JPH10284331A - Low profile chip inductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low profile chip inductor which is easy to be mounted with a high accuracy and does not cause a faulty insulation. SOLUTION: A lead frame electrode is provided with a bifurcated lower electrode 3' and an upper electrode 3. A core 1 in the shape of a drum with a vertical winding 4 wrapped by a magnetic metal sleeve or without sleeve is sandwiched between the two electrodes 3 and 3' and is fixed. The core 1 and the two electrodes 3 and 3' are sealed with resin exclusive of outer terminals 3'f and 3f.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-profile chip inductor used for a thin electronic device, and more particularly to a high-profile low-profile chip inductor.

[0002]

2. Description of the Related Art Conventionally, the structure of a small, low-profile chip inductor used in a thin electronic device is disclosed in,
No. 920 (TDK Corporation) and JP-A-6-44532 (Matsushita Electric Industrial Co., Ltd.) are known and are actually commercially available. 56-692
In the chip inductor described in No. 0, as shown in FIG. 5, a winding 14 is applied to a drum core 11 (drum-shaped core) made of a high-permeability ferrite, and a pair of high-permeability semicircles are provided therearound. The magnetic metal fittings 12 and 12 ′ that do not reach are connected by an adhesive to form a closed magnetic path, a part of these metal fittings is cut and raised to form a connecting piece, and both ends of the winding are connected to these connecting pieces. It is tied to a piece. The arc-shaped magnetic fittings 12, 12 'thus also serve as conductors. In this example, it is difficult to attach the arc-shaped magnetic fittings 12 and 12 ′ to the core 11 with high accuracy, so that
It is difficult to control the gap between 2 'and the core 11 constant, and it is difficult to keep the inductance constant. On the other hand, Japanese Unexamined Patent Publication No.
As shown in FIG. 5, a non-magnetic split ring 17 is placed around a small drum core 11 on which coil winding is applied in the same manner as in FIG. 5, and two connecting metal pieces 17a are formed on the drum core 11. The grooves are fitted and fixed by bonding, and the ends of the coil windings are wrapped around them. In this case, since the split ring 17 is non-magnetic, there is no problem associated with the conventional example of FIG. 5, but there is a problem that when the reflow soldering of the split ring 17 is performed, solder enters from the slit 17b to cause a short circuit. is there. Since the split ring 17 is non-magnetic, only an open magnetic circuit structure is possible and the inductance is low.

[0003]

In the conventional inductor using the split-type magnetic bracket shown in FIG. 5, since a single processed metal bracket is used, the assembly of the inductor is complicated. Not only is the soldering work including the terminal treatment after winding difficult, but also there is a disadvantage that an inductor having a constant inductance cannot be manufactured due to low assembly accuracy. On the other hand, in the conventional inductor using the non-magnetic split ring shown in FIG. 6, there is a gap between the drum-shaped core and the substantially cylindrical non-magnetic ring. In the case of the soldering operation using the solder, the solder invades the gap, causing a short circuit between the windings, and there is a problem in workability and reliability.

[0004]

Accordingly, in order to solve the above-mentioned problems, the present invention utilizes a lead frame as an electrode terminal, and is preferably wrapped with a sleeve-like magnetic metal fitting, and is provided with a winding type vertical type. Wherein the entire drum core is completely sealed with an insulating resin except for the external terminal portions of the electrode terminals. More specifically, the chip inductor of the present invention has a lead frame electrode structure having a bifurcated lower electrode and an upper electrode, and between the two electrodes,
A position is fixed by sandwiching a drum-type core provided with a vertical-type winding, and the core and the two electrodes are sealed with a resin except for the external terminal portions of the two electrodes. In order to configure the chip inductor to have a closed magnetic circuit type, the lead frame electrode shape has a structure having two forked lower electrodes and an upper electrode, and between the two electrodes,
A drum-type core with a vertical-type winding wrapped in a sleeve-shaped magnetic bracket is sandwiched between the cores and the position is fixed, and the core and the two electrodes are sealed with resin except for the external terminal portions of the two electrodes. Stop. The present invention is further characterized in that the adhesiveness between the drum-type core and the magnetic metal fitting is maintained by injecting and curing an ultraviolet curable resin into the gap between the drum-type core and the sleeve-like magnetic metal fitting. The present invention is further characterized in that the bifurcated lower electrode has a height regulating projection projecting downward.

[0005]

The chip inductor of the present invention has a structure in which the lead frame has a bifurcated lower electrode and an upper electrode, so that the position of the drum core can be properly arranged by utilizing these elasticities. By precisely defining the positional relationship between the drum core, the electrodes, and the resin during resin molding, it is possible to provide a chip inductor having excellent characteristics. This position regulation is made more accurate by the positioning projections and guides. In addition, by enclosing the drum-type core provided with the vertical-type winding with a sleeve-shaped magnetic metal fitting having slits, the adhesion between the two is enhanced, and a closed-magnetic-path-type high-inductance inductor can be provided. . In this case, since the sleeve-type magnetic fitting is used, there is no possibility that the gap fluctuates unlike the related art, and it is possible to suppress variations in products and to provide a highly reliable inductor. Furthermore, since the forked lower electrode has a positioning projection that projects downward and comes into contact with the mold cavity surface, the electrode and the drum-shaped core can be accurately positioned with respect to the resin molded body, thereby preventing molding defects. can do. According to the present invention, automatic assembly using a lead frame becomes possible, and by completely sealing with an insulating resin, a soldering method conventionally limited to a reflow furnace specification can be used in a flow furnace specification. It becomes possible.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view showing a chip inductor according to one embodiment of the present invention, and an insulating resin molded body 6 is indicated by a dotted line for easy understanding. 2 is a plan view of FIG. 1, FIG. 3 is a partial cross-sectional view taken along line AA of FIG. 2, and FIG.
It is a BB partial sectional view. In these figures, a drum-type core 1 is a vertical-type drum-type core, and has a core portion provided with a winding 4 and a groove portion 1a formed to be recessed into the center of the upper and lower collar portions. The groove 1a has a conductive internal electrode 5a.
Is formed from a double layer of, for example, a Ni—Cr layer and a Cu layer by a film forming method such as sputtering. Both ends of the winding 4 are drawn up and down through cuts 1 b formed in the flange of the core 1, guided to the grooves 1 a, and provided with the conductive internal electrodes 5.
a. This connection is performed by soldering when attaching the upper and lower electrodes in the assembly process.

When an open magnetic circuit type chip inductor is manufactured, the resulting drum type core is directly incorporated into a lead frame. When a closed magnetic circuit type chip inductor is manufactured, a sleeve-shaped magnetic metal fitting 2 is further fitted. The sleeve-shaped magnetic metal fitting 2 is made of a magnetic metal such as permalloy, has a shape of a split ring having a slit at one location in the circumferential direction, and is formed to have a diameter smaller than the diameter of the drum-type core 1. Thereby, it comes into close contact with the peripheral surface of the core. As shown in the figure, the magnetic metal fitting 2 has clearance for positioning guides 3c, 3c 'formed on the upper electrode 3 and positioning protrusions 3d formed on the forked lower electrode 3' in the lead frame described below. Have notches 2a and 2b, respectively. Preferably, ultraviolet curable resin or the like 5b is injected into a gap formed in the cut portion 1b of the drum type core 1 in which the sleeve-shaped magnetic metal fitting 2 is fitted, and the core 1 and the magnetic metal fitting 2 are instantaneously brought into contact with each other. Join.

The drum-shaped core 1 fitted or not fitted with the magnetic metal fitting 2 has positioning guides 3c, 3c 'formed on the upper electrode 3, positioning protrusions 3d of the bifurcated electrode 3'. Is engaged with the peripheral surface to establish a correct positional relationship with the electrode. Further, the joining terminal 3a of the upper electrode 3 is joined by sandwiching one end of the winding 4 from which the insulating coating has been peeled off between the conductive internal electrode 5a of the groove 1a of the core 1 and performing soldering. Bifurcated lower electrode 3 '
The same applies to the connection between the two joining terminals 3b and 3b 'and the other end of the winding 4. Further, the two joining terminals 3b, 3b 'of the forked lower electrode 3' have height regulating projections 3e, 3e 'projecting downward. These protrusions are made of an insulating resin mold formed of a drum core 1, a magnetic metal fitting 2, upper and lower electrodes 3,
When injection molding around 3 ', it helps to accurately maintain the positional relationship between these members and the resin mold.

As shown by a dotted line in FIG. 1 and a solid line in FIGS. 2 to 4, the mold made of the electrically insulating resin is formed on the entire surface except for the external terminal portions 3f and 3'f exposed to the outside of the upper and lower electrodes. ing.

Next, the automatic assembly of the chip inductor of the present invention using a lead frame will be described. As shown in FIG. 7, a lead frame 8 which is used for assembling the drum core 1 and partially constitutes upper and lower electrodes is stamped and formed from a flat plate having appropriate soldering, and cuts and raises or projects a predetermined portion by stamping. Extrusion such as is performed. At the same time, sprocket holes 9 which are engaged with the feeding means when being set on an automatic machine are formed at regular intervals. FIG. 7 shows a lead frame 8 having one unit of electrode structure, but actually the same electrode structure is formed continuously.
The upper electrode 3 and the bifurcated lower electrode 3 'have a base integrated with the lead frame and extend therefrom in the direction of each other to form the respective parts already described with reference to FIGS.

To explain the assembling process using the lead frame 8, the drum type core 1 formed as described above is connected to the joint terminal 3a of the upper electrode 3 of the lead frame 8 of FIG. 3 ′ is held between the joining terminals 3b and 3b ′. However, the joining terminal 3a is the drum type core 1.
It is processed so that it is slightly lowered below the level of pressing down. For this reason, the pinched core 1 is temporarily attached to that position. Also, as already described, the positioning guide 3c,
3c 'and the positioning protrusions 3d, 3d' both engage the outer periphery of the core 1, so that the relationship between the upper and lower electrodes 3, 3 'and the core 1 is correctly positioned. When soldering is performed in this state, solder connection is made between the upper and lower connection terminals and the winding ends.

Next, it is positioned in an injection mold. If the joining terminals 3b, 3b 'are processed so as to be slightly displaced downward, the height regulating projections 3e, 3e' projecting downward from the lower electrode 3 'come into contact with the bottom surface of the mold cavity. The position of each electrode and the core is always arranged at a fixed height in the mold cavity, and the core and the electrode always have a fixed positional relationship with respect to the resin molded body 6 during resin molding. That is, the occurrence of defects can be avoided.

When the resin molding is completed, the upper and lower electrodes 3, 3 '
Is cut at the locations where the external electrodes 3f and 3'f are to be formed, and this is bent to the side surface of the resin molded body to complete the chip inductor product of the present invention.

[0014]

The chip inductor of the present invention has a structure in which the lead frame has a bifurcated lower electrode and an upper electrode, so that the position of the drum core can be properly adjusted by utilizing their elasticity. The chip inductor having excellent characteristics can be provided by being able to be arranged and always accurately defining the positional relationship between the drum core, the electrode, and the resin during resin molding. This position regulation can be performed even more accurately by utilizing the positioning projections, the positioning guides, and the height positioning projections. Also,
By wrapping the drum-type core provided with the winding of the vertical type with a sleeve-shaped magnetic metal fitting having a slit, the adhesion between the two is enhanced, and a closed magnetic circuit type high inductance inductor can be provided. In this case, since the sleeve-type magnetic fitting is used, there is no possibility that the gap fluctuates unlike the related art, and it is possible to suppress variations in products and to provide a highly reliable inductor. Furthermore, since the forked lower electrode has a positioning projection that projects downward and comes into contact with the mold cavity surface, the electrode and the drum-shaped core are
Positioning can be accurately performed with respect to the resin molded body, and defective molding can be prevented. According to the present invention, automatic assembly using a lead frame becomes possible, and by completely sealing with an insulating resin, a soldering method conventionally limited to a reflow furnace specification can be used in a flow furnace specification. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a chip inductor according to an embodiment of the present invention, in which an insulating resin molded body 6 is indicated by a dotted line for easy understanding.

FIG. 2 is a plan view of the chip inductor of FIG. 1;

FIG. 3 is a partial sectional view taken along line AA of FIG. 2;

FIG. 4 is a partial sectional view taken along line BB of FIG. 2;

FIG. 5 is a perspective view of a conventional chip inductor.
(A) is an assembly drawing, (b) is an exploded view.

FIG. 6 is a perspective view of another example of a conventional chip inductor.

FIG. 7 is a perspective view showing a lead frame for realizing the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drum type core 1a Recessed groove 1b Cut part 2 Sleeve-shaped magnetic metal fitting 3 Upper electrode 3 'Forked lower electrode 3a Upper joint terminal 3b Lower joint terminal 3c Upper electrode positioning guide 3d Lower electrode positioning protrusion 3e Height control protrusion of lower electrode 3f External terminal of upper electrode 3'f External terminal of lower electrode 4 Winding 5 Solder 5a Conductive internal electrode 5b Ultraviolet curing resin 6 Insulating resin molding

Claims (6)

[Claims] 1. A lead frame electrode having a structure having a bifurcated electrode and an upper electrode.
The position is fixed by sandwiching a drum-type core on which a vertical-type winding is applied, and the core and the two electrodes are sealed with a resin except for external terminal portions of the two electrodes, Chip inductor. 2. A drum having a structure in which a lead frame electrode has a bifurcated lower electrode and an upper electrode, and a vertical-type winding wound around a sleeve-shaped magnetic metal fitting between the two electrodes. Hold the mold core and fix the position,
A chip inductor, wherein the core and the two electrodes are sealed with a resin except for the external terminal portions of the two electrodes. 3. The method according to claim 1, wherein an ultraviolet curable resin is injected into a gap between the drum-shaped core and the sleeve-shaped magnetic metal and cured to maintain the adhesion between the drum-shaped core and the magnetic metal. Item 2. The chip inductor of Item 2. 4. The chip inductor according to claim 1, wherein the bifurcated lower electrode has a height regulating projection projecting downward. 5. The chip inductor according to claim 1, wherein the bifurcated lower electrode has a positioning protrusion that protrudes upward and engages with a peripheral surface of the drum-shaped core. 6. The chip inductor according to claim 1, wherein the upper electrode has a positioning guide that engages with a peripheral surface of the drum-shaped core.