US 5,051,712 AGranted

LC filter

AssigneeMurata Manufacturing Co., Ltd.

InventorsYasuyuki Naito, Takeshi Azumi, Horishi Morii, Yoshiaki Kohno

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Abstract

A laminated chip-type LC filter for use as a noise filter is obtained by carrying out the following steps: dielectric layers are laminated on the top and bottom of a magnetic material layer, forming an inductor portion by providing conductive lines inside the magnetic material layer and forming capacitors by providing at least two layers of parallel internal electrodes inside both of the dielectric layers. External electrodes are provided at both ends of the inductor portion. Intermediate external electrodes are provided at both lateral sides in the middle part of the dielectric layers and the magnetic layer. The inductor portion is connected to the external electrodes. The internal electrodes are connected to the intermediate external electrodes and to the external electrodes, respectively. By making the intermediate external electrode the ground, the internal electrodes are grounded so that stray capacitance does not arise between the internal electrodes thus causing less deterioration of the insertion loss characteristic in the high-frequency area.

Claims5

Dependent claims

A .pi.-type LC filter comprising:

a laminate of a middle layer of magnetic material, an upper layer of dielectric material disposed over an upper surface of said middle layer, and a lower layer of dielectric material disposed over a lower surface of said middle layer opposite said upper surface thereof,
the laminate constituting a filter body having opposite ends and opposite sides extending between said ends;
external end electrodes disposed over the ends of said filter body, respectively;
at least one external intermediate electrode disposed over a portion of said filter body intermediate said ends thereof;
at least one line of electrically conductive material extending within said layer of magnetic material and electrically connected to said external end electrodes, whereby said layer of magnetic material and said at least one line of electrically conductive material extending therein form an inductor of the .pi.-type LC filter;
a first pair of capacitor electrodes extending within said upper layer of dielectric material parallel to one another, one of the electrodes of said first pair being remote from said layer of magnetic material and electrically connected to one of said external end electrodes, and the other of the electrodes of said first pair being disposed adjacent said layer of magnetic material and electrically connected to said at least one external intermediate electrode, whereby said first pair of capacitor electrodes and said upper layer of dielectric material form a capacitor of the .pi.-type LC filter;
and
a second pair of capacitor electrodes extending within said lower layer of dielectric material parallel to one another, one of the electrodes of said second pair being remote from said layer of magnetic material and electrically connected to the other of said external end electrodes, and the other of the electrodes of said second pair being adjacent said layer of magnetic material and electrically connected to said at least one external intermediate electrode, whereby said second pairs of capacitor electrodes and said lower layer of dielectric material form another capacitor of the .pi.-type LC filter.

5 more elements

A method of manufacturing a .pi.-type LC filter, said method comprising the steps of:

providing a layer of magnetic material;
laminating an upper layer of dielectric material over an upper surface of the layer of magnetic material and a lower layer of dielectric material over a lower surface of the layer of magnetic material opposite said upper surface, to form a laminated filter body having opposite ends and opposite sides extending between said ends;
disposing external end electrodes over the ends of the filter body, respectively;
disposing at least one external intermediate electrode over a portion of the filter body intermediate the ends thereof;
forming at least one line of electrically conductive material within the layer of magnetic material, and electrically connecting the at least one line of electrically conductive material to the external end electrodes, so as to form an inductor of the .pi.-type LC filter;
forming a first pair of capacitor electrodes within the upper layer of dielectric material so as to extend parallel to one another with one of the electrodes of said first pair being remote from the layer of magnetic material and the other of the electrodes of said first pair being adjacent the layer of magnetic material, electrically connecting said one of the electrodes of said first pair to one of the external end electrodes, and electrically connecting said other of the electrodes of said first pair to the at least one external intermediate electrode, so as to form a capacitor of the .pi.-type LC filter;
and
forming a second pair of capacitor electrodes within the lower layer of dielectric material so as to extend parallel to one another with one of the electrodes of said second pair being remote from the layer of magnetic material and the other of the electrodes of said second pair being adjacent the layer of magnetic material, electrically connecting said one of the electrodes of said second pair to the other of the external end electrodes, and electrically connecting said other of the electrodes of said second pair to the at least one external intermediate electrode, so as to form another capacitor of the .pi.-type LC filter.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/497,078Filed 21 Mar 1990
Priority: JP 1-7357023 Mar 1989
Granted: 24 Sep 1991
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

H01G 4/40
Fixed capacitors; Processes of their manufacture: structural combinations of fixed capacitors with other electric elements, the structure mainly…
H01F 17/0013
Printed inductances: with stacked layers
H01F 17/04
Fixed inductances of the signal type: with magnetic core
H03H 1/0007
Constructional details of impedance networks whose electrical mode of operation is not specified or applicable to more than one type of network:…