JPH0810643B2 - Manufacturing method of positive temperature coefficient thermistor - Google Patents

Description

The present invention relates to a method for manufacturing a positive temperature coefficient thermistor (PTC), and more particularly to a method for manufacturing a positive temperature coefficient thermistor in which a radiation fin is fixed to a positive temperature coefficient thermistor substrate. Regarding improvement.

[Conventional technology]

As shown in FIG. 8, a PTC thermistor of this type has corrugates in which a counter electrode 3 is formed on each main surface of a PTC thermistor substrate 1 and a strip-shaped metal thin plate, for example, an aluminum thin plate is formed in a corrugated shape. It is well known that one peak of the fin 5 is fixed to each counter electrode 3, the fin cover 7 is fixed to the other peak of each corrugated fin 5, and the terminal plate 9 is led out from the fin cover 7. There is.

As a method of fixing the corrugated fins 5 to the counter electrode 3, the corrugated fins 5 to which a brazing material is attached are attached.
There is a brazing method in which the corrugated fins 5 are fixed to the counter electrode 3 by superposing them on the counter electrode 3 and then heating to about 600 ° C. in a vacuum to melt the brazing material.

FIG. 9 shows a state after brazing, and reference numeral 11 is a brazing material.

Such a positive temperature coefficient thermistor can be used as a heat generator when an alternating voltage is applied between the terminal plates 9 to heat the positive temperature coefficient thermistor substrate 1. However, since the resistance value sharply increases at the Curie temperature, the surface temperature of the positive temperature coefficient thermistor increases. However, it has the advantage that it is stable at the Curie temperature and is unlikely to affect ambient temperature and voltage fluctuations.

[Problems to be Solved by the Invention]

However, in the above-mentioned positive temperature coefficient thermistor, when the corrugated fin 5 is brazed to the counter electrode 3 in vacuum,
It was found that there is a problem that PTC characteristics deteriorate, such as the resistance value does not rise so much at the Curie temperature.

As described above, when the corrugated fins 5 are brazed in a vacuum, the cause of deterioration of the PTC characteristics is not clear, but the following reasons can be considered.

That is, since it is generally difficult to form a high vacuum state close to a complete vacuum, the inside of the brazing process container is, for example, 10 ^-5 Torr.
Brazing is performed while forming a high degree of vacuum by using a brazing material mixed with a brazing promoting metal such as magnesium which is easier to activate than the brazing material while maintaining a degree of vacuum. .

Therefore, in the high temperature atmosphere at the time of brazing, the metal component is easily vaporized and precipitated from the brazing material, and the metal component enters from the end face of the positive temperature coefficient thermistor substrate 1 into the internal holes and deteriorates the insulating characteristics of the positive temperature coefficient thermistor. Can be mentioned.

Reference numeral 13 in FIG. 9 is a metal component that enters from the end face of the positive temperature coefficient thermistor substrate 1.

Further, it is conceivable that the oxygen component in the positive temperature coefficient thermistor substrate 1 is partially reduced by the reducing action of the metal component 13 and the PTC characteristic is deteriorated.

In addition, if flux is attached to the corrugated fins 5 and brazed, it is possible to braze without oxidizing the brazing material without brazing in a high vacuum, but it is necessary to apply the flux. The flux must be cleaned after application.

However, since the PTC thermistor substrate 1 is porous, it is difficult for the flux to permeate the inside of the PTC thermistor substrate 1 for cleaning. In order to clean the flux, the flux is removed by acid cleaning or alkali cleaning. Therefore, it may deteriorate PTC characteristics and it is difficult to completely remove the flux.

In this respect, the method of brazing in a high vacuum state without using flux is superior.

The present invention has been made under such circumstances, and it is possible to manufacture a positive temperature coefficient thermistor in which the PTC characteristics are not easily deteriorated even if a metal heat radiation fin is brazed to a counter electrode in a non-oxidizing atmosphere such as a vacuum. It provides a method.

[Means for solving the problem]

In order to solve such a problem, the present invention forms an electrode on the opposing surface of a positive temperature coefficient thermistor substrate, and brazes and fixes a metal radiation fin to the electrode in a non-oxidizing atmosphere, and then 480 ° C. The PTC thermistor is manufactured by exposing the PTC thermistor substrate to an oxidizing atmosphere heated to the above temperature.

[Action]

In the present invention equipped with such means, even if the metal component of the brazing promoting metal material enters the internal pores from the end face of the PTC thermistor substrate in the brazing process, the PTC thermistor substrate is exposed to a high temperature oxidizing atmosphere. When exposed to the inside, the metal component that has entered is oxidized and becomes an insulator, and the reduced PTC thermistor substrate is also restored and the PTC characteristic is restored.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. The same parts as those in the above-mentioned configuration are designated by the same reference numerals.

1 to 3 are process drawings showing an embodiment of a method for manufacturing a positive temperature coefficient thermistor according to the present invention.

First, for example, a rectangular plate having a thickness of several millimeters is formed from a barium titanate-based positive-characteristic ceramic material, and then this is fired to form a positive-characteristic thermistor substrate 1, and an aluminum material is sprayed on the opposing main surface. The counter electrode 3 is formed (FIG. 1).

Next, prepare two corrugated fins 5 each having a corrugated fin formed by bending a metal thin plate having a substantially constant width, for example, an aluminum strip into a corrugated shape. A brazing material is attached to the surface of each corrugated fin 5, and each corrugated fin 5 is formed. One peak is placed on each counter electrode 3 and placed in the vacuum container 15 (FIG. 2). Generally, a brazing-promoting metal such as magnesium is mixed in the brazing material.

Then, the inside of the vacuum vessel 15 is degassed to a vacuum state of about 10 ⁻⁴ to ⁻⁵ Torr, and the inside is heated to the melting temperature of the brazing material or higher,
After heating to about 600 ° C. to melt the brazing material, the temperature is lowered and each corrugated fin 5 is fixed to the counter electrode 3.

Further, as shown in FIG. 3, the positive temperature coefficient thermistor substrate 1 is housed in an oxide treatment container 17, the inside of the oxidation treatment container 17 is heated to about 580 ° C. with the same pressure as the atmospheric pressure, and the positive temperature coefficient is increased. The thermistor substrate 1 is exposed for about 4 hours.

After that, when the PTC thermistor substrate 1 is taken out, the fourth
A positive temperature coefficient thermistor as shown in the figure is obtained.

Even with such a manufacturing method, a metal component such as magnesium is precipitated from the brazing material in the brazing process and enters the internal holes from the end face of the positive temperature coefficient thermistor substrate 1 as shown in FIG. May reduce some of the

However, when the PTC thermistor substrate 1 is subsequently exposed to a high-temperature atmosphere, the metal material that has entered is oxidized and becomes an insulator and the part that has been partially reduced is also oxidized, and good PTC characteristics are restored. To be done.

FIG. 5 is a so-called PTC characteristic diagram showing changes in the specific resistance with respect to the heat generation temperature of the positive temperature coefficient thermistor substrate 1 in the case of manufacturing without heating after brazing (broken line) and the case of manufacturing with heating (solid line).

From this, it can be seen that the positive temperature coefficient thermistor manufactured by the manufacturing method according to the present invention exhibits good PTC characteristics.

By the way, according to the experiments by the present inventor, it was found that the degree of recovery to a predetermined PTC characteristic and the time required for the recovery varied depending on the temperature, the amount of oxygen and the pressure in the air atmosphere.

For example, when the aluminum corrugated fins 5 are also brazed to the aluminum electrodes 3 with a brazing material,
As shown in the figure, when the positive temperature coefficient thermistor substrate 1 was left in the atmosphere at 580 ° C., the characteristics were recovered to practical use in about 4 hours.

FIG. 6 is a characteristic diagram showing the change of the specific resistance with respect to the standing time, and the specific resistance ratio is the positive characteristic thermistor substrate 1.
It is indicated by the maximum resistance value / minimum resistance value during operation.

On the other hand, as shown in Fig. 7, it took about 10 hours to restore the same characteristics in the atmosphere of 560 ° C, 140 hours in the atmosphere of 500 ° C, and 400 hours in the atmosphere of 480 ° C.

In this way, the time required to restore the characteristics becomes shorter if the temperature in the atmosphere is increased.

On the other hand, even if the temperature is lower than 480 ° C, it can be recovered by spending time. However, considering the industrial productivity, the atmospheric temperature in the present invention is preferably 480 ° C or higher.

However, if the ambient temperature is raised too high in order to accelerate the recovery time, the brazing material melts and the joint between the counter electrode 3 and the corrugated fin 5 is easily peeled off. Ah

Therefore, appropriate selection may be made between 480 ° C and above, which is slightly higher than the brazing temperature, depending on the brazing material.

Also, by setting the heating atmosphere at a pressure higher than that of the atmospheric atmosphere, the recovery time can be shortened compared to atmospheric pressure,
Even if the amount of oxygen is increased, the recovery time can be shorter than that in the atmosphere.

Therefore, it is preferable to expose the PTC thermistor substrate 1 in an oxidizing atmosphere heated to a temperature of 480 ° C. or higher under a pressure of atmospheric pressure or higher.

The above-described embodiment is an example of the present invention, and can be implemented with the PTC thermistor substrate 1 and the corrugated fins 5 having various shapes. Even if the vacuum vessel 15 and the oxidation treatment vessel 17 are the same, Good.

Furthermore, in carrying out the present invention, a carrier gas such as nitrogen gas may be added to a vacuum in a vacuum of about 10 ^-2 Torr for brazing, but the important point is that it is in a non-oxidizing atmosphere, preferably at a dew point of -50. The object of the present invention can be achieved by brazing in a non-oxidizing atmosphere at ℃ or below.

By the way, as the material of the corrugated fins 5 in the manufacture of the positive temperature coefficient thermistor, copper, iron, alloys containing these as a main component, or a material obtained by plating a steel plate with zinc, nickel, aluminum or tin is preferable in addition to aluminum.

As for the counter electrode 3, copper, zinc,
Nickel or an alloy material containing nickel as a main component is preferable, and a brazing material may be selected according to these.

Brazing includes soldering in a narrow sense,
A solder material is included as the brazing material.

〔The invention's effect〕

As described above, according to the present invention, a metal radiation fin is brazed and fixed to an electrode formed on a PTC thermistor substrate in a non-oxidizing atmosphere, and then the PTC is exposed in an oxidizing atmosphere at a temperature of 480 ° C. or higher. Since the thermistor substrate is manufactured by exposing it, the PTC characteristics were recovered even if the metal radiation fin was brazed to the counter electrode in a non-oxidizing atmosphere using a brazing material mixed with a brazing promoting metal material. It is possible to obtain a positive temperature coefficient thermistor and suppress an increase in manufacturing cost.

[Brief description of drawings]

1 to 3 are sectional views showing an embodiment of a method for manufacturing a ceramic component according to the present invention, FIG. 4 is a perspective view of a positive temperature coefficient thermistor manufactured according to the present invention, and FIG. 5 is an oxidizing atmosphere. PT showing the relationship of the specific resistance to the heat generation temperature when the PTC thermistor substrate is heated and when it is not heated.
C characteristic diagram, FIG. 6 is a characteristic diagram for explaining the relation between high temperature oxidation treatment and thermistor characteristic, and FIG. 7 is a relation of recovery time when the temperature is changed in the atmosphere to recover the PTC characteristic. FIG. 8, FIG. 8 and FIG. 9 are a sectional view and a partial sectional view of a main part of a positive temperature coefficient thermistor manufactured by a manufacturing method which is a reference of the present invention. 1 ... Positive characteristic thermistor substrate 3 ... Counter electrode 5 ... Radiating fin (corrugated fin) 7 ... Fin cover 9 ... Terminal plate 11 ... Brazing material 15 ... Vacuum container 17 ... Oxidation treatment container

Claims (1)

[Claims] 1. A step of forming an electrode on the opposite surface of a positive temperature coefficient thermistor substrate, a step of brazing and fixing a metal radiation fin to the electrode in a non-oxidizing atmosphere, and after the radiation fin is fixed, And a step of exposing the positive temperature coefficient thermistor substrate to an oxidizing atmosphere heated to a temperature of 480 ° C. or higher, and a method for manufacturing a positive temperature coefficient thermistor.