Process method for optimizing copper lattice to improve binding force of plating layer

Abstract

The invention relates to the technical field of printed circuit boards, and discloses a process method for optimizing a copper lattice to improve the binding force of a plating layer, which comprises the following steps of: glue residue removal treatment: carrying out glue residue removal treatment on a drilled printed circuit board to form a roughened structure on the surface of a hole wall; activating treatment: adsorbing palladium catalytic particles on the coarsened pore wall surface to form a uniformly distributed catalytic center; and chemical copper deposition: immersing the activated plate in a chemical copper solution, controlling the reaction temperature to be 41-45 DEG C, maintaining the concentration of copper ions, alkali and a reducing agent through automatic compensation and liquid mixing, and depositing on the hole wall to form an initial copper layer. The technological method for optimizing the copper lattice to improve the coating binding force aims at solving the problems that in high-density interconnection and high-speed and high-frequency printed circuit board manufacturing, due to the fact that a traditional chemical copper plating technology lacks dynamic regulation and control capacity, the coating binding force is insufficient, the lattice structure is loose, and uniformity is poor.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board technology, specifically to a process method for optimizing copper lattice to improve plating adhesion. Background Technology

[0002] In the printed circuit board (PCB) manufacturing process, electroless copper plating is a crucial step in forming the conductive layer within vias, and its adhesion directly affects the PCB's reliability and signal transmission performance. Current electroless copper plating processes typically include steps such as desmearing, activation treatment, and electroless copper deposition, aiming to form an initial copper layer by roughening the via wall surface, uniformly distributing catalytic centers, and controlling deposition conditions. However, with the development of high-density interconnects and high-speed, high-frequency PCBs, via sizes are continuously shrinking, and higher aspect ratios are required. Traditional processes face severe challenges in terms of plating uniformity, adhesion, and bath stability. Therefore, optimizing the copper lattice structure to improve plating adhesion has become a key requirement for enhancing PCB performance.

[0003] While traditional electroless copper plating processes can complete basic steps such as descaling, activation treatment, and electroless copper deposition, in actual production, the process parameters of each step are often controlled statically or in stages, lacking real-time monitoring and dynamic adjustment capabilities. During electroless copper deposition, the copper ion concentration, reducing agent content, and pH value of the bath will fluctuate due to reaction consumption or impurity accumulation. However, existing technologies cannot achieve continuous and precise control of these parameters, resulting in uneven coating thickness, loose crystal structure, and even localized insufficient adhesion. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of insufficient coating adhesion, loose lattice structure and poor uniformity caused by the lack of dynamic control capability in the traditional chemical copper plating process in the manufacturing of high-density interconnect and high-speed high-frequency printed circuit boards. Therefore, this invention proposes a process method to optimize the copper lattice to improve the coating adhesion.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A process for optimizing copper lattices to improve coating adhesion includes the following steps: S1. Removal of Adhesive Residue: The printed circuit board after drilling is treated to remove adhesive residue, so that the surface of the hole wall is roughened. S2. Activation treatment: Palladium catalytic particles are adsorbed on the roughened pore wall surface to form uniformly distributed catalytic centers; S3, Chemical Copper Deposition: The activated plate is immersed in a chemical copper solution, and the reaction temperature is controlled at 41℃ to 45℃. The concentration of copper ions, alkali and reducing agent is maintained by automatic compensation and mixing, and an initial copper layer is deposited on the hole wall. S4. Tank solution management: The solution is regularly diluted at a ratio of one-third of the total volume and continuously circulated through a filtration system to maintain the dynamic balance of impurity particles in the solution. S5. Dynamic adjustment of process parameters: Adjust process parameters in real time during steps S1 to S4 to ensure the structural uniformity of the chemical copper plating layer.

[0006] Based on the above technical solution, the present invention can be further improved as follows.

[0007] Furthermore, the degumming treatment uses a potassium permanganate solution at a temperature of 70°C to 85°C for a reaction time of 5 to 8 minutes. After treatment, the surface is rinsed with deionized water to remove oxidation products, forming a hydrophilic and micro-coarsened pore wall surface.

[0008] Furthermore, the activation treatment employs a tin-palladium composite solution to form nanoscale palladium nuclei with a distribution density of 3 × 10⁻⁶. 8 Up to 1×10 9 Each square centimeter is treated to reduce palladium metal residue in non-deposited areas through accelerated processing.

[0009] Furthermore, the copper ion concentration in the chemical copper solution is 1.7 to 2.5 g / L, the sodium hydroxide concentration is 9 to 13 g / L, and the formaldehyde concentration is 3.5 to 5.5 g / L. The solution parameters are adjusted in real time through an online monitoring system to ensure the dense and continuous growth of the copper layer.

[0010] Furthermore, the dilution and replenishment of the tank solution are achieved through automatic control equipment, which is equipped with monitoring modules for solution specific gravity, copper ion concentration and formaldehyde concentration, and operates synchronously in conjunction with the filtration system.

[0011] Furthermore, the filtration system includes a pre-filter of 10 microns and a post-filter of 1 micron, with a liquid flow rate of 1.5 to 2.0 meters per second, and particulate contamination is reduced by periodic backwashing or filter replacement.

[0012] Furthermore, after the initial copper layer is deposited, the morphology, thickness, and lattice orientation of the copper layer are detected by microscopic analysis, cross-sectional polishing, and X-ray diffraction. The copper layer thickness is 0.3 to 0.8 micrometers.

[0013] Furthermore, the process also includes an automatic monitoring system that detects the solution specific gravity, temperature, and filtration pressure difference in real time, and triggers corresponding replenishment, dilution, or filtration operations.

[0014] Furthermore, the process method is applicable to high-density interconnect printed circuit boards with four or more layers and high-speed, high-frequency materials, with through-hole size less than 0.25 mm and height-to-thickness ratio greater than 8:1.

[0015] Furthermore, the process parameters can be adaptively adjusted according to the product type and sheet structure, and the process window for subsequent batches can be optimized using historical data.

[0016] Compared with the prior art, the technical solution of this application has the following beneficial technical effects: The roughened pore wall structure formed by the S1 degumming treatment of this invention significantly increases the mechanical anchoring area between the coating and the substrate, improving the interfacial bonding foundation, compared to the problem of insufficient active sites caused by insufficient roughening in traditional processes. The uniform palladium catalytic centers formed by the S2 activation treatment solve the problems of incomplete plating and unbalanced coating growth caused by uneven distribution of catalytic sites in traditional activation processes, ensuring uniform deposition in the future. In S3, the precise temperature control of 41-45℃ combined with automatic compensation and mixing technology overcomes the bottleneck of copper ion, alkali, and reducing agent concentration fluctuations that traditional static control cannot handle, avoiding coating thickness issues. Uneven density and loose lattice promote the formation of dense copper lattice; S4, with periodic dilution at one-third of the bath volume and continuous circulation filtration, effectively solves the problem of decreased bath stability caused by impurity accumulation in traditional processes, maintains bath cleanliness and reactivity, and reduces plating inclusion defects; dynamic adjustment of process parameters throughout the entire process from S1 to S4 completely overcomes the lag of traditional segmented control, ensures the adaptability of parameters in each step, significantly improves the uniformity of high aspect ratio through-hole plating, enhances plating adhesion, avoids the problem of insufficient local adhesion, and meets the reliability requirements of high-density interconnects and high-speed, high-frequency PCBs. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a coating adhesion failure provided in an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating a coating with good adhesion provided by an embodiment of the present invention; Figure 3 This is a schematic diagram of a coating cross-section failure provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a coating with a good cross-section provided by an embodiment of the present invention; Figure 5 This is a schematic diagram of a chemical copper lattice provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of a chemical copper lattice provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of a chemical copper lattice provided in an embodiment of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0019] The optimized copper lattice method of this invention to improve plating adhesion is an improvement on the chemical copper plating process in the manufacturing of high-density interconnect (HDI) and high-speed, high-frequency printed circuit boards (PCBs). This method, through systematic step design and precise parameter control, ensures the uniformity, density, and adhesion of the copper layer within the vias, thereby meeting the high reliability and high performance requirements of modern PCBs.

[0020] 1. Removal of adhesive residue Resin removal is the first step in the electroless copper plating process. Its purpose is to remove resin residue from the surface of the hole walls after drilling and to form a micro-roughened structure, providing a good adhesion base for subsequent activation treatment and electroless copper deposition. This invention uses potassium permanganate solution as the resin remover, with the solution temperature controlled between 70℃ and 85℃ and the treatment time between 5 and 8 minutes. This temperature and time range has been verified through extensive experiments, ensuring thorough removal of resin residue while avoiding excessive corrosion of the hole walls. After treatment, the substrate is rinsed multiple times with deionized water to ensure no residual oxidation products remain on the hole wall surface. Scanning electron microscopy (SEM) analysis shows that the surface roughness (Ra) of the hole walls should reach 0.5 to 1.2 micrometers. This roughness range provides sufficient adhesion area without causing uneven coating due to excessive roughening.

[0021] 2. Activation treatment The activation treatment adsorbs palladium catalytic particles onto the roughened pore wall surface, forming uniformly distributed catalytic centers that provide reaction sites for chemical copper deposition. This invention uses a tin-palladium composite solution for activation treatment, and by optimizing the solution ratio and treatment time, ensures a palladium nuclei distribution density of 3 × 10⁻⁶. 8 Up to 1×10 9 One unit per square centimeter. This density range ensures a uniform distribution of catalytic centers, avoiding incomplete coating coverage due to too low a density or cost waste due to too high a density. After activation treatment, excess palladium salts are removed by accelerating the processing steps, reducing palladium metal residue in non-deposited areas and further improving the uniformity of the catalytic centers.

[0022] 3. Chemical Copper Deposition Chemical copper deposition is the core step of this invention, aiming to form a dense and uniform initial copper layer on the activated pore wall surface. The chemical copper solution used in this invention contains copper ions (1.7 to 2.5 g / L), sodium hydroxide (9 to 13 g / L), and formaldehyde (3.5 to 5.5 g / L), with the reaction temperature strictly controlled between 41°C and 45°C. This temperature range ensures a moderate reduction rate of copper ions, avoiding slow deposition rates due to excessively low temperatures or solution decomposition due to excessively high temperatures. An online monitoring system tracks the solution's pH, copper ion content, and formaldehyde concentration in real time, and utilizes automatic compensation and mixing technology to dynamically adjust solution parameters, ensuring the continuity and uniformity of the copper layer during deposition. In addition, the present invention introduces ultrasonic-assisted stirring (frequency 28 kHz) technology to further enhance the uniformity of copper ion diffusion in the pores and avoid uneven coating thickness caused by insufficient solution fluidity. After the initial copper layer deposition, the morphology, thickness and lattice orientation of the copper layer are detected by microscopic analysis, cross-section polishing and X-ray diffraction. The copper layer thickness is 0.3 to 0.8 micrometers.

[0023] 4. Tank Solution Management Tank solution management is a crucial step in maintaining the stability of the electroless copper plating process. This invention employs a combination of periodic dilution and continuous circulating filtration to ensure the cleanliness and compositional stability of the tank solution. Specifically, dilution is performed every 3 to 5 days, at a ratio of one-third of the total tank solution volume, ensuring that the copper ion concentration after dilution is not less than 1.5 g / L. The filtration system consists of a pre-filter (10 microns) and a post-filter (1 micron), with the tank solution flow rate controlled at 1.5 to 2.0 meters per second. Periodic backwashing or filter replacement effectively reduces particulate contamination during the deposition process. This design achieves a dynamic balance of impurity particles in the tank solution, preventing plating defects caused by impurity accumulation. The tank solution dilution and replenishment are achieved through automated control equipment equipped with monitoring modules for solution specific gravity, copper ion concentration, and formaldehyde concentration, which are synchronized with the filtration system.

[0024] 5. Dynamic adjustment of process parameters The process method of this invention is also equipped with an automatic monitoring system that monitors key parameters such as solution specific gravity, temperature, and filtration pressure difference in real time, and automatically triggers replenishment, dilution, or filtration operations based on data feedback. For example, when the copper ion concentration is detected to be below a set threshold, the system automatically starts the reagent replenishment module; when the filtration pressure difference exceeds the safe range, the system will prompt to replace the filter element or start the backwashing procedure. This dynamic adjustment mechanism can ensure the synergistic optimization of each process step, significantly improving the stability and consistency of the coating quality. The process method also includes an automatic monitoring system that monitors solution specific gravity, temperature, and filtration pressure difference in real time and triggers corresponding replenishment, dilution, or filtration operations.

[0025] This process method is applicable to high-density interconnect printed circuit boards with four or more layers and high-speed, high-frequency materials. The through-hole size is less than 0.25 mm and the height-to-thickness ratio is greater than 8:1. At the same time, the process parameters can be adaptively adjusted according to the product type and board structure, and the process window for subsequent batches can be optimized by using historical data.

[0026] Chemical treatment with potassium permanganate (KMnO4) solution loosens, oxidizes, and removes resin residue, while forming a micro-rough surface to increase the adhesion of subsequent copper layers. Clean the hole walls to prepare for the subsequent activation steps and prevent impurities from being introduced into the expensive activation tank. Using a colloidal palladium solution, the palladium nuclei in the colloidal palladium are encapsulated by a tin shell and adsorbed onto the pore wall; Using formaldehyde (or other reducing agents) and palladium catalysis, copper ions in solution are reduced to metallic copper, which then deposits on the pore walls. The reaction equation simplifies to: Cu 2 ⁺ + 2HCHO + 4OH⁻ → Cu 0 + 2HCOO⁻ + H2↑ + 2H2O; Use cross-section backlight inspection to observe the integrity and uniformity of the copper layer on the hole wall; The copper plating solution in the main PTH section is periodically diluted by 1 / 3 to reduce by-products in the tank and improve the adhesion of the plating layer.

[0027] The parameters of the copper plating bath in the main PTH section were optimized to improve the adhesion of the plating layer.

[0028] The filtration effect of the copper plating solution in the main tank of the PTH section was optimized to reduce by-products of the plating solution and improve the adhesion of the plating layer.

[0029] To address the reasons for poor coating adhesion, eight relevant influencing factors were identified. Further experimental research was conducted to find factors with strong correlations, thereby optimizing process conditions and ensuring ICD test pass rate.

[0030] Factor Project Bulking, oxidation Clean the hole wall Colloidal palladium adsorption Copper ion deposition Backlight inspection Copper plating tank solution dilution Copper plating tank bath parameters optimization Optimization of copper plating tank solution filtration effect 1 Resin residue was effectively removed Good hole wall cleaning effect Colloidal palladium has good adsorption effect Good copper ion deposition rate Backlight without leakage Copper plating tank solution is diluted for each maintenance. Reasonable parameter design The copper plating tank solution has good filtration effect. 2 Resin residue cannot be effectively removed Poor hole wall cleaning effect Colloidal palladium has poor adsorption effect Poor copper ion deposition rate 3-10 backlight leaks Copper plating bath solution is not diluted during each maintenance. Parameter design is unreasonable The copper plating tank solution has poor filtration performance, and solid particles cannot be effectively filtered out. Table 1 Experimental Factors The first five factors are mandatory, and the last three are improvement factors. Optimizing the copper lattice improves the adhesion of the coating. The experimental design is as follows. Drug dilution frequency item 1 time / day 1 time / 2 days 1 time / 3 days 1 time / 4 days 1 time / 5 days 1 time / 6 days 1 time / 7 days Chemical copper lattice excellent excellent excellent excellent good good Poor ICD Test excellent excellent excellent excellent good good Poor FIB Results excellent excellent excellent excellent good good Poor advantage Good coating adhesion and few by-products in the plating bath Good coating adhesion and few by-products in the plating bath Good coating adhesion and few by-products in the plating bath Good coating adhesion, fewer by-products in the plating bath; reduced production costs. Good coating adhesion; reduced production costs Good coating adhesion; reduced production costs Low production cost shortcoming Time-consuming and high production costs Time-consuming and high production costs Time-consuming and high production costs High production costs The amount of by-products in the tank increased; the coating adhesion was poor. The amount of by-products in the tank increased; the coating adhesion was poor. There are many by-products in the tank; the coating adhesion is poor. Table 2 Experimental Design The copper plating solution in the main PTH section is periodically diluted by 1 / 3 to reduce by-products in the tank and improve the adhesion of the plating layer. The optimal cycle is 4 days.

[0031] Slot name Control Project Control range unit copper temperature 41-45 ℃ proportion 1.03-1.14 / Cu2+ 1.7-2.5 g / L NaOH 9~13 g / L HCHO 3.5~5.5 g / L Copper plating rate 0.4-0.7 um / cycle Table 3 Experimental Design The parameters of the copper plating bath in the main PTH section were optimized to improve the adhesion of the plating layer. The optimal parameters are those shown in the figure.

[0032] Factor Project Optimization of copper plating tank solution filtration effect Optimization of copper plating tank solution filtration effect Optimization of copper plating tank solution filtration effect Filter accuracy 10um 5um 1um Table 4 Experimental Design The filtration effect of the copper plating solution in the main tank of the PTH section was optimized to improve the adhesion of the plating layer. The optimal filter element precision is 1µm as shown in the figure.

[0033] To verify the technical effects of the present invention, the specific implementation process and results are described in detail below through three embodiments.

[0034] Example 1: Process Implementation under Standard Parameters This embodiment uses the standardized parameters of the process method of the present invention, which is applicable to the production of most conventional PCBs.

[0035] Descaling treatment: Potassium permanganate solution was applied at 80℃ for 6 minutes, followed by rinsing with deionized water three times. SEM analysis showed that the pore wall roughness (Ra) was 0.9 micrometers, which is within the target range.

[0036] Activation treatment: The density of palladium nuclei in the tin-palladium composite solution is 5 × 10⁻⁶. 8 Each catalytic center was distributed uniformly, with an accelerated processing time of 2 minutes. Electron microscopy revealed no obvious palladium metal residue.

[0037] Chemical copper deposition: The copper ion concentration in the chemical copper solution was 2.0 g / L, the sodium hydroxide concentration was 11 g / L, the formaldehyde concentration was 4.5 g / L, and the reaction temperature was 43℃. The online monitoring system showed that the fluctuation range of the solution parameters was controlled within ±5%. After deposition, the initial copper layer thickness was 0.5 μm. X-ray diffraction (XRD) analysis showed that the (111) orientation of the copper lattice accounted for 85%, indicating that the lattice structure was highly ordered.

[0038] Tank solution management: The tank solution is diluted every 4 days, and the flow rate of the filtration system is 1.8 meters per second. No obvious accumulation of impurities or imbalance of solution composition was observed during the production process.

[0039] Performance testing: The coating adhesion test was conducted according to IPC-650 standard, and the results fully met the requirements. The copper layer inside the through-holes was uniformly covered, without voids or cracks.

[0040] Example 2: Process Implementation of High-Density Interconnect PCB This embodiment optimizes some process parameters for high-density interconnect PCBs with through-hole size less than 0.25 mm and height-to-thickness ratio greater than 8:1.

[0041] Descaling treatment: Potassium permanganate solution was applied at 85℃ for 5 minutes to ensure thorough treatment of the small-sized through-holes. SEM analysis showed that the hole wall roughness was 1.0 micrometers.

[0042] Activation treatment: Palladium nucleus density increased to 1×10 9 Each square centimeter was processed to accelerate the process, extending the time to 3 minutes to enhance the catalytic effect on small pores.

[0043] Chemical copper deposition: The copper ion concentration was adjusted to 2.3 g / L, the sodium hydroxide concentration to 13 g / L, the formaldehyde concentration to 5.0 g / L, and the reaction temperature to 45°C. After deposition, the copper layer thickness was 0.7 μm, with good lattice orientation uniformity.

[0044] Tank solution management: Due to the large production load of high-density boards, the tank solution dilution cycle is shortened to once every 3 days, and the flow rate of the filtration system is increased to 2.0 meters per second.

[0045] Performance testing: The copper layer inside the through-hole is completely covered, with no unplated areas. High-frequency signal transmission tests show a reduction in loss of more than 10%.

[0046] Example 3: Process Implementation of High-Speed ​​and High-Frequency Materials This embodiment focuses on optimizing the lattice structure and signal transmission performance of the coating for high-speed, high-frequency PCB materials.

[0047] Descaling treatment: Potassium permanganate solution was applied at 75℃ for 7 minutes to balance the roughening effect with material properties. SEM analysis showed that the pore wall roughness was 0.8 micrometers.

[0048] Activation treatment: Palladium nucleus density is 3×10 8 Each square centimeter is processed in 1.5 minutes to reduce interference with high-frequency signals.

[0049] Chemical copper deposition: Copper ion concentration was 1.8 g / L, sodium hydroxide concentration was 10 g / L, formaldehyde concentration was 4.0 g / L, and the reaction temperature was 42°C. After deposition, the copper layer thickness was 0.4 μm, and XRD analysis showed very few lattice defects.

[0050] Tank solution management: The dilution cycle is extended to once every 5 days, and the flow rate of the filtration system is 1.6 meters per second to reduce production energy consumption.

[0051] Performance testing: High-frequency signal testing shows that the coating significantly improves signal loss, reducing overall loss by 15%.

[0052] This embodiment focuses on the principle of improving plating adhesion. Through experimental research, it identifies highly relevant influencing factors. During PCB manufacturing, processes incorporating the main influencing factors for improving plating adhesion are optimized to improve process conditions. This ensures that the product is free from hole wall breakage during subsequent customer soldering, guaranteeing reliability, reducing market failure rates and costly after-sales repairs, building brand reputation, and meeting customer needs.

[0053] To fully verify the necessity of each step and technical solution in the process method of this invention, the following three comparative examples are analyzed from the perspectives of missing steps and technical solution failures, illustrating that if a certain key step or technical solution is missing, the expected coating adhesion and lattice optimization effect cannot be achieved.

[0054] Comparative Example 1: Missing steps in the process of removing adhesive residue Experimental Design: Step adjustment: Skip the glue removal step and directly perform activation treatment on the PCB after drilling.

[0055] Other parameters: The remaining steps, such as activation treatment, chemical copper deposition, and bath management, are consistent with those in Example 1.

[0056] Results and Analysis: Hole wall surface condition: The surface of the hole wall that was not treated to remove the resin residue had a large amount of resin and drilling debris remaining. SEM analysis showed that the surface roughness (Ra) was only 0.1 μm, which is far below the target range (0.5~1.2 μm).

[0057] The pore wall surface is hydrophobic, which cannot provide enough attachment sites for subsequent activation treatment.

[0058] Activation treatment failure: The adsorption rate of palladium catalytic particles on the pore wall surface is less than 30%, and the catalytic centers are sparsely distributed (density < 1 × 10⁻⁶). 8 pcs / cm 2 This results in a severe shortage of reaction sites during chemical copper deposition.

[0059] Coating quality: The initial copper layer thickness was only 0.1 μm, and the coverage was uneven, with large unplated areas appearing inside the vias.

[0060] XRD analysis showed that the copper lattice orientation was disordered, with the (111) orientation accounting for less than 40%, and the coating adhesion test failed the IPC-650 standard.

[0061] Descaling is a crucial step in forming roughened pore walls and a hydrophilic surface. Without it, subsequent activation treatment and chemical copper deposition cannot be effectively performed, and the adhesion and uniformity of the coating will be completely lost.

[0062] Comparative Example 2: The tank solution management solution failed (no dynamic filtration and dilution). Experimental Design: Technical solution adjustment: Eliminate the periodic dilution and continuous circulation filtration of the bath solution, and rely solely on the initial bath solution composition for chemical copper deposition.

[0063] Other parameters, such as descaling, activation treatment, and chemical copper deposition temperature, are the same as in Example 2.

[0064] Results and Analysis: Deterioration of the tank solution condition: Impurities (such as copper oxide and glue residue) accumulate rapidly in the unfiltered bath solution, with particles larger than 5 μm accounting for more than 20%.

[0065] The concentration of copper ions gradually decreased to below 1.0 g / L due to deposition and consumption, while the concentration of formaldehyde fluctuated by more than ±30% due to decomposition.

[0066] Coating defects: Numerous granular protrusions appeared on the surface of the initial copper layer (SEM showed a 50% increase in roughness), and the lattice defect density increased significantly.

[0067] The plating thickness inside the through-hole is uneven, with the copper layer thickness in some areas being only 0.2 μm, and microcracks are present.

[0068] Performance testing: The high-frequency signal transmission loss increased by 25%, and in the coating adhesion test, 30% of the through holes showed coating peeling.

[0069] Dynamic filtration and dilution are crucial for maintaining solution cleanliness and compositional stability. Without them, impurity accumulation and compositional imbalances will directly lead to rough coatings, lattice defects, and decreased adhesion.

[0070] Comparative Example 3: Cancellation of the dynamic adjustment system for process parameters Experimental Design: Technical solution adjustment: The automatic monitoring system is turned off, and all process parameters (temperature, concentration, filtration differential pressure) are set to fixed values ​​with no real-time feedback or adjustment.

[0071] Other parameters, such as the removal of adhesive residue, activation treatment, and chemical copper deposition formula, are the same as in Example 3.

[0072] Results and Analysis: Parameter drift: The chemical copper deposition temperature rose to 48°C due to equipment fluctuations (exceeding the 41 to 45°C range), which accelerated formaldehyde decomposition and disrupted solution stability.

[0073] Backwashing was not triggered after the filtration pressure differential exceeded the safety threshold, and the filter element blockage caused the flow rate to drop to 0.5 m / s.

[0074] Coating quality: The copper layer thickness fluctuated from 0.2 to 0.6 μm, and XRD showed that the lattice orientation was dispersed, with the orientation ratio decreasing to 60%.

[0075] The coating surface showed signs of "burning" (due to excessively high local temperatures), and the pass rate for the adhesion test was only 50%.

[0076] Production consistency: The plating performance of PCBs from the same batch varies significantly, failing to meet the reliability requirements of high-density interconnect boards.

[0077] A dynamic adjustment system is crucial for ensuring the coordinated optimization of process parameters. Without it, parameter drift will lead to unstable coating performance, making it impossible to achieve consistent quality in industrial production.

[0078] Comparative analysis of the embodiments and comparative examples fully verifies the superiority of the process method of the present invention. Precise parameter control (such as temperature, palladium nucleus density, and filtration efficiency) and dynamic adjustment mechanisms are key to ensuring high-quality coating. This invention is not only applicable to conventional PCB production but also meets the special needs of high-density interconnects and high-speed, high-frequency materials, demonstrating broad application prospects.

[0079] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0080] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for optimizing copper lattices to improve coating adhesion, characterized in that, Includes the following steps: S1. Removal of Adhesive Residue: The printed circuit board after drilling is treated to remove adhesive residue, so that the surface of the hole wall is roughened. S2. Activation treatment: Palladium catalytic particles are adsorbed on the roughened pore wall surface to form uniformly distributed catalytic centers; S3, Chemical Copper Deposition: The activated plate is immersed in a chemical copper solution, and the reaction temperature is controlled at 41℃ to 45℃. The concentration of copper ions, alkali and reducing agent is maintained by automatic compensation and mixing, and an initial copper layer is deposited on the hole wall. S4. Tank solution management: The solution is regularly diluted at a ratio of one-third of the total volume and continuously circulated through a filtration system to maintain the dynamic balance of impurity particles in the solution. S5. Dynamic adjustment of process parameters: Adjust process parameters in real time during steps S1 to S4 to ensure the structural uniformity of the electroless copper plating layer.

2. The process method for optimizing copper lattice to improve coating adhesion according to claim 1, characterized in that, The degumming treatment uses potassium permanganate solution at a temperature of 70°C to 85°C for a reaction time of 5 to 8 minutes. After treatment, the surface is rinsed with deionized water to remove oxidation products, forming a hydrophilic and micro-coarsened pore wall surface.

3. The process method for optimizing copper lattice to improve coating adhesion according to claim 1, characterized in that, The activation treatment uses a tin-palladium composite solution to form nanoscale palladium nuclei with a distribution density of 3 × 10⁻⁶. 8 Up to 1×10 9 Each square centimeter is treated to reduce palladium metal residue in non-deposited areas through accelerated processing.

4. The process method for optimizing copper lattice to improve coating adhesion according to claim 1, characterized in that, The copper ion concentration in the chemical copper solution is 1.7 to 2.5 g / L, the sodium hydroxide concentration is 9 to 13 g / L, and the formaldehyde concentration is 3.5 to 5.5 g / L. The solution parameters are adjusted in real time through an online monitoring system to ensure the dense and continuous growth of the copper layer.

5. The process method for optimizing copper lattice to improve coating adhesion according to claim 1, characterized in that, The dilution and replenishment of the tank solution are achieved through automatic control equipment, which is equipped with monitoring modules for solution specific gravity, copper ion concentration and formaldehyde concentration, and operates synchronously with the filtration system.

6. The process method for optimizing copper lattice to improve coating adhesion according to claim 1, characterized in that, The filtration system includes a pre-filter of 10 microns and a post-filter of 1 micron. The liquid flow rate is 1.5 to 2.0 meters per second. Particulate contamination is reduced by periodic backwashing or filter replacement.

7. The process method for optimizing copper lattice to improve coating adhesion according to claim 1, characterized in that, After the initial copper layer is deposited, the morphology, thickness and lattice orientation of the copper layer are detected by microscopic analysis, cross-section polishing and X-ray diffraction. The thickness of the copper layer is 0.3 to 0.8 micrometers.

8. The process method for optimizing copper lattice to improve coating adhesion according to claim 1, characterized in that, The process also includes an automatic monitoring system that detects the solution specific gravity, temperature and filtration pressure difference in real time, and triggers corresponding replenishment, dilution or filtration operations.

9. The process method for optimizing copper lattice to improve coating adhesion according to claim 1, characterized in that, The process method is applicable to high-density interconnect printed circuit boards with four or more layers and high-speed, high-frequency materials, with through-hole size less than 0.25 mm and height-to-thickness ratio greater than 8:

1.

10. The process method for optimizing copper lattice to improve coating adhesion according to claim 1, characterized in that, The process parameters can be adaptively adjusted according to the product type and sheet structure, and the process window for subsequent batches can be optimized using historical data.

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