JP5018195B2 - Heat dissipation device - Google Patents

Description

  The present invention relates to a heat radiating device that radiates heat from a heat generating component such as a semiconductor module to a heat radiating member such as a heat sink or a chassis of an electronic device by using a graphite sheet having flexibility and high thermal conductivity and excellent heat dissipation. .

  In recent years, along with the downsizing and high performance of electronic devices, the downsizing and high performance of electronic components have been remarkably advanced, and high performance but high heat generation, such as power amplifiers and solid state relays. Heating parts such as semiconductor modules have been used in small electronic devices.

  When a heat generating component having a large heat generation amount is used in a small electronic device, a means for efficiently transferring heat dissipated from the heat generating component to the outside of the electronic device and dissipating heat is required.

  Conventionally, as heat dissipation means from heat-generating components used in such electronic devices, water is enclosed in a cooling fan that sends air for cooling or a thin tube in a vacuum state, and the latent heat of evaporation of water is used. Heat pipes that carry heat are often used.

  However, especially in thin electronic devices such as mobile phones, the above fans and heat pipes are difficult to use, so a sheet-like heat transfer material is sandwiched between the heat-generating component and the heat-dissipating member to improve thermal coupling. Therefore, a method of performing efficient heat dissipation is taken.

For example, Patent Document 1 is known as prior art document information relating to the invention of the present application.
JP 2005-197601 A

  Heat-generating parts such as semiconductor modules such as power amplifiers and solid-state relays (hereinafter abbreviated as SSR) require adhesion to the heat-dissipating members when they are fixed to heat-dissipating members such as heat sinks and chassis of electronic equipment chassis. However, when mechanically pressurized and brought into close contact, failure such as disconnection inside the heat-generating component may occur.

  For this reason, such a heat-generating component is usually placed in a hard molded resin or metal case having rigidity, and is often used by being fixed to a heat radiating member by screws or the like at both ends of the case.

  At this time, a heat-dissipating member such as a heat sink or a chassis used for heat dissipation is widely used having a rigidity obtained by processing a metal.

  However, as shown in FIG. 7, when both ends of the heat generating component 71 are fastened with mounting fixing screws 72 and 73 and attached to a heat radiating member 74 such as a heat sink, the heat generating component 71 and the heat generating component 71 are A gap 75 may be formed between the heat dissipating member 74.

  When such a gap is formed, the thermal coupling between the heat generating component and the heat radiating member is lowered, and therefore a flexible heat transfer material such as a silicon pad is sandwiched between the heat generating component 71 and the heat radiating member 74. Thermal bonding is performed.

  However, a heat transfer material such as a silicon pad has a thermal conductivity of at most several W / (m · K), and the local heat generation at the center of the heat generating component 71 cannot be spread in the surface direction. There was a problem of becoming low.

  Therefore, the present invention solves the conventional problems as described above, and disperses local heat generation at the center of the heat generating component by the graphite sheet having high thermal conductivity in the plane direction, and between the heat generating component and the heat radiating member. An object of the present invention is to provide a heat dissipating device for effectively performing heat radiation by filling a gap formed and performing heat coupling more efficiently.

  The heat dissipating device of the present invention includes a heat generating component, a heat dissipating member attached to the heat generating component, and a graphite sheet disposed in a gap formed between the heat dissipating member and the heat generating component, The graphite sheet is a heat dissipating device in which a thick part is provided in a part corresponding to the gap part by folding a part thereof.

  A heat dissipation device that sandwiches a graphite sheet with a thick part by folding a part of the graphite sheet into a gap that occurs when a heat-generating component such as a semiconductor module is attached to a heat dissipation member such as a heat sink or chassis of an electronic device. In addition, excellent thermal coupling can be realized by an extremely simple and industrially easy method, and effective heat radiation can be performed from the heat-generating component.

  Hereinafter, an embodiment of a heat dissipation device of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is an exploded perspective view showing an example of a heat radiating device of the present invention. Both ends of a semiconductor module 11 such as a power amplifier or SSR as a heat generating component are sandwiched by a heat radiating member with a graphite sheet 21 having a thick portion 21a interposed therebetween. A heat radiating device 17 is configured by screwing the heat sink 12 to both ends with mounting fixing screws 13 and 14.

  A downward arrow A in FIG. 1 indicates the insertion direction of the mounting fixing screws 13 and 14.

  2 shows a configuration of the graphite sheet 21 having the thick portion 21a used in the heat dissipation device of the first embodiment, and FIG. 2 (a) is a plan view before the thick portion 21a is formed by folding, FIG. FIG. 2B is a plan view after the thick portion 21a is formed, and FIG. 2C is a side view after the thick portion 21a is formed.

  In FIG. 2A, a substantially rectangular graphite sheet 21 is formed with two folding lines 22 and 23 and holes 15b and 16b for fixing by screwing in the vicinity of the center thereof.

  Then, a part of the graphite sheet 21 shown in FIG. 2A is folded by folding lines 22 and 23 to obtain a graphite sheet 21 having a thick portion 21a near the center as shown in FIGS. 2B and 2C. .

  In FIG. 2C, the dimension in the thickness direction is exaggerated for the purpose of folding.

  Here, it is particularly important that the folded graphite sheets are folded in a connected state. For example, instead of the graphite sheet 21 that is folded to form the thick portion 21a, each piece is cut into the same size. Even if the thick sheets 21a are formed by stacking graphite sheets, the effect as in the first embodiment cannot be obtained.

  This is because the graphite sheet has a high thermal conductivity of about 600 to 1200 W / (m · K) in the plane direction due to the anisotropy of the crystal structure of graphite, but the thermal conductivity in the thickness direction is about 10 W / (m -K) Since the thickness is small, the heat transfer between the planes of each graphite sheet is limited in the thick portion formed by lamination with the graphite sheets separated one by one.

  On the other hand, in the graphite sheet used for the heat radiating device of the present invention, since the folded portions are all folded in a plane direction, the heat transmitted from the semiconductor module 11 in FIG. 1 is in the plane direction of the graphite sheet. Since the heat is transmitted to the entire surface and this heat can be transmitted to the wide surface of the heat sink 12, heat can be efficiently radiated.

  Further, when individual cut graphite sheets are used in an overlapping manner, the graphite sheets are very slippery and are likely to be displaced when they are sandwiched between the semiconductor module 11 and the heat sink 12 and tightened with the mounting fixing screws 13 and 14. .

  For this reason, it is difficult to set so that the thickest part comes to the most heat-generating part of the central part of the semiconductor module 11.

  On the other hand, the graphite sheet 21 according to the first embodiment forms the thick part 21a while being connected in the plane direction by folding, so the mounting fixing screws 13 are formed in the holes at both ends of the graphite sheet 21. By inserting and fixing 14, the thick portion 21 a can be fixed to the central portion of the semiconductor module 11 having a high heat generation temperature extremely easily and accurately.

  Since the graphite sheet 21 before folding shown in FIG. 2 (a) is substantially rectangular and simple, there is little punching loss when punching from one large pyrolytic graphite sheet, and the number of punches is the largest. It also has the feature of being able to do.

  In the heat dissipation device 17 configured as described above, the temperature of the semiconductor module 11 when a predetermined power was applied to the semiconductor module 11 was measured.

  The temperature was measured by a thermocouple (not shown) attached to the semiconductor module 11.

  As a result of measurement with the graphite sheet 21 shown in FIG. 2C interposed therebetween, the temperature of the semiconductor module 11 was 85 ° C.

  As a comparative example, the temperature of the semiconductor module 11 when a predetermined power is applied between the semiconductor module 11 and the heat sink 12 in the same manner as described above with the conventional graphite sheet 61 not provided with the thick portion shown in FIG. As a result of measurement, the temperature was 90 ° C.

  From this result, it can be seen that the heat dissipation effect is improved in the heat dissipation device according to the first embodiment as compared with the conventional case.

  This difference in heat dissipation effect is due to the following reasons.

  That is, when the semiconductor module 11 and the heat sink 12 shown in FIG. 1 are fixed by tightening the fixing screws 13 and 14, the lower surface where the semiconductor module 11 contacts the heat sink or the upper surface where the heat sink 12 contacts the semiconductor module 11 is hard molding resin. Since the material is highly rigid such as a metal plate, the upper surface of the semiconductor module 11 is deformed like a bow upward, and a gap is formed between the semiconductor module 11 and the heat sink 12.

  As in the case of the conventional graphite sheet 61 shown in FIG. 6 of the comparative example, when the thickness is the same throughout, this gap cannot be filled, resulting in hindrance to heat transfer, resulting in a decrease in heat dissipation effect. It is what will end up.

  On the other hand, when the graphite sheet 21 shown in FIG. 2C is used, the thick portion 21a is formed in the portion corresponding to the central portion of the semiconductor module 11, so that the gap portion is filled. Thus, the semiconductor module 11 and the heat sink 12 can be in close contact with each other.

  Furthermore, since this thick part 21a is formed by folding a part of one continuous graphite sheet 21, the characteristics of the graphite sheet having a large thermal conductivity in the plane direction can be sufficiently exhibited, and the heat dissipation effect. Can be improved.

  Here, the heat generation of the semiconductor module 11 has a significant effect on the life of the semiconductor module 11 even if the temperature rises by 1 ° C. or 2 ° C. from the rated temperature. Thus, it can be seen that an efficient heat dissipation effect is obtained in the heat dissipation device of the first embodiment.

  Next, a method for producing the graphite sheet 21 will be described.

First, a 75 μm thick polyimide film is heated at 2500 ° C. for 2 hours in an inert atmosphere such as Ar or N ₂ in a baking furnace to produce a pyrolytic graphite sheet.

  The thickness of the graphite sheet after pyrolysis was 130 μm.

  Next, the graphite sheet after thermal decomposition is softened by roller rolling.

  This softening treatment is performed for the purpose of giving the graphite sheet after pyrolysis sufficient flexibility in order to fold the graphite sheet punched into a predetermined shape in a later step.

  The thickness of the graphite sheet after the softening treatment was 100 μm, and the thermal conductivity measured using an optical AC heat radiation constant measuring device (Laser Pit manufactured by ULVAC-RIKO) was 1000 w / (m · K).

  As the graphite sheet, it is possible to use a so-called expanded graphite sheet by an expanding method instead of the pyrolytic graphite sheet. However, the expanded graphite sheet is obtained by pressing a natural graphite powder after acid treatment and then pressing the expanded graphite powder. In the first embodiment, the pyrolytic graphite sheet is used because it is molded and formed into a sheet shape and is not flexible enough to withstand folding, such as a pyrolytic graphite sheet.

  The pyrolytic graphite sheet after the softening treatment is punched using a punching die such as a Thomson die to obtain a graphite sheet 21 having a shape shown in the plan view of FIG.

  As the thickness of the graphite sheet 21 before folding, a thickness after the softening treatment of 100 μm was used, but the thickness is not particularly limited, and a thickness of about 20 μm to 1000 μm is preferable.

  When the thickness of the graphite sheet 21 is less than 20 μm, it becomes difficult to handle, and when the parallelism between the lower surface of the semiconductor module 11 and the upper surface of the heat sink 12 does not come out, there is a place where the graphite sheet 21 does not contact these surfaces. Therefore, the thickness of the graphite sheet 21 is preferably 20 μm or more.

  Further, when the thickness of the graphite sheet 21 exceeds 1000 μm, the graphite sheet has a lower thermal conductivity in the thickness direction than in the planar direction, so that the thermal resistance of the graphite sheet 21 itself increases and the heat dissipation efficiency may decrease. Because there is.

  Hereinafter, other graphite sheets used for the heat dissipation device 17 of the present invention will be described with reference to FIGS.

  3 to 5 show a case where the thick portion 21a of the graphite sheet 21 shown in FIG. 2 is formed in another form, and the same components are denoted by the same reference numerals and description thereof is omitted.

(Embodiment 2)
The graphite sheet used in the second embodiment is the pyrolytic graphite sheet used in the first embodiment having the shape shown in FIG.

  The punched graphite sheet 31 shown in FIG. 3A has a substantially cross shape, and has a main body portion 32 and folding portions 33 and 34 that are folded on the main body portion 32.

  Therefore, the folding parts 33, 34 are formed to face both the upper and lower ends of the main body part 32, and the folding part 34 is first bent so as to overlap the main body part 32 by a folding line 36. Subsequently, the folding part 33 is folded by the folding line 35 so as to overlap the folding part 34, thereby forming a thick part 31a shown in the plan view of FIG. 3B and the side view of FIG. Yes.

  As in Embodiment 1, the graphite sheet 31 folded in this way was sandwiched between the semiconductor module 11 and the heat sink 12 shown in FIG.

  This is because, when the heat sink 12 is fixed to the semiconductor module 11 with screws, the bottom surface of the semiconductor module 11 warps upward and the adhesiveness with the heat sink 12 decreases, whereas the graphite sheet shown in FIG. Since 31 has a thick portion 31a closer to a curved surface, it is considered that the adhesion to the semiconductor module 11 is better than that of the graphite sheet 21 shown in FIG.

(Embodiment 3)
By making the pyrolytic graphite sheet used in Embodiment 1 the shape of the graphite sheet 41 shown in FIG. 4, it is possible to achieve both the number of punches and the heat dissipation effect.

  In the graphite sheet 41 of the third embodiment, the folding portions 43 and 44 have the same shape as shown in FIG.

  And the folding parts 44 and 43 are bend | folded by the folding lines 46 and 45 at the main-body part 42 of the graphite sheet 41, and the thick part 41a shown to the top view of FIG.4 (b) and the side view of FIG.4 (c) is shown. Forming.

  The graphite sheet 41 of FIG. 4A was sandwiched between the semiconductor module 11 and the heat sink 12 as in the first embodiment, and the temperature of the semiconductor module 11 was measured to be 84 ° C.

(Embodiment 4)
The graphite sheet 51 used in the fourth embodiment shown in FIG. 5A is a modification of the graphite sheet 41 shown in FIG. 4A, and the folding parts 53 and 54 are not provided on the upper and lower sides of the main body part 52. 5A, the shape of the graphite sheet 51 after punching is made into a T-shape, the folding portion 54 is folded on the folding portion 53 by a folding line 56, and then the main body is folded by the folding line 55. The graphite sheet 51 has a thick portion 51a as shown in the plan view of FIG. 5B and the side view of FIG.

  Alternatively, first, the folding part 55 is folded so that the folding parts 53 and 54 are on the main body part 52 by the folding line 55, and then the folding part 56 is folded back into a mountain fold so that the folding part 54 comes to the uppermost layer. May be formed.

  The result of measuring the temperature of the semiconductor module 11 using this graphite sheet 51 as in the first embodiment was 84 ° C., which was almost the same as that of the graphite sheet 31 shown in FIG.

  In the graphite sheet 51 of the fourth embodiment, the punching shape is T-shaped, so that the punching loss can be further reduced as compared with the graphite sheet 41 of the third embodiment.

  In the first to fourth embodiments, the graphite sheets having the shapes shown in FIGS. 2 to 5 are used. However, the shape is not limited to these shapes, and any shape that can be folded to form a thick portion at a desired location. Any shape can be used.

  Moreover, although the thickness part 21a, 31a, 41a, 51a showed the example which becomes 3 times the thickness before folding, it is not limited to this, For example, the graphite shown to Fig.3 (a) Only one of the folded portions 33 and 34 of the sheet 31 may be used, and the thickness of the thick portion may be twice the thickness before folding.

  Alternatively, for example, the folded portion on either the upper or lower side of the graphite sheet 41 shown in FIG. 4A is configured such that two folded portions are continuous as shown in FIG. 5A, and the thickness of the thick portion is folded. It can also be 4 times the previous thickness.

  The thickness of the thick portion depends on the tightening pressure by the screw, but if it becomes too thick, a gap portion may be formed between the semiconductor module 11 and the heat sink 12. It is desirable to double.

  When the thickness of the thick part is less than twice, that is, when it is not folded, even if a graphite sheet is used as in Comparative Example 1, an excellent heat dissipation effect cannot be exhibited.

Regarding the tightening of the screw, if the thickness of the folded thick part is 4 times or less than the thickness before the folding, 5-20 g / The semiconductor module 11 and the heat sink 12 can be sufficiently adhered with a pressure of about cm ² .

  In addition, when it is necessary to use an adhesive or an adhesive to ensure the folding of the graphite sheet in assembling the heat dissipation device, these adhesives and adhesives have a large thermal resistance. The thickness of the adhesive is 20 μm or less, preferably 10 μm or less, or an adhesive or adhesive is not applied to the entire folding part, but is applied in a discontinuous spot shape. It is preferable to join the folds at the portion where there is no adhesive to form the thick portion 21a.

  Further, in the first embodiment, as shown in FIG. 1, an example in which the semiconductor module 11 having a rectangular bottom surface (bottom surface) is used is not limited to this. For example, the bottom surface (bottom surface) is an ellipse. A semiconductor module such as a shaped power amplifier may also be used.

  Moreover, the heat sink 12 which is a heat radiating member is not limited to the shape as shown in FIG. 1, and may be a cylindrical shape or a fin extending downward at right angles to the upper surface.

  Further, the heat radiating member may be a chassis of an electronic device casing or a flat metal plate other than the heat sink.

  Moreover, although the example which fixed the both ends of the semiconductor module 11 with the two attachment fixing screws 13 and 14 was shown in the said Embodiment 1-4, it is not limited to this, The both ends of a semiconductor module are fixed. The effect of the present invention can be exhibited in the same manner with three or more mounting fixing screws.

  The heat dissipating device of the present invention is a heat dissipating device that dissipates heat by fixing a heat generating member such as a semiconductor module to a heat sink that is a heat dissipating member, in a portion corresponding to a gap formed between the heat generating component and the heat dissipating member, By sandwiching a graphite sheet with a thick part by folding a part of the graphite sheet, it is possible to achieve excellent heat coupling and efficient heat dissipation by an extremely simple and industrially easy method. It is useful for heat dissipation devices such as electronic devices.

The exploded perspective view of the heat dissipation device of the present invention (A) Plan view of graphite sheet before folding in Embodiment 1 of the present invention, (b) Plan view of graphite sheet after folding, (c) Side view of graphite sheet after folding. (A) Plan view before folding of another graphite sheet in Embodiment 2 of the present invention, (b) Plan view of the graphite sheet after folding, (c) Side view of the graphite sheet after folding. (A) Plan view before folding of still another graphite sheet according to Embodiment 3 of the present invention, (b) Plan view of the graphite sheet after folding, (c) Side view of the graphite sheet after folding. (A) Plan view before folding of still another graphite sheet according to Embodiment 4 of the present invention, (b) Plan view of the graphite sheet after folding, (c) Side view of the graphite sheet after folding. (A) Plan view of a conventional graphite sheet of Comparative Example 1, (b) Side view of the graphite sheet Sectional drawing for demonstrating the clearance gap between heat-emitting components and a thermal radiation member

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Semiconductor module 12 Heat sink 13,14 Mounting fixing screw 15a, 15b, 15c, 16a, 16b, 16c Screw hole 17 Heat radiation device 21, 31, 41, 51 Graphite sheet 21a, 31a, 41a, 51a Thick part 22 , 23 Folding line 32 Main body part 33, 34 Folding part 35, 36 Folding line 42 Main body part 43, 44 Folding part 45, 46 Folding line 52 Main body part 53, 54 Folding part 55, 56 Folding line 61 Graphite sheet

Claims (2)

And heat-generating component includes a heat radiating member attached to the heat generating component, and a substantially rectangular graphite sheets disposed in a gap portion formed between the heat generating component and the heat radiating member, the graphite sheet- A heat dissipating device characterized in that a thick portion is provided at a portion corresponding to the gap portion by folding the portion in the longitudinal direction, and fixing screws are inserted into holes provided at both ends of the graphite sheet . The heat dissipation device according to claim 1, wherein the graphite sheet is a pyrolytic graphite sheet.

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