Method and device for manufacturing bonding pad of circuit board with embedded device

Abstract

The embodiment of the invention relates to the technical field of PCB manufacturing, in particular to a device-embedded circuit board bonding pad manufacturing method and device.The device-embedded circuit board bonding pad manufacturing method comprises the steps that a multi-layer PCB is obtained, and a device-embedded area of the multi-layer PCB is uncovered to manufacture an embedded groove; performing solder mask pretreatment on the PCB multilayer board, performing low solder mask ink spraying treatment on the embedding groove of the PCB multilayer board, and forming ink layers on the surface of the PCB board and the surface of the embedding groove; and performing DI exposure processing, developing processing and curing processing on the PCB multilayer board in sequence to form a target bonding pad at the bottom of the embedded groove. According to the method, the target bonding pad is formed by forming the ink layer on the surface of the embedding groove of the PCB multilayer board and performing exposure, development and curing treatment, so that the stability of a protective layer of the inner bonding pad in the multilayer pressing process is improved, and the welding reliability and the product quality are ensured.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing technology, specifically to a method and apparatus for fabricating circuit board pads for embedded devices. Background Technology

[0002] In the manufacturing process of printed circuit boards (PCBs), solder pads serve as the critical interface for soldering electronic component leads, making their surface treatment and protection crucial. Traditional processes typically involve placing solder pads on the outermost layer of the PCB and coating their perimeter with solder resist ink to prevent solder run-through and short circuits during soldering. This type of solder resist ink possesses excellent insulation, heat resistance, and adhesion, meeting the requirements of conventional reflow soldering and other assembly processes.

[0003] However, as electronic devices evolve towards high-density integration and multilayering, it is sometimes necessary to incorporate pad structures within inner layer circuitry. If the outer layer solder resist ink is used as the surface protection material for the inner layer pads, it presents significant challenges due to subsequent multilayer lamination processes. Since the inner layers undergo multiple laminations and stackings, each lamination process often involves prolonged exposure to high pressure (e.g., not less than 300 psi) and high temperature (e.g., not less than 180°C) conditions (typically 60 to 120 minutes). Existing solder resist inks are prone to embrittlement, cracking, or decreased adhesion under such harsh physical and thermal stress. This not only degrades the surface condition of the pads, affecting the wettability and bonding strength during subsequent component soldering, but may also lead to electrical short circuits or open circuits due to ink damage, severely restricting the reliability and process feasibility of embedded pad structures within multilayer boards. Therefore, there is an urgent need to find an inner layer pad protection solution that can withstand multiple high-temperature and high-pressure lamination processes while maintaining good solder interface performance. Summary of the Invention

[0004] In view of the above problems, embodiments of the present invention provide a method and apparatus for fabricating circuit board pads for embedded devices, which solves the problems that existing solder resist inks are prone to embrittlement, cracking or decreased adhesion under such harsh physical and thermal stress.

[0005] According to one aspect of the present invention, a method for fabricating circuit board pads for embedded devices is provided, the method comprising: Obtain a multilayer PCB board, wherein the multilayer PCB board has an area for embedded components; The embedded device area of ​​the PCB multilayer board is opened to create an embedded groove; The PCB multilayer board is subjected to pre-soldering treatment, and the embedded groove of the PCB multilayer board is treated with low-pressure spray solder resist ink to form an ink layer on the surface of the PCB board and the surface of the embedded groove. The PCB multilayer board is subjected to DI exposure processing, development processing and curing processing in sequence to form target pads at the bottom of the embedded groove.

[0006] In some optional implementations, obtaining the PCB multilayer board specifically includes: A first multilayer board is obtained, and a device embedding area is formed on the first surface of the first multilayer board; Pre-attach the PI composite film to the area where the device is embedded; A pre-set second multilayer board is pressed onto the first surface of the first multilayer board to form a PCB multilayer board, and the thickness of the second multilayer board is greater than or equal to the thickness of the embedded device.

[0007] In some optional embodiments, the embedded device area of ​​the PCB multilayer board is opened to create embedded grooves, specifically including: The first groove is formed in the embedded device area by a depth-controlled milling method, and a dielectric layer is provided between the bottom of the first groove and the PI composite film. The dielectric layer and PI composite film at the bottom of the first groove are cut and embedded into the groove using a laser. The impurities remaining in the buried trench are removed by air blowing or water washing.

[0008] In some optional embodiments, the PCB multilayer board is subjected to a pre-soldering treatment, which includes, in sequence: mechanical / chemical degreasing treatment, first water washing treatment, micro-etching roughening treatment, second water washing treatment, acid washing treatment, third water washing treatment, anti-oxidation treatment, fourth water washing treatment and drying treatment.

[0009] In some alternative implementations, the embedded grooves of the PCB multilayer board are treated with low-coat solder resist ink, specifically including: Solder resist ink is applied to the embedded groove using a spraying pressure of 100psi-300psi, a spray gun movement speed of 200mm / s-600mm / s, and a spraying time of 60min-120min.

[0010] In some alternative embodiments, the thickness of the ink layer is 20±5μm.

[0011] In some optional embodiments, after applying low-coating solder resist ink to the embedded grooves of the PCB multilayer board and before performing DI exposure on the PCB multilayer board, a pre-baking process is further included; the pre-baking process specifically includes: The first stage of baking is carried out on the PCB multilayer board according to the baking temperature of 70℃-85℃ and the baking time of 15min-25min. The second stage of baking is performed on the PCB multilayer board at a baking temperature of 80℃-95℃ and a baking time of 20min-40min to complete the pre-baking of the ink layer of the PCB multilayer board.

[0012] In some optional embodiments, the PCB multilayer board undergoes DI exposure processing, specifically including: The pre-baked PCB multilayer board is fixed in the DI exposure machine and laser scanning exposure is performed according to the preset solder resist data using a laser source in the 355nm-405nm ultraviolet band and an energy density of 80-150mJ / cm².

[0013] In some optional embodiments, the developing process and the curing process specifically include: A sodium carbonate aqueous solution with a mass concentration of 0.8%-1.2% was used to dissolve the ink in the unexposed areas of the PCB multilayer board by spraying, followed by water washing to remove the residual sodium carbonate aqueous solution and ink from the PCB multilayer board. The PCB multilayer board that has completed the developing process is placed in a curing oven and baked at a baking temperature of 140°C-150°C for 30-60 minutes to fix it, thus obtaining the target pad.

[0014] According to one aspect of the present invention, an apparatus for fabricating circuit board pads for embedded devices is provided, characterized in that the apparatus is used to perform the above-described method for fabricating circuit board pads for embedded devices to fabricate a printed circuit board.

[0015] The method and apparatus for fabricating circuit board pads for embedded devices of the present invention have the following advantages: The method for fabricating circuit board pads for embedded devices of the present invention includes obtaining a multilayer PCB board; performing a cover-up process on the embedded device area of ​​the multilayer PCB board to create an embedded groove; performing a pre-solder resist treatment on the multilayer PCB board; and applying a low-coat solder resist ink treatment to the embedded groove of the multilayer PCB board to form an ink layer on the surface of the PCB board and the surface of the embedded groove; and sequentially performing DI exposure treatment, development treatment, and curing treatment on the multilayer PCB board to form a target pad at the bottom of the embedded groove. The present invention, by forming an ink layer on the surface of the embedded groove of the multilayer PCB board and performing exposure, development, and curing treatments to form the target pad, not only improves the stability of the protective layer of the inner layer pads during multilayer lamination, but also ensures welding reliability and product quality.

[0016] The above description is merely an overview of the technical solutions of the embodiments of the present invention. In order to better understand the technical means of the embodiments of the present invention and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0017] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A schematic flowchart of the method for fabricating circuit board pads for embedded devices according to Embodiment 1 of the present invention is shown. Figure 2 A flowchart illustrating step 110 of Embodiment 2 provided by the present invention is shown; Figure 3 A flowchart illustrating step 120 of Embodiment 2 provided by the present invention is shown; Figure 4 A schematic diagram of step 220 of an embodiment provided by the present invention is shown; Figure 5 A schematic diagram of step 230 of an embodiment provided by the present invention is shown; Figure 6 A schematic diagram of step 310 of an embodiment provided by the present invention is shown; Figure 7 A schematic diagram of step 320 of an embodiment provided by the present invention is shown; Figure 8 A schematic diagram of step 130 of an embodiment provided by the present invention is shown; Figure 9 A schematic diagram of step 140 of an embodiment provided by the present invention is shown; Figure label: 1. First multilayer board; 2. PI film layer; 3. Second multilayer board; 4. First groove; 5. Dielectric layer; 6. Embedded groove; 7. Ink layer; 8. Target pad; 10. PCB multilayer board. Detailed Implementation

[0018] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0019] Example 1: Figure 1 The first embodiment of the method for fabricating circuit board pads for embedded devices of the present invention is shown, which solves the problems of existing solder resist inks being prone to embrittlement, cracking or decreased adhesion under such harsh physical and thermal stress.

[0020] 110. Obtain a multilayer PCB board, wherein the multilayer PCB board has an area for embedded components; 120. The embedded component area of ​​the PCB multilayer board is opened to create an embedded groove. 130. Perform pre-soldering treatment on the PCB multilayer board and apply low-coat solder resist ink to the embedded groove of the PCB multilayer board to form an ink layer on the surface of the PCB board and the surface of the embedded groove. 140. The PCB multilayer board is subjected to DI exposure, development and curing processes in sequence to form the target pads at the bottom of the embedded groove.

[0021] In steps 110-140, PCB multilayer board: refers to a printed circuit board made of multiple layers of conductive pattern layers and insulating dielectric layers that are alternately stacked and laminated. This board can realize high-density wiring and complex circuit functions, and is a commonly used substrate in modern electronic products.

[0022] Embedded component area: This refers to a specific space reserved inside a multilayer PCB board for placing or integrating electronic components. This area is typically formed through special structural design and manufacturing processes to achieve embedded component packaging.

[0023] Embedded slot: refers to a groove or cavity formed in the embedded component area of ​​a multilayer PCB board through a capping process. This slot is used to accommodate the embedded component and provide space for subsequent pad fabrication.

[0024] Solder resist pretreatment: This refers to a series of cleaning, activation, and roughening treatments performed on the surface of a multilayer PCB board before applying solder resist ink. This treatment aims to remove surface contaminants and increase surface roughness, thereby enhancing the adhesion of the solder resist ink to the board surface.

[0025] Low-pressure spraying of solder resist ink: This refers to the precise application of solder resist ink to the surface of the embedding grooves on a PCB multilayer board using lower spraying pressure and specific process parameters. This method aims to ensure a uniform and appropriately thick ink layer within the embedding grooves, while avoiding unnecessary contamination of other areas.

[0026] Ink layer: This refers to the protective coating formed on the surface of a multilayer PCB board and the surface of the embedded grooves through low-pressure spraying of solder resist ink. This layer has functions such as insulation, moisture protection, and corrosion protection, and can prevent solder from flowing during subsequent soldering processes.

[0027] DI exposure processing: This refers to the selective exposure of a multilayer PCB board coated with photosensitive solder resist ink using digital imaging (DI) technology. This process uses methods such as laser scanning to precisely form a latent image on the ink layer based on preset graphic data.

[0028] Development process: This refers to the selective removal of the ink layer from unexposed or exposed areas of a PCB multilayer board using a chemical solution after the DI (Display Injection) exposure process. This process aims to convert the latent image into a visible ink pattern, thereby exposing the areas where solder pads need to be formed.

[0029] Curing treatment: This refers to the polymerization reaction of the solder resist ink layer on a multilayer PCB board after development treatment, caused by heating or ultraviolet irradiation, thereby forming a hard and durable protective layer. This treatment aims to improve the mechanical strength, chemical resistance, and adhesion of the ink layer.

[0030] Target pad: This refers to the conductive area formed at the bottom of the embedding trench through the aforementioned series of process steps, used to connect the pins of the embedded device. This pad is the critical interface for the electrical connection between the embedded device and the circuit board.

[0031] This embodiment provides a method for fabricating circuit board pads for embedded devices. The method involves a series of process steps to form target pads at the bottom of the embedding grooves in a multilayer PCB board.

[0032] First, the method involves acquiring a multilayer PCB board with embedded device areas. In practice, acquiring a multilayer PCB board can be done in several ways. For example, a pre-fabricated multilayer board substrate can be purchased from a supplier, with specific areas pre-reserved for embedded devices according to design requirements. Alternatively, a multilayer board with internal circuit connections can be formed by conventionally laminating multiple dielectric and conductive layers, and the placement areas for embedded devices can be planned during the design phase. These areas are typically designated within the board for subsequent device embedding.

[0033] Furthermore, the embedded component area of ​​the PCB multilayer board is opened to create embedded grooves. The purpose of this opening process is to form a recess in the embedded component area to accommodate the embedded components. Specifically, mechanical drilling or milling can be used to process the pre-defined embedded component area to remove part of the board layer, thereby forming a groove with a certain depth and shape. Another method is to use a chemical etching process to selectively remove material and form embedded grooves in designated areas. Both methods can achieve the fabrication of embedded grooves, providing physical space for subsequent pad formation.

[0034] Based on this, a pre-treatment for solder resist is performed on the PCB multilayer board, and a low-coat solder resist ink treatment is applied to the embedded grooves of the PCB multilayer board, forming an ink layer on the surface of the PCB board and the embedded grooves. The pre-treatment for solder resist is fundamental to ensuring good ink adhesion and may include routine surface cleaning, degreasing, and micro-roughening steps to activate the board surface. Subsequently, a low-coat solder resist ink treatment is performed. This treatment can be performed using spraying equipment to uniformly spray the solder resist ink onto the surface of the PCB multilayer board, especially the interior of the embedded grooves, at relatively low pressure. For example, a pneumatic spray gun or electrostatic spraying equipment can be used, and by adjusting the spraying parameters, the ink can cover the sidewalls and bottom of the embedded grooves, forming a continuous ink layer across the entire PCB board surface. After drying, this ink layer provides the basis for subsequent exposure and development.

[0035] Finally, the PCB multilayer board undergoes sequential DI exposure, development, and curing processes to form the target pads at the bottom of the embedding tank. DI exposure can be performed using digital lithography equipment, which directly scans and precisely projects the pre-defined pad pattern onto the ink layer at the bottom of the embedding tank, causing a photochemical reaction in the exposed area. Following this, development is performed by immersing or spraying the exposed PCB multilayer board with a developer solution, selectively dissolving unexposed or exposed ink to expose the conductive layer at the bottom of the embedding tank, forming the pad pattern. For example, an alkaline developer can be used for spray development. After development, the board is washed with water to remove residual developer and ink. Finally, the developed PCB multilayer board is placed in an oven for curing. By baking at a specific temperature for a period of time, the remaining ink layer is completely hardened, forming a robust solder resist layer that protects the area outside the pads and ensures that the target pads at the bottom of the embedding tank have good electrical connection performance and mechanical strength.

[0036] In a specific example, we obtain a pre-designed multilayer PCB board. The board's internal structure pre-plans a specific area for embedded components; for example, this area is located between the second and fifth layers of the board. See [reference needed]. Figure 5 The acquisition of this multilayer PCB board can be completed through the standard board procurement process, ensuring that it meets the size and material requirements for subsequent processing.

[0037] Next, in order to create a space to accommodate the device in the embedded device area, the area is opened to create an embedding groove, see [link to documentation]. Figure 7 Specifically, a high-precision mechanical milling cutter can be used to perform controlled-depth milling in the embedded device area of ​​a multilayer PCB board. This precisely removes the upper dielectric material until the required depth for embedding the device is exposed, forming a sized embedment groove. During the milling process, the depth is monitored in real time to ensure that the conductive layer at the bottom of the embedment groove is not damaged.

[0038] Subsequently, the PCB multilayer board with the embedded grooves fabricated undergoes pre-treatment for solder resist application. This treatment includes ultrasonic cleaning of the board to remove debris and oil generated during processing, followed by micro-etching to increase surface roughness, thereby improving the adhesion of subsequent solder resist ink. After pre-treatment, the embedded grooves of the PCB multilayer board are treated with low-coat solder resist ink, see [link to details]. Figure 8 For example, using an automated spraying machine equipped with fine nozzles, liquid solder resist ink is evenly sprayed onto the entire surface of the PCB multilayer board at a lower spraying pressure and a moderate spray gun movement speed, especially ensuring that the bottom and sidewalls of the embedding grooves are completely covered. In this way, a uniform ink layer is formed on the surface of the PCB board and the surface of the embedding grooves.

[0039] Finally, the PCB multilayer board coated with ink layers undergoes sequential DI exposure, development, and curing processes. In the DI exposure stage, the PCB multilayer board is placed in a DI exposure machine, and the ink layer embedded at the bottom of the tank is selectively exposed precisely using laser scanning based on preset pad pattern data. After exposure, the PCB multilayer board is sent to a developing device, where a weakly alkaline developer is sprayed onto the board to dissolve the ink in unexposed areas, thereby exposing the copper layer embedded at the bottom of the tank and forming a clear pad pattern. See [link to documentation]. Figure 9 After development, the PCB multilayer board is rinsed with water to remove residual developer and ink. Finally, the developed board is placed in an oven for curing. By baking at a specific temperature for a period of time, the remaining solder resist layer is completely hardened, forming a robust insulating protective layer that precisely creates the target pads at the bottom of the embedding groove. These target pads have good flatness and electrical properties and can be used for subsequent soldering of embedded components.

[0040] Based on the above examples, the method provided in this embodiment demonstrates a significant technical contribution in solving the problems of the prior art. Traditional inner-layer pad protection schemes, if using the same outer-layer solder resist ink, are prone to problems such as embrittlement, cracking, or decreased adhesion during subsequent multilayer lamination due to repeated exposure to high temperature and pressure, leading to pad surface deterioration and affecting welding reliability.

[0041] This embodiment employs low-coat solder resist ink treatment after the embedded trench is fabricated, ensuring that the solder resist ink can uniformly and precisely cover the inner surface of the embedded trench. Compared to traditional outer layer ink coating methods, this refined spraying process for the embedded trench can better adapt to the complex structure of the embedded device area, providing a more reliable ink base for subsequent pad formation.

[0042] Furthermore, by combining DI exposure, development, and curing processes, this embodiment enables precise formation of target pads at the bottom of the embedded trench. DI exposure technology provides high-precision pattern transfer capabilities, ensuring the accuracy of pad size and position. Development and curing processes further refine pad formation and impart the necessary mechanical strength and heat resistance to the solder resist layer. This integrated process effectively avoids pad defects caused by insufficient ink performance in traditional processes, thereby improving the reliability and process feasibility of embedded device circuit board pads.

[0043] Overall, the method in this embodiment provides a solution to effectively address the challenges of fabricating pads for embedded devices within multilayer boards by optimizing the fabrication of the embedded trench, the application of solder resist ink, and subsequent patterning processing. This solution helps improve the integration, reliability, and manufacturing efficiency of embedded device circuit boards, providing strong technical support for the development of high-density electronic devices.

[0044] Example 2: Based on Example 1, this example provides a second example of a method for fabricating circuit board pads for embedded devices, to further describe steps 110-140 in Example 1.

[0045] In step 110, a multilayer PCB board is obtained, see [link to relevant documentation]. Figure 2 Specifically, it includes: 210. Obtain a first multilayer board and set an embedded device area on the first surface of the first multilayer board; In step 210, a first multilayer board, which serves as the basic structure of the PCB multilayer board, is obtained, and a specific space for placing the embedded device is pre-planned on one of its main surfaces. This can be achieved by determining the position and size of the embedded device during the PCB design stage, and forming a first multilayer board with corresponding internal circuits and reserved areas through conventional PCB processes such as lamination, drilling, and electroplating during the manufacturing process. Alternatively, a preliminary groove structure for the embedded device area can be formed at a designated location by mechanical milling or laser processing of the prefabricated core board material, followed by subsequent lamination processing.

[0046] 220, Pre-attach the PI composite film to the embedded device area; in step 220, see... Figure 4A polyimide (PI) composite film is laminated onto the surface of the area where the device is embedded. Due to its excellent high-temperature resistance, insulation, and mechanical strength, the PI composite film serves to provide additional electrical insulation protection, enhance mechanical support, or act as a protective layer or depth control layer during subsequent capping processes (such as laser cutting or mechanical milling) to prevent accidental damage to underlying circuitry or structures. This pre-lamination process can employ thermoforming technology, where the pre-cut PI composite film is precisely aligned and then firmly adhered to the surface of the embedded device area by heating and applying pressure. Alternatively, a self-adhesive PI composite film can be used, precisely laminated using automated lamination equipment to ensure a smooth, bubble-free film layer.

[0047] 230. A pre-set second multilayer board is laminated onto the first surface of the first multilayer board to form a PCB multilayer board, wherein the thickness of the second multilayer board is greater than or equal to the thickness of the embedded components. In step 230, see... Figure 5 A second, pre-prepared multilayer board is bonded to the first surface of the first multilayer board via a lamination process. The thickness of the second multilayer board is designed to be greater than or equal to the thickness of the embedded device. This design ensures that after the embedded device is fully embedded, the second multilayer board provides sufficient coverage and protection, preventing the embedded device from protruding from the PCB surface. This provides a flat, uniform, and protected substrate for subsequent surface treatment processes such as solder resist spraying, exposure, development, and curing. The lamination process is typically carried out in specialized lamination equipment. By controlling temperature, pressure, and time, a strong bond is formed between the layers of board and the dielectric. For example, vacuum lamination technology can be used to reduce interlayer bubbles and improve lamination quality.

[0048] In steps 210-230, the present invention ensures reliable integration of the embedded devices and accuracy of subsequent pad fabrication by meticulously constructing a pre-structure for the embedded devices during the initial stage of acquiring the PCB multilayer board. First, by acquiring the first multilayer board and setting the embedded device area, a clear spatial basis is provided for the precise placement of the embedded devices. Next, a PI composite film is pre-attached to this area. This not only provides necessary insulation and protection for the embedded devices but also serves as a depth control layer during subsequent opening processes, effectively preventing accidental damage to the underlying structure. Subsequently, a pre-set second multilayer board is pressed onto the first surface of the first multilayer board, and the thickness of the second multilayer board is greater than or equal to the thickness of the embedded devices. This design ensures that the entire surface of the PCB multilayer board remains flat after the devices are embedded, providing a uniform and protected working surface for subsequent steps such as solder resist spraying, exposure, development, and curing. This avoids process defects caused by uneven device thickness and effectively protects the embedded devices. Through these steps, the present invention precisely constructs the pre-structure of embedded devices at the stage of obtaining the PCB multilayer board, providing a solid and reliable foundation for the subsequent fabrication of embedded slots and formation of target pads, significantly improving the integration quality of embedded devices and the overall reliability of the circuit board.

[0049] The following is a concrete example. When obtaining a multilayer PCB, first prepare a four-layer board made of FR-4 material as the first multilayer board, and designate a rectangular area on its top surface as the embedded device area using design files. Then, using an automated laminator, precisely apply a 25-micron-thick polyimide (PI) composite film to the surface of this rectangular embedded device area, ensuring no air bubbles between the film and the board surface. Next, prepare a two-layer board made of FR-4 material as the second multilayer board, with a total thickness of 0.8 mm, sufficient to cover the intended embedded devices. With the first multilayer board and the embedded device area (with the PI composite film attached) facing upwards, place the second multilayer board on top of the first multilayer board. Use a vacuum laminator at 180 degrees Celsius and 30 atmospheres for 90 minutes to firmly bond the second multilayer board to the first surface of the first multilayer board, forming a complete multilayer PCB.

[0050] The above technical solution enables the precise construction of the pre-structured embedded components in the initial stage of obtaining the PCB multilayer board. By setting the embedded component area on the first multilayer board and pre-applying a PI composite film, reliable insulation protection and structural support are provided for the embedded components, while also providing a precise depth control benchmark for subsequent embedding groove opening. Furthermore, by laminating a second multilayer board with a thickness greater than or equal to the embedded component thickness, the surface flatness of the PCB multilayer board after embedding is effectively ensured, preventing component protrusion or damage. This provides a uniform and protected substrate for subsequent key processes such as solder resist spraying, exposure, development, and curing, significantly improving the integration quality of the embedded components, the overall reliability of the circuit board, and the accuracy of subsequent pad fabrication. This effectively solves the problems of difficult embedded component integration and process defects caused by imperfect initial board structure in traditional methods.

[0051] In step 120, the embedded component area of ​​the PCB multilayer board is opened to create embedded grooves, see [link to relevant documentation]. Figure 3 Specifically, it includes: 310, a first groove is formed in the embedded device area using a controlled-depth milling method, and a dielectric layer is also provided between the bottom of the first groove and the PI composite film; in step 310, see... Figure 6 The first groove is created in the embedded component area using controlled-depth router technology. Controlled-depth router technology is a precise machining technique that, by controlling the depth of the router cutter, can create grooves of a predetermined depth on a multilayer PCB board, thus avoiding unnecessary damage to the underlying structure. For example, a CNC router with a high-precision depth sensor can be used, or a mechanical milling machine with fine-tuning capabilities can be employed. A dielectric layer is also placed between the bottom of the first groove and the PI composite film. This dielectric layer serves as protection and insulation, acting as a buffer layer during controlled-depth router processing to further ensure the integrity of the PI composite film. This dielectric layer can be a prepreg layer, epoxy resin, or other suitable insulating materials.

[0052] 320, the dielectric layer and PI composite film at the bottom of the first groove are cut and embedded into the groove using a laser; in step 320, see... Figure 7 The embedding groove is created by cutting the dielectric layer and PI composite film at the bottom of the first groove using a laser. Laser cutting is a non-contact, high-precision cutting technology that enables fine processing of materials with a minimal heat-affected zone and high resolution. For example, ultraviolet lasers or picosecond lasers can be used for cutting. These lasers have small spot sizes and high energy densities, allowing for precise removal of the dielectric layer and PI composite film, resulting in a precisely sized embedding groove with clean edges.

[0053] 330. After the embedding tank is fabricated, residual impurities are removed by either air blowing or water rinsing. In step 330, after the embedding tank is fabricated, residual impurities are removed by either air blowing or water rinsing. Air blowing typically involves using high-pressure gas (such as compressed air or nitrogen) to blow away debris, dust, and other impurities generated during the manufacturing process from the surface of the embedding tank. Water rinsing typically involves rinsing the embedding tank with deionized water to remove finer particles or water-soluble residues; for example, high-pressure deionized water spraying or a combination of high-pressure and ultrasonic cleaning can be used. These cleaning steps are crucial for ensuring the cleanliness of the embedding tank, preventing impurities from affecting subsequent solder resist coating and pad formation.

[0054] In steps 310-330, when opening the embedded device area of ​​the PCB multilayer board, the present invention first uses a depth-controlled milling method for rough machining to form a first groove with controlled depth. This step cleverly utilizes the dielectric layer as a protective layer, ensuring that the depth-controlled milling tool does not directly damage the underlying PI composite film when reaching the preset depth, thus providing a safety guarantee for subsequent fine machining. Next, a laser is used to precisely cut the remaining dielectric layer and PI composite film at the bottom of the first groove. The non-contact and high-precision characteristics of laser cutting ensure the dimensional accuracy and edge quality of the embedded groove, avoiding stress damage or burrs that may be caused by traditional machining. This step-by-step, refined opening method combines the efficiency of machining with the precision of laser processing, effectively solving the technical challenge of precisely opening the embedded device area while protecting the sensitive underlying structure. Finally, through air blowing or water cleaning, the minute impurities generated during processing are thoroughly removed, ensuring the cleanliness of the embedded groove and laying a solid foundation for subsequent solder resist ink spraying and the formation of target pads.

[0055] As a specific implementation method, after acquiring and pre-processing the PCB multilayer board, a CNC router equipped with a high-precision depth control system can be used to perform controlled-depth router operations in the embedded component area. The router's cutting depth is precisely set so that the bottom of the first groove just stops above the dielectric layer, or only slightly contacts the dielectric layer without touching the PI composite film. For example, if the dielectric layer thickness is 50 micrometers, the router depth can be set to approximately 20-30 micrometers above the PI composite film. After routerging the first groove, the PCB multilayer board is transferred to a laser cutting device. This device uses a 355nm ultraviolet laser to scan and cut the remaining dielectric layer and PI composite film at the bottom of the first groove through a precisely programmed path until it is completely penetrated, forming the required embedded groove. After laser cutting, the embedded groove can be purged with high-pressure clean air to remove larger particles. Then, the PCB multilayer board is immersed in a deionized water bath and subjected to ultrasonic vibration cleaning to thoroughly remove tiny residues and water-soluble impurities, ensuring the cleanliness of the embedded groove.

[0056] Through the above technical solution, this invention enables precise capping of the embedded device area on a multilayer PCB board. The combination of depth-controlled milling and laser methods effectively avoids damage to the PI composite film during capping, while ensuring the dimensional accuracy and edge quality of the embedding groove. The addition of a dielectric layer further enhances the protection of the PI composite film. Furthermore, subsequent air blowing or water rinsing ensures the cleanliness of the embedding groove, preventing impurities from affecting subsequent solder resist coating and target pad formation. This significantly improves the fabrication quality and reliability of the embedded device circuit board pads, providing a solid technical guarantee for the integration of high-performance embedded devices.

[0057] In step 130, the PCB multilayer board is subjected to pre-soldering treatment, which includes, in sequence: mechanical / chemical degreasing treatment, first water washing treatment, micro-etching roughening treatment, second water washing treatment, acid washing treatment, third water washing treatment, anti-oxidation treatment, fourth water washing treatment and drying treatment.

[0058] In this embodiment, the pretreatment for solder resist aims to provide a clean, active surface with good adhesion for subsequent solder resist ink spraying. Its function is to remove contaminants from the surface of the PCB multilayer board and modify the surface to ensure strong adhesion of the ink layer. This treatment can include various methods such as physical cleaning, chemical cleaning, and surface activation. Mechanical / chemical degreasing is used to remove organic contaminants from the PCB multilayer board surface, such as fingerprints, grease, and flux residue. These contaminants severely affect the adhesion of the solder resist ink. Mechanical degreasing can be performed by brushing or wiping; chemical degreasing typically involves soaking or spraying with alkaline degreasing agents or solvent-based cleaning agents. The first water rinse is used to thoroughly remove the degreasing agent and its decomposition products remaining on the PCB multilayer board surface after mechanical / chemical degreasing. Water rinsing can be performed using high-pressure deionized water spraying or through multi-stage soaking and rinsing combined with agitation. Micro-etching roughening treatment slightly etches the copper layer on the PCB multilayer board surface, creating a micro-rough structure, thereby increasing the surface area and mechanical adhesion, significantly improving the adhesion strength of the solder resist ink. The micro-etching agent can be sodium persulfate solution or a mixture of hydrogen peroxide and sulfuric acid. The second water rinse removes any micro-etching agent and its reaction products remaining on the PCB multilayer board surface after the micro-etching roughening treatment. The rinsing method is similar to the first water rinse to ensure no residue remains. Acid pickling aims to remove any oxide layer that may form on the copper surface of the PCB multilayer board and activate the copper surface, making it more readily reactable with subsequent chemicals. Commonly used acid pickling agents are dilute sulfuric acid solution or dilute hydrochloric acid solution. The third water rinse removes any acid pickling agent and its reaction products remaining on the PCB multilayer board surface after the acid pickling treatment. The rinsing method is similar to the aforementioned water rinses to ensure a clean surface. Antioxidant treatment forms a thin protective film on the clean copper surface before solder resist ink is applied to prevent the copper surface from oxidizing again in the air, thereby maintaining the activity and good solderability of the copper surface. Antioxidants can be organic antioxidants (such as imidazole compounds) or benzotriazole (BTA) derivative solutions. The fourth water rinse is used to remove any antioxidant residue remaining on the surface of the PCB multilayer board after the anti-oxidation treatment. The rinsing method is similar to the previous water rinses, ensuring no chemical residue remains on the surface. The drying process thoroughly removes all moisture from the surface of the PCB multilayer board and the embedded grooves, providing a dry base for subsequent solder resist ink application. Drying methods can include hot air drying, infrared drying, or vacuum drying.

[0059] In the fabrication method of circuit board pads for embedded devices, to ensure that the solder resist ink layer can stably and uniformly adhere to the surface of the PCB multilayer board and the embedded groove surface, this invention proposes a series of refined pre-treatment steps for solder resist. These steps are not isolated but interconnected, working together to achieve the best surface preparation effect. First, mechanical / chemical degreasing treatment effectively removes organic contaminants from the surface of the PCB multilayer board, laying a clean foundation for subsequent treatments. The subsequent first water wash thoroughly removes degreasing agent residue, avoiding cross-contamination. Next, micro-etching roughening treatment optimizes the microscopic morphology of the copper surface, forming a rough structure conducive to mechanical anchoring and significantly enhancing the adhesion of the ink. The second water wash further ensures surface cleanliness. Subsequently, acid pickling removes the oxide layer on the copper surface, activating the metal surface and making it easier for it to bond with the solder resist ink. The third water wash removes acid pickling residue. To prevent the clean copper surface from re-oxidizing in a short time, an anti-oxidation treatment provides a protective layer before ink spraying, maintaining surface activity. The fourth water wash ensures no antioxidant residue. Finally, the drying process thoroughly removes moisture to prevent bubbles or adhesion issues during ink curing. Through this series of orderly and comprehensive processes, the surface of the PCB multilayer board is thoroughly cleaned, activated, and its microstructure optimized, providing an ideal substrate for subsequent low-spray solder resist ink treatment. This significantly improves the adhesion and uniformity of the ink layer, effectively solving problems such as ink peeling and blistering caused by improper surface treatment, and ensuring the manufacturing quality and reliability of the target pads embedded in the bottom of the slot.

[0060] Through the aforementioned series of meticulous pre-treatment steps for solder resist, the cleanliness, activity, and micro-roughness of the PCB multilayer board surface and the interior of the embedded trench are significantly improved. This allows the subsequent low-coat solder resist ink to form excellent adhesion with the substrate, effectively preventing defects such as peeling, blistering, or uneven coating of the ink layer during the manufacturing process. Ultimately, this ensures the formation quality and reliability of the target pads at the bottom of the embedded trench, thereby improving the overall manufacturing yield and product performance of the embedded device circuit board.

[0061] In step 130, the embedded grooves of the PCB multilayer board are treated with low-pressure spraying of solder resist ink. Specifically, this includes spraying the embedded grooves with solder resist ink using a spraying pressure of 100psi-300psi, a spray gun movement speed of 200mm / s-600mm / s, and a spraying time of 60min-120min. For details, see [link to details]. Figure 8 The thickness of the ink layer is 20±5μm.

[0062] In this embodiment, spraying pressure refers to the driving force required to spray ink from the spray gun and adhere it to the surface of the PCB multilayer board and the embedded groove during the solder resist ink spraying process. Appropriate spraying pressure ensures that the ink is sprayed out in a uniform and fine atomized state, thereby achieving good coverage of the complex structure inside the embedded groove. Too low a pressure may result in insufficient ink atomization, forming ink layers with large particles and uneven coverage; too high a pressure may cause ink splattering, waste, or even damage to the PCB multilayer board surface. Spraying pressure can be controlled by adjusting the air source pressure of the spraying equipment or the output pressure of the hydraulic pump. Spray gun movement speed refers to the relative movement speed of the spray gun relative to the PCB multilayer board during the spraying process. This speed directly affects the amount of ink deposited per unit area and the uniformity of the ink layer. A slower movement speed may result in excessively thick local ink buildup, while a faster movement speed may result in an ink layer that is too thin or incomplete coverage. Spray gun movement speed can be precisely set and adjusted using the motion control system of a robotic arm or automated spraying equipment. Spraying time refers to the duration of solder resist ink spraying on a specific area. With a fixed spraying pressure and spray gun movement speed, the spraying time determines the amount of ink accumulated in the ink tank, thus affecting the final thickness of the ink layer. A reasonable spraying time ensures the ink layer reaches the desired thickness while avoiding quality problems caused by insufficient or excessive spraying. The spraying time can be precisely controlled through program control of the spraying equipment or manual timing.

[0063] This invention optimizes the solder resist ink spraying process within the embedding tank by precisely controlling three core parameters: spraying pressure, spray gun movement speed, and spraying time. Specifically, spraying pressure determines the fineness of ink atomization and the penetrating power of the spray, ensuring that the ink uniformly covers the microstructures such as the sidewalls and bottom of the embedding tank. Spray gun movement speed controls the ink deposition rate per unit area, avoiding problems of excessively thick or thin ink in certain areas. Spraying time, as a cumulative control of the overall spraying amount, ensures that the ink layer reaches the expected overall thickness. These three parameters work together synergistically to ensure the formation of a uniform, well-adhesive, and defect-free solder resist ink layer within the unique and complex structure of the embedding tank. This refined parameter control effectively solves problems such as uneven ink layer, incomplete coverage, or localized accumulation that may occur with traditional low-pressure spraying methods, laying a high-quality foundation for subsequent DI exposure, development, and curing processes, thereby ensuring the fabrication accuracy and reliability of the target solder pads at the bottom of the embedding tank.

[0064] In one specific implementation, when applying low-pressure solder resist ink to the embedding slots of a multilayer PCB board, an automated spraying device can be used. This device can be equipped with a high-precision spray gun and a multi-axis robotic arm. In actual operation, the spraying pressure can be set to 200 psi to ensure good ink atomization and sufficient penetration to reach deep into the embedding slot. The spray gun movement speed can be set to 400 mm / s to ensure uniform ink deposition on the surface of the embedding slot, avoiding drips or accumulation. The spraying time can be set to 90 minutes to ensure that the ink layer reaches the expected thickness under the set pressure and speed. During the spraying process, the spray gun can move back and forth above the embedding slot along a preset path to ensure that the ink fully covers all surfaces of the embedding slot.

[0065] In one specific embodiment, the thickness of the ink layer is 20±5μm. Here, the ink layer refers to the solder resist ink coating formed on the surface of the PCB multilayer board and the surface of the embedded groove. Its main function is to protect non-pad areas, prevent damage to the circuitry from subsequent processes, and serve as the base layer for DI exposure and development to accurately define the final pad pattern. This ink layer can be uniformly coated onto the PCB surface using various methods such as spraying, screen printing, or roll coating. The thickness of 20±5μm refers to the final thickness range of the ink layer after curing. This thickness range is designed to ensure that the ink layer provides sufficient protection and insulation without being too thick to affect subsequent exposure resolution and development effects, while also ensuring uniform coverage in the special structure of the embedded groove.

[0066] By employing the aforementioned technical solution, the spraying pressure, spray gun movement speed, and spraying time during the solder resist ink spraying process are precisely controlled. This allows for the formation of a uniform, well-adhered, and defect-free solder resist ink layer within the unique structure of the embedded slots in multilayer PCB boards. This effectively avoids problems such as insufficient exposure, incomplete development, or uneven pad edges during subsequent DI exposure and development processes caused by uneven or defective ink layers. It significantly improves the fabrication accuracy and yield of the target pads at the bottom of the embedded slots, thereby enhancing the overall reliability of the circuit board with embedded devices.

[0067] In some optional embodiments, after applying low-coating solder resist ink to the embedded grooves of the PCB multilayer board and before performing DI exposure on the PCB multilayer board, a pre-baking process is also included; the pre-baking process specifically includes: The first stage of baking is carried out on the PCB multilayer board according to the baking temperature of 70℃-85℃ and the baking time of 15min-25min. The second stage of baking is performed on the PCB multilayer board at a baking temperature of 80℃-95℃ and a baking time of 20min-40min to complete the pre-baking of the ink layer of the PCB multilayer board.

[0068] In this embodiment, pre-baking refers to the heat treatment performed on the PCB multilayer board after ink coating and before formal curing or exposure. Its main function is to promote the evaporation of solvents in the ink layer, allowing the ink layer to dry initially and form a uniform surface. Simultaneously, it can release internal stress in the ink layer, improve the adhesion between the ink layer and the substrate, and provide a stable foundation for subsequent DI exposure processing. Pre-baking can be performed using equipment such as a hot air circulating oven, infrared oven, or heating plate. The first stage of baking is the initial heating phase of the pre-baking process, typically using a relatively low temperature and a short time. The main purpose of this stage is to gently remove most of the volatile solvents in the ink layer, avoiding bubbles or surface defects caused by rapid solvent evaporation due to rapid heating. For example, convection heating can be used to slowly heat the PCB multilayer board, ensuring uniform solvent evaporation. The second stage of baking follows immediately after the first stage, typically using a relatively high temperature and a longer time. This stage aims to further and thoroughly remove residual solvents and achieve a more stable ink layer. For example, it promotes cross-linking reactions of some prepolymers in the ink, improving the hardness and abrasion resistance of the ink layer, while also enhancing the adhesion between the ink layer and the PCB multilayer board surface, thus preparing the ink layer for subsequent DI exposure processing. For instance, radiant heating or stronger convection heating can be used. Baking temperature is a key parameter affecting the drying and performance of the ink layer. An appropriate baking temperature can effectively promote solvent evaporation and control the curing rate of the ink. Baking time is another important parameter to ensure the ink layer is fully dried and meets performance standards. A sufficiently long baking time ensures complete solvent evaporation and stabilizes the internal structure of the ink layer.

[0069] This invention effectively solves the problems of insufficient ink drying or uneven surface by introducing a pre-baking process after low-temperature solder resist ink treatment and before DI exposure treatment, and by adopting a segmented baking method. Specifically, after the ink layer is formed on the surface of the embedded groove of the PCB multilayer board, a first-stage baking is performed. In this stage, the PCB multilayer board is gradually heated at a relatively mild baking temperature and time, allowing most of the volatile solvents in the ink layer to slowly and evenly escape, avoiding defects such as bubbles, pinholes, or surface unevenness that may occur due to rapid solvent evaporation caused by rapid heating. Subsequently, a second-stage baking is performed, using a slightly higher baking temperature and a longer baking time, aiming to further and thoroughly remove residual solvents in the ink layer and promote the stabilization of the internal structure of the ink layer. For example, it can promote the initial cross-linking of prepolymers in the ink, thereby improving the density, hardness, and adhesion of the ink layer to the PCB multilayer board. Through this two-stage gradient baking, the ink layer can be fully and uniformly pre-dried and pre-cured, resulting in a smooth surface and release of internal stress, providing an ideal ink state for subsequent DI exposure treatment. This process ensures that during DI exposure, the laser can precisely target a stable and uniform ink layer, thereby forming a clear, high-precision exposure pattern, which ultimately helps to create high-quality target pads at the bottom of the embedding tank.

[0070] By employing the aforementioned technical solution, a segmented pre-baking process is performed on the PCB multilayer board after low-coat solder resist ink treatment and before DI exposure. This effectively removes residual solvent from the ink layer and makes the ink layer surface smoother and more uniform. This significantly improves the adhesion between the ink layer and the PCB multilayer board, reducing defects such as bubbles, pinholes, and blurred exposure patterns caused by solvent evaporation or uneven ink layer during subsequent DI exposure. Therefore, this solution ensures the accuracy and stability of DI exposure, enabling the formation of clearer, more precise, and reliable target pads at the bottom of the embedding tank, thereby improving the overall manufacturing quality and yield of the PCB pads for embedded devices.

[0071] In step 140, the PCB multilayer board is subjected to DI exposure processing, which specifically includes: the pre-baked PCB multilayer board is fixed in the DI exposure machine, and laser scanning exposure is performed according to the preset solder resist data using a laser source in the 355nm-405nm ultraviolet band and an energy density of 80-150mJ / cm².

[0072] In step 140, the pre-baked PCB multilayer board is fixed in the DI exposure machine to ensure its stable position during exposure and prevent deviations in the exposed pattern due to any movement or vibration. This fixing can be achieved in various ways, such as using a vacuum adsorption platform to firmly attach the PCB multilayer board to the stage of the exposure machine, or using mechanical clamps, positioning pins, etc., for precise fixation. Based on preset solder resist data, which is digital graphic data used to guide the DI exposure process, it contains the precise geometry, size, and position information of the target pads. This data is usually in the form of CAD / CAM files (such as Gerber files or ODB++ files) and is read and parsed by the control system of the DI exposure machine. A laser source in the 355nm-405nm ultraviolet band refers to a laser device used to provide exposure energy; its wavelength range falls within the ultraviolet light range and can be effectively absorbed by the photosensitizer in the solder resist ink, thereby triggering a photochemical reaction. The laser source can be of various types, such as a solid-state laser (e.g., a DPSS laser) or a semiconductor laser, with beam shaping and transmission achieved through an optical system. The energy density of 80-150 mJ / cm² refers to the laser energy received per unit area and is a key parameter for controlling the exposure degree of the solder resist ink. This energy density can be precisely controlled by adjusting parameters such as the laser's output power, laser scanning speed, and spot size. Laser scanning exposure refers to the laser beam scanning the ink layer point-by-point or line-by-line according to the pattern path defined in the solder resist material, causing a photochemical reaction in the irradiated area and forming a latent image. This scanning method can employ a galvanometer scanning system, a multi-beam scanning system, or a scanning method combined with platform movement.

[0073] In the aforementioned method for fabricating circuit board pads for embedded devices, to overcome the challenge of high-precision exposure in the embedded trench area, this invention achieves precise patterning of the ink layer by performing DI exposure processing on the PCB multilayer board. Specifically, the pre-baked PCB multilayer board is firmly fixed on the DI exposure machine, which effectively eliminates possible minute displacements during the exposure process, thereby ensuring the geometric accuracy of the exposure. The DI exposure machine guides the laser source for scanning based on preset solder resist data, which precisely defines the pattern of the target pads. By using a laser source in the 355nm-405nm ultraviolet band, its energy can be efficiently absorbed by the solder resist ink, triggering the required photochemical reaction. At the same time, precisely controlling the laser energy density within the range of 80-150mJ / cm² ensures that the ink layer receives uniform and appropriate exposure throughout the entire exposure area, including inside the embedded trench, avoiding problems of underexposure or overexposure. The laser scanning exposure method, combined with the precise control of the above parameters, enables the formation of a clear latent image on the ink layer that is highly consistent with the solder resist material. This provides a high-quality foundation for subsequent development and curing steps, thus effectively solving the technical challenge of creating high-precision solder pad patterns in complex embedded trench structures.

[0074] Through the above technical solution, high-precision and high-uniformity DI exposure of the ink layer on the surface of the PCB multilayer board and within the embedding groove can be achieved during the fabrication of circuit board pads for embedded devices. Precise fixing methods avoid displacement errors during exposure; preset solder resist data ensures the accuracy of the pattern; a specific wavelength laser source and strictly controlled energy density ensure sufficient and uniform exposure of the ink layer, especially in areas with a certain depth such as the embedding groove, effectively avoiding underexposure or overexposure. Laser scanning exposure further enhances the fineness of the pattern and the ability to fabricate complex patterns. Therefore, this solution significantly improves the fabrication accuracy and quality of the target pads, reduces the defect rate, and thus provides a solid foundation for reliable connection of embedded devices.

[0075] In step 140, the developing process and the curing process specifically include: A sodium carbonate aqueous solution with a mass concentration of 0.8%-1.2% was used to dissolve the ink in the unexposed areas of the PCB multilayer board by spraying, followed by water washing to remove the residual sodium carbonate aqueous solution and ink from the PCB multilayer board. The PCB multilayer board that has completed the developing process is placed in a curing oven and baked at a temperature of 140°C-150°C for 30-60 minutes to fix it. Figure 9 As shown, the target pad is obtained.

[0076] In step 140, the developing process selectively dissolves and removes the solder resist ink areas on the PCB multilayer board that have not been exposed to ultraviolet light using a chemical solution, thereby exposing the underlying substrate or conductive layer to form the desired pad pattern. The key to this step is precise control of ink removal to ensure pattern clarity and edge neatness. The curing process involves heating or other methods to cause the solder resist ink layer remaining on the PCB multilayer board after developing to undergo a polymerization reaction, thereby hardening and firmly adhering to the PCB multilayer board surface, improving its mechanical strength, chemical resistance, and insulation properties, providing reliable protection for subsequent manufacturing processes. A sodium carbonate aqueous solution of a specific mass concentration is used as the developer to provide a suitable alkaline environment for efficiently and gently dissolving the unexposed solder resist ink, avoiding excessive erosion of exposed areas. This concentration range is set to balance developing speed and developing precision, ensuring complete ink removal. Developing by spraying allows the developer to contact the PCB multilayer board surface evenly and fully, improving developing efficiency and uniformity, while also helping to promptly wash away dissolved ink particles, reducing residue. Water washing is a necessary step after development. Its purpose is to thoroughly remove residual developer (sodium carbonate aqueous solution) and dissolved ink from the surface of the PCB multilayer board and the embedding tank, preventing these residues from adversely affecting subsequent processes or the performance of the final product. Baking the PCB multilayer board in a curing oven is a common method for thermosetting solder resist inks. The curing oven provides a controlled heating environment that allows the ink to fully cross-link and cure within a set temperature and time. Precise control of the baking temperature and time is crucial for ensuring complete curing of the ink layer, optimal adhesion, and excellent physicochemical properties.

[0077] The present invention utilizes a specific concentration of sodium carbonate aqueous solution for development via spraying after DI exposure treatment. This efficiently and uniformly removes solder resist ink from unexposed areas of the PCB multilayer board, ensuring the clarity and precision of the target pad pattern. Subsequent water washing thoroughly removes residual developer and ink, avoiding chemical contamination and potential short-circuit risks. Based on this, the PCB multilayer board is placed in a curing oven for thermal curing at precisely controlled temperature and time, allowing the exposed and retained solder resist ink layer to fully cross-link and harden, forming a dense and durable protective layer. This refined development and curing process, working closely with the preceding DI exposure treatment, ensures precise shaping and excellent insulation protection of the target pads at the bottom of the embedding tank, thereby significantly improving the overall quality and reliability of the embedded device circuit board pads.

[0078] The above technical solution ensures that the solder resist ink layer of the target pads at the bottom of the embedded slots in PCB multilayer boards has precise pattern definition and excellent curing performance. This effectively avoids problems such as ink residue due to incomplete development or poor ink layer adhesion and weak chemical resistance due to insufficient curing, thereby significantly improving the manufacturing precision and long-term reliability of the embedded device circuit board pads and providing a solid foundation for the stable operation of embedded devices.

[0079] Example 3: Based on Embodiment 1 or Embodiment 2, this embodiment provides an embodiment of a circuit board pad fabrication apparatus for embedded devices. This apparatus is used to execute the circuit board pad fabrication method for embedded devices in Embodiment 1 or Embodiment 2 to fabricate printed circuit boards.

[0080] In this embodiment, the present invention integrates low-spray solder resist ink treatment with precisely controlled DI exposure, development, and curing processes into the device, thereby ensuring the formation of a uniform ink layer with excellent heat-pressing resistance inside the embedding tank. Due to the use of specific low-spray parameters, the ink layer is uniformly distributed and of moderate thickness within the embedding tank, avoiding the problem of uneven ink coverage in complex structures found in traditional methods. Simultaneously, the optimized parameters of the DI exposure and curing processes ensure that the ink layer maintains good adhesion and integrity under the high temperature and pressure conditions of subsequent multilayer lamination, preventing embrittlement or cracking. Through the above technical solution, the technical problem of surface protective layer deterioration of inner layer pads during multiple lamination processes is effectively solved, significantly improving the reliability and process feasibility of embedded device pads. Compared to the limitations of traditional outer layer solder resist inks used in inner layer applications, this device, through systematic optimization of process parameters, enables the ink layer to adapt to harsh lamination environments, ensuring stable pad surface conditions, thereby guaranteeing solder wettability and bonding strength, and avoiding potential electrical short circuits or open circuits caused by ink damage.

[0081] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. Similarly, for the sake of brevity and to aid in understanding one or more aspects of the invention, in the description of exemplary embodiments of the invention above, various features of the embodiments are sometimes grouped together in a single embodiment, figure, or description thereof. The claims, which follow the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0082] Those skilled in the art will understand that the modules in the device of the embodiment can be adaptively changed and placed in one or more devices different from that embodiment. Modules, units, or components in the embodiment can be combined into a single module, unit, or component, and further, they can be divided into multiple sub-modules, sub-units, or sub-components, except that at least some of such features and / or processes or units are mutually exclusive.

[0083] It should be noted that the above embodiments are illustrative of the invention and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several systems, several of these systems may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names. The steps in the above embodiments, unless otherwise specified, should not be construed as limiting the order of execution.

Claims

1. A method for fabricating circuit board pads for embedded devices, characterized in that the method... include: Obtain a multilayer PCB board, wherein the multilayer PCB board has an area for embedded components; The embedded device area of ​​the PCB multilayer board is opened to create an embedded groove; The PCB multilayer board is subjected to pre-soldering treatment, and the embedded groove of the PCB multilayer board is treated with low-pressure spray solder resist ink to form an ink layer on the surface of the PCB board and the surface of the embedded groove. The PCB multilayer board is subjected to DI exposure processing, development processing and curing processing in sequence to form target pads at the bottom of the embedded groove.

2. The method for fabricating circuit board pads for embedded devices according to claim 1, characterized in that, The acquisition of the PCB multilayer board specifically includes: A first multilayer board is obtained, and a device embedding area is formed on the first surface of the first multilayer board; Pre-attach the PI composite film to the area where the device is embedded; A pre-set second multilayer board is pressed onto the first surface of the first multilayer board to form a PCB multilayer board, and the thickness of the second multilayer board is greater than or equal to the thickness of the embedded device.

3. The method for fabricating circuit board pads for embedded devices according to claim 2, characterized in that, The process of creating embedding grooves in the embedded component area of ​​the PCB multilayer board includes: The first groove is formed in the embedded device area by a depth-controlled milling method, and a dielectric layer is provided between the bottom of the first groove and the PI composite film. The dielectric layer and PI composite film at the bottom of the first groove are cut and embedded into the groove using a laser. The impurities remaining in the buried trench are removed by air blowing or water washing.

4. The method for fabricating circuit board pads for embedded devices according to claim 1, characterized in that, The pre-soldering treatment of the PCB multilayer board includes, in sequence: mechanical / chemical degreasing treatment, first water washing treatment, micro-etching roughening treatment, second water washing treatment, acid washing treatment, third water washing treatment, anti-oxidation treatment, fourth water washing treatment and drying treatment.

5. The method for fabricating circuit board pads for embedded devices according to claim 1, characterized in that, Apply low-coating solder resist ink to the embedded grooves of PCB multilayer boards, specifically including: Solder resist ink is applied to the embedded groove using a spraying pressure of 100psi-300psi, a spray gun movement speed of 200mm / s-600mm / s, and a spraying time of 60min-120min.

6. The method for fabricating circuit board pads for embedded devices according to claim 5, characterized in that, The thickness of the ink layer is 20±5μm.

7. The method for fabricating circuit board pads for embedded devices according to claim 1, characterized in that, After applying low-coating solder resist ink to the embedded grooves of the PCB multilayer board, and before performing DI exposure treatment on the PCB multilayer board, a pre-baking treatment of the PCB multilayer board is also included. The pre-baking process specifically includes: The first stage of baking is carried out on the PCB multilayer board according to the baking temperature of 70℃-85℃ and the baking time of 15min-25min. The second stage of baking is performed on the PCB multilayer board at a baking temperature of 80℃-95℃ and a baking time of 20min-40min to complete the pre-baking of the ink layer of the PCB multilayer board.

8. The method for fabricating circuit board pads for embedded devices according to claim 1, characterized in that, The DI exposure process for the PCB multilayer board specifically includes: The pre-baked PCB multilayer board is fixed in the DI exposure machine and laser scanning exposure is performed according to the preset solder resist data using a laser source in the 355nm-405nm ultraviolet band and an energy density of 80-150mJ / cm².

9. The method for fabricating circuit board pads for embedded devices according to claim 1, characterized in that, The developing and curing processes specifically include: A sodium carbonate aqueous solution with a mass concentration of 0.8%-1.2% was used to dissolve the ink in the unexposed areas of the PCB multilayer board by spraying, followed by water washing to remove the residual sodium carbonate aqueous solution and ink from the PCB multilayer board. The PCB multilayer board that has completed the developing process is placed in a curing oven and baked at a baking temperature of 140°C-150°C for 30-60 minutes to fix it, thus obtaining the target pad.

10. A device for fabricating circuit board pads for embedded devices, characterized in that, The apparatus is used to perform the method for fabricating circuit board pads of the embedded device according to any one of claims 1-9, and to fabricate a printed circuit board.

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