Silver-based intermediate alloy for bonding wire, preparation method of silver-based intermediate alloy and bonding wire

Abstract

The invention relates to the technical field of bonding wires, in particular to a silver-based intermediate alloy for a bonding wire, a preparation method of the silver-based intermediate alloy and the bonding wire. The preparation method of the silver-based intermediate alloy for the bonding wire comprises the steps that rare earth metal and silver are evenly mixed and then subjected to hot extrusion forming, and a bar is obtained; the bar is subjected to heat treatment and then cooled, and a treated bar is obtained; and drawing the treated bar to obtain the silver-based intermediate alloy for the bonding wire. According to the method, the rare earth elements can be uniformly distributed in the alloy, so that the performance stability of the bonding wire is remarkably improved, and the problem that the performance of the bonding wire is reduced due to the fact that the rare earth elements react with impurities or matrix metal in the smelting process to generate inclusions is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of bonding wires, and in particular to a silver-based master alloy for bonding wires, a preparation method thereof, and a bonding wire. Background Art

[0002] Bonding wires are the main way to connect electronic components internally. They are widely used in the electronic component manufacturing and packaging industries. Bonding wires are internal leads for packaging. They are used as welding leads between chips and brackets to connect pins, silicon wafers, and transmit electrical signals. They are the key electrical connection functions between chips and external circuits.

[0003] In the process of preparing bonding wires, the performance of bonding wires can be improved by doping them with trace amounts of rare earth elements. Since rare earth elements have unique physical and chemical properties, they can effectively improve the mechanical properties, oxidation resistance, conductivity and corrosion resistance of bonding wires.

[0004] At present, rare earth elements are mainly doped into silver bonding wires by melting master alloys. In this method, silver and rare earth elements in a certain ratio are directly placed in a vacuum melting furnace, heated to a molten state, and dispersed in the melt by electromagnetic stirring.

[0005] However, the solubility of rare earth elements in silver is extremely low, which makes it difficult for rare earth elements to be evenly distributed in the silver matrix in the traditional smelting process, which leads to local enrichment or element segregation, seriously affecting the stability and consistency of the alloy performance. Therefore, it is urgent to develop a new process method to ensure the uniform distribution of rare earth elements in the silver matrix and improve the performance consistency of the bonding wire.

[0006] In addition, rare earth elements easily react with impurities or base metals to form inclusions during the smelting process. The presence of these inclusions often becomes the source of brittle fracture of the material, affecting the ductility and tensile strength of the bonding wire.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] The first object of the present invention is to provide a method for preparing a silver-based master alloy for bonding wire, which can achieve uniform distribution of rare earth elements in the alloy, thereby significantly improving the performance stability of the bonding wire and avoiding the problem that the rare earth elements react with impurities or base metals during the smelting process to generate inclusions, thereby causing the performance of the bonding wire to deteriorate.

[0009] The second object of the present invention is to provide a silver-based master alloy for bonding wires, in which rare earth elements are evenly distributed, and the bonding wires made from the master alloy have good performance consistency.

[0010] A third object of the present invention is to provide a bonding wire having good performance consistency, ductility and tensile strength.

[0011] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0012] The present invention firstly provides a method for preparing a silver-based master alloy for bonding wires, comprising the following steps: uniformly mixing rare earth metals and silver and then hot extruding to obtain a rod; heat-treating the rod and then cooling to obtain a treated rod; and drawing the treated rod to obtain the silver-based master alloy for bonding wires.

[0013] Furthermore, the rare earth metal includes at least one of lanthanum, cerium, praseodymium, neodymium, gadolinium, dysprosium and yttrium.

[0014] Furthermore, the median particle size of the rare earth metal is 20 to 40 μm.

[0015] Furthermore, the median particle size of the silver is 30 to 50 μm.

[0016] Furthermore, the mass ratio of the rare earth metal to the silver is 0.5-3:97-99.5.

[0017] Furthermore, the uniform mixing method includes ball milling.

[0018] Furthermore, the ball-to-material ratio of the ball mill is 5 to 10:1.

[0019] Furthermore, the diameter of the grinding medium used in the ball milling is 5 to 10 mm.

[0020] Furthermore, the ball milling time is ≥60 min.

[0021] Furthermore, the rotation speed of the ball mill is 100 to 300 rpm.

[0022] Furthermore, during the ball milling process, the machine is stopped for cooling for 1 to 30 minutes every 15 to 25 minutes.

[0023] Furthermore, the extrusion temperature of the hot extrusion forming is 600-700°C.

[0024] Furthermore, the extrusion pressure of the hot extrusion forming is 500-700 MPa.

[0025] Furthermore, the extrusion speed of the hot extrusion forming is 0.05-0.2 mm / s.

[0026] Furthermore, the diameter of the rod is 5 to 10 mm.

[0027] Furthermore, the temperature of the heat treatment is 600-700°C.

[0028] Furthermore, the heat treatment has a holding time of 3 to 6 hours.

[0029] Furthermore, the cooling method includes staged cooling.

[0030] Furthermore, the segmented cooling includes: cooling from the heat treatment temperature to 580-620°C at a cooling rate of 2-5°C / min, and keeping warm for 15-30 minutes; then cooling to 480-520°C at a cooling rate of 2-5°C / min, and keeping warm for 15-30 minutes; then cooling to 380-420°C at a cooling rate of 2-5°C / min, and keeping warm for 15-30 minutes; finally cooling to room temperature at a cooling rate of 0.5°C / min.

[0031] Furthermore, the drawing specifically includes: performing a first drawing on the treated rod until the diameter of the obtained thick wire is 1 to 1.5 mm, performing an intermediate annealing treatment, and then performing a second drawing until the diameter of the obtained thin wire is 0.1 to 0.5 mm.

[0032] Furthermore, the surface reduction rate of each pass of the first drawing is 15% to 20%.

[0033] Furthermore, the first drawing speed is 20-50 m / min.

[0034] Furthermore, the temperature of the intermediate annealing treatment is 350-450°C.

[0035] Furthermore, the holding time of the intermediate annealing treatment is 60 to 90 minutes.

[0036] Furthermore, the surface reduction rate of each pass of the second drawing is 10% to 15%.

[0037] Furthermore, the second drawing speed is 150-200 m / min.

[0038] Furthermore, after the drawing, a cutting step is also included.

[0039] The present invention further provides a silver-based master alloy for bonding wires prepared by the method for preparing the silver-based master alloy for bonding wires.

[0040] Furthermore, the silver-based master alloy for bonding wire comprises, by mass percentage, 0.5% to 3% of rare earth elements and the remainder being Ag.

[0041] Furthermore, the rare earth element includes at least one of lanthanum, cerium, praseodymium, neodymium, gadolinium, dysprosium and yttrium.

[0042] The present invention also provides a bonding wire, which is mainly prepared from the silver-based master alloy for bonding wire obtained by the preparation method of the silver-based master alloy for bonding wire, or prepared from the silver-based master alloy for bonding wire.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) The method for preparing the silver-based master alloy for bonding wire provided by the present invention can achieve uniform distribution of rare earth elements in the master alloy, thereby significantly improving the performance stability of the bonding wire prepared from the silver-based master alloy for bonding wire. In addition, the method can avoid the problem that the rare earth elements react with impurities or base metals during the smelting process to form inclusions, thereby causing a decrease in the ductility and tensile strength of the bonding wire.

[0045] (2) The method for preparing the silver-based master alloy for bonding wire provided by the present invention can improve the mechanical properties and oxidation resistance of the master alloy and the bonding wire prepared therefrom.

[0046] (3) The method for preparing the silver-based master alloy for bonding wire provided by the present invention can further improve the uniformity of rare earth element distribution by controlling parameters such as powder selection, mixing process, hot extrusion process, heat treatment process and drawing process.

[0047] (4) The method for preparing the silver-based master alloy for bonding wire provided by the present invention has a simple process and is suitable for large-scale production. It can reduce the cost while improving the quality and consistency of the master alloy, and has a wide range of application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] 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.

[0049] Figure 1 This is the elongation test result of the finished silver-based master alloy for bonding wire prepared in Example 1 provided by the present invention. DETAILED DESCRIPTION

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] In a first aspect, the present invention provides a method for preparing a silver-based master alloy for bonding wires, and also a method for homogenizing a silver-based master alloy containing a sparingly soluble rare earth element, the method comprising the following steps:

[0055] After the rare earth metal and silver are uniformly mixed, hot extrusion is performed to obtain a rod. It is understood that the rare earth metal here refers to a rare earth metal element, and the silver here refers to elemental silver. The shape of the rod includes a rod and a wire. Among them, hot extrusion can form a rod with good surface quality, which is convenient for subsequent heat treatment and subsequent drawing. At the same time, through high pressure and high temperature, the internal defects of the material are reduced and the density is increased.

[0056] In some specific implementations, the rare earth metal and silver are both in powder form.

[0057] In some specific embodiments, the purity of the rare earth metal and silver is greater than 99.99%.

[0058] The rod is then subjected to heat treatment and then cooled to obtain a treated rod. Heat treatment can promote the reaction of silver and rare earth elements to form compounds and achieve material homogenization.

[0059] The treated rod is then drawn to obtain the desired diameter, and finally the silver-based master alloy for bonding wire is obtained. The large deformation during the drawing process can promote further uniform fusion of silver and rare earth elements, that is, further homogenize the internal structure of the material. After obtaining the master alloy of the desired diameter, it is cut into small round rods for use in subsequent continuous casting.

[0060] The invention mixes various raw materials uniformly, performs hot extrusion forming, performs heat treatment, and then draws. The combination of the three steps realizes material homogenization and effectively solves the problem of uneven distribution of insoluble rare earth elements in the silver-based alloy.

[0061] The preparation method of the silver-based master alloy for bonding wire provided by the present invention can realize the uniform distribution of rare earth elements in the master alloy, thereby significantly improving the performance stability of the bonding wire prepared from the silver-based master alloy for bonding wire.

[0062] Furthermore, the method can avoid the problem that the rare earth elements react with impurities or base metals during the smelting process to generate inclusions, thereby causing the ductility and tensile strength of the bonding wire to decrease.

[0063] In some specific embodiments, the rare earth metal includes at least one of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), gadolinium (Gd), dysprosium (Dy), and yttrium (Y); two, three or more of them may also be used. The addition of these rare earth elements helps to improve the mechanical properties and oxidation resistance of the master alloy and the bonding wire made therefrom.

[0064] In some specific embodiments, the median particle size D of the rare earth metal is 50 It is 20-40 μm, including but not limited to any point value of 20 μm, 25 μm, 30 μm, 35 μm, 40 μm or a range value between any two of them.

[0065] In some specific embodiments, the median particle size D of the silver is 50 30-50 μm; including but not limited to any point value of 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or a range value between any two of them.

[0066] By synergistically controlling the particle sizes of rare earth metals and silver, the uniformity of the mixture can be ensured, thereby further improving the uniformity of the alloy and the efficiency of subsequent processes. The above-mentioned particle size matching can promote a better uniform distribution of different components during the mixing process and reduce agglomeration (too large a particle size is not easy to disperse evenly, and too small a particle size is easy to cause powder agglomeration, thereby reducing the uniformity of the mixture).

[0067] In some specific embodiments, the oxygen content in the rare earth metal and silver is less than 300ppm, ensuring that the alloy is not prone to oxidation reaction during the subsequent preparation process. Among them, the formation of oxides may affect the material fluidity during hot extrusion and drawing. Moreover, in the final bonding wire application, the oxides will affect the consistency, strength and reliability of the bonding. The present invention can significantly improve the processing performance, mechanical properties, electrical properties and service life of the alloy by controlling the oxygen content in the rare earth metal and silver to be less than 300ppm, while improving the consistency and reliability of the product.

[0068] In some specific embodiments, the rare earth metal and silver are dried separately before mixing, such as vacuum drying, at a temperature of 100 to 200° C. for 6 to 24 hours, which effectively reduces the gas adsorbed on the powder surface and further reduces the oxygen content.

[0069] In some specific embodiments, the mass ratio of the rare earth metal to the silver is 0.5-3:97-99.5; including but not limited to any point value of 0.5:99.5, 1:99, 1.5:98.5, 2:98, 2.5:97.5, 3:97 or any range value between the two. By controlling the ratio of the rare earth metal to silver, it is beneficial to promote the uniformity of the distribution of rare earth elements in the silver-based master alloy for bonding wire and the bonding wire made thereof, and it is also beneficial to further improve the mechanical properties and oxidation resistance of the master alloy and the bonding wire made thereof.

[0070] In some specific embodiments, the uniform mixing method comprises grinding, and the grinding method includes but is not limited to mixed ball milling.

[0071] In some specific implementations, a double planetary ball mill is used for the mixing.

[0072] In some specific embodiments, before the mixing, a vacuum pump is used to exhaust the air in the ball mill to below 100 Pa, and then argon gas is introduced for protection to avoid oxidation of the powder during the mixing process.

[0073] In some specific embodiments, the ball-to-material ratio of the ball mill is 5 to 10:1, including but not limited to any point value of 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 or any range value between two of them. This ball-to-material ratio can ensure that sufficient grinding media can effectively impact the material during the mixing process to achieve uniform mixing of the powder, while avoiding excessive crushing of the powder caused by too many grinding balls in the ball mill.

[0074] In some specific embodiments, the grinding media used in the ball milling include high-purity alumina balls or zirconium oxide balls. Such grinding media have high hardness and chemical stability and will not react adversely with silver powder or rare earth metal powder.

[0075] In some specific embodiments, the diameter of the grinding media used in the ball mill is 5 to 10 mm, including but not limited to any point value of 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm or any range value between two of them. This size ensures that the powder will not be excessively damaged during the grinding process.

[0076] In some specific embodiments, the ball milling time is ≥ 60 min, including but not limited to any one of 60 min, 70 min, 80 min, 90 min, 100 min, 120 min, 180 min, 240 min, and 300 min, or a range between any two of them.

[0077] In some specific embodiments, the rotation speed of the ball mill is 100-300 rpm, including but not limited to any point value of 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm or a range value between any two of them.

[0078] By adopting the above ball milling time and rotation speed, it is possible to ensure that the powder is evenly distributed without breaking or agglomerating, thereby increasing the uniformity of the material.

[0079] In some specific embodiments, since the ball mill will generate a certain amount of heat when running at high speed, the temperature needs to be monitored during the mixing process, and intermittent ball milling is used. The specific method includes: during the ball milling process, the machine is stopped and cooled for 1 to 30 minutes (including but not limited to 1 minute, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 8 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or any range between the two) every 15 to 25 minutes (including but not limited to any one of 15 minutes, 18 minutes, 20 minutes, 22 minutes, 23 minutes, 25 minutes, or any range between the two). This can effectively prevent the internal temperature of the equipment from rising by more than 50°C, so as to prevent adverse reactions or agglomeration on the surface of rare earth elements or silver powder.

[0080] It is understood that the ball milling time is ≥ 60 min, excluding the cooling time during the milling process.

[0081] In some specific embodiments, the extrusion temperature of the hot extrusion forming is 600-700° C., including but not limited to any point value of 600° C., 620° C., 630° C., 650° C., 660° C., 680° C., and 700° C., or a range value between any two of them. Controlling the extrusion temperature within this temperature range ensures that the powder is fully shaped while avoiding excessive grain growth.

[0082] In some specific embodiments, the extrusion pressure of the hot extrusion molding is 500-700 MPa; including but not limited to any point value of 500 MPa, 550 MPa, 600 MPa, 650 MPa, 700 MPa or any range value between two of them. The use of this extrusion pressure is conducive to complete compaction of the powder. Among them, too low pressure will cause the powder to be unable to be completely compacted, and too high pressure may cause uneven material flow or equipment wear.

[0083] In some specific embodiments, the extrusion speed of the hot extrusion forming is 0.05-0.2 mm / s, including but not limited to any point value of 0.05 mm / s, 0.08 mm / s, 0.1 mm / s, 0.12 mm / s, 0.15 mm / s, 0.18 mm / s, 0.2 mm / s or any range value between two of them. In this way, a round bar blank with a high-precision shape and size can be obtained, ensuring the fine control of the diameter and the surface accuracy of the round bar in subsequent passes.

[0084] In some specific embodiments, the diameter of the rod is 5 to 10 mm, including but not limited to any point value of 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, and 10 mm or a range value between any two of them. By controlling the diameter of the rod within the above range, it is beneficial to finely control the diameter and uniformly distribute the rare earth elements in subsequent drawing.

[0085] In some specific embodiments, during the hot extrusion forming process, the diameter of the die is gradually reduced through the multi-layer composite extrusion die, and the die size is gradually reduced from an initial diameter of 15 to 25 mm to 5 to 10 mm, so as to reduce forming defects and facilitate subsequent continuous drawing.

[0086] In some specific embodiments, the heat treatment temperature is 600-700° C., including but not limited to any one of 600° C., 620° C., 640° C., 650° C., 680° C., and 700° C., or any range between two of them. This temperature range is beneficial to increase the solubility of rare earth elements in the silver matrix, promote the formation of silver and rare earth element compounds, and control the grain size.

[0087] In some specific embodiments, the heat treatment holding time is 3 to 6 hours, including but not limited to any one of 3 hours, 4 hours, 5 hours, and 6 hours or a range between any two of them. The heat treatment time is beneficial to increase the solubility of the rare earth element in the silver matrix, promote the formation of silver and rare earth element compounds, and control the grain size.

[0088] In some specific embodiments, the heat treatment can be performed in any heating equipment commonly used in the art, preferably in a vacuum furnace.

[0089] In some specific embodiments, the cooling method includes segmented cooling, that is, cooling by dynamic cooling technology, or a step-by-step cooling process.

[0090] In some specific embodiments, the segmented cooling includes the following stages in sequence:

[0091] The first stage: cooling the temperature from the heat treatment temperature to 580-620°C (including but not limited to any one of 580°C, 590°C, 600°C, 610°C, 620°C or any range between them) at a cooling rate of 2-5°C / min (including but not limited to any one of 2°C / min, 3°C / min, 4°C / min, 5°C / min or any range between them), and keeping warm for 15-30min (including but not limited to any one of 15min, 20min, 25min, 30min or any range between them).

[0092] The second stage: cooling from 580-620°C to 480-520°C (including but not limited to any one of 480°C, 490°C, 500°C, 510°C, 520°C or any range between them) at a cooling rate of 2-5°C / min (including but not limited to any one of 2°C / min, 3°C / min, 4°C / min, 5°C / min or any range between them), and keeping warm for 15-30 min (including but not limited to any one of 15 min, 20 min, 25 min, 30 min or any range between them).

[0093] The third stage: cooling from 480-520°C to 380-420°C (including but not limited to any one of 380°C, 390°C, 400°C, 410°C, 420°C or any range between them) at a cooling rate of 2-5°C / min (including but not limited to any one of 2°C / min, 3°C / min, 4°C / min, 5°C / min or any range between them), and keeping warm for 15-30 min (including but not limited to any one of 15 min, 20 min, 25 min, 30 min or any range between them).

[0094] The fourth stage: cooling from 380-420°C to room temperature at a cooling rate of 0.1-1°C / min (including but not limited to any point value of 0.1°C / min, 0.3°C / min, 0.5°C / min, 0.6°C / min, 0.8°C / min, 1°C / min or any range value between two thereof).

[0095] The above-mentioned segmented cooling method can effectively eliminate the residual stress inside the material and ensure the stability of the alloy. Specifically, the first, second and third stages are rapidly cooled and the thermal stress is quickly released, which can reduce the accumulation of thermal stress inside the material. The fourth stage is slow cooling, which can ensure that the material will not generate new internal stress or deformation during the cooling process, and maintain the consistency of its mechanical properties and shape.

[0096] In some specific embodiments, the drawing specifically includes: performing a first drawing on the treated rod until the diameter of the obtained thick wire is 1 to 1.5 mm (including but not limited to any one of 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm or a range between any two of them), performing an intermediate annealing treatment, and then performing a second drawing until the diameter of the obtained thin wire is 0.1 to 0.5 mm (including but not limited to any one of 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm or a range between any two of them).

[0097] It can be understood that the first drawing and the second drawing both refer to continuous multi-pass drawing, and the first and the second here are used to distinguish the two drawing processes.

[0098] Through the above drawing, the diameter of the rod or wire can be accurately controlled, and the step-by-step drawing is conducive to improving the uniformity of rare elements. Intermediate annealing during the process can improve the drawing efficiency and the surface quality of the final product.

[0099] In some specific embodiments, the surface reduction rate of each pass of the first drawing is 15% to 20%, including but not limited to any point value of 15%, 16%, 17%, 18%, 19%, 20% or any range value between two of them. By controlling the surface reduction rate of each pass, it is possible to ensure that the material is uniformly stretched during the stretching process, avoid local overload causing material breakage, and maintain the uniformity and surface quality of the wire.

[0100] In some specific embodiments, the drawing speed of the first drawing is 20-50 m / min, including but not limited to any point value of 20 m / min, 25 m / min, 30 m / min, 35 m / min, 40 m / min, 45 m / min, 50 m / min or any range value between two of them. By controlling the drawing speed, material breakage can be avoided and the uniformity and surface quality of the wire can be maintained.

[0101] In some specific embodiments, in order to further improve the drawing efficiency and the surface quality of the silver-based master alloy for bonding wire, the temperature of the intermediate annealing treatment is 350-450°C, including but not limited to any one of 350°C, 360°C, 380°C, 400°C, 430°C, and 450°C or a range between any two of them; the holding time of the intermediate annealing treatment is 60-90min, including but not limited to any one of 60min, 70min, 80min, and 90min or a range between any two of them; and the furnace is naturally cooled after annealing.

[0102] In some specific implementations, during the intermediate annealing process, argon protection is used to control the oxygen content to be less than 10 ppm to prevent oxidation of the material during the annealing process.

[0103] In some specific embodiments, the surface reduction rate of each pass of the second drawing is 10% to 15%, including but not limited to any point value of 10%, 11%, 12%, 13%, 14%, 15%, or any range value between two of them. By controlling the surface reduction rate of each pass, material breakage can be avoided and the uniformity and surface quality of the wire can be maintained.

[0104] In some specific embodiments, the drawing speed of the second drawing is 150-200 m / min, including but not limited to any point value of 150 m / min, 160 m / min, 170 m / min, 180 m / min, 190 m / min, 200 m / min or any range value between two of them. By controlling the drawing speed, material breakage can be avoided and the uniformity and surface quality of the wire can be maintained.

[0105] In some specific implementations, after the drawing, a cutting step is also included.

[0106] In some specific implementations, pulsed laser cutting is used to cut the drawn filaments into small round rods with a length of 1 to 5 mm, thereby ensuring the consistency of the small round rods and the efficiency of the subsequent preparation process.

[0107] The present invention can ensure the uniform distribution of rare earth elements in the silver matrix by controlling powder selection, mixing process, hot extrusion process, heat treatment process and drawing process, thereby further improving the uniformity of the rare earth elements.

[0108] According to statistics, the fluctuation range of rare earth element content in each region of the silver-based master alloy for bonding wires produced by this method is reduced to less than 2%. In addition, the performance consistency of the finished bonding wires produced by this method is significantly improved, and the fluctuation range of elongation is reduced to less than 1.5%.

[0109] In addition, the preparation method of the silver-based master alloy for bonding wire provided by the present invention has a simple process, is suitable for large-scale production, can reduce costs while improving product quality and consistency, and has broad application prospects.

[0110] In a second aspect, the present invention provides a silver-based master alloy for bonding wire prepared by the method for preparing the silver-based master alloy for bonding wire.

[0111] The bonding wire is made of a silver-based master alloy with a uniform distribution of rare earth elements.

[0112] In some specific embodiments, the silver-based master alloy for bonding wire includes, by mass percentage, 0.5% to 3% of rare earth elements, and the balance is Ag. The content of rare earth elements by mass percentage includes, but is not limited to, any one of 0.5%, 1%, 1.5%, 2%, 2.5%, and 3%, or a range between any two of them. The silver-based master alloy for bonding wire having this ratio has excellent mechanical properties and oxidation resistance.

[0113] In some specific embodiments, the rare earth element includes at least one of lanthanum, cerium, praseodymium, neodymium, gadolinium, dysprosium and yttrium. The addition of these rare earth elements helps to improve the mechanical properties and oxidation resistance of the master alloy and the bonding wire.

[0114] In a third aspect, the present invention provides a bonding wire, which is mainly prepared by the silver-based master alloy for bonding wire obtained by the preparation method of the above-mentioned silver-based master alloy for bonding wire, or prepared by the above-mentioned silver-based master alloy for bonding wire.

[0115] The bonding wire has stable performance, good ductility and tensile strength.

[0116] 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.

[0117] Example 1

[0118] The method for preparing the silver-based master alloy for bonding wire provided in this embodiment comprises the following steps:

[0119] (1) Weigh 99 g of Ag metal powder (purity of 99.99%, median particle size of 40 μm, oxygen content of 200 ppm) and 1 g of La metal powder (purity of 99.99%, median particle size of 30 μm, oxygen content of 200 ppm). Then, the two powders were placed in a vacuum drying device for 5 hours, and the temperature was set to 100 °C to further reduce the oxygen content and the gas adsorbed on the surface. After that, the two dried powders were placed in a double planetary ball mill for mixed ball milling, wherein the grinding medium was alumina balls with a diameter of 5 mm, the ball-to-material ratio was 5:1, the mixing time was 60 min, and the ball milling speed was 300 rpm. During the mixed ball milling process, argon protection was used to prevent oxidation. The ball milling speed was adjusted to 200 rpm (reducing the speed can reduce the impact and friction of the grinding medium, thereby reducing the breakage and agglomeration of the powder). During the mixed ball milling process, the machine was stopped for cooling for 10 min every 20 min to ensure that the powder was evenly distributed and not broken or agglomerated.

[0120] (2) The mixed powder obtained in step (1) is subjected to hot extrusion molding, and the diameter of the die is gradually reduced through a multi-layer composite extrusion die. The die diameters are 20 mm, 14 mm, 10 mm, and 8 mm, respectively. The extrusion temperature is 650° C., the extrusion pressure is 600 MPa, and the extrusion speed is 0.1 mm / s. After the extrusion, a round rod with a diameter of 8 mm is obtained.

[0121] (3) Place the extruded round rod obtained in step (2) into a vacuum furnace for heat treatment. The heat treatment temperature is 700°C and the insulation time is 4h. After the insulation is completed, a step-by-step cooling process is adopted, specifically: the first stage: cooling from 700°C to 600°C, the cooling rate is 3°C / min, and the insulation time is 20min. The second stage: cooling from 600°C to 500°C, the cooling rate is 3°C / min, and the insulation time is 20min. The third stage: cooling from 500°C to 400°C, the cooling rate is 3°C / min, and the insulation time is 20min. Finally, slowly cool to room temperature at a rate of 0.5°C / min.

[0122] (4) The cooled round rod obtained in step (3) is drawn to 1.3 mm through a large wire drawing machine, wherein the surface reduction rate of each drawing pass is controlled at 18%, and the drawing speed is 30 m / min. When drawn to 1.3 mm, an intermediate annealing treatment is performed. The intermediate annealing temperature is set to 400°C, the annealing time is 60 min, and argon protection is used. The oxygen content in the argon gas is less than 10 ppm to ensure that no oxidation occurs during the annealing process. After annealing, the fine wire is naturally cooled in the furnace. Subsequently, a medium wire drawing machine is used to continue drawing the fine wire with a diameter of 1.3 mm to 0.3 mm, wherein the surface reduction rate of each drawing pass is controlled at 12%, and the drawing speed is adjusted to 150 m / min to ensure the uniformity and surface finish of the wire.

[0123] (5) Pulse laser cutting technology is used to cut the filaments obtained in step (4) into small round rods (i.e., silver-based intermediate alloy for bonding wire) with a length of 3 mm to ensure the consistency of their size and the efficiency of subsequent processes.

[0124] The silver-based master alloy for bonding wire prepared in this embodiment includes La 1% and Ag 99% by mass.

[0125] The head, middle and tail of the intermediate alloy filament drawn in step (4) of this embodiment were sampled, and the contents of rare earth element La were measured to be 1.01wt.%, 1.008wt.% and 0.996wt.%, respectively, which indicates that the rare earth element La is evenly distributed in the alloy without obvious segregation.

[0126] The finished product of the silver-based intermediate alloy for bonding wire prepared in this embodiment was tested for elongation (tested at 5 points), and the results are as follows: Figure 1 As shown, it can be seen that the elongation is stable between 11.5% and 12.5%, and the elongation fluctuation is less than 1.5%.

[0127] Example 2

[0128] The method for preparing the silver-based master alloy for bonding wire provided in this embodiment is basically the same as that in Embodiment 1, except that in step (1), the masses of Ag metal powder and La metal powder are replaced with 98 g and 2 g, respectively.

[0129] That is, the silver-based master alloy for bonding wire prepared in this embodiment includes 2% La and 98% Ag by mass percentage.

[0130] Example 3

[0131] The preparation method of the silver-based master alloy for bonding wire provided in this embodiment is basically the same as that in Example 1, except that in step (1), the La metal powder is replaced by Ce metal powder (with a purity of 99.99%, a median particle size of 30 μm, and an oxygen content of 200 ppm).

[0132] The silver-based master alloy for bonding wire prepared in this embodiment includes 0.99% Ce and 99.01% Ag by mass percentage.

[0133] Example 4

[0134] The method for preparing the silver-based master alloy for bonding wire provided in this embodiment is basically the same as that in Embodiment 1, except that in step (1), the median particle size of the Ag metal powder is replaced with 50 μm, and the median particle size of the La metal powder is replaced with 40 μm.

[0135] Example 5

[0136] The preparation method of the silver-based master alloy for bonding wire provided in this embodiment is basically the same as that in Example 1, except that in step (1), the parameters of the mixed ball milling are as follows: the grinding medium is an alumina ball with a diameter of 10 mm, the ball-to-material ratio is 10:1, the mixing time is 90 min, and the ball milling speed is 100 rpm.

[0137] Example 6

[0138] The preparation method of the silver-based master alloy for bonding wire provided in this embodiment is basically the same as that in Embodiment 1, except that in step (2), the parameters of hot extrusion forming are as follows: the extrusion temperature is 600° C., the extrusion pressure is 700 MPa, and the extrusion speed is 0.2 mm / s.

[0139] Example 7

[0140] The preparation method of the silver-based intermediate alloy for bonding wire provided in this embodiment is basically the same as that in embodiment 1, except that, in step (3), the step-by-step cooling process is as follows: the first stage: cooling from 700°C to 620°C, the cooling rate is 5°C / min, and the holding time is 30min. The second stage: cooling from 620°C to 510°C, the cooling rate is 4°C / min, and the holding time is 25min. The third stage: cooling from 510°C to 380°C, the cooling rate is 2°C / min, and the holding time is 15min. Finally, slowly cool to room temperature at a rate of 0.3°C / min.

[0141] Example 8

[0142] The preparation method of the silver-based intermediate alloy for bonding wire provided in this embodiment is basically the same as that in Example 1, except that step (4) is: the cooled round rod is drawn to 1.5 mm by a large wire drawing machine, wherein the surface reduction rate of each drawing pass is controlled at 15%, and the drawing speed is 50 m / min. When drawn to 1.5 mm, an intermediate annealing treatment is performed. The intermediate annealing temperature is set to 450°C, the annealing time is 60 min, and argon protection is adopted. The oxygen content in the argon gas is less than 10 ppm to ensure that no oxidation occurs during the annealing process, and the fine wire is naturally cooled with the furnace after annealing. Subsequently, a medium wire drawing machine is used to continue drawing a thin wire with a diameter of 1.5 mm to 0.1 mm, wherein the surface reduction rate of each pass is controlled at 15%, and the drawing speed is adjusted to 200 m / min.

[0143] Example 9

[0144] The preparation method of the silver-based master alloy for bonding wire provided in this embodiment is basically the same as that in Example 1, except that, in step (1), 99.5 g of Ag metal powder (purity of 99.99%, median particle size of 30 μm, oxygen content of 200 ppm) and 0.5 g of Y metal powder (purity of 99.99%, median particle size of 20 μm, oxygen content of 250 ppm) are weighed.

[0145] The silver-based master alloy for bonding wire prepared in this embodiment includes 0.5% Y and 99.5% Ag by mass percentage.

[0146] Comparative Example 1

[0147] The silver-based master alloy for bonding wire is prepared by the traditional smelting method, and the steps are as follows: weigh 99g of Ag metal powder (purity of 99.99%, median particle size of 40μm, oxygen content of 200ppm) and 1g of La metal powder (purity of 99.99%, median particle size of 30μm, oxygen content of 200ppm). Put the silver and lanthanum raw materials directly into the smelting furnace and heat them until the silver and lanthanum are completely melted. Use electromagnetic stirring to ensure that the silver and lanthanum elements are dissolved and mixed. Pour the uniform silver-based alloy melt into a preheated metal mold for casting. After the alloy solidifies, take out the solidified silver-based master alloy.

[0148] Sampling was performed on different regions (head, middle and tail) of the intermediate alloy prepared in this comparative example for ICP composition detection. The lanthanum contents of the three regions were 1.102wt.%, 1.088wt.% and 0.985wt.%, respectively.

[0149] Comparative Example 2

[0150] The preparation method of the silver-based master alloy for bonding wire provided in this comparative example is basically the same as that in Example 1, except that in step (1), the median particle size of the Ag metal powder is replaced with 200 μm, and the median particle size of the La metal powder is replaced with 200 μm.

[0151] The La contents of the intermediate alloy obtained by drawing in step (4) of this comparative example in different regions (head, middle and tail) were 1.072wt.%, 1.018wt.% and 0.992wt.%, respectively.

[0152] Comparative Example 3

[0153] The preparation method of the silver-based master alloy for bonding wire provided in this comparative example is basically the same as that in Example 1, except that in step (1), the parameters of the mixed ball milling are as follows: the grinding medium is an alumina ball with a diameter of 20 mm, the ball-to-material ratio is 2:1, the mixing time is 30 min, and the ball milling speed is 500 rpm.

[0154] The La contents of the intermediate alloy obtained by drawing in step (4) of this comparative example in different regions (head, middle and tail) were 1.078wt.%, 1.047wt.% and 0.990wt.%, respectively.

[0155] Comparative Example 4

[0156] The preparation method of the silver-based intermediate alloy for bonding wire provided in this comparative example is basically the same as that in Example 1, except that in step (2), the parameters of hot extrusion forming are as follows: the extrusion temperature is 500° C., the extrusion pressure is 1000 MPa, and the extrusion speed is 1 mm / s.

[0157] The La contents of the intermediate alloy obtained by drawing in step (4) of this comparative example in different regions (head, middle and tail) were 1.086wt.%, 1.035wt.% and 0.989wt.%, respectively.

[0158] Comparative Example 5

[0159] The preparation method of the silver-based intermediate alloy for bonding wire provided in this comparative example is basically the same as that in Example 1, except that step (4) is: the cooled round rod is drawn to 1.3 mm by a large wire drawing machine, wherein the surface reduction rate of each drawing pass is controlled at 30%, and the drawing speed is 60 m / min. When drawn to 1.3 mm, an intermediate annealing treatment is performed. The intermediate annealing temperature is set to 400°C, the annealing time is 60 min, and argon protection is adopted. The oxygen content in the argon gas is less than 10 ppm to ensure that no oxidation occurs during the annealing process, and the wire is naturally cooled with the furnace after annealing. Subsequently, a medium wire drawing machine is used to continue drawing a thin wire with a diameter of 1.3 mm to 0.3 mm, wherein the surface reduction rate of each pass is controlled at 20%, and the drawing speed is adjusted to 300 m / min.

[0160] The La contents of the intermediate alloy obtained by drawing in step (4) of this comparative example in different regions (head, middle and tail) were 1.049wt.%, 0.985wt.% and 0.994wt.%, respectively.

[0161] Comparative Example 6

[0162] The method for preparing the silver-based master alloy for bonding wire provided in this comparative example is basically the same as that in Example 1, except that, in step (3), no heat treatment is performed.

[0163] The La contents of the intermediate alloy obtained by drawing in step (4) of this comparative example in different regions (head, middle and tail) were 1.079wt.%, 0.987wt.% and 0.993wt.%, respectively.

[0164] It can be seen that compared with Example 1, the difference in La content in different regions in Comparative Examples 1 to Comparative Examples 6 is larger, which indicates that the La element is unevenly distributed.

[0165] 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 a silver-based master alloy for bonding wire, characterized in that: The steps include: The rare earth metal and silver are uniformly mixed and then hot extruded to obtain a rod; The rod is subjected to heat treatment and then cooled to obtain a treated rod; The treated rod is drawn to obtain the silver-based master alloy for the bonding wire.

2. The method for preparing the silver-based master alloy for bonding wire according to claim 1, characterized in that: At least one of the following conditions is met: (1) The rare earth metal includes at least one of lanthanum, cerium, praseodymium, neodymium, gadolinium, dysprosium and yttrium; (2) The median particle size of the rare earth metal is 20 to 40 μm; (3) The median particle size of the silver is 30 to 50 μm; (4) The mass ratio of the rare earth metal to the silver is 0.5-3:97-99.5; (5) The method for uniform mixing comprises ball milling; preferably, the ball-to-material ratio of the ball milling is 5 to 10:1, the diameter of the grinding medium used in the ball milling is 5 to 10 mm, the ball milling time is ≥ 60 min, the rotation speed of the ball mill is 100 to 300 rpm, and the ball milling process is stopped for cooling for 1 to 30 min every 15 to 25 min.

3. The method for preparing the silver-based master alloy for bonding wire according to claim 1, characterized in that: The following conditions are met: (1) The extrusion temperature of the hot extrusion forming is 600-700° C.; (2) The extrusion pressure of the hot extrusion forming is 500-700 MPa; (3) The extrusion speed of the hot extrusion forming is 0.05 to 0.2 mm / s; (4) The diameter of the rod is 5 to 10 mm.

4. The method for preparing the silver-based master alloy for bonding wire according to claim 1, characterized in that: At least one of the following conditions is met: (1) The temperature of the heat treatment is 600-700° C.; (2) The heat treatment holding time is 3 to 6 hours.

5. The method for preparing the silver-based master alloy for bonding wire according to claim 1, characterized in that: The cooling method includes staged cooling; Preferably, the staged cooling includes: cooling from the heat treatment temperature to 580-620°C at a cooling rate of 2-5°C / min, and keeping warm for 15-30 minutes; then cooling to 480-520°C at a cooling rate of 2-5°C / min, and keeping warm for 15-30 minutes; then cooling to 380-420°C at a cooling rate of 2-5°C / min, and keeping warm for 15-30 minutes; finally cooling to room temperature at a cooling rate of 0.1-1°C / min.

6. The method for preparing a silver-based master alloy for bonding wire according to claim 1, characterized in that: The drawing specifically comprises: first drawing the treated rod until the diameter of the obtained thick wire is 1 to 1.5 mm, then performing intermediate annealing, and then performing a second drawing until the diameter of the obtained thin wire is 0.1 to 0.5 mm; Preferably, the surface reduction rate of each pass of the first drawing is 15% to 20%; Preferably, the first drawing speed is 20-50 m / min; Preferably, the intermediate annealing treatment is performed at a temperature of 350 to 450° C. and for a time of 60 to 90 minutes; Preferably, the surface reduction rate of each pass of the second drawing is 10% to 15%; Preferably, the second drawing speed is 150-200 m / min.

7. The method for preparing a silver-based master alloy for bonding wire according to claim 1, characterized in that: After the drawing, a cutting step is also included.

8. The silver-based master alloy for bonding wire produced by the method for producing the silver-based master alloy for bonding wire according to any one of claims 1 to 7.

9. The silver-based master alloy for bonding wire according to claim 8, characterized in that: The silver-based master alloy for bonding wire comprises, by mass percentage: 0.5% to 3% of rare earth elements and the balance being Ag; Preferably, the rare earth element includes at least one of lanthanum, cerium, praseodymium, neodymium, gadolinium, dysprosium and yttrium.

10. A bonding wire, characterized in that: The silver-based master alloy for bonding wire is mainly prepared by the method for preparing the silver-based master alloy for bonding wire according to any one of claims 1 to 7, or is prepared by the silver-based master alloy for bonding wire according to claim 8.

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