Multilayer ceramic capacitor and nano adhesive preparation method thereof

Abstract

The invention discloses a multilayer ceramic capacitor and a nano adhesive preparation method thereof. The method comprises the following steps: preparing a capacitor diaphragm by adopting a ceramic dielectric material; printing an inner electrode on the capacitor diaphragm; multiple layers of capacitor diaphragms are overlapped and bonded in a nano gluing mode, and the nano gluing is specifically as follows: a pGMA thin film is deposited on the surface of the capacitor diaphragm; the two capacitor diaphragms are bonded and assembled on a clamping tool, pressure is applied, the two capacitor diaphragms are placed in an activating solution EDA to be soaked and activated, and ultrasonic cleaning is carried out; and applying pressure to the activated sample to complete a curing cross-linking reaction so as to realize the bonding of the capacitor diaphragm. According to the invention, a plurality of capacitor diaphragms made of the finished ceramic dielectric material are prepared in advance, then the inner electrode is subjected to silk-screen printing, and the bonding of multiple layers of ceramic chips is realized by adopting a nano adhesive connection method, so that the crystal structure of the ceramic dielectric material is not changed in the preparation process, and the co-sintering process of the ceramic chips and the adhesive is effectively avoided; the problems of bubbles and layering caused by volatilization of organic matters can be solved, and the quality and performance of the MLCC can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic capacitors, and in particular to a multilayer ceramic capacitor and a nano-adhesive preparation method thereof. Background Art

[0002] Multilayer ceramic capacitors (MLCC) are the most widely used and fastest growing core components in electronic devices, and are known as the "rice of the electronics industry". They have the advantages of small size, high volume ratio, easy surface mounting (SMT), high reliability and excellent high-frequency characteristics, and are widely used in consumer electronics, communications, automotive electronics, home appliances and other fields.

[0003] MLCC is the most important passive component that can store and release charge, providing high stability and low loss for resonant circuit applications, and high volumetric efficiency for buffer, bypass and coupling applications. The interior of MLCC is a structure of ceramic dielectric materials and metal inner electrodes stacked in an alternating manner, and then packaged with two end electrodes. The stacked structure is equivalent to multiple internal bipolar plate capacitors connected in parallel, but with a smaller volume and thinner layer thickness (equivalent to the distance between the two plates). And compared to ceramic chip capacitors, it is easier for circuit SMT and high integration.

[0004] In industry, MLCC devices are generally prepared through the casting process. The specific process includes ceramic slurry preparation, casting, screen printing, lamination, pressing, cutting, debinding, sintering, chamfering, burning end and testing.

[0005] The manufacturing process of MLCC devices is very complex and precise, and each step will affect the quality of MLCC products, including the quality of cast film (ceramic slurry component ratio, ceramic powder dispersibility, adhesive solvent content, etc.), printing and lamination (organic volatilization causing bubble stratification, assembly line electrode drying), debinding, sintering (temperature control, introduction of sintering aids), and electroplating.

[0006] In order to save costs in actual production and cater to the low melting point characteristics of base metals, the sintering temperature of the system is usually reduced during the preparation process. For example, the BNBCT system is doped with borosilicate, CuV2O6, CuBi2O4, etc. to achieve a low sintering effect, and the sintering temperature is reduced by Fe element substitution doping, etc. Affected by the traditional MLCC preparation process, the quality of MLCC products is restricted by too many factors. Quality problems in each step will become fatal defects of MLCC products. For example, the poor matching degree between the internal slurry and the porcelain powder in the slurry preparation process leads to MLCC delamination and cracking; in the casting process, the thickness (weight) and appearance quality control of the casting film are not accurate; in the printing process, the internal electrode printing is defective; in the lamination process, the lamination effect is not good and the internal electrode is seriously shifted; in the cutting process, the cutting accuracy is not up to standard, which affects the later packaging, or the cutting surface is rough, the cutting is off-center and the delamination occurs during the cutting process; in the debinding process, the debinding effect is poor, resulting in MLCC cracking and delamination; in the sintering process, the temperature in the local temperature zone fluctuates, resulting in abnormal MLCC capacity; or the sintering process temperature is too high, the MLCC grain size is reduced, resulting in a decrease in MLCC capacity; the sintering temperature is too high, the engraving layer thickness in the core-shell structure increases, resulting in a decrease in MLCC capacity; low activation energy of grain boundary conductivity during annealing will lead to oxygen vacancies migrating across the grain boundary, causing insulation resistance degradation; in the end-firing process, open circuit failure caused by weak adhesion of the end electrode.

[0007] In view of this, this application is hereby filed. Summary of the invention

[0008] In order to solve the problems of the prior art, the present invention provides a multilayer ceramic capacitor and a nano-adhesive preparation method thereof. A plurality of capacitor diaphragms of finished ceramic dielectric materials are prepared in advance, and then after silk-screening the inner electrodes, the nano-adhesive bonding method is used to achieve the bonding of the multilayer ceramic sheets. The crystal structure of the ceramic dielectric material will not be changed during the preparation process, and the co-sintering process of the ceramic sheets and the glue can be effectively avoided. The bubbles and stratification caused by the volatilization of organic matter can be solved, and the quality and performance of MLCC can be effectively improved. At the same time, since sintering is not required, the capacitor diaphragm can select the most suitable ceramic dielectric material according to actual needs without considering the influence of the component selection during the sintering process on the quality of the MLCC.

[0009] The present invention is achieved through the following technical solutions:

[0010] In one aspect, the present invention provides a multilayer ceramic capacitor and a method for preparing the same by nano-adhesive bonding, comprising the following steps:

[0011] (1) Using ceramic dielectric materials with high dielectric constant and high upper limit operating temperature to prepare ceramic sheets as capacitor diaphragms;

[0012] (2) Printing inner electrodes on the capacitor film;

[0013] (3) The multi-layer capacitor film printed with internal electrodes is overlapped and bonded by using nano-adhesive bonding.

[0014] In a specific embodiment, the specific preparation method of the nano-adhesive bond is as follows:

[0015] 3.1) Preparation of adhesive layer film: Use induced chemical vapor deposition to deposit a pGMA film on the surface of the capacitor diaphragm to be bonded; 3.2) Activation of the adhesive layer film: Bond two capacitor diaphragms coated with pGMA film and assemble them on a clamping tool, apply appropriate pressure to the sample, and soak it in the activation liquid EDA liquid for 10 to 20 hours. After the activation liquid has fully activated the pGMA film, the sample is ultrasonically cleaned; 3.3) Curing of the activated adhesive layer film: Assemble the bonded samples after activation and cleaning and apply appropriate pressure, air dry, and let it stand for 70 to 75 hours. The pGMA film completes the curing and cross-linking reaction to achieve bonding of the two capacitor diaphragms.

[0016] Affected by the traditional MLCC preparation process, the quality of MLCC products is restricted by too many factors. Quality problems in each step will become fatal defects of MLCC products. For example, the poor matching degree between the internal slurry and the porcelain powder in the slurry preparation process leads to MLCC delamination and cracking; in the casting process, the thickness (weight) and appearance quality control of the casting film are not accurate; in the printing process, the internal electrode printing is defective; in the lamination process, the lamination effect is not good and the internal electrode is seriously shifted; in the cutting process, the cutting accuracy is not up to standard, which affects the later packaging, or the cutting surface is rough, the cutting is off-center and the delamination occurs during the cutting process; in the debinding process, the debinding effect is poor, resulting in MLCC cracking and delamination; in the sintering process, the temperature in the local temperature zone fluctuates, resulting in abnormal MLCC capacity; or the sintering process temperature is too high, the MLCC grain size is reduced, resulting in a decrease in MLCC capacity; the sintering temperature is too high, the engraving layer thickness in the core-shell structure increases, resulting in a decrease in MLCC capacity; low activation energy of grain boundary conductivity during annealing will lead to oxygen vacancies migrating across the grain boundary, causing insulation resistance degradation; in the end-firing process, open circuit failure caused by weak adhesion of the end electrode.

[0017] In order to overcome the above-mentioned problems of the prior art, the present invention prepares a plurality of capacitor diaphragms of finished ceramic dielectric materials in advance, and then, after silk-screening the inner electrodes, a nano-adhesive bonding method is used to achieve the bonding of the multilayer ceramic sheets. The crystal structure of the ceramic dielectric material will not be changed during the preparation process, and the co-sintering process of the ceramic sheets and the glue can be effectively avoided. The bubbles and stratification caused by the volatilization of organic matter can be solved, and the quality and performance of MLCC can be effectively improved. At the same time, since sintering is not required, the capacitor diaphragm can select the most suitable ceramic dielectric material according to actual needs without considering the influence of the component selection during the sintering process on the quality of MLCC.

[0018] In a specific embodiment, the specific method of step 3.1) is: using glycidyl methacrylate (GMA) as a monomer and di-tert-butyl peroxide (DTBP) as an initiator, under the condition of a hot wire heating temperature of 190-210°C, the initiator is fully cracked to induce GMA monomer polymerization, and a pGMA film is deposited on the surface of the cooled capacitor diaphragm to form a pGMA film.

[0019] In a specific embodiment, the surface temperature of the capacitor film to be bonded is 38-42°C.

[0020] In a specific embodiment, the flow ratio of GMA to DTBP is GMA: 33%, DTBP: 66%.

[0021] In a specific embodiment, the ultrasonic cleaning conditions in step 3.2) are: 100 kHz, 300 W, cleaning time 20 seconds, and three cleanings in total, wherein during the cleaning process, the sample to be bonded is always under appropriate pressure.

[0022] In a specific implementation manner, the pressure applied when the capacitor diaphragm is bonded is 8-10N / 5mm×5mm.

[0023] In a specific embodiment, the method for preparing the capacitor film in step (1) is as follows:

[0024] 1.1) Pre-sinter the raw materials of ceramic dielectric materials with high dielectric constant and high upper limit working temperature at a constant temperature of 500-700°C for 1 hour to obtain stable and uniform nano-scale ceramic powder;

[0025] 1.2) Add a dispersant solution to the nano-scale ceramic powder, then add an excess of anhydrous ethanol to form a mixed solution, and ultrasonically disperse for 40-60 minutes. After uniform dispersion, dry the mixture, and grind the mixture to obtain uniformly granulated ceramic powder;

[0026] 1.3) adding the uniformly granulated ceramic powder into an organic solvent and performing ball milling to prepare the slurry. During the ball milling process, the ball mill frequency is 30-45 Hz and the ball milling time is 10-60 min to obtain a ceramic slurry;

[0027] 1.4) The ceramic slurry is evenly coated on the lower substrate of the screen to form a ceramic sheet. After the ceramic sheet on the surface of the lower substrate is fully solidified by constant temperature drying, the upper substrate is pressed on the ceramic surface to form a sandwich, and the sandwiched ceramic sheet is packaged by vacuum packaging;

[0028] 1.5) After the packaged sample is cold isostatically pressed, the upper substrate is pushed open horizontally, and the ceramic sheet is peeled off from the lower substrate to obtain an unsupported ceramic sheet;

[0029] 1.6) The unsupported ceramic sheet is sintered to obtain an unsupported ultra-thin ceramic sheet.

[0030] In a specific embodiment, step (3) further includes external electrode packaging, and the external electrode packaging is packaged by dispensing.

[0031] In a second aspect, the present invention further provides a multilayer ceramic capacitor, which is manufactured using the above-mentioned nano-adhesive bonding preparation method.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] The embodiment of the present invention provides a multilayer ceramic capacitor and a method for preparing the same by nano-adhesive bonding. A plurality of capacitor diaphragms of finished ceramic dielectric materials are prepared in advance, and then after silk-screening the inner electrodes, the nano-adhesive bonding method is used to achieve the bonding of the multilayer ceramic sheets. The crystal structure of the ceramic dielectric material will not be changed during the preparation process, and the co-sintering process of the ceramic sheets and the glue can be effectively avoided. The bubbles and stratification caused by the volatilization of organic matter can be solved, and the quality and performance of MLCC can be effectively improved. At the same time, since sintering is not required, the capacitor diaphragm can select the most suitable ceramic dielectric material according to actual needs without considering the influence of the component selection during the sintering process on the quality of the MLCC. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The illustrative embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0035] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that these specific details need not be employed to practice the present invention. In other embodiments, in order to avoid obscuring the present invention, well-known materials or methods are not specifically described.

[0036] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or subcombination. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0037] Example 1

[0038] The embodiment of the present invention provides a method for preparing nano-bonded multilayer ceramic capacitors, comprising the following steps:

[0039] (1) Using ceramic dielectric materials with high dielectric constant and high upper limit operating temperature to prepare ceramic sheets as capacitor diaphragms

[0040] 1.1) Pre-sinter the raw materials of ceramic dielectric materials with high dielectric constant and high upper limit working temperature at a constant temperature of 500-700°C for 1 hour to obtain stable and uniform nano-scale ceramic powder;

[0041] 1.2) Add a dispersant solution to the nano-scale ceramic powder, then add an excess of anhydrous ethanol to form a mixed solution, and ultrasonically disperse for 40-60 minutes. After uniform dispersion, dry the mixture, and grind the mixture to obtain uniformly granulated ceramic powder;

[0042] 1.3) adding the uniformly granulated ceramic powder into an organic solvent and performing ball milling to prepare the slurry. During the ball milling process, the ball mill frequency is 30-45 Hz and the ball milling time is 10-60 min to obtain a ceramic slurry;

[0043] 1.4) The ceramic slurry is evenly coated on the lower substrate of the screen to form a ceramic sheet. After the ceramic sheet on the surface of the lower substrate is fully solidified by constant temperature drying, the upper substrate is pressed on the ceramic surface to form a sandwich, and the sandwiched ceramic sheet is packaged by vacuum packaging;

[0044] 1.5) After the packaged sample is cold isostatically pressed, the upper substrate is pushed open horizontally, and the ceramic sheet is peeled off from the lower substrate to obtain an unsupported ceramic sheet;

[0045] 1.6) Sintering the unsupported ceramic sheet to obtain an unsupported ultra-thin ceramic sheet;

[0046] 1.7) Mechanical grinding and polishing are used to obtain ceramic slices with excellent surface shape and surface roughness, and then wire cutting or laser cutting is used to obtain ceramic slices of the required size;

[0047] (2) Printing inner electrodes on the capacitor film;

[0048] (3) Overlapping and bonding the multi-layer capacitor diaphragms with internal electrodes by nano-adhesion:

[0049] 3.1) Preparation of adhesive layer film: Glycidyl methacrylate (GMA) is used as a monomer and di-tert-butyl peroxide (DTBP) is used as an initiator. The flow ratio of GMA to DTBP is GMA: 33%, DTBP: 66%. Under the condition of hot wire heating temperature of 190-210°C, the initiator is fully cracked to induce GMA monomer polymerization, and pGMA film is deposited on the surface of the capacitor diaphragm at a cooling surface temperature of 38-42°C.

[0050] 3.2) Activation of adhesive film: Two capacitor diaphragms coated with pGMA film are bonded and assembled on a clamping tool, a pressure of (8-10N) / (5mm×5mm) is applied to the sample, and the sample is immersed in the activation liquid EDA liquid for 10 to 20 hours. After the activation liquid has fully activated the pGMA film, the sample is ultrasonically cleaned. The ultrasonic cleaning conditions are: 100kHz, 300W, cleaning time is 20 seconds, and a total of three cleanings are performed. During the cleaning process, the sample to be bonded is always under a pressure of (8-10N) / (5mm×5mm);

[0051] 3.3) Curing of activated adhesive film: Assemble the activated and cleaned bonding samples and apply a pressure of (8-10N) / (5mm×5mm), air dry, and let stand for 70 to 75 hours. The pGMA film completes the curing and cross-linking reaction to achieve bonding of the two capacitor diaphragms.

[0052] (4) The outer electrodes are packaged by dispensing to obtain a multilayer ceramic capacitor.

[0053] The preparation methods of the capacitor diaphragm ceramic dielectric materials mentioned in the present invention are all prepared by existing conventional methods. The difference is that the present application first fires the ceramic material into a shape, and then forms a multi-layer ceramic overlapping structure by nano-adhesive bonding. Compared with the existing method that requires overlapping of multiple layers of ceramic sheets and then sintering and connecting, the crystal structure of the ceramic dielectric material will not be changed during the preparation process, and the co-sintering process of the ceramic sheets and the glue can be effectively avoided. The bubbles and stratification caused by the volatilization of organic matter can be solved, and the quality and performance of MLCC can be effectively improved. At the same time, since sintering is not required, the capacitor diaphragm can select the most suitable ceramic dielectric material according to actual needs without considering the influence of the component selection during the sintering process on the quality of MLCC.

[0054] Example 2

[0055] The embodiment of the present invention provides a multilayer ceramic capacitor, which is manufactured by the nano-adhesive preparation method described in Embodiment 1.

[0056] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a nano-bonded multilayer ceramic capacitor, characterized in that: The steps include: (1) Using ceramic dielectric materials with high dielectric constant and high upper limit operating temperature to prepare ceramic sheets as capacitor diaphragms; (2) Printing inner electrodes on the capacitor film; (3) The multi-layer capacitor film printed with internal electrodes is overlapped and bonded by using nano-adhesive bonding.

2. The method for preparing a nano-bonded multilayer ceramic capacitor according to claim 1, characterized in that: The specific preparation method of the nano-gel is as follows: 3.1) Preparation of adhesive film: using the initiated chemical vapor deposition method to deposit a pGMA film on the surface of the capacitor film to be bonded; 3.2) Activation of adhesive film: bonding two capacitor films coated with pGMA film and assembling them on a clamping tool, applying appropriate pressure to the sample, soaking it in the activation liquid EDA liquid for 10 to 20 hours, and after the activation liquid has fully activated the pGMA film, ultrasonically cleaning the sample; 3.3) Curing of activated adhesive film: Assemble the activated and cleaned bonding samples and apply appropriate pressure, air dry, and let stand for 70 to 75 hours. The pGMA film completes the curing and cross-linking reaction to achieve bonding of the two capacitor diaphragms.

3. The method for preparing a nano-bonded multilayer ceramic capacitor according to claim 2, characterized in that: The specific method of step 3.1) is: using glycidyl methacrylate (GMA) as a monomer and di-tert-butyl peroxide (DTBP) as an initiator, under the condition of a hot wire heating temperature of 190-210°C, the initiator is fully cracked to induce GMA monomer polymerization, and a pGMA film is deposited on the surface of the cooled capacitor diaphragm to form a pGMA film.

4. The method for preparing a nano-bonded multilayer ceramic capacitor according to claim 3, characterized in that: The surface temperature of the capacitor diaphragm to be bonded is 38-42°C.

5. The method for preparing a multilayer ceramic capacitor by nano-bonding according to claim 3, characterized in that: The flow ratio of GMA and DTBP is GMA: 33%, DTBP: 66%.

6. The method for preparing a nano-bonded multilayer ceramic capacitor according to claim 2, characterized in that: The ultrasonic cleaning conditions in step 3.2) are: 100 kHz, 300 W, cleaning time 20 seconds, and three cleanings in total. During the cleaning process, the sample to be bonded is always under appropriate pressure.

7. The method for preparing a nano-bonded multilayer ceramic capacitor according to claim 2, characterized in that: The pressure applied when bonding the capacitor diaphragm is 8-10N / 5mm×5mm.

8. The method for preparing a nano-bonded multilayer ceramic capacitor according to claim 1, characterized in that: The preparation method of the capacitor diaphragm in step (1) is as follows: 1.1) Pre-sinter the raw materials of ceramic dielectric materials with high dielectric constant and high upper limit working temperature at a constant temperature of 500-700°C for 1 hour to obtain stable and uniform nano-scale ceramic powder; 1.2) Add a dispersant solution to the nano-scale ceramic powder, then add an excess of anhydrous ethanol to form a mixed solution, and ultrasonically disperse for 40-60 minutes. After uniform dispersion, dry the mixture, and grind the mixture to obtain uniformly granulated ceramic powder; 1.3) adding the uniformly granulated ceramic powder into an organic solvent and performing ball milling to prepare the slurry. During the ball milling process, the ball mill frequency is 30-45 Hz and the ball milling time is 10-60 min to obtain a ceramic slurry; 1.4) The ceramic slurry is evenly coated on the lower substrate of the screen to form a ceramic sheet. After the ceramic sheet on the surface of the lower substrate is fully solidified by constant temperature drying, the upper substrate is pressed on the ceramic surface to form a sandwich, and the sandwiched ceramic sheet is packaged by vacuum packaging; 1.5) After the packaged sample is cold isostatically pressed, the upper substrate is pushed open horizontally, and the ceramic sheet is peeled off from the lower substrate to obtain an unsupported ceramic sheet; 1.6) The unsupported ceramic sheet is sintered to obtain an unsupported ultra-thin ceramic sheet.

9. The method for preparing a multilayer ceramic capacitor by nano-bonding according to claim 1, characterized in that: The step (3) further includes external electrode packaging, wherein the external electrode packaging is performed by dispensing.

10. A multilayer ceramic capacitor and a method for preparing the same by nano-bonding, characterized in that: The nano-adhesive bonding preparation method is adopted according to any one of claims 1 to 9.