Breakdown-resistant multilayer ceramic substrate and method of making the same

Abstract

The present application relates to the technical field of ceramic substrate, and proposes a breakdown-resistant multilayer ceramic substrate and a preparation method thereof.The breakdown-resistant multilayer ceramic substrate comprises the following components by weight: 85-95 parts of alumina, 4-6 parts of a first sintering aid, 2-3 parts of a second sintering aid, 2-4 parts of a dispersing agent, 7-9 parts of a binder, 2-3 parts of a plasticizer, and 60-70 parts of water; the preparation method of the first sintering aid comprises the following steps: uniformly mixing silicon dioxide and strontium oxide, melting, and then performing ball milling after water quenching cooling to obtain the first sintering aid; and the second sintering aid is a rare earth oxide.Through the above technical solution, the problem of insufficient breakdown resistance of the multilayer ceramic substrate in the prior art is solved.

Description

Technical Field

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

[0002] Multilayer ceramic substrates, as core packaging materials in the fields of electronic information and power electronics, are widely used in key scenarios such as high-power IGBT modules, 5G base station RF components, and power control systems for new energy vehicles due to their excellent insulation properties, thermal conductivity, and structural integration. The core performance characteristics of these substrates include mechanical strength, thermal stability, and dielectric properties. Among them, breakdown strength, as a key indicator for measuring its insulation reliability, directly determines the withstand voltage level and operational safety of electronic devices.

[0003] Insufficient breakdown strength of multilayer ceramic substrates can trigger a series of adverse consequences: at best, it reduces the withstand voltage of devices, limiting their application in high-voltage scenarios; at worst, it can cause insulation breakdown under high electric fields, leading to sudden failures such as short circuits and chip burnout, and even endangering life and property. Improving the breakdown strength of multilayer ceramic substrates is a core requirement for ensuring the safe and stable operation of electronic devices and promoting the advancement of high-end electronic packaging technology. Therefore, it is necessary to propose a breakdown-resistant multilayer ceramic substrate and its preparation method. Summary of the Invention

[0004] This invention proposes a breakdown-resistant multilayer ceramic substrate and its preparation method, which solves the problem of insufficient breakdown resistance of multilayer ceramic substrates in the prior art.

[0005] The technical solution of the present invention is as follows:

[0006] This invention proposes a breakdown-resistant multilayer ceramic substrate comprising the following raw materials in parts by weight: 85-95 parts alumina, 4-6 parts a first sintering aid, 2-3 parts a second sintering aid, 2-4 parts a dispersant, 7-9 parts a binder, 2-3 parts a plasticizer, and 60-70 parts water; the preparation method of the first sintering aid includes the following steps: mixing strontium oxide and silicon dioxide evenly and then ball-milling and dispersing for 3-5 hours; melting the ball-milled mixture and directly quenching it with water; obtaining glassy fragments of the first sintering aid after cooling; wet ball-milling the glass fragments of the first sintering aid for 24 hours using ethanol as the medium; and obtaining the first sintering aid after ball milling, with a particle size of 3 μm; the second sintering aid is a rare earth oxide.

[0007] As a further technical solution, the mass ratio of strontium oxide to silicon dioxide in the first sintering aid is 1 to 4:4, for example, it can be 1:4, 1:2, 3:4, or 1:1, preferably 3:4.

[0008] In the first sintering aid for breakdown-resistant multilayer ceramic substrates, when the mass ratio of strontium oxide to silica is less than 1:4, the amount of glass phase formed is insufficient and the viscosity is high, which reduces the wetting and filling effect on alumina particles, resulting in a weakened sintering driving force. The substrate is prone to problems such as high porosity and insufficient density, which in turn affects its breakdown resistance and structural stability. When the mass ratio of the two is greater than 1:1, excessive strontium oxide will make the glass phase too fluid, which is prone to over-melting during sintering and easily leads to substrate deformation. When the mass ratio of strontium oxide to silica is 1~4:4, it can ensure the formation of an appropriate amount of low-melting-point glass phase during sintering, providing sufficient liquid phase for the sintering of alumina particles, promoting the formation of a dense structure during sintering, and thus further improving the breakdown resistance of the breakdown-resistant multilayer ceramic substrate.

[0009] As a further technical solution, the second sintering aid is samarium oxide.

[0010] In the raw materials for the breakdown-resistant multilayer ceramic substrate, the second sintering aid is samarium oxide. During the ceramic sintering process, samarium oxide tends to accumulate at the boundaries of alumina grains, hindering ion migration paths and thus suppressing abnormal grain growth caused by excessive ion migration. This prevents the formation of coarse grains and ultimately promotes the formation of a more uniform and fine grain structure in the ceramic matrix, significantly reducing porosity and increasing overall density, thereby further enhancing the breakdown resistance of the multilayer ceramic substrate.

[0011] As a further technical solution, the raw materials also include the following components by weight: 5-7 parts of modified sericite; the modified sericite is obtained by modifying sericite with phenyl carbamate.

[0012] Sericite, with its unique lamellar structure and high breakdown voltage, is often used as a filler to improve the breakdown resistance of multilayer ceramic substrates. However, sericite is prone to agglomeration, which hinders its ability to effectively improve breakdown voltage. This invention modifies the surface of sericite by adding phenyl carbamate, improving its dispersibility and thus further enhancing the breakdown resistance of multilayer ceramic substrates.

[0013] As a further technical solution, the mass ratio of phenyl carbamate to sericite in the modified sericite is 5~9:90, for example, it can be 1:18, 1:15, 7:90, 4:45, 1:10, preferably 7:90.

[0014] As a further technical solution, the preparation method of modified sericite includes the following steps: dispersing phenyl carbamate in anhydrous ethanol, then adding sericite, mixing for 3 hours, and drying to obtain modified sericite; the mass-to-volume ratio of sericite to anhydrous ethanol is 1g:10mL.

[0015] As a further technical solution, the dispersant includes one or more of sodium tripolyphosphate, polyacrylamide, and sodium citrate.

[0016] As a further technical solution, the plasticizer includes one or both of polyethylene glycol and glycerol.

[0017] As a further technical solution, the adhesive includes one or both of polyvinyl alcohol and sodium carboxymethyl cellulose.

[0018] This invention also proposes a method for preparing a breakdown-resistant multilayer ceramic substrate, comprising the following steps:

[0019] S1. Alumina, first sintering aid, second sintering aid, dispersant and water are mixed to obtain a mixture;

[0020] S2. Add the remaining raw materials for resisting the breakdown of multilayer ceramic substrates to the mixture, mix, cast into shape, and dry to obtain green ceramic sheets;

[0021] 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 a multilayer ceramic substrate resistant to puncture.

[0022] As a further technical solution, in step S3, the shape of the hole is circular, and the diameter of the circle is 60~90μm, for example, it can be 60μm, 70μm, 80μm, or 90μm.

[0023] As a further technical solution, in step S3, the sintering temperature is 1200~1400℃, for example, 1200℃, 1300℃, or 1400℃, the sintering time is 30~60min, for example, 30min, 40min, 45min, or 60min, and the sintering atmosphere is nitrogen.

[0024] The working principle and beneficial effects of this invention are as follows:

[0025] The breakdown-resistant multilayer ceramic substrate prepared by this invention is based on alumina. By adding a first sintering aid prepared from silicon dioxide and strontium oxide, and a second sintering aid, the breakdown resistance of the substrate is significantly improved. In the prior art, the sintering aid combines with some alumina during liquid-phase sintering to form a co-fired phase, which destroys the original composition and structure of the ceramic and thus affects its performance. In contrast, the first sintering aid of this invention, prepared from silicon dioxide and strontium oxide, can generate a lower melting point glassy phase during the liquid phase formation during sintering. This low-melting-point glassy phase can not only effectively fill the voids between alumina particles, promoting particle diffusion and densification, but also inhibit excessive alumina grain growth, avoiding structural defects caused by coarse grains, reducing porosity, and thus improving the breakdown resistance of the multilayer ceramic substrate. In addition, the rare earth oxides, as the second sintering aid, can further inhibit grain growth by hindering the migration of other ions and reducing the grain boundary migration rate, helping to form a denser ceramic structure and further enhancing the breakdown resistance of the multilayer ceramic substrate. Detailed Implementation

[0026] 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.

[0027] In the following examples and comparative examples, alumina had a particle size of 20 μm; strontium oxide had a particle size of 180 μm; silica had a particle size of 5 μm; samarium oxide had a particle size of 1 μm; sodium carboxymethyl cellulose (LT-011) was purchased from Renqiu Litian Chemical Co., Ltd.; polyacrylamide had a weight-average molecular weight of 12 million; polyvinyl alcohol (PVA-1788); polyethylene glycol (PEG200); and sericite had a particle size of 44 μm.

[0028] Example 1

[0029] A method for preparing a breakdown-resistant multilayer ceramic substrate includes the following steps:

[0030] S1. Mix 85 parts of alumina, 4 parts of the first sintering aid, 2 parts of samarium oxide, 2 parts of sodium tripolyphosphate and 60 parts of water to obtain a mixture;

[0031] S2. Add 7 parts polyvinyl alcohol and 2 parts polyethylene glycol to the mixture, mix, cast into shape, and dry to obtain raw ceramic tiles;

[0032] S3. Drill holes in the raw ceramic sheet. The holes are circular with a diameter of 70μm. Then, the substrate is printed on the surface, laminated (20 layers), connected to the top and bottom, cut, sintered, and cooled to obtain a breakdown-resistant multilayer ceramic substrate. The sintering temperature is 1300℃, the time is 45min, and the atmosphere is nitrogen.

[0033] The preparation method of the first sintering aid includes the following steps: strontium oxide and silicon dioxide are mixed evenly in a mass ratio of 1:4 and then ball-milled for 4 hours. The ball-milled mixture is then melted at 1720°C and quenched with water. After cooling, glassy fragments of the first sintering aid are obtained. The glass fragments of the first sintering aid are then wet-milled for 24 hours. The medium used in the wet ball milling process is ethanol. After ball milling, the first sintering aid is obtained, and the particle size of the first sintering aid is 3 μm.

[0034] Example 2

[0035] A method for preparing a breakdown-resistant multilayer ceramic substrate includes the following steps:

[0036] S1. Mix 90 parts of alumina, 5 parts of the first sintering aid (same as in Example 1), 2.5 parts of samarium oxide, 2 parts of polyacrylamide, 1 part of sodium citrate and 65 parts of water to obtain a mixture;

[0037] S2. Add 4 parts polyvinyl alcohol, 4 parts sodium carboxymethyl cellulose, 2 parts polyethylene glycol, and 0.5 parts glycerol to the mixture, mix, cast into shape, and dry to obtain raw ceramic tiles.

[0038] S3. Drill holes in the raw ceramic sheet. The holes are circular with a diameter of 70μm. Then, the substrate is printed on the surface, stacked (20 layers), connected to the top and bottom, cut, sintered, and cooled to obtain a multilayer ceramic substrate resistant to breakdown. The sintering temperature is 1300℃, the time is 45min, and the atmosphere is nitrogen.

[0039] Example 3

[0040] A method for preparing a breakdown-resistant multilayer ceramic substrate includes the following steps:

[0041] S1. Mix 95 parts of alumina, 6 parts of the first sintering aid (same as in Example 1), 3 parts of samarium oxide, 4 parts of sodium citrate and 70 parts of water to obtain a mixture;

[0042] S2. Add 9 parts sodium carboxymethyl cellulose and 3 parts glycerol to the mixture, mix, cast into shape, and dry to obtain raw ceramic tiles;

[0043] S3. Drill holes in the raw ceramic sheet. The holes are circular with a diameter of 70μm. Then, the substrate is printed on the surface, stacked (20 layers), connected to the top and bottom, cut, sintered, and cooled to obtain a multilayer ceramic substrate resistant to breakdown. The sintering temperature is 1300℃, the time is 45min, and the atmosphere is nitrogen.

[0044] Example 4

[0045] Compared with Example 3, the only difference in Example 4 is that the mass ratio of strontium oxide to silicon dioxide in the first sintering aid in this example is 3:4.

[0046] Example 5

[0047] Compared with Example 3, the only difference in Example 5 is that the mass ratio of strontium oxide to silicon dioxide in the first sintering aid in this example is 1:1.

[0048] Example 6

[0049] Compared with Example 3, the only difference in Example 6 is that, in the preparation of the breakdown-resistant multilayer ceramic substrate in this example, step S2 is as follows: 9 parts of sodium carboxymethyl cellulose, 3 parts of glycerol, and 6 parts of modified sericite are added to the mixture and mixed, cast into shape, and dried to obtain a raw ceramic sheet.

[0050] The method for preparing modified sericite includes the following steps: dispersing phenyl carbamate in anhydrous ethanol, then adding sericite, mixing for 3 hours, and drying to obtain modified sericite; wherein the mass ratio of phenyl carbamate to sericite is 1:18, and the mass-volume ratio of sericite to anhydrous ethanol is 1g:10mL.

[0051] Example 7

[0052] Compared with Example 6, the only difference in Example 7 is that the mass ratio of phenyl carbamate to sericite in the modified sericite in this example is 7:90.

[0053] Example 8

[0054] Compared with Example 6, the only difference in Example 8 is that the mass ratio of phenyl carbamate to sericite in the modified sericite in this example is 1:10.

[0055] Example 9

[0056] Compared with Example 6, the only difference in Example 9 is that the modified sericite is replaced with an equal amount of sericite in this example.

[0057] Comparative Example 1

[0058] Compared with Example 3, the only difference in Comparative Example 1 is that samarium oxide was replaced with an equal amount of the first sintering aid in this comparative example.

[0059] Comparative Example 2

[0060] Compared with Example 3, the only difference in Comparative Example 2 is that the first sintering aid is replaced with an equal amount of samarium oxide.

[0061] Comparative Example 3

[0062] Compared with Example 3, the only difference in Comparative Example 3 is that the strontium oxide in the first sintering aid is replaced with an equal amount of silicon dioxide.

[0063] Comparative Example 4

[0064] Compared with Example 3, the only difference in Comparative Example 4 is that the silicon dioxide in the first sintering aid is replaced with an equal amount of strontium oxide.

[0065] The resistance to breakdown of multilayer ceramic substrates is tested using the following method:

[0066] 1. Breakdown strength test: The breakdown strength test shall be conducted under DC conditions in accordance with the test method specified in section 5.13 of GB / T 5593-2015 "Structural Ceramic Materials for Electronic Components" with a voltage boost rate of 500V / s.

[0067] The measurement results are shown in Tables 1 and 2:

[0068] Table 1. Breakdown strength test results of multilayer ceramic substrates.

[0069]

[0070] As shown in Table 1, the breakdown strength of the multilayer ceramic substrates in Examples 1-5 is higher than that in Comparative Examples 1-2, indicating that the addition of the first sintering aid and the second sintering aid can reduce the sintering temperature of the multilayer ceramic substrates and improve their breakdown strength. The breakdown strength of the multilayer ceramic substrates in Examples 1-5 is higher than that in Comparative Examples 3-4, indicating that the addition of the first sintering aid composed of strontium oxide and silicon dioxide can improve the breakdown strength of the multilayer ceramic substrates.

[0071] Table 2. Breakdown strength test results of multilayer ceramic substrates.

[0072]

[0073] As can be seen from the data in Table 2, the breakdown strength against the multilayer ceramic substrate in Examples 6-8 is higher than that in Examples 3 and 9, indicating that the addition of phenyl carbamate-modified sericite significantly improves the breakdown strength against the multilayer ceramic substrate.

[0074] 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 multilayer ceramic substrate resistant to breakdown, characterized in that, The raw materials include the following components by weight: 85-95 parts alumina, 4-6 parts first sintering aid, 2-3 parts second sintering aid, 2-4 parts dispersant, 7-9 parts binder, 2-3 parts plasticizer, and 60-70 parts water; the preparation method of the first sintering aid includes the following steps: uniformly mixing silicon dioxide and strontium oxide, melting, quenching in water and cooling, and then ball milling to obtain the first sintering aid; the second sintering aid is samarium oxide; the mass ratio of strontium oxide to silicon dioxide in the first sintering aid is 3:

4.

2. The breakdown-resistant multilayer ceramic substrate according to claim 1, characterized in that, It also includes the following raw materials in parts by weight: 5-7 parts of modified sericite; the modified sericite is obtained by modifying sericite with phenyl carbamate.

3. The breakdown-resistant multilayer ceramic substrate according to claim 2, characterized in that, The mass ratio of phenyl carbamate to sericite in the modified sericite is 5~9:

90.

4. The breakdown-resistant multilayer ceramic substrate according to claim 1, characterized in that, The dispersant includes one or more of sodium tripolyphosphate, polyacrylamide, and sodium citrate.

5. The breakdown-resistant multilayer ceramic substrate according to claim 1, characterized in that, The plasticizer includes one or both of polyethylene glycol and glycerol.

6. The breakdown-resistant multilayer ceramic substrate according to claim 1, characterized in that, The adhesive includes one or both of polyvinyl alcohol and sodium carboxymethyl cellulose.

7. A method for preparing a breakdown-resistant multilayer ceramic substrate, used to prepare the breakdown-resistant multilayer ceramic substrate according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Alumina, first sintering aid, second sintering aid, dispersant and water are mixed to obtain a mixture; S2. Add the remaining raw materials for resisting the breakdown of multilayer ceramic substrates to the mixture, mix, cast into shape, and dry to obtain green ceramic sheets; 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 a multilayer ceramic substrate resistant to puncture.

8. The method for preparing a breakdown-resistant multilayer ceramic substrate according to claim 7, characterized in that, In step S3, the sintering temperature is 1200~1400℃.

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