A copper wire gold plating process

Abstract

The invention discloses a copper wire gold plating treatment process, which belongs to the technical field of integrated circuits. The process comprises the following steps: performing surface cleaning treatment on a palladium-plated copper wire and then immersing the wire in a gold plating solution for gold plating treatment to obtain a gold-plated palladium copper wire; drawing and thinning the gold-plated palladium copper wire to a preset diameter, and then sequentially performing annealing treatment and surface cleaning treatment to obtain the gold-plated palladium copper wire; the gold plating solution comprises a leveler, the leveler takes a polyhydroxy spirobiindene rigid structure as a skeleton, and uses a Mannich reaction to graft 3-hydroxypiperidine with aminomethyl at the α active hydrogen position of the skeleton, and then introduces bromine atoms into the skeleton through a bromination reaction and derives them into a boric acid pinacol ester group, and finally introduces a dithiophene benzothiadiazole structure into the skeleton through a Suzuki coupling reaction to obtain the gold-plated palladium copper wire; the invention adds the leveler into the gold plating solution to improve the bonding strength and flatness of the coating so as to meet the copper wire bonding packaging requirements.

Description

Technical Field

[0001] The invention relates to the technical field of integrated circuits, and in particular to a copper wire gold plating process. Background Art

[0002] Packaging refers to the process of laying out, pasting, fixing and connecting chips on a frame or substrate, bringing out the wiring terminals and fixing them through plastic sealing to form an overall three-dimensional structure. It not only has the functions of placing, fixing, sealing, enhancing heat dissipation and protecting the chip, but also has the function of connecting the internal circuit of the chip with the external circuit. The connection between the internal pad of the chip and the external lead frame is achieved through bonding wires. As one of the four basic key materials in the field of microelectronics packaging (chips, bonding wires, lead frames / substrates, and plastic packaging materials), bonding wires connect semiconductor chips with external circuits for current transmission and signal interconnection. Therefore, packaging has very high requirements on the conductivity, elongation, oxidation resistance, and easy welding of bonding wires.

[0003] In the traditional packaging bonding process, pure gold wire with a gold content of more than 99.99% is often used. Bonding gold wire has the advantages of high conductivity, corrosion resistance, good toughness and easy welding. Since gold is expensive, copper wire, palladium-plated copper wire, gold-plated copper wire, pure silver wire or silver alloy wire are currently used to replace expensive gold wire products. Bonding copper wire is cheap and outperforms gold wire in terms of conductivity, tensile strength, elongation and shear strength. It has been successfully used in the packaging production of products such as DIP, SOP and power devices. However, with the rapid development of the semiconductor integrated circuit industry towards miniaturization, multi-pin high density, the performance requirements for bonding copper wire are becoming more and more stringent. The problems of easy oxidation, easy corrosion, high hardness, poor weldability and wire breakage of bonding copper wire are becoming increasingly prominent, which directly leads to a decrease in product qualification rate. Palladium-plated copper bonding wire uses relatively cheap palladium as the coating, which can control costs while solving the problem of copper wire being easily oxidized and resistant to corrosion. However, the heat generated by palladium in a very small chip package cannot be ignored due to its insufficient conductivity, and the hardness of palladium is slightly higher, which can easily damage the chip. Although gold-plated copper wire overcomes the defects of high hardness and high resistance of palladium-plated copper wire, the stability of this wire itself is not high because the bonding force between gold and copper is not as strong as that between palladium and copper. In response to this problem, gold-plated and palladium-plated bonding wires have begun to appear in the industry. Metal palladium is plated on the surface of the central copper wire to resist oxidation and corrosion, and metal gold is plated on the outer layer of metal palladium to reduce the damage to the chip caused by excessive hardness of the wire during bonding. In the gold plating process, in order to avoid the contact between the filaments after drawing affecting the morphology of the coating, the process of gold plating first and then drawing is usually adopted, but the insufficient bonding force of the coating makes it easy to have uneven coating such as surface delamination, surface cracking and unevenness, thus affecting the bonding effect. Summary of the invention

[0004] In view of the above problems, the present invention provides a copper wire gold plating process.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] A copper wire gold plating process comprises the following steps:

[0007] (1) The palladium-plated copper wire is surface cleaned to obtain a gold-plated substrate. First, the oily stains on the copper wire are cleaned with an organic solvent such as gasoline, anhydrous ethanol or carbon tetrachloride. If the effect of simply rinsing or soaking to remove the oil stains is not good enough, ultrasonic cleaning and degreasing can be used. In the gold plating process, cleaning and drying of the substrate are key processes, because impurity accumulation, plating solution retention and water film formation will affect the formation of the coating during the process, causing problems with reliability of use;

[0008] (2) immersing the gold-plated substrate into a gold-plating solution for gold-plating treatment to obtain a gold-plated palladium copper wire;

[0009] (3) drawing and thinning the gold-plated palladium copper wire to a preset diameter, and then sequentially subjecting the wire to annealing and surface cleaning treatments; the annealing treatment can stabilize the drawn copper wire and improve its mechanical properties;

[0010] The gold plating solution includes a leveling agent, and the preparation method of the leveling agent includes the following steps:

[0011] S1. Weigh 3,3,3',3'-tetramethyl 2,2',3,3'-tetrahydro-1,1-spirobi[1H-indene]-5,5',6,6'-tetrol and dissolve it in the first reaction solvent, add 3-hydroxypiperidine, stir and mix thoroughly, raise the temperature to 55-65°C, add paraformaldehyde, continue to stir and react for 6-12 hours, cool to room temperature after the reaction is completed, concentrate under reduced pressure, wash with cyclohexane, separate the precipitate, and dry to obtain product A;

[0012] S2, dissolving the product A in a second reaction solvent, adding phosphorus tribromide or phosphorus oxybromide under ice-water bath conditions, stirring and reacting at room temperature for 1-4 hours, repeating the operation of adding phosphorus tribromide or phosphorus oxybromide under ice-water bath conditions and stirring and reacting at room temperature for several times, separating and washing the precipitate after the reaction is completed, and drying to obtain product B;

[0013] S3, under a protective atmosphere, dissolving the product B in a dimethyl sulfoxide solvent, adding 1,1'-bis(diphenylphosphino)ferrocenepalladium dichloride and potassium acetate, stirring and mixing thoroughly, adding diboric acid pinacol ester, heating to 70-80°C and stirring and reacting for 3-6 hours, centrifuging and separating the precipitate after the reaction is completed, concentrating the supernatant under reduced pressure, washing with cyclohexane, separating the precipitate, and drying to obtain the product C;

[0014] S4. Under a protective atmosphere, the product C is dissolved in a dimethyl sulfoxide solvent, 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole, tetrakis(triphenylphosphine)palladium and methyltrioctylammonium chloride are added, and a potassium carbonate solution is added. The mixture is stirred thoroughly and then kept stirred at 90-110°C for 24-48 hours. After the reaction is completed, acetone is added to dilute the reaction system, and the precipitate is separated. The precipitate is washed and dried to obtain the product D, which is the leveling agent.

[0015] In some preferred embodiments, the gold plating solution in step (2) comprises the following components, measured by weight: 12-24 parts of gold salt, 20-50 parts of complexing agent, 2-4 parts of antioxidant, 2-10 parts of leveling agent, 0.01-0.1 parts of buffer, and 40-60 parts of deionized water.

[0016] In some preferred embodiments, the gold salt is a mixture of one or more of gold sodium thiosulfate, gold sodium citrate, and gold sodium sulfite.

[0017] In some preferred embodiments, the complexing agent is a mixture of one or more of sodium sulfite, sodium thiosulfite, sodium pyrosulfite, and sodium citrate.

[0018] In some preferred embodiments, the antioxidant is sodium hypophosphite.

[0019] In some preferred embodiments, the buffer is a mixture of one or more of sodium dihydrogen phosphate, ammonium chloride, ammonium oxalate, and ammonium citrate.

[0020] In some preferred embodiments, the gold plating temperature in step (2) is 60-70° C., and the gold plating time is 10-40 min.

[0021] In some preferred embodiments, the atmosphere of the annealing treatment in step (3) is a mixture of argon and hydrogen in a volume ratio of 100:(0.5-2), the annealing temperature is 400-500° C., and the annealing time is 1-2 h.

[0022] In some preferred embodiments, in step S1, the first reaction solvent is methanol, ethanol, dimethyl sulfoxide or tetrahydrofuran.

[0023] In some preferred embodiments, the mass ratio of the 3,3,3',3'-tetramethyl 2,2',3,3'-tetrahydro-1,1-spirobi[1H-indene]-5,5',6,6'-tetrol to the 3-hydroxypiperidine and the polyformaldehyde in step S1 is 10:(14.8-16.4):(12.5-14).

[0024] In some preferred embodiments, the second reaction solvent in step S2 is N,N-dimethylformamide, dichloromethane, chloroform or tetrachloromethane.

[0025] In some preferred embodiments, the mass ratio of the product A to the phosphorus tribromide or phosphorus oxybromide in step S2 is 10:(5-7.2).

[0026] In some preferred embodiments, the mass ratio of the product B to the 1,1'-bis(diphenylphosphinoferrocene)palladium dichloride, the potassium acetate, and the biphenylphosphinothioate in step S3 is 10:(0.05-0.1):(4-5):(6.6-7.8).

[0027] In some preferred embodiments, the mass ratio of the product C to the 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole, the tetrakis(triphenylphosphine)palladium, the methyltrioctylammonium chloride, and the potassium carbonate in step S4 is 10:(9-11):(0.2-0.3):(1.5-2.4).

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

[0029] Aiming at the problem that the gold-plated layer of the existing gold-plated palladium copper wire has insufficient bonding strength, resulting in delamination, unevenness and uneven surface after drawing, the present invention provides a copper wire gold plating treatment process, by adding a leveling agent into the gold plating solution to improve the bonding strength and flatness of the plating layer to meet the packaging requirements of copper wire bonding, specifically, the leveling agent of the present invention uses a polyhydroxy spirobiindene rigid structure as a skeleton, and uses a Mannich reaction to graft 3-hydroxypiperidine with aminomethyl at the α active hydrogen position of the skeleton, and then introduces bromine atoms into the skeleton through a bromination reaction and derives them into boric acid pinacol ester groups, and finally introduces dithiophene benzophenone on the skeleton through a Suzuki coupling reaction. The thiadiazole structure is prepared; since the gold plating bonding is based on the electron exchange deposition of gold-containing ions on the substrate, the present invention uses the polyhydroxy spirobiindene structure grafted with 3-hydroxypiperidine as the electron donor, and introduces the dithiophene benzothiadiazole structure as the electron acceptor to form a donor-acceptor type conjugated structure. Using it as a redox medium can effectively promote the electron exchange between the gold-containing ions and the gold-plated substrate, improve the bonding degree between the plating layer and the substrate, enable the plating layer to deform uniformly during the drawing process, and maintain the integrity of the plating layer. At the same time, the donor-acceptor type conjugated structure can also maintain the uniform diffusion of the gold-containing ions in the gold plating system, and improve the flatness and uniformity of the plating layer. DETAILED DESCRIPTION

[0030] The present invention is further described in conjunction with the following examples.

[0031] Example 1

[0032] This embodiment relates to a copper wire gold plating process, comprising the following steps:

[0033] (1) placing the palladium-plated copper wire in anhydrous ethanol for ultrasonic cleaning, the ultrasonic frequency is 40 kHz, the ultrasonic time is 0.4 h, and then vacuum drying is performed to obtain a gold-plated substrate, wherein the diameter of the palladium-plated copper wire is 936 µm, and the thickness of the palladium-plated layer is 1.2 µm;

[0034] (2) immersing the gold-plated substrate in a gold-plating solution for gold-plating treatment, wherein the gold-plating temperature is 65° C. and the gold-plating time is 25 min, to obtain a gold-plated palladium copper wire; wherein the gold-plating solution comprises the following components by weight: 18 parts of sodium gold sulfite, 42 parts of sodium sulfite, 2.5 parts of sodium hypophosphite, 6.8 parts of a leveling agent, 0.04 parts of sodium dihydrogen phosphate, and 50 parts of deionized water;

[0035] The preparation method of the leveling agent comprises the following steps:

[0036] S1. Weigh 3,3,3',3'-tetramethyl 2,2',3,3'-tetrahydro-1,1-spirobis[1H-indene]-5,5',6,6'-tetrol (CAS No.: 77-08-7) and dissolve it in dimethyl sulfoxide solvent, add 3-hydroxypiperidine, stir and mix thoroughly, heat to 60°C, add paraformaldehyde, continue to stir and react for 8 hours, cool to room temperature after the reaction is completed, concentrate under reduced pressure, wash with cyclohexane, separate the precipitate, and dry to obtain product A; wherein the mass ratio of the 3,3,3',3'-tetramethyl 2,2',3,3'-tetrahydro-1,1-spirobis[1H-indene]-5,5',6,6'-tetrol to the 3-hydroxypiperidine and the paraformaldehyde is 10:15.17:13.23;

[0037] S2, dissolving the product A in N,N-dimethylformamide solvent, adding phosphorus oxybromide under ice-water bath conditions, stirring and reacting at room temperature for 2 hours, repeating the operation of adding phosphorus oxybromide under ice-water bath conditions and stirring and reacting at room temperature for 2 hours for 5 times, separating and washing the precipitate after the reaction is completed, and drying to obtain product B; wherein the mass ratio of the product A to the total amount of phosphorus oxybromide is 10:6;

[0038] S3. Under a protective atmosphere, the product B is dissolved in a dimethyl sulfoxide solvent, 1,1'-bis(diphenylphosphinoferrocenepalladium) dichloride and potassium acetate are added, the mixture is fully stirred and mixed, and then biphenylphosphinoferrocene pinacol (CAS No. 73183-34-3) is added, the temperature is raised to 80°C and the mixture is stirred and reacted for 4 hours. After the reaction is completed, the precipitate is separated by centrifugation, the supernatant is concentrated under reduced pressure and then washed with cyclohexane, the precipitate is separated, and the product C is obtained after drying; wherein the mass ratio of the product B to the 1,1'-bis(diphenylphosphinoferrocenepalladium) dichloride, the potassium acetate, and the biphenylphosphinoferrocene pinacol is 10:0.075:4.35:7.25;

[0039] S4. Under a protective atmosphere, the product C is dissolved in a dimethyl sulfoxide solvent, 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole (CAS No. 288071-87-4), tetrakis(triphenylphosphine)palladium (CAS No. 14221-01-3) and methyl trioctyl ammonium chloride are added, and a 2 mol / L potassium carbonate solution is added. The mixture is stirred and mixed thoroughly, and the mixture is stirred and reacted at 95°C for 30 hours. After the reaction is completed, acetone is added to dilute the reaction system, and the precipitate is separated, and the product D is obtained after washing and drying, which is the leveling agent; wherein the mass ratio of the product C to the 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole, the tetrakis(triphenylphosphine)palladium, the methyl trioctyl ammonium chloride and the potassium carbonate is 10:10:0.2:1.8;

[0040] (3) The gold-plated palladium copper wire was drawn and refined to a diameter of 59 µm, and annealed in a mixed gas atmosphere of argon and hydrogen in a volume ratio of 100:0.8 at a temperature of 460° C. for 1 h, and then placed in deionized water for ultrasonic cleaning at an ultrasonic frequency of 20 kHz for 0.2 h, and vacuum dried to obtain a product.

[0041] Example 2

[0042] This embodiment relates to a copper wire gold plating process, comprising the following steps:

[0043] (1) placing the palladium-plated copper wire in anhydrous ethanol for ultrasonic cleaning, the ultrasonic frequency is 40 kHz, the ultrasonic time is 0.4 h, and then vacuum drying is performed to obtain a gold-plated substrate, wherein the diameter of the palladium-plated copper wire is 936 µm, and the thickness of the palladium-plated layer is 1.2 µm;

[0044] (2) immersing the gold-plated substrate into a gold plating solution for gold plating, wherein the gold plating temperature is 60° C. and the gold plating time is 40 min, to obtain a gold-plated palladium copper wire; wherein the gold plating solution comprises the following components by weight: 24 parts of sodium gold thiosulfate, 50 parts of sodium thiosulfate, 4 parts of sodium hypophosphite, 10 parts of a leveling agent, 0.1 parts of sodium dihydrogen phosphate, and 60 parts of deionized water;

[0045] The preparation method of the leveling agent comprises the following steps:

[0046] S1. Weigh 3,3,3',3'-tetramethyl 2,2',3,3'-tetrahydro-1,1-spirobis[1H-indene]-5,5',6,6'-tetrol and dissolve it in ethanol solvent, add 3-hydroxypiperidine, stir and mix thoroughly, heat to 65°C, add paraformaldehyde, continue to stir and react for 6 hours, cool to room temperature after the reaction is completed, concentrate under reduced pressure, wash with cyclohexane, separate the precipitate, and dry to obtain product A; wherein the mass ratio of the 3,3,3',3'-tetramethyl 2,2',3,3'-tetrahydro-1,1-spirobis[1H-indene]-5,5',6,6'-tetrol to the 3-hydroxypiperidine and the paraformaldehyde is 10:14.8:12.5;

[0047] S2, dissolving the product A in a dichloromethane solvent, adding phosphorus oxybromide under ice-water bath conditions, stirring and reacting at room temperature for 1 hour, repeating the operation of adding phosphorus oxybromide under ice-water bath conditions and stirring and reacting at room temperature for 1 hour 5 times, separating and washing the precipitate after the reaction is completed, and drying to obtain product B; wherein the mass ratio of the product A to the total amount of phosphorus oxybromide is 10:5;

[0048] S3. Under a protective atmosphere, dissolve the product B in a dimethyl sulfoxide solvent, add 1,1'-bis(diphenylphosphinoferrocenepalladium dichloride) and potassium acetate, stir and mix thoroughly, then add diboric acid pinacol ester, heat to 70°C and stir and react for 3 hours, centrifuge and separate the precipitate after the reaction is completed, concentrate the supernatant under reduced pressure, wash with cyclohexane, separate the precipitate, and dry to obtain product C; wherein the mass ratio of the product B to the 1,1'-bis(diphenylphosphinoferrocenepalladium dichloride, the potassium acetate, and the diboric acid pinacol ester is 10:0.05:4:6.6;

[0049] S4. Under a protective atmosphere, the product C is dissolved in a dimethyl sulfoxide solvent, 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole, tetrakis(triphenylphosphine)palladium and methyl trioctyl ammonium chloride are added, and a 2 mol / L potassium carbonate solution is added. The mixture is stirred and mixed thoroughly, and then the mixture is stirred and reacted at 90°C for 48 hours. After the reaction is completed, acetone is added to dilute the reaction system, and the precipitate is separated, and the product D is obtained after washing and drying, which is the leveling agent; wherein the mass ratio of the product C to the 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole, the tetrakis(triphenylphosphine)palladium, the methyl trioctyl ammonium chloride and the potassium carbonate is 10:9:0.3:1.5;

[0050] (3) The gold-plated palladium copper wire was drawn and refined to a diameter of 59 µm, and annealed in a mixed gas atmosphere of argon and hydrogen in a volume ratio of 100:0.5 at a temperature of 400°C for 2 h. The wire was then placed in deionized water for ultrasonic cleaning at an ultrasonic frequency of 20 kHz for 0.2 h, and vacuum dried to obtain a product.

[0051] Example 3

[0052] This embodiment relates to a copper wire gold plating process, comprising the following steps:

[0053] (1) placing the palladium-plated copper wire in anhydrous ethanol for ultrasonic cleaning, the ultrasonic frequency is 40 kHz, the ultrasonic time is 0.4 h, and then vacuum drying is performed to obtain a gold-plated substrate, wherein the diameter of the palladium-plated copper wire is 936 µm, and the thickness of the palladium-plated layer is 1.2 µm;

[0054] (2) immersing the gold-plated substrate in a gold-plating solution for gold-plating treatment, wherein the gold-plating temperature is 70° C. and the gold-plating time is 10 min, to obtain a gold-plated palladium copper wire; wherein the gold-plating solution comprises the following components by weight: 12 parts of sodium gold citrate, 20 parts of sodium pyrosulfite, 2 parts of sodium hypophosphite, 2 parts of a leveling agent, 0.01 parts of sodium dihydrogen phosphate, and 40 parts of deionized water;

[0055] The preparation method of the leveling agent comprises the following steps:

[0056] S1. Weigh 3,3,3',3'-tetramethyl 2,2',3,3'-tetrahydro-1,1-spirobis[1H-indene]-5,5',6,6'-tetrol and dissolve it in tetrahydrofuran solvent, add 3-hydroxypiperidine, stir and mix thoroughly, heat to 55°C, add paraformaldehyde, continue to stir and react for 12 hours, cool to room temperature after the reaction is completed, concentrate under reduced pressure, wash with cyclohexane, separate the precipitate, and dry to obtain product A; wherein the mass ratio of the 3,3,3',3'-tetramethyl 2,2',3,3'-tetrahydro-1,1-spirobis[1H-indene]-5,5',6,6'-tetrol to the 3-hydroxypiperidine and the paraformaldehyde is 10:16.4:14;

[0057] S2, dissolving the product A in chloroform solvent, adding phosphorus tribromide under ice-water bath conditions, stirring and reacting at room temperature for 4 hours, repeating the operation of adding phosphorus tribromide under ice-water bath conditions and stirring and reacting at room temperature for 4 hours 5 times, separating and washing the precipitate after the reaction is completed, and drying to obtain product B; wherein the mass ratio of the product A to the total amount of phosphorus tribromide is 10:7.2;

[0058] S3. Under a protective atmosphere, dissolve the product B in a dimethyl sulfoxide solvent, add 1,1'-bis(diphenylphosphinoferrocenepalladium dichloride) and potassium acetate, stir and mix thoroughly, then add diboric acid pinacol ester, heat to 70°C and stir and react for 6 hours, centrifuge and separate the precipitate after the reaction is completed, concentrate the supernatant under reduced pressure, wash with cyclohexane, separate the precipitate, and dry to obtain product C; wherein the mass ratio of the product B to the 1,1'-bis(diphenylphosphinoferrocenepalladium dichloride, the potassium acetate, and the diboric acid pinacol ester is 10:0.1:5:7.8;

[0059] S4. Under a protective atmosphere, the product C is dissolved in a dimethyl sulfoxide solvent, 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole, tetrakis(triphenylphosphine)palladium and methyl trioctyl ammonium chloride are added, and a 2 mol / L potassium carbonate solution is added. The mixture is stirred and mixed thoroughly, and then the mixture is stirred and reacted at 110°C for 24 hours. After the reaction is completed, acetone is added to dilute the reaction system, and the precipitate is separated, and the product D is obtained after washing and drying, which is the leveling agent; wherein the mass ratio of the product C to the 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole, the tetrakis(triphenylphosphine)palladium, the methyl trioctyl ammonium chloride and the potassium carbonate is 10:11:0.3:2.4;

[0060] (3) The gold-plated palladium copper wire was drawn and refined to a diameter of 59 µm, and annealed in a mixed gas atmosphere of argon and hydrogen in a volume ratio of 100:2 at a temperature of 500°C for 1 hour. The wire was then placed in deionized water for ultrasonic cleaning at an ultrasonic frequency of 20 kHz for 0.2 hour, and vacuum dried to obtain a product.

[0061] Comparative Example 1

[0062] A copper wire gold plating process comprises the following steps:

[0063] (1) placing the palladium-plated copper wire in anhydrous ethanol for ultrasonic cleaning, the ultrasonic frequency is 40 kHz, the ultrasonic time is 0.4 h, and then vacuum drying is performed to obtain a gold-plated substrate, wherein the diameter of the palladium-plated copper wire is 936 µm, and the thickness of the palladium-plated layer is 1.2 µm;

[0064] (2) immersing the gold-plated substrate in a gold-plating solution for gold-plating treatment, wherein the gold-plating temperature is 65° C. and the gold-plating time is 25 min, to obtain a gold-plated palladium copper wire; wherein the gold-plating solution comprises the following components by weight: 18 parts of sodium gold sulfite, 42 parts of sodium sulfite, 2.5 parts of sodium hypophosphite, 0.04 parts of sodium dihydrogen phosphate, and 50 parts of deionized water;

[0065] (3) The gold-plated palladium copper wire was drawn and refined to a diameter of 59 µm, and annealed in a mixed gas atmosphere of argon and hydrogen in a volume ratio of 100:0.8 at a temperature of 460° C. for 1 h, and then placed in deionized water for ultrasonic cleaning at an ultrasonic frequency of 20 kHz for 0.2 h, and vacuum dried to obtain a product.

[0066] Comparative Example 2

[0067] A copper wire gold plating process comprises the following steps:

[0068] (1) placing the palladium-plated copper wire in anhydrous ethanol for ultrasonic cleaning, the ultrasonic frequency is 40 kHz, the ultrasonic time is 0.4 h, and then vacuum drying is performed to obtain a gold-plated substrate, wherein the diameter of the palladium-plated copper wire is 936 µm, and the thickness of the palladium-plated layer is 1.2 µm;

[0069] (2) immersing the gold-plated substrate in a gold-plating solution for gold-plating treatment, wherein the gold-plating temperature is 65° C. and the gold-plating time is 25 min, to obtain a gold-plated palladium copper wire; wherein the gold-plating solution comprises the following components by weight: 18 parts of sodium gold sulfite, 42 parts of sodium sulfite, 2.5 parts of sodium hypophosphite, 6.8 parts of 3,3,3',3'-tetramethyl 2,2',3,3'-tetrahydro-1,1-spirobis[1H-indene]-5,5',6,6'-tetrol, 0.04 parts of sodium dihydrogen phosphate, and 50 parts of deionized water;

[0070] (3) The gold-plated palladium copper wire was drawn and refined to a diameter of 59 µm, and annealed in a mixed gas atmosphere of argon and hydrogen in a volume ratio of 100:0.8 at a temperature of 460° C. for 1 h, and then placed in deionized water for ultrasonic cleaning at an ultrasonic frequency of 20 kHz for 0.2 h, and vacuum dried to obtain a product.

[0071] Comparative Example 3

[0072] A copper wire gold plating process comprises the following steps:

[0073] (1) placing the palladium-plated copper wire in anhydrous ethanol for ultrasonic cleaning, the ultrasonic frequency is 40 kHz, the ultrasonic time is 0.4 h, and then vacuum drying is performed to obtain a gold-plated substrate, wherein the diameter of the palladium-plated copper wire is 936 µm, and the thickness of the palladium-plated layer is 1.2 µm;

[0074] (2) immersing the gold-plated substrate in a gold-plating solution for gold-plating treatment, wherein the gold-plating temperature is 65° C. and the gold-plating time is 25 min, to obtain a gold-plated palladium copper wire; wherein the gold-plating solution comprises the following components by weight: 18 parts of sodium gold sulfite, 42 parts of sodium sulfite, 2.5 parts of sodium hypophosphite, 6.8 parts of 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole, 0.04 parts of sodium dihydrogen phosphate, and 50 parts of deionized water;

[0075] (3) The gold-plated palladium copper wire was drawn and refined to a diameter of 59 µm, and annealed in a mixed gas atmosphere of argon and hydrogen in a volume ratio of 100:0.8 at a temperature of 460° C. for 1 h, and then placed in deionized water for ultrasonic cleaning at an ultrasonic frequency of 20 kHz for 0.2 h, and vacuum dried to obtain a product.

[0076] Comparative Example 4

[0077] A copper wire gold plating process comprises the following steps:

[0078] Steps (1) and (2) are the same as in Example 1;

[0079] (3) The gold-plated palladium copper wire was drawn and thinned to a diameter of 59 µm, and then placed in deionized water for ultrasonic cleaning at an ultrasonic frequency of 20 kHz and an ultrasonic time of 0.2 h, and then vacuum dried to obtain a product.

[0080] Experimental testing

[0081] The surface condition, resistivity, breaking force, and ball soldering shear force of the gold-plated copper wires prepared in Examples 1-3 and Comparative Examples 1-4 were tested, wherein the resistivity test was conducted with reference to GB / T3048.2-2007, and the breaking force of the bonding wire and the ball soldering shear force were tested on an Alpha-W260 push-pull tester, and the test standards were respectively based on MIL-STD-883 and ASTM F1269. The test results are shown in Table 1.

[0082] Table 1 Performance of different gold-plated copper wires

[0083]

[0084] The gold-plated layer obtained by the gold-plating process described in Examples 1-3 of the present invention has a flat and smooth surface after drawing. According to the comparison between Example 1 and Comparative Example 1, it is explained that the leveler of the present invention can improve the bonding between the plated layer and the substrate during the gold-plating process, so that the surface has a flat and smooth surface after drawing; according to the comparison between Example 1 and Comparative Example 2 of the present invention and Example 1 and Comparative Example 3, it is explained that the effect of the leveler of the present invention is obtained by combining a polyhydroxy spirobiindene structure with a dithiophene benzothiadiazole structure rather than a single structure; according to the comparison between Example 1 and Comparative Example 4, it is explained that the annealing treatment of the present invention can improve the mechanical properties of the drawn copper wire after gold plating, which will make the welding firmness of the gold-plated copper wire of the present invention to the chip pad and the lead frame pin higher, and have a more stable shear fracture load, and due to the improvement of mechanical strength, the wire diameter of the bonding wire can be further reduced, the welding spacing can be shortened, and it is more suitable for high-density, multi-pin integrated circuit packaging.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A copper wire gold plating process, characterized in that: The following steps are involved: (1) cleaning the surface of the palladium-plated copper wire to obtain a gold-plated substrate; (2) immersing the gold-plated substrate into a gold-plating solution for gold-plating treatment to obtain a gold-plated palladium copper wire; (3) drawing and thinning the gold-plated palladium copper wire to a preset diameter, and then subjecting the wire to annealing and surface cleaning treatments; The gold plating solution includes a leveling agent, and the preparation method of the leveling agent includes the following steps: S1. Weigh 3,3,3',3'-tetramethyl 2,2',3,3'-tetrahydro-1,1-spirobi[1H-indene]-5,5',6,6'-tetrol and dissolve it in the first reaction solvent, add 3-hydroxypiperidine, stir and mix thoroughly, raise the temperature to 55-65°C, add paraformaldehyde, continue to stir and react for 6-12 hours, cool to room temperature after the reaction is completed, concentrate under reduced pressure, wash with cyclohexane, separate the precipitate, and dry to obtain product A; S2, dissolving the product A in a second reaction solvent, adding phosphorus tribromide or phosphorus oxybromide under ice-water bath conditions, stirring and reacting at room temperature for 1-4 hours, repeating the operation of adding phosphorus tribromide or phosphorus oxybromide under ice-water bath conditions and stirring and reacting at room temperature for several times, separating and washing the precipitate after the reaction is completed, and drying to obtain product B; S3, under a protective atmosphere, dissolving the product B in a dimethyl sulfoxide solvent, adding 1,1'-bis(diphenylphosphino)ferrocenepalladium dichloride and potassium acetate, stirring and mixing thoroughly, adding diboric acid pinacol ester, heating to 70-80°C and stirring and reacting for 3-6 hours, centrifuging and separating the precipitate after the reaction is completed, concentrating the supernatant under reduced pressure, washing with cyclohexane, separating the precipitate, and drying to obtain the product C; S4. Under a protective atmosphere, the product C is dissolved in a dimethyl sulfoxide solvent, 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole, tetrakis(triphenylphosphine)palladium and methyltrioctylammonium chloride are added, and a potassium carbonate solution is added. The mixture is stirred and mixed thoroughly, and then the mixture is stirred and reacted at 90-110° C. for 24-48 hours. After the reaction is completed, acetone is added to dilute the reaction system, and the precipitate is separated. The precipitate is washed and dried to obtain a product D, which is the leveling agent. In terms of weight, the gold plating solution in step (2) comprises the following components: 12-24 parts of gold salt, 20-50 parts of complexing agent, 2-4 parts of antioxidant, 2-10 parts of leveling agent, 0.01-0.1 parts of buffer, and 40-60 parts of deionized water; In step S1, the first reaction solvent is methanol, ethanol, dimethyl sulfoxide or tetrahydrofuran; In step S2, the second reaction solvent is N,N-dimethylformamide, dichloromethane, chloroform or tetrachloromethane.

2. A copper wire gold plating process according to claim 1, characterized in that: The temperature of the gold plating treatment in step (2) is 60-70° C., and the gold plating time is 10-40 minutes.

3. A copper wire gold plating process according to claim 1, characterized in that: The atmosphere of the annealing treatment in step (3) is a mixture of argon and hydrogen in a volume ratio of 100:(0.5-2), the annealing temperature is 400-500°C, and the annealing time is 1-2h.

4. A copper wire gold plating process according to claim 1, characterized in that: The mass ratio of the 3,3,3',3'-tetramethyl 2,2',3,3'-tetrahydro-1,1-spirobi[1H-indene]-5,5',6,6'-tetrol to the 3-hydroxypiperidine and the polyformaldehyde in step S1 is 10:(14.8-16.4):(12.5-14).

5. A copper wire gold plating process according to claim 1, characterized in that: In step S2, the mass ratio of the product A to the phosphorus tribromide or phosphorus oxybromide is 10:(5-7.2).

6. A copper wire gold plating process according to claim 1, characterized in that: In step S3, the mass ratio of the product B to the 1,1'-bis(diphenylphosphino)ferrocenepalladium dichloride, the potassium acetate, and the biphenylboric acid pinacol ester is 10:(0.05-0.1):(4-5):(6.6-7.8).

7. A copper wire gold plating process according to claim 1, characterized in that: The mass ratio of the product C in step S4 to the 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole, the tetrakis(triphenylphosphine)palladium, the methyltrioctylammonium chloride, and the potassium carbonate is 10:(9-11):(0.2-0.3):(1.5-2.4).

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