JPH06260342A - Surface-mount type coil component - Google Patents

Abstract

PURPOSE:To provide a surface-mount type coil component which is of law cost, small and of high performance, and which allows sure welding to a substrate. CONSTITUTION:A high frequency transformer 20 is a surface-mount type coil component wherein, with a general ferrite molded as a magnetic material, a coil 11 is wound up on a coil winding shaft part 2 of a drum magnetic core 10 wherein collar parts are respectively assigned at the top and the bottom ends of column-like coil winding shaft part 2 assigned in the vertical direction 1, and, a bottom end side jaw part 5 of the dram magnetic care 10 is formed to be bigger than a top end side jaw part 3, in box shape, and, multiple projections 7 are aligned wherein end faces 4 and 6 of the bottom end side jaw part 5 include a slot 8 of recession, and further, electrode layer 12 (shaded area) is formed over the entire including a bottom face of the projection, and at the same time, the slot 8 is wound up with the end part of the coil 11 so that conductive connection is made with the electrode layer 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface mounting type coil component such as a high frequency transformer and a choke coil which are surface mounted on a circuit board of an electronic device.

[0002]

2. Description of the Related Art In recent years, there is a strong consumer demand for miniaturization and high performance of electronic devices, and accordingly, transformers, choke coils, etc. of coil components occupying a relatively large volume in electronic components mounted on electronic circuit boards. Has been developed with a structure that is suitable for surface mounting while achieving a small size and thinness.

For example, a high-frequency transformer is used in a DC / DC converter, an inverter, etc., and is generally made of a magnetic material having a shape in which a flange is provided at each of the upper end and the lower end of a columnar coil winding shaft portion arranged in the vertical direction. There are many surface-mount type magnetic cores in which a winding is wound around the coil winding shaft portion.

FIG. 5 is a perspective view showing the structure of the conventional surface mount type high frequency transformer.

In the figure, when the drum-shaped magnetic core 41 is used as the high frequency transformer 50, a plurality of windings are wound, and therefore a plurality of terminals for winding the windings and connecting to the mounting board are required. . Therefore, conventionally, a pedestal 44 made of a synthetic resin is separately prepared, in which the metal lead terminal 43 projects from the side surface and is bent into an S shape, and the tip is in contact with the surface of the mounting substrate. One flange 45 of the drum-shaped magnetic core 41 is adhesively fixed to the upper surface of the drum core 41, the end of the winding is wound around the pedestal root portion 47 of the lead terminal 43, and then wound around the winding shaft of the drum-shaped magnetic core 41. The high frequency transformer 50 is configured by repeating the operation of rotating and winding around another lead terminal, and then dipping the lead terminal 43 by soldering. Further, the choke coil has the same configuration.

Since the drum-shaped magnetic core 41 generally has high resistivity, powder of ferrite (nickel zinc ferrite, manganese zinc ferrite, etc.), which is an oxide magnetic material used as a magnetic core material for high frequencies, is pressure-molded. ,
Made by sintering.

Next, a coil component having a large inductance L as compared with its volume is required as a high performance coil component. Generally, when the effective sectional area of a coil component using a magnetic material is uniform, The following relational expression approximately holds.

(Inductance) L = N ² · μe · A / y where μe: effective magnetic permeability, N: number of turns, A: effective cross-sectional area,
y: Effective magnetic path length As is clear from the above relational expression, in order to increase the inductance L, the number of turns N of the winding wound around the magnetic core and the effective sectional area A
Alternatively, it is necessary to increase the effective magnetic permeability μe or shorten the effective magnetic path length y. Here, the effective permeability μe is the ratio of the magnetic flux density to the external magnetic field in the magnetization characteristic curve drawn by plotting the external magnetic field on the horizontal axis and the magnetic flux density on the vertical axis. It is a numerical value determined by the size and shape.

[0009]

However, the drum-shaped magnetic core 41 and the pedestal 44 made of synthetic resin with the lead terminals are provided.
The coil component having the structure in which (1) is combined has the problem that (1) the pedestal portion becomes thicker and the overall height of the coil component becomes higher, which violates the request for thinning.

(2) When the drum-shaped magnetic core 41 is adhesively fixed to the pedestal 44 made of synthetic resin, since positioning is required, there is a problem that the number of manufacturing processes increases.

(3) The metal lead terminal 43 is apt to be distorted due to tensile stress during the winding process of the winding around the terminal (lead terminal 43 'in the figure), and is used for transportation and other handling of coil parts. There is a problem that the lead terminals may be bent.

(4) The bending of the lead terminals causes a problem in that the coil component is unsatisfactorily seated on the mounting substrate and the electrodes cannot be reliably soldered.

(5) Synthetic resin pedestal 4 with lead terminals
No. 4 has a high cost, and there is an unavoidable problem in manufacturing that the manufacturing cost of the coil component becomes high.

(6) In response to the above-mentioned demand for higher performance (higher inductance) of the coil component, the means for increasing the number of turns N of the winding, the effective cross-sectional area A or the effective magnetic permeability μe is a drum having a conventional structure. As long as the shaped magnetic core is used, all work in the direction of increasing the total volume of the coil component, and means for shortening the effective magnetic path length y are also useful for thinning, but increase the winding thickness and increase the occupied area. There was a problem.

The present invention has been made in view of the above circumstances, and the pedestal and the lead terminal are integrated with the drum-shaped magnetic core, the pedestal with the lead terminal is not required, and the process is simplified. The present invention provides a surface-mounted coil component that prevents the electrode from floating and realizes cost reduction.

[0016]

SUMMARY OF THE INVENTION According to the present invention, the coil winding shaft portion of a drum-shaped magnetic core is made of a magnetic material in which a flange portion is provided at each of an upper end and a lower end of a columnar coil winding shaft portion arranged in a vertical direction. In a surface-mounted coil component formed by winding a winding on the lower end side flange portion of the drum-shaped magnetic core having a larger rectangular parallelepiped shape than the upper end side flange portion, a concave shape is formed on at least one end surface of the lower end side flange portion. A plurality of protrusions having grooves are arranged side by side,
An electrode layer is formed on at least the lower surface of the protrusion, and
The above object is achieved by providing a surface-mounted coil component in which an end of a winding is conductively connected to the electrode layer.

[0017]

In the present invention, the entire drum-shaped magnetic core is formed of the magnetic material. For example, ferrite of the magnetic material has a high resistivity and thus serves as a conventional pedestal as a non-conductor. In other words, it may be considered that the lower end side flange portion of the drum-shaped magnetic core is largely deformed to be a flange and also serves as a pedestal for supporting the coil winding shaft portion. Therefore, a pedestal, which is conventionally required separately, is not required, and the coil component manufacturing process is simplified and the cost is reduced.

Further, since the volume of the lower end side flange portion is larger than that of the conventional drum type magnetic core, the effective magnetic permeability μe of the drum type magnetic core increases, which is apparent from the above relational expression. Thus, a larger inductance L is obtained for the same number of turns N.

On the other hand, since the number of turns N required to obtain the same inductance L is reduced as compared with the conventional product, the wire diameter of the winding can be increased, and copper loss (copper winding) as a transformer / choke coil can be increased. Energy loss due to wire resistance) is reduced.

Further, a plurality of protrusions protruding from at least one end surface of the lower end side flange portion formed in a rectangular parallelepiped shape are juxtaposed, and an electrode layer is formed on at least the lower surface of the protrusions. An input / output terminal with the substrate is formed by winding an end portion of the winding around and electrically connecting. On this occasion,
Since the winding wire is wound around the concave groove provided in a part of the protrusion, the winding portion is not exposed from the protrusion.
Therefore, the metal lead terminals required conventionally are not required, and the lower surface of the projection on which the electrode layer is formed is flat, so that it is comfortable to sit on when mounted on a mounting substrate.

Further, since the lower end side flange portion is larger than the upper end side flange portion, after winding the winding around the plurality of protrusions arranged in parallel on the protruding one end face, the windings are turned downward to form the molten solder bath. By immersing only the protruding portion, solder connection to the electrode layer can be easily performed.

Further, two or more of the protrusions are juxtaposed on one end surface of the lower end side flange portion which is formed in a large rectangular parallelepiped shape, and the mutual distance is sufficiently secured, so that the short circuit between the electrodes on the mounting substrate. Less risk of.

[0023]

Embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the same reference numerals are used for members having the same shape.

FIG. 1 is a perspective view showing a first embodiment of a high frequency transformer as a typical example of the surface mount type coil component according to the present invention, and FIG. 2 is a perspective view showing a second embodiment of the high frequency transformer. . 3 is a perspective view showing an embodiment of the choke coil, and FIG. 4 is a third embodiment of the high frequency transformer.

In FIG. 1, a high frequency transformer 20 is formed by molding a general ferrite as a magnetic material, and flanges are provided at the upper end and the lower end of a columnar coil winding shaft 2 arranged in the vertical direction 1. Drum type magnetic core 10
A surface mount type coil component in which a winding 11 is wound around the coil winding shaft portion 2, wherein the lower end side flange portion 5 of the drum-shaped magnetic core 10 is formed in a rectangular parallelepiped shape larger than the upper end side flange portion 3,
A plurality of protrusions 7 having concave grooves 8 are provided in parallel on the end surfaces 4 and 6 of the lower end side flange portion 5, and an electrode layer 12 (hatched portion) is formed on the entire surface including the lower surface of the protrusions. The end portion of the winding wire 11 is wound around 8 and electrically connected to the electrode layer 12.

Ferrite, which is the material of the drum-shaped magnetic core 10, is an oxide magnetic material, and is made by pressing and sintering raw material powder. Since this ferrite has a relatively large resistance and a small high frequency loss, it is generally used as a magnetic material for high frequencies, and there are types such as nickel ferrite, nickel cobalt ferrite, nickel zinc ferrite, and manganese zinc ferrite.

The drum-shaped magnetic core 10 is entirely made of ferrite, and the drum-shaped magnetic core 10 itself serves as a pedestal, and since metal lead terminals are not used, it is easy to integrally form the ferrite,
The processing steps can be simplified and the cost can be reduced.

Next, the electrode layer 12 is formed by immersing the protrusion 7 in a bath containing Ag paste (comprising Ag powder, glass, vehicle, etc.) and then pulling it up to 150 ° C.
Then, the electrode layer is formed by baking at 600 ° C. to 800 ° C. after drying. Further, the conductive connection method of the winding end is performed by winding the winding 11 (enamel-coated conductor wire, polyurethane-coated conductor wire, etc.) in the concave groove 7 of the projection 7 on which the electrode layer 12 is formed.
The end portions of are wound, and the protrusions 7 are immersed in the molten solder bath together with the wound portions, and then pulled up to perform solder connection. At this time, the concave groove 8 is effective for ensuring the winding of the winding wire 11 around the protrusion 7 and for preventing the winding portion from being exposed from the lower surface of the protrusion 7.

The coating of enamel or polyurethane on the wound winding ends is melted and removed by the heat during immersion in the molten solder bath.

Regarding the winding 11, it is generally desirable to increase the wire diameter to reduce the copper loss if the same inductance is obtained, but in the conventional product, the winding portion of the columnar coil winding shaft portion 2 is Larger and smaller high frequency transformer
It will be against the thinness.

In this respect, the high frequency transformer 2 according to the present invention
At 0, since the volume of the lower end side flange portion 5 is larger than that of the conventional drum type magnetic core, the change in the magnetic flux density with respect to the external magnetic field becomes large. That is, the high frequency transformer 20
The effective magnetic permeability .mu.e is increased, and as can be seen from the above relational expression, the number of turns N required to obtain the same inductance L is small, so that the copper loss can be reduced.

On the other hand, it goes without saying that a larger inductance L can be obtained for the same number of turns N and effective area A.

Further, in the high frequency transformer 20 of the present embodiment, four projections or electrode layers arranged in parallel at equal intervals are arranged on each of the two end faces 4 and 6, so that it is possible to correspond to an eight-terminal coil structure. .

Next, the high frequency transformer 25 according to the second embodiment of FIG. 2 has four protrusions 7 having a concave groove 8 only on one end face 16 of the lower end side flange portion 15 formed in a rectangular parallelepiped shape. It is a configuration in which they are arranged in parallel at intervals. A high frequency transformer having one primary coil and one secondary coil can be dealt with in this embodiment, and the degree of freedom in wiring design of the mounting board is increased.

FIG. 3 shows a choke coil 30 according to the present invention.
FIG. 9 is a perspective view showing an embodiment of the present invention, in which two protrusions having a concave groove 8 are formed only on one end surface 36 of a lower end side flange portion 35 formed in a rectangular parallelepiped shape larger than the upper end side flange portion 33 in the drum-shaped magnetic core 31. This is a configuration in which 7 are arranged in parallel. The lower end side flange portion 35 is larger in size in the winding axis direction and in the direction of the end face 36 having a protrusion than the upper end side flange portion 33.

Also in the choke coil 30 of this embodiment, the cost is low, the electrode layer can be easily formed, and the soldering to the mounting substrate can be surely performed. It goes without saying that it has an effect.

FIG. 4 shows a high frequency transformer 40 showing another structure of the drum-shaped magnetic core 10 in the high frequency transformer 20 of FIG.
The conventional lower end side flange part 45 and the upper end side flange part have the same size and shape, and the entire lower end side flange part 45 can be fitted to the center of the upper surface of a separate ferrite pedestal 51. A concave portion 49 is provided, and the lower end side flange portion 45 has the concave portion 49.
It is supposed to be buried in.

In the above structure, the conventional drum type magnetic core 4 is used.
1 is used to integrally form a drum-shaped magnetic core 1 according to the first embodiment.
It goes without saying that the same effect as 0 can be obtained.

In addition, as a reminder, the shapes of the upper and lower flanges and the shape of the protrusions in the present invention are the same as those of the embodiment, and the difference in the location of the concave groove is different. By forming an electrode layer on at least the lower surface of the protrusion of the lower end side flange portion, it is possible to achieve the miniaturization and high performance of the surface mount type coil component which is the object of the present invention and to solder it to the mounting board. Of course, it is possible to prevent defects and reduce costs.

[0040]

Since the coil component according to the present invention is constructed as described above, it has the following effects.

(1) The pedestal and the metal lead terminal, which are conventionally required separately, are not required, and the coil component is small and compact.
It has an excellent effect of reducing the thickness and reducing the cost.

(2) It has an excellent effect that a larger inductance L can be obtained for the same number of turns N.

(3) The wire diameter of the winding can be made larger than that of the conventional product, which has an excellent effect of reducing copper loss.

(4) It has an excellent effect that the projections on which the electrode layers are formed are stable on the substrate during surface mounting, and soldering can be reliably performed.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of a high frequency transformer according to the present invention.

FIG. 2 is a perspective view showing a second embodiment of the high frequency transformer according to the present invention.

FIG. 3 is a perspective view showing an embodiment of a choke coil according to the present invention.

FIG. 4 is a perspective view showing a third embodiment of the high frequency transformer according to the present invention.

FIG. 5 is a perspective view showing a high-frequency transformer using a conventional drum-shaped magnetic core.

[Explanation of symbols]

 1 Vertical direction 2 Coil winding shaft part 3, 33 Upper end side flange part 4, 6, 16, 36 End surface 5, 35 Lower end side flange part 7 Protrusion (part) 8 Concave groove 10, 15, 31, 41 Drum type magnetic core 11 winding 12 electrode layer 20, 25, 40, 50 high frequency transformer 30 choke coil 43, 43 'metal lead terminal 44 synthetic resin pedestal 45, 46 tsuba 47 lead terminal portion near the pedestal 49 recess 51 ferrite pedestal

Claims (1)

[Claims] 1. A winding is wound around the coil winding shaft portion of a drum-shaped magnetic core made of a magnetic material in which a flange portion is provided at each of an upper end and a lower end of a columnar coil winding shaft portion arranged in a vertical direction. In the surface mount type coil component, the lower end side flange portion of the drum-shaped magnetic core is formed in a rectangular parallelepiped shape larger than the upper end side flange portion, and a plurality of protrusions having concave grooves are arranged on at least one end surface of the lower end side flange portion. A surface-mounted coil component, wherein an electrode layer is formed on at least the lower surface of the protrusion, and an end portion of a winding is conductively connected to the electrode layer.