High surface finish alumina multilayer ceramic substrate and method of making same

Abstract

The application relates to the technical field of ceramic substrates, and discloses high-surface-finish alumina multilayer ceramic substrates and a preparation method thereof. The high-surface-finish alumina multilayer ceramic substrate comprises the following components by weight: 80-90 parts of alumina, 4-6 parts of a sintering aid, 3-4 parts of a dispersing aid, 6-8 parts of a binder and 75-85 parts of a solvent; the dispersing aid comprises triethyl phosphate, fumed silica and a phenyl phosphate compound. The above technical scheme solves the problem of poor surface finish of alumina multilayer ceramic substrates in the related art.

Description

Technical Field

[0001] This invention relates to the field of ceramic substrate technology, and more specifically, to a high-surface-smoothness alumina multilayer ceramic substrate and its preparation method. Background Technology

[0002] Surface finish, as one of the core performance indicators of alumina multilayer ceramic substrates, directly determines the quality of subsequent metallization bonding and the accuracy of circuit patterns. However, in the existing technology, the problem of poor surface finish is common, and its root cause is mainly concentrated in the interaction of material systems.

[0003] The raw materials for alumina ceramic substrates mainly include alumina, sintering aids, organic additives (binders, dispersants) and solvents. Among them, inorganic alumina powder and organic additives are two phases with different properties. The strength of the interaction between the two directly determines the dispersion uniformity of the mixed system and the stability of the microstructure of the green body. When there is insufficient interaction between inorganic alumina powder and organic additives, it will lead to uneven distribution of the two phases, resulting in powder sedimentation and organic phase floating. This will eventually lead to a decrease in the uniformity of the slurry, which in turn causes uneven density of the green body in subsequent tape casting, and defects such as cracking, delamination, and surface depressions in the substrate after sintering, which seriously affects the surface finish of the ceramic substrate.

[0004] Therefore, it is necessary to develop an alumina multilayer ceramic substrate with high surface finish. Summary of the Invention

[0005] This invention proposes a high surface finish alumina multilayer ceramic substrate and its preparation method, which solves the problem of poor surface finish of alumina ceramic substrates in related technologies.

[0006] The technical solution of the present invention is as follows: The present invention proposes a high surface finish alumina multilayer ceramic substrate, comprising the following raw materials in parts by weight: 80-90 parts alumina, 4-6 parts sintering aid, 3-4 parts dispersing aid, 6-8 parts binder, and 75-85 parts solvent; wherein the dispersing aid comprises triethyl phosphate, fumed silica, and phenyl phosphate compound.

[0007] As a further technical solution, the phenyl phosphate compound includes one or both of monophenyl phosphate and diphenyl phosphate, preferably monophenyl phosphate.

[0008] In the alumina multilayer ceramic substrate of the present invention, the phenyl phosphate compound is preferably monophenyl phosphate. Compared with diphenyl phosphate containing two benzene rings, monophenyl phosphate has a moderate phenyl content, which will not excessively prevent the adsorption of other substances on the alumina surface due to steric hindrance, thereby further improving the surface finish of the alumina multilayer ceramic substrate.

[0009] As a further technical solution, the mass ratio of the triethyl phosphate, fumed silica and phenyl phosphate compound is 2:1:0.8~1.

[0010] As a further technical solution, the fumed silica is composed of a first fumed silica and a second fumed silica, wherein the carbon content of the first fumed silica and the second fumed silica is different.

[0011] In this invention, fumed silica is added as a dispersing agent in the alumina multilayer ceramic substrate. The fumed silica is composed of first fumed silica and second fumed silica with different carbon contents. The carbon content of the fumed silica is directly related to its hydrophilic and hydrophobic properties. Fumed silica with high carbon content has its surface silanol groups replaced by a large number of organic carbon chains, resulting in strong hydrophobicity and good compatibility with substances with low polarity (such as polyvinyl butyral). Fumed silica with low carbon content still has silanol groups as the main component on its surface, resulting in strong hydrophilicity and uniform dispersion in polar systems (such as alumina). By using first fumed silica and second fumed silica with different carbon contents together, the dispersion of polar alumina and the compatibility of weakly polar organic additives can be balanced, effectively promoting uniform dispersion and interfacial bonding of the slurry and improving the strength of the alumina multilayer ceramic substrate.

[0012] As a further technical solution, the carbon content of the first fumed silica is 0.7wt%~1.3wt%, and the carbon content of the second fumed silica is 2.0wt%~4.0wt%.

[0013] In the alumina multilayer ceramic substrate of the present invention, the carbon content of the first fumed silica is 0.7wt%~1.3wt%, which belongs to light organic modification. The silanol retention rate on the surface of the fumed silica is relatively high, and sufficient hydrophilicity is retained to adapt to the core polar components of the system. The carbon content of the second fumed silica is 2.0wt%~4.0wt%, which belongs to moderate organic modification. The silanol substitution rate on the surface is slightly higher, which can adapt to the organic phase and avoid sintering defects caused by strong hydrophobicity, thereby improving the strength of the alumina multilayer ceramic substrate.

[0014] As a further technical solution, the mass ratio of the first fumed silica to the second fumed silica is 1~2:1.

[0015] In the alumina multilayer ceramic substrate of the present invention, the mass ratio of the first fumed silica and the second fumed silica is 1~2:1. This ratio range is moderate and can ensure sufficient combination with alumina and polar solvent, avoid inorganic phase agglomeration, meet the requirement of uniform dispersion of organic phase, and avoid decomposition defects caused by excessive carbon chain, thereby further improving the strength of the alumina multilayer ceramic substrate.

[0016] As a further technical solution, the sintering aid is composed of magnesium oxide, silicon dioxide and calcium oxide in a mass ratio of 1:2:1~1.2.

[0017] The present invention adds a sintering aid to an alumina multilayer ceramic substrate. The addition of the sintering aid can inhibit abnormal grain growth, promote grain size uniformity, form a dense structure, and improve the mechanical strength of the ceramic substrate.

[0018] As a further technical solution, the adhesive includes one or two of polyvinyl butyral and polyvinyl alcohol, preferably polyvinyl butyral.

[0019] In this invention, a binder is added to the alumina multilayer ceramic substrate, and the binder is preferably polyvinyl butyral. The binder is a core auxiliary material for connecting powder particles and molding process. The addition of the binder can promote the formation of a green body with complete shape and uniform structure, and ensure the quality of the ceramic substrate.

[0020] As a further technical solution, the solvent includes one or more of isopropanol, ethyl acetate, and anhydrous ethanol.

[0021] As a further technical solution, the solvent is composed of isopropanol and ethyl acetate in a mass ratio of 7:3.

[0022] This invention also proposes a method for preparing a high-surface-smoothness alumina multilayer ceramic substrate, which includes the following steps:

[0023] S1. Mix the alumina, sintering aid, dispersant and solvent to obtain a mixture;

[0024] S2. Add the binder to the mixture, cast it into a film, and dry it to obtain a raw ceramic tile;

[0025] S3. After drilling holes in the raw ceramic sheet, the substrate is then subjected to surface printing, lamination, top and bottom conduction, cutting, sintering, and cooling to obtain the high surface finish alumina multilayer ceramic substrate.

[0026] The working principle and beneficial effects of this invention are as follows:

[0027] In this invention, triethyl phosphate, fumed silica, and phenyl phosphate compound are added to the alumina multilayer ceramic substrate to improve the surface finish of the substrate. In existing technologies, insufficient interaction between the inorganic alumina powder and the organic additives leads to powder sedimentation and organic phase floating, resulting in a decrease in the surface finish of the ceramic substrate. In this invention, triethyl phosphate, fumed silica, and phenyl phosphate compound are added as dispersants. Triethyl phosphate can be adsorbed onto the alumina surface through its ester groups, and its hydrophobic ethyl end can prevent alumina agglomeration. Fumed silica contains silanol groups on its surface, which can interact with each other in the slurry, effectively preventing alumina sedimentation. The addition of the phenyl phosphate compound introduces benzene rings into the surface of the alumina powder, and the steric hindrance of the benzene rings prevents alumina agglomeration. The synergistic effect of triethyl phosphate, fumed silica and phenyl phosphate compounds effectively prevents alumina agglomeration, alleviates alumina sedimentation, and promotes the formation of a uniformly dispersed slurry. After the slurry is cast, the alumina particles are evenly distributed in the green body without local agglomeration or pores, thereby improving the surface finish of the alumina ceramic substrate. Detailed Implementation

[0028] 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.

[0029] In the following examples and comparative examples:

[0030] Alumina: purity 99.6%, average particle size 0.4μm;

[0031] First-phase fumed silica: Model HB-612;

[0032] Second fumed silica: Model HB-132;

[0033] Magnesium oxide: average particle size is 100 nm;

[0034] Calcium oxide: average particle size is 20 nm;

[0035] Silica: Average particle size is 20nm;

[0036] Polyvinyl butyral: Model number BL-1.

[0037] Example 1

[0038] A method for preparing a high-surface-smoothness alumina multilayer ceramic substrate includes the following steps:

[0039] S1. Mix 80 parts of alumina, 4 parts of sintering aid, 3 parts of dispersant and 75 parts of solvent to obtain a mixture;

[0040] S2. Add 6 parts of polyvinyl butyral to the mixture, cast into shape, and dry to obtain raw ceramic tiles;

[0041] S3. After drilling holes in the raw ceramic sheet, surface printing, stacking (30 layers), top and bottom conduction, cutting, sintering at 1200℃ for 2.5h, and cooling are performed to obtain a high surface finish alumina multilayer ceramic substrate.

[0042] The sintering aid consists of magnesium oxide, silicon dioxide and calcium oxide in a mass ratio of 1:2:1;

[0043] The dispersing agent is composed of triethyl phosphate, fumed silica and monophenyl phosphate in a mass ratio of 2:1:0.8, and the fumed silica is the first fumed silica.

[0044] The solvent consists of isopropanol and ethyl acetate in a mass ratio of 7:3.

[0045] Example 2

[0046] A method for preparing a high-surface-smoothness alumina multilayer ceramic substrate includes the following steps:

[0047] S1. Mix 85 parts of alumina, 5 parts of sintering aid, 3.5 parts of dispersant and 80 parts of solvent to obtain a mixture;

[0048] S2. Add 7 parts of polyvinyl butyral to the mixture, cast into shape, and dry to obtain raw ceramic tiles;

[0049] S3. After drilling holes in the raw ceramic sheet, surface printing, stacking (30 layers), top and bottom conduction, cutting, sintering at 1200℃ for 2.5h, and cooling are performed to obtain a high surface finish alumina multilayer ceramic substrate.

[0050] The sintering aid consists of magnesium oxide, silicon dioxide and calcium oxide in a mass ratio of 1:2:1;

[0051] The dispersing agent is composed of triethyl phosphate, fumed silica and monophenyl phosphate in a mass ratio of 2:1:0.8, and the fumed silica is the first fumed silica.

[0052] The solvent consists of isopropanol and ethyl acetate in a mass ratio of 7:3.

[0053] Example 3

[0054] A method for preparing a high-surface-smoothness alumina multilayer ceramic substrate includes the following steps:

[0055] S1. Mix 90 parts of alumina, 6 parts of sintering aid, 4 parts of dispersant and 85 parts of solvent to obtain a mixture;

[0056] S2. Add 8 parts of polyvinyl butyral to the mixture, cast into shape, and dry to obtain raw ceramic tiles;

[0057] S3. After drilling holes in the raw ceramic sheet, surface printing, stacking (30 layers), top and bottom conduction, cutting, sintering at 1200℃ for 2.5h, and cooling are performed to obtain a high surface finish alumina multilayer ceramic substrate.

[0058] The sintering aid consists of magnesium oxide, silicon dioxide and calcium oxide in a mass ratio of 1:2:1;

[0059] The dispersing agent is composed of triethyl phosphate, fumed silica and monophenyl phosphate in a mass ratio of 2:1:0.8, and the fumed silica is the first fumed silica.

[0060] The solvent consists of isopropanol and ethyl acetate in a mass ratio of 7:3.

[0061] Example 4

[0062] The difference between Example 4 and Example 2 is that the dispersant is composed of triethyl phosphate, fumed silica and monophenyl phosphate in a mass ratio of 2:1:1.

[0063] Example 5

[0064] The difference between Example 5 and Example 4 is that monophenyl phosphate is replaced with an equal amount of diphenyl phosphate.

[0065] Example 6

[0066] The difference between Example 6 and Example 4 is that the fumed silica is a second fumed silica.

[0067] Example 7

[0068] The difference between Example 7 and Example 4 is that the fumed silica is composed of a first fumed silica and a second fumed silica in a mass ratio of 1:1.

[0069] Example 8

[0070] The difference between Example 8 and Example 4 is that the fumed silica is composed of a first fumed silica and a second fumed silica in a mass ratio of 2:1.

[0071] Comparative Example 1

[0072] Compared with Example 2, Comparative Example 1 differs in that the dispersant consists of triethyl phosphate and fumed silica in a mass ratio of 2:1.

[0073] Comparative Example 2

[0074] The difference between Comparative Example 2 and Example 2 is that the dispersant consists of triethyl phosphate and monophenyl phosphate in a mass ratio of 2:0.8.

[0075] Comparative Example 3

[0076] Compared with Example 2, Comparative Example 3 differs in that the dispersant consists of fumed silica and monophenyl phosphate in a mass ratio of 1:0.8.

[0077] Comparative Example 4

[0078] The difference between Comparative Example 4 and Example 2 is that the dispersing agent is only triethyl phosphate.

[0079] Comparative Example 5

[0080] The difference between Comparative Example 5 and Example 2 is that monophenyl phosphate was replaced with an equal amount of mono-n-dodecyl phosphate.

[0081] Experimental Example 1

[0082] The surface roughness of the alumina multilayer ceramic substrates prepared in Examples 1-5 and Comparative Examples 1-5 was tested using a surface roughness tester.

[0083] The test results are shown in Table 1:

[0084] Table 1 Performance test results of alumina multilayer ceramic substrates prepared in Examples 1-5 and Comparative Examples 1-5

[0085]

[0086] As shown in Table 1, the surface finish of alumina multilayer ceramic substrates can be improved when triethyl phosphate, fumed silica and phenyl phosphate compounds are added as dispersants.

[0087] Experiment Example 2

[0088] The alumina multilayer ceramic substrates prepared in Examples 4 and 6-8 were tested for bending strength according to the test method specified in GB / T 6569-2006 "Test Method for Bending Strength of Fine Ceramics". The test method adopted was three-point bending.

[0089] The test results are shown in Table 2:

[0090] Table 2 Performance test results of the alumina multilayer ceramic substrates prepared in Examples 4 and 6-8

[0091]

[0092] As shown in Table 2, when the fumed silica is composed of first fumed silica and second fumed silica with different carbon contents, the strength of the alumina multilayer ceramic substrate can be further improved.

[0093] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-surface-smoothness alumina multilayer ceramic substrate, characterized in that, The raw materials include the following components in parts by weight: 80-90 parts alumina, 4-6 parts sintering aid, 3-4 parts dispersant, 6-8 parts binder, and 75-85 parts solvent; the dispersant includes triethyl phosphate, fumed silica, and phenyl phosphate compounds. The fumed silica is composed of a first fumed silica and a second fumed silica; the carbon content of the first fumed silica is 0.7wt%~1.3wt%, and the carbon content of the second fumed silica is 2.0wt%~4.0wt%; the mass ratio of the first fumed silica to the second fumed silica is 1~2:

1.

2. The high surface finish alumina multilayer ceramic substrate according to claim 1, characterized in that, The phenyl phosphate compound includes one or both of monophenyl phosphate and diphenyl phosphate.

3. The high surface finish alumina multilayer ceramic substrate according to claim 1, characterized in that, The mass ratio of the triethyl phosphate, fumed silica, and phenyl phosphate compound is 2:1:0.8~1.

4. The high surface finish alumina multilayer ceramic substrate according to claim 1, characterized in that, The sintering aid is composed of magnesium oxide, silicon dioxide and calcium oxide in a mass ratio of 1:2:1 to 1.

2.

5. The high surface finish alumina multilayer ceramic substrate according to claim 1, characterized in that, The adhesive includes one or both of polyvinyl butyral and polyvinyl alcohol.

6. The high surface finish alumina multilayer ceramic substrate according to claim 1, characterized in that, The solvent includes one or more of isopropanol, ethyl acetate, and anhydrous ethanol.

7. A method for preparing a high surface finish alumina multilayer ceramic substrate, used to prepare the high surface finish alumina multilayer ceramic substrate according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Mix the alumina, sintering aid, dispersant and solvent to obtain a mixture; S2. Add the binder to the mixture, cast it into a film, and dry it to obtain a raw ceramic tile; S3. After drilling holes in the raw ceramic sheet, the substrate is then subjected to surface printing, lamination, top and bottom conduction, cutting, sintering, and cooling to obtain the high surface finish alumina multilayer ceramic substrate.

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