JPH11283811A - Axial lead glass sealed type thermistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermistor of axial lead glass sealed type which enables use in a medium/high temperature region by suppressing the variation of characteristic at the sealing of glass and furthermore giving a leader line to ship parts. SOLUTION: This thermistor is constituted by inserting a chip-type thermistor element 20 into a glass tube 1 and sealing sealing electrodes (slag leads) 3A and 3B to both tips of the tube 1 for sealing the element 20. The element 20 is constituted by giving a glass coating 22 to the four faces, except for both end faces of a rectangular parallelepiped thermistor element assembly made of oxide ceramic and forming a terminal electrode on both of the end faces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an axial-lead glass-sealed thermistor, and more particularly to an axial-lead glass-sealed thermistor using a chip-type thermistor element. More specifically, the present invention relates to a glass-sealed thermistor temperature sensor suitable for use in detecting a temperature in a middle to high temperature range of about 150 to 300 ° C.

[0002]

2. Description of the Related Art A conventional example of an axial type glass-filled thermistor will be described with reference to FIG. As shown in FIG. 2, this thermistor has a thermistor element 2 inserted into a glass tube 1 and sealing electrodes (slag leads) 3A and 3B inserted at both ends of the glass tube 1 to form an inert gas such as nitrogen or argon. Heating in the sealing electrode 3A,
3B is sealed and sealed. 4A and 4B indicate lead wires.

The thermistor element 2 is a flake type thermistor element in which electrode layers are formed on both surfaces of a flake type thermistor body. This thermistor body is made of an oxide ceramic mainly composed of a transition metal oxide.

Conventionally, in such a glass-filled thermistor, Dumet is generally used as the sealing electrodes 3A and 3B.

In the case of Dumet, a cuprous oxide (Cu ₂ O) layer (or borate (Cu ₂ O—Na ₂ B ₄ O ₇ ) layer) is formed on the surface of a wire made of an iron-nickel alloy via a copper intermediate layer. It was done. That is, the main body is made of an Fe-Ni alloy in order to make the coefficient of thermal expansion close to the coefficient of thermal expansion of glass, and the surface layer is made of cuprous oxide or borate for welding with a glass tube. I have. The lead wires 4A and 4B are made of Dumet or Fe-Ni having a copper layer formed on the surface.
Alternatively, an Fe wire is used.

II. A conventional example of a chip type thermistor element will be described with reference to FIG. FIG. 3A is a schematic cross-sectional view of the chip thermistor element 8, and FIG. 3B is a perspective view of the chip thermistor element 8.

The chip-type thermistor element 8 has a rectangular parallelepiped thermistor element 9 formed on a side surface extending in the longitudinal direction with an insulating coat 10 made of glass or a polymer material (eg, epoxy), and a pair of longitudinally isolated insulating members. The terminal electrode 11 is formed on the end face of the substrate.

The terminal electrode 11 comprises a base electrode 12, a nickel (Ni) plating 13 covering the base electrode 12, and a solder plating 14 covering the nickel plating 13.

As the base electrode 12, for example, Ag alone or AgPd having a Pd content of 20 to 50% is used. Ag plating can be prevented by the Ni plating 13. Cr plating may be adopted instead of Ni plating. In some cases, such plating is not performed.

This chip type thermistor element 8 is often used for surface mounting with solder or the like, but an insulated wire is connected to the chip type thermistor element 8 and a metal (for example, SUS, copper) or a resin (for example, epoxy, AB
(S, PBT, etc.) may be inserted into a protective case, and the resin may be molded to form a thermistor temperature sensor.

The chip type thermistor element 8 may be provided with a resistance adjusting electrode.

[0012]

The above-mentioned conventional axial lead glass-sealed thermistor and chip type thermistor element have the following disadvantages (i) and (ii).

(I) The glass sealing process for manufacturing a conventional glass-sealed thermistor is performed in an inert gas such as nitrogen or argon in order to prevent oxidation of a dumet wire used as a slag lead. I have. However, since the thermistor element to be sealed is an oxide ceramic mainly composed of a transition metal, it is affected by the atmosphere at the time of sealing, and the thermistor characteristics change due to the reduction of the element, so that the required characteristics can be adjusted. Had a problem that it was difficult.

(Ii) On the other hand, the chip type thermistor has difficulty in providing a lead wire due to restrictions on its shape, and it has been impossible to apply it to a temperature sensor used in a medium-high temperature range.

An object of the present invention is to solve such a problem and to provide an axial lead glass-sealed thermistor having stable thermistor characteristics.

[0016]

The axial lead glass sealed thermistor of the present invention is an axial lead glass in which a chip type thermistor element is inserted into a glass tube, and sealing electrodes are respectively sealed at both ends of the glass tube. A sealed thermistor, wherein an outer surface of the chip type thermistor element other than the both end faces is coated with glass.

According to this structure, since the thermistor element is glass-coated in advance, it is possible to suppress the occurrence of characteristic fluctuations due to the influence of the atmosphere at the time of sealing the glass, and it is easy to adjust to the required characteristics. . Furthermore, 150 ° C., which was impossible with the conventional chip-type thermistor electrode structure
It is possible to provide a thermistor element having a lead wire used in a medium to high temperature range of about 300 ° C.

[0018]

FIG. 1A is a sectional view of an axial lead glass-sealed thermistor according to an embodiment.
(B) is a perspective view of a thermistor element used in the thermistor.

In this thermistor, a chip type thermistor element 20 is inserted into a glass tube 1 and sealing electrodes (slug leads) 3A and 3B are sealed at both ends of the glass tube 1 to seal the chip type thermistor element 20. The configuration is as follows. 4
A and 4B show lead wires.

The chip type thermistor element 20 has a configuration in which a glass coating 22 is applied to four surfaces other than both end surfaces of a rectangular parallelepiped thermistor element body made of oxide ceramic, and terminal electrodes 21 are formed on both end surfaces. ing. In order to apply the glass coating 22, it is preferable to apply a glass paste to the four surfaces of the thermistor body and heat the glass paste to fuse the glass. When the glass coating 22 is applied, it is preferable that the glass coating 22 be applied first to the four surfaces of the thermistor body, and then the terminal electrode 21 be formed. In this embodiment, the terminal electrode used is not subjected to solder plating.

As the glass for the glass coating 22, a glass having a softening point higher than the temperature at the time of sealing the glass tube described later is used. It is necessary that the glass does not deteriorate at the sealing temperature at the time of sealing the glass tube. In particular,
Amorphous glass having a softening point of 700 ° C. or higher, particularly 700 ° C. to 800 ° C., or crystallized glass is used.

In order to manufacture this thermistor, the chip-type thermistor element 20 is inserted into the glass tube 1 and the sealing electrodes 3A and 3B are inserted at both ends of the glass tube 1 so as to be placed in an inert gas such as nitrogen or argon. And the sealing electrode 3
A and 3B are sealed.

At this time, since the chip type thermistor element 20 is coated with the glass coating 22, the thermistor element does not undergo a reducing action when heated during sealing, and the characteristics of the thermistor element do not change.

[0024]

EXAMPLES Examples and comparative examples will be described below.

Example 1 A chip type thermistor element 20 was inserted into a glass tube 1 made of glass having a softening temperature of 570 ° C., and sealing electrodes 3A and 3B made of Dumet were inserted at both ends. To 650 ° C. for sealing electrodes 3A, 3B
Was sealed to produce an axial lead glass-sealed thermistor. The chip type thermistor element 20 has four surfaces coated with glass having a softening temperature of 700 ° C.

Table 1 shows the characteristics of the thermistor element 20 before and after sealing and the characteristic change rate.

Comparative Example 1 An axial-lead glass-sealed thermistor was manufactured in the same manner as in Example 1 except that a chip-type thermistor element without glass coating was used. Table 1 shows the properties of this thermistor before and after glass sealing and the rate of change of the properties.

[0028]

[Table 1]

As is clear from Table 1, the glass-sealed thermistor of Comparative Example 1 has a reducing action at the time of glass-sealing.
The change in the element characteristics was large, and the rate of change also varied. On the other hand, in the glass-sealed thermistor of Example 1 using the chip-type thermistor coated with glass,
Since the coated glass phase formed on the element surface in advance serves as a barrier and the influence of the surrounding atmosphere during glass sealing is suppressed, almost no change in element characteristics is observed, and variation in the change rate is also suppressed.

[0030]

As described above, the glass-sealed thermistor according to the present invention employs a chip-type thermistor whose outer surfaces other than both end surfaces are glass-coated, as a thermistor element to be sealed. Can be suppressed. This makes it possible to manufacture a high-precision glass-sealed thermistor with high yield. Further, it is possible to provide an element having a lead wire as a temperature sensor element used in a medium to high temperature range of about 150 ° C. to 300 ° C., which was impossible with a conventional chip-type thermistor electrode structure.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an axial lead glass-sealed thermistor according to an embodiment.

FIG. 2 is a configuration diagram of an axial lead glass-sealed thermistor according to a conventional example.

FIG. 3 is a configuration diagram of a conventional chip thermistor element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass tube 2 Thermistor element 3A, 3B Sealing electrode 4A, 4B Lead wire 8 Chip-type thermistor element 9 Thermistor body 10 Insulation coat 11 Terminal electrode 12 Base electrode 13 Nickel plating 14 Solder plating 20 Chip-type thermistor element 21 Terminal electrode 22 Glass coating

Claims (1)

[Claims] 1. An axial lead glass-sealed thermistor having a chip-type thermistor element inserted into a glass tube, and sealing electrodes sealed at both ends of the glass tube, wherein the both ends of the chip-type thermistor element are provided. An axial lead glass-sealed thermistor characterized in that an outer surface other than the surface is coated with glass.