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Researchers Submit Patent Application, "Magnetic Core, Inductor and Module Including Inductor", for Approval

August 27, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors CHATANI, Kenichi (Sendai-shi, JP); IKEDA, Kenji (Sendai-shi, JP); TSUDA, Toshinori (Sendai-shi, JP), filed on February 3, 2014, was made available online on August 14, 2014.

The patent's assignee is Nec Tokin Corporation.

News editors obtained the following quote from the background information supplied by the inventors: "This invention relates to a module comprising a circuit board and an inductor. For example, the module is a power module which is to be installed in an electronic apparatus to supply electric power. This invention also relates to a magnetic core and an inductor which are suitable for the module.

"Generally, an electric component mounted on a circuit board, for example, a switching transistor, a power control Integrated Circuit (IC) or an inductor, generates heat. As the size of the circuit board is reduced, the heat per unit volume increases. Especially, an inductor tends to generate large heat. Accordingly, a module including a circuit board and an inductor is required to have a structure for efficiently radiating heat outward. For example, a module having such a structure is disclosed in Patent Document 1 (USA 2007/0230221), content of which is incorporated herein by reference.

"The module of Patent Document 1 comprises an active layer (a circuit board) and a passive layer. The passive layer includes a Low Temperature Co-fired Ceramics (LTCC) inductor made of an LTCC. The circuit board is placed on the LTCC inductor via a heat spreader. Since the module is thus configured, heat generated by the LTCC inductor and the circuit board can be dissipated through the heat spreader.

"Patent Document 2 (JP A 2002-289419) discloses a magnetic core formed of soft-magnetic-sintered-alloy layers and insulation layers which are stacked alternately on one another. The content of Patent Document 2 is incorporated herein by reference.

"The module of Patent Document 1 is required to include the heat spreader in order to cool the LTCC inductor and the circuit board. Moreover, the module of Patent Document 1 is required to include a heat sink in order to more efficiently radiate the heat generated by the LTCC inductor and the circuit board. In other words, it is necessary to install the members for radiating the heat, namely, the heat spreader, the heat sink and so on, in the module. Accordingly, the module tends to have a complicated structure and a large size. Moreover, ceramics such as the LTCC is a brittle material. Accordingly, the LTCC inductor is easily damaged when pressed against the other member, for example, the member for radiating the heat. Moreover, as described in Patent Document 1, the LTCC inductor has low thermal conductivity. Accordingly, even when the module has the member for radiating the heat, it is difficult to radiate the heat sufficiently.

"Moreover, the aforementioned drawback is not limited to the LTCC inductor. In general, although an inductor is a main heat generator in a module, an existing inductor has low thermal conductivity. Accordingly, it is difficult to efficiently radiate the heat generated by the inductor.

"When an inductor is formed by using the magnetic core disclosed in Patent Document 2, it is necessary to form a window in each of the soft-magnetic-sintered-alloy layers and to form a through hole in each of the insulation layers. Moreover, it is necessary to stack the soft-magnetic-sintered-alloy layers and the insulation layers in such a manner that the windows and the through holes properly overlap one another. The aforementioned process is cumbersome. Thus, it is not easy to form an inductor having a shape and a size which are suitable for a module."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "It is therefore an object of the present invention to provide a module having a simple structure which can efficiently radiate heat generated by an inductor. It is also an object of the present invention to provide a magnetic core and an inductor which are suitable for the module.

"First aspect of the present invention provides a module comprising a circuit board and an inductor. The circuit board has a facing surface and a rear surface which are located at opposite sides to each other in an up-down direction. The inductor has a magnetic core and a coil. The magnetic core is made of a soft magnetic metal material. The magnetic core has a facing surface and a radiating surface which are located at opposite sides to each other in the up-down direction. The facing surface of the magnetic core is arranged to face the facing surface of the circuit board in the up-down direction. The radiating surface of the magnetic core is arranged to be radiatable heat outward. The coil has a coil portion and a connection end. The coil portion winds, at least in part, the magnetic core. The connection end is connected to the facing surface of the circuit board.

"Second aspect of the present invention provides a magnetic core made of a soft magnetic metal powder having flat-like shape and bound by a binder component. The magnetic core has elasticity. The magnetic core includes the soft magnetic metal powder of 60 vol % or more and vacancy between 10 vol % and 25 vol %, both inclusive. The binder component includes a silicon oxide as a principal component.

"Third aspect of the present invention provides an inductor comprising the magnetic core of the second aspect and a coil. The coil has a coil portion and a connection end.

"The magnetic core of the inductor of the module according to the first aspect of the present invention is made of the soft magnetic metal material. Accordingly, the thermal conductivity of the magnetic core can be improved by increasing the volume filling ratio (volume ratio) of the soft magnetic metal material. Moreover, since the radiating surface of the magnetic core, whose thermal conductivity can be thus-improved, is arranged to be radiatable heat outward, the heat generated by the inductor can be efficiently radiated. Moreover, since the magnetic core according to the second aspect of the present invention has elasticity, the magnetic core can be processed easily. Accordingly, it is relatively easy to form the magnetic core and the inductor each of which have a size and a shape suitable for the module.

"An appreciation of the objectives of the present invention and a more complete understanding of its structure may be had by studying the following description of the preferred embodiment and by referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 is a perspective view schematically showing a module according to a first embodiment of the present invention.

"FIG. 2 is a perspective view showing a circuit board of the module of FIG. 1.

"FIG. 3 is a side view showing the module of FIG. 1, wherein electronic components mounted on the circuit board of the module are not illustrated.

"FIG. 4 is a cross-sectional view showing the module of FIG. 1, taken along line IV-IV, wherein the electronic components mounted on the circuit board of the module are not illustrated.

"FIG. 5 is a perspective view showing an inductor of the module of FIG. 1, wherein hidden parts of a coil of the inductor are illustrated by dotted line, and wherein a material of a magnetic core of the inductor is schematically illustrated in an ellipse drawn by chain dotted line.

"FIG. 6 is a perspective view showing the magnetic core of the inductor of FIG. 5, wherein hidden parts of through holes of the magnetic core are illustrated by dotted line.

"FIG. 7 is a perspective view showing the coil of the inductor of FIG. 5, wherein imaginary lines, each of which is a boundary line between a piercing portion and a connection portion of the coil, are illustrated by chain dotted line.

"FIG. 8A is a partially enlarged, perspective view showing the through hole of the magnetic core and the piercing portion of the coil of FIG. 5, wherein the piercing portion is not yet inserted in the through hole.

"FIG. 8B is a partially enlarged, side, cross-sectional view showing the through hole of the magnetic core and the piercing portion of the coil of FIG. 5.

"FIG. 9A is a partially enlarged, plan, cross-sectional view showing the through hole of the magnetic core and the piercing portion of the coil of FIG. 5.

"FIG. 9B is a plan, cross-sectional view showing a modification of the through hole and the piercing portion of FIG. 9A.

"FIG. 9C is a plan, cross-sectional view showing another modification of the through hole and the piercing portion of FIG. 9A.

"FIG. 10 is a perspective view schematically showing a module according to a second embodiment of the present invention, wherein hidden first coupling portions of the coil are illustrated by dotted line, and wherein one of hidden holding holes of the module is also illustrated by dotted line.

"FIG. 11 is a cross-sectional view showing the module of FIG. 10, taken along line XI-XI, wherein the electronic components mounted on the circuit board of the module are not illustrated.

"FIG. 12 is a perspective view schematically showing a module according to a third embodiment of the present invention, wherein the hidden first coupling portions, one of the hidden piercing portions and one of the hidden connection portions of the coil are illustrated by dotted line.

"FIG. 13 is a cross-sectional view showing the module of FIG. 12, taken along line XIII-XIII.

"FIG. 14 is a side view schematically showing an inductor according to a fourth embodiment of the present invention, wherein hidden parts of the coil and a hidden part of a spacer of the inductor are illustrated by dotted line, and wherein components of a magnetic core of the inductor is schematically illustrated in a circle drawn by chain dotted line.

"FIG. 15 is a copy of an image showing a part of a cross-section of the magnetic core according to the fourth embodiment of the present invention.

"FIG. 16 is an exploded perspective view schematically showing components of an inductor of each of Examples 1 to 4 and Comparative Examples 1 to 6 of the present invention.

"FIG. 17 is a perspective view schematically showing the inductor of each of Examples 1 to 3 and Comparative Examples 1 to 6 of the present invention.

"FIG. 18A is a perspective view schematically showing a magnetic core of Example 4 of the present invention and a prepreg holding the magnetic core.

"FIG. 18B is a perspective view schematically showing the inductor of Example 4 of the present invention.

"FIG. 19 is a graph showing inductance versus frequency for the inductors of Example 1 and Comparative Examples 1 to 3 of the present invention.

"FIG. 20 is a graph showing inductance versus bias current for the inductors of Example 1 and Comparative Examples 1 to 3 of the present invention.

"FIG. 21 is a graph showing inductance versus frequency for the inductors of Example 2 and Comparative Examples 4 to 6 of the present invention.

"FIG. 22 is a graph showing inductance versus bias current for the inductors of Example 2 and Comparative Examples 4 to 6 of the present invention.

"FIG. 23 is a graph showing inductance versus frequency for the inductors of Examples 3 and 4, and Comparative Examples 1 to 3 of the present invention.

"FIG. 24 is a graph showing inductance versus bias current for the inductors of Examples 3 and 4, and Comparative Examples 1 to 3 of the present invention.

"While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims."

For additional information on this patent application, see: CHATANI, Kenichi; IKEDA, Kenji; TSUDA, Toshinori. Magnetic Core, Inductor and Module Including Inductor. Filed February 3, 2014 and posted August 14, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=5479&p=110&f=G&l=50&d=PG01&S1=20140807.PD.&OS=PD/20140807&RS=PD/20140807

Keywords for this news article include: Circuit Board, Electronic Components, Nec Tokin Corporation.

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Source: Electronics Newsweekly


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