JPS6220978Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a chip inductor. Various types of chip inductors have been proposed or put into practical use, but they can be roughly divided into two types.
Chip inductors can be classified into two types: one is a chip inductor using a multilayer method, and the other is a chip inductor using a rectangular magnetic core.The common advantage of these is that they are small. The drawings show some of their structures. Figure 1 shows a multilayer chip inductor, with a layer of magnetic (insulating) paint 3 (the boundary between the layers is not shown in the diagram, but this is after firing) for the coil. The conductor 1 is printed and this is repeated several times so that the conductor 1 forms a spiral pattern between the magnetic layers 3 to form a coil, the outer layer is used as a protective layer, and the electrode 2 for the external terminal is printed. are coated on both ends of the laminate to form the lead-out ends of the coil. This type of inductor has the advantages of being completely integrated, compact, and can be soldered directly to a printed circuit board, etc., and has a leadless structure, but the biggest drawback is that the conductor is in the form of a film. Because of this, it has a large distributed capacitance and a low self-resonant frequency point, similar to a multilayer capacitor structure. Therefore, the dielectric loss is also large and the Q is low. Furthermore, if it is desired to change the inductance, the number of laminated layers must be changed accordingly, so the thickness of the inductor changes depending on the inductance value, making it difficult to standardize the dimensions. It is also not easy to control the thickness of the magnetic coating, which causes variations in the L and Q values. Further, it is necessary to use an expensive metal such as silver or silver-palladium for the coil conductor, and since it is a thin film conductor, the direct current resistance is large. Furthermore, since the entire area around the coil conductor is filled with magnetic material, it becomes a closed magnetic circuit structure, resulting in rapid magnetization saturation and poor DC superimposition characteristics. Furthermore, since the number of turns of a coil formed by printing cannot be increased, a large inductance value cannot be achieved.

FIG. 2 shows a conventional example of a chip inductor using a rectangular magnetic core. This inductor has a rectangular parallelepiped shape as a whole, and the central part has grooves on all four sides.A coil is formed by winding 5 in the grooves of a rectangular magnetic core 4, and both lead wires are connected to both end faces of the rectangular magnetic core. These are pulled out and connected to the membrane electrodes 6 with solder 7, and the grooves are filled with resin 8 to protect the coils, making the whole into a flat rectangular parallelepiped shape. Although this example also has various advantages as a chip inductor, it has the disadvantage that the eddy current loss is large and the Q is extremely low (approximately 2 to 10) because the electrode films are provided on the wide surfaces of both ends of the magnetic core. Also, since the groove depth B in the thickness direction (vertical direction in Figure 2) has to be made shallower than the groove depth A in the width direction, the absolute number of turns of the winding cannot be increased, so the inductance value is large. is limited. Additionally, it required casting insulating resin to protect the coil, which required an even more difficult process.

FIG. 3 shows another conventional example using a rectangular magnetic core.
The magnetic core 9 has a shape in which two rectangular ribs with different external dimensions are connected by a rectangular column, and a coil is formed by winding a wire 10 in a groove formed between the ribs. is pulled out to the large brim portion and fixed to the electrode 15 with solder 14, and a protective cap 12 is further fitted. Even in this example, the width dimension cannot be made large, so the inductance cannot be made large, and since the end of the coil is exposed to the outside, disconnection may occur due to external contact, resulting in poor reliability. Since the electrodes are limited to the bottom of the inductor, it is difficult to attach to a printed circuit board, and the connection strength is poor.

The object of the present invention is to provide a chip inductor which eliminates at least a significant part of the drawbacks of the prior art.

The chip inductor of the present invention has a structure that allows the lead end of the coil winding to be reliably pulled out to the outside.In addition to checking the lead end and making accurate electrical connections, the chip inductor is sealed and strengthened, and the printed circuit board Enables a reliable electrical connection to the wiring. This, in combination with the excellent structure of the inductance section which is the main body section, provides remarkable effects.

Hereinafter, embodiments of the chip inductor of the present invention will be described in detail with reference to the drawings.

4 to 16 show the manufacturing process and structure of a chip inductor according to an embodiment of the present invention.
4-5 show a core 20 of magnetic or non-magnetic material such as magnetic ferrite or plastic. The amount of material for the core 20 is selected depending on the application. Core 20
The wire is in the shape of a loop, which is made up of an integrally molded body of large-diameter end portions 21, 22 and a small-diameter shaft portion 23, and around the shaft portion 23 is provided a recessed portion in which the winding wire is accommodated. Concave portions 24 and 25 are formed in the center of the end faces of both end portions 21 and 22 of the hook-shaped winding core 20 for lead stands.

Next, as shown in FIGS. 6 and 7, the recesses 24 and 25
The lead wires 26 and 27 are inserted into the holder and fixed with a thermosetting adhesive 28 such as epoxy resin to form a lead stand. Note that the method for manufacturing the leaded winding core is not limited to the above example. For example, as shown in FIG.
6' and 27' can also be attached at the same time to form leads. Although the following description will be made with respect to the core of the method and structure shown in FIGS. 4 to 7, it should be understood that the present invention can be practiced with any other leaded core as well.

Referring to FIG. 9, the winding 29 is wound the required number of times around the winding core 20 with the leads erected as shown in FIG. Garageru. If necessary, these ends 30 and 31 can be further soldered to the leads 2.
Fixed at 6,27. Next, as shown in FIG. 10, using resin such as epoxy resin, the leads 26, 2
The outer resin molded body 32 is cast and cured around the entire core except for 7. The outer shape of this exterior molded body 32 can be freely selected regardless of the shape of the core 20 inside. For example, it may be formed into a cylindrical shape as shown in FIG. 11 or a prismatic shape as shown in FIG. 12. Next, as shown in FIG. 13 and FIG. 11 or 12, the leads 26, 27 are cut at the end surfaces of the molded body 32 using a suitable cutting machine, leaving end surfaces 33, 34. Finally, as shown in Figure 13, Figure 14 or Figure 15,
A conductive film is formed on the surface where the lead end surfaces 33, 34 are exposed, or on this surface and the area adjacent thereto by baking a conductive paste, electrolytic or electroless plating, or other method, and then forming the outer terminal surface 35, 3.
Set it to 6.

Other methods of forming the external terminals are also possible. FIG. 15 shows an example. When the structure shown in FIG. 10 is obtained, instead of cutting the leads as shown in FIG. 11 or 12, the leads 26 and 27 are placed in the center.
a metal cap 40,4 with a hole equal to the diameter of
1 through the leads 26 and 27 and slid onto both ends of the molded body 32 to be fitted. Next, use a cutting machine to cut the leads 26, 2.
After cutting 7, the lead end faces and caps 40, 41 are connected and fixed with solders 42, 43.
It is even better to apply adhesive to the inner surfaces of the caps 40 and 41.

FIG. 17 shows another example of the structure of the cap. A recess 44 is formed in the cap 40', and a corresponding recess is also formed in the resin molded body 32'. When cutting lead 27 along line 42, recess 44 provides adequate space for solder buildup around the lead cut end surface.

Since the chip inductor of the present invention constructed as described above can be manufactured by resin molding with its outer shape almost unaffected by the size and shape of the core, the shape can be freely selected and the dimensional accuracy is improved. Furthermore, since the lead-out ends of the leads are formed in a film shape on the end face of the chip inductor, unlike ordinary leads, automatic feeding, attachment, and soldering to a printed circuit board becomes possible.

The effective features of the present invention can be summarized as follows.

(1) Dimensional accuracy can be achieved.

Conventionally, the exterior body is made of a magnetic material or the like (ferrite, etc.). For example, in the case of ferrite, the sintering process causes the resulting exterior body to shrink, resulting in large variations in dimensional accuracy. Generally, this shape requires a tolerance of about ±0.2, but since the exterior of the product of this invention is resin molded using a mold, the external dimensions are determined by almost the same as the mold, so generally the tolerance is ±0.2.
0.05 is possible. This means that when handling this product with an automatic insertion machine for printed circuit boards, etc., the individual variations in the product will be reduced, making it easier to handle the machine, and the machine can operate more stably and shape the shape. There are fewer problems such as sticking due to variations.

(2) The manufacturing method of the product is simple.

Since the product and manufacturing method are modified from conventional lead-type inductors, the manufacturing method is simpler, and the biggest advantage is that conventional manufacturing equipment (automated machinery, etc.) can be used as is, and only a few additional equipment are required. There is.

The same parts as the conventional process are ~Winding~Karage~Solder~Resin molding (a mold is required depending on the shape)
Up to this point, conventional equipment can be used as is, but in the case of metal caps, the only thing that needs to be added is a press machine for the cap that is fitted into the main body.

In the case of electrolytic plating, there is an external metal plating factory, so there is no need for anything else other than an automated machine for the masking process of the main body.

(3) The shape of the main body is determined by the shape of the mold for resin molding as mentioned earlier, so it is free as long as you prepare a mold of any shape. There is no need to prepare round or square sintered bodies, and there is no need to redesign each inductance value due to changes in the ferrite cylindrical body.

FIG. 18 shows the chip inductor of the present invention mounted between conductors 45 and 46 on a printed circuit board 47 by soldering. It is rectangular, comfortable to sit on, and has a stable shape, which is an important element that allows it to be used with automatic machines. As described above, the chip inductor of the present invention has no directionality, which facilitates automatic mounting and automatic soldering operations.

In addition to the above-mentioned effects, since the square exterior is used, it is possible to use a cylindrical chain-shaped magnetic core, so there is greater room for selection of the number of windings despite the small size.

Next, the Q of the chip inductor of this invention is the second
It was found that the inductor is larger than the conventional rectangular chip inductor shown in the figure. This seems to be because in the case of the present invention, the eddy current caused by the external terminal electrode is limited to the extent that the bottom of the groove of the core touches the end surface of the lead wire, whereas in the conventional case, it also occurs on the side surface. . Figure 19 shows 30
The Q-f characteristics of the inductor 9 of the present invention and the inductors 6 (without electrodes) and C (with electrodes) shown in FIG. 2 are shown as μH. Obviously, the inductor of the present invention has a high Q with small fluctuations, and is equivalent to the conventional lead type inductor, and the Q of the inductor shown in FIG. 2 drops rapidly from the value b to the value c by attaching the electrodes.

As described above, the present invention was able to provide an excellent chip inductor. It will be clear that many variations are possible within the scope of the invention.

[Brief explanation of the drawing]

Figure 1 shows a conventional chip inductor, A
is a sectional view, B is a perspective view, Fig. 2 shows another conventional chip inductor, A is a perspective view, B is a sectional view, C is an end view, and Fig. 3 shows another conventional chip inductor. , A is a perspective view, B is a sectional view, C is an end view, FIG. 4 is a perspective view showing the winding core of a chip inductor according to an embodiment of the present invention, FIG. 5 is a sectional view of the same, and FIG. is a perspective view of the core with a lead stand;
Fig. 7 is a sectional view of the same, Fig. 8 is a sectional view of the core according to a modified example, Fig. 9 is a sectional view of the winding core with wire winding, and Fig. 10 is a sectional view of the winding core with a resin molded body further applied. A cross-sectional view, Figure 11 is a perspective view of the lead cut away, and Figure 12 is a cross-sectional view.
The figures are also a perspective view of a similar but different shape, Fig. 13 is a sectional view of a completed chip inductor with terminals formed, Fig. 14 is a perspective view of a chip inductor with a circular cross section, and Fig. 15 is a rectangular one. FIG. 16 is a cross-sectional view of a chip inductor according to another embodiment of the present invention;
FIG. 17 is a partial sectional view of a chip inductor with a deformed cap part, FIG. 18 is a perspective view showing how the chip inductor of the present invention is attached to a printed circuit board, and FIG. 19 is a partial cross-sectional view of the chip inductor of the present invention and a conventional one It is a graph showing Qf characteristics comparing inductors. The main parts in the diagram are as follows. 20, 20'...Tangled winding, 26, 26', 27, 27'...Lead, 29...Winding, 30, 31...Winding end, 32
... Resin molded body, 33, 34 ... Lead end surface, 3
5, 36...External terminal, 40, 41...Cap-shaped terminal.

Claims (1)

[Claims for Utility Model Registration] 1. A twisted magnetic winding core, a winding wound around the winding core, a lead erected on both end faces of the winding core and hanging from the ends of the winding, and A chip inductor comprising a resin molded body surrounding the core, the winding and the leads, leaving the end faces of the leads, and a conductive terminal provided on the end face of the molded body and connected to the lead end faces. 2. The chip inductor according to item 1, wherein the conductive terminal is made of a film-like conductor. 3. The chip inductor according to item 1, wherein the conductive terminal is a metal cap.