CN118950735B

CN118950735B - Single crystal metal wire and preparation method thereof

Info

Publication number: CN118950735B
Application number: CN202411462638.7A
Authority: CN
Inventors: 郑瑞晓; 李鹤; 魏大圣; 刘茂文; 王成远; 鲁园园; 马朝利
Original assignee: Tianmu Mountain Laboratory
Current assignee: Tianmu Mountain Laboratory
Priority date: 2024-10-19
Filing date: 2024-10-19
Publication date: 2025-10-14
Anticipated expiration: 2044-10-19
Also published as: CN118950735A

Abstract

The invention discloses a monocrystalline metal wire and a preparation method thereof, wherein a polycrystalline metal blank is a high-purity oxygen-free copper rod with the purity of 99.999 percent or a high-purity nickel rod with the purity of 99.99 percent, and the prepared monocrystalline metal has uniform components and high single crystallization degree. The preparation method comprises the following steps of S1 taking a polycrystalline metal blank rod as a starting raw material, obtaining a polycrystalline metal rod with equiaxed grains through heat treatment, S2 preparing a polycrystalline fine metal rod, S3 preparing a single crystal fine metal rod, S4 carrying out a plurality of passes of drawing on the single crystal fine metal rod in the step (3) to obtain superfine polycrystalline metal filaments with different diameters, S5 carrying out temperature gradient annealing treatment on the polycrystalline metal filaments with different diameters obtained in the step (4) along the axial direction of the wire, and S6 carrying out pickling and drying on the polycrystalline metal filaments in the step (5) to obtain the single crystal metal wire. The invention has the beneficial effects of not only abandoning the limitation of taking expensive single crystal bars as raw materials, but also having simpler operation and lower cost.

Description

Single crystal metal wire and preparation method thereof

Technical Field

The invention relates to the technical field of monocrystalline metal wires, in particular to a monocrystalline metal wire and a preparation method thereof.

Background

The metal nickel wire has good mechanical strength, corrosion resistance and higher heat resistance, and is suitable for manufacturing vacuum devices, electronic instrument elements, filter screens of strong alkali in chemical production and the like. In electronic devices, audio and video cables require no distortion of the transmission signal, and high-speed data transmission and high-fidelity (Hi-Fi) can be ensured by using wires made of copper wires. In addition, the superfine copper wire is used as an inner lead wire for electronic packaging, is one of essential basic materials in the manufacturing process of integrated circuits and semiconductor discrete devices, is a bridge for connecting a silicon chip electrode and an external lead-out terminal of a lead frame, and plays a role in transmitting chip electric signals and radiating heat inside a chip. Compared with gold wires, copper wires are low in price, the price of the copper wires is only 20% -40% of that of gold wires, but the copper wires have higher electric conductivity and thermal conductivity (inferior to silver wires), so that the copper wires become important materials for replacing gold wires and becoming semiconductor packaging leads.

Currently, commercial wires are usually drawn in multiple passes using relatively expensive continuous cast metal rods as the starting material. During drawing, severe work hardening and defect generation are often accompanied, thereby affecting the electrical and mechanical properties of the wire. Compared with a polycrystalline wire, the monocrystalline metal wire has no grain boundary, can effectively reduce electron and phonon scattering, and has better electric conductivity and heat conductivity. Therefore, single crystal copper wires are ideal materials for replacing expensive gold wires as leads for semiconductor packages. In addition, because the single-crystal metal wire does not have grain boundaries, the unstable factors of the structure such as high-temperature grain boundary sliding can be effectively avoided, and excellent high-temperature mechanical properties are generally shown, so that the single-crystal metal wire is widely applied to the fields of manufacturing mechanical hot-end structural components and the like.

In the prior art, the single crystal wire prepared by the continuous casting method generally has a plurality of defects, because a metal sample is in direct contact with a die in the continuous casting process, and the die extrudes a metal product to deform, so that the defects such as subgrain boundaries and the like are easily introduced into crystals, and the performances of the crystals are influenced, and therefore, the high-quality single crystal metal wire is difficult to prepare by the continuous casting method at present. The traditional strain annealing method is easy to cause competitive growth of crystal grains, and large-size monocrystalline metal wires are difficult to prepare, so that batch preparation and large-scale application of the monocrystalline metal wires are hindered. Therefore, the low-cost preparation method for seeking the high-performance monocrystalline metal wire has important scientific value and engineering significance.

Disclosure of Invention

The invention aims to provide a single crystal metal wire and a preparation method thereof.

The method uses the polycrystalline metal rod as an initial raw material, not only abandons the limitation of using an expensive single crystal rod as the raw material, but also has the advantages of simpler operation and lower cost, and the prepared single crystal metal has uniform components and high single crystallization degree.

In order to achieve the above purpose, the present invention is realized by the following technical scheme:

a method for preparing a single crystal wire, comprising the following steps:

S1, taking a polycrystalline metal blank rod as a starting material, and obtaining a polycrystalline metal rod with equiaxed grains through heat treatment;

s2, carrying out multiple drawing treatment on the equiaxed grain polycrystalline coarse metal rod obtained in the step S1 to obtain a polycrystalline fine metal rod;

s3, carrying out temperature gradient annealing on the polycrystalline thin metal rod obtained in the step S2 to obtain a single crystal thin metal rod;

s4, carrying out several passes of drawing on the single-crystal fine metal rod in the S3 to obtain superfine polycrystalline metal filaments with different diameters;

s5, carrying out temperature gradient annealing treatment on the drawn polycrystalline metal filaments with different diameters obtained in the S4 along the axial direction of the wire;

and S6, carrying out acid washing and drying on the metal filament obtained by the heat treatment of the step S5 to obtain the monocrystalline metal filament.

As a further improvement of the present solution, in S1, the specific operation of the heat treatment is as follows:

Carrying out heat treatment on the high-purity metal blank after pickling at 500-900 ℃, wherein the pressure in the furnace is a, and the quantity relation a is less than or equal to 10 ^-3 Pa;

the temperature rising rate is 10 ℃ per minute, the heat treatment time is 12-24 hours, and then the polycrystalline metal rod with equiaxed grains is obtained by furnace cooling.

As a further improvement of the scheme, in S2, the drawing temperature of the polycrystalline blank is 650-950 ℃, a lubricant is used in the operation process, and the lubricant flowing out of a die hole is controlled to be 25-40m.min ^-1, so that the polycrystalline fine metal rod with the diameter of 6-10 mm is obtained.

As a further improvement of the scheme, the lubricant is prepared by adding 25% of flake graphite to No. 45 engine oil.

As a further improvement of the scheme, in S3, a temperature gradient of 2-4 ℃/cm is constructed in a double-temperature-zone tube furnace, wherein the temperature of a high-temperature zone is 10-50 ℃ lower than the melting point, the temperature of a low-temperature zone is controlled to be 50-100 ℃ lower than the melting point, the temperature rising rate is 5-10 ℃/min, and the heat treatment is carried out for 48-96 hours;

And S4, carrying out multi-pass drawing for 50-100 times on the obtained single-crystal thin metal rod by a wire drawing machine driven by a microcomputer program-controlled alternating current servo motor to obtain the polycrystalline metal thin wire with the diameter of 0.018-0.040 mm.

As a further improvement of the scheme, in S5, a temperature gradient of 2-4 ℃/cm is constructed in the double-temperature-zone tube furnace, wherein the temperature of a high-temperature zone is lower than the melting point by 10-50 ℃, the temperature of a low-temperature zone is lower than the melting point by 50-100 ℃, and the temperature rising rate is 5-10 ℃/min.

As a further improvement of the present solution, in S5,

Annealing the polycrystalline metal ultrafine wire material for 12-48 hours in the temperature gradient range to obtain a monocrystalline metal wire material;

the used shielding gas is 2.5-5% hydrogen-argon gas mixture, and the gas flow is controlled at 300-600sccm;

and S6, carrying out surface pickling and cleaning on the monocrystalline metal wire after the heat treatment.

A single crystal wire is prepared by a method of preparing a single crystal wire.

As a further improvement of the scheme, the polycrystalline metal blank is a high-purity oxygen-free copper rod with the purity of 99.999 percent or a high-purity nickel rod with the purity of 99.99 percent.

The monocrystalline metal wire material has the following beneficial effects:

1) The polycrystalline metal blank is a high-purity oxygen-free copper rod with the purity of 99.999 percent or a high-purity nickel rod with the purity of 99.99 percent, and the prepared monocrystal metal has uniform components and high monocrystal degree.

The preparation method of the monocrystalline metal wire material has the following beneficial effects:

1) The novel preparation method of the focused monocrystalline metal wire does not depend on a high-temperature melting environment, namely, the transformation from polycrystalline metal to monocrystalline metal can be realized by utilizing a specially designed high-temperature annealing process, and is different from the traditional melting monocrystalline growth method;

2) The invention adopts a temperature gradient annealing process, which can effectively remove the defect that the crystal grain competitively grows and the crystal boundary cannot be eliminated due to the traditional heat treatment. In addition, the solid polycrystalline metal is used as a raw material, so that impurities introduced by the traditional melting method due to contact of a melt crucible can be effectively avoided, the purity and quality of crystals are improved, and the electrical property of the metal wire is further improved;

3) The invention adopts the non-melting method to prepare the monocrystalline metal wire, and the length of the monocrystalline metal wire is expandable due to the adoption of the polycrystalline raw material, does not depend on expensive equipment, and has the advantages of easily obtained raw material, simple process, easy control, low cost and easy large-scale popularization.

Drawings

FIG. 1 is a schematic flow chart of a method for producing a single-crystal metallic copper wire in example 1 of the present invention;

FIG. 2 is a schematic diagram of a temperature gradient annealing apparatus in example 1 of the present invention;

FIG. 3 is a graph showing the microstructure characterization of the single crystal copper wire prepared in example 1 of the present invention;

FIG. 4 is a graph showing the electrical conductivity of the single crystal copper wire prepared in example 1 of the present invention compared to other single crystal copper samples;

FIG. 5 is a graph showing the morphology of a copper wire under the annealing condition without a temperature gradient prepared in comparative example 1 of the present invention;

FIG. 6 is a graph showing the microstructure of a copper wire after annealing without drawing deformation and with a temperature gradient in comparative example 2 according to the present invention;

FIG. 7 is a graph showing the microstructure characterization of the single crystal nickel wire prepared in example 2 of the present invention.

Fig. 8 is an international annealed copper standard calculation formula.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described below with reference to the following examples and fig. 1 to 8:

example 1

In this embodiment, the specific process flow is as follows:

And (1) pickling a high-purity oxygen-free copper rod with the diameter of 25.4 mm and the purity of 99.999 percent, and then carrying out heat treatment at 600 ℃ to ensure that the pressure in the furnace is lower than 10 ^-3 Pa. The temperature rising rate is 10 ℃ per min, the heat treatment time is 12 hours, and then the polycrystalline copper bar with equiaxed grains is obtained by furnace cooling.

And (2) carrying out drawing forming on the equiaxed grain polycrystalline copper rod annealed in the step (1) to obtain the polycrystalline copper rod with the diameter of 8 mm. The conditions were set to an outflow die speed of 35 m.min ^-1, and a polycrystalline copper rod diameter of 8mm was obtained by adding 25% graphite flakes as a lubricant to a number 45 oil.

And (3) carrying out temperature gradient heat treatment on the polycrystalline fine copper wire with the diameter of 8 mm obtained in the step (4) along the axial direction, and carrying out temperature gradient heat treatment at the temperature close to the melting point to obtain the single crystal copper rod with the diameter of 8 mm. The temperature of the high temperature area is 1050 ℃, the temperature of the low temperature area is 1000 ℃, the temperature rising rate is 10 ℃ per minute, the temperature gradient is 3 ℃ per cm, and the schematic diagram of the annealing device is shown in figure 2. The used shielding gas is 3% hydrogen-argon gas mixture, and the gas flow is controlled at 480 sccm.

And (4) drawing the single-crystal coarse copper rod crystal with the diameter of 8 mm obtained in the step (3) into a polycrystalline fine copper rod with the diameter of 2 mm again, wherein the drawing temperature is 450 ℃, the outflow die hole speed is 50m & min ^-1, and similarly, the 45 # machine oil and 25% flake graphite are used as a lubricant, so that the diameter of the obtained polycrystalline fine copper rod is 2 mm.

Drawing the thin copper rod with the diameter of 2 mm obtained in the steps into a polycrystalline thin copper wire with the diameter of 0.2 mm by a microcomputer program control and alternating current motor driven wire drawing machine;

And (5) preheating the polycrystalline fine copper wire with the diameter of 0.2 mm obtained in the step (4), and then drawing the polycrystalline fine copper wire with the diameter of 0.018 mm on a small wire drawing machine for multiple passes.

And (6) pickling the polycrystalline superfine copper wire obtained in the step (5), and vacuum packaging the pickled and dried polycrystalline copper wire by using a quartz tube, wherein the vacuum degree is lower than 10 ^-3 Pa. And performing temperature gradient heat treatment at the temperature close to the melting point to obtain the monocrystal superfine copper wire. The temperature of the high temperature area is 1000 ℃, the temperature of the low temperature area is 950 ℃, the temperature rising rate is 10 ℃ per minute, the temperature gradient is 2.5 ℃ per cm, and the time is 24 hours, and the schematic diagram of the annealing device is shown in figure 2. And after the annealing is finished, directly taking out the annealed copper wire along with the quartz tube, quenching the annealed copper wire by cold water, and cleaning the surface of the annealed copper wire to obtain the finished product of the monocrystal superfine copper wire.

In this embodiment, the surface of the annealed copper wire is cleaned by immersing the copper wire in 98% alcohol solution, performing ultrasonic treatment in an ultrasonic machine for 1 hour, removing impurities attached to the surface, and cleaning and drying in deionized water after the ultrasonic treatment is completed. In addition, the microstructure of the obtained copper wire was characterized as shown in fig. 3. The morphology observation of the scanning electron microscope shows that the annealed copper wire has regular shape. The electron back scattering spectrum shows that the prepared monocrystal copper wire has uniform components and high monocrystal degree.

In this example, conductivity measurements were performed on surface-cleaned copper wire, and the conductivity of the prepared single crystal copper wire was expressed using the international annealed copper standard (as shown in fig. 8). The results show that the conductivity of the prepared single crystal copper wire is 1.630 multiplied by 10 ^-8 omega-m, namely 105.8 percent IACS, which is higher than that of the single crystal copper wire prepared by the large-field continuous casting method by 102.2 percent IACS and the single crystal copper wire prepared by the Czochralski method by 103.1 percent IACS, and the conductivities of the three are shown in figure 4.

Comparative example 1

In this comparative example, step (6) of example 1 was skipped, i.e., the polycrystalline fine copper wire obtained in example was not subjected to temperature gradient annealing, but was subjected to constant temperature annealing at 1000 ℃.

And (3) cleaning the surface of the annealed copper wire, namely immersing the copper wire in 98% alcohol solution, performing ultrasonic treatment in an ultrasonic machine for 1 hour, removing impurities attached to the surface, and cleaning and drying in deionized water after the ultrasonic treatment is finished. Further, microstructure analysis of the obtained copper wire revealed that the thin copper wire without temperature gradient annealing in comparative example 1 had more grain boundaries and low degree of single crystallization, and it was difficult to form a long-sized single crystal copper wire.

Therefore, the annealing along the axial direction of the fine copper wire is favorable for further eliminating grain boundaries, and is necessary for preparing the long-size single crystal copper wire.

Comparative example 2

In the comparative example, the drawing process of the steps (2) and (4) in the example is skipped, and the equiaxed grain polycrystalline copper bar obtained in the step (1) is subjected to temperature gradient annealing only, namely, is subjected to temperature gradient heat treatment along the axial direction, and is subjected to temperature gradient heat treatment at the temperature close to the melting point, so that the monocrystalline copper bar with the diameter of 8 mm is obtained. The temperature of the high temperature area is 1050 ℃, the temperature of the low temperature area is 1000 ℃, the temperature rising rate is 10 ℃ per minute, the temperature gradient is 3 ℃ per cm, the heat treatment time is 24 hours, and the schematic diagram of the annealing device is shown in figure 2. The used shielding gas is 3% hydrogen-argon gas mixture, and the gas flow is controlled at 480 sccm.

And (3) cleaning the surface of the annealed copper wire, namely immersing the copper wire in 98% alcohol solution, performing ultrasonic treatment in an ultrasonic machine for 1 hour, removing impurities attached to the surface, and cleaning and drying in deionized water after the ultrasonic treatment is finished. In addition, the microstructure of the copper wire after heat treatment was characterized (fig. 6), and it was found that if the copper wire was not subjected to the drawing deformation step (2) (4), only the temperature gradient annealing was performed, so that a large number of coarse grains with different orientations were formed in the sample, and the grain boundaries were more obvious, and it was difficult to form a long-sized single crystal copper wire.

Example 2

In this embodiment, the specific process flow is as follows:

And (1) pickling a high-purity nickel rod with the diameter of 12.7 mm and the purity of 99.99 percent, and then carrying out heat treatment at 800 ℃ to ensure that the pressure in the furnace is lower than 10 ^-3 Pa. The temperature rising rate is 10 ℃ per minute, the heat treatment time is 12 hours, and then the polycrystalline nickel rod with equiaxed grains is obtained by furnace cooling.

And (2) carrying out drawing forming on the isometric crystal grain polycrystalline nickel rod annealed in the step (1) to obtain the polycrystalline nickel rod with the diameter of 6.35 mm. The drawing temperature is set at 800 ℃, the outflow die hole speed is 55 m.min ^-1, and the diameter of the obtained polycrystalline nickel rod is 6.35 mm by using No. 45 engine oil and 25% of flake graphite as a lubricant.

And (3) carrying out temperature gradient heat treatment on the polycrystalline thin nickel rod with the diameter of 6.35 mm obtained in the step (2) along the axial direction, and carrying out temperature gradient heat treatment at the temperature close to the melting point to obtain the single crystal nickel rod with the diameter of 6.35 mm. Wherein the temperature of the high temperature area is 1410 ℃, the temperature of the low temperature area is 1350 ℃, the temperature rising rate is 10 ℃ per minute, the temperature gradient is 3 ℃ per cm, and the heat treatment time is 72 hours. The used shielding gas is 5% hydrogen-argon gas mixture, and the gas flow is controlled at 480 sccm.

And (4) drawing the single crystal coarse nickel rod with the diameter of 6.35 mm obtained in the step (3) into a polycrystalline fine copper rod with the diameter of 2 mm again, wherein the drawing temperature is 750 ℃, the die hole outlet speed is 50m.min ^-1, and similarly, the diameter of the obtained polycrystalline fine copper rod is 2 mm by using No. 45 engine oil and 25% flake graphite as a lubricant.

Step (5), drawing the thin nickel rod with the diameter of 2 mm obtained in the step (4) into polycrystalline nickel wires through a microcomputer program control and alternating current motor driven wire drawing machine;

and (6) carrying out the temperature gradient heat treatment on the polycrystalline nickel obtained in the step (5) at the temperature close to the melting point in a vacuum tube furnace to obtain the monocrystal nickel wire. Wherein the temperature of the high temperature area is 1400 ℃, the temperature of the low temperature area is 1380 ℃, the temperature rising rate is 10 ℃ per minute, the temperature gradient is 2.5 ℃ per cm, and the time is 48 hours. And cooling along with the furnace after the annealing is finished, and cleaning the surface of the annealed nickel wire to obtain the finished product of the monocrystal nickel wire.

In this embodiment, the surface of the annealed nickel wire is cleaned by immersing the nickel wire in 98% alcohol solution, performing ultrasonic treatment in an ultrasonic machine for 1 hour, removing impurities attached to the surface, and cleaning and drying in deionized water after the ultrasonic treatment is completed. In addition, the microstructure of the obtained nickel wire was characterized as shown in fig. 7. The morphology observation of the scanning electron microscope shows that the shape of the annealed fine nickel wire is regular. The electron back scattering spectrum shows that the prepared monocrystal nickel wire has uniform components and high monocrystal degree.

The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the invention, and all equivalent modifications made by the present invention are within the scope of the invention.

Claims

1. A method for preparing a single crystal wire, comprising the steps of:

s6, carrying out acid washing and drying on the metal filaments obtained by the heat treatment of S5 to obtain monocrystalline metal wires;

S2, the drawing temperature of the polycrystalline metal rod is 650-950 ℃, a lubricant is used in the operation process, and the lubricant outflow die hole speed is controlled to be 25-40m.min ^-1, so that the polycrystalline fine metal rod with the diameter of 6-10 mm is obtained;

s3, constructing a temperature gradient of 2-4 ℃ per cm in the double-temperature-zone tube furnace, wherein the temperature of a high-temperature zone is lower than the melting point by 10-50 ℃, the temperature of a low-temperature zone is controlled to be lower than the melting point by 50-100 ℃, the temperature rising rate is 5-10 ℃ per min, and the heat treatment is carried out for 48-96 hours;

S4, carrying out multi-pass drawing for 50-100 times on the obtained single-crystal thin metal rod by a wire drawing machine driven by a microcomputer program-controlled alternating current servo motor to obtain polycrystalline metal thin wires with diameters of 0.018-0.040 mm;

s5, constructing a temperature gradient of 2-4 ℃ per cm in the double-temperature-zone tube furnace, wherein the temperature of a high-temperature zone is lower than the melting point by 10-50 ℃, and the temperature of a low-temperature zone is lower than the melting point by 50-100 ℃ and the temperature rising rate is 5-10 ℃ per min;

In S5, the processing unit is configured to,

Annealing the polycrystalline metal filament for 12-48 hours in the temperature gradient range to obtain a monocrystalline metal filament;

2. A method for producing a single-crystal wire according to claim 1, wherein,

In S1, the specific operation of the heat treatment is as follows:

3. The method of producing single crystal wire according to claim 1, wherein the lubricant is made of No. 45 oil plus 25% graphite flakes.

4. A single crystal wire, characterized in that it is produced by the method for producing a single crystal wire according to any one of claims 1 to 3.

5. The single crystal wire of claim 4 wherein the polycrystalline metal ingot rod is a high purity oxygen free copper rod having a purity of 99.999% or a high purity nickel rod having a purity of 99.99%.