JP2020147631A - Thermal conductive material - Google Patents

Abstract

To provide a thermal conductive material that can prevent deterioration of a binder component, while maintaining excellent thermal conductivity, even when aluminum particles are used as a thermal conductive filler, in a thermal conductive material containing a binder component and the thermal conductive filler.SOLUTION: A thermal conductive filler of a thermal conductive material containing a binder component and a thermal conductive filler contains aluminum particles covered with an aluminum oxide film. A film thickness of the aluminum oxide film that covers the aluminum particles is 50 nm or smaller. Furthermore, regarding the aluminum on a surface of the aluminum particles, a narrow scan (high resolution) spectrum of Al2p peak in an X-ray photoelectron spectroscopy analysis is acquired, a rate of the aluminum oxide calculated therefrom is 85% or larger.SELECTED DRAWING: None

Description

The present invention relates to thermally conductive materials.

For electronic devices such as personal computers and mobile phones, semiconductor devices such as semiconductor chips and semiconductor modules that generate heat when driven are used. Since a semiconductor device may stop operating, malfunction, or malfunction due to heat, it has been conventionally practiced to install a heat radiating body such as a heat sink in the semiconductor device via a heat conductive material. As such a heat conductive material, a material in which a heat conductive filler is dispersed in a binder component is widely used.

By the way, in order to increase the thermal conductivity of a thermally conductive material at low cost, it is desired to use a thermally conductive filler exhibiting good thermal conductivity and available at low cost. Such thermal conductivity A thermally conductive sheet using aluminum particles as a sex filler has been proposed (Patent Document 1). It is assumed that this heat conductive sheet is provided between a heat generating component such as an integrated circuit element and a heat sink, but a heat conductive filler is provided from the end of the heat conductive sheet provided between them. There is concern that a short circuit problem will occur if the product falls off. Therefore, in the examples of Patent Document 1, aluminum particles having an average particle size of 50 μm in which an electrically insulating aluminum oxide film having a thickness of 970 nm is formed are used.

Japanese Unexamined Patent Publication No. 2006-36931

However, although the aluminum particles used in the heat conductive sheet of Patent Document 1 are mainly composed of metallic aluminum having good thermal conductivity, the thickness of the aluminum oxide film is relatively thick, so that the heat conductivity is high. Has the problem that it is much lower than the metallic aluminum particles. For this reason, it is conceivable to reduce the thickness of the aluminum oxide film on the surface of the aluminum oxide film-coated aluminum particles, but not only is there a concern about the occurrence of short circuits as described above, but also on the surface of the aluminum oxide film-coated aluminum particles. There is a problem that the remaining active region accelerates the deterioration of the binder component, impairs the flexibility of the heat conductive sheet, and particularly reduces the compression rate maintenance rate of the heat conductive sheet before and after aging. There is concern that this problem may cause a problem of peeling between the heat conductive sheet and the heat generating component or the heat sink.

The present invention is intended to solve such a conventional problem, and even if aluminum particles are used as the heat conductive filler in a heat conductive material containing a binder component and a heat conductive filler, it is good. The purpose is to prevent deterioration of the binder component while maintaining good thermal conductivity.

The inventor of the present application can impart good thermal conductivity to the aluminum particles used for the thermally conductive material by setting the thickness of the aluminum oxide film on the surface thereof to a predetermined thickness or less. Further, in order to suppress the surface activity of the aluminum particles, the abundance ratio of aluminum oxide on the surface of the aluminum particles is set to a predetermined ratio or more to suppress the deterioration of the binder component, and in particular, the compression ratio of the heat conductive sheet before and after aging. We have found that the decrease in the maintenance rate can be suppressed, and have completed the present invention.

That is, the present invention is a thermally conductive material containing a binder component and a thermally conductive filler.
The thermally conductive filler contains aluminum particles coated with an aluminum oxide film and contains aluminum particles.
The film thickness of the aluminum oxide film covering the aluminum particles is 50 nm or less, and the film thickness is 50 nm or less.
Provided is a thermally conductive material in which a narrow scan (high resolution) spectrum of an Al2p peak in X-ray photoelectron spectroscopic analysis is acquired for aluminum on the surface of the aluminum particles, and the proportion of aluminum oxide calculated from the narrow scan (high resolution) spectrum is 85% or more. ..

The thermally conductive material of the present invention containing a binder component and a thermally conductive filler uses at least aluminum particles coated with an aluminum oxide film having a film thickness of 50 nm or less as the thermally conductive filler. Therefore, good thermal conductivity can be imparted to the thermally conductive material. Further, regarding the aluminum on the surface of the aluminum particles, a narrow scan (high resolution) spectrum of the Al2p peak in the X-ray photoelectron spectroscopy is acquired, and the ratio of aluminum oxide calculated from the narrow scan (high resolution) spectrum is 85% or more. Therefore, the surface activity of the aluminum particles can be suppressed to suppress the deterioration of the binder component, and in particular, the decrease in the compressibility maintenance rate of the heat conductive sheet before and after aging can be suppressed.

Hereinafter, the thermally conductive material of the present invention will be described in detail.

<Thermal conductive material>
The thermally conductive material of the present invention contains a binder component and a thermally conductive filler. This thermally conductive filler contains aluminum particles coated with an aluminum oxide film. The film thickness of this aluminum oxide film is 50 nm or less. Further, for the aluminum on the surface of the aluminum particles, a narrow scan (high resolution) spectrum of the Al2p peak in the X-ray photoelectron spectroscopy is acquired, and the ratio of aluminum oxide calculated from the narrow scan (high resolution) spectrum is 85% or more.

(Thermal conductive filler)
The thermally conductive filler contains aluminum particles coated with an aluminum oxide film. Here, if the content of the heat conductive filler in the heat conductive material is too small, it tends to be difficult to impart high heat conductivity to the heat conductive material, so that it is preferably 60% by volume or more, more preferably 65. It is preferably 90% by volume or less, more preferably 85% by volume or less, because if it is too much, it tends to be difficult to process the heat conductive material into a flexible sheet.

Further, if the content of the aluminum particles coated with the aluminum oxide film in the heat conductive filler is too small, the heat conductivity of the heat conductive material tends to decrease, so it is preferably 5% by volume or more. It is more preferably 10% by volume or more, and if it is too much, problems such as poor curing tend to occur in the heat conductive material, so it is preferably 50% by volume or less, more preferably 30% by volume or less.

The film thickness of the aluminum oxide film covering the surface of the aluminum particles used in the present invention is 50 nm or less, preferably 30 nm or less. This is because if the aluminum oxide film is thicker than 50 nm, there is a concern that the thermal conductivity of the thermally conductive sheet will decrease. On the other hand, the minimum film thickness of the aluminum oxide film is preferably 3 nm or more, more preferably 7 nm or more. This is because if the film thickness is too thin, there is a concern that the surface activity of the aluminum particles cannot be sufficiently suppressed. The aluminum oxide film thickness can be measured from an electron micrograph obtained by using a known transmission electron microscope, but the film thickness is not limited to this, and can be measured by a known thin film measuring method.

The aluminum oxide film on the surface of the aluminum particles can be formed by various surface oxidation methods. For example, the aluminum particles can be formed by performing a treatment (firing treatment) of holding the aluminum particles in an oxygen-containing atmosphere (preferably an atmospheric atmosphere) at a temperature of 300 to 400 ° C. for a predetermined time (for example, 24-72 hours). it can. In this case, the fineness and thickness of the aluminum oxide film can be adjusted by adjusting the oxygen concentration in the atmosphere, the firing temperature, and the firing time. For example, a thick aluminum oxide film can be obtained by increasing the oxygen concentration in the atmosphere or by lengthening the firing time. Further, by raising the firing temperature, a dense aluminum oxide film can be obtained.

For the aluminum on the surface of the aluminum particles used in the present invention, a narrow scan (high resolution) spectrum of the Al2p peak in X-ray photoelectron spectroscopy is obtained, and the ratio of aluminum oxide calculated from the spectrum is 85% or more, preferably 90. % Or more. This is because if this ratio is less than 85%, there is a concern that the surface activity of the aluminum particles cannot be sufficiently suppressed.

Here, the X-ray photoelectron spectroscopic analysis can be performed according to a conventional method using a commercially available X-ray photoelectron spectroscope (for example, KRATOS AXIS-HS manufactured by Shimadzu Corporation). For example, first, the aluminum on the surface of the aluminum particles is subjected to X-ray photoelectron spectroscopy wide scan analysis to identify the Al2p peak region. In this Al2p peak region, not only metallic aluminum peaks but also aluminum oxide peaks (α-type alumina peak, β-type alumina peak, sapphire-type alumina peak) are present in an overlapping manner. Therefore, narrow scan (high resolution) analysis of the Al2p peak region can separate these peaks. The quantitative chemical state can be specified from the peak position and peak shape, and it is calculated as the ratio of aluminum oxide on the surface of aluminum particles.

The average particle size of the aluminum particles coated with the aluminum oxide film is preferably 1 μm or more, more preferably 3 μm or more from the viewpoint of thermal conductivity, and preferably 100 μm or less from the viewpoint of kneading to the binder component. It is preferably 70 μm or less. The average particle size of the aluminum particles can be measured by using, for example, a commercially available laser light scattering type particle size distribution measuring device.

The aluminum particles coated with the aluminum oxide film can take various shapes such as spherical, spindle-shaped, scaly, needle-shaped, rod-shaped, and dice-shaped. Above all, a spindle-shaped shape derived from the particle manufacturing method (atomizing method) is preferable from the viewpoint of kneading property into the binder component.

The thermally conductive filler may be composed of only the aluminum particles coated with the aluminum oxide film described above, but may contain other thermally conductive fillers as long as the effects of the present invention are not impaired. For example, metal nitride fillers such as aluminum nitride and magnesium nitride, and metal oxide / hydroxide fillers such as titanium oxide, alumina, silica, zinc oxide, magnesium oxide and aluminum hydroxide can be used. Further, if necessary, a metal / alloy filler such as gold, silver, titanium, or stainless steel can be used. Carbon fiber can also be used.

Above all, in addition to the aluminum particles coated with the aluminum oxide film, it is preferable to use the aluminum nitride particles in combination from the viewpoint of improving thermal conductivity and kneading property.

When the alumina particles and the aluminum nitride particles are used in combination in addition to the aluminum particles coated with the aluminum oxide film, the average particle size of the alumina particles is preferably 0.5 μm or more from the viewpoint of thermal conductivity. , More preferably 3 μm or more, preferably 100 μm or less, and more preferably 70 μm or less from the viewpoint of kneadability. Regarding the amount used, the amount of alumina particles used is preferably 1 part by volume or more, more preferably 5 parts by volume or more from the viewpoint of kneading property with respect to 100 parts by volume of aluminum particles, and from the viewpoint of thermal conductivity. It is preferably 200 parts by volume or less, 100 parts by volume or less, and more preferably 50 parts by volume or less.

On the other hand, the average particle size of the aluminum nitride particles is preferably 0.8 μm or more, more preferably 1 μm or more from the viewpoint of thermal conductivity, and preferably 100 μm or less, more preferably 90 μm or less from the viewpoint of kneading property. The amount of aluminum nitride particles used is preferably 10 parts by volume or more, more preferably 100 parts by volume or more from the viewpoint of thermal conductivity, and preferably 500 parts by volume or less, more preferably 300 parts by volume from the viewpoint of cost and the like. It is less than a part.

(Binder component)
As the binder component constituting the heat conductive material of the present invention, a binder component used in a known heat conductive material can be applied. For example, silicone resin, (meth) acrylate resin, urethane resin, epoxy resin and the like can be mentioned. Among them, a silicone resin, particularly a two-component heat-curable liquid silicone rubber exhibiting good flexibility, shape followability, heat resistance, etc. after thermosetting can be preferably used. Specific examples of the two-component heat-curable liquid silicone rubber include those represented by trade names: XE14-C3021A agent and XE14-C3021B agent (Momentive Performance Materials Japan LLC). In addition, a silane coupling agent that improves the dispersibility of the thermally conductive filler in the binder component, for example, n-octyltriethoxysilane (Momentive Performance Materials Japan GK) should be used in combination with the binder component. Can be done.

(Antioxidant)
The thermally conductive material of the present invention preferably contains an antioxidant in order to prevent deterioration of the binder component. Known antioxidants can be used, but when a silicone resin is used as the binder component, sulfur compound-based antioxidants, phosphorus compound-based antioxidants, hindered amine-based antioxidants, etc. can be used. A phenolic antioxidant can be preferably used because it may inhibit the curing of the silicone resin. Such a phenolic antioxidant is a hindered type in which a t-butyl group is bonded to each of the two α-positions of the phenolic hydroxyl group, which is the active point thereof, and a t-butyl group is bonded to one of the two α-positions. It can be classified into three types: semi-hindered type and less hindered type in which a t-butyl group is not bonded to two α-positions. In the present invention, it is preferable to use a semi-hindered type phenolic antioxidant in terms of the effect of preventing deterioration of the binder component. As a preferred specific example, 3,9-bis [1,1-dimethyl-2- [β- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] 2,4,8,10 -Tetraoxaspiro [5,5] -Undecane (ADEKA STAB AO-80, ADEKA Co., Ltd .; Smilizer GA-80, Sumitomo Chemical Co., Ltd.) can be exemplified. The phenolic antioxidant can also be preferably applied when a resin other than the silicone resin is used as the binder component.

When such a phenolic antioxidant is used, it is preferably 0.01 part by volume or more, more preferably 0.5 part by volume or more with respect to 100 parts by volume of the binder component from the viewpoint of antioxidant, and inhibits curing. From the viewpoint of suppression and the like, it is preferably 5 parts by volume or less, more preferably 1 part by volume or less.

(Other ingredients)
The thermally conductive material of the present invention can contain various additives used in known thermally conductive materials, if necessary. For example, pigments, antistatic agents, rust preventives, dispersants, sedimentation inhibitors, flame retardants and the like can be contained.

<Manufacturing of thermally conductive materials>
The thermally conductive material of the present invention can be prepared according to a known method. For example, it can be produced by uniformly mixing a heat conductive filler and, if necessary, an antioxidant or the like with a binder component by a conventional method. Further, although this mixture may be put into practical use in a liquid state, it is preferable to form it into a sheet or a film and put it into practical use from the viewpoint of handleability.

<Practical aspects of thermally conductive materials>
The thermally conductive material of the present invention can be put into practical use in the same manner as the conventionally known thermally conductive material. As an example of practical use, when the heat conductive material is a liquid having heat curability, the heat conductive material is applied to a heat generating material such as a semiconductor chip or a semiconductor module to a thickness of 200 μm to 1.5 mm by a conventional method. Then, a heat radiating body such as a heat sink is placed on the coated surface, and the heat conductive material is thermally cured by putting it in a heating chamber to form a structure in which the heat generating body and the heat radiating body are integrated. When the heat conductive material is formed into a sheet or film, the sheet or film heat conductive material is sandwiched between a heat generating material such as a semiconductor chip or a semiconductor module and a heating element such as a heat sink. By thermocompression bonding, a structure in which a heating element and a heat radiating body are integrated can be mentioned.

Experimental example

Hereinafter, the present invention will be specifically described with reference to experimental examples, but the present invention is not limited to these experimental examples. The components used in the experimental examples are as follows.

Silicone resin XE14-C3021A (Momentive Performance Materials Japan LLC)
XE14-C3021B (Momentive Performance Materials Japan LLC)

Silane Coupling Agent A-137 (n-octyltriethoxysilane; Momentive Performance Materials Japan LLC)
Z-6210 (Toray Industries, Inc.)

Antioxidant ADEKA STAB AO-30, ADEKA Corporation; Less Hindered Type Antioxidant ADEKA STAB AO-50, ADEKA Corporation; Hindered Type Antioxidant ADEKA CORPORATION AO-60, Hindered Type Oxidation Inhibitor ADEKA STAB AO-80, ADEKA CORPORATION; Semi-hindered type antioxidant

Aluminum nitride particles average particle size 1 μm, Tokuyama Corporation

Alumina particle average particle size 5 μm, 45 μm, Denka Co., Ltd.

Aluminum particles (spindle shape)
Average particle size 5 μm, 14 μm, 15 μm, Toyo Aluminum Co., Ltd.

Reference example (surface oxidation treatment by annealing aluminum particles)
By subjecting the spindle-shaped aluminum particles (melting point 660 ° C.) to a firing treatment (heat treatment in a constant temperature bath at 350 ° C. for 24 hours or more in an air atmosphere), an oxide film (aluminum oxide film) is formed on the surface of each aluminum particle. Formed. In addition, for the aluminum on the surface of each of the fired aluminum particles and the non-fired aluminum particles, a sample was fixed to a tape, and an X-ray photoelectron spectroscopic analyzer (KRATOS AXIS-HS, Shimadzu Corporation) was used. Using the narrow scan analysis spectrum of each Al2p peak region, detection angle: 90 degrees, X-ray source: monoAl, analysis spot diameter: 1 mmΦ, current: 10 mA, voltage: 14 kV, lens mode: Hybrid, step: 0. It was acquired under the conditions of 05 eV and path energy: 40 eV, and the ratio (%) of aluminum oxide was calculated from the obtained spectral data based on the peak intensity. The results obtained are shown below (“Aluminum oxide ratio (%) on the surface of aluminum particles”).

The thickness of the surface aluminum oxide film of each aluminum particle before and after firing was measured using a transmission electron microscope (JEOL Ltd.). The results are shown below.

(Ratio of aluminum oxide on the surface of aluminum particles)
Aluminum particles with an average particle size of 5 μm Before firing: 80.50%
After firing: 93.00%
Aluminum particles with an average particle size of 14 μm Before firing: 83.00%
After firing: 94.00%
Aluminum particles with an average particle size of 15 μm Before firing: 78.00%
After firing: 88.00%

(Surface oxide film thickness of aluminum particles before and after firing)
Before firing aluminum particles with an average particle size of 5 μm : Cannot be confirmed (estimated to be about 2 nm)
After firing: 8.36 nm or more and 20 nm or less
Before firing aluminum particles with an average particle size of 14 μm : Cannot be confirmed (estimated to be about 2 nm)
After firing: 16.49 nm
Before firing aluminum particles with an average particle size of 15 μm : Cannot be confirmed (estimated to be about 2 nm)
After firing: 16.49 nm

Experimental Example A1 and Experimental Example A2
(Presence / absence of firing of aluminum particles (ratio of aluminum oxide on the surface of aluminum particles)
The compounding components (vol%) in Table 1 were uniformly mixed using a mixer to prepare a thermosetting resin composition, and the obtained composition was applied to a stripped polyethylene terephthalate film with a bar coater so as to have a thickness of 2 mm. Another polyethylene terephthalate film that had been peeled off was placed on the coated surface and heat-cured by holding at 80 ° C. for 6 hours to prepare a heat conductive sheet of Experimental Example A1 and Experimental Example A2.

The thermal conductivity of the obtained thermal conductivity sheet was measured as described below, and the measurement results are shown in Table 1. In addition, the compression rate before and after aging was measured, and the compression retention rate was calculated from these results. The results obtained are shown in Table 1.

(Measurement of thermal conductivity)
The thermal conductivity in the thickness direction of the thermal conductivity sheet was measured under the condition of a load of 1 kgf / cm ² using a thermal conductivity measuring device compliant with ASTMD5470. The results obtained are shown in Table 1.

(Measurement / calculation of compression possession rate)
Three sheets of the same thermal conductivity were prepared, and the initial thickness (t ₀ ) of one of them was measured. Next, the thickness (t ₁ ) when a load of 1 kgf / cm ² was applied to the ^second heat conductive sheet was measured. Next, after aging the third heat conductive sheet at 125 ° C. for 45 hours, the thickness (t ₂ ) when a load of 1 kgf / cm ² was applied was measured. These values were substituted into the following equations to calculate the compression retention rate. The results obtained are shown in Table 1.

(Evaluation of Experimental Example A1 and Experimental Example A2)
In the heat conductive sheet of Experimental Example A1, as a heat conductive filler, the thickness of the surface oxide film is 16.49 nm, which is much less than 50 nm, and the ratio of the surface oxygen amount to the surface saturated oxygen amount exceeds 85% 88. It uses aluminum particles that are 00%. On the other hand, in the heat conductive sheet of Experimental Example A2, as the heat conductive filler, the thickness of the surface oxide film is so thin that the thickness cannot be confirmed (it is estimated that the thickness is 3 nm or less), and the aluminum on the surface of the aluminum particles is X-rayed. Aluminum particles are used in which a narrow scan (high resolution) spectrum of the Al2p peak in the photoelectron spectroscopic analysis is acquired and the ratio of aluminum oxide calculated from the narrow scan (high resolution) spectrum is 78.00%, which is much less than 85%. Therefore, as can be seen from Table 1, the compressive retention rate of the heat conductive sheet of Experimental Example A2 was 4.87%, but the compressive retention rate of the thermal conductive sheet of Experimental Example A1 was 17.70%. It can be seen that there is an improvement over the thermal conductivity sheet of Experimental Example A2.

Experimental Examples B1 to B4
(Effect of firing of aluminum particles and combined use of antioxidant)
The heat conductive sheets of Experimental Examples B1 to B4 were prepared by repeating the operation of Experimental Example A1 other than using the compounding ingredients shown in Table 2. With respect to the obtained thermal conductivity sheet, the thermal conductivity and the compression retention rate were measured in the same manner as in Experimental Example A1. The heat conductive sheet was aged at 200 ° C. for 20 hours. The results obtained are shown in Table 2.

(Evaluation of Experimental Examples B1 to B4)
The heat conductive sheets of Experimental Examples B1 and B2 are both so thin that the thickness of the surface oxide film cannot be confirmed (estimated to be 3 nm or less in thickness), and the aluminum on the surface of the aluminum particles is analyzed by X-ray photoelectron spectroscopy. Aluminum particles are used in which a narrow scan (high resolution) spectrum of the Al2p peak is acquired and the ratio of aluminum oxide calculated from the spectrum is 80.50%, which is much lower than 85%. However, the heat conductive sheet of Experimental Example B1 does not use an antioxidant, but the heat conductive sheet of Experimental Example B2 uses a less hindered type phenolic antioxidant. Therefore, as can be seen from Table 2, the compressive retention rate of the heat conductive sheet of Experimental Example B1 was 2.90%, but the compressive retention rate of the thermal conductive sheet of Experimental Example B2 was 19.00%. It can be seen that there is an improvement over the thermal conductivity sheet of Experimental Example B1.

In the thermal conductive sheets of Experimental Examples B3 and B4, the thickness of the surface oxide film is 8.36 nm, and the narrow scan (high resolution) spectrum of the Al2p peak in the X-ray photoelectron spectroscopy analysis of the aluminum on the surface of the aluminum particles. , And the ratio of aluminum oxide calculated from it is 93.000%, which is much higher than 85%. However, the heat conductive sheet of Experimental Example B4 does not use an antioxidant, but the heat conductive sheet of Experimental Example B3 uses a less hindered type phenolic antioxidant. Therefore, as can be seen from Table 2, the compression retention rate of the heat conductive sheet of Experimental Example B4 was 15.27%, but the compression retention rate of the heat conductivity sheet of Experimental Example B3 was 36.00%. It can be seen that there is an improvement over the thermal conductivity sheet of Experimental Example B4.

Comparing Experimental Example B2 and Experimental Example B3, they both use an antioxidant, but the surface oxide film thickness of the aluminum particles is different. The thermal conductivity sheet of Experimental Example B2, which is considered to have a relatively thin oxide film, has a compression retention rate of 19.00%, whereas the thermal conductivity of Experimental Example B3, which is considered to have a relatively thick oxide film, is 19.00%. It can be seen that the compression retention rate of the sheet is 36.00%, which is improved as compared with the heat conductive sheet of Experimental Example B2.

Comparing Experimental Examples B1 and B4, they do not use an antioxidant, but the surface oxide film thickness of the aluminum particles is different. The heat conductivity of the heat conductive sheet of Experimental Example B1 in which the oxide film is considered to be relatively thin is 2.90%, whereas the heat conductivity of Experimental Example B4 in which the oxide film is considered to be relatively thick is 2.90%. It can be seen that the compression retention rate of the sheet is 15.27%, which is improved as compared with the heat conductive sheet of Experimental Example B1.

Experimental Examples C1 to C4
(Effect of type of antioxidant)
The heat conductive sheets of Experimental Examples C1 to C4 were prepared by repeating the operation of Experimental Example A1 except that the compounding ingredients shown in Table 3 were used. With respect to the obtained thermal conductivity sheet, the thermal conductivity and the compression retention rate were measured in the same manner as in Experimental Example A1. The heat conductive sheet was aged at 150 ° C. for 250 hours. The results obtained are shown in Table 3.

(Evaluation of Experimental Examples C1 to C4)
The heat conductive sheets of Experimental Examples C1 to C4 all use a phenolic antioxidant. Specifically, the heat conductive sheet of Experimental Example C1 uses a less hindered type, and the heat conductive sheet of Experimental Example C2 uses a semi-hindered type, and In the heat conductive sheets of Experimental Example C3 and Experimental Example C4, hindered type sheets are used. Therefore, as can be seen from Table 3, by using a semi-hindered type phenolic antioxidant, the compression retention rate of the heat conductive sheet is higher than that when other types of phenolic antioxidants are used. Can be seen to have improved significantly.

The thermally conductive material of the present invention is an aluminum particle coated with an aluminum oxide film having a thickness of 50 nm or less as a thermally conductive filler, and the aluminum on the surface of the aluminum particle is subjected to X-ray photoelectron spectroscopic analysis. At least aluminum particles in which a narrow scan (high resolution) spectrum of the Al2p peak is acquired and the proportion of aluminum oxide calculated from the narrow scan (high resolution) spectrum is 85% or more are used. Therefore, good thermal conductivity can be imparted to the thermally conductive material, and the surface activity of the aluminum particles can be suppressed to suppress deterioration of the binder component. Therefore, the thermally conductive material of the present invention is useful for removing heat from a heating element such as an integrated circuit provided in various precision electronic devices such as a personal computer and a mobile phone.

Claims (14)

A thermally conductive material containing a binder component and a thermally conductive filler.
The thermally conductive filler contains aluminum particles coated with an aluminum oxide film and contains aluminum particles.
The film thickness of the aluminum oxide film covering the aluminum particles is 50 nm or less, and the film thickness is 50 nm or less.
A thermally conductive material in which a narrow scan (high resolution) spectrum of an Al2p peak in X-ray photoelectron spectroscopic analysis is obtained for the aluminum on the surface of the aluminum particles, and the proportion of aluminum oxide calculated from the narrow scan (high resolution) spectrum is 85% or more. The heat conductive material according to claim 1, wherein the aluminum oxide film has a film thickness of 3 nm or more. The heat conductive material according to claim 1 or 2, wherein the average particle size of the aluminum particles is 1 μm or more and 100 μm or less. The thermally conductive material according to any one of claims 1 to 3, wherein the shape of the aluminum particles is spindle-shaped. The heat conductive material according to any one of claims 1 to 4, wherein the content of the heat conductive filler in the heat conductive material is 60% by volume or more and 90% by volume or less. The heat conductive material according to any one of claims 1 to 5, wherein the content of the aluminum particles in the heat conductive filler is 5% by volume or more and 50% by volume. The heat conductive material according to any one of claims 1 to 6, wherein the heat conductive filler contains alumina particles and aluminum nitride particles. The thermally conductive material according to claim 7, wherein the average particle size of the alumina particles is 0.5 μm or more and 100 μm or less, and the average particle size of the aluminum nitride particles is 1 μm or more and 100 μm or less. The heat conductive material according to claim 7 or 8, which contains 1 volume part or more and 200 parts by volume or less of alumina particles and 10 parts by volume or more and 500 parts by volume or less of aluminum nitride particles with respect to 100 parts by volume of aluminum particles. The thermally conductive material according to any one of claims 1 to 9, further comprising an antioxidant. The heat conductive material according to claim 10, wherein the antioxidant is a phenolic antioxidant. The heat conductive material according to claim 11, wherein the phenolic antioxidant is a semi-hindered type. The heat conductive material according to any one of claims 1 to 12, which is molded into a sheet or a film. A structure in which the heat conductive material according to any one of claims 1 to 13 is sandwiched between a heat generating material and a heat radiating body.