JPH04120701A - Manufacture of ntc thermistor - Google Patents

Abstract

PURPOSE:To manufacture NTC thermistors at low cost and of high reliability with a simple process by providing the steps to form a film consisting mainly of barium titanate on a substrate of conductive material by plasma spraying, and to form a film of conductive material over this film, or other process. CONSTITUTION:An Al substrate electrode 2 of an arbitrary shape is sprayed with BaTiO3 powder by a plasma spray gun which discharges strong reductive plasma spray flames using Ar-H2 plasma gas which contains 5-50% of H2 to form a BaTiO3 film 3, whereby this film is made semiconductive by reduction. Next, leads 5a, 5b are connected to Al electrodes 2, 4 by heat-resistant binding conductive material 6a, 6b, respectively. Then, the BaTiO3 film 3, Al electrodes 2, 4 and junctions 6a, 6b of the Al electrodes 2, 4 and the leads 5a, 5b are hermetically sealed by hot-welding glass 7. This method of manufacturing NTC thermistors facilitates production and suppresses cost.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to N
The present invention relates to a method of manufacturing a TC thermistor.

[Prior Art] NTC thermistors are widely used in temperature sensors, temperature compensation elements, and the like as temperature-sensitive semiconductors whose resistance value decreases as the temperature rises and has a negative temperature coefficient of resistance. Among these, those mainly composed of oxides of transition metals such as Mn and Ni are used for low-temperature measurements, and those mainly composed of SiC-based, corundum, and zirconia-based oxides are used for high-temperature measurements. .

The method of manufacturing these thermistors is to mold the thermistor material using a press molding method or an extrusion method,
There is a method of baking, a method of installing the thermistor paste by screen printing and baking it, or a method of forming the thermistor material into a thin film by sputtering.

[Problems to be Solved by the Invention] However, methods using press molding or extrusion molding require high-temperature firing, and methods using screen printing require printing for producing electrodes and thermistors by screen printing. and firing steps are required, making the manufacturing process complicated, and in the method using sputtering, it must be performed in a high vacuum. Therefore, the above-mentioned conventional method has the disadvantage that the manufacturing cost is high.

The present invention has been made to solve the above-mentioned problems, and is an inexpensive and highly reliable NTC with a simple manufacturing process.
The purpose of the present invention is to provide a method for manufacturing a thermistor.

[Means for Solving the Problems] In order to achieve this object, the method for manufacturing an NTC thermistor of the present invention is to apply a film containing barium titanate as a main component to a conductive material by plasma spraying using Ar-H gas. a step of forming a film of a conductive material above the film; and a step of connecting lead wires to the base material of the conductive material and the film of the conductive material, respectively. step, heating and welding glass to the film containing barium titanate as a main component, the base material of the conductive material, the film of the conductive material, and the connection portion between the lead wire and each conductive material. and a step of sealing.

[Example] Hereinafter, an example embodying the present invention will be described with reference to the drawings.

As shown in FIG. 1, Ba with a Ba to Ti ratio of 1:1, whose particle size is adjusted to 5 to 125 μm by granulation or pulverization, is placed on an AI substrate electrode 2 of an arbitrary shape as shown in FIG.
By spraying TiOs powder with a plasma spray gun 1 that generates a strongly reducing plasma spray flame using ArH2 plasma gas containing 5 to 50% H2, a BaTiO3 film 3 with a film thickness of 300 μm is produced. B a
The TiO3 film 3 is reduced to become a semiconductor. The plasma spraying conditions at this time are shown in FIG. At this time, if the H2 content is less than 5%, the reducing property will be weak and the semiconductor formation will deteriorate, and if it is more than 50%, there is a risk that the nozzle of the plasma spray gun 1 will be severely worn out. Therefore, ArH2 containing 5-50% H2
It is best to make it by blast spraying using plasma gas.

Furthermore, as shown in FIG. 2, BaTi0. AI as an electrode is thermally sprayed from above the film 3 to a thickness of about 50 to 100 μm. The powder and spraying conditions for Al thermal spraying at this time may be the commonly used thermal spraying powder and thermal spraying conditions.

Next, as shown in FIG.
A, 6b are used to connect the lead wires 5a, ! Connect 5b. The lead wires 5a, 5b are Dumet wire, C
u alloy wire, Fe-Ni alloy wire.

It is sufficient to use a core wire made of Fe-Ni-Co alloy wire, Ni-Cr alloy wire, etc., and a Cr-Ni or Ni-based plating coated on the surface.The purpose is to increase heat resistance. A noble metal wire such as Pt may also be used.

Next, as shown in FIG. 4, B a T i 03 film 3,
AI electrodes 2, 4, and AI electrodes 2, 4 and lead wire 5a,
The connecting portions 6a and 6b with the connecting portion 5b are hermetically sealed by heating and welding the glass 7. This prevents the film from being oxidized, resulting in higher weather resistance.
Becomes a highly reliable thermistor.

The thermistor manufactured as described above had a specific resistance of 2600Ω and a B constant of 1576K at room temperature. If you want to lower the specific resistance, you can increase the proportion of I-12 to increase the reducibility of the BaTiO3 film, and if you want to change the B constant, you can change the ratio of Ba and Ti in BaTi03, or A transition metal oxide may be used as a trace additive.

As is clear from the detailed description above, the NT of this example
The method for manufacturing a C thermistor does not require high-temperature firing or processing in a high vacuum, making it easy to manufacture and keeping costs low.

Furthermore, since it is possible to produce a thermistor on a conductive member having an arbitrary shape by plasma spraying, the shape of the thermistor, that is, the area and thickness can be freely set.

In this embodiment, AI was used as the electrode material, but any other material that can provide ohmic contact, such as Ni, may be used.

[Effects of the Invention] As is clear from the above detailed description, the NTC of the present invention
The thermistor manufacturing method does not require high-temperature firing or processing in a high vacuum, so manufacturing is easy and costs can be kept low. Furthermore, since it is possible to fabricate a thermistor on a conductive member of any shape by plasma spraying, the shape of the thermistor, that is, the area and thickness, can be freely set.

[Brief explanation of drawings]

1 to 5 show embodiments embodying the present invention. FIG. 1 is a perspective view of a BaTi0a film being formed on an AI electrode base material by plasma spraying, and FIG. A cross-sectional view of the AI main electrode formed above the B a Ti Oa film, Figure 3 is a cross-sectional view of the AI main electrode lead wire attached, Figure 4 is a cross-sectional view of the state sealed with glass, Figure 5 is a table showing the conditions for plasma spraying. In the figure, 1 is a plasma spray gun, 2 is an A1 electrode base material, 3 is a BaTiO3 film, and 4 is an Al spray electrode. 5a and 5b are lead wires, 6a and 6b are heat-resistant bonding conductive materials, and 7 is glass.

Claims (1)

[Claims] 1. A step of forming a film containing barium titanate as a main component on a base material made of a conductive material by plasma spraying using Ar-H_2 gas, and a step of forming a film of a conductive material above the film. , connecting lead wires to the base material made of the conductive material and the film made of the conductive material, respectively; the film containing barium titanate as a main component, the base material made of the conductive material, and the conductive material; NT characterized by comprising a step of sealing a film of the material and a connecting portion between the lead wire and each conductive material by heating and welding glass.
A method for manufacturing a C thermistor.