High-standard PCB ENIG surface treatment optimization process and device

Abstract

The application is suitable for the field of PCB ENIG surface treatment technology, and provides a high-standard PCB ENIG surface treatment optimization process and device, which comprises the following steps: S1, hierarchical pretreatment: sequentially performing multistage oil removal and accurate micro-etching on the PCB, and controlling the micro-etching depth to be 200-350 muin, S2, segmented composite activation: sequentially performing pre-impregnation protection, colloidal palladium activation and gel breaking strengthening on the micro-etched PCB, and S3, gradient chemical nickel plating. The device solves the problems of poor uniformity of the PCB nickel layer thickness, large fluctuation range of the phosphorus content and difficult control of the thickness deviation under the single-tank plating mode. The device completes the gradient chemical nickel plating through three groups of independent temperature control separation nickel plating tanks, including the plating nucleation, thickening growth and high-temperature leveling. A matching online monitoring liquid supplementing circulation system is provided to realize the real-time concentration control and medicine supplementing, circulating homogenization flow field, stable plating layer phosphorus content, the thickness difference of the nickel layer on the board surface, in the hole and at the corner is less than or equal to 0.2 muin, and the plating uniformity and consistency are improved.

Description

Technical Field

[0001] This invention relates to the field of ENIG surface treatment technology for PCB boards, and more specifically, to an optimized process and apparatus for high-standard ENIG surface treatment of PCB boards. Background Technology

[0002] PCB boards are the core basic components in various electronic devices that carry electronic components and realize electrical connections and signal transmission between components. ENIG, short for chemical nickel immersion gold plating, is a surface treatment process used in the PCB field. It first forms a nickel-phosphorus alloy plating layer on the surface of copper pads through chemical deposition, and then deposits a thin gold layer on the surface of the nickel layer through a displacement reaction. It can provide long-term anti-oxidation protection for the copper surface, while maintaining excellent solderability and conductive contact performance.

[0003] Currently, the mainstream ENIG electroless nickel immersion gold surface treatment process in the PCB industry generally adopts a single-tank constant-temperature electroless nickel plating process. Typically, the copper surface is cleaned through pretreatment processes such as degreasing and micro-etching. After activation, catalytic active sites for electroless nickel plating are formed on the copper surface. The nickel-phosphorus plating layer is then deposited in a single constant-temperature nickel plating tank. Finally, a gold layer is immersed on the nickel layer surface through a displacement reaction, thereby providing solderability protection and a stable conductive interface for the pads and holes of the printed circuit board.

[0004] However, when PCB boards are surface treated using the existing single-tank constant-temperature ENIG process, a constant reaction temperature is maintained in the same nickel plating tank. The PCB board is nickel plated in a single tank. Under the single-tank plating mode, the nickel layer thickness uniformity is poor, the phosphorus content fluctuates greatly, and special areas such as high aspect ratio holes and fine line corners are not plated enough. The thickness deviation is difficult to control. At the same time, the conventional immersion gold process is prone to excessive replacement corrosion of the nickel layer, resulting in black disk defects, and is often accompanied by insufficient plating adhesion. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a high-standard ENIG surface treatment optimization process and apparatus for PCB boards.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a high-standard ENIG surface treatment optimization process for PCB boards, comprising the following steps: S1. Graded pretreatment: The PCB board is subjected to multi-stage degreasing and precise micro-etching in sequence, and the micro-etching depth is controlled to be 200-350μin.

[0007] S2, Segmented Composite Activation: The micro-etched PCB board is sequentially subjected to pre-impregnation protection, colloidal palladium activation, and desizing reinforcement.

[0008] S3, Gradient electroless nickel plating: Electroless nickel plating is performed using a three-stage gradient temperature control process. The PCB board sequentially passes through three independent temperature zones: low temperature start-up, medium temperature thickening, and high temperature leveling to complete the deposition of nickel and phosphorus plating. During the nickel plating process, the concentrations of nickel salt, reducing agent, and complexing agent are monitored online in real time, and the agents are automatically replenished to maintain the phosphorus content of the plating at 11%-13%.

[0009] S4. Controllable rate immersion gold: Low-concentration gold plating solution is used in conjunction with a corrosion inhibition protection system for immersion gold.

[0010] S5. Interface strengthening post-treatment: The PCB board after gold immersion is subjected to pure water hot rinsing, inert gas drying and residual stress elimination treatment in sequence.

[0011] The present invention is further configured such that the three temperature zones in step S3 are independently temperature controlled, and the temperature control accuracy of a single tank is ±0.5℃.

[0012] A high-standard PCB board ENIG surface treatment optimization device is provided to realize the high-standard PCB board ENIG surface treatment optimization process as described above. It includes a graded pretreatment unit, a segmented composite activation unit, a gradient nickel plating unit, a controllable rate immersion gold unit, and an interface strengthening posttreatment unit arranged sequentially along the PCB board conveying direction.

[0013] The gradient nickel plating unit includes a processing rack, three sets of tanks mounted on top of the processing rack, and a conveying assembly located inside one side of the processing rack. The conveying assembly is used to grip and adjust the angle of the PCB board. The three sets of tanks are a low-temperature initiation tank, a medium-temperature thickening tank, and a high-temperature leveling tank. Each tank is equipped with a temperature sensor inside and a heating tube is installed on one side of each tank.

[0014] The conveying assembly includes a horizontal electric slide rail installed inside the processing rack and a vertical electric slide rail that slides vertically on top of the horizontal electric slide rail. A slide plate slides on one side of the vertical electric slide rail, and a baffle is installed on one side of the slide plate. A bracket is provided on one side of the slide plate and above the baffle. An adjusting cylinder is hinged to one side of the slide plate. A through hole is opened on the side wall of the slide plate. The bracket passes through the through hole and is hinged to the side wall of the through hole. The piston rod end of the adjusting cylinder is hinged to one end of the bracket that passes through the through hole.

[0015] Each of the tanks is equipped with a liquid replenishment component on one side, which is used to replenish the liquid inside the corresponding tank to ensure the concentration of the liquid.

[0016] The present invention is further configured such that: a telescopic cylinder is horizontally installed inside the bracket, a gripping mechanism is slidably mounted inside the bracket, and the piston rod of the telescopic cylinder is connected to one side of the gripping mechanism.

[0017] The present invention is further configured such that: the gripping mechanism includes two plates that slide on the top of the support, and a connecting plate is connected to one side of each of the two plates; the two connecting plates are arranged opposite each other; and a clamp for gripping the PCB board is installed at the bottom of each connecting plate.

[0018] The present invention is further configured such that: a lead screw is connected to the side wall of one of the connecting plates, and an elongated hole is opened on the side wall of the other connecting plate, the lead screw passes through the elongated hole and is threaded with a nut on its outer wall.

[0019] The present invention is further configured such that: the replenishment component includes a replenishment pipe disposed on one side of the top of the corresponding tank, one end of the replenishment pipe is connected to a drain pipe, the drain pipe extends into the interior of the corresponding tank, and three sets of replenishment valves are installed on the top of the replenishment pipe.

[0020] The present invention is further configured such that: each of the tanks is provided with a vertical plate inside, one side of the vertical plate is hollow, the drain pipe is connected to the hollow cavity of the vertical plate, and a filter plate is connected to one side of the vertical plate, the filter plate closing the opening of the vertical plate.

[0021] The present invention is further configured such that: a locking mechanism is connected to the inner sidewall of each of the grooves, and the locking mechanism is disposed through the corresponding vertical plate.

[0022] The present invention is further configured such that: each of the tanks is provided with a sampling branch inside, one end of the sampling branch extends to the bottom wall of the tank, the other end of the sampling branch extends to the inside of the processing rack and is connected to the detection module, and a circulation pump is provided on one side of each tank, the inlet end of the circulation pump extends to the inside of the tank.

[0023] In summary, this application includes at least one of the following beneficial technical effects: (1) By setting up three sets of physically separated independent nickel plating tanks, during gradient chemical nickel plating, the three tanks independently control the temperature to complete the initial plating nucleation, thickening growth, and high-temperature leveling processes respectively. An online monitoring and replenishment circulation structure is set up, the sampling branch detects the concentration of the plating solution in real time, and the replenishment component buffers and diffuses the agent to replenish it. The circulation pump drives the tank solution to circulate and homogenize the flow field, stabilize the phosphorus content of the plating layer, and control the thickness difference of the nickel layer on the plate surface, inside the hole and at the corners to be ≤0.2μm, thereby improving the uniformity and consistency of the nickel plating.

[0024] (2) By setting up a gripping mechanism, during the PCB board immersion plating process, the cylinder drives the bracket to drive the PCB board to tilt and swing back and forth, and the telescopic cylinder drives the gripping mechanism to drive the PCB board to move horizontally back and forth, thereby expelling the air bubbles trapped in the high aspect ratio holes, strengthening the plating mass transfer in complex areas such as fine lines and blind buried holes, avoiding local plating defects, and improving the uniformity of plating deposition in complex structural areas. Attached Figure Description

[0025] Figure 1 This is a process flow diagram of the present invention.

[0026] Figure 2 This is a schematic diagram of the gradient nickel plating unit structure in this invention.

[0027] Figure 3 for Figure 2 A partial structural diagram.

[0028] Figure 4 This is a schematic diagram of the conveying component structure in this invention.

[0029] Figure 5 This is a schematic diagram of the gripping mechanism in this invention.

[0030] Figure 6 This is a schematic diagram of the horizontal gripping state of the conveying component in this invention.

[0031] Figure 7 This is a schematic diagram of the conveying component tilting upwards to grasp the PCB board in this invention.

[0032] Figure 8 This is a schematic diagram of the conveying component tilting downwards to grasp the PCB board in this invention.

[0033] Figure 9 for Figure 3 A partial structural diagram.

[0034] Figure 10 This is a schematic diagram of the fluid replenishment component in this invention.

[0035] Explanation of reference numerals in the attached diagram: 1. Processing rack; 2. Tank; 3. Sampling branch; 4. Circulation pump; 5. Conveying assembly; 51. Horizontal electric slide rail; 52. Vertical electric slide rail; 53. Slide plate; 54. Baffle; 55. Bracket; 56. Adjusting cylinder; 57. Telescopic cylinder; 58. Gripping mechanism; 581. Plate body; 582. Connecting plate; 583. Long hole; 584. Lead screw; 585. Nut; 586. Clamp; 6. Liquid replenishment assembly; 61. Liquid replenishment pipe; 62. Drain pipe; 63. Liquid replenishment valve assembly; 64. Vertical plate; 65. Filter plate; 66. Locking mechanism; 7. Temperature sensor; 8. Heating element. Detailed Implementation

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0038] Please see Figures 1-10 The present invention provides the following technical solutions: Example 1: The existing ENIG surface treatment process uses single-tank constant temperature chemical nickel plating, which has problems such as poor uniformity of nickel layer thickness, large fluctuations in phosphorus content, insufficient plating inside high aspect ratio holes and corners, and is prone to immersion gold nickel corrosion and insufficient coating adhesion.

[0039] Therefore, this embodiment addresses the problems existing in the ENIG surface treatment process and provides an optimized ENIG surface treatment process for high-standard PCB boards, including the following steps: S1. Graded pretreatment: The PCB board is subjected to multi-stage degreasing and precise micro-etching in sequence, and the micro-etching depth is controlled to be 200-350μin.

[0040] The more specific steps in S1 are as follows: S11, Weak Alkali Degreasing: The PCB board is placed in a weak alkaline degreasing solution, and organic oil stains, ink residues and fingerprint contaminants on the PCB board surface are dissolved through a saponification reaction.

[0041] S12. Ultrasonic degreasing: The PCB board is transferred to the ultrasonic degreasing tank, and the ultrasonic cavitation effect is used to clean stubborn stains in high aspect ratio holes and fine line gaps.

[0042] S13. Single pure water overflow rinse: The PCB board is rinsed with pure water in overflow mode to remove residual degreasing solution and stripped contaminants from the PCB board surface.

[0043] S14. Precision micro-etching: The PCB board is placed in the micro-etching solution, and the micro-etching depth is controlled to be 200-350μin to form a copper surface with uniform roughness.

[0044] S15. Secondary pure water countercurrent rinsing: The countercurrent rinsing method is used to remove residual micro-etching liquid from the PCB board surface.

[0045] S2, Segmented Composite Activation: The micro-etched PCB board is sequentially subjected to pre-impregnation protection, colloidal palladium activation, and desizing reinforcement.

[0046] The more specific steps of S2 are as follows: S21. Pre-impregnation protection: Immerse the PCB board in a pre-impregnation solution that matches the activation solution to fully wet the board surface and the internal structure of the holes.

[0047] S22, Colloidal Palladium Activation: The PCB board is placed in a colloidal palladium activation solution, so that palladium colloidal particles are uniformly adsorbed on the copper surface, forming catalytic active sites for electroless nickel plating.

[0048] S23. De-adhesive strengthening: The PCB board is moved into the de-adhesive solution to remove the stabilizer on the surface of the palladium colloid, expose the active palladium core, and improve the activation uniformity in high aspect ratio holes and fine line areas.

[0049] S24 Pure Water Rinse: Rinse to remove residual adhesive and activating solution from the board surface.

[0050] S3, Gradient Electroless Nickel Plating: Electroless nickel plating is performed using a three-stage gradient temperature control process. The PCB board sequentially passes through three independent temperature zones: low-temperature initial plating, medium-temperature thickening, and high-temperature leveling to complete the deposition of the nickel-phosphorus coating. The three temperature zones are independently temperature controlled, with a single tank temperature control accuracy of ±0.5℃. During the nickel plating process, the concentrations of nickel salt, reducing agent, and complexing agent are monitored online in real time, and the agents are automatically replenished to maintain the phosphorus content of the coating at 11%-13%.

[0051] The more specific steps for S3 are as follows: S31, Low-temperature plating start-up: The PCB board is sent into a low-temperature nickel plating bath to start the chemical nickel plating reaction in a low-temperature environment, so that nickel and phosphorus are uniformly nucleated at the catalytic sites.

[0052] S32, Medium-temperature thickening: The PCB board is transferred to a medium-temperature nickel plating bath to maintain a stable plating rate and complete the uniform growth of the main nickel layer thickness.

[0053] S33. High-temperature leveling: The PCB board is sent into a high-temperature nickel plating bath. The high temperature enhances the atomic diffusion ability and performs leveling and densification treatment on the nickel layer.

[0054] S34. During the gradient electroless nickel plating process, the concentrations of nickel salt, reducing agent and complexing agent in each tank 2 are monitored online in real time. The agents are automatically replenished to maintain the phosphorus content of the plating layer at 11%-13%. At the same time, the flow field in the tank is homogenized, and the thickness difference of the nickel layer on the PCB board surface, inside the holes and at the corners is controlled to be ≤0.2μm.

[0055] S4. Controllable rate immersion gold: Low-concentration gold plating solution is used in conjunction with a corrosion inhibition protection system for immersion gold.

[0056] The more specific steps for S4 are as follows: S41, Corrosion-inhibiting immersion gold: The PCB board is placed in a low-concentration gold plating solution with added corrosion inhibitors for displacement immersion gold, and the corrosion inhibitors inhibit excessive displacement corrosion of the nickel layer.

[0057] S42. Precise thickness control: By controlling the replacement reaction rate through closed-loop control of gold concentration, the gold layer thickness is controlled at 0.05-0.1μm, forming a dense gold layer without pinholes.

[0058] S43. Pre-rinse after plating: Perform a preliminary rinse with pure water on the PCB board after immersion in gold to remove residual gold plating solution from the surface.

[0059] S5. Interface strengthening post-treatment: The PCB board after gold immersion is subjected to pure water hot rinsing, inert gas drying and residual stress elimination treatment in sequence.

[0060] Through the above-mentioned ENIG surface treatment process, based on the graded pretreatment and segmented activation to ensure interface cleanliness and activation uniformity, a segmented temperature control mode of low-temperature initiation, medium-temperature thickening, and high-temperature leveling is used. Combined with online concentration detection and control, the nickel layer thickness difference is ≤0.2μm and the phosphorus content is stable at 11%-13%. Combined with subsequent corrosion-inhibiting controllable immersion gold and interface strengthening post-treatment, the defects of nickel corrosion black disk are suppressed, the high-temperature adhesion and environmental reliability of the coating are improved, and the consistency of PCB board coating and overall yield are ultimately improved.

[0061] Example 2: In order to achieve the high-standard PCB board ENIG surface treatment optimization process in Example 1, the existing ENIG surface treatment equipment has an adaptability problem. Conventional nickel plating tanks are mostly single-tank integrated structures, which cannot independently partition to achieve three-stage gradient temperature control. In addition, the liquid replenishment structure mostly uses the pipe to directly inject into a single tank, which can easily cause sudden changes in local solution concentration and damage the stability of the plating solution.

[0062] See Figures 1-2 Therefore, this embodiment provides a high-standard PCB board ENIG surface treatment optimization device, which includes a graded pretreatment unit, a segmented composite activation unit, a gradient nickel plating unit, a controllable rate immersion gold unit, and an interface strengthening posttreatment unit arranged sequentially along the PCB board conveying direction. The graded pretreatment unit, segmented composite activation unit, gradient nickel plating unit, controllable rate immersion gold unit, and interface strengthening posttreatment unit are arranged sequentially along the process flow to realize continuous surface treatment of the PCB board.

[0063] See Figure 1 and Figure 2 The gradient nickel plating unit includes a processing rack 1, three sets of tanks 2 installed on the top of the processing rack 1, and a conveying assembly 5 located inside the processing rack 1. The three sets of tanks 2 are a low-temperature initiation tank, a medium-temperature thickening tank, and a high-temperature leveling tank, respectively. The three sets of tanks 2 correspond to the three temperature zones of gradient nickel plating. Physical separation reduces temperature interference between each temperature zone. The conveying assembly 5 is used to transfer the PCB board, causing the PCB board to pass through the low-temperature initiation tank, the medium-temperature thickening tank, and the high-temperature leveling tank in sequence for nickel plating reaction.

[0064] See Figure 2 and Figure 9 Each tank 2 is equipped with a temperature sensor 7 inside and a heating tube 8 is installed on one side of each tank 2. The temperature sensor 7 collects the temperature of the plating solution in the tank in real time, and the heating tube 8 performs heating compensation to achieve a temperature control accuracy of ±0.5℃ for a single tank, so that the three tanks 2 can maintain the corresponding temperatures for low temperature start-up, medium temperature thickening, and high temperature leveling, respectively.

[0065] See Figure 9 and Figure 10 Each tank 2 is equipped with a replenishment component 6 on one side. The replenishment component 6 is used to replenish the chemical solution inside the corresponding tank 2 to ensure the concentration of the chemical solution. Each tank 2 is equipped with a sampling branch 3. One end of the sampling branch 3 extends to the bottom wall inside the tank 2, and the other end extends to the inside of the processing rack 1 and is connected to the detection module. The sampling branch 3 continuously draws plating solution from the corresponding tank 2 and sends it to the detection module to detect the concentration and pH value of nickel salt, reducing agent, and complexing agent in real time, providing data for replenishment. The specific structure of the replenishment component 6 is as follows: See Figure 9 and Figure 10 The replenishment component 6 includes a replenishment pipe 61 located on the top side of the corresponding tank 2. One end of the replenishment pipe 61 is connected to a drain pipe 62, which extends into the interior of the corresponding tank 2. Three sets of replenishment valve groups 63 are installed on the top of the replenishment pipe 61. The three sets of replenishment valve groups 63 are respectively connected to storage tanks of different agents, and control the replenishment of each agent. The replenished agent is introduced into the interior of the tank 2 through the replenishment pipe 61 and the drain pipe 62, thereby realizing the replenishment of multiple agents in the same tank 2, so that the phosphorus content of the coating in the corresponding tank 2 is maintained at 11%-13%.

[0066] See Figure 9 and Figure 10 Each tank 2 has a vertical plate 64 inside, and a locking mechanism 66 is connected to the inner wall of each tank 2. The locking mechanism 66 passes through the corresponding vertical plate 64. The locking mechanism 66 can be a fixing bolt, which is not specifically limited here. The vertical plate 64 is locked to the inner wall of the tank 2 by the locking mechanism 66. One side of the vertical plate 64 is hollow, and the corresponding drain pipe 62 is connected to the hollow cavity of the vertical plate 64. A filter plate 65 is connected to one side of the vertical plate 64, and the filter plate 65 closes the opening of the vertical plate 64.

[0067] The added chemical solution first enters the hollow cavity of the vertical plate 64 for buffering and pressure reduction, and then diffuses evenly into the bath solution through the holes on the filter plate 65. This avoids the added chemical solution from being directly flushed into the reaction zone, causing rapid changes in local concentration and affecting the uniformity of the coating deposition.

[0068] See Figure 9 Each tank 2 is equipped with a circulation pump 4 on one side. The inlet end of the circulation pump 4 extends into the interior of the tank 2, and the outlet end connects to the hollow cavity of the vertical plate 64. During the nickel plating process, the circulation pump 4 draws the plating solution from the bottom of the corresponding tank 2, pressurizes it and sends it into the distribution chamber of the vertical plate 64, and then returns it to the reaction zone through the filter plate 65, driving the plating solution to circulate in the tank 2, homogenizing the flow field in the tank 2, strengthening the mass transfer of the plating solution in the holes and corner areas, and reducing the difference in plating thickness at different locations.

[0069] See Figure 2 and Figure 3 The conveying assembly 5 includes a horizontal electric slide rail 51 installed inside the processing rack 1 and a vertical electric slide rail 52 that slides vertically on top of the horizontal electric slide rail 51. A slide plate 53 slides on one side of the vertical electric slide rail 52. A baffle 54 is installed on one side of the slide plate 53. A bracket 55 is provided on one side of the slide plate 53 and above the baffle 54. A gripping mechanism 58 is provided inside the bracket 55.

[0070] The horizontal electric slide rail 51 drives the vertical electric slide rail 52, slide plate 53, bracket 55, and gripping mechanism 58 to move horizontally as a whole, realizing the transfer of the PCB board between different tanks 2, namely the low-temperature initial plating tank, the medium-temperature thickening tank, and the high-temperature leveling tank. The vertical electric slide rail 52 drives the slide plate 53, bracket 55, and gripping mechanism 58 to rise and fall vertically, realizing the PCB board being immersed in the corresponding tank 2 or lifted out of the corresponding tank 2. The bracket 55 is used to support the gripping mechanism 58, that is, the gripping mechanism 58 is used to grip the PCB board and send the PCB board into the low-temperature initial plating tank, the medium-temperature thickening tank, and the high-temperature leveling tank in sequence for gradient nickel plating.

[0071] See Figure 3 and Figure 4 The gripping mechanism 58 includes two plates 581 that slide on the top of the bracket 55. Each plate 581 has a connecting plate 582 connected to its opposite side. The two connecting plates 582 are arranged opposite each other. Each connecting plate 582 has a clamp 586 installed at its bottom for holding the PCB board. The clamps 586 at the bottom of the two plates 581 jointly clamp the upper edge of the PCB board. Multi-point clamping ensures that the PCB board remains stable during swinging and translation. A lead screw 584 is connected to the side wall of one connecting plate 582, and an elongated hole 583 is opened on the side wall of the other connecting plate 582. The lead screw 584 passes through the elongated hole 583 and is threaded with a nut 585 on its outer wall. The lead screw 584 can slide along the elongated hole 583 to adjust the distance between the two plates 581 to adapt to PCB boards of different widths. After adjusting to a suitable distance, tightening the locking nut 585 will fix the position, improving the adaptability of the device to products of different specifications.

[0072] Example 3: However, the basic conveying mechanism can only realize the translation and lifting of the PCB board. The PCB board is fixed in posture in the tank 2. The mechanical structure has limitations such as the easy retention of air bubbles in the high aspect ratio holes and insufficient exchange of tank liquid.

[0073] Therefore, further improvements were made to the conveyor assembly 5.

[0074] See Figure 3 , Figures 6-8An adjusting cylinder 56 is hinged to one side of the slide plate 53. A through hole is opened on the side wall of the slide plate 53. A bracket 55 passes through the through hole, and the side wall of the bracket 55 is hinged to the side wall of the through hole. The piston rod end of the adjusting cylinder 56 is hinged to one end of the bracket 55 that passes through the through hole.

[0075] See Figures 6-8 As shown, when the adjusting cylinder 56 extends or retracts, it can push the bracket 55 to swing back and forth around the hinge point, causing the gripping mechanism 58 and the clamped PCB board to tilt synchronously. That is, in the initial state, the bracket 55 remains horizontal. When the adjusting cylinder 56 extends, the bracket 55, the gripping mechanism 58 and the PCB board tilt downward. When the adjusting cylinder 56 retracts, the bracket 55, the gripping mechanism 58 and the PCB board tilt upward, thereby changing the relative angle between the PCB board and the solution in the tank 2, causing the air bubbles trapped in the hole to float up and be discharged, avoiding localized plating leaks caused by air bubbles blocking the plating, accelerating the exchange of plating solution in the hole and improving the uniformity of plating deposition in the hole.

[0076] See Figure 3 , Figures 6-8 A telescopic cylinder 57 is horizontally installed inside the bracket 55. The gripping mechanism 58 slides inside the bracket 55. The piston rod of the telescopic cylinder 57 is connected to one side of the gripping mechanism 58. When the telescopic cylinder 57 extends or retracts, it drives the gripping mechanism 58 to reciprocate along the length of the bracket 55, so that the PCB board can perform translational movements in the plating solution in a tilted state or in a state of reciprocating adjustment of the tilt angle, further agitating the plating solution, enhancing the mass transfer of plating solution in complex areas such as fine lines and blind buried holes, and reducing the difference in nickel layer thickness at different positions on the PCB board surface.

[0077] Obviously, the embodiments described above are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A high-standard ENIG surface treatment optimization process for PCB boards, characterized in that, Includes the following steps: S1. Graded pretreatment: The PCB board is subjected to multi-stage degreasing and precise micro-etching in sequence, with the micro-etching depth controlled at 200-350μin. S2, Segmented Composite Activation: The micro-etched PCB board is sequentially subjected to pre-impregnation protection, colloidal palladium activation and de-adhesive strengthening; S3, Gradient Electroless Nickel Plating: Electroless nickel plating is performed using a three-stage gradient temperature control process. The PCB board sequentially passes through three independent temperature zones: low-temperature initial plating, medium-temperature thickening, and high-temperature leveling to complete the deposition of the nickel-phosphorus coating. During the nickel plating process, the concentrations of nickel salt, reducing agent, and complexing agent are monitored online in real time, and the agents are automatically replenished to maintain the phosphorus content of the coating at 11%-13%. S4. Controllable rate immersion gold: Low-concentration gold plating solution combined with corrosion inhibition protection system is used for immersion gold. S5. Interface strengthening post-treatment: The PCB board after gold immersion is subjected to pure water hot rinsing, inert gas drying and residual stress elimination treatment in sequence.

2. The high-standard PCB board ENIG surface treatment optimization process according to claim 1, characterized in that: In step S3, the three temperature zones are independently temperature controlled, and the temperature control accuracy of a single tank is ±0.5℃.

3. A high-standard PCB board ENIG surface treatment optimization device, implementing the high-standard PCB board ENIG surface treatment optimization process as described in any one of claims 1-2, characterized in that: The system includes a graded pretreatment unit, a segmented composite activation unit, a gradient nickel plating unit, a controllable rate immersion gold plating unit, and an interface strengthening posttreatment unit arranged sequentially along the PCB board conveying direction. The gradient nickel plating unit includes a processing rack (1), three sets of tanks (2) installed on the top of the processing rack (1), and a conveying assembly (5) set inside the processing rack (1). The conveying assembly (5) is used to grip the PCB board and adjust its angle. The three sets of tanks (2) are respectively a low temperature initiation tank, a medium temperature thickening tank and a high temperature leveling tank. A temperature sensor (7) is installed inside each tank (2), and a heating tube (8) is installed on one side of each tank (2). The conveying assembly (5) includes a horizontal electric slide rail (51) installed inside the processing rack (1) and a vertical electric slide rail (52) that slides vertically on the top of the horizontal electric slide rail (51). A slide plate (53) slides on one side of the vertical electric slide rail (52). A baffle (54) is installed on one side of the slide plate (53). A bracket (55) is provided on one side of the slide plate (53) and above the baffle (54). An adjusting cylinder (56) is hinged to one side of the slide plate (53). A through hole is opened on the side wall of the slide plate (53). The bracket (55) passes through the through hole, and the side wall of the bracket (55) is hinged to the side wall of the through hole. The piston rod end of the adjusting cylinder (56) is hinged to one end of the bracket (55) that passes through the through hole. Each of the tanks (2) is equipped with a liquid replenishment component (6) on one side. The liquid replenishment component (6) is used to replenish the liquid inside the corresponding tank (2) to ensure the concentration of the liquid.

4. The high-standard PCB board ENIG surface treatment optimization device according to claim 3, characterized in that: A telescopic cylinder (57) is horizontally installed inside the bracket (55), and a gripping mechanism (58) slides inside the bracket (55). The piston rod of the telescopic cylinder (57) is connected to one side of the gripping mechanism (58).

5. The high-standard PCB board ENIG surface treatment optimization device according to claim 4, characterized in that: The gripping mechanism (58) includes two plates (581) that slide on the top of the bracket (55). Each of the two plates (581) has a connecting plate (582) connected to its opposite side. The two connecting plates (582) are arranged opposite each other. Each connecting plate (582) has a clamp (586) for holding the PCB board installed at its bottom.

6. The high-standard PCB board ENIG surface treatment optimization device according to claim 5, characterized in that: A lead screw (584) is connected to the side wall of one of the connecting plates (582), and an elongated hole (583) is opened on the side wall of the other connecting plate (582). The lead screw (584) passes through the elongated hole (583) and is threaded with a nut (585) on its outer wall.

7. The high-standard PCB board ENIG surface treatment optimization device according to claim 3, characterized in that: The replenishment component (6) includes a replenishment pipe (61) disposed on the top side of the corresponding tank (2), one end of the replenishment pipe (61) is connected to a drain pipe (62), the drain pipe (62) extends into the interior of the corresponding tank (2), and three sets of replenishment valve groups (63) are installed on the top of the replenishment pipe (61).

8. The high-standard PCB board ENIG surface treatment optimization device according to claim 7, characterized in that: Each of the tanks (2) is provided with a vertical plate (64) inside. One side of the vertical plate (64) is hollow and is connected to the hollow cavity of the vertical plate (64) corresponding to the drain pipe (62). A filter plate (65) is connected to one side of the vertical plate (64) and the filter plate (65) closes the opening of the vertical plate (64).

9. The high-standard PCB board ENIG surface treatment optimization device according to claim 8, characterized in that: Each of the grooves (2) has a locking mechanism (66) connected to its inner sidewall, and the locking mechanism (66) is installed through the corresponding vertical plate (64).

10. The high-standard PCB board ENIG surface treatment optimization device according to claim 3, characterized in that: Each of the tanks (2) is provided with a sampling branch (3) inside. One end of the sampling branch (3) extends to the bottom wall inside the tank (2), and the other end of the sampling branch (3) extends to the inside of the processing rack (1) and is connected to the detection module. Each of the tanks (2) is provided with a circulation pump (4) on one side. The liquid inlet end of the circulation pump (4) extends into the inside of the tank (2).

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