Heat dissipation material

Abstract

To provide a heat dissipation material composed of a novel alloy composition showing excellent high thermal conductivity and low thermal expansion characteristics.SOLUTION: The heat dissipation material contains, in mass%, Fe: 12.0-27.0%, Cr: 3.0-7.0%, Co: 20.0-42.0%, C: 0.10% or less, O: 0.10% or less, and N: 0.10% or less, with the balance being Cu and inevitable impurities.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a heat dissipation material, and more particularly to a heat dissipation material used in heat dissipation components that dissipate heat from CPUs, liquid crystal displays, and the like mounted on electronic devices. [Background technology]

[0002] In recent years, the increasing operating temperatures of electronic components have created a demand for materials with high thermal conductivity and low thermal expansion. Because semiconductor elements, such as power semiconductors, reach high temperatures, this can shorten the lifespan of surrounding electronic components, making it important to efficiently dissipate heat using heat dissipation substrates. Furthermore, to prevent cracks caused by thermal stress at the joints of heat dissipation substrates, low thermal expansion is necessary.

[0003] Conventionally, Cu-W alloys, Cu-Mo alloys, etc. have been used as heat dissipation materials. As shown in Patent Document 1 below, heat dissipation materials made of Cu-W alloys or Cu-Mo alloys achieve both high thermal conductivity and low thermal expansion by incorporating Cu into a sintered porous body of W or Mo using an infiltration method. However, heat dissipation materials manufactured using the infiltration method have problems in their manufacturability, and if the infiltration process takes a long time, the compact may bulge. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 59-141247 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in light of the above circumstances, with the object of providing a heat dissipation material having a novel alloy composition that is excellent in high thermal conductivity and low thermal expansion. [Means for solving the problem]

[0006] Specific means for solving the above problems include the following aspects. [1] A heat dissipation material containing, by mass%, 12.0 to 27.0% Fe, 3.0 to 7.0% Cr, 20.0 to 42.0% Co, 0.10% or less C, 0.10% or less O, 0.10% or less N, and the remainder being Cu and unavoidable impurities.

[0007] [2] The heat dissipating material according to [1], further containing, by mass%, 0.01 to 0.50% of Mn.

[0008] [3] The heat dissipating material according to [1] or [2], further containing, by mass %, one or more of W: 0.01 to 3.0% and Mo: 0.01 to 3.0%.

[0009] In a heat dissipation material having the alloy composition specified above, the metal structure is separated into a Cu-rich phase with excellent thermal conductivity and an Invar-rich phase mainly composed of Fe, Cr, and Co and with low thermal expansion, and the Invar-rich phase formed around the Cu-rich phase suppresses the thermal expansion of the Cu-rich phase. In the heat dissipation material of this invention, the effects of each alloy element on thermal conductivity and thermal expansion are taken into consideration, and the added amounts of each alloy element are appropriately balanced, thereby ensuring the targeted high thermal conductivity and low thermal expansion as an overall effect. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a scanning electron microscope photograph of the microstructure of a thermally conductive material powder according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Next, a heat dissipation material according to one embodiment of the present invention will be specifically described. The heat dissipation material of this embodiment contains predetermined amounts of Fe, Cr, Co, C, O, and N, with the balance being Cu and unavoidable impurities, and may further contain Mn, W, and Mo.

[0012] The reasons for limiting each chemical component in the heat dissipating material are described in detail below. In the following description, "%" means "% by mass" unless otherwise specified.

[0013] Fe: 12.0 to 27.0% Fe is an important element that forms an invar-rich phase and contributes to lowering the thermal expansion coefficient. If the Fe content is too low, the effect of low thermal expansion becomes insufficient, so the Fe content must be 12.0% or more, preferably 14.0% or more. However, if the Fe content is excessive, the Cu content will be relatively low, resulting in a decrease in the thermal conductivity of the heat dissipation material. Therefore, the Fe content must be 27.0% or less, preferably 25.0% or less, and more preferably 20.0% or less.

[0014] Cr: 3.0 to 7.0% Cr is an element that contributes to low thermal expansion, similar to Fe. To obtain this effect, the Cr content must be 3.0% or more, and preferably 3.5% or more. However, if the Cr content is excessive, the Cu content will be relatively low, resulting in a decrease in the thermal conductivity of the heat dissipation material. Therefore, the Cr content must be 7.0% or less, preferably 6.5% or less, and more preferably 4.0% or less.

[0015] Co: 20.0 to 42.0% Co, like Fe and Cr, is an element that contributes to low thermal expansion. To obtain this effect, the Co content must be 20.0% or more, and preferably 22.0% or more. However, if the Co content is excessive, the Cu content will be relatively low, resulting in a decrease in the thermal conductivity of the heat dissipation material. Therefore, the Co content must be 42.0% or less, preferably 40.0% or less, and more preferably 35.0% or less.

[0016] C: 0.10% or less C is an element that contributes to strengthening the matrix. However, if the C content is excessive, cold workability and ductility are impaired, so the upper limit is set to 0.10%.

[0017] O: 0.10% or less O forms oxide inclusions and has a negative effect on mechanical properties, so the O content must be 0.10% or less.

[0018] N: 0.10% or less Nitrogen forms nitride inclusions and has a negative effect on mechanical properties, so the N content must be 0.10% or less.

[0019] Cu: remainder Cu is an element that enhances the thermal conductivity of the heat dissipation material. However, as the Cu content increases, the proportion of the invar-rich phase decreases relatively, reducing the effect of low thermal expansion. Therefore, the Cu content is preferably 30 to 60%.

[0020] Mn: 0.01 to 0.50% Mn is one of the optional elements added to the heat dissipation material of this embodiment and has the effect of improving hot workability. To obtain this effect, the Mn content is 0.01% or more, preferably 0.10% or more. However, if the Mn content is excessive, the effect of low thermal expansion becomes insufficient, so the Mn content must be 0.50% or less, preferably 0.40% or less.

[0021] W: 0.01 to 3.0% W is one of the optional elements added to the heat dissipation material of this embodiment, and has the effect of improving thermal conductivity. To obtain this effect, the W content is 0.01% or more, preferably 0.10% or more. However, excessive W content reduces workability, so the W content must be 3.0% or less, preferably 1.0% or less.

[0022] Mo: 0.01 to 3.0% Mo is one of the optional elements added to the heat dissipation material of this embodiment, and has the effect of improving thermal conductivity, similar to W. The Mo content to obtain this effect is 0.01% or more, preferably 0.10% or more. However, excessive Mo content reduces workability, so the Mo content must be 3.0% or less, preferably 1.0% or less.

[0023] (Method of manufacturing heat dissipating material) The heat dissipation material of this embodiment can be manufactured in powder form using an atomization method or the like as described below. The molten alloy used to manufacture the heat dissipation material of this embodiment can be obtained by weighing out each raw material so as to obtain a predetermined chemical composition, and melting the weighed raw materials using melting means such as an arc furnace, a high-frequency induction furnace, or a heating furnace.

[0024] Examples of methods for obtaining powder from molten alloy include atomization (gas atomization, water atomization, etc.). The molten alloy is discharged from the tip of the discharge nozzle into the atomization chamber and flows downward continuously (in a rod-like shape). Gas such as N2, Ar, He, etc., or water is sprayed at high pressure onto the molten alloy, pulverizing and cooling the molten alloy. The cooled molten alloy, while still semi-molten, falls freely within the atomization chamber, gradually becoming spherical due to surface tension, yielding powder. In this way, a powdered heat dissipation material can be obtained.

[0025] FIG. 1 is a scanning electron microscope photograph of the microstructure of a heat dissipation material powder according to one embodiment of the present invention, specifically a photograph of the microstructure of a heat dissipation material powder made of a Cu-22.2Fe-5.4Cr-32.4Co alloy produced by gas atomization. The figure shows that the material is separated into two phases: a white Cu-rich phase with excellent thermal conductivity and a gray Invar-rich phase with low thermal expansion. The Cu-rich phase here is a phase mainly composed of Cu and containing 55.0% or more of Cu, and the Invar-rich phase is a phase mainly composed of Fe, Cr, and Co and containing 15.6 to 43.8% Fe, 3.8 to 12.0% Cr, and 21.9 to 61.3% Co. The composition of each phase can be analyzed using an EPMA (electron probe microanalyzer). As can be seen from the figure, an Invar-rich phase with low thermal expansion is formed around a Cu-rich phase that has excellent thermal conductivity but large thermal expansion, and it is presumed that the Invar-rich phase suppresses the thermal expansion of the Cu-rich phase.

[0026] The powdered heat dissipation material thus produced can be sintered using a method such as hot isostatic pressing (HIP) to obtain a sintered body of a predetermined shape. [Example]

[0027] Examples of the present invention will now be described in detail. Here, the thermal expansion characteristics and thermal conductivity characteristics of the heat dissipation materials of Examples and Comparative Examples (total of 17 types) shown in Table 1 below were evaluated.

[0028] 1. Preparation of evaluation materials Each raw material was weighed to obtain the alloy composition shown in Table 1 below. Each weighed raw material was heated and melted using a high-frequency induction furnace to obtain a molten alloy. Then, from each obtained molten alloy, alloy powder was produced using a gas atomization method, and alloy powder (heat dissipation material) with a particle size of 500 μm or less was obtained by classification. The obtained alloy powder was then vacuum-sealed in a stainless steel can with an outer diameter of 50 mm and a length of 100 mm, and subjected to HIP treatment at a hydrostatic pressure of 120 MPa and a temperature of 1000°C for 2 hours. The sintered body obtained by HIP treatment was cut and heat-treated in a vacuum at a temperature of 500°C for 8 hours to obtain materials for evaluation.

[0029] [Table 1]

[0030] 2. Characterization of heat dissipation materials The obtained evaluation material was used to measure and evaluate its thermal expansion coefficient and thermal conductivity.

[0031] <Thermal expansion coefficient> The evaluation material was machined to obtain a cylindrical test piece for measuring the thermal expansion coefficient, measuring φ5 mm x 20 mm. Using a thermomechanical analyzer (TMA), the average thermal expansion coefficient was measured from room temperature to 400°C at a heating rate of 5°C / min using the differential expansion method. The results are shown in Table 1 as the thermal expansion coefficient. The target thermal expansion coefficient was 10 x 10 -6 / K or less.

[0032] <Thermal conductivity> The evaluation material was machined to obtain a disk-shaped test piece for measuring thermal conductivity, measuring φ10 × 2 mm. The thermal conductivity at 100°C was measured using the xenon flash method. The results are shown in Table 1. The target thermal conductivity was 50 W / m K or higher.

[0033] The evaluation results shown in Table 1 reveal the following: In Comparative Examples 1 and 2, the contents of Fe, Cr, and Co, which form the invar-rich phase, all exceed the upper limit of the range specified in this embodiment. As a result, the invar-rich phase increased and the target thermal expansion coefficient was obtained, but the Cu-rich phase decreased relatively and the target thermal conductivity was not obtained.

[0034] In Comparative Examples 3 to 5, the contents of Fe, Cr, and Co, which form the invar-rich phase, are all below the lower limit of the range specified in this embodiment, resulting in a small amount of invar-rich phase (large amount of Cu-rich phase), an insufficient invar effect, and a failure to achieve the target thermal expansion coefficient.

[0035] In contrast, it is clear that the thermally conductive materials of Examples 1 to 12, in which the content of each element falls within the range specified in this embodiment, achieve the targeted thermal conductivity and thermal expansion coefficient.

[0036] Although the embodiments and examples of the present invention have been described in detail above, these are merely examples, and the present invention can be carried out in various modified forms without departing from the spirit and scope of the present invention.

Claims

1. By mass% Fe: 12.0-27.0% Cr: 3.0-7.0% Co:20.0~42.0% C: 0.10% or less O: 0.10% or less N: 0.10% or less and the remainder consisting of Cu and unavoidable impurities.

2. By mass% Mn: 0.01-0.50% The heat dissipating material according to claim 1, further comprising:

3. By mass% W: 0.01~3.0% Mo: 0.01~3.0% The heat dissipation material according to claim 1 or claim 2, further comprising one or more of the following:

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