Method for assembling an electric work machine and a drive unit for driving the motor of the electric work machine.

Abstract

To improve the heat dissipation efficiency of semiconductor switches in electric power tools. [Solution] One aspect of the present disclosure provides an electric work machine comprising a motor, a circuit board, a semiconductor switch, a metal plate, a heat dissipation member, and a male screw. The semiconductor switch is a semiconductor switch on a circuit board, having a first metal surface and a first mounting surface, and is electrically connected to a power supply and a motor. The first mounting surface is opposite to the first metal surface and faces the first circuit surface of the circuit board. The metal plate has a first plate surface bonded to the first metal surface and a second plate surface opposite to the first plate surface. The heat dissipation member is in direct or indirect contact with the second plate surface. The male screw fastens the heat dissipation member and the metal plate.

Description

Technical Field

[0001] The present disclosure relates to a power-operated work machine including a semiconductor switch.

Background Art

[0002] The power tool described in Patent Document 1 includes a tool bit, a motor that generates a driving force for driving the tool bit, and a drive circuit that drives the motor. The drive circuit includes six switching elements.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, power-operated work machines such as power tools have been increasing in output. Therefore, the current flowing through the motor and drive circuit of the power-operated work machine has been increasing. As a result, the amount of heat generated by the switching elements included in the drive circuit has been increasing. Therefore, it is necessary to efficiently release the heat generated in the switching elements.

[0005] It is desirable that one aspect of the present disclosure can improve the heat dissipation efficiency of the semiconductor switch of the power-operated work machine.

Means for Solving the Problems

[0006] In the present disclosure, terms such as "first" and "second" are merely intended to distinguish elements from each other and are not intended to limit the order or number of elements. Therefore, the first element may be referred to as the second element, and similarly, the second element may be referred to as the first element. In addition, the first element may be provided without including the second element, and similarly, the second element may be provided without including the first element.

[0007] One aspect of this disclosure provides an electric work machine comprising a motor, a circuit board, a semiconductor switch, a metal plate, a heat dissipation member, and a male screw. The motor is configured to be driven by receiving power from a power source. The circuit board has a first circuit surface and a second circuit surface opposite to the first circuit surface. The semiconductor switch is a semiconductor switch on the circuit board, having a first metal surface and a first mounting surface, and is electrically connected to the power source and the motor. The first mounting surface is opposite to the first metal surface and faces the first circuit surface. The metal plate has a first plate surface bonded to the first metal surface and a second plate surface opposite to the first plate surface. The heat dissipation member is in direct or indirect contact with the second plate surface. The male screw fastens the heat dissipation member to the metal plate.

[0008] In this type of electric work machine, the heat generated by the semiconductor switch is released to the outside via a metal plate and a heat dissipation member. The placement of the metal plate between the semiconductor switch and the heat dissipation member enhances the heat dissipation path. Furthermore, since the heat dissipation member and the metal plate are fastened together with male screws, the degree of contact between the heat dissipation member and the metal plate is increased, allowing heat to be efficiently transferred from the metal plate to the heat dissipation member. Therefore, the heat dissipation efficiency of the semiconductor switch can be improved.

[0009] Another aspect of the present disclosure provides a method for assembling a drive unit for driving a motor of an electric work machine. The method involves mounting a semiconductor switch of the drive unit on a circuit board of the drive unit, the semiconductor switch having a mounting surface and a metal surface opposite the mounting surface, the mounting surface facing the circuit board, joining a first plate surface of a metal substrate to the metal surface, directly or indirectly contacting a heat dissipation member with a second plate surface opposite to the first plate surface, and fastening the heat dissipation member and the metal plate with screws.

[0010] This method can improve the heat dissipation efficiency of semiconductor switches. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows the external appearance of the electric work machines according to the first and second embodiments. [Figure 2] This figure shows the electrical configuration of the electric work machine according to the first and second embodiments. [Figure 3] This is a plan view showing a circuit board on which the drive circuit according to the first embodiment is mounted. [Figure 4] This figure shows a cross-section of a circuit board according to the first embodiment. [Figure 5] This figure shows a modified example of a cross-section of a circuit board according to the first embodiment. [Figure 6] This figure shows the first circuit surface of a circuit board on which the drive circuit according to the second embodiment is mounted. [Figure 7] This is a diagram showing the second circuit surface of the circuit board according to the second embodiment. [Figure 8] This figure shows the appearance of a metal component inserted into a circuit board according to the second embodiment. [Figure 9] This figure shows the electrical connection between the source terminal of the first semiconductor switch and the drain terminal of the fourth semiconductor switch according to the second embodiment. [Figure 10] This figure shows a cross-section of the circuit board according to the second embodiment. [Modes for carrying out the invention]

[0012] [Summary of Embodiments] One embodiment may provide an electric work machine comprising at least one of the following: Feature 1: A motor configured to be powered and driven by a power source; Feature 2: A circuit board having a first circuit surface and a second circuit surface opposite to the first circuit surface; Feature 3: A semiconductor switch on a circuit board, having a first metal surface and a first mounting surface, and electrically connected to a power supply and a motor; Feature 4: The first mounting surface is opposite the first metal surface and faces the first circuit surface; · Feature 5: A metal plate having a first plate surface joined to the first metal surface and a second plate surface opposite to the first plate surface; · Feature 6: A heat radiating member directly or indirectly contacting the second plate surface; · Feature 7: A male screw fastening the heat radiating member and the metal plate.

[0013] In a power-operated work machine having at least Features 1 to 7, the heat generated in the semiconductor switch is released to the outside through the metal plate and the heat radiating member. Since a metal plate is disposed between the semiconductor switch and the heat radiating member, the heat dissipation path is enhanced. Further, since the heat radiating member and the metal plate are fastened by a male screw and the degree of closeness between the heat radiating member and the metal plate is high, heat is efficiently transmitted from the metal plate to the heat radiating member. Therefore, the heat dissipation efficiency of the semiconductor switch can be improved.

[0014] One embodiment may include, in addition to, or instead of, at least any one of Features 1 to 7, the following: · Feature 8: The heat radiating member has an insertion hole through which the male screw passes; · Feature 9: The metal plate has a female screw that engages with the male screw.

[0015] In a power-operated work machine having at least Features 1 to 9, by screwing the female screw formed on the metal plate with the male screw, the degree of closeness between the heat radiating member and the metal plate can be increased, and heat can be efficiently transmitted from the metal plate to the heat radiating member. Further, since the metal plate has a female screw, the number of parts of the power-operated work machine can be suppressed.

[0016] One embodiment may include, in addition to, or instead of, at least any one of Features 1 to 9, the following: · Feature 10: A conductive elastic member disposed between the first circuit surface and the heat radiating member.

[0017] In an electric work machine having at least features 1 to 7 and 10, the placement of an elastic member between the first circuit surface and the heat dissipation member allows the elastic member to absorb assembly tolerances of the semiconductor switch, metal plate, and heat dissipation member to the circuit board. Furthermore, since the elastic member electrically connects the circuit board to the heat dissipation member, when static electricity is generated on the circuit board, the static electricity is discharged to the heat dissipation member via the elastic member. Therefore, it is possible to suppress local voltage increases on the circuit board due to static electricity. Consequently, electrostatic discharge damage to electronic components on the circuit board can be suppressed.

[0018] One embodiment may include, in addition to or instead of, at least one of features 1 to 10: Feature 11: The metal plate is equipped with through-holes; Feature 12: Circuit components mounted in the first circuit plane at a position opposite the through-hole in the plate; Feature 13: The semiconductor switch has a first height in the direction perpendicular to the circuit board; Feature 14: Circuit components have a second height greater than the first height in the vertical direction.

[0019] In an electric work machine having at least features 1-7 and 11-14, the metal plate has through-holes, so that circuit components having a height greater than the height of the semiconductor switch can be mounted on the first circuit surface.

[0020] One embodiment may include, in addition to or instead of, at least one of features 1 to 14: Feature 15: Circuit components mounted on the first circuit surface; Feature 16: The semiconductor switch has a first height in the direction perpendicular to the circuit board; Feature 17: The circuit component has a second height that is smaller than the first height in the vertical direction.

[0021] In an electric work machine having at least features 1-7 and 15-17, circuit components having a height smaller than the height of a semiconductor switch can be mounted on the first circuit surface.

[0022] The semiconductor switch may be provided in a surface-mount package, more specifically, a top-cooled package or a double-sided cooled package. An example of a top-cooled package is the TO-Leaded Top-side cooling (TOLT) package. An example of a double-sided cooled package is the Double-side-cooling Small Outline Package (DSOP). Examples of semiconductor switches include metal-oxide-semiconductor field-effect transistors (MOSFETs), junction field-effect transistors (JFETs), insulated-gate bipolar transistors (IGBTs), bipolar transistors, solid-state relays (SSRs), and thyristors.

[0023] Examples of electric work equipment include various electrical devices used in work sites such as DIY, manufacturing, gardening, and construction, specifically electric tools for stonework, metalworking, and woodworking, gardening equipment, and equipment for preparing the work site environment, more specifically, electric blowers, electric hammers, electric hammer drills, electric drills, electric screwdrivers, electric wrenches, electric grinders, electric circular saws, electric reciprocating saws, electric jigsaws, electric cutters, electric chainsaws, electric planers, electric nail guns (including rivet guns), electric hedge trimmers, electric lawnmowers, electric grass trimmers, electric brush cutters, electric cleaners, electric sprayers, electric sprayers, electric dust collectors, and battery-powered handcarts.

[0024] One embodiment may provide a method for assembling a drive unit for driving a motor of an electric work machine, comprising at least one of the following: Feature 18: The semiconductor switch of the drive unit is mounted on the circuit board of the drive unit; Feature 19: The semiconductor switch has a mounting surface and a metal surface opposite the mounting surface, with the mounting surface facing the circuit board; Feature 20: Bonding the first surface of the metal substrate to the metal surface; Feature 21: The heat dissipation member is brought into direct or indirect contact with the second plate surface, which is opposite to the first plate surface; Feature 22: The heat dissipation component and the metal plate are fastened together with screws.

[0025] Methods that possess at least features 18-22 can improve the heat dissipation efficiency of semiconductor switches.

[0026] In one embodiment, the above-described features 1 to 22 may be combined in any combination. In one embodiment, any of the above-described features 1 to 22 may be excluded.

[0027] [Specific exemplary embodiments] (1. First Embodiment) <1-1. Configuration of electric work equipment> As shown in Figure 1, the electric work implement 1 is in the form of an electric chainsaw. In another embodiment, the electric work implement 1 may be in the form of an electric work implement other than an electric chainsaw.

[0028] The electric work machine 1 includes a housing 2. The housing 2 is made of synthetic resin. The housing 2 houses a motor 20 inside. The housing 2 also houses a drive unit 25 inside. The drive unit 25 has a circuit board 11 (described later) and a drive circuit 21 mounted on the circuit board 11.

[0029] The terms “up,” “down,” “front,” “back,” “left,” and “right” in the following description are used solely to facilitate an easy understanding of the structure of the electric work implement 1 and its components, and are not intended to limit the orientation of the electric work implement 1 and its components. The electric work implement 1 and its components can be positioned in any orientation.

[0030] The electric work implement 1 is equipped with a guide bar 9. The guide bar 9 is a plate-shaped member. The guide bar 9 protrudes forward from the housing 2 of the electric work implement 1. The electric work implement 1 is equipped with a saw chain 9a. The saw chain 9a includes a plurality of cutters connected to one another. The saw chain 9a is detachably attached to the periphery of the guide bar 9. The saw chain 9a is connected to the rotor shaft (not shown) of the motor 20 via a power transmission mechanism (not shown). The power transmission mechanism includes a sprocket (not shown) configured to which the saw chain 9a is attached.

[0031] Therefore, when the motor 20 is driven, the saw chain 9a, which acts as the working part, moves along the periphery of the guide bar 9. The electric work implement 1 can cut the workpiece with the moving saw chain 9a.

[0032] The electric work machine 1 is equipped with a battery mounting section 5. In this embodiment, the battery mounting section 5 protrudes upward from the rear of the housing 2. A battery pack 12 is detachably mounted in the battery mounting section 5. The battery pack 12 can be mounted on the rear end face of the battery mounting section 5. The battery pack 12 includes a secondary battery, for example, a rechargeable lithium-ion battery. By being mounted in the battery mounting section 5, the battery pack 12 can supply power to the electric work machine 1. The drive circuit 21 receives battery power from the battery pack 12. The drive circuit 21 converts the battery power into three-phase power. The three-phase power includes U-phase, V-phase, and W-phase. The drive circuit 21 supplies the three-phase power to the motor 20. In other words, the motor 20 receives power from the battery pack 12 via the drive circuit 21 and is driven by it.

[0033] In another embodiment, the electric work implement 1 may be equipped with a power cord instead of the battery mounting section 5. The electric work implement 1 may receive power from an AC power source such as a commercial power source via the power cord. The drive circuit 21 may receive power converted from the AC power source to a DC power source.

[0034] The electric work machine 1 is equipped with a handguard 4. The handguard 4 protrudes upward from the front of the housing 2. The electric work implement 1 is equipped with a side handle 3A and a top handle 3B behind the handguard 4. One of the side handle 3A and the top handle 3B may be omitted. The side handle 3A and the top handle 3B are made of synthetic resin.

[0035] The side handle 3A is a pipe-shaped component. The side handle 3A protrudes to the left from the left side of the housing 2. Therefore, the operator of the electric work machine 1 can grasp the side handle 3A with their left hand from the rear of the electric work machine 1.

[0036] The top handle 3B protrudes upward from the top of the housing 2. The rear end of the top handle 3B is connected to the battery mounting section 5, which creates a space between the top handle 3B and the housing 2. Therefore, the operator can insert their fingers into this space and grasp the top handle 3B.

[0037] The electric work implement 1 is equipped with a trigger switch 7 located below the top handle 3B. The trigger switch 7 is operated by the operator (e.g., pulled) to drive the motor 20. When the trigger switch 7 is pulled upward by the operator, the motor 20 is driven. When the operation of the trigger switch 7 is released, the motor 20 stops driving.

[0038] The electric work implement 1 is equipped with a trigger lock lever 8 above the top handle 3B. When the trigger lock lever 8 is pushed downward by the operator, the operation of the trigger switch 7 is permitted.

[0039] <1-2. Control Unit> As shown in Figure 2, the electric work machine 1 includes a control unit 10. The control unit 10 receives power from the battery 12a in the battery pack 12 and controls the motor 20 that rotates the fan. The motor 20 is a three-phase brushless DC motor. In another embodiment, the motor 20 may be a one-phase brushless DC motor, a two-phase brushless DC motor, a four-phase or more brushless DC motor, a brushed motor, an AC motor, or a stepping motor.

[0040] The control unit 10 includes a drive unit 25 having a drive circuit 21, a gate circuit 22, a control circuit 23, and a regulator 24. The drive circuit 21 is a circuit that receives power from the battery 12a and supplies current to each phase winding of the motor 20. The drive circuit 21 is a three-phase full-bridge inverter circuit equipped with first to sixth semiconductor switches Q1 to Q6. In another embodiment, it may be a one-phase, two-phase, or four-phase or more full-bridge inverter circuit, or a half-bridge inverter circuit.

[0041] Specifically, the first to sixth semiconductor switches Q1 to Q6 are FETs. More specifically, the first to sixth semiconductor switches Q1 to Q6 are N-channel MOSFETs. In another embodiment, at least one of the first to sixth semiconductor switches Q1 to Q6 may be a P-channel MOSFET, JFET, IGBT, bipolar transistor, SSR, or thyristor.

[0042] In the drive circuit 21, the first to third semiconductor switches Q1 to Q3 are high-side switches. The first to third semiconductor switches Q1 to Q3 are connected to terminals U, V, and W of the motor 20 and to the power line Lp. The power line Lp is connected to the positive terminal of the battery 12a. In the drive circuit 21, the fourth to sixth semiconductor switches Q4 to Q6 are low-side switches. The fourth to sixth semiconductor switches Q4 to Q6 are connected to terminals U, V, and W of the motor 20 and to the ground line Ln. The ground line Ln is connected to the negative terminal of the battery 12a.

[0043] The first to sixth semiconductor switches Q1 to Q6 each have gate terminals 41, 51, 61, 71, 81, and 91, drain terminals 42, 52, 62, 72, 82, and 92, and source terminals 43, 53, 63, 73, 83, and 93, respectively. The gate terminals 41, 51, 61, 71, 81, and 91 of the first to sixth semiconductor switches Q1 to Q6 are connected to the gate circuit 22. The drain terminals 42, 52, and 62 of the first to third semiconductor switches Q1 to Q3 are connected to the power line Lp. The source terminals 73, 83, and 93 of the fourth to sixth semiconductor switches Q4 to Q6 are connected to the ground line Ln. The source terminal 43 of the first semiconductor switch Q1 is connected to the drain terminal 72 of the fourth semiconductor switch Q4 and to the U phase of the motor 20. The source terminal 53 of the second semiconductor switch Q2 is connected to the drain terminal 82 of the fifth semiconductor switch Q5 and the V-phase of the motor 20. The source terminal 63 of the third semiconductor switch Q3 is connected to the drain terminal 92 of the sixth semiconductor switch Q6 and the W-phase of the motor 20.

[0044] The gate circuit 22, in accordance with the control signal output from the control circuit 23, turns on / off the first to sixth semiconductor switches Q1 to Q6 in the drive circuit 21, thereby supplying current to each phase winding of the motor 20 and causing the motor 20 to rotate.

[0045] The control circuit 23 includes a microcomputer (or microcontroller or microprocessor) not shown. In another embodiment, the control circuit 23 may include an additional microcomputer. In yet another embodiment, instead of or in addition to the microcomputer, the control circuit may include an image processing unit (GPU), wired logic, application-specific integrated circuits (ASICs), application-specific general-purpose products (ASSPs), programmable logic devices (PLDs) (such as field-programmable gate arrays (FPGAs)), discrete electronic components, and / or a combination thereof.

[0046] The regulator 24 receives power from the battery 12a to generate the power supply voltage Vcc necessary to operate the control circuit 23, and supplies the power supply voltage Vcc to the internal circuitry of the control unit 10. The control unit 10 further includes a load switch Q7 and a bootstrap 26. The load switch Q7 is located between the battery 12a and the drive circuit 21 in the power line Lp to protect the drive circuit 21 and / or the motor 20. The load switch Q7 is a semiconductor switch. Specifically, the load switch Q7 is an N-channel MOSFET. In another embodiment, the load switch Q7 may be a P-channel MOSFET, a JFET, an IGBT, a bipolar transistor, or an SSR. In yet another embodiment, the load switch Q7 may be a mechanical relay. The gate terminal of the load switch Q7 is connected to the control circuit 23 via the bootstrap 26. The load switch Q7 is kept ON when the motor 20 is permitted to be driven. The current flowing through the load switch Q7 may be greater than the current flowing through the first to sixth semiconductor switches Q1 to Q6. The voltage applied to the load switch Q7 may be greater than the voltage applied to the first to sixth semiconductor switches Q1 to Q6. Therefore, the rated voltage and rated current of load switch Q7 are higher than the rated voltage and rated current of semiconductor switches Q1 to Q6, respectively.

[0047] The drive circuit 21 includes a first thermistor 27 and a second thermistor 29. The first thermistor 27 is positioned near the first to third semiconductor switches Q1 to Q3 and measures the temperatures of the first to third semiconductor switches Q1 to Q3. The first thermistor 27 transmits a temperature detection signal representing the detected temperature to the control circuit 23. The second thermistor 29 is positioned near the fourth to sixth semiconductor switches Q4 to Q6 and measures the temperatures of the fourth to sixth semiconductor switches Q4 to Q6. The second thermistor 29 transmits a temperature detection signal representing the detected temperature to the control circuit 23.

[0048] <1-3. Drive Unit> <1-3-1. Examples> The drive unit 25 will be described with reference to Figures 3 and 4. The drive unit 25 comprises a circuit board 11, a drive circuit 21 mounted on the circuit board 11, four elastic members 35, two metal plates 100, two heat dissipation members 200, and four male screws 400. Note that in Figure 3, the two metal plates 100, the two heat dissipation members 200, and the four male screws 400 are shown transparently. In reality, the drive circuit 21 on the circuit board 11 has its upper surface covered by the two metal plates 100 and the two heat dissipation members 200.

[0049] The circuit board 11 is a printed circuit board (PCB). The circuit board 11 has a rectangular planar shape. In another embodiment, the circuit board 11 may have a planar shape other than a rectangle. The circuit board 11 has a first circuit surface 11A and a second circuit surface 11B. The second circuit surface 11B is opposite to the first circuit surface 11A.

[0050] The drive circuit 21 includes first to sixth semiconductor switches Q1 to Q6, first and second thermistors 27 and 29, a U-phase terminal 45, a V-phase terminal 55, and a W-phase terminal 65.

[0051] The first to sixth semiconductor switches Q1 to Q6 are surface-mount type. More specifically, the first to sixth semiconductor switches Q1 to Q6 are equipped with a top-cooled package, more specifically, a TOLT package. The first to sixth semiconductor switches Q1 to Q6 are the same model, but are not limited to the same model. The first to sixth semiconductor switches Q1 to Q6 are arranged on the first circuit surface 11A. The first to third semiconductor switches Q1 to Q3 are arranged in a single row along the left-right direction in front of the first circuit surface 11A, and the fourth to sixth semiconductor switches Q4 to Q6 are arranged in a single row along the left-right direction behind the first circuit surface 11A. In addition, the first and fourth semiconductor switches Q1 and Q4 are arranged in the front-to-back direction. The second and fifth semiconductor switches Q2 and Q5 are arranged in the front-to-back direction. The third and sixth switches Q3 and Q6 are arranged in the front-to-back direction.

[0052] Each package of the first to sixth semiconductor switches Q1 to Q6 is plate-shaped and has first ends 46A, 56A, 66A, 76A, 86A, 96A and second ends 46B, 56B, 66B, 76B, 86B, 96B that are opposite the first ends 46A, 56A, 66A, 76A, 86A, 96A. The drain terminals 42, 52, 62, 72, 82, 92 of the first to sixth semiconductor switches Q1 to Q6 protrude from the first ends 46A, 56A, 66A, 76A, 86A, 96A. The gate terminals 41, 51, 61, 71, 81, 91 and source terminals 43, 53, 63, 73, 83, 93 of the first to sixth semiconductor switches Q1 to Q6 protrude from the second ends 46B, 56B, 66B, 76B, 86B, 96B.

[0053] The first semiconductor switch Q1 has a first metal surface 46 and a first mounting surface 48 opposite to the first metal surface 46. The second semiconductor switch Q2 has a second metal surface 56 and a second mounting surface 58 opposite to the second metal surface 56. The third semiconductor switch Q3 has a third metal surface 66 and a third mounting surface 68 opposite to the third metal surface 66. The fourth semiconductor switch Q4 has a fourth metal surface 76 and a fourth mounting surface 78 opposite to the fourth metal surface 76. The fifth semiconductor switch Q5 has a fifth metal surface 86 and a fifth mounting surface 88 opposite to the fifth metal surface 86. The sixth semiconductor switch Q6 has a sixth metal surface 96 and a sixth mounting surface 98 opposite to the sixth metal surface 96.

[0054] The first to sixth metal surfaces 46, 56, 66, 76, 86, and 96 include metal plates (metal pads) bonded to the surfaces of the first to sixth semiconductor switches Q1 to Q6. The metal plates include aluminum, copper, silver, or gold, or are made of aluminum, copper, silver, or gold. The first to sixth semiconductor switches Q1 to Q6 are mounted on the first circuit surface 11A such that the first to sixth mounting surfaces 48, 58, 68, 78, 88, and 98 face the first circuit surface 11A. The first to sixth mounting surfaces 48, 58, 68, 78, 88, and 98 are soldered to the first circuit surface 11A.

[0055] The first to sixth semiconductor switches Q1 to Q6 are arranged such that their first ends 46A, 56A, 66A, 76A, 86A, and 96A face forward, and their second ends 46B, 56B, 66B, 76B, 86B, and 96B face backward. Therefore, on the first circuit plane 11A, the source terminal 43 of the first semiconductor switch Q1 faces the drain terminal 72 of the fourth semiconductor switch Q4. On the first circuit plane 11A, the source terminal 53 of the second semiconductor switch Q2 faces the drain terminal 82 of the fifth semiconductor switch Q5. On the first circuit plane 11A, the source terminal 63 of the third semiconductor switch Q3 faces the drain terminal 92 of the sixth semiconductor switch Q6. Source terminals 43, 53, and 63 are electrically connected to drain terminals 72, 82, and 92, respectively, via printed circuit boards (or traces or conductive tracks), vias, etc. (not shown) located on the first circuit surface 11A. The printed circuit boards are formed from metal foil with relatively high conductivity. More specifically, the metal foil contains copper, silver, or gold. The vias are formed from metal or plated with metal. The metals forming or applied to the vias include copper, silver, or gold.

[0056] The first thermistor 27 is positioned on the first circuit surface 11A between the first semiconductor switch Q1 and the second semiconductor switch Q2. The second thermistor 29 is positioned on the first circuit surface 11A between the fourth semiconductor switch Q4 and the fifth semiconductor switch Q5. In this embodiment, the first to sixth semiconductor switches Q1 to Q6 have a first height H1. The first and second thermistors 27 and 29 have a second height H2. The first height H1 and the second height H2 correspond to the vertical length, and the second height H2 is greater than the first height H1.

[0057] The U-phase terminal 45 is located on the first circuit surface 11A between the first semiconductor switch Q1 and the fourth semiconductor switch Q4. The source terminal 43 of the first semiconductor switch Q1, the drain terminal 72 of the fourth semiconductor switch Q4, and the U-phase terminal 45 are electrically connected to each other. The drain terminal 42 of the first semiconductor switch Q1 is electrically connected to the power line Lp via printed circuit boards, vias, etc. (not shown) located on the first circuit surface 11A. The source terminal 73 of the fourth semiconductor switch Q4 is electrically connected to the ground line Ln via printed circuit boards, vias, etc. (not shown) located on the first circuit surface 11A.

[0058] The V-phase terminal 55 is located on the first circuit plane 11A between the second semiconductor switch Q2 and the fifth semiconductor switch Q5. The source terminal 53 of the second semiconductor switch Q2, the drain terminal 82 of the fifth semiconductor switch Q5, and the V-phase terminal 55 are electrically connected to each other. The drain terminal 52 of the second semiconductor switch Q2 is electrically connected to the power line Lp via printed circuit boards, vias, etc. (not shown) located on the first circuit plane 11A. The source terminal 83 of the fifth semiconductor switch Q5 is electrically connected to the ground line Ln via printed circuit boards, vias, etc. (not shown) located on the first circuit plane 11A.

[0059] The W-phase terminal 65 is located on the first circuit plane 11A between the third semiconductor switch Q3 and the sixth semiconductor switch Q6. The source terminal 63 of the third semiconductor switch Q3, the drain terminal 92 of the sixth semiconductor switch Q6, and the W-phase terminal 65 are electrically connected to each other. The drain terminal 62 of the third semiconductor switch Q3 is electrically connected to the power line Lp via printed circuit boards, vias, etc. (not shown) located on the first circuit plane 11A. The source terminal 93 of the sixth semiconductor switch Q6 is electrically connected to the ground line Ln via printed circuit boards, vias, etc. (not shown) located on the first circuit plane 11A.

[0060] The elastic member 35 is conductive. Specifically, the elastic member 35 is a metal leaf spring made of copper, aluminum, or the like. More specifically, the elastic member 35 has a Z-shaped cross-section, but is not limited to a Z-shape. In another embodiment, the elastic member 35 may be a metal coil spring. Alternatively, the elastic member 35 may be a sponge whose surface is covered with a conductive material.

[0061] The four elastic members 35 are positioned on the first circuit surface 11A to the right of the first semiconductor switch Q1, to the left of the third semiconductor switch Q3, to the right of the fourth semiconductor switch Q4, and to the left of the sixth semiconductor switch Q6. Each elastic member 35 has a first member surface 35A and a second member surface 35B opposite to the first member surface 35A. The first member surface 35A of the elastic member 35 is joined to the first circuit surface 11A by solder or the like.

[0062] The metal plate 100 is a rectangular plate-shaped member. Two metal plates 100 are positioned above the first circuit surface 11A such that their longitudinal direction aligns with the left-right direction. One of the two metal plates 100 is positioned to cover the upper surfaces of three high-side switches (i.e., the first to third semiconductor switches Q1 to Q3). The upper surfaces of the three high-side switches include the first to third metal surfaces 46, 56, and 66. The other metal plate 100 is positioned to cover the upper surfaces of three low-side switches (i.e., the fourth to sixth semiconductor switches Q4 to Q6). The upper surfaces of the three low-side switches include the fourth to sixth metal surfaces 76, 86, and 96. Neither of the two metal plates 100 covers any of the four elastic members 35. The two metal plates 100 are members that enhance the heat dissipation efficiency of the heat generated in the first to sixth semiconductor switches Q1 to Q6. Note that Figure 4 shows a cross-section along the high-side switch, but the circuit structure of the low-side switch is the same as that of the high-side switch. Therefore, the circuit structure of the high-side switch will be explained below, and the explanation of the low-side switch circuit structure will be omitted.

[0063] The metal plate 100 has a first plate surface 100A and a second plate surface 100B opposite to the first plate surface 100A. The first plate surface 100A is joined to each of the first to third metal surfaces 46, 56, and 66 via solder. In another embodiment, the first plate surface 100A may be joined to the first to third metal surfaces 46, 56, and 66 via an adhesive with relatively high thermal conductivity. Examples of adhesives with relatively high thermal conductivity include silicone and epoxy resin.

[0064] The metal plate 100 includes a metal base 140, an insulating layer 130, first to third metal foils 111 to 113, a right insulating portion 121, first and second insulating portions 122 and 123, and a left insulating portion 124. The metal base 140 is an aluminum metal plate. That is, the metal base 140 is a metal plate with relatively high thermal conductivity and excellent heat dissipation. In another embodiment, the metal base 140 may be a metal plate made of another metal such as copper. The metal base 140 can be any metal plate with excellent heat dissipation. The upper surface of the metal base 140 corresponds to the second plate surface 100B.

[0065] The insulating layer 130 is bonded to the underside of the metal base 140. More specifically, the upper surface of the insulating layer 130 is bonded to the underside of the metal base 140 with an adhesive or the like. The insulating layer 130 contains or is formed from a material with excellent insulating and heat dissipation properties. Examples of such materials include silicon and epoxy resin.

[0066] The first to third metal foils 111 to 113, the right insulating portion 121, the first and second insulating portions 122 and 123, and the left insulating portion 124 are joined to the lower surface of the insulating layer 130. The first to third metal foils 111 to 113, the right insulating portion 121, the first and second insulating portions 122 and 123, and the left insulating portion 124 form the first plate surface 100A. In other words, the first to third metal foils 111 to 113, the right insulating portion 121, the first and second insulating portions 122 and 123, and the left insulating portion 124 are included in the first plate surface 100A.

[0067] The first to third metal foils 111 to 113 are rectangular metal foils (metal patches), specifically copper foils. Each of the first to third metal foils 111 to 113 has a size approximately the same as the first to third metal surfaces 46, 56, and 66, respectively. In another embodiment, the first to third metal foils 111 to 113 may be other metal foils such as silver foil or gold foil.

[0068] The first metal foil 111 is positioned on the first board surface 100A opposite to the first metal surface 46. The second metal foil 112 is positioned on the first board surface 100A opposite to the second metal surface 56. The third metal foil 113 is positioned on the first board surface 100A opposite to the third metal surface 66. In other words, the first to third metal foils 111 to 113 are arranged side by side in the left-to-right direction at the same intervals as the first to third semiconductor switches Q1 to Q3.

[0069] The first metal foil 111 is joined to the first metal surface 46 with solder 101. The second metal foil 112 is joined to the second metal surface 56 with solder 102. The third metal foil 113 is joined to the third metal surface 66 with solder 103. The first to third metal foils 111 to 113 are soldered to the first to third metal surfaces 46, 56, and 66, respectively. However, no current flows between the first to third metal foils 111 to 113 and the first to third metal surfaces 46, 56, and 66. The first to third metal foils 111 to 113 are not components for conducting current between the first to third semiconductor switches Q1 to Q3 and the metal plate 100. The first to third metal foils 111 to 113 are components for soldering the metal plate 100 to the first to third semiconductor switches Q1 to Q3. Depending on the type of metal contained in the metal plate 100, soldering may be difficult. In particular, if the metal is aluminum, soldering may be difficult. Because the first plate surface 100A contains the first to third metal foils 111 to 113, the first to third metal surfaces 46, 56, and 66 can be soldered to the first plate surface 100A.

[0070] Solders 101-103 are alloys containing lead and / or tin, and have a higher thermal conductivity than resins, etc. The first to third semiconductor switches Q1-Q3 are joined to the metal plate 100 with solders 101-103, which have high thermal conductivity. Therefore, compared to the case where the first to third semiconductor switches Q1-Q3 are joined to the metal plate 100 with resin, etc., the heat dissipation efficiency of the heat dissipation path from the first to third semiconductor switches Q1-Q3 to the metal plate 100 is improved.

[0071] In another embodiment, the first to third semiconductor switches Q1 to Q3 may be bonded to the metal plate 100 via a thermally conductive material (TIM), and the first to third metal foils 111 to 113 may be removed from the metal plate 100. Examples of TIM include thermal grease, thermal adhesive, thermal sheet, thermal compound, and thermal putty.

[0072] The first and second insulating sections 122, 123, the right insulating section 121, and the left insulating section 124 are solder resist (or solder mask) applied to the first board surface 100A. In another embodiment, the first and second insulating sections 122, 123, the right insulating section 121, and the left insulating section 124 may be formed of an insulating material or may contain an insulating material. Examples of insulating materials include silicon and epoxy resin.

[0073] The first insulating portion 122 is positioned between the first metal foil 111 and the second metal foil 112. The second insulating portion 123 is positioned between the second metal foil 112 and the third metal foil 113. The right insulating portion 121 is positioned to the right of the first metal foil 111. The left insulating portion 124 is positioned to the left of the third metal foil 113.

[0074] The metal plate 100 has a through-hole 160 that penetrates the first insulating portion 122, the insulating layer 130 above it, and the metal base 140. The through-hole 160 faces the first thermistor 27 mounted on the first circuit surface 11A. Since the second height H2 is greater than the first height H1, the first thermistor 27 cannot fit between the first circuit surface 11A and the first insulating portion 122. Therefore, the through-hole 160 is formed in the metal plate 100. A portion of the first thermistor 27 is housed within the through-hole 160.

[0075] The metal plate 100 has two female threads 150 formed therein. The two female threads 150 include helical threads formed on the inner surface of the through holes. One of the two female threads 150 is formed on the inner surface of the through hole that penetrates the right insulating portion 121, the insulating layer 130 above it, and the metal base 140. The other female thread 150 is formed on the inner surface of the through hole that penetrates the left insulating portion 124, the insulating layer 130 above it, and the metal base 140. The threads in both female threads 150 are formed on the inner surface of the metal base 140.

[0076] The adhesion layer 300 is bonded to the second plate surface 100B. The heat dissipation member 200 is indirectly in contact with the second plate surface 100B via the adhesion layer 300. The adhesion layer 300 is formed by applying a material having adhesive properties and a thermal conductivity higher than that of air to the second plate surface 100B, or by attaching a sheet of such material. Specifically, the adhesion layer 300 is formed of TIM, more specifically, a thermal compound. Generally, the second plate surface 100B has fine irregularities. The bottom surface of the heat dissipation member 200 also has fine irregularities. The adhesion layer 300 improves the heat dissipation efficiency of the heat dissipation path from the metal plate 100 to the heat dissipation member 200 by filling the gap between the second plate surface 100B and the bottom surface of the heat dissipation member 200. In another embodiment, the adhesion layer 300 and the heat dissipation member 200 may be excluded from the drive unit 25. If sufficient heat dissipation can be obtained from the metal plate 100 alone, it is not necessary to join the heat dissipation member 200 to the metal plate 100.

[0077] In another embodiment, the adhesion layer 300 may be removed from the drive unit 25, and the heat dissipation member 200 may be directly bonded to the second plate surface 100B. In yet another embodiment, the metal plate 100 and the adhesion layer 300 may be removed from the drive unit 25. An insulating layer may be formed on the bottom surface of the heat dissipation member 200, and three metal foils may be placed on the insulating layer. The three metal foils may then be soldered to the first to third metal surfaces 46, 56, 66 of the first to third semiconductor switches Q1 to Q3.

[0078] The right and left ends of the heat dissipation member 200 are in contact with the second member surfaces 35B of the two elastic members 35. The heat dissipation member 200 is not fixed to the two second member surfaces 35B, but is supported by the elastic force of the two elastic members 35. Therefore, the assembly tolerances of the first to third semiconductor switches Q1 to Q3, the metal plate 100, the adhesion layer 300, and the heat dissipation member 200 are absorbed by the two elastic members 35.

[0079] Furthermore, since the elastic member 35 is conductive, it electrically connects the circuit board 11 to the heat dissipation member 200. Therefore, when static electricity is generated on the circuit board 11, the static electricity is discharged to the heat dissipation member 200 via the elastic member 35. This suppresses the local voltage rise on the circuit board 11 due to static electricity. Consequently, electrostatic discharge damage to electronic components on the circuit board 11 is suppressed.

[0080] In another embodiment, the drive unit 25 may comprise only one heat dissipation member 200, and this single heat dissipation member 200 may cover the upper surfaces of the first to sixth semiconductor switches Q1 to Q6. Alternatively, one elastic member 35 may be installed on the first circuit surface 11A for each heat dissipation member 200, and the heat dissipation member 200 may be supported by one elastic member 35. Or, in yet another embodiment, three or more elastic members 35 may be installed on the first circuit surface 11A for each heat dissipation member 200, and the heat dissipation member 200 may be supported by three or more elastic members 35.

[0081] The heat dissipation member 200 is a metal heat sink made of aluminum, copper, or the like. The heat dissipation member 200 has a base 210, a plurality of fins 220, and one mounting portion 230. The base 210 is plate-shaped and is bonded to the adhesion layer 300 substantially parallel to the circuit board 11 and the metal plate 100. Two through holes 250 are formed in the base 210 that penetrate through it. The two through holes 250 are formed in a position opposite to the female screw 150 in the vertical direction. No screw threads are formed on the inner surface of the two through holes 250, and the inner surface is smooth.

[0082] Each of the multiple fins 220 is plate-shaped. The multiple fins 220 are connected to the base 210 such that their longitudinal direction is aligned with the front-to-back direction. The multiple fins 220 are arranged side by side in the left-to-right direction. In another embodiment, the multiple fins 220 may be arranged on the base 210 side by side in the front-to-back direction such that their longitudinal direction is aligned with the left-to-right direction. In yet another embodiment, the multiple fins 220 may have shapes other than plates, such as a corrugated shape or a pointed shape.

[0083] The mounting portion 230 is plate-shaped and thicker than the fin 220. The mounting portion 230 is connected to the right end of the base 210 such that its longitudinal direction is aligned with the front-rear direction. In another embodiment, the mounting portion 230 may be connected to the left end of the base 210. Alternatively, in another embodiment, the mounting portion 230 may be connected to the front or rear end of the base 210 such that its longitudinal direction is aligned with the left-right direction.

[0084] The heat dissipation member 200 has a first contact surface 200a on the underside of the base 210. The first contact surface 200a is indirectly in contact with each of the first to third semiconductor switches Q1 to Q3 via a metal plate 100 or the like. The heat dissipation member 200 has a second contact surface 200b on the outside of the mounting portion 230. The second contact surface 200b is a different surface of the heat dissipation member 200 from the first contact surface 200a.

[0085] The second contact surface 200b is in contact with the load switch Q7. The load switch Q7 is a through-hole mounting type (insertion mounting type). More specifically, the load switch Q7 is a radial lead type. The rated voltage and rated current of through-hole mounting semiconductor switches are generally higher than those of surface-mount semiconductor switches. To ensure high reliability and / or high durability, the rated voltage and rated current required for the load switch Q7 are higher than those required for each of the first to sixth semiconductor switches Q1 to Q6.

[0086] The load switch Q7 comprises a package body 30, which is rectangular in shape. The load switch Q7 is screwed to the mounting portion 230 such that one surface of the package body 30 is in contact with the outer surface of the mounting portion 230. In another embodiment, the load switch Q7 may be fixed to the mounting portion 230 by being clamped with a clip or the like, such that one surface of the package body 30 is in contact with the outer surface of the mounting portion 230. Alternatively, in another embodiment, one surface of the package body 30 may be adhered to the outer surface of the mounting portion 230 via a thin adhesive sheet.

[0087] The load switch Q7 is directly or indirectly connected to the second contact surface 200b of the heat dissipation member 200. Heat generated in the first to third semiconductor switches Q1 to Q3 is transferred to the heat dissipation member 200 via the metal plate 100 and released to the outside from the heat dissipation member 200. Heat generated in the load switch Q7 is directly transferred to the heat dissipation member 200 and released to the outside from the heat dissipation member 200.

[0088] The load switch Q7 includes a first lead wire 31, a second lead wire 32, and a third lead wire 33. The first lead wire 31 is connected to the gate terminal of the load switch Q7. The second lead wire 32 is connected to the drain terminal of the load switch Q7. The third lead wire 33 is connected to the source terminal of the load switch Q7. Vias 131, 132, and 133 are formed on the circuit board 11. The first to third lead wires 31 to 33 extend downward from the package body 30 and are electrically connected to vias 131, 132, and 133.

[0089] The male screw 400 has a threaded portion 410. The threaded portion 410 is a helical thread formed on the cylindrical side surface of the male screw 400. The threaded portion 410 is formed in a position corresponding to the female screw 150 when the male screw 400 is inserted through the insertion hole 250. The two male screws 400 are each inserted through the insertion hole 250, and the threaded portions 410 are screwed into the female screws 150. By screwing the two threaded portions 410 into the two female screws 150, the heat dissipation member 200 is firmly fixed to the metal plate 100. Furthermore, the degree of adhesion between the heat dissipation member 200, the adhesion layer 300, and the metal plate 100 is increased, improving the heat dissipation efficiency from the metal plate 100 to the heat dissipation member 200.

[0090] In another embodiment, instead of the female screw 150 being formed in the metal plate 100, the drive unit 25 may have two nuts (female screws). Two male screws 400 may be screwed into the two nuts below the right insulator 121 and the left insulator 124.

[0091] After the first to sixth semiconductor switches Q1 to Q6, two metal plates 100, and two heat dissipation members 200 are assembled onto the circuit board 11, the drive unit 25 is held in a mold and molded with resin. The resin-molded drive unit 25 is housed in the housing 2. In another embodiment, after the first to sixth semiconductor switches Q1 to Q6, two metal plates 100, and two heat dissipation members 200 are assembled onto the circuit board 11, the drive unit 25 may be housed in a casing. The drive unit 25 housed in a casing is then housed in the housing 2.

[0092] <1-3-2. Variant Example> A modified version of the drive unit 25 will be described with reference to Figure 5. In this modified version, the first thermistor 27 has a third height H3 instead of a second height H2, which is different from the embodiment described above. Furthermore, in this modified version, the metal plate 100 does not have a through-hole 160 formed therein. The third height H3 is smaller than the first height H1. Therefore, the first thermistor 27 in this modified version fits between the first circuit surface 11A and the first insulating part 122, and thus the metal plate 100 in this modified version does not have a through-hole 160 formed therein.

[0093] <1-3-3. Effects> The first embodiment described in detail above provides the following effects. (1) The heat generated in the first semiconductor switch Q1 is released to the outside via the metal plate 100 and the heat dissipation member 200. The heat dissipation path is enhanced by the placement of the metal plate 100 between the first semiconductor switch Q1 and the heat dissipation member 200. Furthermore, since the heat dissipation member 200 and the metal plate 100 are fastened together with a male screw 400, the degree of contact between the heat dissipation member 200 and the metal plate 100 is increased, so that heat is efficiently transferred from the metal plate 100 to the heat dissipation member 200. Therefore, the heat dissipation efficiency of the first semiconductor switch Q1 can be increased.

[0094] (2) The two female screws 150 formed on the metal plate 100 engage with the two threaded portions 410, increasing the degree of contact between the heat dissipation member 200 and the metal plate 100, thereby efficiently transferring heat from the metal plate 100 to the heat dissipation member 200. Furthermore, the presence of two female screws 150 on the metal plate 100 reduces the number of components in the drive unit 25.

[0095] (3) At least one elastic member 35 is placed between the first circuit surface 11A and the heat dissipation member 200. This allows the assembly tolerances of the first to third semiconductor switches Q1 to Q3, the metal plate 100 and the heat dissipation member 200 to the circuit board 11 to be absorbed by at least one elastic member 35.

[0096] (4) At least one elastic member 35 electrically connects the circuit board 11 to the heat dissipation member 200. As a result, when static electricity is generated on the circuit board 11, the static electricity is discharged to the heat dissipation member 200 via at least one elastic member 35. Therefore, a local voltage rise on the circuit board 11 due to static electricity can be suppressed. Consequently, electrostatic discharge damage to electronic components on the circuit board 11 can be suppressed.

[0097] (5) Since a through-hole 160 is formed in the metal plate 100, a first thermistor 27 having a second height H2 which is greater than the first height H1 can be mounted on the first circuit surface 11A.

[0098] (6) Even if the metal plate 100 does not have a through-hole 160, the first thermistor 27 having a third height H3 that is smaller than the first height H1 can be mounted on the first circuit surface 11A.

[0099] (2. Second Embodiment) <2-1. Differences from the First Embodiment> The second embodiment has the same basic configuration as the first embodiment, so the differences will be explained below. Note that the same reference numerals as in the first embodiment indicate the same components, and refer to the preceding description.

[0100] In the drive unit 25 according to the first embodiment described above, the first to sixth semiconductor switches Q1 to Q6 were mounted on the first circuit surface 11A. In contrast, the drive unit 25 according to the second embodiment differs from the first embodiment in that the high-side switches (i.e., the first to third semiconductor switches Q1 to Q3) are mounted on the first circuit surface 11A, and the low-side switches (i.e., the fourth to sixth semiconductor switches Q4 to Q6) are mounted on the second circuit surface 11B. In other words, in the second embodiment, the drive circuit 21 is mounted on two sides of the circuit board 11. Therefore, the circuit board 11 according to the second embodiment is smaller than the circuit board 11 according to the first embodiment.

[0101] Furthermore, the drive unit 25 according to the second embodiment differs from the first embodiment in that it comprises three metal parts 600, first to third printed wiring 511 to 513, and fourth to sixth printed wiring 521 to 523, and instead of two heat dissipation members 200, it comprises one heat dissipation member 200 and one heat dissipation member 500.

[0102] <2-2. Drive Unit> An embodiment of the drive unit 25 according to the second embodiment will be described with reference to Figures 6 to 10. As shown in Figure 6, the first to third semiconductor switches Q1 to Q3 are arranged in a row along the left-right direction on the first circuit surface 11A. The first to third semiconductor switches Q1 to Q3 are arranged so that the first ends 46A, 56A, and 66A are on the front side and the second ends 46B, 56B, and 66B are on the rear side.

[0103] As shown in Figure 7, the fourth to sixth semiconductor switches Q4 to Q6 are arranged in a single row along the left-right direction on the second circuit surface 11B. Each of the fourth to sixth semiconductor switches Q4 to Q6 faces the first to third semiconductor switches Q1 to Q3 via the circuit board 11. The fourth to sixth semiconductor switches Q4 to Q6 are arranged so that the second ends 76B, 86B, and 96B are on the front side and the first ends 76A, 86A, and 96A are on the rear side.

[0104] Therefore, the source terminal 43 of the first semiconductor switch Q1 faces the drain terminal 72 of the fourth semiconductor switch Q4 via the circuit board 11. The source terminal 53 of the second semiconductor switch Q2 faces the drain terminal 82 of the fifth semiconductor switch Q5 via the circuit board 11. The source terminal 63 of the third semiconductor switch Q3 faces the drain terminal 92 of the sixth semiconductor switch Q6 via the circuit board 11.

[0105] The circuit board 11 has first to third through-holes 501 to 503 that penetrate the circuit board 11. The first to third through-holes 501 to 503 are slits that extend in the left-right direction. The first to third through-holes 501 to 503 are located along the second ends 46B, 56B, 66B of the first to third semiconductor switches Q1 to Q3, and are positioned in close proximity (for example, within 10 mm of the terminals) to the source terminals 43, 53, 63 and the gate terminals 41, 51, 61. In other words, the first to third through-holes 501 to 503 are located along the first ends 76A, 86A, 96A of the fourth to sixth semiconductor switches Q4 to Q6, and are positioned in close proximity to the drain terminals 72, 82, 92.

[0106] The length of the first to third substrate through-holes 501 to 503 in the left-right direction is approximately equal to the width of the first to sixth semiconductor switches Q1 to Q6 in the left-right direction. In another embodiment, the first to third substrate through-holes 501 to 503 may have elliptical, circular, and polygonal horizontal cross-sections.

[0107] Each of the three metal components 600 is inserted into the first to third substrate through-holes 501 to 503. For convenience, Figures 6 and 7 show the state in which the metal components 600 are inserted into the first and second substrate through-holes 501 and 502, and the metal component 600 has been removed from the third substrate through-hole 503. In reality, the metal components 600 are inserted into all of the first to third substrate through-holes 501 to 503.

[0108] The metal component 600 contains or is a metal with relatively high conductivity. Examples of metals include copper, silver, gold, and aluminum. The metal component 600 is a pre-fabricated solid member. In another embodiment, at least one of the three metal components 600 may be a conductive paste that is filled into the first to third substrate through-holes 501 to 503 and cured or sintered. The conductive paste may be a metal paste, more specifically, a gold paste, silver paste, copper paste, or aluminum paste. Furthermore, in yet another embodiment, at least one of the three metal components 600 may be a solder that is filled into the first to third substrate through-holes 501 to 503 and cured.

[0109] As shown in Figure 8, the metal part 600 has a first part 610 and a second part 620. The first part 610 is rectangular parallelepiped. In the horizontal plane, the longitudinal length of the first part 610 is greater than the left-right length of the first to third substrate through holes 501 to 503. In the horizontal plane, the short-side length of the first part 610 is slightly less than, but may be the same as, or greater than, the front-back length of the first to third substrate through holes 501 to 503. The second part 620 is rectangular parallelepiped. In the horizontal plane, the second part 620 is connected to the bottom surface of the first part 610 such that the longitudinal direction of the second part 620 coincides with the longitudinal direction of the first part 610. The longitudinal length of the second part 620 is slightly less than the left-right length of the first to third substrate through holes 501 to 503. The length of the second part 620 in the short direction is slightly less than the length of the first to third substrate through holes 501 to 503 in the front-to-back direction. The height of the second part 620 is approximately equal to the thickness of the circuit board 11. The metal part 600 has a T-shaped vertical cross-section.

[0110] The three metal components 600 are each inserted into the first to third through-holes 501 to 503 of the circuit board, from the first circuit surface 11A to the second circuit surface 11B. The three first parts 610 protrude above the first circuit surface 11A, preventing the three metal components 600 from falling off the circuit board 11. The three second parts 620 are housed in the first to third through-holes 501 to 503 of the circuit board.

[0111] As shown in Figures 6 and 9, the first to third printed circuit boards 511 to 513 are positioned between the source terminals 43, 53, and 63 of the first to third semiconductor switches Q1 to Q3 and the first to third through-holes 501 to 503, respectively. In addition, the first to third printed circuit boards 511 to 513 are positioned behind the first to third through-holes 501 to 503, respectively.

[0112] The first to third printed circuit boards 511 to 513 are electrically connected to source terminals 43, 53, and 63, respectively. Specifically, the first to third printed circuit boards 511 to 513 are soldered to source terminals 43, 53, and 63, respectively. In addition, the first to third printed circuit boards 511 to 513 are electrically connected to metal component 600, respectively. Specifically, the first to third printed circuit boards 511 to 513 are soldered to the first part 610 of metal component 600, respectively. The three metal components 600 are electrically connected to the U-phase terminal 45, V-phase terminal 55, and W-phase terminal 65 by the first to third printed circuit boards 511 to 513, etc.

[0113] Solder resist 15 is applied to the first to third printed circuit boards 511 to 513 between the source terminals 43, 53, 63 and the three metal components 600. Solder resist 15 is also applied to the first to third printed circuit boards 511 to 513 on the rear side of the three metal components 600. Solder resist 15 is not applied to the underside of the first to third mounting surfaces 48, 58, 68. The gate terminals 41, 51, 61, drain terminals 42, 52, 62 and source terminals 43, 53, 63 include pins, and the lower ends of the pins are slightly higher than the first to third mounting surfaces 48, 58, 68. If solder resist 15 is applied to the underside of the first to third mounting surfaces 48, 58, 68, soldering the gate terminals 41, 51, 61, drain terminals 42, 52, 62 and source terminals 43, 53, 63 becomes difficult.

[0114] As shown in Figures 7 and 9, the fourth to sixth printed circuit boards 521 to 523 are positioned between the drain terminals 72, 82, and 92 of the fourth to sixth semiconductor switches Q4 to Q6 and the first to third substrate through-holes 501 to 503, respectively. In addition, the fourth to sixth printed circuit boards 521 to 523 are positioned behind the first to third substrate through-holes 501 to 503, respectively.

[0115] The fourth to sixth printed circuit boards 521 to 523 are electrically connected to the drain terminals 72, 82, and 92, respectively. Specifically, the fourth to sixth printed circuit boards 521 to 523 are soldered to the drain terminals 72, 82, and 92, respectively. In addition, the fourth to sixth printed circuit boards 521 to 523 are electrically connected to the metal component 600, respectively. Specifically, the fourth to sixth printed circuit boards 521 to 523 are soldered to the second part 620 of the metal component 600, respectively. The three metal components 600 are electrically connected to the U-phase terminal 45, the V-phase terminal 55, and the W-phase terminal 65 by the fourth to sixth printed circuit boards 521 to 523, etc.

[0116] Solder resist 15 is applied to the fourth to sixth printed circuit boards 521 to 523 between the drain terminals 72, 82, 92 and the three metal components 600. Solder resist 15 is also applied to the fourth to sixth printed circuit boards 521 to 523 on the rear side of the three metal components 600. Solder resist 15 is not applied to the underside of the first to third mounting surfaces 48, 58, 68. The gate terminals 41, 51, 61, drain terminals 42, 52, 62 and source terminals 43, 53, 63 include pins, and the lower ends of the pins are slightly higher than the first to third mounting surfaces 48 to 68. If solder resist 15 is applied to the underside of the first to third mounting surfaces 48, 58, 68, soldering the gate terminals 41, 51, 61, drain terminals 42, 52, 62 and source terminals 43, 53, 63 becomes difficult.

[0117] The source terminals 43, 53, and 63 of the first to third semiconductor switches Q1 to Q3 are electrically connected to the drain terminals 72, 82, and 92 of the fourth to sixth semiconductor switches Q4 to Q6, respectively, via metal component 600. Therefore, the length of the printed circuit from the source terminals 43, 53, and 63 to the drain terminals 72, 82, and 92 is minimized. This reduces the inductance component of the drive circuit 21. Consequently, surge voltages associated with the switching operation of the first to sixth semiconductor switches Q1 to Q6 are suppressed, allowing the rated voltages of the first to sixth semiconductor switches Q1 to Q6 to be reduced. This, in turn, reduces the amount of heat generated by the first to sixth semiconductor switches Q1 to Q6. Therefore, at least one of the metal plate 100 and the heat dissipation members 200 and 500 can be eliminated or reduced in size. Furthermore, the electronic components on the circuit board 11 can be miniaturized. Consequently, the drive unit 25 can be miniaturized, and costs can be reduced.

[0118] It is also possible to electrically connect the source terminals 43, 53, and 63 to the drain terminals 72, 82, and 92 using printed circuit boards and vias, without using metal component 600. However, when connecting these terminals with printed circuit boards and vias, the printed circuit boards become longer, and the inductance component of the printed circuit boards increases. Consequently, the surge voltage associated with the switching operation of the first to sixth semiconductor switches Q1 to Q6 increases.

[0119] As shown in Figure 10, similar to the first embodiment, the metal plate 100 and the heat dissipation member 200 are bonded to the high-side switch. On the other hand, the metal plate 100 and the heat dissipation member 500 are bonded to the low-side switch. The basic configuration of the heat dissipation member 500 is the same as that of the heat dissipation member 200. The differences between the heat dissipation member 500 and the heat dissipation member 200 will be described below.

[0120] The heat dissipation member 500 comprises a base 510, a plurality of fins 520, and a side wall 540. The base 510 is plate-shaped and has a longer length in the left-right direction than the base 210. The fins 520 have the same shape as the fins 220. The heat dissipation member 500 does not have a mounting portion 230. The plurality of fins 520 are connected to the base 510 so that their longitudinal direction is aligned with the front-rear direction. The plurality of fins 520 are installed side by side in the left-right direction. In another embodiment, the plurality of fins 520 may be arranged on the base 510 side by side in the front-rear direction so that their longitudinal direction is aligned with the left-right direction. In yet another embodiment, the plurality of fins 520 may have shapes other than plates, such as a corrugated shape or a pointed shape.

[0121] The side wall 540 is connected to the upper surface of the base 510. The height of the side wall 540 is approximately the same as the length from the upper surface of the base 510 to the upper end of the heat dissipation member 200. The side wall 540 surrounds the left, right, front, and rear sides of the circuit board 11, the two metal plates 100, and the heat dissipation member 200.

[0122] After the first to sixth semiconductor switches Q1 to Q6, the two metal plates 100, the heat dissipation member 200, and the heat dissipation member 500 are assembled on the circuit board 11, resin is injected into the inside of the side wall 540, and the drive unit 25 is molded with resin. The resin-molded drive unit 25 is then housed in the housing 2.

[0123] In another embodiment, the side wall 540 may be removed from the heat dissipation member 500. If the side wall 540 is removed, the drive unit 25 is held in a mold and molded with resin. The resin-molded drive unit 25 is housed in the housing 2. Alternatively, if the side wall 540 is removed, the drive unit 25 may be housed in a housing. The drive unit 25 housed in a housing is then housed in the housing 2.

[0124] <2-3. Variant Examples> In Figure 10, the first and second thermistors 27 and 29 have a second height H2, and through-holes 160 are formed in the metal plate 100. However, this can be modified as shown in the modified example of the first embodiment in Figure 5. That is, the first and second thermistors 27 and 29 may have a third height H3, and through-holes 160 may not be formed in the metal plate 100.

[0125] <2-4. Effects> The second embodiment described in detail above achieves the effects (1) to (6) of the first embodiment mentioned above.

[0126] (3. Other Embodiments) (a) In the embodiments described above, one metal plate 100 is bonded to three high-side switches and one metal plate 100 is bonded to three low-side switches, but the disclosure is not limited thereto. As shown by the dotted lines in Figures 3, 6 and 7, one metal plate 100 may be bonded to one semiconductor switch. When a different metal plate 100 is bonded to each semiconductor switch in this way, the degree of freedom in arranging the semiconductor switches is increased. That is, the three high-side switches or the three low-side switches do not have to be arranged in a row. Six semiconductor switches can be freely arranged on the first circuit surface 11A, or on the first circuit surface 11A and the second circuit surface 11B. Also, one metal plate 100 may be bonded to two semiconductor switches. Furthermore, one heat dissipation member 200 or one other heat dissipation member may be fastened to one metal plate 100 with a male screw 400. Alternatively, one heat dissipation member 200 or one other heat dissipation member may be fastened to multiple metal plates 100 with male screws 400.

[0127] (b) In each of the above embodiments, the circuit board 11 was mounted with first and second thermistors 27 and 29 having a second height H2, but another circuit component having a second height H2 may be mounted instead of the first and second thermistors 27 and 29. Also, in the modified versions of the above embodiments, the circuit board 11 was mounted with first and second thermistors 27 and 29 having a third height H3, but another circuit component having a third height H3 may be mounted instead of the first and second thermistors 27 and 29. [Explanation of symbols]

[0128] 1...Electric work machine, 11...Circuit board, 11A...First circuit surface, 11B...Second circuit surface, 20...Motor, 21...Drive circuit, 25...Drive unit, 27...First thermistor, 29...Second thermistor, 35...Elastic member, 35A...First member surface, 35B...Second member surface, 41, 51, 61, 71, 81, 91...Gate terminal, 42, 52, 62, 72, 82, 92...Drain terminal, 43, 53, 63, 73, 83, 93...Source terminal, 46, 56, 66, 76, 86, 96...First to sixth metal surfaces, 48, 58, 68, 78, 88, 98...First to 6th mounting surface, 100...metal plate, 100A...1st board surface, 100B...2nd board surface, 101~103...solder, 111~113...1st~3rd metal foil, 122...1st insulating part, 123...2nd insulating part, 150...female screw, 160...board through hole, 200, 500...heat dissipation member, 250...insertion hole, 400...male screw, 410...threaded part, 501~503...1st~3rd substrate through holes, 511~513...1st~3rd printed wiring, 521~523...4th~6th printed wiring, 600...metal component, Q1~Q6...1st~6th semiconductor switch, Q7...load switch.

Claims

1. A motor configured to receive power from a power source and be driven by it, A circuit board having a first circuit surface and a second circuit surface opposite to the first circuit surface, A semiconductor switch on the circuit board having a first metal surface and a first mounting surface, electrically connected to the power supply and the motor, wherein the first mounting surface is opposite to the first metal surface and faces the first circuit surface, A metal plate having a first plate surface joined to the first metal surface and a second plate surface opposite to the first plate surface, A heat dissipation member that is in direct or indirect contact with the second plate surface, The heat dissipation member and the metal plate are fastened together by a male screw, Electric work equipment.

2. The heat dissipation member is provided with an insertion hole through which the male screw is inserted, The metal plate is provided with a female screw that engages with the male screw. The electric work machine according to claim 1.

3. The system further comprises a conductive elastic member disposed between the first circuit surface and the heat dissipation member. The electric work machine according to claim 1 or 2.

4. The aforementioned metal plate is provided with through-holes, The first circuit surface further includes a circuit component mounted at a position opposite to the plate through-hole, The semiconductor switch has a first height in a direction perpendicular to the circuit board, The circuit component has a second height greater than the first height in the vertical direction. An electric work machine according to any one of claims 1 to 3.

5. The circuit further comprises the circuit components mounted on the first circuit surface, The semiconductor switch has a first height in a direction perpendicular to the circuit board, The circuit component has a second height that is smaller than the first height in the vertical direction. An electric work machine according to any one of claims 1 to 3.

6. A method for assembling a drive unit for driving the motor of an electric work machine, The semiconductor switch of the drive unit is mounted on the circuit board of the drive unit, wherein the semiconductor switch has a mounting surface and a metal surface opposite to the mounting surface, and the mounting surface is positioned opposite the circuit board. The first plate surface of the metal substrate is joined to the aforementioned metal surface, The heat dissipation member is brought into direct or indirect contact with the second plate surface, which is opposite to the first plate surface. The heat dissipation member and the metal plate are fastened together with screws, method.

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