A method for obtaining high-performance copper alloy wires by continuous drawing

Abstract

The application discloses a method for obtaining high-performance copper alloy wire through continuous drawing, which comprises the following steps: taking copper as raw material, melting the copper with Be and other alloy components to obtain a metal melt; using a hot-type continuous casting process to form a fixed-length beryllium copper alloy rod blank; using a stretching die to perform two-group continuous stretching operations on the beryllium copper alloy rod blank, using a spraying reinforced composite material to obtain a reinforced interface between the two-group continuous stretching operations, forming a copper alloy shell layer with Mg and Co on the outside of the reinforced interface, repairing the shell layer to the rod diameter size of the rod blank before the second stretching operation, and obtaining a copper alloy wire master batch; then using the stretching die to perform continuous stretching operation on the copper alloy wire master batch again, drawing the copper alloy wire, annealing the copper alloy wire, cleaning the surface of the copper alloy wire, and obtaining a finished product. The high-performance copper alloy wire prepared by the method has high strength and toughness, high tensile strength, high electrical conductivity and excellent processing performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal material processing, in particular to a method for obtaining high-performance copper alloy wire through continuous drawing. BACKGROUND

[0002] With the development of emerging industries and major engineering fields such as microelectronics, new generation mobile communication, new energy vehicles, aerospace, rail transit, etc. in China, the requirements for advanced high-performance metal materials are becoming higher and higher. Copper and copper alloy materials are widely used in the above-mentioned industrial fields due to their good electrical conductivity, better performance and secondary processing performance. The related research on copper materials such as high-strength high-conductivity copper alloy, wear-resistant corrosion-resistant copper alloy, ultra-high-strength elastic copper alloy, advanced copper-based composite material, high-precision high-performance copper and copper alloy wire, etc. is also increasing and diversifying.

[0003] Among them, in the field of microelectronics industry, bonding wire is usually used. As an internal lead for packaging, bonding wire is one of the essential materials in the manufacturing process of integrated circuits and semiconductor discrete devices. It can be used in transistors, integrated circuits, large-scale integrated circuits and other semiconductor devices to realize the electrical connection between the chip and the external circuit, transmit the electrical signal of the chip and carry out the heat generated in the chip. It requires good electrical conductivity, chemical stability, good plasticity, easy bonding, and relatively high physical strength and elasticity.

[0004] Traditional bonding wire is mostly gold wire, but the defect is that the use cost is high. With the application of special packaging equipment for bonding copper wire and the improvement of bonding process, bonding copper wire has the advantages of good mechanical properties, chemical stability, high electrical conductivity and low use cost. It can maintain excellent solder ball head strength and line arc stability during packaging operation, and has become an ideal material to replace bonded gold wire and bonded aluminum-silicon wire. However, the copper-based bonding wire (copper and copper alloy bonding wire) in the prior art has application bottlenecks under the existing technical conditions, and it is difficult to further improve the performance indicators of physical strength and elasticity. It is difficult to balance electrical conductivity and bonding mechanical strength, making it difficult to meet the growing demand in the field. SUMMARY

[0005] The technical problem solved by the present application is to provide a method for obtaining high-performance copper alloy wire through continuous drawing to solve the defects in the above technical background.

[0006] The technical problem solved by the present application is solved by the following technical solution:

[0007] A method for obtaining high-performance copper alloy wire through continuous drawing, specifically comprising the following operation steps:

[0008] S1, after surface cleaning of raw material copper, remove copper skin, put the raw material copper without copper skin into a vacuum melting furnace for vacuum melting treatment, add Be and other alloy components during the melting process, continue to melt until all materials are melted, and then keep for 5-6 hours to obtain a metal melt;

[0009] S2, using the metal melt as raw material, a straight length beryllium copper alloy rod blank with a diameter of 10-20 mm is formed by using hot type continuous casting process; the above beryllium copper alloy rod blank is continuously stretched by using a stretching die to reduce its diameter by 15-20% to obtain a stretched rod material; the stretched rod material is annealed at a temperature of 620-650℃ for 6-10 hours to obtain an annealed stretched rod material;

[0010] S3, after the annealed stretched rod material is stable in properties, a reinforcing composite material is sprayed on the surface of the annealed stretched rod material to obtain a sprayed rod material; the reinforcing composite material is based on a nano graphene sheet carbon nanotube composite slurry, and 1-1.5wt‰ of nano-scale high-purity Ti powder is uniformly dispersed in the reinforcing composite material;

[0011] S4, the sprayed rod material is continuously stretched by using a stretching die to reduce its diameter to 65-75% of the diameter of the sprayed rod material to obtain a second stretched rod material, and the second stretched rod material is used as a core in a rod body mold; at the same time, 0.3-0.5wt% of high-purity Mg and 0.2-1.2wt% of high-purity Co are added to the metal melt obtained in step S1, and then the metal melt is injected into the mold corresponding to the outer edge of the stretched rod material to obtain a shell layer, and the shell layer is repaired to the rod diameter size before stretching of the second stretched rod material to obtain a copper alloy wire mother material;

[0012] S5, the copper alloy wire mother material is continuously stretched by using a stretching die again to draw a copper alloy wire with a diameter of less than 3mm, and then the copper alloy wire is subjected to on-line annealing treatment, and after the treatment is completed, the surface is cleaned to obtain a finished product.

[0013] As a further limitation, when the raw material copper is subjected to surface copper skin removal in step S1, the skin layer is removed by physical means such as a cutter or a sanding wheel, or by chemical means such as immersion in dilute sulfuric acid.

[0014] As a further limitation, the Be content added in the metal melt is 1.85-1.92wt%.

[0015] As a further limitation, the other alloy components added in the metal melt are one or a combination of Fe, Nb, Cr, Sn, Si, and Zn, and the metal materials are added in the form of powders or thin sheet materials with a purity of more than 99.95%, and Si is added in the form of a block material with a purity of more than 99.9%.

[0016] As a further limitation, the purity of the nanoscale high-purity Ti powder, high-purity Mg, and high-purity Co is greater than 99.95%.

[0017] As a further limitation, when the hot type continuous casting process is performed in step S1, a casting mold dummy ingot processed by a graphite material is used, and the smoothness of the inner wall of the casting mold dummy ingot is ▽7~▽8, so as to ensure the smoothness of the surface of the beryllium copper alloy rod blank material after forming and reduce surface scratches and scratches.

[0018] As a further limitation, the purity of the nanoscale high-purity Ti powder, high-purity Mg, and high-purity Co is greater than 99.95%.

[0019] As a further limitation, when the hot type continuous casting process is performed in step S1, a casting mold dummy ingot processed by a graphite material is used, and the smoothness of the inner wall of the casting mold dummy ingot is ▽7~▽8, so as to ensure the smoothness of the surface of the beryllium copper alloy rod blank material after forming and reduce surface scratches and scratches.

[0020] Beneficial effects: The method for obtaining high-performance copper alloy wire by continuous drawing can be used for preparing high-performance copper alloy wire with good mechanical properties and chemical stability, high electrical conductivity, excellent solder ball head strength and line arc stability when used as a bonding copper wire for packaging operation, and has the advantages of good heat conduction performance, wear resistance, corrosion resistance, and smooth surface. DETAILED DESCRIPTION

[0021] In order to make the technical means, creative features, purposes and effects realized by the present application easy to understand, the present application will be further described in conjunction with specific embodiments.

[0022] In the following examples, those skilled in the art can understand that unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as that generally understood by those skilled in the art to which the present application belongs.

[0023] In the present embodiment, the base metal melt for preparing high-performance copper alloy wire includes raw materials with the following mass ratio components:

[0024] Be: 1.90%, Zn 0.15%, Sn 0.09%, Ni 0.18%, Nb 0.03%, Si 0.14%, Cr 1.0%, and the remaining part is composed of Cu and inevitable impurities; wherein Cu is a copper block with a purity of 99.95%, Be, Zn, Sn, Ni, Nb, and Cr are powders with a purity controlled within the range of 99.95~99.98%, and Si is a block with a purity of 99.95%.

[0025] Among the above components, Cu and Be are the main components of beryllium copper alloy, Zn, Ni and Si are used to improve and optimize the strength and electrical conductivity of the alloy; the addition of Sn, Nb and Ni can help to improve the fragmentation of coarse dendritic grains in the cast state, reduce the strength of plastic working, improve the processing performance of beryllium copper, and further improve the overall performance of beryllium copper; Cr can be used to optimize the composition of the alloy and combine the internal structure system.

[0026] During preparation, the copper surface is first cleaned with a sodium carbonate solution at 60°C and a mass concentration of 3% for 10 minutes, and then in order to remove the oxide scale on the surface of the thin copper sheet, it is cleaned in dilute sulfuric acid at a temperature of 45°C and a mass concentration of 4% for 10 minutes, taken out and dried for use.

[0027] A medium-high frequency induction power supply was used as the heating power supply for the vacuum melting furnace. Before the smelting process, the vacuum melting furnace was evacuated to a pressure of 0.008 Pa, and then filled with argon as a protective gas. The pressure in the vacuum melting furnace was adjusted to 0.15 MPa. The peeled Cu and other components were added under an argon protective atmosphere. The heating rate of the vacuum melting furnace was controlled at 50-60°C / min. When the melting temperature reached 1280°C, the melting state was maintained and stirring was continued. After the material in the furnace was completely melted, it was divided into two parts. One part was kept warm for 6 hours to obtain molten metal I; while in the other part, high-purity Mg (purity above 99.95%) accounting for 0.4 wt% of the mass of the molten metal and high-purity Co (purity above 99.95%) accounting for 0.7 wt% of the mass of the molten metal were added to part of the molten metal, and the heat was continued for 6 hours to obtain molten metal II.

[0028] At the same time, 0.3-0.5 wt % of high-purity Mg (99.95% or more) and 0.2-1.2 wt % of high-purity Co (99.95% or more) are added to the molten metal I obtained in step S1.

[0029] The molten metal I is used as a raw material, a graphite mold ingot is used as a tool, the surface finish of the inner wall of the graphite mold ingot is controlled to be ▽7.6, and hot mold continuous casting is performed. The casting operation temperature of the hot mold continuous casting is controlled to be 1150° C. to obtain a high-purity beryllium copper alloy rod blank. The diameter of the obtained high-purity beryllium copper alloy rod blank is controlled to be 10-20 mm to facilitate the stretching operation.

[0030] In the above operation, the graphite casting ingot with a smooth inner wall can ensure the surface finish of the beryllium copper alloy rod blank obtained after molding and reduce surface scratches and nicks; and the hot mold continuous casting process can eliminate the transverse grain boundaries in the alloy, so that the generated high-purity beryllium copper alloy rod blank has no casting defects such as pores, shrinkage cavities, inclusions, and segregation, which is conducive to secondary processing operations including drawing, reduces the annealing treatment time, and can also improve the electrical properties of the wire and enhance its corrosion resistance and fatigue resistance.

[0031] The obtained high-purity beryllium copper alloy rod blank is continuously stretched using a stretching die. The number of stretching times is not limited, and the wire breakage rate is reduced to ensure the stretching quality. After the stretching is completed, the diameter of the high-purity beryllium copper alloy rod blank is reduced by 20% to obtain a stretched rod material; the stretched rod material is annealed at a temperature of 630°C for 8 hours to obtain an annealed stretched rod material.

[0032] A commercially available nanographene sheet / carbon nanotube composite slurry was selected. The slurry was prepared using water as the slurry medium. The slurry parameters included a 96% purity, a 2.1% carbon nanotube content, and a 4:1 ratio of nanographene sheets to carbon nanotubes. Nanoscale high-purity titanium powder (99.96% purity) was evenly dispersed within the slurry, accounting for 1.3% of the slurry by mass. This reinforced composite was then applied to the surface of an annealed, stretched rod using a spin coating method, with the coating thickness controlled to between 0.8 and 1.2 μm. This resulted in a sprayed rod.

[0033] The sprayed rod stock is then continuously stretched again using a stretching die to reduce its diameter to 65-75% of the diameter of the sprayed rod stock, thereby obtaining a secondary stretched rod stock. The secondary stretched rod stock is then vertically inserted as a core into a rod body mold formed of graphite material, and molten metal II is then injected into the rod body mold. After forming, the molten metal II solidifies and forms a shell layer on the surface of the secondary stretched rod stock. The mold cavity size of the rod body mold is controlled so that the shell layer can restore the rod diameter of the secondary stretched rod stock to the rod diameter size before stretching, thereby obtaining a copper alloy wire masterbatch.

[0034] Finally, the copper alloy wire masterbatch is used as raw material and a continuous stretching operation is performed again using a stretching die. This round of continuous stretching operation can directly draw the copper alloy wire masterbatch into a copper alloy wire with a diameter of less than 3 mm. The copper alloy wire is then annealed online, and the annealing temperature of the annealing furnace is controlled at 580°C and the annealing time is controlled at 8 hours. After the treatment is completed, the surface is cleaned to obtain the finished high-performance copper alloy wire.

[0035] The high-performance copper alloy wire obtained by the process of the embodiment was cut into segments for performance testing (ten segments were cut from a 30m long finished high-performance copper alloy wire, with the spacing between two adjacent segments being no less than 2m). The average performance values ​​of the parameters were:

[0036] The density is 8.8 g / cm3, the thermal conductivity is 107 W / mK·20℃, the hardness is 38~41 HRC, the tensile strength (D=8±0.5μm) is 536MPa, the electrical conductivity is 88.5%IACS, and the elongation is 6.5%.

[0037] The reason why the high-performance copper alloy wire of this embodiment can achieve the above performance is that:

[0038] Beryllium copper, a supersaturated solid solution copper-based alloy, is used as a substrate. Drawing it through a tensile die can break down the coarse dendritic grains in the cast state of the high-purity beryllium copper alloy rod into fine equiaxed grains. The increased number of grain boundaries can effectively hinder dislocation movement, thereby achieving fine grain strengthening and improving the mechanical properties of the alloy. Repeated continuous drawing can achieve a treatment effect similar to repeated forging, and compared to forging, its internal refinement of the alloy system is more uniform and stable, effectively refining the grain structure within the alloy system and forming a uniform internal fine equiaxed grain space system, ensuring the strength and toughness of the alloy structure while also ensuring its electrical conductivity.

[0039] During the annealing process, the beryllium copper alloy will begin to undergo eutectoid reaction at 605°C. When annealing in the temperature range of 605-650°C, the main factor affecting the alloy performance is the β phase generated during the recovery recrystallization and eutectoid reaction. The tensile strength and hardness will increase with the increase of annealing temperature, but since the hard particles are β phase, micro cracks are easily generated. In the technical solution of this embodiment, the high-purity beryllium copper alloy rod blank is annealed for a long time at a temperature of 630°C, so that the tensile strength and hardness of the annealed tensile rod material can be improved, and a uniform micro crack layer structure can be formed on the surface. By applying nanostructured carbon to the surface of the micro crack layer structure, the tensile strength and hardness of the annealed tensile rod material can be improved. The reinforced composite material prepared by the carbon nanotube composite slurry of rice graphene sheets and Ti, by introducing carbon nanotubes and graphene to form an interface structure layer with Ti, obtains a carbon nanotube / graphene reinforced copper-based composite material interface with high strength and high electrical conductivity; and the reinforced composite material enters the microcrack layer structure on the surface of the annealed tensile rod material through another drawing operation after coating and forms a stable structure layer. At the same time, the extrusion force generated during the drawing operation can physically extrude and repair the above-mentioned microcrack layer structure, and in the subsequent process, the interface structure layer is sealed when the metal melt II is injected through the rod body mold, forming a stable interface reinforcement structure between the shell layer and the core layer.

[0040] Compared to the core alloy, the addition of trace magnesium to the shell copper alloy refines the grain size, improves the alloy structure, and enhances the overall material performance. This improves the tensile strength of the final copper alloy wire and reduces the elastic aftereffect. This ensures strong surface elasticity and secondary machinability, as well as ball strength and wire arc stability when used as a bonding wire, facilitating operator operation and ensuring the stability and reliability of the balance spring and tensioning wire.

[0041] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for obtaining high-performance copper alloy wire by continuous drawing, characterized in that: The specific steps include the following: S1. After cleaning the surface of the raw copper, remove the copper scale, and place the raw copper after removing the copper scale into a vacuum melting furnace for vacuum melting treatment. During the melting process, Be and other alloy components are added together. The melting is continued until all materials are completely melted and maintained for 5-6 hours to obtain a metal melt; S2. Using molten metal as a raw material, a hot mold continuous casting process is used to form a fixed-length beryllium copper alloy rod blank with a diameter of 10-20 mm; the beryllium copper alloy rod blank is continuously stretched using a stretching die to reduce its diameter by 15-20%, thereby obtaining a stretched rod material; and the stretched rod material is annealed at a temperature of 620-650° C. for 6-10 hours to obtain an annealed stretched rod material. S3. After the properties of the annealed tensile rod material are stabilized, a reinforcing composite material is sprayed on its surface to obtain a sprayed rod material; the reinforcing composite material is based on a nano-graphene sheet carbon nanotube composite slurry, and 1-1.5 wt‰ of nano-grade high-purity Ti powder is uniformly dispersed therein; S4. Continuously stretching the sprayed rod material using a stretching die to reduce its diameter to 65-75% of the diameter of the sprayed rod material to obtain a secondary stretched rod material, and adding the secondary stretched rod material as a core into a rod body mold; simultaneously, adding 0.3-0.5 wt % of high-purity Mg and 0.2-1.2 wt % of high-purity Co to the molten metal obtained in step S1, and then injecting the molten metal into the rod body mold corresponding to the outer edge of the secondary stretched rod material to obtain a shell layer, and repairing the shell layer to the rod diameter size of the secondary stretched rod material before stretching, to obtain a copper alloy wire masterbatch; S5. The copper alloy wire masterbatch is continuously stretched again using a stretching die to be drawn into a copper alloy wire with a diameter of less than 3 mm. The copper alloy wire is then subjected to an online annealing treatment. After the treatment is completed, the surface is cleaned to obtain a finished product.

2. The method for obtaining high-performance copper alloy wire by continuous drawing according to claim 1, characterized in that: In step S1 , when the raw copper is subjected to surface descaling, the skin is removed chemically by immersing in dilute sulfuric acid.

3. The method for obtaining high-performance copper alloy wire by continuous drawing according to claim 1, characterized in that: The Be content added to the metal melt is 1.85-1.92 wt%.

4. The method for obtaining high-performance copper alloy wire by continuous drawing according to claim 1, characterized in that: The other alloy components added to the metal melt are one or a combination of Fe, Nb, Cr, Sn, Si, and Zn. When added, the metal material is added in the form of powder or flakes with a purity of more than 99.95%, and Si is added in the form of blocks with a purity of more than 99.9%.

5. The method for obtaining high-performance copper alloy wire by continuous drawing according to claim 1, characterized in that: When the hot mold continuous casting process is performed in step S1, the starter ingot made of graphite material has a surface finish of ▽7~▽8 on the inner wall.

6. The method for obtaining high-performance copper alloy wire by continuous drawing according to claim 1, characterized in that: The purity of the nano-graphene sheet carbon nanotube composite slurry used in the reinforced composite material is greater than 90wt%, the content of nano-graphene sheet carbon nanotubes is 2-3wt%, and the composite ratio of nano-graphene sheet to carbon nanotube is 4:1-5:

1.

7. The method for obtaining high-performance copper alloy wire by continuous drawing according to claim 1, characterized in that: In step S5 , when the copper alloy wire is subjected to online annealing treatment, the annealing furnace temperature is controlled to be 580-590° C., and the annealing time is controlled to be 7-9 hours.