A method for preparing a double-layer ceramic substrate based on AMB process

Abstract

The application discloses a preparation method of a double-layer ceramic substrate based on an AMB process and relates to the technical field of semiconductors. The specific steps comprise the following: after positioning holes and through holes are obtained by processing micropores on a ceramic layer, the ceramic layer is cleaned, the edge slag of the holes is removed, a single-side metal layer is deposited, after the deposition is completed, the holes are filled by silk screen printing, after the hole filling is completed, drying is performed, a metal foil is arranged between two dried ceramic layers, the two sides of the metal foil are in contact with the single-side deposited metal layers on the two ceramic layers, alignment and stacking are performed by using the positioning holes, an integrated structure is formed by vacuum brazing, and a double-side ceramic substrate is obtained. The composition of the metal layer is one or a combination of multiple of titanium, zirconium, tungsten, copper, nickel and silver; the metal foil is one of tungsten foil, molybdenum foil and tungsten-molybdenum foil obtained by calendering; and the slurry for filling the holes comprises non-fusible metal powder, fusible metal powder and an organic carrier.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, and particularly relates to a preparation method of a double-layer ceramic substrate based on an AMB process. BACKGROUND

[0002] With the continuous development of integrated circuits towards high density and miniaturization, the requirements for the wiring density, heat conduction performance, reliability and the like of packaging materials are also higher, and aluminum nitride (ALN) ceramic has the advantages of high thermal conductivity and a thermal expansion coefficient matched with chips, and thus becomes the preferred material for multilayer substrates. The existing ALN multilayer substrates are prepared by high-temperature co-firing (HTCC) process, and the traditional HTCC process has high difficulty and high cost for preparing the ALN multilayer substrate, and the consistency of the product is limited due to the sintering shrinkage difference. In addition, the ALN multilayer substrate prepared by HTCC needs to be co-fired with W and Mo conductors, which leads to a decrease in the thermal conductivity, and limits the application of the ALN multilayer substrate in the higher power field. SUMMARY

[0003] In view of the problems in the prior art, the present application provides a preparation method of a double-layer ceramic substrate based on an AMB process to solve at least one of the above technical problems. The double-layer ceramic substrate has higher reliability and lower cost.

[0004] To achieve the above object, the present application provides the following technical scheme:

[0005] The present application provides a preparation method of a double-layer ceramic substrate based on an AMB process, which specifically comprises the following preparation steps:

[0006] Step 1: After the positioning hole and the through hole are obtained by micropore processing of the ceramic layer, the ceramic layer is cleaned and the hole edge slag is removed, and then a single-sided metal layer is deposited;

[0007] Step 2: The ceramic layer after deposition is filled with holes by silk screen printing, and then dried after the hole filling is completed;

[0008] Step 3: Two pieces of dried ceramic layers are taken, and a metal foil is placed between the two pieces of ceramic layers, so that the two sides of the metal foil are in contact with the single-sided metal layers on the two pieces of ceramic layers, and the positioning hole is used for alignment and stacking;

[0009] Step 4: The stacked double-layer ceramic substrate is subjected to high-temperature sintering, and an integrated structure is formed by vacuum brazing to obtain a double-sided ceramic substrate.

[0010] Further, the ceramic layer is aluminum nitride ceramic, the thickness is 0.1mm-0.5mm, and the thermal conductivity is 190-250W / m·K.

[0011] Furthermore, the metal layer is composed of one or more combinations of titanium, zirconium, tungsten, copper, nickel, and silver, with a thickness of 0.2 μm-5 μm; the metal layer is obtained by magnetron sputtering, and the magnetron sputtering process parameters include: a vacuum degree of 10... -4 -10 -3 The sputtering parameters are: Pa, argon pressure 0.2-1 Pa, sputtering power 15-25 KW, voltage 500-800 V, time 30-120 min, and sputtering temperature 200-300 ℃.

[0012] Furthermore, the vias are obtained through laser processing; the screen printing paste for filling the vias is one of tungsten paste, molybdenum paste, tungsten-molybdenum paste, tungsten-copper paste, molybdenum-copper paste, or tungsten-molybdenum-copper paste.

[0013] Furthermore, the slurry comprises, by weight percentage: 85-90% metal powder and 10-15% organic carrier; the metal powder comprises, by weight percentage: 70-95% non-fusible metal powder and 5-30% molten metal powder, wherein the non-fusible metal powder is one of tungsten powder, molybdenum powder, or tungsten-molybdenum powder; the molten metal powder is one or more combinations of copper powder, silver powder, or nickel powder; and the organic carrier comprises 65-82% terpineol, 5-15% ethyl cellulose, 2-4% acrylic resin, 2-4% hydrogenated castor oil, 2-6% silane coupling agent, 2-5% tributyl citrate, and 0.5-1.5% dispersant.

[0014] Furthermore, the metal foil is one of tungsten foil, molybdenum foil, or tungsten-molybdenum foil obtained by rolling; the thickness of the metal foil is 5μm-30μm.

[0015] Furthermore, the vacuum brazing temperature is 900-1500℃, the holding time is 20-90 minutes, the vacuum degree is 0.001-0.01Pa, and the pressure is 10-30Pa.

[0016] Furthermore, after etching the ceramic layer, micropores are then fabricated. The etching process includes immersing the ceramic layer in a 4-10% sodium hydroxide solution, heating it to 50-70°C, processing it for 5-8 minutes, and then removing it, cleaning, and drying it.

[0017] Furthermore, the slurry also includes composite diamond, the mass of which is 2-5% of the metal powder. The preparation steps of the composite diamond are as follows: diamond, silicon carbide and silicon are mixed and made into a diamond-silicon carbide composite material under high temperature and high pressure. Then, a titanium layer and a tungsten layer are successively plated on the surface of the diamond-silicon carbide to obtain the composite diamond.

[0018] Furthermore, the mass ratio of diamond to silicon carbide and silicon is (90-95):(2-6):(1-5), the reaction temperature is 1400-1500℃, the reaction time is 10 min, and the reaction pressure is 5.5 GPa. Both the titanium layer and the tungsten layer are sputtered by magnetron sputtering, with the titanium layer thickness being 0.1μm-0.2μm and the tungsten layer thickness being 0.2μm-0.3μm.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. The double-layer ceramic substrate prepared by this invention using the AMB process utilizes sintered aluminum nitride ceramic sheets. During sintering, there is almost no shrinkage; only the two layers of aluminum nitride ceramic sheets need to be brazed together. In contrast, the existing HTCC process, due to the significant shrinkage differences and difficulty in controlling the shrinkage of the green blanks, generally requires multiple layers of green blanks to be stacked and fired, increasing alignment errors and process complexity. The brazing connection between the two layers of aluminum nitride ceramics in this invention, based on the AMB process, results in a strong bond. The non-shrinkage of the metal foil in the brazing layer ensures a continuous, uniform, and dense brazing layer with controllable thickness.

[0021] 2. The via-filling paste used in this invention differs from that used in traditional HTCCs, as it contains no oxides or glass phases, resulting in lower resistance in the vias. Furthermore, the addition of composite diamond to the via-filling paste provides excellent thermal conductivity. Combining diamond with silicon carbide effectively reduces diamond graphitization while improving thermal conductivity. Subsequent deposition of titanium and tungsten layers further enhances interfacial bonding strength. The active metal sputtered through the ceramic via walls undergoes a chemical reaction with the ceramic during high-temperature sintering, similar to the principle of AMB, ensuring a strong bond between the via-filling metal and the ceramic. Moreover, the double-layer ceramic substrate prepared by this invention has a lower sintering temperature than HTCCs, preventing a decrease in the ceramic's thermal conductivity due to high-temperature co-firing. Attached Figure Description

[0022] Figure 1 This is a flowchart of the present invention;

[0023] Figure 2 This is a schematic diagram of the double-layer ceramic stacking of the present invention: 01 is the upper ceramic sheet with sputtered metal layer and filled holes, 02 is the lower ceramic sheet with sputtered metal layer and filled holes, and 03 is the metal foil.

[0024] Figure 3 This is a schematic diagram of the double-layer ceramic substrate structure of the present invention: 011 is the upper ceramic sheet of the double-layer plate, 012 is the metal layer sputtered on the upper ceramic sheet of the double-layer plate, 03 is a metal foil, 021 is the lower ceramic sheet of the double-layer plate, and 022 is the metal layer sputtered on the lower ceramic sheet of the double-layer plate.

[0025] Figure 4 This is a cross-sectional micrograph of the double-layer aluminum nitride ceramic substrate prepared in Example 1;

[0026] Figure 5This is a cross-sectional scanning electron microscope (SEM) image of the double-layer aluminum nitride ceramic substrate prepared in Example 1. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In the experiment, the diamond particle size was 200 nm, the silicon carbide particle size was 1 μm, and the silicon particle size was 100 nm, all purchased from Shanghai Xiaohuang Nanomaterials. The organic carrier in the slurry, by mass percentage, included 80% terpineol, 8% ethyl cellulose, 2% acrylic resin, 4% hydrogenated castor oil, 3% KH550 (γ-aminopropyltriethoxysilane), 2% tributyl citrate, and 1% dispersant BYK-111; among which, the ethyl cellulose (product number 9004-57-3), the acrylic resin (product number 9007-20-9), and the hydrogenated vegetable oil (Einecs number 269-820-6) were all purchased from Nantong Runfeng.

[0029] The thermal conductivity of aluminum nitride ceramic is 220 W / m·K.

[0030] Example 1: This invention provides a method for preparing a double-layer ceramic substrate based on the AMB process, comprising the following steps:

[0031] Step 1: Using a UV picosecond laser drilling device, micro-holes are processed on aluminum nitride ceramic layers with thicknesses of 0.38 mm and 0.2 mm respectively to obtain positioning holes with a diameter of 0.5 mm and through holes with a diameter of 85 μm. Then, the drilled ceramic layers are cleaned with a low-concentration alkaline solution to remove slag from the hole edges.

[0032] Step 2: After thoroughly drying the above-mentioned aluminum nitride ceramic layer, magnetron sputtering is used to deposit the active metal Ti layer and Cu layer sequentially on one side of the microporous aluminum nitride ceramic layer; the drying temperature is 120℃, and the drying time is 2 hours; the sputtering vacuum degree is 10. -4 Pa, argon pressure 0.25 Pa, titanium-palladium sputtering power 7 KW, sputtering for 20 min, copper target sputtering power 16 KW, sputtering for 90 min; sputtering temperature 250℃ for all targets.

[0033] Step 3: Use the alignment screen printing method to screen print and fill the holes in the sputtered aluminum nitride ceramic layer. The filling surface is the non-sputtered surface. After filling, dry. The filling paste is a MoCu paste with a solid content of 88%, and the weight ratio of Mo to Cu is 4:1. The drying temperature is 100℃ and the drying time is 15min.

[0034] Step 4: Take two aluminum nitride ceramic layers that have been filled and dried, place a 15μm metal molybdenum foil between the two ceramic layers, so that both sides of the metal foil are in contact with the Cu layer deposited on one side of the two ceramic layers, and use the positioning holes for alignment and stacking.

[0035] Step 5: Place the stacked double-layer ceramic substrate into a vacuum pressure sintering furnace for high-temperature sintering. Form an integrated structure through vacuum brazing to obtain a double-sided ceramic substrate. The vacuum brazing temperature is 1100℃, the holding time is 40min, the vacuum degree is 0.01Pa, and the pressure is 20MPa.

[0036] Example 2: Referring to Example 1, the thickness of the molybdenum foil was adjusted to 25 μm. The specific steps are as follows:

[0037] Step 1: Using a UV picosecond laser drilling device, micro-holes are processed on aluminum nitride ceramic layers with thicknesses of 0.38 mm and 0.2 mm respectively to obtain positioning holes with a diameter of 0.5 mm and through holes with a diameter of 85 μm. Then, the drilled ceramic layers are cleaned with a low-concentration alkaline solution to remove slag from the hole edges.

[0038] Step 2: After thoroughly drying the above-mentioned aluminum nitride ceramic layer, magnetron sputtering is used to deposit the active metal Ti layer and Cu layer sequentially on one side of the microporous aluminum nitride ceramic layer; the drying temperature is 120℃, and the drying time is 2 hours; the sputtering vacuum degree is 10. -4 Pa, argon pressure 0.25 Pa, titanium-palladium sputtering power 7 KW, sputtering for 20 min, copper target sputtering power 16 KW, sputtering for 90 min; sputtering temperature 250℃ for all targets.

[0039] Step 3: Use the alignment screen printing method to screen print and fill the holes in the sputtered aluminum nitride ceramic layer. The filling surface is the non-sputtered surface. After filling, dry. The filling slurry is MoCu slurry with a solid content of 88% and a Mo to Cu weight ratio of 4:1. The drying temperature is 100℃ and the drying time is 15min.

[0040] Step 4: Take two aluminum nitride ceramic layers that have been filled and dried, place a 25μm metal molybdenum foil between the two ceramic layers, so that both sides of the metal foil are in contact with the Cu layer deposited on one side of the two ceramic layers, and use the positioning holes for alignment and stacking.

[0041] Step 5: Place the stacked double-layer ceramic substrate into a vacuum pressure sintering furnace for high-temperature sintering. Form an integrated structure through vacuum brazing to obtain a double-sided ceramic substrate. The vacuum brazing temperature is 1100℃, the holding time is 40min, the vacuum degree is 0.01Pa, and the pressure is 20MPa.

[0042] Example 3: Referring to Example 1, the sputtering times of the Ti layer and Cu layer were adjusted. The specific steps are as follows:

[0043] Step 1: Using a UV picosecond laser drilling device, micro-holes are processed on aluminum nitride ceramic layers with thicknesses of 0.38 mm and 0.2 mm respectively to obtain positioning holes with a diameter of 0.5 mm and through holes with a diameter of 85 μm. Then, the drilled ceramic layers are cleaned with a low-concentration alkaline solution to remove slag from the hole edges.

[0044] Step 2: After thoroughly drying the above-mentioned aluminum nitride ceramic layer, magnetron sputtering is used to deposit the active metal Ti layer and Cu layer sequentially on one side of the microporous aluminum nitride ceramic layer; the drying temperature is 120℃, and the drying time is 2 hours; the sputtering vacuum degree is 10. -4 Pa, argon pressure 0.25 Pa, titanium-palladium sputtering power 7 KW, sputtering for 10 min, copper target sputtering power 16 KW, sputtering for 50 min; sputtering temperature 250℃ for all targets.

[0045] Step 3: Use the alignment screen printing method to screen print and fill the holes in the sputtered aluminum nitride ceramic layer. The filling surface is the non-sputtered surface. After filling, dry. The filling slurry is MoCu slurry with a solid content of 88% and a Mo to Cu weight ratio of 4:1. The drying temperature is 100℃ and the drying time is 15min.

[0046] Step 4: Take two aluminum nitride ceramic layers that have been filled and dried, place a 15μm metal molybdenum foil between the two ceramic layers, so that both sides of the metal foil are in contact with the Cu layer deposited on one side of the two ceramic layers, and use the positioning holes for alignment and stacking.

[0047] Step 5: Place the stacked double-layer ceramic substrate into a vacuum pressure sintering furnace for high-temperature sintering. Form an integrated structure through vacuum brazing to obtain a double-sided ceramic substrate. The vacuum brazing temperature is 1100℃, the holding time is 40min, the vacuum degree is 0.01Pa, and the pressure is 20MPa.

[0048] Example 4: Referring to Example 1, a ceramic layer etching and composite diamond were added. The specific steps are as follows:

[0049] Step 1: Etch aluminum nitride ceramic layers with thicknesses of 0.38 mm and 0.2 mm. Immerse the ceramic layers in a 4% sodium hydroxide solution, heat to 50°C, process for 5 minutes, remove, clean and dry, and then use a UV picosecond laser drilling device to perform micro-hole processing on the etched aluminum nitride ceramic layers to obtain positioning holes with a diameter of 0.5 mm and through holes with a diameter of 85 μm. Then, clean the drilled ceramic layers with a low-concentration alkaline solution and remove the slag at the edge of the holes.

[0050] Step 2: After thoroughly drying the above-mentioned aluminum nitride ceramic layer, magnetron sputtering is used to deposit the active metal Ti layer and Cu layer sequentially on one side of the microporous aluminum nitride ceramic layer; the drying temperature is 120℃, and the drying time is 2 hours; the sputtering vacuum degree is 10. -4 Pa, argon pressure 0.25 Pa, titanium-palladium sputtering power 7 KW, sputtering for 20 min, copper target sputtering power 16 KW, sputtering for 90 min; sputtering temperature 250℃ for all targets.

[0051] Step 3: Use the alignment screen printing method to screen print and fill the holes in the sputtered aluminum nitride ceramic layer. The filling surface is the non-sputtered surface. After filling, dry. The filling slurry is MoCu-composite diamond slurry with a solid content of 88%. The weight ratio of Mo, Cu and composite diamond is 4:1:0.2. The drying temperature is 100℃ and the drying time is 15min.

[0052] Step 4: Take two aluminum nitride ceramic layers that have been filled and dried, place a 15μm metal molybdenum foil between the two ceramic layers, so that both sides of the metal foil are in contact with the Cu layer deposited on one side of the two ceramic layers, and use the positioning holes for alignment and stacking.

[0053] Step 5: Place the stacked double-layer ceramic substrate into a vacuum pressure sintering furnace for high-temperature sintering, and form an integrated structure through vacuum brazing to obtain a double-sided ceramic substrate. The vacuum brazing temperature is 1100℃, the holding time is 40min, the vacuum degree is 0.01Pa, and the pressure is 20MPa.

[0054] The preparation steps of the composite diamond include: mixing diamond, silicon carbide, and silicon in a mass ratio of 93:5:2, reacting at 1450℃ and 5.5GPa for 10 min to form a diamond-silicon carbide composite material, and then sequentially magnetron sputtering a 0.1μm titanium layer and a 0.3μm tungsten layer on the surface of the diamond-silicon carbide to obtain the composite diamond.

[0055] Comparative Example 1: As a control experiment for Example 1, no single-sided metal layer deposition was performed. The specific steps are as follows:

[0056] Step 1: Using a UV picosecond laser drilling device, micro-holes are processed on aluminum nitride ceramic layers with thicknesses of 0.38 mm and 0.2 mm respectively to obtain positioning holes with a diameter of 0.5 mm and through holes with a diameter of 85 μm. Then, the drilled ceramic layers are cleaned with a low-concentration alkaline solution to remove slag from the hole edges.

[0057] Step 2: After the aluminum nitride ceramic layer is fully dried, screen printing is performed to fill the holes using the alignment screen printing method. After filling the holes, the paste is dried. The filling paste is MoCu paste with a solid content of 88% and a weight ratio of Mo to Cu of 4:1. The drying temperature is 100℃ and the drying time is 15 minutes.

[0058] Step 3: Take two aluminum nitride ceramic layers that have been filled and dried, place a 15μm metal molybdenum foil between the two ceramic layers, and align and stack them using the positioning holes;

[0059] Step 4: Place the stacked double-layer ceramic substrate into a vacuum pressure sintering furnace for high-temperature sintering. Form an integrated structure through vacuum brazing to obtain a double-sided ceramic substrate. The vacuum brazing temperature is 1100℃, the holding time is 40min, the vacuum degree is 0.01Pa, and the pressure is 20MPa.

[0060] Comparative Example 2: As a control experiment for Example 1, the 15μm molybdenum foil was replaced with a 35μm molybdenum foil. The specific steps are as follows:

[0061] Step 1: Using a UV picosecond laser drilling device, micro-holes are processed on aluminum nitride ceramic layers with thicknesses of 0.38 mm and 0.2 mm respectively to obtain positioning holes with a diameter of 0.5 mm and through holes with a diameter of 85 μm. Then, the drilled ceramic layers are cleaned with a low-concentration alkaline solution to remove slag from the hole edges.

[0062] Step 2: After thoroughly drying the above-mentioned aluminum nitride ceramic layer, magnetron sputtering is used to deposit the active metal Ti layer and Cu layer sequentially on one side of the microporous aluminum nitride ceramic layer; the drying temperature is 120℃, and the drying time is 2 hours; the sputtering vacuum degree is 10. -4 Pa, argon pressure 0.25 Pa, titanium-palladium sputtering power 7 KW, sputtering for 20 min, copper target sputtering power 16 KW, sputtering for 90 min; sputtering temperature 250℃ for all targets.

[0063] Step 3: Use the alignment screen printing method to screen print and fill the holes in the sputtered aluminum nitride ceramic layer. The filling surface is the non-sputtered surface. After filling, dry. The filling slurry is MoCu slurry with a solid content of 88% and a Mo to Cu weight ratio of 4:1. The drying temperature is 100℃ and the drying time is 15min.

[0064] Step 4: Take two aluminum nitride ceramic layers that have been filled and dried, place a 35μm metal molybdenum foil between the two ceramic layers, so that both sides of the metal foil are in contact with the Cu layer deposited on one side of the two ceramic layers, and use the positioning holes for alignment and stacking.

[0065] Step 5: Place the stacked double-layer ceramic substrate into a vacuum pressure sintering furnace for high-temperature sintering. Form an integrated structure through vacuum brazing to obtain a double-sided ceramic substrate. The vacuum brazing temperature is 1100℃, the holding time is 40min, the vacuum degree is 0.01Pa, and the pressure is 20MPa.

[0066] Comparative Example 3: As a control experiment for Example 1, the components of the pore-filling slurry were replaced with 80% molybdenum powder, 8% aluminum nitride powder, and 12% organic carrier. The specific steps are as follows:

[0067] Step 1: Using a UV picosecond laser drilling device, micro-holes are processed on aluminum nitride ceramic layers with thicknesses of 0.38 mm and 0.2 mm respectively to obtain positioning holes with a diameter of 0.5 mm and through holes with a diameter of 85 μm. Then, the drilled ceramic layers are cleaned with a low-concentration alkaline solution to remove slag from the hole edges.

[0068] Step 2: After thoroughly drying the above-mentioned aluminum nitride ceramic layer, magnetron sputtering is used to deposit the active metal Ti layer and Cu layer sequentially on one side of the microporous aluminum nitride ceramic layer; the drying temperature is 120℃, and the drying time is 2 hours; the sputtering vacuum degree is 10. -4 Pa, argon pressure 0.25 Pa, titanium-palladium sputtering power 7 KW, sputtering for 20 min, copper target sputtering power 16 KW, sputtering for 90 min; sputtering temperature 250℃ for all targets.

[0069] Step 3: Use the alignment screen printing method to screen print and fill the holes in the sputtered aluminum nitride ceramic layer. The filling surface is the non-sputtered surface. After filling, dry the slurry. The drying temperature of the filling slurry is 100℃ and the drying time is 15 minutes.

[0070] Step 4: Take two aluminum nitride ceramic layers that have been filled and dried, place a 15μm metal molybdenum foil between the two ceramic layers, so that both sides of the metal foil are in contact with the Cu layer deposited on one side of the two ceramic layers, and use the positioning holes for alignment and stacking.

[0071] Step 5: Place the stacked double-layer ceramic substrate into a vacuum pressure sintering furnace for high-temperature sintering. Form an integrated structure through vacuum brazing to obtain a double-sided ceramic substrate. The vacuum brazing temperature is 1100℃, the holding time is 40min, the vacuum degree is 0.01Pa, and the pressure is 20MPa.

[0072] Testing and experimentation:

[0073] Thermal conductivity testing: Following ASTM-E1461, the thermal diffusivity of the double-sided ceramic substrates described in Examples 1-4 and Comparative Examples 1-3 was tested using a laser thermal conductivity meter (LFA 467) at temperatures ranging from room temperature to 500°C, according to ASTM-E1461. The thermal conductivity was calculated, and the data are recorded in Table 1.

[0074] Table 1

[0075] Item Example 1 Example 2 Example 3 Example 4 Thermal conductivity W / m-K 216.31 213.58 211.05 218.16 Item Comparative Example 1 Comparative Example 2 Comparative Example 3 Thermal conductivity W / m-K 181.67 183.71 182.33

[0076] Conclusion: The cross-sectional micrograph of the bilayer ceramic substrate product prepared in Example 1 is as follows: Figure 5 As shown in the figure, the upper and lower ceramics are densely and uniformly bonded without voids, and the through holes are densely filled without defects. Table 1 shows that Example 1 has a higher thermal conductivity than Examples 2 and 3. Example 4, by adding etching and composite diamond, effectively improves the thermal conductivity. Comparative Example 3, which replaced the through-hole filling slurry of Example 1 with a traditional through-hole filling slurry composition, shows a decrease in thermal conductivity.

[0077] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing a double-layer ceramic substrate based on the AMB process, characterized in that, Specifically, the preparation steps include the following: Step 1: After micro-machining the ceramic layer to obtain positioning holes and through holes, clean the ceramic layer and remove the slag at the edge of the holes, and then deposit a metal layer on one side. Step 2: After the ceramic layer has been deposited, screen print holes to fill them, and then dry it. Step 3: Take two dried ceramic layers and place a metal foil between them, so that both sides of the metal foil are in contact with the metal layer deposited on one side of the two ceramic layers. Use the positioning holes to align and stack them. Step 4: The stacked double-layer ceramic substrates are sintered at high temperature and then vacuum brazed to form an integrated structure, thus obtaining a double-sided ceramic substrate. The through holes and positioning holes are obtained by laser processing, wherein the diameter of the positioning holes is 0.8-1.2mm and the diameter of the through holes is 0.08-0.13mm; the screen printing filling paste is one of tungsten paste, molybdenum paste, tungsten-molybdenum paste, tungsten-copper paste, molybdenum-copper paste, and tungsten-molybdenum-copper paste. The slurry comprises, by weight percentage: 85-90% metal powder and 10-15% organic carrier; the metal powder comprises, by weight percentage: 70-95% non-fusible metal powder and 5-30% molten metal powder, wherein the non-fusible metal powder is one of tungsten powder, molybdenum powder, or tungsten-molybdenum powder; the molten metal powder is one or more combinations of copper powder, silver powder, or nickel powder; the organic carrier comprises 65-82% terpineol, 5-15% ethyl cellulose, 2-4% acrylic resin, 2-4% hydrogenated castor oil, 2-6% silane coupling agent, 2-5% tributyl citrate, and 0.5-1.5% dispersant.

2. The method for preparing a double-layer ceramic substrate based on AMB process according to claim 1, characterized in that, The ceramic layer is made of aluminum nitride ceramic with a thickness of 0.1mm-0.5mm and a thermal conductivity of 190-250W / m·K.

3. The method for preparing a double-layer ceramic substrate based on AMB process according to claim 1, characterized in that, The metal layer is composed of one or more combinations of titanium, zirconium, tungsten, copper, nickel, and silver, with a thickness of 0.2 μm-5 μm. The metal layer is obtained by magnetron sputtering, and the magnetron sputtering process parameters include a vacuum level of 10... -4 -10 -3 The sputtering parameters are: Pa, argon pressure 0.2-1 Pa, sputtering power 15-25 KW, voltage 500-800 V, time 30-120 min, and sputtering temperature 200-300 ℃.

4. The method for preparing a double-layer ceramic substrate based on AMB process according to claim 1, characterized in that, The metal foil is one of tungsten foil, molybdenum foil, or tungsten-molybdenum foil obtained by rolling; the thickness of the metal foil is 5μm-30μm.

5. The method for preparing a double-layer ceramic substrate based on AMB process according to claim 1, characterized in that, The temperature for vacuum brazing is 900-1500℃, the holding time is 20-90 minutes, the vacuum degree is 0.001-0.01Pa, and the pressure is 10-30Pa.

6. The method for preparing a double-layer ceramic substrate based on AMB process according to claim 1, characterized in that, After etching the ceramic layer, micropores are then machined. The etching process includes immersing the ceramic layer in a 4-10% sodium hydroxide solution, heating it to 50-70°C, processing it for 5-8 minutes, and then removing it, cleaning and drying it.

7. The method for preparing a double-layer ceramic substrate based on AMB process according to claim 1, characterized in that, The slurry also includes composite diamond, the mass of which is 2-5% of the metal powder. The preparation steps of composite diamond are as follows: diamond, silicon carbide and silicon are mixed and made into diamond silicon carbide composite material under high temperature and high pressure. Then, titanium layer and tungsten layer are successively plated on the surface of diamond silicon carbide to obtain composite diamond.

8. The method for preparing a double-layer ceramic substrate based on AMB process according to claim 7, characterized in that, The mass ratio of diamond to silicon carbide and silicon is (90-95):(2-6):(1-5). The high-temperature and high-pressure process conditions are: reaction temperature of 1400-1500℃, reaction time of 10 min, and reaction pressure of 5.5 GPa. Both the titanium layer and the tungsten layer are sputtered by magnetron sputtering. The thickness of the titanium layer is 0.1μm-0.2μm, and the thickness of the tungsten layer is 0.2μm-0.3μm.

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