JPH02143406A - Laminated inductor - Google Patents

Abstract

PURPOSE:To provide a laminated inductor having an increased conductor length while keeping a reduced size for obtaining a larger inductance value by forming a pair of spiral coils from a plurality of ferrite sheets having a plurality of through holes and connecting these spiral coils in series through the through- holes in the ferrite sheets interposed between the spiral coils. CONSTITUTION:A laminated inductor comprises coil ferrite sheets A, C and E having a plurality of through holes, 11 14, 21-24, and 25-28 and conductor patterns 16-20 and 25-28 and connecting ferrite sheets B and D each having one through-hole 31 and conductors patterns 32, 33. On the top and and bottom of the laminate consisting of the sheets A, C, E and B, D, there are superposed ferrite sheets for dummy F. A pair of spiral coils are formed of the conductor patterns on the sheets A, C, E and B, D connected through the through-holes. These spiral coils are connected in series through the through-holes.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a small multilayer inductor used for noise prevention in high frequency circuits.

<Prior Art> In recent years, regulations regarding noise prevention in high-frequency circuits have been strong, and inductance elements for noise prevention have been attracting attention. Therefore, small multilayer inductors have come to be used in the field of noise prevention.

Conventionally, this type of small-sized multilayer inductor is shown in Figures 8 and 9.
As shown in the figure, on the surface of the intermediate ferrite sheet 1,
An engineered conductor pattern 5 using a conductive paste mainly composed of silver and having external lead-out electrodes 3.4 provided at both ends of the conductive part 2.
A ferrite sheet 6. is printed and applied, and nothing is printed on the top and bottom of this ferrite sheet 1 to serve as dummy sheets.
6 are stacked one on top of the other, pressed flat, and then baked and integrated at an appropriate temperature.

Thereafter, barrel polishing was performed, and a conductive paste was applied to both ends of the laminate so as to be electrically connected to the lead electrode 3.4, and this was baked to form the external electrode 7.8.

<Problem to be solved by the invention> By the way, the multilayer inductor with the above structure has the following problems:
Since the shape is small and the length of the conductive part 5 is short, there is a problem that a necessary inductance value cannot be obtained.

In order to solve the above-mentioned problems, it is an object of the present invention to provide a multilayer inductor that has a long conductor distance and can obtain a small size and a large inductance value due to a completely closed magnetic circuit.

Means for Solving the Problems> In order to solve the above problems, the present invention stacks a plurality of ferrite sheets with a conductor pattern for forming a coil and a conductor pattern for drawing out at both ends interposed between the layers. It is a multilayer inductor with multiple ferrite sheets having multiple through holes in it, and at least two spiral coils are configured with conductor patterns connected by through holes around each ferrite sheet. The spiral coils are connected in series through through holes in a ferrite sheet between the spiral coils.

<Operation> At least two spiral coils are constructed from a plurality of ferrite sheets having a plurality of through holes, and these spiral coils are connected in series by the through holes of the ferrite sheets that exist between these spiral coils. Therefore, the shape is small (but the conductor length can be made long, and a large inductance value can be obtained).

<Embodiments> Hereinafter, embodiments of the present invention will be described based on FIGS. 1 to 7 of the accompanying drawings.

In the first embodiment shown in FIGS. 1 to 6, the types of ferrite sheets used to construct the laminated inductor are as shown in FIG. Ferrite sheet B for connection with only one through hole for A, C, and E,
D, and dummy ferrite sheets F and F, which are stacked on both the upper and lower surfaces of a laminate made by stacking each of the above-mentioned sheets, and three spiral coils are constructed with a conductive pattern centered around the ferrite sheet with a plurality of through holes. , each spiral coil is successively connected to the through hole of the ferrite sheet provided with one through hole.

First, the upper ferrite sheet A for the coil, which has a plurality of through holes, has through holes 11 to 14 and 21 to 24 facing each other on both sides along the longitudinal direction of the ferrite green sheets 1O, as shown in FIG. On the back side of this ferrite green sheet 1O, as shown by the broken lines in FIG. A conductive pattern 25.26.2 is formed using a conductive paste mainly composed of
7. Apply 28 in parallel.

Next, conductive paste mainly made of silver was applied to the surface of the green sheet 10 (to bridge between the through holes 12 and 21, between 13 and 22, and between 14 and 23).
Inclined conductor patterns 17, 18, and 19 are applied in parallel, and a dummy connection pattern 20 is further applied to the external lead pattern 15 reaching the through hole 11 and the through hole 24 on one end side of the green sheet IO. Apply.

As mentioned above, the conductor pattern is printed in the order of through holes 11, 21, 12, etc., so this creates a spiral coil whose cross section is the area of the green sheet's "between through holes x sheet thickness". It becomes.

Therefore, the ferrite green sheet IO has a 3.5 turn spiral coil S between the through holes 11 to 24.
This is a coil sheet with CA.

The ferrite sheet B for connection, which is overlapped on the back side of the ferrite sheet A for the coil, is the ferrite green sheet 3.
0, through hole 24 of the ferrite sheet A
A through hole 31 is provided at a position overlapping with the through hole 31, and connection patterns 32 and 33 are printed on the front and back surfaces of the through hole 31 to connect the sheets stacked one above the other.

The ferrite sheet C for the coil arranged in the middle has a structure in which the external drawer pattern 15 is omitted from the ferrite sheet A, and has a spiral coil SCc. In the following description, the same parts as those of the ferrite sheet A are given the same reference numerals, and the description will be replaced with the same ones. (The same applies to the following sheets.) In this ferrite sheet C, a connection pattern 16 is printed on the surface side of the through hole 11.

The ferrite sheet C constitutes the intermediate portion of the coil, and when increasing the number of turns of the coil, the number of sheets C may be increased.

Further, the connection ferrite sheet D has a structure obtained by rotating the ferrite sheet B by 180 degrees, and the lower coil ferrite sheet E consists of the upper ferrite sheet A rotated by 180 degrees, and the spiral coil SC
It has a lot of features.

The above connection ferrite sheet B is interposed between the coil ferrite sheets A and C, and the spiral coil SCA
and SCc, and the connecting ferrite sheet D is interposed between the coil ferrite sheets C and E to connect the spiral coils S00 and S01, but the ferrite sheets B and D are arranged alternately. It will be interposed between the ferrite sheets for the coil so that

Each of the above ferrite sheets A to E is stacked with A to E in order from the top (or from the bottom) as shown in Figures 1 and 3, and ferrite sheets F and F with nothing printed above and below these are stacked. After stacking one or more sheets,
Perform flat pressure.

In the ferrite sheets A and C1E for coils described above, ferrite sheet A has blank spaces that are not printed between the drawer part 15 and the conductor pattern 25 and between the conductor pattern 28 and the drawer part 15 of the ferrite sheet E when laminated. Sections 41 and 42 are provided, and similarly ferrite sheets C
The ferrite sheet E has blank parts 41 and 42 at both ends thereof.

When flat pressure is applied to these blank areas, the blank areas of the ferrite sheets that overlap each other will adhere to the connection ferrite sheets B and D, respectively, and form magnetic path connection parts. The portion is formed to have an area equal to or larger than the cross-sectional area of the coil formed in the ferrite sheet for coil.

When ferrite sheets are laminated and plane pressure is applied, the electrical connection of each conductor pattern is as follows.

(I) Through hole 24 of ferrite sheet A for coil
The conductor pattern 28 printed on the back surface is connected to the conductor pattern 32 on the front surface of the connecting ferrite sheet B.

(II) The conductor pattern 33 on the back surface of the ferrite sheet B for connection is connected to the conductor pattern 20 on the front surface of the ferrite sheet C for coil.

(III) Next, the conductor pattern 25 on the back side printed in the through hole 11 of the ferrite sheet C for coil
and the conductor pattern 32 on the surface of the ferrite sheet D for connection.
is connected.

(JV) The conductor pattern 33 on the back side of the ferrite sheet D for connection and the conductor pattern 20 on the front side printed on the through hole 24 of the ferrite sheet E for coil are connected.

With this kind of connection, each coil ferrite sheet A
, C, H are connected in series to form a coil having 1025 turns in total.

What is important here is the winding direction of the conductor pattern that becomes the spiral coil.

Although Fig. 1 shows a plan view, the coil ferrite sheets A and C%E both show the same winding direction, and they are stacked as is and their terminals are connected alternately. .

If this is illustrated in terms of the relationship of magnetic lines of force in parallel to FIG. 1 and FIG. 6, it will be as follows.

Note that FIG. 6 shows only the relationship between the ferrite sheets A and C for coils, and representative conductor patterns 17 to 20 and 25 to 28 of each sheet are illustrated.

Here, if we consider the direction in which the current flows from the conductor pattern 16 of the ferrite sheet C for a coil shown in FIG. Through hole 21 → conductor pattern 17 → through hole 12
→Since the current flows in the order of the conductor pattern 26, the lines of magnetic force are directed from right to left as shown in ferrite sheet C in FIG.

And connection pattern 2 at the end of ferrite sheet C
0 is the conductor pattern 33 of the connection ferrite sheet B →
The through hole 31 is connected to the conductor pattern 28 of the ferrite sheet A through the conductor pattern 32.

(b) Inside the ferrite sheet for coil, conductor pattern 28 → through hole 14 → conductor pattern 19 → through hole 23 → conductor pattern 27 → through hole 13 →
Since the current flows in the order of the conductor pattern 18, the lines of magnetic force are directed from left to right as shown in ferrite sheet A in FIG.

The lines of magnetic force generated in this way move from right to left in ferrite sheet C → magnetic path connecting portion 43 - magnetic path connecting portion 41 → ferrite sheet A from left to right → magnetic path connecting portion 42 → magnetic path connecting portion 41 → The ferrite sheet C flows from right to left, forming a closed magnetic path.

Note that the magnetic lines of force within ferrite sheet B flow from ferrite sheets A and C in opposite directions, cancel each other out internally, and do not contribute to the coil configuration.

A coil configured in this way has a certain coefficient and is proportional to the number of turns.

Therefore, the connection of the conductor pattern of each ferrite sheet is
Laminating sheets with conductor pattern configurations in the same direction,
A coil can be constructed by alternately connecting the conductor pattern terminals of each ferrite sheet.

Each ferrite sheet is made into a ferrite sheet by laminating green sheets under the above conditions and applying pressure on a plane, and then firing to form a ferrite sheet.The fired laminate is barrel-polished. As shown in the cross-sectional view of the surface of the ferrite sheet A, a conductive paste mainly made of metal is applied to both ends and baked to form external electrodes 34 and 35, thereby completing the product.

In addition, each through hole 11-14, 21-24 and 31
When printing the conductor pattern, the conductive paste is printed so as to flow into the inner wall of the through hole from the front and back sides, so that the conductor patterns on the front and back sides can be reliably connected.

Next, in the second embodiment shown in FIG. 7, a coil is constructed by laminating two ferrite sheets for coils, and ferrite sheets A, B, and C in the same figure are stacked together to form a coil.
are the ferrite sheets A and B of the first example shown in FIG.
, C, only the ferrite sheet G differs from the ferrite sheet D in FIG.

The method of laminating each ferrite sheet and the method of connecting each conductor pattern in this second embodiment are the same as in the first embodiment.

A coil of 7.0 tar will be constructed.

Incidentally, in the coil according to the present invention, as the thickness of the ferrite sheet provided with the conductive pattern increases, the inductance tends to increase as well.

<Effects of the Invention> As described above, according to the present invention, a plurality of ferrite sheets having a plurality of through holes are used, and at least two spiral coils are formed around the ferrite sheet with conductive patterns connected by the through holes. configure,
These spiral coils are connected in series through the through-holes in the ferrite sheets that exist between these spiral coils, so by selecting the ferrite sheets, multi-turn coils can be designed efficiently (as well as using ferrite sheets). A larger inductance can be obtained by configuring the coil in the cross-sectional area direction within the sheet, and by clearly laminating conductor patterns in the same winding format in the same direction and alternately connecting the pattern terminals.

Further, by providing a magnetic path connecting portion that constitutes a closed magnetic path between the ferrite sheets, a small coil with large inductance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an exploded plan view of a ferrite sheet illustrating a first example of a multilayer inductor according to the present invention, FIG. 2 is a plan view showing through-holes in the ferrite sheet for coils, and FIG. 3 is a ferrite sheet. Fig. 4 is a front view showing the laminated state of the same as above, Fig.
The figure is a cross-sectional plan view of the completed inductor, Figure 6 is an explanatory diagram showing the relationship between magnetic lines of force, Figure 7 is an exploded plane view of a ferrite sheet showing the second example, and Figure 8 is a conventional laminated inductor. The exploded perspective view and FIG. 9 are cross-sectional plan views of the same. l0130... Ferrite green sheet 11-14
．． 21~24.31...Through hole 16~20.2
5-28...Conductor pattern 15...External drawer pattern 32.33...Conductor pattern 41-44...Blank area

Claims (2)

[Claims] (1) A laminated inductor in which a plurality of ferrite sheets are stacked with a conductor pattern for forming a coil and a conductor pattern for drawing out at both ends interposed between the layers, and a ferrite sheet with a plurality of through-holes is interposed between the layers. At least two spiral coils are made up of conductor patterns connected by through holes around each ferrite sheet, and these spiral coils are connected by through holes in the ferrite sheets between these spiral coils. , a multilayer inductor characterized by being connected in series. (2) The multilayer inductor according to claim 1, wherein a magnetic path connection portion having an area equal to or larger than the cross-sectional area of the coil is provided between both ends of the spiral coil-forming conductor pattern and the lead-out conductor pattern. .