JP2003124665A - Heat sink structure for electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sink structure capable of upgrading heat sink characteristics from an electronic component by maintaining the connecting state of the component to a heat diffusing plate even when a temperature change occurs. SOLUTION: The heat sink structure for the electronic device cools the electronic component 10 by transferring the heat generated from the component 10 to the heat diffusing plate 12. The heat sink structure comprises a grading layer 14 provided between the component and the heat diffusing plate and having the same or similar thermal expansion coefficient as or to that of the component at the part of the component side and the thermal expansion coefficient changing in the same or similar manner as or to that of the diffusing plate at the part of the diffusing plate side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat radiating structure for cooling an electronic device by radiating heat from an electronic device such as an arithmetic processing device such as an MPU or an image processing device.

[0002]

2. Description of the Related Art The degree of integration of electronic devices such as arithmetic processing devices and image information processing devices has become higher and higher, and the operating frequency has also increased. Along with this, the amount of heat generated by this type of electronic device is increasing.

When the temperature of an electronic device rises due to heat generation,
Since it may malfunction and may be damaged, it is necessary to actively dissipate heat from the electronic device. Conventionally, for example, a heat sink is used as a means for cooling an electronic device.

When dissipating heat through a heat sink,
Since it is necessary to transfer heat from the electronic device to the heat sink, in order to transfer heat most efficiently, it is sufficient to directly contact the both. However, an electronic device such as an MPU has a circuit formed on a silicon die, and has a structure that attaches importance to electrical characteristics. Therefore, it is difficult to directly attach a heat sink for heat dissipation to the electronic device. .

Therefore, conventionally, a heat dissipation structure has been developed in which a heat spreader is arranged in close contact with the surface of an electronic device, and a heat sink is arranged in close contact with the heat spreader. An example thereof is schematically shown in FIG.
The thermal diffusion plate 1 shown here is, as an example, formed of a metal such as anodized aluminum or copper and has a protrusion 3 protruding from a flat plate portion 2 that is brought into close contact with an electronic device. It is fixed by being fitted into the pedestal portion 4 such as a frame or a substrate.

The above heat diffusion plate 1 is fixed to the pedestal portion 4 together with the die 5 containing the integrated circuit, and is brought into contact with the surface of the die 5 via grease (or jelly) 6 having high thermal conductivity. Moreover, since the heat diffusion plate 1 is formed of a material having a good thermal conductivity such as copper, it is possible to increase the substantial heat transfer area of the die 5 without damaging the die 5 or its circuit.

Therefore, by closely fixing the heat sink 7 to the heat diffusion plate 1, the heat dissipation characteristics of the electronic device can be improved.

In order to improve the heat radiation characteristics by using the heat diffusion plate 1, it is preferable to reduce the thermal resistance between the die 5 and the heat diffusion plate 1 as much as possible. It is possible to replace the grease (or jelly) 6 having a high thermal conductivity filled between the die 5 and the heat diffusion plate 1 with each other, and directly join the die 5 and the heat diffusion plate 1 by means such as soldering. preferable.

[0009]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The electronic components such as are made of a material (for example, silicon) that emphasizes electrical characteristics, while the heat diffusion plate 1
Is made of a material (for example, copper) that places importance on thermal characteristics, and therefore has a large difference in coefficient of thermal expansion (linear expansion coefficient) between the two.

Therefore, the electronic device operates to generate heat,
When the temperature rises accordingly, thermal stress is generated between the electronic components such as the die 5 and the thermal diffusion plate 1, and there is a possibility of damage due to this. In addition, the adhesion between the two is peeled off due to thermal stress, and as a result, the thermal resistance between the die 5 and the heat diffusion plate 1 is increased, and it is possible that the electronic components such as the die 5 cannot be cooled sufficiently. there were.

The present invention has been made by paying attention to the above technical problem, and maintains the joined state between the electronic component and the heat diffusion plate even if the temperature changes, thereby improving the heat radiation characteristic from the electronic component. It is an object of the present invention to provide a heat dissipating structure that can be made into a simple structure.

[0012]

In order to achieve the above object, the invention of claim 1 is an electronic device for cooling an electronic component by transferring heat generated in the electronic component to a heat diffusion plate. In the heat dissipation structure for use, between the electronic component and the heat diffusion plate, the coefficient of thermal expansion in the part on the electronic component side is the same as or close to the coefficient of thermal expansion of the electronic component, and the coefficient of thermal expansion in the part on the side of the thermal diffusion plate. Is a heat dissipation structure characterized in that a grading layer whose thermal expansion coefficient is changed so as to be the same as or close to the thermal expansion coefficient of the thermal diffusion plate is provided.

Therefore, according to the first aspect of the invention, since the grading layer having a different coefficient of thermal expansion between the electronic component and the thermal diffusion plate is provided between the electronic component and the thermal diffusion plate, the electronic component is provided. The difference in the coefficient of thermal expansion between the contact portion between the heat spreader and the grating layer and the difference in the coefficient of thermal expansion between the contact portion between the heat diffusion plate and the grating layer are both small. as a result,
Even if the temperature rises, the thermal stress does not increase, and it is possible to avoid disconnection between the electronic component and the grating layer or disconnection between the thermal diffusion plate and the grating layer. In other words, the thermal resistance between the electronic component and the heat diffusion plate does not increase, and the heat dissipation characteristics from the electronic component can be maintained in a good state.

According to a second aspect of the present invention, in a heat dissipation structure for an electronic device that cools an electronic component by transferring heat generated in the electronic component to the thermal diffusion plate, the heat diffusion plate joined to the electronic component is The heat dissipation structure is made of a material having a coefficient of thermal expansion close to that of the electronic component.

As described in claim 3, the heat diffusion plate can be formed of either nickel steel or aluminum nitride for an electronic component mainly composed of silicon. The nickel steel may be invar, as described in claim 4.

Further, as described in claim 5,
The electronic component and the heat diffusion plate can be integrated via graphite.

Therefore, the difference in the coefficient of thermal expansion between the electronic component and the heat diffusion plate is reduced, and even if the electronic component operates and its temperature rises, the thermal stress between them is suppressed to a small level. As a result, the bonded state between the electronic component and the heat diffusion plate can be maintained well, and the electronic component can be cooled well.

On the other hand, according to the invention of claim 6, in a heat dissipation structure for an electronic device, wherein the heat generated in the electronic component is transferred to the heat diffusion plate to cool the electronic component.
This is a heat dissipation structure characterized in that a chamber having a closed structure in which a working fluid that transports heat as latent heat by repeating evaporation and condensation is enclosed is provided inside.

Therefore, according to the invention of claim 6, the movement of heat inside the heat diffusion plate is caused not only by heat conduction but also by heat transport in the form of latent heat by the working fluid, so that the heat in the heat diffusion plate is The resistance decreases. Therefore, heat dissipation from the electronic component can be promoted and the electronic component can be efficiently cooled.

Further, in the invention of claim 7, in the heat dissipation structure for an electronic device for cooling the electronic component by transmitting the heat generated in the electronic component to the thermal diffusion plate, the thermal diffusion plate is made of aluminum and A surface of the heat diffusion plate on the electronic component side has a structure in which a lubricating member is embedded.

The surface of claim 7 is the same as that of claim 8.
As described in (1), anodization treatment may be performed to form fine cracks on the surface, and the cracks may be filled with molybunden sulfide as the lubricating member.

Therefore, according to the invention of claim 7 or the invention of claim 8, the heat diffusion plate is made of aluminum, and the surface in contact with the electronic component has a structure in which a lubricative member is embedded, so that the heat diffusion is performed. The plate may be in direct contact with the electronic component. With such a configuration, since there is no inclusion between the electronic component and the heat diffusion plate, the thermal resistance between the two can be reduced. Also, since the coefficient of thermal expansion of the surface in contact with the electronic component becomes small,
Even if the electronic component operates and its temperature rises, the thermal stress can be suppressed to be small, and as a result, the electronic component and the thermal diffusion plate do not separate from each other, and an increase in the thermal resistance between them can be prevented. .

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION In FIG. 1, a die 10 which is an electronic component on which a fine circuit is formed is fixed to a pedestal portion 11 such as a substrate or a socket. The die 10 has a structure similar to that of a conventionally known one, and is a rectangular member with a circuit formed on a silicon chip and a thickness of several mm.

A heat diffusion plate 12 is arranged so as to straddle the die 10. The heat diffusion plate 12 is for mediating the transfer of heat from the die 10 to the heat sink 13, and is made of a material having a high thermal conductivity such as copper or aluminum. As shown in FIG. 1, the heat diffusion plate 12 includes a rectangular flat plate portion 12a facing the upper surface of the die 10 in the figure, and leg portions 12b formed at both left and right end portions or four corner portions. And is fixed to the pedestal portion 11 by the legs 12b.

The height of the leg portion 12b is substantially equal to the thickness of the die 10, and thus the lower surface (back surface) of the flat plate portion 12a.
12c and the die 10 closely face each other. And
A grating layer 14 is provided between the flat plate portion 12a and the die 10.

The grating layer 14 is a layer having a different coefficient of thermal expansion between the upper surface side and the lower surface side. For example, as schematically shown in FIG. The coefficient of thermal expansion of the first layer 14a is close to the coefficient of thermal expansion of the die 10, and the coefficient of thermal expansion of the intermediate second layer 14b is the coefficient of thermal expansion of the die 10 and the coefficient of thermal expansion of the thermal diffusion plate 12. The thermal expansion coefficient of the third layer 14c on the upper surface side is close to that of the thermal diffusion plate 12.
Such a multilayer structure can be made by laminating plate pieces of different materials, or can be made by changing the composition of a composite material composed of a plurality of materials in the thickness direction.

The die 1 is placed through the grating layer 14.
A heat sink 13 having an appropriate structure is attached in close contact with the upper surface of the heat diffusion plate 12 joined to 0 in FIG. Then, as shown in FIG. 1, the area of the flat plate portion 12a of the heat diffusion plate 12 is larger than the area of the front surface of the die 10, and the area of the base portion 13a of the heat sink 13 is larger than the area of the flat plate portion 12a. . The die 10, the grating layer 14, and the heat diffusion plate 12 can be joined to each other by soldering, brazing, or an adhesive.

In the above heat dissipation structure, when the die 10 operates to generate heat, the heat is transferred to the heat diffusion plate 12 via the grating layer 14. As a result, the heat diffusion plate 12
Since the temperature of the
To the surrounding atmosphere. Since the heat of the die 10 is dissipated to the atmosphere in this way, the temperature rise of the die 10 is suppressed. That is, the die 10 is cooled.

In this case, the temperature of the heat diffusion plate 12 as well as that of the die 10 rises, and the die 10 is thermally expanded in accordance with the temperature.
Is smaller than the thermal expansion amount of the heat diffusion plate 12. However, since the first layer 14a of the grating layer 14 in direct contact with the die 10 has a thermal expansion coefficient substantially equal to that of the die 10, a large thermal stress does not occur between them. Further, since the third layer 14c of the grating layer 14 in direct contact with the thermal diffusion plate 12 having a large thermal expansion amount has a thermal expansion coefficient substantially equal to that of the thermal diffusion plate 12, a large thermal stress is generated between them. Absent. After all, since the thermal stress between the two members that are in contact with each other is small, the joining of these two members is not separated and a gap is not generated, and the thermal resistance is not increased due to the gap.

As described above, in the structure shown in FIG.
Since a gap or an air layer that hinders heat transfer is prevented from being formed in the heat transfer path from the die 10 to the heat spreader plate 12, the thermal resistance in the heat transfer path from the die 10 to the heat spreader plate 12 is reduced. A small heat resistance can be maintained, and as a result, a heat dissipation structure with good heat dissipation characteristics from the die 10 can be obtained.

Next, another embodiment of the present invention will be described.
In FIG. 3, the thermal diffusion plate 12 arranged so as to straddle the die 10 is formed of a material having a thermal expansion coefficient close to that of silicon forming the die 10. Specifically, the heat diffusion plate 12 is formed of aluminum nitride. Alternatively, Mn: 0.4%, C: 0.2%, N
i: 36%, and the balance Fe is formed of nickel steel (that is, invar).

The heat diffusion plate 12 and the die 10 are joined together by graphite 15 interposed therebetween. For example, the graphite 15 is interposed between the upper surface of the die 10 and the lower surface of the flat plate portion 12a of the heat diffusion plate 12, and the die 10 and the heat diffusion plate 12 are bonded to each other by applying predetermined heat while pressurizing in that state. Have been integrated.

Even with the configuration shown in FIG. 3, heat generated by the operation of the die 10 is transferred to the heat sink 13 via the heat diffusion plate 12 as in the above-described embodiment, from which the atmosphere is released. To the die 10, resulting in efficient cooling of the die 10. In particular, since the die 10 and the heat diffusion plate 12 are joined together, it is possible to reduce the heat resistance between them and improve the heat dissipation efficiency.

When the temperature of the die 10 rises due to heat generation, since the coefficients of thermal expansion of the die 10 and the thermal diffusion plate 12 are similar to each other, there is no great difference in the amount of thermal expansion between them. That is, since no thermal stress is particularly generated between the die 10 and the thermal diffusion plate 12, the joined state of the two is maintained in a good state, and as a result, the thermal resistance is kept small.

The embodiment shown in FIG. 4 is an example in which the thermal conductivity of the thermal diffusion plate 12 is increased to further reduce the thermal resistance as a whole. That is, in the heat diffusion plate 12 shown in FIG. 4, the flat plate portion 12a has a hollow structure. The hollow portion 12d
Can be configured by attaching a lid to a main body portion having a recess. And, this hollow portion 12d is
A non-condensable gas such as air is degassed from the inside thereof, and a condensable fluid such as water is enclosed as the working fluid 12e. That is, it is made into a heat pipe, and a so-called vapor chamber is formed here.

The thermal diffusion plate 12 and the die 10 may be joined by either the above-mentioned joining structure or a conventionally known joining structure.

Therefore, in the structure shown in FIG.
The heat generated in 1 is transmitted to the heat diffusion plate 12 which is in contact with the heat. The heat causes the working fluid 12e in the vapor chamber to evaporate, and the vapor flows to a portion having a low temperature and pressure, that is, the upper surface side in contact with the heat sink 13. Thereafter, the vapor of the working fluid 12e radiates heat and condenses, and the heat of the working fluid 12e is transferred from the upper surface side of the heat diffusion plate 12 to the heat sink 13 and further dissipated from the heat sink 13 to the surrounding air. To be Eventually, the heat of the die 10 is dissipated into the air and the die 10 is cooled.

As described above, in the heat diffusion plate 12, the working fluid 12 enclosed in the vapor chamber is used.
e transports heat as its latent heat. Since the amount of heat is much larger than that due to heat conduction, the substantial thermal resistance of the heat diffusion plate 12 becomes extremely small. As a result, die 1
The thermal resistance between 0 and the heat sink 13 is reduced, and the die 10 can be cooled efficiently.

As described above, a metal suitable for the heat diffusion plate 12 due to its good thermal conductivity, such as copper or aluminum, has a coefficient of thermal expansion larger than that of silicon forming the die 10. Therefore, if the die 10 and the heat diffusion plate 12 are in close contact with each other in a heat transferable manner and the relative movement between the two is smoothed, the generation of thermal stress between the die 10 and the heat diffusion plate 12 is suppressed or Can be prevented. 5 and 6 show an example thereof, and the heat diffusion plate 12 shown in these figures is
It is made of aluminum and its flat plate portion 12
The back surface (lower surface in the figure) 12c in a is anodized, and cracks 16 generated by the anodization
A soft, lubricious material, such as molybdenum sulfide 17
Is filled, and a part of the molybdenum sulfide 17 is exposed. This type of metal is known as "Fujimite" (registered trademark).

Therefore, in the structure shown in FIGS. 5 and 6, the adhesion between the die 10 and the thermal diffusion plate 12 is improved, and the thermal resistance between them is reduced. Further, even if the difference in the coefficient of thermal expansion between the die 10 and the thermal diffusion plate 12 is large and the amount of thermal expansion when the temperature rises due to the heat generation of the die 10 is different, the relative amount of the die 10 and the thermal diffusion plate 12 is increased. Since smooth sliding occurs smoothly, thermal stress does not occur between them. Therefore, even with the configuration shown in FIG. 5 and FIG.
The heat dissipation characteristic from 0, that is, the cooling performance of the die 10 can be improved.

[0041]

As described above, according to the invention of claim 1, between the electronic component and the heat diffusion plate, the grading layer having a different coefficient of thermal expansion between the electronic component side and the heat diffusion plate side. Is provided, the difference in the coefficient of thermal expansion between the contact part between the electronic component and the grating layer and the difference in the coefficient of thermal expansion between the contact part between the thermal diffusion plate and the grating layer are both reduced. As a result, the thermal stress does not increase even when the temperature rises, and it is possible to avoid disconnection between the electronic component and the grating layer or disconnection between the thermal diffusion plate and the grating layer. In other words, the thermal resistance between the electronic component and the heat diffusion plate does not increase, and the heat dissipation characteristics from the electronic component can be maintained in a good state.

According to the invention of claims 2 to 5,
Even if the difference in the coefficient of thermal expansion between the electronic component and the heat diffusion plate becomes small, and the temperature of the electronic component rises due to the operation of the electronic component, the thermal stress between them is suppressed to a small level. As a result, the bonded state between the electronic component and the heat diffusion plate can be maintained well, and the electronic component can be cooled well.

Further, according to the invention of claim 6, the movement of heat inside the heat diffusion plate is caused not only by heat conduction but also by heat transport in the form of latent heat by the working fluid. The thermal resistance at Therefore, heat dissipation from the electronic component can be promoted and the electronic component can be efficiently cooled.

Further, according to the invention of claim 7 or the invention of claim 8, the heat diffusion plate is made of aluminum, and the surface in contact with the electronic component has a structure in which a lubricating member is embedded. The heat diffusion plate may be in direct contact with the electronic component. With such a configuration, since there is no inclusion between the electronic component and the heat diffusion plate, the thermal resistance between the two can be reduced.
Further, since the coefficient of thermal expansion of the surface in contact with the electronic component becomes small, thermal stress can be suppressed to be small even when the electronic component operates and its temperature rises, and as a result, the electronic component and the thermal diffusion plate are Peeling does not occur, and an increase in thermal resistance between the two can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view for explaining the structure of a grating layer used in the heat dissipation structure of FIG.

FIG. 3 is a sectional view schematically showing another embodiment of the present invention.

FIG. 4 is a sectional view schematically showing still another embodiment of the present invention.

FIG. 5 is a sectional view schematically showing still another embodiment of the present invention.

FIG. 6 is a schematic view showing an enlarged VI portion of FIG.

FIG. 7 is a sectional view schematically showing a conventional example.

[Explanation of symbols]

10 ... Die, 12 ... Thermal diffusion plate, 12d ... Hollow part,
12e ... Working fluid, 13 ... Heat sink, 14 ... Gooting layer, 15 ... Graphite, 17 ... Molybdenum sulfide.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5E322 AA11 AB11 DB12 FA01 FA04                       FA09                 5F036 AA01 BA23 BB01 BB21

Claims (8)

[Claims] 1. A heat dissipation structure for an electronic device, wherein heat generated in an electronic component is transferred to a heat diffusion plate to cool the electronic component, wherein a portion on the electronic component side is provided between the electronic component and the heat diffusion plate. The coefficient of thermal expansion is changed so that the coefficient of thermal expansion is the same as or close to the coefficient of thermal expansion of the electronic component, and the coefficient of thermal expansion in the part on the side of the thermal diffusion plate is the same as or similar to that of the thermal diffusion plate. A heat dissipation structure for an electronic device, characterized in that a grading layer is provided. 2. A heat dissipation structure for an electronic device, which cools an electronic component by transferring heat generated in the electronic component to the thermal diffusion plate, wherein the thermal diffusion plate joined to the electronic component has a coefficient of thermal expansion of the electronic component. A heat-dissipating structure for electronic devices, characterized in that it is made of a material close to 3. The electronic device according to claim 2, wherein the electronic component is composed mainly of silicon, and the heat diffusion plate is composed of either nickel steel or aluminum nitride. Heat dissipation structure for equipment. 4. The heat dissipation structure for an electronic device according to claim 3, wherein the nickel steel is Invar. 5. The heat dissipation structure for an electronic device according to claim 2, wherein the electronic component and the heat diffusion plate are integrated via graphite. 6. A heat dissipation structure for an electronic device, wherein heat generated in an electronic component is transferred to a heat diffusion plate to cool the electronic component, wherein the heat diffusion plate transports heat as latent heat by repeating evaporation and condensation. A heat dissipating structure for an electronic device, characterized in that a chamber having a closed structure in which a working fluid is sealed is provided inside. 7. A heat dissipation structure for an electronic device, wherein heat generated in an electronic component is transferred to a heat diffusion plate to cool the electronic component, wherein the heat diffusion plate is made of aluminum and the heat diffusion plate is A heat dissipation structure for an electronic device, wherein a surface on the electronic component side has a structure in which a lubricating member is embedded. 8. The electron according to claim 7, wherein the surface is anodized to form fine cracks, and the cracks are filled with molybundene sulfide as the lubricating member. Heat dissipation structure for equipment.