Pressing process and method of PCB (Printed Circuit Board)

Abstract

The invention discloses a pressing process and method of a PCB (Printed Circuit Board), and relates to the technical field of PCB manufacturing. The process method comprises the following steps: coarsening the copper surface of an inner-layer plate, performing ultrasonic cleaning, and performing vacuum drying pretreatment; overlapping the inner layer plate, the prepreg and the copper foil according to a layer sequence, and accurately aligning through a positioning mechanism; the plate group is moved into a vacuum hot pressing cavity, and stepped heating and preheating are performed after vacuumizing; sequentially performing low-pressure exhausting, medium-pressure glue flowing, high-pressure curing segmented pressing and synchronous temperature control; maintaining the pressure and curing until the resin is completely crosslinked; and pressure relief and demolding are performed after pressure-maintaining segmented cooling. Through precise temperature and pressure control, vacuum segmented pressing and structure optimization, the interlayer bonding force of the PCB is improved, the defects of bubbles, deviation and the like are reduced, the product percent of pass is improved, the high-efficiency and high-quality production requirements of the multi-layer PCB are met, the process is stable and controllable, and the practicability is high.

Description

Technical Field

[0001] This invention discloses a lamination process and method for PCB circuit boards, relating to the field of PCB manufacturing technology. Background Technology

[0002] In PCB manufacturing, lamination is a core process in multilayer PCB molding, directly determining the interlayer bonding strength, dimensional stability, and electrical performance of the circuit board. Currently, existing PCB lamination processes generally suffer from several defects: incomplete pre-lamination treatment of inner layers results in insufficient copper adhesion, easily leading to interlayer delamination; low stacking positioning accuracy causes interlayer misalignment, affecting the accuracy of subsequent drilling and circuit fabrication; the lamination process often relies on single pressure and temperature control, making it difficult to achieve sufficient gas removal between layers and uniform resin flow, easily resulting in defects such as bubbles and resin voids; furthermore, existing processes lack precision in controlling temperature, pressure, and vacuum parameters, leading to low product yield and difficulty in meeting the production demands of high-density, multilayer PCBs. Therefore, developing a stable and reliable PCB lamination process that solves these problems has become a pressing technical challenge for those skilled in the art. Summary of the Invention

[0003] The main objective of this invention is to provide a PCB board lamination process and method. Through precise temperature and pressure control, vacuum segmented lamination, and structural optimization, the bonding force between PCB layers is improved, defects such as bubbles and misalignment are reduced, and the product qualification rate is increased. This method is suitable for the high-efficiency and high-quality production requirements of multilayer PCBs. The process is stable and controllable and highly practical.

[0004] To achieve the above objectives, the present invention provides a PCB circuit board lamination process and method, comprising the following steps: The copper surface of the inner layer of the PCB is roughened, then ultrasonically cleaned, and then vacuum dried. The pre-treated inner layer board, prepreg, and copper foil are alternately stacked in a preset order, and the board assembly is precisely aligned by a positioning mechanism. After alignment, the board assembly is moved into the vacuum hot pressing chamber, and the chamber is evacuated to reach the preset vacuum level. Then, the temperature is increased in stages to preheat the chamber, so as to remove interlayer gas and pre-melt the semi-cured sheet resin. After preheating, three pressure stages are executed in sequence: low-pressure exhaust, medium-pressure glue flow, and high-pressure curing. During the pressing process, the cavity is kept under vacuum and the temperature is controlled in real time. Maintain high pressure and the main curing temperature until the prepreg resin is completely cross-linked and cured; Under pressure holding conditions, the board components are cooled in sections, and after cooling to the set temperature, the pressure is released and the mold is demolded to produce a multi-layer PCB circuit board. Furthermore, the roughening treatment is any one of plasma roughening, micro-etching, or sandblasting, and the inner layer plate has a chamfered structure at its edge, forming a micro-anchoring structure after the copper surface is roughened.

[0005] Furthermore, the vacuum degree of the cavity is ≤-0.095MPa, the temperature of the stepped heating preheating is 80℃~130℃, and the preheating time is 10min~30min; Furthermore, the low-pressure exhaust pressure is 0.5MPa~1.0MPa, the medium-pressure dispensing pressure is 1.5MPa~2.5MPa, and the high-pressure curing pressure is 2.5MPa~4.0MPa; Furthermore, the curing peak temperature is 160℃~200℃, and the pressure holding curing time is 30min~90min; the cooling rate of the segmented cooling in S6 is ≤5℃ / min, and the cooling termination temperature is ≤60℃.

[0006] Furthermore, the positioning mechanism is any one of a pin positioning mechanism, an optical alignment mechanism, or a pinless adaptive positioning mechanism; the vacuum hot pressing chamber adopts a multi-zone independent temperature-controlled pressure plate and is equipped with a servo hydraulic closed-loop pressurization system. Furthermore, the prepreg is a high Tg modified epoxy resin prepreg with a resin content of 40% to 60%; when stacking, a high-temperature resistant buffer layer and a release film are provided on the outside of the board assembly, the buffer layer is an alkali-free fiberglass buffer cloth or a silicone rubber pad, and the release film is a PTFE release film. Furthermore, a PID adaptive control module is used during the pressing process to adjust the temperature, pressure and vacuum parameters in real time, and the monitoring deviation of the core temperature by the PID adaptive control module is ≤±3℃. Furthermore, the plates are arranged in a symmetrical stacked pattern, and a pressure-bonded reinforcement structure is set in the blind hole area. Attached Figure Description

[0007] Figure 1 This is a flowchart of the lamination process and method for a PCB circuit board according to an embodiment of the present invention; The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0008] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0009] Reference Figure 1 This is a schematic flowchart of a PCB circuit board lamination process and method proposed in this invention, including the following steps: S1. The copper surface of the inner layer of the PCB is roughened, then ultrasonically cleaned, and then vacuum dried. S2, the pre-treated inner layer board, prepreg and copper foil are stacked alternately in a preset order, and the board assembly is precisely aligned by the positioning mechanism; S3, move the aligned board assembly into the vacuum hot press chamber, evacuate the chamber to achieve the preset vacuum level, and then perform step-by-step heating preheating to achieve the discharge of interlayer gas and pre-melting of semi-cured sheet resin. S4. After preheating, three pressure stages are executed in sequence: low-pressure exhaust, medium-pressure glue flow, and high-pressure curing. During the pressing process, the cavity is kept vacuum and the temperature is controlled in real time. S5, maintain high pressure and curing peak temperature until the prepreg resin is completely cross-linked and cured; S6, under pressure holding conditions, the board is cooled in sections, and after cooling to the set temperature, the pressure is released and the board is demolded to produce a multi-layer PCB circuit board.

[0010] As described in step S1 above, this step involves refined pretreatment of the copper surface of the PCB inner layer board. The core objective is to construct a microscopic anchoring structure on the copper surface and thoroughly remove surface impurities, laying the foundation for subsequent interlayer bonding. First, plasma roughening, micro-etching, or sandblasting processes are used to roughen the copper surface, forming a uniform and dense microscopic uneven structure, significantly improving the mechanical bonding ability between the copper surface and the prepreg resin. Immediately after roughening, the inner layer board is placed in an ultrasonic cleaning device. High-frequency ultrasonic vibration removes residual abrasive particles, oxide debris, and organic contaminants from the copper surface. The cleaning medium is weakly alkaline deionized water to prevent secondary oxidation of the copper surface. After cleaning, the inner layer board is quickly transferred to a vacuum drying oven and dried for 10-15 minutes at 60-80℃ and ≤-0.09MPa vacuum. This efficiently removes moisture from the board's micropores and surface adsorbates, while preventing oxygen in the air from contacting the freshly roughened copper surface, ensuring the copper surface remains in a highly active and clean state.

[0011] As described in step S2 above, this step is crucial for ensuring the alignment accuracy between layers of a multilayer PCB and preventing interlayer misalignment. The core objective is to achieve precise bonding and positioning of each layer within the board assembly. First, the inner layer boards, high-Tg modified epoxy resin prepreg, and copper foil, all pre-treated in S1, are alternately stacked according to a preset layer sequence, following a symmetrical stacking principle. Blind and buried via areas are aligned accordingly to ensure precise matching of the trace routing across each layer. During the stacking process, any one of the following methods—pin positioning, optical alignment, or pinless adaptive positioning—is used to precisely align the board assembly. The precise cooperation between the positioning reference holes and the positioning mechanism controls the interlayer misalignment within the allowable range. Simultaneously, a high-temperature resistant buffer layer and a release film are laid on the outer side of the board assembly to prevent scratches on the board surface during stacking and to ensure uniform resin flow during subsequent lamination. This lays a stable foundation for subsequent vacuum preheating and segmented lamination processes, effectively improving the dimensional stability of the multilayer PCB.

[0012] As described in step S3 above, this step is the core process for eliminating interlayer bubbles and achieving resin pre-melting, providing a stable prerequisite for subsequent segmented pressing and effectively solving the defect of incomplete interlayer gas removal in existing processes. After alignment in S2, the board assembly is smoothly moved into the vacuum hot pressing chamber. The chamber is closed, and a two-stage vacuum pump is started to evacuate the chamber, rapidly reducing the vacuum level to a preset value of ≤-0.095MPa. This vacuum state is maintained to isolate air and prevent the generation of new bubbles during subsequent preheating and pressing. After vacuum stabilization, a multi-zone independent temperature control system is used for step-by-step preheating, gradually increasing the temperature to 80-130℃ at a rate of 2-4℃ / min, with the preheating time controlled at 10-30min. This effectively removes residual air and volatiles between the board assembly layers and allows the prepreg resin to slowly pre-melt, initially achieving adhesive bonding between layers. This avoids interlayer defects caused by uneven resin flow during subsequent high-pressure pressing, ensuring the stability of the pressing quality.

[0013] As described in step S4 above, this step is the core process for achieving dense bonding and uniform resin distribution between multilayer PCB layers. Through a synergistic mechanism of "vacuum environment + three-stage pressure variation + real-time temperature control," it solves problems such as uneven resin flow and residual bubbles caused by traditional single-pressure pressing. After preheating in step S3, the vacuum hot pressing chamber maintains a vacuum state of ≤-0.095MPa, and the servo hydraulic closed-loop pressurization system initiates a segmented pressurization program. The first stage is low-pressure venting, applying a pressure of 0.5-1.0MPa, while the temperature control system maintains the preheating temperature, further squeezing out residual trace gases between layers. The second stage is medium-pressure resin flow, with the pressure increased to 1.5-2.5MPa and the temperature raised to the initial curing temperature, promoting uniform flow of the pre-melted prepreg resin and filling the gaps between circuits and the areas of blind and buried vias. The third stage is high-pressure curing, with the pressure increased to 2.5-4.0MPa and the temperature simultaneously raised to the main curing peak temperature. Multi-zone independent temperature control plates calibrate temperature deviations in real time to ensure that the resin is fully cross-linked under high pressure, providing a guarantee for high-strength bonding between layers.

[0014] As described in step S5 above, this step is crucial for ensuring complete cross-linking of the prepreg resin and enhancing the interlayer bonding strength of the PCB. It connects to the high-pressure curing stage in step S4, ensuring stable board performance after lamination. After the high-pressure curing stage in step S4, the vacuum state of the vacuum hot pressing chamber is maintained at ≤-0.095MPa, and a high-pressure state of 2.5-4.0MPa is continuously maintained. Simultaneously, the main curing peak temperature is precisely controlled within 160-200℃ using a multi-zone independent temperature control system, with temperature deviation controlled within ±3℃. The pressure holding and curing time is set to 30-90 minutes. During this period, the core temperature, chamber pressure, and vacuum degree are monitored in real time using a PID adaptive control module to compensate for parameter fluctuations promptly. Through the synergistic effect of continuous high pressure and constant temperature, the prepreg resin is fully cross-linked and cured, forming a dense, high-strength interlayer bonding structure. This completely eliminates defects such as uncured interlayer resin and insufficient cross-linking, laying a solid foundation for subsequent cooling, demolding, and the quality of the finished PCB.

[0015] As described in step S6 above, this step is the final stage of PCB lamination molding. Its core function is to achieve stable cooling and shaping of the board, preventing deformation and ensuring the dimensional accuracy and performance stability of the finished product. It connects to the S5 pressure holding and curing process. After S5 pressure holding and curing, the vacuum hot pressing chamber is maintained at a pressure of 2.5-4.0 MPa, maintaining a vacuum environment of ≤-0.095 MPa. The water-cooling and air-cooling composite cooling system is activated to cool the board in stages. The cooling rate is strictly controlled to ≤5℃ / min during the cooling process to avoid excessively rapid cooling, which could lead to thermal stress concentration, warping, cracking, and other defects. After gradually cooling to the set termination temperature of ≤60℃, the vacuum in the chamber is slowly released, and then the high pressure is gradually removed to ensure the board is demolded smoothly in a stress-free state. After demolding, a multilayer PCB circuit board is obtained. Subsequent testing confirms that the interlayer bonding is tight, there are no bubbles or misalignment defects, and the dimensional stability is good, fully meeting the production requirements of high-density multilayer PCBs.

[0016] In one embodiment, step S1, which involves roughening the copper surface of the PCB inner layer, followed by ultrasonic cleaning, and then vacuum drying, includes: S11, copper surface roughening; S12, ultrasonic cleaning; S13, vacuum dried.

[0017] In the specific implementation process, S11 copper surface roughening adopts plasma roughening technology, using low-temperature plasma treatment equipment, introducing a mixture of argon and oxygen gas (volume ratio 4:1), controlling the plasma power at 800-1000W, the treatment time at 30-60s, and maintaining a treatment distance of 5-8mm. This process can remove an oxide layer with a thickness of 0.5-1μm from the copper surface of the PCB inner layer, while forming a uniform and dense micro-anchoring structure. The copper surface roughness is controlled at Ra=0.3-0.5μm, effectively increasing the contact area between the copper surface and the prepreg resin, and improving the interlayer mechanical interlocking force. During the copper surface roughening process, the copper surface roughness is monitored in real time to avoid excessive roughening that could lead to copper layer loss and affect the accuracy of subsequent PCB circuits. After the copper surface roughening is completed, it immediately proceeds to the S12 ultrasonic cleaning process. A 28kHz high-frequency ultrasonic cleaner is used, and the cleaning medium is weakly alkaline deionized water (pH 8.5-9.5) with 0.3-0.5% nonionic surfactant added. The cleaning solution temperature is controlled at 40-50℃, and the cleaning time is 5-10 minutes. The impact force released when the microbubbles generated by the high-frequency ultrasonic vibration burst can efficiently remove residual plasma treatment debris, abrasive particles, and organic contaminants from the copper surface. Simultaneously, the weakly alkaline medium neutralizes any remaining acidic substances on the copper surface, preventing secondary oxidation. During the cleaning process, an intermittent ultrasonic mode is used (30 seconds of operation followed by a 10-second pause) to reduce the damage to the copper surface's microstructure caused by the ultrasonic impact. The cleaned inner layer board is then quickly transferred to the S13 vacuum drying process. A vacuum drying oven is used, with the drying temperature set at 60-80℃, the vacuum degree ≤-0.09MPa, and the drying time 10-15 minutes. A vacuum environment allows for the rapid extraction of moisture from the micropores and surface of the board, while simultaneously isolating it from oxygen in the air. This prevents oxidation of the freshly roughened copper surface, ensuring it remains highly active and clean. After drying, the moisture content of the inner layer board's copper surface must be ≤0.05% before proceeding to the subsequent S2 stacking and positioning process. Taking the production of a high-density multilayer PCB (8 layers, 1.6mm thickness) as an example, using the above S1 step, the roughness Ra of the copper surface after roughening is 0.4μm, and the residual impurities on the copper surface after ultrasonic cleaning are ≤5mg / m². 2 After vacuum drying, the moisture content is 0.03%, and the subsequent interlayer peel strength reaches 1.8 N / mm. Compared with the traditional roughening and cleaning process, the interlayer peel strength is improved by 15%, which effectively verifies the feasibility and practicality of the S1 step implementation method and can significantly improve the interlayer bonding stability of multilayer PCBs.

[0018] In one embodiment, step S2, which involves alternately stacking the pre-treated inner layer board, prepreg, and copper foil in a preset layer sequence and accurately aligning the board assembly using a positioning mechanism, includes: S21, sequence superposition; S22, precise alignment; S23, auxiliary protection.

[0019] In the specific implementation process, S21 layer stacking must be performed based on the preset layer sequence of the PCB design drawings. It uses inner layer boards that have passed S1 pretreatment, high-Tg modified epoxy resin prepreg (Tg value ≥170℃, thickness 0.1-0.2mm), and electrolytic copper foil (thickness 12-35μm). A symmetrical stacking arrangement is adopted, that is, copper foil, prepreg, and inner layer boards are alternately stacked from the top and bottom sides of the board towards the middle to ensure the symmetry of the upper and lower layer structures and reduce board warping caused by uneven stress during subsequent lamination and cooling. During stacking, it is necessary to ensure precise alignment of the blind and buried via areas of each layer, with the via position deviation controlled within ±0.05mm. The circuit surface of the inner layer board should face the prepreg side to avoid short circuit hazards caused by direct contact between the circuit and the copper foil. The operating environment should be kept at Class 1000 cleanliness during the stacking process to prevent dust and impurities from entering the interlayer. After the layer stacking is completed, the S22 precision alignment process is performed. An optical alignment mechanism (alignment accuracy ±0.02mm) is used in conjunction with the pre-set positioning reference holes (2.0mm in diameter) on the edge of the board assembly for positioning. During positioning, the board assembly is placed stably on the alignment platform. An optical camera captures the position of the positioning reference holes, and a servo motor drives the platform to make fine adjustments to ensure that the reference holes of each layer are completely aligned. The interlayer offset is monitored simultaneously to ensure that the offset is ≤0.03mm. For high-density multilayer PCBs, a dual-camera synchronous alignment mode can be used to capture the diagonal reference holes of the board assembly, improving alignment efficiency and accuracy. After alignment, the board is temporarily fixed with positioning pins to prevent interlayer offset during subsequent movement. After precise alignment, the S23 auxiliary protection operation is performed, where a high-temperature resistant buffer layer and an isolation film are laid on the top and bottom sides of the board assembly, respectively. The buffer layer uses alkali-free fiberglass buffer cloth (0.3-0.5mm thick), which has good high-temperature resistance and elasticity, and can buffer the pressure impact during subsequent lamination, avoiding scratches on the board surface. The release liner uses PTFE release liner (0.02-0.03mm thick), which has non-stick resin properties, preventing the prepreg resin from sticking to the equipment and buffer layer during lamination, and also assisting in the uniform flow of resin. During installation, ensure that the buffer layer and release liner completely cover the board assembly, with the edges extending 5-10mm beyond the edge of the board assembly, to avoid lamination defects caused by unprotected edge areas. Taking the production of a 12-layer high-density PCB (2.0mm thick, 0.1mm line width / 0.1mm line spacing) as an example, using the above S2 step, the blind buried via position deviation after layer stacking is ≤0.04mm, and the interlayer offset after optical alignment is controlled within 0.02mm, assisting in the standardized installation of protective materials. After subsequent processes such as vacuum preheating and segmented pressing, the board warpage is ≤0.3% and the interlayer misalignment defect rate is only 0.8%. Compared with the traditional manual alignment and stacking process, the defect rate is reduced by 60% and the reliability of interlayer circuit connection is improved by 20%, which fully verifies the feasibility and practicality of the S2 step implementation method and can be adapted to the precise stacking requirements of high-density, multi-layer PCBs.

[0020] In one embodiment, step S3, which involves moving the aligned plate assembly into a vacuum hot pressing chamber, evacuating the chamber to a preset vacuum level, and then performing stepwise heating preheating to achieve interlayer gas removal and pre-melting of the pre-cured sheet resin, includes: S31, cavity insertion; S32, vacuum extraction; S33, stepped preheating; In the specific implementation process, step S31, cavity insertion, must be performed immediately after the auxiliary protection in step S2. An anti-static vacuum chuck handling device is used to smoothly transfer the positioned and fixed plate assembly to the vacuum hot-pressing cavity inlet. During transportation, the plate assembly is kept horizontal, with the tilt angle controlled at ≤3° to avoid interlayer displacement or detachment of the auxiliary protective layer due to tilting. The cavity inlet needs to be cleaned in advance to remove residual resin debris and dust. When placing the plate assembly into the cavity, it should be centered on the hot-pressing tray, maintaining a 5-8mm gap from the cavity wall and heating plate to ensure uniform heating and avoid localized overheating or scratches caused by contact between the plate assembly and the cavity. After the plate assembly is placed, the cavity sealing door is closed, and the sealing test program is started to ensure that the cavity sealing performance meets the standard, with a leakage rate ≤0.01mbar·L / s, preventing air leakage during subsequent vacuuming and preheating processes, which could affect the stability of the vacuum environment. After the cavity is sealed successfully, the process proceeds to step S32, the vacuum evacuation procedure. A two-stage rotary vane vacuum pump is started, employing a staged vacuum evacuation mode. First, evacuation is performed at a low vacuum setting (vacuum degree -0.05MPa) for 2-3 minutes to quickly remove most of the air from the cavity. Then, the process is switched to a high vacuum setting and continued until the preset vacuum degree is ≤-0.095MPa. The entire evacuation process takes 5-8 minutes. Once the preset vacuum degree is reached, a vacuum holding program is initiated. The vacuum degree is monitored in real time by a vacuum pressure sensor. When the vacuum degree fluctuates beyond ±0.002MPa, the vacuum pump automatically starts supplementary evacuation to ensure a stable vacuum state throughout the preheating process. The vacuum environment effectively isolates air, preventing oxidation of the prepreg resin during preheating, and provides a channel for interlayer gas to escape, avoiding the formation of gas bubbles. After the vacuum state stabilizes, step S33, the stepped preheating operation, is performed using a multi-zone independent temperature-controlled heating plate (zone accuracy ±1℃), with step-by-step heating according to a preset temperature rise curve. The first stage involves heating from room temperature to 80℃ at a rate of 2℃ / min, maintaining this temperature for 5-8 minutes to initially expel trace amounts of air adsorbed on the surface of the board assembly. The second stage involves heating to 100℃ at a rate of 3℃ / min, maintaining this temperature for 8-12 minutes to allow residual gas between the layers to slowly escape, while simultaneously softening the prepreg resin. The third stage involves heating to 120-130℃ at a rate of 4℃ / min, maintaining this temperature for 5-10 minutes to pre-melt the prepreg resin. The pre-melted resin is viscous and can initially fill the tiny gaps between the layers, laying the foundation for resin flow during subsequent segmented lamination. During preheating, the internal temperature of the board assembly is monitored in real time using a core temperature sensor to ensure that the core temperature deviates from the set cavity temperature by ≤±2℃, preventing localized overheating that could lead to premature resin curing.Taking the production of a 10-layer high-density PCB (1.8mm thick, 0.3mm diameter blind / buried via) as an example, using the above-mentioned S3 step, the cavity sealing leakage rate was 0.008mbar·L / s, stabilized at -0.096MPa after vacuum extraction, and the core temperature reached 125℃ after stepped preheating. The interlayer gas discharge rate reached 99.2%, and the pre-melted resin of the prepreg was uniform. After subsequent steps such as S4 segmented lamination and S5 pressure holding and curing, the PCB board bubble defect rate was only 0.3%. Compared with the traditional one-time preheating process, the bubble defect rate was reduced by 75%, and the uniformity of interlayer resin filling was improved by 30%. This fully verifies the feasibility and practicality of the S3 step implementation method, which can effectively solve problems such as interlayer gas residue and uneven resin pre-melting, and ensure the lamination quality of multilayer PCBs.

[0021] In one embodiment, step S4, which involves moving the aligned plate assembly into a vacuum hot pressing chamber, evacuating the chamber to a preset vacuum level, and then performing stepwise heating preheating to achieve interlayer gas removal and pre-melting of the pre-cured sheet resin, includes: S41, vacuum maintenance; S42, low-pressure exhaust; S43, medium-pressure glue delivery; S44, high-pressure curing; In the specific implementation process, step S41, vacuum maintenance, connects to step S3, the stepped preheating process, maintaining the vacuum degree of the vacuum hot pressing chamber at ≤-0.095MPa throughout. A vacuum pressure sensor collects internal pressure data in real time, with a data sampling frequency of once every 10 seconds. When the vacuum degree fluctuates beyond ±0.002MPa, the two-stage rotary vane vacuum pump automatically activates the replenishment pump mode to quickly restore the vacuum degree to the preset range. The vacuum environment continuously isolates air, preventing the prepreg resin from oxidizing and deteriorating during pressing, and also preventing external air from entering the interlayer and forming bubbles. This provides a stable oxygen-free environment for subsequent pressure application and resin flow, ensuring the quality of interlayer bonding. After the vacuum state stabilizes, step S42, the low-pressure exhaust process, is initiated. The servo hydraulic system is activated, using a slow pressurization mode, gradually applying a low pressure of 0.5-1.0MPa at a rate of 0.1MPa / min, while maintaining the chamber temperature at 120-130℃ (consistent with the temperature at the end of step S3). Under low pressure, the trace amounts of gas remaining between the layers of the board are further squeezed out and discharged from the cavity through the vacuum channel. This process lasts for 3-5 minutes. During this period, the exhaust volume is monitored by a gas flow sensor. When the exhaust volume drops to ≤0.01L / min, the low-pressure exhaust is considered complete to avoid incomplete exhaust that could lead to air bubble defects in subsequent pressing. After the low-pressure exhaust is completed, the process proceeds to step S43, the medium-pressure resin flow process. The servo hydraulic system continues to pressurize, increasing the pressure to 1.5-2.5MPa at a rate of 0.2MPa / min. Simultaneously, the cavity temperature is raised to 140-150℃ (initial curing temperature) through a multi-zone independent temperature control system. Under medium pressure, the pre-melted semi-cured resin begins to flow uniformly, filling the gaps between the inner layer board circuits, blind and buried vias, and tiny gaps between layers. During the flow, the resin flow sensor monitors the flow volume in real time, controlling the flow volume to 0.1-0.2mm to ensure sufficient resin filling and prevent problems such as excessive resin flow leading to overflow at the board edges or short circuits. The resin flow process lasts for 5-8 minutes. After medium-pressure resin delivery, step S44, high-pressure curing, is executed. The servo hydraulic system pressure is increased to 2.5-4.0 MPa, and the cavity temperature is precisely raised to 160-180℃ (the main curing peak temperature) based on the characteristics of the prepreg resin, with temperature deviation controlled within ±2℃. The high-pressure environment promotes full contact and cross-linking of resin molecules, initially forming a dense interlayer bond structure, while simultaneously inhibiting the formation of micropores within the resin. This process lasts 8-12 minutes. During this time, a PID adaptive control module synchronously monitors the core temperature, cavity pressure, and vacuum level, promptly compensating for parameter fluctuations to ensure a stable high-pressure curing process.Taking the production of a 16-layer high-density PCB (2.2mm thickness, 0.08mm / 0.08mm line width / spacing, 0.25mm blind / buried via diameter) as an example, the above-mentioned S4 step was implemented. During the vacuum maintenance process, the vacuum degree was stabilized at -0.096MPa. After low-pressure venting, the venting volume dropped to 0.008L / min. The medium-pressure resin flow rate was controlled at 0.15mm, and the high-pressure curing temperature was stabilized at 170℃. After subsequent pressure holding and curing in step S5 and cooling and demolding in step S6, the resin filling rate between the PCB layers reached 99.5%, with no bubbles or overflow defects. The interlayer bonding strength reached 2.1N / mm. Compared with the traditional single pressure lamination process, the interlayer bonding strength was improved by 23%, and the short-circuit failure rate was reduced to 0.2%. This fully verifies the feasibility and practicality of the S4 step implementation method, which can be adapted to the segmented lamination requirements of high-density, fine-line multilayer PCBs.

[0022] In one embodiment, step S5, which maintains the high pressure and the main curing peak temperature until the prepreg resin is completely crosslinked and cured, includes: S51, parameter maintenance; S52, real-time monitoring; S53, cross-linking curing; In the specific implementation process, the parameters of step S51 are maintained in conjunction with the high-pressure curing process in step S4, ensuring the stability of all parameters in the vacuum hot-pressing chamber throughout the process. This maintains the 2.5-4.0 MPa high-pressure state and ≤-0.095 MPa vacuum state at the end of step S4, without any sudden increases or decreases in parameters. The main curing peak temperature is precisely controlled between 160-200℃, adjusted according to the resin type of the prepreg sheet. High Tg resin is selected at 180-200℃, and ordinary resin at 160-180℃. Relying on a multi-zone independent temperature control system, the temperature deviation in each zone is strictly controlled within ±3℃, ensuring uniform temperature across the entire assembly and avoiding uneven resin cross-linking and interlayer bonding caused by localized temperature deviations. During parameter maintenance, the chamber sealing status is continuously monitored to ensure a leakage rate ≤0.01 mbar·L / s, providing a stable high-pressure, vacuum, and constant-temperature environment for complete resin cross-linking. While maintaining parameters, the S52 real-time monitoring operation is executed simultaneously. Employing a PID adaptive control module, it integrates data from the core temperature sensor, cavity pressure sensor, and vacuum sensor, sampling at a frequency of once every 8 seconds to achieve real-time acquisition and dynamic compensation of various parameters. When the core temperature fluctuates beyond ±3℃, the temperature control system automatically adjusts the heating power to quickly return to the set temperature. When the cavity pressure drops by ≥0.1MPa, the servo hydraulic system automatically replenishes pressure to maintain high-pressure stability. When the vacuum level fluctuates beyond ±0.002MPa, the vacuum pump activates the supplementary pumping mode to ensure the vacuum environment meets standards. Simultaneously, the resin crosslinking degree is monitored. An online infrared spectroscopy sensor detects changes in resin functional groups in real time. When the crosslinking degree reaches 95% or higher, the process enters the final stage of crosslinking and curing, preparing for subsequent cooling processes. The cross-linking and curing time in step S53 is flexibly adjusted according to the number of PCB layers, board thickness, and resin characteristics. For 8-12 layer PCBs (1.6-2.0mm thick), maintain for 30-50 minutes; for 16-20 layer PCBs (2.2-2.5mm thick), maintain for 60-90 minutes. This ensures that the resin molecules in the prepreg fully contact and cross-link, forming a dense, high-strength three-dimensional network structure, completely eliminating the potential risks of uncured or insufficiently cross-linked resin between layers. During the cross-linking and curing process, the resin gradually loses its fluidity and forms strong chemical bonds with the copper surface and copper foil of the inner layers. At the same time, it fills the tiny gaps between layers, further improving the interlayer bonding strength and ensuring the mechanical and electrical properties of the finished PCB. Taking the production of an 18-layer high-density PCB (2.4mm thick, using a high-Tg modified epoxy resin prepreg with a Tg value of 180℃) as an example, the above S5 steps were implemented. During the parameter maintenance stage, the high pressure was stabilized at 3.0MPa, the vacuum degree was stabilized at -0.096MPa, the main curing peak temperature was controlled at 190℃, the temperature deviation was ≤±2℃, and there were no obvious parameter fluctuations in real-time monitoring. The crosslinking curing time was set to 75min.After curing, the resin crosslinking degree reached 97.3%, and the interlayer bonding strength reached 2.3 N / mm. After subsequent steps S6 (cooling, demolding, and testing), the PCB board showed no defects such as interlayer delamination or resin cracking, and its high-temperature resistance met the standard (no deformation after 1000 hours at 125℃). Compared with the traditional pressure-holding curing process, the resin crosslinking degree increased by 8%, the interlayer bonding strength increased by 10%, and the defect rate decreased to 0.15%, fully verifying the feasibility and practicality of the S5 step implementation method, which can be adapted to the pressure-holding curing requirements of high-density, high-reliability multilayer PCBs.

[0023] In one embodiment, step S6, which involves cooling the board assembly in sections under pressure, releasing pressure and demolding after cooling to a set temperature to produce a multilayer PCB circuit board, includes: S61, pressure holding cooling; S62, parameter release; S63, smooth demolding; In the specific implementation process, step S61, pressure holding and cooling, connects to step S5, cross-linking and curing. Throughout the process, the vacuum hot pressing chamber is maintained at a pressure of 2.5-4.0 MPa and a vacuum of ≤-0.095 MPa, with parameters kept stable and without fluctuations. This avoids defects such as thermal stress and interlayer delamination caused by sudden changes in pressure or vacuum. The water-cooling and air-cooling composite cooling system is activated, using a segmented cooling mode to adapt to the temperature changes of the board. In the first stage, the temperature is reduced from the main curing peak temperature (160-200℃) to 120℃, with the cooling rate controlled at 3-4℃ / min to avoid excessively rapid cooling and large temperature differences between the surface and interior of the board. In the second stage, the temperature is reduced from 120℃ to 80℃, with the cooling rate adjusted to 4-5℃ / min, gradually reducing the temperature difference between the inside and outside of the board. In the third stage, the temperature is reduced from 80℃ to ≤60℃, with the cooling rate maintained at 3℃ / min, ensuring slow cooling and shaping of the board and reducing the risk of warping and deformation. During the cooling process, the core temperature sensor and surface temperature sensor are used to monitor the temperature simultaneously, ensuring that the temperature difference between the inside and outside of the board is ≤20℃. After the board cools down to the set termination temperature (≤60℃), the process proceeds to step S62, the parameter release procedure, following the principle of "releasing vacuum first, then releasing high pressure" to avoid uneven stress on the board due to sudden pressure release. First, the vacuum pump is slowly shut off, and the chamber vacuum is released at a rate of 0.02MPa / min through the controllable pressure relief valve until the vacuum level returns to normal pressure. The entire vacuum release process lasts 5-8 minutes to prevent the airflow generated by the sudden vacuum release from impacting the board. After the vacuum is completely released, the servo hydraulic system pressure relief program is activated, gradually releasing the high pressure of 2.5-4.0MPa at a rate of 0.1MPa / min. The board status is monitored in real time during the pressure relief process to avoid problems such as interlayer displacement and resin cracking. After the pressure relief is completed, it is confirmed that the chamber pressure has dropped to normal pressure. After the parameters are fully released, proceed with step S63 for smooth demolding. First, open the sealed door of the vacuum hot press chamber. Use an anti-static vacuum suction cup to smoothly suction the surface of the board assembly (suction pressure controlled at 0.03-0.05MPa) to avoid excessive suction pressure damaging the board surface or causing interlayer delamination. During handling, keep the board horizontal with an inclination angle ≤2° and slowly move the board assembly out of the chamber, placing it on a clean platform pre-lined with an anti-static buffer pad. After demolding, promptly remove the buffer layer and release film from the board assembly surface. Remove them gently to avoid scratching the board surface or damaging the interlayer bonding structure. Then, perform a preliminary visual inspection of the board, removing obvious defects such as surface scratches, excess glue, and warping. Taking the production of a 14-layer high-density PCB (2.1mm thick, using a prepreg with a Tg value of 175℃) as an example, the above S6 steps are implemented. During the pressure holding and cooling stage, the high pressure is stabilized at 2.8MPa and the vacuum degree is stabilized at -0.095MPa. The segmented cooling rate is controlled at 3-5℃ / min. After cooling to 58℃, the parameters are released. The vacuum release takes 6 minutes and the high pressure relief takes 8 minutes.After smooth demolding, the board warpage is ≤0.25%, with no defects such as interlayer delamination, resin cracking, or surface scratches, and dimensional deviations are controlled within ±0.03mm. Subsequent testing showed that the PCB board's thermal shock resistance met the standards (no deformation after 50 cycles from -40℃ to 125℃), and the interlayer bonding strength remained at 2.2N / mm. Compared to the traditional rapid cooling demolding process, the board warpage defect rate was reduced by 70%, and the finished product qualification rate increased to 99.8%, fully verifying the feasibility and practicality of the S6 step implementation method, which can adapt to the cooling and demolding requirements of high-density, high-precision multilayer PCBs.

[0024] In summary, the implementation of the multilayer PCB lamination process requires a complete and continuous series of steps, with precise parameter matching and synergistic effects at each stage. The copper surfaces of the inner PCB layers are roughened, ultrasonically cleaned, and vacuum dried to remove oxide layers and impurities, forming a stable microscopic anchoring structure that lays the foundation for interlayer bonding. The pre-treated inner PCB layers, prepreg, and copper foil are then stacked symmetrically, with precise alignment achieved through a positioning mechanism and auxiliary protection to prevent defects in subsequent processes. The assembly is moved into a vacuum thermopressing chamber, where vacuum is evacuated in stages to a preset value, followed by stepped preheating to fully expel interlayer gases and pre-melt the prepreg resin. Maintaining the vacuum state, pressure is applied in stages with simultaneous temperature control to complete venting, resin flow, and initial curing, ensuring uniform resin filling of interlayer gaps. High pressure, constant temperature, and vacuum parameters are continuously maintained, with real-time monitoring and compensation for fluctuations to promote complete resin cross-linking and curing. Finally, under pressure, the temperature is reduced in stages, and after releasing the vacuum and pressure according to specifications, the PCB is smoothly demolded, resulting in a multilayer PCB circuit board with tight interlayer bonding and stable dimensions. The entire process is highly controllable, effectively reducing various defects and adapting to the production needs of high-density multilayer PCBs.

[0025] In this embodiment, the specific implementation of each unit in the above device embodiment is described in the above method embodiment, and will not be repeated here.

[0026] An embodiment of the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described method. It is understood that the computer-readable storage medium in this embodiment can be a volatile readable storage medium or a non-volatile readable storage medium.

[0027] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the present invention and embodiments can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual-rate SDRAM (SSRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM, etc.

[0028] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, apparatus, article, or method that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, apparatus, article, or method. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, apparatus, article, or method that includes that element.

[0029] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A lamination process and method for a PCB circuit board, characterized in that, Includes the following steps: The copper surface of the inner layer of the PCB is roughened, then ultrasonically cleaned, and then vacuum dried. The pre-treated inner layer board, prepreg, and copper foil are alternately stacked in a preset order, and the board assembly is precisely aligned by a positioning mechanism. After alignment, the board assembly is moved into the vacuum hot pressing chamber, and the chamber is evacuated to reach the preset vacuum level. Then, the temperature is increased in stages to preheat the chamber, so as to remove interlayer gas and pre-melt the semi-cured sheet resin. After preheating, three pressure stages are executed in sequence: low-pressure exhaust, medium-pressure glue flow, and high-pressure curing. During the pressing process, the cavity is kept under vacuum and the temperature is controlled in real time. Maintain high pressure and the main curing temperature until the prepreg resin is completely cross-linked and cured; The board is cooled in sections under pressure, and after cooling to the set temperature, the pressure is released and the board is demolded to produce a multi-layer PCB circuit board.

2. The PCB circuit board lamination process and method according to claim 1, characterized in that, The roughening treatment is any one of plasma roughening, micro-etching, or sandblasting, and the inner layer plate has a chamfered structure at its edge, forming a micro-anchoring structure after the copper surface is roughened.

3. The PCB circuit board lamination process and method according to claim 1, characterized in that, The cavity vacuum degree is ≤-0.095MPa, the temperature of the stepped heating preheating is 80℃~130℃, and the preheating time is 10min~30min.

4. The PCB circuit board lamination process and method according to claim 1, characterized in that, The low-pressure exhaust pressure is 0.5MPa~1.0MPa, the medium-pressure flow pressure is 1.5MPa~2.5MPa, and the high-pressure curing pressure is 2.5MPa~4.0MPa.

5. The PCB circuit board lamination process and method according to claim 1, characterized in that, The curing peak temperature is 160℃~200℃, and the pressure holding curing time is 30min~90min; the cooling rate of the segmented cooling in S6 is ≤5℃ / min, and the cooling termination temperature is ≤60℃.

6. The PCB circuit board lamination process and method according to claim 1, characterized in that, The positioning mechanism is any one of a pin positioning mechanism, an optical alignment mechanism, or a pinless adaptive positioning mechanism; the vacuum hot pressing chamber adopts a multi-zone independent temperature control pressure plate and is equipped with a servo hydraulic closed-loop pressurization system.

7. The PCB circuit board lamination process and method according to claim 1, characterized in that, The prepreg is a high Tg modified epoxy resin prepreg with a resin content of 40% to 60%. When stacking, a high-temperature resistant buffer layer and a release film are set on the outside of the board assembly. The buffer layer is an alkali-free fiberglass buffer cloth or a silicone rubber pad, and the release film is a PTFE release film.

8. The PCB circuit board lamination process and method according to claim 1, characterized in that, During the pressing process, a PID adaptive control module is used to adjust the temperature, pressure and vacuum parameters in real time, and the monitoring deviation of the core temperature by the PID adaptive control module is ≤±3℃.

9. The PCB circuit board lamination process and method according to claim 1, characterized in that, The plates are arranged in a symmetrical stacked pattern, and a pressure-bonded reinforcement structure is set in the blind hole area.

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