JPH08167502A - Glass encapsulated thermistor - Google Patents

Abstract

PURPOSE: To provide a glass encapsulated thermistor having little oxidation of a lead wire and high stability in a high temperature region. CONSTITUTION: An electrode 2 of a thermistor device 1, a lead wire connected to the electrode 2, the thermistor device 1 including a part of the lead wire 3 are encapsulated in a glass bulb 4, and the lead wire 3 is an alloy wire comprised of Fe, Cr, Al, Si, Mn, C, and other components and not containing Ni.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass-sealed thermistor which can be continuously used especially in a high temperature region of 400 ° C. or higher.

[0002]

2. Description of the Related Art Thermistors are widely used for temperature measurement, gas concentration measurement, etc. by utilizing the temperature dependence of the electric resistance of the temperature sensitive resistor. In particular, along with the electronic control of various devices, there has been a demand for highly reliable devices under severe conditions such as those for measuring automobile exhaust gas concentration. When a thermistor is used as a temperature sensor for measuring the concentration of exhaust gas in an automobile, it is required to have heat resistance that can withstand continuous use in an environment of a temperature atmosphere of 400 ° C. or higher.

However, since the thermistor chip is fired at a high temperature and glass sealing is performed at a high temperature of 700 to 900 ° C., no particular problem occurs in use in a temperature range of about 400 ° C. Since the lead wire is partially embedded in the sealing glass and connected to the electrode of the thermistor chip, the following problems occur when it is used in a high temperature region. That is, conventionally, a Dumet wire as a lead wire for drawing is attached to the pair of electrodes of the thermistor chip by welding or pasting.

The Dumet wire is a 42% Fe-Ni core wire coated with a Cu material. For Dumet used for applications such as continuous use at a high temperature of 400 ° C.,
The exposed portion from the glass was plated with Ni to prevent oxidation of the Cu material. However, since the Ni plating layer is formed after the thermistor chip is sealed with glass,
When the formation of the plating layer was incomplete, oxidation proceeded from the exposed portion of the Cu material, which was the cause of the resistance failure and open (breakage) failure of the thermistor chip.

In order to solve this problem, a heat-resistant lead wire made of an iron-based alloy such as Fe-Cr-Ni-based or Fe-Cr-based alloy is used as the lead wire, and at least the sealing glass of the lead wire is used. Attempts have been proposed to improve the wettability between the glass and the lead wire by subjecting the contact portion of the above to surface oxidation treatment.

According to this method, the surface oxidation treatment of the lead wire is usually carried out in the atmosphere at a temperature in the range of 800 ° C. to 900 ° C. with an increase in oxidation of 0.30 to 0.70 mg / mm ² , preferably 0.40. done by heating about 2 to 20 minutes so as to ~0.60mg / mm ^2, then after connecting the heat leads to the electrodes of the thermistor chip, the chip preferably a glass tube made of borosilicate glass By inserting, sealing in an inert atmosphere such as an argon gas atmosphere at a temperature of about 750 to 900 ° C., and if necessary, aging at a temperature of 500 to 750 ° C. for 10 to 100 hours. This is to obtain a glass-sealed thermistor (see Japanese Patent Laid-Open No. 2-97001).

However, even with this method, Fe-
The adhesion between the Ni-Cr alloy wire and the lead-based glass material is poor,
There is a drawback that moisture or the like enters the gap between the lead wire and the lead-based glass material, and when glass sealing is performed in the atmosphere, the glass sealing is performed at a temperature equal to or higher than the softening point temperature of the sealing glass material used (60
Since it is performed in a high temperature range (0 ° C), oxygen in the atmosphere oxidizes the alloy wire part in the glass burial part, and similarly, there is a problem that the resistance value failure and open failure of the thermistor element occur. As a further improvement, an attempt was made to use an alkali barium glass material as the sealing glass material and perform the glass sealing in an inert gas or neutral gas atmosphere (JP-A-6-224004). No.).

[0008]

In the above method, since glass sealing is performed in an inert gas or neutral gas atmosphere, the Fe-Ni-Cr alloy in the buried portion is not oxidized during glass sealing. It is possible to more reliably prevent the resistance value failure and the open failure of the thermistor element body.

However, performing glass sealing in an atmosphere of an inert gas or a neutral gas is troublesome in terms of process control. As pointed out in Japanese Unexamined Patent Publication No. 6-224004, when a Fe-Ni-Cr alloy wire is used as a lead wire and this is glass-sealed in the atmosphere, the resistance value failure and the open failure of the thermistor element body occur. The occurrence has been confirmed by the experiments of the present inventors. Fe-Ni- for the lead wire
When Ni is contained like a Cr alloy wire or an Fe-Co-Ni alloy wire, foaming occurs around the lead wire sealed in the glass when the glass is sealed in the atmosphere.

An object of the present invention is to provide a highly reliable glass-sealed thermistor having stable characteristics without causing a resistance value defect or an open defect of the thermistor body even if glass sealing is performed in the atmosphere. Especially.

[0011]

In order to achieve the above object, in the glass-sealed thermistor according to the present invention,
A glass-sealed type thermistor in which a thermistor element is sealed in glass by including a part of a lead wire connected to an electrode of a thermistor body, and the lead wire is Fe, Cr, A.
It is an alloy wire containing 1, 1, Si, Mn, C and other components as effective components, and the weight ratio of Fe is 73% or more and Cr is 17 to 2
1%, 2 to 4% Al, 1.5% or less Si, 1.0% or less Mn, 0.1% or less C, and does not contain Ni in other components.

The thermistor element is a mixed sintered body of an oxide solid solution powder and a compound powder, and the oxide solid solution powder is an oxide solid solution containing at least Mn, Ni, Co, Zn, and a compound. The powder contains at least one of a spinel compound and a perovskite compound.

[0013]

In the glass-sealed thermistor of the present invention,
73% or more of Fe and 17 to 2 of Cr are contained in the lead wire by weight ratio.
1%, Al 2 to 4%, Si 1.5% or less, Mn 1.0% or less, C 0.1% or less, and other components 1.
Since it contains 0% or less and Ni is not contained in a detectable amount, there is no foaming even if glass sealing is performed in the atmosphere,
It is possible to obtain a highly reliable glass-sealed thermistor that has excellent adhesion between the sealing glass material and the lead wire, does not cause a resistance value defect or an open defect of the thermistor body, and has stable characteristics. As the amount of addition of major components such as Fe, Al, and Si among the respective components deviates from the above range, the coefficient of thermal expansion changes, the adhesion to glass decreases, and glass cracks easily occur.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the glass-sealed thermistor according to the present invention. FIG. 1 shows an example applied to a chip type thermistor. The chip type thermistor has electrodes 2 on both surfaces of a square thermistor element 1 facing each other.
In FIG. 2, lead wires 3 and 3 for pulling out are fixed to each other using a parallel gap spot welding method or a conductive heat resistant paint.

In the case of a bead type thermistor, a pair of electrode wires are inserted as electrodes 2 and 2 into a spherical thermistor element 1 as shown in FIG. 2, and lead wires 3 and 3 are welded to the electrodes 2 and 2, respectively. To be done. In either example, the thermistor element 1
Is a glass ball 4 including a part of the pair of lead wires 3, 3.
The inside is sealed to form a glass-sealed thermistor. A glass tube made of lead-based glass, alkali barium-based glass, borosilicate glass, or the like is used for glass sealing, and a thermistor element is inserted into the glass tube, and the temperature is about 800 ° C. in the atmosphere.
It is carried out by heating the glass tube, melting the glass tube, and solidifying it into a spherical shape.

In the present invention, the thermistor element is composed of a mixed sintered body of oxide solid solution powder and compound powder,
In particular, it was selected as a thermistor for measuring gas flame temperature used in the temperature range of 400 to 500 ° C., exhaust gas temperature of automobiles, and other high temperatures.

The oxide solid solution powder is composed of manganese (Mn),
It is an oxide solid solution of nickel (Ni), cobalt (Co), and zinc (Zn), and the compound powder contains one or more compounds selected from spinel compounds or perovskite compounds.

In addition to the above oxide solid solution, one kind of oxide solid solution selected from alumina, magnesium, zirconia and tin may be added to the oxide solid solution powder, if necessary.

The compound powder selectively contains one kind or two kinds or more of any one of the spinel compound and the perovskite compound.

When manganese, nickel, cobalt, or zinc is used for the oxide solid solution powder, Mn should be 5 to 70.
A metal element containing 5% to 70% by mol of Ni, 1 to 40% by mol of Co, and 1 to 40% by mol of Zn is mixed, and the mixing molar ratio is adjusted to 100%.

In addition to manganese, nickel, cobalt and zinc, when one kind of oxide solid solution selected from alumina, magnesium, zirconia and tin is added, Mn is 5 to 70 mol% and Ni is 5 to 5 mol%. 70 mol%, C
o is 1 to 40 mol%, Zn is 1 to 40 mol%, Al,
1 to 1 type of component selected from Mg, Zr and Sn
Five kinds of metal elements containing 40 mol% are mixed, and the mixed molar ratio is adjusted to be 100%.

The spinel compound powder is SnAl ₂ O ₄ , M
nAl ₂ O ₄ , MnCr ₂ O ₄ , MnTi ₂ O ₄ , ZnCr ₂
O ₄ , ZnAl ₂ O ₄ , ZnTi ₂ O ₄ , ZnFe ₂ O ₄ , C
rAl ₂ O ₄ , MgTi ₂ O ₄ , MgAl ₂ O ₄ , MgMn ₂
O ₄ , MgCr ₂ O ₄ , FeAl ₂ O ₄ , FeCr ₂ O ₄ , F
eCo ₂ O ₄ , CoFe ₂ O ₄ , CoAl ₂ O ₄ , CoCr ₂
It was adjusted to be O ₄ , NiCr ₂ O ₄ , and NiAl ₂ O ₄ .

The perovskite compound powder is LaY
_{O 3, LaAlO 3, YCrO 3} , YFeO 3, CaTiO
₃ , CaSnO ₃ , MgCeO ₃ , BaCeO ₃ , CeAl
O ₃ , CeCrO ₃ , CeFeO ₃ , LaTiO ₃ , LaN
It was adjusted to be iO ₃ .

One or more of the spinel compound powder and the perovskite compound powder are selectively added to the oxide solid solution powder and fired as a mixed fired body. When one kind of the compound powder of the spinel compound powder or the perovskite compound powder is added to the oxide solid solution powder, the addition amount is 1.0 to 60% by weight, and the amount of the oxide is When two or more kinds of compound powders are added to the solid solution powder, the addition amount is 1.0 to 60% by weight.

Oxide solid solutions of manganese, nickel, cobalt, zinc and alumina, magnesium, zirconia and tin show low resistance at 250 ° C. and are excellent in sinterability. Further, the spinel compound has a high resistance at 250 ° C., and the perovskite compound is a material having a low resistance.

The thermistor according to the present invention is a mixed sintered body in which materials having the above characteristics are selectively combined, and it is sufficiently sintered at a sintering temperature of 1300 ° C., which is considerably low as a high temperature material, and has an arbitrary variation. A thermistor having a resistance value and a temperature coefficient of resistance is obtained.

The thermistor element is not limited to a bead type in which components kneaded in a paste form are applied between pairs of platinum wires and processed into granules, or a chip cut out from a block of a fired body is enclosed in glass. The performance is obtained, and the manufacturing method of the device is not restricted in any way.

In the present invention, it is important to adjust the components of the thermistor element, especially Zn, Al, Mg, Zr and Sn within the range of 1 to 40 mol%. When it is 1 mol% or less, the high temperature heat resistance is inferior, and when it is 40 mol% or more, the sinterability is lowered, and the variation in the resistance value is increased, and at the same time, the high temperature heat resistance is deteriorated. Become. On the other hand, it is important to adjust the addition amount of the spinel and perovskite compound within the range of 1 to 60% by weight.

When the amount added is 1% by weight or less, the effect of adding the spinel or perovskite compound does not appear conspicuously and the high temperature heat resistance which is the objective of the present invention is not improved.
If it exceeds 0% by weight, the sinterability decreases, the resistance value becomes abnormally high, and the high temperature heat resistance deteriorates.

The mixed sintered body fired by blending these components can be sintered at a relatively low temperature, especially 40
As a thermistor for temperature measurement in a gas flame temperature used in a temperature range of 0 to 550 ° C., an exhaust gas temperature of an automobile, and in a high temperature range of 400 to 550 ° C., the resistance change rate is small and an excellent life characteristic is obtained.

Ag-Pd or Au electrodes are used as electrodes. Iron-chromium heating wire is used for the lead wire. Especially in terms of chemical composition (% by weight), Cr 17-21%, Al 2-4
%, Si 1.5% or less, Mn 1.0% or less, C 0.1%
Hereinafter, an alloy wire containing 1.0% or less of the other components, 73% or more of the remaining components being Fe, and not containing Ni in the 1.0% of the other components is selected and used. Table 1 shows the physical properties of the alloy wire containing the above chemical components, and Table 2 shows the mechanical properties thereof.

[0033]

[Table 1]

[0034]

[Table 2]

As an example, 21% Cr-2.7% Al-
1.0% Si-1.0% Mn 0.3C-0.19Ti-
When an Fe alloy wire was used for the lead wire of the thermistor element shown in FIG. 2 and part of the lead wire was glass-sealed with lead-based glass in the atmosphere, a part of the lead wire was well wetted in the glass. Sealed. However, as a comparative example, 42% Ni-
When a bead type thermistor element was glass-sealed in the atmosphere under the same conditions using a 6% Cr-Fe alloy wire as a lead wire, the periphery of the lead wire part sealed in the glass, especially the lead wire A large number of fine bubbles were generated adhering to the inside. Presumably, a considerable amount of oxygen taken in by the Ni oxide film was released as bubbles by sealing in the atmosphere.

Next, the resistance value R = 1 KΩ obtained in the embodiment.
And about the 10KΩ glass-sealed thermistor 400
FIG. 3 shows the rate of change in resistance with time at ° C. As is clear from FIG. 3, in the case of 1 KΩ, the resistance change rate showed a slightly increasing tendency after 700 hours, but it was 3 even after 5000 hours.
It stopped in the range of%. Those having a resistance of 10 KΩ exhibited excellent stability even after 5000 hours had elapsed.

On the other hand, a glass-sealed thermistor of a comparative example in which a Fe-42% Ni-6% Cr-Fe alloy wire was used as a lead wire in a thermistor element having the same composition as that of the embodiment, the resistance value at 400 ° C. Although the rate of change with time was measured, the resistivity was significantly increased within a relatively short time after the start of the measurement, and the measurement was stopped midway.

[0038]

As described above, according to the present invention, the lead wire of the glass-sealed thermistor is mainly composed of iron, chromium and aluminum, and also contains silicon, manganese, carbon and other components, and does not contain nickel. It is possible to seal glass in the atmosphere using an alloy wire, and at the time of glass sealing, there is no foaming from the lead wire part that is sealed in the glass, and a specific oxide solid solution powder is specified as a component of the thermistor element. By selecting the combination with the compound powder of 1), even if it is used continuously at a high temperature, it has the effect of maintaining a predetermined function stably for a long period of time without causing a defective resistance value or open defect of the thermistor body. .

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a glass-sealed thermistor.

FIG. 2 is a diagram showing another example of a glass-sealed thermistor.

FIG. 3 is a diagram showing a change rate of resistance value with time of a glass-sealed thermistor of an example at 400 ° C.

[Explanation of symbols]

 1 Thermistor element 2 Electrode (electrode wire) 3 Lead wire 4 Glass ball

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Seiichi Matsumoto 1-11-4 Shin-Sayama, Sayama City, Saitama Prefecture Oizumi Manufacturing Co., Ltd.

Claims (2)

[Claims] 1. A glass-sealed thermistor comprising a part of a lead wire connected to an electrode of a thermistor element and sealing the thermistor element in glass, wherein the lead wire is made of Fe, Cr, It is an alloy wire containing Al, Si, Mn, C and other components as effective components, and 73% by weight or more of Fe, 17 to 21% of Cr, 2 to 4% of Al and S by weight.
i is 1.5% or less, Mn is 1.0% or less, C is 0.1%
A glass-sealed thermistor including the following and not containing Ni in other components. 2. The thermistor element is a mixed sintered body of oxide solid solution powder and compound powder, and the oxide solid solution powder is at least Mn, Ni, Co, Z.
The glass-encapsulated thermistor according to claim 1, wherein the compound powder is an oxide solid solution containing n, and the compound powder contains at least one of a spinel compound and a perovskite compound.