JP7197425B2 - Sulfurization detection resistor - Google Patents

Description

The present invention relates to a sulfidation sensing resistor for sensing the cumulative amount of sulfidation in a corrosive environment.

Ag (silver)-based electrode materials with low specific resistance are generally used for the internal electrodes of electronic components such as chip resistors. Since is an insulator, there is a problem that the electronic component is disconnected. Therefore, in recent years, countermeasures against sulfurization have been taken, such as adding Pd (palladium) or Au (gold) to Ag to form electrodes that are difficult to sulfurize, or making electrodes difficult to reach with sulfurizing gas.

However, even if such sulfuration countermeasures are taken for electronic components, disconnection cannot be completely prevented if the electronic component is exposed to sulfuric gas for a long period of time or is exposed to high-concentration sulfuric gas. Therefore, it is necessary to detect disconnection in advance to prevent failures at unexpected timing.

Therefore, conventionally, as described in Patent Document 1, the degree of cumulative sulfuration of electronic parts is detected, and the risk of electronic parts breaking down due to sulfuration disconnection etc. can be detected. A detection sensor has been proposed.

The sulfurization detection sensor described in Patent Document 1 forms a sulfuration detection body mainly composed of Ag on an insulating substrate, and forms a transparent protective film permeable to sulfuric gas so as to cover the sulfurization detection body. , end surface electrodes connected to the sulfurization detector are formed on both side ends of the insulating substrate. After mounting the sulfuration detection sensor configured in this way on a circuit board together with other electronic components, when the circuit board is used in an atmosphere containing a sulfurizing gas, the other electronic components are sulfurized with the passage of time. Since the sulfuric gas permeates the protective film of the sulfurization detection sensor and comes into contact with the sulfurization detection body, the volume of silver constituting the sulfurization detection body decreases according to the concentration of the sulfurization gas and the elapsed time. Therefore, the degree of sulfurization can be detected by detecting a change in the resistance value or disconnection of the sulfurization detector.

Further, in Patent Document 1, a sulfurization detection device is disclosed in which a sulfurization detection body is covered with a protective film permeable to sulfuric acid gas and a protective film impermeable to sulfuric gas, and these are arranged side by side in a direction orthogonal to the inter-electrode direction. A sensor is disclosed. In the sulfurization detection sensor configured in this way, even if the sulfuration detection body in the area covered with the sulfuric gas permeable protective film is disconnected due to sulfurization, the sulfurization detection sensor detects sulfuration in the area covered with the sulfuric gas impermeable protective film. The body is not sulfurized, and then the sulfurized detection body covered with the protective film impermeable to sulfuric gas is gradually sulfurized by the sulfuric gas entering in the lateral direction (width direction) from the boundary between the two protective films. As a result, even if the area covered with the sulfide gas permeable protective film is disconnected due to sulfurization, the resistance value will gradually increase while the continuity is maintained. 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.

JP 2009-250611 A

However, since the sulfuration detection object is a conductor mainly composed of Ag with low specific resistance, the resistance value change of the sulfurization detection object due to the cumulative amount of sulfurization is extremely small, and Ag has a temperature characteristic (TCR). This is very bad, and the change in resistance value due to temperature is large, so it is difficult to accurately detect the degree of sulfurization based on the change in the resistance value of the sulfurization detector. Also, in the case of a sulfurization detection sensor configured to cover the sulfurization detection body with two types of protective films, one permeable to sulfuric acid and the other impermeable to sulfuric acid, in the width direction, the formation position of both protective films may be affected by printing misalignment or the like. Therefore, the disconnection timing of the sulfurized detector covered with the sulfuric gas permeable protective film and the resistance value change rate of the sulfuricized detector covered with the sulfuric gas impermeable protective film vary from product to product. There is also the problem of large individual differences in detection accuracy.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sulfurization detection resistor capable of accurately detecting the degree of sulfurization.

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

In the sulfurization detection resistor configured in this way, the sulfuration detection conductor having the sulfurization detection part and the resistor covered with the protective film are provided separately on both the front and back sides of the insulating substrate. The disconnection of the sulfuration detection part of the sulfuration detection conductor provided in the insulating substrate can be accurately detected by the resistance value of the current flowing through the resistor provided on the back side of the insulating substrate, and the disconnection of the sulfurization detection conductor Even in such a state, the continuity between the external electrodes can be ensured.

In the sulfuration 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. Then, when the insulating substrate on which the sulfuration detection conductor is formed is mounted on the circuit board with the surface side facing upward, a gap is secured between the protective film formed on the back side of the insulating substrate and the circuit board. Therefore, the sulfuration detection resistor can be mounted on the circuit board in a stable posture. In this case, when 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 thick back electrode having a height dimension can be obtained. It is preferable because the electrodes can be easily formed.

In addition, in the sulfurization detection resistor having the above configuration, the sulfuration 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 sulfuration detecting portion is less likely to be affected by contact from the outside, and the external electrodes can be easily plated on both ends of the sulfurization detecting conductor excluding the sulfurization detecting portion.

ADVANTAGE OF THE INVENTION According to this invention, the sulfuration detection resistor which can detect the degree of sulfuration correctly can be provided.

1 is a plan view of a sulfidation detection resistor according to an example embodiment of the present invention; FIG. FIG. 4 is a back view of the sulfurization detection resistor; FIG. 2 is a cross-sectional view taken along line III-III of FIG. 1; It is a top view which shows the manufacturing process of this sulfuration detection resistor. It is a back view which shows the manufacturing process of this sulfuration detection resistor. It is sectional drawing which shows the manufacturing process of this sulfuration detection resistor. FIG. 4 is an explanatory diagram showing a state in which the sulfuration detection resistor is mounted on a circuit board;

1 is a plan view of a sulfurization detection resistor according to an embodiment of the present invention, FIG. 2 is a rear view of the sulfurization detection resistor, and FIG. FIG. 2 is a cross-sectional view taken along line III-III of FIG. 1;

As shown in FIGS. 1 to 3, the sulfurization detection resistor 100 according to this embodiment includes a rectangular parallelepiped insulating substrate 1, a sulfurization detection conductor 2 provided on the surface of the insulation substrate 1, and the sulfurization detection conductor 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 this resistor. a second protective film 6 covering the body 5; a pair of end face electrodes 7 provided on both longitudinal end faces of the insulating substrate 1; and the electrode 8 .

The insulating substrate 1 is obtained by dividing a large substrate, which will be described later, along vertical and horizontal dividing grooves to obtain a large number of substrates.

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

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

The back electrode 4 has a two-layer structure 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. A thick back electrode 4 is constructed. The first back electrode 4a is made of baked silver obtained by screen-printing an Ag-based paste containing silver as a main component, followed by drying and baking. Consists of hardened resinous silver.

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

The second protective film 6 has a two-layer structure of an undercoat layer 6a and an overcoat layer 6b. The undercoat layer 6a is formed by screen-printing a glass paste, dried and baked, and the overcoat layer 6b is formed by screen-printing an epoxy resin paste and heat-curing it. The undercoat layer 6a and the overcoat layer 6b are made of an insulating material that blocks permeation of sulfide gas.

The end face electrodes 7 are obtained by sputtering Ni/Cr on the end face of the insulating substrate 1 or applying Ag-based paste and heating and curing the end faces. It is formed so as to conduct between the back electrode 4 and the back electrode 4 .

The external electrode 8 has a two-layer structure of a barrier layer and an external connection layer, of which the barrier layer is a Ni-plated layer formed by electrolytic plating, and the external connection layer is a Sn-plated layer formed by electrolytic plating. Both ends of the sulfurization detection conductor 2 exposed from the first protective film 3 and the surfaces of the end face electrodes 7 and the back electrode 4 are covered with the external electrodes 8 so as to have a U-shaped cross section. Here, the second back electrode 4b is a back electrode 4 having a thick film structure protruding downward with respect to the surface height of the overcoat layer 6b, and the external electrode 8 covers the 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 this sulfuration detection resistor 100 will be described with reference to FIGS. 4 to 6. FIG. 4(a) to (h) are plan views of the large substrate used in this manufacturing process, FIGS. 5(a) to (h) are back views of the large substrate, and FIGS. 6(a) to (h). 4A to 4H respectively show cross-sectional views corresponding to one chip along the central portion in the longitudinal direction of FIGS.

First, a large substrate from which a large number of insulating substrates 1 are obtained is prepared. This large-sized substrate is provided in advance with primary and secondary dividing grooves in a grid pattern, and each square partitioned by both dividing grooves serves as one chip area. 4 to 6 representatively show a large-sized substrate corresponding to one chip area, in actuality, each process described below is performed on a large-sized substrate corresponding to a large number of chip areas. done in batches.

That is, as shown in FIGS. 4(a), 5(a), and 6(a), Ag-based paste (Ag—Pd 20%) is screen-printed on the back surface of the large-sized substrate 10A, and then dried and 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-sized substrate 10A, dried and fired. , a rectangular sulfuration detection conductor 2 is formed on the surface of the large-sized substrate 10A. Both ends of the sulfurization detection conductor 2 in the longitudinal direction extend to the short side of the large substrate 10A, but the width of the sulfurization detection conductor 2 in the width direction is slightly larger than the length of the short side of the large substrate 10A. set short.

Next, a resistive paste such as ruthenium oxide is screen-printed on the back surface of the large-sized substrate 10A, dried and fired to obtain, 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 baked to form an undercoat layer 6a. A trimming groove (not shown) is formed to adjust the resistance value. Thereafter, an epoxy-based resin paste is screen-printed on the undercoat layer 6a and heat-cured to form the overcoat layer 6b, thereby forming the overcoat layer 6b shown in FIGS. 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 electrodes 4a, this is cured by heating to form a pair of second back electrodes 4b, thereby forming a pair of second back electrodes 4b. ) and as shown in FIGS. 5(e) and 6(e), a rear electrode 4 having a two-layer structure with a large total film thickness is formed.

Next, a resin paste such as silicone resin or fluororesin is screen-printed on the central portion of the sulfurization detection conductor 2, and the paste is cured by heating to obtain the following as shown in FIGS. 3(f) and 4(f). A first protective film 3 permeable to sulfide gas is formed to cover the central portion of the sulfide detection conductor 2 .

Next, after the large-sized substrate 10A is primarily divided into strip-shaped substrates 10B along the primary division grooves, Ni/Cr is sputtered on the divided surfaces of the strip-shaped substrates 10B, thereby forming the substrates shown in FIGS. As shown in g) and FIG. 6(g), a pair of end face electrodes 7 are formed to connect between the sulfuration detecting conductor 2 and the back electrode 4 (the first back electrode 4a and the second back electrode 4b). Instead of sputtering Ni/Cr on the divided surfaces of the strip-shaped substrate 10B, the end surface electrodes 7 may be formed by applying Ag-based paste and curing it by heating.

Next, the strip-shaped substrate 10B is secondarily divided into a plurality of chip-shaped substrates 10C along the secondary division grooves, and electrolytic plating is applied to these chip-shaped substrates 10C to sequentially form Ni plating layers and Sn plating layers. As a result, as shown in FIGS. 4(h), 5(h) and 6(h), both ends of the sulfurization detecting conductor 2 exposed from the first protective film 3, the end surface electrode 7 and the back electrode 4 are separated. A pair of external electrodes 8 are formed to cover the surface. As a result, both ends of the sulfidation detection conductor 2 excluding the central portion are covered with the external electrode 8 impermeable to sulfide gas, and the central portion of the sulfidation detection conductor 2 excluding the region covered with the first protective film 3 is exposed to the sulfide gas. , and the sulfurization detection resistor 100 shown in FIGS. 1 to 3 is completed.

As shown in FIG. 7, the sulfuration detection resistor 100 configured in this manner is mounted on a circuit board 11 together with other electronic components (not shown), and then the circuit board 11 is exposed to an atmosphere containing sulfuration gas. used by At that time, the sulfuration detection resistor 100 is mounted on the circuit board 11 with the surface side of the insulating substrate 1 on which the sulfurization detection conductor 2 is formed facing upward (that is, with the resistor 5 facing downward). However, since the overcoat layer 6b of the second protective film 6 is arranged stepwise 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. Adequate clearance is ensured. As a result, the sulfuration 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 connected. In addition, the solder 13 can be reliably joined.

When the sulfuration detection resistor 100 mounted on the circuit board 11 is exposed to sulfuration gas in this manner, the sulfuration gas permeates the first protective film 3 and contacts the sulfurization detection portion 2a of the sulfurization detection conductor 2. As the cumulative amount of sulfuration increases over time, the sulfuration detection unit 2a breaks inside the first protective film 3. At this point, the degree of sulfurization is accurately detected from the resistance value of the current flowing through the resistor 5. can do. Moreover, even if the sulfuration 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 sulfurized. Conduction can be ensured by resistor 5 .

As described above, in the sulfurization detection resistor 100 according to the present embodiment, the sulfuration detection conductor 2 having the sulfurization detection portion 2a and the resistor 5 covered with the second protective film 6 are formed on both front and back surfaces of the insulating substrate 1. Therefore, when the sulfurization detection part 2a of the sulfuration detection conductor 2 provided on the front side of the insulating substrate 1 is disconnected due to cumulative sulfurization, the resistor provided on the back side of the insulating substrate 1 Accurate detection can be made from the resistance value of the current flowing through the body 5, and the continuity between the external electrodes 8 can be ensured even if the sulfuration detection conductor 2 is disconnected.

In addition, in the sulfuration 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 . Since the second protective film 6 is arranged stepwise in the region sandwiched between the pair of external electrodes 8 covering the back electrode 4, the sulfuration detection conductor 2 is mounted on the circuit board 11 with the surface side of the insulating substrate 1 formed thereon facing upward, between the second protective film 6 formed on the back surface side of the insulating substrate 1 and the circuit board 11 A gap is secured to avoid contact, and the sulfuration 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 dimension can be easily formed.

In addition, in the sulfuration detection resistor 100 according to the present embodiment, the sulfuration detection portion 2a of the sulfuration detection conductor 2 is covered with the first protective film 3 permeable to sulfuration gas, so that the sulfuration detection portion 2a is protected from external interference. The external electrodes 8 can be easily plated on both end portions of the sulfurization detection conductor 2 except for the sulfurization detection portion 2a. However, it is also possible to omit the first protective film 3 and expose the sulfurization detection unit 2a to the outside. The electrodes 8 are formed by plating, and after the external electrodes 8 are formed by plating, the resist film is stripped and removed with a solvent to expose the sulfurization detecting portion 2a.

REFERENCE SIGNS LIST 1 insulating substrate 2 sulfurization detection conductor 2a sulfurization detection part 3 first protective film 4 back electrode 4
4a first back electrode 4b second back electrode 5 resistor 6 second protective film 6a undercoat layer 6b overcoat layer 7 edge electrode 8 external electrode 10A large substrate 10B strip substrate 10c chip substrate 11 circuit substrate 12 wiring pattern 13 Solder 100 Sulfurization detection resistor

Claims (4)

A rectangular parallelepiped insulating substrate, a sulfurization detection conductor that can be sulfurized provided on the surface of the insulating substrate, a pair of back electrodes provided at both ends in the longitudinal direction of the back surface of the insulating substrate, and between the pair of back electrodes. a protective film covering the resistor; a pair of end-face electrodes electrically connecting both longitudinal ends of the sulfurization detection conductor and the back electrode; and a pair of external electrodes covering the end-face electrodes and the back electrode. an electrode;
Both ends in the longitudinal direction of the sulfurization detection conductor are covered with the pair of external electrodes, and the sulfurization detection conductor in a region not covered with the pair of external electrodes serves as a sulfurization detection portion capable of contacting the sulfurization gas. A sulfide detection resistor, characterized in that: The sulfidation detection resistor of claim 1, wherein
A height dimension from the back surface of the insulating substrate to the protective film is set to be smaller than a height dimension from the back surface of the insulating substrate to the external electrode covering the back electrode. sulfide detection resistor. The sulfidation detection resistor of claim 2, wherein
A sulfuration detection resistor, wherein said back electrode includes a first back electrode formed on the back surface of said insulating substrate and a second back electrode laminated on said first back electrode. The sulfidation detection resistor of claim 1, wherein
A sulfuration detection resistor, wherein the sulfurization detection part is covered with a sulfurization gas permeable protective film.

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