1. Field of the Invention
The present invention relates to monolithic ceramic electronic components, and particularly to a monolithic ceramic capacitor manufactured by a method of reducing acoustic noise generated when an electric field is applied to the monolithic ceramic capacitor mounted on a circuit board.
2. Description of the Related Art
As electronic devices produce increasingly less noise, acoustic noise has become more noticeable, caused by vibrations of monolithic ceramic capacitors (referred to as “monolithic capacitors”, below) in power circuits or other components of various apparatuses, such as laptop computers, mobile phones, or digital cameras.
Japanese Unexamined Patent Application Publication No. 2010-186884 describes that acoustic noise occurs when an AC voltage is applied to a monolithic capacitor mounted on a circuit board due to electrostrictive vibrations of the monolithic capacitor propagating through the circuit board.
As illustrated in
These are problems not only for the monolithic capacitor 110 having two outer electrodes 114 but also for a three-terminal monolithic capacitor having three outer electrodes 114. Further, these problems can occur not only in the monolithic capacitor 110, but also in any monolithic ceramic electronic component including a monolithic LC filter.
Accordingly, preferred embodiments of the present invention provide a monolithic ceramic electronic component that overcomes the problems described above.
A monolithic ceramic electronic component according to a preferred embodiment of the present invention includes a ceramic laminate body including dielectric ceramic layers and internal electrodes alternately stacked on top of one another, the ceramic laminate body including an outer periphery defined by an upper surface, a lower surface, two side surfaces, and two end surfaces that are perpendicular or substantially perpendicular to the upper surface, the lower surface, and the two side surfaces; and an outer electrode disposed on one of the two end surfaces and portions of the upper and lower surfaces and portions of the two side surfaces that are continuous with the one of the two end surfaces so as to be electrically connected to the internal electrodes. The outer electrode includes a solder-repellent portion to which molten solder does not adhere and a solder-receivable portion to which the molten solder adheres. The solder-repellent portion includes a main portion that extends over all or substantially all of a portion of the outer electrode provided over the one of the two end surfaces and strip-shaped portions extending at least partially over portions of the outer electrode provided over the portions of the two side surfaces. The solder-receivable portion is provided in a portion of the outer electrode excluding the solder-repellent portion. A dimension of each of the strip-shaped portions extending in a direction from the upper surface to the lower surface is less than a dimension of the main portion extending in the direction from the upper surface to the lower surface.
When a direction in which the dielectric ceramic layers and internal electrodes are stacked defines a vertical direction of the monolithic ceramic electronic component, the solder-receivable portion may preferably include upper and lower portions extending in the vertical direction that are symmetrical with each other.
The solder-repellent portion may preferably include a solder-resistant film attached to the outer electrode.
The solder-resistant film may preferably be made of a heat-resistant resin that is not deformed at a soldering temperature.
The solder-repellent portion may preferably be defined by an oxidized portion of the outer electrode.
The solder-receivable portion may preferably be provided in a portion of the outer electrode that is exposed to the outside.
When a direction in which the dielectric ceramic layers and the internal electrodes are stacked defines a vertical direction of the monolithic ceramic electronic component, the solder-repellant portion may preferably include upper and lower portions extending in the vertical direction that are symmetrical with each other.
The outer electrode may preferably include three layers made of copper, nickel, and tin, respectively, or three layers made of copper, nickel, and gold, respectively.
The dielectric layers may preferably be made of a ferroelectric material.
The dielectric layers may preferably be made of barium titanate.
The internal electrodes may preferably be made of silver-palladium.
The solder-receivable portion may preferably include upper and lower portions disposed above and below the strip-shaped portions.
A monolithic ceramic electronic component according to another preferred embodiment of the present invention includes a laminate body including dielectric ceramic layers and internal electrodes alternately stacked on top of one another, and an outer periphery defined by an upper surface, a lower surface, two side surfaces, and two end surfaces that are perpendicular or substantially perpendicular to the upper surface, the lower surface, and the two side surfaces; and an outer electrode disposed on one of the two end surfaces and portions of the upper and lower surfaces and portions of the two side surfaces that are continuous with the one of the two end surfaces so as to be electrically connected to the internal electrodes. The outer electrode includes a solder-repellent portion to which molten solder does not adhere and a solder-receivable portion to which the molten solder adheres. The the solder-repellent portion includes a main portion that extends over all or substantially all of a portion of the outer electrode provided over the one of the two end surfaces and strip-shaped portions extending at least partially over portions of the outer electrode provided over the two side surfaces. The solder-receivable portion is arranged to partially extend over the portions of the outer electrode provided over the portions of the two side surfaces. A dimension of each of the strip-shaped portions extending in a direction from the upper surface to the lower surface is less than a dimension of the main portion extending in the direction from the upper surface to the lower surface.
In the monolithic ceramic electronic component according to various preferred embodiments of the present invention, each solder-repellent portion includes a main portion that extends over all or substantially all of a portion of the outer electrode provided over the one of the two end surfaces and strip-shaped portions extending at least partially over portions of the outer electrode provided over the portions of the two side surfaces. Thus, molten solder is prevented from adhering to the end surface and the portions of the side surfaces. Consequently, acoustic noise generated when an AC voltage is applied to the monolithic ceramic electronic component mounted on the circuit board is reduced. Further, since each solder-receivable portion is provided in a portion of the corresponding outer electrode other than the solder-repellent portion, the monolithic ceramic electronic component can be firmly connected to the circuit board after being mounted on the circuit board.
The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.
As illustrated in
Herein, for convenience purposes, the monolithic ceramic capacitor 10 is referred to as a monolithic capacitor 10, the dielectric ceramic layer 11 is referred to as a dielectric layer 11, and the ceramic laminate body 13 is referred to as a laminate body 13. In a description of the orientation of the monolithic capacitor 10, the direction in which the dielectric layers 11 are stacked is referred to as a vertical direction, the direction in which the pair of outer electrodes 14 are arranged is referred to as a lengthwise direction, and the direction perpendicular or substantially perpendicular to the vertical direction and the lengthwise direction is referred to as a widthwise direction.
The laminate body 13 preferably has a cuboid or substantially cuboid shape with the corners thereof rounded off, for example. The outer electrodes 14 provided on both end surfaces 15 of the laminate body 13 also have rounded portions so as to correspond to the shape of the corners of the laminate body 13. However, in the first preferred embodiment of the present invention, each end surface 15 of the laminate body 13 may include the above-described rounded portions in addition to a flat portion. Thus, the end surfaces 15 are illustrated as being flat in
In the first preferred embodiment, as illustrated in
Specifically, each solder-repellent portion 17 is preferably defined by a solder-resistant film 19 that is attached to the outer electrode 14. The solder-resistant film 19 is attached to all or substantially all of a portion of the outer electrode 14 that continuously extends from the end surface portion to a portion of the side surface portion, the upper surface portion, and the lower surface portion. For easy understanding, the solder-resistant film 19 is illustrated as being partially removed in
Preferably, the solder-resistant film 19 is made of a material that is not deformed at the soldering temperature (for example, approximately 139° C. or higher), such as a heat-resistant resin, for example. Each outer electrode 14 preferably includes, for example, three layers of copper (Cu), nickel (Ni), and tin (Sn) or copper (Cu), nickel (Ni), and gold (Au). The materials of the outer electrodes 14 allow the molten solder to adhere thereto when the molten solder is brought into contact therewith. Examples of the material of the molten solder include a tin-silver-copper (Sn—Ag—Cu) alloy.
The dielectric layers 11 are preferably made of a ferroelectric material, such as barium titanate, for example. Therefore, when an AC voltage is applied to the pair of outer electrodes 14 of the monolithic capacitor 10, the polarities of the dielectric layers 11 are reversed and thus the electrostrictive phenomenon occurs.
As illustrated in
Further, as illustrated in
In addition, preferably, the solder-receivable portion 18 is configured to include upper and lower portions that are symmetrical with each other. When the monolithic capacitor 10 is configured in this manner, each fillet 3 provided on the corresponding solder-receivable portion 18 will have substantially the same shape regardless of whether the upper surface of the monolithic capacitor 10 faces upward or downward when the monolithic capacitor 10 is mounted on the circuit board 1. Consequently, the amplitudes of vibrations transmitted to the circuit board 1 are substantially the same in both cases, thereby effectively reducing vibrations regardless of whether the upper surface of the capacitor 10 faces upward or downward.
In addition, as described above, the material of the solder-resistant film 19 is preferably a heat-resistant resin that is not deformed at the soldering temperature. Thus, a portion to which the solder is not to be adhered is maintained free from the solder at the soldering temperature when the monolithic capacitor 10 is mounted on the circuit board 1.
Here, a non-limiting example of a method of manufacturing the monolithic capacitor 10 according to the first preferred embodiment is described. First, an internal electrode 12 made of a material such as a silver-palladium (Ag—Pd) alloy, for example, is preferably printed on the surface of a ceramic green sheet made of a barium-titanate-based material, for example. The printing operation is repeated until a predetermined number of ceramic green sheets each including the internal electrode 12 are stacked on top of one another. Then, the stacked sheets are fired at a predetermined temperature to form a laminate body 13. Further, conductive paste is applied to both end portions of the laminate body 13 and the laminate body 13 is fired to form outer electrodes 14. The process described thus far is the same or substantially the same as that in a typical monolithic-capacitor manufacturing method.
In order to obtain the monolithic capacitor 10 according to the first preferred embodiment, solder-resistant films 19 are attached to all or substantially all of both end surface portions of the outer electrodes 14 and to a portion of the upper surface portion, the lower surface portion, and the side surface portions of the outer electrodes 14. The solder-resistant films 19 are preferably attached to these portions by dipping, for example. Specifically, one of the end surfaces 15 and a portion of the upper surface 8, the lower surface 9, and the side surfaces 16 are dipped in a bath filled with a paste material of the solder-resistant film 19. Subsequently, the monolithic capacitor 10 is withdrawn from the bath and the paste material that has adhered to the outer electrode 14 is cured. The solder-resistance film 19 is similarly attached to the end surface portion of the other end surface 15 and other portions of the upper surface 8, the lower surface 9, and the side surfaces 16.
The monolithic capacitor 10 according to the first preferred embodiment can be appropriately modified with respect to the position or the shape of the solder-repellent portions 17.
In
Each solder-resistant film 19A is configured so as to extend over a portion of some of the dielectric ceramic layers 11 on the side surfaces 16 of the laminate body 13. Consequently, the solder-resistant film 19A is firmly adhered to the laminate body 13 and the solder-repellent portion 17A is less likely to be displaced or detached under high temperature conditions, such as during soldering.
The above-described first preferred embodiment and exemplary modification do not limit the present invention defined in the claims and can be modified in various manners within the scope of the present invention. Although a typical monolithic capacitor 10 is described as a non-limiting example in the first preferred embodiment, preferred embodiments of the present invention are applicable not only to a monolithic capacitor 10 including two outer electrodes 14 but also to a three-terminal monolithic capacitor having three outer electrodes 14, for example. In addition, preferred embodiments of the present invention are applicable not only to the monolithic capacitor 10 but also to general monolithic ceramic electronic components, including a monolithic LC filter, for example.
In a monolithic capacitor 20 according to a second preferred embodiment of the present invention, the outer electrodes 14 themselves are not subjected to a molten-solder repelling process. Components that are the same as those in the first preferred embodiment are not described in detail below.
As illustrated in
In the monolithic capacitor 20 according to the second preferred embodiment, molten solder does not adhere to any portion of the end surfaces 15 or to the portion of the upper surface 8, the lower surface 9, and the side surfaces 16 covered by the solder-repellant portion 27. Thus, expansion and contraction that occurs as a result of application of an AC voltage is not substantially transmitted to the circuit board 1. Consequently, vibrations of the circuit board 1 are reduced and acoustic noise is less likely to be generated. Further, since the molten solder adheres to the solder-receivable portions 28 of the outer electrodes 14, fillets 3 are provided so as to connect the solder-receivable portions 28 to the circuit board 1, thus securely connecting the monolithic capacitor 20 and the circuit board 1 together.
Each solder-repellent portion 27 is preferably formed by fixing the monolithic capacitor 20 to a jig and then irradiating the corresponding outer electrode 14 with a laser beam, for example. By being irradiated with a laser beam, the surface of the outer electrode 14 is oxidized. The monolithic capacitor 20 made by the method including the oxidization process can achieve the same effects as those achieved by the monolithic capacitor 10 according to the first preferred embodiment without including another component, such as the solder-resistant film 19.
As in the case of the monolithic capacitor 10 according to the first preferred embodiment, the monolithic capacitor 20 according to the second preferred embodiment can be appropriately modified with regard to the arrangement and the shape of the solder-repellent portions 27 and the solder-receivable portions 28.
While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.
Number | Date | Country | Kind |
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2012-095268 | Apr 2012 | JP | national |
Number | Date | Country | |
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Parent | 13865231 | Apr 2013 | US |
Child | 15000170 | US |