JP7498445B2 - Manufacturing method for multilayer ceramic electronic components - Google Patents

Description

The present invention relates to a method for manufacturing a multilayer ceramic electronic component in which multiple internal electrodes are stacked.

As electronic devices become smaller and more powerful, there is a demand for multilayer ceramic capacitors to be even smaller and have higher capacitance. To achieve this, it is advantageous to make the internal electrodes thinner, thereby increasing the number of layers of the internal electrodes and dielectric while maintaining the volume of the ceramic body.

Generally, printing methods are used to form the internal electrodes of multilayer ceramic capacitors. However, it is difficult to form internal electrodes with a uniform thickness of 1 μm or less using printing methods. As an example, as shown in Patent Document 1, internal electrodes formed thinly using screen printing methods tend to have a large thickness around their edges.

In response to this, Patent Document 2 discloses a technique that allows the formation of internal electrodes by a vacuum deposition method such as vacuum evaporation. With this technique, a thin internal electrode can be formed by forming a conductive film by vacuum deposition from a mask formed in a reverse pattern to the arrangement pattern of the internal electrodes.

JP 2015-141982 A JP 2004-087823 A

In the method of forming the internal electrodes by the vacuum deposition method as described above, the peripheral portion of the internal electrode adjacent to the mask is likely to become thin due to shadowing. In such an internal electrode, the peripheral portion is likely to break due to shrinkage during firing of the ceramic body. This makes it difficult to obtain the desired capacitance in the multilayer ceramic capacitor.

In view of the above circumstances, the object of the present invention is to provide a method for manufacturing a multilayer ceramic electronic component that can form internal electrodes of uniform thickness using a vacuum deposition method.

To achieve the above object, in a method for producing a multilayer ceramic electronic component according to one aspect of the present invention, a ceramic sheet having first and second main surfaces is prepared.
A mask corresponding to an arrangement pattern of a plurality of internal electrodes is formed on the first main surface of the ceramic sheet.
With the second main surface held by a convexly curved surface of the ceramic sheet on which the mask is formed, a conductive film is formed on the first main surface by a vacuum film formation method such as sputtering.
In this configuration, by curving the ceramic sheet in a convex shape to widen the opening of the mask, it is possible to suppress shadowing during the formation of the conductive film by the vacuum deposition method, and thus it is possible to form an internal electrode of uniform thickness on the ceramic sheet.

The conductive film may be formed while conveying the ceramic sheet along the curvature direction of the curved surface.
In this configuration, the thickness of the multiple internal electrodes is less likely to vary.

In the arrangement pattern, the internal electrodes may be arranged in a direction inclined with respect to a curvature direction of the curved surface.
In this configuration, the opening of the mask can be expanded over the entire periphery, so that shadowing can be more effectively suppressed when forming a conductive film by vacuum film formation.

As described above, the present invention provides a method for manufacturing multilayer ceramic electronic components that can form internal electrodes of uniform thickness using a vacuum deposition method.

1 is a perspective view of a multilayer ceramic capacitor according to an embodiment of the present invention; 2 is a cross-sectional view taken along line AA' of the multilayer ceramic capacitor. FIG. 2 is a cross-sectional view taken along line BB' of the multilayer ceramic capacitor. FIG. 4 is a flowchart showing a method for manufacturing the multilayer ceramic capacitor. FIG. 2 is a plan view of a single sheet obtained in step S02 of the manufacturing method. FIG. 11 is a perspective view of a laminated sheet illustrating step S03 of the manufacturing method. FIG. 11 is a plan view of the laminated sheet showing step S04 of the manufacturing method. FIG. 2 is a perspective view of an unfired ceramic body obtained in step S04 of the above manufacturing method. 10 is a flowchart showing a method of forming an internal electrode in step S02 of the manufacturing method. 3 is a plan view showing an arrangement pattern of internal electrodes formed by the above-mentioned forming method. FIG. FIG. 4 is a plan view of the ceramic sheet showing step S21 of the forming method. 12 is a cross-sectional view of the ceramic sheet taken along line CC' in FIG. 11. FIG. 11 is a cross-sectional view showing a comparative example of step S22 of the forming method. FIG. 4 is a cross-sectional view showing step S22 of the forming method. 4 is a cross-sectional view of a single sheet obtained in step S23 of the forming method. FIG. 11A to 11C are plan views showing a modified example of the above-mentioned forming method. 10A to 10C are cross-sectional views showing a modified example of the above-mentioned forming method.

<Multilayer ceramic capacitor 10>
Hereinafter, a multilayer ceramic capacitor 10 according to an embodiment of the present invention will be described with reference to the drawings. In addition, in the drawings, an X-axis, a Y-axis, and a Z-axis that are mutually orthogonal are appropriately shown. The X-axis, the Y-axis, and the Z-axis are common to all the drawings, and define a fixed coordinate system that is fixed with respect to the multilayer ceramic capacitor 10.

[Configuration of Multilayer Ceramic Capacitor 10]
1 to 3 are diagrams showing a multilayer ceramic capacitor 10 according to this embodiment. Fig. 1 is a perspective view of the multilayer ceramic capacitor 10. Fig. 2 is a cross-sectional view of the multilayer ceramic capacitor 10 taken along line AA' in Fig. 1. Fig. 3 is a cross-sectional view of the multilayer ceramic capacitor 10 taken along line BB' in Fig. 1.

The multilayer ceramic capacitor 10 includes a ceramic body 11, a first external electrode 14, and a second external electrode 15. The ceramic body 11 is configured as a hexahedron having first and second end faces perpendicular to the X-axis, first and second side faces perpendicular to the Y-axis, and first and second main faces perpendicular to the Z-axis.

The external electrodes 14, 15 cover both end faces of the ceramic body 11 and face each other in the X-axis direction with the ceramic body 11 in between. The external electrodes 14, 15 extend from each end face of the ceramic body 11 to the main surface and side surfaces. As a result, the cross sections of the external electrodes 14, 15 parallel to the X-Z plane and the cross sections parallel to the X-Y plane are both U-shaped.

The shape of the external electrodes 14, 15 is not limited to that shown in FIG. 1. For example, the external electrodes 14, 15 may extend from both end faces of the ceramic body 11 to only one of the main surfaces, and may have an L-shaped cross section parallel to the X-Z plane. Furthermore, the external electrodes 14, 15 do not have to extend to any of the main surfaces or side surfaces.

The external electrodes 14, 15 are formed from a good electrical conductor. Examples of good electrical conductors that form the external electrodes 14, 15 include metals or alloys whose main components are copper (Cu), nickel (Ni), tin (Sn), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), etc.

The ceramic body 11 has a capacitance forming portion 16, a side margin portion 17, and a cover portion 18. The capacitance forming portion 16 is located in the center in the Y-axis and Z-axis directions. The side margin portion 17 covers the capacitance forming portion 16 from both sides in the Y-axis direction. The cover portion 18 covers the capacitance forming portion 16 from above and below in the Z-axis direction.

The ceramic body 11 has a configuration in which multiple flat ceramic layers extending along the X-Y plane are stacked in the Z-axis direction. The capacitance forming portion 16 includes multiple first and second internal electrodes 12, 13. The internal electrodes 12, 13 are sheet-shaped extending along the X-Y plane, alternately arranged between the multiple ceramic layers, and face each other in the Z-axis direction.

The first internal electrode 12 is extended to the end surface covered by the first external electrode 14. On the other hand, the second internal electrode 13 is extended to the end surface covered by the second external electrode 15. As a result, the first internal electrode 12 is connected only to the first external electrode 14, and the second internal electrode 13 is connected only to the second external electrode 15.

With this configuration, when a voltage is applied between the first external electrode 14 and the second external electrode 15 in the multilayer ceramic capacitor 10, the voltage is applied to the multiple ceramic layers between the first internal electrode 12 and the second internal electrode 13. As a result, a charge corresponding to the voltage between the first external electrode 14 and the second external electrode 15 is stored in the multilayer ceramic capacitor 10.

In the ceramic body 11, a dielectric ceramic having a high dielectric constant is used to increase the capacitance of each ceramic layer between the internal electrodes 12 and 13. An example of a dielectric ceramic having a high dielectric constant is a material having a perovskite structure containing barium (Ba) and titanium (Ti), such as barium titanate ( _BaTiO3 ).

The ceramic layer may be composed of a composition such as strontium titanate ( _SrTiO3 ), calcium titanate ( _CaTiO3 ), magnesium titanate ( _MgTiO3 ), calcium zirconate ( _CaZrO3 ), calcium zirconate titanate (Ca(Zr,Ti) _O3 ), barium zirconate ( _BaZrO3 ), titanium oxide ( _TiO2 ), etc.

The internal electrodes 12, 13 are formed from a good electrical conductor. Typical examples of good electrical conductors that form the internal electrodes 12, 13 include nickel (Ni), as well as metals or alloys whose main components are copper (Cu), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), etc.

[Method of Manufacturing Multilayer Ceramic Capacitor 10]
Fig. 4 is a flowchart showing a method for manufacturing the multilayer ceramic capacitor 10 according to this embodiment. Figs. 5 to 8 are diagrams showing the manufacturing process of the multilayer ceramic capacitor 10. The method for manufacturing the multilayer ceramic capacitor 10 will be described below along with Fig. 4 with appropriate reference to Figs. 5 to 8.

(Step S01: Prepare ceramic sheet)
In step S01, a ceramic sheet S is prepared. The ceramic sheet S is configured as an unfired dielectric green sheet mainly composed of dielectric ceramics. The ceramic sheet S is formed into a sheet shape using, for example, a roll coater or a doctor blade. The thickness of the ceramic sheet S can be appropriately adjusted.

(Step S02: Forming internal electrodes)
In step S02, unsintered first and second internal electrodes 112, 113 are formed on the ceramic sheet S prepared in step S01 to produce the first and second single sheets 101, 102 that constitute the unsintered capacitance forming portion 116 and the side margin portion 117. Note that no internal electrodes are formed on the third single sheet 103 that constitutes the unsintered cover portion 118.

Figure 5 is a plan view of the individual sheets 101, 102, and 103. At this stage, the individual sheets 101, 102, and 103 are configured as large sheets that have not been singulated. Figure 5 shows the cutting lines Lx and Ly used when singulating each multilayer ceramic capacitor 10. The cutting line Lx is parallel to the X-axis, and the cutting line Ly is parallel to the Y-axis.

As shown in FIG. 5, the first single sheet 101 has an unfired first internal electrode 112 corresponding to the first internal electrode 12, and the second single sheet 102 has an unfired second internal electrode 113 corresponding to the second internal electrode 13. The third single sheet 103 may be a ceramic sheet S having a different composition and thickness from the single sheets 101 and 102.

In step S02, a vacuum film forming method is used to form thin internal electrodes 112, 113. Furthermore, step S02 is configured to enable the internal electrodes 112, 113 to be formed with a uniform thickness. The method of forming the internal electrodes 112, 113 in step S02 will be described in detail later.

(Step S03: Lamination)
In step S03, the single sheets 101, 102, and 103 obtained in step S02 are laminated as shown in Fig. 6 to produce a laminated sheet 104. In the laminated sheet 104, the first and second single sheets 101 and 102 corresponding to the capacitance forming portion 116 and the side margin portion 117 are laminated alternately in the Z-axis direction.

In addition, in the laminated sheet 104, third individual sheets 103 corresponding to the cover portion 18 are laminated on the upper and lower surfaces in the Z-axis direction of the alternately laminated individual sheets 101 and 102. In the example shown in FIG. 6, three third individual sheets 103 are laminated, but the number of third individual sheets 103 can be changed as appropriate.

As shown in FIG. 6, the stacked individual sheets 101, 102, and 103 are compressed together to obtain the laminated sheet 104. For example, hydrostatic pressure or uniaxial pressure is preferably used to compress the individual sheets 101, 102, and 103. This makes it possible to densify the laminated sheet 104.

(Step S04: Disconnect)
In step S04, the laminated sheet 104 obtained in step S03 is cut along cutting lines Lx and Ly shown in Fig. 7 to produce an unsintered ceramic body 111 shown in Fig. 8. The ceramic body 111 corresponds to the ceramic body 11 after firing. The laminated sheet 104 can be cut using, for example, a press blade or a rotary blade.

(Step S05: Firing)
In step S05, the ceramic body 111 obtained in step S04 and shown in Fig. 8 is fired to produce the ceramic body 11 of the multilayer ceramic capacitor 10 shown in Figs. 1 to 3. That is, the ceramic body 111 becomes the ceramic body 11 in step S05.

The firing temperature in step S05 can be determined based on the sintering temperature of the ceramic body 111. For example, when a barium titanate (BaTiO ₃ ) based material is used, the firing temperature can be about 1000 to 1300° C. Furthermore, the firing can be performed, for example, in a reducing atmosphere or a low oxygen partial pressure atmosphere.

(Step S06: Forming external electrodes)
In step S06, external electrodes 14, 15 are formed on both ends in the X-axis direction of the ceramic body 11 obtained in step S05, thereby producing the multilayer ceramic capacitor 10 shown in Figures 1 to 3. The method for forming the external electrodes 14, 15 in step S09 can be arbitrarily selected from known methods. In this manner, the multilayer ceramic capacitor 10 is completed.

<Method of forming internal electrodes 112, 113>
Fig. 9 is a flowchart showing the method of forming the internal electrodes 112, 113 in step S02 above. Figs. 10 to 17 are views for explaining the method of forming the internal electrodes 112, 113. The method of forming the internal electrodes 112, 113 will be explained below along Fig. 9 with appropriate reference to Figs. 10 to 17.

Note that in addition to the X-axis, Y-axis, and Z-axis fixed to the multilayer ceramic capacitor 10, Figures 10 to 17 also show the x-axis, y-axis, and z-axis which are mutually orthogonal. The x-axis, y-axis, and z-axis define a real space coordinate system fixed with respect to real space. The x-axis and y-axis extend horizontally, meaning that the x-y plane is the horizontal plane. The z-axis extends vertically, up and down.

(Step S21: Forming mask M)
In step S21, a mask M is formed on a first main surface P1 of the ceramic sheet S on which the internal electrodes 112, 113 are to be formed. The mask M can be formed of, for example, a photoresist. FIG. 10 shows an arrangement pattern of the internal electrodes 112, 113 on the first main surface P1 of the ceramic sheet S in the single sheets 101, 102.

In the arrangement pattern shown in FIG. 10, the X-axis and Y-axis directions of the internal electrodes 112, 113 are aligned with the x-axis and y-axis, respectively, meaning that the internal electrodes 112, 113 are arranged along the x-axis and y-axis. Note that the first internal electrode 112 of the first single sheet 101 and the second internal electrode 113 of the second single sheet 102 are arranged in a mutually offset manner in the x-axis direction.

Figures 11 and 12 show a ceramic sheet S on which a mask M is formed. Figure 11 is a plan view, and Figure 12 is a cross-sectional view taken along line CC' in Figure 11. The mask M is formed in a pattern that is the inverse of the arrangement pattern of the internal electrodes 112, 113 shown in Figure 10. In other words, openings K are patterned in the mask M in the arrangement pattern of the internal electrodes 112, 113.

(Step S22: Sputtering)
In step S22, sputtering is performed on the first main surface P1 of the ceramic sheet S on which the mask M has been formed in step S21. Fig. 13 shows a general sputtering configuration, and Fig. 14 shows a sputtering configuration according to this embodiment. First, problems that arise when sputtering is performed using the general configuration shown in Fig. 13 will be described.

The configuration shown in FIG. 13 uses a holder H0 having a holding surface Q0, which is a flat surface facing upward in the z-axis direction, and a target T facing upward in the z-axis direction to the holding surface Q0. With the ceramic sheet S, the second main surface P2 is held by the holding surface Q0, and sputtered atoms emitted from the target T are irradiated onto the first main surface P1.

As a result, a conductive film E is formed on the first main surface P1 of the ceramic sheet S by deposition of sputtered atoms. In the configuration shown in FIG. 13, shadowing, a phenomenon in which sputtered atoms are blocked by the mask M, is likely to occur at the periphery of the opening K of the mask M. As a result, the thickness of the conductive film E formed within the opening K of the mask M becomes thinner at the periphery.

In contrast, the configuration shown in FIG. 14 uses a holder H having a holding surface Q, which is a curved surface that protrudes upward in the z-axis direction. More specifically, the holding surface Q of the holder H is curved along the y-axis direction so that the central portion in the y-axis direction protrudes in the z-axis direction. Therefore, the ceramic sheet S, whose second main surface P2 is held by the holding surface Q, is also curved along the y-axis direction.

For this reason, in the ceramic sheet S in which the second main surface P2 is held on the holding surface Q, the first main surface protrudes in the z-axis direction, causing the opening K of the mask M to taper in the Y-axis direction toward the target T. This makes it easier for the sputtered atoms to penetrate to both edges of the opening K of the mask M in the Y-axis direction, meaning that shadowing is less likely to occur.

Therefore, a conductive film E of uniform thickness is formed along the Y-axis direction within the openings K of the mask M. The emission surface of the sputtered atoms on the target T can also be a curved surface concave upward in the z-axis direction along the holding surface Q of the holder H. This can reduce the variation in thickness of the conductive film E between each opening K of the mask M.

(Step S23: Remove mask M)
In step S23, the mask M is removed from the ceramic sheet S that has been sputtered in step S22. This results in the single sheets 101 and 102 shown in Fig. 15. In the single sheets 101 and 102 obtained in step S23, the conductive film E having a uniform thickness in the Y-axis direction formed in step S22 becomes the internal electrodes 112 and 113.

(Modification)
The configuration of the method for forming the internal electrodes 112, 113 according to this embodiment is not limited to the above and can be modified in various ways. For example, the holding surface Q of the holder H may be curved along the x-axis direction instead of the y-axis direction. This causes the opening K in the mask M to expand in the X-axis direction, thereby suppressing shadowing at both edges of the opening K in the X-axis direction.

Furthermore, as shown in FIG. 16, the openings K of the mask M may be patterned so that the internal electrodes 112, 113 are arranged in a direction tilted with respect to the x-axis and y-axis. In other words, the X-axis and Y-axis, which are the arrangement directions of the internal electrodes 112, 113, may be tilted with respect to the x-axis and y-axis.

As a result, regardless of whether the curvature direction of the holding surface Q of the holder H is the x-axis direction or the y-axis direction, the opening K of the mask M expands in both directions along the X-axis and the Y-axis. Therefore, by using the configuration shown in FIG. 16, shadowing can be suppressed around the entire periphery of the opening K of the mask M.

In addition, in step S22, as shown in FIG. 17, sputtering may be performed while transporting the ceramic sheet S in the y-axis direction along the holding surface Q of the holder H. This suppresses the variation in thickness between the internal electrodes 112, 113 formed in each opening K of the mask M. In this case, the emission surface of the sputtered atoms of the target T may be made smaller in the y-axis direction.

Furthermore, in the method for forming the internal electrodes 112, 113 according to this embodiment, a sputtering method is used in step S22, but other vacuum film formation methods can be used instead of sputtering. Examples of such vacuum film formation methods include vacuum deposition and ion plating.

<Other embodiments>
Although the embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned embodiment, and various modifications can be made, as a matter of course.

For example, in the above embodiment, the manufacturing method of the multilayer ceramic capacitor 10 was described as an example of a multilayer ceramic electronic component, but the manufacturing method of the present invention can be applied to multilayer ceramic electronic components in general. Examples of such multilayer ceramic electronic components include chip varistors, chip thermistors, and multilayer inductors.

DESCRIPTION OF SYMBOLS 10... Multilayer ceramic capacitor 11, 111... Ceramic body 12, 13, 112, 113... Internal electrodes 14, 15... External electrodes 16, 116... Capacitance forming portion 17, 117... Side margin portion 18, 118... Cover portion 101, 102, 103... Single sheet S... Ceramic sheets P1, P2... Main surface M... Mask K... Opening H... Holder Q... Holding surface T... Target E... Conductive film

Claims (5)

providing a ceramic sheet having first and second major surfaces;
forming a mask on the first main surface of the ceramic sheet according to an arrangement pattern of a plurality of internal electrodes;
a conductive film is formed on the first main surface by a vacuum film forming method while the second main surface is held by a convexly curved surface of the ceramic sheet on which the mask is formed;
removing the mask from the ceramic sheet on which the conductive film is formed;
the curved surface is formed on a holder that is non-rotatably provided. 2. A method for producing a multilayer ceramic electronic component according to claim 1, comprising the steps of:
The vacuum film formation method is a sputtering method,
the holder is disposed facing the target, and the curved surface is positioned so as to maintain a positional relationship with the target. 2. A method for producing a multilayer ceramic electronic component according to claim 1, comprising the steps of:
In the arrangement pattern, the plurality of internal electrodes are arranged along a direction inclined with respect to a curvature direction of the curved surface. A method for producing a multilayer ceramic electronic component according to any one of claims 1 to 3, comprising the steps of:
forming the conductive film while conveying the ceramic sheet along the curvature direction of the curved surface. 5. A method for producing a multilayer ceramic electronic component according to claim 1, comprising the steps of:
the curved surface is curved along a first direction and also curved in a direction different from the first direction.

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