Method for manufacturing an odd number of layers of printed circuit boards

Abstract

The application discloses a manufacturing method of an odd-layer printed circuit board and belongs to the technical field of printed circuit board manufacturing. The method comprises the following steps: performing first electroplating treatment on a target layer of a substrate to deposit conductive material to a first preset thickness on both sides; performing second electroplating treatment on one side after protection treatment and on the other side to a second preset thickness to form differentiated copper thickness; performing first etching treatment on the target layer of the differentiated copper thickness to remove part of the copper layer on the second copper thickness side, and then performing second etching treatment to form line patterns on both sides; performing single-sided pressing on one side of the substrate to form an odd-layer structure by stacking a dielectric layer and a conductive layer; and forming an outer layer line pattern to obtain an odd-layer printed circuit board. The method realizes asymmetric copper thickness and line pattern formation through two-step electroplating and two-step differential etching, realizes odd-layer layer increasing through single-sided pressing, and is completed based on a conventional process throughout the whole process, so that a separable core plate and a separation process are not needed, and manufacturing cost is reduced.

Description

Technical Field

[0001] This application relates to the field of printed circuit board manufacturing technology, and in particular to a method for manufacturing an odd-layer printed circuit board. Background Technology

[0002] As communication equipment places increasingly higher demands on the load-bearing capacity of circuit boards, the number of layers and conductivity of printed circuit boards are constantly improving, leading to a growing need for asymmetric copper-thickness stack-up designs. For the manufacturing of odd-layer printed circuit boards, existing technologies typically employ a coreless process, which uses a separable core board as a temporary carrier. After building circuit layers on both sides, the core board is removed through a separation process to obtain an odd-layer structure.

[0003] However, the Coreless process requires the use of special separable core board materials, adding an extra separation process and reducing production efficiency. At the same time, the outer copper foil is at risk of being scratched during the separation process, and the etching accuracy is difficult to guarantee, ultimately leading to an increase in total cost and hindering efficient mass production. Summary of the Invention

[0004] To address the shortcomings of existing technologies that rely on coreless processes for manufacturing odd-layer printed circuit boards (PCBs), resulting in low production efficiency, high risk of copper foil damage, and increased manufacturing costs, this application provides a method for manufacturing odd-layer PCBs. This method achieves odd-layer layer addition by performing step-by-step electroplating to form differentiated copper thicknesses, step-by-step etching to form differentiated circuit patterns, and single-sided lamination. The entire process is based on conventional layer-by-layer addition processes, enabling the manufacturing of odd-layer boards without using coreless processes. Specifically, this application provides the following technical solutions: This application provides a method for manufacturing an odd-layer printed circuit board, including: A first electroplating process is performed on both sides of the target layer of the substrate to make the first surface of the target layer reach a first preset thickness; The first surface of the target layer is protected. A second electroplating process is performed on the second surface of the target layer to make the second surface reach a second preset thickness, thereby forming a first copper thick surface and a second copper thick surface on both sides of the target layer, wherein the second preset thickness is greater than the first preset thickness, and the first surface and the second surface are opposite to each other. A first etching process is performed on the target layer to remove the first copper layer on the second copper thickness surface; and a second etching process is performed on both sides of the target layer to form corresponding circuit patterns respectively. A single-sided lamination is performed on a dielectric layer and a conductive layer stacked on one side of the substrate to form an odd-numbered layer structure; Based on the odd-layer structure, an outer layer circuit pattern is constructed to obtain an odd-layer printed circuit board.

[0005] Optionally, in the first electroplating process and the second electroplating process, the current density of the first electroplating process is greater than the current density of the second electroplating process.

[0006] Optionally, the protection process includes: A photosensitive film is attached to the first thick copper surface of the target layer to prevent the plating solution from contacting the first thick copper surface during the second electroplating process.

[0007] Optionally, the first etching process uses a first spray pressure and a first etching compensation amount, and the second etching process uses a second spray pressure and a second etching compensation amount; wherein the first spray pressure is greater than the second spray pressure, and the first etching compensation amount is greater than the second etching compensation amount.

[0008] Optionally, the single-sided pressing adopts a stepped heating pressing process, which includes at least one heat preservation section.

[0009] Optionally, the single-sided pressing process further includes: Single-sided grinding is performed on the non-additional layers to control the overall thickness uniformity of the odd-numbered layer printed circuit board.

[0010] Optionally, the second thick copper surface is used to carry power lines and ground lines, while the first thick copper surface is used to carry high-density signal lines.

[0011] Optionally, the first etching process further includes: The etching depth of the second copper thick surface is monitored in real time to obtain the current scattering ratio value of the second copper thick surface; Based on the scattering ratio value, determine the current etching removal ratio; Based on the deviation between the current etching removal ratio and the target removal ratio, the conveying speed of the substrate in the etching chamber is adjusted.

[0012] Optionally, the first etching process and the second etching process further include: Multi-frequency AC perturbation signals are applied to obtain the solution resistance, charge transfer resistance, and diffusion impedance parameters of the etching solution; Based on the solution resistance, the charge transfer resistance, and the diffusion impedance parameters, the real-time predicted etching rate of the etching solution is calculated. The real-time predicted etching rate is compared with the target etching rate, and at least one of the following is adjusted according to the deviation direction and deviation magnitude: etching solution temperature, replenishment volume, and substrate transport speed.

[0013] This application also provides an odd-layer printed circuit board, which is manufactured using the above-described manufacturing method.

[0014] The technical solution provided in this application has the following beneficial effects: 1. By performing two-step electroplating processes on the target layer and combining them with selective protection treatment, differentiated copper thicknesses are achieved on the two sides of the same target layer. This allows the second copper-thickness side to carry high-current lines while the first copper-thickness side can achieve high-density signal wiring, thus meeting the dual requirements of current carrying capacity and signal integrity without increasing the number of layers.

[0015] 2. By controlling the circuit formation process of the second copper thickness surface and the first copper thickness surface through two differential etching processes, the uncontrollable side etching problem caused by the difference in copper thickness in a single etching process is avoided.

[0016] 3. Odd-layer addition is achieved through single-sided lamination. The entire process is based on conventional layer-by-layer addition technology and standard equipment, without the need for special separable core board materials and separation processes, thereby reducing manufacturing costs and eliminating the risk of copper foil damage during separation. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall process for manufacturing an odd-layer printed circuit board according to an embodiment of this application.

[0018] Figure 2 This is a schematic diagram of the module architecture of an odd-layer printed circuit board manufacturing system provided in an embodiment of this application.

[0019] Figure 3 A schematic diagram of the calibration curve provided for an embodiment of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0022] The odd-layer printed circuit board manufacturing method provided in this embodiment, such as Figure 1 As shown, it includes the following steps: S100, Inner Core Board Preparation This document provides a substrate with inner layer circuit patterns. The substrate is a multilayer core board manufactured using conventional printed circuit board inner layer processes, and its inner layer circuit patterns have been formed through standard procedures. These standard procedures include: board cutting, pretreatment, dry film lamination, exposure, development, etching, film removal, and AOI optical inspection. The line widths of each layer of the inner core board are within the design specifications, and the interlayer alignment accuracy meets the alignment requirements of subsequent processes.

[0023] In this embodiment, the inner core board is an even-numbered core board with a symmetrical stacked structure. Specifically, the even-numbered core board includes multiple inner conductor layers and insulating dielectric layers located between adjacent conductor layers. The copper thickness of each inner conductor layer is determined according to the function it carries; for example, inner layers carrying power and ground functions use thicker copper foil, while inner layers carrying signal transmission functions use thinner copper foil. The layers are bonded together with prepreg and cured through a lamination process to form an integral structure.

[0024] In the stack-up design phase, the target stack-up structure for odd-numbered layers is determined based on functional requirements. This stack-up structure involves the following factors: impedance matching requirements, i.e., determining the relationship between dielectric constant and copper thickness based on the characteristic impedance requirements of each signal layer; heat dissipation requirements, i.e., determining the copper thickness based on the power consumption of high-current layers to meet heat conduction requirements; and mechanical strength requirements, i.e., ensuring the total stack-up thickness meets equipment handling requirements, in other words, the board thickness is within the clamping range of equipment used in each process of the production line.

[0025] During the material selection stage, a suitable combination of copper foil and prepreg is chosen. The selection of the copper foil is based on the target copper thickness and in-plane uniformity requirements; the selection of the prepreg is based on resin content, flowability, glass transition temperature, and coefficient of thermal expansion. Furthermore, the coefficient of thermal expansion of the prepreg should match that of the copper foil and the inner core board to reduce interlayer thermal stress and lower the risk of warping during subsequent lamination processes.

[0026] The specific technological processes for forming the inner layer circuit pattern are as follows: The cutting process cuts large-size copper-clad boards into standard work boards according to the production assembly size. After cutting, the edges of the boards are chamfered to eliminate burrs.

[0027] The copper surface is then chemically cleaned and roughened by micro-etching through a pretreatment process. The cleaning solution uses an acidic degreaser at a temperature of 40°C to 50°C to remove oil and oxides from the copper surface. The micro-etching solution uses a sodium persulfate solution at a temperature of 30°C to 35°C to form a uniform micro-rough surface. The roughness is controlled within the range of 0.3 micrometers to 0.8 micrometers to ensure sufficient adhesion between the subsequent dry film and the copper surface.

[0028] The subsequent dry film application process involves applying the photosensitive dry film to the copper surface using a hot roller laminator. The lamination temperature is controlled within the range of 105℃ to 115℃, the lamination pressure within the range of 0.3MPa to 0.5MPa, and the roller speed within the range of 1.5m / min to 2.5m / min. After lamination, the film is allowed to stand for 15 to 30 minutes to allow sufficient adhesion between the dry film and the copper surface to develop.

[0029] The exposure process uses ultraviolet direct imaging equipment or mask exposure equipment to transfer the CAM data of the inner layer circuitry onto the dry film. The exposure energy is determined based on the dry film type and copper thickness; in this embodiment, it is set to 30 mJ / cm². 2 Up to 50 mJ / cm 2 During the exposure process, automatic alignment is performed using a CCD alignment system to ensure that the alignment accuracy between each layer of the pattern is within 25 micrometers.

[0030] The developing process involves developing the exposed dry film using a sodium carbonate solution at a temperature of 28°C to 32°C. The developing pressure is controlled at 1.0 kgf / cm². 2 Up to 1.8 kgf / cm 2 Within this range, the transfer speed is adjusted according to the developing window and the dry film thickness.

[0031] After development, a clear circuit pattern window will be formed on the copper surface. The dry film in the unexposed areas is dissolved and removed, while the dry film in the exposed and cured areas is retained as a resist layer for subsequent etching. The etching process uses copper chloride etching solution to etch the exposed copper surface. The temperature of the etching solution is controlled within the range of 48℃ to 52℃, the spray pressure is set according to the copper thickness, and the etching compensation amount is pre-calculated according to the copper thickness of each layer and the target linewidth and written into the CAM data.

[0032] The stripping process involves using a sodium hydroxide solution at a temperature of 45°C to 55°C to remove the residual dry film resist layer.

[0033] The subsequent AOI optical inspection process involves a comprehensive scan of the inner layer board after the film removal. The inspection equipment uses a high-resolution line-scanning CCD camera to perform point-by-point comparison and inspection of the inner layer circuit pattern. The inspection items include: open circuit defects (broken lines or missing copper), short circuit defects (residual copper connections between adjacent lines), linewidth deviation (whether the difference between the actual linewidth and the designed linewidth exceeds the specification), and notch defects (recessed edges of the lines). The resolution of the AOI inspection can be set to 10 micrometers to detect all circuit defects exceeding the specification. Substrates that fail this inspection are marked as scrapped, while qualified substrates proceed to the next process.

[0034] After the inner core board is prepared and before the first electroplating process, the target layer of the substrate must undergo a desmearing treatment. The purpose of this desmearing treatment is to remove the resin residue remaining on the walls of the vias and the copper surface during drilling or lamination, providing a clean copper substrate surface for subsequent electroplating.

[0035] The specific process for treating the degummed residue includes: Swelling treatment involves swelling and softening the surface of the resin layer in a swelling solution at a temperature of 70°C to 80°C for 5 to 8 minutes. Oxidative degumming involves oxidizing and decomposing the swollen resin in a potassium permanganate solution. The potassium permanganate concentration is 55 g / L to 75 g / L, the treatment temperature is 75°C to 85°C, and the treatment time is 8 min to 15 min. Neutralization and reduction: The residual manganese dioxide on the copper surface is reduced and removed in a reducing solution, restoring the metallic luster of the copper surface.

[0036] It should be noted that the target copper surface after desmearing is clean but lacks the conductive continuity required for electroplating. Chemical copper plating is then performed on the target layer after desmearing to form a conductive substrate layer. This chemical copper plating involves depositing a thin layer of copper on the copper surface and hole walls as a conductive seed layer for subsequent electroplating. The pre-processes for chemical copper plating include: Hole preparation improves the wettability of the hole wall surface; Activation treatment: Palladium-based activation solution is used to form palladium catalytic nuclei on the pore walls and copper surface. Accelerate the process to remove excess activation solution residue. The main components of the chemical copper plating solution are copper sulfate, formaldehyde, sodium hydroxide, and EDTA complexing agent. The copper plating temperature is controlled within the range of 28℃ to 35℃, the copper plating time is 15 min to 25 min, and the copper plating thickness is controlled within the range of 0.3 micrometers to 0.8 micrometers.

[0037] Finally, the conductive substrate layer uniformly covers all copper surface areas on both sides of the target layer, providing a uniform conductive foundation for the subsequent first electroplating process.

[0038] S200, double copper plating of asymmetric thick copper layers The target layer of the substrate undergoes two-step electroplating processes to achieve differentiated copper thicknesses on both sides of the same target layer. The target layer is an inner layer requiring asymmetric copper thickness. Its first thick copper surface (thin copper layer) carries high-density signal lines; its thinner copper thickness allows for finer linewidths and spacings through etching. In this embodiment, the minimum linewidth and minimum line spacing of the first thick copper surface can reach 30 micrometers, accommodating more signal lines within the same area. Fine wiring facilitates the transmission of high-speed digital signals and high-frequency radio frequency signals, enabling precise impedance control and reducing signal loss and distortion. The second thick copper surface (i.e., the thick copper surface) of the target layer carries high-current lines such as power and ground lines. Its larger copper cross-sectional area helps reduce conductor resistance, decrease heat generation during high-current flow, and enhance heat dissipation. Furthermore, when using high-power surface-mount components, the second thick copper surface can rapidly conduct and dissipate heat generated during operation, reducing the internal temperature of the printed circuit board and improving system stability and reliability.

[0039] It should be noted that the asymmetrical copper thickness design here improves wiring density and flexibility. In traditional symmetrical copper thickness designs, both sides use the same copper thickness. If thicker copper is chosen to meet the current carrying capacity requirements of the power layer, the line width and spacing of the signal layer are limited, and the wiring space is locked. This embodiment, through an asymmetrical design, dedicates the second copper thickness side to power and ground lines, and the first copper thickness side to signal lines. This utilizes the advantages of both sides, improving overall wiring space and flexibility.

[0040] Specifically: Before performing the first electroplating process, the surface of the target layer of the substrate undergoes a pretreatment. The pretreatment includes: Micro-etching removes the oxide layer on the copper surface and forms a micro-rough surface to improve the adhesion between the subsequent electroplating layer and the base copper. Pickling is used to remove surface residues and organic contaminants.

[0041] After the pretreatment is completed, the copper surfaces on both sides of the target layer exhibit a uniform micro-roughness, providing good conditions for electroplating adhesion.

[0042] The target layer of the substrate is then subjected to a first electroplating process.

[0043] In the first electroplating process, the substrate is vertically immersed in a copper sulfate electroplating solution, and electroplating is performed at a preset first current density. The electroplating solution contains copper sulfate at a concentration of 60 g / L to 80 g / L, sulfuric acid at a concentration of 180 g / L to 220 g / L, chloride ion at a concentration of 40 ppm to 60 ppm, and appropriate amounts of brightener, leveling agent, and wetting agent are added. The first current density ranges from 1.5 A / dm³.2 Up to 3A / dm 2 In this embodiment, the first current density is set to 2A / dm².

[0044] The first electroplating process is then performed, depositing copper layers simultaneously on both sides of the target layer, and ensuring that the copper thickness on the first surface reaches a first preset thickness, thereby forming a first thick copper surface. In this embodiment, the first preset thickness is 18 micrometers. The electroplating time is calculated based on the target deposition thickness, current density, and the electrochemical equivalent of copper. Specifically, the electrochemical equivalent of copper is approximately 0.3294 g / Ah, and the density of copper is 8.9 g / cm³. 3 Therefore, the required time can be estimated based on the deposition thickness and current density: In the formula, Electroplating time, in units of ; Target deposition thickness, in units of ; Let be the density of copper, and take a value of . ; Current density, in units of ; The electrochemical equivalent of copper is given by a value of [value missing]. .

[0045] For example, in this embodiment, the target deposition thickness for the first electroplating is 18 micrometers, and the current density is 2 A / dm. 2 Substituting into The second electroplating requires the deposition of an additional 52-micron copper layer, with a current density of 1.5 A / dm² (i.e., J = 0.015 A / cm²). 2 Substituting into the equation yields... .

[0046] It should be noted that during the first electroplating process, the temperature of the plating solution needs to be controlled within the range of 22°C to 28°C, and the circulation and stirring rate of the plating solution needs to be controlled to ensure the uniformity of the in-plane copper thickness distribution. The control of the in-plane uniformity also includes: improving the electric field distribution by adjusting the distance between the anode and cathode, optimizing the conductive contact area of ​​the electroplating fixture, and setting auxiliary anodes or shielding plates.

[0047] The optimization of the electric field distribution is achieved based on the cathode current density distribution, i.e., at any position on the cathode surface. Local current density at for: In the formula, For the applied slot voltage, For position The resistance of the solution at that point For position The charge transfer resistance at that point. The solution resistance. Effective distance from anode to cathode The relationship between them is: In the formula, The conductivity of the electroplating solution, in units of ; The effective current conduction cross-sectional area, in units of It's easy to understand that when the distance between the anode and the cathode... When the positions on the board are inconsistent, the values ​​at each position... Differences in current density lead to variations in local current density, resulting in in-plane non-uniformity in copper deposition thickness. In this case, adjusting the anode shape can correct these differences. To achieve consistency, or to reduce the contact resistance of the electroplating fixture by increasing the conductive contact area of ​​the fixture. The additional effects of these factors can all improve the in-plane distribution of current density.

[0048] It should be noted that the mechanism of the auxiliary anode or shield is as follows: due to the geometric tip effect, the electric field lines are concentrated in the edge area of ​​the substrate, and the electric field lines at the edge are concentrated. The current density at the edge is higher than that at the center region. By placing a non-conductive shield at the edge region, the shield blocks part of the electric field path, effectively increasing the solution resistance at the edge. The corrected edge current density is: in The equivalent additional resistance introduced by the baffle plate. This is achieved by adjusting the size and position of the baffle plate. The value satisfies This means achieving a consistency in current density between the edge and center regions.

[0049] The in-plane uniformity is quantified by the copper thickness deviation ratio: in This is the measured value of the maximum copper thickness on the board surface. This is the minimum copper thickness measurement value on the board surface. This is the arithmetic mean of the copper thickness at each measurement point on the board surface. In this embodiment, the first electroplating uses a relatively high current density (2A / dm²). 2 ), corresponding in-plane uniformity The value is ±8% to 10%; the second electroplating uses a lower current density (1.5 A / dm²). 2 With the help of the baffle plate correction, the corresponding in-plane uniformity It should be kept within a range of ±5% to 7%.

[0050] After the first electroplating process is completed, the copper thickness on both sides needs to be measured online to confirm that the copper thickness deviation within the surface is within ±10% of the target value.

[0051] After the first electroplating process is completed, a protective treatment is applied to the first copper thickness surface of the target layer. The specific operation procedure for this protective treatment is as follows: The substrate is removed from the electroplating solution, cleaned, and dried. A photosensitive film is then applied to the first thick copper surface. The photosensitive film uses a dry-film photoresist with a thickness of 15 to 40 micrometers. During the application process, the application temperature is controlled within the range of 100°C to 120°C, the application pressure within the range of 0.3 MPa to 0.5 MPa, and the application speed within the range of 1 m / min to 2 m / min to ensure a tight bond between the photosensitive film and the copper surface and to eliminate any residual air bubbles. Furthermore, the photosensitive film needs to cover the entire surface area of ​​the first thick copper surface to form a sealed protective layer, including the edge areas. After application, an edge inspection is performed to confirm that the edges of the photosensitive film are properly sealed, without any lifting or openings, to prevent plating solution from seeping in from the edges during the subsequent second electroplating process.

[0052] Then, a second electroplating process is performed on the second surface of the target layer, causing the copper layer on the second surface to continue depositing from a first preset thickness to a second preset thickness, thereby forming a second copper thickness surface. The second preset thickness corresponds to the target copper thickness of the second copper thickness surface; in this embodiment, the second preset thickness is 70 micrometers. It is easy to understand that since the first copper thickness surface is protected by the photosensitive film, only the copper thickness area corresponding to the second surface is exposed to the plating solution during the second electroplating process to continue receiving copper deposition. The second electroplating process is performed using a second current density, the value of which ranges from 1 A / dm². 2 Up to 2.5A / dm 2 The second current density is less than the first current density. In this embodiment, the second current density is set to 1.5 A / dm³. 2 .

[0053] It should be noted that the reason why the first current density is greater than the second current density is as follows: In the initial stage of electroplating, the surface of the copper substrate is uniform after pretreatment, and the electric field distribution is relatively ideal. Using a higher current density can improve uniformity while ensuring deposition quality. In the later stage of electroplating, as the copper layer thickness increases, changes in the microstructure of the substrate surface lead to increased non-uniformity of the electric field distribution. Under high current density conditions, current concentration effects are easily formed at the edges and protrusions of the substrate, resulting in local copper deposition rates being higher than those in the central area. At this time, reducing the current density can weaken the current concentration effect and make the deposition rates of each area more uniform.

[0054] The time for the second electroplating process is also calculated based on the target deposition thickness, current density and electrochemical equivalent of copper. For example, from the first preset thickness (18 micrometers) to the second preset thickness (70 micrometers), an additional 52 micrometers of copper layer needs to be deposited.

[0055] In the second electroplating process, the temperature of the plating solution is also controlled within the range of 22°C to 28°C, and the stirring rate is controlled to ensure uniformity.

[0056] After the second electroplating process is completed, the substrate is removed from the plating solution, and the photosensitive protective layer on the first copper thick surface is removed. The removal method is as follows: an alkaline stripping solution is used to treat the substrate at a temperature of 40°C to 50°C, causing the photosensitive film to swell and detach. After stripping, both sides of the target layer are cleaned. The surface cleaning process includes: rinsing with pure water to remove residual stripping solution and plating solution residues; acid pickling to remove the slight oxide layer generated on the copper surface during the stripping process; and drying using hot air drying at a temperature of 60°C to 80°C to completely remove moisture from the board surface.

[0057] Through the two-step electroplating process described above, differentiated copper thicknesses are formed on the two sides of the target layer: the copper thickness on the second thicker side is 70 micrometers, which is a second preset thickness, and the copper thickness on the first thicker side is 18 micrometers, which is a first preset thickness. After the two electroplating processes are completed, the finished thickness and in-plane uniformity of the second and first thicker sides are measured respectively. The measurement methods employ eddy current thickness gauges or X-ray fluorescence thickness gauges, taking multiple measurement points on each side for statistical analysis to confirm that the copper thickness accuracy and in-plane uniformity meet the requirements of subsequent etching processes.

[0058] S300, selective lamination of asymmetric copper thick layers with double etching Two differential etching processes are performed on the target layer with the differentiated copper thickness to form coarse lines on the second copper thickness side and fine lines on the first copper thickness side, respectively. This division of labor in the two etching processes effectively controls the lateral etching amount on both the second and first copper thickness sides, thereby achieving the precision requirements of different line widths and spacings on the two sides. Specifically: Before etching, the circuit pattern is transferred to both sides of the target layer. The pattern transfer process is as follows: Dry film photoresist is applied to both sides, and the designed circuit CAM data is transferred to the dry film through an exposure machine. After development, an anti-etching protective layer of the circuit pattern is formed on the dry film.

[0059] The exposure here uses a direct imaging device, and the exposure energy is set to 35 mJ / cm based on the dry film type. 2 Up to 55mJ / cm 2Within this range, the exposure resolution should meet the linewidth requirements of the first copper thickness surface. Development here is performed using sodium carbonate developer at a temperature of 30°C to 33°C. After development, the integrity of the patterns on both sides is checked to confirm the absence of residual film and broken lines. Generally, CAM data includes etching compensation, which is a pre-calculated and widened linewidth compensation value based on the copper thickness and target linewidth of each surface. Furthermore, the etching compensation for the second copper thickness surface should be greater than that for the first copper thickness surface to compensate for the larger lateral etching during the thick copper etching process.

[0060] Then, a first etching process is performed, which is performed on the second copper thick surface.

[0061] Prior to the first etching process, an additional full-area protective film is applied to the first thick copper surface to completely cover the entire area of ​​the first thick copper surface (including the circuit areas already protected by dry film and the non-circuit areas without dry film protection). This protective film is applied to ensure that the first thick copper surface is not corroded by any etching solution during the first etching process.

[0062] The etching equipment is a horizontal conveyor etching machine, and the substrate passes through the etching chamber horizontally. The first etching process uses a first spray pressure, which ranges from 2.0 kgf / cm². 2 Up to 3.5 kgf / cm 2 In this embodiment, the first spray pressure is set to 2.8 kgf / cm². 2 The etching solution uses copper chloride etching solution or alkaline etching solution, and the temperature of the etching solution is controlled within the range of 48℃ to 52℃; the spray angle of the nozzle used for spraying is set to a larger angle to increase the impact of the etching solution on the copper surface and improve the longitudinal etching rate.

[0063] It should be noted that the first etching process removes 40% to 60% of the copper layer thickness on the second copper thick surface. In this embodiment, the original copper thickness of the second copper thick surface is 70 micrometers, and the first etching process removes approximately 35 micrometers (50%), leaving a remaining copper thickness of approximately 35 micrometers on the second copper thick surface. The purpose of the first etching process here is to remove most of the main copper layer on the second copper thick surface in advance, reducing the burden on the subsequent second etching process. Since the first etching process only needs to remove a large area of ​​copper layer rather than fine patterning, using higher spray pressure and a larger etching compensation amount can accelerate the etching rate, while the precision requirements for side etching are relatively relaxed.

[0064] After the first etching process is completed, the remaining copper thickness on the second copper thick surface is detected to confirm that the removal ratio is within the target range (40% to 60%), and the full-area protective film on the first copper thick surface is removed.

[0065] A second etching process is then performed. In this second etching process, both sides of the target layer are simultaneously finely etched, while the substrate passes through the etching chamber in a horizontal orientation. The second etching process employs a second spray pressure, with a value ranging from 1.0 kgf / cm². 2 Up to 2.0 kgf / cm 2 In this embodiment, the second spray pressure is set to 1.5 kgf / cm². 2 The temperature is lower than the first spray pressure. Similarly, the etching solution temperature is controlled within the range of 42°C to 48°C, slightly lower than the first etching process temperature. The nozzle spray angle is also set to a smaller angle to reduce the impact of the etching solution on the sidewalls and reduce the amount of side etching.

[0066] The second etching process accomplishes two tasks simultaneously in a gentler manner: etching through 18 micrometers of copper layer on the first thick copper surface to form a fine circuit pattern; and etching through the remaining 35 micrometers of copper layer on the second thick copper surface to complete the patterning of the circuit on the second thick copper surface. Since the copper thickness to be removed on both sides in the second etching process is of a similar order of magnitude (i.e., 18 micrometers on the first thick copper surface and the remaining 35 micrometers on the second thick copper surface), using uniform, gentle etching conditions can simultaneously meet the side etching control requirements on both sides. Because the first thick copper surface is thinner, the etching penetration time is shorter, and the amount of side etching is naturally smaller, thus enabling the achievement of finer linewidths and spacing.

[0067] Furthermore, the second etching compensation amount is less than the first etching compensation amount. In this embodiment, the first etching compensation amount for the second copper thickness surface is 25 micrometers to 35 micrometers on one side, and the second etching compensation amount is 10 micrometers to 15 micrometers on one side; the etching compensation amount for the first copper thickness surface is 8 micrometers to 12 micrometers on one side.

[0068] It should be noted that the setting of the etching compensation amount is based on the quantitative relationship of the etching factor. The etching factor is the ratio of the etching depth to the amount of lateral etching on one side; the larger the value, the better the directionality of the etching. Under the etching conditions of this embodiment, the etching factor of the first etching treatment is approximately 2.5 to 3, and the etching factor of the second etching treatment is approximately 3 to 4. Because the second etching treatment uses a lower spray pressure and a lower etch solution temperature, the chemical dissolution rate of the etch solution on the copper layer sidewall is reduced, the ratio of longitudinal etching to lateral etching is increased, and the etching factor is correspondingly increased. As a result, the first copper thick surface penetrates the copper layer in a shorter etching time, and the accumulated amount of lateral etching is smaller, enabling the achievement of fine linewidths at the 30-micron level. Although the remaining copper thickness of the second copper thick surface is relatively large, after pre-removal by the first etching treatment, the residual copper thickness has been reduced to a controllable range, and the circuit patterning can also be completed within an acceptable amount of lateral etching in the second etching treatment.

[0069] After two etching processes, both sides undergo a stripping treatment to remove the dry film resist layer. The stripping is performed using an alkaline stripping solution at a temperature of 45°C to 55°C. After stripping, the linewidth of the second and first copper thick surfaces is measured. In this embodiment, the finished linewidth of the second copper thick surface is 80 to 150 micrometers, and the line spacing is 80 to 120 micrometers; the finished linewidth of the first copper thick surface is 30 to 75 micrometers, and the line spacing is 30 to 60 micrometers. The measurement results confirm that the finished linewidth and line spacing accuracy of both surfaces are within the design specifications.

[0070] S400, single-sided pre-overlay and lamination In this embodiment, a prepreg and copper foil are stacked on one side of the substrate, and a single-sided lamination is performed to form an odd-numbered layer structure. The difficulty of this single-sided lamination lies in the fact that only one side of the substrate is added with a new dielectric and conductive layer, while no material is added to the other side (the air-pressed side). This results in completely different heat and pressure conduction paths between the lamination side and the air-pressed side, and differences in resin flow and curing time between the two sides. If not controlled, this will cause serious board warping problems.

[0071] In this embodiment, the material preparation for single-sided lamination includes: selecting a prepreg with a coefficient of thermal expansion matching that of the substrate as the dielectric layer. The prepreg is a glass cloth substrate with a resin content of 55% to 65%, a glass transition temperature of 150°C to 180°C, and a coefficient of thermal expansion of 12ppm / °C to 16ppm / °C in the X / Y direction. An electrolytic copper foil of suitable thickness is selected as the conductive layer; the copper foil thickness is determined according to the functional requirements of the outer layer, and in this embodiment, it is 12 micrometers to 35 micrometers.

[0072] The prepreg and copper foil are then sequentially stacked on one side of the substrate for pre-stack positioning. This pre-stack positioning ensures accurate layer alignment using a positioning pin system. Specifically, positioning holes are pre-drilled in the substrate and copper foil, and positioning pins are used to precisely align each layer. After pre-stacking, high-temperature resistant tape is used to temporarily secure the edges to prevent misalignment during transport to the press.

[0073] The single-sided pressing was then performed using a stepped heating and pressing program controlled by a hot press. This stepped heating and pressing program addresses the thermal management issues of asymmetrical structures: the pressing surface (the side with the stacked materials) directly contacts the hot press platen, resulting in a rapid temperature rise and earlier resin flow and curing of the prepreg; the air-pressed surface (the side without stacked materials) receives heat through conduction within the substrate, leading to a slower temperature rise and delayed resin curing. If a conventional rapid heating program were used, the large temperature difference between the two sides would cause the resin to cure at different times, generating internal stress and ultimately causing warping of the board surface.

[0074] It should be noted that the stepped heating and pressing process includes the following temperature ranges: Heating Section: The temperature of the press hot plate is raised from room temperature to the first target temperature at a heating rate of 1.5℃ / min to 4.0℃ / min. In this embodiment, the heating rate is set to 2℃ / min, and the first target temperature is 130℃. The principle for selecting the heating rate is that a lower heating rate allows more time for heat to be conducted to the air-pressed surface through the thickness direction of the substrate, thereby reducing the temperature difference between the pressing surface and the air-pressed surface. When the heating rate is too high, the resin on the pressing surface begins to flow while the resin on the air-pressed surface remains in a glassy state, resulting in a large difference in state between the two surfaces.

[0075] First heat preservation stage: Maintaining the temperature at the first target temperature of 130°C for 15 to 30 minutes. The purpose of the first heat preservation stage is to create a time window during which the pressed surface no longer receives additional heat input, and heat is continuously conducted through the substrate to the air-pressed surface, causing the temperature of the air-pressed surface to gradually approach that of the pressed surface. When the temperature difference between the two surfaces narrows to a set range, the resin on both surfaces is in a flowing state, creating conditions for subsequent synchronous curing. In this embodiment, at the end of the first heat preservation stage, the temperature difference between the pressed surface and the air-pressed surface is controlled within 5°C.

[0076] Continued heating phase: The temperature continues to rise from the first target temperature of 130°C at a rate of 2°C / min to 3°C / min until the final pressing temperature is reached. In this embodiment, the final pressing temperature is 180°C to 200°C.

[0077] The second insulation stage involves maintaining the final pressing temperature for 60 to 90 minutes to complete resin curing. Due to the temperature equalization treatment in the first insulation stage, the resin on both sides is in a similar flow state when entering the final curing stage, resulting in near-synchronous curing reactions and a significant reduction in internal stress. It should be noted that the resin must reach a degree of curing of over 95% by the end of the second insulation stage to ensure that the interlayer bonding strength meets the reliability requirements for subsequent processing and long-term use.

[0078] Cooling section: After cooling to below 60°C at a rate not exceeding 3°C / min, the plate is removed from the heat exchanger. The slow cooling here helps to reduce residual stress caused by thermal shock.

[0079] In addition, the pressing pressure is controlled in stages throughout the pressing process: that is, a lower initial pressure (5 kgf / cm²) is applied during the heating stage and the first heat preservation stage. 2 Up to 15 kgf / cm 2 This allows the resin to flow and fill fully; after the heating phase begins, gradually increase the pressure to the final pressing pressure (25 kgf / cm²). 2 Up to 40 kgf / cm 2 This ensures tight bonding between layers and complete resin filling. In this embodiment, the final pressing pressure is set to 30 kgf / cm².2 .

[0080] In addition, the single-sided lamination should be performed in a vacuum environment. To this end, the press chamber must be evacuated to a residual pressure of no more than 5 kPa before lamination. The purpose of the vacuum environment is to remove residual gas between the layers, preventing the formation of air bubbles during resin flow. During the resin flow stage, if residual air exists between layers, this air will be trapped by the flowing resin, forming microbubbles. After curing, these microbubbles become permanent voids, affecting interlayer bonding and long-term reliability. Vacuum lamination allows for the pre-expansion of gas before resin flow, ensuring that the resin is not hindered by gas when filling conductor gaps, achieving the required filling rate. Furthermore, the vacuum level needs to be maintained until the resin enters the gel stage before being released, because the resin in the gel stage has begun cross-linking and curing, and no longer possesses the fluidity to trap gas.

[0081] After the pressing is completed, perform the following tests: Four-corner warpage measurement: The warpage height is measured at each of the four corners of the substrate to confirm that the warpage is within the specification range (in this embodiment, the warpage at room temperature is required to be no more than 0.75%). SEM cross-sectional observation was performed, and the interlayer bonding state of the pressed surface was observed under a scanning electron microscope to confirm that the resin of the prepreg completely filled the gaps between the conductors, there were no voids or delamination, and the copper foil and the prepreg were tightly bonded. For adhesion testing, a standard grid is etched on the copper foil of the bonding surface using the cross-cut adhesion test. The specified tape is then applied and peeled off, and the proportion of copper foil that has fallen off is observed to confirm that the interlayer adhesion level meets the requirements.

[0082] S500, Post-pressing treatment and single-sided grinding After single-sided lamination, the non-advanced layer (air-pressed surface) is ground on one side. The purpose of this single-sided grinding is to control the overall thickness uniformity of the odd-numbered layer printed circuit board and correct the surface unevenness of the non-advanced layer caused by asymmetric lamination. In the asymmetric lamination structure, the lamination surface has added layers of prepreg and copper foil. During the high-temperature curing process, the shrinkage of the resin and the thermal expansion difference of the copper foil will produce micro-undulations on the air-pressed surface. If this is not corrected, it will affect the uniformity of dry film adhesion and the consistency of outer layer copper thickness in subsequent outer layer processes. Specifically: Before performing single-sided grinding, the height distribution of the substrate is measured.

[0083] Here, a flatness measuring instrument or laser thickness gauge is used to perform a comprehensive scan of the non-adjustable surface to obtain height data at various points on the board surface. The scan employs a gridded measurement method, dividing the board surface into measurement points with a grid spacing of 10mm to 20mm. The thickness value at each measurement point is recorded, and each point is measured three times, with the average value taken to eliminate random measurement errors. Based on the height distribution data and the target board thickness, the amount of material removed during grinding in each area is determined.

[0084] The principle for determining the grinding removal depth is as follows: using the lowest point of the board surface as a reference, grind other areas to the same height as the lowest point, while ensuring that the thickness of the board after grinding is not less than the designed minimum thickness. In this embodiment, the maximum height difference of the board surface before grinding is 15 micrometers to 40 micrometers, and the target height difference after grinding is controlled within 5 micrometers.

[0085] The single-sided grinding was then performed using a surface grinding machine.

[0086] Key parameters for control during the grinding process include: grinding pressure controlled at 0.5 kgf / cm². 2 Up to 2kgf / cm 2 Within the specified range, the grinding disc rotation speed is controlled between 30 rpm and 80 rpm, and the substrate feed speed is controlled between 0.5 m / min and 2 m / min.

[0087] In addition, ceramic or non-woven abrasive brushes are used as the abrasive media, and the abrasive particle size is selected according to the removal amount and surface quality requirements. When the target removal amount is greater than 20 micrometers, a two-pass strategy of coarse grinding followed by fine grinding is adopted: coarse grinding uses coarser abrasive media to quickly remove the main material, while fine grinding uses finer abrasive media to correct the surface roughness to the target range. Intermediate measurements are taken on the board surface between the two passes to confirm that the removal amount of coarse grinding has reached the expected level before proceeding to the fine grinding stage.

[0088] During the grinding process, the following safety constraints are controlled: real-time monitoring of the grinding depth to prevent over-grinding that could expose the copper layer or damage the dielectric layer; maintaining a uniform removal rate in the grinding feed direction to avoid localized over-grinding that could create pits; and continuous supply of cooling water during the grinding process to prevent the accumulation of frictional heat that could soften and deform the resin layer. The flow rate of the cooling water is dynamically adjusted according to the grinding pressure and rotation speed, and the temperature in the grinding area is controlled to not exceed 50°C.

[0089] In addition, the stress release effect needs to be monitored during the grinding process. Because the asymmetric structure formed by single-sided lamination stores residual internal stress, the stress balance of the structure changes after grinding removes the material from the air-pressed surface, potentially causing secondary warping of the board surface. To control this stress release effect, a phased, progressive removal strategy is adopted during grinding. Each grinding step removes no more than 10 micrometers of material. After each grinding step, the substrate is left to stand for 5 to 10 minutes in a constant temperature and humidity environment of 23°C to 27°C and 45% to 65% to allow for sufficient stress release and redistribution. The board surface warping is measured to confirm no abnormalities before proceeding to the next grinding step. If a rebound in board warping is observed during grinding that exceeds specifications, grinding is paused, and the substrate undergoes a low-temperature baking stress-relief treatment (temperature 130°C to 150°C, time 30 to 60 minutes). Grinding continues only after the stress release has stabilized.

[0090] After grinding is completed, the following tests will be performed: A thickness gauge was used to measure the thickness at multiple points on the entire board to confirm that the overall thickness deviation was within the target range (in this embodiment, the thickness deviation is required to be no more than ±10%). The corner warp measurement was performed again to confirm that the warp amount did not rebound due to stress release during the grinding process; The surface roughness of the polished surface is measured to confirm that the roughness value meets the requirements for dry film attachment and copper layer adhesion in subsequent outer layer circuitry processes. Specifically, the surface roughness is controlled within the range of Ra 0.2 to 0.5 micrometers after fine polishing.

[0091] The surface morphology of the polished surface was observed under an optical microscope to confirm that there were no microscopic defects such as polishing scratches, pits or resin peeling, and to confirm that the surface of the dielectric layer was intact and the copper layer was not exposed.

[0092] In addition, after grinding and inspection, the substrate undergoes post-processing to meet the surface condition requirements of subsequent outer layer processes. The post-processing includes: Ultrasonic cleaning involves placing the substrate in a deionized water ultrasonic cleaning tank for 3 to 5 minutes to remove particulate residues and grinding dust generated during the grinding process. Acid pickling activation involves immersing the copper surface in a dilute sulfuric acid solution at room temperature for 30 to 60 seconds to remove the oxide film generated during grinding and cleaning, thereby restoring the chemical activity of the copper surface. Browning treatment involves browning (or blackening) the inner copper surface to form a uniform, micro-roughened copper oxide layer. The thickness of this layer is controlled within the range of 0.2 to 0.5 micrometers. Its function is to enhance the adhesion between the copper surface and other materials during subsequent lamination or outer layer processing. The browning solution uses a mixture of hydrogen peroxide and sulfuric acid, the treatment temperature is controlled within the range of 30°C to 40°C, and the treatment time is 60 to 120 seconds.

[0093] After browning, hot air drying is used to ensure that the board surface is completely dry and free of water stains, and that the surface condition of the substrate meets the requirements for subsequent outer layer circuit formation processes.

[0094] S600, Outer Layer Circuit Forming and Final Inspection The outer layer circuit pattern is constructed on the ground odd-layer substrate using a standard pattern electroplating process.

[0095] Specifically, the operational process for forming the outer layer circuit is as follows: pre-treatment of the outer copper surface of the substrate, including micro-etching and acid pickling, to give the copper surface a micro-roughened surface suitable for film application; applying a dry film photoresist to the outer copper surface; transferring the outer layer circuit CAM data to the dry film through exposure; forming windows of the circuit pattern on the dry film after development; performing pattern electroplating in the window area, depositing a copper layer to the required thickness and plating a tin protective layer; removing the dry film to expose the base copper in the non-circuit areas; etching to remove the base copper in the non-circuit areas, while the copper layer in the circuit areas protected by the tin layer is not etched; removing the tin protective layer, and the outer layer circuit pattern is completed.

[0096] The exposure energy and etching parameters for the outer layer circuitry are determined based on the outer copper thickness and the designed linewidth. In this embodiment, when the outer copper thickness is 30 to 50 micrometers, the etching compensation is set to 10 to 18 micrometers per side, and the exposure energy is set to 40 mJ / cm². 2 Up to 60mJ / cm 2 .

[0097] After the outer layer circuitry is formed, surface treatment is performed. Depending on customer requirements, the surface treatment may include immersion gold, solder spraying, electroless silvering, or OSP, to protect the solder pad areas for solderability.

[0098] The final inspection includes the following items: Outer layer line width measurement: Random sampling is performed on the line width and spacing of the outer layer lines to confirm that they are within the design specifications. In this embodiment, the tolerance requirement for the outer layer line width is within ±15% of the design value.

[0099] Characteristic impedance testing: A time-domain reflectometer is used to measure the impedance of signal lines with impedance control requirements. In this embodiment, the deviation between the measured impedance value and the design value is required to be within ±10%.

[0100] Section inspection: Samples are taken for metallographic sectioning, and microstructural parameters such as the thickness of each copper layer, the thickness of the dielectric layer, and the quality of copper plating on the hole walls are observed under a microscope to confirm that they are within the specification range.

[0101] Reliability testing includes thermal shock testing (immersion in tin at 288°C for 10 seconds, repeated multiple times, and checking for delamination or cracks) and high temperature and humidity testing (continuous operation at 85°C and 85% relative humidity for a specified time, followed by checking insulation resistance and appearance) to confirm the product's reliability in extreme environments.

[0102] After all inspections are passed, the finished odd-layer printed circuit board is obtained. During product flow, the finished odd-layer printed circuit board is free from risks such as board jamming, board drop, and excessive board warping. All cross-sections are within specifications, and reliability tests show no abnormalities.

[0103] In another specific implementation, such as Figure 2 As shown, this embodiment also provides an odd-layer printed circuit board manufacturing system, the system comprising: An electroplating module is used to perform two-step electroplating processes on a target layer of a substrate to form differentiated copper thicknesses. The electroplating module includes an electroplating tank, a DC power supply for supplying current to the electroplating tank, a circulating filtration system, a temperature control system for providing temperature control signals to the electroplating tank, and a current density adjustment unit. The current density adjustment unit is used to switch different current density setpoints between a first electroplating process and a second electroplating process.

[0104] An etching module is used to perform two differential etching operations on target layers with varying copper thicknesses to form circuit patterns. The etching module includes a horizontal conveyor etching machine, a spray pressure regulating system, an etching solution circulation and replenishment system for supplying etching solution to the horizontal conveyor etching machine, and a temperature control system. The spray pressure regulating system is used to switch between different spray pressure settings between the first and second etching processes.

[0105] A lamination module is used to stack a dielectric layer and a conductive layer on one side of a substrate and perform single-sided lamination to form an odd-layer structure. The lamination module includes a hot press, a stepped temperature control system, a pressure control system, and a vacuum system. The stepped temperature control system controls the hot press to execute a stepped heating and lamination process that includes a heat preservation section; after the hot press completes lamination, it transfers the substrate to a polishing module.

[0106] The grinding module is used to perform single-sided grinding on non-advanced layers to control the thickness uniformity of the entire board. The grinding module includes a surface grinding machine, a grinding pressure control system, a feed speed control system, and an online thickness monitoring system for thickness monitoring and feedback. After the surface grinding machine completes the grinding, it transfers the substrate to the outer layer processing module.

[0107] The outer layer processing module is used to form the outer layer circuit patterns and perform final inspection; after all inspections are passed, the finished odd-layer printed circuit board is obtained. The outer layer processing module includes outer layer processing equipment such as dry film laminators, exposure machines, developing machines, pattern electroplating lines, and etching lines, as well as various testing equipment.

[0108] Example 2 The difference from Example 1 is that this example provides the following steps: S301, based on optical scattering imaging, the etching depth of the first etching process is monitored in real time and the etching endpoint is automatically determined.

[0109] In this embodiment, etching is monitored in both the first and second etching processes using a real-time etching depth monitoring system. This system utilizes the differences in light scattering characteristics caused by variations in the surface microstructure of the copper surface at different etching depths to perform non-contact, real-time measurement of the etching depth. Based on the measurement results, it automatically determines the etching endpoints and dynamically adjusts the conveying speed.

[0110] The real-time etching depth monitoring system is installed inside the etching chamber, located in the transition section between the spray zone and the rinsing zone. The transition section is equipped with a transparent observation window and a localized air curtain isolation device. The air curtain isolation device forms a high-speed airflow barrier on the surface of the observation window to prevent etching solution from splashing and contaminating the optical components. When the substrate passes through the observation window, the air curtain forms a brief liquid-free window period above the copper surface, exposing the copper surface for optical acquisition.

[0111] The real-time etching depth monitoring system includes a structured light illumination unit, a diffuse light acquisition unit, and a signal processing unit. The structured light illumination unit uses a line laser generator to produce a linear beam parallel to the substrate's transport direction, illuminating the second copper thickness surface of the substrate at a 45-degree incident angle. The line laser wavelength is 635nm, and the beam width covers the entire effective area along the width direction of the substrate. Choosing a 45-degree incident angle maximizes the spatial separation between specular reflection and diffuse scattering, ensuring that the two types of light signals do not interfere with each other spatially, facilitating independent acquisition.

[0112] The scattered light acquisition unit includes two sets of linear CMOS cameras disposed above the substrate. The first set of cameras is located in the direction of the mirror reflection angle, i.e., at a 45-degree exit angle, to receive the light beam component reflected from the copper mirror surface. The signal intensity acquired by the first set of cameras is denoted as... The second set of cameras is located in the normal direction, that is, at a 0-degree exit angle, to receive the component of the light beam diffused by the copper surface. The signal strength acquired by the second set of cameras is denoted as... Both sets of cameras are driven by the same trigger signal to ensure synchronized data acquisition.

[0113] After receiving the image data from the two sets of cameras, the signal processing unit calculates the scattering ratio at each pixel location. : The scattering ratio here is used to represent the current microstructure of the copper surface: the unetched electroplated copper surface exhibits a smooth microstructure and a specular reflection component. Dominant The value is low; as the etching penetration depth increases, etching pits and grain boundary structures appear on the copper surface, and the diffuse reflection component is low. Gradually increase The value increases accordingly; when the etching depth approaches the copper layer penetration point, pinholes and discontinuous areas appear on the copper surface. The value changes abruptly, and so on.

[0114] Before the real-time etching depth monitoring system is put into use, the scattering ratio needs to be established through calibration experiments. With etching depth The correspondence between them.

[0115] The calibration experiment involves taking several calibration samples with the same material and copper thickness as the production substrate, and etching each calibration sample to different preset depths ranging from 0 micrometers to 100% of the target copper thickness, with a step interval of 5% of the target copper thickness.

[0116] Then, optical scattering imaging measurements were performed on the etched surface of each calibration sample, and the corresponding scattering ratio was recorded. The actual etching depth of the etched calibration sample was measured using cross-sectional sections and a metallographic microscope. The measured etching depth was then plotted on the x-axis, and the scattering ratio on the y-axis to obtain the following result: Figure 3 shown - The calibration curve, the final calibration curve, exhibits an S-shaped characteristic: [Etching initial stage] Slowly increase, mid-etching stage Accelerating and increasing in size, approaching penetration. It increased dramatically. Then, in the form of a lookup table, the aforementioned... - The calibration curve is written into the signal processing unit.

[0117] For example, using an original copper thickness of 70 micrometers on the second copper thickness surface as the calibration target, the step interval is 3.5 micrometers. The calibration result is: Etching depth 0 micrometers, corresponding to = 0.05; Etching depth of 14 micrometers, corresponding to = 0.08; Etching depth 28 micrometers, corresponding to = 0.15; Etching depth 35 micrometers, corresponding to = 0.28; Etching depth 42 micrometers, corresponding to = 0.45; Etching depth 49 micrometers, corresponding to = 0.72; Etching depth of 56 micrometers, corresponding to = 1.2; Etching depth 63 micrometers, corresponding to = 2.8; Etching depth 70 micrometers (complete penetration), corresponding to = 8.5.

[0118] From the calibration data above, it can be seen that when When the value increases from 0.15 to 0.72, the corresponding etching depth increases from 28 micrometers to 49 micrometers, which is from 40% to 70% of the copper thickness, covering the target removal range (40% to 60%) of the first etching process.

[0119] During the production process of the first etching process, the etching cavity is provided with three observation windows at equal intervals along the conveying direction, located at the 1 / 4, 1 / 2 and 3 / 4 positions of the etching stroke, respectively.

[0120] When the substrate enters the etching cavity entrance, the signal processing unit performs a reference measurement and records the initial scattering ratio of the second copper thickness surface in the unetched state. .

[0121] As the substrate passes through each observation window position, the signal processing unit performs a scattering measurement, and the measured data... Substitute the value into the calibration curve lookup table to obtain the current etching depth. Simultaneously, the signal processing unit calculates the current etching removal ratio. : ,in The original copper thickness is the second copper thickness surface.

[0122] The signal processing unit then performs automatic etch endpoint determination based on the real-time removal ratio. The endpoint determination logic here includes the following case handling: 1) When the measurement results of the substrate at the second observation window are displayed When the etching progress is within the range of 20% to 30%, the signal processing unit determines that the etching progress is normal, and the substrate continues to pass through the second half of the etching cavity at the current conveying speed. 2) When the measurement results of the substrate at the second observation window are displayed When the etching progress is below 20%, the signal processing unit determines that the etching progress is too slow. The signal processing unit then sends a deceleration command to the conveyor roller controller to reduce the conveying speed of the substrate in the latter half of the etching cavity; the corresponding adjustment amount for the conveying speed is: ,in The measured removal percentage is shown in the second observation window. The theoretically expected removal percentage for this location (25% in this embodiment).

[0123] For example, if the measurement at the second observation window is = 18%, theoretical expected value is 25%, original transmission speed is = 2.0 m / min, then the adjusted conveyor speed is = 2.0 18 / 25 = 1.44 m / min. The substrate passes through at a reduced speed of 1.44 m / min in the latter half, increasing the etching dwell time so that the total removal ratio is compensated to the target range when the board exits.

[0124] 3) When the measurement results of the substrate at the second observation window are displayed When the etching progress exceeds 35%, the signal processing unit determines that the etching progress is too fast. At this time, the signal processing unit sends an acceleration command to the conveyor roller controller to increase the conveying speed of the substrate in the latter half of the etching chamber and shorten the etching dwell time. When the concentration exceeds 35% at the first observation window, the signal processing unit triggers an emergency warning signal and outputs an inspection command indicating abnormal etching solution concentration or spray system status to the operation terminal.

[0125] It should be noted that the dynamic adjustment of the conveying speed is achieved through a variable frequency speed control roller conveyor. The conveying roller conveyor of the etching cavity is divided into at least two independent drive sections, each driven by an independent variable frequency motor. The conveying speed of each section is independently adjustable in the range of 0.5 m / min to 3 m / min.

[0126] The real-time etching depth monitoring system also performs in-plane uniformity monitoring in the width direction of the substrate. The pixel array of the linear CMOS camera covers the entire area in the width direction of the substrate, and the signal processing unit performs statistical analysis on the scattering ratio of each pixel position in the width direction to obtain the etching depth distribution curve in the width direction.

[0127] When the difference between the maximum and minimum depth values ​​in the distribution curve exceeds the in-plane uniformity tolerance threshold (set to 8% of the target etching depth in this embodiment), the signal processing unit generates a spray uniformity abnormality alarm. The alarm information here includes the deviation direction and deviation degree to instruct the operator to perform a blockage check or pressure calibration on the nozzles in the corresponding area.

[0128] S302 performs online evaluation of the reactivity of the etching solution based on electrochemical impedance spectroscopy and adaptively adjusts the etching process parameters.

[0129] In this embodiment, an online electrochemical impedance spectroscopy (EIS) evaluation system is configured in the etching solution circulation pipelines of the first etching process and the second etching process. The online EIS evaluation system applies a small-amplitude AC perturbation signal to the etching solution and analyzes its frequency response characteristics to obtain the charge transfer resistance and diffusion impedance parameters of the etching solution in real time, thereby predicting the real-time reactivity of the etching solution and adaptively adjusting the etching process parameters accordingly.

[0130] The probe of the online electrochemical impedance spectroscopy evaluation system is installed in the reflux section of the etching solution circulation pipeline, near the etching chamber outlet. The probe employs a three-electrode system: the working electrode is a copper sheet electrode made of the same material as the copper surface of the substrate being etched, with an exposure area of ​​1... It is a replaceable consumable part; the reference electrode is an Ag / AgCl electrode, which provides a stable potential reference; the counter electrode is a platinum sheet with an area greater than 10 times that of the working electrode.

[0131] The online electrochemical impedance spectroscopy evaluation system is driven by a frequency response analyzer. The frequency response analyzer applies a sinusoidal AC potential perturbation with an amplitude of 5 mV to 10 mV to the working electrode, ensuring that the electrochemical system remains within its linear response range. A three-frequency point rapid measurement strategy is used instead of full-band scanning, reducing the single measurement time from 30 to 60 seconds required for full-band scanning to 3 to 5 seconds, achieving high-frequency monitoring every 10 seconds. The three characteristic frequency points are: High frequency point The value ranges from 10 kHz to 50 kHz. At this high frequency, the impedance response primarily reflects the solution resistance of the etching solution. The solution resistance It is directly related to the total ion concentration and temperature of the etching solution. An increase in temperature corresponds to a decrease in the concentration of the corresponding ions or a decrease in the liquid temperature.

[0132] Mid-frequency point The value ranges from 10 Hz to 100 Hz. At this mid-frequency point, the charge transfer resistance in the impedance response... The contribution of the charge transfer resistor reaches its maximum value. Reflecting the kinetic rate of copper dissolution reaction in the etching solution, A smaller value indicates that the copper dissolution reaction proceeds more easily, resulting in a higher etching rate. When the concentration of copper ion byproducts in the etching solution is high, the reverse reaction of copper dissolution is promoted. The corresponding increase.

[0133] low frequency point The value ranges from 0.5 Hz to 2 Hz. At this low frequency point, the Warburg diffusion impedance in the impedance response... The contribution is significant. The Warburg diffusion impedance... The diffusion coefficient reflects the mass transfer capacity of oxidizing species in the etching solution to diffuse to the copper surface. When the accumulation of copper ions in the etching solution leads to an increase in solution viscosity, the diffusion coefficient decreases. Increase.

[0134] The signal processing unit constructs an etch rate prediction model based on the three extracted impedance parameters: In the formula, To predict the etching rate, the unit is micrometers per minute. to These are the model coefficients. The correlation coefficients were determined through calibration experiments: etching solution samples with different concentrations, temperatures, and byproduct contents were prepared, and three-frequency point measurements and standard copper sheet etching rate tests were performed on each group of samples. The coefficient values ​​were obtained by fitting the samples using the least squares method.

[0135] For example, in the copper chloride etching solution system of this embodiment, the model coefficients obtained by calibration are: =12.5, = -0.8, = -3.2, = -1.5, = 0.02, = 0.15, = 0.05, = 0.1, = 0.03, =0.08. When measured = 2.1Ω, = 0.8Ω, When = 1.2Ω, substituting, we get = 12.5 + (-0.8) 2.1 + (-3.2) 0.8 + (-1.5) 1.2 + 0.02 × 2.1 2 +0.15×0.82 + 0.05×1.2 2 +0.1 2.1 0.8 +0.03 2.1 1.2 + 0.08 0.8 1.2 = 7.0366 micrometers per minute.

[0136] The signal processing unit will predict the etching rate. With target etching rate After comparison, the following adaptive adjustment logic is executed: when Less than At this point, the etching solution activity is determined to be low. The signal processing unit then diagnoses the primary cause of the decreased activity based on the relative changes in three impedance parameters: like The largest relative change indicates a decrease in solution concentration or a low temperature. A heating command is sent to the etching solution heating system, with a single heating increment not exceeding 2°C, or the replenishment pump is started to replenish fresh etching solution. like The relative change is the largest. The change was minimal, indicating that the high copper ion concentration inhibited the dissolution reaction. Therefore, a drainage and replenishment cycle was initiated to reduce the copper ion concentration. like The relative change was the largest, indicating that the increased solution viscosity was causing limited mass transfer. Therefore, a drain-replenishment cycle was initiated, and the circulation pump flow rate was increased. Simultaneously with the adjustment, the signal processing unit reduced the substrate conveying speed by a reduction of [value missing]. .

[0137] when Greater than If the etching solution activity is too high, the signal processing unit will perform reverse adjustment: lower the etching solution temperature, reduce the replenishment amount, or increase the transmission speed. The calculation method for the increase in transmission speed is the same as when the activity is too low.

[0138] when In to When within the specified range, all current parameters remain unchanged.

[0139] It should be noted that the online electrochemical impedance spectroscopy evaluation system requires probe self-calibration, which includes two modes: timed calibration and cross-validation. Timed calibration performs a full-band scan every 4 hours, comparing the morphology of the full-band Nyquist plot with a standard curve to assess the degree of degradation of the working electrode surface. When the deviation exceeds a set threshold, the system prompts for electrode replacement. Cross-validation is achieved by setting two independent sets of probes at different locations in the etchant circuit. The measurement results of the two sets of probes are compared in real time. When the deviation exceeds the allowable range, it is determined that one set of probes may have failed, and the system automatically switches to the other set of probes as the primary probe.

[0140] S303 performs online detection of the morphology of the etched circuit based on machine vision and feeds forward to correct the etching parameters of the subsequent substrate.

[0141] In this embodiment, an online visual inspection station is set between the outlet of the rinsing section of the etching chamber and the inlet of the stripping section. This online visual inspection station performs real-time inspection of the circuit morphology of the etched substrate still covered with resist dry film, utilizing the natural color contrast between the resist dry film and the etched exposed dielectric layer as a detection signal source. Specifically, the resist dry film is dark (blue or green), and the etched exposed dielectric layer has a light background color (beige or white). The color difference between the two in the CIELAB color space is greater than 40, enabling high-contrast detection without additional marking.

[0142] The online visual inspection station includes a line scan camera, a ring illumination unit, and an image processing unit. The line scan camera is a high-resolution color line scan CMOS camera with a pixel resolution of 5 to 10 micrometers per pixel. The scanning direction is perpendicular to the substrate transport direction, and the scanning width covers the entire substrate. During substrate transport, the line scan camera synchronously triggers line-by-line acquisition according to the transport speed, stitching together to form a full-frame two-dimensional image of the substrate surface. In this embodiment, the pixel resolution is set to 7 micrometers per pixel, the substrate width is 500 mm, and the number of pixels per row is approximately 71,429. The ring illumination unit provides a uniform diffused LED light source at the acquisition position of the line scan camera, eliminating interference from high-gloss areas caused by specular reflection from the copper surface.

[0143] The image processing unit performs the following analysis process on the acquired image data stream: The image processing unit performs HSV color space conversion on each frame of the image and performs threshold segmentation on the H channel. The hue value of the resist dry film falls within the blue to green range (H channel value 120 to 180), and the hue value of the dielectric layer background color falls within the yellow to white range (H channel value 20 to 60). Then, binarization segmentation is performed using the H channel threshold to divide the image into line regions and trench regions. The line regions correspond to the copper layer retained under the dry film coverage, and the trench regions correspond to the portions where the copper layer has been etched away, exposing the dielectric layer.

[0144] The image processing unit extracts the edge contours of the trench region from the segmented binary image, obtaining the left and right edge lines on both sides of each line. The distance between the left and right edges is measured at multiple sampling points on each line to obtain the etched trench width at that location. The sampling interval is 50 micrometers.

[0145] The image processing unit then calculates the actual line width based on the measured groove width. : In the formula, The design spacing between the centers of two adjacent lines is determined automatically by recognizing the periodic repeating structure of the line pattern. value.

[0146] Simultaneously calculate the lateral erosion amount. : In the formula The width of the trench opening designed in the CAM data. A positive value indicates over-etching, i.e., the line is too narrow, and a negative value indicates under-etching, i.e., the line is too wide.

[0147] For example, in this embodiment, the design line spacing of a certain detection area on the first copper thickness surface is... The trench opening width is designed to be 60 micrometers. It is 30 micrometers (corresponding to a design linewidth of 30 micrometers). The measurement was... The actual value is 34 micrometers, therefore the actual linewidth is... = 60 - 34 = 26 micrometers, lateral erosion amount = (34 - 30) / 2 = 2 micrometers. The actual linewidth of 26 micrometers is 4 micrometers narrower than the design value of 30 micrometers, which is 13.3%.

[0148] In addition, the image processing unit has a built-in linewidth compensation model from before to after film removal. Since the top of the line is still covered by dry film during detection, the undercut area obscured by the edge of the dry film is fully exposed after film removal, resulting in a final linewidth slightly narrower than the measured value with film. The compensation model is as follows: In the formula The decoction compensation amount is set to -3 micrometers in this embodiment. In the example above, the predicted final linewidth after decoction is 26 + (-3) = 23 micrometers.

[0149] Finally, the image processing unit performs statistical analysis on the linewidth measurements across the entire board surface, calculating the mean, standard deviation, maximum, and minimum values ​​to generate a spatial distribution map of the linewidth deviation. The image processing unit then feeds the statistical analysis results forward to the etching parameter control system to perform parameter pre-corrections on the substrate subsequently entering the etching chamber. When a systematic linewidth deviation is detected, and the average deviation exceeds 30% of the design tolerance, the etching parameter control system performs one or more of the following adjustments on the subsequent substrate: increasing the transfer speed to reduce etching time, decreasing the spray pressure to reduce etching intensity, and decreasing the etch solution temperature to reduce the reaction rate. The adjustment range of each parameter is proportional to the amount of linewidth deviation.

[0150] When a systematic linewidth deviation is detected and the average deviation exceeds 30% of the design tolerance, the etching parameter control system performs reverse adjustment: reducing the conveying speed, increasing the spray pressure, or increasing the etching solution temperature.

[0151] When a localized deviation is detected, such as a narrower linewidth on the left half of the substrate while the right half is normal, the etching parameter control system determines that the spray uniformity in the corresponding area is abnormal and issues a nozzle status check command. For etching equipment equipped with independent zoned spray pressure control, the etching parameter control system automatically reduces the spray pressure of the nozzle group corresponding to the abnormal area.

[0152] When the linewidth deviation of three consecutive substrates shows a monotonically increasing trend, the etching parameter control system determines that the etching conditions are continuously drifting. In addition to performing real-time parameter correction, it outputs an etching solution status warning to the operation terminal, prompting the operation to perform solution replacement or large-scale solution replenishment, and so on.

[0153] It should be noted that the online visual inspection station and the subsequent AOI final inspection form a dual-layer quality protection system. The online visual inspection station acts as the first line of defense, immediately inspecting after etching with a response delay of 1 to 2 substrates, serving as a trend monitoring and early correction of conditional drift. The AOI final inspection acts as the second line of defense, performing a precise full inspection after film removal and all subsequent processes, serving as the final pass / fail determination. The synergistic effect of these two layers of protection is that the online visual inspection station captures and corrects early drift in etching conditions in a timely manner, reducing the etching-related defect rate flowing into the AOI final inspection by an order of magnitude.

[0154] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

[0155] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit described above can be implemented in hardware.

[0156] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for manufacturing an odd-layer printed circuit board, characterized in that, include: A first electroplating process is performed on both sides of the target layer of the substrate to make the first surface of the target layer reach a first preset thickness; The first surface of the target layer is protected. A second electroplating process is performed on the second surface of the target layer to make the second surface reach a second preset thickness, thereby forming a first copper thick surface and a second copper thick surface on both sides of the target layer, wherein the second preset thickness is greater than the first preset thickness, and the first surface and the second surface are opposite to each other. A first etching process is performed on the target layer to remove the first copper layer on the second copper thickness surface; and a second etching process is performed on both sides of the target layer to form corresponding circuit patterns respectively. A single-sided lamination is performed on a dielectric layer and a conductive layer stacked on one side of the substrate to form an odd-numbered layer structure; Based on the odd-layer structure, an outer layer circuit pattern is constructed to obtain an odd-layer printed circuit board. The first etching process further includes: performing real-time monitoring of the etching depth of the second copper thick surface to obtain the current scattering ratio value of the second copper thick surface; determining the current etching removal ratio based on the scattering ratio value; and adjusting the conveying speed of the substrate in the etching cavity based on the deviation between the current etching removal ratio and the target removal ratio. The first etching process and the second etching process further include: applying a multi-frequency AC perturbation signal to obtain the solution resistance, charge transfer resistance and diffusion impedance parameters of the etching solution; calculating the real-time predicted etching rate of the etching solution based on the solution resistance, the charge transfer resistance and the diffusion impedance parameters; comparing the real-time predicted etching rate with the target etching rate, and adjusting at least one of the etching solution temperature, replenishment volume and substrate transport speed according to the deviation direction and deviation amplitude; The second etching process further includes: performing online visual inspection on the etched substrate, acquiring a full-frame two-dimensional image of the substrate surface using a line scan camera, performing color space conversion and threshold segmentation on the image to distinguish between line areas and trench areas, extracting the edge contour of the trench area to obtain the etching trench width, calculating the actual line width and side etching amount based on the etching trench width, and feeding the statistical analysis results of the line width deviation forward to the etching parameter control system to perform parameter pre-correction on the substrate that subsequently enters the etching cavity.

2. The manufacturing method according to claim 1, characterized in that, In the first electroplating process and the second electroplating process, the current density of the first electroplating process is greater than the current density of the second electroplating process.

3. The manufacturing method according to claim 2, characterized in that, The protection process includes: A photosensitive film is attached to the first thick copper surface of the target layer to prevent the plating solution from contacting the first thick copper surface during the second electroplating process.

4. The manufacturing method according to claim 1, characterized in that, The first etching process uses a first spray pressure and a first etching compensation amount, and the second etching process uses a second spray pressure and a second etching compensation amount; wherein the first spray pressure is greater than the second spray pressure, and the first etching compensation amount is greater than the second etching compensation amount.

5. The manufacturing method according to claim 1, characterized in that, The single-sided pressing adopts a stepped heating and pressing process, which includes at least one heat preservation section.

6. The manufacturing method according to claim 5, characterized in that, The single-sided pressing process also includes: Single-sided grinding is performed on the non-additional layers to control the overall thickness uniformity of the odd-numbered layer printed circuit board.

7. The manufacturing method according to claim 1, characterized in that, The second thick copper surface is used to carry power lines and ground lines, while the first thick copper surface is used to carry high-density signal lines.

8. An odd-layer printed circuit board, characterized in that, Manufactured using the manufacturing method described in any one of claims 1 to 7.

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