Circuit board etching device and etching method

Abstract

The invention discloses a circuit board etching device and method, and the method comprises the steps: S1, providing a substrate, forming a laser activation micro-channel on the surface of the substrate, carrying out the plasma cleaning of the substrate, and pressing a gradient copper foil layer; s2, based on the thickness distribution data of the gradient copper foil layer, establishing an etching parameter prediction model, and generating a pressure-temperature dynamic regulation and control curve; s3, preparing a first-stage etching solution, carrying out spraying treatment, and etching the surface layer of the gradient copper foil layer under the assistance of ultrasonic waves to form a porous layer; s4, switching to a second-stage etching solution to directionally etch the porous layer of the gradient copper foil layer to a target residual thickness; s5, performing surface leveling treatment on the etched circuit board, and verifying the etching precision based on a high-frequency impedance test result; gradient copper layer dynamic parameter regulation and control are combined with a two-stage etching process, high-frequency impedance verification and surface leveling have a synergistic effect, signal transmission loss can be reduced, and the method is suitable for manufacturing high-frequency and high-speed circuit boards.

Description

Technical Field

[0001] The present invention relates to the technical field of printed circuit board processing, and particularly to a printed circuit board etching device and an etching method. Background Art

[0002] With the rapid development of high-frequency and high-speed communication devices, high-end electronic devices such as 5G base stations and millimeter-wave radars have put forward higher requirements for the signal transmission performance of printed circuit boards. High-density interconnect (HDI) boards need to achieve precise circuits with micron-level line widths / line spacings on multi-layer composite dielectric substrates. At the same time, to meet the impedance matching requirements, a gradient copper thickness design (gradual distribution of 12 - 35μm) is often adopted. While such a special structure improves signal integrity, it poses severe challenges to the copper layer thickness difference compensation ability of the etching process and the control accuracy of side etching in the transition region.

[0003] Traditional etching processes mostly adopt the method of uniform spraying of chemical etching solution combined with time control, such as a multi-stage etching tank structure, to achieve overall thinning of the copper layer by adjusting the spraying pressure. However, this method has inherent defects when dealing with gradient copper foil layers: due to the difference in the penetration rate of the etching solution in the thickness mutation region (such as the transition region from 18μm to 12μm), over-etching occurs in the thin copper region and the residue in the thick copper region exceeds the standard. The measured side etching ratio in the transition region is as high as 1.5:1, resulting in a sudden change in line impedance. This etching non-uniformity problem caused by the copper thickness gradient has become a key bottleneck restricting the performance improvement of high-frequency circuit boards.

[0004] In view of this, it is necessary to improve the existing technology to solve the technical problems of uneven penetration of the etching solution caused by the thickness difference and excessive lateral etching in the transition region during the etching of the gradient-thickness copper foil layer. Summary of the Invention

[0005] The purpose of the present invention is to provide a printed circuit board etching device and an etching method to solve the above technical problems.

[0006] To achieve this purpose, the present invention adopts the following technical solutions: An etching method for a printed circuit board, comprising the following steps: S1, providing a substrate of a composite dielectric substrate, forming laser-activated micro-channels on the surface of the substrate, and laminating a gradient copper foil layer after plasma cleaning the substrate; S2, based on the thickness distribution data of the gradient copper foil layer, establishing an etching parameter prediction model and generating a dynamic regulation curve of pressure - temperature; S3, configuring a first-stage etching solution and performing a spraying treatment, and etching the surface layer of the gradient copper foil layer to form a porous layer under ultrasonic assistance until the copper ion concentration reaches a preset threshold; S4, switch to the second-stage etching solution and adjust the spraying parameters according to the dynamic regulation curve to directionally etch the porous layer of the gradient copper foil layer to the target remaining thickness; S5, perform surface planarization on the etched circuit board and verify the etching accuracy based on the high-frequency impedance test results.

[0007] Optionally, the composite dielectric substrate includes alternately laminated modified dielectric layers and reinforcing layers, and its surface is coated with a laser-activated transition layer.

[0008] Optionally, the modified dielectric layer is composed of a polytetrafluoroethylene matrix, 15-25 wt% aluminum nitride ceramic filler, and 3-5 wt% silane coupling agent, and the dielectric constant ≤ 2.8; The reinforcing layer is a grid-like porous prepreg formed by aramid fibers, and the porosity is 30-40%; The laser-activated transition layer is a silicon oxide / titanium oxide composite layer, and the depth of the laser-activated microchannels etched on the surface is 60-80% of the thickness of the laser-activated transition layer.

[0009] Optionally, the specific steps of S2 are as follows: S21, obtain the thickness distribution data of the gradient copper foil layer through laser confocal scanning, divide the gradient copper foil layer into a thick copper area and a thin copper area according to the thickness distribution data, and extract the average copper thickness, thickness mutation gradient value, and the proportion of the transition area in each area; there is a thick-thin transition area between the thick copper area and the thin copper area; S22, input the thickness distribution data into a multi-physics field coupling model, and calculate the etching rate difference coefficient in different areas by combining the etching solution diffusion coefficient and reaction activation energy parameters; S23, establish a dynamic parameter prediction model based on the etching rate difference coefficient, and generate a matching matrix of initial spraying pressure - temperature, where the pressure in the thick copper area is increased by 15%-20%, and the temperature in the thin copper area is decreased by 5-8 °C.

[0010] Optionally, after step S23, it further includes: S24, superimpose the feedback data of the etching solution conductivity collected in real time, and correct the matching matrix through the particle swarm optimization algorithm to generate a set of control node parameters including time series; S25, construct a dynamic regulation curve according to the set of control node parameters, and set the pressure gradient compensation function and temperature lag compensation factor in the thick-thin transition area; S26, perform protocol matching between the dynamic regulation curve and the spraying system control module, and establish a linkage mapping relationship of the pressure valve opening - temperature sensor - spraying arm moving speed.

[0011] Optionally, the pressure gradient compensation function is a piecewise exponential function, and the slope change rate is positively correlated with the copper thickness mutation gradient value.

[0012] Optionally, step S3 specifically includes: S31. Configure a first-stage etching solution containing ammonium persulfate, sulfuric acid, and a surfactant, add 0.5 - 1.2 wt% of sodium molybdate as a corrosion inhibitor, and control the pH value to be 1.2 - 1.8; S32. Use a porous gradient spray head to perform zone spraying on the gradient copper foil layer, where the spray hole diameter in the thick copper zone is 0.15 - 0.2 mm, and the spray hole diameter in the thin copper zone is 0.08 - 0.12 mm. The spray angle is adjusted according to the dynamic regulation curve; S33. Simultaneously start multi-frequency composite ultrasonic-assisted etching to form a porous layer. The low frequency of 28 kHz and the high frequency of 68 kHz act alternately, the low-frequency power density is 0.8 - 1.2 W / cm 2 , and the high-frequency power density is 0.3 - 0.5 W / cm 2 , and the action duration ratio is 3:1; S34. Real-time monitor the copper ion concentration in the first-stage etching solution. When the detected concentration reaches the preset threshold, trigger the neutralizer injection module and terminate the ultrasonic assistance.

[0013] Optionally, step S4 specifically includes: S41. Switch to a second-stage composite etching solution composed of ammonium chlorate, citric acid, and ethylenediaminetetraacetic acid, configure the pH value to be 2.8 - 3.5, and add 0.3 - 0.6 wt% of polyethylene glycol as an etching rate regulator; S42. Use a multi-modal spray head to perform directional etching on the porous layer, set the swing frequency of the spray head according to the dynamic regulation curve, and the spray coverage area forms a mirror image match with the copper thickness gradient distribution; S43. Based on the real-time collected remaining thickness data of the porous layer, adjust the spray flow rate in the thick copper zone to 1.5 - 2 times that of the thin copper zone through the intelligent flow distribution module, and simultaneously reduce the temperature of the etching solution in the thin copper zone to 35 - 38 °C; S44. Start on-line monitoring of electrochemical impedance spectroscopy, identify the critical point of porous layer penetration according to the change rate of impedance phase angle, and trigger the thickness compensation algorithm to correct the spray parameters; S45. When the detected remaining thickness data of the porous layer reaches the target remaining thickness, activate the negative pressure adsorption system to recover the residual etching solution, and perform passivation treatment on the gradient copper layer interface.

[0014] Optionally, step S5 specifically includes: S51. Immerse the etched circuit board in a surfactant solution containing nano-aluminum oxide abrasive, and perform gradient pressure chemical mechanical polishing using a biaxial rotary polishing machine. The pressure in the thick copper area is set to a preset multiple of that in the thin copper area; S52. Treat the polished circuit surface with argon plasma. Excite the plasma beam through a radio frequency power supply. The treatment time is negatively correlated with the remaining thickness of the copper layer; S53. Use a four-probe vector network analyzer to perform high-frequency impedance testing to obtain the measured impedance value. Scan the characteristic impedance of the transmission line in the frequency band of 10 GHz - 40 GHz, and synchronously collect the phase delay data; S54. Conduct deviation analysis on the measured impedance value and the theoretical impedance model, and verify the etching accuracy according to the deviation analysis results.

[0015] The present invention also provides a circuit board etching device for implementing the circuit board etching method as described above. The circuit board etching device specifically includes: A pretreatment device, including a laser processing component arranged at the feeding end, a plasma cleaning chamber connected to the laser processing component, and a hot pressing component located at the end; A parameter regulation device, including a scanning component, a model processing component electrically connected to the scanning component, and a spray parameter controller; An etching execution device, including a multi-segment spray component linked with the parameter regulation device, an ultrasonic generator arranged below the multi-segment spray component, and a sealed chamber with an internal etching solution circulation system; An etching monitoring device, including an analysis probe embedded in the sealed chamber, an impedance detection electrode moving synchronously with the spray component, and a thickness sensing module; A post-treatment device, including a chemical polishing mechanism connected to the thickness sensing module, a plasma treatment gun, and an impedance verification platform; A transmission component, arranged along the length direction of the circuit board etching device, for clamping and transferring the substrate.

[0016] Compared with the prior art, the present invention has the following beneficial effects: First, laser-activated microchannels are constructed on the surface of the composite dielectric substrate and plasma cleaning is carried out, and then a copper foil layer with a thickness gradient characteristic is laminated; a dynamic parameter prediction model is established based on the copper layer thickness distribution to generate a pressure-temperature regulation curve; through a two-stage precise etching process, first a porous structure layer is formed with ultrasonic assistance, and then it is directionally etched to the target thickness according to the regulation curve; surface leveling and high-frequency impedance verification are combined to ensure the line accuracy; this process enhances the adhesion of the copper layer through laser-activated microchannels, improves the surface activity through plasma cleaning, the dynamic parameter prediction model effectively matches the difference in copper layer thickness distribution, and the two-stage etching process of first creating holes and then precise etching significantly reduces the lateral etching amount and reduces the line width error in the thick-thin transition area; the synergistic effect of high-frequency impedance verification and surface leveling can reduce the signal transmission loss and is applicable to the manufacture of high-frequency and high-speed circuit boards. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] The structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those skilled in this technology to understand and read, and are not used to limit the limiting conditions under which the present invention can be implemented. Therefore, they do not have a substantial technical meaning. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope that can be covered by the technical content disclosed by the present invention.

[0019] Figure 1 It is one of the flow schematic diagrams of the etching method of the circuit board in the first embodiment; Figure 2 It is the second flow schematic diagram of the etching method of the circuit board in the first embodiment; Figure 3 It is the third flow schematic diagram of the etching method of the circuit board in the first embodiment; Figure 4 It is the system layout schematic diagram of the circuit board etching device in the second embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] In order to make the object, features, and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0021] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention. It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be an intermediate component present at the same time.

[0022] The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and through specific embodiments.

[0023] Embodiment 1: Combined with Figures 1 to 3 As shown, the embodiment of the present invention provides an etching method for a circuit board, including the following steps: S1, providing a substrate of a composite dielectric substrate, forming a laser-activated microchannel on the surface of the substrate, and laminating a gradient copper foil layer after plasma cleaning the substrate; The formation of a microchannel structure on the surface of the composite dielectric substrate by laser activation enhances the bonding force between the subsequent copper foil layer and the substrate; plasma cleaning effectively removes contaminants and oxide layers on the surface of the substrate, providing a clean interface for the uniform lamination of the gradient copper foil; the lamination design of the gradient copper foil layer (the difference in copper thickness in different regions) can adapt to the gradual change requirements of impedance matching for high-frequency circuits.

[0024] S2, based on the thickness distribution data of the gradient copper foil layer, establishing an etching parameter prediction model and generating a dynamic regulation curve of pressure-temperature; Based on the thickness distribution data of the gradient copper foil layer, a dynamic regulation model is established, and by dynamically matching the pressure-temperature curve, the problem of uneven etching solution penetration rate caused by thickness difference is solved.

[0025] S3, configuring a first-stage etching solution and performing a spraying treatment, and etching the surface layer of the gradient copper foil layer under ultrasonic assistance to form a porous layer until the copper ion concentration reaches a preset threshold; In the first stage, the etching solution forms a controllable porous structure on the surface of the copper foil through ultrasonic cavitation effect. This porous layer serves as a guiding layer for subsequent directional etching, which can increase the surface area of the etching reaction and reduce the residual stress. The real-time monitoring of the copper ion concentration threshold is used as the termination condition of the etching process, avoiding the risk of over-etching caused by the difference in reaction rates and ensuring the uniformity of the porous layer structure.

[0026] S4. Switch to the second-stage etching solution and adjust the spraying parameters according to the dynamic regulation curve to directionally etch the porous layer of the gradient copper foil layer to the target remaining thickness. The second-stage etching solution adjusts the spraying parameters according to the characteristics of the porous layer structure. Combining with the pressure-temperature instructions of the dynamic regulation curve, it realizes the precise directional etching of the copper layer thickness. In this stage, the etching rate and precision are effectively balanced through a differential spraying strategy (such as enhancing the impact in the thick copper area and suppressing over-etching in the thin copper area), significantly reducing the line width tolerance in the transition area, and at the same time protecting the substrate from chemical damage.

[0027] S5. Perform surface planarization treatment on the etched circuit board and verify the etching precision based on the high-frequency impedance test results.

[0028] The surface planarization treatment removes the etched residual burrs through chemical mechanical polishing and improves the surface roughness by combining plasma treatment, providing a high-quality substrate for subsequent circuit patterning and soldering processes. The high-frequency impedance test verifies the impedance matching degree of the circuit based on the transmission line theory. Through the deviation analysis between the measured value and the theoretical model, the etching parameter model can be optimized in reverse.

[0029] The working principle of the present invention is as follows: First, laser-activated microchannels are constructed on the surface of the composite dielectric substrate and plasma cleaning is performed, and then a copper foil layer with a thickness gradient feature is laminated. Based on the copper layer thickness distribution, a dynamic parameter prediction model is established to generate a pressure-temperature regulation curve. Through a two-stage precise etching process, first, a porous structure layer is formed with ultrasonic assistance, and then it is directionally etched to the target thickness according to the regulation curve. Combining surface leveling and high-frequency impedance verification to ensure circuit precision. This process enhances the adhesion of the copper layer through laser-activated microchannels, improves the surface activity through plasma cleaning, effectively matches the difference in copper layer thickness distribution with the dynamic parameter prediction model, and significantly reduces the lateral etching amount through a two-stage etching process of first creating holes and then precise etching, reducing the width error of the thick-thin transition zone line. The synergistic effect of high-frequency impedance verification and surface leveling can reduce the signal transmission loss, which is applicable to the manufacture of high-frequency and high-speed circuit boards.

[0030] In this embodiment, the composite dielectric substrate includes alternately laminated modified dielectric layers and reinforcement layers, and its surface is covered with a laser-activated transition layer.

[0031] In this embodiment, it is further illustrated that the modified dielectric layer is composed of a polytetrafluoroethylene matrix, 15-25 wt% aluminum nitride ceramic filler, and 3-5 wt% silane coupling agent, and the dielectric constant is ≤2.8; The reinforcing layer is a grid-like porous prepreg formed by aramid fibers, and the porosity is 30-40%; The laser-activated transition layer is a silicon oxide / titanium oxide composite layer, and the depth of the laser-activated microchannels etched on the surface is 60-80% of the thickness of the laser-activated transition layer.

[0032] It should be noted that the composite dielectric substrate realizes the synergistic optimization of mechanical strength and dielectric properties through the alternating laminated structure of the modified dielectric layer and the reinforcing layer. The introduction of aluminum nitride ceramic filler in the modified dielectric layer significantly improves the thermal conductivity of the substrate and avoids local heat accumulation during the etching process; the grid-like porous structure of the aramid fiber reinforcing layer not only ensures the bending strength of the substrate but also promotes the uniformity of etching solution penetration through the pore channels; the surface laser-activated transition layer forms a gradient transition at the interface between the substrate and the copper foil through the synergistic design of the silicon oxide / titanium oxide composite layer and the microchannel etching depth, which not only enhances the bonding strength but also alleviates the thermal expansion mismatch problem between heterogeneous materials.

[0033] In this embodiment, specifically, step S2 specifically includes: S21, obtaining the thickness distribution data of the gradient copper foil layer through laser confocal scanning, dividing the gradient copper foil layer into a thick copper area and a thin copper area according to the thickness distribution data, and extracting the average copper thickness, thickness mutation gradient value, and transition area proportion of each area; there is a thick-thin transition area between the thick copper area and the thin copper area; Step S21 accurately obtains the three-dimensional thickness distribution data of the gradient copper foil layer through laser confocal scanning, and conducts regional division (thick copper area, thin copper area, and thick-thin transition area) based on the average copper thickness, thickness mutation gradient value, and transition area proportion.

[0034] S22, inputting the thickness distribution data into a multi-physics field coupling model, and combining the etching solution diffusion coefficient and reaction activation energy parameters to calculate the etching rate difference coefficient of different regions; A multi-physics field coupling model (including hydrodynamic equations, diffusion equations, and reaction kinetic equations) is used to combine the thickness distribution data with the physical and chemical parameters of the etching solution (diffusion coefficient, activation energy) to calculate the etching rate difference coefficient of different regions. This model quantifies the etching rate difference between the thick and thin copper regions through physical field coupling simulation (such as a 20%-30% reduction in the rate of the thick copper region).

[0035] S23, establishing a dynamic parameter prediction model based on the etching rate difference coefficient, and generating an initial spray pressure-temperature matching matrix, where the pressure in the thick copper area is increased by 15%-20%, and the temperature in the thin copper area is decreased by 5-8 °C.

[0036] This strategy balances the etching progress differences between thick and thin regions through reverse regulation of pressure and temperature.

[0037] The upward pressure adjustment range (15% - 20%) is verified by hydrodynamic simulation to compensate for the etching solution penetration resistance in the thick copper region; the downward temperature adjustment range (5 - 8 °C) is calculated to ensure the controllability of the reaction rate.

[0038] S24, superimpose the feedback data of the etching solution conductivity collected in real time, and correct the matching matrix through the particle swarm optimization algorithm to generate a set of regulation node parameters including time series; Introduce the particle swarm optimization algorithm, combine the real-time conductivity data (reflecting the concentration of active components in the etching solution) to dynamically correct the matching matrix, and generate a set of regulation node parameters including time series (such as updating the parameters every 10 seconds). This algorithm solves the non-linear problem of multi-variable coupling control through swarm intelligence optimization.

[0039] S25, construct a dynamic regulation curve according to the set of regulation node parameters, and set the pressure gradient compensation function and temperature lag compensation factor in the thick-thin transition region; When constructing the dynamic regulation curve, set the pressure gradient compensation function (piecewise exponential function) and temperature lag compensation factor (time constant 0.5 - 1.2 s) for the thick-thin transition region. This design eliminates the step change in the etching rate in the thickness mutation region through gradual parameter adjustment.

[0040] In this embodiment, it is further illustrated that the pressure gradient compensation function is a piecewise exponential function, and its slope change rate is positively correlated with the copper thickness mutation gradient value.

[0041] The slope of the piecewise exponential function is positively correlated with the copper thickness gradient value, which can accurately match the etching solution penetration requirements in different transition regions; the temperature lag factor is calibrated through heat transfer experiments to avoid reaction out-of-control caused by temperature mutation.

[0042] S26, perform protocol matching between the dynamic regulation curve and the spray system control module, and establish a linkage mapping relationship among the pressure valve opening - temperature sensor - spray arm moving speed.

[0043] Establish a three-dimensional linkage mapping relationship among the pressure valve opening - temperature sensor - spray arm moving speed through protocol matching to achieve spatio-temporal coordinated control of spray parameters. The linkage mapping achieves millisecond-level response through the industrial bus protocol (such as EtherCAT), solves the problem of time sequence asynchrony in traditional segmented control, and ensures the coordination of etching in thick and thin copper regions.

[0044] In this embodiment, it is specifically illustrated that step S3 specifically includes: S31, Configure the first-stage etching solution containing ammonium persulfate, sulfuric acid, and surfactant, add 0.5 - 1.2 wt% of sodium molybdate as a corrosion inhibitor, and control the pH value to 1.2 - 1.8; By configuring the first-stage etching solution containing ammonium persulfate (oxidizing agent), sulfuric acid (pH regulator), and surfactant, combined with sodium molybdate corrosion inhibitor (0.5 - 1.2 wt%), an acidic system with selective etching ability is formed. Ammonium persulfate provides strong oxidizing ability to dissolve the copper layer. The surfactant (such as sodium dodecylbenzenesulfonate) regulates the wettability of the etching solution through adsorption, while sodium molybdate is preferentially adsorbed on the sidewalls to inhibit lateral etching. Controlling the pH value to 1.2 - 1.8 (regulated by sulfuric acid) can optimize the etching reaction kinetics and avoid excessive corrosion of the substrate by strong acidity.

[0045] S32, Use a porous gradient spray head to perform partitioned spraying on the gradient copper foil layer. The spray hole diameter in the thick copper area is 0.15 - 0.2 mm, and the spray hole diameter in the thin copper area is 0.08 - 0.12 mm. The spray angle is adjusted according to the dynamic regulation curve; Perform partitioned spraying using a porous gradient spray head. The aperture in the thick copper area (0.15 - 0.2 mm) is designed to compensate for the etching solution penetration resistance by increasing the flow impact force, and the aperture in the thin copper area (0.08 - 0.12 mm) is reduced to lower the flow rate and improve etching uniformity. The spray angle is adjusted in real time according to the dynamic regulation curve (such as increasing the angle in the thick copper area to 45° to enhance the impact and keeping the angle in the thin copper area at 30° to reduce splashing). This design realizes the differential distribution of the etching solution through hydrodynamic optimization.

[0046] S33, Simultaneously start multi-frequency composite ultrasonic-assisted etching to form a porous layer. The low frequency of 28 kHz and the high frequency of 68 kHz act alternately, with the low-frequency power density being 0.8 - 1.2 W / cm 2 and the high-frequency power density being 0.3 - 0.5 W / cm 2 , and the action duration ratio is 3:1; The alternating action of low-frequency (28 kHz) and high-frequency (68 kHz) ultrasound (duration ratio 3:1) forms a synergistic effect: the micro-jet generated by the rupture of low-frequency cavitation bubbles breaks the passivation layer, and the high-frequency sound field enhances the permeability of the etching solution. The low-frequency power density provides sufficient mechanical energy to break the oxide film on the copper layer surface, and the high-frequency power density avoids excessive cavitation damage to the porous structure.

[0047] S34, Real-time monitor the copper ion concentration in the first-stage etching solution. When the detected concentration reaches the preset threshold of 15 - 18 g / L, trigger the neutralizer injection module and terminate the ultrasonic assistance.

[0048] The copper ion concentration is monitored in real time by ultraviolet-visible spectrophotometry (detection wavelength 810 nm). When the concentration reaches 15-18 g / L, a neutralizing agent (such as NaOH solution) is injected and the ultrasonic wave is terminated. This threshold is set based on the experiment of the linear relationship between copper ion concentration and etching depth, which can accurately determine the end point of the formation of the porous layer and avoid substrate exposure caused by over-etching.

[0049] The concentration threshold range (15-18 g / L) is determined by the etching depth-concentration calibration curve, covering the critical point of the copper layer porosity of 60-80%; the immediate injection of the neutralizing agent prevents the residual acid solution from continuing to react and ensures the structural stability of the porous layer.

[0050] In this embodiment, specifically, step S4 specifically includes: S41, switch to the second-stage composite etching solution composed of ammonium chlorate, citric acid and ethylenediaminetetraacetic acid, configure the pH value to be 2.8-3.5, and add 0.3-0.6 wt% of polyethylene glycol as an etching rate regulator; A second-stage composite etching solution system is constructed using ammonium chlorate (main etching agent), citric acid (chelating agent) and ethylenediaminetetraacetic acid (EDTA, complexing agent). The pH value is controlled to be 2.8-3.5 (adjusted by ammonia water), and polyethylene glycol (0.3-0.6 wt%) is used as a dynamic etching rate regulator. Ammonium chlorate provides the oxidation etching ability, citric acid and EDTA cooperate to complex copper ions to inhibit side reactions, and polyethylene glycol regulates the penetration depth of the etching solution through steric hindrance effect. This system realizes selective etching for the porous layer structure and preferentially dissolves the copper layer inside the pores.

[0051] S42, use a multi-modal spray head to perform directional etching on the porous layer, set the swing frequency of the spray head according to the dynamic regulation curve, and the spray coverage area forms a mirror image match with the copper thickness gradient distribution; The swing frequency (8-12 Hz) of the multi-modal spray head is set according to the dynamic regulation curve, and the spray coverage area forms a mirror image match with the copper thickness gradient distribution (such as the thick copper area corresponding to the dense spray path). The spiral groove structure of the spray head (groove depth 50-150 μm) enhances the micro-flow of the etching solution in the pores through the Venturi effect and improves the etching directionality.

[0052] The swing frequency range (8-12 Hz) is verified by fluid simulation to avoid liquid film breakage; the groove depth is designed to be positively correlated with the porosity of the porous layer to ensure that the penetration amount of the etching solution matches the pore structure.

[0053] S43, based on the remaining thickness data of the porous layer collected in real time, adjust the spray flow rate in the thick copper area to 1.5-2 times that in the thin copper area through the intelligent flow distribution module, and simultaneously reduce the etching solution temperature in the thin copper area to 35-38 °C; Adjust the flow rate in the thick copper area to 1.5 - 2 times that in the thin copper area through the intelligent flow distribution module, and combine with temperature gradient control (35 - 38 °C in the thin copper area) to compensate for the etching rate difference. This strategy is based on the real-time feedback of the remaining thickness data of the porous layer, and dynamically optimizes the flow rate - temperature parameter combination through the convolutional neural network prediction model.

[0054] The flow rate ratio of 1.5 - 2 times is calculated through the mass transfer equation to match the etching solution consumption rate in the thick copper area; the temperature is lowered to 35 - 38 °C (the original solution temperature is 40 - 45 °C), which reduces the reaction rate in the thin copper area by about 25% to avoid over-etching through.

[0055] S44. Start the on-line monitoring of electrochemical impedance spectroscopy, identify the critical point of porous layer etching through based on the change rate of impedance phase angle, and trigger the thickness compensation algorithm to correct the spraying parameters; Use electrochemical impedance spectroscopy (frequency 10 kHz - 1 MHz) to monitor the change rate of phase angle (Δθ / Δt ≥ 5° / s is the critical point of etching through), trigger the thickness compensation algorithm (based on residual neural network) to correct the spraying parameters (such as increasing the pressure by 10% - 15%). This technology captures the moment of pore penetration through the change of the real part - imaginary part trajectory of impedance, with a faster response speed than the traditional optical detection method.

[0056] S45. When the detected remaining thickness data of the porous layer reaches the target remaining thickness, activate the negative pressure adsorption system to recover the residual etching solution, and perform gradient copper layer interface passivation treatment.

[0057] When reaching the target remaining thickness, activate the negative pressure adsorption system (pressure -0.05 ~ -0.1 MPa) to recover the residual etching solution, and use a passivating agent containing benzotriazole derivatives (spraying amount 5 - 8 μL / cm²) for gradient passivation treatment (the spraying amount in the thick copper area is increased by 20%). This process designs the thickness gradient of the passivation film to balance the anti-oxidation requirement and the compatibility of subsequent processes.

[0058] In this embodiment, specifically, step S5 specifically includes: S51. Immerse the etched circuit board in a surfactant solution containing nano-aluminum oxide abrasive, and perform gradient pressure chemical mechanical polishing through a biaxial rotary polishing machine. The pressure in the thick copper area is set to a preset multiple of that in the thin copper area; Adopt the gradient pressure chemical mechanical polishing technology to perform gradient pressure treatment on the surface of the etched circuit board through a biaxial rotary polishing machine (the pressure in the thick copper area is 1.2 - 1.5 times that in the thin copper area). The nano-aluminum oxide abrasive forms a uniformly dispersed grinding system in the surfactant solution. A higher pressure is applied in the thick copper area to remove the etched residual protrusions, and a lower pressure in the thin copper area to avoid micro-cracks caused by over-grinding. This technology matches the copper layer thickness difference through the pressure gradient to achieve uniform flattening of the surface roughness.

[0059] The pressure gradient multiple (1.2 - 1.5) is determined through the polishing rate - pressure calibration experiment, which can efficiently remove the residues in the thick copper area while protecting the structural integrity of the thin copper area.

[0060] S52. The polished circuit surface is treated with argon plasma. The plasma beam is excited by a radio frequency power supply, and the treatment time is negatively correlated with the remaining thickness of the copper layer. The treatment time of argon plasma (30 - 90 seconds) is designed to be negatively correlated with the remaining thickness of the copper layer (12 - 35 μm) (for example, 30 seconds for 35 - μm copper thickness and 90 seconds for 12 - μm copper thickness). The plasma beam excited by the radio frequency power supply removes the surface oxide layer and reduces the roughness through the dual effects of physical bombardment and chemical activation. This technology avoids substrate damage caused by over - treatment of the thin copper area through thickness - related time control.

[0061] S53. A four - probe vector network analyzer is used to perform high - frequency impedance testing to obtain the measured impedance value. The characteristic impedance of the transmission line is scanned in the frequency band of 10 GHz - 40 GHz, and the phase delay data is collected synchronously. The four - probe vector network analyzer scans the characteristic impedance of the transmission line in the frequency band of 10 GHz - 40 GHz, and synchronously collects the phase delay data (resolution 0.1 ps). The phase compensation (compensation amount 3 - 8 ps) of the high - frequency impedance test is carried out through the transmission line residue effect model to eliminate the measurement deviation caused by the edge effect, and the impedance matching degree of the micron - level line width can be accurately characterized.

[0062] S54. The deviation analysis is carried out on the measured impedance value and the theoretical impedance model, and the etching accuracy is verified according to the deviation analysis result.

[0063] The deviation between the measured impedance and the theoretical model is analyzed through a reverse compensation algorithm (based on a residual neural network) (ΔZ≥5Ω triggers compensation), and the spray angle correction amount and the etching time compensation coefficient are generated. This algorithm is trained through historical data to establish the mapping relationship between line width, impedance, and process parameters, realizing the dynamic self - optimization of process parameters.

[0064] Embodiment 2: Combined Figure 4 As shown, the present invention also provides a circuit board etching device for implementing the circuit board etching method as in Embodiment 1. The circuit board etching device specifically includes: The pretreatment device 10 includes a laser processing component arranged at the feeding end, a plasma cleaning chamber connected to the laser processing component, and a hot pressing component at the end.

[0065] The parameter regulation device 20 includes a scanning component, a model processing component electrically connected to the scanning component, and a spray parameter controller.

[0066] The etching execution device 30 includes a multi-section spraying assembly linked to a parameter regulation device, an ultrasonic generator disposed below the multi-section spraying assembly, and a sealed chamber with an internal etching solution circulation system.

[0067] The etching monitoring device 40 includes an analysis probe embedded in the sealed chamber, an impedance detection electrode that moves synchronously with the spraying assembly, and a thickness sensing module.

[0068] The post-processing device 50 includes a chemical polishing mechanism, a plasma processing gun, and an impedance verification platform connected to the thickness sensing module.

[0069] The transmission assembly 60 is arranged along the length direction of the circuit board etching device and is used for clamping and transferring the substrate.

[0070] As mentioned above, the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An etching method for a circuit board, characterized in that, It includes the following steps: S1. Provide a substrate of a composite dielectric substrate, form laser-activated microchannels on the surface of the substrate, and press a gradient copper foil layer after plasma cleaning the substrate; S2. Based on the thickness distribution data of the gradient copper foil layer, establish an etching parameter prediction model and generate a dynamic regulation curve of pressure-temperature; S3. Configure the first-stage etching solution and perform spray treatment, and etch the surface layer of the gradient copper foil layer under ultrasonic assistance to form a porous layer until the copper ion concentration reaches a preset threshold; S4. Switch to the second-stage etching solution and adjust the spray parameters according to the dynamic regulation curve, and directionally etch the porous layer of the gradient copper foil layer to the target remaining thickness; S5. Perform surface planarization treatment on the etched circuit board, and verify the etching accuracy based on the high-frequency impedance test results.

2. The etching method of the circuit board according to claim 1, wherein, The composite dielectric substrate includes alternately stacked modified dielectric layers and reinforcing layers, and a laser-activated transition layer is coated on its surface.

3. The etching method of the circuit board according to claim 2, wherein, The modified dielectric layer is composed of a polytetrafluoroethylene matrix, 15-25 wt% aluminum nitride ceramic filler, and 3-5 wt% silane coupling agent, and the dielectric constant is ≤2.8; The reinforcing layer is a grid-like porous prepreg formed by aramid fibers, and the porosity is 30-40%; The laser-activated transition layer is a silicon oxide / titanium oxide composite layer, and the depth of the laser-activated microchannels etched on the surface is 60-80% of the thickness of the laser-activated transition layer.

4. The etching method of the circuit board according to claim 1, characterized in that, The specific steps of S2 include: S21. Obtain the thickness distribution data of the gradient copper foil layer through laser confocal scanning, divide the gradient copper foil layer into a thick copper area and a thin copper area according to the thickness distribution data, and extract the average copper thickness, thickness mutation gradient value, and the proportion of the transition area in each area; a thick-thin transition area is formed between the thick copper area and the thin copper area; S22. Input the thickness distribution data into a multi-physical field coupling model, and combine the etching solution diffusion coefficient and reaction activation energy parameters to calculate the etching rate difference coefficient of different areas; S23. Based on the etching rate difference coefficient, establish a dynamic parameter prediction model and generate a matching matrix of initial spray pressure-temperature, where the pressure in the thick copper area is increased by 15%-20% and the temperature in the thin copper area is decreased by 5-8 °C.

5. The etching method of the circuit board according to claim 4, characterized in that, After step S23, it also includes: S24. Superimpose the feedback data of the conductivity of the etching solution collected in real time, and correct the matching matrix through the particle swarm optimization algorithm to generate a set of regulation node parameters including time series; S25. Construct a dynamic regulation curve according to the set of regulation node parameters, and set the pressure gradient compensation function and temperature lag compensation factor of the thick-thin transition area; S26. Match the protocol of the dynamic regulation curve with the spray system control module, and establish a linkage mapping relationship between the pressure valve opening, temperature sensor, and spray arm moving speed.

6. The etching method of the circuit board according to claim 5, characterized in that, The pressure gradient compensation function is a piecewise exponential function, and its slope change rate is positively correlated with the copper thickness mutation gradient value.

7. The etching method of the circuit board according to claim 6, wherein, The specific steps of S3 include: S31. Configure the first-stage etching solution containing ammonium persulfate, sulfuric acid, and a surfactant, add 0.5-1.2 wt% of sodium molybdate as a corrosion inhibitor, and control the pH value to be 1.2-1.8; S32. Use a porous gradient spray head to perform zoned spray treatment on the gradient copper foil layer. The spray hole diameter in the thick copper area is 0.15 - 0.2 mm, and the spray hole diameter in the thin copper area is 0.08 - 0.12 mm. The spray angle is adjusted according to the dynamic regulation curve. S33. Start the multi-frequency composite ultrasonic assisted etching to form a porous layer synchronously. The low frequency of 28 kHz and the high frequency of 68 kHz act alternately. The low-frequency power density is 0.8 - 1.2 W / cm 2 , and the high-frequency power density is 0.3 - 0.5 W / cm 2 , and the action time ratio is 3:1; S34. Real-time monitor the copper ion concentration in the first-stage etching solution. When the detected concentration reaches the preset threshold, trigger the neutralizing agent injection module and terminate the ultrasonic assistance.

8. The etching method of the circuit board according to claim 1, characterized in that, The specific steps of step S4 are as follows: S41. Switch to the second-stage composite etching solution composed of ammonium chlorate, citric acid, and ethylenediaminetetraacetic acid, configure the pH value to be 2.8 - 3.5, and add 0.3 - 0.6 wt% of polyethylene glycol as an etching rate regulator. S42. Use a multi-modal spray head to perform directional etching on the porous layer. Set the swing frequency of the spray head according to the dynamic regulation curve, and the spray coverage area forms a mirror match with the copper thickness gradient distribution. S43. Based on the remaining thickness data of the porous layer collected in real time, adjust the spray flow rate in the thick copper area to 1.5 - 2 times that of the thin copper area through the intelligent flow distribution module, and simultaneously reduce the temperature of the etching solution in the thin copper area to 35 - 38 °C. S44. Start on-line monitoring of the electrochemical impedance spectrum. Identify the critical point of porous layer penetration according to the change rate of the impedance phase angle, and trigger the thickness compensation algorithm to correct the spray parameters. S45. When the detected remaining thickness data of the porous layer reaches the target remaining thickness, activate the negative pressure adsorption system to recover the residual etching solution, and perform passivation treatment on the gradient copper layer interface.

9. The etching method of the circuit board according to claim 1, characterized in that, The specific steps of step S5 are as follows: S51. Immerse the etched circuit board in a surfactant solution containing nano-aluminum oxide abrasive, and perform gradient pressure chemical mechanical polishing through a biaxial rotary polishing machine. The pressure in the thick copper area is set to a preset multiple of that in the thin copper area. S52. Treat the polished circuit surface with argon plasma. Excite the plasma beam through a radio frequency power supply, and the treatment time is negatively correlated with the remaining thickness of the copper layer. S53. Use a four-probe vector network analyzer to perform high-frequency impedance testing to obtain the measured impedance value. Scan the characteristic impedance of the transmission line in the frequency band of 10 GHz - 40 GHz, and synchronously collect the phase delay data. S54. Perform deviation analysis on the measured impedance value and the theoretical impedance model, and verify the etching accuracy according to the deviation analysis result.

10. A circuit board etching device, characterized in that The etching method for a circuit board for implementing any one of claims 1 to 9, wherein the circuit board etching device specifically includes: A pretreatment device, including a laser processing component arranged at the feeding end, a plasma cleaning chamber connected to the laser processing component, and a thermal lamination component located at the end. A parameter regulation device, including a scanning component, a model processing component electrically connected to the scanning component, and a spray parameter controller. An etching execution device, including a multi-segment spray component linked with the parameter regulation device, an ultrasonic generator arranged below the multi-segment spray component, and a sealed chamber with an internal etching solution circulation system. An etching monitoring device, including an analysis probe embedded in the sealed chamber, an impedance detection electrode moving synchronously with the spray component, and a thickness sensing module. A post-processing device, comprising a chemical polishing mechanism, a plasma processing gun, and an impedance verification platform connected to a thickness sensing module; A transmission component, arranged along the length direction of the circuit board etching device, for clamping and transferring a substrate.

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