JP2005217280A - Ferrite core, surface-mounted coil component using same, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ferrite core for which core-less grinding of extremely high working efficiency can be adopted and which can be stably mounted on a circuit board, in the ferrite core having flanges at both ends and a body, to provide a surface-mounted coil component using the same and its manufacturing method. <P>SOLUTION: The ferrite core is comprised of a body around which a winding wire is wound, and integrated flanges provided at both ends of the body. A cross-sectional shape of each of the flanges is made into n-angle ((n) is a natural number of ≥6) approximately right polygonal shape, a cross-sectional shape of the body is made similar to the cross-sectional shape of each of the flanges, and each of angular portions of the body is confronted with each of sides of the flanges. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a ferrite core for a surface mount type coil component such as a transformer or a choke coil, and more particularly to a ferrite core having a polygonal flange and a surface mount type coil component, and a method for manufacturing the same.

Ferrite magnetic cores are widely used in surface mount coil components that constitute inductance elements such as transformers and choke coils used in various electronic devices. As this ferrite magnetic core, a drum core having a body having a circular cross section between circular flanges formed at both ends in the axial direction is well known. Hereinafter, the ferrite magnetic core may be referred to as a drum core. The surface mount type coil component is constituted by winding an insulation-coated conductive wire around a drum core body and fixing the end of the winding to a terminal electrode portion formed on a flange by soldering or the like.
In a surface mount type coil component using a drum core having such a circular flange portion, when the side surface of the flange portion is a mounting surface, it is possible to prevent rolling in order to obtain stable mounting on a circuit board. Necessary. As a means for this, there are ones in which the flanges 10a and 10b are formed in a square shape (FIG. 7), and a surface mount type coil component (FIG. 8) in which a linear portion is provided in a part of the circular flange.

The processing of the drum core having the circular flange portion utilizes its rolling property, and the intermediate workpiece is formed by rotating the ferrite workpiece formed in a cylindrical shape by the adjusting wheel 100 by the coreless grinding machine shown in FIG. Was cut with a grindstone 200 of a grinding wheel and formed as a drum core having a circular saddle portion and a circular cross section between the circular saddle portions at both ends in the axial direction. Such coreless grinding is an extremely high processing efficiency because it is easy to supply and discharge the workpiece and it is not necessary to move the grinding wheel of the grinding wheel during grinding.
On the other hand, in the case of a drum core in which the flange portion is not circular as shown in FIGS. 7 and 8, since the ferrite workpiece to be processed does not have rolling ability or is poor, it is simply coreless grinding. However, even if is applied, there is a problem that the body part cannot be formed or the amount of cut of the body part becomes uneven. Therefore, a concave or convex portion is formed on the end face of the prismatic ferrite workpiece, and the body is processed by rotating the ferrite workpiece with this as a center (Patent Document 1), or the shape of the workpiece In the molding process of ferrite powder, cut part C of the shape of notching part of the peripheral surface is provided only at both ends of the cylindrical body, and the middle part is cut with a grinding wheel by a coreless grinder. Grooves were formed, and the drum core was provided with a flange having the cut portions (straight portions) at both ends (Patent Document 2).
Japanese Patent Laid-Open No. 10-172853 JP 7-147211

In the manufacturing method of Patent Document 1, it is necessary to form the formation position of the concave portion or the convex portion serving as the center without variation. However, at the time of molding, when the ferrite workpiece is taken out from the mold, a spring back is generated to cause a dimensional change, and it is difficult to accurately form the concave portion or the convex portion. In addition, when a concave or convex portion is formed by post-processing on the ferrite workpiece, the number of processing steps increases. Further, at the time of processing, it is necessary to support the concave portion and the convex portion and perform centering, and the production efficiency is extremely low.
Further, the manufacturing method of Patent Document 2 uses a ferrite workpiece 30 in which ferrite powder is molded by a mold and cut portions C each having a shape in which a part of a peripheral surface is notched are provided only at both end portions of a cylindrical body. Is. If it is going to form such a cut part, it is necessary to form a convex part in a part of metallic mold. When the work piece is downsized, the convex portion must be made small as a result, and as a result, it becomes difficult to form a cut portion, and the convex portion is compared with other parts at the time of molding. Due to the large pressure acting, there was a problem that the mold was damaged. Further, if the size is reduced, the cylindrical portion 25 that does not form the cut portion is also reduced. Therefore, the contact between the cylindrical portion 25 and the carrier blade 150 and the grinding wheel 200 of the coreless grinding machine becomes insufficient, and the ferrite workpiece is processed. There has been a problem that sufficient rotational movement cannot be given to the object 30 or stable support cannot be provided, and the cut amount of the body portion 20c becomes uneven.

  Accordingly, an object of the present invention is a ferrite core that can employ coreless grinding with extremely high machining efficiency in a ferrite core having a flange part and a body part at both ends, and a terminal formed on the side surface of the flange part. It is an object of the present invention to provide a ferrite magnetic core that can be stably mounted on a circuit board using an electrode, a surface-mounting coil component using the same, and a manufacturing method thereof.

In a first aspect of the present invention, there is provided a ferrite core including a body portion around which a winding is wound and an integral flange portion provided at both ends of the body portion. 6 or more natural number) Ferrite having a substantially regular polygonal shape, a cross-sectional shape of the body portion similar to the cross-sectional shape of the flange portion, and each corner portion of the body portion facing each side of the flange portion It is a magnetic core.
The ferrite magnetic core of the present invention includes a first terminal electrode formed on a first side surface of the flange and a second side surface continuous with the first side surface, and the first side surface or the The second side surface is the mounting surface on the circuit board. And a second terminal electrode formed on the second side surface and a third side surface continuous with the second side surface and electrically non-conductive with the first terminal electrode. Is preferably the mounting surface on the circuit board. Moreover, it is also preferable to round off the boundary part of the said trunk | drum and a collar part.

  A second invention is a surface mount type coil component in which a winding is wound around a body portion of a ferrite magnetic core according to the first invention, and an end portion of the winding is connected to a terminal electrode formed in a collar portion.

A third invention is a method for manufacturing a ferrite magnetic core according to the first invention, wherein the outer peripheral edge of a rounded n-corner (n is a natural number of 6 or more) substantially regular polygonal columnar ferrite workpiece is adjusted. And rotating the ferrite workpiece with the adjustment wheel, and facing the carrier through the ferrite workpiece, and rotating in the opposite direction to the adjustment wheel. Grinding the ferrite workpiece at the outer peripheral edge of the grinding wheel to form a rounded n-corner (n is a natural number of 6 or more), a substantially regular polygonal collar, and a body similar to the collar It is a manufacturing method of the ferrite magnetic core which has a process to do.
In the present invention, the adjustment wheel and the grinding wheel are fixed at a predetermined interval, and the ferrite workpiece is moved along the rotation outer peripheral edge of the adjustment wheel. It is preferable to form the body portion through the closest portion with the outer periphery of the rotation.

  According to the present invention, in the ferrite core having the body portion and the flange portions at both ends thereof, the flange portion has a substantially regular polygonal shape, and the linear side surface thereof is a mounting surface on the circuit board, thereby enabling stable mounting. It is possible to provide a ferrite core that can be used. Then, it is possible to provide a surface mount type coil component in which a winding is wound around the body portion of the ferrite magnetic core and an end portion thereof is fixed to a terminal electrode formed on the flange portion. Furthermore, in the processing of the ferrite core, a coreless grinding process with extremely high processing efficiency can be adopted, so that the processing efficiency is high, the productivity is excellent, and the inexpensive ferrite core and the surface mount coil component using the same. Can be provided.

FIG. 1 is a perspective view of a ferrite core according to an embodiment of the present invention. The ferrite core 1 includes flange portions 1a and 1b and a body portion 1c around which a winding is wound. The flange portions 1a and 1b have a substantially regular hexagonal cross-sectional shape, and each corner portion has a predetermined dimension. A drum core with rounded corners.
Since the linear portions are provided at six rotationally symmetric portions on the side surface of the collar portion, stable surface mountability can be obtained by utilizing this side surface. Further, by rounding each corner, the rolling property is imparted, and the centerless grinding with reference to the side surface of the flange portion is enabled. If the rounding is too large, the straight part on the side surface of the buttock portion is reduced. Therefore, the preferred rounding amount varies depending on the size of the buttock part and is appropriately set depending on the balance between rolling property and surface mountability. It is set to 05 mm to 0.5 mm. When paying attention to the outer dimensions of the collar portion, the rounding amount R is preferably L / 7 to L / 12 with respect to the diameter L of the circle inscribed by the regular hexagon appearing as a cross section of the collar portion.
FIG. 2 is a plan view of a drum core cross section viewed from the axial direction. The cross-sectional shape of the trunk portion 1c is similar to the cross-sectional shape of the collar portion and is a hexagonal shape. Each corner portion of the body portion 1c is configured to face each side of a regular hexagon that appears as a cross section of the collar portion, and each corner portion is rounded. For this reason, when the coated conductor is wound around the trunk portion 1c, the coating of the conductor is not damaged at the corner. Further, in the case of a small drum core, the conducting wire is a thin wire having a diameter of about 0.08, but disconnection can be prevented by rounding the corner of the body as in the present invention.

In the present invention, the dimension of each part of the drum core is not particularly specified. For example, the flange part dimension is φ1.0 mm or more when represented by the diameter of a circle inscribed by a regular hexagon appearing as a transverse section thereof, and its thickness. Is 0.1 mm or more, and the body part is φ0.5 mm or more in terms of the diameter of a circle inscribed by a regular hexagon appearing as a cross section thereof, and the overall height including the body part and the collar part is 0. 0 mm. It is 5 mm or more.
Moreover, although the collar parts 1a and 1b are hexagonal shape in FIG. 1, it is not limited to this, What is necessary is just an n angle | corner (n is a natural number of 6 or more) substantially regular polygonal shape. Preferably n = 6-10. When n exceeds 10, it becomes easy to roll and it becomes difficult to obtain stable surface mountability. In addition, when n is less than 6, it is difficult to obtain rolling properties even when rounded corners are provided. The most preferred number of corners is n = 8.

Such a ferrite magnetic core is processed by the following method.
FIG. 5 is a conceptual diagram for explaining coreless grinding. A substantially hexagonal columnar ferrite workpiece 30 with rounded corners is aligned with a rail (not shown) in the rolling direction by a charging means such as a parts feeder, and the work holding portion 155 of the carrier blade 150 on the adjustment wheel 100 side. To be supplied. Since the ferrite magnetic core of the present embodiment is a non-directional appearance having a rounded substantially regular hexagonal flange, the substantially hexagonal columnar ferrite workpiece 30 also has no directionality. Bulk supply as described above becomes possible.
The ferrite workpiece 30 is in contact with the carrier blade 150 and the rotating outer peripheral edge of the adjustment wheel 100 and is supported by the work holding portion 155. In the workpiece holding part 155, the ferrite workpiece 30 is rotated by the adjusting wheel 100 in the direction opposite to the rotation direction thereof. The carrier blade 150 rotates at a predetermined speed in a direction opposite to that of the adjustment wheel 100, and the ferrite workpiece 30 is sequentially supplied to the other work holding portions 155. The ferrite workpiece 30 is a molded body or a sintered body, but is preferably used as a molded body from the viewpoint of preventing excessive wear of the grindstone and improving the number of processing.

Due to the rotation of the carrier blade 150, the ferrite workpiece 30 moves along the rotation outer peripheral edge of the adjustment wheel 100, and the rotation outer periphery of the adjustment wheel 100 and the rotation outer periphery of the grinding wheel 200 of the grinding wheel are rotated while rotating. Pass through the tangent.
FIG. 6 is a cross-sectional view of the closest portion. Both ends in the axial direction of the ferrite workpiece 30 are held in a freely rotatable state by positioning plates 170a and 170b. The adjusting wheel 100 and the grinding wheel 200 of the grinding wheel are fixed at a predetermined interval, and the ferrite workpiece 30 is processed according to the outer periphery of the adjusting wheel 100 as a reference. Since the ferrite workpiece 30 has a substantially regular hexagonal shape, when the corner portion comes into contact with the adjustment wheel 100, the cutting amount of the grinding wheel 200 of the grinding wheel increases and decreases in the straight portion. For this reason, the body 1c of the ferrite core 1 after processing is similar to the flanges 1a and 1b, and each corner of the body is rounded and opposed to each side of the flange. It becomes.
Further, if both ends of the grindstone are rounded, the boundary between the body portion 1c and the flange portions 1a and 1b can be rounded to form a curved surface, so that the strength after processing can be increased.

  After passing through the closest portion, the ferrite workpiece 30 processed into a predetermined magnetic core shape moves while rotating on the outer periphery of the adjustment wheel 100 by the carrier blade 150, and a rail (not shown) at the discharge portion. Rolls out to the storage box. In the case where the ferrite workpiece 30 is a molded body, it is fired at a predetermined temperature after that, so that a ferrite magnetic core is obtained.

A ferrite core 1 shown in FIG. 3 is formed by forming terminal electrodes 5 and 6 (indicated by hatching in the figure) on the flange portion of the ferrite core shown in FIG. 1, and has two windings such as a common mode choke coil. It is used for coil parts having
The terminal electrode 5 includes one side surface of the flange portion 1b, a first terminal electrode 5a formed on the other side surface continuous with the side surface, a side surface on which the first terminal electrode 5a is formed, and the side surface. The second terminal electrode 5b is formed on the other side surface continuous with the first terminal electrode 5a and is not electrically connected to the first terminal electrode 5a. Similarly, the terminal electrode 6 includes one side surface of the flange 1a, a third terminal electrode 6a formed on the other side surface continuous with the side surface, a side surface on which the third terminal electrode 6a is formed, The fourth terminal electrode 6b is formed on the other side surface continuous with the side surface, and is electrically disconnected from the third terminal electrode 6a.
A lower layer winding (not shown) is directly wound around the body of the ferrite magnetic core 1 as a first winding, and an upper layer winding (not shown) is further wound thereon. Then, both ends of the lower layer winding are connected to the first external terminal 5a and the third external terminal 6a, and both ends of the upper layer winding are connected to the second external terminal 5b and the fourth external terminal 6b. A surface mount type coil component such as a mode choke coil was used. In the surface mount type coil component of the present embodiment, the side surface of the flange portion where both the external electrodes 5a, 5b are formed and the side surface of the flange portion where both the external electrodes 6a, 6b are formed are the mounting surfaces on the circuit board, By connecting both end portions of the lower layer winding and the upper layer winding to the terminal electrodes on the side surface different from the mounting surface, the mounting height of the coil component can be kept low and stable mounting property can be obtained.
The terminal electrodes 5 and 6 are printed or coated and baked with a conductive paste such as silver paste or copper paste, and further plated with nickel plating, solder plating, tin plating, copper plating, gold plating or the like. Is. Both ends of the lower layer winding and the upper layer winding are connected to the terminal electrode by thermocompression bonding or brazing.

FIG. 4 is a perspective view of a ferrite core 1 according to another embodiment. The difference from the ferrite core of FIG. 1 or FIG. 3 is that notches 15a and 15b are provided on one side of the two flanges. This notch is used, for example, to pull out the end of the winding wound around the trunk to the side surface of the flange. The notches 15a and 15b can be formed by providing a linear groove portion in advance on one side surface of a substantially hexagonal prism-shaped ferrite workpiece and grinding the barrel portion.
Further, since the groove is formed on the side surface of the ferrite workpiece, the rolling property required at the time of coreless grinding is not impaired, and the influence of the groove on the body shape during processing is extremely small. For this reason, the trunk cross-sectional shape can be a substantially regular hexagonal shape as in the case of FIGS.

  In FIG. 4, terminal electrodes 5 and 6 (shown by hatching in the figure) are formed on all side surfaces and main surfaces of the collar portion. The body portion has one winding (not shown), and the end portions thereof are drawn out from the notches 15a and 15b of the flange portion, and are connected to the terminal electrodes on the different main surface portions of the flange portion. Such a coil component can be surface-mounted with a terminal electrode on an arbitrary side surface of the flange portion.

  In the present invention, the ferrite material used for the ferrite core is not particularly limited, and various ferrite materials such as Mn—Zn ferrite and Ni—Zn ferrite can be applied. Further, since the ferrite workpiece has a simple shape of a substantially regular n-square columnar body, a known powder molding method can be applied, and molding means such as powder compression molding and extrusion molding can be employed.

  As described above, according to the present invention, the ferrite core having the flange part and the body part at both ends and capable of being stably mounted on the circuit board on the side surface of the flange part, is wound around the body part. In addition to providing a surface mount type coil component in which the end of the wound winding is fixed to the terminal electrode formed on the flange portion, the coreless grinding process with extremely high processing efficiency is adopted in the processing of the ferrite core. Therefore, it is possible to provide a manufacturing method capable of obtaining an inexpensive ferrite core and a surface-mounting coil component using the same, which have high machining efficiency and high productivity.

It is an external appearance perspective view of the ferrite magnetic core which concerns on one Example of this invention. It is the top view which looked at the trunk | drum cross section of the ferrite magnetic core which concerns on one Example of this invention from the axial direction. It is an external appearance perspective view of the ferrite magnetic core which concerns on the other Example of this invention. It is an external appearance perspective view of the ferrite magnetic core which concerns on the other Example of this invention. It is a mimetic diagram for explaining coreless grinding. It is another schematic diagram for demonstrating coreless grinding. It is an external appearance perspective view which shows an example of the conventional ferrite magnetic core. It is an external appearance perspective view which shows the other example of the conventional ferrite magnetic core. It is an external appearance perspective view which shows the shape before processing of the conventional ferrite magnetic core.

Explanation of symbols

1, 10, 20 Ferrite cores 1a, 1b, 10a, 10b, 20a, 20b ridges 1c, 10c, 20c

Claims (7)

  In a ferrite core composed of a trunk portion around which a winding is wound and integral flange portions provided at both ends of the trunk portion, an n-angle (n is a natural number of 6 or more) in which the cross-sectional shape of the flange portion is rounded. A ferrite having a regular polygonal shape, wherein a cross-sectional shape of the trunk portion is similar to a cross-sectional shape of the flange portion, and each corner portion of the trunk portion faces each side of the flange portion. core.   A first terminal electrode formed on a first side surface of the flange portion and a second side surface continuous with the first side surface, wherein the second side surface is used as a mounting surface on a circuit board; The ferrite magnetic core according to claim 1, which is a feature.   2. A second terminal electrode formed on a second side surface and a third side surface continuous with the second side surface and electrically non-conductive with the first terminal electrode. 2. The ferrite core according to 2.   The ferrite magnetic core according to any one of claims 1 to 3, wherein a boundary portion between the body portion and the flange portion is rounded off.   5. A surface-mounting type comprising a winding wound around the body of the ferrite core according to claim 1 and an end of the winding connected to a terminal electrode formed on a flange. Coil parts.   5. The method of manufacturing a ferrite magnetic core according to claim 1, wherein the outer peripheral edge of a rounded n-corner (n is a natural number of 6 or more) substantially regular polygonal columnar ferrite workpiece is adjusted. A process of rotating the ferrite workpiece by the adjusting wheel, contacting the outer periphery of the rotation and the carrier blade, and grinding rotating opposite to the adjusting wheel, facing the ferrite workpiece. The ferrite workpiece is ground at the outer peripheral edge of the vehicle to form a rounded n-corner (n is a natural number of 6 or more), a substantially regular polygonal collar part, and a body part similar to the collar part. A method for producing a ferrite magnetic core comprising a step.   The adjusting wheel and the grinding wheel are fixed at a predetermined interval, and the ferrite workpiece is moved along the rotating outer peripheral edge of the adjusting wheel, and the rotating outer peripheral edge of the adjusting wheel and the rotating outer peripheral edge of the grinding wheel are 7. The method of manufacturing a ferrite core according to claim 6, wherein the body portion is formed by passing the closest portion.

Images