JP2015012004A - Electronic device with heat sink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic device with a heat sink in which cooling performance of an electronic substrate is not degraded even in the case of natural air-cooling using convection, without using a forced air-cooling heat sink, the weight of the heat sink is prevented from being loaded to a substrate without requiring an extra component, and a structure of high vibration resistance is achieved by increasing the eigen frequency.SOLUTION: The electronic device includes a heat sink 210 including a base 211 and a fin 212 extending in a direction substantially perpendicular to the base 211, an electronic substrate 200 attached to the heat sink 210 and dissipating heat of a heating component 202 via the heat sink 210, and a subrack (structure) 220 for storing the electronic substrate 200 and heat sink 210. The heat sink 210 is supported by the subrack 220, and a channel gap is formed in the convection direction between the fins 212.

Description

  The present invention relates to an electronic device such as an electronic substrate provided with a heat sink, and more particularly to a structure for fixing a large heat sink.

As shown in FIG. 1, a large heat sink needs to be mounted on an electronic board having a heat generating component that generates a large amount of heat during operation. When such a substrate is loaded on a guide rail of a subrack, it may be deformed or damaged due to a load such as vibration or gravity due to the mass of the heat sink. Therefore, it is necessary to adopt a structure that takes into account the heat sink load.
As such a structure, as shown in FIG. 2, there is one that reduces deformation due to a heat sink load by mounting a reinforcing component on the back surface of the substrate. However, it is necessary to add a reinforcing component, resulting in an increase in board dimensions and assembly process. In addition, since the load increases as the heat sink becomes larger, it is necessary to increase the size of the reinforcing parts or to provide a large number of reinforcing parts accordingly.

  As a solution to this problem, as shown in FIGS. 3 and 4, Patent Document 1 discloses that a load is applied to a connector by supporting the load of the heat sink 1 by a guide rail 3 installed in a housing (structure). It has been shown to prevent loading. According to such a structure, since the load of the heat sink 1 is supported by the structure, no load is generated on the substrate, no reinforcing parts for the substrate are required, and even when the heat sink is enlarged, the load on the substrate does not increase. .

JP 2010-225874 A

However, in the support structure shown in FIG. 3, the guide rail 3 supports the fins so as to cover the entire height direction of the fins at the upper and lower ends of the heat sink, and the fins support the guide rails 3 at the upper and lower ends. The fins are arranged in parallel to each other, and are limited to mounting in which the fins are horizontally or inclined to be sideways. Natural air cooling due to upward convection accompanying heat radiation from the fins cannot be used.
If it is applied to mounting in which the fins are vertically oriented, the guide rail 3 is closed in the direction perpendicular to the longitudinal direction of the fins at the upper and lower ends of the fins. descend. That is, the structure shown in Patent Document 1 is premised on a forced air cooling heat sink that forcibly blows cooling air along the surface of the fin using a cooling fan, and the fin has a longitudinal direction in the blowing direction. Even if the fin itself is covered with the guide rail (the dimension from the base to the tip of the fin), the desired cooling can be performed by increasing the capacity and rotation speed of the cooling fan. It is assumed that.

  However, forced air-cooled heat sinks require equipment for blowing air, including an electric motor that drives a cooling fan, which not only increases costs, increases space, and increases power consumption. In such a case, when the power supply is suddenly shut down due to an overhead line accident or the like, the heat generating parts may overheat and cause damage. Therefore, in particular, regarding an electronic board mounted on a railway vehicle, it is preferable to secure a necessary cooling capacity by natural air cooling using convection along fins, but the structure shown in Patent Document 1 is difficult.

  Further, in Patent Document 1, as a means for fixing the heat sink to the structure, as shown in FIG. 3, the heat sink 1 is directly fixed to the structure, and as shown in FIG. The aspect which fixes a heat sink and a structure indirectly is proposed by providing the fixing member 4 between bodies. When both are compared, the former can raise the natural frequency of a heat sink for the following reasons, and it can be set as a structure strong against a vibration.

For example, when directly fixing the heat sink fixing portion to the structure, the natural frequency ω _{1 at the} center of the heat sink is expressed by the following from the heat sink mass m and the spring constant k ₁ from the heat sink center to the heat sink fixing portion (= structure): As given.
ω ₁ = (k ₁ / m) ^1/2

Next, when a fixing member having a spring constant k ₂ is inserted between the heat sink fixing portion and the structure, the spring constant k ₁₂ from the center of the heat sink to the structure is a value obtained by coupling k ₁ and k ₂ in series. Therefore, it becomes as follows.
k ₁₂ = (k ₁ · k ₂ ) / (k ₁ + k ₂ ) <k ₁
Further, the natural frequency ω _{12 at} this time can be obtained as follows.
ω ₁₂ = (k ₁₂ / m) ^1/2

Here, when ω ₁ and ω ₁₂ are compared, since k ₁₂ <k ₁ , ω ₁₂ <ω ₁ , and the natural frequency is higher in the structure in which the heat sink and the structure are directly fixed. That is, a structure resistant to vibration can be obtained. Conversely, as the number of fixing members mounted in series between the heat sink and the structure increases, the structure is more susceptible to vibration. That is, it is desirable to fix the heat sink directly to the structure for the reasons described above.
Therefore, in the structure of FIG. 4, as in the structure of FIG. 3, not only sufficient cooling capacity cannot be obtained by natural air cooling using convection, but also the natural frequency is lowered and the structure is weak against vibration.

  Therefore, an object of the present invention is to reduce the cooling performance of the electronic board without using a forced air-cooled heat sink, even with natural air cooling using convection, and the weight of the heat sink does not require additional components. The object is to provide a structure with high vibration resistance by preventing the load and increasing the natural frequency.

  In order to solve the above problems, for example, the configuration described in the claims is adopted. The present application includes a plurality of means for solving the above-described problems. For example, in an electronic device including a heat sink according to the present invention, a base and a fin extending in a direction substantially perpendicular to the base are provided. A heat sink, an electronic board mounted on the heat sink and dissipating heat from the heat-generating component via the heat sink, and a structure for storing the electronic board and the heat sink, and supporting the heat sink to the structure. A fixing structure for forming a flow passage gap in the convection direction between the fins is provided.

  Further, in the electronic device including the heat sink, a guide rail that supports the heat sink is provided above and below the structure, and a coupling portion that is coupled to the guide rail is provided on the heat sink, and the heat sink is parallel to the base. To be stored in the structure.

According to the electronic device of the present invention, the heat sink can be directly fixed to a structure such as a guide rail or a housing without the need for additional components, and the load of the heat sink is not applied to the electronic board. it can. In addition, by fixing the heat sink directly to the structure, the rigidity is increased and the natural frequency is increased compared to the case where the heat sink is indirectly fixed to the structure through a fixing member, so that it is resistant to vibration. Become. Furthermore, the natural frequency can be further increased by increasing the number of fixing portions between the heat sink and the structure.
In addition, in natural air-cooled heat sinks, it is generally necessary to ensure a sufficient length of the fin (dimension from the base to the tip of the fin), so this can be used to connect the guide rail to the fin. By providing and fixing the fin to the structure, the fixing point between the heat sink and the structure can be increased, the natural frequency can be further increased, and a structure resistant to vibration can be obtained.

  In addition, the guide rail and the connecting portion with the guide rail can be designed as appropriate, and the width can be reduced, so even if rails are installed above and below the vertical heat sink, convection is not blocked and natural air cooling effect is achieved. Can be maximized. In particular, when the rail is formed of a metal having high thermal conductivity, the heat of the heat sink is conducted to the structure such as the subrack via the guide rail, so that the heat dissipation performance of the heat sink can be improved.

In addition, by adopting a structure that allows the fixed part of the heat sink to be inserted into the guide rail, it can be mounted on a heat sink mounting board that is inserted and mounted on a subrack (or a backplane with a rail) equipped with a guide rail. On the other hand, the heat sink is directly fixed to the guide rail simultaneously with the mounting, and the above-described fixing structure and effects can be easily realized.
Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

FIG. 1 is a diagram illustrating a load acting on an electronic board when a large heat sink is mounted. FIG. 2 is a diagram for explaining a conventional technique employing a reinforcing component. FIG. 3 is a diagram showing a heat sink fixing structure in the prior art. FIG. 4 is a diagram showing another example of the heat sink fixing structure in the prior art. FIG. 5 is a perspective view showing a relationship between each fin and a guide rail as a structure in the first embodiment of the present invention. FIG. 6 is a top view of the first embodiment. FIG. 7 is a front view of the first embodiment. FIG. 8 is a diagram illustrating a modification of the first embodiment in which the number of fixed points is changed up and down. FIG. 9 is a diagram illustrating the overall structure of the second embodiment. FIG. 10 is a diagram illustrating a modification of the second embodiment. FIG. 11 is a diagram illustrating a modification of the second embodiment. FIG. 12 is a diagram illustrating a modification of the second embodiment. FIG. 13 is a diagram illustrating the overall structure of the third embodiment. FIG. 14 is a diagram illustrating the overall structure of the fourth embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Example 1]
5 to 7 show Example 1 of an electronic device including a heat sink according to the present invention, and FIG. 5 is a perspective view showing a relationship between each fin of the heat sink and a guide rail as a structure. 6 shows a top view, and FIG. 7 shows a front view.
In addition, a high effect is acquired by applying a present Example to the electronic device mounted in the mobile body with especially large vibrations, such as a rail vehicle, for example. In such a moving body, a large number of electronic components are mounted as typified by the on-board device for ATC. For example, an electronic device divided into functions such as a power supply unit, a transmission unit, a reception unit, and an external connection unit. The component is mounted on a standardized size electronic board. These electronic boards are loaded by inserting them into a standardized guide rail mounted on a subrack as a structure, and they are connected to each other to constitute a transmission / reception unit of an on-board device. Is common.

In this embodiment, instead of inserting the electronic board into the guide rail of the subrack, the heat sink mounted on the electronic board is supported by the guide rail.
Specifically, as shown in FIG. 6, a heat sink 210 is mounted on an electronic substrate 200 on which a heat generating component 202 having a high heat generation amount is mounted, such as a transmission unit, among such substrates. The heat sink 210 is formed of a lightweight material having a high heat transfer coefficient such as aluminum, and includes a fin 212 extending in a direction orthogonal to the electronic substrate 200 and a base 211 substantially parallel to the electronic substrate. When the heat generating component 202 is mounted, the amount of heat generated in the heat generating component 202 is transmitted to the fins 212 via the base 212 and has a function of radiating heat to the outside air.

In this embodiment, as shown in FIG. 7, rail insertion portions 213 a to 213 c are respectively provided at the upper and lower ends of the fins 212 and the base 211 so as to be aligned on a straight line in the board insertion direction substantially parallel to the base 211. ing.
These rail insertion portions 213a to 213c are respectively fitted and coupled to concave portions of guide rails 230a to 230c attached to the sub-rack 220 in the depth direction.
In other words, the rail insertion portions 213a formed on the upper and lower end surfaces of the base 211 extend in parallel with the board insertion direction, that is, the electronic board 200, and are inserted and coupled so as to fit into the recesses of the guide rail 230a.
Similarly, rail insertion portions 213b and 213c extending from the upper and lower end surfaces of the fins 212 are also aligned in parallel with the electronic substrate 200, and are inserted into and coupled to the concave portions of the guide rails 230b and 230c, respectively.

  The width of the guide rail 230 is made as small as possible even when compared with the length of the fin 212 (the dimension from the base to the tip of the fin), and the distance between the guide rails is ensured so that convection can be performed smoothly. Are arranged. Also, as shown in FIG. 6, in this embodiment, the upper and lower surfaces of the subrack 220 are both open to the outside air, so that the guide rail 230 does not block convection. Therefore, the updraft generated by heat radiation from the fins 212 of the heat sink 210 is not hindered, and the outside air introduced from the lower surface of the subrack 220 efficiently exchanges heat with the fins 212, and the upper surface of the subrack 220 is As a result, the heat dissipation performance of the heat sink 210 can be ensured by convection along the longitudinal direction of the fin 212.

According to the present embodiment, the rail insertion portions 213a to 213c formed in the heat sink 210 are fixed to the guide rail 230 attached to the subrack 220, so that the weight of the heat sink 210 is increased on the electronic substrate 200. The structure is not loaded at all.
In the present embodiment, in addition to fixing the base 211 with the guide rail 230a by the rail insertion portion 213a, the fin 212 is provided with a fixing point to the guide rails 230b and 230c, so that the heat sink 210 can be fixed. Can be increased. Further, even when the heat sink 210 having a long fin 212 is mounted, the number of mountable rails 230 can be increased by the length of the fin 212, so the fixing points of the heat sink 210 are increased and the fixing strength is increased. Can be maintained. Furthermore, when the number of fixed points increases, the natural frequency increases for the following reason, so that the vibration strength is improved.

If the heat sink with mass m is fixed to the structure at the fixing point P ₁ , the natural frequency ω ₁ at the center of the heat sink is represented by the following spring coefficient k ₁ from the center of the heat sink to the structure (fixed part P ₁ ). As given.
ω ₁ = (k ₁ / m) ^1/2
Then, if the heat sink has added fixed point P _2, the spring coefficient of the middle of the heat sink to P ₂ When k _2, the spring coefficient k ₁₂ from the heat sink center to structure, the k ₁ and k ₂ in parallel By combining, it is given as follows.
k ₁₂ = k ₁ + k ₂
Therefore, from the natural frequency equation, the natural frequency ω _{12 at the} center of the heat sink when the heat sink is fixed at P ₁ and P ₂ is as follows.
ω ₁₂ = (k ₁₂ / m) ^1/2 = ((k ₁ + k ₂ ) / m) ^1/2 > ω ₁

That is, it can be seen that the natural frequency is higher in the case of fixing with P ₁ and P ₂ than in the case of fixing with P ₁ alone. Further, as the fixed point is increased, the natural coefficient increases because the spring coefficient from the center of the heat sink to the structure increases. A high natural frequency means that the frequency at which the heat sink resonates is high, which means it is resistant to vibration. Therefore, it can be seen that the more the heat sink fixing points, the stronger the fixing structure.
Since the number and position of the fixed points can be arbitrarily designed, for example, as shown in FIG. 8, the number of fixed points at the top and bottom is changed, such as one point at the top and two points at the bottom. Optimal design can be achieved.

In this embodiment, since the upper and lower sides of the heat sink 210 are fixed directly to the guide rail 230 as a structure, no additional parts are required for fixing, and the electronic substrate 200 and the heat sink 210 Fixing is possible without increasing the dimensions.
Furthermore, when fixing only by the upper and lower sides of the fins 212, the flange of the guide rail 230 does not protrude from the heat sink 210 to the electronic substrate 200 side, so there is no interference between the electronic substrate 200 and the guide rail 230. Thus, it is not necessary to make the electronic substrate 200 smaller than the heat sink 210.

  In particular, when this embodiment is applied to a standardized subrack system (for example, a 19-inch rack system), the width of the rail insertion portion 213 is set to the thickness of a standardized electronic board (for example, 1.6 mm). ), The standardized guide rail for inserting the electronic board into the guide rail 230 can be used. Since this guide rail is standardized and inexpensive and easily available, it is not necessary to individually design and manufacture the guide rail 230, and the manufacturing cost can be reduced.

As shown in FIG. 7, a backplane 221 and a guide rail 230 are fixed to the subrack 220. The electronic substrate 200 is mounted with a connector 201 in addition to the heat generating component 202, and the electronic substrate 200 is mounted on the heat sink 210 provided with the rail insertion portion 213 so as to be in contact with the heat generating component 202. The heat sink 210 is guided to the back plane 221 by inserting the rail insertion portions 213a to 213c into the guide rails 230a to 230c, and connects the connector 201 to the back plane 221.
The sub-rack 220 includes a front panel 222 (see FIG. 6). The front panel 222 mounts the electronic substrate 200 on the sub-rack 220, thereby closing the electronic substrate 200 insertion opening of the sub-rack 220, It is fixed to the subrack 220. In addition, the heat sink 210 is fixed by the front panel 222, and thereby indirectly fixed to the subrack 220.
Further, the heat sink 210 may be fixed to the backplane 221. By fixing the heat sink 210 to the front panel 222 and the back plane 221, the heat sink 210 is improved in strength against vibration in the longitudinal direction of the rail.

[Example 2]
In the embodiment shown in FIG. 9, the heat sink 310 mounted on the electronic substrate 300 is fixed by inserting the entire fin 312 into the rail 330. That is, the width of the guide rail 330 is set so as to cover the fins 312 of the heat sink 310 in the length direction, and vent holes 331 are formed on the upper and lower surfaces.
Thereby, even when the heat sink 310 is heated and convection is generated between the fins 312, the heat dissipation performance of the heat sink 310 can be ensured without the guide rail 330 blocking the convection.
As shown in FIG. 10, without providing the guide rail, the sub-rack 320 is directly supported, and the left and right (the tip of the fin 312 and the back of the base 311) are supported by the fixing portion 340 at the upper and lower ends of the heat sink 310. It is good also as a structure to do.

Furthermore, as shown in FIG. 11, a recess may be formed near the center of the fin 321 and may be fitted to a fixing portion 340 formed in the insertion direction. Further, as shown in FIG. 12, the fixing portion 340 may be L-shaped, and the left and right sides may be supported at the upper and lower ends of the heat sink 310.
These fixing portions 340 may be provided continuously in the insertion direction of the heat sink 310 mounted on the electronic substrate 300, or may be provided intermittently.
According to the present embodiment, when the heat sink 310 is loaded on the subrack 320, the processing for providing the rail insertion portions at the top and bottom is not necessary, and the manufacturing cost of the heat sink 310 is reduced.

[Example 3]
FIG. 13 shows an example in which the upper and lower sides of the heat sink 310 are directly supported by the sub-rack 320, the rail insertion component 350 is connected to the heat sink 310, and the upper and lower sides of the electronic substrate 300 are sandwiched. According to the present embodiment, when the sub-rack 320 is loaded, the rail insertion portions formed on the upper and lower sides of the rail insertion component 350 may be inserted into the corresponding guide rails 330, and the fins and the bases may be inserted. In addition, it is not necessary to process the rail insertion part. Further, by forming the rail insertion part 350 with a material having an electromagnetic shielding effect, it is possible to suppress the emission of electromagnetic noise.

[Example 4]
FIG. 14 shows an example in which the rail insertion portion formed in the heat sink 310 and the concave portion formed in the guide rail 330 are brought into contact with each other in a triangular shape. According to the present embodiment, since the angle of the contact portion between the rail insertion portion formed on the heat sink 310 and the guide rail 330 is increased and the contact area can be increased, the stress concentration at the joint portion can be reduced and the strength is improved. In addition, by making the rail insertion portion triangular, it is possible to mount with high positional accuracy even when the dimensional accuracy of the rail insertion portion is low.
The contact shape of both is not limited to a triangle, and various shapes can be adopted depending on the form of the heat sink 310, such as a circular shape or a concave shape that is in close contact with both outer sides of the guide rail. Further, if a resin film such as a self-lubricating resin is formed on both or either of the rail insertion portion formed on the heat sink 310 and the contact portion of the guide rail 330, the insertion into the sub-rack 320 is smooth. And the natural frequency can be increased.

  The present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

100 Electronic board 110 Heat sink 111 Base 112 Fin 113 Rail insertion part 130 Rail 200 Electronic board 201 Connector 202 Heat generating component 210 Heat sink 212 Fin 213 Rail insertion part 220 Subrack 221 Backplane 222 Front panel 230 Guide rail 300 Electronic board 310 Heat sink 330 Rail 331 Fixing part of vent 340

Claims (4)

A heat sink having a base and a fin extending in a direction substantially perpendicular to the base, an electronic board mounted on the heat sink and dissipating heat generated by the heat-generating component via the heat sink, and the electronic board and the heat sink are stored. With a structure,
An electronic apparatus comprising a heat sink, comprising: a fixing structure that supports the heat sink on the structure and that forms a flow passage gap in a convection direction between the fins.   Guide rails that support the heat sink are provided above and below the structure, and a coupling portion that couples to the guide rail is provided on the heat sink so that the heat sink is guided in parallel with the base and stored in the structure. An electronic device comprising the heat sink according to claim 1.   3. The electronic device with a heat sink according to claim 2, wherein a width of the coupling portion is the same as a thickness of the electronic substrate.   4. The electronic device with a heat sink according to claim 3, wherein the guide rail and the coupling portion are disposed corresponding to at least one of the base and the fin of the heat sink.

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