Method for fabricating conductive lines on multilayer co-fired ceramic substrates and the multilayer co-fired ceramic substrate

Abstract

This application discloses a method for fabricating conductive lines on a multilayer co-fired ceramic substrate and the multilayer co-fired ceramic substrate itself, relating to the field of electronic ceramic multilayer co-fired manufacturing technology. The method for fabricating conductive lines on the multilayer co-fired ceramic substrate includes: providing a green ceramic film strip for multilayer stacking and co-firing; forming conductive patterns on the surface of the green ceramic film strip using nanoimprinting technology, aligning and stacking it with at least one other green ceramic film strip, and laminating it to form a stack; and performing adhesive removal and co-firing treatment on the stack to form embedded conductive lines within the stack. The fabrication method proposed in this application can fabricate conductive lines with linewidths and spacings less than 50 μm, achieving embedded forming of conductive lines in multilayer structures. It can be used in conjunction with via drilling / filling and stack alignment processes for precision packaging of three-dimensional integrated circuits such as high-density multilayer wiring, high-frequency and high-speed circuits, and power electronic integration.

Description

Technical Field

[0001] This application relates to the field of electronic ceramic multilayer co-fired manufacturing technology, and in particular to a method for preparing conductive lines of a multilayer co-fired ceramic substrate and the multilayer co-fired ceramic substrate. Background Technology

[0002] In the manufacturing of multilayer co-fired ceramic (LTCC / HTCC) substrates, traditional wiring processes mainly rely on screen printing, where conductive paste is printed onto a green ceramic film using a screen template, followed by drying and co-firing to form the circuitry. However, this process is limited by screen resolution and paste rheological properties, making it difficult to break through the minimum linewidth / spacing of 50 μm. Furthermore, the lines are often rough at the edges and have unstable geometry, limiting high-density wiring and high-frequency signal transmission capabilities. Simultaneously, the flow and shrinkage of conductors during lamination and co-firing can easily lead to short circuits or open circuits, further exacerbating the manufacturing difficulties. Although nanoimprint technology has been applied to the patterning of functional ceramic surfaces, such as forming microstructures through high-temperature sintering of imprinted adhesives containing ceramic nanoparticles, these methods primarily focus on replicating the morphology or controlling the performance of the ceramic material itself. They do not address conductor embedding, lamination alignment, and co-firing interconnection on the surface of multilayer LTCC / HTCC green ceramic films, making it difficult to directly solve the manufacturing bottlenecks of multilayer precision wiring.

[0003] Therefore, how to achieve precise conductor patterns with linewidth / spacing less than 50 μm on the surface of multilayer LTCC / HTCC green ceramic film tapes, and maintain clear geometric boundaries and synergistic densification of conductors and ceramics after lamination and co-firing, while being compatible with processes such as through-hole interconnection and interlayer alignment, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] The main objective of this application is to propose a method for preparing conductive lines on a multilayer co-fired ceramic substrate and a multilayer co-fired ceramic substrate, aiming to solve the problem of poor precision of conductive lines prepared by existing wiring processes on multilayer co-fired ceramic substrates.

[0005] To achieve the above objectives, in a first aspect, this application proposes a method for fabricating conductive lines on a multilayer co-fired ceramic substrate, comprising: A green ceramic film tape is provided, which is used for multi-layer lamination and co-firing; A conductive pattern is formed on the surface of the green ceramic film strip using nanoimprint technology, and then aligned and laminated with at least one other green ceramic film strip to form a laminate. The laminate is subjected to debinding and co-firing processes to form embedded conductive lines within the laminate.

[0006] In some embodiments, the step of forming the conductive pattern includes: An imprintable coating is formed on the surface of the green ceramic film tape. A first micro-nano trench is formed in the imprintable coating using a nanoimprint mold. Conductive paste is then filled into the first micro-nano trench to form the conductive pattern.

[0007] In some embodiments, the imprintable coating includes at least one of thermoplastic imprintable adhesive and photocurable imprintable adhesive; The thickness of the imprintable coating is 1~50 μm.

[0008] In some embodiments, the nanoimprint mold has a periodic microstructure with a structural depth of 1-20 μm and a period of 2-50 μm. In some embodiments, the step of forming the conductive pattern includes: A template is provided, a second micro-nano trench is formed on the template, a conductive paste is filled into the second micro-nano trench to form a conductive pattern precursor, and the conductive pattern precursor is transferred onto the green ceramic film tape to form the conductive pattern.

[0009] In some embodiments, the method for preparing the green ceramic film tape includes: A nanoimprint template is provided, and the green ceramic film strip is formed by casting on the nanoimprint template, so that a third micro-nano trench is formed on the surface of the green ceramic film strip; The step of forming the conductive pattern includes: The conductive paste is filled into the third micro-nano trench to form the conductive pattern.

[0010] In some embodiments, the conductive paste includes at least one selected from silver-based paste, copper-based paste, gold-based paste, tungsten-based paste, molybdenum-based paste, platinum-based paste, and palladium-based paste; The conductive paste contains metal particles with a particle size of less than 5 μm.

[0011] In some embodiments, the filling method of the conductive paste includes at least one of the following: scraping, screen printing, spraying, vacuum-assisted filling, electroplating, and electroless plating.

[0012] In some embodiments, the debinding and co-firing process includes: The laminated body is subjected to a first heat treatment, a second heat treatment, and a third heat treatment in sequence; The temperature of the first heat treatment is 80~120℃, and the time is 2~4 h; The second heat treatment is performed at a temperature of 250~500℃ for 2~4 hours. The third heat treatment is performed at a temperature of 800~1700℃ for a time of 4~10 h.

[0013] Secondly, this application also proposes a multilayer co-fired ceramic substrate, wherein the multilayer co-fired ceramic substrate includes conductive lines embedded therein, and the conductive lines are prepared using the method for preparing conductive lines of the multilayer co-fired ceramic substrate proposed in the first aspect of this application.

[0014] The method for fabricating conductive lines on multilayer co-fired ceramic substrates proposed in this application utilizes nanoimprint technology to fabricate conductive lines with line widths and spacings less than 50 μm, achieving conductor embedding in multilayer structures. This method maintains boundary stability after lamination and co-firing, significantly outperforming traditional screen printing. It is suitable for multilayer and interlayer interconnects and can be used in conjunction with via drilling / filling and stack alignment processes for precision packaging of three-dimensional integrated circuits such as high-density multilayer wiring, high-frequency and high-speed circuits, and power electronics integration.

[0015] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Figure 1 A schematic flowchart illustrating the method for fabricating conductive lines on a multilayer co-fired ceramic substrate provided in this application. Figure 2 A schematic flowchart illustrating the method for fabricating conductive lines on a multilayer co-fired ceramic substrate provided in this application. Figure 3 Microscopic observation of the conductive pattern provided in this application.

[0018] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] 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 a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] It should be noted that if the embodiments of this application involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0021] Furthermore, if the embodiments of this application involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0022] Ceramic substrates are important electronic packaging and interconnect materials, including multilayer co-fired ceramic substrates such as Low Temperature Co-fired Ceramic (LTCC) and High Temperature Co-fired Ceramic (HTCC), as well as high-reliability single-layer ceramic substrates represented by alumina, aluminum nitride, and silicon nitride. LTCC is suitable for multilayer integration and high-frequency devices; while HTCC and ceramic substrates such as alumina / alumina / silicon nitride are widely used in high-power, high-heat-dissipation, and harsh environment packaging. Traditional co-fired ceramic multilayer wiring mainly uses screen printing, that is, conductive paste is printed onto green ceramic film tape through a screen template, and then dried and sintered / co-fired to form the circuit. However, screen printing process has the following limitations: Existing LTCC / HTCC multilayer co-fired wiring processes mostly rely on screen printing of thick film pastes or photolithography-etching / deposition methods. Among these, screen printing is affected by screen resolution and paste rheology, making it difficult to further reduce the minimum linewidth / spacing, and the resulting line edges are rough with fluctuating geometry, limiting high-density wiring. Simultaneously, the flow / contraction coupling of conductors during lamination and co-firing amplifies the risk of short circuits and open circuits. Furthermore, nanoimprinting has been used for surface patterning of functional ceramic materials, typically by preparing imprinting adhesives / precursors containing ceramic nanoparticles and then sintering at high temperatures to obtain ceramic microstructures. However, this approach primarily focuses on replicating the surface morphology or controlling the performance of the ceramic material itself, and does not address conductor embedding, lamination alignment, and co-firing interconnection on the surface of multilayer LTCC green bands, making it difficult to directly solve the manufacturing bottlenecks of multilayer precision wiring.

[0023] Based on the above issues, please refer to Figure 1 In a first aspect, this application proposes a method for fabricating conductive lines on a multilayer co-fired ceramic substrate, comprising: S1. Provide green ceramic film tape, wherein the green ceramic film tape is used for multi-layer lamination and co-firing; S2. A conductive pattern is formed on the surface of a green ceramic film strip using nanoimprint technology, and then aligned and laminated with at least one other green ceramic film strip to form a laminate. S3. Perform debinding and co-firing treatment on the laminate to form embedded conductive lines within the laminate.

[0024] Nanoimprint lithography directly forms conductive patterns on the surface of a green ceramic film, avoiding the complex processes of multiple coating, exposure, and development steps in traditional photolithography, significantly simplifying the fabrication process of conductive lines. Since nanoimprint lithography uses mechanical molding to transfer patterns, its resolution is not limited by the optical diffraction limit, enabling the fabrication of conductive lines with linewidths and spacings less than 50 μm, with high pattern consistency and low defect rate. Further alignment, stacking, lamination, and co-firing of the green ceramic film with conductive patterns embeds the conductive lines into the ceramic substrate, forming an embedded structure. This structure not only eliminates the interface steps between the conductive lines and the ceramic substrate surface, improving surface flatness and facilitating subsequent multilayer high-density assembly, but also protects the embedded lines from the ceramic substrate, improving the environmental reliability of the conductive lines (e.g., resistance to oxidation, corrosion, and mechanical scratches). Furthermore, the conductive lines and the green ceramic film are simultaneously densified during co-firing, achieving a good match between the conductive and ceramic phases and avoiding interface stress problems caused by post-firing processes.

[0025] In some embodiments, in S2, forming a conductive pattern on the surface of a green ceramic film strip by nanoimprinting technology includes: forming an imprintable coating on the surface of the green ceramic film strip, forming a first micro-nano trench in the imprintable coating using a nanoimprinting mold, and filling the first micro-nano trench with conductive paste to form a conductive pattern.

[0026] Conductive patterns are formed on the surface of a green ceramic film strip by employing a process route of imprintable coating, nanoimprinting, and conductive paste filling. The introduction of the imprintable coating solves the problems of high surface roughness and poor imprinting adaptability that may exist in the green ceramic film strip itself. This coating can undergo plastic deformation or photocuring at lower temperatures and pressures, accurately replicating the micro-nano structure of the nanoimprinting mold to form a first micro-nano trench with a high aspect ratio and steep edges. During subsequent filling with conductive paste, the steep sidewalls and smooth bottom of the trench facilitate capillary filling or external force-assisted filling of the conductive paste, reducing defects such as voids and broken lines. Compared with direct imprinting on the green ceramic film strip, the imprintable coating has good interfacial compatibility with the conductive paste, forming a clean conductive-ceramic interface after debinding, reducing contact resistance. At the same time, the imprintable coating is completely decomposed and discharged during the debinding stage without introducing additional impurities, ensuring the purity and dielectric properties of the ceramic substrate after co-firing.

[0027] In some embodiments, the imprinting temperature is 80~180°C. For example, the imprinting temperature can be 80°C, 100°C, 120°C, 140°C, 160°C, or 180°C. The imprinting pressure is 0.1~0.5 MPa. For example, the imprinting pressure can be 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, or 0.5 MPa, etc. The imprinting time is 30~180 s. For example, the imprinting time can be 30 s, 60 s, 90 s, 120 s, 150 s, or 180 s, etc.

[0028] In some embodiments, the imprintable coating includes at least one of thermoplastic imprintable adhesive and photocurable imprintable adhesive. The thickness of the imprintable coating is 1 to 50 μm. For example, the thickness of the imprintable coating can be 1 μm, 5 μm, 10 μm, 20 μm, 25 μm, 30 μm, 40 μm, or 50 μm, etc.

[0029] Thermoplastic imprinting adhesives can be softened by heat before imprinting, offering a wide process window and low equipment requirements; UV-curable imprinting adhesives can cure rapidly at room temperature, making them suitable for high-precision, high-volume applications. Both provide flexible options for different mass production needs. Furthermore, limiting the thickness of the imprintable coating to 1–50 μm balances imprinting accuracy, the current-carrying capacity of the conductive lines, and the reliability of the adhesive removal process. If the thickness is too small (<1 μm), it is difficult to form sufficiently deep trenches, and insufficient conductive line thickness will lead to increased resistance; if the thickness is too large (>50 μm), bubbles and uneven filling are prone to occur during imprinting, and excessive organic matter may cause delamination or bubbling during adhesive removal.

[0030] In some embodiments, the nanoimprint mold has a periodic microstructure with a structural depth of 1–20 μm and a period of 2–50 μm. For example, the structural depth of the periodic microstructure is 1 μm, 5 μm, 10 μm, or 20 μm, and the period is 2 μm, 5 μm, 10 μm, 25 μm, or 50 μm, etc.

[0031] Understandably, the structural depth of the nanoimprint mold corresponds to the thickness range of the conductive lines. A structural depth of 1~20μm can meet diverse needs from signal transmission (thin lines) to power distribution (thick lines). The period corresponds to the linewidth and line spacing of the conductive lines. By setting the period of the periodic microstructure in the range of 2~50 μm, typical line sizes from micrometer to sub-millimeter scale are covered. This ensures compatibility with nanoimprint technology (feasible mold processing and reliable demolding) and meets the requirements of multilayer ceramic substrates for fine lines in high-frequency, high-speed transmission scenarios. The periodic structural design also facilitates alignment recognition during layer stacking, improving interlayer alignment accuracy.

[0032] In some embodiments, in S2, forming a conductive pattern on the surface of a green ceramic film strip by nanoimprinting technology includes: providing a template, forming a second micro-nano trench on the template, filling the second micro-nano trench with conductive paste to form a conductive pattern precursor, and transferring the conductive pattern precursor onto the green ceramic film strip to form a conductive pattern.

[0033] Conductive patterns are formed through a template pre-filling combined with pattern transfer. Specifically, a second micro-nano trench is first formed on the template and filled with conductive paste to form a conductive pattern precursor, which is then transferred as a whole to the surface of the green ceramic film. This process separates the imprinting and filling steps, avoiding problems such as film deformation, contamination, or damage to the green ceramic film due to imprinting pressure that may occur when imprinting and filling on the surface of the green ceramic film. It is particularly suitable for scenarios where the green ceramic film itself is relatively fragile and sensitive to mechanical stress. At the same time, the template can be reused, and the conductive pattern precursor can achieve precise positioning with the green ceramic film during the transfer process, making it suitable for mass production. This method also allows for pretreatment of the conductive pattern precursor before transfer (such as partial drying and sintering) to further optimize its bonding strength with the green ceramic film.

[0034] In some embodiments, in S1, the method for preparing the green ceramic film strip includes: providing a nanoimprint template, casting the green ceramic film strip on the nanoimprint template, and forming a third micro-nano trench on the surface of the green ceramic film strip; in S2, forming a conductive pattern on the surface of the green ceramic film strip by nanoimprint technology includes: filling a conductive paste into the third micro-nano trench to form a conductive pattern.

[0035] This process combines the formation of green ceramic film strips with in-situ imprinting, integrating the creation of conductive patterns into a single process. The green ceramic film strip is directly cast onto a nanoimprinting template, replicating the template's micro / nano structure on the strip surface during the forming process to create a third micro / nano groove, which is then filled with conductive paste. This process eliminates the need for a separate imprinting step, reducing process steps and equipment investment, and avoiding potential film strip stretching, deformation, and alignment errors that can occur during imprinting. Because the grooves are formed simultaneously with the green ceramic film strip formation, there is no interface between them and the film body. After debinding and co-firing, the bonding strength between the conductive lines and the ceramic substrate is higher, resulting in better thermal matching. This method is particularly suitable for large-scale continuous production, significantly improving production efficiency.

[0036] In some embodiments, the conductive paste includes at least one selected from silver-based paste, copper-based paste, gold-based paste, tungsten-based paste, molybdenum-based paste, platinum-based paste, and palladium-based paste. The metal particles in the conductive paste have a particle size of less than 5 μm.

[0037] Metals such as silver, copper, gold, tungsten, molybdenum, platinum, and palladium possess high electrical conductivity, good thermal stability, and co-firing characteristics that match ceramic substrates, meeting the requirements of various applications for conductivity, cost, high-temperature resistance, and oxidation resistance. By setting the metal particle size to less than 5 μm, it is ensured that the slurry can be smoothly filled into micro-nano trenches (trench sizes are typically in the micrometer range), avoiding clogging or uneven filling caused by large particles. Simultaneously, the fine metal particles exhibit higher sintering activity during co-firing, enabling densification at lower temperatures, reducing the co-firing temperature, and minimizing the impact on the performance of the ceramic substrate.

[0038] In some embodiments, the filling method of the conductive paste includes at least one of the following: scraping, screen printing, spraying, vacuum-assisted filling, electroplating, and electroless plating.

[0039] Scraping and screen printing are suitable for large-area, high-efficiency filling; spraying is suitable for uniform coverage of complex morphologies or trenches with high aspect ratios; vacuum-assisted filling can effectively eliminate residual gas at the bottom of the trench, reduce voids and defects, and improve the density and continuity of conductive lines; electroplating and electroless plating can thicken conductive lines on the basis of existing seed layers to meet the requirements of high current transmission. By flexibly selecting or combining the above filling methods, the filling quality and process yield can be optimized according to the linewidth, aspect ratio, rheological properties of the slurry, and mass production requirements of the conductive pattern, ensuring the integrity and consistency of the conductive lines.

[0040] In some embodiments, the debinding and co-firing process includes sequentially subjecting the laminate to a first heat treatment, a second heat treatment, and a third heat treatment. The first heat treatment is performed at a temperature of 80–120°C for 2–4 hours. The second heat treatment is performed at a temperature of 250–500°C for 2–4 hours. The third heat treatment is performed at a temperature of 800–1700°C for 4–10 hours.

[0041] The first heat treatment (80~120℃, 2~4 h) is used to slowly remove free solvents and some low-molecular-weight organic matter from the laminate at low temperature, avoiding rapid expansion of internal pores due to excessive heating, which could lead to delamination or cracking. The second heat treatment (250~500℃, 2~4 h) is the main stage of binder removal. This temperature range covers the thermal decomposition temperature of organic binders in the imprintable coating and green ceramic film. By controlling the heating rate and holding time, the organic matter is fully decomposed and slowly released, ensuring complete binder removal while avoiding local overheating or carbon residue caused by concentrated heat release. The third heat treatment (800~1700℃, 4~10 h) is the co-firing densification stage. At this temperature, ceramic powder and metal particles are sintered separately and diffuse into each other, forming a dense ceramic matrix and a continuous conductive network. By setting three heat treatment stages with different parameters during the debinding and co-firing processes, the conductive lines and ceramic substrate are simultaneously densified, avoiding defects such as line breakage, delamination, or warping caused by mismatched shrinkage rates, and ensuring the dimensional accuracy and reliability of the multilayer ceramic substrate.

[0042] This application also provides a multilayer ceramic substrate, which includes conductive lines embedded therein. The conductive lines are prepared using the conductive line preparation method of the multilayer co-fired ceramic substrate described above.

[0043] In conjunction with the foregoing, the multilayer ceramic substrate provided in this application, through the use of nanoimprint lithography, enables the linewidth, spacing, and alignment accuracy of conductive lines to reach the sub-micron level, meeting the high-density interconnection requirements of system-in-package (SiP) and 3D integration. Furthermore, since the conductive lines are embedded within the ceramic substrate, they are physically protected and chemically isolated by the ceramic material, exhibiting significantly superior resistance to environmental corrosion, mechanical wear, and high-temperature aging compared to surface-mount circuit structures.

[0044] The following specific examples provide further details.

[0045] Example 1 Please refer to Figure 2 This embodiment provides a method for fabricating conductive lines on a multilayer co-fired ceramic substrate, the specific steps of which are as follows: (1) Provide a low-temperature ceramic green ceramic film tape (thickness 50~300 μm), and spin-coat a thermoplastic imprinting adhesive (thickness 10 μm) onto the surface of the green ceramic film tape to form an imprintable coating. (2) Use a silicon-based nanoimprinting mold (structure depth 5 μm, structure period 10 μm) to imprint micro-nano trenches on the imprintable coating. The imprinting temperature is 100℃, the pressure is 0.3 MPa, and the time is 120 s. (3) Fill the micro-nano trenches with gold paste and remove excess paste to form conductive patterns (e.g., gold paste). Figure 3 (4) Align and laminate the green ceramic film tape with conductive patterns with other green ceramic film tapes (including via interconnect layers / dielectric layers) to form a stack. (5) Heat-treat the stack at 100°C for 3 h, heat-treat at 300°C for 3 h to complete the adhesive removal, and heat-treat at 850°C for 6 h to complete the fabrication of the conductive circuit.

[0046] Example 2 This embodiment provides a method for fabricating conductive lines on a multilayer co-fired ceramic substrate, the specific steps of which are as follows: (1) Provide a template with micro-nano trenches and a low-temperature ceramic green film tape (thickness 50~300 μm), apply silver paste to the micro-nano trenches, and remove excess to form a conductive pattern precursor. (2) Transfer the conductive pattern precursor to the green film tape to form a conductive pattern. (3) Align and laminate the green film tape with conductive patterns with other green film tapes (including via interconnect layers / dielectric layers) to form a stack. (4) Heat-treat the stack at 100℃ for 3 h, heat-treat at 300℃ for 3 h to complete the adhesive removal, and heat-treat at 850℃ for 6 h to complete the fabrication of the conductive circuit.

[0047] Example 3 This embodiment provides a method for fabricating conductive lines on a multilayer co-fired ceramic substrate, the specific steps of which are as follows: (1) A nanoimprint template with micro-nano trenches is provided, and a green ceramic film strip is cast on the nanoimprint template to form a structural replica (micro-nano trenches) of the nanoimprint template on the surface of the green ceramic film strip. (2) Palladium metal paste is filled into the micro-nano trenches formed by the green ceramic film strip to form a conductive pattern. (3) The green ceramic film strip with conductive pattern is aligned and laminated with other green ceramic film strips (including via interconnect layers / dielectric layers) to form a stack. (4) The stack is heat-treated at 100℃ for 3 hours, heat-treated at 300℃ for 3 hours to complete the adhesive removal, and heat-treated at 850℃ for 6 hours to complete the fabrication of the conductive circuit.

[0048] Example 4 This embodiment provides a method for fabricating conductive lines on a multilayer co-fired ceramic substrate, the specific steps of which are as follows: (1) Provide a low-temperature ceramic green ceramic film tape (thickness 50~300 μm), and spin-coat a thermoplastic imprinting adhesive (thickness 50 μm) on the surface of the green ceramic film tape to form an imprintable coating. (2) Use a silicon-based nanoimprinting mold (structure depth 20 μm, structure period 50 μm) to imprint micro-nano trenches on the imprintable coating. The imprinting temperature is 180℃, the pressure is 0.5 MPa, and the time is 30s. (3) Fill the micro-nano trenches with gold paste and remove excess paste to form conductive patterns. (4) Align and laminate the green ceramic film tape with conductive patterns with other green ceramic film tapes (including via interconnect layers / dielectric layers) to form a stack. (5) Heat-treat the stack at 80℃ for 2 h, heat-treat at 250℃ for 2 h to complete the adhesive removal, and heat-treat at 800℃ for 4 h to complete the fabrication of conductive circuits.

[0049] Example 5 This embodiment provides a method for fabricating conductive lines on a multilayer co-fired ceramic substrate, the specific steps of which are as follows: (1) Provide an alumina high-temperature ceramic green ceramic film tape (thickness 50~300 μm), and spin-coat a thermoplastic imprinting adhesive (thickness 1 μm) on the surface of the green ceramic film tape to form an imprintable coating. (2) Use a silicon-based nanoimprinting mold (structure depth 1 μm, structure period 2 μm) to imprint micro-nano trenches on the imprintable coating. The imprinting temperature is 80℃, the pressure is 0.1 MPa, and the time is 180 s. (3) Fill the micro-nano trenches with tungsten-based paste and remove excess paste to form conductive patterns. (4) Align and laminate the green ceramic film tape with conductive patterns with other green ceramic film tapes (including via interconnect layers / dielectric layers) to form a stack. (5) Heat-treat the stack at 120℃ for 4 h, heat-treat at 500℃ for 4 h to complete the adhesive removal, and heat-treat at 1700℃ for 10 h to complete the fabrication of conductive circuits.

[0050] Example 6 This embodiment uses the same preparation method as Example 1, except that the low-temperature ceramic green ceramic film belt is replaced with an alumina high-temperature ceramic green ceramic film belt, and the third heat treatment temperature is adjusted from 850℃ to 1600℃, and the time is adjusted from 6 h to 8 h.

[0051] Comparative Example 1 This comparative example uses a traditional screen printing process to prepare conductive lines on a multilayer co-fired ceramic substrate for comparison with Example 1 of this application. The specific steps are as follows: (1) Provide a low-temperature ceramic green ceramic film tape (thickness of 50~300 μm); (2) Use screen printing process to directly print gold paste onto the surface of the green ceramic film tape through a screen template to form a conductive pattern; (3) Align and laminate the green ceramic film tape with conductive pattern with other green ceramic film tapes (including through-hole interconnect layer / dielectric layer) to form a stack; (4) Heat treat the stack at 100℃ for 3 h, heat treat at 300℃ for 3 h to complete the glue removal, and heat treat at 850℃ for 6 h to complete the preparation of the conductive circuit.

[0052] The conductive circuits of the multilayer co-fired ceramic substrates prepared in Examples 1-6 and Comparative Example 1 were tested, and the results are shown in Table 1.

[0053] Table 1. Conductivity performance test of multilayer co-fired ceramic substrates

[0054] Test results show that, compared with Comparative Example 1 which uses traditional screen printing technology, the multilayer co-fired ceramic substrates prepared in Examples 1-6 of this application can break through the process bottleneck of 50 μm in minimum line width and line spacing. The line edges are straighter, the roughness is significantly reduced, and the volume resistivity is lower. This verifies the technical advantages of the nanoimprinting combined with embedded co-firing technology in high-density precision wiring in the embodiments of this application.

[0055] The above description is merely an exemplary embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the technical concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A method of fabricating a conductive circuit of a multilayer co-fired ceramic substrate, characterized by, include: A green ceramic film tape is provided, which is used for multi-layer lamination and co-firing; A conductive pattern is formed on the surface of the green ceramic film strip using nanoimprint technology, and then aligned and laminated with at least one other green ceramic film strip to form a laminate. The laminate is subjected to debinding and co-firing processes to form embedded conductive lines within the laminate.

2. The method for preparing conductive lines on a multilayer co-fired ceramic substrate as described in claim 1, characterized in that, The step of forming the conductive pattern includes: An imprintable coating is formed on the surface of the green ceramic film tape. A first micro-nano trench is formed in the imprintable coating using a nanoimprint mold. Conductive paste is then filled into the first micro-nano trench to form the conductive pattern.

3. The method for preparing conductive lines on a multilayer co-fired ceramic substrate as described in claim 2, characterized in that, The imprintable coating includes at least one of thermoplastic imprintable adhesive and photocurable imprintable adhesive; The thickness of the imprintable coating is 1~50 μm.

4. The method for preparing conductive lines on a multilayer co-fired ceramic substrate as described in claim 2, characterized in that, The nanoimprint mold has a periodic microstructure with a structural depth of 1~20 μm and a period of 2~50 μm.

5. The method for preparing conductive lines on a multilayer co-fired ceramic substrate as described in claim 1, characterized in that, The step of forming the conductive pattern includes: A template is provided, a second micro-nano trench is formed on the template, a conductive paste is filled into the second micro-nano trench to form a conductive pattern precursor, and the conductive pattern precursor is transferred onto the green ceramic film tape to form the conductive pattern.

6. The method for preparing conductive lines on a multilayer co-fired ceramic substrate as described in claim 1, characterized in that, The method for preparing the green ceramic membrane tape includes: A nanoimprint template is provided, and the green ceramic film strip is formed by casting on the nanoimprint template, so that a third micro-nano trench is formed on the surface of the green ceramic film strip; The step of forming the conductive pattern includes: The conductive paste is filled into the third micro-nano trench to form the conductive pattern.

7. The method for preparing conductive lines on a multilayer co-fired ceramic substrate as described in any one of claims 2 to 6, characterized in that, The conductive paste includes at least one of silver-based paste, copper-based paste, gold-based paste, tungsten-based paste, molybdenum-based paste, platinum-based paste, and palladium-based paste. The conductive paste contains metal particles with a particle size of less than 5 μm.

8. The method for preparing conductive lines on a multilayer co-fired ceramic substrate as described in any one of claims 2 to 6, characterized in that, The filling method of the conductive paste includes at least one of the following: scraping, screen printing, spraying, vacuum-assisted filling, electroplating, and electroless plating.

9. The method for preparing conductive lines on a multilayer co-fired ceramic substrate as described in claim 1, characterized in that, The debinding and co-firing process includes: The laminated body is subjected to a first heat treatment, a second heat treatment, and a third heat treatment in sequence; The temperature of the first heat treatment is 80~120℃, and the time is 2~4 h; The second heat treatment is performed at a temperature of 250~500℃ for 2~4 hours. The third heat treatment is performed at a temperature of 800~1700℃ for a time of 4~10 h.

10. A multilayer co-fired ceramic substrate, characterized in that, The multilayer co-fired ceramic substrate includes conductive lines embedded therein, and the conductive lines are prepared by the method for preparing conductive lines of the multilayer co-fired ceramic substrate according to any one of claims 1 to 9.

Images