JP3340700B2 - Ferrite core for inductor and chip inductor using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a choke coil having a large rated current and a general high-inductance magnetic shield type chip inductor used for communication and consumer electronic devices.

[0002]

2. Description of the Related Art As a prior art, Japanese Patent Laid-Open Publication No.
In No. 3, as shown in FIGS. 1 and 2, a magnetic core 13 was provided on a square base plate 11 via a step portion 12, and a flange 14 fitted to a case core was provided at the other end of the magnetic core. A square drum core 10 of sintered ferrite or the like, a winding 15 wound around a magnetic core 13 of the drum core, and a gap between the winding 12 and the step 12 and the flange 14 around the drum core. An inductor including a square case core 16 covered with a spacer protrusion 21 so as to be interposed is disclosed. The ends 18 of the windings 15 are wound in grooves 17 formed at both ends of the rectangular base plate. The fixing between the drum core 10 and the case core 16 is performed by the case core 16.
Notch provided on the bottom of the drum and the drum core square base plate 1
This is performed by injecting the ultraviolet curable resin 20 into a gap between the resin and the substrate. Part of the resin enters the gap between the cores 10 and 16. Japanese Utility Model Application Laid-Open No. 4-44109 discloses an inductor using a square drum core comprising two flanges 22 (corresponding to the square base plate and the flange in FIGS. 1 and 2) and a magnetic core 23 as shown in FIG. Is disclosed. The drum core has a tapered groove 24 on the inner surface of the flange 22 that reaches the magnetic core on the outer peripheral surface.

[0003]

In the inductor having the structure shown in FIGS. 1A, 1B, and 2, resin is applied to fix the square base plate 11 and the case core 16, but the resin is applied to the drum core. There was no resin pool in the square base plate 11 and the adhesive strength to the case core 16 was weak, so that there was a problem in mechanical strength as an inductor. This is because the gap between the step portion 12 of the drum core and the case core 16 is set to be narrow, so that the amount of resin flowing from the rectangular base plate 11 to the winding portion becomes uneven. In some cases, the case core may come off due to external stress, or the drum core may be extremely damaged.

On the other hand, an inductor using a core having a structure shown in FIG. 3 provided with a tapered groove 24 extending from the outer periphery of flanges 22 and 22 of the drum core to the magnetic core is of a type that does not use a case core. Reference numeral 24 has nothing to do with the purpose of fixing the case core with resin. The tapered groove 24 is provided for improving the removal of the mold during compression molding of the drum core. The tapered groove 24 is provided with a removal taper at a position where it does not interfere with the winding to suppress the generation of burrs on the core, thereby facilitating the winding. It was simply devised to be.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a ferrite core for an inductor having a structure capable of providing a sufficient resin reservoir for a resin applied between a square base plate of a drum core and a case core. Another object of the present invention is to improve the mechanical strength of the inductor by stabilizing the fixing between the case core and the drum core and increasing the amount of resin flowing around the winding portion.

[0006]

The present invention solves the above problems by the following means. The present invention provides a rectangular drum core having a magnetic core provided on a rectangular base plate and a rectangular flange fitted to a case core at the other end, and a gap interposed between the rectangular flange around the drum core. A rectangular case core, wherein the rectangular base plate is a ferrite core provided with a binding portion for tying a coil lead terminal and a terminal portion for external connection on one of opposite sides. A ferrite core for an inductor, characterized in that a groove extending from the outer periphery to the core of the drum core is provided on the other opposite side of the core.

Preferably, the groove provided in the rectangular base plate has a step which becomes deeper on the outer peripheral side and shallower on the magnetic core side.
Preferably, the concave groove portion provided in the rectangular base plate has a side surface tapered so as to be wider on an outer peripheral side.

Preferably, the opposing electrode portion for external connection provided on the rectangular base plate has a concave groove of the entangled portion on the bottom surface, and the electrode portion and the magnetic core are provided on the upper surface of the rectangular base plate. And a step portion higher than the upper surface of the electrode portion is provided. This step prevents the case core from interfering with the variation in the height of the windings entangled with the entangled portion of the electrode portion.

In another embodiment, the case core is a pot core having four side surfaces and an upper surface, and the inner surfaces of the side surfaces and the upper surface have protrusions and / or protrusions for spacers that can contact the flange. Are formed.

According to the present invention, there is also provided the above-mentioned ferrite core, wherein a winding is applied to the square drum core, and a wire lead-out portion of the winding is tied to the tying portion of the electrode portion for external connection.
Attaching the rectangular case core from the flange side of the drum core and injecting an adhesive resin into the concave groove portion of the rectangular base plate reaching the magnetic core to fix the rectangular case core to the rectangular drum core. The present invention provides a magnetic shield type chip inductor characterized by the following. In this case, preferably, an insulating resin is applied to the upper surface of the flange of the drum core, the upper surface of the case core (excluding the case of the pot core) and the entire surface including the gap.

[0011]

The object of the present invention is solved by providing a groove for resin pool in the drum core base portion. When this groove is used at the time of winding, the amount of resin pool increases and the fixing of the case core and the drum core is stabilized. In addition, it is possible to increase the amount of resin flowing around the winding portion, and the mechanical strength of the inductor is improved. Actually, after the resin is fully cured, the lateral pressing strength of the product is measured.
The lateral pressing strength was improved about three times as compared with the conventional structure (the lateral pressing strength was about 3 kgf in the related art, and about 6 kgf in the present invention after the improvement).

Further, the present invention provides a method for floating a wire on a bottom portion by attaching a concave groove portion for winding to a lower portion of a base of a square drum core, a groove portion for preventing disconnection on both sides of a base, and a middle portion on an upper portion of the base portion. To improve the flatness by eliminating unevenness due to the wire, and to improve the wire breakage at the tied part due to the contact between products during transport, and to align and wind without being affected by the thickness of the wire at the tied part at the time of main winding It is intended to provide an inductor capable of realizing the above.

Further, by providing a tapered portion or an enlarged portion for storing the resin at both ends of the concave groove portion, when the case core and the drum core are fixed with the resin, in the case of the conventional structure, the resin comes into contact with the rectangular base plate of the coil. The tapered portion of the present invention serves as a resin reservoir when the case core and the drum core are joined, and as a result, the fixed resin of the product after assembly protrudes. In addition, by using the flat groove as described above, the mechanical lateral pushing strength is stabilized by suppressing the variation in the width dimension due to the above.

Further, according to the present invention, the resin application on the upper surface of the case core and the drum core is applied to the gap in the conventional structure shown in FIGS. 1 and 2 by increasing the application area from the gap to the entire upper surface. In this case, the screen printing method was generally used, but the pinhole defect occurred in the gap portion due to the large variation of the product after assembly, but the pinhole defect is also improved by printing the entire upper surface portion. I was able to do it. Moreover, in practice, applying the insulating resin to the upper surface of the product is more advantageous than the case where the core surface is exposed, from the viewpoint of electrical pressure resistance.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. 4 and 5 show a ferrite core for an inductor according to a first embodiment of the present invention. FIG. 4 shows the configuration of a square drum core 1 and FIG. 5 shows the configuration of a square case core 2. These cores are made of soft magnetic sintered ferrite.

First, referring to FIG.
The magnetic core 1j is integrally provided on the square base plate 1b, and a square flange 1a for fitting with the case core 2 (FIG. 5) is integrally provided on the other end of the magnetic core 1j. A T-width portion 1h for preventing chipping of the mold is formed at a ridge line extending in the vertical direction of each of these portions, and an R portion 1g for preventing chipping of the mold is formed at the root of the magnetic core 1j. I have. The square base plate 1b has middle portions 1d on both sides of the magnetic core for regulating the lower end of the coil 6 wound around the magnetic core 1j. The sides provided on the left and right sides of the rectangular base plate 1 b are the case cores 2.
It protrudes more outward, and has a tying part for tying the wire lead-out part and a terminal for external connection. The binding portion has a groove 1e having a semicircular cross section at the bottom of both sides, and a disconnection preventing groove 1f formed on the front and rear surfaces. The coil lead ends are entangled in these grooves. The terminals are the electrodes 3 formed by baking a conductive paste from the end faces of these opposing sides to the grooves 1e. At the time of use, after the coil lead terminals are entangled with these entangled portions, the grooves 1e are filled with solder to make electrical connection.

The upper surface of the middle portion 1d of the rectangular base plate 1b is flat, and the height from the upper surface of the left and right sides to the middle portion 1b is larger than the diameter of the coil conductor. This is to prevent the entangled lead from interfering with the winding when the coil is wound around the magnetic core 1j after one end of the coil lead is entangled with the entangled portion.

A groove 1c extending from the outer periphery to the magnetic core 1j is provided at opposing front and rear sides of the rectangular base plate 1b. The concave groove portion 1c is provided to allow an accurate and sufficient amount of resin to be interposed between the rectangular base plate 1b, the magnetic core, the coil, and the case core when the case core 2 and the drum core 1 are fixed with the resin. Even if the amount of the resin to be injected varies, these concave grooves 1c allow the resin to protrude to the outer peripheral portion of the concave groove, thereby making the amount of resin in the bonding portion constant and eliminating the variation in force. This action is achieved by the shallow flat groove 1i on the magnetic core side.
Further, by providing a step so as to form an enlarged groove portion on the outer side thereof, a larger resin reservoir is formed in the outer peripheral portion to function better. Preferably, the concave groove portion 1c provided in the rectangular base plate 1b is formed as a tapered side surface 1k so as to be wide on the outer peripheral side.

FIG. 5 is a perspective view of a square case core 2 used in combination with the square drum core 1 described above. The case core 2 has a flange 1a when fitted to the drum core 1.
Has four side walls 2c having an upper edge portion surrounding the peripheral surface. A flange 1 is provided at least on the upper end side of the inner surface of the side wall 1c.
A spacer ridge 2a having a constant height and being in contact with the peripheral surface of a is provided vertically. These spacers are used to form an accurate air gap with little variation when increasing the magnetic resistance to form an inductor having good linearity. A notch 2b is provided at the bottom of each side wall 1c. These notches are voids for drawing out the coil leads,
By changing the size, the magnetic resistance can be adjusted.

Next, as shown in FIG. 6, an inductor according to an embodiment of the present invention is formed by using the above-mentioned square drum core and ferrite core. The winding 6 is applied to the magnetic core 1j of the square drum core 1 in a coil shape, and the wire drawing portion 6b of the winding coil 6 is entangled with the right and left sides using the grooves 1e and 1f to form a wire tying portion 6a. Is formed, and a solder connection 4a is made between the winding entangled portion 6a and the terminal electrode 3 at the groove 1e. Next, the square case core 2 is put around the winding coil 6 and the flange 1a, and the entire upper surface including the upper surface of the flange 1a and the upper edge of the square case core 2 is coated with the ultraviolet curing resin 5b. An ultraviolet-curable resin 5a is injected into the groove 1c reaching the magnetic core 1j of the plate 1b,
The resin is cured by applying ultraviolet rays, and the square case core 2 is fixed to the square drum core 1. The resin injected from the resin reservoir groove 1c fixes the case core and goes around between the winding and the magnetic core of the drum core to fix the winding.

In the conventional structure shown in FIGS. 1 and 2, when the resin is applied to the upper portion of the case core and the drum core from the gap portion to the entire upper portion, the resin is generally applied to the gap portion. Although the screen printing method was used in general, pinhole defects occurred in the gap due to large variations in the product after assembly, but pinhole defects can be improved by printing the entire top surface Was. Moreover, in practice, applying the insulating resin to the upper surface of the product is more advantageous than the case where the core surface is exposed, from the viewpoint of electrical pressure resistance. With such a structure, the case core, the winding, and the magnetic core are integrated with the resin, and the mechanical strength of the inductor can be improved.

As a measure of the mechanical strength, there is a method of evaluating the strength when the inductor is pressed from the side. In the conventional structure having no resin puddle, the strength in the lateral direction is 1.5 to 1.5.
In contrast to 3.0 Kgf, in the case of the present invention, it is 5.0 kgf.
Data improved to 0 to 6.0 Kgf is obtained.

Next, a second embodiment of the present invention will be described with reference to FIGS.
An embodiment will be described. In this example, a pot core is used as a case core. The case core shown in FIG. 7 is a pot core 2 ′ including four side surfaces 2 c and an upper surface. On the inner surfaces of the side surfaces and the upper surface, protrusions 2 d and / or protrusions for a spacer that can contact the flange are provided. 2a is formed. Specifically, in order to avoid the influence of magnetic saturation due to contact with the flange 1a of the drum core 1, pyramid-shaped projections 1d are provided at four locations, and similarly, two on each side surface,
A total of eight chevron-shaped protrusions 2a are provided.

FIG. 8 is an assembly diagram of an inductor according to a second embodiment of the present invention in which the above-described square pot core 2 'is combined with the drum core 1 of FIG. As in the previous embodiment, the winding 6 is applied to the magnetic core 1j of the square drum core 1, and the winding lead-out portion 6b is connected to the electrode 3 of the square base plate 1b via solder. . With the predetermined gap maintained between the drum core and the case core, the groove 1
For example, the resin is fixed by injecting and curing a resin such as an ultraviolet curable type 5a into c. Upper flange 1a of drum core
A thermosetting resin may be injected between the surface and the inner surface of the pot-shaped core 2 'for bonding. The upper flange portion 1a of the drum core and the pot-shaped core 2 'are structured so as not to be in contact with each other (prevention of magnetic saturation) by the chevron-shaped protrusion 2a and the pyramid-shaped protrusion 2d provided on the inner surface of the pot-shaped core. With such a structure, it is possible to provide an inductor having a greater magnetic shielding effect than the first embodiment. In FIGS. 7 and 8, reference numeral 2 f denotes a T width portion for preventing chipping of the mold and cracks in molding. 2g is a protrusion.

[0025]

As described above, according to the present invention, the rectangular base plate portion of the drum core is provided with a concave portion from the winding core portion to the side portion, and more preferably, two tapered portions are further provided on the side portion of the concave portion. By providing a resin pool by providing a stepped portion or by providing an enlarged portion via a step portion, a magnetic shield type chip inductor excellent in mechanical strength can be provided. Furthermore, by adopting a structure in which a resin is applied to the entire upper surface of the inductor, the insulating property is improved, and it can be mounted on a substrate having a high integration density.

[Brief description of the drawings]

FIG. 1 is a structural view of a ferrite drum core used in a conventional inductor, wherein a is a plan view and b is a front view.

FIG. 2 is a perspective view of a conventional chip inductor assembled from the drum core and the case core of FIG.

FIG. 3 is a perspective view of another conventional ferrite drum core.

FIG. 4 is a perspective view of a drum core according to the first embodiment of the present invention.

FIG. 5 is a perspective view showing a ferrite case core combined with the drum core of the first embodiment of the present invention.

FIG. 6 is a perspective view of the inductor of the present invention configured using the ferrite core of the first embodiment of the present invention.

FIG. 7 is a perspective view showing an embodiment of a case core according to a second embodiment of the present invention.

FIG. 8 is a perspective view showing another example of the inductor of the present invention configured using the case core of the second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 drum core 1a flange 1b square base plate 1c concave groove 1d middle step 1e binding groove 1j magnetic core 1i flat groove 1k taper 2 case core 2a angled ridge 2b cutout 2c side wall 2d projection 2 'pot core 3 electrode 4 solder 5a 5b UV-curable resin 5c Thermosetting resin 6 Winding 6a Lead entanglement 6b Winding lead

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-11-54333 (JP, A) JP-A-6-260342 (JP, A) JP-A-8-195317 (JP, A) 28902 (JP, Y1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 17/04 H01F 27/02 H01F 37/00 H01F 41/00

Claims (7)

(57) [Claims] A magnetic core is provided on a square base plate,
A square drum core provided with a square flange fitted to the case core at the other end of the magnetic core, and a square case core covered around the drum core so as to interpose a gap between the square flange, In the ferrite core, the rectangular base plate is provided with a entangled portion for tying a coil lead terminal and a terminal portion for external connection on one of the opposed sides, and in the other opposed side of the rectangular base plate, A ferrite core for an inductor, wherein a concave groove portion is provided from an outer periphery to reach a drum core. 2. The ferrite core for an inductor according to claim 1, wherein the concave groove portion provided in the rectangular base plate has a step so that it is deep on the outer peripheral side and shallow on the magnetic core side. 3. The ferrite core for an inductor according to claim 1, wherein the concave groove portion provided in the rectangular base plate has a side surface tapered so as to be wider on an outer peripheral side. 4. The opposed external connection electrode portion provided on the rectangular base plate has a concave groove of the entangled portion on the bottom surface, and the electrode portion and the magnetic core are formed on the rectangular base plate upper surface. The ferrite core for an inductor according to any one of claims 1 to 3, wherein a step portion higher than the upper surface of the electrode portion is provided therebetween. 5. A winding is applied to the square drum core using the ferrite core according to claim 1, and a wire lead-out portion of the winding is connected to the electrode portion for external connection. The rectangular case core is attached from the flange side of the drum core, and the resin for bonding is injected into the concave groove portion of the rectangular base plate that reaches the magnetic core, so that the square case core is A chip inductor fixed to a square drum core. 6. An entire surface including the upper surface of the flange of the drum core, the upper surface of the case core and the gap,
The chip inductor according to claim 5, wherein an insulating resin is applied. 7. The case core is a pot core having four side surfaces and an upper surface, and a projection and / or a ridge for a spacer that can contact the flange is formed on an inner surface of the side surface and the upper surface. The ferrite core according to any one of claims 1 to 4, wherein: