JPS6130725B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic capacitor and a method for manufacturing the same, and more particularly to a magnetic capacitor having a characteristic electrode structure and a method for manufacturing the same.

Silver-coated baked electrodes and nickel-plated electrodes are known as electrodes for ceramic capacitors. The former silver-coated baked electrode is made of electrode materials such as silver, silver oxide, silver-palladium, or silver-platinum, glass frit,
It is formed by applying a conductive paint made of synthetic resin and solvent onto dielectric porcelain and baking it.The latter nickel-plated electrode uses a plating resist to selectively form a nickel layer using an electroless plating method. Alternatively, it can be formed by electroless plating the entire surface and then separating the electrodes by polishing.

By the way, when using a ceramic capacitor, the capacitor electrode is coupled to the wiring conductor of the circuit board, or a terminal member is soldered to the capacitor electrode, and the terminal member is used to couple the capacitor to the wiring conductor. However, when soldering a ceramic capacitor to a wiring conductor on a circuit board, or when soldering a terminal member to a capacitor electrode, if the solder comes into contact with the silver-coated baked electrode, the solder may cause the silver to be corroded by the solder. A phenomenon occurs in which the silver electrode is absorbed, and the capacitor characteristics deteriorate. For this reason, a silver coated baked layer is formed to a thickness of 10 to 20 μm, or palladium or platinum is mixed to improve solder resistance. However, in order to obtain a film thickness of 10 to 20 μm, it is necessary to repeat the application and drying of the conductive paint two to three times, which complicates the manufacturing process and increases the required time. Furthermore, when increasing the amount of palladium (Pd) and platinum (Pe) to reduce the silver corrosion phenomenon caused by solder, not only did the cost of the electrode material increase, but also the wettability of the solder decreased.

On the other hand, although the latter nickel-plated electrode is an inexpensive electrode material, it has the disadvantage of poor electrical properties compared to a silver-coated baked electrode. In addition, it is impossible to apply electrode material to selected areas as in the case of silver-coated baked electrodes, so it is necessary to apply a resist to the electrode separation area and plate it, or to separate the electrodes by polishing after plating the entire surface. It becomes necessary,
The process is not necessarily simplified.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a ceramic capacitor and a method for manufacturing the same, which can prevent the silver cracking phenomenon of electrodes and reduce costs.

To achieve the above object, the present invention comprises a porcelain dielectric and a capacitor electrode formed on the porcelain dielectric, and the capacitor electrode is formed on the porcelain dielectric and contains silver as a main component. A porcelain capacitor comprising a silver electrode layer (for example, the silver coated and baked layer 13 of the embodiment), a nickel layer formed on the silver electrode layer, and a solder layer formed on the nickel layer. It is related.

According to the present invention, since the capacitor electrode has a three-layer structure of the silver electrode layer, the nickel layer, and the solder layer, the nickel layer can prevent the silver electrode layer from curling up. become. Furthermore, since the phenomenon of silver curling in the silver electrode layer is prevented, it is no longer necessary to make this layer thick, and sufficient capacitor characteristics can be obtained by forming an electrode layer of about 5 to 10 μm in thickness with one coating and baking. becomes possible. In addition, it is not necessary to mix expensive platinum or palladium into the silver electrode layer, or even if it is mixed, only a small amount is required, making it possible to reduce costs. Furthermore, since the solder layer is provided on the nickel layer, the solder wettability is good.

The invention related to the method for manufacturing a ceramic capacitor described above includes applying a conductive paint containing silver or silver oxide as a main component to a selected area of a ceramic dielectric, and baking the conductive paint onto the ceramic dielectric to form a silver electrode layer. forming a nickel layer on the silver electrode layer by electroplating; and forming a solder layer on the nickel layer by electroplating.

According to the above method, a silver electrode layer is selectively formed, and a nickel layer and a solder layer are sequentially formed thereon by electroplating. Therefore, the nickel layer and the solder layer can be formed in a specified manner without taking any special measures. It becomes possible to form it into a pattern. That is, with electroplating, the plating adheres only to the silver electrode layer and does not adhere to the porcelain, so that the plating layer can be selectively formed without relying on means such as resist or polishing. Furthermore, plating allows the thickness to be made relatively uniform, reducing variations in electrical characteristics. Further, as in the preferred embodiment, it is possible to employ the barrel plating method, so that it is possible to process a large number of elements of several mm.

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

1 to 4 show a manufacturing method and structure of a cylindrical chip capacitor according to an embodiment of the present invention. In manufacturing this chip capacitor, first, as shown in Fig. 1, a cylindrical porcelain 1
A pin 3 coated with a conductive paint made of silver, glass frit, resin, and solvent is inserted into the hollow part 2, and a roller 5 coated with a conductive paint is inserted onto the outer peripheral surface of the cylindrical porcelain 1. to transfer. The pin 3 is supported by a support plate 6 and inserted so as not to penetrate the hollow part 2, and the roller 5 is provided with a separation groove 7 to separate the first roller part 8 and the second roller part 9. Therefore, the conductive paint 10 adheres only to the selected area. In this case, when the roller 5 is rotated by the motor, the cylindrical porcelain 1 in contact with it rotates around the pin 3, and the cylindrical porcelain 1
The conductive paint 10 adheres relatively uniformly to predetermined areas of the inner circumferential surface 11 and outer circumferential surface 4 of. Furthermore, when the pin 3 coated with conductive paint is inserted into the hollow portion 2, a portion of the conductive paint is attached to one end 12 of the cylindrical porcelain 1, and a conductive paint layer is also formed there. Of course, the first roller part 8 may be a stepped roller part, and the stepped part of the roller may be brought into contact with one end 12, and the conductive paint may be applied thereto. However, in this embodiment, the diameter of the cylindrical porcelain 1 is about 1.8 mm, and the wall thickness 12 is about 0.4 mm, so the conductive paint applied by the pins 3 is sufficient.

After the application of the conductive paint according to the method shown in FIG. 1 is completed, a baking treatment is performed at 500 to 800 DEG C. to form a silver coating baking layer 13 for the inner and outer electrodes as shown in FIG. This silver coated baked layer 13 has 5
Since a thickness of ~10 μm is sufficient, it can be formed in one application.

Next, a large number of cylindrical porcelains 1 on which silver coated and baked layers 13 have been formed are placed in a barrel having electrodes, immersed in a nickel electroplating solution, and electroplated while being rotated or vibrated. Start. As a result, the silver coated and baked layer 13 comes into direct contact with the plating electrode in the barrel, or indirectly contacts the silver coated and baked layer 13 on another capacitor element through the silver coated and baked layer 13 as shown in FIG. A nickel layer 14 is formed. This nickel layer 14 has a thickness of 1 to 10μ.
m, more preferably 4 to 5 μm thick.

Next, a solder layer 15 is formed as shown in FIG. 2 using a barrel plating method similar to nickel plating. This solder layer 15 has a thickness of 1 to 4μ, more preferably 2 to 4μ.
Form to a thickness of 3μ. As a result, as shown in FIG. 2, the inner electrode 16 and the outer electrode 17, which are composed of the silver coated baked layer 13, the nickel layer 14, and the solder layer 15, are separated by the first and second separation regions 18 and 19. formed into a state.

Next, to use it as a chip capacitor,
Using rollers, the first and second
The insulating coating layers 20 and 21 are divided into a region including the first separation region 18 and the center of the outer periphery, and a second region including the other end 22.
and the separation region 19 to form a finished product.

The chip capacitor 23 shown in FIG. 3 is temporarily bonded to a circuit board 24 with an adhesive 25, as shown in FIG.
7 by solder 28 electrically and mechanically.

The structure and manufacturing method described above have the following advantages.

(a) Since the nickel layer 14 is provided on the silver coated baked layer 13, the silver coated baked layer 13 is not held in by the solder even when soldered as shown in FIG. 4, resulting in deterioration of electrical characteristics. do not have.

(b) Since there are no solder holes in the silver coated baking layer 13,
Silver coated baking layer 13 can be coated with conductive paint once for 5~
It is only necessary to form the layer to a thickness of about 10 μm. Therefore, the coating and baking steps are simplified.

(c) Since it is not necessary to expect solder resistance from the silver coated and baked layer 13, it is possible to form electrodes without using expensive materials such as platinum or palladium, thereby reducing costs.

(d) Even though the nickel layer 14 is provided to obtain solder resistance, since the solder layer 15 is further provided on top of the nickel layer 14, the solder wettability is improved.

(e) Since the silver coated and baked layer 13 is selectively formed and the nickel layer 14 and solder layer 15 are formed by electroplating using this silver coated and baked layer 13 as the plating area, the plating area cannot be limited by resist or polished. This eliminates the need for electrode separation, etc., and simplifies the manufacturing process.

(f) Since the parallel plating method is adopted, plating layers can be formed on a large number of devices at the same time.

(g) Since the nickel layer 14 and the solder layer 15 are formed by electroplating, the thickness can be made uniform and variations in electrical characteristics can be reduced.

(h) Conventionally, silver coated baked electrodes were coated multiple times for each unit element in order to form thick electrodes.
Although it took a long time, in the present embodiment, it is only necessary to parallel plate a large number of elements at the same time after one coating and baking process, so the time can be significantly shortened.

(i) Since the conductive paint is applied by the method shown in FIG. 1, it can be applied to the selected area relatively accurately and easily.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned embodiment.
It is also deformable. For example, as shown in FIG. 5, the present invention can also be applied to a type of ceramic capacitor in which metal caps 29 and 30 are soldered to inner and outer electrodes 16 and 17. Moreover, it is applicable not only to cylindrical ceramic capacitors but also to cylindrical through-type ceramic capacitors, plate-like through-hole ceramic capacitors, and other types of capacitor electrodes.

[Brief explanation of the drawing]

Figures 1 to 4 show one embodiment of the present invention, in which Figure 1 is a cross-sectional view showing a state in which conductive paint is applied, Figure 2 is a cross-sectional view of cylindrical porcelain on which electrodes are formed, FIG. 3 is a sectional view of the completed chip capacitor, FIG. 4 is a partially longitudinal front view showing the state in which the chip capacitor is mounted on a circuit board, and FIG. 5 is a front view showing a modified example of the capacitor. In the symbols used in the drawings, 1 is cylindrical porcelain, 10 is conductive paint, 13 is silver coating baking layer,
14 is a nickel layer, 15 is a solder layer, 16 is an inner electrode, and 17 is an outer electrode.

Claims (1)

[Claims] 1. A silver electrode layer consisting of a porcelain dielectric and a capacitor electrode formed on the porcelain dielectric, the capacitor electrode being formed on the porcelain dielectric and containing silver as a main component. A ceramic capacitor comprising: a nickel layer formed on the silver electrode layer; and a solder layer formed on the nickel layer. 2. The silver electrode layer is a silver layer with a thickness of 5 to 10 μm, the nickel layer is a nickel plating layer with a thickness of 1 to 10 μm, and the solder layer is a solder plating layer with a thickness of 1 to 4 μm. A porcelain capacitor according to scope 1. 3. Applying a conductive paint containing silver or silver oxide as a main component to at least two selected areas of the porcelain dielectric, and baking the conductive paint onto the porcelain dielectric to form a silver electrode layer; A method of manufacturing a ceramic capacitor comprising: forming a nickel layer on the layer by electroplating; and forming a solder layer on the nickel layer by electroplating. 4. The method of manufacturing a ceramic capacitor according to claim 3, wherein forming the nickel layer is nickel plating using a barrel plating method, and forming the solder layer is performing solder plating using a barrel plating method. 5. The porcelain dielectric material is cylindrical porcelain, and the application of the conductive paint is performed by inserting a pin to which the conductive paint is attached into the hollow part of the cylindrical porcelain, applying the conductive paint to the surface of the hollow part, and applying the conductive paint to the cylindrical shape. 5. The method of manufacturing a porcelain capacitor according to claim 3 or 4, wherein the conductive paint is selectively applied by rolling a roller coated with the conductive paint onto the outer peripheral surface of the ceramic.