JPS6038242Y2 - Positive characteristic thermistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a positive temperature coefficient thermistor made of barium titanate semiconductor ceramic having a positive temperature coefficient of resistance.

A positive temperature coefficient thermistor can obtain any heat generation temperature by appropriately selecting the Curie temperature, and when a certain temperature is reached, the electrical resistance value increases rapidly, and it has a current control function that automatically controls the current and heat generation temperature. It also has features such as having a self-temperature control function, and is safe and reliable, so it has been widely used as a current control element in various electronic and electrical equipment or as a heat source in various heat generating devices. There is.

In general, a positive temperature coefficient thermistor is provided with ohmic contact electrodes on opposing surfaces of a positive temperature coefficient thermistor body, and a lead-out electrode part that also has ohmic contact is electrically connected to the electrode, and the lead-out electrode part is connected to the outside. The structure was such that lead wires for connection were electrically connected by soldering or eyelet coupling.

However, when the lead electrode part is configured as an ohmic contact in this way, heat generation at the lead electrode part becomes large, and the method of connecting the lead wire or other external connector to the lead electrode or the thermal effect of the external connector itself As the conditions become more severe, thermal deterioration of the connection points occurs, reducing reliability.

In particular, if the distance between the extraction electrodes or between the extraction electrodes and the original electrode is shorter than the distance between the electrodes, the current will concentrate in the short distance, causing local heat generation. As the above-mentioned problems occur, the above-mentioned drawbacks become more noticeable.

The present invention eliminates the above-mentioned conventional drawbacks, suppresses heat generation in the lead electrode part, relaxes the method of connecting the lead wire or other external connector and the lead electrode part, or the thermal design conditions of the external connector itself. The object of the present invention is to provide a positive temperature coefficient thermistor that prevents thermal deterioration of connection points and improves reliability.

In order to achieve the above object, the present invention is characterized in that ohmic contact electrodes are provided on opposing surfaces of a positive temperature coefficient thermistor element body, and a non-ohmic contact lead electrode portion is connected to the electrodes. .

That is, in the present invention, by forming the extraction electrode part, which has conventionally been an ohmic contact, as a non-ohmic contact, a potential barrier is provided on the contact surface between the extraction electrode part and the positive temperature coefficient thermistor body, The flow of current from the lead-out electrode portion to the PTC thermistor body is suppressed to suppress heat generation in the lead-out electrode portion and local heat generation as much as possible.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The content of the present invention will be specifically described below with reference to the accompanying drawings, which are examples.

FIG. 1A is a plan view of a PTC thermistor according to the present invention, and FIG. 1B is a front sectional view taken along line 81-81 in FIG. 1A.

In this embodiment, ohmic contact electrodes 2 and 3 are provided on the inner and outer peripheral surfaces of a cylindrical positive temperature coefficient thermistor element 1, and the electrodes 2 and 3 are provided on both end faces of the positive temperature coefficient thermistor element 1 in the axial direction.
, 3 are each provided with non-ohmic contact lead-out electrode portions 4 and 5 which are electrically connected to each other.

The electrodes 2 and 3 are formed by various methods for forming ohmic contact electrodes on this type of oxide semiconductor ceramic, such as electroless nickel plating, metal spraying, or rubbing In-C; be done.

Furthermore, after forming an ohmic contact electrode, silver or silver compound paste can be coated and baked on the surface to form a two-layer structure, thereby improving adhesion to the element body 1 and soldering properties to lead wires and the like.

Further, the extraction electrode parts 4 and 5 can be formed by forming the electrodes 2.3, applying silver paste or the like so as to cover a part of the edges thereof, and baking the same.

As described above, when the extraction electrode parts 4, 5 are formed as non-ohmic contact electrodes, a potential barrier is formed at the contact surface between the extraction electrode part 4.5 and the element body 1.
Despite the short distance between the extraction electrode parts 4 and 5 and the electrodes 2 and 3, the current flowing from the extraction electrode parts 4 and 5 toward the element body 1 is reduced, and heat generation in the extraction electrode part 4.5 is suppressed. .

If the lead electrode parts 4 and 5 were made into ohmic contact electrodes, the distance from the lead electrode part 4 to the electrode 3 and the distance from the lead electrode part 5 to the electrode 2 would be short, and non-ohmic contact would be required. Since there is no potential barrier as in the case of , current concentrates in this area and generates heat locally.

FIG. 2 shows another embodiment of the positive temperature coefficient thermistor according to the present invention.

The feature of this embodiment is that opposite ends of the inner and outer electrodes 2.3 are connected to the end faces 1a and l of the cylindrical positive temperature coefficient thermistor body 1.
Gap g□ from b.

The non-ohmic contact lead-out electrode portions 4 are placed on the entire surface of the end surfaces 1a and lb of the positive temperature coefficient thermistor element body 1.
5 was established.

In the case of this embodiment, since the current is uniformly distributed over the end faces la and lb of the PTC thermistor body 1, there is an advantage that local heating can be more effectively prevented.

3A and 3B show another embodiment of the positive temperature coefficient thermistor according to the present invention.

In this embodiment, ohmic contact electrodes 2 similar to those described above are provided on both sides in the thickness direction of a flat positive temperature coefficient thermistor body 1.
3, and non-ohmic contact lead-out electrodes 4 and 5 are electrically connected to one end edge of the electrodes 2 and 3.

Through holes 6 and 7 passing through the element body 1 in the thickness direction are provided in the forming regions of the extraction electrode parts 4 and 5.
, 7 has a structure in which a lead wire or the like is connected through an eyelet.

In this embodiment as well, since the extraction electrode parts 4 and 5 are in non-ohmic contact, local heat generation in the extraction electrode parts 4 and 5 can be prevented.

FIG. 4 shows yet another embodiment.

The feature of this embodiment is that ohmic contact electrodes 2.
are provided on opposite sides of the PTC thermistor element 1,
This is because the extraction electrode portion 4.5 is provided for non-ohmic contact.

The positive temperature coefficient thermistor shown in this example is used when configuring a so-called harmonica-type heat generating device in which a plurality of them are arranged at appropriate intervals to serve as an airflow path, or when directly soldered to the wiring pattern of a printed circuit board. This is suitable for use as a chip type.

As described above, the present invention is characterized in that ohmic contact electrodes are provided on opposite surfaces of the positive temperature coefficient thermistor element body, and an ohmic contact lead electrode portion is connected to the electrodes. In addition to reducing the heat generation at the parts as much as possible, relaxing the method of connecting external connectors such as lead wires and the extraction electrodes, and relaxing the thermal design conditions of the external connectors themselves, this also prevents thermal deterioration of the connection points and improves reliability. It is possible to provide a positive characteristic thermistor with improved characteristics.

[Brief explanation of the drawing]

FIG. 1A is a front view of a positive temperature coefficient thermistor according to the present invention, FIG. 1B is a sectional view taken along the line B□-a of FIG.
The figure is a sectional view of another embodiment of the PTC thermistor according to the present invention, FIG. 3A is a front view of another embodiment of the PTC thermistor according to the present invention, and FIG.
A sectional view taken along line B2 and FIG. 4 are further perspective views of the embodiment. 1... Positive temperature coefficient thermistor element body, 2, 3... Bent electrode, 4, 5... Extracted electrode part.

Claims (1)

[Scope of utility model registration request] In a positive temperature coefficient thermistor in which ohmic contact electrodes are provided on both sides in the thickness direction of a positive temperature coefficient thermistor body, and a non-ohmic contact lead electrode portion is connected to the electrodes, the positive temperature coefficient thermistor body has a cylindrical shape. The ohmic contact electrodes are formed on the inner and outer peripheries of the positive temperature coefficient thermistor body, and the lead electrode portion is provided on an end face of the positive temperature coefficient thermistor body in the axial direction. A thermistor with characteristics.