A manufacturing method for improving the BGA area flatness of a glass-embedded outer layer circuit board

Abstract

The application relates to the technical field of electronic circuit board manufacturing, and discloses a glass-embedded outer-layer circuit board BGA area flatness improvement manufacturing method, which comprises the following steps: material preparation and pretreatment, selecting two or three copper-clad plates, particularly designing the second layer as a ground layer, and flexibly designing the third layer; meanwhile, preparing a glass sheet with accurate size and resin with low DK and low CTE characteristics; deeply cleaning the copper-clad plates and the glass to ensure that no dirt and oxide residues are left; pattern etching and depth-controlled milling, removing the copper layer at the specified position on the second copper-clad plate through pattern etching to reserve space for glass embedding, and meanwhile, the third layer design is reserved; then, depth-controlled milling is carried out to accurately control the milling depth. The purpose of the glass-embedded outer-layer circuit board BGA area flatness improvement manufacturing method is to solve the defects of traditional circuit boards in BGA area flatness control.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit board manufacturing technology, specifically a manufacturing method for improving the flatness of the BGA area in a glass-embedded outer layer circuit board. Background Technology

[0002] In the design of high-speed data transmission module circuit boards, the flatness of the BGA (Ball Grid Array) area plays a crucial role. The flatness of this area not only directly affects the soldering quality but also has a profound impact on the stability of component connections. If there is unevenness in the BGA area, the solder balls may not be evenly distributed during the soldering process, leading to serious problems such as poor soldering, short circuits, or open circuits. In addition, uneven BGA areas will increase the contact resistance between components and the circuit board, reduce signal transmission efficiency, and even affect the stability and reliability of the entire system.

[0003] In the manufacturing process of traditional circuit boards, due to differences in the physical properties of materials such as CTE and Young's modulus, it is often difficult to achieve ideal flatness. This inconsistency in material properties can cause uneven expansion or deformation of the circuit board when heated or stressed, resulting in significant height differences in the BGA area. As a critical part of the connection between the circuit board and components, the flatness of the BGA area directly affects the soldering quality and the stability of component connections. Large height differences in the BGA area not only increase the difficulty of soldering but may also lead to faults such as poor soldering, short circuits, or open circuits, seriously affecting the overall performance and reliability of the circuit board. In addition, due to the limitations of the manufacturing process, it is often difficult to precisely control the flatness of the BGA area in traditional circuit board manufacturing. Even with some remedial measures, such as adding fillers and adjusting process parameters, it is difficult to fundamentally solve the flatness problem caused by differences in material properties. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of traditional circuit boards in controlling the flatness of the BGA area, and to propose a manufacturing method for improving the flatness of the BGA area in glass-embedded outer circuit boards.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] A manufacturing method for improving the flatness of the BGA area in a glass-embedded outer layer circuit board includes the following steps:

[0007] S10. Material preparation and pretreatment: Select two or three layers of copper clad laminate, with the second layer specially designed as a ground layer and the third layer designed flexibly. At the same time, prepare glass sheets with precise dimensions and resin with low DK and low CTE properties, and perform deep cleaning on the copper clad laminate and glass to ensure that there is no dirt or oxide residue.

[0008] S20, Pattern Etching and Controlled Depth Milling: Pattern etching removes the copper layer at a specified location on the second copper-clad laminate to reserve space for glass embedding while retaining the third layer design. Subsequently, controlled depth milling is performed to precisely control the milling depth, ensuring that the glass cloth is penetrated without damaging the underlying copper foil. Laser scanning further burns off the resin, exposing the copper foil and providing clear and accurate positioning for glass embedding.

[0009] S30, Resin Coating and Glass Embedding: Low DK and low CTE resins are precisely coated under the glass. The glass size is carefully designed to ensure perfect filling of the gap with the copper-clad laminate. After the glass is embedded, the resin is evenly filled into the gap by vacuum light pressure to form a tightly bonded structure.

[0010] S40, Drilling, Cleaning and Silver Plating: The glass is precisely drilled according to the etched alignment holes, then cleaned to remove impurities, followed by silver plating. Through a complex chemical reaction, a silver surface is formed on the glass surface and the inner wall of the hole. Finally, copper electroplating is performed to integrate the silver and copper, achieving metal fusion between the glass and the circuit board.

[0011] S50, lamination and subsequent processing: The copper-clad laminate, prepreg and copper foil are laminated to form an integrated circuit board. The lamination process strictly controls the temperature, pressure and time to ensure the quality of the circuit board. The subsequent processing includes traditional processing steps such as drilling and copper plating, as well as cutting and testing as needed.

[0012] Based on the above technical solution, the present invention can be further improved as follows.

[0013] Furthermore, in step S10, when selecting two or three layers of copper-clad laminate, it is also necessary to specify key parameters such as the copper thickness, insulating layer material, dielectric constant, and coefficient of thermal expansion of the copper-clad laminate to meet product design requirements. The selected copper-clad laminate is batch verified to ensure its quality is stable and free from internal defects such as bubbles and cracks. In addition to precise dimensions, the selection of glass sheets also needs to consider their thermal stability, corrosion resistance, and compatibility with resin to ensure that they are not easily broken or deformed during processing.

[0014] Furthermore, in step S10, a ground copper layer corresponding to the BGA area is provided on the ground copper clad laminate, and the ground copper layer is connected to the ground terminal of the circuit board through a preset conductive path to ensure the grounding performance of the BGA area. Step S10 also includes surface roughening treatment of the copper clad laminate and glass, using sandblasting or chemical oxidation to increase the micro-roughness of the copper clad laminate and glass surfaces. In the pretreatment stage, the copper clad laminate and glass are dried to completely remove surface moisture.

[0015] Furthermore, in step S20, the pattern etching is performed using chemical etching or laser etching technology, and the flatness of the copper layer edge after etching is controlled within ±5μm to ensure the space reserved for glass embedding. In the controlled-depth milling process of step S20, a high-precision CNC milling machine is used for milling operations, and the milling depth control accuracy reaches ±2μm to ensure that the glass cloth is penetrated without damaging the underlying copper foil.

[0016] Furthermore, in step S30, the coating of the low DK and low CTE resins is carried out using precision coating technology, and the coating thickness uniformity is controlled within ±3μm to ensure a tight bond between the glass and the copper-clad laminate and complete filling of the gaps.

[0017] Furthermore, in the silver plating process of step S40, the complex chemical reaction includes forming a dense silver plating layer on the glass surface and the inner wall of the hole, and the thickness of the silver plating layer is controlled between 0.5μm and 1.5μm to ensure the firmness and conductivity of the silver and copper electroplating. In the pressing process of step S50, the pressing temperature and pressure are controlled within preset ranges, and the pressing time is precisely calculated according to the size and thickness of the circuit board to ensure the quality and flatness of the circuit board.

[0018] Furthermore, after step S30 and before step S40, the resin should be cured using a heating curing oven to ensure that the resin is fully cured at the appropriate temperature and time. After step S40 and before step S50, the surface should be polished using professional polishing equipment and processes to remove unevenness and defects from the glass surface and the circuit board surface.

[0019] Furthermore, the subsequent processing in step S50 also includes surface treatment and anti-oxidation treatment of the circuit board to improve the surface quality and corrosion resistance of the circuit board. Throughout the manufacturing process, X-ray inspection or ultrasonic inspection is used to monitor and evaluate the internal structure, defects and performance of the circuit board in real time.

[0020] Compared with the prior art, the technical solution of this application has the following beneficial technical effects:

[0021] In the material preparation and pretreatment stage, this invention effectively solves the problem of uncontrollable flatness in traditional circuit boards due to differences in material properties by specially designing the second layer as a ground layer, flexibly designing the third layer, selecting resins with low DK and low CTE characteristics, and performing deep cleaning treatment. This material selection and treatment method can significantly reduce the expansion or deformation of the circuit board under heat or stress, thereby improving the flatness of the BGA area. Secondly, in the pattern etching and controlled-depth milling stage, precise control of the milling depth and laser scanning to burn off the resin provides clear and accurate positioning for glass embedding. The precise control of this step ensures the accuracy and stability of glass embedding, avoiding the problem of uncontrollable flatness of the BGA area due to process limitations in traditional methods. Furthermore, in the resin coating and glass embedding stage, low DK and low CTE characteristics are used. CTE resin is precisely coated beneath the glass, and then vacuum pressure is used to evenly fill the gaps, forming a tightly bonded structure. This tight bond further reduces the deformation of the circuit board under heat or stress, thereby improving the flatness of the BGA area. Furthermore, during the drilling, cleaning, and silver plating stages, precise drilling, cleaning, and silver plating achieve metal fusion between the glass and the circuit board. This step not only improves the connection strength between the glass and the circuit board but also further ensures the flatness and stability of the BGA area. Finally, in the lamination and subsequent processing stages, strict control of the temperature, pressure, and time during the lamination process, along with subsequent traditional processing procedures and testing, ensures the quality and performance of the circuit board. This rigorous control further consolidates the results achieved in the preceding steps, ultimately improving and guaranteeing the flatness of the BGA area. Attached Figure Description

[0022] Figure 1 This is a flowchart of a manufacturing method for improving the flatness of the BGA area in a glass-embedded outer circuit board according to the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Combination Figure 1 As shown, the present invention provides a manufacturing method for improving the flatness of the BGA area in a glass-embedded outer layer circuit board, comprising the following steps:

[0025] S10. Material preparation and pretreatment: Select two or three layers of copper clad laminate, with the second layer specially designed as a ground layer and the third layer designed flexibly. At the same time, prepare glass sheets with precise dimensions and resin with low DK and low CTE properties, and perform deep cleaning on the copper clad laminate and glass to ensure that there is no dirt or oxide residue.

[0026] S20, Pattern Etching and Controlled Depth Milling: Pattern etching removes the copper layer at a specified location on the second copper-clad laminate to reserve space for glass embedding while retaining the third layer design. Subsequently, controlled depth milling is performed to precisely control the milling depth, ensuring that the glass cloth is penetrated without damaging the underlying copper foil. Laser scanning further burns off the resin, exposing the copper foil and providing clear and accurate positioning for glass embedding.

[0027] S30, Resin Coating and Glass Embedding: Low DK and low CTE resins are precisely coated under the glass. The glass size is carefully designed to ensure perfect filling of the gap with the copper-clad laminate. After the glass is embedded, the resin is evenly filled into the gap by vacuum light pressure to form a tightly bonded structure.

[0028] S40, Drilling, Cleaning and Silver Plating: The glass is precisely drilled according to the etched alignment holes, then cleaned to remove impurities, followed by silver plating. Through a complex chemical reaction, a silver surface is formed on the glass surface and the inner wall of the hole. Finally, copper electroplating is performed to integrate the silver and copper, achieving metal fusion between the glass and the circuit board.

[0029] S50, lamination and subsequent processing: The copper-clad laminate, prepreg and copper foil are laminated to form an integrated circuit board. The lamination process strictly controls the temperature, pressure and time to ensure the quality of the circuit board. The subsequent processing includes traditional processing steps such as drilling and copper plating, as well as cutting and testing as needed.

[0030] In a preferred embodiment, the present invention can be further configured as follows: In step S10, when selecting two or three layers of copper-clad laminate, it is also necessary to specify key parameters such as the copper thickness, insulating layer material, dielectric constant, and coefficient of thermal expansion of the copper-clad laminate to meet product design requirements. Batch verification of the selected copper-clad laminate is conducted to ensure stable quality and absence of internal defects such as bubbles and cracks. In addition to precise dimensions, the selection of the glass sheet must also consider its thermal stability, corrosion resistance, and compatibility with the resin to ensure it is not easily broken or deformed during processing. In step S10, it is explicitly required that the key parameters of the selected two or three layers of copper-clad laminate be specified, including copper thickness, insulating layer material, dielectric constant, and coefficient of thermal expansion. Precise parameter control is fundamental to ensuring that product design requirements are met. Batch verification of copper-clad laminates ensures stable quality and the absence of internal defects such as bubbles and cracks. This step greatly reduces the risk of circuit board performance instability caused by material quality issues. In addition, the selection of glass sheets requires not only precise dimensions but also consideration of their thermal stability, corrosion resistance, and compatibility with resins. This comprehensive consideration of characteristics ensures that the glass sheets are not easily broken or deformed during processing, thereby further improving the flatness and stability of the BGA area. Especially in high-speed data transmission module circuit boards, these characteristics are crucial for ensuring the efficiency and stability of signal transmission.

[0031] In a preferred embodiment, the present invention can be further configured as follows: In step S10, a ground copper layer corresponding to the BGA area is provided on the ground copper-clad laminate, and the ground copper layer is connected to the ground terminal of the circuit board through a preset conductive path to ensure the grounding performance of the BGA area. Step S10 also includes surface roughening treatment of the copper-clad laminate and glass, using sandblasting or chemical oxidation to increase the micro-roughness of the copper-clad laminate and glass surfaces. In the pretreatment stage, the copper-clad laminate and glass are dried to completely remove surface moisture. In step S10, it is particularly emphasized that a ground copper layer corresponding to the BGA area is provided on the ground copper-clad laminate and connected to the ground terminal of the circuit board through a preset conductive path. This design not only ensures good grounding performance of the BGA area and effectively reduces electromagnetic interference and noise, but also improves the stability and reliability of signal transmission. This is especially important for high-speed data transmission module circuit boards because good grounding is crucial. Ground performance is one of the key factors in ensuring data transmission efficiency and system stability. Furthermore, the text mentions surface roughening treatment of the copper-clad laminate (CCL) and glass, using sandblasting or chemical oxidation methods to increase the micro-roughness of the CCL and glass surfaces. This step significantly enhances the bonding force between the CCL and glass, allowing the resin to fill the gaps more evenly, thereby further improving the flatness of the BGA area and the overall structural stability. Simultaneously, surface roughening treatment also helps improve soldering quality and component connection stability, reducing the risk of failures due to poor contact. In addition, during the pretreatment stage, the CCL and glass are dried to completely remove surface moisture, effectively preventing the influence of moisture on subsequent processing and ensuring the quality stability and reliability of the circuit board during manufacturing. The drying process also helps improve resin wetting and curing effects, further enhancing the overall performance of the circuit board.

[0032] In a preferred embodiment, the present invention can be further configured as follows: In step S20, the pattern etching employs chemical etching or laser etching technology, and the flatness of the copper layer edge after etching is controlled within ±5μm to ensure the reserved space size for glass embedding. In the controlled-depth milling process of step S20, a high-precision CNC milling machine is used for milling operations, and the milling depth control accuracy reaches ±2μm to ensure penetration of the glass cloth without damaging the underlying copper foil. In step S20, the pattern etching technology is explicitly required to use either chemical etching or laser etching, both of which can achieve high-precision etching effects. By precisely controlling the etching process, the flatness of the copper layer edge after etching is strictly controlled within ±5μm. This precision control is crucial for… Ensuring the reserved space for glass embedding is crucial. It effectively avoids problems such as difficulty in glass embedding or positional deviation caused by inaccurate space dimensions. At the same time, high-precision etching can also ensure the overall structural stability and signal transmission efficiency of the circuit board. In addition, during the controlled-depth milling process, a high-precision CNC milling machine is used to operate, and the milling depth is strictly controlled to an accuracy of ±2μm. This high-precision milling operation not only ensures that the glass cloth can be penetrated without damaging the underlying copper foil, but also further improves the flatness of the BGA area and the stability of the overall structure. Because the precise control of the milling depth can avoid unnecessary damage to the underlying copper foil, it reduces the risk of performance degradation or failure due to processing errors.

[0033] In a preferred embodiment, the present invention can be further configured as follows: in step S30, the coating of low DK and low CTE resins employs precision coating technology, and the coating thickness uniformity is controlled within ±3μm to ensure a tight bond between the glass and the copper-clad laminate and complete filling of the gaps. In step S30, low DK and low CTE resins... The coating of CTE resin is explicitly required to employ precision coating technology. This technology ensures that the resin is uniformly and precisely coated under the glass. By strictly controlling the coating thickness uniformity within ±3μm, not only is a tight bond between the glass and the copper-clad laminate achieved, but also complete filling of the gaps is ensured. This precision control is crucial for improving the flatness of the BGA area, as it effectively avoids structural instability and performance degradation caused by uneven resin coating or incomplete gap filling. The adoption of precision coating technology further enhances the overall quality and reliability of the circuit board. The uniform coating and complete filling of the resin not only strengthens the bonding force between the glass and the copper-clad laminate but also improves the circuit board's resistance to bending and deformation. This is particularly important for high-performance applications such as high-speed data transmission module circuit boards, which have extremely high requirements for circuit board flatness and structural stability. In addition, the selection of low DK and low CTE resins also brings significant benefits. These resins have the characteristics of low dielectric constant and low coefficient of thermal expansion, which can effectively reduce the expansion or deformation of the circuit board when heated or stressed, thereby further improving the flatness and stability of the BGA area.

[0034] In a preferred embodiment, the present invention can be further configured as follows: during the silver plating process in step S40, a complex chemical reaction includes forming a dense silver plating layer on the glass surface and the inner wall of the hole, and the thickness of the silver plating layer is controlled between 0.5 μm and 1.5 μm to ensure the strong bond and conductivity of the silver and copper electroplating. During the pressing process in step S50, the pressing temperature and pressure are controlled within preset ranges, and the pressing time is precisely calculated according to the size and thickness of the circuit board to ensure the quality and flatness of the circuit board. During the silver plating process in step S40, a dense silver plating layer is formed on the glass surface and the inner wall of the hole through a complex chemical reaction. The thickness of this silver plating layer is precisely controlled between 0.5 μm and 1.5 μm. This range ensures both the strong bond and conductivity of the silver plating layer and the copper electroplating. The dense silver plating layer provides both stability and excellent conductivity, effectively preventing corrosion and oxidation, thus improving the durability and reliability of the circuit board. Furthermore, precise thickness control of the silver plating layer avoids performance degradation or processing difficulties caused by excessive thickness or thinness, further enhancing the overall quality of the circuit board. In addition, during the pressing process in step S50, the pressing temperature and pressure are strictly controlled within a preset range, and the pressing time is precisely calculated based on the size and thickness of the circuit board. This precise control of pressing parameters ensures that the circuit board achieves uniform pressure and temperature distribution during pressing, thereby avoiding circuit board deformation or structural instability caused by uneven pressing. Simultaneously, precise pressing time calculation ensures sufficient resin curing and stable formation of the circuit board structure, further improving the quality and flatness of the circuit board.

[0035] In a preferred embodiment, the present invention can be further configured as follows: after step S30 and before step S40, a resin curing process is performed using a heating curing oven to ensure complete curing of the resin at appropriate temperature and time. After step S40 and before step S50, a surface polishing process is performed using professional polishing equipment and processes to polish the glass surface and the circuit board surface to remove surface unevenness and defects. The resin curing process after step S30 and before step S40 is a crucial step. By using a heating curing oven to cure the resin under appropriate temperature and time conditions, it is ensured that the resin can be completely cured, forming a stable and robust structure. This step not only enhances the bonding force between the resin and the glass and copper-clad laminate, but also improves the circuit... The overall structural stability and heat resistance of the board, along with the fully cured resin, effectively prevent deformation or cracking during subsequent processing, thus ensuring the quality and flatness of the circuit board. Furthermore, the surface polishing process, performed after step S40 and before step S50, is a crucial step. Using professional polishing equipment and techniques, the glass and circuit board surfaces are finely polished to remove unevenness and imperfections, resulting in a smoother and flatter surface. This step not only enhances the aesthetics of the circuit board but, more importantly, ensures better bonding during lamination, reducing problems such as poor lamination or air bubbles caused by uneven surfaces. Simultaneously, a smooth circuit board surface facilitates subsequent component mounting and soldering, improving the reliability and durability of the circuit board.

[0036] In a preferred embodiment, the present invention can be further configured such that, in the subsequent processing of step S50, surface treatment and anti-oxidation treatment of the circuit board are also performed to improve the surface quality and corrosion resistance of the circuit board. Throughout the manufacturing process, X-ray inspection or ultrasonic inspection is used to monitor and evaluate the internal structure, defects, and performance of the circuit board in real time. In the subsequent processing of step S50, surface treatment and anti-oxidation treatment of the circuit board are crucial steps. Surface treatment can improve the physical and chemical properties of the circuit board surface, such as improving surface smoothness, roughness, and wettability, thereby enhancing the bonding force and welding quality between the circuit board and subsequent components. Anti-oxidation treatment, by forming a protective film on the surface of the circuit board, effectively prevents performance degradation caused by oxidation during manufacturing, storage, and use. Regarding reliability, these treatment measures not only improve the surface quality of the circuit board but also significantly enhance its corrosion resistance and service life. Furthermore, throughout the manufacturing process, real-time monitoring and evaluation of the circuit board's internal structure, defects, and performance using X-ray or ultrasonic testing are crucial for ensuring circuit board quality. X-ray testing can penetrate the circuit board material, clearly revealing its internal structure, including circuits, holes, and fillers, thus enabling the timely detection of potential defects and problems. Ultrasonic testing utilizes the propagation characteristics of ultrasound in materials to accurately measure and evaluate the circuit board's thickness, density, and defects. These testing methods not only offer advantages such as non-destructive testing, high efficiency, and accuracy but also allow for real-time monitoring of the circuit board's manufacturing process, enabling timely detection and correction of problems, thereby ensuring the overall quality and performance of the circuit board.

[0037] The example is as follows: S10, material preparation and pretreatment

[0038] Material selection:

[0039] Two or three layers of copper clad laminate are selected, where the second layer is designed as a ground layer with a copper thickness of 35μm, the insulating material is epoxy resin with a dielectric constant (DK) of 3.5 and a coefficient of thermal expansion (CTE) of 16ppm / ℃; the third layer is designed flexibly, with a copper thickness of 35μm as well.

[0040] The glass sheet is 100mm×100mm in size, has high thermal stability, strong corrosion resistance, good compatibility with resin, and its thickness is the same as that of the glass cloth in the copper clad laminate, i.e., 0.1mm.

[0041] Low DK and low CTE resin, with DK of 3.0 and CTE of 12 ppm / ℃.

[0042] Preprocessing:

[0043] Deep cleaning of copper-clad laminates and glass is performed using an ultrasonic cleaner with a special cleaning agent to ensure no dirt or oxide residue remains.

[0044] The copper-clad laminate and glass are roughened by sandblasting to increase the surface micro-roughness.

[0045] The copper-clad laminate and glass are dried at 100°C for 1 hour to completely remove surface moisture.

[0046] S20, Pattern Etching and Depth Control Milling

[0047] Pattern Etching:

[0048] Chemical etching technology is used to remove the copper layer at a specified location on the second copper-clad laminate, leaving space for the glass to be embedded. After etching, the flatness of the copper layer edge is controlled within ±5μm.

[0049] The third layer design is retained, but no etching is performed.

[0050] Controlled depth milling and fishing:

[0051] High-precision CNC milling machines are used for milling operations to precisely control the milling depth, ensuring that the glass cloth is penetrated without damaging the underlying copper foil. The milling depth control accuracy reaches ±2μm.

[0052] Laser scanning further burns away the resin, exposing the copper foil and providing clear and accurate positioning for glass embedding.

[0053] S30, Resin Coating and Glass Embedding

[0054] Resin coating:

[0055] Using precision coating technology, low DK and low CTE resins are precisely coated under the glass, with the coating thickness uniformity controlled within ±3μm.

[0056] The glass is designed to be 4μm smaller on each side than the etching frame of the copper-clad laminate, ensuring perfect filling of the gap with the copper-clad laminate.

[0057] Glass embedding:

[0058] A glass plate is placed on a copper-clad laminate coated with resin, and the resin is uniformly filled into the gaps by gentle vacuum pressure to form a tightly bonded structure.

[0059] S35, Resin Curing Treatment

[0060] The resin is cured in a heating curing oven at 150°C for 2 hours to ensure complete curing at the appropriate temperature and time.

[0061] S40, Drilling, Cleaning and Silver Plating

[0062] Drilling holes:

[0063] Precisely drill holes in the glass according to the etched alignment holes, and the depth of the holes should penetrate the glass.

[0064] Cleaning:

[0065] Use deionized water to clean and remove impurities.

[0066] Silver plating:

[0067] Silver nitrate is dissolved in water, and then ammonia and sodium hydroxide solution are added to prepare a silver plating solution.

[0068] Invert sugar was used as a reducing agent.

[0069] Sensitize with a dilute stannous chloride solution, then wash thoroughly.

[0070] The silver plating solution and reducing solution are mixed and immediately poured onto the surface to form a dense silver plating layer on the glass surface and the inner wall of the hole. The thickness of the silver plating layer is controlled at 1 μm.

[0071] A copper plating process is performed to integrate the silver and copper plating.

[0072] S45, Surface polishing

[0073] Professional polishing equipment and processes are used to polish the glass and circuit board surfaces to remove unevenness and defects.

[0074] S50, lamination and subsequent processing

[0075] Pressing:

[0076] The copper-clad laminates, prepregs, and copper foils are laminated together to form an integrated circuit board.

[0077] The pressing temperature is controlled at 180℃, the pressure is 5MPa, and the pressing time is precisely calculated to be 2 hours based on the size and thickness of the circuit board to ensure the quality and flatness of the circuit board.

[0078] Follow-up processing:

[0079] Traditional processing steps such as drilling holes in circuit boards and electroplating with copper plating are performed.

[0080] The circuit board is cut and tested as needed.

[0081] Surface treatment and anti-oxidation treatment are applied to the circuit board to improve surface quality and corrosion resistance.

[0082] Real-time monitoring and assessment

[0083] Throughout the manufacturing process, X-ray or ultrasonic testing is used to monitor and evaluate the internal structure, defects, and performance of the circuit boards in real time to ensure product quality.

[0084] By implementing the above detailed steps and specific parameters, a glass-embedded outer layer circuit board was successfully manufactured, which significantly improved the flatness of the BGA area and met the product design requirements.

[0085] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0086] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A glass-embedded outer layer wiring board BGA area flatness improvement manufacturing method, characterized by, Includes the following steps: S10. Material preparation and pretreatment: Select two or three layers of copper clad laminate, design the second layer as the ground layer, and at the same time, prepare glass sheets with precise dimensions and resin with low DK and low CTE properties. Perform deep cleaning on the copper clad laminate and glass to ensure that there is no dirt or oxide residue. S20, Pattern Etching and Controlled Depth Milling: Pattern etching removes the copper layer at a specified location on the second copper-clad laminate to reserve space for glass embedding while retaining the third layer design. Subsequently, controlled depth milling is performed to precisely control the milling depth, ensuring that the glass cloth is penetrated without damaging the underlying copper foil. Laser scanning further burns off the resin, exposing the copper foil and providing clear and accurate positioning for glass embedding. S30, Resin Coating and Glass Embedding: Low DK and Low CTE resins are precisely coated under the glass. The glass size is designed to ensure the filling of the gap with the copper-clad laminate. After the glass is embedded, the resin is evenly filled into the gap by vacuum light pressure to form a tightly bonded structure. S40, Drilling, Cleaning and Silver Plating: The glass is precisely drilled according to the etched alignment holes, then cleaned to remove impurities, followed by silver plating. Through a complex chemical reaction, a silver surface is formed on the glass surface and the inner wall of the hole. Finally, copper electroplating is performed to integrate the silver and copper, achieving metal fusion between the glass and the circuit board. S50, lamination and subsequent processing: Lamination of each layer of copper-clad laminate, prepreg and copper foil to form an integrated circuit board. The lamination process strictly controls temperature, pressure and time to ensure the quality of the circuit board. Subsequent processing includes traditional processing steps such as drilling and copper plating, as well as cutting and testing. In step S20, the pattern etching is performed using chemical etching or laser etching technology, and the flatness of the copper layer edge after etching is controlled within ±5μm to ensure the space reserved for glass embedding. In the controlled depth milling process of step S20, a high-precision CNC milling machine is used for milling operations, and the milling depth control accuracy reaches ±2μm to ensure that the glass cloth is penetrated without damaging the underlying copper foil. In step S30, the coating of the low DK and low CTE resins is carried out using precision coating technology, and the coating thickness uniformity is controlled within ±3μm to ensure a tight bond between the glass and the copper-clad laminate and complete filling of the gaps. After step S30 and before step S40, the resin should be cured using a heating curing oven to ensure that the resin is fully cured at the appropriate temperature and time. After step S40 and before step S50, the surface should be polished using professional polishing equipment and processes to remove unevenness and defects from the glass surface and the circuit board surface.

2. The glass-embedded outer layer wiring board BGA area flatness improvement manufacturing method according to claim 1, characterized by, In step S10, when selecting two or three layers of copper clad laminate, it is also necessary to specify the key parameters of the copper thickness, insulating layer material, dielectric constant and thermal expansion coefficient of the copper clad laminate to meet the product design requirements. The selected copper clad laminate is batch verified to ensure that its quality is stable and free of internal defects. In addition to accurate dimensions, its thermal stability, corrosion resistance and compatibility with resin must also be considered to ensure that it is not easy to crack or deform during processing.

3. The manufacturing method for improving the flatness of the BGA area of ​​a glass-embedded outer circuit board according to claim 1, characterized in that, In step S10, a ground copper layer corresponding to the BGA area is provided on the ground copper clad laminate, and the ground copper layer is connected to the ground terminal of the circuit board through a preset conductive path to ensure the grounding performance of the BGA area. Step S10 also includes surface roughening treatment of the copper clad laminate and glass, using sandblasting or chemical oxidation to increase the micro-roughness of the copper clad laminate and glass surfaces. In the pretreatment stage, the copper clad laminate and glass are dried to completely remove surface moisture.

4. The manufacturing method for improving the flatness of the BGA area of ​​a glass-embedded outer circuit board according to claim 1, characterized in that, In the silver plating process of step S40, the complex chemical reaction includes forming a dense silver plating layer on the glass surface and the inner wall of the hole, and the thickness of the silver plating layer is controlled between 0.5μm and 1.5μm to ensure the firmness and conductivity of the silver and copper electroplating. In the pressing process of step S50, the pressing temperature and pressure are controlled within a preset range, and the pressing time is calculated according to the size and thickness of the circuit board to ensure the quality and flatness of the circuit board.

5. The manufacturing method for improving the flatness of the BGA area of ​​a glass-embedded outer circuit board according to claim 1, characterized in that, The subsequent processing in step S50 also includes surface treatment and anti-oxidation treatment of the circuit board to improve the surface quality and corrosion resistance of the circuit board. Throughout the manufacturing process, X-ray inspection or ultrasonic inspection is used to monitor and evaluate the internal structure, defects and performance of the circuit board in real time.

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