Strong-adsorption and high-conductivity gold coating for PI substrate and preparation method of high-adsorption and high-conductivity gold coating

Abstract

The invention provides a high-adsorption and high-conductivity gold coating for a PI substrate and a preparation method of the high-adsorption and high-conductivity gold coating, and belongs to the technical field of electronic functional materials. The preparation method comprises the following steps: synthesizing tert-dodecylmercaptan gold, and mixing the tert-dodecylmercaptan gold with a first organic solvent to obtain an organic gold coating; and the pretreated PI substrate is coated with the organic gold coating and annealed, and the gold coating is obtained. According to the method, mercaptan molecules are effectively used as a bifunctional bridge to cooperatively create an organic-inorganic hybrid interface with high bonding strength and good stability, the inherent defect of poor adhesion of a pure gold coating is overcome, the sheet resistance of the prepared gold coating is lower than 0.3 omega / sq, the adhesion reaches the 5B level, the resistance is not obviously changed in an environmental adaptability test, the adhesion is still the 5B level, and the prepared gold coating has a good application prospect. And high conductivity, strong substrate adhesion and excellent environmental stability of the gold coating are realized.

Description

Technical Field

[0001] This invention belongs to the field of electronic functional materials technology, specifically relating to a strongly adsorbed, highly conductive gold coating for PI substrates and its preparation method. Background Technology

[0002] Flexible electronics technology has become a key direction leading the development of the next generation of electronics industry due to its broad application prospects in wearable devices, biomedical sensing, flexible displays, and advanced packaging. As a core component of flexible electronic devices, flexible electrodes not only need to have excellent conductivity, but also must meet mechanical flexibility requirements such as bendability and stretchability, and maintain long-term performance stability in complex operating environments.

[0003] Polyimide (PI) is a polymer material containing imide groups. It is mainly formed by the polymerization of diamines and dianhydrides into polyamic acid polymers, which are then coated into films and subjected to high-temperature imidization and dehydration. Therefore, among many substrate materials, PI films are widely used as core substrate materials for flexible electronics due to their excellent high-temperature resistance, high insulation strength, superior mechanical properties, and dimensional stability. However, in the high-end segments of the PI film industry chain, especially in gold-plated PI films used for high-performance interconnects, the technology and market have long been monopolized by a few international companies, and domestic companies in this field are highly dependent on imported products.

[0004] Traditional methods for preparing metal (especially gold) coatings on flexible substrates such as polyimide (PI) mainly rely on vacuum deposition techniques (such as evaporation and sputtering) or electrochemical deposition (such as electroplating). While these methods can yield high-quality thin films, they generally suffer from the following inherent drawbacks: 1) They rely on complex and expensive vacuum equipment, resulting in high initial investment and maintenance costs; 2) The process steps are cumbersome, leading to low production efficiency and making it difficult to achieve large-area, low-cost manufacturing; 3) Material utilization is low, with waste caused by masking; 4) They have poor adaptability to substrate shapes, making it difficult to handle complex three-dimensional structures or wires; 5) Some processes (such as certain electroplating processes) may generate environmental pollutants.

[0005] To overcome the aforementioned limitations, solution processing methods based on functional slurries or coatings have received widespread attention in recent years. This method involves formulating metal precursors into inks or coatings, forming films using simple methods such as spin coating, spraying, or brushing, and then converting them into functional metal layers through subsequent processing. It offers significant advantages such as simple processing, low cost, applicability to various substrates and shapes, and ease of large-scale production. Currently, developed conductive coating systems mainly include silver-based, copper-based, carbon-based (such as graphene and carbon nanotubes), and conductive polymers. While silver and copper possess high intrinsic conductivity, their susceptibility to oxidation and corrosion leads to poor long-term reliability, especially in humid or corrosive environments. Carbon-based materials and conductive polymers, on the other hand, have much lower conductivity than metals, making it difficult to meet the requirements of high-density, high-performance interconnects.

[0006] In contrast, gold possesses extremely high chemical inertness, excellent corrosion resistance, superior conductivity, and good biocompatibility, making it an ideal material for highly reliable flexible electrodes and interconnects. However, in existing technologies, achieving high conductivity, strong substrate adhesion, and excellent environmental stability of gold coatings on flexible substrates (especially polyimide) simultaneously through simple solution processes remains a significant challenge.

[0007] Therefore, there is an urgent need in this field for an organic gold coating with a simple process that does not require vacuum equipment and its supporting treatment method, so as to prepare a flexible gold coating with strong adhesion and high conductivity that can be comparable to or even better than traditional vacuum gold plating. Summary of the Invention

[0008] To address the aforementioned technical problems in the prior art, this invention provides a highly adsorbed and highly conductive gold coating for PI substrates and its preparation method. By synthesizing a gold solution and then preparing an organic gold coating, which is then applied to a PI substrate, the gold coating achieves high conductivity, strong substrate adhesion, and excellent environmental stability.

[0009] This invention provides a method for preparing a strongly adsorbed, highly conductive gold coating for a PI substrate, comprising the following steps: (1) Synthesize tert-dodecyl mercaptan gold, and mix tert-dodecyl mercaptan gold with a first organic solvent to obtain an organic gold coating; (2) Apply the organic gold coating onto the pretreated PI substrate and anneal it to obtain a gold coating.

[0010] This invention synthesizes tert-dodecylthiol gold and then prepares an organo-gold coating. It effectively utilizes the thiol molecule as a bifunctional bridge, with one end binding to gold nanoparticles or the gold surface via a strong Au-S bond, and the other end forming a strong chemical or physical interaction with the PI substrate. Simultaneously, the tight van der Waals force stacking and stress buffering capability provided by the long alkyl chain synergistically create a highly strong and stable organic-inorganic hybrid interface, buffering thermal or physical stress between the gold coating and the substrate. This overcomes the inherent defect of poor adhesion in pure gold coatings, achieving high conductivity, strong substrate adhesion, and excellent environmental stability in the gold coating.

[0011] Preferably, resin is also added during mixing in step (1).

[0012] Preferably, the resin is one or more selected from terpene resin, rosin resin, epoxy resin, phenolic resin, and acrylic resin.

[0013] Preferably, the resin accounts for 0%-22.2% of the organic gold coating by weight.

[0014] Adding resin within the above range can effectively improve the electrical properties of the gold coating, significantly reducing the sheet resistance of the annealed gold coating. Furthermore, the amount of resin added will not significantly interfere with the resistance of the gold coating, and the electrical properties remain stable.

[0015] More preferably, the resin accounts for 0%-18% of the organic gold coating by weight.

[0016] More preferably, the resin accounts for 0%, 6.67%, 12.5%, and 17.6% of the organic gold coating by weight.

[0017] Preferably, by mass, the first organic solvent accounts for 55.6%-71.4% of the organic gold coating, and the tert-dodecyl mercaptan gold accounts for 22.2%-28.6% of the organic gold coating.

[0018] Preferably, in step (1), the first organic solvent is selected from one or more of terpineol, turpentine, toluene, xylene, pinene, ethyl acetate, butyl acetate, petroleum ether, chloroform, and camphor oil.

[0019] More preferably, the first organic solvent is a mixture of camphor oil and terpineol, wherein the mass ratio of camphor oil to terpineol does not exceed 0.5.

[0020] Preferably, the synthesis of tert-dodecylthiol gold in step (1) includes: (1-1) Dissolve gold particles in aqua regia and heat to obtain a gold solution. Mix the gold solution with a second organic solvent to obtain a first solution. (1-2) Under stirring at room temperature, dimethyl sulfide was added dropwise to the first solution, followed by tert-dodecyl mercaptan, to obtain a white oily substance; (1-3) The white oily substance was dissolved in a third organic solvent and a second organic solvent was added. After drying, the final oily substance was obtained.

[0021] Preferably, in step (1-1), the heating temperature is 80 °C and the heating time is 16 h.

[0022] More preferably, concentrated hydrochloric acid is added during the heating process to remove excess concentrated nitric acid.

[0023] Preferably, in step (1-1), the second organic solvent is methanol.

[0024] Preferably, the volume ratio of the gold solution to the second organic solvent is 2 to 5:10.

[0025] More preferably, the volume ratio of the gold solution to the second organic solvent is 1:3.

[0026] Preferably, in steps (1-2), the molar ratio of dimethyl sulfide to gold in the first solution is 2-4:1; and the molar ratio of tert-dodecyl mercaptan to gold in the first solution is 1-1.5:1.

[0027] More preferably, in steps (1-2), the molar ratio of dimethyl sulfide to gold in the first solution is 3:1; and the molar ratio of tert-dodecyl mercaptan to gold in the first solution is 1.12:1.

[0028] More preferably, in steps (1-2), after adding dimethyl sulfide, the mixture is stirred for at least 10 min; after adding tert-dodecyl mercaptan, the mixture is stirred for at least 2 h.

[0029] Preferably, in steps (1-3), the third organic solvent is ethyl acetate.

[0030] Preferably, in steps (1-3), the volume ratio of the third organic solvent to the second organic solvent is 5~14:100.

[0031] More preferably, in steps (1-3), the volume ratio of the third organic solvent to the second organic solvent is 1:10.

[0032] Preferably, in steps (1-3), the drying temperature is 40-50 °C and the drying time is at least 12 h.

[0033] Preferably, the PI substrate is in the shape of a block or filament.

[0034] Preferably, in step (2), the pretreatment of the PI substrate includes: sequential ultrasonic cleaning with acetone for 15-45 min, ultrasonic cleaning with ethanol for 15-45 min, and finally oxygen plasma treatment at 5-15℃ for 5-10 min.

[0035] Preferably, in step (2), the coating method is brushing, spraying or spin coating.

[0036] Preferably, the annealing heating rate in step (2) is 5-10 ℃ / min, the annealing temperature is 300-400 ℃, and the annealing time is 100-150 min.

[0037] At the above annealing temperature, tert-dodecyl mercaptan gold first decomposes into gold particles, which then gradually aggregate and settle onto the PI substrate to form a gold film, improving conductivity and ensuring uniformity of the gold coating surface.

[0038] The present invention also provides a strongly adsorbed, highly conductive PI-based gold coating prepared using the preparation method described above.

[0039] Preferably, the sheet resistance of the strongly adsorbed, highly conductive PI-based gold coating is less than 0.3 Ω / sq, and the adhesion reaches grade 5B.

[0040] Compared with the prior art, the present invention has the following beneficial effects: (1) Based on the thiol molecule as a bifunctional bridge, the present invention synergistically creates an organic-inorganic hybrid interface with high bonding strength and good stability, which is applied to the surface of PI substrate, significantly improving the high conductivity, strong substrate adhesion and excellent environmental stability of the gold coating.

[0041] (2) The method for preparing a PI base gold coating with strong adsorption and high conductivity provided by the present invention realizes the solution application process of the PI base gold coating with both high conductivity and strong adhesion, and has strong environmental adaptability in a variety of complex corrosive chemical environments and harsh temperature conditions, thus eliminating the dependence on high vacuum equipment.

[0042] (3) The strongly adsorbed and highly conductive PI base gold coating prepared by the preparation method described above has a sheet resistance of less than 0.3 Ω / sq and an adhesion of 5B grade. In the environmental adaptability test, the resistance does not change significantly and the adhesion is still 5B grade. The product performance reaches or even exceeds the vacuum coating level in some aspects, and has significant innovation and economy. Attached Figure Description

[0043] Figure 1 This is a photograph of the PI-based gold coating prepared in Example 1.

[0044] Figure 2The effect of different resin addition amounts prepared in Examples 1-4 on the electrical properties of PI-based gold coatings.

[0045] Figure 3 Images showing the adhesion strength of the PI-based gold coatings prepared in Examples 1-4.

[0046] Figure 4 The images are scanning electron microscope (SEM) images of the PI-based gold coatings obtained at different annealing temperatures in Examples 3, 5, and 6; wherein, Figure 4 In the image, a1 is a SEM image of the PI-based gold coating surface prepared in Example 3. Figure 4 a2 in the image is a SEM image of the PI-based gold coating surface prepared in Example 5. Figure 4 a3 in the image is a SEM image of the PI-based gold coating surface prepared in Example 6.

[0047] Figure 5 Electrical properties of the PI-based gold coating prepared in Example 1 after complex environmental treatment.

[0048] Figure 6 The image shows the adhesion strength of the PI-based gold coating prepared in Example 1 after undergoing complex environmental treatment.

[0049] Figure 7 Images showing the electrical properties and adhesion strength of the PI-based gold coating prepared in Example 1 after bending cycle and finger friction cycle tests; wherein, Figure 7 In this context, 'a' represents the electrical properties of the PI-based gold coating after a bending cycle test. Figure 7 In the image, b represents the adhesion strength of the PI-based gold coating after a bending cycle test. Figure 7 In this context, 'c' represents the electrical properties of the PI-based gold coating after a finger-friction cycle test. Figure 7 In the image, d represents the adhesion strength of the PI base gold coating after a finger rubbing cycle test.

[0050] Figure 8 The LED conduction test diagram is shown for the PI wire coated with gold coating prepared in Example 7. Detailed Implementation

[0051] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely to provide a better understanding of the present invention by illustrating examples of the invention, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0052] All raw materials are sourced from the market.

[0053] Example 1 This invention provides a method for preparing a strongly adsorbed, highly conductive gold coating for a PI substrate, comprising the following steps: (1) Immerse the commercial PI block in acetone, clean it under ultrasonic conditions for 45 min, then transfer it to ethanol, clean it under ultrasonic conditions for 45 min, and finally perform plasma treatment at 5~15℃ for 5 min to remove oxides and achieve surface activation. (2) Synthesis of gold tert-dodecyl mercaptan: Weigh 0.8 g of gold particles and dissolve them in an appropriate amount of aqua regia (concentrated hydrochloric acid: concentrated nitric acid = 3:1). Heat at 80 °C and add concentrated hydrochloric acid to remove excess concentrated nitric acid. After heating for 16 h, a gold solution is obtained. Solution A was prepared by mixing a gold solution with methanol at a volume ratio of 1:3. Dimethyl sulfide (DMS) was slowly added dropwise to solution A (the molar ratio of DMS to gold in solution A was 3:1) at room temperature and with vigorous stirring. A pale yellow precipitate was immediately formed during the addition process. The mixture was stirred for 10 min. Then, an excess of tert-dodecyl mercaptan was slowly added dropwise to solution A (the molar ratio of tert-dodecyl mercaptan to gold in solution A was 1.12:1), and stirred for 2 h. During the stirring process, the light yellow precipitate turned into a white oily substance. After the reaction was completed, the white oily substance was collected by filtration, dissolved in ethyl acetate, and then excess methanol was slowly added (the volume ratio of ethyl acetate to methanol was 1:10). The mixture was then filtered to obtain a white oily precipitate. The precipitate was washed 3-5 times with a large amount of methanol to thoroughly remove reaction byproducts and unreacted raw materials. The washed solid product was placed in a vacuum drying oven and dried at 40-50 °C for 12 h to obtain a white tert-dodecyl mercaptan gold oil with a gold content of 48.97 wt.%.

[0054] (3) Preparation of organic gold coating: The prepared tert-dodecyl mercaptan gold oil is dissolved in an appropriate amount of terpineol and camphor oil mixed solution, wherein the mass ratio of tert-dodecyl mercaptan gold oil to terpineol and camphor oil mixed solution is 2:5, the mass ratio of terpineol and camphor oil is 7:3, and 17.6 wt.% terpene resin is added. After ultrasonic dispersion, the mixture is fully mixed to obtain organic gold coating. (4) The organogold coating obtained in step (3) is applied to the pretreated commercial PI in step (1) by brushing. After completion, the sample is transferred to a tube furnace, and the heating rate is set to 10 ℃ / min. The sample is then annealed at 350 ℃ for 120 min in an air atmosphere. After annealing, the sample is removed after the tube furnace has cooled down. A PI-based gold coating with strong adhesion (5B grade) and high conductivity (sheet resistance less than 0.3 Ω / sq) is obtained. Figure 1 This is a photograph of the prepared PI-based gold coating.

[0055] Example 2 The preparation method of Example 2 is the same as that of Example 1, except that terpene resin is not added in step (3) when preparing the organic gold coating.

[0056] Example 3 The preparation method of Example 3 is the same as that of Example 1, except that 6.67 wt.% of terpene resin is added in step (3) during the preparation of the organogold coating.

[0057] Example 4 The preparation method of Example 4 is the same as that of Example 1, except that 12.5 wt.% terpene resin is added in step (3) during the preparation of the organogold coating.

[0058] Example 5 The preparation method of Example 5 is the same as that of Example 3, except that the annealing temperature in step (4) is 250 °C.

[0059] Example 6 The preparation method of Example 6 is the same as that of Example 3, except that the annealing temperature in step (4) is 300 °C.

[0060] Example 7 The preparation method of Example 7 is the same as that of Example 3, except that in step (1), the commercial PI filament is soaked in acetone.

[0061] Detection Example 1 The effects of different amounts of terpene resin added in Examples 1-4 on the electrical properties and adhesion strength of the gold coating were studied, and the test methods are as follows: Sheet resistance: Place the sample to be tested horizontally on the test stage, use a four-probe resistivity meter, press the probe vertically down to make it contact the sample, and the sheet resistance value can be obtained.

[0062] Adhesion: Place the sample to be tested horizontally on the test platform, use a cross-cutting tool to evenly cut out squares of a certain size, and evaluate the integrity of the coating in the test area.

[0063] Figure 2 Examples 1-4 illustrate the effect of different amounts of terpene resin added on the electrical properties of the gold coating. The results show that the addition of terpene resin can significantly increase the electrical properties of the gold coating. The flexible gold coating obtained after annealing without the addition of terpene resin has a high sheet resistance, while the flexible gold coating obtained after annealing with the addition of terpene resin has a sheet resistance that is reduced by about an order of magnitude, and the resin content has little effect on the sheet resistance of the gold coating.

[0064] Figure 3The PI base gold coatings obtained in Examples 1-4 all have extremely high adhesion strength (5B).

[0065] Detection Example 2 The PI-based gold coatings prepared at different annealing temperatures in Examples 3, 5 and 6 were investigated. Figure 4 Table 1 shows the surface SEM images of the PI-based gold coatings obtained at different annealing temperatures in Examples 3, 5, and 6. Table 1 shows the sheet resistance and adhesion strength grades of the PI-based gold coatings obtained at different annealing temperatures in Examples 3, 5, and 6.

[0066] Table 1

[0067] Combination Figure 4 As can be seen from the results in Table 1, at the above annealing temperature, tert-dodecyl mercaptan gold first decomposes into gold particles, and then the gold particles gradually aggregate into a gold film; as the annealing temperature increases, the gold coating surface becomes more uniform and the conductivity improves.

[0068] Detection Example 3 Adaptability testing of PI-based gold coatings in complex environments: To test the adaptability of the PI-based gold coating in complex environments, the PI-based gold coating prepared in Example 1 was immersed in concentrated hydrochloric acid for 12 h, 1 M sodium hydroxide solution for 12 h, concentrated sulfuric acid for 12 h, 5% potassium chloride solution for 12 h, and in an ultra-low temperature environment (-100 ℃) for 30 min. The change in sheet resistance of the gold coating before and after the treatment was calculated, and the adhesion was tested according to ASTM D3359 standard.

[0069] Figure 5 and Figure 6 The diagrams show the sheet resistance and adhesion strength of the PI-based gold coatings obtained after treatment under different conditions. It can be seen that the sheet resistance of the PI-based gold coating prepared in Example 1 remains below 0.3 Ω / sq after treatment, and the adhesion test result is still 5B. This indicates that the PI-based gold coating prepared in Example 3 maintains high conductivity and strong adhesion even after treatment with strong acids, strong alkalis, strong oxidizing agents, strong corrosive solutions, and ultra-low temperature environments, demonstrating excellent environmental adaptability in various complex environments.

[0070] Detection Example 4 Fatigue testing of PI-based gold coating: To test the durability of the PI base gold coating, a multimeter was connected to both ends of the PI base gold coating prepared in Example 1. The gold coating was rubbed back and forth with a finger 500 times. After every 50 cycles, the sheet resistance was measured, and the adhesion was tested according to ASTM D3359 standard. A bending tester was set up. The PI base gold coating prepared in Example 1 was placed on the bending tester and bent and folded 2000 times. The sheet resistance was measured after every 50 cycles, and the adhesion was tested according to ASTM D3359 standard.

[0071] Figure 7 The changes in sheet resistance and adhesion strength of the prepared PI-based gold coating after flexibility testing were demonstrated. After finger rubbing and bending tests, the sheet resistance of the gold coating showed no significant change, and the adhesion test remained at 5B. This indicates that the PI-based gold coating prepared in Example 1 maintains high conductivity and strong adhesion even after fatigue testing, demonstrating extremely high durability.

[0072] Case 5 Figure 8 To test the conductivity of an LED circuit by connecting a gold-coated PI wire to an LED circuit, the LED remained conductive after the gold-coated PI wire was connected, demonstrating that the organic gold coating of the present invention still has wide applicability in the field of linear PI surface metallization.

[0073] In summary, the gold coating disclosed in this invention has a simple application method and excellent conductivity and adhesion.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a strongly adsorbed, highly conductive gold coating for a PI substrate, characterized in that, Includes the following steps: (1) Synthesize tert-dodecyl mercaptan gold, and mix tert-dodecyl mercaptan gold with a first organic solvent to obtain an organic gold coating; (2) Apply the organic gold coating onto the pretreated PI substrate and anneal it to obtain a gold coating.

2. The preparation method according to claim 1, characterized in that, Resin is also added during mixing in step (1); The resin is one or more of terpene resin, rosin resin, epoxy resin, phenolic resin, and acrylic resin.

3. The preparation method according to claim 2, characterized in that, By weight, resin accounts for 0%-22.2% of the organic gold coating.

4. The preparation method according to any one of claims 1-3, characterized in that, By weight, the first organic solvent accounts for 55.6%-71.4% of the organic gold coating; Tert-dodecyl mercaptan gold accounts for 22.2%-28.6% of organometallic coatings.

5. The preparation method according to claim 4, characterized in that, In step (1), the first organic solvent is one or more of terpineol, turpentine, toluene, xylene, pinene, ethyl acetate, butyl acetate, petroleum ether, chloroform, and camphor oil.

6. The preparation method according to claim 5, characterized in that, The first organic solvent is a mixture of camphor oil and terpineol, wherein the mass ratio of camphor oil to terpineol does not exceed 0.

5.

7. The preparation method according to claim 1, characterized in that, The synthesis of gold tert-dodecylthiol in step (1) includes: (1-1) Dissolve gold particles in aqua regia and heat to obtain a gold solution. Mix the gold solution with a second organic solvent to obtain a first solution. (1-2) Under stirring at room temperature, dimethyl sulfide was added dropwise to the first solution, followed by tert-dodecyl mercaptan, to obtain a white oily substance; (1-3) The white oily substance was dissolved in a third organic solvent and a second organic solvent was added. After drying, the final oily substance was obtained.

8. The preparation method according to claim 7, characterized in that, In step (1-1), the volume ratio of the gold solution to the second organic solvent is 2~5:10; In steps (1-2), the molar ratio of dimethyl sulfide to gold in the first solution is 2-4:1; the molar ratio of tert-dodecyl mercaptan to gold in the first solution is 1-1.5:

1. In steps (1-3), the volume ratio of the third organic solvent to the second organic solvent is 5~14:

100.

9. A strongly adsorbed, highly conductive PI-based gold coating prepared by the preparation method according to any one of claims 1-8.

10. The strongly adsorbed, highly conductive PI-based gold coating according to claim 9, characterized in that, The sheet resistance of the highly adsorbent and highly conductive PI-based gold coating is less than 0.3 Ω / sq, and the adhesion reaches grade 5B.

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