JPS6115575B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a cylindrical ceramic capacitor, and more particularly to a method for manufacturing a ceramic capacitor that allows mass production of capacitor elements using plating.

If the electrodes of a ceramic capacitor are formed by the known silver baking method, electrodes with excellent electrical characteristics and solderability can be obtained, but on the other hand, it is difficult to mass produce and silver is expensive. It is inevitable that the cost of the completed ceramic capacitor will be high. In order to solve this drawback, a method has been proposed in which capacitor electrodes are formed by electroless plating. However, in either method, for example, the length is 5.5 mm,
After forming the microporcelain cylinder with an outer diameter of 1.8 mm and an inner diameter of 1 mm, the capacitor electrode had to be formed. For this reason, it has been impossible to significantly improve mass productivity. In order to solve this kind of drawback, the applicant of the present application proposed in Japanese Patent Application No. 13789/1989 (Japanese Patent Application No. 106854/1989) to form an electrode in the form of a longitudinal porcelain cylinder. If this method is adopted, mass productivity will be improved. However, since a through hole must be provided in order to lead out the electrode provided inside the cylinder to the outside, problems such as a decrease in the strength of the capacitor chip arise.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing a cylindrical ceramic capacitor that can improve mass productivity without using through holes for connection.

To achieve the above object, the present invention includes a step of forming a hollow porcelain cylinder having a length capable of forming a pair of cylindrical capacitor chips, and a step of forming a hollow porcelain cylinder having a length that allows formation of a pair of cylindrical capacitor chips, and one capacitor electrode on the outer circumferential side of the porcelain cylinder. forming a plating-resistant insulating layer in a region to be separated from the other capacitor electrode; forming an electrode metal layer on the surface of the ceramic cylinder by plating;
The porcelain cylinder on which the electrode metal layer is formed is divided into two parts, one capacitor electrode is provided on the inside of the porcelain cylinder and a part of the outside continuous to the inside, and the other is provided on the outside of the porcelain cylinder. The present invention relates to a method of manufacturing a cylindrical ceramic capacitor, which includes a step of obtaining a pair of cylindrical capacitor chips having capacitor electrodes.

According to the present invention, connecting one electrode of a pair of cylindrical capacitor chips from the inside of the cylinder to the outside is completed at the same time. Then, if it is divided into two parts, the exposed part becomes a separation area between one electrode and the other electrode, and a pair of capacitor chips can be easily completed. Therefore, work efficiency is greatly improved and capacitor costs can be reduced.

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

1 to 6 show, in order of steps, a method for manufacturing a cylindrical ceramic capacitor according to a first embodiment of the present invention.

In this example, first, a long porcelain cylinder (not shown) whose main component is strontium titanate from which a large number of cylindrical capacitor chips can be obtained is prepared. A double-length hollow porcelain cylinder 1 capable of forming a capacitor chip is assumed. Note that the shallow groove 2 formed in the part where the ceramic cylinder 1 is to be divided between the first capacitor chip part 1a on the left side and the second capacitor chip part 1b on the right side is formed before the ceramic cylinder 1 is divided into double-length ceramic cylinders 1. Form in advance. Although this groove 2 may be provided after forming the double-length porcelain cylinder 1, it is easier to form it at the stage of the unfired porcelain molding.
Further, if these grooves are provided at intervals between unit capacitor chips, they can also serve as marks when forming the double-length porcelain cylinder 1. Also, the left end 3 and right end 4 of the double-length porcelain cylinder 1 are polished so that they have some curvature. To give an example of the geometric dimensions of this double-length porcelain cylinder 1, its length is about 11 mm, its outer diameter is about 1.8 mm, and its inner diameter is about 1 mm.

Next, the double-length porcelain cylinder 1 is washed with a neutral detergent, an organic solvent, an inorganic acid (nitric acid, hydrofluoric acid), etc. to remove dirt from the body. After the above washing steps are completed, remove the sensitizer containing stannous chloride (SnCl ₂ ).
for 3 to 5 minutes at room temperature.

Next, it is washed with water, and then treated with an activator containing palladium chloride (PdCl ₂ ) at a ratio of 0.07 to 0.4 grams in an aqueous solution of 40 to 60%.
Activation treatment is performed for 3 to 5 minutes at ℃. Next, it is washed with water and then heat treated at a temperature of 80 to 600°C for 5 to 60 minutes. As a result, the porcelain cylinder 1 is dried and the palladium film is brought into close contact with the porcelain cylinder 1.

Next, as shown in FIG. 2, there is a planned separation area between the first capacitor electrode, generally called the inner electrode, and the second capacitor electrode, generally called the outer electrode, in the first and second capacitor chip parts 1a and 1b. Plating-resistant insulating layers 5 and 6 are provided in a ring shape. At the same time, a plating-resistant insulating layer 7 is provided in a ring shape in the boundary region between the first capacitor chip portion 1a and the second capacitor chip portion 1b. These plating-resistant insulating layers 5, 6, and 7 are formed by bringing rollers coated with insulating paint into contact with each other. These insulating layers 5, 6, and 7 are made of thermosetting resin such as epoxy resin or photocuring resin, which has moisture resistance, electrical insulation, and chemical resistance, and has high adhesion strength to porcelain. do.

Next, the porcelain cylinder 1 is immersed in an electroless plating solution containing sodium hypophosphite (NaH ₂ PO ₂ ) and nickel sulfate (NiSO ₄ ) to form a nickel layer 8 with a thickness of 2 μm or more as shown in FIG. Form as shown. This electroless plating is performed by a chemical change as shown in the following formula.

NaH ₂ PO ₂ +H ₂ O→NaH ₂ PO ₃ +H ₂ NaH ₂ PO ₃ +NiSO ₄ → Ni+H ₂ SO _{4 +} NaPO generate. At this time, a nickel layer 8 is formed on all the cylindrical surfaces except the plating-resistant insulating layers 5, 6, and 7. Therefore, the left end 3 and the right end 4
The nickel layer 8a on the inner circumferential surface 9 of the cylinder and the nickel layer 8b on the outer circumferential surface 10 are joined by the nickel layer at the end.

Once the nickel layer 8 shown in FIG. 3 has been formed, the porcelain cylinder 1 is plated for heat treatment.
is placed in a furnace and subjected to heat treatment. This heat treatment is performed in the air or in a neutral atmosphere (argon or carbon dioxide gas).

Next, a pair of independent capacitor chips 12, as shown in FIG. 13. The pair of capacitor chips 12 and 13 have a portion 14a of one capacitor electrode 14 on the outer peripheral surface 10, and have the other capacitor electrode 15 separated by the insulating layer 5. Further, one capacitor electrode 14 is formed on the inner circumferential surface 9 of the cylinder, and this is connected to a part 14 of the outer circumferential surface by the nickel layer 8 on the respective ends 3 and 4.
connected to a. Of course, no electrode is formed on the respective ends 16 and 17 exposed by cutting, and one capacitor electrode 14 and the other capacitor electrode 15 are separated here.

capacitor chip 12 formed as described above;
13 can be used as is by connecting one capacitor electrode 14 and the other capacitor electrode 15 provided on the outer peripheral surface 10 to printed circuit wiring, etc., but if necessary, the sixth capacitor electrode 13 can be used as is.
As shown in the figure, a pair of metal caps 18 are covered and sealed with an insulator 19. At this time, in order to easily and reliably fit the metal cap 18, for example, four elastic protrusions 20 are provided inside the cap. The capacitor element 12a formed as shown in FIG. 6 is used in conjunction with printed circuit wiring in the same manner as the capacitor chip 12 shown in FIGS. 4 and 5. That is, a pair of metal caps 18 are connected to the printed wiring using solder or the like. If necessary, a lead wire may be connected to the metal cap 18, and the lead wire may be used to connect to a printed circuit or the like.

According to the above method, a pair of capacitor chips 1
It becomes possible to simultaneously form the external leads of the inner capacitor electrodes 14 of 2 and 13, which improves productivity.Also, since the electrodes are separated at the same time by dividing, a special electrode separation process is not required. , mass productivity is improved. Incidentally, insulating layers 5 and 6 are provided to form one side of the electrode separation region, but since these are the outer circumferential surface of the cylinder 1, they can be formed relatively easily, and mass productivity is not significantly reduced. I won't let you.

Furthermore, in this embodiment, since the insulating layer 7 is also provided at the boundary between the pair of capacitor chips 1a and 1b, the withstand voltage between the inner capacitor electrode 14 and the outer capacitor electrode 15 can be improved.

Further, since the groove 2 is provided at the boundary between the pair of capacitor chip portions 1a and 1b, cutting is facilitated.

Also, since the pair of grooves 3 and 4 have a curvature,
The nickel layer 8 is reliably formed even at the ends.

In addition, after plating pretreatment with an activator,
Since the insulating layers 5, 6, 7 are provided, the insulating layers 5, 6,
Even if the cylinder 1 with the insulating layers 5, 6, and 7 is immersed in an electroless nickel plating solution, the surfaces of the insulating layers 5, 6, and 7 are not activated by the activator, and nickel remains on the surfaces of the insulating layers 5, 6, and 7. Almost no adhesion occurs, and the insulating layers 5, 6, and 7 can be used as they are for moisture proofing, solder flow prevention, and the like.

Next, FIGS. 7 and 8 showing a second embodiment of the present invention will be described. However, codes 1, 3 to 6, 8
1 to 17 are the same as those indicated by the same reference numerals in FIGS. 1 to 4, and therefore their explanations will be omitted. In this second embodiment, as shown in FIG. 7, a nickel layer 8 is formed without providing a groove or an insulating layer in the divided region, and by cutting along a chain line 11, a pair of layers shown in FIG. 8 are formed. Capacitor chip 12,1
Complete 3. This method also allows the pair of capacitor chips 12 and 13 to be made substantially simultaneously, greatly improving mass productivity.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be further modified. For example, one capacitor electrode 14 and the other capacitor electrode 15 may be separated by removing the insulating layers 5, 6, and 7 after plating. That is, the insulating layers 5, 6, and 7 may be used only as plating masks. Furthermore, after providing the insulating layers 5, 6, and 7, a plating pretreatment may be performed. Also the fourth
Only the electrically connected portions on the outer periphery of the capacitor chip shown in the figures and FIG. 5 may be exposed, and the other portions may be covered with an insulating material such as synthetic resin. It is also possible to provide the insulating layers 5, 6, 7 in advance on the cylinder before forming the double-length porcelain cylinder 1.

[Brief explanation of the drawing]

1, 2, 3, and 4 are cross-sectional views of each step in the method for manufacturing a ceramic capacitor according to the first embodiment of the present invention, and FIG. 5 is a diagram of a completed capacitor chip. The front view and FIG. 6 are cross-sectional views of a capacitor element with a metal cap. 7 and 8 are cross-sectional views showing a method of manufacturing a ceramic capacitor according to a second embodiment of the present invention. In the symbols used in the drawings, 1 is a porcelain cylinder, 5, 6, and 7 are plating-resistant insulating layers, 8 is a nickel layer, 14 is one capacitor electrode, and 15 is the other capacitor electrode.

Claims (1)

[Claims] 1. A step of forming a hollow porcelain cylinder with a length capable of forming a pair of cylindrical capacitor chips, and forming one capacitor electrode and the other capacitor electrode on the outer circumferential side of the porcelain cylinder. forming an electrode metal layer on the surface of the porcelain cylinder by plating; separating the two porcelain cylinders with the electrode metal layer formed thereon; obtaining a pair of cylindrical capacitor chips having one capacitor electrode on the inside of the porcelain cylinder and a part of the outside continuous to the inside, and the other capacitor electrode on the outside of the porcelain cylinder. A method for manufacturing a cylindrical porcelain capacitor comprising: 2. The method of manufacturing a cylindrical ceramic capacitor according to claim 1, wherein the electrode metal layer is formed by nickel plating. 3. The method for manufacturing a cylindrical ceramic capacitor according to claim 1 or 2, wherein the porcelain cylinder is divided into two parts by cutting the porcelain cylinder using a groove provided in advance.