Processing method of second-order special blind slot printed board

Abstract

The invention discloses a method for processing a second-order special blind slot printed board. The method comprises the following steps: a step of preparing a blocking adhesive before lamination: attaching a PI adhesive tape to a preset position of a to-be-processed area of the printed board before lamination; a pressing step: overlapping and pressing the inner-layer core plate and the prepreg; a first-order blind groove uncovering step: processing a first-order blind groove at a preset position of the printed board by adopting a mechanical depth-controlled milling process, and removing the PI adhesive tape to expose an area needing to be reserved at the bottom of the blind groove; a first-order blind groove dispensing step: after uncovering is completed, liquid glue is filled into the first-order blind groove by adopting dispensing equipment, and the glue forms an isolation layer on the side wall of the blind groove and is cured so as to prevent a metal layer from being deposited on the side wall of the first-order blind groove in a subsequent copper deposition process and provide support for a subsequent drilling process; a drilling step: drilling a through hole in the bottom of the first-order blind groove; a copper deposition step: performing copper deposition treatment on the through hole to form a plated-through hole wall; and a blind groove glue taking step: removing the cured glue in the first-order blind groove.

Description

Technical Field

[0001] This invention relates to the field of PCB processing technology, and in particular to a method for processing second-order special blind slot printed circuit boards. Background Technology

[0002] As electronic devices evolve towards miniaturization, high density, and high frequency, the design and manufacturing of printed circuit boards (PCBs) face increasingly higher integration requirements. To meet the needs of embedded component mounting, precise positioning, and signal shielding, blind slot structures are widely used in PCB design. A blind slot is a recessed structure that extends inward from only one surface of the circuit board but does not penetrate the entire thickness of the board, effectively improving space utilization.

[0003] In some highly integrated products, a more complex type of printed circuit board (PCB) called a "second-order special blind slot" has emerged. This type of PCB typically includes blind slot structures at varying depths. For example, a first-order blind slot is formed on the substrate surface, while a second-order blind slot with a depth less than the first-order blind slot is formed in the edge region. The bottom of the first-order blind slot also features metallized vias for interlayer connections. This complex stacked structure places extremely high demands on the manufacturing process.

[0004] Currently, for PCBs with complex blind slot structures, the traditional mainstream manufacturing processes are either slotting the target layer first and then laminating, or laminating first and then slotting. Both of these traditional processes are prone to quality problems such as glue overflow and delamination during lamination.

[0005] On the other hand, for structures like first-order blind trenches that require bottom-metallized through-holes but retain non-metallized sidewalls, traditional processes struggle to effectively prevent copper plating from depositing a metal layer on the sidewalls of the blind trench while simultaneously achieving bottom-metallization, leading to unexpected sidewall metallization. Furthermore, if a metallization-then-capping sequence is adopted, the mechanical milling force during capping can easily cause microcracks or even tearing in the already completed copper layer at the hole opening. These intertwined problems have made it difficult to improve the processing yield of first-order blind trenches in the long term. Summary of the Invention

[0006] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a second-order special blind slot printed circuit board processing method, which can avoid the quality problems of blind slot glue overflow and delamination, and improve the yield rate.

[0007] According to an embodiment of the present invention, a method for processing a second-order special blind slot printed circuit board includes a first-order blind slot on the substrate surface of the second-order special blind slot printed circuit board and a second-order blind slot with a depth different from the first-order blind slot. An isolation ring is provided at the bottom of the first-order blind slot, and the bottom of the first-order blind slot has a non-blocking metallized through hole. The sidewall of the first-order blind slot is in a non-metallized state. The processing method includes the following steps: Preparing adhesive barrier before lamination: Before the lamination process, attach PI tape to the preset position of the area to be processed on the printed circuit board. The size of the PI tape is not greater than the design size of the first-order blind groove. Lamination step: The inner core board and the prepreg are stacked and laminated to form a multilayer printed circuit board substrate; First-order blind slot opening steps: The first-order blind slot is machined at a predetermined position on the printed circuit board using mechanical depth control milling process, and the PI tape is removed to expose the area to be retained at the bottom of the blind slot; First-order blind slot dispensing step: After the cover is opened, liquid adhesive is filled into the first-order blind slot using dispensing equipment. The adhesive forms an isolation layer on the side wall of the blind slot and cures the adhesive to prevent the subsequent copper plating process from depositing a metal layer on the side wall of the first-order blind slot and to provide support for the subsequent drilling process. Drilling steps: Drill a through hole at the bottom of the first-stage blind groove; Plating copper step: Plating copper is applied to the through holes to form metallized hole walls; Blind groove adhesive removal step: Remove the cured adhesive from the first-stage blind groove.

[0008] It has at least the following beneficial effects: By placing PI tape 50 at the target depth of the groove before lamination, it can effectively prevent the prepreg from flowing into the first-order blind groove 10 during lamination and capping; after capping and before drilling, the adhesive is applied, allowing the adhesive to play two roles simultaneously: firstly, to form an isolation layer on the sidewall to prevent subsequent copper deposition on the sidewall; secondly, to provide structural support for subsequent drilling; drilling after adhesive application avoids the risk of hole tearing caused by drilling before capping in traditional processes. The requirement for non-metallization of the sidewall, combined with the adhesive isolation layer, allows for precise control of the sidewall state through physical blocking.

[0009] According to some embodiments of the present invention, in the pre-pressing adhesive preparation step, the application of the PI tape specifically includes: applying the entire PI tape to the area to be processed; and using laser cutting to ensure that the tape size is not larger than the design size of the first-order blind groove, so as to form a reserved gap.

[0010] According to some embodiments of the present invention, in the first-order blind groove opening step, after removing the PI tape, any trace amount of excess adhesive that may exist in the reserved gap is removed by manual repair.

[0011] According to some embodiments of the present invention, the adhesive in the first-order blind slot dispensing step forms a physical isolation layer after curing, which prevents the copper plating solution from depositing a metal layer on the sidewall of the blind slot in the copper plating step, thus ensuring that the sidewall of the blind slot remains in a non-metallic state.

[0012] According to some embodiments of the present invention, the drilling step is performed after the first-order blind slot dispensing step. The cured adhesive provides structural support for the drilling and absorbs the stress that may remain from the capping step, preventing microcracks or tearing of the copper layer at the opening of the metallized through hole.

[0013] According to some embodiments of the present invention, the blind groove adhesive removal step specifically includes: using a pad to protect the printed circuit board, exposing the blind groove location area, and removing the cured adhesive in the first-order blind groove by physical manual peeling.

[0014] According to some embodiments of the present invention, the depth ratio of the first-order blind groove is greater than 1:1, that is, the depth of the blind groove is greater than its opening width.

[0015] According to some embodiments of the present invention, after the blind groove adhesive removal step, the following steps are further included: Full-board copper plating process: The entire printed circuit board is copper plated. External light imaging steps: Create outer layer circuit patterns on the surface of the printed circuit board; Pattern plating steps: Thicken the outer layer circuit pattern with electroplating; Alkaline etching step: Etching removes excess copper layer to form outer layer circuitry; Steps for fabricating the isolation ring pattern: The required circuit pattern is fabricated at the bottom of the first-order blind slot using a laser soldering process. The second-order blind groove processing steps are as follows: A composite process combining mechanical depth-controlled milling and laser blind groove is used to process the second-order blind groove in the edge area of ​​the plate.

[0016] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a schematic diagram of the structure after the pressing step in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure after the first-order blind groove opening step in an embodiment of the present invention (PI tape not removed). Figure 3 This is a schematic diagram of the structure after the first-order blind groove dispensing step in an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure after the drilling step in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure after the copper plating step in an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure after the blind groove adhesive removal step in an embodiment of the present invention; Figure 7 This is a schematic diagram of the structure after the alkaline etching step in an embodiment of the present invention; Figure 8 This is a schematic diagram of the structure after the isolation ring pattern fabrication steps in an embodiment of the present invention; Figure 9 This is a schematic diagram of the structure after mechanical deep milling in the second-order blind groove machining step of the present invention; Figure 10 This is a schematic diagram of the structure after laser blind slot processing in the second-order blind slot processing step of the present invention.

[0018] Reference numerals: 10 for first-order blind groove, 20 for second-order blind groove, 30 for isolation ring, 40 for metallized through hole, and 50 for PI tape. Detailed Implementation

[0019] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0020] In the description of this invention, the use of "first" and "second" is for the purpose of distinguishing technical features only, and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.

[0021] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0022] Reference Figures 1 to 10 This invention discloses a method for processing a second-order special blind slot printed circuit board, wherein the second-order special blind slot printed circuit board has a first-order blind slot 10 on the substrate surface and a second-order blind slot 20 with a different depth than the first-order blind slot 10. An isolation ring 30 is provided at the bottom of the first-order blind slot 10, and the bottom of the first-order blind slot 10 has a non-pluggable metallized through-hole 40. The sidewalls of the first-order blind slot 10 are non-metallized.

[0023] It should be noted that in some embodiments of the present invention, the two sides of the second-order blind groove 20 are the outer edges of the substrate. The substrates on both sides of the second-order blind groove 20 will be removed in subsequent processes, and the bottom of the second-order blind groove 20 will protrude from the board surface to form an island blind groove.

[0024] The processing method includes the following steps: Preparing the adhesive barrier before lamination: Before the lamination process, attach PI tape 50 to the preset position of the area to be processed on the printed circuit board. The size of PI tape 50 should not be larger than the design size of the first-order blind groove 10. Lamination step: The inner core board and the prepreg are stacked and laminated to form a multilayer printed circuit board substrate; Steps for opening a first-order blind slot: Using mechanical depth-controlled milling, a first-order blind slot 10 is machined at a predetermined position on the printed circuit board, and the PI tape 50 is removed to expose the area to be retained at the bottom of the blind slot. First-stage blind trench dispensing step: After opening the cover, use dispensing equipment to fill the first-stage blind trench 10 with liquid adhesive. The adhesive forms an isolation layer on the side wall of the blind trench and cures the adhesive to prevent the subsequent copper plating process from depositing a metal layer on the side wall of the first-stage blind trench and to provide support for the subsequent drilling process. Drilling steps: Drill a through hole at the bottom of the first-stage blind groove 10; Plating copper: Plating copper is applied to the through holes to form metallized hole walls; Blind groove adhesive removal steps: Remove the cured adhesive from the first-stage blind groove 10.

[0025] Understandably, placing PI tape 50 at the target depth of the groove before lamination effectively prevents the prepreg from flowing into the first-order blind groove 10 during lamination and capping. Applying adhesive after capping and before drilling allows the adhesive to serve two purposes: firstly, it forms an isolation layer on the sidewall to prevent subsequent copper deposition; secondly, it provides structural support for subsequent drilling. Drilling after adhesive application avoids the risk of hole tearing caused by drilling before capping in traditional processes. The requirement for non-metallization of the sidewall, combined with the adhesive isolation layer, precisely controls the sidewall condition through physical blocking.

[0026] Furthermore, in the pre-pressing adhesive preparation step, the application of PI tape 50 specifically includes: applying the entire PI tape 50 to the area to be processed; and using laser cutting to ensure that the tape is no larger than or less than the design size of the first-order blind groove 10, so as to form a reserved gap.

[0027] A laser-cut PI tape with a size no larger than the first-order blind groove of 10 is used to create a pre-reserved gap. During the pressing process, the molten resin can flow orderly along the pre-reserved gap, avoiding resin accumulation at the edge of the tape and the formation of large pieces of overflow. The small amount of overflow formed by the pre-reserved gap is evenly distributed and its position is controllable, making it easy to remove manually later, avoiding the trouble of cleaning overflow with special equipment in traditional processes.

[0028] Furthermore, in the first-stage blind groove 10 opening step, after removing the PI tape 50, any trace amounts of excess adhesive that may exist in the reserved gap are removed manually.

[0029] Furthermore, the adhesive in the first-stage blind trench 10-dot adhesive step forms a physical isolation layer after curing, which prevents the copper plating solution from depositing a metal layer on the sidewall of the blind trench during the copper plating step, ensuring that the sidewall of the blind trench remains in a non-metallic state.

[0030] After the adhesive cures, it forms a physical isolation layer that prevents the copper plating solution from depositing a metal layer on the sidewalls of the blind tank during the copper plating process, ensuring that the sidewalls remain non-metallic. This physical isolation effectively solves the technical challenge of "difficulty in preventing metal deposition on the sidewalls while simultaneously achieving metallization of the bottom through-holes," ensuring the product fully complies with design specifications. If chemical methods (such as selective copper plating solutions) are used to control sidewall metallization, it may affect other areas or introduce new sources of contamination. This solution uses physical isolation, which is safe and reliable and does not affect other processes. The isolation layer formed after the adhesive cures remains stable in the chemical solutions used in the copper plating process, without dissolving or peeling off, ensuring the reliability of the protective effect.

[0031] Furthermore, the drilling step is performed after the first-order blind groove 10-dot adhesive step. The cured adhesive provides structural support for the drilling and absorbs the stress that may remain from the capping step, preventing microcracks or tearing of the copper layer at the opening of the metallized through hole.

[0032] Understandably, the cured adhesive provides structural support for the drilling and absorbs any residual stress that may have been generated during the capping process, preventing microcracks or tearing of the copper layer at the opening of the metallized through-hole.

[0033] Furthermore, the blind groove adhesive removal step specifically includes: using a pad to protect the printed circuit board, exposing the blind groove location area, and removing the cured adhesive in the first-order blind groove by physical manual peeling.

[0034] The use of a protective pad prevents scratches or contamination from tools or fingers touching the board surface during manual operation, ensuring the integrity of the printed circuit board surface. The manual peeling method is highly flexible and can adapt to blind grooves of various shapes and sizes. In particular, for blind grooves with irregular shapes, mechanical methods are difficult to completely remove them, while manual methods can achieve thorough cleaning. If chemical dissolution is used to remove glue, it may cause corrosion to the bottom or sidewalls of the blind groove. The physical manual peeling method is safe and harmless.

[0035] Furthermore, the depth ratio of the first-order blind groove 10 is greater than 1:1, that is, the depth of the blind groove is greater than its opening width.

[0036] Understandably, for deep blind slots, the problems of glue overflow, sidewall metallization control, and orifice cracking are more prominent in traditional processes.

[0037] Furthermore, after the blind groove adhesive removal step, the following steps are also included: Full-board copper plating process: The entire printed circuit board is copper plated. External light imaging steps: Create outer layer circuit patterns on the surface of the printed circuit board; Pattern plating steps: Thicken the outer layer circuit pattern with electroplating; Alkaline etching step: Etching removes excess copper layer to form outer layer circuitry; Steps for fabricating the isolation ring pattern: The required circuit pattern is fabricated at the bottom of the first-order blind slot 10 using a laser soldering process. The second-order blind groove processing steps are as follows: A composite process combining mechanical depth control milling and laser blind groove is used to process a second-order blind groove 20 in the edge area of ​​the plate.

[0038] Understandably, the first-order blind trench 10 has a relatively large depth (depth ratio > 1:1). When using traditional etching processes to fabricate the bottom circuitry, the flow and exchange of the etching solution are restricted within the narrow, deep blind trench, easily leading to over-etching or incomplete etching of the circuitry, failing to meet high precision requirements. Laser tinning, a non-contact processing method, is not limited by the depth and shape of the blind trench, enabling precise patterned deposition within a narrow space, completely solving this technological challenge. Laser tinning utilizes the thermal effect of lasers to selectively deposit tin material in the areas where circuitry needs to be formed. The deposition location is precisely controllable, and linewidth and spacing can achieve micron-level precision. Compared to the "subtractive" processing of traditional etching, laser tinning is an "additive" process, with high material utilization and no impact on non-patterned areas.

[0039] In the machining of second-order blind grooves, mechanical deep milling can quickly remove most of the dielectric material, offering high processing efficiency and suitability for mass production. Laser blind groove machining, on the other hand, is responsible for the final finishing, ensuring the contour accuracy and sidewall quality of the blind groove. The combination of these two methods avoids the drawbacks of sacrificing precision for efficiency in mechanical machining alone, and also avoids the inefficiency of sacrificing precision for precision in laser machining alone, achieving a harmonious balance between efficiency and precision. Laser blind groove machining features extremely short pulse durations (picoseconds), with energy instantly focused on a micro-area of ​​the material. Heat is absorbed before it can diffuse, resulting in material ablation—a typical "cold processing" method. This method fundamentally avoids the problems of dielectric material carbonization and molten residue caused by heat accumulation in traditional laser processing, while also eliminating the risk of interlayer separation (delamination) caused by cutting stress in mechanical machining, significantly improving the machining quality of second-order blind grooves. Second-order blind grooves are located in the edge region of a plate and may form a raised structure with suspended edges after machining, requiring extremely high forming precision. Mechanical deep milling first roughs the material to form a pre-formed cavity, creating a good working space for laser finishing. Laser blind slotting, with its high energy density and precise controllability, can accurately ablate the remaining medium material in the pre-formed cavity, and even complex three-dimensional structures can be formed in one go.

[0040] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0041] Of course, the present invention is not limited to the above-described embodiments. Those skilled in the art can make equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A method for processing a second-order special blind slot printed circuit board, characterized in that, The substrate surface of the second-order special blind slot printed circuit board has a first-order blind slot and a second-order blind slot with a different depth than the first-order blind slot. An isolation ring is provided at the bottom of the first-order blind slot. The bottom of the first-order blind slot has a non-plugged metallized through hole. The sidewall of the first-order blind slot is in a non-metallized state. The processing method includes the following steps: Preparing adhesive barrier before lamination: Before the lamination process, attach PI tape to the preset position of the area to be processed on the printed circuit board. The size of the PI tape is not greater than the design size of the first-order blind groove. Lamination step: The inner core board and the prepreg are stacked and laminated to form a multilayer printed circuit board substrate; First-order blind slot opening steps: The first-order blind slot is machined at a predetermined position on the printed circuit board using mechanical depth control milling process, and the PI tape is removed to expose the area to be retained at the bottom of the blind slot; First-order blind slot dispensing step: After the cover is opened, liquid adhesive is filled into the first-order blind slot using dispensing equipment. The adhesive forms an isolation layer on the side wall of the blind slot and cures the adhesive to prevent the subsequent copper plating process from depositing a metal layer on the side wall of the first-order blind slot and to provide support for the subsequent drilling process. Drilling steps: Drill a through hole at the bottom of the first-stage blind groove; Plating copper step: Plating copper is applied to the through holes to form metallized hole walls; Blind groove adhesive removal step: Remove the cured adhesive from the first-stage blind groove.

2. The method for processing a second-order special blind slot printed circuit board according to claim 1, characterized in that, In the pre-pressing adhesive preparation step, the application of the PI tape specifically includes: applying the entire PI tape to the area to be processed; and using laser cutting to ensure that the tape size is not larger than the design size of the first-order blind groove, so as to form a reserved gap.

3. The method for processing a second-order special blind slot printed circuit board according to claim 2, characterized in that, In the first-order blind groove opening step, after removing the PI tape, any trace amount of excess adhesive that may exist in the reserved gap is removed manually.

4. The method for processing a second-order special blind slot printed circuit board according to claim 1, characterized in that, The adhesive used in the first-order blind slot dispensing step forms a physical isolation layer after curing, which prevents the copper plating solution from depositing a metal layer on the sidewall of the blind slot during the copper plating step, ensuring that the sidewall of the blind slot remains in a non-metallic state.

5. The method for processing a second-order special blind slot printed circuit board according to claim 1, characterized in that, The drilling step is performed after the first-order blind slot dispensing step. The cured adhesive provides structural support for the drilling and absorbs the stress that may remain from the capping step, preventing microcracks or tearing of the copper layer at the opening of the metallized through hole.

6. The method for processing a second-order special blind slot printed circuit board according to claim 1, characterized in that, The blind groove adhesive removal step specifically includes: using a pad to protect the printed circuit board, exposing the blind groove location area, and removing the cured adhesive in the first-order blind groove by physical manual peeling.

7. The method for processing a second-order special blind slot printed circuit board according to claim 1, characterized in that, The depth ratio of the first-order blind groove is greater than 1:1, that is, the depth of the blind groove is greater than its opening width.

8. A method for processing a second-order special blind slot printed circuit board according to any one of claims 1 to 7, characterized in that, Following the blind groove adhesive removal step, the following steps are also included: Full-board copper plating process: The entire printed circuit board is copper plated. External light imaging steps: Create outer layer circuit patterns on the surface of the printed circuit board; Pattern plating steps: Thicken the outer layer circuit pattern with electroplating; Alkaline etching step: Etching removes excess copper layer to form outer layer circuitry; Steps for fabricating the isolation ring pattern: The required circuit pattern is fabricated at the bottom of the first-order blind slot using a laser soldering process. The second-order blind groove processing steps are as follows: A composite process combining mechanical depth-controlled milling and laser blind groove is used to process the second-order blind groove in the edge area of ​​the plate.

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