JP2002329823A - Circuit unit and method of manufacturing heat sink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit unit that has a heat sink (heat-conducting body 21), on one surface of which is fixed a circuit element (FET 2) in the state fixed to a circuit board 1 and on the other surface of which is fixed a case 4, where the circuit unit is not required to have a processing (secondary working) for forming prepared holes, is free from problems caused by the deformation of the prepared holes, and can be reduced in size. SOLUTION: The heat conducting body 21 is formed to have two side plate sections 23 and 24 on both sides of a central board section 22 by bending a board to have a U-shaped cross section. The prepared holes 22a are formed in the central board section 22 to fix the body 21 to the circuit board 1 and, in addition, slits 25 are formed at bending positions on both sides of the holes 22a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure and a manufacturing method of a heat sink in a circuit unit constituting, for example, a control device of an automobile.

[0002]

2. Description of the Related Art In recent years, vehicles equipped with a control device for driving a large-current actuator such as a motor or a lamp of an automobile by a semiconductor or a circuit unit such as an inverter using a semiconductor are increasing. Semiconductors are used for duty control of high-current actuators such as motors and lamps, switching circuits of inverters, etc., for the purpose of extending the life of the device, or achieving the purpose of reducing the weight of the device. is there. In general, in such a circuit unit, a case covering the surface of the unit is formed of a material having good heat conductivity (for example, aluminum or an aluminum alloy), and a heat conductor made of a similar material is formed on the inner surface of the case. By attaching a semiconductor (so-called heat sink) in a joined state and attaching the semiconductor to the surface of the heat conductor in a joined state, heat generated when driving a high-current actuator or the like using the semiconductor is transferred to the outside of the unit. Heat is dissipated. In addition, usually, a configuration in which the heat conductor is fixed to the circuit board (that is, a configuration in which the semiconductor is fixed to the circuit board via the heat conductor) is employed in order to prevent the semiconductor (particularly, a portion connected to the circuit board) from mechanical stress. It is firmly fixed to the circuit board while protecting.

FIG. 4 shows an example of the structure of this type of circuit unit. In FIG. 4A, reference numeral 1 denotes a circuit board, reference numeral 2 denotes an FET which is a kind of a semiconductor transistor,
Reference numeral 3 denotes a heat conductor (heat sink) manufactured by extruding aluminum or the like, reference numeral 4 denotes a case, and reference numeral 5 denotes a tapping screw as a fastening member. As shown in FIG. 4B, a plurality of pilot holes 3a corresponding to the tapping screws 5 (or rivets; the same applies hereinafter) are formed on the front, back, and lower surfaces of the heat conductor 3. Using FE
T 2, case 4 and substrate 1 are fixed to heat conductor 3. That is, the lower surface side of the heat conductor 3 is joined to the upper surface of the substrate 1 and is fixed to the substrate 1 by the screw 5 inserted from the rear surface side (lower side) of the substrate 1 and screwed into the lower hole 3a of the lower surface side. ing. Further, as shown in FIG. 4 (b), the FET 2 is arranged in a joined state in front of the heat conductor 3 and
The FET 2 is fixed to the heat conductor 3 by a screw 5 inserted from the front of T2 and screwed into the pilot hole 3a on the front side. Further, the back surface of the heat conductor 3 is joined to the inner surface of the case 4, and is fixed to the case 4 by a screw 5 inserted from the outside of the case 4 and screwed into the prepared hole 3 a on the back surface. Note that FET2 is
As shown in (c), a large number of the heat conductors are often provided to constitute a bridge circuit for driving the motor, and in such a case, the heat conductor 3 becomes a member that is considerably long in the arrangement direction of the FETs 2. , Pilot hole 3a (especially, a pilot hole on the front side for fixing FET 2) is provided in the longitudinal direction.

[0004]

As described above, in the above-described conventional circuit unit, a plurality of prepared holes (round holes having a circular cross section) are provided on each surface of the heat conductor manufactured by extrusion molding of aluminum or the like. Since the structure is formed and each component is fastened around the heat conductor, productivity is poor and cost reduction is difficult. This is because the above-mentioned pilot hole must be formed by machining (secondary processing) after forming the basic shape of the heat conductor, and it takes a very long time. For example, after manufacturing the basic shape of the heat conductor (without pilot holes) by extruding aluminum, it must be installed in a machine for drilling holes on each surface to process many pilot holes. The number of man-hours for producing the heat conductor increases. The heat conductor constituting the heat sink is formed by pressing and bending a plate material like the heat conductor 11 shown in FIG. In the processing step (before bending), for example, by forming the hole at the same time as the outer shape, the problem of an increase in the number of steps due to the necessity of the secondary machining of the prepared hole can be solved. However, in the case of a configuration such as the heat conductor 11 shown in FIG. 5, the width L must be relatively large, and there is a problem that it is difficult to reduce the size of the circuit unit.

The heat conductor 11 shown in FIG. 5 is formed by bending a plate material into a U-shaped cross section, and has two side plate portions 13 and 14 on both sides of a central plate portion 12. The FET 2 is fixed to the side plate 13, the case 4 is fixed to the other side plate 14, and the circuit board 1 is fixed to the center plate 12. That is, a pilot hole 13a for fixing the FET 2 is formed in the side plate portion 13, a pilot hole 14a for fixing the case 4 is formed in the side plate portion 14, and the central plate portion 1 is formed.
2, a pilot hole 12a for fixing the circuit board 1 must be formed. The thickness T of the heat conductor 11 in this case is the minimum thickness for screwing (for example, about 2 mm).
The radius of curvature R of the bent portion needs to be equal to or larger than the normal thickness T for bending. For this reason, if the width L is set to a length as small as possible (for example, 10 mm or less) for the purpose of miniaturization, the prepared hole 12a of the central plate portion 12 is distorted due to the bending process (specifically, FIG. This results in an elliptical shape that is long in the width direction as shown in (2)), which makes it impossible to properly use for fastening such as screwing. In addition, such a problem with the heat sink exists not only in a circuit unit of an automobile but also in a field other than an automobile as long as it is a circuit unit having a circuit element that generates considerable heat. Accordingly, the present invention is a circuit unit having a heat sink in which a circuit element is fixed on a circuit board in a state in which the circuit element is fixed on one surface side, and a case is fixed on the other surface side, and a pilot hole for fixing in the heat sink ( It is an object of the present invention to provide a circuit unit which does not require secondary processing), has no problem of distortion of the prepared hole, and can be downsized, and a method of manufacturing a heat sink therefor.

[0006]

A circuit unit according to the present invention is a circuit unit having a heat sink in which circuit elements are fixed on a circuit board in a state where the circuit elements are fixed on one side, and a case is fixed on the other side. And the heat sink is
The plate is bent into a U-shaped cross section, and has two side plates on both sides of the center plate. The center plate has a lower portion for a fastening member for fixing to the circuit board. A hole is formed, and slits are formed at bending positions on both sides of the pilot hole. Here, as the “fastening member”, for example, there may be a tapping screw in which the tip of the shaft is screwed into the prepared hole of the heat sink, or a rivet whose tip of the shaft is pressed into the prepared hole of the heat sink.

According to the circuit unit of the present invention, the heat sink can be easily manufactured by pressing and bending a plate material, and a pilot hole for a fastening member is formed, for example, in an outer shape in a pressing process (before bending). If the holes are formed at the same time, the secondary machining of the pilot hole as described above becomes unnecessary, and the problem of an increase in the number of steps due to this machining can be solved. For example, as in the method of manufacturing a heat sink according to the present invention, a pressing step of manufacturing a developed product of the heat sink by pressing a plate material, and bending the developed product manufactured in the pressing process into a U-shaped cross section. A bending step, wherein in the pressing step, the pilot hole is formed by pressing, and a heat sink is manufactured by a manufacturing method of forming a slit at a bending position on both sides of the pilot hole, the pilot hole as described above. This eliminates the need for secondary machining, and eliminates the need for secondary machining of the slit.

In addition, since the slit does not affect the shape of the prepared hole in the center plate, deformation of the prepared hole in the center plate does not occur even if the width L of the heat sink is reduced as much as possible. As a result, it is possible to contribute to the downsizing of the heat sink (and the downsizing of the circuit unit). In this case, the thickness on both sides of the prepared hole in the center plate portion (the distance between the prepared hole in the center plate portion and the slit, for example, FIG.
Until the bending position (the position at which the slit is formed) is moved to the center side until the width D becomes as small as possible to secure the fastening member. Can be smaller. In a preferred aspect of the present invention, a notch that is concave toward the center of the center plate is formed at an end of the slit in the heat sink. According to this configuration, while maintaining the thickness of both sides of the prepared hole in the central plate portion to the minimum necessary thickness, the width dimension L
Can be further reduced. This is because, if the notch as described above is present, even when the bending position is closer to the center side relative to the center position of the slit and the width dimension L is further reduced, the influence of the deformation at the time of bending is lower than the above. This is because the action that does not reach the hole can be maintained.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. The same elements as those in the conventional example shown in FIG. 4 are denoted by the same reference numerals, and redundant description will be omitted. FIG. 1A is a main configuration of a circuit unit constituting, for example, an AC inverter of an automobile (a structure around a heat conductor).
FIG. 1B is a perspective view showing a heat conductor 21 in the same circuit unit, and FIG. 2 is a plan view showing an intermediate product (developed product) in a process of manufacturing the heat conductor 21. is there. In addition, the heat conductor 21 and the case 4 may be referred to as a heat sink.
Corresponds to the heat sink of the present invention.

The heat conductor 21 is formed by bending a plate material into a U-shaped cross section, and has two side plate portions 23 on both sides of a central plate portion 22.
In the central plate portion 22, a pilot hole 22a for a screw 5 for fixing to the circuit board 1 is formed, and in the side plate portion 23, a screw 5 for fixing the FET 2 is formed.
And a side plate 24 is provided with a case 4
There is formed a pilot hole 24a for the screw 5 for fixing the screw. These pilot holes 22a, 23a and 24a are shown in FIG.
And a screw portion can be screwed or crimped by inserting a shaft portion of a tapping screw 5 (or a rivet, the same applies hereinafter), whereby each surface (in this case, both side surfaces and the lower surface) of the heat conductor 21 is ), FET2 (in this case, 7
), The circuit board 1 and the case 4 are fixed. The slits 25 are located at the bending positions on both sides of the pilot hole 22a (the positions indicated by alternate long and short dash lines indicated by reference numerals X1 and X2 in FIG. 2).
(Elongated openings) are formed. Also slit 25
Has a notch 26 that is concave toward the center of the central plate 22 at both ends.

Next, the heat conductor 21 is manufactured, for example, as follows. First, a developed product 20 as shown in FIG. 2 is manufactured by pressing an aluminum plate material (pressing step). Thereafter, the developed product 20 manufactured in this pressing step is bent at a right angle at bending positions X1 and X2 shown in FIG. 2 to form a U-shaped cross section (bending step).
Thus, the heat conductor 21 shown in FIG. 1 can be easily and inexpensively manufactured. In addition, the prepared holes 22a (in this case, two pieces) and the prepared holes 2
3a (7 in this case), pilot hole 24a (4 in this case),
The slits 25 (four in this case) including the cutouts 26 at both ends are formed, for example, in the above-described pressing process by using, for example, the developed product 2.
It is cut simultaneously with the outer shape of 0 (rectangular shape).

The substrate 1 is fixed to the case 4 by a fastening structure (for example, screwing) not shown, and is not shown in the opening on the lower surface side of the case 4 (the back surface side of the substrate 1). A base member is attached, and the lower surface side of the circuit unit is covered by the base member. The circuit unit is mounted on a vehicle or the like by a mounting portion (screw hole) provided on the base member. Rivets (not shown)
Has a wedge-shaped shaft part whose outer diameter becomes thinner toward the tip end, and this shaft part is press-fitted into the prepared hole side. Usually, a claw for preventing falling off is provided on the outer periphery of the shaft part. Can be If such a rivet is used instead of the tapping screw 5,
There is an advantage that dust due to tapping (screw cutting) is not generated.

With the circuit unit described above, the secondary processing of the heat conductor 21 (post-processing of each prepared hole or slit) becomes completely unnecessary. In other words, the heat conductor 21 can be manufactured as a final product only by a pressing step and a bending step with good productivity. For this reason, a significant improvement in productivity and cost reduction can be realized. In particular, in the case of a fastening structure using a large number of fastening members (such as screws 5) as in the circuit unit of the present embodiment, the number of pilot holes is very large, and processing of the pilot holes has conventionally required much labor. However, since these are all unnecessary, the effect is very large. In addition, since the slit 25 prevents the deformation during bending from affecting the prepared hole 22a of the central plate 22, even if the width L of the heat sink is reduced as much as possible, the distortion of the prepared hole 22a of the central plate 22 is reduced. As a result, it is possible to contribute to downsizing of the heat conductor 21 (heat sink) (and downsizing of the circuit unit). In this case, the thickness of the central plate portion 22 on both sides of the prepared hole 22a (the prepared hole 22a
Until the screw 5 (fastened member) has the minimum necessary thickness for fixing the screw 5 (fastening member). The width L can be reduced as much as possible by shifting the position of formation to the center side. In particular, in the case of the present embodiment, a notch 26 having a concave shape toward the center of the central plate portion is formed at the end of the slit 25. For this reason, the pilot hole 22
The width L can be further reduced while maintaining the thickness D on both sides of a at the minimum necessary thickness (for example, when the plate thickness is 2 mm, the width L can be less than 10 mm).
Because of the above notch 26, as shown in FIG. 2, the bending positions X1 and X2 are relatively closer to the center with respect to the center position of the slit 25, and the width L is further reduced. This also ensures that the effect of deformation during bending does not affect the pilot hole 22a.

Note that the present invention is not limited to the above embodiment. For example, the heat sink of the present invention is shown in FIG.
As in the heat conductor 21a shown in FIG.
It may have a slit 25a where no 6 is formed. Even in this case, there is an effect that the width dimension L can be reduced by avoiding distortion of the pilot hole 22a as compared with the configuration of FIG. However, in the case of the configuration like the heat conductor 21a (the configuration having no notch 26), the center position of the slit 25a is relatively closer to the center side as compared with the embodiment shown in FIG. (In the direction approaching the pilot hole 22a), it is relatively difficult to secure the above-mentioned thickness D,
The effect of reducing the width L by that amount is reduced. In that respect, the configuration in which the notch 26 as shown in FIG. 1B is provided is excellent. Further, the heat sink of the present invention may have a slit 25b extending to the end face of the heat conductor, like the heat conductor 21b shown in FIG. 3B. In this case, it is preferable that the notch 26b is formed at the end of the slit 25b as shown in FIG.

[0015]

According to the present invention, the secondary processing of the heat sink (post-processing of each prepared hole) is completely unnecessary. In other words, the heat sink can be manufactured as a final product only by the pressing and bending processes with high productivity. For this reason, a significant improvement in productivity and cost reduction can be realized. Moreover, the presence of the slits provided on both sides of the prepared hole of the center plate of the heat sink does not affect the deformation of the prepared hole at the time of bending, so that even if the width L of the heat sink is made as small as possible, the prepared hole is not affected. No longer occurs, which can contribute to downsizing of the heat sink and, consequently, downsizing of the circuit unit.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a main part of a circuit unit constituting an in-vehicle inverter.

FIG. 2 is a plan view showing a developed product of a heat sink of the circuit unit.

FIG. 3 is a perspective view showing another configuration example of the heat sink.

FIG. 4 is a diagram illustrating a configuration example of a conventional circuit unit.

FIG. 5 is a perspective view of a heat sink for explaining a conventional problem.

[Description of Signs] 1 Circuit board 2 FET (circuit element) 4 Case 5 Tapping screw (fastening member) 20 Deployed product 21, 21a, 21b Heat conductor (heat sink) 25, 25a, 25b Slit 26, 26b Notch

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hidetoshi Yoshikawa 2254, Kirin, Iida-shi, Nagano Prefecture OMRON Iida Co., Ltd. F-term (reference) 5F036 AA01 BB01 BC03 BC33 BE03

Claims (3)

[Claims] 1. A circuit unit having a heat sink in which a circuit element is fixed on a circuit board in a state where the circuit element is fixed on one surface side, and a case is fixed on the other surface side, wherein the heat sink has a plate member having a U-shaped cross section. It has two side plates on both sides of the center plate,
A circuit, wherein a prepared hole for a fastening member for fixing to the circuit board is formed in the center plate portion, and slits are formed at bending positions on both sides of the prepared hole. unit. 2. The circuit unit according to claim 1, wherein a notch that is concave toward the center of the central plate is formed at an end of the slit in the heat sink. 3. A sheet material is bent into a U-shaped cross section,
A method of manufacturing a heat sink having two side plate portions on both sides of a center plate portion and having at least a prepared hole for a fastening member in the center plate portion, wherein a plate material is pressed to form a developed product of the heat sink. A pressing step of manufacturing, and a bending step of bending the developed product manufactured in the pressing step into a U-shaped cross section. In the pressing step, the pilot hole is formed, and both sides of the pilot hole are formed. A method for manufacturing a heat sink, wherein a slit is formed at a bending position.