Palladium-plated / gold-palladium-plated copper bonding wire with high corrosion resistance and high conductivity, and production process therefor

Abstract

The present invention relates to the technical field of bonding wires. Disclosed are a palladium-plated / gold-palladium-plated copper bonding wire with high corrosion resistance and high conductivity, and a production process therefor. In the present invention, in order to enhance the corrosion resistance of the bonding wire, the bonding wire is improved by modifying a core material and preparing a composite coating. Firstly, according to the present invention, a core layer is improved, wherein by means of adding graphene to the core layer, the corrosion potential of the core material is significantly increased, and a copper core has a good heat dissipation performance and high-temperature conductivity, thereby preventing heat accumulation and temperature rise in the bonding wire. On this basis, according to the present invention, the coating is also improved, wherein by means of reducing the concentration of metal ions in an electroplating solution, adding a via filling agent and using pulse current electroplating, the surface morphology of the electroplated coating is improved. Furthermore, by means of an annealing treatment, a diffusion layer is formed between a graphene-copper alloy core and different electroplated layers, thereby improving the bonding strength therebetween and improving the usage performance of the bonding wire.

Description

A high corrosion-resistant and high conductivity palladium / gold-plated palladium-copper bonding wire and its manufacturing process Technical Field

[0001] This invention relates to the field of bonding wire technology, specifically to a high corrosion-resistant and high conductivity palladium / gold-plated palladium-copper bonding wire and its manufacturing process. Background Technology

[0002] Bonding wires are one of the key components in semiconductor packaging. They are mainly used to connect the pads on the semiconductor chip to the external pins or package base to achieve electrical connection. Due to the high degree of centralization of electronic components, their heat generation is also much greater. The increase in heat generation often has a significant impact on the conductivity of the bonding wire. Furthermore, due to the wide range of applications, bonding wires need to remain stable under various environmental conditions, such as temperature, humidity and other external factors, to prevent oxidation in high temperature and high humidity environments, which would affect their conductivity and reliability.

[0003] Therefore, to achieve the above objectives, current mainstream technologies mostly use oxygen-free copper as the core material. A uniform palladium layer is deposited on the surface of the core material through electroplating or chemical plating, thereby avoiding oxidation of the copper wire during welding and improving the welding performance and stability of the core material after welding. However, if the coating is damaged, a galvanic cell reaction can easily occur between the palladium layer and the copper core, which can further reduce the reliability of the product and affect its use. Summary of the Invention

[0004] The purpose of this invention is to provide a high corrosion resistance and high conductivity palladium / gold palladium-copper bonding wire and its manufacturing process, so as to solve the problems raised in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a high corrosion-resistant and high conductivity palladium / gold palladium-copper bonding wire, which has the following technical features: the high corrosion-resistant and high conductivity palladium / gold palladium-copper bonding wire is composed of a graphene copper alloy core and a composite coating layer covering the outside of the graphene copper alloy core.

[0006] The diameter of the high corrosion resistance and high conductivity palladium / gold palladium-copper bonding wire is 15-500μm, and the thickness of the composite coating is 51-185nm.

[0007] The composite coating consists of a first palladium layer, an intermediate gold layer, a second palladium layer, and a top gold layer from bottom to top.

[0008] Furthermore, the grain size within the interface of the graphene-copper alloy core is 0.1-200 μm;

[0009] The graphene copper alloy core contains 100-10000ppm of graphene and 5-5000ppm of reinforcing metal material.

[0010] The reinforcing metal material is any one or more of Ag, Pd, Au, Pt, Li, P, Ca, Ni, Be, Y, La, Ce, Zr, In, Ge, and Sc.

[0011] Furthermore, the graphene copper alloy core contains 300-3000 ppm of graphene and 0-3000 ppm of reinforcing metal material.

[0012] The reinforcing metal material is any one or more of Au, Pd, In, P, Ni, Ca, Li, and Sc;

[0013] When the reinforced metal material contains any one of P, Li, or Sc, the amount of each component added is 0-300 ppm.

[0014] Furthermore, in the composite coating, the thickness of the first palladium layer is 10-20 nm, the thickness of the intermediate gold layer is 20-80 nm, the thickness of the second palladium layer is 20-80 nm, and the thickness of the top gold layer is 1-5 nm.

[0015] Furthermore, a method for preparing a highly corrosion-resistant and highly conductive palladium / gold-plated palladium-copper bonding wire includes the following steps:

[0016] S1. Preparation of graphene-copper alloy core;

[0017] S11. The graphene copper mixed raw material is protected under a nitrogen atmosphere and dried in an environment of 40-80℃ for 1-12 hours. It is then pressed into a billet and placed in an SPS sintering furnace under an argon atmosphere. A pressure of 100-1000kN is applied to the billet, and the temperature is raised to 900-1200℃ at a rate of 90-110℃ / min. After sintering into a block, it is cooled to room temperature with the furnace to obtain the graphene copper alloy ingot.

[0018] S12. Mix the graphene copper alloy ingot with the reinforcing metal material, protect it with an argon atmosphere, heat it to 1050-1250℃ by electromagnetic induction and melt it. After stirring and mixing for 10s-15min, continuously cast the molten metal into a mother rod with a diameter of 8mm.

[0019] S13. Perform multiple wire drawing and lengthening processes on the mother rod until its diameter is 15-500μm to obtain a graphene copper alloy core;

[0020] S2. Preparation of composite coating;

[0021] S21. Prepare the first palladium layer;

[0022] The cleaned graphene-copper alloy core was placed in a first palladium plating solution at a temperature of 70-75℃, and the pulse current was set to 3-5 mA / cm.2 Each pulse has a conduction time of 0.5-1s and a turn-off time of 0.5-2s. After electroplating to the required first palladium layer thickness, the pulse is stopped, the graphene copper alloy core is removed, and after washing and drying, the first palladium layer is formed.

[0023] S22. Preparation of intermediate gold layer;

[0024] The graphene-copper alloy core treated in step S21 is placed in an intermediate gold plating solution at a temperature of 70-80℃, and the electroplating pulse current is set to 5-15mA / cm. 2 Each pulse has a conduction time of 1.5-3s and a turn-off time of 0.5-2s. After electroplating to the required thickness, the pulse is stopped, the graphene copper alloy core is removed, and after washing and drying, an intermediate gold layer is formed.

[0025] S23. Place the graphene-copper alloy core treated in step S22 into a second palladium electroplating solution at a temperature of 70-80℃, and set the current to 10-60 mA / cm. 2 After electroplating to the required thickness, the graphene copper alloy core is removed, washed, and dried to form the second palladium layer;

[0026] S24. Place the graphene-copper alloy core treated in step S23 into a top-layer gold plating solution at a temperature of 70-80℃, and set the current to 10-60mA / cm. 2 After electroplating to the required thickness, the graphene copper alloy core is removed, washed and dried to form a top gold layer, resulting in a graphene copper alloy core with a composite coating.

[0027] S3. Anneal the graphene copper alloy core with composite coating at a temperature of 400-700℃, a furnace length of 600-1000mm, and an annealing speed of 40-140m / min. After annealing, a high corrosion-resistant and high conductivity palladium / gold-plated palladium copper bonding wire is obtained.

[0028] Furthermore, the preparation method of the graphene-copper hybrid raw material includes the following steps:

[0029] a1. Prepare the electrolyte;

[0030] Copper sulfate, sulfuric acid and deionized water are mixed to prepare a mixed solution with a sulfuric acid concentration of 10-200 g / L and a copper ion concentration of 10-100 g / L. 1-20 g / L of graphene is added to the electrolyte. After electromagnetic stirring and ultrasonic dispersion to make the graphene evenly dispersed, the electrolyte is obtained.

[0031] b1. Using high-purity copper with an impurity element content of 0-10 ppm as the anode and a pure copper plate as the cathode, electrodeposition is performed with an applied voltage of 2-10 V and a current density of 1-10 mA / cm². 2After electrodeposition for 10-60 minutes, the cathode is removed, washed with deionized water, and the graphene copper powder on the cathode surface is collected. After drying, XPS analysis is performed to determine that the carbon-copper bond ratio is 35-45%. The graphene copper powder is then mixed with oxygen-free copper powder and melted uniformly under an argon atmosphere. After cooling, XPS analysis is performed again to determine that the carbon-copper bond ratio is 3-5%. The graphene copper powder is then mixed with pure copper powder, melted uniformly, and ball-milled to obtain the graphene copper mixed raw material.

[0032] Furthermore, the preparation method of the graphene-copper hybrid raw material includes the following steps:

[0033] a2. Disperse graphene in ultrapure water, stir electromagnetically and ultrasonically disperse and wash for 0.5-1 h, then filter by suction filtration. Repeat 2-3 times and test the pH value of the filtrate. If the pH value is within the range of 6.3-7, the cleaning is qualified. Otherwise, repeat the above steps to wash the graphene with ultrapure water until the pH value of the filtrate is qualified. Dry the cleaned graphene in a nitrogen atmosphere and cool it for later use.

[0034] b2. After cleaning, the graphene is mixed with high-purity oxygen-free copper powder and then ball-milled at low temperature for 3-24 hours. The ball milling speed is 100-1200 rpm, the protective gas is nitrogen, and the plasma working power is 10-400W. After the ball milling is completed, the graphene-copper mixture raw material is obtained.

[0035] Furthermore, the first palladium plating solution comprises palladium tetraaminoacetate, p-carboxybenzenesulfonamide, and a composite pore-filling agent;

[0036] In the first palladium electroplating solution, the concentration of palladium tetraaminoacetate is 3-5 g / L, the concentration of p-carboxybenzenesulfonamide is 5-15 mg / L, and the concentration of composite pore filler is 25-55 mg / L.

[0037] The composite pore-filling agent is a composition of diethyl dithiophosphate ammonium salt and L-alanine benzyl ester p-toluenesulfonate in a mass ratio of 1:1;

[0038] The second palladium electroplating solution includes palladium tetraaminodichloride, p-carboxybenzenesulfonamide, and β-cyanoalanine;

[0039] In the second palladium electroplating solution, the concentration of tetraaminodichloride palladium is 5-10 g / L, the concentration of p-carboxybenzenesulfonamide is 5-10 mg / L, and the concentration of β-cyanoalanine is 10-20 mg / L.

[0040] The intermediate gold plating solution includes gold cyanide and a composite pore filler;

[0041] In the intermediate gold plating solution, the concentration of gold cyanide is 4-8 g / L, and the concentration of composite pore filler is 50-80 mg / L;

[0042] The top gold plating solution includes gold cyanide, with a gold cyanide concentration of 5-15 g / L;

[0043] When using the intermediate gold plating solution and the top gold plating solution, the pH value is adjusted to 10-12 with ammonia water.

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] In order to improve the corrosion resistance of the bonding wire, this invention improves the bonding wire by modifying the core material and preparing a composite coating.

[0046] This invention first improves the core layer by adding graphene and calcining it to form the core material. This method ensures that the metal covalent bonds formed between graphene and the copper substrate are evenly distributed, thereby significantly increasing the corrosion potential of the core material and reducing the corrosion current and halogen corrosion weight loss. Also, due to the even distribution of the metal covalent bonds formed between graphene and the copper substrate, the copper core has good heat dissipation performance and high-temperature conductivity. As a result, the bonding wire prepared by this invention has a conductivity at 150°C that is more than 30% higher than that of traditional oxygen-free copper.

[0047] Furthermore, graphene itself has extremely high thermal conductivity, which can accelerate heat conduction and prevent heat accumulation and temperature rise in the bonding wire, thus further improving the high-temperature reliability of the product. Also, due to the addition of graphene, the grain structure in the copper core is improved, which can effectively inhibit the growth of intermetallic compounds and improve the working performance of the bonding wire.

[0048] Based on this, the present invention further improves the coating treatment;

[0049] Before electroplating the composite coating, this invention first refines the graphene copper alloy core by drawing it into finer wires. This avoids stress damage to the electroplated layer caused by the wire drawing after coating preparation, which would affect the bonding strength between the coating and the graphene copper alloy core. Furthermore, the coating prepared in this application is a composite coating. In preparing the bottom layer coating, namely the first palladium layer and the intermediate gold layer, this application limits both the electroplating solution and the electroplating method. By reducing the metal ion concentration in the electroplating solution, increasing the pore-filling agent, and using pulsed current electroplating, the bottom electroplating layer can effectively electroplat the surface of the drawn graphene copper alloy core and smooth its surface. The addition of the composite pore-filling agent can effectively improve and prevent roughness caused by the wire drawing process. The surface tip discharge phenomenon causes micropores in the electroplated layer, while the lower metal ion concentration and pulsed current can effectively improve the deposition rate of the metal layer during electroplating and reduce defects in the plating deposition. After the first palladium layer and the intermediate gold layer are smoothed, the surface is electroplated again with a large current, which can effectively improve the electroplating efficiency and accelerate the production speed. Furthermore, the present invention performs a further annealing treatment on the bonding wire after the preparation of the electroplated layer, so that the wire eliminates the processing stress and reorganizes the grains. This process can also form a diffusion layer between the graphene copper alloy core and different electroplated layers, improve the bonding strength between them, avoid the peeling of the coating, and improve the performance of the bonding wire. Attached Figure Description

[0050] Figure 1 is a diagram of the grain structure within the interface of the graphene-copper alloy core prepared in Example 1 of the present invention. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0052] The operating methods of Examples 1-30 and Comparative Examples 1-5 in this application are as follows:

[0053] A method for preparing a highly corrosion-resistant and highly conductive palladium / gold-plated palladium-copper bonding wire includes the following steps:

[0054] S1. Preparation of graphene-copper alloy core;

[0055] S11. The graphene copper mixed raw material was protected under a nitrogen atmosphere and dried at 80°C for 8 hours. It was then pressed into a billet and placed in an SPS sintering furnace under an argon atmosphere. After applying a pressure of 800kN to the billet, the temperature was increased to 1000°C at a rate of 100°C / min. After sintering into a block, it was cooled to room temperature with the furnace to obtain the graphene copper alloy ingot.

[0056] The preparation method of the graphene-copper hybrid raw material is as follows:

[0057] a2. Disperse graphene in ultrapure water, stir electromagnetically and ultrasonically disperse and wash for 1 hour, filter by suction, repeat 3 times, and test the pH value of the filtrate. If the pH value is within the range of 6.3-7, the cleaning is qualified. Otherwise, repeat the above steps to wash graphene with ultrapure water until the pH value of the filtrate is qualified. Dry the cleaned graphene in a nitrogen atmosphere and cool it for later use.

[0058] b2. After cleaning, the graphene was mixed with high-purity oxygen-free copper powder and then ball-milled at low temperature for 12 hours. The ball milling speed was 800 rpm, the protective gas was nitrogen, and the plasma working power was 120W. After the ball milling was completed, the graphene-copper mixture was obtained.

[0059] S12. Mix the graphene copper alloy ingot with the reinforcing metal material, protect it with an argon atmosphere, heat it to 1200℃ by electromagnetic induction and melt it. After stirring and mixing for 3 minutes, continuously cast the molten metal liquid into a mother rod with a diameter of 8mm.

[0060] S13. Perform multiple wire drawing and lengthening processes on the mother rod until its diameter is 15-500μm to obtain a graphene copper alloy core;

[0061] S2. Preparation of composite coating;

[0062] S21. Prepare the first palladium layer;

[0063] The cleaned graphene-copper alloy core was placed in a first palladium plating solution at 70°C, and the pulse current was set to 3 mA / cm. 2 Each pulse has a conduction time of 0.5s and a turn-off time of 1.5s. After electroplating to the required first palladium layer thickness of 20nm, the pulse is stopped, the graphene copper alloy core is removed, and after washing and drying, the first palladium layer is formed.

[0064] In the first palladium electroplating solution, the concentration of palladium tetraaminoacetate is 4 g / L, the concentration of p-carboxybenzenesulfonamide is 8 mg / L, and the concentration of composite pore filler is 30 mg / L.

[0065] The composite pore-filling agent is a composition of diethyl dithiophosphate ammonium salt and L-alanine benzyl ester p-toluenesulfonate in a mass ratio of 1:1;

[0066] S22. Preparation of intermediate gold layer;

[0067] The graphene-copper alloy core treated in step S21 was placed in an intermediate gold plating solution at a temperature of 75°C, and the electroplating pulse current was set to 10 mA / cm. 2Each pulse has a conduction time of 1.5s and a turn-off time of 1.5s. After electroplating to an intermediate gold layer thickness of 80nm, the pulse is stopped, the graphene copper alloy core is removed, and after washing and drying, an intermediate gold layer is formed.

[0068] The intermediate gold plating solution contains gold cyanide at a concentration of 4-8 g / L and composite filler at a concentration of 50-80 mg / L. Ammonia is used to adjust the pH to 11 during use.

[0069] S23. Place the graphene-copper alloy core treated in step S22 into a second palladium electroplating solution at a temperature of 75°C, and set the current to 50 mA / cm². 2 After electroplating to a second palladium layer thickness of 80nm, the graphene copper alloy core is removed, washed, and dried to form the second palladium layer.

[0070] In the second palladium electroplating solution, the concentration of palladium tetraaminodichloride is 10 g / L, the concentration of p-carboxybenzenesulfonamide is 8 mg / L, and the concentration of β-cyanoalanine is 15 mg / L.

[0071] S24. Place the graphene-copper alloy core treated in step S23 into a top-layer gold plating solution at a temperature of 80°C, and set the current to 15 mA / cm. 2 After electroplating to a gold layer thickness of 5nm, the graphene copper alloy core is removed, washed and dried to form a top gold layer, thus obtaining a graphene copper alloy core with a composite coating.

[0072] The concentration of gold cyanide in the top gold plating solution is 12 g / L, and the pH value is adjusted to 11 with ammonia water during use.

[0073] S3. The graphene copper alloy core with composite coating is annealed at a temperature of 600℃, a furnace length of 800mm, and an annealing speed of 40m / min. After annealing, a high corrosion-resistant and high conductivity palladium / gold-plated palladium copper bonding wire is obtained.

[0074] The operation method of Embodiment 31 in this application is as follows:

[0075] A method for preparing a highly corrosion-resistant and highly conductive palladium / gold-plated palladium-copper bonding wire includes the following steps:

[0076] S1. Preparation of graphene-copper alloy core;

[0077] S11. The graphene copper mixed raw material was protected under a nitrogen atmosphere and dried at 80°C for 8 hours. It was then pressed into a billet and placed in an SPS sintering furnace under an argon atmosphere. After applying a pressure of 800kN to the billet, the temperature was increased to 1000°C at a rate of 100°C / min. After sintering into a block, it was cooled to room temperature with the furnace to obtain the graphene copper alloy ingot.

[0078] The preparation method of the graphene-copper hybrid raw material is as follows:

[0079] a1. Prepare the electrolyte;

[0080] Copper sulfate, sulfuric acid, and deionized water were mixed to prepare a mixed solution with a sulfuric acid concentration of 120 g / L and a copper ion concentration of 50 g / L. 5.8 g / L of graphene was added to the electrolyte, and the graphene was evenly dispersed by electromagnetic stirring and ultrasonic dispersion to obtain the electrolyte.

[0081] b1. Using high-purity copper with an impurity element content of 4 ppm as the anode and a pure copper plate as the cathode, electrodeposition was performed at a voltage of 6 V and a current density of 2 mA / cm². 2 After electrodeposition for 40 minutes, the cathode was removed, washed with deionized water, and the graphene copper powder on the cathode surface was collected. After drying, XPS analysis was performed to determine that the carbon-copper bond ratio was 35-45%. The powder was then mixed with oxygen-free copper powder and melted uniformly under an argon atmosphere. After cooling, XPS analysis was performed again to determine that the carbon-copper bond ratio was 3-5%. The powder was then mixed with pure copper powder and melted uniformly. Finally, it was ball-milled to obtain the graphene copper mixed raw material.

[0082] S12. Mix the graphene copper alloy ingot with the reinforcing metal material, protect it with an argon atmosphere, heat it to 1200℃ by electromagnetic induction and melt it. After stirring and mixing for 3 minutes, continuously cast the molten metal liquid into a mother rod with a diameter of 8mm.

[0083] S13. Perform multiple wire drawing and lengthening processes on the mother rod until its diameter is 15-500μm to obtain a graphene copper alloy core;

[0084] S2. Preparation of composite coating;

[0085] S21. Prepare the first palladium layer;

[0086] The cleaned graphene-copper alloy core was placed in a first palladium plating solution at 70°C, and the pulse current was set to 3 mA / cm. 2 Each pulse has a conduction time of 0.5s and a turn-off time of 1.5s. After electroplating to the required first palladium layer thickness of 20nm, the pulse is stopped, the graphene copper alloy core is removed, and after washing and drying, the first palladium layer is formed.

[0087] In the first palladium electroplating solution, the concentration of palladium tetraaminoacetate is 4 g / L, the concentration of p-carboxybenzenesulfonamide is 8 mg / L, and the concentration of composite pore filler is 30 mg / L.

[0088] The composite pore-filling agent is a composition of diethyl dithiophosphate ammonium salt and L-alanine benzyl ester p-toluenesulfonate in a mass ratio of 1:1;

[0089] S22. Preparation of intermediate gold layer;

[0090] The graphene-copper alloy core treated in step S21 was placed in an intermediate gold plating solution at a temperature of 75°C, and the electroplating pulse current was set to 10 mA / cm. 2 Each pulse has a conduction time of 1.5s and a turn-off time of 1.5s. After electroplating to an intermediate gold layer thickness of 80nm, the pulse is stopped, the graphene copper alloy core is removed, and after washing and drying, an intermediate gold layer is formed.

[0091] The intermediate gold plating solution contains gold cyanide at a concentration of 4-8 g / L and composite filler at a concentration of 50-80 mg / L. Ammonia is used to adjust the pH to 11 during use.

[0092] S23. Place the graphene-copper alloy core treated in step S22 into a second palladium electroplating solution at a temperature of 75°C, and set the current to 50 mA / cm². 2 After electroplating to a second palladium layer thickness of 80nm, the graphene copper alloy core is removed, washed, and dried to form the second palladium layer.

[0093] In the second palladium electroplating solution, the concentration of palladium tetraaminodichloride is 10 g / L, the concentration of p-carboxybenzenesulfonamide is 8 mg / L, and the concentration of β-cyanoalanine is 15 mg / L.

[0094] S24. Place the graphene-copper alloy core treated in step S23 into a top-layer gold plating solution at a temperature of 80°C, and set the current to 15 mA / cm. 2 After electroplating to a gold layer thickness of 5nm, the graphene copper alloy core is removed, washed and dried to form a top gold layer, thus obtaining a graphene copper alloy core with a composite coating.

[0095] The concentration of gold cyanide in the top gold plating solution is 12 g / L, and the pH value is adjusted to 11 with ammonia water during use.

[0096] S3. The graphene copper alloy core with composite coating is annealed at a temperature of 600℃, a furnace length of 800mm, and an annealing speed of 40m / min. After annealing, a high corrosion-resistant and high conductivity palladium / gold-plated palladium copper bonding wire is obtained.

[0097] In this application, the reinforcing metal materials used in the embodiments and comparative examples are any one or more of Ag, Pd, Au, Pt, Li, P, Ca, Ni, Be, Y, La, Ce, Zr, In, Ge, and Sc;

[0098] The components of Examples 1-31 and Comparative Examples 1-5 of this application are shown in Tables 1 and 2 below:

[0099] Table 1.

[0100] Table 2.

[0101] Performance tests were performed on the above embodiments and comparative examples;

[0102] High-temperature oxidation resistance test: The core material was processed to 0.8 mil, and wire bonding was performed using a KS ProCuPLUS wire bonding machine with the Coulomb method. The bonding diameter was 35 μm, the pad temperature was 220°C, and the holding time on the pad after bonding was 2 minutes. The color of the solder balls was checked using a 200x optical microscope. Solder balls with 1 / 3 red or black color were considered unacceptable; solder balls with an overall red color were considered average; solder balls with a light yellow color were considered acceptable; solder balls with more than 80% silver-white color and less than 5% light yellow color were considered good; solder balls with all silver-white color were considered excellent.

[0103] FAB testing: The core material is processed to 0.8 mil. Using a KSProCuPLUS wire bonding machine with the Coulomb process, empty-burned balls are produced. EFO conditions are: current 60 mA, time 200 μs, EFOGAP 30 mil, tail elongation 10 mil, nitrogen-hydrogen mixture protection - flow rate 0.5 L / min. The diameter distribution and ball roundness are checked. The target ball diameter is 34 μm. The standard deviation is checked, as well as the roundness and eccentricity of the balls. During testing, 100 empty-burned balls are used. A standard deviation greater than 1.0 is considered unacceptable; a standard deviation between 0.7 and 1 is considered average; a standard deviation between 0.5 and 0.7 is considered acceptable; a standard deviation between 0.3 and 0.5 is considered good; and a standard deviation less than 0.3 is considered excellent.

[0104] HAZ Testing: The core material was processed to 0.8 mil, and empty sintered balls were prepared using a KSProCuPLUS wire bonding machine with the Coulomb process. The EFO conditions were: current 60 mA, time 200 μs, EFOGAP 30 mil, tail elongation 10 mil, nitrogen-hydrogen mixed gas protection - flow rate 0.5 L / min. A standard-length empty sintered ball was taken and attached to an aluminum sample stage using carbon tape. It was then polished with an argon ion polisher at 15° for 30 min. The length of the heat-affected zone (HAZ) of the processed sample was checked using SEM, with the absence of recrystallization of the grains as the boundary. During testing, a HAZ length greater than 150 μm was considered unacceptable, between 130-150 μm was considered average, between 110-130 μm was considered acceptable, between 90-110 μm was considered good, and less than 90 μm was considered excellent.

[0105] Long-line arc shape inspection: The core material is processed to 0.8mil, and a 10mm long arc is formed using a KSProCuPLUS wire forming machine with the Kuleshov method. SEM is used to inspect the arc and detect the deviation from the target straight line. A deviation of 1.5 times the wire diameter is considered a deviation. During inspection, a deviation of more than 2 times the wire diameter is considered unacceptable; 1.5-2 times the wire diameter is considered average; 1.3-1.5 times the wire diameter is considered acceptable; 1.1-1.3 times the wire diameter is considered good; and 1.1 times the wire diameter is considered excellent.

[0106] One-point thrust test: The core material is processed to 0.8mil, and wire bonding is performed normally using a KSProCuPLUS wire bonding machine. After bonding, a TST-8300D push-pull force tester is used to push off one solder ball to measure the thrust. The higher the thrust value, the better. During the test, a thrust less than 12g is unqualified; a thrust between 12-14g is fair; a thrust between 14-16g is qualified; a thrust between 16-20g is good; and a thrust greater than 20g is excellent.

[0107] Two-point tensile strength test: The core material is processed to 0.8mil. A KSProCuPLUS wire bonding machine using the Coulomb method is used for normal wire bonding. After bonding, a TST-8300D push-pull force tester is used to measure the two-point tensile strength by hooking the apex of the wire arc. The higher the push force value, the better. During the test, a two-point tensile strength of less than 3g is unqualified, between 3-4g is fair, between 4-5g is qualified, between 5-6g is good, and greater than 6g is excellent.

[0108] Cleaver wear test: The core material was processed to 0.8 mil. A KS ProCuPLUS wire bonding machine with an SPT SU-25063-303F-RU34TP cleaver was used for normal wire bonding. After bonding 40W points, the spherical and fishtail morphologies of each solder joint were examined using a high-power microscope. SEM was then used to observe the wear morphology of the CD area at the cleaver tip. The spheres were intact, the protein was uniform, and the fishtail was uniform without any missing corners. The smaller the wear in the CD area, the better the performance. During testing, a fishtail width less than 1.5 times the wire width was considered unqualified; between 1.5 and 2 times was considered average; between 2 and 2.5 times was considered qualified; between 2.5 and 3 times was considered good; and between 2.5 and 3 times was considered excellent.

[0109] Aluminum extrusion detection: Process the core material to 0.8 mil. Use the Kulico KS ProCuPLUS wire bonding machine and the SPT SU-25063-303F-RU34TP split blade for normal wire bonding. Use a high-power microscope to check the size of the aluminum extrusion at a point. The smaller the size, the better. During the detection, if the Al extrusion size exceeds 2.5 times the wire diameter, it is unqualified; if the Al extrusion size is within 2 - 2.2 times the wire diameter, it is average; if the Al extrusion size is within 1.9 - 2 times the wire diameter, it is qualified; if the Al extrusion size is within 1.8 - 1.9 times the wire diameter, it is good; if the AL extrusion size is within 1.8 times the wire diameter, it is excellent;

[0110] Crater detection: Process the core material to 0.8 mil. Use the Kulico KS ProCuPLUS wire bonding machine and the SPT SU-25063-303F-RU34TP split blade. Set the power of a point to the maximum for wire bonding. Observe whether there is any damage after the chip pad is combined with the bonding ball. Before observation, use a mixed solution of nitric acid and hydrochloric acid to remove the bonding ball without affecting the chip. After removing the bonding wire, if there are obvious visible pits on the silicon layer, gently scratch around the solder ball with a small knife. If there is an obvious pit in the touch feeling, it is a serious defect and unqualified; if there are slight pit marks on the aluminum layer, gently scratch around the solder ball with a small knife. If there is no obvious pit in the contact, it is a minor defect and qualified; if the silicon layer surface is smooth without pit marks, it is qualified. During the detection, if there is an obvious pit in the touch feeling when gently scratching around the solder ball with a small knife, it is a serious defect and unqualified; if there are slight pits on the aluminum layer, and there is no obvious pit in the contact when gently scratching around the solder ball with a small knife, it is a minor defect. If the proportion of minor pits in the number of test chips is more than 25%, it is average; if the proportion of minor pits in the number of test chips is within 5 - 10%, it is qualified; if the proportion of minor pits in the number of test chips is within 5%, it is good; if the silicon layer surface is smooth without pit marks, it is excellent;

[0111] Hast detection: Process the core material to 0.8 mil. Use the Kulico KS ProCuPLUS wire bonding machine and the SPT SU-25063-303F-RU34TP split blade. After normal wire bonding and encapsulation, 23 pieces are subjected to a high-pressure steam cooking test for accelerated testing (HAST, the detection conditions are a temperature of 130°C and 85% RH). It is required that all 23 pieces pass the OS open / short circuit test after the accelerated test to be considered passed. If it fails within 192H, it is unqualified; if it passes within 192H, it is average; if it passes within 480H, it is qualified; if it passes within 672H, it is good; if it passes within 864H, it is excellent;

[0112] Conductivity testing: Cut 1m of the finished wire and measure the wire diameter using a laser diameter gauge. Then measure its resistance at ambient temperatures of 20℃ and 100℃: Resistance greater than 2.4μΩ·cm at room temperature is unacceptable; resistance less than 1.9μΩ·cm at room temperature and less than 2.4μΩ·cm at high temperature is acceptable; resistance less than 1.85μΩ·cm at room temperature and less than 2.3μΩ·cm at high temperature is acceptable; resistance less than 1.8μΩ·cm at room temperature and less than 2.2μΩ·cm at high temperature is good; resistance less than 1.75μΩ·cm at room temperature and less than 2.0μΩ·cm at high temperature is excellent.

[0113] The test results are shown in Tables 3 and 4 below. The results are presented from left to right, and from worst to best: a→b→c→d→e.

[0114] Among them, a corresponds to unqualified, b corresponds to average, c corresponds to qualified, d corresponds to good, and e corresponds to excellent.

[0115] Table 3.

[0116] Table 4.

[0117] Another set of comparative examples 6-8;

[0118] In Comparative Example 6, compared to Example 1, no composite pore-filling agent was added to the first palladium plating solution and the intermediate gold plating solution.

[0119] Compared with Example 1, Comparative Example 7 did not use pulsed current electroplating when electroplating the first palladium layer and the intermediate gold layer.

[0120] Compared with Example 1, Comparative Example 8 did not use a composite pore filler and pulsed current electroplating when electroplating the first palladium layer and the intermediate gold layer.

[0121] The bonding fibers prepared in Example 1 and Comparative Examples 6-8 were drawn again, with a stretching elongation of 12%, and were tested after stretching.

[0122] The appearance morphology of the coatings in Example 1 and Comparative Examples 6-8 was examined using an optical microscope.

[0123] The bonding wires prepared in Example 1 and Comparative Examples 6-8 were subjected to a relative bending-straightening test repeated 50 times. The bending point showed a semicircle with a diameter of 1 cm. After the test, the appearance of the coating was checked.

[0124] The inspection results are shown in Table 5 below;

[0125] Table 5.

[0126] The micrograin size of the cross section of Example 1 was also measured, and the results are shown in Figure 1.

[0127] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A highly corrosion-resistant and highly conductive palladium / gold-plated palladium-copper bonding wire, characterized in that: The high corrosion-resistant and high conductivity palladium / gold-plated palladium-copper bonding wire consists of a graphene copper alloy core and a composite coating covering the outside of the graphene copper alloy core. The diameter of the high corrosion resistance and high conductivity palladium / gold palladium-copper bonding wire is 15-500μm, and the thickness of the composite coating is 51-185nm. The composite coating consists of a first palladium layer, an intermediate gold layer, a second palladium layer, and a top gold layer from bottom to top.

2. The high corrosion resistance and high conductivity palladium / gold palladium-copper bonding wire according to claim 1, characterized in that: The grain size within the interface of the graphene-copper alloy core is 0.1-200 μm; The graphene copper alloy core contains 100-10000ppm of graphene and 5-5000ppm of reinforcing metal material. The reinforcing metal material is any one or more of Ag, Pd, Au, Pt, Li, P, Ca, Ni, Be, Y, La, Ce, Zr, In, Ge, and Sc.

3. The high corrosion resistance and high conductivity palladium / gold palladium-copper bonding wire according to claim 2, characterized in that: The graphene copper alloy core contains 300-3000 ppm of graphene and 0-3000 ppm of reinforcing metal material. The reinforcing metal material is any one or more of Au, Pd, In, P, Ni, Ca, Li, and Sc; When the reinforced metal material contains any one of P, Li, or Sc, the amount of each component added is 0-300 ppm.

4. The high corrosion resistance and high conductivity palladium / gold palladium-copper bonding wire according to claim 1, characterized in that: In the composite coating, the thickness of the first palladium layer is 10-20 nm, the thickness of the intermediate gold layer is 20-80 nm, the thickness of the second palladium layer is 20-80 nm, and the thickness of the top gold layer is 1-5 nm.

5. A method for preparing a high corrosion-resistant and high conductivity palladium / gold-plated palladium-copper bonding wire as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Preparation of graphene-copper alloy core; S11. The graphene copper mixed raw material is protected under a nitrogen atmosphere and dried in an environment of 40-80℃ for 1-12 hours. It is then pressed into a billet and placed in an SPS sintering furnace under an argon atmosphere. A pressure of 100-1000kN is applied to the billet, and the temperature is raised to 900-1200℃ at a rate of 90-110℃ / min. After sintering into a block, it is cooled to room temperature with the furnace to obtain the graphene copper alloy ingot. S12. Mix the graphene copper alloy ingot with the reinforcing metal material, protect it with an argon atmosphere, heat it to 1050-1250℃ by electromagnetic induction and melt it. After stirring and mixing for 10s-15min, continuously cast the molten metal into a mother rod with a diameter of 8mm. S13. Perform multiple wire drawing and lengthening processes on the mother rod until its diameter is 15-500μm to obtain a graphene copper alloy core; S2. Preparation of composite coating; S21. Prepare the first palladium layer; The cleaned graphene-copper alloy core was placed in a first palladium plating solution at a temperature of 70-75℃, and the pulse current was set to 3-5 mA / cm. 2 Each pulse has a conduction time of 0.5-1s and a turn-off time of 0.5-2s. After electroplating to the required first palladium layer thickness, the pulse is stopped, the graphene copper alloy core is removed, and after washing and drying, the first palladium layer is formed. S22. Preparation of intermediate gold layer; The graphene-copper alloy core treated in step S21 is placed in an intermediate gold plating solution at a temperature of 70-80℃, and the electroplating pulse current is set to 5-15mA / cm. 2 Each pulse has a conduction time of 1.5-3s and a turn-off time of 0.5-2s. After electroplating to the required thickness, the pulse is stopped, the graphene copper alloy core is removed, and after washing and drying, an intermediate gold layer is formed. S23. Place the graphene-copper alloy core treated in step S22 into a second palladium electroplating solution at a temperature of 70-80℃, and set the current to 10-60 mA / cm. 2 After electroplating to the required thickness, the graphene copper alloy core is removed, washed, and dried to form the second palladium layer; S24. Place the graphene-copper alloy core treated in step S23 into a top-layer gold plating solution at a temperature of 70-80℃, and set the current to 10-60mA / cm. 2 After electroplating to the required thickness, the graphene copper alloy core is removed, washed and dried to form a top gold layer, resulting in a graphene copper alloy core with a composite coating. S3. Anneal the graphene copper alloy core with composite coating at a temperature of 400-700℃, a furnace length of 600-1000mm, and an annealing speed of 40-140m / min. After annealing, a high corrosion-resistant and high conductivity palladium / gold-plated palladium copper bonding wire is obtained.

6. The method for preparing the high corrosion resistance and high conductivity palladium / gold palladium-copper bonding wire according to claim 5, characterized in that: The preparation method of the graphene-copper hybrid raw material includes the following steps: a1. Prepare the electrolyte; Copper sulfate, sulfuric acid and deionized water are mixed to prepare a mixed solution with a sulfuric acid concentration of 10-200 g / L and a copper ion concentration of 10-100 g / L. 1-20 g / L of graphene is added to the electrolyte. After electromagnetic stirring and ultrasonic dispersion to make the graphene evenly dispersed, the electrolyte is obtained. b1. Using high-purity copper with an impurity element content of 0-10 ppm as the anode and a pure copper plate as the cathode, electrodeposition is performed with an applied voltage of 2-10 V and a current density of 1-10 mA / cm². 2 After electrodeposition for 10-60 minutes, the cathode is removed, washed with deionized water, and the graphene copper powder on the cathode surface is collected. After drying, XPS analysis is performed to determine that the carbon-copper bond ratio is 35-45%. The graphene copper powder is then mixed with oxygen-free copper powder and melted uniformly under an argon atmosphere. After cooling, XPS analysis is performed again to determine that the carbon-copper bond ratio is 3-5%. The graphene copper powder is then mixed with pure copper powder, melted uniformly, and ball-milled to obtain the graphene copper mixed raw material.

7. The method for preparing the high corrosion resistance and high conductivity palladium / gold palladium-copper bonding wire according to claim 5, characterized in that: The preparation method of the graphene-copper hybrid raw material includes the following steps: a2. Disperse graphene in ultrapure water, stir electromagnetically and ultrasonically disperse and wash for 0.5-1 h, then filter by suction filtration. Repeat 2-3 times and test the pH value of the filtrate. If the pH value is within the range of 6.3-7, the cleaning is qualified. Otherwise, repeat the above steps to wash the graphene with ultrapure water until the pH value of the filtrate is qualified. Dry the cleaned graphene in a nitrogen atmosphere and cool it for later use. b2. After cleaning, the graphene is mixed with high-purity oxygen-free copper powder and then ball-milled at low temperature for 3-24 hours. The ball milling speed is 100-1200 rpm, the protective gas is nitrogen, and the plasma working power is 10-400W. After the ball milling is completed, the graphene-copper mixture raw material is obtained.

8. The method for preparing the high corrosion resistance and high conductivity palladium / gold palladium-copper bonding wire according to claim 5, characterized in that: The first palladium plating solution comprises palladium tetraaminoacetate, p-carboxybenzenesulfonamide, and a composite pore-filling agent; In the first palladium electroplating solution, the concentration of palladium tetraaminoacetate is 3-5 g / L, the concentration of p-carboxybenzenesulfonamide is 5-15 mg / L, and the concentration of composite pore filler is 25-55 mg / L. The composite pore-filling agent is a composition of diethyl dithiophosphate ammonium salt and L-alanine benzyl ester p-toluenesulfonate in a mass ratio of 1:1; The second palladium electroplating solution includes palladium tetraaminodichloride, p-carboxybenzenesulfonamide, and β-cyanoalanine; In the second palladium electroplating solution, the concentration of tetraaminodichloride palladium is 5-10 g / L, the concentration of p-carboxybenzenesulfonamide is 5-10 mg / L, and the concentration of β-cyanoalanine is 10-20 mg / L. The intermediate gold plating solution includes gold cyanide and a composite pore filler; In the intermediate gold plating solution, the concentration of gold cyanide is 4-8 g / L, and the concentration of composite pore filler is 50-80 mg / L; The top gold plating solution includes gold cyanide, with a gold cyanide concentration of 5-15 g / L; When using the intermediate gold plating solution and the top gold plating solution, the pH value is adjusted to 10-12 with ammonia water.

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