A printing process for flexible circuit board

Abstract

The present application relates to the field of printed circuit boards, and more specifically, to a printing process for flexible circuit boards. The process comprises: inkjet printing a conductive ink onto a substrate surface, curing the ink to form a conductive pattern on the substrate surface, and obtaining a printed flexible circuit board; the conductive ink comprises a conductive filler and a dispersion binder in a weight ratio of 1:(1-5); the dispersion binder comprises a boron-modified phenolic resin, a reactive toughening monomer, a modified polyester acrylate, a polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer, a modified rosin resin, N-aminoethyl-3-aminopropylmethyldimethoxysilane, a reactive diluent, an initiator, a solvent, and a processing aid, and uniformly mixing them to obtain a dispersion binder. The conductive ink exhibits excellent overall performance and can prevent the circuit pattern of the flexible circuit board from peeling, corrosion, and wear.

Description

Technical Field

[0001] The present application relates to the field of circuit board printing, and more particularly, to a printing process for a flexible circuit board. Background Art

[0002] Flexible printed circuits (FPCs), as bendable and foldable circuit boards, are widely used in various electronic devices, especially in the field of smart wearable devices. Such devices typically include health monitoring sensors, smart clothing integration, smart patches, etc., which require high flexibility, lightweight and miniaturization. FPCs are made of polyimide or polyester film as a substrate and have the advantages of high wiring density, light weight, thin thickness and good bendability. Therefore, they have been widely used in smart wearable devices. However, with the diversification of smart wearable device functions and technological advancements, the requirements for FPCs are also increasing, especially in terms of durability and stability.

[0003] In existing flexible circuit board manufacturing processes, a common method involves adhering copper foil to the substrate surface, followed by development and etching to form a circuit pattern on the substrate surface. While this method can achieve high-precision circuit production, it suffers from complex processes and low production efficiency. To simplify the production process and improve production efficiency, a new method is currently available: directly printing conductive ink on the substrate surface and curing it to form the desired circuit pattern. This method eliminates the traditional development and etching steps, greatly simplifying the production process and improving production efficiency.

[0004] While printing conductive inks has, to some extent, addressed the complexity of traditional processes, some shortcomings remain in practical applications. In particular, in smart wearable devices, flexible circuit boards (FPCBs) frequently come into contact with the skin and are susceptible to corrosion from substances such as sweat and cosmetics. They can also be subject to frequent friction during daily use. These issues can lead to printed circuit patterns becoming susceptible to detachment or performance degradation, severely impacting the reliability and service life of FPCBs. Therefore, improving the durability and stability of printed circuit patterns on FPCBs has become a critical issue that needs to be addressed. Summary of the Invention

[0005] In order to improve the corrosion resistance of circuit patterns such as sweat, wear resistance, and anti-falling effect, the present application provides a printing process for a flexible circuit board.

[0006] The present application provides a printing process for a flexible circuit board, which is produced by the following method:

[0007] The conductive ink is printed on the surface of the substrate by inkjet printing and cured to form a conductive pattern on the surface of the substrate to obtain a printed flexible circuit board;

[0008] The conductive ink is composed of a conductive filler and a dispersed connecting material in a weight ratio of 1:(1-5);

[0009] Dispersion binder: weigh boron-modified phenolic resin, reactive toughening monomer, modified polyester acrylate, polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer, modified rosin resin, N-aminoethyl-3-aminopropylmethyldimethoxysilane, reactive diluent, initiator, solvent and processing aid in a weight ratio of (2-5): (10-20): (2-8): (1-3): (13-20): (8-15): (1-3): (0-3): 100, and mix them evenly to obtain a dispersion binder;

[0010] The active toughening monomer is one or more of epoxy soybean oil acrylate, methacryloyloxyethyl maleate, and N,N'-methylenebisacrylamide; and the modified polyester acrylate is hyperbranched polyester acrylate and / or caprolactone-modified polyester acrylate.

[0011] By adopting the above technical solution, the boron-modified phenolic resin, reactive toughening monomer, modified polyester acrylate, polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer, modified rosin resin, and N-aminoethyl-3-aminopropylmethyldimethoxysilane in the conductive ink work together to form an ink layer that is uniformly dispersed, stably adheres, and exhibits excellent conductivity. The boron-modified phenolic resin improves the ink's heat resistance and chemical stability, the reactive toughening monomer increases the ink's toughness and wear resistance, the modified polyester acrylate provides flexibility and weather resistance, the polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer improves the ink's rheological properties and adhesion, the modified rosin resin strengthens the ink's adhesion to the substrate, and the N-aminoethyl-3-aminopropylmethyldimethoxysilane improves the ink's dispersion stability and adhesion to the substrate. The synergistic effect of these ingredients gives the printed flexible circuit board excellent conductivity, adhesion stability and wear resistance, making it particularly suitable for use in smart wearable devices. It can effectively resist the erosion of sweat and cosmetics, prevent the circuit pattern from falling off or performance degradation, and greatly improve the practicality and reliability of the flexible circuit board.

[0012] Furthermore, one or more of epoxy soybean oil acrylate, methacryloyloxyethyl maleate, and N,N'-methylenebisacrylamide are used as activating toughening agents, and the modified polyester acrylate is a hyperbranched polyester acrylate and / or caprolactone-modified polyester acrylate, which can interact with boron-modified phenolic resin, polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer, modified rosin resin, and N-aminoethyl-3-aminopropylmethyldimethoxysilane to achieve a better synergistic effect, further improving the comprehensive performance of the conductive ink. When used in the printing process of flexible circuit boards, a conductive ink circuit pattern with stable adhesion, precise and uniform consistency is formed on the surface of the substrate. When the flexible circuit board is used in smart wearable devices, it can reduce the phenomenon of sweat erosion or friction shedding, thereby improving its durability.

[0013] Preferably, the inkjet printing speed is 1-3 m / s and the inkjet pressure is 0.08-0.2 MPa.

[0014] By adopting this technical solution, the inkjet printing speed is controlled at 1-3 m / s and the inkjet pressure is controlled at 0.08-0.2 MPa, ensuring uniform application of the conductive ink to the substrate surface, avoiding ink splashing or uneven coating caused by excessive speed or pressure. Furthermore, the curing temperature is controlled at 100-130°C, which effectively promotes the full reaction of the conductive ink components, forming a stable conductive pattern and improving the ink's adhesion and conductivity. This not only ensures high-quality production of flexible circuit boards, but also enhances their reliability and durability in practical applications.

[0015] Preferably, the active toughening monomer is composed of epoxy soybean oil acrylate, methacryloyloxyethyl maleate, and N,N'-methylenebisacrylamide in a weight ratio of 3:(1-1.5):(0.5-1).

[0016] By adopting the above technical solution, the active toughening monomer is composed of epoxy soybean oil acrylate, methacryloyloxyethyl maleate, and N,N'-methylenebisacrylamide in a weight ratio of 3:(1-1.5):(0.5-1), which acts synergistically and can significantly improve the overall performance of the conductive ink. Epoxidized soybean oil acrylate imparts good flexibility and wear resistance to the ink, methacryloyloxyethyl maleate enhances the cohesion and toughness of the ink, and N,N'-methylenebisacrylamide acts as a crosslinking agent, forming a crosslinked structure and further enhancing the toughness of the ink. These monomers work together to improve the adhesion and dispersibility of the ink, ensuring the uniform distribution of the conductive filler in the ink, thereby forming a stable and uniformly thick conductive ink circuit pattern on the substrate surface, improving the durability and reliability of flexible circuit boards in smart wearable devices.

[0017] Preferably, the modified polyester acrylate is composed of caprolactone-modified polyester acrylate and hyperbranched polyester acrylate in a weight ratio of 1:(0.2-0.8).

[0018] By adopting the above technical solution, the modified polyester acrylate is composed of caprolactone-modified polyester acrylate and hyperbranched polyester acrylate in a weight ratio of 1: (0.2-0.8), which can significantly improve the flexibility and wear resistance of the conductive ink. Caprolactone-modified polyester acrylate improves the flexibility and toughness of polyester acrylate by introducing caprolactone units, making the ink less likely to crack or break when subjected to external forces. The unique hyperbranched structure of hyperbranched polyester acrylate increases the cross-linking points and entanglement points between the molecular chains, enhancing the cohesion and tear resistance of the ink. The combination of these two modified polyester acrylates can also interact with other components in the ink to form stronger adhesion, ensuring a firm connection between the conductive filler and the substrate. In addition, this combination can also optimize the inkjet printing performance of the ink, ensuring that the printed circuit pattern is clear, accurate and of uniform thickness, thereby improving the durability and reliability of flexible circuit boards in wearable smart devices.

[0019] Preferably, the modified rosin is rosin-modified phenolic resin and / or hydrogenated rosin.

[0020] By employing the above-mentioned technical solution, the combination of rosin-modified phenolic resin and hydrogenated rosin significantly improves the adhesion and wear resistance of conductive inks. The rosin-modified phenolic resin, with its unique honeycomb structure, provides excellent pigment wetting and a certain degree of viscoelasticity, improving the ink's toughness and adhesion. Hydrogenated rosin further enhances the ink's adhesion, allowing it to adhere better to the substrate and form a stable and durable circuit pattern. Furthermore, hydrogenated rosin improves the ink's fluidity and drying speed, thereby enhancing printing efficiency and quality. These improvements contribute to the enhanced durability and reliability of flexible circuit boards in smart wearable devices.

[0021] Preferably, the modified rosin is composed of rosin-modified phenolic resin and hydrogenated rosin in a weight ratio of 1:(1-3).

[0022] By adopting the above technical solution, the modified rosin, composed of rosin-modified phenolic resin and hydrogenated rosin in a weight ratio of 1:(1-3), can significantly improve the adhesion and durability of the ink. The rosin-modified phenolic resin provides good pigment wetting and viscoelasticity, enhancing the toughness of the ink and making it more resistant to deformation and cracking when subjected to external forces. The hydrogenated rosin significantly improves the adhesion of the ink, ensuring that the conductive ink forms a stable and durable circuit pattern on the substrate. In addition, the hydrogenated rosin improves the ink's fluidity and drying speed, making it easier to form a uniform and stable coating during the inkjet printing process, thereby improving printing efficiency and quality.

[0023] Preferably, the reactive diluent is THFA diluent and / or NVP diluent.

[0024] By adopting the above technical solution, the use of THFA diluent and / or NVP diluent can effectively improve the fluidity and viscosity of the conductive ink, enhancing the ink's jetting performance and wettability during the inkjet printing process. These diluents help the conductive filler disperse more evenly in the ink, reducing agglomeration, thereby improving the conductive performance and stability of the conductive ink. Furthermore, they promote uniform coating of the ink on the substrate surface, ensuring that the resulting conductive pattern has good adhesion and wear resistance. Especially in smart wearable device applications, they can effectively resist the erosion of sweat and cosmetics, extending the service life of the flexible circuit board.

[0025] THFA diluent, i.e. tetrahydrofurfuryl acrylate; NVP diluent, i.e. N-vinyl pyrrolidone.

[0026] Preferably, the substrate is polyimide or polyester film.

[0027] By adopting the above technical solution and selecting polyimide or polyester film as the substrate, the excellent properties of both materials can be fully utilized. Polyimide has excellent high-temperature resistance, chemical corrosion resistance, and mechanical strength, while polyester film has good flexibility and transparency. These properties make flexible circuit boards more stable and durable in smart wearable devices. In particular, they can effectively prevent the circuit pattern from falling off or performance degradation in the face of erosion caused by sweat, cosmetics, and frequent friction, thereby improving the overall reliability and service life of the flexible circuit board.

[0028] Preferably, the processing aid is one or more of a thixotropic agent, a filler, a defoaming agent, a wetting agent, and a colorant.

[0029] By adopting the above technical solutions, the addition of processing aids can significantly improve the rheological properties and construction performance of conductive inks. Thixotropic agents can effectively adjust the viscosity of the ink, avoid sagging during the inkjet printing process, and ensure uniform coating of the ink. Fillers can improve the mechanical strength and durability of the ink and reduce performance degradation caused by the external environment. Defoamers can eliminate bubbles in the ink and ensure the smoothness and uniformity of the ink. Wetting agents can improve the wetting properties of the ink on the substrate surface and enhance the adhesion between the ink and the substrate. The addition of colorants can make the conductive ink more visually recognizable, facilitating quality control during production and testing. In summary, the rational combination and use of these processing aids can significantly improve the comprehensive performance of the conductive ink and ensure the reliability and durability of the flexible circuit board in smart wearable devices.

[0030] Preferably, the thickness of the conductive ink circuit pattern is 10-100 μm.

[0031] By adopting the above technical solution, the thickness of the conductive ink circuit pattern is controlled within the range of 10-100μm, effectively ensuring the circuit pattern's conductivity and mechanical strength. This thickness range not only ensures the uniformity and continuity of the circuit pattern, but also maintains good adhesion to the flexible substrate, reducing the risk of short circuits caused by insufficient thickness or substrate deformation caused by excessive thickness. Especially in smart wearable devices, circuit patterns within this thickness range can better withstand the erosion of sweat and cosmetics, while also exhibiting excellent wear and impact resistance, thereby improving the reliability and service life of the flexible circuit board.

[0032] In summary, this application includes at least one of the following beneficial technical effects:

[0033] 1. By using a dispersion binder containing multiple ingredients such as boron-modified phenolic resin, active toughening monomer, and modified polyester acrylate, the overall performance of the conductive ink is significantly improved, significantly enhancing its conductivity, adhesion stability, and wear resistance on flexible circuit boards. This effectively solves the problem in existing technologies where printed circuit patterns are easily eroded by sweat and cosmetics, as well as detached due to friction.

[0034] 2. A specific proportion of active toughening monomers (such as epoxy soybean oil acrylate, methacryloyloxyethyl maleate, and N,N'-methylenebisacrylamide) not only enhances the toughness of the ink, but also improves its adhesion to the substrate, making the printed circuit pattern more solid and extending the service life of the flexible circuit board;

[0035] 3. By optimizing the speed, pressure, and curing temperature of inkjet printing, the conductive ink is uniformly sprayed and cured on the substrate surface, forming a circuit pattern with uniform thickness and stable conductive performance, thereby improving the reliability and practicality of flexible circuit boards in smart wearable devices. DETAILED DESCRIPTION

[0036] The present application is further described in detail below with reference to the embodiments.

[0037] Some raw material description:

[0038] Thixotropic agent: BYK-P 2710;

[0039] Defoaming agent: silicone defoaming agent, the manufacturer of which is preferably Jinan Delan Chemical Co., Ltd., with a pH value of 6.5-7.5;

[0040] Boron-modified phenolic resin: Jining Tangyi Chemical Co., Ltd., model DA-22;

[0041] Polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer: molecular formula: [C2H4O]n[C3H6O]m[C2H4O]n, where n is 5-15 and m is 5-18;

[0042] Epoxidized soybean oil acrylate: allnex EBECRYL 5848;

[0043] Methacryloyloxyethyl maleate: CAS No. 26560-94-1

[0044] N,N'-methylenebisacrylamide: molecular formula C7H 10 N2O2;

[0045] Caprolactone modified polyester acrylate: Jining Tangyi Chemical Co., Ltd. Model WDS-60A;

[0046] Hyperbranched polyester acrylate: Jining Fangyu Chemical Co., Ltd. Model RYOJI;

[0047] Rosin-modified phenolic resin: Jining Tangyi Chemical Co., Ltd., model BM04;

[0048] Hydrogenated rosin: CAS No. 65997-06-0;

[0049] The solvent is composed of ethyl acetate and ethylene glycol monomethyl ether in a weight ratio of 1:1.

[0050] Example

[0051] Example 1

[0052] A printing process for a flexible circuit board comprises the following steps:

[0053] Conductive ink is sprayed onto the surface of a polyimide substrate through a nozzle using an inkjet printing device at an inkjet printing speed of 1 m / s and an inkjet pressure of 0.08 MPa. The substrate is then transferred to a curing device for curing. UV curing is first performed using a UV lamp (wavelength 320-400 nm) for 5 seconds, followed by thermal curing at a curing temperature of 120°C for 2 minutes to form a conductive pattern on the surface of the substrate, thereby obtaining a printed flexible circuit board.

[0054] The conductive ink is made by mixing a conductive filler and a dispersed binder in a weight ratio of 1:1. The conductive filler is carbon nanotubes. The thickness of the conductive ink circuit pattern is 10 μm.

[0055] Dispersion binder: Boron-modified phenolic resin, reactive toughening monomer, modified polyester acrylate, polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer, modified rosin resin, N-aminoethyl-3-aminopropylmethyldimethoxysilane, reactive diluent, initiator, solvent and processing aid are weighed and uniformly mixed in a weight ratio of 2:20:8:1:13:8:3:3:50 to obtain a dispersion binder;

[0056] The active toughening monomer is epoxy soybean oil acrylate; the modified polyester acrylate is caprolactone-modified polyester acrylate; the modified rosin is or hydrogenated rosin; the active diluent is composed of THFA diluent and NVP diluent in a weight ratio of 1:1. The processing aid is composed of a thixotropic agent and a defoaming agent in a weight ratio of 1:1. The initiator is composed of photoinitiator 184 and benzoyl oxide in a weight ratio of 1:2.

[0057] Example 2

[0058] Example 2 differs from Example 1 in that the weight ratio of the boron-modified phenolic resin, reactive toughening monomer, modified polyester acrylate, polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer, modified rosin resin, N-aminoethyl-3-aminopropylmethyldimethoxysilane, reactive diluent, initiator, and solvent is 3.2:16:5:2:17:11:2:3:50. The conductive ink is prepared by uniformly mixing a conductive filler and a dispersed binder in a weight ratio of 1:2.3. The thickness of the conductive ink circuit pattern is 50 μm.

[0059] Example 3

[0060] Example 3 differs from Example 1 in that the boron-modified phenolic resin, reactive toughening monomer, modified polyester acrylate, polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer, modified rosin resin, N-aminoethyl-3-aminopropylmethyldimethoxysilane, reactive diluent, initiator, and solvent are prepared in a weight ratio of 5:10:2:3:20:15:1:3:50. The conductive ink is prepared by uniformly mixing a conductive filler and a dispersed binder in a weight ratio of 1:5. The thickness of the conductive ink circuit pattern is 100 μm.

[0061] Example 4

[0062] The difference between Example 4 and Example 1 is that the inkjet printing speed is 2 m / s and the inkjet pressure is 0.1 MPa.

[0063] Example 5

[0064] The difference between Example 5 and Example 1 is that the inkjet printing speed is 3 m / s and the inkjet pressure is 0.2 MPa.

[0065] Example 6

[0066] The difference between Example 6 and Example 2 is that the active toughening monomer is methacryloyloxyethyl maleate.

[0067] Example 7

[0068] The difference between Example 7 and Example 2 is that the active toughening monomer is N,N'-methylenebisacrylamide.

[0069] Example 8

[0070] The difference between Example 8 and Example 2 is that the active toughening monomer consists of epoxy soybean oil acrylate, methacryloyloxyethyl maleate, and N,N'-methylenebisacrylamide in a weight ratio of 3:1:1.

[0071] Example 9

[0072] The difference between Example 9 and Example 2 is that the active toughening monomer consists of epoxy soybean oil acrylate, methacryloyloxyethyl maleate, and N,N'-methylenebisacrylamide in a weight ratio of 3:1.3:0.7.

[0073] Example 10

[0074] The difference between Example 10 and Example 2 is that the active toughening monomer consists of epoxy soybean oil acrylate, methacryloyloxyethyl maleate, and N,N'-methylenebisacrylamide in a weight ratio of 3:1.5:0.5.

[0075] Example 11

[0076] The difference between Example 11 and Example 2 is that the modified polyester acrylate is caprolactone-modified polyester acrylate.

[0077] Example 12

[0078] The difference between Example 12 and Example 2 is that the modified polyester acrylate consists of caprolactone-modified polyester acrylate and hyperbranched polyester acrylate in a weight ratio of 1:0.2.

[0079] Example 13

[0080] The difference between Example 13 and Example 9 is that the modified polyester acrylate consists of caprolactone-modified polyester acrylate and hyperbranched polyester acrylate in a weight ratio of 1:0.2.

[0081] Example 14

[0082] The difference between Example 14 and Example 9 is that the modified polyester acrylate consists of caprolactone-modified polyester acrylate and hyperbranched polyester acrylate in a weight ratio of 1:0.8.

[0083] Example 15

[0084] The difference between Example 15 and Example 2 is that the modified rosin is a rosin-modified phenolic resin.

[0085] Example 16

[0086] The difference between Example 16 and Example 2 is that the modified rosin consists of rosin-modified phenolic resin and hydrogenated rosin in a weight ratio of 1:1.

[0087] Example 17

[0088] The difference between Example 17 and Example 9 is that the modified rosin consists of rosin-modified phenolic resin and hydrogenated rosin in a weight ratio of 1:1.

[0089] Example 18

[0090] The difference between Example 18 and Example 13 is that the modified rosin consists of rosin-modified phenolic resin and hydrogenated rosin in a weight ratio of 1:1.

[0091] Example 19

[0092] The difference between Example 19 and Example 13 is that the modified rosin consists of rosin-modified phenolic resin and hydrogenated rosin in a weight ratio of 1:3.

[0093] Comparative Example

[0094] Comparative Example 1

[0095] The difference between Comparative Example 1 and Example 1 is that the active toughening monomer is replaced by modified rosin resin in equal amounts.

[0096] Comparative Example 2

[0097] The difference between Comparative Example 2 and Example 1 is that the modified rosin resin is replaced by polyurethane acrylate in equal amount.

[0098] Comparative Example 3

[0099] The difference between Comparative Example 3 and Example 1 is that the boron-modified phenolic resin is replaced by an equal amount of modified rosin resin.

[0100] Comparative Example 4

[0101] The difference between Comparative Example 4 and Example 1 is that the modified polyester acrylate is replaced by modified rosin resin in equal amount.

[0102] Comparative Example 5

[0103] The difference between Comparative Example 5 and Example 1 is that the polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer is replaced by modified rosin resin in equal amounts.

[0104] Comparative Example 6

[0105] The difference between Comparative Example 6 and Example 1 is that an equal amount of N-aminoethyl-3-aminopropylmethyldimethoxysilane is replaced by modified rosin resin.

[0106] Performance testing

[0107] The printed flexible circuit boards obtained in Examples 1-19 and Comparative Examples 1-6 were subjected to the following performance tests.

[0108] Test method / test method Adhesion fastness: Refer to national standard GB / T 13217.7-2009 to test the conductive ink circuit pattern of printed flexible circuit boards.

[0109] Wear resistance: Refer to GB / T5237-2008 to test the conductive ink circuit pattern of the printed flexible circuit board and observe the time it takes for the conductive ink circuit pattern to show through.

[0110] Durability: Place the test sample in the test liquid, soak it for 120 hours, then take it out and air-dry it in a 50℃ bellows for 1 minute to dry the moisture on the surface. The sample is then tested for adhesion and abrasion resistance. The test method is the same as above, and the reduction in adhesion / transmittance time is calculated. The reduction in adhesion is equal to the adhesion before immersion in the test liquid minus the adhesion after immersion.

[0111] The test solution consists of standard artificial sweat with a pH of 4.7, anhydrous ethanol, and propylene glycol in a weight ratio of 10:1:1.

[0112] The above specific experimental data are shown in Table 1;

[0113] Table 1 Experimental data of Examples 1-19 and Comparative Examples 1-6

[0114]

[0115]

[0116] Combining Example 1 and Comparative Examples 1-6 with Table 1, it can be seen that the adhesion fastness and bottom-through time of Comparative Examples 1-6 are higher than those of Example 1, while the reduction in adhesion fastness / bottom-through time is lower than that of Example 1. This shows that the present application uses boron-modified phenolic resin, active toughening monomer, modified polyester acrylate, polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer, modified rosin resin, N-aminoethyl-3-aminopropylmethyldimethoxysilane and other ingredients to work together to improve the comprehensive performance of the conductive ink. When applied to the production process of the present application, a stable, wear-resistant, and sweat-resistant conductive ink circuit pattern is formed, thereby improving the durability and practicality of the flexible circuit board.

[0117] Comparing Examples 8-10 with Example 2 and combining with Table 1, it can be seen that the adhesion fastness and bottom-through time of Examples 8-10 are higher than those of Example 2, while the reduction in adhesion fastness and the reduction in bottom-through time are lower than those of Example 2. This shows that the monomers composed of epoxy soybean oil acrylate, methacryloyloxyethyl maleate, and N,N'-methylenebisacrylamide are compounded to achieve a better synergistic effect. The resulting conductive ink is applied to the flexible circuit board printing process, which can achieve a better synergistic effect, reduce wear, corrosion, and shedding of the conductive ink circuit pattern obtained after printing, and improve its practicality.

[0118] By comparing Example 9 and Example 14 and combining them with Table 1, it can be seen that the adhesion fastness and bottom-through time of Example 14 are higher than those of Example 9, while the reduction in adhesion fastness and the reduction in bottom-through time are lower than those of Example 9, indicating that the compounding of caprolactone-modified polyester acrylate and caprolactone-modified polyester acrylate has a synergistic effect, further enhancing the overall performance of the conductive ink circuit pattern of the flexible circuit board.

[0119] Comparing Example 13 and Example 18 and combining them with Table 1, it can be seen that the adhesion fastness and bottom-through time of Example 18 are higher than those of Example 13, while the reduction in adhesion fastness and the reduction in bottom-through time are lower than those of Example 13. This shows that the compounding of rosin-modified phenolic resin and hydrogenated rosin has a synergistic effect, further improving the overall performance of the conductive ink circuit pattern of the flexible circuit board.

[0120] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A printing process for a flexible circuit board, characterized in that: Prepared by the following method: The conductive ink is printed on the surface of the substrate by inkjet printing and cured to form a conductive pattern on the surface of the substrate to obtain a printed flexible circuit board; The conductive ink is composed of a conductive filler and a dispersed connecting material in a weight ratio of 1: (1-5); Dispersion binder: Boron-modified phenolic resin, active toughening monomer, modified polyester acrylate, polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer, modified rosin resin, N-aminoethyl-3-aminopropylmethyldimethoxysilane, active diluent, initiator, solvent and processing aid are weighed and mixed uniformly in a weight ratio of (2-5): (10-20): (2-8): (1-3): (13-20): (8-15): (1-3): (0-3): 100 to obtain a dispersion binder; The active toughening monomer is composed of epoxy soybean oil acrylate, methacryloyloxyethyl maleic acid monoester, and N,N'-methylenebisacrylamide in a weight ratio of 3: (1-1.5): (0.5-1); the modified polyester acrylate is composed of caprolactone-modified polyester acrylate and hyperbranched polyester acrylate in a weight ratio of 1: (0.2-0.8).

2. The printing process for a flexible circuit board according to claim 1, characterized in that: The inkjet printing speed is 1-3 m / s, and the inkjet pressure is 0.08-0.2 MPa.

3. The printing process for a flexible circuit board according to claim 1, characterized in that: The modified rosin is rosin-modified phenolic resin and / or hydrogenated rosin.

4. The printing process for a flexible circuit board according to claim 3, characterized in that: The modified rosin consists of rosin-modified phenolic resin and hydrogenated rosin in a weight ratio of 1:(1-3).

5. The printing process for a flexible circuit board according to claim 1, characterized in that: The active diluent is THFA diluent and / or NVP diluent.

6. The printing process for a flexible circuit board according to claim 1, characterized in that: The substrate is a polyimide or polyester film.

7. The printing process for a flexible circuit board according to claim 1, characterized in that: The processing aid is one or more of a thixotropic agent, a filler, a defoaming agent, a wetting agent, and a colorant.

8. The printing process for a flexible circuit board according to claim 1, characterized in that: The thickness of the conductive ink circuit pattern is 10-100 μm.

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