Heat dissipation material

Abstract

Provided is a novel heat-dissipating material composed of an alloy and having excellent high thermal conductivity and low thermal expansion. The heat dissipation material contains, in mass%, 12.0 to 27.0% of Fe, 3.0 to 7.0% of Cr, 20.0 to 42.0% of Co, 0.10% or less of C, 0.10% or less of O, and 0.10% or less of N, with the remainder being Cu and unavoidable impurities.

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 such as a CPU and liquid crystal mounted in electronic equipment. Background Art

[0002] In recent years, the increasing operating temperatures of electronic components have necessitated the demand for materials with high thermal conductivity and low thermal expansion. High temperatures in semiconductor components, such as power semiconductors, can shorten the lifespan of surrounding electronic components, making it crucial to use heat dissipation substrates to efficiently dissipate heat. Furthermore, reducing thermal expansion is necessary to prevent cracking caused by thermal stress at the joints of the heat dissipation substrate.

[0003] Conventionally, heat dissipation materials such as Cu-W alloys and Cu-Mo alloys have been used. As shown in Patent Document 1 below, heat dissipation materials composed of Cu-W alloys and Cu-Mo alloys achieve high thermal conductivity and low thermal expansion by infiltrating a sintered porous body of W or Mo. However, heat dissipation materials manufactured using the infiltration method face difficulties in manufacturability, and prolonged infiltration processes can lead to expansion of the formed body.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 59-141247 Summary of the Invention

[0007] Technical problem to be solved by the invention

[0008] The present invention is based on the above situation, and an object of the present invention is to provide a heat dissipating material having a novel alloy composition excellent in high thermal conductivity and low thermal expansion.

[0009] Technical solutions to technical problems

[0010] Furthermore, specific means for solving the above-mentioned problems include the following aspects.

[0011] [1] A heat dissipation material comprising, by mass%, 12.0 to 27.0% Fe, 3.0 to 7.0% Cr, 20.0 to 42.0% Co, less than 0.10% C, less than 0.10% O, less than 0.10% N, with the remainder being Cu and unavoidable impurities.

[0012] [2] The heat dissipation material according to [1], further comprising, by mass%, 0.01 to 0.50% of Mn.

[0013] [3] The heat dissipation material according to [1] or [2], further comprising, in mass %, at least one of W: 0.01 to 3.0% and Mo: 0.01 to 3.0%.

[0014] In the heat dissipation material having the alloy composition specified above, the metal structure is separated into a Cu-rich phase with excellent thermal conductivity and a Richinvar phase composed primarily of Fe, Cr, and Co and having low thermal expansion. The Richinvar phase formed around the Cu-rich phase suppresses the thermal expansion of the Cu-rich phase. In the heat dissipation material of the present invention, the effects of each alloying element on thermal conductivity and thermal expansion are considered, and the amounts of each alloying element added are appropriately balanced. As a whole, the desired high thermal conductivity and low thermal expansion are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a scanning electron microscope microstructure photograph of the heat dissipation material powder according to one embodiment of the present invention. DETAILED DESCRIPTION

[0016] Next, a heat dissipation material according to an embodiment of the present invention will be described in detail.

[0017] The heat dissipating material of this embodiment contains predetermined amounts of Fe, Cr, Co, C, O, and N, with the remainder being Cu and inevitable impurities. Furthermore, Mn, W, and Mo may also be contained.

[0018] The reasons for limiting the chemical components in the present heat dissipating material are described in detail below. In the following description, "%" means "mass %" unless otherwise specified.

[0019] Fe: 12.0~27.0%

[0020] Fe is an important element that forms the Richter phase and contributes to reducing the thermal expansion coefficient. If the Fe content is too low, the effect of reducing thermal expansion is insufficient, so the Fe content needs to be at least 12.0%. Preferably, it is at least 14.0%.

[0021] However, if the Fe content is excessive, the Cu content becomes relatively low, resulting in a decrease in thermal conductivity within the heat dissipation material. Therefore, the Fe content needs to be 27.0% or less, preferably 25.0% or less, and more preferably 20.0% or less.

[0022] Cr: 3.0~7.0%

[0023] Cr, like Fe, is an element that contributes to low thermal expansion. To achieve this effect, the Cr content needs to be 3.0% or more, preferably 3.5% or more.

[0024] However, if the Cr content is excessive, the Cu content becomes relatively low, resulting in a decrease in thermal conductivity within the heat sink. Therefore, the Cr content needs to be 7.0% or less, preferably 6.5% or less, and even more preferably 4.0% or less.

[0025] Co: 20.0~42.0%

[0026] Co, like Fe and Cr, is an element that contributes to low thermal expansion. To achieve this effect, the Co content needs to be 20.0% or more, preferably 22.0% or more.

[0027] However, if the Co content is excessive, the Cu content becomes relatively low, resulting in a decrease in thermal conductivity in the heat dissipation material. Therefore, the Co content needs to be 42.0% or less, preferably 40.0% or less, and more preferably 35.0% or less.

[0028] C: 0.10% or less

[0029] C is an element that contributes to matrix strengthening. However, if the C content is excessive, cold workability and ductility are impaired, so the upper limit is 0.10%.

[0030] O: 0.10% or less

[0031] O forms oxide inclusions, which adversely affect mechanical properties. Therefore, the amount of O must be 0.10% or less.

[0032] N: 0.10% or less

[0033] Nitrogen forms nitride inclusions, which adversely affect mechanical properties. Therefore, the amount of nitrogen must be 0.10% or less.

[0034] Cu: remaining part

[0035] Cu is an element that improves the thermal conductivity of heat dissipation materials. However, if the Cu content increases, the ratio of the Fuinvar phase decreases, and the effect of reducing thermal expansion decreases. Therefore, the Cu content is preferably 30-60%.

[0036] Mn: 0.01~0.50%

[0037] Mn is one of the optional additive elements in the heat dissipation material of this embodiment and has the effect of improving hot workability. To achieve this effect, the Mn content is preferably 0.01% or more, more preferably 0.10% or more.

[0038] However, if the Mn content is excessive, the effect of reducing thermal expansion becomes insufficient. Therefore, the Mn content is preferably 0.50% or less, and more preferably 0.40% or less.

[0039] W: 0.01~3.0%

[0040] W is one of the arbitrary added elements in the heat dissipation material of the present embodiment, and has an effect of improving thermal conductivity. The content of W for obtaining such an effect is preferably 0.01% or more, and more preferably 0.10% or more.

[0041] However, if the content of W is excessive, the workability is reduced. Therefore, the content of W is preferably 3.0% or less, and more preferably 1.0% or less.

[0042] Mo: 0.01 to 3.0%

[0043] Mo is one of the arbitrary added elements in the heat dissipation material of the present embodiment, and has an effect of improving thermal conductivity as with W. The content of Mo for obtaining such an effect is preferably 0.01% or more, and more preferably 0.10% or more.

[0044] However, if the content of Mo is excessive, the workability is reduced. Therefore, the content of Mo is preferably 3.0% or less, and more preferably 1.0% or less.

[0045] Mg: 0.10% or less

[0046] Mg is an element that is inevitably mixed due to manufacturing reasons. Since Mg reduces thermal conduction, it is desirable to reduce it as much as possible. Therefore, even in the case where it is inevitably mixed, the upper limit of the content of Mg is 0.10% or less.

[0047] Al: 0.10% or less

[0048] Al is an element that is inevitably mixed due to manufacturing reasons. Since Al reduces thermal conduction, it is desirable to reduce it as much as possible. Therefore, even in the case where it is inevitably mixed, the upper limit of the content of Al is 0.10% or less.

[0049] Si: 0.10% or less

[0050] Si is an element that is inevitably mixed due to manufacturing reasons. Since Si reduces thermal conduction, it is desirable to reduce it as much as possible. Therefore, even in the case where it is inevitably mixed, the upper limit of the content of Si is 0.10% or less.

[0051] B: 0.10% or less

[0052] B is an element that is inevitably mixed due to manufacturing reasons. Since B reduces thermal conduction, it is desirable to reduce it as much as possible. Therefore, even in the case where it is inevitably mixed, the upper limit of the content of B is 0.10% or less.

[0053] (Method for manufacturing heat dissipation material)

[0054] The heat dissipating material of this embodiment can be manufactured into a powder form by using an atomization method or the like as described below.

[0055] The alloy melt used in the production of the heat dissipating material of this embodiment can be obtained by measuring each raw material so as to have a predetermined chemical composition and melting the measured raw materials using a melting device such as an arc furnace, a high-frequency induction furnace, or a heating furnace.

[0056] An example of a method for producing a powder from a molten alloy is atomization (gas atomization, water atomization, etc.). A high-pressure spray of gas or water, such as N2, Ar, or He, is applied to the molten alloy, which flows continuously downward (in a rod-like shape) from the tip of a hot water nozzle into a spray chamber. This pulverizes the molten alloy and cools it. The cooled molten alloy, in a semi-molten state, falls freely within the spray chamber, where surface tension causes it to become spherical, resulting in a powder. This method produces a powdered heat dissipation material.

[0057] Figure 1 This is a scanning electron microscope microstructure photograph of a heat dissipation material powder according to one embodiment of the present invention, specifically, a microstructure photograph of a heat dissipation material powder composed of a Cu-22.2Fe-5.4Cr-32.4Co alloy produced by a gas atomization method.

[0058] As can be seen from the figure, two phases are separated: a Cu-rich phase having excellent thermal conductivity (white) and a Rich Invar phase having low thermal expansion (gray).

[0059] The Cu-rich phase is primarily composed of Cu, containing 55.0% or more of Cu. The Invar-rich phase is primarily composed of Fe, Cr, and Co, 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 EPMA (electron probe microanalyzer).

[0060] As can be seen from the figure, a Rich Invar phase with low thermal expansion is formed around a Cu-rich phase with excellent thermal conductivity and large thermal expansion, and the thermal expansion of the Cu-rich phase is suppressed by the Rich Invar phase.

[0061] Then, if the powdered heat dissipation material manufactured in this way is sintered using a method such as hot isostatic pressing (HIP), a sintered body of a predetermined shape can be obtained. It should be noted that promoting phase separation by performing a heat treatment at 400°C to 900°C after the HIP treatment is effective in improving thermal expansion and heat conduction. As for the time of the heat treatment, considering the cost of the heat treatment, it is preferably carried out within 24 hours. Although the thermal expansion / heat conduction of the sintered body depends on the alloy composition, the thermal expansion / heat conduction can be improved by performing the above-mentioned heat treatment at 400°C to 900°C.

[0062] The heat dissipation material of the present invention preferably has a thermal expansion coefficient that satisfies 10×10 -6 / K or less and the thermal conductivity is 50W / m·K or more.

[0063] [Example]

[0064] Next, examples of the present invention will be described in detail. Here, the thermal expansion characteristics and thermal conductivity characteristics of the heat dissipation materials of Examples and Comparative Examples (a total of 17 types) shown in Table 1 below were evaluated.

[0065] 1. Preparation of evaluation materials

[0066] The raw materials were weighed to form the alloy compositions shown in Table 1. The weighed raw materials were heated and melted in a high-frequency induction furnace to form alloy melts. Alloy powders were then produced from the resulting alloy melts using a gas atomization method. Classification was then performed to obtain alloy powders (heat dissipation materials) with a particle size of 500 μm or less.

[0067] The resulting 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 a HIP treatment at a hydrostatic pressure of 120 MPa and a temperature of 1000°C for 2 hours. The sintered body obtained by the HIP treatment was cut and heat treated in a vacuum at a temperature of 500°C for 8 hours to obtain evaluation materials.

[0068] [Table 1]

[0069]

[0070] 2. Evaluation of heat dissipation material characteristics

[0071] The thermal expansion coefficient and thermal conductivity of the obtained evaluation material were measured and evaluated.

[0072] <Coefficient of Thermal Expansion>

[0073] The thermal expansion coefficient was measured using a thermomechanical analyzer (TMA) using the differential expansion method (JIS Z2285:2003) at a heating rate of 5°C / min from room temperature to 400°C. The results are shown in Table 1 as the thermal expansion coefficient. The target thermal expansion coefficient was 10×10 -6 / K or less.

[0074] <Thermal conductivity>

[0075] The thermal conductivity of the evaluation material was measured at 100°C using the xenon flash method on disk-shaped thermal conductivity test pieces with a diameter of 10 mm and a thickness of 2 mm, obtained by machining the evaluation material. The results are shown in Table 1. The target thermal expansion coefficient was 50 W / m˙K or higher.

[0076] The following points can be seen from the evaluation results shown in Table 1.

[0077] In Comparative Examples 1 and 2, the contents of Fe, Cr, and Co, which form the Richinvar phase, all exceed the upper limit of the range specified in this embodiment. As a result, it is believed that the Richinvar phase increases, achieving the target thermal expansion coefficient, but the Cu-rich phase decreases relatively, failing to achieve the target thermal conductivity.

[0078] In Comparative Examples 3 to 5, the contents of Fe, Cr, and Co, which form the Rich Invar phase, were all below the lower limit of the range specified in this embodiment. As a result, the Rich Invar phase was reduced (and the Cu-rich phase increased), resulting in an insufficient Invar effect and, presumably, an inability to achieve the target thermal expansion coefficient.

[0079] In this regard, it can be seen that the heat dissipation materials of Examples 1 to 12, in which the content of each element is within the range specified in this embodiment, can achieve the target thermal conductivity and thermal expansion coefficient.

[0080] While the embodiments and examples of the present invention have been described in detail above, these are merely examples, and the present invention can be implemented in various modified forms without departing from the spirit and scope of the present invention.

[0081] This application is based on Japanese Patent Application No. 2024-061546 filed on April 5, 2024 and Japanese Patent Application No. 2025-012108 filed on January 28, 2025, the contents of which are incorporated herein by reference.

Claims

1. A heat dissipation material, characterized in that: In terms of mass %, it contains 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 balance is Cu and inevitable impurities.

2. The heat dissipation material according to claim 1, wherein In terms of mass %, it further contains 0.01 to 0.50% Mn.

3. The heat dissipation material according to claim 1 or 2, wherein: In terms of mass %, it further contains at least one of 0.01 to 3.0% of W and 0.01 to 3.0% of Mo.

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