JPH07320936A - Laminated chip inductor - Google Patents

Abstract

PURPOSE:To avoid the generation of a stress due to a step and to make thick the internal electrodes of a laminated chip inductor by a method wherein one spiral conductor drawing a spiral in the direction parallel to a ferrite sheet is formed along with upper conductor wires and lower conductor wires and moreover, terminal electrodes, which are connected with the spiral conductor, are respectively provided on both end surfaces of an integrally calcined laminated material. CONSTITUTION:A laminated chip inductor 30 is constituted into a structure wherein lateral upper conductor wires 25a and lateral lower conductor wires 25b, which are parallel to a ferrite sheet printed with slits filled with a conductor paste, are formed, a ferrite sheet printed with through holes filled with a conductor paste is superposed on the middle layer of a laminated material to form vertical conductor wires 25c and 25d (A showing of the 25d in the diagram is omitted.), one spiral conductor 25 drawing a spiral in the direction parallel to the ferrite sheet is formed in the interior of a magnetic material along with the conductor wires 25a and 25b and moreover, terminal electrodes 23 and 24, which are respectively connected with both point parts 25e and 25f of the spiral conductor 25, are respectively provided on both end surfaces of the integrally calcined laminated material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a laminated chip inductor, and more particularly to a laminated chip inductor having a structure in which a direct current resistance of an internal conductor is reduced and a stress between a conductor and a ferrite sheet is reduced.

[0002]

2. Description of the Related Art In recent years, there has been a strong consumer demand for miniaturization and high performance of electronic devices, and along with this, inductors that occupy a relatively large volume in electronic components mounted on electronic circuit boards are being miniaturized. So-called chip inductors suitable for mounting automation have been developed.

The above-mentioned chip inductors are roughly classified into winding type and printing type according to the manufacturing method of the winding, and the winding type is further classified into an air core and a magnetic core (ferrite core) depending on the type of winding core. The latter is divided into a bare linear type, a resin mold type, and a magnetic shield type depending on the product form.

On the other hand, the printed type is a closed magnetic circuit type magnetic shield type using a laminated ferrite sheet (a plate-like sheet obtained by mixing a ferrite magnetic powder with a resin and kneading the resin) as a winding core, and is shown in FIG. As shown in FIG. 6, the internal electrode 2 spirally formed in the vertical direction is sealed with the ferrite resin 1 and the terminal electrodes 4 are provided at both ends.
As described above, the ferrite sheet corresponding to the magnetic core and the conductor paste corresponding to the winding (which becomes the internal electrode) are alternately laminated by the printing method and laminated, and simultaneously fired.

That is, (a) first, (b) the first conductor paste 7 is printed on the underlying ferrite sheet 6,
(C) 1/2 ferrite sheet 8 is laminated, (d) second 1/2 conductor paste 9 is printed, (e) 1/2 ferrite sheet 10 is laminated, (f) last conductor paste 1
1 is printed, (g) the upper ferrite sheet 12 is laminated, (h) the laminated body is fired, and (i) finally, the terminal electrodes 4 are formed on the exposed end faces of the conductor pastes 7 and 11 and completed. Yes (when the number of turns is 1).

The multilayer chip inductor described above has a space factor of 100% with no space between the winding and the magnetic core and has a space factor of 100% as compared with the conventional method of winding the coil around the bobbin and mounting the magnetic core. Is possible.

Further, since this multilayer chip inductor is a shield type with a completely closed magnetic circuit, it has the advantage that there is no influence of leakage inductance and the degree of freedom in board layout is high.

On the other hand, Japanese Unexamined Patent Publication No. 253906/1989 discloses a chip inductor of a type in which a metal coil is embedded in a resin mold in which magnetic powder is mixed. Disclosed is a method for manufacturing a chip inductor of a type in which a spiral conductor is confined in a resin mold and fired by extruding a body (ferrite) paste and simultaneously extruding a conductor paste in a thin spiral shape inside the magnetic paste. ing.

[0009]

However, since the conventional laminated chip inductor has a structure in which the conductor paste is transversely printed on the stepped portion 13 of the ferrite sheet, stress is easily applied to the stepped portion, and in order to avoid this, a conductor is applied. If the paste is thinned, the DC resistance of the conductor will increase, and conversely, if conductors are overprinted to increase the current capacity, stress will be applied and the current limiting effect of the inductor such as noise removal will decrease. It was

Further, if the number of windings of the internal electrode is increased, the number of laminated layers increases, the number of manufacturing steps increases, and the manufacturing cost increases.

On the other hand, a chip inductor of the type in which a metal coil is embedded in a resin mold mixed with the magnetic powder is difficult to miniaturize as compared with the laminated type, and the number of coil turns is limited, so that a sufficient inductance is required if necessary. However, it is basically the same structure as the magnetic shield type chip inductor, and is not an improvement of the laminated type chip inductor.

Also, the chip inductor of the type in which the internal electrodes are spirally sealed inside the magnetic body by the above-mentioned extrusion molding and fired is not the laminated type, but the existing metal coil is sealed as compared with the above chip inductor. It is very similar only to the difference between stopping or embedding a conductor paste and co-firing.

Therefore, in addition to the above-mentioned problems pointed out, there is a question of whether an appropriate spiral conductor can be obtained by the above-mentioned extrusion molding method, and a special manufacturing apparatus is required. Remains.

The present invention has been made in view of the above circumstances, and has an internal electrode structure in which one spiral conductor that draws a spiral in a direction parallel to the laminated ferrite sheet is formed, and stress due to a step is avoided, and the internal electrode is formed. It is intended to provide a laminated chip inductor having a structure capable of increasing the thickness.

[0015]

According to the present invention, plate-like ferrite sheets obtained by mixing and kneading a resin with ferrite magnetic powder are laminated on top and bottom to form a closed magnetic circuit, and a spiral conductor is sealed inside and fired. In the laminated chip inductor having a structure in which a terminal electrode connected to the spiral conductor is provided on the end face, a plurality of slits parallel to the upper and lower ferrite sheets are provided, and a conductor paste is embedded and printed in the slits to form a sheet. Parallel upper and lower conductor wires are formed in the horizontal direction, and through holes are provided in the middle layer at positions located at both ends of each slit in the upper and lower ferrite sheets, and a conductor paste is embedded in the through holes. By stacking multiple printed ferrite sheets to form vertical conductor wires,
A single spiral conductor that draws a spiral in a direction parallel to the ferrite sheet is formed together with the upper conductor wire and the lower conductor wire, and terminal electrodes connected to the spiral conductor are provided on both end faces of the integrally fired laminate. The above object is achieved by providing a characteristic multilayer chip inductor.

[0016]

In the multilayer chip inductor according to the present invention, (1) a plurality of parallel slits provided in the upper and lower ferrite sheets are each provided with a conductor paste which becomes an upper conductor line and a lower conductor line in the lateral direction. It is embedded and printed,
The thickness of the internal electrode portion can be freely set by adjusting the thickness of the ferrite sheet, adjusting the slit width, or overlapping.

(2) Similarly, the thickness of the vertical conductor wire can be freely set by adjusting the size of the hole of the through hole of the ferrite sheet of the middle layer. Therefore, the direct current resistance can be reduced.

(3) The through-holes in the middle layer portion are overlapped with each other to form a conductor wire in the vertical direction having a thickness equal to the thickness of all ferrite sheets in the middle layer portion by means of the conductor paste which is embedded and printed.
In addition, the upper conductor wire and the lower conductor wire are connected so as to form a single conductor wire. That is, both ends of the upper conductor wire and the lower conductor wire are alternately connected in a spiral shape by through holes.

When the parallel slits of the upper and lower sheets are viewed from above so that the through-holes are vertically straight, the slits in each of the upper and lower ferrite sheets are formed as / \ / \ /. Position both ends so that they are continuous.

(4) The spiral conductor, that is, the number of turns of the internal electrode is equal to the number of slits formed in one ferrite sheet, and it is possible to design the inductance value with a high degree of freedom as required. Therefore, there is no direct relationship between the number of turns and the number of laminated ferrite sheets.

(5) Since the spiral conductor is not configured to be stressed with the ferrite sheet, the current limiting effect (noise removing effect) does not deteriorate.

[0022]

Embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a manufacturing process diagram for explaining the structure of the multilayer chip inductor according to the present invention, and FIG. 2 is a perspective view showing an internal spiral conductor of the multilayer chip inductor. 3 is a perspective view for explaining the stacking relationship of the upper, middle, and lower ferrite sheets, and FIG.
FIG. 4 is a vertical cross-sectional view passing through the central axis of the multilayer chip inductor.

1 and 2, the laminated chip inductor 30 has plate-like ferrite sheets 15a to 15n, which are obtained by mixing and mixing a resin with ferrite magnetic powder, to form a closed magnetic circuit and to form a closed magnetic path inside. Conductor 2
5 is sealed and fired, and terminal electrodes 23 and 24 for connecting to the tip of the spiral conductor 25 are provided on the end face, and in particular, the upper and lower ferrite sheets 15 in FIG.
A plurality of slits 17 and 18 parallel to k, 15m and 15b and 15c are provided, and a conductive paste is embedded and printed in the slits to form upper conductor lines 25a and lower conductor lines 25b in the horizontal direction parallel to the sheet, In the middle layer, the upper and lower ferrite sheets 15b, 15c,
Both ends 17a, 17 of each slit at 15k, 15m
Through holes 19 are provided at positions b, 18a, and 18b.
Ferrite sheets 15d to 15 in which a and 19b are provided and conductor paste is embedded and printed in the through holes
The upper conductor wire 25a and the lower conductor wire 25 are formed by stacking seven sheets of j to form vertical conductor wires 25c and 25d.
A spiral conductor 25, which draws a spiral in a direction parallel to the ferrite sheet, is formed inside the magnetic body together with b, and both ends of the spiral conductor 25 are formed on both end faces of the integrally fired laminate.
It is characterized in that terminal electrodes 23 and 24 respectively connected to e and 25f are provided.

Each member of the multilayer chip inductor 30 will be described in detail below.

First, the ferrite sheets 15a are formed by mixing ferrite resin, which is generally used as an oxide magnetic material, with a binder resin and a solvent and kneading the mixture into a sheet-like thickness. Since the above-mentioned ferrite has a relatively large resistance and a high-frequency loss is small, it is widely used as a magnetic core material especially for high frequencies, and there are types such as nickel-cobalt ferrite, nickel-zinc ferrite, and manganese-zinc ferrite. In particular, nickel-zinc based ferrite has a high resistivity, so that the electrode can be directly attached.

Next, the terminal electrodes 23, 24 are coated with Ag paste or Ag-Pd paste (comprising Ag-Pd alloy powder, glass, vehicle, etc.), dried at around 150 ° C., and then baked at 600-800 ° C. It becomes. A solder layer is formed by printing or applying solder dip or paste solder on this, or by applying solder plating to facilitate conductive connection.

The conductor paste is obtained by mixing and kneading electrode material powder containing silver or a silver-palladium alloy as a main component with a resin and a solvent.

Next, the manufacturing process will be outlined. The slits 17 and 18 and the through holes 19a and 19b of each of the ferrite sheets 15b to 15m are preliminarily processed at the same time when the ferrite sheet is formed.

For embedding and printing the conductor paste in the slits and through holes, for example, a mask plate having through holes of the same shape at the same positions as the slits and through holes is placed on the ferrite sheet to remove the conductor paste. The method of pressing and pouring is adopted.

Next, as shown in FIG. 3, the positional relationship between the slits and the through holes of the upper, middle, and lower layer ferrite sheets is the ferrite sheets 15m, 15f, and 1.
5b is taken as an example, the end portion 20b of the wiring portion 20 reaching the end surface of the middle layer sheet 15f is electrically connected to the end portion 18b of the slit 18 of the upper layer sheet 15m through the through hole, and the other end 18a is passed through the through hole 19a to form the lower layer sheet. 15
The upper sheet 1 reaches the end portion 17a of the slit 17 of FIG.
It reaches the end 18b of the slit 18 'next to 5m. By repeating the above, both ends of the upper conductor wire 25a and the lower conductor wire 25b embedded in the slits of the upper and lower layer sheets are alternately connected in a spiral shape with the vertical conductor wire 25c by the through hole of the middle layer sheet. Of.

The vertical stacking of the through holes 19a and 19b is such that the upper and lower parallel slits have a shape of / \ / \ / when viewed from above so that the upper and lower parallel slits are straight, and end portions 18a and 17a are formed. It is essential that the are connected continuously.

The lower ferrite sheets 15b and 15c
Are the same, and the middle-layer ferrite sheets 15d to 15j are the same (however, the wiring portions 20 for connecting to the terminal electrodes are additionally provided up to the end faces in 15f and 15g, as described above), and the upper-layer ferrites. Sheet 15k, 1
5m is equivalent. The plurality of equivalent ferrite sheets are stacked in order to secure the thickness of the spiral conductor 25 as an internal electrode, and the number of stacked layers can be set arbitrarily. Therefore, it is possible to reduce the DC resistance of the internal electrodes.

The spiral conductor 25 inside the ferrite laminate.
As is clear from the cross-sectional view of FIG. 4, since the sheet is not sandwiched between the sheets but penetrates through the sheet, the stress of the ferrite sheets 15a to 15n is not applied and the current limiting effect (noise removing effect) is reduced. Never.

The multilayer chip inductor according to the present invention is generally rectangular parallelepiped and the ferrite sheet is also rectangular, but there is no particular limitation.

[0036]

Since the multilayer chip inductor according to the present invention is constructed as described above, (1) no stress is applied to the spiral conductor of the internal electrode,
It has an excellent effect that the current limiting effect (noise removing effect) does not decrease.

(2) Further, since the thickness of the internal electrodes can be increased, the direct current resistance can be reduced and the current capacity can be increased.

(3) The number of windings of the internal electrode can be easily adjusted by increasing or decreasing the number of slits, and the number of laminated ferrite sheets does not increase, so that the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram for explaining the structure of a multilayer chip inductor according to the present invention.

FIG. 2 is a perspective view showing an internal spiral conductor of the multilayer chip inductor.

FIG. 3 is a perspective view for explaining the stacking relationship of the upper, middle, and lower ferrite sheets.

FIG. 4 is a vertical cross-sectional view passing through the central axis of the multilayer chip inductor.

FIG. 5 is a partially cutaway perspective view showing the internal structure of a conventional multilayer chip inductor.

FIG. 6 is a partially cutaway perspective view showing an internal structure of the conventional multilayer chip inductor in the manufacturing process.

[Explanation of symbols]

 1 Ferrite Sheet 2 Internal Electrodes 4, 23, 24 Terminal Electrode 6 Base Ferrite Sheet 7 First Conductor Paste 8, 10 1/2 Ferrite Sheet 9 Second 1/2 Conductor Paste 11 Last Conductor Paste 12 Ferrite sheet 13 Steps of ferrite sheet 15a to 15n Ferrite sheet 17, 18, 18 'Slits 17a, 17b Slit ends 19a, 19b Through hole 20 Wiring portion 25 Spiral conductor 25a Upper conductor wire 25b Lower conductor wire 25c Vertical conductor wire 25d, 25e spiral tip 30 laminated chip inductor

Claims (1)

[Claims] 1. A plate-shaped ferrite sheet obtained by mixing and kneading a resin with ferrite magnetic powder is laminated on top and bottom to form a closed magnetic circuit, and a spiral conductor is sealed inside and fired to connect the spiral conductor to an end face. In a laminated chip inductor having a structure in which a terminal electrode is provided, a plurality of parallel slits are provided in the upper and lower ferrite sheets, and conductive paste is embedded and printed in the slits to form an upper conductor wire in a horizontal direction parallel to the sheet. And lower conductor lines are formed, and through holes are provided in the middle layer at positions located at both ends of each slit in the upper and lower ferrite sheets, and a plurality of ferrite sheets are printed by embedding conductor paste in the through holes. By forming a vertical conductor wire by using the upper conductor wire and the lower conductor wire, A multilayer chip inductor, wherein one spiral conductor that draws a spiral in a direction parallel to the sheet is formed, and terminal electrodes connected to the spiral conductor are provided on both end faces of the integrally fired laminate.