JP2016162929A - Heat dissipation grease, and semiconductor cooling structure using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat dissipation grease capable of exhibiting excellent heat dissipation even if the thickness is reduced, and to provide a semiconductor cooling structure using the same.SOLUTION: A heat dissipation grease 1 interposed between adherends 18, 19, and used under pressure, and a semiconductor cooling structure using the same are provided. The heat dissipation grease 1 contains a silicone oil 11, and a heat conduction filler 12 dispersed into the oil. The heat conduction filler 12 has a Mohs hardness of 4 or less, and a heat conductivity of 80 W/mK or more. In the semiconductor cooling structure, a semiconductor module, an insulator, and a cooling pipe are pressurized and brought into close contact with each other, and the heat dissipation grease 1 is interposed between the semiconductor module and the insulator and between the insulator and the cooling pipe.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a heat dissipating grease excellent in heat dissipation and a semiconductor cooling structure using the same.

  For example, in order to improve the cooling performance by enhancing the adhesion between the adherend having a heating element and another adherend having a cooling means, a grease or an adhesive having heat dissipation may be interposed between the adherends. Has been done. As such an adhesive, for example, conductive particles and heat conductive particles made of metal particles having an average particle size smaller than the conductive particles and having an insulating layer formed on the surface are dispersed in the adhesive component. An anisotropic conductive adhesive has been developed (see Patent Document 1).

JP 2014-676720 A

  By increasing the blending amount of the heat conductive filler such as the heat conductive particles, it is possible to improve the heat dissipation of the grease and the adhesive. However, when a large amount of heat conductive filler is blended in a resin material such as grease or adhesive, the viscosity increases. In addition, in order to improve heat dissipation, it is necessary to close-pack a large amount of heat-conducting filler, and as a result, it is necessary to combine a filler with a large particle size and a filler with a small particle size as in the above-described prior art. is there. However, when a grease or an adhesive having a high viscosity and a filler having a large particle size is used, the thickness of the grease or the adhesive interposed between the adherends inevitably increases. As a result, it has been difficult for conventional grease and adhesives to achieve both reduction in thickness and improvement in heat dissipation.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a heat dissipating grease capable of exhibiting excellent heat dissipating property even when the thickness is reduced, and a semiconductor cooling structure using the heat dissipating grease.

One aspect of the present invention is a heat dissipating grease interposed between adherends and used under pressure,
Silicone oil,
A heat conductive filler dispersed in the silicone oil,
The thermal conductive filler is in a heat radiation grease characterized by having a Mohs hardness of 4 or less and a thermal conductivity of 80 W / mK or more.

Another aspect of the present invention is a semiconductor cooling structure in which a semiconductor module, an insulator, and a cooling pipe are pressure-contacted to each other on their main surfaces,
The heat dissipating grease is interposed between the main surface of the semiconductor module and the main surface of the insulator, and between the other main surface of the insulator and the main surface of the cooling pipe. It is in the semiconductor cooling structure.

  The heat dissipating grease contains a silicone oil and a heat conductive filler having a predetermined Mohs hardness and thermal conductivity dispersed in the silicone oil. And the thermal radiation grease is interposed between the adherends and used under pressure. Therefore, the heat conductive filler having a low Mohs hardness can be deformed between adherends as described above, and the heat conductive filler can sufficiently transfer heat between the adherends. Therefore, even if the thickness of the heat dissipating grease applied between the adherends is reduced, the heat dissipating grease can exhibit excellent heat dissipation. Moreover, even if it reduces the compounding quantity of a heat conductive filler, the thermal radiation grease can exhibit the outstanding heat dissipation.

  In the semiconductor cooling structure, the semiconductor module, the insulator, and the cooling pipe are pressure-contacted with each other on each main surface, and the above-described heat release grease is interposed between the main surfaces. In other words, the above-described heat dissipating grease is disposed between the adherends (semiconductor module, insulator, cooling pipe) in a pressurized state. Therefore, in the semiconductor cooling structure, even if the thickness of the heat dissipation grease is reduced, the heat dissipation grease can exhibit excellent heat dissipation. Therefore, the semiconductor cooling structure is excellent in heat dissipation.

Sectional drawing of the thermal radiation grease which interposes to a to-be-adhered body in the pressurization state in 1st Embodiment. Explanatory drawing which shows the relationship between the pressure of the thermal radiation grease of Example 1- Example 4, the comparative example 1, and the comparative example 2, and thermal resistance. Sectional drawing of the semiconductor cooling structure in 2nd Embodiment. The perspective view of the laminated | stacked semiconductor cooling structure in 2nd Embodiment.

(First embodiment)
In the present embodiment, a plurality of heat dissipation greases according to Examples and Comparative Examples are produced, and the heat dissipation characteristics of the heat dissipation grease under pressure conditions are evaluated. As shown in FIG. 1, the thermal radiation grease 1 in this embodiment is interposed between the adherends 18 and 19 and used under pressure. The heat dissipating grease 1 includes a silicone oil 11 and a large number of thermally conductive fillers 12 dispersed in the silicone oil 11.

As the thermal conductive filler 12, aluminum (Al; Example 1), boron nitride (BN; Example 2), graphite (Example 3), acid value magnesium (MgO; Example 4), alumina (Al ₂ O ₃₎ Comparative Example 1) or aluminum nitride (AlN; Comparative Example 2) was used. The Mohs hardness, thermal conductivity, average particle diameter, shape, and volume resistance value of these thermal conductive fillers 12 are shown in Table 1 described later. The average particle diameter means a particle diameter at a volume integrated value of 50% in a particle size distribution obtained by a laser diffraction / scattering method.

  Six types of heat radiation grease 1 (Examples 1 to 4, Comparative Example 1, and Comparative Example 2) were prepared by mixing each thermal conductive filler 12 with the silicone oil 11. As the silicone oil 11, a commercial product (KF-96 manufactured by Shin-Etsu Chemical Co., Ltd.) was used. The blending amount (filling amount) of the heat conductive filler 12 in each heat radiation grease 1 is shown in Table 1 described later.

  Next, the thermal resistance of the heat release grease 1 of each example and comparative example was measured under pressure. The thermal resistance was measured with a thermal resistance measuring device (thermal conductivity measuring device TCM-1000 manufactured by Resuka Co., Ltd.) using a steady method. With this thermal resistance measuring device, the thermal resistance (W / K) of the thermal grease 1 was measured while pressurizing the thermal grease 1. The measurement range is 0.03 to 50 WmK (thermal conductivity). The relationship between the pressure applied to the heat dissipation grease 1 and the thermal resistance of the heat dissipation grease 1 is shown in FIG. Table 1 shows the thermal resistance of the heat dissipating grease when the pressure applied to the heat dissipating grease 1 is 0.73 MPa.

  As is known from Table 1, the heat dissipation grease 1 of Examples 1 to 4 has a much lower heat resistance during pressurization than Comparative Examples 1 and 2, and is excellent in heat dissipation. That is, as in Examples 1 to 4, the heat dissipating grease 1 in which the heat conductive filler 12 having a Mohs hardness of 4 or less and a heat conductivity of 80 W / mK or more is dispersed in the silicone oil 11 is excellent. It can show heat dissipation. This is because, in the heat dissipation grease 1 of Examples 1 to 4, as shown in FIG. 1, the heat conductive filler 12 having a low Mohs hardness is deformed by the pressurization between the adherends 18 and 19 and is deformed. It is thought that this is because it is interposed between the adherends 18 and 19. Therefore, in the heat dissipation grease 1 of Examples 1 to 4, the excellent thermal conductivity of the heat conductive filler 12 is sufficiently utilized, and the heat dissipation grease 1 can exhibit excellent heat dissipation as described above.

  Further, as is known from Table 1, the heat dissipation grease 1 of Examples 1 to 4 has a smaller proportion of the heat conductive filler 12 than the comparative examples 1 and 2, and the heat conductive filler 12 occupies the silicone oil 11. Despite the small proportion, excellent heat dissipation can be shown as described above. Therefore, the heat radiation grease 1 of Examples 1 to 4 can exhibit sufficiently excellent heat dissipation even when the coating thickness is reduced.

  In addition, as is known from FIG. 2, the heat dissipation grease 1 of Examples 1 to 4 has a significantly reduced thermal resistance under pressure conditions of 0.1 MPa or more as compared with Comparative Examples 1 and 2. That is, the heat radiation grease 1 (Examples 1 to 4) containing the heat conductive filler 12 having a Mohs hardness of 4 or less and a heat conductivity of 80 W / mK or more is used under pressure conditions of a pressure of 0.1 MPa or more. It is preferably used. In this case, the heat dissipating grease 1 can exhibit a sufficiently excellent heat dissipating property. From the same viewpoint, the heat dissipating grease 1 is more preferably used under pressure conditions of a pressure of 0.2 MPa or more, and even more preferably used under pressure conditions of a pressure of 0.3 MPa or more. If the applied pressure becomes too large, it is necessary to increase the structure of the adherends 18 and 19 in order to increase pressure resistance, or it is necessary to increase the pressing means such as a spring necessary for pressurization. There is a fear. As a result, it is necessary to enlarge the structure in order to increase the pressure resistance of the structure around the heat dissipating grease 1, and it may be difficult to cope with downsizing. From this viewpoint, it is preferable that the heat dissipating grease 1 is used at a pressure of 2 MPa or less.

  The Mohs hardness of the heat conductive filler 12 is preferably 4 or less as described above. In this case, deformation due to pressurization becomes relatively easy, so that the heat dissipating grease 1 can exhibit the above excellent heat dissipating property between the adherends 18 and 19. From the viewpoint of easier deformation, the Mohs hardness is more preferably 3 or less, and even more preferably 2 or less.

  The thermal conductivity of the thermal conductive filler 12 is preferably 80 W / mK or more. When the thermal conductivity of the filler 12 is less than 80 W / mK, the effect of improving the heat dissipation due to the addition of the filler 12 is reduced, and the heat dissipation of the heat dissipation grease may not be sufficiently improved. As such a heat conductive filler 12, metal particles, ceramic particles, or the like can be used. In addition, it is preferable that the heat conductivity of the heat conductive filler 12 is 400 W / m or less from a viewpoint that acquisition is difficult.

  The average particle size of the heat conductive filler 12 is preferably 5 μm or less, and more preferably 2.5 μm or less. When the average particle size is increased, the coating thickness between the adherends 18 and 19 may be increased.

  The heat conductive filler 12 is preferably made of at least one selected from the group consisting of Al, BN, MgO, and graphite. In this case, as shown in the above-described embodiment, the heat dissipating grease 1 having excellent heat dissipating properties can be reliably realized. Further, from the viewpoint of enhancing the electrical insulation of the heat dissipating grease 1, it is more preferable that the heat conductive filler 12 is made of BN and / or MgO. That is, in this case, since the heat dissipation grease 1 can have both heat dissipation and electrical insulation, it is suitable for applications requiring not only heat dissipation but also electrical insulation.

  The heat conductive filler 12 may be, for example, spherical, scale-like, angular, plate-like, or aggregate-like. Preferably, the aspect ratio of the heat conductive filler 12 is greater than 1. In this case, since the heat conductive filler 12 having a large aspect ratio in the heat dissipation grease 1 can easily transfer heat, heat dissipation can be further improved.

  The heat dissipation grease 1 can contain an additive such as a surfactant in the silicone oil 11. As such an additive, those commonly used for silicone grease can be employed.

  As the adherends 18 and 19, there are various combinations. For example, it is preferable that either one of the adherends 18 and 19 includes a heating element and the other includes a cooling unit. In this case, the heat from the heating element can be sufficiently transmitted to the cooling means via the heat radiation grease 1. Therefore, the excellent heat dissipation performance of the heat dissipation grease 1 is fully utilized.

(Second Embodiment)
Next, an embodiment of a semiconductor cooling structure including a semiconductor module, an insulator, and a cooling pipe as the adherend will be described. As shown in FIG. 3, in the semiconductor cooling structure 2 in the present embodiment, the semiconductor module 3, the insulator 4, and the cooling pipe 5 are press-contacted with each other on their main surfaces. The insulator 4 is sandwiched between the semiconductor module 3 and a cooling pipe 5 that cools the semiconductor module 3. The semiconductor module 3 incorporates a semiconductor element (not shown) and has a plate shape as a whole. The cooling pipe 5 is made of aluminum and has a plate shape as a whole. The insulator 4 is made of an insulating ceramic plate.

  As shown in FIG. 3, the semiconductor module 3 has a double-sided cooling structure, and the insulator 4 and the cooling pipe 5 are stacked on both main surfaces 35 of the semiconductor module 3. Further, between the main surface 35 of the semiconductor module 3 and the main surface 45 of the insulator 4 and between the other main surface 46 of the insulator 4 and the main surface 55 of the cooling pipe 5, the heat radiation grease 1 is provided. Intervene. That is, the insulator 4 is stacked on both main surfaces 35 of the semiconductor module 3 via the heat dissipating grease 1, and the cooling pipe 5 is stacked on the main surface 46 of each insulator 4 via the heat dissipating grease 1. Yes. Furthermore, the insulator 4 and the semiconductor module 3 are laminated on the opposite side of the cooling pipe 5 arranged as described above with the grease 1 interposed therebetween. As a whole, as shown in FIG. 4, the cooling pipes 5 and the semiconductor modules 3 are alternately stacked via the insulators 4 and the grease 1. In addition, between the pair of cooling pipes 5, two semiconductor modules 3 are sandwiched in a state of being arranged in parallel on the left and right.

  The semiconductor module 3 incorporates a semiconductor element (not shown) such as an IGBT, and further incorporates a heat radiating plate (not shown) that transmits heat generated from the semiconductor element to the main surface 35 side. The semiconductor module 3 is provided with an external connection terminal 31 for electrical conduction. The external connection terminal 31 includes a main electrode terminal 311 and a signal terminal 312 that protrudes in a direction that is approximately 180 degrees different from the protruding direction of the main electrode terminal 311.

  As shown in FIG. 3, the cooling pipe 5 has a refrigerant flow path 51 inside thereof, and is configured so that a cooling medium can flow in the flow path 51. Also, as shown in FIG. 4, bellows pipes 501 that connect both ends of the plurality of cooling pipes 5 are arranged, and two header portions 502 are formed. In addition, a refrigerant inlet 503 and a refrigerant outlet 504 connected to the cooling pipe 5 are respectively provided at one end of these two header portions 502. Thus, the cooler 50 formed by arranging a plurality of cooling pipes 5 in parallel is configured. The semiconductor module 3 can be cooled from both sides by sandwiching the semiconductor module 3 between the adjacent cooling pipes 5 as described above and circulating the cooling medium in the cooling pipe 5. A semiconductor cooling structure 2 including a plurality of stacked semiconductor modules 3 and a plurality of cooling pipes 5 shown in FIG. 4 constitutes a part of a power conversion device such as an inverter for an automobile, for example.

  When the semiconductor module 3, the insulator 4, and the cooling pipe 5 are assembled, the heat dissipating grease 1 is disposed between the main surfaces 35, 45, 46, 55, and the semiconductor module 3, the insulator 4, and the cooling pipe 5. Then, a pressing force is applied in the stacking direction X. At this time, the heat dissipation grease 1 is between the main surface 35 of the semiconductor module 3 and the main surface 45 of the insulator 4 or between the other main surface 46 of the insulator 4 and the main surface 55 of the cooling pipe 5. , Spread in all directions. The application amount and the pressing force of the heat dissipation grease 1 are adjusted to such an extent that the heat dissipation grease 1 does not protrude. However, depending on the case, the heat dissipation grease 1 may be connected to the end of the contact surface between the semiconductor module 3 and the insulator 4 or the insulation. It may protrude from the end of the contact surface between the body 4 and the cooling pipe 5. The semiconductor module 3, the insulator 4, and the cooling pipe 5 are pressurized with a pressure of 0.1 MPa or more in the stacking direction X, and a pressure of 0.1 MPa or more is applied to the heat dissipation grease 1. As the heat radiation grease 1, for example, the above-described Examples 1 to 4 can be used.

  Next, the effect of this embodiment is demonstrated. In the semiconductor cooling structure 2, the semiconductor module 3, the insulator 4, and the cooling pipe 5 are in pressure contact with each other on the main surfaces 35, 45, 46, and 55. The above-mentioned heat radiation grease 1 is interposed between them. As the heat dissipating grease 1, grease in which a heat conductive filler 12 having a Mohs hardness of 4 or less and a heat conductivity of 80 W / mK or more is dispersed in a silicone oil 11 is used. The heat dissipating grease 1 is attached to an adherend (semiconductor module). 3, the insulator 4 and the cooling pipe 5) are arranged in a pressurized state. Therefore, in the semiconductor cooling structure 2, the heat dissipation grease 1 exhibits the excellent heat dissipation shown in the first embodiment, and the semiconductor cooling structure 2 can also exhibit the excellent heat dissipation. Moreover, even if the thickness of the heat dissipation grease 1 is reduced, excellent heat dissipation can be exhibited.

  In the semiconductor cooling structure 2, the heat conductive filler 12 in the heat radiation grease 1 is deformed by pressurization (see FIG. 1). Due to this deformation, the heat dissipation of the heat dissipation grease 1 is improved, and the semiconductor cooling structure 2 can exhibit the excellent heat dissipation as described above. The semiconductor cooling structure 2 is particularly suitable for cooling a semiconductor module (power card) used for a power control unit (PCU) for a hybrid vehicle (HV) in order to exhibit such excellent heat dissipation.

  As the heat radiation grease 1 in the semiconductor cooling structure 2, it is preferable to use a heat conductive filler 12 made of BN and / or MgO as in the second and fourth embodiments. In this case, since the thermal radiation grease 1 can exhibit electrical insulation, electrical insulation between the semiconductor module 3 and the cooling pipe 5 can be ensured.

  Thus, according to this embodiment, the semiconductor cooling structure 2 excellent in heat dissipation can be provided.

  As mentioned above, although embodiment of the thermal radiation grease and the semiconductor cooling structure was described, this invention is not limited to these embodiment, A various change is possible within the range which does not impair the meaning of this invention. It is.

1 Heat Dissipation Grease 11 Silicone Oil 12 Thermal Conductive Filler 18 Substrate 19 Adherent

Claims (6)

A heat dissipating grease (1) that is interposed between adherends (18, 19) and used under pressure,
Silicone oil (11);
A thermally conductive filler (12) dispersed in the silicone oil,
The heat conduction filler (12) has a Mohs hardness of 4 or less and a heat conductivity of 80 W / mK or more, and a heat radiation grease (1).   The heat dissipation grease (1) according to claim 1, wherein the heat dissipation grease (1) is used under a pressurized condition of 0.1 MPa or more.   The heat-dissipating grease (1) according to claim 1 or 2, wherein the heat-conducting filler (12) is interposed between the adherends (18, 19) in a deformed state.   The heat-dissipating grease (1) according to any one of claims 1 to 3, wherein the heat-conducting filler (12) comprises at least one selected from the group consisting of Al, BN, MgO, and graphite. ).   The heat-dissipating grease (1) according to any one of claims 1 to 4, wherein the heat-conducting filler (12) is made of BN and / or MgO. A semiconductor cooling structure (2) in which a semiconductor module (3), an insulator (4), and a cooling pipe (5) are pressure-contacted to each other on their main surfaces,
Between the main surface (35) of the semiconductor module (3) and the main surface (45) of the insulator (4), and the other main surface (46) of the insulator (4) and the cooling pipe (5) The semiconductor cooling structure (2), wherein the heat-dissipating grease (1) according to any one of claims 1 to 5 is interposed between the main surface (55) and the main surface (55).

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