Interlayer alignment and laser processing method of AI server mainboard

Abstract

The invention relates to an AI server mainboard interlayer alignment and laser processing method, which comprises the following steps: a product design step: designing a multi-layer mainboard, arranging a blind hole structure in an outer layer area of a laser layer, arranging an inner target on a board edge to avoid dry film coverage, and adopting oversized material distribution; the machining process includes the steps that pressing target drilling, first-time laser drilling, outer-layer windowing, second-time laser drilling and post-procedure processes are sequentially executed, the first-time laser drilling forms an inner target and an alignment mark, and the outer-layer windowing and the second-time laser drilling are aligned based on the same alignment system. According to the interlayer alignment and laser processing method for the AI server mainboard, through staged laser processing and unified alignment system design, the problem of interlayer offset is solved, and the processing precision and the yield are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of high-density printed circuit board (PCB) manufacturing, and is particularly applicable to the inter-layer alignment and laser processing technology of multi-layer AI server motherboards. The invention involves blind hole structure design, phased laser drilling, and unified alignment system optimization. Background Art

[0002] As AI servers demand higher computing power, their motherboards must have features such as high-density wiring, multi-layer stacking, and long-term stable operation. In traditional multi-layer PCB manufacturing, the inter-layer alignment accuracy is limited by the following factors: Thermal expansion and material stress: Ultra-large motherboards (≥610mm×610mm) are prone to deformation due to temperature changes during processing, resulting in interlayer offset.

[0003] Errors from multiple alignment systems: Traditional processes use different alignment systems to complete drilling, window opening and other processes, resulting in significant cumulative errors.

[0004] Interference caused by dry film coverage: The positioning mark (target) on the edge of the board is difficult to identify accurately after being covered by dry film, which affects the accuracy of secondary processing.

[0005] Existing technologies make it difficult to achieve both precision control and yield improvement for ultra-large motherboards, and an innovative processing method is urgently needed. Summary of the Invention

[0006] In view of this, the present invention provides an interlayer alignment and laser processing method for an AI server motherboard. Through phased laser processing and a unified alignment system design, the interlayer offset problem is solved and the processing accuracy and yield are improved.

[0007] The purpose of the present invention is achieved through the following technical solutions: A method for interlayer alignment and laser processing of an AI server motherboard includes the following steps: Product design steps: Design a multi-layer motherboard, set a blind hole structure in the outer area of ​​the laser layer, set an inner target on the edge of the board to avoid dry film coverage, and use oversized material; Processing steps: press-fit drilling target, first laser drilling, outer windowing, second laser drilling and post-processing steps are performed in sequence. The first laser drilling forms the inner target and alignment mark, and the outer windowing and second laser drilling are aligned based on the same alignment system.

[0008] This method effectively solves the problem of inter-layer alignment deviation of oversized motherboards caused by thermal expansion, material stress or processing equipment limitations through the design of phased laser processing and a unified alignment system. The internal target and alignment mark formed by the first laser drilling provide a unified positioning reference for subsequent outer layer window opening and secondary laser drilling, avoiding the cumulative error introduced by multiple alignment systems in traditional processes. The design of oversized material delivery combined with the blind hole structure not only meets the high-density wiring requirements of high-performance server motherboards, but also avoids the interference of dry film covering on the positioning marks through the layout of the internal target on the edge of the board, significantly improving the processing accuracy and yield. In addition, the phased processing flow can flexibly respond to the process requirements of different processes, ensure the alignment consistency of complex multi-layer structures, and is suitable for the manufacture of AI server motherboards that work under long-term high loads, reduce the risk of board explosion and extend product life.

[0009] Preferably, the alignment marks are laser hole matrices distributed at the four corners of the board surface, and the hole spacing and the degree of overlap of the holes meet the requirements of high-precision positioning.

[0010] The matrix of laser holes distributed at the four corners enhances the ability of oversized motherboards to resist thermal deformation and mechanical stress during processing through a symmetrical layout and redundant design. The optimization of hole spacing and wrap-around overlap ensures the clarity and stability of the marking, maintaining uniform positioning accuracy even within the large-sized board area. This design effectively offsets the errors that may be caused by local material deformation or equipment vibration in single-point positioning through multi-point collaborative positioning, and is particularly suitable for long-cycle, high-precision continuous processing scenarios. In addition, the matrix marking can be quickly captured through image recognition technology, improving the alignment efficiency of automated equipment, while providing multi-dimensional data support for offset compensation in subsequent processes, further enhancing the robustness and repeatability of the process.

[0011] Preferably, in the outer layer window opening step, the dry film is laminated while avoiding the alignment mark area, and exposure positioning is completed through the alignment mark.

[0012] The design that actively avoids the alignment mark area during dry film lamination completely solves the problem of recognition failure or reduced accuracy caused by dry film covering the positioning mark in traditional processes. Through direct exposure and positioning of the alignment mark, the secondary error that may be introduced by indirect calibration is avoided, ensuring strict alignment of the outer window and the inner layer structure. This method is particularly suitable for high-density interconnect (HDI) design, and can accurately control the relative position of the window edge and the blind hole to prevent short circuits or open circuits caused by alignment deviation. At the same time, directly using the alignment mark exposure can reduce auxiliary calibration steps, simplify the process flow and shorten the production cycle, significantly improving processing efficiency. In addition, this design enhances compatibility with different dry film materials and reduces sensitivity to film thickness and viscosity, making it suitable for stable production in complex environments.

[0013] Preferably, in the secondary laser drilling process, the inner target and the outer window structure are aligned synchronously, and the size of the inner target is adapted to the size of the outer copper PAD.

[0014] By synchronously aligning the inner target and the outer window structure, precise matching of the cross-layer structure is achieved, especially in the processing of high-aspect-ratio blind holes, avoiding the risk of misalignment between the hole wall and the line. The size adaptation design of the inner target and the outer copper PAD ensures the uniform distribution of laser energy when penetrating different layers of materials, reducing overburning or non-penetration defects caused by mismatch between the aperture and the target. This method uses size linkage design to physically couple the inner positioning reference with the outer functional structure, enhancing the mechanical stability and electrical connection reliability of the interlayer structure. At the same time, this adaptation relationship is compatible with design changes of different line widths and apertures, improving the flexibility and scalability of the process, and meeting the customization needs of diverse server motherboards.

[0015] Preferably, in the step of pressing the drilling target, a fool-proof verification hole is drilled, and the verification hole does not participate in the alignment calibration.

[0016] The introduction of fool-proofing verification holes has significantly reduced the risk of batch processing errors caused by human error or equipment anomalies. The verification holes are independent of the core alignment system and are only used for physical fool-proofing verification, which not only avoids redundant data interfering with the main positioning process, but also provides operators with an intuitive and quick detection method. This design is particularly suitable for mixed production lines with multiple batches and multiple specifications of products, and can effectively prevent problems such as incorrect plate orientation, inverted layer order, or incorrect equipment parameter settings. At the same time, the non-participatory design of the verification holes ensures that they have zero impact on the main processing flow, without the need for additional adjustments to the alignment algorithm or increased equipment load, thereby maintaining the efficiency of the process while improving safety. In addition, the position and number of verification holes can be flexibly configured according to specific production needs, enhancing the universality and customizability of the method.

[0017] Preferably, the post-etching control parameters of the outer window are set according to the proportional relationship between the laser hole size and the window width.

[0018] By dynamically matching the proportional relationship between the laser hole size and the window width, precise control of the etching process is achieved, effectively avoiding problems such as residual holes caused by overly narrow windows or insufficient line spacing caused by overly wide windows. Proportional parameter settings can adapt to different design specifications to ensure the best match between the window edge and the blind hole position after etching, improving the reliability of electrical connections and signal transmission quality. This method reduces dependence on absolute dimensions by introducing proportional control logic and enhances the process's tolerance to fluctuations in etching rates of different materials. At the same time, the proportional relationship can be dynamically adjusted in combination with real-time monitoring data to form a closed-loop control, further optimizing etching uniformity and consistency. It is particularly suitable for gradient compensation between the edge and center areas of oversized panels, significantly improving overall processing quality.

[0019] Preferably, the first laser drilling and the second laser drilling are performed using segmented processing equipment to accommodate the processing of oversized plates.

[0020] Segmented processing equipment, through modular workbenches and collaborative positioning mechanisms, breaks through the physical limitations of traditional equipment on processing size, making continuous high-precision processing of ultra-large motherboards possible. The segmented processing strategy divides the board surface into multiple collaborative working areas, effectively distributing the equipment load and avoiding localized precision degradation caused by mechanical structure deformation or heat accumulation. This design not only improves processing efficiency, but also compensates for deformation differences in different locations on the board surface through regional parameter fine-tuning, ensuring overall processing consistency. In addition, segmented equipment supports parallel processing and dynamic path planning, reducing idle movement time, making it particularly suitable for long-cycle, high-volume production scenarios, significantly reducing unit costs while ensuring quality.

[0021] Preferably, in the outer layer window opening step, multi-station exposure equipment is used to ensure uniform processing of oversized panels.

[0022] Multi-station exposure equipment solves the problem of uneven exposure at the edges and centers of oversized boards due to light intensity attenuation or scattering through distributed light sources and collaborative exposure control. The multi-station design can achieve gradient compensation of exposure energy and smooth transition of overlapping areas, ensuring the reaction consistency of the photoresist across the entire board and avoiding line width fluctuations or graphic distortion after development. This method can adapt to differences in material properties in different areas, such as uneven heat dissipation at the center and edge of the board or substrate warping, by dynamically adjusting the exposure parameters of each station. At the same time, multi-station parallel operation significantly shortens the single exposure cycle, improves production efficiency, and can achieve rapid fault switching through redundant station configuration to ensure the stability of continuous production. It is especially suitable for the manufacturing of AI server motherboards with high yield requirements.

[0023] Preferably, the outer frame and inner frame structure of the alignment mark form a nested design, and the inner layer target of the blind hole is adapted to the bottom plate PAD.

[0024] The nested circuit outer frame and inner frame structure enhances the anti-interference ability of the positioning mark through geometric coupling, and can maintain a stable relative position relationship even under external mechanical stress or temperature changes. The adaptive design of the blind hole inner layer target and the base plate PAD realizes the self-alignment characteristics of the cross-layer structure. During the secondary laser drilling, the physical structure can be used to guide precise positioning, reducing the reliance on complex algorithms. This nested architecture not only improves the mechanical strength of the mark itself, but also improves the system fault tolerance through multi-level reference system redundancy. Even if some marks are damaged, high-precision alignment can still be achieved through the remaining marks. In addition, the adaptive design enables the inner layer target and the functional PAD to form process synergy, simplifying the production data preparation process, and automatically optimizing the layout through design rule checking (DRC), significantly shortening the R&D cycle.

[0025] Preferably, the laser processing deviation compensation parameters are adjusted in real time by analyzing the target morphology after the outer layer window etching.

[0026] A real-time compensation mechanism based on target topography analysis upgrades traditional static process parameters to a dynamic adaptive system capable of automatically correcting systematic deviations caused by equipment wear, environmental fluctuations, or material batch differences. High-precision optical inspection and machine learning algorithms can quickly identify microscopic deformation characteristics of the target after etching (such as edge burrs and uneven copper thickness), and reversely derive the optimized parameters for laser drilling energy, focal length, or scanning path. This closed-loop control system significantly improves long-term production stability and reduces the frequency of manual intervention. It also continuously optimizes the compensation model through the accumulation of historical data, enabling the self-evolution of process parameters. Furthermore, real-time compensation allows for differentiated adjustments to different areas of the board surface, effectively addressing gradient offset issues in ultra-large-scale processing and ensuring submicron overall accuracy to meet the extreme performance requirements of next-generation AI server motherboards.

[0027] The beneficial effects of the present invention compared to the prior art are: The interlayer alignment and laser processing method of the AI ​​server motherboard of the present invention effectively solves the problem of interlayer alignment deviation of the oversized motherboard caused by thermal expansion, material stress or processing equipment limitations through the design of phased laser processing and a unified alignment system. The inner target and alignment mark formed by the first laser drilling provide a unified positioning reference for the subsequent outer layer window opening and secondary laser drilling, avoiding the cumulative error introduced by multiple sets of alignment systems in traditional processes. The design of oversized material delivery combined with the blind hole structure not only meets the high-density wiring requirements of high-performance server motherboards, but also avoids the interference of dry film covering on the positioning mark through the layout of the inner target on the edge of the board, significantly improving the processing accuracy and yield. In addition, the phased processing flow can flexibly respond to the process requirements of different processes, ensure the alignment consistency of complex multi-layer structures, and is suitable for the manufacture of AI server motherboards working under long-term high loads, reduce the risk of board explosion and extend product life. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 FIG. 1 is a schematic diagram of the position of the alignment target according to an embodiment of the present invention.

[0030] Figure 2 Schematic diagram of the positions of the alignment target and the outer copper PAD according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0033] It should be noted that similar numbers and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further defined and explained in the subsequent figures. In the description of the embodiments of the present application, it should be understood that the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "vertical", "horizontal", etc. is based on the orientation or position relationship shown in the drawings, or is the orientation or position relationship in which the product of the application is usually placed when in use, or is the orientation or position relationship commonly understood by those skilled in the art. It is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0034] It should be noted that, unless there is any conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0035] The technical solution in this application will be described below with reference to the accompanying drawings.

[0036] This embodiment provides Example 1: Processing method A method for interlayer alignment and laser processing of an AI server motherboard includes the following steps: Product design steps: Design a 28-layer motherboard, set laser blind holes on the outer layers L1-2 and L28-27 of the laser layer, set inner targets on the L2 layer and L27 layer on the edge of the board to avoid dry film coverage, and the material size is 620*880mm; Processing steps: Press-fit drilling target, laser drilling 1, outer layer windowing, laser drilling 2 and post-processing steps are performed in sequence. Laser drilling 1 burns out the inner target and alignment target of the L2 layer and L27 layer, and the outer layer windowing and laser drilling 2 are aligned based on the same alignment system.

[0037] In this embodiment, in the laser drilling 1 process, the alignment target is a matrix of laser holes distributed at four corners, with a single hole diameter of 0.1 mm, a spacing of 0.25 mm, and a burning overlap of 50%.

[0038] In this embodiment, in the outer layer window opening step, the dry film avoids the alignment target area during lamination, and exposure alignment is performed based on the alignment target.

[0039] In this embodiment, during the laser drilling 2 process, the inner target and the outer mask window are synchronously aligned by the same alignment system. The inner target has a diameter of 20 mil (0.508 mm), and the outer copper PAD has a diameter of 20 mil (0.508 mm).

[0040] In this embodiment, during the step of pressing the drill target, alignment tooling holes are drilled for laser positioning and foolproofing. The tooling holes are only used for foolproofing verification and do not participate in alignment calibration.

[0041] In this embodiment, the post-etching control parameters of the outer window are: Corresponding to 6±2mil laser perforation design, 9-10mil window; Corresponding to 8+2 / -4mil laser perforation design, 11-12mil window; Corresponding to the 10+2 / -4mil laser perforation design, the 13-14mil window is designed.

[0042] In this embodiment, laser drilling 1 and laser drilling 2 are produced using a double-table machine to accommodate processing of oversized panels.

[0043] In this embodiment, in the outer layer window opening step, the exposure machine uses a double-table device to ensure uniform exposure of the oversized board surface.

[0044] In this embodiment, the alignment target is designed to be a circuit outer frame of 5.08*5.08mm, an inner frame square PAD of 3.68*3.68mm, and an inner target size of the blind hole inner layer of 20mil.

[0045] In this embodiment, during the processing flow, a high-precision optical sensor (resolution 0.1 μm) is used to collect target morphology data in real time, and a machine learning model is used to dynamically correct laser parameters.

[0046] The beneficial effects of this embodiment are mainly reflected in the following aspects: High-precision interlayer alignment technology: A dual positioning system design, combining targets within the L2 / L27 layers with alignment targets, combined with continuous use of the same alignment system, achieves ±5μm interlayer alignment accuracy. The 20mil (0.508mm) equal diameter design of the inner layer targets and outer copper pads creates optical feature matching, effectively improving X-ray image recognition. A matrix alignment target design with 50% overlap creates high-contrast positioning features through a 20×20 micro-hole array, improving positioning stability by over 30% compared to traditional single-target solutions.

[0047] Adaptability for ultra-large panel processing: The dual-table system (pressing / exposure / laser) combined with the ultra-large 620×880mm sheet size achieves a panel utilization rate of ≥95%. Dual-table simultaneous exposure technology controls illumination variation within ±3% along the 880mm length, resolving the issue of underexposure at the edges of traditional single-table equipment. A specially developed tooling hole error prevention system reduces the handling error rate for ultra-large panels to below 0.1%.

[0048] Dynamic Compensation Process System: Based on real-time detection of post-etching target convexity (sampling frequency 200 points / m²), a self-learning model for laser compensation parameters is established. Through big data analysis, dynamic adjustment of the compensation value within ±3μm / drilling is achieved, reducing the secondary laser drilling deviation rate from the industry average of 1.2% to 0.35%. The gradient design of the window size (9-14mil steps) creates an aperture tolerance buffer zone, improving laser scattering compensation efficiency by 40%.

[0049] Enhanced process stability: Dry film target avoidance technology combined with a 3.68mm inner frame design for the inner copper PAD eliminates positioning anomalies caused by lamination wrinkles. Alignment targets at the four corners form a thermal expansion compensation benchmark, keeping dimensional deviations caused by temperature fluctuations (±5°C) to within 0.8μm / °C. A 20mil inner target in the inner layer of the blind via, combined with an optimized laser focusing algorithm, achieves consistent penetration through a 60μm-thick dielectric layer.

[0050] Production cost optimization: The integrated process reduces the use of traditional FPC alignment film, reducing single-board material costs by 12%. Timing optimization in the laser double drilling process increases equipment utilization to 85%, saving 18% energy compared to a segmented processing solution. Closed-loop control of compensation parameters reduces the scrap rate from the industry average of 3.5% to below 1.2%.

[0051] Example 2: Interlayer Alignment and Laser Processing Method for AI Server Motherboard 1. Product design steps Motherboard structure: Design a 28-layer high-density interconnect (HDI) motherboard, in which blind via structures are set in the outer layers L1-2 and L28-27, and the blind via depth covers the adjacent signal layers; Inner target layout: Set inner targets on the L2 and L27 layers in the board edge area (within 5 mm of the board edge). The inner target diameter is larger than the blind hole diameter to ensure that it is not covered during dry film lamination. Material size: Use super large size substrate (for example, 620mm×880mm), the material is high frequency low loss copper clad laminate, and the copper thickness is conventional 18μm.

[0052] 2. Processing steps Step 1: Press the drill target together Use a CNC drill to drill foolproofing verification holes (2mm in diameter) at the four corners of the substrate. The verification holes have no direct correlation with the subsequent alignment marks and are only used for physical foolproofing verification; The calibration holes are located 10 mm from the edge of the board and are symmetrically distributed.

[0053] Step 2: First laser drilling Use an ultraviolet laser drilling machine (wavelength 355nm, pulse energy 1.5mJ) to process alignment marks on the four corners of the board: The alignment mark is a 5×5 laser hole matrix with a single hole diameter of 0.1mm, a hole spacing of 0.25mm, and a wrap-around overlap of 50%; At the same time, the inner target (diameter 20mil) is processed on the L2 layer and the L27 layer, and the position of the inner target avoids the window area of ​​the outer layer.

[0054] Processing parameters: laser power 80%, scanning speed 5m / s, and focus depth dynamically adjusted according to the thickness of the copper layer.

[0055] Step 3: Outer window opening Dry film lamination: Use a vacuum laminator to attach dry film (30μm thickness), avoiding the four corner alignment marks when laminating; Exposure positioning: The CCD camera captures the alignment mark and accurately aligns the exposure pattern (outer layer circuit) with the alignment mark, with the error controlled within ±5μm; Etching control: Set the window width ratio (1.5 times) according to the laser hole diameter (e.g. 0.1mm). The window edge flatness after etching is ≤2μm.

[0056] Step 4: Secondary laser drilling Using the same alignment system, the inner target (L2 / L27 layer) and the outer fenestration structure are aligned synchronously based on the alignment marks; Laser parameter optimization: According to the size matching relationship between the inner target and the outer copper PAD (for example, an inner target diameter of 20 mil corresponds to an outer PAD diameter of 20 mil), adjust the laser focal length and energy distribution to ensure that the deviation between the blind hole and the PAD center is ≤10μm.

[0057] Step 5: Post-process flow Electroplating filling: Pulse electroplating process is used to fill blind holes, and the copper thickness uniformity in the hole is ≥90%; Lamination and final inspection: X-ray inspection is used to detect the inter-layer alignment accuracy, and the acceptance standard is a total offset of ≤25μm.

[0058] 3. Technical effect verification Alignment accuracy: By unifying the alignment system, the inter-layer offset is reduced from 50μm in traditional processes to 15μm; Improved yield: The failure rate of printed circuit boards has been reduced from 8% to 0.5%, making it suitable for 24 / 7 high-load server scenarios. Production efficiency: Segmented processing equipment shortens the processing cycle of oversized plates by 30%.

[0059] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for interlayer alignment and laser processing of an AI server motherboard, characterized in that: The following steps are involved: Product design steps: Design a multi-layer motherboard, set a blind hole structure in the outer area of ​​the laser layer, set an inner target on the edge of the board to avoid dry film coverage, and use oversized material; Processing steps: press-fit drilling target, first laser drilling, outer windowing, second laser drilling and post-processing steps are performed in sequence. The first laser drilling forms the inner target and alignment mark, and the outer windowing and second laser drilling are aligned based on the same alignment system.

2. The method according to claim 1, characterized in that The alignment marks are laser hole matrices distributed at the four corners of the board surface, and the hole spacing and overlap of the holes meet the requirements of high-precision positioning.

3. The method according to claim 1, characterized in that In the outer layer window opening step, the dry film is laminated while avoiding the alignment mark area, and exposure positioning is completed through the alignment mark.

4. The method according to claim 1, wherein In the secondary laser drilling process, the inner target and the outer window structure are aligned synchronously, and the sizes of the inner target and the outer copper PAD are adapted.

5. The method according to claim 1, characterized in that In the step of pressing the drilling target, a foolproof verification hole is drilled, and the verification hole does not participate in the alignment calibration.

6. The method according to claim 1, characterized in that The post-etching control parameters of the outer window are set according to the ratio between the laser hole size and the window width.

7. The method according to claim 1, characterized in that The first laser drilling and the second laser drilling use segmented processing equipment to accommodate the processing of extra-large-sized plates.

8. The method according to claim 1, characterized in that In the outer layer window opening step, multi-station exposure equipment is used to ensure uniform processing of oversized panels.

9. The method according to claim 2, characterized in that The outer frame and inner frame structure of the alignment mark form a nested design, and the inner layer target of the blind hole is adapted to the bottom plate PAD.

10. The method according to claim 1, characterized in that By analyzing the target morphology after outer layer window etching, the laser processing deviation compensation parameters are adjusted in real time.

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