Highly insulating, high flexural strength alumina multilayer ceramic substrate and method of making same

Abstract

The application relates to the technical field of ceramic substrate, and discloses an insulating high-bending-resistance alumina multilayer ceramic substrate and a preparation method thereof. The insulating high-bending-resistance alumina multilayer ceramic substrate comprises the following raw materials in parts by weight: 60-70 parts of alumina, 2-3 parts of a dispersing agent, 2-4 parts of a plasticizer, 6-10 parts of a binder, 6-9 parts of a modified sintering aid and 70-80 parts of water; and the modified sintering aid is obtained by coating a sintering aid with pectin. Through the technical scheme, the problem of low bending strength and poor bending resistance of the ceramic substrate in the related art is solved.

Description

Technical Field

[0001] This invention relates to the field of ceramic substrate technology, and more specifically, to an insulating, high-flexural-resistance alumina multilayer ceramic substrate and its preparation method. Background Technology

[0002] Multilayer ceramic substrates can meet the high-reliability packaging requirements of a single bare chip and the high-reliability assembly requirements of multiple bare chips. Sintering is crucial in the fabrication of alumina ceramic substrates. During sintering, metal oxides are typically added as sintering aids to promote sintering. However, these aids often exhibit poor dispersibility in the slurry and tend to agglomerate. Inhomogeneous mixing of the sintering aids can lead to uneven grain growth in some areas due to excessively high concentrations, while in other areas, excessively low concentrations result in abnormal grain growth. This results in a microstructure with uneven grain size, leading to lower flexural strength and poor flexural performance in the prepared ceramic substrate. Summary of the Invention

[0003] This invention proposes an insulating, high-flexural-strength alumina multilayer ceramic substrate and its preparation method, which solves the problems of low flexural strength and poor flexural performance of ceramic substrates in related technologies.

[0004] The technical solution of the present invention is as follows:

[0005] This invention proposes an insulating, high-flexural-resistance alumina multilayer ceramic substrate, comprising the following raw materials in parts by weight: 60-70 parts alumina, 2-3 parts dispersant, 2-4 parts plasticizer, 6-10 parts binder, 6-9 parts modified sintering aid, and 70-80 parts water.

[0006] The modified sintering aid is obtained by coating a sintering aid with pectin.

[0007] As a further technical solution, the preparation method of the modified sintering aid includes the following steps:

[0008] A1. Add the metal oxide and pectin to the water and stir to obtain a mixture;

[0009] A2. The mixture is added dropwise to a calcium chloride solution for mixing, filtered, washed with water, and dried to obtain the modified sintering aid.

[0010] As a further technical solution, the metal oxide is one or more of MgO, TiO2, and MnO2;

[0011] The pectin is low-fat pectin;

[0012] The degree of esterification of the low-fat pectin is 30% to 50%.

[0013] As a further technical solution, the mass ratio of the metal oxide to pectin is 0.05:6~8;

[0014] The calcium chloride solution is an aqueous solution of calcium chloride with a mass fraction of 3% to 4%.

[0015] In the present invention, during the preparation of the modified sintering aid, the mass ratio of metal oxide to pectin is adjusted to 0.05:6~8, which improves the stability, strength and elasticity of the gel. Therefore, the pectin coating layer formed on the surface of the sintering aid is more stable, and the prepared modified sintering aid has better dispersibility, thereby improving the flexural strength of the alumina multilayer ceramic substrate.

[0016] As a further technical solution, the mass-to-volume ratio of the metal oxide and water is 0.05g:50~100mL;

[0017] Preferably, the mass-to-volume ratio of the metal oxide to water is 0.05 g: 50 mL.

[0018] As a further technical solution, the dispersant includes one or both of sodium polyacrylate and sodium pyrophosphate.

[0019] In the insulating high flexural strength alumina multilayer ceramic substrate of the present invention, since alumina powder is prone to agglomeration when mixed with slurry, adding a dispersant to the slurry formulation can control the surface potential of alumina powder, generate repulsive force between particles, thereby reducing the surface energy of alumina powder, wetting the alumina surface and dispersing it evenly in the slurry.

[0020] As a further technical solution, the adhesive includes polyacrylamide.

[0021] In the present invention, an insulating high-flexural-resistance alumina multilayer ceramic substrate is constructed by introducing a binder into the slurry. During the early forming stage of the ceramic green body, the binder molecules connect the ceramic particles to form a green body structure with both a fixed shape and a certain strength. This effectively improves the problem of loose bonding between ceramic particles, reduces the defect rate, and enables the green body to be densified during subsequent sintering, thus ensuring the flexural resistance of the alumina multilayer ceramic substrate.

[0022] As a further technical solution, the plasticizer includes one or both of polyethylene glycol and polyacryl alcohol.

[0023] In the insulating high flexural strength alumina multilayer ceramic substrate of the present invention, the addition of binder leads to poor slurry flowability. The addition of plasticizer can improve the slurry flowability and film formation, so that the prepared alumina multilayer ceramic substrate has higher flexural strength and improves the flexural performance of the alumina multilayer ceramic substrate.

[0024] This invention also proposes a method for preparing an insulating, high-flexural-resistance multilayer alumina ceramic substrate, comprising the following steps:

[0025] S1. After mixing the raw materials, cast them into a mold, and then dry them to obtain raw ceramic tiles;

[0026] S2. The raw ceramic sheet is punched, filled, surface printed, laminated, connected to the top and bottom, cut, sintered, and cooled to obtain the insulating high flexural strength alumina multilayer ceramic substrate.

[0027] As a further technical solution, the sintering process involves first heating the temperature to 1200℃ at a heating rate of 10~15℃ / min and holding it at that temperature for 30~50min; then heating the temperature to 1520~1580℃ at a heating rate of 5~8℃ / min and holding it at that temperature for 70~90min.

[0028] In this invention, by optimizing the process parameters in the sintering process, adopting stepwise heating, and controlling the sintering temperature and heating rate, the densification of the ceramic substrate is promoted and the formation of pores is reduced, thereby improving the flexural strength of the prepared alumina multilayer ceramic substrate.

[0029] As a further technical solution, during the cooling process, the temperature is first reduced to 850°C at a cooling rate of 8~10°C / min, and then reduced to room temperature at a cooling rate of 15°C / min.

[0030] As a further technical solution, the number of layers in the alumina multilayer ceramic substrate is 15 to 20.

[0031] The working principle and beneficial effects of this invention are as follows:

[0032] In this invention, the flexural strength of the prepared multilayer ceramic substrate is improved by coating the sintering aid with pectin. Since pectin is an anionic polymer, the sintering aid coated with pectin disperses more evenly in the slurry due to strong electrostatic repulsion, resulting in more uniform grain size during sintering. This contributes to the formation of a dense microstructure, enhancing the flexural strength of the ceramic substrate and giving the prepared alumina multilayer ceramic substrate excellent flexural properties. Detailed Implementation

[0033] 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.

[0034] In the following examples and comparative examples, the degree of esterification of pectin was 30%~40%, and the manufacturer was Wuhan Jiyesheng Chemical Co., Ltd.; the particle size of MgO was 20nm; the particle size of TiO2 was 45nm; the particle size of MnO2 was 40nm; the particle size of alumina was 25μm; the weight-average molecular weight of polyacrylamide was 300,000; the molecular weight of polyethylene glycol was 400Da; and the weight-average molecular weight of polyacrylic acid was 1800.

[0035] Example 1

[0036] The method for preparing modified MgO includes the following steps:

[0037] A1. Add 0.05g MgO and 5g pectin to 50mL of water, stir, and obtain a mixture;

[0038] A2. Add the mixture dropwise to 150 mL of 3% calcium chloride solution, mix, filter, wash with water, and dry to obtain modified MgO;

[0039] A method for preparing an insulating, high-flexural-resistance alumina multilayer ceramic substrate includes the following steps:

[0040] S1. Mix 60 parts of alumina, 2 parts of calcium 2,5-dihydroxybenzenesulfonate, 2 parts of polyethylene glycol, 6 parts of polyacrylamide, 6 parts of modified MgO, and 70 parts of water, then cast the mixture into a film and dry it to obtain a raw ceramic tile.

[0041] S2. Punch and fill holes in the green ceramic sheet, and use tungsten paste material for surface printing with a printing thickness of 10μm. After stacking and pressing 15 layers of green ceramic sheets, making the top and bottom conductive, and cutting them, sinter them. After sintering, first cool down to 850℃ at a cooling rate of 8℃ / min, and then cool down to room temperature at a cooling rate of 15℃ / min to obtain an insulating high flexural strength alumina multilayer ceramic substrate.

[0042] During the above sintering process, the temperature is first raised to 1200℃ at a heating rate of 8℃ / min and held for 30min. Then, the temperature is raised to 1520℃ at a heating rate of 3℃ / min and held for 90min.

[0043] Example 2

[0044] The method for preparing modified MgO includes the following steps:

[0045] A1. Add 0.05g MgO and 9g pectin to 50mL of water, stir, and obtain a mixture;

[0046] A2. Add the mixture dropwise to 150 mL of 4% calcium chloride solution, mix, filter, wash with water, and dry to obtain modified MgO;

[0047] The preparation methods for modified MnO2 and modified TiO2 are the same as those for modified MgO.

[0048] A method for preparing an insulating, high-flexural-resistance alumina multilayer ceramic substrate includes the following steps:

[0049] S1. Mix 70 parts of alumina, 1.5 parts of calcium 2,5-dihydroxybenzenesulfonate, 1.5 parts of sodium pyrophosphate, 2 parts of polyethylene glycol, 2 parts of polyacrylic acid, 10 parts of polyacrylamide, 3 parts of modified MgO, 3 parts of modified TiO2, 3 parts of modified MnO2, and 80 parts of water, then cast the mixture into a film and dry it to obtain a raw ceramic tile.

[0050] S2. Punch and fill holes in the green ceramic sheet, and use tungsten paste material for surface printing with a thickness of 10μm. After stacking and pressing 18 layers of green ceramic sheets, making the top and bottom conductive, and cutting them, sinter them. After sintering, first cool down to 850℃ at a cooling rate of 10℃ / min, and then cool down to room temperature at a cooling rate of 15℃ / min to obtain an insulating high flexural strength alumina multilayer ceramic substrate.

[0051] During the above sintering process, the temperature is first raised to 1200℃ at a heating rate of 8℃ / min and held for 50min. Then, the temperature is raised to 1580℃ at a heating rate of 3℃ / min and held for 70min.

[0052] Example 3

[0053] The method for preparing modified MgO includes the following steps:

[0054] A1. Add 0.05g MgO and 5g pectin to 50mL of water, stir, and obtain a mixture;

[0055] A2. Add the mixture dropwise to 150 mL of 3% calcium chloride solution, mix, filter, wash with water, and dry to obtain modified MgO;

[0056] A method for preparing an insulating, high-flexural-resistance alumina multilayer ceramic substrate includes the following steps:

[0057] S1. Mix 65 parts of alumina, 2.5 parts of sodium pyrophosphate, 3 parts of polyacrylic acid, 8 parts of polyacrylamide, 8 parts of modified MgO, and 75 parts of water, then cast and dry to obtain raw ceramic tiles.

[0058] S2. Punch and fill holes in the green ceramic sheet, and use tungsten paste material for surface printing with a thickness of 10μm. Stack 20 layers of green ceramic sheets together, make the top and bottom conductive, cut them, and then sinter them. After sintering, first cool down to 850℃ at a cooling rate of 9℃ / min, and then cool down to room temperature at a cooling rate of 15℃ / min to obtain an insulating high flexural strength alumina multilayer ceramic substrate.

[0059] During the above sintering process, the temperature is first raised to 1200℃ at a heating rate of 8℃ / min and held for 40min. Then, the temperature is raised to 1550℃ at a heating rate of 3℃ / min and held for 80min.

[0060] Example 4

[0061] The difference between this embodiment and Embodiment 3 is that during the sintering process, the temperature is first raised to 1200°C at a heating rate of 10°C / min and held for 40 minutes, and then raised to 1550°C at a heating rate of 3°C / min and held for 80 minutes.

[0062] Example 5

[0063] The difference between this embodiment and Embodiment 3 is that during the sintering process, the temperature is first raised to 1200°C at a heating rate of 15°C / min and held for 40 minutes, and then raised to 1550°C at a heating rate of 3°C / min and held for 80 minutes.

[0064] Example 6

[0065] The difference between this embodiment and Embodiment 3 is only that during the sintering process, the temperature is first raised to 1200°C at a heating rate of 12°C / min and held for 40 minutes, and then raised to 1550°C at a heating rate of 3°C / min and held for 80 minutes.

[0066] Example 7

[0067] The difference between this embodiment and Embodiment 3 is that during the sintering process, the temperature is first raised to 1200°C at a heating rate of 18°C / min and held for 40 minutes, and then raised to 1550°C at a heating rate of 3°C / min and held for 80 minutes.

[0068] Example 8

[0069] The difference between this embodiment and Embodiment 6 is only that during the sintering process, the temperature is first raised to 1200°C at a heating rate of 12°C / min and held for 40 minutes, and then raised to 1550°C at a heating rate of 5°C / min and held for 80 minutes.

[0070] Example 9

[0071] The difference between this embodiment and Embodiment 6 is only that during the sintering process, the temperature is first raised to 1200°C at a heating rate of 12°C / min and held for 40 minutes, and then raised to 1550°C at a heating rate of 8°C / min and held for 80 minutes.

[0072] Example 10

[0073] The difference between this embodiment and Embodiment 6 is only that during the sintering process, the temperature is first raised to 1200°C at a heating rate of 12°C / min and held for 40 minutes, and then raised to 1550°C at a heating rate of 6°C / min and held for 80 minutes.

[0074] Example 11

[0075] The difference between this embodiment and Embodiment 6 is that during the sintering process, the temperature is first raised to 1200°C at a heating rate of 12°C / min and held for 40 minutes, and then raised to 1550°C at a heating rate of 10°C / min and held for 80 minutes.

[0076] Example 12

[0077] The only difference between this embodiment and Example 10 is that 6g of pectin is added in step A1 during the preparation of modified MgO.

[0078] Example 13

[0079] The only difference between this embodiment and Example 10 is that 8g of pectin is added in step A1 during the preparation of modified MgO.

[0080] Example 14

[0081] The only difference between this embodiment and Example 10 is that 9g of pectin is added in step A1 during the preparation of modified MgO.

[0082] Comparative Example 1

[0083] The only difference between this comparative example and Example 3 is that the modified MgO is replaced with MgO.

[0084] Experimental Example 1

[0085] The flexural strength of the alumina multilayer ceramic substrates prepared in Examples 1-14 and Comparative Example 1 was tested to evaluate their flexural performance.

[0086] Flexural strength: The flexural strength was tested according to the method specified in GB / T 5593-2015 "Structural Ceramic Materials for Electronic Components". The test results are shown in Table 1.

[0087] Table 1 Flexural strength test results

[0088]

[0089] Comparing the data from Example 3 and Comparative Example 1, the alumina multilayer ceramic substrate prepared by coating the sintering aid MgO with pectin in Example 3 showed significantly higher flexural strength than that in Comparative Example 1, indicating that coating the sintering aid with pectin can significantly improve the flexural strength of the prepared alumina multilayer ceramic substrate. Comparing the data from Examples 10 and 12-14, the ceramic substrate prepared in Examples 12-13 by controlling the mass ratio of MgO to pectin at 0.05:6-8 had higher flexural strength, indicating that by adjusting the mass ratio of metal oxide to pectin, and when the mass ratio of metal oxide to pectin is 0.05:6-8, the flexural strength of the prepared alumina multilayer ceramic substrate can be further improved.

[0090] Comparing the data from Examples 3 to 11, the alumina multilayer ceramic substrates prepared in Examples 8 to 10 showed higher flexural strength, indicating that by controlling the heating rate of the sintering process, and by first heating to the specified temperature at a heating rate of 10 to 15 °C / min, and then heating at a heating rate of 5 to 8 °C / min, the flexural strength of the prepared alumina multilayer ceramic substrate can be significantly improved.

[0091] Experiment Example 2

[0092] The insulation properties of the alumina multilayer ceramic substrates prepared in Examples 12 and 13 were tested respectively.

[0093] The alumina multilayer ceramic substrates prepared in Examples 12-13 were tested for breakdown strength according to the method specified in GB / T 5593-2015 "Structural Ceramic Materials for Electronic Components". The test results are shown in Table 2.

[0094] Table 2 Insulation test results

[0095]

[0096] As shown in Table 2, the alumina multilayer ceramic substrates prepared in Examples 12-13 of the present invention have a breakdown strength of over 25.2 kV / mm and exhibit good insulation properties.

[0097] 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. An insulating, high-flexural-resistance alumina multilayer ceramic substrate, characterized in that, The raw materials include the following parts by weight: 60-70 parts alumina, 2-3 parts dispersant, 2-4 parts plasticizer, 6-10 parts binder, 6-9 parts modified sintering aid, and 70-80 parts water; The modified sintering aid is obtained by coating a sintering aid with pectin; The preparation method of the modified sintering aid includes the following steps: A1. Add metal oxides and pectin to water, stir, and obtain a mixture; A2. The mixture is added dropwise to a calcium chloride solution for mixing, filtered, washed with water, and dried to obtain the modified sintering aid; The mass ratio of the metal oxide to pectin is 0.05:6~8; A method for preparing an insulating, high-flexural-resistance alumina multilayer ceramic substrate, characterized by comprising the following steps: S1. After mixing the raw materials, cast them into a mold, and then dry them to obtain raw ceramic tiles; S2. The raw ceramic sheet is punched, filled, surface printed, laminated, connected to the top and bottom, cut, sintered and cooled to obtain the insulating high flexural strength alumina multilayer ceramic substrate. The sintering process involves first heating the temperature to 1200℃ at a rate of 10-15℃ / min and holding it for 30-50 minutes; then heating the temperature to 1520-1580℃ at a rate of 5-8℃ / min and holding it for 70-90 minutes.

2. The insulating, high-flexural-resistance alumina multilayer ceramic substrate according to claim 1, characterized in that, The metal oxide is one or more of MgO, TiO2, and MnO2; The pectin is low-fat pectin; The degree of esterification of the low-fat pectin is 30% to 50%.

3. The insulating, high-flexural-resistance alumina multilayer ceramic substrate according to claim 1, characterized in that, The calcium chloride solution is a calcium chloride aqueous solution with a mass fraction of 3% to 4%.

4. The insulating, high-flexural-resistance alumina multilayer ceramic substrate according to claim 1, characterized in that, The dispersant includes one or both of sodium polyacrylate and sodium pyrophosphate.

5. The insulating, high-flexural-resistance alumina multilayer ceramic substrate according to claim 1, characterized in that, The plasticizer includes one or both of polyethylene glycol and polyacryl alcohol.

6. The insulating, high-flexural-resistance alumina multilayer ceramic substrate according to claim 1, characterized in that, The adhesive includes polyacrylamide.

7. The method for preparing an insulating, high-flexural-resistance alumina multilayer ceramic substrate according to claim 1, characterized in that, During the cooling process, the temperature is first reduced to 850°C at a cooling rate of 8-10°C / min, and then reduced to room temperature at a cooling rate of 15°C / min.

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