JPS634928B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a leadless fixed inductor, a so-called chip inductor.

Fixed inductors, like various electronic components, have become smaller in recent years, and chip inductors, in which electrodes are directly surface-connected to the circuit pattern of a synthetic resin or ceramic substrate, are being used; It is a very small shape that can fit into a cube of 4 mm to 3 mm. The electrodes are formed by fixing linear or plate-shaped metal pieces to the flange of the core, or by printing, baking, or vapor depositing silver or the like.

FIG. 1 shows a cross-sectional view of an example of a conventional chip inductor, which is fixed to the lower flange 30 of the drum core around which the wire is wound so that the cross section is L-shaped from the bottom surface 31 to the side surface 32. An electrode 33 is formed of the metal plate, and this electrode 33
is solder-dipped and soldered directly to the circuit pattern. The lead of the wound coil is the electrode 33
connected by series resistance welding, etc.

However, since the chip inductor has a microstructure as described above, there are various unresolved technical problems during manufacturing. For example, it is difficult to make a small sintered ferrite drum core around which the wire is wound, and accidents in which part of the collar breaks off frequently occur.
It is one. Also, it is not easy to freely wind a thin wire with a wire diameter of around 0.05 mm in a range of several turns to more than 100 turns in order to obtain the desired inductance in a narrow interval of about 1 mm to 2 mm between the tsuba. In the past, when the wire got stuck in the collar, it was easy to break, which was a big problem when automating the winding process.

Therefore, the yield was poor and mass production of chip inductors was difficult. Furthermore, it was difficult to attach a case to the core, so when it was mounted on a board, the characteristics were easily influenced by other circuit components, resulting in poor reliability.

The purpose of the present invention is to solve these various technical problems and provide a manufacturing method suitable for mass production.

The method for manufacturing a leadless type fixed inductor of the present invention is to form a pre-wound and formed coil into one body with a flange and a rod-shaped part standing upright at the center of the sintered ferrite core. The feature is that the core is fitted into the core, and then another tsuba is attached to the core.

The following Figure 2a shows an example of the manufacturing method of the present invention.
to FIG. 2e, and will be explained with reference to FIG. 3. Figures 2a to 2e are diagrams of the chip inductor in the manufacturing process. Figures 2a and 2e are perspective views, and Figures 2b to 2d are front views. There is. FIG. 3 is an exploded perspective view of the completed chip inductor.

1 in Figure 2a to Figure 2e and Figure 3.
2 is a coil, 2 is a core, 3 is a flange, 4 is an electrode formed from a metal plate such as copper, and 5 and 6 are metal films. The coil 1 is pre-wound and molded using an adhesive or the like so that it does not lose its shape.
For this purpose, a wire material such as Sorbon wire (trade name), which can temporarily melt and harden the coating film on the surface, may be used. The core 2 is formed from sintered ferrite by integrating a square collar 7 and a rod-shaped portion 8 with a circular cross section standing upright in the center, and the cross section of the rod-shaped portion 8 can be inserted into the hole 9 in the center of the coil 1. It's sized. A metal film 6 is adhered to the bottom surface 10 of the collar by printing and baking silver along two opposing sides. The flange 3 is made of rectangular sintered ferrite, and when attached to the core 2 serves as a tsuba separate from the flange 7 of the core.
A metal film 5 is adhered to the surface of the collar 3 along two opposing sides, and one end of an electrode 4 extending long and thin and protruding from the surface along the surface is fixed to the metal film 5 by welding. A recess 11 into which the rod-shaped portion 8 of the core is fitted is formed on the back surface of the collar 3.

In the manufacturing method of the present invention, the constituent parts of such a chip inductor are prepared and assembled. First, the rod-shaped part 8 of the core is inserted into the hole 9 of the coil.
Insert as shown in Figure b. Next, fit the tip of the rod-shaped portion 8 protruding from the hole 9 of the coil into the recess 11 of the flange 3, and insert the flange 3 into the core 2 as shown in FIGS. 2c and 2d.
Attach to. At this time, it is preferable to tie the coil lead 12 to the electrode 4 and solder it as shown in FIG. 2d. The electrode 4 to which the lead 12 is connected is bent into a U-shape, and one end of the electrode 4 is fixed to the metal film 6 of the core flange by welding to obtain a completed chip inductor as shown in FIG. 2e. The electrode 4 sandwiches the collars 7 and 3 of the chip inductor from above and below to prevent the chip inductor from disassembling, and also serves as a coupling member. Furthermore, lead 12
is connected to the electrode 4 and soldered, but it may also be connected to the electrode 4 by welding. Further, the electrode 4 may be fixed to the metal film 5 and the metal film 6 by soldering, or may be fixed using an adhesive having good heat resistance without using the metal film.

4 and 5 are diagrams showing other embodiments of the manufacturing method of the present invention. FIG. 4 is an exploded perspective view of a chip inductor, and FIG. 5 is a perspective view of the chip inductor in the manufacturing process.

In FIGS. 4 and 5, 13 is a coil, 14
1 is a core, 15 is a flange, and 16 and 17 are metal films.
The coil 13 is pre-wound in the same way as the coil 1, and is molded using an adhesive or the like so that it does not lose its shape. The core 14 is formed from sintered ferrite by integrating a square flange 18 and a rod-shaped portion 19 with a circular cross section at the center, and the cross section of the rod-shaped portion 19 is large enough to be inserted into the hole 20 at the center of the coil 13. It is set as. A metal film 17 is attached to the bottom surface 21 of the collar 18 by printing and baking silver along two opposing sides. The flange 15 is formed from sintered ferrite in the shape of a U-shape, and is attached to the core 14 on the flange 18 of the core, and serves as a flange separate from the flange 18 of the core with its upper surface 22. A metal film 16 is adhered to the front side of the upper surface 22 along two opposing sides, and one end of a plate-shaped electrode 23 extending slenderly and protruding from the upper surface 22 along the front surface is welded to the metal film 16. It is fixed by. Although not shown, a recess into which the rod-shaped portion 19 of the core is fitted is formed on the back side of the upper surface 22.

Then, as in the first embodiment, hole 2 of the coil
Insert the rod-shaped part 19 of the core into the hole 2 of the coil.
The tip of the rod-shaped portion 19 protruding from 0 is fitted into the recess on the upper surface of the flange 15 to attach the flange 15 to the core 14. As shown in FIG. 5, which shows the core with the bottom surface 21 of the flange facing upward, the coil lead 25 passing through the groove 24 of the flange is fixed to the metal film 17 by welding. Furthermore, the electrode 23 is bent into a U-shape along the side surface 26 and bottom surface 21 of the collar 15, and the lead 25
The chip inductor is completed by superimposing it on the metal film 17 and fixing it to the metal film 17. The electrodes 23 sandwich the collars 18 and 15 of the chip inductor from above and below to prevent the chip inductor from disassembling, and also serve as a coupling member. Of course, an adhesive may also be used to join the core and the flange.
Further, in this embodiment, even without the recessed portion of the flange 15, the flange 15 can be stably attached to the core 14 by its side surface 26. Furthermore, the presence of the side surface 26 provides a chip inductor with a closed magnetic circuit structure. Furthermore, in each of the embodiments, only one coil was described, but two or more coils may be combined to form a transformer. In that case, three or more electrodes may be formed.

As described above, in the method of manufacturing a chip inductor of the present invention, a preformed coil is fitted into a rod-shaped portion of a core, and another collar is attached to the core at the tip of the rod-shaped portion. The core has only a rod-shaped portion and one flange into which the coil can be fitted, and the other flange is square or U-shaped, both of which have simple shapes and are easy to manufacture. Furthermore, since the coil is wound separately from the core, it is possible to completely prevent wire breakage accidents caused by the collar of the core.

Furthermore, if the chip inductor has a closed magnetic circuit structure as shown in Figures 4 and 5, a chip inductor with a closed magnetic circuit structure can be obtained, but even when mounted on a board, the characteristics may become unstable due to electromagnetic influence from other circuit components. Moreover, its own leakage magnetic flux does not adversely affect surrounding circuit components.

Thus, according to the manufacturing method of the present invention, core damage and coil disconnection accidents are eliminated, and the yield is improved, making it possible to produce highly reliable and inexpensive chip inductors in large quantities.

[Brief explanation of the drawing]

Figure 1: A sectional view of a conventional chip inductor, Figures 2a to 2e: A perspective view and a front view of a chip inductor in a manufacturing process showing an embodiment of the manufacturing method of the present invention, Figure 3: Chip inductor An exploded perspective view of the chip inductor in another embodiment of the manufacturing method of the present invention, FIG. 5:
A perspective view of a chip inductor in the manufacturing process. 1, 13: coil, 2, 14: core, 3, 1
5: Tsuba, 4, 23: Electrode, 5, 6, 16, 17:
Metal film, 7, 18: Tsuba, 8, 19: Rod-shaped part,
9, 20: hole, 10, 21: bottom, 11: recess, 1
2, 25: Lead, 22: Top surface, 24: Groove, 2
6: Side.

Claims (1)

[Claims] 1. A coil that has been wound and formed in advance is fitted into a rod-shaped portion of a sintered ferrite core that is formed by integrating one collar and a rod-shaped portion at the center, and then a metal A method for manufacturing a leadless fixed inductor, which comprises attaching to the core another collar to which an electrode, which also serves as a coupling member made of a plate, is fixed in advance. 2. The method of manufacturing a leadless fixed inductor according to claim 1, wherein the other flange has a U-shaped cross section.