JPH0493006A - Laminated beads inductor - Google Patents

Abstract

PURPOSE:To use mainly for noise suppression with small size and high impedance by winding conductor layers by a turn or more per layer and by making a magnetic material layer twice or more as thick as the conductor layer. CONSTITUTION:Conductor layers 3 are wound by a turn or more per layer. Too much winding turns per layer make it difficult to form patterns and do not allow miniaturization. Thus, it is preferable that the winding turns per layer are l-2.5 turns, particularly, 1-1.5 turns. The post-burning thickness of a magnetic material layer 2 is preferably twice or below that of the conductor layer 3. Ranging the thickness of the magnetic material layer 2 within this range can provide much higher impedance. It is preferable that the thickness of the magnetic material layer 2 is 0.5-2 times that of the conductor layer 3, particularly, 0.5-1.5 times.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a laminated bead inductor in which a magnetic layer and a conductive layer are laminated by thick film technology.

<Prior Art> In order to suppress noise in various electronic circuits, bead cores made of a magnetic material such as ferrite or an amorphous magnetic alloy are used.

There are various types of conventional bead cores, including those manufactured by winding a thin plate of magnetic material, that is, single cores with a small toroidal bead shape, forming types with wires, and axial and radial taping types. do.

Some of these are used by being attached directly to the leads of electronic components or electrically connected to circuits. The need for taping for automatic mounting and leadless for surface mounting is rapidly increasing.

On the other hand, surface-mountable multilayer inductors used as ordinary coils, LC composite parts, etc. have been put into practical use.

A multilayer inductor is manufactured by alternately stacking magnetic layers and conductive layers of less than one turn using thick film technology, and then firing the layers.

<Problems to be Solved by the Invention> Under these circumstances, the present inventors are conducting research on using a multilayer inductor as a bead core for noise suppression.

However, in order to use a multilayer inductor as a bead core for noise suppression, the impedance decreases as the element becomes smaller.
Impedance at about MHz is insufficient.

Furthermore, increasing the number of laminated layers in order to increase impedance increases the number of manufacturing steps, increases cost, and is extremely disadvantageous in terms of mass production.

An object of the present invention is to provide a small, high-impedance multilayer bead inductor that is mainly used for noise suppression.

<Means for Solving the Problems> The above objects are achieved by the following inventions (1) to (5).

(1) A multilayer bead inductor in which a magnetic layer and a conductive layer are laminated by thick film technology, wherein the conductive layer has a number of turns of one turn or more per layer, and a pair of adjacent conductive layers A multilayer bead inductor characterized in that a through hole is formed in the magnetic layer between the body layers, and the ends of the pair of adjacent conductive layers are electrically connected through the through hole.

(2) The multilayer bead inductor according to (1) above, wherein the thickness of the magnetic layer is twice or less the thickness of the conductive layer.

(3) The laminated bead inductor according to (1) or (2) above, wherein the number of laminated conductor layers is two.

(4) The multilayer bead inductor according to any one of (1) to 3), wherein the through hole is wider than the width of the end portions of the pair of adjacent conductor layers.

(5) Among the pair of adjacent conductor layers, one conductor layer is located above at least a portion of the other conductor layer, and when projected in the thickness direction, the one conductor layer is located above at least a portion of the other conductor layer. The multilayer bead inductor according to any one of ( ]) to (4) above, which has non-overlapping portions.

<Function> In the multilayer bead inductor of the present invention, one or more conductive layers are formed per layer.

Therefore, compared to a multilayer bead inductor with the same number of laminated layers in which the number of turns per conductor layer is less than one turn, a higher impedance can be obtained at the operating frequency, for example, 50 to 300 MHz.

In addition, high impedance can be obtained without increasing the number of laminated layers, which is very advantageous for mass production.

<Specific configuration> Hereinafter, the specific configuration of the present invention will be explained in detail.

1, 2, and 3 show preferred examples of the multilayer bead inductor of the present invention.

FIG. 1 is a cross-sectional view of a multilayer bead inductor, and the second
The figure is a sectional view taken along II-II' in FIG. 1, and FIG. 3 is a sectional view taken along III-Ill' in FIG.

A multilayer bead inductor 1 includes a chip body 10 configured by alternately laminating magnetic layers 2 and conductive layers 3.
has.

The conductive layer 3 is formed in a pattern, and adjacent conductive layers 3 are electrically connected to each other as shown in FIG. 1, thereby forming a coil.

Further, on the surface of this chip body 10, an external electrode 5 that is electrically connected to the conductor layer 3 is provided.

In the present invention, the number of turns of the conductor layer 3 is set to one or more turns per half.

If it is less than one turn, the impedance is insufficient.

However, if the number of turns per layer is too large, it will be difficult to form a pattern, and furthermore, it will not be suitable for miniaturization.

Therefore, the number of turns per layer is 1 to 2.5 turns,
In particular, it is preferably 1 to 1.5 turns.

In addition, in order to make the number of windings per layer 1 turn or more, the conductor layers 3 should not be in contact with each other in the same plane.
The spiral arrangement is such that, for example, 1.25 turns means that one of the inner circumferential ring and the outer circumferential ring is present four times in one layer of the other.

Although there is no particular restriction on the winding pattern, it is preferable to use a rectangular shape as shown in FIGS. 2 and 3 from the viewpoint of chip shape and high impedance.

There are no particular restrictions on the dimensions of the conductor layer 3, and it usually has a thickness of 5 to 5.
The line width of the pattern may be about 100 to 350 houses.

The number of laminated conductor layers 3 is determined in such a way that it does not increase the manufacturing process.
Preferably, there are two layers.

However, three or more layers may be used as necessary.

Note that the pattern shape, dimensions, etc. of the conductor layer 3 may be the same or may differ from layer to layer.

As shown in FIG. 1, the ends 31 and 33 of a pair of adjacent conductor layers 3.3 are connected to each other through a through hole formed in the magnetic layer 2 between the conductor layers 3.3. They are conductive to each other.

Note that since FIG. 1 is a completed diagram, the through holes in the magnetic layer are filled with the conductive layer and the uppermost magnetic layer.

Further, in the present invention, it is preferable that the patterns of a pair of adjacent conductor layers 3.3 are shifted from each other.

That is, a pair of adjacent conductor layers 3.3 are surrounded by the areas a, b, c, and d in FIG. 2 and the points e, f, g, and h in FIG. 3. It is preferable that the pattern is formed such that when the regions are projected in the thickness direction of the conductor layer 3, there are portions that do not overlap with each other.

In this case, in the illustrated example, the pattern of the conductive layer 3 is shifted in the direction of the gap between the external electrodes 5.5, and a portion where the projections do not overlap exists in the direction of the gap between the external electrodes 5.5. , or in addition to this, there may be a shift in a direction perpendicular to the gap, and a portion where the projections do not overlap may exist in a direction perpendicular to the gap.

Since the patterns are shifted from each other, stray capacitance is reduced and high frequency characteristics are further improved.

The length of the mutually shifted portions of the conductor layers 3 in the longitudinal direction may be 20 to 100% of the length of one conductor layer 3 located above the other conductor layer 3. .

Further, it is preferable that the amount of deviation between the mutually deviated portions, that is, the gap between the conductive layers 3, be about 20 to 40% of the distance between the conductive layers 1.

As the material for the conductor layer 3, any conventionally known conductor layer material can be used.

For example, Ag, Cu, Pd, or an alloy thereof may be used, and among these, Ag or an Ag alloy, particularly Ag, is preferable.

Ag alloys include Ag-P containing 70% by weight or more of Ag;
d alloy etc. are suitable.

Such a conductive layer 3 is formed by applying a conductive layer paste and then firing it as described later.

As the material for the magnetic layer 2 of the multilayer bead inductor 1, any conventionally known magnetic layer material can be used. For example, various spinel soft ferrites having a spinel structure can be used, but it is preferable to use Ni-based ferrite, particularly Ni-Cu-Zn ferrite, due to the firing temperature.

Ni-Cu-Zn ferrite is a low temperature firing material,
In addition, since it is a good insulator, when such a magnetic layer is used, the multilayer bead inductor of the present invention has a 900
Suitable for firing at temperatures below about ℃ and provides excellent properties.

Examples of Ni-based ferrite include Ni ferrite, N 1-
Cu ferrite, Ni-Zn ferrite, Ni-Cu-
Examples include Zn ferrite.

In this case, the Ni content is 45 to 5 in terms of NiO.
5mo1% is preferable, and a part of this Ni is Cu and/or
Alternatively, Zn may be substituted in an amount of about 40 mo1% or less.

Such a ferrite-based magnetic layer 2 is made of a conductive layer paste described below at a temperature of 800~], OO0°C, especially 850°C.
It can be formed by simultaneous firing at a firing temperature of ~950°C.

As shown in FIGS. 5 and 6, a through hole 4 is formed in the magnetic layer 2 between a pair of adjacent conductive layers 3. , conductor layer 3
and conductor layer 3 are electrically connected.

The position of the through hole 4 is opposite the ends 31 and 33 of the conductor layer 3, and both conductor layers 3.3 are normally wound from the outer circumference to the inner circumference, and the ends 31.33 are wound inside. In the illustrated example, it is formed almost at the center of the magnetic layer 2.

The shape and dimensions of the through hole 4 are not particularly limited, and may be appropriately selected depending on the purpose, use, etc.

For example, when the through-hole 4 has a size that is approximately the same as or smaller than the line width of the pattern of the conductor layer 3, the green sheet method is usually used, and the end portion 31 of the conductor layer 3 is and 33 are closer to the through hole 4, so that both conductor layers 3.3 are electrically connected through the through hole 4 even if their positions are slightly shifted during lamination.

More preferably, the pattern of the conductive layer 3 is formed to have approximately the same width up to the end, and the through hole 4 is formed wider than the width of each end 31 and 33 in a region that includes the ends 31 and 33. do.

With this configuration, it is possible to prevent misalignment between the conductor layer 3 and the through hole 4 during lamination, and in addition, the end portion l of the conductor layer 3 can be made small, which is useful when downsizing the inductor. Even if the conductive layer is finely patterned, short circuits can be prevented.

Note that the maximum width of the through hole 4 in the 11 directions of the conductor layer 3 is preferably about 1.5 to 2.5 times the width of the conductor layer 3.

Moreover, when the external shape of the cross section of the through hole 4 is made circular, its diameter should normally be about 100 to 500 units.

Although there is no particular restriction on the thickness of the magnetic layer 2 after firing, it is preferably at most twice the thickness of the conductive layer 3.

When the thickness of the magnetic layer 2 is within the above range, even higher impedance can be obtained.

However, if it is too thin, the conductor layer 3 will be electrically conductive, so the thickness of the magnetic layer 2 should be 0.5 of the thickness of the conductor layer 3.
~2 times, especially 0.5~], preferably 5 times.

Note that the thickness of the magnetic layer 2 may normally be about 8 to 40 μm.

There are no particular restrictions on the external shape or dimensions of the chip body 10 having such a configuration, and they may be selected as appropriate depending on the application, etc., but usually the external shape is approximately rectangular parallelepiped, and the dimensions are 1.6 to 1.6 mm in length.
Approximately 3.2mm, 1]08~1.6mm, thickness 0.
It may be about 8 to 1.2 mm.

There are no particular restrictions on the material of the external electrodes 5.5 (various conductive materials, such as printed films, plating films, vapor deposited films, etc. of Ag, Ni, Cu, etc. or alloys thereof such as Ag-Pd, etc.). Any of an ion blating film, a sputtered film, or a laminated film thereof can be used.

The thickness of the external electrode 5.5 is arbitrary and may be appropriately determined depending on the purpose and use, but is usually about 50 to 200p.

The multilayer bead inductor of the present invention is used for suppressing noise in various electronic circuits.

The frequency used is about 50 to 300 M)Iz, especially 10
Approximately 0 MHz is preferable.

In the present invention, even if the inductor is miniaturized as described above, the frequency is 100 MI (at z, the impedance is 150 to 35
A resistance of about 0Ω can be achieved.

Next, a method for manufacturing the laminated bead inductor of the present invention will be described.

First, a magnetic layer paste, a conductive layer paste, and an external electrode paste are manufactured.

The paste for the magnetic layer, the paste for the conductor layer, and the paste for the external electrode may be each manufactured by a conventional method.

For example, in order to manufacture a ferrite paste as a paste for a magnetic layer, a predetermined amount of Ni01ZnO, Cub, F
Ferrite raw material powder such as e20a is wet mixed using a ball mill or the like.

The average particle size of each raw material powder used is usually about 0.1 to 10 particles.

] 5 The wet-mixed mixture is usually dried using a spray dryer or the like, and then calcined. This is usually
Wet pulverization is performed using a ball mill or the like until the average particle size becomes approximately 0.01 to 0.1 units, and then dried using a spray dryer or the like.

The obtained mixed ferrite powder, a binder such as ethylcellulose or acrylic resin, and a solvent such as terpineol or butylcarpitol are mixed and kneaded using, for example, three rolls to form a paste (slurry).

In this case, various glasses and oxides can be contained in the paste.

In addition to ferrite powder, various magnetic particles can also be used.

A paste for a conductive layer usually contains conductive particles, a binder, and a solvent.

The material of the conductive particles is not particularly limited as long as it is conventionally used in pastes for conductive layers, and metals, metal oxides, and other materials that become metal after firing may be used.

In this case, the metal component is Ag, Cu, Pd, etc.
Single metals containing more than one species or alloys thereof are preferred.

In particular, Ag, Ag alloys, and oxides thereof are suitable.

Note that the shape of the conductive particles is not particularly limited, but a spherical shape is preferred.

In addition, the average particle size of the conductive particles is usually 0.1 to 0.5
− degree.

As the binder, any known binder can be used, such as ethyl cellulose, acrylic resin, butyral resin, and the like.

Further, the binder content is usually about 0 to 5% by weight.

As the solvent, any known solvent can be used, such as terpineol, butylcarpitol, kerosene, and the like.

The solvent content is usually about 20 to 55% by weight. In addition, if necessary, within a total amount of about 10% by weight or less,
Dispersants such as sorbitan fatty acid ester and glycerin fatty acid ester, plasticizers such as dibutyl phthalate, dibutyl phthalate, butyl phthalyl glycolate,
For the purpose of preventing delamination, suppressing sintering, etc., various ceramic powders such as dielectric materials, magnetic materials, and insulators can be added.

These compositions are mixed and kneaded using, for example, three rolls to form a paste (slurry).

There are no particular restrictions on the paste for external electrodes, and Ag, Ag alloy, etc., are used in the same manner as the conductor material described above, and the paste is 2 to 10% by weight.
A paste containing a certain amount of glass may be used.

Such a paste for a magnetic layer and a paste for a conductive layer are laminated by a printing method, a transfer method, a green sheet method, or the like.

For example, in the case of the printing method, as shown in FIG. 4, first a coating film 20 of paste for a magnetic layer is formed, and a coating film 30 of a paste for a conductive layer in a predetermined pattern is formed thereon. .

Next, when forming the coating film 20 of the paste for the magnetic layer on this, as shown in FIG. A through hole 4 is formed.

Next, as shown in FIG. 6, a coating film 30 of the conductive layer paste is formed in a predetermined pattern, and the pair of adjacent coating films 30 of the conductive layer paste are electrically connected.

Then, as shown in FIG. 7, a coating film 20 of a magnetic layer paste is formed, the laminate is cut into a predetermined size, and then fired.

Note that, if necessary, the magnetic layer may be formed by a green sheet method.

The firing conditions and firing atmosphere may be appropriately determined depending on the material and the like, but are usually as follows.

Firing temperature: 2850 to 950°C Firing time: 20.5 to 5 hours The firing atmosphere should be a non-oxidizing atmosphere when Cu, Ni, etc. are used for the conductor layer, and in addition, Ag, Pd, etc. In some cases, it may be used in the atmosphere.

The end face of the thus obtained chip body 10 is polished by, for example, barrel polishing or sandblasting, and an external electrode paste is baked to form external electrodes 5.5.

Then, if necessary, a pad layer is formed by plating or the like on the external electrodes 5.5.

<Example> Hereinafter, the present invention will be explained in further detail by giving specific examples of the present invention.

Example 1 Spherical Ag particles having an average particle diameter of 0.2 μm and predetermined amounts of butyl carbitol, terpineol, and ethyl cellulose were kneaded using three rolls to form a slurry to prepare a paste for a conductive layer.

Next, NjOlCub, ZnO, and Few Oa powders with a particle size of about 0.1 to 1,000 were used as ferrite raw materials and wet mixed using a ball mill. The powder was dried and calcined at 750°C to form granules, which were ground in a ball mill and dried in a spray dryer to obtain powder with an average particle size of 0.1-.

Next, this powder was dissolved in terpineol along with a predetermined amount of ethyl cellulose and mixed in a Henschel mixer to prepare a paste for a magnetic layer of Nj-Cu-Zn ferrite.

Laminated bead inductor samples No. 1 (present invention) and No. 2 shown in FIGS. 1 to 3 were prepared using the obtained conductive layer pastes and magnetic layer pastes by a printing lamination method. (the present invention) was manufactured.

In this case, the firing temperature was 900°C, the firing time was 2 hours, and the firing atmosphere was air.

The number of laminated conductor layers is two, and each conductor layer is
As shown in FIGS. 2 and 3, a rectangular pattern with one or more winding turns (approximately 1.25 turns) was formed, and the layers were laminated with a slight offset from each other.

In addition, the thickness of the conductive layer is 20 μm, the line width of the pattern is 200-, and the thickness of the magnetic layer is No. 1 to 12.
11m, No. 2 was set to 25 μm.

Note that the cross section of the through hole in the magnetic layer was circular with a diameter of 400 tones.

The external electrodes were made of Ag-Pd paste.

The dimensions of the obtained multilayer bead inductor were 2.0 mm.
X 1.2m Xo, 8mm.

Also, is the number of turns per N1 layer of conductor less than 1 turn? @(
Comparative samples No. 3 were produced in the same manner, except that the magnetic material layer had a thickness of about 0.75 turns) and the thickness of the magnetic layer was 12 pm.

For each sample, frequency 50 MHz, 100 MHz
The impedance was measured at z and 300 MHz.

The results are shown in Table 1.

Table 1 No.

0MHz 100MHz 100MHz 1 (present invention) 2 (present invention) 3 (comparison) The effects of the present invention are clear from the results shown in Table 1.

In addition, when samples were manufactured with different materials, dimensions, etc., similar effects were obtained.

<Effects of the Invention> The multilayer bead inductor of the present invention can obtain high impedance with a small number of laminated layers.

Therefore, production costs are reduced and production efficiency is improved, which is extremely advantageous for mass production.

The operating frequency is about 50 to 300 MHz, especially 1
Noise can be effectively removed at approximately 0.00 MHz.

In addition, in the present invention, when using a printing method, by forming the conductive layer conduction through holes in the magnetic layer to be wider than the line width of the pattern of the conductive layer, even if the inductor is miniaturized, the conductive layer can be Can prevent short circuits.

As a result, the production yield when downsizing the inductor is significantly improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of the multilayer bead inductor of the present invention. 2 is a cross-sectional view at TI-II'' in FIG. 1. FIG. 3 is a cross-sectional view at TIT-II+' in FIG. 1. It is a top view for explaining the manufacturing method of the laminated bead inductor of the invention. Explanation of symbols 1...Laminated bead inductor 10...Chip body 2...Magnetic layer 20...Magnetic layer Coating film of paste for conductor layer 3... Conductor layer 30... Coating film of paste for conductor layer 31, 33... End portion 4... Through hole 5... External electrode patent applicant T.D.K. Co., Ltd. Agent Patent Attorney Hikaru Ishii Patent Attorney
Increase 1) Tatsuya Fl G, 4 FIG, 5 FIG, 6 G, A Specification November 8, 1991

Claims (5)

[Claims] (1) A multilayer bead inductor in which a magnetic layer and a conductive layer are laminated by thick film technology, wherein the conductive layer has a number of turns of one turn or more per layer, and a pair of adjacent conductive layers A multilayer bead inductor characterized in that a through hole is formed in the magnetic layer between the body layers, and the ends of the pair of adjacent conductive layers are electrically connected through the through hole. (2) The multilayer bead inductor according to claim 1, wherein the thickness of the magnetic layer is twice or less the thickness of the conductive layer. (3) The multilayer bead inductor according to claim 1 or 2, wherein the number of laminated conductor layers is two. (4) The multilayer bead inductor according to any one of claims 1 to 3, wherein the through hole is wider than the width of the end portions of the pair of adjacent conductor layers. (5) Among the pair of adjacent conductor layers, one conductor layer is located above at least a portion of the other conductor layer, and when projected in the thickness direction, the at least one conductor layer is located above the other conductor layer. The multilayer bead inductor according to any one of claims 1 to 4, having non-overlapping portions.