JP3411758B2 - Surface mount inductor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connecting terminal structure for an inductor such as a choke coil which is surface-mounted on a circuit board of an electronic device, and more particularly to an improvement of a hooking structure for a metal piece which is directly attached to the bottom surface of a lower flange of a drum core. It is about.

[0002]

2. Description of the Related Art In recent years, there has been a strong consumer demand for miniaturization and high performance of electronic equipment, and along with this, inductors such as transformers and choke coils that occupy a relatively large volume in electronic components mounted on electronic circuit boards. A structure that is suitable for surface mounting is being developed while developing miniaturization and low profile.

As shown in the perspective view (A) and vertical sectional view (B) of FIG. 3, a conventional surface mount inductor using a drum-shaped core has electrodes 3A and 3B protruding from side surfaces 4a and 4b, and is S-shaped. A drum-shaped core 1 (generally a ferrite core) having a winding 2 wound around the center of an upper surface 4c of a pedestal 4 made of synthetic resin, which is bent so as to be in contact with the surface of a mounting substrate. In general, the bottom side of the lower brim portion 1b is bonded and fixed with an adhesive 5.

There has also been proposed a surface-mount inductor having a low profile structure in which a metal electrode is directly fixed to the bottom side of the lower flange portion 1b of the drum-shaped core 1 with an adhesive agent.

However, in general, the adhesive 5 (generally a vinyl acetate-based, rubber-based or epoxy-based adhesive) that fixes the metal piece to the core by heat (at 230 ° C. to 270 ° C.) during solder reflow after mounting. And the like) are softened to weaken the adhesive strength, and there is a problem that the metal piece (electrode) is peeled or displaced from the drum-shaped core 1.

Therefore, the present applicant has proposed a metal piece having a hooking structure for a drum-shaped core for strengthening the fixation of the metal piece to the core, which is insufficient with the above adhesive alone, and improving the pressing force in all directions. Was done.

Japanese Patent Application No. 7-3 filed by the applicant of the present application first
The surface mount inductor in the invention of No. 10971 is, for example, a plan view (A) showing the drum core of FIG. 4 with the upper flange removed, and a vertical cross-sectional view taken along line BB in the plan view (A) of the surface mount inductor ( B), as shown in the plan development view (C) of the metal piece, the end of the winding wire 2 is attached to the drum-shaped core 1 having the upper and lower flanges 1a and 1b at both ends of the columnar winding shaft. The barb terminal portion 11 for bark and solder connection, the electrode parts 13A and 13B for mounting and soldering, and the tip claw portion 1 bent on the peripheral edge of the lower flange part 1b of the drum-shaped core and on the upper surface of the lower flange part.
A metal piece 19 (also referred to as a connection terminal member) integrally formed from a metal plate material with a protrusion 18 to which 7 is hooked is attached to the bottom surface side of the lower flange portion 1b of the drum-shaped core with an adhesive 5. In the structure of directly adhering and fixing, the metal piece 19 is not only adhered and fixed to the bottom surface of the lower flange portion 1b of the drum-shaped core with an adhesive, but also the protrusion portion as shown in FIG. 18
The tip claw portion 17 (the entire projecting portion of which is formed in an L shape) is bent inside the upper surface of the lower collar portion 1b, and the metal piece 19 is hooked.

The metal piece 19 is further provided with a central protrusion 14 which fits in a recess 12 provided in the center of the lower collar 1b.

In the above surface mount inductor, the tip claw portion 17 extends in a direction (right angle) different from the bending direction of the bending of the protrusion 18.
Since the drum core is bent to the inside of the upper surface of the lower brim portion 1b, the hooked tip claw portion 17 has an advantage that it has high strength against external stress in the vertical direction.

[0010]

However, the following problems have been found in the surface mount inductor previously proposed by the applicant of the present application.

First, with the miniaturization of surface mount inductors, the distance between the barb terminal 11 and the protrusion 18 standing perpendicular to the lower brim portion is close, and the barb terminal is soldered. Alternatively, there is a problem that the tip claw portions 17 of the protrusions also get wet with solder during the solder reflow.

If the solder adheres to an unnecessary place, the extra solder adhered may melt at the time of subsequent solder reflow or the like to cause a short circuit or other defects.

Secondly, conventionally, it was assumed that the metal piece 19 would be sufficiently fixed if the metal piece 19 was hooked to the drum-shaped core. Since the twisting process after winding the wire gives a large tensile stress to the metal piece, even in the hooking structure in which the tip claw portion 17 is bent to the inner side of the upper surface of the lower collar portion 1b, the metal piece 19 itself is thin and once bent. Since the bending strength in the direction opposite to the bending direction is weak, even if the tip claw portion 17 maintains the hook structure against external stress that separates the metal piece and the drum core in the vertical direction, Metal piece 1 on the bottom of the lower collar 1b of the core 1
The bending root portion f of the protruding portion 18 bent from 9 cannot bear the bending strength, and is twisted away from the peripheral edge of the lower collar portion, and finally the hooked state of the metal piece 19 may be released. Probably exists.

Therefore, with the miniaturization of the surface mount inductor, it is necessary to find the optimum design condition of the size of the protrusion as a means for hooking the metal piece on the drum core.

The present invention has been made in view of the above circumstances, and provides a structure for retaining the protrusion of the metal piece against external stress against the drum-shaped core. The present invention provides a protrusion structure that prevents the solder from getting wet due to the proximity of.

[0016]

According to the present invention, (1) a barb terminal in which a winding is coiled and soldered to a drum-shaped core having upper and lower flanges at both ends of a columnar winding shaft. Part, an electrode part to be mounted and soldered, and a projection part that is bent around the lower flange part of the drum-shaped core and a tip claw part is hooked on the upper surface of the lower flange part, are integrally molded from a metal plate material. In a surface mount inductor having a structure in which the formed metal piece is directly adhered and fixed to the bottom surface side of the lower flange portion of the drum-shaped core with an adhesive, the lateral width of the protrusion of the metal piece bent around the lower flange portion ( a)
The above object is achieved by providing a surface mount inductor characterized in that the vertical width (b) of the tip claw portion of the protrusion has a relation of a> b.

(2) Further, the shape of the protruding portion of the metal piece according to the above (1) including the tip claw portion is substantially L-shaped, and all or part of the upper surface of the protruding portion with respect to the upper surface of the lower collar portion. By providing a surface mount inductor characterized in that the angle θ has a taper of 30 to 60 degrees,
The above object is achieved.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the same members as the conventional ones are designated by the same reference numerals.

FIG. 1 is a perspective view for explaining a hooking structure of a lower flange portion of a drum-shaped core of a surface-mount inductor according to the present invention and a protruding portion of a metal piece. FIG. If the tip claw of the section is L-shaped, (B) is approximately T
Two form examples in the case of a letter shape are shown.

FIG. 2 is an enlarged perspective view of (A) of the embodiment shown in FIG.

1 and 2, a surface mount inductor (eg, a choke coil) according to the present application has upper and lower flange portions at both ends of a columnar winding shaft portion, as in the above-described conventional surface mount inductor. In the drum-shaped core 1 which is provided, the bending-shaped terminals 21 and 22 for winding and soldering the winding, the electrode portion 23 for mounting and soldering, and the drum-shaped core 1 bent around the lower flange portion. The tip claw portion 27 is provided on the upper surface 31 of the lower collar portion 1b.
Or a metal piece 25 or 35 (usually
This metal piece is provided in two pieces, one of which is omitted in FIG. 1) is directly attached and fixed to the bottom side of the lower flange portion 1b of the drum-shaped core with an adhesive. Is.

In particular, as a first feature, as shown in FIG. 2, the lateral width a of the protrusion 28 of the metal piece 25 bent along the peripheral edge of the lower flange (together with the side surface 29) and the protrusion. Both dimensions of the vertical width b of the tip claw portion 27 of the portion have a relation of a> b. In addition, this relationship is shown in FIG.
The same applies to 8.

As described above, by maintaining the relationship that the lateral width a of the protrusion and the vertical width b of the tip claw portion of the protrusion are a> b, the protrusion of the metal piece body on the bottom surface of the drum-shaped core lower flange portion is maintained. The bending strength of the root portion f becomes equal to or higher than the bending strength of the tip claw portion against external stress in the vertical direction, and an optimum hooking structure between the metal piece and the drum core is obtained.

Of course, the dimension of the lateral width a of the protrusion is not limited, and it must be set within a range determined by the size of the metal pieces 25 to 35. On the other hand, if the vertical width b of the tip claws 27 to 37 is large, it is likely to be affected by solder wetting, which will be described later. Therefore, it should be avoided as much as possible while obtaining a sufficient locking force. Is.

As a supplement to this point, as is apparent from the enlarged perspective view of FIG. 2, the protrusion 28 indicated by the alternate long and short dash line is vertically attached to the side face 29 of the lower flange 1b at the base portion f with respect to the metal piece body. Although bent as indicated by an arrow K, the tip claw portion 27 is bent in a direction H perpendicular to the bending direction K (bent in a direction toward the center of the lower flange upper surface 31). Since the tip claw portion 27 is provided with the tip claw portion 27, even if the dimension b is relatively short, the hooking force of the tip claw portion (strength against the stress of pulling the metal piece upward and downward with respect to the drum core to remove) is On the other hand, when the width dimension a of the protrusion is relatively small (a <b), even if the tip claw portion 27 retains its shape sufficiently, the root portion f of the protrusion 28 loses the stress first. , The protrusion bends in the direction away from the side surface 29 of the lower collar portion (the direction opposite to the bending direction K). It's that.

As a second feature, as shown in FIG. 2, the tip claw portion 27 of the projection portion 28 is substantially L-shaped, and a lower collar portion is formed on a part 27a of the upper surface of the projection portion 28. The shape is such that the angle θ with respect to the upper surface 31 forms a taper of 30 to 60 degrees.

As described above, the corners on the side close to the barb terminals 21, 22 which are part of the vertical end surface of the tip claw portion are tapered (in other words, they are largely chamfered). The solder wettability is less likely to occur than when the upper surface of the protrusion is flat (when there is a right-angled corner) during soldering at the time of wire twisting to the twisted terminal portion.

Of course, it is needless to say that the entire upper surface of the tip claw portion may be tapered instead of providing only a part of the taper as shown in FIG.

Further, as shown in FIG.
It is desirable that at least two metal pieces be provided on one metal piece, and the metal pieces be spaced apart from both ends of the metal piece so that the metal piece can be stably held by the lower collar portion 1b.

The metal pieces 25 or 35 are appropriately arranged (generally symmetrical) in accordance with the shape of the lower flange portion 1b of the drum core 1 as shown in FIG. 4C shown in the conventional example. A phosphor bronze thin plate is press-molded so as to form a plurality of continuous lead frames and solder-dipped, and the tip claw portion 27 of the protrusion is bent during press molding. Is desirable.

Similarly, the bending of the electrode portion 23 and the protruding portion 28,
If the bending of 38 at an angle of about 20 degrees at the point f is performed at the same time during press molding, the subsequent bending process becomes easy and the positioning of the drum-shaped core 1 on the metal piece becomes easy. Ah

[0032]

Since the surface mount inductor according to the present invention has the above-described structure, the metal piece serving as the connection terminal is fixed with a sufficient latching force against the drum core, and the soldering treatment of the barbed terminal portion is performed. In this case, there is an excellent effect that the solder is prevented from getting wet on the protrusions and the reliability is improved.

[Brief description of drawings]

FIG. 1 is a perspective view for explaining a hooking structure of a lower flange portion of a drum-shaped core of a surface-mount inductor according to the present invention and a protrusion portion of a metal piece, FIG. In the case where the tip claw shape is substantially L-shaped, (B) shows two form examples in the case of substantially T-shaped.

FIG. 2 is an enlarged perspective view of (A) of the embodiment shown in FIG.

FIG. 3 is a diagram for explaining the structure of a conventional surface-mount inductor using a drum-shaped core, FIG.
(B) is a longitudinal sectional view.

FIG. 4 is a plan view (A) showing the drum-shaped core of the surface-mount inductor in which the electrodes are directly bonded and fixed to the drum-shaped core with the upper flange removed, and a vertical cross section taken along the line BB in the plan view (A). FIG. 3B is a plane development view of the metal piece.

[Explanation of symbols]

1 Drum type core 1a Upper collar part 1b Lower collar part 1c Reel part 2 windings 3A, 3B electrodes 4 pedestals 4a, 4b Side of pedestal 4c Upper surface of pedestal 5 adhesive 10 surface mount inductor 11, 21, 22 Barbed terminals 12 recess 13A, 13B, 23 Electrode part 14 Central protrusion 19, 25, 35 metal pieces 17, 27, 37 Tip claw 18, 28, 38 Projection 29 Side of lower collar part 31 Upper surface of lower flange f Root of protrusion K Bending direction of protrusion H Bending direction of tip claw

Continuation of the front page (56) References JP-A-7-272951 (JP, A) Actual development 5-33506 (JP, U) Actual development 2-33413 (JP, U) (58) Fields investigated (Int .Cl. ⁷ , DB name) H01F 27/06 H01F 27/29 H05K 1/18

Claims (2)

(57) [Claims] 1. A drum-shaped core having upper and lower flange portions at both ends of a columnar winding shaft portion, and a barbed terminal portion for winding and soldering a winding wire, and an electrode portion for mounting and soldering. A metal piece integrally molded from a metal plate with a protrusion bent at the periphery of the lower flange of the drum core and having a tip claw portion hooked on the upper surface of the lower flange is formed under the drum core. In a surface-mount inductor having a structure in which it is directly adhered and fixed to the bottom surface side of the flange portion with an adhesive, the lateral width (a) of the protrusion portion of the metal piece bent around the lower flange portion and the tip claw portion of the protrusion portion A surface mount inductor characterized in that the vertical width (b) has a relationship of a> b. 2. The shape of the protrusion of the metal piece including the tip claw portion is substantially L-shaped, and the angle θ with respect to the upper surface of the lower flange portion of all or part of the upper surface of the protrusion is 30 to 60.
The surface mount inductor according to claim 1, wherein the surface mount inductor has a taper degree.