JP7147352B2 - Substrate heat dissipation structure, electronic equipment, and substrate mounting method - Google Patents

Description

The present invention relates to a substrate heat radiation structure, an electronic device, and a substrate mounting method, and more particularly to a technique for radiating heat generated in a heat generating portion of a substrate using a heat sink.

2. Description of the Related Art There is known a technique of dissipating heat generated by a heat-generating component (IC package, CPU, etc.) mounted on a substrate using a heat sink. Japanese Patent Laid-Open No. 2004-100000 describes a board heat dissipation structure that is capable of reliably removing heat by elastically pressing a heat sink against a CPU mounted on a board to bring it into close contact with the CPU.
In the substrate heat dissipation structure described in Patent Literature 1, the substrate supports the heat sink at a plurality of locations around the heat-generating component with fixing screws. The heat radiating plate is pressed against the heat-generating component by the elastic repulsive force of the coil spring attached to the fixing screw.

JP 2011-081437 A

In the substrate heat dissipation structure described in Patent Document 1, the substrate supports the heat dissipation plate around the heat dissipation component, so the pattern utilization efficiency of the substrate surface is reduced. In addition, if the plurality of fixing screws are not uniformly tightened, the elastic repulsive force of the coil springs will vary and the substrate will remain deformed.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a substrate heat radiation structure, an electronic device, and a method of attaching a substrate, in which the pattern utilization efficiency of the substrate surface is not reduced and the reliability is maintained.

In order to solve the above problems, the present invention has the following configurations and procedures.
1) a frame;
a substrate having a heat generating portion and attached to the frame only at a portion near the edge;
a heat sink in contact with the heat generating portion;
an elastic support that supports the heat sink on the frame and elastically presses it against the heat generating part;
a guide having a support notch that engages one edge of the substrate;
with
When the orientation of the substrate attached to the frame is set to a first orientation,
The substrate heat dissipation structure , wherein the guide allows the substrate to rotate from a second posture inclined with respect to the first posture to the first posture about the support cut portion as a fulcrum. is.
2 ) The substrate heat dissipation structure described in 1);
and a housing that accommodates the substrate heat dissipation structure.
3 ) A method of mounting a substrate, wherein a heat sink and a substrate having a heat-generating portion are mounted on a frame capable of being mounted in a first posture in which the substrate is separated from the heat sink on a first side and parallel to the heat sink. ,
a heat sink attaching step of attaching the heat sink to the frame by resiliently biasing the heat sink toward the first side;
a first mounting step in which the substrate is rotated from the first posture with the one edge portion as a fulcrum to assume a second posture in which the one edge portion is supported by a guide;
a second mounting step in which the substrate supported by the guide is rotated from the second posture to the first posture in which the heat sink contacts and elastically biases the heat generating portion; ,
a board mounting step of mounting the vicinity of the edge of the board in the second posture to the frame;
including
In the mounting method of the substrate, the heat generating portion and the heat sink are separated from each other when the substrate is in the second posture .

According to the present invention, it is possible to obtain the effect that the pattern utilization efficiency of the substrate surface is not reduced and the reliability is maintained.

FIG. 1 is a perspective view showing a substrate assembly G1 provided with a substrate heat dissipation structure HK, which is an example of a substrate heat dissipation structure according to an embodiment of the present invention. FIG. 2 is a perspective view of the frame 1 included in the board assembly G1. FIG. 3 is a front view of the substrate 2 included in the substrate assembly G1. 4 is a right side view of the substrate 2. FIG. FIG. 5 is a top view of a part of the heat sink 3 included in the substrate assembly G1. FIG. 6 is a partial right side view of the guide 4 of the board assembly G1. FIG. 7 is an assembly diagram of the elastic support G7 that the substrate assembly G1 has. FIG. 8 is a partial top view for explaining the mounting state of the substrate 2 and the heat sink 3 in the substrate assembly G1, and is a view along the arrow Y1 in FIG. FIG. 9 is a first diagram for explaining the assembly process of the substrate assembly G1. FIG. 10 is a second diagram for explaining the assembly process of the substrate assembly G1. FIG. 11 is a side view of an electronic device including a board assembly G1 having a board heat dissipation structure HK.

A substrate heat dissipation structure according to an embodiment of the present invention will be described with reference to a substrate assembly G1 having a substrate heat dissipation structure HK as an example.

(Example)
FIG. 1 is a perspective view of the board assembly G1. For convenience of explanation, the directions of up, down, left, right, front and back are defined by the directions of the arrows shown in FIG. These directions do not limit the use attitude and assembly attitude of the board assembly G1.

The substrate assembly G1 has a frame 1, a substrate 2 screwed to the frame 1, a heat sink 3, and a guide 4. As shown in FIG. In the example shown in FIG. 1, the board assembly G1 also has an insertion board 5 which is guided by the guide 4 and attached to the board 2 via the connector 21A.

The frame 1, as also shown in FIG. 2, is formed in a substantially U-shape that is open upward. The material of the frame 1 is, for example, a surface-treated steel plate.
The frame 1 has a bottom plate 1a, and a left side plate 1b and a right side plate 1c rising upward from both left and right ends of the bottom plate 1a.
Four female screw portions 1a1 are formed on the bottom plate 1a. The guide 4 is fixed by tightening a screw N3 to each female screw portion 1a1 (see FIG. 1).

The left side plate 1b has substrate support portions 11a and 11b bent rightward at upper and lower portions of the rear edge, respectively. Similarly, the right side plate 1c has board support portions 11c and 11d bent leftward at the upper and lower portions of the rear edge, respectively.
The substrate supporting portions 11a to 11d are formed so that their rear surfaces are flush with the substrate mounting surface Sf2, and have female screw portions 11a1 to 11d1 each formed by a forward convex burring.
The lower substrate support portions 11b and 11d have dowel portions 11b2 and 11d2 which are formed by half-punching and protrude backward above the female screw portions 11b1 and 11d1.

The left side plate 1b has a heat sink supporting portion 11e that is bent rightward at the center of the rear edge in the vertical direction. Similarly, the right side plate 1c has a heat sink supporting portion 11f that is bent leftward at the vertical central portion of the rear edge.
The heat sink support portions 11e and 11f have female screw portions 11e1 and 11f1 formed by rear convex burring. The female threaded portions 11e1 and 11f1 are formed as a pair which are vertically separated from each other.
The heatsink supporting portions 11e and 11f are formed so that the front surfaces thereof are coplanar heatsink mounting surfaces Sf3.
The front surfaces (heat sink mounting surfaces Sf3) of the heat sink supporting portions 11e and 11f are shifted forward by a distance d2 from the rear surfaces (substrate mounting surfaces Sf2) of the substrate supporting portions 11a to 11d (see also FIG. 8).

Although the above description is repeated, the rear surfaces of the substrate supporting portions 11a to 11d are commonly referred to as a substrate mounting surface Sf2, and the front surfaces of the heat sink supporting portions 11e and 11f are commonly referred to as a heat sink mounting surface Sf3.
That is, the board mounting surface Sf2 and the heat sink mounting surface Sf3 are parallel surfaces with a distance d2 in the front-rear direction.
In this example, it is assumed that the board mounting surface Sf2 and the heat sink mounting surface Sf3 are vertical surfaces as shown in FIG.

As shown in FIGS. 3 and 4, the substrate 2 has a rectangular outer shape and has through holes 2b at its four corners through which screws N1 for attachment to the frame 1 are passed.
The substrate 2 has dowel holes 2c1 and 2c2 for engaging the dowel portions 11b2 and 11d2 right above the lower through hole 2b.

As shown in FIGS. 3 and 4, the substrate 2 has heat-generating portions 22 and 23 spaced apart from each other in the center in the vertical direction, and a heat-generating portion 24 slightly below the center in the left-right direction.
The heat-generating portions 22 to 24 are mounted components that generate heat during operation, and are respectively IC packages 22a, 23a, and 24a mounted on the front surface 2e of the substrate 2, and front surfaces (top surfaces) of the IC packages 22a, 23a, and 24a. and heat transfer sheets 22b, 23b, and 24b attached to.

In this example, IC packages 22a and 23a have the same thickness, and IC package 24a has a thinner thickness. Therefore, the heat transfer sheet 24b attached to the IC package 24a is made thicker than the heat transfer sheets 22b and 23b attached to the IC packages 22a and 23a.
Specifically, the distance from the substrate 2 to the front surfaces 22b1 and 23b1 of the heat transfer sheets 22b and 23b and the distance from the substrate 2 to the front surface 24b1 of the heat transfer sheet 24b are the same distance d3. The thickness of each of the heat sheets 22b-24b is determined.

A connector 21A whose mounting direction is the front-rear direction is mounted on the lower portion of the substrate 2 at the center position in the left-right direction. A receptacle 21B mounted on the insertion board 5 is attached to the connector 21A.
In the lower edge of the substrate 2, a pair of cut portions 2a cut upward are formed so as to be separated from each other in the left-right direction.

As shown in FIG. 5, the heat sink 3 is obtained by cutting an extruded aluminum material having a predetermined cross-sectional shape into a predetermined length. FIG. 5 shows the external shape in the direction orthogonal to the extrusion direction.
Specifically, the heat sink 3 includes a flat plate-shaped base 31, a plurality of fins 32 erected forward from the base 31, and a pair of support flanges 33 projecting laterally outward from left and right ends of the base 31. have.
Each of the support flanges 33 has a pair of through holes 33a separated in the vertical direction.

The rear surface of the base portion 31 is a contact surface 31a that contacts the heat generating portions 22 to 24 of the substrate 2, and is formed as a flat plane.
The contact surface 31a exists as a parallel surface separated from the rear surface 33b of the support flange 33 by a distance d1 on the rear side.
This distance d1 is set to be larger than the distance obtained by subtracting the distance d3 in the substrate 2 from the distance d2 in the longitudinal direction between the substrate mounting surface Sf2 and the heat sink mounting surface Sf3 in the frame 1 . i.e.
Distance d2<distance d1+distance d3 (Formula 1)
is.

As shown in FIG. 1, the guide 4 has a base 4k, a pair of side guide walls 4b, 4b, and a pair of guide ribs 4d, 4d.
The base 4k is formed in the shape of a rectangular flat plate, and has two pairs of flanges 4a projecting outward from left and right edges. Each collar portion 4a is formed with a through hole through which the screw N3 is passed.
The pair of side guide walls 4b, 4b are formed as wall portions extending in the front-rear direction and rising upward at the left and right edges of the base portion 4k.
Between the pair of side guide walls 4b, 4b, an insertion board 5, which will be described later, is guided laterally and vertically, and the receptacle 21B of the insertion board 5 is smoothly attached to the connector 21A.

The pair of guide ribs 4d, 4d are formed at positions corresponding to the pair of notches 2a, 2a of the substrate 2 on the rear edge of the base 4k.
As shown in FIG. 6, each guide rib 4d is formed as a rib-like portion that extends forward and backward and protrudes upward.

The guide rib 4d has, at its front portion, an inclined guiding portion 4d1 inclined upward toward the rear, and an abutment portion 4d2 connected to the upper end of the inclined guiding portion 4d1.
The inclined guiding portion 4d1 and the abutment portion 4d2 are guiding portions that guide the insertion board 5 when the insertion board 5 is attached to the board 2. As shown in FIG. That is, the insertion board 5 inserted rearward from the front side along the guide 4 is guided to the abutting portion 4d2 via the inclined guiding portion 4d1, and is positionally regulated downwardly and rearwardly.

The guide rib 4d has, at its rear portion, a support cut portion 4e cut downward in a generally rectangular shape.
An inclined portion 4e1 is formed on the upper portion of the inner surface on the rear side of the support cut portion 4e.
The cut portion 2a of the substrate 2 is engaged with the support cut portion 4e from the upper side downward. Specifically, the engagement between the support cutout portion 4e and the cutout portion 2a is the engagement between the recesses in the orthogonal posture. At the final position of engagement, the substrate 2 is positioned in the left-right and front-rear directions with respect to the guide ribs 4d, and its downward movement is restricted.

As shown in FIG. 1, the heat sink 3 is attached to the heat sink support portions 11e and 11f of the frame 1 by means of elastic supports G7. FIG. 7 is an assembly diagram of the elastic support G7, showing a case where it is used for the heat sink support 11f. The structure of the elastic support G7 is, of course, the same when it is used for the heat sink support 11e.

The elastic support G7 has a screw N7, a collar 71 and a coil spring 72.
A threaded portion of the screw N7 is passed through the collar 71, and a coil spring 72 is attached to the outer side of the collar 71.
The collar 71 can be inserted through the through hole 33 a of the support collar portion 33 of the heat sink 3 , and the coil spring 72 cannot be inserted through the through hole 33 a.

Using the elastic support G7, the collar 71 and the screw N7 passed through the collar 71 are passed through the through hole 33a of the support flange 33 of the heat sink 3. As shown in FIG. By tightening the screw N7 to the female screw portion 11f1 of the heat sink support portion 11f, the heat sink 3 can be attached to the heat sink support portion 11f so as to be elastically movable forward.
The coil spring 72 is compressed by tightening the screw N7, and the heat sink 3 is naturally urged (pressed) against the heat sink supporting portion 11f by its elastic repulsive force.

Next, a procedure for assembling the board assembly G1 using the above members will be described. Here, a case of manual assembly is shown, but a robot may be used for assembly.

First, the guide 4 is attached to the bottom plate 1a of the frame 1 shown in FIG. 2 with screws N3.

Next, the heat sink 3 is attached to the heat sink attachment surface Sf3 of the heat sink support portions 11e and 11f of the frame 1 from the front side using the elastic support member G7. Specifically, the heat sink 3 is attached by applying an elastic support G7 to each of the female screw portions 11e1 and 11f1 and tightening the screws N7. As described above, the attached heat sink 3 is naturally pressed against the heat sink attachment surface Sf3. Further, the heat sink 3 can be moved forward by applying forward force against the elastic repulsive force of the coil spring 72 .

Next, from the rear upper side of the frame 1, the substrate 2 is engaged with the support cutouts 4e of the guide ribs 4d of the guide 4 and mounted.
Specifically, first, the position of the substrate 2 in the left-right direction is aligned so that the cut portion 2a corresponds to the support cut portion 4e.

Next, as shown in FIG. 9, the substrate 2 is placed in an inclined posture with the lower side slightly forward, and the notch 2a is engaged with the support notch 4e from above (see arrow DR1).
Since the inclined portion 4e1 is formed in the support cut portion 4e, the substrate 2 can be engaged in an inclined posture at the initial stage of engagement, and the engagement is smooth.

Next, as shown in FIG. 10(a), while pushing the substrate 2 downward (arrow DR2), the upper portion thereof is pushed forward with a force Fa that resists the repulsive force of the coil spring 72 (arrow DR3). to a vertical position.
By this posture change operation, as shown in FIG. 10B, which is an enlarged view of the portion A in FIG. The position of the substrate 2 in the vertical and horizontal directions can be determined with high accuracy.

Further, when the board 2 is placed in a vertical position while applying a force Fa with the cutout 2a engaged with the support cutout 4e, the board 2 comes into contact with the board mounting surfaces Sf2 of the board support parts 11a to 11d of the frame 1. FIG. Further, from the above (Equation 1), the heat transfer sheets 22b to 24b and the coil spring 72 of the heat generating portions 22 to 24 are each compressed according to their elasticity.
Therefore, as shown in FIG. 8, the heat sink 3 moves forward against the elastic repulsive force of the coil spring 72, moves forward against the repulsive force of the coil spring 72, and moves forward from the heat sink mounting surface Sf3. Separated by a distance d5.
As a result, the contact between the heat transfer sheets 22b to 24b and the contact surface 31a of the heat sink 3 is improved.
In FIG. 8, for convenience, the heat generating portion 22 and the heat generating portion 24 having different thicknesses of the heat transfer sheets are shown side by side.

The operator continuously applies force Fa from the rear side so as to maintain the substrate 2 in the vertical posture.
With the board 2 in the vertical position, screws N1 are tightened from the rear side to the female threads 11a1 to 11d1 of the board support parts 11a to 11d of the frame 1 through the through holes 2b.

Before the screw N1 is tightened, the elastic repulsive force of the coil spring 72 is absorbed by the forward movement of the heat sink 3 and the compression of the heat transfer sheets 22b to 24b. Good match.
Therefore, there is almost no longitudinal deformation of the substrate 2 caused by tightening the screw N1, and the accompanying residual stress is suppressed to a negligible level.

Further, among the four screws N1, the screws N1 may be tightened first to the board support portions 11b and 11c having the lower dowel portions 11b2 and 11d2. As a result, the positioning of the substrate 2 in the horizontal and vertical directions by the engagement of the dowel portions 11b2 and 11d2 with the dowel holes 2c1 and 2c2 becomes more reliable. The residual stress of 2 is also further reduced.

After the heat sink 3 and the substrate 2 are attached to the frame 1 as described above, the insertion substrate 5 is inserted along the side guide walls 4b, 4b of the guide 4, and the receptacle 21B is attached to the connector 21A of the substrate 2. do.
In the example shown in FIG. 1, a pair of guide ribs 4d with which the circuit board 2 is engaged are installed close to the left and right sides of the connector 21A. As a result, the deformation of the board 2 due to mounting resistance when the receptacle 21B is mounted to the connector 21A is well suppressed, and the high reliability of the board 2 is maintained.
By the above procedure, the board assembly G1 having the board heat dissipation structure HK is assembled.

In the substrate heat dissipation structure HK described above, the positions at which the substrate 2 is attached to the frame 1 by screws are not the vicinity of the heat generating portions 22 to 24 but only the vicinity of the edge of the substrate 2 . Specifically, when the substrate 2 is rectangular, only four corners are provided. Therefore, the pattern utilization efficiency of the substrate 2 is not reduced, and the substrate 2 has good patterning efficiency.

The substrate heat dissipation structure HK has a structure in which a heat sink 3 as heat dissipation means is brought into contact with the heat generating portions 22 to 24 of the substrate 2 and pressed elastically. Nevertheless, the heat sink 3 and the substrate 2 are maintained parallel and attached to the frame 1 with negligible residual stress.
Therefore, the substrate 2 is less likely to have problems due to residual stress such as pattern peeling, and the substrate 2 has a high degree of reliability, and the reliability is maintained for a long period of time.

The substrate heat dissipation structure HK has a support notch 4e that engages the substrate 2 while allowing the substrate 2 to be attached to the guide 4 in an initial oblique mounting and then to be rotated to a vertical position.
The operator puts the substrate 2 in a tilted posture in which the upper portion is rotated backward with respect to a predetermined mounting posture (vertical posture in this example), and engages the lower edge portion, which is one edge portion, with the support notch portion 4e. After that, it can be turned around the support cutout 4e as a fulcrum to change its attitude to a predetermined mounting attitude, and can be screwed. The heat generating portions 22 to 24 and the heat sink 3 are separated from each other when the substrate 2 is tilted.
As a result, the substrate 2 is attached to the frame 1 in a state in which the elastic repulsive force received from the coil springs 72 is evenly distributed to the four corners of the substrate 2 .
As a result, the stress remaining in the substrate 2 attached to the frame 1 becomes negligible.

A substrate assembly G1 having a substrate heat dissipation structure HK is provided in an electronic device 51 shown in FIG. 11, for example. An electronic device 51 in FIG. 11 is an imaging device having a housing 511 and a lens unit 512, and the housing 511 accommodates a substrate assembly G1.
In this case, the IC packages 22a to 24a of the substrate 2 in the substrate assembly G1 generate heat by performing image processing, for example.

The embodiments described in detail above are not limited to the configurations and procedures described above, and may be modified without departing from the scope of the present invention.

The substrate assembly G1 with the substrate heat dissipation structure HK may not include the plug-in substrate 5 in its construction. In that case, the guide 4 may have the guide rib 4d and may not have the side guide wall 4b.

The heat-generating parts 22 to 24 are not limited to those including IC packages, and may include other mounting components or the substrate itself.
The mounting posture of the board assembly G1 to the electronic device 51 is not limited. When it is necessary to consider the direction in which gravity is applied, such as when the rear shown in FIG. , the front side shown in FIG.
The electronic device 51 is not limited to an imaging device, and may be a device mounted on a mobile body such as an automobile, a wireless device, an audio device, an image display device, or the like.

Reference Signs List 1 frame 1a bottom plate 1a1 female threaded portion 1b left side plate 1c right side plate 11a, 11b, 11c, 11d substrate supporting portion 11a1, 11b1, 11c1, 11d1 female threaded portion 11b2, 11d2 dowel portion 11e, 11f heat sink supporting portion 11e1, 11f1 Female screw part 2 Board 2a Notch 2b Through hole 2c1, 2c2 Dowel hole 2e Front face 21A Connector 21B Receptacle 22 to 24 Heat generating part (mounted component) 22a to 24a IC package 22b to 24b Heat transfer sheet 22b1, 23b1 Front face 3 heat sink 31 base 31a contact surface 32 fin 33 support flange 33a through hole 33b rear surface 4 guide 4a flange 4b side guide wall 4d guide rib 4d1 inclined guide portion 4d2 abutment portion 4e support notch portion 4e1 Inclined portion 4k Base portion 5 Insertion substrate 51 Electronic device (imaging device) 511 Housing 512 Lens portion 71 Collar 72 Coil springs d1, d2, d3, d5 Distance Fa Force HK Substrate heat dissipation structure G1 Substrate assembly G7 Elasticity Supports N1, N3, N7 Screw Sf2 Substrate mounting surface Sf3 Heat sink mounting surface

Claims (4)

a frame;
a substrate having a heat generating portion and attached to the frame only at a portion near the edge;
a heat sink in contact with the heat generating portion;
an elastic support that supports the heat sink on the frame and elastically presses it against the heat generating part;
a guide having a support notch that engages one edge of the substrate;
with
When the posture of the substrate attached to the frame is set to the first posture,
The substrate heat dissipation structure , wherein the guide allows the substrate to rotate from a second posture inclined with respect to the first posture to the first posture about the support cut portion as a fulcrum. . 2. The substrate heat dissipation structure according to claim 1 , wherein the heat generating portion and the heat sink are separated from each other when the substrate is in the second posture. A substrate heat dissipation structure according to claim 1 or claim 2 ,
An electronic device comprising: a housing that accommodates the board heat dissipation structure therein. A method for mounting a substrate, comprising mounting a heat sink and a substrate having a heat-generating portion on a frame capable of being mounted in a first posture in which the substrate is separated from the heat sink and parallel to the first side, the method comprising:
a heat sink attaching step of attaching the heat sink to the frame by resiliently biasing the heat sink toward the first side;
a first mounting step in which the substrate is rotated from the first posture with the one edge portion as a fulcrum to assume a second posture in which the one edge portion is supported by a guide;
a second mounting step in which the substrate supported by the guide is rotated from the second posture to the first posture in which the heat sink contacts and elastically biases the heat generating portion; ,
a board mounting step of mounting the vicinity of the edge of the board in the second posture to the frame;
including
A mounting method of a substrate , wherein the heat generating portion and the heat sink are separated from each other when the substrate is in the second posture .

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