Aluminum-magnesium alloy billet and preparation method thereof, bonding wire and application thereof

Abstract

The present invention relates to the technical field of bonding wires, and in particular to an aluminum-magnesium alloy billet and a preparation method thereof, a bonding wire and an application thereof. The present invention lays a magnesium strip on the surface of an aluminum sheet and covers the magnesium strip with CaF 2 , folded aluminum sheet wrapped with magnesium ribbon and CaF 2 , obtain magnesium feed; heat and melt the metal aluminum to obtain aluminum liquid, add the magnesium feed into the aluminum liquid, and perform electromagnetic stirring at a frequency of ≤5Hz, and obtain aluminum-magnesium melt after vacuum melting; and obtain aluminum-magnesium alloy billet after cooling the aluminum-magnesium melt. 2 Preparation of magnesium feed, CaF 2 The evaporation of magnesium during the vacuum evacuation process during vacuum melting can be avoided. At the same time, the magnesium added during melting can sink to the bottom of the aluminum liquid, and there is basically no burn loss of magnesium, so the precise control of the composition can be achieved. In addition, low-frequency oscillation is used for electromagnetic stirring, and the fusion efficiency of low-density magnesium and high-density aluminum is high, and the composition is uniform.

Description

Technical Field

[0001] The present invention relates to the technical field of bonding wires, and in particular to an aluminum-magnesium alloy billet and a preparation method thereof, a bonding wire and applications thereof. Background Art

[0002] In recent years, integrated circuits and semiconductor devices have developed towards multi-lead packaging, high density, and miniaturization, requiring the use of increasingly fine aluminum-magnesium wires for narrow pitch and long distance bonding. Aluminum-magnesium alloy bonding wires, as inner leads for microelectronic packaging, are one of the four basic materials for integrated circuits and discrete semiconductor devices.

[0003] Aluminum-magnesium alloy bonding wire can be processed by vertical drawing or horizontal continuous casting technology. Pure aluminum and pure magnesium are mixed, then smelted and directionally solidified to form a cast rod blank, and then through multiple drawing processes, intermediate and final heat treatments, until it is processed into finished wires of various specifications.

[0004] However, in continuous casting of aluminum-magnesium bonding wire, aluminum is usually melted first and then solidified in the crystallizer. When magnesium is added later, it is difficult for magnesium to fuse evenly with aluminum, resulting in large deviations in the composition of the head, middle and tail of the continuous casting billet. In addition, the density of magnesium is much lower than that of aluminum, and magnesium has a low flash point and is easily burned, making it difficult to accurately control the composition and uniformity of the continuous casting billet.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The first purpose of the present invention is to provide a method for preparing an aluminum-magnesium alloy billet, wherein magnesium feed is prepared by covering the surface of a magnesium strip with CaF2, and CaF2 can prevent the evaporation of magnesium during vacuum smelting. At the same time, the magnesium feed added during smelting can sink to the bottom of the aluminum liquid, and the magnesium is basically free of burnout, and precise control of the composition can be achieved; in addition, electromagnetic stirring is performed by low-frequency oscillation (≤5Hz frequency), and the fusion efficiency of low-density magnesium and high-density aluminum is high, and the composition is uniform. The technical problems that the composition of the continuous casting billet is uneven due to the difficulty in fusing magnesium and aluminum, and the composition and uniformity of the continuous casting billet are difficult to precisely control due to the low density and flash point of magnesium and the easy burnout.

[0007] A second object of the present invention is to provide an aluminum-magnesium alloy billet having precise and uniform composition.

[0008] The third object of the present invention is to provide a bonding wire with precise composition, good batch stability, wire diameter consistency and hardness uniformity, low wire breakage rate, high production efficiency and yield rate.

[0009] A fourth object of the present invention is to provide an application of a bonding wire in integrated circuits and semiconductor devices.

[0010] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0011] The present invention first provides a method for preparing an aluminum-magnesium alloy billet, comprising the following steps:

[0012] Laying a magnesium strip on the surface of an aluminum sheet, and covering the surface of the magnesium strip with CaF2, and then folding the aluminum sheet so that the aluminum sheet wraps the magnesium strip and the CaF2, to obtain a magnesium feed;

[0013] After heating and melting metallic aluminum to obtain aluminum liquid, the magnesium feed is added into the aluminum liquid, and electromagnetic stirring is performed at a frequency of ≤5 Hz, and after vacuum melting is completed, an aluminum-magnesium melt is obtained;

[0014] After the aluminum-magnesium melt is cooled, the aluminum-magnesium alloy billet is obtained.

[0015] Furthermore, the mass of the magnesium ribbon is 10% to 20% of the mass of the CaF2.

[0016] Furthermore, the thickness of the aluminum sheet is 0.2-1.5 mm.

[0017] Furthermore, the heating temperature is 680-700°C.

[0018] Furthermore, degassing is performed before adding the magnesium feed, and the degassing method includes: vacuuming to 1×10 -2 ~5×10 -2 Pa, and then an inert gas is introduced to reach standard atmospheric pressure.

[0019] Furthermore, the vacuum degree of the vacuum melting is 0.5-1Pa.

[0020] Furthermore, the cooling method includes vacuum cooling, which includes: first filling the inert gas to standard atmospheric pressure, and after the aluminum-magnesium melt is completely solidified, evacuating to 1×10 -3 ~5×10 -3 Pa and maintain it until the aluminum-magnesium melt is completely cooled.

[0021] Furthermore, an anti-oxidation layer is provided on the surface of the metal aluminum, and main components of the anti-oxidation layer include MgCl2 and KCl.

[0022] Furthermore, the anti-oxidation layer comprises 35% to 50% of MgCl2 and 50% to 65% of KCl in terms of mass percentage.

[0023] Furthermore, the mass of the anti-oxidation layer is 8% to 15% of the mass of the metal aluminum.

[0024] Furthermore, the method for preparing the anti-oxidation layer comprises: uniformly mixing MgCl2, KCl and a solvent and coating the mixture on the surface of metal aluminum, followed by drying to obtain the anti-oxidation layer.

[0025] Furthermore, the mass of the solvent is 40% to 60% of the sum of the masses of the MgCl2 and the KCl.

[0026] Furthermore, the solvent includes anhydrous ethanol.

[0027] The present invention further provides an aluminum-magnesium alloy billet, which is prepared by adopting the preparation method of the aluminum-magnesium alloy billet.

[0028] Furthermore, the mass fraction of magnesium element in the aluminum-magnesium alloy billet is 0.3% to 0.7%.

[0029] The present invention further provides a bonding wire, which is mainly prepared from the aluminum-magnesium alloy billet obtained by the preparation method of the aluminum-magnesium alloy billet or the aluminum-magnesium alloy billet.

[0030] The invention also provides application of the bonding wire in integrated circuits and semiconductor devices.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The method for preparing an aluminum-magnesium alloy billet provided by the present invention is to prepare a magnesium feed by covering the surface of a magnesium strip with CaF2, wherein the CaF2 can prevent the evaporation of magnesium during the vacuum evacuation process during vacuum melting; at the same time, the magnesium feed added during melting can sink to the bottom of the aluminum liquid, and the magnesium is basically not burned; these two aspects simultaneously achieve precise control of the composition. In addition, electromagnetic stirring is performed by low-frequency oscillation (frequency ≤5Hz), and the fusion efficiency of low-density magnesium and high-density aluminum is high, and the composition is uniform.

[0033] (2) The method for preparing the aluminum-magnesium alloy billet provided by the present invention has high degassing and impurity removal efficiency through multiple vacuuming and inert gas filling, and the formed aluminum-magnesium alloy billet is free of defects and inclusions.

[0034] (3) The method for preparing the aluminum-magnesium alloy billet provided by the present invention adopts a vacuum cooling method to avoid air absorption inclusions during casting and ensure the quality of the aluminum-magnesium alloy billet.

[0035] (4) The method for preparing the aluminum-magnesium alloy billet provided by the present invention can prevent the oxidation of the aluminum when it is heated by setting an anti-oxidation layer on the surface of the metal aluminum. At the same time, the anti-oxidation materials (MgCl2 and KCl) in the molten state can dissolve trace amounts of aluminum oxide on the surface, thereby reducing the presence of aluminum oxide inclusions with a density similar to that of the aluminum melt in the liquid aluminum melt.

[0036] (5) The aluminum-magnesium alloy billet provided by the present invention has precise and uniform composition.

[0037] (6) The aluminum-magnesium alloy billet provided by the present invention is free of defects and inclusions. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 This is a metallographic picture of the aluminum-magnesium alloy billet prepared in Example 1 provided by the present invention. DETAILED DESCRIPTION

[0040] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0041] If there is no special explanation, in the present invention, "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "the first", "the second", "the third", "the fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0042] If there is no special explanation, the "include" and "comprising" mentioned in the present invention represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0043] If there is no special explanation, in the present invention, "one or more" or "at least one" refers to any one, any two or more of the listed items. Among them, "several" refers to any two or more of the listed items.

[0044] In a first aspect, the present invention provides a method for preparing an aluminum-magnesium alloy billet, wherein the aluminum-magnesium alloy billet includes an alloy billet for an aluminum-magnesium bonding wire, and the preparation method comprises the following steps:

[0045] A magnesium strip is laid on the surface of an aluminum sheet, and CaF2 is covered on the surface of the magnesium strip. Then, the aluminum sheet is folded so that the aluminum sheet completely wraps the magnesium strip and the CaF2, thereby obtaining a magnesium feed.

[0046] The purity of the aluminum sheet is preferably not less than 99.999%, and the purity of the magnesium ribbon is preferably not less than 99.99%.

[0047] The laying methods include tiling.

[0048] The aluminum metal is heated to completely melt to obtain aluminum liquid, and then the magnesium feed is added to the aluminum liquid, and the magnesium feed sinks to the bottom under the action of gravity, and electromagnetic stirring is performed at a frequency of ≤5Hz, vacuum melting is performed, and aluminum-magnesium melt is obtained after vacuum melting is completed. The frequency of electromagnetic stirring includes but is not limited to any point value of 5Hz, 4Hz, 3Hz, 2Hz, 1Hz, 0.5Hz or any range value between two of them.

[0049] After the aluminum-magnesium melt is cooled, the aluminum-magnesium alloy billet is obtained.

[0050] In some specific embodiments, the smelting and cooling steps specifically include: opening the vacuum furnace cover, putting magnesium feed into the aluminum liquid, the magnesium feed sinks to the bottom under the action of gravity, closing the furnace cover, and starting the frequency conversion power supply to convert the 50 / 60Hz industrial frequency alternating current into a 3-phase low-frequency power supply with a frequency of 0.5 to 5.0Hz, performing electromagnetic stirring, and quickly evacuating to 1Pa at the same time, until no bubbles emerge from the liquid surface, stopping electromagnetic stirring and heating, filling the furnace with high-purity argon gas to standard atmospheric pressure, and evacuating to 10 after the melt is completely solidified. -3 Pa, maintain this vacuum degree until it is completely cooled, and then open the furnace to obtain the aluminum-magnesium alloy billet.

[0051] The present invention prepares magnesium feed by covering CaF2 on the surface of a magnesium strip, wherein the CaF2 can prevent the evaporation of magnesium during the vacuum extraction process during vacuum melting; at the same time, the magnesium feed added during melting can sink to the bottom of the aluminum liquid, and the magnesium is basically not burned; these two aspects simultaneously achieve precise control of the composition.

[0052] In addition, by using low-frequency oscillation (frequency ≤ 5 Hz) for electromagnetic stirring, the fusion efficiency of low-density magnesium and high-density aluminum is high and the composition is uniform.

[0053] In some specific embodiments, the mass of the magnesium strip is 10% to 20% of the mass of the CaF2, including but not limited to any point value of 10%, 12%, 13%, 15%, 18%, 20% or any range value between two of them. Calcium fluoride has a large density, which facilitates the sinking of magnesium feed.

[0054] In some specific embodiments, the thickness of the aluminum sheet is 0.2-1.5 mm, including but not limited to any point value of 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.8 mm, 1 mm, 1.3 mm, 1.5 mm or a range value between any two of them.

[0055] In some specific embodiments, the heating temperature is 680-700°C, including but not limited to any point value of 680°C, 685°C, 690°C, 695°C, 700°C or a range value between any two of them.

[0056] In some specific implementations, the heating method includes: using a vacuum melting furnace, starting an induction power supply, and performing induction heating.

[0057] In some specific embodiments, degassing is performed before adding the magnesium feed, and the degassing method includes: vacuuming to 1×10 -2 Pa~5×10 -2 Pa (e.g. 2×10 -2 Pa, 3×10 -2 Pa or 4×10 -2 Pa), when there are no bubbles in the aluminum liquid, inert gas is introduced to the standard atmospheric pressure.

[0058] In some specific embodiments, the inert gas includes but is not limited to argon.

[0059] In some specific implementations, the vacuum degree of the vacuum melting is 0.5-1 Pa, for example, 0.6 Pa, 0.7 Pa, 0.8 Pa or 0.9 Pa.

[0060] The invention achieves high degassing and impurity removal efficiency by multiple vacuuming and inert gas filling, and the formed aluminum-magnesium alloy billet is free of defects and inclusions.

[0061] In some specific embodiments, the cooling method includes vacuum cooling, which includes: first filling the inert gas to standard atmospheric pressure, and after the aluminum-magnesium melt is completely solidified, evacuating to 1×10 -3 ~5×10 -3 Pa (e.g. 2×10 -3 Pa, 3×10 -3 Pa or 4×10 -3Pa) and maintain until the aluminum-magnesium melt is completely cooled. Wherein, the inert gas includes but is not limited to argon.

[0062] The present invention adopts a vacuum cooling method, thereby avoiding air absorption inclusion during casting and ensuring the quality of the aluminum-magnesium alloy billet.

[0063] In some specific embodiments, the metal aluminum has an anti-oxidation layer on its surface, and the main components of the anti-oxidation layer include MgCl2 and KCl. MgCl2 and KCl are near-eutectic components with low melting points and good covering effects.

[0064] The present invention can prevent oxidation of aluminum when heated by arranging an anti-oxidation layer on the surface of metal aluminum. At the same time, the molten anti-oxidation material (MgCl2 and KCl) can dissolve trace aluminum oxide on the surface, reducing the appearance of aluminum oxide inclusions with a density similar to that of the aluminum melt in the liquid aluminum melt.

[0065] In some specific embodiments, the anti-oxidation layer includes 35% to 50% MgCl2 and 50% to 65% KCl by mass percentage. MgCl2 includes but is not limited to any point value of 35%, 36%, 38%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 48%, 50% or any range value between the two by mass percentage; KCl includes but is not limited to any point value of 50%, 52%, 55%, 58%, 60%, 63%, 65% or any range value between the two by mass percentage. If a single component is used, the melting point is high, higher than the melting point of aluminum, and the covering effect is poor.

[0066] In some specific embodiments, the mass of the anti-oxidation layer is 8% to 15% of the mass of the metal aluminum, including but not limited to any point value of 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or any range value between two of them. In this way, sufficient coverage can be achieved and the anti-oxidation effect is good.

[0067] In some specific embodiments, the method for preparing the anti-oxidation layer comprises: uniformly mixing MgCl2, KCl and a solvent and coating the mixture on the surface of metal aluminum, followed by drying to obtain an anti-oxidation layer.

[0068] In some specific embodiments, the mixing method comprises ball milling.

[0069] In some specific embodiments, the purity of metallic aluminum is not less than 99.999%.

[0070] In some specific implementations, the drying method may be oven drying, and the drying temperature may be, for example, 80-100°C.

[0071] In some specific embodiments, the mass of the solvent is 40% to 60% of the sum of the masses of the MgCl2 and the KCl; for example, 40%, 45%, 50%, 55% or 60%.

[0072] In some specific embodiments, the solvent comprises anhydrous ethanol.

[0073] In a second aspect, the present invention provides an aluminum-magnesium alloy billet, which is prepared by the aluminum-magnesium alloy billet preparation method.

[0074] The aluminum-magnesium alloy billet prepared by the above method has precise and uniform composition.

[0075] Furthermore, the aluminum-magnesium alloy billet produced by the method has no defects and inclusions, and the quality of the aluminum-magnesium alloy billet is good.

[0076] In some specific implementations, the mass fraction of magnesium in the aluminum-magnesium alloy billet is 0.3% to 0.7%, for example, 0.4%, 0.5% or 0.6%.

[0077] In a third aspect, the present invention provides a bonding wire, which is mainly prepared from the aluminum-magnesium alloy billet obtained by the preparation method of the aluminum-magnesium alloy billet or the aluminum-magnesium alloy billet.

[0078] The bonding wire produced by the aluminum-magnesium alloy billet provided by the present invention has accurate composition, good batch stability, wire diameter consistency and hardness uniformity, low wire breakage rate, and high production efficiency and yield rate.

[0079] In a fourth aspect, the present invention provides applications of the bonding wire in integrated circuits and semiconductor devices.

[0080] The applications of bonding wires in integrated circuits and semiconductor devices include, but are not limited to, welding and connection, signal transmission and power supply, packaging connection, optical fiber connection and photoelectric conversion. In addition, bonding wires are also widely used in microelectronics, LED lighting, aerospace, communication equipment, automotive electronics and smart cards, etc., which are not limited in the present invention.

[0081] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0082] Example 1

[0083] The method for preparing the aluminum-magnesium alloy billet provided in this embodiment comprises the following steps:

[0084] (1) Treatment of high-purity aluminum raw materials: 45% MgCl2 and 55% KCl are weighed as high-temperature anti-oxidation substances by mass percentage, and are ball-milled with anhydrous ethanol to form a paste, wherein the mass of anhydrous ethanol is 50% of the mass of the high-temperature anti-oxidation substances. The paste-like mixed material obtained after ball milling is then applied to the surface of a high-purity metal aluminum block (purity of 99.999%) and dried at 90° C. to obtain an anti-oxidation layer of uniform thickness, wherein the mass of the anti-oxidation layer accounts for 15% of the mass of the high-purity metal aluminum block.

[0085] (2) Preparation of magnesium feed: A pure magnesium ribbon (purity of 99.99%) is laid flat on the surface of a high-purity aluminum sheet (purity of 99.999%) with a thickness of 1 mm, and CaF2 is covered on the surface of the pure magnesium ribbon. The high-purity aluminum sheet is then folded so that the high-purity aluminum sheet completely covers the pure magnesium ribbon and CaF2 to obtain the magnesium feed. The mass of the pure magnesium ribbon is 10% of the mass of the CaF2.

[0086] (3) Melting of high-purity aluminum metal block with anti-oxidation layer: Using a vacuum melting furnace, start the induction power supply, and perform induction heating until the high-purity aluminum metal block with the anti-oxidation layer is completely melted to obtain aluminum liquid, wherein the heating temperature is 700°C.

[0087] (4) Primary degassing: vacuum to 10 -2 Pa, when there are no bubbles in the aluminum liquid, high-purity argon gas is filled in to the standard atmospheric pressure.

[0088] (5) Aluminum-magnesium fusion: Open the vacuum furnace cover and put magnesium into the aluminum liquid. Under the action of gravity, the magnesium sinks to the bottom of the aluminum liquid. Close the furnace cover and start the frequency conversion power supply to convert the 50 / 60Hz industrial frequency AC power into a 3-phase low-frequency power supply with a frequency of 0.5Hz. Perform electromagnetic stirring and quickly evacuate to 1Pa. When no bubbles emerge from the liquid surface, stop electromagnetic stirring and heating, fill the furnace with high-purity argon gas to standard atmospheric pressure, and evacuate to 10 after the aluminum-magnesium melt is completely solidified. -3 Pa, and maintain this vacuum degree until it is completely cooled, and then the aluminum-magnesium alloy billet is obtained by opening the furnace.

[0089] The mass fraction of magnesium element in the aluminum-magnesium alloy billet is 0.49%.

[0090] Example 2

[0091] The preparation method of the aluminum-magnesium alloy billet provided in this embodiment is basically the same as that in Example 1, except that, in step (1), 35% by mass of MgCl2 and 65% by mass of KCl are weighed as high-temperature anti-oxidation substances.

[0092] Example 3

[0093] The preparation method of the aluminum-magnesium alloy billet provided in this embodiment is basically the same as that in Example 1, except that in step (1), 50% by mass of MgCl2 and 50% by mass of KCl are weighed as high-temperature anti-oxidation substances.

[0094] Example 4

[0095] The method for preparing the aluminum-magnesium alloy billet provided in this embodiment is basically the same as that in Embodiment 1, except that in step (1), the mass of the anti-oxidation layer accounts for 12% of the mass of the high-purity metal aluminum block.

[0096] Example 5

[0097] The method for preparing the aluminum-magnesium alloy billet provided in this embodiment is basically the same as that in Embodiment 1, except that in step (1), the mass of the anti-oxidation layer accounts for 8% of the mass of the high-purity metal aluminum block.

[0098] Example 6

[0099] The method for preparing the aluminum-magnesium alloy billet provided in this embodiment is basically the same as that in Embodiment 1, except that in step (2), the mass of the pure magnesium strip is 20% of the mass of CaF2.

[0100] Example 7

[0101] The preparation method of the aluminum-magnesium alloy billet provided in this embodiment is basically the same as that of Embodiment 1, except that the mass of the aluminum block is adjusted so that the mass fraction of the magnesium element in the prepared aluminum-magnesium alloy billet is 0.3%.

[0102] Example 8

[0103] The method for preparing the aluminum-magnesium alloy billet provided in this embodiment is basically the same as that in Embodiment 1, except that, in step (5), electromagnetic stirring is performed at a frequency of 4 Hz.

[0104] Example 9

[0105] The method for preparing the aluminum-magnesium alloy billet provided in this embodiment comprises the following steps:

[0106] (1) Treatment of high-purity aluminum raw materials: 40% of MgCl2 and 60% of KCl are weighed as high-temperature anti-oxidation substances by mass percentage, and are ball-milled with anhydrous ethanol to form a paste, wherein the mass of anhydrous ethanol is 40% of the mass of the high-temperature anti-oxidation substances. The paste-like mixed material obtained after ball milling is then applied to the surface of a high-purity metal aluminum block (purity of 99.999%) and dried at 100° C. to obtain an anti-oxidation layer of uniform thickness, wherein the mass of the anti-oxidation layer accounts for 15% of the mass of the high-purity metal aluminum block.

[0107] (2) Preparation of magnesium feed: A pure magnesium ribbon (purity of 99.99%) is laid flat on the surface of a high-purity aluminum sheet (purity of 99.999%) with a thickness of 1.5 mm, and CaF2 is covered on the surface of the pure magnesium ribbon. The high-purity aluminum sheet is then folded so that the high-purity aluminum sheet completely covers the pure magnesium ribbon and CaF2 to obtain the magnesium feed. The mass of the pure magnesium ribbon is 15% of the mass of the CaF2.

[0108] (3) Melting of high-purity aluminum metal block with an anti-oxidation layer: Using a vacuum melting furnace, start the induction power supply, and perform induction heating until the high-purity aluminum metal block with an anti-oxidation layer is completely melted to obtain aluminum liquid, wherein the heating temperature is 680°C.

[0109] (4) Primary degassing: vacuum to 2×10 -2 Pa, when there are no bubbles in the aluminum liquid, high-purity argon gas is filled in to the standard atmospheric pressure.

[0110] (5) Aluminum-magnesium fusion: Open the vacuum furnace cover and put magnesium into the aluminum liquid. Under the action of gravity, the magnesium sinks to the bottom of the aluminum liquid. Close the furnace cover and start the frequency conversion power supply to convert the 50 / 60Hz industrial frequency AC power into a 3-phase low-frequency power supply with a frequency of 2Hz. Perform electromagnetic stirring and quickly evacuate to 0.5Pa. When no bubbles emerge from the liquid surface, stop electromagnetic stirring and heating, fill the furnace with high-purity argon gas to standard atmospheric pressure, and evacuate to 3×10 -3 Pa, and maintain this vacuum degree until it is completely cooled, and then the aluminum-magnesium alloy billet is obtained by opening the furnace.

[0111] The mass fraction of magnesium element in the aluminum-magnesium alloy billet is 0.7%.

[0112] Comparative Example 1

[0113] The preparation method of the aluminum-magnesium alloy billet provided in this comparative example is basically the same as that of Example 1, except that CaF2 is not added in step (2).

[0114] Comparative Example 2

[0115] The preparation method of the aluminum-magnesium alloy billet provided in this comparative example is basically the same as that of Example 1, except that step (2) is not performed, and instead a magnesium block is directly added in step (5) (the aluminum-magnesium ratio is the same as that of Example 1).

[0116] Comparative Example 3

[0117] The preparation method of the aluminum-magnesium alloy billet provided in this comparative example is basically the same as that in Example 1, except that in step (5), electromagnetic stirring is performed at a frequency of 20 Hz.

[0118] Comparative Example 4

[0119] The method for preparing the aluminum-magnesium alloy billet provided in this comparative example is basically the same as that in Example 1, except that step (4) is not performed.

[0120] Comparative Example 5

[0121] The preparation method of the aluminum-magnesium alloy billet provided in this comparative example is basically the same as that in Example 1, except that in step (5), after the aluminum-magnesium melt is completely solidified, no vacuum is drawn, that is, it is cooled at standard atmospheric pressure.

[0122] Comparative Example 6

[0123] The preparation method of the aluminum-magnesium alloy billet provided in this comparative example is basically the same as that in Example 1, except that MgCl2 and KCl are not added in step (1), that is, step (3) uses a high-purity metal aluminum block (without an anti-oxidation layer, and the quality of the aluminum block is the same as that in Example 1).

[0124] Experimental example

[0125] A tensile test was conducted on a continuous casting rod billet with a diameter of 8 mm. Referring to GB / T228.1-2010 "Tensile Test of Metallic Materials Part 1: Room Temperature Test Method", an MTS C45.105 microcomputer-controlled mechanical electronic universal testing machine was used to conduct a tensile test at room temperature on the aluminum-magnesium alloy billets of Example 1 and Comparative Examples 1 to Comparative Examples 6 at a speed of 5 mm / min. The tensile performance test results of the samples were taken as the average value of 5 samples, and the results are shown in Table 1. The magnesium content in the aluminum-magnesium alloy billet was determined using an iCAP6300-Radial spectrometer, and the results are shown in Table 1.

[0126] Table 1 Tensile properties test results

[0127]

[0128] Among them, excellent wire drawing performance is the characteristic mark of fine wire drawing. In order to compare the quality of aluminum-magnesium alloy billets, the wire breakage rate index of the finished product can be used, that is, the average wire weight that can be drawn each time the wire breaks.

[0129] As can be seen from Table 1, the present invention prepares magnesium feed by covering the surface of magnesium strip with CaF2, wherein CaF2 can prevent the evaporation of magnesium during vacuum smelting; at the same time, the magnesium feed added during smelting can sink to the bottom of aluminum liquid, and magnesium is basically not burned; these two aspects achieve precise control of the composition. In addition, the tensile properties of the aluminum-magnesium alloy billets prepared in various embodiments of the present invention are more excellent, ensuring the quality of the aluminum-magnesium alloy billets.

[0130] Furthermore, the aluminum-magnesium alloy billets formed in each embodiment are free of defects and inclusions. Figure 1 The figure shows the metallographic picture of the aluminum-magnesium alloy billet prepared in Example 1. It can be seen that there are no defects or inclusions.

[0131] However, in Comparative Example 1, no CaF2 was added; in Comparative Example 2, no magnesium feed was prepared but magnesium blocks were directly used; in Comparative Example 3, a higher frequency of electromagnetic stirring was used; in Comparative Example 4, no degassing was performed; in Comparative Example 5, no cooling was performed under vacuum; and in Comparative Example 6, no MgCl2 and KCl were added, resulting in a significant decrease in various tensile properties.

[0132] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing an aluminum-magnesium alloy billet, characterized in that: The steps include: Laying a magnesium strip on the surface of an aluminum sheet, and covering the surface of the magnesium strip with CaF2, and then folding the aluminum sheet so that the aluminum sheet wraps the magnesium strip and the CaF2, to obtain a magnesium feed; After heating and melting metallic aluminum to obtain aluminum liquid, the magnesium feed is added to the aluminum liquid, and electromagnetic stirring is performed at a frequency of ≤5 Hz, and after vacuum melting is completed, an aluminum-magnesium melt is obtained; After the aluminum-magnesium melt is cooled, the aluminum-magnesium alloy billet is obtained.

2. The method for preparing an aluminum-magnesium alloy billet according to claim 1, characterized in that: At least one of the following conditions is met: (1) The mass of the magnesium ribbon is 10% to 20% of the mass of the CaF2; (2) The thickness of the aluminum sheet is 0.2 to 1.5 mm.

3. The method for preparing the aluminum-magnesium alloy billet according to claim 1, characterized in that: At least one of the following conditions is met: (1) The heating temperature is 680-700° C.; (2) Degassing is performed before adding the magnesium feed, and the degassing method includes: vacuuming to 1×10 -2 ~5×10 - 2 Pa, then introduce inert gas to standard atmospheric pressure; (3) The vacuum degree of the vacuum melting is 0.5-1 Pa.

4. The method for preparing the aluminum-magnesium alloy billet according to claim 1, characterized in that: The cooling method includes vacuum cooling, which includes: first filling inert gas to standard atmospheric pressure, and after the aluminum-magnesium melt is completely solidified, evacuating to 1×10 -3 ~5×10 -3 Pa and maintain it until the aluminum-magnesium melt is completely cooled.

5. The method for preparing the aluminum-magnesium alloy billet according to claim 1, characterized in that: The metal aluminum has an anti-oxidation layer on its surface, and main components of the anti-oxidation layer include MgCl2 and KCl.

6. The method for preparing the aluminum-magnesium alloy billet according to claim 5, characterized in that: The anti-oxidation layer comprises 35% to 50% of MgCl2 and 50% to 65% of KCl in terms of mass percentage; And / or, the mass of the anti-oxidation layer is 8% to 15% of the mass of the metal aluminum.

7. The method for preparing the aluminum-magnesium alloy billet according to claim 5, characterized in that: The preparation method of the anti-oxidation layer comprises: uniformly mixing MgCl2, KCl and a solvent and coating the mixture on the surface of the metal aluminum, and then drying the mixture to obtain an anti-oxidation layer; Preferably, the mass of the solvent is 40% to 60% of the sum of the mass of the MgCl2 and the KCl; Preferably, the solvent comprises anhydrous ethanol.

8. An aluminum-magnesium alloy billet, characterized in that: The aluminum-magnesium alloy billet is prepared by the method for preparing the aluminum-magnesium alloy billet according to any one of claims 1 to 7; Preferably, the mass fraction of magnesium element in the aluminum-magnesium alloy billet is 0.3% to 0.7%.

9. A bonding wire, characterized in that: The aluminum-magnesium alloy billet is mainly prepared by the aluminum-magnesium alloy billet prepared by the preparation method of the aluminum-magnesium alloy billet according to any one of claims 1 to 7 or the aluminum-magnesium alloy billet according to claim 8.

10. Use of the bonding wire as claimed in claim 9 in integrated circuits and semiconductor devices.

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