JPH04320301A - Critical temperature resistor and its manufacture - Google Patents

Abstract

PURPOSE:To enable an allowable current value to be increased and a degree of selection of a resistance value to be increased by laminating a plurality of semiconductor ceramic plates with thermistor characteristics. CONSTITUTION:Internal electrode layers 2a-2d and insulation resistance layers 4a-4d are included between layers of a plurality of semiconductor ceramic plates 1a-1e with critical temperature resistor characteristics, thus enabling external electrodes 5, 5 to be formed at both edges of a lamination body.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a rapid change thermistor whose electrical resistance changes rapidly at a certain temperature, and a method for manufacturing the same.

0002

2. Description of the Related Art A rapid change thermistor (CTR) is a semiconductor element whose electrical resistance rapidly decreases as the temperature rises within a certain temperature range. The sudden change thermistor currently in practical use is V
The basic composition is O2, and the crystal structure of VO2 is 7
It utilizes the semiconductor←→metal transition at around 0°C.

[0003] Normally, a sudden change thermistor has a voltage of V2 O5
, Si, P, Mg, Ca, Sr, Ba, La, Pb, etc. are mixed, and 800%
It is manufactured by heat treating at ~900°C, pulverizing, forming into a bead shape, firing in a reducing atmosphere at 1000°C, and then rapidly cooling.

0004

[Problems to be Solved by the Invention] In the conventional sudden change thermistors, the sudden change resistance characteristics are largely dependent on the manufacturing process, and it is necessary to set detailed manufacturing conditions in order to obtain good sudden change characteristics.

[0005] In particular, the quenching step, like the reducing atmosphere treatment step, is the step that most affects the rapid change characteristics, and in order to obtain good characteristics, the quenching step must be performed at 900° C. or higher. For this reason, it is difficult to obtain good sudden change characteristics with large sudden change thermistors such as disk types that are difficult to cool uniformly, and small elements such as bead types and thin film types have become mainstream. However, in such a small device, the allowable current value is limited to several tens of mA or less, and furthermore, the degree of freedom in selecting the resistance value in the usage range is low. For this reason, it has not been possible to meet a wide range of demands, such as for use as inrush current suppressing elements.

An object of the present invention is to provide a sudden change thermistor that has a high allowable current value and a high degree of freedom in selecting resistance values, and a method for manufacturing the same.

[0007]

[Means for Solving the Problems] In order to increase the allowable current value, it is necessary to increase the size of the entire device and to perform the rapid cooling process reliably. The inventors have discovered that by rapidly cooling thin-layer ceramic plates to form a plurality of semiconductor ceramic plates each having sudden change thermistor characteristics, and by laminating these plates, a sudden change thermistor without the above-mentioned drawbacks can be obtained.

The rapid change thermistor of the present invention is composed of a laminate of a plurality of semiconductor ceramic plates having sudden change thermistor characteristics, and has an internal electrode layer at the electrical connection portion between the plurality of semiconductor ceramic plates, and an insulating layer at the electrically insulating portion. The present invention is characterized in that resin layers are respectively formed, and external electrodes that commonly connect the internal electrode layers are formed on the end faces of the laminate.

[0009] Furthermore, in the method of manufacturing a sudden change thermistor of the present invention, a plurality of semiconductor ceramic plates having sudden change thermistor characteristics are laminated with internal electrode layers interposed therebetween, a gap layer is formed outside the area where the internal electrode layer is formed, and the gap is The method is characterized in that, after injecting an insulating resin into the layer and curing it, external electrodes that commonly connect the internal electrodes are formed on the end faces of the laminate.

0010

[Operation] The sudden change thermistor of the present invention is composed of a laminate of a plurality of semiconductor ceramic plates having sudden change thermistor characteristics, and includes an internal electrode layer at the electrical connection part between the plurality of semiconductor ceramic plates, and an insulating resin at the electrically insulating part. The layers are formed respectively, and external electrodes that commonly connect the internal electrode layers are formed on the end faces of the laminate. With this structure, a plurality of semiconductor ceramic plates having abruptly changing thermistor characteristics are laminated and integrated via an internal electrode layer and a resin layer, and are electrically connected via an internal electrode and an external electrode. By stacking a plurality of semiconductor ceramic plates having abruptly changing thermistor characteristics in this way, the overall capacitance increases and the allowable current value increases. Further, a desired resistance value can be obtained over a wide range depending on the thickness of the semiconductor ceramic plate, the number of layers thereof, etc.

Further, in the method for manufacturing a sudden change thermistor of the present invention, a plurality of semiconductor ceramic plates having sudden change thermistor characteristics are laminated with internal electrode layers interposed therebetween, and a void layer is formed outside the internal electrode formation area. Insulating resin is injected into the void layer. Then, external electrodes that commonly connect the internal electrodes are formed on the end faces of the laminate. As a result, a sudden change thermistor is obtained in which an internal electrode layer and an insulating resin layer are interposed between a plurality of semiconductor ceramic plates each having sudden change thermistor characteristics.

[0012] By previously forming a material such as carbon paste that disappears by baking together with a conductive paste outside the internal electrode forming area, a void layer can be formed outside the internal electrode forming area during lamination baking of semiconductor ceramic plates. can do. Further, an insulating resin can be injected into the void layer by vacuum degassing and pressure impregnation.

[0013]

EXAMPLES A sudden change thermistor and a method for manufacturing the same, which are examples of the present invention, will be explained in the order of manufacturing steps.

First, V2 O5, P2 O5, Ba
Weigh the desired amount of O and mix evenly. This mixed powder is heated and melted into a glassy state, and then heat-treated in a reducing atmosphere and pulverized to create a raw material powder. Add vinyl acetate binder, dispersant and plasticizer to this raw powder,
Create a green sheet using the doctor blade method.

[0015] The above green sheet is 50.0×20.0
After cutting the sheets into mm size, they are stacked and thermocompressed so that the sheet thickness is 0.3 mm. Then, the stacked pressure-bonded sheets were cut into a size of 7.0 x 6.3 mm.

After the cut pressure-bonded sheet is fired at 1000° C. for 5 minutes, it is taken out of the furnace and rapidly cooled. As a result, a semiconductor ceramic plate having a rapidly changing thermistor characteristic composed of VO2 and oxides of P and Ba is obtained.

Next, a conductive paste for forming an electrode layer and a carbon paste for forming a gap layer are respectively printed on the semiconductor ceramic plate. FIG. 1 is a perspective view showing a state before lamination of semiconductor ceramic plates each printed with a conductive paste and a carbon paste. In FIG. 1, 1a to 1e are semiconductor ceramic plates having abruptly changing thermistor characteristics, respectively;
2a to 2d are conductive pastes, and 3a to 3d are carbon pastes. Here, as the conductive paste, a paste obtained by kneading Ag, an ohmic component, a varnish, a frit, and a solvent is used. Further, as the carbon paste, a paste obtained by kneading carbon powder, varnish, and a solvent is used.

The semiconductor ceramic plates printed with the conductive paste and carbon paste are stacked as shown in FIG. 2. Thereafter, baking is performed to form Ag electrode layers 2a to 2d, respectively. On the other hand, the carbon pastes 3a to 3d are burnt out by baking to form a void layer as shown in FIG.

Next, the laminate is immersed in a polystyrene-based or epoxy-based resin solution, vacuum degassed, and impregnated under pressure. Thereafter, the resin-impregnated laminate is heated or air-dried to harden the resin. Thereafter, excess resin is removed to form resin layers 4a to 4d as shown in FIG.

Thereafter, as shown in FIGS. 5 and 6, external electrodes 5, 5 are formed at both ends of the laminate, and internal electrodes 2a are formed.
Make an electrical connection with ~2d.

Note that in FIGS. 1 to 5, the number of layers of the semiconductor ceramic plate is shown to be small for the sake of explanation, but assuming that 50 layers of the semiconductor ceramic plate have abruptly changing thermistor characteristics, the size is 5.8.
When a sudden change thermistor of 5.0 x 15.0 mm was prepared and its characteristics were measured, the resistance value was 0.1 kΩ and the allowable current value was 1 A.

[0022]

[Effects of the Invention] According to the present invention, since each semiconductor ceramic plate in the laminate forming the sudden change thermistor is in the form of a small thin plate, rapid cooling treatment can be easily performed, and good sudden change thermistor characteristics can be obtained. It will be done. By laminating a large number of semiconductor ceramic plates having this sudden change thermistor characteristic, the overall capacitance is increased and a sudden change thermistor with a high allowable current value can be obtained. Moreover, the resistance value can be set over a wide range by changing the dimensions and number of laminated layers of each semiconductor ceramic plate without changing the composition of the semiconductor ceramic plate. Therefore, it can be applied to, for example, an inrush current suppressing element.

[0023]

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a state in the middle of manufacturing a sudden change thermistor.

FIG. 2 is a cross-sectional view of the laminate before baking.

FIG. 3 is a cross-sectional view of the laminate after baking.

FIG. 4 is a cross-sectional view of the laminate after resin injection.

FIG. 5 is a cross-sectional view after forming external electrodes.

FIG. 6 is a perspective view of a completed sudden change thermistor.

[Explanation of symbols]

1a to 1e - Semiconductor ceramic plates 2a to 2d - Conductive paste and internal electrodes 3 after baking
a to 3d - Carbon paste 4a to 4d - Insulating resin layer 5 - External electrode

Claims (2)

[Claims] Claim 1: Consisting of a laminate of a plurality of semiconductor ceramic plates having abruptly changing thermistor characteristics, an internal electrode layer is formed at the electrical connection part between the plurality of semiconductor ceramic plates, and an insulating resin layer is formed at the electrically insulating part. A sudden change thermistor characterized in that an external electrode is formed on an end face of the laminate to commonly connect the internal electrode layers. 2. A plurality of semiconductor ceramic plates having abruptly changing thermistor characteristics are laminated via internal electrode layers, a void layer is formed outside the internal electrode layer formation area, an insulating resin is injected into this void layer, and then hardened. and then forming an external electrode that commonly connects the internal electrodes on the end face of the laminate.