Patent ID: 12262497

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Initially, modes of the present disclosure will be enumerated and described.

A circuit structure of the present disclosure is as follows.

A circuit structure including a first busbar, a second busbar, an insulating member including an insulating portion located between the first busbar and the second busbar, a first wiring board provided on one main surface of the first busbar, one main surface of the second busbar and the insulating portion, and a first electronic component provided on the first wiring board, the electronic component having a first connection terminal electrically connected to the first busbar and bonded to the first wiring board and a second connection terminal electrically connected to the second busbar and bonded to the first wiring board. According to this disclosure, the first connection terminal electrically connected to the first busbar and the second connection terminal electrically connected to the second busbar are both bonded to the first wiring board. Even if the first busbar, the second busbar and the insulating portion therebetween deform due to changes in ambient temperature, the bonding portions of the first connection terminal and the second connection terminal are thereby less likely to be affected by deformation of the first busbar, the second busbar and the insulating portion. Therefore, stress is less likely to occur in the bonding portions of the first connection terminal and the second connection terminal. As a result, the reliability of the bonding portions of the connection terminals of the electronic component can be improved.

The first wiring board may have a first open hole, the circuit structure may include a conductive first raised part protruding from the first busbar into the first open hole, and the first connection terminal may be electrically connected to the first raised part protruding inside the first open hole. In this case, the conductive first raised part protrudes from the first busbar into the first open hole in the first wiring board. The first connection terminal on the first wiring board can thus be easily electrically connected to the first busbar, by electrically connecting the first connection terminal to the first raised part protruding inside the first open hole.

The first raised part may be constituted by part of the first busbar. In this case, electrical resistance between the first connection terminal and the first busbar can be reduced.

The first connection terminal may be bonded to the first raised part. In this case, electrical resistance between the first connection terminal and the first busbar can be reduced.

The first wiring board may have a second open hole, the circuit structure may include a conductive second raised part protruding from the second busbar into the second open hole, the second connection terminal may be electrically connected to the second raised part protruding inside the second open hole. In this case, the conductive second raised part protrudes from the second busbar into the second open hole in the first wiring board. The second connection terminal on the first wiring board can thus be easily electrically connected to the second busbar, by electrically connecting the second connection terminal to the second raised part protruding inside the second open hole.

The first wiring board may have a land to which the second connection terminal is bonded, and a conductive extension region extending from the land and located around the second open hole, and the circuit structure may further include a conductive piece bonded to an end face of the second raised part protruding inside the second open hole and to the extension region. In this case, the conductive piece bonded to the extension region extending from the land to which the second connection terminal is bonded and located around the second open hole and to the end face of the second raised part protruding inside the second open hole is provided. Due to this conductive piece, electrical resistance between the second connection terminal and the second busbar can be reduced. Also, given that transfer of heat generated by the first electronic component to the second busbar is facilitated by the conductive piece, local increases in temperature are less likely to occur.

The circuit structure may include a second wiring board provided on another main surface of the first busbar, another main surface of the second busbar and the insulating portion, and a second electronic component provided on the second wiring board, and the second electronic component may have a third connection terminal electrically connected to the first busbar and bonded to the second wiring board, and a fourth connection terminal electrically connected to the second busbar and bonded to the second wiring board. In this case, the third connection terminal electrically connected to the first busbar and the fourth connection terminal electrically connected to the second busbar are both bonded to the second wiring board. Even if the first busbar, the second busbar and the insulating portion therebetween deform due to changes in ambient temperature, the bonding portions of the third connection terminal and the fourth connection terminal are thereby less likely to be affected by deformation of the first busbar, the second busbar and the insulating portion. Therefore, stress is less likely to occur in the bonding portions of the third connection terminal and the fourth connection terminal. Furthermore, given that the electronic components are located on both main surfaces of the busbars, the plane size of the circuit structure can be reduced.

The circuit structure may further include a heat dissipation member provided on the other main surface of the first busbar while avoiding a region where the second wiring board is provided. In this case, given that the heat dissipation member is provided on the other main surface of the first busbar while avoiding the region where the second wiring board is provided, the thickness of the circuit structure can be suppressed while improving heat dissipation of the circuit structure.

Specific examples of a circuit structure of the present disclosure will be described below with reference to the drawings. Note that the disclosure is not limited to these illustrative examples and is defined by the claims, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Outline of Circuit Structure

FIGS.1and2are schematic perspective views showing an example of a circuit structure1.FIG.2shows the circuit structure1viewed from the opposite side toFIG.1.FIG.3is a schematic diagram showing an example of a state in which a molded resin11has been removed from the circuit structure1shown inFIG.2. Hereafter, for convenience of description, the side shown inFIG.1will be taken as the upper surface side or upper side of the circuit structure1, and the side shown inFIG.2will be taken as the lower surface side or lower side of the circuit structure1.

The circuit structure1is incorporated in an electrical junction box1000(seeFIG.34referred to below), for example. The electrical junction box1000is provided on a power supply path between a battery and various electrical components in an automobile, for example. Application of the electrical junction box1000is not limited thereto.

As shown inFIGS.1to3, the circuit structure1includes an input-side busbar2, an output-side busbar3, a relay busbar4(seeFIGS.6,9, etc. referred to below), and an insulating member5for insulating the input-side busbar2, the output-side busbar3and the relay busbar4from each other. The circuit structure1includes a plurality of electronic components6, a plurality of connectors7, a plurality of conductive pieces8, a wiring board9, a wiring board19, a plurality of heat dissipation members10, and the molded resin11.

The input-side busbar2(simply referred to as the busbar2), the output-side busbar3(simply referred to as the busbar3), and the relay busbar4(simply referred to as the busbar4) are conductive members. The electronic components6are switching elements, for example. The electronic components6are MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), for example. A MOSFET is a type of semiconductor switching element. The electronic components6each include a drain terminal, a source terminal and a gate terminal, for example. The drain terminal, the source terminal and the gate terminal can also be said to be connection terminals. Hereafter, the electronic components6may be referred to as MOSFETs6. The electronic components6may be switching elements other than MOSFETs. Also, the electronic components6may be electronic components other than switching elements.

The plurality of electronic components6include a plurality of electronic components16on the wiring board9and a plurality of electronic components26on the wiring board19. The plurality of electronic components16include a plurality of electronic components16aand a plurality of electronic components16b. The plurality of electronic components26includes a plurality of electronic components26aand a plurality of electronic components26b. Hereafter, the electronic components16,16a,16b,26,26aand26bmay be referred to respectively as MOSFETs16,16a,16b,26,26aand26b.

The drain terminals of the plurality of MOSFETs16aare electrically connected to each other, for example. The drain terminals of the plurality of MOSFETs16bare electrically connected to each other, for example. The source terminals of the plurality of MOSFETs16aare electrically connected to each other, for example. The source terminals of the plurality of MOSFETs16bare electrically connected to each other, for example.

The drain terminals of the plurality of MOSFETs26aare electrically connected to each other, for example. The drain terminals of the plurality of MOSFETs26bare electrically connected to each other, for example. The source terminals of the plurality of MOSFETs26aare electrically connected to each other, for example. The source terminals of the plurality of MOSFETs26bare electrically connected to each other, for example.

The drain terminals of the MOSFETs16aand16bare electrically connected to each other, for example. The drain terminals of the MOSFETs26aand26bare electrically connected to each other, for example. The source terminals of the MOSFETs16a,16b,26aand26bare electrically connected to each other, for example.

The drain terminals of the MOSFETs16aand26aare electrically connected to the input-side busbar2. The drain terminals of the MOSFETs16band26bare electrically connected to the output-side busbar3. The source terminals of the MOSFETs16a,16b,26aand26bare electrically connected to the relay busbar4. In the present example, the circuit structure1includes sixteen MOSFETs6, but the number of MOSFETs6included in the circuit structure1is not limited thereto.

The input-side busbar2is a metal member, and includes a main body part20and an input terminal part21protruding from the main body part20, for example. The input terminal part21has an open hole21athat passes through in the thickness direction thereof. A wiring member extending from the battery is connected to the input terminal part21by utilizing the open hole21a, for example. The output voltage of the battery is applied to the input terminal part21through the wiring member. The output voltage of the battery applied to the input terminal part21is applied to the drain terminals of the MOSFETs16aand26athrough the main body part20.

The output-side busbar3is a metal member, and includes a main body part30and an output terminal part31protruding from the main body part30. The output terminal part31has an open hole31athat passes through in the thickness direction thereof. A wiring member extending from an electrical component is connected to the output terminal part31by utilizing the open hole31a, for example. The voltage that is output by the drain terminals of the MOSFETs16band26bis applied to the output terminal part31. The voltage applied to the output terminal part31is applied as a power supply to the electrical component through the wiring member, for example.

The relay busbar4is a metal member. The relay busbar4is located between the main body part20of the busbar2and the main body part30of the busbar3. The relay busbar4can be said to be sandwiched between the main body part20and the main body part30.

The plurality of heat dissipation members10are each a plate-like metal member, for example. The plurality of heat dissipation members10include a heat dissipation member10aon the busbar2and a heat dissipation member10bon the busbar3. The heat dissipation member10ais provided on the lower main surface of the busbar2. The heat dissipation member10bis provided on the lower main surface of the busbar3. Heat generated by the MOSFETs16aand26athat is transferred through the busbar2is dissipated externally by the heat dissipation member10a. Heat generated by the MOSFETs16band26bthat is transferred through the busbar3is dissipated externally by the heat dissipation member10b.

The insulating member5holds the busbars2,3and4and the plurality of heat dissipation members10while electrically insulating the busbars2,3and4from each other. The insulating member5is molded as one piece with the busbars2,3and4and the plurality of heat dissipation members10, for example. The insulating member5is molded as one piece with the busbars2,3and4and the plurality of heat dissipation members10by insert molding, for example.

The wiring board9is a plate-like member that is long in one direction, for example. The wiring board9is provided on the upper main surfaces of the busbars2,3and4. The wiring board9is a rigid board, for example. The wiring board9may be a sheet-like flexible board or a composite board integrating a rigid board and a flexible board. The wiring board9has a conductive layer. The gate terminal of each MOSFET16is electrically connected to the conductive layer of the wiring board9.

The wiring board19is a plate-like member that is long in one direction, for example. The wiring board19is provided on the lower main surfaces of the busbars2,3and4. The wiring board19is a rigid board, for example. The wiring board19may be a sheet-like flexible board or a composite board integrating a rigid board and a flexible board. The wiring board19has a conductive layer. The gate terminal of each MOSFET26is electrically connected to the conductive layer of the wiring board19.

The plurality of connectors7each include a plurality of connection terminals70. Each connection terminal70is constituted by a metal, for example. The plurality of connectors7include connectors7aand7b. The connector7ais provided on the upper main surface of the wiring board9. The gate terminals of the plurality of MOSFETs16are electrically connected to the plurality of connection terminals70included in the connector7athrough the conductive layer of the wiring board9. Switching control of the MOSFETs16is performed externally through the connector7a.

The connector7bis provided on the upper main surface of the wiring board19. An opening is provided in the relay busbar4and the wiring board9. The connector7bis provided on a portion of the wiring board19that is exposed through this opening. The gate terminals of the plurality of MOSFETs26are electrically connected to the plurality of connection terminals70included in the connector7bthrough the conductive layer of the wiring board19. Switching control of the MOSFETs26is performed externally through the connector7b.

The plurality of conductive pieces8include a plurality of conductive pieces18on the wiring board9and a plurality of conductive pieces28on the wiring board19. The plurality of conductive pieces18respectively correspond to the plurality of MOSFETs16a. Each conductive piece18is a member for reducing electrical resistance between the source terminal of the MOSFET16acorresponding thereto and the busbar4. The plurality of conductive pieces18also respectively correspond to the plurality of MOSFETs16b. Each conductive piece18is also a member for reducing electrical resistance between the source terminal of the MOSFET16bcorresponding thereto and the busbar4.

The plurality of conductive pieces28respectively correspond to the plurality of MOSFETs26a. Each conductive piece28is a member for reducing electrical resistance between the source terminal of the MOSFET26acorresponding thereto and the busbar4. The plurality of conductive pieces28also respectively correspond to the plurality of MOSFETs26b. Each conductive piece28is also a member for reducing electrical resistance between the source terminal of the MOSFET26bcorresponding thereto and the busbar4.

The molded resin11covers the wiring board19and the plurality of MOSFETs26and the plurality of conductive pieces28on the wiring board19. The inside of the circuit structure1is thereby protected.

Detailed Description of Circuit Structure

FIG.4is a schematic top view showing an example of the circuit structure1.FIG.5is an enlarged schematic top view showing part of the circuit structure1shown inFIG.4.FIG.6is a schematic diagram showing an example of the cross-sectional structure taken along a line indicated by arrows A-A inFIGS.4and5.FIG.7is a schematic bottom view showing an example of the circuit structure1with the molded resin11removed.FIG.8is an enlarged schematic bottom view showing part of the structure shown inFIG.7.FIG.9is a schematic perspective view from the upper surface side showing an example of a state in which the wiring board9is separated from a structure obtained by removing the plurality of MOSFETs16, the plurality of connectors7and the plurality of conductive pieces18from the circuit structure1.FIG.10is a schematic perspective view showing an example of a state in which the busbars2,3and4and the insulating member5are viewed from the upper surface side.FIG.11is a schematic top view showing an example of the busbars2,3and4and the insulating member5.FIG.12is a schematic perspective view from the lower surface side showing an example of a state in which the wiring board19is separated from a structure obtained by removing the molded resin11, the plurality of MOSFETs26and the plurality of conductive pieces28from the circuit structure1.FIG.13is a schematic perspective view showing an example of a state in which the busbar2,3and4, the insulating member5and the plurality of heat dissipation members10are viewed from the lower surface side.FIG.14is a schematic bottom view showing an example of the busbars2,3and4, the insulating member5, and the plurality of heat dissipation members10.

Example Configuration of Busbars

The input-side busbar2is constituted by copper, for example. The busbar2may be constituted by oxygen-free copper, for example. Oxygen-free copper C1020 specified in Japanese Industrial Standards (JIS), for example, is employed as this oxygen-free copper. The coefficient of linear expansion of the busbar2constituted by oxygen-free copper is 17 ppm/° C., for example. The coefficient of linear expansion may also be referred to as the coefficient of thermal expansion. The busbar2may also be constituted by a metal other than copper.

As shown inFIGS.10,11,13,14and other diagrams, the busbar2is a plate-like metal member that is long in one direction, for example. The main body part20of the busbar2is a rectangular plate-like portion, for example. The input terminal part21of the busbar2protrudes from one end of the main body part20in the long direction thereof.

The busbar2has a main surface200and a main surface210on the opposite side to the main surface200. The main surface200is located on the upper side and the main surface210is located on the lower side. Hereafter, the main surface200may be referred to as the upper main surface200, and the main surface210may be referred to as the lower main surface210.

As shown inFIGS.10,11and other diagrams, the upper main surface200has a region201that is one step lower than other regions thereof. This region201is a board mounting region201on which the wiring board9is mounted. The board mounting region201is provided in the main body part20, for example.

The board mounting region201is provided with a plurality of conductive raised parts202. The plurality of raised parts202are constituted by part of the busbar2, for example. The raised parts202can be said to be molded as one piece with the busbar2. In the present example, the raised parts202are part of the busbar2, and are thus constituted by copper, for example. The plurality of raised parts202are aligned in the long direction of the busbar2.

The raised parts202have a disk shape, for example. When the wiring board9is mounted on the board mounting region201, the plurality of raised parts202are respectively inserted into a plurality of open holes92adescribed later provided in the wiring board9. The circular end faces of the raised parts202lie in the same plane as regions of the upper main surface200other than the board mounting region201, for example. The role of the raised parts202will be described in detail later.

As shown inFIGS.13,14and other diagrams, the lower main surface210has a region211that is one step lower than other regions thereof. This region211is a board mounting region211on which the wiring board19is mounted. The board mounting region211is provided in the main body part20, for example.

The board mounting region211is provided with a plurality of conductive raised parts212. The plurality of raised parts212are constituted by part of the busbar2, for example. In the present example, the raised parts212are part of the busbar2, and are thus constituted by copper, for example. The plurality of raised parts212are aligned in the long direction of the busbar2.

The raised parts212have a disk shape, for example. When the wiring board19is mounted on the board mounting region211, the plurality of raised parts212are respectively inserted into a plurality of open holes92bdescribed later provided in the wiring board19. The circular end faces of the raised parts212lie in the same plane as regions of the lower main surface210other than the board mounting region211, for example. The role of the raised parts212will be described in detail later.

The output-side busbar3is constituted by copper, for example. The busbar3may be constituted by oxygen-free copper, for example. Oxygen-free copper C1020 specified in JIS, for example, is employed as this oxygen-free copper. The busbar3may also be constituted by a metal other than copper.

As shown inFIGS.10,11,13,14and other diagrams, the busbar3is a plate-like metal member that is long in one direction, for example. The main body part30of the busbar3is a rectangular plate-like portion, for example. The output terminal part31of the busbar3protrudes from one end of the main body part30in the long direction thereof.

The busbar3has a main surface300and a main surface310on the opposite side to the main surface300. The main surface300is located on the upper side and the main surface310is located on the lower side. Hereafter, the main surface300may be referred to as the upper main surface300, and the main surface310may be referred to as the lower main surface310.

As shown inFIGS.10,11and other diagrams, the upper main surface300has a region301that is one step lower than other regions thereof. This region301is a board mounting region301on which the wiring board9is mounted. The board mounting region301is provided in the main body part30, for example.

The board mounting region301is provided with a plurality of conductive raised parts302. The plurality of raised parts302are constituted by part of the busbar3, for example. In the present example, the raised parts302are part of the busbar3, and are thus constituted by copper, for example. The plurality of raised parts302are aligned in the long direction of the busbar3.

The raised parts302have a disk shape, for example. When the wiring board9is mounted on the board mounting region301, the plurality of raised parts302are respectively inserted into a plurality of open holes92bprovided in the wiring board9. The end faces of the raised parts302lie in the same plane as regions of the upper main surface300other than the board mounting region301, for example. The role of the raised parts302will be described in detail later.

As shown inFIGS.13,14and other diagrams, the lower main surface310has a region311that is one step lower than the other regions thereof. This region311is a board mounting region311on which the wiring board19is mounted. The board mounting region311is provided in the main body part30, for example.

The board mounting region311is provided with a plurality of conductive raised parts312. The plurality of raised parts312are constituted by part of the busbar3, for example. In the present example, the raised parts312are part of the busbar3, and are thus constituted by copper, for example. The plurality of raised parts312are aligned in the long direction of the busbar3.

The raised parts312have a disk shape, for example. When the wiring board19is mounted on the board mounting region311, the plurality of raised parts312are respectively inserted into a plurality of open holes92adescribed later provided in the wiring board19. The end faces of the raised parts312lie in the same plane as regions of the lower main surface310other than the board mounting region311, for example. The role of the raised parts312will be described in detail later.

The relay busbar4is constituted by copper, for example. The busbar4may be constituted by oxygen-free copper, for example. Oxygen-free copper C1020 specified in JIS, for example, is employed as this oxygen-free copper. The busbar4may also be constituted by a metal other than copper.

As shown inFIGS.10,11,13,14and other diagrams, the busbar4is a rectangular plate-like metal member, for example. The busbars2,3and4lie in the same plane, for example. The busbars2and3are disposed opposite each other with a gap therebetween such that the long directions thereof are parallel to each other. The busbar4is located between the busbars2and3such that the long direction thereof is parallel to the long directions of the busbars2and3. The busbar4is located between the main body part20of the busbar2and the main body part30of the busbar3.

The busbar4has a main surface400and a main surface410on the opposite side to the main surface400. The main surface400is located on the upper side and the main surface410is located on the lower side. The wiring board9is mounted on the main surface400, and the wiring board19is mounted on the main surface410. Hereafter, the main surface400may be referred to as the upper main surface400, and the main surface410may be referred to as the lower main surface410.

As shown inFIGS.10,11and other diagrams, the upper main surface400is provided with a plurality of conductive raised parts402. The plurality of raised parts402are constituted by part of the busbar4, for example. In the present example, the raised parts402are part of the busbar4, and are thus constituted by copper, for example. The plurality of raised parts402are aligned in the long direction of the busbar4. The plurality of raised parts402are located between the plurality of raised parts202of the busbar2and the plurality of raised parts302of the busbar3.

The raised parts402have a disk shape, for example. When the wiring board9is mounted on the upper main surface400, the plurality of raised parts402are respectively inserted into a plurality of open holes92cdescribed later provided in the wiring board9. The end faces of the raised parts402lie in the same plane as the end faces of the raised parts202of the busbar2and the end faces of the raised parts302of the busbar3, for example.

Regions of the upper main surface400of the busbar4where the raised parts402are not provided lie in the same plane as regions of the board mounting region201of the busbar2where the raised parts202are not provided, for example. Also, regions of the upper main surface400of the busbar4where the raised parts402are not provided lie in the same plane as regions of the board mounting region301of the busbar3where the raised parts302are not provided, for example. The role of the raised parts402will be described in detail later.

As shown inFIGS.13,14and other diagrams, the lower main surface410is provided with a plurality of conductive raised parts412. The plurality of raised parts412are constituted by part of the busbar4, for example. In the present example, the raised parts412are part of the busbar4, and are thus constituted by copper, for example. The plurality of raised parts412are aligned in the long direction of the busbar4. The plurality of raised parts412are located between the plurality of raised parts212of the busbar2and the plurality of raised parts312of the busbar3.

The raised parts412have a disk shape, for example. When the wiring board19is mounted on the lower main surface410, the plurality of raised parts412are respectively inserted into a plurality of open holes92cdescribed later provided in the wiring board19. The end faces of the raised parts412lie in the same plane as the end faces of the raised parts212of the busbar2and the end faces of the raised parts312of the busbar3, for example.

Regions of the lower main surface410of the busbar4where the raised parts412are not provided lie in the same plane as regions of the board mounting region211of the busbar2where the raised parts212are not provided, for example. Also, regions of the lower main surface410of the busbar4where the raised parts412are not provided lie in the same plane as regions of the board mounting region311of the busbar3where the raised parts312are not provided, for example. The role of the raised parts412will be described in detail later.

An opening420is provided in one end of the busbar4in the long direction thereof. The opening420passes through the busbar4in the thickness direction of the busbar4. The connector7bis disposed in this opening420as described later.

The thickness of the thickest portion in the busbar2is set to 3 mm, for example. Also, the thickness of the thickest portion in the busbar3is set to 3 mm, for example. Also, the thickness of the thickest portion in the busbar4is set to 3 mm, for example. The thicknesses of busbars2,3and4are not limited thereto.

Example Configuration of Heat Dissipation Members

The heat dissipation members10are constituted by aluminum, for example. The plate-like heat dissipation members10can also be said to be heat sinks. The heat dissipation members10may be constituted by pure aluminum. Pure aluminum A1050 specified in JIS, for example, is employed as this pure aluminum. The heat dissipation members10may be constituted by a metal other than aluminum. The thickness of the heat dissipation members10is set to 1.5 mm, for example. The thickness of the heat dissipation members10is not limited thereto.

As shown inFIGS.6,12,13and other diagrams, the heat dissipation member10ais provided on the lower main surface210of the busbar2. The heat dissipation member10ais provided on the lower main surface of the main body part20of the busbar2, for example. The heat dissipation member10ais provided on a region of the lower main surface of the main body part20other than the board mounting region211, for example. The heat dissipation member10ais diffusion-bonded to the busbar2using pressure treatment and heat treatment, for example. The main surface of the heat dissipation member10aon the opposite side to the main surface bonded to the busbar2(in other words, the exposed main surface) is anodized, for example. Electrical insulation between the heat dissipation member10aand members other than the circuit structure1can thereby be enhanced.

The heat dissipation member10bis provided on the lower main surface310of the busbar3. The heat dissipation member10bis provided on the lower main surface of the main body part30of the busbar3, for example. The heat dissipation member10bis provided on a region of the lower main surface of the main body part30other than the board mounting region311, for example. The heat dissipation member10bis diffusion-bonded to the busbar3using pressure treatment and heat treatment, for example. The main surface of the heat dissipation member10bon the opposite side to the main surface bonded to the busbar3(in other words, the exposed main surface) is anodized, for example. Electrical insulation between the heat dissipation member10band members other than the circuit structure1can thereby be enhanced.

Example Configuration of Insulating Member

The insulating member5is constituted by an insulating resin, for example. The insulating member5is constituted by PPS (Polyphenylene Sulfide), for example. The insulating member5is molded as one piece with the busbars2,3and4and the plurality of heat dissipation members10, for example. The coefficient of linear expansion of the insulating member5constituted by PPS is 40 ppm/° C., for example.

As shown inFIGS.11,14and other diagrams, the insulating member5includes a frame-like insulating portion50and straight insulating portions51and52that are joined to the insulating portion50. The frame-like insulating portion50is attached to the main body part20of the busbar2, the heat dissipation member10aon the main body part20, the busbar4, the main body part30of the busbar3and the heat dissipation member10bon the main body part30, so as to surround the main body part20, the heat dissipation member10a, the busbar4, the main body part30and the heat dissipation member10b. The insulating portion51is located between the main body part20and the busbar4. The busbars2and4are electrically insulated from each other by the insulating portion51. The insulating portion52is located between the main body part30and the busbar4. The busbars3and4are electrically insulated from each other by the insulating portion52.

As shown inFIG.11and other diagrams, the board mounting region201on the upper side of the busbar2and the upper main surface400of the busbar4are adjacent to each other via the insulating portion51. The board mounting region301on the upper side of the busbar3and the upper main surface400of the busbar4are adjacent to each other via the insulating portion52.

As shown inFIG.14and other diagrams, the board mounting region211on the lower side of the busbar2and the lower main surface410of the busbar4are adjacent to each other via the insulating portion51. The board mounting region311on the lower side of the busbar3and the lower main surface410of the busbar4are adjacent to each other via the insulating portion52.

Example Configuration of MOSFET

FIG.15is a schematic back view showing an example of the MOSFET6. Here, for convenience of description, the configuration of the MOSFET6will be described with the right side and the left side inFIG.15respectively being the right side and the left side of the MOSFET6, and the up-down direction inFIG.15being the up-down direction of the MOSFET6.

The MOSFET6is a surface mount component, for example. As shown inFIG.15, the MOSFET6includes a package60in which a semiconductor device and the like are housed. The package60is a leadless package, for example. The package60includes a main body part65, a gate terminal61, a plurality of source terminals62and a drain terminal63. The gate terminal61, the plurality of source terminals62and the drain terminal63are provided on the back surface of the main body part65.

The main body part65is constituted by a resin such as epoxy resin, for example. The plurality of source terminals62are electrically connected to each other inside the main body part65. The gate terminal61, the source terminals62and the drain terminal63are constituted by a metal, for example. The gate terminal61, the source terminals62and the drain terminal63may be constituted by oxygen-free copper, for example. Oxygen-free copper C1020 specified in JIS, for example, is employed as this oxygen-free copper. The gate terminal61, the source terminals62and the drain terminal63may also be constituted by a copper alloy. The gate terminal61, the source terminals62and the drain terminal63have a flat plate-like shape, for example.

On the right edge portion of the back surface of the main body part65, the gate terminal61and the plurality of source terminals62are aligned in a row in the up-down direction. The gate terminal61and the plurality of source terminals62protrude slightly outward from the right edge of the back surface of the main body part65. The left edge of the drain terminal63is uneven, and a plurality of protruding parts63aaligned in the up-down direction are provided on the left edge. The plurality of protruding parts63aprotrude slightly outward from the left edge of the back surface of the main body part65.

Note that the shape of the package60is not limited to the above example. The shape of the drain terminal63may, for example, be other than the shape inFIG.15. Also, the number of source terminals62that are included in the package60may be other than three. Also, the package60may be a leaded package.

Example Configuration of Wiring Boards

FIG.16is a schematic perspective view showing an example of the wiring board9. As shown inFIGS.9,16and other diagrams, the wiring board9includes an insulating board90and the insulating board90is provided with a conductive layer95, for example. The insulating board90may be a ceramic board or a board containing a resin, for example. In the latter case, the insulating board90may be a glass epoxy board or another board containing a resin. The thickness of the insulating board90may be set from 0.4 mm to 0.6 mm inclusive, for example. The conductive layer95may be constituted by copper or may be constituted by another metal. The conductive layer95is provided on one main surface of the insulating board90, for example. The wiring board9has the conductive layer95on one main surface thereof. Hereinafter, for convenience of description, the main surface on the conductive layer95side of the wiring board9and insulating board90will be referred to as the front main surface, and the main surface on the opposite side will be referred to as the back main surface.

The wiring board9may be a single-layer board or a multilayer board. The wiring board9may have a conductive layer not only on the front main surface but also on the back main surface, and may have a conductive layer as an inner layer. Note that, inFIG.6, illustration of the conductive layer95is omitted.

The wiring board9includes a first portion9aon which the MOSFETs6and the conductive pieces8are installed, and a second portion9band a third portion9cthat protrude from the first portion9a. The outer shape of the first portion9ais substantially rectangular, for example. The outer shapes of the second portion9band the third portion9care substantially square, for example. The second portion9bprotrudes from one end of the first portion9ain the long direction thereof. The third portion9cprotrudes from the other end of the first portion9ain the long direction thereof.

The first portion9aincludes a plurality of open holes92that pass through in the thickness direction thereof. The plurality of open holes92include a plurality of open holes92aprovided in one edge portion of the first portion9ain the short direction thereof, so as to be aligned in the long direction of the wiring board9. Also, the plurality of open holes92include a plurality of open holes92bprovided in the other edge portion of the first portion9ain the short direction thereof, so as to be aligned in the long direction of the wiring board9. Furthermore, the plurality of open holes92include a plurality of open holes92cprovided in the middle portion of the first portion9ain the short direction thereof, so as to be aligned in the long direction of the wiring board9. The plurality of open holes92care located between the plurality of open holes92aand the plurality of open holes92b.

The conductive layer95of the wiring board9includes a plurality of conductive regions96, as shown inFIGS.9,16and other diagrams. The plurality of conductive regions96respectively correspond to the plurality of MOSFETs16. Furthermore, the conductive layer95includes a plurality of extension regions98and a conductive region99. The conductive region99corresponds to the connector7a.

Each conductive region96has a land960to which the gate terminal61of the MOSFET16corresponding thereto is bonded. Each conductive region96has a plurality of lands961to which the plurality of source terminals62of the MOSFET16corresponding thereto are respectively bonded. Each conductive region96has a land962to which the drain terminal63of the MOSFET16corresponding thereto is bonded. Each land962has a plurality of protruding parts962ato which the plurality of the protruding parts63aof the drain terminal63are respectively bonded. Lands to which a terminal or the like is bonded are also referred to as pads.

The plurality of conductive regions96include a plurality of conductive regions96aand a plurality of conductive regions96b. The plurality of conductive regions96arespectively correspond to the plurality of MOSFETs16a. The plurality of conductive regions96brespectively correspond to the plurality of MOSFETs16b.

In the present example, the MOSFETs16aand the MOSFETs16bare disposed so as to oppose each other one-to-one. One MOSFET16aand one MOSFET16bdisposed opposing each other constitute a first FET pair. The circuit structure1includes a plurality of first FET pairs on the upper side.

The plurality of extension regions98respectively correspond to the plurality of first FET pairs. The extension regions98are regions extending from the plurality of lands961to which the plurality of source terminals62of the MOSFET16aincluded in the first FET pair corresponding thereto are bonded. The extension regions98are also regions extending from the plurality of lands961to which the plurality of source terminals62of the MOSFET16bincluded in the first FET pair corresponding thereto are bonded. The plurality of lands961to which the plurality of source terminals62of the MOSFET16aincluded in each first FET pair are bonded are connected to the plurality of lands961to which the plurality of source terminals62of the MOSFET16bincluded in that first FET pair are bonded, by the extension region98corresponding to that first FET pair. The lands961can also be said to be protruding parts protruding from the extension regions98.

The plurality of conductive regions96arespectively correspond to the plurality of open holes92a. Also, the plurality of conductive regions96brespectively correspond to the plurality of open holes92b. The land962of each conductive region96ais located around the open hole92acorresponding to that conductive region96a. The land962of each conductive region96bis located around the open hole92bcorresponding to that conductive region96b. The lands962are provided so as to surround the opening edges of the open holes92(specifically, the opening edges on the main surface on the conductive layer95side of the wiring board9). The open holes92can also be said to be provided in the lands962.

The plurality of extension regions98respectively correspond to the plurality of open holes92c. Each extension region98is located around the open hole92ccorresponding thereto. The extension regions98are provided so as to surround the opening edges of the open holes92c(specifically, the opening edges on the main surface on the conductive layer95side of the wiring board9). The open holes92ccan also be said to be provided in the extension regions98.

In the present example, the open holes92are through holes in which a conductive region is formed on the inner circumferential surface thereof, for example. The conductive region on the inner circumferential surface of the open holes92is constituted by a metal, for example. The conductive region on the inner circumferential surface of the open holes92may be constituted by the same material as the conductive layer95or may be constituted by a different material. The conductive region on the inner circumferential surface of each open hole92ais joined to the land962around that open hole92a. The conductive region on the inner peripheral surface of each open hole92bis joined to the land962around that open hole92b. The conductive region on the inner peripheral surface of each open hole92cis connected to the extension region98around that open hole92c. Note that a conductive region may not be formed on the inner circumferential surface of the open holes92.

The conductive region99corresponding to the connector7aincludes a plurality of lands990to which the plurality of connection terminals70included in the connector7aare respectively bonded. The plurality of connection terminals70of the connector7aare bonded to the plurality of lands990by solder, for example. The main component of the solder is tin.

The conductive layer95includes a plurality of first wires respectively electrically connected to the gate terminals61of the plurality of MOSFETs16. The plurality of first wirings are respectively joined at one end to the plurality of lands960to which the gate terminals61of the plurality of MOSFETs16are bonded. The plurality of first wirings are respectively joined at the other end to the plurality of lands990to which the plurality of connection terminals70of the connector7aare bonded. The gate terminals61are electrically connected to the connection terminals70of the connector7athrough the first wirings.

FIG.17is a schematic perspective view showing an example of the wiring board19. The wiring board19has a substantially similar structure to the wiring board9. As shown inFIGS.12,17and other diagrams, the wiring board19has an insulating board90and a conductive layer95, similarly to the wiring board9. Also, the wiring board19includes a first portion19aon which the MOSFETs6and the conductive pieces8are installed, and a second portion19band a third portion19cthat protrude from the first portion19a. The first portion19ahas a similar structure to the first portion9aof the wiring board9. The first portion19ahas a plurality of open holes92, a plurality of conductive regions96, and a plurality of extension regions98. Hereafter, for convenience of description, the main surface on the conductive region96side of the wiring board19will be referred to as the front side main surface, and the main surface on the opposite side will be referred to as the back main surface.

The outer shapes of the second portion19band the third portion19care substantially square, for example. The second portion19bprotrudes from one end of the first portion9ain the long direction thereof. The third portion19cprotrudes from the other end of the first portion9ain the long direction thereof. Unlike the second portion9b, the second portion19bis not provided with a conductive region. A conductive region93corresponding to the connector7bis provided in the third portion19c, on the main surface on the back main surface side of the wiring board19(seeFIG.9, etc.).

In the wiring board19, the plurality of conductive regions96respectively correspond to the plurality of MOSFETs26. The plurality of conductive regions96arespectively correspond to the plurality of MOSFETs26b, and the plurality of conductive regions96brespectively correspond to the plurality of MOSFETs26a. The gate terminal61of the MOSFET26to which each conductive region96corresponds is bonded to the land960of that conductive region96. The plurality of source terminals62of the MOSFET26corresponding to each conductive region96are respectively bonded to the plurality of lands961of that conductive region96. The drain terminal63of the MOSFET26corresponding to each conductive region96is bonded to the land962of that conductive region96.

In the present example, as shown inFIG.3and other diagrams, the MOSFETs26aand the MOSFETs26bare disposed so as to oppose each other one-to-one. One MOSFET26aand one MOSFET26bdisposed opposing each other constitute a second FET pair. The circuit structure1includes a plurality of second FET pairs on the lower side.

The plurality of extension regions98of the wiring board19respectively correspond to the plurality of second FET pairs. Each extension region98is a region extending from the plurality of lands961to which the plurality of source terminals62of the MOSFET26aincluded in the second FET pair corresponding thereto are bonded. Also, each extension region98is a region extending from the plurality of lands961to which the plurality of source terminals62of the MOSFET26bincluded in the second FET pair corresponding thereto are bonded. The plurality of lands961to which the plurality of source terminals62of the MOSFET26aincluded in each second FET pair are bonded are connected to the plurality of lands961to which the plurality of source terminals62of the MOSFET26bincluded in that second FET pair are bonded, by the extension region98corresponding to that second FET pair.

The conductive region93provided in the third portion19chas a similar shape to the conductive region99corresponding to the connector7a. The conductive region93includes a plurality of lands930to which the plurality of connection terminals70included in the connector7bare respectively bonded. The plurality of connection terminals70of the connector7bare bonded to the plurality of lands930by solder, for example.

The conductive layer95of the wiring board19has a plurality of second wirings that are respectively electrically connected to the gate terminals61of the plurality of MOSFETs26, instead of the plurality of first wirings. The plurality of second wirings are respectively joined at one end to the plurality of lands960to which the gate terminals61of the plurality of MOSFETs26are bonded. The plurality of second wirings are respectively joined at the other end to the plurality of lands930to which the plurality of connection terminals70of the connector7bare bonded. The gate terminals61of the MOSFETs26are electrically connected to the connection terminals70of the connector7bthrough the second wirings.

The wiring board9having a configuration such as the above is mounted on the board mounting region201of the busbar2, the insulating portion51between the busbar2and the busbar4, the upper main surface400of the busbar4, the insulating portion52between the busbar4and the busbar3, and the board mounting region301of the busbar3. Hereafter, the board mounting region201, the insulating portion51, the upper main surface400of the busbar4, the insulating portion52and the board mounting region301on which the wiring board9is mounted may be collectively referred to as the upper board mounting region. Also, the raised parts202on the board mounting region201, the raised parts302on the board mounting region301, and the raised parts402on the upper main surface400of the busbar4may respectively be referred to as upper raised parts.

The wiring board19is mounted on the board mounting region211of the busbar2, the insulating portion51between the busbar2and the busbar4, the lower main surface410of the busbar4, the insulating portion52between the busbar4and the busbar3, and the board mounting region311of the busbar3. Hereafter, the board mounting region211, the insulating portion51, the lower main surface410of the busbar4, the insulating portion52and the board mounting region311on which the wiring board19is mounted may be collectively referred to as the lower board mounting region. Also, the raised parts212on the board mounting region211, the raised parts312on the board mounting region311, and the raised parts412on the lower main surface410of the busbar4may respectively be referred to as lower raised parts.

FIG.18is a diagram illustrating an example of a state in which the wiring board9is mounted on the upper board mounting region.FIG.19is a diagram illustrating an example of a state in which the wiring board19is mounted on the lower board mounting region.

As shown inFIG.18and other diagrams, the wiring board9is provided on the upper board mounting region, such that the back main surface thereof opposes the upper board mounting region. The wiring board9is fixed to the upper board mounting region, using a bonding material12a(seeFIG.6), for example. The bonding material12amay be an adhesive sheet or may be another member.

When the wiring board9is mounted on the upper board mounting region, the plurality of upper raised parts are respectively inserted into the plurality of open holes92in the wiring board9. Specifically, the plurality of raised parts202of the busbar2are respectively inserted into the plurality of open holes92ain the wiring board9. Also, the plurality of raised parts302of the busbar3are respectively inserted into the plurality of open holes92bin the wiring board9. Also, the plurality of raised parts402of the busbar4are respectively inserted into the plurality of open holes92cin the wiring board9.

In the state where the wiring board9is mounted on the upper board mounting region, the raised parts202protrude inside the open holes92afrom the busbar2, the raised parts302protrude inside the open holes92bfrom the busbar3, and the raised parts402protrude inside the open holes92cfrom the busbar4. The diameter of the upper raised parts is set slightly smaller than the diameter of the open holes92. The upper raised parts can also be said to fit into the open holes92.

The front main surface of the insulating board90of the wiring board9mounted on the upper board mounting region is flush with regions of the upper main surface200of the busbar2other than the board mounting region201and regions of the upper main surface300of the busbar3other than the board mounting region301. Note that the surface of the conductive layer95on the insulating board90may lie in the same plane as regions of the upper main surface200of the busbar2other than the board mounting region201and regions of the upper main surface300of the busbar3other than the board mounting region301.

The circular end faces of the upper raised parts inside the open holes92lie in the same plane as the flat surface of the conductive layer95on the insulating board90, for example. Accordingly, the end faces of the raised parts202protruding inside the open holes92aare flush with the surfaces of the conductive regions96aaround the open holes92a. Also, the end faces of the raised parts302protruding inside the open holes92bare flush with the surfaces of the conductive regions96baround the open holes92b. Furthermore, the end faces of the raised parts402protruding inside the open holes92care flush with the surfaces of the extension regions98around the open holes92c. Note that the end faces of the upper raised parts may lie in the same plane as the front main surface of the insulating board90.

Also, the wiring board9is provided on the upper board mounting region, such that an opening91provided in the third portion9copposes the opening420provided in the end portion of the busbar4. The opening91and the opening420thereby communicate to constitute a single opening.

As shown inFIG.19and other diagrams, the wiring board19is provided on the lower board mounting region, such that the back main surface thereof opposes the lower board mounting region. The wiring board19is fixed to the lower board mounting region, using a bonding material12b(seeFIG.6), for example. The bonding material12bmay be an adhesive sheet or may be another member.

When the wiring board19is mounted on the lower board mounting region, the plurality of lower raised parts are respectively inserted into the plurality of open holes92in the wiring board19. Specifically, the plurality of raised parts212of the busbar2are respectively inserted into the plurality of open holes92bin the wiring board19. Also, the plurality of raised parts312of the busbar3are respectively inserted into the plurality of open holes92ain the wiring board19. Furthermore, the plurality of raised parts412of the busbar4are respectively inserted into the plurality of open holes92cin the wiring board19. The diameter of the lower raised parts is set slightly smaller than the diameter of the open holes92.

The front main surface of the insulating board90of the wiring board19mounted on the lower board mounting region is flush with regions of the lower main surface210of the busbar2other than the board mounting region211and regions of the lower main surface310of the busbar3other than the board mounting region311. Note that the surface of the conductive layer95of the wiring board19may lie in the same plane as regions of the lower main surface210of the busbar2other than the board mounting region211and regions of the lower main surface310of the busbar3other than the board mounting region311.

The end faces of the lower raised parts protruding inside the open holes92lie in the same plane as the surface of the conductive layer95, for example. Accordingly, the end faces of the raised parts212protruding inside the open holes92bare flush with the surfaces of the conductive regions96baround the open holes92b. Also, the end faces of the raised parts312protruding inside the open holes92aare flush with the surfaces of the conductive regions96aaround the open holes92a. Furthermore, the end faces of the raised parts412protruding inside the open holes92care flush with the surfaces of the extension regions98around the open holes92c. Note that the end faces of the lower raised parts may lie in the same plane as the front main surface of the insulating board90.

The front main surface of the wiring board19mounted on the lower board mounting region is slightly lower than the exposed main surfaces of the heat dissipation members10aand10b. On the surface on the wiring board19side of the structure shown inFIG.19, a depression surrounded by the frame-like insulating portion50of the insulating member5and the heat dissipation members10aand10bis formed. The plurality of MOSFETs26and the plurality of conductive pieces28are disposed in this depression.

Also, the wiring board19is provided on the lower board mounting region, such that the conductive region93provided in the third portion19copposes the opening420in the busbar4. As a result, when the busbars2,3and4and the insulating member5on which the wiring boards9and19are installed are viewed from the wiring board9side, the conductive region93of the wiring board19is exposed through the openings91and420, as shown inFIGS.9,18and other diagrams.

Regarding Conductive Pieces

As shown inFIGS.1,4,5,6and other diagrams, the plurality of conductive pieces18on the wiring board9are respectively bonded to the plurality of raised parts402that are exposed through the front main surface of the wiring board9. Also, the plurality of conductive pieces18are respectively bonded to the plurality of extension regions98of the wiring board9. The conductive pieces18are provided on the wiring board9so as to cover the end faces of the raised parts402protruding inside the open holes92cin the wiring board9and a peripheral portion of the open holes92c. The conductive pieces18cover the opening edges of the open holes92c(specifically, the opening edges on the front main surface side of the wiring board9). The thickness of the conductive pieces18may be set from 0.2 mm to 0.5 mm inclusive, for example.

The conductive pieces18are bonded by a conductive bonding material101to the end faces of the raised parts402protruding inside the open holes92cand to the extension regions98around the open holes92c(seeFIG.6). Solder, for example, is employed as the conductive bonding material101. The conductive bonding material101bonds the back surfaces of the conductive pieces18to the end faces of the raised parts402and the surfaces of the extension regions98, and bonds the peripheral end faces of the conductive pieces18to the surfaces of the extension regions98. The conductive bonding material101includes portions located between the raised parts402and the conductive pieces18and between the extension regions98and the conductive pieces18. Also, the conductive bonding material101enters the open holes92c, for example. In this case, the conductive region on the inner peripheral surface of the open holes92cwhich are through holes is bonded to the raised parts402protruding inside the open holes92cby the conductive bonding material101.

The plurality of conductive pieces18are respectively provided in correspondence with the plurality of first FET pairs. Each conductive piece18is provided in order to reduce electrical resistance between the source terminals62of the MOSFETs16aand16bconstituting the first FET pair corresponding thereto and the busbar4.

As shown inFIGS.3,6,7,8and other diagrams, the plurality of conductive pieces28on the wiring board19are respectively bonded to the plurality of raised parts412that are exposed through the front main surface of the wiring board19. Also, the plurality of conductive pieces28are respectively bonded to the plurality of extension regions98of the wiring board19. The conductive pieces28are provided on the wiring board19so as to cover the end faces of the raised parts412protruding inside the open holes92cin the wiring board19and a peripheral portion of the open holes92c. The conductive pieces28cover the opening edges of the open holes92c(specifically, the opening edges on the front main surface side of the wiring board19). The thickness of the conductive pieces28may be set from 0.2 mm to 0.5 mm inclusive, for example.

The conductive pieces28are bonded by a conductive bonding material102to the end faces of the raised parts412protruding inside the open holes92cand the extension regions98around the open holes92c(seeFIG.6). Solder, for example, is employed as the conductive bonding material102. For example, the conductive pieces28are bonded by the conductive bonding material102to the raised parts412and the extension regions98, in a similar manner to the case where the conductive pieces18are bonded by the conductive bonding material101to the raised parts402and the extension regions98.

The plurality of conductive pieces28are respectively provided in correspondence with the plurality of second FET pairs. Each conductive piece28is provided in order to reduce electrical resistance between the source terminals62of the MOSFETs26aand26bconstituting the second FET pair corresponding thereto and the busbar4.

Example of Mounting Electronic Components

As shown inFIG.6and other diagrams, the MOSFETs16aon the upper side are provided on the wiring board9, so as to straddle between both the busbar2and the busbar4, for example. Given that the insulating portion51is located between the busbar2and the busbar4, the MOSFETs16aare located on the busbars2and4so as to straddle the insulating portion51.

The drain terminals63of the plurality of MOSFETs16aare respectively bonded to the lands962of the plurality of conductive regions96a. The plurality of protruding parts63aof the drain terminals63of the MOSFETs16aare respectively bonded to the plurality of protruding parts962aof the lands962.

The drain terminal63of each MOSFET16ais also bonded to the raised part202exposed through the land962to which that drain terminal63is bonded. The drain terminals63of the MOSFETs16acover the end faces of the raised parts202protruding inside the open holes92ain the wiring board9and a peripheral portion of the open holes92a. The drain terminals63of the MOSFETs16acover the opening edges of the open holes92a(specifically, the opening edges on the front main surface side of the wiring board9).

The drain terminal63of each MOSFET16ais bonded by a conductive bonding material111to the land962and the end face of the raised part202exposed through that land962(seeFIG.6). Solder, for example, is employed as the conductive bonding material111. The conductive bonding material111bonds the back surfaces of the drain terminals63to the surfaces of the lands962and the end faces of the raised parts202, and bonds the end faces of the drain terminals63to the surfaces of the lands962. The conductive bonding material111includes portions located between the raised parts202and the drain terminals63and between the lands962and the drain terminals63. Also, the conductive bonding material111enters the open holes92a, for example. The conductive region on the inner peripheral surface of the open holes92awhich are through holes is bonded to the raised parts202protruding inside the open holes92aby the conductive bonding material111. Due to the drain terminals63of the MOSFETs16abeing bonded to the raised parts202, the drain terminals63of the MOSFETs16aare electrically connected to the busbar2. The voltage that is input to the input terminal part21of the busbar2is input to the drain terminals63of the MOSFETs16bthrough the busbar2.

The gate terminals61of the plurality of MOSFETs16aare respectively bonded by a conductive bonding material to the lands960of the plurality of conductive regions96a. Solder, for example, is employed as the conductive bonding material. The conductive bonding material bonds the back surfaces and end faces of the gate terminals61to the lands960, for example. The conductive bonding material includes portions located between the gate terminals61and the lands960. The gate terminal61of each MOSFET16ais electrically connected to the connection terminal70of the connector7athrough the land960of the conductive region96a, the first wiring joined to that land960, and the land990of the conductive region99joined to that first wiring. Switching control of the MOSFETs16ais performed externally through the connector7a.

The plurality of source terminals62of each MOSFET16aare respectively bonded by a conductive bonding material112to the plurality of lands961of the conductive region96acorresponding to that MOSFET16a(seeFIG.6). Solder, for example, is employed as the conductive bonding material112. The conductive bonding material112bonds the back surfaces and end faces of the source terminals62to the lands961, for example. The conductive bonding material112includes portions located between the source terminals62and the lands961. Each source terminal62is electrically connected to the relay busbar4, through the land961, the extension region98joined to that land961, the conductive piece18bonded to that extension region98, and the conductive raised part402to which that conductive piece18is bonded. The conductive pieces18function as relay terminals that electrically connect the source terminals62of the MOSFETs16ato the raised parts402.

Also, the MOSFETs16bon the upper side are provided on the wiring board9so as to straddle between both the busbar3and the busbar4, for example, as shown inFIG.6and other diagrams. Given that the insulating portion52is located between the busbar3and the busbar4, the MOSFETs16bare located on the busbars3and4so as to straddle the insulating portion52.

The drain terminals63of the plurality of MOSFETs16bare respectively bonded to the lands962of the plurality of conductive regions96b. The drain terminal63of each MOSFET16bis also bonded to the raised part302exposed through the land962to which that drain terminal63is bonded. The drain terminal63of each MOSFET16bis bonded by a conductive bonding material113to the land962and the end face of the raised part302exposed through that land962(seeFIG.6). Solder, for example, is employed as the conductive bonding material113. For example, the drain terminals63of the MOSFETs16bare bonded by the conductive bonding material113to the raised parts302and the lands962, in a similar manner to the case where the drain terminals63of the MOSFETs16aare bonded by the conductive bonding material111to the raised parts202and the lands962.

The gate terminals61of the plurality of MOSFETs16bare respectively bonded by a conductive bonding material to the lands960of the plurality of conductive regions96b. Solder, for example, is employed as the conductive bonding material. The gate terminal61of each MOSFET16bis electrically connected to the connection terminal70of the connector7athrough the land960of the conductive region96b, the first wiring joined to that land960, and the land990of the conductive region99joined to that first wiring. Switching control of the MOSFETs16bis performed externally through the connector7a. For example, the gate terminals61of the MOSFETs16bare bonded to the lands960, in a similar manner to the case where the gate terminals61of the MOSFETs16aare bonded to the lands960.

The plurality of source terminals62of each MOSFET16bare respectively bonded by a conductive bonding material114to the plurality of lands961of the conductive region96bcorresponding to that MOSFET16b(seeFIG.6). Solder, for example, is employed as the conductive bonding material114. Each source terminal62of the MOSFET16bis electrically connected to the relay busbar4, through the land961, the extension region98joined to that land961, the conductive piece18bonded to that extension region98, and the conductive raised part402to which that conductive piece18is bonded. The conductive pieces18function as relay terminals that electrically connect the source terminals62of the MOSFETs16bto the raised parts402. The source terminals62of the MOSFETs16bare electrically connected to the source terminals62of the MOSFET16athrough the relay busbar4. For example, the source terminals62of the MOSFETs16bare bonded to the lands961by the conductive bonding material114, in a similar manner to the case where the source terminals62of the MOSFETs16aare bonded to the lands961by the conductive bonding material112.

The MOSFETs26aon the lower side are provided on the wiring board19, so as to straddle between both the busbar2and the busbar4, similarly to the MOSFETs16aon the upper side, for example.

The drain terminals63of the plurality of MOSFETs26aare respectively bonded to the lands962of the plurality of conductive regions96bof the wiring board19. The drain terminal63of each MOSFET26ais also bonded to the raised part212exposed through the land962to which that drain terminal63is bonded. The drain terminal63of each MOSFET26ais bonded by a conductive bonding material115to the land962and the end face of the raised part212exposed through that land962(seeFIG.6). Solder, for example, is employed as the conductive bonding material115. Due to the drain terminals63of the MOSFETs26abeing bonded to the raised parts212, the drain terminals63of the MOSFET26aare electrically connected to the busbar2. The voltage that is input to the input terminal part21of the busbar2is input to the drain terminals63of the MOSFETs26athrough the busbar2. For example, the drain terminals63of the MOSFETs26aare bonded by the conductive bonding material115to the raised parts212and the lands962, in a similar manner to the case where the drain terminals63of the MOSFETs16aare bonded by the conductive bonding material111to the raised parts202and the lands962.

The gate terminals61of the plurality of MOSFETs26aare respectively bonded by a conductive bonding material to the lands960of the plurality of conductive regions96bof the wiring board19. Solder, for example, is employed as the conductive bonding material. The gate terminal61of each MOSFET26ais electrically connected to the connection terminal70of the connector7bthrough the land960of the conductive region96b, the second wiring joined to that land960, and the land930of the conductive region93joined to that second wiring. Switching control of the MOSFETs26ais performed externally through the connector7b. For example, the gate terminals61of the MOSFETs26aare bonded to the lands960, in a similar manner to the case where the gate terminals61of the MOSFETs16aare bonded to the lands960.

The plurality of source terminals62of each MOSFET26aare respectively bonded by a conductive bonding material116to the plurality of lands961of the conductive region96bcorresponding to that MOSFET26a(seeFIG.6). Solder, for example, is employed as the conductive bonding material116. Each source terminal62of the MOSFET26ais electrically connected to the relay busbar4, through the land961, the extension region98joined to that land961, the conductive piece28bonded to that extension region98, and the conductive raised part412to which that conductive piece28is bonded. The conductive pieces28function as relay terminals that electrically connect the source terminals62of the MOSFETs26ato the raised parts412. For example, the source terminals62of the MOSFETs26aare bonded to the lands961by the conductive bonding material116, in a similar manner to the case where the source terminals62of the MOSFETs16aare bonded to the lands961by the conductive bonding material112.

The MOSFETs26bare provided on the wiring board19, so as to straddle between both the busbar3and the busbar4, for example, as shown inFIG.6and other diagrams. The drain terminals63of the plurality of MOSFETs26bare respectively bonded to the lands962of the plurality of conductive regions96a. The drain terminal63of each MOSFET26bis also bonded to the raised part312exposed through the land962to which that drain terminal63is bonded. The drain terminal63of each MOSFET26bis bonded by a conductive bonding material117to the land962and the end face of the raised part312exposed through that land962(seeFIG.6). Solder, for example, is employed as the conductive bonding material117. Due to the drain terminals63of the MOSFETs26bbeing bonded to the raised parts312, the drain terminals63of the MOSFETs26bare electrically connected to the busbar3. The output voltage of the drain terminals63of the MOSFETs26bis output externally from the output terminal part31of the busbar3. For example, the drain terminals63of the MOSFETs26bare bonded by the conductive bonding material117to the raised parts312and the lands962, in a similar manner to the case where the drain terminals63of the MOSFETs16aare bonded to the raised parts202and the lands962by the conductive bonding material111.

The gate terminals61of the plurality of MOSFETs26bare respectively bonded by a conductive bonding material to the lands960of the plurality of conductive regions96a. Solder, for example, is employed as the conductive bonding material. The gate terminal61of each MOSFET16bis electrically connected to the connection terminal70of the connector7bthrough the land960of the conductive region96a, the second wiring joined to that land960, and the land930of the conductive region93joined to that second wiring. Switching control of the MOSFETs26bis performed externally through the connector7b. For example, the gate terminals61of the MOSFETs26bare bonded to the lands960, in a similar manner to the case where the gate terminals61of the MOSFETs16aare bonded to the lands960.

The plurality of source terminals62of each MOSFET26bare respectively bonded by a conductive bonding material118to the plurality of lands961of the conductive region96acorresponding to that MOSFET26b(seeFIG.6). Solder, for example, is employed as the conductive bonding material118. Each source terminal62is electrically connected to the relay busbar4through the land961, the extension region98joined to that land961, the conductive piece28bonded to that extension region98, and the conductive raised part412to which that conductive piece28is bonded. The conductive pieces28function as relay terminals that electrically connect the source terminals62of the MOSFETs26bto the raised parts412. The source terminals62of the MOSFETs26bare electrically connected to the source terminals62of the MOSFET26athrough the relay busbar4. For example, the source terminals62of the MOSFETs26bare bonded to the lands961by the conductive bonding material118, in a similar manner to the case where the source terminals62of the MOSFETs16aare bonded to the lands961by the conductive bonding material112.

Example Configuration of Molded Resin

The molded resin11is constituted by a thermoset resin such as epoxy resin, for example. The coefficient of linear expansion of the molded resin11is set smaller than the coefficient of linear expansion of the insulating member5, for example. The coefficient of linear expansion of the molded resin11constituted by epoxy resin is 30 ppm/° C., which is smaller than the coefficient of linear expansion (e.g., 40 ppm/° C.) of the insulating member5constituted by PPS, for example.

As shown inFIGS.2,3and other diagrams, the molded resin11is provided on the front main surface of the wiring board19so as to cover the MOSFETs26and the conductive pieces28. The molded resin11covers the front main surface of the wiring board19. The exposed surface of the molded resin11is flush and continuous with the exposed surfaces of the heat dissipation members10, for example. The molded resin11protects the inside of the circuit structure1, and reduces the possibility of water getting into the circuit structure1, for example.

Example of Manufacturing Method of Circuit Structure

In the case of manufacturing the circuit structure1having a configuration such as the above, first, a metal plate600for producing the busbar4and a metal plate610for producing the busbars2and3are prepared.FIG.20is a schematic perspective view showing an example of the metal plate600.FIG.21is a schematic perspective view showing an example of the metal plate610.

Next, the metal plate600is molded into a predetermined shape by cold forging or cutting, for example. The plurality of raised parts402are then provided on one main surface of the molded metal plate600, and the plurality of raised parts412are provided on the other main surface. The opening420is then provided in the molded metal plate600. The relay busbar4shown inFIGS.22to24is thereby completed.FIGS.22and23are schematic perspective views showing the relay busbar4.FIG.24is a schematic diagram showing a cross-sectional structure of the relay busbar4in the long direction thereof.

Also, the metal plate610is molded into a predetermined shape by cold forging or cutting and a molded metal plate forming the basis of the busbar2and a molded metal plate forming the basis of the busbar3are produced, for example. Next, the open hole21ais provided in the metal plate forming the basis of the busbar2. Also, the plurality of raised parts202are provided on one main surface of the metal plate forming the basis of the busbar2, and the plurality of raised parts212are provided on the other main surface. The busbar2shown inFIGS.25and26is thereby completed. Similarly, the open hole31ais provided in the metal plate forming the basis of the busbar3. Also, the plurality of raised parts302are provided on one main surface of the metal plate forming the basis of the busbar3, and the plurality of raised parts312are provided on the other main surface. The busbar3shown inFIGS.25and26is thereby completed.

Next, as shown inFIG.27, the heat dissipation members10aand10bare prepared. Next, the heat dissipation member10ais diffusion-bonded to the main surface210of the busbar2using pressure treatment and heat treatment, for example. Also, the heat dissipation member10bis diffusion-bonded to the main surface310of the busbar3using pressure treatment and heat treatment, for example. The structure shown inFIGS.28and29is thereby obtained.

Next, as shown inFIGS.30and31, the busbars2,3and4and the heat dissipation members10aand10bare disposed in a mold for insert molding. InFIGS.30and31, illustration of the mold for insert molding is omitted. A thermoplastic resin having excellent heat resistance such as PPS is then injected into the mold for insert molding by an injection molding machine, and the busbars2,3and4and the heat dissipation members10aand10bare molded as one piece with the resin. As shown inFIGS.10,11,13and14referred to above, an integrally molded article in which the busbars2,3and4and the heat dissipation members10aand10bare molded as one piece with the insulating member5is thereby obtained.

Next, the wiring board9is fixed by the bonding material12ato the upper board mounting region provided in the produced integrally molded article. Also, the wiring board19is fixed by the bonding material12bto the lower board mounting region provided in the produced integrally molded product. The structure shown inFIGS.18and19referred to above is thereby obtained.

Next, as shown inFIG.32, a solder paste13is applied to predetermined regions of the front main surface of the wiring board19. InFIG.32, the solder paste13is shaded. The plurality of MOSFETs26and the plurality of conductive pieces28are then soldered with a reflow method to the regions where the solder paste13was applied. The structure shown inFIGS.3and7referred to above is thereby obtained.

Next, a depression formed on the surface on the wiring board19side of the structure shown inFIGS.3and7and surrounded by the frame-like insulating portion50and the heat dissipation members10aand10bis filled with a thermoplastic resin and heat-cured. The molded resin11covering the wiring board19, the MOSFETs26and the conductive pieces28is thereby formed (seeFIG.2).

Next, as shown inFIG.33, a solder paste14is applied to predetermined regions of the front main surface of the wiring board9. The solder paste14is also applied to the conductive region93of the wiring board19exposed through the opening420in the busbar4and the opening91in the wiring board9. InFIG.33, the solder paste14is shaded. The plurality of MOSFETs16, the plurality of conductive pieces18and the connectors7aand7bare then soldered with a reflow method to the regions where the solder paste14was applied. The above-described circuit structure1shown inFIGS.1and2is thereby completed. Given that the MOSFETs26and the conductive pieces28are covered by the molded resin11, the MOSFETs26and the conductive pieces28can be prevented from dropping out when the MOSFETs16and other components are soldered with the reflow method.

Thereafter, a control board that controls the MOSFETs6is attached to the circuit structure1. A case999covering the wiring board9, the plurality of MOSFETs16, the plurality of connectors7and the plurality of conductive pieces18is then attached to the busbars2and3. The electrical junction box1000is thereby completed, as shown inFIG.34.

As described above, in the present embodiment, the drain terminals63electrically connected to the busbar2and the source terminals62electrically connected to the busbar4are both bonded to the wiring board9or the wiring board19. On the other hand, due to the difference in coefficient of linear expansion of the busbars2and4with the insulating portion51, the busbar2, the busbar4, and the insulating portion51could possibly deform due to changes in ambient temperature. In the present example, given that both the drain terminals63and the source terminals62are bonded to the wiring board9or the wiring board19, the bonding portions of the drain terminals63and the source terminals62are less likely to be affected by deformation of the busbar2, the busbar4, and the insulating portion51. Therefore, stress is less likely to occur in the bonding portions of the drain terminals63and the source terminals62. As a result, the reliability of the bonding portions of the drain terminals63and the source terminals62can be improved.

Also, in the present embodiment, the conductive raised parts202protrude from the busbar2into the open holes92in the wiring board9. The drain terminals63on the wiring board9can thus be easily electrically connected to the busbar2, by electrically connecting the drain terminals63to the raised parts202protruding inside the open holes92. In other words, the drain terminals63on the wiring board9can be easily electrically connected to the busbar2, utilizing the raised parts202. Also, since heat generated by the MOSFETs6on the wiring board9can be transferred to the busbar2, local increases in temperature are less likely to occur. Similarly, given that the conductive raised parts212protrude from the busbar2into the open holes92in the wiring board19, the drain terminals63on the wiring board19can be easily electrically connected to the busbar2, utilizing the raised parts212.

Also, in the present embodiment, given that the conductive raised parts302protrude from the busbar3into the open holes92in the wiring board9, the drain terminals63on the wiring board9can be easily electrically connected to the busbar3, utilizing the raised parts302. Also, since heat generated by the MOSFETs6on the wiring board9can be transferred to the busbar3, local increases in temperature are less likely to occur. Similarly, given that the conductive raised parts312protrude from the busbar3into the open holes92in the wiring board19, the drain terminals63on the wiring board19can be easily electrically connected to the busbar3, utilizing the raised parts312.

Also, in the present embodiment, since the conductive raised parts402protrude from the busbar4into the open holes92in the wiring board9, the source terminals62on the wiring board9can be easily electrically connected to the busbar4, utilizing the raised parts402. Also, since heat generated by the MOSFETs6on the wiring board9can be transferred to the busbar4, local increases in temperature are less likely to occur. Similarly, given that the conductive raised parts412protrude from the busbar4into the open holes92in the wiring board19, the source terminals62on the wiring board19can be easily electrically connected to the busbar4, utilizing the raised parts412.

Also, in the present embodiment, given that the raised parts202and212are constituted by part of the busbar2, electrical resistance between the drain terminals63and the busbar2can be reduced. Also, given that the raised parts302and312are constituted by part of the busbar3, electrical resistance between the drain terminals63and the busbar3can be reduced. Also, given that the raised parts402and412are constituted by part of the busbar4, electrical resistance between the source terminals62and the busbar4can be reduced.

In the present embodiment, given that the drain terminals63on the busbar2are bonded to the raised parts202or the raised parts212, as shown inFIG.6, electrical resistance between the drain terminals63and the busbar2can be reduced. Also, given that the drain terminals63on the busbar3are bonded to the raised parts302or the raised parts312, electrical resistance between the drain terminals63and the busbar3can be reduced.

Also, in the present embodiment, the conductive pieces18bonded to the extension regions98that extend from the lands961to which the source terminals62of the upper MOSFETs16are bonded and are located around the open holes92and to the end faces of the raised parts402protruding inside the open holes92are provided. Due to these conductive pieces18, electrical resistance between the source terminals62and the busbar4can be reduced. Also, given that transfer of heat generated by the MOSFETs16to the busbar4is facilitated by the conductive pieces18, local increases in temperature are less likely to occur.

Also, the conductive pieces28bonded to the extension regions98that extend from the lands961to which the source terminals62of the lower MOSFETs26are bonded and are located around the open holes92and to the end faces of the raised parts412protruding inside the open holes92are provided. Due to these conductive pieces28, electrical resistance between the source terminals62and the busbar4can be reduced. Also, given that transfer of heat generated by the MOSFET26to the busbar4is facilitated by the conductive pieces28, local increases in temperature are less likely to occur.

Also, in the present embodiment, the upper extension regions98surround the open holes92, and the conductive pieces18cover the opening edges of the open holes92. The bonding area of the conductive pieces18with the extension regions98and the raised parts402can thereby be increased. As a result, electrical resistance between the source terminals62and the busbar4can be further reduced.

Also, the lower extension regions98surround the open holes92, and the conductive pieces28cover the opening edges of the open holes92. The bonding area of the conductive pieces28with the extension regions98and the raised parts412can thereby be increased. As a result, electrical resistance between the source terminals62and the busbar4can be further reduced.

In the present embodiment, given that the MOSFETs6are located on both main surfaces of the busbars2,3and4, the plane size of the circuit structure1can be reduced.

Also, in the present embodiment, given that the heat dissipation member10ais provided on the lower main surface210of the busbar2, the allowable heat generation of the circuit structure1increases. Also, given that the heat dissipation member10bis provided on the lower main surface310of the busbar3, the allowable heat generation of the circuit structure1increases. Therefore, it becomes possible to mount a plurality of MOSFETs6at a high density, for example.

Also, in the present embodiment, given that the heat dissipation member10ais provided on the lower main surface210of the busbar2while avoiding the region where the wiring board19is provided, the thickness of the circuit structure1can be suppressed while improving heat dissipation of the circuit structure1. Similarly, given that the heat dissipation member10bis provided on the lower main surface310of the busbar3while avoiding the region where the wiring board19is provided, the thickness of the circuit structure1can be suppressed while improving heat dissipation of the circuit structure1

Also, in the present embodiment, given that the gate terminal61and the source terminals62of each MOSFET16are insulated from each other on the wiring board9, the gate terminal61and the source terminals62can be appropriately insulated from each other, even if the interval between the gate terminal61and the source terminals62is small. Therefore, a narrow pitch package having a narrow terminal spacing can be employed as the package60of the MOSFETs16. Similarly, given that the gate terminal61and the source terminals62of each MOSFET26are insulated from each other on the wiring board19, the gate terminal61and the source terminals62can be appropriately insulated from each other, even if the interval between the gate terminal61and the source terminals62is small. Therefore, a narrow pitch package having a narrow terminal spacing can be employed as the package60of the MOSFETs26.

Also, in the present embodiment, given that the extension regions98to which the conductive pieces18are bonded extend from both the lands961to which the source terminals62of the MOSFETs16aare bonded and the lands961to which the source terminals62of the MOSFETs16bare bonded and are located around the open holes92c, the extension regions98can be shared by the MOSFETs16aand16b. Electrical resistance between the source terminals62of the MOSFETs16aand the busbar4and electrical resistance between the source terminals62of the MOSFETs16band the busbar4can thereby be reduced with a simple configuration.

Other Examples of Circuit Structure

The structure of the circuit structure1is not limited to the above examples. For example, a configuration may be adopted in which either or both the raised parts202and212are constituted separately from the busbar2, rather than being constituted by part of the busbar2. In this case, either or both the raised parts202and212may be bonded by a conductive bonding material such as solder to the main surface of the busbar2. Similarly, either or both the raised parts302and312may be constituted separately from the busbar3. Also, either or both the raised parts402and412may be constituted separately from the busbar4.

Also, the circuit structure1may not include the conductive pieces18. In this case, the raised part402protruding inside each open hole92may be bonded to the extension region98around that open hole92by solder or the like. Also, the circuit structure1may not include the conductive pieces28. In this case, the raised part412protruding inside each open hole92may be bonded to the extension region98around that open hole92by solder or the like.

Also, the circuit structure1may not include the heat dissipation members10. Also, the MOSFETs6and the conductive pieces8may not be provided on one main surface of the busbars2,3and4.

To facilitate solder-bonding of the terminals and the like to the busbars2,3and4, to reduce contact resistance between the wiring members and the input terminal part21, and to reduce contact resistance between the wiring members and the output terminal part31, the busbars2,3and4may have metal plating such as nickel plating on both main surfaces. In this case, the busbars2,3and4may be copper plates whose surfaces have been metal plated.

Although the circuit structure1has been described in detail above, the foregoing description is illustrative in all respects, and the disclosure is not limited thereto. The various modifications described above can be applied in combination as long as there are no mutual inconsistencies. Also, it should be understood that numerous modifications not illustrated herein can be contemplated without departing from the scope of this disclosure.