JP2022160336A - circuit board - Google Patents

Abstract

To realize miniaturization and cost reduction in a circuit board with a single configuration in addition to improving heat dissipation.SOLUTION: In a multi-layer single circuit board 23 which is fixed to a bearing holder 13 on the opposite output side of a motor 15 and has a heating element (FET) mounted on a first surface opposite to a second surface facing the bearing holder 13, a via-covered first via 41a is provided immediately below a first region 31a to which a first electrical terminal 22 of the heating element is connected, and a via-covered second via 43a is provided immediately below a second region 32a to which a second electrical terminal 24 of the heating element is connected. Through these first and second vias as heat conducting paths, the heat generated by the heating element is radiated to the bearing holder 13 arranged in close contact with the circuit board 23.SELECTED DRAWING: Figure 4

Description

The present invention relates to a circuit board used, for example, in a motor control device or the like.

In motor control devices that drive and control the motors of vehicles such as automobiles, not only are the motors and electronic control units (ECUs) integrated to reduce the size, but also the circuit boards mounted on the devices and the electronic components mounted on the boards are miniaturized. As a result, the component mounting area on the surface of the circuit board is reduced, and the board as a whole is made denser and smaller.

2. Description of the Related Art In recent years, as motor control devices and the like have become more sophisticated and multi-functional, electronic components mounted on circuit boards have become highly integrated, and the amount of heat generated by the electronic components has also increased due to higher driving speeds. An inverter circuit that supplies driving power to a motor is mounted in a motor control device, and switching elements such as MOSFETs that constitute the inverter circuit generate heat due to switching loss and the like.

Thus, the heat generated by the heat-generating components mounted on the circuit board must be efficiently released to the outside of the board. Examples of the heat dissipation structure include a type that dissipates heat from the back surface of the board-mounted FET, a type that dissipates heat from the bottom surface of the board-mounted FET via a thermal conductor material (copper inlay, etc.), and a type that dissipates heat from the bottom surface of the board-mounted FET. There are known a type in which heat is radiated through a heat radiating via, a configuration in which generated heat is radiated to a bearing holder, and the like.

In the driving device of Patent Document 1, the substrate and the frame member are arranged close to each other, and the heat from the heating elements such as the driving element, the current detection element, and the integrated circuit component (ASIC) mounted on the substrate is transferred to the frame member. Heat is dissipated from the back.

In Patent Document 2, the housing of the electric motor is used as an external radiator, and a copper inlay, which is a metal penetrating member, secures a heat conduction path from one surface side to the other surface side of the circuit board to transfer heat. , discloses a circuit board that enables heat dissipation.

As another example of heat dissipation, a structure is known in which the heat of an electronic component is dissipated to the outside through a heat dissipation substrate on the surface through thermal vias. For example, in the load driving device of Patent Document 3, a group of thermal vias is provided directly below the heat-generating electronic components mounted on the board, and the heat generated from the heat-generating electronic components is transferred to the back side of the board by the thermal via group. It conducts heat.

Japanese Patent No. 6179476 Japanese Patent Application Laid-Open No. 2020-4887 JP 2019-80471 A

As in Patent Document 1, the heat from the MOSFET, which is a heating element, is radiated from the rear surface of the MOSFET to the bearing holder of the motor. be done. Since the types of MOSFETs that can dissipate heat from the rear surface are limited and are expensive, there is a problem that the cost of the entire circuit board cannot be reduced by using them.

In the case of Patent Document 2, since the copper inlay as the thermal conductor material is expensive, using it as the main heat dissipation means leads to an increase in the cost of the circuit board. On the other hand, the heat dissipation by thermal vias adopted in Patent Document 3 may cause solder to flow into the vias from the pads on the bottom surface of the MOSFET on the circuit board, flow out to the back surface of the substrate, and cause electrical shorts with the heat sink. There are issues with gender, etc.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to reduce the size and cost of a circuit board having a single configuration and to improve heat dissipation.

The following configuration is provided as one means for achieving the above objects and solving the above problems. That is, the circuit board according to the exemplary first invention of the present application is fixed to the bearing holder on the counter-output side opposite to the output side of the motor, and the second surface opposite to the second surface facing the bearing holder. A single multi-layer circuit board having a heating element mounted on one surface thereof, in the thickness direction of the circuit board immediately below a first region to which a first electrical terminal of the heating element is connected. A first via that extends and is covered at a predetermined portion and a second area that is connected to a second electrical terminal of the heating element, extends in the thickness direction of the circuit board, and extends at a predetermined portion. and a second via covered by the via, wherein the heat generated by the heating element is radiated to the bearing holder arranged in close contact with the circuit board by using the first via and the second via as a heat conducting path. characterized by

A second exemplary invention of the present application is a motor control device for driving a multiphase motor having three or more phases, comprising: a bearing holder that holds a bearing that rotatably supports a shaft of the motor; The circuit board according to the exemplary first invention is fixed to a connector portion having a terminal for connecting an external power supply and a terminal for connecting an external signal at one end of the circuit board. The control unit determines a command signal for driving the motor based on at least the external signal, and the driving unit drives the motor according to the command signal.

An exemplary third invention of the present application is a power steering system in which the motor control device according to the exemplary second invention is used as a motor control device for an electric power steering that assists a driver's operation of a steering wheel of a vehicle or the like. characterized by a system.

An exemplary fourth invention of the present application is characterized by a vehicle equipped with the power steering system according to the exemplary third invention.

ADVANTAGE OF THE INVENTION According to this invention, while obtaining the high heat radiation efficiency with respect to the heat-generating component mounted on the circuit board of a single structure, size reduction of a circuit board and cost reduction can be carried out.

FIG. 1 is an exploded perspective view of a motor control device on which a circuit board according to an embodiment of the invention is mounted. FIG. 2 is a plan view of the circuit board according to the embodiment. 3(a) partially shows the front surface of the circuit board having the first heat dissipation structure, and FIG. 3(b) shows the back surface of the circuit board corresponding to FIG. 3(a). FIG. 4 is a cross-sectional view of the circuit board taken along the line BB' of FIG. 3(a). FIG. 5(a) partially shows the front surface of the circuit board having the second heat dissipation structure, and FIG. 5(b) shows the back surface of the circuit board corresponding to FIG. 5(a). FIG. 6 is a cross-sectional view of the circuit board cut along the line CC' of FIG. 5(a). FIG. 7 is a circuit diagram of the driving side of the circuit board. FIG. 8 is a diagram schematically showing the arrangement of heat dissipation vias in the second heat dissipation structure corresponding to the circuit configuration of FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is an exploded perspective view of a motor control device on which a circuit board according to an embodiment of the present invention is mounted and integrated with the circuit board.

In the motor control device 10 shown in FIG. 1 , the heat sink 13 is arranged above the motor 15 covered with the motor cover 14 in the axial direction, and above the bearing holder 13 and on the opposite side of the motor 15 in the axial direction. A circuit board 20 according to the embodiment is placed and fixed to the bearing holder 13 with screws or the like.

The bearing holder 13 is a metal heat sink that holds the bearing mechanism of the motor 15, functions as a member for dissipating heat generated from the circuit board 20, and is formed by, for example, die-cast aluminum. By using the bearing holder 13 of the motor 15 as an external radiator, the number of parts of the circuit board 20 can be reduced.

The circuit board 20 is fixed to the bearing holder 13 in a state in which the back surface of the circuit board 20 (the side opposite to the component mounting surface) and the bearing holder 13 are in close contact with each other via a thermally conductive insulating resin (compound). . As a result, the heat generated by the heat-generating components of the circuit board 20 is efficiently radiated to the heat sink 13 through the heat-dissipating vias, which will be described later.

The upper part of the circuit board 20 fixed to the bearing holder 13 is covered with the unit cover 12 made of metal. The external connector 16 is a terminal for connecting power to the motor 15 and control signals to the circuit board 20 , is covered with a connector case, and is fixed to the bearing holder 13 .

The circuit board 20 and the bearing holder 13 for supporting and fixing the circuit board 20 arranged with their planes opposed to each other have substantially the same outer shape and area when viewed from above.

The motor 15 is an integrated electromechanical type motor (brushless motor) in which a drive section and a control section of the motor are integrally formed. By adopting the electromechanical integrated type, the heat generated by the heat generating element, which will be described later, can be efficiently dissipated.

FIG. 2 is a plan view of the circuit board 20 according to the present embodiment. As shown in FIG. 2 , on the surface of the board body 23 of the circuit board 20 , control system devices including signal processing components such as a microprocessor 30 for controlling the motor 15 , various sensors such as a current sensor, and the motor 15 . and a drive system device related to energization of the drive current, etc. are mounted.

It should be noted that the arrangement positions of the individual components (devices) on the substrate body 23 in FIG. 2 are an example, and can be changed as appropriate according to the specifications of the device on which the circuit board 20 is mounted.

The drive system device is a power system device, and includes FET1 to FET6 that constitute an FET bridge circuit related to the generation of the motor drive current, switching FETs (FET9 to FET11) that apply the drive current to the motor, and an electrolytic capacitor for the motor drive current. It consists of C1 to C3 and the like.

Semiconductor switching elements (FETs) are also called power elements, and switching elements such as MOSFETs (Metal-Oxide Semiconductor Field-Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors) are used. A semiconductor switching element is a small switching element having an external size of, for example, 5×6 mm class or smaller.

Note that the 5×6 mm class includes 5.15×6.15 mm and the like, and the 5×6 mm class and below include the 3×4 mm class and the like.

A rotation sensor IC 28, which is a rotation angle sensor, is mounted on the surface of the substrate body 23 so as to be aligned with the central axis P of the motor. The rotation sensor IC 28 is formed of, for example, a magnetoresistive element or a Hall element, and is arranged at a position facing the motor rotation shaft (anti-output shaft of the motor) to detect the magnetic field generated by the magnet arranged on the motor rotation shaft. is detected to detect the rotation angle of the rotor.

The drive system device described above is arranged on one side of the circuit board 20 with respect to the rotation sensor IC 28 (below the one-dot chain line 18 in FIG. 2, also called the drive side), and the control system device is arranged on the other side (one point above the dashed line 18, also called the control side).

Output terminals 27 for the U, V, and W phase currents supplied to the motor 15 are arranged on the drive side. By doing so, the wiring distance from the three-phase inverter circuit or the like to the motor 15 can be shortened, and the power loss caused by the low resistance value due to the short pattern length of the power supply path can be reduced.

Next, the heat dissipation structure of the circuit board according to this embodiment will be described in detail.

<First heat dissipation structure>
A first heat dissipation structure in the circuit board according to this embodiment will be described. FIG. 3A partially shows the surface of the circuit board 20a having the first heat dissipation structure, and corresponds to the A portion of the circuit board 20 shown in FIG. FIG. 3(b) is a diagram showing the back surface of the circuit board 20a corresponding to FIG. 3(a). 4 is a cross-sectional view of the circuit board 20a taken along the line BB' of FIG. 3(a).

In the circuit board 20a, when each switching FET (FET1 in FIG. 3A) arranged on the driving side is viewed from above, the first region 31a immediately below the switching FET is as shown in FIG. As shown, this is the area where the first electrical terminal (drain terminal) 22 of FET 1 is connected to the substrate by solder 25a. A first heat dissipation via 41a extending in the thickness direction of the circuit board 20a is formed in the first region 31a. The inside of the via is a conductor plated with copper, for example.

Thereby, the first electrical terminal 22 of the FET1 is electrically connected to the first heat dissipation via 41a through the solder 25a.

Similarly, the second region 32a when the FET 1 is viewed from above is a region on the upper surface of the substrate body 23 to which the second electrical terminal (source terminal) 24 of the FET 1 is connected by solder 25b as shown in FIG. is. A second heat dissipation via 43a extending in the thickness direction of the circuit board 20a is formed in the second region 32a.

As shown in FIG. 3B, on the back surface of the circuit board 20a, a solder resist 51b is applied to the entire surface of the area 31b corresponding to the area 31a of the board surface and the area 32b corresponding to the area 32a.

That is, in the first heat dissipation structure, as shown in FIG. 4, a first heat dissipation via 41a is arranged directly below the first electrical terminal 22 of the switching FET, and a The arranged second heat dissipation vias 43a are covered with a solder resist 51b applied to the openings on the back surface of the substrate and do not penetrate the substrate.

Inside the layers of the circuit board 20a, as shown in FIG. 4, the first heat dissipation vias 41a are electrically connected to each other by the conductor patterns 38a, 38b, 38c provided in the layers 23a, 23c, 23e sandwiching the insulating layers 23b, 23d. It is connected. The second heat dissipation via 43a also has a structure connected to the conductor patterns 39a, 39b and 39c.

The back surface of the circuit board 20 a is in close contact with the bearing holder 13 via the compound 52 . The compound 52 has excellent thermal conductivity and electrical insulation.

As shown in FIG. 4, in the first heat dissipation structure, the conductor patterns 38c, 39c closest to the back surface of the substrate body 23 have a larger area in the planar direction of the inner layer than the other conductor patterns 38a, 38b, 39a, 39b. .

As a result, the heat generated by the switching FET, which is a heat-generating element surface-mounted on the circuit board 20a, and conducted through the first heat-dissipating via 41a and the second heat-dissipating via 43a is transferred to the conductor patterns 38c, 39c and the compound. Heat is efficiently radiated to the bearing holder 13 via 52 .

In addition, since the current flows through the first electrical terminal 22 and the second electrical terminal 24 of the switching FET, it is possible to obtain a high heat radiation effect by dissipating heat through the vias directly below the respective terminals. Become.

<Second heat dissipation structure>
A second heat dissipation structure in the circuit board according to this embodiment will be described. FIG. 5(a) partially shows the surface of the circuit board 20b having the second heat dissipation structure, and corresponds to the A portion of the circuit board 20 shown in FIG. FIG. 5(b) is a diagram showing the back surface of the circuit board 20b corresponding to FIG. 5(a). FIG. 6 is a cross-sectional view of the circuit board 20b cut along the line CC' of FIG. 5(a).

In the circuit board 20b, when each switching FET (FET1 in FIG. 5(a)) arranged on the drive side is viewed from above, in the third region 31c which is the region directly below it, there is shown in FIG. 5(a) 6, a first electrical terminal (drain terminal) 22 of FET 1 is connected to a substrate body 23 by solder 25a.

A third heat dissipation via 41b extending in the thickness direction of the circuit board 20b is formed in the third region 31c. Therefore, the first electrical terminal 22 of FET1 is electrically connected to the third heat dissipation via 41b through the solder 25a.

Furthermore, as shown in FIGS. 5A and 6, the second electrical terminal (source terminal) 24 of the FET 1 is connected to the fifth region 32c when the FET 1 is viewed from above with solder 25b. , and a fifth heat dissipation via 43b extending in the thickness direction of the circuit board 20b is formed in the region 32c.

Furthermore, in the second heat dissipation structure, as shown in FIG. 5(a), near regions (adjacent regions) 33a, 32c directly under the FETs (directly under the electrical terminals) mounted on the circuit board 20b. A fourth heat dissipation via 41c and a sixth heat dissipation via 43c are formed in each 35a.

As shown in FIG. 5(b), on the back surface of the circuit board 20b, a solder resist 51b is applied over the entire surfaces of regions 31d and 32d corresponding to the regions 31c and 32c on the board surface. On the other hand, in areas 33a and 35a on the front surface of the circuit board 20b and areas 33b and 35b on the corresponding back surface thereof, solder resists 51a and 51a are applied to areas excluding the opening portions of the fourth heat dissipation via 41c and the sixth heat dissipation via 43c. 51b is applied.

Therefore, as shown in FIGS. 5B and 6, the circuit board 20b according to the second heat dissipation structure has the opening portions of the third heat dissipation vias 41b and the fifth heat dissipation vias 43b on the back surface of the board body 23. By applying the solder resist 51b to the regions 31d and 32d, the third heat dissipation via 41b and the fifth heat dissipation via 43b are covered and do not penetrate the substrate 23. FIG.

Solder resists 51a and 51b are applied to the front and back surfaces of the circuit board 20b, avoiding the openings of the fourth heat dissipation via 41c and the sixth heat dissipation via 43c. The via hole is exposed at the part, and the via penetrates, resulting in a via open state.

Inside the layers of the circuit board 20b, as shown in FIG. 6, the third heat-dissipating via 41b and the fourth heat-dissipating via 41c form conductor patterns 48a provided on the layers 23a, 23c, and 23e sandwiching the insulating layers 23b and 23d. , 48b and 48c.

Furthermore, inside the layers of the circuit board 20b, the fifth heat dissipation via 43b and the sixth heat dissipation via 43c are electrically connected to each other by conductor patterns 49a, 49b, 49c provided in the layers 23a, 23c, 23e. there is

Therefore, as shown in FIG. 6, the heat generated at the first electrical terminal (drain terminal) 22 of the switching FET 1, which is a heating element surface-mounted on the circuit board 20, is absorbed by the via provided directly below the FET 1. Through the compound 52 having excellent thermal conductivity and electrical insulation, which conducts the third heat dissipation via 41b and the fourth heat dissipation via 41c and is arranged between the back surface of the circuit board 20b and the bearing holder 13. , the heat is radiated to the bearing holder 13 .

The heat generated at the second electrical terminal (source terminal) 24 of the switching FET 1 is conducted through the fifth heat dissipation via 43 b and the sixth heat dissipation via 43 c and radiated to the bearing holder 13 via the compound 52 .

With respect to the heat-generating components mounted on the circuit board in this way, the first heat dissipation structure and the second heat dissipation structure described above make it possible to heat the heat-generating components by contacting the back surface of the heat-generating components with the heat sink, thereby dissipating heat. A heat dissipation effect can be obtained.

The area of the circuit board where the heat dissipation vias in the via-open state are provided is not limited to the above areas 33a and 35a. For example, as shown in FIG. 5A, in addition to the regions 33a and 35a, a region 37a is also provided with thermal vias in a via-open state (referred to as seventh thermal vias 45), and these thermal vias are arranged inside the layers of the substrate. may be electrically connected. By carrying out like this, heat dissipation can be improved more.

The number of heat dissipation vias shown in FIGS. 4, 6, etc. is also an example, and can be increased or decreased as appropriate according to the area on the substrate.

Next, the relationship between the motor control circuit and the via arrangement in the circuit board according to this embodiment will be described.

FIG. 7 is a circuit diagram of the driving side of the circuit boards 20a and 20b described above. FIG. 8 schematically shows the arrangement of heat dissipation vias in the second heat dissipation structure of the circuit board 20b corresponding to the circuit configuration of FIG.

7 and 8, B+ and B- are input terminals for the positive and negative potentials of the drive power source (battery BT) for the motor 15 and the like, and are connected to the external connector 16 in FIG. On the driving side of the circuit board 20 b , the power input side has a noise filter composed of a coil 56 and an electrolytic capacitor 53 . The noise filter can absorb noise and the like contained in the power supplied to the circuit board 20b and smooth the power supply voltage.

The coil 56 is a common mode coil including, for example, two coils. The electrolytic capacitor 53 is composed of, for example, three electrolytic capacitors C1 to C3 connected in parallel as shown in FIG.

On the drive side of the power module, the FET7 functions as a power relay that cuts off the power supply when an abnormality occurs in the power supply voltage from the battery BT, and the reverse connection protection prevents reverse current flow when the battery is connected in reverse. It has FET8 as a relay.

Further, a switching circuit 54, which is a three-phase inverter circuit (FET bridge circuit) composed of six FETs 1 to 6, is provided for supplying drive current (three-phase AC current) to the motor 15. FIG. FETs 1, 3 and 5 are high potential side semiconductor switching elements corresponding to each of the three phases (U, V, W), and FETs 2, 4 and 6 are low potential side switching elements corresponding to each of the three phases. is.

The six FET1 to FET6 constituting the switching circuit 54 are turned on or off by driving their gates by signals from a control circuit (not shown) composed of, for example, a microcomputer, a pre-driver, or the like. The U, V, and W phase currents generated by this ON/OFF control are drive currents supplied to the electric motor 15 via an output terminal section 27 consisting of three terminals U, V, and W.

As shown in FIG. 8, in regions directly below the FETs 7 and 8, the above-described third heat dissipation vias (heat dissipation via structure indicated by reference numeral 41b in FIG. 6) are formed. A third heat dissipation via is formed in a region immediately below each FET described below.

Since L10 in FIG. 7 is a region adjacent to the power supply portion (drain terminal) to the FET 7, the above-described fourth heat dissipation via (heat dissipation via structure indicated by reference numeral 41c in FIG. 6) is formed. Further, since the connecting portion (L11 in FIGS. 7 and 8) of the FET7 and the FET8 is a region where the source terminals of the FET7 and the FET8 are connected to each other, it is indicated by the fifth heat dissipation via (reference numeral 43b in FIG. 6). heat dissipation via configuration) are formed.

As shown in FIG. 7, FET1 and FET2 are connected between a positive power supply line L1 and a negative potential line (GND) L2 to generate a U-phase current flowing through the U winding of the motor 15. FIG. FET3 and FET4 are connected between a positive power source line L1 and a negative potential (GND) line L2, and generate a V-phase current that flows through the V winding of the electric motor 15 . FET5 and FET6 are connected between a positive power supply line L1 and a negative potential (GND) line L2, and generate a W-phase current flowing through a W winding of the electric motor 15. FIG.

Furthermore, as shown in FIG. 7, between the connection node P1 between the FET1 and the FET2 and the output terminal U to the motor 15, an FET9, which is a semiconductor relay capable of interrupting the U-phase current, is provided. Similarly, the FET 10 provided between the connection node P2 between the FET3 and the FET4 and the output terminal V to the motor 15 functions as a semiconductor relay capable of interrupting the V-phase current, and the connection node P3 between the FET5 and the FET6. , and the output terminal W to the motor 15, the FET 11 functions as a semiconductor relay capable of interrupting the W-phase current.

As shown in FIG. 7, the drain terminal of FET 8 on the power supply side and the drain terminals of FETs 1, 3 and 5 are electrically connected by a high potential pattern L1 which is a positive power supply line. Therefore, as shown in FIG. 8, a fourth heat dissipation via is formed in the area of the high potential pattern L1 of the circuit board 20b.

In the switching circuit 54, the source terminals of the FETs 1, 3 and 5 and the drain terminals of the FETs 2, 4 and 6 are electrically connected by medium potential patterns L3, L4 and L5. Connection nodes P1, P2 and P3 are connected to source terminals of FETs 9, 10 and 11, respectively.

Therefore, as shown in FIG. 8, in the regions of the patterns L3, L4, and L5 on the circuit board 20b, the FETs 1, 3, and 5 side and the FETs 9, 10, and 11 side have the fifth and sixth heat dissipation vias (see FIG. 8). 6) are formed, and a fourth heat dissipation via is formed on the FET 2, 4, 6 side.

As a result, in the circuit board 20b, in the regions of the patterns L3, L4, and L5, the fourth heat dissipation via, the fifth heat dissipation via, and the sixth heat dissipation via are electrically connected to each other inside the layers of the board. have

On the other hand, in regions of patterns L6, L7, and L8 connecting drain terminals of FETs 9, 10, and 11 to output terminals U, V, and W, fourth heat dissipation vias are formed.

Further, on the driving side of the circuit board 20b, as shown in FIG. 7, shunt resistors R1, R2, and R3 are provided between FET2 and GND line L2, between FET4 and GND line L2, and between FET6 and GND line L2. is provided. R1, R2, and R3 function as current sensors (current detection elements) that detect U-phase, V-phase, and W-phase currents, respectively.

A pattern L12 between the FET2 and the shunt resistor R1, a pattern L13 between the FET4 and the shunt resistor R2, and a pattern L14 between the FET6 and the shunt resistor R3 form low potential patterns and are connected to the source terminals of the FET2, 4 and 6. . Therefore, a fifth heat dissipation via is formed on the FET2, 4, 6 side of the patterns L12, L13, L14, and a sixth heat dissipation via is formed on the resistance side.

In addition, the parts of the shunt resistors R1, R2, and R3 on the opposite side connected to the source terminals of the FETs 2, 4, and 6 are electrically connected to each other to form a ground (GND) pattern L2.

Each of the high-potential pattern L1, the medium-potential patterns L3, L4, L5, the low-potential patterns L12, L13, L14, and the GND pattern L2 described above is projected on the side opposite to the mounting side of the FET (semiconductor switching element) on the circuit board 20. A solid pattern is formed.

As described above, in the circuit board according to the present embodiment, the heat generated by the heat-generating elements (semiconductor switching elements) surface-mounted on the board is dissipated into the atmosphere on the mounting surface side, Heat can be dissipated to the bearing holder through the covered via provided directly under the heat generating element as in the heat dissipating structure of (1).

Furthermore, according to the second heat dissipation structure, in addition to the via-covered vias in the first heat dissipation structure, heat can be efficiently dissipated to the bearing holder via the via-opened vias provided in the vicinity thereof. As a result, in the circuit board on which the heat-generating electronic component is mounted, the rear side of the heat-generating electronic component does not need to be heat-dissipated, and the heat-dissipating property and productivity of the substrate can be improved at a low cost.

At that time, by covering the vias with a solder resist coating, the vias do not penetrate the board, so the solder for mounting the heating elements does not flow to the back side of the board through the vias, preventing short circuits and preventing the occurrence of short circuits. Productivity of implementation can be improved.

By covering the vias by applying a solder resist, vias that do not penetrate the board can be formed without increasing the cost. At the same time, since the thickness of the applied solder resist on the back surface of the board becomes uniform over the area where the via-opened vias are arranged and the area where the via-covered vias are arranged, the circuit board and the bearing holder Improves adhesion with As a result, the amount of compound to be filled between the circuit board and the bearing holder can be minimized, thereby enabling cost reduction.

Furthermore, a high-potential solid pattern in which specific electrical terminals of each high-potential-side semiconductor switching element corresponding to each phase of the motor are electrically connected to each other, and other electrical terminals of each of these high-potential-side semiconductor switching elements , a medium potential solid pattern electrically connecting specific electrical terminals of each of the low potential side switching elements corresponding to each phase, other electrical terminals of each of the low potential side switching elements, and the current corresponding to each phase A semiconductor switching element that constitutes a bridge circuit or the like, such as a low-potential solid pattern electrically connecting one end of the detection element and a GND solid pattern electrically connecting the other ends of the current detection elements of each phase. By providing a solid pattern corresponding to the potential of the substrate on the inner layer of the substrate, it is possible to obtain a high heat dissipation efficiency for the heat-generating component.

On the other hand, by adopting the heat dissipation structure described above in the circuit board mounted on the motor control device, the heat generated by the heat-generating components on the circuit board can be dissipated at low cost and with high efficiency. Moreover, by installing a motor control device having such an efficient heat dissipation mechanism in a power steering system, it becomes possible to reduce the size and cost of the power steering system.

Furthermore, by using the above power steering system in a vehicle, it is possible to increase the heat dissipation of the vehicle and reduce the cost.

10 Motor control device 12 Unit cover 13 Bearing holder 14 Motor cover 15 Motor 16 External connectors 20, 20a, 20b Circuit board 22 First electrical terminals 23 Board body 24 Second electrical terminals 25a, 25b Solder 27 Output terminal section 28 rotation sensor IC
30 Microprocessors 38a to 38c, 39a to 39c, 48a to 48c, 49a to 49c Conductor pattern 41a First heat dissipation via 41b Third heat dissipation via 41c Fourth heat dissipation via 43a Second heat dissipation via 43b Fifth heat dissipation via 43c Sixth heat dissipation vias 51a, 51b Solder resist 52 Compound 53, C1-C3 Electrolytic capacitor 54 Switching circuit 56 Coil BT Battery L1 Power supply line L2 Ground (GND) line

Claims (13)

A multi-layer single circuit board fixed to a bearing holder on the counter-output side opposite to the output side of the motor, and having a heating element mounted on a first surface opposite to a second surface facing the bearing holder. and
a first via extending in the thickness direction of the circuit board directly under the first region to which the first electrical terminal of the heating element is connected and covered with a via at a predetermined portion;
a second via extending in the thickness direction of the circuit board directly under the second region to which the second electrical terminal of the heating element is connected and covered with a via at a predetermined portion;
with
A circuit board that dissipates heat generated by the heating element to the bearing holder that is arranged in close contact with the circuit board by using the first via and the second via as a heat conducting path. 2. The circuit board according to claim 1, wherein said first via and said second via are covered with a solder resist applied to said second surface. Each of the first via and the second via is electrically connected to a solid pattern formed in at least one layer of the multilayer, and the solid pattern of the layer closest to the second surface is the solid pattern. 2. The circuit board according to claim 1, wherein the area of the solid pattern is wider than that of other solid patterns. a third via penetrating in the thickness direction of the circuit board provided in a third region near the first region in plan view;
a fourth via penetrating in the thickness direction of the circuit board provided in a fourth region near the second region in plan view;
further comprising
Said first via and said third via are electrically connected in at least one layer of said multilayer, and said second via and said fourth via are electrically connected in at least one layer of said multilayer. Item 1. The circuit board according to item 1. 2. The circuit board according to claim 1, wherein the motor is an electromechanically integrated motor in which a drive section and a control section are integrally formed. 6. The circuit board according to claim 5, wherein the driving section has a bridge circuit that generates an AC power supply for driving the motor, and the heating element is a semiconductor switching element that constitutes the bridge circuit. The motor is a multiphase motor having three or more phases, and the semiconductor switching elements include high potential side semiconductor switching elements and low potential side switching elements corresponding to the respective phases of the polyphase,
The inner layer of the circuit board includes:
a high-potential solid pattern formed by electrically connecting the first electrical terminals of the high-potential-side semiconductor switching elements;
a medium potential solid pattern in which the second electrical terminal of each of the high potential side semiconductor switching elements and the first electrical terminal of each of the low potential side switching elements are electrically connected for each phase; ,
a low-potential solid pattern in which the second electrical terminal of each of the low-potential-side switching elements and one end of the current detection element are electrically connected for each phase;
A ground (GND) solid pattern formed by electrically connecting the other ends of the current detection element to each other is arranged,
7. The circuit board according to claim 6, wherein each of said high-potential solid pattern, said medium-potential solid pattern, and said low-potential solid pattern forms a solid pattern projected on a side of said circuit board opposite to a mounting side of said heating element. . directly below the fifth region to which the first electrical terminals of the motor relay semiconductor switching elements corresponding to the respective polyphases connected between the bridge circuit and the motor are connected; a fifth via extending in the thickness direction and covered with a via at a predetermined portion;
a sixth via extending in the thickness direction of the circuit board directly under the sixth region to which the second electrical terminal of the motor relay semiconductor switching element is connected;
further comprising
8. The circuit board according to claim 7, wherein the sixth via and the medium potential solid pattern are electrically connected in an inner layer of the circuit board. Directly below the seventh region to which the first electrical terminal of the semiconductor switching element for a power relay that cuts off the supply of power to the motor is connected, the circuit board extends in the thickness direction of the circuit board at a predetermined portion. a via-covered seventh via;
An eighth via penetrating in the thickness direction of the circuit board provided in an eighth region in the vicinity of the seventh region in plan view and the second electrical terminal of the power relay semiconductor switching element are connected. a ninth via extending in the thickness direction of the circuit board directly under the ninth region where the via is covered at a predetermined portion;
A tenth region extending in the thickness direction of the circuit board and via-covered at a predetermined portion immediately below the tenth region to which the first electrical terminal of the semiconductor switching element for the reverse connection protection relay of the power supply is connected. a beer;
an eleventh via penetrating in the thickness direction of the circuit board provided in an eleventh region near the tenth region in plan view;
a twelfth via extending in the thickness direction of the circuit board and covered with a predetermined portion directly under the twelfth region to which the second electrical terminal of the semiconductor switching element for reverse connection protection relay is connected; ,
further comprising
8. The circuit according to claim 7, wherein the ninth via and the twelfth via are electrically connected in an inner layer of the circuit board, and the eleventh via is electrically connected to the high potential solid pattern. substrate. 7. The circuit board according to claim 6, wherein said semiconductor switching element has a package with an outer size of 5*6 mm class or less. A motor control device for driving a multiphase motor having three or more phases,
a bearing holder that holds a bearing that rotatably supports the shaft of the motor;
The circuit board according to any one of claims 1 to 10, which is fixed to the bearing holder;
with
The circuit board has a connector section having a terminal for connecting an external power supply and a terminal for connecting an external signal on one end side thereof, and the control section issues an instruction to drive the motor based on at least the external signal. A motor controller for determining a signal, and for driving the motor in response to the command signal. 12. A power steering system in which the motor control device according to claim 11 is used as a motor control device for electric power steering for assisting steering wheel operation of a driver of a vehicle. A vehicle comprising the power steering system according to claim 12.

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