Manufacturing method of capacitor-embedded resistor-embedded ceramic mixed-voltage circuit board

Abstract

The invention discloses a preparation method and structure of a multilayer board based on a ceramic substrate. A ceramic substrate is used as a core substrate and is laminated with a conventional FR4 core plate and a prepreg to form a multi-layer plate laminated structure, and all layers of circuits are connected through drilling and electroplating. Meanwhile, the components are printed or / and mounted on the ceramic substrate in a surface-mounted manner, so that the components are pre-embedded, the performance and the integration level of the circuit board are improved, and the development requirements of miniaturization and high performance of electronic equipment are met; therefore, better heat management can be realized. Due to the fact that the periphery is made of the conventional FR4 plate, the production difficulty is reduced, the production efficiency is improved, and the production cost is reduced due to the mature technology and large-size production.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit board processing, and in particular to a manufacturing process of a ceramic mixed-pressed circuit board with embedded capacitance and resistance. Background Art

[0002] As electronic devices continue to rapidly advance towards miniaturization and higher performance, stringent requirements are being placed on the performance of printed circuit boards (PCBs). On the one hand, as circuit integration continues to climb, the demand for embedded capacitance and resistance in PCBs is becoming increasingly urgent to meet the needs of miniaturized electronic device layouts and high-speed signal processing. On the other hand, the increasing power of electronic devices has made heat dissipation an increasingly critical issue, placing even higher demands on the thermal conductivity and heat dissipation capabilities of PCBs.

[0003] In the field of circuit board manufacturing, conventional FR4 sheet materials, with their mature manufacturing process, are widely used in many fields. However, with the rapid development of electronic circuits towards high frequencies and high speeds, the limitations of FR4 sheet materials in high-frequency and high-speed performance have become increasingly prominent, making it difficult to meet the stringent signal transmission speed and stability requirements of today's complex circuits. Ceramic substrates, on the other hand, excel in high-frequency and high-speed performance. Their excellent thermal conductivity effectively ensures stable and reliable circuits under high loads, laying a solid foundation for the efficient operation of electronic devices. However, ceramic substrates are not perfect. The high production cost and inherent brittleness of the material significantly limit the feasibility of large-scale production, making their application in large-scale applications challenging. Therefore, there is an urgent need to explore innovative methods that combine the advantages of FR4 sheet materials and ceramic substrates. While reducing overall costs and improving production efficiency, they can also fully utilize the high performance of ceramic substrates to optimize PCB layout and achieve a more rational arrangement of components. This will meet the demand for smaller and more high-performance PCBs driven by the continuous development of electronic circuits and promote the development of the electronics manufacturing industry. Summary of the Invention

[0004] To effectively overcome these technical challenges, the present invention focuses on process improvements, aiming to cleverly integrate ceramic substrates with FR4 fiberglass to create high-performance circuit boards centered around ceramic substrates. This method fully leverages the unique performance advantages of ceramic substrates. By pre-embedding electronic components such as resistors and capacitors within the PCB, it provides strong support for achieving more compact and miniaturized circuit board designs. Specifically, by embedding the ceramic substrate within the FR4 substrate, the present invention successfully overcomes the technical bottleneck that hinders large-scale production of ceramic substrates due to their brittle material. Furthermore, considering the heat dissipation requirements and the special signal transmission requirements of high-frequency components, the ceramic substrate is partially uncovered. This innovative approach not only accommodates larger components but also significantly enhances the heat dissipation capacity of high-heat components, facilitating the installation of large components and heat sinks, and further optimizing thermal management. By implementing these measures, the overall performance of electronic devices can be significantly and comprehensively improved. Leveraging the proven experience of traditional PCB manufacturing processes, this method effectively reduces production complexity and costs while significantly expanding the application range of high-performance circuit boards in various fields.

[0005] The present invention provides a method for manufacturing a ceramic substrate and FR4 glass fiber. The embedded capacitor and embedded resistor high-frequency ceramic hybrid circuit board is composed of a ceramic substrate, a prepreg, an FR4 substrate, copper foil, and electronic devices. The specific operation steps are as follows: Step S1, making a ceramic substrate, casting and sintering a green film: adding additives to the ceramic raw materials to make a slurry with good fluidity, evenly coating to form a continuous and uniform ceramic green film, and then sintering the green film at high temperature. High-temperature sintering can also be performed after the drilling process and after the circuit is fabricated; Step S2, drilling and copper plating, drilling holes on the ceramic, and then depositing a metal film on the surface. Direct copper plating (DPC), direct copper bonding (DBC), active brazing metallization (AMB) and other processes can be used on the ceramic substrate to deposit a metal film on the ceramic surface; Step S3, circuit fabrication: A conductive pattern is formed through electroplating, dry film, exposure and development, and etching. Circuit fabrication can be performed by exposing and developing on a dry film using a positive or negative film method to achieve image transfer, and then etching to form a conductive circuit. Circuit patterns can also be produced by screen printing a conductive paste on a non-copper-plated sintered green film and then performing a high-temperature sintering process. Step S4: Install electronic components. Pre-embedded electronic components are achieved by printing and mounting. Printing electronic components involves printing capacitor slurry and resistor slurry on the ceramic substrate circuit, drying and curing them, and then sintering them. Mounting electronic components involves first making a solder mask layer with photosensitive ink on the ceramic core board, then printing solder paste, mounting components, and then connecting the electronic components to the ceramic core board through reflow soldering. Step S5, preparing an FR4 core board: After pattern transfer and etching of the FR4 core board with the same thickness as the ceramic core board using photosensitive ink to prepare the inner layer circuit, the area where the ceramic substrate is to be placed is hollowed out, and then the copper surface is roughened; Step S6, embedding and laminating: Place the prepared ceramic core board in the middle of the prepared FR4 core board, place prepregs on the top and bottom, and place copper foil and / or FR4 substrate on the outermost side, and bond them into a whole using a laminating machine; Step S7, connecting each layer: For the pressed PCB board, first drill holes, then deposit copper and plate copper, and connect the inner and outer copper foils of the ceramic core board through conductive holes to establish the upper and lower layers and the inner and outer layers of the circuit; Step S8, circuit fabrication: The outer copper foil of the laminated multilayer board is subjected to electroplating, dry film coating, exposure and development, and etching to produce a conductive pattern. Circuit fabrication can be performed by exposing and developing on the dry film using a positive or negative film method to achieve image transfer, and then an acid or alkaline etching process is used to produce a conductive circuit. Step S9, multi-layer expansion: If the design requirements have not been met, repeat the process from steps S7 to S9 to continue adding circuit patterns; Step S10, opening the cover: For components with high heat and components with larger dimensions that need to be mounted on a ceramic substrate, use a laser or a gong machine to remove excess material from the opening area;

[0006] Compared with existing technologies, the present invention has the following advantages: fully utilizing ceramic substrates reduces signal loss and distortion during transmission, improves the data transmission rate and accuracy, and meets the demand for high-frequency and high-speed circuit boards in fields such as communications and high-speed computing. Furthermore, the ceramic substrates can be used to embed components such as capacitors and resistors, reducing the number of components on the circuit board surface, optimizing circuit layout, and increasing the integration of circuit boards, providing strong support for the miniaturization of electronic devices. By introducing the mature manufacturing process of conventional FR4 multilayer boards, this process reduces process difficulty, reduces product costs, improves thermal management capabilities, and avoids the undesirable defect of ceramic substrates being fragile. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 1 is a diagram of the stacked structure of a six-layer PCB board provided in an embodiment of the present invention.

[0008] Figure 2 1 is a diagram of the stacked structure of a four-layer PCB board provided in an embodiment of the present invention.

[0009] Figure 3 FIG. 4 is a diagram of the stacked structure of an eight-layer PCB board provided in an embodiment of the present invention.

[0010] Figure 4Schematic diagram of an FR4 inner core board embedded in a ceramic substrate of a PCB board according to an embodiment of the present invention.

[0011] Figure 5 This is a schematic diagram of a method for manufacturing a ceramic hybrid circuit board with embedded capacitance and resistance according to the present invention.

[0012] The main component symbols are described as follows: 1. FR4 inner core embedded in a ceramic substrate 2. Prepreg 3. Copper foil 4. Cover opening area 5. FR4 inner core 11. FR4 inner core circuitry 12. Ceramic substrate circuitry 13. Embedded electronic components 14. Solder mask and cover opening area DETAILED DESCRIPTION

[0013] To help those skilled in the art better understand the technical solutions of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific examples. However, it should be understood that the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent. To better illustrate this embodiment, some components in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some structures and their descriptions in the accompanying drawings may be omitted. The positional relationships described in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0014] A method for manufacturing a PCB board, a ceramic hybrid circuit board with embedded capacitors and resistors, used in Example 1. The hybrid circuit board is composed of a ceramic substrate, a prepreg, an FR4 substrate, copper foil, and electronic devices. The specific steps of the manufacturing method are as follows.

[0015] Step S1: Prepare a ceramic substrate. According to existing techniques, appropriate additives (such as binders and dispersants) are added to aluminum nitride ceramic raw materials. After uniform mixing, a slurry with good fluidity is formed. A tape casting machine is used to evenly coat the slurry onto a support belt to form a continuous and uniform ceramic green film. The thickness and width of the green film are controlled by adjusting the tape casting machine parameters. The film is then cut to the appropriate size according to product design requirements. The green film is then sintered at a high temperature of 1600°C to 2000°C. The holding time is 2-40 hours. Appropriately increasing the sintering temperature and extending the holding time can improve the density of the aluminum nitride ceramic.

[0016] Step S2, drilling and copper plating, using laser drilling to drill electrical holes and pattern positioning holes on the green film. The position, size and density of the holes are determined according to the circuit design requirements. According to the existing technology, vacuum sputtering copper is used on the ceramic substrate. In a high vacuum environment, an ion beam is used to bombard a metal target material, so that the target material atoms are sputtered out and deposited on the surface of the ceramic green film. The copper plating thickness is 2~5um. A metal film is deposited on the ceramic surface, and then copper is electroplated. The copper plating makes the hole copper thickness reach about 20um, meeting the copper thickness required by the customer.

[0017] Step S3, circuit production, according to the existing technology, the inner layer circuit is produced, the inner layer is affixed with a dry film, and then the dry film is exposed and developed to make the alignment PAD, target hole pattern, and circuit negative pattern, and then the circuit pattern is etched out with acid. After etching, the film is stripped to remove the dry film that protects the circuit pattern.

[0018] Step S4: Print electronic devices, and print capacitor slurry and resistor slurry on the ceramic substrate circuit respectively. According to the circuit pattern design, make the corresponding steel screen printing screen. During the printing process, the scraper transfers the metal slurry to the surface of the ceramic green film through the pattern on the screen at a certain pressure and speed. The resistor slurry contains metal oxides (such as ruthenium oxide, etc.) and glass phase, organic carrier and other components. Different metal oxides and their ratios will produce different resistance temperature coefficients, resistance ranges and other characteristics. They need to be accurately selected according to the circuit design requirements. The capacitor slurry is composed of metal oxides (such as barium titanate, etc.), glass materials, organic additives, etc. Ferroelectric materials such as barium titanate have a high dielectric constant and can effectively increase the capacitance of the capacitor. Using printing equipment, capacitor and resistor pastes are applied to the pads of the ceramic substrate circuit board. The placement and amount of paste are precisely controlled based on the specific circuit design requirements to ensure the distribution of capacitors and resistors meets the design requirements. The printed circuit boards are then placed in a drying oven at temperatures typically ranging from tens to over 100 degrees Celsius. The printed circuit boards are then dried to remove any moisture or volatile solvents from the pastes and allow them to initially solidify. The firing temperature is then set appropriately based on the characteristics of the capacitor and resistor pastes. After firing, the resistance and capacitance parameters of the fired ceramic circuit boards, now incorporating resistors and capacitors, are measured. Using specialized measuring instruments, the actual values ​​of the resistors and capacitors are accurately determined. Based on the measured values, laser micro-engraving is then performed. The thermal or photochemical effects of the laser cause the resistor and capacitor materials to undergo physical and chemical changes, such as evaporation, melting, and recrystallization, altering their physical dimensions. This allows for precise adjustment of the resistance and capacitance values ​​to ensure they remain within the required design parameters. Solder mask ink is printed on the exposed areas of the ceramic substrate. After exposure and development, the pads are exposed. Characters are then printed where needed for text markings, and the product is cured by high-temperature baking. Solder paste is then printed on the ceramic core board, and electronic components are mounted on the PCB using a placement machine. The mounted and encapsulated components are then securely soldered using a reflow soldering process.

[0019] Step S5, preparing the FR4 core board: After the FR4 core board of the same thickness as the ceramic core board is pattern-transferred by photosensitive ink and etched to prepare the inner layer circuit, the area where the ceramic substrate is to be placed is hollowed out, and then the copper surface is roughened.

[0020] Step S6, embedding and lamination, the ceramic core board prepared above is first subjected to pre-pressing treatment, and after plasma activation, the core board is embedded in the middle of the FR4 inner core board of the same thickness, F semi-cured sheets are placed on both sides, and two layers of copper foil are placed on the outside. The pressing equipment is used to bond them under high temperature and high pressure. The cured semi-cured sheet will bond the ceramic substrate containing embedded capacitors and resistors and the top and bottom layers of copper foil together to form a mixed pressure structure of the multi-layer circuit board. At the protruding position of the electronic components, the middle of the non-glue FR4 semi-cured sheet is hollowed out and then pressed.

[0021] Step S7: All layers are connected. For the laminated PCB, holes are first drilled and then copper deposited to metalize the holes. Backlight testing is performed to level 10, and the copper deposited in the holes is 0.5μm thick. Full-board electroplating: Full-board electroplating is performed at a current density of 1.8ASD to reduce the copper deposited in the holes to 4-6μm, establishing a circuit path between the inner and outer layers of the ceramic core board.

[0022] Step S8: Circuit production: The outer copper foil of the laminated multilayer board is subjected to dry film, exposure, development, electroplating, and etching to produce the circuit pattern. Production of the outer layer circuit (positive process): The outer layer positive pattern is produced according to the finished product pattern requirements. The positions to be retained are thickened with copper. The hole copper reaches 20μm and is electroplated with tin for protection. After stripping the film, the required pattern is etched out and the tin is stripped.

[0023] Step S9, multi-layer expansion, this board is a six-layer board, and two more layers of circuits need to be made. The circuits made in the previous process are chips, prepregs are added on both sides, and copper foil is added to the outermost side for lamination, and then drilling is done. The outer layer circuits are made after copper plating. The method is the same as the previous lamination and circuit making method. This six-layer board can also be made with an FR4 inner core board with an embedded ceramic substrate sandwiched between two FR4 chips. The reason for adopting this design is based on the customer's design requirements.

[0024] Step S10, open the cover. For components with high heat generation and areas with larger components that need to be installed on the ceramic base, some areas need to be opened. Use fiber laser to expose the positions of the ceramic core board where components need to be installed, so as to facilitate subsequent patch installation of components.

[0025] Step S11, post-process: liquid photosensitive solder resist green oil is coated on the line surface, and after exposure and development, it is solidified to obtain the solder resist layer on the line surface, and then white character ink is printed on the PCB through a silk screen. After baking, the ink is solidified to obtain clear characters on the PCB board surface. Then, the PCB board is processed through a gong process, and a test process is passed to test whether the open circuit, short circuit and impedance meet the requirements. The PCB board is surface treated with a gold immersion process to prevent copper surface oxidation, thereby obtaining an embedded capacitor and embedded resistor ceramic hybrid circuit board.

[0026] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for manufacturing a ceramic hybrid circuit board with embedded capacitors and resistors, comprising a ceramic substrate, a prepreg, an FR4 substrate, copper foil, and electronic components, characterized in that: The production method comprises the following steps: Step S1, preparing a ceramic substrate, adding additives to ceramic raw materials to prepare a slurry with good fluidity, uniformly coating to form a continuous and uniform ceramic green film, and sintering the green film at a high temperature; Step S2, metallizing holes and ceramic surfaces, first drilling holes on the ceramic substrate, and then depositing a metal film on the ceramic substrate; Step S3: Circuit fabrication: forming a circuit pattern through electroplating, dry film, exposure and development, and etching, or using screen printing of conductive paste and high-temperature sintering to fabricate a circuit pattern; Step S4: Install electronic components. Embedded electronic components are achieved through printing and mounting. Printing electronic components involves printing capacitor slurry and resistor slurry on the ceramic substrate circuit, drying and curing them, and then sintering them. Mounting electronic components involves printing solder paste on the ceramic core board and mounting the packaged components. Step S5: Prepare an FR4 core board. After pattern transfer and etching of the FR4 core board with the same thickness as the ceramic core board using photosensitive ink, prepare the inner layer circuit. Then, hollow out the area where the ceramic substrate is placed, and then roughen the copper surface of the circuit. Step S6, embedding and laminating: Place the prepared ceramic core board in the middle of the prepared FR4 core board, place prepregs on the top and bottom, and place copper foil and / or FR4 substrate on the outside, and bond them into a whole using a press; Step S7: Conducting each layer: Drilling holes in the laminated PCB board, followed by copper deposition and copper plating, to establish electrical conduction between the inner copper foil and the outer copper foil of the ceramic core board; Step S8: Circuit production: the outer copper foil of the laminated multilayer board is subjected to dry film, exposure, development, and etching to produce a circuit pattern; Step S9: Multi-layer expansion. If the design requirements have not been met, repeat the process from Steps S7 to S9 to continue adding circuit patterns. Step S10: opening the cover. Opening the cover is performed on components with high heat generation and areas where components with larger sizes need to be mounted on the ceramic substrate.

2. A method for manufacturing a ceramic hybrid circuit board, characterized in that The invention is composed of a ceramic substrate, an FR4 prepreg or an FR4 substrate and a copper foil, and is characterized in that the manufacturing method comprises the following steps: Step S1, preparing a ceramic substrate, adding additives to ceramic raw materials to prepare a slurry with good fluidity, uniformly coating to form a continuous and uniform ceramic green film, and sintering the green film at a high temperature; Step S2, metallizing holes and ceramic surfaces, first drilling holes on the ceramic substrate, and then depositing a metal film on the ceramic substrate; Step S3: Circuit fabrication: forming a circuit pattern through electroplating, dry film, exposure and development, and etching, or using screen printing of conductive paste and high-temperature sintering to fabricate a circuit pattern; Step S4: Prepare an FR4 core board. After transferring the pattern of the FR4 core board to the ceramic core board through photosensitive ink, etch and prepare the inner layer circuit. Then, hollow out the area where the ceramic substrate is placed, and then roughen the copper surface of the circuit. Step S5, embedding and laminating: Place the prepared ceramic core board in the middle of the prepared FR4 core board, place prepregs on the top and bottom, and place copper foil and / or FR4 substrate on the outside, and bond them into a whole using a laminating machine; Step S6: Conducting each layer: For the pressed PCB board, first drill holes, then deposit copper and plate copper, so as to establish circuit conduction between the inner copper foil and the outer copper foil of the ceramic core board; Step S7: Circuit production: the outer copper foil of the laminated multilayer board is subjected to dry film, exposure, development, and etching to produce a circuit pattern; Step S8: Multi-layer expansion. If the design requirements have not been met, repeat the process from step S5 to step S7 to continue adding circuit patterns. Step S9: opening the cover. Opening the cover is performed on components with high heat generation and areas where components with larger sizes need to be mounted on the ceramic substrate.

3. The method for manufacturing a hybrid circuit board with embedded capacitance and embedded resistance ceramics according to claim 1, characterized in that Step S1: Casting and sintering the green film. The sintering process can also be performed after drilling or circuit production.

4. The method for manufacturing a hybrid circuit board with embedded capacitance and embedded resistance ceramics according to claim 1, characterized in that : Step S2 drilling and copper plating are not mandatory and need to be determined based on actual design requirements.

5. The method for manufacturing a hybrid circuit board of embedded capacitance and embedded resistance ceramics according to claim 1, characterized in that : Step S4 is to install electronic components. Printing and mounting can be both adopted, or only one of them can be adopted to install electronic components.

6. The method for manufacturing a ceramic hybrid circuit board according to claim 2, characterized in that Step S1: Casting and sintering the green film. The sintering process can also be performed after drilling or circuit production.

7. The method for manufacturing a ceramic hybrid circuit board according to claim 2, characterized in that : Step S2 drilling and copper plating are not mandatory and need to be determined based on actual design requirements.

8. The ceramic materials according to claim 1 and claim 2 include pure ceramic materials such as alumina ceramics, aluminum nitride ceramics, boron nitride ceramics, beryllium oxide ceramics, silicon carbide ceramics, cordierite ceramics, barium titanate ceramics, etc., and also include high-frequency substrates with ceramics as fillers.

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