Base material surface modification and adhesive force enhancement method for curved surface circuit three-dimensional printing

Abstract

The invention discloses a curved circuit three-dimensional printing-oriented base material surface modification and adhesive force enhancement method, which comprises the following steps of: performing surface modification on the surface of an insulating curved surface base material, and integrally plating copper after modification, so that a layer of uniform conductive copper film is formed on the surface of the base material; anti-etching mask ink is selectively jet-printed on the base material, curing is carried out after jet printing is completed until the anti-etching mask ink is completely dried, and an anti-etching film with a conductive pattern is formed on the surface of the insulation curved surface base material; then, the conductive copper film is soaked in etching liquid for selective etching, and the conductive copper film which is not covered with the anti-etching film is gradually dissolved until the original insulating curved surface base material is exposed; and then soaking in an alkaline solution until the anti-etching film with the conductive pattern is completely dissolved and falls off to obtain the insulating curved-surface base material with a clean surface and a complete conductive pattern. According to the method disclosed by the invention, the adhesive force between the conductive material and the insulating curved surface base material is greatly enhanced, and high-precision and high-reliability preparation of the curved surface circuit is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of three-dimensional printed curved circuits, and in particular relates to a method for surface modification and adhesion enhancement of a substrate for three-dimensional printing of curved circuits. Background Art

[0002] With the rapid development of technologies such as flexible electronics, wearable devices, and smart sensors, traditional planar circuit manufacturing processes have been unable to meet the needs of these emerging fields for complex-shaped circuit designs. Curved circuit 3D printing technology has emerged as the times require. It can directly print conductive circuits on curved or irregular substrates, adapting to the needs of curved electronic devices for flexible design, and has the potential to shorten production cycles and reduce costs. However, in the process of 3D printing of curved circuits, the conductive material needs to be tightly attached to the surface of the substrate to ensure the stability and conductivity of the circuit pattern. However, due to the characteristics of the substrate and the compatibility of the conductive material, the adhesion between the conductive layer and the curved substrate is often insufficient, which can easily lead to problems such as circuit warping, peeling, or decreased conductivity, especially on flexible, smooth, or highly hydrophobic substrates.

[0003] A Chinese patent with announcement number CN117247588B proposes a coating composition for enhancing the adhesion of a transparent polyimide film and its application. The composition includes a polyurethane resin, an adhesion promoter, a thermosetting agent and an auxiliary agent. The polyurethane resin is a terminal hydroxyl polyurethane, the adhesion promoter is a bisphenol A type epoxy resin, and the thermosetting agent is an isocyanate curing agent. The transparent polyimide film is surface treated to significantly enhance its adhesion. However, this solution is only applicable to transparent polyimide films, has poor material compatibility, and can only perform full coverage treatment, and cannot achieve on-demand preparation of complex conductive patterns.

[0004] E.C. Skorupski et al. (E.C. Skorupski, J.T. Gray, J.A. Andrezakis, et al. Substrates with enhanced adhesion to films [P]. United States: CN02809198.1 [P]. CN1505918 [2024-12-10]) proposed a substrate with enhanced adhesion to films, by coating a polymer film on the surface of an etched polymer substrate and then laminating a metal foil layer to obtain a circuit board with high inter-layer adhesion and excellent electrical insulation. However, this solution is only applicable to flat circuit boards and cannot be used for the manufacture of curved circuits. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method for substrate surface modification and adhesion enhancement for three-dimensional printing of curved circuits. By modifying the surface of the insulating curved substrate and adopting inkjet printing technology, combined with a surface etching process, the adhesion between the conductive material and the curved substrate can be enhanced, thereby achieving high-precision and high-reliability preparation of curved circuits, solving the technical problems of insufficient adhesion of existing curved circuits after inkjet printing and the inability to prepare on-demand conductive patterns by surface treatment, and promoting the application of curved circuit three-dimensional printing technology in electronics, medical care, aerospace and other fields.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for surface modification and adhesion enhancement of a substrate for three-dimensional printing of curved circuits, comprising the following steps:

[0008] Step 1: Surface modification is performed on the surface of the insulating curved substrate, and copper plating is performed on the entire surface after modification to form a uniform conductive copper film on the surface of the substrate;

[0009] Step 2: selectively printing the anti-etching mask ink on the insulating curved surface substrate with a uniform conductive copper film obtained in step 1 by using an inkjet printing device, and curing the ink after printing until the anti-etching mask ink is completely dry to form an anti-etching film with a conductive pattern on the surface of the insulating curved surface substrate;

[0010] Step 3: Immerse the insulating curved surface substrate with the anti-etching film formed on the surface in step 2 in an etching solution for selective etching, and gradually dissolve the conductive copper film not covered with the anti-etching film until the original insulating curved surface substrate is exposed, and then clean it with clean water;

[0011] Step 4: Soak the insulating curved surface substrate after selective etching in step 3 in an alkaline solution until the anti-etching film with the conductive pattern is completely dissolved and falls off, and then wash it with clean water to obtain an insulating curved surface substrate with a clean surface and a complete conductive pattern.

[0012] The process of forming a uniform conductive copper film in step 1 is as follows:

[0013] Step 1.1: treating the insulating curved surface substrate with oxygen plasma, and then washing it with deionized water and anhydrous ethanol in sequence, and drying it after washing; soaking the dried insulating curved surface substrate in an adhesive liquid, and then washing it with deionized water and ethanol in sequence after soaking, and drying it after washing, to obtain an insulating curved surface substrate with an adhesive layer;

[0014] Step 1.2: soaking the insulating curved surface substrate with the adhesive layer in step 1.1 in the catalyst solution, and drying it naturally at room temperature after soaking to obtain a surface-modified insulating curved surface substrate;

[0015] Step 1.3: Soak the surface-modified insulating curved surface substrate of step 1.2 in a mixed solution of a deposition liquid and a reducing agent until metallic copper is evenly deposited on the surface of the surface-modified insulating curved surface substrate, wash it with deionized water and ethanol in turn after soaking, and dry it after washing to obtain an insulating curved surface substrate with a uniform conductive copper film on the surface; by volume ratio, the deposition liquid: reducing agent = 100: (2.5-2.7).

[0016] The deposition liquid in step 1.3 includes sodium hydroxide with a mass concentration of 12 g / L, potassium ferrocyanide with a mass concentration of 10 mg / L, potassium sodium tartrate with a mass concentration of 21.49 g / L, disodium ethylenediaminetetraacetate with a mass concentration of 22.14 g / L, 2'2-bipyridine mixture with a mass concentration of 20 mg / L, and copper sulfate pentahydrate with a mass concentration of 14 g / L.

[0017] The adhesive solution in step 1.1 is a mixture of polyethyleneimine solution and tannic acid solution; the catalyst solution in step 1.2 is an ammonium tetrachloropalladate solution with a mass concentration of 0.142 g / L; and the reducing agent in step 1.3 is a formaldehyde solution with a mass fraction of 37%.

[0018] The process conditions of the oxygen plasma treatment in step 1.1 are: power of 100 W, treatment time of 10-15 min, oxygen flow rate of 40-50 sccm; the immersion time in step 1.1 is 11-13 h, the immersion time in step 1.2 is 20-40 min, and the immersion time in step 1.3 is 5-10 min.

[0019] In step 2, the printing resolution is 300 or 600 DPI, and 10-20 layers are printed.

[0020] After the printing in step 2 is completed, a UV lamp with a wavelength of 395 nm is used to cure at 300-600 W for 10-30 seconds.

[0021] The etching solution in step 3 comprises the following weight percentages: 8-10wt% ferric chloride, 5wt% hydrochloric acid, and the remainder water; the temperature of the etching solution is 40-60°C.

[0022] The alkaline solution in step 4 is a sodium hydroxide solution with a mass fraction of 10%.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention performs modification treatment on the surface of the insulating curved surface substrate through step 1, and copper-plating the entire substrate after the modification, so that a uniform conductive copper film is formed on the surface of the substrate, and uniform conductive coverage without dead angles is achieved, thereby ensuring the reliability of subsequent circuit manufacturing; through step 2, high-precision inkjet printing technology is used to selectively print the anti-etching mask ink at the position where the conductive pattern needs to be retained, so as to protect the copper layer in the specific area from being affected by subsequent etching, thereby greatly improving the accuracy of the circuit pattern, making the adhesion of the circuit more firm and uniform, and avoiding the disadvantage of unstable adhesion effect in the traditional surface treatment method; through step 3, the overall copper plating layer is selectively etched, and the copper plating layer not covered by the anti-etching mask ink is completely removed, and the retained conductive circuit is tightly combined with the surface of the substrate, thereby greatly improving the adhesion and durability of the circuit; through step 4, the anti-etching liquid protective film is removed, so that the high-precision manufacturing of the conductive pattern can be achieved while maintaining the integrity of the circuit, thereby ensuring the conductive performance of the curved circuit; the method of the present invention greatly enhances the adhesion between the conductive material and the insulating curved surface substrate, and realizes the high-precision and high-reliability preparation of the curved circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a flow chart of a method for surface modification and adhesion enhancement of a substrate for three-dimensional printing of curved circuits.

[0026] Figure 2 This is the adhesion curve between the insulating curved substrate and the conductive pattern prepared by the common inkjet method.

[0027] Figure 3 : is the adhesion curve between the insulating curved surface substrate and the conductive pattern prepared by Example 2 of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0029] like Figure 1 As shown, a method for surface modification and adhesion enhancement of a substrate for three-dimensional printing of curved circuits comprises the following steps:

[0030] Step 1: Surface modification is performed on the surface of the insulating curved substrate, and copper is plated on the entire surface after modification to form a uniform conductive copper film on the surface of the substrate; the thickness of the conductive copper film is 20-40 nm;

[0031] Step 1.1: using a plasma cleaning machine to treat the insulating curved surface substrate with oxygen plasma at a power of 100W, and improving the hydrophilicity by providing polar groups such as hydroxyl groups; the treatment time is 10-15min, and the oxygen flow rate is 40-50sccm; after the oxygen plasma treatment, the insulating curved surface substrate is sequentially cleaned with deionized water and anhydrous ethanol, and then dried at 30°C for 30min; the dried insulating curved surface substrate is immersed in an adhesive solution for 11-13h, and then washed with deionized water and ethanol in turn after soaking, and then dried at 30°C for 30min to obtain an insulating curved surface substrate with an adhesive layer; the adhesive solution is a mixture of a polyethyleneimine solution and a tannic acid solution;

[0032] Weigh 3 g of tannic acid powder, add it to 600 ml of deionized water and stir until dissolved to obtain a tannic acid solution; weigh 0.6 g of polyethyleneimine (PEI), add it to 6 ml of Tris-HCl buffer solution with a pH value of 8.5 and stir it evenly so that the polyethyleneimine (PEI) can be maintained at a pH of 8.5 to obtain a polyethyleneimine solution; then slowly drop the prepared polyethyleneimine solution into the tannic acid solution and stir to mix evenly;

[0033] Step 1.2: Soak the insulating curved surface substrate with the adhesion layer in step 1.1 in a catalyst solution for 20-40 minutes to adsorb ammonium tetrachloropalladate ions, and dry naturally at room temperature after soaking to obtain a surface-modified insulating curved surface substrate; the catalyst solution is an ammonium tetrachloropalladate solution with a mass concentration of 0.142 g / L;

[0034] Step 1.3: Soak the surface-modified insulating curved surface substrate of step 1.2 in a mixed solution of a deposition liquid and a reducing agent for 5-10 minutes until uniformly deposited metallic copper appears on the surface of the surface-modified insulating curved surface substrate, wash it with deionized water and ethanol in turn after soaking, and dry it at 30° C. for 4 hours after washing to obtain an insulating curved surface substrate with a uniform conductive copper film on the surface; the reducing agent is a formaldehyde solution with a mass fraction of 37%; by volume ratio, the deposition liquid: reducing agent = 100: (2.5-2.7);

[0035] The deposition liquid in step 1.3 includes sodium hydroxide with a mass concentration of 12 g / L, potassium ferrocyanide with a mass concentration of 10 mg / L, potassium sodium tartrate with a mass concentration of 21.49 g / L, disodium ethylenediaminetetraacetate with a mass concentration of 22.14 g / L, 2'2-bipyridine with a mass concentration of 20 mg / L, and copper sulfate pentahydrate with a mass concentration of 14 g / L; and sodium hydroxide, potassium ferrocyanide, potassium sodium tartrate, disodium ethylenediaminetetraacetate and 2'2-bipyridine are mixed and stirred until there are no crystalline particles, and then copper sulfate pentahydrate is added and continued to be mixed and stirred until it is completely dissolved, which can prevent other side reactions from occurring and generate Cu(OH)2 precipitate to obtain a deposition liquid;

[0036] Step 2: using a high-precision inkjet printing device to selectively print the anti-etching mask ink on the insulating curved surface substrate with a uniform conductive copper film obtained in step 1 to protect the conductive copper film with a conductive pattern from being affected by subsequent etching; the model of the anti-etching mask ink is BroadElex ER310; the printing resolution is 300 or 600 DPI, and 10-20 layers are printed to ensure that the printed pattern is clear and fully covered; after the printing is completed, a UV lamp with a wavelength of 395nm is used to cure it at 300-600W for 10-30s until the anti-etching mask ink is completely dry, and an anti-etching film with a conductive pattern is formed on the surface of the insulating curved surface substrate;

[0037] Step 3: Soak the insulating curved surface substrate with the anti-etching film formed on the surface in step 2 in an etching solution for selective etching, wherein the temperature of the etching solution is 40-60° C.; during this process, the conductive copper film not covered with the anti-etching film will gradually dissolve until the original insulating curved surface substrate is exposed, while the conductive copper film covered by the anti-etching film remains intact; after the conductive copper film in the exposed area is completely etched, take it out and wash it with clean water until the yellow-brown color is completely removed; the etching solution includes the following weight percentages: 8-10wt% ferric chloride, 5wt% hydrochloric acid, and the rest is water;

[0038] Step 4: Soak the insulating curved surface substrate after selective etching in step 3 in an alkaline solution until the anti-etching film with the conductive pattern is completely dissolved and falls off, and wash it with clean water at least twice to obtain an insulating curved surface substrate with a clean surface and a complete conductive pattern; the alkaline solution is a sodium hydroxide solution with a mass fraction of 10%.

[0039] Example 1

[0040] A method for surface modification and adhesion enhancement of a substrate for three-dimensional printing of curved circuits, comprising the following steps:

[0041] Step 1: modifying the surface of the insulating curved surface substrate, and copper-plating the entire surface after modification to form a uniform conductive copper film on the surface of the substrate; the thickness of the conductive copper film is 20 nm; the insulating curved surface substrate in this embodiment is a photosensitive resin;

[0042] Step 1.1: using a plasma cleaning machine to treat the insulating curved surface substrate with oxygen plasma at a power of 100 W for 10 minutes, with an oxygen flow rate of 40 sccm; after the oxygen plasma treatment, the insulating curved surface substrate is cleaned with deionized water and anhydrous ethanol in turn, and dried at 30° C. for 30 minutes after cleaning; the dried insulating curved surface substrate is immersed in an adhesive liquid for 11 hours, and after soaking, it is washed with deionized water and ethanol in turn, and dried at 30° C. for 30 minutes after cleaning to obtain an insulating curved surface substrate with an adhesive layer; the adhesive liquid is a mixture of a polyethyleneimine solution and a tannic acid solution;

[0043] Weigh 3 g of tannic acid powder, add it to 600 ml of deionized water and stir until dissolved to obtain a tannic acid solution; weigh 0.6 g of polyethyleneimine (PEI), add it to 6 ml of Tris-HCl buffer solution with a pH value of 8.5 and stir it evenly so that the polyethyleneimine (PEI) can be maintained at a pH of 8.5 to obtain a polyethyleneimine solution; then slowly drop the prepared polyethyleneimine solution into the tannic acid solution and stir to mix evenly;

[0044] Step 1.2: Soak the insulating curved surface substrate with the adhesion layer in step 1.1 in an ammonium tetrachloropalladate solution with a mass concentration of 0.142 g / L for 20 minutes, and dry it naturally at room temperature after soaking to obtain a surface-modified insulating curved surface substrate;

[0045] Step 1.3: Soak the surface-modified insulating curved surface substrate in step 1.2 in a mixed solution of a deposition liquid and a formaldehyde solution with a mass fraction of 37% for 5 minutes until uniformly deposited metallic copper appears on the surface of the surface-modified insulating curved surface substrate, wash it with deionized water and ethanol in turn after soaking, and dry it at 30° C. for 4 hours after washing to obtain an insulating curved surface substrate with a uniform conductive copper film on the surface; by volume ratio, the deposition liquid: reducing agent = 100: 2.5;

[0046] The deposition liquid in step 1.3 includes sodium hydroxide with a mass concentration of 12 g / L, potassium ferrocyanide with a mass concentration of 10 mg / L, potassium sodium tartrate with a mass concentration of 21.49 g / L, disodium ethylenediaminetetraacetate with a mass concentration of 22.14 g / L, 2'2-bipyridine with a mass concentration of 20 mg / L, and copper sulfate pentahydrate with a mass concentration of 14 g / L; and sodium hydroxide, potassium ferrocyanide, potassium sodium tartrate, disodium ethylenediaminetetraacetate and 2'2-bipyridine are mixed and stirred until there are no crystalline particles, and then copper sulfate pentahydrate is added and continued to be mixed and stirred until it is completely dissolved, which can prevent other side reactions from occurring and generate Cu(OH)2 precipitate to obtain a deposition liquid;

[0047] Step 2: using a high-precision inkjet printing device to selectively print the anti-etching mask ink on the insulating curved surface substrate with a uniform conductive copper film obtained in step 1 to protect the conductive copper film with a conductive pattern from being affected by subsequent etching; the model of the anti-etching mask ink is BroadElex ER310; the printing resolution is 300 DPI, and 10 layers are printed to ensure that the printed pattern is clear and fully covered; after the printing is completed, a UV lamp with a wavelength of 395 nm is used to cure it at 300 W for 20 seconds until the anti-etching mask ink is completely dry, and an anti-etching film with a conductive pattern is formed on the surface of the insulating curved surface substrate;

[0048] Step 3: Immerse the insulating curved surface substrate with the anti-etching film formed on the surface in step 2 in an etching solution at 40° C. for selective etching, and the conductive copper film not covered with the anti-etching film will gradually dissolve until the original insulating curved surface substrate is exposed, while the conductive copper film covered by the anti-etching film remains intact; after the conductive copper film in the exposed area is completely etched, take it out and wash it with clean water until the yellow-brown color is completely removed; the etching solution includes the following weight percentages: 8wt% ferric chloride, 5wt% hydrochloric acid, and the rest is water;

[0049] Step 4: Soak the insulating curved surface substrate after selective etching in step 3 in a 10% by mass sodium hydroxide solution until the anti-etching film with the conductive pattern is completely dissolved and falls off, and wash it twice with clean water to obtain an insulating curved surface substrate with a clean surface and a complete conductive pattern.

[0050] Example 2

[0051] A method for surface modification and adhesion enhancement of a substrate for three-dimensional printing of curved circuits, comprising the following steps:

[0052] Step 1: modifying the surface of the insulating curved surface substrate, and copper-plating the entire surface after modification to form a uniform conductive copper film on the surface of the substrate; the thickness of the conductive copper film is 40 nm; the insulating curved surface substrate in this embodiment is a photosensitive resin;

[0053] Step 1.1: using a plasma cleaning machine to treat the insulating curved surface substrate with oxygen plasma at a power of 100 W for 13 minutes, with an oxygen flow rate of 45 sccm; after the oxygen plasma treatment, the insulating curved surface substrate is sequentially cleaned with deionized water and anhydrous ethanol, and then dried at 30° C. for 30 minutes; the dried insulating curved surface substrate is immersed in an adhesive liquid for 12 hours, and then washed with deionized water and ethanol in turn after soaking, and then dried at 30° C. for 30 minutes after washing, to obtain an insulating curved surface substrate with an adhesive layer; the adhesive liquid is a mixture of a polyethyleneimine solution and a tannic acid solution;

[0054] Weigh 3 g of tannic acid powder, add it to 600 ml of deionized water and stir until dissolved to obtain a tannic acid solution; weigh 0.6 g of polyethyleneimine (PEI), add it to 6 ml of Tris-HCl buffer solution with a pH value of 8.5 and stir it evenly so that the polyethyleneimine (PEI) can be maintained at a pH of 8.5 to obtain a polyethyleneimine solution; then slowly drop the prepared polyethyleneimine solution into the tannic acid solution and stir to mix evenly;

[0055] Step 1.2: Soak the insulating curved surface substrate with the adhesion layer in step 1.1 in an ammonium tetrachloropalladate solution with a mass concentration of 0.142 g / L for 30 minutes, and dry it naturally at room temperature after soaking to obtain a surface-modified insulating curved surface substrate;

[0056] Step 1.3: Soak the surface-modified insulating curved surface substrate in step 1.2 in a mixed solution of a deposition liquid and a formaldehyde solution with a mass fraction of 37% for 8 minutes until uniformly deposited metallic copper appears on the surface of the surface-modified insulating curved surface substrate, wash it with deionized water and ethanol in turn after soaking, and dry it at 30° C. for 4 hours after washing to obtain an insulating curved surface substrate with a uniform conductive copper film on the surface; by volume ratio, the deposition liquid: reducing agent = 100: 2.6;

[0057] The deposition liquid in step 1.3 includes sodium hydroxide with a mass concentration of 12 g / L, potassium ferrocyanide with a mass concentration of 10 mg / L, potassium sodium tartrate with a mass concentration of 21.49 g / L, disodium ethylenediaminetetraacetate with a mass concentration of 22.14 g / L, 2'2-bipyridine with a mass concentration of 20 mg / L, and copper sulfate pentahydrate with a mass concentration of 14 g / L; and sodium hydroxide, potassium ferrocyanide, potassium sodium tartrate, disodium ethylenediaminetetraacetate and 2'2-bipyridine are mixed and stirred until there are no crystalline particles, and then copper sulfate pentahydrate is added and continued to be mixed and stirred until it is completely dissolved, which can prevent other side reactions from occurring and generate Cu(OH)2 precipitate to obtain a deposition liquid;

[0058] Step 2: using a high-precision inkjet printing device to selectively print the anti-etching mask ink on the insulating curved surface substrate with a uniform conductive copper film obtained in step 1 to protect the conductive copper film with a conductive pattern from being affected by subsequent etching; the model of the anti-etching mask ink is BroadElex ER310; the printing resolution is 600 DPI, and 20 layers are printed to ensure that the printed pattern is clear and fully covered; after the printing is completed, a UV lamp with a wavelength of 395 nm is used to cure at 600 W for 30 seconds until the anti-etching mask ink is completely dry, and an anti-etching film with a conductive pattern is formed on the surface of the insulating curved surface substrate;

[0059] Step 3: Immerse the insulating curved surface substrate with the anti-etching film formed on the surface in step 2 in an etching solution at 50° C. for selective etching, and the conductive copper film not covered with the anti-etching film will gradually dissolve until the original insulating curved surface substrate is exposed, while the conductive copper film covered by the anti-etching film remains intact; after the conductive copper film in the exposed area is completely etched, take it out and wash it with clean water until the yellow-brown color is completely removed; the etching solution includes the following weight percentages: 9wt% ferric chloride, 5wt% hydrochloric acid, and the rest is water;

[0060] Step 4: Soak the insulating curved surface substrate after selective etching in step 3 in a 10% by mass sodium hydroxide solution until the anti-etching film with the conductive pattern is completely dissolved and falls off, and wash it twice with clean water to obtain an insulating curved surface substrate with a clean surface and a complete conductive pattern.

[0061] Example 3

[0062] A method for surface modification and adhesion enhancement of a substrate for three-dimensional printing of curved circuits, comprising the following steps:

[0063] Step 1: modifying the surface of the insulating curved surface substrate, and copper-plating the entire surface after modification to form a uniform conductive copper film on the surface of the substrate; the thickness of the conductive copper film is 30 nm; the insulating curved surface substrate in this embodiment is a photosensitive resin;

[0064] Step 1.1: using a plasma cleaning machine to treat the insulating curved surface substrate with oxygen plasma at a power of 100 W for 15 minutes, with an oxygen flow rate of 50 sccm; after the oxygen plasma treatment, the insulating curved surface substrate is cleaned with deionized water and anhydrous ethanol in turn, and dried at 30° C. for 30 minutes after cleaning; the dried insulating curved surface substrate is immersed in an adhesive liquid for 13 hours, and after soaking, it is washed with deionized water and ethanol in turn, and dried at 30° C. for 30 minutes after cleaning to obtain an insulating curved surface substrate with an adhesive layer; the adhesive liquid is a mixture of a polyethyleneimine solution and a tannic acid solution;

[0065] Weigh 3 g of tannic acid powder, add it to 600 ml of deionized water and stir until dissolved to obtain a tannic acid solution; weigh 0.6 g of polyethyleneimine (PEI), add it to 6 ml of Tris-HCl buffer solution with a pH value of 8.5 and stir it evenly so that the polyethyleneimine (PEI) can be maintained at a pH of 8.5 to obtain a polyethyleneimine solution; then slowly drop the prepared polyethyleneimine solution into the tannic acid solution and stir to mix evenly;

[0066] Step 1.2: Soak the insulating curved surface substrate with the adhesive layer in step 1.1 in an ammonium tetrachloropalladate solution with a mass concentration of 0.142 g / L for 40 minutes, and dry it naturally at room temperature after soaking to obtain a surface-modified insulating curved surface substrate;

[0067] Step 1.3: Soak the surface-modified insulating curved surface substrate in step 1.2 in a mixed solution of a deposition liquid and a formaldehyde solution with a mass fraction of 37% for 10 minutes, until uniformly deposited metallic copper appears on the surface of the surface-modified insulating curved surface substrate, wash it with deionized water and ethanol in turn after soaking, and dry it at 30° C. for 4 hours after washing to obtain an insulating curved surface substrate with a uniform conductive copper film on the surface; by volume ratio, the deposition liquid: reducing agent = 100: 2.7;

[0068] The deposition liquid in step 1.3 includes sodium hydroxide with a mass concentration of 12 g / L, potassium ferrocyanide with a mass concentration of 10 mg / L, potassium sodium tartrate with a mass concentration of 21.49 g / L, disodium ethylenediaminetetraacetate with a mass concentration of 22.14 g / L, 2'2-bipyridine with a mass concentration of 20 mg / L, and copper sulfate pentahydrate with a mass concentration of 14 g / L; and sodium hydroxide, potassium ferrocyanide, potassium sodium tartrate, disodium ethylenediaminetetraacetate and 2'2-bipyridine are mixed and stirred until there are no crystalline particles, and then copper sulfate pentahydrate is added and continued to be mixed and stirred until it is completely dissolved, which can prevent other side reactions from occurring and generate Cu(OH)2 precipitate to obtain a deposition liquid;

[0069] Step 2: using a high-precision inkjet printing device to selectively print the anti-etching mask ink on the insulating curved surface substrate with a uniform conductive copper film obtained in step 1 to protect the conductive copper film with a conductive pattern from being affected by subsequent etching; the model of the anti-etching mask ink is BroadElex ER310; the printing resolution is 600 DPI, and 10 layers are printed to ensure that the printed pattern is clear and fully covered; after the printing is completed, a UV lamp with a wavelength of 395 nm is used to cure it at 600 W for 20 seconds until the anti-etching mask ink is completely dry, and an anti-etching film with a conductive pattern is formed on the surface of the insulating curved surface substrate;

[0070] Step 3: Immerse the insulating curved surface substrate with the anti-etching film formed on the surface in step 2 in an etching solution at 60° C. for selective etching, and the conductive copper film not covered with the anti-etching film will gradually dissolve until the original insulating curved surface substrate is exposed, while the conductive copper film covered by the anti-etching film remains intact; after the conductive copper film in the exposed area is completely etched, take it out and wash it with clean water until the yellow-brown color is completely removed; the etching solution includes the following weight percentages: 10wt% ferric chloride, 5wt% hydrochloric acid, and the rest is water;

[0071] Step 4: Soak the insulating curved surface substrate after selective etching in step 3 in a 10% by mass sodium hydroxide solution until the anti-etching film with the conductive pattern is completely dissolved and falls off, and wash it twice with clean water to obtain an insulating curved surface substrate with a clean surface and a complete conductive pattern.

[0072] Comparative Example 1

[0073] The common inkjet preparation process is as follows:

[0074] High-precision inkjet printing equipment is used to selectively print conductive ink on the insulating curved surface substrate, with a printing resolution of 600DPI and 20 layers. After printing, a near-infrared laser is used for laser sintering until the conductive ink is completely dry, forming a conductive pattern on the surface of the insulating curved surface substrate. Figure 2 The adhesion test of the insulating curved substrate with conductive pattern prepared by ordinary inkjet method was carried out using a digital pull-off adhesion tester, and the diameter of the test column was 10mm; Figure 2 It can be seen that when the peak pressure is 0.06 KN, the conductive pattern is peeled off from the insulating curved surface substrate, and the corresponding adhesion between the conductive pattern and the insulating curved surface substrate is only 0.8 MPa.

[0075] See also Figure 3 The adhesion test of the insulating curved surface substrate with a complete conductive pattern prepared in Example 2 of the present invention was carried out using a digital display pull-off adhesion tester, and the diameter of the test column was 10 mm; Figure 3 It can be seen that when the peak pressure is 0.93KN, the conductive pattern is peeled off from the insulating curved substrate, and the corresponding adhesion between the conductive pattern and the insulating curved substrate is 11.8MPa. Compared with the preparation by ordinary inkjet method, the adhesion between the insulating curved substrate and the conductive pattern obtained by the adhesion enhancement method of the present invention is greatly improved.

Claims

1. A method for surface modification and adhesion enhancement of a substrate for three-dimensional printing of curved circuits, characterized in that: The steps include: Step 1: Surface modification is performed on the surface of the insulating curved substrate, and copper plating is performed on the entire surface after modification to form a uniform conductive copper film on the surface of the substrate; Step 2: selectively printing the anti-etching mask ink on the insulating curved surface substrate with a uniform conductive copper film obtained in step 1, and curing the ink after printing until the anti-etching mask ink is completely dry to form an anti-etching film with a conductive pattern on the surface of the insulating curved surface substrate; Step 3: Immerse the insulating curved surface substrate with the anti-etching film formed on the surface in step 2 in an etching solution for selective etching, and gradually dissolve the conductive copper film not covered with the anti-etching film until the original insulating curved surface substrate is exposed, and then clean it with clean water; Step 4: Soak the insulating curved surface substrate after selective etching in step 3 in an alkaline solution until the anti-etching film with the conductive pattern is completely dissolved and falls off, and then wash it with clean water to obtain an insulating curved surface substrate with a clean surface and a complete conductive pattern.

2. The method for surface modification and adhesion enhancement of a substrate for three-dimensional printing of curved circuits according to claim 1, characterized in that: The process of forming a uniform conductive copper film in step 1 is as follows: Step 1.1: treating the insulating curved surface substrate with oxygen plasma, and then washing it with deionized water and anhydrous ethanol in sequence, and drying it after washing; soaking the dried insulating curved surface substrate in an adhesive liquid, and then washing it with deionized water and ethanol in sequence after soaking, and drying it after washing, to obtain an insulating curved surface substrate with an adhesive layer; Step 1.2: soaking the insulating curved surface substrate with the adhesive layer in step 1.1 in the catalyst solution, and drying it naturally at room temperature after soaking to obtain a surface-modified insulating curved surface substrate; Step 1.3: Soak the surface-modified insulating curved surface substrate of step 1.2 in a mixed solution of a deposition liquid and a reducing agent until metallic copper is evenly deposited on the surface of the surface-modified insulating curved surface substrate, wash it with deionized water and ethanol in turn after soaking, and dry it after washing to obtain an insulating curved surface substrate with a uniform conductive copper film on the surface; by volume ratio, the deposition liquid: reducing agent = 100: (2.5-2.7).

3. The method for surface modification and adhesion enhancement of a substrate for three-dimensional printing of curved circuits according to claim 2, characterized in that: The deposition liquid in step 1.3 includes sodium hydroxide with a mass concentration of 12 g / L, potassium ferrocyanide with a mass concentration of 10 mg / L, potassium sodium tartrate with a mass concentration of 21.49 g / L, disodium ethylenediaminetetraacetate with a mass concentration of 22.14 g / L, 2'2-bipyridine with a mass concentration of 20 mg / L, and copper sulfate pentahydrate with a mass concentration of 14 g / L.

4. The method for surface modification and adhesion enhancement of a substrate for three-dimensional printing of curved circuits according to claim 2, characterized in that: The adhesive solution in step 1.1 is a mixture of polyethyleneimine solution and tannic acid solution; the catalyst solution in step 1.2 is an ammonium tetrachloropalladate solution with a mass concentration of 0.142 g / L; and the reducing agent in step 1.3 is a formaldehyde solution with a mass fraction of 37%.

5. The method for surface modification and adhesion enhancement of a substrate for three-dimensional printing of curved circuits according to claim 2, characterized in that: The process conditions of the oxygen plasma treatment in step 1.1 are: power of 100 W, treatment time of 10-15 min, oxygen flow rate of 40-50 sccm; the immersion time in step 1.1 is 11-13 h, the immersion time in step 1.2 is 20-40 min, and the immersion time in step 1.3 is 5-10 min.

6. The method for surface modification and adhesion enhancement of substrates for three-dimensional printing of curved circuits according to claim 1, characterized in that: In step 2, the printing resolution is 300 or 600 DPI, and 10-20 layers are printed.

7. The method for surface modification and adhesion enhancement of substrate for three-dimensional printing of curved circuits according to claim 1, characterized in that: After the printing in step 2 is completed, a UV lamp with a wavelength of 395 nm is used to cure at 300-600 W for 10-30 seconds.

8. The method for surface modification and adhesion enhancement of a substrate for three-dimensional printing of curved circuits according to claim 1, characterized in that: The etching solution in step 3 comprises the following weight percentages: 8-10wt% ferric chloride, 5wt% hydrochloric acid, and the remainder water; the temperature of the etching solution is 40-60°C.

9. The method for surface modification and adhesion enhancement of substrate for three-dimensional printing of curved circuits according to claim 1, characterized in that: The alkaline solution in step 4 is a sodium hydroxide solution with a mass fraction of 10%.

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