Coil structure, lead frame, and inductor

A coil structure includes metal plates each including a spiral conductor, and a row of terminals, aligned in a predetermined direction on an outer side of the conductor, and formed by plate portions thicker than the conductor. Two ends of the conductor are connected to two adjacent plate portions for each metal plate. The row of terminals of a first metal plate is bonded to the row of terminals of a second, adjacent metal plate. The position where the two ends of the conductor connect to the two adjacent plate portions shifts one place toward the second end for each upward increase in level within a laminate along a laminated direction of the metal plates, so that the conductors of each of the metal plates are connected in series to form a spiral coil.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims priority to Japanese Patent Application No. 2020-082413, filed on May 8, 2020, the entire contents of which are incorporated herein by reference.

FIELD

Certain aspects of the embodiments discussed herein are related to coil structures, methods for manufacturing the coil structures, lead frames, and inductors.

BACKGROUND

In electric circuits, inductors may be used for purposes of stabilizing currents, converting voltages, or the like. In recent years, the size reduction of electronic devices, such as game consoles, smartphones, or the like, has accelerated. Consequently, there are demands to also reduce the size of the inductors provided in such electronic devices, and surface-mount type inductors have been proposed.

An example of such an inductor provided in the electronic device may have a configuration in which a coil structure is encapsulated by a resin. The coil structure may include windings formed from a thin metal plate, for example.

For example, Japanese Laid-Open Patent Publication No. 2020-027820 proposes an inductor having a relatively thin configuration.

In the coil structure having the windings formed from the thin metal plate, it is necessary to increase the number of turns in order to obtain a large induced electromotive force, however, it is difficult to increase the number of turns.

SUMMARY

Accordingly, it is an object in one aspect of the embodiments to provide a coil structure having a configuration which can easily increase the number of turns.

According to one aspect of the embodiments, a coil structure includes n metal plates that are laminated, where n is a natural number greater than or equal to two, wherein each of the n metal plates includes a spiral conductor, and a row of terminals, aligned in a predetermined direction on an outer side of the conductor, and formed by n+1 or more plate portions thicker than the conductor, wherein two ends of the conductor are connected to two adjacent plate portions for each of the n metal plates, wherein the row of terminals of a first metal plate is bonded to the row of terminals of a second metal plate which is adjacent to the first metal plate, among the n metal plates that are laminated, and wherein the two ends of the conductor of a lowermost metal plate among the n metal plates are connected to the two adjacent plate portions located at a first end of the lowermost metal plate, the two ends of the conductor of a second lowest metal plate among the n metal plates are connected to the two adjacent plate portions located at a position shifted one place toward a second end opposite to the first end of the second lowest metal plate, and the position where the two ends of the conductor connect to the two adjacent plate portions shifts one place toward the second end for each upward increase in level within a laminate along a laminated direction of the n metal plates, so that the conductors of each of the n metal plates are connected in series to form a spiral coil.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, those parts that are the same are designated by the same reference numerals, and a repeated description of the same parts may be omitted.

A description will now be given of a coil structure, a method for manufacturing the coil structure, a lead frame, and an inductor according to each of the embodiments of the present invention.

First Embodiment

FIG.1AandFIG.1Bare plan views illustrating an example of the coil structure according to a first embodiment.FIG.1Aillustrates an overall view, andFIG.1Billustrates an enlarged view of a vicinity of one product region (or product area) M inFIG.1A.FIG.2is a perspective view of one product region M illustrated inFIG.1A.

As illustrated inFIG.1A,FIG.1B, andFIG.2, a coil structure1has a configuration in which a plurality of metal plates are laminated, and vertically adjacent metal plates are bonded to each other. The plurality of metal plates may be at least two layers, and in this case, the coil structure1has a two-layer configuration. However, in this embodiment, the example of the coil structure1is described as having a six-layer configuration in which a first metal plate10, a second metal plate20, a third metal plate30, a fourth metal plate40, a fifth metal plate50, and a sixth metal plate60are successively laminated.

The coil structure1has a plurality of product regions M arranged vertically and horizontally in a checkerboard pattern in a plan view. Each product region M becomes an inductor after the entire coil structure1is encapsulated by a resin and singulated. A frame N having a picture-frame shape, which supports each product region M from a periphery thereof, is formed around each product region M. Adjacent frames N are integrally formed and connected to each other.FIG.1Aillustrates an example in which 18 (3 rows by 6 columns) product regions M are arranged, however, the number of product regions M is not particularly limited.

FIG.3AthroughFIG.5Bare plan views illustrating an example of the vicinity of the product region of each metal plate before lamination. More particularly,FIG.3Ais a plan view of the first metal plate10, andFIG.3Bis a plan view of the second metal plate20.FIG.4Ais a plan view of the third metal plate30, andFIG.4Bis a plan view of the fourth metal plate40.FIG.5Ais a plan view of the fifth metal plate50, andFIG.5Bis a plan view of the sixth metal plate60.

Each of the first metal plate10, the second metal plate20, the third metal plate30, the fourth metal plate40, the fifth metal plate50, and the sixth metal plate60has a planar shape similar to that ofFIG.1A.FIG.3AthroughFIG.5Billustrate an example of a portion (near one product region) of each metal plate corresponding toFIG.1B. InFIG.3AthroughFIG.5B, a portion indicated in grey illustrates a thin plate portion, and a portion indicated by a halftone dot pattern illustrates a thick plate portion which is formed to be thicker than the thin plate portion and protrude below the thin plate portion. The thin plate portion and the thick plate portion are integrally formed.

The product regions M illustrated inFIG.3AthroughFIG.5Binclude a product region M1of the first metal plate10, a product region M2of the second metal plate20, a product region M3of the third metal plate30, a product region M4of the fourth metal plate40, a product region M5of the fifth metal plate50, and a product region M6of the sixth metal plate60. Further, the frames N illustrated inFIG.3AthroughFIG.5Binclude a frame N1of the first metal plate10, a frame N2of the second metal plate20, a frame N3of the third metal plate30, a frame N4of the fourth metal plate40, a frame N5of the fifth metal plate50, and a frame N6of the sixth metal plate60.

FIG.6AthroughFIG.6Gare cross sectional views of the first metal plate10along lines A-A through G-G inFIG.3A, respectively. More particularly,FIG.6Ais the cross sectional view of the first metal plate10along the line A-A inFIG.3A.FIG.6Bis the cross sectional view of the first metal plate10along the line B-B inFIG.3A.FIG.6Cis the cross sectional view of the first metal plate10along the line C-C inFIG.3A.FIG.6Dis the cross sectional view of the first metal plate10along the line D-D inFIG.3A.FIG.6Eis the cross sectional view of the first metal plate10along the line E-E line inFIG.3A.FIG.6Fis the cross sectional view of the first metal plate10along the line F-F inFIG.3A.FIG.6Gis the cross sectional view of the first metal plate10along the line G-G inFIG.3A. For the sake of convenience inFIG.6AthroughFIG.6G, a portion of a row of terminals connected to a conductor (or wire) is indicated by a hatching different from other portions, and the same may be applied to the subsequent figures.

As illustrated inFIG.3AthroughFIG.6G, the product region M1of the first metal plate10includes a conductor (or wire)11formed in a generally rectangular spiral shape, and a row12of terminals aligned in a predetermined direction on an outer side the generally rectangular spiral shape formed by the conductor11. The conductor11is connected to the frame N1by a plurality of connections13(six connections13in this example) extending from the inside of the product region M1toward the outside of the product region M1. The number and connecting positions of connections13may be arbitrarily determined, respectively, as long as the conductor11can be stably supported on the frame N1. However, the connections13are preferably disposed near the corners of the generally rectangular spiral shape of the conductor11.

The row12of terminals includes a terminal portion121, a connecting portion122, and support portions1231through1235that are arranged in this order from the left side ofFIG.3Aat predetermined intervals. The conductor11, the connections13, and the frame N1are thin plate portions formed to a predetermined thickness, and the terminal portion121, the connecting portion122, and the support portions1231through1235are thick plate portions having the same thickness that is thicker than the conductor11or the like. The planar shapes of the terminal portion121, the connecting portion122, and the support portions1231through1235are square or oblong shapes, for example.

Upper surfaces (surfaces on the side of the second metal plate20) of the conductor11, the connections13, and the frame N1are approximately coplanar with upper surfaces (surfaces on the side of the second metal plate20) of the terminal portion121, the connecting portion122, and the support portions1231through1235. On the other hand, lower surfaces of the conductor11, the connections13, and the frame N1are located at positions recessed toward the second metal plate20from lower surfaces of the terminal portion121, the connecting portion122, and the support portions1231through1235. In this example, when an inductor is manufactured from the coil structure1and mounted on a substrate, the surface facing the substrate is regarded as the lower surface, and the surface facing the opposite side is regarded as the upper surface, and the same shall apply hereinafter.

The frame N1may include a first portion having the same thickness as the conductor11, and a second portion having the same thickness as the thick plate portion forming the row12of terminals. For example, in order to reinforce the frame N1and prevent inclination of the metal plate, a reinforcing portion14may be provided, as the second portion, at the four corners of the frame N1. In this case, a lower surface of the reinforcing portion14is approximately coplanar with the lower surface of the terminal portion121or the like. The reinforcing portion14may be formed to an L-shape, for example. In order to reinforce the frame N1and prevent the inclination of the metal plate, the second portion (thick plate portion) may be provided at positions other than the corners of the frame N1, in place of or in addition to the reinforcing portion14.

Thicknesses of the terminal portion121, the connecting portion122, and the support portions1231through1235may be approximately 50 μm to approximately 500 μm, for example. Thicknesses of the conductor11, the connections13, and the frame N1may be approximately one-half of the thickness of the terminal portion121or the like, for example. In the case where the reinforcing portion14is provided on the frame N1, the thickness of the reinforcing portion14may be approximately the same as the thickness of the terminal portion121or the like.

The terminal portion121is disposed inside the product region M1, and has one end thereof extending outside the product region M1and connected to the frame N1. The extending portion of the terminal portion121is a thin plate portion similar to the connections13. The other end of the terminal portion121is connected to a start point111of the conductor11. The connecting portion122is disposed inside the product region M1, and has one thereof extending outside the product region M1and connected to the frame N1. The extending portion of the connecting portion122is a thin plate portion similar to the connections13. The other end of the connecting portion122is connected to an end point112of the conductor11.

The support portions1231through1235are disposed inside the product region M1, and respectively have one end thereof extending outside the product region M1and connected to the frame N1. The extending portion of each of the support portions1231through1235is a thin plate portion similar to the connections13. The other end of each of the support portions1231through1235is not connected to the conductor11. In other words, the support portions1231through1235and the conductor11are not electrically connected. Hence, in the row12of terminals of the first metal plate10, the thick plate portions other than the thick plate portions (the terminal portion121and the connecting portion122) connected to both ends of the conductor11are electrically isolated from the conductor11, and function as support portions supporting the thick plate portions of the rows of terminals of other metal plates.

As illustrated inFIG.3B, the second metal plate20differs from the first metal plate10in that positions where the start point and the end point of the conductor connect to the row of terminals are shifted one place toward the right with respect to the first metal plate10. Otherwise, the overall shape and thickness of the second metal plate20are the same as those of the first metal plate10.

More particularly, the product region M2of the second metal plate20includes a conductor21formed in a generally rectangular spiral shape, and a row22of terminals aligned in a predetermined direction on an outer side the generally rectangular spiral shape formed by the conductor21. The conductor21is connected to the frame N2by a plurality of connections23(six connections23in this example) extending from the inside of the product region M2toward the outside of the product region M2. The number and connecting positions of connections23may be arbitrarily determined, respectively, as long as the conductor21can be stably supported on the frame N2. However, the connections23are preferably disposed near the corners of the generally rectangular spiral shape of the conductor21.

The row22of terminals includes a support portion2231, a connecting portion2221, a connecting portion2222, and support portions2232through2235that are arranged in this order from the left side ofFIG.3Bat predetermined intervals. The conductor21, the connections23, and the frame N2are thin plate portions formed to a predetermined thickness, and the connecting portion2221, the connecting portion2222, and the support portions2231through2235are thick plate portions having the same thickness that is thicker than the conductor21or the like. The planar shapes of the connecting portion2221, the connecting portion2222, and the support portions2231through2235are the same as the planar shapes of the terminal portion121, the connecting portion122, and the support portions1231through1235, for example.

Upper surfaces (surfaces on the side of the third metal plate30) of the conductor21, the connections23, and the frame N2are approximately coplanar with upper surfaces (surfaces on the side of the third metal plate30) of the connecting portion2221, the connecting portion2222, and the support portions2231through2235. On the other hand, lower surfaces of the conductor21, the connections23, and the frame N2are located at positions recessed toward the third metal plate30from lower surfaces of the connecting portion2221, the connecting portion2222, and the support portions2231through2235.

The frame N2may include a first portion having the same thickness as the conductor21, and a second portion having the same thickness as the thick plate portion forming the row22of terminals. For example, in order to reinforce bonding with the adjacent metal plate and prevent inclination of the metal plate, a reinforcing portion24may be provided, as the second portion, at the four corners of the frame N2. In this case, a lower surface of the reinforcing portion24is approximately coplanar with the lower surface of the connecting portion2221or the like. The reinforcing portion24may be formed to an L-shape, for example. In order to reinforce the bonding with the adjacent metal plate and prevent the inclination of the metal plate, the second portion (thick plate portion) may be provided at positions other than the corners of the frame N2, in place of or in addition to the reinforcing portion24.

Thicknesses of the conductor21, the connections23, and the frame N2may be the same as that of the conductor11or the like, for example. Thicknesses of the connecting portion2221, the connecting portion2222, and the support portions2231through2235may be the same as that of the terminal portion121or the like, for example.

The connecting portions2221and2222are disposed inside the product region M2, and have one end thereof extending outside the product region M2and connected to the frame N2. The extending portion of each of the connecting portions2221and2222is a thin plate portion similar to the connections23. The other end of the connecting portion2221is connected to a start point211of the conductor21. The other end of the connecting portion2222is connected to an end point212of the conductor21.

The support portions2231through2235are disposed inside the product region M2, and respectively have one end thereof extending outside the product region M2and connected to the frame N2. The extending portion of each of the support portions2231through2235is a thin plate portion similar to the connections23. The other end of each of the support portions2231through2235is not connected to the conductor21. In other words, the support portions2231through2235and the conductor21are not electrically connected. Hence, in the row22of terminals of the second metal plate20, the thick plate portions other than the thick plate portions (the connecting portions2221and2222) connected to both ends of the conductor21are electrically isolated from the conductor21, and function as support portions supporting the thick plate portions of the rows of terminals of other metal plates.

As illustrated inFIG.4A, the third metal plate30differs from the second metal plate20in that positions where the start point and the end point of the conductor connect to the row of terminals are shifted one place toward the right with respect to the second metal plate20. Otherwise, the overall shape and thickness of the third metal plate30are the same as those of the second metal plate20.

More particularly, the product region M3of the third metal plate30includes a conductor31formed in a generally rectangular spiral shape, and a row32of terminals aligned in a predetermined direction on an outer side the generally rectangular spiral shape formed by the conductor31. The conductor31is connected to the frame N2by a plurality of connections33(six connections33in this example) extending from the inside of the product region M3toward the outside of the product region M3. The number and connecting positions of connections33may be arbitrarily determined, respectively, as long as the conductor31can be stably supported on the frame N3. However, the connections33are preferably disposed near the corners of the generally rectangular spiral shape of the conductor31.

The row32of terminals includes support portions3231and3232, a connecting portion3221, a connecting portion3222, and support portions3233through3235that are arranged in this order from the left side ofFIG.4Aat predetermined intervals. The conductor31, the connections33, and the frame N3are thin plate portions formed to a predetermined thickness, and the connecting portion3221, the connecting portion3222, and the support portions3231through3235are thick plate portions having the same thickness that is thicker than the conductor31or the like. The planar shapes of the connecting portion3221, the connecting portion3222, and the support portions3231through3235are the same as the planar shapes of the terminal portion121, the connecting portion122, and the support portions1231through1235, for example.

Upper surfaces (surfaces on the side of the fourth metal plate40) of the conductor31, the connections33, and the frame N3are approximately coplanar with upper surfaces (surfaces on the side of the fourth metal plate40) of the connecting portion3221, the connecting portion3222, and the support portions3231through3235. On the other hand, lower surfaces of the conductor31, the connections33, and the frame N3are located at positions recessed toward the fourth metal plate40from lower surfaces of the connecting portion3221, the connecting portion3222, and the support portions3231through3235.

The frame N3may include a first portion having the same thickness as the conductor31, and a second portion having the same thickness as the thick plate portion forming the row32of terminals. For example, in order to reinforce bonding with the adjacent metal plate and prevent inclination of the metal plate, a reinforcing portion34may be provided, as the second portion, at the four corners of the frame N3. In this case, a lower surface of the reinforcing portion34is approximately coplanar with the lower surface of the connecting portion3221or the like. The reinforcing portion34may be formed to an L-shape, for example. In order to reinforce the bonding with the adjacent metal plate and prevent the inclination of the metal plate, the second portion (thick plate portion) may be provided at positions other than the corners of the frame N3, in place of or in addition to the reinforcing portion34.

Thicknesses of the conductor31, the connections33, and the frame N3may be the same as that of the conductor11or the like, for example. Thicknesses of the connecting portion3221, the connecting portion3222, and the support portions3231through3235may be the same as that of the terminal portion121or the like, for example.

The connecting portions3221and3222are disposed inside the product region M3, and have one end thereof extending outside the product region M3and connected to the frame N3. The extending portion of each of the connecting portions3221and3222is a thin plate portion similar to the connections33. The other end of the connecting portion3221is connected to a start point311of the conductor31. The other end of the connecting portion3222is connected to an end point312of the conductor31.

The support portions3231through3235are disposed inside the product region M3, and respectively have one end thereof extending outside the product region M3and connected to the frame N3. The extending portion of each of the support portions3231through3235is a thin plate portion similar to the connections33. The other end of each of the support portions3231through3235is not connected to the conductor31. In other words, the support portions3231through3235and the conductor31are not electrically connected. Hence, in the row32of terminals of the third metal plate30, the thick plate portions other than the thick plate portions (the connecting portions3221and3222) connected to both ends of the conductor31are electrically isolated from the conductor31, and function as support portions supporting the thick plate portions of the rows of terminals of other metal plates.

As illustrated inFIG.4B, the fourth metal plate40differs from the third metal plate30in that positions where the start point and the end point of the conductor connect to the row of terminals are shifted one place toward the right with respect to the third metal plate30. Otherwise, the overall shape and thickness of the fourth metal plate40are the same as those of the third metal plate30.

More particularly, the product region M4of the fourth metal plate40includes a conductor41formed in a generally rectangular spiral shape, and a row42of terminals aligned in a predetermined direction on an outer side the generally rectangular spiral shape formed by the conductor41. The conductor41is connected to the frame N4by a plurality of connections43(six connections43in this example) extending from the inside of the product region M4toward the outside of the product region M4. The number and connecting positions of connections43may be arbitrarily determined, respectively, as long as the conductor41can be stably supported on the frame N4. However, the connections43are preferably disposed near the corners of the generally rectangular spiral shape of the conductor41.

The row42of terminals includes support portions4231through4233, a connecting portion4221, a connecting portion4222, and support portions4234and4235that are arranged in this order from the left side ofFIG.4Bat predetermined intervals. The conductor41, the connections43, and the frame N4are thin plate portions formed to a predetermined thickness, and the connecting portion4221, the connecting portion4222, and the support portions4231through4235are thick plate portions having the same thickness that is thicker than the conductor41or the like. The planar shapes of the connecting portion4221, the connecting portion4222, and the support portions4231through4235are the same as the planar shapes of the terminal portion121, the connecting portion122, and the support portions1231through1235, for example.

Upper surfaces (surfaces on the side of the fifth metal plate50) of the conductor41, the connections43, and the frame N4are approximately coplanar with upper surfaces (surfaces on the side of the fifth metal plate50) of the connecting portion4221, the connecting portion4222, and the support portions4231through4235. On the other hand, lower surfaces of the conductor41, the connections43, and the frame N4are located at positions recessed toward the fifth metal plate50from lower surfaces of the connecting portion4221, the connecting portion4222, and the support portions4231through4235.

The frame N4may include a first portion having the same thickness as the conductor41, and a second portion having the same thickness as the thick plate portion forming the row42of terminals. For example, in order to reinforce bonding with the adjacent metal plate and prevent inclination of the metal plate, a reinforcing portion44may be provided, as the second portion, at the four corners of the frame N4. In this case, a lower surface of the reinforcing portion44is approximately coplanar with the lower surface of the connecting portion4221or the like. The reinforcing portion44may be formed to an L-shape, for example. In order to reinforce the bonding with the adjacent metal plate and prevent the inclination of the metal plate, the second portion (thick plate portion) may be provided at positions other than the corners of the frame N4, in place of or in addition to the reinforcing portion44.

Thicknesses of the conductor41, the connections43, and the frame N4may be the same as that of the conductor11or the like, for example. Thicknesses of the connecting portion4222, the connecting portion4222, and the support portions4231through4235may be the same as that of the terminal portion121or the like, for example.

The connecting portions4221and4222are disposed inside the product region M4, and have one end thereof extending outside the product region M4and connected to the frame N4. The extending portion of each of the connecting portions4221and4222is a thin plate portion similar to the connections43. The other end of the connecting portion4221is connected to a start point411of the conductor41. The other end of the connecting portion4222is connected to an end point412of the conductor41.

The support portions4231through4235are disposed inside the product region M4, and respectively have one end thereof extending outside the product region M4and connected to the frame N4. The extending portion of each of the support portions4231through4235is a thin plate portion similar to the connections43. The other end of each of the support portions4231through4235is not connected to the conductor41. In other words, the support portions4231through4235and the conductor41are not electrically connected. Hence, in the row42of terminals of the fourth metal plate40, the thick plate portions other than the thick plate portions (the connecting portions4221and4222) connected to both ends of the conductor41are electrically isolated from the conductor41, and function as support portions supporting the thick plate portions of the rows of terminals of other metal plates.

As illustrated inFIG.5A, the fifth metal plate50differs from the fourth metal plate40in that positions where the start point and the end point of the conductor connect to the row of terminals are shifted one place toward the right with respect to the fourth metal plate40. Otherwise, the overall shape and thickness of the fifth metal plate50are the same as those of the fourth metal plate40.

More particularly, the product region M5of the fifth metal plate50includes a conductor51formed in a generally rectangular spiral shape, and a row52of terminals aligned in a predetermined direction on an outer side the generally rectangular spiral shape formed by the conductor51. The conductor51is connected to the frame N5by a plurality of connections53(six connections53in this example) extending from the inside of the product region M5toward the outside of the product region M5. The number and connecting positions of connections53may be arbitrarily determined, respectively, as long as the conductor51can be stably supported on the frame N5. However, the connections53are preferably disposed near the corners of the generally rectangular spiral shape of the conductor51.

The row52of terminals includes support portions5231through5234, a connecting portion5221, a connecting portion5222, and a support portion5235that are arranged in this order from the left side ofFIG.5Aat predetermined intervals. The conductor51, the connections53, and the frame N5are thin plate portions formed to a predetermined thickness, and the connecting portion5221, the connecting portion5222, and the support portions5231through5235are thick plate portions having the same thickness that is thicker than the conductor51or the like. The planar shapes of the connecting portion5221, the connecting portion5222, and the support portions5231through5235are the same as the planar shapes of the terminal portion121, the connecting portion122, and the support portions1231through1235, for example.

Upper surfaces (surfaces on the side of the sixth metal plate60) of the conductor51, the connections53, and the frame N5are approximately coplanar with upper surfaces (surfaces on the side of the sixth metal plate60) of the connecting portion5221, the connecting portion5222, and the support portions5231through5235. On the other hand, lower surfaces of the conductor51, the connections53, and the frame N5are located at positions recessed toward the sixth metal plate60from lower surfaces of the connecting portion5221, the connecting portion5222, and the support portions5231through5235.

The frame N5may include a first portion having the same thickness as the conductor51, and a second portion having the same thickness as the thick plate portion forming the row52of terminals. For example, in order to reinforce bonding with the adjacent metal plate and prevent inclination of the metal plate, a reinforcing portion54may be provided, as the second portion, at the four corners of the frame N5. In this case, a lower surface of the reinforcing portion54is approximately coplanar with the lower surface of the connecting portion5221or the like. The reinforcing portion54may be formed to an L-shape, for example. In order to reinforce the bonding with the adjacent metal plate and prevent the inclination of the metal plate, the second portion (thick plate portion) may be provided at positions other than the corners of the frame N5, in place of or in addition to the reinforcing portion54.

Thicknesses of the conductor51, the connections53, and the frame N5may be the same as that of the conductor11or the like, for example. Thicknesses of the connecting portion5221, the connecting portion5222, and the support portions5231through5235may be the same as that of the terminal portion121or the like, for example.

The connecting portions5221and5222are disposed inside the product region M5, and have one end thereof extending outside the product region M5and connected to the frame N5. The extending portion of each of the connecting portions5221and5222is a thin plate portion similar to the connections53. The other end of the connecting portion5221is connected to a start point511of the conductor51. The other end of the connecting portion5222is connected to an end point512of the conductor51.

The support portions5231through5235are disposed inside the product region M5, and respectively have one end thereof extending outside the product region M5and connected to the frame N5. The extending portion of each of the support portions5231through5235is a thin plate portion similar to the connections53. The other end of each of the support portions5231through5235is not connected to the conductor51. In other words, the support portions5231through5235and the conductor51are not electrically connected. Hence, in the row52of terminals of the fifth metal plate50, the thick plate portions other than the thick plate portions (the connecting portions5221and5222) connected to both ends of the conductor51are electrically isolated from the conductor51, and function as support portions supporting the thick plate portions of the rows of terminals of other metal plates.

As illustrated inFIG.5B, the sixth metal plate60differs from the fifth metal plate50in that positions where the start point and the end point of the conductor connect to the row of terminals are shifted one place toward the right with respect to the fifth metal plate50. Otherwise, the overall shape and thickness of the sixth metal plate60are the same as those of the fifth metal plate50.

More particularly, the product region M6of the sixth metal plate60includes a conductor61formed in a generally rectangular spiral shape, and a row62of terminals aligned in a predetermined direction on an outer side the generally rectangular spiral shape formed by the conductor61. The conductor61is connected to the frame N6by a plurality of connections63(six connections63in this example) extending from the inside of the product region M6toward the outside of the product region M6. The number and connecting positions of connections63may be arbitrarily determined, respectively, as long as the conductor61can be stably supported on the frame N6. However, the connections63are preferably disposed near the corners of the generally rectangular spiral shape of the conductor61.

The row62of terminals includes support portions6231through6235, a connecting portion622, and a terminal portion621that are arranged in this order from the left side ofFIG.5Bat predetermined intervals. The conductor61, the connections63, and the frame N6are thin plate portions formed to a predetermined thickness, and the terminal portion621, the connecting portion622, and the support portions6231through6235are thick plate portions having the same thickness that is thicker than the conductor61or the like. The planar shapes of the terminal portion621, the connecting portion622, and the support portions6231through6235are the same as the planar shapes of the terminal portion121, the connecting portion122, and the support portions1231through1235, for example.

Upper surfaces (surfaces on the side opposite from the fifth metal plate50) of the conductor61, the connections63, and the frame N6are approximately coplanar with upper surfaces (surfaces on the side opposite from the fifth metal plate50) of the terminal portion621, the connecting portion622, and the support portions6231through6235. On the other hand, lower surfaces of the conductor61, the connections63, and the frame N6are located at positions recessed toward a direction opposite from the fifth metal plate50from lower surfaces of the terminal portion621, connecting portion622, and the support portions6231through6235.

The frame N6may include a first portion having the same thickness as the conductor61, and a second portion having the same thickness as the thick plate portion forming the row62of terminals. For example, in order to reinforce bonding with the adjacent metal plate and prevent inclination of the metal plate, a reinforcing portion64may be provided, as the second portion, at the four corners of the frame N6. In this case, a lower surface of the reinforcing portion64is approximately coplanar with the lower surface of the connecting portion622or the like. The reinforcing portion64may be formed to an L-shape, for example. In order to reinforce the bonding with the adjacent metal plate and prevent the inclination of the metal plate, the second portion (thick plate portion) may be provided at positions other than the corners of the frame N6, in place of or in addition to the reinforcing portion64.

Thicknesses of the conductor61, the connections63, and the frame N6may be the same as that of the conductor11or the like, for example. Thicknesses of the terminal portion621, the connecting portion622, and the support portions6231through6235may be the same as that of the terminal portion121or the like, for example.

The connecting portion622is disposed inside the product region M6, and has one end thereof extending outside the product region M6and connected to the frame N6. The extending portion of the connecting portion622is a thin plate portion similar to the connections63. The other end of the connecting portion622is connected to a start point611of the conductor61. The terminal portion621is disposed inside the product region M6, and has one end thereof extending outside the product region M6and connected to the frame N6. The extending portion of the terminal portion621is a thin plate portion similar to the connections63. The other end of the terminal portion621is connected to an end point612of the conductor61.

The support portions6231through6235are disposed inside the product region M6, and respectively have one end thereof extending outside the product region M6and connected to the frame N6. The extending portion of each of the support portions6231through6235is a thin plate portion similar to the connections63. The other end of each of the support portions6231through6235is not connected to the conductor61. In other words, the support portions6231through6235and the conductor61are not electrically connected. Hence, in the row62of terminals of the sixth metal plate60, the thick plate portions other than the thick plate portions (the connecting portion622and the terminal portion621) connected to both ends of the conductor61are electrically isolated from the conductor61, and function as support portions supporting the thick plate portions of the rows of terminals of other metal plates.

FIG.7Ais a cross sectional view of the coil structure1along the line A-A inFIG.3A, andFIG.7Bis a cross sectional view of the coil structure1along the line B-B inFIG.3A.FIG.8Ais a cross sectional view of the coil structure1along the line C-C inFIG.3A, andFIG.8Bis a cross sectional view of the coil structure1along the line D-D inFIG.3A.FIG.9Ais a cross sectional view of the coil structure1along the line E-E inFIG.3A, andFIG.9Bis a cross sectional view of the coil structure1along the line F-F inFIG.3A.FIG.10is a cross sectional view of the coil structure1along the line G-G inFIG.3A. InFIG.7AthroughFIG.10, the illustration of some of the reference numerals are omitted for the sake of convenience.

As illustrated inFIG.7AthroughFIG.10, in addition toFIG.1AthroughFIG.6G, the adjacent metal plates of the coil structure1are bonded to each other. The adjacent metal plates may be bonded to each other by diffusion bonding, for example. The diffusion bonding is suited for bonding two adjacent metal plates without interposing a material, such as a solder or the like, having a different electrical conductivity or thermal conductivity, and is favorable for bonding the adjacent metal plates from a viewpoint of reducing a voltage loss generated at a junction between the adjacent metal plates.

More particularly, the row22of terminals of the second metal plate20is laminated on the row12of terminals of the first metal plate10, and the two rows22and12of terminals are bonded to each other. In other words, the support portion2231is laminated on the terminal portion121, the connecting portion2221is laminated on the connecting portion122, the connecting portion2222is laminated on the support portion1231, the support portion2232is laminated on the support portion1232, the support portion2233is laminated on the support portion1233, the support portion2234is laminated on the support portion1234, and the support portion2235is laminated on the support portion1235. In addition, one reinforcing portion24is bonded to each reinforcing portion14.

Accordingly, the connecting portion122connected to the end point112of the conductor11, and the connecting portion2221connected to the start point211of the conductor21, are electrically connected, thereby connecting the conductor11and the conductor21in series. In addition, because the conductors11and21are made thinner than the rows12and22of terminals, the upper surface of the conductor11and the lower surface of the conductor21do not make contact with each other. Moreover, because one of the thick plate portions of the row12of terminals is always disposed below each thick plate portion of the row22of terminals, the vertically adjacent metal plates, that is, the first and second metal plates10and20, can easily be bonded to each other.

Similarly, the row32of terminals of the third metal plate30is laminated on the row22of terminals of the second metal plate20, and the two rows32and22of terminals are bonded to each other. The support portion3231is laminated on the support portion2231, the support portion3232is laminated on the connecting portion2221, the connecting portion3221is laminated on the connecting portion2222, the connecting portion3222is laminated on the support portion2232, the support portion3233is laminated on the support portion2233, the support portion3234is laminated on the support portion2234, and the support portion3235is laminated on the support portion2235. In addition, one reinforcing portion34is bonded to each reinforcing portion24.

Accordingly, the connecting portion2222connected to the end point212of the conductor21, and the connecting portion3221connected to the start point311of the conductor31, are electrically connected, thereby connecting the conductor21and the conductor31in series. In addition, because the conductors21and31are made thinner than the rows22and32of terminals, the upper surface of the conductor21and the lower surface of the conductor31do not make contact with each other. Moreover, because one of the thick plate portions of the row22of terminals is always disposed below each thick plate portion of the row32of terminals, the vertically adjacent metal plates, that is, the second and third metal plates20and30, can easily be bonded to each other.

Similarly, the row42of terminals of the fourth metal plate40is laminated on the row32of terminals of the third metal plate30, and the two rows42and32of terminals are bonded to each other. The support portion4231is laminated on the support portion3231, the support portion4232is laminated on the support portion3232, the support portion4233is laminated on the connecting portion3221, the connecting portion4221is laminated on the connecting portion3222, the connecting portion4222is laminated on the support portion3233, the support portion4234is laminated on the support portion3234, and the support portion4235is laminated on the support portion3235. In addition, one reinforcing portion44is bonded to each reinforcing portion34.

Accordingly, the connecting portion3222connected to the end point312of the conductor31, and the connecting portion4221connected to the start point411of the conductor41, are electrically connected, thereby connecting the conductor31and the conductor41in series. In addition, because the conductors31and41are made thinner than the rows32and42of terminals, the upper surface of the conductor31and the lower surface of the conductor41do not make contact with each other. Moreover, because one of the thick plate portions of the row32of terminals is always disposed below each thick plate portion of the row42of terminals, the vertically adjacent metal plates, that is, the third and fourth metal plates30and40, can easily be bonded to each other.

Similarly, the row52of terminals of the fifth metal plate50is laminated on the row42of terminals of the fourth metal plate40, and the two rows52and42of terminals are bonded to each other. The support portion5231is laminated on the support portion4231, the support portion5232is laminated on the support portion4232, the support portion5233is laminated on the support portion4233, the support portion5234is laminated on the connecting portion4221, the connecting portion5221is laminated on the connecting portion4222, the connecting portion5222is laminated on the support portion4234, and the support portion5235is laminated on the support portion4235. In addition, one reinforcing portion54is bonded to each reinforcing portion44.

Accordingly, the connecting portion4222connected to the end point412of the conductor41, and the connecting portion5221connected to the start point511of the conductor51, are electrically connected, thereby connecting the conductor41and the conductor51in series. In addition, because the conductors41and51are made thinner than the rows42and52of terminals, the upper surface of the conductor41and the lower surface of the conductor51do not make contact with each other. Moreover, because one of the thick plate portions of the row42of terminals is always disposed below each thick plate portion of the row52of terminals, the vertically adjacent metal plates, that is, the fourth and fifth metal plates40and50, can easily be bonded to each other.

Similarly, the row62of terminals of the sixth metal plate60is laminated on the row52of terminals of the fifth metal plate50, and the two rows62and52of terminals are bonded to each other. The support portion6231is laminated on the support portion5231, the support portion6232is laminated on the support portion5232, the support portion6233is laminated on the support portion5233, the support portion6234is laminated on the support portion5234, the support portion6235is laminated on the connecting portion5221, the connecting portion622is laminated on the connecting portion5222, and the terminal portion621is laminated on the support portion5235. In addition, one reinforcing portion64is bonded to each reinforcing portion54.

Accordingly, the connecting portion5222connected to the end point512of the conductor51, and the connecting portion622connected to the start point611of the conductor61, are electrically connected, thereby connecting the conductor51and the conductor61in series. In addition, because the conductors51and61are made thinner than the rows52and62of terminals, the upper surface of the conductor51and the lower surface of the conductor61do not make contact with each other. Moreover, because one of the thick plate portions of the row52of terminals is always disposed below each thick plate portion of the row62of terminals, the vertically adjacent metal plates, that is, the fifth and sixth metal plates50and60, can easily be bonded to each other.

According to the configuration of the coil structure1described above, the end point112of the conductor11and the start point211of the conductor21, the end point212of the conductor21and the start point311of the conductor31, the end point312of the conductor31and the start point411of the conductor41, the end point412of the conductor41and the start point511of the conductor51, and the end point512of the conductor51and the start point611of the conductor61, are successively connected. For this reason, a single spiral coil is formed from the start point111of the conductor11to the end point612of the conductor61.

FIG.11AthroughFIG.12Bare diagrams illustrating examples of manufacturing processes of the coil structure according to the first embodiment.FIG.11AthroughFIG.12Bcorrespond to cross sectional views along the line B-B inFIG.3A, and illustrate only one product region.

First, in the process illustrated inFIG.11A, a plate-shaped metal100having a uniform thickness and a planar shape illustrated inFIG.1Ais prepared. The plate-shaped metal100is a member that ultimately becomes the first metal plate10, and is formed of copper, copper alloys, 42-alloys such as Fe—Ni alloys or the like, or the like, for example. The thickness of the plate-shaped metal100may be in a range of approximately 50 μm to approximately 500 μm, for example. A plurality of product regions are defined on the plate-shaped metal100. A resist layer310is formed on the entire upper surface of the plate-shaped metal100, and a resist layer320is formed on the entire lower surface of the plate-shaped metal100. The resist layers310and320may be formed by laminating a photosensitive dry film resist, for example.

Next, in the process illustrated inFIG.11B, the resist layer310is exposed and developed, to form openings310xselectively exposing the upper surface of the plate-shaped metal100. In addition, the resist layer320is exposed and developed, to form openings320xselectively exposing the lower surface of the plate-shaped metal100.

Next, in the process illustrated inFIG.11C, the plate-shaped metal100exposed inside the openings310xis half-etched from the upper surface of the plate-shaped metal100, and the plate-shaped metal100exposed inside the openings320xis half-etched from the lower surface of the plate-shaped metal100. As a result, the plate-shaped metal100is patterned, thereby forming the first metal plate10having the conductor11, the row12of terminals, or the like.

In the plate-shaped metal100, a region where the resist layers310and320overlap in the plan view, maintains the original thickness because this region is not etched, thereby forming the thick plate portion. Moreover, a region where both the resist layers310and320are not formed in the plan view, are half-etched from both the upper and lower surfaces of the plate-shaped metal100, thereby forming a through hole. In addition, a region where only the resist layer310is formed in the plan view is half-etched only from the lower surface of the plate-shaped metal100, thereby forming the thin plate portion having a thickness which is approximately one-half the original thickness. In a case where the plate-shaped metal100is copper, a ferric chloride solution, for example, may be used for the half-etching.

Next, in the process illustrated inFIG.12A, the second metal plate20, the third metal plate30, the fourth metal plate40, the fifth metal plate50, and the sixth metal plate60are manufactured in the same manner as inFIG.11AthroughFIG.11C. The planar shapes of the metal plates are as illustrated inFIG.3BthroughFIG.5B, and the cross sectional shapes of the metal plates are as illustrated inFIG.6AthroughFIG.10.

Next, in the process illustrated inFIG.12B, the metal plates are laminated, and the thick plate portions of the adjacent metal plates, including the rows of terminals, are bonded to each other. More particularly, the metal plates are laminated in the order illustrated inFIG.12B, to form a laminate, and the laminate is pressed in a vertical direction in a vacuum atmosphere and heated to perform the diffusion bonding. As a result, the thick plate portions of the adjacent metal plates are directly bonded to each other, thereby completing the coil structure1. When the diffusion bonding is performed, one of the thick plate portions of the row of terminals of the lower layer is always disposed below each thick plate portion of the row of terminals except the lowermost layer. For this reason, the bonding of each of the thick plate portions can be performed in one bonding operation. The metal plates are preferably made of the same material, so that excellent bonding of the adjacent metal plates can be achieved by the diffusion bonding.

The coil structure1can be completed by the processes described above. However, an inductor2can be manufactured by continuing to perform the processes illustrated inFIG.13AandFIG.13B.

In the process illustrated inFIG.13A, an encapsulating resin70is formed on the coil structure1illustrated inFIG.12B. An insulating resin used for the encapsulating resin70may be a thermosetting resin or a thermoplastic resin, such as epoxy-based resins, polyimide-based resins, phenolic-based resins, acrylic-based resins, or the like, for example. The encapsulating resin70is formed so that the lower surface of the row12of terminals of the first metal plate10is exposed from a lower surface of the encapsulating resin70. After the encapsulating resin70is formed, the lower surface of the encapsulating resin70is preferably subjected to a polishing or blast process to remove resin burrs on the lower surface of the row12of terminals. A low-pressure molding, such as a transfer molding, a compression molding, or the like, for example, may be used to form the encapsulating resin70.

Next, in the process illustrated inFIG.13B, the structure illustrated inFIG.13Ais cut at positions of cutting-plane lines L using a dicing blade or the like, and singulated to form the inductor2. The structure illustrated inFIG.13Amay be singulated by pressing or etching. The cutting-plane lines L are located at positions corresponding to broken lines indicating the product region M inFIG.1B. The cutting exposes side surfaces of the rows12,22,32,42,52, and62of terminals from one side surface of the encapsulating resin70. From each product region M, the surface-mount type inductor2illustrated inFIG.14AandFIG.14Bis formed. The planar shape of the inductor2may be an approximately rectangular shape, such as a square shape, a oblong shape, or the like, for example.

The side surface and the lower surface of the terminal portion121of the row12of terminals, the side surface of the support portion2231of the row22of terminals, the side surface of the support portion3231of the row32of terminals, the side surface of the support portion4231of the row42of terminals, the side surface of the support portion5231of the row52of terminals, and the side surface of the support portion6231of the row62of terminals, exposed from the encapsulating resin70, respectively form an external connection terminal1A. In addition, the side surface and the lower surface of the support portion1235of the row12of terminals, the side surface of the support portion2235of the row22of terminals, the side surface of the support portion3235of the row32of terminals, the side surface of the support portion4235of the row42of terminals, the side surface of the support portion5235of the row52of terminals, and the side surface of the terminal portion621of the row62of terminals, exposed from the encapsulating resin70, respectively form an external connection terminal1B.

FIG.14Bis a view ofFIG.14Aviewed from the lower surface thereof. In other words,FIG.14Bis a diagram corresponding toFIG.14Awhich is rotated 180 degrees in a left-to-right (or clockwise) direction on paper, that is, turned upside down. For example, the planar shape of the inductor2may be an approximately rectangular shape having a size of approximately 3 mm×3 mm. The thickness of the inductor2may be approximately 1.0 mm, for example.

FIG.15AandFIG.15Bare cross sectional views for explaining a method for mounting the inductor according to the first embodiment.FIG.15Aillustrates a cross section along a cutting-plane line H inFIG.14AandFIG.14B, andFIG.15Billustrates a cross section along a cutting-plane line I inFIG.14AandFIG.14B. InFIG.15AandFIG.15B, the inductor2is mounted on a substrate200. More particularly, a pad210is formed on an upper surface of the substrate200, and a portion of an upper surface of the pad210is exposed inside an opening220xof a solder resist layer220. The upper surface of the pad210exposed inside the opening220xis electrically connected to the external connection terminals1A and1B of the inductor2, via a solder230.

As described above, the coil structure1has the configuration in which the six metal plates are laminated. Each metal plate includes a conductor formed in a spiral shape, and a row of terminals aligned in a predetermined direction on an outer side the spiral shape formed by the conductor, where the row of terminals includes seven thick plate portions having the same thickness which is thicker than the conductor. Six such metal plates are laminated, and the terminals of the adjacent metal plates are bonded to each other. In addition, both ends of the conductor of each metal plate are connected to two adjacent thick plate portions, among the thick plate portions forming the row of terminals of each metal plate.

Both ends of the conductor11of the lowermost metal plate are connected to the terminal portion121and the connecting portion122, which are two thick plate portions located on a first end (left side in the example illustrated inFIG.3Aor the like) of the row12of terminals, and the positions of the thick plate portions connected to both ends of the conductor are shifted one place toward a second end (right side) of the row of terminals, opposite to the first end, for each upward increase in level within the laminate along a laminated direction (direction toward an uppermost metal plate in this example) of the metal plates. According to this configuration, the conductors of the metal plates are connected in series to form a single spiral coil.

According to the configuration described above, it is easy to increase the number of turns of the coil by increasing the number of metal plates that are laminated. As a result, by using the coil structure1, it is possible to form the inductor2which has a small size but can obtain a large induced electromotive force. In other words, by encapsulating the coil structure1by the encapsulating resin70so as to expose the external connection terminals1A and1B, it is possible to form the inductor2which is small but can obtain the large induced electromotive force.

The number of metal plates that are laminated is not limited to six, and may be n, where n is a natural number greater than or equal to two. In this case, each metal plate may include the conductor having the spiral shape, and the row of terminals aligned in the predetermined direction on the outer side the spiral shape formed by the conductor, where the row of terminals includes n+1 thick plate portions having the same thickness which is thicker than the conductor. Alternatively, the number of thick plate portions forming the row of terminals may be greater than or equal to n+1. For example, when using a common metal plate and varying the number of metal plates that are laminated depending on the application, the number of thick plate portions forming the row of terminals may be greater than or equal to n+1.

For example, if n metal plates were laminated, and the number of thick plate portions forming the row of terminals were less than or equal to n, the support from the lower end would become insufficient when the metal plates are bonded by applying heat and pressure in the vertical direction, thereby causing some thick plate portions to assume a floating state. Such a floating state of the thick plate portions would make the bonding difficult.

On the other hand, according to the coil structure1, each of the n metal plates includes the conductor having the spiral shape, and the row of terminals, aligned in the predetermined direction on the outer side the spiral shape formed by the conductor, includes n+1 thick plate portions. For this reason, the metal plates can be easily bonded together by the diffusion bonding or the like.

Moreover, in the coil structure1, the six thick plate portions laminated at one end of the row of terminals become the external connection terminal1A, and the six thick plate portions laminated at the other end of the row of terminals become the external connection terminal1B. In other words, the support portions2231,3231,4231,5231, and6231are successively laminated on the terminal portion121, thereby forming the external connection terminal1A. Further, the support portions2235,3235,4235, and5235, and the terminal portion621are successively laminated on the support portion1235, thereby forming the external connection terminal1B.

Because one end of the row of terminals of each of the metal plates is laminated on the terminal portion121of the first metal plate10in the external connection terminal1A, an external connection to an external device or the like can be made by an arbitrary metal plate of the external connection terminal1A. Similarly, because the other end of the row of terminals of each of the metal plates is laminated on the support portion1235of the first metal plate10in the external connection terminal1B, the external connection to the external device or the like can be made by an arbitrary metal plate of the external connection terminal1B.

In the example described above, the side of the conductor11is regarded as the start point, and the side of the conductor61is regarded as the end point, for the sake of convenience. However, because the coil structure1is non-polar, the current may flow from the external connection terminal1A toward the external connection terminal1B, or may flow from the external connection terminal1B toward the external connection terminal1A.

The coil structure1may be shipped as a product, or the inductor2may be shipped as a product. In addition, any one or more of the first metal plate10, the second metal plate20, the third metal plate30, the fourth metal plate40, the fifth metal plate50, and the sixth metal plate60before the lamination may be shipped as a lead frame. In other words, in the lead frame that is shipped, the metal plate may include the conductor formed in the spiral shape, and the row of terminals aligned in the predetermined direction on the outer side the spiral shape formed by the conductor, where the row of terminals includes three or more thick plate portions having the same thickness which is thicker than the conductor, and both ends of the conductor of the metal plate are connected to two adjacent thick plate portions among the thick plate portions forming the row of terminals of the metal plate.

Second Embodiment

A second embodiment illustrates an example in which the conductor or the like is covered by an insulating film. In the second embodiment, those parts that are the same as those corresponding parts of the first embodiment are designated by the same reference numerals, and a description thereof may be omitted.

FIG.16is a cross sectional view illustrating the coil structure according to the second embodiment, and illustrates a cross section corresponding toFIG.7B. As illustrated inFIG.16, a coil structure3differs from the coil structure1(refer toFIG.7Bor the like) in that the coil structure3includes an insulating film80which covers the surface of each metal plate.

More particularly, the insulating film80is formed on the surfaces of each of the conductor11, the connections13, and the frame N1of the first metal plate10; the conductor21, the connections23, and the frame N2of the second metal plate20; the conductor31, the connections33, and the frame N3of the third metal plate30; the conductor41, the connections43, and the frame N4of the fourth metal plate40; the conductor51, the connections53, and the frame N5of the fifth metal plate50; and the conductor61, the connections63, and the frame N6of the sixth metal plate60. In addition, the insulating film80is formed on the surfaces of the laminated structure in which each portion (terminal portion, connecting portion, and support portion) of the rows12,22,32,42,52, and62of terminals is laminated.

A material used for the insulating film80may be an insulating resin, such as epoxy-based resins, polyimide-based resins, or the like, for example. A thickness of the insulating film80may be approximately 10 μm, for example. The insulating film80may be formed by electrodeposition, for example. When the insulating film80is formed by the electrodeposition, an insulating film having an approximately uniform thickness can be formed on the surfaces of each of the metal plates.

FIG.17is a cross sectional view illustrating an example of the inductor according to the second embodiment. As illustrated inFIG.17, an inductor4can be formed by encapsulating the coil structure3illustrated inFIG.16with an encapsulating resin71, and cutting encapsulated coil structure3at predetermined positions. The planar shape of the inductor4may be a rectangular shape, such as a square shape, an oblong shape, of the like, for example. An insulating resin used for the encapsulating resin71may include a magnetic filler, for example.

Soft magnetic powder, for example, may be used for the magnetic filler. Examples of the soft magnetic powder include iron-based amorphous alloy powder, carbonyl iron powder, ferrite or permalloy powder, or the like. Examples of the insulating resin include thermosetting resins or thermoplastic resins, such as epoxy-based resins, polyimide-based resins, phenolic-based resins, acrylic-based resins, or the like. A blending or mixing ratio of the magnetic filler material and the insulating resin may be adjusted so as to secure the required permeability and moldability.

In order to form the inductor4, the insulating film80is formed on the surfaces of each of the metal plates of the structure by the electrodeposition or the like, as illustrated inFIG.12B, and the encapsulating resin71is formed thereafter by the low-pressure molding, such as the transfer molding or the compression molding, as illustrated inFIG.18A, for example. Then, as illustrated inFIG.18B, the insulating film80covering the lower surface of the structure illustrated inFIG.18Ais removed by the polishing or blasting, thereby exposing the lower surface of the row12of terminals from the encapsulating resin71. Thereafter, the structure illustrated inFIG.18Bis cut at the positions of the cutting-plane lines L using the dicing blade or the like, and singulated to form the inductor4. From each product region M, the surface-mount type inductor4illustrated inFIG.19AandFIG.19Bis formed.FIG.19Bis a view ofFIG.19Aviewed from the lower surface thereof. In other words,FIG.19Bis a diagram corresponding toFIG.19Awhich is rotated 180 degrees in a left-to-right (or clockwise) direction on paper, that is, turned upside down. For example, the planar shape of the inductor4may be an approximately rectangular shape having a size of approximately 3 mm×3 mm. The thickness of the inductor4may be approximately 1.0 mm, for example.

FIG.20AandFIG.20Bare cross sectional views for explaining the method for mounting the inductor according to the second embodiment.FIG.20Aillustrates a cross section along the cutting-plane line H inFIG.19AandFIG.19B, andFIG.20Billustrates a cross section along the cutting-plane line I inFIG.19AandFIG.19B. InFIG.20AandFIG.20B, the inductor4is mounted on the substrate200. More particularly, the pad210is formed on the upper surface of the substrate200, and a portion of the upper surface of the pad210is exposed inside the opening220xof the solder resist layer220. The upper surface of the pad210exposed inside the opening220xis electrically connected to the external connection terminals1A and1B of the inductor4, via the solder230.

As described above, because the coil structure3of the inductor4is encapsulated with the encapsulating resin71made of the insulating resin including the magnetic filler, it is possible to improve the inductance of the inductor4. Further, because the surfaces of each of the metal plates are covered by the insulating film80, it is possible to prevent the adjacent metal plates from becoming electrically connected to each other via the filler.

Although the preferred embodiments are described above in detail, various variations, modifications, and substitutions may be made in each of the embodiments, without departing from the scope of the present disclosure.

For example, the planar shapes of the conductor and the frame of each of the metal plates are not limited to the generally rectangular shapes, and may have a circular shape, an elliptical shape, or the like, including other and more complex shapes.

According to the disclosed technique, it is possible to provide a coil structure having a configuration which can easily increase the number of turns.

Various aspects of the subject-matter described herein may be set out non-exhaustively in the following numbered clauses:1. A method for manufacturing a coil structure including n metal plates that are laminated, where n is a natural number greater than or equal to two, the method comprising:forming each of the n metal plates respectively including a spiral conductor, and a row of terminals, aligned in a predetermined direction on an outer side of the conductor, and formed by n+1 or more plate portions thicker than the conductor, by patterning a plate-shaped metal; andbonding the rows of terminals of adjacent metal plates by laminating each of the n metal plates,wherein the forming includes connecting two ends of the conductor to two adjacent plate portions for each of the n metal plates, andwherein the bonding includes connecting the two ends of the conductor of a lowermost metal plate among the n metal plates to the two adjacent plate portions located at a first end of the lowermost metal plate, connecting the two ends of the conductor of a second lowest metal plate among the n metal plates to the two adjacent plate portions located at a position shifted one place toward a second end opposite to the first end of the second lowest metal plate, so that the position where the two ends of the conductor connect to the two adjacent plate portions shifts one place toward the second end for each upward increase in level within a laminate along a laminated direction of the n metal plates, thereby connecting the conductors of each of the n metal plates in series to form a spiral coil.2. The method for manufacturing the coil structure according to clause 1, wherein the bonding includes forming external connection terminals at the plate portions laminated at the first end of the row of terminals, and at the plate portions laminated at the second end of the row of terminals form external connection terminals.3. The method for manufacturing the coil structure according to clause 1 or 2, wherein the bonding laminates each of the n metal plates, so that the plate portions in the row of terminals of each of the n metal plates, other than the plate portions connected to both ends of the conductor, are electrically isolated from the conductor and function as support portions which support the plate portions of the row of terminals of other metal plates.4. The method for manufacturing the coil structure according to any one of clauses 1 to 3, further comprising:forming an insulating film which covers surfaces of each of the n metal plates.5. The method for manufacturing the coil structure according to any one of clauses 1 to 4, further comprising:forming an encapsulating resin which covers the coil structure so that a portion of the row of terminals is exposed.

Although the embodiments are numbered with, for example, “first,” or “second,” the ordinal numbers do not imply priorities of the embodiments. Many other variations and modifications will be apparent to those skilled in the art.