Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2003-02-24
2004-07-06
Martin, David (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S760000, C361S752000, C361S728000, C174S250000, C174S260000
Reexamination Certificate
active
06760227
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to multilayer ceramic electronic components and manufacturing methods thereof, and more particularly, to an improvement in the formation of terminal electrodes in a multilayer ceramic electronic component having a cover.
2. Description of the Related Art
A multilayer ceramic electronic component and a manufacturing method thereof are disclosed in Japanese Unexamined Patent Application Publication No. 8-37251. This publication describes the following method for manufacturing a multilayer ceramic electronic component.
A plurality of ceramic green sheets is first prepared, throughholes are formed in predetermined ceramic green sheets, and terminal via hole conductors are formed in the throughholes. The terminal via hole conductors may be a conductor filled in the throughhole or a conductor provided on the internal surface of the throughhole. In addition, on predetermined ceramic green sheets, wiring conductors, such as conductive films or via hole conductors other than the terminal via hole conductors described above, are formed.
Next, the ceramic green sheets are laminated to each other and are then pressed, thereby forming a green mother electronic component. This mother electronic component is formed such that when being divided along predetermined dividing lines, electronic component bodies for forming a plurality of multilayer ceramic electronic components are obtained.
Next, at locations where the terminal via hole conductors of the green mother electronic component are to be divided, penetrating holes are formed, and as a result, the terminal via hole conductors are exposed at the internal surfaces of the penetrating holes. In the step described above, one penetrating hole is formed for each terminal via hole conductor.
The green mother electronic component is fired. After firing is performed, a plating film composed of, for example, Ni/Au or Ni/Sn, is formed by wet plating on the terminal via hole conductor exposed at the internal surface of the penetrating hole.
Subsequently, elements are mounted on one major surface of the mother electronic component at which one major surface of each laminated ceramic body is formed.
Next, the mother electronic component is divided along the dividing lines passing through the penetrating holes. Accordingly, by dividing the terminal via hole conductors as described above, a plurality of the electronic component bodies is formed having terminal electrodes formed at main surfaces of notches which are formed by dividing the penetrating holes. The division described above is typically performed in a so-called chocolate-break manner via grooves formed in both major surfaces of the mother electronic component along the dividing lines. The grooves are formed before or after the firing of the mother electronic component.
Next, although not specifically disclosed in the publication described above, a cover is disposed such that an opening thereof faces the laminated ceramic body to cover the elements mounted thereon. In the case described above, since the notches provided with the terminal electrodes at the main surfaces thereof are formed by the division of the penetrating holes, as described above, at least one foot portion, to be disposed in at least one of the notches, is preferably provided on the cover. Hence, when the foot portion is disposed in the notch provided with ground terminal electrodes and is bonded thereto via soldering or other suitable material, the cover is fitted to the laminated ceramic body.
As described above, since the notches are formed in the laminated ceramic body, and the terminal electrodes are formed in these notches, when the cover is fitted to the laminated ceramic body, the following advantages can be obtained.
That is, first, since the foot portion is disposed in the notch, the cover can be easily positioned with respect to the laminated ceramic body.
In addition, since the foot portion and the ground terminal electrode are bonded to each other in the notch, solder used for bonding remains in the notch, and the solder is not likely to cause short-circuiting with another terminal electrode.
The multilayer ceramic electronic component thus formed is mounted on a wiring substrate through the terminal electrodes by soldering. However, when the soldering is performed to bond the foot portion to the ground terminal electrode, the solder provided therebetween may remelt when the soldering is performed for the wiring substrate as described above. In this case, the solder bonding the foot portion to the ground terminal electrode may melt and flow to another terminal electrode. However, since the ground terminal electrodes are formed in the notches, as described above, the solder is prevented from flowing out.
However, the conventional technique described above has the following problems that must be overcome.
First, problems occur when the alignment pitch of the terminal electrodes is decreased, for example, to 0.6 mm or less.
In order to decrease the alignment pitch of the terminal electrodes, in addition to a decrease in the diameter of the penetrating hole provided for dividing the terminal via hole conductor, the width thereof exposed at the internal surface of the penetrating hole must be decreased.
However, when the size of the penetrating hole is decreased, the flow of a wet plating solution used for plating the exposed area of the terminal electrode becomes inferior, and as a result, it is difficult to appropriately form the plating film. In addition, since the exposed width of the terminal via hole conductor is decreased, it is more difficult to form an appropriate plating film.
In addition, in order to decrease the alignment pitch of the terminal electrodes, the pitch of the penetrating holes must also be decreased. However, when the pitch described above is decreased, a portion between the adjacent penetrating holes is subject to breakage in a step of forming the penetrating hole or a firing step.
When the pitch of the penetrating holes is decreased, projections having a sawtooth shape are formed between the adjacent notches provided in the laminated ceramic body obtained by the division described above, and hence when the laminated ceramic body is handled, these sawtooth projections often cause chipping.
In addition, in order to form a greater number of the terminal electrodes, the number of the penetrating holes is increased, and as a result, the number of steps of forming the penetrating hole is also increased.
SUMMARY OF THE INVENTION
To overcome the problems described above, preferred embodiments of the present invention provide a greatly improved multilayer ceramic electronic component including a cover and a manufacturing method thereof.
A multilayer ceramic electronic component according to a preferred embodiment of the present invention includes a laminated ceramic body including a plurality of ceramic layers laminated on each other, in which a first major surface and a second major surface face each other, and first, second, third, and fourth side surfaces, each of which extends between the first and the second major surfaces. In this arrangement, the first and the third side surfaces face each other, and the second and the fourth side surfaces face each other.
First, second, third, and fourth notches are provided in the first, second, third, and fourth side surfaces, respectively, of the laminated ceramic body described above.
Ground terminal electrodes are provided at main surfaces of the first and third notches, and a plurality of terminal electrodes are arranged in parallel at a main surface of each of the second and fourth notches. The plurality of terminal electrodes disposed at the main surface of each of the second and fourth notches may include ground terminal electrodes electrically connected to the ground terminal electrodes provided at the main surfaces of the first and third notches.
At least one element is mounted on the first major surface of the laminated ceramic body.
A cover is arranged such that
Kato Isao
Sakai Norio
Keating & Bennett LLP
Levi Dameon E.
Martin David
Murata Manufacturing Co. Ltd.
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