Surface modification treatment method for PCBA board

Abstract

The invention discloses a surface modification treatment method for a PCBA board, and belongs to the technical field of printed circuit board surface treatment. Comprising the following steps that S1, a PCBA board is placed in a thin film deposition device, and active gas is introduced after vacuumizing; s2, turning on a power supply to pre-treat the surface of the PCBA board; s3, after the vacuum degree is adjusted, vinyl triethoxy silane gas which is heated and vaporized is introduced, and meanwhile auxiliary gas is introduced; and S4, adjusting the frequency of the microwave radio frequency power supply, and depositing a film. Vinyltriethoxysilane and inert gas are used as plasmas to be subjected to chemical polymerization reaction with the PCBA board, a firm nano hydrophobic film is formed on the surface of a base material, the corrosion-resistant function is achieved, the PCBA board can be effectively protected, and excellent air permeability and hydrophobicity are achieved. Meanwhile, by controlling the gas flow, the reaction temperature, the power frequency and the like, the laminating quality can be improved, the whole treatment process is completely clean and environmentally friendly, and industrial production is facilitated.

Description

Technical Field

[0001] This application belongs to the technical field of printed circuit board surface treatment, and specifically relates to a surface modification treatment method for PCBA boards. Background Art

[0002] The PCBA circuit board is the entire manufacturing process of a PCB bare board through SMT component mounting and then DIP plug-in components, abbreviated as PCBA, also known as a printed circuit board or printed wiring board. It is an important electronic component, a support for electronic components, and a provider of electrical connection for electronic components. In case of water ingress, it will cause the circuit board to short-circuit and rust spots to appear on the plug terminals, and then gradually cause corrosion of the metal part, resulting in poor contact of the circuit. Seriously, it may even cause a short-circuit burnout phenomenon. Specifically, the metal parts on the circuit board, such as copper traces, solder joints, component pins, etc., may be oxidized and corroded when exposed to water, thus affecting the long-term stability and reliability of the circuit. Water ingress may also cause sensitive components on the circuit board, such as capacitors and resistors, to be damaged or their performance to decline due to moisture. Therefore, in case of water ingress, it will not only reduce the performance of the insulating material on the circuit board, resulting in a decline in electrical performance, but also promote the growth of microorganisms on the circuit board, leading to corrosion and other damages.

[0003] In the prior art, in order to prevent problems caused by water ingress in PCBA circuit boards, a protective coating is generally applied on the circuit board, such as silicone, polyurethane, etc., which can isolate moisture and air, thus protecting the circuit board from the influence of a humid environment. However, this protective coating is prone to generate harmful substances during the production process, and has complex processes, high costs, and poor durability. Summary of the Invention

[0004] The purpose of this application is to provide a surface modification treatment method for PCBA boards, which can significantly reduce the risk of problems occurring in PCBA circuit boards due to water ingress, thereby ensuring the stability and service life of electronic products.

[0005] To achieve the above objective, the present invention provides a surface modification treatment method for PCBA boards, including the following steps:

[0006] S1. Place the PCBA board in a thin film deposition device, evacuate the air, and then introduce an active gas.

[0007] S2. Turn on the power supply to pre-treat the surface of the PCBA board.

[0008] S3. After adjusting the vacuum degree, introduce heated and vaporized vinyltriethoxysilane gas, and at the same time introduce an auxiliary gas.

[0009] S4. Adjust the frequency of the microwave radio frequency power supply to deposit a film, and that's it.

[0010] Further, in the step S1, the vacuum degree is controlled to be 20 mTorr to 100 mTorr, preferably 30 mTorr to 70 mTorr.

[0011] Further, in the step S1, the active gas is carbon tetrafluoride or hydrogen, and the flow rate of the active gas is 30 sccm to 120 sccm, preferably 30 sccm to 80 sccm.

[0012] Further, in the step S2, the power of the pretreatment is 70 W to 200 W, preferably 70 W to 100 W, and the pretreatment time is 5 min to 10 min.

[0013] Further, in the step S3, the vacuum degree is adjusted to 20 mTorr to 70 mTorr.

[0014] Further, in the step S3, the vaporization temperature is 80 °C to 200 °C, preferably 80 °C to 120 °C, and the flow rate of the vinyltriethoxysilane gas is 10 sccm to 60 sccm.

[0015] Further, the auxiliary gas is an inert gas or nitrogen, and the flow rate of the auxiliary gas is 30 sccm to 120 sccm.

[0016] Further, in the step S4, the microwave radio frequency power supply frequency is 80 W to 300 W, and the film coating thickness is 50 nm to 1000 nm.

[0017] Further, the temperature in the vacuum chamber of the thin film deposition device is maintained at 40 °C to 55 °C, preferably 45 °C.

[0018] In summary, the present invention has the following advantages:

[0019] The present application discloses that after the surface of the PCBA board is surface-modified by the surface modification treatment method, a uniform nano-film coating is deposited on its surface, which has the advantages of uniform coating, strong adhesion, and can improve the durability of the PCBA board. At the same time, the modification process is efficient and belongs to an environmentally friendly treatment method. The nano-film generated on the surface of the PCBA board substrate in the present application not only has the function of corrosion resistance and can effectively protect the PCBA board, but also has good air permeability and hydrophobicity. The nano-film prepared in the present application is a nano-polymer coating, which is tightly combined with the substrate through covalent bonds, thereby improving the adhesion of the nano-polymer coating to the PCBA board substrate. The surface modification treatment process described in the present application is all completed in a vacuum environment, and the process is clean and environmentally friendly without generating harmful emissions.

[0020] Specifically, (1) By using the plasma deposition thin film technology, a uniform and dense nano - coating can be formed on the surface of the PCBA board because the plasma can be evenly distributed on the surface of the substrate.

[0021] (2) Plasma treatment can improve the activity of the surface of the PCBA board, enabling vinyltriethoxysilane molecules to better bind to the surface of the substrate, forming strong covalent bonds, thereby improving the adhesion of the coating.

[0022] (3) The surface modification treatment process described in this application is carried out at a relatively low temperature, thus avoiding thermal damage to the sensitive electronic components on the PCBA board caused by high temperature; by adjusting the power and vacuum degree of the microwave radio - frequency power supply, the thickness and properties of the coating can be precisely controlled to meet different application requirements.

[0023] (4) The surface modification treatment process described in this application uses relatively few chemicals and gases and is carried out in a vacuum - closed system, thereby reducing the impact on the environment and reducing the impact of air pollutants on the coating quality.

[0024] (5) The nano - coating can provide good protection, such as moisture - proof, corrosion - proof, and improved wear resistance, thereby extending the service life of the PCBA board. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic flow chart of the surface modification treatment method for PCBA boards described in the embodiments of this application;

[0026] Figure 2 is a schematic diagram of the system composition of the PECVD coating equipment described in the embodiments of this application;

[0027] Figure 3 is a schematic diagram of the surface protection coating after the surface modification treatment of the PCBA board described in the embodiments of this application;

[0028] Figure 4 is a schematic diagram of the changes after the surface protection coating after the surface modification treatment of the PCBA board described in the embodiments of this application and the traditional ENEPIG immersion gold - nickel - palladium protection coating are treated under high - temperature and high - humidity conditions. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The principles and features of this application are described below in conjunction with embodiments. The examples given are only for explaining this application and are not intended to limit the scope of this application. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0030] The present application provides a surface modification method for PCBA boards, comprising the following steps:

[0031] S1. Place the PCBA board in a thin film deposition device, evacuate the air, and then introduce an active gas.

[0032] S2. Turn on the power supply to pre-treat the surface of the PCBA board.

[0033] S3. After adjusting the vacuum degree, introduce the heated and vaporized vinyltriethoxysilane (VTES) gas, and at the same time introduce an auxiliary gas.

[0034] S4. Adjust the frequency of the microwave radio frequency power supply to deposit a coating film, and that's it.

[0035] In the present application, as Figure 1 shown, the PECVD coating equipment used is a Plasma Enhanced Chemical Vapor Deposition (PECVD) equipment, which is a technology for depositing thin films by using plasma under low pressure. The PECVD coating equipment combines the advantages of Chemical Vapor Deposition (CVD) and Physical Vapor Deposition (PVD) technologies, and can prepare high-quality thin films at relatively low temperatures. The working principle of the PECVD coating equipment adopted in the present application is to introduce gas into a vacuum chamber. Under the action of plasma, the gas decomposes into ions and free radicals, and deposits on the surface of the substrate to form a thin film. The reaction gas is introduced into the vacuum chamber through an electrode, and forms plasma under the action of an electric field. The electrons in the plasma are heated and excited to generate high-energy and highly active particles such as ions and free radicals. These particles can chemically react with the reaction gas and deposit into a thin film on the surface of the substrate.

[0036] Using the PECVD coating equipment has many advantages in the method provided by the present application. For example, PECVD can deposit a coating film at a relatively low temperature to avoid thermal damage to the substrate. This is very important for materials with low melting points and thermal sensitivity. PECVD can also achieve selective deposition of thin films, and control the composition and properties of the thin film by adjusting the composition of the reaction gas.

[0037] Specifically, as Figure 1 shown, the PECVD coating equipment is a conventional equipment, mainly including a vacuum chamber, a gas supply system, a vacuum pump, a heating device and a pressure relief device. There are four pairs of vertically placed electrodes in the vacuum chamber, and the electrodes are connected to a microwave radio frequency power supply, and two of the electrodes are grounded.

[0038] During use, first open the door of the vacuum chamber, place the sample to be processed between the electrodes, then close the door, evacuate the vacuum chamber and maintain the vacuum degree at the same time, and then introduce the active gas into the vacuum chamber through the gas supply system; turn on the microwave radio frequency power supply, adjust the power of the microwave radio frequency power supply, generate a medium microwave electric field between the electrode plates, and electrolytically separate the active gas in the electric field. The active gas is electrolytically separated into plasma under the action of the medium microwave electric field to activate the surface of the substrate; under the action of the active gas plasma on the surface of the substrate, the impurity particles on the surface will be cleaned into a suitable state for processing, and this process is the cleaning and activation process of the substrate. After the treatment, evacuate the vacuum chamber again, then load the VTES liquid into the heating device, adjust the heating temperature, heat and vaporize the VTES liquid to obtain steam, and then introduce the VTES steam into the vacuum chamber; at the same time, introduce the auxiliary gas, and adjust the power of the microwave radio frequency power supply again to electrolytically separate the gas in the vacuum chamber; the VTES steam and the auxiliary gas are electrolytically separated into plasma again under the action of the medium microwave electric field, and a chemical polymerization reaction occurs with the surface of the substrate to deposit a coating on the surface of the substrate. During the entire surface modification process, control the temperature of the vacuum chamber of the PECVD coating equipment within a certain range (40°C to 55°C). After modification by the above method, a thin film layer, that is, a nano-coating, can be obtained on the surface of the PCBA board. The combination of the coating and the substrate is very firm and there will be no peeling phenomenon. At the same time, the nano-coating is a hydrophobic thin film, which can also improve the waterproof performance of the PCBA board.

[0039] In this application, vinyltriethoxysilane (VTES) is used as the raw material for the nano-film. Vinyltriethoxysilane is a commonly used silane coupling agent, which has the following advantages: (1) It can firmly bond the nano-film to the surface of the PCBA board through chemical bonds, thereby improving the adhesion between materials such as coatings and coatings and the substrate; (2) The formed nano-film can effectively block the intrusion of moisture and other corrosive substances, thereby improving the moisture resistance and moisture-proof performance of the PCBA; (3) The nano-film can protect the PCBA board from chemical erosion and improve its chemical stability such as acid and alkali resistance and solvent resistance; (4) The nano-film formed by the silane coupling agent has excellent insulation performance, which helps to maintain the electrical insulation of the PCBA; (5) The nano-film can enhance the mechanical strength of the PCBA board and improve its impact resistance and wear resistance; (6) VTES helps to improve the interfacial compatibility between different materials and reduce the internal stress caused by different material expansion coefficients; (7) Compared with other types of surface treatment agents, VTES usually has a lower environmental impact, meets the requirements of green environmental protection production, and the formation of the nano-film helps to improve the heat dissipation performance of the PCBA and prevent heat accumulation; (8) The formed nano-film has good long-term stability, which can ensure the reliability of the PCBA during long-term use. In summary, using vinyltriethoxysilane to surface-treat the PCBA board in this application can significantly improve the performance of the board, enhance its applicability and service life.

[0040] In some alternative embodiments of the present application, the vacuum degree in step S1 is controlled to be 20 mTorr to 100 mTorr. The vacuum degree can be any value between 20 mTorr and 100 mTorr. For example, it can be 20 mTorr, 30 mTorr, 40 mTorr, 50 mTorr, 60 mTorr, 70 mTorr, 80 mTorr, 90 mTorr, and 100 mTorr, etc. If the vacuum degree is too low (high air pressure), the residual air, water vapor and other impurities increase, which may cause the reactive gas (such as oxygen or argon) to react with the pollutants, reducing the surface cleaning or activation effect and affecting the subsequent film adhesion. The higher air pressure will also cause uneven plasma glow discharge, and the local excessive energy may damage the surface of the PCBA or cause uneven treatment. When the vacuum degree is too low, the gas molecule collisions are frequent, the diffusion of active groups is blocked, and the surface modification effect is weakened. When the vacuum degree is too low, impurities may be introduced into the film, resulting in pinholes or loose structures in the film layer. If the vacuum degree exceeds 100 mTorr, the gas molecule density is low, which will lead to insufficient supply of reactants, a significant decrease in the deposition rate, and an extension of the process time. At the same time, under low air pressure, the collisions between electrons and gas molecules decrease, the plasma energy and density decrease, and the surface cleaning or activation ability is weakened. The average free path of the gas is too long, which may cause uneven distribution of active groups on the substrate surface, forming a film layer with different thicknesses.

[0041] In some alternative embodiments of the present application, the reactive gas in step S1 is carbon tetrafluoride or hydrogen, and the flow rate of the reactive gas is 30 sccm to 120 sccm. Using the reactive gas can further clean the surface, promote chemical reactions, and improve the adhesion between the coating film and the substrate. Among them, by precisely controlling the flow rate of the reactive gas within the range of 30 sccm to 120 sccm, the present application can ensure the uniformity of surface cleaning and modification, and avoid excessive etching or uneven surface treatment. If carbon tetrafluoride (hereinafter referred to as CF4) is selected as the reactive gas, it can be used to slightly etch the surface of the PCBA board to remove the weakly bonded atomic layer without damaging the substrate. CF4 is a relatively stable gas and is not prone to violent reactions with the PCBA board, which is beneficial to controlling the treatment process. CF4 has selectivity for etching certain materials and can protect the parts that are not desired to be etched. If hydrogen (hereinafter referred to as H2) is selected as the reactive gas, H2 has strong reducibility and can reduce the oxides on the surface, improving the metal activity of the surface. H2 treatment can increase the adhesion between the metal and the coating film, which is beneficial to forming a more firm interface. In summary, whether carbon tetrafluoride or hydrogen is selected as the reactive gas, controlling the flow rate can ensure the uniform distribution of the reactive gas, thereby achieving uniform surface modification. At the same time, controlling an appropriate flow rate can shorten the treatment time and improve production efficiency. By precisely controlling the flow rate, the consumption of the reactive gas can be reduced, and the cost can be lowered.

[0042] In some alternative embodiments of the present application, the power of the pretreatment in step S2 is 70 W to 200 W. By turning on the power supply to pretreat the surface of the PCBA board, the surface contaminants, oxide layers, and organic residues can be removed, and the surface activity can be improved, thereby enhancing the adhesion of the subsequent coating film. If the power is lower than 70 W, it may lead to insufficient plasma energy, making it difficult to effectively excite gas molecules, resulting in weakened surface cleaning or activation effects, and the residual contaminants or oxide layers may not be fully removed; it will also cause the substrate surface to not be fully activated, and the binding force of the subsequently deposited VTES film layer will decrease, and peeling or cracking is likely to occur. If the power is higher than 200 W, it may lead to the risk of surface thermal damage. High-energy ion bombardment may cause local overheating of the PCBA substrate, resulting in carbonization of the epoxy resin, oxidation of the copper foil, or deformation of the solder pads. It may also cause changes in material properties. Excessive etching may damage the solder mask ink or microstructure on the PCB surface layer, affecting circuit performance (such as insulation and impedance stability).

[0043] In some alternative embodiments of the present application, the vacuum degree in step S3 is adjusted to 20 mTorr to 70 mTorr. The vacuum degree within this range can improve the mixing uniformity of VTES gas and auxiliary gas, and avoid uneven composition or decreased adhesion of the deposited film layer due to too low vacuum degree; it can accelerate the deposition rate, and avoid too low gas density due to too high vacuum degree, resulting in a reduction in the number of molecules participating in the reaction per unit time and a decrease in process efficiency. And performing thin film deposition in a vacuum environment can reduce the interference of oxygen and water vapor, thereby improving the purity and quality of the thin film.

[0044] In some alternative embodiments of the present application, the vaporization temperature in step S3 is 80 °C to 200 °C, and the flow rate of vinyltriethoxysilane gas is 10 sccm to 60 sccm. By heating and vaporizing VTES gas, it can be ensured that it is deposited on the surface of the PCBA board uniformly in a gaseous state to form a uniform nano-film. Specifically, vaporizing VTES within the temperature range of 80 °C to 200 °C can ensure that its molecules have sufficient kinetic energy when reaching the surface of the PCBA board, promoting chemical reactions with the board surface and forming stable chemical bonds. The appropriate vaporization temperature helps VTES molecules to be deposited on the surface of the PCBA board uniformly, thereby forming a uniform and dense nano-film and improving the quality of the coated film. By adjusting the flow rate of VTES gas within the range of 10 sccm to 60 sccm in the present application, the thickness of the coated film can be precisely controlled to meet the requirements of different applications for the thickness of the coated film, and it also helps to reduce excessive use and lower the material cost. A low vaporization temperature will result in insufficient vaporization of VTES, and liquid VTES may remain in the pipeline or vaporization chamber, causing liquid droplets to sputter onto the surface of the PCBA, forming pinholes or nodules in the film layer; it will also result in insufficient reaction activity, and the unvaporized monomer molecules are difficult to polymerize effectively, resulting in a loose film layer or incomplete chemical bonding. A high vaporization temperature will cause thermal decomposition of VTES, and high temperature may damage the molecular structure of VTES (such as breaking the Si-O bond or vinyl group), generating by-products (such as SiO2 particles), contaminating the film layer or reducing its function. And if the heat is transferred to the PCBA, it may cause deformation of the epoxy resin substrate, oxidation of the copper foil, or abnormal melting point of the solder. A flow rate lower than 10 sccm will result in too slow deposition rate and a significant extension of the film layer growth time, and the thickness may not meet the standard due to insufficient process time. A flow rate higher than 60 sccm may not participate in the reaction in time, forming unpolymerized molecular clusters, resulting in a rough film layer or pores. By vaporizing VTES within the temperature range of 80 °C to 200 °C and controlling its flow rate within the range of 10 sccm to 60 sccm, the method provided by the present application can effectively improve the effect of surface modification treatment of the PCBA board, while ensuring the controllability, economy, and safety of the treatment process.

[0045] In some alternative embodiments of the present application, the auxiliary gas is an inert gas or nitrogen, and the flow rate of the auxiliary gas is 30 sccm to 120 sccm. The introduction of the auxiliary gas helps to control the chemical reactions during the film coating process and optimize the structure and properties of the film. For example, inert gases (such as argon, helium, etc.) or nitrogen do not react chemically with the surface of the VTES or PCBA board, so the oxidation of the board surface during the film coating process can be effectively prevented. By adjusting the flow rate of the auxiliary gas, the reaction rate of the VTES gas on the surface of the PCBA board can be controlled, avoiding the influence of too fast or too slow reaction rate on the film coating quality. The use of inert gases or nitrogen helps to reduce defects in the film coating, such as bubbles, pinholes, etc., thereby improving the overall quality of the film coating. It is also worth mentioning that the presence of the auxiliary gas can reduce unnecessary reactions of the VTES gas, thereby reducing the consumption of the VTES gas; by adjusting the flow rate of the auxiliary gas, the deposition rate of the VTES gas can be indirectly controlled, thereby controlling the thickness of the film coating. If the flow rate is too low (<30 sccm), the plasma stability will decrease. For example, if the auxiliary gas is argon, its function of diluting or maintaining the plasma will weaken, which may lead to unstable glow discharge; too low flow rate (<30 sccm) may also cause the failure of reaction regulation. For example, if the auxiliary gas is oxygen, its etching or oxidation function is insufficient and it cannot effectively regulate the VTES polymerization process. If the flow rate is too high (>120 sccm), the concentration of VTES will be overly diluted, the proportion of reactants will be unbalanced, the deposition rate will be greatly reduced, and even the film formation will be interrupted; the film layer composition will shift. If the auxiliary gas participates in the reaction (such as the copolymerization of oxygen and VTES), the excessive gas may change the chemical composition of the film and affect its properties (such as hydrophobicity or heat resistance). In summary, the present application uses an inert gas or nitrogen as the auxiliary gas, which can optimize the surface modification process of the PCBA board, improve the quality and efficiency of the film coating, and ensure the safety and economy of the treatment process.

[0046] In some alternative embodiments of the present application, in step S4, the frequency of the microwave radio frequency power supply is 80W - 300W, and the thickness of the coated film is 50nm - 1000nm. Adjusting the frequency of the microwave radio frequency power supply can precisely control the deposition rate and thickness of the coated film, thereby obtaining the desired film properties. For example, when the frequency is lower than 80W, the nano-film will be loose and porous, the particle energy is insufficient, the intermolecular binding force is weak, the film layer has poor compactness, and it is easy to absorb moisture or be corroded. It will also result in poor adhesion, insufficient activation of the substrate surface, low bonding strength between the film layer of the nano-film and the PCBA interface, and easy peeling. When the frequency is higher than 300W, there is a risk of thermal damage to the substrate. The high-energy ion bombardment causes local high temperature, which may cause carbonization of the epoxy resin substrate, oxidation of the copper foil, or deformation of the solder pad. It will also cause an increase in the internal stress of the film layer. The overly dense film layer cracks due to stress accumulation, especially during subsequent thermal cycling or mechanical bending. By adjusting the microwave radio frequency power supply, uniform and controllable film deposition can be achieved, improving the consistency and repeatability of the coated film. If the thickness of the coated film is too thin, it will result in insufficient functionality and cannot effectively block water vapor. If the thickness of the coated film is too thick (higher than 1000nm), there is a risk of stress cracking. The internal stress of the film layer accumulates with the increase in thickness and is prone to cracking especially when the temperature changes.

[0047] In some alternative embodiments of the present application, the temperature in the vacuum chamber of the film deposition device is maintained at 40°C - 55°C. That is, the reaction temperature of the present application should be maintained within 40°C - 55°C, and it can be 40°C, 40.5°C, 41°C, 42°C, 43°C, 43.5°C, 45°C, 46°C, 47°C, 47.5°C, 48°C, 49°C, 50°C, and 55°C, etc. The electronic components and solder joints in the PCBA board are sensitive to high temperatures. Controlling the reaction temperature at 40°C - 55°C can avoid thermal damage to the board caused by high temperatures and maintain the performance of the electronic components and the integrity of the solder joints. If the temperature is too low, it may affect the diffusion and adsorption of gases, but if the temperature is too high, it may cause the decomposition of the precursor. At the same time, the temperature range of 40°C - 55°C also has the following advantages: (1) Improving the uniformity of the coated film: The lower temperature helps the VTES gas to be uniformly deposited on the surface of the PCBA board, reducing the non-uniform coated film caused by the temperature gradient; (2) Controlling the chemical reaction: At a temperature of 40°C - 55°C, the chemical reaction rate between VTES and the surface of the PCBA board is moderate, which is conducive to forming stable and uniform chemical bonds, thereby improving the quality of the coated film; (3) Reducing volatiles: The lower temperature can reduce the evaporation of VTES and other possible volatiles, reducing the impact on the environment; (4) Strong adaptability: This low-temperature treatment method is applicable to various types of PCBA boards, including those sensitive to high temperatures.

[0048] In summary, by adopting the surface modification method of the present application, the corrosion resistance can be improved, that is, the film can effectively protect the PCBA board from environmental corrosion and extend its service life; the electrical performance can be enhanced, that is, the nano-film can improve the insulation performance of the PCBA, reduce leakage and signal interference; the mechanical strength can be increased, that is, the film can enhance the mechanical strength of the PCBA board and improve its bending and impact resistance; the adhesion performance can be optimized, that is, through surface modification, the adhesion between the film and the PCBA board is enhanced, which is beneficial to the subsequent welding and assembly processes. And the surface modification method of the present application simplifies the steps, is clear, easy to automate, helps to improve production efficiency. Compared with the traditional electroless plating or electroplating process, this method may reduce the use of harmful chemicals and reduce environmental pollution. At the same time, by precisely controlling the film coating process, material waste can be reduced and production costs can be lowered. In short, this method provides an efficient, controllable and environmentally friendly surface modification means for the PCBA board, which helps to improve the overall performance and reliability of the PCBA.

[0049] The following is an illustration of the present application in conjunction with specific embodiments.

[0050] Example 1

[0051] This example provides a surface modification method for PCBA boards, including the following steps:

[0052] (1) Open the door of the vacuum chamber, place the PCBA board between the electrodes, then close the door, evacuate the vacuum chamber, and maintain the vacuum degree at 40 mTorr.

[0053] (2) Pass carbon tetrafluoride into the vacuum chamber through the gas supply system, and the flow rate of carbon tetrafluoride is 120 sccm. Turn on the microwave radio frequency power supply, adjust the power of the microwave radio frequency power supply to 200 W, generate a medium microwave electric field between the electrode plates, and electrolytically separate the carbon tetrafluoride in the electric field. Under the action of the medium microwave electric field, carbon tetrafluoride is electrolytically separated into plasma to activate the surface of the substrate. Under the action of the carbon tetrafluoride plasma on the surface of the substrate, the impurity particles on the surface will be cleaned into a suitable state for treatment, and the treatment time is 40 min.

[0054] (3) Evacuate the vacuum chamber again, maintain the vacuum degree at 20 mTorr, then load the VTES liquid into the heating device, adjust the heating temperature to 100 °C, heat and vaporize the VTES liquid, then pass the VTES vapor into the vacuum chamber, control the gas flow rate at 18 sccm, and at the same time pass argon as an auxiliary gas, and control the argon flow rate at 120 sccm.

[0055] (4) Readjust the power of the microwave radio frequency power supply to 250W, electrolytically separate the gas in the vacuum chamber. VTES vapor and argon are electrolytically separated into plasma again under the action of the medium microwave electric field, and undergo a chemical polymerization reaction with the substrate surface to deposit an adherent coating on the substrate surface. The time for the adherent coating process is 30 min, and the temperature of the vacuum chamber of the PECVD coating equipment is always maintained at 55 °C.

[0056] After the surface modification treatment in this embodiment, a nano - coating is deposited on the surface of the PCBA board, which is a hydrophobic film with a thickness of 100 nm, similar to a silica film. The film photo is as Figure 3 shown.

[0057] Example 2

[0058] This embodiment provides a surface modification treatment method for PCBA boards, including the following steps:

[0059] (1) Open the door of the vacuum chamber, place the PCBA board between the electrodes, then close the door, evacuate the vacuum chamber, and maintain the vacuum degree at 20 mTorr.

[0060] (2) Pass carbon tetrafluoride into the vacuum chamber through the gas supply system, and the flow rate of carbon tetrafluoride is 90 sccm. Turn on the microwave radio frequency power supply, adjust the power of the microwave radio frequency power supply to 100W, generate a medium microwave electric field between the electrode plates, and electrolytically separate the carbon tetrafluoride in the electric field. Carbon tetrafluoride is electrolytically separated into plasma under the action of the medium microwave electric field to activate the substrate surface. Under the action of the carbon tetrafluoride plasma on the substrate surface, the impurity particles on the surface will be cleaned into a state suitable for treatment, and the treatment time is 40 min.

[0061] (3) Evacuate the vacuum chamber again, maintain the vacuum degree at 30 mTorr, then load the VTES liquid into the heating device, adjust the heating temperature to 120 °C, heat and vaporize the VTES liquid, then pass the VTES vapor into the vacuum chamber, control the gas flow rate at 50 sccm, and simultaneously pass argon as an auxiliary gas, controlling the argon flow rate at 120 sccm.

[0062] (4) Readjust the power of the microwave radio frequency power supply to 250W, electrolytically separate the gas in the vacuum chamber. VTES vapor and argon are electrolytically separated into plasma again under the action of the medium microwave electric field, and undergo a chemical polymerization reaction with the substrate surface to deposit an adherent coating on the substrate surface. The time for the adherent coating process is 30 min, and the temperature of the vacuum chamber of the PECVD coating equipment is always maintained at 45 °C.

[0063] Example 3

[0064] This embodiment provides a surface modification method for PCBA boards, including the following steps:

[0065] (1) Open the door of the vacuum chamber, place the PCBA board between the electrodes, then close the door, evacuate the vacuum chamber, and maintain a vacuum degree of 60 mTorr.

[0066] (2) Pass carbon tetrafluoride into the vacuum chamber through the gas supply system, with a carbon tetrafluoride flow rate of 100 sccm. Turn on the microwave radio frequency power supply, adjust the power of the microwave radio frequency power supply to 180 W, generate a medium microwave electric field between the electrode plates, and electrolytically separate the carbon tetrafluoride in the electric field. The carbon tetrafluoride is electrolytically separated into plasma under the action of the medium microwave electric field, activating the surface of the substrate. Under the action of the carbon tetrafluoride plasma on the surface of the substrate, the impurity particles on the surface will be cleaned into a state suitable for treatment, and the treatment time is 40 min.

[0067] (3) Evacuate the vacuum chamber again, maintain the vacuum degree at 70 mTorr, then load the VTES liquid into the heating device, adjust the heating temperature to 200 °C, heat and vaporize the VTES liquid, and then pass the VTES vapor into the vacuum chamber, control the gas flow rate at 20 sccm, and at the same time pass argon as an auxiliary gas, control the argon flow rate at 90 sccm.

[0068] (4) Adjust the power of the microwave radio frequency power supply to 100 W again, electrolytically separate the gas in the vacuum chamber, and the VTES vapor and argon are electrolytically separated into plasma again under the action of the medium microwave electric field, and chemically polymerize with the surface of the substrate to deposit an attachment coating on the surface of the substrate. The time for the attachment coating process is 30 min, and the temperature of the vacuum chamber of the PECVD coating equipment is always maintained at 40 °C.

[0069] Test Example

[0070] Perform the following experiments on the surface-modified PCBA board (surface protection coating) processed in Example 1, and the results are shown in Table 1 and Figure 4 as follows.

[0071] Table 1

[0072]

[0073]

[0074] Figure 4The difference between the surface of the PCBA board treated in Example 1 and the traditional ENEPIG nickel palladium immersion gold protective coating under high temperature and high humidity test conditions, wherein the ENEPIG nickel palladium immersion gold protective coating is a typical structure of metal surface treatment, which is nickel plating on the copper surface for about 120μm to 240μm (3μm to 6μm), followed by palladium plating for about 4μm to 20μm (0.1μm to 0.5μm), and finally immersion gold treatment, with a thickness of about 1μm to 4μm (0.02μm to 0.1μm), the palladium layer can prevent excessive corrosion of the nickel layer, and the operation is produced by immersion plating. ENEPIG can provide good flatness and is a relatively versatile final metal surface treatment. It can bear the function of nickel immersion gold treatment, and palladium treatment is also an ideal gold wire surface. When the parts are processed, palladium and gold will eventually be fully or partially integrated into the solder, and the contacts will produce nickel / tin intermetallics. When bonding, aluminum and gold wires are bonded to the surface of the palladium.

[0075] From Table 1 and Figure 4 It can be seen that the protective coating obtained after the PCBA surface treatment of Example 1 of the present application has been verified by bipolar temperature aging. The first is high temperature and high humidity aging (80°C / 85% RH) to simulate the hot and humid environment of Southeast Asia (equivalent to the MIL-STD-202G standard) to verify the stability of the crosslinking density of the three-proof paint (FTIR shows that the crosslinking degree remains> 95%); the second is low temperature aging (-40°C) to evaluate the glass transition temperature Tg offset (DSC test ΔTg<3°C) to ensure the ability to resist microcracks under extremely cold working conditions. After accelerated corrosion verification, the salt spray test (5% NaCl) is equivalent to the coastal industrial atmospheric environment (ISO 9227C5 level). The SEM-EDS test proves that the Cr / Zn content ratio in the passivation layer is maintained at 6:1, and no Cl is detected. - Penetration. It has also been certified for chemical safety compliance, such as perfluorinated compound control, GC-MS detection limit <0.1ppm (10 times higher than EPA3550C requirements), compliance with EU POPs Regulation (EU) 2019 / 1021, alternative fluorinated resin (C6 fluorocarbon chain) surface energy 18mN / m, balancing protection and environmental protection needs. No delamination after 50 thermal shocks (ASTM D3359 4B grade adhesion), proving that silane coupling agent treatment makes the interface binding energy >50J / m 2 .

[0076] Although the specific implementation methods of this application are described in detail, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A surface modification method for PCBA board material, characterized in that: The following steps are involved: S1. Place the PCBA sheet in a thin film deposition device, evacuate the device and introduce active gas; S2, turn on the power to pre-treat the surface of the PCBA board; S3, after adjusting the vacuum degree, introducing the heated and vaporized vinyltriethoxysilane gas, and at the same time introducing the auxiliary gas; S4. Adjust the frequency of the microwave radio frequency power supply and deposit the coating.

2. The surface modification method for PCBA sheet material according to claim 1, characterized in that: In the step S1, the vacuum degree is controlled to be 20 mTorr to 100 mTorr.

3. The surface modification method for PCBA sheet material according to claim 1, characterized in that: In the step S1, the active gas is carbon tetrafluoride or hydrogen, and the flow rate of the active gas is 30 sccm to 120 sccm.

4. The surface modification method for PCBA sheet material according to claim 1, characterized in that: The power of the pretreatment in step S2 is 70W to 200W.

5. The surface modification method for PCBA sheet material according to claim 1, characterized in that: In step S3, the vacuum degree is adjusted to 20 mTorr to 70 mTorr.

6. The surface modification method for PCBA sheet material according to claim 1, characterized in that: In the step S3, the vaporization temperature is 80° C. to 200° C., and the flow rate of vinyltriethoxysilane gas is 10 sccm to 60 sccm.

7. The surface modification method for PCBA sheet material according to claim 1, characterized in that: The auxiliary gas is an inert gas or nitrogen, and the flow rate of the auxiliary gas is 30 sccm to 120 sccm.

8. The surface modification method for PCBA sheet material according to claim 1, characterized in that: In step S4, the frequency of the microwave radio frequency power supply is 80W to 300W.

9. The surface modification method for PCBA sheet material according to claim 1, characterized in that: The film thickness in step S4 is 50 nm to 1000 nm.

10. The surface modification method for PCBA sheet material according to claim 1, characterized in that: The temperature inside the vacuum chamber of the thin film deposition device is maintained at 40°C to 55°C.

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