JPH05299290A - Porcelain capacitor - Google Patents

Abstract

PURPOSE:To obtain a porcelain capacitor where migration is prevented from occurring and an electrode and a lead terminal are prevented from deteriorating in bonding strength between them. CONSTITUTION:Electrodes 8 and 9 mainly formed of silver are provided onto a substrate 7 of dielectric porcelain, and electrodes 10 and 11 whose main component is zinc provided to the peripheral parts of the electrodes 8 and 9. Furthermore, lead terminals 12 and 13 are bonded to the electrodes 8 and 9, and the board 7 is covered with sheathing material 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-mounted porcelain capacitor used in general electronic equipment and the like.

[0002]

2. Description of the Related Art FIG. 6 is a side sectional view showing a conventional ceramic capacitor. In FIG. 6, reference numeral 1 is a substrate made of dielectric ceramic, reference numerals 2 and 3 are electrodes formed on both side surfaces of the substrate 1, and electrodes 2 and 3 are made of a material containing silver as a main component. The lead terminals 4 and 5 are joined to the electrodes 2 and 3, respectively, and the lead terminals 4 and 5 are joined to the electrodes 2 and 3 by soldering or a conductive adhesive. 6 is an exterior material provided to cover the substrate 1 and the lead terminals 4 and 5, and
The exterior material 6 is made of insulating synthetic resin or the like. At this time, the ends of the lead terminals 4 and 5 are exposed on the surface of the exterior material 6.

[0003]

However, in the above-mentioned conventional structure, since the electrodes 2 and 3 are composed of a material containing silver as a main component, in the environment of high temperature and high humidity of 60 ° C. and 98% humidity. , Moisture enters through the exterior material 6, and as a result, migration occurs between the electrodes 2 and 3, and the substrate 1
A current flows through the side surface of the electrode and causes a short circuit between the electrodes 2 and 3. Here, if an electrode containing zinc as a main component is used as the material of the electrode, the above problem does not occur, but there is a problem that the bonding force with the lead terminals 4 and 5 is poor.

The present invention solves the above-mentioned conventional problems, and an object thereof is to provide a porcelain capacitor which prevents the occurrence of migration and at the same time does not deteriorate the bonding strength between the electrode and the lead terminal.

[0005]

To achieve this object, an electrode containing silver as a main component is provided on a substrate, and an electrode containing zinc as a main component is provided so as to cover the outer peripheral portion of the electrode.

[0006]

With this structure, even if an electrode that easily causes migration and has a large bonding force with the lead terminal, that is, an electrode mainly composed of silver is formed on the substrate, the migration does not occur.

[0007]

1 and 2 are a plan view and a side sectional view of a main portion showing a ceramic capacitor according to an embodiment of the present invention.

In FIGS. 1 and 2, reference numeral 7 denotes a substrate made of a dielectric ceramic, and the substrate 7 has the following structure.
First, each raw material containing barium titanate as the main component and calcium carbonate, an additive such as silica as an accessory component is mixed and dried by an ordinary ceramic method, a binder such as polyvinyl alcohol is added, and granulated. To do. Thereafter, the granulated product is molded into a disk having a diameter of 6.0 mm and a thickness of 1.0 mm at a pressure of about 1 t / cm ² . This molded body is fired in the air at a temperature of 1300 ° C to 1400 ° C to have an outer shape of 5.0 m.
A substrate 7 having a thickness of 0.8 mm is prepared.

Reference numerals 8 and 9 are electrodes formed on both sides of the substrate 7 and containing silver as a main component. The electrodes 8 and 9 have an outer diameter of 3.0 mm and are screened with a silver electrode paste. It is formed by printing with a pattern for printing and baking at 800 ° C. for 15 minutes. Electrodes 10 and 11 are formed on the outer peripheral portions of the electrodes 8 and 9 and have zinc as a main component.
1 is formed as follows. A zinc electrode paste containing zinc as a main component and glass frit, copper, nickel or the like as an accessory component was prepared, and the paste was used as a screen pattern on the outer peripheral portions of the electrodes 8 and 9 to have an outer diameter of 4.0 mm and an inner diameter of 2. 5
The electrodes 10 and 11 are formed by printing in a ring shape of mm and baking at 600 ° C. for 15 minutes.

After the electrodes 10 and 11 are formed in this way, lead terminals are attached as shown in FIG. In FIG. 3, reference numerals 12 and 13 denote lead terminals joined to the electrodes 8 and 9, respectively. The lead terminals 12 and 13 are mainly composed of iron and are made of a material such as nickel or copper. A conductive adhesive is applied to the lead terminals 12 and 13 and the electrodes 8 and 9,
The conductive adhesive is dried by a dryer at 150 ° C. for 30 minutes and cured to bond the conductive adhesive.

When the lead terminals are further attached, an exterior material 14 is provided so as to cover the substrate 7 as shown in FIG. The exterior material 14 is formed as follows. First, lead terminal 1
The substrates on which Nos. 2 and 13 were attached were fixed in a transfer mold molding die preheated to 170 ° C., and 100 kg / cm of a tablet-shaped epoxy resin having an outer diameter of 30 mm and a thickness of 15 mm was formed by the transfer mold molding machine.
^As shown in FIG. 4, by press-fitting with a plunger at a pressure of ² for 120 seconds, the exterior material 14 has a dimension of 9.0 mm in the X direction, 8.0 mm in the Y direction, and 3.0 mm in the Z direction.
To form.

Finally, as shown in FIG. 5, the lead terminals 12 and 13 protruding from the exterior material 14 are bent from the side surface to the bottom surface of the exterior material 14.

A durability test was conducted on the porcelain capacitor constructed as described above and a conventional porcelain capacitor (one in which a zinc electrode was not provided around a silver electrode). The results will be described below. The durability test has the same configuration as that of the present embodiment except that the porcelain capacitor according to the present embodiment and the conventional porcelain capacitor, that is, the zinc electrode is not provided on the outer peripheral portion of the silver electrode. 100 pieces of each of the porcelain capacitors of the present example and the conventional example were produced, and those samples were made at a temperature of 60.
The sample was placed in a high temperature and high humidity humid atmosphere tank having a temperature of 95 ° C. and a humidity of 95%, a voltage of DC 3 kV was applied to each sample, and the time until the samples short-circuited was measured. The results are shown in (Table 1).

[0014]

[Table 1]

As can be seen from these results, it takes longer to make a short circuit in this embodiment than in the conventional example. That is, it can be seen that the present embodiment is extremely excellent in facing. Specifically, in the present example, the first short-circuited sample was generated 3670 hours after the voltage was applied, whereas it was 1820 hours in the conventional example.

As described above, in this embodiment, the electrodes 8 and 9 are provided on both side surfaces of the substrate 7, and the electrodes 10 and 11 are provided on the outer peripheral portions thereof, respectively. Can be suppressed.
As described above, the porcelain capacitor of this embodiment does not deteriorate the durability and the joint strength between the lead terminals 12 and 13 and the electrodes 8 and 9.

[0017]

According to the present invention, an electrode containing silver as a main component is provided on a substrate, and an electrode containing zinc as a main component is provided so as to cover the outer peripheral portion of the electrode, so that migration easily occurs, and An electrode with a large bonding force with the lead terminal,
That is, even if an electrode containing silver as a main component is formed on a substrate, migration does not occur, so defects such as short circuits can be suppressed, and the bonding strength does not decrease.

[Brief description of drawings]

FIG. 1 is a plan view of a main portion showing a porcelain capacitor according to an embodiment of the present invention.

FIG. 2 is a side sectional view showing a main part of a porcelain capacitor according to an embodiment of the present invention.

FIG. 3 is a side sectional view showing a porcelain capacitor in one embodiment of the present invention.

FIG. 4 is a perspective view showing a porcelain capacitor in one embodiment of the present invention.

FIG. 5 is a side sectional view showing a porcelain capacitor in one embodiment of the present invention.

FIG. 6 is a side sectional view showing a conventional porcelain capacitor.

[Explanation of symbols]

 7 substrate 8 electrode 9 electrode 10 electrode 11 electrode 12 lead terminal 13 lead terminal 14 exterior material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Sasaki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A first electrode containing silver as a main component is provided on both sides of a substrate made of a dielectric ceramic, and a second electrode containing zinc as a main component so as to cover an outer peripheral portion of the first electrode. And a lead terminal attached to the first electrode.