Preparation method of high-strength n-BN / Cu bonding wire material

Abstract

The present invention relates to a preparation method of a high-strength n-BN / Cu bonding wire material, belonging to the technical field of composite material preparation. First, the present invention uses a jet mill to perform nano-scale crushing treatment on micron boron nitride (m-BN) to obtain zero-dimensional boron nitride nanoparticles (n-BN) with a particle size less than 100 nm, and then obtains a uniformly dispersed n-BN / Cu composite powder through electrostatic adsorption, reduction and ball milling "embedding" treatment; a composite material with uniformly distributed reinforcements in the copper matrix grains is prepared by hot pressing sintering (HP) and hot rolling deformation, and finally the sintered billet is subjected to hot rolling treatment. The obtained n-BN / Cu composite material of the present invention exhibits more excellent mechanical properties, has a high tensile strength, and the tensile strength is increased by more than 50% compared with that of pure copper, providing guidance for obtaining high-strength bonding wire materials.

Description

Technical Field

[0001] The present invention relates to a preparation method of a high-strength n-BN / Cu bonding wire material, belonging to the technical fields of composite material preparation and powder metallurgy. Background Art

[0002] As a key material for electronic packaging, the bonding wire is used to connect electronic components such as chips and circuit boards together, playing roles of signal transmission, mechanical connection and support. Although the widely used gold bonding wire and silver bonding wire have good ductility and excellent electrical conductivity, they are expensive, have low tensile strength, and are prone to wire breakage under high bonding force conditions. In contrast, the copper bonding wire is not only inexpensive but also has excellent comprehensive properties and is expected to replace the expensive gold / silver bonding wire. With the continuous increase in the power density of integrated circuits, higher requirements are put forward for the bonding strength of the bonding wire. Preparing a high-strength copper bonding wire is of great significance for the sustainable development and innovation of the electronics industry.

[0003] Boron nitride is also known as "white graphene", and its structure is similar to that of graphene. The unique two-dimensional structure of boron nitride endows it with mechanical properties similar to those of graphene (Young's modulus: 900 GPa; tensile strength: 61 GPa), and the preparation cost of boron nitride is relatively low. Therefore, boron nitride is an ideal reinforcement for copper-based composites, providing a new opportunity for preparing a high-strength copper bonding wire.

[0004] At present, the preparation of boron nitride-reinforced copper composites faces the following problems: the interfacial bonding between copper and boron nitride is weak, which is prone to interfacial debonding. In addition, the boron nitride commonly used in industry is micron-sized (>10 μm), with a relatively large size, and it is easy to agglomerate at the grain boundaries of copper, resulting in local stress concentration, thereby weakening its reinforcement effect. Existing studies have shown that zero-dimensional reinforcements at the nanoscale are easy to distribute within the grains, avoiding the stress localization defects caused by the above-mentioned grain boundary distribution, and can effectively improve the properties of the material. However, there is currently a lack of an effective process for preparing zero-dimensional boron nitride nanoparticles, and there are few reports on obtaining the intragranular distribution of zero-dimensional boron nitride nanoparticles and achieving a breakthrough in the properties of boron nitride-reinforced copper composites, thereby preparing a high-strength copper bonding wire. Summary of the Invention

[0005] Based on the above background, the present invention uses zero-dimensional boron nitride nanoparticles (n-BN) crushed by a jet mill as the reinforcement, and prepares a high-strength n-BN / Cu bonding wire material through a powder metallurgy technical route. This method crushes micron boron nitride (m-BN) raw materials into n-BN by a jet mill, adsorbs n-BN on copper particles through electrostatic adsorption, and finally "embeds" n-BN inside copper particles by high-energy ball milling to further improve the dispersion of n-BN and the interfacial bonding strength. After reducing the above powder, a boron nitride nanoparticle-reinforced copper (n-BN / Cu) composite material with uniformly distributed n-BN in copper grains is prepared by hot pressing sintering (HP) combined with hot rolling treatment.

[0006] The object of the present invention is achieved by the following technical solutions.

[0007] A preparation method of a high-strength n-BN / Cu bonding wire material, the steps are as follows:

[0008] (1) Nanoscale crushing of boron nitride

[0009] Weigh 0.3 g to 3 g of micron boron nitride (m-BN, ~10 μm) raw materials and put them into the hopper of a jet mill. Pass high-speed nitrogen to accelerate through a high-speed rotating grinding disc, and use the high-speed airflow to impact and friction the m-BN powder. Spray the obtained powder into the classification screening chamber under the action of the airflow, and screen it to obtain zero-dimensional boron nitride nanoparticles (n-BN) with a particle size less than 100 nm;

[0010] Among them, the airflow velocity of the jet mill is 300 m / s to 600 m / s, and the compressed air pressure of the jet mill is 0.8 MPa to 1.5 MPa;

[0011] Preferably, the boron nitride is hexagonal boron nitride with a graphite-like structure, and the number of layers is 20 to 30.

[0012] (2) Preparation of boron nitride nanoparticle-reinforced copper (n-BN / Cu) composite powder

[0013] Weigh 0.3 g to 3 g of the above-crushed n-BN and disperse it in deionized water and ultrasonicate for 10 min to 60 min to make the n-BN evenly dispersed. Disperse 30 g to 150 g of electrolytic copper powder in deionized water under mechanical stirring. Mix the two suspensions, adjust to alkaline with NaOH solution, and then stir and heat in a water bath for 1 h to 5 h. After filtration and drying, reduce the obtained powder in a reducing atmosphere of 85% N 2 + 15% H 2 to obtain an n-BN / Cu composite powder. Finally, perform high-energy ball milling on the n-BN / Cu composite powder to "embed" n-BN inside copper grains.

[0014] Among them, the morphology of the electrolytic copper powder can be spherical, flaky, or any irregular shape;

[0015] Preferably, the particle size of the electrolytic copper powder is 20 μm to 50 μm;

[0016] Preferably, the mass fraction of n-BN is 0.5 wt% to 5 wt%;

[0017] Preferably, the pH value of the suspension is adjusted to 9 to 12 with a NaOH solution;

[0018] Among them, the stirring speed of the water bath is 800 rpm to 2000 rpm, and the heating temperature is 40 °C to 80 °C;

[0019] Among them, the drying temperature is 40 to 80 °C, and the time is 3 to 5 h;

[0020] Among them, the reduction parameters are: the initial vacuum degree ≤ 10 Pa, the heating rate 5 °C / min to 10 °C / min, the reduction temperature 300 °C to 600 °C, and the reduction time 3 h to 6 h.

[0021] Among them, the rotation speed of high-energy ball milling is 400 rpm to 600 rpm, and the time is 10 h to 20 h;

[0022] (3) Preparation of n-BN / Cu composite block

[0023] Sinter the n-BN / Cu composite powder by hot pressing sintering (HP) to obtain a consolidated sintered compact.

[0024] Among them, the sintering parameters are: the initial vacuum degree ≤ 10 Pa, the initial pressure ≤ 1.5 MPa, the heating rate 50 °C / min to 100 °C / min, the sintering temperature 500 °C to 800 °C, the sintering pressure 50 MPa to 200 MPa, and the sintering time 1 h to 3 h.

[0025] (4) Hot deformation processing

[0026] Under a heating environment of 600 °C to 900 °C, hot roll the sintered n-BN / Cu compact prepared above with a hot rolling mill.

[0027] Among them, the hot rolling is carried out for 4 to 8 passes, the reduction per pass ≤ 2 mm, the rolling deformation ≤ 20%; the total rolling deformation ≥ 80%.

[0028] The beneficial effects of the present invention are:

[0029] (1) The present invention provides a method for efficiently preparing zero-dimensional boron nitride nanoparticles. By using the gas flow crushing method, boron nitride with uniform size and nanoscale is obtained. Then, n-BN is adsorbed on copper particles through electrostatic adsorption, and finally, n-BN is "embedded" inside copper particles by high-energy ball milling to further improve the dispersibility and interfacial bonding strength of n-BN.

[0030] (2) The present invention realizes the uniform distribution of boron nitride nanoparticles within copper crystals through powder metallurgy technology. Compared with the traditional boron nitride-reinforced copper composites with grain boundary distribution, the obtained n-BN / Cu composite material of the present invention exhibits more excellent mechanical properties, has a higher tensile strength, and the tensile strength is increased by more than 50% compared with that of pure copper.

[0031] (3) The preparation method of the present invention has high universality and strong practicability, and the experimental process is simple and easy to operate, providing guidance for the development of high-strength bonding wire materials. Description of the Drawings

[0032] Figure 1 It is the TEM (transmission electron microscope) image of the micron boron nitride raw material in step (1) of Example 1.

[0033] Figure 2 It is the TEM image and HRTEM (high-resolution TEM) image of zero-dimensional boron nitride nanoparticles (n-BN) in step (1) of Example 1.

[0034] Figure 3 It is the TEM image of the distribution of n-BN within copper crystals in Example 1.

[0035] Figure 4 It is the stress-strain curve and hardness histogram of boron nitride nanoparticle-reinforced copper (n-BN / Cu) composite powder and pure copper (Pure Cu) in Example 1 and Comparative Example 1.

[0036] Figure 5 It is the stress-strain curve and hardness histogram of n-BN / Cu and micron boron nitride-reinforced copper (m-BN / Cu) composite powder in Example 2 and Comparative Example 2.

[0037] Figure 6 It is the stress-strain curve and hardness histogram of n-BN / Cu and m-BN / Cu composite powder in Example 3 and Comparative Example 3. Detailed Embodiments

[0038] The present invention will be further described below in conjunction with the drawings and specific embodiments. Among them, the methods are all conventional methods unless otherwise specified, and the raw materials can all be obtained from public commercial channels unless otherwise specified.

[0039] In the following examples:

[0040] The purity of boron nitride is 90 at%, the number of layers is 5 - 30 layers, the thickness < 5 nm, the sheet diameter: 5 - 10 μm, Jiangsu Xianfeng Nano Materials Technology Co., Ltd.;

[0041] The pure copper powder is near-spherical electrolytic copper powder, with a particle size of 20 μm - 50 μm and a purity of 99.9%, Shanghai Naiou Nano Technology Co., Ltd.;

[0042] NaOH is of analytical purity, Tianjin Fengchuan Chemical Reagent Technology Co., Ltd.;

[0043] Scanning electron microscope: Nova Nano-450, FEI, USA;

[0044] Transmission electron microscope: Talos F200C, FEI, USA;

[0045] Characterization of the mechanical properties of the composite material: Tensile experiments were carried out at room temperature using a universal tensile testing machine (AUTOGRAPH AG-I, Shimadzu Corporation, Japan), and the tensile rate was 0.18 mm / min.

[0046] Example 1

[0047] A preparation method of a high-strength n-BN / Cu bonding wire material, the specific steps are as follows:

[0048] (1) Nano-scale fragmentation of boron nitride

[0049] Weigh 0.5 g of m-BN raw material and put it into the hopper of the air flow crusher. Pass high-speed nitrogen to accelerate through the high-speed rotating grinding disc, and use the high-speed air flow to impact and friction the m-BN powder. The obtained powder is sprayed into the classification and screening chamber under the action of the air flow, and it is screened to obtain n-BN with a particle size less than 100 nm. Among them, the air flow velocity of the air flow crusher is 300 m / s, and the compressed air pressure is 1.0 MPa. Finally, the obtained n-BN is vacuum dried.

[0050] (2) Preparation of n-BN / Cu composite powder

[0051] Weigh 0.3 g of the above-mentioned crushed n-BN and disperse it in 300 ml of deionized water and ultrasonic for 10 min to make the n-BN evenly dispersed. Weigh 30 g of electrolytic copper powder and disperse it in 500 ml of deionized water, and mechanically stir for 5 min. Mix the above two suspensions, adjust the pH value of the suspension to 9 with NaOH solution, and magnetically stir for 5 h at 40 °C in a water bath environment until evenly mixed (the rotation speed is 800 rpm). After filtration, dry at 40 °C in a vacuum drying oven for 5 h, and the obtained composite powder is in 85% N 2 + 15% H 2Reduction treatment is carried out under a reducing atmosphere. Among them, the initial vacuum degree is 10 Pa, the heating rate is 5 °C / min, the reduction temperature is 300 °C, and the reduction time is 6 h. The sample is cooled with the furnace to obtain the n-BN / Cu composite powder. Finally, the n-BN / Cu composite powder is subjected to high-energy ball milling at a rotational speed of 600 rpm for 10 h.

[0052] (3) Preparation of n-BN / Cu composite block

[0053] Transfer the above-mentioned n-BN / Cu composite powder into a cylindrical hot work steel mold with a diameter of 20 mm (Φ20 mm) (2Cr3Mo2NiVSi), and then transfer it to a hot pressing sintering furnace (HIGH-MULTI 500, Fuji Denpa Kogyo Co., Ltd., Japan). Set the initial vacuum degree in the furnace cavity to 10 Pa and the initial pressure to 1.5 MPa. Start heating at a rate of 50 °C / min, and at the same time slowly increase the sintering pressure. When the sintering temperature rises to 500 °C, the sintering pressure is increased to 200 MPa, and keep the temperature for 3 h. Finally, the sample is cooled with the furnace, and the pressure is removed when the furnace temperature drops to 50 °C, and the sample is taken out to obtain a consolidated nano boron nitride reinforced copper (n-BN / Cu) sintered blank.

[0054] (4) Hot working deformation

[0055] Under the heating environment of 900 °C, the n-BN / Cu sintered blank prepared by HP is hot rolled by a hot rolling machine. The rotation speed of the rolling roll is 10 mm / s, the rolling deformation amount per pass is 20%, and the sample is returned to the furnace for 2 min immediately after each rolling. A total of 6 rollings are carried out.

[0056] It can be seen from Figure 1 that the sheet diameter of the raw material m-BN is about 4 microns, and the sheets are stacked together, making it difficult to achieve close bonding with the copper matrix. The m-BN is impacted and rubbed by high-speed air flow by an air flow crusher, causing erosion and collision wear, so as to obtain n-BN. As shown in Figure 2 (a), the average particle size of the crushed n-BN is about 100 nm, achieving a good separation effect between the sheets, which is beneficial to the subsequent intragranular distribution of n-BN in the copper matrix. Further, the HRTEM of the crushed n-BN shows that the crystallinity of boron nitride is good (as shown in Figure 2 (b)), and the chemical structure is not significantly damaged. Figure 3 This is the TEM morphology after hot rolling deformation. The results show that n-BN (indicated by the arrow) is basically distributed inside the copper grains, and the uniform dispersion of n-BN is better achieved. This result helps to relieve the stress concentration near the grain boundaries of boron nitride and copper during the tensile process, promote the uniform deformation of the grain boundaries and the interiors of copper grains in the composite material, and achieve a relatively high strength-plasticity phase balance relationship.

[0057] Comparative Example 1

[0058] (1) Weigh 30 g of electrolytic copper powder and place it in a Φ20 mm cylindrical hot-work steel mold, then transfer it to a hot-pressing sintering furnace. The initial vacuum in the furnace cavity is 10 Pa, and the initial pressure is 1.5 MPa. Start heating at a rate of 50 °C / min while slowly increasing the sintering pressure. When the sintering temperature reaches 500 °C, the sintering pressure is increased to 200 MPa, and hold for 3 h. Finally, the sample is cooled with the furnace, and the pressure is removed when the furnace temperature drops to 50 °C, and the sample is taken out to obtain a consolidated pure copper (Pure Cu) sintered body.

[0059] (2) Under a heating environment of 900 °C, the Pure Cu sintered body prepared by HP is subjected to rolling deformation treatment using a hot rolling mill. The rotation rate of the rolling rolls is 10 mm / s, the rolling deformation amount per pass is 20%, and it is immediately returned to the furnace for 2 min after each rolling. A total of 6 rollings are carried out.

[0060] The hardness and tensile mechanical properties of the materials prepared in Example 1 and Comparative Example 1 were tested respectively, and the dynamic performance test results are as Figure 4 shown.

[0061] As Figure 4 shown, the strength of the prepared n-BN / Cu composite material is significantly improved compared with Pure Cu, reaching 385 MPa, an increase of 67%. The reason is attributed to the high hardness and high strength of BN. Its addition can provide higher rigidity and strength for the composite material. n-BN is distributed in the copper matrix, which helps to improve the load transfer ability of the composite material. The interaction between boron nitride and the copper matrix can increase the tensile strength and hardness of the material. It should be noted that the plasticity of the n-BN / Cu composite material does not decrease significantly, and its elongation is about 25%, achieving a relatively high strength-plasticity balance relationship.

[0062] Example 2

[0063] A preparation method of a high-strength n-BN / Cu bonding wire material, the specific steps are as follows:

[0064] (1) Nanoscale fragmentation of boron nitride

[0065] Weigh 3 g of m-BN raw material and place it in the hopper of a jet mill. Pass high-speed nitrogen gas through a high-speed rotating grinding disc to impact and friction the m-BN powder with the high-speed gas flow. The obtained powder is sprayed into a classification screening chamber under the action of the gas flow and screened to obtain n-BN with a particle size less than 100 nm. Among them, the gas flow rate of the jet mill is 500 m / s, and the compressed air pressure is 1.5 MPa. Finally, the obtained n-BN is dried in vacuum.

[0066] (2) Preparation of n-BN / Cu Composite Powder

[0067] Weigh 2 g of the above-mentioned crushed n-BN and disperse it in 400 ml of deionized water, then ultrasonicate for 50 min to make the n-BN evenly dispersed. Weigh 38 g of electrolytic copper powder and disperse it in 600 ml of deionized water, and mechanically stir for 5 min. Mix the above two suspensions, adjust the pH value of the suspension to 11 with NaOH solution, and magnetically stir at 80 °C in a water bath environment for 1 h until evenly mixed (rotation speed is 2000 rpm). After suction filtration, dry it in a vacuum drying oven at 80 °C for 3 h. The obtained composite powder is in 85% N 2 + 15% H 2 under a reducing atmosphere for reduction treatment. Among them, the initial vacuum degree is 10 Pa, the heating rate is 10 °C / min, the reduction temperature is controlled at 600 °C, and the reduction time is 3 h. Finally, the sample is cooled with the furnace to obtain the n-BN / Cu composite powder. Finally, the n-BN / Cu composite powder is subjected to high-energy ball milling at a rotation speed of 400 rpm for 20 h.

[0068] (3) Preparation of n-BN / Cu Composite Block

[0069] Transfer the above-mentioned n-BN / Cu composite powder into a cylindrical hot-work steel mold with a diameter of Φ20 mm, and then transfer it to a hot-pressing sintering furnace. Set the initial vacuum degree in the furnace cavity to 10 Pa and the initial pressure to 1.5 MPa, start heating at a rate of 100 °C / min, and slowly increase the sintering pressure at the same time. When the sintering temperature rises to 800 °C, the sintering pressure is increased to 50 MPa, and keep it warm for 1 h. Finally, the sample is cooled with the furnace, and the pressure is removed when the furnace temperature drops to 50 °C, and the sample is taken out to obtain a consolidated n-BN / Cu sintered blank.

[0070] (4) Hot Working Deformation Treatment

[0071] Under the heating environment of 600 °C, use a hot rolling mill to perform rolling deformation treatment on the n-BN / Cu sintered blank prepared by HP. The rotation speed of the rolling roll is 10 mm / s, the rolling deformation amount per pass is 15%, and it is immediately returned to the furnace for 2 min after each rolling. A total of 8 rollings are performed.

[0072] Comparative Example 2

[0073] (1) Weigh 2 g of m-BN raw materials and disperse them in 400 ml of deionized water, then ultrasonicate for 50 min to make the m-BN evenly dispersed. Weigh 38 g of electrolytic copper powder and disperse it in 600 ml of deionized water, and mechanically stir for 5 min for later use. Mix the above two suspensions, adjust the pH value of the suspension to 11 with NaOH solution, and magnetically stir at 80 °C in a water bath environment for 1 h until evenly mixed (rotation speed is 2000 rpm). After suction filtration, dry at 80 °C in a vacuum drying oven for 3 h. Subject the obtained composite powder to reduction treatment in a reducing atmosphere of 85% N 2 + 15% H 2 . Among them, the initial vacuum degree is 10 Pa, the heating rate is 10 °C / min, the reduction temperature is controlled at 600 °C, and the reduction time is 3 h. Finally, the sample is cooled with the furnace to obtain micron boron nitride reinforced copper (m-BN / Cu) composite powder. Subsequently, perform high-energy ball milling on the m-BN / Cu composite powder, with a rotation speed of 400 rpm and a time of 20 h.

[0074] (2) Transfer the above m-BN / Cu composite powder into a Φ20 mm cylindrical hot work steel mold, and then transfer it to a hot pressing sintering furnace. Set the initial vacuum degree in the furnace cavity to 10 Pa and the initial pressure to 1.5 MPa, start heating at a rate of 100 °C / min, and slowly increase the sintering pressure at the same time. When the sintering temperature rises to 800 °C, the sintering pressure increases to 50 MPa, and keep warm for 1 h. Finally, the sample is cooled with the furnace, and the pressure is removed when the furnace temperature drops to 50 °C, and the sample is taken out to obtain a consolidated m-BN / Cu sintered compact.

[0075] (3) Under a heating environment of 600 °C, use a hot rolling machine to perform rolling deformation treatment on the m-BN / Cu sintered compact prepared by HP. The rotation speed of the rolling roll is 10 mm / s, the rolling deformation amount per pass is 15%, and the sample is immediately returned to the furnace for 2 min after each rolling. Roll a total of 8 times.

[0076] Test the hardness and tensile mechanical properties of the composites prepared in Example 2 and Comparative Example 2 respectively, and the test results are as Figure 5 shown.

[0077] Example 3

[0078] A preparation method of a high-strength n-BN / Cu bonding wire material, the specific steps are as follows:

[0079] (1) Nano-scale crushing of boron nitride

[0080] Weigh 0.5 g of m-BN raw material and put it into the hopper of the air-flow crusher. Pass high-speed nitrogen gas to accelerate through the high-speed rotating grinding disc, and use the high-speed gas flow to impact and friction the m-BN powder. Spray the obtained powder into the classification and screening chamber under the action of the gas flow, and screen it to obtain n-BN with a particle size less than 100 nm. Among them, the gas flow rate of the air-flow crusher is 600 m / s, and the compressed air pressure is 0.8 MPa. Finally, dry the obtained n-BN in vacuum.

[0081] (2) Preparation of n-BN / Cu composite powder

[0082] Weigh 0.2 g of the above-mentioned crushed n-BN and disperse it in 200 ml of deionized water, and ultrasonicate for 60 min to make the n-BN evenly dispersed. Weigh 40 g of electrolytic copper powder and disperse it in 800 ml of deionized water, and mechanically stir for 5 min. Mix the above two suspensions, adjust the pH value of the suspension to 12 with NaOH solution, and magnetically stir for 3 h at 60 °C in a water bath environment until evenly mixed (rotation speed is 1500 rpm). After filtration, dry in a vacuum drying oven at 60 °C for 4 h, and reduce the obtained composite powder in a reducing atmosphere of 85% N 2 + 15% H 2 . Among them, the initial vacuum degree is 10 Pa, the heating rate is 10 °C / min, the reduction temperature is controlled at 500 °C, and the reduction time is 4 h. Finally, the sample is cooled with the furnace to obtain the n-BN / Cu composite powder. Finally, perform high-energy ball milling on the n-BN / Cu composite powder, with a rotation speed of 500 rpm and a time of 15 h.

[0083] (3) Preparation of n-BN / Cu composite block

[0084] Transfer the above-mentioned n-BN / Cu composite powder into a cylindrical hot-work steel mold with a diameter of Φ20 mm, and then transfer it to a hot-pressing sintering furnace. Set the initial vacuum degree in the furnace cavity to 10 Pa and the initial pressure to 1.5 MPa, start heating at a rate of 100 °C / min, and slowly increase the sintering pressure at the same time. When the sintering temperature rises to 600 °C, the sintering pressure increases to 150 MPa, and keep it warm for 2 h. Finally, the sample is cooled with the furnace, and the pressure is removed when the furnace temperature drops to 50 °C, and the sample is taken out to obtain a consolidated n-BN / Cu sintered blank.

[0085] (4) Hot working deformation treatment

[0086] Under the heating environment of 700 °C, use a hot rolling mill to perform rolling deformation treatment on the n-BN / Cu sintered blank prepared by HP. The rotation speed of the rolling roll is 10 mm / s, the rolling deformation amount per pass is 20%, and the sample is immediately returned to the furnace for 2 min after each rolling. A total of 4 rollings are performed.

[0087] Comparative Example 3

[0088] (1) Weigh 0.2 g of m-BN raw material and disperse it in 200 ml of deionized water, then ultrasonicate for 60 min to make the m-BN evenly dispersed. Weigh 40 g of electrolytic copper powder and disperse it in 800 ml of deionized water, and mechanically stir for 5 min for standby. Mix the above two suspensions, adjust the pH value of the suspension to 12 with NaOH solution, and magnetically stir for 3 h at 60 °C in a water bath environment until evenly mixed (rotation speed is 1500 rpm). After suction filtration, dry it in a vacuum drying oven at 60 °C for 4 h. The obtained composite powder is reduced in a reducing atmosphere of 85% N 2 + 15% H 2 . Among them, the initial vacuum degree is 10 Pa, the heating rate is 10 °C / min, the reduction temperature is controlled at 500 °C, and the reduction time is 4 h. Finally, the sample is cooled with the furnace to obtain micron boron nitride reinforced copper (m-BN / Cu) composite powder. Subsequently, the m-BN / Cu composite powder is subjected to high-energy ball milling at a rotation speed of 500 rpm for 15 h.

[0089] (2) Transfer the above m-BN / Cu composite powder into a Φ20 mm cylindrical hot work steel mold, and then transfer it to a hot press sintering furnace. Set the initial vacuum degree in the furnace cavity to 10 Pa and the initial pressure to 1.5 MPa, and start heating at a rate of 100 °C / min. At the same time, slowly increase the sintering pressure. When the sintering temperature rises to 600 °C, the sintering pressure increases to 150 MPa, and keep it warm for 2 h. Finally, the sample is cooled with the furnace, and the pressure is removed when the furnace temperature drops to 50 °C, and the sample is taken out to obtain a consolidated m-BN / Cu sintered compact.

[0090] (3) Under the heating environment of 700 °C, use a hot rolling machine to perform rolling deformation treatment on the m-BN / Cu sintered compact prepared by HP. The rotation speed of the rolling roll is 10 mm / s, the rolling deformation amount per pass is 20%, and it is immediately returned to the furnace for 2 min after each rolling. A total of 4 rollings are performed.

[0091] The hardness and tensile mechanical properties of the composites prepared in Example 3 and Comparative Example 3 are tested respectively, and the test results are as Figure 6 shown.

[0092] From Figure 5 and Figure 6It can be clearly seen that, compared with the m-BN / Cu composite material, the mechanical properties of the n-BN / Cu composite material are more excellent. Among them, the tensile strength is increased by about 27%, and the hardness is increased by about 34%. This is mainly because m-BN is mainly distributed at the grain boundaries of copper, and the interfacial bonding between copper and boron nitride is weak, which is prone to interfacial debonding when the stress increases. The intragranular distribution of nano-boron nitride can effectively avoid the above defects. When stress is applied to the composite material, cracks tend to propagate from the grain boundaries, and dispersing nano-boron nitride in the grains can hinder the propagation path of cracks, thereby improving the mechanical properties of the material.

[0093] The above are only the preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Preparation method of a high-strength n-BN / Cu bonding wire material Characterized in that: The specific steps of the method are as follows: (1) Nano-scale fragmentation of boron nitride Put micron boron nitride raw materials with a particle size less than 10 μm into a jet mill, introduce high-speed nitrogen for fragmentation, and screen the fragmented boron nitride to obtain zero-dimensional boron nitride nanoparticles with a particle size less than 100 nm; (2) Preparation of n-BN / Cu composite powder reinforced with boron nitride nanoparticles Disperse n-BN and copper powder in deionized water respectively, mix the two suspensions, adjust to alkaline with NaOH solution, stir and heat in a water bath, filter, dry and reduce to obtain n-BN / Cu composite powder, and finally high-energy ball mill the n-BN / Cu composite powder; among them, the rotation speed of high-energy ball milling is 400 rpm to 600 rpm, the time is 10 h to 20 h; the mass fraction of n-BN is 0.5 wt% to 5 wt%; (3) Preparation of n-BN / Cu composite block Sinter the n-BN / Cu composite powder by hot pressing sintering to obtain a consolidated sintered body; (4) Hot deformation processing Under a heating environment of 600 °C to 900 °C, use a hot rolling processing device to perform hot rolling treatment on the n-BN / Cu sintered body prepared by HP; the hot rolling is 4 to 8 passes, the reduction per pass ≤ 2 mm, and the total rolling deformation ≥ 80%.

2. The preparation method of a high-strength n-BN / Cu bonding wire material according to claim 1, Characterized in that: In step (1), the gas flow rate of the jet mill is 300 m / s to 600 m / s, and the compressed air pressure of the jet mill is 0.8 MPa to 1.5 MPa.

3. The preparation method of a high-strength n-BN / Cu bonding wire material according to claim 1, Characterized in that: In step (1), the boron nitride is hexagonal boron nitride with a graphene-like structure, and the number of layers is 20 to 30.

4. The preparation method of a high-strength n-BN / Cu bonding wire material according to claim 1, Characterized in that: In step (2), the copper powder is electrolytic copper powder, its particle size is 20 μm to 50 μm, and the morphology of the copper powder is spherical or any irregular shape.

5. The preparation method of a high-strength n-BN / Cu bonding wire material according to claim 1, Characterized in that: In step (2), the pH value of the suspension mixture is adjusted to 9 to 12 with NaOH solution.

6. The preparation method of a high-strength n-BN / Cu bonding wire material according to claim 1, Characterized in that: In step (2), the reducing atmosphere is a mixed gas of 85% N 2 + 15% H 2 , the reduction temperature is 300°C to 600°C, and the reduction time is 3 h to 6 h.

7. The preparation method of a high-strength n-BN / Cu bonding wire material according to claim 1, Characterized in that: In step (3), the sintering temperature is 500 °C to 800 °C, the sintering pressure is 50 MPa to 200 Mpa, and the sintering time is 1 h to 3 h.

8. The preparation method of a high-strength n-BN / Cu bonding wire material according to claim 1, Characterized in that: In step (4), the rolling deformation per pass of hot rolling should ≤ 20%.

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