A method for improving dielectric properties of an MLCC device

Abstract

The application discloses a method for improving dielectric properties of MLCC devices. The application belongs to the technical field of ferroelectric ceramic materials, and the improvement method is based on surface layer effect. By optimizing the degassing, sintering and heat treatment processes of the cast film ceramic, a thin film ceramic with significant surface layer effect is prepared, and the dielectric constant and capacitance value are improved by more than 7%. The method shows that the thinner the cast film, the higher the volume proportion of the surface layer, and the stronger the regulation and control effect on the dielectric properties. The method provides technical support for the performance improvement of ultrathin dielectric layer MLCC devices, and the capacitance of the optimized MLCC device is improved by more than 5%. The method does not need to change the ceramic formula and does not need to greatly modify the existing equipment, has good process compatibility and industrial application prospect, and is suitable for performance optimization of MLCC devices and various ferroelectric cast film ceramic materials.

Description

Technical Field

[0001] This invention belongs to the field of ferroelectric ceramic materials technology, specifically relating to a method for improving the dielectric properties of MLCC devices. Background Technology

[0002] Multilayer ceramic capacitors (MLCCs), as key components in the modern electronics industry, are multilayer monolithic structures composed of alternating layers of dielectric ceramic films and internal electrodes. They are widely used in consumer electronics, automotive electronics, communication equipment, and many other fields, and their performance directly affects the stability and reliability of end products. Currently, MLCCs are rapidly developing towards higher performance and miniaturization, placing continuous demands on increasing device capacitance. Besides optimizing the ceramic matrix composition to improve dielectric properties, increasing the number of layers and reducing the dielectric layer thickness are also common techniques for improving MLCC capacitance. As the dielectric layer thickness of commercially available MLCCs gradually decreases to the submicron to tens of micrometer scale, the requirements for the dielectric properties of the dielectric ceramic also increase significantly.

[0003] To address the technical challenges of miniaturization and high capacity in MLCCs, existing dielectric performance research largely focuses on ceramic composition optimization, doping modification, and sintering process control, primarily relying on adjusting material formulations and optimizing conventional processes to improve MLCC device performance. However, these research approaches generally suffer from long development cycles, high costs, and significant performance bottlenecks. Therefore, a reliable, low-cost, and easily industrialized technical method for effectively and universally improving the dielectric performance of dielectric layer cast ceramics and MLCC devices remains lacking. It is worth noting that a significant surface layer effect exists in bulk ferroelectric ceramics, playing a crucial role in regulating the material's electrical properties. Since the dielectric layer of most currently commercially available MLCCs uses ferroelectric ceramic materials, this provides a new potential direction for controlling the dielectric performance of MLCCs. Summary of the Invention

[0004] The existing barium titanate-based cast film ceramics used in multilayer ceramic capacitors (MLCCs) suffer from bottlenecks in dielectric performance improvement, making it difficult to meet the development demands for high performance and miniaturization in MLCCs. Therefore, this invention proposes a method to improve the dielectric performance of MLCC devices. This invention employs a suitable heat treatment process to form a surface layer structure with a surface layer effect on the surface of the cast film ceramic. Without changing the substrate material formulation, this significantly improves the room-temperature dielectric performance of the barium titanate-based cast film ceramic, thereby effectively enhancing the dielectric performance of MLCCs.

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

[0006] A method for improving the dielectric properties of MLCC devices includes the following steps:

[0007] (1) Barium titanate-based ceramic thin film green blanks were prepared by tape casting process;

[0008] (2) The ceramic green body was debinded and sintered in air atmosphere to obtain a cast ceramic film sample with a thickness of 25 μm to 100 μm;

[0009] (3) The cast film ceramic samples were treated to retain the original sintered surface layer and to remove the original sintered surface layer, respectively, and metal electrodes were prepared on the sample surface;

[0010] (4) Test the dielectric properties of samples with and without the original sintered surface layer to determine the contribution of the surface layer to the dielectric properties.

[0011] (5) Heat treatment is performed on the cast ceramic sample with the surface layer removed to form a surface layer structure with surface layer effect, thereby restoring and further improving the dielectric properties;

[0012] (6) Heat treatment is performed on MLCC device samples with a single ceramic dielectric layer thickness of 1~2 μm to form a surface layer structure with surface layer effect, thereby improving its dielectric properties without changing the ceramic matrix formula.

[0013] In the above technical solution, after sintering, the cast film ceramic forms a surface layer structure with a surface layer effect, and the surface layer can be removed by physically polishing the sample.

[0014] In the above technical solution, the heat treatment temperature is higher than the Curie temperature or dielectric peak temperature of the ceramic material, and the heat treatment time is 1 to 1200 minutes.

[0015] In the above technical solution, metal electrodes are prepared on the surface of cast film ceramics after different surface treatments and in MLCC devices by magnetron sputtering or printing co-firing. The electrodes are composed of one or more of gold, nickel, and copper metals.

[0016] In the above technical solutions, among cast ceramic films of different thicknesses, the smaller the sample thickness, the more significant the surface layer effect and the more obvious the improvement in dielectric constant.

[0017] In the above technical solution, the dielectric constant of the heat-treated cast film ceramic is increased by at least 7%.

[0018] In the above technical solution, the heat treatment process conditions can effectively form a surface layer structure with surface layer effect, improve dielectric properties, and maintain the structural integrity and repeatability of the sample.

[0019] In the above technical solution, the method for improving the dielectric properties of cast ceramic films is also applicable to the optimization of MLCC fabrication processes and the improvement of device performance.

[0020] In the above technical solution, by subjecting the MLCC device to heat treatment above the Curie temperature or dielectric peak temperature, the ceramic dielectric layer can be effectively formed to form a surface layer structure with surface layer effect, thereby improving the dielectric performance of the MLCC device.

[0021] In the above technical solution, the heat treatment can improve the dielectric properties of cast film ceramics of different thicknesses and commercial MLCC devices without changing the ceramic matrix formula and molding process, and has good process compatibility and industrial application prospects.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) The process of this invention is stable and controllable, and the improvement effect is significant. Without changing the basic material formula, the dielectric constant of barium titanate-based cast film ceramics can be significantly improved by at least 7%. The technology is highly practical and easy to promote industrially.

[0024] (2) It specifically addresses the technical bottleneck that limits the improvement of dielectric performance of the dielectric layer in existing MLCCs. By making reasonable use of the surface layer effect, it breaks through the performance limit of traditional processes and achieves a significant improvement in the dielectric performance of MLCCs, which can be improved by at least 5%, effectively meeting the development needs of high performance and miniaturization of MLCCs.

[0025] (3) This technology does not require modification of existing casting, sintering and other production equipment, and is highly compatible with existing MLCC large-scale production processes, and has the prospect of rapid industrialization. Attached Figure Description

[0026] Figure 1 : Schematic diagram of the surface layer structure of cast ceramic film.

[0027] Figure 2 Surface morphology and structure of barium titanate-based cast ceramic films. Figure 2 (a) is 25 μm. Figure 2 (b) is 100 μm.

[0028] Figure 3 Comparison of room temperature dielectric properties of cast ceramic samples before and after surface layer removal and before and after heat treatment. Figure 3 (a) is the frequency dependence curve of room temperature dielectric properties; Figure 3 (b) is a comparative bar chart of the room temperature dielectric constant at a frequency of 1 kHz.

[0029] Figure 4 Comparison of dielectric properties of cast ceramic films of different thicknesses. Figure 4 (a) is the temperature dependence curve of dielectric properties at a frequency of 1 kHz; Figure 4 (b) is a comparative bar chart of dielectric constants at 1 kHz frequency and 30℃.

[0030] Figure 5 Dielectric temperature spectrum curves of different MLCC devices at 1 kHz frequency. Figure 5 (a) is the dielectric temperature spectrum curve of device 1; Figure 5 (b) is the dielectric temperature spectrum curve of device 2.

[0031] Figure 6 Comparison of room temperature capacitance values ​​of different MLCC devices before and after heat treatment at 1 kHz frequency. Figure 6 (a) is a comparison chart of the capacitance values ​​of device 1; Figure 6 (b) is a comparison chart of the capacitance values ​​of device 2.

[0032] Figure 7 Comparison of room temperature capacitance performance of different MLCC devices at 1 kHz frequency after heat treatment at 150 ℃ for different times. Figure 7 (a) shows a comparison of the capacitance performance of device 1; Figure 7 (b) shows the comparison of the capacitance performance of device 2. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. However, the following embodiments are only for explaining the present invention, and the scope of protection of the present invention should include all the contents of the claims. Moreover, through the description of the following embodiments, those skilled in the art can fully implement all the contents of the claims of the present invention.

[0034] This invention achieves overall performance optimization of cast film ceramics and MLCC devices by rationally utilizing the surface layer effect, providing a universally applicable method for MLCC production. Using barium titanate-based cast film ceramics and commercial MLCC devices as examples, this invention verifies the feasibility of the method. To clarify the importance of the surface layer effect in cast film ceramics and its role in improving dielectric properties, and to promote its application in MLCC devices, this invention uses mainstream industrial casting processes to prepare barium titanate-based ceramic film green bodies. By optimizing the debinding and high-temperature sintering processes, denser cast film ceramic samples are obtained. Specifically, barium titanate-based cast film green bodies of different thicknesses are cut into green ceramic sheets of specific sizes, and debinding and sintering are completed in a high-temperature furnace under an air atmosphere to obtain thin ceramic samples that meet testing requirements. To reveal the mechanism by which the surface layer effect affects the dielectric properties of cast film ceramics, this invention uses magnetron sputtering to prepare metal electrodes on samples with different surface states. These different surface states are obtained through differentiated sample processing, including retaining the original sintered surface layer, polishing to remove the surface layer, and heat treatment to restore the surface layer.

[0035] The core of this invention lies in leveraging the surface layer effect, which is prevalent in bulk ferroelectric ceramics, to significantly improve the dielectric properties of barium titanate-based cast ceramic films without altering the substrate material formulation, and then optimizing their performance in finished MLCC devices. This invention first directly confirms the objective existence of the surface layer effect in cast ceramic films by comparing the room-temperature dielectric properties of samples with and without the original sintered surface layer. Figure 1 The structural diagram is shown in the figure. Based on this, comparing the dielectric properties of the polished sample after surface layer removal and subsequent heat treatment demonstrates that heat treatment at a temperature slightly above the Curie temperature can effectively repair the surface layer and further improve dielectric properties. By comparing the dielectric properties of cast ceramic films of different thicknesses, the intrinsic relationship between ceramic thickness and the surface layer effect is revealed: the thinner the thin-film ceramic, the higher the proportion of the surface layer in the volume, and the more significant its effect on regulating dielectric properties. This conclusion provides important technical support for improving the performance of ultra-thin dielectric layer MLCC devices. Appropriate heat treatment of commercial MLCC devices can effectively utilize the surface layer effect to optimize and improve device performance.

[0036] Example 1:

[0037] Part 1: Preparation of barium titanate-based cast ceramic samples.

[0038] Barium titanate-based ceramic film green bodies were prepared using a casting process. Green bodies of different thicknesses were cut into 1.5 cm × 1.5 cm green ceramic sheets. The casting film thicknesses investigated in this example were 25 μm, 50 μm, and 100 μm. The green ceramic sheets were placed in an air atmosphere and held at 600°C for 2 hours in a high-temperature furnace to complete the debinding process. Subsequently, a two-step sintering method was used to sinter the debinded green bodies in an air atmosphere at high temperature: first, the temperature was held at 1300°C for 1 minute, and then the temperature was rapidly reduced to 800°C and held for 20 hours. Finally, casting film ceramic samples that met the testing requirements were obtained.

[0039] See Figure 1 In this embodiment, the cast ceramic film formed obvious surface layer structures on both the upper and lower surfaces. The morphology of cast ceramic films of different thicknesses was characterized, such as... Figure 2 (a) and Figure 2 The results in (b) show that the sample prepared by the above process has well-developed and relatively dense grains. Figure 2 The image shows a scanning electron microscope (SEM) image of the cast ceramic film. It can be seen that regardless of whether the film thickness is 25 μm or 100 μm, the grain size of the sample is controlled within the range of 400-500 nm.

[0040] Metal electrodes were fabricated on the surface of cast ceramic samples using magnetron sputtering; in this embodiment, gold electrodes were selected. The electrodes serve only as a conductive layer, and their material selection has virtually no impact on the dielectric properties of the sample.

[0041] Part Two: Removal of the ceramic surface layer of the cast film and testing of its dielectric properties.

[0042] First, the cast ceramic film sample (sample 1) with its original surface layer retained was subjected to room temperature dielectric spectrum testing after electrode fabrication. The test results showed that the dielectric constant of this sample at 1 kHz was 2270. Subsequently, the surface layer of the sample was removed by surface polishing (polishing thickness approximately 5 μm) to obtain sample 2. After polishing, the electrode was re-fabricated and subjected to room temperature dielectric spectrum testing under the same conditions. Its dielectric constant at 1 kHz was 2115. Specific test results are as follows: Figure 3 (a) and Figure 3 As shown in (b) of the diagram.

[0043] Part Three: Heat treatment and dielectric property testing of cast ceramic film after surface layer removal.

[0044] The cast ceramic sample with the surface layer removed was placed in a muffle furnace and heat-treated at 200℃ for 30 minutes, followed by electrode fabrication. The room temperature dielectric spectrum of this heat-treated sample (sample 3) was measured, and its dielectric constant at 1 kHz was 2293. The results are as follows: Figure 3(a) and Figure 3 As shown in (b) of the diagram.

[0045] Part 4: Dielectric property testing of cast ceramic films of different thicknesses.

[0046] Electrodes were fabricated from cast ceramic samples of varying thicknesses retaining the original surface layer, and dielectric temperature spectroscopy was performed. Their dielectric properties at 1 kHz were as follows: Figure 4 As shown in (a) above, the test results show that the dielectric properties of the cast ceramic film gradually increase as the thickness decreases; to clearly compare the improvement in dielectric properties, Figure 4 (b) shows the comparison of dielectric properties of cast ceramic films of different thicknesses at 30℃, where the dielectric constants of the 25 μm, 50 μm, and 100 μm thick samples are 2730, 2496, and 2285, respectively. This result further confirms that the smaller the thickness of the cast ceramic film, the higher the proportion of its surface layer in the volume, and the corresponding dielectric properties are enhanced.

[0047] Example 2: Commercial MLCC Devices

[0048] This embodiment uses commercially available MLCC finished devices (referred to as Device 1 and Device 2) manufactured by Guangdong Fenghua Advanced Technology Co., Ltd., both of which have barium titanate-based ceramic dielectric layers with a single ceramic dielectric layer thickness of 1~2 μm. First, dielectric temperature spectroscopy was performed on the two types of device samples to determine the appropriate heat treatment temperature. The results are as follows: Figure 5 (a) and Figure 5 As shown in (b) of the figure. Based on the results of the dielectric temperature spectrum, a temperature above the dielectric peak temperature is selected for heat treatment of the sample. In this embodiment, the selected heat treatment temperatures for device 1 and device 2 are 200℃ and 150℃, respectively, and the holding time is 30 minutes for both.

[0049] Capacitance tests were performed on untreated device 1 and device 2 samples, and their measured capacitance values ​​were 63.81 μF and 8.96 μF, respectively. The results are as follows: Figure 6 (a) and Figure 6 As shown in (b) above. After heat treatment, the capacitance of both models of samples was tested again, increasing to 71.09 μF and 9.44 μF respectively, as also shown in [the diagram]. Figure 6 The results show that the dielectric properties of the finished MLCC device were also improved by introducing an appropriate heat treatment process, with a capacitance increase of at least 5%. This improvement mainly stems from the surface layer effect exhibited by the dielectric layers within the MLCC. Furthermore, heat treatment of the MLCC device for different holding times yielded the following results: Figure 7 (a) and Figure 7 As shown in (b) in the figure, the capacitance performance of the samples was significantly improved under all heat treatment conditions.

[0050] The above results demonstrate that by utilizing the surface layer effect, the dielectric properties of barium titanate-based cast ceramic films can be effectively improved, and the performance of MLCC devices can be optimized, thus verifying the feasibility of the present invention. The heat treatment process used in this embodiment is only for verifying the feasibility of the method. From the perspective of the mechanism of action, other heat treatment processes that can excite and utilize the surface layer effect of dielectric cast ceramic films can achieve similar performance improvement effects. Furthermore, this method has good universality and can be applied to ferroelectric ceramic systems with different compositions and their corresponding MLCC devices.

[0051] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for improving the dielectric properties of MLCC devices, characterized in that, Includes the following steps: (1) Barium titanate-based ceramic thin film green blanks were prepared by tape casting process; (2) The ceramic film green body is debonded and sintered in air atmosphere to obtain a cast ceramic film sample; (3) The cast film ceramic samples were treated to retain the original sintered surface layer and to remove the original sintered surface layer, respectively, and metal electrodes were prepared on the sample surface; (4) Test the dielectric properties of samples with and without the original sintered surface layer to determine the contribution of the surface layer to the dielectric properties. (5) Heat treatment is performed on the cast film ceramic sample with the original sintered surface layer removed to form a surface layer structure with surface layer effect, thereby restoring and further improving the dielectric properties; (6) Heat treatment is performed on the MLCC device sample containing a single layer of barium titanate-based ceramic thin film dielectric layer with a thickness of 1~2 μm prepared in the above steps, so that the barium titanate-based ceramic thin film dielectric layer forms a surface layer structure with surface layer effect, thereby improving its dielectric properties without changing the ceramic matrix formula.

2. The method for improving the dielectric properties of MLCC devices according to claim 1, characterized in that, Among cast ceramic films of different thicknesses, the smaller the sample thickness, the more significant the surface layer effect and the more obvious the improvement in dielectric constant.

3. The method for improving the dielectric properties of MLCC devices according to claim 1, characterized in that, The method described is applicable to the optimization of MLCC fabrication processes and the improvement of device performance.

4. The method for improving the dielectric properties of MLCC devices according to claim 1, characterized in that, By subjecting the MLCC device to heat treatment above the Curie temperature or dielectric peak temperature, the ceramic dielectric layer is effectively formed into a surface layer structure with a surface layer effect, thereby improving the dielectric performance of the MLCC device.

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