Metallic tin for manufacturing solder ball

Abstract

Provided is a means for producing a tin ball having a diameter of greater than about 1 mm and a high real ball property at a high yield from metallic tin having a surface tension of 490 * 10-3 Nm <-1 > or more at a temperature of 1,000 K and 390 * 10-3 Nm <-1 > or more at a temperature of 1,300 K as measured by electromagnetic suspension.

Description

Technical Field

[0001] The invention relates to metal tin for manufacturing tin balls. Background Art

[0002] Industrial-scale production of metal balls is an extremely important basic technology. Therefore, industrial-scale production technology of metal balls has been developed in the past.

[0003] As a general method for manufacturing metal balls, there is a ball manufacturing method using mechanical processing such as pressurization and grinding. However, since it is accompanied by 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, since soft metal materials such as solders such as tin, lead and their alloys are not suitable for mechanical processing such as grinding, a method for manufacturing metal balls using casting is used.

[0004] As a classic example of manufacturing a metal ball using a soft metal material, there is a known method for manufacturing shotguns. This method is to drop molten lead from a high altitude (for example, more than 50 meters) and recover it in a water tank. It is a large-scale method that builds a tower for manufacturing. Of course, the obtained lead ball has a large deviation, and it is not a method intended to control purity or sphericity.

[0005] Patent document 1 (Japanese Patent Publication No. 11-221662) discloses a technique for making solder balls by dropping molten solder into soybean oil. However, Patent document 1 does not describe the size, sphericity, and purity of the solder balls obtained, and only discloses a classic technique for obtaining solder in a spherical shape.

[0006] Patent document 2 (Japanese Patent Publication No. 54-085171) discloses that a metal ball is obtained by rotating a rotating plate having a cut hole and simultaneously ejecting molten metal of a solder alloy from a nozzle into silicone oil. However, the size of the obtained metal ball is 1 mm in diameter, and no technology for obtaining a metal ball of a larger size is disclosed.

[0007] Patent document 3 (Japanese Patent Publication No. 55-158875) discloses that iron balls are obtained by dropping iron melt into water. However, in this technology, if the diameter of the iron ball exceeds 1 mm, the breakage rate increases sharply. For example, if the diameter is 8 mm, the breakage rate reaches 70%. In addition, there is no description of the sphericity and purity of the obtained iron ball.

[0008] Patent Document 4 (Japanese Patent Application Laid-Open No. 2001-226705) discloses the following technique: while imparting vibration to a molten solder by a piezoelectric element, it is ejected into a chamber filled with nitrogen mixed with hydrogen to produce fine metal balls with a diameter of about 400 μm. The diameter of the fine metal balls obtained by this technique is as small as about 400 μm, and the deviation in diameter or sphericity is also large.

[0009] Patent Document 5 (Japanese Patent Application Laid-Open No. 50-17363) discloses a technique for producing copper particles by dropping a molten copper through a stainless steel wire mesh into OF oil. However, in Patent Document 5, there is no description of the purity or sphericity of the obtained copper particles, and according to the enlarged photograph of Patent Document 5, the deviation in size or sphericity is extremely large.

[0010] Patent Document 6 (Japanese Patent Application Laid-Open No. 60-114508) discloses a technique for obtaining alloy particles by dropping droplets of a molten solution of Co-W alloy, Ni-B alloy, and Cu-B alloy from a nozzle into cooling oil. However, in Patent Document 6, there is no description of the purity, size, or sphericity of the obtained alloy particles, and it is only evaluated as "good" based on the weight and its distribution.

[0011] Patent Document 7 (Japanese Patent Application Laid-Open No. 2000-8104) discloses the following technique: while vibrating the molten metal of solder by a stainless steel shaft, it is dropped from a nozzle into machine oil or edible oil to produce spherical metal particles. However, the average particle diameter of the particles obtained in Patent Document 7 is about 0.30 mm to 0.76 mm, which is a technique with an average particle diameter of 1 mm or less.

[0012] Thus, when melting a soft metal such as tin to form particles, there has not been an appropriate technique so far as a technique for obtaining particles with an average particle diameter greater than 1 mm and excellent sphericity (true sphericity), and such a technique is needed.

[0013] In Non-Patent Document 1 and Non-Patent Document 2, there is disclosed a Rayleigh formula (refer to Non-Patent Document 1) and a modified formula of Cummings & Blackburn (refer to Non-Patent Document 2) that can be used to calculate the surface tension from the frequency applied to droplets of a molten metal sample and the sample mass.

[0014] Background Art Documents

[0015] Patent Documents

[0016] Patent Document 1: Japanese Patent Application Laid-Open No. 11-221662

[0017] Patent Document 2: Japanese Patent Application Laid-Open No. 54-085171

[0018] Patent Document 3: Japanese Unexamined Patent Publication No. 55-158875

[0019] Patent Document 4: Japanese Unexamined Patent Publication No. 2001-226705

[0020] Patent Document 5: Japanese Unexamined Patent Publication No. 50-17363

[0021] Patent Document 6: Japanese Unexamined Patent Publication No. 60-114508

[0022] Patent Document 7: Japanese Unexamined Patent Publication No. 2000-8104

[0023] Non-Patent Documents

[0024] Non-Patent Document 1: Lord Rayleigh, “On the Capillary Phenomena of Jets”, Proceedings of the Royal Society of London, pp. 71-97, 1879.

[0025] Non-Patent Document 2: D.L. Cummings, D.A. Blackburn, “Oscillations of magnetically levitated aspherical droplets”, J. Fluid Mech, vol. 224, pp. 395-416, 1991. Summary of the Invention

[0026] Problems to be Solved by the Invention

[0027] Accordingly, an object of the present invention is to provide a means for manufacturing tin balls having a diameter greater than about 1 mm and true sphericity at a high yield.

[0028] Technical Means for Solving the Problems

[0029] As a result of intensive studies by the present inventors, it has been found that the above object can be achieved by the following means, and the present invention has been completed.

[0030] That is, in the prior art, when attempting to manufacture tin balls having a diameter greater than about 1 mm and high true sphericity (accuracy of spherical shape) at a high yield by improving the manufacturing process, in the present invention, this object is achieved by using a specific tin for manufacturing tin balls.

[0031] Accordingly, the present invention includes the following (1): (1)

[0033] A kind of metallic tin, the surface tension of which measured by the electromagnetic levitation method is 490×10 -3 Nm -1 or more at a temperature of 1,000 K, and 390×10 -3 Nm -1 or more at a temperature of 1,300 K.

[0034] Effects of the Invention

[0035] According to the present invention, high-purity tin balls having a diameter greater than about 1 mm and high true sphericity can be manufactured with a high yield. Description of the Drawings

[0036] Figure 1 is a schematic diagram of a device for measuring the surface tension of molten metallic tin.

[0037] Figure 2 is a graph showing the results of measuring the surface tension of molten metallic tin of high-purity tin (specimen 1) (Example) and high-purity tin (specimen 2) (Comparative Example).

[0038] Figure 3 is a schematic diagram of a tin ball manufacturing device.

[0039] Figure 4 is a method for determining whether a tin ball is qualified or not.

[0040] Figure 5 is a determination result of whether a tin ball is qualified or not.

[0041] Figure 6A is a photograph showing the appearance of the tin balls manufactured in the Example.

[0042] Figure 6B is a photograph showing the appearance of the tin balls manufactured in the Comparative Example.

[0043] Figure 7 is a photograph showing the appearance of an aggregate of spherical tin balls remaining after visual classification and rolling classification in Example 1. Detailed Description of the Invention

[0044] Specific embodiments are given below to describe the present invention in detail. The present invention is not limited to the specific embodiments disclosed below.

[0045] [Tin for Manufacturing Tin Balls]

[0046] The metallic tin of the present invention is a metallic tin for manufacturing tin balls, and the surface tension measured by the electromagnetic levitation method is 490×10 -3 Nm -1 or more at a temperature of 1,000 K, and 390×10​​​​​​​​-3 Nm -1 Above.

[0047] If the metallic tin for manufacturing solder balls of the present invention is used, high-purity solder balls having a diameter greater than about 1 mm and high sphericity can be manufactured with high yield.

[0048] When spherical particles are obtained by solidifying molten metallic tin, surface tension can be cited as a theoretical force that functions to form the particles.

[0049] However, before the present invention, the relationship between the surface tension of molten metallic tin and particle formation has not been clarified as a specific technique. That is, it is not clear what kind of particles are formed when the specific surface tension value of molten metallic tin is what kind of value.

[0050] Although the reason is not clear, it is considered that one of the reasons is that the measurement of the surface tension of molten metallic tin itself is extremely difficult.

[0051] That is, if the surface tension of molten metallic tin is to be measured, the molten metallic tin is usually placed on a certain substrate for measurement. However, due to the contact with the substrate, the surface tension of the molten metallic tin itself is affected, resulting in a non-negligible difference in the measured value.

[0052] However, this time, as shown in the following examples, the present invention can suspend molten metallic tin in a hollow and measure the surface tension of molten metallic tin without contacting any substrate material. Moreover, by studying the relationship between the surface tension measured in this way and the formed particles, it was found that tin having a specific surface tension is a particle having an average particle diameter greater than 1 mm and is particularly excellent for obtaining particles having excellent sphericity (true sphericity), and the present invention was completed.

[0053] [Surface tension measured by electromagnetic levitation method]

[0054] In a preferred embodiment, the surface tension of the metallic tin of the present invention measured by the electromagnetic levitation method at a temperature of 1,000 K can be set to, for example, 490×10 -3 Nm -1 or more, preferably 495×10 -3 Nm -1 or more, more preferably 500×10 -3 Nm -1 or more, or 505×10 -3 Nm -1 or more, preferably 510×10 -3 Nm -1 or more, and at a temperature of 1,300 K, it can be set to, for example, 390×10 -3 Nm -1Above, preferably 395×10 -3 Nm -1 Above, more preferably 400×10 -3 Nm -1 Above, or 405×10 -3 Nm -1 Above, preferably 410×10 -3 Nm -1 Above.

[0055] The measurement of the surface tension using the electromagnetic levitation method can be carried out by the following means in the examples.

[0056] In a suitable embodiment, the surface tension of the metallic tin of the present invention measured by the electromagnetic levitation method at a temperature of 1,000 K can be set, for example, to 490×10 -3 Nm -1 ~510×10 -3 Nm -1 In the range of, preferably 495×10 -3 Nm -1 ~510×10 - 3 Nm -1 In the range of, more preferably 500×10 -3 Nm -1 ~510×10 -3 Nm -1 In the range of, or 500×10 -3 Nm -1 ~505×10 -3 Nm -1 In the range of, or 490×10 -3 Nm -1 ~505×10 -3 Nm -1 In the range of, preferably 490×10 -3 Nm -1 ~500×10 -3 Nm -1 In the range of, more preferably 495×10 -3 Nm -1 ~500×10 -3 Nm -1 In the range of, or 490×10 -3 Nm -1 ~495×10 -3 Nm -1 In the range.

[0057] In a suitable embodiment, the surface tension of the metallic tin of the present invention measured by the electromagnetic levitation method at a temperature of 1,300 K can be set to 390×10-3 Nm -1 ~410×10 -3 Nm -1 in the range of, preferably 395×10 -3 Nm -1 ~410×10 - 3 Nm -1 in the range of, more preferably 400×10 -3 Nm -1 ~410×10 -3 Nm -1 in the range of, or 400×10 -3 Nm -1 ~405×10 -3 Nm -1 in the range of, or 390×10 -3 Nm -1 ~405×10 -3 Nm -1 in the range of, preferably 390×10 -3 Nm -1 ~400×10 -3 Nm -1 in the range of, more preferably 395×10 -3 Nm -1 ~400×10 -3 Nm -1 in the range of, or 390×10 -3 Nm -1 ~395×10 -3 Nm -1 in the range of.

[0058] In a preferred embodiment, the surface tension of the metallic tin of the present invention measured by the electromagnetic levitation method at a temperature of 1,000 K can be set to 490×10 -3 Nm -1 ~510×10 -3 Nm -1 in the range of, and at a temperature of 1,300 K can be set to 390×10 -3 Nm -1 ~410×10 -3 Nm -1 in the range of.

[0059] In a preferred embodiment, the surface tension of the metallic tin of the present invention measured by the electromagnetic levitation method at a temperature of 1,000 K can be set to 495×10 -3 Nm -1 ~510×10 -3 Nm -1The range can be set to 395×10 -3 Nm -1 ~410×10 -3 Nm -1 in the range.

[0060] In a preferred embodiment, the surface tension of the metallic tin of the present invention measured by the electromagnetic levitation method can be set to 500×10 -3 Nm -1 ~510×10 -3 Nm -1 in the range, and can be set to 400×10 -3 Nm -1 ~410×10 -3 Nm -1 in the range at a temperature of 1,300K.

[0061] In a preferred embodiment, the surface tension of the metallic tin of the present invention measured by the electromagnetic levitation method can be set to 490×10 -3 Nm -1 ~505×10 -3 Nm -1 in the range, and can be set to 390×10 -3 Nm -1 ~405×10 -3 Nm -1 in the range at a temperature of 1,300K.

[0062] In a preferred embodiment, the surface tension of the metallic tin of the present invention measured by the electromagnetic levitation method can be set to 490×10 -3 Nm -1 ~500×10 -3 Nm -1 in the range, and can be set to 390×10 -3 Nm -1 ~400×10 -3 Nm -1 in the range at a temperature of 1,300K.

[0063] In a preferred embodiment, the surface tension of the metallic tin of the present invention measured by the electromagnetic levitation method can be set to 495×10 -3 Nm -1 ~500×10 -3 Nm -1 in the range, and can be set to 395×10 -3 Nm -1 ~400×10 -3 Nm -1range.

[0064] In a preferred embodiment, the surface tension of the metallic tin of the present invention measured by the electromagnetic levitation method may be set in the range of 490×10 -3 Nm -1 to 495×10 -3 Nm -1 at a temperature of 1,000 K, and may be set in the range of 390×10 -3 Nm -1 to 395×10 -3 Nm -1 at a temperature of 1,300 K.

[0065] In a preferred embodiment, the surface tension of the metallic tin of the present invention measured by the electromagnetic levitation method may be set in the range of 500×10 -3 Nm -1 to 505×10 -3 Nm -1 at a temperature of 1,000 K, and may be set in the range of 400×10 -3 Nm -1 to 405×10 -3 Nm -1 at a temperature of 1,300 K.

[0066] [Manufacture of Tin Balls]

[0067] The metallic tin of the present invention can be heated and melted to form a molten solution of metallic tin, and tin balls can be manufactured by using this molten solution of metallic tin.

[0068] The means for heating and melting the metallic tin of the present invention to form a molten solution of metallic tin can use known means. For example, heating and melting can be carried out by radiant heating or induction heating to prepare a molten solution of metallic tin.

[0069] In a preferred embodiment, tin balls can be suitably manufactured by a method including the following steps: dropping the molten solution of the metallic tin of the present invention into a cooling liquid medium; and cooling the droplets of metallic tin while they fall in the cooling liquid medium to form solid tin balls.

[0070] In a preferred embodiment, a cooling liquid medium capable of dropping the molten solution of the metallic tin of the present invention can be applied if it is stable at a temperature higher than the melting point of metallic tin. Examples of such a cooling liquid medium include: animal and vegetable oils, mineral oils, synthetic oils. Preferred examples include: lubricating oils, silicone oils. Most preferably, silicone oil can be used.

[0071] In a preferred embodiment, there is no particular limitation on the means for introducing the molten solution of metallic tin of the present invention into the liquid cooling medium, provided that it can be dropped, and known means can be used. For example, gravity dropping and power dropping can be cited. Preferred examples include natural dropping and ejection using a pump. Particularly preferably, ejection using a pump can be used.

[0072] In a preferred embodiment, after dropping the molten solution of metallic tin of the present invention into the liquid cooling medium, it is cooled while falling in the liquid cooling medium to form solid tin balls. The falling is due to gravity, and preferably, the height of the liquid cooling medium is set such that the distance is sufficient for the formation of solid tin balls while falling.

[0073] [Tin balls]

[0074] The tin balls produced using the molten solution of metallic tin of the present invention have a surface tension as measured by the electromagnetic levitation method as described above, and high-purity tin balls with a diameter greater than about 1 mm and high sphericity can be produced with a high yield.

[0075] In the present invention, the high sphericity of the produced tin balls means that in the aggregate of the produced tin balls, both the proportion of spherical products is large and the proportion of spherical products with a diameter difference ratio of less than 0.04 is large.

[0076] [Proportion of spherical products]

[0077] In a preferred embodiment, the proportion of spherical products (%) calculated by the following formula in the aggregate of the solid tin balls produced using the molten solution of metallic tin of the present invention can be set to, for example, 80% or more, preferably 90% or more, and more preferably 95% or more.

[0078] "Proportion of spherical products" = "Weight of spherical products (g)" / ("Weight of spherical products (g)" + "Weight of non-spherical products (g)") × 100%

[0079] In a preferred embodiment, there is no particular limitation on the upper limit of the proportion of spherical products (%) calculated by the above formula in the aggregate of the solid tin balls produced using the molten solution of metallic tin of the present invention. For example, it can be set to 100% or less, 99.5% or less, 99% or less, 98.5% or less, 98% or less.

[0080] In a suitable embodiment, the proportion (%) of spherical products calculated by the above formula in the aggregate of solid tin balls formed by using the molten solution of metallic tin of the present invention 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%. For example, it can be 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, it can be 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%.

[0081] The screening of spherical and non-spherical products of the tin balls in the present invention can be implemented by the means disclosed in the following examples.

[0082] When manufacturing a plurality of balls, it is useful to measure the weights of the like in the aggregate of tin balls for quality control, and the above-mentioned proportion of spherical products becomes an index suitable for such quality control.

[0083] [Ratio of different diameters]

[0084] In a suitable embodiment, the proportion of spherical products with a ratio of different diameters calculated by the following formula less than 0.04 in the aggregate of spherical products obtained from the aggregate of solid tin balls formed by using the molten solution of metallic tin of the present invention can be, for example, 50% or more, preferably 55% or more, preferably 60% or more.

[0085] "Ratio of different diameters" = "Difference in diameter (mm) measured according to the provisions of JIS B1509:2009" / "Average diameter (mm)"

[0086] In a suitable embodiment, the upper limit of the proportion (%) of spherical products with a ratio of different diameters calculated by the above formula less than 0.04 in the aggregate of solid tin balls formed by using the molten solution of metallic tin of the present invention is not particularly limited. For example, it can be 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, 75% or less.

[0087] In a suitable embodiment, the proportion of spherical articles with a diameter difference ratio calculated by the following formula of less than 0.04 among the aggregate of spherical articles obtained from the aggregate of solid tin balls manufactured using the molten solution of metallic tin of the present invention can be set, 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, in the range of 55% to 100%, 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%.

[0088] The measurement of the diameter difference (mm) and the average diameter (mm) of the tin balls in the present invention according to the provisions of JIS B1509:2009 can be carried out by the means disclosed in the following examples.

[0089] [Diameter]

[0090] In a suitable embodiment, the diameter of the tin balls manufactured using the molten solution of metallic tin of the present invention can be set to a diameter greater than about 1 mm. Regarding the diameter of the tin balls, for 10 tin balls collected from the aggregate of tin balls, the average diameter of each individual tin ball is calculated, and the average value of the average diameters of these individuals, that is, the average value of the average diameters, can be set, for example, in the range of 1 mm to 5 mm, preferably in the range of 1.5 mm to 4.5 mm, preferably in the range of 2 mm to 4 mm.

[0091] [Suitable embodiments of the present invention]

[0092] As a suitable embodiment, the present invention includes the following (1) and below. (1)

[0094] A metallic tin having a surface tension measured by the electromagnetic levitation method of 490×10 -3 Nm -1 or more at a temperature of 1,000 K, and 390×10 -3 Nm -1 or more at a temperature of 1,300 K. (2)

[0096] The metallic tin described in (1) has a surface tension measured by the electromagnetic levitation method in the range of 490×10 -3 Nm -1 ~510×10 -3 Nm -1 at a temperature of 1,000 K, and in the range of 390×10 -3 Nm -1 ~410×10 - 3 Nm -1 at a temperature of 1,300 K. (3)

[0098] The metallic tin described in (1) is the metallic tin for manufacturing tin balls. (4)

[0100] A method for manufacturing tin balls, which manufactures tin balls using the molten solution of the metallic tin described in (1). (5)

[0102] A method for manufacturing tin balls, which is a method for manufacturing tin balls and includes the following steps:

[0103] Dripping the molten solution of the metallic tin described in (1) into a cooling liquid medium;

[0104] The droplets of the metallic tin are cooled while falling in the cooling liquid medium to form solid tin balls. (6)

[0106] According to the manufacturing method described in (5), among the aggregate of the formed solid tin balls, the proportion (%) of spherical products calculated by the following formula is 80% or more.

[0107] "Proportion of spherical products" = "Weight (g) of spherical products" / ("Weight (g) of spherical products" + "Weight (g) of non-spherical products") × 100% (7)

[0109] According to the manufacturing method described in (5), among the aggregate of spherical products obtained from the aggregate of the formed solid tin balls, the proportion of spherical products with a diameter difference ratio of less than 0.04 calculated by the following formula is 50% or more.

[0110] "Diameter difference ratio" = "Diameter difference (mm) measured according to JIS B1509:2009" / "Average diameter (mm)" (8)

[0112] According to the manufacturing method described in (5), the diameter of the tin balls is in the range of 1 mm to 5 mm.

[0113] [Embodiment]

[0114] Embodiments are given below to explain the present invention in detail. The present invention is not limited to the embodiments illustrated below.

[0115] [Example 1: Production of High-Purity Tin (Specimen 1)]

[0116] [Casting]

[0117] 1.7 kg of raw tin (purity 99.999 wt%) was heated and melted in a graphite crucible to a temperature above 300°C. After removing the floating slag, it was poured into a graphite mold to obtain two plates with a thickness of about 10 mm, a width of 70 mm, and a height of 150 mm.

[0118] [Electrolytic Melting]

[0119] One plate-shaped raw tin was used as the anode and arranged in an electrolytic cell opposite to a titanium plate (width 70 mm, height 150 mm) serving as the cathode. Furthermore, the cathode plate was placed in a cathode box with an anion exchange membrane installed on the surface opposite to the anode. An aqueous sulfuric acid solution with a concentration of 9 normal was placed in the cathode box and connected to an outer container through a tube pump to circulate the sulfuric acid aqueous solution. Dilute sulfuric acid with a concentration of 0.5 normal was added inside the electrolytic cell outside the cathode box. Subsequently, the raw tin cast into a plate shape was connected to the positive electrode of a rectifier through electrical wiring, and the titanium plate was connected to the negative electrode of the rectifier.

[0120] Electrolysis was carried out at a current density of 2 A / dm 2 to obtain 3 L of a stannous sulfate solution with a tin concentration of 90 g / L.

[0121] 5 g / L of strontium carbonate was added to the obtained stannous sulfate solution and stirred for 1 hour. The precipitated solid components were filtered and separated. 5 g / L of hydroquinone and 5 g / L of Blaunon N-514 (manufactured by Aoki Oil & Fat Co., Ltd.) as a surfactant were added to the obtained filtrate, and stirring and dissolution were carried out to obtain 2.8 L of a stannous sulfate electrolyte solution.

[0122] [Electrolytic Refining]

[0123] The stannous sulfate electrolyte solution obtained above was diluted with pure water to a tin concentration of 20 g / L and placed on the anode side of the electrolytic cell to form an anolyte. Also, the above stannous sulfate electrolyte solution was placed on the cathode side of the electrolytic cell without dilution to form a catholyte. In the electrolytic cell, the raw tin cast into a plate shape was placed as the anode, and a titanium plate of the same size as above was placed as the cathode.

[0124] The positive electrode of the rectifier was connected to the raw tin, and the negative electrode of the rectifier was connected to the titanium plate. At a current density of 1.5 A / dm2 Electrolysis was carried out. While replacing the anolyte and catholyte, the above operation was repeated to obtain about 600 g of plate-shaped electrolytic tin.

[0125] [Vacuum casting]

[0126] After thoroughly cleaning and drying the obtained electrolytic tin, it was placed in a graphite crucible, heated in the atmosphere to remove slag, and directly cooled and solidified. Subsequently, it was placed in a vacuum melting furnace, heated to 1,000 °C and held for 16 hours, and then cooled and solidified to obtain a high-purity tin ingot.

[0127] [Cutting and cleaning]

[0128] The surface of the high-purity tin ingot was cut off to make only the sound part inside.

[0129] Small pieces were cut out from the high-purity tin that was only the sound part by machining, and acid cleaning and pure water cleaning were carried out.

[0130] Thus, high-purity tin (specimen 1) was obtained. The impurity analysis of the obtained high-purity tin (specimen 1) was carried out using GD-MS. The results of the obtained impurity analysis are shown in Table 1 below. In Table 1, unless otherwise specified, the unit of the value is wtppm.

[0131] [Table 1]

[0132]

[0133] [Example 2: Manufacture of high-purity tin (specimen 2)]

[0134] The high-purity tin (specimen 2) used in the comparative example was manufactured in the following manner.

[0135] Electrolysis was carried out in the same manner as the high-purity tin (specimen 1) manufactured in Example 1 to obtain plate-shaped electrolytic tin. Subsequently, after thoroughly cleaning and drying the obtained electrolytic tin, it was placed in a graphite crucible, heated in the atmosphere to remove slag, and directly cooled and solidified. The surface of the obtained tin ingot was cut off, and only the sound part inside was used. Small pieces were cut out from the tin that was only the sound part by machining, and acid cleaning and pure water cleaning were carried out to be used as high-purity tin (specimen 2).

[0136] The results of the impurity analysis of the high-purity tin (specimen 2) are shown in Table 2 below. In Table 2, unless otherwise specified, the unit of the value is wtppm.

[0137] [Table 2]

[0138]

[0139] [Example 3: Measurement of the surface tension of high-purity tin (specimen 1)]

[0140] [Apparatus for Measuring Surface Tension]

[0141] The surface tension of the obtained high-purity tin (specimen 1) was measured.

[0142] Figure 1 It is an explanatory diagram showing an outline of an apparatus for measuring surface tension.

[0143] Figure 1 The shown measuring apparatus includes a sealed quartz chamber 4 and has the following structure: gas can be introduced into the interior of the quartz chamber 4 from a gas introduction pipe 7, and gas can be discharged from a gas discharge pipe 8. Inside the quartz chamber 4, a specimen holder 5 for holding a specimen is provided. The specimen holder 5 has the following structure: it can place tin 1 as a specimen, hold it at a position where it can be induction-heated by a coil 2, and at the same time has the following structure: the specimen (tin 1) induction-heated by the coil 2 can melt and float, and at the same time lower. The measuring apparatus has a high-frequency power supply outside the quartz chamber 4 that can supply high-frequency current to the coil. An observation window 6 for observing the interior is provided at the upper part of the quartz chamber 4, and the interior can be photographed at high speed through this observation window 6 by a camera 9.

[0144] [Order of Measuring Surface Tension]

[0145] Using Figure 1 the shown measuring apparatus, the surface tension of high-purity tin was measured in the following manner.

[0146] The high-purity tin (specimen 1) was cut to collect it in a square shape (about 5 mm on one side) to be 420 - 480 mg.

[0147] Using an ultrasonic cleaner, the surface of the collected square tin specimen was etched with a 3 vol.% hydrochloric acid aqueous solution, and then acetone cleaning was carried out.

[0148] The tin specimen was set on the quartz glass holder of the electromagnetic levitation chamber.

[0149] The inside of the measurement system was evacuated (10 -7 atm), and then the ambient gas (argon - helium) was introduced from the upper part at 2 L / min. The oxygen partial pressure of the ambient gas (argon - helium) was 1×10 -7 atm (volume concentration: 0.1 vol.ppm).

[0150] High-frequency alternating current was passed through the electromagnetic levitation coil to make the specimen levitate electromagnetically and at the same time heat it. In order to separate the specimen from the holder before the specimen melts, the sample holder was heated and at the same time lowered.

[0151] Measure the temperature using two monochromatic radiation thermometers with different wavelengths.

[0152] Wavelength 1: 1.64 μm

[0153] Wavelength 2: 1.4 μm

[0154] At the chamber inlet, measure the ambient oxygen partial pressure of the introduced gas using a zirconia oxygen sensor operating at 1,008 K.

[0155] Record the surface vibration behavior of the droplets after the sample melts from above using a high-speed camera (500 FPS, 8,192 frames (16.384 seconds)).

[0156] Immediately after recording, blow helium gas at 20 L / min from above the sample to perform rapid solidification.

[0157] Measure the mass of the sample using an electronic balance.

[0158] Perform image analysis on the changes in the center-of-gravity movement, radius, and area of the droplets from the droplet projection images to identify the vibration frequencies of m = 0, m = ±1, m = ±2 for the l = 2 mode and m = 0, m = ±1 for the l = 1 mode.

[0159] Using the obtained frequencies and the sample mass, calculate the surface tension using the Rayleigh formula (refer to Non-Patent Document 1) and the Cummings & Blackburn modified formula (refer to Non-Patent Document 2).

[0160] [Measurement Results of Surface Tension]

[0161] Show the measurement results of the surface tension obtained in this way in Figure 2 .

[0162] [Example 4: Measurement of the Surface Tension of High-Purity Tin (Sample 2)]

[0163] Measure the surface tension of high-purity tin (sample 2) in the same manner as the high-purity tin (sample 1) measured in Example 3. Summarize and show the measurement results of the surface tension obtained in Figure 2 .

[0164] [Evaluation of the Measurement Results of Surface Tension]

[0165] According to the graph of Figure 2 , the surface tension of sample 1 as an example is 500 (490 - 510) × 10 -3 N / m -1 or more at a temperature of 1,000 K, and 400 (390 - 410) × 10 -3 N / m -1Above, in contrast, the surface tension of the specimen 2 as a comparative example was measured in the same manner, and the result was 440 to 460×10 -3 Nm -1 above at a temperature of 1,000K, and 330 to 350×10 -3 Nm -1 above at a temperature of 1,300K. From this result, it can be seen that in this specimen, there is a negative correlation between temperature and surface tension, and also, the surface tension of the specimen 1 as an example is higher than that of the specimen 2 as a comparative example.

[0166] [Example 5: Manufacture of Tin Balls (Examples 1 to 3)]

[0167] [Manufacturing Apparatus for Tin Balls]

[0168] Using the obtained high-purity tin (specimen 1), tin balls were manufactured.

[0169] Figure 3 It is an explanatory diagram showing an outline of a manufacturing apparatus for manufacturing tin balls.

[0170] Figure 3 The shown manufacturing apparatus includes a melting container 14 which is used to melt and accommodate tin as a raw material for manufacturing tin balls. The tin in the melting container 14 is heated by a heater 15 to become a molten state. The melting container 14 is sealed, and when silicone oil accommodated in a silicone oil container 17 is introduced through a silicone oil delivery pipe 18 by a pump 19, due to this pressure, the molten tin in the melting container 14 is dropped through a tin delivery pipe 16 into the silicone oil filled in a granulation container 12. A heater 13 is provided at the upper part of the granulation container 12, and the molten tin is maintained in a molten state at the upper part of the granulation container 12. The space in the manufacturing apparatus is filled with argon instead of air, and the oxidation of the molten tin is suppressed. The droplets of molten tin introduced through the tin delivery pipe 16 and dropped into the silicone oil filled in the granulation container 12 first become spherical during the period of freely falling in the silicone oil filled in the granulation container 12, and then cool and solidify to become tin balls 11, which accumulate at the bottom of the granulation container 12.

[0171] [Sequence of Manufacturing Tin Balls]

[0172] Using high-purity tin (specimen 1), tin balls were manufactured in the following manner.

[0173] 2,000 g of small pieces of pickled and washed high-purity tin (specimen 1) were put into the melting container of a tin ball manufacturing apparatus made of quartz. On the other hand, the granulation container was filled with silicone oil. The lids of the melting container and the granulation container were covered, and high-purity argon was continuously flowed at a flow rate of 1 L / minute until the oxygen concentration inside the granulation container became 0.1 vol% or less.

[0174] The upper parts of the melting container and the granulation container are heated by an external heater.

[0175] After the high-purity tin in the melting container is melted, the pump is started, and the molten tin is ejected from the melting container into the granulation container, where it is dropped while being dripped, and spheroidized by surface tension during the free fall. Since the lower part of the granulation container is not heated, the molten tin solidifies and accumulates in a spheroidized state.

[0176] After the ejection is completed, the power supplies of the ejection pump and the heater are turned off. After cooling, the argon gas flow is stopped, and the tin balls are taken out.

[0177] In order to remove the silicone oil from the taken-out tin balls, they are washed with toluene and then with dilute hydrochloric acid.

[0178] The tin balls are classified according to their shape and size.

[0179] Through the above procedure, the manufacture of tin balls is repeated 3 times as Examples 1 to 3.

[0180] [Example 6: Manufacture of Tin Balls (Comparative Examples 1 to 3)]

[0181] When manufacturing the tin balls of the comparative examples, the above-mentioned high-purity tin (specimen 2) is used instead of high-purity tin (specimen 1) as the raw material. Through the same apparatus and procedure as in Example 5, the manufacture of tin balls is repeated 3 times to manufacture the tin balls of Comparative Examples 1 to 3.

[0182] [Example 7: Evaluation of Tin Balls]

[0183] [Sequence of Evaluation of Tin Balls]

[0184] Among the 6 aggregates of tin balls obtained from Examples 1 to 3 and Comparative Examples 1 to 3, the diameters of the tin balls are in the range of 3.2 to 3.6 mm.

[0185] These tin balls are evaluated through the following procedure. The explanatory diagram showing the procedure of the evaluation of the tin balls is labeled Figure 4 .

[0186] [Visual Classification]

[0187] Those that are extremely large, extremely small, or deformed in shape under visual inspection are removed.

[0188] [Rolling Classification]

[0189] Subsequently, they are rolled on a metal angle bent at 90°, and those that do not roll are removed.

[0190] [Screening of Spherical and Abnormal-Shaped Products]

[0191] Those remaining after visual classification and rolling classification are regarded as spherical products. Those removed after visual classification and rolling classification are regarded as non-spherical products.

[0192] [Spherical product ratio]

[0193] From the weights of the spherical products and the non-spherical products, the spherical product ratio (%) is calculated by the following formula.

[0194] "Spherical product ratio" = "Weight of spherical products" / ("Weight of spherical products" + "Weight of non-spherical products") × 100%

[0195] [Ratio of different diameters]

[0196] Randomly take out 10 balls from the spherical products. Referring to the provisions of JIS B1509:2009, use a micrometer instead of a measuring plane and a measuring instrument perpendicular thereto, change the measuring position, and perform 10 measurements on each ball separately. Calculate the difference in diameter using the 10 measured values. In the present invention, the arithmetic mean of the 10 measured values obtained for each ball is used as the average diameter of each ball, and the ratio of the difference in diameter to the average diameter is used to obtain the ratio of different diameters.

[0197] [Results of evaluation of solder balls]

[0198] The results of calculating the ratio of the spherical products obtained for the solder ball aggregates of Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Figure 5 .

[0199] As Figure 5 shown, the spherical product ratios of Examples 1 to 3 are all values exceeding 80%. In contrast, the spherical product ratios of Comparative Examples 1 to 3 are all values below 80%. Thus, it can be said that the samples of the examples are suitable for manufacturing spherical products.

[0200] The appearances of the spherical products and non-spherical products obtained from the solder ball aggregates of Examples 1 to 3 are illustrated in Figure 6A . The appearances of the spherical products and non-spherical products obtained from the solder ball aggregates of Comparative Examples 1 to 3 are illustrated in Figure 6B .

[0201] As Figure 6A and Figure 6B illustrated, the spherical products are in a shape very close to a sphere. Also, as Figure 6A and Figure 6B illustrated, as non-spherical products, products in a shape formed by combining a plurality of balls or products in a shape in which the shape of a ball is deformed are observed. Although the numerical values of the data are not shown, among the non-spherical products formed by combining a plurality of balls, the non-spherical products formed by combining 2 balls in Examples 1 to 3 account for the majority. In contrast, in Comparative Examples 1 to 3, a plurality of non-spherical products formed by combining more than 2 balls are observed.

[0202] The measurement results of the average diameter obtained from the solder ball aggregates 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 solder ball taken out for measurement. In Table 3, unless otherwise specified, the unit of the numerical value is mm.

[0203] [Table 3]

[0204]

[0205] As shown in Table 3, the obtained solder balls have an average diameter (average of the average diameters) between 3 and 4 mm, and are sufficiently large balls.

[0206] The measurement results of the diameter difference ratios obtained from the solder ball aggregates 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 solder ball taken out for measurement.

[0207] [Table 4]

[0208] No. Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 1 0.024 0.028 0.035 0.039 0.024 0.031 2 0.044 0.032 0.057 0.048 0.058 0.046 3 0.033 0.044 0.024 0.061 0.040 0.047 4 0.061 0.024 0.052 0.039 0.043 0.037 5 0.021 0.042 0.022 0.042 0.046 0.067 6 0.038 0.023 0.035 0.044 0.027 0.045 7 0.041 0.040 0.030 0.026 0.032 0.046 8 0.040 0.020 0.037 0.044 0.053 0.051 9 0.021 0.023 0.022 0.013 0.062 0.055 10 0.017 0.044 0.047 0.042 0.029 0.036 Proportion less than 0.04 60％ 60％ 70％ 40％ 40％ 30％ Average value 0.035 0.032 0.036 0.040 0.041 0.046

[0209] As shown in Table 4, in Examples 1 to 3, the proportion of the diameter difference ratio not reaching 0.04 accounts for more than 50% of the total. On the other hand, in Comparative Examples 1 to 3, the proportion of the diameter difference ratio not reaching 0.04 is less than 50% of the total. Thus, even in the case of comparison among spherical products, the sphericity of the specimens in the examples is higher than that in the comparative examples, indicating that the specimens in the examples are suitable for manufacturing spherical products. Furthermore, if the average value of the measured diameter difference ratios of the specimens is taken, it does not reach 0.04 in Examples 1 to 3 and is 0.04 or more in Comparative Examples 1 to 3. From this, it can also be seen that the sphericity of the specimens in the examples is higher than that of the specimens in the comparative examples.

[0210] In Example 1, an external appearance photograph of the aggregate of solder balls remaining as spherical products after visual classification and rolling classification is shown in Figure 7 . According to the high-purity tin of the present invention, it is possible to efficiently manufacture a plurality of high-quality solder balls for spherical products such as Figure 7 .

[0211] [Relationship between surface tension and evaluation results of solder balls]

[0212] The surface tension of the tin of the present invention measured by the electromagnetic levitation method is 492×10 -3 Nm -1 at a temperature of 1,000 K and 397×10 -3 Nm -1, the proportion of spherical products other than deformed products contained in the solder balls made of this solder is as high as 96.9 - 97.5%.

[0213] On the other hand, the surface tension measured for solder with a surface tension lower than this by the electromagnetic levitation method is 455×10 -3 Nm -1 at a temperature of 1,000K, and is 365×10 -3 Nm -1 at a temperature of 1,300K. The proportion of spherical products other than deformed products contained in the solder balls made of this solder is as low as 70.1 - 75.9%.

[0214] [Possibility of contributing to the SDGs]

[0215] According to an embodiment of the present invention, there is provided a solder ball having a large diameter and excellent true sphericity. Since the high-precision of materials and components has become important in the development of IoT and AI technologies, an embodiment of the present invention can contribute to the development of IoT, AI technologies, etc. Therefore, an embodiment of the present invention can contribute to Goal 9 of the Sustainable Development Goals (SDGs) led by the United Nations, "Promote the construction of resilient infrastructure, inclusive and sustainable industrialization, and the advancement of innovation."

[0216] [Industrial applicability]

[0217] According to the present invention, it is possible to manufacture solder balls having a large diameter and high true sphericity with a high yield. The present invention is an industrially useful invention.

Claims

1. A metallic tin having a surface tension of 490×10 -3 Nm -1 above, and at a temperature of 1,300 K is 390×10 -3 Nm -1 above.

2. The metallic tin according to claim 1, wherein the surface tension thereof measured by electromagnetic levitation method at a temperature of 1,000 K is 490×10 -3 Nm -1 ~510×10 -3 Nm -1 range, and at a temperature of 1,300 K it is 390×10 -3 Nm -1 ~410×10 -3 Nm -1 range. The metallic tin according to claim 1 , which is metallic tin for manufacturing solder balls.

4. A method for producing a solder ball, comprising producing the solder ball using the molten metal tin according to claim 1.

5. A method for manufacturing a solder ball, which is a method for manufacturing a solder ball, comprising the following steps: Adding the molten metal tin according to claim 1 dropwise into the cooling liquid medium; The metallic tin droplets cool down while falling in the cooling liquid medium, and form solid tin balls.

6. The manufacturing method according to claim 5, wherein: In the aggregate of the formed solid solder balls, the proportion (%) 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 irregular-shaped products (g)") × 100%.

7. The manufacturing method according to claim 5, wherein: In the aggregate of spherical products obtained from the aggregate of the formed solid solder balls, the proportion of spherical products having a diameter difference ratio of less than 0.04 calculated by the following formula is 50% or more: "Diameter difference ratio" = "Diameter difference (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 solder ball is in the range of 1 mm to 5 mm.

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