JP4089300B2 - Substrate storage box - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a board housing box that houses a circuit board in a box body provided with a heat radiating section, and in particular, efficiently transfers heat generated in the circuit board to the heat radiating section.
[0002]
[Prior art]
Conventionally, various control circuit boards are housed in a board housing box in order to ensure waterproofness and dustproofness in addition to protecting the board itself. Further, when the heat generation amount of the circuit board to be accommodated is large, in order to prevent the occurrence of trouble due to heat, a heat radiation part is provided in the board housing box so that the generated heat is radiated to the outside. Such a substrate storage box is used in various places, and in particular, it is often mounted on a vehicle and used for controlling various electrical components of the vehicle.
[0003]
FIG. 7 is a cross-sectional view of a conventional substrate storage box 1. The board housing box 1 is used for controlling an electric power steering device of a vehicle, and a power circuit board 4 for controlling power supply and a control circuit board 5 for controlling various signals are provided in the box body 2 at intervals. They are housed in a stacked state, and the cover 8 covers the opening of the box body 2.
[0004]
The box body 2 is provided with a heat sink 3 made of aluminum at the bottom of a synthetic resin peripheral wall 2a formed by insert molding and a mounting portion 2b for the control circuit board 5 protruding from the peripheral wall 2a. In the power circuit board 4, a power circuit conductor 4b is formed on a ceramic substrate portion 4a, and a power semiconductor 4c such as a power transistor for power control that generates a large amount of heat is mounted. On the other hand, the control circuit board 5 is also formed with a control circuit conductor 5b on the board portion 5a and mounted with a control semiconductor 5c and the like.
[0005]
The power circuit board 4 is fixed with the synthetic adhesive 6 in a state where it is placed on the heat sink 3, and the generated heat is transmitted to the heat sink 3 to be radiated from the heat sink 3 to the outside. On the other hand, the control circuit board 5 is fixed to the mounting portion 2 a spaced from the power circuit board 4 with the synthetic adhesive 6 so as not to be affected by the heat generated in the power circuit board 4. In addition, the power circuit board 4 and the control circuit board 5 are connected to both the boards 4 and 5 by connecting the relay line 7 with a connector.
[0006]
[Problems to be solved by the invention]
In the substrate storage box 1, the heat of the power circuit board 4 is radiated from the heat sink 3, but the synthetic adhesive 6 is interposed between the power circuit board 4 and the heat sink 3. The synthetic adhesive 6 is necessary for fixing the power circuit board 4 to the heat sink 3, but since a resin component or the like is included, the heat generated in the power circuit board 4 is hindered from being transmitted to the heat sink 3, and the heat radiation efficiency is reduced. There is a problem to do.
[0007]
For such a problem, it can be assumed that a screw hole is provided in the heat sink 3 and the power circuit board 4 is fixed to the heat sink 3 with bolts. However, in such a screw fixing structure, it is necessary to form a screw hole in the heat sink 3 having a complicated shape, and a crack is generated in the board portion 4a of the ceramic power circuit board 4 by a fastening force by screwing. Such a fixing structure is not preferable.
[0008]
On the other hand, in the substrate storage box 1 shown in FIG. 7, the power circuit board 4 and the control circuit board 5 are connected by the relay line 7 to form a required circuit. A connector or the like must be provided on the board 4 and the control circuit board 5, which increases the costs associated with the boards 4 and 5 and also requires a troublesome connection to the relay line 7.
[0009]
The present invention has been made in view of such problems, and an object of the present invention is to provide a board housing box that can efficiently dissipate heat generated in a circuit board such as a power circuit board from a heat sink.
It is another object of the present invention to provide a substrate housing box that securely fixes a circuit board such as a power circuit board to a heat sink with a configuration that does not cause problems such as cracks in the board portion.
Furthermore, an object of the present invention is to provide a board storage box that reduces the labor involved in connecting circuits between a plurality of circuit boards to be stored.
[0010]
[Means for Solving the Problems]
A substrate housing box according to a first aspect of the present invention is a substrate housing box in which a circuit board is placed on the heat radiating portion and housed in a box body provided with a heat radiating portion, and the first circuit board placed on the heat radiating portion. And projecting from the peripheral wall of the box body in parallel to the first circuit board, and a mounting portion in which a through screw hole is formed, and the mounting portion is mounted on the mounting portion, In a state where the second circuit board is formed with a through hole communicating with the through screw hole and the second circuit board is fixed to the mounting portion by screwing with the through screw hole through the through hole. The tip portion includes a pressing screw that presses the first circuit board against the heat radiating portion.
[0011]
In the first invention, the first circuit board is pressed without using the synthetic adhesive because the first circuit board is pressed against the heat radiating part by using a pressing screw for fixing the second circuit board to the mounting part. Can be fixed in a state of being in direct contact with the heat radiating portion, and a state excellent in thermal conductivity can be ensured to improve heat dissipation. Further, since the pressing screw is screwed into the through screw hole of the mounting portion, it is not necessary to process a screw hole in the heat radiating portion.
[0012]
In order to prevent the first circuit board from warping when pressed, at least the four corners and the center of the first circuit board are pressed with a pressing screw to evenly press the first circuit board to the heat radiating portion. It is preferable. In addition, when the board area of the first circuit board is large, it is preferable to further press the surrounding sides and the vicinity of the center with a pressing screw in addition to the five places in order to surely press the heat radiating portion. Furthermore, depending on the surface roughness of each surface where the first circuit board and the heat radiating part come into contact, even if the first circuit board is pressed against the heat radiating part, a gap may be formed between them. It is preferable to fill with transmission grease or the like.
[0013]
The first circuit board is preferably a power circuit board or the like that generates a larger amount of heat than the second circuit board. In this way, heat generated by the first circuit board is dissipated. It is possible to reduce problems such as malfunction of the second circuit board such as a control circuit board that radiates heat from the portion and generates a small amount of heat. Note that the second circuit board having a small amount of heat generation is not limited to one, but by providing a mounting portion on the box body in the stacking direction, a plurality of second circuit boards can be accommodated in the board housing box. Also good.
[0014]
The board storage box according to a second aspect of the invention is characterized in that the pressing screw includes an elastic part that biases the first circuit board toward the heat radiating part.
In the second invention, by providing an elastic portion on the pressing screw, it is possible to appropriately set the pressing load on the heat radiating portion of the first circuit board, reducing the pressing load on the first circuit board, and radiating portion without difficulty. It can be made to contact. In addition, a leaf | plate spring, a coil spring, etc. are applicable to an elastic part.
[0015]
According to a third aspect of the present invention, there is provided the substrate storage box, wherein the first circuit board includes an exposed first circuit conductor, and a tip end portion of the pressing screw is in contact with the first circuit conductor. .
In the third invention, by pressing the first circuit conductor with the pressing screw, the first circuit board is surely radiated with the required pressing force in a state where the burden on the first circuit board is further reduced. Can be pressed against the part.
[0016]
According to a fourth aspect of the present invention, there is provided the substrate storage box, wherein the second circuit board includes a second circuit conductor exposed, and the pressing screw is formed of a conductive material and is in contact with the second circuit conductor. It is characterized by being.
In the fourth invention, the pressing screw itself can be used as a relay conductive member by bringing the pressing screw formed of a conductive material into contact with each circuit conductor of both circuit boards. Conventionally, between the two circuit boards, The relay line required for circuit connection can be eliminated, and circuit connection between circuit boards can be easily performed.
[0017]
In addition, as a conductive material for forming the pressing screw, a material such as aluminum, copper, gold, or silver can be applied. In addition to forming the pressing screw with the various materials described above, the pressing screw may be formed with a non-conductive material and the pressing screw may be covered with the various materials described above to ensure conductivity.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof.
FIG. 1 is a cross-sectional view of a substrate storage box 10 according to an embodiment of the present invention. The board storage box 10 of this embodiment is mounted on a vehicle and connected to a steering assist motor 22 and a torque sensor 23 in the electric power steering apparatus 21 shown in FIG. 2 to control the rotation of the motor 22. .
[0019]
The substrate housing box 10 includes a power circuit board 14 that controls power supply and a control circuit board 15 that controls a signal related to rotation of the motor 22 inside a box body 12 provided with a heat sink 13 as a heat radiating part at the bottom. The box main body 12 is covered with the cover 18 by being fixedly accommodated by the pressing screws 11 in a stacked state at intervals.
[0020]
As shown in FIG. 3, the box body 12 is provided with a peripheral wall 12 a that surrounds three sides, and the four corners inside the peripheral wall 12 a are parallel to the upper surface 13 a of the heat sink 13 at a location spaced from the heat sink 13. Each of the mounting portions 12b protrudes in the direction, and a central mounting portion 12c that protrudes from the central portion in the side direction to the central portion of the box body 12 is provided on one of the three peripheral walls 12a. . Each of the mounting portions 12b and the central mounting portion 12c is formed with a through screw hole 12d.
[0021]
The box body 12 is made of synthetic resin, and is formed integrally with the heat sink 13 by insert molding together with the aluminum heat sink 13. The cover 18 is formed in a substantially L shape that covers the opening 12e above the box body 12 and the opening 12f on the side.
[0022]
On the other hand, the power circuit board 14 shown in FIG. 1 has a power for controlling the power supply as well as causing the first circuit conductor 14b to be exposed on the upper surface 14d in accordance with the circuit shape by etching the ceramic substrate portion 14a. A semiconductor 14c is mounted. In addition, the power circuit board 14 of this embodiment is a portion facing the through screw holes 12d of the mounting portion 12b and the central mounting portion 12c in a plan view direction while being accommodated in the box body 12 shown in FIG. The circuit shape is such that the first circuit conductor 14b exists.
[0023]
The power circuit board 14 described above corresponds to a first circuit board, and a current from a power source (vehicle-mounted battery) having a high voltage value flows in a circuit formed by the first circuit conductor 14b and the like. The amount of heat generated by 14c and the like is larger than that of the control circuit board 15 corresponding to the second circuit board.
[0024]
In the control circuit board 15 shown in FIG. 1, the second circuit conductor 15b is exposed on the upper surface 15d of the board portion 15a in accordance with the circuit shape, and various semiconductors 15c for control are mounted. Further, as shown in FIG. 4, the control circuit board 15 has a circuit shape in which the second circuit conductor 15 b exists at a position facing the through screw hole 12 d in a state of being accommodated in the box body 12 like the power circuit board 14. In addition, through holes 15e are formed at locations corresponding to the respective through screw holes 12d.
[0025]
Note that the current value of the current flowing through the second circuit conductor 15b of the control circuit board 15 is very small compared to the current value flowing through the first circuit conductor 14b of the power circuit board 14. Further, a part of the circuit formed by the second circuit conductor 15b of the control circuit board 15 needs to be connected to a required circuit formed by the first circuit conductor 14b of the power circuit board 14 for power supply or the like. A press screw 11 is used for circuit connection between the control circuit board 15 and the power circuit board 14.
[0026]
As shown in FIG. 5A, the pressing screw 11 is formed integrally with a screw head portion 11a, a screw portion 11b, and a leaf spring-like spring portion 11c which is an elastic portion having a required urging force. The material is copper, which is a conductive material. The threaded portion 11b is set to a size to be screwed with each through screw hole 12d of the box body 12, and the spring portion 11c at the time of no load is gently adjusted within the range of the diameter of the through screw hole 12d. A curved shape is used so that the direction of bending when the load is applied is uniform.
[0027]
Next, the assembly procedure of the substrate storage box 10 according to the present embodiment will be described.
First, the heat transfer grease 20 is applied to the upper surface 13a of the heat sink 13 of the box body 12 shown in FIG. 3 as shown in FIGS. 1 and 5A and 5B. After applying the heat transfer grease 20, the power circuit board 14 is inserted from the side opening 12 f of the box body 12 and placed on the upper surface 13 a of the heat sink 13. Further, the control circuit board 15 is housed inside the opening 12e above the box body 12 and placed on the placement part 12b and the central placement part 12c.
[0028]
By placing the control circuit board 15 in this way, as shown in FIGS. 1, 5A and 5B, the through holes 15e, the placement part 12b, and the central mounting part of the control circuit board 15 are provided. The through screw holes 12d of the mounting portion 12c are in communication with each other. Next, when the pressing screw 11 is inserted into each through hole 15e and the through screw hole 12d and rotated in the screwing direction, as shown in FIG. The first circuit conductor 14b. In this state, the screw head 11 a of the pressing screw 11 is not in contact with the second circuit conductor 15 b of the control circuit board 15.
[0029]
When the pressing screw 11 is further rotated in the screwing direction from the above-described state, the spring portion 11c is bent and completely screwed into the through screw hole 12d. As shown in FIG. The second circuit conductor 15b comes into contact with 15 and the control circuit board 15 is fastened and fixed to the mounting portion 12b and the central mounting portion 12c. On the other hand, the screwed press screw 11 is in a state where an appropriate load is applied by pressing the power circuit board 14 to the heat sink 13 evenly with a required urging force by interposing the heat transfer grease 20 due to the bending of the spring portion 11c. It is fixed with. Thus, after fixing the power circuit board 14 and the control circuit board 15 to the box main body 12, the cover 18 is covered and the board | substrate storage box 10 is completed.
[0030]
In the completed substrate storage box 10, the power circuit board 14 is pressed against the heat sink 13 with the heat transfer grease 20 interposed therebetween, so that there is no gap between the power circuit board 14 and the heat sink 13. The heat generated in the circuit board 14 is reliably transmitted to the heat sink 13 and radiated to the outside. Further, since the power circuit board 14 presses the rigid first circuit conductor 14b with the pressing screw 11 having the spring part 11c, the burden on the pressing of the board part 14a is compared with the case where it is directly fixed with the screw. It is less likely to cause defects such as cracks.
[0031]
Further, the pressing screw 11 is in contact with the first circuit portion 14 of the power circuit board 14 at the spring portion 11c, and is in contact with the second circuit conductor 15b of the control circuit board 15 at the screw head portion 11a. The required circuit connection between the two boards is performed by conducting the circuit itself, and the board storage box 10 eliminates the connecting relay line and reduces the labor involved in the circuit relay.
[0032]
In addition, the board | substrate storage box 10 which concerns on this invention is not limited to the form mentioned above, A various modification can be applied. For example, like a pressing screw 31 shown in FIG. 6A, a coil spring-like one can be applied to the spring portion 31c, and the spring portion 31c may be rotated separately from the screw portion 31b, or rotate together. You may do it. Further, like the pressing screw 41 shown in FIG. 6B, a spring part 41c may be provided in the middle of the screw part 41b. Furthermore, as shown in FIG. 6C, the inside of the screw part 51b. It is also possible to apply a plunger-type pressing screw 51 incorporating a spring portion 51c.
[0033]
Further, the pressing screw 11 (including the pressing screw of the modified example, the same applies hereinafter) can be made of aluminum, gold, or silver as a material other than copper in order to ensure conductivity, When manufacturing with a material having low conductivity, the surface may be covered with aluminum, copper, gold, or silver by plating or the like to ensure conductivity. In addition, when the circuit connection between the power circuit board 14 and the control circuit board 15 is not necessary, it is not necessary to secure the conductivity to the pressing screw 11, and the second circuit conductor of the pressing screw 11 and the control circuit board 15 is not required. There is no need to contact 15b.
[0034]
Further, the substrate portion 14a of the power circuit board 14 may be formed of a metal such as aluminum having an insulating layer in addition to being formed of ceramic. Thus, the substrate portion 14a is formed of metal and the power circuit board. When it is not necessary to connect a circuit between the control circuit board 15 and the control circuit board 15, the board part 14a may be directly pressed by the pressing screw 11.
[0035]
Further, the substrate housing box 10 accommodates a plurality of control circuit boards 15 with respect to one power circuit board 14 by providing a plurality of mounting portions 12b and the like on the peripheral wall 12a of the box body 12 in the board stacking direction. You may make it do.
[0036]
【The invention's effect】
As described above in detail, in the first invention, since the first circuit board can be fixed to the heat radiating portion in a state excellent in thermal conductivity, the heat radiating property can be improved as compared with the conventional one.
In the second invention, the first circuit board can be pressed to the heat radiating portion with an appropriate load, the pressure load on the board of the first circuit board is reduced, and the first circuit board is in good condition for heat dissipation. Can be pressed against the heat dissipation part.
[0037]
In the third invention, the burden on the first circuit board related to the pressing can be further reduced.
In the fourth aspect of the invention, a required circuit between the circuit boards can be connected by the press screw that secures conductivity, and the connection efficiency between the circuit boards can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a substrate storage box according to an embodiment of the present invention.
FIG. 2 is an overall schematic diagram of an electric power steering apparatus to which a substrate housing box is applied.
FIG. 3 is a perspective view of a disassembled state of a box body and a cover of a substrate storage box.
FIG. 4 is a perspective view of a main part of a control circuit board.
5A is a schematic diagram of a state before the pressing screw is inserted into the through hole and the through screw hole, and FIG. 5B is a diagram illustrating a state where the control circuit board is mounted by screwing the pressing screw into the through screw hole. It is the schematic of the state before fixing to.
FIGS. 6A, 6B, and 6C are schematic front views of modified pressing screws.
FIG. 7 is a cross-sectional view of a conventional substrate storage box.
[Explanation of symbols]
10 Substrate housing box 11 Press screw 11c Spring part (elastic part)
12 box main body 12a peripheral wall 12b mounting part 12d through screw hole 13 heat sink (heat radiation part)
14 Power circuit board 14b First circuit conductor 15 Control circuit board 15b Second circuit conductor 15e Through hole

Claims (4)

In the substrate housing box that houses the circuit board placed on the heat radiating portion in the box body where the heat radiating portion is provided,
A first circuit board placed on the heat dissipating part;
A mounting portion projecting from the peripheral wall of the box body in parallel with the first circuit board, and having a through screw hole formed thereon;
A second circuit board mounted on the mounting portion and having a through hole communicating with the through screw hole;
A pressing screw that inserts through the through hole and fixes the second circuit board to the mounting portion by screwing with the through screw hole, and a tip portion presses the first circuit board to the heat radiating portion; A substrate storage box comprising: 2. The substrate storage box according to claim 1, wherein the pressing screw includes an elastic portion that biases the first circuit board toward the heat radiating portion. The first circuit board includes an exposed first circuit conductor;
The substrate storage box according to claim 1, wherein a tip end portion of the pressing screw is in contact with the first circuit conductor. The second circuit board includes a exposed second circuit conductor;
The board accommodation box according to claim 3, wherein the pressing screw is made of a conductive material and is in contact with the second circuit conductor.

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