Manufacturing method for embedding ceramic substrate into copper-based PCB

Abstract

The invention discloses a manufacturing method for embedding a ceramic substrate into a copper-based printed circuit board. The manufacturing method comprises the following steps: manufacturing a ceramic substrate; manufacturing a copper substrate; mounting a ceramic substrate; and laminating and manufacturing the copper-based PCB. According to the invention, a plurality of ceramic substrates made of materials such as aluminum nitride or silicon nitride are embedded into the copper substrate, so that the ceramic substrates are used as efficient heat dissipation media of the chip and are directly thermally connected with the copper substrate. In addition, the prepreg and the copper foil are overlaid on the surface of the copper substrate, the surface of the copper substrate is flush with the ceramic substrate through a lamination process, and then high-density circuit wiring is formed through graphical processing. Compared with the prior art, excellent thermal management performance and high-density interconnection capability are considered, and the heat dissipation efficiency and integration density of the device are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of electronic packaging technology, specifically relating to a method for manufacturing a ceramic substrate embedded in a copper-based PCB. Background Technology

[0002] With the continuous increase in computing power demand in data centers and the widespread application of high-density computing scenarios, server heat dissipation has become a key bottleneck restricting the improvement of system performance and energy efficiency. Traditional air cooling technology is limited by the physical characteristics of air, such as low thermal conductivity (thermal conductivity of only about 0.026 W / (m·K)) and small specific heat capacity. It is gradually becoming inadequate in dealing with the heat load of high-power devices such as CPUs, GPUs, and high-bandwidth memory, making it difficult to meet the requirements of green, low-carbon, efficient, and quiet data center development. As a new generation of high-efficiency heat dissipation solution, liquid-cooled servers use liquid as the cooling medium. With its high specific heat capacity and high thermal conductivity (about 1000 times that of air), it can effectively remove a large amount of heat generated by key components such as chips through direct contact (immersion) or indirect contact (cold plate), significantly reducing the PUE (Power Usage Effectiveness) of data centers, while reducing noise pollution and cooling energy consumption, and achieving stable operation under high computing density. It has become an important technical path for high-performance computing and large-scale data center deployment. In liquid cooling architecture, the thermal management performance of the packaging substrate and PCB is crucial in the heat conduction path between the chip and the cooling system.

[0003] Currently, mainstream servers still commonly use aluminum-based or copper-based metal substrates with high thermal conductivity prepregs for heat conduction design. However, the thermal conductivity of conventional high thermal conductivity prepregs is only 2–5 W / (m·K), becoming a "thermal resistance bottleneck" in the entire heat dissipation chain, severely limiting the rapid diffusion of heat, leading to increased chip junction temperature, and affecting device reliability and lifespan. In contrast, advanced ceramic materials, due to their excellent thermo-electrical-mechanical properties, show great potential for replacement. Among them, aluminum nitride (AlN) has a thermal conductivity as high as 170–280 W / (m·K); silicon nitride (Si3N4) has good thermal conductivity (80–100 W / (m·K)) and possesses extremely low dielectric constant and ultra-high insulation resistivity (>10). 14 With its excellent thermal expansion coefficient (CTE) of approximately 4.5 × 10⁻⁶ Ω·cm and superior breakdown resistance, it enables close-range mounting of power devices without the risk of leakage current; the CTE of both is approximately 4.5 × 10⁻⁶ Ω·cm. -6 K -1 With 3.5×10 -6 K -1Highly compatible with semiconductor materials such as silicon (Si) and gallium nitride (GaN), ceramic substrates can effectively suppress thermal stress accumulation during temperature cycling, preventing cracking or interface delamination caused by thermal mismatch and ensuring long-term operational reliability. Therefore, embedding high-performance ceramic substrates into copper-based PCB structures to construct a "ceramic + metal" composite heat dissipation platform can not only significantly improve overall thermal conductivity but also balance electrical insulation, structural strength, and reliability, making it an ideal technological direction to overcome existing heat dissipation bottlenecks. However, the integration of ceramic materials and metal substrates in existing processes still faces problems such as low interface bonding strength, complex processes, and high costs. There is a lack of a ceramic substrate embedded copper-based PCB manufacturing method that combines process simplicity, mass production feasibility, and high thermal conductivity. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a simple, cost-controllable, and mass-producible method for embedding a ceramic substrate into a copper-based PCB, so as to achieve efficient heat dissipation at the chip level, improve the thermal management capability, operational stability and long-term reliability of the server under high load conditions, and meet the dual needs of liquid-cooled servers and high-end computing equipment for high-density computing power and green and low-carbon coordinated development.

[0005] To address the above problems, this invention provides a method for fabricating a ceramic substrate embedded in a copper-based PCB, comprising the following steps: S1. Fabrication of ceramic substrates: material cleaning, magnetron sputtering, ceramic substrate circuit diagram conversion, electroplating thickening, film removal and etching, thickness and dimension measurement, laser cutting and appearance inspection. S2. Fabrication of copper substrate: material cutting, target hole drilling and depth controlled milling; S3, Ceramic substrate mounting: Solder paste printing, ceramic substrate mounting, reflow soldering; S4, lamination; S5, Copper-based PCB fabrication: Copper reduction, full-board electroplating, copper substrate pattern transfer, pattern copper-tin plating, etching / tin removal.

[0006] Furthermore, step S1 specifically includes: Material cleaning: The ceramic substrate is cleaned to remove surface oil, dust and impurities to ensure the adhesion of magnetron sputtering; Magnetron sputtering: In a vacuum environment, a magnetic field is used to control the bombardment of ions on a target material, causing titanium and copper atoms on the target material to be sputtered and deposited on the surface of a ceramic substrate to form a dense metal film. Ceramic substrate pattern transfer: The designed circuit pattern is copied to the surface of the ceramic substrate through a process of coating, exposure, development and photolithography to form a mask layer with the circuit pattern. Electroplating thickening: Using sputtered titanium-copper thin film as a substrate, metallic copper is deposited in the circuit area after pattern transfer through electroplating technology to thicken the thin film circuit to 80-90μm; Film removal etching: First, remove the remaining mask layer on the surface of the substrate, then use a micro-etching solution of sulfuric acid + hydrogen peroxide to remove the copper layer that is not covered by the thickened metal, and use a solution of sodium persulfate + ammonium fluoride to remove the titanium layer, forming a ceramic substrate with a blank area of ​​0.05mm on all sides. Thickness and dimensional measurement: Using a plate thickness detection device, ceramic substrates with a thickness of 0.5mm ± 0.025mm were selected to detect the thickness of the metal plating layer, the width of the blank space, and the dimensional parameters of the substrate. Laser cutting: using the thermal effect of a high-energy laser beam to precisely cut and shape the processed substrate; Visual inspection: Check the surface of the ceramic substrate for scratches, stains, edge burrs and other visual defects using both manual visual inspection and automated testing equipment.

[0007] Furthermore, step S2 specifically includes: Material cutting: Cut the copper base into the required PNL shape dimensions using a fiber laser cutting machine according to the dimensions in the drawing; Drilling positioning holes: Drilling positioning holes in the copper base to provide a precise positioning reference for subsequent processing and avoid processing deviation; Controlled depth milling: The depth is controlled using a fiber laser with a wavelength of 1064nm. The controlled depth dimension is 0.05mm larger on one side than the formed ceramic substrate. The controlled depth is equal to the thickness of the ceramic substrate minus 0.13mm. The surface is then smoothed using a green laser with a wavelength of 532nm.

[0008] Furthermore, step S3 specifically includes: Printing solder paste: Make grooved jig 1 and grooved jig 2 with the same shape and a steel mesh corresponding to the grooved jig 1. First, put the ceramic substrate into the grooved jig 1 and scrape the solder paste onto the ceramic substrate through the steel mesh. Then, flip the ceramic substrate on the grooved jig 1 onto the grooved jig 2 to form a ceramic substrate with the solder paste side down. Ceramic substrate mounting: The ceramic substrate is picked up by a suction cup and mounted in the depth control groove on the copper substrate with the solder paste side facing down. Reflow soldering: Vacuum reflow soldering is used for soldering, which includes a preheating section, a homogenization section, a reflow section, and a cooling section. The temperature in the preheating section is controlled at 60~120℃, with a heating rate of 0.5~2℃ / s and a holding time of 60~150s. The temperature in the homogenization section is controlled at 150~180℃, with a holding time of 60~120s and a temperature difference of ≤±5℃. In the reflow section, the peak temperature is 20~40℃ higher than the melting point of the solder paste, and the time above the melting point is 30~60s, with a cooling rate of ≤3℃ / s. In the cooling section, the temperature is cooled to below 80℃, using a combination of air cooling and water cooling to ensure dense solder joint formation.

[0009] Furthermore, in the solder paste printing step, the groove size of groove jig one and groove jig two is 0.05mm larger than the single-side dimension of the ceramic substrate, and the groove depth is 1 / 2 of the ceramic substrate.

[0010] Furthermore, in the solder paste printing step, the area for printing solder paste is reduced by 0.15mm from the edge of the ceramic substrate on one side, and the stencil for printing solder paste is spaced diagonally at 0.05mm intervals every 0.3mm width, in order to reduce the solder bubble rate during soldering.

[0011] Further, step S4 specifically includes: Browning, prepreg cutting, fusion, layout, vacuum pressing and post-processing; multi-layer core board and prepreg are stacked according to the design, and after high temperature, high pressure and vacuum treatment, copper base, prepreg and copper foil are pressed together accordingly.

[0012] Further, step S5 specifically includes: Copper reduction: After lamination and grinding, measure the copper thickness of FR4 and reduce the copper to 40-50um; Full-board electroplating: The copper thickness at the joint between ceramic and FR4 is not less than 52.9um, and the height difference between the joint and the surrounding area is less than 5um; Copper substrate pattern transfer: TL layer film is used for road surface, BL layer film is used for reverse lettering (copper base surface), and the BL surface is completely exposed. Patterned copper-tin plating: On the exposed and developed board, the copper foil lines that need to be retained are electroplated. First, the copper layer is thickened to the specified thickness, and then a tin layer is plated. Photoresist removal / etching / tin stripping / titanium stripping: Remove dry film photoresist with NaOH solution; etch excess copper foil without tin protection on the board with chemical etching solution, leaving only the target circuit covered by tin layer; after etching, remove the protective tin layer on the surface of the circuit with tin stripping solution to expose the pure copper circuit; for boards with titanium clad laminate / titanium layer protection, remove excess titanium layer next to the circuit.

[0013] Compared to existing technologies, this invention uses a copper substrate as a backing plate, pre-mounting a ceramic substrate onto the copper substrate. This allows the ceramic substrate to serve as a highly efficient heat dissipation medium for the chip, achieving direct thermal connection with the copper substrate. A prepreg and copper foil are then stacked on the copper substrate surface, and a lamination process is used to make their surfaces flush with the ceramic substrate. Finally, patterning is applied to form high-density circuit wiring. This method balances excellent thermal management performance with high-density interconnect capabilities, significantly improving the device's heat dissipation efficiency and integration density. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a cross-sectional view of the ceramic substrate embedded in a copper-based PCB according to the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0017] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0018] It should also be understood that the terminology used in this application specification is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this application specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0019] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0020] In addition, this embodiment also provides a method for fabricating a ceramic substrate embedded in a copper-based PCB, which includes the following steps: S1. Fabrication of ceramic substrates: material cleaning, magnetron sputtering, ceramic substrate circuit diagram conversion, electroplating thickening, film removal and etching, thickness and dimension measurement, laser cutting and appearance inspection. Among them, material cleaning: the ceramic substrate is cleaned to remove surface oil, dust and other impurities to ensure the adhesion of magnetron sputtering.

[0021] Magnetron sputtering: In a vacuum environment, a magnetic field is used to control the bombardment of ions on a target material, causing titanium and copper atoms on the target material to be sputtered and deposited on the surface of a ceramic substrate to form a dense metal film.

[0022] Ceramic substrate pattern transfer: The designed circuit pattern is copied to the surface of the ceramic substrate through photolithography processes such as coating, exposure, and development to form a mask layer with the circuit pattern.

[0023] Electroplating thickening: Using sputtered titanium-copper thin films as substrates, metallic copper is deposited in the circuit area after pattern transfer through electroplating technology, thickening the thin film circuit by 80-90μm.

[0024] Film stripping etching: First, remove the remaining mask layer on the substrate surface, then use a micro-etching solution of sulfuric acid and hydrogen peroxide to remove the copper layer that is not covered by the thickened metal, and use a solution of sodium persulfate and ammonium fluoride to remove the titanium layer, forming a ceramic substrate with a 0.05mm blank area on all sides.

[0025] Thickness and size measurement: Using plate thickness detection equipment, ceramic substrates with a thickness of 0.5mm±0.025mm are selected, and those that do not meet the thickness requirements are rejected; the thickness of the metal plating, the width of the blank space, the size of the substrate and other indicators of the ceramic substrate are detected.

[0026] Laser cutting: using the thermal effect of a high-energy laser beam to precisely cut / shape the processed substrate.

[0027] Visual inspection: Check the surface of the ceramic substrate for scratches, stains, edge burrs and other appearance defects through manual visual inspection and automated inspection equipment.

[0028] S2. Fabrication of copper substrate: material cutting, target hole drilling and depth controlled milling; Among them, material cutting: cut the copper base into the required PNL shape size using a fiber laser cutting machine according to the dimensions of the drawing.

[0029] Drilling locating holes: Drilling locating holes in the copper base to provide a precise positioning reference for subsequent processing and avoid processing deviation.

[0030] Controlled depth milling: The depth is controlled using a fiber laser with a wavelength of 1064nm. The controlled depth dimension is 0.05mm larger on one side than the formed ceramic substrate. The controlled depth is equal to the thickness of the ceramic substrate minus 0.13mm. The surface is then smoothed using a green laser with a wavelength of 532nm.

[0031] S3, Ceramic substrate mounting: Solder paste printing, ceramic substrate mounting, reflow soldering; Among them, printing solder paste: make grooved jig 1 and grooved jig 2 with the same shape and a steel mesh corresponding to the grooved jig 1. First, put the ceramic substrate into the grooved jig 1 and scrape the solder paste onto the ceramic substrate through the steel mesh. Then, flip the ceramic substrate on the grooved jig 1 to the grooved jig 2 to form a ceramic substrate with the solder paste side down. In the solder paste printing step, the groove dimensions of groove jig 1 and groove jig 2 are 0.05mm larger on each side than the ceramic substrate dimensions, and the groove depth is 1 / 2 the size of the ceramic substrate. The area for printing solder paste is reduced by 0.15mm on each side from the edge of the ceramic substrate, and the stencil for printing solder paste is spaced diagonally at 0.05mm intervals every 0.3mm width to reduce the solder bubble rate during soldering.

[0032] Ceramic substrate mounting: The ceramic substrate is picked up by a suction cup and mounted into the depth control groove on the copper substrate.

[0033] Reflow Soldering: Vacuum reflow soldering is used, which includes a preheating section, a homogenization section, a reflow section, and a cooling section. The preheating section has a temperature of 60~120℃, a heating rate of 0.5~2℃ / s, and a holding time of 60~150s. The homogenization section has a temperature of 150~180℃, a holding time of 60~120s, and a temperature difference ≤±5℃. The reflow section has a peak temperature 20~40℃ higher than the solder paste melting point (typically 217~245℃), a time above the melting point of 30~60s, and a cooling rate ≤3℃ / s. The cooling section cools to below 80℃ using a combination of air and water cooling to ensure dense solder joint formation. Vacuum level: typically 50~500mbar. Holding time: 20~40s under vacuum to ensure sufficient expulsion of air bubbles from the solder. Vacuum breaking method: Slowly introduce dry nitrogen / argon gas (oxygen content ≤500ppm) to avoid oxidation of solder joints, and the vacuum breaking rate ≤100mbar / s.

[0034] S4. Lamination; including: browning, prepreg cutting, fusion, layout, vacuum pressing, post-processing and other steps. Auxiliary materials include release film, buffer pad, aluminum foil / steel plate. The multi-layer core board and prepreg (PP) are stacked according to the design, and the copper base, prepreg and copper foil are pressed together under high temperature, high pressure and vacuum.

[0035] S5, Copper-based PCB fabrication: Copper reduction, full-board electroplating, copper substrate pattern transfer, pattern copper-tin plating, etching / tin removal.

[0036] Copper reduction: After lamination and grinding, measure the FR4 copper thickness and reduce the copper to 40-50um.

[0037] Full-board electroplating: The copper thickness at the joint between ceramic and FR4 is not less than 52.9um, and the height difference between the joint and the surrounding area is less than 5um.

[0038] Copper substrate pattern transfer: TL layer film is used for road surface, and BL layer film is used for reverse lettering on the copper base surface. The BL surface is completely exposed.

[0039] Patterned copper-tin plating: On the board after exposure and development, the copper foil lines that need to be retained are electroplated. First, the copper layer is thickened to the specified thickness (to meet the conductivity / current resistance requirements), and then a tin layer is plated as a protective barrier for the copper lines in the subsequent etching process to prevent the lines from being corroded by the etching solution.

[0040] Photoresist removal / etching / tin stripping / titanium stripping: Remove dry film photoresist with a certain concentration of NaOH; use chemical etching solution to etch excess copper foil on the board without tin protection, leaving only the target circuit covered by tin; after etching, use tin stripping solution to remove the protective tin layer on the surface of the circuit, exposing the pure copper circuit; for boards with titanium clad laminate / titanium layer protection, remove excess titanium layer next to the circuit.

[0041] Etching inspection: Visually inspect the circuit board using a magnifying glass and testing equipment to confirm the absence of issues such as side etching, broken pins, residual copper, out-of-tolerance line width, and exposed copper, thus preventing defective products from entering subsequent processes.

[0042] Drill tool holes: Drill holes at the edge / specified location of the board for positioning, fixing, transferring, and tooling clamping of the board in processes such as solder resist, lettering, and immersion nickel gold.

[0043] Solder resist: A layer of insulating solder resist is applied to the surface of the formed copper circuit board, leaving only the solder pads (component soldering positions) exposed. This process involves a secondary solder resist application. Characters: Printing text, symbols, and numbers on the PCB surface to facilitate subsequent component soldering, board identification, repair, and testing.

[0044] Immersion nickel-gold plating: A layer of nickel and a top gold layer are chemically deposited in key areas such as solder pads / gold fingers. The nickel layer acts as a base to enhance adhesion, while the gold layer (an inert metal) provides anti-oxidation and improves solder wettability.

[0045] Drilling: Using a CNC drilling machine to drill mounting holes of different sizes on the board to fix components / PCB boards.

[0046] Apply high-temperature tape: High-temperature tape made of PI material is applied to the copper base to prevent nickel and gold from forming on the surface.

[0047] Grinding: The copper surface of the PCB is polished using physical grinding methods to remove the oxide layer, oil, glue residue, and burrs on the surface, so that the copper surface forms a uniform rough surface. The core function is to improve the adhesion of subsequent copper plating, solder mask, and immersion nickel gold, and to prevent the plating / green solder mask from peeling off.

[0048] Flight test: Uses movable probes to contact the pads / test points on the PCB to quickly detect problems such as open circuits, short circuits, poor insulation, and abnormal resistance.

[0049] Electric milling: using a CNC electric milling machine to mill out the required external dimensions.

[0050] Finished product cleaning: Use pure water, ultrasound, and cleaning agents to remove impurities such as solder paste residue, oil, dust, and chemical residue from the surface of the board, while improving the appearance and reliability of the PCB.

[0051] Antioxidant: A thin organic protective film is chemically formed on the copper-based surface.

[0052] Warp leveling: Using specialized hot press leveling equipment, the board is flattened by high temperature and high pressure to make the PCB warp meet industry / customer standards.

[0053] Finished product inspection: Both automatic appearance inspection machines and manual inspection are used. The inspection items include: appearance, dimensions, surface treatment, warpage, etc.

[0054] The ceramic substrate fabricated according to the above method is embedded in a copper-based PCB, as shown in... Figure 1 As shown in the figure, the red part is a copper substrate with a thickness of 1.8mm. A groove with a depth of 0.39mm + / -0.05mm is opened on the copper substrate, and a ceramic substrate (the green part in the figure corresponds to the ceramic back copper, which has a thickness of 0.06mm) is embedded in the groove. A solder paste with a thickness of 0.1mm is printed on the lower surface of the ceramic back copper, and an aluminum nitride layer (or silicon nitride layer) with a thickness of 0.38mm is formed on the upper surface.

[0055] After embedding the ceramic substrate, a 0.15mm thick PP sheet (the gray prepreg in the figure) is attached to the copper substrate, and then a 0.06mm thick copper foil (the yellow part in the figure) is laminated on top. As shown in the figure, this invention uses the copper substrate as a backing plate, pre-attaching the ceramic substrate onto the copper substrate, so that the ceramic substrate acts as a highly efficient heat dissipation medium for the chip, directly achieving thermal connection with the copper substrate.

[0056] The specific embodiments of the invention have been described in detail above, but they are only examples, and the invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications or substitutions to the invention are also within the scope of the invention. Therefore, all equivalent transformations, modifications, and improvements made without departing from the spirit and principles of the invention should be covered within the scope of the invention.

Claims

1. A method for fabricating a ceramic substrate embedded in a copper-based PCB, characterized in that, Including the following steps: S1. Fabrication of ceramic substrates: material cleaning, magnetron sputtering, ceramic substrate circuit diagram conversion, electroplating thickening, film removal and etching, thickness and dimension measurement, laser cutting and appearance inspection. S2. Fabrication of copper substrate: material cutting, target hole drilling and depth controlled milling; S3, Ceramic substrate mounting: Solder paste printing, ceramic substrate mounting, reflow soldering; S4, lamination; S5, Copper-based PCB fabrication: Copper reduction, full-board electroplating, copper substrate pattern transfer, pattern copper-tin plating, etching / tin removal.

2. The method for fabricating a ceramic substrate embedded in a copper-based PCB according to claim 1, characterized in that, Step S1 specifically includes: Material cleaning: The ceramic substrate is cleaned to remove surface oil, dust and impurities to ensure the adhesion of magnetron sputtering; Magnetron sputtering: In a vacuum environment, a magnetic field is used to control the bombardment of ions on a target material, causing titanium and copper atoms on the target material to be sputtered and deposited on the surface of a ceramic substrate to form a dense metal film. Ceramic substrate pattern transfer: The designed circuit pattern is copied to the surface of the ceramic substrate through a process of coating, exposure, development and photolithography to form a mask layer with the circuit pattern. Electroplating thickening: Using sputtered titanium-copper thin film as a substrate, metallic copper is deposited in the circuit area after pattern transfer through electroplating technology to thicken the thin film circuit to 80-90μm; Film removal etching: First, remove the remaining mask layer on the surface of the substrate, then use a micro-etching solution of sulfuric acid + hydrogen peroxide to remove the copper layer that is not covered by the thickened metal, and use a solution of sodium persulfate + ammonium fluoride to remove the titanium layer, forming a ceramic substrate with a blank area of ​​0.05mm on all sides. Thickness and dimensional measurement: Using a plate thickness detection device, ceramic substrates with a thickness of 0.5mm ± 0.025mm were selected to detect the thickness of the metal plating layer, the width of the blank space, and the dimensional parameters of the substrate. Laser cutting: using the thermal effect of a high-energy laser beam to precisely cut and shape the processed substrate; Visual inspection: Check the surface of the ceramic substrate for scratches, stains, edge burrs and other visual defects using both manual visual inspection and automated testing equipment.

3. The method for fabricating a ceramic substrate embedded in a copper-based PCB according to claim 2, characterized in that, Step S2 specifically includes: Material cutting: Cut the copper base into the required PNL shape dimensions using a fiber laser cutting machine according to the dimensions in the drawing; Drilling positioning holes: Drilling positioning holes in the copper base to provide a precise positioning reference for subsequent processing and avoid processing deviation; Controlled depth milling: The depth is controlled using a fiber laser with a wavelength of 1064nm. The controlled depth dimension is 0.05mm larger on one side than the formed ceramic substrate. The controlled depth is equal to the thickness of the ceramic substrate minus 0.13mm. The surface is then smoothed using a green laser with a wavelength of 532nm.

4. The method for fabricating a ceramic substrate embedded in a copper-based PCB according to claim 3, characterized in that, Step S3 specifically includes: Printing solder paste: Make grooved jig 1 and grooved jig 2 with the same shape and a steel mesh corresponding to the grooved jig 1. First, put the ceramic substrate into the grooved jig 1 and scrape the solder paste onto the ceramic substrate through the steel mesh. Then, flip the ceramic substrate on the grooved jig 1 onto the grooved jig 2 to form a ceramic substrate with the solder paste side down. Ceramic substrate mounting: The ceramic substrate is picked up by a suction cup and mounted in the depth control groove on the copper substrate with the solder paste side facing down. Reflow soldering: Vacuum reflow soldering is used for soldering, which includes a preheating section, a homogenization section, a reflow section, and a cooling section. The temperature in the preheating section is controlled at 60~120℃, with a heating rate of 0.5~2℃ / s and a holding time of 60~150s. The temperature in the homogenization section is controlled at 150~180℃, with a holding time of 60~120s and a temperature difference of ≤±5℃. In the reflow section, the peak temperature is 20~40℃ higher than the melting point of the solder paste, and the time above the melting point is 30~60s, with a cooling rate of ≤3℃ / s. In the cooling section, the temperature is cooled to below 80℃, using a combination of air cooling and water cooling to ensure dense solder joint formation.

5. The method for fabricating a ceramic substrate embedded in a copper-based PCB according to claim 4, characterized in that, In the solder paste printing step, the groove size of groove jig 1 and groove jig 2 is 0.05mm larger than the single side size of the ceramic substrate, and the groove depth is 1 / 2 of the ceramic substrate.

6. The method for fabricating a ceramic substrate embedded in a copper-based PCB according to claim 5, characterized in that, In the solder paste printing step, the area for printing solder paste is reduced by 0.15mm from the edge of the ceramic substrate on one side, and the stencil for printing solder paste is spaced diagonally at 0.05mm intervals every 0.3mm width to reduce the solder bubble rate during soldering.

7. The method for fabricating a ceramic substrate embedded in a copper-based PCB according to claim 6, characterized in that, Step S4 specifically includes: Browning, prepreg cutting, fusion, layout, vacuum pressing and post-processing; multi-layer core board and prepreg are stacked according to the design, and after high temperature, high pressure and vacuum treatment, copper base, prepreg and copper foil are pressed together accordingly.

8. The method for fabricating a ceramic substrate embedded in a copper-based PCB according to claim 7, characterized in that, Step S5 specifically includes: Copper reduction: After lamination and grinding, measure the copper thickness of FR4 and reduce the copper to 40-50um; Full-board electroplating: The copper thickness at the joint between ceramic and FR4 is not less than 52.9um, and the height difference between the joint and the surrounding area is less than 5um; Copper substrate pattern transfer: TL layer film is used for road surface, BL layer film is used for reverse lettering (copper base surface), and the BL surface is completely exposed. Patterned copper-tin plating: On the exposed and developed board, the copper foil lines that need to be retained are electroplated. First, the copper layer is thickened to the specified thickness, and then a tin layer is plated. Photoresist removal / etching / tin stripping / titanium stripping: Remove dry film photoresist with NaOH solution; etch excess copper foil without tin protection on the board with chemical etching solution, leaving only the target circuit covered by tin layer; after etching, remove the protective tin layer on the surface of the circuit with tin stripping solution to expose the pure copper circuit; for boards with titanium clad laminate / titanium layer protection, remove excess titanium layer next to the circuit.

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