Method for manufacturing ceramic electronic component and ceramic electronic component

Abstract

A method for manufacturing a ceramic electronic component in which a plated electrode can be formed in a region of the surface of a ceramic base body formed of a titanium-containing metal oxide. The method includes preparing a ceramic base body containing a titanium-containing metal oxide, forming a low-resistance section by modifying the metal oxide through irradiation of part of a surface layer portion of the ceramic base body with a pulse laser with a peak power density of 1×10.sup.6 W/cm.sup.2 to 1×10.sup.9 W/cm.sup.2 and a frequency of 500 kHz or less, and forming an electrode on the low-resistance section by electroplating. The laser irradiation generates an O defect in a titanium-containing metal oxide, such as BaTiO.sub.3 to form an n-type semiconductor. Since this semiconductor section has a lower resistance value than the metal oxide, plating metal can be selectively deposited by electroplating.

Claims

1. A method for manufacturing a ceramic electronic component, the method comprising: preparing a ceramic base body containing a titanium-containing metal oxide; forming a low-resistance section by modifying the metal oxide through irradiation of part of a surface layer portion of the ceramic base body with a pulse laser; and forming an electrode on the low-resistance section by electroplating, wherein the irradiation with the pulse laser is performed with a peak power density of 1×10.sup.6 W/cm.sup.2 to 1×10.sup.9 W/cm.sup.2 and a frequency of 500 kHz or less.

2. The method for manufacturing a ceramic electronic component according to claim 1, wherein the metal oxide is formed into an n-type semiconductor in the low-resistance section.

3. The method for manufacturing a ceramic electronic component according to claim 1, wherein the irradiation with the pulse laser is performed with a peak power density of 1×10.sup.6 W/cm.sup.2 to 1×10.sup.8 W/cm.sup.2 and a frequency of 10 kHz to 100 kHz.

4. The method for manufacturing a ceramic electronic component according to claim 1, wherein the ceramic base body contains BaTiO.sub.3.

5. The method for manufacturing a ceramic electronic component according to claim 1, wherein the ceramic electronic component is a multilayer ceramic capacitor; a plurality of end portions of inner electrodes is exposed on each of both end surfaces of the ceramic electronic component; the low-resistance section is formed in at least one side surface adjacent to the both end surfaces of the ceramic electronic component in such a manner that the low-resistance section is formed in each of portions of the side surface that adjoin the respective end surfaces; and the electrode is continuously formed on each end surface and each low-resistance section of the ceramic electronic component.

6. The method for manufacturing a ceramic electronic component according to claim 2, wherein the irradiation with the pulse laser is performed with a peak power density of 1×10.sup.6 W/cm.sup.2 to 1×10.sup.8 W/cm.sup.2 and a frequency of 10 kHz to 100 kHz.

7. The method for manufacturing a ceramic electronic component according to claim 2, wherein the ceramic base body contains BaTiO.sub.3.

8. The method for manufacturing a ceramic electronic component according to claim 3, wherein the ceramic base body contains BaTiO.sub.3.

9. The method for manufacturing a ceramic electronic component according to claim 6, wherein the ceramic base body contains BaTiO.sub.3.

10. The method for manufacturing a ceramic electronic component according to claim 2, wherein the ceramic electronic component is a multilayer ceramic capacitor; a plurality of end portions of inner electrodes is exposed on each of both end surfaces of the ceramic electronic component; the low-resistance section is formed in at least one side surface adjacent to the both end surfaces of the ceramic electronic component in such a manner that the low-resistance section is formed in each of portions of the side surface that adjoin the respective end surfaces; and the electrode is continuously formed on each end surface and each low-resistance section of the ceramic electronic component.

11. The method for manufacturing a ceramic electronic component according to claim 3, wherein the ceramic electronic component is a multilayer ceramic capacitor; a plurality of end portions of inner electrodes is exposed on each of both end surfaces of the ceramic electronic component; the low-resistance section is formed in at least one side surface adjacent to the both end surfaces of the ceramic electronic component in such a manner that the low-resistance section is formed in each of portions of the side surface that adjoin the respective end surfaces; and the electrode is continuously formed on each end surface and each low-resistance section of the ceramic electronic component.

12. The method for manufacturing a ceramic electronic component according to claim 4, wherein the ceramic electronic component is a multilayer ceramic capacitor; a plurality of end portions of inner electrodes is exposed on each of both end surfaces of the ceramic electronic component; the low-resistance section is formed in at least one side surface adjacent to the both end surfaces of the ceramic electronic component in such a manner that the low-resistance section is formed in each of portions of the side surface that adjoin the respective end surfaces; and the electrode is continuously formed on each end surface and each low-resistance section of the ceramic electronic component.

13. The method for manufacturing a ceramic electronic component according to claim 6, wherein the ceramic electronic component is a multilayer ceramic capacitor; a plurality of end portions of inner electrodes is exposed on each of both end surfaces of the ceramic electronic component; the low-resistance section is formed in at least one side surface adjacent to the both end surfaces of the ceramic electronic component in such a manner that the low-resistance section is formed in each of portions of the side surface that adjoin the respective end surfaces; and the electrode is continuously formed on each end surface and each low-resistance section of the ceramic electronic component.

14. The method for manufacturing a ceramic electronic component according to claim 7, wherein the ceramic electronic component is a multilayer ceramic capacitor; a plurality of end portions of inner electrodes is exposed on each of both end surfaces of the ceramic electronic component; the low-resistance section is formed in at least one side surface adjacent to the both end surfaces of the ceramic electronic component in such a manner that the low-resistance section is formed in each of portions of the side surface that adjoin the respective end surfaces; and the electrode is continuously formed on each end surface and each low-resistance section of the ceramic electronic component.

15. The method for manufacturing a ceramic electronic component according to claim 8, wherein the ceramic electronic component is a multilayer ceramic capacitor; a plurality of end portions of inner electrodes is exposed on each of both end surfaces of the ceramic electronic component; the low-resistance section is formed in at least one side surface adjacent to the both end surfaces of the ceramic electronic component in such a manner that the low-resistance section is formed in each of portions of the side surface that adjoin the respective end surfaces; and the electrode is continuously formed on each end surface and each low-resistance section of the ceramic electronic component.

16. The method for manufacturing a ceramic electronic component according to claim 9, wherein the ceramic electronic component is a multilayer ceramic capacitor; a plurality of end portions of inner electrodes is exposed on each of both end surfaces of the ceramic electronic component; the low-resistance section is formed in at least one side surface adjacent to the both end surfaces of the ceramic electronic component in such a manner that the low-resistance section is formed in each of portions of the side surface that adjoin the respective end surfaces; and the electrode is continuously formed on each end surface and each low-resistance section of the ceramic electronic component.

17. A ceramic electronic component comprising: a ceramic base body containing a titanium-containing metal oxide; a low-resistance section formed in part of a surface layer portion of the ceramic base body and obtained by modifying the metal oxide; and an electrode formed on the low-resistance section and made of a plating metal, wherein the metal oxide is formed into an n-type semiconductor in the low-resistance section.

18. The ceramic electronic component according to claim 17, wherein the ceramic base body contains BaTiO.sub.3.

19. The ceramic electronic component according to according to claim 17, wherein the ceramic electronic component is a multilayer ceramic capacitor; a plurality of end portions of inner electrodes is exposed on each of both end surfaces of the ceramic electronic component; the low-resistance section is formed in at least one side surface adjacent to the both end surfaces of the ceramic electronic component in such a manner that the low-resistance section is formed in each of portions of the side surface that adjoin the respective end surfaces; and the electrode made of a plating metal is continuously formed on each end surface and each low-resistance section of the ceramic electronic component.

20. The ceramic electronic component according to according to claim 18, wherein the ceramic electronic component is a multilayer ceramic capacitor; a plurality of end portions of inner electrodes is exposed on each of both end surfaces of the ceramic electronic component; the low-resistance section is formed in at least one side surface adjacent to the both end surfaces of the ceramic electronic component in such a manner that the low-resistance section is formed in each of portions of the side surface that adjoin the respective end surfaces; and the electrode made of a plating metal is continuously formed on each end surface and each low-resistance section of the ceramic electronic component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of a multilayer ceramic capacitor in a first embodiment of a ceramic electronic component according to the present disclosure;

(2) FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor illustrated in FIG. 1;

(3) FIG. 3A illustrates a schematic view of the irradiation of a titanium-based metal oxide with a pulse laser, and FIG. 3B illustrates a schematic view of the irradiation of a titanium-based metal oxide with a continuous wave laser; and

(4) FIG. 4 is a figure illustrating changes in power of the pulse laser.

DETAILED DESCRIPTION

(5) FIG. 1 and FIG. 2 illustrate a multilayer ceramic capacitor 1 in a first embodiment of a ceramic electronic component according to the present disclosure. In FIG. 1, the bottom surface of the capacitor 1 faces upward. The capacitor 1 includes a ceramic base body 10 having a substantially rectangular parallelepiped shape; inner electrodes 12 and 13 formed inside the ceramic base body 10 and alternately exposed on the respective end surfaces; and outer electrodes 14 and 15 continuously formed on the respective end surfaces and the bottom surface. All the drawings including FIG. 1 illustrate schematic views, and the sizes, the aspect ratios, and the like may not be drawn to scale.

(6) The ceramic base body 10 is made of, for example, a sintered ceramic material containing a titanium-based metal oxide, such as BaTiO.sub.3. As illustrated in FIG. 2, low-resistance sections 11a and 11b are formed in both end portions of the bottom surface of the ceramic base body 10, that is, in portions that adjoin the both end surfaces on the bottom surface side. The low-resistance sections 11a and 11b are formed of an n-type-semiconductor obtained by modifying the titanium-based metal oxide through irradiation with a pulse laser described below.

(7) For example, in the case of BaTiO.sub.3, the following reaction may occur through irradiation with a pulse laser.
BaTiO.sub.3+pulse laser.fwdarw.BaTiO.sub.x+O.sub.2↑

(8) BaTiO.sub.x is a type of semiconductor, and x is larger than 2 and smaller than 3.

(9) Since the low-resistance sections 11a and 11b have a lower resistance value than other sections (metal oxide), a plating metal can be deposited on the low-resistance sections 11a and 11b by electroplating. The outer electrodes 14 and 15 formed of the plating metal are continuously formed on the respective end surfaces and the respective low-resistance sections 11a and 11b of the ceramic base body 10. Since the end portions of the inner electrodes 12 and 13 are exposed on the respective end surfaces of the ceramic base body 10, the plating metal can be deposited without special resistance reduction. It should be understood that a low-resistance section may be formed in each end surface as needed.

(10) The outer electrodes 14 and 15 have an L-shape in front view in this embodiment. The outer electrodes 14 and 15 may have a U-shape when the low-resistance sections 11a and 11b are further formed on the top surface side. In addition, by selecting a pulse-laser irradiation range, low-resistance sections can be formed in given regions, and outer electrodes can further be formed in given regions. The outer electrodes 14 and 15 are formed of a single plating layer in FIG. 2, but may be formed of plural plating layers. For example, an underlying plating layer may be formed on each of the low-resistance sections 11a and 11b, and a plating layer made of a different metal may be formed on the underlying plating layer in order to improve corrosion resistance and wettability. The plating layers that constitute the outer electrodes 14 and 15 may be made of a given material and may have a given number of layers.

(11) FIGS. 3A and 3B illustrate examples of laser radiation for forming low-resistance sections on a surface layer portion of the ceramic base body 10 formed of a titanium-based metal oxide. FIG. 3A illustrates the cross section of the surface layer portion irradiated with a pulse laser PL. FIG. 3B illustrates the cross section of the surface layer portion irradiated with a continuous wave laser CL. A continuous wave laser with low power fails to reduce resistance, whereas a continuous wave laser with high power tends to generate a crack C. FIG. 3B illustrates generation of a crack C. A pulse laser can form a low-resistance section S without generating a crack when the peak power density and the frequency are appropriately selected.

(12) As illustrated in FIG. 4, a pulse laser can concentrate its energy in a short time period to provide a high peak power. In FIG. 4, d is a pulse width, the height h is a peak power, and the area (d×h) is a peak energy. The broken line indicates an average power. The peak energy is divided by the laser spot area to produce a pulse power density, that is, peak energy density. The average power density and peak power density of a pulse laser have the following relationship.
Average power density(W/cm.sup.2)=peak power density(W/cm.sup.2)×pulse width(s)×frequency(Hz)

Example 1

(13) Next, the pulse-laser irradiation experiment was carried out at various peak power densities and various frequencies by using a BaTiO.sub.3-based ceramic single plate as a substrate. A YVO.sub.4 fiber laser was used as a pulse laser, the laser scanning condition was 100 mm/s, and the pitch interval was 30 μm. The laser-irradiation range was a 5 mm×5 mm square region. The reduction in resistance was determined by measuring the resistance in the laser-irradiated area. The results are shown in Table 1. The O marks in the results indicate that the low-resistance section was formed.

(14) TABLE-US-00001 TABLE 1 Peak Power Frequency Wavelength Density (W/cm.sup.2) (kHz) (nm) Results .sup. 2.0 × 10.sup.11 100 355 abrasion .sup. 8.8 × 10.sup.10 100 532 abrasion .sup. 1.4 × 10.sup.10 600 1064 abrasion .sup. 1.4 × 10.sup.10 100 1064 crack 7.0 × 10.sup.9 600 1064 abrasion 7.0 × 10.sup.9 100 1064 crack 1.0 × 10.sup.9 100 1046 ◯ 7.8 × 10.sup.8 600 532 crack 7.8 × 10.sup.8 500 532 ◯ 7.8 × 10.sup.8 5 1064 ◯ 2.8 × 10.sup.8 100 532 ◯ 2.5 × 10.sup.8 40 532 ◯ 1.3 × 10.sup.8 1 248 ◯ 7.1 × 10.sup.7 20 1064 ◯ 5.2 × 10.sup.7 100 1064 ◯ 5.0 × 10.sup.7 200 1064 ◯ 4.2 × 10.sup.6 200 1064 ◯ 3.8 × 10.sup.6 20 1064 ◯ 1.0 × 10.sup.6 20 1064 ◯ 4.2 × 10.sup.5 20 1064 no resistance reduction 4.2 × 10.sup.5 4.5 1064 crack 7.0 × 10.sup.5 1.5 1064 crack 4.2 × 10.sup.5 1.5 1064 no resistance reduction

(15) The above experimental results show that suitable combinations of the peak power density and the frequency enable the surface layer portion of the BaTiO.sub.3-based ceramic single plate to have low resistance. Specifically, the low-resistance section can be formed when the peak power density of the pulse laser is 1×10.sup.6 W/cm.sup.2 to 1×10.sup.9 W/cm.sup.2 and the frequency is 500 kHz or less. If the frequency is too large even with a suitable peak power density, the once heated surface is irradiated with next pulse light before sufficiently cooled, and a crack may be generated due to heat accumulation. The irradiation with a peak power density below the foregoing range failed to form a low-resistance section or generated a crack. The irradiation with a high peak power density generated a crack or abrasion. It can be said that the effect of wavelength is not great. In particular, when the peak power density of the pulse laser is 1×10.sup.6 W/cm.sup.2 to 1×10.sup.8 W/cm.sup.2 and the frequency is 10 kHz to 100 kHz in the foregoing ranges, a low-resistance section with good plating deposition properties can be formed while generation of a fine crack is suppressed.

(16) For comparison, the continuous wave laser-irradiation experiment was carried out at various average power densities by using the same BaTiO.sub.3-based ceramic single plate as that used in the above experiment. Specifically, an Yb fiber laser was used, the scanning speed was 100 mm/s, and the pitch interval was 30 μm. The laser-irradiation range was a 5 mm×5 mm square region. The results are shown in Table 2.

(17) TABLE-US-00002 TABLE 2 Laser type Yb Continuous wave laser Wavelength 1064 nm Scanning speed 100 mm/s Pitch 30 μm Average power 8.8 × 10.sup.5 W/cm.sup.2 6.6 × 10.sup.5 W/cm.sup.2 density Results crack is generated non-modified section is present

(18) As shown in the results in Table 2, a crack was generated in the irradiation with a continuous wave laser of 8.8×10.sup.5 W/cm.sup.2, and no low-resistance section was formed in the irradiation with a continuous wave laser of 6.6×10.sup.5 W/cm.sup.2.

Example 2

(19) As illustrated in FIG. 1 and FIG. 2, only both end portions of the bottom surface of the ceramic base body 10 containing BaTiO.sub.3 as a base material were irradiated with a pulse laser under the conditions described in Table 3. Electrolytic Ni plating was performed on the laser-irradiated ceramic base body 10 under the conditions described in Table 4, and Ni was continuously deposited on the laser-irradiated areas (low-resistance sections) and both end surfaces on which the inner electrodes were exposed. Ni plating is not deposited unless the degree of resistance reduction is particularly large. Under the conditions shown in Table 3, the low-resistance sections with low resistance values were formed, and suitable plated electrodes were thus formed.

(20) TABLE-US-00003 TABLE 3 Laser Irradiation Conditions in Example 2 Laser type YVO.sub.4 pulse laser Wavelength 1064 nm Pulse width 25 ns Peak power density 5 MW/cm.sup.2 Frequency 20 kHz Scanning speed 100 mm/s Pitch 10 μm

(21) TABLE-US-00004 TABLE 4 Electrolytic Ni Plating Conditions in Example 2 Plating bath Watts bath Plating method barrel plating using mixture of media balls and works Current 20 A Plating time 60 min

Example 3

(22) As illustrated in FIG. 1 and FIG. 2, the ceramic base body 10 containing BaTiO.sub.3 as a base material was irradiated with a YVO.sub.4 solid-state SHG laser (wavelength: 532 nm) under the conditions shown in Table 5. An attenuator was used during irradiation. The peak power density is a value in consideration of light attenuation provided by the attenuator. The irradiation range is the same as in Example 2. Electrolytic Cu plating was performed on the laser-irradiated ceramic base body 10 under the conditions described in Table 6, and Cu plating was deposited on the laser-irradiated areas (low-resistance sections) and both end surfaces.

(23) TABLE-US-00005 TABLE 5 Laser Irradiation Conditions in Example 3 Laser type YVO.sub.4 pulse laser Wavelength 532 nm Pulse width 25 ns Peak power density 85 MW/cm.sup.2 Frequency 100 kHz Scanning speed 100 mm/s Pitch 20 μm

(24) TABLE-US-00006 TABLE 6 Electrolytic Cu Plating Conditions in Example 3 Plating bath Cu pyrophosphate bath Plating method barrel plating using mixture of media balls and works Current  5 A Plating time 275 min

(25) The pulse-laser irradiation pitch may be smaller or larger than the laser-irradiation spot diameter. In other words, the adjacent low-resistance sections do not necessarily overlap each other and may be distant from each other at a predetermined distance. Even when the low-resistance sections are distant from each other, plating grows in a plane shape from the metal deposited on the low-resistance sections by electroplating such that the metal serves as a nucleus for plating growth, which enables formation of continuous electrodes.

(26) Examples described above illustrate application of the present disclosure to formation of the outer electrodes of the multilayer ceramic capacitor of the present disclosure. The present disclosure is not limited to these Examples. The electronic components targeted for the present disclosure are not limited to multilayer ceramic capacitors, and the present disclosure can be applied to any ceramic electronic component formed of a titanium-based metal oxide in which semiconductor sections (low-resistance sections) may be formed by pulse-laser irradiation. In other words, the material of the ceramic base body is not limited to BaTiO.sub.3.

(27) To form low-resistance sections, one pulse laser may be split into laser beams, and the laser beams may be emitted toward plural positions simultaneously. Moreover, the laser may be out of focus, which may result in a larger laser-irradiation range than that with a laser in focus.

(28) The present disclosure is not limited to the case where all the electrodes formed on the surface layer portion of the ceramic base body are composed of only plated electrodes. In other words, the present disclosure can also be applied to the case where the electrodes are formed of plural materials. For example, underlying electrodes may be formed on part of the surface of the ceramic base body by using, for example, a conductive paste, sputtering, and vapor deposition, and low-resistance sections may be formed in regions adjacent to the underlying electrodes, and plated electrodes may be continuously formed on the low-resistance sections and the underlying electrodes. In addition, the regions in which the low-resistance sections are formed can be freely selected.