Miniature electronic apparatus

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a heat dissipation means of a small electronic device in which a component such as an electronic integrated circuit having a large power consumption is present.

【0002】

[Conventional technology]

In recent years, along with the sophistication of small electronic devices, the performance of heat-generating components such as electronic integrated circuits has improved, and the power consumption of these electronic integrated circuits has increased, that is, the amount of heat generated has increased. Conventionally, heat dissipation of an electronic integrated circuit in such a case depends on natural heat dissipation.

【0003】

Hereinafter, a configuration of a conventional small electronic device will be described as an example with reference to FIG.

【0004】

FIG. 6 is a diagram showing the configuration of a conventional small electronic device. 1 is an upper housing, 2 is a lower housing, and 3 is an area junction component such as CSP or BGA, which is an electronic integrated circuit with high power consumption. Is. 4 is a circuit board on which the electronic integrated circuit 3 is mounted, 5a and 5b are ventilation holes inlets for heat dissipation provided in the lower housing 2, and 6 is for heat dissipation provided in the upper housing 1. The ventilation hole outlets, 7a, 7b, and 7c are the air paths from the upper part of the electronic integrated circuit 3 to the ventilation hole outlet 6, and 8a and 8b are the inflow air in the housing that flows from the outside of the housing to the inside of the housing. , 9 are the outflow air outside the housing that flows out to the outside of the housing.

【0005】

Next, in a small electronic device having such a configuration, heat dissipation means of the electronic integrated circuit 3 will be described.

【0006】

First, when a small electronic device operates and heat is generated from the electronic integrated circuit 3, the heat is transferred to the air above the electronic integrated circuit 3 to heat it. As a result, the density of the air above the electronic integrated circuit 3 becomes low, causing buoyancy and rising. After that, according to the paths represented by the air paths 7a, 7b, and 7c, the air is discharged from the ventilation hole outlet 6 as the outflow air 9 outside the housing. In addition, new cold air having the same capacity as the discharged outflow air 9 is discharged from the outside to the inside of the housing composed of the upper housing 1 and the lower housing 2, and the inflow air 8a and 8b inside the housing. As a result, it will be sucked from the ventilation hole entrances 5a and 5b. The natural convection is generated in this way to dissipate heat from the electronic integrated circuit 3.

【0007】

[Problems to be Solved by the Invention]

However, the heat dissipation means of the electronic integrated circuit of the small electronic device having the above-described configuration has the following problems.

【0008】

The power consumption of heat-generating components such as electronic integrated circuits is increasing due to high performance and high functionality, and the amount of heat generated is increasing. However, on the other hand, in terminal devices for which miniaturization is being promoted, there is a limit to the increase in size of the housing itself, and the high-density mounting of circuit boards is progressing. It is difficult to secure space. Therefore, stagnation occurs in air convection, natural convection is not smooth, and a forced air cooling device such as a heat sink or a fan having a large volume cannot be added, so that efficient heat dissipation of heat generating parts cannot be performed. As a result, the temperature rise in the internal space of the housing increases, and the temperature rise of the touchable part on the surface of the housing, which the user can easily touch, also increases, causing danger, or the heat generating component itself or other parts. There is a problem that it may cause a failure of heat-sensitive parts.

【0009】

Therefore, the present invention solves the above-mentioned problems and provides a small electronic device having improved heat dissipation efficiency of heat-generating components such as an electronic integrated circuit by configuring so as to promote natural convection in the vicinity of the heat-generating components. The purpose.

【0010】

[Means for solving problems]

In order to solve this problem, the means for constructing a small electronic device of the present invention includes a circuit board on which a heat generating element is mounted, a housing in which the circuit board is housed and a ventilation port is formed, and at least one end of the ventilation. It has a protruding portion including a part of the mouth and extends toward the inside of the housing, and the opening at the other end of the protruding portion is arranged above the heat generating element.

【0011】

With this configuration, the air warmed by transferring heat from the heat generating component, that is, the air in the space surrounded by the protruding portion, is discharged to the outside of the housing through the ventilation holes without stagnation, and on the other hand, the discharged capacity. The same volume of air as above will be sucked into the space surrounded by the protrusion, promoting smooth natural convection, and effective heat dissipation of heat generating parts with a very simple configuration. It will be possible.

【0012】

Further, the air in the space surrounded by the protrusion does not diffuse to the outside other than this space, and therefore the temperature rise in the internal space of the housing is suppressed, which causes danger to the user and failure of parts. No inconvenience will occur.

【0013】

From the above, it is possible to provide a small electronic device having high heat dissipation means for heat generating parts and having high safety and reliability.

【0014】

BEST MODE FOR CARRYING OUT THE INVENTION

The invention according to claim 1 of the present invention includes a circuit board on which a heat generating element is mounted, a housing in which the circuit board is housed and a ventilation port is formed, and one end side including at least a part of the ventilation port inside the housing. It has a protrusion extending toward it, and the opening at the other end of the protrusion is arranged above the heat generating element. With this configuration, the air warmed by transferring heat from the heat generating element, that is, the air in the space surrounded by the protrusions, is discharged to the outside of the housing through the ventilation port without stagnation, and on the other hand, with the discharged capacity. Air of the same capacity will be sucked into the space surrounded by the protrusion, smooth natural convection will be promoted, and effective heat dissipation of heat generating parts will be possible with a very simple configuration. Become. In addition, the air in the space surrounded by the protrusions does not diffuse to the outside other than this space, and therefore the temperature rise in the internal space of the housing is suppressed, which is inconvenient such as danger to the user and failure of parts. Has the effect of not occurring.

【0015】

The invention according to claim 2 of the present invention is characterized in that, in the configuration of the small electronic device according to claim 1 of the present invention, the protruding portion is provided so as to be inclined from the surface of the housing. With this configuration, the amount of movement of the warmed air is increased, that is, the air in a long section is kept at a high temperature in the protrusion, so that the buoyancy is increased. As a result, the wind power is also increased, the natural convection is further promoted, and the heat dissipation of the heat generating parts becomes more effective.

【0016】

The invention according to claim 3 of the present invention houses a circuit board on which a heat generating element is mounted, a ventilation pipe made of a heat good conductor having a contact portion in contact with the heat generating element on one end side, and a circuit board and a ventilation pipe. It has a housing in which a ventilation port is formed, and the ventilation pipe is arranged so that the contact portion is in contact with the heat generating element and the first opening on the other end side faces at least a part of the ventilation port. It is characterized in that a second opening that allows air in the housing to be sucked is provided in the ventilation pipe on the one end side that forms the contact portion of the ventilation pipe. With this configuration, in addition to the action according to claim 1 or 2 of the present invention, the heat that is directly transferred from the heat generating element to the ventilation pipe made of a heat good conductor and then conducted through the ventilation pipe is expected to promote natural convection. The more, it can be positively transmitted to the space surrounded by the ventilation pipe. That is, the promotion of natural air cooling and the function of the heat-good conductor of the ventilation pipe as a heat-dissipating plate synergistically increase the heat-dissipating effect, and have the effect of significantly improving the heat-dissipating efficiency of the heat-generating element.

【0017】

In the invention according to claim 4 of the present invention, in the configuration of the small electronic device according to claim 3 of the present invention, the circuit board is thermally conductive over the area occupied by the heat generating element at the mounting position of the heat generating element. A through-hole portion is provided, and the contact portion of the ventilation pipe is arranged in contact with the through-hole portion. With this configuration, in addition to the above-described operation according to claim 3 of the present invention, heat transferred to the heat good conductor, which is a ventilation tube, is transmitted from the outside of the housing even on the side opposite to the side on which the heat generating element of the circuit board is mounted. It is further transmitted to the inflowing cold air, and has the effect of further improving the heat dissipation effect.

【0018】

The invention according to claim 5 of the present invention includes a circuit board on which a heat generating element is mounted, a heat-resistant conductor having a contact portion with the heat-generating element, and a housing including the circuit board and the heat-generating conductor. The body is provided with a ventilation hole that allows air to be sucked and discharged from the inside and outside of the housing, and a protruding portion that extends from the general circumference of the ventilation hole toward the inside of the housing so as to surround the ventilation hole. When the heat-good conductor is incorporated into the housing, the heat-good conductor is formed so as to include a part of the heat-good conductor and to surround the space up to the periphery of the ventilation hole by the protruding portion. With this configuration, in addition to the action described in claim 3 of the present invention, even when there are a plurality of heat generating elements, there is an action that effective heat dissipation can be achieved with a simple configuration.

【0019】

The invention according to claim 6 of the present invention is a through that is thermally conductive at a position where it is in contact with or joined with a heat generating element of a circuit board in the configuration of the small electronic device according to claim 5 of the present invention. It is characterized in that a hole is provided and the thermal conductor is configured to be in contact with the through hole. With this configuration, in addition to the above-described operation according to claim 5 of the present invention, the heat transferred to the heat good conductor also flows in from the outside of the housing on the side opposite to the side on which the heat generating element of the circuit board is mounted. It is further transmitted to cold air, and has the effect of further improving the heat dissipation effect.

【0020】

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 5. In these drawings, the same members are designated by the same reference numerals, and duplicate description is omitted.

【0021】

(Embodiment 1) FIG. 1 is a diagram showing a configuration of a small electronic device according to the first embodiment of the present invention.

【0022】

In FIG. 1, 11 is an upper housing, 12 is a lower housing, and 13 is an area junction component such as CSP or BGA, which is an electronic integrated circuit with high power consumption. Reference numeral 14 denotes a circuit board on which the electronic integrated circuit 13 is mounted, 15a and 15b are ventilation hole inlets for heat dissipation provided in the lower housing 12, and 16 is a ventilation hole inlet provided in the upper housing 11 for heat dissipation. It is a ventilation hole exit. Reference numeral 17 denotes a protruding portion that encloses a part or the whole of the ventilation hole outlet 16 and protrudes toward the inside of the housing. The opening on the side of the electronic integrated circuit 13 of 17 is larger than the outer shape of the electronic integrated circuit 13, and the space from the roughly upper portion of the electronic integrated circuit 13 to the ventilation hole outlet 16 is surrounded by the protruding portion 17. Reference numeral 18 is the inflow air in the protrusion that flows into the space surrounded by the protrusion 17, 19 is the outflow air outside the housing, and 20a and 20b are the inflow air inside the housing.

【0023】

Next, in a small electronic device having such a configuration, heat dissipation means of the electronic integrated circuit 13 will be described.

【0024】

First, when a small electronic device operates and heat is generated from the electronic integrated circuit 13, the air in the space surrounded by the protrusion 17 located at the upper part of the electronic integrated circuit 13 is warmed. The warmed air becomes less dense and buoyant and rises. After that, the air is discharged from the ventilation hole outlet 16 as the outflow air 19 outside the housing. In addition, new cold air having the same capacity as the discharged outflow air 19 is sucked from the outside of the space surrounded by the protrusion 17 into the space surrounded by the protrusion 17 as the inflow air 18 inside the protrusion. become. Further, new cold air having the same capacity as the capacity of the discharged out-of-housing air 19 (the capacity of the inflow air 18 in the protrusion sucked into the space surrounded by the protrusion 17) is introduced into the upper housing 11 and the lower housing. The housing composed of the body 12 is sucked from the outside to the inside as the inflow air 20a and 20b in the housing from the ventilation hole inlets 15a and 15b.

【0025】

As described above, in the heat radiating means according to the embodiment of the present invention, the air warmed by transferring heat from the electronic integrated circuit 13, that is, the air in the space surrounded by the projecting portion 17, does not stagnate and creates a ventilation hole. Since the air is smoothly discharged to the outside of the housing through the air, the air is efficiently discharged and sucked in the space surrounded by the projecting portion 17. As a result, natural convection in the space surrounded by the protrusion 17 is promoted, and heat dissipation of the electronic integrated circuit 13 can be effectively performed with such a simple configuration.

【0026】

Further, the air that can be warmed is only the air in the space surrounded by the protrusion 17, and does not diffuse to the outside of this space. Therefore, the entire inside of the housing is warmed and the touchable portion on the surface of the housing becomes hot. It does not cause damage or damage the heat-sensitive parts mounted on the circuit board 14.

【0027】

In the first embodiment, the protrusion 17 is described in the case of 1, but a plurality of protrusions may be provided depending on the number of electronic integrated circuits or heat generating parts, and the protrusions may be provided with a plurality of protrusions. A plurality of electronic integrated circuits or heat generating components may be arranged.

【0028】

(Embodiment 2) FIG. 2 is a diagram showing a configuration of a small electronic device according to the second embodiment of the present invention.

【0029】

In FIG. 2, on the circuit board 14, the electronic integrated circuit 13 is arranged at a position away from directly below the ventilation hole outlet 16, and as a result, the moving distance of the air surrounded by the protrusion 17 to the ventilation hole outlet 16 is increased. The protrusion 17 is longer than the case where the protrusion 17 is provided perpendicular to the upper housing 11.

【0030】

In such a configuration, the suction operation of the inflow air 18 in the protruding portion and the inflow air 20a and 20b in the housing and the discharge operation of the outflow air 19 outside the housing are the same as those in the first embodiment.

【0031】

However, as in the second embodiment, when the moving distance of the warmed air becomes long, that is, the air in the long section is kept at a high temperature in the protrusion 17, the buoyancy increases, and the protrusion 17 increases accordingly. The airflow inside the project will also increase, and therefore the capacity of the inflow air 18 in the protrusion will also increase. In this way, in the heat radiating means of the present invention, the chimney effect is further exerted and the natural convection is further promoted, so that the heat radiating effect of the electronic integrated circuit 13 is further improved.

【0032】

In this way, in the heat radiating means of the present invention, natural convection is further promoted, so that the heat radiating effect of the electronic integrated circuit 13 is further improved.

【0033】

(Embodiment 3) FIG. 3 is a diagram showing a configuration of a small electronic device according to the third embodiment of the present invention.

【0034】

In FIG. 3, 30 is a sheet metal, and the sheet metal 30 is made of a thermally good conductor such as copper or aluminum, and is formed so as to surround the space from the upper part of the electronic integrated circuit 13 to the ventilation hole outlet 16. It is in contact with the circuit 13 at the contact portion 31. 32 is the space inside the sheet metal, which is the space from the upper part of the electronic integrated circuit 13 surrounded by the sheet metal 30 to the ventilation hole outlet 16, 33 is the air inflow hole provided in the sheet metal 30, and 34 is the air inflow. It is the inflow air in the sheet metal that flows into the sheet metal inner space 32 from the hole 33.

【0035】

Next, in a small electronic device having such a configuration, heat dissipation means of the electronic integrated circuit 13 will be described.

【0036】

First, when a small electronic device operates and heat is generated from the electronic integrated circuit 13, heat is transferred to the sheet metal 30 via the contact portion 31. This transferred heat is transferred to the air in the sheet metal inner space 32 and the air outside the sheet metal inner space 32. After that, the heat transferred to the air in the sheet metal inner space 32 warms the air in the sheet metal inner space 32. This warmed air becomes less dense and buoyant and rises. After that, the air is discharged directly from the ventilation hole outlet 16 as the outflow air 19 outside the housing. Further, new cold air having the same capacity as the discharged out-of-housing air 19 is sucked from the outside of the sheet metal inner space 32 into the sheet metal inner space 32 as the inflow air 34 in the sheet metal through the air inflow hole 33. .. Further, new cold air having the same capacity as the discharged outflow air 19 (capacity of the inflow air 34 in the sheet metal sucked into the sheet metal inner space 32) is discharged from the upper housing 11 and the lower housing 12. The air flowing into the housing from the outside to the inside is sucked from the ventilation hole inlets 15a and 15b as the inflow air 20a and 20b.

【0037】

As described above, in the heat radiating means according to the embodiment of the present invention, the warmed air in the sheet metal inner space 32 is smoothly discharged to the outside of the housing through the ventilation holes without stagnation. Air discharge and suction in space 32 will proceed efficiently. As a result, natural convection in the sheet metal inner space 32 is promoted, and the heat transferred from the electronic integrated circuit 13 to the sheet metal 30 is further positively transferred to the air in the sheet metal inner space 32. Become. Therefore, the cooling of the sheet metal 30 is enhanced, that is, the heat dissipation of the electronic integrated circuit 13 can be promoted extremely effectively.

【0038】

Further, since heat is positively transferred to the air in the sheet metal inner space 32, the ratio of heat transferred to the space outside the sheet metal inner space 32 becomes extremely small, and the entire inside of the housing is warmed and the housing is warmed. The touchable part on the surface of the body does not become hot, and the heat-sensitive parts mounted on the circuit board 14 are not damaged.

【0039】

As described above, the promotion of natural air cooling in the sheet metal inner space 32 and the function of the sheet metal 30 as a heat sink synergistically increase the heat dissipation effect, and the heat dissipation efficiency of the electronic integrated circuit 13 is significantly improved. ..

【0040】

(Embodiment 4) FIG. 4 is a diagram showing a configuration of a small electronic device according to the fourth embodiment of the present invention.

【0041】

In FIG. 4, 40 is a thermally conductive through hole (hereinafter referred to as a thermal via) provided on the circuit board 14 directly below the electronic integrated circuit 13, and 41 is a part of the sheet metal 30 and is referred to as the thermal via 40. It is the contact part of.

【0042】

Next, in a small electronic device having such a configuration, heat dissipation means of the electronic integrated circuit 13 will be described.

【0043】

First, when a small electronic device operates and heat is generated from the electronic integrated circuit 13, the heat is transferred to the air and the thermal via 40 in the sheet metal inner space 32 located above the electronic integrated circuit 13. The heat transferred to the thermal via 40 is transferred to the sheet metal 30 via the contact portion 41, conducted inside the sheet metal 30, and then to the air in the sheet metal inner space 32 or to the air outside the sheet metal inner space 32. Or, it will be transmitted to the space on the side opposite to the side on which the electronic integrated circuit 13 of the circuit board 14 is mounted. After that, the heat transferred to the air in the sheet metal inner space 32 warms the air in the sheet metal inner space 32. This warmed air becomes less dense and buoyant and rises. The subsequent suction operation of the inflow air 34 in the sheet metal and the inflow air 20a and 20b in the housing and the discharge operation of the outflow air 19 outside the housing are the same as those in the third embodiment. Further, the heat transferred to the space on the side opposite to the side on which the electronic integrated circuit 13 of the circuit board 14 is mounted is further transferred to the fresh cold inflow air 20a and 20b in the housing flowing from the outside of the housing. Will be done.

【0044】

As described above, in the heat radiating means according to the embodiment of the present invention, in addition to obtaining the same effect as that of the third embodiment, the space on the side opposite to the side on which the electronic integrated circuit 13 of the circuit board 14 is mounted is obtained. The heat dissipation effect of the sheet metal 30 is further improved, and therefore the heat dissipation effect of the electronic integrated circuit 13 is also dramatically improved.

【0045】

Of course, as in the third embodiment, it goes without saying that the ratio of heat transferred to the air outside the sheet metal inner space 32 is extremely small.

【0046】

(Embodiment 5) FIG. 5 is a top view showing the configuration of a small electronic device according to the fifth embodiment of the present invention.

【0047】

In FIG. 5, 50a and 50b are area junction components such as CSP and BGA, and are electronic integrated circuits with high power consumption. 51a, 51b, 51c and 51d are ventilation holes for heat dissipation provided in the lower housing 12, and 52a, 52b, 52c and 52d are ventilation holes for heat dissipation provided in the upper housing 11. 53a and 53b are upper protrusions protruding from the periphery of the ventilation hole outlets 52a and 52d toward the inside of the housing, and are in close contact with the side surfaces of the upper housing 11. 54a and 54b are downward protrusions protruding from the periphery of the ventilation hole inlets 51a and 51d toward the inside of the housing, and are in close contact with the side surfaces of the lower housing 12. Further, 55a is an internal space formed by an upper protrusion 53a, a lower protrusion 54a, an upper housing 11 and a lower housing 12, and 55b is an upper protrusion 53b, a lower protrusion 54b, an upper housing 11, and a lower housing. It is an internal space formed by 12. 56a, 56b, 56c, 56d are the outflow air outside the housing, and 57a, 57b, 57c, 57d are the inflow air inside the housing. 58a and 58b are thermally conductive through holes (hereinafter referred to as thermal vias) provided on the circuit boards 14 directly below the electronic integrated circuits 50a and 50b, respectively, and 59 is sheet metal in the internal spaces 55a and 55b. Some of them are included. 60a and 60b are a part of the sheet metal 59 and are contact portions with the thermal vias 58a and 58b, respectively.

【0048】

Next, in a small electronic device having such a configuration, heat dissipation means of the electronic integrated circuits 50a and 50b will be described.

【0049】

First, when a small electronic device operates and heat is generated from the electronic integrated circuits 50a and 50b, the heat is transferred to the air and thermal vias 58a and 58b in the housing internal space located above the electronic integrated circuits 50a and 50b. Is transmitted. The heat transferred to the thermal vias 58a and 58b is transferred to the sheet metal 59 via the contact portions 60a and 60b, and then to the space on the circuit board 14 opposite to the side on which the electronic integrated circuits 50a and 50b are mounted. There is heat transferred to the air in the internal spaces 55a and 55b through the sheet metal 59. In the case of heat that is conducted through the sheet metal 59 and transferred to the air in the internal spaces 55a and 55b, the air in the internal spaces 55a and 55b warmed by this heat becomes less dense and buoyant and rises. Subsequent suction operations of the inflow air 57a and 57d inside the housing and discharge operations of the outflow air 56a and 56d outside the housing are the same as those of the first to fourth embodiments. Further, in the case of heat transferred to the space on the side opposite to the side on which the electronic integrated circuits 50a and 50b of the circuit board 14 are mounted, the heat transfer is promoted by the same heat dissipation operation as in the fourth embodiment. Become.

【0050】

As described above, the heat radiating means according to the embodiment of the present invention has the same effect as that of the fourth embodiment as described above. Of course, as in the third embodiment, it goes without saying that the ratio of heat transferred to the air in the housing internal space located above the electronic integrated circuits 50a and 50b is extremely small.

【0051】

Furthermore, even when there are a plurality of electronic integrated circuits, it is not necessary to take the measures described in the first to fourth embodiments for each of the electronic integrated circuits, and a very efficient heat dissipation can be obtained with a simple structure. Will be.

【0052】

Although the present embodiment has been described as an application to the fourth embodiment, there is no problem even if the present embodiment is applied to the third embodiment.

【0053】

[Effect of the invention]

As described above, according to the present invention, natural convection in the vicinity of heat-generating components as represented by electronic integrated circuits is promoted, so that extremely efficient heat dissipation becomes possible. In addition, the temperature rise in the internal space of the housing is suppressed, and inconveniences such as danger to the user and failure of parts do not occur, and a safe and highly reliable small electronic device becomes possible.

【0054】

Furthermore, by bringing a heat-generating component, such as a sheet metal, into contact with the heat-generating component, and surrounding the space from the top of the heat-generating component to the general circumference of the ventilation hole, air can flow into this space. In addition, the function as a heat sink for heat-generating parts of a heat-good conductor is added, and the heat dissipation effect can be synergistically improved.

【0055】

In addition, a thermal via is provided at the position where it is in contact with or joined to the heat-generating component of the circuit board, and the heat-generating component of the circuit board is opposite to the side where the heat-generating component is mounted by configuring the thermal conductor to contact the thermal via. It is possible to dissipate heat to the side as well, further improving the heat dissipation effect.

【0056】

Furthermore, a portion generally made by forming so as to surround the space up to the surrounding contain and vents a portion of the heat conductor by provided separately, originating even if there is a plurality of heat components, a simple structure Effective heat dissipation is possible.

[Simple explanation of drawings]

[Figure 1]

The figure which showed the structure of the small electronic device in Embodiment 1 of this invention. [Figure 2]

The figure which showed the structure of the small electronic device in Embodiment 2 of this invention. [Fig. 3]

The figure which showed the structure of the small electronic device in Embodiment 3 of this invention. [Fig. 4]

The figure which showed the structure of the small electronic device in Embodiment 4 of this invention. [Fig. 5]

Top view showing the configuration of the small electronic device according to the fifth embodiment of the present invention. [Fig. 6]

Diagram showing the configuration of a conventional small electronic device [Explanation of symbols]

11 Upper housing 12 Lower housing 13 Electronic integrated circuit 14 Circuit board 15a, 15b Ventilation hole entrance 16 Ventilation hole exit 17 Overhang 18 Inflow air in the protrusion 19 Outflow air from the housing 20a, 20b Inflow air in the housing 30 sheet metal 31 Contact 32 Sheet metal space 33 Air inflow hole 34 Inflow air in sheet metal 40 Through hole (thermal via) 41 Contact 50a, 50b electronic integrated circuits 51a ~ 51d Ventilation hole entrance 52a ~ 52d Ventilation hole exit 53a, 53b Upper protrusion 54a, 54b Lower protrusion 55a, 55b Interior space 56a ~ 56d Outflow air outside the housing 57a ~ 57d Inflow air inside the housing 58a, 58b Through hole (thermal via) 59 sheet metal 60a, 60b contact