JPH0670202U - Positive characteristic thermistor - Google Patents

Abstract

(57) [Summary] [Object] To provide a positive temperature coefficient thermistor capable of effectively preventing damage to the positive temperature coefficient thermistor element by making the coefficients of thermal expansion of the positive temperature coefficient thermistor element and the heat sink substantially equal to each other. A positive temperature coefficient thermistor according to the present invention comprises a positive temperature coefficient thermistor element 2 having electrode layers 1 and 1 formed on both main surfaces thereof, and an adhesive 4 on at least one of the electrode layers 1 to form a unitary structure. The heat dissipation plate 10 is joined to the heat dissipation plate 10. The heat dissipation plate 10 is made of ceramic, and the extraction electrode layer 11 is electrically connected to the electrode layer 1 over both main surfaces thereof. Is formed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a positive temperature coefficient thermistor used for overcurrent protection of a DC motor, and more particularly to a heat sink structure thereof.

[0002]

[Prior art]

 Conventionally, in a low-voltage DC motor, a positive characteristic thermistor that functions for overcurrent protection has been incorporated, and such a positive characteristic thermistor is used as shown in FIG. Conductive adhesion between a positive temperature coefficient thermistor element (hereinafter referred to as PTC element) 2 having electrode layers 1 and 1 formed on the main surface and heat dissipation plates 3 and 3 made of a metal such as copper having good heat dissipation property. Generally, it has a structure in which it is joined by the agent 4. The reason why such a structure is adopted is that the PTC element 2 is reinforced by the heat radiating plates 3 and 3, and at the same time, the operating time is extended while the low resistance and the withstand voltage characteristics are improved.

[0003]

[Problems to be solved by the device]

 By the way, the conventional PTC thermistor is constructed by joining the PTC element 2 made of ceramic and the heat radiating plates 3, 3 made of metal. However, the thermal expansion coefficients of these two greatly differ from each other. Therefore, the following inconveniences were to occur. That is, first, when the conductive adhesive 4 is baked to bond the PTC element 2 and the heat sinks 3 and 3, the stress generated by the difference in the coefficient of thermal expansion is applied to the PTC element 2. As a result, the PTC element 2 may be damaged. In addition, since the PTC element 2 generates heat by itself during use, stress due to the difference in the coefficient of thermal expansion from the heat dissipation plates 3 and 3 is applied to the PTC element 2 as well. It may break.

The present invention was devised in view of such inconvenience, and makes the thermal expansion coefficients of the PTC element and the heat dissipation plate approximately the same, and effectively prevents damage to the PTC element. The purpose is to provide a positive temperature coefficient thermistor.

[0005]

[Means for Solving the Problems]

 The positive temperature coefficient thermistor according to the present invention comprises a PTC element having electrode layers formed on both main surfaces thereof, and a heat dissipation plate integrally bonded on at least one of the electrode layers with an adhesive. The heat dissipation plate is made of ceramics, and the extraction electrode layer electrically connected to the electrode layer is formed on both main surfaces of the heat dissipation plate.

[0006]

[Action]

 According to the above configuration, since the PTC element and the heat sink are both made of ceramic, both of them have substantially the same coefficient of thermal expansion.

[0007]

【Example】

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

FIG. 1 is a sectional perspective view showing a schematic structure of a positive temperature coefficient thermistor according to the present embodiment, FIG. 2 is a sectional perspective view showing a first modification of the heat radiating plate, and FIG. It is a section perspective view showing an example of 2 modification. Since the entire structure of this positive temperature coefficient thermistor is basically the same as that of the conventional example, the same reference numerals are given to the same or corresponding parts and portions as in FIG. 4 in FIGS.

As shown in FIG. 1, the PTC thermistor according to the present embodiment is composed of a PTC element 2 made of a ceramic having a predetermined thickness on which electrode layers 1 and 1 are formed on both main surfaces, and a conductive adhesive. 4, the heat dissipation plates 10 and 10 are integrally bonded on the electrodes 1 and 1 of the PTC element 2 respectively. Each of the heat sinks 10 and 10 is formed in a flat plate shape having a predetermined thickness by using a ceramic such as barium titanate or alumina, and a conductive adhesive 4 is provided over the entire periphery thereof. The lead-out electrode layer 11 that is electrically connected to the electrode layer 1 of the PTC element 2 is formed by baking silver paste or the like. Here, the adhesive for joining the PTC element 2 and the heat dissipation plate 10 is not limited to one having conductivity, and for example, even if an adhesive having an insulating property is used, the PTC element 2 Of course, in some cases, it may be possible to secure substantial conduction from the relationship with the surface roughness of each of the heat sinks 10.

That is, in this positive temperature coefficient thermistor, since the PTC element 2 and the heat sinks 10 and 10 are both made of ceramic, they both have substantially the same coefficient of thermal expansion. Become. Therefore, when heat is applied to the PTC thermistor having such a configuration, the PTC element 2 and the heat sinks 10 and 10 are extended to the same extent, and only one of them is extended. As a result of no excessive stress being applied, the stress applied to the PTC element 2 will be significantly relieved as compared with the conventional example. By the way, although not shown in the drawing, for each of the lead electrode layers 11 located outside the heat sinks 10 and 10 in the above-described positive temperature coefficient thermistor, lead terminals are soldered or spring terminals are not provided. The final product will be constructed after being applied.

Furthermore, in the present embodiment, the entire surface around the heat dissipation plate 10 is covered with the extraction electrode layer 11, but the present invention is not limited to this, and as shown in FIG. A structure in which the extraction electrode layers 11a and 11b formed on both main surfaces are connected by an end face electrode 11c formed on one end face of the heat dissipation plate 10, and as shown in FIG. It is also possible to adopt a structure in which the extraction electrode layers 11a and 11b are connected to each other by a peripheral surface electrode 11d formed on the inner peripheral surface of the through hole provided at the position along the thickness direction. Further, in FIG. 1, the heat sinks 10 and 10 are respectively joined to both main surfaces of the PTC element 2, but the heat sink 10 is joined only to at least one main surface of the PTC element 2. Of course, it may be.

[0012]

[Effect of device]

 As described above, according to the positive temperature coefficient thermistor according to the present invention, both the PTC element and the heat sink are made of ceramic, and as a result, both of them have substantially the same coefficient of thermal expansion. become. Therefore, even when heat is applied to this PTC thermistor, excessive stress is not applied to only one of the PTC element and the heat sink, and the stress applied to the PTC element is larger than in the conventional example. Relaxed in width. As a result, it becomes impossible for the PTC element to be broken or cracked by the action of stress generated based on the difference in the coefficient of thermal expansion as in the conventional example.

[Brief description of drawings]

FIG. 1 is a sectional perspective view showing a schematic structure of a positive temperature coefficient thermistor according to the present embodiment.

FIG. 2 is a sectional perspective view showing a first modified example of the heat dissipation plate according to the present embodiment.

FIG. 3 is a sectional perspective view showing a second modification of the heat dissipation plate according to the present embodiment.

FIG. 4 is a sectional perspective view showing a schematic structure of a positive temperature coefficient thermistor according to a conventional example.

[Explanation of symbols]

 1 Electrode Layer 2 PTC Element (Positive Characteristic Thermistor Element) 4 Conductive Adhesive (Adhesive) 10 Heat Sink 11 Extraction Electrode Layer

Claims (1)

[Scope of utility model registration request] 1. A positive temperature coefficient thermistor element (2) having electrode layers (1, 1) formed on both main surfaces, and an adhesive (4) on at least one of the electrode layers (1), which are integrated with each other. A heat spreader (10) bonded to a positive temperature coefficient thermistor, wherein the heat sink (10) is made of ceramic, and the electrode layer (1) is formed on both main surfaces thereof. A positive temperature coefficient thermistor characterized in that an extraction electrode layer (11) which is electrically connected to is formed.