JPH05258909A - Glass-sealed thermistor - Google Patents

Abstract

PURPOSE:To obtain a glass-sealed thermistor, to be used for various electric apparatuses and motorcar apparatuses having heat-resisting property of 200 deg.C or higher and excellent acid-resisting property in which a lead wire can be connected to a thermistor element easily, and the removal of the oxide film on the surface of the lead wire is unnecessitated even after glass sealing operation is conducted. CONSTITUTION:The tips of lead wires 6a and 6b, consisting of an iron-nickel alloy on the surface of which platinum layers 5a and 5b are formed by plating or coating, are connected by parallel welding to the electrodes 2a and 2b of a thermistor element 1 on which electrodes 2a and 2b are formed on both opposing surfaces. By hermetically sealing the thermistor element 1 by heat-welding glass 4 to the thermistor element and the tips, including the welded part, of the lead wires 6a and 6b, a glass-sealed thermistor having excellent heat-resisting property, acid-resisting property and productivity can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to home appliances, household appliances,
The present invention relates to a glass-encapsulated thermistor which is used as a temperature sensor in automobile equipment and is particularly useful in fields where high heat resistance and high reliability are required.

[0002]

2. Description of the Related Art In recent years, demands for higher heat resistance and higher accuracy of thermistors have been increasing from the industries of home electric appliances, household appliances, automobile equipment and the like.

Conventionally, this type of glass-enclosed thermistor has a structure as shown in the sectional view of FIG. In FIG. 2, reference numeral 1 is a thermistor element body in which electrodes 2a and 2b are formed on opposite surfaces, and dumet lead wires 3a and 3b are connected to the electrodes 2a and 2b. Then, the thermistor element body 1 is hermetically sealed by welding glass 4 to the tip portion including the connecting portion of the thermistor element body 1 and the dumet lead wires 3a and 3b.

[0004]

However, the conventional structure as described above has the following problems.

(1) Since the dumet lead wire having a copper layer is used as the lead wire, the dumet lead wire can be used if left in a high temperature atmosphere exceeding 200 ° C., an oxidizing atmosphere, an oxidizing liquid, or the like. The oxidation of the copper layer proceeds to the inside of the Dumet lead wire sealed in the glass, and eventually leads to the occurrence of cracks in the glass and deterioration and damage of the thermistor element body.

(2) Since the insulating layer of cuprous oxide is present on the surface of the dumet lead wire, a method for connecting the thermistor element body and the dumet lead wire is to use the insulating layer of cuprous oxide of the dumet lead wire. How to perform welding after removing the
Alternatively, a method using a conductive paint has been carried out, but the manufacturing process is complicated by these methods, and it is impossible to manufacture at low cost.

(3) When the glass is sealed in air or in an atmosphere containing oxygen, an oxide film is formed on the surface of the Dumet lead wire that is drawn out from the glass after the glass is sealed. In actual use, it is necessary to remove this oxide film.

The present invention solves the above problems and has a heat resistance of 200 ° C. or higher, an excellent acid resistance, and a lead wire can be easily connected to the thermistor body.
Moreover, it is an object of the present invention to provide a glass-enclosed thermistor which does not require removal of an oxide film on the surface of a lead wire even after glass sealing.

[0009]

To achieve this object, the glass-encapsulated thermistor of the present invention has a structure using a lead wire made of an iron-nickel alloy having a noble metal layer provided on the surface by plating or coating.

[0010]

According to this structure, by using the iron-nickel alloy containing no copper for the lead wire, heat resistance of 200 ° C. or higher and excellent acid resistance can be obtained, and the surface of the lead wire can be extremely By providing a noble metal layer that is difficult to oxidize, the electrode formed on the thermistor body and the lead wire can be connected easily and stably by welding, and the lead wire surface is oxidized even after glass sealing. There is no such thing.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a glass-enclosed thermistor according to an embodiment of the present invention. However, the same parts as those in the conventional example of FIG. 1 in FIG.
Is a thermistor element body in which electrodes 2a and 2b are formed on opposite surfaces, and iron containing 48 to 52% by weight of nickel having platinum layers 5a and 5b formed on the surfaces of the electrodes 2a and 2b by plating or coating. The tips of the lead wires 6a and 6b made of nickel alloy are connected by parallel welding. Furthermore, the thermistor body 1 and the lead wire 6
The thermistor body 1 is hermetically sealed by heating and welding the glass 4 to the tip portion including the welded portions a and 6b.

The glass-enclosed thermistor according to this embodiment was subjected to a high temperature storage test at 400 ° C., and as a result, 10
Even after being held for 00 hours, deterioration of the lead wires 6a and 6b, occurrence of cracks in the glass 4 and change in resistance value of 5% or more were not observed. Further, the change in resistance value of the thermistor element body 1 due to parallel welding was 5% or less. Further, in the present embodiment, the iron-nickel alloy of the lead wires 6a and 6b has a composition of 48 to 52% by weight of nickel. However, an iron-nickel alloy having a nickel amount slightly smaller or slightly larger than the above composition range is used. Even when it was present, the deterioration of the lead wires 6a and 6b and the occurrence of cracks in the glass 4 were very small. Further, even when other noble metal layers such as gold were formed instead of the platinum layers 5a and 5b, the above-mentioned deterioration and crack generation were small.

As described above, since the glass-enclosed thermistor of this embodiment uses the iron-nickel alloy containing no copper in the lead wires 6a and 6b, it has heat resistance of 200 ° C. or higher and excellent acid resistance. Further, since the platinum layers 5a and 5b, which are extremely hard to be oxidized, are provided on the surfaces of the lead wires 6a and 6b, the electrodes 2a and 2b formed on the thermistor body 1 and the lead wires 6a and 6b can be easily and stably welded. The connection is cheaper and the lead wires 6a and 6 are sealed with glass.
It is not necessary to remove the oxide film on the surface b.

[0015]

As described above, the glass-enclosed thermistor of the present invention has the following effects by using the iron-nickel alloy having the platinum layer formed on the surface of the lead wire, and its practical value is It is great.

(1) By using an iron-nickel alloy containing no copper for the lead wire, heat resistance of 200 ° C. or higher and excellent acid resistance can be obtained.

(2) By providing the surface of the lead wire with the noble metal layer which is extremely difficult to be oxidized, the electrode formed on the thermistor element and the lead wire can be easily and stably connected by welding. Further, it is unnecessary to remove the oxide film on the surface of the lead wire even after the glass sealing.

[Brief description of drawings]

FIG. 1 is a sectional view of a glass-enclosed thermistor according to an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional glass-enclosed thermistor.

[Explanation of symbols]

 1 Thermistor body 2a, 2b Electrode 4 Glass 5a, 5b Platinum layer 6a, 6b Lead wire

Claims (2)

[Claims] 1. A tip of a lead wire made of an iron-nickel alloy having a noble metal layer on the surface thereof is connected to each of the electrodes formed on opposite sides of the thermistor body, and the thermistor body and the thermistor body are formed. A glass-encapsulated thermistor in which glass is heated and welded to a tip portion including a connecting portion of a lead wire to hermetically seal the thermistor body. 2. The glass-encapsulated thermistor according to claim 1, wherein the lead wire is made of an iron-nickel alloy containing 48 to 52% by weight of nickel and provided with a platinum layer.