Copper-photosensitive polyimide film with excellent interface strength and preparation method and application thereof

Abstract

The invention discloses a copper-photosensitive polyimide film with excellent interface strength and a preparation method and application thereof, and relates to the technical field of integrated circuit packaging materials. According to the copper-photosensitive polyimide film with excellent interface strength prepared by the preparation method disclosed by the invention, by improving polar surface energy and introducing a uniform nucleating mechanism, the formation of initial holes and pinholes is reduced, and the residual stress and foaming risk are reduced. Compared with the traditional strong chemical coarsening and thick adhesive layer scheme, the bonding strength, the damp heat / welding reliability, the fine line adaptability and the high-frequency dielectric loss are better balanced. The technology is particularly suitable for application scenes such as high-density interconnection, 5G / 6G radio frequency flexible antennas, folding display and wearable devices, and the fields provide consideration requirements for the thin type, high toughness, high stability, low dielectric loss and other performances of substrate materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of integrated circuit packaging materials, in particular to a copper-photosensitive polyimide film with excellent interfacial strength and a preparation method and application thereof. BACKGROUND

[0002] With the development of integrated circuits (IC) towards high density, high performance and miniaturization, the performance of the packaging board as the core component connecting the chip and the external circuit directly determines the reliability and signal transmission efficiency of the device. Polyimide (PI) substrate has become an important alternative material for high-end integrated circuit boards due to its excellent high temperature resistance, low dielectric constant, good mechanical strength and flexibility. However, in practical applications, the interfacial bonding force between the metal layer (such as copper foil) and the substrate during the metallization process of the traditional polyimide substrate is insufficient, resulting in poor adhesion. When subjected to thermal stress or mechanical stress, the metal layer is prone to delamination, warping and even falling off, which seriously restricts the reliability and service life of the packaged device.

[0003] Flexible copper clad laminate (FCCL) is a key substrate for flexible circuits, foldable displays, wearable electronics and high-frequency communication modules, and its performance also faces challenges. The traditional FCCL that uses adhesives to achieve copper / polyimide (PI) adhesion has problems such as solder blistering, wet heat failure, ion residue, etc., due to the limited thermal stability and dielectric loss of the organic adhesive layer, resulting in a decrease in product reliability. In addition, the adhesive layer also increases the dielectric constant and loss tangent, which is not conducive to the integrity of high-frequency signals.

[0004] To improve the interfacial bonding force of copper / PI, existing technologies mostly use strong chemical roughening, coupling agent introduction, and metal adhesion layer stacking, but these methods generally have the following problems: the weak boundary layer at the interface is not effectively removed, causing the peeling path to expand along the contaminated or degraded layer; excessive roughening increases the dielectric loss and line edge roughness, which adversely affects micro-line fabrication and high-frequency performance; the adhesion modification process conflicts with the development / exposure / demolding window of photosensitive PI, which can easily cause pattern collapse or insufficient development; high temperature or strong oxidation treatment can damage the PI main chain or photosensitive groups, causing the material density and mechanical properties to deteriorate.

[0005] In the prior art, plasma treatment has been widely used for surface modification of polyimide substrates, aiming to enhance the interfacial adhesion with metal layers. For example, patent CN113652675B proposes a method for plasma modification of polyimide film, which successfully introduces polar groups such as amide groups and aldehyde groups on the film surface by using a mixed gas of hydrogen and argon for plasma treatment, significantly improving the surface activity and roughness of the polyimide film, and effectively improving the adhesion between the metal layer and the polyimide substrate, providing new possibilities for the application of flexible electronic devices.

[0006] However, there is still room for improvement in the current technology, therefore, there is an urgent need for a method that can simultaneously achieve decontamination, functionalization and moderate roughening under low temperature and short process conditions, and this method needs to be compatible with the photolithography process of photosensitive PI; at the same time, it can generate a chemical-physical composite transition layer in situ at the interface, ultimately significantly improving the interfacial adhesion and service reliability of copper / PI without sacrificing the dielectric performance and microcircuit preparation capability. SUMMARY

[0007] The present application provides a copper-photosensitive polyimide film with excellent interfacial strength and its preparation method and application, to overcome the problem of insufficient adhesion between the metal layer and the substrate in the prior art, and to provide a new path for high-performance and high-reliability manufacturing of high-end integrated circuit carriers.

[0008] To achieve the above-mentioned purpose, the technical scheme of the embodiments of the present application is:

[0009] The first aspect of the present application provides a preparation method of a copper-photosensitive polyimide film with excellent interfacial strength, comprising:

[0010] 4,4'-diamino diphenyl ether is added to N,N'-dimethylacetamide solvent in multiple times, and after stirring and reaction under ice bath, a first mixed solution is obtained;

[0011] 3,3',4,4'-biphenyl tetracarboxylic dianhydride is added to the first mixed solution in multiple times, and after uniform mixing under ice bath, a second mixed solution is obtained;

[0012] 2NH2-photosensitive monomer is added to the second mixed solution in multiple times, and after uniform mixing at room temperature, a third mixed solution is obtained;

[0013] Copper sulfate pentahydrate, ethylenediaminetetraacetic acid, potassium sodium tartrate, polyethylene glycol, potassium ferrocyanide, 2,2-bipyridine and sodium hydroxide solution are uniformly mixed in deionized water to obtain a copper plating solution;

[0014] The third mixed solution is coated into a thin film, and sequentially subjected to drying, ultraviolet exposure, plasma treatment, rinsing with a palladium solution, and thermal cyclization in an inert atmosphere to obtain a photosensitive polyimide film.

[0015] The photosensitive polyimide film is immersed in the copper plating solution containing the formaldehyde solution to obtain a copper-photosensitive polyimide film with excellent interface strength.

[0016] In combination with the first aspect, preferably, the molar ratio of the 4,4'-diamino diphenyl ether, the 3,3',4,4'-biphenyl tetracarboxylic dianhydride, and the 2NH2-photosensitive monomer is 1:(1-3):1.

[0017] In combination with the first aspect, preferably, the solid content of the N,N'-dimethylacetamide solvent is 5-25%.

[0018] In combination with the first aspect, preferably, when the third mixed solution is coated into a thin film, the coating method is one of blade coating, casting, and spin coating.

[0019] In combination with the first aspect, preferably, when the third mixed solution is coated into a thin film, the coating amount of the third mixed solution is 100-300 μL / cm 2 ;

[0020] In combination with the first aspect, preferably, when the third mixed solution is coated into a thin film, the thickness of the thin film is 100-300 μm.

[0021] In combination with the first aspect, preferably, when the 3,3',4,4'-biphenyl tetracarboxylic dianhydride is added to the first mixed solution in multiple times and mixed uniformly under ice bath, the ice bath mixing temperature is 0-5°C, and the ice bath mixing time is 0.5-3h.

[0022] In combination with the first aspect, preferably, when the 2NH2-photosensitive monomer is added to the second mixed solution in multiple times and mixed uniformly at room temperature, the room temperature mixing temperature is 20-30°C, and the room temperature mixing time is 8-15h.

[0023] In combination with the first aspect, preferably, when the copper sulfate pentahydrate, ethylenediaminetetraacetic acid, potassium sodium tartrate, polyethylene glycol, potassium ferrocyanide, 2,2-bipyridine, and sodium hydroxide solution are mixed uniformly in deionized water, the mixing temperature is 20-30°C, and the mixing time is 24-38h.

[0024] In combination with the first aspect, preferably, the pH value of the copper plating solution is 13-14.

[0025] In combination with the first aspect, preferably, in the copper plating solution containing the formaldehyde solution, the addition amount of the formaldehyde solution is 100-500 uL.

[0026] Preferably in combination with the first aspect, when the third mixture is coated into a film, and sequentially dried, exposed to ultraviolet light, treated by plasma, rinsed by palladium solution, and then heat-cyclized in an inert atmosphere, the drying temperature is 70-80℃, and the drying time is 5-30min.

[0027] Preferably, the exposure intensity is 5-20mW / cm 2 , and the exposure time is 5-20min.

[0028] Preferably, the rinsing time is 5-20s.

[0029] Preferably, the inert atmosphere is nitrogen.

[0030] Preferably, the heat-cyclization is performed by heating to 100, 150, 200, 250, and 300℃ at a rate of 2-8℃ / min, and holding at each temperature for 60-80min.

[0031] Preferably in combination with the first aspect, the plasma treatment is by introducing any one or more of Ar, NH3, CF4, and air.

[0032] Preferably, the plasma treatment time is 10-60min.

[0033] Preferably, the plasma treatment power is 100-200W.

[0034] The second aspect of the present application provides a copper-photosensitive polyimide film with excellent interfacial strength, prepared by any of the methods of the first aspect, and having a tensile test data of 15MPa or more.

[0035] The third aspect of the present application provides the use of a copper-photosensitive polyimide film with excellent interfacial strength, prepared by any of the methods of the first aspect, in a flexible polyimide plate.

[0036] Compared with the prior art, the present application has at least the following advantages or beneficial effects:

[0037] The copper-photosensitive polyimide film with excellent interfacial strength provided by the application constructs a composite interface structure of a polar functional group-nano-roughening-gradient transition layer on a flexible polyimide plate through plasma multimodal surface engineering technology. The structure promotes the adhesion mechanism of the copper / polyimide (PSPI) interface from physical adsorption dominated by van der Waals force to a synergistic mode with chemical bonding and coordination bonding as the core and supplemented by nanoscale mechanical interlocking. The crack deflects and branches at the interface, significantly improving the interfacial fracture energy. Without introducing traditional adhesives, the interfacial peeling strength can be stably reached 25 MPa. At the same time, by precisely controlling the surface roughness to keep it in the optimal range, the mechanical interlocking effect is ensured, and the rise of high-frequency insertion loss caused by excessive roughness is avoided. On the other hand, by increasing the polar surface energy and introducing a uniform nucleation mechanism, the formation of initial holes and pinholes is reduced, and the residual stress and blistering risk are reduced. Compared with traditional strong chemical roughening and thick adhesive layer solutions, the application achieves a better balance between adhesion strength, humidity and heat / welding reliability, micro-line adaptability and high-frequency dielectric loss. The technology is particularly suitable for high-density interconnection, 5G / 6G radio frequency flexible antenna, folding display and wearable devices, etc. Application scenarios, which require the performance of substrate materials such as thinness, high toughness, high stability and low dielectric loss to be considered. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The SEM image of the plasma non-thermal cyclization film provided by the application is shown in the left figure, and the right figure is the SEM image of the plasma treated film;

[0039] Figure 2 The CF4 characterization result graph of XPS provided by the application is shown in the figure;

[0040] Figure 3 The NH3 characterization result graph of XPS provided by the application is shown in the figure. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below in combination with the drawings. The described embodiments should not be regarded as limiting the application. All other embodiments obtained by those skilled in the art without creative labor fall within the scope of the application.

[0042] In the following description, reference is made to "some embodiments", which describe a subset of all possible embodiments, but it is understood that "some embodiments" can be the same subset or different subsets as each other and can be combined with each other, without conflict. Unless otherwise defined, all technical and scientific terms used in the embodiments of the present application have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of the present application belong. The terms used in the embodiments of the present application are only for the purpose of describing the embodiments of the present application and are not intended to limit the present application.

[0043] In the following description of the embodiments of the present application, the terms "comprising", "containing", "having" and "including" and the like are open-ended terms, i.e., they mean including but not limited to.

[0044] It should be noted that all raw materials / reagents in the embodiments of the present application can be purchased on the market or prepared according to conventional methods well known to those skilled in the art; the term "and / or" in the embodiments of the present application is only used to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B means that there are three cases of A alone, B alone and A and B together, wherein A and B can be singular or plural, and the character " / " generally represents an "or" relationship between the associated objects before and after it.

[0045] In the following description of the embodiments of the present application, the term "at least one" means one or more, and "a plurality of" means two or more. "At least one of the following" or the like means any combination of the items, including any combination of single item or multiple items. For example, "at least one of a, b or c", or "at least one of a, b and c", can mean a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b and c can be single or multiple.

[0046] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of the serial numbers does not mean the order of execution, and some or all steps can be executed in parallel or in sequence, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0047] The terms used in the embodiments of the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the present application. The singular forms "a" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0048] It should be understood by those skilled in the art that the numerical ranges in the embodiments of the present application are to be understood as specifically disclosing each and every intermediate value within the upper and lower limits of the range. Intermediates between any stated values and intermediate ranges within stated ranges, as well as any other stated or intervening values or ranges, are also included within the application. The upper and lower limits of these smaller ranges can independently be included or excluded in the ranges.

[0049] Unless otherwise defined, all technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred methods and materials are described. All documents mentioned herein are incorporated by reference for the disclosure and description in connection with the methods and / or materials associated with the documents. In the case of conflict, the present document will control.

[0050] It should be noted that all raw materials and / or reagents in the embodiments of the present application are purchased on the market or prepared according to conventional methods well known to those skilled in the art.

[0051] In a first aspect, the embodiments of the present application provide a copper-photosensitive polyimide film with excellent interfacial strength, and a preparation method thereof, which comprises:

[0052] 4,4'-diamino diphenyl ether is added to N,N'-dimethylacetamide solvent in multiple portions, and after stirring and reaction under ice bath, a first mixed solution is obtained;

[0053] 3,3',4,4'-biphenyl tetracarboxylic dianhydride is added to the first mixed solution in multiple portions, and after uniform mixing under ice bath, a second mixed solution is obtained;

[0054] 2NH2-photosensitive monomer is added to the second mixed solution in multiple portions, and after uniform mixing at room temperature, a third mixed solution is obtained;

[0055] Copper sulfate pentahydrate, ethylenediaminetetraacetic acid, potassium sodium tartrate, polyethylene glycol, potassium ferrocyanide, 2,2-bipyridine, and sodium hydroxide solution are uniformly mixed in deionized water to obtain a copper plating solution;

[0056] The third mixed solution is coated into a thin film, and is sequentially subjected to drying, ultraviolet exposure, plasma treatment, palladium solution rinsing, and thermal cyclization in an inert atmosphere environment to obtain a photosensitive polyimide film;

[0057] The photosensitive polyimide film is immersed in the copper plating solution containing formaldehyde solution to obtain a copper-photosensitive polyimide film with excellent interfacial strength.

[0058] The copper-photosensitive polyimide film with excellent interfacial strength provided by the application constructs a composite interface structure of a polar functional group-nano-roughening-gradient transition layer on a flexible polyimide plate through a plasma multimodal surface engineering technology. The structure promotes the adhesion mechanism of the copper / polyimide (PSPI) interface to change from a physical adsorption action dominated by van der Waals force to a synergistic mode with chemical bonding and coordination bonding as the core and supplemented by nanoscale mechanical interlocking. The crack deflects and branches at the interface, significantly improving the interfacial fracture energy. Without introducing traditional adhesives, the interfacial peeling strength can be stably reached 25 MPa. At the same time, by accurately controlling the surface roughness to keep it in the optimal interval, the mechanical interlocking effect is ensured, and the rise of high-frequency insertion loss caused by excessive roughness is avoided. On the other hand, by increasing the polar surface energy and introducing a uniform nucleation mechanism, the formation of initial holes and pinholes is reduced, and the residual stress and blistering risk are reduced. Compared with the traditional strong chemical roughening and thick adhesive layer scheme, the application achieves a better balance between adhesion strength, humidity and heat / welding reliability, microcircuit adaptability and high-frequency dielectric loss. The technology is particularly suitable for high-density interconnection, 5G / 6G radio frequency flexible antenna, folding display and wearable devices, etc. Application scenarios, which require the performance of substrate materials such as thinness, high toughness, high stability and low dielectric loss to be considered.

[0059] It should be noted that the first mixed solution in the embodiment of the application is obtained by adding 4,4'-diamino diphenyl ether into N,N'-dimethylacetamide solvent in at least three times, with an interval of 2-3 min each time to ensure complete dissolution of the solid, and stirring under the condition of ice bath at 0-5 ℃ after reaction. Here, stirring can be magnetic stirring or mechanical stirring, and the stirring rate can be slightly faster, i.e. 500-800 rpm, when the initial reactant is added to ensure rapid dispersion of the solid reagent; the stirring rate can be appropriately reduced, i.e. 200-300 rpm, after the reaction is stable, to avoid temperature fluctuations in the system due to vigorous stirring.

[0060] In the application, the purpose of using ice bath low-temperature environment is to reduce the activation energy of the reaction and control the reaction rate, and to inhibit side effects and maintain system stability. Specifically, the ice bath reduces the collision frequency and energy of the reaction molecules by reducing the temperature of the system, thereby slowing down the reaction rate and avoiding temperature runaway due to excessive reaction. The ice bath can inhibit the oxidation of the diamine monomer and the premature cyclization of the polyamic acid.

[0061] It should be noted that the reaction of 3,3',4,4'-biphenyl tetracarboxylic dianhydride BPDA with the first mixed solution is an exothermic condensation reaction, that is, an amide bond is generated and a large amount of heat is released. If a large amount of BPDA is added at one time, the local temperature will rise rapidly due to rapid heat release, and the ice bath environment of 0-5°C can stabilize the system temperature in the low temperature interval by continuously absorbing reaction heat, avoiding the chain reaction problem caused by too high temperature. For example, inhibiting the hydrolysis side reaction of BPDA.

[0062] It should be noted that the 2NH2-photosensitive monomer in the above step needs to react with the anhydride group or carboxyl group at the end of the polyamic acid molecular chain, so as to introduce the photosensitive group into the polymer chain.

[0063] It should be noted that copper sulfate pentahydrate is first dissolved in deionized water and stirred until completely dissolved, at which time the solution is light blue. Then, ethylenediaminetetraacetic acid EDTA and potassium sodium tartrate are added, and the stirring reaction is continued. Here, EDTA and potassium sodium tartrate as a complexing agent will form a stable chelate with Cu 2+ , so that the color of the solution changes to deep blue, so as to avoid Cu 2+ precipitation under subsequent alkaline conditions. Then, polyethylene glycol, potassium ferrocyanide and 2,2-bipyridine are added in turn, and each reagent is stirred until completely dissolved. Slowly add sodium hydroxide solution while stirring, adjust the pH of the system to 13-14. Continue to stir uniformly to obtain a deep blue copper plating solution.

[0064] Here, EDTA and potassium sodium tartrate as a complexing agent form a stable chelate with Cu 2+ , control the free Cu 2+ concentration, avoid its precipitation under alkaline conditions, and adjust the reduction rate of Cu 2+ .

[0065] In specific embodiments, the molar ratio of 4,4'-diamino diphenyl ether, 3,3',4,4'-biphenyl tetracarboxylic dianhydride and 2NH2-photosensitive monomer is preferably 1:(1-3):1; more preferably, the molar ratio of 4,4'-diamino diphenyl ether, 3,3',4,4'-biphenyl tetracarboxylic dianhydride and 2NH2-photosensitive monomer is more preferably 1:2:1.

[0066] In specific embodiments, the solid content of the N,N'-dimethylacetamide solvent is preferably 5-25%.

[0067] It should be noted that when the solid content of the N,N'-dimethylacetamide solvent is less than 5%, that is, the excess solvent will dilute the concentration of each component in the system, making it difficult for the grafting reaction of 2NH2-photosensitive monomer and polyamic acid chain to proceed uniformly: locally, the grafting may be insufficient due to the low concentration of photosensitive monomer, and locally, the grafting may be excessive due to diffusion lag, ultimately resulting in the photosensitive group being distributed in island form on the molecular chain. This unevenness will directly affect the subsequent photolithography performance. In addition, low solid content will result in extremely low solution viscosity, making it difficult to control the thickness during coating, and multiple coatings are required to achieve the target film thickness, but multiple coatings will lead to poor interlayer bonding and the generation of pinholes, wrinkles or cracks due to uneven solvent evaporation rate during drying.

[0068] It should be noted that when the solid content of the N,N'-dimethylacetamide solvent is greater than 25%, effective convection is difficult to form during stirring, which can lead to monomer dispersion and grafting reaction only in local areas, forming photosensitive enrichment or photosensitive deficiency areas.

[0069] In specific embodiments, when the third mixed solution is coated into a thin film, the coating method is preferably one of blade coating, casting, and spin coating.

[0070] In specific embodiments, when the third mixed solution is coated into a thin film, the coating amount of the third mixed solution is preferably 100-300 μL / cm 2 .

[0071] It should be noted that when the coating amount of the third mixed solution is too large, the penetration depth of ultraviolet light is insufficient, resulting in insufficient crosslinking of the photosensitive group in the deep layer of the thin film. During development, the un-crosslinked resin in the deep layer will remain, causing tailing or residual layers at the bottom of the pattern, and the resolution will decrease to 20 μm or more, which cannot meet the demand for fine lines. At the same time, during plasma treatment before copper plating, the surface modification depth of the excessively thick thin film is limited, and the deep layer has insufficient polarity groups, resulting in the copper layer being able to only bond with the surface layer of the thin film, and the stress concentration in the internal layer of the thin film can cause interlayer peeling, ultimately reducing the copper / PI interface bonding force.

[0072] When the coating amount of the third mixed solution is too small, the intermolecular interaction is weak, the tensile strength decreases, and the elongation at break decreases, which can easily cause brittle fracture during the bending process of flexible electronic devices. At the same time, the sensitivity of the excessively thin thin film to environmental humidity and temperature increases, and it is easy to cause dielectric performance fluctuations due to moisture absorption during long-term service. At the same time, when the thin film is leached with palladium solution, palladium ions can penetrate the thin film and react with the substrate, resulting in copper layer bonding with the substrate during subsequent copper plating, forming false bonding; even if the copper layer is successfully deposited, the PI thin film will also lack sufficient support, which can cause the copper layer to fall off during actual application such as etching and welding.

[0073] In specific embodiments, when the third mixed solution is coated into a thin film, the thickness of the thin film is preferably 100-300 μm.

[0074] It should be noted that the film thickness of 100-300 μm can ensure a moderate solvent evaporation rate, avoiding local concentration being too high or too low. In the subsequent ultraviolet exposure step, the ultraviolet light can uniformly penetrate the film, so that the photosensitive monomers at different depths all undergo crosslinking reaction, ensuring the uniformity of the crosslinking degree of each layer of the film; in the thermal cyclization stage, water and residual solvent can be released in an orderly manner, and the internal stress is uniformly distributed, without the risk of local overheating or cracking.

[0075] In specific embodiments, the 3,3',4,4'-biphenyl tetracarboxylic dianhydride is added to the first mixed solution in multiple portions, and mixed uniformly under ice bath, preferably at an ice bath mixing temperature of 0-5°C, and for a mixing time of 0.5-3 h.

[0076] In specific embodiments, the 2NH2-photosensitive monomer is added to the second mixed solution in multiple portions, and mixed uniformly at room temperature, preferably at a room temperature mixing temperature of 20-30°C, and for a mixing time of 8-15 h.

[0077] In specific embodiments, the copper sulfate pentahydrate, ethylenediaminetetraacetic acid, potassium sodium tartrate, polyethylene glycol, potassium ferrocyanide, 2,2-bipyridine, and sodium hydroxide solution are mixed uniformly in deionized water, preferably at a mixing temperature of 20-30°C, and for a mixing time of 24-38 h.

[0078] In specific embodiments, the pH value of the copper plating solution is preferably 13-14.

[0079] In specific embodiments, in the copper plating solution containing formaldehyde solution, the addition amount of formaldehyde solution is preferably 100-500 uL.

[0080] In specific embodiments, the third mixed solution is coated into a film, and sequentially subjected to drying, ultraviolet exposure, plasma treatment, and rinsing with palladium solution, and then subjected to thermal cyclization in an inert atmosphere, preferably at a drying temperature of 70-80°C, and for a drying time of 5-30 min.

[0081] In specific embodiments, the exposure intensity is preferably 5-20 mW / cm 2 , and the exposure time is preferably 5-20 min.

[0082] In specific embodiments, the rinsing time is preferably 5-20 s.

[0083] In specific embodiments, the inert atmosphere is preferably nitrogen.

[0084] In specific embodiments, the conditions for thermal cyclization are preferably as follows: increasing the temperature to 100, 150, 200, 250, and 300°C at a heating rate of 2-8°C / min, and maintaining the temperature at each temperature for 60-80 min.

[0085] In specific embodiments, the plasma treatment is preferably any one or more of Ar / NH3 / CF4 / air.

[0086] In specific embodiments, the plasma treatment is preferably any one or more of Ar / NH3 / CF4 / air.

[0087] In specific embodiments, the plasma treatment is preferably any one or more of Ar / NH3 / CF4 / air.

[0088] In specific embodiments, the plasma treatment is preferably any one or more of Ar / NH3 / CF4 / air.

[0089] In specific embodiments, the plasma treatment is preferably any one or more of Ar / NH3 / CF4 / air.

[0090] The technical method of the present application will be further described below in conjunction with specific embodiments.

[0091] Embodiment 1

[0092] Embodiment 1 provides a method for preparing a copper-photosensitive polyimide film with excellent interfacial strength, which comprises the following steps:

[0093] Step S1, 1399.05 mg of N,N'-dimethylacetamide (DMAc) solvent and 50.06 mg of 4,4'-oxydianiline (ODA) were added to a 25 mL round-bottom flask. After stirring and dissolving, the ODA was fully dissolved by stirring at a speed of 200 rpm in an ice water bath at 5-8°C for 20 min. Then, 110.33 mg of BPDA was added in three portions, with an interval of no less than 10 min to avoid excessive reaction leading to explosive polymerization. During the whole process, the ice water bath environment and the stirring speed of 200 rpm were maintained. The reaction system was continuously stirred in the ice water bath for 2 h to stabilize the system. Subsequently, 86.5 mg of 2NH2-photosensitive monomer (dimethyl 4-(5-(4-((4,4"-diamino-[1,1':3',1"-terphenyl]-5'-yl)oxy)butoxy)-2-nitrophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate) was added, the ice water bath was removed, and the stirring was continued at room temperature for 12 h (with the aid of an ice bag for temperature control during the period), and finally a photosensitive polyamide acid (PAA) solution was prepared.

[0094] Step S2, filter the 100 μL PAA dilute solution using an oily filter membrane with a pore size of 0.22 μm to remove impurities. Thin film preparation is performed using a doctor blade method. Specifically, a 3 cm x 3 cm glass sheet is first treated with UV light for 30 min to enhance its surface properties, and then 200 μL of the filtered photosensitive polyamide acid (PS-PAA) dilute solution is uniformly coated on the surface of the 3 cm x 3 cm glass sheet using a doctor blade method, with a coating thickness of 200 μm, and the substrate temperature is maintained at 60°C to ensure uniform distribution of the solution and formation of a uniform thin film. Subsequently, the coated glass sheet is placed on a hot stage and dried at 80°C for 4 to 6 min to preliminarily form the photosensitive polyamide acid PS-PAA thin film and remove residual solvents.

[0095] Step S3, after the thin film is preliminarily formed, it is placed in a high-precision UV exposure machine for photolithography processing. During the exposure process, the exposure intensity is set to 10 mW / cm 2 to ensure that sufficient energy penetrates the thin film and initiates the crosslinking reaction of the photosensitive monomer. The exposure time is 10 min to ensure that the thin film uniformly and sufficiently completes the photochemical reaction during the photolithography process.

[0096] Step S4, the thin film is then placed in a plasma surface treatment instrument for 900 s at a power of 200 W with air introduced.

[0097] Step S5, the treated polymer thin film is immersed in a 0.1 mol / L PdCl2 / EtOH solution for 10 s, then washed with anhydrous ethanol and blown dry with compressed air.

[0098] The preparation method of the 0.1 mol / L PdCl2 / EtOH solution is as follows: 1.7743 g of PdCl2 solid is dissolved in an appropriate amount of ethanol, stirred until completely dissolved, then transferred to a 100 mL volumetric flask and diluted to the mark with ethanol, and shaken to obtain a 0.1 mol / L PdCl2 / EtOH solution.

[0099] Step S6, for the conversion process from PAA to PI, a rubber calender is used for thermal cyclization treatment. Specifically, the temperature is gradually increased and maintained at 60°C for 30 min, 150°C for 30 min, 200°C for 30 min, 250°C for 30 min, and 300°C for 30 min, respectively, to complete the thermal cyclization reaction, and finally obtain a photosensitive polyimide thin film.

[0100] Step S7, then the copper plating process, to the 40℃ of the copper plating solution is added 1 mL of NaOH, see PH test paper for purple red PH = 14, after the photosensitive polyimide film film into the copper plating solution, two times of formaldehyde can be added, can add more formaldehyde, bubble to the sample plating copper as long as, about 2 min. Again, the sample from the copper plating solution, finally get the copper-photosensitive polyimide film with excellent interface bonding strength.

[0101] Preparation of copper plating solution:

[0102] Preparation of copper plating solution, first take 1L deionized water, sequentially add 24g CuSO4·5H2O, 21g EDTA, stirring until completely dissolved to form a copper complex; then add 10g potassium sodium tartrate, 1g polyethylene glycol (PEG 20000), 70mg potassium ferrocyanide and 8mg 2,2-bipyridine, stirring to fully dissolved; finally slowly add 16g NaOH (or appropriate amount of NaOH solution), while stirring, the pH is adjusted to 13-14. Stirring at room temperature for 24h, the speed is 200rpm / min, the copper plating solution can be obtained.

[0103] Comparative Example 1

[0104] As a control experiment of Example 1, the same method as Example 1 is used to prepare, the difference is only in step S4, the gas introduced is Ar / NH3.

[0105] Comparative Example 2

[0106] As a control experiment of Example 1, the same method as Example 1 is used to prepare, the difference is only in step S4, the gas introduced is Ar / CF4.

[0107] It should be noted that here is first 3min of Ar, then 12min of CF4.

[0108] Comparative Example 3

[0109] As a control experiment of Example 1, the same method as Example 1 is used to prepare, the difference is only in step S4, the film is not plasma treated.

[0110] Test Example 1

[0111] This embodiment provides a SEM test experiment of surface topography.

[0112] The SEM topography of the copper-photosensitive polyimide film PS-PAA with excellent interface strength prepared by Example 1 after exposure and plasma treatment (right) and without plasma treatment (left) is compared, and the results are shown in Figure 1 .

[0113] Depend on Figure 1 It is evident that plasma-treated surfaces exhibit significant changes. Plasma treatment primarily alters the surface properties of materials through the interaction of high-energy plasma with the material surface, thereby increasing the number of surface-active groups. For photosensitive polyimide films, plasma treatment can introduce polar groups, increasing surface energy and thus improving wettability, adhesion, and reactivity. This treatment can significantly enhance the bonding strength between the film and subsequent coatings or plating layers, while also removing surface impurities and further optimizing the film's surface properties.

[0114] Test Example 2

[0115] This embodiment provides a test experiment for XPS.

[0116] A comparison of the Ar / CF4 ratio of the copper-photosensitive polyimide film PS-PAA with excellent interfacial strength prepared in Example 1 after exposure and plasma treatment with the untreated film is shown in the following results. Figure 2 As shown.

[0117] Depend on Figure 2 It can be seen that, compared with the untreated film, the film treated with Ar-CF4 plasma showed a significant F1s characteristic peak in XPS analysis, indicating that fluorine was successfully introduced.

[0118] Test Example 3

[0119] This embodiment provides a test experiment for XPS.

[0120] A comparison of the Ar / NH3 ratio of the copper-photosensitive polyimide film PS-PAA with excellent interfacial strength prepared in Example 1 after exposure and plasma treatment with the untreated film is shown in the following results. Figure 3 As shown.

[0121] Depend on Figure 3 It can be seen that, compared with the untreated film, the film treated with Ar-NH3 plasma showed obvious amine characteristic peak C-NH2 in XPS analysis.

[0122] Test Example 3

[0123] This embodiment provides a pull-out test for a copper-photosensitive polyimide film with excellent interfacial strength.

[0124] The results obtained from the preparation of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown in Table 1.

[0125] Table 1 Summary of pull-out tests of PS-PAA prepared in Example 1

[0126]

[0127] From Table 1, it can be seen that the drawing test results of the samples with and without plasma treatment have a large difference, and the effect of the plasma treatment is obviously good.

[0128] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a copper-photosensitive polyimide film with excellent interfacial strength, characterized in that, include: 4,4'-diaminodiphenyl ether was added to N,N'-dimethylacetamide solvent in multiple portions, and the mixture was stirred in an ice bath to obtain the first mixture. 3,3',4,4'-biphenyltetracarboxylic dianhydride was added to the first mixture in multiple portions and mixed thoroughly under ice bath conditions to obtain the second mixture. The 2NH2- photosensitive monomer was added to the second mixture in multiple portions and mixed evenly at room temperature to obtain the third mixture. The copper plating solution is obtained by mixing copper sulfate pentahydrate, ethylenediaminetetraacetic acid, potassium sodium tartrate, polyethylene glycol, potassium ferrocyanide, 2,2-bipyridine and sodium hydroxide solution evenly in deionized water. The third mixture was coated into a thin film, and then dried, exposed to ultraviolet light, subjected to plasma treatment, and rinsed with palladium solution in sequence. Finally, it was thermally cyclized in an inert atmosphere to obtain a photosensitive polyimide film. The photosensitive polyimide film is immersed in the copper plating solution containing formaldehyde solution to obtain a copper-photosensitive polyimide film with excellent interfacial strength.

2. The method for preparing a copper-photosensitive polyimide film with excellent interfacial strength according to claim 1, characterized in that, The molar ratio of the 4,4'-diaminodiphenyl ether, the 3,3',4,4'-biphenyltetracarboxylic dianhydride, and the 2NH2-photosensitive monomer is 1:(1-3):1; And / or, the solid content of the N,N'-dimethylacetamide solvent is 5% to 25%.

3. The method for preparing a copper-photosensitive polyimide film with excellent interfacial strength according to claim 1, characterized in that, When the third mixture is coated into a thin film, the coating method is one of the following: blade coating, casting, or spin coating. And / or, when the third mixture is coated into a thin film, the coating amount of the third mixture is 100–300 μL / cm. 2 ; And / or, when the third mixture is coated into a thin film, the thickness of the film is 100 to 300 μm.

4. The method for preparing a copper-photosensitive polyimide film with excellent interfacial strength according to claim 1, characterized in that, When 3,3',4,4'-biphenyltetracarboxylic dianhydride is added to the first mixture in multiple portions and mixed evenly under an ice bath, the ice bath mixing temperature is 0-5°C and the ice bath mixing time is 0.5-3 hours. And / or, when the 2NH2-photosensitive monomer is added to the second mixture in multiple portions and mixed evenly at room temperature, the room temperature mixing temperature is 20-30°C and the room temperature mixing time is 8-15 hours. And / or, when copper sulfate pentahydrate, ethylenediaminetetraacetic acid, potassium sodium tartrate, polyethylene glycol, potassium ferrocyanide, 2,2-bipyridine, and sodium hydroxide solution are mixed evenly in deionized water, the mixing temperature is 20-30°C and the mixing time is 24-38 hours. And / or, the pH value of the copper plating solution is 13-14; And / or, in the copper plating solution containing formaldehyde solution, the amount of formaldehyde solution added is 100-500 μL.

5. The method for preparing a copper-photosensitive polyimide film with excellent interfacial strength according to claim 1, characterized in that, The process of coating the third mixture into a thin film and then sequentially drying, UV exposure, plasma treatment, and palladium solution rinsing followed by thermal cyclization in an inert atmosphere involves drying at a temperature of 70–80°C for 5–30 minutes. And / or, the exposure intensity is 5–20 mW / cm 2 The exposure time is 5 to 20 minutes; And / or, the rinsing time is 5 to 20 seconds; And / or, the inert atmosphere is nitrogen; And / or, the conditions for thermal circulation are: heating to 100, 150, 200, 250 and 300 °C respectively at a heating rate of 2 to 8 °C / min, and holding at each temperature for 60 to 80 min.

6. The method for preparing a copper-photosensitive polyimide film with excellent interfacial strength according to claim 1, characterized in that, The plasma treatment involves introducing one or more of Ar, NH3, CF4, or air. And / or, the plasma treatment duration is 10–60 min; And / or, the plasma processing power is 100-200W.

7. A copper-photosensitive polyimide film with excellent interfacial strength prepared by any one of claims 1-6 has a pull-out test data of 15 MPa or higher.

8. The application of a copper-photosensitive polyimide film with excellent interfacial strength prepared by any one of claims 1-6 in a flexible polyimide board.

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