JP6977519B2 - Heat dissipation structure of electronic components - Google Patents

Description

The present invention relates to a heat dissipation structure that releases heat of an electronic component mounted on a substrate to a housing.

Conventionally, there is a heat dissipation structure in which a groove is formed between electronic components in a flat surface portion of a case for accommodating a substrate on which electronic components are mounted, and a heat transfer sheet is sandwiched between the electronic components and the flat surface portion (see Patent Document 1). .. In the heat dissipation structure described in Patent Document 1, a part of the heat transfer sheet is a loosely shaped portion that enters the space inside the groove without coming into contact with the case. The loosened shape absorbs the stress applied to the heat transfer sheet and reduces the reaction force that the electronic component receives from the heat transfer sheet.

Japanese Patent No. 5640616

By the way, in the heat dissipation structure described in Patent Document 1, since the heat transfer sheet has a loose shape portion that enters the space inside the groove without contacting the case, the reaction force received from the heat transfer sheet by the electronic component is Although it becomes smaller, the heat dissipation property is lowered.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a heat dissipation structure of an electronic component capable of improving heat dissipation while suppressing stress generated in a heat transfer sheet. ..

The first means for solving the above problems is a heat dissipation structure of electronic components.
A substrate on which a plurality of electronic components including electronic components having different heights are mounted on a predetermined surface, and
A housing having a planar top surface facing each electronic component and having each protruding portion that protrudes greatly as the height of each facing electronic component decreases.
It is sandwiched between the electronic components and the protrusions, abuts on the electronic components, forms a gap between the electronic components on the substrate, and the protrusions and the housing. The heat transfer sheet in contact with the intermediate portion of each of the protrusions in
To prepare for.

According to the above configuration, a plurality of electronic components including electronic components having different heights are mounted on a predetermined surface of the substrate. The housing includes each protrusion. Each protruding portion has a planar top surface facing each electronic component, and the lower the height of each facing electronic component, the larger the protrusion. Therefore, even if the electronic component has a low height, it is possible to prevent the distance to the facing protrusion from becoming long. A heat transfer sheet is sandwiched between each electronic component and each protrusion. Since the heat transfer sheet is in contact with each electronic component, heat is transferred from each electronic component to the heat transfer sheet, and heat can be efficiently transferred from the heat transfer sheet to each protrusion.

Here, the heat transfer sheet forms a gap between the electronic components on the substrate. Therefore, the portion of the heat transfer sheet pushed and brought together by each electronic component can be released to the space between the electronic components. Therefore, the stress generated in the heat transfer sheet can be suppressed. Further, the heat transfer sheet is in contact with each protrusion and a portion between each protrusion in the housing. Therefore, heat can be efficiently transferred from the heat transfer sheet not only to each protrusion but also to the intermediate portion of each protrusion in the housing. Therefore, the heat transfer efficiency from the heat transfer sheet to the housing can be improved, and the heat dissipation can be improved.

In the second means, the plurality of electronic components include a first electronic component and a second electronic component having a height higher than the height of the first electronic component, and the electronic component is described in a direction parallel to the predetermined surface. The distance between the top surface of the first protrusion, which is the protrusion facing the first electronic component, and the second electronic component is the top surface of the second protrusion, which is the protrusion facing the second electronic component. Is shorter than the distance between the first electronic component and the first electronic component.

According to the above configuration, the plurality of electronic components include a first electronic component and a second electronic component. The height of the second electronic component is higher than the height of the first electronic component. Therefore, the first protruding portion, which is a protruding portion facing the first electronic component, protrudes more than the second protruding portion, which is a protruding portion facing the second electronic component. The distance between the top surface of the first protrusion and the second electronic component is shorter than the distance between the top surface of the second protrusion and the first electronic component in the direction parallel to the predetermined surface of the substrate. .. Therefore, the ratio of the first protruding portion having a larger protrusion between the first electronic component and the second electronic component can be made larger than the ratio occupied by the second protruding portion. Therefore, the heat transfer efficiency from the heat transfer sheet to the housing can be further improved.

In the third means, in the housing, the shortest distance with respect to the second electronic component between the top surface of the first protrusion and the top surface of the second protrusion is the second electron. A slope shorter than the shortest distance between the component and the top surface of the second protrusion is formed.

According to the above configuration, a slope is formed in the housing between the top surface of the first protrusion and the top surface of the second protrusion. The shortest distance between the second electronic component and the slope is shorter than the shortest distance between the second electronic component and the top surface of the second protrusion. Therefore, heat can be efficiently transferred from the second electronic component to the slope via the heat transfer sheet, and heat dissipation can be further improved.

In the fourth means, the heat transfer sheet is formed to have a uniform thickness before being sandwiched between the electronic components and the protrusions. Therefore, in a heat dissipation structure using a general heat transfer sheet having a uniform thickness, it is possible to improve heat dissipation while suppressing stress generated in the heat transfer sheet.

In the fifth means, the distances between the opposing electronic components and the top surfaces of the protrusions are equal to each other. Therefore, it is possible to suppress the occurrence of electronic components having low heat dissipation in a plurality of electronic components.

Sectional drawing of the heat dissipation structure of 1st Embodiment. Sectional drawing of the heat dissipation structure of 1st comparative example. The cross-sectional view of the heat dissipation structure of the 2nd comparative example. Sectional drawing of the heat dissipation structure of 2nd Embodiment. Sectional drawing of the heat dissipation structure of 3rd Embodiment. Sectional drawing of the heat dissipation structure of 4th Embodiment.

(First Embodiment)
Hereinafter, the first embodiment embodied in the PLC (programmable logic controller) will be described with reference to the drawings. The PLC of this embodiment is used as a control device for controlling a robot system having a plurality of robots, for example, in a factory or the like.

As shown in FIG. 1, the PLC 10 includes a substrate 20, a housing 30, a heat transfer sheet 40, and the like. The substrate 20, the housing 30, and the heat transfer sheet 40 form a heat dissipation structure for the electronic components 21, 22, and 23.

The substrate 20 is formed in a plate shape by an insulating material such as glass epoxy. A wiring pattern (not shown) is formed by copper foil on the first surface 20a and the second surface 20b of the substrate 20. Electronic components 21, 22, and 23 are mounted on the first surface 20a (predetermined surface). Specifically, the electronic components 21, 22, and 23 are joined to the wiring pattern on the first surface 20a by soldering. Electronic components 21, 22, and 23 are components that generate heat during operation, such as ICs and FETs that make up a CPU. The height h1 of the electronic component 21 is lower than the height h2 of the electronic component 22, and is equal to the height h3 of the electronic component 23. That is, the electronic components 21, 22 and 23 include electronic components 21 (23) and 22 having different heights h1 (h3) and h2 from each other. In addition to the electronic components 21 and 22, 23, other electronic components and elements such as resistors, capacitors, and switches are mounted on the substrate 20. Electronic components and elements may also be mounted on the second surface 20b of the substrate 20.

The housing 30 is formed in a hollow rectangular parallelepiped shape (box shape) by a material having high thermal conductivity such as metal. Protruding portions 31, 32, 33 are formed on the bottom portion 30a of the housing 30. The protrusions 31, 32, 33 have planar top surfaces 31a, 32a, 33a, respectively. The top surfaces 31a, 32a, 33a are formed on a flat surface. The top surfaces 31a, 32a, and 33a face the electronic components 21, 22, and 23, respectively. That is, the protrusions 31, 32, and 33 are formed in the housing 30 at positions corresponding to the positions of the electronic components 21, 22, and 23 mounted on the substrate 20. The shapes of the top surfaces 31a, 32a, 33a correspond to the shapes of the electronic components 21, 22, 23 facing each other. The area of the top surfaces 31a, 32a, 33a is larger than the area of the facing portions of the electronic components 21, 22, 23. The protrusion amount t1 of the protrusion 31 is larger than the protrusion amount t2 of the protrusion 32, and is equal to the protrusion amount t3 of the protrusion 33. That is, the protruding portions 31, 32, and 33 project larger as the heights h1, h2, and h3 of the opposing electronic components 21, 22, and 23 are lower.

The distance x1 between the electronic component 21 and the top surface 31a of the protrusion 31, the distance x2 between the electronic component 22 and the top surface 32a of the protrusion 32, and the distance x3 between the electronic component 23 and the top surface 33a of the protrusion 33. Are equal (x1 = x2 = x3). That is, the distances x1, x2, x3 between the electronic components 21, 22 and 23 facing each other and the top surfaces 31a, 32a, 33a of the protrusions 31, 32, 33 are equal to each other.

The heat transfer sheet 40 is formed in a sheet shape by a material having high thermal conductivity and elasticity such as silicon rubber. The thermal conductivity of the heat transfer sheet 40 is smaller than the thermal conductivity of the housing 30. The heat transfer sheet 40 is formed to have a uniform thickness before being sandwiched between the electronic components 21, 22, 23 and the protrusions 31, 32, 33. The heat transfer sheet 40 is sandwiched between the electronic components 21, 22, 23 and the protrusions 31, 32, 33. Then, the substrate 20 is fixed to the housing 30 in a state where the heat transfer sheet 40 is compressed by a predetermined amount by the electronic components 21, 22, 23 and the protrusions 31, 32, 33.

Here, the heat transfer sheet 40 is in contact with the electronic components 21, 22, and 23. The heat transfer sheet 40 forms a gap with respect to the portions 20c and 20d between the electronic components 21 and 22 and 23 on the substrate 20. On the other hand, the heat transfer sheet 40 is in contact with the protrusions 31, 32, 33 and the portion between the protrusions 31, 32, 33 (not shown in FIG. 1) in the housing 30. A similar heat dissipation structure is formed not only in the cross section of FIG. 1 but also in other cross sections perpendicular to the substrate 20.

FIG. 2 is a cross-sectional view of the heat dissipation structure of the first comparative example. The same parts as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As shown in the figure, when the protrusions 31, 32, 33 are not formed on the bottom 130a of the housing 130, the heat is transmitted according to the heights h1, h2, h3 of the electronic components 21, 22, 23. It is necessary to change the thickness of the heat sheets 141, 142, 143. Therefore, it is necessary to prepare a plurality of types of heat transfer sheets 141, 142, and 143, which increases the types and numbers of members and makes the assembly work complicated.

FIG. 3 is a cross-sectional view of the heat dissipation structure of the second comparative example. The same parts as those in the first embodiment and the first comparative example are designated by the same reference numerals, and the description thereof will be omitted.

As shown in the figure, when the protrusions 31, 32, 33 are not formed on the bottom 130a of the housing 130, heat transfer is performed by the difference in height h1, h2, h3 of the electronic components 21, 22, 23. It can also be absorbed by the sheet 240. The heat transfer sheet 240 is formed to have a uniform thickness before being sandwiched between the electronic components 21, 22, 23 and the protrusions 31, 32, 33. The thickness of the heat transfer sheet 240 is larger than the thickness of the heat transfer sheet 40 of the first embodiment. In this case, in the heat transfer sheet 240, the portion between the electronic components 21 and 23 and the bottom 130a becomes thick. Therefore, the thermal conductivity from the electronic components 21 and 23 to the bottom 130a is lowered, and the heat dissipation is lowered.

On the other hand, the first embodiment has the following advantages.

The projecting portions 31, 32, 33 have planar top surfaces 31a, 32a, 33a facing the electronic components 21, 22, 23, respectively, and the heights h1, of the facing electronic components 21, 22, 23. The lower the h2 and h3, the larger the protrusion. Therefore, even in the electronic components 21 and 23 having low heights h1 and h3, it is possible to prevent the distances x1 and x3 from the facing protrusions 31 and 33 from becoming long. The heat transfer sheet 40 is sandwiched between the electronic components 21, 22, 23 and the protrusions 31, 32, 33. Since the heat transfer sheet 40 is in contact with the electronic components 21, 22, 23, heat is conducted (transferred) from the electronic components 21, 22, 23 to the heat transfer sheet 40, and the protrusions 31, 32 from the heat transfer sheet 40. , 33 can be efficiently transferred heat. Then, heat is released from the housing 30 to the outside.

The heat transfer sheet 40 forms a gap with respect to the portions 20c and 20d between the electronic components 21 and 22 and 23 on the substrate 20. Therefore, the portion of the heat transfer sheet 40 that has been pushed and brought together by the electronic components 21, 22, 23 can be released to the space between the electronic components 21, 22, 23. Therefore, the stress generated in the heat transfer sheet 40 can be suppressed.

The heat transfer sheet 40 is in contact with the protrusions 31, 32, 33 and the portion between the protrusions 31, 32, 33 in the housing 30. Therefore, heat can be efficiently transferred from the heat transfer sheet 40 not only to the protrusions 31, 32, 33 but also to the portion between the protrusions 31, 32, 33 in the housing 30. Therefore, the heat conduction efficiency (heat transfer efficiency) from the heat transfer sheet 40 to the housing 30 can be improved, and the heat dissipation can be improved.

The heat transfer sheet 40 is formed to have a uniform thickness before being sandwiched between the electronic components 21, 22, 23 and the protrusions 31, 32, 33. Therefore, in a heat dissipation structure using a general heat transfer sheet 40 having a uniform thickness, it is possible to improve heat dissipation while suppressing stress generated in the heat transfer sheet 40. Further, a heat transfer structure can be formed by one heat transfer sheet 40.

The distances x1, x2, x3 between the facing electronic components 21, 22, 23 and the top surfaces 31a, 32a, 33a of the protrusions 31, 32, 33 are equal to each other. Therefore, it is possible to suppress the generation of electronic components having low heat dissipation in the plurality of electronic components 21, 22, 23.

(Second Embodiment)
Hereinafter, the second embodiment will be described focusing on the differences from the first embodiment. The same parts as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 4, the top surface 31a of the projecting portion 31 (first projecting portion) facing the electronic component 21 (first electronic component) in a direction parallel to the first surface 20a (predetermined surface) of the substrate 20. The distance y1 from the electronic component 22 (second electronic component) is shorter than the distance y2 between the top surface 32a of the protruding portion 32 (second protruding portion) facing the electronic component 22 and the electronic component 21. The relationship between the electronic components 22 and 23 and the protrusions 32 and 33 is the same. Other configurations are the same as those of the first embodiment.

According to the above configuration, in addition to the same advantages as in the first embodiment, the following advantages are obtained. The plurality of electronic components 21, 22, and 23 include an electronic component 21 and an electronic component 22. The height h2 of the electronic component 22 is higher than the height h1 of the electronic component 21. Therefore, the protruding portion 31 facing the electronic component 21 protrudes more than the protruding portion 32 facing the electronic component 22. The distance y1 between the top surface 31a of the protrusion 31 and the electronic component 22 in the direction parallel to the first surface 20a is shorter than the distance y2 between the top surface 32a of the protrusion 32 and the electronic component 21. .. Therefore, the proportion of the protruding portion 31 that protrudes larger between the electronic component 21 and the electronic component 22 can be made larger than the proportion of the protruding portion 32. Therefore, the heat transfer efficiency from the heat transfer sheet 40 to the housing 30 can be further improved.

(Third Embodiment)
Hereinafter, the third embodiment will be described focusing on the differences from the first and second embodiments. The same parts as those in the first and second embodiments are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 5, the top surface 31a of the projecting portion 31 (first projecting portion) facing the electronic component 21 (first electronic component) in a direction parallel to the first surface 20a (predetermined surface) of the substrate 20. The distance y1 from the electronic component 22 (second electronic component) is shorter than the distance y2 between the top surface 32a of the protruding portion 32 (second protruding portion) facing the electronic component 22 and the electronic component 21. The relationship between the electronic components 22 and 23 and the protrusions 32 and 33 is the same.

Further, in the housing 30, the shortest distance z1 with respect to the electronic component 22 between the top surface 31a of the protrusion 31 and the top surface 32a of the protrusion 32 is such that the electronic component 22 and the top surface 32a of the protrusion 32 have a shortest distance z1. A slope 35 shorter than the shortest distance z2 is formed (z1 <z2). The slope 35 (the portion between the protrusions 31 and 32 in the housing 30) connects the top surface 31a and the top surface 32a.

According to the above configuration, in addition to the same advantages as in the second embodiment, the following advantages are obtained. In the housing 30, a slope 35 is formed between the top surface 31a of the protrusion 31 and the top surface 32a of the protrusion 32. The shortest distance z1 between the electronic component 22 and the slope 35 is shorter than the shortest distance z2 between the electronic component 22 and the top surface 32a of the protrusion 32. Therefore, heat can be efficiently transferred from the electronic component 22 to the slope 35 via the heat transfer sheet 40, and heat dissipation can be further improved.

It should be noted that, with respect to the second and third embodiments, the distance y1 between the top surface 31a of the protrusion 31 and the electronic component 22 and the top surface 32a and the electronic component of the protrusion 32 in the direction parallel to the first surface 20a. The distance y2 from 21 can be made equal.

(Fourth Embodiment)
Hereinafter, the fourth embodiment will be described focusing on the differences from the first embodiment. The same parts as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 6, even in this embodiment, the protrusion amount t4 of the protrusion 31 is larger than the protrusion amount t5 of the protrusion 32 and is equal to the protrusion amount t6 of the protrusion 33. That is, the protruding portions 31, 32, and 33 project larger as the heights of the electronic components 21, 22, and 23 facing each other are lower.

However, the distance x4 between the electronic component 21 and the top surface 31a of the protrusion 31 is shorter than the distance x5 between the electronic component 22 and the top surface 32a of the protrusion 32, and the distance x5 between the electronic component 23 and the top surface 33a of the protrusion 33 Is equal to the distance x6 of (x4 = x6 <x5).

Further, the heat transfer sheet 40A is not formed to have a uniform thickness before being sandwiched between the electronic components 21, 22, 23 and the protrusions 31, 32, 33. Specifically, the thickness of the portion of the protrusion 31 that abuts on the top surface 31a is smaller than the thickness of the portion that abuts on the top surface 32a of the protrusion 32, and is equal to the thickness of the portion that abuts on the top surface 33a of the protrusion 33. It has become. Other configurations are the same as those of the first embodiment.

According to the above configuration, in a configuration in which the distance between the bottom portion 30a of the housing 30 and the electronic components 21 and 23 is longer than the distance between the bottom portion 30a of the housing 30 and the electronic component 22, the heat dissipation of the electronic components 21 and 23 is long. Can be improved. Further, in the heat transfer sheet 40A, the thickness of the portion of the protrusions 31, 33 that abuts on the top surfaces 31a, 33a is smaller than the thickness of the portion that abuts on the top surface 32a of the protrusion 32. Therefore, it is possible to prevent the heat transfer sheet 40A from being excessively compressed by the electronic components 21 and 23 and the top surfaces 31a and 33a. Others have the advantages according to the first embodiment.

It should be noted that each of the above embodiments can be modified and implemented as follows. The same parts as those of the above embodiments are designated by the same reference numerals, and the description thereof will be omitted.

-As the material of the heat transfer sheets 40 and 40A, not only silicon rubber but also acrylic rubber having high thermal conductivity can be used.

The shapes of the top surfaces 31a, 32a, 33a of the protruding portions 31, 32, 33 are not limited to the shapes corresponding to the facing portions of the electronic components 21, 22, 23, and can be arbitrarily changed. However, it is desirable that the entire surface of the electronic components 21, 22, 23 on the top surfaces 31a, 32a, 33a faces the top surfaces 31a, 32a, 33a, respectively.

When electronic components 21, 22, 23, etc. are mounted on the second surface 20b (predetermined surface) of the substrate 20, a heat dissipation structure similar to that of each of the above embodiments is formed on the second surface 20b side. May be good.

The heat dissipation structure of the electronic component of each of the above embodiments can be applied not only to the substrate 20 and the housing 30 of the PLC 10 but also to the board and the housing of other ECUs (Electronic Control Units) and the like.

20 ... Substrate, 20a ... First surface, 20c ... Intermittent part, 20d ... Intermittent part, 21 ... Electronic component, 22 ... Electronic component, 23 ... Electronic component, 30 ... Housing, 30a ... Bottom, 31 ... Protruding portion, 31a ... top surface, 32 ... protrusion, 32a ... top surface, 33 ... protrusion, 33a ... top surface, 35 ... slope, 40 ... heat transfer sheet, 40A ... heat transfer sheet.

Claims (4)

A substrate on which a plurality of electronic components including electronic components having different heights are mounted on a predetermined surface, and
A housing having a planar top surface facing each electronic component and having each protruding portion that protrudes greatly as the height of each facing electronic component decreases.
It is sandwiched between the electronic components and the protrusions, abuts on the electronic components, forms a gap between the electronic components on the substrate, and the protrusions and the housing. The heat transfer sheet in contact with the intermediate portion of each of the protrusions in
Equipped with
The plurality of electronic components include a first electronic component and a second electronic component having a height higher than the height of the first electronic component.
The distance between the top surface of the first protruding portion, which is the protruding portion facing the first electronic component, and the second electronic component in the direction parallel to the predetermined surface is the protrusion facing the second electronic component. A heat dissipation structure of an electronic component, which is shorter than the distance between the top surface of the second protruding portion, which is a portion, and the first electronic component. In the housing, the shortest distance with respect to the second electronic component between the top surface of the first protrusion and the top surface of the second protrusion is the second electronic component and the second protrusion. The heat dissipation structure of an electronic component according to claim 1 , wherein a slope shorter than the shortest distance from the top surface of the portion is formed. The heat transfer structure for an electronic component according to claim 1 or 2 , wherein the heat transfer sheet is formed to have a uniform thickness before being sandwiched between the electronic component and each protrusion. The heat dissipation structure of the electronic component according to any one of claims 1 to 3 , wherein the distance between each of the facing electronic components and the top surface of each of the protrusions is equal to each other.

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