JP2008124162A - Low height chip coil, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low height chip coil which takes advantage of the property of coating resin, whose feature is not degraded, and which is designed to be infinitely thin, and to provide its manufacturing method. <P>SOLUTION: In order to achieve a low height chip coil, taking advantage of the property of the coil on which coating resin is applied, the coating resin is previously formed thick. After the coating resin is formed, a portion of the coating resin which does not influence a feature is ground to form the coating resin in an aimed shape. That is, a winding wire 3 is rolled around a core 2 having an outer terminal 5 at one end, a periphery other than a portion of the outer terminal 5 is formed with the coating resin 4, and then the coating resin 4 on the upper surface of a core is polished to be flat. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a low-profile chip coil used for a portable device and the like and a manufacturing method thereof.

  As mobile devices become smaller and thinner, electronic components are rapidly becoming chips, and electronic components that can be mounted at higher density are required. Chip inductors used in portable devices are required to be small, low profile and high performance, and in particular, the product height is required to be less than 1.0 mm. Thus, in order to mount electronic components at high density, a chip coil made of an exterior resin is disclosed in Patent Document 1 as a minimum shape that can satisfy conventional characteristics.

FIG. 4 shows the chip coil.
In the chip coil 6 shown in FIG. 4, 2 is a core, 3 is a winding, 4 is an exterior resin, and 5 is a configuration of an external terminal. The chip coil 6 includes a winding 3 wound around the winding axis of the core 2 using an insulating film conductor or the like. An external terminal is provided on the bottom surface of the core 2 to connect a terminal of the winding and to connect to an external circuit. The outer periphery of the core is molded with the exterior resin 4 except for a part of the external terminals. The chip coil 1 to which this exterior resin is applied is highly weatherproof and mechanically reliable, and can be easily reflowed even when mounted on a substrate.

On the other hand, as shown in FIG. 5, blisters a, sink marks b, voids (bubbles) c in the molding process of the exterior resin, unfilled and misalignment between the molding die and the core, core breakage failure due to component variations, and the like occur. . Therefore, it was necessary to ensure a sufficient thickness of the exterior resin. For example, when a low-profile chip coil having a height of 1.0 mm is commercialized with an exterior resin, it is necessary to secure a necessary exterior resin thickness of about 0.16 mm for the inner core. Therefore, it is necessary to secure the characteristics by reducing the height of the inner core, reducing the diameter of the winding shaft, and increasing the number of turns even if the height dimension is the same.
JP-A-9-316328

  Further, in the case of an inductor or a coil, reducing the core results in a low inductance value, or when trying to obtain the same inductance value, a thin wire is wound to increase the direct current resistance, or the direct current superimposition characteristics are degraded. In addition, the degree of freedom of design is narrowed, such as the range of the inductance value is narrowed, and the effect of reducing the core is large. As described above, the use of the exterior resin increases the weather resistance and mechanical reliability, but on the other hand, the inner core is made smaller, so sometimes the core strength is insufficient and sufficient electrical characteristics cannot be obtained. There's a problem.

  An object of the present invention is to provide a low-profile chip coil and a method for manufacturing the same, which are intended to eliminate the above-described problems and to reduce the thickness as much as possible without deteriorating the characteristics.

The low-profile chip coil of the present invention is
In order to realize a low-profile chip coil by taking advantage of the characteristics of the conventional coil with exterior resin, it is necessary to mold the exterior resin thickly in advance, and after molding, trim the exterior resin that does not affect the characteristics to make the target shape Features. That is, a winding is wound around a core having an external terminal at one end, the outer periphery excluding a part of the external terminal is molded with an exterior resin, and then the exterior resin on the upper surface of the core is polished flat. To do.
A method for manufacturing a low-profile chip coil according to the present invention includes a step of winding a winding around a core having an external terminal at one end, a step of molding an outer periphery excluding a part of the external terminal with an exterior resin, and an upper surface of the core A step of polishing the exterior resin flatly is provided.

  By the above means, it is possible to realize a low-profile chip coil that makes the best use of the characteristics of the conventional exterior resin and aims to reduce the thickness as much as possible without deteriorating the characteristics.

Hereinafter, an embodiment of a low-profile chip coil according to the present invention will be described with reference to the drawings.
FIG. 1 shows an external view (a) and a cross-sectional view (b) taken along line AA of a low-profile chip coil according to an embodiment.
In the low-profile chip coil 1 shown in FIG. 1, the core 2 is made of ferrite or the like and is provided with a flange on both ends and is provided with a winding shaft, and the winding 3 is wound around the winding shaft of the core 2 using an insulating coating wire. 4 is an exterior resin, and 5 is a configuration of external terminals provided on the bottom surface of the core 2.
The low-profile chip coil 1 is obtained by molding a wound core 2 with an exterior resin 4 and then cutting unnecessary exterior resin on the upper surface of the inner core to make the surface flat. Here, the external terminal 5 uses a conductive metal plate to connect the terminal of the winding 3 and is used for connection to an external circuit. The external terminal 3 is formed by molding an exterior resin and then bending it with a press or the like. The external terminal 3 may be a planar electrode that is previously coated on the bottom surface of the core with a silver paste layer and a solder plating layer that are directly attached.

Next, the manufacturing method will be described with reference to FIG.
A winding step of winding the winding 3 around the winding shaft of the core 2 with the external terminal 5 fixed to the bottom surface of the lower iron, and a molding step of molding the outer periphery of the core 2 excluding a part of the external terminal 5 with the exterior resin 4 After the molding, a step of polishing the exterior resin 4 on the upper surface of the core flatly is provided.
Here, as shown in FIG. 2 (a), the mold in the molding process of the exterior resin has a shape in which the thickness t of the exterior resin 4 on the upper surface of the upper surface of the core 2 is taken into consideration in accordance with the molding conditions. It is desirable to do.

  Then, in the polishing step, as shown in FIG. 2B, the upper surface of the core upper collar is polished flat so that the unnecessary exterior resin thickness t indicated by the broken line becomes a predetermined height using a polishing machine. . At this time, it is desirable to polish the upper surface of the core so as to be shallow enough to obtain characteristics and flatness of the upper surface. In particular, when the resin is thinly covered on the upper and upper surfaces of the core, peeling of the resin, polishing residue, and the like remain, which may cause suction clogging and adsorption mistakes in the mounting machine. In addition, if the upper surface of the core is shaved too much, the effect on the characteristics will increase.

Here, the effect on the characteristics is confirmed by using an epoxy resin mixed with a magnetic material (mixed with about 63 wt%) as an exterior resin for a magnetic shield, which will affect the characteristics when the exterior resin is polished. .
The sample has a height of 1.16 mm from the bottom of the external terminal, a rectangular shape of 2.9 mm in length and width, and the inner core has a height including the external terminal of 1.00 mm, a core diameter of 2.5 mmφ, and a core thickness of 0.25 mm. A sample was prepared.

FIG. 3 shows the inductance value change rate (L value change rate%) and the rated current change rate (%). In FIG. 3, the horizontal axis indicates the amount of cutting (mm), and the vertical axis indicates the rate of change (%). The characteristics were compared based on the state during molding (without polishing).
As a result, there was no change in the inductance value change rate even when polished by 0.25 mm (about 0.1 mm above the core). The rate of change in the rated current value starts to change from 0.15 mm from the top surface and decreases by about 5% at the top surface of the core core (0.16 mm). The upper surface is cut by about 0.05 mm). For these reasons, the rated current value has no practical problem if it is polished on the upper surface of the core upper surface.

  As described above, the low-profile chip coil according to the present invention has a thickness of the exterior resin molding in advance in order to realize a low-profile chip coil aiming at making it thin as much as possible by utilizing the features of the conventional exterior resin. The coil is molded to the expected height, and in the subsequent process, the exterior resin that does not affect the characteristics is polished to the target height of the product.

  The low-profile chip coil according to the present invention is not limited to the above embodiments, and can be variously modified within the scope of the gist thereof. For example, the core may have a round or square cross section. Further, the exterior resin may be a product compression-molded using a magnetic composition mixed with ferrite magnetic powder or metal magnetic powder, or an injection molded product using a liquid magnetic composition. Further, the external terminal may be configured by printing electrodes on the core instead of using a metal plate.

The perspective view (a) and sectional drawing (b) of the low profile type | mold chip coil which are one Example of this invention Sectional drawing (a), (b) for demonstrating the manufacturing method of the low profile chip coil of this invention Characteristics of inductance value change rate and rated current change rate in the embodiment Cross-sectional view of a conventional chip coil Cross-sectional view showing defects in conventional chip coil

Explanation of symbols

1 Low profile chip coil 2 Core 3 Winding 4 Exterior resin 5 External terminal

Claims (3)

In a low-profile chip coil in which a winding is wound around a core having an external terminal at one end, and the outer periphery excluding a part of the external terminal is molded with an exterior resin, the exterior of the top surface of the core is molded with the exterior resin A low-profile chip coil obtained by polishing a resin flatly. A step of winding a winding around a core having an external terminal at one end, a step of molding an outer periphery excluding a part of the external terminal with an exterior resin, a step of polishing the exterior resin on the top surface of the core flatly, A method for manufacturing a low-profile chip coil, comprising: 3. The low-profile chip coil according to claim 1, wherein the exterior resin is polished to the core surface.

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