A method for fabricating a high-order HDI stepped gold finger circuit board

Abstract

This invention relates to the field of PCB manufacturing technology, and in particular to a method for fabricating a high-order HDI stepped gold finger circuit board. The method for fabricating a high-order HDI stepped gold finger circuit board provided by this invention includes: sequentially fabricating an inner core board, a daughter board, and a mother board; in the process of fabricating the inner core board, after inner layer inspection, the board is sequentially baked, browned, baked again, and laminated; in the process of fabricating the daughter board, after laser drilling, plasma adhesive removal and blind via bottom inspection are sequentially performed, after through-hole electroplating, blind via inspection is performed, after daughter board inspection, HCT testing is performed, and after browning, the board is baked; in the process of fabricating the mother board, after laser drilling, plasma adhesive removal and blind via bottom inspection are sequentially performed, and after outer layer inspection, HCT testing is performed. This fabrication method improves the dimensional stability and reliability of the high-order HDI stepped gold finger circuit board.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing technology, and in particular to a method for preparing a high-order HDI stepped gold finger circuit board. Background Technology

[0002] High-order HDI stepped gold fingers are a special connection structure used in high-frequency, high-reliability electronic devices. Printed circuits are conductive patterns, including printed lines, printed components, or a combination of both, fabricated on an insulating substrate according to a predetermined design; the finished board made in this way is called a printed circuit board (PCB). High-order HDI stepped gold fingers are a key interconnect structure on PCBs.

[0003] High-order HDI stepped gold fingers are mainly used in the field of AI server accelerator cards. The design characteristics of the PCB board of the AI ​​accelerator card that carries the GPU are as follows: (1) High-order HDI design. The improvement of AI computing power requires more dense circuit patterns on the same size PCB, resulting in an increase in the HDI order and the total number of layers of the product; it poses challenges to the dimensional stability and reliability of the material under multiple pressing, and also poses challenges to the reliability of the laser blind hole multi-level stacked hole of the PCB and the alignment of the multi-level blind hole. (2) The AI ​​accelerator card retains the hot-swappable attribute of the PCIe gold fingers of conventional graphics card products. Since the gold finger insertion and removal requires a fixed board thickness, the board thickness requirement at the gold finger position is inconsistent with the overall board thickness of the product, which brings about the design of stepped gold fingers. The stepped gold fingers require the use of PCB peeling process, which further increases the complexity of its manufacturing. (3) AI servers require high-frequency and high-speed signal transmission and low signal loss, which means that the dielectric loss and other performance of copper-clad laminates need to be continuously improved. In terms of material selection, after the PCIe bus upgrade, the server requires CCL materials to reach very low loss and ultra-low loss levels, and such materials need to be processed with special process parameters.

[0004] In view of this, this invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for fabricating a high-order HDI stepped gold finger circuit board, which can successfully produce a high-order HDI stepped gold finger circuit board with excellent dimensional stability and reliability.

[0006] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0007] This invention provides a method for fabricating a high-order HDI stepped gold finger circuit board, comprising: sequentially fabricating an inner core board, fabricating a daughter board, and fabricating a mother board;

[0008] In the process of preparing the inner core board, after the inner layer inspection, the board is baked, browned, baked again, and pressed in sequence.

[0009] In the process of preparing the sub-board, after laser drilling, plasma desmearing and blind hole bottom inspection are performed in sequence; after hole filling electroplating, blind hole inspection is performed; after sub-board inspection, HCT test is performed; and after browning, board is baked.

[0010] In the process of preparing the motherboard, after laser drilling, plasma degumming and blind hole bottom inspection are performed in sequence; after hole filling electroplating, blind hole inspection is performed; and after outer layer inspection, HCT test is performed.

[0011] Furthermore, the method for fabricating the high-order HDI stepped gold finger circuit board includes: sequentially fabricating an inner core board, fabricating sub-board I, fabricating sub-board II, fabricating sub-board III, fabricating sub-board IV, and fabricating a motherboard;

[0012] The process for preparing the inner core board includes: sequentially performing material cutting, inner layer dry film, inner layer etching, inner layer inspection, board baking, browning, board baking and pressing;

[0013] The process for preparing sub-board I includes the following steps in sequence: target drilling, laser drilling, mechanical drilling, plasma adhesive removal, blind hole bottom inspection, copper plating, hole filling electroplating, blind hole inspection, resin plugging, ceramic grinding, sub-board dry film, acid etching, sub-board inspection, HCT testing, sub-board solder resist, sub-board wet film, sub-board dry film, sub-board development, gold finger plating, film removal, sub-board dry film, sub-board development, lead etching, film removal, high-temperature adhesive application, fast pressing, laser cutting, fast pressing, browning, board baking, and lamination.

[0014] The processes for preparing sub-board II, sub-board III, and sub-board IV include: sequentially performing target drilling, laser drilling, drilling of board edge holes, plasma adhesive removal, blind hole bottom inspection, copper plating, hole filling electroplating, blind hole inspection, sub-board dry film, acid etching, sub-board inspection, HCT testing, browning, board baking, and lamination.

[0015] The process for preparing the motherboard includes: sequentially performing target drilling, laser drilling, plasma adhesive removal, blind hole bottom inspection, copper plating, hole filling electroplating, blind hole inspection, copper reduction, target drilling, drilling, plasma adhesive removal, copper plating, electroplating, resin plugging, ceramic grinding, copper reduction, target drilling, drilling, plasma adhesive removal, copper plating, board surface electroplating, outer dry film, outer layer development, pattern electroplating, outer alkaline etching, outer layer inspection and HCT testing, solder resist, lettering, surface treatment, shaping, controlled depth milling, and finished product cleaning.

[0016] Furthermore, the resin material of the insulating layer in the high-order HDI stepped gold finger circuit board includes PPO.

[0017] Furthermore, it includes at least one of the following features (1) to (3);

[0018] (1) Before browning, the temperature of the baking plate is 170-190℃ and the time is 2-4h;

[0019] (2) After browning, the temperature of the baking plate is 115-125℃ and the time is 30-60min;

[0020] (3) After browning, the dwell time between the baking plate and the pressing is ≤24h.

[0021] Furthermore, the blind hole inspection is performed after the hole-filling electroplating to ensure that the depression value after hole-filling electroplating is ≤10μm.

[0022] Furthermore, a laser blind via is formed by laser drilling. The single-sided ring width between the laser blind via and the corresponding second outer copper pad is 2 to 3 mil, and the alignment offset between the corresponding second outer copper pad and the laser blind via does not exceed the single-sided ring width.

[0023] And / or, the alignment method of the laser drilling is as follows: positioning is achieved by using the board edge positioning hole, ablation is performed to create the target of the corresponding sub-outer layer of the laser blind hole, and alignment is achieved by grabbing the sub-outer layer target to realize the alignment between the laser blind hole and the corresponding sub-outer layer copper pad.

[0024] Furthermore, the alignment method for pattern exposure of the sub-board and the motherboard is as follows: alignment is performed using a combination target of one mechanical drill hole and 4 to 20 laser blind holes located around the mechanical drill hole. The 4 to 20 laser blind holes are made by laser drilling, and the mechanical drill hole is made by alignment using the target of each layer of drill. During line exposure, a CCD camera is used to capture the combination target of laser blind holes and mechanical drill holes for alignment, and algorithm processing is performed to compensate for matching.

[0025] Furthermore, the sub-plate I includes gold fingers; the manufacturing process of the gold fingers includes the following steps:

[0026] Copper leads are drawn at the gold-plated finger positions on sub-board I to connect the lines in the gold finger area to the copper on the board edge; solder mask is applied to the non-gold finger positions in the uncovered area of ​​sub-board I; wet film is applied or dry film is applied to the gold finger leads; then dry film is applied to the entire board surface, and after exposure and development, the gold-plated finger area is exposed; gold plating is applied to the gold finger positions, and after film removal, film is applied to the entire board surface, exposed, and developed to expose the gold finger leads; the gold finger leads are etched away to obtain the gold fingers;

[0027] Apply high-temperature adhesive to the area where the cover is removed. The high-temperature adhesive has two sides, A and B. Side A of the high-temperature adhesive includes PI adhesive, and side B includes adhesive components. Side B of the high-temperature adhesive is bonded to the gold fingers.

[0028] Furthermore, the high-temperature adhesive application process includes: attaching the B side of the high-temperature adhesive to the position of the gold finger, pressing quickly at 170-190°C for 1-3 minutes, then performing laser cutting, removing high-temperature adhesive waste, and pressing quickly at 170-190°C for 1-3 minutes.

[0029] And / or, in the process of preparing the mother plate, the controlled-depth milling includes: milling the uncovered area.

[0030] Furthermore, the high-order HDI stepped gold finger circuit board includes 10 to 30 layers of 3 to 10-step HDI stepped gold finger circuit boards.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] The high-order HDI stepped gold finger circuit board of the present invention produces circuit board products with excellent dimensional stability and overall reliability; good reliability of multi-order laser blind via stacking; good alignment and matching of multi-order laser blind vias and through holes; and the circuit board meets the requirements of stepped gold fingers. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the laser blind hole and its corresponding outermost copper pad of the present invention.

[0035] Figure 2 This is a schematic diagram illustrating the cumulative alignment deviation of the laser blind hole according to the present invention.

[0036] Figure 3 This is a schematic diagram showing a short circuit between the drilled hole and the inner copper layer of the motherboard of the present invention.

[0037] Figure 4 This describes the alignment method for pattern exposure of the daughter board and mother board in this invention.

[0038] Figure 5 This is a cross-sectional structural diagram of the high-order HDI stepped gold finger circuit board of Embodiment 1 of the present invention. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0040] The following is a detailed description of a method for fabricating a high-order HDI stepped gold finger circuit board according to an embodiment of the present invention.

[0041] In some embodiments of the present invention, a method for fabricating a high-order HDI stepped gold finger circuit board is provided, comprising: sequentially fabricating an inner core board, fabricating a sub-board, and fabricating a mother board;

[0042] In the process of preparing the inner core board, after the inner layer inspection, the board is baked, browned, baked again, and pressed in sequence.

[0043] In the process of preparing the sub-board, after laser drilling, plasma desmearing and blind hole bottom inspection are performed in sequence; after hole filling electroplating, blind hole inspection is performed; after sub-board inspection, HCT test is performed; and after browning, board is baked.

[0044] In the process of preparing the motherboard, after laser drilling, plasma desmearing and blind hole bottom inspection are performed in sequence. After hole filling electroplating, blind hole inspection is performed. After outer layer inspection, HCT test is performed.

[0045] The circuit board prepared by the method of the present invention for manufacturing a high-order HDI stepped gold finger circuit board has the following advantages:

[0046] The circuit board exhibits excellent dimensional stability and overall reliability.

[0047] The circuit board meets the reliability requirements for multi-level laser blind via stacking;

[0048] The circuit board exhibits good alignment and matching of multi-stage laser-guided blind vias and through-holes;

[0049] The circuit board meets the requirements for stepped gold fingers.

[0050] The insulating layer material in the high-end HDI stepped gold finger circuit board of the present invention is a high-speed material with ultra-low loss level. The resin system of this type of material is PPO, which requires matching specific process parameters and corresponding adhesive removal methods. Adhesive removal after drilling requires plasma adhesive removal, and traditional potassium permanganate adhesive removal is no longer applicable.

[0051] To ensure the dimensional stability of high-end HDI stepped gold finger circuit boards, a baking step is added to the inner core board manufacturing process after inner layer inspection. Since the copper foil is partially etched away after inner layer etching, the stress balance (warp and weft fiberglass stress) of the PCB is broken. The change in size requires the establishment of a new stress balance. Baking can accelerate this stress release process and improve the dimensional stability of the product.

[0052] Because the selected materials are high-speed materials with ultra-low loss ratings (such as materials with a loss factor Df≤0.008), the PPO resin system materials are prone to moisture absorption. In the preparation process of the inner core board and sub-board, the boards need to be baked to remove moisture before and after browning. Baking can prevent excessive moisture residue during the high-temperature and high-pressure pressing process. If water vapor cannot be effectively discharged, it will lead to white spots, delamination, air bubbles and voids, poor bonding force, and reliability risks such as delamination and board bursting of the product.

[0053] To ensure the reliability of multi-stage blind via stacking, this invention includes a blind via bottom inspection after each laser drilling. The bottom of the hole is inspected after plasma desmearing to ensure that there is no residual adhesive before proceeding to the next step of manufacturing. This is because residual adhesive at the bottom of the hole can cause blind via detachment defects, which can easily lead to separation at the copper boundary of the blind via during product use, resulting in product failure.

[0054] To ensure the reliability of multi-stage blind via stacking, a blind via inspection is set after the filling electroplating. If a large depression appears at the blind via, it will cause difficulties in the subsequent process, such as the subsequent laser drilling not being able to burn through, or the depression of the blind via accumulated in the subsequent electroplating filling.

[0055] To further ensure the reliability of multi-stage stacked blind vias, an HCT test is added after the outer layer inspection of each stage. HCT is a high current surge test, which is a test method for testing the reliability of blind via interconnects in HDI products. By adding this step to each stage of the blind via manufacturing process, the reliability of HDI blind via stacks can be verified.

[0056] In some embodiments of the present invention, the method for fabricating a high-order HDI stepped gold finger circuit board includes: sequentially fabricating an inner core board, fabricating sub-board I, fabricating sub-board II, fabricating sub-board III, fabricating sub-board IV, and fabricating a motherboard;

[0057] The process for preparing the inner core board includes: sequentially performing material cutting, inner layer dry film, inner layer etching, inner layer inspection, board baking, browning, board baking and lamination;

[0058] The process for preparing sub-board I includes the following steps in sequence: target drilling, laser drilling, mechanical drilling, plasma adhesive removal, blind hole bottom inspection, copper plating, hole filling electroplating, blind hole inspection, resin plugging, ceramic grinding, sub-board dry film, acid etching, sub-board inspection, HCT testing, sub-board solder mask, sub-board wet film, sub-board dry film, sub-board development, gold finger plating, film removal, sub-board dry film, sub-board development, lead etching, film removal, high-temperature adhesive application, fast pressing, laser cutting, fast pressing, browning, board baking, and lamination.

[0059] The processes for preparing sub-board II, sub-board III, and sub-board IV include: sequentially performing target drilling, laser drilling, drilling of board edge holes, plasma desmearing, blind hole bottom inspection, copper plating, hole filling electroplating, blind hole inspection, sub-board dry film, acid etching, sub-board inspection, HCT testing, browning, board baking, and lamination.

[0060] The process for preparing the motherboard includes: sequentially performing target drilling, laser drilling, plasma adhesive removal, blind hole bottom inspection, copper plating, hole filling electroplating, blind hole inspection, copper reduction, target drilling, drilling, plasma adhesive removal, copper plating, electroplating, resin plugging, ceramic grinding, copper reduction, target drilling, drilling, plasma adhesive removal, copper plating, board surface electroplating, outer dry film, outer layer development, pattern electroplating, outer alkaline etching, outer layer inspection, HCT testing, solder mask, lettering, surface treatment, shaping, controlled depth milling, and finished product cleaning.

[0061] In some embodiments of the present invention, the resin material of the insulating layer in the high-end HDI stepped gold finger circuit board includes PPO (epoxy polyphenylene oxide). The insulating layer material in the high-end HDI stepped gold finger circuit board of the present invention includes a high-speed material with ultra-low loss rating (such as a material with a loss factor Df ≤ 0.008). The resin system of this type of material is PPO, and corresponding bonding parameters, drilling parameters, and other process parameters need to be matched.

[0062] In some embodiments of the present invention, before browning, the temperature of the baking plate is 170-190°C and the time is 2-4 hours; typically, but not limitingly, for example, before browning, the temperature of the baking plate can be 170°C, 180°C, 190°C or any two of these, and the time can be 2 hours, 3 hours, 4 hours or any two of these.

[0063] In the preparation method of the high-order HDI stepped gold finger circuit board of the present invention, before browning, baking the board at 170-190°C for 2-4 hours can accelerate the stress release process and improve the dimensional stability of the product.

[0064] In some embodiments of the present invention, after browning, the temperature of the drying plate is 115-125°C and the time is 30-60 min; typically, but not limitingly, for example, after browning, the temperature of the drying plate is 120°C and the time can be 30 min, 40 min, 50 min, 60 min or any range between two of them.

[0065] In the preparation method of the high-order HDI stepped gold finger circuit board of the present invention, after browning, the board is baked at 120°C for 30 to 60 minutes to remove moisture, which is beneficial to the subsequent lamination.

[0066] In some embodiments of the present invention, the dwell time between the baking plate and the pressing after browning is ≤24h.

[0067] To further control the water absorption of the materials, the dwell time between baking the browning board and pressing is controlled within 24 hours to prevent the products from becoming damp due to prolonged exposure. Dehumidification treatment is also performed on materials such as prepregs.

[0068] In some embodiments of the present invention, blind hole inspection is performed after the hole-filling electroplating to ensure that the depression value after hole-filling electroplating is ≤10μm.

[0069] A blind hole inspection step is set after the hole filling electroplating to ensure that the depression value after the hole filling electroplating is ≤10μm, thereby ensuring that no large depressions are generated at the blind holes.

[0070] In some embodiments of the present invention, laser blind vias are formed by laser drilling. The single-sided ring width between the laser blind via and the corresponding second outer copper pad is 2 to 3 mil, and the alignment offset between the corresponding second outer copper pad and the laser blind via does not exceed the single-sided ring width.

[0071] In some embodiments of the present invention, the alignment method of laser drilling is as follows: positioning is achieved by using board edge positioning holes, ablation is performed to create a target corresponding to the outermost layer of the laser blind hole, and alignment is achieved by grabbing the target of the outermost layer, thereby realizing the alignment between the laser blind hole and the corresponding outermost layer copper pad.

[0072] There are difficulties in aligning multi-order blind holes: see [link / reference] Figure 1 This invention addresses the alignment between laser-drilled blind vias and their corresponding outermost copper pads. The single-sided ring width between the corresponding outermost copper pad and the laser-drilled blind via is 2-3 mil, and the alignment offset between the corresponding outermost copper pad and the laser-drilled blind via does not exceed the single-sided ring width. To meet this alignment requirement, the alignment method used in laser drilling is as follows: positioning is achieved using board-edge positioning holes, and a target corresponding to the outermost layer of the laser-drilled blind via is ablated. Alignment is then achieved by gripping the outermost target, thus aligning the laser-drilled blind via with the corresponding outermost copper pad. Simultaneously, the exposure of the subsequent sub-layer dry film of this laser-drilled blind via layer is also aligned using the board-edge laser-drilled blind via created in this laser drilling process.

[0073] In some embodiments of the present invention, the alignment method for pattern exposure of the sub-board and the motherboard is as follows: alignment is performed using a combination target of one mechanical drill hole and 4 to 20 laser blind holes located around the mechanical drill hole. The 4 to 20 laser blind holes are made by laser drilling, and the mechanical drill hole is made by alignment using the target of each layer of drill. During line exposure, a CCD camera is used to capture the combination target of laser blind holes and mechanical drill holes for alignment, and algorithm processing is performed to compensate for matching.

[0074] Alignment issues between laser-drilled blind vias, through-holes, and buried vias are common problems in multi-stage HDI. (See also...) Figure 2 and Figure 3 For multi-level HDI, the alignment of multi-level blind via stacking needs to be considered. If alignment deviations occur in each level of laser drilling, and the alignment holes used during daughterboard circuit exposure are only blind vias created by laser drilling, then the alignment deviations of the laser blind vias are likely to accumulate in the same direction. The more levels of laser blind via stacking, the larger the accumulated deviation value. Mechanical drilling of the daughterboard and motherboard can easily cause short circuits with the inner copper layers. To solve the above problems, for example, the alignment method of the daughterboard and motherboard during pattern exposure in this invention is as follows: Figure 4 The board edge alignment hole design shown uses a combination of 18 peripheral laser blind holes and 1 central mechanical drill hole as a target for comprehensive alignment. The 18 laser blind holes are made by laser drilling and have a high degree of alignment matching with the outermost layer. The central mechanical drill hole is made by alignment using a comprehensive target of drilling targets for each layer, and has an even higher degree of alignment matching with the mechanical drill hole. During circuit exposure, the CCD camera captures the laser blind holes and the mechanical drill hole, and after certain algorithm processing, it can compensate for the matching between the laser blind holes and through holes and buried holes. This alleviates the alignment deviation between the laser blind holes and through holes and buried holes.

[0075] In some embodiments of the present invention, the sub-plate I includes gold fingers; the preparation process of the gold fingers includes the following steps:

[0076] Copper leads are drawn at the gold-plated finger positions on sub-board I to connect the lines in the gold finger area to the copper on the board edge; solder mask is applied to the non-gold finger positions in the uncovered area of ​​sub-board I; wet film is applied or dry film is applied to the gold finger leads; then dry film is applied to the entire board surface, and after exposure and development, the gold-plated finger area is exposed; gold plating is applied to the gold finger positions, and after film removal, film is applied to the entire board surface, exposed, and developed to expose the gold finger leads; the gold finger leads are etched away to obtain the gold fingers;

[0077] Apply high-temperature adhesive to the area where the cover is removed. The high-temperature adhesive has two sides, A and B. Side A of the high-temperature adhesive includes PI adhesive, and side B includes adhesive components. Side B of the high-temperature adhesive is bonded to the gold fingers.

[0078] In some embodiments of the present invention, applying high-temperature adhesive to the opening position includes: attaching the B side of the high-temperature adhesive to the position of the gold finger, pressing quickly at 170-190°C for 1-3 minutes, then performing laser cutting, removing high-temperature adhesive waste, and pressing quickly at 170-190°C for 1-3 minutes.

[0079] In some embodiments of the present invention, the process of preparing the mother plate includes controlled-depth milling, which involves milling the area where the cover is to be removed.

[0080] The high-end HDI stepped gold finger circuit board features a special board thickness (1.57mm±0.13mm) for PCIe gold finger insertion and removal, requiring stepped gold fingers. Stepped gold fingers necessitate a PCB peeling process. The challenges include: the gold finger layer is an internal layer, requiring multiple lamination processes after lead electroplating on the daughterboard; ensuring no glue overflow at the gold finger location; and successfully completing the peeling process. The gold finger fabrication and uncovering process of this invention is as follows: First, copper leads are drawn at the gold finger locations on sub-board I to connect the lines in the gold finger area to the copper edge of the board, facilitating current transfer between the board edge and the gold finger location during electroplating. Before electroplating the gold fingers, solder mask is first applied to the non-gold finger locations in the uncovered area of ​​the sub-board layer where the gold fingers are located. After the solder mask is applied, an anti-plating effect is achieved. Simultaneously, wet film or dry film treatment is applied to the gold finger leads to prevent gold plating (the leads will be etched away later, and gold plating would inhibit etching). Finally, dry film is applied to the entire board surface. After exposure and development, the area requiring gold finger plating is exposed. The finger area is gold-plated. After gold plating, the film is removed, including the wet or dry film at the lead wires and the dry film on the entire board surface. After removal, the entire board surface is laminated, exposed, and developed to expose the gold finger lead wires. The lead wires are then etched away, resulting in the gold fingers. After the gold fingers are made, the areas where the cover needs to be removed are treated with high-temperature adhesive. The high-temperature adhesive prevents adhesive overflow during the lamination process. Specifically, this high-temperature adhesive has an A side and a B side. Under high temperature and high pressure lamination conditions, the PI adhesive contained in the A side can polymerize tightly with the resin, while the B side is partially bonded to the gold fingers. However, at room temperature, the adhesion between the B side and the gold fingers decreases, making it easier to remove the cover and forming a stepped shape. The high-temperature adhesive prevents resin from flowing onto the gold fingers and also prevents the chemicals from the browning process before lamination from seeping into the gold finger area. It can also withstand multiple laminations.

[0081] The process of applying high-temperature adhesive is as follows: After attaching the B side of the high-temperature adhesive to the gold finger position, it is placed in a high-speed press for high-speed pressing. High-speed pressing can increase the adhesion between the high-temperature adhesive and the gold finger. Then, laser cutting is performed to make the corresponding shape at the corresponding position. After removing the waste of high-temperature adhesive, it is pressed again to ensure that the high-temperature adhesive and the gold finger are tightly bonded. At this point, the application of high-temperature adhesive is completed.

[0082] In the motherboard manufacturing process, the area to be uncovered is milled to a certain depth through controlled depth milling. The presence of this high-temperature adhesive makes uncovering easier, and the final uncovered area forms a stepped gold finger.

[0083] In some embodiments of the present invention, the high-order HDI stepped gold finger circuit board includes 10 to 30 layers of 3 to 10-step HDI stepped gold finger circuit boards.

[0084] Example 1

[0085] See Figure 5 The 18-layer 6-step HDI stepped gold finger circuit board provided in this embodiment includes 3 inner core boards and 3 inner core boards that are first laminated into a sub-board I, second laminated into a sub-board II, third laminated into a sub-board III, fourth laminated into a sub-board IV, and fifth laminated into a mother board; wherein, the insulating layer material in the circuit board includes a material with a loss factor Df≤0.008, and the resin system of the material is PPO;

[0086] The preparation method includes: sequentially preparing the inner core board, preparing sub-board I, preparing sub-board II, preparing sub-board III, preparing sub-board IV, and preparing the mother board;

[0087] The process for preparing the inner core board includes: sequentially performing material cutting, inner layer dry film, inner layer etching, inner layer inspection, board baking, browning, board baking and lamination;

[0088] The specific steps include: after the inner core board is cut to the corresponding size, it is laminated, exposed, and etched to obtain the inner circuit pattern. After the inner layer is inspected, it is baked at 180℃ for 2 hours, browned, baked at 120℃ for 30 minutes, and then pressed within 24 hours; the prepreg is dehumidified in the process of preparing the inner core board.

[0089] The process for preparing sub-board I (the layer where the gold fingers are located) includes: target drilling, laser drilling, mechanical drilling, plasma adhesive removal, blind hole bottom inspection, copper plating, hole filling electroplating, blind hole inspection, resin plugging, ceramic grinding, sub-board dry film, acid etching, sub-board inspection, HCT testing, sub-board solder mask, sub-board wet film, sub-board dry film, sub-board development, gold finger plating, film removal, sub-board dry film, sub-board development, lead etching, film removal, high-temperature adhesive application, fast pressing, laser cutting, fast pressing, browning, board baking and lamination;

[0090] The specific steps include: after laminating the inner core board, prepreg, and copper foil, drilling is performed on the target, followed by laser drilling to create laser blind holes and mechanical drilling to create mechanical buried holes; see [link to relevant documentation]. Figure 1For the alignment between the laser-drilled blind via and its corresponding outermost copper pad, the single-sided ring width between the copper pad and the laser-drilled blind via is 2 mil, and the alignment offset between the copper pad and the laser-drilled blind via does not exceed the single-sided ring width (2 mil). The alignment method for laser drilling is to use the board edge positioning hole for positioning, ablate the target corresponding to the laser-drilled blind via in this layer, and use the method of grabbing the outermost target to align the laser-drilled blind via with the corresponding copper pad. At the same time, the exposure of the dry film of the subsequent sub-board layer of this laser-drilled blind via layer is also aligned using the board edge laser-drilled blind via created in this laser drilling. Sub-board I includes laser-drilled blind vias and mechanically buried vias. The pattern exposure of the sub-board... The alignment method for optical exposure is to use a combination of 18 peripheral laser blind holes and 1 central mechanical drill hole as a target for alignment. The 18 laser blind holes are made by laser drilling and have a high degree of alignment matching with the outermost layer. The central mechanical drill hole is made by alignment using a comprehensive target of drilling targets for each layer, and has an even higher degree of alignment matching with the mechanical drill hole. During line exposure, the CCD camera captures the laser blind holes and the mechanical drill hole, and after certain algorithm processing, it can compensate for the matching between the laser blind holes and the mechanical through holes and mechanical buried holes. This alleviates the alignment deviation between the laser blind holes and the mechanical through holes and mechanical buried holes.

[0091] After mechanical drilling is completed, plasma degumming is performed to clean the residual adhesive inside the hole.

[0092] After plasma desmearing, a blind hole bottom inspection is performed. The bottom of the hole is inspected to ensure that there is no residual adhesive before proceeding to the next step.

[0093] After the blind hole bottom inspection, copper plating and electroplating are performed in sequence. Laser blind holes are filled with copper, and mechanically drilled holes are electroplated with copper.

[0094] After electroplating and filling the holes, blind hole inspection is performed to ensure that the depression value after electroplating is ≤10μm.

[0095] After blind via inspection, resin plugging, ceramic grinding plate and circuit pattern fabrication of sub-board I are performed on the mechanical buried vias. Since sub-board I is the layer where the gold fingers are located, the gold fingers also need to be fabricated. Therefore, gold finger electroplating leads are set on the circuit layer of sub-board I. Specifically, copper leads are pulled at the positions where gold fingers need to be plated on sub-board I, so that the circuit in the gold finger area is connected to the copper on the board edge, which facilitates the connection between the board edge and the gold finger position during the electroplating of the gold fingers. After film application, exposure, development and etching, the circuit pattern of sub-board I is obtained.

[0096] After the circuit pattern of sub-board I is inspected, it undergoes HCT testing (high current surge test).

[0097] Subboard I is the layer where the gold fingers are located. The gold finger preparation process includes: drawing copper leads at the locations of the gold fingers to be plated on subboard I, connecting the lines in the gold finger area to the copper on the board edge, facilitating the connection between the board edge and the gold finger location during electroplating; before electroplating the gold fingers, firstly, solder mask is applied to the non-gold finger locations in the areas to be uncovered on the subboard layer where the gold fingers are located. After the solder mask is made, an anti-plating effect is achieved. At the same time, wet film or dry film treatment is also required for the gold finger leads to prevent gold plating on the leads (the leads need to be etched away later, and gold plating will inhibit etching); finally, dry film treatment is performed on the entire board surface, and after exposure and development, the areas to be plated with gold fingers are exposed. Gold plating is then performed on the gold finger locations. After gold plating, the film is removed. This film removal includes the wet or dry film at the leads and the dry film on the entire board surface. After film removal, the entire board surface is then covered with film, exposed, and developed to expose the gold finger leads. The leads are then etched away to obtain the gold fingers.

[0098] After the gold fingers are made, high-temperature adhesive is applied to the areas where the cap needs to be removed. The high-temperature adhesive includes side A and side B. Under high temperature and high pressure, the PI glue contained in side A can polymerize tightly with the resin. Side B contains adhesive components. Side B is bonded to the gold fingers, but the adhesion between side B and the gold fingers will decrease under room temperature conditions, which makes it easier to remove the cap and form a stepped shape.

[0099] The high-temperature adhesive application process includes: attaching the B side of the high-temperature adhesive to the gold finger position, pressing it in a high-speed press (180℃, 2min), then laser cutting to create the corresponding shape at the corresponding position, removing the high-temperature adhesive waste, and pressing it again (180℃, 2min).

[0100] Finally, the following steps were performed: browning, baking at 120℃ for 30 minutes, and pressing.

[0101] The process for preparing sub-board II includes: target drilling, laser drilling, drilling of board edge holes, plasma desmearing, blind hole bottom inspection, copper plating, hole filling electroplating, blind hole inspection, sub-board dry film, acid etching, sub-board inspection, HCT test, browning, board baking and lamination.

[0102] The specific steps include: pressing sub-board I with prepreg and copper foil to obtain sub-board II; after drilling the target on sub-board II, laser drilling and edge drilling are performed sequentially. The purpose of drilling the edge holes is to... Figure 4 The mechanically drilled holes in the alignment target shown are used for alignment during pattern exposure of sub-board II;

[0103] Then, after plasma desmearing of the laser blind vias, the bottom of the blind vias is inspected. After copper plating is completed, the vias are filled with electroplating. The blind vias are inspected to ensure that the depression value after filling the vias is ≤10μm. Then, the pattern of sub-board II is made, specifically by film application, exposure, development, and etching to obtain the pattern circuit layer of sub-board II. After inspection, HCT test is performed, followed by browning, baking at 120℃ for 30 minutes, and lamination.

[0104] The fabrication processes for sub-plates III and IV are the same as those for sub-plate II;

[0105] The process for preparing the motherboard includes: sequentially performing target drilling, laser drilling, plasma adhesive removal, blind hole bottom inspection, copper plating, hole filling electroplating, blind hole inspection, copper reduction, target drilling, drilling, plasma adhesive removal, copper plating, electroplating, resin plugging, ceramic grinding, copper reduction, target drilling, drilling, plasma adhesive removal, copper plating, board surface electroplating, outer dry film, outer layer development, pattern electroplating, outer alkaline etching, outer layer inspection, HCT testing, solder mask, lettering, surface treatment, shaping, controlled depth milling, and finished product cleaning.

[0106] The specific steps include: After laminating the sub-board IV with the prepreg and copper foil, a master board is obtained. The master board has both laser-drilled blind holes and mechanical through holes (the alignment method during pattern exposure of the master board is the same as that of the sub-board); after drilling the target on the master board, laser drilling, plasma desmearing, blind hole bottom inspection, copper plating, and hole-filling electroplating are performed. Afterward, blind hole inspection is conducted to ensure that the depression value after hole-filling electroplating is ≤10μm. After the laser-drilled blind holes are completed, mechanical through holes are then fabricated. First, through holes requiring resin plugging are drilled, followed by plasma desmearing and copper plating. Then, resin plugging, ceramic grinding, and copper reduction are performed to obtain the resin-plugged through holes. After drilling holes, non-resin-filled through holes are drilled. Similarly, target drilling, hole drilling, plasma adhesive removal, blind hole bottom inspection, copper plating, and electroplating are performed. Then, the outer layer circuit pattern is made. Specifically, the outer layer dry film is applied, and after development, the pattern is electroplated and the outer layer alkaline etching is performed to obtain the outer layer circuit pattern. After inspection, HCT testing is performed. Solder mask and characters are made, surface treatment is performed, and after shaping, controlled depth milling is performed (controlled depth milling refers to the process of removing the cover at the gold finger position, and the position that needs to be removed is cut to a certain depth). After the finished product is cleaned, an 18-layer 6-step HDI stepped gold finger circuit board is obtained.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for manufacturing a high-order HDI stepped gold finger circuit board, characterized in that, The method comprises the following steps: Preparation of inner core board, preparation of sub-board I, preparation of sub-board II, preparation of sub-board III, preparation of sub-board IV and preparation of master board are sequentially performed; The preparation of inner core board comprises the following steps: cutting, inner layer dry film, inner layer etching, inner layer inspection, baking, brown, baking and pressing are sequentially performed; The preparation of sub-board I comprises the following steps: drilling target, laser drilling, mechanical drilling, plasma degreasing, blind hole bottom inspection, copper deposition, hole filling plating, blind hole inspection, resin plug hole, ceramic grinding plate, sub-board dry film, acid etching, sub-board inspection, HCT test, sub-board solder mask, sub-board wet film, sub-board dry film, sub-board development, gold plating finger, film stripping, sub-board dry film, sub-board development, etching lead, film stripping, high-temperature adhesive, fast pressing, laser cutting, fast pressing, brown, baking and pressing are sequentially performed; The preparation of sub-board II, the preparation of sub-board III and the preparation of sub-board IV comprises the following steps: drilling target, laser drilling, drilling edge hole, plasma degreasing, blind hole bottom inspection, copper deposition, hole filling plating, blind hole inspection, sub-board dry film, acid etching, sub-board inspection, HCT test, brown, baking and pressing are sequentially performed; The preparation of master board comprises the following steps: drilling target, laser drilling, plasma degreasing, blind hole bottom inspection, copper deposition, hole filling plating, blind hole inspection, copper reduction, drilling target, drilling hole, plasma degreasing, copper deposition, plating, resin plug hole, ceramic grinding plate, copper reduction, drilling target, drilling hole, plasma degreasing, copper deposition, surface plating, outer layer dry film, outer layer development, pattern plating, outer layer alkaline etching, outer layer inspection, HCT test, solder mask, character, surface treatment, molding, depth control milling and finished product cleaning are sequentially performed; The alignment mode during the pattern exposure of the sub-boards and the master board is that a combined target of 1 mechanical drilling hole and 4-20 laser blind holes is used for alignment, the 4-20 laser blind holes are formed by laser drilling, the mechanical drilling hole is formed by aligning the target of drilling target at each level, a CCD camera is used to capture the combined target of the laser blind hole and the mechanical drilling hole for alignment during line exposure, and algorithm processing is performed to compensate and match.

2. The method of claim 1, wherein the method further comprises: The resin material of the insulating layer in the high-order HDI stepped gold finger circuit board comprises PPO.

3. The method of claim 1, wherein the method further comprises: At least one of the following features (1) to (3) is included; (1) In the preparation of the inner core board, the temperature of the baking plate is 170-190°C and the time is 2-4h before the brown; (2) In the preparation of the inner core board, the temperature of the baking plate is 115-125°C and the time is 30-60min after the brown; (3) In the preparation of the inner core board, the residence time between the baking and the pressing is ≤24h after the brown.

4. The method of claim 1, wherein the method further comprises: The blind hole inspection is performed after the hole filling plating, so that the recess value after the hole filling plating is ≤10µm.

5. The method of claim 1, wherein the method further comprises: The laser blind hole is formed by the laser drilling, the single-side ring width between the laser blind hole and the corresponding secondary outer copper pad is 2-3mil, and the alignment offset between the corresponding secondary outer copper pad and the laser blind hole does not exceed the single-side ring width; And / or, the laser drilling alignment mode is: using plate edge positioning hole positioning, ablation out of laser blind hole corresponding secondary outer layer target, using grabbing secondary outer layer target mode alignment, realizing the alignment between the laser blind hole and the corresponding secondary outer layer copper pad.

6. The method of claim 1, wherein the method further comprises: The sub-board I includes a gold finger; the preparation process of the gold finger includes the following steps: Copper leads are pulled at the gold finger plated position of the sub-board I, the circuit of the gold finger area is connected with the plate edge copper, and the non-gold finger position of the cover stripping area of the sub-board I is subjected to solder mask printing; the gold finger lead is subjected to wet film or dry film covering treatment, then the sub-board is subjected to dry film pasting treatment on the whole plate surface, and after exposure and development, the gold finger plated area is exposed; the gold finger position is subjected to gold plating treatment, after film removal, the whole plate surface is subjected to film pasting, exposure and development, the gold finger lead is exposed, the gold finger lead is etched and removed, and the gold finger is obtained; The cover stripping position is subjected to high-temperature glue pasting treatment, the high-temperature glue includes an A surface and a B surface, the A surface of the high-temperature glue includes PI glue, the B surface includes glue components, and the B surface of the high-temperature glue is bonded with the gold finger.

7. The method of claim 6, wherein the method further comprises: The high-temperature glue pasting treatment includes: after the B surface of the high-temperature glue is pasted with the position of the gold finger, fast pressing is performed at 170-190 DEG C for 1-3 min, then laser cutting is performed, high-temperature glue waste is removed, and fast pressing is performed at 170-190 DEG C for 1-3 min after the laser cutting; And / or, in the process of preparing the mother board, the depth control milling includes: opening the cover stripping position.

8. The method of claim 7, wherein the method further comprises: The high-order HDI step gold finger circuit board includes 10-30 layers of 3-10 order HDI step gold finger circuit boards.

Images