JP2009266983A - Heat dissipation structure and manufacturing method therefor, and heat radiator using heat-dissipating structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-dissipating structure, capable of providing high heat radiation performance and eliminating the failures due to high thermal resistance, leakage from a coating section, or the like, generated by using thermocondcutive grease. <P>SOLUTION: The heat dissipation structure comprises: a substrate, namely an insulating material; an aluminum carbide phase or an aluminum oxide phase formed on at least the entire surface of the substrate or on one portion thereof; and an aluminum carbide whisker layer or an alumina whisker layer formed by erecting a plurality of aluminum carbide whiskers or alumina whiskers from the aluminum carbide phase or aluminum oxide phase on the substrate surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heat dissipation structure with extremely high heat dissipation, a method for manufacturing the heat dissipation structure, and a power module heat dissipation device using the heat dissipation structure.

  Conventionally, a power module in which a plurality of power elements (power MOSFET, IGBT, etc.) are connected on a ceramic substrate or the like and incorporated in one package is known. The power module is provided with a power element on the front surface side, and is configured to release heat mainly from the back surface side. A heat conductive grease is applied to the back surface of the power module, and the power module is fixed to the cooler with screws through the heat conductive grease. And the structure which raised the cooling efficiency by radiating heat from both surfaces of a heat generating element is also invented (refer patent document 1).

When the power module is fixed to the cooler, pressure is applied in order to improve the familiarity between the cooler and the heat conductive grease, and further, the heat conductive grease spreads during fixing because the screw is tightened and fixed. For this reason, if the pressure applied when fixing the power module to the cooler is large or the applied grease is thick, the thermally conductive grease may enter the screw holes. When the heat conductive grease enters the screw hole, there is a problem that the tightening torque of the screw decreases with time, the distance between the power module and the cooler is widened, and heat dissipation is deteriorated. As an invention for solving such a problem, Patent Document 2 is devised to prevent grease from entering the screw holes.
However, in these methods, since the thermal resistance of the grease is large, sufficient cooling performance cannot be obtained.

JP-A-2005-150420 Japanese Patent No. 3644428

  This invention makes it a subject to provide the thermal radiation structure which can express high thermal radiation performance in view of the said point. It is another object of the present invention to provide a heat dissipation structure in which defects caused by the use of heat conductive grease, such as high heat resistance and leakage from the application portion, are eliminated.

As a result of intensive studies to solve the above problems, the present inventor has developed a heat dissipation structure having an aluminum carbide whisker or alumina whisker layer (hereinafter sometimes referred to simply as a whisker layer without distinguishing both) on the surface of the substrate. It has been found that it is effective to use. That is, the present inventors have found that the whisker layer on the substrate surface can efficiently contact the unevenness of the heat source without using grease to obtain a low contact resistance and exhibit high heat dissipation performance.
It has also been found that when used in combination with grease, higher heat dissipation performance is exhibited.

The present invention has the following configuration.
(1) A heat dissipation structure according to the present invention includes a substrate which is an insulating material, an aluminum carbide phase or an aluminum oxide phase formed on the entire surface or a part of at least a surface of the substrate, and an aluminum carbide phase or an oxidation on the surface of the substrate. It has an aluminum carbide whisker layer or an alumina whisker layer formed by standing a plurality of aluminum carbide whiskers or alumina whiskers from an aluminum phase.
(2) The heat dissipation structure according to (1), wherein the substrate has an aluminum phase around an aluminum carbide phase or an aluminum oxide phase.
(3) The heat dissipation structure according to (1) or (2), wherein the substrate is any one of Si ₃ N ₄ , AlN, and SiC.
(4) The heat dissipation structure according to any one of (1) to (3), wherein the plurality of aluminum carbide whiskers or alumina whiskers are grown substantially perpendicular to the substrate surface. And
(5) The heat dissipation structure according to any one of (1) to (4) above, wherein a thickness of the aluminum carbide whisker layer or the alumina whisker layer is 1 μm or more.
(6) The heat dissipation structure according to (5), wherein the aluminum carbide whisker layer or the alumina whisker layer has a thickness of 10 μm or more.
(7) The heat dissipation structure according to any one of (1) to (6), wherein the aluminum carbide whisker layer or the alumina whisker layer is impregnated with grease.

(8) In the method for manufacturing a heat dissipation structure according to the present invention, an insulating substrate having at least a part or the entire surface of aluminum is placed in a space containing a hydrocarbon-containing substance and heated, and the surface of the substrate is aluminum carbide. It includes a first step of forming a whisker layer.
(9) The method for manufacturing a heat dissipation structure according to (8) above, wherein after the first step, the substrate on which the aluminum carbide whisker layer is formed is heated in an oxidizing atmosphere, and the aluminum carbide whisker layer And a second step of converting the carbon to an alumina whisker layer.
(10) The method for manufacturing a heat dissipation structure according to (9), including a step of impregnating an aluminum carbide whisker layer or an alumina whisker layer with grease after the first step or the second step. It is characterized by.
(11) The method for manufacturing a heat dissipation structure according to any one of (8) to (10), wherein the substrate is any one of Si ₃ N ₄ , AlN, or SiC.

(12) A heat dissipation device according to the present invention is a heat dissipation device in which heat generated from a heat generating surface of a heat generating element having at least a heat generating element is transferred to a heat dissipation plate and / or a cooler via a heat dissipation structure. Is the heat dissipation structure according to any one of (1) to (7) above.
(13) In the heat dissipation device according to (12), the heating element includes any one of a heat dissipation block, a heat dissipation plate, and a semiconductor substrate in addition to the heating element, and the heating surface of the heating element is It is one or more of the heating element, the heat dissipation block, the heat dissipation plate, and the semiconductor substrate.
(14) The heat dissipation device according to (12) or (13), wherein heat is radiated from both surfaces of the heat generating element.

The aluminum carbide whisker or the alumina whisker has a special feature to follow the unevenness of the surface of the heat source. Since the aluminum carbide whisker or the alumina whisker is formed on the substrate surface, the heat dissipation structure according to the present invention has a low thermal resistance and can exhibit high heat dissipation performance without using a heat conductive grease. Further, even when a heat conductive grease is used in combination, it is possible to improve the heat radiation performance without causing problems due to leakage of conventional grease. In particular, it is effective as a heat radiating device for power devices such as automobile parts.
Moreover, the manufacturing method of the heat dissipation structure according to the present invention makes it possible to provide a heat dissipation structure with low thermal resistance and high heat dissipation performance at low cost.

  The heat dissipation structure according to the present invention includes a substrate made of an insulating material, an aluminum carbide phase or an aluminum oxide phase formed on at least a part of the surface, and an aluminum carbide phase or an aluminum oxide phase on the substrate surface. And a whisker layer formed by standing aluminum carbide whiskers or alumina whiskers. Since the aluminum carbide whisker or the alumina whisker is a fine cocoon-like substance, the tip of the aluminum carbide whisker or the alumina whisker follows the fine irregularities on the surface of the counterpart material and efficiently contacts. For this reason, the heat dissipation structure according to the present invention has low contact thermal resistance with the counterpart material without using grease or the like, and can exhibit excellent heat dissipation performance (see FIG. 1). Also, when used in combination with grease, lower thermal resistance can also be exhibited). Also in this case, since the grease is impregnated in the whisker layer, it is possible to eliminate the problem of leaking from the application part as in the conventional case.

When the heat dissipation structure according to the present invention is used for a power module heat dissipation device for the purpose of heat dissipation of the power module, the heat dissipation structure needs to be insulative. For this reason, the substrate is preferably an insulating substrate. In particular, any of Si ₃ N ₄ , AlN and SiC is preferable.
The whisker layer may be formed on the entire surface of the substrate. However, the whisker layer is formed on a part of the surface of the substrate, and heat is released by radiation at other surface portions of the substrate, or is in contact with other cooling members. In order to achieve this, it may be formed at a plurality of locations on the substrate surface.

  The plurality of aluminum carbide whiskers or alumina whiskers are preferably grown and oriented substantially perpendicularly from the substrate surface. If the whisker is formed almost perpendicular to the substrate surface, the tip of the whisker faces the direction of the heating element or the cooling body, so that the tip easily penetrates into fine irregularities and efficiently reduces the contact thermal resistance. It becomes possible to make it. However, it is not always necessary to completely face the vertical direction, and some of them may be randomly oriented to the random direction, and it is only necessary to face the vertical direction. Further, from the same viewpoint of following the fine unevenness, the thickness of the whisker layer is preferably 1 μm or more, and more preferably 10 μm or more.

The heat dissipation structure according to the present invention includes an insulating substrate and aluminum carbide whiskers or alumina whiskers formed on the surface thereof, and is synthesized by the following method.
That is, a first step in which a substrate having at least a part or the entire surface of aluminum is placed in a space containing a hydrocarbon-containing substance and heated to form an aluminum carbide whisker on the substrate surface; A second step of heating the formed substrate in an oxidizing atmosphere to convert the aluminum carbide whisker to alumina whisker is included. According to the present invention, a layer made of alumina whiskers can be formed on the surface of aluminum by a simple process in which an aluminum substrate is placed in a space containing a hydrocarbon-containing substance and heated. FIG. 2 is a diagram schematically showing a cross-sectional structure of an alumina whisker layer as one embodiment of the present invention.

By heating the aluminum substrate in an atmosphere containing a hydrocarbon-containing substance, a phase mainly composed of aluminum carbide is formed on at least a part of the substrate surface. An aluminum carbide phase may be formed on the front surface of the substrate surface, or an aluminum carbide phase may be formed on a part of the substrate surface, and an aluminum phase may remain around the aluminum carbide phase. From the surface of the aluminum carbide phase, an aluminum carbide whisker phase mainly composed of aluminum carbide grows so as to extend in a whisker-like form. Since a plurality of aluminum carbide whiskers are formed from the aluminum carbide phase on the substrate surface, the aluminum carbide whiskers are layered and an aluminum carbide whisker layer is formed on the substrate surface. The aluminum carbide whisker phase grown from the substrate surface contains, for example, Al ₄ C ₃ crystal, but may contain amorphous. Moreover, it may contain various impurities contained in the aluminum of the substrate.

  When aluminum is carbonized and converted into aluminum carbide, a structure as shown in FIG. 2B is obtained. The structure of FIG. 2B is obtained when the heating temperature is 300 ° C. or higher. Considering the reaction efficiency, 450 ° C. or higher is preferable, and the upper limit is below the melting point of aluminum. There are various alloys of aluminum, and the temperature may be lower than the melting point of each.

  The kind of the hydrocarbon-containing substance used is not particularly limited. For example, paraffinic hydrocarbons such as methane, ethane, propane, n-butane, isobutane and pentane, olefinic hydrocarbons such as ethylene, propylene, butene and butadiene, acetylenic hydrocarbons such as acetylene, etc., or these hydrocarbons And derivatives thereof. Among these hydrocarbons, paraffinic hydrocarbons such as methane, ethane, and propane are preferable because they become gaseous in the process of heating the aluminum foil. More preferred is any one of methane, ethane and propane. The most preferred hydrocarbon is methane.

Moreover, the mass ratio of the hydrocarbon-containing substance introduced into the space in which aluminum is arranged is not particularly limited, but is usually in the range of 0.1 to 50 parts by mass in terms of carbon with respect to 100 parts by mass of aluminum. It is preferable that the content is within the range of 0.5 parts by mass or more and 30 parts by mass or less. Although the heating time depends on the heating temperature and the like, it is generally in the range of 1 hour to 100 hours.
Further, all of the aluminum on the surface of the substrate may be completely converted to aluminum carbide. In this case, since the generation density of alumina whiskers increases, the thermal resistance decreases. (See Figure 3)

  Aluminum carbide easily reacts with moisture and may have a problem with moisture resistance. In this case, it is preferable to convert it to alumina. Since aluminum carbide is a material that is extremely easy to oxidize, it is easily converted into alumina whiskers by heating in an oxidizing atmosphere (FIG. 2C). Thermodynamically, aluminum carbide is converted to alumina even at room temperature, but considering the efficiency of the process, the temperature for conversion to alumina is preferably 300 ° C. or higher. Preferably it is 450 degreeC or more, and an upper limit is below melting | fusing point of aluminum. Thus, in the present invention, alumina whiskers can be obtained from an aluminum substrate by a very simple method.

  The main component of the converted alumina whisker is amorphous. Amorphous alumina whiskers have a lower thermal conductivity than crystalline alumina whiskers, and are therefore preferably made crystalline in order to reduce thermal resistance. In order to convert it to crystalline, heat treatment at 1500 ° C. or higher is generally required. However, since the substrate is not suitable for a metal such as aluminum, in this case, for example, a ceramic or a refractory metal is used as the substrate and the surface thereof is used. After coating aluminum, the entire aluminum may be converted into a phase mainly composed of aluminum carbide so that the aluminum does not remain (FIG. 3).

In the present invention, since the whisker grows directly from the substrate surface, it can be said that the thermal resistance between the substrate and the whisker is substantially zero. Further, when the substrate on which all the aluminum on the substrate surface is carbonized is oxidized, an alumina whisker layer is formed on the entire surface, and when a substrate in which only a part of the substrate surface is carbonized is used, The aluminum phase remains around the aluminum carbide phase.
In the heat radiating device for a power module according to the present invention, since the insulating structure is required for the heat radiating structure used, it is preferably a sintered body of Si ₃ N ₄ or AlN. If the specific resistance is small, SiC may be used.

The required thickness of the whisker layer varies, of course, depending on the surface roughness of the counterpart material such as the cooling body and the degree of surface waviness, but when the thickness is 1 μm or more, the effect of reducing thermal resistance is high. When the thickness is 10 μm or more, almost any mating material can be handled. That is, even when there is macro deflection on the surface of the counterpart material, the whisker layer on the substrate surface can be deformed to follow the counterpart material.
Moreover, the manufacturing method of the thermal radiation structure which concerns on this invention has the process of impregnating grease to an aluminum carbide whisker layer or an alumina whisker layer after said 1st process or 2nd process. When the heat conductive resin is used in combination, the contact property is further increased. As the thermally conductive resin, for example, grease having excellent thermal conductivity is preferable.

  The heat dissipating device according to the present invention is a heat dissipating device in which heat generated at least from a heat generating surface of a heat generating element having a heat generating element is transferred to a heat dissipating plate and / or a cooler via a heat dissipating structure, wherein the heat dissipating structure is the book. It is one of the heat dissipation structures according to the invention. Since the heat dissipation structure according to the present invention has a whisker layer on the surface thereof, it exhibits low contact thermal resistance, but the whisker layer itself has no adhesiveness, so that it is sandwiched and fixed between a heating element and a cooling element. It is preferable to be used for a heat dissipation device.

  That is, as shown in FIG. 4, when the heating element is packaged and a heating element having a heat radiation plate on the outer surface is brought into contact with the cooler, the heat dissipation structure according to the present invention is interposed. In FIG. 4, the heat generating surface of the heat generating element means a heat radiating plate provided on the surface of the heat generating element in which the heat generating elements are packaged. As described above, the heat dissipating device according to the present invention can satisfactorily apply the heat generating element in which the heat generating elements are packaged by the conventional method by using any of the heat dissipating structures according to the present invention.

As described above, since the heating element and the cooling body are conventionally brought into contact with the heat conductive grease or the like, the contact thermal resistance with the cooling body is increased, or the grease enters the screw hole of the fixing member. However, in the heat dissipating device according to the present invention, the use of the heat dissipating structure eliminates the need for grease, thus eliminating the problem. The heat radiation from the heat generating element may be from only one side, but it is preferable to radiate heat from both sides because efficiency is improved.
Of course, grease may be used in combination. Since the whisker layer is not a dense layer but a porous layer, when the pores of the whisker layer are impregnated with grease, the contact property is further improved, so that the thermal conductivity is further reduced. Since the grease is held in the pores of the whisker layer, there is an advantage that the grease is less likely to evaporate and the reliability is improved than when the grease is used alone.

  Further, in the heat dissipation device according to the present invention, the heating element includes any one of a heat dissipation block, a heat dissipation plate, and a semiconductor substrate in addition to the heating element, and the heating surface of the heating element includes the heating element and the heat dissipation element. It is one or more of a block, the heat radiating plate, and the semiconductor substrate. That is, as shown in FIG. 5, the heat generating element (so-called die) may be packaged so as to be in contact with the heat dissipation structure according to the present invention, and the heat generating element and the cooler may be connected via the heat dissipation structure. In this case, the heating surface of the heating element means the surface of the heating element.

  In the heat radiating device shown in FIG. 5, it is possible to transfer the heat from the heating element to the cooler without passing through the heat radiating plate, and it is possible to radiate heat more efficiently. At this time, in the heat dissipation structure according to the present invention, the whisker layer may be formed only on the portion in contact with the heating element on the surface side in contact with the heating element, but more on the surface in contact with the cooler. In order to enhance the heat dissipation effect, a whisker layer is preferably formed on the front surface.

Moreover, when a heat generating body has a heat block or a heat sink (what is called a heat spreader) other than a heat generating element, it is also possible to interpose the heat radiating structure concerning this invention in these mutual contact surfaces. In this case, the heat generating surface of the heat radiator refers to any one of a heat generating element, a heat block, and a heat radiating plate.
Furthermore, as shown in FIG. 6, for example, when a cooler such as a heat sink is used at a location away from the heat generating element, the heat dissipation structure according to the present invention is interposed between the heat generating element and the heat radiating plate, thereby radiating heat. A portion of the plate may be in contact with the cooler. Further, a heat dissipation structure according to the present invention may be interposed between the heat sink and the heat dissipation plate. In FIG. 6, the heating surface of the heating element means the surface of the heating element, the semiconductor substrate, and the surface of the heat sink.
In the heat radiating device according to the present invention, it is preferable to radiate heat from both surfaces of the heat generating element in order to enhance the heat radiating effect.

  Since the heat dissipation structure according to the present invention has a whisker layer on its surface, it exhibits low contact thermal resistance. However, since the whisker itself has no adhesiveness, it is sandwiched and fixed between a heating element and a cooling element. It is preferably used for a heat dissipation device. For this reason, it is preferable to use a device that can change the contact pressure as appropriate, such as the device in Patent Document 1. In the case where an adhesive resin is used as the thermally conductive grease, a usage mode that does not require contact pressure is also possible.

FIG. 7 is a schematic diagram showing the overall configuration of an example of a heat dissipation device according to the present invention that cools both sides of a double-sided heat-dissipating semiconductor in contact with a cooler.
First, a semiconductor as a heating element in the heat dissipation device will be described. The heat radiating device shown in FIG. 7 includes a semiconductor chip as a heat generating element, a heat radiating plate (so-called heat spreader), a heat sink block as a heat radiating block, a bonding material interposed therebetween, and a resin for molding them. Configured.

In the case of this configuration, the lower surface of the semiconductor element and the upper surface of the lower heat radiating plate are bonded by, for example, a bonding material made of solder or the like. Similarly, the upper surface of the semiconductor element and the lower surface of the heat sink block are also bonded by a bonding material. And these heat sink and the semiconductor chip are molded with resin.
Furthermore, the heat dissipation structure according to the present invention is interposed between the upper surface of the heat sink block and the lower surface of the upper heat dissipation plate. Similarly, the lower heat sink and the lower cooler are in contact with the heat dissipation structure according to the present invention.

  Thus, in the above configuration, heat is radiated through the bonding material, the heat sink block, the bonding material, and the upper heat radiating plate on the upper surface of the semiconductor element, and heat is radiated from the bonding material through the lower heat radiating plate on the lower surface of the semiconductor element. Is done. The heating element is not particularly limited, and is composed of a power semiconductor element such as an IGBT (insulated gate bipolar transistor) or a thyristor. In this case, the device structure of the semiconductor chip is preferably a trench gate type. It may be configured to use other types of device structures.

The shape of the semiconductor element can be, for example, a rectangular thin plate. The lower heat sink, the upper heat sink and the heat sink block also function as electrodes and heat radiators, and are made of a metal having good thermal conductivity and electrical conductivity such as copper alloy or aluminum alloy. Yes. Moreover, you may use a general iron alloy as a heat sink block.
In the case of this configuration, the lower heat radiating plate and the upper heat radiating plate are also electrically connected to respective main electrodes (not shown) of the semiconductor element (for example, a collector electrode and an emitter electrode) via a bonding material.

  Further, the lower heat radiating plate can be a substantially rectangular plate material as a whole, for example. In addition, a terminal portion projects from the lower heat radiating plate. The heat sink block can be a rectangular plate having a size that is slightly smaller than the semiconductor element, for example. Furthermore, the upper heat radiating plate may be formed of, for example, a substantially rectangular plate material as a whole. Similarly, a terminal portion projects from the upper radiator plate.

The terminal part of the lower heat sink and the terminal part of the upper heat sink are electrically connected to the collector electrode and emitter electrode of the semiconductor element. Each terminal part is provided in order to connect with external wiring members, such as a bus bar and a circuit board, for example. Further, as shown in FIG. 6, resin is filled and sealed in the gap between the pair of heat sinks and the peripheral portions of the semiconductor element and the heat sink block.
In addition, normal mold materials, such as an epoxy resin, can be employ | adopted for resin, for example. Further, when the heat sink or the like is molded with resin, it can be easily performed by a transfer mold method using a molding die (not shown) composed of upper and lower molds.

  Further, in the resin, a terminal portion (control terminal) made of a lead frame (not shown) is provided around the semiconductor element. Further, the terminal portion and a gate electrode (not shown) of the semiconductor element are connected by a wire and are electrically connected. The wire is formed by wire bonding or the like and is made of gold, aluminum, or the like.

Next, a method of manufacturing the heat dissipation device having the above configuration will be briefly described with reference to FIG. Here, an example in which solder is used as the bonding material will be described. First, a process of soldering a semiconductor element on the upper surface of the lower heat sink is executed.
In this case, for example, a semiconductor element is laminated on the upper surface of the lower radiator plate via a solder foil, and a heat sink block is laminated on the semiconductor element via the solder foil. Thereafter, the solder foil is melted by a heating device (reflow device) and then cured.

Subsequently, a step of wire bonding the control electrode (eg, gate electrode) of the semiconductor element and the terminal portion is performed. As a result, the wire is formed, and the control electrode and the terminal portion of the semiconductor element are connected and electrically connected by the wire.
Next, a process of soldering the upper heat sink on the heat sink block is performed. In this case, the upper heat sink is placed on the heat sink block via the solder foil, and the solder foil is melted by a heating device and then cured.
When the molten solder foil is cured, the cured solder is configured as a bonding material. Then, the bonding and electrical / thermal connection between the lower heat radiating plate, the semiconductor element, the heat sink block, and the upper heat radiating plate are completed via the bonding material.

Finally, using a mold (not shown), a step (molding step) of filling a resin in the gap and the outer periphery of the pair of heat sinks is performed. As a result, as shown in FIG. 6, the gap and the outer periphery of the heat sink are filled with the resin, and almost the entire semiconductor device is sealed with the resin. Then, after the resin is cured, the semiconductor device is completed by removing the semiconductor device from the mold.
In the semiconductor device, in the case of the above configuration, resin molding is performed so that the lower surface of the lower heat radiating plate and the upper surface of the upper heat radiating plate are exposed as heat radiating surfaces, respectively. Thereby, the heat dissipation of a heat sink is improved.

The coolers are in contact with both heat radiation surfaces of such a semiconductor device, that is, the lower surface of the lower heat radiation plate and the upper surface of the upper heat radiation plate, which are exposed from the resin, through insulating plates as insulating materials, respectively. . Thereby, an example of the heat radiating device according to the present invention is configured.
Here, the insulating plate is the heat dissipation structure according to the present invention described above. In addition, as a comparative material, a heat radiating device using only an electrically insulating plate made of ceramic such as aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), silicon carbide (SiC), or the like was also produced.

  The cooler may be made of, for example, aluminum (Al) or the like, and may be a water-cooled type in which cooling water flows or an air-cooled type having fins. However, in this embodiment, the cooler is internally cooled. A cooling water channel through which water flows is provided, and heat from the heat radiating plate is cooled by the cooling water in the cooling water channel and heat exchange is performed.

  Further, conventionally, between the cooler and the insulating plate, and between the insulating plate and each heat radiating plate, if necessary, a heat transfer material such as grease or gel having electrical insulating properties and heat transfer properties. However, when the heat dissipation structure according to the present invention is used, it is not necessary to use grease or gel.

As described above, the heat dissipating device shown in FIG. 6 has a structure having a laminated structure of a cooler, a heat dissipating structure, a semiconductor device, a heat dissipating structure, and a cooler from the lower side. And in this structure, the clamping member is provided in the both outer sides of the cooler which opposes across the semiconductor device. The pinching member is for holding the cooler and the semiconductor device together by applying a load so that the semiconductor device is sandwiched by the cooler.
The load applied so as to sandwich the semiconductor device by the cooler is expressed as a load indicated by an arrow in FIG. That is, the load is applied in the stacking direction of the heat dissipation device.

  Here, the clamping member applies a load by the action of a fastening force via an elastic body or the like. Specifically, the pinching member has a fixed portion that applies a load from one of the two outer sides of the cooler that faces each other across the semiconductor device, and a movable portion that applies a load from the other. The upper and lower coolers are sandwiched between the movable parts. As shown in FIG. 6, in the clamping member, a bolt having a male screw (feed screw) is connected to the fixed portion. The bolt is passed through a through hole provided in the movable part and fastened with a nut via an elastic body. Here, in addition to the illustrated coil spring, a rubber tube, an O-ring, a spring washer, or the like can be employed as the elastic body.

Further, the cooler, the fixed portion, and the movable portion are plate members extending in the direction perpendicular to the paper surface in FIG. 6, and a plurality of semiconductor devices are arranged along the direction perpendicular to the paper surface.
And in this heat radiating device, when screwing with the nut of a pinching member is performed, a movable part will approach a fixed part by the effect | action of the fastening force via the elastic force of an elastic body. That is, the pinching member performs weighting so that the semiconductor device is pinched by the cooler by the action of the fastening force via the elastic body. As a result, the cooler and the semiconductor device are held together.

The heat dissipation device is assembled as follows. First, a cooler, an insulating plate (a heat dissipation structure according to the present invention), a semiconductor device, an insulating plate, and a cooler are stacked. In the case of a conventional heat radiating device as a comparative example, it is assembled so that a heat transfer material such as grease is interposed on both surfaces of the insulating plate.
Thereafter, the clamping device is used to clamp and fix the semiconductor device so that the semiconductor device is sandwiched between the upper and lower coolers. At this time, the elastic body and the nut serve as a load adjustment mechanism to adjust the load. Thus, the heat dissipation device of this embodiment is formed. The semiconductor device is connected to a bus bar or a circuit board through each terminal portion. The heat from the semiconductor element is radiated to the cooler via the heat radiating plates and the insulating plates on both sides. And the heat dissipation characteristic is improved because the heat sink is cooled by the cooler.

The semiconductor chip, which is a heat generating element, generates heat when driven. Here, the amount of heat generated is 65 W.
As the insulating plate, a heat dissipation structure according to the present invention, a plate material having a thickness of 0.35 mm made of aluminum nitride (AlN) and silicon nitride (Si ₃ N ₄ ) as a comparative material was used. In the comparative material, grease was used as the heat transfer material. The flow rate of the cooling water flowing through the cooling water flow path of the cooler was 6 liter / min, and the water temperature of the cooling water was 40 ° C.

The thermal resistance is a thermal resistance in a heat radiation path from the semiconductor chip to the cooling water flow path of the cooler through each heat sink and insulating plate. Specifically, assuming that the temperature of the semiconductor chip is Tc, the temperature of the cooling water is Tw, and the calorific value of the semiconductor chip is Q, the thermal resistance is (Tc−Tw) / Q (unit: K / W (Kelvin / Watt). )).
Then, the relationship between the contact pressure P (unit: MPa) and the thermal resistance (unit: K / W) when the parallelism H (unit: μm) was changed under the above-described examination conditions was investigated.

<Used heat dissipation material>
The AlN and Si ₃ N ₄ substrates were prepared by coating aluminum films with various thicknesses in advance by hot-dip aluminum plating.
Various substrates were heated at various temperatures, times, and gas atmospheres to produce aluminum carbide whiskers on both surfaces of the substrate. Some samples were further heated under atmospheric pressure to convert aluminum carbide into alumina whiskers, thereby forming alumina whisker layers on both sides of the substrate.

<Result>
The results are shown in Table 1.
By using the heat dissipation structure according to the present invention, a lower thermal resistance was obtained than when grease was used. It has been found that when the length of aluminum carbide whiskers or alumina whiskers is long, even lower thermal resistance is obtained. Moreover, the thermal resistance was further reduced by using grease together.

In the present invention, the whisker layer is formed on the surface of the insulating substrate.
When the cooling member is made of aluminum, an aluminum carbide whisker or an alumina whisker layer may be formed on the surface of the cooling member. The same thermal resistance can be reduced.

It is a figure which shows the outline of an example of the usage example of the thermal radiation structure which concerns on this invention. It is a figure which shows the outline of an example of the manufacturing process of the thermal radiation structure which concerns on this invention. It is a figure which shows the outline of another example of the manufacturing process of the thermal radiation structure which concerns on this invention. It is a figure which shows the outline of an example of the thermal radiation apparatus which concerns on this invention. It is a figure which shows the outline of another example of the thermal radiation apparatus which concerns on this invention. It is a figure which shows the outline of another example of the thermal radiation apparatus which concerns on this invention. It is a figure which shows the outline of the thermal radiation apparatus used in the Example.

Claims (14)

A substrate that is an insulating material;
An aluminum carbide phase or an aluminum oxide phase formed on at least the entire surface of the substrate;
An aluminum carbide whisker layer or an alumina whisker layer formed by standing a plurality of aluminum carbide whiskers or alumina whiskers from an aluminum carbide phase or an aluminum oxide phase on the substrate surface;
The heat dissipation structure characterized by having.   2. The heat dissipation structure according to claim 1, wherein an aluminum phase is provided around an aluminum carbide phase or an aluminum oxide phase in the substrate. The heat dissipation structure according to claim 1, wherein the substrate is any one of Si ₃ N ₄ , AlN, or SiC.   The heat dissipation structure according to any one of claims 1 to 3, wherein the plurality of aluminum carbide whiskers or alumina whiskers are grown substantially perpendicular to the substrate surface.   The heat dissipation structure according to any one of claims 1 to 4, wherein a thickness of the aluminum carbide whisker layer or the alumina whisker layer is 1 µm or more.   The heat dissipation structure according to claim 5, wherein the aluminum carbide whisker layer or the alumina whisker layer has a thickness of 10 μm or more.   The heat dissipation structure according to any one of claims 1 to 6, wherein the aluminum carbide whisker layer or the alumina whisker layer is impregnated with grease.   A first step of forming an aluminum carbide whisker layer on the substrate surface by heating an insulating substrate having at least a part or the entire surface of aluminum disposed in a space containing a hydrocarbon-containing substance; A method for manufacturing a heat dissipation structure.   After the first step, the method includes a second step of heating the substrate on which the aluminum carbide whisker layer is formed in an oxidizing atmosphere to convert the aluminum carbide whisker layer into an alumina whisker layer. Item 9. A method for manufacturing a heat dissipation structure according to Item 8.   The method for manufacturing a heat dissipation structure according to claim 9, further comprising a step of impregnating the aluminum carbide whisker layer or the alumina whisker layer with grease after the first step or the second step. The method for manufacturing a heat dissipation structure according to any one of claims 8 to 10, wherein the substrate is any one of Si ₃ N ₄ , AlN, and SiC.   In a heat dissipation device in which heat generated from a heat generating surface of a heat generating element having at least a heat generating element is transferred to a heat dissipation plate and / or a cooler via a heat dissipation structure, the heat dissipation structure is any one of claims 1 to 7. A heat dissipation device having the heat dissipation structure described above.   The heating element has any of a heat dissipation block, a heat dissipation plate, or a semiconductor substrate in addition to the heat generation element, and the heat generation surface of the heat generation element is the heat generation element, the heat dissipation block, the heat dissipation plate, or the semiconductor substrate. It is any one or more, The heat radiating device of Claim 12.   The heat radiating device according to claim 12 or 13, wherein heat is radiated from both surfaces of the heat generating element.

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