A method for high-precision photoetching metal patterning on a polyimide surface

Abstract

The application discloses a method for realizing high-precision photoetching metal patterning on a polyimide surface, and belongs to the fields of material surface treatment, photoetching and electronic circuit manufacturing technology. The method can realize efficient and high-precision patterning of metal on a polyimide under the premise that the polyimide film is not pretreated by using harsh means, and meets the increasing demand of the FPCB industry for metal patterning on a polyimide substrate.

Description

Technical Field

[0001] This invention belongs to the fields of material surface treatment, photolithography, and electronic circuit manufacturing technology, and specifically relates to a method for achieving high-precision photolithographic metal patterning on the surface of polyimide. Background Technology

[0002] In the field of electronic circuit manufacturing, flexible printed circuit boards (FPCBs) are increasingly widely used. Polyimide (PI), as a high-performance organic polymer material, has become a commonly used substrate material for FPCBs due to its excellent thermal stability, chemical stability, mechanical properties, and insulation properties. In the FPCB manufacturing process, achieving metal patterning on the polyimide surface is a crucial step, playing a decisive role in realizing the electrical connections and functions of the circuit.

[0003] Currently, the main methods for metal patterning on polyimide have the following common techniques and drawbacks:

[0004] Traditional chemical etching first requires coating a polyimide surface with photoresist, forming a patterned photoresist mask using photolithography, and then using a chemical etching solution to etch the metal layer not protected by the photoresist to obtain the desired metal pattern. However, this method has many drawbacks. On the one hand, chemical etching solutions are usually highly corrosive, requiring sophisticated production equipment and special anti-corrosion treatment, increasing equipment costs. On the other hand, the etching process generates a large amount of chemical waste, causing significant environmental pollution, and the treatment of this waste also requires additional costs. Moreover, chemical etching has limited precision; when creating intricate circuit patterns, it is prone to problems such as uneven edges and line width deviations, making it difficult to meet the growing demand for high-precision circuit manufacturing.

[0005] Another common method, physical vapor deposition (PVD) combined with photolithography, can achieve high-precision metal patterning, but this method requires a high-vacuum environment, and the equipment is complex and expensive, resulting in high operating and maintenance costs. Furthermore, the low deposition rate of metal atoms during PVD leads to low production efficiency, limiting its application in large-scale production.

[0006] Some methods require stringent pretreatment of polyimide, such as treatment with strong acids or alkalis, or high-temperature plasma treatment. While these pretreatment methods can improve the adhesion between the polyimide surface and the metal to some extent, they can damage the properties of the polyimide itself, such as reducing its flexibility and mechanical strength, thus affecting the quality and reliability of the final FPCB product. Moreover, the stringent pretreatment conditions place high demands on the production environment and operators, increasing the difficulty and risk of production.

[0007] In summary, existing techniques for metal patterning on polyimide suffer from drawbacks such as high cost, significant environmental pollution, limited precision, and damage to polyimide properties. There is an urgent need for a new, more efficient metal patterning method that minimizes the impact on polyimide properties. Summary of the Invention

[0008] This invention aims to provide a method for achieving high-precision photolithographic metal patterning on the surface of polyimide, thereby solving the problems of high cost, low precision, and damage to polyimide performance in existing technologies. The method of this invention can achieve efficient and high-precision patterning of metals on polyimide without using harsh pretreatment methods for the polyimide film, meeting the growing demand of the FPCB industry for metal patterning on polyimide substrates.

[0009] The present invention provides a method for achieving high-precision photolithographic metal patterning on a polyimide surface, comprising the following steps:

[0010] (1) Cleaning of polyimide film: Select commercial polyimide film, such as the common Kapton material. Soak the polyimide in anhydrous ethanol-water-anhydrous ethanol in sequence and ultrasonically clean for 10-30 minutes.

[0011] (2) Spin coating of ink: Prepare an ink containing poly(4-vinylpyridine) (P4VP) and a photoinitiator, transfer it to the cleaned polyimide surface, and coat it by spin coating.

[0012] (3) Photopatterning: A transparent patterned photomask is applied to the surface of a polyimide spin-coated with ink, and then illuminated with an LED light source. Under illumination, the selected photoinitiator (benzophenone or photoinitiator 819) induces a photochemical reaction between poly(4-vinylpyridine) and the polyimide surface through hydrogen abstraction-coupling (Type II) or direct cleavage-initiation (Type I) mechanisms, thereby forming a stable poly(4-vinylpyridine) pattern in the exposed area. This pattern can selectively adsorb Pd. 2+ This guides subsequent metal deposition.

[0013] (4) Development treatment: The polyimide described in step (3) is developed with dichloromethane to remove ink from unreacted areas, and then dried to remove surface solvent.

[0014] (5) Palladium ion adsorption and reduction: The developed polyimide is immersed in a palladium chloride solution to allow the Pd ions to be adsorbed and reduced. 2+ The Pd ions are adsorbed by coordination with P4VP fixed on the polyimide substrate, then washed with deionized water, and then reduced at high temperature to reduce the Pd ions into catalytically active atoms, which serve as catalytic sites for subsequent metal deposition.

[0015] (6) Metal patterning deposition: Immerse the polyimide treated in step (5) in a chemical metal plating solution at room temperature for 20-40 minutes, then remove and dry.

[0016] In step (2), the concentration of poly(4-vinylpyridine) in the ink is 1 wt%-5 wt%, preferably 1 wt%-2 wt%;

[0017] In step (2), the photoinitiator is selected from benzophenone or photoinitiator 819, which can be initiated by ultraviolet light and visible light, respectively, and the concentration is 1wt%-5wt%, preferably 1wt%-2wt%.

[0018] In step (2), the solvent used for the ink is isopropanol, cyclopentanone, isobutanol, DMF, 1-pentanol or 3-pentanol.

[0019] In step (2), the ink distribution is adjusted by controlling the spin coater speed and time. The initial speed is 200-1000 rpm (preferably 500-800 rpm), maintained for 5-20 seconds (preferably 10-15 seconds) to make the ink initially evenly distributed. Then the speed is increased to 1000-3000 rpm (preferably 1500-2000 rpm) and maintained for 30-90 seconds (preferably 40-60 seconds) to form a uniform ink film.

[0020] When the photoinitiator is benzophenone, step (3) involves irradiation with ultraviolet light at a wavelength of 365 nm and a light intensity of 10-50 mW / cm. 2 The preferred value is 20-40 mW / cm 2 Irradiation is performed for 10-30 minutes, preferably 15-25 minutes. When the photoinitiator is photoinitiator 819, visible light with a wavelength of 405 nm is used for irradiation in step (3), with a light intensity of 10-50 mW / cm². 2 The preferred value is 20-30 mW / cm 2 Irradiate for 10-30 minutes, preferably 15-25 minutes.

[0021] In step (5), the palladium chloride solution is prepared by mixing palladium chloride with ammonium chloride, water, hydrogen peroxide and isopropanol in a mass ratio of 1~5:1~5:500~600:1~5:30~50 and stirring for 1-2 hours.

[0022] In step (5), the soaking time is 1-10 minutes, preferably 1-2 minutes.

[0023] In step (5), the polyimide surface is washed with deionized water to remove unadsorbed palladium chloride solution, and then the adsorbed Pd is... 2+ The polyimide ions are reduced at a high temperature of 250-350℃ for 10-30 minutes (preferably 15-20 minutes) to reduce Pd2+ The ions are reduced to catalytically active Pd atoms, which serve as catalytic sites for subsequent metal deposition.

[0024] In step (6), the chemical metal plating solution is a copper plating solution, a silver plating solution, or a nickel plating solution.

[0025] The copper plating solution consists of two components, solution A and solution B, which are prepared fresh for each use. The components and concentrations of solution A are as follows: anhydrous copper sulfate (CuSO4·5H2O) 10-50 g / L, ethylenediaminetetraacetic acid (EDTA) 10-50 g / L, 2,2'-bipyridine 10-50 mg / L, potassium sodium tartrate 50-500 mg / L, and sodium hydroxide (NaOH) 10-50 g / L. Solution B is a formaldehyde (HCHO) solution at a concentration of 1-20 mL / L.

[0026] The components and concentrations in the silver plating solution are as follows: silver nitrate (AgNO3) 1-10 g / L, ethylenediamine 1-50 g / L, potassium sodium tartrate 5-50 g / L, and 3,5-diiodotyrosine 0.1-1 g / L.

[0027] The components and concentrations in the nickel plating solution are as follows: nickel sulfate pentahydrate 20-50 g / L, sodium citrate 10-30 g / L, lactic acid 5-20 g / L, and dimethylamine borane 0.1-5 g / L.

[0028] The beneficial effects of this invention are reflected in:

[0029] Cost reduction: No need for complex and expensive high-vacuum equipment, reducing equipment costs; increased utilization of polyimide materials, reducing material costs; mild process conditions reduce production environment requirements, reducing additional cost inputs.

[0030] Material performance retention: By avoiding harsh pretreatment methods, the excellent thermal stability, chemical stability, flexibility and mechanical strength of polyimide are retained to the greatest extent, thereby improving the quality and reliability of FPCB products and extending their service life.

[0031] High-precision patterning: By precisely controlling each step of the process, high-precision metal patterning is achieved, with a minimum line width of 2 micrometers, meeting the FPCB industry's demand for fine circuit pattern manufacturing.

[0032] Excellent versatility: Not only is it suitable for patterning copper metal, but by simply changing the plating solution, it can also be used to pattern metals such as silver and nickel on polyimide, thus broadening its application range in the field of electronic materials and device manufacturing. Attached Figure Description

[0033] Figure 1 An image of the surface metal pattern obtained in Example 1 is shown.

[0034] Figure 2 An image of the surface metal pattern obtained in Example 2 is shown.

[0035] Figure 3 An image of the surface metal pattern obtained in Example 5 is shown.

[0036] Figure 4 Images of the surface metal pattern obtained in Example 6 are shown. Figure (b) is a magnified micrograph of Figure (a). Detailed Implementation

[0037] The technical solution of the present invention will be further analyzed and explained through specific embodiments below.

[0038] Example 1:

[0039] (1) Select a commercial polyimide film and ultrasonically clean the polyimide film by sequentially immersing it in anhydrous ethanol-water-anhydrous ethanol. Each cleaning session lasts 15 minutes to ensure the surface is thoroughly cleaned.

[0040] (2) Dissolve poly(4-vinylpyridine) (5wt%) and benzophenone (1wt%) in isopropanol to prepare an ink. Spin coat the ink onto the surface of the polyimide film obtained in step (1) using a spin coating method. The initial rotation speed is 500 rpm, held for 5 seconds, and then the rotation speed is increased to 1300 rpm for 45 seconds to form a uniform ink film.

[0041] (3) Cover the polyimide surface obtained in step (2) with a matrix array mask. Irradiate with ultraviolet light at a wavelength of 365 nm and an intensity of 36 mW / cm². 2 Irradiate for 15 minutes. The ink in the light-transmitting area of ​​the photomask reacts, while the ink in the light-blocking area remains unchanged.

[0042] (4) The polyimide obtained in step (3) after light irradiation was cleaned with dichloromethane, developed, and then dried.

[0043] (5) Palladium chloride, ammonium chloride, water, hydrogen peroxide and isopropanol are mixed and stirred for 1 h in a mass ratio of 1:1:590:4:30 to obtain a palladium chloride solution. The polyimide obtained in step (4) is immersed in the palladium chloride solution for 1 minute, and then the surface of the polyimide is washed with deionized water.

[0044] (6) Reduce the polyimide obtained in step (5) at a high temperature of 300°C using a hot plate and keep it warm for 15 minutes.

[0045] (7) Prepare two copper plating solutions by mixing them in a 1:1 volume ratio. Solution A consists of 20 g / L anhydrous copper sulfate, 20 g / L ethylenediaminetetraacetic acid, 20 mg / L 2,2'-bipyridine, 100 mg / L sodium potassium tartrate, and 20 g / L sodium hydroxide; Solution B consists of 5 mL / L formaldehyde solution. Immerse the polyimide obtained in step (6) in the copper plating solution at room temperature for 30 minutes. Under Pd catalysis, copper ions in the solution are reduced and deposited in the patterned area to form a copper metal pattern.

[0046] The surface metal pattern obtained above is as follows Figure 1 As shown. From Figure 1 As can be seen, a copper metal matrix array pattern with a linewidth of 50 micrometers was formed on the surface of polyimide.

[0047] Example 2:

[0048] (1) Select a commercial polyimide film and ultrasonically clean the polyimide film by sequentially immersing it in anhydrous ethanol-water-anhydrous ethanol. Each cleaning session lasts 15 minutes to ensure the surface is thoroughly cleaned.

[0049] (2) Dissolve poly(4-vinylpyridine) (5wt%) and photoinitiator 819 (1wt%) in cyclopentanone to prepare an ink. Spin coat the ink onto the surface of the polyimide film obtained in step (1) using a spin coating method. The initial rotation speed is 500 rpm, held for 5 seconds, and then the rotation speed is increased to 1300 rpm for 45 seconds to form a uniform ink film.

[0050] (3) Cover the polyimide surface obtained in step (2) with a rectangular array photomask. Irradiate with visible light at a wavelength of 405 nm and an intensity of 36 mW / cm². 2 Irradiate for 15 minutes. The ink in the light-transmitting area of ​​the photomask reacts, while the ink in the light-blocking area remains unchanged.

[0051] (4) The polyimide obtained in step (3) after light irradiation was cleaned with dichloromethane, developed, and then dried.

[0052] (5) Palladium chloride, ammonium chloride, water, hydrogen peroxide and isopropanol are mixed and stirred for 1 h in a mass ratio of 1:1:590:4:30 to obtain a palladium chloride solution. The polyimide obtained in step (4) is immersed in the palladium chloride solution for 1 minute, and then the surface of the polyimide is washed with deionized water.

[0053] (6) Reduce the polyimide obtained in step (5) at a high temperature of 300°C using a hot plate and keep it warm for 15 minutes.

[0054] (7) Prepare two copper plating solutions by mixing them in a 1:1 volume ratio. Solution A consists of 20 g / L anhydrous copper sulfate, 20 g / L ethylenediaminetetraacetic acid, 20 mg / L 2,2'-bipyridine, 100 mg / L sodium potassium tartrate, and 20 g / L sodium hydroxide; Solution B consists of 5 mL / L formaldehyde solution. Immerse the polyimide obtained in step (6) in the copper plating solution at room temperature for 30 minutes.

[0055] The surface metal pattern obtained above is as follows Figure 2 As shown. From Figure 2 As can be seen, a rectangular array pattern of copper metal with a linewidth of 50 micrometers was formed on the surface of polyimide.

[0056] Example 3:

[0057] (1) Select a commercial polyimide film and ultrasonically clean the polyimide film by sequentially immersing it in anhydrous ethanol-water-anhydrous ethanol. Each cleaning session lasts 15 minutes to ensure the surface is thoroughly cleaned.

[0058] (2) Dissolve 5 wt% of poly(4-vinylpyridine) in isopropanol to prepare an ink. Spin coat the ink onto the surface of the polyimide film obtained in step (1) using a spin coating method. The initial rotation speed is 500 rpm, held for 5 seconds, and then the rotation speed is increased to 1300 rpm for 45 seconds to form a uniform ink film.

[0059] (3) Cover the polyimide surface obtained in step (2) with a rectangular array photomask. Irradiate with ultraviolet light at a wavelength of 365 nm and an intensity of 36 mW / cm². 2 Irradiate for 15 minutes. The ink in the light-transmitting area of ​​the photomask reacts, while the ink in the light-blocking area remains unchanged.

[0060] (4) The polyimide obtained in step (3) after light irradiation was cleaned with dichloromethane, developed, and then dried.

[0061] (5) Palladium chloride, ammonium chloride, water, hydrogen peroxide and isopropanol are mixed and stirred for 1 h in a mass ratio of 1:1:590:4:30 to obtain a palladium chloride solution. The polyimide obtained in step (4) is immersed in the palladium chloride solution for 1 minute, and then the surface of the polyimide is washed with deionized water.

[0062] (6) Reduce the polyimide obtained in step (5) at a high temperature of 300°C using a hot plate and keep it warm for 15 minutes.

[0063] (7) Prepare two copper plating solutions by mixing them in a 1:1 volume ratio. Solution A consists of 20 g / L anhydrous copper sulfate, 20 g / L ethylenediaminetetraacetic acid, 20 mg / L 2,2'-bipyridine, 100 mg / L sodium potassium tartrate, and 20 g / L sodium hydroxide; Solution B consists of 5 mL / L formaldehyde solution. Immerse the polyimide obtained in step (6) in the copper plating solution at room temperature for 30 minutes.

[0064] The above operations did not result in a photoreaction because no photoinitiator was added to the ink, and therefore no metallic pattern was formed on the polyimide surface.

[0065] Example 4:

[0066] (1) Select a commercial polyimide film and ultrasonically clean the polyimide film by sequentially immersing it in anhydrous ethanol-water-anhydrous ethanol. Each cleaning session lasts 15 minutes to ensure the surface is thoroughly cleaned.

[0067] (2) Dissolve benzophenone (1 wt%) in isopropanol to prepare ink, and apply the ink to the surface of the polyimide film obtained in step (1) by spin coating. The initial rotation speed is 500 rpm, held for 5 seconds, and then the rotation speed is increased to 1300 rpm for 45 seconds to form a uniform ink film.

[0068] (3) Cover the polyimide surface obtained in step (2) with a rectangular array photomask. Irradiate with ultraviolet light at a wavelength of 365 nm and an intensity of 36 mW / cm². 2 Irradiate for 15 minutes. The ink in the light-transmitting area of ​​the photomask reacts, while the ink in the light-blocking area remains unchanged.

[0069] (4) The polyimide obtained in step (3) after light irradiation was cleaned with dichloromethane, developed, and then dried.

[0070] (5) Palladium chloride, ammonium chloride, water, hydrogen peroxide and isopropanol are mixed and stirred for 1 h in a mass ratio of 1:1:590:4:30 to obtain a palladium chloride solution. The polyimide obtained in step (4) is immersed in the palladium chloride solution for 1 minute, and then the surface of the polyimide is washed with deionized water.

[0071] (6) Reduce the polyimide obtained in step (5) at a high temperature of 300°C using a hot plate and keep it warm for 15 minutes.

[0072] (7) Prepare two copper plating solutions by mixing them in a 1:1 volume ratio. Solution A consists of 20 g / L anhydrous copper sulfate, 20 g / L ethylenediaminetetraacetic acid, 20 mg / L 2,2'-bipyridine, 100 mg / L sodium potassium tartrate, and 20 g / L sodium hydroxide. Solution B consists of 5 mL / L formaldehyde solution. Immerse the polyimide obtained in step (6) in the copper plating solution at room temperature for 30 minutes.

[0073] The above operations did not form a metallic pattern on the polyimide surface because no poly(4-vinylpyridine) that can adsorb the catalyst was added to the ink.

[0074] Example 5:

[0075] (1) Select a commercial polyimide film and ultrasonically clean the polyimide film by sequentially immersing it in anhydrous ethanol-water-anhydrous ethanol. Each cleaning session lasts 15 minutes to ensure the surface is thoroughly cleaned.

[0076] (2) Dissolve poly(4-vinylpyridine) (5wt%) and benzophenone (1wt%) in isopropanol to prepare an ink. Spin coat the ink onto the surface of the polyimide film obtained in step (1) using a spin coating method. The initial rotation speed is 500 rpm, held for 5 seconds, and then the rotation speed is increased to 1300 rpm for 45 seconds to form a uniform ink film.

[0077] (3) Cover the polyimide surface obtained in step (2) with a USAF photomask. Irradiate with ultraviolet light at a wavelength of 365 nm and an intensity of 36 mW / cm². 2 Irradiate for 15 minutes. The ink in the light-transmitting area of ​​the photomask reacts, while the ink in the light-blocking area remains unchanged.

[0078] (4) The polyimide obtained in step (3) after light irradiation was cleaned with dichloromethane, developed, and then dried.

[0079] (5) Palladium chloride, ammonium chloride, water, hydrogen peroxide and isopropanol are mixed and stirred for 1 h in a mass ratio of 1:1:590:4:30 to obtain a palladium chloride solution. The polyimide obtained in step (4) is immersed in the palladium chloride solution for 1 minute, and then the surface of the polyimide is washed with deionized water.

[0080] (6) Reduce the polyimide obtained in step (5) at a high temperature of 300°C using a hot plate and keep it warm for 15 minutes.

[0081] (7) Prepare two copper plating solutions by mixing them in a 1:1 volume ratio. Solution A consists of 20 g / L anhydrous copper sulfate, 20 g / L ethylenediaminetetraacetic acid, 20 mg / L 2,2'-bipyridine, 100 mg / L sodium potassium tartrate, and 20 g / L sodium hydroxide; Solution B consists of 5 mL / L formaldehyde solution. Immerse the polyimide obtained in step (6) in the copper plating solution at room temperature for 30 minutes.

[0082] The surface metal pattern obtained above is as follows Figure 3 As shown. From Figure 3 As can be seen, copper metal patterns were formed on the surface of polyimide, but the edge roughness of the pattern lines was low, and copper could not be plated in areas with narrow line widths, resulting in low line width accuracy.

[0083] Example 6:

[0084] (1) Select a commercial polyimide film and ultrasonically clean the polyimide film by sequentially immersing it in anhydrous ethanol-water-anhydrous ethanol. Each cleaning session lasts 15 minutes to ensure the surface is thoroughly cleaned.

[0085] (2) Dissolve poly(4-vinylpyridine) (1 wt%) and benzophenone (1 wt%) in isopropanol to prepare ink. Spin coat the ink onto the surface of the polyimide film obtained in step (1) by spin coating. The initial rotation speed is 500 rpm, held for 5 seconds, and then the rotation speed is increased to 1300 rpm for 45 seconds to form a uniform ink film.

[0086] (3) Cover the polyimide surface obtained in step (2) with a USAF photomask. Irradiate with ultraviolet light at a wavelength of 365 nm and an intensity of 36 mW / cm². 2 Irradiate for 15 minutes. The ink in the light-transmitting area of ​​the photomask reacts, while the ink in the light-blocking area remains unchanged.

[0087] (4) The polyimide obtained in step (3) after light irradiation was cleaned with dichloromethane, developed, and then dried.

[0088] (5) Palladium chloride, ammonium chloride, water, hydrogen peroxide and isopropanol are mixed and stirred for 1 h in a mass ratio of 1:1:590:4:30 to obtain a palladium chloride solution. The polyimide obtained in step (4) is immersed in the palladium chloride solution for 1 minute, and then the surface of the polyimide is washed with deionized water.

[0089] (6) Reduce the polyimide obtained in step (5) at a high temperature of 300°C using a hot plate and keep it warm for 15 minutes.

[0090] (7) Prepare two copper plating solutions by mixing them in a 1:1 volume ratio. Solution A consists of 20 g / L anhydrous copper sulfate, 20 g / L ethylenediaminetetraacetic acid, 20 mg / L 2,2'-bipyridine, 100 mg / L sodium potassium tartrate, and 20 g / L sodium hydroxide; Solution B consists of 5 mL / L formaldehyde solution. Immerse the polyimide obtained in step (6) in the copper plating solution at room temperature for 30 minutes.

[0091] The surface metal pattern obtained above is as follows Figure 4 As shown. From Figure 4 As shown in Figure (a), a copper metal pattern was formed on the polyimide surface with good line edge roughness. Figure (b) is a magnified microscopic view of Figure (a), showing that the minimum line width can reach 2 micrometers.

[0092] Comparing Examples 5 and 6, it can be seen that, under essentially the same process conditions, the concentration of poly(4-vinylpyridine) in the ink has a significant impact on the linewidth resolution and line edge quality of the final metallic pattern. In Example 5, the mass fraction of poly(4-vinylpyridine) in the ink was 5 wt%. The higher concentration of poly(4-vinylpyridine) resulted in a thicker polymer layer after spin coating, which enhanced light scattering and absorption within the film layer during exposure, leading to unclear boundaries of the photochemical reaction. In contrast, in Example 6, the mass fraction of poly(4-vinylpyridine) in the ink was reduced to 1 wt%. The lower concentration of P4VP formed a thinner and more uniform functional layer on the polyimide surface, which is beneficial for obtaining clearer photolithographic reaction boundaries during exposure.

[0093] Example 7:

[0094] (1) Select a commercial polyimide film and ultrasonically clean the polyimide film by sequentially immersing it in anhydrous ethanol-water-anhydrous ethanol. Each cleaning session lasts 15 minutes to ensure the surface is thoroughly cleaned.

[0095] (2) Dissolve poly(4-vinylpyridine) (1 wt%) and benzophenone (1 wt%) in isopropanol to prepare ink. Spin coat the ink onto the surface of the polyimide film obtained in step (1) by spin coating. The initial rotation speed is 500 rpm, held for 5 seconds, and then the rotation speed is increased to 1300 rpm for 45 seconds to form a uniform ink film.

[0096] (3) Cover the polyimide surface obtained in step (2) with a USAF photomask. Irradiate with ultraviolet light at a wavelength of 365 nm and an intensity of 36 mW / cm². 2 Irradiate for 15 minutes. The ink in the light-transmitting area of ​​the photomask reacts, while the ink in the light-blocking area remains unchanged.

[0097] (4) The polyimide obtained in step (3) after light irradiation was cleaned with dichloromethane, developed, and then dried.

[0098] (5) Palladium chloride, ammonium chloride, water, hydrogen peroxide and isopropanol are mixed and stirred for 1 hour in a mass ratio of 1:1:590:4:30 to obtain a palladium chloride solution. The polyimide obtained in step (4) is immersed in the palladium chloride solution for 1 minute, and then the surface of the polyimide is washed with deionized water.

[0099] (6) Reduce the polyimide obtained in step (5) at a high temperature of 300°C using a hot plate and keep it warm for 15 minutes.

[0100] (7) Prepare a fresh silver plating solution with 1 g / L silver nitrate (AgNO3), 2 g / L ethylenediamine, 10 g / L sodium potassium tartrate, and 0.1 g / L 3,5-diiodotyrosine. Immerse the polyimide obtained in step (6) in the silver plating solution at room temperature for 30 minutes.

[0101] Under the above conditions, poly(4-vinylpyridine) is selectively immobilized on the exposed areas of the polyimide surface after photolithography, and adsorbs and immobilizes palladium catalytic sites during subsequent processing. During electroless silver plating, silver ions are reduced and deposited only within the photolithographic area under the influence of the palladium catalytic sites, thereby forming a silver metal pattern on the polyimide surface consistent with the photomask pattern. The unexposed areas, lacking catalytic sites, do not experience silver metal deposition, indicating that the method of this invention can achieve selective patterning of silver metal on the polyimide surface.

[0102] Example 8:

[0103] (1) Select a commercial polyimide film and ultrasonically clean the polyimide film by sequentially immersing it in anhydrous ethanol-water-anhydrous ethanol. Each cleaning session lasts 15 minutes to ensure the surface is thoroughly cleaned.

[0104] (2) Dissolve poly(4-vinylpyridine) (1 wt%) and benzophenone (1 wt%) in isopropanol to prepare ink. Spin coat the ink onto the polyimide in step (1) using a spin coating method. The initial rotation speed is 500 rpm, held for 5 seconds, and then the rotation speed is increased to 1300 rpm for 45 seconds to form a uniform ink film.

[0105] (3) Cover the polyimide surface obtained in step (2) with a USAF photomask. Irradiate with ultraviolet light at a wavelength of 365 nm and an intensity of 36 mW / cm². 2 Irradiate for 15 minutes. The ink in the light-transmitting area of ​​the photomask reacts, while the ink in the light-blocking area remains unchanged.

[0106] (4) The polyimide obtained in step (3) after light irradiation was cleaned with dichloromethane, developed, and then dried.

[0107] (5) Palladium chloride, ammonium chloride, water, hydrogen peroxide and isopropanol are mixed and stirred for 1 h in a mass ratio of 1:1:590:4:30 to obtain a palladium chloride solution. The polyimide obtained in step (4) is immersed in the palladium chloride solution for 1 minute, and then the surface of the polyimide is washed with deionized water.

[0108] (6) Reduce the polyimide obtained in step (5) at a high temperature of 300°C using a hot plate and keep it warm for 15 minutes.

[0109] (7) Prepare a nickel plating solution on the spot, with nickel sulfate pentahydrate 40 g / L, sodium citrate 20 g / L, lactic acid 10 g / L, and dimethylamine borane 1 g / L. Immerse the polyimide obtained in step (6) in the nickel plating solution at room temperature for 30 minutes.

[0110] Similarly, in the electroless nickel plating system used in Example 8, the palladium catalytic sites fixed in the photolithographic region on the polyimide surface can effectively initiate the reduction reaction of nickel ions, causing nickel metal to be selectively deposited in the region, thereby forming a nickel metal pattern corresponding to the photolithographic pattern; no nickel metal deposition occurs in the region where no photolithographic reaction occurs, indicating that the photolithography-electroless plating synergistic method of the present invention is also applicable to nickel metal systems, demonstrating good versatility.

[0111] Example 9:

[0112] (1) Select a commercial polyimide film and ultrasonically clean the polyimide film by sequentially immersing it in anhydrous ethanol-water-anhydrous ethanol. Each cleaning session lasts 15 minutes to ensure the surface is thoroughly cleaned.

[0113] (2) Dissolve poly(4-vinylpyridine) (5wt%) and benzophenone (1wt%) in isobutanol to prepare ink. Spin coat the ink onto the surface of the polyimide film obtained in step (1) by spin coating. The initial rotation speed is 500 rpm, held for 5 seconds, and then the rotation speed is increased to 1300 rpm for 45 seconds to form a uniform ink film.

[0114] (3) Cover the polyimide surface obtained in step (2) with a square photomask. Irradiate with ultraviolet light at a wavelength of 365 nm and an intensity of 36 mW / cm². 2 Irradiate for 15 minutes. The ink in the light-transmitting area of ​​the photomask reacts, while the ink in the light-blocking area remains unchanged.

[0115] (4) The polyimide obtained in step (3) after light irradiation was cleaned with dichloromethane, developed, and then dried.

[0116] (5) Palladium chloride, ammonium chloride, water, hydrogen peroxide and isopropanol are mixed and stirred for 1 h in a mass ratio of 1:1:590:4:30 to obtain a palladium chloride solution. The polyimide obtained in step (4) is immersed in the palladium chloride solution for 1 minute, and then the surface of the polyimide is washed with deionized water.

[0117] (6) Reduce the polyimide obtained in step (5) at a high temperature of 300°C using a hot plate and keep it warm for 15 minutes.

[0118] (7) Prepare two copper plating solutions by mixing them in a 1:1 volume ratio. Solution A consists of 20 g / L anhydrous copper sulfate, 20 g / L ethylenediaminetetraacetic acid, 20 mg / L 2,2'-bipyridine, 100 mg / L sodium potassium tartrate, and 20 g / L sodium hydroxide; Solution B consists of 5 mL / L formaldehyde solution. Immerse the polyimide obtained in step (6) in the copper plating solution at room temperature for 30 minutes. Under Pd catalysis, copper ions in the solution are reduced and deposited in the patterned area to form a copper metal pattern.

[0119] Under the above conditions, after spin coating and photolithography, the ink prepared using isobutanol as a solvent allows poly(4-vinylpyridine) to be stably fixed on the photolithographic region of the polyimide surface. During subsequent palladium ion adsorption and electroless plating, copper metal is selectively deposited in this region, thereby forming a copper metal pattern on the polyimide surface that matches the photomask pattern. This demonstrates that the method of the present invention can still achieve effective metal patterning even with different solvents.

[0120] Example 10:

[0121] (1) Select a commercial polyimide film and ultrasonically clean the polyimide film by sequentially immersing it in anhydrous ethanol-water-anhydrous ethanol. Each cleaning session lasts 15 minutes to ensure the surface is thoroughly cleaned.

[0122] (2) Dissolve poly(4-vinylpyridine) (5wt%) and benzophenone (1wt%) in DMF to prepare ink. Spin coat the ink onto the surface of the polyimide film obtained in step (1) by spin coating. The initial rotation speed is 500 rpm, held for 5 seconds, and then the rotation speed is increased to 1300 rpm for 45 seconds to form a uniform ink film.

[0123] (3) Cover the polyimide surface obtained in step (2) with a square photomask. Irradiate with ultraviolet light at a wavelength of 365 nm and an intensity of 36 mW / cm². 2 Irradiate for 15 minutes. The ink in the light-transmitting area of ​​the photomask reacts, while the ink in the light-blocking area remains unchanged.

[0124] (4) The polyimide obtained in step (3) after light irradiation was cleaned with dichloromethane, developed, and then dried.

[0125] (5) Palladium chloride, ammonium chloride, water, hydrogen peroxide and isopropanol are mixed and stirred for 1 h in a mass ratio of 1:1:590:4:30 to obtain a palladium chloride solution. The polyimide obtained in step (4) is immersed in the palladium chloride solution for 1 minute, and then the surface of the polyimide is washed with deionized water.

[0126] (6) Reduce the polyimide obtained in step (5) at a high temperature of 300°C using a hot plate and keep it warm for 15 minutes.

[0127] (7) Prepare two copper plating solutions by mixing them in a 1:1 volume ratio. Solution A consists of 20 g / L anhydrous copper sulfate, 20 g / L ethylenediaminetetraacetic acid, 20 mg / L 2,2'-bipyridine, 100 mg / L sodium potassium tartrate, and 20 g / L sodium hydroxide; Solution B consists of 5 mL / L formaldehyde. Immerse the polyimide obtained in step (6) in the copper plating solution at room temperature for 30 minutes. Under Pd catalysis, copper ions in the solution are reduced and deposited in the patterned area to form a copper metal pattern.

[0128] Under the above conditions, inks prepared with DMF as a solvent can also form stable photolithographic reaction patterns on the polyimide surface, fix palladium catalytic sites and trigger subsequent chemical copper plating reactions, so that copper metal is selectively deposited in the photolithographic area and no metal deposition occurs in the unexposed area, indicating that the method of the present invention has good adaptability to polar solvent systems.

[0129] Example 11:

[0130] (1) Select a commercial polyimide film and ultrasonically clean the polyimide film by sequentially immersing it in anhydrous ethanol-water-anhydrous ethanol. Each cleaning session lasts 15 minutes to ensure the surface is thoroughly cleaned.

[0131] (2) Dissolve 4-vinylpyridine (5wt%) and benzophenone (1wt%) in 1-pentanol to prepare an ink. Spin coat the ink onto the surface of the polyimide film obtained in step (1) using a spin coating method. The initial rotation speed is 500 rpm, held for 5 seconds, and then the rotation speed is increased to 1300 rpm for 45 seconds to form a uniform ink film.

[0132] (3) Cover the polyimide surface obtained in step (2) with a square photomask. Irradiate with ultraviolet light at a wavelength of 365 nm and an intensity of 36 mW / cm². 2 Irradiate for 15 minutes. The ink in the light-transmitting area of ​​the photomask reacts, while the ink in the light-blocking area remains unchanged.

[0133] (4) The polyimide obtained in step (3) after light irradiation was cleaned with dichloromethane, developed, and then dried.

[0134] (5) Palladium chloride, ammonium chloride, water, hydrogen peroxide and isopropanol are mixed and stirred for 1 h in a mass ratio of 1:1:590:4:30 to obtain a palladium chloride solution. The polyimide obtained in step (4) is immersed in the palladium chloride solution for 1 minute, and then the surface of the polyimide is washed with deionized water.

[0135] (6) Reduce the polyimide obtained in step (5) at a high temperature of 300°C using a hot plate and keep it warm for 15 minutes.

[0136] (7) Prepare two copper plating solutions by mixing them in a 1:1 volume ratio. Solution A consists of 20 g / L anhydrous copper sulfate, 20 g / L ethylenediaminetetraacetic acid, 20 mg / L 2,2'-bipyridine, 100 mg / L sodium potassium tartrate, and 20 g / L sodium hydroxide; Solution B consists of 5 mL / L formaldehyde solution. Immerse the polyimide obtained in step (6) in the copper plating solution at room temperature for 30 minutes. Under Pd catalysis, copper ions in the solution are reduced and deposited in the patterned area to form a copper metal pattern.

[0137] In the 1-pentanol solvent system used under the above conditions, the ink can still achieve patterning and fixation of poly4-vinylpyridine on the polyimide surface after spin coating and photolithography, and obtain copper metal deposition results corresponding to the photomask pattern under palladium catalysis, further demonstrating that the method of the present invention has good process versatility for different types of organic solvents.

[0138] Example 12:

[0139] (1) Select a commercial polyimide film and ultrasonically clean the polyimide film by sequentially immersing it in anhydrous ethanol-water-anhydrous ethanol. Each cleaning session lasts 15 minutes to ensure the surface is thoroughly cleaned.

[0140] (2) Dissolve poly(4-vinylpyridine) (5wt%) and benzophenone (1wt%) in 3-pentanol to prepare an ink. Spin coat the ink onto the surface of the polyimide film obtained in step (1) using a spin coating method. The initial rotation speed is 500 rpm, held for 5 seconds, and then the rotation speed is increased to 1300 rpm for 45 seconds to form a uniform ink film.

[0141] (3) Cover the polyimide surface obtained in step (2) with a square photomask. Irradiate with ultraviolet light at a wavelength of 365 nm and an intensity of 36 mW / cm². 2 Irradiate for 15 minutes. The ink in the light-transmitting area of ​​the photomask reacts, while the ink in the light-blocking area remains unchanged.

[0142] (4) The polyimide obtained in step (3) after light irradiation was cleaned with dichloromethane, developed, and then dried.

[0143] (5) Palladium chloride, ammonium chloride, water, hydrogen peroxide and isopropanol are mixed and stirred for 1 h in a mass ratio of 1:1:590:4:30 to obtain a palladium chloride solution. The polyimide obtained in step (4) is immersed in the palladium chloride solution for 1 minute, and then the surface of the polyimide is washed with deionized water.

[0144] (6) Reduce the polyimide obtained in step (5) at a high temperature of 300°C using a hot plate and keep it warm for 15 minutes.

[0145] (7) Prepare two-component copper plating solutions by mixing them in a 1:1 volume ratio; Solution A consists of 20 g / L anhydrous copper sulfate, 20 g / L ethylenediaminetetraacetic acid, 20 mg / L 2,2'-bipyridine, 100 mg / L sodium potassium tartrate, and 20 g / L sodium hydroxide; Solution B consists of 5 mL / L formaldehyde. Immerse the polyimide obtained in step (6) in the copper plating solution at room temperature for 30 minutes. Under Pd catalysis, copper ions in the solution are reduced and deposited in the patterned area to form a copper metal pattern.

[0146] In Example 12, the ink prepared using 3-pentanol as a solvent, after photolithography and subsequent processing, can achieve selective deposition of copper metal on the polyimide surface within the photolithography area. The resulting metal pattern is consistent with the photomask pattern, further demonstrating that the method of the present invention has good process versatility for different types of organic solvents.

Claims

1. A method for achieving high-precision photolithographic metal patterning on a polyimide surface, characterized in that: After cleaning, a polyimide film is spin-coated with an ink containing poly(4-vinylpyridine) and a photoinitiator. A transparent patterned photomask is then placed over the ink-coated polyimide surface. Irradiation with an LED light source initiates a photochemical reaction between the poly(4-vinylpyridine) and the polyimide surface, achieving the initial patterning. Subsequently, the photo-irradiated polyimide is developed using poly(4-vinylpyridine) as a good solvent. The developed polyimide is then immersed in a palladium chloride solution, where the Pd in ​​the solution is coordinated. 2+ Ions are adsorbed on the patterned region and then reduced at high temperature, causing Pd to... 2+ Ions are reduced to catalytically active Pd atoms, which serve as catalytic sites for subsequent metal deposition; the palladium-reduced polyimide is immersed in a chemical metal plating bath for metal patterning deposition. Includes the following steps: (1) Cleaning of polyimide film: Select commercial polyimide film and clean it by ultrasonic cleaning in anhydrous ethanol, water and anhydrous ethanol in sequence; (2) Spin coating of ink: Prepare an ink containing poly(4-vinylpyridine) and a photoinitiator, transfer it to a cleaned polyimide surface, and coat it by spin coating; the concentration of poly(4-vinylpyridine) in the ink is 1wt%-2wt%, and the concentration of the photoinitiator is 1wt%-2wt%; (3) Photopatterning: A light-transmitting patterned photomask is applied to the surface of polyimide coated with ink and then illuminated with an LED light source; (4) Development treatment: The polyimide described in step (3) is developed with dichloromethane to remove ink from unreacted areas, and then dried to remove surface solvent; (5) Palladium ion adsorption and reduction: The developed polyimide is immersed in a palladium chloride solution for 1-10 minutes to allow the Pd ions to adsorb and reduce. 2+ The Pd chloride solution was adsorbed by coordination with P4VP immobilized on the polyimide substrate. The polyimide surface was then washed with deionized water to remove unadsorbed palladium chloride solution. The adsorbed Pd chloride was then... 2+ The polyimide ions are reduced at a high temperature of 250-350℃ for 10-30 minutes, causing Pd to... 2+ The ions are reduced to catalytically active Pd atoms, which serve as catalytic sites for subsequent metal deposition. (6) Metal patterning deposition: Immerse the polyimide treated in step (5) in a chemical metal plating solution at room temperature for 20-40 minutes, then remove and dry. In step (2), the photoinitiator is selected from benzophenone or photoinitiator 819; In step (5), the palladium chloride solution is prepared by mixing palladium chloride with ammonium chloride, water, hydrogen peroxide and isopropanol in a mass ratio of 1~5:1~5:500~600:1~5:30~50.

2. The method according to claim 1, characterized in that: The solvent for the ink is isopropanol, cyclopentanone, isobutanol, DMF, 1-pentanol, or 3-pentanol.

3. The method according to claim 1, characterized in that: In step (2), the ink distribution is adjusted by controlling the spin coater speed and time. The initial speed is 200-1000 rpm, maintained for 5-20 seconds to make the ink initially evenly distributed. Then the speed is increased to 1000-3000 rpm and maintained for 30-90 seconds to form a uniform ink film.

4. The method according to claim 1, characterized in that: In step (6), the chemical metal plating solution is a copper plating solution, a silver plating solution, or a nickel plating solution.

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