JP2001313214A - Surface-mounting small transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a surface-mounting small transformer to be lessened in thickness and improved in reliability by protecting it against disconnection. SOLUTION: A surface-mounting small transformer is equipped with a lower core 3, an upper core 1, and a winding coil 2. The core 1 is integrally molded like a cap composed of a center column 4 and a circumferential part 5 surrounding the center column 4 and possessing cutouts 6 and 7, the core 3 is integrally molded nearly like a disk, and both are formed using the sintered magnetic metal powder. A conductive pattern 13 is formed on the peripheral part of the lower core 3, a lead wire 17 provided to the winding coil 2 is bonded to the conductive pattern 13 by thermocompression, an annular insulating film for setting a gap is provided to the lower core 3, and the peripheral part of the winding coil is positioned and fixed with an adhesive agent by getting into a stepped part 19 between the annular insulating film and the lower core 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer having a winding coil sealed with a magnetic material, and more particularly to a thin surface-mount type transformer which is surface-mounted on a printed circuit board.

This type of surface mount type transformer is used, for example, for an inverter for driving electroluminescence, and is often incorporated in a small device such as a mobile phone or a camera. Has been requested. Conventionally, this type of surface mount type transformer has a structure as shown in FIGS. FIG. 13 is a top view of a conventional surface mount type transformer, and FIG.
4 is a cross-sectional view, and the right side of the surface mount transformer of FIG. 14 is a line segment ox perpendicular to the paper of the surface mount transformer of FIG.
And the left side shows a cross-sectional view taken along a plane perpendicular to the paper and passing through a line segment oy. An upper core 20 and a lower core 21 made of a cap-shaped magnetic material having a central cylindrical portion and a peripheral portion surrounding the cylindrical portion and having two notches are opposed to each other, and a very thin winding is formed in the cylindrical portion. Wire coil 22
Is wound, and the bobbin 23 is inserted.

The bobbin 23 is formed by injection molding of plastic and has two projecting portions 24 and 25. A metal lead terminal 28 is insert-molded on the projecting portion 24 as shown in FIG. And are provided integrally. The projecting portion 24 of the bobbin projects outward at the cutout portions 30 and 31 of the upper core and the lower core, and
The end of the winding is pulled out at the notch 31, entangled with the lead terminal 28, soldered and fixed. The lead terminal 28 is formed in a crank shape as shown in FIG.
The bent bottom surface is soldered and fixed to the circuit board. The upper core 20 and the lower core 21 are bonded and fixed at the mating surface. However, a fixed gap is provided and fixed in order to increase the pressure rising efficiency. This gap is formed by sandwiching a spacer made of an insulating material having a constant thickness between the mating surfaces.

[0004]

On the other hand, the above-mentioned conventional surface-mount type transformer has a cap shape for both the upper core and the lower core, so that it is difficult to reduce the thickness.

In the conventional structure, the lead wire is routed from the center of the bobbin to the lead terminal. Therefore, the length of the lead wire is increased, the wire is easily broken by vibration or the like, and if the lead wire is wound around the bobbin ear to fix the lead wire. The lead wire and the core come into contact with each other due to repetition of vibration or the like, which causes a drop in coil performance or disconnection.

Further, since the metal lead terminal is formed by insert molding, the holding force is weakened by aging vibration or heat, the lead terminal moves, and a pulling force is applied to the lead wire.
Disconnection may occur. Further, since the lead wire from the winding coil is entangled with the terminal and soldered, disconnection easily occurs. Therefore, a defect is apt to occur and the yield is deteriorated.

In addition, since a bobbin is used, the number of components increases and the cost increases accordingly. In addition, there is a disadvantage that the thickness is increased accordingly.

The gap between the upper core and the lower core is adjusted by interposing a spacer made of an insulating material between the mating surfaces.
This puts the spacer between very small areas,
It is a rather time-consuming operation and has problems.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, to further reduce the thickness of the surface mount type transformer, and to reduce the manufacturing cost by adopting a simple structure.

[0010]

Means for Solving the Problems In order to solve the above problems, a surface mount type small transformer of the present invention employs the following configuration.

[0011] In the surface mount type small transformer according to the present invention, the lower core, the upper core, and the winding coil are provided. The upper core is formed integrally with each other in a cap shape including a central cylindrical portion and an outer peripheral portion surrounding the cylindrical portion.

The surface mount type small transformer according to the present invention comprises a lower core, an upper core, and a winding coil wound on a bobbin, wherein both the lower core and the upper core are formed by sintering magnetic metal powder. Are formed integrally with each other in the form of a flat plate, and the upper core is formed integrally with each other in the form of a cap having a central cylindrical portion and an outer peripheral portion surrounding the cylindrical portion.

In the surface mount type small transformer of the present invention, a protrusion is integrally formed on the outer periphery of the lower core or on the outer periphery of the upper core, and an insulating film is formed on the upper surface, the outer surface, and the lower surface of the protrusion. On top of this insulating film, the upper surface, the outer surface,
A conductive pattern connected to the lower surface is formed, and an adhesive is applied to the conductive pattern after the lead wire of the winding coil is heated and pressed.

[0014] In the surface mount type compact transformer of the present invention, the left and right outer peripheral portions of the lower core are cut into D shapes, and an insulating film is formed over the upper surface, the outer surface, and the lower surface of the D cut portion. A conductive pattern formed by connecting the upper surface, the outer surface, and the lower surface to each other, and the adhesive is applied to the conductive pattern after the lead wire of the winding coil is heated and pressed.

In the surface mount type compact transformer of the present invention, at least one or more through holes are provided at a plurality of locations on the outer periphery of the lower core, and an insulating film is formed over the upper, lower and inner diameter surfaces of these through holes. And
A conductive pattern is formed on the insulating film. The conductive pattern connects the upper surface, the inner diameter surface, and the lower surface, and the conductive pattern is coated with an adhesive after the lead wire of the coil is heated and pressed. And

In the surface mount type compact transformer according to the present invention, the upper core has a cutout portion on the outer periphery, and the lead wire of the winding coil is drawn out from the cutout portion and is fixed by an adhesive. It is characterized by.

In the surface mount type small transformer according to the present invention, the lower core has a ring-shaped insulating film for setting a gap between the upper core and the lower core.

In the small surface-mount type transformer according to the present invention, the outer peripheral surface of the winding coil is positioned so as to fit into the step between the ring-shaped insulating film formed on the lower core and the lower core.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a small surface-mount type transformer according to the best mode for carrying out the present invention will be described below with reference to the drawings. FIGS. 1, 2 and 3 show a first embodiment of a surface-mount type small transformer according to the present invention. FIG. 1 is a perspective view, FIG. 2 is a top view, and FIG. The left side of the small surface-mount type transformer of FIG. 3 is a sectional view of the surface-mount small type transformer of FIG. ing. FIG. 4 is a sectional view of a second embodiment of the surface-mount type small transformer according to the present invention. FIGS. 5, 6, and 7 show a third embodiment of the surface-mount small transformer of the present invention. FIG. 8 shows a fourth embodiment of the surface-mount small transformer of the present invention. I have. FIGS. 9, 10, and 11 show a fifth embodiment of the surface-mount small transformer of the present invention, and FIG. 12 shows a sixth embodiment of the surface-mount small transformer of the present invention. It is. Each embodiment will be described below with reference to FIGS. 1 to 12 as appropriate.

First, a first embodiment of the surface mount type small transformer according to the present invention will be described. In FIG. 1, the small surface-mount type transformer includes an upper core 1, a winding coil 2, and a lower core 3. The upper core 1 includes a central cylindrical portion 4 integrally formed by sintering of a metal powder and an outer peripheral portion 5 surrounding the cylindrical portion 4. The outer peripheral portion 5 has two cutout portions 6 and notch portions 7. Is formed.

The lower core 3 is formed by sintering a magnetic metal powder in the same manner as the upper core, and has a projection 9 and a projection 10 at two locations on the outer periphery thereof. As shown in FIGS. 2 and 3, an insulating film 15 and an insulating film 16 coated with a resin are formed on the upper surface, the outer surface, and the lower surface of the two projecting portions 9 and 10, respectively. The conductive pattern 11 and the conductive pattern 12 are formed on the insulating film 15.
A conductive pattern 13 and a conductive pattern 14 are formed on the upper surface 6 so as to be connected to the upper surface, the outer surface, and the lower surface. These conductive patterns are formed by printing a conductive metal powder such as silver, graphite, or copper into a paste. A substantially ring-shaped insulating film 8 formed by printing a resin on a portion of the upper surface of the lower core 3 which is to be a mating surface with the upper core 1 described later.
Is formed.

The upper core 1 and the lower core 3 are
The surface on which the insulating film 8 is formed is on the upper surface side, and two notches 6 and 7 of the upper core 1 and two protrusions 9 of the lower core 3 are provided.
And 10 are combined so that they match. Winding coil 2
Is mounted inside the upper core 1 surrounded by the upper core 1 and the lower core 3 such that the air core of the coil 2 is inserted into the cylindrical portion 4 of the upper core 1.

In order to prevent the wound coil 2 from directly contacting the upper core 1 and the lower core 3, the outer peripheral surface of the wound coil 2 is hardened by coating an insulating adhesive such as a UV curing resin. . As shown in the cross-sectional view of FIG. 3, the winding coil 2 is positioned such that its lower outer surface fits into the step 19 with the substantially ring-shaped insulating film 8 formed on the lower core 3.

The lead wire 17 of the coil 2 is drawn out from the cutout 6 of the upper core 1 and overheated and crimped to the conductive pattern 13 provided on the upper surface side of the protruding portion 10 of the lower core 3 to conduct electricity. An adhesive is applied to the joint between the lead wire 17 and the conductive pattern 13 and the notch 6 to prevent the lead wire 17 from peeling off and to prevent the upper core 1 and the lower core 3 from coming out.
And the winding coil 2 and the lower core 3 are bonded and fixed. On the other hand, the conductive patterns 11, 12, 13, and 14 provided on the lower surfaces of the protruding portions 9, 10 are joined to the circuit board for integration. In the present embodiment, the connection between the lead wire 17 and the conductive pattern 13 is performed by a heating and pressure bonding method, but another method such as soldering may be used.

The insulating film 8 formed in a substantially ring shape is provided for setting a gap between the upper core 1 and the lower core 3, and the gap changes the inductance, thereby affecting the boosting efficiency. In order to increase the boosting efficiency, it is appropriate to design the gap in a range of approximately 10 to 60 μm. Although it is necessary to strictly control this gap so as to be within the design range, it can be relatively easily achieved by using the thickness of the insulating film.

Next, a second embodiment of the surface mount type small transformer according to the present invention will be described. As shown in FIG. 4, the transformer according to the present embodiment simplifies the transformer according to the first embodiment, and the gap is set to 0 without providing the insulating film 8 on the lower core 3. Further, a bobbin 18 is provided, and a winding coil is formed on the bobbin 18. With such a structure, electrical conduction between the core and the winding is eliminated, and disconnection of the winding is prevented. In addition, since winding is performed inside the bobbin, the winding operation is facilitated.

Next, the third embodiment of the surface mount type transformer according to the present invention will be described.
An embodiment will be described. 5 is a perspective view, FIG. 6 is a top view, and FIG. 7 is a sectional view. As shown in FIG. 5, the materials, generation methods, shapes, and the like of the upper core 1 and the winding coil 2 are the same as those in the first embodiment. Similarly to the upper core 1, the lower core 3 is formed by sintering magnetic metal powder, and two right and left peripheral portions thereof are cut into a D shape.
And a D-cut portion 41 are provided. The upper, outer, and lower surfaces of the two D-cut portions 40 and 41 are shown in FIG.
As shown in FIG. 7, an insulating film 47 coated with a resin is formed. Further, a conductive pattern 44 and a conductive pattern 45 are formed on the insulating film 47, and a conductive pattern 42 and a conductive pattern 43 are formed on the insulating film formed in the D-cut portion 40. It is connected to and formed. A substantially ring-shaped insulating film 8 is formed by printing a resin on a portion of the upper surface of the lower core 3 that is to be a mating surface with the upper core 1.

The notch 6 and the notch 7 of the upper core 1 are assembled with the D-cut 41 and the D-cut 40 of the lower core 3, respectively. Step 1 of lower core 3
9, positioning of the winding coil 2 and conduction between the lead wire of the winding coil 2 and the conduction pattern of the D-cut portion and the processing method, setting of the gap between the upper core 1 and the lower core 3 and the like are the first.
Since the third embodiment is the same as the first embodiment, a detailed description is omitted.
Since the protrusion of the lower core is eliminated as compared with the transformer of the first embodiment, the width of the lower core 3 can be reduced. Further, the core material can be reduced by that much, so that the cost can be reduced. Although the D cut portions 40 and 41 of the lower core 3 in this embodiment are provided with D cuts so as not to be smaller than the inner diameter of the circumferential portion 5 of the upper core 1, they are not shown, It is also possible to provide a D-cut so that it is slightly smaller than the inner diameter of the circumferential portion 5 and slightly larger than the outer diameter of the coil 2. When such a D-cut dimension is set, a gap is generated at the D-cut portion on the mating surface between the lower core 3 and the upper core 1. By utilizing this gap, the lead wire of the coil 2 can be drawn out from this gap and joined to the conduction pattern to achieve conduction. With this structure, there is no need to provide a cutout in the upper core 1.

A fourth embodiment of the surface mount type small transformer according to the present invention will be described. As shown in FIG. 8, in the transformer according to the present example, the gap is set to 0 without providing the insulating film 8 on the lower core 3 by simplifying the transformer of the third embodiment. Further, a bobbin 18 is provided, and a winding coil is formed on the bobbin 18. By adopting such a structure, while eliminating electrical conduction between the core and the winding,
Prevents winding breakage. In addition, since winding is performed inside the bobbin, the winding operation is facilitated.

Next, a fifth embodiment of the surface mount type small transformer according to the present invention will be described. FIG. 9 is a perspective view, FIG.
0 is a top view and FIG. 11 is a sectional view. As shown in FIG. 9, the materials of the upper core 1 and the winding coil 2, the generation method, the shape, and the like are the same as those in the first embodiment. Similarly to the upper core 1, the lower core 3 is formed by sintering magnetic metal powder, and has two through holes at two locations on the left and right sides of the outer peripheral portion. As shown in FIG. 9, through holes 50 and 51 are provided on the right side of the lower core 3, and through holes 52 and
53 is formed. Each of these through holes is
An insulating film 54 and a conductive pattern 55 are formed on the upper surface, the lower surface, and the inner diameter surface. The insulating film 54 and the conduction pattern 5
5 can be applied to the inner surface of the through hole by working while vacuuming the through hole during printing. A substantially ring-shaped insulating film 8 is formed by printing a resin on a portion of the upper surface of the lower core 3 which is to be mated with the upper core 1.

The notch 6 and the notch 7 of the upper core 1 and the through holes 52 and 53 and the through holes 50 and 51 of the lower core 3 are assembled so as to be aligned with each other. The positioning of the winding coil 2 by the step 19 of the lower core 3, the conduction between the lead wire of the winding coil 2 and the through hole and the processing method, the setting of the gap between the upper core 1 and the lower core 3, and the like are described in the first embodiment. Therefore, detailed description is omitted. Since the protrusion of the lower core is eliminated as compared with the transformer of the first embodiment, the width of the lower core 3 can be reduced. Also, since printing on the side surface can be eliminated, the number of printing steps for the lower core is reduced, and the cost can be reduced.

In this embodiment, there are two through holes at the left and right,
Each of the two through holes is provided. However, the number of through holes is not particularly limited to two at the left and right, and a plurality of through holes may be provided according to the number of lead wires of the winding coil. Also, the number of through holes may be set according to the number of lead lines.

A sixth embodiment of the surface-mount small transformer according to the present invention will be described. As shown in FIG. 12, the transformer according to the present embodiment simplifies the transformer according to the fifth embodiment, and the gap is reduced to 0 without providing the insulating film 8 on the lower core 3.
It is. Also, a bobbin 18 is provided, and the bobbin 18 is provided.
To form a winding coil. With such a structure, electrical conduction between the core and the winding is eliminated, and disconnection of the winding is prevented.

[0034]

As described above, according to the surface mount type compact transformer of the present invention, the upper core is formed into a cap shape and the lower core is formed into a substantially disc shape by sintering the magnetic metal powder. A thin transformer suitable for mounting can be formed.

As shown in the third, fourth, fifth, and sixth embodiments of the present invention, by eliminating the protrusion of the lower core, the lower core can be made smaller in width, so that the size can be reduced. Further, the core material can be reduced by that much, so that the cost can be reduced.

Since the winding coil is positioned at the step portion of the insulating film and the outer peripheral surface is fixed from the cutout portion with an adhesive,
Contact with the core due to vibration or the like can be prevented. Therefore,
The performance of the wound coil does not deteriorate over time.

Since the conductive pattern is formed on the insulating film of the lower core, it is possible to prevent the lead wire from being disconnected due to a tensile force applied thereto. Further, since the lead wire is heat-pressed to the conductive pattern and fixed with an adhesive, it is possible to prevent the occurrence of disconnection.

Further, the gap adjustment is relatively easy because it is performed with the thickness of the insulating film, and the steps required for the gap adjustment are shortened. Therefore, it is possible to reduce the number of assembly steps and increase the boosting efficiency.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of a surface-mount small transformer according to the present invention.

FIG. 2 is a top view of the first embodiment of the surface-mount small transformer according to the present invention.

FIG. 3 is a cross-sectional view of the first embodiment of the surface-mount small transformer according to the present invention.

FIG. 4 is a cross-sectional view of a second embodiment of the surface-mounted small transformer according to the present invention.

FIG. 5 is a perspective view showing a third embodiment of the surface-mount small transformer according to the present invention.

FIG. 6 is a top view of a third embodiment of the surface-mount small transformer according to the present invention.

FIG. 7 is a cross-sectional view of a third embodiment of the surface-mount small transformer according to the present invention.

FIG. 8 is a cross-sectional view of a fourth embodiment of the surface-mount small transformer according to the present invention.

FIG. 9 is a perspective view showing a fifth embodiment of the surface-mounted small transformer according to the present invention.

FIG. 10 is a top view of a fifth embodiment of the surface-mount small transformer according to the present invention.

FIG. 11 is a sectional view of a fifth embodiment of the surface-mount small transformer according to the present invention.

FIG. 12 is a sectional view of a sixth embodiment of the surface-mount small transformer according to the present invention.

FIG. 13 is a top view of a conventional surface-mount small transformer.

FIG. 14 is a cross-sectional view of a conventional surface-mount small transformer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Upper core 2 Winding coil 3 Lower core 4 Column part 5 Circular part 6,7 Notch part 8,15,16,40,41,46,47,54 Insulating film 9,10 Projection part 11,12,13 , 14, 42, 43, 44, 45, 5
5 Conduction pattern 50, 51, 52, 53 Through hole 17 Lead wire 18 Bobbin 19 Step

Claims (8)

[Claims] 1. A lower core, an upper core, and a winding coil, wherein the lower core and the upper core are each formed by sintering magnetic metal powder, the lower core is formed into a flat plate shape, and the upper core is formed into a central column and a column. In the shape of a cap consisting of the outer periphery surrounding the part,
Surface mounted small transformers characterized by being integrally molded. 2. A lower core, an upper core, and a winding coil wound on a bobbin, wherein the lower core and the upper core are each formed by sintering magnetic metal powder, the lower core is formed in a flat plate shape, and the upper core is formed in the center. A compact surface mount type transformer characterized by being formed integrally with each other in a cap shape comprising a cylindrical portion and an outer peripheral portion surrounding the cylindrical portion. 3. A projecting portion is integrally formed on an outer peripheral edge of the lower core or an outer peripheral portion of the upper core, and an insulating film is formed on an upper surface, an outer surface, and a lower surface of the projecting portion. 3. The surface according to claim 1, wherein a conductive pattern is formed by connecting the side surface and the lower surface, and an adhesive is applied to the conductive pattern after heating / compression bonding of the lead wire of the winding coil. Mounting type small transformer. 4. An outer peripheral portion of the lower core is cut into two right and left portions in a D shape, and an insulating film is formed over an upper surface, an outer surface, and a lower surface of the D cut portion, and the upper surface, the outer surface, and the lower surface are formed on the insulating film. And a conductive pattern formed by connecting a lead wire of the winding coil to the conductive pattern after heating and pressure bonding.
Or the surface-mounted small transformer according to 2. 5. At least one or more through holes are provided at a plurality of positions on the outer peripheral portion of the lower core, and an insulating film is formed over the upper surface, the lower surface, and the inner diameter surface of these through holes. 3. The conductive pattern according to claim 1, wherein a conductive pattern connecting the inner diameter surface and the lower surface is formed, and an adhesive is applied to the conductive pattern after the lead wire of the winding coil is heated and pressed. Surface mount type small transformer. 6. The upper core has a notch in an outer peripheral portion,
The small surface mount type transformer according to any one of claims 1 to 5, wherein a lead wire of the winding coil is drawn out from the cutout portion and is fixed by an adhesive. 7. The small surface mount type transformer according to claim 1, wherein the lower core has a ring-shaped insulating film for setting a gap between the upper core and the lower core. 8. The winding coil according to claim 1, wherein an outer peripheral surface of the winding coil is positioned so as to fit into a step between the ring-shaped insulating film formed on the lower core and the lower core.
8. The surface mount type small transformer according to any one of claims 1 to 7.