Indium silver alloy and preparation method and application thereof

Abstract

The invention discloses an indium-silver alloy and a preparation method and application thereof, and relates to the technical field of precious metal material manufacturing. The preparation method of the indium-silver alloy comprises the following steps: S1. heating and melting raw materials indium and raw materials silver respectively to obtain molten indium and molten silver; S2. pouring the molten silver obtained in step S1 into the molten indium obtained in step S1 and uniformly mixing them into an alloy melt; S3. cooling and solidifying the alloy melt obtained in step S2; S4. heating and melting the solidified alloy obtained in step S3 under a vacuum environment and keeping the temperature to obtain an alloy melt again, and cooling to obtain an indium-silver alloy. The present invention does not require heating all raw materials to a high temperature to uniformly disperse silver in an indium matrix, thereby reducing material loss caused by volatilization and oxidation. By repeatedly melting the alloy in a vacuum at a relatively low temperature, on the one hand, gas inclusions in the alloy are reduced and the alloy composition is made uniform, and on the other hand, the volatilization of indium in the degassing process is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of precious metal material manufacturing, and more specifically, to an indium-silver alloy and a preparation method and application thereof. Background Art

[0002] Indium silver alloy is a low-temperature special solder with the advantages of good fatigue resistance and ductility, good electrical and thermal conductivity, and high reliability. It is widely used in the packaging of semiconductor integrated circuits such as high-performance chips, MEMS (micro-electromechanical systems) sensors, and is one of the important solder varieties in the semiconductor industry.

[0003] Vacuum melting is an important process for obtaining high-quality solder alloys, which can effectively reduce the oxygen content in the alloy. In the prior art, the preparation methods of the alloy include the following two methods: one is to mix all the metal raw materials and then heat and melt them, and control the heating temperature to be between the melting points of the two metals, and use the metal with a lower melting point to dissolve the metal with a higher melting point. However, this method will cause the composition of the alloy to be uneven.

[0004] Another method is to heat and melt all the metal raw materials after mixing them, and control the heating temperature to make all the metals melt. For example, the prior art discloses a method for preparing an indium-silver alloy material, comprising the following steps: (a). Providing silver metal particles and indium metal particles; (b). Mixing the silver metal particles and the indium metal particles to form a silver-indium metal mixture; (c). Performing a vacuum heating step on the silver-indium metal mixture to melt the silver-indium metal mixture into a uniform molten state of silver and indium, and the vacuum heating temperature is 1000-1030°C; (d). Performing a vacuum cooling step on the silver-indium metal mixture to form a silver-indium alloy primary product, and the silver-indium alloy primary product is a solid solution of silver and indium coexisting solid and liquid; (e). Performing a vacuum annealing step on the silver-indium alloy primary product to form a silver alloy material, wherein the silver alloy material has a solid-liquid coexistence zone.

[0005] However, the preparation method of the indium-silver alloy still has the following technical problems: since the melting point of indium is 156.6°C and the melting point of silver is 960°C, the temperature of vacuum heating of the silver-indium metal mixture in the above prior art is 1000-1030°C. Indium is easy to volatilize at this high temperature, which not only pollutes the smelting equipment, but also causes a large loss of indium, resulting in a decrease in the indium content in the alloy. Since indium and silver are both precious metal raw materials, the preparation of indium-silver alloys especially needs to reduce losses. Summary of the invention

[0006] In order to overcome the shortcomings of high raw material loss and uneven composition when the existing smelting technology is applied to the preparation of indium silver alloy, the present invention provides a method for preparing indium silver alloy, which has low raw material loss and the prepared indium silver alloy has excellent composition uniformity.

[0007] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0008] A method for preparing an indium-silver alloy comprises the following steps:

[0009] S1. The raw material indium and the raw material silver are heated and melted to obtain molten indium and molten silver;

[0010] S2. The molten silver obtained in step S1 is poured into the molten indium obtained in step S1 and uniformly mixed into an alloy melt;

[0011] S3. The alloy melt obtained in step S2 is cooled and solidified;

[0012] S4. The solidified alloy obtained in step S3 is heated and melted in a vacuum environment and kept warm again to obtain an alloy melt, and then cooled to obtain an indium silver alloy;

[0013] Wherein, in step S4, the heating temperature is 200°C to 400°C, and the insulation time is 10min to 30min.

[0014] The present invention heats and melts raw indium and raw silver separately, and then pours the silver melt into the indium melt to mix them in a liquid state. The silver can be evenly dispersed in the indium matrix without heating all the raw materials to a high temperature, thereby obtaining an indium-silver alloy with uniform composition, reducing material loss due to volatilization and oxidation, and being beneficial to improving smelting efficiency and reducing smelting time. In addition, it is also beneficial to improving the uniformity of alloy composition.

[0015] Moreover, the present invention repeatedly melts the alloy in vacuum at a relatively low temperature in step S4, which reduces gas inclusions in the alloy and further makes the alloy composition more uniform. On the other hand, due to the relatively low heating temperature, the volatilization of indium in the degassing process can be reduced.

[0016] In step S4, if the heating temperature is too high, the volatilization loss of indium will be increased. If the heating temperature is too low, the oxygen content in the alloy will be too high, and when the alloy is used as solder, it will increase the welding voids and reduce the welding quality.

[0017] In step S4, if the holding time is too long, the volatilization loss of indium will be increased, while if the holding time is too short, the effect of reducing gas inclusions in the alloy will not be obvious.

[0018] In step S4 of the present invention, the heating temperature can be 200°C, 250°C, 300°C, 350°C, or 400°C.

[0019] In step S4 of the present invention, the insulation time can be 10 min, 15 min, 20 min, 25 min, or 30 min.

[0020] In practical applications, the preparation method of indium silver alloy may include the following steps:

[0021] S1. The raw indium and raw silver are placed in different crucibles and heated to melt to obtain molten indium and molten silver;

[0022] S2. The molten silver obtained in step S1 is poured into the molten indium obtained in step S1 and uniformly mixed into an alloy melt;

[0023] S3. The molten alloy obtained in step S2 is poured into a mold and cooled and solidified;

[0024] S4. The solidified alloy ingot obtained in step S3 is placed in a crucible, heated and melted in a vacuum environment and kept warm to obtain an alloy melt again, and the melt is poured and cooled to obtain an indium silver alloy.

[0025] Preferably, in step S4, the heating temperature is 200°C to 300°C.

[0026] Preferably, in step S4, the insulation time is 15 min to 25 min.

[0027] Preferably, in step S1, the heating temperature of indium is 200°C to 400°C.

[0028] The melting point of indium is 156.6°C. Heating indium to 200°C~400°C is conducive to obtaining molten indium, and can also avoid the volatilization of indium at high temperature and reduce the loss of indium.

[0029] The heating temperature of indium may be 200°C, 250°C, 300°C, 350°C, or 400°C.

[0030] Preferably, in step S1, the heating temperature of silver is 1000°C to 1200°C.

[0031] The melting point of silver is 960°C. Heating silver to 1000°C~1200°C is conducive to obtaining molten silver.

[0032] The heating temperature of silver may be 1000°C, 1050°C, 1100°C, 1150°C, or 1200°C.

[0033] The heating temperature of silver is slightly lower, which can reduce metal loss, but may cause the uniformity of the alloy to be slightly worse. This may be because the heating temperature of silver is slightly lower, and the dissolution rate of silver in indium is slower, resulting in uneven distribution of silver in different areas.

[0034] Preferably, in step S4, the air pressure of the vacuum environment does not exceed 20Pa.

[0035] The lower the air pressure in the vacuum environment, the more conducive it is to reducing the gas inclusions in the alloy.

[0036] More preferably, in step S4, the air pressure of the vacuum environment does not exceed 10Pa.

[0037] Preferably, in step S1, the mass fraction of silver in the raw material is 0.5% to 5%.

[0038] The indium-silver alloy prepared from the raw materials of indium and silver can be used as solder in the semiconductor industry.

[0039] The present invention also protects an indium-silver alloy prepared by any of the above-mentioned methods for preparing the indium-silver alloy.

[0040] Preferably, the oxygen content in the indium-silver alloy is not higher than 0.008 wt.%.

[0041] The present invention also protects the application of the above-mentioned indium silver alloy in solder.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The present invention provides a method for preparing an indium-silver alloy. By heating and melting raw indium and raw silver separately, and then mixing the silver melt with the indium melt in a liquid state, the silver can be evenly dispersed in an indium matrix without heating all raw materials to a high temperature, thereby obtaining an alloy with uniform composition, reducing material loss due to volatilization and oxidation, and facilitating the improvement of smelting efficiency and the reduction of smelting time, and also facilitating the improvement of alloy composition uniformity. Moreover, the present invention repeatedly melts the alloy in a vacuum at a relatively low temperature, thereby reducing gas inclusions in the alloy and further making the alloy composition uniform, and reducing the volatilization of indium during the degassing process. DETAILED DESCRIPTION

[0044] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0045] Example 1

[0046] A method for preparing an indium-silver alloy comprises the following steps:

[0047] S1. Putting raw indium and raw silver into different crucibles and heating and melting them respectively to obtain molten indium and molten silver; wherein the mass fraction of indium is 97% and the heating temperature is 250°C, and the mass fraction of silver is 3% and the heating temperature is 1100°C;

[0048] S2. The molten silver obtained in step S1 is poured into the molten indium obtained in step S1 and uniformly mixed into an alloy melt;

[0049] S3. The molten alloy obtained in step S2 is poured into a mold, and the ingot is removed after cooling and solidification;

[0050] S4. The ingot obtained in step S3 is placed in a crucible, heated and melted in a vacuum environment and kept warm to obtain an alloy melt again, and the melt is poured and cooled to obtain the desired indium silver alloy, wherein the vacuum degree is 5 Pa, the heating temperature is 200° C., and the holding time is 10 min.

[0051] Example 2

[0052] A method for preparing an indium-silver alloy comprises the following steps:

[0053] S1. Putting raw indium and raw silver into different crucibles and heating and melting them respectively to obtain molten indium and molten silver; wherein the mass fraction of indium is 97% and the heating temperature is 250°C, and the mass fraction of silver is 3% and the heating temperature is 1100°C;

[0054] S2. The molten silver obtained in step S1 is poured into the molten indium obtained in step S1 and uniformly mixed into an alloy melt;

[0055] S3. The molten alloy obtained in step S2 is poured into a mold, and the ingot is removed after cooling and solidification;

[0056] S4. The ingot obtained in step S3 is placed in a crucible, heated and melted in a vacuum environment and kept warm to obtain an alloy melt again, and the melt is poured and cooled to obtain the desired indium silver alloy, wherein the vacuum degree is 5 Pa, the heating temperature is 300° C., and the holding time is 10 min.

[0057] The difference from Example 1 is that in step S4, the heating temperature is 300°C.

[0058] Example 3

[0059] A method for preparing an indium-silver alloy comprises the following steps:

[0060] S1. Putting raw indium and raw silver into different crucibles and heating and melting them respectively to obtain molten indium and molten silver; wherein the mass fraction of indium is 97% and the heating temperature is 250°C, and the mass fraction of silver is 3% and the heating temperature is 1100°C;

[0061] S2. The molten silver obtained in step S1 is poured into the molten indium obtained in step S1 and uniformly mixed into an alloy melt;

[0062] S3. The molten alloy obtained in step S2 is poured into a mold, and the ingot is removed after cooling and solidification;

[0063] S4. The ingot obtained in step S3 is placed in a crucible, heated and melted in a vacuum environment and kept warm to obtain an alloy melt again, and the melt is poured and cooled to obtain the desired indium silver alloy, wherein the vacuum degree is 5 Pa, the heating temperature is 400° C., and the holding time is 10 min.

[0064] The difference from Example 1 is that in step S4, the heating temperature is 400°C.

[0065] Example 4

[0066] A method for preparing an indium-silver alloy comprises the following steps:

[0067] S1. Putting raw indium and raw silver into different crucibles and heating and melting them respectively to obtain molten indium and molten silver; wherein the mass fraction of indium is 97% and the heating temperature is 250°C, and the mass fraction of silver is 3% and the heating temperature is 1100°C;

[0068] S2. The molten silver obtained in step S1 is poured into the molten indium obtained in step S1 and uniformly mixed into an alloy melt;

[0069] S3. The molten alloy obtained in step S2 is poured into a mold, and the ingot is removed after cooling and solidification;

[0070] S4. The ingot obtained in step S3 is placed in a crucible, heated and melted in a vacuum environment and kept warm to obtain an alloy melt again, and the melt is poured and cooled to obtain the desired indium silver alloy, wherein the vacuum degree is 5 Pa, the heating temperature is 200° C., and the holding time is 20 min.

[0071] The difference from Example 1 is that in step S4, the insulation time is 20 minutes.

[0072] Example 5

[0073] A method for preparing an indium-silver alloy comprises the following steps:

[0074] S1. Putting raw indium and raw silver into different crucibles and heating and melting them respectively to obtain molten indium and molten silver; wherein the mass fraction of indium is 97% and the heating temperature is 250°C, and the mass fraction of silver is 3% and the heating temperature is 1100°C;

[0075] S2. The molten silver obtained in step S1 is poured into the molten indium obtained in step S1 and uniformly mixed into an alloy melt;

[0076] S3. The molten alloy obtained in step S2 is poured into a mold, and the ingot is removed after cooling and solidification;

[0077] S4. The ingot obtained in step S3 is placed in a crucible, heated and melted in a vacuum environment and kept warm to obtain an alloy melt again, and the melt is poured and cooled to obtain the desired indium silver alloy, wherein the vacuum degree is 5 Pa, the heating temperature is 200° C., and the holding time is 30 min.

[0078] The difference from Example 1 is that in step S4, the insulation time is 30 minutes.

[0079] Example 6

[0080] A method for preparing an indium-silver alloy comprises the following steps:

[0081] S1. Putting raw indium and raw silver into different crucibles and heating and melting them respectively to obtain molten indium and molten silver; wherein the mass fraction of indium is 97% and the heating temperature is 250°C, and the mass fraction of silver is 3% and the heating temperature is 1100°C;

[0082] S2. The molten silver obtained in step S1 is poured into the molten indium obtained in step S1 and uniformly mixed into an alloy melt;

[0083] S3. The molten alloy obtained in step S2 is poured into a mold, and the ingot is removed after cooling and solidification;

[0084] S4. The ingot obtained in step S3 is placed in a crucible, heated and melted in a vacuum environment and kept warm to obtain an alloy melt again, and the melt is poured and cooled to obtain the desired indium silver alloy, wherein the vacuum degree is 20 Pa, the heating temperature is 200° C., and the holding time is 10 min.

[0085] The difference from Example 1 is that in step S4, the vacuum degree is 20Pa.

[0086] Comparative Example 1

[0087] Indium and silver are placed in the same crucible and heated to melt in a vacuum environment. The mass fraction of indium is 97%, the mass fraction of silver is 3%, the heating temperature is 1100℃, and the vacuum degree is 5Pa. After the smelting is completed, the melt is poured and cooled to obtain the desired indium silver alloy.

[0088] Comparative Example 2

[0089] A method for preparing an indium-silver alloy comprises the following steps:

[0090] S1. Putting raw indium and raw silver into different crucibles and heating and melting them respectively to obtain molten indium and molten silver; wherein the mass fraction of indium is 97% and the heating temperature is 250°C, and the mass fraction of silver is 3% and the heating temperature is 1100°C;

[0091] S2. The molten indium obtained in step S1 is poured into the molten silver obtained in step S1 and uniformly mixed into an alloy melt;

[0092] S3. The molten alloy obtained in step S2 is poured into a mold, and the ingot is removed after cooling and solidification;

[0093] S4. The ingot obtained in step S3 is placed in a crucible, heated and melted in a vacuum environment and kept warm to obtain an alloy melt again, and the melt is poured and cooled to obtain the desired indium silver alloy, wherein the vacuum degree is 5 Pa, the heating temperature is 200° C., and the holding time is 10 min.

[0094] The difference from Example 1 is: S2. The molten indium obtained in step S1 is poured into the molten silver obtained in step S1 and mixed evenly into an alloy melt.

[0095] Comparative Example 3

[0096] A method for preparing an indium-silver alloy comprises the following steps:

[0097] S1. Putting raw indium and raw silver into different crucibles and heating and melting them respectively to obtain molten indium and molten silver; wherein the mass fraction of indium is 97% and the heating temperature is 250°C, and the mass fraction of silver is 3% and the heating temperature is 1100°C;

[0098] S2. The molten silver obtained in step S1 is poured into the molten indium obtained in step S1 and uniformly mixed into an alloy melt;

[0099] S3. The molten alloy obtained in step S2 is poured into a mold, and the ingot is removed after cooling and solidification;

[0100] S4. The ingot obtained in step S3 is placed in a crucible, heated and melted in a vacuum environment and kept warm to obtain an alloy melt again, and the melt is poured and cooled to obtain the desired indium silver alloy, wherein the vacuum degree is 5 Pa, the heating temperature is 170° C., and the holding time is 10 min.

[0101] The difference from Example 1 is that in step S4, the heating temperature is 170°C.

[0102] Comparative Example 4

[0103] A method for preparing an indium-silver alloy comprises the following steps:

[0104] S1. Putting raw indium and raw silver into different crucibles and heating and melting them respectively to obtain molten indium and molten silver; wherein the mass fraction of indium is 97% and the heating temperature is 250°C, and the mass fraction of silver is 3% and the heating temperature is 1100°C;

[0105] S2. The molten silver obtained in step S1 is poured into the molten indium obtained in step S1 and uniformly mixed into an alloy melt;

[0106] S3. The molten alloy obtained in step S2 is poured into a mold, and the ingot is removed after cooling and solidification;

[0107] S4. The ingot obtained in step S3 is placed in a crucible, heated and melted in a vacuum environment and kept warm to obtain an alloy melt again, and the melt is poured and cooled to obtain the desired indium silver alloy, wherein the vacuum degree is 5 Pa, the heating temperature is 450° C., and the holding time is 10 min.

[0108] The difference from Example 1 is that in step S4, the heating temperature is 450°C.

[0109] Comparative Example 5

[0110] A method for preparing an indium-silver alloy comprises the following steps:

[0111] S1. Putting raw indium and raw silver into different crucibles and heating and melting them respectively to obtain molten indium and molten silver; wherein the mass fraction of indium is 97% and the heating temperature is 250°C, and the mass fraction of silver is 3% and the heating temperature is 1100°C;

[0112] S2. The molten silver obtained in step S1 is poured into the molten indium obtained in step S1 and uniformly mixed into an alloy melt;

[0113] S3. The molten alloy obtained in step S2 is poured into a mold, and the ingot is removed after cooling and solidification;

[0114] S4. The ingot obtained in step S3 is placed in a crucible, heated and melted in a vacuum environment and kept warm to obtain an alloy melt again, and the melt is poured and cooled to obtain the desired indium silver alloy, wherein the vacuum degree is 5 Pa, the heating temperature is 200° C., and the holding time is 5 min.

[0115] The difference from Example 1 is that in step S4, the insulation time is 5 minutes.

[0116] Comparative Example 6

[0117] A method for preparing an indium-silver alloy comprises the following steps:

[0118] S1. Putting raw indium and raw silver into different crucibles and heating and melting them respectively to obtain molten indium and molten silver; wherein the mass fraction of indium is 97% and the heating temperature is 250°C, and the mass fraction of silver is 3% and the heating temperature is 1100°C;

[0119] S2. The molten silver obtained in step S1 is poured into the molten indium obtained in step S1 and uniformly mixed into an alloy melt;

[0120] S3. The molten alloy obtained in step S2 is poured into a mold, and the ingot is removed after cooling and solidification;

[0121] S4. The ingot obtained in step S3 is placed in a crucible, heated and melted in a vacuum environment and kept warm to obtain an alloy melt again, and the melt is poured and cooled to obtain the desired indium silver alloy, wherein the vacuum degree is 5 Pa, the heating temperature is 200° C., and the holding time is 40 min.

[0122] The difference from Example 1 is that in step S4, the insulation time is 40 minutes.

[0123] Results

[0124] The embodiment and the comparative example adopt the same smelting raw material ratio, and test the composition, oxygen content and smelting loss of the prepared indium silver alloy (In97Ag3). XRF is used to detect the alloy composition, an oxygen and nitrogen analyzer is used to detect the alloy oxygen content, and an analytical balance is used to weigh the material weight before and after smelting. The melting loss calculation formula is:

[0125] Melting loss = weight of alloy obtained by smelting / total weight of smelting raw materials × 100%.

[0126] Composition uniformity test: The method is to measure the composition of different positions of the alloy, and the range of indium content is used to characterize the uniformity. The calculation formula is:

[0127] The extreme value of indium content = (maximum indium content - minimum indium content) × 100%.

[0128] The test results of each embodiment are shown in Table 1. The test results of each comparative example are shown in Table 2.

[0129] Table 1: Test results of various embodiments

[0130]

[0131] Table 2: Test results of various comparative examples

[0132]

[0133] It can be seen from Table 1 and Table 2 that, compared with the comparative example, when the indium silver alloy is prepared by the embodiment of the present invention, the material loss is significantly reduced, the actual alloy composition deviates less from the theoretical value, the alloy has good uniformity, and the oxygen content in the alloy is below 0.008wt.%, which can also be controlled at a relatively low level, and can meet the application requirements.

[0134] It can be seen from the embodiment and comparative example 1 that the method of preparing indium-silver alloy by placing indium and silver in the same crucible and heating and melting in a vacuum environment results in excessive melting loss, and the actual alloy composition deviates greatly from the theoretical value.

[0135] It can be seen from the embodiment and comparative example 2 that when molten indium is poured into molten silver and uniformly mixed into an alloy melt, the uniformity of the prepared alloy is too poor, and the oxygen content in the alloy is too high. When the alloy is used as a solder, it will lead to an increase in welding voids and a decrease in welding quality.

[0136] It can be seen from the embodiment and comparative examples 3 and 4 that in step S4, if the heating temperature is too high, the volatilization loss of indium will be increased. If the heating temperature is too low, the oxygen content in the alloy will be too high, and when the alloy is used as solder, it will cause more welding voids and reduce welding quality.

[0137] It can be seen from the embodiment and comparative examples 5 and 6 that in step S4, if the holding time is too long, the volatilization loss of indium will be increased, and if the holding time is too short, the effect of reducing gas inclusions in the alloy is not obvious.

[0138] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing an indium silver alloy, characterized in that: The steps include: S1. The raw material indium and the raw material silver are heated and melted to obtain molten indium and molten silver; S2. The molten silver obtained in step S1 is poured into the molten indium obtained in step S1 and uniformly mixed into an alloy melt; S3. The alloy melt obtained in step S2 is cooled and solidified; S4. The solidified alloy obtained in step S3 is heated and melted in a vacuum environment and kept warm again to obtain an alloy melt, and then cooled to obtain an indium silver alloy; in, In step S1, the mass fraction of silver in the raw material is 0.5% to 5%; In step S1, the heating temperature of indium is 200°C to 400°C, and the heating temperature of silver is 1000°C to 1200°C; In step S4, the heating temperature is 200°C to 400°C, and the holding time is 10min to 30min; In the indium silver alloy, the oxygen content is not higher than 0.008wt.% and not lower than 0.0039wt.%.

2. The method for preparing the indium silver alloy according to claim 1, characterized in that: In step S4, the heating temperature is 200°C to 300°C.

3. The method for preparing the indium silver alloy according to claim 1, characterized in that: In step S4, the insulation time is 15 min to 25 min.

4. The method for preparing the indium silver alloy according to claim 1, characterized in that: In step S4, the air pressure of the vacuum environment does not exceed 20Pa.

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