JP2008021895A - Capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a thin-shaped capacitor with a high withstand voltage whose utility value is very high on an industry in a simple and short process by a spraying method. <P>SOLUTION: In the capacitor, a dielectric layer is constituted by a rare earth element oxide formed by the spraying method, and a pair of electrodes are provided in face to face with each other through the dielectric layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a capacitor having a dielectric layer formed of a rare earth element oxide, which can be manufactured by a simple process, has a high breakdown voltage, is thin, and has high reliability.

  Ceramic capacitors using a titanium compound as a dielectric layer are widely used as high-withstand-voltage thin capacitors in terms of electrical characteristics and reliability.

  These capacitors have a long manufacturing process and are expensive as described below. In addition, since a high-temperature sintering process is required, it is impossible to form a capacitor directly on a relatively heat-sensitive substrate such as resin or glass.

<General capacitor manufacturing process>
Crushing raw material powder → Binder mixing → Drying → Molding → Degreasing → Sintering → Applying electrode paste → Drying → Baking.

On the other hand, Japanese Patent Laid-Open No. 2006-66854 (Patent Document 1) proposes a method of directly forming a capacitor on a resin printed board by a thermal spraying method. Although this method has a great advantage in that the number of steps is reduced and the labor of component mounting can be saved, the materials used are titanium compounds, Ta ₂ O ₅ and Al ₂ O ₃ whose valences are easily changed. The thermal spraying method involves a change of high temperature melting → injection → rapid cooling in a relatively low oxygen atmosphere, so that these materials cause oxygen defects, resulting in unstable dielectric properties and low dielectric strength films. There was a problem.

JP 2006-66854 A

  The present invention has been made in view of the above circumstances, and provides a thin and high withstand voltage capacitor which uses a rare earth element oxide as a dielectric material and is formed by a simple and short process by a thermal spraying method. With the goal.

  In order to solve the above problems, the present inventors have searched for a dielectric material that hardly changes in valence and has excellent withstand voltage characteristics. As a result, in the case of a rare earth element oxide, a capacitor is formed by a thermal spraying method. Even in this case, the present invention was completed by knowing that oxygen defects do not occur and the dielectric strength is high.

Accordingly, the present invention provides the following capacitor.
Claim 1:
A capacitor comprising a dielectric layer made of a rare earth element oxide formed by a thermal spraying method and a pair of electrodes facing each other with the derivative layer interposed therebetween.
Claim 2:
The capacitor according to claim 1, wherein one or both of the electrodes are made of a conductive material formed by a thermal spraying method.
Claim 3:
The dielectric breakdown voltage when the thickness of the dielectric layer is 0.3 mm is 3 kV or more, and the capacitance per unit area at the thickness is 0.3 μF / m ² or more. Item 3. The capacitor according to Item 1 or 2.
Claim 4:
The capacitor according to claim 1, 2 or 3, wherein the electrode has a structure formed on an insulating base material by a thermal spraying method.
Claim 5:
The capacitor according to claim 4, wherein the insulating base material is made of glass, resin, or ceramics.
Claim 6:
6. The insulator base material has a structure in which a conductor which is a part of an electric circuit is combined, and the conductor and an electrode by thermal spraying are electrically joined. The capacitor as described.

  According to the present invention, a thin and high withstand voltage capacitor can be obtained in a simple and short process by a thermal spraying method, and its utility value is extremely high in industry.

  Hereinafter, the present invention will be described in more detail. In the capacitor of the present invention, a dielectric layer is made of a rare earth element oxide formed by a thermal spraying method, and a pair of electrodes facing each other through the dielectric layer is provided. This is a capacitor having a structure.

In the present invention, Sc, Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu are suitable as the rare earth element, and it is effective to use these oxides. is there.
Rare earth element oxides are more strongly associated with oxygen than other oxides, and exist stably without generating oxygen defects even under thermal spraying conditions of high temperature melting → injection → rapid cooling. However, among rare earth elements, elements such as Ce, Pr, and Tb tend to fluctuate in valence, so that electric characteristics are likely to fluctuate. Therefore, it is preferable not to apply to this application.

  In the capacitor of the present invention, as a first step, a dielectric film is formed by melting, spraying, and depositing a rare earth element oxide on an electrode serving as a substrate by a thermal spraying method, and as a second step, a rare earth element oxidation is performed. A conductive material can be formed on the dielectric film made of a material as a counter electrode, and if necessary, the capacitor can be manufactured by covering the surface of the capacitor with an insulating material as a third step.

  Here, as a base electrode, when a single capacitor is formed, a metal plate or a metal tube is made of a conductor such as copper, brass, stainless steel, nickel, aluminum, molybdenum, tungsten, or the like. Such a conductive substrate can be used, and the conductive substrate itself can be used as one electrode. Moreover, it can form with insulators, such as glass, resin, ceramics, and can form an electrode with conductors, such as a metal, on this insulator base material. The method for producing this electrode is not particularly limited, but is preferably formed by a thermal spraying method. In addition, when producing an electrode by a thermal spraying method in this way, in order to form a sprayed film (electrode), average particle diameters, such as copper, brass, stainless steel, nickel, aluminum, molybdenum, tungsten, 5-200 micrometers, especially 20- It is preferable to use a metal powder having a thickness of 200 μm and a thickness of 10 to 300 μm, particularly 50 to 200 μm. When the average particle diameter is outside the above range, the film density is lowered, and the reliability of the capacitor may be lowered. Also, if the thickness is less than 10 μm, the exposed dielectric film or insulator base material is not completely covered, and the exposed part may occur, and the reliability of the capacitor may be reduced. When the thickness exceeds 300 μm, There may be problems in terms of cost.

  Furthermore, as a base material, an electric circuit made of a metal such as copper is formed on an insulating base material such as a resin such as a printed circuit board, and a conductor that is a part of the electric circuit is combined with the insulating base material. Can also be used. Thus, when a capacitor is directly formed on an insulating base material including an electric circuit such as a printed circuit board, first, a conductive material is formed on a necessary portion on the base material by a thermal spraying method or the like. It may be an electrode.

  The first step of the present invention is to form a dielectric film by melting, spraying, and depositing a rare earth element oxide on the electrode serving as a base material by a thermal spraying method.

The rare earth element oxide used in the present invention is in the form of a powder having an average particle size of 5 to 80 μm, preferably 10 to 40 μm. If the average particle diameter is less than 5 μm, the particles are not sufficiently accelerated, so that the relative density of the dielectric film is less than 90%, and the withstand voltage is lowered. If the thickness exceeds 80 μm, particles are formed in an incompletely melted state even by the highest temperature spraying method such as plasma spraying, so that the relative density of the dielectric film is also less than 90% and the withstand voltage is lowered. .
In addition, in this invention, an average particle diameter is the value measured with the Nikkiso MICRACRAC FRA type particle size distribution measuring apparatus.

  In this case, as the thermal spraying method and the thermal spraying conditions, a known method and known conditions can be employed, for example, a plasma spraying method can be employed. In the case where the dielectric layer is formed thereon by the thermal spraying method, the rare earth oxide has a higher melting point than that of the titanium compound and the like, so that it is less than the relatively low temperature thermal spraying method such as the flame spraying method. When a high temperature spraying method such as a plasma spraying method is selected, the particles are completely melted, so that the film density is easily increased and the withstand voltage characteristics are improved.

  The thickness of the dielectric film formed by thermal spraying is preferably 0.3 mm or more, and can be appropriately selected depending on desired capacitance and withstand voltage characteristics, but is usually 5 mm or less.

In the present invention, the dielectric film has a dielectric breakdown voltage of 3 kV or higher and preferably higher when the film thickness is 0.3 mm, but is usually 20 kV or lower, and the capacitance per unit area at the film thickness. Is 0.3 μF / m ² or more, and in this case, the higher the better, but usually it is preferably 10 μF / m ² or less.

  The second step of the present invention is to form a conductive material on the dielectric film made of rare earth element oxide as a counter electrode to the electrode.

  Similarly, it is preferable to use a thermal spraying method as a method of forming the counter electrode. Although the outermost surface of the dielectric coating formed by thermal spraying is in a relatively rough and sparse state, the interface part of the dielectric layer is also in a high density due to the compaction effect by spraying the conductive material from above. And withstand voltage characteristics become better. In a method such as conductive paste or plating, fine holes are easily formed between the dielectric layer and the electrode layer, and when used under a high voltage, a discharge phenomenon may occur in the holes.

  In addition, as a manufacturing method of the counter electrode by a thermal spraying method, it can operate similarly to the case where the above-mentioned one electrode is manufactured by thermal spraying, and it is preferable that the film thickness shall also be 10-300 micrometers, especially 50-200 micrometers. .

Furthermore, if necessary, the capacitor surface can be covered with an insulating material as a third step of the present invention. The insulating material may be an organic insulating material such as an epoxy resin, or an inorganic insulating material such as Al ₂ O ₃ or a rare earth element oxide. The coating of the capacitor surface with these insulating materials can also be formed by thermal spraying.

The thickness of the coating layer made of this insulating material is only required to prevent discharge and protect the capacitor, and is preferably about 10 to 300 μm.
A capacitor can be fabricated by connecting a pair of electrodes facing each other obtained as described above by a conventional method.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Example 1]
As shown in the process diagram of FIG. 1, a brass cylindrical tube 1 was used as an electrode base material, and yttrium oxide powder was sprayed as a dielectric on the outer surface to form a dielectric layer 2 having a thickness of 0.3 mm. . Next, after masking 3 the end portion, brass powder was sprayed on the outer surface of the dielectric layer to form a counter electrode layer 4 having a thickness of 0.1 mm, and then the mask 3 was removed. As a result of measuring the electrical characteristics of the completed capacitor, the capacitance was 63.8 pF, and the dielectric breakdown voltage was 4.8 kV. The capacitance per unit area was 0.38 μF / m ² , and a thin and high withstand voltage capacitor was obtained.

[Example 2]
A capacitor was formed in the same manner as in Example 1 except that erbium oxide was used as the dielectric. The electrical characteristics of this capacitor were a capacitance of 81.6 pF and a breakdown voltage of 5.7 kV. The capacitance per unit area was 0.49 μF / m ² , and a thin and high withstand voltage capacitor was obtained.

Example 3
As shown in the process diagram of FIG. 2, a cylindrical case 5 made of aluminum was used as an electrode substrate, and yttrium oxide powder was sprayed on the outer surface to form a dielectric layer 6 having a thickness of 0.3 mm. Next, after masking 7 the edge, aluminum powder was sprayed on the outer surface of the dielectric layer 6 to form a counter electrode layer 8 having a thickness of 0.1 mm, and then the mask 7 was removed. As a result of measuring the electrical characteristics of the completed capacitor, the capacitance was 57.5 pF, and the dielectric breakdown voltage was 4.4 kV. The capacitance per unit area was 0.39 μF / m ² , and a thin and high withstand voltage capacitor was obtained.

Example 4
As shown in the process diagram of FIG. 3, a copper-clad epoxy substrate 9 was used as a substrate [FIG. 3 (a)]. Reference numeral 10 denotes a copper circuit, and 11 denotes a conductive pin. A portion of this base material 9 was masked 12 [FIG. 3B], and brass powder was sprayed on the surface to form a base electrode layer 13 having a thickness of 0.1 mm [FIG. 3C]. Next, a part of the mask 12 is removed and a part of the masking 14 is separately applied [FIG. 3 (d)], and the surface of the base electrode layer 13 is sprayed with yttrium oxide powder to obtain a thickness of 0.3 mm. A dielectric layer 15 was formed [FIG. 3 (e)]. Next, brass powder was sprayed on the outer surface of the dielectric layer 15 on a portion of the mask removed [FIG. 3 (f)] to form a counter electrode layer 16 having a thickness of 0.1 mm [FIG. 3 (g). ]. Further, after removing all the mask [FIG. 3 (h)], yttrium oxide powder was sprayed on the whole to form an insulator layer 17 having a thickness of 0.2 mm [FIG. 3 (i)]. As a result of measuring the electrical characteristics of the formed capacitor, the capacitance was 47.7 pF and the dielectric breakdown voltage was 5.1 kV. The capacitance per unit area was 0.48 μF / m ² , and a thin and high withstand voltage capacitor was obtained on the printed circuit board.

[Comparative Example 1]
A capacitor was formed in the same manner as in Example 1 except that the dielectric was aluminum oxide. The electrical characteristics of this capacitor were a capacitance of 43.2 pF and a dielectric breakdown voltage of 2.4 kV. The capacitance per unit area was 0.26 μF / m ² , and a capacitor with inferior capacitance and withstand voltage characteristics was obtained.

[Comparative Example 2]
A capacitor was formed in the same manner as in Example 1 except that the dielectric was barium titanate. The electrical characteristics of this capacitor were 1470 pF and dielectric breakdown voltage 0.8 kV. The capacitance per unit area was 8.8 μF / m ² , and although the capacitance was high, a capacitor having inferior withstand voltage characteristics was obtained.

The process figure which obtains the capacitor of Example 1 is shown, (a) is sectional drawing of the cylindrical tube made from brass of Example 1, (b) is sectional drawing after the dielectric material spraying of Example 1, (c) is Sectional drawing after mask attachment of Example 1, (d) is a sectional view after conductive material spraying of Example 1, and (e) is a sectional view after removing the mask of Example 1. FIG. The process figure which obtains the capacitor of Example 3 is shown, (a) is sectional drawing of the aluminum cylindrical case of Example 3, (b) is sectional drawing after the dielectric material spraying of Example 3, (c) is (c). Sectional drawing after mask attachment of Example 3, (d) is a sectional view after conductive material spraying of Example 3, and (e) is a sectional view after removing the mask of Example 3. The process figure which obtains the capacitor of Example 4 is shown, (a) is sectional drawing of the copper-clad epoxy board | substrate of Example 4, (b) is sectional drawing after masking of Example 4, (c) is Sectional view after conductive material spraying of Example 4, (d) is a sectional view after partial mask removal and partial pasting of Example 4, (e) is after dielectric spraying of Example 4 Cross-sectional view, (f) is a cross-sectional view after removing a partial mask of Example 4, (g) is a cross-sectional view after conductive material spraying of Example 4, and (h) is after removing the mask of Example 4. (I) is sectional drawing after the insulator spraying of Example 4. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Brass cylindrical tube 2, 6, 15, 17 Dielectric layer 3, 7, 12, 14 Mask 4, 8, 13, 16 Electrode layer 5 Aluminum cylindrical case 9 Copper epoxy board 10 Copper circuit 11 Conductive pin

Claims (6)

  A capacitor comprising a dielectric layer made of a rare earth element oxide formed by a thermal spraying method and a pair of electrodes facing each other with the derivative layer interposed therebetween.   The capacitor according to claim 1, wherein one or both of the electrodes are made of a conductive material formed by a thermal spraying method. The dielectric breakdown voltage when the thickness of the dielectric layer is 0.3 mm is 3 kV or more, and the capacitance per unit area at the thickness is 0.3 μF / m ² or more. Item 3. The capacitor according to Item 1 or 2.   The capacitor according to claim 1, 2 or 3, wherein the electrode has a structure formed on an insulating base material by a thermal spraying method.   The capacitor according to claim 4, wherein the insulating base material is made of glass, resin, or ceramics. 6. The insulator base material has a structure in which a conductor which is a part of an electric circuit is combined, and the conductor and an electrode by thermal spraying are electrically joined. The capacitor as described.

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