A method for manufacturing a large-sized aluminum nitride multilayer substrate for a thin film process

Abstract

The application relates to the field of ceramic substrates, and discloses a preparation method of a large-size aluminum nitride multilayer substrate for a thin film process, which comprises the following steps: ball-milling and dispersing aluminum nitride powder, a sintering aid, a mixed solvent and a dispersant to obtain ceramic slurry; adding modified silicon nitride whiskers, a binder and a plasticizer to the ceramic slurry for secondary ball-milling to obtain casting slurry; performing casting forming on the casting slurry to obtain a casting green tape; performing cutting, warm pressing lamination and cold isostatic pressing treatment on the casting green tape to obtain a casting blank; performing sintering on the casting blank after glue removal treatment; the modified silicon nitride whiskers are prepared by coating the silicon nitride whiskers with boron nitride and pyrolytic carbon for double-layer interface coating, polyvinyl butyral is selected as the binder, dibutyl phthalate is selected as the plasticizer, the mixed solvent is prepared by mixing anhydrous ethanol and toluene, and the mechanical properties and the size stability of the substrate are improved by adding the modified silicon nitride whiskers and adopting a two-step sintering process.

Description

Technical Field

[0001] This invention belongs to the field of ceramic substrate technology, and specifically relates to a method for preparing a large-size aluminum nitride multilayer substrate for thin film processing. Background Technology

[0002] Large-size aluminum nitride multilayer substrates serve as the core packaging carrier supporting high-power chips, typically with a single substrate having an effective area exceeding 200 cm². 2 Furthermore, by combining multi-layer ceramic green body stacking with metallized wiring, it achieves an integrated functional component that integrates circuit signal transmission, heat dissipation channel construction, and device mechanical support.

[0003] However, large-size aluminum nitride multilayer substrates generally face the defect of easy shrinkage and deformation during the manufacturing process. This is mainly because the aluminum nitride green blank needs to be mixed with ceramic powder by organic binder. During the subsequent high-temperature sintering process, the organic binder will gradually decompose and volatilize, while the ceramic powder will undergo densification and shrinkage. Due to the large in-plane dimensions of large-size substrates, the volatilization rate of binder and the degree of powder densification in different regions of the substrate are prone to differences, resulting in uneven distribution of shrinkage stress and deformation. This will seriously harm the reliability and production yield of electronic packaging.

[0004] In addition, the bending strength and fracture toughness of large-size aluminum nitride multilayer substrates need to be further improved in practical applications. As a packaging carrier for high-power chips, the substrate needs to withstand various mechanical stresses during subsequent thin film metallization, chip mounting, wire bonding and service. If the bending strength of the substrate is too low, it is prone to brittle fracture under mechanical stress. If the fracture toughness is insufficient, tiny cracks or defects can easily propagate rapidly during service, leading to the overall failure of the substrate and seriously threatening the long-term reliability of electronic packaging. Summary of the Invention

[0005] To address the shortcomings mentioned in the background art, the present invention aims to provide a method for preparing a large-size aluminum nitride multilayer substrate for thin film processing. The method uses polyvinyl butyral as a binder, dibutyl phthalate as a plasticizer, and a mixed solvent composed of anhydrous ethanol and toluene. Modified silicon nitride whiskers are added in conjunction with a two-step sintering process to improve the mechanical properties and dimensional stability of the substrate.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing includes the following steps: S1. Aluminum nitride powder, sintering aid, mixed solvent and dispersant are mixed and then ball-milled to disperse to obtain ceramic slurry; S2. Add modified silicon nitride whiskers, binder and plasticizer to ceramic slurry and perform secondary ball milling to obtain casting slurry. The modified silicon nitride whiskers are made by double-layer interface coating of silicon nitride whiskers with boron nitride and cracked carbon. S3. Pour the casting slurry into the casting machine trough for casting to obtain a casting green belt; S4. The cast green strip is cut, warm-pressed and laminated, and then cold isostatically pressed to obtain the cast green body. S5. After debinding the cast blank, sinter it to prepare a large-size aluminum nitride multilayer substrate for thin film processing.

[0007] Preferably, the sintering aid is a mixture of yttrium oxide and cerium oxide in a mass ratio of 3:1 to 3.

[0008] Preferably, the method for preparing the modified silicon nitride whiskers includes the following steps: A. Dissolve boric acid and urea in a mixed solution of deionized water and ethanol, stir and mix evenly to form a precursor solution, then add silicon nitride whiskers and polyvinylpyrrolidone to the precursor solution, sonicate for 30 min, then magnetically stir for 12 h, filter, dry and place in a tube furnace and heat to 1000℃ under nitrogen protection for 2 h to prepare boron nitride coated silicon nitride whiskers; B. Phenolic resin was dissolved in ethanol, and then boron nitride-coated silicon nitride whiskers were added and mixed. The mixture was ultrasonically vibrated for 30 min, followed by magnetic stirring for 12 h. After filtration, the mixture was dried and placed in a tube furnace and heated to 900 °C under vacuum for 2 h to prepare modified silicon nitride whiskers.

[0009] Preferably, in step A, the mass ratio of boric acid, urea, silicon nitride whiskers and polyvinylpyrrolidone is 0.3~0.35:1.5~2:1:0.05~0.08; and in step B, the mass ratio of phenolic resin and boron nitride-coated silicon nitride whiskers is 0.15~0.2:1.

[0010] Preferably, the mixed solvent is composed of anhydrous ethanol and toluene mixed in a mass ratio of 1:1.

[0011] Preferably, the dispersant is trioleic acid glyceride or triethyl phosphate; the binder is polyvinyl butyral; and the plasticizer is dibutyl phthalate.

[0012] Preferably, the mass ratio of the aluminum nitride powder, sintering aid, modified silicon nitride whiskers, mixed solvent, dispersant, binder and plasticizer is 95:6:1.2~3:50:3~6:7:7.

[0013] Preferably, the casting speed of the casting process is 0.1~0.35m / min.

[0014] Preferably, the debinding process is carried out in a vacuum reactor at 550~600℃, with a heating rate of 0.5~3℃ / min.

[0015] Preferably, the sintering adopts a two-step sintering process, specifically heating to 1750℃ at a heating rate of 10℃ / min and holding for 1~4h, and then cooling to 1500℃ at a cooling rate of 10℃ / min and holding for 3h.

[0016] The beneficial effects of this invention are: This invention utilizes a boron acid and urea impregnation process to coat silicon nitride whiskers with boron nitride. A layered boron nitride interface phase is formed on the surface of the silicon nitride whiskers, effectively improving the mechanical properties of the aluminum nitride ceramic substrate. Furthermore, the layered boron nitride interface phase exhibits excellent thermal stability. Subsequently, the boron nitride-coated silicon nitride whiskers are further coated with pyrolytic carbon using high-temperature carbonization and pyrolysis of phenolic resin, resulting in modified silicon nitride whiskers. The double-layer interface of boron nitride and pyrolytic carbon in these modified silicon nitride whiskers can reduce the shrinkage rate of the aluminum nitride ceramic substrate and improve dimensional stability. At the same time, it effectively inhibits the interfacial reaction between the silicon nitride whiskers and the aluminum nitride ceramic matrix, forming a weak bonding interface. This facilitates crack deflection, bridging, and whisker pull-out, significantly improving the fracture toughness and flexural strength of the aluminum nitride ceramic substrate.

[0017] This invention uses polyvinyl butyral as a binder and dibutyl phthalate as a plasticizer. The mixed solvent is composed of anhydrous ethanol and toluene in a mass ratio of 1:1. The molecular weight of polyvinyl butyral is highly compatible with the toluene / ethanol solvent system, which can form a uniform coating layer on the surface of aluminum nitride particles. A three-dimensional network skeleton is constructed through molecular chain entanglement and hydrogen bonding, which improves the bending strength of the green body while maintaining excellent flexibility. The heating rate during the debinding process is set to 2~3℃ / min. The debinding process is carried out under vacuum to prevent oxidation. The debinding temperature is set to 550~600℃. The green body surface is free of cracks and the organic components are completely removed. Combined with a two-step sintering process, the mechanical properties and dimensional stability of the aluminum nitride ceramic substrate are further improved. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1: A method for preparing modified silicon nitride whiskers includes the following steps: A. Dissolve 0.31g boric acid and 1.8g urea in a mixed solution of 100mL deionized water and 100mL ethanol, stir and mix evenly to form a precursor solution, then add 1g silicon nitride whiskers and 0.05g polyvinylpyrrolidone to the precursor solution, sonicate for 30min, then stir magnetically for 12h, filter, dry and place in a tube furnace and heat to 1000℃ for 2h under nitrogen protection to prepare boron nitride coated silicon nitride whiskers; B. Dissolve 0.19g of phenolic resin in 50mL of ethanol, then add 1g of boron nitride-coated silicon nitride whiskers and mix. Sonicate for 30min, then magnetically stir for 12h. After filtration, dry and place in a tube furnace, heat to 900℃ under vacuum and hold for 2h to prepare modified silicon nitride whiskers.

[0020] Example 2: A method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing, comprising the following steps: S1. Add aluminum nitride powder (average particle size of 1.2 μm), sintering aid (yttrium oxide and cerium oxide mixed in a mass ratio of 3:1), mixed solvent (anhydrous ethanol and toluene mixed in a mass ratio of 1:1) and dispersant trioleic acid glyceride into a ball mill jar, and ball mill at 300 r / min for 4 h to obtain ceramic slurry; S2. Add the modified silicon nitride whiskers prepared in Example 1, the binder polyvinyl butyral, and the plasticizer dibutyl phthalate to the ceramic slurry and perform a second ball milling at 300 r / min for 2 h. The mass ratio of aluminum nitride powder, sintering aid, modified silicon nitride whiskers prepared in Example 1, mixed solvent, dispersant, binder, and plasticizer is 95:6:1.4:50:4:7:7 to obtain the casting slurry. S3. Pour the casting slurry into the casting machine trough for casting and forming to obtain a casting green belt. Set the casting machine scraper height to 200μm and the casting speed to 0.1m / min. S4. Cut the cast green strip, stack it together according to a fixed pattern, press it in a stacking press at 60 MPa and 80℃ for 10 minutes to stack the sheets, and then perform cold isostatic pressing at 200 MPa for 10 minutes to obtain the cast green body. S5. The cast blank is debonded in a vacuum reactor at 550℃ with a heating rate of 2℃ / min. After debonding, a two-step sintering process is carried out. Specifically, the temperature is raised to 1750℃ at a heating rate of 10℃ / min and held for 1 hour. Then, the temperature is lowered to 1500℃ at a cooling rate of 10℃ / min and held for 3 hours to prepare a large-size aluminum nitride multilayer substrate for thin film processing.

[0021] Example 3: A method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing, comprising the following steps: S1. Add aluminum nitride powder (average particle size of 1.2 μm), sintering aid (yttrium oxide and cerium oxide mixed in a mass ratio of 3:2), mixed solvent (anhydrous ethanol and toluene mixed in a mass ratio of 1:1) and dispersant trioleic acid glyceride into a ball mill jar, and ball mill at 300 r / min for 4 h to obtain ceramic slurry; S2. Add the modified silicon nitride whiskers prepared in Example 1, the binder polyvinyl butyral, and the plasticizer dibutyl phthalate to the ceramic slurry and perform a second ball milling at 300 r / min for 2 h. The mass ratio of aluminum nitride powder, sintering aid, modified silicon nitride whiskers prepared in Example 1, mixed solvent, dispersant, binder, and plasticizer is 95:6:2.1:50:5:7:7 to obtain the casting slurry. S3. Pour the casting slurry into the casting machine trough for casting and forming to obtain a casting green belt. Set the casting machine scraper height to 200μm and the casting speed to 0.1m / min. S4. Cut the cast green strip, stack it together according to a fixed pattern, press it in a stacking press at 60 MPa and 80℃ for 10 minutes to stack the sheets, and then perform cold isostatic pressing at 200 MPa for 10 minutes to obtain the cast green body. S5. The cast blank is debonded in a vacuum reactor at 580℃ with a heating rate of 2.2℃ / min. After debonding, a two-step sintering process is carried out. Specifically, the temperature is raised to 1750℃ at a heating rate of 10℃ / min and held for 2 hours. Then, the temperature is lowered to 1500℃ at a cooling rate of 10℃ / min and held for 3 hours to prepare a large-size aluminum nitride multilayer substrate for thin film processing.

[0022] Example 4: A method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing, comprising the following steps: S1. Add aluminum nitride powder (average particle size of 1.2 μm), sintering aid (yttrium oxide and cerium oxide mixed in a mass ratio of 3:3), mixed solvent (anhydrous ethanol and toluene mixed in a mass ratio of 1:1) and dispersant trioleic acid glyceride into a ball mill jar, and ball mill at 300 r / min for 4 h to obtain ceramic slurry; S2. Add the modified silicon nitride whiskers prepared in Example 1, the binder polyvinyl butyral, and the plasticizer dibutyl phthalate to the ceramic slurry and perform a second ball milling at 300 r / min for 2 h. The mass ratio of aluminum nitride powder, sintering aid, modified silicon nitride whiskers prepared in Example 1, mixed solvent, dispersant, binder, and plasticizer is 95:6:2.8:50:6:7:7 to obtain the casting slurry. S3. Pour the casting slurry into the casting machine trough for casting and forming to obtain a casting green belt. Set the casting machine scraper height to 200μm and the casting speed to 0.1m / min. S4. Cut the cast green strip, stack it together according to a fixed pattern, press it in a stacking press at 60 MPa and 80℃ for 10 minutes to stack the sheets, and then perform cold isostatic pressing at 200 MPa for 10 minutes to obtain the cast green body. S5. The cast blank is debonded in a vacuum reactor at 600℃ with a heating rate of 3℃ / min. After debonding, a two-step sintering process is carried out. Specifically, the temperature is raised to 1750℃ at a heating rate of 10℃ / min and held for 1 hour. Then, the temperature is lowered to 1500℃ at a cooling rate of 10℃ / min and held for 3 hours to prepare a large-size aluminum nitride multilayer substrate for thin film processing.

[0023] Comparative Example 1: A method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing, comprising the following steps: S1. Add aluminum nitride powder (average particle size of 1.2 μm), sintering aid (yttrium oxide and cerium oxide mixed in a mass ratio of 3:2), mixed solvent (anhydrous ethanol and toluene mixed in a mass ratio of 1:1) and dispersant trioleic acid glyceride into a ball mill jar, and ball mill at 300 r / min for 4 h to obtain ceramic slurry; S2. Add silicon nitride whiskers, binder polyvinyl butyral, and plasticizer dibutyl phthalate to the ceramic slurry and ball mill for a second time at 300 r / min for 2 h. The mass ratio of aluminum nitride powder, sintering aid, modified silicon nitride whiskers prepared in Example 1, mixed solvent, dispersant, binder and plasticizer is 95:6:2.1:50:5:7:7 to obtain the casting slurry. S3. Pour the casting slurry into the casting machine trough for casting and forming to obtain a casting green belt. Set the casting machine scraper height to 200μm and the casting speed to 0.1m / min. S4. Cut the cast green strip, stack it together according to a fixed pattern, press it in a stacking press at 60 MPa and 80℃ for 10 minutes to stack the sheets, and then perform cold isostatic pressing at 200 MPa for 10 minutes to obtain the cast green body. S5. The cast blank is debonded in a vacuum reactor at 580℃ with a heating rate of 2.2℃ / min. After debonding, a two-step sintering process is carried out. Specifically, the temperature is raised to 1750℃ at a heating rate of 10℃ / min and held for 2 hours. Then, the temperature is lowered to 1500℃ at a cooling rate of 10℃ / min and held for 3 hours to prepare a large-size aluminum nitride multilayer substrate for thin film processing.

[0024] Comparative Example 2: A method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing, comprising the following steps: S1. Add aluminum nitride powder (average particle size of 1.2 μm), sintering aid (yttrium oxide and cerium oxide mixed in a mass ratio of 3:2), mixed solvent (anhydrous ethanol and toluene mixed in a mass ratio of 1:1) and dispersant trioleic acid glyceride into a ball mill jar, and ball mill at 300 r / min for 4 h to obtain ceramic slurry; S2. Add the modified silicon nitride whiskers prepared in Example 1, the binder polyvinyl butyral, and the plasticizer dibutyl phthalate to the ceramic slurry and perform a second ball milling at 300 r / min for 2 h. The mass ratio of aluminum nitride powder, sintering aid, modified silicon nitride whiskers prepared in Example 1, mixed solvent, dispersant, binder, and plasticizer is 95:6:2.1:50:5:7:7 to obtain the casting slurry. S3. Pour the casting slurry into the casting machine trough for casting and forming to obtain a casting green belt. Set the casting machine scraper height to 200μm and the casting speed to 0.1m / min. S4. Cut the cast green strip, stack it together according to a fixed pattern, press it in a stacking press at 60 MPa and 80℃ for 10 minutes to stack the sheets, and then perform cold isostatic pressing at 200 MPa for 10 minutes to obtain the cast green body. S5. The cast blank is debonded in a vacuum reactor at 580℃ with a heating rate of 2.2℃ / min. After debonding, it is sintered at a heating rate of 10℃ / min. Nitrogen is introduced as a protective gas and sintered at 1750℃ under normal pressure for 3 hours to prepare a large-size aluminum nitride multilayer substrate for thin film processing.

[0025] Performance testing (1) The substrates prepared in Examples 2-4 and Comparative Examples 1-2 were subjected to a three-point bending test in standard GB / T 6569-2006 to determine the bending strength of the samples. The data results are shown in Table 1.

[0026] (2) The fracture toughness of the substrates prepared in Examples 2-4 and Comparative Examples 1-2 was determined by indentation method. A load of 20 kg was applied to the polished surface of the sample to form an indentation, and the loading time was 10 s. Then, the indentation size and crack propagation length were observed and measured by optical microscope. The measurement results were substituted into the formula for calculation: In the formula, KIC represents the fracture toughness of the material (MPa·m). 1 / 2 c: half the length of the crack in the material (m); a: half the length of the diagonal of the indentation in the material; HV: Vickers hardness of the material. The data results are shown in Table 1.

[0027] (3) The dimensions of the substrates prepared in Examples 2-4 and Comparative Examples 1-2 before and after sintering were measured respectively, and the shrinkage rate of the sample was calculated. The shrinkage rate = (size before sintering - size after sintering) / size before sintering × 100%. The thickness of the sample was 1 mm. The data results are shown in Table 1.

[0028] Table 1 Sample performance test results

[0029] As can be seen from the data in Table 1, the substrates prepared in Examples 2-4 of this invention exhibit high bending strength and fracture toughness, as well as good dimensional stability. In Comparative Example 1, no modification treatment was performed on the silicon nitride whiskers. In Comparative Example 2, a one-step sintering process was used. The bending strength and fracture toughness of Comparative Examples 1-2 were found to be lower than those in Examples 2-4, while the lateral shrinkage rate was higher. This indicates that the addition of modified silicon nitride whiskers and the two-step sintering process both improved the bending strength, fracture toughness, and dimensional stability of the samples to a certain extent, reducing the risk of deformation in large-size aluminum nitride multilayer substrates.

[0030] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0031] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing, characterized in that, Includes the following steps: S1. Aluminum nitride powder, sintering aid, mixed solvent and dispersant are mixed and then ball-milled to disperse to obtain ceramic slurry; S2. Add modified silicon nitride whiskers, binder and plasticizer to ceramic slurry and perform secondary ball milling to obtain casting slurry. The modified silicon nitride whiskers are made by double-layer interface coating of silicon nitride whiskers with boron nitride and cracked carbon. S3. Pour the casting slurry into the casting machine trough for casting to obtain a casting green belt; S4. The cast green strip is cut, warm-pressed and laminated, and then cold isostatically pressed to obtain the cast green body. S5. After debinding the cast blank, sinter it to prepare a large-size aluminum nitride multilayer substrate for thin film processing.

2. The method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing according to claim 1, characterized in that, The sintering aid is composed of yttrium oxide and cerium oxide mixed in a mass ratio of 3:1 to 3.

3. The method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing according to claim 1, characterized in that, The method for preparing the modified silicon nitride whiskers includes the following steps: A. Dissolve boric acid and urea in a mixed solution of deionized water and ethanol, stir and mix evenly to form a precursor solution, then add silicon nitride whiskers and polyvinylpyrrolidone to the precursor solution, sonicate for 30 min, then magnetically stir for 12 h, filter, dry and place in a tube furnace and heat to 1000℃ under nitrogen protection for 2 h to prepare boron nitride coated silicon nitride whiskers; B. Phenolic resin was dissolved in ethanol, and then boron nitride-coated silicon nitride whiskers were added and mixed. The mixture was ultrasonically vibrated for 30 min, followed by magnetic stirring for 12 h. After filtration, the mixture was dried and placed in a tube furnace and heated to 900 °C under vacuum for 2 h to prepare modified silicon nitride whiskers.

4. The method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing according to claim 3, characterized in that, In step A, the mass ratio of boric acid, urea, silicon nitride whiskers, and polyvinylpyrrolidone is 0.3~0.35:1.5~2:1:0.05~0.08; in step B, the mass ratio of phenolic resin and boron nitride-coated silicon nitride whiskers is 0.15~0.2:

1.

5. The method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing according to claim 1, characterized in that, The mixed solvent is composed of anhydrous ethanol and toluene in a mass ratio of 1:

1.

6. The method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing according to claim 1, characterized in that, The dispersant is trioleic acid glyceride or triethyl phosphate; the binder is polyvinyl butyral; and the plasticizer is dibutyl phthalate.

7. The method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing according to claim 1, characterized in that, The mass ratio of the aluminum nitride powder, sintering aid, modified silicon nitride whiskers, mixed solvent, dispersant, binder and plasticizer is 95:6:1.2~3:50:3~6:7:

7.

8. The method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing according to claim 1, characterized in that, The casting speed is 0.1~0.35m / min.

9. The method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing according to claim 1, characterized in that, The debinding process is carried out in a vacuum reactor at 550~600℃, with a heating rate of 0.5~3℃ / min.

10. The method for preparing a large-size aluminum nitride multilayer substrate for thin-film processing according to claim 1, characterized in that, The sintering process employs a two-step process: the temperature is raised to 1750℃ at a rate of 10℃ / min and held for 1-4 hours, followed by a cooling rate of 10℃ / min to 1500℃ and held for 3 hours.

Images