Power supply equipment circuit board for severe environment and preparation method thereof

Abstract

The invention belongs to the technical field of ocean engineering power supplies, and particularly relates to a power supply equipment circuit board for a severe environment and a preparation method thereof. N layers of films are sequentially plated on the surface of the circuit board to obtain the power supply equipment circuit board for the severe environment, N is a positive integer larger than or equal to 2, a film layer 1 is in direct contact with the circuit board, and the film layer 1 is one of a silicon dioxide film layer, an aluminum oxide film layer, a silicon nitride film layer, a titanium dioxide film layer and an aluminum nitride film layer. According to the invention, reliable protection can be provided for the circuit board and electronic components on the circuit board, so that the circuit board can be better used in severe environments such as ocean.

Description

Technical Field

[0001] The present invention belongs to the technical field of marine engineering power supplies, and particularly relates to a circuit board for a power supply device used in harsh environments and a preparation method thereof. Background Art

[0002] For special marine engineering power supplies, how to achieve stable and reliable operation is a key factor for their development. However, due to the high humidity, high salinity, and extreme temperature variations in the marine environment, the reliability requirements for power supply devices used in marine engineering are particularly high, different from conventional power supply products. The circuit board contains the most core chips and circuit components of the power supply system and is at the same time exposed to the environment, making it the most vulnerable core component of the marine engineering power supply system. How to ensure the stability of the PCB board is the key to ensuring the reliability of special marine engineering power supply devices.

[0003] The marine environment poses a great threat to the performance and lifespan of the circuit board, accelerating its aging and failure. To protect the circuit board from these harsh environments, the three-proof protection technology has emerged, aiming to improve the reliability and durability of the circuit board. The three-proof protection technology for the circuit board of marine engineering power supply devices mainly addresses the issues of moisture-proof, salt spray-proof, and mildew-proof in the marine environment. Currently, the status quo of the three-proof protection technology includes coating the circuit board with various materials to form a protective layer. These materials include acrylic resin (AR), modified epoxy resin (ER), silicone resin (SR), polyurethane resin (UR), and parylene (XY), etc. For example, Chinese Patent Application CN210432038U discloses a circuit board coated with three-proof paint, including a printed circuit board, on which a protective film layer formed by curing the three-proof paint is coated. The printed circuit board is characterized in that there are through holes penetrating up and down, and columnar structures formed by curing the three-proof paint are provided in the through holes; the through holes are within the coverage of the protective film layer, and the columnar structures are connected to the protective film layer. In addition to this, there are also direct potting of silicone rubber, epoxy resin glue, etc., to completely pot the circuit board. Although this method can improve the comprehensiveness and reliability of protection to a certain extent, it will inevitably reduce the improvement of the circuit board's resistance to humidity and heat, and the overall cost will also increase, and the difficulty of maintenance and inspection will also increase significantly.

[0004] Generally speaking, although the above technical solutions are adopted in the prior art, it is still difficult to meet the industry's requirements for the long-term reliable operation of marine engineering power supplies, such as applications in some unmanned areas, tropical extreme areas, immersion environments, etc. Moreover, due to the insufficient reliability of the prior art, the maintenance cycle of power supply devices is shorter, increasing the use cost and restricting the application development of the industry. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a circuit board for power supply equipment in harsh environments and a preparation method thereof. The present invention can provide more reliable protection for the circuit board and the electronic components thereon to better cope with the use in harsh environments such as the ocean.

[0006] The technical solution of the present invention is as follows:

[0007] A preparation method of a circuit board for power supply equipment in harsh environments, where N layers of films are sequentially plated on the surface of the circuit board to obtain the circuit board for power supply equipment in harsh environments, N is a positive integer greater than or equal to 2, the film layer 1 is in direct contact with the circuit board, and the film layer 1 is one of a silicon dioxide film layer, an aluminum oxide film layer, a silicon nitride film layer, a titanium dioxide film layer, and an aluminum nitride film layer.

[0008] Further, when N>2, the film layers 2 to (N - 1) are each one of an aluminum oxide film layer, a silicon nitride film layer, a titanium dioxide film layer, and an aluminum nitride film layer; the film layer N is one of an acrylic resin three-proof paint film layer, a modified epoxy resin three-proof paint film layer, a silicone resin three-proof paint film layer, a polyurethane resin three-proof paint film layer, and a parylene three-proof paint film layer.

[0009] Further, the thickness of the film layer 1 is 20 - 100 nm, and the thickness of the film layer N is 500 - 1500 m; when N>2, the thicknesses of the film layers 2 to (N - 1) are 100 - 500 nm.

[0010] Further, the preparation method of the circuit board for power supply equipment in harsh environments includes the following steps:

[0011] S1 Send the circuit board into an atmosphere-vacuum isolation buffer chamber, evacuate the air, and then send the circuit board into a buffer pretreatment + gas vacuum flushing chamber;

[0012] S2 Evacuate the buffer pretreatment + gas vacuum flushing chamber, pre-clean the circuit board with gas and perform dynamic jet flushing cleaning, and evacuate the air after the cleaning;

[0013] S3 Send the circuit board after the cleaning treatment into a glow discharge cleaning chamber, and clean the circuit board with a working gas;

[0014] S4 Send the processed circuit board into a coating chamber equipped with a target, and perform coating using a vacuum coating process to sputter the first to (N - 1) layers of films;

[0015] S5 Send the circuit board coated with films obtained in step S4 into a buffer chamber and a vacuum-atmosphere isolation buffer chamber in sequence, and then spray the Nth layer of film after sending the circuit board out.

[0016] Further, in step S1, the vacuum is pumped to 1 to 10 Pa; in step S2, the vacuum is pumped to 1×10-3 Pa to 5×10-3 Pa; the gas in step S2 is argon or nitrogen; the working gas in step S3 is argon or nitrogen.

[0017] Further, the specific operation of the pre-cleaning in step S2 is as follows: a gas with a pressure of 0.1 to 0.5 bar is introduced, the gas flow rate during pre-cleaning is 5 to 10 L / min, and the pre-cleaning time is 10 s to 1 min; when performing dynamic jet flushing and cleaning in step S2, the motor drives the exhaust pipe to move, and the stroke speed of the exhaust pipe is 0.1 to 0.3 m / s; for gas jet control, the gas pressure is 0.5 to 2.0 bar, and the spraying time is 2 to 10 minutes.

[0018] Through the synergistic effect of dynamic jet flushing and cleaning and the vacuum environment, the present invention can not only improve the cleanliness of the circuit board before vacuum coating and enhance the quality of subsequent coating, but also reduce the secondary pollution during the transmission and transfer process after conventional liquid cleaning, adapting to the production characteristics of this industry.

[0019] The step of performing dynamic jet flushing and cleaning on the circuit board is carried out in a buffer pre-treatment + gas vacuum flushing chamber. The buffer pre-treatment + gas vacuum flushing chamber is a vacuum box body, and a dynamic exhaust pipe is designed in this vacuum box body. The motor drives the exhaust pipe to reciprocate up and down, combined with uniformly distributed small-hole jetting, so that high-pressure gas (such as nitrogen, argon) uniformly sprays on the surface of the workpiece, realizing more uniform cleaning coverage. Utilizing the air flow shear force and the low-resistance characteristics in the vacuum environment, combined with high-pressure gas spraying, the cleaning efficiency is improved, the cleaning effect is enhanced, while the gas consumption is reduced, and pollutants such as particles and grease are efficiently removed, realizing the efficient and comprehensive cleaning of the workpiece, laying a foundation for improving the quality of subsequent coating.

[0020] For the circuit boards just produced by surface mount reflow soldering, cleaning treatment is usually carried out to remove the residues in the soldering process, such as welding slag, flux and other substances, to avoid causing circuit short circuits and open circuits in the future, which will affect power-on and conduction. It is also necessary to remove chemical substances such as acids, alkalis, and organic substances that may be left during processing from contaminating the circuit board. If not cleaned in time, it will corrode the circuit board and affect its conductivity and service life. The existing technology generally uses manual chemical cleaning or ultrasonic cleaning methods, and drying is also required after cleaning to ensure the performance of the circuit board. There is a significant contradiction between the high requirements of the vacuum coating process for the cleanliness of the substrate and the current situation of the PCBA production environment. In the field of power product manufacturing, the circuit board surface mount workshop generally adopts a cleanliness standard of 100,000 levels, and some enterprises even lack basic clean workshop facilities. This production environment makes it extremely easy for the cleaned circuit boards to be re-attached by pollutants such as dust, particulate matter, and hair in the environment during the drying and transportation processes. Especially for PCBA boards that need to be vacuum coated, these micron-level pollutants will seriously affect the uniformity and bonding strength of the coating layer, directly leading to fluctuations in the product qualification rate. In response to this industry pain point, the present invention innovatively introduces a dynamic jet flushing cleaning technology, which effectively removes the residual pollutants on the surface of the circuit board through physical flushing under the existing production environment conditions, and successfully solves the quality hidden danger caused by insufficient environmental cleanliness in the traditional process.

[0021] Further, the vacuum coating process in step S4 is one of magnetron sputtering method, chemical vapor deposition method, molecular beam epitaxy method, and atomic layer deposition method.

[0022] In the existing technology, even when the circuit board is coated with three-proof material film layers such as acrylic resin (AR), modified epoxy resin (ER), silicone resin (SR), polyurethane resin (UR), and parylene (XY), or sealed with potting glue, the circuit board will still fail in a harsh environment. The present invention uses a vacuum coating process to prepare a bottom film layer that directly contacts the circuit board. By controlling the parameter conditions in the vacuum coating process, the growth of the thin film can be made more dense, effectively avoiding the appearance of tiny bubbles and impurities between the film layer and the circuit board, and avoiding the formation of failure centers, which can provide more reliable protection for the circuit board and the electronic components on it to better cope with the use in harsh environments such as the ocean. The circuit board sealing and protection film layer composed of the composite film system in the present invention, and the film systems cooperate with each other to jointly achieve excellent protection effects.

[0023] Further, the vacuum coating process is the magnetron sputtering method, and the magnetron sputtering reaction pressure is 0.5 - 1 Pa.

[0024] Further, the temperature of the buffer pretreatment + gas vacuum flushing chamber, glow discharge cleaning chamber, and coating chamber is 50 - 80 °C; in step S5:

[0025] The buffer chamber is in a high-vacuum environment, and the pressure of the high vacuum is 1×10-3 Pa to 5×10-3 Pa;

[0026] During the process that the circuit board coated with film obtained in step S4 enters the vacuum-atmosphere isolation buffer chamber, the vacuum-atmosphere isolation buffer chamber is in a low-vacuum environment, and the pressure of the low vacuum is 1 to 10 Pa. After entering, the valve of the vacuum-atmosphere isolation buffer chamber is closed, and the atmosphere is filled to make the pressure in the vacuum-atmosphere isolation buffer chamber return to the atmospheric pressure level.

[0027] Another object of the present invention is to provide a power supply device circuit board for harsh environments prepared by the preparation method of the power supply device circuit board for harsh environments described above.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] (1) The power supply device circuit board for harsh environments provided by the present invention is composed of a circuit board and multiple layers of films stacked, and the composite film layer can provide better protection for the circuit board.

[0030] (2) The power supply device circuit board for harsh environments provided by the present invention can provide more reliable protection for the circuit board and the electronic components thereon to better cope with the use in harsh environments such as the ocean. Description of the Drawings

[0031] Figure 1 It is a structural decomposition diagram of the power supply device circuit board for harsh environments of the present invention;

[0032] Figure 2 It is a schematic flow chart of preparing a power supply device circuit board for harsh environments by using a line array continuous multi-chamber magnetron sputtering device in Embodiments 1-3 of the present invention;

[0033] Figure 3 It is a schematic structural diagram of a line array continuous multi-chamber magnetron sputtering device;

[0034] Figure 4 It is a schematic longitudinal sectional view of the box body of the 2# chamber vacuum cleaning chamber;

[0035] Figure 5 It is another schematic longitudinal sectional view of the box body of the 2# chamber vacuum cleaning chamber;

[0036] Figure 6 It is a schematic principle diagram of cleaning the circuit board;

[0037] Figure 7 It is a schematic structural diagram of the power supply device circuit board for harsh environments in Embodiments 1-3 of the present invention.

[0038] In the figure, 11, circuit board; 1, film layer 1; 2, film layer 2; 3, film layer 3; N, film layer N; 4, cavity air inlet joint; 5, vacuum cavity wall; 6, exhaust pipe; 7, air outlet; 8, bellows; 9, air inlet; 10, air inlet pipe; 12, MFC mass flowmeter; 13, motor; 14, cam-connecting rod mechanism; 15, sliding rod; 16, magnetic fluid seal; 17, pin sleeve. DETAILED DESCRIPTION

[0039] The present invention is further illustrated below through the description of specific implementation modes, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of ​​the present invention, but as long as they do not deviate from the basic idea of ​​the present invention, they are all within the scope of the present invention.

[0040] The structural exploded diagram of the circuit board of the power supply device for harsh environment of the present invention is as follows Figure 1 The power supply device circuit board for harsh environment of the present invention is composed of a circuit board and a multi-layer film stacked together, and the composite film layer provides better protection for the circuit board.

[0041] In the present invention, different film layers use different materials to achieve diversified functions, enhance protection performance, and meet the needs of circuit board protection, but all need to select materials with good insulation performance and good thermal conductivity, and be as strong as possible and have good light transmission performance. Specifically:

[0042] For example Figure 1 As shown, for the film layer 1 (i.e., the film layer in direct contact with the circuit board), the present invention adopts a material with extremely high chemical stability and excellent corrosion resistance, such as silicon dioxide (SiO2) film, which can avoid the film preparation process causing the more fragile capacitor components on the circuit board to be exposed to a high temperature environment, resulting in premature performance degradation.

[0043] For film layers 2 to N, other film layers that can improve the characteristics of film layer 1 are selected to form a film system with more comprehensive performance in all aspects, such as aluminum oxide (Al2O3) film, silicon nitride (Si3N4) film, titanium dioxide (TiO2) film, aluminum nitride, etc.

[0044] For the top layer, that is, Figure 1 The Nth layer is coated with traditional three-proof materials, such as acrylic resin (AR), modified epoxy resin (ER), silicone resin (SR), polyurethane resin (UR) and polyparaxylene (XY).

[0045] After completing the construction of the above film system, for applications with high reliability requirements, it is also possible to combine the traditional potting and sealing method and use potting materials such as organic silicone to pot the entire circuit board with the composite film system to form a more reliable sealing system.

[0046] Example 1. Preparation Method of Power Equipment Circuit Board for Harsh Environments

[0047] For the preparation method of the power equipment circuit board for harsh environments, three layers of films are sequentially deposited on the surface of the circuit board to obtain the power equipment circuit board for harsh environments. Film layer 1 is in direct contact with the circuit board. Film layer 1 is a silicon dioxide film layer with a thickness of 20 nm. Film layer 2 is an aluminum oxide film layer with a thickness of 500 nm. Film layer 3 is a polyurethane resin three-proof paint film layer located on the top layer with a thickness of 500 μm.

[0048] The schematic flow chart of preparing the power equipment circuit board for harsh environments by using a linear continuous multi-chamber magnetron sputtering equipment in Example 1 of the present invention is as Figure 2 shown.

[0049] The schematic structural diagram of the linear continuous multi-chamber magnetron sputtering equipment is as Figure 3 shown, where:

[0050] (1) Each chamber is hermetically separated by a closed valve to ensure independence and no gas leakage between each other;

[0051] (2) Chamber 1# is an air-vacuum isolation buffer chamber (equipment inlet buffer chamber), which continuously inflates and evacuates, and continuously switches between a low vacuum state (1 - 10 Pa) and an atmospheric pressure state, so that the circuit board to be coated can enter the coating equipment from the outside;

[0052] (3) Chamber 2# is a buffer pretreatment + gas vacuum flushing chamber, which is usually in a high vacuum state (10 -3 Pa), used to transfer the circuit board to be coated from the low vacuum chamber to the high vacuum state, and at the same time perform appropriate heating treatment (50 °C) on it to improve the film forming quality of the film layer;

[0053] (4) Chambers 2# - 5# are all equipped with heating devices, so that the coated circuit board can be maintained at the required temperature (50 °C);

[0054] (5) Chamber 3# is an Ar gas glow discharge cleaning chamber. High-purity argon gas (Ar) is introduced into the chamber to maintain the pressure in the chamber within a certain range, generally 0.1 - 1 Pa (this pressure range can ensure the stable formation of subsequent glow discharge);

[0055] (6) Chamber 4# is coating chamber 1 (sputtering SiO2 thin film), equipped with a SiO2 target, used for magnetron sputtering reaction to sputter SiO2 thin film. This chamber is in a high vacuum state (10 -3 Pa) for a long time;

[0056] (7) Chamber 5# is the coating chamber 2 (for sputtering Al2O3 thin film), equipped with an Al2O3 target, used for magnetron sputtering reaction to sputter Al2O3 thin film. This chamber is in a high vacuum state (10 -3 Pa) for a long time;

[0057] (8) Chamber 6# is the buffer chamber, which is usually in a high vacuum state (10 -3 Pa), used for buffering and isolating the circuit board with the film deposited from the high vacuum chamber to the low vacuum state to ensure the high vacuum purity of Chambers 4# and 5#, so as to avoid the decline of film forming quality caused by pollution;

[0058] (9) Chamber 7# is the atmosphere-vacuum isolation buffer chamber (equipment outlet chamber), which continuously inflates and pumps air, and continuously switches between the low vacuum state (1 - 10 Pa) and the atmospheric pressure state, so that the circuit board with the film deposited can be switched from the high vacuum chamber to the low vacuum state and enter the atmospheric pressure state to be sent out of the equipment;

[0059] The specific preparation steps of the circuit board of the power supply equipment for harsh environments are as follows:

[0060] Before starting production, the magnetron sputtering equipment has been pumped to a vacuum state by a vacuum pump. Among them, Chambers 1#, 3#, and 7# are in the low vacuum state (1 - 10 Pa), and Chambers 2#, 4#, 5#, and 6# are in the high vacuum state (10 -3 Pa).

[0061] Step 1: Perform a simple treatment of blowing and dust removal on the circuit board to be coated to ensure that there are fewer dust and debris on the circuit board before entering the vacuum coating equipment.

[0062] Step 2: As shown above Figure 3 At this time, open the air release valve of Chamber 1# of the magnetron sputtering equipment to introduce the atmosphere into the chamber to make it reach the atmospheric pressure level. Since the atmospheric pressure in Chamber 1# and the outside is the same at this time, then open Valve A, and send the circuit board to be coated into Chamber 1# through the conveyor belt, and close Valve A.

[0063] Step 3: As shown above Figure 3 After the circuit board to be coated is sent into Chamber 1# and sealed, start to pump Chamber 1# to a vacuum and pump it to the low vacuum state (1 - 10 Pa). At this time, the pressure difference between Chamber 1# and Chamber 2# (high vacuum state) is very small. Open Valve B, and send the circuit board to be coated into Chamber 2# through the conveyor belt, and close Valve B to make Chamber 2# return to the high vacuum state.

[0064] Step 4: Chamber 2# is the buffer pretreatment + gas vacuum flushing chamber (vacuum cleaning chamber box). The longitudinal sectional view of the vacuum cleaning chamber box of Chamber 2# is as shown in Figure 4As shown, another longitudinal sectional view of the 2# chamber vacuum cleaning chamber box body is as Figure 5 shown. The 2# chamber includes a box body. There is a cavity air inlet joint 4 outside the box body. Inside the box body, there is a vacuum cavity wall 5. Inside the vacuum cavity wall, there is an exhaust pipe 6. There are evenly distributed air outlet holes 7 on the exhaust pipe 6. The middle section of the exhaust pipe 6 is connected to the cavity air inlet joint 4 through a metal bellows 8 with good telescopic performance. There is an air inlet 9 outside the box body that communicates with the vacuum cavity wall 5. The vacuum cavity wall 5 and the air inlet 9 are connected through an air inlet pipe 10. There is an MFC mass flowmeter 12 on the air inlet pipe 10. The air inlet 9 and the exhaust pipe 6 are connected through the bellows 8. The air inlet pipe 10 and the bellows 8 are connected through the cavity air inlet joint 4. There is a motor 13 outside the box body. Inside the box body, there is a cam-link mechanism 14. The rotating shaft of the motor 13 uses magnetic fluid sealing 16. The air inlet 9 and the exhaust pipe 6 of the vacuum chamber are connected through the bellows 8, so that the exhaust pipe 6 can move up and down. The motor 13 rotates to drive the cam-link mechanism 14 to drive the exhaust pipe 6 to move vertically up and down reciprocally. There are 2 slide bars 15 on the exhaust pipe 6. The slide bars 15 are sleeved in the pin sleeves 17 fixed on the inner wall of the vacuum box body. This ensures that when the exhaust pipe 6 moves up and down reciprocally, it can move vertically on the plane where the two pin sleeves 17 are located and will not swing randomly. The section connecting the cavity air inlet joint and the exhaust pipe inside the cavity is a metal bellows with good telescopic performance, which can meet the requirements of up and down reciprocating movement. The air inlet and the exhaust pipe of the vacuum chamber are connected through the bellows, so that the exhaust pipe can move up and down. The exhaust pipe is driven to move up and down by the motor. There is a heater (not shown in the figure) in the 2# chamber, which preheats the circuit board to be coated that enters, so that it gradually reaches a temperature of 50 °C, which is convenient for high-quality sputtering film formation.

[0065] The circuit board is pretreated, including the steps of vacuum pumping and pre-cleaning, dynamic air jet flushing cleaning in the 2# chamber, and cleaning in the 3# argon glow discharge cleaning chamber. The specific steps of processing in the 2# chamber are as follows:

[0066] The 2# chamber is pumped to a high vacuum degree (1×10-3 Pa). The circuit board to be coated is pre-cleaned in the 2# chamber. Low-pressure argon gas Ar (0.1 - 0.5 bar) is introduced for spraying to remove loose pollutants. The pre-cleaning gas flow rate: 5 L / min, the pre-cleaning duration: 10 min; the circuit board is subjected to dynamic air jet flushing cleaning, which specifically includes 1) the motor drives the exhaust pipe to move: movement parameters: stroke range 200 mm, the exhaust pipe stroke speed 0.1 m / s, 2) gas injection control: gas pressure: 0.5 bar, spraying time: 2 minutes, 3) vacuum dynamic balance: the pressure is monitored in real time through a vacuum gauge, and the intake valve and the pump speed are adjusted to maintain the vacuum degree fluctuation ≤ ±5%;

[0067] The schematic diagram of the principle of cleaning the circuit board is asFigure 6 As shown, the cleaning is carried out in a low-vacuum environment, using high-purity Ar gas. The gas enters the intake pipe from the gas inlet, is transported through the intake pipe and ejected from the exhaust pipe to rinse the circuit board placed in the middle. The intake port and the exhaust pipe of the vacuum chamber are connected by a corrugated pipe to enable the exhaust pipe to move up and down. Then, a motor drives the exhaust pipe to move up and down reciprocally to achieve gas spraying on the surface of the circuit board and remove possible impurities.

[0068] After the rinsing is completed, close the intake valve and use a vacuum pump to pump the indoor vacuum to a high-vacuum state (reaching the order of 10-3 Pa);

[0069] Step 5: As Figure 3 shown, open the C valve, send the circuit board to be coated into the 3# argon glow discharge cleaning chamber, and perform glow discharge plasma cleaning using argon gas Ar. The cleaning time is controlled within 3 min. By bombarding the contaminant molecules on the surface of the workpiece with high-energy argon ions, they are detached from the surface of the workpiece. For organic contaminants such as oil stains and photoresist, the bombardment of argon ions can decompose them into small molecule fragments, and then these fragments will be pumped away by the vacuum pump. For inorganic contaminants such as metal oxides and dust particles, argon ions can knock them off the surface. Through glow discharge plasma cleaning, the cleanliness of the circuit board is further improved, and the quality of the subsequent coating is enhanced;

[0070] Step 6: Open the D valve, send the circuit board to be coated into the 4# chamber through the conveyor belt, and then close the D valve. There is a SiO2 target here. At this time, an inert gas (argon gas Ar) is introduced into the chamber. When the reaction pressure reaches 0.5-1 Pa, turn on the power supply and apply it to the target to excite glow discharge, start sputtering the SiO2 target, and form a film on the surface of the circuit board. The sputtering power density is controlled at 3 W / cm 2 . Due to the need to maintain the vacuum and stable reaction pressure, as well as the consumption of the sputtering process itself, the argon gas is continuously reduced, and argon gas needs to be continuously introduced during the reaction process, which is regulated and controlled by a flow meter. A film thickness meter can be added here to measure the thickness of the SiO2 thin film formed on the circuit board. When the thin film reaches the predetermined thickness (20 nm), the sputtering can be turned off, the inflow of argon gas can be closed, and the high-vacuum state can be pumped.

[0071] Step 7: After the SiO2 thin film in the 4# chamber is sputtered and the air is pumped back to the high-vacuum state, open the E valve, send the circuit board to be coated into the 5# chamber through the conveyor belt, and then close the E valve. There is an Al2O3 target here. At this time, an inert gas (argon gas Ar) is introduced into the chamber. When the reaction pressure reaches 0.5-1 Pa, turn on the power supply and apply it to the target to excite glow discharge, start sputtering the Al2O3 target, and form a film on the surface of the circuit board. The sputtering power density is controlled at 6 W / cm 2。Due to the need to maintain a vacuum and a stable reaction pressure, as well as the consumption of the sputtering process itself, the argon gas is continuously reduced, and argon gas needs to be continuously introduced during the reaction process, which is regulated and controlled by a flow meter. A film thickness gauge can be added here to measure the thickness of the Al2O3 film formed on the circuit board. When the film reaches the predetermined thickness (500 nm), the sputtering can be turned off, the inflow of argon gas can be closed, and it can be pumped to a high vacuum state.

[0072] Step 8: After the Al2O3 film is fabricated in Chamber 5 and the chamber is restored to a high vacuum state, open Valve F, and send the circuit board with the film deposited through the conveyor belt into the high-vacuum Buffer Chamber 6. Close Valve F.

[0073] Step 9: Open Valve G, and send the circuit board into Chamber 7 (vacuum-atmosphere isolation buffer chamber) with a low vacuum. Close Valve G, and fill the chamber with air to restore the pressure in Chamber 7 to the atmospheric pressure level. At this time, the pressure in Chamber 7 is the same as that of the external environment, there is no pressure difference, open Valve H, and send the circuit board with the film deposited out through the conveyor belt to complete the processes of magnetron sputtering SiO2 film and Al2O3 film.

[0074] Step 10: Take the circuit board with the film deposited and send it into an automatic three-proof paint spraying device, and then spray a layer of polyurethane resin three-proof paint film layer on the circuit board by a nozzle, and its thickness is controlled to be 500 μm.

[0075] Step 11: Send the circuit board with the polyurethane resin three-proof paint film layer sprayed into an infrared curing furnace for curing, or air dry it naturally to complete the fabrication.

[0076] The structural schematic diagram of the circuit board of the power supply device for harsh environments is as Figure 7 shown.

[0077] In the present invention, the first directly contacted film layer 1 deposited on the circuit board uses a SiO2 film, and the SiO2 film is prepared at a temperature below 80 °C, which can avoid the premature decline in performance of the relatively fragile capacitor components on the circuit board due to exposure to a high-temperature environment during the film preparation process. The film layer 2 is then prepared by a low-temperature process to form an alumina (Al2O3) film covering the SiO2 film to improve its thermal conductivity and hydrophilicity, so that the SiO2 film can be protected and the entire film system is made more reliable. On the top layer (i.e., Figure 7Apply a layer of conventional polyurethane resin (UR) three-proof paint film layer to the middle film layer 3). This belongs to the current conventional three-proof treatment technology for circuit boards. Adding this layer of film can further protect the film layers 1 and 2 located inside. On the one hand, it can further reduce their direct contact with the environment, improve the environmental tolerance of the entire film layer, and better protect the circuit board and its components. On the other hand, since the film layers 1 and 2 adopt the vacuum coating process, the prepared thin films are relatively thin (usually at the nm level) and are easily worn through during installation and other operations. While the film layer 3 adopts the coating or spraying process, and the prepared film layer is relatively thick (usually at the millimeter level), the film layer 3 can effectively protect the film layers 1 and 2 from being worn during production and shipping. The use of the film layer 3 can further improve the reliability of the overall film layer.

[0078] Example 2. A preparation method of a circuit board for a power supply device in a harsh environment

[0079] For the preparation method of the circuit board for the power supply device in a harsh environment, three layers of films are sequentially plated on the surface of the circuit board to obtain the circuit board for the power supply device in a harsh environment. The film layer 1 is in direct contact with the circuit board. The film layer 1 is a silicon dioxide film layer, and the thickness of the film layer 1 is 100 nm; the film layer 2 is an aluminum oxide film layer, and the thickness of the film layer 2 is 100 nm; the film layer 3 is a polyurethane resin three-proof paint film layer located at the top layer, and the thickness of the film layer 3 is 1500 μm.

[0080] The schematic flow chart of preparing the circuit board for the power supply device in a harsh environment by using a linear continuous multi-chamber magnetron sputtering device in Example 2 of the present invention is as Figure 2 shown.

[0081] The schematic structural diagram of the linear continuous multi-chamber magnetron sputtering device is as Figure 3 shown, where:

[0082] (1) Each chamber is hermetically separated by a closed valve to ensure independence and no gas leakage between each other;

[0083] (2) The 1# chamber is an air-vacuum isolation buffer chamber (equipment inlet buffer chamber), which continuously inflates and evacuates, and continuously switches between a low vacuum state (1 - 10 Pa) and an atmospheric pressure state, so that the circuit board to be coated can enter the coating equipment from the outside;

[0084] (3) The 2# chamber is a buffer pretreatment chamber + gas vacuum flushing, which is usually in a high vacuum state (10 -3 Pa), used to transfer the circuit board to be coated from the low vacuum chamber to the high vacuum state, and at the same time perform appropriate heating treatment (80 °C) on it to improve the film forming quality of the film layer;

[0085] (4) Chambers 2# - 5# are all equipped with heating devices to keep the coated circuit board at the required temperature (80 °C).

[0086] (5) Chamber 3# is an Ar glow discharge cleaning chamber. High-purity argon gas (Ar) is introduced into the chamber to maintain the chamber pressure within a certain range, generally 0.1 - 1 Pa (this pressure range can ensure the stable formation of subsequent glow discharge).

[0087] (5) Chamber 4# is Coating Chamber 1 (sputtering SiO2 film), equipped with a SiO2 target for magnetron sputtering reaction to sputter the SiO2 film. This chamber is in a high vacuum state (10 -3 Pa) for a long time.

[0088] (6) Chamber 5# is Coating Chamber 2 (sputtering Al2O3 film), equipped with an Al2O3 target for magnetron sputtering reaction to sputter the Al2O3 film. This chamber is in a high vacuum state (10 -3 Pa) for a long time.

[0089] (7) Chamber 6# is a buffer chamber, which is usually in a high vacuum state (10 -3 Pa). It is used for buffering and isolating the coated circuit board when entering from the high vacuum chamber to the low vacuum state to ensure the high vacuum purity of Chambers 4# and 5#, so as to avoid the decline of film formation quality caused by pollution.

[0090] (8) Chamber 7# is an atmosphere-vacuum isolation buffer chamber (equipment outlet chamber), which continuously inflates and pumps air, constantly switching between the low vacuum state (1 - 10 Pa) and the atmospheric pressure state, so that the coated circuit board can be switched from the high vacuum chamber to the low vacuum state and enter the atmospheric pressure state to be sent out of the equipment.

[0091] The specific preparation steps of the circuit board of the power supply equipment for harsh environments are as follows:

[0092] Before starting production, the magnetron sputtering equipment has been evacuated to a vacuum state by a vacuum pump. Among them, Chambers 1#, 3#, and 7# are in the low vacuum state (1 - 10 Pa), and Chambers 2#, 4#, 5#, and 6# are in the high vacuum state (10 -3 Pa).

[0093] Step 1: Perform a simple treatment of blowing and dust removal on the circuit board to be coated to ensure that there are fewer dust and debris on the circuit board before entering the vacuum coating equipment.

[0094] Step 2: As above Figure 3As shown, at this time, open the air release valve of Chamber 1 of the magnetron sputtering equipment to introduce the atmosphere into the chamber until it reaches the atmospheric pressure level. Since both Chamber 1 and the outside are at atmospheric pressure at this time and the pressures are the same, then open Valve A, send the circuit board to be coated into Chamber 1 through the conveyor belt, and close Valve A.

[0095] Step 3: As above Figure 3 As shown, after the circuit board to be coated is sent into Chamber 1 and sealed, start to evacuate Chamber 1 to a low vacuum state (1 - 10 Pa). At this time, the pressure difference between Chamber 1 and Chamber 2 (high vacuum state) is very small. Open Valve B, send the circuit board to be coated into Chamber 2 through the conveyor belt, and close Valve B to restore Chamber 2 to the high vacuum state.

[0096] Step 4: Chamber 2 is a buffer pretreatment + gas vacuum flushing chamber (vacuum cleaning chamber box). The longitudinal sectional view of the vacuum cleaning chamber box of Chamber 2 is as Figure 4 shown, and another longitudinal sectional view of the vacuum cleaning chamber box of Chamber 2 is as Figure 5 shown. Chamber 2 includes a box body. There is a cavity air inlet joint 4 outside the box body. There is a vacuum cavity chamber wall 5 inside the box body. There is an exhaust pipe 6 inside the vacuum cavity chamber wall. There are evenly distributed air outlet holes 7 on the exhaust pipe 6. The middle section of the exhaust pipe 6 is connected to the cavity air inlet joint 4 through a metal bellows 8 with good telescopic performance. There is an air inlet 9 outside the box body that communicates with the vacuum cavity chamber wall 5. The vacuum cavity chamber wall 5 and the air inlet 9 are connected through an air inlet pipe 10. There is an MFC mass flowmeter 12 on the air inlet pipe 10. The air inlet 9 and the exhaust pipe 6 are connected through the bellows 8. The air inlet pipe 10 and the bellows 8 are connected through the cavity air inlet joint 4. There is a motor 13 outside the box body, and a cam link mechanism 14 inside the box body. The rotating shaft of the motor 13 uses magnetic fluid sealing 16. The air inlet 9 of the vacuum chamber and the exhaust pipe 6 are connected through the bellows 8, so that the exhaust pipe 6 can move up and down. The motor 13 rotates to drive the cam link mechanism 14 to drive the exhaust pipe 6 to move vertically up and down reciprocally. There are 2 sliding rods 15 on the exhaust pipe 6. The sliding rods 15 are sleeved in the pin sleeves 17 fixed on the inner wall of the vacuum box. This ensures that when the exhaust pipe 6 moves up and down reciprocally, it can move vertically in the plane where the two pin sleeves 17 are located and will not swing randomly. The section connecting the cavity air inlet joint and the exhaust pipe inside the cavity is a metal bellows with good telescopic performance, which can meet the requirements of up and down reciprocating movement. The air inlet of the vacuum chamber and the exhaust pipe are connected through the bellows, so that the exhaust pipe can move up and down. The exhaust pipe is driven to move up and down by the motor. There is a heater in Chamber 2, which preheats the circuit board to be coated entering it so that it gradually reaches a temperature of 80 °C, which is convenient for high-quality sputtering film formation.

[0097] Pretreat the circuit board, including the steps of evacuating and pre-cleaning in Chamber 2#, dynamic jet shower cleaning, and cleaning in the 3# argon glow discharge cleaning chamber. The specific steps for processing in Chamber 2# are as follows:

[0098] Evacuate Chamber 2# to a high vacuum degree (1×10-3 Pa). Pre-clean the circuit board to be coated in Chamber 2#. Introduce low-pressure argon gas Ar (0.1 - 0.5 bar) for spraying to remove loose contaminants. Pre-cleaning gas flow rate: 10 L / min, pre-cleaning duration: 1 min. Conduct dynamic jet shower cleaning on the circuit board, specifically including 1) Motor-driven exhaust pipe movement: Movement parameters: Stroke range 500 mm, exhaust pipe stroke speed 0.3 m / s. 2) Gas injection control: Gas pressure: 2.0 bar, spraying time: 10 minutes. 3) Vacuum dynamic balance: Monitor the pressure in real time through a vacuum gauge, adjust the intake valve and pump speed to maintain the vacuum degree fluctuation ≤ ±5%. After the flushing is completed, close the intake valve and use a vacuum pump to evacuate the chamber to a high vacuum state (reaching the order of 10-3 Pa).

[0099] Step 5: As Figure 3 shown, open Valve C and send the circuit board to be coated into the 3# argon glow discharge cleaning chamber. Perform glow discharge plasma cleaning with argon gas Ar. Control the cleaning time within 10 min. High-energy argon ions impact the contaminant molecules on the workpiece surface, causing them to detach from the workpiece surface. For organic contaminants such as oil stains and photoresist, the bombardment of argon ions can decompose them into small molecule fragments, and then these fragments will be pumped away by the vacuum pump. For inorganic contaminants such as metal oxides and dust particles, argon ions can knock them off the surface. Further improve the cleanliness of the circuit board through glow discharge plasma cleaning and enhance the quality of subsequent coating.

[0100] Step 6: Open Valve D and send the circuit board to be coated into Chamber 4# through a conveyor belt, then close Valve D. There is a SiO2 target installed here. At this time, introduce an inert gas (argon gas Ar) into the chamber. When the reaction pressure reaches 0.5 - 1 Pa, turn on the power supply and apply it to the target to excite glow discharge, start sputtering the SiO2 target, and form a film on the surface of the circuit board. Control the sputtering power density at 10 W / cm 2 . Due to the need to maintain vacuum and stable reaction pressure, as well as the consumption of the sputtering process itself, the argon gas is continuously reduced, and argon gas needs to be continuously introduced during the reaction process, which is controlled by adjusting through a flow meter. A film thickness gauge can be added here to measure the thickness of the SiO2 thin film formed on the circuit board. When the thin film reaches the predetermined thickness (100 nm), the sputtering can be turned off, the inflow of argon gas can be closed, and the chamber can be evacuated to a high vacuum state.

[0101] Step 7: After the sputtering of the SiO2 thin film in the 4# chamber is completed and the air is pumped out to restore the high-vacuum state, open the E valve, send the circuit board to be coated into the 5# chamber through the conveyor belt, then close the E valve. There is an Al2O3 target here. At this time, introduce an inert gas (argon Ar) into the chamber. When the reaction pressure reaches 0.5 - 1 Pa, turn on the power supply and apply it to the target to excite the glow discharge, start sputtering the Al2O3 target, and form a film on the surface of the circuit board. The sputtering power density is controlled at 12 W / cm 2 . Due to the need to maintain the vacuum and stable reaction pressure, as well as the consumption during the sputtering process itself, the argon gas is continuously reduced, and argon gas needs to be continuously introduced during the reaction process, which is controlled by adjusting the flowmeter. A thickness gauge can be added here to measure the thickness of the Al2O3 thin film formed on the circuit board. When the thin film reaches the predetermined thickness (100 nm), the sputtering can be turned off, the inflow of argon gas can be closed, and the high-vacuum state can be pumped out.

[0102] Step 8: After the Al2O3 thin film is made in the 5# chamber and the high-vacuum state is restored, open the F valve, and send the circuit board with the film coated through the conveyor belt into the high-vacuum 6# buffer chamber. Close the F valve.

[0103] Step 9: Open the G valve, and send the circuit board into the low-vacuum 7# chamber (vacuum-atmosphere isolation buffer chamber). Close the G valve, and fill the chamber with air to restore the pressure in the 7# chamber to the atmospheric pressure level. At this time, the pressure in the 7# chamber is the same as the external environment, and there is no pressure difference. Open the H valve, and send the circuit board with the film coated out through the conveyor belt to complete the process of magnetron sputtering SiO2 thin film and Al2O3 thin film.

[0104] Step 10: Take down the circuit board with the film coated and send it into the automatic three-proof paint spraying equipment, and then spray a layer of polyurethane resin three-proof paint film layer on the circuit board by the nozzle, and its thickness is controlled at 1500 μm.

[0105] Step 11: Send the circuit board with the polyurethane resin three-proof paint film layer sprayed into the infrared curing furnace for curing, or air-dry it naturally to complete the production.

[0106] The structural schematic diagram of the circuit board of the power supply equipment for harsh environments is as Figure 7 shown.

[0107] Example 3. A preparation method of a circuit board of a power supply equipment for harsh environments

[0108] The preparation method of the power supply device circuit board for harsh environments involves sequentially plating three layers of film on the circuit board surface to obtain the circuit board for power supply devices in harsh environments. Film layer 1 is in direct contact with the circuit board. Film layer 1 is a silicon dioxide film layer with a thickness of 50 nm. Film layer 2 is an aluminum oxide film layer with a thickness of 300 nm. Film layer 3 is a polyurethane resin three-proof paint film layer located on the top layer with a thickness of 1000 μm.

[0109] The schematic process diagram of preparing the power supply device circuit board for harsh environments using a linear continuous multi-chamber magnetron sputtering device in Embodiment 3 of the present invention is as Figure 2 shown.

[0110] The schematic structural diagram of the linear continuous multi-chamber magnetron sputtering device is as Figure 3 shown, where:

[0111] (1) Each chamber is hermetically separated by a sealed valve to ensure independence and no gas leakage between each other.

[0112] (2) Chamber 1# is an air-vacuum isolation buffer chamber (equipment inlet buffer chamber), which continuously inflates and pumps air, and continuously switches between a low vacuum state (1 - 10 Pa) and an atmospheric pressure state, so that the circuit board to be coated can enter the coating equipment from the outside.

[0113] (3) Chamber 2# is a buffer pretreatment chamber + gas vacuum flushing, which is usually in a high vacuum state (10 -3 Pa), used to bring the circuit board to be coated from the low vacuum chamber to the high vacuum state, and at the same time perform appropriate heat treatment (65 °C) on it to improve the film formation quality of the film layer.

[0114] (4) Chambers 2# - 5# all have heating devices to keep the coated circuit board at the required temperature (65 °C).

[0115] (5) Chamber 3# is an Ar gas glow discharge cleaning chamber. High-purity argon gas (Ar) is introduced into the chamber to maintain the chamber pressure within a certain range, generally 0.1 - 1 Pa (this pressure range can ensure the stable formation of subsequent glow discharge).

[0116] (6) Chamber 4# is Coating Chamber 1 (sputtering SiO2 thin film), equipped with a SiO2 target, used for magnetron sputtering reaction to sputter SiO2 thin film. This chamber is in a high vacuum state (10 -3 Pa) for a long time.

[0117] (7) Chamber 5# is Coating Chamber 2 (sputtering Al2O3 thin film), equipped with an Al2O3 target, used for magnetron sputtering reaction to sputter Al2O3 thin film. This chamber is in a high vacuum state (10 -3 Pa) for a long time.

[0118] (8) The 6# chamber is a buffer chamber, which is usually in a high vacuum state (10 -3 Pa), used to buffer and isolate the circuit board with the film deposited from the high vacuum chamber to the low vacuum state, so as to ensure the high vacuum purity of the 4# and 5# reaction chambers and prevent the film forming quality from decreasing due to contamination;

[0119] (9) The 7# chamber is an atmosphere-vacuum isolation buffer chamber (equipment outlet chamber), which continuously inflates and evacuates, and continuously switches between the low vacuum state (1 - 10 Pa) and the atmospheric pressure state, so that the circuit board with the film deposited can be switched from the high vacuum chamber to the low vacuum state and enter the atmospheric pressure state to be sent out of the equipment;

[0120] The specific preparation steps of the circuit board of the power supply equipment for harsh environments are as follows:

[0121] Before starting production, the magnetron sputtering equipment has been evacuated to a vacuum state by a vacuum pump. Among them, the 1# chamber, 3# chamber, and 7# chamber are in the low vacuum state (1 - 10 Pa), and the 2# chamber, 4# chamber, 5# chamber, and 6# chamber are in the high vacuum state (10 -3 Pa).

[0122] Step 1: Perform a simple treatment of blowing and dust removal on the circuit board to be coated to ensure that there are fewer dust and debris on the circuit board before entering the vacuum coating equipment.

[0123] Step 2: As shown above Figure 3 At this time, open the air release valve of the 1# chamber of the magnetron sputtering equipment to introduce the atmosphere into the chamber to make it reach the atmospheric pressure level. Since both the 1# chamber and the outside are at the atmospheric pressure at this time and the pressures are the same, then open valve A, and send the circuit board to be coated into the 1# chamber through the conveyor belt, and close valve A.

[0124] Step 3: As shown above Figure 3 After the circuit board to be coated is sent into the 1# chamber and sealed, start to evacuate the 1# chamber to the low vacuum state (1 - 10 Pa). At this time, the pressure difference between the 1# and 2# chambers (high vacuum state) is very small. Open valve B, and send the circuit board to be coated into the 2# chamber through the conveyor belt, and close valve B to make the 2# chamber return to the high vacuum state.

[0125] Step 4: The 2# chamber is a buffer pretreatment + gas vacuum flushing chamber (vacuum cleaning chamber box). The longitudinal sectional view of the vacuum cleaning chamber box of the 2# chamber is as shown in Figure 4 As shown, and the other longitudinal sectional view of the vacuum cleaning chamber box of the 2# chamber is as shown in Figure 5As shown in the figure. The 2# chamber includes a box body, with a cavity air inlet connector 4 provided outside the box body. Inside the box body, there is a vacuum cavity chamber wall 5. Inside the vacuum cavity chamber wall, there is an exhaust pipe 6. The exhaust pipe 6 is provided with evenly distributed air outlet holes 7. The middle section of the exhaust pipe 6 is connected to the cavity air inlet connector 4 through a metal bellows 8 with good telescopic performance. Outside the box body, there is an air inlet 9 connected to the vacuum cavity chamber wall 5. The vacuum cavity chamber wall 5 and the air inlet 9 are connected through an air inlet pipe 10. An MFC mass flowmeter 12 is provided on the air inlet pipe 10. The air inlet 9 and the exhaust pipe 6 are connected through the bellows 8. The air inlet pipe 10 and the bellows 8 are connected through the cavity air inlet connector 4. Outside the box body, there is a motor 13. Inside the box body, there is a cam-link mechanism 14. The rotating shaft of the motor 13 adopts magnetic fluid sealing 16. The air inlet 9 and the exhaust pipe 6 of the vacuum chamber are connected through the bellows 8, enabling the exhaust pipe 6 to move up and down. The rotation of the motor 13 drives the cam-link mechanism 14 to drive the exhaust pipe 6 to move vertically up and down reciprocally. Two slide bars 15 are installed on the exhaust pipe 6. The slide bars 15 are sleeved in the pin sleeves 17 fixed on the inner wall of the vacuum box body, which ensures that when the exhaust pipe 6 moves up and down reciprocally, it can move vertically on the plane where the two pin sleeves 17 are located without random swinging. The section connecting the cavity air inlet connector and the exhaust pipe inside the cavity is a metal bellows with good telescopic performance, which can meet the requirements of up and down reciprocating movement. The air inlet and the exhaust pipe of the vacuum chamber are connected through the bellows, enabling the exhaust pipe to move up and down. The exhaust pipe is driven to move up and down by the motor. A heater is provided in the 2# chamber, which preheats the circuit board to be coated entering it, gradually raising its temperature to 65 °C, facilitating high-quality sputtering film formation.

[0126] The circuit board is pre-treated, including the steps of evacuating and pre-cleaning in the 2# chamber, dynamic jet flushing cleaning, and cleaning in the 3# argon glow discharge cleaning chamber. The specific steps for treatment in the 2# chamber are as follows:

[0127] The 2# chamber is evacuated to a high vacuum degree (1×10-3 Pa). The circuit board to be coated is pre-cleaned in the 2# chamber, and low-pressure argon gas Ar (0.1 - 0.5 bar) is introduced for spraying to remove loose contaminants. The pre-cleaning gas flow rate: 7 L / min, pre-cleaning duration: 30 s. Dynamic jet flushing cleaning is performed on the circuit board, specifically including 1) Motor-driven movement of the exhaust pipe: Movement parameters: Stroke range 300 mm, exhaust pipe stroke speed 0.2 m / s, 2) Gas injection control: Gas pressure: 1 bar, spraying time: 5 minutes, 3) Vacuum dynamic balance: The pressure is monitored in real time through a vacuum gauge, and the intake valve and pump speed are adjusted to maintain the vacuum degree fluctuation ≤ ±5%;

[0128] After the flushing is completed, the intake valve is closed, and the vacuum in the chamber is evacuated to a high vacuum state (reaching the order of 10-3 Pa) by a vacuum pump;

[0129] Step 5: As shown in Figure 3 , open Valve C, and send the circuit board to be coated into the 3# argon glow discharge cleaning chamber. Perform glow discharge plasma cleaning with argon gas Ar, and control the cleaning time within 5 minutes. By bombarding the contaminant molecules on the workpiece surface with high-energy argon ions, they are detached from the workpiece surface. For organic contaminants such as oil stains and photoresist, the bombardment of argon ions can decompose them into small molecule fragments, and then these fragments will be pumped away by the vacuum pump. For inorganic contaminants such as metal oxides and dust particles, argon ions can knock them off the surface. Further improve the cleanliness of the circuit board through glow discharge plasma cleaning and enhance the quality of subsequent coating;

[0130] Step 6: Open Valve D, send the circuit board to be coated into Chamber 4 through the conveyor belt, and then close Valve D. There is a SiO2 target installed here. At this time, introduce an inert gas (argon gas Ar) into the chamber. When the reaction pressure reaches 0.5 - 1 Pa, turn on the power supply and apply it to the target to excite glow discharge, start sputtering the SiO2 target, and form a film on the surface of the circuit board. The sputtering power density is controlled at 6 W / cm 2 . Due to the need to maintain vacuum and stable reaction pressure, as well as the consumption of the sputtering process itself, the argon gas is continuously reduced, and argon gas needs to be continuously introduced during the reaction process, which is adjusted and controlled by a flow meter. A film thickness gauge can be added here to measure the thickness of the SiO2 thin film formed on the circuit board. When the thin film reaches the predetermined thickness (50 nm), the sputtering can be turned off, the inflow of argon gas can be closed, and it can be pumped to a high vacuum state.

[0131] Step 7: After the SiO2 thin film in Chamber 4 is sputtered and the air is pumped back to a high vacuum state, open Valve E, send the circuit board to be coated into Chamber 5 through the conveyor belt, and then close Valve E. There is an Al2O3 target installed here. At this time, introduce an inert gas (argon gas Ar) into the chamber. When the reaction pressure reaches 0.5 - 1 Pa, turn on the power supply and apply it to the target to excite glow discharge, start sputtering the Al2O3 target, and form a film on the surface of the circuit board. The sputtering power density is controlled at 10 W / cm 2 . Due to the need to maintain vacuum and stable reaction pressure, as well as the consumption of the sputtering process itself, the argon gas is continuously reduced, and argon gas needs to be continuously introduced during the reaction process, which is adjusted and controlled by a flow meter. A film thickness gauge can be added here to measure the thickness of the Al2O3 thin film formed on the circuit board. When the thin film reaches the predetermined thickness (300 nm), the sputtering can be turned off, the inflow of argon gas can be closed, and it can be pumped to a high vacuum state.

[0132] Step 8: After the Al2O3 thin film is fabricated in Chamber 5 and the chamber is restored to a high vacuum state, open Valve F, and send the coated circuit board into the high-vacuum 6# buffer chamber through the conveyor belt. Close Valve F.

[0133] Step 9: Open valve G and send the circuit board into chamber 7# (vacuum-atmosphere isolation buffer chamber) with low vacuum. Close valve G and fill the chamber with air to restore the pressure in chamber 7# to atmospheric pressure. At this time, the pressure in chamber 7# is the same as that of the external environment, and there is no pressure difference. Open valve H and send out the circuit board with the film plated through the conveyor belt, completing the processes of magnetron sputtering SiO2 film and Al2O3 film.

[0134] Step 10: Take down the circuit board with the film plated and send it into the automatic three-proof paint spraying equipment. Then, spray a layer of polyurethane resin three-proof paint film layer on the circuit board by the nozzle, and its thickness is controlled to be 1000μm.

[0135] Step 11: Send the circuit board with the polyurethane resin three-proof paint film layer sprayed into the infrared curing furnace for curing, or let it dry naturally to complete the production.

[0136] The structural schematic diagram of the circuit board of the power supply equipment for harsh environment is as Figure 7 shown.

[0137] Comparative Example 1: The circuit board in this comparative example has no protective film layer.

[0138] Comparative Example 2: Preparation method of the circuit board of the power supply equipment

[0139] The preparation method of the circuit board of the power supply equipment is that only a conventional polyurethane resin (UR) three-proof paint film layer is sprayed on the surface of the circuit board for protection, and its thickness is the same as that of the polyurethane resin three-proof paint film layer in Example 3.

[0140] Comparative Example 3: Preparation method of the circuit board of the power supply equipment

[0141] The preparation method of the circuit board of the power supply equipment is that three layers of films are sequentially plated on the surface of the circuit board to obtain the circuit board of the power supply equipment for harsh environment. Film layer 1 is in direct contact with the circuit board. Film layer 1 is a silicon dioxide film layer, and the thickness of film layer 1 is 50nm; film layer 2 is an aluminum oxide film layer, and the thickness of film layer 2 is 300nm; film layer 3 is a polyurethane resin three-proof paint film layer located on the top layer, and the thickness of film layer 3 is 1000μm.

[0142] The preparation method of the circuit board of this comparative example power supply equipment is similar to that of Example 3.

[0143] The difference from Example 3 is that the preparation method of the circuit board of the power supply equipment does not include the step of dynamically jetting and flushing the circuit board for cleaning.

[0144] Test Example 1: Performance test

[0145] 1. Test materials: The circuit board of the power supply device for harsh environments prepared in Example 3, the circuit board without a protective film layer in Comparative Example 1, and the circuit board of the power supply device prepared by spraying and protecting with a conventional polyurethane resin (UR) three-proof paint film layer in Comparative Example 2.

[0146] 2. Test methods:

[0147] Before the experiment, refer to Method 302 Insulation Resistance Test in GJB 360A-96 "Test Methods for Electronic and Electrical Components" to detect the insulation resistance of the circuit board of the power supply device for harsh environments prepared in Example 3, the circuit board without a protective film layer in Comparative Example 1, and the circuit board of the power supply device prepared by spraying and protecting with a conventional polyurethane resin (UR) three-proof paint film layer in Comparative Example 2. Use an insulation resistance tester to apply a 500V DC voltage and read the measured value 1 minute after power-on. Refer to Method 301 Dielectric Withstanding Voltage Test in GJB 360A-96 "Test Methods for Electronic and Electrical Components" to test the dielectric withstand voltage of the circuit board of the power supply device for harsh environments prepared in Example 3, the circuit board without a protective film layer in Comparative Example 1, and the circuit board of the power supply device prepared by spraying and protecting with a conventional polyurethane resin (UR) three-proof paint film layer in Comparative Example 2.

[0148] Refer to GJB150.11A-2009 "Environmental Test Methods for Military Equipment Laboratory - Part 11: Salt Spray Test" to conduct a salt spray test on the circuit board of the power supply device for harsh environments prepared in Example 3, the circuit board without a protective film layer in Comparative Example 1, and the circuit board of the power supply device prepared by spraying and protecting with a conventional polyurethane resin (UR) three-proof paint film layer in Comparative Example 2. The test temperature is (35±2)°C, the mass fraction of the salt solution is 5%±1% (NaCl), the pH value of the salt solution is 6.5 - 7.2, and the salt spray deposition rate is (1.0 - 2.0) mL / (80cm 2 ·h); the spraying method is continuous. After 240h of the salt spray test, conduct a damp heat test. The damp heat test is carried out according to the humidity resistance test in GJB 360A-96 "Test Methods for Electronic and Electrical Components", with a total of 10 cycles, and a 100V DC polarization voltage is applied during the test. One cycle is 24h, divided into three stages: heating up, high-temperature holding, and cooling down, and high humidity conditions are maintained during this period. After 240h of the damp heat test, observe the appearance of the materials after the experiment, and detect the insulation resistance and dielectric withstand voltage of the materials after the experiment. Refer to Method 301 Dielectric Withstanding Voltage Test in GJB 360A-96 "Test Methods for Electronic and Electrical Components" to test the dielectric withstand voltage of the samples in Example 3, Comparative Example 1, and Comparative Example 2.

[0149] 3. The test results are shown in Table 1.

[0150] Table 1: Performance test results

[0151]

[0152]

[0153] As can be seen from Table 1, after the experiment of the circuit board of the power supply equipment for harsh environments prepared in Example 3 of the present invention, slight corrosion appears on the appearance, a small amount of rust appears in the plated holes, and slight patchy corrosion appears on the coating layer. After the experiment of the circuit board without a protective film layer in Comparative Example 1, severe corrosion appears on the appearance, corrosion appears in the plated holes, and patchy corrosion and pinholes appear everywhere on the coating layer; after the experiment of the circuit board of the power supply equipment prepared in Comparative Example 2, patchy corrosion appears on the appearance, corrosion appears in the plated holes, and patchy corrosion appears on the coating layer. The change in insulation resistance of the circuit board of the power supply equipment for harsh environments prepared in Example 3 of the present invention before and after the experiment is significantly smaller than that of Comparative Example 1 and Comparative Example 2; after the experiment of the circuit board of the power supply equipment for harsh environments prepared in Example 3 of the present invention, the dielectric withstand voltage is normal, while the dielectric withstand voltage of the circuit board without a protective film layer in Comparative Example 1 breaks down after the experiment, and sparks appear in the dielectric withstand voltage of the circuit board of the power supply equipment prepared in Comparative Example 2 after the experiment. Thus, compared with Comparative Example 1 and Comparative Example 2, the circuit board of the power supply equipment for harsh environments prepared in Example 3 of the present invention has excellent damp heat and salt spray resistance performance and can better cope with the use in harsh environments such as the ocean.

[0154] Test Example 2: Long-term salt spray test

[0155] 1. Test materials: The circuit board of the power supply equipment for harsh environments prepared in Example 3, and the circuit board of the power supply equipment prepared by spraying and protecting with a conventional polyurethane resin (UR) three-proof paint film layer in Comparative Example 2.

[0156] 2. Test method:

[0157] Take 6 circuit boards of the same batch. The circuit boards are all qualified and all functions are normal after being powered on. Among them, 3 circuit boards are made into circuit boards of power supply equipment for harsh environments according to the method of Example 3, and 3 circuit boards are made into circuit boards of power supply equipment according to the method of Comparative Example 2. The 6 circuit boards after being subjected to the protection treatment are all put into a salt spray test chamber for long-term salt spray test. The test method refers to GJB150.11A-2009 "Environmental Test Methods for Military Equipment in Laboratories - Part 11: Salt Spray Test". The test temperature is (35 ± 2) °C, the mass fraction of the salt solution is 5% ± 1% (NaCl), the pH value of the salt solution is 6.5 - 7.2, and the salt spray deposition rate is (1.0 - 2.0) mL / (80 cm 2 ·h); the spraying method is continuous. After 4 days of the test, take out the circuit boards every other day and power them on to test whether their functions are running normally. Record their average failure time.

[0158] 3. The test results are shown in Table 2.

[0159] Table 2 Long-term salt spray test results

[0160]

[0161] As can be seen from Table 2, compared with the power supply device circuit board prepared in Comparative Example 2, the power supply device circuit board for harsh environments prepared in Example 3 of the present invention has more excellent long-term salt spray resistance performance.

[0162] Test Example Three

[0163] 1. Test materials: The power supply device circuit board for harsh environments prepared by the dynamic jet spray cleaning process in Example 3, and the power supply device circuit board prepared in Comparative Example 3 without using the dynamic jet spray cleaning process.

[0164] 2. Test method:

[0165] Take 6 circuit boards of the same batch. The circuit boards are all qualified, and all functions are normal after being powered on. Among them, 3 circuit boards are made into power supply device circuit boards for harsh environments according to the method of Example 3, and the other 3 circuit boards are made into power supply device circuit boards according to the method of Comparative Example 3. The 6 circuit boards after being subjected to the protection treatment are all put into a salt spray test chamber for long-term salt spray test. The test method refers to GJB150.11A-2009 "Environmental Test Methods for Military Equipment in Laboratory Part 11: Salt Spray Test". The test temperature is (35±2)°C, the mass fraction of the salt solution is 5%±1% (NaCl), the pH value of the salt solution is 6.5-7.2, and the salt spray deposition rate is (1.0-2.0) mL / (80 cm 2 ·h); the spraying method is continuous. After 4 days of the test, take out the circuit boards every other day and power them on to test whether their functions are running normally. Record their average failure time.

[0166] 3. The test results are shown in Table 3.

[0167] Table 3 Long-term Salt Spray Test Results

[0168]

[0169] As can be seen from Table 3, compared with the power supply device circuit board prepared in Comparative Example 3 without using the dynamic jet spray cleaning process, the power supply device circuit board for harsh environments prepared by the dynamic jet spray cleaning process in Example 3 of the present invention has more excellent long-term salt spray resistance performance. In the pre-treatment process of the circuit board of the present invention, the use of the dynamic jet spray cleaning process can improve the cleanliness of the circuit board before vacuum coating, ensure the film-forming quality of the vacuum coating of the circuit board, and thus improve the long-term salt spray performance of the product.

Claims

1. A method for preparing a circuit board for a power supply device for a harsh environment, characterized in that: The power supply equipment circuit board for harsh environments is obtained by sequentially coating N layers of film on the surface of the circuit board, N is a positive integer ≥ 2, and film layer 1 is in direct contact with the circuit board. The film layer 1 is one of a silicon dioxide film layer, an aluminum oxide film layer, a silicon nitride film layer, a titanium dioxide film layer and an aluminum nitride film layer.

2. The method for preparing a circuit board for power supply equipment for harsh environments according to claim 1, characterized in that: When N>2, film layer 2 to film layer (N-1) are respectively one of an aluminum oxide film layer, a silicon nitride film layer, a titanium dioxide film layer and an aluminum nitride film layer; film layer N is one of an acrylic resin conformal coating film layer, a modified epoxy resin conformal coating film layer, a silicone resin conformal coating film layer, a polyurethane resin conformal coating film layer and a polyparaxylene conformal coating film layer.

3. The method for preparing a circuit board for power supply equipment for harsh environments according to claim 1, characterized in that: The thickness of the film layer 1 is 20-100 nm, the thickness of the film layer N is 500-1500 nm; when N>2, the thickness of the film layer 2 to the film layer (N-1) is 100-500 nm.

4. The method for preparing a circuit board for power supply equipment for harsh environments according to claim 1, characterized in that: The following steps are involved: S1 sends the circuit board into the atmosphere-vacuum isolation buffer chamber, evacuates the chamber, and then sends the circuit board into the buffer pretreatment + gas vacuum flushing chamber; S2 evacuates the buffer pretreatment + gas vacuum flushing chamber, uses gas to pre-clean the circuit board and perform dynamic jet flushing cleaning, and then evacuates the chamber after cleaning; S3 sends the cleaned circuit board into a glow discharge cleaning chamber and uses working gas to clean the circuit board; S4 sends the processed circuit board into a coating chamber equipped with a target material, and uses a vacuum coating process to sputter the 1st to N-1th layers of film; S5 sends the coated circuit board obtained in step S4 into the buffer chamber and the vacuum-atmosphere isolation buffer chamber in sequence, and sprays the Nth layer of film after the circuit board is sent out.

5. The method for preparing a circuit board for power supply equipment for harsh environments according to claim 4, characterized in that: In step S1, the vacuum is pumped to 1-10Pa; in step S2, the vacuum is pumped to 1×10-3Pa-5×10-3Pa; in step S2, the gas is argon or nitrogen; in step S3, the working gas is argon or nitrogen.

6. The method for preparing a circuit board for power supply equipment for harsh environments according to claim 4, characterized in that: The specific operation of the pre-cleaning in step S2 is: introducing gas with a pressure of 0.1 to 0.5 bar, the gas flow rate during pre-cleaning is 5 to 10 L / min, and the pre-cleaning time is 10s to 1min; during the dynamic jet shower cleaning in step S2, the motor drives the exhaust pipe to move, and the exhaust pipe stroke speed is 0.1 to 0.3m / s; gas jet control, the gas pressure is 0.5 to 2.0bar, and the spraying time is 2 to 10 minutes.

7. The method for preparing a circuit board for power supply equipment for harsh environments according to claim 4, characterized in that: The vacuum coating process in step S4 is one of magnetron sputtering, chemical vapor deposition, molecular beam epitaxy and atomic layer deposition.

8. The method for preparing a circuit board for power supply equipment for harsh environments according to claim 7, characterized in that: The vacuum coating process is a magnetron sputtering method, and the magnetron sputtering reaction pressure is 0.5-1Pa.

9. The method for preparing a circuit board for power supply equipment for harsh environments according to claim 4, characterized in that: The temperature of the buffer pretreatment + gas vacuum flushing chamber, glow discharge cleaning chamber and coating chamber is 50-80°C; in step S5: The buffer chamber is a high vacuum environment with a high vacuum pressure of 1×10-3Pa~5×10-3Pa; During the process of the coated circuit board obtained in step S4 entering the vacuum-atmosphere isolation buffer chamber, the vacuum-atmosphere isolation buffer chamber is a low vacuum environment with a low vacuum pressure of 1 to 10 Pa. After entering, the valve of the vacuum-atmosphere isolation buffer chamber is closed and the atmosphere is filled in to restore the pressure in the vacuum-atmosphere isolation buffer chamber to the atmospheric pressure level.

10. A circuit board for a power supply device for a harsh environment prepared by the method for preparing a circuit board for a power supply device for a harsh environment according to any one of claims 1 to 9.

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