Tin balls and method for producing tin balls

Abstract

Provided is a method for producing tin balls, the method comprising: a step for dropping molten metal tin into a cooling liquid medium; and a step whereby solid tin balls are formed as a result of the metal tin droplets being cooled while falling through the cooling liquid medium. Also provided are tin balls with excellent sphericity and diameters greater than approximately 1 millimeter by virtue of being tin balls with diameters in the range from 1 mm to 5 mm.

Description

Tin balls and manufacturing method thereof

[0001] The present invention relates to a tin ball with excellent sphericity and a method for producing the same.

[0002] The production of metal spheres on an industrial scale is an extremely important basic technology, and therefore, techniques for producing metal spheres on an industrial scale have been developed.

[0003] A common method for manufacturing metal balls is by mechanical processing such as pressing and polishing. However, because this involves machining, it is a method suitable for hard metal materials such as high-carbon chromium bearing steel and stainless steel. On the other hand, soft metal materials such as tin, lead, and their alloys (solder) are not suitable for mechanical processing such as polishing, so metal balls are manufactured by casting.

[0004] A classic example of the production of metal balls using soft metal materials is the production of shotgun shells. This method involves dropping molten lead from a high place (e.g., 50 meters or more) and collecting it in a water tank, and it was a large-scale method that required the construction of a tower for production. Of course, the lead balls obtained vary widely, and it is not a method intended to control purity or sphericity.

[0005] Patent Document 1 (JP 11-221662 A) discloses a technique for producing solder balls by dropping molten solder into soybean oil. However, Patent Document 1 does not mention the size, sphericity, or purity of the obtained solder balls, and discloses a classic technique that simply requires obtaining solder in a ball shape.

[0006] Patent Document 2 (Japanese Patent Laid-Open Publication No. 54-085171) discloses that metal spheres are obtained by spraying molten solder alloy metal from a nozzle into silicone oil while rotating a rotating plate with cutting holes. However, the size of the obtained metal spheres is 1 mm in diameter, and no technology is disclosed for obtaining metal spheres larger than this.

[0007] Patent Document 3 (Japanese Patent Laid-Open Publication No. 55-158875) discloses that iron balls are obtained by dropping droplets of molten iron into water. However, with this technique, the crack rate increases sharply when the diameter of the iron ball exceeds 1 mm, and for example, the crack rate reaches 70% when the diameter is 8 mm. Furthermore, there is no description of the sphericity or purity of the obtained iron balls.

[0008] Patent Document 4 (JP 2001-226705 A) discloses a technique for producing microscopic metal spheres with a diameter of approximately 400 μm by ejecting molten solder into a chamber filled with nitrogen gas mixed with hydrogen gas while vibrating the molten solder with a piezoelectric element. The microscopic metal spheres obtained by this technique are small, with a diameter of approximately 400 μm, and there is a large variation in diameter and sphericity.

[0009] Thus, when forming particles by melting a soft metal such as tin, there has been no suitable technique to date for obtaining particles having an average particle diameter of more than 1 mm and excellent spherical shape accuracy (sphericity), and such a technique is desired.

[0010] Japanese Patent Laid-Open No. 11-221662 Japanese Patent Laid-Open No. 54-085171 Japanese Patent Laid-Open No. 55-158875 Japanese Patent Laid-Open No. 2001-226705

[0011] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a tin ball having a diameter greater than about 1 millimeter and excellent sphericity.

[0012] As a result of extensive research, the present inventors have found that the above object can be achieved by the means described below, and have arrived at the present invention.

[0013] Therefore, the present invention includes the following (1): (1) A method for producing tin balls, comprising the steps of: dropping molten tin metal into a liquid cooling medium; and cooling the tin metal droplets as they fall through the liquid cooling medium to form solid tin balls.

[0014] According to the present invention, high purity tin spheres having diameters greater than about 1 millimeter and excellent sphericity can be obtained.

[0015] FIG. 1 is an explanatory diagram showing an overview of the manufacturing apparatus (tin ball manufacturing apparatus) used to manufacture the tin ball of Example 1. FIG. 2 is an image illustrating the appearance of the tin ball of Example 1 (Sample 1) obtained in Example 1. FIG. 3 is an image illustrating the appearance of the tin ball of Example 2 (Sample 2) obtained in Example 2. FIG. 4 is an image illustrating the appearance of the tin ball of Comparative Example 1 (Sample 3) obtained in Example 3. FIG. 5 is an image illustrating the appearance of the tin ball of Comparative Example 2 (Sample 4) obtained in Example 4.

[0016] The present invention will be described in detail below with reference to specific embodiments, but the present invention is not limited to the specific embodiments disclosed below.

[0017] [Method for manufacturing tin balls] The method for manufacturing tin balls according to the present invention is a method for manufacturing tin balls, which includes the steps of: dropping molten tin metal into a liquid cooling medium; and cooling the droplets of tin metal as they fall through the liquid cooling medium, thereby forming solid tin balls.

[0018] [Metallic tin molten metal] Any known means can be used to heat and melt metallic tin to form a molten metallic tin. For example, metallic tin can be heated and melted by radiant heating or induction heating to prepare a molten metallic tin.

[0019] In a preferred embodiment, the raw material metallic tin used to prepare the molten metal of metallic tin can be any metallic tin that can be heated and melted to form a molten metal, and is preferably high-purity metallic tin. The high-purity metallic tin that can be used as a raw material has a tin purity of, for example, 99% by mass or more, preferably 99.9% by mass or more, preferably 99.99% by mass or more, preferably 99.995% by mass or more, preferably 99.999% by mass or more, preferably 99.9995% by mass or more, preferably 99.9996% by mass or more, preferably 99.9997% by mass or more, preferably 99.9998% by mass or more, and preferably 99.9999% by mass or more.

[0020] [Liquid Cooling Medium] In a preferred embodiment, any liquid cooling medium that is stable at temperatures higher than the melting point of metallic tin can be suitably used. More specifically, a liquid medium that does not have a boiling point or flash point at temperatures below the melting point of metallic tin can be suitably used.

[0021] In a preferred embodiment, the boiling point of the cooling liquid medium can be, for example, 231.9° C. or higher, preferably 240° C. or higher, preferably 250° C. or higher, preferably 260° C. or higher, preferably 270° C. or higher, preferably 280° C. or higher, preferably 290° C. or higher, preferably 300° C. or higher, or preferably 310° C. In a preferred embodiment, a particularly preferred cooling liquid medium is one that has no boiling point.

[0022] In a preferred embodiment, the flash point temperature of the cooling liquid medium can be, for example, 231.9°C or higher, preferably 240°C or higher, preferably 250°C or higher, preferably 260°C or higher, preferably 270°C or higher, or preferably 280°C or higher.

[0023] In a preferred embodiment, the liquid cooling medium may be selected from the group consisting of mineral oil, vegetable oil, liquid paraffin, engine oil, and silicone oil, preferably selected from the group consisting of lubricating oil and silicone oil, and particularly preferably silicone oil.

[0024] [Dripping] In a preferred embodiment, the means for introducing the molten metal tin into the liquid cooling medium is not particularly limited as long as it is dripping, and any known means can be used, such as gravity dripping and power dripping, preferably natural dripping and discharge by a pump, and particularly preferably natural dripping by gravity.

[0025] [Formation of solid tin spheres] In a preferred embodiment, molten tin metal is dropped into a liquid cooling medium, and then cooled while falling through the liquid cooling medium to form solid tin spheres. The drop is due to gravity, and it is preferable to set the height of the liquid cooling medium so that the molten tin can fall a distance sufficient to form the solid tin spheres.

[0026] [Falling Distance] In a preferred embodiment, the falling distance of the metallic tin droplets in the liquid cooling medium can be, for example, 500 mm or more, preferably 600 mm or more, preferably 700 mm or more, preferably 800 mm or more, preferably 900 mm or more, or 1000 mm or more, 1100 mm or more, 1200 mm or more, 1300 mm or more, or 1400 mm or more.

[0027] In a preferred embodiment, the distance that the metallic tin droplets fall within the liquid cooling medium has no particular upper limit from the viewpoint of sufficient cooling, but can be, for example, 3000 mm or less, 2500 mm or less, 2000 mm or less, 1800 mm or less, 1600 mm or less, 1500 mm or less, or 1400 mm or less.

[0028] In a preferred embodiment, the distance that the metallic tin droplets fall within the liquid cooling medium can be in the range of, for example, 500 to 3000 mm, preferably 600 to 3000 mm, preferably 600 to 2500 mm, preferably 600 to 2000 mm, preferably 600 to 1800 mm, preferably 600 to 1600 mm, preferably 600 to 1500 mm, preferably 700 to 1500 mm, or preferably 800 to 1500 mm.

[0029] [Temperature of Liquid Cooling Medium] In a preferred embodiment, the temperature of the liquid cooling medium at the position where the falling of metallic tin droplets starts can be set to, for example, a range of 232 to 350°C, preferably a range of 232 to 330°C, or a range of 232 to 310°C, preferably a range of 232 to 290°C.

[0030] In a preferred embodiment, the temperature of the cooling liquid medium at the position where the falling of the metallic tin droplets ends can be, for example, 100°C or less, preferably 80°C or less, preferably 50°C or less, and can be, for example, in the range of 100 to -20°C, or 80 to -20°C, preferably 60 to -20°C, or 50 to 0°C, preferably 40 to 0°C, preferably 40 to 10°C, preferably 40 to 15°C, preferably 40 to 20°C.

[0031] In a preferred embodiment, the temperature of the cooling liquid medium at the position where the falling of the metallic tin droplets ends can be a temperature near the room temperature of the location where the manufacturing apparatus is installed, and can be, for example, within a range of +30°C to -30°C from the room temperature of the location where the manufacturing apparatus is installed, preferably within a range of +20°C to -20°C, and preferably within a range of +10°C to -10°C. In a preferred embodiment, the room temperature of the location where the manufacturing apparatus is installed can be, for example, -10 to 40°C, alternatively 0 to 35°C, alternatively 5 to 35°C, alternatively 10 to 35°C, alternatively 15 to 35°C, alternatively 20 to 35°C, or alternatively 20 to 30°C.

[0032] [Tin spheres] According to the present invention, high-purity tin metal spheres having a diameter of more than about 1 mm and excellent sphericity can be produced. The present invention also relates to high-purity tin metal spheres produced by the above-mentioned production method. "Excellent sphericity" means that the diameter variation ratio, which will be described later, is smaller than the value described later, and preferably equal to or less than the value described later.

[0033] [Diameter of the tin ball] In a preferred embodiment, the diameter of the metallic tin ball of the present invention can be greater than about 1 millimeter. The diameter of the metallic tin ball can be measured by the means described later in the Examples. For a particular tin ball to be measured, 10 diameter measurement points are selected and measured, and the measured values ​​at these 10 points are averaged to calculate the average diameter of the individual tin ball to be measured.

[0034] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 1 mm to 5 mm, preferably 1 mm to 4.5 mm, preferably 1 mm to 4.3 mm, or 1 mm to 4.2 mm, 1 mm to 4.1 mm, 1 mm to 4.0 mm, 1 mm to 3.9 mm, 1 mm to 3.8 mm, 1 mm to 3.7 mm, 1 mm to 3.6 mm, or 1 mm to 3.5 mm.

[0035] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 1.1 mm to 5 mm, 1.2 mm to 5 mm, 1.3 mm to 5 mm, or 1.4 mm to 5 mm.

[0036] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 1.5 mm to 5 mm, preferably 1.5 mm to 4.5 mm, preferably 1.5 mm to 4.3 mm, alternatively 1.5 mm to 4.2 mm, 1.5 mm to 4.1 mm, 1.5 mm to 4.0 mm, 1.5 mm to 3.9 mm, 1.5 mm to 3.8 mm, 1.5 mm to 3.7 mm, 1.5 mm to 3.6 mm, or 1.5 mm to 3.5 mm.

[0037] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 1.6 mm to 5 mm, or 1.7 mm to 5 mm.

[0038] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 1.8 mm to 5 mm, preferably 1.8 mm to 4.5 mm, preferably 1.8 mm to 4.3 mm, alternatively 1.8 mm to 4.2 mm, 1.8 mm to 4.1 mm, 1.8 mm to 4.0 mm, 1.8 mm to 3.9 mm, 1.8 mm to 3.8 mm, 1.8 mm to 3.7 mm, 1.8 mm to 3.6 mm, or 1.8 mm to 3.5 mm.

[0039] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 1.9 mm to 5 mm, preferably 1.9 mm to 4.5 mm, preferably 1.9 mm to 4.3 mm, alternatively 1.9 mm to 4.2 mm, 1.9 mm to 4.1 mm, 1.9 mm to 4.0 mm, 1.9 mm to 3.9 mm, 1.9 mm to 3.8 mm, 1.9 mm to 3.7 mm, 1.9 mm to 3.6 mm, or 1.9 mm to 3.5 mm.

[0040] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 2.0 mm to 5 mm, preferably 2.0 mm to 4.5 mm, preferably 2.0 mm to 4.3 mm, alternatively 2.0 mm to 4.2 mm, 2.0 mm to 4.1 mm, 2.0 mm to 4.0 mm, 2.0 mm to 3.9 mm, 2.0 mm to 3.8 mm, 2.0 mm to 3.7 mm, 2.0 mm to 3.6 mm, or 2.0 mm to 3.5 mm.

[0041] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 2.1 mm to 5 mm, preferably 2.1 mm to 4.5 mm, preferably 2.1 mm to 4.3 mm, alternatively 2.1 mm to 4.2 mm, 2.1 mm to 4.1 mm, 2.1 mm to 4.0 mm, 2.1 mm to 3.9 mm, 2.1 mm to 3.8 mm, 2.1 mm to 3.7 mm, 2.1 mm to 3.6 mm, or 2.1 mm to 3.5 mm.

[0042] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 2.2 mm to 5 mm, preferably 2.2 mm to 4.5 mm, preferably 2.2 mm to 4.3 mm, alternatively 2.2 mm to 4.2 mm, 2.2 mm to 4.1 mm, 2.2 mm to 4.0 mm, 2.2 mm to 3.9 mm, 2.2 mm to 3.8 mm, 2.2 mm to 3.7 mm, 2.2 mm to 3.6 mm, or 2.2 mm to 3.5 mm.

[0043] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 2.3 mm to 5 mm, preferably 2.3 mm to 4.5 mm, preferably 2.3 mm to 4.3 mm, alternatively 2.3 mm to 4.2 mm, 2.3 mm to 4.1 mm, 2.3 mm to 4.0 mm, 2.3 mm to 3.9 mm, 2.3 mm to 3.8 mm, 2.3 mm to 3.7 mm, 2.3 mm to 3.6 mm, or 2.3 mm to 3.5 mm.

[0044] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 2.4 mm to 5 mm, preferably 2.4 mm to 4.5 mm, preferably 2.4 mm to 4.3 mm, alternatively 2.4 mm to 4.2 mm, 2.4 mm to 4.1 mm, 2.4 mm to 4.0 mm, 2.4 mm to 3.9 mm, 2.4 mm to 3.8 mm, 2.4 mm to 3.7 mm, 2.4 mm to 3.6 mm, or 2.4 mm to 3.5 mm.

[0045] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 2.6 mm to 5 mm, preferably 2.6 mm to 4.5 mm, preferably 2.6 mm to 4.3 mm, alternatively 2.6 mm to 4.2 mm, 2.6 mm to 4.1 mm, 2.6 mm to 4.0 mm, 2.6 mm to 3.9 mm, 2.6 mm to 3.8 mm, 2.6 mm to 3.7 mm, 2.6 mm to 3.6 mm, or 2.6 mm to 3.5 mm.

[0046] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 2.8 mm to 5 mm, preferably 2.8 mm to 4.5 mm, preferably 2.8 mm to 4.3 mm, alternatively 2.8 mm to 4.2 mm, 2.8 mm to 4.1 mm, 2.8 mm to 4.0 mm, 2.8 mm to 3.9 mm, 2.8 mm to 3.8 mm, 2.8 mm to 3.7 mm, 2.8 mm to 3.6 mm, or 2.8 mm to 3.5 mm.

[0047] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 2.9 mm to 5 mm, preferably 2.9 mm to 4.5 mm, preferably 2.9 mm to 4.3 mm, alternatively 2.9 mm to 4.2 mm, 2.9 mm to 4.1 mm, 2.9 mm to 4.0 mm, 2.9 mm to 3.9 mm, 2.9 mm to 3.8 mm, 2.9 mm to 3.7 mm, 2.9 mm to 3.6 mm, or 2.9 mm to 3.5 mm.

[0048] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 3.0 mm to 5 mm, preferably 3.0 mm to 4.5 mm, preferably 3.0 mm to 4.3 mm, alternatively 3.0 mm to 4.2 mm, 3.0 mm to 4.1 mm, 3.0 mm to 4.0 mm, 3.0 mm to 3.9 mm, 3.0 mm to 3.8 mm, 3.0 mm to 3.7 mm, 3.0 mm to 3.6 mm, or 3.0 mm to 3.5 mm.

[0049] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 3.1 mm to 5 mm, preferably 3.1 mm to 4.5 mm, preferably 3.1 mm to 4.3 mm, alternatively 3.1 mm to 4.2 mm, 3.1 mm to 4.1 mm, 3.1 mm to 4.0 mm, 3.1 mm to 3.9 mm, 3.1 mm to 3.8 mm, 3.1 mm to 3.7 mm, 3.1 mm to 3.6 mm, or 3.1 mm to 3.5 mm.

[0050] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 3.2 mm to 5 mm, preferably 3.2 mm to 4.5 mm, preferably 3.2 mm to 4.3 mm, alternatively 3.2 mm to 4.2 mm, 3.2 mm to 4.1 mm, 3.2 mm to 4.0 mm, 3.2 mm to 3.9 mm, 3.2 mm to 3.8 mm, 3.2 mm to 3.7 mm, 3.2 mm to 3.6 mm, or 3.2 mm to 3.5 mm.

[0051] In a preferred embodiment, the diameter of the metal tin ball of the present invention can be, for example, 3.3 mm to 5 mm, 3.4 mm to 5 mm, 3.5 mm to 5 mm, 3.6 mm to 5 mm, 3.7 mm to 5 mm, 3.8 mm to 5 mm, or 3.9 mm to 5 mm.

[0052] [Diameter Variation Ratio] In a preferred embodiment, the tin ball of the present invention can have a diameter variation ratio calculated by the following formula of, for example, 0.15 or less: "Diameter Variation Ratio" = "Diameter variation (mm) measured in accordance with the provisions of JIS B1509:2009" / "Average diameter (mm)"

[0053] The diameter variation (mm) and average diameter (mm) of the tin balls in the present invention can be measured in accordance with the provisions of JIS B1509:2009 by the means disclosed in the examples described below.

[0054] In a preferred embodiment, the diameter variation ratio of the tin ball of the present invention can be, for example, 0.15 or less, or 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, or 0.04 or less. There is no lower limit to the preferred diameter variation ratio, but it can be, for example, 0.001 or more, 0.005 or more, 0.01 or more, 0.02 or more, or 0.03 or more.

[0055] [Purity of tin balls] In a preferred embodiment, the purity of the metallic tin in the tin balls can be, for example, 99.99% by mass or more, preferably 99.995% by mass or more, preferably 99.999% by mass or more, preferably 99.9995% by mass or more, preferably 99.9995% by mass or more, preferably 99.9996% by mass or more, preferably 99.9997% by mass or more, preferably 99.9998% by mass or more, preferably 99.9999% by mass or more.

[0056] [Preferred Embodiments of the Present Invention] As preferred embodiments, the present invention includes the following (1). (1) A method for producing tin balls, comprising the steps of: dropping molten metal tin into a liquid cooling medium; and cooling the metal tin droplets as they fall through the liquid cooling medium to form solid tin balls. (2) A manufacturing method according to (1), in which the liquid cooling medium is a liquid medium that has no boiling point or flash point at a temperature below the melting point of metal tin. (3) A manufacturing method according to any one of (1) to (2), in which the liquid cooling medium is a liquid cooling medium selected from the group consisting of mineral oil, vegetable oil, liquid paraffin, engine oil, and silicone oil. (4) A manufacturing method according to any one of (1) to (3), in which the distance the metal tin droplets fall through the liquid cooling medium is 500 mm or more. (5) A manufacturing method according to any one of (1) to (4), wherein the temperature of the liquid cooling medium is in the range of 232 to 350°C at the position where the falling of the metallic tin droplets starts, and is in the range of 100°C or less at the position where the falling of the tin droplets ends. (6) A manufacturing method according to any one of (1) to (5), wherein the diameter of the tin ball is in the range of 1 mm to 5 mm. (7) A manufacturing method according to any one of (1) to (6), wherein the diameter variation ratio of the tin ball calculated by the following formula is 0.15 or less: "Diameter variation ratio" = "Diameter variation (mm) measured in accordance with the provisions of JIS B1509:2009" / "Average diameter (mm)". (8) A manufacturing method according to any one of (1) to (7), wherein the purity of the metallic tin in the tin ball is 99.999% by mass or more. (9) A tin ball having a diameter in the range of 1 mm to 5 mm. (10) The tin ball according to (9), wherein the diameter variation ratio of the tin ball calculated by the following formula is 0.15 or less: "Diameter variation ratio" = "Diameter variation (mm) measured in accordance with the provisions of JIS B1509:2009" / "Average diameter (mm)". (11) The tin ball according to any one of (9) to (10), wherein the purity of the metallic tin of the tin ball is 99.999% by mass or more.

[0057] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the examples illustrated below.

[0058] [Example 1: Production of tin balls (Example 1)] [Tin ball production apparatus] High-purity metallic tin with a purity of 99.999% by mass was prepared as the raw tin. This high-purity metallic tin (purity 99.999% by mass) was used as the raw material to produce the tin balls of Example 1. Figure 1 is an explanatory diagram showing an overview of the production apparatus (tin ball production apparatus) used to produce the tin balls of Example 1.

[0059] The tin ball manufacturing apparatus shown in FIG. 1 includes a melting vessel 14 for melting and storing tin, the raw material used to manufacture tin balls. The tin in the melting vessel 14 is heated by a heater 15 and melted. The molten tin in the melting vessel 14 drips by gravity through a tin delivery pipe 16 into the silicone oil filled in the granulation vessel 12. A heater 13 is provided above the granulation vessel 12, and the molten tin is maintained in a molten state above the granulation vessel 12. The space within the manufacturing apparatus is filled with argon gas rather than air, preventing oxidation of the molten tin. The molten tin droplets introduced through the tin delivery pipe 16 and dropped into the silicone oil filled in the granulation vessel 12 become spherical as they freely fall through the silicone oil filled in the granulation vessel 12, then cool and solidify, becoming tin balls 11 that accumulate at the bottom of the granulation vessel 12.

[0060] [Procedure for manufacturing tin balls using a tin ball manufacturing apparatus] Using high purity tin (purity 99.999% by mass), tin balls were manufactured using a tin ball manufacturing apparatus as follows.

[0061] 2,000 g of small pieces of high-purity tin (purity 99.999% by mass) that had been pickled and washed with water were placed in a melting vessel of a quartz tin ball manufacturing device. Meanwhile, the granulation vessel was filled with silicone oil (KF-96 manufactured by Shin-Etsu Silicone Co., Ltd., boiling point: no boiling point, flash point temperature: 300°C or higher). The lids of the melting vessel and the granulation vessel were closed, and high-purity argon gas was allowed to flow at a flow rate of 1 L / min until the oxygen concentration inside the granulation vessel reached 0.1 vol% or less.

[0062] The melting vessel was heated with an external heater to 280°C, exceeding the melting point of tin, 231.9°C. The upper part of the granulation vessel was heated to 280°C, exceeding the melting point of tin, 231.9°C. The lower part of the granulation vessel was not heated and was maintained at about 20°C, which was room temperature during the experiment.

[0063] High-purity tin was melted in the melting vessel, and the molten tin was discharged from the melting vessel into the granulating vessel by its own weight, and allowed to drip and fall freely. During this free-fall process, the molten tin became spherical due to surface tension. Since the lower part of the granulating vessel was not heated, the molten tin solidified and accumulated while remaining spherical.

[0064] After the discharge was completed, the heater was turned off, the mixture was allowed to cool, the flow of argon gas was stopped, and the tin ball was removed.

[0065] The removed tin ball was washed with toluene to remove the silicone oil, and then washed with dilute hydrochloric acid to obtain a tin ball (sample 1) produced in Example 1.

[0066] From the tin balls (sample 1) produced in Example 1, tin balls to be measured were randomly extracted, and impurity analysis was performed using a GD-MS (AstruM manufactured by Nu Corporation) at a resolution of 4000 or more. The tin purity was calculated by the difference method and was found to be 99.999 mass% or more.

[0067] [Example 2: Production of tin balls (Example 2)] High-purity metallic tin with a purity of 99.9999% by mass was prepared as the raw tin. Using this high-purity metallic tin (purity 99.9999% by mass) as the raw material, tin balls were produced using the above-mentioned tin ball production apparatus in the same manner as in the production of the tin balls in Example 1. In this way, the tin balls produced in Example 2 (Sample 2) were obtained.

[0068] From the tin balls (sample 2) produced in Example 2, tin balls to be measured were randomly selected, and impurity analysis was performed in the same manner as the impurity analysis and calculation of tin purity for the tin balls in Example 1, and the tin purity was calculated to be 99.9999 mass% or more.

[0069] [Example 3: Production of tin balls (Comparative Example 1)] [Procedure for producing tin balls using a tin ball production apparatus] Tin balls were produced using the tin ball production apparatus used in Example 1 using high purity tin (purity 99.999% by mass).

[0070] However, while silicone oil was used as the cooling liquid medium in the production of the tin balls in Example 1, pure water was used as the cooling liquid medium instead of silicone oil in the production of the tin balls in Example 3.

[0071] The melting vessel was heated with an external heater to 280°C, exceeding the melting point of tin, which was 231.9°C. The upper part of the granulation vessel was heated to 85°C. The lower part of the granulation vessel was not heated and was maintained at about 20°C, which was room temperature during the experiment.

[0072] Thus, tin balls were produced and removed in the same manner as in Example 1, except that pure water was used as the cooling liquid medium and the temperature of the granulation vessel was controlled.

[0073] The removed tin ball was washed with dilute hydrochloric acid to obtain the tin ball produced in Example 3 (Sample 3).

[0074] [Example 4: Production of tin balls (Comparative Example 2)] [Procedure for producing tin balls using a tin ball production apparatus] Using high-purity tin (purity 99.999% by mass), tin balls were produced using the tin ball production apparatus used in Example 1.

[0075] However, while silicone oil was used as the cooling liquid medium in the production of the tin balls in Example 1, ethanol was used as the cooling liquid medium instead of silicone oil in the production of the tin balls in Example 4.

[0076] The melting vessel was heated with an external heater to 280°C, exceeding the melting point of tin, which was 231.9°C. The upper part of the granulation vessel was not heated, but was maintained by heat transferred from the melting vessel. The lower part of the granulation vessel was not heated, but was maintained at approximately 20°C, which was room temperature during the experiment.

[0077] Thus, tin balls were produced and removed in the same manner as in Example 1, except that ethanol was used as the cooling liquid medium and the temperature of the granulation vessel was controlled.

[0078] The removed tin ball was washed with dilute hydrochloric acid to obtain a tin ball produced according to Example 4 (Sample 4).

[0079] [Example 5: Evaluation of tin balls] The tin ball of Example 1 obtained in Example 1 (Sample 1), the tin ball of Example 2 obtained in Example 2 (Sample 2), the tin ball of Comparative Example 1 obtained in Example 3 (Sample 3), and the tin ball of Comparative Example 2 obtained in Example 4 (Sample 4) were each evaluated using the following procedure.

[0080] [Evaluation of the tin balls of Example 1 obtained in Example 1] The evaluation of the tin balls of Example 1 (Sample 1) obtained in Example 1 was performed by randomly selecting five tin balls to be measured from the group of tin balls obtained as the tin balls of Example 1 (Sample 1) obtained in Example 1 and measuring them.

[0081] Specifically, the measurement was carried out in accordance with the provisions of JIS B1509:2009, with each of the tin balls to be measured (measurement objects 1 to 5) being measured, using a micrometer instead of a measurement plane and a probe perpendicular to it, and measuring 10 times for each ball while changing the measurement point, and the maximum and minimum values ​​were identified from the 10 measured values, and the diameter variation was calculated as the difference between the maximum and minimum values. In the present invention, the arithmetic mean value of the 10 measured values ​​measured for each ball was taken as the average diameter value of each ball, and the diameter variation ratio was calculated as the ratio of the diameter variation to the average diameter value.

[0082] The results obtained are summarized in Table 1 below.

[0083]

[0084] The diameter variation ratio of the tin balls of Example 1 was 0.14 or less for all of the tin balls measured, indicating excellent sphericity. Furthermore, one of the tin balls measured in Example 1 had a diameter variation ratio of 0.04 or less, indicating excellent sphericity. The average diameter variation ratio of the tin balls of Example 1 in Table 1 was 0.0987, indicating excellent sphericity.

[0085] An image illustrating the appearance of the tin ball of Example 1 (Sample 1) obtained in Example 1 is shown in FIG.

[0086] [Evaluation of the tin balls of Example 2 obtained in Example 2] The evaluation of the tin balls of Example 2 (sample 2) obtained in Example 2 was carried out by randomly selecting five tin balls to be measured from the group of tin balls obtained as the tin balls of Example 2 (sample 2) obtained in Example 2. The evaluation of the tin balls of Example 2 (sample 2) obtained in Example 2 was carried out in the same manner as the operation performed on the tin balls of Example 1 (sample 1) obtained in Example 1.

[0087] The results obtained are summarized in Table 2 below.

[0088]

[0089] The diameter variation ratio of the tin balls measured in Example 2 was 0.14 or less for all of the tin balls measured, indicating excellent sphericity. Furthermore, the diameter variation ratio of two of the tin balls measured in Example 2 was 0.04 or less, indicating excellent sphericity. The average diameter variation ratio of the tin balls measured in Example 2 in Table 2 was 0.0828, indicating excellent sphericity.

[0090] An image illustrating the appearance of the tin ball of Example 2 (Sample 2) obtained in Example 2 is shown in FIG.

[0091] [Evaluation of the tin balls of Comparative Example 1 obtained in Example 3] In order to evaluate the tin balls of Comparative Example 1 (sample 3) obtained in Example 3, we attempted to randomly extract five tin balls to be measured from the group of tin balls obtained as the tin balls of Comparative Example 1 (sample 3) obtained in Example 3. However, the tin balls of Comparative Example 1 (sample 3) obtained in Example 3 contained many metallic tin balls that had become irregular in shape, and it was not possible to extract such objects to be measured.

[0092] An image illustrating the appearance of the tin ball (sample 3) of Comparative Example 1 obtained in Example 3 is shown in FIG.

[0093] [Evaluation of the tin balls of Comparative Example 2 obtained in Example 4] In order to evaluate the tin balls of Comparative Example 2 obtained in Example 4 (Sample 4), we attempted to randomly extract five tin balls to be measured from the group of tin balls obtained as the tin balls of Comparative Example 2 obtained in Example 4 (Sample 4). However, the tin balls of Comparative Example 2 obtained in Example 4 (Sample 4) contained many metallic tin balls that had become irregular in shape, and it was not possible to extract such balls to be measured.

[0094] An image illustrating the appearance of the tin ball (sample 4) of Comparative Example 2 obtained in Example 4 is shown in FIG.

[0095] [Evaluation of the tin balls in the examples and comparative examples] For example, water is an excellent cooling solvent, and is often used to cool objects at temperatures exceeding 100°C. Ethanol is also used as an excellent cooling solvent. It is unclear why such a large difference occurs between excellent cooling solvents such as water and ethanol and silicone oil. However, in the present invention, which aims to form tin balls from molten tin, the inventor believes that simple cooling is insufficient, and that the very small bubbles that occur during cooling, or the phenomenon of localized microbubbles, may hinder the formation of tin balls with excellent sphericity. In other words, the inventor believes that the fact that silicone oil, in relation to its boiling point, does not cause the phenomenon of localized microbubbles, itself, may have made it possible to form tin balls with excellent sphericity.

[0096] [Potential Contribution to SDGs] According to one embodiment of the present invention, tin balls with large diameters and excellent sphericity are provided. Since high precision materials and components are important for the development of IoT and AI technologies, one embodiment of the present invention has the potential to contribute to the development of IoT, AI, and other technologies. Therefore, one embodiment of the present invention has the potential to contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), which is to "Build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation."

[0097] The present invention provides a tin ball with a large diameter and excellent sphericity, and is an industrially useful invention.

Claims

1. A method for producing tin balls, comprising the steps of: dripping molten tin metal into a liquid cooling medium; and cooling the tin metal droplets as they fall through the liquid cooling medium to form solid tin balls.

2. The manufacturing method according to claim 1, wherein the cooling liquid medium is a liquid medium that has neither a boiling point nor a flash point at a temperature below the melting point of metallic tin.

3. The manufacturing method according to claim 1, wherein the cooling liquid medium is selected from the group consisting of mineral oil, vegetable oil, liquid paraffin, engine oil, and silicone oil.

4. The manufacturing method according to claim 1, wherein the distance that the metallic tin droplets fall in the liquid cooling medium is 500 mm or more.

5. The manufacturing method according to claim 1, wherein the temperature of the cooling liquid medium is in the range of 232 to 350°C at the position where the falling of the metallic tin droplets starts, and is in the range of 100°C or less at the position where the falling of the tin droplets ends.

6. The manufacturing method according to any one of claims 1 to 5, wherein the diameter of the tin ball is in the range of 1 mm to 5 mm.

7. A manufacturing method according to any one of claims 1 to 5, wherein the diameter variation ratio of the tin balls calculated by the following formula is 0.15 or less: "diameter variation ratio" = "diameter variation (mm) measured in accordance with the provisions of JIS B1509:2009" / "average diameter (mm)".

8. The manufacturing method according to any one of claims 1 to 5, wherein the purity of the metallic tin in the tin balls is 99.999% by mass or more.

9. Tin balls with diameters ranging from 1mm to 5mm.

10. The tin ball according to claim 9, wherein the diameter variation ratio of the tin ball calculated by the following formula is 0.15 or less: "Diameter variation ratio" = "Diameter variation (mm) measured in accordance with the provisions of JIS B1509:2009" / "Average diameter (mm)".

11. The tin ball according to claim 9, wherein the purity of the metallic tin in the tin ball is 99.999% by mass or more.

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