WO2020208931A1

WO2020208931A1 - Sulfidation detection resistor

Info

Publication number: WO2020208931A1
Application number: PCT/JP2020/005320
Authority: WO
Inventors: 太郎木村; 松本　健太郎
Original assignee: Koa株式会社
Priority date: 2019-04-12
Filing date: 2020-02-12
Publication date: 2020-10-15
Also published as: JP7197425B2; JP2020173200A

Abstract

Provided is a sulfidation detection resistor that can accurately detect degree of sulfidation.　A sulfidation detection resistor (100) that comprises a rectangular insulating substrate (1), a sulfidation detection conductor (2) that is provided on the surface of the insulating substrate (1), a pair of rear electrodes (4) that are provided at either longitudinal-direction end part of a rear surface of the insulating substrate (1), a resistor (5) that connects the pair of rear electrodes (4), a second protection layer (6) that covers the resistor (5), a pair of end surface electrodes (7) that electrically connect either end of the sulfidation detection conductor (2) and the rear electrodes (4), and a pair of outer electrodes (8) that cover either longitudinal-direction end part of the sulfidation detection conductor (2), the end surface electrodes (7), and the rear electrodes (4). A center part of the sulfidation detection conductor (2) that is not covered by the pair of outer electrodes (8) is a sulfidation detection part (2a) that can contact sulfidizing gas.

Description

Sulfide detection resistor

The present invention relates to a sulfurization detection resistor 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 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 electrode a structure that is difficult for sulfurized gas to reach.

However, even if such sulfurization measures 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 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 sulfurized gas, the other electronic components are sulfurized with the passage of time. Since the sulfide gas permeates the protective film of the sulfide detection sensor and comes into contact with the sulfide detector, the volume of silver constituting the sulfide detector decreases according to the concentration of the sulfide gas and the elapsed time. Therefore, the degree of sulfurization can be detected by detecting the change in the resistance value of the sulfurization detector or the disconnection.

Further, in Patent Document 1, a sulfurization detector is covered with a sulfurization gas permeable protective film and a sulfurization gas impermeable protective film, and these are arranged side by side in a direction orthogonal to the direction between electrodes. The sensor is disclosed. With the sulfurization detection sensor configured in this way, even if the sulfurization detector in the region covered with the sulfurization gas permeable protective film is broken by sulfurization, the sulfurization detection in the region covered with the sulfurization gas impermeable protective film is detected. The body does not sulfide, and then the sulfide detector covered with the sulfide gas impermeable protective film gradually sulfides due to the sulfide gas that invades laterally (width direction) from the boundary between the two protective films. As a result, even if the region covered with the sulfide gas permeable protective film is broken due to sulfurization, the resistance value gradually increases in the state where the conduction state is secured, so by measuring the resistance value, Since the degree of sulfurization can be detected, and the progress of sulfurization in the lateral direction is particularly slow, it is a sulfurization detection sensor suitable for detecting sulfurization over a long period of time.

Japanese Unexamined Patent Publication No. 2009-250611

However, since the sulfurization detector is a conductor mainly composed of Ag having a low specific resistance, the change in the resistance value of the sulfurization detector with the cumulative amount of sulfurization is extremely small, and Ag has a temperature characteristic (TCR). Since it is very bad and the resistance value changes greatly with temperature, it is difficult to accurately detect the degree of sulfurization based on the resistance value change of the sulfurization detector. Further, in the case of a sulfurization detection sensor configured to cover the sulfurization detector with two types of protective films, sulfide gas permeable and sulfurization gas impermeable, in the width direction, the formation positions of both protective films due to printing misalignment or the like. The timing of disconnection of the sulfurized detector covered with the sulfurized gas permeable protective film and the rate of change in the resistance value of the sulfurized detector covered with the sulfurized gas impermeable protective film vary from product to product. Therefore, there is also a problem that individual differences in detection accuracy are large.

The present invention has been made in view of the actual situation of such a prior art, and an object of the present invention is to provide a sulfurization detection resistor capable of accurately detecting the degree of sulfurization.

In order to achieve the above object, the sulfurization detection resistor of the present invention comprises a rectangular body-shaped insulating substrate, a sulfurizable sulfurization detection conductor provided on the surface of the insulating substrate, and a longitudinal direction on the back surface of the insulating substrate. A pair of back electrodes provided at both ends, a resistor connecting the pair of back electrodes, a protective film covering the resistor, and both ends in the longitudinal direction of the sulfide detection conductor and the back electrode are conductive. A pair of end face electrodes, a pair of external electrodes covering the end face electrodes and the back electrode, and both ends in the longitudinal direction of the sulfurization detection conductor are covered with the pair of the external electrodes, and the pair of the external electrodes The sulfide detection conductor in the region not covered with is a sulfide detection portion that can come into contact with the sulfide gas.

In the sulfide detection resistor configured in this way, the sulfide detection conductor having the sulfide detection portion and the resistor covered with the protective film are separately provided on both the front and back surfaces of the insulating substrate, so that the surface side of the insulating substrate is provided. It is possible to accurately detect that the sulfide detection part of the sulfide detection conductor provided in the above is broken by the resistance value of the current flowing through the resistor provided on the back surface side of the insulating substrate, and the sulfide detection conductor is broken. It is possible to ensure the continuity between the external electrodes even in this state.

In the sulfurization detection resistor having the above configuration, the height dimension from the back surface of the insulating substrate to the protective film is set to be smaller than the height dimension from the back surface of the insulating substrate to the external electrode covering the back electrode. When mounted on the circuit board with the front side of the insulating substrate on which the sulfurization detection conductor is formed facing upward, a gap is secured between the protective film formed on the back surface side of the insulating substrate and the circuit board. Therefore, the sulfurization detection resistor can be mounted on the circuit board in a stable posture. In this case, if the back electrode includes a first back electrode formed on the back surface of the insulating substrate and a second back electrode laminated on the first back electrode, a back electrode having a large height dimension is provided. It is preferable that the electrode can be easily formed.

Further, in the sulfurization detection resistor having the above configuration, the sulfurization detection portion of the sulfurization detection conductor may be directly exposed to the outside from between the pair of external electrodes, but the sulfurization detection portion is covered with a sulfurization gas permeable protective film. As a result, the sulfurization detection unit is less susceptible to external contact, and external electrodes can be easily plated on both ends of the sulfurization detection conductor excluding the sulfurization detection unit.

According to the present invention, it is possible to provide a sulfurization detection resistor capable of accurately detecting the degree of sulfurization.

It is a top view of the sulfurization detection resistor which concerns on embodiment of this invention. It is a back view of the sulfurization detection resistor. It is sectional drawing which follows the line III-III of FIG. It is a top view which shows the manufacturing process of the sulfurization detection resistor. It is a back view which shows the manufacturing process of the sulfurization detection resistor. It is sectional drawing which shows the manufacturing process of the sulfurization detection resistor. It is explanatory drawing which shows the state which mounted the sulfurization detection resistor on a circuit board.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of the sulfurization detection resistor according to the embodiment of the present invention, FIG. 2 is a back view of the sulfurization detection resistor, and FIG. It is sectional drawing which follows the line III-III of FIG.

As shown in FIGS. 1 to 3, the sulfide detection resistor 100 according to the present embodiment includes a rectangular-shaped insulating substrate 1, a sulfide detection conductor 2 provided on the surface of the insulation substrate 1, and the sulfide detection conductor. A first protective film 3 provided in the central portion of 2, a pair of back electrodes 4 provided at both ends in the longitudinal direction of the back surface of the insulating substrate 1, a resistor 5 connecting between the back electrodes 4, and a resistor thereof. A second protective film 6 that covers the body 5, a pair of end face electrodes 7 provided on both end faces in the longitudinal direction of the insulating substrate 1, and a pair of outer surfaces that cover both ends of the sulfurization detection conductor 2, end face electrodes 7, and back electrodes 4. It is mainly composed of an electrode 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 them, and the main component of the large-format substrate is a ceramic substrate containing alumina as a main component.

The sulfide detection conductor 2 is obtained by screen-printing an Ag paste containing silver as a main component, drying and firing, and the sulfide detection conductor 2 is formed on the surface of the insulating substrate 1. Both ends of the sulfurization detection conductor 2 in the longitudinal direction are covered with external electrodes 8 that block the permeation of the sulfurization gas, but the central portion of the sulfurization detection conductor 2 is a sulfurization detection portion 2a that can come into contact with the sulfurization gas.

The first protective film 3 is made of a sulfide gas permeable insulating material, and is obtained by screen-printing a resin paste such as a silicone resin or a fluororesin and heat-curing it. The first protective film 3 is formed so as to cover the sulfurization detection portion 2a of the sulfurization detection conductor 2, and the sulfurization gas permeates through the first protective film 3 and comes into contact with the sulfurization detection portion 2a. As will be described later, when the sulfurization detection resistor 100 is mounted on the circuit board and used for detecting the sulfurization gas, the sulfurization detection unit 2a is covered with the first protective film 3, so that the sulfurization detection unit 2a is used. It is less susceptible to external contact.

The back electrode 4 has a two-layer structure consisting of a first back electrode 4a formed on the back surface of the insulating substrate 1 and a second back electrode 4b laminated on the first back electrode 4a, and has a total height. A thick back electrode 4 is configured. The first back electrode 4a is made of calcined silver obtained by screen-printing an Ag-based paste containing silver as a main component, drying and firing, and the second back electrode 4b is screen-printed and heated by an Ag paste containing silver as a main component. It consists of hardened resin silver.

The resistor 5 is made by screen-printing a resistor paste such as ruthenium oxide, drying and firing, and both ends of the resistor 5 overlap the first back electrode 4a.

The second protective film 6 has a two-layer structure of an undercoat layer 6a and an overcoat layer 6b, and the second back electrode 4b overlaps both ends of the second protective film 6. The undercoat layer 6a is a glass paste screen-printed and dried / fired, and the overcoat layer 6b is an epoxy-based resin paste screen-printed and heat-cured. The undercoat layer 6a and the overcoat layer 6b are made of an insulating material that blocks the permeation of sulfide gas, and the entire resistor 5 is covered with such a second protective film 6.

The end face electrode 7 is obtained by sputtering Ni / Cr on the end face of the insulating substrate 1 or applying an Ag-based paste and heat-curing the end face electrode 7. The end face electrode 7 corresponds to both ends of the sulfurization detection conductor 2 in the longitudinal direction and the corresponding ends. It is formed so as to be conductive with the back electrode 4.

The external electrode 8 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. By the external electrode 8, both ends of the sulfurization detection conductor 2 exposed from the first protective film 3 and the surfaces of the end face electrode 7 and the back electrode 4 are covered in a U-shaped cross section. Here, the second back electrode 4b is a back electrode 4 having a thick film structure that protrudes downward with respect to the surface height of the overcoat layer 6b, and the external electrode 8 covers such a second back electrode 4b. Therefore, the height dimension from the back surface of the insulating substrate 1 to the overcoat layer 6b is smaller than the height dimension from the back surface of the insulating substrate 1 to the external electrode 8 covering the second back electrode 4b.

Next, the manufacturing process of the sulfurization detection resistor 100 will be described with reference to FIGS. 4 to 6. 4 (a) to 4 (h) are plan views of the large format substrate used in this manufacturing process, FIGS. 5 (a) to 5 (h) are back views of the large format substrate, and FIGS. 6 (a) to 6 (h) are shown. 4 (a) to 4 (h) show cross-sectional views corresponding to one chip along the central portion in the longitudinal direction.

First, prepare a large-format board on which a large number of insulating boards 1 are taken. 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 corresponding to one chip region is represented in FIGS. 4 to 6, each step described below is actually performed for the large-format substrate corresponding to a large number of chip regions. It is done all at once.

That is, as shown in FIGS. 4 (a), 5 (a) and 6 (a), an Ag-based paste (Ag-Pd 20%) was screen-printed on the back surface of the large-format substrate 10A, and then dried. It is fired to form a pair of first back electrodes 4a.

Next, as shown in FIGS. 4 (b), 5 (b) and 6 (b), an Ag paste containing silver as a main component is screen-printed on the surface of the large-format substrate 10A, dried and baked. , A rectangular sulfide detection conductor 2 is formed on the surface of the large-format substrate 10A. Both ends of the sulfide detection conductor 2 in the longitudinal direction extend to a position reaching the short side of the large format substrate 10A, but the dimension of the sulfide detection conductor 2 in the lateral direction is slightly larger than the short side length of the large format substrate 10A. It is set short.

Next, a resistor paste such as ruthenium oxide was screen-printed on the back surface of the large-format substrate 10A, dried and fired, as shown in FIGS. 4 (c), 5 (c) and 6 (c). A resistor 5 having both ends overlapping the first back electrode 4a is formed.

Next, after screen-printing a glass paste on the area covering the resistor 5, the glass paste is dried and fired to form an undercoat layer 6a, and if necessary, the resistor 5 is formed from above the undercoat layer 6a. A trimming groove (not shown) is formed to adjust the resistance value. After that, the epoxy resin paste is screen-printed on the undercoat layer 6a and heat-cured to form the overcoat layer 6b, whereby FIGS. 4 (d), 5 (d) and 6 (D) and FIG. As shown in d), a second protective film 6 having a two-layer structure covering the entire resistor 5 is formed.

Next, after screen-printing an Ag-based paste containing silver as a main component so as to overlap the first back electrode 4a, this is heat-cured to form a pair of second back electrodes 4b, whereby FIG. 4 (e). ), And as shown in FIGS. 5 (e) and 6 (e), a back electrode 4 having a two-layer structure with a large total film thickness is formed.

Next, a resin paste such as a silicone resin or a fluororesin is screen-printed on the central portion of the sulfide detection conductor 2, and this is heat-cured to form as shown in FIGS. 3 (f) and 4 (f). A sulfide gas permeable first protective film 3 that covers the central portion of the sulfide detection conductor 2 is formed.

Next, the large-format substrate 10A is first divided into strip-shaped substrates 10B along the primary dividing groove, and then Ni / Cr is sputtered on the divided surfaces of the strip-shaped substrate 10B to show FIGS. 4 (g) and 5 (g). As shown in g) and FIG. 6 (g), a pair of end face electrodes 7 connecting the sulfurization detection conductor 2 and the back electrode 4 (the first back electrode 4a and the second back electrode 4b) are formed. Instead of sputtering Ni / Cr on the divided surface of the strip-shaped substrate 10B, the end face electrode 7 may be formed by applying an Ag-based paste and heat-curing it.

Next, the strip-shaped substrate 10B is secondarily divided into a plurality of chip-shaped substrates 10C along the secondary dividing groove, and the chip-shaped substrates 10C are electrolytically plated to sequentially form a Ni plating layer and a Sn plating layer. By doing so, as shown in FIGS. 4 (h), 5 (h), and 6 (h), both ends of the sulfide detection conductor 2 exposed from the first protective film 3, the end face electrode 7, and the back electrode 4 A pair of external electrodes 8 are formed to cover the surface. As a result, both ends of the sulfurization detection conductor 2 except the central portion are covered with the sulfur gas impermeable external electrode 8, and the central portion of the sulfurization detection conductor 2 excluding the region covered with the first protective film 3 is sulfurized gas. The sulfurization detection resistor 100 shown in FIGS. 1 to 3 is completed with the sulfurization detection unit 2a that can come into contact with

As shown in FIG. 7, the sulfurization detection resistor 100 configured in this way is mounted on the circuit board 11 together with other electronic components (not shown), and then the circuit board 11 is exposed to an atmosphere containing sulfur gas. Used by At that time, the sulfide detection resistor 100 is mounted on the circuit board 11 in a posture in which the surface side of the insulating substrate 1 on which the sulfide detection conductor 2 is formed faces upward (that is, a posture in which the resistor 5 faces downward). However, since the overcoat layer 6b of the second protective film 6 is arranged in a stepped manner between the pair of external electrodes 8 covering the back electrode 4, there is a step between the second protective film 6 and the circuit board 11. A considerable amount of gap is secured. As a result, the sulfurization detection resistor 100 can be mounted on the circuit board 11 in a stable posture, and the wiring pattern 12 provided on the surface of the circuit board 11 and the external electrode 8 of the sulfurization detection resistor 100 can be easily mounted. Moreover, it can be reliably joined with the solder 13.

When the sulfurization detection resistor 100 mounted on the circuit board 11 is exposed to the sulfurization gas in this way, the sulfurization gas permeates through the first protective film 3 and comes into contact with the sulfurization detection portion 2a of the sulfurization detection conductor 2. As the cumulative amount of sulfurization increases over time, the sulfurization detection unit 2a breaks inside the first protective film 3, and at this point, the degree of sulfurization is accurately detected by the resistance value of the current flowing through the resistor 5. can do. Moreover, even if the sulfide detection conductor 2 provided on the front surface side of the insulating substrate 1 is disconnected, the resistor 5 provided on the back surface side of the insulating substrate 1 is not sulfided, so that between the pair of external electrodes 8. Conduction can be ensured by the resistor 5.

As described above, in the sulfide detection resistor 100 according to the present embodiment, the sulfide detection conductor 2 having the sulfide detection portion 2a and the resistor 5 covered with the second protective film 6 are both front and back surfaces of the insulating substrate 1. A resistor provided on the back surface side of the insulating substrate 1 that the sulfide detecting portion 2a of the sulfide detecting conductor 2 provided on the front surface side of the insulating substrate 1 was broken due to cumulative sulfide. It can be accurately detected by the resistance value of the current flowing through the body 5, and moreover, the conduction between the external electrodes 8 can be ensured even if the sulfide detection conductor 2 is disconnected.

Further, in the sulfurization detection resistor 100 according to the present embodiment, the height dimension from the back surface of the insulating substrate 1 to the second protective film 6 is the height from the back surface of the insulating substrate 1 to the external electrode 8 covering the back electrode 4. The size is smaller than the size, and the second protective film 6 is arranged in a stepped-down shape in the region sandwiched between the pair of external electrodes 8 covering the back electrode 4, so that the sulfurization detection conductor 2 When mounted on the circuit board 11 in a posture in which the front surface side of the insulating substrate 1 formed with the above is facing upward, both are placed between the second protective film 6 formed on the back surface side of the insulating substrate 1 and the circuit board 11. A gap for avoiding contact is secured, and the sulfurization detection resistor 100 can be mounted on the circuit board 11 in a stable posture. Moreover, the back electrode 4 has a laminated structure (two-layer structure) of the first back electrode 4a formed on the back surface of the insulating substrate 1 and the second back electrode 4b laminated on the first back electrode 4a. Therefore, the back electrode 4 having a large height can be easily formed.

Further, in the sulfurization detection resistor 100 according to the present embodiment, since the sulfurization detection unit 2a of the sulfurization detection conductor 2 is covered with the first protective film 3 that is permeable to sulfurization gas, the sulfurization detection unit 2a is from the outside. In addition to being less susceptible to contact, external electrodes 8 can be easily plated on both ends of the sulfurization detection conductor 2 excluding the sulfurization detection portion 2a. However, it is also possible to omit the first protective film 3 so that the sulfide detection part 2a is exposed to the outside. In that case, the sulfide detection part 2a is covered with a melt-release type resist film and is exposed to the outside. The electrode 8 may be plated, and after the external electrode 8 is plated, the resist film may be peeled off and removed with a solvent to expose the sulfide detection unit 2a.

1 Insulated substrate 2 Sulfurization detection conductor 2a Sulfurization detection unit 3 First protective film 4 Back electrode 4
4a 1st back electrode 4b 2nd back electrode 5 Resistor 6 2nd protective film

6a Undercoat layer

6b Overcoat layer 7 End face electrode 8 External electrode 10A Large format board 10B Strip-shaped board 10c Chip-shaped board 11 Circuit board 12 Wiring pattern 13 Solder 100 Sulfurization detection resistor

Claims

Between a rectangular body-shaped insulating substrate, a sulphurizable sulfide detection conductor provided on the surface of the insulating substrate, a pair of back electrodes provided at both ends in the longitudinal direction on the back surface of the insulating substrate, and a pair of back electrodes. A resistor that connects the resistors, a protective film that covers the resistor, a pair of end face electrodes that conduct longitudinal ends of the sulfurization detection conductor and the back electrode, and a pair of external electrodes that cover the end face electrode and the back electrode. With electrodes,
Both ends of the sulfurization detection conductor in the longitudinal direction are covered by the pair of external electrodes, and the sulfurization detection conductor in a region not covered by the pair of external electrodes serves as a sulfurization detection portion capable of contacting the sulfurization gas. A sulfurization detection resistor characterized by being present.
In the sulfurization detection resistor according to claim 1.
The height dimension from the back surface of the insulating substrate to the protective film is set to be smaller than the height dimension from the back surface of the insulating substrate to the external electrode covering the back electrode. Sulfurization detection resistor.
In the sulfurization detection resistor according to claim 2.
A sulfurization detection resistor, characterized in that the back electrode includes a first back electrode formed on the back surface of the insulating substrate and a second back electrode laminated on the first back electrode.
In the sulfurization detection resistor according to claim 1.
A sulfurization detection resistor characterized in that the sulfurization detection portion is covered with a sulfurization gas permeable protective film.