insulating resin 7 is made of a resin material that is impermeable to sulfur gas, and is formed by forming a thick film of a resin paste such as an epoxy resin or a phenol resin by screen printing and then heat-curing it. The second insulating resin 7 is formed with the same width as the length in the short direction (Y-axis direction) of the insulating substrate 2 so as to cover the entire upper surfaces of the first insulating resin 6 and both resistors 5, and the connection portion between the front electrode 3 and the resistors 5 is also covered with the second insulating resin 7. As shown in FIG. 3, the end face of the first insulating resin 6 that is separated from the side surface on the long side of the insulating substrate 2 is covered with the second insulating resin 7, but the end face of the first insulating resin 6 that extends to the side surface on the long side of the insulating substrate 2 is not covered with the second insulating resin 7, and one end face of the first insulating resin 6 along the Y-axis direction is an exposed portion 6a that is exposed to the outside.

[0021] The pair of back electrodes 8 are formed by forming a thick film of Ag paste by screen printing and then drying and firing, or by forming a thin film of Cu or the like by sputtering and then patterning it, and these back electrodes 8 are formed in positions corresponding to the front electrodes 3 on the front side of the insulating substrate 2.

[0022] The pair of end electrodes 9 are formed by sputtering Ni / Cr on the end surfaces of the insulating substrate 2, and these end electrodes 9 are formed with a U-shaped cross section so as to electrically connect the corresponding front electrode 3 and back electrode 8.

[0023] The pair of external electrodes 10 each have a two-layer structure consisting of a barrier layer 11 and an external connection layer 12. The barrier layer 11 is a Ni-plated layer formed by electrolytic plating, and the external connection layer 12 is a Sn-plated layer formed by electrolytic plating. The end electrodes 9 are covered with the external electrodes 10.

[0024] Next, a method for manufacturing the sulfide detection sensor 1 configured as above will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a plan view showing the manufacturing process of the sulfide detection sensor 1, and Fig. 5 is a cross-sectional view showing the manufacturing process of the sulfide detection sensor 1.

[0025] First, a large-sized substrate from which a large number of insulating substrates 2 are to be produced is prepared. Primary and secondary dividing grooves are provided in advance in a lattice pattern on this large-sized substrate, and each of the squares separated by the dividing grooves becomes one chip area. Although large-sized substrate 2A corresponding to one chip area is shown as a representative in Figures 4 and 5, in reality, each process described below is performed collectively on a large-sized substrate corresponding to many chip areas.

[0026] In the first step, a Cu-based paste is screen-printed on the surface of the large-sized substrate 2A, and then dried and fired to form a pair of front electrodes 3 facing each other with a specified gap on the surface of the large-sized substrate 2A, and a rectangular sulfide detection conductor 4 located midway between the pair of front electrodes 3, as shown in Fig. 4(a) and Fig. 5(a). Simultaneously or before or after this, an Ag paste is screen-printed on the back surface of the large-sized substrate 2A, and then dried and fired to form a pair of back electrodes 8 facing each other with a specified gap on the back surface of the large-sized substrate 2A.

[0027] Next, a resistor paste such as ruthenium oxide is screen-printed on the surface of the large-sized substrate 2A, and then dried and fired to form a pair of resistors 5 whose both ends are connected to the front electrode 3 and the sulfide detection conductor 4, as shown in FIG. 4(b) and FIG. 5(b).

[0028] Next, a silicone resin paste is screen-printed on the front surface of the large substrate 2A, and then dried and baked to form a rectangular first insulating resin 6 that covers the upper surface of the sulfide detection conductor 4, including the connection portion with the resistor 5, as shown in Figures 4(c) and 5(c). At this time, one end of the first insulating resin 6 in the Y-axis direction is formed to a position straddling the secondary dividing groove of the large substrate 2A, and the other end of the first insulating resin 6 in the Y-axis direction is positioned inwardly and spaced from the secondary dividing groove.

[0029] Next, an epoxy resin paste is screen-printed on the first insulating resin 6 and then heat-cured to form a second insulating resin 7 that covers the first insulating resin 6 and the entire upper surfaces of both resistors 5, as shown in Figures 4(d) and 5(d). The second insulating resin 7 also covers the end faces of the first insulating resin 6 that are away from the secondary dividing grooves, and the connection parts between the front electrodes 3 and the resistors 5.

[0030] The steps up to this point have been a batch process for the large-sized substrate 2A, but in the next step, the large-sized substrate 2A is primarily divided along the primary division grooves to obtain rectangular substrates 2B.

[0031] Thereafter, Ni / Cr is sputtered toward the divided surfaces of the rectangular substrate 2B to form a pair of end electrodes 9 that electrically connect the front electrode 3 and the back electrode 8, as shown in Fig. 4(e) and Fig. 5(e). At this time, the end electrodes 9 are formed to have a U-shaped cross section so as to cover the surfaces of the front electrode 3 and the back electrode 8.

[0032] Next, the rectangular substrate 2B is secondarily divided along the secondary dividing groove to obtain a plurality of chip-like substrates 2C. By this secondary division, one end face of the first insulating resin 6 formed across the secondary dividing groove is exposed, and this end face becomes an exposed portion 6a that is not covered by the second insulating resin 7.

[0033] Thereafter, the chip-shaped substrates 2C are sequentially subjected to electrolytic Ni plating and electrolytic Sn plating to form external electrodes 10 having a two-layer structure (barrier layer 11 and external connection layer 12) covering the surfaces of the end electrodes 9, as shown in Fig. 4(f) and Fig. 5(f). This completes the sulfide detection sensor 1 shown in Figs. 1 to 3.

[0034] In the manufacturing method of the sulfide detection sensor 1 shown in Figures 4 and 5, the electrodes (front electrode 3, back electrode 8), the sulfide detection conductor 4, and the resistor 5 are formed as thick films, but they may also be formed as thin films by a photolithography process.

[0035] Fig. 6 is an explanatory diagram showing a current path accompanying sulfidation in the sulfidation detection sensor 1 according to the first embodiment, and Fig. 7 is an explanatory diagram showing the relationship between elapsed time and resistance value in the sulfidation detection sensor 1. Note that the end electrode 9 and the external electrode 10 are omitted in Fig. 6.

[0036] When the sulfide detection sensor 1 is placed in an atmosphere containing sulfide gas, the sulfide gas does not penetrate into the second insulating resin 7, which is impermeable to sulfide gas, but penetrates into the first insulating resin 6, which is made of a resin material permeable to sulfide gas, from the exposed portion 6a. As a result, sulfurization starts from one end side (lower end side in FIG. 6) of the sulfide detection conductor 4 facing the exposed portion 6a, and progresses to the other end side (upper end in FIG. 6) of the sulfide detection conductor 4, as shown by the blackened portion in FIG. 6(b). Here, the resistance value of the silver sulfide or copper sulfide of the sulfide detection conductor 4, which has been changed by sulfurization, increases to several MΩ or more, so that the current path flowing between the pair of front electrodes 3 changes from the state shown in FIG. 6(a) before the sulfurization of the sulfide detection conductor 4 to the state shown in FIG. 6(b) as the sulfurization of the sulfide detection conductor 4 progresses. In this way, the current path changes with the progress of sulfurization, so that the resistance value of the sulfurization detection sensor 1 gradually increases with the passage of time, as shown in FIG.

[0037] As described above, as the sulfurization of the sulfide detection conductor 4 progresses, the volume of the sulfide sulfurized in response to the sulfide gas increases, and as shown in the blackened portion of FIG. 6(b), the volume of the sulfide sulfurized in response to the sulfide gas is greater than the volume of the material of the sulfide detection conductor 4 before the reaction. In the sulfide detection sensor 1 according to the first embodiment, the first insulating resin 6 covering the sulfide detection conductor 4 is made of a resin material permeable to sulfide gas, and the second insulating resin 7 covering the first insulating resin 6 is made of a resin material impermeable to sulfide gas. Therefore, the two-layered resin material and the porous structure of the first insulating resin 6 having a large number of pores absorb the stress caused by the volumetric expansion of the sulfide, and the first insulating resin 6 and the second insulating resin 7 are prevented from peeling off from the insulating substrate 2.

[0038] As described above, in the sulfur detection sensor 1 according to the first embodiment, a pair of resistors 5 are connected in series between a pair of front electrodes 3 via a sulfur detection conductor 4, the sulfur detection conductor 4 is covered with a first insulating resin 6 that is permeable to sulfur gas, and the upper surface of the first insulating resin 6 is covered with a second insulating resin 7 that is impermeable to sulfur gas, and the first insulating resin 6 has an exposed portion 6a that is not covered by the second insulating resin 7. Therefore, when the sulfur detection sensor 1 is placed in an atmosphere containing sulfur gas, the sulfur detection conductor 4 reacts with the sulfur gas that has entered the inside from the exposed portion 6a of the first insulating resin 6, and is sulfurized from one end side to the other end side. Then, the resistance value of the sulfur detection conductor 4 that has changed due to sulfurization increases, and as the sulfurization progresses, the current path flowing between the pair of front electrodes 3 changes, and the resistance value of the sulfur detection sensor 1 gradually increases accordingly. As a result, the degree of sulfurization can be accurately detected based on the continuous change in resistance value accompanying the progress of sulfurization.

[0039] Moreover, the sulfide gas that has entered the first insulating resin 6 from the exposed portion 6a flows slower than the surrounding sulfide gas, and the sulfide gas stagnates and concentrates in the first insulating resin 6, causing the corrosion rate to be faster than that of the surrounding electronic components, making it possible to reliably detect corrosion before the surrounding electronic components corrode. Furthermore, since the sulfide detection conductor 4 is entirely covered with the first insulating resin 6 and the second insulating resin 7, no masking is required to cover the sulfide detection conductor 4 in the plating process for forming the external electrode 10, and the manufacturing process can be simplified.

[0040] As the sulfurization of the sulfur detection conductor 4 progresses, the volume of the sulfide that reacts with the sulfur gas and is sulfurized increases compared to the material before the reaction, but in the sulfur detection sensor 1 according to the first embodiment, the stress caused by the volume expansion of the sulfide can be absorbed by the synergistic effect of the two-layer resin material in which the second insulating resin 7 is laminated on the first insulating resin 6, and the porous structure of the first insulating resin 6 that is permeable to sulfur gas. This suppresses the peeling of the first insulating resin 6 from the insulating substrate 2, and prevents detection failures caused by the peeling of the first insulating resin 6.

[0041] In the sulfide detection sensor 1 according to the first embodiment, the exposed portion 6a is formed only on one end surface along the Y-axis direction (second direction) of the first insulating resin 6, but the exposed portion 6a may be formed on both end surfaces along the Y-axis direction of the first insulating resin 6. With this configuration, the speed at which the sulfide detection conductor 4 sulfides increases, and the detection speed can be increased.

[0042] FIG. 8 is a plan view of a sulfide detection sensor according to a second embodiment of the present invention, FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 8, and FIG. 10 is an explanatory diagram showing the relationship between elapsed time and resistance value in the sulfide detection sensor, in which the same reference numerals are used to refer to parts corresponding to those in FIGS. 1 to 3.

[0043] As shown in Figures 8 and 9, in the sulfide detection sensor 20 of the second embodiment, a resistor 5 is formed on the surface of an insulating substrate 2 so as to provide electrical continuity between a pair of front electrodes 3, and a sulfide detection conductor 4 is formed on this resistor 5, and the other configurations are basically the same as those of the sulfide detection sensor 1 of the first embodiment.

[0044] The resistor 5 is formed by forming a thin film of NiCr or the like on the surface of the insulating substrate 2 by sputtering and patterning it. The resistor 5 has a first belt-shaped pattern 5a connected to one (left side in the figure) of the front electrodes 3 and extending in the longitudinal direction (X-axis direction) of the insulating substrate 2, a second belt-shaped pattern 5b connected to the other (right side in the figure) of the front electrodes 3 and extending in the longitudinal direction of the insulating substrate 2, and a third belt-shaped pattern 5c connecting the first belt-shaped pattern 5a and the second belt-shaped pattern 5b and extending along the lateral direction (Y-axis direction) of the insulating substrate 2, and is generally formed in a crank shape. The sulfide detection conductor 4 is formed by forming a thin film of Cu or the like by sputtering and patterning it, and is formed on the third belt-shaped pattern 5c of the resistor 5. The entire sulfur detection conductor 4 and resistor 5 are covered with a first insulating resin 6 that is permeable to sulfide gas, and the entire upper surface of the first insulating resin 6 and resistor 5, including the connection portion between the front electrode 3 and resistor 5, are covered with a second insulating resin 7 that is impermeable to sulfide gas. However, both ends of the first insulating resin 6 in the Y-axis direction (second direction) are not covered with the second insulating resin 7, and both ends of the first insulating resin 6 along the Y-axis direction are exposed to the outside as exposed portions 6a.

[0045] When the sulfide detection sensor 20 thus configured is placed in an atmosphere containing sulfide gas, sulfidation starts from both ends of the sulfide detection conductor 4 in response to the sulfide gas that has entered the inside from the exposed portion 6a of the first insulating resin 6, and the sulfidation progresses sequentially toward the center of the sulfide detection conductor 4. As the sulfidation of the sulfide detection conductor 4 progresses, the area of ​​the third belt-shaped pattern 5c located under the sulfidation detection conductor 4 increases, and the resistance value of the resistor 5 is higher than the resistance value of the sulfidation detection conductor 4 before sulfidation. As shown in FIG. 10, the resistance value of the sulfidation detection sensor 20 increases linearly with time. This allows the degree of sulfidation to be accurately detected based on the continuous change in resistance value as the sulfidation progresses.

[0046] FIG. 11 is a plan view of a sulfide detection sensor according to a third embodiment of the present invention, and parts corresponding to those in FIG. 8 are given the same reference numerals.

[0047] As shown in FIG. 11, in the sulfide detection sensor 30 according to the third embodiment, the resistor 5 is formed in a meandering shape having multiple turn portions, and the other configuration is basically the same as that of the sulfide detection sensor 20 according to the second embodiment.

[0048] That is, the resistor 5 has a plurality of (e.g., three) third belt-like patterns 5c connected between the first belt-like pattern 5a and the second belt-like pattern 5b, and the sulfide detection conductor 4 is formed on each of the third belt-like patterns 5c. Each of the sulfide detection conductors 4 is covered with a first insulating resin 6 that is permeable to sulfide gas, and the entire upper surface of the first insulating resin 6 and the resistor 5 is covered with a second insulating resin 7 that is impermeable to sulfide gas. However, both ends of the first insulating resin 6 in the Y-axis direction (second direction) are not covered with the second insulating resin 7, and both ends along the Y-axis of the first insulating resin 6 are exposed to the outside (not shown).

[0049] The sulfide detection sensor 30 configured in this manner has multiple resistors 5 and sulfide detection conductors 4 arranged alternately in series in a serpentine manner, thereby making it possible to increase the change in resistance value per unit time in response to sulfide gas, enabling early detection.

[0050] FIG. 12 is a plan view of a sulfide detection sensor according to a fourth embodiment of the present invention, and the same reference numerals are used to designate parts corresponding to those in FIGS. 1 to 3. In FIG.

[0051] As shown in FIG. 12, in the sulfide detection sensor 40 according to the fourth embodiment, the resistor 5 has a rectangular protruding portion 5A formed at the center position on the surface of the insulating substrate 2, and a pair of strip-shaped portions 5B extending in the longitudinal direction (X-axis direction) of the insulating substrate 2 so as to electrically connect the protruding portion 5A and the front electrode 3, and the protruding portion 5A has a slit 41 extending along the lateral direction (Y-axis direction) of the insulating substrate 2. The resistor 5 and the sulfide detection conductor 4 are covered with a first insulating resin 6 that is permeable to sulfide gas, and the upper surface of the first insulating resin 6 including the connection portion between the resistor 5 and the front electrode 3 is covered with a second insulating resin 7 that is impermeable to sulfide gas. However, one end of the first insulating resin 6 in the Y-axis direction (the lower end in FIG. 12) is not covered with the second insulating resin 7, and one end face of the first insulating resin 6 along the Y-axis direction is an exposed portion (not shown) exposed to the outside.

[0052] FIG. 13 is an explanatory diagram showing a current path caused by sulfidation in the sulfidation detection sensor 40 according to the fourth embodiment, in which the end electrodes 9 and the external electrodes 10 are omitted.

[0053] As shown in FIG. 13(a), in the sulfurization detection sensor 40 before the sulfurization of the sulfurization detection conductor 4, the current path between the pair of front electrodes 3 is a straight path from one belt-shaped portion 5B through the sulfurization detection conductor 4 to the other belt-shaped portion 5B. When the sulfurization detection sensor 40 is placed in an atmosphere containing sulfurization gas, sulfurization starts from one end side (lower end side of FIG. 13) of the sulfurization detection conductor 4 in response to the sulfurization gas that has entered the inside from the exposed portion of the first insulating resin 6, and as shown by the blackened portion in FIG. 13(b), sulfurization progresses sequentially to the other end side (upper end of FIG. 13). Here, since a slit 41 is formed in the protruding portion 5A of the lower layer on which the sulfurization detection conductor 4 is formed, the current path between the pair of front electrodes 3 changes from the state shown in FIG. 13(a) before the sulfurization of the sulfurization detection conductor 4 to the state shown in FIG. 13(b) as the sulfurization of the sulfurization detection conductor 4 progresses. This makes it possible to accurately detect the degree of sulfurization based on the continuous change in resistance value that accompanies the progress of sulfurization.

[0054] The present invention is not limited to the above-mentioned embodiment, and various modifications are possible without departing from the gist of the present invention, and all technical matters included in the technical ideas described in the claims are the subject of the present invention. The above-mentioned embodiment shows a preferred example, but a person skilled in the art can realize various alternatives, modifications, variations, or improvements from the contents disclosed in this specification, and these are included in the technical scope described in the attached claims.

[0055] For example, in each of the above embodiments, a pair of front electrodes 3 is formed at both ends of the insulating substrate 2 in the longitudinal direction, and the exposed portion 6a of the first insulating resin 6 is formed at the end of the insulating substrate 2 in the lateral direction. However, a pair of front electrodes 3 may be formed at both ends of the insulating substrate 2 in the lateral direction, and the exposed portion 6a of the first insulating resin 6 may be formed at the end of the insulating substrate 2 in the longitudinal direction. In this case, the lateral direction of the insulating substrate 2 is the first direction, and the longitudinal direction of the insulating substrate 2 is the second direction.

[0056] In addition, in the first embodiment, the sulfide detection conductor 4 is connected to the pair of front electrodes 3 via the resistor 5, but the resistor 5 may be omitted and the sulfide detection conductor 4 may be directly connected to the pair of front electrodes 3. [Explanation of symbols]

[0057] 1,20,30,40 Sulfur detection sensor 2. Insulating substrate 3 Surface electrodes 4. Sulfide detection conductor 5 Resistor 5a First band pattern 5b Second band pattern 5c 3rd band pattern 5c 5A protrusion 5B Belt 6 First insulating resin 6a Exposed part 7 Second insulating resin 8 Back electrode 9 End electrode 10 External electrode 41 Slit

Claims

1. The insulating substrate has a rectangular parallelepiped shape; a pair of front electrodes formed at both ends in a first direction on a main surface of the insulating substrate with a predetermined distance therebetween; a sulfide detection conductor formed so as to be conductive to the pair of front electrodes; a first insulating resin which is permeable to sulfide gas and which is formed so as to cover the sulfide detection conductor; and a second insulating resin which is non-permeable to sulfide gas and which is formed so as to cover an upper surface of the first insulating resin. The sulfide detection sensor according to claim 1, wherein the first insulating resin has an exposed portion that is not covered by the second insulating resin.

2. 2. The sulfide detection sensor according to claim 1, wherein the first insulating resin has the exposed portion on both ends of the insulating substrate in a second direction perpendicular to the first direction.

3. 2. The sulfur detection sensor according to claim 1, further comprising a resistor disposed between said sulfur detection conductor and said front electrode.

4. 2. The sulfur detection sensor according to claim 1, wherein a resistor is formed on the main surface of the insulating substrate to electrically connect a pair of the front electrodes, and the sulfur detection conductor is formed on the resistor at a position spaced apart from the front electrodes.

5. 5. The sulfur detection sensor according to claim 4, wherein the resistor has a first band-shaped pattern extending along the first direction of the insulating substrate, a second band-shaped pattern extending parallel to the first band-shaped pattern, and a third band-shaped pattern extending along the second direction of the insulating substrate and connecting between the first band-shaped pattern and the second band-shaped pattern, and the sulfur detection conductor is formed on the third band-shaped pattern.

6. 6. The sulfide detection sensor according to claim 5, wherein the resistor is formed in a crank shape having one of the third band-like patterns.

7. 6. The sulfide detection sensor according to claim 5, wherein the resistor is formed in a meandering shape having a plurality of the third band-shaped patterns.

8. 5. The sulfide detection sensor according to claim 4, wherein the resistor has a protrusion which is a base layer of the sulfide detection conductor, and a pair of strip-shaped portions extending along the first direction of the insulating substrate so as to provide electrical conductivity between the protrusion and the front electrode, and a slit is formed in the protrusion, the slit extending along the second direction of the insulating substrate with the exposed portion as a starting end.

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