PECVD (Plasma Enhanced Chemical Vapor Deposition)-based multifunctional nano composite protective film and preparation method thereof

Abstract

The invention belongs to the field of chemical vapor deposition, and relates to a multifunctional nano-composite protective film based on PECVD (Plasma Enhanced Chemical Vapor Deposition) cyclic deposition and a preparation method thereof. The multifunctional nano-composite protective film comprises a silane base layer, a hydrophobic layer and a soft and hard alternate middle layer located between the silane base layer and the hydrophobic layer. The soft and hard alternate middle layer is an alternate film layer of a middle soft film layer and a middle hard film layer; preparing a middle soft film layer by using the first monomer steam through chemical vapor deposition; wherein the first monomer steam comprises at least one unsaturated hydrocarbon derivative with a long-chain fluoroalkyl substituent group, at least one fluorine-containing organosilane compound and at least one silane compound with an unsaturated functional group, and preparing an intermediate hard film layer by utilizing second monomer steam through chemical vapor deposition; wherein the second monomer steam comprises at least one acrylate derivative with a fluoroalkyl substituent group and at least one ether unsaturated derivative with a polyvinyl functional group.

Description

Technical Field

[0001] This invention belongs to the field of chemical vapor deposition and relates to a multifunctional nanocomposite protective film based on PECVD cyclic deposition and its preparation method. Background Technology

[0002] With the miniaturization of PCB boards for electronic devices, the high integration of semiconductor devices, and the rapid development of new energy equipment (such as offshore photovoltaics and power batteries), the demand for high-performance protective films is becoming increasingly urgent. In particular, the application requirements of electronic device PCBs in complex environments, such as insulation failure, metal migration short circuits, and chemical corrosion in humid, salt spray, acid and alkali corrosion, or underwater electrical conduction environments, place higher demands on the protective performance of PCB surface films, especially in terms of resistance to underwater electrical conduction, acid and alkali resistance, and corrosion resistance.

[0003] Traditional PCB protection processes for electronic devices include conformal coating technology: organic coatings (such as acrylic resin, silicone resin, and polyurethane) are applied to the PCB surface through spraying, brushing, or dipping, and then cured by heating or room temperature to form a protective film. Potting technology involves injecting liquid epoxy resin, silicone, or polyurethane potting compound into the entire casing or around the component, which then cures completely to form a hard solid. Perylene coating involves heating and vaporizing solid perylene dimers in a vacuum environment, then decomposing them at high temperatures into active monomers, which are then deposited onto the PCB surface and polymerized to form a completely conformal polymer film. However, conformal coating is difficult to control precisely in terms of film thickness; physical adsorption is prone to cracking and peeling under thermal shock and mechanical vibration, failing from the edges; solvent-based conformal coatings contain VOCs, which are harmful to health; potting technology greatly hinders heat dissipation, easily leading to component overheating and damage; and perylene equipment investment and raw material costs are extremely high, typically only used in high-reliability, high-value-added military, aerospace, and medical fields, unsuitable for industrial production.

[0004] PECVD technology, due to its ability to form high-quality thin films at low temperatures and its high deposition rate, allows for precise control of the film's structure and properties by adjusting conditions such as plasma power, gas flow rate, and reaction atmosphere. This enables the regulation of the film's insulation, protective properties, hydrophobicity, and corrosion resistance, meeting the requirements of electronic devices for multifunctional films. It has gradually become an ideal process for preparing surface protective films for electronic devices. Patents CN111696849A and CN113628970A, which use PECVD to prepare SiNx and SiOx thin films, exhibit high dielectric strength and high insulation, but their hydrophobic angles are generally <90°, and their resistance to acid and alkali corrosion is poor. Patent CN107587119A, through multifunctional monomer control of the coating's free volume and density, deposits an organosilicon coating on a high-insulation coating and performs surface hardening treatment to form a dense, hard coating. This requires switching between PECVD and CVD processes, and the bonding strength between different material layers may vary, leading to insufficient overall film stability and a tendency for multilayer interfacial stress mismatch, resulting in film delamination. PECVD technology offers an advanced solution for the fabrication of high-performance nanocomposite films on PCB surfaces, particularly suitable for addressing the demands of thinner, more integrated, and more reliable electronic products. However, existing technologies demonstrate that traditional approaches such as single PECVD, multilayer "hybridization," or simple composite of functional materials still suffer from bottlenecks including insufficient functional synergy, poor process adaptability, and a lack of protective mechanisms for specific scenarios. Therefore, developing multifunctional nanocomposite films based on PECVD deposition and their fabrication methods, and achieving component gradient and structural densification through dynamic parameter optimization, is a key path to filling the gap in high-performance PCB protection technology. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a multifunctional nanocomposite protective film based on PECVD cyclic deposition and its preparation method. Utilizing PECVD technology, a strategy of alternating soft and hard layer deposition is employed to achieve excellent bonding with various substrates (including plastics, metals, silicon wafers, etc.) at low temperatures. Within a single vacuum chamber, by cyclically switching the precursor gas and deposition parameters, in-situ, alternating, nanoscale precision deposition of soft and hard layers is achieved, resulting in a nanocomposite film integrating high insulation, high barrier protection, high hydrophobicity, resistance to underwater electrical conduction, and resistance to acid and alkali corrosion. This invention is achieved through the following technical solutions: In a first aspect, the present invention provides a multifunctional nanocomposite protective film based on PECVD cyclic deposition, comprising: a silane underlayer, a hydrophobic layer, and an alternating soft and hard intermediate layer between the silane underlayer and the hydrophobic layer; the alternating soft and hard intermediate layer is configured as an alternating film layer of an intermediate soft film layer and an intermediate hard film layer; the intermediate soft film layer is prepared by chemical vapor deposition using a first monomer vapor; wherein the first monomer vapor comprises at least one unsaturated hydrocarbon derivative having a long-chain fluorinated alkyl substituent, at least one fluorinated organosilane compound, and at least one silane compound having an unsaturated functional group, wherein the fluorinated organosilane compound accounts for 1% to 50% of the mass percentage of the first monomer vapor, and the silane compound having an unsaturated functional group accounts for 0.1% to 5% of the mass percentage of the first monomer vapor; the intermediate hard film layer is prepared by chemical vapor deposition using a second monomer vapor; wherein the second monomer vapor comprises at least one acrylate derivative having a fluorinated alkyl substituent and at least one ether unsaturated derivative having a polyvinyl functional group, wherein the ether unsaturated derivative having a polyvinyl functional group accounts for 5% to 50% of the mass percentage of the second monomer vapor.

[0006] In an optional embodiment, a silane underlayer is prepared by chemical vapor deposition using silane monomer vapor; the silane monomer is one or more of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexadecyltrimethoxysilane, vinylcyclotetrasiloxane, and tetramethyltetravinylcyclotetrasiloxane.

[0007] In optional embodiments, the unsaturated hydrocarbon derivatives having long-chain fluorinated alkyl substituents include one or more mixtures of perfluorobutyl ethyl methacrylate, perfluorohexyl ethyl methacrylate, perfluorooctyl ethyl methacrylate, perfluorodecyl ethyl methacrylate, or perfluorododecyl ethyl methacrylate; the fluorinated organosilane compounds include one or more mixtures of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, and 1H,1H,2H,2H-perfluorododecyltrimethoxysilane; and the silane compounds having unsaturated functional groups include one or more mixtures of 3-(acryloyloxy)propyltrimethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, 3-(isobutenoyloxy)propyltrimethoxysilane, or γ-aminopropyltriethoxysilane.

[0008] In optional embodiments, acrylate derivatives having fluoroalkyl substituents include one or more of perfluorobutyl ethyl acrylate, tridecylfluorooctyl acrylate, perfluorooctyl ethyl acrylate, perfluorodecyl ethyl acrylate, or perfluorododecyl ethyl acrylate; and ether unsaturated derivatives having polyvinyl functional groups include triethylene glycol divinyl ether and / or polyethylene glycol divinyl ether.

[0009] In an optional implementation, the thickness of the silane underlayer is less than 500 nm, the thickness of the alternating soft and hard hydrophobic intermediate layer is less than 1000 nm, and the thickness of the hydrophobic layer is less than 400 nm.

[0010] In an optional implementation, the intermediate soft film layer and the intermediate hard film layer have the same number of layers.

[0011] In an optional embodiment, a hydrophobic layer is prepared by chemical vapor deposition using hydrophobic monomer vapor; preferably, the hydrophobic monomer is a first monomer vapor.

[0012] Secondly, this invention provides a method for preparing a multifunctional nanocomposite protective film based on PECVD cyclic deposition. The preparation method includes the following steps: Step (1): Prepare a silane underlayer on the substrate surface by chemical vapor deposition using silane monomer vapor; Step (2): An intermediate soft film layer is prepared on the surface of the substrate obtained in step (1) by chemical vapor deposition using a first monomer vapor; wherein, the first monomer vapor includes at least one unsaturated hydrocarbon derivative having a long-chain fluorinated alkyl substituent, at least one fluorinated organosilane compound, and at least one silane compound having an unsaturated functional group; wherein, the fluorinated organosilane compound accounts for 1% to 50% of the mass percentage of the first monomer vapor, and the silane compound having an unsaturated functional group accounts for 0.1% to 5% of the mass percentage of the first monomer vapor; Step (3): An intermediate hard film layer is prepared on the surface of the substrate obtained in step (2) by chemical vapor deposition using a second monomer vapor; wherein the second monomer vapor includes at least one acrylate derivative having a fluorinated alkyl substituent and at least one ether unsaturated derivative having a polyvinyl functional group; wherein the ether unsaturated derivative having a polyvinyl functional group accounts for 5% to 50% of the mass percentage of the second monomer vapor; Step (4): A hydrophobic layer is prepared on the surface of the substrate obtained in step (3) by chemical vapor deposition using hydrophobic monomer vapor. Step (5), post-processing.

[0013] In an optional implementation, steps (3) and (4) are used as loop units. Before step (4), the number of loops is N, where N is 2 to 20.

[0014] In an optional implementation, in step (1), chemical vapor deposition adopts a continuous radio frequency discharge mode; the discharge power is 50~300W and the duration is 300~600s.

[0015] In an optional implementation, in steps (2) and (3), chemical vapor deposition adopts a pulsed discharge mode; the discharge power is 100~300W, the pulse duty cycle is 10%~50%, and the duration is 150s~600s.

[0016] In an optional implementation, in step (4), chemical vapor deposition adopts a pulsed discharge mode; the discharge power is 30~80W, the pulse duty cycle is 10%~50%, and the duration is 300s~600s.

[0017] In an optional embodiment, step (5) includes: stopping the introduction of monomer vapor, stopping plasma discharge, stopping vacuuming, waiting for the reaction chamber to return to normal pressure, and taking out the substrate.

[0018] In an optional embodiment, the preparation method further includes a pretreatment step before step (1); the pretreatment includes placing the substrate in a PECVD vacuum reaction chamber, continuously evacuating the reaction chamber, introducing an inert gas, and activating plasma discharge to activate the substrate.

[0019] Thirdly, the present invention provides a multifunctional nanocomposite protective film based on PECVD cyclic deposition. The multifunctional nanocomposite protective film based on PECVD cyclic deposition is obtained according to the preparation method described above. Detailed Implementation

[0020] The present invention is further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention. The following exemplarily illustrates a method for preparing a multifunctional nanocomposite protective film based on PECVD cyclic deposition.

[0021] Pretreatment. The purpose of the pretreatment stage is to bombard the substrate surface with high-energy particles from plasma, breaking the chemical bonds on the surface and generating a large number of dangling bonds and free radicals, thereby improving the chemical activity of the surface and providing a large number of reaction sites for the subsequent chemical bonding of the thin film.

[0022] The substrate is placed in the PECVD vacuum reaction chamber. The substrate includes, but is not limited to, PCB boards, SIR boards, etc. The reaction chamber is continuously evacuated. For example, the vacuum level in the reaction chamber is evacuated to 10-100 mTorr. An inert gas is introduced, and plasma discharge is initiated to activate the substrate. The pretreatment stage involves continuous discharge. For example, the discharge power is 50-200 W, and the duration is 50-300 s. The inert gas can be one or a combination of Ar or He. The flow rate of the inert gas can be 10-200 sccm.

[0023] A silane underlayer is prepared. The purpose of the silane underlayer is to establish a gradient transition layer in chemical composition and mechanical properties between the activated substrate surface and the subsequent functional film layer, alleviating internal stress caused by the mismatch between thermal expansion coefficients and moduli. One end of the silane monomer molecule (such as -Si-OR or -Si-Cl) undergoes a surface chemical reaction with active sites such as hydroxyl groups (-OH) on the substrate surface, forming a dense film mainly composed of a Si-O-Si network and containing some organic groups through polymerization and crosslinking. The other end provides organic groups, exhibiting good compatibility with the subsequent organic film layer. An ethylene layer underlayer is an organic polymer layer with a hydrocarbon structure; the substrate layer of this invention is a silane-based layer, an inorganic film layer with a silicon-oxygen structure. Organic layer underlayers are more suitable for flexible substrates such as plastics and PET, while silane-based underlayers are more suitable for rigid substrates such as electronic devices.

[0024] Silane monomer vapor is introduced into the reaction chamber. The silane monomer includes, but is not limited to, one or more combinations of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexadecyltrimethoxysilane, vinylcyclotetrasiloxane, and tetramethyltetravinylcyclotetrasiloxane. Chemical vapor deposition is performed using a continuous plasma radio frequency discharge mode. The discharge power can be 50-300 W, and the duration can be 300-600 s. The silane gas flow rate can be 50-300 sccm. For example, the thickness of the silane underlayer is less than 500 nm.

[0025] A nanocomposite protective film was prepared. The nanocomposite protective film was configured as an alternating layer of intermediate soft film and intermediate hard film.

[0026] Prepare an intermediate soft film layer. Introduce a first monomer vapor into the reaction chamber and initiate plasma discharge deposition of the soft film layer. For example, the first monomer vapor is a mixture of at least one unsaturated hydrocarbon derivative with a long-chain fluorinated alkyl substituent, at least one fluorinated organosilane compound, and at least one silane compound with an unsaturated functional group. The fluorinated organosilane compound may account for 1% to 50% of the first monomer vapor by mass, and the silane compound with an unsaturated functional group may account for 0.1% to 5% of the first monomer vapor by mass. The unsaturated hydrocarbon derivative with a long-chain fluorinated alkyl substituent is perfluorobutyl ethyl methacrylate, perfluorohexyl ethyl methacrylate, perfluorooctyl ethyl methacrylate, perfluorodecyl ethyl methacrylate, or perfluorododecyl ethyl methacrylate, etc. The fluorinated organosilane compounds include 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, or 1H,1H,2H,2H-perfluorododecyltrimethoxysilane, etc. The silane compounds containing unsaturated functional groups include 3-(acryloyloxy)propyltrimethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, 3-(isobutenoyloxy)propyltrimethoxysilane, or γ-aminopropyltriethoxysilane, etc. The soft film deposition stage is performed by pulsed discharge. The discharge power can be 100~300W, the pulse duty cycle can be 10%~50%, and the duration can be 150s~600s. The flow rate of the first monomer vapor can be 50~400sccm. In a preferred embodiment, the fluorinated organosilane compound accounts for 1% to 30% of the mass percentage of the first monomer vapor, and the silane compound containing unsaturated functional groups accounts for 0.1% to 2% of the mass percentage of the first monomer vapor. In a more preferred embodiment, the fluorinated organosilane compound accounts for 5% to 10% of the mass percentage of the first monomer vapor, and the silane compound containing unsaturated functional groups accounts for 0.1% to 1% of the mass percentage of the first monomer vapor.

[0027] An intermediate hard film layer is prepared. Next, a second monomer vapor is introduced into the reaction chamber to deposit the hard film layer. The second monomer vapor is a mixture of at least one acrylate derivative with a fluorinated alkyl substituent and at least one ether unsaturated derivative with a polyvinyl functional group. The ether unsaturated derivative with a polyvinyl functional group accounts for 5% to 50% of the mass percentage of the second monomer vapor. The acrylate derivative with a fluorinated alkyl substituent includes perfluorobutyl ethyl acrylate, tridecafluorooctyl acrylate, perfluorooctyl ethyl acrylate, perfluorodecyl ethyl acrylate, or perfluorododecyl ethyl acrylate, etc. The mixture of ether unsaturated derivatives with a polyvinyl functional group includes triethylene glycol divinyl ether or polyethylene glycol divinyl ether, etc. The hard film layer deposition stage is performed by pulsed discharge. The discharge power can be 100~300W, the pulse duty cycle can be 10%~50%, and the duration can be 150s~600s. The flow rate of the second monomer vapor can be 50~400sccm. In a preferred embodiment, the ether-based unsaturated derivative having polyvinyl functional groups accounts for 5% to 40% of the mass percentage of the second monomer vapor. In a more preferred embodiment, the ether-based unsaturated derivative having polyvinyl functional groups accounts for 10% to 30% of the mass percentage of the second monomer vapor.

[0028] In an optional embodiment, the intermediate soft film layer and the intermediate hard film layer have the same number of layers. For example, the thickness of the alternating soft and hard intermediate layer is less than 1000 nm. In this embodiment, the outermost intermediate soft film layer of the alternating soft and hard intermediate layer is closer to the silane underlayer, and the outermost intermediate hard film layer (on the other side) of the alternating soft and hard intermediate layer is closer to the hydrophobic layer.

[0029] The preparation of the intermediate soft film layer and intermediate hard film layer is repeated at least twice. A nanocomposite structure mimicking the natural "brick-and-mortar" structure is constructed by cyclically depositing alternating soft and hard films. The first monomer vapor polymerizes under pulsed plasma conditions to form a flexible polymer film rich in –CHx, –Si–C–, and –CFx. This layer acts as the "mortar" or "binder," absorbing energy and buffering external impacts. During plasma discharge, the second monomer vapor's high-energy electrons break the CH and CC bonds in the monomers and remove as many hydrogen atoms as possible, promoting sp… 2 and sp 3The formation of carbon hybrid bonds, or the formation of a highly cross-linked Si-O-Si inorganic network, and the pulsed mode are used to prevent the film from becoming embrittled or warping due to excessive bombardment. This layer acts as the "brick," providing the main hardness and wear resistance. Multiple cycles of alternating deposition of soft and hard film layers multiply this "brick-and-mortar" structure at the nanoscale, effectively dispersing locally concentrated stress over a larger volume, greatly improving the film's toughness, load-bearing capacity, and durability. Finally, a low surface energy hydrophobic layer is constructed on the surface of the composite protective film, giving it waterproof, antifouling, and self-cleaning properties. It also reduces the corrosion and erosion of the film by water vapor and electrolytes to a certain extent, enhancing the overall protective performance.

[0030] Preparation of the hydrophobic layer. Hydrophobic monomer vapor is introduced into the reaction chamber, and plasma discharge is initiated to deposit the hydrophobic layer. This stage is a pulsed discharge. The discharge power can be 30~80W, and the pulse duty cycle can be 10~50%. The duration can be 300s~600s. It should be understood that any hydrophobic monomer commonly used in the art is applicable. Including but not limited to, the hydrophobic monomer is selected from 3-(perfluoro-5-methylhexyl)-2-hydroxypropyl methacrylate, 2-(perfluorodecyl)ethyl methacrylate, 2-(perfluorohexyl)ethyl methacrylate, 2-(perfluorododecyl)ethyl acrylate, 2-perfluorooctyl acrylate, 1H,1H,2H,2H-perfluorooctyl acrylate, 2-(perfluorobutyl)ethyl acrylate, (2H-perfluoropropyl)-2-acrylate, (perfluorocyclohexyl) methacrylate, 3,3,3-trifluoro-1-propyne, 1-ethynyl-3,5-difluorobenzene or 4-ethynyltrifluorotoluene, ethoxylated trimethylolpropane triacrylate, tripropylene glycol diacrylate, divinylbenzene, polyethylene glycol diacrylate, 1 The hydrophobic monomer vapor is selected from at least one of the following: 6-hexanediol diacrylate, ethylene glycol diacrylate, diethylene glycol divinyl ether or neopentyl glycol diacrylate, 3,3,3-trifluoro-1-propyne, 1-ethynyl-3,5-difluorobenzene or 4-ethynyltrifluorotoluene, ethoxylated trimethylolpropane triacrylate, dipropylene glycol diacrylate, divinylbenzene, polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, ethylene glycol diacrylate, diethylene glycol divinyl ether, neopentyl glycol diacrylate, fluorosilanes or siloxanes, silanes or siloxanes containing hydrophobic groups, and cyclic silanes or siloxanes. In an optional embodiment, the hydrophobic monomer vapor is a first monomer vapor. Among commonly used hydrophobic monomers or monomer combinations, the first monomer vapor exhibits superior hydrophobic properties as a hydrophobic surface layer, with a higher hydrophobic angle and better hydrophobic performance. Therefore, the first monomer vapor is selected as the hydrophobic monomer in each embodiment. The flow rate of hydrophobic monomer vapor can be 50~350 sccm. The thickness of the hydrophobic layer can be less than 400 nm.

[0031] Post-processing. Stop the introduction of monomer vapor, stop plasma discharge, stop vacuuming, wait for the reaction chamber to return to normal pressure, and then remove the substrate.

[0032] Compared with the prior art, the present invention has the following advantages: (1) Compared with the single film layer in the prior art, the present invention constructs a nanoscale composite structure by cyclically depositing a "soft film layer" and a "hard film layer". This structure mimics the natural "brick and mortar" structure, in which the hard film layer provides mechanical strength and wear resistance like a "brick", while the soft film layer absorbs stress, increases toughness and adhesion like "mortar", so that the film has high hardness, high wear resistance, good toughness, bending resistance and impact resistance at the same time; (2) The film adopts a hierarchical structure of silane as the base layer, alternating soft and hard nanocomposite film layer and hydrophobic layer, so that the film has excellent adhesion, wear resistance, corrosion resistance and hydrophobicity at the same time. (3) Through the cyclic deposition of soft and hard film layers, the film structure is uniform and the thickness is controllable, avoiding stress concentration and cracking problems of single-layer film, and improving the stability and service life of film. (4) The functional layer is deposited using a "pulse discharge" mode instead of continuous discharge. The pulse mode allows the reactive groups to diffuse fully during the "off" time, avoiding excessive cross-linking, excessive internal stress, and pulverization that may occur with continuous discharge; (5) An additional hydrophobic layer is added on top of the nanocomposite protective film. This hydrophobic layer can impart hydrophobic, antifouling, moisture-proof, and corrosion-resistant properties to the surface, further improving the service life of the film; (6) All process parameters are within the range that PECVD technology can easily achieve, with good repeatability and easy to scale up production; by adjusting the number of cycles (n>2), the total thickness of the film and the ratio of soft and hard layers can be precisely controlled, making it easy to design composite films with different properties according to application requirements, and with very wide applicability.

[0033] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0034] Example 1

[0035] The preparation method of multifunctional nanocomposite protective films based on PECVD cyclic deposition includes the following steps: (1) Place the PCB board in the PECVD vacuum reaction chamber, continuously evacuate the reaction chamber to a vacuum level of 10 mTorr, and introduce Ar with a gas flow rate of 100 sccm. Turn on the plasma discharge with a power of 200W and a discharge time of 60s.

[0036] (2) Hexadecyltrimethoxysilane vapor is introduced into the reaction chamber at a flow rate of 150 sccm until the vacuum degree is 30 mTorr. Then, the plasma continuous radio frequency discharge mode is turned on to perform chemical vapor deposition with a discharge power of 300 W and a duration of 600 s.

[0037] (3) The first monomer vapor is introduced into the reaction chamber at a flow rate of 150 sccm, and plasma discharge is initiated to deposit a soft film layer for 360 s. The first monomer vapor is a mixture of perfluorodecyl ethyl methacrylate, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, and 3-(isobutyryloxy)propyltrimethoxysilane. The mass fraction of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane is 10%, and the mass fraction of 3-(isobutyryloxy)propyltrimethoxysilane is 0.1%. Then, the second monomer vapor is introduced at a flow rate of 150 sccm to deposit a hard film layer for 360 s. The second monomer vapor is a mixture of perfluorooctyl ethyl acrylate and polyethylene glycol divinyl ether. The mass fraction of polyethylene glycol divinyl ether is 10%. Both the soft and hard film deposition stages were performed using pulsed discharge, with a discharge power of 300W, a pulse frequency of 2500Hz, and a pulse duty cycle of 30%.

[0038] (4) Repeat step (3) above until alternating deposition a total of 5 times.

[0039] (5) The first monomer vapor is introduced into the reaction chamber at a flow rate of 100 sccm, and plasma discharge is activated to deposit a hydrophobic layer for a duration of 600s. This stage is a pulse discharge with a discharge power of 40W, a pulse frequency of 2500Hz, and a pulse duty cycle of 30%.

[0040] (6) Stop the introduction of monomer vapor, stop plasma discharge, stop vacuuming, wait for the reaction chamber to return to normal pressure, and take out the substrate.

[0041] Example 2

[0042] The preparation method of multifunctional nanocomposite protective films based on PECVD cyclic deposition includes the following steps: (1) Place the PCB board in the PECVD vacuum reaction chamber, continuously evacuate the reaction chamber to a vacuum level of 10 mTorr, and introduce He with a gas flow rate of 100 sccm. Turn on the plasma discharge with a power of 200W and a discharge time of 60s.

[0043] (2) Octamethylcyclotetrasiloxane vapor is introduced into the reaction chamber at a flow rate of 100 sccm until the vacuum degree is 45 mTorr. The continuous radio frequency discharge mode of plasma is turned on to perform chemical vapor deposition with a discharge power of 300W and a duration of 600s.

[0044] (3) Introduce the first monomer vapor into the reaction chamber at a flow rate of 150 sccm, and initiate plasma discharge deposition of a soft film layer for 225 s. The first monomer vapor is a mixture of perfluorooctyl ethyl acrylate, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, and 3-(isobutenoyloxy)propyltrimethoxysilane. The mass fraction of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is 5%, and the mass fraction of 3-(isobutenoyloxy)propyltrimethoxysilane is 0.2%. Then, introduce the second monomer vapor at a flow rate of 150 sccm to deposit a hard film layer for 225 s. The second monomer vapor is a mixture of tridecylfluorooctyl acrylate and polyethylene glycol divinyl ether, wherein the mass fraction of polyethylene glycol divinyl ether is 20%. Both the soft and hard film deposition stages were performed using pulsed discharge, with a discharge power of 300W, a pulse frequency of 2500Hz, and a pulse duty cycle of 40%.

[0045] (4) Repeat step (3) above until alternating depositions are performed a total of 8 times.

[0046] (5) Introduce the first monomer vapor into the reaction chamber at a flow rate of 100 sccm, and start plasma discharge to deposit a hydrophobic layer for 600s. This stage is a pulse discharge with a discharge power of 50W, a pulse frequency of 2500Hz, and a pulse duty cycle of 30%.

[0047] (6) Stop the introduction of monomer vapor, stop plasma discharge, stop vacuuming, wait for the reaction chamber to return to normal pressure, and take out the substrate.

[0048] Example 3

[0049] The preparation method of multifunctional nanocomposite protective films based on PECVD cyclic deposition includes the following steps: (1) Place the PCB board in the PECVD vacuum reaction chamber, continuously evacuate the reaction chamber to a vacuum level of 10 mTorr, and introduce Ar with a gas flow rate of 200 sccm. Turn on the plasma discharge with a power of 200W and a discharge time of 120s.

[0050] (2) Hexamethylcyclotrisiloxane vapor is introduced into the reaction chamber at a flow rate of 150 sccm until the vacuum degree is 45 mTorr. The plasma continuous radio frequency discharge mode is turned on to perform chemical vapor deposition with a discharge power of 300 W and a duration of 600 s.

[0051] (3) The first monomer vapor is introduced into the reaction chamber to initiate plasma discharge deposition of a soft film layer for 180 s. The first monomer vapor is a mixture of perfluorododecylethyl methacrylate, 1H,1H,2H,2H-perfluorododecyltrimethoxysilane, and γ-aminopropyltriethoxysilane. The mass fraction of 1H,1H,2H,2H-perfluorododecyltrimethoxysilane is 9%, and the mass fraction of γ-aminopropyltriethoxysilane is 1%. Then, the second monomer vapor is introduced to deposit a hard film layer for 180 s. The second monomer vapor is a mixture of perfluorodecylethyl acrylate and triethylene glycol divinyl ether. The mass fraction of triethylene glycol divinyl ether is 30%. Both the soft and hard film deposition stages are pulsed discharges with a discharge power of 300 W, a pulse frequency of 2500 Hz, and a pulse duty cycle of 50%.

[0052] (4) Repeat step (3) above until alternating depositions are performed a total of 10 times.

[0053] (5) Introduce the first monomer vapor into the reaction chamber and start plasma discharge to deposit a hydrophobic layer for 600s. This stage is a pulse discharge with a discharge power of 80W, a pulse frequency of 2500Hz, and a pulse duty cycle of 40%.

[0054] (6) Stop the introduction of monomer vapor, stop plasma discharge, stop vacuuming, wait for the reaction chamber to return to normal pressure, and take out the substrate.

[0055] Comparative Example 1 It is basically the same as Example 1, except that silane was not prepared for the underlayer, that is, the above step (2) was not performed.

[0056] Comparative Example 2 It is basically the same as Example 2, except that a hydrophobic layer was not prepared, that is, the above step (5) was not performed.

[0057] Comparative Example 3 The soft and hard alternating intermediate layer is prepared in a single cycle. It is basically the same as in Example 3, except that in step (3), the first monomer vapor is introduced into the reaction chamber, and the plasma discharge is turned on to deposit the soft film layer for 1800s; then the second monomer vapor is introduced to deposit the hard film layer for 1800s; and step (4) is omitted.

[0058] Comparative Example 4 It is basically the same as Example 1, except that the order of introducing the first monomer steam and the second monomer steam in step (3) is changed.

[0059] Water resistance: Fill the sealed container with sufficient deionized water to ensure complete immersion of the sample. Completely immerse the sample in water. To ensure consistent conditions across all areas, maintain a certain distance between the sample and the bottom, walls, and other parts of the container. Cover the container to reduce the ingress of airborne contaminants and moisture evaporation. Place the container in a constant temperature environment and start timing. After the specified time, remove the sample, dry it, and observe the film under a magnifying glass or microscope for defects such as blistering, wrinkling, peeling, and discoloration.

[0060] Acid and alkali resistance: Pour the two solutions into two clearly marked acid and alkali resistant containers. Immerse the sample in each solution. Immersion depth can be full or partial (partial immersion allows for comparison of corrosion at the surface, submerged, and above the liquid level). Place the containers in a fume hood and allow them to stand at room temperature. After the specified time, remove the sample and rinse the surface with deionized water for at least 1 minute to thoroughly remove any residual acid or alkali. Inspect the film under a magnifying glass or microscope for corrosion, dissolution, peeling, blistering, or loss of luster.

[0061] Neutral salt spray resistance: Place the sample at a 15°~30° angle on the support inside the salt spray chamber. This allows the salt spray to settle evenly on the surface. The front of the sample should face the direction of the salt spray and should not touch each other. Close the chamber door and start the test. The salt spray chamber will automatically spray, heat the saturator, and maintain the temperature. After the test, remove the sample. Rinse the surface salt deposits with running deionized water and allow the sample to recover under standard atmospheric conditions for 1~2 hours. Carefully inspect the film surface for corrosion spots, blistering, peeling, and for corrosion products such as verdigris and white rust on the base metal (e.g., pads, leads).

[0062] Water immersion resistance under different voltages: Secure the sample to the sample holder, ensuring its stability. Inject sufficient deionized water into the test container to completely immerse the test area on the sample. Connect the electrodes to the test points on the sample surface. Set the output voltage to a fixed value and the leakage current to 1mA. Turn on the data recording system to record the real-time voltage and leakage current. Turn on the power and continue the test until the leakage current reaches or exceeds 1mA, indicating a test failure.

[0063] Resistance to acid and alkali sweat immersion under a certain voltage: The procedure is basically the same as the above underwater electrification procedure, except that a sufficient amount of acidic sweat with a pH of 4.7 or alkaline sweat with a pH of 9.5 is injected into the test container.

[0064] The performance test results of the PCB boards with deposited multifunctional nanocomposite protective films obtained in the above embodiments and comparative examples are as follows: Table 1 Hydrophobicity and Oleophobicity

[0065] Table 2 Water immersion resistance and corrosion resistance (indicates the time during which no corrosion occurs)

[0066] Table 3. Water immersion performance under different voltages (indicating the time required for leakage current to reach 1mA)

[0067] Table 4. Resistance to acid and alkali immersion in sweat under a certain voltage (indicating the time required for leakage current to reach 1mA). . Example 4

[0068] It is basically the same as Example 2, except that the composition ratio of the first monomer vapor or the second monomer vapor in step (3) is different.

[0069] Table 5

[0070] Table 6

[0071] It should be understood that any modifications made to this invention without altering its spirit are within the scope of protection of this invention.

Claims

1. A multifunctional nanocomposite protective film based on PECVD cyclic deposition, characterized in that, include: The system comprises a silane underlayer, a hydrophobic layer, and an alternating soft and hard intermediate layer between the silane underlayer and the hydrophobic layer; the alternating soft and hard intermediate layer is configured as an alternating film layer of intermediate soft film layer and intermediate hard film layer; the intermediate soft film layer is prepared by chemical vapor deposition using a first monomer vapor; wherein the first monomer vapor includes at least one unsaturated hydrocarbon derivative having a long-chain fluorinated alkyl substituent, at least one fluorinated organosilane compound, and at least one silane compound having an unsaturated functional group, wherein the fluorinated organosilane compound accounts for 1% to 50% of the mass percentage of the first monomer vapor, and the silane compound having an unsaturated functional group accounts for 0.1% to 5% of the mass percentage of the first monomer vapor; the intermediate hard film layer is prepared by chemical vapor deposition using a second monomer vapor; wherein the second monomer vapor includes at least one acrylate derivative having a fluorinated alkyl substituent and at least one ether unsaturated derivative having a polyvinyl functional group, wherein the ether unsaturated derivative having a polyvinyl functional group accounts for 5% to 50% of the mass percentage of the second monomer vapor.

2. The multifunctional nanocomposite protective film based on PECVD cyclic deposition according to claim 1, characterized in that, A silane underlayer is prepared by chemical vapor deposition using silane monomer vapor; the silane monomer is one or more of the following: hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexadecyltrimethoxysilane, vinylcyclotetrasiloxane, and tetramethyltetravinylcyclotetrasiloxane.

3. The multifunctional nanocomposite protective film based on PECVD cyclic deposition according to claim 1 or 2, characterized in that, Unsaturated hydrocarbon derivatives having long-chain fluorinated alkyl substituents include one or more of perfluorobutyl ethyl methacrylate, perfluorohexyl ethyl methacrylate, perfluorooctyl ethyl methacrylate, perfluorodecyl ethyl methacrylate, or perfluorododecyl ethyl methacrylate; fluorinated organosilane compounds include one or more of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, 1H,1H,2H,2H-perfluorododecyltrimethoxysilane; silane compounds having unsaturated functional groups include one or more of 3-(acryloyloxy)propyltrimethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, 3-(isobutenoyloxy)propyltrimethoxysilane, or γ-aminopropyltriethoxysilane.

4. The multifunctional nanocomposite protective film based on PECVD cyclic deposition according to any one of claims 1 to 3, characterized in that, Acrylate derivatives having fluoroalkyl substituents include one or more of perfluorobutyl ethyl acrylate, tridecylfluorooctyl acrylate, perfluorooctyl ethyl acrylate, perfluorodecyl ethyl acrylate, or perfluorododecyl ethyl acrylate; ether unsaturated derivatives having polyvinyl functional groups include triethylene glycol divinyl ether and / or polyethylene glycol divinyl ether.

5. The multifunctional nanocomposite protective film based on PECVD cyclic deposition according to any one of claims 1 to 4, characterized in that, The intermediate soft membrane layer and the intermediate hard membrane layer have the same number of layers.

6. The multifunctional nanocomposite protective film based on PECVD cyclic deposition according to any one of claims 1 to 5, characterized in that, A hydrophobic layer is prepared by chemical vapor deposition using hydrophobic monomer vapor; preferably, the hydrophobic monomer is a first monomer vapor.

7. A method for preparing a multifunctional nanocomposite protective film based on PECVD cyclic deposition, characterized in that, The preparation method includes the following steps: Step (1): Prepare a silane underlayer on the substrate surface by chemical vapor deposition using silane monomer vapor; Step (2): An intermediate soft film layer is prepared on the surface of the substrate obtained in step (1) by chemical vapor deposition using a first monomer vapor; wherein, the first monomer vapor includes at least one unsaturated hydrocarbon derivative having a long-chain fluorinated alkyl substituent, at least one fluorinated organosilane compound, and at least one silane compound having an unsaturated functional group; wherein, the fluorinated organosilane compound accounts for 1% to 50% of the mass percentage of the first monomer vapor, and the silane compound having an unsaturated functional group accounts for 0.1% to 5% of the mass percentage of the first monomer vapor; Step (3): An intermediate hard film layer is prepared on the surface of the substrate obtained in step (2) by chemical vapor deposition using a second monomer vapor; wherein the second monomer vapor includes at least one acrylate derivative having a fluorinated alkyl substituent and at least one ether unsaturated derivative having a polyvinyl functional group; wherein the ether unsaturated derivative having a polyvinyl functional group accounts for 5% to 50% of the mass percentage of the second monomer vapor; Step (4): A hydrophobic layer is prepared on the surface of the substrate obtained in step (3) by chemical vapor deposition using hydrophobic monomer vapor. Step (5), post-processing.

8. The preparation method according to claim 7, characterized in that, Steps (3) and (4) are treated as loop units. Before step (4), the number of loop units is N, where N is 2 to 20.

9. The preparation method according to claim 8, characterized in that, In step (1), chemical vapor deposition adopts continuous radio frequency discharge mode; the discharge power is 50~300W and the duration is 300~600s.

10. The preparation method according to claim 8 or 9, characterized in that, In steps (2) and (3), chemical vapor deposition adopts pulsed discharge mode; the discharge power is 100~300W, the pulse duty cycle is 10%~50%, and the duration is 150s~600s.

11. The preparation method according to any one of claims 8 to 10, characterized in that, In step (4), chemical vapor deposition adopts pulsed discharge mode; the discharge power is 30~80W, the pulse duty cycle is 10%~50%, and the duration is 300s~600s.

12. The preparation method according to any one of claims 8 to 11, characterized in that, In step (5), the post-processing includes: stopping the introduction of monomer vapor, stopping plasma discharge, stopping vacuuming, waiting for the reaction chamber to return to normal pressure, and taking out the substrate.

13. A multifunctional nanocomposite protective film based on PECVD cyclic deposition, characterized in that, The multifunctional nanocomposite protective film based on PECVD cyclic deposition is obtained by the preparation method according to any one of claims 8 to 12.

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