JPS6214923B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wound ceramic varistor, which is particularly small in size, has a low varistor voltage (varistor voltage is defined as the voltage between the electrodes when 1 mA is applied to the element, V _{1 mA} ), and has high surge resistance. The present invention aims to provide a large wound ceramic varistor.

In recent years, with the shift to semiconductors and ICs in various electronic devices, circuit voltages have been decreasing. On the other hand, when switching a circuit, such as in the electrical circuits of automobiles, many switching surges occur due to the inductive load contained in the circuit, which causes the fatal problem of destroying semiconductor elements in electronic devices. ing. In order to absorb such surges, ceramic varistors, which are mainly composed of zinc oxide and whose sintered body itself is non-ohmic, have recently come into widespread use due to their versatility. but,
Ceramic varistors used in low voltage circuits do not have sufficient performance in terms of characteristics, ie, varistor voltage and surge resistance. For conventional low voltage ceramic varistors, attempts have been made to make the ceramic varistor thin in order to lower the varistor voltage, and to lower the voltage from the material composition of the ceramic varistor. The strength and productivity are low, and the latter leads to a significant deterioration of other properties, so it has not been fully put into practical use.

In view of the problems of conventional ceramic varistors as described above, the present invention realizes a wound ceramic varistor that is small, has a low varistor voltage, and has a high surge resistance.

The wound ceramic varistor of the present invention has a cylindrical body or a disc body in which a ceramic having varistor characteristics and an internal electrode are spirally filled to the inside, and an internal electrode is provided on one end surface of the cylindrical body or disc body. One of the electrodes is exposed on the other end face, and the other internal electrode is exposed on the other end face, and an electrode is formed on each end face. With this structure, the thickness of the ceramic with varistor properties can be made thinner without considering mechanical strength, and the electrode area can be increased, achieving the above objectives. be able to. Further, since the shape is cylindrical or disk-shaped, it is easy to form electrodes of normal axial leads or radial leads, and also to directly fix it to a printed circuit board as a chip part. Another feature is that the capacitance can be increased compared to conventional disc-shaped ceramic varistors of the same size.

Next, an embodiment of a wound ceramic varistor according to the present invention will be described with reference to the drawings.
FIG. 1 shows a green sheet containing a predetermined zinc oxide varistor powder and having a required thickness cut into a predetermined length. As shown in FIG. 2, a green sheet 1 is formed by printing internal electrodes 3 using a Pt-based conductive paste on a green sheet 1, leaving a predetermined insulation margin, and a green sheet 2 having internal electrodes 4 in the same manner.
form. The above green sheets 1 and 2 are stacked so that the insulation margins are on opposite end faces and one of the green sheets 1 and 2 is positioned between the internal electrodes 3 and 4 as shown in Figure 3. The molded product A shown in FIG. 4 is obtained by crimping and winding the product. Next, the molded product A is fired under predetermined conditions to obtain a wound ceramic varistor B. FIG. 5a shows the structure of this wound ceramic varistor, and 5 is a ceramic having varistor characteristics;
6 and 7 are spiral internal electrodes exposed on each end face. Figure 5b shows its cross-sectional structure.
Ceramic 5 with varistor properties even inside
and internal electrodes 6 and 7 are filled. FIG. 6 shows a cross section of a wound ceramic varistor B with external electrodes 8 and 9 made of glazed thick film conductors formed on both end faces.

As is clear from the above embodiments, the present invention forms a cylinder or a disc in which ceramic having varistor characteristics and internal electrodes are spirally filled to the inside, and both end surfaces of the cylinder or disc are formed. It has a structure in which internal electrodes are exposed at the top. According to this method, it is possible to obtain a wound ceramic varistor that is small, has a low varistor voltage, and has a high surge resistance, so it can be used for surge absorption, and because it has a large capacitance, it can be used as a noise filter for multifunctional devices. This will make a major contribution.
In addition, the quality and productivity are good, and high-density mounting on printed circuit boards as chip components has been realized.
This not only greatly contributes to the miniaturization of devices, but also improves the safety and reliability of circuits.

[Brief explanation of the drawing]

1 to 4 are diagrams showing the basic manufacturing process of an embodiment of the wound ceramic varistor according to the present invention, and FIG. 5a is a perspective view showing the structure of the obtained wound ceramic varistor. FIG. 6B is a cross-sectional view thereof, and FIG. 6 is a cross-sectional view of an embodiment in which external electrodes are formed. 1, 2... Ceramic green sheet, 3, 4
...Internal electrode, 5... Ceramic having varistor characteristics, 6, 7... Internal electrode, 8, 9... External electrode.

Claims (1)

[Scope of Claims] 1. A ceramic having varistor characteristics and a pair of opposing internal electrodes form a circular cylinder or a disc that is filled to the inside in a spiral shape, and one end of the one internal electrode is connected to the cylinder or the internal electrode. One end of the other internal electrode is exposed on one end surface of the disc body, and one end of the other internal electrode is exposed on the other end face of the cylindrical body or the disc body, and external electrodes connected to the internal electrodes are formed on the end faces, respectively. A rolled ceramic varistor that is characterized by 2. The wound ceramic varistor according to claim 1, wherein the ceramic having varistor characteristics is a zinc oxide varistor. 3. The wound ceramic varistor according to claim 1, wherein the internal electrode is made of a conductive material that can be fired at the same time as the ceramic having varistor properties. 4. The wound ceramic varistor according to claim 1, wherein the external electrode is connected to the internal electrode by a glazed thick film conductor.