Printing type FPC (Flexible Printed Circuit) production process

Abstract

The invention relates to a printing type FPC (Flexible Printed Circuit) production process, and belongs to the technical field of high polymer materials. The printed FPC sequentially comprises a base material layer, a circuit layer and an ink layer from bottom to top, the circuit layer is formed by printing copper and silver mixed type conductive paste on the surface of the base material layer through a silk screen, the ink layer is formed by printing ink on the surface of the circuit layer, and the base material layer is PI or PET; the printing ink comprises the following raw materials in parts by weight: 5-10 parts of titanium dioxide, 5-30 parts of modified resin, 10-40 parts of aldehyde ketone resin, 40-60 parts of an ethanol solution with the concentration of 95%, 5-20 parts of menthol, 0.5-2 parts of an emulsified silicone oil defoaming agent and 0.5-2 parts of an ethylene-acetic acid copolymer dispersing agent. The printed FPC manufactured by the method can replace the traditional resistance increasing process through the loop impedance of the circuit, so that the current standard is reached, and the traditional copper etching process is replaced.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a printing-type FPC production process. Background Technology

[0002] With social development and progress, people are paying increasing attention to quality of life and comfort, and their requirements for the quality of printed products are becoming more and more stringent. FPC is a type of printed flexible circuit board, which is generally produced using a chemical wet process. Common production processes include dry film lamination, circuit exposure and shaping, circuit development, circuit etching, and dry film removal. It is widely used in aerospace and military industries, mobile phones, Bluetooth headsets, wearable electronic devices, automobiles, and other fields.

[0003] However, traditional FPCs require the addition of resistive components to control the current of the LED light strips. At the same time, the copper foil etching process used for this process causes adverse effects on the surrounding environment and human health, resulting in serious pollution and making it extremely unfriendly to the environment, thus limiting its application scope. Therefore, the development of high-performance printed FPCs has significant practical significance and application value. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a printing-type FPC production process.

[0005] The objective of this invention can be achieved through the following technical solutions: A printed FPC comprises, from bottom to top, a substrate layer, a circuit layer, and an ink layer. The circuit layer is formed by screen printing a copper-silver mixed conductive paste onto the surface of the substrate layer. The ink layer is formed by printing ink onto the surface of the circuit layer. The substrate layer is PI or PET. Further, the ink comprises the following raw materials in parts by weight: 5-10 parts titanium dioxide, 5-30 parts modified resin, 10-40 parts aldehyde-ketone resin, 40-60 parts 95% ethanol solution, 5-20 parts menthol, 0.5-2 parts emulsified silicone oil defoamer, and 0.5-2 parts ethylene-acetic acid copolymer dispersant. Furthermore, the modified resin is prepared by the following method: Step A1: Neopentyl glycol, dimethylolpropionic acid and p-toluenesulfonic acid are mixed and stirred evenly. Under argon protection, the mixture is heated to 145°C and reacted for 3 hours. After the reaction is complete, the reaction system is cooled to 70°C, acetone is added and stirred, and the mixture is allowed to stand and then dried under vacuum to obtain compound a. Furthermore, the ratio of neopentyl glycol, dimethylolpropionic acid, p-toluenesulfonic acid, and acetone is 0.01-0.03 mol: 0.02-0.06 mol: 0.02-0.08 g: 10-30 mL; First, compound a was prepared by reacting the hydroxyl group of neopentyl glycol with the carboxyl group of dimethylolpropionic acid. Step A2: Mix compound a and acrylic acid, stir at 110°C until homogeneous, add p-toluenesulfonic acid under argon protection, stir at 200 rpm for 5 h, and wash when the system temperature drops to 60°C to obtain preproduct 1. Furthermore, the ratio of compound a to acrylic acid is 0.01-0.03 mol: 0.04-0.12 mol, and the amount of p-toluenesulfonic acid accounts for 0.5% of the total mass of the reactants in step A2; Preproduct 1 was prepared by reacting the hydroxyl group of compound a with the carboxyl group of acrylic acid. Step A3: Disperse nano-silica in an ethanol-water mixed solution, stir at 50°C for 5 hours, adjust the pH of the system to 10, add 3-butenetriethoxysilane and mix evenly, react at 50°C for 10 hours, filter and wash, place in a Soxhlet extractor for 20 hours, dry at 80°C for 24 hours to obtain preproduct 2. Furthermore, the ratio of nano-silica, ethanol-water mixed solution, and 3-butenetriethoxysilane is 0.01-0.03 mol: 40-80 mL: 0.02-0.06 mol, and the mass ratio of ethanol to water in the ethanol-water mixed solution is 2:1. Secondly, preproduct 2 was prepared by reacting the silanol groups from the hydrolysis of 3-butenetriethoxysilane with the hydroxyl groups of nano-silica. Step A4: Mix vinyl chloride, vinyl isobutyl ether, preproduct 1, preproduct 2, butyl acrylate, methyl methacrylate and methyl propionate, stir for 10 min, then add azobisisobutyronitrile and ethanol and mix, mechanically stir for 30 min at 600-700 rpm, heat to 70-80℃, react for 3 h, cool to room temperature to obtain the modified resin; Furthermore, the molar ratio of vinyl chloride, vinyl isobutyl ether, preproduct 1, preproduct 2, butyl acrylate, methyl methacrylate, methyl propionate, azobisisobutyronitrile, and ethanol is 0.01-0.03 mol: 0.01-0.03 mol: 0.01-0.03 mol: 0.01-0.03 mol: 0.01-0.03 mol: 0.01-0.03 mol: 0.35-0.55 g: 20 mL; Finally, the modified resin was prepared by reacting the carbon-carbon double bonds of preproduct 1, preproduct 2, vinyl chloride, vinyl isobutyl ether, butyl acrylate, methyl methacrylate and methyl propionate.

[0006] A manufacturing process for printed FPCs specifically includes the following steps: S1. A copper-silver mixed conductive paste is screen-printed onto the surface of a PI or PET substrate to obtain a circuit layer. S2. Mix and stir the modified resin, aldehyde-ketone resin and 95% ethanol solution, filter, then add ethylene acetate copolymer dispersant and titanium dioxide in sequence while stirring, grind to below 5μm after thorough stirring, then add emulsified silicone oil defoamer and menthol, stir and disperse evenly to obtain ink. S3. Print an ink layer on the surface of the circuit layer, exposing only the conductive area where the LED light source needs to be attached and the power driving position. Gold plate the exposed conductive area, and attach the LED light source through SMT process to obtain a printed FPC.

[0007] The beneficial effects of this invention are: The printed FPC of this invention can achieve the current standard by replacing the traditional process of increasing resistance through the loop impedance of the circuit itself, thus replacing the traditional copper etching process.

[0008] The ink of this invention enables printed FPCs to possess high hardness and good adhesion, while also exhibiting excellent water resistance. The modified resin obtained in this invention is first prepared by reacting the hydroxyl groups of neopentyl glycol with the carboxyl groups of dimethylolpropionic acid to obtain compound a; then, by reacting the hydroxyl groups of compound a with the carboxyl groups of acrylic acid to obtain preproduct 1; next, by reacting the silanol groups from the hydrolysis of 3-butenetriethoxysilane with the hydroxyl groups of nano-silica to obtain preproduct 2; finally, by reacting the carbon-carbon double bonds of preproduct 1, preproduct 2, vinyl chloride, vinyl isobutyl ether, butyl acrylate, methyl methacrylate, and methyl propionate to obtain the final product. In this modified resin, the steric hindrance of the vinyl chloride molecular side chains is increased, and the structure contains a large number of ether bonds, giving the resin excellent flexibility during use. The introduction of vinyl chloride monomer gives the resin acid and alkali resistance, making it suitable for chemical etching and cleaning processes in FPC production. At the same time, the isobutyl ether groups on the side chains easily form hydrogen bonds with the material surface, enhancing the adhesion of the coating film. In addition, the cross-linking network of the modified resin and the reinforcing effect of nano-silica ensure that the ink maintains high viscosity stability during printing, preventing ink flow caused by substrate bending. The barrier effect of nano-silica can block water vapor penetration, improve the moisture resistance of the ink layer, extend the service life of the coating, prevent material oxidation, and improve the durability of the material. Furthermore, vinyl chloride and vinyl isobutyl ether form a chloroether resin structure, further improving the durability of the material, preventing degradation, gold bloom, and chalking, and extending the service life of the material. Detailed Implementation

[0009] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0010] Example 1: A printed FPC, comprising a substrate layer, a circuit layer and an ink layer from bottom to top. The circuit layer is formed by screen printing a copper-silver mixed conductive paste onto the surface of the substrate layer. The ink layer is formed by printing ink onto the surface of the circuit layer. The substrate layer is PET. Its production process includes the following steps: S1. A copper-silver mixed conductive paste is screen-printed onto the surface of a PET substrate to obtain a circuit layer; S2. Weigh the raw materials according to the weight parts, mix and stir 5 parts of modified resin (prepared in this example), 10 parts of aldehyde-ketone resin (CT-120, Jinan Dahui Chemical) and 40 parts of 95% ethanol solution, filter, then add 0.5 parts of ethylene acetate copolymer dispersant and 5 parts of titanium dioxide in sequence while stirring, grind to below 5μm after thorough stirring, then add 0.5 parts of emulsified silicone oil defoamer and 5 parts of menthol, stir and disperse evenly to obtain ink; S3. Print an ink layer on the surface of the circuit layer, exposing only the conductive area where the LED light source needs to be attached and the power driving position. Gold plate the exposed conductive area, and attach the LED light source through SMT process to obtain a printed FPC. Furthermore, the modified resin is prepared by the following method: Step A1: Mix 0.01 mol neopentyl glycol, 0.02 mol dimethylolpropionic acid and 0.02 g p-toluenesulfonic acid, stir until homogeneous, heat to 145 °C under argon protection, react for 3 h. After the reaction is complete, cool the reaction system to 70 °C, add 10 mL acetone and stir, let stand, and dry under vacuum to obtain compound a. Step A2: Mix 0.01 mol of compound a and 0.04 mol of acrylic acid, stir at 110°C until homogeneous, add p-toluenesulfonic acid under argon protection, stir at 200 rpm for 5 h, and wash when the system temperature drops to 60°C to obtain preproduct 1. The amount of p-toluenesulfonic acid used accounts for 0.5% of the total mass of the reactants in step A2. Step A3: Disperse 0.01 mol of nano-silica in 40 mL of ethanol-water mixed solution, stir at 50 °C for 5 h, adjust the pH of the system to 10, then add 0.02 mol of 3-butenetriethoxysilane and mix well. React at 50 °C for 10 h. After the reaction is complete, filter, wash, and circulate in a Soxhlet extractor for 20 h. Dry at 80 °C for 24 h to obtain preproduct 2. The mass ratio of ethanol to water in the ethanol-water mixed solution is 2:1. Step A4: Mix 0.01 mol vinyl chloride, 0.01 mol vinyl isobutyl ether, 0.01 mol preproduct 1, 0.01 mol preproduct 2, 0.01 mol butyl acrylate, 0.01 mol methyl methacrylate and 0.01 mol methyl propionate, stir for 10 min, then add 0.35 g azobisisobutyronitrile and 20 mL ethanol and mix. Mechanically stir for 30 min at 600 rpm, heat to 70 °C, react for 3 h, cool to room temperature to obtain the modified resin.

[0011] Example 2: A printed FPC, comprising a substrate layer, a circuit layer and an ink layer from bottom to top. The circuit layer is formed by screen printing a copper-silver mixed conductive paste onto the surface of the substrate layer. The ink layer is formed by printing ink onto the surface of the circuit layer. The substrate layer is PET. Its production process includes the following steps: S1. A copper-silver mixed conductive paste is screen-printed onto the surface of a PET substrate to obtain a circuit layer; S2. Weigh the raw materials according to the weight parts, mix and stir 17 parts of modified resin (prepared in this example), 25 parts of aldehyde-ketone resin (CT-120, Jinan Dahui Chemical) and 50 parts of 95% ethanol solution, filter, then add 1 part of ethylene acetate copolymer dispersant and 7 parts of titanium dioxide in sequence while stirring, grind to below 5μm after thorough stirring, then add 1 part of emulsified silicone oil defoamer and 12 parts of menthol, stir and disperse evenly to obtain ink; S3. Print an ink layer on the surface of the circuit layer, exposing only the conductive area where the LED light source needs to be attached and the power driving position. Gold plate the exposed conductive area, and attach the LED light source through SMT process to obtain a printed FPC. Furthermore, the modified resin is prepared by the following method: Step A1: Mix 0.02 mol neopentyl glycol, 0.04 mol dimethylolpropionic acid and 0.05 g p-toluenesulfonic acid, stir well, heat to 145 °C under argon protection, react for 3 h. After the reaction is complete, cool the reaction system to 70 °C, add 20 mL acetone and stir, let stand, and dry under vacuum to obtain compound a. Step A2: Mix 0.02 mol of compound a and 0.08 mol of acrylic acid, stir at 110°C until homogeneous, add p-toluenesulfonic acid under argon protection, stir at 200 rpm for 5 h, and wash when the system temperature drops to 60°C to obtain preproduct 1. The amount of p-toluenesulfonic acid used accounts for 0.5% of the total mass of the reactants in step A2. Step A3: Disperse 0.02 mol of nano-silica in 60 mL of ethanol-water mixed solution, stir at 50 °C for 5 h, adjust the pH of the system to 10, then add 0.04 mol of 3-butenetriethoxysilane and mix well. React at 50 °C for 10 h. After the reaction is complete, filter, wash, and circulate in a Soxhlet extractor for 20 h. Dry at 80 °C for 24 h to obtain preproduct 2. The mass ratio of ethanol to water in the ethanol-water mixed solution is 2:1. Step A4: Mix 0.02 mol vinyl chloride, 0.02 mol vinyl isobutyl ether, 0.02 mol preproduct 1, 0.02 mol preproduct 2, 0.02 mol butyl acrylate, 0.02 mol methyl methacrylate and 0.02 mol methyl propionate, stir for 10 min, then add 0.45 g azobisisobutyronitrile and 20 mL ethanol and mix. Mechanically stir for 30 min at 650 rpm, heat to 75 °C, react for 3 h, cool to room temperature to obtain the modified resin.

[0012] Example 3: A printed FPC, comprising a substrate layer, a circuit layer and an ink layer from bottom to top. The circuit layer is formed by screen printing a copper-silver mixed conductive paste onto the surface of the substrate layer. The ink layer is formed by printing ink onto the surface of the circuit layer. The substrate layer is PET. Its production process includes the following steps: S1. A copper-silver mixed conductive paste is screen-printed onto the surface of a PET substrate to obtain a circuit layer; S2. Weigh the raw materials according to the weight parts, mix and stir 30 parts of modified resin (prepared in this example), 40 parts of aldehyde-ketone resin (CT-120, Jinan Dahui Chemical) and 60 parts of 95% ethanol solution, filter, then add 2 parts of ethylene acetate copolymer dispersant and 10 parts of titanium dioxide in sequence while stirring, grind to below 5μm after thorough stirring, then add 2 parts of emulsified silicone oil defoamer and 20 parts of menthol, stir and disperse evenly to obtain ink; S3. Print an ink layer on the surface of the circuit layer, exposing only the conductive area where the LED light source needs to be attached and the power driving position. Gold plate the exposed conductive area, and attach the LED light source through SMT process to obtain a printed FPC. Furthermore, the modified resin is prepared by the following method: Step A1: Mix 0.03 mol neopentyl glycol, 0.06 mol dimethylolpropionic acid and 0.08 g p-toluenesulfonic acid, stir well, heat to 145 °C under argon protection, react for 3 h. After the reaction is complete, cool the reaction system to 70 °C, add 30 mL acetone and stir, let stand, and dry under vacuum to obtain compound a. Step A2: Mix 0.03 mol of compound a and 0.12 mol of acrylic acid, stir at 110°C until homogeneous, add p-toluenesulfonic acid under argon protection, stir at 200 rpm for 5 h, and wash when the system temperature drops to 60°C to obtain preproduct 1. The amount of p-toluenesulfonic acid used accounts for 0.5% of the total mass of the reactants in step A2. Step A3: Disperse 0.03 mol of nano-silica in 80 mL of ethanol-water mixed solution, stir at 50 °C for 5 h, adjust the pH of the system to 10, then add 0.06 mol of 3-butenetriethoxysilane and mix well. React at 50 °C for 10 h. After the reaction is complete, filter, wash, and circulate in a Soxhlet extractor for 20 h. Dry at 80 °C for 24 h to obtain preproduct 2. The mass ratio of ethanol to water in the ethanol-water mixed solution is 2:1. Step A4: Mix 0.03 mol vinyl chloride, 0.03 mol vinyl isobutyl ether, 0.03 mol preproduct 1, 0.03 mol preproduct 2, 0.03 mol butyl acrylate, 0.03 mol methyl methacrylate and 0.03 mol methyl propionate, stir for 10 min, then add 0.55 g azobisisobutyronitrile and 20 mL ethanol and mix. Stir mechanically for 30 min at 700 rpm, heat to 80 °C, react for 3 h, cool to room temperature to obtain the modified resin.

[0013] Comparative Example 1: This comparative example is a printed FPC. The difference between this example and Example 3 is that an equal amount of acrylic resin is used instead of the modified resin prepared in Example 3. All other aspects are the same.

[0014] Performance testing: The inks prepared in Examples 1-3 and Comparative Example 1 were made into standard test sizes, and their adhesion was tested according to the method described in standard reference ISO 4624. The water resistance of the coating film was tested according to GB-T1733-93, and hardness and electrolyte resistance were also tested.

[0015] Table 1

[0016] As can be seen from the test data in Table 1, the printed FPC prepared by the present invention has good loop impedance effect. Table 1 also shows that the printed FPC prepared by the present invention has good high hardness and good adhesion, thus extending its service life.

[0017] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A printing-type FPC manufacturing process, characterized in that, This printed FPC consists of a substrate layer, a circuit layer, and an ink layer from bottom to top. The circuit layer is formed by screen printing a copper-silver mixed conductive paste onto the surface of the substrate layer. The ink layer is formed by printing ink onto the surface of the circuit layer. The substrate layer is PI or PET. Its production process includes the following steps: S1. A copper-silver mixed conductive paste is screen-printed onto the surface of a PI or PET substrate to obtain a circuit layer. S2. Weigh the raw materials according to the weight parts, mix and stir 5-30 parts of modified resin, 10-40 parts of aldehyde-ketone resin and 40-60 parts of 95% ethanol solution, filter, then add 0.5-2 parts of ethylene acetate copolymer dispersant and 5-10 parts of titanium dioxide in sequence while stirring, grind to below 5μm after thorough stirring, then add 0.5-2 parts of emulsified silicone oil defoamer and 5-20 parts of menthol, stir and disperse evenly to obtain ink; S3. Print an ink layer on the surface of the circuit layer, exposing only the conductive area where the LED light source needs to be attached and the power driving position. Gold plate the exposed conductive area, and attach the LED light source through SMT process to obtain a printed FPC. The modified resin is prepared by the following method: Step A1: Neopentyl glycol, dimethylolpropionic acid and p-toluenesulfonic acid are mixed and stirred evenly. Under argon protection, the mixture is heated to 145°C and reacted for 3 hours. After the reaction is complete, the reaction system is cooled to 70°C, acetone is added and stirred, and the mixture is allowed to stand and then dried under vacuum to obtain compound a. Step A2: Mix compound a and acrylic acid, stir at 110°C until homogeneous, add p-toluenesulfonic acid under argon protection, stir at 200 rpm for 5 h, and wash when the system temperature drops to 60°C to obtain preproduct 1. Step A3: Disperse nano-silica in an ethanol-water mixed solution, stir at 50°C for 5 hours, adjust the pH of the system to 10, add 3-butenetriethoxysilane and mix evenly, react at 50°C for 10 hours, filter and wash, place in a Soxhlet extractor for 20 hours, dry at 80°C for 24 hours to obtain preproduct 2. Step A4: Mix vinyl chloride, vinyl isobutyl ether, preproduct 1, preproduct 2, butyl acrylate, methyl methacrylate and methyl propionate, stir for 10 min, then add azobisisobutyronitrile and ethanol and mix, mechanically stir for 30 min at 600-700 rpm, heat to 70-80℃, react for 3 h, cool to room temperature, and obtain the modified resin.

2. The printing FPC production process according to claim 1, characterized in that, In step A1, the ratio of neopentyl glycol, dimethylolpropionic acid, p-toluenesulfonic acid, and acetone is 0.01-0.03 mol: 0.02-0.06 mol: 0.02-0.08 g: 10-30 mL.

3. The printing FPC production process according to claim 1, characterized in that, In step A2, the ratio of compound a to acrylic acid is 0.01-0.03 mol: 0.04-0.12 mol, and the amount of p-toluenesulfonic acid accounts for 0.5% of the total mass of the reactants in step A2.

4. The printing FPC production process according to claim 1, characterized in that, In step A3, the ratio of nano-silica, ethanol-water mixed solution, and 3-butenetriethoxysilane is 0.01-0.03 mol: 40-80 mL: 0.02-0.06 mol, and the mass ratio of ethanol to water in the ethanol-water mixed solution is 2:

1.

5. The printing FPC production process according to claim 1, characterized in that, In step A4, the ratio of vinyl chloride, vinyl isobutyl ether, preproduct 1, preproduct 2, butyl acrylate, methyl methacrylate, methyl propionate, azobisisobutyronitrile, and ethanol is 0.01-0.03 mol: 0.01-0.03 mol: 0.01-0.03 mol: 0.01-0.03 mol: 0.01-0.03 mol: 0.01-0.03 mol: 0.01-0.03 mol: 0.35-0.55 g: 20 mL.

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