Compositions, electronic components, and semiconductor devices

Abstract

To provide a composition containing gallium (Ga) or a gallium alloy and a thermally conductive ceramic filler that exhibits excellent operability and workability. [Solution] A composition comprising (A) Ga or a Ga alloy, (B) a thermally conductive ceramic filler, and (C) a metal powder having a melting point of 900°C or higher.

Description

Technical Field

[0001] The present invention relates to a composition containing a liquid metal and a thermally conductive ceramic filler, an electronic component containing the composition, and a semiconductor device.

Background Art

[0002] With the high functionality and high performance of electronic devices, miniaturization and high density of electronic components are progressing. Therefore, it is important to dissipate heat generated from electronic components more efficiently.

[0003] For example, in order to efficiently dissipate heat generated from electronic components, a thermal interface material is used. A thermal interface material is a material for relaxing the thermal resistance of a path for allowing heat generated from a semiconductor element to escape to a heat sink or a housing, etc., and various forms such as a sheet, a gel, and a grease are used. As the thermal interface material, a composition in which a thermally conductive filler such as a metal filler, a ceramic filler, or diamond is filled in a silicone resin or an epoxy resin is known.

[0004] For example, in Patent Document 1, an invention related to a thermally conductive silicone composition containing an organopolysiloxane having a kinematic viscosity at 25°C of 10 to 500,000 mm 2 / s, a thermally conductive filler having an average particle size of 0.01 to 100 μm, gallium or a gallium alloy having a melting point of -20 to 100°C, and an alkoxysilane compound having a specific structure is disclosed. The thermally conductive filler described in Patent Document 1 is specifically zinc oxide, alumina, boron nitride, aluminum nitride, aluminum hydroxide, magnesium oxide, etc., and the thermally conductive filler and gallium or a gallium alloy mainly play a role in improving the thermal conductivity of the silicone composition.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] In recent years, electronic components have become smaller and more densely packed, requiring superior heat dissipation and thus demanding thermal interface materials with high thermal conductivity. While the thermally conductive silicone composition described in Patent Document 1 above possesses a certain degree of heat dissipation, it is difficult to significantly improve its thermal conductivity because its matrix is ​​an organic silicone resin.

[0007] Gallium (Ga) or Ga alloys, also known as liquid metals, have a relatively low melting point, excellent workability, and a certain thermal conductivity. However, it is difficult to create a material with excellent heat dissipation using Ga or Ga alloys alone. Furthermore, because Ga or Ga alloys are in a low-viscosity liquid state at high temperatures, there is a possibility of leakage from the application site, raising reliability issues.

[0008] Therefore, the inventors investigated compositions containing Ga or a Ga alloy and a thermally conductive ceramic filler. However, it was found that simply using a thermally conductive ceramic filler resulted in reduced fluidity of the composition, preventing it from becoming a homogeneous paste, and causing separation of the matrix and filler, leading to poor handling and workability. Against this backdrop, the object of the present invention is to provide a composition containing Ga or a Ga alloy and a thermally conductive ceramic filler that offers excellent handling and workability. [Means for solving the problem]

[0009] The inventors diligently conducted research to achieve the above objectives. As a result, they discovered that the above problems can be solved by adding a metal powder with a melting point of 900°C or higher to a composition containing Ga or a Ga alloy and a thermally conductive ceramic filler, and thus completed the present invention.

[0010] In other words, the present invention is a composition comprising (A) Ga or a Ga alloy, (B) a thermally conductive ceramic filler, and (C) a metal powder having a melting point of 900°C or higher.

[0011] The (C) metal powder with a melting point of 900°C or higher preferably contains transition metals belonging to the 4th and 5th periods. The (B) thermally conductive ceramic filler filling rate is preferably 30 to 70 volume%. Furthermore, the (C) metal powder with a melting point of 900°C or higher filling rate is preferably 1 to 20 volume%.

[0012] Furthermore, the present invention can include an electronic component containing the above-mentioned composition. Moreover, the present invention can include a semiconductor device containing the above-mentioned composition. [Effects of the Invention]

[0013] The present invention makes it possible to provide a composition containing Ga (gallium) or a Ga alloy and a thermally conductive ceramic filler that exhibits excellent fluidity. [Modes for carrying out the invention]

[0014] Hereinafter, an example of an embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiments described below, and can be modified and implemented as such without departing from the spirit of the invention.

[0015] (A) Ga or Ga alloy The composition of the present invention comprises (A)Ga or a Ga alloy. The Ga alloy can be used without particular limitation as long as it contains Ga. Since (A)Ga or a Ga alloy has a higher thermal conductivity than resin, the thermal conductivity of the composition can be increased compared to conventional compositions in which a thermally conductive ceramic filler such as aluminum nitride is filled into a resin.

[0016] (A) The melting point of Ga or Ga alloy is not particularly limited, but is preferably -25 to 60°C, and more preferably -20 to 40°C. When the melting point of Ga or Ga alloy is within the above range, it melts easily when preparing a composition with thermally conductive ceramic fillers, thus improving workability.

[0017] Ga is metallic gallium, and its melting point is 28-30°C. The melting point of Ga alloys can be adjusted by the composition of the Ga alloy. The melting point can be determined, for example, by differential scanning calorimetry (DSC).

[0018] (A) Among Ga or Ga alloys, Ga alloys are preferred from the viewpoint of having a low melting point and improving the fluidity of the composition. A Ga alloy is an alloy of Ga and another metal other than Ga. The other metal is not particularly limited, but examples include one or more metals selected from the group consisting of In (indium), Sn (tin), Zn (zinc), and Bi (bismuth). Examples of Ga alloys include Ga-In (gallium-indium alloy), Ga-In-Sn (gallium-indium-tin alloy), Ga-Sn-Zn (gallium-tin-zinc alloy), and Ga-In-Bi-Sn (gallium-indium-bismuth-tin alloy). Among these, Ga-In-Sn (gallium-indium-tin alloy) is preferred from the viewpoint of availability. The proportion of Ga in a Ga alloy is not particularly limited and may be adjusted as appropriate from the viewpoint of adjusting the melting point and thermal conductivity of the Ga alloy, but for example it is 5% by mass or more, preferably 30% by mass or more, and more preferably 50% by mass or more.

[0019] The amount of (A)Ga or Ga alloy in the composition of the present invention is not particularly limited, but is preferably 25% to 70% by volume, and more preferably 35% to 60% by volume. By keeping the amount of (A)Ga or Ga alloy within these ranges, a composition can be made that combines good fluidity and high thermal conductivity.

[0020] (B) Thermally conductive ceramic filler The composition of the present invention contains (B) a thermally conductive ceramic filler. Since the (B) thermally conductive ceramic filler has a high thermal conductivity, the composition containing the thermally conductive ceramic filler is excellent in heat dissipation.

[0021] (B) Known thermally conductive ceramic fillers can be used, and examples include aluminum nitride, boron nitride, silicon nitride, aluminum oxide (alumina), magnesium oxide, zinc oxide, silica, silicon carbide, and diamond. Among them, aluminum nitride, boron nitride, alumina, zinc oxide, silicon carbide, and diamond are preferred, and aluminum nitride and diamond are particularly preferred. As these thermally conductive ceramic fillers, commercially available products can be used without particular limitation. Also, multiple types of thermally conductive ceramic fillers can be combined and used.

[0022] (B) The lower limit of the D50 of the thermally conductive ceramic filler is not particularly limited, but it is preferably 0.5 μm or more, more preferably 1 μm or more, and even more preferably 5 μm or more. When the D50 is at or above these lower limit values, it becomes easier to increase the thermal conductivity of the composition. (B) The upper limit of the D50 of the thermally conductive ceramic filler is not particularly limited, but it is preferably 150 μm or less, more preferably 125 μm or less, and even more preferably 100 μm or less. When the D50 is at or below these upper limit values, it becomes easier to use the composition as a thin thermal interface material.

[0023] In this specification, D50 is the particle size at which the volume accumulation is 50% in the particle size distribution curve obtained by the laser diffraction / scattering method. D50 can be obtained, for example, by using a solution in which a thermally conductive ceramic filler is dispersed as a sample, measuring the particle size distribution of the sample using a laser diffraction type particle size distribution measuring device, and determining it from the obtained particle size distribution curve.

[0024] The filling rate of the (B) thermally conductive ceramic filler in the composition of the present invention is not particularly limited, but from the viewpoints of the fluidity of the composition and the improvement of the thermal conductivity of the composition, it is preferably 25% by volume or more and 70% by volume or less, more preferably 35% by volume or more and 60% by volume or less, based on the whole composition.

[0025] (C) metal powder having a melting point of 900 °C or higher The composition of the present invention contains (C) metal powder having a melting point of 900 °C or higher. By containing such metal powder, a composition excellent in fluidity can be obtained. Although the reason is not clear, the present inventors consider it as follows. The present invention is not limited thereto.

[0026] (A) Ga or a Ga alloy has a large interfacial tension, so the wettability to the surface of the (B) thermally conductive ceramic filler is poor. Therefore, even when (A) Ga or a Ga alloy and (B) thermally conductive ceramic filler are mixed, they do not mix well, and it is considered difficult to obtain a composition excellent in fluidity. On the other hand, since the metal powders are metals, they are easily wetted. Therefore, when metal powder is added to (A) Ga or a Ga alloy, the viscosity of (A) Ga or a Ga alloy increases and the interfacial tension decreases, the wettability to the surface of the (B) thermally conductive ceramic filler is improved, the fluidity is improved, and it is considered that separation of (A) Ga or a Ga alloy and (B) thermally conductive ceramic filler can be prevented when a shearing force is applied. [[ID= (A) Ga or a Ga alloy has a large interfacial tension, so the wettability to the surface of the (B) thermally conductive ceramic filler is poor. Therefore, even when (A) Ga or a Ga alloy and (B) thermally conductive ceramic filler are mixed, they do not mix well, and it is considered difficult to obtain a composition excellent in fluidity. On the other hand, since the metal powders are metals, they are easily wetted. Therefore, when metal powder is added to (A) Ga or a Ga alloy, the viscosity of (A) Ga or a Ga alloy increases and the interfacial tension decreases, the wettability to the surface of the (B) thermally conductive ceramic filler is improved, the fluidity is improved, and it is considered that separation of (A) Ga or a Ga alloy and (B) thermally conductive ceramic filler can be prevented when a shearing force is applied.|11]]

[0027] Here, (A) Ga or Ga alloys have low melting points, are easily mixed with other metals, and readily undergo alloying. In particular, alloying readily occurs with metals with low melting points. For example, In, Sn, Zn, and Bi are metals with low melting points of 500°C or less, and readily dissolve in (A) Ga or Ga alloys to form alloys. Furthermore, with metals with low melting points, the grain boundaries tend to be unstable, so Ga easily diffuses and erodes into the metal lattice, and alloying readily occurs from within the metal. For example, Ga erodes the grain boundaries of Al (aluminum), making Al brittle, thus easily forming an alloy. This alloying adversely affects the fluidity of the composition, so even if metal powders with low melting points are used, it is not possible to obtain a composition with excellent fluidity. On the other hand, if (C) metal powders with a melting point of 900°C or higher are used, they do not readily form alloys with (A) Ga or Ga alloys. Therefore, it is presumed that it is possible to improve the compatibility between (A) Ga or Ga alloys and (B) thermally conductive ceramic fillers while avoiding the aforementioned adverse effects, thereby providing a composition with excellent fluidity.

[0028] (C) Metal powders with a melting point of 900°C or higher are preferably transition metals belonging to the 4th and 5th periods. Transition metals belonging to the 4th and 5th periods have d-orbital electrons, but these are also distributed in the outer s-orbitals. Due to this property of having a large number of electrons widely distributed, many electrons are involved in metallic bonding, contributing to an increase in bonding strength, and therefore transition metals belonging to the 4th and 5th periods exhibit higher melting points than typical metals. In fact, all transition metals belonging to the 4th and 5th periods have a melting point of 900°C or higher. In this specification, transition metals belonging to the 4th and 5th periods refer to metals from Group 3 to Group 11 belonging to the 4th and 5th periods, and include scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, and silver. In the present invention, from the viewpoint of availability, (C) the metal powder having a melting point of 900°C or higher preferably contains titanium, chromium, manganese, iron, cobalt, nickel, copper, niobium, molybdenum, and silver, and particularly preferably contains chromium, nickel, copper, and silver.

[0029] (C) As metal powders with a melting point of 900°C or higher, commercially available powders can be used without particular restrictions. In addition, multiple types of metal powders can be used in combination. Furthermore, alloys composed of two or more metals may also be used. Particularly preferred are chromium powder, nickel powder, copper powder, and silver powder.

[0030] (C) For metal powders with a melting point of 900°C or higher, the upper limit of the melting point is not particularly limited, but it can be, for example, 3000°C or lower.

[0031] (C) The particle size of the metal powder with a melting point of 900°C or higher is not particularly limited, but is preferably 0.1 μm to 200 μm, more preferably 0.5 μm to 175 μm, and even more preferably 1 μm to 150 μm. When the particle size is within these ranges, it is easy to obtain a composition with good fluidity.

[0032] In this specification, particle size refers to the major axis of a particle observed in a scanning electron microscope image taken at 500x magnification. The particle size is defined as the major axis of the particle that accounts for 90% of the cumulative total of the particles with the smallest major axis, obtained by observing 100 or more particles and measuring the major axis of each particle.

[0033] The filling ratio of (C) metal powder having a melting point of 900°C or higher in the composition of the present invention is not particularly limited, but from the viewpoint of improving the fluidity of the composition and the thermal conductivity of the composition, it is preferably 1% to 20% by volume, and more preferably 2% to 10% by volume, relative to the whole composition.

[0034] (Other ingredients) The composition of the present invention may contain components other than (A) Ga or Ga alloy, (B) thermally conductive ceramic filler, and (C) metal powder with a melting point of 900°C or higher, to the extent that they do not impair the effects of the present invention. Examples of other components include dispersants, antioxidants, and colorants.

[0035] Furthermore, the composition of the present invention may contain organic substances such as silicone resins and epoxy resins, but from the viewpoint of improving the thermal conductivity and fluidity of the composition, it is preferable to keep the amount of organic substances as small as possible. The amount of organic substances in the composition of the present invention is preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0% by mass.

[0036] Furthermore, the composition of the present invention may contain metal powder having a melting point of less than 900°C. However, as described above, low-melting-point metal powder may form an alloy with (A)Ga or a Ga alloy, making it difficult to improve fluidity, and the formation of the alloy may progress over time, potentially reducing the storage stability of the composition. For this reason, in the composition of the present invention, the content of metal powder having a melting point of less than 900°C is preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0% by mass.

[0037] (Thermal conductivity of the composition) Unlike conventional materials that use resins such as silicone resins as a matrix, the composition of the present invention uses Ga or a Ga alloy as its matrix, resulting in excellent thermal conductivity. Furthermore, because it has good fluidity, when the composition of the present invention is used as a thermal interface material in the manufacture of electronic components or semiconductor devices, for example, the matrix (Ga or Ga alloy) and filler are less likely to separate due to shear forces applied during manufacturing, making it easier to achieve high thermal conductivity. The thermal conductivity of the composition of the present invention is, for example, 30 W / (m·K) or higher. The upper limit of the thermal conductivity is not particularly limited, but it can be, for example, 150 W / (m·K) or lower. The thermal conductivity can be measured by the method described in the examples.

[0038] (Method of manufacturing the composition) The method for producing the composition of the present invention is not particularly limited, and it can be produced by mixing each component using known methods with various kneaders. During the mixing, each component may be added to the kneader and mixed simultaneously, or each component may be added to the kneader and mixed sequentially. The order of addition is not particularly limited. Furthermore, the mixing may be carried out under heating (for example, 40 to 150°C) or under an adjusted atmosphere such as an inert gas atmosphere, if necessary.

[0039] (Form of composition) The liquid metal composition of the present invention is preferably in paste or liquid form at room temperature for easy use.

[0040] (Use of the copyrighted material) The composition of the present invention has high fluidity, maintains paste-like properties even when the filling rate of thermally conductive ceramic fillers is increased, and offers good workability. Furthermore, because the composition of the present invention has high thermal conductivity, it can be suitably used as a thermal interface material with excellent heat dissipation properties in various electronic components and semiconductor devices. [Examples]

[0041] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The various materials used and the conditions for measuring their physical properties are described below.

[0042] (A) Ga or Ga alloy A-1: Ga-In-Sn (Gallium-Indium-Tin alloy, composition (mass%): Ga / In / Sn = 62 / 25 / 13, manufactured by Kojunsei Chemical Co., Ltd., melting point: 5℃)

[0043] (B) Thermally conductive ceramic filler • B-1: Aluminum nitride (manufactured by Tokuyama Corporation, D50: 18μm) • B-2: Aluminum nitride (manufactured by Tokuyama Corporation, D50: 30μm) • B-3: Irregularly shaped diamond (manufactured by Tomei Diamond Co., Ltd., D50: 25μm) • B-4: Hexaoctahedron diamond (manufactured by Tomei Diamond Co., Ltd., D50: 28μm)

[0044] (C) Metal powder with a melting point of 900°C or higher • C-1: Chromium powder (manufactured by High Purity Chemicals Co., Ltd., particle size: 10 μm) • C-2: Chromium powder (manufactured by High Purity Chemicals Co., Ltd., particle size: <63 μm) • C-3: Nickel powder (manufactured by High Purity Chemicals Co., Ltd., particle size: 2-3 μm) • C-4: Nickel powder (manufactured by High Purity Chemicals Co., Ltd., particle size: <75 μm) • C-5: Nickel powder (Aldrich, particle size: <150 μm) ·C-6: Copper powder (manufactured by Kojundo Kagaku Co., Ltd., particle size: 1μm) ·C-7: Copper powder (manufactured by Kojundo Kagaku, particle size: <45μm) ·C-8: Copper powder (manufactured by Kojundo Kagaku Co., Ltd., particle size: <75μm) ·C-9: Silver powder (manufactured by Kojundo Kagaku Co., Ltd., particle size: 1μm) ·C-10: Silver powder (manufactured by Kojundo Kagaku Co., Ltd., particle size: <45μm) ·C-11: Silver powder (manufactured by Kojundo Kagaku Co., Ltd., particle size: <75μm) Furthermore, it has been confirmed that the particle size of all metal powders is 1 μm or larger.

[0045] <Measurement of thermal conductivity> The compositions prepared in each example and comparative example were applied to a 10 mm x 10 mm silicon chip, and another 10 mm x 10 mm silicon chip was placed on top to sandwich the composition between the two silicon chips. A sample was obtained by crushing the sample with a force of 50 N for 60 seconds using a push-pull gauge (Imada Corporation, SVH-1000N). Next, the thickness of the sample was measured using a micrometer (Mitutoyo Corporation, high-precision digital micrometer MDH-25MB). Then, the thickness of the composition alone in the sample was calculated by subtracting the previously measured thickness of the silicon chip from the thickness of the obtained sample. The thermal conductivity at 25°C was measured using the laser flash method (NETZSCH, LFA467 HyperFlash) with this sample. The value obtained by subtracting the previously measured thermal conductivity of the silicon chip was taken as the thermal conductivity of the composition.

[0046] <Evaluation of compound handling characteristics> The composition (compound) prepared in each example and comparative example was placed on a 76mm x 26mm x 1mm glass slide in an amount roughly the size of a grain of rice, and its behavior was observed when shear force was applied to stretch it. The operability of the compound was then evaluated according to the following criteria. ○: The filler does not separate and spreads as a homogeneous paste. ×: The filler has separated and partially turned into a powder, resulting in an uneven state.

[0047] [Example 1] A composition was obtained by mixing (A) 50 volume% of A-1 as Ga or a Ga alloy, (B) 48 volume% of B-1 as a thermally conductive ceramic filler, and (C) 2 volume% of C-1 as a metal powder. The evaluation results of the operability and thermal conductivity of the composition are shown in Table 1.

[0048] [Examples 2-16, Comparative Examples 1-4] A composition was obtained in the same manner as in Example 1, except that the amounts of each component were changed as shown in Tables 1 and 2. The evaluation results of the operability and thermal conductivity of the composition are shown in Tables 1 and 2.

[0049] [Table 1]

[0050] [Table 2]

[0051] Regarding the evaluation results, the compositions of Examples 1 to 16, which satisfy the requirements of the present invention, were pastes with good operability and did not separate even when shear force was applied. In contrast, the compositions of Comparative Examples 1 to 4, which do not contain metal powder with a melting point of 900°C or higher, were paste-like before shear force was applied, but when shear force was applied, the filler separated, resulting in poor operability.

[0052] Furthermore, the compositions of Comparative Examples 1 to 4 exhibited inferior thermal conductivity compared to the examples containing the same thermally conductive ceramic filler. This is thought to be because the low fluidity of the paste caused the filler to separate when preparing the thermal conductivity measurement sample, and the separated areas became the thermal resistance.

Claims

1. A composition comprising (A) Ga or a Ga alloy, (B) a thermally conductive ceramic filler, and (C) a metal powder having a melting point of 900°C or higher.

2. The composition according to claim 1, wherein the (C) metal powder having a melting point of 900°C or higher comprises transition metals belonging to the fourth and fifth periods.

3. The composition according to claim 1, characterized in that the filling rate of the (B) thermally conductive ceramic filler is 25 to 70 volume percent.

4. The composition according to claim 1, characterized in that the filling rate of the metal powder having a melting point of 900°C or higher is 1 to 20% by volume.

5. An electronic component comprising the composition according to any one of claims 1 to 4.

6. A semiconductor device comprising the composition according to any one of claims 1 to 4.

Images