JP2000306763A - Laminated ceramic capacitor and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce defective capacitors due to leakage, stabilize tanδ characteristic, and improve reliability in a laminated ceramic capacitor used to various kinds of electronic equipment. SOLUTION: Inner electrodes 7 exposing in layer like on a pair of facing both sidewall surface of a ceramic element assembly, that a dielectric ceramics 6 and the inner electrode 7 are mutually laminated and sintered like a piece (chip), are covered with a conductive metallic layers 9a and 9b by the electroless plating method so as to form external connection terminals 8a and 8b, the connection between the inner electrode 7 and the external connection terminals 8a and 8b is stabilized, the production yield is improved, and a laminated ceramic capacitor superior in reliability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer ceramic capacitor used for various electronic devices and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, demands for multilayer ceramic capacitors have been remarkably increasing with the reduction in size and weight of electronic devices and their performance.

As shown in FIG. 2, a conventional multilayer ceramic capacitor is obtained by alternately stacking and sintering a dielectric ceramic 1 such as barium titanate and an internal electrode 2 made of a high melting point metal such as palladium or nickel. External connection terminals 3a, 3b are formed by a sintered body of silver and glass connected to the internal electrode 2 at a pair of opposite ends of the flaky ceramic body.
Is formed. Nickel or copper layers 4a and 4b are formed on the surfaces of the external connection terminals 3a and 3b, and tin or solder layers 5a and 5b are formed thereon for surface mounting.

[0004]

However, in such a multilayer ceramic capacitor, the internal electrodes exposed in layers on a pair of opposite end faces of a ceramic sintered body in which dielectric ceramics 1 and internal electrodes 2 are alternately laminated. 2 is an extremely thin layer, it is difficult to reliably expose the internal electrode 2 to the surface, and the internal electrode 2
Are external connection terminals 3a, 3
Since the equivalent series resistance with b becomes high and the electrical connection becomes unstable, there is a problem that the capacity loss is poor and the tan δ characteristic is deteriorated, thereby deteriorating the reliability.

An object of the present invention is to provide a multilayer ceramic capacitor which solves the drawbacks of the conventional example and which is excellent in reliability by preventing poor capacity loss and deterioration of tan δ characteristics.

[0006]

In order to achieve the above object, a multilayer ceramic capacitor according to the present invention is a ceramic having a piece shape obtained by alternately laminating and sintering internal electrodes made of dielectric ceramic and high melting point metal. The surface of the internal electrode exposed in layers at a pair of opposite ends of the body is coated with a metal layer having excellent conductivity by electroless plating, and an external connection terminal layer is provided thereon.

According to this structure, a metal layer having excellent conductivity is attached by electroless plating to the exposed surfaces of the internal electrodes, which are exposed in layers on the pair of opposite end surfaces of the ceramic body, thereby providing external connection terminals. The electrical connection between the capacitor and the internal electrodes can be stabilized, and a multilayer ceramic capacitor having excellent reliability can be obtained.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a ceramic element having a piece shape obtained by alternately laminating and sintering internal electrodes made of dielectric ceramics and refractory metals. A conductive metal layer was applied by electroless plating to the internal electrodes exposed in layers on the pair of both side walls, and external connection terminals were provided on a pair of opposite ends of the ceramic material so as to cover the internal electrodes. Multilayer ceramic capacitor with a highly conductive metal layer at the interface between the internal electrode and the external connection terminal, which increases the connection area between the two and stabilizes the electrical connection. Excellent multilayer ceramic capacitors can be obtained.

According to a second aspect of the present invention, there is provided a multilayer ceramic capacitor in which the external connection terminals are formed of a sintered body of metal and glass or a conductive resin. A multilayer ceramic capacitor having excellent reliability of electrical connection with electrodes can be obtained.

According to a third aspect of the present invention, a ceramic body having the shape of an individual piece obtained by alternately laminating and sintering internal electrodes made of dielectric ceramics and a high melting point metal is immersed in an electroless plating solution. Then, after applying a conductive metal layer to the internal electrodes exposed in layers on the pair of opposite side walls of the ceramic body, a pair of opposed ceramic bodies is provided so as to cover the internal electrodes. This is a method of manufacturing a multilayer ceramic capacitor that provides external connection terminal layers at both ends.Electronic plating is used to apply a highly conductive metal layer to the exposed internal electrodes in a simple process. A multilayer ceramic capacitor having excellent reliability in connection with terminals can be obtained.

According to a fourth aspect of the present invention, there is provided a multilayer ceramic capacitor in which a conductive metal layer is applied to inner electrodes exposed in layers on a pair of opposite side walls of a ceramic body by a displacement plating method. Yes, by applying a conductive metal layer to the exposed surface of the internal electrode by displacement plating, the metal layer can be more easily and reliably applied, and a highly reliable multilayer ceramic capacitor can be obtained. Things.

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows a multilayer ceramic capacitor according to the present invention. In FIG. 1, reference numeral 6 denotes a dielectric ceramic, which is mainly composed of barium titanate or the like.

Reference numeral 7 denotes an internal electrode made of a high melting point metal such as palladium or nickel.

Reference numerals 8a and 8b denote external connection terminals formed at a pair of opposite ends of the ceramic sintered body. The sintered body is made of a metal powder such as silver powder, copper powder, nickel powder or the like and a glass, or the metal powder is epoxy-coated. It is made of a conductive resin dispersed and cured in a synthetic resin such as a resin or a polyimide resin.

Reference numerals 9a and 9b denote conductive metal layers applied by electroless plating to the internal electrodes 7 exposed in layers on a pair of opposing side walls of the individual sintered ceramic body. , Copper, nickel, cobalt, gold, silver, palladium and the like.

Further, reference numerals 10a and 10b denote external connection terminals 8.
a, nickel or copper layer provided on the surface of 8b, 11
Reference numerals a and 11b denote tin or solder layers provided on the surfaces of the nickel or copper layers 10a and 10b. By forming these, a multilayer ceramic capacitor for surface mounting is formed.

In the present embodiment, first, an internal electrode 7 is formed by printing a conductive paste based on a metal powder such as palladium or nickel on a green sheet of a dielectric ceramic 6 such as barium titanate. After stacking and molding an arbitrary number of such sheets to have a desired capacity, the external dimensions are 1.0 × 0.5 mm, 1.6 ×
0.8 mm, 2.5 x 1.25 mm, 3.2 x 1.6 m
m and cut into a rectangular parallelepiped shape and fired at a high temperature in the air or in a nitrogen atmosphere to produce a piece-shaped (chip-shaped) ceramic body.

In this case, the sintered piece-shaped ceramic body has a structure in which the internal electrodes 7 are exposed in layers on a pair of opposite side walls. Then, the individual ceramic body is immersed in an electroless plating solution to form a layered internal electrode 7 on a pair of opposite side walls of the ceramic body.
Layers 9a and 9b having excellent conductivity on the surface thereof
Was precipitated.

As the metal layers 9a and 9b deposited on the exposed surface of the internal electrode 7 by the electroless plating method, many metals such as copper, nickel, gold, silver, platinum and palladium or alloys thereof can be deposited. However, in the present embodiment, particularly, copper, nickel, gold, palladium metal is selected,
Each metal was deposited by barrel plating.

In this case, copper, nickel and palladium are
Using a complex compound of each metal salt and a self-catalytic electroless plating solution consisting of a reducing agent, immerse the ceramic body that has been subjected to pretreatment such as activation treatment in this plating solution to form a layer. Using the exposed internal electrode 7 made of nickel or palladium metal as a nucleus, a thin conductive metal layer 9a, 9b having a thickness of about 0.1 to 1.0 μm is deposited on the surface or layered internal electrode 7. Was.

On the other hand, utilizing the fact that gold can be easily precipitated by a substitution reaction with nickel or palladium metal constituting the internal electrode 7, a gold plating solution containing gold ions, such as gold cyanide or gold sulfite, is added to the ceramic element. Was immersed to selectively replace and deposit gold on the layered exposed surface of the internal electrode 7.

The method of depositing gold by the displacement plating method is extremely effective for confirming the exposed state of the internal electrode 7 because gold is faithfully deposited only on the exposed surface of the internal electrode 7. In addition, since the presence or absence of exposure of the internal electrode 7 during the manufacturing process can be confirmed, defective products can be easily selected. In addition, abnormalities on the dielectric ceramic surface as compared with the self-catalytic electroless plating method can be improved. Precipitation was avoided, and the production yield was significantly improved.

After the metal layers 9a and 9b having excellent conductivity are attached to the exposed surfaces of the internal electrodes 7 in this manner, a pair of opposite ends of the ceramic body are covered so as to cover the internal electrodes 7. External connection terminals 8a and 8b were formed in the portions.

In forming the external connection terminals 8a and 8b, a glass-based conductive paste obtained by dispersing and kneading a metal fine powder of silver, nickel, copper or the like and a glass frit in a resin binder is used. Was selectively applied to a pair of opposite ends, and fired at a high temperature of 600 to 800 ° C. (in air or a nitrogen atmosphere) to form a sintered body of metal and glass.

On the other hand, in another embodiment, silver, copper,
Using a resin-based conductive paste made by mixing and dispersing a fine metal powder such as nickel in an epoxy resin or a polyimide resin, and applying to both ends of the ceramic body, the temperature of 150 ° C to 250 ° C in air The external connection terminals 8a and 8b were formed by curing the resin.

The external connection terminals 8a, 8b
In order to improve the solderability, if necessary, the metal layers 10a and 10b of copper, nickel, etc. are plated on the surface by a barrel electroplating method, and the outermost layer is kept in good solderability. Metal layer 1 such as tin or solder
1a and 11b were covered to complete a multilayer ceramic capacitor.

[0028]

As described above, the multilayer ceramic capacitor according to the present invention has a laminated ceramic body formed by alternately laminating dielectric ceramics and internal electrodes and sintering the laminated ceramic body in layers on a pair of opposite side walls. A metal layer with excellent conductivity is applied to the exposed internal electrode by electroless plating, and an external connection terminal is provided on the metal layer.A metal with excellent conductivity is provided at the interface between the internal electrode and the external connection terminal. Intervening layers,
By increasing the contact area between the two, the equivalent series resistance is reduced, and the electrical connection is stabilized, so that the production yield of the multilayer ceramic capacitor is improved and the reliability is significantly improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a conventional multilayer ceramic capacitor.

[Explanation of symbols]

 6 Dielectric ceramics 7 Internal electrode 8a, 8b External connection terminal 9a, 9b Conductive metal layer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Itakura 1006 Kadoma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. F term (reference) 5E001 AB03 AC09 AF06 AH07 AJ03 5E082 AA01 AB03 BC30 BC38 EE04 EE23 EE35 FG26 FG54 GG10 GG26 GG28 JJ03 JJ23 JJ26 LL01 MM24

Claims (4)

[Claims] An internal electrode composed of dielectric ceramics and a high melting point metal is alternately laminated and sintered. A multilayer ceramic capacitor comprising a metal layer having conductivity applied by plating, and external connection terminals provided at a pair of opposite ends of the ceramic body so as to cover internal electrodes. 2. The multilayer ceramic capacitor according to claim 1, wherein the external connection terminals are formed of a sintered body of metal and glass or a conductive resin. 3. A ceramic element having a piece shape obtained by alternately laminating and sintering internal electrodes made of dielectric ceramics and a high melting point metal is immersed in an electroless plating solution, and a pair of the ceramic elements is opposed to each other. After a conductive metal layer is applied to the internal electrodes exposed in layers on both side walls of the ceramic body, external connection terminal layers are provided on a pair of opposite ends of the ceramic body so as to cover the internal electrodes. Manufacturing method of capacitor. 4. The method for manufacturing a multilayer ceramic capacitor according to claim 3, wherein a conductive metal layer is applied to the internal electrodes exposed in a layer form on a pair of opposite side walls of the ceramic body by displacement plating.