JP2002003830A - High thermal conductive composition and its use - Google Patents

Abstract

(57) [Summary] [Problem] A highly thermally conductive composition which fluidizes at a predetermined temperature and has excellent heat dissipation characteristics and low heat resistance, and microscopically adheres to respective joining surfaces of heat-generating electronic components and heat dissipation fins. To provide a heat dissipating member that can be made to work. A wax and / or paraffin having a melting point of 40 to 100 ° C, a thermoplastic resin softening at 40 to 100 ° C, a sphericity of 0.78 or more and an average particle size of 3 µm
A highly thermally conductive composition characterized by mixing the above spherical alumina. A heat dissipating member of a heat generating electronic component and a heat dissipating fin integrated heat generating electronic component using the high thermal conductive composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high heat conductive composition and its use.

[0002]

2. Description of the Related Art In recent years, the demand for higher heat conductivity of heat dissipating members has been increasing with the increase in density of heat-generating electronic components.
In addition, electronic devices such as portable personal computers are becoming smaller, thinner, and lighter. Accordingly, heat dissipating members used in these electronic devices are required to have high thermal conductivity.

Conventionally, as a method for improving the thermal conductivity of a heat dissipating member, a heat dissipating grease containing a highly heat conductive filler or a flexible and resilient matrix such as silicone rubber is dispersed in a highly heat-reactive particle. What has been done is the mainstream.

However, heat radiation grease tends to be avoided due to problems such as poor workability in a coating process and contamination of peripheral parts. Moreover, since the initial thickness is relatively thick in the flexible member in which the particles having high thermal conductivity are dispersed, even when the heat radiation member itself has a high thermal conductivity when mounted between the heat-generating electronic component and the radiation fin, It was difficult to extremely reduce the thermal resistance, which is a heat transfer index based on mounting.

That is, the thermal conductivity of the heat dissipating member itself is increased, and the heat dissipating member microscopically follows and closely adheres to the joining surfaces of the heat generating electronic components and the heat dissipating fins, thereby reducing thermal contact resistance. At the same time, it is ideal to make the member thickness as thin as possible.

On the other hand, aluminum oxide powder is widely used as a high thermal conductive filler, and many heat dissipating members using the same have been proposed (JP-A-58-2192).
59, JP-A-63-251466, JP-A-64-24859, and JP-B-7-91468. However, even if these high thermal conductive fillers are dispersed in the heat dissipating member as described above, it is difficult to drastically reduce the thermal resistance, although the thermal conductivity of the heat dissipating member itself can be improved. Further, these publications disclose a resin / rubber filled with aluminum oxide powder, and do not suggest the present invention.

On the other hand, JP-A-10-67910 discloses a thermally stable wax comprising a methylsiloxane host and a polyorganosiloxane graft polymer of a linear hydrocarbon having an unsaturated bond at a single terminal, alumina, An interface material comprising a thermally conductive particulate solid viscosity stabilizer selected from the group consisting of boron nitride, graphite, silicon carbide, diamond, metal powder or mixtures thereof has been disclosed. Since the siloxane graft polymer is expensive and has a relatively high melt viscosity, the amount of the high thermal conductive filler to be filled is extremely limited in order to achieve the desired fluidity.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above, and has as its object to provide a spherical aluminum oxide as a filler, a wax and / or a matrix as a matrix.
Or, with paraffin, preferably using a thermoplastic resin,
It is an object of the present invention to provide a highly thermally conductive composition which is easily fluidized by heating. In addition, by using the composition as a molded body having a reduced thickness, it can be fluidized at a predetermined temperature, and can be microscopically adhered to the respective joining surfaces of the heat-generating electronic component and the radiation fins, and at the same time, the heat-generating property can be obtained. An object of the present invention is to provide a heat dissipating member having excellent heat dissipating characteristics and low heat resistance by minimizing the distance between an electronic component and a heat dissipating fin.

[0009]

That is, the present invention is as follows. (Claim 1) High thermal conductivity comprising wax and / or paraffin having a melting point of 40 to 100 ° C. and spherical aluminum oxide powder having a sphericity of 0.78 or more and an average particle diameter of 3 μm or more. Composition. (Claim 2) A wax and / or paraffin having a melting point of 40 to 100 ° C, a thermoplastic resin softening at 40 to 100 ° C, a sphericity of 0.78 or more and an average particle diameter of 3
A highly thermally conductive composition comprising a spherical aluminum oxide powder having a diameter of at least μm. (3) The high thermal conductivity according to (1) or (2), comprising 30 to 70% by volume of a spherical aluminum oxide powder having a sphericity of 0.78 or more and an average particle diameter of 3 μm or more. Composition. (4) A heat-dissipating member for a heat-generating electronic component, comprising a molded article of the high thermal conductive composition according to any one of (1) to (3). (5) The heat-dissipating member for a heat-generating electronic component according to (4), wherein the heat-dissipating member is a sheet. (6) A heat-radiating fin-integrated heat-generating electronic component structure, wherein the heat-generating electronic component and the heat-radiating fin are bonded using the heat-radiating member according to claim 4 or 5.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. A major feature of the present invention is that by filling spherical aluminum oxide powder into wax and / or paraffin, a highly heat-conductive composition having excellent fluidity at a required temperature can be obtained.

The wax or paraffin used in the present invention has a melting point in the range of 40 to 100 ° C., and is therefore solid at room temperature and becomes a low-viscosity liquid upon heating. When the heat-generating electronic component and the heat-dissipating fin are joined by heating and pressing using a heat-dissipating member having a matrix of wax and / or paraffin, the fluidity is good, so that each joint surface can be microscopically followed. The heat contact resistance can be reduced by sufficiently filling the gap, and the generated heat can be smoothly transmitted in the direction of the radiation fins. Further, both can be brought as close as possible to each other, so that the heat radiation property is improved.

If the melting point of the wax or paraffin used in the present invention is less than 40 ° C., the composition liquefies in a high temperature period such as summer when used as a molded article,
There is a concern that the shape cannot be maintained, and the melting point is 100 ° C.
Exceeding the temperature is not preferable because the temperature of the electronic component is increased when it is heated and melted and bonded to the heat-generating electronic component.

Examples of the type of wax include microcrystalline wax, montanic acid wax, montanic acid ester wax, and the like, but are not limited to these as long as the melting point satisfies the above conditions. Paraffin includes paraffin wax, and paraffin that is solid at room temperature with respect to liquid paraffin is particularly referred to as paraffin wax. Specific examples of these are "Paraffin Wax Series" and "Microcrystalline Wax Hi-Mic" manufactured by Nippon Seiwa.
・ Series ”and the like. These waxes and paraffins may be used alone or in combination of two or more.

The thermoplastic resin of the present invention which softens at 40 to 100 ° C. has improved moldability when mixed with wax or paraffin.
This shows the effect of improving brittleness. For example, ethylene-based resins, propylene-based resins, ethylene-α-olefin copolymers, ethylene-vinyl acetate copolymers and the like can be cited, but those that exhibit the above effects are not limited thereto. Absent. When the wax or paraffin is heated and melted at a temperature equal to or higher than the melting point and mixed, it is preferable that the wax or paraffin be uniformly mixed. As specific examples of these, "Hi Wax 110P" and "Hi Wax N" manufactured by Mitsui Chemicals, Inc.
P055 "," Tuffmer P-0180 "," Evaflex 150 "manufactured by DuPont-Mitsui Polychemicals, and the like.

Further, since the above-mentioned thermoplastic resin has relatively higher thermal conductivity than wax or paraffin, it can be expected to have an effect of improving the heat radiation characteristics of the heat radiation member.

The above-mentioned thermoplastic resin can be mixed with wax and / or paraffin at 40% by volume or less. If the mixing ratio exceeds 40% by volume, when heated and pressed as a heat dissipating member, the fluidity becomes poor, and the adhesion between the heat-generating electronic component and the heat dissipating fins becomes poor,
Therefore, it is difficult to sufficiently fill the gap between the two. Further, it is necessary to increase the pressure in order to increase the adhesion, which is not preferable for the reliability of the electronic component.

The spherical aluminum oxide powder having a sphericity of 0.78 or more and an average particle diameter of 3 μm or more in the present invention includes “Spherical Alumina AS-1” manufactured by Showa Denko KK
0 "," AS-20 "," AS-30 "," AS-4 "
0 "," AS-50 "," CB-A05 "," CB-A
10, "CB-A20S", "CB-A30S",
“CB-A40”, “CB-A50” and the like can be exemplified.

Here, the sphericity is calculated by squaring the "average circularity" measured using a flow type particle image analyzer FPIA manufactured by Sysmex. Those having a sphericity of less than 0.78 are difficult to finely pack, and therefore have poor filling properties, and their shape factor deteriorates the fluidity of wax or paraffin at the melting temperature.

If the average particle diameter of the spherical aluminum oxide powder is less than 3 μm, the fluidity of wax or paraffin at the melting temperature is deteriorated. When the particle diameter is large, a heat conduction path is generated and heat transfer is easily performed, which is preferable. However, if the particle size is too large, the heat-generating electronic components and the heat radiation fins which are close to each other may come into contact with each other, which may hinder their proximity. Therefore, the average particle size is desirably 3 to 50 μm.

The content of the spherical aluminum oxide powder used in the present invention is preferably from 30 to 70% by volume, particularly preferably from 40 to 65% by volume, based on the whole composition. If it is less than 30% by volume, it is difficult to obtain the required thermal conductivity, and if it exceeds 70% by volume, the fluidity of the matrix wax and / or paraffin at the melting temperature becomes poor.

On the other hand, in the present invention, two or more spherical aluminum oxide powders may be used in combination.

In the present invention, it is also possible to use the above-mentioned spherical aluminum oxide powder and fine powder having good thermal conductivity in combination. Such fine powders having good thermal conductivity include aluminum nitride, silicon nitride, boron nitride, silicon carbide,
Examples include zinc oxide, graphite, and metal powder. The above-mentioned fine powders having good thermal conductivity may be used alone or in combination of two or more. The content of the mixed powder of the spherical aluminum oxide powder and the fine powder having good thermal conductivity is preferably 75% by volume or less based on the total composition. If it exceeds 75% by volume, the fluidity of the matrix wax and / or paraffin at the melting temperature deteriorates.

The composition of the present invention may further contain a softening agent such as a hydrocarbon-based synthetic oil or an α-olefin oligomer, if necessary, as long as it does not affect the thermal conductivity and fluidity. Flame retardants such as halogen-based and phosphate-based,
Powder surface modifiers such as silane-based and titanate-based coupling agents, oxidation-resistant agents such as bisphenol-based and hindered phenol-based, antibacterial agents such as pyridine-based and triazine-based, and colorants such as benga and cobalt aluminate Can coexist.

The composition of the present invention is obtained by blending wax and / or paraffin, spherical aluminum oxide powder, thermoplastic resin and, if necessary, fine powder having good thermal conductivity with a blender at a temperature not lower than the melting point of wax and / or paraffin. Alternatively, it can be prepared by mixing using a mixer or the like.

The composition of the present invention can be molded and used as a heat dissipating member. The molding method may be a general molding method such as a pressing method, an extrusion method, or a doctor blade method. It is possible to manufacture.

The heat dissipating member of the present invention can be formed into a shape suitable for the intended use, but is preferably a sheet in consideration of mass productivity and mountability.

The heat radiation member of the present invention has a thermal conductivity of 1.0 W /
Desirably, it is not less than mK. More preferably 2.0
W / mK or more.

The heat radiating member obtained as described above is used in contact with a heat-generating electronic component. More specifically,
The heat dissipating member (preferably, a sheet) is sandwiched between the heat generating electronic component and the heat dissipating fins, and the heat dissipating member is melted and spread between the heat dissipating member and the heat dissipating fin by applying pressure while heating. At the same time, the heat-generating electronic component and the radiation fin can be brought as close as possible.

The heating condition at this time may be a temperature not lower than the melting point of the wax and / or paraffin used and not lower than the temperature at which the thermoplastic resin is softened. In order not to damage the electronic components, the pressure is preferably in the range of 0.05 to 1.0 MPa.

[0030]

The present invention will be further described below with reference to examples and comparative examples.

Example 1 Paraffin Wax 115 (melting point 47, manufactured by Nippon Seiro Co., Ltd.)
C.) and a spherical aluminum oxide powder, "Spherical Alumina AS-50" (average particle diameter = 10 μm) manufactured by Showa Denko KK
m, sphericity = 0.83) at a mixing ratio shown in Table 1.
C. to obtain a slurry. The slurry was vacuum-degassed while maintaining the temperature at 80 ° C., poured into a mold in which a PET film treated with a release agent was set, and pressed into a sheet at room temperature. After the pressing, the sample was taken out together with the PET film, and the high-temperature conductive composition cured at room temperature was peeled off from the PET film to obtain a sheet having a thickness of 0.18 mm. The thermal resistance and the thermal conductivity were measured by the method described below, and a self-weight bending test was performed to evaluate the blocking property. The results are shown in Table 1.

Example 2 "Evaflex EV150" manufactured by DuPont-Mitsui Polychemicals Co., Ltd. was prepared as an ethylene-vinyl acetate copolymer while a predetermined amount of "Paraffin Wax 115" manufactured by Nippon Seirowa Co., Ltd. was heated and melted at 80 ° C. A fixed amount was added and mixed with heating until uniform. Then, "Spherical Alumina AS-50" manufactured by Showa Denko KK was used as spherical aluminum oxide powder in Table 1.
To obtain a slurry. Then, a sheet having a thickness of 0.18 mm was obtained in the same manner as in Example 1.
The results are shown in Table 1.

Examples 3 to 6 As spherical aluminum oxide powder, "Spherical Alumina AS-10" (average particle size = 37 μm, sphericity =
0.79) ”,“ CB-A10 (average particle size = 10 μm)
m, sphericity = 0.90) ", and" CB-A30S (average particle diameter = 29 μm, sphericity = 0.89) ", except that the mixing ratio was as shown in Table 1. 0.18
mm sheet was obtained. The results are shown in Table 1.

Comparative Examples 1 to 3 The mixture was mixed at 80 ° C. in the same manner as in Example 1 except that the spherical aluminum oxide powder shown in Table 2 was used. I couldn't.

Thermal Resistance The thermal resistance in the present invention is defined as follows: a sheet-like high thermal conductive composition is placed between a TO-3 type copper heater case and a copper plate by 0.3.
After screwing so as to apply a pressure of 4 MPa, the heater case and the copper plate were heated until the temperature reached 55 ° C., and then cooled to room temperature.
, And the temperature difference between the copper heater case and the copper plate when held for 4 minutes was measured and calculated by the following equation (1). Thermal resistance (° C / W) = temperature difference (° C) / applied power (W) (1)

Thermal conductivity The thermal conductivity in the present invention was calculated by the following equation (2). Here, the sample thickness is the thickness at the time of thermal resistance measurement (the sample thickness when the sample is screwed so that a pressure of 0.34 MPa is applied to the sample, the heater case and the copper plate are heated to 55 ° C., and then cooled to room temperature). is there. The heat transfer area is set to 0.006 m ² of the TO-3 type heat transfer area. Thermal conductivity (W / mK) = [sample thickness (m)] / [thermal resistance (° C./W)×heat transfer area (m ² )] (2)

Although there are various methods for measuring the thermal resistance and thermal conductivity of the heat radiating member, the above measuring method most accurately reflects the state when the heat radiating member is mounted on the heat-generating electronic component. .

Self-weight bending test The sheeted high thermal conductive compositions of Examples 1 to 6
Punched into a strip shape of × 50 × 0.18mm, and its length 5
20 mm of 0 mm was protruded, placed on a flat plate, and allowed to stand at room temperature for 7 days, and then the bending displacement of the tip due to its own weight bending was measured. The smaller the value is, the more the creep property is improved, the shape stability is excellent when the heat dissipation member is used, and the variation in the heat dissipation property is small.

Blocking resistance The sheeted high thermal conductive compositions of Examples 1 to 6 were treated with 50
The sheets were stacked and stored at room temperature for one month. The blocking resistance of the sheet at that time was evaluated. ：: Almost no blocking. Δ: Blocking is observed in some sheets (accordingly,
Such a sheet needs to consider the storage method. )

[0040]

[Table 1]

Further, when the sheet was peeled off from the PET film after the preparation of the sheet, care was required because the sheet of Example 1 was easily cut when peeled off from the film, but there was no problem in the other examples.

[0042]

[Table 2]

Examples 7 to 9 The sheets obtained in Examples 1, 3 and 6 were sandwiched between heat dissipating electronic components and heat dissipating fins, and heated to 55 ° C.
A heat generating fin-integrated heat-generating electronic component was produced by applying a pressure of 4 MPa. It was confirmed that the sheet was microscopically followed and adhered to the joint surface between the heat dissipating electronic component and the heat dissipating fin, and the gap between the two was sufficiently filled.

[0044]

According to the present invention, there is provided a high heat conductive composition which is easily fluidized by heat.

Further, according to the present invention, there is provided a heat dissipating member having excellent heat dissipating characteristics, which microscopically adheres to the respective joining surfaces of the heat generating electronic component and the heat dissipating fins.

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Claims (6)

[Claims] A high thermal conductivity comprising wax and / or paraffin having a melting point of 40 to 100 ° C. and spherical aluminum oxide powder having a sphericity of 0.78 or more and an average particle diameter of 3 μm or more. Composition. 2. A wax and / or paraffin having a melting point of 40 to 100 ° C., a thermoplastic resin softening at 40 to 100 ° C., a sphericity of 0.78 or more and an average particle diameter of 3 or more.
A highly thermally conductive composition comprising a spherical aluminum oxide powder having a diameter of at least μm. 3. The high thermal conductivity according to claim 1, wherein the powder contains 30 to 70% by volume of a spherical aluminum oxide powder having a sphericity of 0.78 or more and an average particle diameter of 3 μm or more. Composition. 4. A heat-dissipating member for a heat-generating electronic component, comprising a molded product of the highly heat-conductive composition according to claim 1. 5. The heat dissipating member for a heat-generating electronic component according to claim 4, wherein the heat dissipating member is a sheet. 6. A heat-radiating fin-integrated heat-generating electronic component structure comprising a heat-generating electronic component and a heat-radiating fin bonded to each other using the heat-radiating member according to claim 4.