Electronic device

Abstract

To improve the vibration resistance of electrolytic capacitors 28 and 29 by applying a moisture-proof coating agent while preventing the moisture-proof coating agent from adhering to an application-prohibited area N1.SOLUTION: Three electrolytic capacitors 29A, 29B, 29C of one system are lined up in a line along the center line M of a circuit board 3, and similarly, three electrolytic capacitors 29A, 29B, 29C of the other system are lined up in a line. A moisture-proof coating agent is sprayed with a spray gun on a coating area C4 between the two rows. By applying the moisture-proof coating agent, the electrolytic capacitors 29A, 29B, and 29C are fixed to the substrate surface, and vibration resistance is improved. Since the electrolytic capacitors 29A, 29B, and 29C are lined up in a wall shape, adhesion of the moisture-proof coating agent to the coating-prohibited area N1 is suppressed.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an electronic device in which an electronic component including a chip component having a low protrusion height from the substrate surface and a tall component having a higher protrusion height from the substrate surface than the chip component is mounted on a circuit board.

Background Art

[0002] In order to prevent moisture from entering a circuit board disposed in a housing of an electronic device, a moisture-proof coating agent may be applied to the circuit board. Patent Document 1 discloses a configuration in which the moisture-proof coating agent is applied over the entire circumference of the base of an electrolytic capacitor mounted in a standing state on the substrate surface, thereby suppressing vibration of the electrolytic capacitor on the substrate surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The moisture-proof coating agent is generally applied by spraying it onto the substrate. However, if it is applied around the entire circumference of the base of the electrolytic capacitor as in Patent Document 1, the working time becomes long, which is not preferable. In particular, when a plurality of electrolytic capacitors are provided on the circuit board, it is necessary to perform a spraying operation around the entire circumference of each, resulting in a long working time.

Means for Solving the Problems

[0005] One aspect of the present invention is an electronic device in which a circuit board on which an electronic component including a chip component having a low protrusion height from the substrate surface and a tall component having a higher protrusion height from the substrate surface than the chip component is mounted is housed in a housing. A plurality of tall components are arranged in a row. On one side of this component row, a moisture-proof coating agent is sprayed onto the coating area extending from the substrate surface to the base of the tall component.

Effect of the Invention

[0006] According to the configuration of the present invention, it is possible to collectively apply a moisture-proof coating agent to a plurality of tall components on one side of a component row formed by the plurality of tall components, and it is possible to efficiently improve the vibration resistance of the tall components.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0008] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0009] First, the overall configuration of an electronic device according to an embodiment of the present invention will be briefly described. In one embodiment, the present invention is applied to an electric actuator device 101 of an electric power steering device of an automobile shown in FIG. 1. Note that the basic configuration of this electric actuator device 101 is disclosed in, for example, Japanese Patent Application Laid-Open No. 2020-148639, so only the minimum necessary description will be given here.

[0010] FIG. 1 is an exploded perspective view of an electric actuator device 101 that provides a steering assist force to a steering mechanism (not shown) in an electric power steering device. This electric actuator device 101 includes a cylindrical motor unit 1, an inverter - power module 2, a circuit board 3 composed of a multilayer circuit board bent in a substantially U - shape, a connector member 4 in which a plurality of connectors are integrally assembled, and a motor cover 5 attached to one end of the motor unit 1 so as to cover the inverter - power module 2, the circuit board 3, and the connector member 4.

[0011] The motor unit 1 houses a three - phase AC motor inside a cylindrical housing 7. The tip of the rotating shaft 6 protruding from the tip surface of the housing 7 has a connecting portion 6a such as a gear or a spline, and is connected to the steering mechanism via this connecting portion 6a. The motor is a three - phase permanent - magnet brushless motor, with the stator having three - phase coils and permanent magnets arranged on the outer peripheral surface of the rotor. Also, the motor is provided with two sets of coils and corresponding permanent magnets in order to provide redundancy.

[0012] One end of the housing 7 on the side opposite to the connecting portion 6a is configured as a bottom wall portion 7a having a horseshoe - shaped contour with a part of the outer peripheral edge extending in the radial direction. A motor cover 5 having a horseshoe - shaped contour corresponding to the bottom wall portion 7a is attached so as to cover the bottom wall portion 7a. And, the inverter - power module 2, the circuit board 3, and the connector member 4 are accommodated in an overlapping manner in the axial direction of the rotating shaft 6 in the space formed between the bottom wall portion 7a and the motor cover 5. Here, both ends of each coil of the motor penetrate the bottom wall portion 7a as coil terminal portions 9 and protrude toward the motor cover 5 side, and are respectively connected to the corresponding terminals of the inverter - power module 2 by TIG welding or the like.

[0013] The inverter power module 2 includes two inverter modules 2A for driving the motor and a relay module 2B serving as the neutral point relay of the coil, and these three components are arranged in a substantially U-shape surrounding the rotating shaft 6. And these inverter modules 2A and relay module 2B are fixed to the end face of the motor unit 1 via a pressing member 2C. Also, these inverter modules 2A and relay module 2B are provided with a plurality of pin-shaped terminals 10. These terminals 10 extend toward the circuit board 3 along the axial direction of the rotating shaft 6, penetrate through the through holes 11 of the circuit board 3, and are conductively connected to the wiring of the circuit board 3 by individual soldering.

[0014] The connector member 4 includes three connectors that point in the same direction along the axial direction of the rotating shaft 6. Specifically, a power supply connector 4a located in the center, a sensor input connector 4b to which signals from sensors (such as a steering angle sensor and a torque sensor) arranged on the steering mechanism side are input, and a communication connector 4c for performing communication (such as CAN communication) with other control devices in the vehicle. These connectors 4a, 4b, 4c protrude to the outside through the opening 8 of the motor cover 5.

[0015] The circuit board 3 is composed of a multilayer printed wiring board, for example, a so-called 8-layer printed wiring board having 8 metal foil layers (such as copper foil layers). This multilayer printed wiring board is formed by laminating several base materials made of, for example, glass epoxy with metal foil layers on one or both sides via a prepreg (adhesive layer) and then integrating them by heating and pressing. And a desired circuit pattern is formed by etching each metal foil layer and forming vias extending in the lamination direction.

[0016] The circuit board 3 is arranged between the bottom wall portion 7a of the housing 7 and the connector member 4 in a shape bent into a substantially U-shape. The circuit board 3 is fixed to the housing 7 via four screws 12. Also, the connector member 4 is fixed to the circuit board 3 via four screws 13.

[0017] Figure 2 shows the circuit board 3 in a deployed state. The circuit board 3 includes a first rigid portion 21 which is a power system board on which an electronic component group through which a relatively large current flows for driving a motor via an inverter power module 2 is mounted, a second rigid portion 22 which is a control system board on which control system electronic components through which a relatively small current flows are mounted, and a flexible portion 23 with the number of base material layers between the two reduced. The circuit board 3 is housed between a housing 7 serving as a casing and a motor cover 5 in a state where the flexible portion 23 is bent and deformed such that the first rigid portion 21 and the second rigid portion 22 overlap each other in the axial direction of the rotation shaft 6. The first rigid portion 21 and the second rigid portion 22 in a bent state are separated from each other by a distance such that the electronic components mounted on each do not contact each other, and are supported in a state of being parallel to each other while maintaining a planar state.

[0018] As shown in Figure 2, a large number of electronic components arranged on the circuit board 3 are surface-mounted by reflow soldering mainly on the first surface 3A of the circuit board 3 which is on the inner side in the bent state. That is, land portions for connecting each electronic component are formed on the metal foil layer on the surface layer of the circuit board 3 made of a multilayer printed circuit board. After applying a solder resist, cream solder is printed on these land portions by a printing technique using masking. Then, after mounting the electronic components at predetermined positions respectively, the circuit board 3 is heated in a furnace to melt the solder, thereby performing soldering. Although some electronic components are mounted on the second surface on the opposite side to the first surface 3A, these are also reflow soldered simultaneously.

[0019] Here, as the electronic components mounted on the circuit board 3, it includes chip components with a low protrusion height from the substrate surface and high-profile components with a higher protrusion height from the substrate surface than the chip components. The chip components are represented by the CPU 25, MOS-FET 26, or rotation sensor 27, and are components having a flat resin package. The high-profile components are components with a relatively large protrusion height from the substrate surface with respect to the dimensions of the mounting surface (the length of one side if rectangular, the diameter if circular) (that is, the ratio of the two is greater than 1), as represented by the electrolytic capacitors 28 and 29. The electrolytic capacitor 28 is combined with a coil 30 having a rectangular case to form a filter section. The electrolytic capacitor 29 includes three electrolytic capacitors 29A, 29B, and 29C corresponding to the three phases of U, V, and W as a power supply capacitor section. Note that although the coil 30 of the filter section is a relatively large component, it has a flat shape and a lower protrusion height than the electrolytic capacitors 28 and 29, so the vibration resistance is not particularly problematic, and thus it is not classified as a high-profile component.

[0020] As described above, the motor is provided with two sets of coils and corresponding permanent magnets in order to provide redundancy. Correspondingly, the control and drive circuit for driving the motor also includes two sets of circuits so as to have redundancy. On the circuit board 3, the component parts and wiring patterns of each set are arranged in a paired form so as to be substantially symmetric with respect to the center line M along the longitudinal direction of the circuit board 3 shown in FIG. 2 so that the two sets of circuits have the same characteristics. Therefore, the entire circuit board 3 is provided with a total of six electrolytic capacitors 29, which are two filter sections (coil 30 and electrolytic capacitor 28) and an electrolytic capacitor section.

[0021] The electrolytic capacitors 28 and 29 are so-called aluminum electrolytic capacitors. As illustrated in FIG. 5, they include a capacitor body 31 having a cylindrical aluminum case, and a synthetic resin pedestal 32 attached to one end of the capacitor body 31 for surface mounting. The pedestal 32 includes a plate-shaped seating portion 32a having a rectangular bottom surface, and a total of four support pieces 32b provided at each of the four corners of the seating portion 32a. A cylindrical capacitor body 31 is fitted inside the four support pieces 32b, and the capacitor body 31 is supported in an upright state. A pair of terminals (not shown) are led out from the lower part of the pedestal 32, and the electrolytic capacitors 28 and 29 are mounted on the circuit board 3 by soldering the pair of terminals to the land portions of the circuit board 3.

[0022] As shown in FIG. 2, the three electrolytic capacitors 29A, 29B, and 29C in each power capacitor section of each system are arranged in a row along the center line M. The gaps between two adjacent electrolytic capacitors 29 (that is, between the electrolytic capacitor 29A and the electrolytic capacitor 29B, and between the electrolytic capacitor 29B and the electrolytic capacitor 29C) are set to be sufficiently small. And the three electrolytic capacitors 29A, 29B, and 29C of one system and the three electrolytic capacitors 29A, 29B, and 29C of the other system are symmetrically arranged so as to face each other with the center line M interposed therebetween. In other words, the six electrolytic capacitors 29 are arranged in two rows. There are no other electronic components (such as chip components) between the two electrolytic capacitors 29 facing each other across the center line M. Also, the interval between the two electrolytic capacitors 29 facing each other across the center line M is the largest between the two electrolytic capacitors 29A located at the longitudinal ends of the circuit board 3, and gradually decreases in the order of the electrolytic capacitor 29B and the electrolytic capacitor 29C. However, all of them are relatively small. For example, there is only a space about the size of one electrolytic capacitor 29 between the two electrolytic capacitors 29A.

[0023] Regarding the electrolytic capacitor 28 in the filter section, one electrolytic capacitor 28 of one system and the electrolytic capacitor 28 of the other system are symmetrically arranged with the center line M in between. Therefore, the two electrolytic capacitors 28 are arranged side by side in a row in the direction orthogonal to the center line M. Each of these electrolytic capacitors 28 is arranged between the coil 30 and the MOS-FET 26, respectively.

[0024] Figure 3 is an explanatory diagram showing the area where the moisture-proof coating agent is applied to the circuit board 3 shown in Figure 2 with hatching. Here, only the first rigid part 21, which is the main part, is shown. In the illustrated example, the application of the moisture-proof coating agent is carried out in the unfolded state before the circuit board 3 is assembled into the housing 7. The areas where the moisture-proof coating agent is applied are roughly classified into areas C1, C2, C3, and C4, for example. Further, Figure 3 also shows, with cross-hatching, the areas where the adhesion of the moisture-proof coating agent is not preferable (referred to as coating prohibited areas). This coating prohibited area mainly corresponds to the locations that require soldering in subsequent processes and the locations that require electrical conduction by contact, etc. In the illustrated example, the circumferences of the through holes 11 corresponding to the plurality of terminals 10 of the inverter module 2A and the relay module 2B (indicated by reference numerals N1 and N2) and the circumferences of the mounting holes through which the screws 12 and 13 for mounting the circuit board 3, which are part of the ground wiring, pass (indicated by reference numeral N3) are coating prohibited areas. Also, the entire flexible part 23 is a coating prohibited area (indicated by reference numeral N4).

[0025] Among the coating areas C1, C2, C3, and C4 of the moisture-proof coating agent, area C1 (not shown) is widely provided in the second rigid part 22 so as to cover the CPU 25 and other small components in the second rigid part 22. Area C2 is provided in a relatively small range that covers the rotation sensor 27 at the center of the first rigid part 21. These areas C1 and C2 are not intended for the vibration resistance of the tall components, but are provided for moisture-proofing and component protection, which are the original purposes of the moisture-proof coating agent. In contrast, the moisture-proof coating agents in the coating areas C3 and C4 are provided for the purpose of fixing (improving vibration resistance) the electrolytic capacitors 28 and 29, which are tall components, in addition to moisture-proofing.

[0026] The coating region C3 is formed by spraying a moisture-proof coating agent from the substrate surface to the base of the electrolytic capacitors 28 over a range on one side of the column of these electrolytic capacitors 28 with respect to two electrolytic capacitors 28 arranged in a row in a direction orthogonal to the center line M. As shown in FIG. 3, it is provided in a range that partially covers the MOS-FET 26 and small components near the flexible portion 23.

[0027] By applying the moisture-proof coating agent in this way on one side of the column of the electrolytic capacitors 28, at least one side of the rectangular pedestal 32 will be firmly fixed to the circuit board 3 via the moisture-proof coating agent, and the vibration resistance of the electrolytic capacitor 28, which is a tall component, will be improved. The application in this coating region C3 can be performed once using a spray gun, and since two electrolytic capacitors 28 can be processed together with a linear application, the working efficiency is high. Also, since the moisture-proof coating agent does not exist on the entire circumference of the pedestal 32 and at least a part of the sides remain exposed, a gas release path for the explosion prevention of the electrolytic capacitor 28 is ensured. That is, the moisture-proof coating agent is sprayed along one side of the rectangular bottom surface of the pedestal 32, and the moisture-proof coating agent does not adhere to the side opposite to this side.

[0028] The coating region C4 is provided in the region sandwiched between the two columns of component rows for a total of six electrolytic capacitors 29A, 29B, 29C arranged in two rows. The entire region between the two columns of component rows is the coating region C4. Therefore, for the three electrolytic capacitors 29A, 29B, 29C in one row, the moisture-proof coating agent is sprayed over a range from the substrate surface to the base of the electrolytic capacitors 29A, 29B, 29C on one side of the component row, and similarly, for the three electrolytic capacitors 29A, 29B, 29C in the other row, the moisture-proof coating agent is sprayed over a range from the substrate surface to the base of the electrolytic capacitors 29A, 29B, 29C on one side of the component row.

[0029] For example, as shown in FIG. 4, a single spray gun 35 is arranged between the columns of two rows of electrolytic capacitors 29A, 29B, 29C, and while moving the spray gun 35 parallel to the center line M, it is applied in a strip shape to form a coating region C4. Therefore, the application work of the moisture-proof coating agent to the six electrolytic capacitors 29A, 29B, 29C can be easily performed collectively.

[0030] Here, although a coating prohibited region N1 is located on the side opposite to the coating region C4 across the columns of three electrolytic capacitors 29A, 29B, 29C each, since the three electrolytic capacitors 29A, 29B, 29C are continuously arranged so as to form a wall shape, during the coating operation by the spray gun 35, the droplets of the moisture-proof coating agent are blocked by the electrolytic capacitors 29A, 29B, 29C, and the moisture-proof coating agent does not adhere to the coating prohibited region N1. In other words, by applying the moisture-proof coating agent to the side opposite to the coating prohibited region across the columns of the electrolytic capacitors 29A, 29B, 29C, the unintended adhesion of the moisture-proof coating agent in the coating prohibited region can be avoided.

[0031] By applying the moisture-proof coating agent to one side of the columns of the electrolytic capacitors 29A, 29B, 29C in this way, at least one side of the rectangular pedestal 32 is firmly fixed to the circuit board 3 via the moisture-proof coating agent, and the vibration resistance of the electrolytic capacitors 29A, 29B, 29C, which are tall components, is improved. The coating in this coating region C4 can be performed once using the spray gun 35, and the six electrolytic capacitors 29 can be collectively processed by a linear coating, so the working efficiency is high. Also, since the moisture-proof coating agent does not exist on the entire circumference of the pedestal 32 and at least a part of the sides remain exposed, a gas release path for the explosion prevention of the electrolytic capacitor 29 is ensured. That is, the moisture-proof coating agent is sprayed along one side of the rectangular bottom surface of the pedestal 32, and the moisture-proof coating agent does not adhere to the side opposite to this side.

[0032] FIG. 5 is a perspective view showing electrolytic capacitors 28 and 29 to which a moisture-proof coating agent is sprayed from one side of a component row. The moisture-proof coating agent adheres to one side of the electrolytic capacitors 28 and 29, and a moisture-proof coating agent layer 37 is formed to cover the boundary between the pedestal 32 and the substrate surface along one side of the rectangular pedestal 32. Similarly, a moisture-proof coating agent layer 38 is also formed at the contact portion between the pedestal 32 and the capacitor body 31. That is, the contact portion between the pedestal 32 and the capacitor body 31 is also included in the coating regions C3 and C4. Therefore, when the moisture-proof coating agent is applied, the pedestal 32 is firmly supported by the circuit board 3, and at the same time, the capacitor body 31 is firmly supported by the pedestal 32, so that vibrations of the electrolytic capacitors 28 and 29 due to vibration input during vehicle travel, for example, are suppressed.

[0033] As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, the electrolytic capacitors 28 and 29 provided with the pedestal 32 as the tall component are described as an example. However, the present invention is applicable to tall components other than electrolytic capacitors and electrolytic capacitors not provided with the pedestal 32. Further, an electronic device other than the electric actuator device 101 may be used. Also, the moisture-proof coating agent may be applied after the circuit board is attached to the housing.

Description of Reference Numerals

[0034] 3... Circuit board, 7... Housing, 28, 29... Electrolytic capacitors, 31... Capacitor body, 32... Pedestal, 35... Spray gun, C3, C4... Coating regions, N1, N2, N3... Coating prohibited regions.

Claims

1. In an electronic device in which a circuit board on which an electronic component including a chip component having a low protrusion height from the substrate surface and a tall component having a higher protrusion height from the substrate surface than the chip component is mounted is housed in a housing, a plurality of tall components are arranged in a row, and a moisture-proof coating agent is sprayed on a coating area extending from the substrate surface to the base of the tall component on one side of this component row. The electronic device.

2. The tall component is an electrolytic capacitor mounted in a standing state on the substrate surface. The electronic device according to Claim 1.

3. The electrolytic capacitor is composed of a cylindrical capacitor body and a synthetic resin pedestal having a rectangular bottom surface, and at least a part of the contact portion between the capacitor body and the pedestal is included in the coating area. The electronic device according to Claim 2.

4. The moisture-proof coating agent is sprayed along one side of the rectangular bottom surface of the pedestal, and the moisture-proof coating agent does not adhere to the side opposite to this side. The electronic device according to Claim 3.

5. On the substrate surface on the side opposite to the coating area across the row of the tall components, there is an area where it is not preferable for the moisture-proof coating agent to adhere. The electronic device according to any one of Claims 1 to 4.

6. It includes two rows of component rows in which a plurality of tall components form rows respectively, and the coating area is located between these two rows of component rows. The electronic device according to any one of Claims 1 to 5.

7. The moisture-proof coating agent is sprayed on the entire area sandwiched between the two rows of component rows. The electronic device according to Claim 6.

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