A multilayer printed circuit board stack-up structure and a lamination method based thereon.

Abstract

This application relates to the field of printed circuit board lamination technology, specifically providing a multilayer printed circuit board stack structure and a lamination method based thereon. The stack structure includes prepreg and core board arranged alternately from top to bottom. The top and bottom layers of the stack structure are both prepregs. At least one core board has a lower surface including a wiring area and a non-wiring area. At least one prepreg has a pressing auxiliary area on its surface facing the core board. The pressing auxiliary area and the non-wiring area are correspondingly arranged in the stack thickness direction. The surface of the pressing auxiliary area has multiple raised micro-plates, and the thickness of at least one raised micro-plate is greater than the thickness of the wiring layer in the wiring area. The method includes the following steps: S1, preparing the core board and prepreg and performing pretreatment; S2, setting positioning holes on the core board and prepreg; S3, stacking the core board and prepreg to form a stack structure and fixing it; S4, laminating the stack structure; S5, after removing excess adhesive, performing post-curing treatment.

Description

Technical Field

[0001] This application relates to the field of printed circuit board lamination technology, and more specifically, to a multilayer printed circuit board stack structure and a lamination method based thereon. Background Technology

[0002] Multilayer printed circuit boards (PCBs) are formed by stacking multiple core boards and prepregs in a predetermined stacking order and then curing them under thermoforming. The surface of the core boards features conductive structures such as circuit patterns, pads, and copper foil, according to the circuit design. Prepregs are placed between adjacent core boards to achieve interlayer bonding and electrical insulation during thermoforming. During lamination, the B-stage resin in the prepreg softens upon heating and enters a low-viscosity flow state. Under pressure, it fills the gaps between core boards, the height differences in the copper layer patterns, and the microscopic unevenness of the core board surface. Subsequently, the resin further cross-links and cures, forming a stable interlayer insulating adhesive layer. Good lamination quality requires that the cured prepregs ensure a tight bond between adjacent core boards, sufficient wetting between the resin layer and the core board substrate surface and the copper layer surface, achieving reliable bonding and avoiding bubbles, voids, insufficient adhesive, or unbonded areas. A continuous and dense interlayer adhesive layer can improve the mechanical strength, interlayer bonding force, dielectric stability, and long-term reliability of multilayer printed circuit boards. Conversely, gaps or air bubbles in the adhesive layer will disrupt the interlayer insulation and bonding continuity, severely affecting reliability. Therefore, in the lamination process of multilayer printed circuit boards, ensuring the prepreg resin flows fully, vents air, and cures into a continuous, gapless insulating adhesive layer is a crucial step in guaranteeing product quality.

[0003] According to circuit design requirements, different copper layer distribution areas are typically formed on the surface of the core board. Areas containing copper layers, circuitry, pads, or copper foil are designated as wiring areas or copper plating areas, while areas without circuitry or with low copper layer coverage are designated as non-wiring areas or copper-free areas. Because copper layers exist on the surface of wiring areas, the copper layers on the surface of non-wiring areas are removed, creating a height difference in copper layer thickness between the two. When the non-wiring area is large, large depressions appear. During hot pressing, the prepreg resin flows into and fills these depressions. When the non-wiring area is large, the resin flow distance is long, and the gas escape path is also long. Simultaneously, localized pressure, heat, and resin flow are affected by differences in the surrounding copper layer distribution, leading to problems such as insufficient local resin flow, edge closure, and difficulty in gas escape from the center. Specifically, in the initial stage of lamination, the resin in the prepreg softens and comes into contact with the core board surface. If the resin forms a continuous film at the edge or local location of the non-wiring area, the air between the core board and the prepreg will be trapped inside the non-wiring area. As the temperature continues to rise, although the resin can continue to flow and fill, the trapped air, moisture, or volatile small molecules are difficult to expel along the interface in time, thus forming bubbles, voids, or areas with insufficient adhesive between layers. Bubbles and insufficient adhesive will lead to discontinuity of the interlayer insulation medium, reducing the mechanical bonding strength and dielectric properties of the multilayer board. At the same time, bubbles become crack initiation points and stress concentration points during thermal cycling, drilling, electroplating, and welding processes, causing risks such as interlayer separation, decreased hole wall reliability, local breakdown, short circuits, or open circuits. In severe cases, it will affect the overall board reliability and even lead to product scrap.

[0004] In existing technologies, to reduce the generation of bubbles and insufficient adhesive during lamination, methods such as adjusting lamination temperature and pressure curves, extending preheating and venting times, vacuum lamination, drying and dehumidifying the core board and prepreg, increasing the roughness of the copper surface, or setting copper fillers, grid copper, and residual copper balance patterns in large copper-free areas are employed. However, adjusting lamination temperature, pressure, and time parameters depends on equipment capabilities and process windows, and has limited adaptability to different board thicknesses, copper thicknesses, and non-wiring area areas. It is difficult to eliminate the problems caused by geometric height differences and excessively long venting paths in large copper-free areas. Vacuum lamination and extending venting time increase equipment costs and production cycle time, and after the resin has partially sealed the gas, the external vacuum is insufficient to effectively expel the trapped gas. Copper fillers or grid copper are mainly located on the copper layer side of the core board, which can block the resin flow path or form new sealed areas, causing gas to stagnate in local gaps. Therefore, existing methods cannot reliably meet the requirements of bubble-free, adhesive-free, and dense interlayer bonding after lamination of large non-wiring areas. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing a multilayer printed circuit board stack-up structure and a lamination method based thereon, so as to solve the problem that existing methods are unable to reliably meet the requirements of no air bubbles, no missing adhesive, and dense interlayer bonding after lamination of large-area non-wiring areas.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This application provides a multilayer printed circuit board stack structure, which includes prepreg and core board arranged alternately from top to bottom. The top and bottom layers of the stack structure are both prepregs. The lower surface of at least one core board includes a wiring area and a non-wiring area. At least one prepreg has a pressing auxiliary area on its side surface facing the core board. The pressing auxiliary area and the non-wiring area are arranged correspondingly in the stack thickness direction. The surface of the pressing auxiliary area is provided with a plurality of raised microplates. The thickness of at least one raised microplate is greater than the thickness of the wiring layer in the wiring area.

[0007] In this application, the raised micro-plates are located on the prepreg, corresponding to the non-wiring area of ​​the core board, and can directly act on the non-wiring area during hot pressing. The raised micro-plates are made of resin material, providing a localized source of adhesive for the non-wiring area. This prevents the molten resin from relying entirely on the long-distance flow of resin from the surrounding prepreg, shortening the resin filling path and reducing the risk of insufficient adhesive in the center of the non-wiring area. Simultaneously, at least one raised micro-plate has a thickness greater than the wiring layer thickness in the wiring area. The raised micro-plates participate in contact and pressure earlier than the area near the wiring area during the initial hot pressing stage, forming local support points within the non-wiring area. This avoids the non-wiring area edges being compacted and sealed first due to support only from the surrounding wiring area. Furthermore, discontinuous micro-gaps are formed between multiple raised micro-plates, preventing the prepreg resin from rapidly adhering to the surface of the non-wiring area as a complete, continuous film during initial softening. Instead, it forms a multi-point contact, multi-path flow pattern, facilitating air expulsion along the gaps between the micro-plates and allowing for gradual resin backfilling. The laminated structure of this application improves the filling, venting and resin flow conditions in non-wiring areas, reducing the risk of bubbles, voids and missing adhesive after lamination.

[0008] Furthermore, the raised micro-plates include central raised plates and edge raised plates, with the central raised plate being thicker than the edge raised plates. The central area of ​​the non-wiring zone is farther from the surrounding wiring area, board edge, or venting area, resulting in a longer air venting path and making it more prone to air trapping and resin shortages. Conversely, the edge area of ​​the non-wiring zone is relatively closer to the peripheral venting path and resin inflow path, offering better venting and resin filling conditions. Making the central raised plate thicker creates a more significant temporary support space in the center of the non-wiring zone during the initial hot pressing phase, delaying the complete bonding and sealing of the central area by the prepreg resin, allowing for a longer air venting time. The thinner edge raised plates reduce flow resistance in the edge area of ​​the non-wiring zone, allowing air vented from the center to continue migrating towards the edge, enabling molten resin to smoothly enter from the edge area and fill the micro-gaps. For heat transfer, the thicker central and thinner edge structure gives the central raised plate a larger heat capacity and a slower softening and collapse rate, helping to maintain its shape during the initial hot pressing phase; the thinner edge raised plates soften and fuse more easily during subsequent heating, reducing resin resistance at the edges. During stress transfer, the higher central tabs share the pressure load in the middle of the non-wiring area, reducing the edge stress concentration caused by the surrounding wiring area bearing pressure alone; the lower edge tabs reduce local indentation and interlayer stress abrupt changes at the boundary of the non-wiring area.

[0009] Furthermore, the upper surface of the intermediate tab is provided with elongated protrusions. These elongated protrusions form a secondary microstructure on the surface of the intermediate tab. In the initial stage of hot pressing, the tops of the elongated protrusions can contact the surface of the adjacent core board earlier, forming narrow strip-shaped supports. This prevents the intermediate tab from directly adhering to the non-wiring area of ​​the core board in a full-surface manner, and retains slender micro-venting channels between the elongated protrusions. Compared with dot-shaped or non-directional protrusions, the elongated protrusions have a clear direction of extension, which can guide the gas along the channels between adjacent elongations to the edge of the non-wiring area, improving the directionality and continuity of air exhaust in the middle. The molten resin undergoes diversion, flow around, and re-convergence around the elongated protrusions, dividing the continuous planar adhesive flow into multiple local flow fronts, reducing the probability of the continuous adhesive film prematurely trapping air. The elongated protrusions increase the surface area of ​​the central protrusion, allowing the main resin to more fully wet the area around the protrusion during subsequent heating, promoting gradual softening and fusion. Simultaneously, the elongated, rib-like structure maintains its shape initially, preventing immediate overall collapse. The elongated protrusions also form linear supports, which, compared to sharp, point-like supports, result in less localized stress concentration. This helps distribute the pressing pressure along a longer path, reducing the risk of localized indentations, resin extrusion, and interface defects.

[0010] Furthermore, the thickness of the raised microplates should be 0.8-1.2 times the thickness of the wiring layer. If the thickness of the raised microplates is too small, for example, significantly less than the thickness of the wiring layer, the copper layer in the wiring area will mainly provide support during the initial lamination process. The raised microplates will have difficulty approaching or contacting the surface of the non-wiring area in time, failing to delay the sealing of the non-wiring area by the continuous adhesive film, thus weakening the venting and turbulence effects. At the same time, the amount of local resin provided by the microplates will be insufficient, limiting the compensation effect for insufficient adhesive. If the thickness of the raised microplates is too large, it will become an excessively high local support point during the initial lamination process, leading to local pressure concentration and excessive extrusion of the prepreg's main resin, resulting in insufficient adhesive around the prepreg, uneven board thickness, or interface stress concentration. Excessively thick microplates will also not soften completely and fuse with the main resin during subsequent heating, forming a residual interface and causing dielectric discontinuity. Controlling the thickness of the raised microplates to 0.8-1.2 times the thickness of the wiring layer provides sufficient height for temporary support and venting in the non-wiring area while avoiding excessive protrusion that could hinder resin flow or generate excessive local stress.

[0011] Furthermore, the length and width of the raised microplates in the plane are 5-20 times their thickness. The raised microplates have a flat, sheet-like structure, with their planar dimensions larger than their thickness dimensions. This flat, sheet-like structure provides a large contact area with the surface of the prepreg, facilitating stable adhesion during preparation, handling, positioning, and stacking, and reducing the likelihood of displacement or agglomeration. When multiple flat, raised microplates are arranged at intervals, lateral micro-venting gaps extending along the surface of the prepreg can be formed between adjacent microplates, promoting gas migration along the planar direction rather than stagnation in localized point spaces. The flat microplates allow for more stable flow and distribution of molten resin around them, preventing the adhesive from rapidly advancing in a continuous planar film manner. Simultaneously, their smaller thickness makes them easier to wet, soften, and fuse with the host resin after subsequent heating. Furthermore, the flat, sheet-like structure has a large heat-receiving surface area, which facilitates sufficient heat exchange and gradual fusion with the surrounding resin in the later stages of hot pressing, preventing the formation of difficult-to-soften blocky structures. The flat structure has a larger pressure-bearing area, which can reduce the pressure per unit area, reduce the point stress concentration caused by sharp protrusions, and make the pressing load more smoothly transferred to the interface between the prepreg and the core board.

[0012] Furthermore, the coverage of the raised microplates in the pressing auxiliary area is 15%-45%. This coverage determines the amount of resin added, the degree of support, and the continuity of the micro-venting gaps within the pressing auxiliary area. If the coverage is too low, the number of raised microplates is insufficient, limiting the local resin replenishment available in the corresponding non-wiring areas. This results in a weak disturbance effect on the resin flow front and makes it difficult to form a stable and continuous micro-venting path, causing gas to stagnate in large copper-free areas. If the coverage is too high, the gaps between the raised microplates are too small, hindering the flow and backfilling of molten resin in the non-wiring areas. It may even form new closed structures at the edges or in localized areas of the pressing auxiliary area, making it difficult for air to escape. Simultaneously, excessively high coverage increases the local resin volume and support stiffness, leading to uneven pressing pressure distribution, impeded resin flow, or insufficient subsequent fusion. Setting the coverage rate to 15%-45% ensures that there are enough raised micro-plates in the pressing auxiliary zone to achieve local glue filling, disturb the glue flow and provide initial support, while retaining enough micro-venting gaps and resin flow channels so that air can be discharged along the gaps and the molten resin can be gradually backfilled and cured after venting.

[0013] Furthermore, the raised microflakes are made of one or more of the following: B-type bisphenol A solid epoxy resin, phenolic epoxy resin, and o-cresol epoxy resin. These materials have good chemical compatibility and interfacial affinity with the epoxy resin system in common FR-4 prepregs. In the later stages of hot pressing, they can mutually wet, soften, fuse, and co-cur with the prepreg's main resin, avoiding the formation of foreign interfaces, delamination interfaces, or dielectric discontinuities. Compared to low-molecular-weight liquid epoxy resins, B-type bisphenol A solid epoxy resin, phenolic epoxy resin, and o-cresol epoxy resin have higher molecular weights, higher softening temperatures, or higher morphology retention capabilities. This allows the raised microflakes to maintain a certain sheet-like morphology in the early stages of hot pressing, rather than immediately melting and collapsing completely when the prepreg's main resin begins to soften and flow. This provides short-term microchannels for air expulsion and damping and diverting the adhesive flow front. As the temperature continues to rise and the subsequent heat preservation and curing stage begins, the raised micro-sheets can gradually soften, swell, or fuse with the main resin, eventually cross-linking and curing together to form a continuous insulating adhesive layer.

[0014] This application also proposes a lamination method for multilayer printed circuit boards, the lamination method comprising the following steps: S1. Prepare the core board and prepreg, and perform pretreatment. S2, positioning holes are provided on the core board and the prepreg; S3, stack the core board and prepreg to form a laminated structure and fix it in place; S4, laminating the multilayer structure; S5, after removing the excess adhesive from the edges, perform post-curing treatment; The stacked structure is the stacked structure described above.

[0015] Further, step S1 includes determining the non-wiring area of ​​the core board, determining the area of ​​the pressing auxiliary area on the prepreg based on the non-wiring area, and preparing raised micro-sheets on the pressing auxiliary area.

[0016] Furthermore, the pretreatment includes drying at 80-120℃ for 30-120 minutes to remove moisture.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This application establishes a pressing auxiliary zone on the side of the prepreg facing the non-wiring area of ​​the core board, and sets multiple raised micro-plates on the surface of the pressing auxiliary zone. This prevents the prepreg from directly participating in the pressing process with a flat, continuous surface at the corresponding position in the non-wiring area. Since the thickness of at least one raised micro-plate is greater than the thickness of the wiring layer in the wiring area, the raised micro-plate can preferentially contact the non-wiring area of ​​the core board during the initial stage of hot pressing, forming local support within the non-wiring area and preventing premature closure of the non-wiring area edge due to pressure being borne solely by the surrounding wiring area. The spaced arrangement of multiple raised micro-plates causes the resin to flow around, split, and gradually backfill during softening and flow, reducing the possibility of rapid air closure in the continuous adhesive film. At the same time, the raised micro-plates themselves act as a local source of resin replenishment, softening and fusing with the main resin of the prepreg during subsequent heating, shortening the resin filling distance to the non-wiring area. This improves the venting, filling, and adhesive flow uniformity in the non-wiring area, reducing the risk of bubbles, voids, and insufficient adhesive after lamination. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a multilayer printed circuit board stack structure provided in Embodiment 1 of the present invention; Figure 2 A schematic diagram of the arrangement of raised microplates in another multilayer printed circuit board stack structure provided in Embodiment 1 of the present invention. Figure 3 This is a top view of the protruding ribs in the stacked structure of a multilayer printed circuit board provided in Embodiment 2 of the present invention. Figure 4 This is a schematic diagram of the lamination method for a multilayer printed circuit board provided in Example 3; Figure 5 This is a schematic diagram of the positioning hole structure in step S2 of the lamination method for the multilayer printed circuit board provided in Example 3; Figure 6 This is a schematic diagram of the loading structure placed in the lamination carrier in step S3 of the lamination method for multilayer printed circuit boards provided in Example 3. Figure 7 The temperature and pressure change curves over time during step S4 of the lamination process in the multilayer printed circuit board lamination method provided in Example 3.

[0019] Icons: 1-Pressurized sheet; 2-Core board; 3-Pressure auxiliary area; 4-Raised micro-sheet; 5-Raised rib; 6-Positioning hole; 7-Kraft paper; 8-Stainless steel plate; 9-Demolding material; 10-Positioning pin. Detailed Implementation

[0020] To make the implementation process of this invention clearer, a detailed description will be provided below in conjunction with the accompanying drawings.

[0021] Example 1:

[0022] This embodiment provides a multilayer printed circuit board stack-up structure, such as... Figure 1 As shown, the laminated structure includes multiple prepreg sheets 1 and multiple core boards 2 arranged alternately along the thickness direction. The top and bottom layers of the laminated structure are both prepreg sheets 1, meaning the number of prepreg sheets 1 is the number of core board 2 layers plus one. The outer prepreg sheets 1 can subsequently serve as an outer layer bonding medium for bonding with outer copper foil or adjacent conductive layers, facilitating the formation of the copper-clad structure required for the outer layer circuitry. The core board 2 is an FR-4 core board or a BT resin core board. The core board 2 includes an insulating substrate and a wiring layer formed on at least one surface of the insulating substrate. The wiring layer is a copper layer, which, after pattern transfer and etching, forms wiring areas and non-wiring areas. The wiring areas are regions where wiring, copper foil, pads, or other conductive patterns are retained, while the non-wiring areas are regions where the copper layer is removed or has low copper layer coverage. Because the wiring areas retain the wiring layer, while the non-wiring areas expose the core board 2 substrate without copper layer coverage, a height difference in wiring layer thickness is formed between the wiring areas and the non-wiring areas. The thickness of the wiring layer is 17-140 μm, specifically determined by design requirements.

[0023] A prepreg 1 is disposed between adjacent core boards 2. The prepreg 1 comprises fiberglass cloth and B-stage resin impregnated in the fiberglass cloth. Before hot pressing, the prepreg 1 is a sheet structure. During hot pressing, it softens and flows upon heating, and then cross-links and cures to form an interlayer insulating adhesive layer. At least one prepreg 1 has a pressing auxiliary area 3 on its surface facing the core board 2. The pressing auxiliary area 3 is correspondingly disposed to the non-wiring area on the lower surface of the core board 2 in the stack thickness direction. That is, when the stacked structure is stacked in a predetermined order, the pressing auxiliary area 3 is located directly below the non-wiring area, so that the structure in the pressing auxiliary area 3 can directly participate in the glue filling, venting, and glue flow adjustment of the non-wiring area during hot pressing.

[0024] The shape of the lamination auxiliary area 3 is determined based on the shape of the non-wiring area of ​​the core board 2. Since the non-wiring area on the core board 2 is usually irregularly shaped, for ease of design and manufacturing, the outer contour of the non-wiring area needs to be approximately transformed into a circle, ellipse, rectangle, polygon, or a combination of these regular shapes, and a corresponding lamination auxiliary area 3 is formed on the prepreg 1. This embodiment uses an approximately circular non-wiring area as an example, and the lamination auxiliary area 3 is set as a circular area. The diameter of the lamination auxiliary area 3 is slightly larger than the equivalent diameter of the non-wiring area; for example, the outer boundary of the lamination auxiliary area 3 extends outward by 0.2-1 mm relative to the outer boundary of the non-wiring area to ensure that the lamination auxiliary area 3 can cover the edge of the non-wiring area, where gas confinement and uneven resin flow are more pronounced.

[0025] The raised micro-plates 4 are made of one or more of the following: B-type bisphenol A solid epoxy resin, phenolic epoxy resin, and o-cresol phenolic epoxy resin. Multiple raised micro-plates 4 are disposed on the surface of the pressing auxiliary area 3, with each raised micro-plate 4 protruding at least partially from the surface of the prepreg 1 facing the core board 2. At least one raised micro-plate 4 has a thickness greater than the thickness of the wiring layer in the wiring area, allowing the raised micro-plate 4 located at the corresponding position in the non-wiring area to pre-contact and bear pressure during the initial stage of hot pressing, preventing the edges of the non-wiring area from being prematurely compacted and sealed due to support from the surrounding wiring area. The thickness of the raised micro-plate 4 is 0.8-1.2 times the thickness of the wiring layer; a thickness close to the wiring layer thickness facilitates the formation of appropriate local support and micro-venting space during the initial stage of hot pressing, while not significantly hindering subsequent resin flow and backfilling. The length and width (or diameter) of the raised micro-plate 4 in the plane are 5-20 times its thickness, giving the raised micro-plate 4 an overall flat sheet structure. The coverage of the raised microplate 4 on the pressing auxiliary area 3 is 15%-45%.

[0026] Furthermore, such as Figure 2As shown, the pressing auxiliary area 3 includes a central region and an edge region. A circular raised microplate 4 is positioned at the center of the central region, located at or near the center of the pressing auxiliary area 3. Multiple layers of rectangular raised microplates 4 are arranged around the outer periphery of the raised microplate 4, extending from the central region towards the edge region. Specifically, the raised microplate 4 includes a circular central raised microplate and rectangular edge raised microplates, with the central raised microplate being thicker than the edge raised microplates. The diameter of the central circular raised microplate 4 is 250-400 μm; the gap between the central circular raised microplate 4 and its innermost outer rectangular raised microplate 4 is 50-100 μm. A circular raised microplate 4 is used at the center position. Preferably, the circular raised microplate 4 has the largest thickness, which can form a stable short-term support at the center position and prevent the central area from being completely adhered to by the main resin of the semi-cured sheet 1 in the initial stage of hot pressing. At the same time, the circular raised microplate 4 has a continuous circumferential contour and no sharp long edges, so it will not block the gas migration in any direction in the central area. Thus, the compressed air at the center can be dispersed in multiple directions along the outer periphery of the circular raised microplate 4 and enter the radial exhaust gap formed between the surrounding rectangular raised microplates 4.

[0027] Multiple rectangular protruding microplates 4 are arranged in a multi-layered ring around a central circular protruding microplate 4, with the long side of each rectangular protruding microplate 4 positioned radially along the pressing auxiliary zone 3. That is, the length direction of the rectangular protruding microplates 4 extends from the center of the pressing auxiliary zone 3 to its edge. This creates radially extending venting gaps between adjacent rectangular protruding microplates 4, allowing air around the central circular protruding microplate 4 and air in the central region to escape along a path from the center to the edge. The radial arrangement prevents the formation of annular obstructions within the pressing auxiliary zone 3, avoiding the trapping of gas in the inner region. Simultaneously, the radial arrangement guides the molten resin to gradually enter the non-wire area along both sides of the rectangular protruding microplates 4, transforming the resin flow front from a continuous planar advance to a multi-stream dispersed advance, reducing the risk of edge blockage followed by difficulty in venting air from the center.

[0028] The adjacent rectangular raised microplates 4 are slightly misaligned radially, with the misalignment width not exceeding one-quarter of the width. The gaps between adjacent rectangular raised microplates 4 are at least partially connected, and the channel extends from the outer periphery of the central circular raised microplate 4 to the edge region of the pressing auxiliary area 3. This ensures that gas can be discharged from the central region to the edge region along the radial channel, reducing the risk of gas trapping in the center, while avoiding the formation of a completely straight and excessively wide low-resistance channel. This prevents the molten resin from flowing too quickly along a single path in the early stages of hot pressing, causing excessive local resin flow or premature edge closure. During resin flow, encountering the misaligned edge will cause flow around it, changing the local resin flow velocity, making the resin flow front more gentle, while maintaining a continuous venting path, allowing gas to be discharged smoothly and resin to be backfilled in a controlled manner.

[0029] From the center of the lamination auxiliary area 3 towards the edge, the length of the multilayer rectangular raised microplates 4 gradually increases, while the width gradually decreases. Specifically, the inner rectangular raised microplates 4 near the central circular raised microplate 4 have a length of 200-400 μm and a width of 120-250 μm; the rectangular raised microplates 4 in the middle region have a length of 250-500 μm and a width of 100-220 μm; and the rectangular raised microplates 4 in the edge region have a length of 350-800 μm and a width of 80-180 μm. Correspondingly, the circumferential gap between the inner rectangular raised microplates 4 near the central circular raised microplate 4 is 40-100 μm, the circumferential gap between adjacent rectangular raised microplates 4 in the middle region is 50-140 μm, and the circumferential gap between adjacent rectangular raised microplates 4 in the edge region is 80-220 μm. The specific number of layers is determined according to the size of the non-wiring area, and at least one layer of rectangular raised microplates 4 is included. In this way, the relatively short and wide inner rectangular protruding microplates 4 can create more local turbulence and diversion points, preventing the molten resin from spreading rapidly in a continuous plane. This delays the sealing of the central area by the adhesive film, allowing time for air to escape. The rectangular protruding microplates 4 in the edge area are longer, narrower, and have larger gaps, resulting in lower flow resistance in the radial exhaust channel at the outer periphery, allowing gas to escape more smoothly after reaching the edge. At the same time, the larger edge gaps prevent resin from accumulating and blocking the outlet prematurely. After the gas is exhausted, the molten resin gradually flows back and fills along both sides of the microplates, achieving a balance between venting and resin replenishment.

[0030] The arrangement in this application also improves heat and stress transfer. Heat can be gradually transferred from the circumferential edge of the circular raised microplate 4 and its multiple gaps to the central area, promoting uniform heating and softening of the resin in the central position. The multi-layered radial rectangular raised microplates 4 arranged around the circular raised microplate 4 have their long sides aligned with the gas exhaust direction and resin backfill direction, providing a guiding channel without forming a continuous annular barrier that hinders heat transfer inward. The larger gaps in the edge area allow for more sufficient contact and heat exchange between the main resin and the core plate 2, enabling earlier softening and backfilling at the edge. The relatively concentrated raised microplates 4 in the central and middle areas allow the central area to maintain a longer exhaust window in the early stages of hot pressing. At the same time, the central circular raised microplate 4 forms a stable support point in the center of the non-wiring area, reducing the risk of sudden collapse in the central area; the multi-layered radial rectangular raised microplates 4 distribute local pressure step by step along multiple radial strips, avoiding the concentration of pressing pressure at the boundary of the non-wiring area. The rectangular protruding microplates 4 with narrower edge areas and larger gaps can also reduce the sudden change in stiffness at the outer periphery of the non-wiring area, so that the pressing load gradually transitions from the central area through the middle area to the wiring area, thereby reducing local indentation, resin extrusion and interlayer stress concentration.

[0031] Example 2:

[0032] Based on Example 1, such as Figure 3As shown, the upper surface of the intermediate protrusion is provided with raised ribs 5, which are elongated raised strips comprising multiple parallel ribs. The width of each raised rib 5 is 20-50 μm, the height of each raised rib 5 is 10-40 μm, and the channel width between adjacent raised ribs 5 is 40-80 μm. The raised ribs 5 are configured as multiple parallel or approximately parallel strip structures. These raised ribs 5 extend radially towards the edge of the pressing auxiliary area 3 along the radial direction of the intermediate protrusion. The raised ribs 5 on the intermediate protrusion transform the surface contact of the intermediate protrusion into line contact. The raised ribs 5 can be integrally formed with the intermediate protrusion or attached after the intermediate protrusion is formed.

[0033] The raised rib 5 and the intermediate protrusion are formed of the same or compatible resin material, which can be one or more of B-stage bisphenol A type solid epoxy resin, B-stage phenolic epoxy resin, and B-stage o-cresolic epoxy resin. The cross-sectional shape of the raised rib 5 is an isosceles triangle with an obtuse apex angle. The width of the top surface of the raised rib 5 near the core plate 2 is smaller than the width of its bottom surface at the connection with the intermediate protrusion. In this way, in the initial stage of hot pressing, the top of the raised rib 5 contacts the non-wiring area of ​​the core plate 2 with a small contact area, which can form a linear support first, so that the intermediate protrusion does not immediately adhere to the entire surface of the core plate 2. As the hot pressing pressure and temperature increase, the top of the raised rib 5 is gradually blunted, softened or collapsed, and the contact width gradually increases. The supporting effect gradually transitions from the initial light contact to a more stable surface contact, forming a progressive support. This avoids the raised rib 5 forming a large-area closed contact in the initial stage of hot pressing, while gradually increasing the support area in the subsequent pressing process, preventing excessive local pressure concentration. Furthermore, the spacing between the multiple raised ribs 5 gradually increases from the middle to the edge, with the middle raised ribs 5 having a smaller spacing, forming more narrow channels. This prevents the main resin of the prepreg 1 from quickly forming a continuous film to seal the central air during the initial stage of hot pressing. At the same time, the multiple narrow channels can disperse the compressed air in the center into multiple airflows, preventing the gas from concentrating and forming large bubbles, thereby avoiding the formation of bubbles.

[0034] In the initial stage of hot pressing, the main resin of the prepreg 1 begins to soften. The raised ribs 5, made of epoxy resin with a higher B-order degree or a higher softening temperature, maintain a certain morphology. The raised ribs 5 form multiple slender linear support strips in the central region; the channels between adjacent raised ribs 5 serve as micro-venting channels, allowing air in the non-wiring area to migrate outwards along the channels. The raised ribs 5 are strip-shaped and extend along the venting direction, resulting in low venting resistance. Simultaneously, the channels between the raised ribs 5 are multiple micro-channels, preventing the molten resin from rapidly rushing in along a single path and blocking the outlet in the initial stage of hot pressing. Instead, it forms a controlled flow and dispersed propulsion on both sides of the raised ribs 5. Therefore, the raised ribs 5 simultaneously delay the overall bonding, provide venting paths, and regulate the adhesive flow front.

[0035] As the temperature continues to rise, the main resin of the prepreg 1 enters a low-viscosity flow stage, gradually flowing along the two sides of the raised ribs 5 and the channels between the raised ribs 5. The cross-section of the raised ribs 5, narrow at the top and wide at the bottom, guides the resin through a gradually expanding interface during flow, allowing the resin to form a stable thin layer along the sides of the ribs without sudden accumulation at the front end of the raised ribs 5. Multiple parallel raised ribs 5 divide the resin flow into multiple fine streams, which gradually converge at the ends or edges of the raised ribs 5, transforming the continuous planar advance of the resin flow into a multi-path, dispersed advance. This prevents air in the non-wiring area from being trapped by a single resin flow front and allows for a longer time for gas to escape before resin backfilling. After the gas is expelled, the molten resin backfills along the channels between the raised ribs 5, reducing the formation of air bubbles after curing.

[0036] The raised ribs 5 increase the surface area of ​​the intermediate convex sheet. Heat is transferred to the interior of the intermediate convex sheet through the top, sides, and resin in adjacent channels of the raised ribs 5, preventing the intermediate convex sheet from forming a thick block structure that would cause lag in heating. Because there are channels between the raised ribs 5, the resin of the prepreg 1 can gradually enter the channels and contact the sides of the raised ribs 5 after softening, thereby increasing the heat exchange contact area and enabling the raised ribs 5 and the intermediate convex sheet to heat up, soften, and fuse more evenly in the later stages of hot pressing. If the surface of the intermediate convex sheet is a completely flat structure, surface contact is easily formed in the early stages of hot pressing, which can hinder the entry of local resin into the interface. With the raised ribs 5, heat and resin can enter the intermediate area along multiple channels, making the softening process more gradual and reducing the risk of gas trapping caused by local sealing and subsequent softening.

[0037] In this embodiment, the raised rib 5 is prepared by integrally pressing and then transferring it to the surface of the prepreg 1. Specifically, a groove pattern with the opposite shape to the central raised piece and the raised rib 5 is first prepared on the surface of the release film. The groove pattern includes elongated grooves that form the raised rib 5. Then, B-stage epoxy resin slurry is coated on the surface of the release film, allowing the resin slurry to enter the groove pattern. Excess resin is removed by scraping and rolling to ensure uniform filling. Afterward, pre-baking is performed at a low temperature to make the resin reach a B-stage state that is peelable and still has the ability to be co-cured. Then, the release film with resin microstructure is aligned and bonded to the pressing auxiliary area 3 of the prepreg 1. The resin micro-sheets are embedded into the surface of the prepreg 1 by low-temperature hot pressing. Finally, the release film is peeled off, and the central raised piece with raised rib 5 is obtained on the surface of the prepreg 1. Regular microstructures are first formed on the release film, and then patterned preparation is completed by coating, pressing, pre-baking and transfer, which is suitable for roll-to-roll or sheet-to-sheet batch processing.

[0038] Example 3:

[0039] This embodiment provides a lamination method for multilayer printed circuit boards, such as... Figure 4 As shown, the lamination method includes the following steps: S1. Prepare core board 2 and prepreg 1, and perform pretreatment.

[0040] Based on the multilayer printed circuit board (PCB) stack-up design, multiple core boards 2 and multiple prepreg sheets 1 are prepared. The core board 2 is a core board with completed circuit pattern processing, and its surface includes wiring areas and non-wiring areas. The prepreg sheet 1 is a sheet material formed by impregnating glass fiber cloth with B-stage resin, wherein at least one prepreg sheet 1 has a raised micro-plate 4 formed on its surface in the pressing auxiliary area 3. When preparing the raised micro-plate 4, the position, shape, and size of the non-wiring area on the core board 2 are first determined, and then the outer contour of the non-wiring area is approximately converted into a circle, ellipse, rectangle, polygon, or a combination of the above regular shapes. The pressing auxiliary area 3 is then determined at the corresponding position of the prepreg sheet 1. Subsequently, multiple B-grade resin protruding micro-sheets 4 are pre-prepared on the release film, arranged according to a preset pattern in the pressing auxiliary area 3. The release film with the protruding micro-sheets 4 is then aligned and bonded to the pressing auxiliary area 3 of the prepreg 1, with the protruding micro-sheets 4 facing the surface of the prepreg 1. Light pressure or roller pressing is then applied at 40-80℃ to embed the lower surface portion of the protruding micro-sheets 4 into the surface resin of the prepreg 1, with a pressure of 0.05-0.3 MPa and a time of 10-60 seconds. Finally, the release film is peeled off, leaving the protruding micro-sheets 4 on the surface of the pressing auxiliary area 3 of the prepreg 1. This eliminates the need for direct laser or mechanical processing on the surface of the prepreg 1, reducing resin debris and microstructural damage, and facilitating patterned batch transfer via the release film.

[0041] Before lamination, the core board 2 and the prepreg 1 are pretreated. Pretreatment includes cleaning and drying / dehumidification. Cleaning involves sequentially wiping the surface of the core board 2 with a lint-free cloth, ionizing air blowing, and cleaning with anhydrous ethanol to remove surface dust, resin debris, and oil, preventing impurities from forming localized voids, delamination, or dielectric defects after lamination. For the prepreg 1, ionizing air or clean, dry nitrogen is used to blow along the microstructure channel extension direction from the center of the lamination auxiliary area 3 towards the edge at low pressure. Drying / dehumidification removes moisture adsorbed in the core board 2 substrate, the copper roughening layer, and the prepreg 1, reducing the risk of moisture vaporization and bubble formation during hot pressing. Specifically, the core board 2 is dried at 100-120℃ for 60-120 minutes, and the prepreg 1 is dried at 80-100℃ for 30-60 minutes to prevent premature over-reaction of the resin in the prepreg 1, which would reduce subsequent flowability and filling capacity. After drying, place the core board 2 and the semi-cured sheet 1 in a clean, low-humidity environment for later use to reduce the risk of moisture absorption.

[0042] S2, positioning holes 6 are provided on the core board 2 and the prepreg 1.

[0043] Positioning holes 6 are provided on the core board 2 and the prepreg 1. In this application, the positioning hole 6 is a combination of a round hole and an oblong hole, such as... Figure 5As shown, the oblong hole refers to a hole structure with semicircular ends and a straight line segment connecting them. The circular hole serves as the main positioning hole, defining the reference position of the core board 2 and the prepreg 1 in the plane. The oblong hole serves as an auxiliary positioning hole, defining the stacking direction and absorbing minor deviations in the core board 2 and prepreg 1 caused by dimensional tolerances or moisture shrinkage before cutting, drying, and hot pressing. The diameter of the circular hole is 1.5-5.0 mm, the width of the oblong hole is 1.5-5.0 mm, and the length is 1.5-3 times its width. The positioning hole 6 is preferably located at the process edge or in a non-effective circuit area to avoid affecting the functional area of ​​the circuit. The positioning hole 6 is used to cooperate with the positioning pin 10 or the stacking positioning mold to ensure accurate alignment of each core board 2, prepreg 1, and subsequent outer copper foil during stacking. Positioning through the positioning hole 6 reduces the risk of inner layer pattern misalignment, drilling deviation, and interlayer connection misalignment. For the prepreg 1 with raised microplates 4, the pressing auxiliary area 3 should be accurately aligned with the non-wiring area of ​​the core board 2 in the stack thickness direction so that the raised microplates 4 can act on the non-wiring area in the subsequent hot pressing.

[0044] S3, stack the core board 2 and the prepreg 1 to form a laminated structure and fix it.

[0045] In a clean environment, the core board 2 and the prepreg 1 are stacked sequentially according to a preset stacking order to form a laminated structure to be laminated. During stacking, the lamination auxiliary area 3 with the protruding micro-plates 4 is aligned with the non-wiring area of ​​the corresponding core board 2, and the lamination auxiliary area 3 and the non-wiring area are aligned in the thickness direction of the laminate. The laminated structure is detailed in Example 1. During the stacking process, each layer is pre-positioned by the positioning pins 10 passing through the positioning holes 6. Alternatively, the laminated structure can be pre-fixed by riveting, hot melt bonding, local dispensing, clamping, or pin positioning to prevent relative slippage of the laminated structure during handling, molding, or vacuuming. During pre-fixing, excessive local pressure should be avoided on the lamination auxiliary area 3. The pre-fixing pressure is 0.02-0.05 MPa to prevent the protruding micro-plates 4 from collapsing or shifting in position before formal lamination.

[0046] After lamination is completed, the laminated structure to be pressed is placed in the lamination carrier. The lamination carrier includes upper and lower stainless steel plates 8, release material 9, and kraft paper 7. The stainless steel plate 8 and kraft paper 7 are placed between the laminated structure and the upper and lower heating plates. The order from top to bottom is: kraft paper 7, stainless steel plate 8, release material 9, laminated structure, release material 9, stainless steel plate 8, and kraft paper 7. Figure 6As shown. The kraft paper 7 has a thickness of 0.2-1.0 mm and is used to compensate for minor flatness errors between the heating plate and the stainless steel plate 8, buffer local pressure peaks, and transfer heat to the stainless steel plate 8 in a more gentle and uniform manner. The release material 9 is a polytetrafluoroethylene film, fluorinated release film, polyimide release film, or a high-temperature resistant polyester film that has undergone release treatment, with a thickness of 25-100 μm; it is used to isolate the resin overflowing from the edge of the laminated structure during the lamination process, prevent resin from adhering to the surface of the stainless steel plate 8, and ensure that the plate surface is clean and flat after demolding.

[0047] S4, laminating the multilayer structure.

[0048] The loaded laminated structure is placed between the upper and lower heating plates of the laminator, with the upper heating plate in contact with the upper kraft paper 7 and the lower heating plate in contact with the lower kraft paper 7. The upper and lower heating plates provide heat and apply pressure to the laminated structure, causing the B-stage resin in the prepreg 1 to undergo softening, melting, degassing, gap filling, gelation, and curing processes. Lamination can be performed using non-vacuum lamination or vacuum lamination. This embodiment uses vacuum lamination, where the lamination chamber is evacuated before heating and pressurizing or during the pre-pressing stage to reduce the residual air content inside the laminated structure and at the interlayer interfaces, and to promote the removal of moisture, low-boiling-point solvents, and volatiles, thereby reducing the risk of bubbles, lamination voids, and localized missing adhesive. The vacuum level can be determined based on the equipment capacity and material system, and is generally between -80 kPa and -100 kPa.

[0049] The lamination process includes a pre-compression stage, a heating and resin flow stage, a full-pressure curing stage, and a pressure holding and cooling stage. The temperature and pressure changes in each stage are as follows: Figure 7 As shown. The pre-compression stage is an initial pressurization stage performed at a lower pressure to allow the layers of material to initially adhere and to expel interlayer air before the resin in the prepreg 1 has fully gelled. During the pre-compression stage, the pressure is 0.3-1.0 MPa, and the time is 3-10 minutes. Excessive pressure will cause the wiring area to be over-pressurized before the resin has fully softened, resulting in premature closure of the edges of the non-wiring area and hindering the expulsion of air from the center.

[0050] During the heating and resin flow stage, the upper and lower heating plates continue to transfer heat to the laminated structure, causing the main resin of the prepreg 1 to gradually soften and enter a low-viscosity flow state. The heating rate is 3-4℃ / min. If the heating rate is too fast, the surface resin of the prepreg 1 softens rapidly and locally traps gas, making it difficult for internal gas to escape; if the heating rate is too slow, the pressing cycle is prolonged, and the resin begins to gel prematurely, affecting subsequent gap filling. For the FR-4 epoxy system prepreg 1, it begins to soften when the temperature reaches 80-90℃, and enters a more sufficient resin flow window when the temperature reaches 115-125℃. At this time, the raised micro-plates 4 in the pressing auxiliary zone 3, due to the use of B-stage bisphenol A type solid epoxy resin, phenolic epoxy resin, or o-cresol phenolic epoxy resin, soften slightly later than the main resin of the prepreg 1, and can maintain a certain morphology when the main resin begins to flow. The raised microplates 4 first form local support at the corresponding position in the non-wiring area to prevent the main resin of the semi-cured sheet 1 from forming a continuous closed film too early; at the same time, the gaps between the raised microplates 4, the space around the central circular raised microplate 4, the channels between the radial rectangular raised microplates 4, and the grooves between the raised ribs 5 together form temporary exhaust and adhesive guiding channels, so that the air in the non-wiring area is discharged from the center to the edge.

[0051] When the resin temperature reaches 115-125℃, the pressure changes from low to high. The pressure during the full-pressure stage is 1.5-2.5 MPa, the full-pressure holding temperature is 170-180℃, and the holding time is 60-120 minutes. During the full-pressure stage, the main resin of the prepreg 1 continues to fill the gaps between the core boards 2, the height difference between the wiring area and the non-wiring area, and the micro-venting gaps in the pressing auxiliary area 3 under pressure. As the temperature rises and the holding time increases, the raised micro-plates 4 and raised ribs 5 gradually soften, swell, and fuse with the main resin of the prepreg 1, and the channels used for venting are gradually backfilled by the resin. Air in the non-wiring area is expelled first, and then the resin completes the filling and curing, which can reduce defects such as bubbles, voids, and missing glue.

[0052] After full-pressure curing, the laminate enters the pressure-holding cooling stage. Pressure-holding cooling involves gradually cooling the laminate while maintaining a certain pressure, allowing the resin to shrink under controlled conditions after curing. This reduces stress concentration caused by the difference in thermal expansion coefficients among the four regions (copper layer, fiberglass resin, and raised microplates) during cooling. The pressure during cooling is 60%-100% of the full-pressure pressure, until the laminate temperature drops to room temperature, at which point the pressure is released. Releasing pressure immediately before the laminate has fully cooled can lead to warping, interlayer misalignment, or localized cracking due to internal thermal stress. Pressure-holding cooling helps reduce laminate warping and internal stress, improving interlayer bonding quality.

[0053] In the pre-pressing stage, the resin in the prepreg undergoes initial venting; during the heating and adhesive flow stage, it flows in a controlled manner along the channels formed by the raised microplates 4; during the full-pressing stage, it completes gap filling and curing; and during the pressure holding and cooling stage, it reduces internal stress. The pressing auxiliary area 3 in this application is correspondingly positioned to the non-wiring area. The raised microplates 4 form short-term support and venting paths in the initial stage of hot pressing, regulate the adhesive flow front in the middle stage of hot pressing, and soften, fuse, and transform into a continuous insulating adhesive layer in the later stage of hot pressing.

[0054] S5, after removing the excess adhesive from the edges, perform post-curing treatment.

[0055] After the laminated structure cools to room temperature, the laminator is opened after depressurization. The laminated multilayer board structure is then removed, along with auxiliary materials such as positioning pins 10, release material 9, kraft paper 7, and stainless steel plate 8. During lamination, the resin in the prepreg 1 may flow out from the board edge or process edge, forming irregular excess resin edges. To ensure subsequent processing dimensions and board edge quality, the excess resin edges are trimmed and removed. Positioning holes 6 are retained during trimming to avoid damaging the effective circuit area.

[0056] After removing excess adhesive, the laminated multilayer board undergoes post-curing. This is carried out in an electrically heated constant-temperature drying oven at 140℃ for 4 hours. Post-curing allows the interlayer resins to further complete the cross-linking reaction, releases some residual stress from hot pressing, reduces board warpage, and improves interlayer adhesion stability. After post-curing, the multilayer board is inspected for thickness, warpage, layer misalignment, bubbles, insufficient adhesive, and delamination. Once it passes inspection, it proceeds to subsequent processes such as drilling, copper plating, electroplating, outer layer circuitry, solder mask application, and surface treatment.

[0057] Example 4:

[0058] Based on Example 3, a pressure control step is set before the end of the heating and resin flow stage and the start of the full-pressure curing stage. Specifically, when the temperature of the laminated structure rises to 125-140°C, the main resin of the prepreg 1 has entered a relatively fully flowing state, while the raised microplates 4 and raised ribs 5 in the pressing auxiliary zone 3 have not yet completely softened and collapsed. The pressure is first increased from the low pre-pressure to 1.2-1.6 MPa and maintained for 1-3 minutes, so that the molten resin initially enters the gap between the raised microplates 4, the outer peripheral space of the central circular raised microplate 4, and the channels between the raised ribs 5 under moderate pressure. At the same time, it pushes the raised microplates 4 to compress, so that they retain part of the support height and air guiding channels. The pressure is then reduced to 0.6-1.0 MPa and maintained for 2-5 minutes to temporarily decrease the resin pressure that has entered the micro-venting channels. This prevents the resin front from momentarily blocking the outlet, allowing any remaining gas to escape from the resin front, the sides of the raised micro-plates 4, and the channels of the raised ribs 5 during pressure release. The pressure is then increased to 1.5-2.5 MPa and maintained at 170-180°C to further soften and swell the raised micro-plates 4 and raised ribs 5, allowing them to fuse with the main resin of the semi-cured sheet 1. The original venting channels are then stably backfilled and cured by the resin. In other words, by adjusting the pressure by first increasing, then decreasing, and then increasing again, the raised micro-plates 4 function as pre-filling guides, provide short-term support for venting, and ultimately fuse and fill the gaps. This avoids the problems of the raised micro-plates 4 collapsing under direct full pressure, premature closure of the edge resin flow, and encapsulation of residual gas in the center. This improves the uniformity of resin filling in non-wiring areas and reduces defects such as bubbles, voids, and insufficient resin.

[0059] Furthermore, during the initial stages of the heating and resin flow stages and the full-pressure curing stages, micro-reciprocating vibrations are applied to the laminated structure along the board surface direction to promote gas expulsion and molten resin backfilling in the non-wiring areas. Specifically, a vibration actuator is positioned on the side of the lower stainless steel plate 8 of the laminator, allowing vibration to be transmitted to the laminated structure through the stainless steel plate 8. The vibration actuator is an electromagnetic linear vibrator or a piezoelectric ceramic vibrator. The amplitude of the micro-vibration is 10-50 μm, the frequency is 1-10 Hz, and the vibration direction is set along the board surface direction. The micro-vibration is applied during the heating and resin flow stage from the time the prepreg 1 begins to soften until it enters the full resin flow window, and continues for 1-5 minutes in the early stage of the full-pressure curing stage, stopping after the resin begins to gel. During the heating and resin flow stage, micro-vibration disturbs the residual gas between the raised micro-plates 4, between the raised ribs 5, and around the outer periphery of the central circular raised micro-plate 4, causing bubbles to detach from their localized stagnation locations and migrate towards the edges along the micro-venting channels. In the early stage of full-pressure curing, micro-vibration reduces localized stagnation and bridging of molten resin within the micro-channels, allowing resin to gradually backfill along the sides of the raised micro-plates 4, the channels of the raised ribs 5, and the radial venting gaps, thereby improving the uniformity of resin filling in non-wiring areas. Small-amplitude micro-shearing and periodic disturbances reduce the risk of gas stagnation and localized resin accumulation, preventing the formation of bubbles, voids, and insufficient resin.

[0060] Furthermore, when multiple parallel raised ribs 5 are provided on the intermediate convex plate, the vibration direction of the in-plane micro-vibration is parallel to the extension direction of the raised ribs 5. Since a slender channel is formed between adjacent raised ribs 5, the gas and molten resin mainly migrate along the channel direction. When the vibration direction is parallel to the raised ribs 5, the periodic shearing action is transmitted along the exhaust and return channels, making it easier for the bubbles in the channel to move along the low resistance direction after being driven by reciprocating motion, and causing the molten resin to generate axial micro-flow along the channel, thereby more fully utilizing the gas guiding, resin guiding and resin flow homogenization functions of the raised ribs 5.

[0061] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multilayer printed circuit board stacked structure, the stacked structure comprising prepreg and core board arranged alternately from top to bottom, wherein the top and bottom layers of the stacked structure are both the prepreg, and at least one of the core board has a lower surface including a wiring area and a non-wiring area, characterized in that: At least one of the prepreg sheets has a pressing auxiliary area on one side surface facing the core board. The pressing auxiliary area is correspondingly arranged with the non-wiring area in the stack thickness direction. The surface of the pressing auxiliary area is provided with a plurality of raised micro-plates, and the thickness of at least one of the raised micro-plates is greater than the thickness of the wiring layer in the wiring area.

2. The multilayer printed circuit board stacked structure according to claim 1, characterized in that, The raised microplate includes a central raised piece and an edge raised piece, wherein the thickness of the central raised piece is greater than the thickness of the edge raised piece.

3. The multilayer printed circuit board stacked structure according to claim 2, characterized in that, The upper surface of the intermediate protrusion is provided with a long strip-shaped protrusion.

4. The multilayer printed circuit board stacked structure according to claim 1, characterized in that, The thickness of the raised microplate is 0.8-1.2 times the thickness of the wiring layer.

5. The multilayer printed circuit board stacked structure according to claim 1, characterized in that, The length and width of the raised microplate in the plane are 5-20 times the thickness of the raised microplate.

6. The multilayer printed circuit board stacked structure according to claim 1, characterized in that, The raised microplates cover 15%-45% of the pressing auxiliary area.

7. The multilayer printed circuit board stacked structure according to claim 1, characterized in that, The material of the raised micro-sheets is one or more of the following: B-type bisphenol A solid epoxy resin, phenolic epoxy resin, and o-cresol epoxy resin.

8. A lamination method for a multilayer printed circuit board, the lamination method comprising the following steps: S1. Prepare the core board and prepreg, and perform pretreatment. S2, positioning holes are provided on the core board and the prepreg; S3, stack the core board and the prepreg to form a laminated structure and fix it; S4, the laminated structure is laminated; S5, after removing the excess adhesive from the edges, perform post-curing treatment; Its features are, The stacked structure is the stacked structure as described in claim 1.

9. The lamination method for multilayer printed circuit boards according to claim 8, characterized in that, Step S1 includes determining the non-wiring area of ​​the core board, determining the area of ​​the pressing auxiliary area on the prepreg based on the non-wiring area, and preparing raised micro-sheets on the pressing auxiliary area.

10. The lamination method for multilayer printed circuit boards according to claim 9, characterized in that, The pretreatment includes drying at 80-120℃ for 30-120 minutes to remove moisture.

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