JP2005136173A - Capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitor whose electrostatic capacity will not be deteriorated and which generates hardly a structural defect such as crack or the like even when the capacitor is mounted on a wiring substrate. <P>SOLUTION: The widths of a first internal electrode 3 and a second internal electrode 4 in the opposing region of both of the internal electrodes are widened gradually toward both of upper and lower sides compared with those at the central area in the widthwise direction of a laminate. The rate of the minimum value to the maximum value of the electrode width in the opposing region of the first internal electrode 3 and the second internal electrode 4 is specified as 96%-99%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a capacitor structure.

  As a conventional capacitor, for example, as shown in FIG. 5, a dielectric layer 22 having a rectangular shape is laminated with first internal electrodes 23 and second internal electrodes 24 interposed therebetween, There is known a structure in which external terminals 25 and 26 that are electrically connected to one internal electrode 23 and a second internal electrode 24 are arranged, respectively. 2 functions as a capacitor by applying a predetermined voltage between the two internal electrodes 24 and forming a predetermined capacitance in the dielectric layer 22 disposed between the two internal electrodes (for example, Patent Document 1). reference.).

  The above-described conventional capacitor is designed to secure a large area of the internal electrode by making the outer periphery of all the internal electrodes as close as possible to the outer periphery of the capacitor body in order to obtain the largest possible capacitance.

When such a capacitor is mounted on a wiring board such as a mother board, a conductive adhesive such as solder is interposed between the external terminals 25 and 26 and the connection pads of the wiring board. Then, the solder and the like are heated and melted at a high temperature, so that the internal electrodes 23 and 24 of the capacitor are connected to the wiring board via the external terminals 25 and 26 and the solder or the like. It is electrically connected to the wiring conductor.
JP-A-1-226130

  However, in the above-described conventional capacitor, in order to obtain as large a capacitance as possible, the area of the internal electrodes 23 and 24 is ensured as wide as possible by keeping the outer periphery of all the internal electrodes as close as possible to the outer periphery of the capacitor body. The area of the region where the upper and lower adjacent dielectric layers are in direct contact with each other is extremely narrow. Therefore, the adhesion strength between the dielectric layers seems to be insufficient, and when an external impact or heat is applied, a large stress is applied particularly to the central region in the thickness direction of the capacitor, and the dielectric constituting the capacitor The drawbacks are that the layers peel in the central region in the thickness direction and cracks are generated inside.

  The present invention has been devised in view of the above-described drawbacks, and its purpose is to provide a capacitor that can effectively prevent peeling of the dielectric layer and generation of cracks in the central region in the thickness direction while ensuring a large capacitance. Is to provide.

  The capacitor according to the present invention includes a first internal electrode and a second internal electrode between adjacent dielectric layers in a stacked body formed by stacking a plurality of dielectric layers to form a rectangular parallelepiped shape. Wherein the first internal electrode and the second internal electrode have an electrode width in a region where the internal electrodes are opposed to each other. It is characterized by being gradually wider toward the upper and lower sides than the central region in the thickness direction of the body.

  In the capacitor of the present invention, the distance from the edge portion of the first internal electrode and the second internal electrode in the facing region to the end surface of the multilayer body gradually increases from the central region in the thickness direction of the multilayer body toward the upper and lower sides. It is characterized by being shortened.

  Furthermore, the capacitor of the present invention is characterized in that the ratio of the minimum value to the maximum value of the electrode width in the opposed region of the first internal electrode and the second internal electrode is 96% to 99%. .

  Furthermore, in the capacitor of the present invention, the ratio of the minimum value to the maximum value of the distance from the edge portion in the facing region of the first internal electrode and the second internal electrode to the end face of the multilayer body is 96% to 99%. It is characterized by being.

  Furthermore, in the capacitor of the present invention, the ratio of the minimum value to the maximum value of the distance from the edge portion in the opposed region of the first internal electrode and the second internal electrode to the end face of the multilayer body is 96% to 99%. It is characterized by being.

  According to the present invention, the electrode width in the opposing region of both the first internal electrode and the second internal electrode is gradually increased toward the upper and lower sides from the central region in the thickness direction of the laminated body, whereby the internal electrode Since the area of the part without the gap can be made relatively small and the area of the dielectric layer having a high adhesion strength can be made relatively large, it becomes possible to improve the mechanical strength of the central region in the thickness direction where the stress is strong. After mounting the capacitor on the wiring board, a large impact is applied to the capacitor or the wiring board, or even if thermal stress is repeatedly applied and the wiring board is deformed, defects such as cracks occur in the capacitor. Can be effectively prevented.

  According to the invention, the distance from the edge portions of the first internal electrode and the second internal electrode in the opposing region to the end surface of the multilayer body is gradually shortened from the central region in the thickness direction of the multilayer body toward the upper and lower sides. As a result, the same effect as the internal electrode width described above can be obtained in the internal electrode length direction. In this way, in the thickness central region where a strong stress is applied, the adhesion strength in the internal electrode width direction and the length direction can be kept relatively high, and it is possible to effectively prevent the occurrence of defects such as cracks in the capacitor. Can do.

  Further, according to the present invention, the area of the internal electrode is gradually changed from the central region in the thickness direction of the laminate toward the upper and lower sides, and the internal electrode width in the opposing region of the first internal electrode and the second internal electrode is changed. Since the ratio of the minimum value to the maximum value is 96% to 99%, the facing area of the first internal electrode and the second internal electrode does not change greatly in the thickness direction, so that the capacitance can be kept high. .

  Furthermore, according to the present invention, the ratio of the minimum value to the maximum value of the distance from the edge portion in the facing region of the first internal electrode and the second internal electrode to the end face of the multilayer body is 96% to 99%. Therefore, the same effect as the internal electrode width direction described above can be obtained in the internal electrode length direction.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

  1 is an external perspective view of a capacitor according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line AA ′ of the capacitor shown in FIG. 1, FIG. 3 is a cross-sectional view taken along the line BB ′ of the capacitor shown in FIG. FIG. 2 is a cross-sectional view of the capacitor of FIG. 1, wherein 1 is a multilayer body, 2 is a dielectric layer, 3 is a first internal electrode, 4 is a second internal electrode, and 5 and 6 are external terminals.

  The capacitor shown in FIG. 1 is formed by laminating a plurality of rectangular dielectric layers 2 to form a substantially rectangular parallelepiped laminated body 1, and in each of the dielectric layers 2-2 within the laminated body 1. The first internal electrode 3 and the second internal electrode 4 are alternately interposed in a partially opposed state, and are further electrically connected to the first internal electrode 3 at both ends of the laminate 1. The external terminal 5 and the external terminal 6 electrically connected to the second internal electrode 4 are attached and formed.

  The dielectric layer 2 is formed to a thickness of 1 μm to 3 μm per layer by a dielectric material mainly composed of, for example, barium titanate, calcium titanate, strontium titanate, and the like. For example, the laminated body 1 is formed by laminating only 70 to 600 layers.

  For example, when the dielectric layer 2 is made of a dielectric material mainly composed of barium titanate, an appropriate organic solvent, glass frit, organic binder, or the like is added to and mixed with the barium titanate powder. In addition, this is formed into a ceramic green sheet having a predetermined shape and thickness by a conventionally known doctor blade method or the like, and then a predetermined number of ceramic green sheets are obtained by a conventionally known green sheet laminating method or the like. The ceramic green sheet laminate is formed by laminating and pressing only, and finally the laminate is produced by firing at a temperature of 1100 ° C. to 1400 ° C., for example. In addition, the shrinkage | contraction rate accompanying baking of the ceramic green sheet used in this process is set to about 10%-20%, for example.

  On the other hand, the first internal electrode 3 and the second internal electrode 4 interposed between the dielectric layers 2 are made of a conductive material whose main component is a metal such as nickel, copper, nickel / copper, silver / palladium. For example, when the outer dimension is 2 mm × 2 mm, the thickness per layer is set to 0.5 μm to 2.0 μm.

  Such a capacitor applies a predetermined voltage to the adjacent inter-electrode 3-3 via the external electrode 5, and forms a predetermined electrostatic capacity in the dielectric layer 2 disposed between the internal electrodes 3-3. Function as a capacitor.

  When the first internal electrode 3 and the second internal electrode 4 are made of nickel / copper, for example, an appropriate organic solvent, glass frit, organic binder, or the like is added to and mixed with the nickel / copper powder. Before the above-mentioned ceramic green sheets are laminated, the width of the conductor paste applied to the main surface of each ceramic green sheet is gradually changed by a conventionally known screen printing method, ink jet method, etc. After being printed and applied to the ceramic green sheet, which is interposed between the ceramic green sheets and coated with a wide width of the conductive paste, and after this width is minimized in the central area in the thickness direction, Laminate 1 is obtained by laminating the wider one. When the laminated body 1 is fired, it is fired simultaneously to become the first internal electrode 3 and the second internal electrode 4.

  Further, the first internal electrode 3 and the second internal electrode 4 are formed so that, for example, a metal plating film deposited by electrolytic plating and electroless plating is formed on the main surface of the support in the shape of the predetermined internal electrodes 3 and 4. What was formed by performing an etching process on can be used. Alternatively, the internal electrodes 3 and 4 may be produced by electrolytic plating while masking areas other than the formation region of the internal electrodes 3 and 4 so that predetermined internal electrodes 3 and 4 are obtained on the main surface of the support. Alternatively, the metal plating film may be produced by a thin film forming method such as ion plating, sputtering, chemical vapor deposition, etc., and the forming method is not particularly limited.

  When the internal electrodes 3 and 4 are made of a metal plating film such as nickel, a metal plating film having substantially the same shape is formed on the main surface of the ceramic green sheet, and then laminated and fired without causing an area difference in the internal electrodes. The capacitor of the present invention can be obtained.

  By transferring the metal plating film thus prepared to the ceramic green sheet, the first internal electrode 3 is interposed between the ceramic green sheets and simultaneously fired when the laminate of the ceramic green sheets is fired. This becomes the second internal electrode 4.

  The first internal electrode 3 and the second internal electrode 4 are such that the electrode width in the opposing region of both internal electrodes gradually increases from the central region in the thickness direction of the laminate 1 toward the upper and lower sides. The distance from the edge portions of the first internal electrode 3 and the second internal electrode 4 to the end face of the multilayer body 1 in this opposing region is gradually shortened from the central area in the thickness direction of the multilayer body 1 toward the upper and lower sides. .

  The ratio of the minimum value to the maximum value of the electrode width in the opposing region of the first internal electrode 3 and the second internal electrode 4 is preferably 96% to 99%. Furthermore, the ratio of the minimum value to the maximum value of the distance from the edge portions of the first internal electrode 3 and the second internal electrode 4 to the end face of the multilayer body 1 in this facing region should be 96% to 99%. preferable.

  By making such a structure, the adhesion strength between the dielectric layers is higher when the adhesion strength between the internal electrode and the dielectric layer is compared with the adhesion strength between the dielectric layers. If the area of the dielectric layer is increased, the adhesion strength of the capacitor is improved, and a relatively strong mechanical strength can be obtained.

  Therefore, after mounting the capacitor 8 on the wiring board, even if a large impact is applied, or a thermal stress is repeatedly applied and the wiring board is deformed, the stress is generated in the central area of the capacitor or in the thickness direction of the capacitor. It is possible to effectively prevent cracks from occurring.

  On the other hand, from the viewpoint of capacitance, the opposing areas of the first internal electrode and the second internal electrode do not change greatly in the thickness direction, so that the capacitance can be kept high.

  In addition, the external terminals 5 and 6 provided at both ends of the laminate 1 described above are connected to the connection pads of the wiring board via a conductive adhesive such as solder when the capacitor is mounted on the wiring board such as a mother board. And functions as an external connection terminal that is electrically connected to each other, and a conductive paste for an external electrode is applied to both ends of the laminated body 1 and fired. It is formed by depositing a metal having good properties to a predetermined thickness by a conventionally known electrolytic plating method or the like.

  Such a capacitor applies a predetermined voltage to the adjacent inter-electrode 3-3 via the external electrode 5, and forms a predetermined electrostatic capacity in the dielectric layer 2 disposed between the internal electrodes 3-3. Function as a capacitor.

  The present invention is not limited to the above-described embodiments, and various changes and improvements can be made without departing from the scope of the present invention.

  For example, in the above-described embodiment, the area of the internal electrodes is gradually changed from the central region in the thickness direction of the laminate toward both the upper and lower sides. The group may be manufactured and the group may be gradually laminated on the upper and lower sides from the central region in the thickness direction of the laminate.

  Further, in the above-described embodiment, the case where one capacitor is manufactured alone has been described as an example, but instead of this, a so-called 'multiple picking' method is adopted and cut out from a large laminate. It goes without saying that a plurality of capacitors may be obtained simultaneously by firing a plurality of pieces.

  In addition, the dielectric layer outside the internal electrodes in the thickness direction of the capacitor may use a dielectric material different from the dielectric between the internal electrodes. Furthermore, the thickness of the dielectric layer can be arbitrarily changed according to the purpose.

1 is an external perspective view of a capacitor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA ′ of the capacitor in FIG. 1. FIG. 2 is a cross-sectional view taken along the line BB ′ of the capacitor in FIG. 1. FIG. 2 is a cross-sectional view of the capacitor of FIG. It is sectional drawing of the conventional capacitor | condenser.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laminated body 2 ... Dielectric layer 3 ... 1st internal electrode (internal electrode)
4 ... 2nd internal electrode (internal electrode)
5, 6 ... External terminals

Claims (4)

The first internal electrode and the second internal electrode are connected to each other between the adjacent dielectric layers in the laminated body formed in a rectangular parallelepiped shape by laminating a plurality of dielectric layers. Capacitors that are alternately interposed so as to face each other,
The capacitor in which the first internal electrode and the second internal electrode have an electrode width in an opposing region of both internal electrodes gradually wider toward the upper and lower sides than the central region in the thickness direction of the laminate. . The distance from the edge part of the 1st internal electrode in the said opposing area | region and the 2nd internal electrode to the end surface of the said laminated body is gradually shortened toward the up-and-down both sides from the thickness direction center area | region of the said laminated body. The capacitor according to claim 1. 2. The capacitor according to claim 1, wherein a ratio of a minimum value to a maximum value of an electrode width in the opposing region of the first internal electrode and the second internal electrode is 96% to 99%. The ratio of the minimum value to the maximum value of the distance from the edge part in the opposing region of the first internal electrode and the second internal electrode to the end face of the multilayer body is 96% to 99%. Item 3. The capacitor according to item 2.

Images