Tin balls and methods for manufacturing tin balls

Abstract

To provide a tin ball having a diameter larger than about 1 mm and excellent sphericity.SOLUTION: A method for manufacturing a tin ball, comprising: dropping molten metal tin into a liquid cooling medium; and forming a solid tin ball by cooling a droplet of the molten metal tin while the droplet of the molten metal tin falls in the liquid cooling medium, wherein the tin ball has a radius ranging from 1mm to 5mm.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to solder balls excellent in sphericity and a method for manufacturing the same.

Background Art

[0002] Manufacturing metal balls on an industrial scale is an extremely important basic technology. Therefore, conventionally, manufacturing technologies for metal balls on an industrial scale have been developed.

[0003] As a general method for manufacturing metal balls, there is a method for manufacturing balls by machining such as pressing and polishing. However, since 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, since soft metal materials such as solder, which is an alloy of tin, lead, and the like, are not suitable for machining such as polishing, a method for manufacturing metal balls by casting is used.

[0004] As a classical example of manufacturing metal balls using a soft metal material, a method for manufacturing shotgun pellets is known. This is a method of dropping molten lead from a high place (for example, 50 m or more) and collecting it in a water tank, and it was a large-scale method of building a tower for manufacturing. Of course, the variation in the obtained lead balls is large, and it is not a method intended to control purity and sphericity.

[0005] Patent Document 1 (Japanese Patent Laid-Open No. 11-221662) discloses a technique for manufacturing solder balls by dropping molten solder into soybean oil. However, Patent Document 1 does not describe the size, sphericity, and purity of the obtained solder balls, and discloses a classical technique that merely requires obtaining solder in a ball shape.

[0006] Patent Document 2 (Japanese Patent Laid-Open No. 54-085171) discloses that metal balls were obtained by ejecting a molten metal of a solder alloy from a nozzle into silicone oil while rotating a rotating plate having a cutting hole. However, the size of the obtained metal balls is 1 mm in diameter, and a technique for obtaining metal balls of a size larger than this is not disclosed.

[0007] Patent Document 3 (Japanese Unexamined Patent Publication No. 55-158875) discloses a method for obtaining iron balls by dropping droplets of molten iron into water. However, in this technique, the cracking rate increases sharply when the diameter of the iron ball exceeds 1 mm, reaching as high as 70% when the diameter reaches 8 mm. Furthermore, there is no description of the sphericity or purity of the obtained iron balls.

[0008] Patent document 4 (Japanese Patent Publication No. 2001-226705) discloses a technique for manufacturing fine metal spheres with a diameter of approximately 400 μm by injecting molten solder into a chamber filled with nitrogen gas mixed with hydrogen gas while applying vibration with a piezoelectric element. The fine metal spheres obtained by this technique are small, with a diameter of approximately 400 μm, and exhibit large variations in diameter and sphericity.

[0009] Thus, when melting soft metals such as tin to form particles, there has been no suitable technology to date that produces particles with an average particle diameter of more than 1 mm and excellent spherical shape accuracy (perfect sphericity), and such technology is in demand. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 11-221662 [Patent Document 2] Japanese Patent Publication No. 54-085171 [Patent Document 3] Japanese Patent Publication No. 55-158875 [Patent Document 4] Japanese Patent Publication No. 2001-226705 [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] Therefore, an object of the present invention is to provide a solder ball having a diameter larger than about 1 millimeter and excellent sphericity.

Means for Solving the Problems

[0012] As a result of intensive research, the present inventor has found that the above object can be achieved by the means described below, and has reached the present invention.

[0013] Therefore, the present invention includes the following (1): (1) A method for manufacturing a solder ball, comprising: a step of dropping a molten metal tin into a cooling liquid medium; a step of cooling the liquid droplets of metal tin while falling in the cooling liquid medium to form solid solder balls. A method for manufacturing a solder ball, including the above steps.

Advantages of the Invention

[0014] According to the present invention, a high-purity solder ball having a diameter larger than about 1 millimeter and excellent sphericity can be obtained.

Brief Description of the Drawings

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

Modes for Carrying Out the Invention

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

[0017] [Method for manufacturing solder balls] The method for manufacturing solder balls according to the present invention is A method for manufacturing solder balls, comprising a step of dropping molten metal tin into a liquid cooling medium, a step in which the metal tin droplets are cooled while falling in the liquid cooling medium to form solid solder balls, and is a method for manufacturing solder balls.

[0018] [Molten metal tin] For the means for heating and melting metal tin into the form of molten metal tin, known means can be used. For example, it can be heated and melted by radiation heating or induction heating to prepare molten metal tin.

[0019] In a preferred embodiment, the raw material metal tin used to prepare molten metal tin can be used without particular limitation as long as it is, for example, metal tin that can be heated and melted into the form of molten metal. Preferably, high-purity metal tin can be used. Examples of the high-purity metal tin that can be used as a raw material include tin having a 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, preferably, 99.9999% by mass or more.

[0020] [Liquid cooling medium]<了 In a preferred embodiment, the liquid cooling medium that can be used can be preferably used as long as it is stable at a temperature higher than the melting point of metal tin. More specifically, a liquid medium having no boiling point and flash point at a temperature below the melting point of metal tin can be preferably 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, and preferably 310°C or higher. In a preferred embodiment, a particularly preferred cooling liquid medium is one that does not have a 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, and preferably 280°C or higher.

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

[0024] [Drip] In a preferred embodiment, known means can be used for introducing molten metallic tin into a cooling liquid medium, as long as it is by dripping, without any particular restrictions. Examples include gravity dripping and powered dripping, preferably free dripping and discharge by a pump, and particularly preferably free dripping by gravity.

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

[0026] [Distance to fall] In a preferred embodiment, the distance over which a droplet of metallic tin falls within the cooling liquid 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 over which a droplet of metallic tin falls within the cooling liquid medium is not particularly upper 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 over which a droplet of metallic tin falls within the cooling liquid medium can be, for example, in the range of 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, and preferably 800 to 1500 mm.

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

[0030] In a preferred embodiment, at the position where the metallic tin droplets have finished falling, the temperature of the cooling liquid medium can be, for example, 100°C or less, preferably 80°C or less, preferably 50°C or less, 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, and preferably 40 to 20°C.

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

[0032] [Tin ball] According to the present invention, it is possible to manufacture high-purity metallic tin balls with a diameter larger than approximately 1 millimeter and excellent sphericity. The present invention also applies to high-purity metallic tin balls manufactured by the above manufacturing method. Excellent sphericity means that the diameter difference ratio, as described below, is smaller than the value described below, preferably less than or equal to the value described below.

[0033] [Diameter of the tin ball] In a preferred embodiment, the diameter of the tin sphere of the present invention can be greater than about 1 millimeter. The diameter of the tin sphere can be measured by means described later in the examples. For a given tin sphere to be measured, 10 points can be selected as diameter measurement points and measured. The average of the measurements at these 10 points can then be averaged to calculate the average diameter of the tin sphere to be measured.

[0034] In a preferred embodiment, the diameter of the tin metal 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 tin metal 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 tin metal 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, or 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 tin metal 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 tin metal 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, or 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 tin metal 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, or 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 tin metal 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, or 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 tin metal 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, or 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 tin metal 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, or 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 tin metal 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, or 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 tin metal 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, or 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 tin metal 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, or 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 tin metal 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, or 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 tin metal 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, or 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 tin metal 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, or 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 tin metal 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, or 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 tin metal 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, or 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 metallic tin ball of the present invention can be, for example, 3.3mm to 5mm, 3.4mm to 5mm, 3.5mm to 5mm, 3.6mm to 5mm, 3.7mm to 5mm, 3.8mm to 5mm, or 3.9mm to 5mm.

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

[0053] The measurement of the diameter variation (mm) and the average diameter (mm) of the tin balls in this invention, in accordance with the provisions of JIS B1509:2009, can be carried out by the means disclosed in the embodiments described later.

[0054] In a preferred embodiment, the diameter variability ratio of the tin spheres 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 variability 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 ball can be, for example, 99.99% by mass or higher, preferably 99.995% by mass or higher, preferably 99.999% by mass or higher, preferably 99.9995% by mass or higher, preferably 99.9996% by mass or higher, preferably 99.9997% by mass or higher, preferably 99.9998% by mass or higher, and preferably 99.9999% by mass or higher.

[0056] [Preferred embodiments of the present invention] In preferred embodiments, the present invention includes (1) and the following: (1) A method for manufacturing tin balls, A process of dropping molten tin into a cooling liquid medium, A process in which a droplet of metallic tin is cooled as it falls through a cooling liquid medium, forming a solid tin sphere. A method for manufacturing tin balls, including the method described above. (2) The manufacturing method according to (1), wherein the cooling liquid medium is a liquid medium that does not have a boiling point or flash point at a temperature below the melting point of metallic tin. (3) The manufacturing method according to (1), wherein the cooling liquid medium is a cooling liquid medium selected from the group consisting of mineral oil, vegetable oil, liquid paraffin, engine oil, and silicone oil. (4) The manufacturing method according to (1), wherein the distance over which a droplet of metallic tin falls within the cooling liquid medium is 500 mm or more. (5) The manufacturing method according to (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 metallic tin droplets begins, and in the range of 100°C or less at the position where the falling of tin droplets ends. (6) A manufacturing method according to any of (1) to (5), wherein the diameter of the tin ball is in the range of 1 mm to 5 mm. (7) The manufacturing method described in any of (1) to (5), wherein the ratio of tin ball diameter differences 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 (1) to (5), wherein the purity of the metallic tin in the tin ball is 99.999% by mass or higher. (9) Tin balls with a diameter ranging from 1mm to 5mm. (10) The tin balls described in (9) have a diameter difference ratio of 0.15 or less, calculated by the following formula: "Diameter variation ratio" = "Diameter variation (mm) measured according to the provisions of JIS B1509:2009" / "Average diameter (mm)". (11) The tin ball described in (9), wherein the purity of the metallic tin in the tin ball is 99.999% by mass or higher. [Examples]

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

[0058] [Example 1: Manufacturing of tin balls (Example 1)] [Tin ball manufacturing equipment] As the raw material, we prepared high-purity metallic tin with a purity of 99.999% by mass. This high-purity metallic tin (99.999% by mass purity) was used as the raw material to manufacture the tin balls of Example 1. Figure 1 is an explanatory diagram showing an overview of the manufacturing equipment (tin ball manufacturing equipment) used to produce the tin balls in Example 1.

[0059] The tin ball manufacturing apparatus shown in Figure 1 is equipped with a molten container 14 for melting and storing tin, which is the raw material used to manufacture tin balls. The tin in the molten container 14 is heated by a heater 15 and remains in a molten state. The molten tin in the molten container 14 is dripped by gravity into the silicone oil filling the granulation container 12 via a tin delivery pipe 16. A heater 13 is provided at the top of the granulation container 12, and the molten tin remains molten at the top of the granulation container 12. The space inside the manufacturing apparatus is filled with argon gas, not air, to suppress oxidation of the molten tin. The droplets of molten tin introduced by the tin delivery pipe 16 and dripped into the silicone oil filling the granulation container 12 become spherical as they free-fall through the silicone oil in the granulation container 12, then cool and solidify to form tin balls 11, which accumulate at the bottom of the granulation container 12.

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

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

[0062] The molten container was heated using an external heater, exceeding the melting point of tin (231.9°C) and reaching 280°C. The upper part of the granulation container was also heated, exceeding the melting point of tin (231.9°C) and reaching 280°C. The lower part of the granulation container was not heated and was maintained at approximately 20°C, the room temperature during the experiment.

[0063] High-purity tin was melted in a molten container, and the molten tin was discharged from the molten container into a granulation container by gravity, then allowed to drip and free-fall. During this free-fall process, the molten tin became spherical due to surface tension. Since the lower part of the granulation container was not heated, the molten tin solidified and accumulated while remaining spherical.

[0064] Once the discharge was complete, the heater was turned off, and after cooling, the flow of argon gas was stopped and the tin ball was removed.

[0065] The extracted tin balls were washed with toluene to remove the silicone oil, and then washed with dilute hydrochloric acid to obtain the tin balls (sample 1) produced according to Example 1.

[0066] From the tin balls (sample 1) manufactured according to Example 1, a randomly selected tin ball was used for measurement, and impurity analysis was performed using GD-MS (AstruM, manufactured by Nu Inc.) at a resolution of 4000 or higher. The tin purity was calculated using the difference method and was found to be 99.999% by mass or higher.

[0067] [Example 2: Manufacturing of tin balls (Example 2)] As the raw material, we prepared high-purity metallic tin with a purity of 99.9999% by mass. Using this high-purity metallic tin (purity 99.9999 mass%) as a raw material, tin balls were manufactured using the tin ball manufacturing apparatus described above, in the same manner as in the production of tin balls in Example 1. In this way, tin balls manufactured according to Example 2 (sample 2) were obtained.

[0068] From the tin balls (sample 2) manufactured according to Example 2, a tin ball to be measured was 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. The tin purity was calculated to be 99.9999% by mass or higher.

[0069] [Example 3: Manufacturing of tin balls (Comparative Example 1)] [Procedure for manufacturing tin balls using a tin ball manufacturing machine] High-purity tin (99.999% by mass) was used to produce tin balls using the tin ball manufacturing apparatus used in Example 1.

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

[0071] Furthermore, the molten container was heated using an external heater, exceeding the melting point of tin (231.9°C) and reaching 280°C. The upper part of the granulation container was heated to 85°C. The lower part of the granulation container was not heated and was maintained at approximately 20°C, the room temperature during the experiment.

[0072] Thus, tin balls were manufactured and extracted 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 container was controlled.

[0073] The extracted tin balls were washed with dilute hydrochloric acid to obtain the tin balls produced according to Example 3 (Sample 3).

[0074] [Example 4: Manufacturing of tin balls (Comparative Example 2)] [Procedure for manufacturing tin balls using a tin ball manufacturing machine] High-purity tin (99.999% by mass) was used to produce tin balls using the tin ball manufacturing apparatus used in Example 1.

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

[0076] Furthermore, the molten container was heated using an external heater, exceeding the melting point of tin (231.9°C) and reaching 280°C. The upper part of the granulation container was not heated, but maintained by the heat transferred from the molten container. The lower part of the granulation container was not heated and was maintained at approximately 20°C, the room temperature during the experiment.

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

[0078] The extracted tin balls were washed with dilute hydrochloric acid to obtain the tin balls produced according to Example 4 (Sample 4).

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

[0080] [Evaluation of the tin balls obtained in Example 1] The evaluation of the tin balls (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 (sample 1) of Example 1, and measuring them.

[0081] Specifically, the measurement involved taking 10 measurements of each tin sphere (measurement targets 1-5) using a micrometer instead of a measuring plane and a measuring probe perpendicular to it, while changing the measurement point, in accordance with the provisions of JIS B1509:2009. The maximum and minimum values ​​were identified from these 10 measurements, and the diameter variation was calculated as the difference between these maximum and minimum values. In this invention, the arithmetic mean of the 10 measurements taken for each sphere was taken as the average diameter of each sphere, and the diameter variation ratio was determined as the ratio of the diameter variation to the average diameter.

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

[0083] [Table 1]

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

[0085] Figure 2 shows an image illustrating the appearance of the tin ball (sample 1) obtained in Example 1.

[0086] [Evaluation of the tin balls obtained in Example 2] The evaluation of the tin balls (sample 2) obtained in Example 2 was performed by randomly selecting 5 tin balls to be measured from the group of tin balls obtained as Example 2 (sample 2) in Example 2. The evaluation of the tin balls (sample 2) obtained in Example 2 was performed in the same manner as the procedure performed for the tin balls (sample 1) obtained in Example 1 (sample 1).

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

[0088] [Table 2]

[0089] In Example 2, all of the tin balls measured had a diameter variability ratio of 0.14 or less, indicating excellent sphericity. Furthermore, two of the tin balls measured in Example 2 had a diameter variability ratio of 0.04 or less, demonstrating extremely excellent sphericity. The average value of the diameter variability ratio of the tin balls in Example 2, shown in Table 2, was 0.0828, indicating extremely excellent sphericity.

[0090] Figure 3 shows an image illustrating the appearance of the tin ball (sample 2) obtained in Example 2.

[0091] [Evaluation of the tin ball of Comparative Example 1 obtained in Example 3] In order to evaluate the tin balls (sample 3) of Comparative Example 1 obtained in Example 3, we attempted to randomly select five tin balls to be measured from the group of tin balls obtained as Comparative Example 1 (sample 3) in Example 3. However, many of the tin balls (sample 3) of Comparative Example 1 obtained in Example 3 had irregular shapes, making it impossible to select such samples for measurement.

[0092] Figure 4 shows an image illustrating the appearance of the tin ball (sample 3) of Comparative Example 1 obtained in Example 3.

[0093] [Evaluation of the tin balls of Comparative Example 2 obtained in Example 4] In order to evaluate the tin balls (sample 4) of Comparative Example 2 obtained in Example 4, we attempted to randomly select five tin balls to be measured from the group of tin balls obtained as Comparative Example 2 (sample 4) in Example 4. However, many of the tin balls (sample 4) of Comparative Example 2 obtained in Example 4 had irregular shapes, making it impossible to select such samples for measurement.

[0094] Figure 5 shows an image illustrating the appearance of the tin ball (sample 4) of Comparative Example 2 obtained in Example 4.

[0095] [Evaluation of tin balls in the examples and comparative examples] For example, water is an excellent cooling solvent and is often used to cool objects exceeding 100°C. Similarly, ethanol is also used as an excellent cooling solvent. It is unclear why such a large difference arises between excellent cooling solvents like water and ethanol and silicone oil, but in the present invention, which aims to form tin spheres with molten tin, simply cooling is insufficient. The inventors believe that the minute bubbles generated during the cooling process, or the phenomenon of minute bubbles forming locally, may be hindering the formation of tin spheres with excellent spherical properties. In other words, the inventors believe that the fact that such a phenomenon of minute bubbles forming locally did not occur with silicone oil, in relation to its boiling point, may have enabled the formation of tin spheres with excellent spherical properties.

[0096] [Potential contribution to SDGs] One embodiment of the present invention provides a tin ball with a large diameter and excellent sphericity. Since high precision of materials and components is 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 and AI technologies. For this reason, one embodiment of the present invention has the potential to contribute to Goal 9 of the United Nations Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation." [Industrial applicability]

[0097] This invention provides tin balls with a large diameter and excellent spherical properties. This invention is industrially useful.

Claims

1. A method for manufacturing tin balls, A process of dropping molten tin into a cooling liquid medium, A process in which a droplet of metallic tin is cooled as it falls through a cooling liquid medium, forming a solid tin sphere. Includes, The cooling liquid medium is a liquid medium that does not have a boiling point or flash point at a temperature below the melting point of metallic tin. The temperature of the cooling liquid medium is in the range of 232 to 350°C at the position where the metallic tin droplets begin to fall, and in the range of 80 to 10°C at the position where the tin droplets end to fall. The diameter of the tin ball is in the range of 1.1 mm to 5 mm. A method for manufacturing tin balls, wherein the purity of the metallic tin in the tin balls is 99.999% by mass or higher.

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

3. The manufacturing method according to claim 1, wherein the distance over which a droplet of metallic tin falls within the cooling liquid medium is 500 mm or more.

4. The manufacturing method according to any one of claims 1 to 3, wherein the diameter difference ratio of the tin balls calculated by the following formula is 0.15 or less: "Diameter variation ratio" = "Diameter variation measured according to the provisions of JIS B1509:2009 (mm)" / "Average diameter (mm)".

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