JPS6010701A - Positive temperature coefficient thermistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a positive temperature coefficient thermistor that is inexpensive and has stable characteristics.

Generally, positive temperature coefficient thermistors using barium titanate-based semiconductor ceramics are provided with an ohmic electrode film by electroless plating of nickel. However, since this plating film is usually heat treated for stabilization, 1. An oxide film is formed on its surface. Therefore, when soldering lead wires onto this plated electrode film, it is necessary to use strong flux or perform other physical or chemical surface treatments to prevent solder from adhering. This has the drawback of not only deteriorating the characteristics of the positive temperature coefficient thermistor but also significantly increasing the processing cost.

Conventionally, therefore, a silver electrode was layered on a nickel-plated electrode film, but this had the disadvantage of increasing costs due to the use of expensive silver. In the case shown in the first figure, the amount of silver electrode used is minimized to suppress the increase in cost. In the figure, 1 is a positive temperature coefficient thermistor body, 2 is a nickel-plated electrode film, 3 is a silver electrode, 4 is a lead wire, and 5 is solder. In other words, the silver electrode 3 has a size necessary for soldering the lead wire 4.
is applied to the center of the plated electrode film 2. However, when this product is actually used, it does not matter if the current that flows is relatively small, but if it is used in applications where several tens of amperes of current flows during rush, such as in the degaussing circuit of a color television. However, the two-layer electrode film 2, which had a thin film thickness, caused sparks and broke the electrode film, which was disadvantageous, and it was not desirable in terms of practicality.

The present invention has been made in view of the above-mentioned drawback □.
A metal film of one of aluminum, nickel, and copper is applied to 50 to 90% of the area of the electrode film, and a silver electrode is applied to the remaining area on the electrode film. The present invention aims to provide a thermistor with the following characteristics.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a side sectional view showing a first example of the present invention, and FIG. 3 is a perspective view thereof. In both figures, 11 is a positive temperature coefficient thermistor element made of barium titanate semiconductor ceramic, 12 is an electroless nickel plated electrode film applied on both hands of this element 11, and 13 is the center of this electrode film 12. A metal film of any one of aluminum, nickel, or copper is applied to the remaining part of the electrode film 12, and 14 is a silver electrode that is applied to the remaining part of the electrode film 12, that is, the central part where the metal film 13 is not applied. It is. In this case, the area to which the metal film 13 is applied is selected to be 50 to 90% of the area of the electrode film 12, and is opposed to this area.

The area to which the silver electrode 14 is applied is selected to be 10 to 50% of the area, and the metal film 13 and the silver electrode 14 are applied so as to cover the entire surface of the electrode film 12.

Next, an example of a specific method for actually manufacturing a positive temperature coefficient thermistor configured as described above will be described. First, a disk-shaped positive temperature coefficient thermistor body 11 is prepared, and electroless nickel plated electrode films 12 are applied to both surfaces thereof by a conventional method.

Since this electrode film 12 is initially applied to the entire surface of the element body 11,
Afterwards, it is necessary to remove the electrode film on the outer surface portion as appropriate. Next, a metal paste of one of aluminum, nickel, and copper is applied onto both electrode films 12 except for the center portion thereof, and then baked to form a metal film 13. Thereafter, a silver paste is applied and baked on the 712-electrode film 12 on which the metal film 13 is not formed, thereby forming the silver electrode 14. This place 0・″a fa m < −1′r− & tjja <
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FIG. 4 shows an example in which a lead 3 wire is soldered to such a positive temperature coefficient thermistor of the present invention. As can be seen from this example, the lead wire 15 is firmly fixed onto the silver electrode 14 to which solder and solder 16 easily adhere. In this case, the metal film 13
Due to the material of the metal film or the oxide film formed during baking, the solder 16 hardly adheres to the metal film. Fifth
The illustrated one is a positive temperature coefficient thermistor of the present invention with a spring terminal 17.
are pressed together and held together. In the figure, 18 is a holding portion for the spring terminal 17, which constitutes a part of the case. In this example as well, the spring terminal 17 is brought into contact with the silver electrode 14 to provide a good conductive connection.

Figures 6 to 8 are all positive characteristic thermistor elements 11.
This figure shows an example of the shape of the metal film 13 and silver electrode 14 formed in the figure. In either example, the area where the silver electrode 14 is applied needs to be within a range of 10 to 50% of the area of the electrode film 12.

It should be noted that the embodiments and drawings shown above are for the purpose of facilitating understanding of the present invention, and it goes without saying that the present invention is not limited to these.

4- As described above, the positive temperature coefficient thermistor of the present invention greatly eliminates the use of silver electrodes to make conductive connections with lead wires and spring terminals, making it cheaper. Since the nickel-plated electrode film is completely covered with the metal film, the electrode film will not be destroyed even if a large amount of current flows, and the characteristics can be made stable.

[Brief explanation of drawings]

Fig. 1 is a side sectional view showing an example of the structure of a conventional PTC thermistor, Fig. 2 is a side sectional view showing an embodiment of the PTC thermistor of the present invention, Fig. 3 is a perspective view thereof, Figs. FIG. 5 is a sectional view showing an application example of the PTC thermistor of the present invention, and FIGS. 6 to 8 are plan views showing further embodiments of the PTC thermistor of the present invention. 11-Positive temperature coefficient thermistor element 12-Nickel plated electrode film 13-Metal film 14-Silver electrode Patent applicant Murata Manufacturing Co., Ltd.

Claims (1)

[Claims] A nickel-plated electrode film is applied to the positive temperature coefficient thermistor body, and a metal film of one of aluminum, nickel, and copper is applied on the electrode film in an area of 50 to 90% of the area of the electrode film, A characteristic thermistor characterized in that a silver electrode is provided on the remaining area on the electrode film.