Exothermic materials

Abstract

This invention provides a novel heat dissipation material with an alloy composition exhibiting excellent high thermal conductivity and low thermal expansion. [Solution] The heat dissipation material contains Cr: 8.5~10.5%, Co: 53.0~57.0%, Cu: 0.5~10.0%, C: 0.20% or less, O: 0.10% or less, and N: 0.10% or less, with the remainder being Fe and unavoidable impurities.

Description

Technical Field

[0001] This invention relates to a heat dissipation material, and particularly to a heat dissipation material used for heat dissipation components such as CPUs and liquid crystals mounted on electronic devices to dissipate heat.

Background Art

[0002] In recent years, due to the increase in the operating temperature of electronic components, materials having high thermal conductivity and low thermal expansion have been demanded. Since semiconductor elements such as power semiconductors become hot, they may shorten the life of peripheral electronic components, and it is important to efficiently dissipate heat using a heat dissipation substrate. In addition, in order to suppress cracks due to thermal stress at the joint in the heat dissipation substrate, it is necessary to reduce thermal expansion.

[0003] As a thermally stable alloy with low thermal expansion, an Invar alloy as shown in Patent Document 1 below is known. The Invar alloy has a characteristic (Invar effect) of showing an extremely low thermal expansion rate or a negative thermal expansion rate in a predetermined temperature range, but has a problem in terms of low thermal conductivity and efficient heat dissipation.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made for the purpose of providing a heat dissipation material having a novel alloy composition excellent in high thermal conductivity and low thermal expansion, based on the above circumstances.

Means for Solving the Problems

[0006] Specific means for solving the above problems include the following aspects. [1] A heat dissipation material containing, by mass%, Cr: 8.5-10.5%, Co: 53.0-57.0%, Cu: 0.5-10.0%, C: 0.20% or less, O: 0.10% or less, and N: 0.10% or less, with the remainder being Fe and unavoidable impurities.

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

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

[0009] In a heat dissipation material consisting of the alloy components defined above, the combination of Fe, Co, and Cr, which yields the Invar effect, and Cu, an element that enhances thermal conductivity, are included. By appropriately balancing the amount of each alloying element added, the target high thermal conductivity and low thermal expansion can be ensured as an overall effect. [Modes for carrying out the invention]

[0010] Next, we will specifically describe the heat dissipation material according to one embodiment of the present invention. The heat dissipation material of this embodiment contains predetermined amounts of Cr, Co, Cu, C, O, and N, with the remainder being Fe and unavoidable impurities. It may also further contain Mn, W, and Mo.

[0011] The reasons for the limitations on each chemical component in this heat dissipation material are detailed below. In the following explanation, unless otherwise specified, "%" refers to "mass%".

[0012] Cr: 8.5~10.5% Cr is an element that, when combined with Fe and Co, contributes to reducing the thermal expansion coefficient of heat dissipation materials. To obtain this effect, the Cr content needs to be 8.5% or higher, preferably 9.0% or higher. However, if the Cr content is excessive, the Invar effect decreases and the low thermal expansion effect becomes insufficient, so the Cr content must be 10.5% or less. Preferably, it is 10.0% or less.

[0013] Co: 53.0~57.0% Co, when combined with Fe and Cr, is an element that contributes to reducing the thermal expansion coefficient of heat dissipation materials. To obtain this effect, the Co content needs to be 53.0% or higher, preferably 54.0% or higher. However, if the Co content is excessive, the Invar effect decreases and the low thermal expansion effect becomes insufficient, so the Co content must be 57.0% or less. Preferably, it is 56.0% or less.

[0014] Cu: 0.5~10.0% Cu is an element that enhances the thermal conductivity of heat dissipation materials. If the Cu content is too low, the effect of improving thermal conductivity will be insufficient, so the Cu content must be 0.5% or more. Preferably, it is 1.0% or more. However, if the Cu content is excessive, the amounts of Fe, Co, and Cr will be relatively low, resulting in insufficient low thermal expansion. Therefore, the Cu content must be 10.0% or less. Preferably, it is 9.0% or less.

[0015] C: 0.20% or less Carbon (C) is an element that contributes to strengthening the base material. However, since excessive carbon content impairs cold workability and ductility, the upper limit is set at 0.20%.

[0016] O: 0.10% or less Oxygen (O) forms oxide inclusions, which adversely affect the mechanical properties. Therefore, the Oxygen content must be 0.10% or less.

[0017] N: 0.10% or less N generates nitride inclusions, which adversely affect the mechanical properties. Therefore, the amount of N must be 0.10% or less.

[0018] Mn: 0.01~0.50% Mn is one of the optional additive elements in the heat dissipation material of this embodiment and has the effect of improving hot workability. The Mn content for obtaining such an effect is 0.01% or more, preferably 0.10% or more. However, when the Mn content becomes excessive, the effect of low thermal expansion becomes insufficient. Therefore, the Mn content needs to be 0.50% or less. Preferably, it is 0.40% or less.

[0019] W: 0.01 - 3.0% W is one of the optional additive elements in the heat dissipation material of this embodiment and has the effect of improving thermal conductivity. The W content for obtaining such an effect is 0.01% or more, preferably 0.10% or more. However, when the W content becomes excessive, the workability deteriorates. Therefore, the W content needs to be 3.0% or less. Preferably, it is 1.0% or less.

[0020] Mo: 0.01 - 3.0% Mo is one of the optional additive elements in the heat dissipation material of this embodiment and has the effect of improving thermal conductivity, similar to W. The Mo content for obtaining such an effect is 0.01% or more, preferably 0.10% or more. However, when the Mo content becomes excessive, the workability deteriorates. Therefore, the Mo content needs to be 3.0% or less. Preferably, it is 1.0% or less.

[0021] (Manufacturing method of heat dissipation material) The heat dissipation material of this embodiment can be manufactured in powder form by using an atomization method or the like as follows. The molten alloy used for manufacturing the heat dissipation material of this embodiment can be obtained by weighing each raw material so as to have a predetermined chemical composition and melting the weighed raw materials using melting means such as an arc furnace, a high-frequency induction furnace, a heating furnace, etc.

[0022] One example of a method for obtaining powder from molten alloy is the atomization method (gas atomization, water atomization, etc.). In this method, molten alloy is dispensed from the tip of a nozzle into a spray chamber and flows continuously (in a rod shape) downwards. High-pressure gas or water containing N2, Ar, He, etc., is sprayed onto the molten metal, pulverizing and cooling it. The cooled molten metal, while still semi-molten, free-falls within the spray chamber and approaches a spherical shape due to surface tension, yielding powder. In this way, a powdered heat dissipation material can be obtained. The atomization method is effective in avoiding partial changes in properties caused by the aggregation and segregation of some component elements.

[0023] Then, by sintering the powdered heat dissipation material produced in this manner using methods such as hot isostatic pressing (HIP), a sintered body of a predetermined shape can be obtained. [Examples]

[0024] Next, embodiments of the present invention will be described in detail. Here, the thermal expansion characteristics and thermal conductivity characteristics of the heat dissipation materials of the embodiments and comparative examples (13 types in total) shown in Table 1 below were evaluated.

[0025] 1. Creation of evaluation materials Each raw material was weighed to achieve the alloy composition shown in Table 1 below. The weighed raw materials were heated and melted in a high-frequency induction furnace to obtain molten alloy. Alloy powder was then produced from each of the obtained molten alloys using the gas atomization method, and alloy powder (heat dissipation material) with a particle size of 500 μm or less was obtained by classification. Next, the obtained alloy powder was 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 from the HIP treatment was cut to obtain evaluation material.

[0026] [Table 1]

[0027] 2. Characterization of heat dissipation materials The obtained evaluation materials were used to measure and evaluate their thermal expansion coefficient and thermal conductivity.

[0028] <Coefficient of thermal expansion> For cylindrical test specimens measuring the coefficient of thermal expansion, measuring φ5 mm × 20 mm and obtained by machining evaluation material, the average coefficient of thermal expansion was measured from room temperature to 400°C using a thermomechanical analyzer (TMA) with a differential expansion method at a heating rate of 5°C / min. The results are shown in Table 1 as the coefficient of thermal expansion. The target coefficient of thermal expansion is 3.0 × 10⁻⁶. -6 It is less than or equal to / K.

[0029] <Thermal conductivity> The thermal conductivity of a φ10 × 2 mm disc-shaped test specimen for thermal conductivity measurement, obtained by machining the evaluation material, was measured at 100°C using the xenon flash method. The results are shown in Table 1. The target thermal conductivity is 13.2 W / m·K or higher.

[0030] The following can be seen from the evaluation results shown in Table 1. Comparative Examples 1 and 2 were both examples that did not contain Cu, and therefore the target thermal conductivity could not be obtained. Comparative Example 3 had a Cu content exceeding the upper limit of the range defined in this embodiment, and Comparative Example 4 had Cu and Mn content exceeding the upper limit of the range defined in this embodiment. As a result, in Comparative Examples 3 and 4, the content of Fe, Co, and Cr, which are capable of producing the Invar effect, was relatively small compared to Cu and Mn, and the target thermal expansion coefficient could not be obtained.

[0031] In contrast, the heat dissipation materials of Examples 1 to 9, in which the content of each element is within the range specified in this embodiment, can be seen to have achieved the target thermal conductivity and thermal expansion coefficient.

[0032] Although embodiments and examples of the present invention have been described in detail above, these are merely illustrative examples. For example, the heat dissipation material in the present invention is not limited to powder obtained by atomization or the like, but can also be used as a heat dissipation material in the present invention if it is molten material obtained in an arc furnace, high-frequency induction furnace, heating furnace, etc. The present invention can be implemented in various modified forms without departing from its spirit.

Claims

1. by mass % Cr: 8.5-10.5% Co:53.0-57.0% Cu: 0.5-10.0% C: 0.20% or less O: 0.10% or less N: 0.10% or less A heat dissipation material containing [a certain substance], with the remainder consisting of Fe and unavoidable impurities.

2. by mass % Mn: 0.01-0.50% The heat dissipation material according to claim 1, further comprising the above.

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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