Pattern transfer and partition electroplating method for PCB (Printed Circuit Board) thick copper process and product thereof

Abstract

The invention discloses a pattern transfer and partition electroplating method for a PCB thick copper process and a product, and belongs to the field of PCB thick copper manufacturing, and the method comprises the following steps: S1, carrying out composite pretreatment on a PCB substrate, sequentially carrying out laser micro roughening, degreasing agent and activating solution treatment, and finally washing to be neutral; s2, depositing a transition layer on the surface of the pretreated substrate, and then forming an initial copper layer; s3, manufacturing an anti-corrosion pattern on the surface of the initial copper layer; s4, the substrate is put into the electroplating liquid, corresponding current densities are applied according to different pattern areas, and partition gradient thick copper electroplating is completed; s5, demolding, etching the initial copper layer and micro-etching the edge of the thick copper layer in sequence; and S6, performing surface cleaning after the stress of the heat-treated substrate is released. According to the method, ultraviolet laser micro coarsening and the nickel-phosphorus transition layer are synergistically and strongly combined to prevent delamination, the quality of the copper layer is improved through partition gradient electroplating and pulse crystal grain optimization, step-by-step exposure and current buffer strip design are adopted to control precision and reduce loss, and the qualified rate is improved through whole-process monitoring.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board (PCB) manufacturing technology, and more particularly to a pattern transfer and partitioning electroplating method for thick copper processes in PCBs and the products thereof. Background Technology

[0002] As electronic devices develop towards higher power and higher integration, thick copper PCBs with a copper layer thickness of ≥70μm are widely used in new energy vehicles, industrial control, and communication base stations due to their excellent current carrying capacity, heat dissipation performance, and mechanical strength. However, existing manufacturing processes have several key issues: 1. Poor substrate pretreatment: Mechanical roughening leads to uneven surface roughness, and chemical roughening poses a risk of contamination; improper degreasing and activation can easily lead to insufficient coating adhesion or even delamination. 2. Poor matching between the transition layer and the initial copper layer: Improper control of the parameters of the transition layer (such as the nickel-phosphorus layer) may fail to improve the adhesion or increase the plating stress; poor uniformity of the initial electroplated copper thickness may create hidden defects for subsequent processes. 3. Low pattern transfer accuracy: Fine lines (≤100μm) and large-area copper foils have different requirements for exposure and resist film. Unifying parameters can easily lead to development problems and bubbles. The edges of the resist film have no buffer, and electroplating is prone to concentrated current ablation. 4. Poor uniformity of thick copper electroplating: The single current density causes the "tip effect" of fine lines (excessive copper layer thickness, burrs), and the deposition efficiency of large areas is low; without real-time monitoring, the batch quality fluctuates greatly.

[0003] 5. Numerous defects in etching and post-processing: residual film removal, uncontrolled etching solution leading to uneven etching; high roughness (Ra≥5μm) after etching of thick copper edges, affecting signal transmission; routine cleaning cannot release stress; PCB warpage exceeds the standard (≥1mm / m).

[0004] 6. The electroplating system has a single function: it cannot control the flow in different zones, lacks a grain optimization device, and it is difficult to meet the requirements of low resistivity (≤1.8μΩ・cm) and high (111) crystal plane ratio (≥60%) for thick copper.

[0005] Therefore, there is an urgent need to develop a thick copper PCB manufacturing process that can solve the above problems, improve the quality of thick copper layers, reduce defect rates, and meet the requirements of high-reliability electronic devices. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problems of uniformity, precision, adhesion and signal loss in existing thick copper manufacturing processes. This invention provides a pattern transfer and partitioning electroplating method and its products for thick copper PCB manufacturing.

[0007] The technical solution adopted in this invention is as follows: A method for pattern transfer and partitioned electroplating in PCB thick copper processes, comprising the following steps: S1: PCB substrate composite pretreatment, first the PCB substrate surface is laser micro-roughened, then treated with degreasing agent and activating liquid in sequence, and finally rinsed until neutral; S2: The transition layer and the initial copper layer are formed together. The transition layer is deposited on the surface of the pretreated PCB substrate, and then the initial copper layer is formed on the surface of the transition layer. S3: Pattern partitioning transfer, forming a resist pattern on the surface of the initial copper layer; S4: Gradient thick copper plating in zones involves placing the PCB substrate in an electroplating solution and applying different current densities to different pattern areas to form a thick copper layer. S5: Multi-stage etching, sequentially performing film removal, etching the initial copper layer, and micro-etching the edge of the thick copper layer; S6: Post-stress relief treatment, the PCB substrate is heat-treated to release stress and the surface is cleaned.

[0008] Preferably, in step S1, the laser micro-roughening is performed using an ultraviolet laser to form uniformly distributed micron-sized pits on the substrate surface; the substrate is treated with an alkaline degreasing agent; the acidic activation solution is a sulfuric acid solution, and the substrate is treated with the acidic activation solution.

[0009] Preferably, in step S2, the thickness of the transition layer is 0.1-0.3 μm and the phosphorus content is 8%-12%; the initial copper layer is formed by chemical copper plating and has a thickness of 0.8-1.5 μm.

[0010] Preferably, step S3 specifically involves: coating a high-temperature resistant anti-corrosion film with a Tg ≥ 180℃ onto the surface of the initial copper layer; employing a step-by-step exposure process to apply different exposure energies to the fine line area and the large area respectively; developing with potassium carbonate solution to form an anti-corrosion pattern; and setting a current buffer band at the edge of the copper area to be thickened in the anti-corrosion pattern.

[0011] Preferably, in step S4, the electroplating solution includes: copper sulfate, sulfuric acid, chloride ions, brightener, and stress reliever; a zoned current control device is used to apply different current densities to different pattern areas for electroplating. The zoned current control device includes multiple independent electrode units, each unit corresponding to a pattern area of ​​the PCB substrate, and the distance between the electrode unit and the PCB substrate is adjustable; during electroplating, different current densities are applied to fine line areas and large area areas respectively for electroplating, and the fluctuation of current density in each area is monitored in real time.

[0012] Preferably, after electroplating in step S4, the process further includes step S42: thick copper layer grain optimization, in which the PCB substrate is placed in a pulsed current field for treatment, so as to refine the grain size of the thick copper layer and increase the proportion of crystal orientation.

[0013] Preferably, step S5 specifically involves: firstly, using sodium hydroxide solution to remove the film; then, using an acidic etching solution to etch the initial copper layer that is not covered by the thick copper layer, wherein the acidic etching solution contains copper chloride, hydrochloric acid, and a corrosion inhibitor, and the concentration of the etching solution is monitored in real time and the mother liquor is replenished during etching; finally, using ammonium persulfate solution for micro-etching to improve the edge roughness of the thick copper layer.

[0014] Preferably, in step S6, the stress relief post-treatment specifically involves: placing the PCB substrate in an oven with a protective atmosphere, heating and maintaining the temperature to release stress, and monitoring the substrate warpage in real time; then cooling and hot air drying; and finally plasma cleaning.

[0015] Preferably, in step S4, the system for the partitioned gradient thick copper electroplating step includes: an electroplating tank for containing the composite electroplating solution; a partitioned flow control device, which includes multiple independently controllable electrode units, the positions of which are adjustable to match different pattern areas on the PCB substrate; a real-time monitoring and feedback system for monitoring the current density of each electrode unit; and a pulse current generator for applying a pulse current field to the substrate after electroplating.

[0016] A PCB board prepared by any of the methods described above includes: a PCB substrate; a transition layer formed on the substrate; and a thick copper circuit layer formed on the transition layer. The thick copper circuit layer has a specific thickness and possesses low resistivity, high substrate adhesion, low internal stress, and low signal transmission loss at a specific frequency.

[0017] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: This invention leverages the synergistic effect of ultraviolet laser micro-roughening and a nickel-phosphorus transition layer to significantly improve the bonding performance between the substrate and the thick copper layer, effectively preventing delamination. Combining zoned gradient electroplating with pulsed grain optimization technology enables grain refinement of the thick copper layer, reducing resistivity and controlling internal stress, fully meeting the requirements for high reliability. Through step-by-step exposure processes and current buffer band design, precise control of fine line accuracy is achieved, reducing edge roughness of the thick copper layer while minimizing signal transmission loss and ensuring signal transmission quality. A real-time monitoring and feedback system runs throughout the pretreatment, electroplating, and etching processes, effectively improving batch-to-batch product yield and ensuring stable and reliable production. The alkaline degreasing, acid activation, and plasma cleaning processes employed all comply with RoHS standards, while reducing wastewater discharge, balancing production needs and environmental requirements. Attached Figure Description

[0018] Figure 1 : Flowchart of the steps of the pattern transfer and partitioned electroplating method of the present invention; Figure 2 : A schematic diagram of the cross-sectional structure of the PCB board of this invention; Figure 3 : A schematic diagram of the partitioned electroplating system of the present invention; In the diagram: 1-Electroplating tank, 2-Zone flow control device, 3-Real-time monitoring and feedback system, 4-Pulse current generator, 5-PCB substrate clamping mechanism, 51-PCB substrate, 52-Transition layer, 53-Thick copper circuit layer. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0020] like Figure 1 As shown, this embodiment provides a pattern transfer and partitioning electroplating method for PCB thick copper processes, including the following steps: S1: Pre-treatment of PCB substrate 51: First, laser micro-roughening is performed on the surface of PCB substrate 51 to control the roughness Ra to 0.2-0.5μm. Then, alkaline degreasing agent and acidic activation solution are used in sequence, and finally rinsed until neutral. S2: The transition layer 52 is formed together with the initial copper layer. First, a nickel-phosphorus alloy transition layer 52 is deposited on the surface of the pretreated PCB substrate 51 by magnetron sputtering, and then the initial copper layer is formed on the surface of the transition layer 52 by chemical copper plating. S3: Pattern partitioning transfer, forming a resist pattern on the surface of the initial copper layer, wherein the resist pattern has a current buffer band at the edge of the area to be thickened copper; S4: Partition gradient thick copper electroplating, the PCB substrate 51 is placed in the composite electroplating solution, and the partition flow control device 2 is used to apply different current densities to different pattern areas for electroplating. At the same time, stress relief agent is added to the electroplating solution to form a low-stress thick copper layer. S5: Multi-stage etching, sequentially performing film removal, etching the initial copper layer, and micro-etching the edge of the thick copper layer; S6: Post-stress relief treatment: The PCB substrate 51 is heat-treated in a protective atmosphere to relieve stress and then the surface is cleaned.

[0021] Further, in step S1, the laser micro-coarsening uses an ultraviolet laser with a pulse width of 10-20 ns, a scanning rate of 500-800 mm / s, and a laser energy density of 8-12 J / cm². 2 The process involves forming uniformly distributed micron-sized pits with a diameter of 5-10 μm and a depth of 0.1-0.3 μm on the surface of the PCB substrate; the alkaline degreasing agent treatment conditions are 50-60℃ for 10-15 min; the acidic activating solution is a sulfuric acid solution with a volume fraction of 3%-5%, and the treatment conditions are 25-30℃ for 3-5 min.

[0022] Further, in step S2, the transition layer 52 has a thickness of 0.1-0.3 μm, a phosphorus content of 8%-12%, and is deposited using a radio frequency magnetron sputtering process with a sputtering power of 300-400 W and a vacuum degree ≤5×10⁻ 3 Pa; The initial copper layer is formed by chemical copper plating, with a thickness of 0.8-1.5 μm. The copper plating solution contains 5-8 g / L copper sulfate, 10-15 mL / L formaldehyde, and 25-35 g / L disodium EDTA. The copper plating process is carried out at 45-50℃ and pH 12.5-13.5 under the protection of inert gas.

[0023] Further, step S3 specifically involves: coating the initial copper layer surface with an epoxy resin-type high-temperature resistant anti-corrosion film with a Tg ≥ 180℃, the coating thickness being 20-30μm; and using a step-by-step exposure process to apply 80-100mJ / cm² to the fine line areas (line width ≤ 0.2mm). 2 Exposure energy of 60-70 mJ / cm² is applied to a large area. 2 The exposure energy is specified; a 2%-3% potassium carbonate solution is used for development at 30-35℃ to form a resist pattern; the current buffer bandwidth is 0.1-0.2mm, and laser trimming is used after development to control the accuracy to ±0.02mm.

[0024] Further, in step S4, the composite electroplating solution comprises: 220-260 g / L copper sulfate, 60-90 g / L sulfuric acid, 80-120 mg / L chloride ions, 0.8-1.5 g / L brightener, and 0.3-0.8 g / L stress reliever, all in an organic amine compound. The zoned flow control device 2 comprises multiple independent electrode units, each corresponding to a patterned area of ​​the PCB substrate 51. The distance between the electrode unit and the PCB substrate 51 is adjustable between 3-8 cm. During electroplating, an A / dm² pressure of 1.5-2.5 A is applied to the fine line areas (line width ≤ 0.2 mm). 2 Electroplating at a current density of 3-5 A / dm² for 40-60 minutes, applying the current density to a large area. 2 Electroplating was performed at a current density of 30-50 minutes, with real-time monitoring of current density fluctuations in each area, and the accuracy was controlled within ±0.1 A / dm². 2 .

[0025] Furthermore, after electroplating in step S4, step S42 is also included: thick copper layer grain optimization, the PCB substrate 51 is placed in a pulsed current field for 10-15 minutes, the pulse frequency is 500-800Hz, the duty cycle is 30%-50%, so that the thick copper layer grain size is refined to 5-10μm, and the (111) crystal plane orientation ratio is increased.

[0026] Further, step S5 specifically involves: first, using a 5%-8% sodium hydroxide solution to demold the film at 40-50℃ for 5-8 minutes; then, using an acidic etching solution to etch the initial copper layer that is not covered by the thick copper layer. The acidic etching solution contains 180-220 g / L copper chloride, 60-90 mL / L hydrochloric acid, and 2-5 g / L thiourea derivative as a corrosion inhibitor. The etching is performed using a spray method with a pressure of 0.2-0.3 MPa, and the concentration is monitored in real time. When the concentration of copper chloride is lower than 160 g / L, the mother liquor is added; finally, using a 1%-2% ammonium persulfate solution for 30-60 seconds of micro-etching is performed to make the edge roughness Ra of the thick copper layer ≤ 0.5 μm.

[0027] Further, in step S6, the stress relief post-treatment specifically involves: placing the PCB substrate 51 in a protective oven with nitrogen purity ≥99.99%, heating it to 120-150℃ at a rate of 5℃ / min and holding it at that temperature for 30-40min, while monitoring the substrate warpage in real time to ≤0.1mm / m; then cooling it to 60-70℃ for hot air drying; and finally cleaning it with plasma at a power of 200-300W for 5-8min, wherein the plasma uses a mixture of oxygen and argon in a volume ratio of 1:3 and a working pressure of 5-10Pa.

[0028] like Figure 2 As shown, a PCB board prepared by any of the methods described above includes the following structural layers (from bottom to top or from inside to outside): PCB substrate: FR-4 substrate, metal substrate (such as aluminum-based or copper-based) or ceramic substrate, with a thickness of 0.2-3mm, selected according to the application scenario.

[0029] Transition layer 52: formed on the PCB substrate, made of nickel-phosphorus alloy, with a thickness of 0.1-0.3μm and a phosphorus content of 8%-12%; the bonding force between the transition layer 52 and the substrate and the initial copper layer is ≥1.5kgf / cm, which can effectively inhibit plating peeling.

[0030] Thick copper circuit layer 53: formed on transition layer 52, with a thickness of 70-300μm (adjusted according to design requirements), resistivity ≤1.75μΩ・cm, internal stress ≤50MPa; circuit edge roughness Ra≤2μm, signal transmission loss ≤0.5dB / cm at 1-10GHz frequency, meeting the requirements of high frequency and low loss signal transmission.

[0031] like Figure 3 As shown, the system for the partitioned gradient thick copper electroplating step includes the following core components: Electroplating tank 1: Made of PP or PVC, with a volume of 50-500L, and a built-in heating and temperature control device (temperature control accuracy ±1℃) and a stirring device (stirring speed 50-200rpm), used to contain composite electroplating solution and maintain a stable electroplating environment.

[0032] Zoned current control device 2: Includes 10-20 independent electrode units (made of titanium coated with ruthenium). Each electrode unit is position-adjustable (adjustment accuracy 0.1mm) via a precision guide rail and a fine-tuning knob, which can match graphic areas of different sizes and positions on the PCB substrate; each electrode unit is equipped with an independent current controller, supporting 0.5-10A / dm 2 Current density adjustment.

[0033] Real-time monitoring and feedback system 3: It consists of a Hall current sensor (accuracy ±1%), a concentration sensor (monitoring the concentration of copper sulfate and chloride ions in the electroplating solution) and a central controller; the sensor collects data in real time and transmits it to the central controller. When the parameters exceed the set range, the controller automatically adjusts the electrode current or replenishes the electroplating solution mother liquor to ensure the stability of the electroplating process.

[0034] Pulse current generator 4: Output pulse frequency 500-2000Hz, current density 0.5-1.5A / dm³ 2 It is used in conjunction with electroplating tank 1 for grain optimization treatment of thick copper layers after electroplating.

[0035] Auxiliary components include a PCB substrate clamping mechanism 5 (capable of 360° rotation to ensure uniform electroplating, no diagram provided), a filtration device (filtration accuracy 1-5μm to remove impurities from the electroplating solution), and a waste liquid recycling device (to reduce environmental pollution).

[0036] Specifically, the spatial arrangement is centered around the 50-500 LPP / PVC electroplating tank 1, and the layout is as follows: Inside the tank: a built-in heating and temperature control device (±1℃), a stirring device (50-200rpm), and PCB substrate clamping mechanisms 5 that can rotate 360° on both sides (to fix the PCB and immerse it). Around the tank: 2 zoned flow control devices (10-20 titanium-coated ruthenium electrode units, positioned by guide rails and fine-tuning knobs, with an accuracy of 0.1mm) are mounted on the upper / side brackets; Hall current sensors are placed near the electrodes, and concentration sensor slots are placed near the stirring area; 4 pulse current generators are placed in the side electrical cabinet. External auxiliary facilities: A filter device (1-5μm) is connected to the bottom / side of the tank via a pipeline, and a waste liquid recovery device is connected downstream of the filter device; a central controller electrical cabinet is installed on the side.

[0037] The connection relationships are as follows: Electrical signals: The central controller is connected to the heating temperature control, stirring, and zone current control (adjusting electrode current 0.5-10A / dm).2 ), concentration sensor (triggers mother liquor replenishment when out of range), pulse device (output 500-2000Hz, 0.5-1.5A / dm³). 2 Signal); Fluid flow: Electroplating tank 1 → Filtration device (circulating impurities) → Waste liquid recovery; Mother liquor replenishment device → Electroplating tank 1 (controlled by command trigger); Mechanical: Electrode unit connected to guide rail (translation and positioning); PCB substrate clamping mechanism with 5 slots and internal support (rotation).

[0038] The system works as follows: Pretreatment: Inject electroplating solution, maintain constant temperature, and stir to homogenize the solution; mount the PCB, and adjust the PCB substrate clamping mechanism 5 to align the substrate with the electrodes and immerse it. Gradient electroplating: The electrode unit is positioned and aligned with the PCB pattern area, and the controller adjusts the current of each electrode (0.5-10A / dm). 2 The sensor transmits current and concentration data in real time; if the data is out of range, the current is adjusted or the mother liquor is added. Post-processing: After electroplating, the controller triggers the pulse device to output pulses to optimize the copper layer grains; Auxiliary protection: The filtration device continuously filters impurities during electroplating, and the waste liquid is discharged to the recycling device after the process is completed.

[0039] Specific embodiments are provided below. These embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way.

[0040] Example 1: Pattern Transfer and Partition Electroplating Method for Thick Copper PCB Process S1: PCB substrate 51 composite pretreatment FR-4 type PCB substrate 51 (1.6mm thick) was selected, and micro-roughening was performed using an ultraviolet laser with a pulse width of 15ns, a scanning rate of 650mm / s, and a laser energy density of 10J / cm². 2 Uniform micron-sized pits with a diameter of 7-8 μm and a depth of 0.2 μm are formed on the substrate surface. The substrate is then placed in an alkaline degreasing agent (mainly composed of sodium hydroxide and surfactant) at 55°C for 12 min. It is then placed in a sulfuric acid solution at 28°C with a volume fraction of 4% for 4 min to activate it. Finally, it is rinsed with deionized water until pH=7.

[0041] S2: Transition layer 52 is co-formed with the initial copper layer. A nickel-phosphorus transition layer 52 was deposited on the surface of the pretreated substrate using radio frequency magnetron sputtering at a sputtering power of 350W and a vacuum degree of 3×10⁻. 3Pa, the transition layer 52 is 0.2 μm thick and has a phosphorus content of 10%; then a chemical copper plating process is used, the copper plating solution contains 6 g / L copper sulfate, 12 mL / L formaldehyde and 30 g / L disodium EDTA, and nitrogen gas is introduced under the conditions of 48℃ and pH=13 to form an initial copper layer with a thickness of 1.2 μm.

[0042] S3: Graphics partition transfer An epoxy resin-based high-temperature resistant anti-corrosion film with a Tg of 200℃ was coated onto the initial copper layer surface using a roller coating method, with a coating thickness of 25μm. A step-by-step exposure machine was used to apply 90mJ / cm² to the fine line areas (line width 0.15mm). 2 Exposure energy, for large areas (area ≥ 1cm) 2 Apply 65mJ / cm 2 Exposure energy; then develop with a 32℃, 2.5% potassium carbonate solution for 3 minutes to form a resist pattern, with a current buffer bandwidth of 0.15mm. After development, laser trimming is used to control the accuracy to ±0.02mm.

[0043] S4: Partitioned gradient thick copper plating The electroplating solution consists of: 240 g / L copper sulfate, 75 g / L sulfuric acid, 100 mg / L chloride ions, 1.2 g / L brightener (sodium polydisulfide dipropane sulfonate), and 0.5 g / L stress reliever (triethanolamine). The distance between the electrode unit and the substrate in the zoned flow control device 2 is adjusted to 5 cm, applying 2.0 A / dm² to the fine line area. 2 Electroplating at a current density of 4 A / dm for 50 minutes was applied to a large area. 2 Electroplating at current density for 40 minutes; real-time monitoring of current density fluctuations, with accuracy controlled within ±0.1 A / dm². 2 This forms a thick copper layer with a thickness of 120μm.

[0044] S42: Thick copper layer grain optimization The substrate was placed in a pulsed current field for 12 minutes with a pulse frequency of 650 Hz and a duty cycle of 40%. After treatment, the grain size of the thick copper layer was refined to 7-8 μm, and the (111) crystal plane orientation ratio was increased to 65%.

[0045] S5: Multi-stage etching The film was removed by using a 6% sodium hydroxide solution at 45°C for 6 min; the acidic etching solution consisted of 200 g / L copper chloride, 75 mL / L hydrochloric acid, and 3 g / L corrosion inhibitor (thiourea derivative), and was sprayed at 0.25 MPa pressure. The concentration of copper chloride was monitored in real time, and the mother solution was added when it was below 160 g / L; finally, the film was micro-etched with a 1.5% ammonium persulfate solution for 45 s, and the edge roughness of the thick copper layer was Ra=0.3 μm.

[0046] S6: Post-stress relief treatment The substrate was placed in an oven with nitrogen purity of 99.995% and heated to 135℃ at a rate of 5℃ / min, held for 35min, and the substrate warpage was monitored to be 0.08mm / m. The substrate was then cooled to 65℃ for hot air drying. Finally, it was cleaned with 250W plasma for 6min. The plasma used was a 1:3 mixture of oxygen and argon gas at a working pressure of 8Pa.

[0047] Example 2: PCB board prepared by the method of Example 1 The PCB structure is as follows: FR-4 substrate (1.6mm) → nickel-phosphorus transition layer 52 (0.2μm, phosphorus content 10%) → thick copper circuit layer 53 (120μm). Testing showed that the resistivity of the thick copper circuit layer 53 was 1.6μΩ・cm, the bonding strength with the substrate was 2.3kg / cm, the internal stress was 42MPa, and the signal transmission loss at 1GHz was 0.25dB / cm, meeting the performance requirements for PCBs in new energy vehicles.

[0048] Example 3: A system for implementing zoned gradient thick copper electroplating The system includes: Electroplating tank 1: Made of PP, with a volume of 50L, equipped with a temperature control device (temperature control accuracy ±1℃). Zoned current control device 2: Contains 8 independent electrode units (made of pure copper), electrode position adjustment range 3-8cm, current adjustment range 0.5-10A / dm 2 ; Real-time monitoring and feedback system 3: Employs a current sensor (accuracy ±0.05A / dm). 2 The data sampling frequency is 1Hz, and the electrode current is automatically adjusted when the error exceeds the tolerance. Pulse current generator 4: Pulse frequency adjustment range 300-1000Hz, duty cycle adjustment range 20%-60%, output current 0-5A.

[0049] The system operated stably during the electroplating process in Example 1, with current density fluctuations in each region ≤0.08 A / dm². 2 This meets the requirements for process precision.

[0050] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for pattern transfer and partitioned electroplating in PCB thick copper processes, characterized in that, Includes the following steps: S1: PCB substrate composite pretreatment, first the PCB substrate surface is laser micro-roughened, then treated with degreasing agent and activating liquid in sequence, and finally rinsed until neutral; S2: The transition layer and the initial copper layer are formed together. The transition layer is deposited on the surface of the pretreated PCB substrate, and then the initial copper layer is formed on the surface of the transition layer. S3: Pattern partitioning transfer, forming a resist pattern on the surface of the initial copper layer; S4: Gradient thick copper plating in zones involves placing the PCB substrate in an electroplating solution and applying different current densities to different pattern areas to form a thick copper layer. S5: Multi-stage etching, sequentially performing film removal, etching the initial copper layer, and micro-etching the edge of the thick copper layer; S6: Post-stress relief treatment, the PCB substrate is heat-treated to release stress and the surface is cleaned.

2. The pattern transfer and partitioned electroplating method for PCB thick copper processes according to claim 1, characterized in that, In step S1, the laser micro-roughening uses an ultraviolet laser to form uniformly distributed micron-sized pits on the substrate surface; the substrate is treated with an alkaline degreasing agent. The acidic activation solution is a sulfuric acid solution, and the substrate is treated with the acidic activation solution.

3. The pattern transfer and partitioned electroplating method for PCB thick copper processes according to claim 1, characterized in that, In step S2, the thickness of the transition layer is 0.1-0.3 μm and the phosphorus content is 8%-12%; the initial copper layer is formed by chemical copper plating and has a thickness of 0.8-1.5 μm.

4. The pattern transfer and partitioning electroplating method for PCB thick copper processes according to claim 1, characterized in that, Step S3 specifically involves: coating a high-temperature resistant resist film with a Tg ≥ 180℃ onto the surface of the initial copper layer; applying different exposure energies to the fine line area and the large area using a step-by-step exposure process; developing the resist pattern using a potassium carbonate solution; and setting a current buffer band at the edge of the copper area to be thickened in the resist pattern.

5. The pattern transfer and partitioned electroplating method for PCB thick copper processes according to claim 1, characterized in that, In step S4, the electroplating solution includes: copper sulfate, sulfuric acid, chloride ions, brightener, and stress reliever; a zoned current control device is used to apply different current densities to different pattern areas for electroplating. The zoned current control device includes multiple independent electrode units, each unit corresponding to a pattern area of ​​the PCB substrate, and the distance between the electrode unit and the PCB substrate is adjustable; during electroplating, different current densities are applied to fine line areas and large area areas respectively, and the fluctuation of current density in each area is monitored in real time.

6. The pattern transfer and partitioning electroplating method for PCB thick copper processes according to claim 5, characterized in that, After electroplating in step S4, step S42 is also included: thick copper layer grain optimization, in which the PCB substrate is placed in a pulsed current field for treatment, so that the grain size of the thick copper layer is refined and the crystal orientation ratio is increased.

7. The pattern transfer and partitioning electroplating method for PCB thick copper processes according to claim 1, characterized in that, Step S5 specifically involves: firstly, using sodium hydroxide solution to remove the film; then, using an acidic etching solution to etch the initial copper layer that is not covered by the thick copper layer. The acidic etching solution contains copper chloride, hydrochloric acid, and a corrosion inhibitor. During etching, the concentration of the etching solution is monitored in real time and the mother liquor is replenished; finally, using ammonium persulfate solution for micro-etching to improve the edge roughness of the thick copper layer.

8. The pattern transfer and partitioned electroplating method for PCB thick copper processes according to claim 1, characterized in that, In step S6, the stress relief post-treatment specifically involves: placing the PCB substrate in an oven with a protective atmosphere, heating and maintaining the temperature to release stress, and monitoring the substrate warpage in real time; then cooling and hot air drying; and finally plasma cleaning.

9. The pattern transfer and partitioning electroplating method for PCB thick copper processes according to claim 1, characterized in that, In step S4, the system for the partitioned gradient thick copper electroplating step includes: an electroplating tank for containing the composite electroplating solution; a partitioned flow control device, which includes multiple independently controllable electrode units, the positions of which are adjustable to match different pattern areas on the PCB substrate; a real-time monitoring and feedback system for monitoring the current density of each electrode unit; and a pulse current generator for applying a pulse current field to the substrate after electroplating.

10. A PCB board article prepared by any one of the methods described in claims 1-9, characterized in that, include: PCB substrate; A transition layer formed on the substrate; A thick copper circuit layer is formed on the transition layer; the thick copper circuit layer has a specific thickness and features low resistivity, high substrate adhesion, low internal stress, and low signal transmission loss at a specific frequency.

Images