Electronic device and method for assembling electronic device

Abstract

An electronic device according to an embodiment comprises a housing, a heat sink, a power substrate, and a busbar. A hole penetrating one surface is formed in the housing, and the housing has a fastening part around the hole. The housing is made of an insulating resin. A heat sink is provided so as to be partially exposed from the hole. The power substrate is disposed so as to contact the heat sink on the side thereof opposite the exposed side thereof which is exposed from the hole, and an electronic component is mounted to the power substrate. The busbar is fixed to the housing at the fastening part while in a state of contacting the electrical conduction pattern of the power substrate.

Description

Electronic device and method for assembling electronic device

[0001] The present invention relates to an electronic device and a method for assembling an electronic device.

[0002] In an electronic device through which a large current flows, such as an inverter, a heat sink is provided to dissipate heat from a power substrate on which a power element is mounted and suppress a temperature rise of the power substrate. For example, a technique is known in which a power substrate is sandwiched between a clamping component and a heat sink, and the clamping component is screwed to the heat sink (for example, Patent Document 1).

[0003] Japanese Unexamined Patent Publication No. 2021-44984

[0004] In the above technique, it is conceivable to use a bus bar for energization of the electronic device instead of a clamping component which is a dedicated product for clamping the power substrate, and screw the bus bar to the heat sink. This eliminates the need for a dedicated product for clamping the power substrate, and can reduce the number of components.

[0005] However, when screwing a bus bar to a heat sink, for example, it is necessary to provide an insulating washer for each screw hole to prevent energization between the bus bar and the heat sink via the screw. Therefore, even when screwing a bus bar to a heat sink, there is room for improvement in terms of reducing the number of components.

[0006] The present invention has been made in view of the above, and an object thereof is to reduce the number of components and suppress a temperature rise of a power substrate.

[0007] An electronic device according to one aspect of an embodiment includes a housing, a heat sink, a power substrate, and a bus bar. The housing is formed with a hole penetrating through one surface, and has a fastening portion around the hole. The housing is made of an insulating resin. The heat sink is provided such that a part thereof is exposed from the hole. The power substrate is arranged so as to be in contact with the heat sink on the opposite side to the exposed side exposed from the hole, and an electronic component is mounted thereon. The bus bar is fixed to the housing at the fastening portion in a state of being in contact with an energization pattern of the power substrate.

[0008] The electronic device according to this embodiment can sandwich the power board between a busbar and a heatsink. Furthermore, the electronic device can ensure insulation between the busbar and the heatsink by fixing the busbar to an insulating resin housing. As a result, the electronic device can maintain contact between the heatsink and the power board without using, for example, a component to ensure insulation between the busbar and the heatsink. Therefore, the electronic device can reduce the number of components and suppress the temperature rise of the power board.

[0009] Figure 1 is a perspective view of an electronic device according to an embodiment. Figure 2 is an exploded view (part 1) showing a part of the electronic device according to an embodiment. Figure 3 is a perspective view of the housing. Figure 4 is a plan view showing a part of the electronic device according to an embodiment. Figure 5 is a cross-sectional view taken along line V-V in Figure 4. Figure 6 is a cross-sectional view taken along line VI-VI in Figure 4. Figure 7 is an exploded view (part 2) showing a part of the electronic device according to an embodiment. Figure 8 is a cross-sectional view illustrating a method for fixing a busbar in an electronic device according to a comparative example.

[0010] The electronic device and the assembly method of the electronic device according to the embodiment will be described in detail below with reference to the attached drawings. However, this embodiment does not limit the present invention. The electronic device is a device through which a large current flows. For example, the electronic device is an inverter that controls the current supplied to a motor for driving a vehicle. The motor is a three-phase motor driven by three-phase alternating current obtained by converting direct current using the inverter. However, the electronic device is not limited to this.

[0011] The electronic device 1 according to the embodiment will be described with reference to Figures 1 to 7. Figure 1 is a perspective view of the electronic device 1 according to the embodiment. Figure 2 is an exploded view (part 1) showing a part of the electronic device 1 according to the embodiment. Figure 3 is a perspective view of the housing 2. Figure 4 is a plan view showing a part of the electronic device 1 according to the embodiment. Figure 5 is a cross-sectional view taken along line V-V in Figure 4. Figure 6 is a cross-sectional view taken along line VI-VI in Figure 4. Figure 7 is an exploded view (part 2) showing a part of the electronic device 1 according to the embodiment. Note that the illustration and explanation of some of the components of the electronic device 1 will be omitted.

[0012] Figure 1 and other diagrams illustrate a three-dimensional Cartesian coordinate system for clarity. In the Cartesian coordinate system, the positive Z-axis is defined as upward, and the negative Z-axis is defined as downward. The X-axis coincides with the longitudinal direction of the electronic device 1, which is perpendicular to the Z-axis. The Y-axis coincides with the short-side direction of the electronic device 1, which is perpendicular to the Z-axis.

[0013] Here, we will describe an electronic device 1 that is roughly rectangular in plan view as an example, but it is not limited to this. For example, the electronic device 1 may be roughly square in plan view.

[0014] As shown in Figure 1 or Figure 2, the electronic device 1 comprises a housing 2, a control board 3, a capacitor board 4, a power board 5, a busbar 6, and a heat sink 7.

[0015] The housing 2 is made of insulating resin. The housing 2 is formed in a box shape. As shown in Figure 3, the housing 2 comprises a first side wall portion 10, a second side wall portion 11, and a bottom portion 12. The first side wall portion 10 is formed to extend along the longitudinal direction (X-axis) of the housing 2. The second side wall portion 11 is formed to connect the ends of the two first side wall portions 10. The second side wall portion 11 is formed to extend along the short direction (Y-axis) of the housing 2. The bottom portion 12 is formed to connect the lower ends of the first side wall portions 10 and the second side wall portions 11. The housing 2 is formed so that the end opposite to the bottom portion 12 is open. That is, the housing 2 has an opening 13 at its upper end.

[0016] As shown in Figure 1, a connector 8 is attached to one of the first side walls 10. A harness for connecting the control board 3 to an external device is connected to the connector 8.

[0017] As shown in Figure 3, a hole 12a is formed in the bottom surface 12. The hole 12a is formed to penetrate through one side of the bottom surface 12. The hole 12a is formed to be rectangular in shape when viewed from above. For example, the hole 12a is formed to be approximately rectangular in shape when viewed from above.

[0018] The housing 2 comprises fastening portions 15 and wall portions 16. The fastening portions 15 are provided around the hole 12a. As shown in Figure 4, the fastening portions 15 are provided in two rows along the inner wall surface of each first side wall portion 10, extending in the longitudinal direction of the housing 2. As shown in Figure 3, the fastening portions 15 are provided outside the hole 12a.

[0019] Each row of fastening portion 15 includes a first fastening portion 18 and a second fastening portion 19. Multiple first fastening portions 18 are provided at predetermined intervals along the longitudinal direction of the housing 2. That is, the first fastening portions 18 are arranged at predetermined intervals along the longitudinal direction of the housing 2. The second fastening portions 19 are provided between the first fastening portions 18. Two second fastening portions 19 are provided for each fastening portion 15.

[0020] As shown in Figures 5 and 6, the busbar 6 is fixed to the first fastening portion 18. The first fastening portion 18 is equipped with a nut 18a. The nut 18a is made of a metal component. The nut 18a is an insert nut embedded in the first fastening portion 18. The nut 18a is embedded in the first fastening portion 18 by insert molding. The first fastening portions 18 are provided in pairs, with the hole 12a in between.

[0021] The control board 3 (see Figure 1) is fixed to the second fastening portion 19. The second fastening portion 19 is formed to extend to the vicinity of the opening 13. The second fastening portion 19 is formed to extend toward the opening 13 than the first fastening portion 18. That is, the second fastening portion 19 is provided at a higher position (above the Z axis) than the first fastening portion 18. The second fastening portion 19 is equipped with a nut 19a (see Figure 3), similar to the first fastening portion 18. The second fastening portion 19 is provided in a pair with the hole 12a, similar to the first fastening portion 18.

[0022] As shown in Figure 3, the wall portion 16 protrudes from the first fastening portion 18 on the side opposite to the bottom portion 12 of the housing 2. Specifically, the wall portion 16 is formed to extend upward from the end of the first fastening portion 18 in the longitudinal direction (X-axis) of the housing 2. Two wall portions 16 may be formed for one first fastening portion 18, or one may be formed. When two wall portions 16 are formed for one first fastening portion 18, the two wall portions 16 are formed at both ends of the first fastening portion 18 in the longitudinal direction of the housing 2. When one wall portion 16 is formed for one first fastening portion 18, the one wall portion 16 is formed at one end of the first fastening portion 18 in the longitudinal direction of the housing 2.

[0023] The wall portion 16 positions the mounting position of the busbar 6 relative to the housing 2 when the busbar 6 is fixed to the first fastening portion 18 (see Figures 5 and 6). The wall portion 16 restricts the movement of the busbar 6 in the longitudinal direction of the housing 2. The second fastening portion 19 functions as part of the wall portion 16.

[0024] As shown in Figure 1, the control board 3 is provided on the side of the opening 13 in the housing 2. A cover (not shown) is provided on the side of the opening 13 that is closer to the control board 3. Various electronic components for controlling the switches of the switching elements 5a (see Figure 7) of the power board 5 are mounted on the control board 3. Multiple holes 3a are formed in the control board 3.

[0025] As shown in Figures 5 and 6, the capacitor board 4 is located near the center of the housing 2 in the vertical direction. The capacitor board 4 is located on the bottom surface 12 side of the housing 2, relative to the control board 3 (see Figure 1). As shown in Figures 2 and 4 to 6, a plurality of smoothing capacitors 4a are mounted on the capacitor board 4. The smoothing capacitors 4a are mounted so as to protrude toward the control board 3 (see Figure 1). As shown in Figure 2, holes 4b are formed in the capacitor board 4. Multiple holes 4b are formed.

[0026] As shown in Figures 5 and 6, the power board 5 is located on the bottom surface 12 side of the housing 2, closer to the capacitor board 4. As shown in Figure 4, the power board 5 is located inside the fastening portion 15. In other words, the fastening portion 15 is located outside the power board 5. As shown in Figures 5 and 6, the power board 5 is located between a pair of first fastening portions 18 in the short direction (Y-axis) of the housing 2. Electronic components such as a switching element 5a are mounted on the main surface (mounting surface) of the power board 5, as shown in Figure 7. A current-carrying pattern 5b is formed on the main surface of the power board 5, which contacts the busbar 6 and is electrically connected to the busbar 6. The power board 5 is in contact with the heat sink 7 on its back surface, which is opposite to the main surface. For example, the back surface of the power board 5 is in contact with the heat sink 7 via an insulating member.

[0027] As shown in Figures 5 and 6, the heatsink 7 is provided on the bottom surface 12 side of the housing 2, relative to the power board 5. The heatsink 7 is provided so that a portion of it is exposed through the hole 12a in the housing 2. The heatsink 7 is made of a metal material. The heatsink 7 is made of a metal with excellent thermal conductivity. The heatsink 7 comprises a block portion 20 and fins 21.

[0028] The block portion 20 is formed to be rectangular in a plan view. The block portion 20 is located inside the fastening portion 15. The block portion 20 is located between the pair of first fastening portions 18 in the short direction (Y-axis) of the housing 2. The block portion 20 is located between the bottom surface 12 of the housing 2 and the power board 5. The block portion 20 abuts against the bottom surface 12 of the housing 2. The block portion 20 on the opposite side from the bottom surface 12 abuts against the power board 5.

[0029] The fins 21 are formed to protrude from the block portion 20. Specifically, the fins 21 are formed to protrude from the block portion 20, through the hole 12a in the housing 2, and to the outside of the housing 2. As shown in Figure 2, multiple fins 21 are formed in a row along the longitudinal direction (X-axis) of the housing 2.

[0030] As shown in Figures 2, 4, and 7, the busbar 6 includes a first busbar 25 and a second busbar 26. The first busbar 25 is made of a metal component. As shown in Figure 5, the first busbar 25 contacts and is electrically connected to the capacitor board 4 and the power board 5. The first busbar 25 has a fixing portion 30 and a contact portion 31.

[0031] The fixing portion 30 is provided on both ends of the first busbar 25 in the short direction (Y-axis) of the housing 2. The fixing portion 30 is fixed to the housing 2. Specifically, the fixing portion 30 is fixed to the first fastening portion 18 of the housing 2. A hole 30a is formed in the fixing portion 30. The hole 30a is formed to penetrate the fixing portion 30 in the vertical direction. A fixing bolt 32 is inserted into the hole 30a. The first busbar 25 is fixed to the housing 2 by fastening the fixing bolt 32 to the nut 18a of the first fastening portion 18.

[0032] The contact portion 31 is formed to protrude toward the power board 5 side from the fixing portion 30. The contact portion 31 is provided between the two fixing portions 30. The contact portion 31 contacts the energizing pattern 5b of the power board 5 (see Figure 7). Specifically, the surface (bottom surface) of the contact portion 31 on the power board 5 side contacts the energizing pattern 5b of the power board 5. The first busbar 25 is electrically connected to the power board 5 by the contact portion 31. The first busbar 25 is fixed to the housing 2 at the first fastening portion 18 while in contact with the energizing pattern 5b of the power board 5.

[0033] In the first busbar 25, the fixed portion 30 is formed at a higher position (above the Z-axis) than the contact portion 31. The first busbar 25 is provided with an inclination from the fixed portion 30 to the contact portion 31. Specifically, the first busbar 25 has inclined surfaces 25b and 25c that connect the fixed portion 30 and the contact portion 31. The inclined surfaces 25b and 25c connect the fixed portion 30 and the contact portion 31 in the short-side direction (Y-axis) of the housing 2.

[0034] The first busbar 25 connects the fixing portion 30 and the contact portion 31 by inclined surfaces 25b and 25c, thereby increasing the force that presses the contact portion 31 against the power board 5 when the first busbar 25 is fixed to the housing 2. In other words, the force that the first busbar 25 exerts on the power board 5 can be increased.

[0035] As shown in Figure 5, fixing holes 25a are formed in the first busbar 25. The fixing holes 25a are formed from the side (top surface) facing the capacitor substrate 4 toward the power substrate 5. The fixing holes 25a do not penetrate the first busbar 25. The fixing holes 25a are formed between the two fixing parts 30. Multiple fixing holes 25a are formed. For example, two fixing holes 25a are formed. The number of fixing holes 25a is not limited to this. Fixing bolts 33 are fastened to the fixing holes 25a. The capacitor substrate 4 is fixed to the first busbar 25 by inserting the fixing bolts 33 into the holes 4b of the capacitor substrate 4 and fastening the fixing bolts 33 to the fixing holes 25a.

[0036] The first busbar 25 is electrically connected to the capacitor board 4 by the surface (top surface) facing the capacitor board 4 contacting the current-carrying pattern (not shown) of the capacitor board 4.

[0037] The second busbar 26 is made of a metal component. As shown in Figure 6, the second busbar 26 is in contact with the power board 5 and electrically connected. The second busbar 26 includes a fixing portion 40 and a contact portion 41.

[0038] The fixing portion 40 is provided on both ends of the second busbar 26 in the short direction (Y-axis) on the housing 2. The fixing portion 40 is fixed to the housing 2. Specifically, the fixing portion 40 is fixed to the first fastening portion 18 of the housing 2. A hole 40a is formed in the fixing portion 40. The hole 40a is formed to penetrate the fixing portion 40 in the vertical direction. A fixing bolt 42 is inserted into the hole 40a. The second busbar 26 is fixed to the housing 2 by fastening the fixing bolt 42 to the nut 18a of the first fastening portion 18.

[0039] The contact portion 41 is formed to protrude towards the power board 5 side from the fixing portion 40. The contact portion 41 is provided between the two fixing portions 40. The contact portion 41 contacts the energizing pattern 5b (see Figure 7) of the power board 5. Specifically, the surface (bottom surface) of the contact portion 41 on the power board 5 side contacts the energizing pattern 5b of the power board 5. The second busbar 26 is electrically connected to the power board 5 by the contact portion 41. The second busbar 26 is fixed to the housing 2 at the first fastening portion 18 while in contact with the energizing pattern 5b of the power board 5.

[0040] In the second busbar 26, the fixed portion 40 is formed at a higher position (above the Z-axis) than the contact portion 41. The second busbar 26 is provided with an inclination from the fixed portion 40 to the contact portion 41. Specifically, the second busbar 26 has inclined surfaces 26a and 26b that connect the fixed portion 40 and the contact portion 41. The inclined surfaces 26a and 26b connect the fixed portion 40 and the contact portion 41 in the short-side direction (Y-axis) of the housing 2.

[0041] The second busbar 26 connects the fixing portion 40 and the contact portion 41 by inclined surfaces 26a and 26b, thereby increasing the force that presses the contact portion 41 against the power board 5 when the second busbar 26 is fixed to the housing 2. In other words, the force that the second busbar 26 exerts on the power board 5 can be increased.

[0042] Furthermore, the second busbar 26 is formed so as not to come into contact with the capacitor substrate 4. From the surface that comes into contact with the power substrate 5, the length (vertical length) of the second busbar 26 on the capacitor substrate 4 side is shorter than the corresponding length (vertical length) of the first busbar 25.

[0043] Next, the main assembly procedure for the electronic device 1 will be described. The electronic device 1 is assembled with the holes 12a of the housing 2 facing downwards.

[0044] First, the heat sink 7 is placed on the housing 2. Specifically, the heat sink 7 is accommodated in the housing 2 such that the fins 21 pass through the hole 12a of the housing 2 and protrude to the outside of the housing 2. That is, the heat sink 7 is provided such that a part thereof is exposed from the hole 12a. The block portion 20 of the heat sink 7 is in contact with the bottom surface portion 12 of the housing 2 and is supported by the bottom surface portion 12 of the housing 2.

[0045] Next, the power substrate 5 is placed on the housing 2. The power substrate 5 is placed on the upper surface of the block portion 20 of the heat sink 7. The power substrate 5 is arranged so as to be in contact with the heat sink 7 on the opposite side (upper side) to the exposed side (lower side) exposed from the hole 12a of the housing 2.

[0046] Next, the first bus bar 25 and the second bus bar 26 are fixed to the housing 2. The first bus bar 25 and the second bus bar 26 are positioned and arranged by the wall portion 16 of the housing 2. For the positioned and arranged first bus bar 25 and second bus bar 26, the contact portions 31 and 41 are in contact with the energization pattern 5b of the power substrate 5. Then, the fixing bolts 32 and 42 are inserted into the hole 30a of the first bus bar 25 or the hole 40a of the second bus bar 26. The fixing bolts 32 and 42 are fastened to the nut 18a of the first fastening portion 18. When the fixing bolts 32 and 42 are fastened to the nut 18a, the first bus bar 25 and the second bus bar 26 are fixed to the housing 2. In this way, the first bus bar 25 and the second bus bar 26 are fixed to the housing 2 at the first fastening portion 18 in a state where they are in contact with the energization pattern 5b of the power substrate 5.

[0047] By fixing the first bus bar 25 and the second bus bar 26 to the housing 2, the power substrate 5 and the block portion 20 of the heat sink 7 are clamped between the first bus bar 25, the second bus bar 26, and the bottom surface portion 12 of the housing 2. That is, the power substrate 5 and the heat sink 7 are clamped between the bus bar 6 and the housing 2. Accordingly, the power substrate 5 and the heat sink 7 are also fixed to the housing 2.

[0048] Since the bus bar 6 is fixed to the housing 2, the power substrate 5 and the heat sink 7 are fixed, so that the electronic device 1 can be easily assembled.

[0049] Since the nut 18a of the first fastening portion 18 is formed of a metal member, the electronic device 1 can improve the durability of the first fastening portion 18 when the fixing bolts 32 and 42 are fastened to the nut 18a.

[0050] For example, in the first bus bar 25, the contact portion 31 protrudes closer to the power substrate 5 side than the fixing portion 30, so the electronic device 1 allows the first bus bar 25 to be easily brought into contact with the current-carrying pattern 5b of the power substrate 5 by the contact portion 31. Further, in the electronic device 1, for example, when the fixing portion 30 of the first bus bar 25 is fixed to the housing 2, the power substrate 5 and the heat sink 7 are clamped between the contact portion 31 of the first bus bar 25 and the housing 2. Therefore, the electronic device 1 can maintain the contact portion 31 in contact with the current-carrying pattern 5b of the power substrate 5.

[0051] Since the bus bar 6 can be positioned by the wall portion 16 of the housing 2, in the electronic device 1, the attachment of the bus bar 6 to the first fastening portion 18 is facilitated.

[0052] Next, the capacitor substrate 4 is fixed to the first bus bar 25. The capacitor substrate 4 is placed on the upper surface of the first bus bar 25. A fixing bolt 33 is inserted into the hole 4b of the capacitor substrate 4. The fixing bolt 33 is fastened to the fixing hole 25a of the first bus bar 25. When the fixing bolt 33 is fastened to the fixing hole 25a of the first bus bar 25, the capacitor substrate 4 is fixed to the first bus bar 25. Note that the first bus bar 25 may be fixed to the housing 2 in a state where the capacitor substrate 4 is fixed to the first bus bar 25.

[0053] Next, the control substrate 3 is fixed to the housing 2. The control substrate 3 is placed on the second fastening portion 19. A fixing bolt (not shown) is inserted into the hole 3a of the control substrate 3. The fixing bolt is fastened to the nut 19a of the second fastening portion 19. When the fixing bolt is fastened to the nut 19a, the control substrate 3 is fixed to the housing 2.

[0054] In the electronic device 1, in each row of fastening parts 15, first fastening parts 18 and second fastening parts 19, which have different heights (positions in the Z-axis direction), are provided side by side in the longitudinal direction of the housing 2. Therefore, the electronic device 1 can align the positions of one row of first fastening parts 18 and second fastening parts 19 in the short direction of the housing 2. As a result, the length of the housing 2 in the short direction of the electronic device 1 can be shortened.

[0055] In the electronic device 1, the heat generated by the power board 5 is transferred to the heat sink 7, which is in contact with the power board 5. The heat transferred to the heat sink 7 is then dissipated through the fins 21. As a result, the temperature rise of the power board 5 is suppressed in the electronic device 1.

[0056] In the comparative example electronic device 100, for example, as shown in Figure 8, the busbar 101 is fixed to the heat sink 103 by bolts 102. In the comparative example electronic device 100, the power board 104 is sandwiched between the busbar 101 and the heat sink 103, thereby fixing the power board 104. Figure 8 is a cross-sectional view illustrating the method of fixing the busbar 101 in the comparative example electronic device 100.

[0057] In the comparative example electronic device 100, a hole 104a for passing a bolt 102 is formed in the power substrate 104. Also in the comparative example electronic device 100, a fixing hole 103a for fastening the bolt 102 is formed in the heat sink 103. In the comparative example electronic device 100, the contact area between the power substrate 104 and the heat sink 103 decreases in proportion to the number of holes 104a and fixing holes 103a.

[0058] In contrast, in the electronic device 1 according to this embodiment, the busbar 6 is fixed to the housing 2 at a first fastening portion 18. Specifically, the busbar 6 is fastened to the housing 2 at a first fastening portion 18 located outside the power board 5. By fixing the busbar 6 to the housing 2, the power board 5 and the heat sink 7 are sandwiched between the busbar 6 and the housing 2. As a result, the power board 5 and the heat sink 7 are fixed to the housing 2.

[0059] The electronic device 1 can fix the power board 5 to the housing 2 without forming holes in the power board 5 for fixing the power board 5. Furthermore, the electronic device 1 can fix the power board 5 to the housing 2 without forming fixing holes in the heat sink 7 for fixing the power board 5. Therefore, the electronic device 1 can increase the contact area between the power board 5 and the heat sink 7, thereby increasing the amount of heat transferred from the power board 5 to the heat sink 7. Consequently, the electronic device 1 can suppress the temperature rise of the power board 5. For example, the temperature rise of the inverter that outputs to the motor can be suppressed. Additionally, the electronic device 1 can suppress the temperature rise of the power board 5 by using a smaller power board 5 and a smaller heat sink 7. Therefore, the electronic device 1 can reduce the cost of the heat sink 7, for example, and thus reduce the cost of the electronic device 1. Furthermore, since the electronic device 1 does not require the work of forming fixing holes in the heat sink 7, the processing cost of the heat sink 7 can be reduced.

[0060] Furthermore, in the comparative example electronic device 100 shown in Figure 8, it is necessary to prevent short circuits by electrically connecting the busbar 101 and the heat sink 103 with bolts 102. In the comparative example electronic device 100, the bolts 102 are inserted into the holes 101a of the busbar 101 via insulating resin washers 105. Since insulating resin washers 105 are required in proportion to the number of holes 101a in the busbar 101 into which the bolts 102 are inserted, the comparative example electronic device 1 has a larger number of parts.

[0061] In contrast, in the electronic device 1 according to this embodiment, the busbar 6 is fixed to the insulating housing 2, so that insulation between the busbar 6 and the heat sink 7 can be ensured. That is, the electronic device 1 can maintain insulation between the busbar 6 and the heat sink 7 without using other members (for example, insulating resin washers 105) to ensure insulation between the busbar 6 and the heat sink 7. Therefore, the electronic device 1 can maintain contact between the heat sink 7 and the power board 5 without using other members to ensure insulation between the busbar 6 and the heat sink 7. Consequently, the electronic device 1 can reduce the number of parts and suppress the temperature rise of the power board 5. Furthermore, the electronic device 1 does not need to use a metal housing 2, thus reducing the cost of the housing 2.

[0062] As an addendum, the features of the present invention are as follows: <Addendum> (1) An electronic device comprising: a housing of insulating resin having a hole formed through one surface and fastening portion around the hole; a heat sink provided such that a portion is exposed from the hole; a power board on which electronic components are mounted, arranged to contact the heat sink on the side opposite to the exposed side exposed from the hole; and a bus bar fixed to the housing at the fastening portion while in contact with the current-carrying pattern of the power board. (2) The electronic device according to (1), wherein the fastening portion comprises a nut made of a metal member, and the bus bar is fixed to the housing by fastening a bolt to the nut. (3) The electronic device according to (1) or (2), wherein the bus bar comprises a contact portion that contacts the current-carrying pattern and a fixing portion that is fixed to the housing, and the contact portion protrudes toward the power board side than the fixing portion. (4) The fixing portion is formed at a higher position than the contact portion, and the busbar is inclined from the fixing portion to the contact portion, as described in (3). (5) The housing has a wall portion that protrudes from the fastening portion to the side opposite to the one side, and the wall portion positions the mounting position of the busbar to the housing, as described in any one of (1) to (4). (6) The power board and the heat sink are sandwiched between the busbar and the housing, as described in any one of (1) to (5). (7) The fastening portion is provided outside the power board, as described in any one of (1) to (6). (8) The electronic device according to any one of (1) to (7), wherein the fastening portion is provided in two rows extending in the longitudinal direction of the housing, and one row of fastening portions has a first fastening portion to which the busbar is fixed, and a second fastening portion provided at a higher position than the first fastening portion to which the control board is fixed. (9) The electronic device according to any one of (1) to (8), wherein the electronic device is configured as an inverter that provides output to a motor.(10) A method for assembling an electronic device, comprising: an insulating resin housing having a hole that penetrates one surface and fastening parts around the hole; a heat sink provided such that a portion of it is exposed from the hole; a power board on which electronic components are mounted being positioned so as to be in contact with the heat sink on the side opposite to the exposed side that is exposed from the hole; and a busbar being fixed to the housing at the fastening parts while in contact with the energizing pattern of the power board.

[0063] Further effects and modifications can be readily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and their equivalents.

[0064] 1 Electronic device 2 Housing 4 Capacitor board 5 Power board 5b Conductive pattern 6 Busbar 7 Heat sink 12 Bottom surface (one side) 12a Hole 15 Fastening part 16 Wall part 18 First fastening part 18a Nut 19 Second fastening part 19a Nut 25 First busbar 26 Second busbar 30, 40 Fixing parts 31, 41 Contact parts 32, 42 Fixing bolts

Claims

1. An electronic device comprising: a housing made of insulating resin having a hole that penetrates one surface and fastening portions around the hole; a heat sink provided so as to be partially exposed from the hole; a power board on which electronic components are mounted, positioned to be in contact with the heat sink on the side opposite to the exposed side that is exposed from the hole; and a bus bar fixed to the housing at the fastening portion while in contact with the energizing pattern of the power board.

2. The electronic device according to claim 1, wherein the fastening portion comprises a nut made of a metal member, and the busbar is fixed to the housing by fastening a bolt to the nut.

3. The electronic device according to claim 1, wherein the busbar comprises a contact portion that contacts the energizing pattern and a fixed portion that is fixed to the housing, and the contact portion protrudes toward the power board side from the fixed portion.

4. The electronic device according to claim 3, wherein the fixing portion is formed at a higher position than the contact portion, and the busbar is inclined from the fixing portion to the contact portion.

5. The electronic device according to claim 1, wherein the housing includes a wall portion that protrudes from the fastening portion toward the opposite side from the one side, and the wall portion positions the mounting position of the busbar relative to the housing.

6. The electronic device according to claim 1, wherein the power board and the heat sink are sandwiched between the busbar and the housing.

7. The electronic device according to claim 1, wherein the fastening portion is provided outside the power substrate.

8. The electronic device according to claim 1, wherein the fastening portions are provided in two rows extending in the longitudinal direction of the housing, and each row of fastening portions includes a first fastening portion to which the busbar is fixed, and a second fastening portion provided at a higher position than the first fastening portion to which the control board is fixed.

9. The electronic device according to claim 1, wherein the electronic device is configured as an inverter that provides output to a motor.

10. A method for assembling an electronic device, comprising: a housing made of insulating resin having a hole that penetrates one surface and fastening parts around the hole; a heat sink provided such that a portion of it is exposed from the hole; a power board on which electronic components are mounted being positioned so as to be in contact with the heat sink on the side opposite to the exposed side that is exposed from the hole; and a busbar being fixed to the housing at the fastening parts while in contact with the energizing pattern of the power board.

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