JPS6129527B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a wound ceramic chip capacitor having a very large area electrode in a compact, integral dielectric.

Recently, as electronic devices have become more complex, there has been a strong trend toward smaller and higher density electronic circuits, and capacitors are required to be extremely small and large in capacity due to the limits of allowable volume. In order to obtain large capacitance, efforts have been made to develop materials with high dielectric constants and techniques to safely create thin films. In particular, much research has been conducted into the use of barium titanate, titanium oxide, and similar ceramic materials as dielectric materials for capacitors, as they have a high dielectric constant that cannot be obtained with other materials and are highly heat resistant. It's here. Furthermore, as a method for forming dielectric layers, a technique has been developed in which thin ceramic dielectric layers sandwiched between electrodes are laminated in multiple layers. A capacitor and a method for manufacturing the same that take advantage of the excellent characteristics of ceramics are disclosed in US Pat. No. 3,004,197.

This method creates a small, high-capacity cylindrical capacitor that has an electrode area several times larger than the capacitor's external shape, and has a continuous dielectric and an electrode that are in close contact with each other, making it mechanically strong and easy to handle, and a method for manufacturing the same. This is what we provide. Specifically, a slip made by mixing finely ground ceramic dielectric powder with about 10 to 20% wt of plastic along with a plasticizer is coated onto a support substrate and dried to form a shape-retaining and flexible unfired ceramic sheet. After cutting to appropriate dimensions, a noble metal paste such as platinum or palladium is applied, and this is wound around a thin unfired ceramic rod to form a spiral and heated to an appropriate temperature in the range of 1148℃ to 1426℃. The dielectric material and the electrode are baked at a high temperature to expel the organic matter in the sheet and the growth of ceramic microcrystals causes the dielectric material and the electrode to be firmly baked together.Next, silver electrodes are baked on both end surfaces to form a terminal, and the terminal is further bonded to the dielectric material and the electrode. The lead wires are soldered to form a cylindrical capacitor.

However, ceramic chip capacitors obtained by winding, laminating, and firing such unfired ceramic sheets may, depending on the state of the winding and lamination,
Even after firing, the dielectric material may not be uniformly integrated, and delamination may occur between the layers. This layer delamination phenomenon is
As a result, this occurs because the ceramic particles in the unfired ceramic sheet were not in sufficient contact with each other between the layers before firing, but in order to bring all the ceramic particles into contact between the layers, something must be done. It is necessary to apply pressure between the sheets in a method. In wound ceramic chip capacitors, it is not easy to apply pressure between layers, especially in unfired ceramic sheets with low tensile strength. After winding the ceramic sheet, the core of the unfired ceramic rod is rotated several times to tighten the winding and press the layers together. However, due to the mechanical strength limitations of the unfired ceramic sheet and the unfired ceramic rod, it is not easy to perform sufficient winding with this method, and there is a strong risk that the above-mentioned layer delamination will occur. As a result, there are problems such as a decrease in the moisture absorption characteristics and mechanical strength of the capacitor, and furthermore, damage to the dielectric layer during high temperature processing such as soldering.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate these drawbacks and provide a highly reliable method for manufacturing a small, large-capacity wound ceramic chip capacitor.

The structure of the present invention is that electrodes are printed on an unfired ceramic dielectric sheet leaving an insulating margin, and at least two unfired ceramic sheets are stacked on top of each other so that the insulating margins are located on opposite sides of each other. It is characterized by the fact that it is rolled up, then rolled and tightened for post-firing. Ceramic chip capacitors obtained by this method have internal electrodes facing each other with a ceramic dielectric in a spiral shape, and are filled to the inside of the circular disk or cylinder. , has a basic structure in which one side is exposed on one end side, and the other side is exposed on the other end side.

The winding shaft here refers to something that does not burn out even if it is fired, or something that does not chemically react with unfired ceramic sheets or electrodes when fired, or something that does not burn out even if it is fired. Any material may be used as long as it does not create a gap between it and the sheet. For example, it is preferable to use a material having the same composition as the unfired ceramic sheet, or an unfired material having the same composition as that used for the green ceramic sheet. Furthermore, the same effect can be obtained by using a fired ceramic dielectric material as a winding shaft.

In addition, the winding operation refers to a pre-rolled product in which an unfired ceramic sheet is wrapped around a winding shaft.
This is a method in which a pre-rolled product is held between two flat plates, and the flat plates are relatively moved in the direction of winding the pre-rolled product while applying pressure.

According to the method of the present invention, since the rolled product of the unfired ceramic sheet is further wound around the winding shaft, a disc-shaped or cylindrical molded product can be produced in a high-density spiral shape. . and,
Since the roll is fired without removing the roll, not only does it not leave any hollow holes behind the roll, there is no need to be careful about the structure of the rolled sheet being disturbed when the roll is removed. It can be wound with strong force from the beginning. Furthermore, since a wrapping operation is added on top of this, the molded product has an extremely high density and each layer is well bonded. By firing this, a capacitor whose interior is filled with ceramic dielectric and electrodes can be obtained.

Hereinafter, embodiments of the method of the present invention will be described in detail with reference to the drawings.

Figure 1 shows a method for manufacturing a winding shaft of a ceramic composition. A composition of barium titanate dielectric powder with a dielectric constant of 16,000, a resin, and a plasticizer is extruded from a nozzle 1, and a cylindrical rod-shaped winding shaft 2 is made. obtain. Figure 2 shows the method for manufacturing unfired ceramic sheets. A slurry made of the same dielectric powder as used for the winding shaft, specified resin, plasticity, solvent, etc. is made using a pipe coder 3 to form an unfired ceramic sheet of approximately 30 μm. Ceramic sheet 4 is used. Then, leave a predetermined insulation margin on this sheet 4 as shown in FIG. 3A,
A large number of electrodes 5 are marked with Pd paste. Similarly, electrodes 5 are printed on another sheet 4 as shown in FIG. Two sheets 4, 4 on which electrodes are printed are placed facing each other so that one of them is located between the electrodes 5, 6, and the insulation margins of both sheets are placed on opposite edges to each other, as shown in FIG. A pressure bonding sheet 6 as shown is obtained. This pressure-bonded sheet 6 is wound around the winding shaft 2 as shown in FIG. 5, and then it is sandwiched between a pair of flat plates 7 and 8 as shown in FIG. Tighten by moving relatively in the tightening direction. This results in an integrated molded product. Next, when this molded product is cut into a predetermined position, that is, into a disk or cylinder, the cutting is done so that one of the internal electrodes is exposed on one end surface, and the other internal electrode is exposed on the other end surface. As a result, an unfired chip capacitor shown in FIG. 7 is obtained. Next, this is fired in air at 1350°C, and both end faces of the obtained sintered body are polished to form a ceramic body filled with electrodes 9, 10 and ceramic dielectric 11 without any gaps, as shown in FIG. A chip capacitor 12 is obtained.

Furthermore, if necessary, as shown in Figure 9,
The external electrodes 13 and 14 may be provided by applying silver paste to each end face of the ceramic chip capacitor 12 and baking it at a temperature of 850°C.

FIG. 10 shows an example of embedding a chip capacitor obtained by the method of the present invention into a printed circuit board. 1.6mm thick printed circuit board 1
4 has a through hole 1 with a diameter similar to that of the capacitor 12.
5, embed the capacitor 12 described above, and glue the conductors 16 and 17 on both sides of the circuit board 14 and the spiral internal electrodes 9 and 10 exposed on both end faces of the capacitor 12 with a conductive adhesive 18. ,1
Electrical connections are made in step 9 to complete the capacitor-embedded circuit board.

As is clear from this example, the ceramic chip capacitor obtained by the method of the present invention is easy to embed in a printed circuit board, and it can be electrically connected to a conductor using a conductive adhesive or the like without having to attach external electrodes to the capacitor in advance. Can be connected.

Furthermore, the capacitor of the present invention can be used as a general capacitor by attaching lead wires to both ends thereof.

[Brief explanation of the drawing]

The drawings are for explaining the manufacturing method of the ceramic chip capacitor according to the present invention, and FIGS. 1 to 8 are diagrams showing the manufacturing process of one embodiment thereof, and FIG. A perspective view of the chip capacitor, and Figure B is a sectional view thereof. Figure 9 is a sectional view showing another example of a chip capacitor;
The figure is a sectional view showing a state in which a chip capacitor is embedded and mounted on a printed circuit board. 2... Winding shaft, 4... Unfired ceramic dielectric sheet, 5... Electrode paste, 6... Crimping sheet, 7, 8... Flat plate used for winding operation.
9, 10... Internal electrode, 11... Ceramic dielectric, 12... Ceramic chip capacitor, 1
3, 14...external electrode.

Claims (1)

[Claims] 1. An electrode is printed on an unfired ceramic sheet of a ceramic dielectric material with an insulating margin left, and at least two unfired ceramic sheets are sequentially stacked so that the insulating margin is located on opposite end faces. A method for producing a ceramic chip capacitor, which comprises winding the combined state onto a winding shaft, and then performing a winding operation to obtain a high-density unfired ceramic sheet molded body, which is then fired. 2. The method of manufacturing a ceramic chip capacitor according to claim 1, wherein the winding shaft is made of the same composition as the unfired ceramic sheet of the ceramic dielectric. 3. The method for manufacturing a ceramic chip capacitor according to claim 1 or 2, wherein the winding shaft is an unfired product. 4. A method for manufacturing a ceramic chip capacitor according to claim 1 or 2, characterized in that a titanate dielectric or a titanium oxide dielectric is used as the ceramic dielectric. 5. While sandwiching the pre-spiral molded product between two flat plates and applying pressure, move the two flat plates parallel to each other and laterally along the outward winding direction of the pre-spiral molded product. A method for manufacturing a ceramic chip capacitor according to claim 1, characterized in that a winding operation is performed.