Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Reexamination Certificate
2002-07-16
2003-12-02
Dinkins, Anthony (Department: 2831)
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
C361S310000, C361S306100, C361S321200
Reexamination Certificate
active
06657848
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multilayer electronic device reducing the equivalent serial inductance (ESL) and able to be used as a capacitor array and a method for producing the same, more particularly relates to a multiterminal multilayer capacitor and a method for producing the same.
2. Description of the Related Art
In the past, capacitors have been made wide use of as types of electronic devices. Multilayer ceramic capacitors are also being used in power supply circuits of LSIs.
On the other hand, in a power supply circuit of a CPU or other LSI in which the capacitor shown in
FIG. 10
is arranged, sharp fluctuations in current sometimes occur at the time of operation of the LSI. Along with the fluctuations in current, the voltage of the power supply circuit widely fluctuates due to the inductance (L) and resistance (R) of the interconnections and the ESL and equivalent serial resistance (ESR) of the capacitor, so that the operation of the LSI is sometimes hampered.
Therefore, in the past, in a power supply circuit of an LSI, a capacitor with a low ESL has been used to suppress fluctuations in voltage accompanying sharp fluctuations in current and to thereby stabilize the power supply circuit.
In particular, recent CPUs have been required to be reduced further in ESL since operating frequencies and currents have been made higher along with higher operating speeds. Therefore, in multiterminal capacitors, one example of a multilayer ceramic chip capacitor, the directions of the currents have been controlled to become opposite between the nearby terminal electrodes.
As shown in Japanese Unexamined Patent Publication (Kokai) No. 9-17693, Japanese Unexamined Patent Publication (Kokai) No. 11-144996, U.S. Pat. No. 5,880,925, etc., the main part of a conventional reduced ESL multiterminal capacitor is comprised of a rectangular parallelopiped body configured by a plurality of internal electrodes superposed via ceramic layers so as to give an electrostatic capacity by the ceramic layers forming the body.
Further, each of these internal electrodes has two leads each led out to two or more side faces among the four side faces of the body.
Terminal electrodes connected to these leads are attached to these side faces. Note that voltages are supplied with alternatingly opposite polarities to the nearby terminal electrodes connected to the leads of the nearby internal electrodes in the stacking direction. Since the polarities of the voltages supplied to the nearby leads differ, the magnetic fluxes generated due to the high frequency currents flowing from the terminal electrodes are canceled out between these adjoining leads and therefore the ESL is reduced.
On the other hand, the stabilization of a power supply circuit depends to a large extent on the ESR of the capacitor as well. In a conventional reduced ESL capacitor, since, as mentioned above, the electrical resistance becomes smaller along with the provision of the plurality of leads. As a result, the ESR becomes extremely small, therefore the power supply circuit using such a capacitor lacked stability.
That is, the conventional reduced ESL capacitor had an extremely small ESR, so when resonance was caused due to inductance of the peripheral circuits, the voltage dropped sharply or ringing or other attenuation vibration easily occurred.
On the other hand, along with the increasing integration of circuits, capacitors etc. for power supply circuits are now being required to be a single capacitor comprised of a plurality of component capacitors giving electrostatic capacities differing in accordance with a plurality of circuits.
Further, along with the increasing integration of circuits, capacitors etc. for power supply circuits have been required to be a single capacitor comprised of a plurality of internal electrodes, but if fabricating internal electrodes differing in pattern of leads along with the number of internal electrodes, the production process is liable to become complicated and the manufacturing costs increase.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a multilayer electronic device and method of producing a multilayer electronic device not only able to prevent the ESR from becoming extremely small while reducing the ESL, but also enabling the manufacturing costs to be reduced.
A second object of the present invention is to provide a multilayer electronic device able to reduce the ESL and able to be used as a capacitor array or composite electronic device etc.
To achieve the object, a first multilayer electronic device of the present invention is comprised of a capacitor body formed by stacking dielectric layers; a plurality of internal electrodes separated by dielectric layers inside the capacitor body, each having at least one lead led out toward any side face of the capacitor body, and differing in position of arrangement of the leads with the nearby internal electrodes; and a plurality of terminal electrodes arranged at the outside surface of the capacitor body and connected to any of the plurality of internal electrodes through the leads; wherein the internal electrodes being divided into blocks of electrode patterns of a plurality of internal electrodes adjoining each other via the dielectric layers, and the electrode patterns of the internal electrodes belonging to the different blocks being the same in the shapes of the electrode patterns, but different in rotational positions about an axis perpendicular to the planes of the electrode patterns.
As a result, when supplying a current to the multilayer electronic device, the plurality of internal electrodes of each blocks connected to the outside circuits via the leads constitute electrodes arranged in parallel while facing each other to form capacitors.
According to the first multilayer electronic device of the present invention, since the leads are led out from the internal electrodes toward the side faces of the capacitor body, positive and negative currents are supplied in opposite directions to the nearby leads to cancel the magnetic fluxes. Therefore, the parasitic inductance of the multilayer electronic device itself can be reduced and the ESL is reduced.
On the other hand, by having just a single lead be led out from the portion of the internal electrode giving the electrostatic capacity and connected to a terminal electrode, it is possible to supply current concentratedly to this single lead and to increase the electrical resistance at the lead. As a result of the increase in the electrical resistance at the lead in this way, even if ESL reduction technology is adopted for supplying positive and negative currents in opposite directions between the nearby leads and canceling out the magnetic fluxes is adopted, the ESR can be prevented from becoming overly small.
Further, according to the first multilayer electronic device of the present invention, by stacking a plurality of blocks of the same repeating electrode pattern structure changed only in rotational position, there is no longer a need to fabricate internal electrodes with different lead patterns to match the number of internal electrodes, so that the production process is simplified and the manufacturing costs reduced.
Still further, according to the first multilayer electronic device of the present invention, it is also possible to incorporate a plurality of capacitors into a single multilayer electronic device. Therefore, by reducing the number of multilayer electronic devices to be mounted in an electrical product, the manufacturing costs can be reduced and, along with the increased integration of circuits, the required space can be reduced.
In the first electronic device of the present invention, preferably the capacitor body is shaped as a hexagon and the plurality of terminal electrodes are arranged at each of at least two side faces among the four side faces of the hexagonal capacitor body.
In this case, since the capacitor body is formed in a hexagonal shape—the easiest to manufacture as a multila
Ahiko Taisuke
Honjyo Osamu
Togashi Masaaki
Dinkins Anthony
Oliff & Berridg,e PLC
TDK Corporation
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