Air knife structure, printed circuit board tin spraying method and printed circuit board

Abstract

The application discloses a kind of wind knife structure, printed circuit board tin spraying method and printed circuit board, wind knife structure includes wind knife body, wind knife body is equipped with spray pipe, spray pipe and wind knife body form a spray cavity, spray cavity and the gas outlet of spray pipe and the gas outlet of wind knife are communicated, gas entering from spray pipe enters spray cavity after the gas outlet of spray pipe, then, enters the gas outlet of wind knife.The wind knife structure of the application is designed, and the circuit board engineering design and process technical parameter are optimized, thereby effectively solve the tin high, continuous tin and other adverse problems that appear in the area of existing tin spraying product about large copper surface, dense PAD and PTH welding ring, thereby improve the yield of product, save production cost.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing technology, and in particular to an air knife structure, a method for soldering printed circuit boards, and a printed circuit board. Background Technology

[0002] Tin spraying, also known as hot air leveling, involves immersing a flux-coated PCB (circuit board) in molten solder via a tin spraying machine guide rail. This coats the PCB surface with solder, and then heated compressed air is used to smooth out excess solder using an air knife. The molten solder adheres evenly to the copper surface, completing the tin spraying process. The resulting solder layer effectively protects the copper and circuitry from corrosion and oxidation, increasing their mechanical properties and lifespan. However, current tin spraying treatments for PCBs with large copper areas, dense pads, and PTH solder rings often result in solder bridging, short circuits, solder flattening (solder cakes), and misalignment of the cursor points due to high solder density, leading to quality issues. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide an air knife structure, a tin spraying method for printed circuit boards, and a printed circuit board.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] In a first aspect, the present invention provides an air knife structure, including an air knife body, the air knife body being provided with a nozzle, the nozzle and the air knife body forming a spray chamber, the spray chamber being connected to the air outlet of the nozzle and the air outlet of the air knife, gas entering from the nozzle entering the spray chamber through the air outlet of the nozzle, and then entering the air outlet of the air knife.

[0006] Furthermore, the air knife body is provided with a slot, the nozzle is disposed in the slot, and the gap between the inner sidewall of the slot and the outer wall of the nozzle forms the spray cavity.

[0007] Furthermore, the spray chamber has a ring-shaped structure.

[0008] Furthermore, the air outlet of the air knife and the air outlet of the nozzle are arranged opposite each other along the spray cavity.

[0009] Secondly, the present invention also provides a method for soldering printed circuit boards, wherein the soldering operation is performed based on a soldering device, the soldering device including a soldering machine track, a clamp, a solder tank, and the aforementioned air knife structure, wherein there are two air knives, namely a front air knife and a rear air knife, the front air knife and the rear air knife are mounted on the soldering machine track and can move and have their angle adjusted relative to the soldering machine track, the soldering machine track is connected to the circuit board to be processed through the clamp, the solder tank contains molten solder, and the circuit board to be processed can be immersed in the molten solder through the soldering machine track; the method includes:

[0010] Micro-etching is performed on the circuit board to be processed;

[0011] Solder bars are used in conjunction with front and rear air knives to perform solder spraying on the micro-etched circuit boards;

[0012] The circuit board after tin plating is then subjected to a brushing process.

[0013] The circuit board after brushing is subjected to ultrasonic water washing.

[0014] The circuit board after ultrasonic water washing is dried.

[0015] Hole inspection is performed on the dried circuit board.

[0016] Furthermore, the process of using solder bars in conjunction with front and rear air knives to perform solder spraying on the micro-etched circuit board includes:

[0017] Lead-free solder bars are placed in the solder bath as the solder spraying material, and the temperature of the solder bath is controlled at 260℃-280℃.

[0018] Adjust the front wind blade to the first angle and the rear wind blade to the second angle, wherein the first angle is less than or equal to the second angle;

[0019] First, turn on the front air knife to start working, then turn on the rear air knife to start working, and the air pressure of the front air knife is less than that of the rear air knife.

[0020] Furthermore, when the circuit board thickness is less than 0.8mm, the time to descend into the solder bath is 1.9s; when the circuit board thickness is less than 0.8mm-2.0mm, the time to descend into the solder bath is 1s; when the circuit board thickness is greater than 2mm, the time to descend into the solder bath is 1.8s; and the time for the circuit board to be immersed in the solder bath is 4.5s.

[0021] Furthermore, it also includes:

[0022] When the spacing between two adjacent pads on a circuit board is 0.2mm-0.15mm, the pads are designed with green solder mask bridges; if the distance from the trace to the edge of the pad is less than 5mil, the two adjacent pads are designed with an H-type connection.

[0023] Furthermore, it also includes:

[0024] If the distance between the hole rings or between the hole ring and the pad is less than 0.4mm, the hole rings should be shaped and the copper foil removed.

[0025] Thirdly, the present invention also provides a printed circuit board, which is prepared by the printed circuit board tin spraying method described above.

[0026] The beneficial effects of this invention compared to existing technologies are as follows: An air knife structure includes an air knife body with a nozzle. The nozzle and the air knife body form a spray chamber, which is connected to the air outlet of the nozzle and the air outlet of the air knife. Gas entering from the nozzle passes through the nozzle's outlet into the spray chamber and then into the air outlet of the air knife. This invention, through its designed air knife structure and optimized circuit board engineering design and process parameters, effectively solves the defects such as high solder content and solder bridging in existing solder-plated products, particularly in areas with large copper surfaces, dense pads, and PTH solder rings. This improves product yield and saves production costs.

[0027] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other objectives, features and advantages of the present invention more obvious and understandable, preferred embodiments are described in detail below. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A schematic diagram of a wind knife structure provided in a specific embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the tin-spraying device provided in a specific embodiment of the present invention;

[0031] Figure 3 A comparison diagram of the anti-weld bridge design provided for a specific embodiment of the present invention and an existing design;

[0032] Figure 4A comparison diagram of the H-type connection method provided in a specific embodiment of the present invention and an existing design;

[0033] Figure 5 A comparison diagram of the hole-cutting ring and copper foil treatment used in a specific embodiment of the present invention with that of an existing design;

[0034] Figure 6 A schematic diagram of multiple lines in the process edge design provided for a specific embodiment of the present invention;

[0035] Figure 7 A flowchart of a printed circuit board soldering method provided in a specific embodiment of the present invention.

[0036] Figure Labels

[0037] 1. Air knife body; 11. Nozzle; 111. Nozzle outlet; 12. Nozzle chamber; 13. Air knife outlet; 2. Tin spraying machine track; 3. Fixture; 4. Tin cylinder; 100. Circuit board to be processed; 1A. Front air knife; 1B. Rear air knife. Detailed Implementation

[0038] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0040] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0041] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0043] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0044] like Figure 1 As shown, this embodiment of the invention provides an air knife structure, including an air knife body 1. The air knife body 1 is provided with a nozzle 11. The nozzle 11 and the air knife body 1 form a spray chamber 12. The spray chamber 12 is connected to the air outlet 111 of the nozzle 11 and the air outlet 13 of the air knife. The gas entering from the nozzle 11 enters the spray chamber 12 through the air outlet 111 of the nozzle 11 and then enters the air outlet 13 of the air knife.

[0045] The air knife body 1, as the main component of the entire air knife structure, is made of metal materials, such as stainless steel, to ensure good strength and corrosion resistance under high temperature and high pressure working environments. The air knife body 1 has a specific shape and size, the design of which needs to be based on the actual application scenario.

[0046] The nozzle 11 is mounted on the air knife body 1, and is made of a high-temperature resistant and corrosion-resistant metal. The diameter of the nozzle 11 affects the gas velocity and flow rate, thus affecting the working effect of the air knife. In practical applications, a nozzle 11 with an appropriate diameter can be selected according to the required gas pressure and flow rate. For example, for situations requiring a larger airflow impact force to remove excess solder from a PCB board, a nozzle 11 with a slightly larger diameter can be selected. The nozzle 11 can be installed on the air knife body 1 by welding or threaded connection to ensure a secure connection and prevent gas leakage.

[0047] A spray cavity 12 is formed between the nozzle 11 and the air knife body 1. In one embodiment, the air knife body 1 has a slot, and the nozzle 11 is disposed within the slot. The space between the inner wall of the slot and the outer wall of the nozzle 11 forms the spray cavity 12. This structural design is simple and easy to manufacture. The shape of the slot can be circular, rectangular, etc., and the shape of the nozzle 11 must be adapted to the slot to ensure the sealing of the spray cavity 12 and the smooth flow of gas.

[0048] The gas entering from the nozzle 11 first enters the spray chamber 12 through the outlet 111 of the nozzle 11. The outlet 111 of the nozzle 11 can be designed in various shapes, such as circular, elliptical, or slit-shaped. Different outlet shapes will affect the initial distribution of the gas entering the spray chamber 12. After entering the spray chamber 12, due to the special structural design of the spray chamber 12, the gas will undergo a certain degree of mixing and diffusion within the spray chamber 12, and then be blown out from the outlet 13 of the air knife. The outlet 13 of the air knife and the outlet 111 of the nozzle 11 are arranged opposite to each other along the spray chamber 12. This relative arrangement can enable the gas to form a relatively stable flow path within the spray chamber 12, ensuring that the gas blown out from the outlet of the air knife has a uniform pressure and velocity distribution.

[0049] Through the coordinated design of the nozzle 11, the spray chamber 12 and the air knife outlet, the gas entering from the nozzle 11 can be blown in the opposite direction from the air knife outlet after passing through the spray chamber 12, making the air pressure more uniform, improving the uniformity of the solder thickness on the solder surface, and avoiding the problem of excessive solder.

[0050] In one embodiment, the spray chamber 12 has an annular structure. The annular spray chamber 12 enables a more uniform distribution of gas within the chamber. When gas enters the annular spray chamber 12 from the nozzle 11, due to the symmetry of the annular structure, the gas can diffuse uniformly within the annular space, avoiding gas accumulation in local areas or uneven flow rates. In the PCB board solder plating process, the airflow blown from the air knife outlet has a more uniform distribution on the PCB board surface, which can more effectively level the molten solder and reduce problems such as solder spikes and solder bridging.

[0051] This invention also provides a method for solder spraying on printed circuit boards, which involves performing the solder spraying operation using a solder spraying device, such as... Figure 2 As shown, the tin spraying device includes a tin spraying machine track 2, a clamp 3, a tin cylinder 4, and the aforementioned air knife structure. There are two air knife structures, namely a front air knife 1A and a rear air knife 1B. The front air knife 1A and the rear air knife 1B are installed on the tin spraying machine track 2 and can move and be angled relative to the tin spraying machine track 2. The tin spraying machine track 2 is connected to the circuit board 100 to be processed through the clamp 3. The tin cylinder 4 contains molten tin, and the circuit board 100 to be processed can be immersed in the molten tin through the tin spraying machine track 2.

[0052] The tin plating machine track 2 is made of high-strength metal materials, such as aluminum alloy or stainless steel. The track is straight, and its length is determined according to the space of the production site and actual production needs. The cross-sectional shape of the track can be rectangular or I-shaped.

[0053] The main function of the solder spraying machine track 2 is to provide a moving path for the fixture 3 and the circuit board 100 to be processed. It is fixed to the worktable of the solder spraying equipment by a support structure installed at the bottom. The support structure can be height-adjustable anchor bolts to adjust the level of the track according to actual production needs.

[0054] The design of clamp 3 needs to be customized according to the size, shape, and material of the circuit board. For common rectangular PCB boards, a jaw-type clamp 3 can be used. The jaws are usually made of high-temperature resistant plastics or metals, such as PTFE or aluminum alloy. The inner side of the jaws can be designed with anti-slip textures or rubber pads to increase friction with the circuit board and prevent the circuit board from slipping during movement. The clamp 3 can be opened and closed manually by rotating a screw or pulling a handle, which is suitable for small-batch production or experimental stages; or it can be pneumatic or electric, using compressed air or a motor to control the movement of the jaws, which is suitable for large-scale production and can improve production efficiency and operational consistency.

[0055] The fixture 3 is connected to the solder spraying machine track 2 via a slider or roller. The slider or roller is typically made of wear-resistant engineering plastic or metal, such as nylon or carbon steel. This connection method allows the fixture 3 to move smoothly on the track, and the moving speed can be adjusted according to the production process requirements.

[0056] Solder bath 4 is used to hold molten solder and is made of stainless steel to ensure its corrosion resistance and strength in high-temperature environments. Solder bath 4 is rectangular or cylindrical in shape, and its dimensions are determined based on production scale and the number of circuit boards processed at one time. A heating device, such as an electric heating wire or a gas-fired furnace, is installed at the bottom of solder bath 4 to melt the solder bars and maintain the temperature of the molten solder within a suitable range.

[0057] The front air knife 1A and the rear air knife 1B are mounted on the soldering machine track 2, and can be fixed by an adjustable bracket. The bracket is made of metal, such as aluminum alloy or carbon steel, and has sufficient strength and stability. The bracket is equipped with an adjustment mechanism to allow the air knife to move and adjust its angle relative to the soldering machine track 2. For example, the adjustment mechanism can be a translation adjustment device consisting of a screw and a nut, where rotating the nut allows the air knife to move back and forth along the track direction; the angle adjustment device can be composed of a hinge and an angle dial, where loosening the hinge bolt adjusts the angle of the air knife, and then tightening the bolt to fix it.

[0058] The front air knife 1A and the rear air knife 1B work together during operation. The front air knife 1A is activated first, using lower air pressure and a smaller angle to initially blow and level the molten solder on the surface of the circuit board rising from the solder bath 4, removing excess solder. The rear air knife 1B is then activated, using higher air pressure and a slightly larger angle to further clean and level the circuit board surface, ensuring that the molten solder adheres more evenly to the circuit board surface.

[0059] With its movable and angle-adjustable air knife structure, the position and angle of the air knife can be precisely adjusted according to the shape, size, and solder plating process requirements of different circuit boards. This allows the airflow from the air knife to act more effectively on the circuit board surface, uniformly removing excess solder and avoiding problems such as solder buildup and bridging, thereby improving the quality of solder plating. For example, for PCBs with complex shapes and dense circuitry, precise adjustment of the air knife angle ensures that the airflow reaches every area that needs to be treated, resulting in a uniform solder layer coverage.

[0060] The combined design of the solder spraying machine track 2, clamp 3, and adjustable air knife allows this solder spraying device to adapt to the solder spraying needs of circuit boards of different sizes, shapes, and materials.

[0061] like Figure 7 As shown, a method for soldering printed circuit boards includes the following steps: S10-S60.

[0062] S10. Perform micro-etching on the circuit board 100 to be processed.

[0063] The main components of the micro-etching solution are H2SO4 (concentration 3%) and Na2S2O8 (concentration 120±20g / L). The micro-etching depth is controlled at 0.8±0.1μm, the delivery speed is 3000±100mm / min, and the spraying pressure is 1.3±0.3kgf / cm2.

[0064] S20. Solder bars are used in conjunction with front air knife 1A and rear air knife 1B to perform solder spraying on the circuit board after micro-etching.

[0065] In one embodiment, step S20 specifically includes the following steps: S201-S203.

[0066] S201. Place the lead-free solder bar as the solder spraying material in the solder bath 4, and control the temperature of the solder bath 4 at 260℃-280℃.

[0067] S202. Adjust the front wind blade 1A to the first angle and the rear wind blade 1B to the second angle, wherein the first angle is less than or equal to the second angle.

[0068] S203. First, turn on the front air knife 1A to start working, then turn on the rear air knife 1B to start working, and the air pressure of the front air knife 1A is less than the air pressure of the rear air knife 1B.

[0069] For steps S201-S203, the angle of the front air knife 1A is set to 2-4°, the angle of the rear air knife 1B is set to 4-6°, the temperature of the air outlet 13 of the air knife is 360°, and the distance between the front air knife 1A and the rear air knife 1B on the solder spraying machine track 2 is 2-4mm. The air pressure of the front air knife 1A is set to 3.8kg / cm², and the air pressure of the rear air knife 1B is set to 4.3kg / cm². The front air knife 1A is turned on first, followed by the rear air knife 1B. Since the air pressure of the front air knife 1A is lower than that of the rear air knife 1B, the front air knife 1A is turned on first. The hot air flattens the solder on the front PCB board pads, and the solder in the hole ring will be blown to the back, causing the solder in the hole ring to accumulate. Then the rear air knife 1B is turned on and the air pressure is increased. This removes and flattens the excess solder on the hole ring on the back.

[0070] Specifically, when the circuit board thickness is less than 0.8mm, the time to descend into the solder bath 4 is 1.9s; when the circuit board thickness is less than 0.8mm-2.0mm, the time to descend into the solder bath 4 is 1s; when the circuit board thickness is greater than 2mm, the time to descend into the solder bath 4 is 1.8s; the time for the circuit board to be immersed in the solder bath 4 is 4.5s, and the time for the circuit board to rise after soldering is 2.5s.

[0071] Additionally, if production stops for 3 minutes or more during the tin spraying process, it is necessary to perform two empty spraying cycles and a 10-second soak before resuming production to prevent solder contamination that could lead to high solder levels or bridging. Furthermore, after spraying every 60 circuit boards, the front air knife 1A and rear air knife 1B must be cleaned to prevent solder slag from clogging the air knives and leaving residue on the board surface.

[0072] S30. Perform a brushing process on the circuit board after the tin plating treatment.

[0073] The PCBs after tin plating are conveyed at a speed of 4000 mm / min to ensure they maintain an appropriate pace during subsequent processing. This prevents incomplete processing due to excessive speed or reduced production efficiency due to insufficient speed. The air-floating bed is a device that uses airflow to suspend and convey the PCBs. During this process, it is crucial to prevent the boards from overlapping, as this can cause friction during transport, scratching the already tinned surface and affecting the PCB's appearance and performance.

[0074] After the PCB board is tin-plated, it is transported to the designated location and then treated with a brush. This effectively removes any burrs, debris, or uneven tin layers that may be present on the PCB board surface, making the board surface smoother and flatter.

[0075] S40. Perform ultrasonic water washing on the circuit board after brushing.

[0076] After brushing, the PCB board is further cleaned using ultrasonic water washing. Ultrasonic water washing utilizes the cavitation effect generated by ultrasound in a liquid, causing tiny bubbles in the liquid to rapidly generate, grow, and burst under the action of ultrasound, producing powerful impact force and micro-jet, which can penetrate deep into the fine channels and gaps of the PCB board, thoroughly cleaning away debris, residual abrasive, and other impurities generated during the brushing process, ensuring the cleanliness of the PCB board.

[0077] S50. Dry the circuit board after ultrasonic water washing.

[0078] After brushing and ultrasonic washing, residual moisture remains on the PCB surface, requiring drying. The drying process removes moisture from the PCB surface and holes, preventing moisture residue from causing short circuits, corrosion, and other problems during subsequent use. It also provides a dry surface for inspection, facilitating clearer observation and testing.

[0079] S60. Perform hole inspection on the dried circuit board.

[0080] After drying, the PCB board needs to undergo a comprehensive inspection, with a focus on checking for any blocked holes. Blocked holes can affect the electrical connection performance of the PCB board, leading to problems such as poor signal transmission or short circuits. Therefore, each hole needs to be carefully inspected to ensure that there are no obstructions inside, guaranteeing that the quality and performance of the PCB board meet the requirements.

[0081] It should be noted that, as Figure 3 As shown, when the distance between two adjacent pads on a circuit board is 0.2mm-0.15mm, the pads adopt a green solder mask bridge design. This design can prevent solder bridging and short circuits during soldering due to the small distance between the pads.

[0082] It should also be noted that, such as Figure 4 As shown, for the same network pad, if the distance from the trace to the edge of the pad is less than 5mil, the two adjacent pads should be designed as H-type connections, or anti-tombstone design should be adopted to avoid the risk of solder bridging after SMT.

[0083] It should also be noted that, such as Figure 5 As shown, if the distance between the hole rings or between the hole ring and the pad is less than 0.4mm, the hole rings are shaped and copper is removed. This design increases the hole ring spacing and prevents short circuits caused by solder bridging.

[0084] It should also be noted that, such as Figure 6 As shown, multiple lines are designed on the process side to improve the connection between the fixture 3 and the PCB board during the solder spraying process, and to prevent the PCB board from falling into the solder pot 4 during the solder spraying process, which would cause problems such as high solder level, solder bridging and board damage.

[0085] This invention also provides a printed circuit board, which is manufactured using the tin-spraying method described above.

[0086] This invention, through the design of an air knife structure and optimization of circuit board engineering design and process parameters, effectively solves the defects such as high solder content and solder bridging in existing tin-plated products in areas such as large copper surfaces, dense PADs, and PTH solder rings, thereby improving product yield and saving production costs.

[0087] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for solder plating on a printed circuit board, characterized in that, The tin spraying operation is performed using a tin spraying device, which includes a tin spraying machine track, a fixture, a tin cylinder, and an air knife structure. The air knife structure includes an air knife body with a nozzle. The nozzle and the air knife body form a spray chamber, which is connected to the air outlet of the nozzle and the air outlet of the air knife. Gas entering from the nozzle enters the spray chamber through the air outlet of the nozzle and then enters the air outlet of the air knife. The air outlet of the air knife and the air outlet of the nozzle are arranged opposite to each other along the spray chamber. The air knife structure has two air knives, a front air knife and a rear air knife, which are mounted on the tin spraying machine track and can move and have their angle adjusted relative to the tin spraying machine track. The tin spraying machine track is connected to the circuit board to be processed through the fixture. The tin cylinder contains molten tin, and the circuit board to be processed can be immersed in the molten tin through the tin spraying machine track. The printed circuit board soldering method includes: Micro-etching is performed on the circuit board to be processed; Solder bars are used in conjunction with front and rear air knives to perform solder spraying on the micro-etched circuit boards; The circuit board after tin plating is then subjected to a brushing process. The circuit board after brushing is subjected to ultrasonic water washing. The circuit board after ultrasonic water washing is dried. Hole inspection is performed on the dried circuit board. The printed circuit board soldering method further includes: When the spacing between two adjacent pads on a circuit board is 0.2mm-0.15mm, the pads should be designed with green solder mask bridges; if the distance from the trace to the edge of the pad is less than 5mil, the two adjacent pads should be designed with an H-type connection. The printed circuit board soldering method further includes: If the distance between the hole rings or between the hole ring and the pad is less than 0.4mm, the hole rings should be shaped and the copper foil removed.

2. The method for solder plating on a printed circuit board according to claim 1, characterized in that, The air knife body has a slot, the nozzle is disposed in the slot, and the space between the inner wall of the slot and the outer wall of the nozzle forms the spray cavity.

3. The method for solder plating on a printed circuit board according to claim 1, characterized in that, The spray chamber has a ring-shaped structure.

4. The method for solder plating on a printed circuit board according to claim 1, characterized in that, The process of applying solder bars, along with front and rear air knives, to the micro-etched circuit board for solder plating includes: Lead-free solder bars are placed in the solder bath as the solder spraying material, and the temperature of the solder bath is controlled at 260℃-280℃; Adjust the front wind blade to the first angle and the rear wind blade to the second angle, wherein the first angle is less than or equal to the second angle; First, turn on the front air knife to start working, then turn on the rear air knife to start working, and the air pressure of the front air knife is less than that of the rear air knife.

5. A method for solder plating on a printed circuit board according to claim 4, characterized in that, When the circuit board thickness is less than 0.8mm, the time to descend into the solder bath is 1.9s; when the circuit board thickness is less than 0.8mm-2.0mm, the time to descend into the solder bath is 1s; when the circuit board thickness is greater than 2mm, the time to descend into the solder bath is 1.8s; the immersion time of the circuit board in the solder bath is 4.5s.

6. A printed circuit board, characterized in that, The printed circuit board is manufactured using the tin-plating method for printed circuit boards as described in any one of claims 1-5.

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