JP2007013029A - Manufacturing method of multilayer ceramic electronic component and multilayer ceramic electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain with high efficiency a laminated ceramic electric component which can prevent a plating liquid or water from entering a ceramic raw body, has excellent humidity resistance, and does not have a structural defect. <P>SOLUTION: In a method for manufacturing the laminated ceramic electronic component by forming conductive films by dipping both end surfaces of the ceramic raw body 1 in which an internal electrode 3 is buried in conductive paste, forming substrate electrodes 4a and 4b on both the end surfaces of the ceramic raw body 1 by baking the conductive films, and then forming external electrodes 2a and 2b by coating the substrate electrodes 4a and 4b with plating films 5a and 5b, and 6a and 6b; both the end surfaces of the ceramic raw body 1 are formed into concave surfaces, so that the size ratio A/B of the maximum dimension to the minimum dimension A between the end surfaces 1a and 1b of the ceramic raw body 1 is 0.985 to 0.990. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a multilayer ceramic electronic component such as a multilayer ceramic capacitor, and a multilayer ceramic electronic component manufactured by the manufacturing method.

  A multilayer ceramic electronic component such as a multilayer ceramic capacitor has an internal electrode embedded in a ceramic body, and ground electrodes are formed on both end faces of the ceramic body, and the ground electrode is covered with a plating film. The electrode and the plating film constitute an external electrode.

  As a base electrode forming method, a dip method has been widely used conventionally.

  In this dip method, as shown in FIG. 5A, the ceramic body 101 is immersed in a conductive paste layer 104 formed on the surface plate 103 with one end face 101a of the ceramic body 101 facing down. Then, as shown in FIG. 5B, the ceramic body 101 is pulled upward and dried, and then the ceramic body 101 is turned upside down and immersed in the conductive paste layer 104 also on the other end face 101b. A conductive paste is applied and dried, and then a baking process is performed, thereby forming a base electrode.

  However, in this base electrode forming method, immediately after being immersed in the conductive paste layer 104, as shown in FIG. 6A, the conductive paste wets the vicinity of the end surface 101a of the ceramic body 101 (in the drawing, As shown in FIG. 6B, when the ceramic body 101 is pulled upward, the conductive film 105 is moved in the direction of the arrow d by its own weight as shown in FIG. 6B. It hangs down. At this time, since the conductive film 105 is in contact with the ceramic body 101, the wet dimension e does not vary greatly. However, if this state is left to dry the conductive film 105, the conductive film 105 becomes thicker at the substantially central portion l with the passage of time, and the thickness w in the other portions, particularly in the vicinity of the end face corners, is reduced. . In this state, the conductive film 105 is baked and solidified to form a base electrode.

  However, when the thickness w near the corners of the end face is reduced, the ceramic body is immersed in a plating solution in a subsequent plating process, or the product is exposed to a multilayer ceramic electronic component under high temperature and high humidity for a long time. Moisture permeates into the ceramic body and the interface between the internal electrode and the ceramic layer, or into the voids in the external electrode, resulting in a problem that various characteristics as an electronic component are deteriorated.

  On the other hand, Patent Document 1 proposes a multilayer ceramic electronic component in which both end surfaces of a ceramic body (ceramic sintered body) are concave surfaces.

  In Patent Document 1, since both end surfaces of the ceramic body are concave surfaces, even if the conductive paste hangs down due to its own weight, the film thickness of the base electrode, in particular, the film thickness in the vicinity of the corners of the end surface is somewhat increased. It is thought that it can be secured.

JP 2000-49032 A

  However, in Patent Document 1, since both end faces of the ceramic body are concave surfaces in order to avoid the so-called tombstone phenomenon, the depth of the concave surface, that is, the amount of dents is small. There is a problem in that a sufficient thickness of the base electrode near the end face cannot be secured.

  That is, the tombstone phenomenon is a phenomenon in which, when the end surface portion of the ceramic body is rolled into an R shape, the multilayer ceramic electronic component rises before the solder is solidified when the multilayer ceramic electronic component is mounted on the printed circuit board. However, in Patent Document 1, since both end faces of the ceramic body are formed in a concave surface in order to cope with such a tombstone phenomenon, the amount of recesses in the concave surface may be relatively small. In the case of a multilayer ceramic capacitor having a length of 1.6 mm, a width of 0.8 mm, and a thickness of 0.8 mm, a dent amount of 3 μm is sufficient. And if the amount of dents is increased, the production cost is increased and the manufacturing process becomes complicated. Therefore, it is not normally considered to increase the amount of dents more than necessary.

  However, according to the experiment results of the present inventors, with the amount of dents disclosed in Patent Document 1, it is not possible to ensure a sufficient film thickness in the vicinity of the corners of the end face of the base electrode. If exposed to high humidity for a long time, the plating solution and moisture enter the ceramic body and the interface between the internal electrode and the ceramic layer, resulting in deterioration of moisture resistance and causing structural defects such as delamination and cracks. It has been found.

  On the other hand, if the thickness of the base electrode is increased in order to ensure the thickness of the base electrode at the corners of the both end faces of the ceramic body, the consumption of the conductive paste is increased, resulting in an increase in cost. The shape may also be distorted.

  The present invention has been made in view of such problems, and can prevent the plating solution and moisture from entering the inside of the base electrode, has good moisture resistance, and has structural defects. It is an object of the present invention to provide a method for manufacturing a multilayer ceramic electronic component that can obtain a multilayer ceramic electronic component that does not have a high efficiency, and a multilayer ceramic electronic component manufactured using the manufacturing method.

  The present inventor conducted intensive research to achieve the above object, and as a result, both end faces of the ceramic body were processed into a concave shape, and the minimum dimension A and the maximum dimension B between the end faces processed into the concave shape were determined. By setting the ratio A / B to 0.985 to 0.990, there is no penetration of plating solution or moisture into the inside through the base electrode, it has good moisture resistance, and structural defects are generated. The knowledge that the suppressed multilayer ceramic electronic component can be obtained was obtained.

  The present invention has been made on the basis of such knowledge, and the method of manufacturing a multilayer ceramic electronic component according to the present invention includes a conductive paste in which both end faces of a ceramic body in which internal electrodes are embedded are immersed in a conductive paste. A multilayer ceramic electronic in which a film is formed and then the conductive film is baked to form a base electrode on both end faces of the ceramic body, and then the base electrode is covered with a plating film to form an external electrode. In the part manufacturing method, both end faces of the ceramic body are concave so that a dimensional ratio A / B between the minimum dimension A and the maximum dimension B between the end faces of the ceramic body is 0.985 to 0.990. It is characterized by forming.

  A multilayer ceramic electronic component according to the present invention is manufactured by the above manufacturing method.

  According to the method for manufacturing a multilayer ceramic electronic component and the multilayer ceramic electronic component of the present invention, the dimensional ratio A / B between the minimum dimension A and the maximum dimension B between the end faces of the ceramic body is 0.985 to 0.990. Thus, since the both end surfaces of the ceramic body are formed in a concave shape, the amount of the recesses is moderately large, the surface area of the end surface is also increased, and sagging due to the weight of the conductive film can be prevented. Therefore, the base electrode can secure a desired film thickness even in the vicinity of the corners of the end face, even if the ceramic body is immersed in a plating solution, or even if the multilayer ceramic electronic component as a product is exposed to high temperature and high humidity for a long time, A multilayer ceramic electronic component that can prevent the plating solution and moisture from entering the inside of the ceramic body and the interface between the internal electrode and the ceramic layer, has good moisture resistance, and can suppress the occurrence of structural defects is obtained. be able to. In addition, since the lower limit of the dimension ratio A / B is set to 0.985 or more so that the amount of dents does not become excessively large, fine cavities (pinholes) are not formed inside the external electrode.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic perspective view showing an embodiment of a multilayer ceramic capacitor as a multilayer ceramic electronic component manufactured by the manufacturing method according to the present invention. The multilayer ceramic capacitor is a dielectric material such as BaTiO _3. External electrodes 2a and 2b are formed on both ends of the ceramic body 1 made of

  2 is a cross-sectional view taken along the line XX of FIG.

  That is, internal electrodes 3 a to 3 f mainly composed of Ni or the like are arranged in parallel in the stacking direction inside the ceramic body 1, and Cu, Ag—Pd, or the like is mainly disposed at both ends of the ceramic body 1. The base electrodes 4a and 4b are formed, and Ni coatings 5a and 5b are formed on the surface of the base electrodes 4a and 4b from the viewpoint of improving heat resistance. Alternatively, the Ni coatings 5a and 5b are formed from the viewpoint of improving wettability. Sn surfaces 6a and 6b are formed by plating on the surface, and the base electrodes 4a and 4b, Ni coatings 5a and 5b, and Sn coatings 6a and 6b constitute external electrodes 2a and 2b. The internal electrodes 3a, 3c, 3e are electrically connected to the base electrode 4b, the internal electrodes 3b, 3d, 3f are electrically connected to the base electrode 4a, and the internal electrodes 3a, 3c, 3e and the internal electrode 3b, Capacitance is formed between the surfaces facing 3d and 3f.

  Furthermore, in the present embodiment, both end faces 1a, 1b of the ceramic body 1 are formed in a concave shape, and the dimensional ratio A / B between the minimum dimension A and the maximum dimension B between the end faces is 0.985-0. .990.

  That is, when the end face of the ceramic body 1 is formed in a substantially flat shape, when the base electrodes 4a and 4b are formed by dipping in the paste layer as described later, As described in the section, the applied conductive paste hangs down under its own weight and collects in the vicinity of the center, so that the film thickness at the end face corners becomes thin. Therefore, if the plating solution penetrates into the ceramic body 1 in the subsequent plating step, or if it is exposed to high temperature and humidity for a long time, moisture penetrates into the ceramic body and impairs moisture resistance. As a result, the electrical characteristics of the multilayer ceramic capacitor may be deteriorated.

  Therefore, in the present embodiment, the end faces 1a and 1b of the ceramic body 1 are formed in a concave shape, thereby ensuring the film thickness in the vicinity of the end face corners.

  The reason why the dimensional ratio A / B is set to 0.985 to 0.990 is as follows.

  When the dimensional ratio A / B is less than 0.985, the concave shape of the end face becomes acute, and when baking is performed after coating, a fine cavity, that is, a pinhole is formed near the deepest portion of the concave shape. There is a risk that a plating solution or moisture may enter through the pinhole. On the other hand, if the dimensional ratio A / B exceeds 0.990, the desired effect cannot be achieved, and the film thickness at the corners of the end faces of the base electrodes 4a and 4b becomes thin, so that the plating solution and moisture can enter. May be incurred.

  Therefore, in this embodiment, the dimensional ratio A / B is set to 0.985 to 0.990.

  Next, a method for manufacturing the multilayer ceramic capacitor will be described in detail.

First, a predetermined amount of ceramic raw materials such as BaCO ₃ , CaCO ₃ , SrCO ₃ , TiO ₂ , ZrO ₂ are weighed, and then these ceramic raw materials are put into a ball mill, mixed and pulverized in a wet manner, and then dried. Then, a calcination process is performed under a predetermined condition to obtain a dielectric ceramic raw material.

  Next, an organic binder and an organic solvent are added to the dielectric ceramic raw material and wet-mixed in a ball mill to produce a ceramic slurry. The ceramic slurry is then molded using a molding method such as a doctor blade method. Then, it is cut into a predetermined size to obtain a rectangular ceramic green sheet.

  Next, a conductive paste for internal electrodes containing Ni as a main component is applied onto the ceramic green sheet using a screen printing method or the like to form a conductive pattern.

  Next, a plurality of ceramic green sheets on which conductive patterns are formed are stacked in a predetermined direction, sandwiched between ceramic green sheets on which conductive patterns are not formed, and pressed to produce a ceramic stacked body.

  Thereafter, the ceramic laminate is subjected to a binder removal process under a predetermined condition, and then subjected to a firing process under the predetermined condition, thereby obtaining the ceramic body 1 in which the internal electrode 3 is embedded.

  Next, the end faces 1a and 1b are processed into a concave shape so that the dimensional ratio A / B between the end faces of the ceramic body 1 is 0.985 to 0.990.

  As a method of processing the end surfaces 1a and 1b into a concave shape, a method of cutting the end surfaces 1a and 1b of the ceramic body 1 using a convex blade, or sandblasting or laser beaming the end surfaces 1a and 1b. There is a method of processing with a drilling machine or the like.

  Next, as shown in FIG. 3, the ceramic body 1 having an end surface formed in a concave shape is immersed in a paste layer 8 having Cu as a main component formed on the surface plate 7 as shown in FIG. The ceramic body 1 is pulled up and dried, and then the ceramic body 1 is inverted and the other end face is immersed in the paste layer 8 and then subjected to baking treatment to form the base electrodes 4a and 4b.

  FIG. 4 is a view showing the formation process of the conductive film 9 to be the base electrode 4a over time.

  That is, immediately after the ceramic body 1 is immersed in the paste layer, as shown in FIG. 4A, the conductive paste wets up in the vicinity of the end face 1a of the ceramic body 1 (indicated by the wetting dimension E in the figure). ), The conductive film 9 is formed. When the ceramic body 1 is lifted upward, immediately after the pulling, the conductive film 9 is dispersed in the direction of arrow D as shown in FIG. Becomes elliptical. Next, when the conductive film 9 is dried by leaving this state, the conductive film having a thickness L at a substantially central portion and a thickness W in the vicinity of an end face corner portion that can prevent infiltration of a plating solution or moisture. 7 is formed, and the base electrode 4a in which a desired film thickness is secured by the baking process can be obtained.

  Thereafter, electrolytic plating is performed to form Ni coatings 5a and 5b on the surfaces of the base electrodes 4a and 4b, and Sn coatings 6a and 6b are further formed on the surfaces of the Ni coatings 5a and 5b. Is manufactured.

  Thus, in the present embodiment, both end faces of the ceramic body 1 are concave so that the dimensional ratio A / B between the minimum dimension A and the maximum dimension B between the end faces 1a and 1b is 0.985 to 0.990. Since it is processed into a shape, even if a conductive paste is applied to the end faces 1a and 1b by the dipping method, it is possible to suppress the conductive paste from sagging under its own weight as much as possible. The film thickness at the end face corners can be ensured so that liquid and moisture can be prevented from entering, and the occurrence of structural defects and deterioration in moisture resistance can be prevented.

  In addition, in order to secure the film thickness at the end face corners, it is not necessary to increase the film thickness of the base electrodes 4a and 4b more than necessary, so that the paste consumption can be reduced and the cost can be reduced. The shape can also be good.

  The present invention is not limited to the above embodiment. In the above embodiment, the Ni films 5a and 5b and the Sn films 6a and 6b are formed by plating on the surfaces of the base electrodes 4a and 4b. However, Cu, solder, or the like may be formed by plating.

  In the above embodiment, the multilayer ceramic capacitor has been described. However, the multilayer ceramic capacitor can be applied as long as the base electrode is formed by a dip method. For example, the multilayer ceramic capacitor is also applicable to various multilayer ceramic electronic components such as a multilayer piezoelectric component. Needless to say, you can.

  Next, examples of the present invention will be specifically described.

First, a predetermined amount of BaCO ₃ and TiO ₂ as ceramic raw materials are weighed, and then these ceramic raw materials are put into a ball mill, wet mixed and pulverized, and then subjected to a drying process in an air atmosphere at 800 to 1300. A calcining treatment was performed at a temperature of about 2 hours for about 2 hours to obtain a dielectric ceramic material made of BaTiO ₃ .

  Next, an organic binder and an organic solvent are added to the dielectric ceramic raw material and wet mixed in a ball mill to produce a ceramic slurry. The ceramic slurry is then fired using a doctor blade method to a film thickness of 3 μm. Then, it was cut into a predetermined size to obtain a rectangular ceramic green sheet.

  Next, a conductive paste for internal electrodes containing Ni as a main component was screen-printed on a ceramic green sheet to form a predetermined conductive pattern.

  Next, a plurality of ceramic green sheets on which conductive patterns were formed were laminated in a predetermined direction, sandwiched between ceramic green sheets on which conductive patterns were not formed, and pressed to produce a ceramic laminate. The effective number of laminated ceramic green sheets was 300.

  After that, the ceramic laminate is heated to a temperature of about 500 ° C. in an air atmosphere to burn the organic binder, and further subjected to a firing treatment at a temperature of 850 to 1000 ° C. in a predetermined reducing atmosphere. A ceramic body with embedded internal electrodes was obtained.

  Next, the end surface was processed into a concave shape by sand blasting so that the ceramic body had a dimension between end surfaces as shown in Table 1.

  Next, a paste layer having a thickness as shown in Table 1 is formed on a surface plate, and one end surface of the ceramic body is immersed in the paste layer and dried, and then the ceramic body 1 is inverted to the other end surface. Was immersed in the paste layer, dried, and then subjected to a baking treatment. Sample No. 1 having a length of about 3.2 mm, a width: about 2.5 mm, and a thickness: about 2.5 mm where the base electrode was formed. ~ 15 samples were made.

Next, 72 samples were left to stand for 1000 hours under high temperature and high humidity at a temperature of 70 ° C. and a relative humidity of 95% to conduct a moisture resistance test. Next, the capacitance and dielectric loss tan δ before and after the moisture resistance test were measured with a capacitor meter (4268A manufactured by Hewlett-Packard Company), and the insulation resistance was measured by applying a voltage of 6.3 V for 120 seconds using an insulation resistance measuring machine. IR was measured. A product that does not satisfy any of the following: the capacitance change rate before and after the moisture resistance test is within 30%, the dielectric loss tan δ is 40% or less, and the insulation resistance IR is 2.5 × 10 ⁵ Ω or more. The number was counted and the moisture resistance was evaluated.

  In addition, the cross section of 200 samples was observed with an electron microscope to confirm whether or not pinholes were formed in the recesses of the base electrode, and the samples with pinholes were counted.

  Table 1 shows the dimensions between the end faces, the paste layer thickness, the minimum film thickness and the maximum film after baking of the base electrode, the number of moisture resistance defects, and the number of pinholes generated.

  Here, the maximum film thickness indicates an average value of the film thickness of the base electrode at a position corresponding to the B dimension of the ceramic body (see FIG. 2), and the minimum film thickness is the A dimension of the ceramic body (FIG. 2). The average value of the film thickness of the base electrode at the position corresponding to (reference) is shown.

この表１から明らかなように、試料番号１〜３は、端面が略平坦状に形成されているため、下地電極の最小膜厚が３〜８μｍと薄く、このため、水分がセラミック素体内部に浸入し、耐湿性不良が認められる試料が生じることが分かった。 In addition, the dimension between end faces was measured with a micrometer. The minimum film thickness and the maximum film thickness of the base electrode were measured by polishing the cut surface of the multilayer ceramic capacitor and expanding the image data 200 times. Specifically, the minimum film thickness was obtained by measuring the thickness of the base electrode at the corner of the ceramic body in the cross section of the multilayer ceramic capacitor. The maximum film thickness was obtained by measuring the thickness of the base electrode at the deepest portion of the end face recess of the ceramic body in the cross section of the multilayer ceramic capacitor.

As apparent from Table 1, since the end faces of Sample Nos. 1 to 3 are formed in a substantially flat shape, the minimum film thickness of the base electrode is as thin as 3 to 8 μm. It was found that a sample infiltrating into the slag and having poor moisture resistance was produced.

  Sample Nos. 4 to 6 have a dimensional ratio A / B of 0.995 and the end face is formed in a slightly concave shape, so the incidence of poor moisture resistance tends to decrease, but poor moisture resistance. The occurrence rate could not be “0”.

  In Sample Nos. 13 to 15, since the dimensional ratio A / B was 0.980 and less than 0.985, air remained in the recesses, and samples having pinholes were confirmed. Further, as shown in Sample Nos. 14 and 15, it was found that when the dimensional ratio A / B is reduced to 0.980, the minimum film thickness is also reduced, resulting in a sample with reduced moisture resistance. This is presumably because the paste that should go around to the end face side is absorbed by the recess.

  On the other hand, since sample numbers 7 to 12 have a dimensional ratio A / B of 0.985 to 0.990, it was confirmed that moisture resistance could be secured and pinholes were not generated. In particular, as is clear from Sample Nos. 9 and 12, it was found that even if the paste layer was made as thin as 30 μm, a minimum film thickness of 10 μm could be ensured, and good moisture resistance could be obtained.

  Further, from the results of Table 1, it was also found that a decrease in moisture resistance can be avoided by ensuring a minimum film thickness of 10 μm.

1 is a perspective view showing an embodiment of a multilayer ceramic capacitor as a multilayer ceramic electronic component according to the present invention. It is XX sectional drawing of FIG. It is a figure which shows the state which the ceramic body of this invention was immersed in the electrically conductive paste layer. It is a figure which shows the time-dependent change of electrically conductive film formation in this invention. It is a figure which shows the state which immersed the ceramic body with a flat end surface in the electrically conductive paste layer. It is a figure which shows the time-dependent change of electrically conductive film formation in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ceramic body 1a, 1b End surface 3 Internal electrode 8 Paste layer 4a, 4b Base electrode 5a, 5b Ni film | membrane 6a, 6b Sn film | membrane

Claims (2)

A conductive film is formed by immersing both end faces of the ceramic body in which the internal electrodes are embedded in a conductive paste, and then the conductive film is baked to form base electrodes on both end faces of the ceramic body. Then, in the method for manufacturing a multilayer ceramic electronic component in which the base electrode is coated with a plating film to form an external electrode,
Both end surfaces of the ceramic body are formed in a concave shape so that a dimensional ratio A / B between the minimum dimension A and the maximum dimension B between the end faces of the ceramic body is 0.985 to 0.990. A method for manufacturing a multilayer ceramic electronic component.   A multilayer ceramic electronic component manufactured by the manufacturing method according to claim 1.

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