A high-density interconnect PCB grouting manufacturing method and system

Abstract

This invention relates to the field of PCB manufacturing and packaging technology, and discloses a method and system for grouting high-density interconnect PCBs. The method includes the following steps: acquiring the board structure information and grouting area information of the high-density interconnect PCB, and determining grouting shrinkage-sensitive areas based on the board structure information and the grouting area information; performing a compression and flow-guiding treatment on the grouting shrinkage-sensitive areas to form a compression and flow-guiding structure; performing differentiated grouting treatment on the grouting area based on the compression and flow-guiding structure to form a grouting layer structure; and performing a segmented temperature-controlled curing treatment on the grouting layer structure to obtain a finished high-density interconnect PCB board. This invention reduces the risks of interface gaps, peeling, and insulation failure in the grouting layer of automotive high-density interconnect PCBs.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing and packaging technology, and in particular to a method and system for manufacturing high-density interconnect PCBs using a grouting process. Background Technology

[0002] High-density interconnect PCBs are increasingly used in automotive control modules, commonly found in products such as battery management units, domain controllers, sensor interface boards, and motor drive auxiliary boards. These PCBs typically feature microvias, blind vias, fine-pitch pads, large copper areas, and localized heat-generating components, resulting in high circuit density and complex interlayer connections. To improve moisture resistance, insulation, and vibration resistance, some automotive high-density interconnect PCBs undergo partial or full-area grouting during the finished product stage, ensuring the grouting material covers critical board areas and fills gaps around components.

[0003] Current grouting processes primarily focus on whether the grout material can flow smoothly into the target area and whether there are obvious air bubbles, insufficient adhesive, or surface cracks after curing. For ordinary PCBs, methods such as vacuum degassing, dispensing, and thermosetting can usually meet basic protection requirements. However, in automotive high-density interconnect PCBs, the differences in board structure are more pronounced. Areas with dense microvias, large copper layer proximity areas, and device heat source proximity areas do not have consistent heat absorption, dissipation, and thermal expansion characteristics. When the grout material cures in these areas, it is prone to different shrinkage rates and stress release directions.

[0004] In actual production, even if the grout layer appears intact on the surface, hidden interface voids may still form near the microvia chains or copper layer edges. These defects may not initially manifest as obvious visual abnormalities, but under the effects of wide-temperature cycling, vibration, and localized heating during vehicle operation, these interface voids may continue to expand, leading to decreased insulation performance, localized bulging, grout layer peeling, or long-term reliability failure. Existing processes typically treat the grouting area as a whole, lacking specific identification, stress relief, and differentiated grouting control for grout shrinkage-sensitive areas. Therefore, there is an urgent need for a manufacturing solution that can control the curing shrinkage path and reduce the risk of interface failure in densely populated microvia areas and areas near heat sources during the grouting process of high-density interconnect PCBs. Summary of the Invention

[0005] This invention provides a method and system for manufacturing high-density interconnect PCB grout, which at least solves the problems of interface voids, peeling and insulation failure caused by uneven curing shrinkage in the grout layer of automotive high-density interconnect PCBs in the prior art.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for manufacturing a high-density interconnect PCB using a grouting process, the method comprising the following steps: Obtain the board structure information and grouting area information of the high-density interconnect PCB, and determine the grouting shrinkage sensitive area based on the board structure information and the grouting area information; The shrinkage-sensitive area of ​​the grouting is subjected to a flow-blocking and flow-guiding treatment to form a flow-blocking and flow-guiding structure; Based on the aforementioned flow-guiding structure, differentiated grouting treatment is performed on the area to be grouted to form a grouting layer structure; The grouting layer structure is subjected to segmented temperature-controlled curing treatment to obtain a high-density interconnect PCB finished board.

[0007] In one embodiment, the board structure information includes micro-hole distribution information, large-area copper layer distribution information, and device heat source distribution information; Identify areas sensitive to grout shrinkage, including: The micropore distribution information, the large-area copper layer distribution information, the device heat source distribution information, and the grouting area information are superimposed to determine the grouting area located in the micropore dense area, the large-area copper layer adjacent area, or the device heat source adjacent area as the grouting shrinkage sensitive area.

[0008] In one embodiment, the constriction and diversion process includes: A shallow groove structure extending along a predetermined stress-relieving direction is formed within the grouting shrinkage sensitive area; The shallow trench structure is formed on the insulating surface or non-conductive covering layer surface within the area to be grouted, and avoids conductive pads, exposed lines and functional openings. The shallow groove structure has a groove width of 40μm-120μm, a groove depth of 10μm-30μm, and a spacing of 0.3mm-1.0mm between adjacent shallow groove structures.

[0009] In one embodiment, the preset stress relief direction is determined based on the micropore arrangement direction within the grouting shrinkage sensitive area and the heat flow direction from the device heat source to the large-area copper layer; When the angle between the micropore arrangement direction and the heat flow direction is less than 45°, the shallow groove structure is configured to extend along the micropore arrangement direction.

[0010] In one embodiment, the differentiated grouting treatment includes: The first grouting treatment is performed on the grouting shrinkage sensitive area to form a first grouting layer; A second grouting treatment is performed on non-grouting shrinkage-sensitive areas to form a second grouting layer; The thickness of the first grouting layer is less than the thickness of the second grouting layer.

[0011] In one embodiment, the thickness of the first grouting layer is 0.15mm-0.35mm, and the thickness of the second grouting layer is 0.30mm-0.70mm; A thickness transition zone is formed between the first grouting layer and the second grouting layer.

[0012] In one embodiment, the differentiated grouting treatment includes: Before the grouting material enters the grouting shrinkage sensitive area, the grouting shrinkage sensitive area is pre-wetted. The pre-wetting treatment uses a low-viscosity grouting material with a viscosity of 300 mPa·s-900 mPa·s and a pre-wetting time of 30 s-120 s.

[0013] In one embodiment, the segmented temperature-controlled curing process includes: Keep the grouting material at 40℃-60℃ for 10min-30min to allow it to level and release residual gas. Pre-cur at 70℃-90℃ for 20-50 minutes; The grouting layer structure is formed by primary curing at 110℃-130℃ for 40-90 minutes.

[0014] In one embodiment, after obtaining the high-density interconnect PCB finished board, the grouting shrinkage sensitive area is subjected to ultrasonic scanning or X-ray detection. When a continuous interface void with a length greater than 0.5 mm appears in the grouting shrinkage sensitive area, or an internal bubble with a diameter greater than 100 μm appears, the corresponding high-density interconnect PCB finished board will be judged as an abnormal finished board.

[0015] To achieve the above objectives, a second aspect of the present invention also provides a high-density interconnect PCB grouting manufacturing system, the system comprising: a first module, configured to acquire board surface structure information and grouting area information of the high-density interconnect PCB, and determine grouting shrinkage sensitive areas based on the board surface structure information and the grouting area information; The second module is used to perform a flow-blocking and flow-guiding treatment on the grouting shrinkage-sensitive area to form a flow-blocking and flow-guiding structure. The third module is used to perform differentiated grouting treatment on the area to be grouted based on the constriction and flow guiding structure, so as to form a grouting layer structure; The fourth module is used to perform segmented temperature-controlled curing treatment on the grouting layer structure to obtain a high-density interconnect PCB finished board.

[0016] The beneficial effects of this invention are as follows: it can identify areas in high-density interconnect PCBs prone to shrinkage failure before grouting, and provide a preset shrinkage release path for the grouting material through a shrinkage-guiding structure, reducing stress concentration in areas with dense micropores, copper layer proximity, and heat source proximity. Differentiated grouting treatment enables the formation of matching grout layer thicknesses in different board surface structural areas, reducing the risk of shrinkage voids caused by local curing volume differences. Segmented temperature-controlled curing treatment helps control the leveling, venting, and curing shrinkage processes of the grouting material. The resulting high-density interconnect PCB can reduce the risk of voids, peeling, and insulation failure at the grout layer interface, and improve the reliability of grouting protection under wide-temperature vibration conditions in automotive applications. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the steps of the high-density interconnect PCB grouting manufacturing method in an embodiment of the present invention. Figure 2 This is a partial schematic diagram of the shallow channel structure for flow guidance in an embodiment of the present invention; Figure 3 This is a schematic diagram of the high-density interconnect PCB grouting manufacturing process in an embodiment of the present invention; Figure 4 This is a structural block diagram of a high-density interconnect PCB grouting manufacturing system according to an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] This invention provides a method for manufacturing high-density interconnect PCBs using a grouting process, referring to... Figure 1 , Figure 1 This is a schematic flowchart of the high-density interconnect PCB grouting manufacturing method according to an embodiment of the present invention.

[0020] In this embodiment, a high-density interconnect PCB grouting manufacturing method includes the following steps: S10: Obtain the board structure information and grouting area information of the high-density interconnect PCB, and determine the grouting shrinkage sensitive area based on the board structure information and the grouting area information.

[0021] Specifically, the board surface structure information includes micropore distribution information, large-area copper layer distribution information, and device heat source distribution information; determining the grouting shrinkage sensitive area includes: superimposing the micropore distribution information, the large-area copper layer distribution information, the device heat source distribution information, and the grouting area information, and determining the grouting area located in the micropore dense area, the large-area copper layer adjacent area, or the device heat source adjacent area as the grouting shrinkage sensitive area.

[0022] In this embodiment of the invention, the board structure information of the high-density interconnect PCB can be derived from PCB design data, CAM engineering data, or process layer data from the manufacturing execution system. The board structure information includes microvia distribution information, large-area copper layer distribution information, and device heat source distribution information. Microvia distribution information indicates the arrangement of blind vias, buried vias, or micro-vias on the board surface. Large-area copper layer distribution information indicates the location of power copper foil, heat dissipation copper areas, or grounding areas. Device heat source distribution information indicates the mounting areas corresponding to power chips, driver devices, power converter devices, or heating resistors. The information on the area to be grouted is used to determine the actual board surface area covered by the subsequent grouted material.

[0023] In specific processing, the micropore distribution information, large-area copper layer distribution information, device heat source distribution information, and the information of the area to be grouted are superimposed according to the same board edge reference, positioning hole reference, or process target reference. After superposition, if the area to be grouted falls in a location with a dense arrangement of micropores, or is close to the boundary of a large-area copper layer, or is located around a device heat source, then this area to be grouted is identified as a grouted shrinkage sensitive area. Here, the grouted shrinkage sensitive area does not refer to the entire grouted area, but rather to areas where the grouted material is more prone to shrinkage differences, interface voids, or localized delamination after curing.

[0024] For example, in the high-density interconnect PCB of an automotive battery management unit, there is often a dense array of microvias around the sampling chip, and a large copper layer may be placed at the power supply end. After the grouting material covers this area, the local interface near the microvia chain is complex, and the large copper layer will change the heating and cooling rates. If the device heats up, the grouting layer is prone to local shrinkage during curing and subsequent thermal cycling. By identifying the grouting shrinkage-sensitive area before grouting, the subsequent shrinkage-conducting treatment, differentiated grouting treatment, and segmented temperature-controlled curing treatment can have a clear target. The protection scope is not limited to specific graphic overlay software; as long as the grouting area prone to shrinkage failure can be identified based on the above board structure information and the information of the area to be grouted, it can be used as the implementation method of this step.

[0025] Step S20: Perform a flow-blocking and flow-guiding treatment on the grouting shrinkage-sensitive area to form a flow-blocking and flow-guiding structure.

[0026] Specifically, the compression and flow guiding treatment includes: forming a shallow groove structure extending along a preset stress relief direction within the grouting shrinkage sensitive area; the shallow groove structure is formed on the insulating surface or non-conductive covering layer surface within the grouting area, and avoids conductive pads, exposed lines and functional orifices; the groove width of the shallow groove structure is 40μm-120μm, the groove depth is 10μm-30μm, and the spacing between adjacent shallow groove structures is 0.3mm-1.0mm.

[0027] Specifically, the preset stress relief direction is determined based on the micropore arrangement direction within the grouting shrinkage sensitive area and the heat flow direction from the device heat source to the large-area copper layer; when the angle between the micropore arrangement direction and the heat flow direction is less than 45°, the shallow trench structure is set to extend along the micropore arrangement direction.

[0028] In this embodiment of the invention, the shrinkage-guiding treatment is used to pre-construct a microstructure capable of receiving grouting material within the grouting shrinkage-sensitive area. The grouting shrinkage-sensitive area is generally located in a densely packed micropore region, and may also be near a large-area copper layer or a device heat source. During subsequent grouting and curing, the shrinkage direction of the grouting material in such areas is easily affected by the micropore arrangement, copper layer thermal conductivity, and device heating. If grouting is performed directly, the cured grout layer is prone to shrinkage concentration near the micropore chain edges or copper layer boundaries.

[0029] In practice, shallow trench structures extending along a predetermined stress-relieving direction are formed within the grouting shrinkage-sensitive area. These shallow trench structures are formed on the insulating surface or non-conductive overlay surface of the area to be grouted, such as the surface of a solder mask, insulating protective film, or an existing non-conductive coating. The shallow trench structures avoid conductive pads, exposed traces, and functional vias, without altering the original conductive paths of the high-density interconnect PCB, and without affecting the electrical connection function of microvias, blind vias, or pads. The shallow trench structures can be formed using laser micro-engraving, precision micro-milling, or controlled plasma etching.

[0030] Figure 2 A shallow trench structure is demonstrated, with a trench width of 40μm-120μm, a trench depth of 10μm-30μm, and a spacing between adjacent shallow trench structures of 0.3mm-1.0mm. This size range allows the grouting material to be partially embedded after entering the shallow trench structure without significantly weakening the integrity of the insulation layer. Too small a trench width will make it difficult for the grouting material to fully penetrate the shallow trench structure. Too large a trench depth may damage the underlying solder mask layer, dielectric layer, or adjacent circuitry. The spacing between adjacent shallow trench structures can be selected based on the viscosity of the grouting material, the area to be grouted, and the micropore density.

[0031] The preset stress relief direction is determined based on the micropore arrangement direction within the grout shrinkage-sensitive area and the heat flow direction from the device heat source to the large-area copper layer. The micropore arrangement direction reflects the extension trend of local interface weak points. The heat flow direction reflects the main thermal deformation direction of the grout material during curing and service heating.

[0032] When the angle between the micropore arrangement direction and the heat flow direction is less than 45°, it indicates that their influence on the shrinkage deformation of the grout layer is relatively similar. In this case, the shallow groove structure is set to extend along the micropore arrangement direction. During the curing and shrinkage of the grouting material, controlled release can occur along the shallow groove structure, reducing the concentration of shrinkage stress at the edges of the micropore chains. For angles not less than 45°, the shallow groove structure can be arranged along the heat flow direction, the micropore arrangement direction, or a compromise between the two, depending on the plate space and the shape of the area to be grouted. This constriction-damping and flow-guiding structure is not used as a conductive structure; its function is to provide a stable interface foundation for subsequent differentiated grouting treatments.

[0033] In another embodiment, within the grouting shrinkage sensitive area, some shallow groove structures are configured as blind-end shallow grooves according to the micropore arrangement direction. One end of the blind-end shallow groove faces the dense micropore area, and the other end terminates inside the area to be grouted. The termination position of the blind-end shallow groove maintains a preset safe distance from the conductive pads, exposed lines, and functional orifices.

[0034] This structure is primarily suitable for automotive HDI boards with dense microvia arrays but small gaps between surrounding components. After the grouting material enters the blind-end shallow trench, it forms a localized saturation point at the trench's end. During subsequent curing and shrinkage, this saturation point absorbs some of the tensile stress transmitted along the microvia chain, reducing direct stress transfer to component solder joints or orifice edges. The length of the blind-end shallow trench can be set from 0.8mm to 2.5mm, and the blind-end end can be rounded or teardrop-shaped to avoid the formation of new sharp corner stress concentrations.

[0035] For grouting shrinkage-sensitive areas near the edge of the main control chip or adjacent to the crystal oscillator, through shallow trenches and blind shallow trenches can be arranged alternately. Through shallow trenches are used to guide the overall spreading of grouting material, while blind shallow trenches are used to form flexible stress-relieving nodes in local areas.

[0036] Step S30: Perform differentiated grouting treatment on the area to be grouted based on the constriction and flow guiding structure to form a grouting layer structure.

[0037] Specifically, the differentiated grouting treatment includes: performing a first grouting treatment on the grouting shrinkage-sensitive area to form a first grouting layer; performing a second grouting treatment on the non-grouting shrinkage-sensitive area to form a second grouting layer; the thickness of the first grouting layer is less than the thickness of the second grouting layer.

[0038] Specifically, the thickness of the first grouting layer is 0.15mm-0.35mm, and the thickness of the second grouting layer is 0.30mm-0.70mm; a thickness transition zone is formed between the first grouting layer and the second grouting layer.

[0039] Specifically, the differentiated grouting treatment further includes: performing a pre-wetting treatment on the grouting shrinkage sensitive area before the grouting material enters the grouting shrinkage sensitive area; the pre-wetting treatment uses a low-viscosity grouting material with a viscosity of 300 mPa·s-900 mPa·s and a pre-wetting holding time of 30s-120s.

[0040] In this embodiment of the invention, the constriction-guiding structure has already formed local shallow grooves and stress-relieving paths within the grouting shrinkage-sensitive area. When subsequent grouting material enters this area, it can spread along the shallow groove structure and form a local embedding. This treatment does not employ a uniform thickness grouting method across the entire area, but rather controls the grouting thickness according to the structural differences between the grouting shrinkage-sensitive area and the non-grouting shrinkage-sensitive area.

[0041] In practice, before the grouting material enters the shrinkage-sensitive area, a pre-wetting treatment can be performed on the shrinkage-sensitive area. The pre-wetting treatment uses a low-viscosity grouting material with a viscosity of 300 mPa·s-900 mPa·s, and the pre-wetting time is 30-120 seconds. The low-viscosity grouting material can first penetrate shallow groove structures, micropore edge gaps, and minor depressions on local insulating surfaces, forming a continuous wetting interface between the subsequent grouting material and the board surface. The pre-wetting time should not be too short, otherwise the grouting material will not be able to spread sufficiently. If the holding time is too long, the low-viscosity material may diffuse into non-target areas, affecting thickness control.

[0042] After pre-wetting, a first grouting treatment is performed on the shrinkage-sensitive area to form a first grout layer. This first grout layer covers the shrinkage-sensitive area and fills the shrinkage-resistant flow-guiding structure, with a thickness controlled between 0.15mm and 0.35mm. This thickness provides basic insulation and protective coverage while reducing the volume of cured material within the shrinkage-sensitive area, thus mitigating the risk of shrinkage due to thick adhesive curing near micropore chains, copper layer boundaries, or heat sources. For areas with densely packed micropores and small device gaps, a thinner first grout layer can be used. For areas requiring coverage of higher device edges or solder mask steps, a thicker first grout layer can be used.

[0043] A second grouting treatment is performed on non-grout shrinkage-sensitive areas to form a second grouting layer. The thickness of the second grouting layer is 0.30mm-0.70mm. The surface structure of non-grout shrinkage-sensitive areas is relatively uniform, and the risk of interfacial voids is low, allowing for a thicker grouting layer to provide moisture protection, vibration resistance, and mechanical protection. A thickness transition zone is established between the first and second grouting layers. This transition zone can be formed by slowing down the dispensing path, gradually changing the dispensing amount, or using a leveling process, allowing the grouting layer thickness to gradually transition from the first to the second grouting layer. This transition zone avoids the formation of new stress abrupt changes at the interface between the two grouting thicknesses.

[0044] In some embodiments, the first grouting treatment and the second grouting treatment can use the same grouting material, with the thickness difference created by the dispensing amount and the dispensing speed. Alternatively, grouting materials with different moduli after curing can be used. The protection scope is not limited to specific dispensing equipment or grouting material models; any implementation method that creates a differentiated grouting layer structure for grout shrinkage-sensitive and non-grout shrinkage-sensitive areas based on the constriction-guiding structure can be considered as part of this step.

[0045] Step S40: Perform segmented temperature-controlled curing treatment on the grouting layer structure to obtain a high-density interconnect PCB finished board.

[0046] Specifically, the segmented temperature-controlled curing process includes: holding at 40℃-60℃ for 10min-30min to allow the grouting material to complete leveling and release residual gas; pre-curing at 70℃-90℃ for 20min-50min; and main curing at 110℃-130℃ for 40min-90min to form the cured grouting layer structure.

[0047] In this embodiment of the invention, segmented temperature-controlled curing is used to enable the grouting layer structure to complete leveling, venting, and curing under controlled temperature conditions. The grouting layer structure has already formed a first grouting layer, a second grouting layer, and a thickness transition zone between them in step S30. The grouting thickness varies in different regions, and there are also differences in thermal response near the dense micropore area, the copper layer adjacent area, and the device heat source adjacent area. If high-temperature curing is directly applied, the surface layer of the grouting material is prone to cross-linking first, and residual gas and local shrinkage stress inside are not easily released, potentially leading to voids or bulges at the interface.

[0048] In practice, the high-density interconnect PCB after grouting is placed in a hot air circulating oven, tunnel furnace, or zoned heating platform and held at 40℃-60℃ for 10-30 minutes. This stage primarily maintains the fluidity of the grout material, allowing it to continue filling the shallow trench structure, micropore edge gaps, and thickness transition zones, while simultaneously allowing micro-air bubbles entrained within the grout material to migrate outwards. This relatively low temperature range prevents the grout material from rapidly gelling, making it suitable for leveling and releasing residual gases.

[0049] Furthermore, pre-curing is performed at 70℃-90℃ for 20-50 minutes. This stage allows the grouting material to gradually acquire initial morphological stability, preventing significant sagging or localized accumulation of the grouting material during subsequent heating. For the first grouting layer with a relatively small thickness, a shorter pre-curing time can be used. For the second grouting layer with a larger thickness or the area covering the edge of the device, the pre-curing time can be appropriately extended.

[0050] After pre-curing, the grouting material undergoes primary curing at 110℃-130℃ for 40-90 minutes to complete the main cross-linking reaction, forming the cured grouting layer structure. The primary curing temperature and time can be determined based on the grouting material system, the temperature resistance rating of the board, and the grout thickness. After segmented temperature-controlled curing, the grouting layer structure forms a stable bond with the flow-guiding structure in the grouting shrinkage-sensitive area, covering the grouting area of ​​the high-density interconnect PCB, resulting in the finished high-density interconnect PCB board.

[0051] Preferably, after obtaining the high-density interconnect PCB finished board, the grouting shrinkage sensitive area is subjected to ultrasonic scanning or X-ray detection; when a continuous interface void with a length greater than 0.5 mm or an internal bubble with a diameter greater than 100 μm appears in the grouting shrinkage sensitive area, the corresponding high-density interconnect PCB finished board is determined to be an abnormal finished board.

[0052] In this embodiment of the invention, after obtaining the high-density interconnect PCB finished board, defect detection is performed on the grout shrinkage sensitive area. The detection target is mainly the grout shrinkage sensitive area determined in step S10, rather than making an indiscriminate judgment on the entire grout layer. This area is close to the dense micropore area, the area adjacent to the large copper layer, or the area adjacent to the heat source of the device, and is more likely to have interface voids, internal bubbles, or local debonding after curing.

[0053] For specific testing, ultrasonic scanning or X-ray inspection can be used. Ultrasonic scanning is suitable for identifying the interface continuity between the grout layer and the board surface, especially interface gaps, local debonding, and delamination defects. X-ray inspection is suitable for identifying air bubbles, cavities, and localized incomplete filling within the grout layer. For high-density interconnect PCBs with complex structures, X-ray inspection of internal air bubbles can be used first, followed by ultrasonic scanning to inspect the interface bonding status.

[0054] When a continuous interface gap longer than 0.5 mm appears within the grout shrinkage sensitive area, it indicates that a continuous separation zone has formed between the grout layer and the board surface at that location. This type of defect is prone to further expansion under humid, hot, and vibrating conditions. When internal bubbles with a diameter greater than 100 μm appear within the grout shrinkage sensitive area, it indicates localized insufficient filling or inadequate venting in that area. For automotive high-density interconnect PCBs, these bubbles may weaken local insulation distances and may also form the starting point for bulging during temperature cycling.

[0055] If the test results meet any of the above conditions, the corresponding high-density interconnect PCB finished board will be judged as an abnormal finished board. Abnormal finished boards can enter the re-inspection, rework, or scrapping process. The test results can also serve as the basis for subsequent adjustments to the shallow trench structure spacing, the thickness of the first grouting layer, the pre-wetting holding time, and the segmented temperature-controlled curing parameters.

[0056] Example: like Figure 3 As shown, taking a high-density interconnect PCB for a vehicle domain controller as an example, the PCB is 1.2mm thick and adopts a 6-layer HDI structure. Micro-via arrays, main control chips, crystal oscillators and multiple fine-pitch surface mount components are set in some areas. Figure 3 In the diagram, (a) represents the original local board surface state of the HDI, with the area to be grouted located between the microvia array, the device area to the left of the main control chip, and the area adjacent to the crystal oscillator. During manufacturing, microvia distribution information, large-area copper layer distribution information, and device heat source distribution information are first extracted from the CAM data and overlaid with the information of the area to be grouted. It was determined that the area near the microvia array and the edge of the main control chip are sensitive areas for grouted shrinkage.

[0057] like Figure 3 As shown in (b), a shallow groove structure for flow guidance is formed within the grouting shrinkage sensitive area. The shallow groove structure is formed on the surface of the solder mask layer, avoiding microvia openings, exposed pads, and surface mount device solder joints. The width of the shallow groove is controlled to be 70 μm, the depth to be 18 μm, and the spacing between adjacent shallow grooves to be 0.5 mm. The extension direction of the shallow groove is determined based on the microvia arrangement direction and the heat flow direction from the main control chip to the large-area copper layer. When the included angle between the two is less than 45°, the shallow groove is arranged along the microvia arrangement direction, providing a release interface path during subsequent grouting layer curing and shrinkage.

[0058] Subsequently, differentiated grouting treatment was performed. First, a low-viscosity grouting material with a viscosity of 600 mPa·s was used to pre-wet the shrinkage-sensitive areas, maintaining the grouting material for 60 seconds to allow it to penetrate the shallow trench structure and local micro-gaps. Then, a first grouting layer with a thickness of 0.25 mm was formed on the shrinkage-sensitive areas; a second grouting layer with a thickness of 0.50 mm was formed on the non-shrinkage-sensitive areas, with a gradual thickness transition zone between the two layers.

[0059] like Figure 3 As shown in (c), after grouting, a segmented temperature-controlled curing process was performed. First, the grout was kept at 50℃ for 20 minutes to allow the grouting material to level and release residual gas; then, it was pre-cured at 80℃ for 35 minutes; finally, it was main-cured at 120℃ for 60 minutes, resulting in a high-density interconnect PCB board with complete coverage and continuous boundaries. After curing, ultrasonic scanning was used to detect grout shrinkage-sensitive areas. No continuous interface voids longer than 0.5 mm or internal bubbles with a diameter greater than 100 μm were found, indicating that the PCB board met the requirements for subsequent automotive reliability verification.

[0060] Reference Figure 4 , Figure 4 This is a schematic diagram of the high-density interconnect PCB grouting manufacturing system according to an embodiment of the present invention.

[0061] like Figure 4 As shown, the high-density interconnect PCB grouting manufacturing system proposed in this embodiment of the invention includes: The first module is used to acquire the board structure information and the grouting area information of the high-density interconnect PCB, and to determine the grouting shrinkage sensitive area based on the board structure information and the grouting area information. The second module is used to perform a flow-blocking and flow-guiding treatment on the grouting shrinkage-sensitive area to form a flow-blocking and flow-guiding structure. The third module is used to perform differentiated grouting treatment on the area to be grouted based on the constriction and flow guiding structure, so as to form a grouting layer structure; The fourth module is used to perform segmented temperature-controlled curing treatment on the grouting layer structure to obtain a high-density interconnect PCB finished board.

[0062] It is understood that in the description of this specification, references to terms such as "one embodiment," "another embodiment," "other embodiments," or "first embodiment to Nth embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0063] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0064] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A method for manufacturing high-density interconnect PCBs using a grouting process, characterized in that, The method includes the following steps: Obtain the board structure information and grouting area information of the high-density interconnect PCB, and determine the grouting shrinkage sensitive area based on the board structure information and the grouting area information; The shrinkage-sensitive area of ​​the grouting is subjected to a flow-blocking and flow-guiding treatment to form a flow-blocking and flow-guiding structure; Based on the aforementioned flow-guiding structure, differentiated grouting treatment is performed on the area to be grouted to form a grouting layer structure; The grouting layer structure is subjected to segmented temperature-controlled curing treatment to obtain a high-density interconnect PCB finished board.

2. The high-density interconnect PCB grouting manufacturing method as described in claim 1, characterized in that, The board surface structure information includes micro-hole distribution information, large-area copper layer distribution information, and device heat source distribution information; Identify areas sensitive to grout shrinkage, including: The micropore distribution information, the large-area copper layer distribution information, the device heat source distribution information, and the grouting area information are superimposed to determine the grouting area located in the micropore dense area, the large-area copper layer adjacent area, or the device heat source adjacent area as the grouting shrinkage sensitive area.

3. The high-density interconnect PCB grouting manufacturing method as described in claim 1, characterized in that, The flow-constriction and diversion process includes: A shallow groove structure extending along a predetermined stress-relieving direction is formed within the grouting shrinkage sensitive area; The shallow trench structure is formed on the insulating surface or non-conductive covering layer surface within the area to be grouted, and avoids conductive pads, exposed lines and functional openings. The shallow groove structure has a groove width of 40μm-120μm, a groove depth of 10μm-30μm, and a spacing of 0.3mm-1.0mm between adjacent shallow groove structures.

4. The high-density interconnect PCB grouting manufacturing method as described in claim 3, characterized in that, The preset stress relief direction is determined based on the micropore arrangement direction within the grouting shrinkage sensitive area and the heat flow direction from the device heat source to the large-area copper layer. When the angle between the micropore arrangement direction and the heat flow direction is less than 45°, the shallow groove structure is configured to extend along the micropore arrangement direction.

5. The high-density interconnect PCB grouting manufacturing method as described in claim 1, characterized in that, The differentiated grouting treatment includes: The first grouting treatment is performed on the grouting shrinkage sensitive area to form a first grouting layer; A second grouting treatment is performed on non-grouting shrinkage-sensitive areas to form a second grouting layer; The thickness of the first grouting layer is less than the thickness of the second grouting layer.

6. The high-density interconnect PCB grouting manufacturing method as described in claim 5, characterized in that, The thickness of the first grouting layer is 0.15mm-0.35mm, and the thickness of the second grouting layer is 0.30mm-0.70mm; A thickness transition zone is formed between the first grouting layer and the second grouting layer.

7. The high-density interconnect PCB grouting manufacturing method as described in claim 5, characterized in that, The differentiated grouting treatment also includes: Before the grouting material enters the grouting shrinkage sensitive area, the grouting shrinkage sensitive area is pre-wetted. The pre-wetting treatment uses a low-viscosity grouting material with a viscosity of 300 mPa·s-900 mPa·s and a pre-wetting time of 30 s-120 s.

8. The high-density interconnect PCB grouting manufacturing method as described in claim 1, characterized in that, The segmented temperature-controlled curing process includes: Keep the grouting material at 40℃-60℃ for 10min-30min to allow it to level and release residual gas. Pre-cur at 70℃-90℃ for 20-50 minutes; The grouting layer structure is formed by primary curing at 110℃-130℃ for 40-90 minutes.

9. The high-density interconnect PCB grouting manufacturing method as described in claim 1, characterized in that, After obtaining the high-density interconnect PCB finished board, the grouting shrinkage sensitive area is subjected to ultrasonic scanning or X-ray detection. When a continuous interface void with a length greater than 0.5 mm appears in the grouting shrinkage sensitive area, or an internal bubble with a diameter greater than 100 μm appears, the corresponding high-density interconnect PCB finished board will be judged as an abnormal finished board.

10. A high-density interconnect PCB grouting manufacturing system, characterized in that, The system includes: The first module is used to acquire the board structure information and the grouting area information of the high-density interconnect PCB, and to determine the grouting shrinkage sensitive area based on the board structure information and the grouting area information. The second module is used to perform a flow-blocking and flow-guiding treatment on the grouting shrinkage-sensitive area to form a flow-blocking and flow-guiding structure. The third module is used to perform differentiated grouting treatment on the area to be grouted based on the constriction and flow guiding structure, so as to form a grouting layer structure; The fourth module is used to perform segmented temperature-controlled curing treatment on the grouting layer structure to obtain a high-density interconnect PCB finished board.

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