Metallic tin for producing tin spheres

Abstract

Provided is a high-yield means for producing highly spherical tin spheres having a diameter larger than about 1 millimeter, through the use of a metallic tin that has a surface tension, as measured by electromagnetic levitation, of at least 490 × 10-3Nm-1 at a temperature of 1,000 K and at least 390 × 10-3Nm-1 at a temperature of 1,300 K.

Description

Metal tin for tin ball manufacturing

[0001] The present invention relates to metallic tin for making tin balls.

[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] Patent Document 5 (JP 50-17363 A) discloses a technique for producing copper granules by passing molten copper through a stainless steel wire mesh and dropping it into OF oil. However, Patent Document 5 does not describe the purity or sphericity of the obtained copper granules, and enlarged photographs in Patent Document 5 show that there is a great deal of variation in size and sphericity.

[0010] Patent Document 6 (Japanese Patent Laid-Open Publication No. 60-114508) discloses a technique for obtaining alloy grains by dropping droplets of molten Co—W alloy, Ni—B alloy, and Cu—B alloy from a nozzle into cooling oil. However, Patent Document 6 does not describe the purity, size, or sphericity of the obtained alloy grains, and simply evaluates them as "good" based on their weight and distribution.

[0011] Patent Document 7 (JP 2000-8104 A) discloses a technique for producing spherical metal particles by vibrating molten solder metal with a stainless steel shaft and dropping it from a nozzle into engine oil or cooking oil. However, the average particle size of the particles obtained in Patent Document 7 is approximately 0.30 mm to 0.76 mm, which is a technique that results in an average particle size of 1 mm or less.

[0012] 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.

[0013] Non-Patent Documents 1 and 2 disclose the Rayleigh equation (see Non-Patent Document 1) and the Cummings & Blackburn correction equation (see Non-Patent Document 2), which are useful for calculating the surface tension from the frequency applied to a droplet of a molten metal sample and the mass of the sample.

[0014] 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 Japanese Patent Laid-Open No. 50-17363 Japanese Patent Laid-Open No. 60-114508 Japanese Patent Laid-Open No. 2000-8104

[0015] Lord Rayleigh, “On the Capillary Phenomena of Jets”, Proceedings of the Royal Society of London, pp. 71-97, 1879. D. L. Cummings, D. A. Blackburn, “Oscillations of magnetically levulated aspherical droplets”, J. Fluid Mech, vol. 224, pp. 395-416, 1991.

[0016] It is therefore an object of the present invention to provide a means for producing tin balls with diameters and sphericity greater than about 1 millimeter in high yield.

[0017] 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.

[0018] In other words, while conventional technology has attempted to produce tin balls with a diameter of more than about 1 millimeter and high sphericity (accuracy of spherical shape) at a high yield by innovating the manufacturing process, the present invention achieves this goal by using specific tin for manufacturing tin balls.

[0019] Therefore, the present invention includes the following (1): (1) A surface tension measured by an electromagnetic levitation method is 490 x 10 at a temperature of 1,000 K. －３ Nm －１ At a temperature of 1,300 K, the －３ Nm －１ That's it, metallic tin.

[0020] According to the present invention, high-purity tin spheres having diameters greater than about 1 millimeter and high sphericity can be produced with high yield.

[0021] Figure 1 is a schematic diagram of an apparatus for measuring the surface tension of molten tin metal. Figure 2 is a graph showing the results of measuring the surface tension of molten tin metal for high-purity tin (sample 1) (Example) and high-purity tin (sample 2) (Comparative Example). Figure 3 is a schematic diagram of a tin ball manufacturing apparatus. Figure 4 shows a method for determining whether a tin ball passes or fails. Figure 5 shows the results of determining whether a tin ball passes or fails. Figure 6A is a photograph showing the appearance of a tin ball manufactured in the Example. Figure 6B is a photograph showing the appearance of a tin ball manufactured in the Comparative Example. Figure 7 is a photograph showing the appearance of a group of tin balls, which are spherical products remaining after visual sorting and rolling sorting in Example 1.

[0022] 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.

[0023] [Tin for manufacturing tin balls] The metallic tin of the present invention is metallic tin for manufacturing tin balls, and has a surface tension of 490×10 at a temperature of 1,000 K as measured by an electromagnetic levitation method. －３ Nm －１ At a temperature of 1,300 K, the －３ Nm －１ That's all there is to metallic tin.

[0024] By using metallic tin for producing tin balls according to the present invention, high-purity tin balls having a diameter of more than about 1 millimeter and high sphericity can be produced in high yield.

[0025] When spherical particles are obtained by solidifying molten metallic tin, the principal force acting to form the particles is surface tension.

[0026] However, prior to the present invention, the relationship between the surface tension of molten metallic tin and particle formation had not been clarified as a specific technique. In other words, it had not been clarified what type of particle formation occurs when a specific value of the surface tension of molten metallic tin is specified.

[0027] The reason for this is unclear, but one possible reason is that it is extremely difficult to measure the surface tension of molten metallic tin.

[0028] That is, when trying to measure the surface tension of molten metallic tin, the molten metallic tin is usually placed on some kind of substrate before measurement, but the surface tension of the molten metallic tin itself is affected by contact with the substrate, resulting in a non-negligible difference in the measured value.

[0029] However, in the present invention, as shown in the examples described below, it was possible to measure the surface tension of molten metallic tin by suspending the molten metallic tin in midair without contacting it with any substrate material. By examining the relationship between the surface tension measured in this way and the particles formed, it was discovered that tin having a specific surface tension is particularly suitable for obtaining particles with an average particle diameter of more than 1 mm and excellent spherical shape accuracy (sphericity), and this led to the present invention.

[0030] [Surface tension measured by electromagnetic levitation method] In a preferred embodiment, the surface tension of the metallic tin of the present invention measured by electromagnetic levitation method is, for example, 490 × 10 －３ Nm －１ or more, preferably 495 x 10 －３ Nm －１ More preferably, 500×10 －３ Nm －１ or more, or 505 x 10 －３ Nm －１ More than 510 × 10 －３ Nm －１ or more, for example, 390×10 －３ Nm －１ or more, preferably 395 x 10－３ Nm －１ More preferably, 400×10 －３ Nm －１ or more, or 405 x 10 －３ Nm －１ More than 410x10 －３ Nm －１ It can be more than that.

[0031] The measurement of surface tension by the electromagnetic levitation method can be carried out by the means described later in the Examples.

[0032] In a preferred embodiment, the metallic tin of the present invention has a surface tension of, for example, 490×10 at a temperature of 1,000 K, as measured by an electromagnetic levitation method. －３ Nm －１ ~510 x 10 －３ Nm －１ range, preferably 495×10 －３ Nm －１ ~510 x 10 －３ Nm －１ range, more preferably 500 × 10 －３ Nm －１ ~510 x 10 －３ Nm －１ range, or 500 x 10 －３ Nm －１ ~505 x 10 －３ Nm －１ range, or 490 x 10 －３ Nm －１ ~505 x 10 －３ Nm －１ range, preferably 490×10 －３ Nm －１ ~500 x 10 －３ Nm －１ range, more preferably 495 × 10 －３ Nm －１ ~500 x 10 －３ Nm －１ range, or 490 x 10 －３ Nm －１ ~495 x 10 －３ Nm －１ The range can be:

[0033] In a preferred embodiment, the metallic tin of the present invention has a surface tension of, for example, 390×10 at a temperature of 1,300 K as measured by an electromagnetic levitation method. －３ Nm －１ ~410 x 10 －３ Nm －１ range, preferably 395×10 －３ Nm －１ ~410 x 10 －３ Nm －１ range, more preferably 400 × 10 －３ Nm －１ ~410 x 10 －３ Nm －１ range, or 400 x 10 －３ Nm －１ ~405 x 10 －３ Nm －１ range, or 390 x 10 －３ Nm －１ ~405 x 10 －３ Nm －１ range, preferably 390×10 －３ Nm －１ ~400 x 10 －３ Nm －１ range, more preferably 395 × 10 －３ Nm －１ ~400 x 10 －３ Nm －１ range, or 390 x 10 －３ Nm －１ ~395 x 10 －３ Nm －１ The range can be:

[0034] In a preferred embodiment, the metallic tin of the present invention has a surface tension of 490×10 at a temperature of 1,000 K, as measured by an electromagnetic levitation method. －３ Nm －１ ~510 x 10 －３ Nm －１ range, 390 x 10 at a temperature of 1,300 K. －３ Nm －１ ~410 x 10 －３ Nm －１ The range can be:

[0035] In a preferred embodiment, the metallic tin of the present invention has a surface tension of 495×10 at a temperature of 1,000 K, as measured by an electromagnetic levitation method. －３ Nm －１ ~510 x 10 －３ Nm －１ range, 395 x 10 at a temperature of 1,300 K. －３ Nm －１ ~410 x 10 －３ Nm －１ The range can be:

[0036] In a preferred embodiment, the metallic tin of the present invention has a surface tension of 500×10 at a temperature of 1,000 K, as measured by an electromagnetic levitation method. －３ Nm －１ ~510 x 10 －３ Nm －１ range, 400 x 10 at a temperature of 1,300 K. －３ Nm －１ ~410 x 10 －３ Nm －１ The range can be:

[0037] In a preferred embodiment, the metallic tin of the present invention has a surface tension of 490×10 at a temperature of 1,000 K, as measured by an electromagnetic levitation method. －３ Nm －１ ~505 x 10 －３ Nm －１ range, 390 x 10 at a temperature of 1,300 K. －３ Nm －１ ~405 x 10 －３ Nm －１ The range can be:

[0038] In a preferred embodiment, the metallic tin of the present invention has a surface tension of 490×10 at a temperature of 1,000 K, as measured by an electromagnetic levitation method. －３ Nm －１ ~500 x 10 －３ Nm －１ range, 390 x 10 at a temperature of 1,300 K. －３ Nm －１ ~400 x 10 －３ Nm －１ The range can be:

[0039] In a preferred embodiment, the metallic tin of the present invention has a surface tension of 495×10 at a temperature of 1,000 K, as measured by an electromagnetic levitation method. －３ Nm －１ ~500 x 10 －３ Nm －１ range, 395 x 10 at a temperature of 1,300 K. －３ Nm －１ ~400 x 10 －３ Nm －１ The range can be:

[0040] In a preferred embodiment, the metallic tin of the present invention has a surface tension of 490×10 at a temperature of 1,000 K, as measured by an electromagnetic levitation method. －３ Nm －１ ~495 x 10 －３ Nm －１ range, 390 x 10 at a temperature of 1,300 K. －３ Nm －１ ~395 x 10 －３ Nm －１ The range can be:

[0041] In a preferred embodiment, the metallic tin of the present invention has a surface tension of 500×10 at a temperature of 1,000 K, as measured by an electromagnetic levitation method. －３ Nm －１ ~505 x 10 －３ Nm －１ range, 400 x 10 at a temperature of 1,300 K. －３ Nm －１ ~405 x 10 －３ Nm －１ The range can be:

[0042] [Production of Tin Balls] The metallic tin of the present invention can be heated and melted to form a molten metal tin, and this molten metal tin can be used to produce tin balls.

[0043] As a means for heating and melting the metallic tin of the present invention to form a molten metallic tin, known means can be used, and for example, molten metallic tin can be prepared by heating and melting it by radiant heating or induction heating.

[0044] In a preferred embodiment, tin balls can be suitably manufactured by a method including the steps of dropping the molten tin metal of the present invention into a liquid cooling medium, and cooling the tin metal droplets as they fall through the liquid cooling medium to form solid tin balls.

[0045] In a preferred embodiment, the cooling liquid medium that can be used to drip the molten tin of the present invention can be any liquid that is stable at temperatures higher than the melting point of the tin. Examples of such cooling liquid medium include animal and vegetable oils, mineral oils, and synthetic oils, and preferably lubricating oils and silicone oils, with silicone oil being particularly preferred.

[0046] In a preferred embodiment, the means for introducing the molten metal of the present invention into the liquid cooling medium is not particularly limited as long as it is dropwise, and any known means can be used, such as gravity dropwise or power dropwise, preferably natural dropwise or pumped discharge, and particularly preferably pumped discharge.

[0047] In a preferred embodiment, the molten metal of the present invention is dropped into a liquid cooling medium, and then cooled while falling through the liquid cooling medium to form a solid tin ball. The fall is by gravity, and it is preferable to set the height of the liquid cooling medium so that the molten metal can fall a distance sufficient to form a solid tin ball.

[0048] [Tin spheres] The tin spheres produced using the molten tin metal of the present invention have the above-mentioned surface tension as measured by the electromagnetic levitation method, and as such, high-purity tin spheres with a diameter of more than about 1 millimeter and high sphericity are produced in high yields.

[0049] In the present invention, the high sphericity of the manufactured tin balls means that in the group of manufactured tin balls, the proportion of spherical products as described below is high, and at the same time, the proportion of spherical products with a diameter variation ratio of less than 0.04 is high.

[0050] [Ratio of Spherical Products] In a preferred embodiment, the tin spheres produced using the molten metal of the present invention can have a ratio (%) of spherical products in the mass of solid tin spheres formed, calculated by the following formula, of, for example, 80% or more, preferably 90% or more, and preferably 95% or more: "Ratio of Spherical Products" = "Weight of Spherical Products (g)" / ("Weight of Spherical Products (g)" + "Weight of Irregularly Shaped Products (g)") x 100%

[0051] In a preferred embodiment, the tin balls produced using the molten tin metal of the present invention have no particular upper limit on the percentage of spherical products (%) calculated by the above formula in the group of solid tin balls formed, but can be, for example, 100% or less, 99.5% or less, 99% or less, 98.5% or less, or 98% or less.

[0052] In a preferred embodiment, the tin spheres produced using the molten metal of the present invention have a spherical product percentage (%) calculated by the above formula in the group of solid tin spheres formed, which can be, for example, in the range of 80% to 100%, preferably in the range of 80% to 99.5%, preferably in the range of 80% to 99%, preferably in the range of 80% to 98.5%, preferably in the range of 80% to 98%, and can be, for example, in the range of 90% to 100%, preferably in the range of 90% to 99.5%, preferably in the range of 90% to 99%, preferably in the range of 90% to 98.5%, preferably in the range of 90% to 98%, and can be, for example, in the range of 95% to 100%, preferably in the range of 95% to 99.5%, preferably in the range of 95% to 99%, preferably in the range of 95% to 99%, preferably in the range of 95% to 98.5%, preferably in the range of 95% to 98%.

[0053] In the present invention, the selection of spherical and irregularly shaped tin balls can be carried out by the means disclosed in the examples described below.

[0054] When manufacturing a large number of balls, it is useful to measure the weight of a group of tin balls for quality control, and the above-mentioned spherical product ratio is an index suitable for such quality control.

[0055] [Diameter Variation Ratio] In a preferred embodiment, the tin spheres produced using the molten metal of the present invention can have a ratio of spherical products in a group of spherical products obtained from a group of formed solid tin spheres, the ratio of which is less than 0.04 in diameter variation ratio calculated by the following formula, for example, 50% or more, preferably 55% or more, and preferably 60% or more: "Diameter Variation Ratio" = "Diameter Variation (mm) measured in accordance with the provisions of JIS B1509:2009" / "Average Diameter (mm)"

[0056] In a preferred embodiment, the tin balls produced using the molten tin metal of the present invention have no particular upper limit on the percentage (%) of spherical products in the group of solid tin balls formed that have a diameter variation ratio calculated by the above formula of less than 0.04, but can be, for example, 100% or less, 99% or less, 98% or less, 97% or less, 96% or less, 95% or less, 90% or less, 85% or less, 80% or less, or 75% or less.

[0057] In a preferred embodiment, the tin spheres produced using the molten metal of the present invention have a diameter variation ratio calculated by the following formula in a group of spherical products obtained from a group of formed solid tin spheres, and the ratio of spherical products having a diameter variation ratio of less than 0.04, calculated by the following formula, can be, for example, in the range of 50% to 100%, preferably in the range of 50% to 99%, preferably in the range of 50% to 95%, preferably in the range of 50% to 90%, preferably in the range of 50% to 85%, preferably in the range of 50% to 80%, preferably in the range of 50% to 75%, and for example, in the range of 55% to 100%. It may be in the range of 0%, preferably in the range of 55% to 99%, preferably in the range of 55% to 95%, preferably in the range of 55% to 90%, preferably in the range of 55% to 85%, preferably in the range of 55% to 80%, preferably in the range of 55% to 75%, for example in the range of 60% to 100%, preferably in the range of 60% to 99%, preferably in the range of 60% to 95%, preferably in the range of 60% to 90%, preferably in the range of 60% to 85%, preferably in the range of 60% to 80%, preferably in the range of 60% to 75%.

[0058] 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.

[0059] [Diameter] In a preferred embodiment, the diameter of the tin balls produced using the molten tin metal of the present invention can be greater than about 1 millimeter. The diameter of these tin balls can be determined by calculating the average diameter of each of 10 tin balls sampled from a group of tin balls and averaging the average diameters of these individual tin balls, i.e., the average diameter can be in the range of, for example, 1 mm to 5 mm, preferably 1.5 mm to 4.5 mm, and preferably 2 mm to 4 mm.

[0060] [Preferred Embodiment of the Invention] As a preferred embodiment, the present invention includes the following (1): (1) A liquid having a surface tension of 490 x 10 at a temperature of 1,000 K measured by an electromagnetic levitation method. －３ Nm －１ At a temperature of 1,300 K, the －３ Nm －１ (2) The surface tension measured by the electromagnetic levitation method is 490 x 10 at a temperature of 1,000 K. －３ Nm －１ ~510 x 10 －３ Nm －１ at a temperature of 1,300 K is in the range of 390 × 10 －３ Nm －１ ~410 x 10 －３ Nm －１(3) Metallic tin according to (1), which is metallic tin for producing tin balls. (4) A method for producing tin balls using the molten metal of tin according to (1). (5) A method for producing tin balls, comprising: a step of dropping the molten metal of tin according to (1) into a liquid cooling medium; and a step of cooling the droplets of metallic tin while falling through the liquid cooling medium to form solid tin balls. (6) A manufacturing method according to (5), in which the proportion of spherical products (%) in the group of solid tin balls formed is 80% or more, as calculated by the following formula: "Spherical product proportion" = "Weight of spherical products (g)" / ("Weight of spherical products (g)" + "Weight of irregularly shaped products (g)") × 100%. (7) A manufacturing method according to (5), in which the proportion of spherical products having a diameter variation ratio of less than 0.04, as calculated by the following formula, is 50% or more, as calculated by the following formula: "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 (5), in which the diameter of the tin balls is in the range of 1 mm to 5 mm.

[0061] 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.

[0062] [Example 1: Production of high-purity tin (sample 1)] [Casting] 1.7 kg of raw material tin (purity 99.999 wt%) was heated to 300°C or higher and melted in a graphite crucible. After removing the floating slag, the mixture was poured into a graphite mold to obtain two plates measuring approximately 10 mm in thickness, 70 mm in width, and 150 mm in height.

[0063] [Electrolytic dissolution] One sheet of raw tin was used as the anode and placed in an electrolytic cell facing a titanium plate (70 mm wide, 150 mm high) used as the cathode. The cathode plate was placed in a cathode box with an anion exchange membrane attached to the surface facing the anode. A 9N sulfuric acid aqueous solution was placed in the cathode box, which was connected to an outer container with a tube pump so that the sulfuric acid aqueous solution was circulated. Dilute sulfuric acid with a 0.5N concentration was placed outside the cathode box and in the electrolytic cell. Then, the raw tin cast into a plate shape was connected to the positive pole of the rectifier, and the titanium plate was connected to the negative pole of the rectifier with electrical wiring.

[0064] Current density 2A / dm ２ Electrolysis was carried out at 1000 kJ / s to obtain 3 L of a tin sulfate solution having a tin concentration of 90 g / L.

[0065] To the resulting tin sulfate solution, 5 g / L of strontium carbonate was added and stirred for 1 hour, and the precipitated solids were filtered off. To the resulting filtrate, 5 g / L of hydroquinone and 5 g / L of Brownon N-514 (manufactured by Aoki Oil & Fat Industries Co., Ltd.) as a surfactant were added and dissolved with stirring to obtain 2.8 L of tin sulfate electrolyte.

[0066] [Electrowinning] The tin sulfate electrolyte obtained above was diluted with pure water to a tin concentration of 20 g / L and placed in the anode side of an electrolytic cell to form an anode-side electrolyte (anolyte). The tin sulfate electrolyte was also placed in the cathode side of the electrolytic cell without dilution to form a cathode-side electrolyte (catholyte). The electrolytic cell contained the raw tin cast into a plate shape as described above as the anode, and a titanium plate of the same size as the above as the cathode. The positive pole of a rectifier was connected to the raw tin, and the negative pole of the rectifier was connected to the titanium plate, and a current density of 1.5 A / dm ２ The above procedure was repeated while switching between anolyte and catholyte, yielding about 600 g of plate-shaped electrolytic tin.

[0067] [Vacuum Casting] The obtained electrolytic tin was thoroughly washed and dried, then placed in a graphite crucible and heated in the air to remove the slag, and then cooled and solidified. Thereafter, it was placed in a vacuum melting furnace, heated to 1,000°C, held there for 16 hours, and then cooled and solidified to obtain a high-purity tin ingot.

[0068] [Cutting and Cleaning] The surface of the high-purity tin ingot was cut and removed to leave only the healthy part inside.

[0069] Small pieces were machined off from the remaining healthy high-purity tin, and then washed with acid and pure water.

[0070] In this way, high-purity tin (Sample 1) was obtained. Impurity analysis of the obtained high-purity tin (Sample 1) was carried out using GD-MS. The results of the obtained impurity analysis are shown in Table 1 below. Unless otherwise specified in Table 1, the units of values ​​are wtppm.

[0071]

[0072] [Example 2: Production of high-purity tin (sample 2)] The high-purity tin (sample 2) used in the comparative example was produced as follows. Electrolysis was carried out in the same manner as for the high-purity tin (sample 1) produced in Example 1, to obtain plate-shaped electrolytic tin. Next, the obtained electrolytic tin was thoroughly washed and dried, and then placed in a graphite crucible and heated in the air to remove the slag, and then cooled and solidified as is. The surface of the obtained tin ingot was cut off, and only the sound part inside was used. The tin that now contained only the sound part was cut into small pieces by machining, washed with acid, and washed with pure water, and used as high-purity tin (sample 2).

[0073] The results of the impurity analysis of high purity tin (sample 2) are shown in Table 2 below. In Table 2, unless otherwise specified, the units of values ​​are wtppm.

[0074]

[0075] [Example 3: Measurement of surface tension of high purity tin (sample 1)] [Surface tension measuring device] The surface tension of the obtained high purity tin (sample 1) was measured. Figure 1 is an explanatory diagram showing an outline of the measuring device used for measuring the surface tension.

[0076] The measurement device shown in Figure 1 includes a sealed quartz chamber 4, into which gas can be introduced through a gas inlet pipe 7 and which can be discharged through a gas outlet pipe 8. A sample holder 5 for holding a sample is provided inside the quartz chamber 4. The sample holder 5 is designed to hold a sample, tin 1, in a position where it can be inductively heated by a coil 2, and is also designed to allow the sample (tin 1) inductively heated by the coil 2 to melt, float, and be pulled down at the same time. The measurement device includes a high-frequency power supply outside the quartz chamber 4 that can supply high-frequency current to the coil. An observation window 6 is provided at the top of the quartz chamber 4 for observing the interior, and high-speed photography of the interior can be performed through this observation window 6 using a camera 9.

[0077] [Procedure for Measuring Surface Tension] Using the measuring device shown in FIG. 1, the surface tension of high-purity tin was measured as follows.

[0078] High-purity tin (sample 1) was cut into 420 to 480 mg square pieces (each side approximately 5 mm) and collected.

[0079] The surface of the collected rectangular tin sample was etched with a 3 vol. % aqueous solution of hydrochloric acid using an ultrasonic cleaner, and then further washed with acetone.

[0080] The tin sample was placed in a quartz glass holder in an electromagnetic levitation chamber.

[0081] The measurement system was evacuated (10 －７ After the pressure was increased to 100 psi (atm), an atmospheric gas (argon-helium) was introduced from the top at 2 L / min. The oxygen partial pressure of the atmospheric gas (argon-helium) was 1×10 －７ The concentration was adjusted to 0.1 vol. ppm atm.

[0082] A high-frequency AC current was passed through the electromagnetic levitation coil, and the sample was heated simultaneously with the electromagnetic levitation. To separate the sample from the holder before the sample melted, the sample holder was pulled down simultaneously with the start of heating.

[0083] The temperature was measured using two monochromatic radiation thermometers with different wavelengths: Wavelength 1: 1.64 μm Wavelength 2: 1.4 μm

[0084] At the chamber inlet, the atmospheric oxygen partial pressure of the introduced gas was measured with a zirconia type oxygen sensor operated at 1,008K.

[0085] The surface vibration behavior of the droplet after the sample melted was recorded from above using a high-speed camera (500 FPS, 8192 images (16.384 seconds)).

[0086] Immediately after recording, helium gas was sprayed onto the sample from above at 20 L / min to rapidly cool and solidify it.

[0087] The mass of the sample was measured using an electronic balance.

[0088] The droplet projection images were analyzed to determine the movement of the droplet's center of gravity, radius, and area, and the m=0, m=±1, and m=±2 frequencies of the l=2 mode and the m=0, m=±1 frequencies of the l=1 mode were identified.

[0089] From the obtained frequency and sample mass, the surface tension was calculated using the Rayleigh equation (see Non-Patent Document 1) and the Cummings & Blackburn correction equation (see Non-Patent Document 2).

[0090] [Measurement Results of Surface Tension] The measurement results of the surface tension measured in this manner are shown in FIG.

[0091] [Example 4: Measurement of surface tension of high purity tin (sample 2)] The surface tension of high purity tin (sample 2) was measured in the same manner as for high purity tin (sample 1) measured in Example 3. The results of the measured surface tensions are summarized in Figure 2.

[0092] [Evaluation of Surface Tension Measurement Results] From the graph in FIG. 2, the surface tension of Sample 1 in this example was 500 (490 to 510) × 10 at a temperature of 1,000 K. －３ Nm －１ Above, at a temperature of 1,300 K, 400 (390-410) x 10 －３ Nm －１ In contrast, the surface tension of Sample 2, which is used as a comparative example, was measured in the same manner, and found to be 440 to 460×10 at a temperature of 1,000 K. －３ Nm －１Above, 330 to 350 x 10 at a temperature of 1,300 K －３ Nm －１ From these results, it was found that there is a negative correlation between the temperature and the surface tension of the present samples, and that the surface tension of Sample 1, which is an example, is higher than that of Sample 2, which is a comparative example.

[0093] [Example 5: Production of tin balls (Examples 1 to 3)] [Tin ball production apparatus] Tin balls were produced using the obtained high purity tin (Sample 1). Figure 3 is an explanatory diagram showing an overview of the production apparatus used to produce the tin balls.

[0094] The manufacturing apparatus shown in Figure 3 is equipped with 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 to a molten state by a heater 15. The melting vessel 14 is sealed, and when silicone oil stored in a silicone oil container 17 is introduced by a pump 19 through a silicone oil delivery pipe 18, the pressure causes the molten tin in the melting vessel 14 to drip through a tin delivery pipe 16 into the silicone oil filled in the granulating vessel 12. A heater 13 is provided above the granulating vessel 12, and the molten tin is maintained in a molten state above the granulating vessel 12. The space within the manufacturing apparatus is filled with argon gas rather than air, preventing the molten tin from oxidizing. The droplets of molten tin introduced through the tin delivery pipe 16 and dropped into the silicone oil filled in the granulation vessel 12 first become spherical as they freely fall through the silicone oil filled in the granulation vessel 12, then cool and solidify, becoming tin balls 11 and depositing at the bottom of the granulation vessel 12.

[0095] [Procedure for manufacturing tin balls] High purity tin (sample 1) was used to manufacture tin balls as follows.

[0096] 2,000 g of small pieces of high-purity tin (Sample 1) that had been pickled and washed with water were placed in the melting vessel of a quartz tin ball manufacturing device. Meanwhile, the granulation vessel was filled with silicone oil. The lids of the melting vessel and 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 fell to 0.1 vol% or less.

[0097] The melting vessel and the upper part of the granulating vessel were heated by an external heater.

[0098] Once the high-purity tin in the melting vessel had melted, the pump was started, and the molten tin was discharged from the melting vessel into the granulating vessel, where it dripped and fell 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.

[0099] After the discharge was completed, the power supply to the discharge pump and heater was turned off, and after cooling, the flow of argon gas was stopped and the tin ball was removed.

[0100] The removed tin ball was washed with toluene to remove the silicone oil, and then washed with dilute hydrochloric acid.

[0101] The tin balls were sorted according to their shape and size.

[0102] The above procedure was repeated three times to produce tin balls, resulting in Examples 1 to 3.

[0103] [Example 6: Production of tin balls (Comparative Examples 1 to 3)] In producing the tin balls of the comparative examples, the above-mentioned high-purity tin (Sample 2) was used as the raw material instead of the high-purity tin (Sample 1). Using the same equipment and procedures as in Example 5, the production of tin balls was repeated three times to produce the tin balls of Comparative Examples 1 to 3.

[0104] [Example 7: Evaluation of tin balls] [Procedure for evaluation of tin balls] The groups of six tin balls obtained in Examples 1 to 3 and Comparative Examples 1 to 3 had tin ball diameters in the range of 3.2 to 3.6 mm.

[0105] These tin balls were evaluated according to the following procedure: An explanatory diagram showing the procedure for evaluating the tin balls is shown in FIG.

[0106] [Visual sorting] Items that were extremely large, extremely small, or misshapen were visually removed.

[0107] [Rolling Sorting] Next, the samples were rolled on a metal angle bent at 90° to remove samples that did not roll.

[0108] [Sorting of spherical and irregularly shaped products] After visual sorting and rolling sorting, the remaining products were classified as spherical products. After visual sorting and rolling sorting, the removed products were classified as irregularly shaped products.

[0109] [Ratio of Spherical Products] The ratio of spherical products (%) was calculated from the weight of spherical products and the weight of irregularly shaped products using the following formula: "Ratio of spherical products" = "Weight of spherical products" / ("Weight of spherical products" + "Weight of irregularly shaped products") x 100%

[0110] [Diameter Variation Ratio] Ten balls were randomly selected from the spherical products, and measurements were taken 10 times for each ball, using a micrometer instead of a measurement plane and a probe perpendicular to it, while changing the measurement location, in accordance with the provisions of JIS B1509:2009. The diameter variation was calculated using the 10 measurements. In the present invention, the arithmetic mean value of the 10 measurements taken 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.

[0111] [Evaluation Results of Tin Balls] The calculation results of the percentage of spherical products obtained for the tin ball populations of Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in FIG.

[0112] 5, the percentage of spherical products in Examples 1 to 3 all exceeded 80%, while the percentage of spherical products in Comparative Examples 1 to 3 all fell below 80%. This suggests that the samples of the Examples are more suitable for producing spherical products.

[0113] The appearances of the spherical and irregularly shaped products obtained from the tin ball masses of Examples 1 to 3 are shown in Fig. 6A. The appearances of the spherical and irregularly shaped products obtained from the tin ball masses of Comparative Examples 1 to 3 are shown in Fig. 6B.

[0114] As shown in Figures 6A and 6B, the spherical products had shapes very similar to those of a sphere. Also, as shown in Figures 6A and 6B, irregularly shaped products were observed, including products with shapes that resembled multiple spheres bonded together and products with shapes that appeared to have been deformed from a spherical shape. Although no numerical data is provided, the majority of irregularly shaped products in which multiple spheres were bonded together in Examples 1 to 3 were irregularly shaped products in which two spheres were bonded together, whereas in Comparative Examples 1 to 3, many irregularly shaped products in which more than two spheres were bonded together were observed.

[0115] The results of measuring the average diameters obtained from the tin ball groups of Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Table 3. In Table 3, No. is the number assigned to each individual tin ball taken out for measurement. Unless otherwise specified in Table 3, the units of values ​​are mm.

[0116]

[0117] As shown in Table 3, the diameter of the obtained tin balls (average of the average diameter values) was between 3 and 4 mm, and they were sufficiently large spheres.

[0118] The measurement results of the diameter variation ratio obtained from the tin ball groups of Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Table 4. In Table 4, No. is the number assigned to each individual tin ball taken out for measurement.

[0119]

[0120] As shown in Table 4, in Examples 1 to 3, the proportion of samples with a diameter variation ratio of less than 0.04 accounted for 50% or more of the total. On the other hand, in Comparative Examples 1 to 3, the proportion of samples with a diameter variation ratio of less than 0.04 was less than 50% of the total. This indicates that even when comparing spherical products, the sphericity of the samples of the Examples is higher than that of the Comparative Examples, making the samples of the Examples more suitable for producing spherical products. Furthermore, the average diameter variation ratios of the measured samples were all less than 0.04 in Examples 1 to 3, and all were 0.04 or higher in Comparative Examples 1 to 3, indicating that the sphericity of the samples of the Examples was higher than that of the Comparative Examples.

[0121] Figure 7 shows a photograph of the appearance of a group of tin balls, which are spherical products that remained after visual sorting and rolling sorting in Example 1. Using the high-purity tin of the present invention, a large number of high-quality spherical tin balls like those shown in Figure 7 could be efficiently produced simultaneously.

[0122] [Relationship between surface tension and evaluation results of tin ball] The surface tension of the tin of the present invention measured by the electromagnetic levitation method is 492 × 10 at a temperature of 1,000 K. －３ Nm －１ , 397 x 10 at a temperature of 1,300 K －３ Nm －１ The proportion of spherical products excluding irregularly shaped products contained in the tin balls manufactured using this tin was high at 96.9 to 97.5%.

[0123] On the other hand, the surface tension of tin, which has a lower surface tension than this, measured by the electromagnetic levitation method is 455 x 10 at a temperature of 1,000 K. －３ Nm －１ , 365 x 10 at a temperature of 1,300 K －３ Nm －１ The proportion of spherical products excluding irregularly shaped products contained in the tin balls produced using this tin was low at 70.1 to 75.9%.

[0124] [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."

[0125] According to the present invention, tin balls having a large diameter and high sphericity can be produced with a high yield. The present invention is an industrially useful invention.

Claims

1. The surface tension measured by the electromagnetic levitation method is 490 x 10 at a temperature of 1,000 K. －３ Nm －１ At a temperature of 1,300 K, the －３ Nm －１ That's it, metallic tin.

2. The surface tension measured by the electromagnetic levitation method is 490 x 10 at a temperature of 1,000 K. －３ Nm －１ ~510 x 10 －３ Nm －１ At a temperature of 1,300 K, the －３ Nm －１ ~410 x 10 －３ Nm －１ The tin metal of claim 1, wherein the tin content is in the range of 3. The metallic tin according to claim 1, which is metallic tin for producing tin balls.

4. A method for manufacturing tin balls using the molten metal of claim 1.

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

6. The manufacturing method according to claim 5, wherein the percentage of spherical products in the group of solid tin spheres formed is 80% or more, as calculated by the following formula: "Percentage of spherical products" = "Weight of spherical products (g)" / ("Weight of spherical products (g)" + "Weight of irregularly shaped products (g)") x 100%.

7. The manufacturing method according to claim 5, wherein in a group of spherical products obtained from a group of solid tin balls formed, the ratio of spherical products having a diameter variation ratio of less than 0.04 calculated by the following formula is 50% or more: "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 claim 5, wherein the diameter of the tin ball is in the range of 1 mm to 5 mm.

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