JPH0145963B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a glass-encapsulated PTC thermistor.

As is well known, a thermistor is used to detect only temperature, so the thermistor element is encapsulated in resin or glass to protect it from influences other than temperature, such as gas and humidity. . In particular, NTC thermistors include, in addition to resin-filled disk-type thermistors, glass-filled thermistors that are inexpensive, mass-producible, and have stable characteristics have been put into practical use.

However, glass-encapsulated PTC thermistors have not been put into practical use, and only resin-encapsulated disk-type thermistors and PTC thermistors with metal mechanically pressed against electrodes for heaters have been put into practical use, and have not been mass-produced. Currently, inexpensive glass-encapsulated PTC thermistors with excellent performance have not been put into practical use.

As a result of intensive studies regarding the manufacture of glass-encapsulated PTC thermistors, the inventors of the present invention have discovered that PTC thermistors with good characteristics have been developed.
Having succeeded in producing a thermistor, we would like to present a method for its production.

According to research conducted by the present inventors, conventional NTC thermistors have been encapsulated by glass welding in _N2 gas, Ar gas, or vacuum to prevent oxidation of the composite wire and heater. When applied to a thermistor, it was found that the characteristics of the PTC thermistor would be significantly impaired due to glass welding and encapsulation in a reducing atmosphere.

As a result of various experimental studies, the present inventors have found that a thermistor with excellent PTC characteristics can be obtained by welding and encapsulating glass in a mixed atmosphere of air and O ₂ gas (with air being 0% or more and 100% or less by volume). I got the knowledge that it can be obtained.

The present invention is based on this knowledge, and provides excellent characteristics as described below.

Figure 1 shows the characteristics of a PTC thermistor that is sealed by glass welding with various gases flowing into it.
Here, we used glass with a softening point of 560°C, and welded and encapsulated a PTC thermistor element with a Curie point of 120°C at 610°C.

As can be seen from the figure, glass welding and encapsulation in O ₂ gas or air is more effective than in vacuum, inert gas, or reducing atmosphere.
A PTC thermistor with excellent PTC characteristics can be obtained.
Although FIG. 1 shows only the atmosphere in O ₂ gas and air, almost the same characteristics can be obtained in a mixed atmosphere of air and O ₂ gas. Furthermore, although the results were carried out here for a PTC thermistor element with a Curie point of 120°C, similar results can be obtained with a PTC thermistor element having a different Curie point.

Figure 2 shows glass with a softening point of 536°C and a Curie point of 120°C in O ₂ gas and air.
FIG. 3 is a resistance and temperature characteristic diagram of a PTC thermistor in which a PTC thermistor element is sealed by glass welding.

As can be seen from the figure, a PTC thermistor can be obtained that has characteristics with a large resistance change that is almost the same as the characteristics before sealing.

Although only O ₂ gas and air are shown in FIG. 2, almost the same characteristics can be obtained even in a mixed atmosphere of air and O ₂ gas. Further, although the results were carried out here for a PTC thermistor element with a Curie point of 120°C, similar results can be obtained with a PTC thermistor element having a different Curie point.

Examples of the present invention will be described below.

FIG. 3 shows each process of the example. First,
Semiconducted barium titanate porcelain 1 is sliced to a desired thickness corresponding to the length of the glass tube, silver electrodes 2, 2 are applied to both sides of the element, and this is heated at 600°C for 20 minutes.
Burn. FIG. 1a is a cross-sectional view of the device after baking the silver electrode. Next, as shown in FIG. 3b, the element is cut into an arbitrary length corresponding to the diameter of the glass tube.
The vertical and horizontal lines are cutting lines.

This element is placed in a glass tube 4 with a softening point of 536°C.
As shown in FIG.
3 is inserted, and the glass tube 4 is welded and sealed using a carbon heater jig in a mixed atmosphere of air and O ₂ gas.

The working temperature for this welding and sealing is determined by the softening point of the glass, and is generally performed at a temperature 50° C. or more higher than the glass softening point.

Note that although a carbon heater jig is used here as the heater for welding and sealing, other heater jig, such as a meta-heater jig, may be used.

The PTC thermistor manufactured in this manner has excellent characteristics as shown in FIG. 2, and can be provided at low cost.

[Brief explanation of drawings]

FIGS. 1 and 2 are temperature-resistivity characteristic diagrams of products manufactured under different manufacturing conditions, respectively, and FIG. 3 is a diagram showing the manufacturing process of an embodiment of the present invention. 1...PTC thermistor element, 2...silver electrode,
3...Dimmet wire, 4...Glass tube.

Claims (1)

[Claims] 1. A PTC characterized by glass welding and enclosing semiconductor porcelain having positive resistance-temperature characteristics in an atmosphere of air, _O2 gas, or a mixture thereof (with the exception that air is 0% or more and 100% or less in volume percentage).
Manufacturing method of thermistor.