Flexible printed circuit board and processing technology thereof

Abstract

The invention relates to the technical field of printed circuit boards, in particular to a flexible printed circuit board and a processing technology thereof. The preparation method comprises the following steps: S1, uniformly mixing urethane acrylate, epoxy acrylate, modified polyimide, a reactive diluent, a photoinitiator and silicon dioxide, and vacuumizing and defoaming to obtain a photocuring adhesive; and S2, coating the surface of the polyimide film with a photocuring adhesive, overlapping the polyimide film with a copper foil, and performing ultraviolet irradiation to obtain the flexible printed circuit board. The modified polyimide is prepared by modifying amino-terminated polyimide by fluorine-containing epoxy-terminated organosilicon and epoxidized soybean oil acrylate, so that the interface bonding force between the copper foil and the polyimide film is enhanced, and the heat resistance of the copper foil and the polyimide film is also improved.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit boards, in particular to a flexible printed circuit board and a processing technology thereof. Background Art

[0002] Printed circuit boards (PCBs) can be divided into rigid printed circuit boards and flexible printed circuit boards (FPCs). Flexible printed circuit boards are usually composed of a flexible substrate (such as polyimide or polyester film) and a metal conductive layer (such as copper foil), and the required circuit pattern is formed through etching, printing and other processes.

[0003] With the increasing trend of miniaturization and lightweight of electronic equipment, flexible printed circuit boards have gradually become an indispensable part of the modern electronics industry. However, during use, circuit boards are susceptible to corrosion from external environmental factors such as moisture, mold, and vibration. Commonly used flexible printed circuit board adhesives mainly include acrylate adhesives, polyimide adhesives, epoxy resin adhesives, polyurethane adhesives, modified nitrile adhesives, etc. Among them, acrylate adhesives are a more important category, with unique performance and a wide variety. They have unique advantages such as good fluidity, ease of use, and excellent chemical resistance. However, acrylate adhesives may not have sufficient adhesion on certain substrates (such as polyimide), especially in high temperature or high humidity environments, which may lead to bonding failure. At the same time, compared with polyimide adhesives, acrylate adhesives have weaker heat resistance and cannot maintain good bonding ability in high temperature processes. In addition, the long curing time may limit production efficiency.

[0004] Therefore, we propose a flexible printed circuit board and a processing technology thereof. Summary of the invention

[0005] The object of the present invention is to provide a flexible printed circuit board and a processing technology thereof to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions: A processing technology for a flexible printed circuit board comprises the following steps: Step S1: uniformly mixing polyurethane acrylate, epoxy acrylate, modified polyimide, reactive diluent, photoinitiator and silicon dioxide, and performing vacuum degassing to obtain a light-curing adhesive; Step S2: coating a photocurable adhesive on the surface of the polyimide film, laminating it with a copper foil, and irradiating it with ultraviolet light to obtain a flexible printed circuit board.

[0007] Furthermore, the photocurable adhesive comprises the following raw materials in parts by weight: 30-50 parts of polyurethane acrylate, 20-40 parts of epoxy acrylate, 15-30 parts of modified polyimide, 10-25 parts of reactive diluent, 3-5 parts of photoinitiator, and 3-8 parts of silicon dioxide.

[0008] Furthermore, the preparation method of the modified polyimide is as follows: Step A: under nitrogen protection, diamine, dianhydride and N-methyl-2-pyrrolidone are mixed to carry out polycondensation reaction to obtain a diamine-terminated polyamic acid solution, toluene is added and mixed evenly, and imidization reaction is carried out to obtain an amine-terminated polyimide; Step B: Under nitrogen protection, fluorine-containing terminal hydrogen silicone oil and allyl glycidyl ether are mixed, and reacted at 80-120° C. for 5-8 hours under the catalysis of chloroplatinic acid to obtain fluorine-containing terminal epoxy silicone; Step C: Evenly mix the fluorine-terminated epoxy silicone and the epoxy soybean oil acrylate, add the terminal amine-terminated polyimide, react for 6-10 hours, and vacuum degassing to obtain the modified polyimide.

[0009] Furthermore, the diamine is one or more of 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 2,2-bis[(4-aminophenoxy)phenyl]propane, 4,4'-diaminodiphenylmethane, 1,4-butanediamine and 1,4-bis(4-aminophenoxy)benzene.

[0010] Furthermore, the dianhydride is one or more of 3,3',4,4'-biphenyl dianhydride, bisphenol A diether dianhydride, 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 4,4'-biphenyl ether dianhydride, pyromellitic acid dianhydride and 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride.

[0011] Furthermore, the molar ratio of the diamine to the dianhydride is 1:(0.3-0.8).

[0012] Furthermore, the polycondensation reaction is carried out at a temperature of 0°C and for a period of 5-20 hours.

[0013] Furthermore, the temperature of the imidization reaction is 200-260° C., and the time is 5-10 hours.

[0014] Furthermore, the mass of the toluene is 10-20% of the mass of the diamine-terminated polyamic acid solution.

[0015] Furthermore, in the step B, the mass ratio of fluorine-containing terminal hydrogen silicone oil, allyl glycidyl ether, and chloroplatinic acid is (40-60):1:(0.0008-0.002).

[0016] Furthermore, the preparation method of the fluorine-containing hydrogen-terminated silicone oil is as follows: Under nitrogen protection, octamethylcyclotetrasiloxane, hydrogen-containing double cap and trifluoropropylmethyldimethoxysilane are mixed evenly, reacted at 60-70°C for 7-9h under the catalysis of concentrated sulfuric acid, and after neutralization and filtration, fluorine-containing hydrogen-terminated silicone oil is obtained.

[0017] Furthermore, the mass concentration of the concentrated sulfuric acid is 98%, and the weight ratio of octamethylcyclotetrasiloxane, hydrogen-containing double head, trifluoropropylmethyldimethoxysilane, and concentrated sulfuric acid is (50-100): (5-10): (50-100): (2-5).

[0018] Furthermore, the mass ratio of the fluorine-containing epoxy-terminated silicone, epoxy soybean oil acrylate and amine-terminated polyimide is 1:(2-4):(3-6).

[0019] Furthermore, the active diluent is one or more of isobornyl acrylate, isobornyl methacrylate, isooctyl acrylate, isooctyl methacrylate, tetrahydrofuran acrylate, tetrahydrofuran methacrylate, trimethylolpropane triacrylate, and ethoxylated trimethylolpropane triacrylate.

[0020] Furthermore, the photoinitiator is one or more of 2-hydroxy-methylphenylpropane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-(4-methylthiophenyl)-2-morpholinyl-1-propanone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0021] Furthermore, the process conditions of the ultraviolet irradiation are 500-2000 mW / cm 2 Irradiate under a high pressure mercury lamp for 10-60s.

[0022] Compared with the prior art, the present invention has the following beneficial effects: A flexible printed circuit board and a processing technology thereof of the present invention limit the molar ratio of diamine to dianhydride to 1: (0.3-0.8), control the excess of diamine, and directionally synthesize terminal amine-terminated polyimide (PI-NH2), wherein the terminal amine group (-NH2) provides a highly efficient reaction site for subsequent ring-opening crosslinking with epoxy groups, thereby avoiding the problem of insufficient interface bonding force of traditional polyimide due to inactive terminal groups; In order to further improve the waterproof performance and bonding strength of the adhesive, the scheme uses terminal amine-capped polyimide to undergo a ring-opening reaction with the epoxy groups in fluorinated terminal epoxy silicone and epoxy soybean oil acrylate to form a "rigid-flexible-loose" multi-scale cross-linked network, in which the polyimide main chain has high rigidity and provides high-temperature dimensional stability; the siloxane segment improves the flexibility of PI, increases toughness, and improves the wettability and ductility of the adhesive, thereby enhancing the bonding strength; the fluorine element helps to improve the chemical stability of the adhesive, and is not prone to oxidation, hydrolysis and other reactions, thereby ensuring the long-term reliability of the bond; at the same time, a UV-curable double-bond photosensitive group is introduced, which can achieve rapid pre-curing with the assistance of ultraviolet light (UV), greatly shortening the production cycle compared to traditional heat-curing adhesives; In addition, the modified polyimide prepared by the present invention has good compatibility with the polyimide-based film and can improve the bonding strength between the adhesive and the polyimide; the modified polyethyleneimine molecule contains multiple unsaturated double bonds, which can enable the adhesive to form a three-dimensional cross-linked network structure, which is beneficial to improving the heat resistance of the adhesive and improving the solder immersion resistance. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In this embodiment, the diamine is 4,4'-diaminodiphenyl ether; the dianhydride is 4,4'-biphenyl ether dianhydride; the active diluent is isobornyl acrylate; the photoinitiator is 2-hydroxy-methylphenylpropane-1-one; polyurethane acrylate: brand name is allnex EBECRYL 4150; epoxy acrylate: brand name is allnex EBECRYL 3700; epoxy soybean oil acrylate: brand name is allnex EBECRYL 5848; silicon dioxide: particle size is 30-50nm, sourced from Shanghai Kain Chemical Co., Ltd.; polyimide film: thickness 50μm, model Kapton-50EN, sourced from Dongguan Youlun Electronic Materials Technology Co., Ltd.; copper foil: roughened electrolytic copper foil, thickness 35μm, sourced from Shanghai Jiaxian Metal Materials Co., Ltd.

[0025] In the following examples and comparative examples, 1 part is equal to 10 g.

[0026] Embodiment 1: A process for processing a flexible printed circuit board, comprising the following processes: Step S1: 30 parts of polyurethane acrylate, 20 parts of epoxy acrylate, 15 parts of modified polyimide, 10 parts of reactive diluent, 3 parts of photoinitiator, and 3 parts of silicon dioxide are mixed evenly, and vacuum degassing is performed to obtain a light-curing adhesive; Step S2: Apply the light-curing adhesive on the surface of the polyimide film (coating thickness is 15 μm), overlap it with the copper foil, and 2 Irradiate under a high pressure mercury lamp for 60 seconds to obtain a flexible printed circuit board; The preparation method of modified polyimide is as follows: Step A: Under nitrogen protection, diamine, dianhydride and N-methyl-2-pyrrolidone are mixed evenly, and polycondensation reaction is carried out at 0°C for 5 hours to obtain a diamine-terminated polyamic acid solution, 10% toluene by mass of the diamine-terminated polyamic acid solution is added and mixed evenly, and imidization reaction is carried out at 200°C for 10 hours, cooled to room temperature, slowly poured into deionized water for precipitation, filtered, washed, and vacuum dried to obtain terminal amine-terminated polyimide; the molar ratio of diamine to dianhydride is 1:0.3; Step B: Under nitrogen protection, 5 parts of octamethylcyclotetrasiloxane, 0.5 parts of hydrogen-containing double-capped silane, and 5 parts of trifluoropropylmethyldimethoxysilane were mixed evenly, reacted at 60° C. for 7 hours under the catalysis of 0.2 parts of 98wt% concentrated sulfuric acid, and after neutralization and filtration, fluorine-containing hydrogen-terminated silicone oil was obtained; 5 parts of fluorine-containing hydrogen-terminated silicone oil and 0.125 parts of allyl glycidyl ether were mixed, and reacted at 80° C. for 5 hours under the catalysis of 0.0001 parts of chloroplatinic acid to obtain fluorine-containing epoxy-terminated silicone; Step C: 5 parts of fluorine-terminated epoxy silicone and 10 parts of epoxy soybean oil acrylate were mixed evenly, and 15 parts of amine-terminated polyimide were added, reacted for 6 hours, and vacuum degassing was performed to obtain modified polyimide.

[0027] Embodiment 2: A processing technology for a flexible printed circuit board, comprising the following processes: Step S1: 40 parts of polyurethane acrylate, 30 parts of epoxy acrylate, 20 parts of modified polyimide, 15 parts of reactive diluent, 4 parts of photoinitiator, and 5 parts of silicon dioxide are mixed evenly, and vacuum degassing is performed to obtain a light-curing adhesive; Step S2: Apply the light-curing adhesive on the surface of the polyimide film (coating thickness is 15 μm), overlap it with the copper foil, and 2 Irradiate under a high pressure mercury lamp for 40 seconds to obtain a flexible printed circuit board; The preparation method of modified polyimide is as follows: Step A: Under nitrogen protection, diamine, dianhydride and N-methyl-2-pyrrolidone are mixed evenly, and polycondensation reaction is carried out at 0°C for 10 hours to obtain a diamine-terminated polyamic acid solution, 15% toluene by mass of the diamine-terminated polyamic acid solution is added and mixed evenly, and imidization reaction is carried out at 240°C for 8 hours, cooled to room temperature, slowly poured into deionized water for precipitation, filtered, washed, and vacuum dried to obtain terminal amine-terminated polyimide; the molar ratio of diamine to dianhydride is 1:0.5; Step B: Under nitrogen protection, 6 parts of octamethylcyclotetrasiloxane, 0.8 parts of hydrogen-containing double-capped silane, and 8 parts of trifluoropropylmethyldimethoxysilane were mixed evenly, reacted at 65° C. for 8 hours under the catalysis of 0.3 parts of 98wt% concentrated sulfuric acid, and after neutralization and filtration, fluorine-containing hydrogen-terminated silicone oil was obtained; 5 parts of fluorine-containing terminal hydrogen silicone oil and 0.1 parts of allyl glycidyl ether were mixed, and reacted at 100°C for 6 hours under the catalysis of 0.0001 parts of chloroplatinic acid to obtain fluorine-containing terminal epoxy silicone; Step C: 5 parts of fluorine-terminated epoxy silicone and 15 parts of epoxy soybean oil acrylate were mixed evenly, and 20 parts of amine-terminated polyimide were added, reacted for 8 hours, and vacuum degassing was performed to obtain modified polyimide.

[0028] Embodiment 3: A processing technology for a flexible printed circuit board, comprising the following processes: Step S1: 45 parts of polyurethane acrylate, 35 parts of epoxy acrylate, 25 parts of modified polyimide, 20 parts of reactive diluent, 4.5 parts of photoinitiator, and 7 parts of silicon dioxide are mixed evenly, and vacuum degassing is performed to obtain a light-curing adhesive; Step S2: Apply the light-curing adhesive on the surface of the polyimide film (coating thickness is 15 μm), overlap it with the copper foil, and 2 Irradiate under a high pressure mercury lamp for 30 seconds to obtain a flexible printed circuit board; The preparation method of modified polyimide is as follows: Step A: Under nitrogen protection, diamine, dianhydride and N-methyl-2-pyrrolidone are mixed evenly, and polycondensation reaction is carried out at 0°C for 15 hours to obtain a diamine-terminated polyamic acid solution, 18% toluene by mass of the diamine-terminated polyamic acid solution is added and mixed evenly, and imidization reaction is carried out at 250°C for 9 hours, cooled to room temperature, slowly poured into deionized water for precipitation, filtered, washed, and vacuum dried to obtain terminal amine-terminated polyimide; the molar ratio of diamine to dianhydride is 1:0.7; Step B: Under nitrogen protection, 8 parts of octamethylcyclotetrasiloxane, 0.9 parts of hydrogen-containing double-capped silane, and 8 parts of trifluoropropylmethyldimethoxysilane were mixed evenly, reacted at 65° C. for 8 hours under the catalysis of 0.4 parts of 98wt% concentrated sulfuric acid, and after neutralization and filtration, fluorine-containing hydrogen-terminated silicone oil was obtained; 5.5 parts of fluorine-containing terminal hydrogen silicone oil and 0.1 parts of allyl glycidyl ether were mixed, and reacted at 110° C. for 7 hours under the catalysis of 0.00015 parts of chloroplatinic acid to obtain fluorine-containing terminal epoxy silicone; Step C: 5 parts of fluorine-terminated epoxy silicone and 17.5 parts of epoxy soybean oil acrylate were mixed evenly, and 25 parts of amine-terminated polyimide were added, reacted for 9 hours, and vacuum degassing was performed to obtain modified polyimide.

[0029] Embodiment 4: A processing technology for a flexible printed circuit board, comprising the following processes: Step S1: 50 parts of polyurethane acrylate, 40 parts of epoxy acrylate, 30 parts of modified polyimide, 25 parts of reactive diluent, 5 parts of photoinitiator, and 8 parts of silicon dioxide are mixed evenly, and vacuum degassing is performed to obtain a light-curing adhesive; Step S2: Apply the light-curing adhesive on the surface of the polyimide film (coating thickness is 15 μm), overlap it with the copper foil, and 2 Irradiate under a high pressure mercury lamp for 10 seconds to obtain a flexible printed circuit board; The preparation method of modified polyimide is as follows: Step A: Under nitrogen protection, diamine, dianhydride and N-methyl-2-pyrrolidone are mixed evenly, and polycondensation reaction is carried out at 0°C for 20 hours to obtain a diamine-terminated polyamic acid solution, 10-20% toluene by mass of the diamine-terminated polyamic acid solution is added and mixed evenly, and imidization reaction is carried out at 260°C for 5 hours, cooled to room temperature, slowly poured into deionized water for precipitation, filtered, washed, and vacuum dried to obtain terminal amine-terminated polyimide; the molar ratio of diamine to dianhydride is 1:0.8; Step B: Under nitrogen protection, 10 parts of octamethylcyclotetrasiloxane, 1 part of hydrogen-containing double-capped silane, and 10 parts of trifluoropropylmethyldimethoxysilane were mixed evenly, reacted at 70° C. for 9 hours under the catalysis of 0.5 parts of 98wt% concentrated sulfuric acid, and after neutralization and filtration, fluorine-containing hydrogen-terminated silicone oil was obtained; 6 parts of fluorine-containing terminal hydrogen silicone oil and 0.1 parts of allyl glycidyl ether were mixed, and reacted at 120° C. for 8 hours under the catalysis of 0.0002 parts of chloroplatinic acid to obtain fluorine-containing terminal epoxy silicone; Step C: 5 parts of fluorine-terminated epoxy silicone and 20 parts of epoxy soybean oil acrylate are mixed evenly, and 30 parts of amine-terminated polyimide are added, reacted for 10 hours, and vacuum degassing is performed to obtain modified polyimide.

[0030] Comparative Example 1: A processing technology for a flexible printed circuit board, comprising the following processes: Step S1: 40 parts of polyurethane acrylate, 30 parts of epoxy acrylate, 25 parts of terminal amine-terminated polyimide, 15 parts of reactive diluent, 4 parts of photoinitiator, and 5 parts of silicon dioxide are mixed evenly, and vacuum degassing is performed to obtain a light-curing adhesive; Step S2: Apply the light-curing adhesive on the surface of the polyimide film (coating thickness is 15 μm), overlap it with the copper foil, and 2 Irradiate under a high pressure mercury lamp for 30 seconds to obtain a flexible printed circuit board; Compared with Example 2, in Comparative Example 1, the modified polyimide is replaced with an amine-terminated polyimide of the same mass, and the other steps are the same as those of Example 2.

[0031] Comparative Example 2: A processing technology for a flexible printed circuit board, comprising the following processes: Step S1: 40 parts of polyurethane acrylate, 30 parts of epoxy acrylate, 15 parts of reactive diluent, 4 parts of photoinitiator, and 5 parts of silicon dioxide are mixed evenly, and vacuum degassing is performed to obtain a light-curing adhesive; Step S2: Apply the light-curing adhesive on the surface of the polyimide film (coating thickness is 15 μm), overlap it with the copper foil, and 2 Irradiate under a high pressure mercury lamp for 30 seconds to obtain a flexible printed circuit board; Compared with Example 2, no modified polyimide is added in Comparative Example 2, and other steps are the same as those in Example 2.

[0032] Comparative Example 3: A processing technology for a flexible printed circuit board, comprising the following processes: The preparation method of modified polyimide is as follows: Step A: Under nitrogen protection, diamine, dianhydride and N-methyl-2-pyrrolidone are mixed evenly, and polycondensation reaction is carried out at 0°C for 10 hours to obtain a diamine-terminated polyamic acid solution, 15% toluene by mass of the diamine-terminated polyamic acid solution is added and mixed evenly, and imidization reaction is carried out at 240°C for 8 hours, cooled to room temperature, slowly poured into deionized water for precipitation, filtered, washed, and vacuum dried to obtain terminal amine-terminated polyimide; the molar ratio of diamine to dianhydride is 1:0.5; Step B: 15 parts of epoxy soybean oil acrylate and 25 parts of terminal amine-terminated polyimide were mixed evenly, reacted for 8 hours, and vacuum degassing was performed to obtain modified polyimide.

[0033] Compared with Example 2, Comparative Example 3 does not add fluorine-terminated epoxy silicone, and other steps are the same as Example 2.

[0034] Comparative Example 4: A processing technology for a flexible printed circuit board, comprising the following processes: The preparation method of modified polyimide is as follows: Step A: Under nitrogen protection, diamine, dianhydride and N-methyl-2-pyrrolidone are mixed evenly, and polycondensation reaction is carried out at 0°C for 10 hours to obtain a diamine-terminated polyamic acid solution, 15% toluene by mass of the diamine-terminated polyamic acid solution is added and mixed evenly, and imidization reaction is carried out at 240°C for 8 hours, cooled to room temperature, slowly poured into deionized water for precipitation, filtered, washed, and vacuum dried to obtain terminal amine-terminated polyimide; the molar ratio of diamine to dianhydride is 1:0.5; Step B: Under nitrogen protection, 6 parts of octamethylcyclotetrasiloxane, 0.8 parts of hydrogen-containing double-capped silane, and 8 parts of trifluoropropylmethyldimethoxysilane were mixed evenly, reacted at 65° C. for 8 hours under the catalysis of 0.4 parts of 98wt% concentrated sulfuric acid, and after neutralization and filtration, fluorine-containing hydrogen-terminated silicone oil was obtained; 5 parts of fluorine-containing terminal hydrogen silicone oil and 0.1 parts of allyl glycidyl ether were mixed, and reacted at 100°C for 6 hours under the catalysis of 0.0001 parts of chloroplatinic acid to obtain fluorine-containing terminal epoxy silicone; Step C: 5 parts of fluorine-terminated epoxy silicone and 5 parts of epoxy soybean oil acrylate were mixed evenly, and 25 parts of amine-terminated polyimide were added, reacted for 8 hours, and vacuum degassing was performed to obtain modified polyimide; Compared with Example 2, the mass ratio of fluorine-terminated epoxy silicone, epoxy soybean oil acrylate and terminal amine-terminated polyimide in Comparative Example 4 is 1:1:4, and the other steps are the same as those in Example 2.

[0035] Experiment: Take the flexible printed copper clad laminates obtained in Examples 1-4 and Comparative Examples 1-4 to prepare samples, test their properties respectively and record the test results: Peel strength test: Use Suzhou Yano Tianxia CRS / YN CPT05G peel strength tester to test the peel strength in accordance with GB / T13557-2017 standard. The test size is 200mm×3mm, the peel rate is 50mm / min, and the peel angle is 90°.

[0036] Solder heat resistance test: refer to IPC-TM-650 2.4.13, use JFT001S stainless steel tin furnace to test the solder heat resistance of flexible copper clad laminate, the sample size is 50mm×50mm, the test conditions are: 320℃, 10s, 3 times, if there is no delamination or blistering after 10s of immersion soldering test, it passes the test, otherwise it fails.

[0037] Water absorption test: The test was conducted in accordance with GB / T 13557-2017 standard. The sample size was 100mm×100mm. The sample was completely immersed in deionized water for 24 hours. The mass of the sample before and after immersion was recorded, and the water absorption was calculated.

[0038] The test results are shown in Table 1: Table 1: Various properties of the flexible printed copper clad laminates prepared in Examples 1-4 and Comparative Examples 1-4

[0039] According to the data in the above table, we can clearly draw the following conclusions: Compared with Examples 1-4, the peel strength and water absorption of the products obtained in Comparative Examples 1-4 are both reduced. It can be seen that in Comparative Example 1, since fluorine-terminated epoxy silicone and epoxy soybean oil acrylate were not introduced, the interfacial bonding force between the adhesive layer and the polyimide base film was insufficient, and the peel strength and water absorption were both reduced; Comparative Example 2 did not add modified polyimide, and its heat resistance was significantly reduced, and it failed to pass the dip soldering test; Comparative Example 3 did not add fluorine-terminated epoxy silicone, and its water absorption increased, and the peel strength decreased; In Comparative Example 4, the amount of epoxy soybean oil acrylate added was reduced, resulting in a decrease in cross-linking sites, thereby reducing the peel strength.

[0040] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A process for processing a flexible printed circuit board, characterized in that: The steps include: Step S1: uniformly mixing polyurethane acrylate, epoxy acrylate, modified polyimide, reactive diluent, photoinitiator and silicon dioxide, and performing vacuum degassing to obtain a light-curing adhesive; Step S2: coating a photocurable adhesive on the surface of the polyimide film, laminating it with a copper foil, and irradiating it with ultraviolet light to obtain a flexible printed circuit board.

2. The processing technology of a flexible printed circuit board according to claim 1, characterized in that: The photocurable adhesive comprises the following raw materials in parts by weight: 30-50 parts of polyurethane acrylate, 20-40 parts of epoxy acrylate, 15-30 parts of modified polyimide, 10-25 parts of active diluent, 3-5 parts of photoinitiator, and 3-8 parts of silicon dioxide.

3. The processing technology of a flexible printed circuit board according to claim 1, characterized in that: The preparation method of the modified polyimide is as follows: Step A: under nitrogen protection, diamine, dianhydride and N-methyl-2-pyrrolidone are mixed to carry out polycondensation reaction to obtain a diamine-terminated polyamic acid solution, toluene is added and mixed evenly, and imidization reaction is carried out to obtain an amine-terminated polyimide; Step B: mixing fluorine-containing terminal hydrogen silicone oil and allyl glycidyl ether, reacting at 80-120° C. for 5-8 hours under the catalysis of chloroplatinic acid to obtain fluorine-containing terminal epoxy silicone; Step C: Evenly mix the fluorine-terminated epoxy silicone and the epoxy soybean oil acrylate, add the terminal amine-terminated polyimide, react for 6-10 hours, and vacuum degassing to obtain the modified polyimide.

4. The processing technology of a flexible printed circuit board according to claim 3, characterized in that: The molar ratio of the diamine to the dianhydride is 1:(0.3-0.8).

5. The processing technology of a flexible printed circuit board according to claim 3, characterized in that: In the step B, the mass ratio of fluorine-containing hydrogen-terminated silicone oil to allyl glycidyl ether is (40-60):

1.

6. The process for manufacturing a flexible printed circuit board according to claim 5, characterized in that: The preparation method of the fluorine-containing hydrogen-terminated silicone oil is as follows: Under nitrogen protection, octamethylcyclotetrasiloxane, hydrogen-containing double cap and trifluoropropylmethyldimethoxysilane are mixed evenly, reacted at 60-70°C for 7-9h under the catalysis of concentrated sulfuric acid, and after neutralization and filtration, fluorine-containing hydrogen-terminated silicone oil is obtained.

7. The processing technology of a flexible printed circuit board according to claim 3, characterized in that: The mass ratio of the fluorine-containing epoxy-terminated silicone, epoxy soybean oil acrylate and amine-terminated polyimide is 1:(2-4):(3-6).

8. The process for manufacturing a flexible printed circuit board according to claim 2, characterized in that: The photoinitiator is one or more of 2-hydroxy-methylphenylpropane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-(4-methylthiophenyl)-2-morpholinyl-1-propanone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

9. The process for manufacturing a flexible printed circuit board according to claim 1, characterized in that: The process conditions of the ultraviolet irradiation are 500-2000mW / cm 2 Irradiate under a high pressure mercury lamp for 10-60s.

10. A flexible printed circuit board manufactured according to the processing technology described in any one of claims 1 to 9.

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