JP2005197557A - Manufacturing method of laminated ceramic electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the inconvenience that, as a laminated ceramic electronic component is highly laminated, there happens a level difference due to the thickness of an internal electrode at positions where a pattern for the internal electrode is formed and at positions where the same is not formed, the total amount of the level differences is more increased as the number of laminates is more increased, hence any external crack and internal structure defects occur, and upper and lower surfaces of a laminate after calcination have irregular shape like a bulging pillar. <P>SOLUTION: A laminate block is prepared by laminating alternately a ceramic sheet and an internal electrode, which is then cut down into laminate pieces which are pressurized vertically. Accordingly, any level difference caused by the thickness of the internal electrode is moderated to suppress the occurrence of the external crack, the internal structure defects, and an irregular shape like a bulging pillar. <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 ceramic capacitor.

  A conventional method for manufacturing a multilayer ceramic capacitor will be described.

  In multilayer ceramic electronic components such as multilayer ceramic capacitors, the ceramic layers and internal electrodes are becoming thinner and higher in order to reduce size and increase performance. Products with more than 100 layers are being produced. Along with this increase in the number of layers, there is always a step due to the thickness of the internal electrode between the place where the internal electrode pattern is formed and the place where it is not formed. The greater the number of layers, the greater the total amount of the step. However, there are inconveniences such as external cracks, internal structural defects, and a pillow-like irregular shape in which the upper and lower surfaces of the laminated body swelled, and in order to eliminate this, the steps formed by the internal electrodes are eliminated Various methods have been proposed. For example, Patent Document 1 discloses a method of stacking with a step-resolving pattern interposed.

When a laminated body having a step due to the internal electrode is fired, the upper and lower surfaces of the laminated body after firing are in a pillow-like shape because the portion where the internal electrode pattern is not formed has a pressure during lamination. This is because it is difficult to apply and firing shrinkage increases, and in such a pillow-like shape, the four corners of the rectangular parallelepiped multilayer ceramic electronic component are rounded, so that the mounting machine can accurately recognize when mounting on a circuit board or the like. It will not be possible and will cause a bug in the implementation.
JP-A-6-96991

  However, in the method of interposing the step elimination pattern as described above, the number of laminated layers increases, so that the manufacturing process of the multilayer ceramic capacitor becomes long, and the step elimination pattern is formed at the location where the internal electrode is formed. It is necessary to arrange the parts with high accuracy other than the above, and there is a problem that the process becomes complicated.

  Therefore, the present invention provides a multilayer ceramic electronic component capable of suppressing internal / external defects and pillow-like irregularities by a simple method suitable for mass production without using the above-described pattern for eliminating a step difference. An object of the present invention is to provide a manufacturing method.

  In order to achieve the above object, the present invention has the following configuration.

  According to the first aspect of the present invention, a laminate block is produced by alternately laminating ceramic sheets and internal electrodes, and this is cut into individual laminates and then pressed from above and below to cut the internal electrodes. The steps due to the thickness can be alleviated, and the occurrence of external cracks, internal structural defects and pillow-like irregularities can be suppressed.

  In the invention according to claim 2 of the present invention, in particular, the laminated body block is cut by a rotary blade, and a cutting groove is reliably formed by the blade width of the rotary blade. It is possible to prevent the adjacent laminated body pieces that have been cut from sticking to each other again, to relieve a step due to the thickness of the internal electrode by effective pressurization, and to suppress the occurrence of internal structural defects and pillow-like irregular shapes.

  In the invention according to claim 3 of the present invention, in particular, the cutting of the laminated body block in the second step is performed by using a wire saw that performs cutting by reciprocating movement of the stretched filament, The cutting groove is reliably formed by the reciprocating motion, so that it is possible to prevent the adjacent laminated body pieces that are cut by the pressurization after cutting from sticking again. It can alleviate and suppress the occurrence of external cracks, internal structural defects and pillow-like irregular shapes.

  In the invention according to claim 4 of the present invention, in particular, pressure is applied so that the thickness of the laminate after pressurization is in the range of 90% to 99% of the thickness before pressurization. By controlling the change in thickness, the applied pressure can be in an appropriate range, so that deformation of the laminated body piece due to excessive pressurization can be prevented, and steps due to the internal electrode thickness can be more effectively mitigated, and internal structural defects and Generation | occurrence | production of the pillow-shaped unusual shape can be suppressed.

  The invention according to claim 5 of the present invention is to adjust the capacity of the multilayer ceramic capacitor after firing, particularly by pressurizing the cut multilayer body, and finely adjust the capacity by moderate pressurization. Thus, a multilayer ceramic capacitor with high capacity accuracy can be obtained.

  In the invention according to claim 6 of the present invention, in particular, by pressing the laminated body after cutting, a longitudinal direction perpendicular to the thickness direction of the laminated body (the direction in which external electrodes are formed at both ends, the L direction) The side shape of the longitudinal direction (L direction) is easy to be deformed into a concave shape after firing, because pressure is difficult to apply and the shrinkage due to firing is larger than the upper and lower surfaces. By flattening the shape, it is possible to obtain a multilayer ceramic capacitor that does not cause a reduction in the mounting rate even when the side surfaces are adsorbed.

  In the invention described in claim 7 of the present invention, in particular, the laminated body after cutting is pressurized so that the dimension of the central part is 1 to 4% larger than the dimension of the upper and lower parts in the side surface shape in the longitudinal direction (L direction). As a result, the shape of the side surface in the longitudinal direction can be flattened, so that a multilayer ceramic capacitor that does not cause a reduction in the mounting rate even when the side surface is adsorbed can be obtained.

  The multilayer ceramic capacitor according to the present invention is capable of suppressing deformation to an abnormal shape such as a pillow after firing by pressing the laminated body from above and below in the thickness direction, and can prevent problems during mounting. Thus, it is possible to improve the mountability and to enable fine capacitance adjustment and to obtain a multilayer ceramic capacitor with high capacitance accuracy.

(Embodiment)
Hereinafter, claims 1 to 7 of the present invention will be described using an embodiment.

  FIG. 1 is a cross-sectional view for explaining the cutting process of the laminated body block 11 in Embodiment 1 of the present invention. The laminated body block 11 is placed on the support base 10 and cooled by the cooling device 13. The water is cut by the rotary blade 12 while spraying water from the cooling nozzle 14.

  FIG. 2 is a cross-sectional view for explaining a pressurizing step of pressurizing the laminated body from above and below after cutting the laminated body block and dividing the laminated body into individual pieces. The laminate piece 21 is pressed from above and below by the pressure head 23. Reference numeral 22 denotes a cutting groove, and an arrow in the figure indicates a pressing direction.

  FIG. 3 is a perspective view of the laminate piece 31 cut and individually separated, 32 is a cut surface, 33 is an internal electrode, 34 is a side surface in the longitudinal direction (L direction) (that is, orthogonal to the width direction and the thickness direction). Side).

  Next, a method for manufacturing a multilayer ceramic electronic component according to the present embodiment will be described using a multilayer ceramic capacitor as an example.

  First, an inorganic powder mainly composed of barium titanate, a binder such as acrylic resin or polyvinyl butyral resin, and a plasticizer such as dibutyl phthalate are mixed, and a ceramic sheet is prepared by a doctor blade method.

  Next, an electrode paste is screen-printed on the surface of the ceramic sheet to form a plurality of internal electrodes.

  The electrode paste contains Ni powder as a main component and is mixed with ethyl cellulose, acrylic resin, polyvinyl butyral resin, or the like.

  Next, the ceramic sheets on which the internal electrodes are formed are alternately laminated so that the internal electrodes face each other with the ceramic sheet interposed therebetween, thereby producing a 260-layer laminate.

  Next, the laminate block 11 having a thickness of 1.0 mm is manufactured by pressurizing at 5 MPa to 20 MPa while being heated to a temperature at which the ceramic sheet is softened.

  Thereafter, the laminated body block 11 is fixed to the pedestal 10 as shown in FIG. 1, and the rotary blade 12 is moved perpendicularly to the upper surface of the laminated body block 11 by the rotary blade 12 from one of the planned cutting positions to the other. Cut while moving. The rotary blade 12 is disk-shaped and has diamond particles or SiC particles fixed to a metal substrate, and the blade width is generally 100 μm to 500 μm.

  Next, the rotary blade 12 is moved in parallel, and the laminate block 11 is cut in the same manner a plurality of times while confirming the cutting position.

  Next, the laminated body block 11 is rotated 90 degrees with respect to the rotary blade 12 and similarly cut several times, and the length (length in the L direction) is about 1.8 mm, the width is about 1.0 mm, and the thickness is 1. A 0 mm-shaped laminated body piece is obtained.

  Subsequently, the thickness of the laminate before and after pressing is 0.87 mm, 0.90 mm, 0.93 mm, 0.95 mm, and 0.97 mm from the vertical direction of the laminate individual pieces (the thickness dimension change rate is 87 for each. %, 90%, 93%, 95%, 97%), and pressurizing while adjusting the applied pressure to separate from the support base.

  The rate of change in thickness was shown as a percentage of the value obtained by dividing the thickness after pressing by the thickness before pressing.

  The dimension of the center part of the side surface in the longitudinal direction (L direction) after pressurization was the numerical value shown in (Table 1) compared with the dimension of the upper and lower parts of the side surface.

  Next, after removing the organic matter in nitrogen gas, the temperature is raised to 1300 ° C. in a nitrogen-hydrogen mixed gas atmosphere in which Ni serving as an internal electrode is not excessively oxidized, and a sintered body is obtained.

  Next, the sintered body is chamfered to completely expose the conductor layers on both end faces. Subsequently, after applying an electrode paste mainly composed of copper to both end faces and end faces of the sintered body, an external electrode is formed by baking in a nitrogen atmosphere at 800 ° C., and nickel and solder are plated thereon. To produce a multilayer ceramic capacitor.

  Moreover, in order to show the effect of the present invention more clearly, a micrograph of a cross section of sample No. 1 which is not pressurized after cutting the laminate block 11 is shown in FIG. 4 and a sample pressurized by the method shown in the embodiment A photomicrograph of the cross section of No. 4 is shown in FIG.

  As is clear from FIG. 4, the upper and lower surfaces of Sample No. 1 have a pillow-like irregular shape, and the left and right surfaces in FIG. 4 (that is, the longitudinal cross section) have a slightly recessed central portion. As shown in FIG. 5, in Sample No. 2, no abnormal shape was observed, and a clean rectangular parallelepiped shape was obtained.

  Further, when a mounting test was performed using 5000 pieces of the multilayer ceramic capacitors manufactured under the conditions of sample number 1 and sample numbers 2 to 5, the mounting failure rate of sample number 1 was 5%. The mounting failure rate of 2 to 5 was 0.

  Here, the mounting failure rate is the percentage of the number of samples that could not be mounted normally due to an adsorption error or a recognition error out of 5000 samples.

  Further, external electrodes were formed on both end faces where the internal electrodes of the fired multilayer ceramic capacitor were exposed, and the capacitance was measured for 100 manufactured samples, and the average value was calculated.

  The results are also shown in (Table 1).

  As is clear from the results of (Table 1), the side surface (in which the rate of change in the thickness dimension of the laminate is within a range of 90% to 99% by pressing after cutting and orthogonal to the thickness direction by pressing ( Side surface in the direction of internal electrode) Sample numbers 2 to 5 pressurized so that the dimensional change rate in the central portion is 1 to 4%, while no mounting failure was found in the mounting test, while the sample not pressurized In No. 1, mounting failure is large due to an adsorption error due to deformation of the sample.

  Furthermore, in the above sample numbers 2 to 5, no mounting mistake due to suction failure was found in a mounting experiment in which the longitudinal side surface orthogonal to the thickness direction and the width direction was sucked.

  In addition, the average value of the capacitance measured by sampling 100 samples before pressing was 4.2 μF, which is just below the lower limit of the standard, and the capacitance yield was about 40%, whereas the thickness dimension. In the sample pressed in the thickness direction so that the rate of change in the thickness becomes 90 to 99%, the capacity increases as shown in Sample Nos. 2 to 5, and the capacitance yield also improves to 90 to 98%. I was able to.

  Here, regarding the electrostatic capacitance values of these samples, a non-defective product satisfying the standard is within a range of 4.7 μF ± 10%.

  The capacitance yield is required to be as close as possible to 100%, but in actual mass production, the yield is preferably 80% or more.

  In the above embodiment, a rotary blade is used for cutting, but the same effect can be obtained when using a so-called wire saw that performs cutting by reciprocating movement of a stretched wire.

  When cutting with a rotary blade or a wire saw, the cutting may be performed with a plurality of rotary blades or filaments attached at a predetermined interval in advance, and in this case, the time required for cutting can be drastically reduced. At the same time, since a large number of cutting grooves can be formed at one time, it is possible to more reliably prevent a problem in which the adjacent laminated body pieces are stuck again after cutting.

  In the above embodiment, the multilayer ceramic capacitor has been described. However, the same effect can be obtained in a multilayer ceramic electronic component formed by laminating ceramic sheets such as a multilayer varistor, a multilayer thermistor, a multilayer coil, and a ceramic multilayer substrate. .

  The method for manufacturing a multilayer ceramic electronic component according to the present invention is capable of preventing irregular shape of the multilayer ceramic electronic component after firing, increasing the mounting efficiency and efficiently adjusting the capacitance after stacking. It is useful for a method of manufacturing a multilayer ceramic electronic component.

Sectional drawing of the cutting process in Embodiment 1 of this invention Sectional drawing for demonstrating the pressurization process of the thickness direction Perspective view of laminate Sectional view of sample number 1 (when no pressure is applied after cutting) Sectional view of sample number 4 (with pressure after cutting)

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Support stand 11 Laminated body block 12 Rotating blade 13 Cooling device 14 Cooling nozzle 21 Laminated body piece 22 after cutting 22 Cutting groove 23 Pressurizing head 31 Laminated body piece after pressurization and separation 32 Cut surface 33 Internal electrode 34 Longitudinal Directional side

Claims (7)

A first step of alternately laminating ceramic sheets and internal electrodes prepared by mixing inorganic powder and organic matter to obtain a laminate block, and a second step of cutting the laminate block into individual laminates And a third step of pressurizing the cut laminated body in the vertical direction and a fourth step of firing the laminated body. The method of manufacturing a multilayer ceramic electronic component according to claim 1, wherein the cutting in the second step is cutting with a rotary blade. 2. The method for manufacturing a multilayer ceramic electronic component according to claim 1, wherein the cutting in the second step is cutting using a wire saw that performs cutting by reciprocating movement of a stretched wire. The method for producing a multilayer ceramic electronic component according to claim 1, wherein the pressurization in the third step is performed such that the thickness of the laminate after pressurization is in the range of 90% to 99% of the thickness before pressurization. The method for producing a multilayer ceramic electronic component according to claim 1, wherein the capacity is adjusted by pressurization in the third step. The manufacturing method of the multilayer ceramic electronic component of Claim 1 which makes the shape of the side surface of the longitudinal direction orthogonal to the thickness direction of a laminated body bulge in the center part by the pressurization in a 3rd process. The method for producing a multilayer ceramic electronic component according to claim 6, wherein in the side shape in the width direction, pressurization is performed so that the dimension of the center part is 1 to 4% larger than the dimension of the upper and lower parts.