Integrated low temperature co-fired ceramic substrate rapid prototyping method with integrated air bridges

Abstract

This invention provides a rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridges, relating to the technical field of hybrid integrated circuits. The rapid prototyping method specifically includes: preparation of an LTCC green substrate; preparation of an organic solvent; preparation of a pre-converter slurry for the isolation layer; preparation of a support layer slurry; air bridge printing; and air bridge sintering. This invention uses a printing process to prepare the air bridge structure, combined with a low-temperature co-fired ceramic process, to form the air bridge structure simultaneously with the preparation of the integrated LTCC substrate. The integrated air bridge process is fully compatible with the LTCC process, and simultaneous sintering saves processing time and eliminates the need for additional specialized equipment, significantly reducing production costs. The air bridge structure prepared by this invention possesses higher temperature resistance and lower parasitic capacitance (superior microwave performance) compared to air bridge structures prepared by traditional photolithography processes, thus meeting the needs of more application environments and exhibiting higher reliability.

Description

Technical Field

[0001] This invention relates to the technical field of hybrid integrated circuits, and more specifically to a rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with an integrated air bridge. Background Technology

[0002] Low-temperature co-fired ceramic substrate (LTCC) technology offers advantages such as high-density wiring and passive integration, enabling large-scale integration and high-density packaging of passive components. Particularly for high-power microwave devices, the rapidly increasing characteristic frequencies and power levels place higher demands on interconnects. Therefore, there is a need to develop an interconnect technology with low parasitic capacitance, low resistance, and simple fabrication processes.

[0003] Air bridges, as an interconnect technology, are widely used in various active and passive devices. Utilizing air, which has the lowest dielectric constant, air bridges minimize parasitic capacitance and inductance per unit area at interconnect intersections, improving device frequency characteristics while reducing device area, increasing integration density, and saving manufacturing costs. Furthermore, in designs with complex microstrip line wiring, such as delay circuits and power divider circuits, air bridge structures are also necessary to further improve integration and microwave performance while reducing parasitic effects caused by interconnects.

[0004] Traditional methods for fabricating air bridges, such as those disclosed in applications 202311684530.8 and 202310731446.0, all require first setting photoresist on a substrate, then setting bridge piers on the photoresist. This photoresist layer serves as a reserved air layer, which is removed in subsequent fabrication processes through photolithography, i.e., exposure, development, etching, and stripping, thereby forming the air bridge.

[0005] LTCC substrates are typically fabricated through thick-film printing and sintering. On one hand, the green ceramic and most annealed ceramics in LTCC substrates cannot withstand the damage caused by acidic and alkaline solutions during development and etching processes, leading to penetration corrosion and a significant reduction in strength. On the other hand, the printed circuit patterns on the surface of the LTCC substrate are susceptible to sputtering contamination and corrosion from developing solutions, resulting in reduced adhesion between the central conductive metal layer and the ground metal layer, thus decreasing reliability. Therefore, traditional air bridge fabrication methods cannot be applied to LTCC substrates, and there are currently no reports of integrating air bridges on LTCC substrates.

[0006] In summary, this invention provides a rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with an integrated air bridge. This method is compatible with LTCC substrate processing technology, does not affect the ceramic body and surface circuit pattern of the LTCC substrate, and ensures stable improvement of the relevant performance of the LTCC substrate. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] To address the shortcomings of existing technologies, this invention provides a rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridges. This method solves the technical problem that traditional air bridge fabrication methods cannot integrate air bridges on LTCC substrates, and also addresses the technical problems of limited height and large parasitic capacitance of traditional air bridges.

[0009] (II) Technical Solution

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridges, comprising the following steps:

[0012] Step 1-1: Preparation of LTCC green body matrix

[0013] An LTCC green blank containing interlayer interconnect vias and circuit patterns is prepared. Positioning marks, a central conductor strip, and a grounding metal layer are printed on the surface of the LTCC green blank. The grounding metal layer is located on both sides of the central conductor strip to obtain an LTCC green blank substrate with coplanar waveguides for later use.

[0014] Step 2-1: Preparation of organic solvent

[0015] Terpineol, ethanol, butyl phthalate, ethyl cellulose, and trioleic acid glyceride were mixed and stirred evenly to prepare an organic solvent for later use.

[0016] Step 3-1: Preparation of the precursor slurry for the isolation layer

[0017] Coke powder and carbon black powder are stirred and mixed evenly, and then ground to obtain a mixed powder, which is used as the functional solid phase of the isolation layer.

[0018] Take the above-mentioned organic solvent, add the functional solid phase of the isolation layer into the organic solvent, mix and stir evenly, and then ball mill and vacuum degas to obtain the isolation layer precursor slurry for later use.

[0019] Step 4-1: Air Bridge Printing

[0020] When the height of the air bridge is ≤15μm:

[0021] Separate stencils for the isolation layer and the metal layer were prepared.

[0022] Printing the isolation layer: Use positioning marks for alignment, use the isolation layer stencil to print the isolation layer paste across the center guide belt and overlap it with the grounding metal layer. After printing, let it stand for 15-30 minutes to dry, and the isolation layer is obtained. The isolation layer can be printed repeatedly to increase the overall height of the air bridge.

[0023] Printed air bridges: Air bridges are printed on the isolation layer using a metal-layer stencil to form an air bridge structure;

[0024] Step 5-1: Air bridge sintering

[0025] The printed LTCC green substrate is placed on a firing plate with the side with the air bridge structure facing up, and then placed in a muffle furnace for sintering. After the furnace body cools naturally, the sintered integrated LTCC ceramic is removed, and the residue of the isolation layer on the substrate surface is removed to obtain an integrated LTCC substrate with an integrated air bridge structure.

[0026] A rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridges, comprising the following steps:

[0027] When the air bridge height is >15μm, first perform steps 1-1, 2-1, and 3-1 as described in claim 1, and then proceed with the following steps:

[0028] Step 4-2: Preparation of support layer slurry

[0029] Alumina powder, zirconium oxide powder, calcium oxide and borosilicate glass powder are mixed and stirred evenly, and then ground to obtain a mixed powder which is used as the functional solid phase of the support layer.

[0030] Take the above-mentioned organic solvent, add the functional solid phase of the support layer into it, mix and stir evenly, and then ball mill and vacuum degas to obtain the support layer precursor slurry for later use.

[0031] Step 5-2: Air Bridge Printing

[0032] Separately prepare stencils for the isolation layer, support layer, and metal layer.

[0033] Printing the isolation layer: Use positioning marks for alignment, use the isolation layer stencil to print the isolation layer paste across the center guide belt and overlap it with the grounding metal layer. After printing, let it stand for 15-30 minutes to dry, and the isolation layer is obtained. The isolation layer can be printed repeatedly to increase the overall height of the air bridge.

[0034] Printing support layer: Alignment is performed using positioning marks. Support layer paste is printed on the isolation layer using a support layer stencil. The width of the support layer is 100-200μm smaller than that of the isolation layer. The overlap length between the support layer and the grounding metal layers on both sides exceeds that of the isolation layer by 100-200μm. After printing, the support layer is dried by standing for 15-30 minutes.

[0035] Printed overpass: Overpasses are printed on the support layer. The width of the overpass is not greater than the width of the support layer. The overlap length between the overpass and the grounding metal layers on both sides exceeds the support layer by 100-200μm, forming an air bridge structure.

[0036] Step 6-2: Air bridge sintering

[0037] The printed LTCC green substrate is placed on a firing plate with the side with the air bridge structure facing up, and then placed in a muffle furnace for sintering. After the furnace body cools naturally, the sintered integrated LTCC ceramic is removed, and the residue of the isolation layer on the substrate surface is removed to obtain an integrated LTCC substrate with an integrated air bridge structure.

[0038] Preferably, the printing paste used for the central conductor strip, the grounding metal layer, and the crossover bridge can be any one of gold paste, silver paste, or copper paste.

[0039] Preferably, the organic solvent contains the following components in the following proportions: terpineol (60-80% by mass), ethanol (2-5% by mass), butyl phthalate (10-20% by mass), ethyl cellulose (5-10% by mass), and trioleic acid glyceride (2-5% by mass).

[0040] Preferably, the proportion of the isolation layer functional solid phase in the isolation layer slurry is 60-75%.

[0041] Preferably, the proportion of the functional solid phase of the support layer in the support layer precursor slurry is 70-90%.

[0042] Preferably, in the functional solid phase of the support layer, the mass fraction of alumina powder is 30-40%, the mass fraction of zirconium oxide powder is 5%-10%, the mass fraction of calcium oxide is 5%-10%, and the mass fraction of borosilicate glass powder is 50-60%.

[0043] Preferably, the drying conditions after printing the isolation layer, support layer, or crossover are: oven temperature 65-80℃, drying time 30-60min.

[0044] Preferably, the thickness of the stencil photoresist in the isolation layer is 10–50 μm; the thickness of the stencil photoresist in the support layer is 10–50 μm; and the thickness of the stencil photoresist in the crossover bridge is 10–35 μm.

[0045] Preferably, the sintering conditions for the integrated LTCC substrate are as follows: holding at 230–310°C for 1–2 hours, raising the temperature to 460–500°C and holding for 2–4 hours; then raising the temperature to 855–875°C and holding for 15–20 minutes.

[0046] At 230–310℃ and 460–500℃, the LTCC substrate undergoes debinding. After debinding and foaming, the substrate blank becomes porous, with most particles separated and increased interparticle porosity. As the sintering temperature rises to 855–875℃, the ceramic powder begins to soften by absorbing heat, and the ceramic particles continuously come into contact and rearrange, gradually eliminating large pores and forming closed pores. During the sintering stage at 855–875℃, the coke and carbon black in the isolation layer are partially burned into ash, and the internal structure becomes porous and easy to separate. Afterward, the sintered isolation layer is removed to form air bridges.

[0047] (III) Beneficial Effects

[0048] This invention provides a rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridges. Compared with the prior art, it has the following advantages:

[0049] 1. This invention uses a printing process to prepare an air bridge structure and then combines it with a low-temperature ceramic co-firing process to form an air bridge structure while preparing an integrated LTCC substrate. The integrated air bridge process is fully compatible with the LTCC process and is sintered and formed simultaneously, saving processing time and eliminating the need for additional special equipment, which can significantly reduce production costs.

[0050] 2. The air bridge structure prepared by this invention is taller than the air bridge prepared by traditional methods. In particular, the air bridge with the support layer structure can reach a height of hundreds of micrometers. Therefore, it has smaller parasitic capacitance and better microwave performance.

[0051] 3. The air bridge structure prepared by this invention can withstand high temperatures of over 600°C, which is much higher than the high temperature resistance of existing air bridge structures prepared by photolithography.

[0052] 4. The air bridge structure prepared by this invention has better high-temperature resistance and smaller parasitic capacitance (superior microwave performance) compared to air bridge structures prepared by traditional photolithography processes. Therefore, it can meet the needs of more application environments and has higher reliability.

[0053] 5. This invention is the first to integrate an air bridge structure on an LTCC substrate. The key dimensions of the obtained air bridge structure, such as height, bandwidth, and spacing, can be customized according to product design needs without being limited by raw materials, processes, or equipment, making operation flexible and convenient. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 The diagram shows the structure of the LTCC green substrate with coplanar waveguide in Embodiment 1 or Embodiment 2 of the present invention, wherein Figure a is a top view and Figure b is a cross-sectional view;

[0056] Figure 2 This is a schematic diagram of the printed isolation layer in Embodiment 1 or Embodiment 2 of the present invention;

[0057] Figure 3 This is a schematic diagram of the printed crossover bridge (without support layer) according to Embodiment 1 of the present invention;

[0058] Figure 4 This is a schematic diagram of the air bridge without support layer after sintering in Embodiment 1 of the present invention;

[0059] Figure 5 This is a schematic diagram of the printed support layer in Embodiment 2 of the present invention;

[0060] Figure 6 This is a schematic diagram of the printed crossover bridge (with a support layer) according to Embodiment 2 of the present invention;

[0061] Figure 7 This is a schematic diagram of the air bridge with a support layer after sintering in Embodiment 2 of the present invention.

[0062] Among them, 1. center conductor; 2. grounding metal layer; 3. LTCC green substrate; 4. isolation layer; 5. support layer; 6. crossover bridge; 7. air dielectric; 8. sintered center conductor; 9. sintered grounding metal layer; 10. sintered LTCC substrate; 11. sintered crossover bridge; 12. sintered support layer. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] This invention provides a rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridges. This solves the technical problems of traditional air bridge fabrication methods being unable to integrate air bridges on LTCC substrates, as well as the limitations of traditional air bridge height and large parasitic capacitance. This invention is the first to integrate an air bridge structure on an LTCC substrate. The fabricated air bridge structure exhibits better high-temperature resistance, smaller parasitic capacitance, and superior microwave performance compared to air bridge structures fabricated using traditional photolithography processes. Therefore, it can meet the needs of more application environments and has higher reliability.

[0065] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0066] Example 1:

[0067] like Figure 1 As shown, the rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridges includes the following steps:

[0068] Step 1: Substrate Preparation

[0069] A 15-layer LTCC green substrate 3 containing interlayer interconnect vias and circuit patterns is prepared by conventional punching, filling, printing, lamination and static pressing processes. The surface of the LTCC green substrate 3 is printed with a circular positioning mark, a central guide strip 1 and a ground metal layer 2. The ground metal layer 2 is located on both sides of the central guide strip 1 and is not connected to the central guide strip 1. The printing paste for the circular positioning mark, the central guide strip 1 and the ground metal layer 2 is gold paste.

[0070] The width of the central conductive strip 1 is 0.29 mm, and the distance between the central conductive strip 1 and the two ground metal layers 2 is 0.25 mm. The thickness of the ground metal layer 2 is 10 μm. The resulting LTCC green substrate 3 with coplanar waveguide is ready for use.

[0071] Step 2: Preparation of organic solvents

[0072] Weigh 280g of terpineol and 20g of ethanol, mix and stir, then add 20g of ethyl cellulose and continue stirring until completely dissolved. Then weigh 60g of butyl phthalate and 20g of trioleic acid glyceride, add them to the above mixed solution and continue stirring until homogeneous to obtain an organic solvent for later use.

[0073] Step 3: Preparation of the isolation layer slurry

[0074] Mix 48g of coke powder and 72g of carbon black powder evenly, and grind them in a mortar for 15-30 minutes. The resulting mixed powder is used as the functional solid phase of the isolation layer 4.

[0075] Take 80g of the organic solvent prepared above and ball mill it together with the functional solid phase of the isolation layer 4 in a ball mill jar for 6 hours, and then remove bubbles under vacuum to obtain the precursor slurry of the isolation layer 4.

[0076] Step 4: Air Bridge Printing

[0077] The required air bridge height is ≤15μm. Prepare the stencil for the isolation layer and the stencil for the metal layer. The screen mesh count is 325, the wire diameter is 23μm, the screen tension is 30N, the photosensitive emulsion thickness is 18μm, the printing screen distance is 1.5mm, and the printing speed is 100mm / s.

[0078] Printing the isolation layer: Alignment is achieved using positioning marks, and the isolation layer stencil is used to print the isolation layer 4 paste on the central guide belt 1; the printing width of the isolation layer 4 is 0.6mm; the overlap length between the isolation layer 4 and the grounding metal layers 2 on both sides is 100μm; after printing, let it stand for 30min, and then put it into a 70℃ oven for 30min to dry.

[0079] Printed bridge: Select gold paste and use a metal layer stencil to print another layer of metal guide strip on the isolation layer 4 as bridge 6. The width of the printed metal guide strip is 0.29mm. Then put it into a 70℃ oven for 30 minutes to dry, forming an air bridge structure.

[0080] Step 5: Air bridge sintering

[0081] The integrated LTCC green substrate 3 with the printed air bridge structure was placed on a quartz firing plate with the air bridge structure facing up and placed in a muffle furnace for firing. The LTCC green substrate 3 was held at 250°C for 2 hours, then heated to 460°C and held for 2 hours. Subsequently, the temperature was raised to 855°C and held for 15 minutes. After the furnace body cooled naturally, the sintered integrated LTCC ceramic was removed, and the residue of the isolation layer 4 on the substrate surface was removed to obtain the integrated LTCC substrate with integrated air bridge structure.

[0082] Example 2:

[0083] like Figure 2 As shown, the rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridges includes the following steps:

[0084] Step 1: Substrate Preparation

[0085] A 20-layer LTCC green substrate 3 containing interlayer interconnecting vias and circuit patterns is prepared by conventional punching, filling, printing, lamination, and static pressing processes. The surface of the LTCC green substrate 3 is printed with a circular positioning mark, a central guide strip 1, and a grounding metal layer 2. The grounding metal layer 2 is located on both sides of the central guide strip 1 and is not connected to the central guide strip 1. The printing paste for the circular positioning mark, the central guide strip 1, and the grounding metal layer 2 is gold paste.

[0086] The width of the central conductor 1 is 0.22 mm, and the distance between the central conductor 1 and the two ground metal layers 2 is 0.25 mm. The thickness of the ground metal layer 2 is 12 μm. The resulting LTCC green substrate 3 with coplanar waveguide is ready for use.

[0087] Step 2: Preparation of organic solvents

[0088] Weigh 320g of terpineol and 8g of ethanol, mix and stir, then add 24g of ethyl cellulose and continue stirring until completely dissolved. Then weigh 40g of butyl phthalate and 8g of trioleic acid glyceride, add them to the above mixed solution and continue stirring until homogeneous to obtain an organic solvent for later use.

[0089] Step 3: Preparation of the isolation layer slurry

[0090] Mix 70g of coke powder and 70g of carbon black powder evenly, and grind them in a mortar for 20 minutes. The resulting mixed powder is used as the functional solid phase of the isolation layer 4.

[0091] Take 60g of the organic solvent prepared above and ball mill it together with the functional solid phase of the isolation layer 4 in a ball mill jar for 6 hours, and then remove bubbles under vacuum to obtain the precursor slurry of the isolation layer 4.

[0092] Step 4: Preparation of support layer slurry

[0093] 42g of alumina powder, 7g of zirconium oxide powder, 7g of calcium oxide and 84g of borosilicate glass powder were stirred and mixed evenly, and then ground in a mortar for 30 minutes. The resulting mixed powder was used as the functional solid phase of the support layer 5.

[0094] Take 60g of organic solvent and ball mill it together with the functional solid phase of support layer 5 in a ball mill jar for 12 hours, and then degas under vacuum to obtain the precursor slurry of support layer 5.

[0095] Step 5: Air Bridge Printing

[0096] The required air bridge height is >15μm. Prepare the stencils for the isolation layer, support layer, and metal layer. The screen mesh count is 400, the screen tension is 27N, the photosensitive emulsion thickness is 25μm, the printing screen distance is 2mm, and the printing speed is 80mm / s.

[0097] Printing the isolation layer: Alignment is achieved using positioning marks, and the isolation layer stencil is used to print the isolation layer 4 paste on the central guide belt 1; the printing width of the isolation layer 4 is 0.5mm; the overlap length between the isolation layer 4 and the grounding metal layers 2 on both sides is 150μm; after printing, let it stand for 30 minutes, and then put it into a 75℃ oven for 60 minutes to dry.

[0098] Printing support layer: Alignment is performed using positioning marks, and support layer stencil is used to print support layer 5 paste on isolation layer 4. The width of support layer 5 is 200μm smaller than that of isolation layer 4. The overlap length between support layer 5 and the ground metal layers 2 on both sides exceeds that of isolation layer 4 by 2200μm. After printing, let it stand for 30 minutes to dry, and then put it in a 75℃ oven for 60 minutes to dry, thus obtaining support layer 5.

[0099] Printed crossover bridge: Select gold paste and use a metal layer stencil to print another layer of metal guide strip on the isolation layer 4 as crossover bridge 6. The width of the printed metal guide strip is 0.22mm. Then put it into a 75℃ oven for 60 minutes to dry, forming an air bridge structure.

[0100] Step 6: Air bridge sintering

[0101] The integrated LTCC green substrate 3 with the printed air bridge structure was placed on a quartz firing plate with the air bridge structure facing up and placed in a muffle furnace for firing. The LTCC green substrate 3 was held at 230°C for 3 hours, then heated to 480°C and held for 3 hours. Subsequently, the temperature was raised to 875°C and held for 16 minutes. After the furnace body cooled naturally, the sintered integrated LTCC ceramic was removed, and the residue of the isolation layer 4 on the substrate surface was removed to obtain the integrated LTCC substrate with the integrated air bridge structure.

[0102] In summary, compared with existing technologies, it has the following beneficial effects:

[0103] 1. This invention uses a printing process to prepare an air bridge structure and then combines it with a low-temperature ceramic co-firing process to form an air bridge structure while preparing an integrated LTCC substrate. The integrated air bridge process is fully compatible with the LTCC process and is sintered and formed simultaneously, saving processing time and eliminating the need for additional special equipment, which can significantly reduce production costs.

[0104] 2. The air bridge structure prepared by this invention is taller than the air bridge prepared by traditional methods. In particular, the air bridge with the support layer structure can reach a height of hundreds of micrometers. Therefore, it has smaller parasitic capacitance and better microwave performance.

[0105] 3. The air bridge structure prepared by this invention can withstand high temperatures of over 600°C, which is much higher than the high temperature resistance of existing air bridge structures prepared by photolithography.

[0106] 4. The air bridge structure prepared by this invention has better high-temperature resistance and smaller parasitic capacitance (superior microwave performance) compared to air bridge structures prepared by traditional photolithography processes. Therefore, it can meet the needs of more application environments and has higher reliability.

[0107] 5. This invention is the first to integrate an air bridge structure on an LTCC substrate. The key dimensions of the obtained air bridge structure, such as height, bandwidth, and spacing, can be customized according to product design needs without being limited by raw materials, processes, or equipment, making operation flexible and convenient.

[0108] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0109] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridges, characterized in that, The specific steps include: Step 1-1: Preparation of LTCC green body matrix An LTCC green blank containing interlayer interconnect vias and circuit patterns is prepared. Positioning marks, a central conductor strip, and a grounding metal layer are printed on the surface of the LTCC green blank. The grounding metal layer is located on both sides of the central conductor strip to obtain an LTCC green blank substrate with coplanar waveguides for later use. Step 2-1: Preparation of organic solvent Terpineol, ethanol, butyl phthalate, ethyl cellulose, and trioleic acid glyceride were mixed and stirred evenly to prepare an organic solvent for later use. Step 3-1: Preparation of the precursor slurry for the isolation layer Coke powder and carbon black powder are stirred and mixed evenly, and then ground to obtain a mixed powder, which is used as the functional solid phase of the isolation layer. Take the above-mentioned organic solvent, add the functional solid phase of the isolation layer into the organic solvent, mix and stir evenly, and then ball mill and vacuum degas to obtain the isolation layer precursor slurry for later use. Step 4-1: Air Bridge Printing When the air bridge height is ≤15μm, stencils with isolation layer and stencils with metal layer are prepared respectively. Printing the isolation layer: Use positioning marks for alignment, use the isolation layer stencil to print the isolation layer paste across the center guide belt and overlap it with the grounding metal layer. After printing, let it stand for 15-30 minutes to dry, and the isolation layer is obtained. The isolation layer can be printed repeatedly to increase the overall height of the air bridge. Printed air bridges: Air bridges are printed on the isolation layer using a metal-layer stencil to form an air bridge structure; Step 5-1: Air bridge sintering The printed LTCC green substrate is placed on a firing plate with the side with the air bridge structure facing up, and then placed in a muffle furnace for sintering. After the furnace body cools naturally, the sintered integrated LTCC ceramic is removed, and the residue of the isolation layer on the substrate surface is removed to obtain an integrated LTCC substrate with an integrated air bridge structure.

2. A rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridges, characterized in that, The specific steps include: When the air bridge height is >15μm: First, perform steps 1-1, 2-1, and 3-1 as described in claim 1, and then proceed with the following steps: Step 4-2: Preparation of support layer slurry Alumina powder, zirconium oxide powder, calcium oxide and borosilicate glass powder are mixed and stirred evenly, and then ground to obtain a mixed powder which is used as the functional solid phase of the support layer. Take the above-mentioned organic solvent, add the functional solid phase of the support layer into it, mix and stir evenly, and then ball mill and vacuum degas to obtain the support layer precursor slurry for later use. Step 5-2: Air Bridge Printing Separately prepare stencils for the isolation layer, support layer, and metal layer. Printing the isolation layer: Use positioning marks for alignment, use the isolation layer stencil to print the isolation layer paste across the center guide belt and overlap it with the grounding metal layer. After printing, let it stand for 15-30 minutes to dry, and the isolation layer is obtained. The isolation layer can be printed repeatedly to increase the overall height of the air bridge. Printing support layer: Alignment is performed using positioning marks. Support layer paste is printed on the isolation layer using a support layer stencil. The width of the support layer is 100-200μm smaller than that of the isolation layer. The overlap length between the support layer and the grounding metal layers on both sides exceeds that of the isolation layer by 100-200μm. After printing, the support layer is dried by standing for 15-30 minutes. Printed overpass: Overpasses are printed on the support layer. The width of the overpass is not greater than the width of the support layer. The overlap length between the overpass and the grounding metal layers on both sides exceeds the support layer by 100-200μm, forming an air bridge structure. Step 6-2: Air bridge sintering The printed LTCC green substrate is placed on a firing plate with the side with the air bridge structure facing up, and then placed in a muffle furnace for sintering. After the furnace body cools naturally, the sintered integrated LTCC ceramic is removed, and the residue of the isolation layer on the substrate surface is removed to obtain an integrated LTCC substrate with an integrated air bridge structure.

3. The rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridge as described in claim 1 or 2, characterized in that, The printing paste used for the central conductor, the grounding metal layer, and the crossover bridge can be any one of gold paste, silver paste, or copper paste.

4. The rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridge as described in claim 1 or 2, characterized in that, The organic solvent contains the following components in the following proportions: terpineol (60-80% by mass), ethanol (2-5% by mass), butyl phthalate (10-20% by mass), ethyl cellulose (5-10% by mass), and trioleic acid glyceride (2-5% by mass).

5. The rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridge as described in claim 1 or 2, characterized in that, The proportion of the functional solid phase of the isolation layer in the isolation layer slurry is 60-75%.

6. The rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridge as described in claim 2, characterized in that, The proportion of the functional solid phase of the support layer in the precursor slurry is 70-90%.

7. The rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridge as described in claim 2, characterized in that: In the functional solid phase of the support layer, the mass fraction of alumina powder is 30-40%, the mass fraction of zirconium oxide powder is 5%-10%, the mass fraction of calcium oxide is 5%-10%, and the mass fraction of borosilicate glass powder is 50-60%.

8. The rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridge as described in claim 1 or 2, characterized in that: The drying conditions after printing the isolation layer, support layer, or crossover are: oven temperature 65-80℃, drying time 30-60min.

9. The rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridge as described in claim 1 or 2, characterized in that: The thickness of the stencil photoresist in the isolation layer is 10–50 μm; the thickness of the stencil photoresist in the support layer is 10–50 μm; and the thickness of the stencil photoresist in the crossover bridge is 10–35 μm.

10. The rapid prototyping method for an integrated low-temperature co-fired ceramic substrate with integrated air bridge as described in claim 1 or 2, characterized in that: The sintering conditions for the integrated LTCC substrate are as follows: hold at 230–310°C for 1–2 hours, raise the temperature to 460–500°C and hold for 2–4 hours; then raise the temperature to 855–875°C and hold for 15–20 minutes.

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