JP7534693B1 - Metal and Electronic Devices - Google Patents

Abstract

[Problem] To provide a metal or the like which contains Ga and is resistant to oxidation while containing liquid metal. [Solution] A metal according to one aspect of the present invention comprises a liquid metal or liquid metal and solid metal at 35°C consisting of 2-30 mass% Sn, 0.01-2 mass% Zn, 0.01-30 mass% Bi, and the balance being Ga. A metal according to another aspect of the present invention comprises a liquid metal or liquid metal and solid metal at 35°C consisting of 1-35 mass% In, 5-20 mass% Sn, 0.01-2 mass% Zn, 0.01-30 mass% Bi, and the balance being Ga. A metal according to yet another aspect of the present invention comprises a liquid metal or liquid metal and solid metal at 35°C consisting of 0-20 mass% In, 0-6 mass% Sn, 0.1-3.5 mass% Zn, 0.1-1.0 mass% Bi, and the balance being Ga. [Selected Figure] Figure 1

Description

The present invention relates to metals and electronic devices using such metals.

There have been attempts to provide liquid metals in the past. For example, Patent Document 1 proposes providing a conductive shear-thinning gel composition that includes a eutectic gallium alloy and a gallium oxide sheet distributed as a microstructure within the gallium alloy, the mixture of the eutectic gallium alloy and gallium oxide having about 59.9% to about 99.9% eutectic gallium alloy by weight percent (wt%) and about 0.1% to about 2.0% gallium oxide by wt%.

Special Publication No. 2019-516208

Liquid metals have been attracting attention in recent years, particularly in solders and conductive adhesives, due to their high heat dissipation effect. On the other hand, metals that contain Ga-containing liquid metals, such as those disclosed in Patent Document 1, have the problem that Ga is easily oxidized, and as oxides grow while generating hydrogen, this can cause shape changes and reduce heat dissipation. In particular, Ga has a strong tendency to be selectively oxidized under high temperature and humidity conditions.

The present invention provides a metal that contains Ga and is liquid metal but is resistant to oxidation, and an electronic device that uses this metal.

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

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

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

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

[Concept 5]
In the metal according to any one of concepts 1 to 4,
The alloy may contain Bi in an amount of 1.5 mass % or less.

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

[Concept 7]
In the metal according to concept 6,
The Sn content may be 4.5 mass % or less.

[Concept 8]
In the metal according to any one of concepts 1 to 7,
The balance may further contain 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 a portion of Ga.

[Concept 9]
Metals according to any one of concepts 1 to 8 may be used as heat dissipation materials.

[Concept 10]
The electronic device according to the present invention comprises:
Metals according to any one of concepts 1 to 8 may be used as heat dissipation materials.

The present invention can provide metals that contain Ga and are liquid metals but are resistant to oxidation.

FIG. 4 is a schematic diagram for explaining a test method A. Photograph showing the initial state before being placed in an 85° C., 85% RH environment in Test Method A. Photograph showing the state of Ga-14Sn-3In after 150 hours in test method A. Photograph showing the state of Ga-14Sn-3In-0.8Bi-0.025Zn after 150 hours in test method A. Photograph showing the state of Ga-14Sn-3In-0.8Bi-1.0Zn after 150 hours in test method A. Photograph showing the state of Ga-14Sn-3In-0.8Bi-0.1Zn after 150 hours in test method A. Photograph showing the state of Ga-14Sn-3In-0.8Bi after 150 hours in test method A. Photograph showing the state of Ga-14Sn-3In-0.8Bi-0.5Zn after 150 hours in test method A. Photograph showing the state of Ga-14Sn-3In-0.8Bi-1.5Zn after 150 hours in test method A. A through-hole board which is a test board used in test method B. Photograph of the test substrate after filling with metal in test method B, viewed from the front side. 13 is an enlarged photograph of the front side of a test substrate after filling with metal in test method B. Photograph of the test substrate after filling with metal in test method B, viewed from the back. 1 is an example of an image obtained using test method B. Photographs showing the change over time for Ga-3.5Sn-5.5In-0.25Bi-1.0Zn in test method C. Photographs showing the change over time for Ga-7.5Sn-3.0In-0.5Bi-1.0Zn in test method C. Photographs showing the change over time for Ga-13Sn-3.0In-0.6Bi-0.5Zn in test method C. Photographs showing the change over time for Ga-13Sn-3.0In in test method C.

In a first aspect of this embodiment, the metal is composed of 2-30% by mass Sn, 0.01-2% by mass Zn, 0.01-30% by mass Bi, and the remainder Ga, and may be a liquid metal at 35°C, or may be an aspect that contains liquid metal and solid metal at 35°C.

In a second embodiment, the metal of this embodiment is composed of 1-35% by mass In, 5-20% by mass Sn, 0.01-2% by mass Zn, 0.01-30% by mass Bi, and the remainder Ga, and may be a liquid metal at 35°C, or may contain both liquid and solid metals at 35°C.

In the first and second aspects, the lower limit of Bi is preferably 0.03 mass%, more preferably 0.06 mass%, and even more preferably 0.1 mass% relative to the entire metal (the entire liquid metal in the case of a liquid metal, or the entire mixture in the case of a mixture of liquid metal and solid metal). If the Bi content is too high, heat dissipation performance deteriorates, so the upper limit is preferably 25 mass%, more preferably 20 mass%, even more preferably 15 mass%, and even more preferably 10 mass%. By adopting the first and second aspects, oxide growth can be more effectively suppressed even in a high-temperature and high-humidity environment for a long period of time, such as 140 to 150 hours.

The inventors have confirmed that the amount of Bi contained in the liquid metal is limited. For this reason, in each of the above two embodiments, from the viewpoint of containing Bi as a liquid and having an excellent heat dissipation effect, the upper limit of the Bi content is preferably 1.5 mass%, more preferably 1.0 mass%, and even more preferably 0.8 mass%. Furthermore, if the only consideration is to ensure that Bi is present as a liquid, an embodiment with an upper limit of 0.4 mass% can also be adopted.

Furthermore, as a third aspect, the metal of this embodiment is composed of 0-20% by mass In, 0-6% by mass Sn, 0.1-3.5% by mass Zn, 0.1-1.0% by mass Bi, and the remainder Ga, and may be a liquid metal at 35°C, or may contain liquid metal and solid metal at 35°C. When this aspect is adopted, oxide growth can be more effectively suppressed even in a high temperature and humidity environment for a fairly long time, such as 400-700 hours.

In the third embodiment, too, the upper limit of the Bi content is preferably 0.8 mass% from the viewpoint of containing Bi as a liquid and having an excellent heat dissipation effect. Also, if it is important to ensure that Bi is present as a liquid, an embodiment with an upper limit of 0.4 mass% can be adopted.

Either or both of the liquid metal and the solid metal may be an alloy. The composition of the alloy in the liquid metal may be different from that in the solid metal. However, this is not limited to such an embodiment, and the composition of the alloy in the liquid metal may be the same as that in the solid metal. The metal in this embodiment may be a Ga-based metal. The metal in this 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, a metal containing a liquid metal or a mixture of a liquid metal and a solid metal can be provided by using Ga as a base. 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 the metal can be made into a liquid state by containing Ga, the lower limit is preferably 30% by mass, more preferably 40% by mass, and even more preferably 50% by mass.

The metal of this embodiment is typically used as a heat dissipation material such as heat dissipation grease. In this embodiment, an electronic device using such a metal is also provided. As an example, in the electronic device of this embodiment, electronic components are placed on a circuit board via heat dissipation grease made of liquid metal or liquid metal and solid metal. The metal of this 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.

The metal in this embodiment may be Zn, Bi, Ga and unavoidable impurities, In, Zn, Bi, Ga and unavoidable impurities, Sn, Zn, Bi, Ga and unavoidable impurities, or In, Sn, Zn, Bi, Ga and unavoidable impurities. In this application, unavoidable impurities means impurities that are not intentionally added. The metal in this embodiment may be a eutectic metal alloy, but it does not have to be a eutectic metal alloy.

In addition, in the above embodiment, 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 in place of a portion of Ga. Note that even in the embodiment described in the closed claim of this application, unavoidable impurities are included. Inevitable impurities refer to impurities that are not intentionally included.

The applicant of the present application has filed Japanese Patent Application No. 2022-182319, and as described in the specification of the application, the inventors of the present application conducted intensive research into the problem of Ga oxides in metals containing liquid metal, and found that the oxidation of Ga can be suppressed by including Bi. Although this is merely speculation, the mechanism by which the oxidation of Ga can be suppressed by using Bi is thought to be as follows.
Bi is an element classified as an acidic oxide, and has the property of reacting with water to generate an acid. Therefore, by including Bi, an acid is generated, and the generated acid reacts with Ga to generate a hydroxide on the surface of the alloy. It is believed that the generation of such a hydroxide on the surface of the alloy can suppress the reaction between Ga and water, and thus suppress the generation of the oxide of Bi.

The inventors of the present application further conducted research and confirmed that by including Zn in addition to Bi (by adopting the first or second aspect), the generation of oxides can be suppressed even for long periods of time under high temperature and humidity conditions. They also confirmed that even a very small amount of Zn content is effective in suppressing the generation of oxides. Furthermore, they confirmed that by setting the contents of Sn, Zn, Bi, and In within a certain range (by adopting the third aspect), the growth of oxides can be more effectively suppressed even under high temperature and humidity conditions for a considerable period of time.

The tendency for oxide generation to be suppressed in hot and humid conditions is
(1) A metal consisting of 2 to 30 mass% Sn, 0.01 to 2 mass% Zn, 0.01 to 30 mass% Bi, and the balance being Ga;
(2) a metal consisting of 1 to 35 mass% In, 5 to 20 mass% Sn, 0.01 to 2 mass% Zn, 0.01 to 30 mass% Bi, and the balance being Ga, and (3) a metal consisting of 0 to 6 mass% Sn, 0.1 to 3.5 mass% Zn, 0.1 to 1.0 mass% Bi, 0 to 20 mass% In, and the balance being Ga. 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.
In the above embodiments (1) to (3), it has been confirmed that the generation of oxides tends to be suppressed even in metals that contain 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 portion of 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 each be contained in the range of 0.005 to 0.10 mass%. The lower limit of the content of any one or more elements 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 0.01 mass % and the upper limit may be 0.05 mass %.

[Aspect (1)]
In a metal consisting of Sn, Zn, Bi, Ga and inevitable impurities, or a metal containing 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 a portion of Ga, more preferable upper and lower limit values of each element will be described.

In this embodiment, the lower limit of Sn is preferably 5% by mass, and more preferably 10% by mass. The upper limit of Sn is preferably 25% by mass, and more preferably 20% by mass.

The lower limit of Zn is preferably 0.03 mass%, more preferably 0.05 mass%. From the viewpoint of suppressing oxide growth, the upper limit of Zn is preferably 1.0 mass%, more preferably 0.8 mass%. In the embodiment (1), the upper limit of Zn may be less than 0.3.

As mentioned above, the lower limit of Bi is preferably 0.03 mass%, more preferably 0.06 mass%, and even more preferably 0.1 mass%. The upper limit of Bi is preferably 25 mass%, more preferably 20 mass%, even more preferably 15 mass%, and even more preferably 10 mass%. From the viewpoint that Bi exists as a liquid, the upper limit of Bi is preferably 1.5 mass%, more preferably 1.0 mass%, and even more preferably 0.8 mass%.

[Aspect (2)]
In a metal consisting of In, Sn, Zn, Bi, Ga and inevitable impurities, or a metal containing 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 a portion of Ga, more preferable upper and lower limit values of each element will be described.

In this embodiment, the lower limit of In is preferably 2% by mass, more preferably 3% by mass. The upper limit of In is preferably 25% by mass, more preferably 20% by mass.

The lower limit of Sn is preferably 5% by mass, and more preferably 10% by mass.

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

As mentioned above, the lower limit of Bi is preferably 0.03 mass%, more preferably 0.06 mass%, and even more preferably 0.1 mass%. The upper limit of Bi is preferably 25 mass%, more preferably 20 mass%, even more preferably 15 mass%, and even more preferably 10 mass%. From the viewpoint that Bi exists as a liquid, the upper limit of Bi is preferably 1.5 mass%, more preferably 1.0 mass%, and even more preferably 0.8 mass%.

[Aspect (3)]
More preferable upper and lower limits of each element in a metal consisting of Zn, Bi, Ga and unavoidable impurities, Sn, Zn, Bi, Ga and unavoidable impurities, In, Zn, Bi, Ga and unavoidable impurities, or In, Sn, Zn, Bi, Ga and unavoidable impurities, or a metal containing 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 a portion of Ga, will be described.

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

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

The lower limit of Zn is preferably 0.6 mass%, more preferably 0.8 mass%. From the viewpoint of suppressing the growth of oxides, the upper limit of Zn is preferably 3.0 mass%, more preferably 2.5 mass%.

The lower limit of Bi is preferably 0.2% by mass. From the viewpoint that Bi exists as a liquid, the upper limit of Bi is preferably 0.8% by mass.

The heat dissipation material containing the metal of this embodiment may further contain an amine, a resin, a solvent, etc. In this case, it may contain 10 to 90 mass % of the metal of this embodiment (liquid metal or a mixture of liquid metal and solid metal), 10 to 90 mass % of the amine, 10 to 90 mass % of the resin, and 10 to 90 mass % of the solvent, totaling 100 mass %. In addition, it may be an embodiment in which the metal is 10 to 90 mass % and the remainder is an activator, or an activator and a solvent.

Amines include, for example, 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, aminomethyl, cyclohexane, 2-ethylhexylamine, dibutylamine, diisobutylamine, 1,1,3,3-tetramethylbutylamine, 1-cyclohexylethylamine, and N,N-dimethylcyclohexylamine. Examples of aromatic amines include aniline, diethylaniline, pyridine, diphenylguanidine, and ditolylguanidine. Examples of imidazoles include imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, and 1-benzyl-2-phenylimidazole.

Examples of resins include epoxy resins, rosin resins, (meth)acrylic resins, urethane resins, polyester resins, phenoxy resins, vinyl ether resins, terpene resins, modified terpene resins (e.g., aromatic modified terpene resins, hydrogenated terpene resins, hydrogenated aromatic modified terpene resins, etc.), terpene phenol resins, modified terpene phenol resins (e.g., hydrogenated terpene phenol resins, etc.), styrene resins, modified styrene resins (e.g., styrene acrylic resins, styrene maleic resins, etc.), xylene resins, modified xylene resins (e.g., phenol modified xylene resins, alkylphenol modified xylene resins, phenol modified resol type xylene resins, polyol modified xylene resins, polyoxyethylene adduct xylene resins, etc.), etc.

Examples of solvents include alcohol-based solvents, glycol ether-based solvents, terpineols, hydrocarbons, esters, water, etc.

The present embodiment will be described in detail below with examples and comparative examples. Note that the present embodiment is not limited to these examples.

[Test Method A]
1. Method for preparing test metals In a beaker, Ga was previously heated to 40° C. to make it liquid, and a predetermined amount of an additive element (an element shown in each table, other than Bi) was weighed and added (the amount added was the amount shown in each table described later), and the mixture was heated on a hot plate at 250° C. for 1 hour to prepare a master alloy.
The master alloy was weighed out in a beaker, a predetermined amount of Bi was added (the amount added was the amount shown in each table described later), and the mixture was heated on a hot plate at 250° C. for 1 hour and cooled to room temperature to prepare a test sample.

2. Evaluation method: Liquid metal was poured into a glass tube with an inner diameter of 4 mm, and the initial filling area was measured using a stereomicroscope (see Figures 1 and 2).
The glass tube was left standing in an environment of 85° C. and 85% RH for 150 hours, after which the glass tube was taken out and the areas of the corroded and liquid parts were measured using a stereomicroscope (see FIGS. 3 to 9).
The volume change rate was calculated from the measured values using the following formula. If oxides are generated, the volume change rate will be large, so a smaller value is better from the viewpoint of suppressing oxides.
Volume change rate (%) = area of liquid part after 150 hours / initial area of liquid part × 100
100% to less than 200%: Rank 1
200% to less than 300%: Rank 2
300% or more: Rank 3

The results of the examples and comparative examples are shown in the following table. In this specification, the remainder is indicated as "Bal." In addition, in each table, when the alloy is made of liquid metal, the mass percentage of the entire liquid metal is indicated, and when the alloy is made of a mixture of liquid metal and solid metal, the mass percentage of the entire mixture is indicated.

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

Tables 2 and 3 show the results for alloys containing In, Sn, Zn, Bi, and Ga. By including a certain amount of Zn and In in addition to Bi, the growth of oxides could be more effectively suppressed even in a long period of time of 150 hours, in a high temperature and humidity environment. The embodiment shown as a reference example in Tables 2 and 3 is an embodiment in Japanese Patent Application No. 2022-182319. It has been confirmed that the embodiment of the present application can more effectively suppress the growth of oxides, compared to the embodiment in Japanese Patent Application No. 2022-182319.
Furthermore, as shown in Table 2, it was confirmed that in the embodiment containing In, the surface tension can be reduced. A smaller surface tension is beneficial in that the surface area can be increased and the heat dissipation effect can be enhanced. Points marked with "-" in the surface tension indicate that they have not been measured at the present time. Note that the embodiment not containing In, as shown in Table 1, is beneficial in that costs can be reduced.

The surface tensions shown in Table 2 were measured at 25°C using the pendant drop method with a DMo-501 made by Kyowa Interface Science Co., Ltd.

[Test Method B]
1. Test Metal Preparation Method Test samples were prepared by the method described in Test Method A, “Test Metal Preparation Method.”

2. Method for Preparing Test Pieces Test pieces were prepared by filling a through-hole board shown in FIG. 10 with metal.
The test boards, which are through-hole boards, are as follows.
Material: FR4 (copper foil, no resist)
・ Plate thickness: 0.50 mm
・ Hole diameter Φ0.525mm
Number of holes: 14 x 14 = 196 holes Hole pitch: 0.90 mm
(1) The through-holes of the test board were filled with the test samples.
(2) Excess metal on the front and back surfaces was wiped off with IPA.
(3) The back side was sealed with Kapton tape to prepare a test specimen.
(4) The prepared test pieces were treated in an environment of 85°C and 85% RH (relative humidity) for 48 hours, and the growth state of the oxide was measured. Figures 11 and 12 are photographs of the test substrate after filling with metal, as seen from the front side, and Figure 13 is a photograph of the test substrate after filling with metal, as seen from the back side.

3. Evaluation method The maximum height of the oxide from the substrate surface in each hole was measured using a VK-X1000 laser microscope manufactured by KEYENCE Corporation.
The criteria are as follows (see FIG. 14):
Maximum height of oxide Rank A: Less than 250 μm Rank B: 250 μm or more and less than 500 μm Rank C: 500 μm or more and less than 750 μm Rank D: 750 μm or more and less than 1000 μm Rank E: 1000 μm or more and less than 1500 μm 0000
Rank F: 1500 μm or more and less than 1750 μm Rank G: 2000 μm or more

The results of the examples and comparative examples are shown in the table below. As can be seen from the experimental results shown in the table below, although the 48 hours was a short time compared to test method A, oxide growth was effectively suppressed for each composition. Furthermore, by increasing the Bi content, oxide growth was effectively suppressed.

Table 4 shows the results for alloys containing Sn, Zn, Bi, and Ga. It was confirmed that the inclusion of Sn, Bi, and Zn can effectively suppress the growth of oxides.

Table 5 shows the results for alloys containing In, Sn, Zn, Bi, and Ga. It was confirmed that the inclusion of Sn, Bi, In, and Zn can effectively suppress the growth of oxides.

[Test Method C]
1. Test Metal Preparation Method Test samples were prepared by the method described in Test Method A, “Test Metal Preparation Method.”

2. Evaluation method: Liquid metal was poured into a glass tube with an inner diameter of 4 mm, and the initial filling area was measured using a stereomicroscope (see Figure 15).
The glass tube was left standing in an environment of 85° C. and 85% RH for 400 hours, after which the glass tube was taken out and the areas of the corroded and liquid parts were measured using a stereomicroscope (see FIG. 15).
The volume change rate was calculated from the measured values using the following formula. If oxides are generated, the volume change rate will be large, so a smaller value is better from the viewpoint of suppressing oxides.
Volume change rate (%) = area of liquid part after 400 hours / initial area of liquid part × 100
100% to less than 200%: Rank 1
200% to less than 300%: Rank 2
300% or more: Rank 3

Test method C was performed in the same manner as test method A, except that the volume change rate was changed from "150 hours" to "400 hours."

Tables 6 and 7 show the results for alloys containing at least Zn, Bi, and Ga. By using Ga as the base material and adjusting the contents of In to 0 to 20 mass %, Sn to 0 to 6 mass %, Zn to 0.1 to 3.5 mass %, and Bi to 0.1 to 1.0 mass %, it was possible to more effectively suppress the growth of oxides even for a fairly long time of 400 hours under a high temperature and high humidity environment.

Figure 15 is a photograph showing the change over time for Ga-3.5Sn-5.5In-0.25Bi-1.0Zn, Figure 16 is a photograph showing the change over time for Ga-7.5Sn-3.0In-0.5Bi-1.0Zn in test method C, Figure 17 is a photograph showing the change over time for Ga-13Sn-3.0In-0.6Bi-0.5Zn in test method C, and Figure 18 is a photograph showing the change over time for Ga-13Sn-3.0In in test method C.

The metal consisting of 7.5% Sn, 3.0% In, 0.5% Bi, 1.0% Zn, and the balance Ga, the test results of which are shown in Figure 16, and the metal consisting of 13% Sn, 3.0% In, 0.6% Bi, 0.5% Zn, and the balance Ga, the test results of which are shown in Figure 17, are examples of the second aspect, and are able to more effectively suppress oxide growth even in a high-temperature and high-humidity environment for a long period of 140 hours. However, when viewed for a fairly long period of 400 hours, it was confirmed that oxides grow in a high-temperature and high-humidity environment. From this, it was confirmed that according to the third aspect, oxide growth can be more effectively suppressed even when viewed for a fairly long period of 400 hours. In addition, the metal consisting of 13% by mass Sn, 3.0% by mass In, and the remainder Ga, whose test results are shown in Figure 18, is a comparative example, and it was confirmed that oxides grew when placed in a high-temperature, high-humidity environment for 140 hours, and it was also confirmed that the second embodiment, whose test results are shown in Figures 16 and 17, could more effectively suppress oxide growth over a long period of 140 hours.

The above description of the embodiment, the description of the examples, and the disclosure of the drawings are merely examples for explaining the invention described in the claims, and the above description of the embodiment or the disclosure of the drawings does not limit the invention described in the claims.

Claims (10)

A metal which is liquid metal or contains liquid metal and solid metal at 35° C. and which consists of 2 to 30 mass % Sn, 0.01 to less than 0.3 mass % Zn, 0.01 to 30 mass % Bi, and the balance Ga. A metal which is liquid metal or contains liquid metal and solid metal at 35° C. and which consists of 1 to 35 mass % In, 5 to 20 mass % Sn, 0.01 to less than 0.1 mass % Zn, 0.01 to 1.5 mass % Bi, and the balance being Ga. The metal according to claim 1 , containing 1.5 mass % or less of Bi. A metal which is liquid metal or contains liquid metal and solid metal at 35° C. and which consists of 0.5 to less than 1 mass % In, 0 to 6 mass % Sn, 0.1 to 3.5 mass % Zn, 0.1 to 1.0 mass % Bi, and the balance being Ga. A metal which is liquid metal or contains liquid metal and solid metal at 35° C. and which consists of 0.5 to 20 mass % In, 0 to less than 5 mass % Sn, 0.1 to 3.5 mass % Zn, 0.1 to 1.0 mass % Bi, and the balance being Ga. A metal which is liquid metal or contains liquid metal and solid metal at 35° C. and which consists of 0 to 20 mass % In , 0.1 to less than 1.0 mass % Zn, 0.1 to 1.0 mass % Bi, and the balance being Ga. A metal which is liquid metal or contains liquid metal and solid metal at 35° C. and which consists of 0 to 6 mass % Sn, 0.1 to less than 0.3 mass % Zn, 0.1 to 1.0 mass % Bi, and the balance being Ga. 8. The metal according to claim 4, 5 or 7 , containing 4.5 mass % or less of Sn. The metal according to any one of claims 1 to 7, further comprising 0.005 to 0.10 mass% of any one or more of Ag, Sb, Cu, Fe, Al, As, Ni, Au, Ti, Cr, La, Mg, Mn, Co, Ge , Cd, Pb, P, S, and Si in place of a portion of Ga. An electronic device comprising the metal according to claim 1 as a heat dissipation material.