A method for substrate surface modification and adhesion enhancement for 3D printing of curved circuits

Abstract

The present invention discloses a method for surface modification and adhesion enhancement of a substrate for three-dimensional printing of curved circuits, comprising: performing surface modification on the surface of an insulating curved substrate, and copper plating the entire substrate after modification to form a uniform conductive copper film on the surface of the substrate; selectively spray-printing an anti-etching mask ink on the substrate, and curing the substrate after the spray-printing is completed until the anti-etching mask ink is completely dry, thereby forming an anti-etching film with a conductive pattern on the surface of the insulating curved substrate; then immersing the substrate in an etching solution for selective etching, and gradually dissolving the conductive copper film not covered by the anti-etching film until the original insulating curved substrate is exposed; then immersing the substrate in an alkaline solution until the anti-etching film with the conductive pattern is completely dissolved and falls off, thereby obtaining an insulating curved substrate with a clean surface and a complete conductive pattern. The method of the present invention greatly enhances the adhesion between the conductive material and the insulating curved substrate, thereby achieving high-precision and high-reliability preparation of curved circuits.

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 become 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 print conductive circuits directly on curved or irregular substrates, meeting the needs of curved electronic devices for flexible design, and has the potential to shorten production cycles and reduce costs. However, during the 3D printing process 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] Chinese patent publication number CN117247588B proposes a coating composition for enhancing the adhesion of transparent polyimide films and its application. The composition includes a polyurethane resin, an adhesion promoter, a thermosetting agent, and an auxiliary agent. The polyurethane resin is a hydroxyl-terminated polyurethane, the adhesion promoter is a bisphenol A 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, making it impossible to 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. A polymer film is coated on the surface of an etched polymer substrate and then a metal foil layer is laminated to produce 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, using inkjet printing technology, and combining it 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. The technical problems of insufficient adhesion of existing curved circuits after inkjet printing and the inability to prepare on-demand conductive patterns due to surface treatment are solved, thereby 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 substrate surface modification and adhesion enhancement 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: Using an inkjet printing device, selectively printing an anti-etching mask ink on the insulating curved surface substrate having a uniform conductive copper film obtained in step 1. After printing, curing is performed until the anti-etching mask ink is completely dry, thereby forming an anti-etching film having 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. The conductive copper film not covered with the anti-etching film gradually dissolves until the original insulating curved surface substrate is exposed, and then rinse 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 rinse 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, then washing it with deionized water and anhydrous ethanol in sequence, and drying it after washing; immersing the dried insulating curved surface substrate in an adhesive solution, 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 adhesion layer in step 1.1 in the catalyst solution, and then naturally drying at room temperature to obtain a surface-modified insulating curved surface substrate;

[0015] 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 reducing agent until metallic copper is evenly deposited on the surface of the surface-modified insulating curved surface substrate. After soaking, the substrate is washed with deionized water and ethanol in sequence, and then dried to obtain an insulating curved surface substrate having a uniform conductive copper film on the surface. The volume ratio of the deposition liquid to the reducing agent is 100:(2.5-2.7).

[0016] The deposition solution 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 the film at 300-600 W for 10-30 seconds.

[0021] The etching solution in step 3 comprises the following weight percentages: 8-10 wt % ferric chloride, 5 wt % 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 comprises the following steps: step 1, modifying the surface of an insulating curved surface substrate, and copper-plating the entire substrate after the modification, so that a uniform conductive copper film is formed on the surface of the substrate, achieving uniform conductive coverage without dead angles, and ensuring the reliability of subsequent circuit manufacturing; step 2, using high-precision inkjet printing technology, selectively printing an anti-etching mask ink at a position where the conductive pattern needs to be retained, protecting the copper layer in a specific area from the influence of subsequent etching, greatly improving the precision of the circuit pattern, making the adhesion of the circuit more firm and uniform, and avoiding the disadvantage of unstable adhesion effect in traditional surface treatment methods; step 3, selectively etching the entire copper plating layer, completely removing the copper plating layer not covered by the anti-etching mask ink, and closely combining the retained conductive circuit with the substrate surface, greatly improving the adhesion and durability of the circuit; step 4, removing the anti-etching liquid protective film, and realizing high-precision manufacturing of the conductive pattern 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 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 substrate surface modification and adhesion enhancement 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 ordinary inkjet method.

[0027] Figure 3 1 is an 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 will be further described below with reference to the accompanying drawings and specific embodiments.

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

[0030] 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; the thickness of the conductive copper film is 20-40 nm;

[0031] Step 1.1: Using a plasma cleaning machine, treat the insulating curved surface substrate with oxygen plasma at 100 W power to improve hydrophilicity by providing polar groups such as hydroxyl groups; the treatment time is 10-15 minutes, and the oxygen flow rate is 40-50 seem; after the oxygen plasma treatment, the 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 solution for 11-13 hours, and then washed with deionized water and ethanol, and then dried at 30°C for 30 minutes 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] 3 g of tannic acid powder was weighed and added to 600 ml of deionized water, and stirred until dissolved to obtain a tannic acid solution. 0.6 g of polyethyleneimine (PEI) was weighed and added to 6 ml of Tris-HCl buffer with a pH of 8.5, and mechanically stirred to maintain the polyethyleneimine (PEI) at a pH of 8.5, thereby obtaining a polyethyleneimine solution. The prepared polyethyleneimine solution was then slowly added dropwise to the tannic acid solution and stirred to mix evenly.

[0033] Step 1.2: Soaking 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 then naturally drying at room temperature 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: Soaking the surface-modified insulating curved surface substrate obtained in 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. After soaking, the substrate is sequentially rinsed with deionized water and ethanol, and then dried at 30° C. for 4 hours to obtain an insulating curved surface substrate having a uniform conductive copper film on the surface. The reducing agent is a 37% by mass formaldehyde solution. The volume ratio of the deposition liquid to the reducing agent is 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 the 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 the copper sulfate pentahydrate is added and the mixing and stirring are continued until it is completely dissolved, which can prevent other side reactions from occurring and form Cu(OH)2 precipitate to obtain a deposition liquid;

[0036] Step 2: Using a high-precision inkjet printing device, selectively print an etch-resistant 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 subsequent etching; the model of the etch-resistant 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 printing, use a UV lamp with a wavelength of 395 nm at 300-600 W for 10-30 seconds until the etch-resistant mask ink is completely dry, forming an etch-resistant film with a conductive pattern on the surface of the insulating curved surface substrate;

[0037] Step 3: Immerse the insulating curved surface substrate with the anti-etching film formed on its 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 gradually dissolves 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, it is removed and rinsed with clean water until the yellow-brown color is completely removed. The etching solution comprises the following weight percentages: 8-10 wt% ferric chloride, 5 wt% hydrochloric acid, and the remainder 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 rinse 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 substrate surface modification and adhesion enhancement for three-dimensional printing of curved circuits, comprising the following steps:

[0041] Step 1: Surface modification is performed on the surface of the insulating curved surface substrate, and copper plating is performed on the entire surface of the substrate 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, treat the insulating curved surface substrate with oxygen plasma at a power of 100 W for 10 minutes and an oxygen flow rate of 40 sccm; after the oxygen plasma treatment, wash the substrate with deionized water and anhydrous ethanol in sequence, and then dry it at 30°C for 30 minutes; soak the dried insulating curved surface substrate in an adhesive solution for 11 hours, then wash it with deionized water and ethanol in sequence, and then dry it at 30°C for 30 minutes 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;

[0043] 3 g of tannic acid powder was weighed and added to 600 ml of deionized water, and stirred until dissolved to obtain a tannic acid solution. 0.6 g of polyethyleneimine (PEI) was weighed and added to 6 ml of Tris-HCl buffer with a pH of 8.5, and mechanically stirred to maintain the polyethyleneimine (PEI) at a pH of 8.5, thereby obtaining a polyethyleneimine solution. The prepared polyethyleneimine solution was then slowly added dropwise to the tannic acid solution and stirred to mix evenly.

[0044] Step 1.2: Soaking the insulating curved surface substrate with the adhesion layer in step 1.1 in a 0.142 g / L ammonium tetrachloropalladate solution for 20 minutes, and then naturally drying at room temperature to obtain a surface-modified insulating curved surface substrate;

[0045] Step 1.3: Soaking the surface-modified insulating curved surface substrate obtained in step 1.2 in a mixture of a deposition solution and a 37% formaldehyde solution for 5 minutes until uniformly deposited metallic copper appears on the surface of the surface-modified insulating curved surface substrate. After soaking, the substrate is sequentially rinsed with deionized water and ethanol, and then dried at 30°C for 4 hours to obtain an insulating curved surface substrate having a uniform conductive copper film on the surface. The volume ratio of the deposition solution to the reducing agent is 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 the 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 the copper sulfate pentahydrate is added and the mixing and stirring are continued until it is completely dissolved, which can prevent other side reactions from occurring and form Cu(OH)2 precipitate to obtain a deposition liquid;

[0047] Step 2: Using a high-precision inkjet printing device, selectively print an etch-resistant mask ink on the insulating curved substrate with a uniform conductive copper film obtained in step 1 to protect the conductive copper film with a conductive pattern from subsequent etching; the model of the etch-resistant 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 printing, use a UV lamp with a wavelength of 395 nm at 300 W for 20 seconds until the etch-resistant mask ink is completely dry, forming an etch-resistant film with a conductive pattern on the surface of the insulating curved substrate;

[0048] Step 3: Immerse the insulating curved surface substrate with the anti-etching film formed on its surface in Step 2 in an etching solution at 40°C for selective etching. The conductive copper film not covered by the anti-etching film gradually dissolves 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, remove it and rinse it with clean water until the yellow-brown color is completely removed. The etching solution comprises the following weight percentages: 8wt% ferric chloride, 5wt% hydrochloric acid, and the remainder 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 rinse 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 substrate surface modification and adhesion enhancement for three-dimensional printing of curved circuits, comprising the following steps:

[0052] Step 1: Surface modification is performed on the surface of the insulating curved surface substrate, and copper plating is performed on the entire surface of the substrate 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, treat the insulating curved surface substrate with oxygen plasma at a power of 100 W for 13 minutes and an oxygen flow rate of 45 seem; after the oxygen plasma treatment, wash the substrate with deionized water and anhydrous ethanol in sequence, and then dry it at 30°C for 30 minutes; soak the dried insulating curved surface substrate in an adhesive solution for 12 hours, then wash it with deionized water and ethanol in sequence, and then dry it at 30°C for 30 minutes 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;

[0054] 3 g of tannic acid powder was weighed and added to 600 ml of deionized water, and stirred until dissolved to obtain a tannic acid solution. 0.6 g of polyethyleneimine (PEI) was weighed and added to 6 ml of Tris-HCl buffer with a pH of 8.5, and mechanically stirred to maintain the polyethyleneimine (PEI) at a pH of 8.5, thereby obtaining a polyethyleneimine solution. The prepared polyethyleneimine solution was then slowly added dropwise to the tannic acid solution and stirred to mix evenly.

[0055] Step 1.2: Soaking the insulating curved surface substrate with the adhesion layer in step 1.1 in a 0.142 g / L ammonium tetrachloropalladate solution for 30 minutes, and then naturally drying at room temperature to obtain a surface-modified insulating curved surface substrate;

[0056] Step 1.3: Soaking the surface-modified insulating curved surface substrate obtained in step 1.2 in a mixture of a deposition solution and a 37% formaldehyde solution for 8 minutes until uniformly deposited metallic copper appears on the surface of the surface-modified insulating curved surface substrate. After soaking, the substrate is sequentially rinsed with deionized water and ethanol, and then dried at 30°C for 4 hours to obtain an insulating curved surface substrate having a uniform conductive copper film on the surface. The volume ratio of the deposition solution to the reducing agent is 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 the 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 the copper sulfate pentahydrate is added and the mixing and stirring are continued until it is completely dissolved, which can prevent other side reactions from occurring and form Cu(OH)2 precipitate to obtain a deposition liquid;

[0058] Step 2: Using a high-precision inkjet printing device, selectively print an etch-resistant 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 subsequent etching; the model of the etch-resistant 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 printing, use a UV lamp with a wavelength of 395 nm at 600 W for 30 seconds until the etch-resistant mask ink is completely dry, forming an etch-resistant film with a conductive pattern 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 its surface in Step 2 in an etching solution at 50°C for selective etching. The conductive copper film not covered by the anti-etching film gradually dissolves 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, remove it and rinse it with clean water until the yellow-brown color is completely removed. The etching solution comprises the following weight percentages: 9wt% ferric chloride, 5wt% hydrochloric acid, and the remainder 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 rinse 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 substrate surface modification and adhesion enhancement for three-dimensional printing of curved circuits, comprising the following steps:

[0063] Step 1: Surface modification is performed on the surface of the insulating curved surface substrate, and copper plating is performed on the entire surface of the substrate 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, treat the insulating curved surface substrate with oxygen plasma at a power of 100 W for 15 minutes and an oxygen flow rate of 50 sccm; after the oxygen plasma treatment, wash the substrate with deionized water and anhydrous ethanol in sequence, and then dry it at 30°C for 30 minutes; soak the dried insulating curved surface substrate in an adhesive solution for 13 hours, then wash it with deionized water and ethanol in sequence, and then dry it at 30°C for 30 minutes 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;

[0065] 3 g of tannic acid powder was weighed and added to 600 ml of deionized water, and stirred until dissolved to obtain a tannic acid solution. 0.6 g of polyethyleneimine (PEI) was weighed and added to 6 ml of Tris-HCl buffer with a pH of 8.5, and mechanically stirred to maintain the polyethyleneimine (PEI) at a pH of 8.5, thereby obtaining a polyethyleneimine solution. The prepared polyethyleneimine solution was then slowly added dropwise to the tannic acid solution and stirred to mix evenly.

[0066] Step 1.2: Soaking the insulating curved surface substrate with the adhesion layer in step 1.1 in a 0.142 g / L ammonium tetrachloropalladate solution for 40 minutes, and then naturally drying at room temperature to obtain a surface-modified insulating curved surface substrate;

[0067] Step 1.3: Soaking the surface-modified insulating curved surface substrate obtained in step 1.2 in a mixture of a deposition solution and a 37% formaldehyde solution for 10 minutes until uniformly deposited metallic copper appears on the surface of the surface-modified insulating curved surface substrate. After soaking, the substrate is sequentially rinsed with deionized water and ethanol, and then dried at 30°C for 4 hours to obtain an insulating curved surface substrate having a uniform conductive copper film on the surface. The volume ratio of the deposition solution to the reducing agent is 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 the 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 the copper sulfate pentahydrate is added and the mixing and stirring are continued until it is completely dissolved, which can prevent other side reactions from occurring and form Cu(OH)2 precipitate to obtain a deposition liquid;

[0069] Step 2: Using a high-precision inkjet printing device, selectively print an etch-resistant 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 subsequent etching; the model of the etch-resistant 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 has complete coverage; after printing, use a UV lamp with a wavelength of 395 nm at 600 W for 20 seconds until the etch-resistant mask ink is completely dry, forming an etch-resistant film with a conductive pattern 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 its surface in Step 2 in an etching solution at 60°C for selective etching. The conductive copper film not covered by the anti-etching film gradually dissolves 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, remove it and rinse it with clean water until the yellow-brown color is completely removed. The etching solution comprises the following weight percentages: 10wt% ferric chloride, 5wt% hydrochloric acid, and the remainder 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 rinse 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 general 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 display pull-off adhesion tester, the test column diameter 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 force 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 conducted using a digital pull-off adhesion tester, with a test column diameter of 10 mm. Figure 3 It can be seen that when the peak pressure is 0.93 KN, 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 11.8 MPa. Compared with the preparation method of 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 substrates 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 1.1: treating the insulating curved surface substrate with oxygen plasma, then washing it with deionized water and anhydrous ethanol in sequence, and drying it after washing; immersing the dried insulating curved surface substrate in an adhesive solution, 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 adhesion layer in step 1.1 in the catalyst solution, and then naturally drying at room temperature to obtain a surface-modified insulating curved surface substrate; Step 1.3: Soaking the surface-modified insulating curved surface substrate obtained in step 1.2 in a mixed solution of a deposition liquid and a reducing agent until metallic copper is uniformly deposited on the surface of the surface-modified insulating curved surface substrate. After soaking, the substrate is sequentially rinsed with deionized water and ethanol, and then dried to obtain an insulating curved surface substrate having a uniform conductive copper film on the surface. The volume ratio of the deposition liquid to the reducing agent is 100:(2.5-2.7). Step 2: Selectively printing the anti-etching mask ink on the insulating curved surface substrate having the uniform conductive copper film obtained in step 1, and curing the ink after printing until the anti-etching mask ink is completely dry, thereby forming an anti-etching film having 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. The conductive copper film not covered with the anti-etching film gradually dissolves until the original insulating curved surface substrate is exposed, and then rinse 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 rinse 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 deposition solution in step 1.3 includes a mixture of 12 g / L sodium hydroxide, 10 mg / L potassium ferrocyanide, 21.49 g / L potassium sodium tartrate, 22.14 g / L disodium ethylenediaminetetraacetic acid, 20 mg / L 2'2-bipyridine, and 14 g / L copper sulfate pentahydrate.

3. The method for substrate surface modification and adhesion enhancement for three-dimensional printing of curved circuits according to claim 1, 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%.

4. The method for substrate surface modification and adhesion enhancement for three-dimensional printing of curved circuits according to claim 1, 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.

5. The method for substrate surface modification and adhesion enhancement 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.

6. The method for substrate surface modification and adhesion enhancement 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 the film at 300-600 W for 10-30 seconds.

7. The method for substrate surface modification and adhesion enhancement 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: 8-10 wt % ferric chloride, 5 wt % hydrochloric acid, and the remainder water; the temperature of the etching solution is 40-60° C.

8. The method for substrate surface modification and adhesion enhancement 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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