JPS59132604A - Laminated inductor - Google Patents

Abstract

PURPOSE:To make it possible to obtain a laminated inductor which is small in size and large in inductance, by disposing a single conductor within a magnetic member such that the conductor is coiled about predetermined two points and loops of the conductor intersect with each other through the magnetic member at a position intermediate between the two points, and connecting the conductor to external electrodes. CONSTITUTION:On sheets 21 constituting a magnetic member, loops constituting a coil are formed such as to have two centers 22 and 23, thus forming a pattern in which the loops intersect each other at the center 24 of the sheets 21. The intersecting pattern is constituted by two patterns respectively formed on the sheets constituting the magnetic member composed of two layers, that is, a pattern 25 shown by the broken line and a pattern 26 shown by the solid line are formed on the respective sheets. A through hole 27 is provided such that the two patterns are connected in series. Since the thus obtained laminated inductor has closed magnetic path formed within only the two loops, it is posible to allow the chip dimensions and the coil external dimensions to be substantially equal to each other. Accordingly, it is advantageously possible to increase the magnetic path in sectional area and to obtain a large inductance with respect to a relatively small size.

Description

[Detailed description of the invention] The present invention relates to the structure of a multilayer inductor.

In recent years, due to the demand for smaller and thinner electronic devices and devices, there has been a rapid demand for smaller and thinner electronic components to be mounted. Research is being carried out on composite parts that combine these elements, rather than single elements, and are being put into practical use.

Regarding resistors and capacitors, products with standardized shapes such as chip resistors, Melf-type resistors, chip capacitors, and Melf-type ceramic capacitors are available, and composite parts are also available in resistor arrays or
They have started to be seen in electronic devices and devices that require smaller size and thinner features such as CR parts.

On the other hand, with regard to elements such as coils and transformers, there is a rapid movement towards chips due to the demand for smaller and thinner devices.

There are two types of chip coils, one of which uses a ferrite core as a magnetic core, winds a thin copper wire around the core, forms electrodes at both ends, and molds it into a chip. One is a laminated lid made by printing a pattern of conductive material on a sheet of magnetic material, which has the function of being small and thin, and has an inductance value of 0.1 to 47 μH.

It is known that the inductance of such a coil is expressed as when a closed magnetic path is formed using the magnetic core material, and it can be seen that the larger the cross-sectional area A is and the shorter the magnetic path length l, the larger the inductance.9 . For this reason, it becomes necessary to increase the diameter of the loop forming the coil and to increase the cross-sectional area within the loop forming the magnetic circuit.

However, since the shape of a chip component is required to be as small as possible, in the pattern shape shown in Figure 1, increasing the loop diameter will reduce the cross-sectional area of the magnetic circuit outside the loop, and conversely, the inductance will increase. It becomes smaller. For this reason, it is not possible to obtain efficient inductance with the inductor having the above-mentioned loop structure.

Furthermore, since the multilayer chip inductor having such a structure has a stacked conductor pattern 11, it has a large line capacitance.

Such line capacitance Co is expressed by Furthermore, the thickness t between the lines must be increased.

However, when the pattern width is made smaller, the conductor resistance increases, and usable circuits are limited. moreover,
In order to increase the thickness between the lines, the thickness of the sheet forming the pattern must be increased, or a dummy insulating sheet must be inserted. Therefore, the chip shape becomes thick in the thickness direction.

An object of the present invention is to eliminate these drawbacks and provide a structure that can obtain a large inductance by taking advantage of its small size and small line capacitance.

That is, the present invention provides a laminated inductor in which a magnetic material and a conductive material are laminated, in which one conductive material orbits around two predetermined points within the magnetic material, and
The conductors are arranged so as to intersect with each other through the magnetic material at a midpoint between the points, and both ends of the conductive material are connected to two external electrodes formed on different surface portions of the magnetic material. This is a multilayer inductor with special features.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

The magnetic material used in the examples of the present invention is Fe2o.

50 parts by weight, 20 parts by weight of NiO, 24 parts by weight of Zn0, C
CVt0. The raw material was powder that was mixed in a ball mill using a composition in which 0.5 parts by weight of . This magnetic material and polyvinyl butyral as an organic binder,
Ethyl cellosolve and butyl calpitol as organic solvents, and ethylene glycol mobutyl ether as a plasticizer are stirred and mixed using a homomixer to form a slurry. Next, the slurry was applied onto an organic film with a thickness of 50 μm to 50 μm using a slip casting method using a doctor blade.
A film with a thickness of 200 μm is formed. The magnetic green sheet formed on the organic film is peeled from the film and then punched into a shape of 100 x 70 m to form a magnetic green sheet used for the chip L.

FIG. 2 is a diagram of a coil pattern showing one embodiment of the present invention, in which a sheet 21 forming a magnetic material is formed with a loop forming a coil having two centers 22 and 23; The pattern intersects at the center 24 of the sheet 21.

This intersecting pattern is divided into sheets forming two layers of the magnetic material, and a pattern 25 shown by a broken line and a pattern 26 shown by a solid line in the figure are formed on separate sheets. A through hole 27 is provided so that these two patterns are connected in series.

FIG. 3 shows the lamination relationship showing an example of a multilayer structure.

The sheet 31 of each layer in the figure shows the two stacked sheets shown in FIG. It is formed of two patterns 33 that go inside, and these are stacked alternately, and furthermore, a sheet 35 for holding the extraction terminal 34 and a dummy sheet 36 for holding the suppurative reservoir on the upper and lower surfaces are formed. Laminate pressing at a temperature of 130°C and a pressure of 200 to 300°C, cutting process and debinding process to 950°C to 1050°C in diameter.
A multilayer inductor is obtained by firing the inductor.

FIG. 4 is a perspective view of the appearance of the multilayer inductor of the present invention obtained in FIG. 3, in which external electrodes 41 are formed at both ends of the chip for connection to the lead-out terminals.

FIG. 5 is a cross-sectional view of the sintered body of the present invention taken through the two centers 22 and 23 in FIG. 2.

The coil pattern starts from one external electrode 50, and is connected to the subscripts 1 to 38 of each cross-sectional conductor.
8 is connected to the other external electrode 51.

Therefore, the magnetic field in the loop on the left side of the center and the magnetic field in the loop on the right side are in opposite directions, and the magnetic field in loop 5
2, a closed magnetic path can be obtained only between the two loops.

As described above, since the multilayer inductor of the present invention has a closed magnetic path only within the two loops, the dimensions of the chip and the external dimensions of the coil can be made almost the same, and the cross-sectional area of the magnetic path can be increased. Therefore, the conventional disadvantage of reduced dimensional efficiency caused by the chip shape and the cross-sectional area of the magnetic path is eliminated, and the advantage of having a large inductance relative to the shape is obtained.

Furthermore, since a plurality of turns are formed on one sheet, a dummy sheet can be placed, compared to an inductor obtained with a conventional one-turn configuration, resulting in an inductor with much smaller line capacitance.

In this example, the chip size is 4 m x 8111, the conductor pattern width is 100 μm, and the conductor pattern width is 100 μm, tm interval is 100/jm, and one sheet has 3 turns, and the inside dimensions of the turns are 6.6 x 1.05.
Formed with i++o, 9, 2 layers of sheets total 1
It has a structure in which 0 sets are laminated and there are 60 effective turns.

A chip inductor constructed in this way and fired at 1050o has μ: 250 (IIG(z) and L=
An inductance of 9 μH was obtained, which is about four times that of the conventional inductance.

On the other hand, since the inter-line capacitance can be distributed as a plurality of turns on one sheet, its value can be reduced, resulting in better high-frequency characteristics.

In the embodiment of the present invention, the coil pattern is obtained by through-hole connection near the center intersection, but the through-holes may be located at any point on the sheet, and the number of turns of the coil on the sheet may be Since the number of turns is also limited by the dimensions of the sheet, it is obvious that the number of turns can be designed so as to obtain the desired inductance.

Also, in this example, the sheet shape is rectangular, but
If two intersecting loops can exist on one sheet, the sheet shape is not limited, and by increasing the length in the intersecting direction, a pattern with a shorter magnetic path length can be obtained. It is clear that efficiency increases.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of a conventional multilayer chip inductor, FIG. 2 is a coil pattern diagram of the present invention, and FIG. 3 is a diagram showing an example of the configuration of a multilayer inductor of the present invention when multilayered. FIG. 4 is an external view of a laminated and sintered multilayer inductor of the present invention, and FIG. 5 is a central sectional view of the multilayer inductor of the present invention. In the figure, 11... Conductor pattern 21... Sheet forming a magnetic material. 22 and 23...center of coil pattern. 24... Center of sheet, 25... Hap of first layer -
7. 26...Second layer pattern. 31...Sheet made by combining the first layer and the second layer. 32...A pattern that goes from inside to outside. 33...A pattern that enters from the outside to the inside. 34... Takeout terminal, 35... Sheet forming magnetic material, 36... Dummy sheet. 41...External electrode. 50...One external electrode, 51...Another external electrode, 52...Magnetic field loop Representative Patent Attorney Susumu Uchihara 1st issue Fig. 2 22 23 Fig. 5

Claims (1)

[Claims] An inductor formed by laminating a magnetic material and a conductive material, in which one conductive material orbits around two predetermined points within the magnetic material, and the magnetic material is placed at a position midway between the two points. A multilayer inductor characterized in that the conductors are arranged so as to intersect with each other, and both ends of the conductor are respectively connected to two external electrodes formed on different surface portions of the magnetic body.