Laminated electronic component

A laminated electronic component includes a laminated block in which a plurality of electrically insulating layers are laminated. An external conductor film is disposed on a surface of the laminated block. An additional conductor film which is at the same potential as the external conductor film is arranged such that it faces the external conductor film with an insulating layer disposed therebetween. The additional conductor film and the external conductor film are electrically connected to each other through a via-hole conductor so that they are at the same potential.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to laminated electronic components, and more particularly to a laminated electronic component provided with an external conductor film on an exposed exterior surface.

2. Description of the Related Art

FIG. 5is a sectional view illustrating a known laminated electronic component1disclosed in Japanese Unexamined Patent Application Publication No. 2001-267448.

The laminated electronic component1is mounted on a board2indicated by an imaginary line and is provided with a laminated block4. The laminated block4is formed by laminating a plurality of electrically insulating layers3along a thickness direction of the laminated block4. The insulating layers3are generally formed of ceramic material.

The laminated block4is provided with a cavity7having an opening6at least on one main surface, for example, on a first main surface5facing the mounting board2. In the cavity7, a chip component8, for example, an IC chip or a surface acoustic wave (SAW) filter, is stored therein. The cavity7may sometimes be filled with an electrically insulating resin after receiving the chip component8therein, though it is not shown.

Several internal conductor films and several via-hole conductors are disposed within the laminated block4so as to provide wiring patterns required for the laminated electronic component1, though details of such an arrangement are not shown. These internal conductor films and via-hole conductors are sometimes disposed in the laminated block4such that they form capacitors, inductors, delay lines, or filters. Within the laminated block4, not only the internal conductor films, but also resistor films for defining resistors may be provided.

InFIG. 5, there is shown in which a pair of capacitor-forming conductor films9and10for defining a capacitor are disposed as the internal conductor films such that they face each other with a specific insulating layer3therebetween. In the laminated block4, the first main surface5, a second main surface11facing the first main surface5, and a bottom surface12of the cavity7are exposed on the exterior of the insulating layers3. An external conductor film3is provided on the first main surface5, an external conductor film14is provided on the second main surface11, and an external conductor film15is provided on the cavity12.

The external conductor film13functions as a conductive land for establishing an electrical connection with the board (motherboard)2on which the laminated electronic component1is mounted. The external conductor film14functions as a conductive land for establishing an electrical connection with a chip component16mounted on the second main surface11. The external conductor film15provides a die bonding surface for bonding the chip component8housed in the cavity7.

The chip components16mounted on the second main surface11of the laminated block4include electronic components defining capacitors, inductors, resistors, diodes, ICs, memory devices, SAW filters, or quartz oscillators.

A certain impact is imposed on the external conductor films13,14, and15on the following respective occasions: when the laminated electronic component1is mounted on the board2, when the chip components16are mounted, and when the chip component8is mounted. A stress resulting from such an impact may cause cracks in the insulating layers3positioned adjacent to the external conductor films13,14, and15. Particularly, such cracks easily occur when the insulating layers3are formed of ceramics. Cracks may also occur, for example, when the laminated electronic component1is dropped or when it collides with another component.

When cracks occur in ceramics positioned adjacent to the external conductor films13,14, and15as described above, the following problems may arise.

It is now assumed, for example, that a crack occurs in the insulating layer3adjacent to the external conductor layer15, and in this state, the laminated electronic component1is used while a ground potential is supplied to the external conductor film15. In this case, since a constant DC bias is applied between the external conductor film15and, for example, the capacitor-forming conductor film10, migration of metal materials forming the external conductor film15and the capacitor-forming conductor film10may be facilitated therebetween, causing short-circuiting or leakage, thereby impairing the functions of the laminated electronic component1. The above-described problem also applies to the external conductor films13and14.

SUMMARY OF THE INVENTION

In order to overcome the problems described above, preferred embodiments of the present invention provide a laminated electronic component including a laminated block having a structure in which a plurality of electrically insulating layers and an internal conductor film formed along a specific interface between the insulating layers are laminated along the thickness of the laminated block, an external conductor film disposed on a surface exposed on the exterior of the laminated block, and an additional conductor film which is at the same potential as the external conductor film and which is arranged along a specific interface between the insulating layers such that the additional conductor film faces the external conductor film.

With this unique configuration, even if cracks occur in the insulating layer adjacent to the external conductor film, an electric field is not generated between the external conductor film and the additional conductor film since they are at the same potential, thereby preventing the occurrence of migration of metal materials therebetween. As a result, failures, such as short-circuiting and leakage, in the laminated electronic component are reliably prevented.

The additional conductor film also prevents cracks from further expanding inwards into the laminated block, thereby preventing the laminated electronic component from being mechanically destroyed.

Preferably, only one of the insulating layers may be interposed between the additional conductor film and the external conductor film.

The thickness of the insulating layer between the additional conductor film and the external conductor film may preferably range from about 10 μm to about 150 μm. With this arrangement, the advantages obtained by the provision of the additional conductor film can be effectively exhibited without increasing the height of the laminated electronic component.

The area of the additional conductor film may preferably be greater than or equivalent to the area of the external conductor film, and may be formed such that the additional conductor film covers the external conductor film therein when viewed from above or below. With this arrangement, the advantages obtained by the provision of the additional conductor film can be reliably exhibited, and also, a plating liquid penetrating into the insulating layers through cracks can be effectively prevented by the additional conductor film.

The additional conductor film and the external conductor film may be electrically connected to each other via a via-hole conductor or via a conductor disposed on an outer surface of the laminated block so that they are at the same potential.

Preferred embodiments of the present invention particularly become effective when a DC bias is applied between the external conductor film and the internal conductor film when the laminated electronic component is being used. Thus, the advantages obtained by preferred embodiments of the present invention can be noticeably exhibited.

The laminated block may include a first main surface and a second main surface facing the first main surface, and the external conductor film may be disposed on at least one of the first and second main surfaces. In this case, the external conductor film may be used for establishing an electrical connection with a chip component disposed on the same surface on which the external conductor film is disposed, or may be used for establishing an electrical connection with a board (motherboard) on which the laminated electronic component is mounted.

A cavity having an opening positioned on at least one of the main surfaces of the laminated block may be provided for the laminated block, and the external conductor film may be disposed on the bottom surface of the cavity. If a chip component is housed in the cavity, the external conductor film may provide a die bonding surface for bonding the chip component.

In this case, the external conductor film and the chip component are not necessarily electrically connected to each other, and the external conductor film may be used for mechanically fixing or shielding the chip component.

With the provision of the above-described cavity, when the additional conductor film and the external conductor film are electrically connected to each other through a via-hole conductor, the via-hole conductor may preferably positioned in an area outside the bottom surface of the cavity so as to improve the flatness of the bottom surface of the cavity. With this arrangement, the possibility of allowing a plating liquid to penetrate along the via-hole conductor can be reduced, and the flatness of the bottom surface of the cavity can be enhanced without the via-hole conductor.

Preferred embodiments of the present invention particularly become effective when the insulating layers are formed of ceramics, which would normally facilitate the occurrence of cracks.

Other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments with reference to the attached drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1is a sectional view illustrating a laminated electronic component21constructed in accordance with a first preferred embodiment of the present invention.

The laminated electronic component21is mounted on a board22indicated by an imaginary line, and is provided with a laminated block24. The laminated block24is formed by laminating a plurality of electrically insulating layers23along the thickness of the laminated block24. Although the insulating layers23are preferably formed of ceramics, they may be formed of another electrically insulating material, such as resin.

The laminated block24is provided with a cavity27having an opening26at least on one main surface, for example, on a first main surface25facing the mounting board22. In the cavity27, a chip component28, for example, an IC chip or a SAW filter, is stored therein. The chip component28is electrically connected to a conductive land of the laminated block24by wire bonding or flip chip bonding (bump connection), though it is not shown inFIG. 1. The cavity27may be filled with an electrically insulating resin after receiving the chip component28therein, though it is not shown.

In the laminated block24, the above-described first main surface25, a second main surface29facing the first main surface25, and a bottom surface30of the cavity27are extended substantially parallel with the insulating layers23, and are also exposed on the exterior side of the insulating layers23. An external conductor film31is provided on the second main surface29, and an external conductor film32is provided on the bottom surface30of the cavity27.

The external conductor film31defines a conductive land for establishing an electrical connection with a chip component33mounted on the second main surface29of the laminated block24. The external conductor film32defines a die bonding surface for bonding the chip component28housed in the cavity27. The external conductor film32extends beyond the bottom surface30of the cavity27toward the inside of the laminated block24so as to connect with an internal conductor film and a via-hole conductor, which are described below. Such an arrangement, however, is not essential.

The chip components33mounted on the second main surface29include electronic components defining capacitors, inductors, resistors, diodes, ICs, memory devices, SAW filters, or quartz oscillators.

At edges of the first main surface25, terminal conductors34, which define input/output terminals, and external conductor films63connected to the terminal conductors34are provided. The terminal conductors34and the external conductor films63are used for establishing an electrical connection with the mounting board22. The terminal conductors34are formed by dividing a via-hole conductor, which is formed before the laminated blocks24are divided from a mother laminated block, simultaneously with dividing the mother laminated block. In this preferred embodiment, a groove for forming the above-described via-hole conductor is formed before dividing the mother laminated block into the laminated blocks24, and steps35resulting from the formation of the groove are generated at side surfaces of the laminated block24.

The terminal conductors34may be formed by providing a conductor, such as a conductive paste, at the side surfaces of the divided laminated block24. The above-described conductor films63do not necessarily have to be formed.

The laminated electronic component21may be provided with a metal housing cover36indicated by imaginary lines. The metal housing cover36is fixed on the second main surface29of the laminated block24such that it covers the chip components33. The metal housing cover36is soldered to the specific terminal conductor34, such as that to which a ground potential is supplied so that it is electrically connected and mechanically fixed to the terminal conductor34.

In the laminated block24, several internal conductor films are disposed along the specific interfaces between the insulating layers23, and several via-hole conductors are arranged such that they pass through the specific insulating layers23, though details of such an arrangement are not shown. These internal conductors and via-hole conductors are arranged such that they provide wiring patterns required for the laminated electronic component21, and so that they define capacitors, inductors, delay lines, or filters as needed or desired. Within the laminated block24, not only the above-described internal conductor films, but also resistor films for providing resistors may sometimes be provided.

As another characteristic configuration of preferred embodiments of the present invention, an additional conductor film42is provided within the laminated block24along a specific interface between the insulating layers23such that it faces the external conductor film32. The additional conductor film42is electrically connected to the external conductor film32through via-hole conductors43so that it is at the same potential as the external conductor film32. By the provision of the additional conductor film42, the following advantages are provided.

It is now assumed that the internal conductor films37,38, and39are provided for, for example, forming capacitors, and that a ground potential is supplied to the external conductor film32while the laminated electronic component21is being used. In this case, a constant DC bias is sometimes applied to the external conductor film32. Under this condition, even if cracks occur in the insulating layer23adjacent to the external conductor film32, an electric field is not generated between the external conductor film32and the additional conductor film42since they are at the same potential, thereby preventing the occurrence of migration of metal materials therebetween. As a result, failures, such as short-circuiting and leakage, in the laminated electronic component21can be reliably prevented.

The additional conductor film42also prevents cracks from further expanding inwards into the laminated block24.

As the thickness of the insulating layer23between the additional conductor film42and the external conductor film32is greater, the possibility of the occurrence of cracks becomes smaller, and accordingly, the possibility of the occurrence of migration becomes smaller. On the other hand, a greater thickness of the insulating layer23increases the height of the laminated electronic component21. Thus, by considering these tradeoffs, the thickness of the insulating layer23between the additional conductor film42and the external conductor film32may preferably be about 10 μm to 150 μm, and more preferably about 25 μm to about 150 μm. The laminated block24is preferably designed such that only the single insulating layer23intervenes between the additional conductor film42and the external conductor film32.

In order to effectively exhibit the advantages achieved by the provision of the additional conductor film42, the additional conductor film42is preferably formed such that the area thereof is greater than or equivalent to that of the external conductor film32and such that the additional conductor film42covers the external conductor film32therein when viewed from above. With this arrangement, even if a plating liquid penetrates into the insulating layers23through cracks, the provision of the additional conductor film42can effectively inhibit further penetration of the plating liquid into the insulating layers23.

The additional conductor film42is also preferably arranged such that it covers the internal conductor films37,38, and39therein when viewed from the bottom.

The via-hole conductors43are preferably positioned in an area outside the bottom surface30of the cavity27. That is, since the via-hole conductors43are not disposed adjacent to the bottom surface30of the cavity27, the possibility of the above-described penetration of a plating liquid through the via-hole conductors43can be minimized, and also, the flatness of the bottom surface30can be greatly improved without the via-hole conductors43.

FIG. 2is a sectional view illustrating a laminated electronic component51constructed in accordance with a second preferred embodiment of the present invention. InFIG. 2, elements equivalent to those shown inFIG. 1are indicated by like reference numerals, and an explanation thereof is thus omitted.

In a laminated block52provided with the laminated electronic component51, an additional conductor film53is arranged along the specific interface between the insulating layers23such that it faces the external conductor film31disposed on the second main surface29. The additional conductor film53is electrically connected to the external conductor film31through a via-hole conductor54so that it is at the same potential as the external conductor film31.

InFIG. 2, internal conductor films55,56, and57are arranged to define the internal conductor films formed within the laminated block52. The internal conductor films55,56, and57have the function of forming capacitors or wiring, and are sometimes used while a constant DC bias is applied between the internal conductor films55,56, and57and the external conductor film31. Accordingly, any crack occurring adjacent to the insulating layer23of the external conductor film31may bring about failures, such as short-circuiting or leakage caused by the above-described migration.

However, by the provision of the additional conductor film53shown inFIG. 2, as well as by the provision of the additional conductor film42shown inFIG. 1, the above-described failures are reliably prevented. The additional conductor film53also increases the resistance against the peeling-off or dropping of the external conductor film31.

FIG. 3is a sectional view illustrating a laminated electronic component61constructed in accordance with a third preferred embodiment of the present invention. InFIG. 3, elements equivalent to those shown inFIG. 1are designated with like reference numerals, and an explanation thereof is thus omitted.

In a laminated block62provided for the laminated electronic component61shown inFIG. 3, an external conductor film63, which defines an input/output terminal for establishing an electrical connection with the mounting board22, is provided on the first main surface25facing the mounting board22. An additional conductor film64is disposed along the specific interface between the insulating layers23such that it faces the external conductor film63.

The additional conductor film64and the external conductor film63are electrically connected to each other via a conductor65disposed on an outer surface, for example, a side surface, of the laminated block62so that they are at the same potential. The conductor65can be formed in a manner substantially similar to the terminal conductor34shown inFIG. 1.

InFIG. 3, internal conductor films66,67, and68are arranged to define the internal conductor films located within the laminated block62. The internal conductor films66,67, and68have the function of forming capacitors or providing a ground potential or wiring, and thus, a constant DC bias is sometimes applied to the external conductor film63. Accordingly, any crack occurring adjacent to the insulating layer23of the external conductor film63may bring about failures, such as short-circuiting or leakage caused by the above-described migration.

However, by the provision of the additional conductor film64shown inFIG. 3, as well as by the provision of the additional conductor film42shown inFIG. 1, the above-described failures are reliably prevented.

FIG. 4is a sectional view illustrating a laminated electronic component71constructed in accordance with a fourth preferred embodiment of the present invention. InFIG. 4, elements equivalent to those shown inFIG. 1are indicated by like reference numerals, and an explanation thereof is thus omitted.

In a laminated block72provided for the laminated electronic component71shown inFIG. 4, an external conductor film73structured as, for example, a land grid array (LGA), is provided on the first main surface25facing the mounting board22. The external conductor film73is used for establishing an electrical connection with the mounting board22. An additional conductor film74is disposed along the specific interface between the insulating layers23such that it faces the external conductor film73. The additional conductor film74and the external conductor film73are electrically connected to each other through a via-hole conductor75so that they are at the same potential.

InFIG. 4, internal conductor films76,77, and78are provided as the internal conductor films formed within the laminated block72. The internal conductor films76,77, and78have the function of forming capacitors or providing a ground potential or wiring, and thus, a constant DC bias is sometimes applied to the external conductor film73. Accordingly, any crack occurring adjacent to the insulating layer23of the external conductor film73may bring about failures, such as short-circuiting or leakage caused by the above-described migration.

However, by the provision of the additional conductor film74shown inFIG. 4, as well as by the provision of the additional conductor film42shown inFIG. 1, the above-described failures are reliably prevented. The additional conductor film74also increases the resistance against the peeling-off or dropping of the external conductor film73.

While the present invention has been described through illustration of preferred embodiments with reference to the accompanying drawings, various modifications and changes can be made without departing from the spirit of the invention.

For example, the number of laminated insulating layers, or the arrangement of internal conductor films, via-hole conductors, and external conductor films provided for a laminated block may be changed as desired according to the design of a laminated electronic component.

Additionally, the characteristic configurations of the first through fourth preferred embodiments may be combined suitably.

In the foregoing preferred embodiments, a single additional conductor film is provided for a single external conductor film. However, if a plurality of external conductor films are disposed adjacent to each other and are at the same potential, a common additional conductor film may be provided for the plurality of external conductor films such that it faces the external conductor films.