JP2005093707A - Method for manufacturing lamination ceramic electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a lamination ceramic electronic component in which a resin is uniformly filled in the hole of a ceramic sintered body 10 at a desired filling factor. <P>SOLUTION: The resin is permeated into the ceramic sintered body 10 under vacuum in a state that the viscosity of the resin is low, and the resin adhered to the surface of the ceramic sintered body is cleaned with a solvent in a state that the viscosity of the resin is high. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a multilayer ceramic electronic component such as a multilayer inductor or a multilayer capacitor.

  2. Description of the Related Art Some multilayer ceramic electronic components such as multilayer inductors and multilayer capacitors having an internal electrode of a predetermined shape inside a ceramic sintered body impregnate a ceramic sintered body with a resin.

  For example, in the invention described in Patent Document 1, the electrical characteristics are prevented from deteriorating by impregnating the pores present on the surface of the sintered body with a resin. In the present invention, the surface is washed with gasoline after the chip is immersed in a mixed solution of a solvent (gasoline) and a silicone resin and vacuum impregnated.

In addition, although not disclosed yet, in the Japanese Patent Application No. 2003-91063, the present applicant has obtained a multilayer ceramic electronic component in which pores are formed in a ceramic sintered body at a rate of 35 to 80 vol%, and the pores are filled with a resin. is suggesting.
JP-A-5-326316

  In the technique described in Patent Document 1, the impregnation of the resin is performed to close the pores formed on the surface of the ceramic sintered body. On the other hand, in Japanese Patent Application No. 2003-91063, voids are positively formed in the ceramic sintered body by kneading and burning the burned material into the green sheet, and the voids are impregnated with resin or glass. It has been found that the electrical characteristics can be improved.

  In the invention described in Japanese Patent Application No. 2003-91063, since the porosity is relatively high as 35 to 80 vol%, it is more than ever to fill the resin at a desired ratio with respect to the pores. It is important from the viewpoint of securing electrical characteristics and bending strength, and it is particularly important to sufficiently fill not only the holes on the chip surface but also the holes in the center of the chip.

  Here, in the multilayer ceramic electronic component of Japanese Patent Application No. 2003-91063, when a method similar to Patent Document 1, that is, a method of vacuum impregnating a resin diluted with a solvent and washing the resin adhering to the surface with a solvent, The following problems occurred:

  That is, in general, the lower the viscosity of the resin, the more easily the pores inside the sintered body are sufficiently impregnated, and the higher the viscosity of the resin, the less elution in the washing step. Therefore, when a resin with low viscosity is used, the resin is likely to be impregnated relatively uniformly at a desired ratio up to the vicinity of the center of the sintered body in the vacuum impregnation step, but it is likely to be eluted by washing with a solvent. In addition, there is a problem that the resin impregnation rate decreases or becomes non-uniform near the surface. On the other hand, when a high-viscosity resin that hardly causes undesired elution by a solvent is used, there is a problem that the resin is not sufficiently and uniformly impregnated to the vicinity of the center of the sintered body in the vacuum impregnation step.

  Thus, when pores are formed at a relatively high rate in the ceramic sintered body, it is difficult to impregnate the resin uniformly at the desired rate, and the selection of the viscosity of the resin and the selection of the solvent used for cleaning are difficult. It is difficult to obtain desired characteristics.

  Accordingly, an object of the present invention is to provide a multilayer ceramic electronic component in which the resin near the center of the sintered body is sufficiently and uniformly filled, and the resin near the surface of the sintered body is less likely to cause undesired elution in a solvent cleaning process. It is to provide a manufacturing method.

  In order to solve the above problems, a method of manufacturing a multilayer ceramic electronic component according to the present invention includes a step of laminating a predetermined number of ceramic green sheets to form a multilayer body, and firing the multilayer body to form a ceramic sintered body. A step of impregnating the resin, including a step of forming, a step of impregnating a resin in pores existing in the ceramic sintered body, and a step of cleaning the resin adhering to the surface of the ceramic sintered body The viscosity of the resin in is lower than the viscosity of the resin in the step of washing the resin.

  Thus, the resin is sufficiently impregnated in the step of impregnating the resin into the pores, and the resin is impregnated at a desired ratio without causing undesired elution of the impregnated resin in the step of washing the resin. An impregnated laminated ceramic electronic component can be obtained.

  In the method for manufacturing a multilayer ceramic electronic component according to the present invention, in the step of impregnating the resin, the viscosity of the resin is made lower by heating the resin than in the step of washing the resin. Features.

  That is, the viscosity of the resin can be easily changed by changing the viscosity of the resin according to the temperature.

  Furthermore, the method for manufacturing a multilayer ceramic electronic component according to the present invention is characterized in that a burned-out material is kneaded in at least a part of the ceramic green sheet.

  In multilayer ceramic electronic parts that are intentionally formed with pores by kneading the burned material into the green sheet, the resin is sufficiently impregnated to the vicinity of the center of the sintered body, while preventing unwanted elution of the resin in the cleaning process. It was difficult. Therefore, the present invention becomes more effective by applying the present invention to such a multilayer ceramic electronic component.

  The method for manufacturing a multilayer ceramic electronic component according to the present invention includes a step of laminating a predetermined number of ceramic green sheets kneaded with at least a part of a fired material to form a multilayer body, and firing the multilayer body to form a ceramic. A step of forming a sintered body, a step of impregnating a resin in pores existing in the ceramic sintered body, and a step of cleaning the resin adhering to the surface of the ceramic sintered body. The viscosity of the resin in the step of impregnating the resin is 100 to 350 mPa · s, and the viscosity of the resin in the step of washing the resin is 1200 to 1500 mPa · s.

  As a result, in the multilayer ceramic electronic component in which pores are intentionally formed by kneading the burned material into the green sheet, the resin is sufficiently impregnated to the vicinity of the center of the sintered body, and undesired resin in the cleaning process is removed. Elution can be prevented.

  As described above, according to the present invention, it is possible to prevent the resin impregnated in the pores in the washing step from being undesirably eluted while sufficiently impregnating the pores with the resin, and to burn out the ceramic green sheet. The present invention is particularly effective when applied to a multilayer ceramic electronic component in which pores are intentionally formed by kneading.

  Examples of the present invention will be described below. FIG. 1 is a cross-sectional view schematically showing a multilayer coil as an example of a multilayer ceramic electronic component according to the present invention.

  The laminated coil includes a ceramic sintered body 10 provided with a coil conductor 20 therein, and external electrodes 30 formed on both end surfaces of the ceramic sintered body 10 and electrically connected to the coil conductor 20. FIG. 2 is a view showing a cross section of the ceramic sintered body. The ceramic sintered body 10 is formed with 35 to 80 vol% voids 40, and the voids 40 are filled with a resin 50. In the present invention, the porosity is given by the following formula (1).

Porosity = 1-{(X / Y) / Z} (1)
Here, X is the weight of the ceramic sintered body 10, Y is the volume of the ceramic sintered body 10, and Z is the theoretical density of the ceramic sintered body 10. Note that the porosity determined by this equation is not unavoidably generated by sintering in addition to the pores 40 intentionally formed by adding a burned-out material as will be described later. Air bubbles).

  The pores 40 have an average diameter of 5 to 20 μm. The holes 40 include open holes (open pores) and closed holes (closed pores). Of the holes 40, 30 to 70 vol% is filled with the resin 50. The filling rate (vol%) of the resin 50 with respect to the pores 40 is obtained by first obtaining the porosity of the ceramic sintered body 10 before impregnation of the resin 50 from the above formula, and the weight of the ceramic sintered body 10 after impregnation of the resin 50 From the increase, the volume of the ceramic sintered body 10 and the specific gravity of the resin 50, the volume of the resin 50 impregnated with respect to the volume of the ceramic sintered body 10 is obtained, and this is divided by the porosity.

  Here, the manufacturing method of this laminated coil is demonstrated. First, an oxide such as Fe, Ni, Cu, and Zn is mixed at a predetermined ratio, calcined at 800 ° C. for 1 hour, pulverized by a ball mill, and dried to obtain a ferrite powder raw material. To the obtained ferrite powder raw material, a binder, a dispersant, and a solvent are added, and a commercially available spherical polymer (burned material) is added and mixed so as to have a predetermined porosity (35 vol% here). A ceramic green sheet having a thickness of 40 μm was prepared by a doctor blade method. The burned-out material used had an average particle size of 7-8 μm.

By adopting a spherical polymer with a large surface area and shape retaining property and excellent adhesion to the binder as a burned-out material for forming pores, the ratio of the burned-out material can be reduced by reducing the binder ratio without reducing the yield. The ratio can be increased, and the porosity can be increased.

  Next, as shown in FIG. 3, a conductor pattern 21 and a via hole 22 having a predetermined shape are formed on the ceramic green sheet 11 with a conductive paste. A coil conductor 20 is formed by the conductor pattern 21 and the via hole 22 that connects predetermined ends of the conductor pattern 21. Further, both ends of the coil conductor 20 are drawn out to the end face of the ceramic sintered body 10 by the via holes 23. These ceramic green sheets 11 are laminated, pressed and cut into a predetermined size.

  Here, all the ceramic green sheets 11 are kneaded with the burned material, but ceramic green sheets 11 that are not kneaded with the burned material may be used in combination.

The resulting laminate was heat treated at 400 ° C. for 3 hours to remove the binder,
By firing at 5 ° C. for 2 hours, a ceramic sintered body having a porosity of 35 vol% was obtained. The ratio of the pores can be adjusted by changing the amount of the organic material (particularly the burned-out material) to be mixed.

  Next, a conductive paste containing Ag as a main component is baked at 850 ° C. on both end faces of the ceramic sintered body 10 as a base for the external electrode 30.

  Next, the laminate 10 is immersed in a solvent in which the epoxy resin 50 is diluted with an organic solvent so as to have a predetermined viscosity, and defoamed using a vacuum pump. In this state, vacuum impregnation was performed for about 10 minutes, and the pores 40 were filled with epoxy resin. At this time, the epoxy resin was impregnated by heating to 50 ° C. to lower the viscosity.

  After cooling to room temperature (25 ° C.), the resin adhering to the surface of the ceramic sintered body was washed with alcohol. At this time, since the epoxy resin is at room temperature, the viscosity is higher than that during the above-described vacuum impregnation.

  After cleaning, the epoxy resin is cured for several hours at 120 ° C., and Ni plating and Sn plating are applied to the base of the external electrode to complete the laminated coil shown in FIG.

  Here, the following experiment was conducted to confirm the effect of the present invention. First, the laminated coil is formed by the above-described process using an epoxy resin having a viscosity at the time of heating at 50 ° C., that is, a viscosity at the time of resin impregnation of 320 mPa · s and a viscosity at room temperature (25 ° C.), that is, a viscosity at the time of washing of 1000 mPa · s. Created (Example 1). In addition, a laminated coil was formed by the above-described process using an epoxy resin having a viscosity of 250 mPa · s when heated at 50 ° C. and a viscosity of 1200 mPa · s at room temperature (Example 2). Furthermore, as a comparative example, using a resin having a viscosity at room temperature of 1200 mPa · s, both vacuum impregnation and cleaning were performed at room temperature to prepare a laminated coil (comparative example).

  About each of these, the resin impregnation rate, the bending strength, and the characteristic change rate were measured. The characteristic change rate was obtained by the following equation (2) by performing a humidity resistance test for 100 hours under the conditions of 120 ° C., humidity 100%, and 2 atm, measuring the impedance at 100 MHz before and after the moisture resistance test.

Characteristic change rate = (B−A) / A (2)
Here, A is the impedance before the moisture resistance test, and B is the impedance after the moisture resistance test.

  Table 1 shows the resin impregnation rate, bending strength, and property change rate of Examples 1 and 2 and Comparative Example.

  In both Examples 1 and 2, the resin impregnation rate was higher than that of the comparative example, but this is because the viscosity at the time of vacuum impregnation is lower than that of the comparative example. Is due to impregnation. It can be seen that since the resin was uniformly impregnated into the pores near the center, both the bending strength and the moisture resistance were increased.

  Note that the resin impregnation rate in Example 2 was higher than that in Example 1 because the viscosity of the epoxy resin at the time of washing was higher in Example 2, so that an undesired resin from the pores near the ceramic sintered body surface. This is because elution of is difficult to occur.

  In the present invention, when the pores are formed by mixing the burned material with the ceramic green sheet, the viscosity of the resin when impregnated with the resin is preferably 100 to 350 mPa · s. If a resin with a lower viscosity is used, the impregnated resin may flow down, and if a resin with a higher viscosity is used, the resin may not be impregnated to the center of the sintered body. is there.

  In addition, when the pores are formed by mixing the burned material with the ceramic green sheet, the viscosity of the resin during the cleaning is preferably 500 to 1500 mPa · s, and the viscosity of the resin during the cleaning is 1200 to 1500 mPa · s. More preferably, s. If the viscosity of the resin is lower than this, the resin may be undesirably eluted by the solvent. If the viscosity of the resin is higher than this, the resin adhering to the surface of the sintered body will be sufficiently removed. There is a risk that it will not be.

  In the above embodiment, the ceramic sintered body is a ferrite sintered body, but may be a dielectric. Moreover, although epoxy resin was used as resin, you may use a phenol resin and a silicone resin. Furthermore, although alcohol was used to wash the resin adhering to the surface of the sintered body, any other liquid may be used as long as it has an action of dissolving the resin. A solvent can be used. In addition, it goes without saying that various modifications may be made to the above-described embodiments within the scope of the present invention.

It is sectional drawing which shows the laminated coil of this invention typically. It is sectional drawing which shows the ceramic sintered compact of the laminated coil of this invention. It is a perspective view which shows the laminated structure of the laminated coil of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Ceramic sintered body 11 Ceramic green sheet 20 Coil conductor 21 Conductor pattern 22, 23 Via hole 30 External electrode 40 Hole 50 Resin (epoxy resin)

Claims (4)

A step of laminating a predetermined number of ceramic green sheets to form a laminate;
Firing the laminate to form a ceramic sintered body;
Impregnating a resin into pores present in the ceramic sintered body;
Cleaning the resin adhering to the surface of the ceramic sintered body,
The method for producing a multilayer ceramic electronic component, wherein the viscosity of the resin in the step of impregnating the resin is lower than the viscosity of the resin in the step of washing the resin.   2. The method of manufacturing a ceramic electronic component according to claim 1, wherein in the step of impregnating the resin, the resin is heated to lower the viscosity of the resin than in the step of washing the resin. A method for producing a multilayer ceramic electronic component.   3. The method for manufacturing a ceramic ceramic electronic component according to claim 1, wherein at least a part of the ceramic green sheet is kneaded with a burned-out material. A step of forming a laminate by laminating a predetermined number of ceramic green sheets kneaded with at least a part of the burned material;
Firing the laminate to form a ceramic sintered body;
Impregnating a resin into pores present in the ceramic sintered body;
Cleaning the resin adhering to the surface of the ceramic sintered body,
In the multilayer ceramic electronic component, the viscosity of the resin in the step of impregnating the resin is 100 to 350 mPa · s, and the viscosity of the resin in the step of cleaning the resin is 1200 to 1500 mPa · s. Production method.

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