High-reliability gold-plated palladium copper wire for IC packaging and preparation method thereof

Abstract

The application belongs to the technical field of integrated circuits, and particularly relates to a high-reliability gold-plated palladium copper wire for IC packaging and a preparation method thereof. The high-reliability gold-plated palladium copper wire for IC packaging comprises a copper wire base body, a palladium plating layer coated on the surface of the copper wire base body, and a gold plating layer coated on the surface of the palladium plating layer. The copper wire base body comprises the following raw materials in percentage by mass: Mg 0.001-0.01%, Pd 0.045-0.1%, Ce 0.008-0.03%, and the balance of Cu. The high-reliability gold-plated palladium copper wire for IC packaging has good mechanical properties, high bonding push-pull force, and high bonding reliability.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuit technology, specifically relating to a high-reliability gold-plated palladium-copper wire for IC packaging and its preparation method. Background Technology

[0002] The role of IC (integrated circuit) packaging is to support and protect semiconductor devices, preventing physical and chemical damage while ensuring a reliable electrical connection between the chip and external circuits. Bonding wires are one of the key materials in semiconductor packaging, responsible for establishing the electrical connection between the semiconductor chip and its pins, acting as the current introducer and extractor. Types of bonding wires include copper, aluminum, silver, gold, and alloy wires. However, bonding wires made of a single material have different drawbacks. For example, while copper bonding wires are low-cost, they have poor oxidation resistance and high hardness; gold bonding wires offer high reliability but are expensive. Therefore, developing low-cost, high-performance, and high-reliability bonding wires using composite and modified methods is of great significance.

[0003] Gold-plated palladium copper wire is a composite bonding wire made by first plating palladium on the surface of copper wire and then flash plating gold. Compared with bonded copper wire, it has a longer shelf life and better oxidation resistance, and it can form a more stable arc than bonded alloy wire, while also being cheaper.

[0004] The applicant has previously conducted research and development on gold-plated palladium-copper wire and applied for a Chinese invention patent for a gold-plated palladium-copper wire and its preparation method, publication number CN118685830A. The preparation method includes the following steps: Step 1, annealing treatment to obtain a first copper wire substrate; Step 2, ultrasonic cleaning to obtain a second copper wire substrate; Step 3, palladium plating treatment to obtain a third copper wire substrate; Step 4, gold plating treatment to obtain a fourth copper wire substrate; Step 5, ultrasonic cleaning treatment to obtain the gold-plated palladium-copper wire. The palladium or gold layer treated by this invention not only has a more uniform surface distribution and better flatness, but is also less prone to delamination and delamination, thus maintaining the surface uniformity of the gold-plated palladium-copper wire. Furthermore, the gold-plated palladium-copper wire prepared by this invention also exhibits superior strength and salt spray resistance. However, the applicant found that the balling reliability and bonding reliability of this technical solution need improvement. Based on this, the applicant hereby proposes this invention. Summary of the Invention

[0005] The present invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial solution. Specifically, the present invention provides a high-reliability gold-plated palladium-copper wire for IC packaging and a method for preparing the same. The prepared gold-plated palladium-copper wire has good mechanical properties, high bonding push-pull force, and high bonding reliability.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a high-reliability gold-plated palladium copper wire for IC packaging, comprising a copper wire substrate, a palladium plating layer covering the surface of the copper wire substrate, and a gold plating layer covering the surface of the palladium plating layer.

[0008] The copper wire matrix comprises the following raw materials in the following mass percentages: Mg 0.001-0.01%, Pd 0.045-0.1%, Ce 0.008-0.03%, with the balance being Cu.

[0009] In some preferred embodiments, the purity of Cu is 99.999%.

[0010] In some preferred embodiments, the diameter of the copper wire substrate is 55-85 μm.

[0011] In some preferred embodiments, the thickness of the palladium coating is 60-100 nm.

[0012] In some preferred embodiments, the thickness of the gold plating layer is 1-10 nm.

[0013] The copper wire matrix of this invention, by doping with specific amounts of trace elements Mg, Pd, and Ce, achieves the following beneficial effects: First, it forms low-density compounds with impurities in the copper raw material, producing scum, floating and stratifying, or forming high-melting-point compounds with impurities, becoming the nucleation core, thereby shielding harmful impurities in the copper raw material that cannot be completely removed, thus purifying the copper wire matrix; Second, it significantly improves the oxidation resistance and sulfidation resistance of the copper wire matrix; Third, it significantly improves the corrosion resistance of the copper wire matrix; Fourth, it significantly improves the comprehensive mechanical properties of the copper wire matrix: refining grains while improving strength and plasticity; grain boundary pinning, enhancing strength; changing the Young's modulus of the substrate, increasing the plasticity of the material; Fifth, it significantly increases the surface tension of the molten state of the matrix, strengthening the uniformity of spheroidization.

[0014] Furthermore, and more importantly, by doping with specific amounts of trace elements Mg, Pd, and Ce, this invention, during bonding, allows these trace elements to co-generate Cu-Al-Me ternary or higher compounds with Cu and Al, altering the morphology of the IMC (intermetallic compound) and improving its brittleness, thereby further enhancing the reliability of the solder joint. In addition, the Au and Pd plating layer at the bottom of the FAB spherical (airless) structure also participates in the formation of a ternary alloy that is soluble in Cu9Al4, altering the crystal structure and mitigating brittleness. It can also adsorb at the CuAl2 and CuAl grain boundaries to inhibit diffusion growth, thus enabling the gold-plated palladium copper wire of this invention to have high reliability.

[0015] Secondly, the present invention provides a method for preparing the above-mentioned high-reliability gold-plated palladium-copper wire for IC packaging, comprising the following steps:

[0016] S1. Under the protection of an inert gas atmosphere, Mg, Pd and Ce are added to Cu and melted and cast into round bars. The round bars are drawn into wires to obtain copper wire matrix.

[0017] S2. The copper wire substrate obtained in step S1 is electrolyzed for degreasing and acid pickling activation, and then plated with palladium and gold to obtain a semi-finished product.

[0018] S3. The semi-finished product obtained in step S2 is annealed for the first time to obtain the finished product. The finished product is drawn and annealed for the second time to obtain the gold-plated palladium copper wire.

[0019] The electroplating process for the high-reliability gold-plated palladium copper wire provided by this invention is a semi-finished product electroplating process, that is, after plating palladium and gold on the copper wire substrate, wire drawing is continued. This process can seal the pinholes in the electroplating layer, obtaining a dense and smooth finished wire. Due to the good quality of the plating layer, the reliability is further improved.

[0020] In some preferred embodiments, in step S1, the melting and casting conditions are: melting and casting at 1150-1300℃ for 60-80 minutes, and cooling by water cooling at a rate of 2-10L / h.

[0021] This invention reduces the burn-off of active components by using specific casting conditions, ensuring uniform composition. At the same time, it promotes axial orientation crystallization of the cast rod, which facilitates subsequent wire drawing, ensures uniform grain size in the finished product, improves the density of the round rod, and reduces defects and voids in the round rod.

[0022] In some preferred embodiments, in step S2, the degreasing solution used for electrolytic degreasing includes the following raw materials: sodium hydroxide 8-15 g / L, sodium carbonate 1-5 g / L, sodium silicate 0.5-2 g / L, gluconic acid 0.03-0.06 g / L, natural protein 0.03-0.06 g / L, and the balance being deionized water.

[0023] Preferably, in step S2, the degreasing solution used for electrolytic degreasing includes the following raw materials: sodium hydroxide 12g / L, sodium carbonate 3g / L, sodium silicate 1g / L, gluconic acid 0.05g / L, natural protein 0.05g / L, and the balance being deionized water.

[0024] In some preferred embodiments, the natural protein is natural L-methionine.

[0025] In some preferred embodiments, in step S2, the electrolytic degreasing process involves first using cathode electrolysis to remove oil, and then using an anode electrode to remove oil.

[0026] In some preferred embodiments, the temperature for cathode electrolysis is 40-50°C, and the current density is 1-5 A / dm³. 2The speed is 5-30 m / min.

[0027] In some preferred embodiments, the temperature for anodic electrolysis is 40-50°C, and the current density is 3-8 A / dm³. 2 The speed is 5-30 m / min.

[0028] Before electroplating, the copper wire substrate needs to be thoroughly cleaned, usually by electrolytic degreasing in an alkaline environment. Studies have found that when using cathodic electrolysis for degreasing, due to the small atomic fraction of hydrogen, a large amount of atomic hydrogen can be generated at a certain current density, resulting in good dispersion, small bubble size, strong emulsification, good degreasing effect, fast degreasing speed, and no corrosion to parts. However, there are also disadvantages: the generated hydrogen may penetrate into the metal and cause hydrogen embrittlement. In addition, when the electrolyte solution contains a small amount of active metal particles, a layer of spongy metal will be deposited on the surface of the copper wire substrate, which will contaminate the copper wire substrate and affect the adhesion of the coating. When using anodic electrolysis for degreasing, oxygen is generated on the copper wire substrate. At a certain current density, the number of atomic oxygen bubbles generated is small and large. Compared with cathodic electrolysis, its emulsification ability is weaker, so the efficiency of anodic electrolysis is relatively low. In addition, due to the discharge of hydroxide ions, the pH value of the solution on the anode surface decreases, which is not conducive to degreasing. However, anodic electrolysis does not produce hydrogen embrittlement, and there is no spongy substance deposited on the copper wire substrate.

[0029] The electrolytic degreasing process provided by this invention first employs cathodic electrolytic degreasing, followed by a short-time anodic electrolytic degreasing. During cathodic degreasing, hydrogen gas that has penetrated into the metal can be almost completely removed during anodic degreasing, while the surface of the copper wire substrate will not be excessively oxidized or corroded.

[0030] Existing degreasing solutions are typically alkaline sodium hydroxide solutions. However, sodium hydroxide is highly corrosive; while it can remove oil stains, it can also easily damage the surface of the copper wire substrate. The degreasing solution provided by this invention, through the combined action of its components, not only avoids the excessive use of sodium hydroxide but also prevents damage to the copper wire substrate surface. In particular, the addition of natural protein, utilizing its buffering properties, can effectively adsorb suspended colloidal oil particles and cause them to agglomerate, thus effectively removing various types of oil stains, thereby improving the adhesion of the coating and enhancing the reliability of the gold-plated palladium copper wire.

[0031] In some preferred embodiments, the activator used in step S2 for acid washing activation includes the following raw materials: 10-35 g / L of branched fatty alcohol alkoxyl surfactant, 15-120 g / L of active protein, 20-45 g / L of inorganic acid, and the balance being deionized water.

[0032] In some preferred embodiments, the active protein is chloromeththiobutyric acid or D-2-amino-4-meththiobutyric acid.

[0033] In some preferred embodiments, the inorganic acid is sulfuric acid or phosphoric acid.

[0034] In some preferred embodiments, the pickling activation temperature is 20-50°C and the rate is 5-30 m / min.

[0035] After electrolytic degreasing, the copper wire substrate requires surface activation to facilitate plating. The activator provided by this invention is an acidic system primarily composed of sulfuric acid / phosphoric acid, employing specific branched fatty alcohol alkoxylated surfactants and active proteins. The branched fatty alcohol alkoxylated surfactants drive other components to penetrate into the oxide layer, causing self-peeling of the oxide layer. This, combined with acidic ions, accelerates the removal of the oxide layer and microscopic protrusions on the copper wire substrate surface. The active protein ensures the copper wire substrate is not severely corroded. Simultaneously, the synergistic effect of the active protein and sulfuric acid / phosphoric acid activates the copper wire substrate surface, shielding it from the adverse effects of slightly soluble Cu ions on palladium plating and ensuring the adhesion between the plating layer and the copper wire substrate. Furthermore, the synergistic effect of the branched fatty alcohol alkoxylated surfactants, active proteins, and sulfuric acid / phosphoric acid makes the copper wire substrate surface smoother, achieving a brightening, polishing, and leveling effect, ultimately achieving rapid oxide layer removal and further enhancing the adhesion of the plating layer to the copper wire substrate.

[0036] In some preferred embodiments, in step S2, the palladium plating solution used for palladium plating includes the following raw materials: 10-25 g / L dichlorodiaminopalladium, 20-30 g / L ammonium chloride, 35-60 g / L ammonia water, and the balance being deionized water.

[0037] In some preferred embodiments, the palladium plating current is 45-130mA and the plating speed is 3-8m / s.

[0038] In some preferred embodiments, in step S2, the gold plating solution used for gold plating includes the following raw materials: potassium gold citrate 6-12 g / L, potassium carbonate 40-60 g / L, dodecylpyridine hydrochloride 0.4-1 g / L, pyridine sulfonic acid 0.3-0.8 g / L, triethanolamine 0.2-0.5 g / L, and the balance is deionized water, with the pH adjusted to 5.5-6.5 using a pH adjuster.

[0039] In some preferred embodiments, the pH adjuster is selected from at least one of sulfuric acid, sulfurous acid, sodium hydroxide, potassium hydroxide, and ammonia.

[0040] In some preferred embodiments, the electroplating current for gold plating is 10-50 mA, and the electroplating speed is 5-30 m / s.

[0041] In some preferred embodiments, in step S3, the atmosphere for the first annealing is nitrogen and hydrogen in a volume ratio of 95:5, the temperature is 400-650°C, and the speed is 45-60 m / min.

[0042] In some preferred embodiments, in step S3, the atmosphere for the second annealing is nitrogen, the temperature is 350-550°C, and the speed is 47-100 m / min.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1. By doping with specific amounts of trace elements such as Mg, Pd and Ce, the gold-plated palladium copper wire of this invention has good mechanical properties, with a maximum force of 7.22 gf, a total elongation at break of 11.08%, and a Young's modulus of elasticity of 1997.12 MPa, improving workability, widening the working window, and increasing reliability.

[0045] 2. This invention adopts a cathode-anode electrolytic degreasing process, which improves the reliability of gold-plated palladium copper wire under specific degreasing solution and activator. The bonding thrust reaches 30.01gf, the first weld pull reaches 6.64gf, the second weld pull reaches 6.67gf, the third weld pull reaches 5.75gf, and the IMC thickness is less than 1μm. Attached Figure Description

[0046] Figure 1 The images shown are electron microscope images of the ball-shaped, first-weld, and second-weld points of the high-reliability gold-plated palladium-copper wire bonding FAB for IC packaging according to Embodiment 1 of the present invention.

[0047] Figure 2 This is an appearance diagram of a high-reliability gold-plated palladium-copper wire bonding solder joint for IC packaging according to Embodiment 1 of the present invention.

[0048] Figure 3 For comparison, electron microscope images of the gold-plated palladium copper wire bonded FAB spheres, first weld, and second weld point of sample 1 are shown.

[0049] Figure 4 For comparison, see the appearance of the gold-plated palladium-copper wire bonding solder joint of sample 1;

[0050] Figure 5 This is a spherical electron microscope image of the gold-plated palladium-copper wire bonded FAB of Comparative Example 1 of the present invention;

[0051] Figure 6 This is a spherical electron microscope image of the gold-plated palladium-copper wire bonded FAB of Comparative Example 4 of the present invention;

[0052] Figure 7 This is a spherical electron microscope image of the gold-plated palladium-copper wire bonded FAB of Comparative Example 6 of the present invention. Detailed Implementation

[0053] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0054] Unless otherwise specified, the raw materials, reagents or apparatus used in the following examples and comparative examples are available from conventional commercial sources or can be obtained by existing known methods.

[0055] In this invention, the conversion of mass percentage units is as follows: 1 ppm = 0.0001%. For ease of description, ppm is used to express mass percentage in both the examples and comparative examples.

[0056] The following is some information about the raw materials:

[0057] The natural protein is natural L-methionine, sourced from Hubei Hanwei Chemical Co., Ltd.

[0058] The active protein is chloromethylthiobutyric acid, produced by Shanghai Jizhi Biochemical Technology Co., Ltd.

[0059] Branched fatty alcohol alkoxylated surfactant: Dow TERGITOL CA-60;

[0060] Comparison Sample 1: Manufacturer Nippon Steel, gold-plated palladium copper wire model: EX1p, diameter: 20μm;

[0061] Comparison sample 2, manufactured by Nippon Tanaka, uses gold-plated palladium copper wire, model CLR-1A, with a diameter of 20μm.

[0062] Comparison sample 3 is from Korea Mke, with gold-plated palladium copper wire model: APC, and a diameter of 20μm.

[0063] Example 1

[0064] This embodiment provides a high-reliability gold-plated palladium copper wire for IC packaging, including a copper wire substrate (diameter of 58.72μm), a palladium plating layer (thickness of 80nm) covering the surface of the copper wire substrate, and a gold plating layer (thickness of 2nm) covering the surface of the palladium plating layer.

[0065] The copper wire matrix comprises the following raw materials by mass percentage: Mg 60ppm, Pd 800ppm, Ce 200ppm, with the balance being Cu with a purity of 99.999%.

[0066] The above-mentioned method for preparing high-reliability gold-plated palladium-copper wire for IC packaging includes the following steps:

[0067] S1. Under the protection of an inert gas atmosphere, Mg, Pd and Ce are added to Cu, and the mixture is melted and cast at 1200℃ for 70 min. Water cooling is used for cooling, with a cooling water volume of 5 L / h. The mixture is melted and cast into round bars, and the round bars are drawn into wires to obtain copper wire matrix.

[0068] S2. The copper wire substrate obtained in step S1 is electrolyzed for degreasing and acid pickling activation, and then plated with palladium and gold to obtain a semi-finished product.

[0069] In step S2, the degreasing solution used includes the following raw materials: sodium hydroxide 12g / L, sodium carbonate 3g / L, sodium silicate 1g / L, gluconic acid 0.05g / L, natural protein 0.05g / L, and the balance is deionized water;

[0070] The activator used includes the following raw materials: 20 g / L branched fatty alcohol alkoxylated surfactant, 80 g / L active protein, 40 g / L phosphoric acid, and the balance being deionized water;

[0071] The palladium plating solution used includes the following raw materials: 15 g / L dichlorodiaminopalladium, 25 g / L ammonium chloride, 45 g / L ammonia water, and the balance being deionized water;

[0072] The gold plating solution used includes the following raw materials: potassium gold citrate 8g / L, potassium carbonate 50g / L, dodecylpyridine hydrochloride 0.6g / L, pyridine sulfonic acid 0.5g / L, triethanolamine 0.3g / L, and the balance is deionized water. The pH is adjusted to 6.0 by a pH adjuster, which is sodium hydroxide.

[0073] S3. The semi-finished product obtained in step S2 is annealed for the first time to obtain the finished product. The finished product is drawn and annealed for the second time to obtain the gold-plated palladium-copper wire with a diameter of 20μm.

[0074] The above electrolytic degreasing process first uses cathodic electrolytic degreasing (temperature 45℃, current density 3A / dm³). 2 At a speed of 20 m / min, oil is removed using an anode electrode (temperature 45℃, current density 6 A / dm). 2 The pickling activation temperature was 40℃, and the plating speed was 20 m / min. The palladium plating current was 70 mA, and the plating speed was 5 m / s. The gold plating current was 30 mA, and the plating speed was 20 m / s. The first annealing atmosphere was nitrogen and hydrogen in a volume ratio of 95:5, at a temperature of 500℃ and a plating speed of 50 m / min. The second annealing atmosphere was nitrogen, at a temperature of 450℃, and a plating speed of 80 m / min.

[0075] Example 2

[0076] This embodiment provides a high-reliability gold-plated palladium copper wire for IC packaging, including a copper wire substrate (diameter of 58.72μm), a palladium plating layer (thickness of 80nm) covering the surface of the copper wire substrate, and a gold plating layer (thickness of 2nm) covering the surface of the palladium plating layer.

[0077] The copper wire matrix comprises the following raw materials by mass percentage: Mg 30ppm, Pd 600ppm, Ce 100ppm, with the balance being Cu with a purity of 99.999%.

[0078] The above-mentioned method for preparing high-reliability gold-plated palladium-copper wire for IC packaging includes the following steps:

[0079] S1. Under the protection of an inert gas atmosphere, Mg, Pd and Ce are added to Cu, and the mixture is melted and cast at 1200℃ for 70 min. Water cooling is used for cooling, with a cooling water volume of 5 L / h. The mixture is melted and cast into round bars, and the round bars are drawn into wires to obtain copper wire matrix.

[0080] S2. The copper wire substrate obtained in step S1 is electrolyzed for degreasing and acid pickling activation, and then plated with palladium and gold to obtain a semi-finished product.

[0081] In step S2, the degreasing solution used includes the following raw materials: sodium hydroxide 8g / L, sodium carbonate 1g / L, sodium silicate 0.54g / L, gluconic acid 0.03g / L, natural protein 0.03g / L, and the balance is deionized water;

[0082] The activator used includes the following raw materials: 15 g / L branched fatty alcohol alkoxylated surfactant, 40 g / L active protein, 20 g / L sulfuric acid, and the balance being deionized water;

[0083] The palladium plating solution used includes the following raw materials: 15 g / L dichlorodiaminopalladium, 25 g / L ammonium chloride, 45 g / L ammonia water, and the balance being deionized water;

[0084] The gold plating solution used includes the following raw materials: potassium gold citrate 8g / L, potassium carbonate 50g / L, dodecylpyridine hydrochloride 0.6g / L, pyridine sulfonic acid 0.5g / L, triethanolamine 0.3g / L, and the balance is deionized water. The pH is adjusted to 6.0 by a pH adjuster, which is sodium hydroxide.

[0085] S3. The semi-finished product obtained in step S2 is annealed for the first time to obtain the finished product. The finished product is drawn and annealed for the second time to obtain the gold-plated palladium-copper wire with a diameter of 20μm.

[0086] The above electrolytic degreasing process first uses cathodic electrolytic degreasing (temperature 45℃, current density 3A / dm³). 2At a speed of 20 m / min, oil is removed using an anode electrode (temperature 45℃, current density 6 A / dm). 2 The pickling activation temperature was 40℃, and the plating speed was 20 m / min. The palladium plating current was 70 mA, and the plating speed was 5 m / s. The gold plating current was 30 mA, and the plating speed was 20 m / s. The first annealing atmosphere was nitrogen and hydrogen in a volume ratio of 95:5, at a temperature of 500℃ and a plating speed of 50 m / min. The second annealing atmosphere was nitrogen, at a temperature of 450℃, and a plating speed of 80 m / min.

[0087] Example 3

[0088] This embodiment provides a high-reliability gold-plated palladium copper wire for IC packaging, including a copper wire substrate (diameter of 58.72μm), a palladium plating layer (thickness of 80nm) covering the surface of the copper wire substrate, and a gold plating layer (thickness of 2nm) covering the surface of the palladium plating layer.

[0089] The copper wire matrix comprises the following raw materials by mass percentage: Mg 100ppm, Pd 800ppm, Ce 300ppm, with the balance being Cu with a purity of 99.999%.

[0090] The above-mentioned method for preparing high-reliability gold-plated palladium-copper wire for IC packaging includes the following steps:

[0091] S1. Under the protection of an inert gas atmosphere, Mg, Pd and Ce are added to Cu, and the mixture is melted and cast at 1200℃ for 70 min. Water cooling is used for cooling, with a cooling water volume of 5 L / h. The mixture is melted and cast into round bars, and the round bars are drawn into wires to obtain copper wire matrix.

[0092] S2. The copper wire substrate obtained in step S1 is electrolyzed for degreasing and acid pickling activation, and then plated with palladium and gold to obtain a semi-finished product.

[0093] In step S2, the degreasing solution used includes the following raw materials: sodium hydroxide 15g / L, sodium carbonate 5g / L, sodium silicate 1.38g / L, gluconic acid 0.06g / L, natural protein 0.06g / L, and the balance is deionized water;

[0094] The activator used includes the following raw materials: 35 g / L branched fatty alcohol alkoxylated surfactant, 100 g / L active protein, 45 g / L phosphoric acid, and the balance being deionized water;

[0095] The palladium plating solution used includes the following raw materials: 15 g / L dichlorodiaminopalladium, 25 g / L ammonium chloride, 45 g / L ammonia water, and the balance being deionized water;

[0096] The gold plating solution used includes the following raw materials: potassium gold citrate 8g / L, potassium carbonate 50g / L, dodecylpyridine hydrochloride 0.6g / L, pyridine sulfonic acid 0.5g / L, triethanolamine 0.3g / L, and the balance is deionized water. The pH is adjusted to 6.0 by a pH adjuster, which is sodium hydroxide.

[0097] S3. The semi-finished product obtained in step S2 is annealed for the first time to obtain the finished product. The finished product is drawn and annealed for the second time to obtain the gold-plated palladium-copper wire with a diameter of 20μm.

[0098] The above electrolytic degreasing process first uses cathodic electrolytic degreasing (temperature 45℃, current density 3A / dm³). 2 At a speed of 20 m / min, oil is removed using an anode electrode (temperature 45℃, current density 6 A / dm). 2 The pickling activation temperature was 40℃, and the plating speed was 20 m / min. The palladium plating current was 70 mA, and the plating speed was 5 m / s. The gold plating current was 30 mA, and the plating speed was 20 m / s. The first annealing atmosphere was nitrogen and hydrogen in a volume ratio of 95:5, at a temperature of 500℃ and a plating speed of 50 m / min. The second annealing atmosphere was nitrogen, at a temperature of 450℃, and a plating speed of 80 m / min.

[0099] Comparative Example 1

[0100] This comparative example provides a gold-plated palladium copper wire, which differs from Example 1 only in that the copper wire matrix includes the following raw materials in the following mass percentages: Mg 160ppm, Pd 400ppm, Ce 500ppm, and the balance being Cu with a purity of 99.999%; all other components are the same.

[0101] Comparative Example 2

[0102] This comparative example provides a gold-plated palladium copper wire, which differs from Example 1 only in that the copper wire matrix includes the following raw materials in the following mass percentages: Mg 5ppm, Pd 1005ppm, Ce 50ppm, and the balance being Cu with a purity of 99.999%; all other components are the same.

[0103] Comparative Example 3

[0104] This comparative example provides a gold-plated palladium-copper wire, which differs from Example 1 only in that Mg is replaced with an equal mass of Ni; all other aspects are the same.

[0105] Comparative Example 4

[0106] This comparative example provides a gold-plated palladium-copper wire, which differs from Example 1 only in that the oil solution used is a 2% sodium hydroxide solution; all other aspects are the same.

[0107] Comparative Example 5

[0108] This comparative example provides a gold-plated palladium-copper wire, which differs from Example 1 only in that the degreasing solution used includes the following raw materials: sodium hydroxide 12g / L, sodium carbonate 3g / L, sodium silicate 1g / L, gluconic acid 0.05g / L, and natural protein 0g / L; all other components are the same.

[0109] Comparative Example 6

[0110] This comparative example provides a gold-plated palladium-copper wire, which differs from Example 1 only in that the activator is a 1% sulfuric acid solution; all other aspects are the same.

[0111] Comparative Example 7

[0112] This comparative example provides a gold-plated palladium-copper wire, which differs from Example 1 only in that the branched fatty alcohol alkoxylating surfactant is replaced with octylphenol polyoxyethylene ether; all other aspects are the same.

[0113] Test Example 1: Mechanical Performance Test

[0114] The gold-plated palladium-copper wires (diameter 20 μm) obtained from Examples 1-3, Comparative Examples 1-7, and Comparative Sample 1 were subjected to mechanical property testing using a universal testing machine. The test was conducted 5 times, and the average value was taken. The results are shown in Table 1.

[0115] Table 1

[0116]

[0117]

[0118] As can be seen from Table 1, the gold-plated palladium-copper wires provided in Examples 1-3 of the present invention have comparable mechanical properties to comparative sample 1;

[0119] In Comparative Examples 1-3, since the raw material composition of the copper wire matrix is ​​not within the scope of protection of this invention, the mechanical properties of the corresponding gold-plated palladium copper wires are significantly reduced, with a maximum breaking rate of less than 6 gf, a total elongation at break of less than 8.5%, and a Young's modulus of elasticity of less than 1900 MPa. In Comparative Examples 4-7, since the degreasing solution and activator are not within the scope of protection of this invention, the mechanical properties of the corresponding gold-plated palladium copper wires are slightly reduced, but the overall performance is not as good as the gold-plated palladium copper wires obtained in Comparative Examples 1-3.

[0120] Test Example 2: First weld push force, first weld pull force, and second weld pull force test

[0121] Ball bonding tests were conducted on aluminum pads using gold-plated palladium-copper wires (20 μm in diameter) obtained from Examples 1-3, Comparative Examples 1-7, and Comparative Samples 1-3. During the bonding process, nitrogen and hydrogen in a volume ratio of 95:9 were used as protective gases, with a protective gas flow rate of 0.4 L / min, a contact pressure of 85 g, a bonding pressure of 45 g, and a bonding time of 9 ms. The push-pull force after bonding was then tested using a bonding push-pull tester, and the results are shown in Table 2.

[0122] The bonding morphology of Example 1 is as follows: Figure 1 and Figure 2 As shown; the bonding morphology of sample 1 is compared as follows. Figure 3 and Figure 4 As shown;

[0123] The bonding morphology of Comparative Example 1 is as follows Figure 5 As shown; the bonding morphology of Comparative Example 4 is as follows. Figure 6 As shown; the bonding morphology of Comparative Example 6 is as follows: Figure 7 As shown.

[0124] Test Example 3: High-Temperature Storage Test of IMC (Intermetallic Compound) Thickness

[0125] Ball bonding tests were conducted on aluminum pads using gold-plated palladium-copper wires (20 μm in diameter) obtained in Examples 1-3, Comparative Examples 1-7, and Comparative Samples 1-3. Nitrogen and hydrogen in a volume ratio of 95:9 were used as protective gases during the bonding process. The protective gas flow rate was 0.4 L / min, the contact pressure was 85 g, the bonding pressure was 45 g, and the bonding time was 9 ms. A high-temperature storage test was then conducted at 150 °C for 1000 h to measure the IMC thickness. The results are shown in Table 2.

[0126] Table 2

[0127]

[0128] The first weld push, first weld pull, and second weld pull can characterize the weld strength of the weld point, and the higher the value, the better. Under high temperature conditions, intermediate compounds (IMCs) are generated after metal bonding. They are generally brittle. Over time, the IMC will increase and thicken. The increase in IMC thickness will affect the weld strength and lead to a decrease in reliability.

[0129] As can be seen from Table 2, the gold-plated palladium-copper wires provided in Examples 1-3 of the present invention have comparable first-weld push force, first-weld pull force, and second-weld pull force to comparative samples 1-3. However, after the high-temperature storage test, the IMC thickness is 0.88-0.95μm, which can reduce the risk of brittle failure of the solder joint compared to comparative samples 1-3.

[0130] In Comparative Examples 1-3, since the raw material composition of the copper wire matrix is ​​not within the scope of protection of this invention, the first weld push force, first weld pull force, and second weld pull force of the corresponding gold-plated palladium copper wire are significantly reduced; after the high-temperature storage test, the IMC thickness is significantly increased, reducing the stability of the solder joint.

[0131] In Comparative Examples 4-7, since the degreasing solution and activator are not within the scope of protection of this invention, the first weld push, first weld pull, and second weld pull of the corresponding gold-plated palladium copper wire also decreased significantly. After the high-temperature storage test, the IMC thickness increased significantly, reducing the stability of the weld.

[0132] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A high-reliability gold-plated palladium-copper wire for IC packaging, characterized in that, It includes a copper wire substrate, a palladium plating layer covering the surface of the copper wire substrate, and a gold plating layer covering the surface of the palladium plating layer; The copper wire matrix comprises the following raw materials in the following mass percentages: Mg 0.001-0.01%, Pd 0.045-0.1%, Ce 0.008-0.03%, with the balance being Cu; the purity of the Cu is 99.999%.

2. The high-reliability gold-plated palladium-copper wire for IC packaging according to claim 1, characterized in that, The thickness of the palladium plating layer is 60-100 nm; the thickness of the gold plating layer is 1-10 nm.

3. The method for preparing the high-reliability gold-plated palladium-copper wire for IC packaging according to claim 1 or 2, characterized in that, Includes the following steps: S1. Under the protection of an inert gas atmosphere, Mg, Pd and Ce are added to Cu and melted and cast into round bars. The round bars are then drawn into wires to obtain a copper wire matrix. S2. The copper wire substrate obtained in step S1 is electrolyzed for degreasing and acid pickling activation, and then plated with palladium and gold to obtain a semi-finished product. S3. The semi-finished product obtained in step S2 is annealed for the first time to obtain the finished product. The finished product is drawn and annealed for the second time to obtain the gold-plated palladium copper wire.

4. The method for preparing high-reliability gold-plated palladium-copper wire for IC packaging according to claim 3, characterized in that, In step S1, the melting and casting conditions are: melting and casting at 1150-1300℃ for 60-80 minutes, and cooling by water cooling at a rate of 2-10L / h.

5. The method for preparing high-reliability gold-plated palladium-copper wire for IC packaging according to claim 3, characterized in that, In step S2, the degreasing solution used for electrolytic degreasing includes the following raw materials: sodium hydroxide 8-15g / L, sodium carbonate 1-5g / L, sodium silicate 0.5-2g / L, gluconic acid 0.03-0.06g / L, natural protein 0.03-0.06g / L, and the balance being deionized water.

6. The method for preparing high-reliability gold-plated palladium-copper wire for IC packaging according to claim 5, characterized in that, In step S2, the electrolytic degreasing process involves first using cathode electrolysis for degreasing, followed by anode electrolysis for degreasing. The cathode electrolysis temperature is 40-50℃, the current density is 1-5A / dm2, and the speed is 5-30m / min. The anode electrolysis temperature is 40-50℃, the current density is 3-8A / dm2, and the speed is 5-30m / min.

7. The method for preparing high-reliability gold-plated palladium-copper wire for IC packaging according to claim 3, characterized in that, In step S2, the activator used for acid washing activation includes the following raw materials: 10-35 g / L of branched fatty alcohol alkoxylated surfactant, 15-120 g / L of active protein, 20-45 g / L of inorganic acid, and the balance being deionized water.

8. The method for preparing high-reliability gold-plated palladium-copper wire for IC packaging according to claim 7, characterized in that, The inorganic acid is sulfuric acid or phosphoric acid; the acid washing activation temperature is 20-50℃ and the rate is 5-30m / min.

9. The method for preparing high-reliability gold-plated palladium-copper wire for IC packaging according to claim 3, characterized in that, In step S2, the palladium plating solution used for palladium plating includes the following raw materials: 10-25 g / L of dichlorodiaminopalladium, 20-30 g / L of ammonium chloride, 35-60 g / L of ammonia water, and the balance being deionized water.

10. The method for preparing high-reliability gold-plated palladium-copper wire for IC packaging according to claim 3, characterized in that, In step S2, the gold plating solution used for gold plating includes the following raw materials: Potassium citrate 6-12 g / L, potassium carbonate 40-60 g / L, dodecylpyridine hydrochloride 0.4-1 g / L, pyridine sulfonic acid 0.3-0.8 g / L, triethanolamine 0.2-0.5 g / L, with the balance being deionized water. The pH is adjusted to 5.5-6.5 using a pH adjuster.

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