A method for manufacturing a high-density interconnection control printed circuit board

Abstract

This invention proposes a method for fabricating a high-density interconnect control printed circuit board. The method involves sequentially fabricating inner layer circuitry, etching, and optical inspection after substrate preparation, followed by browning and laminating with a prepreg and outer copper foil to obtain a laminated board. The laminated board is then routerted, browned to reduce copper content, laser-drilled to form blind vias, and mechanically drilled to form through-holes. Sequential processes include desmearing and shadow removal, via filling with electroplating to the target thickness, and grinding to the target copper thickness. A comprehensive quality evaluation of the copper surface is performed, and based on the results, micro-etching, reduction, or cleaning treatments are selected. The outer layer circuitry is fabricated and etched. The outer layer undergoes automated optical inspection to obtain the finished product. This method improves interlayer alignment accuracy, blind via quality, and copper surface adhesion through multi-step closed-loop control.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board manufacturing technology, and in particular to a method for preparing a high-density interconnect control printed circuit board. Background Technology

[0002] High-density interconnect printed circuit boards (PCBs) are one of the core components of electronic products, enabling high-density electrical connections between electronic components. They are widely used in many fields such as communications, computers, consumer electronics, and automotive electronics. Their performance and quality directly affect the reliability, stability, and signal transmission quality of the entire electronic product.

[0003] As electronic devices evolve towards higher performance, smaller size, and higher integration, the number of layers and interconnect density of HDI boards are continuously increasing. Current HDI board manufacturing processes mainly face the following technical challenges: First, HDI boards of order five or higher require multiple lamination processes. After each lamination, the flow characteristics of the prepreg, the ductility of the copper foil, and the cumulative tolerances of each layer all affect the uniformity of the dielectric layer thickness and the accuracy of interlayer alignment. Existing technologies mainly involve pre-compensating for material expansion and contraction before lamination (e.g., establishing an expansion and contraction library before producing inner layer films), or measuring expansion and contraction values ​​after lamination and labeling them in batches, subsequently using corresponding compensation data based on the batching. However, both of these methods belong to the open-loop control mode of "pre-compensation before lamination" or "measurement and batching after lamination"—the temperature and pressure during the lamination process are dynamically changing, and the real-time expansion and contraction of the material during heating cannot be accurately predicted before lamination, nor can it be corrected after lamination. The lack of real-time monitoring and dynamic intervention methods for the expansion and contraction state during lamination leads to the long-standing problem of interlayer misalignment.

[0004] Secondly, laser drilling leaves resin residue on the walls and bottom of blind holes. If this residue is not removed, it will affect the quality of the hole walls and the adhesion of the electroplated layer. In existing technologies, residual adhesive removal mainly employs preset plasma adhesive removal or two independent adhesive removal processes. Automated optical inspection occurs after the adhesive removal process to detect the removal effect, rather than providing feedback control during the process. In other words, the existing residual adhesive removal method is an open-loop model of "removing according to preset parameters first, then inspecting," which cannot make real-time adjustments based on the actual residual adhesive state of each blind hole, making it difficult to guarantee the thoroughness and consistency of adhesive removal.

[0005] Third, while the grinding process removes excess copper, it may introduce problems such as uneven surface roughness, localized oxidation, or contamination. In existing technologies, roughness testing, oxide layer testing, and cleanliness testing are all independent testing methods, used for different quality control purposes, without forming a systematic and comprehensive evaluation system. Copper surface treatment methods are also relatively simple, typically employing uniform micro-etching or browning of the entire board, making it impossible to select a targeted treatment method based on the actual condition of the copper surface (whether the roughness meets standards, whether oxidation is present, or whether contamination exists). Summary of the Invention

[0006] In view of the above, the main objective of this invention is to provide a method for manufacturing a high-density interconnect control printed circuit board in order to solve the above-mentioned technical problems.

[0007] This invention proposes a method for fabricating a printed circuit board for high-density interconnect control, the method comprising the following steps: Step 1: Obtain the substrate and cut it to obtain the cut substrate; sequentially perform inner layer circuit fabrication, inner layer etching, and inner layer automatic optical inspection on the cut substrate to obtain the core board with inner layer circuits; perform browning treatment on the core board with inner layer circuits to obtain the browned core board; press the browned core board with the prepreg and the outer copper foil to obtain the laminated board. Step 2: Routing the edges of the laminated board removes excess material, resulting in a routerd laminated board; Browning and copper reduction are performed on the routerd laminated board to reduce the thickness of the outer copper foil, resulting in a copper-reduced laminated board; Laser drilling is performed on the copper-reduced laminated board to form blind holes, resulting in a laser-drilled laminated board; Mechanical drilling is performed on the laser-drilled laminated board to form through holes, resulting in a drilled laminated board. Step 3: After drilling, the laminated board is subjected to descaling and shadow treatment in sequence to obtain a shadow treatment board; the shadow treatment board is then subjected to hole-filling electroplating to plate the copper in the blind holes and through holes to the target thickness to obtain a hole-filling electroplated board; the hole-filling electroplated board is then subjected to grinding treatment to grind the surface copper thickness to the target thickness of the outer layer circuit fabrication to obtain a surface copper compliant board. Step 4: Conduct a comprehensive evaluation of the copper surface quality of the copper-compliant board. Based on the comprehensive evaluation results, select at least one of the following methods to treat the copper surface: micro-etching, reduction, or cleaning, to obtain a qualified copper surface board. Step 5: Fabricate the outer layer circuitry on the qualified copper surface board to obtain a circuit board with outer layer circuitry; perform outer layer etching on the circuit board with outer layer circuitry to remove excess copper foil and obtain the etched circuit board. Step 6: Perform automatic optical inspection on the outer layer of the etched circuit board to obtain the finished high-density interconnect control printed circuit board.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention monitors the expansion and contraction status of each layer in real time during the pressing process and dynamically adjusts the pressing parameters. After pressing, the layers are grouped according to the amount of expansion and contraction, and different laser drilling compensation coefficients are used for laser drilling in different groups. This achieves the coordinated cooperation between active compensation during the pressing process and differentiated drilling after pressing. A closed-loop control of expansion and contraction is formed from the pressing process to subsequent drilling, which effectively improves the alignment accuracy between layers.

[0009] 2. This invention detects residual adhesive at the bottom of blind holes after laser drilling, adjusts laser parameters based on the detection results until the amount of residual adhesive is below a threshold, and removes it online by increasing the number of laser pulses or adjusting the laser energy density when the amount of residual adhesive exceeds the threshold. This establishes a closed-loop removal mechanism of "detection-judgment-feedback adjustment", which can detect and adjust the actual residual adhesive state of each blind hole in real time, greatly improving the thoroughness and consistency of residual adhesive removal.

[0010] 3. This invention performs a comprehensive evaluation of the copper surface quality after grinding. The comprehensive evaluation includes at least one of roughness detection, oxide layer detection and cleanliness detection. Based on the results of each test, micro-etching treatment, reduction treatment or cleaning treatment is selected respectively. This realizes a multi-dimensional comprehensive evaluation and differentiated treatment of the copper surface quality after grinding, and can select a targeted treatment method according to the actual quality state of the copper surface. Attached Figure Description

[0011] Figure 1 This is a flowchart of the fabrication method of the high-density interconnect control printed circuit board proposed in this invention; Figure 2 This is a schematic diagram of the X-Ray target shape and layer markings for monitoring compression expansion and contraction provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the laser drilling alignment target pattern structure provided in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the daisy chain graphic structure for laser aperture misalignment detection provided in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the model hole and coefficient hole positions for calibrating the tensile coefficient of the laser drill strip provided in Embodiment 1 of the present invention. Detailed Implementation

[0012] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0013] These and other aspects of the embodiments of the present invention will become clear from the following description and accompanying drawings. In these descriptions and drawings, some specific embodiments of the present invention are specifically disclosed to illustrate some ways of implementing the principles of the embodiments of the present invention; however, it should be understood that the scope of the embodiments of the present invention is not limited thereto.

[0014] Example 1 Please see Figure 1 This embodiment provides a method for fabricating a printed circuit board for high-density interconnect control, the method comprising the following steps: Step 1: Obtain the substrate and cut it to obtain the cut substrate; sequentially perform inner layer circuit fabrication, inner layer etching, and inner layer automatic optical inspection on the cut substrate to obtain the core board with inner layer circuits; perform browning treatment on the core board with inner layer circuits to obtain the browned core board; press the browned core board with the prepreg and the outer copper foil to obtain the laminated board. During the lamination process, an online X-ray monitoring system is used to monitor the expansion and contraction status of each layer in real time. Based on the monitoring results, lamination parameters are dynamically adjusted to compensate for interlayer expansion and contraction offsets. Specifically, when the expansion and contraction offset of a certain layer exceeds a preset value, at least one of the following is adjusted: lamination temperature (adjustment range ±5℃), pressure (adjustment range ±0.5MPa), and holding time (adjustment range ±3min), resulting in a lamination plate after expansion and contraction compensation. After the lamination step is completed, the lamination plates after expansion and contraction compensation are grouped according to the amount of expansion and contraction, with a grouping tolerance of ±3mil. Different laser drilling compensation coefficients are used for subsequent laser drilling for different expansion and contraction groups. Step 2: Routing the edges of the laminated board removes excess material, resulting in a routerd laminated board; Browning and copper reduction are performed on the routerd laminated board to reduce the thickness of the outer copper foil, resulting in a copper-reduced laminated board; Laser drilling is performed on the copper-reduced laminated board to form blind holes, resulting in a laser-drilled laminated board; Mechanical drilling is performed on the laser-drilled laminated board to form through holes, resulting in a drilled laminated board. During laser drilling, a laser confocal scanning microscope is used to detect residual adhesive at the bottom of the blind hole after laser drilling. The residual adhesive threshold is 5% of the bottom area of ​​the blind hole. The laser parameters are adjusted according to the detection results until the residual adhesive is lower than the residual adhesive threshold. When the residual adhesive exceeds the residual adhesive threshold, it is removed online by increasing the number of laser pulses (increasing by 1-2 pulses each time) or adjusting the laser energy density (adjustment range ±0.5J / cm²). Step 3: After drilling, the laminated board undergoes desmearing and shadow removal treatments to obtain a shadow-treated board. The shadow-treated board is then subjected to through-hole plating, where copper is plated into the blind and through holes to the target thickness, resulting in a through-hole plated board. During the through-hole plating process, the copper thickness is measured in real-time, and the plating parameters are dynamically adjusted based on the measurement results to control the copper thickness within the target range. The target copper thickness range is the target thickness of the outer layer circuitry plus 3μm-8μm. When the measured copper thickness exceeds the upper limit of the target range, the plating current density is reduced by 0.1-0.3A / m². The through-hole plated board is then ground to achieve the target copper thickness for the outer layer circuitry, resulting in a board with acceptable copper thickness. Step 4: Conduct a comprehensive evaluation of the copper surface quality of the qualified copper board. The comprehensive evaluation includes roughness detection using a white light interferometer, oxide layer detection using X-ray photoelectron spectroscopy, and cleanliness detection using contact angle measurement. When the roughness Ra value is greater than or equal to 0.2 μm, micro-etching is selected; when the oxide layer thickness is greater than or equal to 5 nm, reduction is selected; and when the water contact angle is greater than or equal to 60°, cleaning is selected, resulting in a qualified copper surface board. Step 5: Fabricate the outer layer circuitry on the qualified copper-coated board to obtain a circuit board with outer layer circuitry; perform outer layer etching on the circuit board with outer layer circuitry to remove excess copper foil, resulting in an etched circuit board. During the outer layer etching process, the etching uniformity is monitored in real time, and the spray parameters are dynamically adjusted based on the uniformity monitoring results, including adjusting the pressure ratio of the upper and lower sprays, to maintain the etching uniformity above 97%. Step 6: Perform automatic optical inspection on the outer layer of the etched circuit board to obtain the finished high-density interconnect control printed circuit board.

[0015] Please see Figures 2 to 5 As a preferred embodiment, in Embodiment 1, during substrate cutting and inner layer circuit fabrication, the following pattern is designed on the board edge: the layer type (e.g., L3-6, L2-7) is marked next to the target shape of each inner layer, and 3 main targets and 4 sub-targets are set ( Figure 2 Each laser target layer has a laser alignment target pattern designed at each of its four corners and along its short and long sides. The outer frame is a 3×3mm square with a frame thickness of 0.3mm. The center is a circular PAD with a diameter of 0.5mm. The target is 1.5mm from the outer edge and 20-80mm from the edge of the board. The layer type (e.g., LS1-2, LS2-3) is marked next to the target. At the same time, a laser hole is added in the laser drilling tape at the center of the target. Figure 3 ); Design a daisy chain pattern on each of the four corners and along each side of the layer with laser-drilled holes (8 in total). The daisy chain PAD is 3 mil larger on each side than the smallest hole diameter in the unit. Each pattern contains 30 holes (3 rows × 10 rows). The center-to-center spacing of the PADs is 0.66 mm. The outer layers are connected accordingly. Solder mask windows are opened on the left and right test PADs. Figure 4 Design a model hole at the edge of the plate, and design a coefficient hole of 0.105mm 3mm behind it. Figure 5 These graphics are used for precise positioning and inspection during subsequent pressing, laser drilling, and expansion / contraction compensation.

[0016] Example 2 This embodiment provides a method for fabricating a printed circuit board for high-density interconnect control, the method comprising the following steps: Step 1: Obtain the substrate and cut it to obtain the cut substrate; sequentially perform inner layer circuit fabrication, inner layer etching, and inner layer automatic optical inspection on the cut substrate to obtain the core board with inner layer circuits; perform browning treatment on the core board with inner layer circuits to obtain the browned core board; press the browned core board with the prepreg and the outer copper foil to obtain the laminated board. During the lamination process, an online X-ray monitoring system is used to monitor the expansion and contraction status of each layer in real time. Based on the monitoring results, lamination parameters are dynamically adjusted to compensate for interlayer expansion and contraction offsets. Specifically, when the expansion and contraction offset of a certain layer exceeds a preset value, at least one of the following is adjusted: lamination temperature (adjustment range ±3℃), pressure (adjustment range ±0.3MPa), and holding time (adjustment range ±2min), resulting in a lamination plate after expansion and contraction compensation. After the lamination step is completed, the lamination plates after expansion and contraction compensation are grouped according to the amount of expansion and contraction, with a grouping tolerance of ±3mil. Different laser drilling compensation coefficients are used for subsequent laser drilling for different expansion and contraction groups. Step 2: Routing the edges of the laminated board removes excess material, resulting in a routerd laminated board; Browning and copper reduction are performed on the routerd laminated board to reduce the thickness of the outer copper foil, resulting in a copper-reduced laminated board; Laser drilling is performed on the copper-reduced laminated board to form blind holes, resulting in a laser-drilled laminated board; Mechanical drilling is performed on the laser-drilled laminated board to form through holes, resulting in a drilled laminated board. During laser drilling, a laser confocal scanning microscope is used to detect residual adhesive at the bottom of the blind hole after laser drilling. The residual adhesive threshold is 5% of the bottom area of ​​the blind hole. The laser parameters are adjusted according to the detection results until the residual adhesive is lower than the residual adhesive threshold. When the residual adhesive exceeds the residual adhesive threshold, it is removed online by increasing the number of laser pulses (increasing by 1 pulse each time) or adjusting the laser energy density (adjustment range ±0.3J / cm²). Step 3: After drilling, the laminated board undergoes desmearing and shadow removal treatments to obtain a shadow-treated board. The shadow-treated board is then subjected to through-hole plating, where copper is plated into the blind and through holes to the target thickness, resulting in a through-hole plated board. During the through-hole plating process, the copper thickness is measured in real-time, and the plating parameters are dynamically adjusted based on the measurement results to control the copper thickness within the target range. The target copper thickness range is the target thickness of the outer layer circuitry plus 3μm-8μm. When the measured copper thickness exceeds the upper limit of the target range, the plating current density is reduced by 0.2A / m². The through-hole plated board is then ground to achieve the target copper thickness for the outer layer circuitry, resulting in a board with acceptable copper thickness. Step 4: Conduct a comprehensive evaluation of the copper surface quality of the qualified copper board. The comprehensive evaluation includes roughness detection using a white light interferometer, oxide layer detection using X-ray photoelectron spectroscopy, and cleanliness detection using contact angle measurement. When the roughness Ra value is greater than or equal to 0.2 μm, micro-etching is selected; when the oxide layer thickness is greater than or equal to 5 nm, reduction is selected; and when the water contact angle is greater than or equal to 60°, cleaning is selected, resulting in a qualified copper surface board. Step 5: Fabricate the outer layer circuitry on the qualified copper-coated board to obtain a circuit board with outer layer circuitry; perform outer layer etching on the circuit board with outer layer circuitry to remove excess copper foil, resulting in an etched circuit board. During the outer layer etching process, the etching uniformity is monitored in real time, and the spray parameters are dynamically adjusted based on the uniformity monitoring results, including adjusting the pressure ratio of the upper and lower sprays, to maintain the etching uniformity above 98%. Step 6: Perform automatic optical inspection on the outer layer of the etched circuit board to obtain the finished high-density interconnect control printed circuit board.

[0017] Example 3 This embodiment provides a method for fabricating a printed circuit board for high-density interconnect control, the method comprising the following steps: Step 1: Obtain the substrate and cut it to obtain the cut substrate; sequentially perform inner layer circuit fabrication, inner layer etching, and inner layer automatic optical inspection on the cut substrate to obtain the core board with inner layer circuits; perform browning treatment on the core board with inner layer circuits to obtain the browned core board; press the browned core board with the prepreg and the outer copper foil to obtain the laminated board. During the lamination process, an online X-ray monitoring system is used to monitor the expansion and contraction status of each layer in real time. Based on the monitoring results, lamination parameters are dynamically adjusted to compensate for interlayer expansion and contraction offsets. Specifically, when the expansion and contraction offset of a certain layer exceeds a preset value, at least one of the following is adjusted: lamination temperature (adjustment range ±8℃), pressure (adjustment range ±0.8MPa), and holding time (adjustment range ±5min) to obtain a lamination plate after expansion and contraction compensation. After the lamination step is completed, the lamination plates after expansion and contraction compensation are grouped according to the amount of expansion and contraction, with a grouping tolerance of ±3mil. Different laser drilling compensation coefficients are used for subsequent laser drilling for different expansion and contraction groups. Step 2: Routing the edges of the laminated board removes excess material, resulting in a routerd laminated board; Browning and copper reduction are performed on the routerd laminated board to reduce the thickness of the outer copper foil, resulting in a copper-reduced laminated board; Laser drilling is performed on the copper-reduced laminated board to form blind holes, resulting in a laser-drilled laminated board; Mechanical drilling is performed on the laser-drilled laminated board to form through holes, resulting in a drilled laminated board. During laser drilling, a laser confocal scanning microscope is used to detect residual adhesive at the bottom of the blind hole after laser drilling. The residual adhesive threshold is 5% of the bottom area of ​​the blind hole. Laser parameters are adjusted based on the detection results until the residual adhesive amount is below the threshold. When the residual adhesive amount exceeds the threshold, online removal is performed by increasing the number of laser pulses (increasing by 2 pulses each time) or adjusting the laser energy density (adjustment range ±0.8 J / cm²). Step 3: After drilling, the laminated board undergoes desmearing and shadow treatment sequentially to obtain a shadow-treated board. The shadow-treated board is then subjected to through-hole plating, where copper is plated into the blind and through holes to the target thickness, resulting in a through-hole plated board. During the through-hole plating process, the copper thickness is measured in real-time, and the plating parameters are dynamically adjusted based on the measurement results to control the copper thickness within the target range. The target copper thickness range is the target thickness of the outer layer circuitry plus 3μm-8μm. When the measured copper thickness exceeds the upper limit of the target range, the plating current density is reduced by 0.3A / m². The through-hole plated board is then ground to achieve the target copper thickness for the outer layer circuitry, resulting in a board with acceptable copper thickness. Step 4: Conduct a comprehensive evaluation of the copper surface quality of the qualified copper board. The comprehensive evaluation includes roughness detection using a white light interferometer, oxide layer detection using X-ray photoelectron spectroscopy, and cleanliness detection using contact angle measurement. When the roughness Ra value is greater than or equal to 0.2 μm, micro-etching is selected; when the oxide layer thickness is greater than or equal to 5 nm, reduction is selected; and when the water contact angle is greater than or equal to 60°, cleaning is selected, resulting in a qualified copper surface board. Step 5: Fabricate the outer layer circuitry on the qualified copper-coated board to obtain a circuit board with outer layer circuitry; perform outer layer etching on the circuit board with outer layer circuitry to remove excess copper foil, resulting in an etched circuit board. During the outer layer etching process, the etching uniformity is monitored in real time, and the spray parameters are dynamically adjusted based on the uniformity monitoring results, including adjusting the pressure ratio of the upper and lower sprays, to maintain the etching uniformity above 97.5%. Step 6: Perform automatic optical inspection on the outer layer of the etched circuit board to obtain the finished high-density interconnect control printed circuit board.

[0018] Example 4 This embodiment provides a method for fabricating a printed circuit board for high-density interconnect control. The difference from Embodiment 1 is that step 1 does not involve real-time expansion and contraction monitoring and dynamic adjustment during the lamination process; instead, a traditional pre-compensation method before lamination is used. The method includes the following steps: Step 1: Obtain the substrate and cut it into blanks to obtain the blanked substrate. Then, sequentially perform inner layer circuit fabrication, inner layer etching, and automatic optical inspection on the blanked substrate to obtain a core board with inner layer circuitry. Next, perform a browning treatment on the core board with inner layer circuitry to obtain a browned core board. Establish a shrinkage library based on historical shrinkage data, and pre-compensate the film based on the shrinkage library before producing the inner layer film. Finally, press the browned core board with the prepreg and outer copper foil according to preset pressing parameters to obtain a laminated board. After pressing, measure the shrinkage value of the laminated board and mark it for stacking. Subsequent adjustments will be made based on the stacking data using corresponding compensation data. Step 2: Routing the edges of the laminated board removes excess material, resulting in a routerd laminated board; Browning and copper reduction are performed on the routerd laminated board to reduce the thickness of the outer copper foil, resulting in a copper-reduced laminated board; Laser drilling is performed on the copper-reduced laminated board to form blind holes, resulting in a laser-drilled laminated board; Mechanical drilling is performed on the laser-drilled laminated board to form through holes, resulting in a drilled laminated board. During laser drilling, a laser confocal scanning microscope is used to detect residual adhesive at the bottom of the blind hole after laser drilling. The residual adhesive threshold is 5% of the bottom area of ​​the blind hole. The laser parameters are adjusted according to the detection results until the residual adhesive is lower than the residual adhesive threshold. When the residual adhesive exceeds the residual adhesive threshold, it is removed online by increasing the number of laser pulses (increasing by 1-2 pulses each time) or adjusting the laser energy density (adjustment range ±0.5J / cm²). Step 3: After drilling, the laminated board undergoes desmearing and shadow removal treatments to obtain a shadow-treated board. The shadow-treated board is then subjected to through-hole plating, where copper is plated into the blind and through holes to the target thickness, resulting in a through-hole plated board. During the through-hole plating process, the copper thickness is measured in real-time, and the plating parameters are dynamically adjusted based on the measurement results to control the copper thickness within the target range. The target copper thickness range is the target thickness of the outer layer circuitry plus 3μm-8μm. When the measured copper thickness exceeds the upper limit of the target range, the plating current density is reduced by 0.1-0.3A / m². The through-hole plated board is then ground to achieve the target copper thickness for the outer layer circuitry, resulting in a board with acceptable copper thickness. Step 4: Conduct a comprehensive evaluation of the copper surface quality of the qualified copper board. The comprehensive evaluation includes roughness detection using a white light interferometer, oxide layer detection using X-ray photoelectron spectroscopy, and cleanliness detection using contact angle measurement. When the roughness Ra value is greater than or equal to 0.2 μm, micro-etching is selected; when the oxide layer thickness is greater than or equal to 5 nm, reduction is selected; and when the water contact angle is greater than or equal to 60°, cleaning is selected, resulting in a qualified copper surface board. Step 5: Fabricate the outer layer circuitry on the qualified copper-coated board to obtain a circuit board with outer layer circuitry; perform outer layer etching on the circuit board with outer layer circuitry to remove excess copper foil, resulting in an etched circuit board. During the outer layer etching process, the etching uniformity is monitored in real time, and the spray parameters are dynamically adjusted based on the uniformity monitoring results, including adjusting the pressure ratio of the upper and lower sprays, to maintain the etching uniformity above 97%. Step 6: Perform automatic optical inspection on the outer layer of the etched circuit board to obtain the finished high-density interconnect control printed circuit board.

[0019] Example 5 This embodiment provides a method for fabricating a high-density interconnect control printed circuit board. The difference from Embodiment 1 is that, in step 2, after laser drilling, the residual adhesive at the bottom of the blind holes is not detected and removed in real time; instead, a traditional plasma adhesive removal process is used. The method includes the following steps: Step 1: Obtain the substrate and cut it to obtain the cut substrate; sequentially perform inner layer circuit fabrication, inner layer etching, and inner layer automatic optical inspection on the cut substrate to obtain the core board with inner layer circuits; perform browning treatment on the core board with inner layer circuits to obtain the browned core board; press the browned core board with the prepreg and the outer copper foil to obtain the laminated board. During the lamination process, an online X-ray monitoring system is used to monitor the expansion and contraction status of each layer in real time. Based on the monitoring results, lamination parameters are dynamically adjusted to compensate for interlayer expansion and contraction offsets. Specifically, when the expansion and contraction offset of a certain layer exceeds a preset value, at least one of the following is adjusted: lamination temperature (adjustment range ±5℃), pressure (adjustment range ±0.5MPa), and holding time (adjustment range ±3min), resulting in a lamination plate after expansion and contraction compensation. After the lamination step is completed, the lamination plates after expansion and contraction compensation are grouped according to the amount of expansion and contraction, with a grouping tolerance of ±3mil. Different laser drilling compensation coefficients are used for subsequent laser drilling for different expansion and contraction groups. Step 2: The laminated board is routerd to remove excess material from the edges, resulting in a routerd laminated board. The routerd laminated board is then subjected to copper reduction (browning) to decrease the thickness of the outer copper foil, resulting in a copper-reduced laminated board. Laser drilling is performed on the copper-reduced laminated board to create blind holes, resulting in a laser-drilled laminated board. Finally, mechanical drilling is performed on the laser-drilled laminated board to create through holes, resulting in a drilled laminated board. After laser drilling, all blind holes are uniformly de-adhesive treated with plasma according to preset parameters. The de-adhesive removal effect is then tested using automated optical inspection equipment. Step 3: After drilling, the laminated board undergoes desmearing and shadow removal treatments to obtain a shadow-treated board. The shadow-treated board is then subjected to through-hole plating, where copper is plated into the blind and through holes to the target thickness, resulting in a through-hole plated board. During the through-hole plating process, the copper thickness is measured in real-time, and the plating parameters are dynamically adjusted based on the measurement results to control the copper thickness within the target range. The target copper thickness range is the target thickness of the outer layer circuitry plus 3μm-8μm. When the measured copper thickness exceeds the upper limit of the target range, the plating current density is reduced by 0.1-0.3A / m². The through-hole plated board is then ground to achieve the target copper thickness for the outer layer circuitry, resulting in a board with acceptable copper thickness. Step 4: Conduct a comprehensive evaluation of the copper surface quality of the qualified copper board. The comprehensive evaluation includes roughness detection using a white light interferometer, oxide layer detection using X-ray photoelectron spectroscopy, and cleanliness detection using contact angle measurement. When the roughness Ra value is greater than or equal to 0.2 μm, micro-etching is selected; when the oxide layer thickness is greater than or equal to 5 nm, reduction is selected; and when the water contact angle is greater than or equal to 60°, cleaning is selected, resulting in a qualified copper surface board. Step 5: Fabricate the outer layer circuitry on the qualified copper-coated board to obtain a circuit board with outer layer circuitry; perform outer layer etching on the circuit board with outer layer circuitry to remove excess copper foil, resulting in an etched circuit board. During the outer layer etching process, the etching uniformity is monitored in real time, and the spray parameters are dynamically adjusted based on the uniformity monitoring results, including adjusting the pressure ratio of the upper and lower sprays, to maintain the etching uniformity above 97%. Step 6: Perform automatic optical inspection on the outer layer of the etched circuit board to obtain the finished high-density interconnect control printed circuit board.

[0020] Example 6 This embodiment provides a method for fabricating a high-density interconnect control printed circuit board. The difference from Embodiment 1 is that step 4 does not involve a comprehensive quality evaluation of the copper surface; instead, a uniform micro-etching process is used. The method includes the following steps: Step 1: Obtain the substrate and cut it to obtain the cut substrate; sequentially perform inner layer circuit fabrication, inner layer etching, and inner layer automatic optical inspection on the cut substrate to obtain the core board with inner layer circuits; perform browning treatment on the core board with inner layer circuits to obtain the browned core board; press the browned core board with the prepreg and the outer copper foil to obtain the laminated board. During the lamination process, an online X-ray monitoring system is used to monitor the expansion and contraction status of each layer in real time. Based on the monitoring results, lamination parameters are dynamically adjusted to compensate for interlayer expansion and contraction offsets. Specifically, when the expansion and contraction offset of a certain layer exceeds a preset value, at least one of the following is adjusted: lamination temperature (adjustment range ±5℃), pressure (adjustment range ±0.5MPa), and holding time (adjustment range ±3min), resulting in a lamination plate after expansion and contraction compensation. After the lamination step is completed, the lamination plates after expansion and contraction compensation are grouped according to the amount of expansion and contraction, with a grouping tolerance of ±3mil. Different laser drilling compensation coefficients are used for subsequent laser drilling for different expansion and contraction groups. Step 2: Routing the edges of the laminated board removes excess material, resulting in a routerd laminated board; Browning and copper reduction are performed on the routerd laminated board to reduce the thickness of the outer copper foil, resulting in a copper-reduced laminated board; Laser drilling is performed on the copper-reduced laminated board to form blind holes, resulting in a laser-drilled laminated board; Mechanical drilling is performed on the laser-drilled laminated board to form through holes, resulting in a drilled laminated board. During laser drilling, a laser confocal scanning microscope is used to detect residual adhesive at the bottom of the blind hole after laser drilling. The residual adhesive threshold is 5% of the bottom area of ​​the blind hole. The laser parameters are adjusted according to the detection results until the residual adhesive is lower than the residual adhesive threshold. When the residual adhesive exceeds the residual adhesive threshold, it is removed online by increasing the number of laser pulses (increasing by 1-2 pulses each time) or adjusting the laser energy density (adjustment range ±0.5J / cm²). Step 3: After drilling, the laminated board undergoes desmearing and shadow removal treatments to obtain a shadow-treated board. The shadow-treated board is then subjected to through-hole plating, where copper is plated into the blind and through holes to the target thickness, resulting in a through-hole plated board. During the through-hole plating process, the copper thickness is measured in real-time, and the plating parameters are dynamically adjusted based on the measurement results to control the copper thickness within the target range. The target copper thickness range is the target thickness of the outer layer circuitry plus 3μm-8μm. When the measured copper thickness exceeds the upper limit of the target range, the plating current density is reduced by 0.1-0.3A / m². The through-hole plated board is then ground to achieve the target copper thickness for the outer layer circuitry, resulting in a board with acceptable copper thickness. Step 4: Perform uniform micro-etching treatment directly on the copper-compliant board to obtain the copper-treated board; Step 5: Fabricate the outer layer circuitry on the copper-faced board to obtain a circuit board with outer layer circuitry; perform outer layer etching on the circuit board with outer layer circuitry to remove excess copper foil, resulting in the etched circuit board. During the outer layer etching process, the etching uniformity is monitored in real time, and the spray parameters are dynamically adjusted based on the uniformity monitoring results, including adjusting the pressure ratio of the upper and lower sprays, to maintain the etching uniformity above 97%. Step 6: Perform automatic optical inspection on the outer layer of the etched circuit board to obtain the finished high-density interconnect control printed circuit board.

[0021] To more clearly illustrate the technical effects of the method of the present invention, performance tests were conducted on the printed circuit boards prepared in the above embodiments, and the test results are shown in Table 1: Table 1. Performance test results of printed circuit boards prepared in each embodiment.

[0022] The test results in Table 1 show that: Regarding interlayer alignment accuracy, the average offset in Examples 1-3 was 15-22 μm with a standard deviation of 3.8-5.1 μm, while the average offset in Example 4 was 52 μm with a standard deviation of 12.6 μm. This indicates that the present invention, by monitoring the expansion and contraction state of each layer in real time during the pressing process and dynamically adjusting the pressing parameters, combined with a collaborative control method of grouping by expansion and contraction amount after pressing and using different laser drilling compensation coefficients, can effectively improve interlayer alignment accuracy and significantly reduce interlayer offset and its dispersion. Example 4, using the traditional pre-compensation before pressing and post-pressing stacking method, cannot cope with the real-time expansion and contraction changes of the material during pressing, resulting in a more serious interlayer offset problem. Regarding the removal of residual adhesive in blind holes, the adhesive removal rates of Examples 1-3 were 96.9%-98.5%, with a standard deviation of 0.9%-1.5% for consistency. However, the adhesive removal rate of Example 5 was only 89.3%, with a standard deviation of 5.8%. This indicates that the present invention establishes a closed-loop removal mechanism of "detection-judgment-feedback adjustment" by real-time detection of residual adhesive at the bottom of blind holes after laser drilling and dynamic adjustment of laser parameters based on the detection results. This mechanism can instantly detect and adjust the actual residual adhesive state of each blind hole, significantly improving the thoroughness and consistency of adhesive removal. Example 5 uses a uniform plasma adhesive removal process, which cannot differentiate treatment based on the actual residual adhesive state of different blind holes, resulting in unstable adhesive removal effects. Regarding the adhesion and yield of the outer layer circuitry, the peel strength of Examples 1-3 was 1.08-1.22 N / mm, with a yield of 95%-97%; while the peel strength of Example 6 was only 0.85 N / mm, with a yield of 90%. This indicates that the present invention, through a multi-dimensional comprehensive evaluation of the roughness, oxide layer, and cleanliness of the polished copper surface, and by selectively choosing micro-etching, reduction, or cleaning treatments based on the evaluation results, can effectively improve the quality of the copper surface, enhance the adhesion between the outer layer circuitry and the copper surface, and thus improve the product yield. Example 6 adopted a uniform micro-etching treatment method, which could not be tailored to the actual quality state of the copper surface, resulting in some copper surface quality problems not being effectively resolved. In summary, the method for manufacturing high-density interconnect control printed circuit boards provided by this invention effectively solves the technical problems in the prior art, such as insufficient interlayer alignment accuracy, incomplete removal of residual adhesive, and lack of targeted copper surface treatment, through the coordinated control of real-time expansion and contraction compensation during the lamination process and differentiated drilling after lamination, closed-loop online removal of residual adhesive from laser drilling, and multi-dimensional comprehensive evaluation and differentiated treatment of copper surface quality after grinding. This significantly improves the interlayer alignment accuracy, blind via quality, and product yield of printed circuit boards.

[0023] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0024] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for fabricating a printed circuit board for high-density interconnect control, characterized in that, The method includes the following steps: Step 1: Obtain the substrate and cut it to obtain the cut substrate; sequentially perform inner layer circuit fabrication, inner layer etching, and inner layer automatic optical inspection on the cut substrate to obtain the core board with inner layer circuits; perform browning treatment on the core board with inner layer circuits to obtain the browned core board; press the browned core board with the prepreg and the outer copper foil to obtain the laminated board. Step 2: Routing the edges of the laminated board removes excess material, resulting in a routerd laminated board; Browning and copper reduction are performed on the routerd laminated board to reduce the thickness of the outer copper foil, resulting in a copper-reduced laminated board; Laser drilling is performed on the copper-reduced laminated board to form blind holes, resulting in a laser-drilled laminated board; Mechanical drilling is performed on the laser-drilled laminated board to form through holes, resulting in a drilled laminated board. Step 3: After drilling, the laminated board is subjected to descaling and shadow treatment in sequence to obtain a shadow treatment board; the shadow treatment board is then subjected to hole-filling electroplating to plate the copper in the blind holes and through holes to the target thickness to obtain a hole-filling electroplated board; the hole-filling electroplated board is then subjected to grinding treatment to grind the surface copper thickness to the target thickness of the outer layer circuit fabrication to obtain a surface copper compliant board. Step 4: Conduct a comprehensive evaluation of the copper surface quality of the copper-compliant board. Based on the comprehensive evaluation results, select at least one of the following methods to treat the copper surface: micro-etching, reduction, or cleaning, to obtain a qualified copper surface board. Step 5: Fabricate the outer layer circuitry on the qualified copper surface board to obtain a circuit board with outer layer circuitry; perform outer layer etching on the circuit board with outer layer circuitry to remove excess copper foil and obtain the etched circuit board. Step 6: Perform automatic optical inspection on the outer layer of the etched circuit board to obtain the finished high-density interconnect control printed circuit board.

2. The method for fabricating a high-density interconnect control printed circuit board according to claim 1, characterized in that, In step 1, during the lamination of the brown core board with the prepreg and the outer copper foil, the expansion and contraction state of each layer is monitored in real time. The lamination parameters are dynamically adjusted according to the monitoring results to compensate for the expansion and contraction offset between layers, resulting in a lamination board after expansion and contraction compensation. After the lamination step is completed and before the lamination board is milled, the lamination board after expansion and contraction compensation is grouped according to the amount of expansion and contraction. Different laser drilling compensation coefficients are used for laser drilling of different expansion and contraction groups.

3. The method for fabricating a high-density interconnect control printed circuit board according to claim 2, characterized in that, During the real-time monitoring of the expansion and contraction status of each layer, an online X-ray monitoring system is used to dynamically adjust the pressing parameters, including adjusting at least one of the pressing temperature, pressure, and holding time. When grouping by expansion and contraction amount, the grouping tolerance is ±3mil.

4. The method for fabricating a high-density interconnect control printed circuit board according to claim 1, characterized in that, In step 2, during the laser drilling process of the copper-reduced laminated board, residual adhesive is detected at the bottom of the blind holes after laser drilling. The laser parameters are adjusted according to the detection results until the amount of residual adhesive is lower than the residual adhesive threshold. When the amount of residual adhesive exceeds the residual adhesive threshold, it is removed online by increasing the number of laser pulses or adjusting the laser energy density.

5. The method for fabricating a high-density interconnect control printed circuit board according to claim 4, characterized in that, During the process of detecting residual adhesive at the bottom of blind holes after laser drilling, a laser confocal scanning microscope was used for residual adhesive detection, and the threshold for residual adhesive was 5% of the bottom area of ​​the blind hole.

6. The method for fabricating a high-density interconnect control printed circuit board according to claim 1, characterized in that, In step 3, during the via-filling electroplating process on the shadow processing board, the surface copper thickness is measured in real time. The electroplating parameters are dynamically adjusted based on the measurement results to control the surface copper thickness within the target surface copper range. The target surface copper range is the target thickness of the outer layer circuitry plus 3μm-8μm. When the real-time measured surface copper thickness exceeds the upper limit of the target surface copper range, the electroplating current density is reduced by 0.1-0.3A / m².

7. The method for fabricating a high-density interconnect control printed circuit board according to claim 1, characterized in that, In step 4, the comprehensive evaluation of copper surface quality includes at least one of roughness detection, oxide layer detection, and cleanliness detection on the copper surface plate; when the roughness exceeds the first threshold, micro-etching is selected; when the oxide layer exceeds the second threshold, reduction is selected; and when the cleanliness exceeds the third threshold, cleaning is selected.

8. The method for fabricating a high-density interconnect control printed circuit board according to claim 7, characterized in that, During the roughness inspection of the copper-coated compliant board, a white light interferometer was used for roughness monitoring. The first threshold was that the roughness Ra value of the copper surface was greater than or equal to 0.2 μm. The oxide layer was detected using X-ray photoelectron spectroscopy, and the second threshold was that the oxide layer thickness of the copper surface was greater than or equal to 5 nm. The cleanliness was detected using the contact angle measurement method, and the third threshold was that the water contact angle of the copper surface was greater than or equal to 60°.

9. A method for fabricating a high-density interconnect control printed circuit board according to claim 1, characterized in that, In step 5, during the outer layer etching process of the circuit board with outer layer circuitry, the etching uniformity is monitored in real time, and the spray parameters are dynamically adjusted according to the uniformity monitoring results to keep the etching uniformity within the target range; the dynamic adjustment of the spray parameters includes adjusting the pressure ratio of the upper spray and the lower spray.

10. A method for fabricating a high-density interconnect control printed circuit board according to claim 9, characterized in that, The target range for etching uniformity is above 97%.

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