JP3431576B2 - Thermal conductive material - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention belongs to the technical field of heat-conducting materials.

[0002]

2. Description of the Related Art A heat sink is attached to a CPU of a computer in order to efficiently dissipate generated heat. If the contact between the heat sink and the outer surface of the CPU is not good (there is a gap), the heat dissipation efficiency is lowered. Therefore, an interface material having good thermal conductivity is filled between the heat sink and the CPU to prevent the gap.

The heat conductive material as the interface material is a base material such as resin in which a filler such as ceramics is dispersed, for example, a heat conductive material obtained by kneading vulcanized EPDM resin and ceramic powder. Alternatively, there is a heat conductive material obtained by kneading paraffin and ceramic powder.

[0004]

By the way, it is known that the heat transfer amount (Q) by the plate-shaped heat-conducting base material has the relationship shown in the following mathematical formula 1.

[0005]

[Equation 1] Q: Heat transfer amount λ: Thermal conductivity [Kcal / mh ° C.] Q ₁ -Q ₂ : Temperature difference between front and back x: Plate thickness F: Surface area T: Time Therefore, in order to increase the heat transfer efficiency (heat transfer amount Q should be large. In order to do so, a material having a good thermal conductivity λ may be used or the plate thickness x may be reduced.

By the way, a great deal of research is usually required to improve the thermal conductivity λ (that is, to improve the thermal conductive material).
The human and financial burden is large. There is also a feeling that the research was done by the ancestors. Compared to this, the method of reducing the plate thickness x is relatively easy. However, when the plate thickness x of the heat-conducting base material is reduced, for example, the rigidity becomes low, which makes it difficult to handle.

A conventional heat conductive material (for example, vulcanized EPD)
Thermal conductive material made by kneading M resin and ceramic powder)
Was solid under the temperature conditions during its use, so CP
There is also a problem that it does not deform following the shape of U or a heat sink, and a minute air gap is generated between the surface of the CPU and the surface of the heat sink, and a sufficient heat conduction effect cannot be obtained. there were. It should be noted that such a problem is not limited to the CPU but is a problem common to electronic components that generate heat during use.

An object of the present invention is to solve the problem of handling when the plate thickness x of the heat conductive base material is reduced.

[0009]

Means for Solving the Problems, Embodiments of the Invention and Effects of the Invention The heat conductive material according to claim 1 for solving the above problems has a melting point in the range of 30 to 70 ° C. and a temperature of 100 ° C.
In an organic material having a viscosity of 70,000 cP or more,
Disperse the filler in a proportion of 30 to 90% by weight relative to the whole.
At a temperature above the melting point of the organic material, a plate-shaped heat-conducting base material having a thickness of 1 mm or less, which has a property of being deformed following the shape of the surface of the mounted body when pressed against the surface of the mounted body. And a protective sheet attached to two or one surface of the heat conductive base material.

The heat conductive substrate has a melting point in the range of 30 to 70 ° C.
The viscosity at 100 ° C is 70,000 cP or more.
30 to 90% by weight of the whole organic material
Of the filler, and the temperature is higher than the melting point of the organic material.
When it is pressed toward the surface of the mounted object (for example, CPU), it has the property of following the shape of the surface and deforming.
Moreover, it has a plate shape with a thickness of 1 mm or less. In short, it is difficult to maintain the posture in a flat plate shape only with the heat conductive base material, but since the protective sheet is attached to two or one side, the protective sheet serves as a support and the heat conductive base material. Prevent excessive deformation of. Therefore, the heat conductive material is, for example, C
When it is attached to the surface of the PU, it is easy to handle and the workability is improved.

The work of interposing the heat conductive material between the electronic component (for example, CPU) and the heat sink is performed as follows, for example. First, one surface of the heat conductive material is exposed (if the protective sheet is attached to the two surfaces, one is peeled off). With the protective sheet attached to one surface of the heat conductive base material, the exposed surface of the heat conductive base material is brought into contact with the target surface of the electronic component (for example, CPU). Then, for example, the heat conduction base material is brought into close contact with the surface of the electronic component by pressing or heating (thermal transfer) from the side of the protective sheet, and then the protective sheet is peeled off. A heat sink is applied to the surface from which the protective sheet has been peeled off, and fixed to an electronic component with a screw or the like.

At this time, a force (for example, a tightening force) due to a screw or the like acts as a force (sandwiching force) for sandwiching the heat conductive base material between the heat sink and the electronic component. The heat-conducting substrate has a plate shape with a thickness of 1 mm or less, and at a temperature equal to or higher than the melting point of the organic material, it follows the shape of the surface of the mounted object (for example, CPU) when pressed against the surface. When the heat conductive base material is sandwiched between the electronic component and the heat sink, the sandwiching force = pressing force deforms following the surface shapes of both the electronic component and the heat sink. As a result, the heat-conducting base material is brought into close contact with both the electronic component serving as the heat source and the heat sink for heat dissipation. Since no fine gap is generated between the heat conductive base material and the surfaces of the electronic component and the heat sink, a sufficient heat conductive effect can be obtained.

If the thickness of the heat conducting substrate is 1 mm or less, good heat conducting efficiency can be obtained, but needless to say, the thinner it is, the better. Therefore, preferably 0.5m
m or less. However, if it is made too thin, even if there is a protective sheet or the support material according to claim 3,
The possibility of breakage during mounting work increases. In addition, the support material may be exposed on the surface of the heat conductive base material due to bending during mounting work. Therefore, the plate thickness of the heat conductive base material is preferably 0.1 mm or more. That is, the thickness of the heat conductive base material is preferably 0.5 mm or less and 0.1 mm or more.

Note that, as an example of being deformed following the shape of the surface of the mounted object when pressed against it, there is plastic deformation or elastic deformation. That is, plasticity and elasticity are exemplified as the property of such deformation. Further, if the rigidity of the protective sheet is too high, the workability described above may be deteriorated, so it is desirable to use a material having a certain degree of flexibility, such as paper or a plastic film.

According to a second aspect of the present invention, in the heat conducting material according to the first aspect, the protective sheet can be peeled off without damaging the surface of the heat conducting base material. As mentioned above, it is necessary to remove the protective sheet when attaching the heat conductive material to electronic parts, so when removing the protective sheet, part of the surface of the heat conductive base material should be peeled off to the protective sheet side. That is not preferable. Therefore,
It is preferable that the heat conductive substrate can be peeled off without damaging the surface thereof.

For that purpose, so-called release paper may be used as the protective sheet, or a release layer may be provided between the protective sheet and the heat conductive base material. The heat conductive material according to claim 3,
The heat conductive material according to claim 1 or 2, further comprising: a support material which is wholly or partially disposed inside the heat conductive base material and supports the heat conductive base material.

Since all or part of the support material is arranged inside the heat conductive base material, the heat conductive base material can be supported from the inside. Therefore, the protective sheet can be made thinner or more flexible. Also,
Even after the protective sheet is peeled off, the support material supports the heat-conducting base material, so that workability is further improved.

However, since the support material remains integrated with the heat conductive base material even when the heat conductive material is used, the heat conductivity of the support material must be good. Such a support material can be realized by, for example, the metal foil according to claim 4. In particular, a metal foil having a high thermal conductivity such as gold, silver, copper or aluminum is preferable. Moreover, if a metal foil is used, an electromagnetic shielding effect can be expected. The support material is not limited to the metal foil as long as it has good thermal conductivity.

When a metal foil is used, it is simply a foil
Since the heat conductive base material on both sides of the foil may separate from each other, holes (a large number of holes) are provided in the metal foil as described in claim 5, and the heat conductive material on both sides of the metal foil is formed. Should be continuous through the hole. Whether the holes are made by physical processing (for example, drill or laser) or by chemical processing,
either will do. Moreover, the direction of the holes may be perpendicular to the surface of the metal foil, may be inclined with respect to the surface, or may be bent in the middle. However, it is preferable that the arrangement of the holes is not biased.

The heat conductive base material of the heat conductive material of the present invention has a melting point of
Viscosity at 30-70 ° C and 100 ° C is 70,000c
30 to 90% by weight of the heat conductive substrate in an organic material of P or more
The filler is dispersed.

The organic material which is the base material of the heat conducting base material is an olefin resin, specifically, an olefin resin such as vinyl acetate-ethylene copolymer, polyethylene, polyisobutylene, ethylene-ethyl alcohol. Satisfying the above conditions (melting point: 30 to 70 ° C., viscosity at 100 ° C .: 70,000 cP or more), molecular weight 7
Examples include vulcanized EPDM (unvulcanized ethylene-propylene rubber) of 000 to 50,000, but any vulcanized EPDM (unvulcanized ethylene-propylene rubber) can be used without particular limitation as long as it satisfies the above melting point and viscosity.

As the filler, ceramics, one type thereof, soft ferrite, metal powder, metal magnetic material, carbon fiber and the like can be used. Since ceramics have high thermal conductivity, the thermal conductivity of the thermal conductive substrate can be improved. Examples of ceramics include silicon carbide, boron nitride, alumina, aluminum hydroxide, zinc oxide, magnesia, magnesium hydroxide, silicon nitride, aluminum nitride and the like.

Examples of soft ferrite include Ni-Zn type ferrite and Mn-Zn ferrite. Since soft ferrite has a high magnetic shield effect, a heat conductive base material having a high magnetic shield effect can be realized by using this as a filler. In the case of metal powder, gold, silver, copper, aluminum, etc. can be used. Since these metal powders have high thermal conductivity and are also excellent in the electric field shielding effect, by using them as a filler, it is possible to realize a heat conducting base material excellent in both the heat conducting effect and the electric field shielding effect.

As the metal magnetic material, silicon steel (Fe-S
i), permalloy (Fe-Ni), sendust (Fe-
Al-Si), permendur (Fe-Co), Su
There is S (Fe-Cr). Since such a metal magnetic material has a high magnetic shield effect, a heat conductive base material having an excellent magnetic shield effect can be realized by using them as a filler.

Carbon fiber is PAN type, pitch type, VGC
F, graphite, curled, etc. can be used. Since carbon fibers have a high thermal conductivity and a high electric field shielding effect at the same time, by using them as a heat conducting base material, a heat conducting base material excellent in both heat conduction effect and electric field shielding effect can be realized.

The filler is not limited to the ones exemplified above. Further, one kind of filler may be used alone, or a plurality of kinds may be mixed. As the shape of the constituent unit of the filler, a granular shape, a flake shape, a fibrous shape or the like can be used.

The melting point of the organic material constituting the heat conductive substrate is 3
Since it is in the temperature range of 0 to 70 ° C., the organic material is liquefied when heated above the melting point. However, 10 of organic materials
Since the viscosity at 0 ° C. is 70,000 cP or more, the viscosity is higher than that near the melting point. For this reason, even if the temperature exceeds the melting point and liquefies, it is extremely difficult to flow.
In addition, the filler dispersed in the organic material prevents excessive fluidization of the organic material. Therefore, the heat conductive base material exhibits plasticity such as clay. The plasticity (fluidity) of the heat conductive base material in the liquefied state of this organic material can be adjusted by the blending ratio of the filler. In this case, although depending on the types (combinations) of the organic material and the filler, the blending ratio of the filler may be in the range of 30 to 90% by weight of the heat conductive base material.

As described above, since it has plasticity at a relatively low temperature (above the melting point of the organic material), it is heated above the melting point of the organic material in contact with the surface of the electronic component to follow the surface shape of the electronic component. It can be plastically deformed, and thereby can be brought into close contact with the surface of the electronic component. At that time, if the heat conductive base material is sandwiched between the electronic component and the heat sink, the heat conductive base material can be brought into close contact with both the electronic component and the heat sink.

If the melting point of the organic material is set to be high (a temperature close to 70 ° C.), it is unlikely that the heat conductive base material has plasticity in the normal use state of electronic parts. In this case, the electronic component may be used after the thermal conductive base material is sandwiched between the electronic component and the heat sink as described above to be adhered by being plasticized.

If the melting point of the organic material is set to a low value (a temperature close to 30 ° C.), the temperature is raised by the heat from the electronic component with which the heat conductive base material comes into contact, and the organic material becomes plastic. Then, it deforms following the surface shapes of the electronic component and the heat sink, and adheres well to the electronic component and the heat sink. Since the viscosity is high as described above, it does not flow out (drip) due to heat generation of the electronic component.

Two types of use can be made as described above depending on the degree of heat generation of the electronic component and the setting of the melting point of the organic material. In either case, the heat conductive base material can be adhered to the electronic component and the heat sink well. it can. As a result, the heat conduction efficiency through the heat conduction base material becomes good, and the heat of the electronic component can be radiated well.

Further, since the electronic components and the heat sink are deformed by following the surface shapes of the electronic components faithfully, the load applied from the heat sink to the electronic components is evenly distributed, and an uneven load is not applied to a part of the electronic components. Furthermore, if an organic material having plasticity at room temperature is used, it is possible to follow the surface shape of the electronic component and plastically deform it when applying the heat-conducting base material to the surface of the electronic component. This improves the adhesiveness when the organic material is liquefied.

[0033]

EXAMPLES (Heat Conductive Substrate) The following organic materials and fillers were kneaded using a two-roll kneader and then molded into a sheet-shaped heat conductive substrate (Examples 1, 2 and Comparative Example). Examples 1 and 2) were obtained. Comparative Example 1 is an unvulcanized EPD as an organic material.
The sheet M is formed by independently molding M. The heat conductive substrates of Examples 1 and 2 and Comparative Example 2 have a structure in which a filler is dispersed in an organic material as illustrated in FIG. <Example 1> Unvulcanized EPDM (organic material): 100 parts by weight SiC (filler): 230 parts by weight <Example 2> Unvulcanized EPDM (organic material): 100 parts by weight BN (filler): 120 Parts by weight <Comparative Example 1> Only unvulcanized EPDM <Comparative Example 2> Paraffin (molecular weight 1000) (organic material): 100 parts by weight Al ₂ O ₃ (filler): 150 parts by weight These Examples 1, 2 and comparison The properties of the heat conductive base materials of Examples 1 and 2 are as shown in Table 1. The viscosity was measured using a B-type viscometer, and the thermal conductivity was measured using a thermal conductivity meter QTM-500 sold by Kyoto Electronics Manufacturing.

[0034]

[Table 1] Here, dripping refers to a phenomenon in which the heat conductive base material is fluidized and flows out when the heat conductive base material is used by being sandwiched between the electronic component and the heat sink.

As is clear from Table 1, the heat-conducting base materials of Examples 1 and 2 have high thermal conductivity and do not drip at 100 ° C., which is significantly higher than the melting point of the organic material. On the other hand, in the case of Comparative Example 1, dripping occurs at 100 ° C. From this, it is understood that the use of the filler is effective in preventing dripping. In addition, the heat conductive base material of Comparative Example 2 has a low heat conductivity,
Dripping occurs at 100 ° C. (Heat Conductive Material) Using the heat conductive base materials of Examples 1 and 2, the heat conductive material having the structure shown in FIG. 2A was manufactured. The heat conductive material 10 is composed of a heat conductive base material 11 of Example 1 (or Example 2), a mesh copper foil 12, and a release paper 13. The mesh copper foil 12 has a mesh shape having a large number of holes (mesh) as shown in FIG. 2 (b), and the upper and lower heat conductive base materials 11 are continuous through the mesh. The thickness of the heat conductive material 10 (including the release paper 13) is 1 mm or less (in this embodiment, the total thickness of the upper and lower heat conductive base materials 11 is about 0.5).
mm), and the thickness of the mesh copper foil 12 is about 30 μm. Note that FIG. 2 schematically shows the cross-sectional structure of the heat conductive material 10, and does not reflect the actual dimensions.

The heat conductive material 10 is used by inserting the mesh copper foil 12 between the electronic component and the heat sink in a posture along the surface of the electronic component (for example, CPU). The mounting procedure is as follows. First, the upper surface (the surface not covered with the release paper 13) of the heat conductive material 10 in FIG. 2A is brought into contact with the heat radiation surface of the CPU, and is heated from about 100 ° C. while being pressed from the release paper 13 side. To do. Then, the heat conductive base material 11 is plasticized and comes into close contact with the heat radiation surface of the CPU (that is, thermal transfer is performed).

After that, the release paper 13 is peeled off, a heat sink is applied to the surface from which the release paper 13 is peeled off, and the electronic paper is fixed to the electronic component with screws or the like. A force (for example, a tightening force) due to the screw or the like is applied to the heat conductive base material 11 by the heat sink and the electronic component.
It acts as a force to pinch (clamping force).

The heat-conducting base material 11 is a plate having a thickness of 1 mm or less (about 0.5 mm in the embodiment), and when pressed against the surface of the CPU or heat sink, it deforms following the shape of the surface. Because of its nature, if the heat conductive base material 11 is sandwiched between the CPU and the heat sink, the sandwiching force = pressing force deforms following the surface shapes of both the CPU and the heat sink. As a result, the heat conductive base material 11 is brought into close contact with both the CPU as a heat source and the heat sink for heat dissipation.
Since no fine gaps are formed between the heat conductive base material 11 and the surfaces of the CPU and the heat sink, a sufficient heat conductive effect can be obtained.

Alternatively, after the heat sink is attached, the heat conducting base material 11 may be heated again to be plasticized and then closely adhered to the surface of the heat sink. Alternatively, if the heat-conducting base material 11 is heated by the heat generated by the use of the CPU, the heat-conducting base material 11 is plasticized by the heat-conducting base material 11 and adheres to the surfaces of the CPU and the heat sink. In either case, the heat conductive base material 11 can be brought into good contact with the CPU and the heat sink. as a result,
The heat conduction efficiency through the heat conduction base material 11 becomes good, and C
The heat of PU can be radiated well.

Further, since the surface shapes of the CPU and the heat sink are faithfully followed and deformed, the heat sink is changed to CP.
The load applied to U is evenly distributed, and an uneven load is not applied to a part of the CPU. In the attachment work of the heat conductive material 10, the release paper 13 corresponding to the protective sheet and the mesh copper foil 12 corresponding to the support material support the heat conductive base material 11 and support the heat conductive base material 11. Get better

Since the mesh copper foil 12 has good thermal conductivity,
Does not impede conduction from the CPU to the heat sink. Also,
The electromagnetic shielding effect of the copper foil 12 can be expected. Copper foil 1
2 is arranged inside the heat conductive base material 11, the CPU
Alternatively, the adhesion with the heat sink is secured by the heat conductive base material 11.

Moreover, since the heat conducting base materials 11 on both sides of the copper foil 12 are continuous with each other in the mesh of the mesh, there is no possibility that the heat conducting base material 11 is separated from the copper foil 12. Note that FIG.
As illustrated in (a), a release paper 13 (or another protective sheet) is attached to both surfaces of the heat conductive base material 11, or a support material as illustrated in FIGS. 3B and 3C. It is also possible to adopt a structure without using. In that case,
As shown in (b), the release paper 13 is provided on one surface of the heat conductive substrate 11.
Even with the structure in which the (protection sheet) is attached, FIG.
As described above, the release paper 13 (protective sheet) may be attached to both surfaces of the heat conductive base material 11, and either structure may be used.

Although the present invention has been described above, it is needless to say that the present invention is not limited to the above-mentioned examples and can be variously implemented without departing from the gist of the present invention. For example, the thickness of the heat conductive base material is about 0.5 mm, but it is possible to make it thinner (for example, about 0.1 mm). The smaller this thickness, the higher the heat transfer efficiency, that is, the heat dissipation efficiency from the electronic component such as the CPU to the heat sink.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an internal structure of a heat conductive base material of an example.

FIG. 2 is an explanatory diagram of a heat conductive material using the heat conductive base material of the embodiment.

FIG. 3 is an explanatory diagram of another heat conductive material using the heat conductive base material of the embodiment.

[Explanation of symbols]

10 Thermal conductive material 11 Heat conductive base material 12 mesh copper foil (support material) 13 Release paper (protective sheet)

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 23/34-23/473

Claims (5)

(57) [Claims] 1. A melting point in the range of 30 to 70 ° C. and 100
In an organic material having a viscosity of 70,000 cP or more at ℃
The filler in a proportion of 30 to 90% by weight based on the total weight.
A plate-like heat conduction layer having a thickness of 1 mm or less, which is dispersed and has a property of being deformed by following the shape of the surface of the mounted body at a temperature higher than the melting point of the organic material when pressed against the surface of the mounted body. A heat conductive material comprising a base material and a protective sheet attached to two or one surface of the heat conductive base material. 2. The heat conductive material according to claim 1, wherein the protective sheet is peelable without damaging the surface of the heat conductive base material. 3. The heat conductive material according to claim 1, further comprising a support material which is wholly or partially disposed inside the heat conductive base material and supports the heat conductive base material. A heat conducting material. 4. The heat conductive material according to claim 3, wherein the support material is a metal foil. 5. The heat conductive material according to claim 4, wherein the metal foil is provided with holes.