JPS6248366B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a capacitor using thin-walled cylindrical porcelain. As shown in FIG. 1, an internal electrode 2 is provided on the inner circumferential surface of the hollow cylindrical porcelain 1 and a part of the outer circumferential surface continuous thereto, and an external electrode is provided on the outer circumferential surface of the porcelain 1 in a state separated from the internal electrode 2. A ceramic capacitor having a structure in which lead wires 4 and 5 are wound around the inner electrode 2 and the outer electrode 3 is already known. By the way, in order to meet the demand for miniaturization of electronic components, the wall thickness of the porcelain 1 was reduced to about 0.15 mm or less, and for example,
Publication No. 15345, Special Publication No. 1973-3086, Special Publication No. 1973
- Lead wires 4 and 5 with a diameter of approximately 0.2 mm are wound in a headband shape using an automatic machine as shown in Publication No. 10465, etc., to form a ladder-like structure in which multiple elements are connected by the lead wires. Then, solder the lead wire 4,
If 5 is fixed, fine cracks will occur in the porcelain 1 in its axial direction. More specifically, when observed with a 20x microscope, it is found that due to variations in the strength of porcelain 1,
It can be seen that cracks occur at a rate of 54 out of 10,000, or 0.54%. Therefore, if a ceramic capacitor as shown in FIG. 1 is used as the capacitor C of a filter circuit consisting of a coil L and a capacitor C as shown in FIG. This causes a problem in that the insulation resistance between the electrodes decreases and capacitance is lost. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a cylindrical ceramic capacitor that can prevent or reduce the occurrence of cracks. To achieve the above object, the present invention includes a step of forming a thin-walled hollow cylindrical porcelain, and forming an internal electrode on an inner circumferential surface of the cylindrical porcelain and a part of an outer circumferential surface continuous with the inner circumferential surface. and a step of forming an external electrode on the outer circumferential surface of the cylindrical porcelain, and forming a surface of the inner electrode, the outer electrode, and the porcelain so that a ring-shaped exposed portion remains on the outer circumferential surface portion of the inner electrode and the outer electrode. forming an insulating resin coating layer on the
Wrapping each lead wire once or multiple times in a headband shape around the ring-shaped exposed portions of the internal electrode and the external electrode of the cylindrical capacitor element on which the insulating resin coating layer is formed; The present invention relates to a method of manufacturing a cylindrical ceramic capacitor, which includes a step of soldering to an internal electrode and the external electrode, respectively. According to the present invention, the insulating resin coating layer is provided on the internal electrode and the external electrode so that the ring-shaped exposed portion is formed, and then the lead wire is wound around the ring-shaped exposed portion, so that the porcelain is reinforced with the insulating resin coating layer. This prevents or reduces the occurrence of cracks in the porcelain during the lead wire winding process, soldering process, etc. Therefore, a decrease in insulation resistance due to migration hardly occurs, making it possible to provide a highly reliable capacitor. Embodiments of the present invention will be described below with reference to FIGS. 3 to 7. First, a hollow cylindrical ceramic 1 having a length of 5.4 mm, an outer diameter of 1.8 mm, and a wall thickness of 0.12 mm is formed using a titanium-based dielectric ceramic composition as shown in FIG. Then selectively apply silver paste, dry and
By baking at about 700° C. for about 1 hour, internal electrodes 2 and external electrodes 3 are formed in the same manner as in FIG. Next, as shown in FIG. 4, a silicon-modified epoxy resin is selectively applied to the internal electrode 2 and external electrode 3 so that ring-shaped exposed parts 2a and 3a are formed near the ends of the porcelain 1, and dried. The insulating resin coating layer 6 is formed on the electrodes 2 and 3 and the porcelain 1 by curing at about 200° C. for 2 hours. Next, as shown in FIG. 5, the lead wires 4 and 5 are wrapped around the ring-shaped exposed parts 2a and 3a in a headband shape using an automatic machine, and then soldered with solders 7 and 8 using an automatic soldering iron. The lead wires 4 and 5 are fixed to the ring-shaped exposed parts 2a and 3a. Incidentally, the lead wires 4 and 5 are wound as shown in FIG. 6 using an automatic lead wire winding device as described in Japanese Patent Publication No. 39-15345 mentioned above. That is, while intermittently transferring the plurality of capacitor elements 9, the lead wires 4, 5 are connected to the ring-shaped exposed parts 2a, 3a.
is wound twice each to hold a plurality of capacitor elements 9 in a ladder shape. Then, an automatic soldering iron is applied to the winding start and winding end of the ring-shaped exposed portions 2a, 3a of the lead wires 4, 5, and each electrode 2,
Attach lead wires 4 and 5 to 3. Next, in order to improve moisture resistance, the elements 9 are transferred while maintaining the state shown in FIG. 6, and each element 9 is immersed in molten wax, pulled up, dried, and wound onto a reel. After that, rewind from the reel and connect lead wires 4 and 5.
By cutting the capacitor, an independent capacitor as shown in FIG. 7 is obtained. Note that the lead wires 4 and 5 may not be cut at the manufacturing stage, but may be cut when the capacitor is assembled into the circuit board. In this way, the element can be easily transferred during automatic assembly. In order to investigate the effect of the above manufacturing method, the insulating resin coating layer 6 and electrodes 2 and 3 were dissolved and removed from the element shown in FIG. 7 using a diluted solution of nitric acid, and the state of the bare porcelain 1 was magnified.
When examined under a 20x microscope, 4 out of 10,000 pieces (0.04%) had tiny cracks. With the conventional method, cracks occurred in 54 out of 10,000 pieces, so
According to the method of this embodiment, cracks are significantly reduced. In addition, in order to perform a humidity load test, 10,000 capacitor elements shown in Figure 7 and 10,000 conventional capacitor elements were placed in an atmosphere with a temperature of 60°C and a humidity of 90 to 95%, and a direct current was applied between electrodes 2 and 3. The insulation resistance between electrodes 2 and 3 was measured after 100 hours, 500 hours, and 1000 hours had elapsed with a voltage of 12 V applied, and the quality was determined, and the results shown in the following table were obtained. The initial insulation resistance of both the conventional capacitor and the capacitor of the present invention was 10 ⁴ MΩ or more. Also, 10 ³ MΩ
The following were considered defective.

[Table] As is clear from the results, according to the method of the present invention, no defects occur even after a 1000-hour humidity load test. This means that the cracks that occur at a rate of about 0.04% in one embodiment of the present invention are small and have little effect on insulation deterioration due to migration, and that the insulation resistance of 10 ³ MΩ or more is maintained. It means something like forgiving something. Therefore, it is possible to obtain a reliability of 0.01% of the user's request. In contrast, with conventional capacitors, about half of the capacitors that crack become defective after 100 hours, and about 80% become defective after 1000 hours. Therefore, cracks that occur in the conventional method are cracks that cause migration that affects reliability.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing a conventional cylindrical ceramic capacitor, Fig. 2 is a circuit diagram showing a filter, and Figs.
FIG. 7 shows a cylindrical ceramic capacitor according to an embodiment of the present invention, FIG. 3 is a sectional view showing the state after electrode formation, FIG. 4 is a sectional view showing the state after forming an insulating coating layer, and FIG. Figure 5 is a cross-sectional view showing the lead wires wrapped and soldered, Figure 6 is a perspective view of the lead wires wrapped in a ladder shape, and Figure 7 is a perspective view showing the elements separated into individual elements. be. In the symbols used in the drawings, 1 is porcelain, 2 is an internal electrode, 3 is an external electrode, 2a and 3a are ring-shaped exposed parts, 4 and 5 are lead wires, 6 is an insulating resin coating layer, and 7 , 8 is solder.

Claims (1)

[Claims] 1. A step of forming a thin-walled hollow cylindrical porcelain;
forming an internal electrode on the inner circumferential surface of the cylindrical porcelain and a part of the outer circumferential surface continuous with the inner circumferential surface, and forming an external electrode on the outer circumferential surface of the cylindrical porcelain; forming an insulating resin coating layer on the surfaces of the internal electrode, the external electrode, and the porcelain so that a ring-shaped exposed portion remains on the external electrode; Wrapping the respective lead wires in a headband shape once or multiple times around the ring-shaped exposed portions of the internal electrodes and the external electrodes; and Soldering the respective lead wires to the internal electrodes and the external electrodes, respectively. , A method for manufacturing a cylindrical ceramic capacitor.