Ceramic chip in multilayer ceramic capacitor

Abstract

The invention aims to provide the preparation process of the ceramic chip in the multilayer ceramic capacitor so as to reduce the deformation of the ceramic chip and the delamination rate between dielectric layers, compared with the traditional ceramic chip preparation process, the preparation process has the advantages that the two processes of lamination and lamination are omitted, the deformation of the ceramic chip caused by the two processes is also avoided, and the production efficiency is improved. The preparation method is simple, the cost is low, the time and the cost are greatly saved for a production enterprise, the dipping method adopted in the SiC ceramic layer preparation process can enable a polycarbosilane solution to be filled into the barium titanate layer and holes in the surface of each subsequent SiC ceramic layer, the inner electrode can be wrapped, and after polycarbosilane is subjected to oxidation crosslinking and high-temperature cracking, the surface of the barium titanate layer and the holes in the surface of each subsequent SiC ceramic layer can be coated with the polycarbosilane solution. And the barium titanate layer and the SiC ceramic layer, the SiC ceramic layers and the inner electrode and the SiC ceramic layer are attached more tightly, so that the delamination rate between dielectric layers of the ceramic chip is greatly reduced.

Description

Technical Field

[0001] The invention relates to a ceramic chip, in particular to a ceramic chip in a multilayer ceramic capacitor. Background Art

[0002] Multilayer ceramic capacitors (MLCC) are characterized by high specific capacitance, high reliability, high withstand voltage, and good frequency characteristics. They are widely used in electronic information, computers, automatic control, and communications. With the development of electronic equipment and components towards miniature, thin layers, and hybrid integration, as well as the rapid development of integrated circuit surface mounting technology, the demand for high-performance MLCC is increasing day by day. In recent years, with the continuous advancement of electronic information technology, the high density of electronic circuits, and the high requirements for miniaturization of electronic components, the miniaturization and high capacity of multilayer ceramic capacitors have developed rapidly. At the same time, multilayer ceramic capacitors are developing in the direction of thinning the dielectric layer, and dielectric materials that can ensure the reliability of the capacitor even if the layer is thin are required. In particular, the miniaturization and high capacity of medium and high voltage multilayer ceramic capacitors used under high temperature and high pressure put forward very high requirements on the reliability of the dielectric materials constituting the dielectric layer.

[0003] Barium titanate (BaTiO3) is a commonly used matrix material in MLCC with a high dielectric constant. When barium titanate is applied to MLCC, barium titanate powder is usually prepared into a slurry, cast into a film, and then the electrode is printed, laminated, pressed, and cut to form a green body with a certain shape and size, and then sintered into porcelain. However, barium titanate ceramics manufactured in this way generally have the problem of relatively poor bending resistance. During the assembly and use of the device, any operation that may cause bending deformation will cause the device porcelain body to crack, thereby causing the MLCC product to fail. However, such a manufacturing method has the following problems: Due to the difference in shrinkage between the dielectric layer and the internal electrode layer during the sintering process, it is easy to cause the formed ceramic chip to be easily deformed, and cracks or delamination will occur between the dielectric layer and the internal electrode layer or between the dielectric layer and the dielectric layer. Summary of the invention

[0004] The object of the present invention is to provide a preparation process of a ceramic chip in a multilayer ceramic capacitor to reduce the deformation of the ceramic chip and the delamination rate between dielectric layers.

[0005] To achieve the above object, the present invention provides a process for preparing a ceramic chip of a multilayer ceramic capacitor, comprising the following steps:

[0006] (1) A barium titanate (BaTiO3) ceramic substrate is impregnated with a polycarbosilane solution by an immersion method, and after pre-oxidation, cross-linking, and high-temperature cracking, a first layer of SiC ceramic is obtained, and then an inner electrode is screen-printed on the first layer of SiC ceramic.

[0007] (2) Based on step (1), impregnation, oxidation cross-linking, and high-temperature cracking are repeated to obtain a second layer of SiC ceramic, and then the inner electrode is screen-printed on the second layer of SiC ceramic.

[0008] (3) Repeat step (2) to obtain more layers of SiC ceramic layers printed with inner electrodes, the number of layers being greater than or equal to 3, and the outermost layer being a SiC ceramic layer without inner electrodes.

[0009] Compared with the traditional ceramic chip preparation process, the above preparation process omits the two steps of lamination and pressing, and also avoids the deformation of the ceramic chip caused by these two steps, and greatly saves time and cost for the production enterprises. Silicon carbide is a compound with extremely strong covalent bonds and can maintain high bonding strength under high temperature conditions. This structural feature of silicon carbide determines its high strength, high temperature resistance, oxidation resistance, excellent chemical stability and a series of excellent properties that are not corroded by most acid and alkali solutions. In addition, the impregnation method used in the preparation of the SiC ceramic layer can fill the polycarbosilane solution into the holes on the surface of the barium titanate layer and each subsequent SiC ceramic layer, and can wrap the inner electrode. The polycarbosilane forms a SiC ceramic layer after oxidative cross-linking and high-temperature cracking. The barium titanate layer and the SiC ceramic layer, the SiC ceramic layer and the SiC ceramic layer, and the inner electrode and the SiC ceramic layer are more closely bonded, thereby greatly reducing the delamination rate between the dielectric layers of the ceramic chip. Studies have shown that the SiC ceramic layer formed by oxidative cross-linking and high-temperature cracking of polycarbosilane is a β-SiC crystal phase, which has a high dielectric constant and is suitable for the manufacture of multilayer ceramic capacitors.

[0010] Preferably, the concentration of the polycarbosilane solution is 5% to 40%. The concentration of the polycarbosilane solution will affect the viscosity of the polycarbosilane solution. The greater the viscosity, the worse the impregnation effect.

[0011] Preferably, the solute of the polycarbosilane solution is xylene;

[0012] Preferably, the immersion time is 10 min to 60 min, and the length of the immersion time also has a great influence on the immersion effect;

[0013] Preferably, the impregnation process can be carried out in multiple times;

[0014] Preferably, the pre-oxidation temperature is 150°C to 180°C;

[0015] Preferably, the high temperature cracking temperature is 1000°C to 1300°C;

[0016] Preferably, the impregnation method can be carried out in an inert gas atmosphere such as argon or nitrogen;

[0017] Preferably, the thickness of the single-layer SiC ceramic layer is 0.1 μm to 2 μm. By preparing a thin layer of dielectric material, the capacity of the MLCC can be increased, the volume can be reduced, and the production cost can be reduced, thereby meeting the requirements of the continuous miniaturization and large capacity of electronic communication equipment.

[0018] Compared with the prior art, the beneficial effect of the present invention is that the preparation process provided by the present invention omits the two processes of lamination and pressing compared with the traditional ceramic chip preparation process, and also avoids the deformation of the ceramic chip caused by these two processes, and greatly saves time and cost for the production enterprise. The impregnation method used in the preparation of the SiC ceramic layer allows the polycarbosilane solution to be filled into the holes on the surface of the barium titanate layer and each subsequent SiC ceramic layer, and can wrap the inner electrode. After oxidative cross-linking and high-temperature cracking, the barium titanate layer and the SiC ceramic layer, the SiC ceramic layer and the SiC ceramic layer, and the inner electrode and the SiC ceramic layer are more closely attached, thereby greatly reducing the delamination rate between the dielectric layers of the ceramic chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art description:

[0020] Figure 1 A schematic cross-sectional view of a ceramic chip in a multilayer ceramic capacitor

[0021] Among them, 1 barium titanate; 2 SiC ceramic; 3 inner electrode. DETAILED DESCRIPTION

[0022] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0023] Example 1

[0024] (1) A barium titanate (BaTiO3) ceramic substrate was immersed in a 10% polycarbosilane solution for 60 minutes, pre-oxidized and cross-linked at 170°C, and then pyrolyzed at 1200°C in a protective atmosphere tube furnace and kept warm for 60 minutes to obtain a first layer of SiC ceramic. Then, an inner electrode was screen-printed on the first layer of SiC ceramic. A nickel electrode was used as the inner electrode.

[0025] (2) Based on step (1), impregnation, oxidation cross-linking, and high-temperature cracking are repeated to obtain a second layer of SiC ceramic, and then the inner electrode is screen-printed on the second layer of SiC ceramic.

[0026] (3) Repeat step (2) to obtain 12 layers of SiC ceramic layers printed with inner electrodes, the outermost layer being a SiC ceramic layer without inner electrodes.

[0027] Example 2

[0028] (1) A barium titanate (BaTiO3) ceramic substrate was immersed in a 20% polycarbosilane solution for 60 minutes, pre-oxidized and cross-linked at 170°C, and then pyrolyzed at 1200°C in a protective atmosphere tube furnace and kept warm for 60 minutes to obtain a first layer of SiC ceramic. Then, an inner electrode was screen-printed on the first layer of SiC ceramic. A nickel electrode was used as the inner electrode.

[0029] (2) Based on step (1), impregnation, oxidation cross-linking, and high-temperature cracking are repeated to obtain a second layer of SiC ceramic, and then the inner electrode is screen-printed on the second layer of SiC ceramic.

[0030] (3) Repeat step (2) to obtain 10 layers of SiC ceramic layers printed with inner electrodes, the outermost layer being a SiC ceramic layer without inner electrodes.

[0031] Example 3

[0032] (1) A barium titanate (BaTiO3) ceramic substrate was immersed in a 30% polycarbosilane solution for 60 minutes, pre-oxidized and cross-linked at 170°C, and then pyrolyzed at 1200°C in a protective atmosphere tube furnace and kept warm for 60 minutes to obtain a first layer of SiC ceramic. Then, an inner electrode was screen-printed on the first layer of SiC ceramic. A nickel electrode was used as the inner electrode.

[0033] (2) Based on step (1), impregnation, oxidation cross-linking, and high-temperature cracking are repeated to obtain a second layer of SiC ceramic, and then the inner electrode is screen-printed on the second layer of SiC ceramic.

[0034] (3) Repeat step (2) to obtain 8 layers of SiC ceramic layers printed with inner electrodes, the outermost layer being a SiC ceramic layer without inner electrodes.

[0035] Comparative Example 1

[0036] The ceramic chip in the ceramic capacitor is prepared by using barium titanate material through the process of film casting, electrode printing, lamination, pressing, cutting, debinding and sintering. Nickel electrodes are used as internal electrodes, and the number of dielectric layers is 8.

[0037] Comparative Example 2

[0038] The ceramic chip in the ceramic capacitor is prepared by using barium titanate material through the process of film casting, electrode printing, lamination, pressing, cutting, debinding and sintering. Nickel electrodes are used as internal electrodes, and the number of dielectric layers is 12.

[0039] The results of each embodiment are compared in the following table:

[0040]

[0041] Since the ceramic chip preparation process provided by the present invention omits the two steps of lamination and pressing, deformation of the ceramic chip caused by these two steps is avoided, and the production enterprise is greatly saved time and cost.

Claims

1. A ceramic chip in a multilayer ceramic capacitor, characterized in that: The barium titanate (BaTiO3) ceramic substrate is impregnated with a polycarbosilane solution by an immersion method, and after pre-oxidation, cross-linking, and high-temperature cracking, a first layer of SiC ceramic is obtained, and then an inner electrode is screen-printed on the first layer of SiC ceramic.

2. A ceramic chip in a multilayer ceramic capacitor as claimed in claim 1, characterized in that: Based on the steps of claim 1, impregnation, oxidation cross-linking and high-temperature cracking are repeatedly performed to obtain a second layer of SiC ceramic, and then the internal electrode is screen-printed on the second layer of SiC ceramic.

3. The ceramic chip in a multilayer ceramic capacitor according to claim 1, characterized in that: Repeat the steps of claim 2 to obtain more SiC ceramic layers printed with inner electrodes, the number of layers being greater than or equal to 3, and the outermost layer being a SiC ceramic layer without inner electrodes.

4. The ceramic chip in a multilayer ceramic capacitor according to claim 1, characterized in that: The concentration of the polycarbosilane solution is 5% to 40%.

5. The ceramic chip in a multilayer ceramic capacitor according to claim 1, characterized in that: The solute of the polycarbosilane solution is xylene.

6. The ceramic chip in a multilayer ceramic capacitor according to claim 1, characterized in that: The immersion time is 10 min to 60 min.

7. The ceramic chip in a multilayer ceramic capacitor according to claim 1, characterized in that: The impregnation process can be carried out in multiple times.

8. The ceramic chip in a multilayer ceramic capacitor as claimed in claim 1, characterized in that: The pre-oxidation temperature is 150°C to 180°C.

9. The ceramic chip in a multilayer ceramic capacitor according to claim 1, characterized in that: The high temperature cracking temperature is 1000°C to 1300°C.

10. The ceramic chip in a multilayer ceramic capacitor according to claim 1, characterized in that: The impregnation method can be performed in an inert gas atmosphere such as argon or nitrogen.

11. A ceramic chip in a multilayer ceramic capacitor as claimed in claims 1, 2 and 3, characterized in that: The thickness of the single-layer SiC ceramic layer is 0.1 μm to 2 μm.

Images