JP2002043168A - Capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent unwanted high frequencies from entering a capacitor from an external circuit, without having to change the size of the capacitor. SOLUTION: A region, positioned at both ends of the main surface of the capacitor body 1, of input/output terminals 5, 6 is covered with an insulating layer 8, and a region 7a formed on one main surface of a ground terminal 7 is extended over the whole surface of the one main surface of the capacitor body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor, and more particularly, to a capacitor used as a filter having a function of removing noise entering an electronic circuit or radiating from the electronic circuit.

[0002]

2. Description of the Related Art The structure of a capacitor conventionally used as a noise filter will be described with reference to FIGS. In addition, a through-type capacitor 40 mainly used as a noise filter among capacitors will be described. 3 is an external perspective view of the feedthrough capacitor 40, FIG. 4 is an exploded perspective view of the feedthrough capacitor 40 of FIG. 3, and FIG. 5 shows an equivalent circuit of the feedthrough capacitor 40 of FIG.

A feed-through capacitor 40 includes a capacitor body 41 having a plurality of dielectric layers 42 stacked thereon, and a dielectric layer 42.
The through conductors 44 disposed therebetween and the ground electrodes 43 disposed between the dielectric layers 42 are alternately laminated. The through conductor 44 is led out to both end faces of the capacitor body 41, and input / output terminals 45 and 46 connected to the through conductor 44 are formed on the end faces. The ground electrode 43 is connected to the input / output terminal 45 of the capacitor body 41,
It is led out to another pair of end faces different from the end face on which the 46 is formed, and a ground terminal 47 connected to a part of the ground electrode 43 is formed on the end face. Here, as shown in the equivalent circuit of FIG. 5, the feed-through capacitor 40 is conventionally provided with input / output terminals 45 and 46 on the signal line side of the circuit pattern of the circuit board and the ground side of the circuit pattern by a surface mounting method. And ground terminals 47 are respectively soldered.

The above-described structure of the feedthrough capacitor 40 forms a predetermined capacitance component depending on the facing area between the feedthrough conductor 44 and the ground electrode 43, the thickness of the dielectric layer 42, and its dielectric constant.

Here, the feedthrough capacitor 40 is soldered on a circuit pattern (not shown, the same applies hereinafter) by a surface mounting method. The input / output terminals 45 and 46 are connected to a signal line or a transmission line of the circuit pattern, and the ground terminal 47 is connected to the ground line of the circuit pattern. A signal flows to the terminal electrode 46 or 45 for use. In general, in a circuit pattern, a passing digital signal is composed of a combination of harmonics that are sine waves. If there are many higher-order harmonics, unnecessary radiation noise is generated on a signal line (transmission line) pattern. There is a problem. Thus, by passing such a digital signal through the feedthrough capacitor 40, unnecessary higher-order harmonics are made to the ground terminal 47 via the ground electrode 43.

In the capacitor body 41 of such a feedthrough capacitor 40, a conductor film serving as a ground electrode 43 is formed on the unfired dielectric layer 2, and becomes a through conductor 44 on the unfired dielectric layer 42. A conductor film is formed, the plurality of dielectric layers 42 are alternately laminated, and the unfired dielectric layer 42 and the conductor film are integrally sintered. Thereafter, input / output terminals 45 and 46 are formed on one end surface of the capacitor body 42 so as to connect both ends of the through conductor 44, and a ground terminal 47 is formed on the other end surface so as to be connected to a part of the ground electrode 43. Have been.

[0007]

However, according to the feedthrough capacitor 40 shown in FIG. 3, even if unnecessary harmonics flow to the ground terminal 47 via the ground electrode 43, the signal is not transmitted to the feedthrough conductor 44 and the ground. After passing through the overlapping portion of the electrode 43, there is a problem that unnecessary harmonics enter from a non-overlapping portion from an external circuit. In these, the problem of unnecessary harmonics cannot be ignored as the number of electrodes increases as the number of layers increases and the number of layers of the multilayer capacitor increases.

In order to solve such a problem, a method is conceivable in which the ground terminal orbits the outer peripheral surface of the capacitor body by utilizing the fact that metal does not transmit electromagnetic waves. Further, it is more effective to increase the area of the ground terminal that goes around the outer peripheral surface.

However, when the area of the ground terminal is simply increased, there is a problem that conduction between the ground conductor on the surface facing the mounting surface and the input / output terminal is likely to occur.

Accordingly, an object of the present invention is to prevent the conduction of the ground conductor and the input / output terminal, and to effectively suppress the entry of unnecessary harmonics from an external circuit, thereby achieving a reduction in size. It is an object of the present invention to provide a feedthrough capacitor that can be used.

[0011]

In order to achieve the above object, a capacitor according to the present invention comprises a capacitor body having a plurality of dielectric layers laminated inside a capacitor body having a pair of opposite end faces. A through conductor derived from the part,
A ground electrode that faces the through conductor and that extends to at least one main surface of the capacitor body is formed from a pair of opposed end surfaces of the capacitor body to both main surface edges. A capacitor provided with a pair of input / output terminals connected to both ends of the through conductor, and a ground terminal circulating from both main surfaces to both side surfaces of the capacitor body and connected to the ground electrode. Of the output terminals, a region located on the edge of the one main surface of the capacitor body is covered with an insulating layer, and a region formed on one main surface of the ground terminal is substantially the same as the one main surface of the capacitor body. It is characterized by being extended to the whole surface.

The capacitor according to the present invention maximizes the area of the ground terminal on the one main surface while preventing conduction between the ground terminal and the input / output terminal by forming the insulating layer of the capacitor body as described above. be able to. For this reason, since the metal does not transmit electromagnetic waves, the metal functions as an electrostatic shield, and it is possible to effectively prevent unnecessary harmonics from entering from an external circuit.

The harmonics coming from the external circuit are
If one main surface of the capacitor body is used as the mounting surface, it often enters the element from that one main surface, but since the insulating layer is formed, the area of the ground terminal on this surface is maximized. It is effective.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the feedthrough capacitor according to the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is an external perspective view of a feedthrough capacitor 10 among the capacitors. FIG. 2 shows the feedthrough capacitor 10 of FIG.
(A) is a sectional view taken along the line AA, and (b) is a sectional view taken along the line BB.

As shown in FIGS. 1 and 2, the feedthrough capacitor 10 includes a ceramic sheet 2 having a through conductor 3 formed on the surface and a ceramic sheet 2 having a ground electrode 4 formed on the surface. The capacitor body 1 is obtained by laminating a plurality of sheets alternately so as to obtain a capacitor body 4 and sintering them.

A pair of input / output terminals 5 and 6 connected to the through conductor 3 are provided on both end surfaces of the capacitor body 1. One ends of the input / output terminals 5 and 6 extend around at least the edges of both main surfaces. Ground terminals 7 are provided so as to go around both side surfaces and both main surfaces of capacitor body 1.
Is provided.

The dielectric layer 2 is made of a dielectric material such as barium titanate or strontium titanate. The material of the ground electrode 3, the through conductor 4, the input / output terminals 5, 6, and the ground terminal 7 is P
d, noble metal material such as Ag-Pd alloy, or Ni, C
A base metal such as u is used.

A feature of the present invention is that an insulating coating film 8 is formed under the ground electrode 7a on the main surface 1a facing the main surface 1b of the capacitor body 1 corresponding to the mounting surface of the circuit board (not shown). Is provided. The insulating coating film 8 includes an insulating resin coating film made of a thermosetting resin such as an epoxy resin and a phenol resin, and an insulating glass coating film made of a low-melting glass component such as lead borosilicate. The thickness of the insulating coating film 8 is about 20 to 100 μm. That is, 20 μm
If it is less than 3, the withstand voltage reliability is low. For example, even if the operating voltage on the circuit board is about 3 to 5 V, sufficient reliability cannot be obtained. If the thickness exceeds 100 μm, it becomes difficult to reduce the height of the device.

The portion covered with the insulating coating film 8 is shown in FIG.
As shown in FIG. 2, the capacitor is formed on substantially the entire surface of the main surface 1a of the capacitor body 1. However, the present invention is not limited to this. . In addition, the coating of the insulating coating film 8 may be formed from the main surface 1a side of the capacitor body 1 to four adjacent end surfaces and side surfaces. In this case, the length from the main surface 1a of the height H of the capacitor body 1 may be covered up to about 1/3.

Here, the insulating coating film 8 of the capacitor body 1
Although the ground terminal 7a may be formed on the surface on which is formed as large as possible, for example, over the entire surface, the ground terminal 7a and the input / output terminals 5 and 6 are prevented from conducting.
In the present embodiment, the ground terminal 7a is also formed on a portion of the input / output terminals 5 and 6 so as to facilitate the formation of the ground terminal 7a. During mounting on the substrate, the surface of the capacitor body 1 on which the insulating coating film 8 is formed becomes the main surface 1a facing the mounting surface.

When the insulating coating film 8 is made of resin, the adhesion between the insulating coating film 8 and the input / output terminals 5, 6 and the capacitor body 1 and the heat treatment for soldering the feed-through capacitor 10 are performed. Temperature needs to be considered. In view of this, the desirable materials are the epoxy resin and the phenol resin as described above.

When the insulating coating film 8 is made of glass, cracks are not generated in the capacitor body 1 due to the heat shrinkage stress of the dielectric layer of the capacitor body 1 when the insulating coating film 8 is formed. In addition, it is necessary to prevent the glass component from diffusing into the dielectric layer 2 of the capacitor body 1 to change the dielectric characteristics. In view of these, a preferable material is a lead borosilicate glass that can be baked at a temperature lower than 600 ° C. as described above.

In the figure, a capacitance is generated between the through conductor 3 and the ground electrode 4 in the capacitor body 1.

The input / output terminals 5 and 6 are formed from the edge of the mounting surface of the capacitor body 1 to the edge of the surface facing the mounting surface via the end surface, and are formed on the surface facing the mounting surface. An insulating coating film 8 is formed so as to cover the input / output terminals 5 and 6 formed at the edge portions thereof, and a ground terminal 7a is formed on substantially the entire surface of the insulating coating film 8. Therefore, while preventing conduction between the ground terminal 7 and the input / output terminals 5 and 6, the ground terminal 7a on the main surface facing the mounting surface is prevented.
Area can be maximized. Further, since the metal does not transmit electromagnetic waves, the metal functions as an electrostatic shield, and it is possible to effectively prevent unnecessary harmonics from entering from an external circuit.

Next, a method for manufacturing the feedthrough capacitor 10 of the present invention will be described. Solvent for dielectric powder and sintering aid,
From the slip in which the dispersant, the binder, and the like are mixed, a ceramic green sheet to be the dielectric layer 2 is formed by a doctor blade method. For the molding method, another method, a pulling method, a die coater, a gravure roll coater, or the like may be used.

A metal ink for forming the ground electrode 4 and the through conductor 3 is printed on the dielectric layer 2 by a screen printing method.
After that, the dielectric layer 2 on which the metal ink is printed is laminated in the order shown in FIG. 3, and then thermocompression-bonded to obtain a block-shaped capacitor body.

Next, the block-shaped capacitor main body is cut into a capacitor block to be the capacitor main body 1 with a push-cutting blade. When the block-shaped capacitor body is thick, it is desirable to cut it by a dicing method. Next, the capacitor block is pre-fired in a furnace at 250 ° C. to 400 ° C. to remove the binder component, and then put into a main firing furnace to simultaneously form the dielectric ceramic 2, the through conductor 3, and the ground electrode 4 at an appropriate temperature of the ceramic material. High temperature sintering is performed at 1250-1300 ° C.

Thereafter, in order to electrically connect the through conductor 3 to the outside, input / output terminals 5 and 6 are formed on the end surfaces of the sintered body by a suitable electrode forming method.

Thereafter, an insulating coating film made of, for example, an epoxy-based insulating resin paste is applied to the main surface extending portion facing the mounting surface of the input / output terminals 5 and 6 which appears on the main surface facing the mounting surface of the capacitor body 1. Is formed and thermally cured at 150 to 200 ° C. to form an insulating coating film 8. The insulating coating film 8
Is formed of a glass member, a coating film is formed with a low melting point glass paste such as lead borosilicate,
And formed by baking.

Incidentally, when the capacitor body 1 is aligned, the insulating coating film 8 is formed on the surface side which appears on the upper side.
In forming the insulating coating film 8, there is no need to determine and align the main surface and the lower surface facing the mounting surface.

In forming a coating film using a resin paste or a low-melting glass paste, in addition to forming a coating film by a printing method using a screen having a predetermined shape, the main components of the through-type capacitor 1 are placed in these paste tanks. Face 1
A coating film may be formed by dipping only that surface, or by dipping from the main surface 1a of the capacitor body 1 to about １ ／ of the height H in FIG.

Thereafter, strip-shaped ground terminals 7 for connecting the upper and lower main surfaces and the left and right end surfaces of the sintered body are formed on the mounting surface and the left and right end surfaces of the sintered body by a suitable electrode forming method.

The input / output terminals 5 and 6 and the ground terminal 7
Can be formed by applying and baking a conductive paste by a method such as screen printing, or by a suitable conductive film forming method such as electroless plating and sputtering. Thus, a feedthrough capacitor 10 as shown in FIG. 1 is obtained.

The present invention is not limited to the above embodiment, but can be variously modified within the scope of the invention. For example, in the above-described embodiment, the surface perpendicular to the stacking direction of the through conductors 3 and the ground electrodes 4 is the mounting surface.
The parallel surface is a mounting surface, and one or two ground electrodes 4 are provided.
It may be derived into three aspects.

The present invention can also be applied to a feedthrough capacitor array in which two or more feedthrough capacitors are formed inside one ceramic capacitor body.

In the above-described embodiment, the ceramic sheets on which the through conductors are formed are stacked and then integrally fired. However, the present invention is not necessarily limited to this. A ceramic sheet that has been sintered in advance may be used. Further, a feedthrough capacitor may be formed by a manufacturing method described below. After a ceramic layer is formed from a paste-like ceramic material by printing or the like, a paste-like conductor material is applied to the surface of the ceramic layer to form an arbitrary through conductor. Next, a paste-like ceramic material is applied from above the through conductor to form a ceramic layer containing the through conductor. Similarly, a through-type capacitor having a laminated structure can be obtained by successively coating.

[0036]

According to the above description, the input / output terminals are formed from the pair of end surfaces of the capacitor body to the edges of both main surfaces, and the area located at the edge of one main surface of the capacitor body is formed. Since the area formed on one main surface of the ground terminal extends almost all over the one main surface of the capacitor body while being covered with the insulating layer, the extended ground terminal is made of metal and does not transmit electromagnetic waves. As a result, it functions as an electrostatic shield, effectively preventing unwanted harmonics from entering the external circuit, and preventing shorts between the ground terminal and input / output terminals without changing the size of the capacitor. Can be prevented.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a capacitor according to the present invention.

FIG. 2 is a cross-sectional view of the capacitor of FIG.

FIG. 3 is an external perspective view of a conventional capacitor.

FIG. 4 is an exploded perspective view of the capacitor of FIG.

FIG. 5 is an equivalent circuit diagram of the capacitor of FIG. 3;

[Explanation of symbols]

 10, 40 Through-type capacitor 1, 41 Capacitor body 2, 42 Dielectric layer 3, 44 Ground electrode 4, 43 Through conductor 5, 6, 45, 46 Input / output terminal 7, 47 Ground terminal 7a Ground terminal facing the mounting surface 8 Insulation coating film

Claims (1)

[Claims] 1. A capacitor having a plurality of dielectric layers laminated therein, a through conductor whose both ends are led out to a pair of opposing end surfaces of the capacitor body, facing each other with the through conductor interposed therebetween, and A ground electrode leading to at least one main surface of the capacitor main body is disposed, and formed from a pair of opposed end surfaces of the capacitor main body to edges of both main surfaces, and is connected to both ends of the through conductor. A pair of input / output terminals, and a ground terminal that circulates from both main surfaces to both side surfaces of the capacitor body and is connected to the ground electrode, wherein one of the input / output terminals is one of the capacitor body. A region located on the edge of the main surface is covered with an insulating layer, and a region formed on one main surface of the ground terminal is formed on one main surface of the capacitor body. Capacitor, characterized in that substantially is extended over the entire surface of the.