Inductor bridge and electronic device

Abstract

An inductor bridge is configured to bridge-connect a first circuit and a second circuit to each other, and includes a flexible flat plate base body, a first connector at a first end portion of the base body and connected to the first circuit, a second connector at a second end portion of the base body and connected to the second circuit, and an inductor section in the base body between the first connector and the second connector. The inductor section includes conductor patterns including a plurality of layers. The inductor bridge further includes a bending portion between the inductor section and the first connector, and a slot at an inner side of the bending portion that reduces a thickness of the base body.

Claims

1. An inductor bridge configured to bridge-connect a first circuit and a second circuit to each other, the inductor bridge comprising: a flexible flat plate base body; a first electrode at a first end portion of the base body; a second electrode at a second end portion of the base body; a first connector at the first end portion of the base body, mounted on the first electrode and connected to the first circuit; a second connector at the second end portion of the base body, mounted on the second electrode and connected to the second circuit; and an inductor section in the base body between the first connector and the second connector, the inductor section being connected to the first electrode and the second electrode; wherein the inductor section includes conductor patterns including a plurality of layers; the conductor patterns of the inductor section include a pattern width on a layer closer to a surface of the base body that is smaller than a pattern width on a layer at an inner side of the base body; the inductor bridge includes a bending portion between the inductor section and the first connector; the second circuit is in contact with a member different from a member with which the first circuit is in contact; and the member in contact with the first circuit and the member in contact with the second circuit are not included in the inductor bridge.

2. The inductor bridge according to claim 1, wherein the inductor section defines a coil with a helical or substantially helical shape.

3. An electronic device comprising: an inductor bridge configured to bridge-connect a first circuit and a second circuit to each other; the first circuit; and the second circuit; wherein the inductor bridge includes: a flexible flat plate base body; a first electrode at a first end portion of the base body; a second electrode at a second end portion of the base body; a first connector at the first end portion of the base body, mounted on the first electrode and connected to the first circuit; a second connector at the second end portion of the base body, mounted on the second electrode and connected to the second circuit; and an inductor section in the base body between the first connector and the second connector, the inductor section being connected to the first electrode and the second electrode; the inductor section includes conductor patterns including a plurality of layers; the conductor patterns of the inductor section include a pattern width on a layer closer to a surface of the base body that is smaller than a pattern width on a layer at an inner side of the base body; the first circuit is in contact with a mounting board inside the electronic device; the conductor patterns of the inductor bridge are provided at a position opposing a surface-mounted component on the mounting board; the inductor bridge includes a bending portion between the inductor section and the first connector; the second circuit is in contact with a member different from the mounting board; and the mounting board in contact with the first circuit and the member in contact with the second circuit are not included in the inductor bridge.

4. The electronic device according to claim 3, wherein the inductor section defines a coil with a helical or substantially helical shape.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A is a perspective view of an inductor bridge according to a first preferred embodiment of the present invention when looking at the inductor bridge from the connector side, and FIG. 1B is a perspective view of the inductor bridge when looking at the inductor bridge from the rear side.

(2) FIG. 2A is an exploded perspective view of the inductor bridge according to the first preferred embodiment of the present invention in a manufacturing process, and FIG. 2B is a perspective view of a base body.

(3) FIG. 3A is a sectional view of the inductor bridge according to the first preferred embodiment of the present invention in a bent (folded) state, and FIG. 3B is a sectional view of the inductor bridge in a state arranged along an external member.

(4) FIG. 4A is a circuit diagram illustrating an example of an application of the inductor bridge to an electronic device, and FIG. 4B is an equivalent circuit diagram thereof.

(5) FIG. 5A is a block diagram illustrating another example of an application of the inductor bridge, and FIG. 5B is an equivalent circuit diagram thereof.

(6) FIG. 6 is an exploded perspective view of an inductor bridge according to a second preferred embodiment of the present invention in a manufacturing process.

(7) FIG. 7 is a sectional view of the inductor bridge according to the second preferred embodiment of the present invention in a bent (folded) state.

(8) FIG. 8 is an exploded perspective view of an inductor bridge according to a third preferred embodiment of the present invention in a manufacturing process.

(9) FIG. 9 is a sectional view of the inductor bridge according to the third preferred embodiment of the present invention in a state assembled into an electronic device.

(10) FIG. 10 is a sectional view of an inductor bridge according to a fourth preferred embodiment of the present invention in a state assembled into an electronic device, the sectional view illustrating a state where a mounting board and an antenna board are connected to each other by the inductor bridge.

(11) FIG. 11 is a sectional view of a principal portion of an inductor bridge according to a fifth preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(12) Preferred embodiments of the present invention will be described below in connection with several practical examples by referring to the drawings. In the drawings, the same components are denoted by the same signs. The following preferred embodiments are merely illustrative, and constituent elements of the different preferred embodiments can be partly replaced or combined in optional ways.

(13) First Preferred Embodiment

(14) FIG. 1A is a perspective view of an inductor bridge 101 according to a first preferred embodiment of the present invention when looking at the inductor bridge from the connector side, and FIG. 1B is a perspective view of the inductor bridge when looking at the inductor bridge from the rear side.

(15) The inductor bridge 101 is an element configured to bridge-connect a first circuit and a second circuit to each other. As is apparent from FIG. 1A, the inductor bridge 101 includes a base body 10 preferably in the form of a flat plate having flexibility, a first connector 51, and a second connector 52. An inductor section, described later, is preferably provided inside the base body 10. The first connector 51 is disposed in a first end portion of the base body 10 and is connected to the first circuit through mechanical contact between them. The second connector 52 is disposed in a second end portion of the base body and is connected to the second circuit through mechanical contact between them. The first connector 51 corresponds to a first connecting portion, and the second connector 52 corresponds to a second connecting portion. Furthermore, as is apparent from FIG. 1B, a slot (groove) 10D is provided in the base body 10 to reduce a thickness of the base body 10. The slot 10D is preferably provided in a bending portion between the inductor section and the first connecting portion.

(16) FIG. 2A is an exploded perspective view of the inductor bridge 101 according to the first preferred embodiment in a manufacturing process, and FIG. 2B is a perspective view of the base body 10.

(17) As is apparent from FIG. 2A, the base body 10 preferably is formed by laminating flexible resin base materials 11, 12, 13 and 14 that are each, e.g., a liquid crystal polymer (LCP). The laminated resin base materials 12, 13 and 14 provide an inductor section 30 that includes conductor patterns 31, 32 and 33 and interlayer connecting conductors (hereinafter referred to as via conductors). The inductor section 30 constitutes a coil preferably having a rectangular or substantially rectangular helical shape with a coil axis oriented in a direction perpendicular or substantially perpendicular to surfaces of the resin base materials 12, 13 and 14 (i.e., perpendicular or substantially perpendicular to a principal surface of the base body). A first end of a wiring pattern 21 is connected to one end of the conductor pattern 31.

(18) Connector mounting electrodes 41 and 42 to mount the connectors 51 and 52, respectively, are provided on the resin base material 11. The connector mounting electrode 41 is connected to a second terminal of the wiring pattern 21 through the via conductor. The connector mounting electrode 42 is connected to one end of the conductor pattern 33 through the via conductor.

(19) A resist layer 61 is provided on a lower surface of the resin base material 11, and a resist layer 62 is provided on an upper surface of the resin base material 14. It is to be noted that the resist layer 62 is not essential and it may be omitted in some cases.

(20) The slot 10D illustrated in FIGS. 1A and 1B is formed preferably by laser processing, for example. In particular, when the resin base materials are each the liquid crystal polymer (LCP), exposed inner surfaces of the slot are fusion-bonded together by carrying out the laser processing. Therefore, gaps between laminated layers are less likely to occur, and the interface between adjacent two layers of the plural resin base materials is harder to peel off. As a result, reliability of the inductor bridge 101 is ensured, and ingress of moisture through the interface is less apt to occur.

(21) The slot 10D may be formed by cutting work using a dicer, for example. Alternatively, the slot 10D may be obtained by previously forming a slit in a region of each of predetermined ones of the plural resin base materials to be laminated, where the slot is to be formed after laminating the resin base materials.

(22) A non-limiting example of a method for manufacturing the inductor bridge 101 is as follows.

(23) First, various electrodes and conductor patterns are formed on the resin base materials 11 to 14 by laminating, for each layer, the resin base material and a metal foil (e.g., a copper foil), and by patterning the metal foil with photolithography, for example. Then, the via conductors are formed through the resin base materials 12, 13 and 14. The via conductors are each formed by boring a penetration hole in the resin base material with a laser, for example, putting a conductive paste, which contains copper, silver, tin or the like, in the penetration hole, and by solidifying the conductive paste in a subsequent heating and pressing step.

(24) A laminate is obtained by stacking the resin base materials 11 to 14, and by heating and pressing them.

(25) The resist layers 61 and 62 are formed respectively on opposite surfaces of the laminate by printing.

(26) The slot 10D is formed.

(27) The individual inductor bridges 101 are obtained by cutting a collective board into pieces.

(28) The inductor bridge 101 is bent at the slot 10D while the base body of the inductor bridge 101 is heated.

(29) The connectors 51 and 52 are mounted by soldering.

(30) FIG. 3A is a sectional view of the inductor bridge 101 according to the first preferred embodiment in a bent (folded) state, and FIG. 3B is a sectional view of the inductor bridge 101 in a state arranged along an external member 85. The inductor bridge 101 is used in the state folded at the slot 10D such that the slot 10D is positioned at the inner side of bending (i.e., the inner peripheral side of a bent portion).

(31) Thus, since the slot (groove) 10D is preferably provided at the inner side of the bending portion to reduce the thickness of the base body 10, the inductor bridge 101 is capable of being easily bent at the slot 10D and is able to be bent with a large curvature. Furthermore, since the inductor bridge 101 is folded at the position of the slot 10D, a position at which the inductor bridge 101 is folded is reliably and accurately defined, and electrical characteristics are stabilized. In other words, since a position at which the inductor section 30 is formed is less susceptible to bending, fluctuations of the electrical characteristics are kept smaller when the inductor bridge 101 defines and functions as an inductor.

(32) Besides, the slot 10D preferably has a sectional shape such that a width of the slot is larger at the front opening side (i.e., the inner side when viewed in a bending direction) than at the inner bottom side. Therefore, the inductor bridge is capable of being folded with a larger curvature.

(33) Even when the slot is provided at the outer side of the bending (i.e., at the outer peripheral side of the bent portion), for example, the inductor bridge also is capable of being folded with a large curvature. However, such a case accompanies the problem that cracking or breakage is more likely to occur in the slot.

(34) In FIG. 3A, a stray capacitance CS represents a stray capacitance generated particularly between the conductor pattern 33 and the wiring pattern 21. When the inductor bridge 101 is bent (folded), an opposing component area between the conductor pattern 33 and the wiring pattern 21 is increased, and the spacing between them is narrowed. Accordingly, the stray capacitance CS is generated. On the other hand, in the inductor bridge 101, the slot 10D is provided in the base body 10 at the bent (folded) position, and the slot 10D provides a space in which the base body 10 having a certain dielectric constant is not provided, the space being filled with air. Hence the stray capacitance CS is held relatively small. As a result, the self-resonance frequency of the inductor is kept relatively high, and the inductor bridge is able to be used over a wider band.

(35) FIG. 4A is a circuit diagram illustrating an example of application of the inductor bridge 101 to an electronic device, and FIG. 4B is an equivalent circuit diagram thereof. An inductor L1 in FIGS. 4A and 4B corresponds to the inductor bridge 101. An antenna element pattern 91 is provided on an antenna board, for example. The first connector 51 of the inductor bridge 101 is connected to a feeding point of the antenna element pattern 91 or to a position extended from the feeding point. The second connector 52 of the inductor bridge 101 is connected to a connecting portion that is provided on an upper surface of a mounting board.

(36) As illustrated in FIG. 4A, impedance matching between a feed circuit (RFIC) and an antenna ANT and frequency characteristics of the antenna are determined by the inductor L1 that is connected between the antenna ANT and the RFIC.

(37) FIG. 5A is a block diagram illustrating another example of application of the inductor bridge, and FIG. 5B is an equivalent circuit diagram thereof. In this example, an antenna is preferably configured by inserting an inductor between a ground connecting point of an inverted F-type antenna and a ground.

(38) In FIGS. 5A and 5B, an inductor L2 corresponds to the inductor bridge 101. The inductor L2 is connected between an antenna ANT and the ground, thus constituting the inverted F-type antenna. More specifically, as illustrated in FIG. 5B, the inductor L2 is connected between one end of an antenna element pattern 91 and the ground, and a feed circuit (RFIC) is connected to the antenna element pattern 91 at a position near the inductor L2.

(39) Second Preferred Embodiment

(40) FIG. 6 is an exploded perspective view of an inductor bridge 102 according to a second preferred embodiment in a manufacturing process. FIG. 7 is a sectional view of the inductor bridge 102 in a bent (folded) state.

(41) A floating electrode (dummy electrode) 36 is provided on the resin base material 13 in addition to the conductor pattern 32 of the inductor section 30. The other points preferably are the same as those in the inductor bridge 101, illustrated in FIGS. 2A and 2B, described in the first preferred embodiment. The slot 10D is also illustrated in FIG. 6.

(42) The floating electrode 36 is provided at a position overlapping the slot 10D when looking at the base body 10 in a plan view. Because the floating electrode 36 is plastically deformed, the inductor bridge 101 is more apt to plastically deform at the slot 10D. Furthermore, because the floating electrode 36 acts to relieve stress concentrated on a bent portion, the occurrence of breakage of the bent portion and disconnection of the wiring pattern 21 is significantly reduced or prevented. The floating electrode 36 may be provided in the layer positioned farther than the wiring pattern 21 when viewed from the slot 10D.

(43) Additionally, the floating electrode 36 is provided at the position not overlapping the wiring pattern 21 when looking at the base body 10 in a plan view. Therefore, the influence of the floating electrode 36 upon the electrical characteristics is small.

(44) The floating electrode 36 may be provided at a position entirely overlapping the position where the slot 10D is formed. With such a structure, when the slot 10D is preferably formed by the laser processing, the floating electrode 36 preferably is used as a stopper for a laser beam, and accuracy in depth of the slot 10D is increased.

(45) Third Preferred Embodiment

(46) FIG. 8 is an exploded perspective view of an inductor bridge 103 according to a third preferred embodiment of the present invention in a manufacturing process. FIG. 9 is a sectional view of the inductor bridge 103 in a state assembled into an electronic device.

(47) As is apparent from FIG. 8, an inductor section 30 including conductor patterns 31, 32 and 33 and via conductors is formed in three 12 to 14 of resin base materials 11 to 15. The inductor section 30 constitutes a coil preferably with a rectangular or substantially rectangular helical shape. A first end of a wiring pattern 21 is connected to one end of the conductor pattern 31.

(48) A base body of the inductor bridge 103 is preferably formed by laminating the above-mentioned plural resin base materials. Line widths of the conductor patterns 31 and 33 provided in layers closer to both surfaces of the base body are smaller than that of the conductor pattern 32 provided in a layer positioned at the inner side of the base body. Therefore, as described later, it is possible to reduce an undesired capacitance that is generated between the conductor patterns provided in the layers closer to the surfaces of the base body and an external conductor.

(49) Connector mounting electrodes 41 and 42 to mount the connectors 51 and 52 are provided on the resin base materials 11 and 15, respectively. The connector mounting electrode 41 is connected to a second terminal of the wiring pattern 21 through the via conductor. The connector mounting electrode 42 is connected to an end portion of a wiring pattern 22 through the via conductor.

(50) When looking at the base body in a plan view, a slot 10D1 is provided at a position intersecting the wiring pattern 21. Moreover, a slot 10D2 is provided at a position intersecting the wiring pattern 22. With such an arrangement, the inductor bridge 103 is able to be used in a state bent at two bending portions.

(51) FIG. 9 is a sectional view illustrating a state where a mounting board 201 and an antenna board 301 are connected to each other by the inductor bridge 103.

(52) The above-mentioned antenna element pattern 91 is provided on the antenna board 301. The second connector 52 of the inductor bridge 103 is connected to an end portion of the antenna element pattern 91 or to a position extended from the relevant end portion. The first connector 51 of the inductor bridge 103 is connected to a connecting portion that is provided on an upper surface of the mounting board 201.

(53) The inductor bridge 103 of this preferred embodiment is applied, for example, to an inductor portion in the circuit illustrated in FIGS. 4A and 4B or illustrated in FIGS. 5A and 5B.

(54) A surface-mounted component 86 is mounted to the mounting board 201.

(55) The conductor pattern 31 as a portion of the inductor section 30 of the inductor bridge 103 is provided at a position opposing to the surface-mounted component 86. Since the line width of the conductor pattern 31 is relatively small as described above, an undesired capacitance generated between the conductor pattern 31 and the surface-mounted component 86 is small.

(56) Furthermore, as denoted by one-dot-chain lines in FIG. 9, the conductor patterns of the inductor section 30 are configured such that their ends are positioned near the slots 10D1 and 10D2 along respective shapes of lateral surfaces of the slots 10D1 and 10D2. More specifically, referring to FIG. 8, the conductor patterns 31, 32 and 33 are gradually shifted in a lengthwise direction of the base body in an obliquely arrayed fashion. Stated in another way, the conductor patterns 31, 32 and 33 are configured such that a coil winding axis of the inductor section 30 is inclined obliquely with respect to the direction perpendicular or substantially perpendicular to the base body. With such a structure, a line length of the conductor patterns 31, 32 and 33 in the inductor section 30 is substantially increased, and the overall size is reduced.

(57) Fourth Preferred Embodiment

(58) FIG. 10 is a sectional view of an inductor bridge 104 according to a fourth preferred embodiment of the present invention in a state assembled into an electronic device, the sectional view illustrating a state where a mounting board 201 and an antenna board 301 are connected to each other by the inductor bridge 104. The inductor bridge 104 preferably has the same structure as that in the third preferred embodiment of the present invention illustrated in FIG. 8.

(59) As illustrated in FIG. 10, the above-mentioned antenna element pattern is provided on the antenna board 301. The second connector 52 of the inductor bridge 104 is connected to an end portion of the antenna element pattern or to a position extended from the relevant end portion. The first connector 51 of the inductor bridge 104 is connected to a connecting portion that is provided on an upper surface of the mounting board 201. The connecting portion on the mounting board 201 is electrically conducted to a ground conductor GND extending in a planar shape.

(60) The inductor bridge 104 is disposed such that the inductor section 30 thereof extends in a direction perpendicular or substantially perpendicular to the mounting board 201. With such an arrangement, a coil winding axis of the inductor section 30 lies parallel or substantially parallel to the ground conductor GND that is formed in the mounting board 201. Therefore, the inductor section 30 is made less susceptible to the influence of the ground conductor GND. In other words, undesired coupling between the inductor section 30 and the ground conductor GND is significantly reduced or prevented, and an eddy current generated in the ground conductor GND is also significantly reduced or prevented.

(61) It is to be noted that the coil winding axis of the inductor section 30 is not always required to be perfectly parallel to the mounting board 201, and that insofar as the coil winding axis is set at least to be not perpendicular to the mounting board 201, the above-mentioned effect is generated at a certain extent depending on an angle of the coil winding axis with respect to the mounting board 201. For the purpose of reducing the eddy current, an angle defined between a plane defined by the inductor section 30 and the mounting board is preferably within a range of about 60 to about 120, for example. More preferably, such an angle is within a range of about 80 to about 100, for example.

(62) Fifth Preferred Embodiment

(63) FIG. 11 is a sectional view of a principal portion of an inductor bridge according to a fifth preferred embodiment of the present invention. While, in the preferred embodiments described above, the slot having an inverted trapezoidal shape in section is preferably provided in the base body 10, the sectional shape of the slot is not limited to the inverted trapezoidal shape. The slot may have a step-shaped configuration as illustrated in FIG. 11.

(64) While the preferred embodiments have been described above in connection with an example in which the base body of the inductor bridge is folded at an angle of about 90, for example, the folded angle may be an acute angle or an obtuse angle. Moreover, while the preferred embodiments have been described above in connection with an example in which the base body of the inductor bridge is bent (folded) at one or two positions, it may be bent (folded) at three or more positions.

(65) While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.