Vacuum fast-pressing pre-lamination method and device for multilayer PCB

Abstract

This invention relates to a vacuum fast-pressing pre-stacking method and apparatus for multilayer PCBs, comprising the following steps: cleaning and surface roughening the sub-board, and pre-baking the prepreg; stacking the sub-board, PET film, prepreg, PET film, and sub-board in an alternating sequence on the lower pressure platform of a vacuum fast-pressing apparatus to form a stacked structure; closing the vacuum chamber and starting the vacuum system to evacuate to a predetermined vacuum level; performing at least one contact venting operation during the evacuation process; maintaining the vacuum environment; fast-pressing pre-fixing the stacked structure; after holding the pressure for a predetermined time, introducing a cooling medium to cool the stacked structure; releasing the pressure, opening the vacuum chamber, and removing the stacked structure. This invention, by introducing a contact venting operation during the vacuuming process, forces residual gases between layers and low-molecular-weight substances volatilized from the prepreg by heat to be expelled in advance, effectively reducing bubbles and voids after final pressing and improving the interlayer bonding quality.

Description

Technical Field

[0001] This invention relates to the field of PCB boards, and more particularly, to a vacuum fast-pressing pre-stack method and apparatus for multilayer PCB boards. Background Technology

[0002] As electronic devices evolve towards higher performance and greater integration, the number of layers in multilayer PCBs continues to increase. Multilayer boards are commonly found in high-end applications such as communication equipment, server backplanes, and automotive electronic control units. Currently, before final lamination, multilayer boards typically require pre-stacking to ensure the relative positions of each layer remain unchanged, facilitating transfer to the laminator for final forming. In traditional pre-stacking processes, localized hot pressing or dispensing is often used to fix the positions of each layer. However, localized heating can cause the prepreg to melt and overflow, potentially contaminating the pads or vias on the sub-board surface, affecting subsequent electroplating and soldering quality. Furthermore, during the prepreg stacking process, air inevitably gets trapped between layers, easily leading to weak localized lamination, circuit deformation, or even complete board failure. Summary of the Invention

[0003] In view of this, the present invention provides a vacuum fast-pressing pre-stacking method and apparatus for multilayer PCBs that effectively reduces stacking bubbles and improves lamination quality.

[0004] The objective of this invention is achieved through the following technical solution: A vacuum fast-press pre-stack method for a multilayer PCB board, the multilayer PCB board comprising N sub-boards, N-1 layers of prepreg and 2 (N-1) layers of PET release film, comprising the following steps: S1. Clean and roughen the surfaces of the N sub-boards, and pre-bake the N-1 layer of prepreg. S2. Sub-plates, PET film, prepreg, PET film, and sub-plates are stacked in an alternating order on the lower pressure table of the vacuum fast press device to form a stacked structure. The sub-plates at the bottom are fixed by vacuum adsorption. S3. Close the vacuum chamber and start the vacuum system to evacuate to the predetermined vacuum level; during the evacuation process, perform at least one contact venting operation: control the upper pressure platform to descend to a predetermined distance from the surface of the laminated structure, stay for a predetermined time, and then rise back to its original position; S4. Maintain a vacuum environment, control the upper pressure platform to descend rapidly, and apply a predetermined pressure and temperature to the laminated structure for rapid pressure pre-fixation. S5. After holding the pressure for a predetermined time, a cooling medium is introduced to cool the laminated structure. After depressurization, the vacuum chamber is opened and the laminated structure is removed.

[0005] In the above technical solution, by introducing a contact-type exhaust operation during the vacuuming process, the upper pressure platform descends to the vicinity of the surface of the laminated structure, forcing the residual gas between the layers and the low molecular weight substances volatilized by the heat of the semi-cured sheet to be discharged in advance. Combined with the vacuum environment, this effectively reduces bubbles and voids after final pressing and improves the quality of interlayer bonding.

[0006] In addition, the bottom layer is fixed by vacuum adsorption, and the alternating stacking sequence maintains the relative position of each layer before fast pressing. The contact venting operation further smooths the interlayer warping and avoids interlayer slippage caused by pressure impact during fast pressing, ensuring the accurate dimensions of the pre-fixed stacked structure.

[0007] Optionally, in one possible implementation, the contact venting operation in step S3 is as follows: the upper pressure platform descends to a distance of 0.5mm-2mm from the surface of the stacked structure, stays for 1-2 seconds, and then rises back to its original position, and this process is repeated 3-5 times during the venting process.

[0008] In the above technical solution, the appropriate gap setting will not compact the prepreg, avoiding premature curing or adhesive overflow, while also generating a local micro-negative pressure suction effect, forcing millimeter- or even micrometer-sized residual air bubbles between layers to rupture and be extracted. Repeating this 3–5 times is equivalent to performing multiple "gentle venting" operations on each layer interface, which can significantly reduce the amount of residual gas compared to a single venting operation.

[0009] Optionally, in one possible implementation, in step S4, the changes in the thickness of the laminate are recorded in real time by an online thickness monitoring system. When the rate of change of the thickness of the laminate structure drops below a predetermined threshold, it is determined that the pre-compression is completed and step S4 ends.

[0010] In the above technical solution, by monitoring the thickness change rate in real time, when the change rate is lower than the predetermined threshold, that is, close to zero, it indicates that the prepreg has fully filled the gap between the sub-boards and the flow has basically stopped. At this time, the pre-pressing is stopped immediately to prevent insufficient interlayer bonding caused by under-pressure, and to avoid excessive extrusion of the prepreg, glue overflow or sub-board deformation caused by over-pressure.

[0011] Alternatively, in one possible implementation, in step S2, a layer of release paper is laid on the surface of the lower pressure table before placing the sub-plate located at the bottom.

[0012] In the above technical solution, during the vacuum fast pressing process, a small amount of resin may overflow from the prepreg after being heated. If the bottom sub-board directly contacts the lower pressing platform, the overflowed resin will stick to the surface of the pressing platform, making it difficult to remove after pressing or even damaging the sub-board. The release paper, as an isolation layer, utilizes its low surface energy properties to effectively prevent resin adhesion, allowing the sub-board to be easily separated after pressing, avoiding scratches or delamination of the board surface caused by forced prying.

[0013] Optionally, in one possible implementation, in step S4, the laminated structure is subjected to rapid pressing using the following parameters: a predetermined pressure of 0.8 MPa-1.5 MPa, an upper pressing stage temperature of 140℃-180℃, a lower pressing stage temperature of 130℃-170℃, and a rapid pressing time of 15 seconds-40 seconds.

[0014] In the above technical solution, within this temperature range, the viscosity of the resin (such as epoxy resin) in ordinary prepregs decreases significantly, entering a molten flow state; simultaneously, the pressure of 0.8–1.5 MPa provides sufficient driving force to allow the resin to fill the micro-roughened areas on the surface of the sub-plate. 15–40 seconds is sufficient to complete flow and initial cross-linking (gelation), but not enough to achieve complete curing. The pre-fixed laminate has sufficient handling strength, is not prone to interlayer misalignment, and retains the ability to further cure during subsequent formal pressing.

[0015] Optionally, in one possible implementation, in step S5, the cooling medium is water or cooling gas, the cooling time is 5-20 seconds, and the cooling rate is greater than 5°C / second.

[0016] In the above technical solution, the precured sheet only needs to reach partial curing during the pre-compression stage to obtain sufficient pre-fixed strength. If the cooling is slow, the residual heat will cause the resin to continue cross-linking, resulting in excessive curing and insufficient fluidity during subsequent formal pressing, affecting interlayer bonding. However, rapid cooling at a rate of >5℃ / second, reducing the lamination temperature below the resin's glass transition temperature within 5–20 seconds, immediately "freezes" the curing process and precisely controls the degree of pre-curing.

[0017] Optionally, in one possible implementation, in step S2, after the stacked structure is stacked, an automatic pusher is used to apply thrust to the stacking mechanism from the transverse and longitudinal directions of the stacked structure, respectively.

[0018] In the above technical solutions, when stacking layers manually or by a robotic arm, there will be slight positional deviations between the layers. The automatic pusher applies controllable pushing force from two orthogonal directions, horizontal and vertical, forcing all sub-boards, prepregs, and PET release films to slide in the horizontal plane to their respective aligned positions, thereby further improving the interlayer overlap accuracy.

[0019] Optionally, in one possible implementation, step S6 is further included: performing ultrasonic scanning and / or X-ray inspection on the extracted stacked structure to assess the internal bubble condition and interlayer offset.

[0020] In the above technical solution, ultrasonic scanning can sensitively detect tiny air bubbles, delamination, voids, and uneven bonding between layers; X-ray inspection can quantify the horizontal offset between inner sub-boards. Defects can be identified during the pre-pressing stage, allowing unqualified laminates to be rejected or reworked, avoiding the time-consuming and costly high-temperature and high-pressure pressing process, and reducing material and energy waste.

[0021] A vacuum fast-pressing pre-stacking device for implementing the above method, characterized in that it comprises: A vacuum chamber is used to provide a vacuum working environment; An upper pressure platform and a lower pressure platform are disposed within the vacuum chamber. The upper pressure platform is movable and integrates heating and cooling functions. The lower pressure platform integrates a vacuum adsorption system for fixing the bottom sub-plate. A vacuum system, connected to the vacuum chamber, is used to evacuate the chamber. A cooling system, connected to the upper pressure platform and / or the lower pressure platform, is used to provide a cooling medium; The positioning system includes a main positioning pin disposed on the lower pressing platform and a movable side push plate, the side push plate being used to push the stacked structure from the horizontal direction so that the positioning holes of each layer are tightly attached to the main positioning pin; The online thickness monitoring system is used to monitor changes in the thickness of the laminate in real time and output a thickness signal to control the pre-compression endpoint.

[0022] In the above technical solution, the vacuum chamber, in conjunction with the vacuum system, provides a low-oxygen, low-humidity working environment, fundamentally suppressing bubble formation. The upper pressure platform integrates heating and cooling functions, enabling the entire process of heating, pressurizing, and rapid cooling to be completed at the same station, avoiding secondary contamination or interlayer misalignment during the transfer process, and significantly improving the quality and efficiency of pre-fixation. Furthermore, integrating the vacuum chamber, heating pressure platform, cooling channel, vacuum adsorption, positioning system, and thickness monitoring module into one unit results in a compact equipment structure, reducing equipment investment and maintenance costs.

[0023] Optionally, in one possible implementation, the lateral pusher includes a transverse pusher and a longitudinal pusher, the transverse pusher and the longitudinal pusher being driven by separate cylinders.

[0024] In the above technical solution, the transverse push plate and the longitudinal push plate are driven by independent cylinders, which can apply controllable thrust in both the X and Y directions. First, push in one direction to make the positioning holes of each layer fit tightly against one side of the main positioning pin, and then push in the other direction to make them fit tightly against the other side, so as to avoid the resultant force direction deviation or jamming when force is applied at the same time. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the stacked structure in this embodiment.

[0027] Figure labels: 1-sub-plate; 2-PET release film; 3-preservative sheet. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0030] Please refer to Figure 1 This embodiment provides a vacuum fast-pressing pre-stack method for multilayer PCB boards. The multilayer PCB board includes N sub-boards 1, N-1 layers of prepreg 3 and 2 (N-1) layers of PET release film 2, and includes the following steps.

[0031] S1. Clean and roughen the surface of N sub-boards 1, and pre-bake the N-1 layer of prepreg 3.

[0032] This embodiment uses a multilayer board with 6 sub-boards 1 (each sub-board 1 is 500mm×400mm in size and 1.0m thick), 5 layers of prepreg 3 (0.2mm thick / layer), 10 layers of PET release film 2 (75μm thick), and a finished board thickness of approximately 6.2mm as an example. First, the sub-boards 1 need to be processed. After the inner layer circuitry is fabricated, the 6 sub-boards 1 are chemically cleaned on the film removal line to remove surface oxides and oil stains. The surface is roughened by a mechanical brush (600# nylon brush) to increase the adhesion with the prepreg 3. Then, Φ3.175mm positioning holes (6 holes per board) are drilled at the four corners and edges of the sub-boards 1.

[0033] Meanwhile, 5 layers of FR-4 prepreg 3 (type 1080, resin content approximately 55%) were baked in a vacuum oven at 100°C for 45 minutes, and then cooled to room temperature in a drying oven. The flowability was tested to be 20%. 10 layers of PET release film 2 (single-sided silicone release) were cut, with dimensions of 510mm × 410mm and a release force of 35g / inch.

[0034] S2. Sub-plate 1, PET film, prepreg 3, PET film, and sub-plate 1 are stacked in an alternating order on the lower pressure table of the vacuum fast press device to form a stacked structure. Sub-plate 1 at the bottom is fixed by vacuum adsorption.

[0035] Before placing the first sub-board 1 at the bottom, a layer of release paper is laid on the surface of the lower pressure table. The release paper is 0.1mm thick Teflon glass cloth. Then, the first sub-board 1 is placed on the lower pressure table and positioned using positioning holes and positioning pins. The vacuum adsorption system is activated to achieve a vacuum level of -0.09MPa, firmly fixing the first sub-board 1. After the first sub-board 1 is fixed, the first PET film, the first prepreg 3, the second PET film, the second sub-board 1... and the sixth sub-board 1 are placed in sequence.

[0036] During vacuum pressing, a small amount of resin may overflow from the prepreg 3 after heating. If the bottom sub-plate 1 directly contacts the pressing platform, the overflowed resin will stick to the surface of the pressing platform, making it difficult to remove after pressing or even damaging the sub-plate 1. The release paper, as an isolation layer, utilizes its low surface energy properties to effectively prevent resin adhesion, allowing the sub-plate 1 to be easily separated after pressing, avoiding scratches or delamination of the board surface caused by forced prying.

[0037] It should be noted that the release paper is usually made of porous materials (such as high-temperature resistant release paper or breathable release film) or pre-punched at the corresponding vacuum adsorption holes to ensure that the vacuum suction of the lower pressure platform can penetrate the paper and act on the bottom sub-plate 1, thus achieving reliable fixation. At the same time, the paper itself can absorb a small amount of excess adhesive, preventing the adhesive from clogging the vacuum holes.

[0038] After the stacked structures are assembled, an automatic pusher plate applies thrust to the stacking mechanism from both the lateral and longitudinal directions. Specifically, the stacked structures are gently pushed from both the lateral and longitudinal directions with a thrust of 10N.

[0039] When stacking layers manually or by a robotic arm, there will be slight positional deviations between the layers. The automatic pusher applies controllable pushing force from two orthogonal directions, horizontal and vertical, forcing all sub-plates 1, prepreg 3 and PET release film 2 to slide in the horizontal plane to their respective aligned positions, thereby further improving the accuracy of interlayer overlap.

[0040] S3. Close the vacuum chamber and start the vacuum system to evacuate to the predetermined vacuum level. During the evacuation process, perform at least one contact venting operation: control the upper pressure platform to descend to a predetermined distance from the surface of the laminated structure, stay for a predetermined time, and then rise back to its original position. Under normal conditions, the initial air pressure in the chamber is 101325 Pa (atmosphere), and the vacuum level reaches 35 Pa after 60 seconds of evacuation.

[0041] Specifically, the contact venting operation is as follows: the upper pressure platform descends to a distance of 0.5mm-2mm from the surface of the laminated structure, pauses for 1-2 seconds, and then rises back to its original position. This process is repeated 3-5 times during venting. This operation causes slight mechanical vibration to the laminate, promoting the rupture and expulsion of interlayer bubbles.

[0042] A suitable gap setting will not compact the prepreg 3, avoiding premature curing or adhesive overflow, while also creating a localized micro-negative pressure suction effect, forcing millimeter- or even micrometer-sized residual air bubbles between layers to burst and be extracted. Repeating this 3–5 times is equivalent to performing multiple "gentle venting" operations on each layer interface, which significantly reduces the amount of residual gas compared to a single venting operation.

[0043] The distance is controlled at more than 0.5mm to ensure that the upper pressure table does not directly contact the surface of the sub-board 1 (considering the possible slight warping of the sub-board 1, 0.5mm is the safety boundary), thus eliminating the risk of scratches on the copper foil of the sub-board 1, damage to the PET release film 2, or dents in the circuit due to hard contact. At the same time, a short dwell time of 1-2 seconds avoids local heat accumulation that could damage the surface.

[0044] Traditional methods require a long wait for the vacuum level to drop to an extremely low value (e.g., <50Pa) before passive venting. This solution, however, uses active mechanical assisted venting, requiring only 3–5 short actions, each lasting 1–2 seconds, to achieve the same or even better venting effect at a relatively low vacuum level. In actual production, this can reduce vacuuming time by 30%–50% while simultaneously reducing the load on the vacuum pump.

[0045] S4. Maintain a vacuum environment, control the upper pressure platform to descend rapidly, and apply predetermined pressure and temperature to the laminated structure for rapid pre-fixation.

[0046] After the vacuum level stabilized at 35 Pa, rapid pressing was performed using the following parameters on the laminated structure: predetermined pressure of 0.8 MPa-1.5 MPa, upper press temperature of 140℃-180℃, lower press temperature of 130℃-170℃, and rapid pressing time of 15-40 seconds. At the predetermined vacuum level, this combination of temperature and pressure ensured that the flow of the prepreg 3 was not hindered by residual gas; the moderate pressure prevented air bubbles from being compressed into tiny closed voids; and the sufficient time allowed the resin to fully impregnate the interface.

[0047] Within this temperature range, the viscosity of the resin (such as epoxy resin) in the conventional prepreg 3 decreases significantly, entering a molten flow state; simultaneously, the pressure of 0.8–1.5 MPa provides sufficient driving force to allow the resin to fill the micro-roughened areas on the surface of the sub-plate 1. 15–40 seconds is sufficient to complete flow and initial cross-linking (gelation), but not enough to achieve complete curing. The pre-fixed laminate possesses sufficient handling strength, preventing interlayer misalignment, while retaining the ability to further cure during subsequent formal lamination.

[0048] The upper pressure stage is about 10°C hotter than the lower pressure stage, causing the prepreg 3 at the top of the laminate to soften and flow first, which helps guide gases and volatiles to the upper opening for discharge. The lower pressure stage is slightly cooler, which prevents the resin under the bottom sub-board 1 from curing prematurely or flowing out excessively, ensuring good bonding and non-adhesion at the bottom. The temperature difference also reduces the thermal stress on both sides of the sub-board 1, reducing the risk of warping.

[0049] 0.8–1.5 MPa falls within the low to medium pressure range, far below the final bonding pressure (typically 2.5–3.5 MPa). This pressure is sufficient to compact the laminate and expel residual gas without causing crushing or deformation of the sub-board 1 or inner layer circuitry, making it particularly suitable for pre-fixing highly multilayer boards containing multiple prepreg sheets 3 with a relatively thin total thickness.

[0050] Compared to traditional pre-compression, 15–40 seconds significantly shortens the single-board cycle time, making it suitable for automated production lines. This time range can also be adjusted based on the actual material reactivity: 15 seconds for high-flow prepreg and 40 seconds for low-flow or thicker prepreg, ensuring universality across different batches of materials without frequent parameter changes.

[0051] Furthermore, during the rapid pressing process, the thickness change of the laminate is recorded in real time through an online thickness monitoring system. When the thickness change rate of the laminate structure drops below a predetermined threshold, the pre-pressing is deemed complete and step S4 ends. Specifically, taking a 6-layer board as an example, the initial thickness is 6.35mm, which is compressed to 6.08mm within 0.5 seconds after pressurization (compression amount 0.27mm, mainly due to the elastic compression of the PET film and prepreg 3). Subsequently, the thickness slowly decreases to 5.98mm within 25 seconds (due to resin flow after the prepreg 3 softens). When the thickness change rate drops to 0.008mm / second (approximately at the 22nd second).

[0052] By monitoring the thickness change rate in real time, when the change rate is lower than the predetermined threshold, that is, close to zero, it indicates that the prepreg 3 has fully filled the gap of the sub-board 1 and the flow has basically stopped. At this time, the pre-pressing is stopped immediately to prevent insufficient interlayer bonding caused by under-pressure, and to avoid excessive extrusion of the prepreg 3, glue overflow or deformation of the sub-board 1 caused by over-pressure.

[0053] Understandably, since the actual total thickness, resin content, and reactivity of each PCB stack may vary slightly, using the thickness change rate as an adaptive endpoint ensures that different stacks achieve the same degree of densification. Even if material batches are changed or the ambient temperature and humidity change, the system automatically adjusts the pre-compression time to ensure that the thickness and bonding state of all products after pre-fixation are highly consistent, thereby improving the yield of multilayer PCB products.

[0054] S5. After holding the pressure for the predetermined time, introduce cooling medium to cool the laminated structure. After depressurization, open the vacuum chamber and remove the laminated structure.

[0055] The cooling medium is water or cooling gas, the cooling time is 5-20 seconds, and the cooling rate is greater than 5℃ / second. Specifically, immediately after the rapid pressing is completed, the pressure holding and cooling stage begins, maintaining a constant pressure of 1.2MPa, and 20℃ cooling water is introduced at a flow rate of 8L / min for 10 seconds, during which the stack temperature drops from 145℃ to 58℃ (cooling rate 8.7℃ / second).

[0056] During the pre-compression stage, the precured sheet 3 only needs to reach partial curing to obtain sufficient pre-fixed strength. If the cooling is slow, the residual heat will cause the resin to continue cross-linking, resulting in excessive curing and insufficient fluidity during subsequent formal pressing, affecting interlayer bonding. However, rapid cooling at a rate of >5℃ / second, reducing the lamination temperature below the resin's glass transition temperature within 5–20 seconds, immediately "freezes" the curing process and precisely controls the degree of pre-curing.

[0057] Step S6: Perform ultrasonic scanning and / or X-ray inspection on the extracted laminated structure to evaluate the internal bubble situation and interlayer offset. This embodiment uses the lamination result of one multilayer board as an example, scanning the laminated structure with a 50MHz probe. The inspection results show: 3 bubbles, the largest bubble size is 0.6mm × 0.4mm, all less than 1mm², which is acceptable. The relative offset of the four corner positioning holes was measured, with a maximum offset of 0.07mm (6th sub-board 1 relative to 1st sub-board 1), which is acceptable (≤0.1mm). There is slight adhesive overflow at the edges (width 0.5-1.5mm, height approximately 0.1mm), which does not contaminate the circuit area; the unbonded area accounts for approximately 2%, which is acceptable.

[0058] Ultrasonic scanning can sensitively detect tiny air bubbles, delamination, voids, and uneven bonding between layers; X-ray inspection can quantify the horizontal offset between inner sub-boards. Defects can be identified during the pre-pressing stage, allowing unqualified laminates to be rejected or reworked, avoiding the time-consuming and costly high-temperature and high-pressure pressing process, and reducing material and energy waste.

[0059] If the test finds that a batch of products has a general excess of air bubbles or an out-of-tolerance deviation, the abnormal link in step S1 (cleaning and roughening, pre-baking), step S3 (venting times and distance), or step S4 (pressure, temperature, time) can be traced back to achieve rapid process closed-loop optimization and prevent batch defects.

[0060] This embodiment introduces a contact-type exhaust operation during the vacuuming process, with the upper pressure platform descending to near the surface of the laminated structure. This forces the residual gas between layers and the low-molecular-weight substances volatilized by the heat of the semi-cured sheet 3 to be discharged in advance. Combined with the vacuum environment, this effectively reduces bubbles and voids after final pressing, thereby improving the quality of interlayer bonding.

[0061] In addition, the bottom layer sub-board 1 is fixed by vacuum adsorption at the bottom, and the alternating stacking sequence maintains the relative position of each layer before fast pressing; the contact venting operation further smooths the interlayer warping, avoids interlayer slippage caused by pressure impact during fast pressing, and ensures the accurate dimensions of the pre-fixed stacked structure.

[0062] This embodiment also provides a vacuum fast-pressing pre-stacking device for implementing the above method, comprising: A vacuum chamber is used to provide a vacuum working environment; The upper and lower pressure stages are located within the vacuum chamber. The upper pressure stage is movable and integrates heating and cooling functions; the lower pressure stage integrates a vacuum adsorption system for fixing the bottom sub-plate 1. A vacuum system, connected to a vacuum chamber, used to evacuate the chamber; A cooling system, connected to the upper pressure platform and / or the lower pressure platform, is used to provide a cooling medium; The positioning system includes a main positioning pin set on the lower pressure platform and a movable side push plate. The side push plate is used to push the stacked structure from the horizontal direction so that the positioning holes of each layer are tightly attached to the main positioning pin. The online thickness monitoring system is used to monitor changes in the thickness of the laminate in real time and output a thickness signal to control the pre-compression endpoint.

[0063] The vacuum chamber, in conjunction with the vacuum system, provides a low-oxygen, low-humidity operating environment, fundamentally suppressing bubble formation. The upper pressure platform integrates heating and cooling functions, enabling the entire process of heating, pressurizing, and rapid cooling to be completed at the same station, avoiding secondary contamination or interlayer misalignment during transfer and significantly improving pre-fixation quality and efficiency. Furthermore, the integration of the vacuum chamber, heating pressure platform, cooling channel, vacuum adsorption, positioning system, and thickness monitoring module into a single unit results in a compact equipment structure, reducing equipment investment and maintenance costs.

[0064] The pressure stage has a built-in vacuum adsorption system that firmly fixes the bottom sub-board 1. The main positioning pin and the movable lateral push plate work together: the main positioning pin provides reference hole positioning, and the lateral push plate pushes the stack from the horizontal direction, forcing the positioning holes of each layer to fit tightly against the main positioning pin, automatically eliminating the cumulative offset between layers. By monitoring the changes in the stack thickness in real time and outputting a thickness signal, the pre-pressure is automatically terminated when the thickness change rate drops to a preset threshold, avoiding the overpressure or underpressure defects of traditional timed or constant pressure methods.

[0065] The lateral pusher in this embodiment includes a transverse pusher and a longitudinal pusher, which are driven by independent cylinders.

[0066] The transverse and longitudinal push plates are driven by independent cylinders, allowing controllable thrust to be applied in both the X and Y directions. First, push in one direction to make the positioning holes of each layer fit tightly against one side of the main positioning pin, then push in the other direction to make them fit tightly against the other side, preventing the resultant force from shifting or jamming when forces are applied simultaneously.

[0067] In the description of this invention, it should be understood that terms such as "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0068] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0069] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A vacuum fast-pressing pre-lamination method of a multi-layer PCB board, the multi-layer PCB board comprising N sub-boards, N-1 layers of prepreg, and 2(N-1) layers of PET release film, characterized in that, Includes the following steps: S1. Clean and roughen the surfaces of the N sub-boards, and pre-bake the N-1 layer of prepreg. S2. Sub-plates, PET film, prepreg, PET film, and sub-plates are stacked in an alternating order on the lower pressure table of the vacuum fast press device to form a stacked structure. The sub-plates at the bottom are fixed by vacuum adsorption. S3. Close the vacuum chamber and start the vacuum system to evacuate to the predetermined vacuum level; during the evacuation process, perform at least one contact venting operation: control the upper pressure platform to descend to a predetermined distance from the surface of the laminated structure, stay for a predetermined time, and then rise back to its original position; S4. Maintain a vacuum environment, control the upper pressure platform to descend rapidly, and apply a predetermined pressure and temperature to the laminated structure for rapid pressure pre-fixation. S5. After holding the pressure for a predetermined time, a cooling medium is introduced to cool the laminated structure. After depressurization, the vacuum chamber is opened and the laminated structure is removed.

2. The vacuum fast-pressing pre-stacking method for multilayer PCBs according to claim 1, characterized in that, The contact venting operation in step S3 is as follows: the upper pressure platform descends to a distance of 0.5mm-2mm from the surface of the stacked structure, stays for 1-2 seconds, and then rises back to its original position. This process is repeated 3-5 times during the venting process.

3. The vacuum fast-pressing pre-stacking method for multilayer PCBs according to claim 1, characterized in that, In step S4, the thickness change of the stack is recorded in real time by the online thickness monitoring system. When the thickness change rate of the stack structure drops below a predetermined threshold, the pre-compression is determined to be completed and step S4 ends.

4. The vacuum fast-pressing pre-stacking method for multilayer PCBs according to claim 1, characterized in that, In step S2, before placing the sub-plate located at the bottom, a layer of anti-stick paper is first laid on the surface of the lower pressure table.

5. The vacuum fast-pressing pre-stacking method for multilayer PCBs according to claim 1, characterized in that, In step S4, the following parameters are used to perform rapid pressing on the laminated structure: the predetermined pressure is 0.8MPa-1.5MPa, the upper pressing table temperature is 140℃-180℃, the lower pressing table temperature is 130℃-170℃, and the rapid pressing time is 15 seconds-40 seconds.

6. The vacuum fast-pressing pre-stacking method for multilayer PCBs according to claim 1, characterized in that, In step S5, the cooling medium is water or cooling gas, the cooling time is 5-20 seconds, and the cooling rate is greater than 5°C / second.

7. The vacuum fast-pressing pre-stacking method for multilayer PCBs according to claim 1, characterized in that, In step S2, after the stacked structure is stacked, an automatic pusher is used to apply a pushing force to the stacking mechanism from the horizontal and vertical directions of the stacked structure, respectively.

8. The vacuum fast-pressing pre-stacking method for multilayer PCBs according to claim 1, characterized in that, The method also includes step S6: performing ultrasonic scanning and / or X-ray inspection on the extracted stacked structure to assess the internal bubble condition and interlayer offset.

9. A vacuum fast-pressing pre-stacking device for implementing the method according to any one of claims 1-8, characterized in that, include: A vacuum chamber is used to provide a vacuum working environment; An upper pressure platform and a lower pressure platform are disposed within the vacuum chamber. The upper pressure platform is movable and integrates heating and cooling functions. The lower pressure platform integrates a vacuum adsorption system for fixing the bottom sub-plate. A vacuum system, connected to the vacuum chamber, is used to evacuate the chamber. A cooling system, connected to the upper pressure platform and / or the lower pressure platform, is used to provide a cooling medium; The positioning system includes a main positioning pin disposed on the lower pressing platform and a movable side push plate, the side push plate being used to push the stacked structure from the horizontal direction so that the positioning holes of each layer are tightly attached to the main positioning pin; The online thickness monitoring system is used to monitor changes in the thickness of the laminate in real time and output a thickness signal to control the pre-compression endpoint.

10. The vacuum fast-pressing pre-stacking method for multilayer PCBs according to claim 9, characterized in that, The lateral push plate includes a transverse push plate and a longitudinal push plate, and the transverse push plate and the longitudinal push plate are each driven by an independent cylinder.

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