Metallic tin for producing tin spheres

Abstract

To provide high-yield means for producing highly spherical tin spheres having a diameter larger than about 1 millimeter.SOLUTION: Metallic tin herein has a surface tension, as measured by electromagnetic levitation, of at least 490×10-3 Nm-1 at the temperature of 1,000 K and at least 390×10-3 Nm-1 at the temperature of 1,300 K.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to metallic tin for the manufacture of tin balls. [Background technology]

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

[0003] A common method for manufacturing metal balls is to use mechanical processing such as pressing and polishing. However, because this involves mechanical processing, 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 such as solder are not suitable for mechanical processing such as polishing, so a casting method is used to manufacture metal balls.

[0004] A classic example of metal ball manufacturing using soft metal materials is the manufacturing method of shotgun shells. This method involves dropping molten lead from a high place (e.g., 50m or more) and collecting it in a water tank, and it was a large-scale method that required the construction of a tower for manufacturing. 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 Patent Publication No. 11-221662) discloses a technique for producing solder balls by dropping molten solder into soybean oil. However, Patent Document 1 does not disclose the size, sphericity, or purity of the obtained solder balls, and discloses a classic technique that only requires the production of solder in a ball-shaped form.

[0006] Patent Document 2 (JP Patent Publication 54-085171 A) discloses that metal spheres are obtained by spraying molten solder alloy metal from a nozzle into silicon 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 size.

[0007] Patent Document 3 (JP Patent Publication 55-158875 A) 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 about the sphericity and purity of the obtained iron balls.

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

[0009] Patent Document 5 (JP Patent Publication 50-17363 A) discloses a technique for producing copper particles by passing molten copper through a stainless steel wire mesh and dropping it into OF oil. However, Patent Document 5 does not disclose the purity or sphericity of the obtained copper particles, and a magnified photograph of Patent Document 5 shows that there is a very large variation in size and sphericity.

[0010] Patent Document 6 (JP Patent Publication 60-114508 A) 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 disclose the purity, size, or sphericity of the obtained alloy grains, and only evaluates them as "good" based on their weight and distribution.

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

[0012] Thus, when melting a soft metal such as tin to form particles, no suitable technology has existed to date that can obtain particles with an average particle diameter of more than 1 mm and excellent spherical shape accuracy (sphericity), and such a technology is needed.

[0013] Non-Patent Document 1 and Non-Patent Document 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. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Japanese Patent Application Laid-Open No. 11-221662 [Patent Document 2] JP 54-085171 A [Patent Document 3] JP 55-158875 A [Patent Document 4] JP 2001-226705 A [Patent Document 5] JP 50-17363 A [Patent Document 6] JP 60-114508 A [Patent Document 7] JP 2000-8104 A [Non-patent literature]

[0015] [Non-Patent Document 1] Lord Rayleigh, “On the Capillary Phenomena of Jets”, Proceedings of the Royal Society of London, pp.71-97, 1879. [Non-Patent Document 2] DLCummings, DA Blackburn, “Oscillations of magnetically levutated aspherical droplets”, J.Fluid Mech, vol.224, pp.395-416, 1991. Summary of the Invention [Problem to be solved by the invention]

[0016] It is therefore an object of the present invention to provide a means for producing tin spheres having diameters and sphericity greater than about 1 millimeter in high yields. [Means for solving the problem]

[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 attempted to produce tin balls with a diameter greater 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 objective by using specific tin for producing tin balls.

[0019] Therefore, the present invention includes the following (1): (1) The surface tension measured by the electromagnetic levitation method is At a temperature of 1,000 K, it is 490 x 10 -3 Nm -1 That's all. 390 x 10 at a temperature of 1,300 K -3 Nm -1 That's it, metallic tin. Effect of the Invention

[0020] According to the present invention, high purity tin spheres having a diameter of greater than about 1 millimeter and high sphericity can be produced in high yields. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram of an apparatus for measuring the surface tension of molten tin metal. [Diagram 2] FIG. 2 is a graph showing the results of measuring the surface tension of molten metallic tin of high purity tin (sample 1) (Example) and high purity tin (sample 2) (Comparative Example). [Diagram 3] FIG. 3 is a schematic diagram of a tin ball manufacturing apparatus. [Figure 4] Figure 4 shows the method for determining whether a tin ball is acceptable or not. [Diagram 5] Figure 5 shows the pass / fail result for the tin ball. [Figure 6A] FIG. 6A is a photograph showing the appearance of the tin ball produced in the example. [Figure 6B] FIG. 6B is a photograph showing the appearance of the tin ball produced in the comparative example. [Figure 7] FIG. 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 making 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 value is 390 × 10 -3 Nm -1 That's all for tin metal.

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

[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 given.

[0027] The reason for this is unclear, but one possible reason is that measuring the surface tension of molten tin metal is itself extremely difficult.

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

[0029] However, this time, as shown in the examples described later, the present invention was able to measure the surface tension of molten metallic tin by suspending the molten metallic tin in midair without contacting 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 invention of the present application.

[0030] [Surface tension measured by electromagnetic levitation] In a preferred embodiment, the surface tension of the metallic tin of the present invention, as measured by an electromagnetic levitation method, is, for example, 490×10 -3 Nm -1 More than 495×10 -3 Nm -1 More preferably, 500×10 -3 Nm -1 or more, or 505 x 10-3 Nm -1 More than 510x10, preferably -3 Nm -1 At a temperature of 1,300 K, for example, 390 x 10 -3 Nm -1 More than 395×10 -3 Nm -1 More preferably, 400×10 -3 Nm -1 or more, or 405 x 10 -3 Nm -1 More than 410x10, preferably -3 Nm -1 It can be more than that.

[0031] The surface tension can be measured by the electromagnetic levitation method using the means described later in the Examples.

[0032] In a preferred embodiment, the surface tension of the metallic tin of the present invention, as measured by an electromagnetic levitation method, is, for example, 490×10 -3 Nm -1 ~510×10 -3 Nm -1 range, preferably 495×10 -3 Nm -1 ~510×10 -3 Nm -1 More preferably, in the range of 500×10 -3 Nm -1 ~510×10 -3 Nm -1 or 500×10 -3 Nm -1 ~505×10 -3 Nm -1 or 490×10 -3 Nm -1 ~505×10 -3 Nm -1 range, preferably 490×10 -3 Nm -1 ~500×10 -3 Nm -1 and more preferably in the range of 495×10 -3 Nm -1 ~500×10-3 Nm -1 or 490×10 -3 Nm -1 ~495×10 -3 Nm -1 The range may be:

[0033] In a preferred embodiment, the surface tension of the metallic tin of the present invention, as measured by an electromagnetic levitation method, is, for example, 390×10 -3 Nm -1 ~410×10 -3 Nm -1 range, preferably 395×10 -3 Nm -1 ~410×10 -3 Nm -1 and more preferably in the range of 400×10 -3 Nm -1 ~410×10 -3 Nm -1 or 400×10 -3 Nm -1 ~405×10 -3 Nm -1 or 390×10 -3 Nm -1 ~405×10 -3 Nm -1 range, preferably 390×10 -3 Nm -1 ~400×10 -3 Nm -1 and more preferably in the range of 395×10 -3 Nm -1 ~400×10 -3 Nm -1 or 390×10 -3 Nm -1 ~395×10 -3 Nm -1 The range may be:

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

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

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

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

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

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

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

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

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

[0043] In the present invention, the means for heating and melting the metallic tin to form a molten metal tin can be any known means, and for example, the molten metal 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 dripping 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 metal of the present invention can be any liquid that is stable at a temperature higher than the melting point of metal tin. Examples of such cooling liquid medium include animal and vegetable oils, mineral oils, and synthetic oils, and preferably lubricating oils and silicone oils, and more preferably silicone oils.

[0046] In a preferred embodiment, the means for introducing the molten tin 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, for example, gravity dripping and power dripping, preferably natural dripping and discharge by a pump, and particularly preferably discharge by a pump.

[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 ball] 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 a result, high-purity tin spheres with a diameter of more than about 1 millimeter and high sphericity are produced in a high yield.

[0049] In the present invention, the high sphericity of the manufactured tin balls means that, in the population 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] [Spherical product ratio] In a preferred embodiment, the tin balls produced using the molten tin metal of the present invention can have a spherical product percentage (%) calculated by the following formula in a group of solid tin balls formed, for example, of 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 mass of solid tin balls formed, but it 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 balls produced using the molten metal of the present invention have a spherical product ratio (%) calculated by the above formula in the group of solid tin balls formed, 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%, 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%, 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 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 to control the quality, and the above-mentioned spherical product ratio is an index suitable for such quality control.

[0055] [Diameter discrepancy] In a preferred embodiment, the tin spheres produced using the molten tin metal of the present invention can have a ratio of spherical products having a diameter variation ratio of less than 0.04 calculated by the following formula in a group of spherical products obtained from a group of solid tin spheres formed, for example, 50% or more, preferably 55% or more, and preferably 60% or more: "Diameter variation ratio" = "Diameter variation measured in accordance with the provisions of JIS B1509:2009 (mm)" / "Average diameter value (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 population of solid tin balls formed that have a diameter variation ratio calculated by the above formula of less than 0.04, but it 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 ratio of spherical products having a diameter variation ratio of less than 0.04 calculated by the following formula in a group of spherical products obtained from a group of formed solid tin spheres, which 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%, for example, 55% to 100%. The range may be 0%, preferably 55% to 99%, preferably 55% to 95%, preferably 55% to 90%, preferably 55% to 85%, preferably 55% to 80%, preferably 55% to 75%, for example, 60% to 100%, preferably 60% to 99%, preferably 60% to 95%, preferably 60% to 90%, preferably 60% to 85%, preferably 60% to 80%, preferably 60% to 75%.

[0058] The diameter variation (mm) and average diameter (mm) of the tin ball 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 metal of the present invention can be greater than about 1 mm. The diameter of the tin balls can be determined by calculating the average diameter of each of 10 tin balls taken from a group of tin balls, and averaging the average diameters of each of the individual tin balls, i.e., the average diameter value, for example, can be in the range of 1 mm to 5 mm, preferably in the range of 1.5 mm to 4.5 mm, and preferably in the range of 2 mm to 4 mm.

[0060] [Preferred embodiment of the present invention] As a preferred embodiment, the present invention includes the following (1) and the following: (1) The surface tension measured by the electromagnetic levitation method is At a temperature of 1,000 K, it is 490 x 10 -3 Nm -1 That's all. 390 x 10 at a temperature of 1,300 K -3 Nm -1 That's it, metallic tin. (2) The surface tension measured by the electromagnetic levitation method is At a temperature of 1,000 K, it is 490 x 10 -3 Nm -1 ~510×10 -3 Nm -1 is in the range of 390 x 10 at a temperature of 1,300 K -3 Nm -1 ~410×10 -3 Nm -1 The metallic tin described in (1) above, in which the content is in the range of (3) The metallic tin described in (1) above, which is metallic tin for manufacturing tin balls. (4) A method for manufacturing tin balls using the molten tin metal described in (1). (5) A method for producing tin balls, comprising the steps of: A step of dropping the molten metal tin described in (1) into a liquid medium for cooling; a step in which the droplets of metallic tin are cooled as they fall through a liquid cooling medium to form solid tin spheres; A method for producing a tin ball, comprising: (6) The manufacturing method according to (5), wherein the percentage of spherical products (%) calculated by the following formula is 80% or more in the group of solid tin balls formed: "Ratio 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 (5), wherein in a group of spherical products obtained from a group of solid tin spheres 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 measured in accordance with the provisions of JIS B1509:2009 (mm)" / "Average diameter value (mm)" (8) The manufacturing method according to (5), wherein the diameter of the tin ball is in the range of 1 mm to 5 mm. EXAMPLES

[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 tin (purity 99.999 wt%) was heated to over 300°C and melted in a graphite crucible. After removing the floating slag, the tin 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] [Electrolysis] A sheet of raw tin was used as the anode and placed in the 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 solution was placed in the cathode box, which was connected to an outer container with a tube pump so that the sulfuric acid solution was circulated. Dilute sulfuric acid with a concentration of 0.5N was placed outside the cathode box and in the electrolytic cell. After that, 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 400° C. to obtain 3 L of tin sulfate solution with a tin concentration of 90 g / L.

[0065] 5g / L of strontium carbonate was added to the obtained tin sulfate solution and stirred for 1 hour, and the precipitated solid matter was filtered and removed. 5g / L of hydroquinone and 5g / L of Brownon N-514 manufactured by Aoki Oil Industries Co., Ltd. were added to the obtained filtrate as a surfactant, and the mixture was stirred and dissolved to obtain 2.8L 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 the electrolytic cell to prepare the anode side electrolyte (anolyte). The tin sulfate electrolyte was also placed in the cathode side of the electrolytic cell without dilution to prepare the cathode side electrolyte (catholyte). The electrolytic cell contained the raw tin cast into the plate shape described above as the anode, and a titanium plate of the same size as the above as the cathode. The positive pole of the rectifier was connected to the raw tin, and the negative pole of the rectifier was connected to the titanium plate, and the current density was 1.5A / dm 2 The above procedure was repeated while replacing the anolyte with the catholyte, and about 600 g of plate-shaped electrolytic tin was obtained.

[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, then cooled and solidified. It was then 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, leaving only the healthy internal portion.

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

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

[0071] [Table 1]

[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 atmosphere to remove the slag, and then cooled and solidified. The surface of the obtained tin lump was cut and removed, and only the healthy part inside was used. Small pieces were cut out of the tin that was left with only the healthy part by machining, and were washed with acid and pure water to be 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] [Table 2]

[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. FIG. 1 is an explanatory diagram showing an overview of the measuring device used for measuring the surface tension.

[0076] The measurement device shown in FIG. 1 is equipped with 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 structured so that tin 1, which is a sample, can be placed and held in a position where it can be inductively heated by a coil 2, and is also structured so that the sample (tin 1) inductively heated by the coil 2 can be melted and floated, and then pulled down at the same time. The measurement device is equipped with a high-frequency power source capable of supplying a high-frequency current to the coil outside the quartz chamber 4. An observation window 6 for observing the inside of the quartz chamber 4 is provided at the top of the quartz chamber 4, and high-speed photography of the inside can be performed through this observation window 6 with a camera 9.

[0077] [Surface tension measurement procedure] 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 rectangular pieces (each side approximately 5 mm) and collected.

[0079] The surfaces of the rectangular tin samples were etched with a 3 vol.% hydrochloric acid solution using an ultrasonic cleaner, and then 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 -7After the pressure was increased to 1.0 atm, 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 atm (volume concentration: 0.1 vol. ppm).

[0082] A high-frequency AC current was passed through the electromagnetic levitation coil, and the sample was heated simultaneously with electromagnetic levitation. In order to separate the sample from the holder before the sample melted, the sample holder was pulled down at the same time that heating began.

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

[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 with a high-speed camera. (500FPS, 8192 frames (16.384 seconds)).

[0086] Immediately after recording, helium gas was sprayed onto the sample 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 Rayleigh's formula (see Non-Patent Document 1) and the correction formula of Cummings & Blackburn (see Non-Patent Document 2).

[0090] [Surface tension measurement results] The results of the surface tension measurements 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 that of high purity tin (sample 1) measured in Example 3. The results of the surface tension measurements are summarized in FIG.

[0092] [Evaluation of surface tension measurement results] From the graph in FIG. 2, the surface tension of the sample 1 in the example is 500 (490-510) × 10 at a temperature of 1,000 K. -3 Nm -1 Above, at a temperature of 1,300K, 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 -1 At a temperature of 1,300 K, the -3 Nm -1 From these results, it was found that there is a negative correlation between the temperature and the surface tension of the samples, and that the surface tension of Sample 1, which is an example, is higher than the surface tension of Sample 2, which is a comparative example.

[0093] [Example 5: Production of tin balls (Examples 1 to 3)] [Tin ball manufacturing equipment] The obtained high purity tin (sample 1) was used to manufacture tin balls. FIG. 3 is an explanatory diagram showing an overview of the manufacturing apparatus used to manufacture the tin balls.

[0094] The manufacturing apparatus shown in FIG. 3 is equipped with a melting vessel 14 for melting and storing tin, which is a raw material used for manufacturing tin balls. The tin in the melting vessel 14 is heated by a heater 15 and is in a molten state. The melting vessel 14 is sealed, and when the silicon oil stored in a silicon oil vessel 17 is introduced by a pump 19 through a silicon oil delivery pipe 18, the molten tin in the melting vessel 14 is dripped through a tin delivery pipe 16 into the silicon oil filled in the granulation vessel 12 by the pressure. 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 in the manufacturing apparatus is filled with argon gas instead of air, which suppresses oxidation of the molten tin. Droplets of molten tin are introduced through the tin delivery pipe 16 and dropped into the silicone oil filled in the granulating vessel 12. As they freely fall through the silicone oil filled in the granulating vessel 12, they first become spherical, then cool and solidify, becoming tin balls 11 and piling up on the bottom of the granulating vessel 12.

[0095] [Procedure for manufacturing tin balls] Using high purity tin (sample 1), tin balls were manufactured as follows.

[0096] 2,000g 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 silicon oil. 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 1L / min until the oxygen concentration inside the granulation vessel was 0.1vol% or less.

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

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

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

[0100] The tin ball was removed, 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, giving Examples 1 to 3.

[0103] [Example 6: Production of tin balls (Comparative Examples 1 to 3)] In the manufacture of 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). The manufacture of tin balls was repeated three times using the same equipment and procedures as in Example 5 to manufacture the tin balls of Comparative Examples 1 to 3.

[0104] [Example 7: Evaluation of tin balls] [Procedure for evaluating 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. Figure 4 shows an explanatory diagram of the procedure for evaluating the tin balls.

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

[0107] [Rolling sorting] They were then rolled over a metal angle bent at 90 degrees to remove any that would 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 products removed were classified as irregularly shaped products.

[0109] [Spherical product ratio] The percentage of spherical products (%) was calculated from the weight of the spherical products and the weight of the 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 disparity] Ten balls were randomly selected from the spherical products, and measurements were taken ten times for each ball, changing the measurement points, using a micrometer instead of a measurement plane and a probe perpendicular to the plane, in accordance with the provisions of JIS B1509:2009, and the diameter variation was calculated using the ten measured values. In the present invention, the arithmetic mean value of the ten measured values ​​for each ball was taken as the average diameter value for each ball, and the diameter variation ratio was calculated as the ratio of the diameter variation to the average diameter value.

[0111] [Tin ball evaluation results] The calculation results of the ratio of spherical products obtained for the tin ball populations in Examples 1 to 3 and Comparative Examples 1 to 3 are shown in FIG.

[0112] 5, the spherical product ratios of Examples 1 to 3 all exceeded 80%, whereas the spherical product ratios of Comparative Examples 1 to 3 all fell below 80%. This shows 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 Fig. 6A and Fig. 6B, the spherical products had a shape very close to a sphere. As shown in Fig. 6A and Fig. 6B, irregularly shaped products were observed, including products with a shape in which multiple spheres were bonded together and products with a shape that was deformed from a sphere. Although no numerical data was shown, in the irregularly shaped products in which multiple spheres were bonded together, the majority of the irregularly shaped products in which two spheres were bonded together were observed in Examples 1 to 3, whereas many irregularly shaped products in which more than two spheres were bonded together were observed in Comparative Examples 1 to 3.

[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 a number assigned to each individual tin ball taken out for measurement. Unless otherwise specified in Table 3, the unit of values ​​is mm.

[0116] [Table 3]

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

[0118] The measurement results of the diameter non-uniformity 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 a number assigned to each individual tin ball taken out for measurement.

[0119] [Table 4]

[0120] As shown in Table 4, in Examples 1 to 3, the ratio of the diameter variation ratio less than 0.04 was 50% or more of the total. On the other hand, in Comparative Examples 1 to 3, the ratio of the diameter variation ratio less than 0.04 was less than 50% of the total. From this, even when comparing spherical products, the sphericity of the samples of the Examples is higher than that of the Comparative Examples, indicating that the samples of the Examples are more suitable for manufacturing spherical products. In addition, when the average value of the diameter variation ratio of the measured samples is taken, it is less than 0.04 in all of Examples 1 to 3, and is 0.04 or more in all of Comparative Examples 1 to 3, which also indicates that the sphericity of the samples of the Examples is 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. By using the high purity tin of the present invention, it was possible to efficiently produce a large number of high quality spherical tin balls like those in Figure 7 at the same time.

[0122] [Relationship between surface tension and tin ball evaluation results] The surface tension of the tin of the present invention measured by the electromagnetic levitation method is 492×10 -3 Nm -1 , 397 × 10 at a temperature of 1,300 K -3 Nm -1 The percentage of spherical products, excluding irregularly shaped products, contained in the tin balls produced 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 455×10 at a temperature of 1,000 K. -3 Nm -1 , 365 × 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, ranging from 70.1 to 75.9%. [Industrial Applicability]

[0124] According to the present invention, tin balls having a large diameter and high sphericity can be produced at 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 1,000K －３ Nm －１ That's all. 390 x 10 at a temperature of 1,300K －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 1,000K －３ Nm －１ ~510 x 10 －３ Nm －１ is in the range of 390 x 10 at a temperature of 1,300K －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 tin metal according to claim 1, which is tin metal for producing tin balls.

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

5. A method for producing tin balls, comprising the steps of: A step of dropping the molten metal of claim 1 into a liquid medium for cooling; a step in which the droplets of metallic tin are cooled as they fall through a liquid cooling medium to form solid tin spheres; A method for producing a tin ball, comprising:

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

7. The method according to claim 5, wherein in a group of spherical products obtained from the group of solid tin spheres 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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