JP2021012067A - Sulfuration detection sensor - Google Patents

Abstract

To provide a sulfuration detection sensor that can prevent bursting of a sulfuration detection body and can accurately detect the degree of sulfuration.SOLUTION: A sulfuration detection sensor 10 comprises: an insulating substrate in a rectangular parallelepiped shape; a pair of front electrodes 2 that are formed at both ends of a principal surface of the insulating electrode; an intermediate electrode 3 that is formed between the pair of front electrodes 2; a resistor 4 that is formed between the intermediate electrode 3 and one front electrode 2; a sulfuration detection conductor 5 that is formed between the intermediate electrode 3 and the other front electrode 2; and a sulfurated gas non-permeable protective film 6 that covers at least the resistor 4. The sulfuration detection conductor 5 is formed of silver (Ag), and the front electrode 2 and intermediate electrode 3 are formed of a material containing palladium (Pd) in an amount of 5 to 40% by mass.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sulfurization detection sensor for detecting the cumulative amount of sulfurization in a corrosive environment.

Generally, Ag (silver) -based electrode materials with low resistivity are used as internal electrodes of electronic components such as chip resistors, but silver becomes silver sulfide when exposed to sulfide gas, and silver sulfide. Since is an insulator, there is a problem that the electronic component is broken. Therefore, in recent years, sulfurization measures such as adding Pd (palladium) or Au (gold) to Ag to form an electrode that is difficult to sulfurize, or making the electrode a structure that is difficult for sulfurized gas to reach have been taken.

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

Therefore, conventionally, as described in Patent Document 1, sulfurization 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. Detection sensors have been proposed. The sulfurization detection sensor described in Patent Document 1 forms a sulfurization detector mainly composed of Ag on an insulating substrate, and forms a transparent and sulfide gas permeable protective film so as to cover the sulfurization detector. , The end face electrodes connected to the sulfurization detector are formed on both side ends of the insulating substrate.

When the sulfurization detection sensor configured in this way is mounted on a circuit board together with other electronic components and then used in an atmosphere containing sulfurization gas, the sulfurization gas permeates the protective film of the sulfurization detection sensor and becomes sulfurized. Since it is in contact with the detector, the silver that constitutes the sulfide detector changes to silver sulfide according to the concentration of the sulfide gas and the elapsed time, and the resistance value of the sulfide detection sensor gradually increases accordingly, and finally, It leads to disconnection of the sulfurization detector. Therefore, it is possible to detect the degree of sulfurization by detecting the change in the resistance value of the sulfurization detector and the disconnection.

Japanese Unexamined Patent Publication No. 2009-250611

However, in the sulfurization detection sensor described in Patent Document 1, since the sulfurization gas permeates the sulfurization gas permeable protective film and comes into contact with the sulfurization detector, the surface side of the sulfurization detector in contact with the protective film. When sulfurizing in the film thickness direction, the protective film may be denatured due to the heat generated by the sulfurized detector whose film thickness has become thinner. In that case, since the permeability of the sulfide gas by the protective film is lowered, the detection accuracy of the sulfide gas is significantly deteriorated.

It is conceivable that the sulfurization detector is not covered with a protective film that is permeable to sulfurization gas, and the sulfurization gas is configured to come into direct contact with the sulfurization detector. In that case, the sulfurization detection whose film thickness is reduced by sulfurization When the body generates heat, it becomes easy to explode when the sulfurization detector is disconnected, and there is a risk that the silver constituting the sulfurization detector may scatter around and short-circuit the circuit on the circuit board.

The present invention has been made in view of the actual conditions of the prior art, and an object of the present invention is to detect sulfurization, which can prevent the explosion of the sulfurization detector and detect the degree of sulfurization with high accuracy. It is to provide a sensor.

In order to achieve the above object, the sulfurization detection sensor of the present invention has a rectangular body-shaped insulating substrate, a pair of front electrodes formed on both ends of the main surface of the insulating substrate, and a pair of front electrodes. An intermediate electrode formed, a resistor formed between the intermediate electrode and one of the surface electrodes, a sulfurization detection conductor formed between the intermediate electrode and the other surface electrode, and at least the above. A sulfide gas impermeable protective film covering the resistor is provided, the sulfide detection conductor is made of silver, and the front electrode and the intermediate electrode are made of a material containing 5 to 40% by mass of palladium in silver. It is a feature.

In the sulfurization detection sensor configured in this way, the current flowing through the sulfurization detection conductor is limited by the resistor, so that the heat generation of the sulfurization detection conductor, which has become thinner due to sulfurization, is suppressed, and the sulfurization detection conductor is disconnected. You can prevent it from exploding when you do it. Moreover, an intermediate electrode (a material containing 5 to 40% by mass of palladium in silver) that is difficult to sulfide is interposed between the sulfide detection conductor and the resistor, and the silver of the sulfide detection conductor is placed on the resistor side by the intermediate electrode. Even if a resistor is connected, the detection accuracy of the sulfide detection conductor will not be adversely affected. If the content of palladium in the intermediate electrode is less than 5% by mass, the effect of suppressing the diffusion of silver becomes insufficient, and if the content of palladium exceeds 40% by mass, the resistance value becomes high. It's too much and it's not preferable.

In the sulfide detection sensor having the above configuration, a protective film impermeable to sulfide gas may be formed so as to cover the entire intermediate electrode, but the intermediate electrode has an exposed portion exposed from the protective film, and the exposed portion is provided. When an external connection layer is formed on the surface, the external connection layer can be mounted on a circuit board having a three-dimensional wiring structure by using the external connection layer as a connection portion for wire bonding.

Further, in the sulfurization detection sensor having the above configuration, if a trimming groove for adjusting the resistance value is formed in the resistor and the entire resistor including the trimming groove is covered with a protective film, both ends of the resistor are formed. The resistance value of the resistor can be adjusted with high accuracy in a state where the detection probe for measurement is in contact with the surface electrode and the intermediate electrode connected to the unit.

According to the present invention, by connecting a resistor in series to the sulfide detection conductor, it is possible to prevent explosion when the sulfide detection conductor is broken, and an intermediate electrode is provided between the sulfide detection conductor and the resistor. By interposing it, it is possible to prevent the silver of the sulfide detection conductor from diffusing toward the resistor side, and to detect the degree of sulfide with high accuracy.

It is a top view of the sulfurization detection sensor which concerns on 1st Embodiment of this invention. It is sectional drawing which follows the line II-II of FIG. It is a top view which shows the manufacturing process of the sulfurization detection sensor. It is sectional drawing which shows the manufacturing process of the sulfurization detection sensor. It is a top view of the sulfurization detection sensor which concerns on 2nd Embodiment of this invention. It is sectional drawing which follows the VI-VI line of FIG. It is a top view of the sulfurization detection sensor which concerns on 3rd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of the sulfurization detection sensor according to the first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the line II-II of FIG. Is.

As shown in FIGS. 1 and 2, the sulfurization detection sensor 10 according to the first embodiment has a rectangular body-shaped insulating substrate 1 and a pair of surface electrodes 2 formed on both ends in the longitudinal direction on the surface of the insulating substrate 1. And the intermediate electrode 3 formed between the pair of surface electrodes 2, the resistor 4 formed between the intermediate electrode 3 and one (left side in the drawing) surface electrode 2, the intermediate electrode 3 and the other ( A sulfide detection conductor 5 formed between the surface electrode 2 on the right side of the drawing, a sulfide gas impermeable protective film 6 covering the entire intermediate electrode 3 and the resistor 4 and a part of the sulfide detection conductor 5 A pair of back electrodes 7 formed on both ends in the longitudinal direction of the back surface of the insulating substrate 1, a pair of end face electrodes 8 formed on both ends in the longitudinal direction of the insulating substrate 1, a front electrode 2, a back electrode 7, and an end face electrode. It is mainly composed of a pair of external electrodes 9 formed on the surface of 8.

The insulating substrate 1 is obtained by dividing a large-format substrate, which will be described later, along vertical and horizontal dividing grooves and taking a large number of the insulating substrate 1, and the main component of the large-format substrate is a ceramic substrate containing alumina as a main component.

The pair of surface electrodes 2 are obtained by screen-printing an Ag-based paste containing 5 to 40% by mass of palladium (Pd) in silver (Ag), drying and firing, and these two surface electrodes 2 have a predetermined interval. It is formed at both ends in the longitudinal direction of the insulating substrate 1 so as to face each other. The intermediate electrode 3 is also made by screen-printing an Ag-based paste containing 5 to 40% by mass of palladium in silver, drying and firing, and the intermediate electrode 3 is formed at an intermediate position between the pair of surface electrodes 2.

The resistor 4 is obtained by screen-printing a resistor paste such as ruthenium oxide, drying and firing it. Both ends of the resistor 4 are connected to one of the surface electrodes 2 and the intermediate electrode 3, and the resistor 4 is formed with a trimming groove 4a for adjusting the resistance value. Although not shown, the resistor 4 is covered with a glass coat layer, and a trimming groove 4a is formed in the resistor 4 by irradiating a laser beam from above the glass coat layer.

The sulfide detection conductor 5 is obtained by screen-printing an Ag paste containing silver as a main component, drying and firing, and both ends of the sulfide detection conductor 5 are connected to the other surface electrode 2 and the intermediate electrode 3. That is, the resistor 4 is connected in series between the pair of surface electrodes 2 via the intermediate electrode 3. Both ends of the sulfurization detection conductor 5 are covered with a protective film 6, and the sulfurization detection conductor 5 exposed from the protective film 6 is a sulfurization detection unit 5a capable of detecting sulfurized gas.

The protective film 6 is obtained by screen-printing an epoxy resin paste and heat-curing it, and the protective film 6 is formed so as to cover the entire intermediate electrode 3 and the resistor 4. Further, both ends of the sulfurization detection conductor 5 are also covered with the protective film 6, and as described above, the sulfurization detection portion 5a of the sulfurization detection conductor 5 is not covered by the protective film 6 and is exposed to the outside.

The pair of back electrodes 7 are made by screen-printing an Ag-based paste, drying and firing, and these back electrodes 7 are formed at positions corresponding to the front electrodes 2 on the front surface side of the insulating substrate 1.

The pair of end face electrodes 8 are obtained by sputtering Ni / Cr on the end faces of the insulating substrate 1, and these end face electrodes 8 are formed so as to conduct electricity between the corresponding front electrode 2 and the back electrode 7.

The pair of external electrodes 9 has a two-layer structure consisting of a barrier layer and an external connection layer, of which the barrier layer is a Ni plating layer formed by electrolytic plating and the external connection layer is a Sn plating layer formed by electrolytic plating. .. The surfaces of the front electrode 2, the back electrode 7, and the end face electrode 8 are covered with these external electrodes 9.

Next, the manufacturing process of the sulfurization detection sensor 10 configured in this way will be described with reference to FIGS. 3 and 4. 3 (a) to 3 (f) are topographical views of the large-format substrate used in this manufacturing process, and FIGS. 4 (a) to 4 (f) are the lengths of FIGS. 3 (a) to 3 (f). Cross-sectional views corresponding to one chip along the central portion of the direction are shown.

First, a large-format substrate on which a large number of insulating substrates 1 are taken is prepared. The large-format substrate is provided with a primary dividing groove and a secondary dividing groove in a grid pattern in advance, and each of the squares divided by both dividing grooves serves as a chip area for one piece. Although the large-format substrate 11A corresponding to one chip region is represented in FIGS. 3 and 4, each step described below with respect to the large-format substrate corresponding to a large number of chip regions is actually shown. Is done all at once.

That is, as shown in FIGS. 3 (a) and 4 (a), an Ag-based paste is screen-printed on the back surface of the large-format substrate 11A, and then dried and fired to determine on the back surface of the large-format substrate 11A. A pair of back electrodes 7 facing each other with a gap are formed.

Next, an Ag-based paste containing 5 to 40% by mass of Pd was screen-printed on the surface of the large-format substrate 11A, and then dried and fired as shown in FIGS. 3 (b) and 4 (b). In addition, a pair of surface electrodes 2 and intermediate electrodes 3 are simultaneously formed on the surface of the large-format substrate 11A. These front electrodes 2 are formed at positions corresponding to the pair of back electrodes 7, and the intermediate electrodes 3 are formed at intermediate positions of the pair of front electrodes 2. The front electrode 2 and the intermediate electrode 3 and the back electrode 7 described above may be formed in the reverse order, or both may be formed at the same time.

Next, by screen-printing the Ag paste on the surface of the large-format substrate 11A, drying and firing, both ends are the intermediate electrode 3 and the table on the right side of the drawing as shown in FIGS. 3 (c) and 4 (c). The sulfide detection conductor 5 connected to the electrode 2 is formed. Around this time, a resistor paste such as ruthenium oxide is screen-printed on the surface of the large-format substrate 11A, dried and fired to connect both ends to the intermediate electrode 3 and the surface electrode 2 on the left side of the drawing. Form body 4.

Although not shown, after forming the resistor 4, the glass paste is screen-printed, dried and fired to form a glass coat layer covering the resistor 4 from above the glass coat layer. A trimming groove 4a is formed in the resistor 4 to adjust the resistance value. At that time, the resistance value of the resistor 4 can be measured in a state where the detection probe is in contact with the surface electrode 2 and the intermediate electrode 3 connected to both ends of the resistor 4, and the resistance value of the resistor 4 can be measured. Since the resistance value component of the sulfide detection conductor 5 is not involved, the resistance value adjustment of the resistor 4 can be performed with high accuracy.

Next, the epoxy resin paste was screen-printed on the surface side of the large-format substrate 11A and heat-cured to cure the entire resistor 4 and the intermediate electrode 3 as shown in FIGS. 3 (d) and 4 (d). And a protective film 6 that covers a part of the sulfide detection conductor 5 is formed. Most of the sulfurization detection conductor 5 except both ends is exposed to the outside without being covered with the protective film 6, and this exposed portion becomes the sulfurization detection portion 5a.

Next, the large-format substrate 11A is first divided into strip-shaped substrates 11B along the primary dividing groove, and then Ni / Cr is sputtered on the divided surfaces of the strip-shaped substrate 11B to show FIGS. 3 (e) and 4 (e). As shown in e), end face electrodes 8 for connecting the front electrode 2 and the back electrode 7 are formed at both ends of the strip-shaped substrate 11B.

Next, the strip-shaped substrate 11B is secondarily divided into a plurality of chip-shaped substrates 11C along the secondary dividing groove, and then the chip-shaped substrates 11C are electrolytically plated to form a Ni—Sn plating layer. As a result, as shown in FIGS. 3 (f) and 4 (f), external electrodes 9 covering the surfaces of the front electrode 2, the back electrode 7, and the end face electrode 8 are formed at both ends of the chip-shaped substrate 11C. The sulfurization detection sensor 10 shown in 1 and 2 is completed.

The sulfurization detection sensor 10 configured in this way is used by mounting the circuit board together with other electronic components on a circuit board (not shown) and then exposing the circuit board to an atmosphere containing sulfur gas. Then, as the volume of Ag constituting the sulfurization detection conductor 5 decreases with the passage of time, the resistance value between the pair of surface electrodes 2 increases, and finally the sulfurization detection of the sulfurization detection conductor 5 The part 5a is disconnected. At that time, the resistor 4 is connected in series to the sulfurization detection conductor 5, and the current flowing through the sulfurization detection conductor 5 is limited by the resistor 4, so that the sulfurization detection conductor 5 having a thin film thickness generates heat. It is suppressed, and it is possible to prevent the sulfurization detection conductor 5 from exploding when the wire is broken.

As described above, in the sulfurization detection sensor 10 according to the first embodiment, the resistor 4 is connected in series to the sulfurization detection conductor 5, and the current flowing through the sulfurization detection conductor 5 is limited by the resistor 4. Therefore, it is possible to prevent the sulfurization detection conductor 5 from exploding when the wire is broken. Moreover, since the intermediate electrode 3 is interposed between the sulfide detection conductor 5 and the resistor 4, and the intermediate electrode 3 is made of a material containing 5 to 40% by mass of palladium in silver, the intermediate electrode 3 is used. It is possible to prevent the silver of the sulfide detection conductor 5 from diffusing toward the resistor 4, and prevent the resistors 4 connected in series from adversely affecting the detection accuracy of the sulfide detection conductor 5. If the content of palladium in the intermediate electrode 3 is less than 5% by mass, the effect of suppressing the diffusion of silver becomes insufficient, and if the content of palladium exceeds 40% by mass, the resistance value is high. It is not preferable because it becomes too much.

Further, in the sulfide detection sensor 10 according to the first embodiment, a trimming groove 4a for adjusting the resistance value is formed in the resistor 4 connected in series with the sulfide detection conductor 5, and the resistance including the trimming groove 4a. Since the entire body 4 is covered with the protective film 6, when adjusting the resistance value of the resistor 4, the detection probe is brought into contact with the surface electrode 2 and the intermediate electrode 3 connected to both ends of the resistor 4. The resistance value can be measured in the state. Therefore, the resistance value component of the sulfurization detection conductor 5 is no longer involved in the resistance value measurement of the resistor 4, and the resistance value adjustment of the resistor 4 can be performed with high accuracy.

5 is a plan view of the sulfurization detection sensor 20 according to the second embodiment of the present invention, FIG. 6 is a cross-sectional view taken along the line VI-VI of FIG. 5, and the parts corresponding to FIGS. 1 and 2 are the same. It is coded.

As shown in FIGS. 5 and 6, in the sulfurization detection sensor 20 according to the second embodiment, the intermediate electrode 3 has an exposed portion not covered by the protective film 6, and the exposed portion has an external connection layer. 21 is formed. The external connection layer 21 has a two-layer structure in which a Sn plating layer is laminated on a Ni plating layer, and the external connection layer 21 and a pair of external electrodes 9 can be formed at the same time. Since the external connection layer 21 can be used as a connection portion (bonding electrode) for wire bonding, the sulfurization detection sensor 20 is mounted on a circuit board having a three-dimensional wiring structure by using both soldering and wire bonding. It is possible. Specifically, the pair of external electrodes 9 may be soldered to an arbitrary wiring pattern on the circuit board, and both ends of the wire may be fixed to the external connection layer 21 and other wiring patterns on the circuit board.

Further, in the sulfurization detection sensor 20 according to the second embodiment, a sulfurization gas permeable protective film 22 is formed so as to cover the sulfurization detection conductor 5, and the sulfurization gas permeates the protective film 22 to penetrate the sulfurization detection conductor. It comes in contact with 5. Even when the sulfurization detection conductor 5 is covered with the protective film 22 in this way, the current flowing through the sulfurization detection conductor 5 is limited by the resistor 4, so that the sulfurization detection conductor 5 becomes thinner due to sulfurization. It is possible to prevent the heat generation of the protective film 22 from being lowered due to the heat generation of the sulfurization detection conductor 5. In the sulfurization detection sensor 20 according to the second embodiment, the protective film 22 covering the sulfurization detection conductor 5 is omitted, and the sulfurization detection conductor 5 is exposed to the outside as in the first embodiment. It may have a structure having a part.

FIG. 7 is a plan view of the sulfurization detection sensor 30 according to the third embodiment of the present invention, and the parts corresponding to FIGS. 1 and 2 are designated by the same reference numerals.

As shown in FIG. 7, in the sulfurization detection sensor 30 according to the third embodiment, the protective film 6A covering the entire resistor 4 and the protective film 6B covering the connection portion between the intermediate electrode 3 and the sulfurization detection conductor 5 are used. A protective film 6C that covers the connection portion between the sulfide detection conductor 5 and the surface electrode 2 is provided, and an external connection layer 21 is formed on the surface of the intermediate electrode 3 sandwiched between the protective film 6A and the protective film 6B. Here, since the protective film 6A on the left side and the protective film 6C on the right side are formed in a symmetrical shape with the protective film 6B in the middle as the axis of symmetry, the divided surface of the strip-shaped substrate obtained by primary division of the large-format substrate When the end face electrode 8 is formed by sputtering, a plurality of strip-shaped substrates can be superposed in a stable posture.

1 Insulated substrate 2 Front electrode 3 Intermediate electrode 4 Resistor 5 Sulfurization detection conductor 5a Sulfurization detection unit 6,6A, 6B, 6C Sulfurized gas impermeable protective film 7 Back electrode 8 End face electrode 9 External electrode 10, 20, 30 Sulfurization Detection sensor 11A Large format board 11B Strip-shaped board 11C Chip-shaped board 21 External connection layer 22 Sulfurized gas permeable protective film

Claims (3)

A rectangular-shaped insulating substrate, a pair of surface electrodes formed on both ends of the main surface of the insulating substrate, an intermediate electrode formed between the pair of the table electrodes, the intermediate electrode and one of the surface electrodes. A sulfide detection conductor formed between the intermediate electrode and the other surface electrode, and at least a sulfide gas impermeable protective film covering the resistor are provided.
A sulfurization detection sensor, wherein the sulfurization detection conductor is made of silver, and the front electrode and the intermediate electrode are made of a material containing 5 to 40% by mass of palladium in silver. In the sulfurization detection sensor according to claim 1,
A sulfurization detection sensor characterized in that the intermediate electrode has an exposed portion exposed from the protective film, and an external connection layer is formed on the exposed portion. In the sulfurization detection sensor according to claim 1,
A sulfurization detection sensor characterized in that a trimming groove for adjusting a resistance value is formed in the resistor, and the entire resistor including the trimming groove is covered with the protective film.

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