JP2007096209A - Bead inductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost bead inductor with an aim to eliminate the forming of an external terminal in an assembly process to simplify the assembly process as well as improving reliability of connection of an external terminal prepared on a plate conductor and a substrate. <P>SOLUTION: The bead inductor is made up of a plate conductor sandwiched by two flat plate cores, wherein both ends of the plate conductor 3 are provided with external terminals 4 that are formed into the U shape, two flat plate cores 1 and 2 or either one of the flat plate cores includes a groove 5 at a surface in contact with the other flat plate core, the groove 5 for storing the plate conductor 3, and both sides of one flat plate core of the two flat plate cores include a groove 6 for fitting the external terminal 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a bead inductor used for the purpose of noise countermeasures.

A bead inductor is used as a noise countermeasure component, particularly as a noise countermeasure component for a microprocessor or the like that needs to pass a large current. A conventional bead inductor includes a plate-like conductor provided inside a flat core made of ferrite, and is composed of external terminals made of a plate-like conductor. An example of this type of bead inductor is shown in FIGS.
FIG. 7 is a schematic perspective view of a conventional bead inductor, and FIG. 8 is a side view showing different external terminals.

  The bead inductor 21 shown in FIG. 7 includes two flat cores 1 and 2 made of a magnetic material such as ferrite, and a plate-like conductor 3 made of a metal sandwiched between the flat cores 1 and 2. Further, the external terminals 4 provided at both ends of the plate-like conductor are previously formed into a U-shape and cut.

  In the bead inductor 21 having such a configuration, the plate-like conductor 3 is inserted in accordance with at least one of the flat plate cores 1 and 2, for example, the groove 5 provided in the flat plate core 2. The plate-like conductor 3 is sandwiched and fixed with an adhesive. In this bead inductor, the external terminal 4 formed in a U-shape is in contact with the circuit board surface and is electrically connected by board solder.

  The bead inductor 22 of FIG. 8A is different in the forming shape of the bead inductor 21 of FIG. 7 from the external terminal 4, the tip is bent at right angles along the side surface of the flat core 2, and the tip (cut surface c). Are in contact with the circuit board and electrically connected by board solder.

  A conventional bead inductor having such an external terminal shape is electrically connected to a circuit board as a surface mounting terminal by a reflow soldering device, but the tip of the external terminal becomes a cut surface c, and the metal background is exposed. In addition, cutting burrs and the like are likely to occur and are not flat. Therefore, it is difficult to plate and is generally used without plating. Therefore, the cut surface is rough and the solder is not wet. In particular, as the thickness of the plate-like conductor increases, the portion where the solder does not get wet increases, and the connection reliability of the solder becomes a problem.

  The bead inductor of FIG. 8B has a structure in which the external terminal 23 is a method in which the cut surface of the external terminal is not used, and the distal end portion (cut surface c) of the external terminal 4 is bent from the side surface of the flat core 2 to the bottom surface. It is what. The solder between the external terminal 4 and the circuit board ensures solder wettability on the outer peripheral side surface. However, the external terminal 4 must be formed after the plate-like conductor 3 and the flat cores 1 and 2 are assembled. For this reason, external pressure is applied to the side and bottom corners of the flat core 2 in contact with the external terminals 4 to cause core breakage or the like. In addition, if the forming is poor, the flatness of the surface in contact with the circuit board is impaired, and solderability with an external circuit becomes a problem.

JP 10-335146 A JP 2000-164431 A

  An object of the present invention is to eliminate the disadvantages of the conventional bead inductor described above, simplify the assembly process by eliminating external terminal forming in the assembly process, and provide an external terminal and a circuit board provided on the plate-like conductor. An inexpensive bead inductor is provided for the purpose of improving connection reliability.

The present invention is characterized in that a bead inductor constituted by a plate-like conductor sandwiched between two flat cores is provided with external terminals in which both ends of the plate-like conductor are formed in a U-shape.
Further, two flat cores or one of the flat cores is provided with a groove for accommodating the flat conductor on the surface in contact with the other flat core, and the outer sides of the flat conductors are provided on both side surfaces of one flat core of the two flat cores. A groove for inserting the terminal is provided.
Further, a concave portion is provided on the surface of the other flat plate core in contact with one flat core, and the internal conductor is incorporated in the concave portion.

  The U-shaped external terminal of the plate-shaped conductor has a plane in contact with the circuit board surface, extends and bends outward, and the height of the bent portion is equal to or greater than the thickness of the plate-shaped conductor, and the circuit board surface. The thickness is not more than the thickness of one of the flat cores in contact with.

  Therefore, in the bead inductor according to the present invention, a plate-like conductor having an external terminal previously formed in a U shape is sandwiched between two flat cores. Then, by providing grooves on both side surfaces of one flat core, the positioning of the external terminals is facilitated, and it is an easy task of dropping the external terminals into the grooves, thereby simplifying the assembly process. Further, since the forming process and equipment in the assembly process are not required, it is possible to reduce the manufacturing cost and to prevent the flat core damage due to the forming.

  And by providing the external terminal bent in the U shape toward the outside, the flatness with the circuit board surface to be mounted can be increased, the mounting reliability is improved, the solder wettability is improved, and the circuit Connection reliability with the substrate can be improved.

The bead inductor according to the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view of a bead inductor according to a first embodiment of the present invention.
FIG. 2 is an exploded perspective view of the bead inductor of FIG. In the following, the same components as those in FIG.

A bead inductor 10 shown in FIGS. 1 and 2 is composed of flat cores 1 and 2 made of a magnetic material such as ferrite, and a plate-like conductor 3 made of a metal material.
The plate-like conductor 3 is a conductor having a small direct current resistance and is a rectangular plate having a wide cross section, or a copper plate punched with a mold or the like, and has external terminals 4 at both ends. This external terminal 4 is previously formed into a U shape by a mold or the like.

  A groove having the same cross-sectional area as the cross-sectional area of the plate-like conductor is provided on the surface of the two flat cores or at least one of them. A groove having the same cross-sectional area as that of the plate-like conductor is provided on both side surfaces of the other flat core in contact with the circuit board. For example, as shown in the figure, the flat core 2 is provided with a groove 5 having the same cross-sectional area as the cross-sectional area of the plate-like conductor 3 on the surface in contact with the flat-plate core 1 and grooves 6 on both side surfaces. The terminal 4 is inserted in alignment with the groove 6. The flat core 1 has the same outer dimensions as the length including the external terminals of the plate conductor 3.

Next, a method for assembling the bead inductor 10 will be described.
First, the plate-like conductor is put into the groove 5 on the surface of the flat core 2 in contact with the flat core 1 and the external terminal 4 is fitted into the groove 6 on both side surfaces, and then inserted. And the adhesive agent is apply | coated to the surface which the flat cores 1 and 2 contact, and the flat cores 1 and 2 are adhere | attached and fixed. Note that the drying of bonding is performed based on the specification conditions of the adhesive.

FIG. 3A shows a cross-sectional view of the bead inductor 10 of FIG.
As can be seen from the cross-sectional view of this bead inductor 10, the external terminal 4 protrudes from the width 6 a of the longitudinal groove 6 of the flat core 2, so that it is easy to confirm the solder state when mounted on the circuit board. This involves deformation of the U-shaped external terminal (particularly when the plate-shaped conductor is thin) due to contact with a single bead inductor, external pressure, or the like.

  As a countermeasure against this, as shown in the sectional view of the bead inductor 11 in FIG. 3B, the width 6b of the groove on the side surface of the flat core 2 is made substantially the same as the width of the U-shaped external terminal 4, By making the external dimensions 2 include external terminals, it is possible to prevent deformation of the external terminals due to contact, external pressure, etc. with a single bead inductor.

FIG. 4 is a cross-sectional view of a bead inductor according to a second embodiment of the present invention.
This bead inductor 12 is a modification of the bead inductor 11 according to the first embodiment, and is the same as the cross-sectional area of the plate-like conductor 3 that houses the plate-like conductor 3 on the surface in contact with the plate core 2 on the flat plate core 1 side. A recess 7 having a size is provided. The flat core 2 is provided with grooves 6 for inserting U-shaped external terminals only on both side surfaces as in the first embodiment. This can prevent displacement of the flat cores 1 and 2 and the plate conductor.

FIG. 5 explains in detail the shape of a plate-like conductor having an external terminal used in the bead inductor of the present invention.
The external terminal 4 of the plate-like conductor 3 is bent so as to straddle the flat core 2 in contact with the substrate surface, and is provided with a flat portion 4a in contact with the circuit board surface in the outward direction, and further from the flat portion 4a to the folded portion 4b. Is formed by a mold or the like.

Here, the length 4a of the flat portion 4a is set in consideration of the thickness t of the plate-like conductor so that the surface is not cracked or cracked during forming. The length b1 of the folded portion 4b is longer than the plate thickness 3t of the plate conductor, the cut surface c of the external terminal tip is higher than the height of the solder fillet of the circuit board, and is larger than the thickness 2t of the flat core 2. Shorten it so that a U-shaped external terminal can be accommodated. Further, in order to improve the solder fillet in connection with the circuit board, the angle of the folded portion 4b is preferably about 90 degrees.
For example, the external dimensions of the bead inductor in this embodiment are approximately 10 mm long, 7 mm wide, and 5 mm high, the width of the plate conductor is 3.0 mm, the thickness is 0.25 mm, and the height of the folded portion is 1.0 mm to A good solder fillet can be formed at 2.0 mm.

FIG. 6 is a cross-sectional view for explaining the solder state of the circuit board.
FIG. 6A shows a solder finish when the angle of the folded portion is 90 degrees.
FIG. 6B shows the solder finish when the angle of the folded portion is greater than 90 degrees.
FIG. 6C shows the solder finish when the angle of the folded portion is smaller than 90 degrees.

  As clearly shown in FIGS. 6A, 6B, and 6C, the amount of solder increases in FIG. 6B, and the rise (Manhattan) phenomenon peculiar to the chip component may occur depending on the reflow solder feeding direction. There is. Further, in the case of FIG. 6C, there is a risk that cracking, cracking or the like occurs in the bent portion when forming the external terminal, and there is a risk that the solder wettability is inferior, and the amount of solder is reduced. From these, it can be seen that the angle of the bent portion of the U-shaped external terminal of the plate-like conductor is preferably about 90 degrees.

  As described above, the bead inductor according to the present invention sandwiches a plate-like conductor having an external terminal formed in a U shape in advance between two flat cores, and provides grooves on both side surfaces of one flat core, thereby Positioning is facilitated, and it is only necessary to drop the external terminal into the groove, so that the assembly process can be simplified. Further, since the forming process and equipment in the assembly process are not required, it is possible to reduce the manufacturing cost and to prevent the flat core damage due to the forming.

  As described above, the bead inductor of the present invention is not limited to the embodiments, and various modifications can be made without departing from the scope of the present invention. For example, the surface groove of the flat core that accommodates the plate electrode is only one embodiment, but half the thickness of the plate conductor may be divided into two flat cores.

1 is a perspective view showing a bead inductor according to a first embodiment of the present invention. The disassembled perspective view of the bead inductor of this invention shown in FIG. Sectional drawing (a) and its modification (b) of the bead inductor of this invention shown in FIG. Sectional drawing of the bead inductor which is the 2nd Example of this invention. Explanatory drawing of the external terminal used for the bead inductor of this invention. The solder finish when the bead inductor is mounted on the circuit board. The disassembled perspective view which shows the conventional bead inductor. Side views (a) and (b) showing a conventional bead inductor.

Explanation of symbols

1, 2 Flat core 3 Plate conductor 4 External terminals 5, 6 Groove

Claims (5)

2. A bead inductor comprising a plate-like conductor sandwiched between two flat cores, wherein the bead inductor includes an external terminal formed in a U-shape at both ends of the plate-like conductor. 2. The bead inductor according to claim 1, wherein a groove for receiving the plate-like conductor is provided on a surface of the two flat cores or one of the flat cores in contact with the other flat core. The bead inductor according to claim 1 or 2, wherein grooves for inserting external terminals of the plate-like conductor are provided on both side surfaces of one of the two flat cores. 4. The bead inductor according to claim 3, wherein a concave portion is provided on a surface of the other flat core in contact with the one flat core, and the internal conductor is incorporated in the concave portion. The U-shaped external terminal of the plate-like conductor has a flat surface in contact with the circuit board surface, extends and bends outward, and the height of the bent portion is equal to or greater than the thickness of the plate-like conductor and the circuit board surface. The bead inductor according to any one of claims 1 to 4, wherein the thickness is equal to or less than a thickness of one flat plate core in contact with the bead inductor.

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