Bonding wire, preparation method thereof and LED device

Abstract

To provide a bonding wire having superior mechanical properties, high-temperature stability, and reliability.SOLUTION: The present invention belongs to the technical field of packaging materials, and particularly relates to a bonding wire, a preparation method thereof, and an LED device. The bonding wire of the present invention includes a core material, and the core material contains, in percentage by mass, 5 wt.% to 10 wt.% of Cu, 2 wt.% to 7 wt.% of graphene, 0.25 wt.% to 0.5 wt.% of Sm, and 1 wt.% to 1.5 wt.% of Zr, and the balance of Ag. The present invention adds a Zr element and graphene into the bonding wire, and reasonably controls contents of the Zr element and the graphene. At the same time, by cooperation of the Zr element and the graphene with a Cu element and an Sm element, the present invention improves mechanical properties, corrosion resistance, high-temperature stability, electromigration resistance, and reliability of the silver alloy bonding wire. The present invention can meet bonding requirements of high-power LED devices in complex bonding environments such as low loop formation and sustained high temperature.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention belongs to the technical field of packaging materials, and particularly relates to bonding wires, a method for preparing the same, and LED devices.

Background Art

[0002] Wire bonding is the most common interconnection means in IC packaging. As an important path of the lead frame for chip connection, it plays the functions of signal transmission and electrical connection, and is one of the essential basic raw materials in the repackaging manufacturing processes of integrated circuits, semiconductor discrete devices, and LED light source devices. Bonding wires mainly include gold wires, silver wires, copper wires, aluminum wires, etc.

Summary of the Invention

Problems to be Solved by the Invention

[0003] With the development of multi-lead, high integration, and miniaturization of integrated circuits and semiconductor packaging, the influence of bonding wires on devices is becoming increasingly significant. There is a requirement for narrow pitch and long distance bonding using bonding wires with a thinner wire diameter and better electrochemical performance. Gold bonding wires are expensive, copper bonding wires are very easily oxidized and have poor performance, and aluminum wires are applied to low-end products. In contrast, silver bonding wires are widely used in microelectronic packaging because they have excellent electrical and thermal performance, can reduce the high-frequency noise of devices, can reduce the heat generation of high-power LEDs, have good stability, and are of appropriate cost. However, when silver bonding wires are used, there are often problems such as low bonding strength, unstable performance, poor corrosion resistance and high-temperature stability, and the functions of high-power devices becoming unavailable due to heat generation, and its development is greatly restricted. In view of this, the present invention was devised.

[0004] The first object of the present invention is to provide a bonding wire having excellent mechanical properties, high-temperature stability and reliability.

[0005] The second object of the present invention is to provide a method for preparing a bonding wire, which can improve the mechanical properties, high-temperature stability and reliability of the bonding wire.

[0006] The third object of the present invention is to provide an LED device having excellent bonding reliability.

[0007] In order to achieve the above objects of the present invention, in particular, the following technical solutions are adopted.

Means for Solving the Problems

[0008] The present invention provides a bonding wire. The bonding wire includes a core material, and the core material contains, by mass fraction, Cu: 5 wt% - 10 wt%, graphene: 2 wt% - 7 wt%, Sm: 0.25 wt% - 0.5 wt%, Zr: 1 wt% - 1.5 wt%, and the balance is Ag.

[0009] Furthermore, the mass ratio of the Cu to the Sm is (19 - 21):1.

[0010] Furthermore, at least one of the following is included: (1) the graphene includes single-layer graphene; (2) the particle size of the single-layer graphene is 0.1 - 0.5 μm; and (3) the thickness of the single-layer graphene is less than 1 nm.

[0011] Furthermore, it further includes a protective layer provided on the surface of the core material, and / or the protective layer provided on the surface of the core material includes one or more of Al2O3, ZrO2 and SiO2.

[0012] Furthermore, the bonding wire includes at least one of the following: (1) the diameter ranges from 15 to 25 μm; (2) the thickness of the protective layer is from 0.3 to 2 μm; and (3) the ratio of the thickness of the protective layer to the diameter is from (0.02 to 0.08):1.

[0013] The present invention further provides a method for preparing the above bonding wire. The preparation method includes: Step S1 of performing vacuum gas atomization on an Ag / Cu / Sm intermediate alloy to obtain intermediate alloy powder; and Step S2 of mixing the intermediate alloy powder, Zr powder, and graphene powder, and then performing mold pressing, vacuum sintering, extrusion, and drawing in sequence to obtain a wire.

[0014] Furthermore, in Step S1, the pressure of the vacuum gas atomization is from 10 to 12 MPa, and / or the particle size D50 of the intermediate alloy powder is from 35 to 50 μm.

[0015] Furthermore, in Step S2, the method includes at least one of the following: (1) the pressure of the mold pressing is from 150 to 200 MPa; (2) the vacuum sintering includes sintering at 780 to 800 °C for 3 to 5 h; and (3) the temperature of the extrusion is from 750 to 780 °C, and the speed of the extrusion is from 4 to 7 mm / s.

[0016] Furthermore, the method for preparing the above bonding wire further includes a step of performing vapor growth on the surface of the wire to obtain a protective layer, and / or further includes a step of performing vapor growth on the surface of the wire to obtain a protective layer, and after the vapor growth, performing wire drawing treatment.

[0017] The present invention further provides an LED device. The LED device includes the above bonding wire or a bonding wire prepared by the above method for preparing a bonding wire.

[0018] Compared with the prior art, the present invention has the following beneficial effects. 1. The bonding wire according to the present invention optimizes the components of the silver alloy, adds Zr element and graphene to the silver alloy, and through cooperation with Cu element and Sm element, improves the mechanical properties of the silver alloy bonding wire, has relatively high strength and tensile breaking force, enables microfabrication, improves the electromigration resistance, high-temperature resistance and reliability of the bonding wire, can meet the requirements of high-power LED packaging, and can be used for bonding high-power LED devices in complex bonding environments such as low loops and continuous high temperatures. 2. The bonding wire according to the present invention can further improve the corrosion resistance of the bonding wire by providing a protective layer on the surface of the silver alloy core material. 3. The preparation method of the bonding wire according to the present invention adopts the processes of powder preparation by atomization, mold pressing, vacuum sintering and extrusion, introduces graphene with a high melting point and uniformly distributes it in the bonding wire system, and can prepare a bonding wire with excellent performance.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, the technical solution of the present invention will be clearly and completely described using specific embodiments. As those skilled in the art will understand, the described embodiments are only some embodiments of the present invention, not all embodiments, and are only for explaining the present invention and do not limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without using inventive ability also belong to the protection scope of the present invention. In the embodiments, for the cases where specific conditions are not specified, it is possible to carry out under conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the preparation manufacturer, commercially available conventional products can be used.

[0020] It should be noted that the term "and / or" used in this specification represents the relationship of related objects and indicates that there are three types of relationships. For example, A and / or B represents three types of relationships: only A exists, both A and B exist, and only B exists.

[0021] Some embodiments of the present invention provide a bonding wire. The bonding wire includes a core material, and the core material contains, by mass fraction, Cu: 5 wt% to 10 wt%, graphene: 2 wt% to 7 wt%, Sm: 0.25 wt% to 0.5 wt%, Zr: 1 wt% to 1.5 wt%, and the balance is Ag.

[0022] The bonding wire according to the present invention includes a core material, and the core material is a silver alloy. In the core material, according to the addition of the Zr element, it contributes to the refinement of crystal grains and can improve the high-temperature stability of the bonding wire. Graphene, as a nano-strengthening phase, can increase the strength of the bonding wire, pin the stacking defects and grain boundaries, effectively inhibit the thermal movement of the stacking defects and grain boundaries, and significantly improve the thermal stability of the bonding wire. According to the addition of the Cu element, the ductility and strength of the bonding wire can be increased. By adding the Sm element, the Sm element accumulates at the grain boundaries, reduces the diffusion effect along the grain boundaries, and can improve the electromigration resistance and reliability.

[0023] The present invention can contribute to the improvement of the strength and high-temperature stability of the bonding wire by adding the Zr element and graphene to the bonding wire and reasonably controlling their contents. And through the cooperation of the Cu element and the Sm element, it can contribute to the improvement of cycle temperature stability, strength, electromigration resistance, etc. As described above, through the cooperation of each element, the basic performance and application reliability of the bonding wire can be improved.

[0024] The bonding wire according to the present invention has excellent mechanical properties, relatively high strength and tensile breaking force, can be microfabricated, has excellent corrosion resistance, high-temperature resistance and electromigration resistance, and can meet the requirements of high-power LED device bonding in complex bonding environments such as low loops and continuous high temperatures.

[0025] In some embodiments of the present invention, by way of representative and non-limiting examples, for instance, in the core material, the mass fraction of Cu is a value within the range of 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 10 wt%, or a value within the range consisting of any two of these values; the mass fraction of graphene is a value within the range of 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, or a value within the range consisting of any two of these values; the mass fraction of Sm is a value within the range of 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, or a value within the range consisting of any two of these values; and the mass fraction of Zr is a value within the range of 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, or a value within the range consisting of any two of these values.

[0026] In some embodiments of the present invention, the core material contains, by mass fraction, Cu: 6.5 wt% - 7.5 wt%, graphene: 4.5 wt% - 5.5 wt%, Sm: 0.3 wt% - 0.4 wt%, Zr: 1.1 wt% - 1.3 wt%, and the balance is Ag.

[0027] If the present invention further optimizes the components of the core material and makes each component within the above-mentioned ranges, a bonding wire with more excellent performance can be obtained.

[0028] In some embodiments of the present invention, the mass ratio of Cu to Sm is (19 - 21):1, preferably 20:1. According to the cooperation of Cu element and Sm element, it can contribute to the improvement of the strength and cycle temperature stability of the bonding wire.

[0029] In some embodiments of the present invention, in the core material, the total mass fraction of Cu and graphene is 12%. According to the cooperation of Cu and graphene, it can contribute to the improvement of the strength, high-temperature stability and reliability of the bonding wire.

[0030] In some embodiments of the present invention, the graphene includes monolayer graphene.

[0031] In some embodiments of the present invention, the particle size of the monolayer graphene is 0.1 - 0.5 μm.

[0032] In some embodiments of the present invention, the thickness of the monolayer graphene is less than 1 nm.

[0033] If the particle size of the graphene is too large, it will cause deterioration of the mechanical properties of the alloy. If the particle size of the graphene is too small, it will cause aggregation during melting and cannot be evenly distributed.

[0034] In some embodiments of the present invention, the bonding wire further includes a protective layer provided on the surface of the core material.

[0035] In some embodiments of the present invention, the protective layer includes one or more of Al2O3, ZrO2, and SiO2. For example, the protective layer is an Al2O3 layer, a ZrO2 layer, or an SiO2 layer.

[0036] The protective layer according to the present invention has insulation, corrosion resistance, and wear resistance, and can further improve the strength of the bonding wire in cooperation with the core material.

[0037] In some embodiments of the present invention, the diameter of the bonding wire is 15 - 25 μm. As representative and non-limiting examples, for example, 15 μm, 20 μm, 25 μm, or a value within the range consisting of any two of them.

[0038] In some embodiments of the present invention, the thickness of the protective layer is 0.3 - 2 μm. As representative and non-limiting examples, for example, 0.3 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, or a value within the range consisting of any two of them.

[0039] In some embodiments of the present invention, the ratio of the thickness of the protective layer to the diameter of the bonding wire is (0.02 to 0.08):1.

[0040] In some embodiments of the present invention, the tensile breaking force of the bonding wire is 5 to 6 g, preferably 5.5 to 6 g.

[0041] In some embodiments of the present invention, the elongation rate of the bonding wire is 8% to 9%, preferably 8.5% to 9%.

[0042] In some embodiments of the present invention, the minimum loop height of the bonding wire is 80 μm, preferably less than 70 μm.

[0043] Some embodiments of the present invention further provide the above-mentioned method for preparing a bonding wire. The preparation method includes the following steps.

[0044] Step S1: Perform vacuum gas atomization on the Ag / Cu / Sm master alloy to obtain master alloy powder.

[0045] Step S2: After mixing the master alloy powder, Zr powder, and graphene powder, perform mold pressing, vacuum sintering, extrusion, and drawing in sequence to obtain a wire.

[0046] The method for preparing a bonding wire according to the present invention employs the processes of powder preparation by atomization, mold pressing, vacuum sintering, and extrusion, introduces graphene with a high melting point into the silver alloy system, uniformly distributes it in the silver alloy, and utilizes the characteristics of high strength, high thermal conductivity, and ultra-high high-temperature stability of graphene to improve the strength, high-temperature stability, and electromigration resistance of the bonding wire.

[0047] In some embodiments of the present invention, the method for preparing the Ag / Cu / Sm master alloy in step S1 includes the following.

[0048] Weigh the Ag raw material, Cu raw material, and Sm raw material according to the blending ratio, put them into a crucible in a vacuum furnace, close the furnace door, and evacuate to 3×10 -2 Pa, fill with argon gas to 0.1 - 0.3 Pa, and when heating up to 600 - 800 °C, evacuate again to 2×10 -2 Pa, then fill with argon gas to 0.1 - 0.3 Pa, heat up to 1150 - 1200 °C and refine for 20 - 30 min. During this period, stir along one direction using a magnetic stirrer bar. After furnace cooling, obtain the Ag / Cu / Sm intermediate alloy. Preferably, the purity of each of the Ag raw material, Cu raw material, and Sm raw material is over 99.99%. The crucible includes a high-purity graphite crucible.

[0049] In some embodiments of the present invention, in step S1, the pressure of vacuum gas atomization is 10 - 12 MPa.

[0050] In some embodiments of the present invention, in step S1, during the vacuum gas atomization process, the cooling rate of the molten metal is 100 - 105 °C / s.

[0051] In some embodiments of the present invention, in step S1, the particle size D50 of the intermediate alloy powder is 35 - 50 μm.

[0052] In some embodiments of the present invention, in step S2, the mixing includes weighing the intermediate alloy powder, Zr powder, and graphene powder according to the blending relationship and performing ball milling. Preferably, the rotation speed of the ball milling is 300 - 500 r / min. The time of the ball milling is 5 - 7 h. The volume ratio of the balls to the material in the ball milling is 3:1. Preferably, the Zr powder has a purity of 99.9% or more and a particle size of 35 - 50 μm.

[0053] In some embodiments of the present invention, in step S2, the pressure of the mold press is 150 - 200 MPa. Preferably, the mold press includes performing preliminary press forming on the mixed material after mixing with a mold having a size of φ30 - 50 mm.

[0054] In some embodiments of the present invention, in step S2, the vacuum sintering includes sintering at 780 - 800 °C for 3 - 5 h. Preferably, the degree of vacuum in the vacuum sintering process is 2×10 -2 Pa.

[0055] In some embodiments of the present invention, in step S2, the temperature of the extrusion is 750 - 780 °C and the speed of the extrusion is 4 - 7 mm / s. Preferably, a bar having a size of φ12 - 15 mm is obtained by extrusion.

[0056] In some embodiments of the present invention, the drawing includes at least two wire drawing processes, and heat treatment is performed each time the wire drawing process is carried out to perform the next wire drawing process. Preferably, the drawing includes performing the first wire drawing process, heat treatment, and the second wire drawing process in sequence.

[0057] In some embodiments of the present invention, in step S2, the first wire drawing process is performed on the bar obtained by extrusion to obtain a wire having a size of φ0.6 - 1.0 mm. When the diameter of the wire is more than 6 mm, the deformation rate of the wire is 12% - 15%. When the diameter of the wire is less than 6 mm, the deformation rate is 8% - 10%.

[0058] In some embodiments of the present invention, in step S2, the heat treatment includes heat-treating the wire after the first wire drawing process at 400 - 450 °C for 3 - 5 h. Preferably, the heating rate of the heat treatment is 2 - 3.5 °C / s, and the degree of vacuum of the heat treatment is more than 10 -2 Pa.

[0059] In some embodiments of the present invention, the second wire drawing process in step S2 includes performing multi-pass drawing and extraction on the wire after heat treatment to obtain a wire with a size of φ0.07 to 0.1 mm. When the diameter of the wire is more than 0.5 mm, the deformation rate is 8% to 11%, and the wire drawing speed is 7 to 10 m / s. When the diameter of the wire is less than 0.5 mm, the deformation rate is 7% to 10%, and the wire drawing speed is 3 to 5 m / s.

[0060] In some embodiments of the present invention, the method for preparing a bonding wire includes performing vapor phase growth on the surface of a core material to obtain a protective layer.

[0061] In some embodiments of the present invention, the method for preparing a protective layer includes the following steps.

[0062] For the wire after the second wire drawing process, using a continuous vacuum coating device, with high-purity Al or Si or Ti as the target material, high-purity Ar2 and O2 as the sputtering gas and reaction gas, adopting the magnetron sputtering vacuum coating technology, uniformly sputtering on the surface to form a protective layer with a thickness of 1 to 10 μm.

[0063] In some embodiments of the present invention, after vapor phase growth, it further includes a wire drawing process. Preferably, a wire drawing process is performed on the wire after vapor phase growth to obtain a bonding wire with a diameter of 15 to 25 μm. The wire drawing process has a drawing speed of 2 to 4 m / s and a deformation rate of 6% to 8%.

[0064] Some embodiments of the present invention further provide an LED device. The LED device includes the above-mentioned bonding wire or a bonding wire prepared by the above-mentioned method for preparing a bonding wire.

[0065] The bonding wire according to the present invention can meet the requirements of high-power LED packaging and can be used for bonding high-power LED devices in complex bonding environments such as low loops and continuous high temperatures.

[0066] <Example 1> This example provided a method for preparing a bonding wire. The components and contents (mass fraction) of the core material of the bonding wire that could be prepared are shown in Table 1.

[0067]

Table 1

[0068] Specifically, the method for preparing the bonding wire described above includes the following steps.

[0069] Step S1: Weigh Ag, Cu, and Sm raw materials with a purity exceeding 99.99%. According to the compounding relationship, put the weighed raw materials into a high-purity graphite crucible in a vacuum furnace, close the furnace door, evacuate to 3×10 -2 Pa, fill with argon gas to 0.1 - 0.3 Pa, and when heating to 600 - 800 °C, evacuate to 2×10 -2 Pa again, then fill with argon gas to 0.1 - 0.3 Pa, heat to 1150 - 1200 °C and refine for 20 - 30 min. During this period, use a magnetic stirrer bar to stir in one direction, and cool in the furnace to obtain an Ag / Cu / Sm intermediate alloy.

[0070] Step S2: Perform vacuum gas atomization on the Ag / Cu / Sm intermediate alloy to obtain intermediate alloy powder with a particle size D50 of 35 - 50 μm. The atomization gas pressure is 10 - 12 MPa, and the cooling rate of the molten metal is 100 - 105 °C / s.

[0071] Step S3: According to the compounding relationship, perform ball milling on the weighed intermediate alloy powder, Zr powder (purity: 99.9%, particle size: 35 - 50 μm), and single-layer graphene powder (particle size D50: 0.1 - 0.5 μm, thickness: less than 1 nm) to obtain a mixed material. The volume ratio of the balls to the material is 3:1, the rotation speed is 300 - 500 r / min, and the ball milling time is 5 - 7 h.

[0072] Step S4: Press-mold the mixed material in a mold with a diameter of φ30 - 50 mm at a pressure of 150 - 200 MPa, and sinter it at a temperature of 780 - 800 °C for 3 - 5 h under a vacuum degree of 2×10 -2 Pa.

[0073] Step S5: After sintering, perform extrusion to obtain a bar with a size of φ12 - 15 mm. The extrusion temperature is 750 - 780 °C, and the extrusion speed is 4 - 7 mm / s.

[0074] Step S6: Use a wire drawing machine to draw a bar with a size of φ12 - 15 mm into a wire with a size of φ0.6 - 1.0 mm. When the diameter of the wire is more than 6 mm, the deformation rate of the wire is 12% - 15%; when it is less than 6 mm, the deformation rate is 8% - 10%.

[0075] Step S7: Put the wire with a size of φ0.6 - 1.0 mm into a vacuum annealing furnace, heat it up to 400 - 450 °C at a rate of 2 - 3.5 °C / s under a vacuum degree exceeding 10 -2 Pa, and perform heat treatment for 3 - 5 h.

[0076] Step S8: Use a multi-wire drawing machine to perform multi-pass drawing and drawing on the wire after heat treatment to make it into a wire with a size of φ0.07 - 0.1 mm. When the diameter of the wire is more than 0.5 mm, the deformation rate is 8% - 11%, and the wire drawing speed is 7 - 10 m / s; when the diameter of the wire is less than 0.5 mm, the deformation rate is 7% - 10%, and the wire drawing speed is 3 - 5 m / s.

[0077] Step S9: For the wire with a size of φ0.07 - 0.1 mm, use continuous vacuum film-forming equipment, use Si as the target material, adopt P-type single-crystal Si, use high-purity Ar2 and O2 as sputtering gas and reaction gas, adopt magnetron sputtering vacuum film-forming technology, and uniformly sputter on the surface to form a SiO2 protective layer with a thickness of 1 - 10 μm.

[0078] Step S10: The wire after magnetron sputtering was drawn by a wire drawing machine to a diameter of 15 μm, the drawing speed was 2 - 4 m / s, the deformation rate was 6% - 8%, and then it was cleaned by ultrasonic cleaning for more than 30 min, blown with nitrogen gas to dry, wound on a reel and packaged to obtain a bonding wire.

[0079] <Comparative Example 1> This comparative example provided a method for preparing a bonding wire. The components and contents (mass fraction) of the core material of the bonding wire that could be prepared are shown in Table 2.

[0080]

Table 2

[0081] For the method for preparing the above bonding wire, refer to Example 1.

[0082] <Test Example 1> Mechanical property tests were performed on the bonding wires with a diameter of 15 μm according to each of Example 1 and Comparative Example 1, and the results are shown in Table 3.

[0083] For the tests of tensile breaking force and elongation rate, refer to the IPC - 9702 standard.

[0084] Tests were performed using the bonding wires according to each of Example 1 and Comparative Example 1 on the Al pads of the memory, and the results are shown in Table 3.

[0085] HTST (High - Temperature Storage Test): The test conditions were 150°C, referring to the standard JESD22 - A103 - A.

[0086] TCT (Temperature Cycle Aging Test): The test conditions were - 55 - 125°C, referring to the standard JESD22 - A104 - A.

[0087]

Table 3

[0088] As can be seen from Table 3, for Comparative Example 1, the bonding wire according to the present invention had a greater tensile breaking force and elongation rate, a relatively small minimum loop height, and better bonding reliability.

[0089] Each of the above embodiments is only for explaining the technical solution of the present invention and does not limit it. Although the present invention has been described in detail with reference to each of the above embodiments, those skilled in the art may modify the technical solutions described in each of the above embodiments, or perform equivalent substitutions for some or all of the technical features therein. These modifications or substitutions do not deviate from the essence of the corresponding technical solutions from the scope of the technical solutions of each embodiment of the present invention.

Claims

1. Including the core material, The core material contains, by mass fraction, Cu: 5 wt% to 10 wt%, graphene: 2 wt% to 7 wt%, Sm: 0.25 wt% to 0.5 wt%, Zr: 1 wt% to 1.5 wt%, and the remainder is Ag.

2. The bonding wire according to claim 1, characterized in that the mass ratio of Cu to Sm is (19-21):

1.

3. (1) The graphene includes a single-layer graphene; (2) the particle size of the single-layer graphene is 0.1 to 0.5 μm; and (3) the thickness of the single layer graphene is less than 1 nm; 2. The bonding wire according to claim 1, comprising at least one of:

4. Further comprising a protective layer provided on the surface of the core material; Alternatively, the present invention further includes a protective layer provided on the surface of the core material, the protective layer being made of Al ２ O ３ , ZrO ２ and SiO ２ 2. The bonding wire according to claim 1, comprising one or more of the following:

5. (1) the diameter is 15 to 25 μm; (2) the thickness of the protective layer is 0.3 to 2 μm; and (3) the ratio of the thickness of the protective layer to the diameter is (0.02-0.08):1; 5. The bonding wire according to claim 4, comprising at least one of:

6. A method for preparing a bonding wire according to any one of claims 1 to 5, comprising the steps of: Step S1: subjecting the Ag / Cu / Sm intermediate alloy to vacuum gas atomization to obtain an intermediate alloy powder; and step S2 of mixing the intermediate alloy powder, Zr powder, and graphene powder, and then performing mold pressing, vacuum sintering, extrusion, and drawing in that order to obtain a wire.

7. In step S1, The pressure of the vacuum gas atomization is 10 to 12 MPa. And / or the particle size D50 of the intermediate alloy powder is 35-50 μm.

8. In step S2, (1) the pressure of the mold press is 150 to 200 MPa; (2) The vacuum sintering includes sintering at 780 to 800°C for 3 to 5 hours; and (3) the temperature of the extrusion is 750-780°C and the speed of the extrusion is 4-7 mm / s; 7. The method for preparing a bonding wire according to claim 6, further comprising at least one of:

9. The method further includes the step of performing vapor deposition on the surface of the wire to obtain a protective layer. Alternatively, the method for preparing a bonding wire according to claim 6 further comprises a step of performing vapor phase growth on the surface of the wire to obtain a protective layer, and performing a wire drawing process after the vapor phase growth.

10. An LED device comprising a bonding wire according to any one of claims 1 to 5.

Images