JP4005678B2 - Heat dissipation structure for electronic parts - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat dissipation structure used to promote heat dissipation from an electronic component such as an integrated circuit.
[0002]
[Background Art and Problems to be Solved by the Invention]
In recent years, the development of CPUs (Central Processing Units) capable of high-speed operation has dramatically improved the performance of computers. Along with this, a large amount of heat generated from the CPU is efficiently dissipated, and a heat radiator with a large number of fins is fixed to the upper surface of the CPU so that the CPU does not malfunction. Consideration such as hitting is made.
[0003]
Moreover, as what is emitted from an electronic component, not only heat but electromagnetic waves may be a problem. In other words, not only heat but also electromagnetic waves are emitted from the fins and the like to the periphery, adversely affecting the operation of other electronic components in the vicinity of the electronic component, and the electronic device to which the electronic component is applied. There are concerns about the damage caused by electromagnetic waves leaking to the surrounding area. Such a problem occurs not only in the CPU but also in various electronic components.
[0004]
The present invention has been made in view of such a problem, and an object of the present invention is to make it possible to satisfactorily absorb not only heat but also electromagnetic waves emitted from electronic components in a heat dissipation structure for electronic components .
[0005]
[Means for Solving the Problems]
The heat dissipation structure for an electronic component according to claim 1 of the present invention, which has been made to solve such a problem, is absorbed by at least a plate-shaped electromagnetic wave absorber and an electromagnetic wave absorber on the upper surface of the electronic component to be radiated. A metal plate for reflecting unsuccessful electromagnetic waves to the electromagnetic wave absorber, a plate-like dielectric, and a heat radiator provided with a plurality of heat radiation fins are laminated in this order, and the electromagnetic wave absorption The body is characterized in that an adjustment hole which is a through hole for adjusting a matching frequency is formed on an absorption substrate which is a plate having a thickness of 0.1 to 1 mm made of a radio wave absorption material .
[0007]
According to a second aspect of the present invention, in the heat dissipation structure for an electronic component according to the first aspect, the heat dissipating body is grounded.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The heat dissipating structure for an electronic component according to claim 1 includes a plate-shaped electromagnetic wave absorber, a metal plate, a plate-shaped dielectric, and a plurality of heat dissipating fins on an upper surface of an electronic component such as a CPU. Are stacked in this order. In addition to this, for example, a putty or an adhesive for fixing the electromagnetic wave absorber to the upper surface of the electronic component may be laminated. The “upper surface” of the electronic component refers to a surface away from a printed circuit board or the like on which the electronic component is mounted. Therefore, when an electronic component is mounted on the back surface of the horizontal printed circuit board, the upper surface faces downward.
[0009]
In this heat dissipation structure for electronic parts, electromagnetic waves emitted from the electronic parts are first absorbed to some extent by the electromagnetic wave absorber. A portion of the electromagnetic wave that has penetrated without being absorbed is partially reflected by the metal plate and again absorbed by the electromagnetic wave absorber. The remaining electromagnetic wave remains as an eddy current on the metal plate, but a capacitive element is formed by sandwiching a dielectric between the metal plate and the heat dissipator. Combined with the current, a kind of LC filter is made. This LC filter attenuates eddy currents, and very little electromagnetic waves are emitted to the outside from the fins of the heat dissipating body.
[0010]
Therefore, according to the heat dissipation structure for an electronic component, the heat of the electronic component can be efficiently released and the electromagnetic wave can be efficiently absorbed. Here, examples of the dielectric include resins, ceramics, and resins obtained by kneading fillers. Here, examples of the resin include epoxy, polyethylene, polycarbonate, and silicone, and examples of the ceramic include barium titanate, SiC, Al2O3, BeO, MgO, AlN, and BN. Electromagnetic wave absorbers include ferrite (pulverized and sintered iron oxide), composite material of ferrite and synthetic resin, metal magnetic powder (iron aluminum silicon alloy (Sendust), iron nickel alloy (Permalloy), iron (A silicon alloy) and a synthetic resin composite material .
[0011]
As an electromagnetic wave absorber of the heat dissipation structure for electronic components according to claim 1 , a through hole for adjusting a matching frequency is formed on an absorption substrate made of a radio wave absorbing material in a plate shape having a thickness of 0.1 to 1 mm. The one with an adjustment hole is used.
In general, the thickness of the electromagnetic wave absorber is uniquely determined from the material constant of the material constituting the radio wave absorption substrate and the frequency of the radio wave to be absorbed. For example, the thickness of the microwave band is as thin as 1.0 mm or less. Conventionally, it has been considered extremely difficult. The reason why such a thinness was realized is that an adjustment hole was formed in the absorption substrate. This will be described with reference to FIGS.
[0012]
Fig.1 (a) is a perspective view which shows the test subject used for experiment, FIG.1 (b) is a front view of an absorption board | substrate. As shown in FIG. 1 (a), the test subject is the one in which the absorbing substrate 11 formed in a disk shape having a diameter of 19.44 mm and a thickness of 0.9 mm is loaded at the end of the coaxial tube 13. Rubber ferrite was used as a radio wave absorbing material for forming the film. The coaxial tube 13 includes an outer conductor 15 and an inner conductor 17, and a conductor plate 19 that short-circuits the outer conductor 15 and the inner conductor 17 is provided on the back side of the absorption substrate. And as shown in FIG.1 (b), the adjustment hole (diameter 2mm) 21 was formed in the board | substrate on the periphery of a diameter 11.0mm at equal intervals. The thing which formed the adjustment hole 21, the thing which formed four, and the thing which formed eight were prepared. The central hole 23 of the absorption substrate 11 is a hole through which the inner conductor 17 passes.
[0013]
These three kinds of absorption substrates 11 are respectively attached to the coaxial tube 13 and irradiated with a TEM wave from the left side of the figure, and the radio wave reflection attenuation amount calculated from the intensity of the radio wave measured on the same side is shown. It is a graph of FIG. In the graph of FIG. 2, the horizontal axis represents frequency and the vertical axis represents radio wave reflection attenuation measured at each frequency. As shown in the figure, by forming eight adjustment holes 21, a radio wave reflection attenuation amount of −20 dB is exhibited at a frequency of 2.2 to 3 GHz. That is, even in the thin absorption substrate 11 of 0.9 mm, by forming a large number of minute adjustment holes, the matching characteristics of the absorption substrate 11 can be improved compared to the case where it is not formed, and absorption is possible in the range of 2.2 to 3 GHz. Can be.
[0014]
FIG. 3 shows a graph when the thickness of the absorption substrate 11 is changed to 0.8 mm. As shown in FIG. 3, when the thickness is 0.8 mm, the matching frequency when the number of adjustment holes is 8 is 1.5 to 2.2 GHz. That is, even if the thickness is 1 mm or less, by appropriately providing an adjustment hole, in an embodiment using rubber ferrite, radio waves having a frequency of 1 GHz or more can be absorbed.
[0015]
This is, as a result of an experiment conducted by the present inventor, that, when a through hole is formed in an absorption substrate having a thickness of 1 mm or less, contrary to expectation, the imaginary part of the relative permeability value μr = μr′−jμr ″. Due to the fact that the frequency at which the real part becomes 1 decreases and the frequency at which the real part becomes 1. Specifically, μr ″> μr ′ (where μr ′ is approximately 1), which is a condition for magnetic wave absorbers to absorb radio waves.
This relationship is maintained even if through holes are provided. In this case, when the absorption substrate has a thickness of 2 to 8 mm, when the through-hole is formed, both μr ′ and μr ″ increase, and in particular, the magnetic permeability μr ′ related to the matching frequency is approximately 1. Shifts to a high frequency range. However, when the thickness is less than 1 mm, the values of the real part μr ′ and the imaginary part μr ″ of the magnetic permeability begin to decrease from the increased state by providing a through hole, and the frequency at which μr ′ becomes 1 shifts again to the low frequency side. Come. However, in this case, the value of μr ″ still maintains the relationship of (1) above and takes a value equal to or slightly larger than the value of μr ″ at the time of original alignment (when no through hole is provided). As a result, it is possible to provide characteristics equivalent to the matching characteristics at the original matching thickness (for example, 8 mm) by forming through holes in the absorption substrate having a thickness of only 1 mm or less. This through hole is the adjustment hole of the present invention.
[0016]
Thus, according to the heat dissipation structure for an electronic component according to claim 1 , since the electromagnetic wave absorber is as thin as 1 mm or less, it is not bulky even when laminated with a metal plate or dielectric, Since the plate operates in the same manner as the conductor plate 19 shown in FIG. 1, it is possible to effectively absorb radio waves leaking from the electronic component.
[0017]
In the heat dissipating structure for electronic parts according to claim 2 , the heat dissipating body is grounded. As a result, the electromagnetic wave reaching the heat radiating body can flow to the ground or the housing, and leakage of the electromagnetic wave to the periphery of the electronic component can be steadily prevented.
[0018]
【Example】
Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 4 is a side view showing a state in which the electronic component heat dissipation structure as the first embodiment of the present invention is applied to the integrated circuit 24. As shown in this figure, a putty 27, an electromagnetic wave absorber 29, a metal plate 31, and a dielectric 33 are laminated from the integrated circuit 24 between the integrated circuit 24 and the radiator 25. . The integrated circuit 24 is mounted on a printed circuit board 35 , and the heat radiating body 25 is grounded by a conducting wire 37. In addition, the capacitor 33 is formed by sandwiching the dielectric 33 between the metal plate 31 and the radiator 25.
[0019]
According to such a heat dissipation structure for electronic components, the electromagnetic wave emitted from the integrated circuit 24 and penetrating the putty 27 is absorbed to some extent by the electromagnetic wave absorber 29. A part of the electromagnetic wave not absorbed here is reflected by the metal plate 31 and is again absorbed by the electromagnetic wave absorber 29. The remaining electromagnetic wave remains as an eddy current on the metal plate 31, but the laminated structure of this portion is combined with the eddy current by the capacitive element composed of the metal plate 31, the dielectric 33, and the radiator 25. Do a kind of LC filter. The eddy current is attenuated by this LC filter. Moreover, since the heat radiating body 25 is grounded by the conducting wire 37, the electromagnetic wave emitted from the fins of the heat radiating body 25 to the outside is very small.
[0020]
Therefore, according to the heat dissipation structure for an electronic component, not only the heat of the integrated circuit 24 can be efficiently released from the heat radiator 25 but also the electromagnetic wave can be effectively prevented from leaking out.
Next, a second embodiment of the present invention is shown in FIG. 5A is a side view showing a state in which the electronic component heat dissipation structure of the second embodiment is applied to the integrated circuit 24, and FIG. 5B is an enlarged view of only the absorption substrate 11 and the metal plate 31 taken out. FIG. 5C is a cross-sectional view showing another aspect of the absorption substrate 11 and the metal plate 31.
[0021]
In the heat dissipation structure for electronic parts of the second embodiment, the electromagnetic wave absorber 29 in the first embodiment is changed to the absorption substrate 11. As shown in FIG. 5 (b), the absorption substrate 11 is formed with large and small through holes 21a and 21b together with a metal plate 31 laminated thereon. These adjustment holes 21a and 21b can improve the absorption characteristics of the absorption substrate 11, and the absorption substrate 11 exhibits an absorption effect equivalent to that of the electromagnetic wave absorber 29 of the first embodiment.
[0022]
Although the embodiments to which the present invention is applied have been described above, the present invention is not limited to these embodiments and can be implemented in various modes.
For example, depending on the frequency of the electromagnetic wave to be absorbed, as shown in FIG. 5C, the adjustment hole 21 may be formed only in the absorption substrate 11 or the size thereof may be made uniform. If the electromagnetic wave having a desired frequency cannot be absorbed even in this way, the adjustment hole 21 may be filled with a dielectric. In this way, the frequency that can be absorbed can be shifted to the lower side.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a subject of an experiment conducted to show the effect of the present invention.
FIG. 2 is a graph showing the results of an experiment conducted using the subject shown in FIG.
FIG. 2 is a graph showing the results of an experiment conducted by changing the thickness of the absorption substrate.
FIG. 4 is a side view showing a first embodiment of the present invention.
FIG. 5 is an explanatory view showing a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11, 11a, 11b ... Absorption board | substrate 13 ... Coaxial pipe 15 ... Outer conductor 17 ... Inner conductor 19 ... Conductor board 21, 22a, 22b ... Adjustment hole 24 ... Integrated circuit 25 ... Radiator 27 ... Putty 29 ... Electromagnetic wave absorber 31 ... Metal plate 33 ... Dielectric 35 ... Printed circuit board

Claims (2)

On the upper surface of the electronic component to be radiated, at least a plate-like electromagnetic wave absorber, a metal plate for reflecting electromagnetic waves that could not be absorbed by the electromagnetic wave absorber to the electromagnetic wave absorber, and a plate-like dielectric The body and the heat dissipating body having a plurality of heat dissipating fins are laminated in this order ,
The electromagnetic wave absorber is obtained by forming an adjustment hole, which is a through hole for adjusting a matching frequency, on an absorption substrate in which a radio wave absorption material is formed in a plate shape having a thickness of 0.1 to 1 mm <br / > Heat dissipation structure for electronic parts. The heat dissipating structure for an electronic component according to claim 1, wherein the heat dissipating member is grounded .

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