Microwave induction heating device and method for high speed simultaneous sintering of multilayer ceramic capacitors using the same

Abstract

The present invention relates to a method for rapid simultaneous sintering of multilayer ceramic capacitors using a microwave induction heating device, comprising the steps of: inserting one or more multilayer ceramic capacitors (MLCCs) into a transparent tube of the microwave induction heating device; creating a low vacuum state or an inert gas state inside the transparent tube of the microwave induction heating device; rapidly increasing the temperature from room temperature to a dielectric sintering temperature of the multilayer ceramic capacitors (MLCCs) at a predetermined heating rate using the microwave induction heating device; and maintaining the dielectric sintering temperature for a certain period of time and then naturally cooling the multilayer ceramic capacitors (MLCCs).

Description

[Technical field]

[0001] The present invention relates to a process for manufacturing multi-layer ceramic capacitors (MLCCs), and more particularly to a method for rapidly co-sintering multi-layer ceramic capacitors (MLCCs) using a microwave induction heating device. [Background technology]

[0002] Microwaves are a type of electromagnetic wave, also known as ultra-high frequency waves, with a wavelength of 1mm to 1m and a frequency of 300MHz to 300GHz. Microwaves were developed and used for radar during World War II, and have since been widely used in communication devices. Their use has increased, especially in mobile phones and wireless LANs. In 1946, during the development of radar, the phenomenon that microwaves can heat food rapidly was accidentally discovered, which led to the invention of the microwave oven. Microwave heating technology has been developed and applied not only for home use but also for industrial heating methods. In the mid-1980s, microwave heating began to be applied to chemical analysis, such as ashing, extraction, and digestion, and in 1986, chemical synthesis was attempted using microwave heating, and it was reported that the reaction occurred about 1,000 times faster than with conventional heating methods. In the 1990s, products developed by microwave chemical equipment manufacturers became more and more technologically advanced and came into widespread use.

[0003] One of the heating mechanisms by microwaves is the dipolar polarization heating mechanism, which is a process in which heat is generated from polar molecules and is the principle of dielectric heating. When polar molecules try to align themselves with the direction and phase of an electric field oscillating at an appropriate frequency, the forces between the molecules resist and they are unable to follow the electric field, which induces random molecular movement, which leads to the generation of heat. This heating mechanism can effectively heat water, organic solvents, oxides, etc.

[0004] Another heating mechanism by microwaves is the electric resistance heating mechanism, which is a principle where heat is generated by resistance to electric current. An oscillating electric field causes the vibration of electrons or ions in a conductor to generate an electric current, which generates heat due to internal resistance. This heating principle is due to the flow of electric current generated by an electric field, and can be called conduction heating. This microwave conduction heating can occur when a microwave electric field is applied to a non-dielectric conductive material with polar molecules such as water or an organic solvent. However, when a conductive material is present in a microwave resonator, it has a very large effect on the electromagnetic field distribution in the resonator depending on the conductivity value, size, or shape of the material. Metallic materials with very good conductivity reflect most of the microwaves and are hardly heated, and if they are sharp or thin, they are prone to discharge due to the phenomenon of electric field concentration, which can damage the material. Conductive materials with low conductivity such as graphite can be heated to a certain extent, but there is a risk of discharge depending on the size or shape, so there is a risk of discharge damage when attempting to heat at high temperatures with high output.

[0005] Induction heating, a conventional technique for heating conductive materials such as metals, is a technique that creates a magnetic field by winding a coil through which a current with a frequency of several tens of kHz flows, generating an induced current in nearby metals and heating them. In particular, if the metal is magnetic, it can be heated more effectively due to hysteresis loss. Induction heating is widely used in industrial applications such as metal heat treatment and high-temperature melting furnaces, and is also widely used in households as cookware. The penetration depth of the induced current generated on the metal surface in induction heating is closely correlated with the conductivity of the metal, but the higher the frequency, the lower the penetration depth. Usually, the frequency used for induction heating is several hundred kHz at most, so the penetration depth of the induced current in metals is about 1 mm, making it suitable for heating materials with a thickness of millimeters, such as cookware. However, thin conductive materials with a thickness of 1 μm or less are much thinner than the penetration depth of induced currents with frequencies of several tens to several hundred kHz, so the magnetic field penetrates the conductive material without generating much induced current, and cannot be heated. When attempting to heat thin conductive materials (i.e. conductive thin films) of less than 1 μm thickness using the electrical resistance heating mechanism of existing microwave heating, discharges are likely to occur due to the electric field concentrated at the ends of the conductive thin film, making it virtually unusable.

[0006] Microwave induction heating technology has been proposed to solve these problems. It is a new induction heating technology that uses a magnetic field in the microwave band used in microwave ovens to heat conductive materials. The penetration depth of the induced current in the metal surface of microwaves used in microwave ovens is about 1 um, so it is a technology suitable for heating very thin thin films of less than a few micrometers or nanometers. Microwave induction heating technology can selectively directly heat only the conductive thin films that require heat, and has a high efficiency of about 70% in converting electrical energy into thermal energy, making it a technology that can heat quickly and efficiently without wasting thermal energy.

[0007] Meanwhile, a multi-layer ceramic capacitor (MLCC) is a conductive material and is a representative passive element that accounts for about 60% of passive components in electronic devices such as mobile phones, personal PCs, notebook computers, and display devices. The MLCC can play various roles such as decoupling noise, removing DC components of signals, and smoothing signals in power supply circuits for active elements such as integrated circuits (ICs), and is an important passive element that is comparable to semiconductors, which are representative active elements. The MLCC is formed by alternately stacking ceramic dielectric layers that do not conduct electricity and internal electrode layers (e.g., Ni electrode layers) that conduct electricity.

[0008] Currently, the sintering process in the MLCC manufacturing process, which densifies the dielectric, is carried out at high temperatures of up to 1200°C for a long period of time of over 18 hours, making it a very important process in achieving the performance level and quality of the MLCC. Nickel (Ni), the electrode material, begins to sinter at over 800°C, while the dielectric begins to sinter at over 1200°C. Therefore, it is very important to prevent nickel (Ni) oxidation at the high temperature of 1200°C where the dielectric is sintered. For this reason, the oxygen partial pressure is set at approximately 10 -12 The electrodes and dielectric are sintered simultaneously in a reducing atmosphere at a temperature close to the melting point. However, high-temperature sintering in a reducing atmosphere causes oxygen vacancies in the oxide dielectric, which form Schottky junctions at the interface between the nickel (Ni) electrode and the dielectric, causing current leakage and insulation resistance degradation, ultimately leading to reliability problems in MLCC devices. Moreover, high-temperature sintering of the dielectric for a long period of time causes many process problems, such as nickel (Ni) diffusing into the dielectric layer, dielectric grain growth, and difficulty in introducing volatile dopants. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention aims to solve the above-mentioned problems and other problems, and to provide a microwave induction heating apparatus capable of simultaneously sintering a dielectric layer and an internal electrode layer of a multilayer ceramic capacitor (MLCC) at high speed using a magnetic field in the microwave band.

[0010] It is yet another object of the present invention to provide a method for rapid co-sintering of multi-layer ceramic capacitors (MLCCs) using a microwave induction heating device having a dielectric resonator of a predetermined shape. [Means for solving the problem]

[0011] In order to achieve the above or other objects, according to one aspect of the present invention, there is provided a method for rapid simultaneous sintering of multilayer ceramic capacitors using a microwave induction heating device, the method including: inserting one or more multilayer ceramic capacitors (MLCCs) into a transparent tube of a microwave induction heating device; creating a low vacuum state or an inert gas state inside the transparent tube of the microwave induction heating device; rapidly increasing a temperature from room temperature to a dielectric sintering temperature of the multilayer ceramic capacitors (MLCCs) at a predetermined heating rate using the microwave induction heating device; and maintaining the dielectric sintering temperature for a certain period of time and then naturally cooling the multilayer ceramic capacitors (MLCCs).

[0012] According to another aspect of the present invention, there is provided a microwave induction heating device including: a microwave input section to which microwaves are input; a microwave coupler coupled to the microwave input section to transmit the microwaves; a dielectric resonator having a through hole for inserting one or more conductive materials, and generating a resonant mode electromagnetic field pattern based on the microwaves transmitted from the microwave coupler to inductively heat the conductive materials; a microwave shielding container disposed to surround the dielectric resonator and blocking external leakage of the microwaves; and a temperature sensor disposed in the through hole of the dielectric resonator to measure a temperature of the conductive material. Effect of the Invention

[0013] The effects of the microwave induction heating apparatus and the method for rapid simultaneous sintering of multilayer ceramic capacitors (MLCCs) using the same according to the embodiment of the present invention will now be described.

[0014] According to at least one of the embodiments of the present invention, by performing high-temperature simultaneous sintering of multilayer ceramic capacitors (MLCCs) in a very short time using a microwave induction heating device, problems such as dielectric reduction, electrode oxidation, and electrode discontinuity that occur when performing the sintering for a long time in a conventional high-temperature heating furnace can be minimized, and a multilayer ceramic capacitor (MLCC) with higher performance and durability can be manufactured.

[0015] However, the effects that can be achieved by the microwave induction heating apparatus and the method for rapid simultaneous sintering of multilayer ceramic capacitors (MLCCs) using the same according to the embodiments of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those having ordinary skill in the art to which the present invention pertains from the following description. [Brief description of the drawings]

[0016] The accompanying drawings, which are included as part of the detailed description to aid in understanding the present invention, provide examples of the present invention and, together with the detailed description, explain the technical concepts of the present invention.

[0017] [Figure 1] 1 is a diagram referred to for explaining electric field patterns and magnetic field patterns in a dielectric resonator for implementing microwave induction heating according to the present invention. FIG. [Diagram 2] This is a diagram referred to in order to explain the electromagnetic field pattern change and surface induced current in a dielectric resonator for implementing microwave induction heating according to the present invention when the dielectric resonator is surrounded by a conductive material. [Diagram 3]FIG. 1 is a diagram referred to for explaining the position of a conductive material capable of microwave induction heating when a dielectric resonator for implementing microwave induction heating according to the present invention is surrounded by a conductive material. [Figure 4] FIG. 2 is a diagram referred to for explaining heating of a conductive material arranged on the central axis of a dielectric resonator for implementing microwave induction heating according to the present invention. [Diagram 5] 1 is a diagram illustrating a microwave induction heating device according to an embodiment of the present invention. [Figure 6] 1 is a diagram referred to for explaining the principle of induction heating of an electrode layer of an MLCC using a microwave induction heating device. [Figure 7] 1 is a flowchart illustrating a method for rapid simultaneous sintering of MLCCs using a microwave induction heating device. [Figure 8] FIG. 2 is a diagram referred to for explaining the rapid simultaneous sintering process of MLCCs by microwave induction heating. [Figure 9] FIG. 2 is a diagram referred to for explaining the rapid simultaneous sintering process of MLCCs by microwave induction heating. [Figure 10] FIG. 2 is a diagram referred to for explaining the mass sintering process of MLCCs by microwave induction heating. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The present invention will be described in detail below with reference to the accompanying drawings. In this case, the same components in each drawing are denoted by the same reference numerals as much as possible. Also, detailed description of already known functions and / or configurations will be omitted. The contents disclosed below will be described with a focus on parts necessary for understanding the operation of various embodiments, and description of elements that may make the gist of the description unclear will be omitted. Also, some components in the drawings may be exaggerated, omitted, or shown in a schematic manner. The size of each component does not entirely reflect the actual size, and therefore the contents described herein are not limited by the relative size or spacing of the components depicted in each drawing.

[0019] When describing the embodiments of the present invention, if it is determined that a detailed description of the known technology according to the present invention may make the gist of the present invention unclear, the detailed description will be omitted. The terms described below are defined in consideration of the functions of the present invention, and may vary depending on the intention or practice of the user or operator. Therefore, the definitions should be based on the contents of the entire specification. The terms used in the detailed description are merely for describing the embodiments of the present invention and should not be limiting in any way. Unless otherwise specified, expressions in the singular form include the plural form. In this description, expressions such as "include" or "comprise" are intended to represent any feature, number, step, operation, element, part or combination thereof, and should not be interpreted as excluding the presence or possibility of one or more other features, numbers, steps, operations, elements, parts or combinations thereof other than those described.

[0020] The present invention proposes a microwave induction heating device capable of simultaneously sintering a dielectric layer and an internal electrode layer of a multilayer ceramic capacitor (MLCC) at high speed using a microwave magnetic field.The present invention also proposes a method for simultaneously sintering a multilayer ceramic capacitor (MLCC) at high speed using a microwave induction heating device having a dielectric resonator of a predetermined shape.

[0021] Hereinafter, in this specification, conductive thin films, fine wires, conductive fibers, chip devices having thin film electrodes, etc. that are subject to induction heating using microwaves are collectively referred to as conductive materials.

[0022] Advanced devices such as displays, semiconductor devices, solar cells, and multilayer ceramic capacitors (MLCCs) all have thin-film electrodes. These devices require high-temperature heat treatment during the manufacturing process to create materials with the required performance, but existing heating methods often require long heat treatment times, resulting in low productivity and high energy consumption, or in many cases, heat treatment at a high enough temperature is not possible due to the heating temperature limit of the substrate. If such thin-film conductive materials could be selectively heated at high speed, it would be possible to achieve productivity and device performance that exceeds existing processes.

[0023] Various embodiments of the present invention will now be described in detail with reference to the drawings.

[0024] FIG. 1 is a diagram to be referred to for explaining electric field patterns and magnetic field patterns in a dielectric resonator for implementing microwave induction heating according to the present invention.

[0025] Among the components of a microwave induction heating device, the most important component for implementing microwave induction heating is the dielectric resonator, which generally uses a dielectric material with a dielectric constant of 3 or more and a loss tangent of 0.0005 or less.

[0026] As shown in Fig. 1, the electromagnetic field pattern of the basic resonant mode formed by the dielectric resonator 10 is composed of an electric field pattern (left diagram) that rotates with respect to the central axis of the dielectric resonator 10, and a magnetic field pattern (right diagram) that goes out along the central axis, goes around the outer periphery, and returns to the central axis. The electric field pattern of the dielectric resonator 10 has a value of 0 on the central axis, and approaches 0 and almost disappears when moving away from the outer periphery of the dielectric resonator 10 by a certain distance or more. When implementing microwave induction heating, the most important fact about the electromagnetic field pattern formed by the dielectric resonator 10 is that the electric field exists mainly in the form of a loop that rotates within the dielectric resonator 10, and the magnetic field exists in the form of a loop that comes out from the central axis, spreads around the outer periphery, and returns to the central axis.

[0027] FIG. 2 is a diagram to be referred to in order to explain the change in electromagnetic field pattern and surface induced current in a dielectric resonator for implementing microwave induction heating according to the present invention when the dielectric resonator is surrounded by a conductive material.

[0028] As shown in Fig. 2, when the dielectric resonator 20 is surrounded by a conductive material 21, the electromagnetic field pattern of the microwave is transformed into a compressed form in the internal space. At this time, due to the general boundary conditions of the electromagnetic field, only an electric field perpendicular to the surface of the conductive material 21 and a magnetic field parallel to the surface of the conductive material 21 can exist. As a result, when the dielectric resonator 20 is surrounded by the conductive material 21, no electric field exists in the conductive material 21, and only a magnetic field parallel to the surface of the conductive material 21 exists, and an induced current 22 is generated on the surface of the conductive material 21 by the magnetic field. The electromagnetic field of this pattern can ensure that the conductive material 21 is not exposed to the risk of discharge due to the electric field and is only inductively heated by the magnetic field.

[0029] FIG. 3 is a diagram to be referred to in order to explain the position of a conductive material capable of microwave induction heating when a dielectric resonator for implementing microwave induction heating according to the present invention is surrounded by a conductive material.

[0030] 3, when the dielectric resonator 30 is surrounded by a rectangular parallelepiped conductive material (or conductive thin film) 31, the position of the conductive material 31 that can be microwave-induced heated is the entire surface of the conductive material 31 located on the outer periphery of the top, bottom and side surfaces of the dielectric resonator 30. All positions of such conductive material 31 may be heated simultaneously, or only one side may be heated, and the other side may not be used for heating.

[0031] FIG. 4 is a diagram to be referred to for explaining heating of a conductive material disposed on the central axis of a dielectric resonator for implementing microwave induction heating according to the present invention.

[0032] The central axis of the dielectric resonator 40 is a region where no electric field exists, similar to the outer periphery, but where a strong magnetic field exists. Therefore, as shown in FIG. 4A, a region of 1 μm or less (or a sheet resistance of 0.1 Ω / m) placed on the central axis of the dielectric resonator 40 is 2 It is possible to effectively heat a conductive material 41 such as a metal or conductive thin film, fine wire, conductive fiber, nano-thin film, etc. having a thickness of 100 nm or more. Also, as shown in Fig. 4(b), it is possible to effectively heat a conductive material 42 in the form of a chip element having a thin film electrode placed on the central axis of a dielectric resonator 40.

[0033] Based on the above-mentioned principle, the dielectric resonator according to the present invention heats a material to be subjected to microwave induction heating (i.e., a material to be heated) with a magnetic field in the microwave band. For example, a material to be heated arranged on the upper surface side, lower surface side, side surface side, or central axis of the through hole of the dielectric resonator is induction heated with a magnetic field in the microwave band. The dielectric resonator may be formed in a cylindrical or hexagonal prism shape, a spherical shape, a rounded corner shape, a predetermined arbitrary shape without symmetry, a shape with a through hole in the center, a shape in which one resonator is divided vertically or horizontally and arranged at a predetermined distance apart, or a shape in which a plurality of resonators are combined. In the following embodiment, a dielectric resonator with a through hole formed in the center will be described.

[0034] Meanwhile, the material to be heated includes conductive materials at the micrometer level or less, such as metal or conductive thin films with a thickness of 1 μm or less, fine wires, conductive fibers, conductive oxides, nano-thin films such as carbon nanotubes and graphene, and chip devices having thin-film electrodes. The material to be heated may have various shapes, such as a flat surface, a spherical or curved surface, a cylindrical surface, or a combination thereof. Hereinafter, in this embodiment, the material to be subjected to microwave induction heating will be described as a multilayer ceramic capacitor (MLCC).

[0035] FIG. 5 is a diagram illustrating a microwave induction heating device according to one embodiment of the present invention, and FIG. 6 is a diagram referred to for explaining the principle of induction heating of an electrode layer of an MLCC using a microwave induction heating device.

[0036] 5 and 6, a microwave induction heating device 100 according to an embodiment of the present invention may include a microwave input unit 110, a microwave coupler 120, a dielectric resonator 130, a microwave blocking container 140, a temperature measurement port 150, a temperature sensor 160, and a transparent tube 170. Meanwhile, although not shown, the microwave induction heating device 100 may further include a control device for controlling the overall operations of the above-mentioned components 110 to 170.

[0037] The microwave input unit 110 is disposed in one area of ​​the microwave shielding container 140 and serves to input external microwaves into the microwave shielding container 140 .

[0038] The microwave input 110 may be in the form of a coaxial waveguide. For example, the microwave input 110 may be in the form of a coaxial waveguide that couples to a region of the microwave blocking vessel 140. The microwave input 110 may be in the form of a square or circular waveguide. The form of the microwave input 110 is preferably determined by the form of the microwave coupler 120.

[0039] The microwave coupler 120 is coupled to the microwave input section 110 and serves to transmit the microwave received from the microwave input section 110 to the dielectric resonator 130 .

[0040] The microwave coupler 120 may be, but is not limited to, a loop-shaped metal or a rod-shaped metal arranged at a predetermined distance from the dielectric resonator 130. The microwave coupler 120 may be arranged in a direction perpendicular to the longitudinal direction of the microwave input part 110 or in a direction parallel to the longitudinal direction of the microwave input part 110.

[0041] The microwave coupler 120 can adjust the distance between the dielectric resonator 130 and the coupler 120 (e.g., the end of the coupler can move along a predetermined guide) according to a control command from a control device (not shown) based on the coupling coefficient with the dielectric resonator 130, thereby adjusting the amount of microwaves transmitted to the dielectric resonator 130.

[0042] The dielectric resonator 130 generates an electromagnetic field pattern for implementing microwave induction heating and generates an induced current in the heating target element (i.e., multi-layer ceramic capacitor (MLCC) 200). In this case, the dielectric resonator 130 can generate an electric field pattern and a magnetic field pattern in a fundamental resonant mode.

[0043] The overall shape of the dielectric resonator 130 may be a columnar shape such as a cylinder, a rectangular parallelepiped, or a cube. The dielectric resonator 130 may be formed in a form in which a through hole for accommodating a transparent tube 170 in which a multilayer ceramic capacitor (MLCC) 200 is mounted is disposed in the center. The central axis of the dielectric resonator 130 is a region in which no electric field exists, similar to the outer periphery, and in which a strong and uniform magnetic field exists. Therefore, the multilayer ceramic capacitor (MLCC) 200 disposed in the through hole of the dielectric resonator 130 can be uniformly heated using a microwave band magnetic field formed in the direction of the central axis of the dielectric resonator 130.

[0044] The microwave shielding container 140 is disposed so as to surround the dielectric resonator 130, and serves to block microwaves from leaking to the outside. The microwave shielding container 140 can also have a function of adjusting the distance away from the dielectric resonator 130 (for example, a part / all of the side wall can move along a predetermined guide) according to a control command from a control device, and adjusting the resonant frequency of the electromagnetic field when the dielectric resonator 130 is in a resonant mode.

[0045] The overall shape of the microwave shielding container 140 may be a columnar shape such as a cylinder, a rectangular parallelepiped, a cube, etc. Also, the microwave shielding container 140 may be made of a metal material. The microwave shielding container 140 can be used as a tool for dealing with an error in the resonant frequency caused by the limit of the manufacturing accuracy of the dielectric resonator 130 or a change in the frequency of the supplied microwave.

[0046] The microwave blocking container 140 may include a first opening to which the microwave input unit 110 is coupled, a second opening to which the transparent tube 170 is coupled, and a third opening to which the temperature measurement port 150 is coupled. In this case, the first to third openings may be manufactured based on a cutoff frequency design so that microwave leakage does not occur. Thus, the first to third openings may be choke cavity-shaped openings that do not allow microwaves of a specific frequency to pass through.

[0047] The temperature measurement port 150 is disposed in one area of ​​the microwave shielding container 140 and serves to guide infrared rays emitted from the temperature sensor 160 toward the multilayer ceramic capacitor (MLCC) 200 .

[0048] The temperature sensor 160 is installed in an area adjacent to the temperature measurement port 150 and serves to measure the temperature of the multilayer ceramic capacitor (MLCC) 200 using infrared rays (IR).

[0049] The transparent tube 170 is a kind of loader and has a function of loading the multilayer ceramic capacitor (MLCC) 200 by moving it so that its heating portion is positioned at a predetermined distance from the dielectric resonator 130, or unloading the multilayer ceramic capacitor (MLCC) 200 after induction heating is completed so that it is removed from the heating position. Also, the transparent tube 170 has a space for accommodating the multilayer ceramic capacitor (MLCC) 200, and has a function of creating and maintaining a waiting environment for sintering the MLCC.

[0050] The transparent tube 170 may be formed to be inserted into a region of the microwave shielding container 140 or removed from the microwave shielding container 140. The transparent tube 170 may be disposed to cross a through-hole formed in the center of the dielectric resonator 130. The transparent tube 170 may be made of, but is not limited to, a quartz material having excellent heat resistance.

[0051] The MLCC 200 may be inserted from the outside through a transparent tube 170. In addition, since the MLCC 200 is heated to a high temperature of 1300° C. or more, a holder made of a material that can withstand high temperatures and does not absorb microwaves, such as alumina, can be used to insert and transport the MLCC 200.

[0052] The microwave induction heating device 100 uses a microwave magnetic field to generate an induced current in a conductive material, and heats the conductive material with the resulting resistance heat. For example, as shown in Fig. 6, when a microwave magnetic field 610 is applied to a multilayer ceramic capacitor (MLCC) 200, a rotating induced current 620 is generated in an internal electrode layer 250 made of nickel (Ni) metal, and the material can be heated. The thickness of the internal electrode layer of a general multilayer ceramic capacitor is 1 μm or less, so it can be heated very effectively using a microwave induction heating method, and the thickness of the dielectric layer between the internal electrode layers is several μm or less, so even if the dielectric layer is not directly heated, the heat generated in the internal electrode layer is conducted to the dielectric layer almost simultaneously, resulting in almost the same temperature.

[0053] As described above in detail, the microwave induction heating device according to an embodiment of the present invention can selectively heat the internal electrode layer of the multilayer ceramic capacitor (MLCC) arranged in the through hole of the dielectric resonator by using a magnetic field in the microwave band. In addition, the microwave induction heating device can simultaneously sinter the dielectric layer and the internal electrode layer of the multilayer ceramic capacitor (MLCC) at high speed by using a magnetic field in the microwave band.

[0054] In a long-term sintering process using a conventional heating furnace, the dielectric of a multilayer ceramic capacitor (MLCC) is usually sintered (fired) at about 1200°C. In contrast, in the sintering process using microwave induction heating according to the present invention, the temperature is raised to a maximum of 1300°C or more in order to quickly sinter the MLCC. The sintering process of a multilayer ceramic capacitor (MLCC) using microwave induction heating may be performed as follows.

[0055] Fig. 7 is a flow chart for explaining a method for rapid simultaneous sintering of MLCCs using a microwave induction heating device, and Fig. 8 is a diagram for explaining the rapid simultaneous sintering process of MLCCs by microwave induction heating. Hereinafter, the simultaneous sintering process described in this embodiment refers to a process carried out after a binder burnout process in the manufacturing process of a multilayer ceramic capacitor (MLCC).

[0056] 7 and 8, a microwave induction heating device having a dielectric resonator of a predetermined shape is provided (S710). At this time, the microwave induction heating device may include a transparent tube for accommodating a multilayer ceramic capacitor (MLCC). The transparent tube is a kind of loader, and has a function of moving the multilayer ceramic capacitor (MLCC) so that its heating portion is positioned at a predetermined distance from the dielectric resonator, and a function of unloading the multilayer ceramic capacitor (MLCC) after induction heating so that it is removed from the heating position.

[0057] A multilayer ceramic capacitor (MLCC) is inserted into a transparent tube of a microwave induction heating device (S720). Here, a plurality of dielectric layers and a plurality of internal electrode layers constituting the multilayer ceramic capacitor (MLCC) may be in a granular state.

[0058] The inside of the transparent tube of the microwave induction heating device is made into a low vacuum state or an inert gas state (S730), where the pressure of the low vacuum state may be 0.1 Torr or less.

[0059] Thereafter, the temperature is rapidly increased from room temperature to a temperature at which sintering of the dielectric layer of the multilayer ceramic capacitor (MLCC) starts (i.e., dielectric sintering start temperature, e.g., 1200°C) at a predetermined heating rate (or temperature increase rate) using a microwave induction heating device (S740). Here, the predetermined heating rate may be appropriately selected within a range of 5°C / s to 200°C / s, but is not necessarily limited thereto.

[0060] The heating speed of a multilayer ceramic capacitor (MLCC) is limited by the occurrence of cracks due to pressure caused by gasification of the residual binder, but the occurrence of cracks can be prevented by controlling the initial heating speed below a certain speed. The internal electrode layer of a multilayer ceramic capacitor (MLCC) begins to shrink as it sinters at about 800℃, which is lower than the sintering temperature of the dielectric layer, but in order to minimize the problem of electrode connection loss caused by the internal electrode layer shrinking before the dielectric layer, it is important to raise the temperature to the dielectric sintering temperature as quickly as possible.

[0061] When the temperature of the multilayer ceramic capacitor (MLCC) reaches the dielectric sintering start temperature, the dielectric sintering start temperature is maintained for a certain period of time using a microwave induction heating device (S750). Here, the time for which the dielectric sintering start temperature is maintained constant may be appropriately selected from a range of 1 second to 10 minutes, but is not necessarily limited thereto. Once the temperature reaches the temperature at which the dielectric layer starts to sinter, it is important to control the temperature so that the entire MLCC can be sintered uniformly and stably, and therefore, by maintaining the temperature for a certain period of time, the temperature deviation inside the MLCC can be minimized.

[0062] Finally, after maintaining the dielectric sintering start temperature for a certain period of time, the microwave induction heating is stopped and the MLCC is naturally cooled (S760). In this embodiment, it is preferable that the time (T) during which the temperature is maintained at about 800°C or higher, at which the internal electrode layer of the MLCC is oxidized, is within 10 minutes.

[0063] Meanwhile, as another embodiment, as shown in Fig. 9, when the temperature of the multilayer ceramic capacitor (MLCC) reaches the dielectric sintering start temperature, the dielectric sintering start temperature is maintained for a certain period of time, and then the temperature is increased to the maximum sintering temperature (e.g., 1300°C) at a predetermined heating rate. After maintaining the maximum sintering temperature for a certain period of time, microwave induction heating is stopped and the multilayer ceramic capacitor (MLCC) is allowed to cool naturally. At the maximum sintering temperature, the dielectric layer at the edge of the MLCC, farthest from the internal electrode layer where heat is generated, is completely sintered.

[0064] When the MLCC chips are stopped, the heating temperature can be controlled by controlling the microwave output. However, when MLCCs are to be sintered in a large volume, as shown in Fig. 10, the MLCCs are continuously loaded in a line and heating begins as they enter the dielectric resonator, and as the MLCCs are moved, the temperature of the MLCCs is rapidly increased from room temperature to the dielectric sintering temperature, and at the end of the dielectric resonator, the microwave output is controlled to accurately maintain a constant temperature while monitoring the temperature of the MLCCs with a temperature sensor, and the MLCCs can be naturally cooled as they leave the dielectric resonator.

[0065] The high-speed simultaneous sintering method of multilayer ceramic capacitors (MLCCs) by microwave induction heating according to the embodiment of the present invention can minimize problems such as dielectric reduction, electrode oxidation, and electrode discontinuity that occur when sintering is performed for 18 hours or more in a conventional high-temperature heating furnace, and can manufacture multilayer ceramic capacitors (MLCCs) with higher performance and durability. For example, when a multilayer ceramic capacitor (MLCC) for electric field is sintered within one minute using microwave induction heating technology, the continuity of the internal electrode layer is almost perfect at 99% or more, and the capacitance measurement by the external electrode shows an improvement in performance with a dissipation factor value reduced to a level of 28%. In addition, since only the multilayer ceramic capacitor (MLCC) is heated to a high temperature in a very short time, the sintering process can be performed using much less energy than in a conventional heating furnace, and the space occupied by the device is much smaller, so the associated costs are significantly less than those of the conventional method that requires a large space.

[0066] Although the present invention has been described above by using specific details such as specific components, and limited examples and drawings, these are merely provided to aid in a more comprehensive understanding of the present invention, and the present invention is not limited to the above examples, and various modifications and variations may be made by those skilled in the art to which the present invention pertains without departing from the essential characteristics of the present invention. Therefore, the idea of ​​the present invention should not be limited by the described examples, and all technical ideas that are equivalent or have equivalent modifications to the scope of the claims, in addition to the scope of the claims described below, should be interpreted as being included in the scope of the present invention.

Claims

1. A method for high speed simultaneous sintering of multilayer ceramic capacitors using a microwave induction heating device, comprising: Inserting one or more multilayer ceramic capacitors (MLCCs) into the transparent tube of the microwave induction heating device; creating a low vacuum state or an inert gas state inside the transparent tube of the microwave induction heating device; generating a microwave-band magnetic field in a dielectric resonator of the microwave induction heating device, and rapidly increasing a temperature of the multilayer ceramic capacitor (MLCC) from room temperature to a dielectric sintering temperature at a predetermined heating rate using the microwave-band magnetic field; and then allowing the multilayer ceramic capacitor (MLCC) to cool naturally after maintaining the dielectric sintering temperature for a certain period of time.

2. 2. The method of claim 1, wherein the low vacuum pressure is 0.1 Torr or less.

3. 2. The method of claim 1, wherein the heating rate is determined within a range of 5° C. / s to 200° C. / s.

4. 2. The method of claim 1, wherein the predetermined time is selected from the range of 1 second to 10 minutes.

5. 2. The method of claim 1, wherein the time during which the multilayer ceramic capacitor (MLCC) is kept at a temperature at which the internal electrode layers are oxidized is within 10 minutes.

6. The natural cooling step includes: maintaining the dielectric sintering temperature for a certain period of time, and then increasing the temperature to a maximum sintering temperature at a predetermined heating rate; 2. The method of claim 1, further comprising: maintaining the maximum sintering temperature for a certain period of time and then allowing the multilayer ceramic capacitor (MLCC) to cool naturally.

7. The step of charging comprises:

2. The method of claim 1, wherein the multilayer ceramic capacitor (MLCC) is moved using the transparent tube and loaded so that a heating portion of the MLCC is positioned at a predetermined distance from a dielectric resonator of the microwave induction heating device.

8. 2. The method of claim 1, further comprising the steps of continuously loading the multilayer ceramic capacitors (MLCCs) in a row into the transparent tube and sintering the loaded multilayer ceramic capacitors (MLCCs) while moving the loaded multilayer ceramic capacitors (MLCCs).

9. a microwave input section to which microwaves are input; a microwave coupler coupled to said microwave input for transmitting said microwaves; a dielectric resonator having a through hole for inserting one or more conductive materials therein, the dielectric resonator generating a resonant mode electromagnetic field pattern based on the microwaves transmitted from the microwave coupler to inductively heat the conductive materials; a microwave shielding container disposed to surround the dielectric resonator and blocking leakage of the microwaves to the outside; a temperature sensor for measuring a temperature of a conductive material disposed in the through hole of the dielectric resonator; the microwave shielding container includes at least one opening coupled to a transparent tube for receiving the conductive material; The at least one opening is formed in a choke cavity type structure so that microwaves of a specific frequency do not pass through, The transparent tube forms a waiting environment for sintering the MLCC.

10. 10. The microwave induction heating device according to claim 9, further comprising a temperature measurement port disposed in a region of the microwave blocking container and guiding infrared rays emitted from the temperature sensor toward the conductive material.

11. 10. The microwave induction heating device according to claim 9, wherein the transparent tube is made of quartz, which has excellent heat resistance.

12. 10. The microwave induction heating device of claim 9, further comprising a control device that adjusts a distance between the microwave coupler and the dielectric resonator based on a coupling coefficient between the microwave coupler and the dielectric resonator, and adjusts an amount of microwaves transmitted from the microwave coupler to the dielectric resonator.

13. The microwave induction heating device according to claim 12, wherein the control device adjusts a distance between the microwave blocking container and the dielectric resonator to adjust a resonant frequency of the microwave when the dielectric resonator is in a resonant mode.

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