Antioxidant Cu-based bonding wire and preparation method and device thereof

Abstract

The invention relates to the technical field of materials for electronic packaging, in particular to an antioxidant Cu-based bonding wire and a preparation method and device thereof. The preparation method comprises the following steps: S1, taking a copper wire blank, enabling the copper wire blank to pass through silver paste containing nano silver powder at a constant speed, and then carrying out sintering curing and drawing sizing to obtain a first copper wire of which the surface is plated with a silver layer; and S2, enabling the first copper wire to pass through the palladium slurry containing the nano palladium powder at a constant speed, then carrying out sintering curing and drawing sizing, and plating a palladium layer on the surface of the first copper wire to obtain the antioxidant Cu-based bonding wire. According to the method, the copper bonding wire penetrates through the silver paste and the palladium paste for coating and is sintered and cured, the silver layer and the palladium layer are formed on the surface of the copper bonding wire, the surface of the bonding wire cannot be shielded in the plating process, the coating speed is controllable, and the plating layer is good in uniformity and stability; and continuous production can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of materials for electronic packaging, in particular to an oxidation-resistant Cu-based bonding wire and a preparation method and device thereof. BACKGROUND

[0002] With the development of integrated circuit manufacturing and packaging industry, bonding wire (internal lead between chip and frame) as one of the four basic materials for semiconductor packaging, its market demand is growing; the vigorous development of microelectronics industry makes the chip continue to advance towards high performance, high density and miniaturization, so it needs thinner wire, better electrochemical performance and stronger oxidation resistance for narrow pitch and long distance bonding.

[0003] In order to alleviate the problem of high cost of gold bonding wire, copper bonding wire has gradually attracted attention. Copper has the advantages of low price, good thermal and electrical conductivity, high mechanical strength, etc., and under the same conditions, it shows stronger support and toughness than gold wire, which is conducive to realizing large-span drawing and smaller pitch of wire arrangement, and meets the future development trend of technology. In addition, after bonding, the intermetallic compound structure formed between the copper wire and the aluminum layer electrode of the chip is stable and grows slowly, which helps to reduce the contact resistance and heat generation, thereby improving the bonding strength, welding reliability and overall performance of the device, and prolonging the service life of the chip.

[0004] However, copper bonding wire is prone to surface oxidation during storage or bonding, which seriously affects its bonding performance. The commonly used anti-oxidation method is to coat a plating layer on the surface of the copper wire. The traditional method usually immerses the copper wire as a whole into the plating tank for treatment. However, due to the dense stacking of copper wires, large surface area and mutual shielding, the plating speed is not easy to control, which affects the uniformity and stability of the plating layer (see patents CN202110450753.2 and CN202410764183.8). In addition, whether it is a chemical plating or an electroplating process, a large amount of chemical reagents need to be used, which will cause certain environmental pollution problems.

[0005] Therefore, it is urgent to develop a new type of copper bonding wire plating technology to avoid environmental pollution while improving the uniformity, stability and oxidation resistance of the plating layer.

[0006] In view of this, the present application is proposed. SUMMARY

[0007] The purpose of the present application is to provide an oxidation-resistant Cu-based bonding wire and a preparation method and device thereof, to solve the problems of uneven plating layer, poor stability and process prone to chemical pollution of traditional Cu bonding wire.

[0008] In order to achieve the above-mentioned purpose of the present application, the following technical solutions are adopted: A method for preparing antioxidant Cu-based bonding wire includes the following steps: S1. Take a copper wire blank, pass it through a silver paste containing nano-silver powder at a uniform speed, and then perform sintering, solidification and drawing to sizing to obtain the first copper wire with a silver coating on the surface. S2. The first copper wire is passed through a palladium paste containing nano-palladium powder at a uniform speed, and then sintered, solidified, and drawn to a sizing degree. A palladium layer is plated on the surface of the first copper wire to obtain the antioxidant Cu-based bonding wire.

[0009] Preferably, by mass percentage, the silver paste comprises 2%-5% alicyclic epoxy resin, 0.1%-0.5% curing agent, 2%-5% first organic solvent, 0-1.5% organic additive, 0.1%-0.5% first modifying component, and the balance being nano silver powder.

[0010] Preferably, the alicyclic epoxy resin includes at least one of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, hexahydrophthalic acid diglycidyl ester, and tetrahydrophthalic acid diglycidyl ester.

[0011] Preferably, the curing agent includes at least one selected from 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, and 2-phenylimidazole.

[0012] Preferably, the first organic solvent includes at least one of diethylene glycol butyl ether acetate, diethylene glycol butyl ether, dodecyl alcohol ester, terpineol, ethylene glycol phenyl ether, diethylene glycol diethyl ether, and dimethyl adipate.

[0013] Preferably, the organic additive includes at least one of silane coupling agents, titanate coupling agents, aluminate coupling agents, and acrylic monomers.

[0014] Preferably, the first modified component includes at least one of carbon fiber, carbon nanotubes, and graphene.

[0015] Preferably, the particle size of the nano-silver powder is 5-20 nm.

[0016] Preferably, the viscosity of the silver paste is 180-360 Pa·s.

[0017] Preferably, by mass percentage, the palladium paste comprises 4%-7% organic coating agent, 2%-7% second organic solvent, 0.1%-0.5% second modifying component, and the balance being nano-palladium powder.

[0018] Preferably, the organic coating agent includes at least one of n-butanethiol, cyclopentanethiol, allylthiol, pentamethylthiol, octanethiol, tert-octanethiol, tetradecanethiol, n-pentadecanethiol, hexadecanethiol, n-octadecethiol, 1-decanethiol, 1-undecanethiol, 2-phenylethylthiol, benzylthiol, cyclohexanethiol, and 1-hexanethiol.

[0019] Preferably, the second organic solvent includes at least one selected from ethanol, ethylene glycol, tert-butanol, diethylene glycol, terpineol, triethylene glycol, α-terpineol, β-terpineol, γ-terpineol, and δ-terpineol.

[0020] Preferably, the second modified component includes at least one of carbon fiber, carbon nanotubes, and graphene.

[0021] Preferably, the particle size of the palladium nanoparticles is 10-40 nm.

[0022] Preferably, the viscosity of the palladium paste is 210-400 Pa·s.

[0023] Preferably, in step S1, the diameter of the copper wire blank is 250-300 μm.

[0024] Preferably, in step S1, the copper wire blank passes through the silver paste at a speed of 2-3 m / s.

[0025] Preferably, in step S1, the sintering and solidification temperature is 150-180℃.

[0026] Preferably, in step S1, the diameter after drawing and sizing is 90-105 μm.

[0027] Preferably, in step S2, the speed at which the first copper wire passes through the palladium paste is 2-3 m / s.

[0028] Preferably, in step S2, the sintering and solidification temperature is 160-220℃.

[0029] Preferably, in step S2, the diameter after drawing and sizing is 15-22 μm.

[0030] An antioxidant Cu-based bonding wire is prepared by the method described in any one of the foregoing embodiments.

[0031] An apparatus for preparing antioxidant Cu-based bonding wires, applicable to the method for preparing antioxidant Cu-based bonding wires as described in any of the foregoing embodiments, includes a first coating unit, a first sintering unit, a first sizing and drawing unit, a second coating unit, a second sintering unit, a second sizing and drawing unit, and a wire winding unit arranged sequentially. The first coating unit and the second coating unit have the same structure, both including a box containing slurry. The box has an inlet and an outlet for the metal wire to enter and exit. The box is provided with a first guide wheel, a second guide wheel and a third guide wheel in sequence along the moving direction of the metal wire. The second guide wheel is located in the slurry.

[0032] Preferably, a plurality of fourth guide wheels are provided on the lower circumference of the second guide wheel, and the fourth guide wheels mesh with the second guide wheel.

[0033] Preferably, the outlet is funnel-shaped, and the diameter of the opening at one end inside the box is larger than the diameter of the opening at the other end outside the box.

[0034] Preferably, the first sintering unit includes an induction coil; and / or, the second sintering unit includes an induction coil.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The method of the present invention coats copper bonding wires by passing them through silver and palladium pastes, followed by sintering and curing to form silver and palladium layers on the surface of the copper bonding wires. The bonding wire surface is not obstructed during the plating process, the coating speed is controllable, and the coating uniformity and stability are good. The plating paste used in the present invention is mainly plating metal powder. Compared with traditional electroplating and chemical plating, the method of the present invention uses very little reagent, does not involve post-treatment of the plating solution, has low pollution, and is safe and reliable.

[0036] (2) Adding carbon fiber, carbon nanotubes and graphene to silver paste and palladium paste helps to reduce the resistivity of bonded wires and improve conductivity.

[0037] (3) Due to the complexing and buffering effects of the silver plating layer, palladium can be more evenly deposited on the surface of the bonding wire, resulting in a dense palladium layer with high coverage and less detachment from the copper baseline. The presence of the silver layer can alleviate the impact on the pad during the first solder joint and reduce damage to the pad. The presence of the palladium layer can improve the oxidation resistance of the Cu bonding wire.

[0038] (4) The equipment of the present invention is simple to operate, has a short process flow, can achieve continuous coating of anti-oxidation Cu-based bonding lines, achieve the purpose of automated production, and has high production efficiency. Attached Figure Description

[0039] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of a continuous production apparatus for antioxidant Cu-based bonding wires provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the first coating unit and the second coating unit; Figure 3 This is a macroscopic image of the antioxidant Cu-based bonding wire prepared in Example 1 of this invention after 30 days of storage; Figure 4 This is a macroscopic image of the antioxidant Cu-based bonding wire prepared in Comparative Example 2 of this invention after 30 days of storage. Detailed Implementation

[0041] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting 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 creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0042] The first aspect of this invention provides a method for preparing antioxidant Cu-based bonding wires, comprising the following steps: S1. Take a copper wire blank, pass it through a silver paste containing nano-silver powder at a uniform speed, and then perform sintering, solidification and drawing to sizing to obtain the first copper wire with a silver coating on the surface. S2. Pass the first copper wire through the palladium paste containing nano-palladium powder at a uniform speed, then perform sintering, solidification, and drawing for sizing. Plate a palladium layer on the surface of the first copper wire to obtain an antioxidant Cu-based bonding wire.

[0043] This invention sequentially deposits a silver layer and a palladium layer on the surface of a copper baseline. The silver layer mitigates the impact on the solder pads during the first solder joint, reducing damage to the pads, while the palladium layer enhances the oxidation resistance of the Cu-based bonding wires. This method avoids the uneven plating caused by the copper baseline being obscured in traditional hot-dip plating by continuously passing the copper baseline through the silver or palladium paste. The coating speed is controllable, resulting in good coating uniformity and stability.

[0044] In this invention, steps S1 and S2 can be performed continuously or separately; preferably, they can be performed continuously, as the method of this invention can achieve continuous production and has high production efficiency.

[0045] In some specific embodiments of the present invention, the silver paste comprises, by mass percentage, 2%-5% alicyclic epoxy resin, 0.1%-0.5% curing agent, 2%-5% first organic solvent, 0-1.5% organic additive, 0.1%-0.5% first modifying component, and the balance being nano silver powder.

[0046] Alicyclic epoxy resins contain various functional groups, and after curing, they can form a high crosslinking density and rigid alicyclic structure, which can provide excellent mechanical strength, hardness, modulus, and adhesion for the sintered and cured coating, ensuring the mechanical and weldability after sintering and curing. The curing agent can promote the curing and hardening of the silver paste, thereby improving the tensile, flexural, and impact strength of the silver layer. The role of the first organic solvent is to dilute the silver paste and adjust its viscosity and flowability. The role of the organic additive is to improve the dispersion of silver powder to obtain better interfacial properties. The first modifying component is mainly used to enhance the conductivity of the bonding wires. Nano-silver powder is used as the coating metal source to form the silver coating.

[0047] Existing electroplating or electroless plating solutions are complex in composition, have poor stability, use large amounts of acids and alkalis, and are cumbersome to maintain, adjust pH, regenerate, and treat waste liquids, resulting in high material costs. In contrast, the silver paste in this invention is mainly composed of nano-silver powder, uses very little chemical reagent, has low pollution, does not involve post-treatment of the plating solution, has good stability, and is easy to maintain.

[0048] In some specific embodiments, typically but not limitingly, for example, the mass percentage of the alicyclic epoxy resin in the silver paste can be any one value or a range of any two values ​​from 2%, 3%, 4%, and 5%; the mass percentage of the curing agent in the silver paste can be any one value or a range of any two values ​​from 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%; the mass percentage of the first organic solvent in the silver paste can be any one value or a range of any two values ​​from 2%, 3%, 4%, and 5%; the mass percentage of the organic additive in the silver paste can be any one value or a range of any two values ​​from 0%, 0.5%, 1%, and 1.5%; and the mass percentage of the first modifying component in the silver paste can be any one value or a range of any two values ​​from 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%.

[0049] In some specific embodiments of the present invention, the alicyclic epoxy resin includes at least one of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, hexahydrophthalic acid diglycidyl ester, and tetrahydrophthalic acid diglycidyl ester.

[0050] In some specific embodiments of the present invention, the curing agent includes at least one selected from 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole and 2-phenylimidazole.

[0051] In some specific embodiments of the present invention, the first organic solvent includes at least one selected from diethylene glycol butyl ether acetate, diethylene glycol butyl ether, dodecyl alcohol ester, terpineol, ethylene glycol phenyl ether, diethylene glycol diethyl ether, and dimethyl adipate.

[0052] In some specific embodiments of the present invention, the organic additives include at least one of silane coupling agents, titanate coupling agents, aluminate coupling agents, and acrylic monomers.

[0053] In some specific embodiments of the present invention, the first modifying component includes at least one of carbon fiber, carbon nanotubes and graphene.

[0054] In some specific embodiments of the present invention, the particle size of the nano-silver powder used is 5-20nm. For example, it can be any single value or a range of any two values ​​among 5nm, 10nm, 15nm, and 20nm.

[0055] In some specific embodiments of the present invention, the viscosity of the silver paste is 180-360 Pa·s, for example, it can be any single value or a range of any two values ​​among 180 Pa·s, 200 Pa·s, 250 Pa·s, 300 Pa·s, and 360 Pa·s. When the viscosity of the silver paste is too high, the silver paste has poor fluidity, uneven coating, and may even cause cracking of the silver layer after sintering, resulting in poor protective performance; while when the viscosity of the silver paste is too low, on the one hand, severe leveling will occur, making the silver layer very thin, and on the other hand, the viscosity is too low, resulting in excessive organic solvent. Since the organic components need to be slowly and uniformly evaporated and thermally decomposed during the sintering process, excessive organic solvent will increase the evaporation time, requiring an increased sintering time. The continuously moving metal wire may not be able to achieve sufficient sintering of the silver paste by sintering and solidifying only through the induction coil.

[0056] In some specific embodiments of the present invention, the palladium paste comprises, by mass percentage, 4%-7% of an organic coating agent, 2%-7% of a second organic solvent, 0.1%-0.5% of a second modifying component, and the balance being nano-palladium powder.

[0057] In the palladium slurry, the organic coating agent reduces the surface energy of the powder, improves the dispersion stability of the palladium powder, and achieves anti-settling and anti-agglomeration effects. The second organic solvent dilutes the palladium slurry and adjusts its viscosity and flowability. The second modifying component enhances the conductivity of the bonding wires. Nano-palladium powder serves as the coating metal source for forming the palladium coating. In this invention, the main component of the palladium slurry is nano-palladium powder, with very little chemical reagent used, resulting in minimal pollution. It does not involve post-treatment of the plating solution, exhibits good stability, and is easy to maintain.

[0058] In some embodiments, typically but not limitingly, for example, the mass percentage of the organic coating agent in the palladium paste can be any one of 4%, 5%, 6%, 7%, or a range of any two of these values; the mass percentage of the second organic solvent in the palladium paste can be any one of 2%, 3%, 4%, 5%, 6%, 7%, or a range of any two of these values; and the mass percentage of the second modifying component in the palladium paste can be any one of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or a range of any two of these values.

[0059] In some specific embodiments of the present invention, the organic coating agent includes at least one of n-butanethiol, cyclopentanethiol, allylthiol, pentamethylthiol, octanethiol, tert-octanethiol, tetradecanethiol, n-pentadecanethiol, hexadecanethiol, n-octadecethiol, 1-decanethiol, 1-undecanethiol, 2-phenylethylthiol, benzylthiol, cyclohexanethiol, and 1-hexanethiol.

[0060] In some specific embodiments of the present invention, the second organic solvent includes at least one selected from ethanol, ethylene glycol, tert-butanol, diethylene glycol, terpineol, triethylene glycol, α-terpineol, β-terpineol, γ-terpineol, and δ-terpineol.

[0061] In some specific embodiments of the present invention, the second modifying component includes at least one of carbon fiber, carbon nanotubes and graphene.

[0062] In some specific embodiments of the present invention, the particle size of the palladium nanoparticles used is 10-40 nm. For example, it can be any single value or a range of any two values ​​among 10 nm, 20 nm, 30 nm, and 40 nm.

[0063] In some specific embodiments of the present invention, the viscosity of the palladium paste is 210-400 Pa·s, for example, it can be any single value or a range of any two values ​​among 210 Pa·s, 250 Pa·s, 300 Pa·s, 350 Pa·s, and 400 Pa·s. When the viscosity of the palladium paste is too high, the fluidity is poor, the coating is uneven, and even the surface palladium layer may crack after sintering, resulting in poor protective performance; while when the viscosity is too low, on the one hand, severe leveling will occur, making the palladium layer very thin and the protective performance poor; on the other hand, the sintering time needs to be increased, and the continuously moving metal wire may not be able to achieve sufficient sintering of the silver paste by sintering and solidifying only through the induction coil.

[0064] In some specific embodiments of the present invention, the diameter of the copper wire blank used in step S1 is 250-300μm. For example, it can be any one value or a range of any two values ​​among 250μm, 260μm, 270μm, 280μm, 290μm, and 300μm.

[0065] In some specific embodiments of the present invention, the speed at which the copper wire blank passes through the silver paste in step S1 is 2-3 m / s. For example, it can be any one value or a range of any two values ​​among 2 m / s, 2.2 m / s, 2.5 m / s, 2.8 m / s, and 3 m / s.

[0066] In some specific embodiments of the present invention, the sintering and curing temperature in step S1 is 150-180°C. For example, it can be any value among 150°C, 160°C, 170°C, and 180°C, or a range of any two values. When the temperature is below 150°C, the crosslinking reaction rate between the epoxy resin and the curing agent will be very slow, or even unable to react completely, resulting in the resin failing to form a robust three-dimensional network structure. Excessively high temperatures will cause the epoxy resin to oxidize, decompose, or become over-crosslinked. Over-crosslinking will make the resin brittle, leading to decreased adhesion and increased internal stress. 150-180°C is the relatively effective and complete curing temperature range for this reaction system.

[0067] In some specific embodiments of the present invention, the diameter after drawing and sizing in step S1 is 90-105 μm. For example, it can be any one value or a range of any two values ​​among 90 μm, 95 μm, 100 μm, and 105 μm.

[0068] In some specific embodiments of the present invention, the speed at which the first copper wire passes through the palladium paste in step S2 is 2-3 m / s. For example, it can be any one value or a range of any two values ​​among 2 m / s, 2.2 m / s, 2.5 m / s, 2.8 m / s, and 3 m / s.

[0069] In some specific embodiments of the present invention, the sintering and solidification temperature in step S2 is 160-220°C. For example, it can be any one value or a range of any two values ​​among 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, and 220°C.

[0070] In some specific embodiments of the present invention, the diameter after drawing and sizing in step S2 is 15-22 μm. For example, it can be any one value or a range of any two values ​​among 15 μm, 17 μm, 19 μm, 20 μm, and 22 μm.

[0071] A second aspect of the present invention provides an antioxidant Cu-based bonding wire, which is prepared by the method for preparing antioxidant Cu-based bonding wire described in any of the foregoing embodiments.

[0072] like Figure 1 and Figure 2 As shown, a third aspect of the present invention provides an apparatus for preparing antioxidant Cu-based bonding wires, applicable to the method for preparing antioxidant Cu-based bonding wires as described in any of the foregoing embodiments, comprising a first coating unit, a first sintering unit, a first sizing and drawing unit, a second coating unit, a second sintering unit, a second sizing and drawing unit, and a wire winding unit arranged sequentially. The first coating unit and the second coating unit have the same structure, both including a box 1 containing a slurry. The box of the first coating unit contains silver paste, and the box of the second coating unit contains palladium paste. The box 1 is provided with an inlet 3 and an outlet 6 for the metal wire to enter and exit. The inlet 3 is provided with a wire-passing tube 2 for the metal wire to pass through. The wire-passing tube 2 is replaceable and has low friction with the metal wire. Inside the box 1, along the direction of movement of the metal wire, there are a first guide wheel 4, a second guide wheel 7, and a third guide wheel 5. The first guide wheel 4 is located at the inlet 3, the third guide wheel 5 is located at the outlet 6, and the second guide wheel 7 is located in the slurry. The height of the second guide wheel 7 is lower than that of the first guide wheel 4 and the third guide wheel 5. The first guide wheel 4, the second guide wheel 7, and the third guide wheel 5 serve as guides to allow the metal wire (copper wire blank or first copper wire with a silver coating) to pass through the slurry for coating. After coating, the metal wire is sintered and cured by the sintering unit to form a coating on the surface of the metal wire.

[0073] In some specific embodiments of the present invention, a plurality of fourth guide wheels 8 are provided on the lower periphery of the second guide wheel 7. The fourth guide wheels 8 mesh with the second guide wheel 7 to generate compressive stress on the surface of the metal wire, thereby ensuring the coating of silver paste or palladium paste on the surface of the metal wire.

[0074] In some specific embodiments of the present invention, the outlet 6 is trumpet-shaped, and the diameter of the opening at one end inside the box 1 is larger than the diameter of the opening at the other end outside the box 1. The purpose is to prevent the silver paste or palladium paste from falling off when the slurry exits the box 1, and to ensure that the surface of the metal wire is smooth.

[0075] In some specific embodiments of the present invention, the first sintering unit includes an induction coil; and / or, the second sintering unit includes an induction coil.

[0076] The coating process of this invention is simple, and the coating speed and thickness can be adjusted by controlling the gap between the second and fourth guide wheels, the outlet gap of the coating chamber, and the sizing and drawing unit, thus achieving autonomous control over the speed and coating thickness. On the one hand, it can avoid uneven coating thickness caused by uneven distribution of electric field lines during electroplating; on the other hand, it can also avoid various coating defects caused by excessively fast reaction speed during chemical plating.

[0077] The following detailed description of some embodiments of the present invention is provided in conjunction with specific application examples. Unless otherwise specified, all raw materials used in the embodiments can be obtained commercially available.

[0078] Example 1 S1. Select a Cu wire blank with a diameter of 250 μm, and pass it through the silver paste at a uniform speed of 2 m / s. After sintering and solidification at 160℃, draw it to a diameter of 105 μm to obtain the first copper wire with a silver coating on the surface. The composition of the silver paste by mass percentage is: 94 wt.% silver powder with a particle size of 5-20 nm, 2 wt.% diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylic acid, 0.5 wt.% 2-methylimidazole, 2 wt.% diethylene glycol butyl ether acetate, 1 wt.% γ-aminopropyltriethoxysilane, and 0.5 wt.% carbon fiber. The viscosity of the Ag paste is 280 Pa·s. S2. The first copper wire obtained in step S1 is passed through the palladium paste at a uniform speed of 2 m / s. After sintering and solidification at 200℃, it is drawn to a diameter of 22 μm to obtain an antioxidant Cu-based bonding wire, which is then wound into a coil. The palladium paste consists of the following components by mass percentage: 93.5 wt.% palladium powder with a particle size of 10-40 nm, 4 wt.% n-butanethiol, 2 wt.% ethanol, and 0.5 wt.% carbon fiber. The viscosity of the palladium paste is 330 Pa·s.

[0079] Example 2 S1. Select a 250μm Cu wire blank and pass it through the silver paste at a uniform speed of 2m / s. After sintering and solidification at 160℃, draw it to a diameter of 105μm to obtain the first copper wire with a silver coating on the surface. The composition of the silver paste by mass percentage is: 90 wt.% silver powder with a particle size of 5-20nm, 3.5 wt.% 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 0.5 wt.% 2-ethyl-4-methylimidazolium, 4 wt.% diethylene glycol butyl ether, 1.5 wt.% bis(dioctylpyrophosphoryloxy)ethylene titanate, and 0.5 wt.% carbon nanotubes. The viscosity of the Ag paste is 290 Pa·s. S2. The first copper wire obtained in step S1 is passed through the palladium paste at a uniform speed of 2 m / s. After sintering and solidification at 200℃, it is drawn to a diameter of 22 μm to obtain an antioxidant Cu-based bonding wire, which is then wound into a coil. The palladium paste consists of the following components by mass percentage: 92 wt.% palladium powder with a particle size of 10-40 nm, 5 wt.% n-butanethiol, 2.5 wt.% ethanol, and 0.5 wt.% carbon nanotubes. The viscosity of the palladium paste is 310 Pa·s.

[0080] Comparative Example 1 The traditional hot-dip plating method is used to perform silver and palladium plating on the surface of Cu bonding wires. The specific steps are as follows: A Cu wire blank with a diameter of 15 μm was selected as the billet. Silver plating layer: The obtained 15μm wire is transported to a vacuum immersion plating equipment. The vacuum equipment is evacuated to a vacuum degree of 0.2Pa. Then, the prepared nano-silver plating solution is transported into the working chamber, and the wire is immersed in the nano-silver plating solution. The wire is immersed at 400℃ for 10 minutes to form a stable bonding layer between the nano-silver in the plating solution and the copper contact surface. After that, it is vacuum dried at 200℃ for 3 minutes. The above operation is repeated for a total of 5 hot immersion platings. The nano-silver plating solution consists of 8% by mass of 10-30nm nano-silver powder as the coating metal source, 5% ethanol as an auxiliary agent, 3% N-methylpyrrolidone as a stabilizer and dispersant, and the balance is water. Surface palladium plating: The obtained silver-plated wire is transported again to the vacuum immersion plating equipment. The vacuum equipment is evacuated to a vacuum degree of 0.1 Pa. Then, the prepared nano-palladium plating solution is transported into the working chamber, and the wire is immersed in the nano-palladium plating solution. It is immersed at 300°C for 10 min to form a palladium plating layer on its surface. After that, it is vacuum dried at 150°C for 5 min. The above operation is repeated for a total of 5 hot immersion platings. The nano-palladium plating solution consists of 8% by mass of 30-50 nm nano-palladium powder as the coating metal source, 5% ethanol as an auxiliary agent, 3% N-methylpyrrolidone as a stabilizer and dispersant, and the balance is water. The fully plated product was dried under vacuum heating at 100℃ for 5 minutes and then annealed at 680℃ for 10 minutes to obtain Cu-based bonding wires with silver and palladium layers on the surface.

[0081] Comparative Example 2 Comparative Example 2 is similar to Example 1, except that the content of diethylene glycol butyl ether acetate in the silver paste is reduced to 1 wt.%, the content of nano silver powder is increased to 95 wt.%, and the contents of other components remain unchanged. At this time, the viscosity of the silver paste is 410 Pa·s, and the other conditions are the same as those in Example 1.

[0082] Comparative Example 3 Comparative Example 3 is similar to Example 1, except that the ethanol content in the palladium slurry is reduced to 1 wt.%, the nano-palladium powder is increased to 94.5 wt.%, and the contents of other components remain unchanged. At this time, the viscosity of the palladium slurry is 550 Pa·s, and all other conditions are the same as in Example 1.

[0083] Comparative Example 4 Comparative Example 4 is similar to Example 1, except that no carbon fiber is added to either the silver paste or the palladium paste, and all other conditions are the same as in Example 1.

[0084] Test case The appearance of the copper-based bonding wires prepared in each embodiment and comparative example was observed, their resistivity was tested, a tensile-bending test was performed 50 times and the condition at the bending point was observed, and the appearance changes were observed after 30 days of storage at room temperature; the results are shown in Table 1.

[0085] Table 1

[0086] As can be seen from the data in Table 1, the copper-based bonding wires prepared according to this embodiment have a smooth surface, good conductivity, strong adhesion of the surface coating, strong resistance to deformation, and excellent oxidation resistance.

[0087] Depend on Figure 3 and Figure 4 It can be seen that the copper-based bonding wire prepared according to this embodiment remained smooth and bright on the surface after being placed at room temperature for 30 days, without any obvious discoloration; while in Comparative Example 2, obvious oxidation and blackening occurred, indicating poor antioxidant performance.

[0088] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing an antioxidant Cu-based bonding wire, characterized in that, Includes the following steps: S1. Take a copper wire blank, pass it through a silver paste containing nano-silver powder at a uniform speed, and then perform sintering, solidification and drawing to sizing to obtain the first copper wire with a silver coating on the surface. S2. The first copper wire is passed through a palladium paste containing nano-palladium powder at a uniform speed, and then sintered, solidified, and drawn to a sizing degree. A palladium layer is plated on the surface of the first copper wire to obtain the antioxidant Cu-based bonding wire.

2. The method for preparing antioxidant Cu-based bonding wires according to claim 1, characterized in that, The silver paste comprises, by weight percentage, 2%-5% alicyclic epoxy resin, 0.1%-0.5% curing agent, 2%-5% first organic solvent, 0-1.5% organic additive, 0.1%-0.5% first modifying component, and the balance being nano silver powder.

3. The method for preparing antioxidant Cu-based bonding wires according to claim 2, characterized in that, It meets at least one of the following characteristics: (1) The alicyclic epoxy resin includes at least one of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, hexahydrophthalic acid diglycidyl ester, and tetrahydrophthalic acid diglycidyl ester. (2) The curing agent includes at least one of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole and 2-phenylimidazole; (3) The first organic solvent includes at least one of diethylene glycol butyl ether acetate, diethylene glycol butyl ether, dodecyl alcohol ester, terpineol, ethylene glycol phenyl ether, diethylene glycol diethyl ether and dimethyl adipate; (4) The organic additives include at least one of silane coupling agents, titanate coupling agents, aluminate coupling agents and acrylic monomers; (5) The first modified component includes at least one of carbon fiber, carbon nanotube and graphene; (6) The particle size of the nano-silver powder is 5-20 nm; (7) The viscosity of the silver paste is 180-360 Pa·s.

4. The method for preparing antioxidant Cu-based bonding wires according to claim 1, characterized in that, The palladium paste comprises, by weight percentage, 4%-7% of an organic coating agent, 2%-7% of a second organic solvent, 0.1%-0.5% of a second modifying component, and the balance being palladium nanoparticles.

5. The method for preparing antioxidant Cu-based bonding wire according to claim 4, characterized in that, It meets at least one of the following characteristics: (1) The organic coating agent includes at least one of n-butanethiol, cyclopentanethiol, allylthiol, pentamethylthiol, octanethiol, tert-octanethiol, tetradecanethiol, n-pentadecanethiol, hexadecanethiol, n-octadecethiol, 1-decanethiol, 1-undecanethiol, 2-phenylethylthiol, benzylthiol, cyclohexanethiol, and 1-hexanethiol; (2) The second organic solvent includes at least one of ethanol, ethylene glycol, tert-butanol, diethylene glycol, terpineol, triethylene glycol, α-terpineol, β-terpineol, γ-terpineol and δ-terpineol; (3) The second modified component includes at least one of carbon fiber, carbon nanotube and graphene; (4) The particle size of the nano-palladium powder is 10-40 nm; (5) The viscosity of the palladium paste is 210-400 Pa·s.

6. The method for preparing antioxidant Cu-based bonding wires according to claim 1, characterized in that, In step S1, at least one of the following characteristics is satisfied: (1) The diameter of the copper wire blank is 250-300 μm; (2) The copper wire blank passes through the silver paste at a speed of 2-3 m / s; (3) The sintering and solidification temperature is 150-180℃; (4) The diameter after drawing and sizing is 90-105 μm.

7. The method for preparing antioxidant Cu-based bonding wire according to claim 1, characterized in that, In step S2, at least one of the following characteristics is satisfied: (1) The first copper wire passes through the palladium paste at a speed of 2-3 m / s; (2) The sintering and solidification temperature is 160-220℃; (3) The diameter after drawing and sizing is 15-22 μm.

8. An antioxidant Cu-based bonding wire, characterized in that, It was prepared by the method for preparing antioxidant Cu-based bonding wires according to any one of claims 1-7.

9. An apparatus for preparing antioxidant Cu-based bonding wires, applicable to the method for preparing antioxidant Cu-based bonding wires according to any one of claims 1-7, characterized in that, It includes a first coating unit, a first sintering unit, a first sizing and drawing unit, a second coating unit, a second sintering unit, a second sizing and drawing unit, and a wire winding unit arranged in sequence; The first coating unit and the second coating unit have the same structure, both including a box containing slurry. The box has an inlet and an outlet for the metal wire to enter and exit. The box is provided with a first guide wheel, a second guide wheel and a third guide wheel in sequence along the moving direction of the metal wire. The second guide wheel is located in the slurry.

10. The apparatus for preparing antioxidant Cu-based bonding wires according to claim 9, characterized in that, It meets at least one of the following characteristics: (1) The lower circumference of the second guide wheel is also provided with a plurality of fourth guide wheels, which mesh with the second guide wheel; (2) The outlet is funnel-shaped, and the diameter of the opening at one end inside the box is larger than the diameter of the opening at the other end outside the box; (3) The first sintering unit includes an induction coil; and / or the second sintering unit includes an induction coil.

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