JPH06163272A - Impedance element - Google Patents

Abstract

PURPOSE:To obtain an impedance element which can exhibit sufficient characteristics in a very small limited volume, and be surely mounted on a board. CONSTITUTION:At least one penetrating hole 13 penetrating the part between a first surface 11 and a second surface 12 of a rectangular ferrite element body which surfaces are different from the board fixing surface and face with each other is formed, and a penetrating conductor is formed in the penetrating hole. In the case of one penetrating hole, both surfaces of the penetrating conductor are connected with electrode surfaces 8 formed on the third surface and a fourth surface of the ferrite element body which surfaces are different from the board fixing surface of the ferrite element body and face with each other. In the case of a plurality of penetrating holes, both ends of an electric coupler formed by connecting a plurality of penetrating conductors in series are connected with the electrode surfaces 8. An insulating film is formed on at least one out of the above first surface 11 and the second surface 12 which cats as electrically active planes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impedance element, and more particularly to an impedance element suitable for application to a bead filter.

[0002]

2. Description of the Related Art Conventionally, a bead filter is formed by forming a magnetic material in a cylindrical shape and passing a conductor through the hole.
It is mainly used as an inductor in the low frequency region and as a resistance element in the high frequency region. The impedance Z of such a bead filter is obtained by comparing the magnetic permeability of a magnetic material with the complex magnetic permeability (μ
= Μ ′ + jμ ″)

[0003]

[Equation 1]

It is represented by Here, μ ₀ is the magnetic permeability of vacuum (4π × 10 ⁻⁷ H / m), ln is the natural logarithm, O _D , I
_D and l are the outer diameter, inner diameter, length, and N of the cylindrical magnetic body, respectively.
Is the number of turns (1 in the case of a bead filter), j = √−1. Therefore, as can be seen from the equation (1), the bead filter as described above has a small inner diameter and a long
The larger the outer diameter, the higher the impedance.

However, in such a conventional bead filter, an increase in impedance is unavoidable when the impedance is increased, and the characteristics cannot be sufficiently exhibited in a limited volume.

A plurality of through holes penetrating from the board mounting surface to the surface opposite to this surface is provided, and both ends of the electrical coupling body, in which the conductors passed through the through holes are continuously coupled, are connected to the electrode surfaces, respectively. By configuring the impedance element so that the insulating film is provided at least on the board mounting surface, a desired large impedance value can be obtained in a limited volume, and the impedance element and the land mounted on the board are provided. Good electrical insulation from live parts such as patterns is achieved.

[0007]

However, when the insulating film is provided on the board mounting surface as described above, when the impedance element is soldered to the board by a reflow method or the like, an element called Manhattan phenomenon is formed. There is a risk that the phenomenon of floating will occur. this is,
One electrode surface is pulled downward by the surface tension of the solder, and the other electrode surface is lifted from the substrate with the edge of the insulating film as a fulcrum.

The present invention has been made in order to solve the above problems, and is an extremely small impedance element which can exhibit sufficient characteristics in a limited volume and can be reliably mounted on a substrate. Is intended to provide.

[0009]

According to the present invention, at least one through hole penetrating between a first surface and a second surface of a rectangular plate-shaped ferrite body different from the substrate mounting surface and facing each other. And a through conductor is provided in the through hole, and both ends of the through conductor are connected when there is one through hole, and a plurality of through conductors are connected in series through a conductor pattern when there are a plurality of through holes. The both ends of the dynamic coupling body are respectively connected to the electrode surfaces formed on the third surface and the fourth surface, which are different from the substrate mounting surface of the ferrite element body, respectively, and form the active surface. There is provided an impedance element in which an insulating film is provided on at least one of the surface and the second surface.

It is preferable that the electrical coupling body is a series connection of the through conductors so that the magnetic fluxes from the through conductors in the adjacent through holes do not cancel each other out.

[0011]

Since the first surface and the second surface which are the live surfaces are different from the board mounting surface of the ferrite body, the insulating film is formed on at least one of the live surfaces. In addition, the mounting yield is improved without causing inconvenience such as floating of the element when mounted on the substrate. It goes without saying that a desired large impedance value can be obtained with a limited volume.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments of the present invention, impedance elements considered prior to the present invention will be described with reference to the drawings.

1 (a) to 1 (c) are views showing examples of impedance elements prior to the present invention, in which (a) is a plan view, (b) is a bottom view, and (c) is (a). FIG. 9 is a sectional view taken along line AA ′ of FIG. The insulating film 10 is omitted in FIGS. 2A and 2B for the sake of clarity.

In the impedance element 1 of this prior art example,
Six through holes 3, 3a to 3 in the thickness direction of the rectangular plate-shaped ferrite element body 2, that is, in the direction of penetrating the mounting surface to the substrate.
f is formed as shown. Through-hole conductors 4 are formed in each through-hole 3, and these through-hole conductors 4 are electrically connected in series by a conductor pattern 7 on the front surface 5 and the rear surface 6 of the element body 2. Further, the through-hole conductors at both ends of the electrically coupled body connected in series are connected to the electrodes 8 provided at opposite ends of the element body 2 by conductor patterns 7 '.

Therefore, the electrical connection is made by: electrode 8-conductor pattern 7'-through hole conductor (through hole 3a) -conductor pattern 7-through hole conductor (through hole 3b) -conductor pattern 7-through hole conductor (through hole). 3c) -Conductor pattern 7-Through hole conductor (through hole 3d) -Conductor pattern 7
-Through hole conductor (through hole 3e) -Conductor pattern 7-
Through hole conductor (through hole 3f) -conductor pattern 7'-
It becomes like the electrode 8.

In the case of this example, the size of the impedance element 1 is preferably 3.2 mm in length, 4.5 mm in width, and 1.5 mm in height. When the number of holes is 1, the length is 1.2 mm, the width is 2.0 mm, and the height is 0.9 mm.
1.6 mm long, 3.2 mm wide, 1.1 m high
When m is 4 holes, the length is 2.5 mm, the width is 3.2 mm,
Chip elements with a height of 1.3 mm are preferably used.

The material of the ferrite element body 2 is mainly M
n-Zn ferrite, Ni-Cu-Zn ferrite, N
i-Zn ferrite or the like is used.

For example, when the element body 2 is powder-molded, the through hole 3 is formed by forming a predetermined number of holes having an appropriate diameter with a jig before firing and firing (at a temperature of about 1000 to 1300 ° C.). To form. The hole diameter is preferably 0.01 mm or more. If it is smaller than this, it becomes difficult to provide the through hole conductor 4 in the through hole 3.

The through-hole conductor 4 and the conductor patterns 7 and 7'are formed by a method in which they are formed in close contact with the element body 2 by, for example, baking a conductive paste or plating.

In this prior art example, when the impedance element 1 is mounted on a substrate or the like, it is electrically insulated from the live parts (lands, patterns, etc.) provided on the surface of the substrate. An insulating film 10 is applied to the surfaces 5 and 6 so as not to cover the electrode 8. It is preferable that the insulating film 10 be formed using a fast-curing resin. When the thermosetting resin is used, the resin is softened at the time of overheating, so that a pin hole is generated in the hole portion on the chip surface, which adversely affects the electrical characteristics. For example, when the impedance element 1 is mounted on the substrate and solder dipping is performed, the solder enters the holes and the characteristic value changes. Therefore, it is preferable to use a fast-curing resin because it is necessary to cure the resin instantly after application in order to prevent generation of pinholes. As the quick-curing resin, an ultraviolet-curing resin or an inexpensive resin is generally used. The insulating film 10 may contain ferrite powder or the like. By doing so, there is an advantage that a shielding effect is generated, unevenness in the coloring and cracks can be reduced, and the heat resistance can be further improved.

The impedance element 1 thus formed has a structure as shown in FIG. 2, and is composed of an element such as six cylindrical beads having an inner diameter I _D , an imaginary outer diameter O _D and a length l connected in series. Become. In FIG. 2, symbols

[0022]

[Outer 1]

Indicates that the current flows in the direction from the front side to the back side of the drawing,

[0024]

[Outside 2]

[0025] indicates that the current flows in the direction from the back side of the drawing to the front side, and the arrow indicates the direction of the magnetic flux.
The current directions are opposite to each other between the adjacent through holes 3, and the magnetic flux is not canceled. The theoretical impedance Z of the device of this example can be calculated by the following equation. Each parameter is the same as that used in the above equation (1).

[0026]

[Equation 2]

In FIG. 3, μ'at 10 MHz is 220,
Ferrite body with μ ″ of 300 has I _D of 0.4 mm and O _D
2 is a graph showing the results of measuring the impedance characteristics of an element formed by forming 6 holes, where is 1.6 mm and 1 is 1.5 mm. In theoretical calculation, the impedance value is about 60Ω at 10 MHz, which is almost the same as the measured data.

As is apparent from FIG. 3, the impedance of the impedance element of this example is low in the low frequency region and high in the high frequency region. Therefore, this impedance element can be used, for example, as a noise filter in a TV tuner circuit.

In FIG. 4, the length 1 is 0.5 mm each.
It is a graph showing the impedance characteristics of the element when (a), 1.0 mm (b) and 1.5 mm (c).
This also agrees with the theoretical value.

According to the above-mentioned configuration, the impedance can be arbitrarily adjusted by changing the outer size of the element body, the thickness, the number of holes, the conductor pattern, and the like, and a bead filter having desired characteristics is constructed. can do. Further, the lead wire of the terminal portion attached to the conventional bead filter can be eliminated to form a leadless chip-like element, which is also suitable for automatic attachment of an impedance element to a circuit by an automatic mounting device. . Moreover, since the insulating film is provided on the live surface of the element, when the element is mounted on the substrate, the element is surely insulated from the live part provided on the substrate.

Although the impedance element having a plurality of through holes has been described, an impedance element having a single through hole as shown in FIG. 5 is also applicable. In FIG. 5, elements similar to those in (a) to (c) of FIG. 1 are designated by the same reference numerals, and the insulating film is omitted to make the structure easy to understand. Such a single through-hole type impedance element not only exhibits the same performance as a conventional bead filter, but also a through-hole conductor and a conductor pattern are formed into a body by a method such as baking a conductor paste or plating. By forming them in close contact, a leadless type chip-shaped element can be obtained. Compared to the conventional beaded filter with leads, there is less influence from the leads, so there is less variation in characteristics, and there is no need to attach the leads when soldering. Therefore, it is suitable for automatic mounting by an automatic mounting device.

6 and 7 show an embodiment of the present invention. In the above-mentioned prior art example, the through hole is provided in the thickness direction of the rectangular plate-shaped ferrite element body, that is, in the direction penetrating the mounting surface to the substrate, but according to one embodiment of the present invention, As shown in FIG. 6, a through hole 13 is provided in the width direction of the rectangular plate-shaped element body, that is, from the surface 11 different from the mounting surface to the substrate to the surface 12 opposite thereto. The insulating films on the surfaces 11 and 12 are not shown in FIG. Further, according to another embodiment of the present invention, as shown in FIG. 7 (insulating film omitted), from the surface 14 different from the mounting surface to the substrate in the longitudinal direction of the rectangular plate-shaped element, Through holes 16 are provided in the surfaces 15 facing each other. The insulating films on the surfaces 14 and 15 are not shown in FIG. 7.

As described above, the surface of the ferrite element body different from the substrate mounting surface forms an active surface in which the through holes appear, and the insulating film is formed on these active surfaces. Therefore,
Since the insulating film does not exist on the board mounting surface of the ferrite body, the inconvenience that the element is lifted up by the surface tension of the solder at the time of mounting on the board can be prevented by this insulating film. As a result, the mounting yield of the impedance element when mounted on the substrate is significantly improved. It goes without saying that it is possible to provide a very small impedance element having a large impedance with a minimum volume. Also, a conductor pattern,
Since the thickness of the through-hole conductor and the like can be easily increased, there is an advantage that Q can be increased. Further, since the live surface of the element is covered with the insulating film, it is possible to ensure electrical insulation from the live parts provided in these when the element is mounted on the substrate or the like. Furthermore, the element may be in the form of a leadless chip, and in this case, mounting by an automatic mounting device can be preferably used.

In the present invention, since the conductor is linear and does not form a coil, the inductance component becomes smaller than that when a coil is formed. This is
This means that the resonance frequency due to the inductance is higher and the impedance is higher at a higher frequency than in the case where a coil is formed, and when applied to a noise filter or the like, the effect of removing noise is very large.

[0035]

As described above in detail, according to the present invention, at least one of the rectangular plate-shaped ferrite element bodies which penetrates between the first surface and the second surface which are different from the substrate mounting surface and which face each other. One through hole is provided, and a through conductor is provided in the through hole. When there is one through hole, both ends of the through conductor are connected, and when there are a plurality of through holes, a plurality of the through conductors are connected in series through a conductor pattern. The both ends of the electrical coupling body formed as described above are respectively connected to the electrode surfaces formed on the third surface and the fourth surface, which are different from the substrate mounting surface of the ferrite element body and face each other, and form the live surface. Since the insulating film is provided on at least one of the first surface and the second surface, the insulating film does not exist on the board mounting surface of the ferrite element body, and the insulating film prevents the solder from being attached to the board. The surface tension of Will up come inconvenience can be prevented in advance. As a result, the mounting yield of the impedance element when mounted on the substrate is significantly improved. It goes without saying that it is possible to provide a very small impedance element having a large impedance with a minimum volume.

[Brief description of drawings]

1A to 1C are a plan view, a bottom view, and a sectional view of an impedance element prior to the present invention.

FIG. 2 is a schematic diagram of an impedance element for theoretical explanation.

FIG. 3 is a graph showing the measurement results of frequency-impedance characteristics of a device with 6 holes.

FIG. 4 is a graph showing measurement results of impedance transition when the position is changed.

FIG. 5 is a plan view of an example applied to a single through-hole type impedance element.

FIG. 6 is a perspective view showing an embodiment of the present invention in which a through hole is provided in the width direction of the element body.

FIG. 7 is a perspective view showing another embodiment of the present invention in which a through hole is provided in the length direction of the element body.

[Explanation of symbols]

 1 Circuit Element 2 Ferrite Element 3, 13, 16 Through Hole 4 Through Hole Conductor 7 Conductor Pattern 8 Electrode 10 Insulating Film 11, 12, 14, 15 Surface

Claims (3)

[Claims] 1. A rectangular plate-shaped ferrite element is provided with at least one through hole penetrating between a first surface and a second surface opposite to each other different from a board mounting surface, and a through conductor is provided in the through hole. A third surface, which is provided on both ends of the through conductor or both ends of an electrical coupling body in which a plurality of the through conductors are connected in series via a conductor pattern, is opposite to the substrate mounting surface of the ferrite element body and faces each other. An impedance element, characterized in that an insulating film is provided on at least one of the first surface and the second surface, which are connected to the electrode surfaces respectively formed on the fourth surfaces and are active surfaces. 2. A plurality of through holes penetrating between a first surface and a second surface of the rectangular plate-shaped ferrite body different from the board mounting surface and facing each other, and each of the through holes has a through conductor. And a plurality of the through conductors connected in series via a conductor pattern to both ends of an electrical coupling body on a third surface and a fourth surface opposite to the board mounting surface of the ferrite element body. An impedance element, characterized in that an insulating film is provided on at least one of the first surface and the second surface, which are connected to the respective formed electrode surfaces and form an active surface. 3. The electrical coupling body is formed by continuously connecting the through conductors in series so that magnetic fluxes generated by the through conductors in adjacent through holes do not cancel each other. 2. The impedance element according to 2.