Metal and electronic device

Abstract

To provide a metal or the like that contains Ga and a liquid metal, and is resistant to oxidation.SOLUTION: A metal according to one embodiment of the present invention includes, at 35°C, a liquid metal or a liquid metal and a solid metal consisting of 2-30 mass% of Sn, 0.01-2 mass% of Zn, 0.01-30 mass% of Bi, and the balance of Ga. A metal according to another embodiment of the present invention includes, at 35°C, a liquid metal or a liquid metal and a solid metal consisting of 1-35 mass% of In, 5-20 mass% of Sn, 0.01-2 mass% of Zn, 0.01-30 mass% of Bi, and the balance of Ga. A metal according to yet another embodiment of the present invention includes, at 35°C, a liquid metal or a liquid metal and a solid metal consisting of 0-20 mass% of In, 0-6 mass% of Sn, 0.1-3.5 mass% of Zn, 0.1-1.0 mass% of Bi, and the balance of Ga.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a metal and an electronic device using the metal.

Background Art

[0002] Conventionally, attempts have been made to provide liquid metal. For example, in Patent Document 1, a eutectic gallium alloy and a gallium oxide sheet distributed as a microstructure in the gallium alloy are provided, and a mixture of the eutectic gallium alloy and gallium oxide has a eutectic gallium alloy of about 59.9% to about 99.9% by weight percent (wt%) and gallium oxide of about 0.1% to about 2.0% by wt%, and a conductive shear-thinning gel composition has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Since liquid metal has a high heat dissipation effect, it has recently attracted attention, especially in solders and conductive adhesives. On the other hand, in a metal containing liquid metal containing Ga as disclosed in Patent Document 1, due to the property that Ga is easily oxidized, oxides grow while generating hydrogen, resulting in problems such as shape change and reduction in heat dissipation. Especially under high temperature and high humidity, the tendency of Ga to be selectively oxidized becomes stronger.

[0005] The present invention provides a metal containing Ga and containing liquid metal, but being difficult to oxidize, and an electronic device using the metal.

Means for Solving the Problems

[0006] [Concept 1] The metal according to the present invention is It may contain liquid metal or liquid metal and solid metal at 35°C, consisting of 2 to 30% by mass of Sn, 0.01 to 2% by mass of Zn, 0.01 to 30% by mass of Bi, and the balance being Ga.

[0007] [Concept 2] The metal according to the present invention It may contain liquid metal or liquid metal and solid metal at 35°C, consisting of 1 to 35% by mass of In, 5 to 20% by mass of Sn, 0.01 to 2% by mass of Zn, 0.01 to 30% by mass of Bi, and the balance being Ga.

[0008] [Concept 3] In the metal according to Concept 1, Zn may be contained in an amount of less than 0.5% by mass.

[0009] [Concept 4] In the metal according to Concept 2, Zn may be contained in an amount of less than 1% by mass.

[0010] [Concept 5] In the metal according to any one of Concepts 1 to 4, Bi may be contained in an amount of 1.5% by mass or less.

[0011] [Concept 6] The metal according to the present invention It may contain liquid metal or liquid metal and solid metal at 35°C, consisting of 0 to 20% by mass of In, 0 to 6% by mass of Sn, 0.1 to 3.5% by mass of Zn, 0.1 to 1.0% by mass of Bi, and the balance being Ga.

[0012] [Concept 7] In the metal according to Concept 6, Sn may be contained in an amount of 4.5% by mass or less.

[0013] [Concept 8] In the metal according to any one of Concepts 1 to 7, The remainder may further contain any one or more of Ag, Sb, Cu, Fe, Al, As, Ni, Au, Ti, Cr, La, Mg, Mn, Co, Ge, Ga, Cd, Pb, P, S, and Si instead of some Ga.

[0014] [Concept 9] The metal according to any one of Concepts 1 to 8 may be used as a heat dissipation material.

[0015] [Concept 10] In the electronic device according to the present invention, the metal according to any one of Concepts 1 to 8 may be used as a heat dissipation material.

Advantages of the Invention

[0016] According to the present invention, it is possible to provide a metal that contains Ga, contains liquid metal, and is difficult to oxidize.

Brief Description of the Drawings

[0017]

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Embodiments for Carrying Out the Invention

[0018] As a first aspect of the present embodiment, the metal may consist of 2 to 30% by mass of Sn, 0.01 to 2% by mass of Zn, 0.01 to 30% by mass of Bi, and the balance being Ga, and may be a liquid metal at 35°C, or may be a state containing a liquid metal and a solid metal at 35°C.

[0019] As a second aspect, the metal of the present embodiment comprises 1 to 35% by mass of In, 5 to 20% by mass of Sn, 0.01 to 2% by mass of Zn, 0.01 to 30% by mass of Bi, and the balance being Ga, and may be a liquid metal at 35°C, or may be a form containing a liquid metal and a solid metal at 35°C.

[0020] In the first and second aspects, for the entire metal (the entire liquid metal when it consists of a liquid metal, and the entire mixture when it is a mixture of a liquid metal and a solid metal), the lower limit value of Bi is preferably 0.03% by mass, more preferably 0.06% by mass, and even more preferably 0.1% by mass. Since the heat dissipation property deteriorates if the content of Bi is too high, the upper limit value is preferably 25% by mass, more preferably 20% by mass, even more preferably 15% by mass, and even more preferably 10% by mass. By adopting the first and second aspects, the growth of oxides can be more effectively suppressed even in an environment of high temperature and high humidity for a long time such as 140 to 150 hours.

[0021] In addition, as the inventors have confirmed, the amount of Bi contained in the liquid metal is limited. Therefore, in each of the above two aspects, from the viewpoint that Bi is contained as a liquid and it has excellent heat dissipation effect, the upper limit of the content of Bi is preferably 1.5% by mass, more preferably 1.0% by mass, and even more preferably 0.8% by mass. Also, if only emphasizing that Bi exists as a liquid more surely, an aspect with an upper limit value of 0.4% by mass can also be adopted.

[0022] Furthermore, as a third aspect, the metal of the present embodiment comprises 0 to 20% by mass of In, 0 to 6% by mass of Sn, 0.1 to 3.5% by mass of Zn, 0.1 to 1.0% by mass of Bi, and the balance being Ga, and may be a liquid metal at 35°C, or may be a form containing a liquid metal and a solid metal at 35°C. When this aspect is adopted, the growth of oxides can be more effectively suppressed even in an environment of high temperature and high humidity for a considerably long time such as 400 to 700 hours.

[0023] Also in the third aspect, Bi is contained as a liquid, and from the viewpoint of excellent heat dissipation effect, the upper limit of the Bi content is preferably 0.8% by mass. Further, if only emphasizing that Bi surely exists as a liquid, an embodiment with an upper limit value of 0.4% by mass can also be adopted.

[0024] Each or one of the liquid metal and the solid metal may be an alloy. The composition of the alloy in the liquid metal and the composition of the alloy in the solid metal may be different. However, it is not limited to such an embodiment, and the composition of the alloy in the liquid metal and the composition of the alloy in the solid metal may be the same composition. The metal of the present embodiment may be a Ga-based metal. The metal of the present embodiment preferably contains a liquid metal or a liquid metal and a solid metal at 30°C. Since the melting point of Ga is about 30°C, by using Ga as a matrix, a metal containing a liquid metal or a mixture of a liquid metal and a solid metal can be provided. Ga may be contained in an amount of 25% by mass or more and less than 100% by mass. Ga is a metal with a high heat dissipation effect, and since Ga can be made into a liquid state by containing it, its lower limit is preferably 30% by mass, more preferably 40% by mass, and even more preferably 50% by mass.

[0025] The metal of the present embodiment is typically used as a heat dissipation material such as heat dissipation grease. In the present embodiment, an electronic device using such a metal is also provided. As an example, in the electronic device of the present embodiment, an electronic component is mounted on a circuit board via a heat dissipation grease made of a liquid metal or a liquid metal and a solid metal. The metal of the present embodiment may be printed on a circuit board such as a printed wiring board using a squeegee, may be printed using an inkjet printer, or may be applied using a dispensing device.

[0026] The metal of this embodiment may be composed of Zn, Bi, Ga and inevitable impurities, In, Zn, Bi, Ga and inevitable impurities, Sn, Zn, Bi, Ga and inevitable impurities, or In, Sn, Zn, Bi, Ga and inevitable impurities. The inevitable impurities in this application mean impurities that are not intentionally added. The metal of this embodiment may be a eutectic metal alloy, but it may not be a eutectic metal alloy.

[0027] Also, in the above aspect, instead of some Ga, any one or more of Ag, Sb, Cu, Fe, Al, As, Ni, Au, Ti, Cr, La, Mg, Mn, Co, Ge, Ga, Cd, Pb, P, S and Si may be included. Note that even in the aspect described in the closed claims of this application, inevitable impurities are included. Inevitable impurities mean impurities that are not intentionally contained.

[0028] The applicant of this application has filed Japanese Patent Application No. 2022-182319. As described in the specification of the application, when the inventors of this application conducted intensive research on the problem of oxides of Ga in metals containing liquid metal, they found that the oxidation of Ga can be suppressed by containing Bi. Although it is only speculation, the mechanism by which the oxidation of Ga can be suppressed by using Bi is considered as follows. Bi is an element classified as an acidic oxide and has the property of reacting with water to produce an acid. Therefore, by containing Bi, an acid is generated, and the generated acid reacts with Ga to produce a hydroxide on the surface of the alloy. When such a hydroxide is generated on the surface of the alloy, the reaction between Ga and water can be suppressed, and it is considered that the formation of Bi oxide can be suppressed.

[0029] As the inventors of the present application further conducted research, it was confirmed that by containing Zn in addition to Bi (by adopting the first or second aspect), the generation of oxides can be suppressed even in a situation of high temperature and high humidity for a long time. Also, it was confirmed that even if the content of Zn is quite small, there is an effect of suppressing the generation of oxides. Furthermore, by setting the contents of Sn, Zn, Bi, and In within a certain range (by adopting the third aspect), it was also confirmed that the growth of oxides can be more effectively suppressed even in an environment of high temperature and high humidity for a considerably long time.

[0030] The tendency that the generation of oxides is suppressed in a situation of high temperature and high humidity is (1) A metal consisting of 2 to 30% by mass of Sn, 0.01 to 2% by mass of Zn, 0.01 to 30% by mass of Bi, and the balance being Ga, (2) A metal consisting of 1 to 35% by mass of In, 5 to 20% by mass of Sn, 0.01 to 2% by mass of Zn, 0.01 to 30% by mass of Bi, and the balance being Ga, and (3) A metal consisting of 0 to 6% by mass of Sn, 0.1 to 3.5% by mass of Zn, 0.1 to 1.0% by mass of Bi, 0 to 20% by mass of In, and the balance being Ga has been confirmed. Here, (1) corresponds to the first aspect described above, (2) corresponds to the second aspect described above, and (3) corresponds to the third aspect described above. Also, in the aspects (1) to (3) above, even a metal containing any one or more of Ag, Sb, Cu, Fe, Al, As, Ni, Au, Ti, Cr, La, Mg, Mn, Co, Ge, Ga, Cd, Pb, P, S, and Si instead of a part of Ga has been confirmed to have a tendency of suppressing the generation of oxides. Any one or more of the elements Ag, Sb, Cu, Fe, Al, As, Ni, Au, Ti, Cr, La, Mg, Mn, Co, Ge, Ga, Cd, Pb, P, S, and Si may each be contained in the range of 0.005 to 0.10% by mass. The lower limit value of the content of any one or more of the elements Ag, Sb, Cu, Fe, Al, As, Ni, Au, Ti, Cr, La, Mg, Mn, Co, Ge, Ga, Cd, Pb, P, S, and Si may be 0.01% by mass, and the upper limit value may be 0.05% by mass.

[0031] [Aspect (1)] Describe the more preferable upper and lower limits of each element in a metal composed of Sn, Zn, Bi, Ga, and inevitable impurities, or a metal containing any one or more of Ag, Sb, Cu, Fe, Al, As, Ni, Au, Ti, Cr, La, Mg, Mn, Co, Ge, Ga, Cd, Pb, P, S, and Si in place of some Ga.

[0032] In this aspect, the lower limit of Sn is preferably 5% by mass, more preferably 10% by mass. The upper limit of Sn is preferably 25% by mass, more preferably 20% by mass.

[0033] The lower limit of Zn is preferably 0.03% by mass, more preferably 0.05% by mass. From the viewpoint of suppressing the growth of oxides, the upper limit of Zn is preferably 1.0% by mass, more preferably 0.8% by mass. In aspect (1), the upper limit of Zn may be less than 0.3.

[0034] As described above, the lower limit of Bi is preferably 0.03% by mass, more preferably 0.06% by mass, and even more preferably 0.1% by mass. The upper limit of Bi is preferably 25% by mass, more preferably 20% by mass, even more preferably 15% by mass, and even more preferably 10% by mass. From the viewpoint of Bi existing as a liquid, the upper limit of Bi is preferably 1.5% by mass, more preferably 1.0% by mass, and even more preferably 0.8% by mass.

[0035] [Aspect (2)] Describe the more preferable upper and lower limits of each element in a metal composed of In, Sn, Zn, Bi, Ga, and inevitable impurities, or a metal containing any one or more of Ag, Sb, Cu, Fe, Al, As, Ni, Au, Ti, Cr, La, Mg, Mn, Co, Ge, Ga, Cd, Pb, P, S, and Si in place of some Ga.

[0036] In this aspect, the lower limit value of In is preferably 2% by mass, more preferably 3% by mass. The upper limit value of In is preferably 25% by mass, more preferably 20% by mass.

[0037] The lower limit value of Sn is preferably 5% by mass, more preferably 10% by mass.

[0038] The lower limit value of Zn is preferably 0.03% by mass, more preferably 0.05% by mass. From the viewpoint of suppressing the growth of the oxide, the upper limit value of Zn is preferably 1.0% by mass, more preferably 0.8% by mass. In the aspect of (2), the upper limit value of Zn may be less than 0.1.

[0039] As described above, the lower limit value of Bi is preferably 0.03% by mass, more preferably 0.06% by mass, and even more preferably 0.1% by mass. The upper limit value of Bi is preferably 25% by mass, more preferably 20% by mass, even more preferably 15% by mass, and even more preferably 10% by mass. From the viewpoint of Bi existing as a liquid, the upper limit value of Bi is preferably 1.5% by mass, more preferably 1.0% by mass, and even more preferably 0.8% by mass.

[0040] [Aspect of (3)] For the more preferable upper limit and lower limit values of each element in a metal composed of Zn, Bi, Ga and inevitable impurities, Sn, Zn, Bi, Ga and inevitable impurities, In, Zn, Bi, Ga and inevitable impurities, or In, Sn, Zn, Bi, Ga and inevitable impurities, or a metal containing any one or more of Ag, Sb, Cu, Fe, Al, As, Ni, Au, Ti, Cr, La, Mg, Mn, Co, Ge, Ga, Cd, Pb, P, S and Si in place of some Ga, an explanation will be given.

[0041] As exemplified by Zn, Bi, Ga, and inevitable impurities, and Sn, Zn, Bi, Ga, and inevitable impurities, in this embodiment, In may not be contained and may be 0% by mass. The lower limit of In is preferably 3% by mass, and more preferably 5% by mass.

[0042] As exemplified by Zn, Bi, Ga, and inevitable impurities, and In, Zn, Bi, Ga, and inevitable impurities, in this embodiment, Sn may not be contained and may be 0% by mass. The upper limit of Sn may be less than 5.0% by mass, preferably 4.5% by mass, and more preferably 4.0% by mass.

[0043] The lower limit of Zn is preferably 0.6% by mass, and more preferably 0.8% by mass. From the viewpoint of suppressing the growth of the oxide, the upper limit of Zn is preferably 3.0% by mass, and more preferably 2.5% by mass.

[0044] The lower limit of Bi is preferably 0.2% by mass. From the viewpoint of Bi existing as a liquid, the upper limit of Bi is preferably 0.8% by mass.

[0045] The heat dissipation material containing the metal of this embodiment may further contain an amine, a resin, a solvent, etc. In this case, 10 to 90% by mass of the metal (liquid metal or a mixture of liquid metal and solid metal) according to this embodiment, 10 to 90% by mass of the amine, 10 to 90% by mass of the resin, and 10 to 90% by mass of the solvent may be contained so that the total is 100% by mass. Also, with respect to 10 to 90% by mass of the metal, the balance may be in a form of an activator, or an activator and a solvent.

[0046] Examples of the amine include linear, branched and / or cyclic saturated or unsaturated aliphatic amines, aromatic amines, and imidazoles. Examples of the aliphatic amine include methylamine, ethylamine, dimethylamine, 1-aminopropane, isopropylamine, trimethylamine, n-ethylmethylamine, allylamine, n-butylamine, diethylamine, sec-butylamine, tert-butylamine, N,N-dimethylethylamine, isobutylamine, pyrrolidine, 3-pyrroline, n-pentylamine, dimethylaminopropane, 1-aminohexane, triethylamine, diisopropylamine, dipropylamine, hexamethyleneimine, 1-methylpiperidine, 2-methylpiperidine, 4-methylpiperidine, cyclohexylamine, diallylamine, n-octylamine, aminomethylcyclohexane, 2-ethylhexylamine, dibutylamine, diisobutylamine, 1,1,3,3-tetramethylbutylamine, 1-cyclohexylethylamine, and N,N-dimethylcyclohexylamine. Examples of the aromatic amine include aniline, diethylaniline, pyridine, diphenylguanidine, and ditolylguanidine. Examples of the imidazoles include imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, and 1-benzyl-2-phenylimidazole.

[0047] Examples of the resin include, for example, epoxy resin, rosin-based resin, (meth)acrylic-based resin, urethane-based resin, polyester-based resin, phenoxy resin, vinyl ether-based resin, terpene resin, modified terpene resin (for example, aromatic-modified terpene resin, hydrogenated terpene resin, hydrogenated aromatic-modified terpene resin, etc.), terpene phenol resin, modified terpene phenol resin (for example, hydrogenated terpene phenol resin, etc.), styrene resin, modified styrene resin (for example, styrene acrylic resin, styrene maleic resin, etc.), xylene resin, modified xylene resin (for example, phenol-modified xylene resin, alkylphenol-modified xylene resin, phenol-modified resol-type xylene resin, polyol-modified xylene resin, polyoxyethylene-added xylene resin, etc.), and the like.

[0048] Examples of the solvent include, for example, alcohol-based solvents, glycol ether-based solvents, terpineols, hydrocarbons, esters, water, and the like.

Examples

[0049] Hereinafter, the present embodiment will be described in detail with reference to Examples and Comparative Examples. Note that the present embodiment is not limited to these examples.

[0050] [Test Method A] 1. Method for preparing test metal Into a beaker, a predetermined amount of additive elements (elements shown in each table, excluding Bi) was weighed and added to Ga, which had been preheated to 40°C and made liquid (the added amount is the amount shown in each table described later), and heated on a 250°C hot plate for 1 hour to prepare a master alloy. The master alloy was weighed into a beaker, a predetermined amount of Bi was added (the added amount is the amount shown in each table described later), heated on a 250°C hot plate for 1 hour, and cooled to room temperature to obtain a test sample.

[0051] 2. Judgment method · Liquid metal was put into a glass tube with an inner diameter of 4 mm, and the initial filling area was measured with a stereomicroscope (see FIGS. 1 and 2). · The glass tube was left standing in an environment of 85°C and 85% RH. After 150 hours had elapsed, the glass tube was taken out, and the areas of the corroded part and the liquid part were measured using a stereomicroscope (see Figures 3 to 9). · From the measured values, the volume change rate was calculated using the following formula. When oxides are generated, the volume change rate increases. Therefore, from the perspective of being able to suppress oxides, the smaller the value, the better. Volume change rate (%) = Area of the liquid part after 150 hours / Area of the initial liquid part × 100 100% or more and less than 200%: Rank 1 200% or more and less than 300%: Rank 2 300% or more: Rank 3

[0052] The results of the examples and comparative examples are shown in the following table. In this specification, the remainder is shown as "Bal". Also, in each table, when the alloy consists of a liquid metal, the mass % in the entire liquid metal is shown, and when it consists of a mixture of a liquid metal and a solid metal, the mass % in the entire mixture is shown.

[0053] Table 1 shows the results for alloys containing Sn, Zn, Bi, and Ga. By containing a certain amount of Zn in addition to Bi, the growth of oxides could be more effectively suppressed even in a high-temperature and high-humidity environment for a long time of 150 hours. What is shown as a reference example is the embodiment that is an example in Japanese Patent Application No. 2022-182319. It has been confirmed that the embodiment of the example can more effectively suppress the growth of oxides compared to the embodiment that is an example in Japanese Patent Application No. 2022-182319.

Table 1

[0054] Tables 2 and 3 show the results for alloys containing In, Sn, Zn, Bi, and Ga. By adding a certain amount of Zn and In in addition to Bi, the growth of oxides could be more effectively suppressed even in a high-temperature and high-humidity environment for a long time of 150 hours. What is shown as a reference example in Tables 2 and 3 is the embodiment that is an example in Japanese Patent Application No. 2022-182319. Even when compared with the embodiment that is an example in Japanese Patent Application No. 2022-182319, it has been confirmed that in the embodiment of the present application, the growth of oxides can be more effectively suppressed. Also, as shown in Table 2, it was confirmed that in the embodiment containing In, the surface tension could be reduced. When the surface tension is reduced, it is beneficial in that the surface area can be increased and the heat dissipation effect can be enhanced. The places indicated by "-" in the surface tension indicate that they have not been measured at the present time. In addition, in the embodiment shown in Table 1 that does not contain In, it is beneficial in that the cost can be suppressed.

Table 2

[0055]

Table 3

[0056] Regarding the surface tension shown in Table 2, it was measured at a temperature of 25°C using the pendant drop method with DMo-501 manufactured by Kyowa Interface Science Co., Ltd.

[0057] [Test Method B] 1. Method for fabricating test metal Test samples were prepared by the method described in the "Method for fabricating test metal" of Test Method A.

[0058] 2. Method for fabricating test piece The through-hole substrate shown in Fig. 10 was filled with metal to obtain a test piece. The test substrate made of a through-hole substrate is as follows. · Material FR4 (without copper foil and resist) · Board thickness: 0.50 mm · Hole diameter: Φ0.525 mm · Number of holes: 14×14 = 196 · Hole pitch: 0.90 mm (1) The test holes of the test substrate were filled with test samples. (2) Excess metal on the front and back surfaces was wiped off with IPA. (3) The back surface was sealed with Kapton tape to make a test piece. (4) The prepared test piece was treated in an environment of 85°C and 85% RH (relative humidity) for 48 hours, and the growth state of oxides was measured. Figures 11 and 12 are photos of the test substrate after filling with metal seen from the front side, and Figure 13 is a photo of the test substrate after filling with metal seen from the back side.

[0059] 3. Judgment method The maximum height of oxides from the substrate surface of each hole was measured. As the measuring instrument, the VK-X1000 laser microscope manufactured by KEYENCE was used. The judgment criteria are as follows (see Figure 14). Maximum height of oxides Grade A: Less than 250 μm Grade B: 250 μm or more and less than 500 μm Grade C: 500 μm or more and less than 750 μm Grade D: 750 μm or more and less than 1000 μm Grade E: 1000 μm or more and less than 1500 μm Grade F: 1500 μm or more and less than 1750 μm Grade G: 2000 μm or more

[0060] The results of the examples and comparative examples are shown in the following table. As can be understood from the experimental results shown in the following table, although it is a shorter time compared to test method A of 48 hours, the growth of oxides could be effectively suppressed in each composition. Also, by increasing the Bi content, the growth of oxides could be effectively suppressed.

[0061] Table 4 shows the results for alloys containing Sn, Zn, Bi, and Ga. It was confirmed that the growth of oxides can be effectively suppressed by adding Sn, Bi, and Zn.

Table 4

[0062] Table 5 shows the results for alloys containing In, Sn, Zn, Bi, and Ga. It was confirmed that the growth of oxides can be effectively suppressed by adding Sn, Bi, In, and Zn.

Table 5

[0063] [Test method C] 1. Method for preparing test metal Test samples were prepared by the method described in the "Method for preparing test metal" of Test method A.

[0064] 2. Judgment method · Liquid metal was put into a glass tube with an inner diameter of 4 mm, and the initial filling area was measured with a stereomicroscope (see Fig. 15). · The glass tube was left standing in an environment of 85°C and 85% RH. After 400 hours, the glass tube was taken out, and the areas of the corroded part and the liquid part were measured with a stereomicroscope (see Fig. 15). · From the measured values, the volume change rate was calculated using the following formula. When oxides are generated, the volume change rate increases. Therefore, a smaller value is better from the perspective of suppressing oxides. Volume change rate (%) = Area of the liquid part after 400 hours / Area of the initial liquid part × 100 100% or more and less than 200%: Rank 1 200% or more and less than 300%: Rank 2 300% or more: Rank 3

[0065] Test method C was carried out in the same manner as Test method A, except that "150 hours" was changed to "400 hours" for the volume change rate.

[0066] Tables 6 and 7 show the results for alloys containing at least Zn, Bi, and Ga. By setting the content to 0 to 20% by mass of In, 0 to 6% by mass of Sn, 0.1 to 3.5% by mass of Zn, and 0.1 to 1.0% by mass of Bi while using Ga as the matrix, the growth of oxides could be more effectively suppressed even in a high-temperature and high-humidity environment for a fairly long time of 400 hours. [Table 6]

[0067] [Table 7]

[0068] Figure 15 is a photograph showing the change patterns at each time for Ga-3.5Sn-5.5In-0.25Bi-1.0Zn, Figure 16 is a photograph showing the change patterns at each time for Ga-7.5Sn-3.0In-0.5Bi-1.0Zn in Test Method C, Figure 17 is a photograph showing the change patterns at each time for Ga-13Sn-3.0In-0.6Bi-0.5Zn in Test Method C, and Figure 18 is a photograph showing the change patterns at each time for Ga-13Sn-3.0In in Test Method C.

[0069] The metal consisting of 7.5% by mass of Sn, 3.0% by mass of In, 0.5% by mass of Bi, 1.0% by mass of Zn, and the balance being Ga, whose test results are shown in Fig. 16, and the metal consisting of 13% by mass of Sn, 3.0% by mass of In, 0.6% by mass of Bi, 0.5% by mass of Zn, and the balance being Ga, whose test results are shown in Fig. 17, fall under the examples of the second aspect. In the case of a long time of 140 hours, even in a high-temperature and high-humidity environment, the growth of the oxide can be more effectively suppressed. However, when looking at a considerably long time of 400 hours, it was confirmed that the oxide grows in a high-temperature and high-humidity environment. From this, according to the third aspect, it was confirmed that even when looking at a considerably long time of 400 hours, the growth of the oxide can be more effectively suppressed. Incidentally, the metal consisting of 13% by mass of Sn, 3.0% by mass of In, and the balance being Ga, whose test results are shown in Fig. 18, is a comparative example. It was confirmed that when placed in a high-temperature and high-humidity environment for 140 hours, the oxide grows. It was also confirmed that in the second aspect shown in Figs. 16 and 17, the growth of the oxide can be more effectively suppressed even in a long time of 140 hours.

[0070] The description of the above-described embodiments, the description of the examples, and the disclosure of the drawings are merely examples for explaining the invention described in the claims, and the invention described in the claims is not limited by the description of the above-described embodiments or the disclosure of the drawings.

Claims

1. A metal containing 2 to 30% by mass of Sn, 0.01 to 2% by mass of Zn, 0.01 to 30% by mass of Bi, and the balance being Ga, which is a liquid metal or a metal containing a liquid metal and a solid metal at 35°C.

2. A metal containing 1 to 35% by mass of In, 5 to 20% by mass of Sn, 0.01 to 2% by mass of Zn, 0.01 to 30% by mass of Bi, and the balance being Ga, which is a liquid metal or a metal containing a liquid metal and a solid metal at 35°C.

3. The metal according to claim 1, containing less than 0.5% by mass of Zn.

4. The metal according to claim 2, containing less than 1% by mass of Zn.

5. The metal according to claim 1 or 2, containing 1.5% by mass or less of Bi.

6. A metal containing 0 to 20% by mass of In, 0 to 6% by mass of Sn, 0.1 to 3.5% by mass of Zn, 0.1 to 1.0% by mass of Bi, and the balance being Ga, which is a liquid metal or a metal containing a liquid metal and a solid metal at 35°C.

7. The metal according to claim 6, containing 4.5% by mass or less of Sn.

8. The metal according to any one of claims 1 to 3, 6, and 7, wherein the balance further contains any one or more of Ag, Sb, Cu, Fe, Al, As, Ni, Au, Ti, Cr, La, Mg, Mn, Co, Ge, Ga, Cd, Pb, P, S, and Si instead of a part of Ga.

9. The metal according to any one of claims 1 to 3, 6, and 7, which is used as a heat dissipation material.

10. An electronic device in which the metal according to any one of claims 1 to 3, 6, and 7 is used as a heat dissipation material.

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