JP2000286039A - Resistance element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent in durability, easily-manufacturable and inexpensive resistance element capable of preventing the occurrence of a crack or the like, even if temperature increase from a room temperature to 1,000 deg.C or more and temperature reduction in the reverse direction are repeated. SOLUTION: This element has a resistance element body made of ceramics 22, an inner conductor 14 embedded inside the resistance element body 22, an external terminal electrode 24 installed on the rear end side of the resistance element body 22, for being connected to the inner conductor 14, lead wires 26 for being connected to the external terminal electrode 24, and an insulator comprising an inorganic adhesive, for covering integrally the rear end part of the resistance element body 22, the external terminal electrode 24, and the tip parts of the lead wires 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance element and a method for manufacturing the same, and more particularly, to a method for manufacturing a resistance element from room temperature to 1000.
° C or higher or vice versa
The present invention relates to a resistance element which does not generate cracks or cracks, has excellent durability, is easy to manufacture and is inexpensive, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a current-carrying type ignition resistance element using ceramics has been generally used for igniting gaseous fuel or liquid fuel such as natural gas, propane gas, and kerosene. This kind of ignition resistance element takes 10 to 2 seconds.
In order to withstand a rapid temperature rise of at least 00 ° C. and a high temperature of about 1550 ° C. in air, it is required to have excellent thermal shock resistance and oxidation resistance.

Further, a resistance element for a high-temperature thermistor that instantaneously measures a high temperature of 1000 ° C. or more is required to have excellent thermal shock resistance and oxidation resistance. In this type of resistance element, an internal conductor is buried inside a ceramic body, and an extraction electrode portion of the internal conductor is formed at a position away from a heat generating portion of the element. External terminal electrodes are joined to the extraction electrode portion with a brazing material or the like. External terminal electrodes
Lead wires are connected.

In order to protect the external terminal electrodes and the leading ends of the lead wires and to facilitate the handling of the resistance element, the rear end of the resistance element is usually made of a metal or alumina porcelain tube or square. It is put in a mold and fixed with an inorganic adhesive.

However, conventionally used inorganic adhesives have only an adhesive function and cannot form a bulk-shaped insulator only with the adhesive, and thus necessarily require a separate insulator from the adhesive.

[0006] Portland cement capable of forming a bulk decomposes at a high temperature, and may burst in an extreme case, so that it cannot be applied to a resistance element which may be at a high temperature. In addition, high-temperature type alumina cement that does not decompose at high temperatures cannot expect strength as a molded body until solidification, and solidification requires a high temperature of 1000 ° C. or more. The production conditions are the same. Therefore, in a ceramic resistance element to which a lead wire is attached, the alumina cement cannot be used because the lead wire portion cannot withstand heating at 1000 ° C. or more.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and cracks and cracks may occur even if the temperature is repeatedly increased and decreased from room temperature to 1000 ° C. or higher. It is an object of the present invention to provide an inexpensive resistance element which is excellent in durability, easy to manufacture, and inexpensive, and a method for manufacturing the same.

[0008]

Means for Solving the Problems The inventor of the present invention has set the room temperature from one to one.
Even if the temperature was repeatedly increased and decreased at a temperature of 000 ° C. or higher, cracks and cracks did not occur, the durability was excellent, and the production was easy and inexpensive. As a result, it solidifies at room temperature,
In addition, a silica-zircon adhesive or a water glass-silicon nitride adhesive is suitable as an adhesive that can withstand a high temperature of 1300 ° C., has properties close to the thermal expansion coefficient of silicon nitride ceramics, and can be formed in bulk. They have found and completed the present invention.

That is, a resistance element according to the present invention is connected to a ceramic resistance element body, an internal conductor embedded inside the resistance element body, and the internal conductor (directly or via an external terminal electrode). And an insulator made of an inorganic adhesive that integrally covers the rear end of the resistor element body and the front end of the lead wire.

In a method of manufacturing a resistance element according to the present invention, a step of manufacturing a ceramic resistance element main body in which an internal conductor is embedded, and connecting a lead wire (directly or via an external terminal electrode) to the internal conductor. A step, a rear end of the resistance element body and a front end of the lead wire are arranged in a mold, an inorganic adhesive is injected into the mold and cured, and a rear end of the resistance element body is formed. And forming an insulator that integrally covers the tip of the lead wire.

The inorganic adhesive is cured at a temperature of 200 ° C. or less, and the thermal expansion coefficient of the insulator obtained after the curing is preferably substantially the same as the thermal expansion coefficient of the ceramics constituting the resistance element body. . Preferably, the inorganic adhesive is a silica-zircon adhesive or a water glass-silicon nitride adhesive.

In the resistance element and the method of manufacturing the same according to the present invention, an insulator for the resistance element can be manufactured at the same time only by the step of injecting the inorganic adhesive, without using an expensive metal or ceramic insulator, and by nitriding. An insulator having a thermal expansion coefficient close to that of silicon can be manufactured integrally with the resistance element. Therefore, even when used as an insulator of a resistance element that frequently repeats temperature rise and fall from high temperature to room temperature or vice versa, it is possible to effectively prevent cracks and cracks from being formed in the insulator portion, and to improve durability. An excellent resistance element can be realized.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments shown in the drawings. FIG. 1 is a perspective view of a resistance element according to one embodiment of the present invention, and FIG. 2 is a perspective view showing a manufacturing process of the resistance element shown in FIG.

[0014] As shown in resistive element Figure 1, the resistance element 20 of the present embodiment, for example, is used as a high-temperature thermistor (temperature sensor) or a small heat generating element has a resistance element body 22, the internal resistance element body 22 Are formed with a predetermined pattern of internal conductors. The inner conductor 14 includes a pair of extraction electrode portions 14a.
And a thin resistive pattern 14b formed of a pattern for interconnecting the electrode portions 14a. When the resistance element 20 is used as a heating element, the resistance pattern 14b serves as a heating section that generates Joule heat when energized. When the resistance element 20 is used as a high-temperature thermistor, the resistance pattern 14b has a temperature that changes in resistance according to temperature. It becomes a sensor unit.

A pair of extraction electrode portions 14 of the internal conductor 14
As shown in FIG. 1, a is formed on each of two rear side surfaces of the element body 22 and is joined to the external terminal electrode 24. Lead wires 26 are connected to the respective external terminals 24. When the resistance element 20 is used as a heating element,
When a current is supplied from the lead wire 26 and the resistance element 20 is used as a high-temperature thermistor, a temperature detection signal is extracted from the lead wire 26.

In this embodiment, the resistance element main body 22 is made of, for example, ceramics such as silicon nitride, and the internal conductor 14 is made of tungsten carbide (WC, W ₂ C),
It is made of a high melting point metal (including an alloy) such as tungsten (W) and molybdenum (Mo). The lead wire 26 is made of, for example, a copper stranded wire. The external terminal electrode 24
For example, nickel, tungsten, molybdenum, gold,
It is composed of silver, copper and a combination of the above.

The rear end of the resistance element body 22, the external terminal electrode 24 and the front end of the lead wire 26 are integrally covered with an insulator 30 made of an inorganic adhesive. In the present embodiment, the shape of the insulator 30 is a cylindrical shape, but the shape of the insulator 30 is not particularly limited, and may be a rectangular parallelepiped shape or another shape.

The insulator 30 is hardened at a temperature of 200 ° C. or lower, and is made of an inorganic adhesive whose thermal expansion coefficient after hardening is substantially the same as the thermal expansion coefficient of the ceramics constituting the resistor element body. I have. Examples of such an adhesive include a silica-zircon adhesive or a water glass-silicon nitride adhesive.

The composition of the silica-zircon adhesive is not particularly limited. For example, 50 to 53% by weight of ZrO
₂ , 25 to 26% by weight of SiO ₂ and 13 to 21
% By weight of MgO.

Manufacturing Method of Resistive Element To manufacture the resistive element 20 shown in FIG. 1, first, as shown in FIG. 2, an internal conductor 14 is formed on the surface in a predetermined repetitive pattern by a screen printing method or the like. A green sheet 12 and a green sheet 16 on which no internal conductor 14 is formed are prepared.

In the present embodiment, the green sheets 12 and 16 are formed by adding an aqueous solution containing an organic binder or an organic solvent-based solution to a powder of a raw material mixture that is usually used, for example, in order to manufacture a ceramic sintered body. It is shaped and dried. Examples of the method for forming a sheet include a doctor blade method and an extrusion method.

The raw material mixture is not particularly limited, and examples thereof include one or more mixtures of metals, such as oxides, carbides, nitrides, borides, silicides, and the like, or compounds that can be changed to these by firing. can do. Also, as a binder added to the powder of the raw material mixture,
Although not particularly limited, for example, polyvinyl alcohol,
Acrylic resin and the like can be exemplified. The average particle size of the powder of the raw material mixture is not particularly limited, but is preferably about 0.1 to 1.5 μm.

Examples of the above metal oxides include, for example, alumina (Al ₂ O ₃ ), beryllia (Be
O) and oxides such as thoria (ThO ₂ ). Examples of metal carbides include, for example, carbides such as silicon carbide (SiC) and titanium carbide (TiC). Examples of nitrides of metals, for example, boron nitride (BN), silicon nitride _{(Si 3 N} 4), nitrides such as aluminum nitride (AlN) are exemplified.
Examples of metal borides include, for example, titanium boride (T
Borides such as iB ₂ ) and zirconium boride (ZrB ₂ ) are exemplified. Examples of metal silicides include, for example, silicides such as molybdenum silicide (MoSi ₂ ) and boron silicide (SiB ₃ , SiB ₆ ). Among them, preferred is nitride, and more preferred is Si ₃ N having a small coefficient of thermal expansion and high strength.
₄ .

The compounds which can be replaced with these compounds include the corresponding metal carbonates, silicates, polysilane compounds, metal + boron mixtures, metal oxide + carbon, metal oxide + carbon + nitrogen, and the like.

The inner conductor 14 formed on the surface of the green sheet 12 is co-fired with the raw material mixture.
The material is preferably a material having characteristics of a high melting point, a low coefficient of thermal expansion, and a low electric resistivity, and is not particularly limited. For example, a conductive paste containing tungsten (W), carbon (C), and the like at a predetermined ratio. A composition or the like is used.

The thickness of the green sheets 12 and 16 is
Although not particularly limited, it is generally 50 to 1500 μm. The thickness of the inner conductor 14 formed on the surface of the green sheet 12 by screen printing or the like is not particularly limited, but is preferably 5 to 50 μm, more preferably 15 μm.
２５25 μm.

As shown in FIG. 2, a single or a plurality of green sheets 16 are laminated on the upper and lower surfaces of the green sheet 12 on which the pattern of the internal conductors 14 is formed to form a laminated unit 10. By laminating a large number of 10 via a release agent layer not shown and pre-pressing, a block-shaped preform is obtained. The release agent layer is not particularly limited, but may be, for example, boron nitride (B
N) A sheet or the like is used.

Before the preform is mounted on a hot press, it is placed in a binder removal furnace and subjected to a binder removal treatment. The heating temperature at the time of the binder removal treatment varies depending on the type of the binder to be subjected to the binder removal treatment and the like, but is generally 400 to 1,000 ° C. The time for the binder removal treatment varies depending on the size of the preform, the heating temperature, and the like, but is generally several hours to several tens of hours.

Thereafter, the preformed body 1 after the binder removal treatment
0 is set in a hot press apparatus, and hot press molding is performed. In the hot press molding, it is preferable to use an inert gas atmosphere such as a nitrogen gas or an argon gas. The firing temperature of the hot press is not particularly limited, but is usually 1,300 to 2,100 ° C, preferably 1,500 to 1,900 ° C. Further, the pressing force at the time of hot pressing is preferably 100 to 600 kg / c.
m ² , more preferably 200 to 300 kg / cm
² . The pressurization time is generally 10 to 120 minutes.

By such forming, the pre-formed body is fired in a pressurized state, and the green sheets 12 and 16 shown in FIG.
Are sintered integrally, and then cut by a diamond cutter or the like, whereby the resistance element body 22 shown in FIG. 1 is obtained.

As a result, as shown in FIG.
On two rear sides of the body 22, there are provided extraction electrodes of the internal conductor 14.
The portion 14a is exposed. Then, these extraction electrode portions 1
4a and the external terminal electrode 24, a brazing material was supplied.
For example, the two are joined using a vacuum baking method or the like. Burning
The setting is, for example, 1.3 × 10^-2~ 1.3 × 10
^-3Temperature conditions of 800 to 980 ° C in a vacuum of about Pa
Do with. The brazing material is not particularly limited.
For example, silver brazing material is used. Silver brazing materials include titanium and jill
Active metals such as conium are preferred.
No. The addition of active metal to brazing filler metal
Adhesion to both the mic and the inner conductor that is the resistive material
This is to ensure sufficient strength.
The addition is preferably about 1% to 5% by weight. like this
Within a suitable range, the adhesive strength is sufficient and the brazing material
The flexibility of the material is also sufficient.

After that, the lead wire 26 is bonded to the external terminal electrode 24. The joining of the lead wire 26 can also be performed by the silver brazing described above.

Next, in the present embodiment, the rear end of the resistor element body 22 is shown in a state in which the heat generating portion on the tip end side of the resistor element body 22 and the lead wire 26 shown in FIG. The portion, the external terminal electrode 24 and the tip of the lead wire are arranged in a cylindrical cavity of a mold, and an inorganic adhesive is injected into the cavity. As the inorganic adhesive, a silica-zircon adhesive or a water glass-silicon nitride adhesive having the above-described composition is used.

These inorganic adhesives can be bulk-molded at room temperature, and are cured at room temperature by being injected into a mold. As shown in FIG. A cylindrical insulator 30 that integrally covers the external terminal electrode 24 and the tip of the lead wire 26 is formed. This insulator 30 can withstand a high temperature of 1300 ° C.
In addition, since molding is only performed by injecting an adhesive, it is extremely easy to manufacture, and the manufacturing cost is reduced to about 1/10 compared to conventional metal insulators or alumina porcelain insulators. Can be. Further, in use, even if the temperature is repeatedly increased and decreased from room temperature to room temperature or vice versa, cracks and cracks do not occur in the insulator 30.

Other Embodiments The present invention is not limited to the above-described embodiments, but can be variously modified within the scope of the present invention. For example, in the above-described embodiment, as the resistance element, the one having the multilayered resistance element body 22 is exemplified, but the specific structure of the resistance element body according to the present invention is not particularly limited, and the multilayered resistance element is not limited. In addition to the main body, a cylindrical roll-shaped resistive element main body or a cylindrical resistive element main body may be used.

In the embodiment described above, the hot press firing method is employed as the firing method.
The firing method is not particularly limited, and a known method, a normal pressure firing method, a nitrogen gas pressure firing method, or the like may be used. Further, in the present invention, the material and shape of the external terminal electrode 24 are not particularly limited. In addition, in the present invention, the external terminal electrode 24 is not necessary if the lead wire 26 can be directly joined to the extraction electrode portion 14a of the internal conductor 14 without necessarily requiring the external terminal electrode 24. In that case,
The insulator 30 is provided between the tip of the lead wire 26 and the resistance element body 22.
The outer periphery of the rear end portion is integrally covered.

[0037]

EXAMPLES Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples.

Example 1 100 mol of α-type Si ₃ N ₄ powder, Al ₂ O ₃
6.86 mol of powder and 10 mol of SiO ₂ powder were mixed to obtain a mixed powder. To 100 parts by weight of this mixed powder, an appropriate amount of an acrylic resin, ethanol and toluene were added and mixed to prepare a slurry, and a 1 mm-thick ceramic green sheet 12 was formed by a doctor blade method.
And 16 were made.

On the surface of the green sheet 12, for example,
Tungsten (W), carbon (C) and silicon nitride (Si
_{3 N 4)} and by using a conductive paste containing a predetermined ratio, by screen printing, thereby forming a pattern of internal conductor 14.

On the upper and lower surfaces of the green sheet 12 on which the pattern of the internal conductor 14 is printed, two green sheets 14 on which no pattern of the internal conductor 14 is printed are laminated so that the total number of the green sheets 14 is five. A plurality of these were laminated via a BN sheet to form a preform. Next, the preformed body was debindered at 500 ° C. in a nitrogen atmosphere. After that, the preform 10 is set in the hot press 30 and set in a nitrogen atmosphere at 1700 °.
C, hot press firing under the condition of 250 kg / cm ² . After firing, it was cut with a diamond cutter to obtain the resistor element body 22 shown in FIG.

The internal conductor 1 is provided inside the resistance element body 22.
4 is built-in, and the extraction electrode portion 14a which is an exposed portion thereof is provided.
Then, a silver brazing material containing an active metal was applied thereto, covered with an external terminal electrode 24 made of a Ni plate electrode, and baked in a vacuum of 2 × 10 ⁻⁴ Torr at 850 ° C. for 5 minutes for bonding. Thereafter, a lead wire 26 made of a copper wire was joined to the external terminal electrode 24 by silver brazing.

Next, the connection portion of the lead wire 26 is placed in a metal mold, and the lead wire and the heat-generating portion are put out of the metal mold, and a zircon adhesive (made by Nikkato) is placed in the mold. Was implanted and left at room temperature for 1 hour to solidify. Then, the mold was removed, and the resistive element 20 was fabricated.

Even if 20 of the obtained resistance elements were dropped on a concrete floor from a height of 50 cm, no damage was found at the insulator 30 part. In addition, heating and cooling of the 20 elements from room temperature to 1500 ° C. as one cycle,
When the insulator 30 was subjected to 500,000 cycles, cracks, cracks and the like were not observed.

[0044]

As described above, according to the present invention, even if the temperature is increased from room temperature to 1000 ° C. or more, or vice versa, cracks and cracks are not generated and the durability is improved. This makes it possible to realize an inexpensive resistance element which is excellent in manufacturing and easy to manufacture.

[Brief description of the drawings]

FIG. 1 is a perspective view of a resistance element according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a manufacturing process of the resistance element shown in FIG.

[Explanation of symbols]

 12, 16 ... Green sheet 14 ... Internal conductor 14a ... Extraction electrode part 20 ... Resistor 22 ... Resistor main body 24 ... External terminal electrode 26 ... Lead wire 30 ... Insulator

Claims (5)

[Claims] 1. A ceramic resistance element main body, an internal conductor embedded in the resistance element main body, a lead wire connected to the internal conductor, a rear end of the resistance element main body and a tip of the lead wire. And an insulator made of an inorganic adhesive that integrally covers the portion. 2. The inorganic adhesive is cured at a temperature of 200 ° C. or less, and a thermal expansion coefficient of the insulator obtained after the curing is substantially the same as a thermal expansion coefficient of a ceramic constituting the resistance element body. The resistance element according to claim 1, wherein: 3. The adhesive according to claim 1, wherein the inorganic adhesive is a silica-zircon adhesive or a water glass-silicon nitride adhesive.
Or the resistance element according to 2. 4. A step of manufacturing a ceramic resistance element main body in which an internal conductor is embedded, a step of connecting a lead wire to the internal conductor, and a step of connecting a rear end of the resistance element main body and a front end of the lead wire.
Forming an insulator that covers the rear end of the resistance element body and the front end of the lead wire integrally by disposing the adhesive inside the mold, injecting an inorganic adhesive into the mold, and curing the same. A method for manufacturing a resistance element. 5. The method according to claim 4, wherein a silica-zircon adhesive or a water glass-silicon nitride adhesive is used as the inorganic adhesive.