JPH11144905A - Positive temperature coefficient thermistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive temperature coefficient thermistor, of which constant current F proofness is improved, while the F proofness is kept high in a positive temperature coefficient thermistor with a lead wire. SOLUTION: This positive temperature coefficient thermistor is formed of a plate-like positive temperature coefficient thermistor element 11, recessed parts 18 and 19 formed on the main surface opposite thereto, electrodes 12 and 13 formed on the main surface facing opposite thereto including the recesses 18 and 19, and lead wires 14 and 15 whose tip ends are inserted into the recesses 18 and 19 and the periphery around the tip end is fixed to the element 11 with solder. Thus the amount of solder for fixing the tip end of the lead wire to the positive temperature coefficient thermistor can be reduced, the breakdown strength of the positive temperature coefficient thermistor can be enhanced, and the positive temperature coefficient thermistor in compliance with approved requirements be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive temperature coefficient thermistor with a lead wire, and more particularly to a positive temperature coefficient thermistor for demagnetization which requires a breakdown resistance against an inrush current, and a positive temperature coefficient for overcurrent protection. It relates to a thermistor.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 1, a lead-type positive temperature coefficient thermistor is connected to electrodes 2, 3 formed on opposing main surfaces of a plate-shaped positive temperature coefficient thermistor element 1, as shown in FIG. 5 and 5 are connected and fixed by solders 6 and 7 so as to be perpendicular to the opposing main surfaces of the PTC thermistor element 1.

[0003]

However, in the above-mentioned positive temperature coefficient thermistor with lead wires, the contact area between the lead wires 4 and 5 and the electrodes 2 and 3 of the positive temperature coefficient thermistor element 1 is small, and the leading ends of the lead wires 4 and 5 are small. In order to fix the portion to the main surface of the positive temperature coefficient thermistor element 1, a certain amount or more of solder 6, 7 is required,
The soldering area on the main surface of the positive temperature coefficient thermistor element 1 tends to be large.

When the amount of solder is large, heat dissipation from the PTC thermistor element 1 when voltage is applied concentrates on the solder portion, and the difference in temperature distribution in the PTC thermistor element 1 increases. Therefore, the resistance of the low temperature part in the positive temperature coefficient thermistor element 1 becomes low, and the current concentrates on the low resistance part. Therefore, there is a problem that the dielectric breakdown of the positive temperature coefficient thermistor element 1 occurs and the breakdown voltage becomes low. .

In recent years, in the market, not only the conventional F resistance but also the F resistance (constant current F resistance) with a limited current value, which indicates the breakdown voltage resistance against inrush current, has been developed.
Resistance is established by an official standard, and a positive temperature coefficient thermistor element having a high level of constant current F resistance as well as conventional F resistance is required. However, in the conventional PTC thermistor element, both F
It is difficult to increase the resistance at the same time to a high level, and in the conventional product, the constant current F resistance did not meet the official standard conditions.

An object of the present invention is to provide a positive temperature coefficient thermistor having improved constant current F resistance while maintaining F resistance at a high level.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention has completed a positive temperature coefficient thermistor.

A positive temperature coefficient thermistor according to the present invention comprises a plate-shaped positive temperature coefficient thermistor element, a concave portion formed on a main surface facing the positive temperature coefficient thermistor element, and an electrode formed on an opposing main surface including the concave portion. The tip is fitted into the concave portion, and the vicinity of the tip consists of a lead wire fixed to the positive temperature coefficient thermistor element by solder.

As a result, the amount of solder for fixing the tip of the lead wire to the PTC thermistor is reduced, so that the PTC thermistor is improved in the breakdown resistance of the PTC thermistor, and a PTC thermistor which satisfies the official standard conditions of the constant current F resistance. Obtainable.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the embodiment shown in FIG.

First, a PTC thermistor element 11 is prepared. This positive temperature coefficient thermistor element 11 has concave portions 18 and 19 as lead wire attaching portions at the center of each of both main surfaces. This positive temperature coefficient thermistor element 11 is manufactured by using a positive temperature coefficient thermistor raw material mainly composed of a barium titanate-based ceramic semiconductor to produce a disk-shaped molded body by dry molding.
It is obtained by forming concave portions 18 and 19 in the respective central portions on both sides and then firing. Next, on both main surfaces of the obtained positive temperature coefficient thermistor element 11, an electrode composed of a Ni layer (first layer) formed by electroless plating and an Ag baking layer (second layer) having a smaller area than the Ni layer. 12 and 13 are formed. The positive temperature coefficient thermistor element 11, which is a measuring element, has a disk shape of 8.2 mm in diameter and 2.5 mm in thickness, and has a concave portion 1 at the center of the circle.
8 and 19 have a diameter of 1 mm and a depth of 0.25 mm, and have a resistance of 20Ω at room temperature.

Next, lead wires 14 and 15 to be attached to the PTC thermistor element 11 are prepared. These lead wires 14 and 15 are L-shaped Cu lead wires having a thickness of 0.6.
mm.

After preparing the above-mentioned positive temperature coefficient thermistor element 11 and lead wires 14 and 15, the leading end of the lead wire is fitted into the concave portions 18 and 19 at the center of the positive temperature coefficient thermistor element 11 and soldered with solders 16 and 17. Fixed.

Next, the F resistance and the constant current F resistance of the positive temperature coefficient thermistor were measured. Table 1 shows the results. The conventional product in Table 1 has a shape in which the concave portions 18 and 19 in FIG. 2 are not formed.

[0015] The constant current F resistance is a flash withstand voltage in which a specific resistance is connected in series to the positive characteristic thermistor to limit the current flowing through the positive characteristic thermistor.

[0016]

[Table 1]

As is clear from Table 1, the PTC thermistor according to the present invention satisfies all of the official standard conditions for the constant current F, which were not satisfied by the conventional product.

The shape of the concave portions 18 and 19 formed on the main surface of the positive temperature coefficient thermistor element 11 is arbitrary, and may be a semi-concave spherical shape.

[0019]

As described above, according to the present invention, the amount of solder is reduced by fitting the tip of the lead wire into the recess formed in the main surface of the PTC thermistor element, thereby reducing the amount of solder. , And it is possible to easily obtain a positive temperature coefficient thermistor having improved constant current F resistance while maintaining F resistance at a high level.

Further, the positioning of the lead wire can be easily performed, and the lead wire can be mounted almost perpendicularly to the main surface of the positive temperature coefficient thermistor element without variation, so that the workability is improved and the lead wire tensile strength is further improved. Also improve.

[Brief description of the drawings]

FIG. 1 is a sectional view of a positive temperature coefficient thermistor with a lead wire for explaining a conventional example.

FIG. 2 is a sectional view of a positive temperature coefficient thermistor with a lead wire for explaining an embodiment of the present invention.

[Explanation of symbols]

 11 Positive characteristic thermistor element 12, 13 Electrode 14, 15 Lead wire 16, 17 Solder 18, 19 Recess

Claims (1)

[Claims] 1. A plate-shaped positive temperature coefficient thermistor element, a concave portion formed on an opposing main surface of the positive temperature coefficient thermistor element, an electrode formed on an opposing main surface including the concave portion, and a tip fitted into the concave portion. And a lead wire whose tip is fixed to the positive-characteristic thermistor element with solder.