JP3019703B2 - Manufacturing method of ceramic electronic components - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic electronic component such as a multilayer capacitor, and more particularly to a method for manufacturing a ceramic electronic component in which an external electrode forming step is improved.

[0002]

2. Description of the Related Art As an example of a conventional method for manufacturing a ceramic electronic component, a method for manufacturing a multilayer capacitor is shown in FIGS.
This will be described with reference to FIG.

[0003] A ceramic electronic component body 1 made of a sintered body in which a plurality of internal electrodes 2 to 6 are arranged so as to overlap with each other via a dielectric ceramic layer is prepared. In order to cover both end surfaces 1a and 1b of the ceramic electronic component body 1,
The external electrodes 7 and 8 are formed by applying and baking an Ag-containing conductive paste.

The external electrodes 7 and 8 are used for electrical connection with the outside. However, since the external electrodes 7 and 8 are mainly made of Ag, the external electrodes 7 and 8 may be broken by soldering when soldering is performed.
8 is lost or corroded. Therefore, conventionally, as shown in an enlarged view of one external electrode 8 side in FIG. 2, after forming the external electrode 8, a first plating film 9 made of Ni is further formed by wet plating. Further, since the first plating film 9 made of Ni has insufficient solderability, the second plating film 1 made of Sn or Sn—Pb is formed on the first plating film 9 in order to enhance the solderability.
0 was formed by wet plating.

[0005]

However, the external electrodes 7, 8 mainly composed of Ag formed by baking a conductive paste have a large number of pores. Therefore, as shown by the arrow in FIG. 2, the strongly acidic plating solution used in the wet plating passes through the external electrode 8 and forms the ceramic electronic component body 1, especially the ceramic electronic component body 1. In some cases reached the interface between the ceramic layer and the internal electrode.

When a strongly acidic plating solution enters the ceramic electronic component body 1, delamination occurs between the internal electrodes and the ceramic layer, and in the case of a bare layer, cracks reaching the internal electrodes adjacent in the thickness direction. Occurred, and the insulation resistance was sometimes significantly reduced. This is considered to occur by the following mechanism.

That is, during the wet plating, the plating solution reaches the interface between the ceramic layer and the internal electrode through the pores of the external electrodes 7 and 8 made of Ag. During plating, since the ceramic electronic component body 1 is usually on the cathode side, an oxide of a metal constituting the internal electrode, which is considered to be present at the interface between the internal electrode and the ceramic layer, for example, NiO is reduced. This causes a delamination phenomenon at the interface. Further, it is considered that the above-mentioned reduction reaction progresses to the inside with the passage of time, and a crack that straddles between the opposing internal electrodes occurs at a certain point in time, and the insulation resistance is considered to be significantly reduced.

On the other hand, when the external electrodes 7 and 8 are baked, a metal oxide powder such as Al ₂ O ₃ powder is usually used as a lint powder. That is, as shown in FIG. 3, after the conductive paste is applied on the external electrodes 7 and 8, the ceramic electronic component body 1 is placed on the flat surface 12 on which the laying powder 11 is scattered, and the conductive paste is baked. I was Since the bedding powder must be finally removed, the conductive paste is usually baked and then removed by washing with water. However,
In the above-mentioned washing with water, the bedding powder could not be completely and completely removed.

As a result, the powders are partially present on the surfaces of the external electrodes 7 and 8, and the glass frit in the conductive paste is deposited unevenly. When 9 and 10 are formed, the first and the first with uniform thickness
The second plating films 9 and 10 could not be formed, and the gloss of the plating film surface tended to decrease.

[0010] An object of the present invention is to form a plating film on an external electrode by suppressing the intrusion of a plating solution into a ceramic electronic component body, and providing a plating film having a good gloss to a uniform thickness. It is another object of the present invention to provide a method for manufacturing a ceramic electronic component having a step of enabling stable formation.

[0011]

SUMMARY OF THE INVENTION The present invention provides a process for applying a conductive paste to a ceramic electronic component body and baking the conductive paste to form an external electrode; A method for manufacturing a ceramic electronic component, comprising: a step of polishing; and a step of forming at least one plating film on the external electrode by wet plating after barrel polishing.

[0012]

According to the method of the present invention, after the external electrode is formed, the surface of the external electrode is smoothed by barrel polishing. Therefore, the pores on the surface of the external electrode are closed by the polishing, whereby
It is possible to prevent the plating solution from entering the ceramic electronic component during plating.

Further, since the surface of the external electrode is smoothed by the above-mentioned polishing, a plating film having a uniform thickness can be stably formed thereon, and the gloss of the plating film can be improved.

That is, the present invention is characterized in that a step of closing pores inevitably formed in an external electrode formed by baking a conductive paste by polishing and smoothing the surface of the external electrode is provided. .

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be clarified by describing embodiments of the present invention. Experimental Example 1 According to a conventional method, a ceramic electronic component element having a dimension of 3.2 × 1.6 × 1.25 mm for a multilayer capacitor was prepared. Next, Ag was applied to both end faces of the ceramic electronic component body.
An external electrode was formed by applying and baking the paste to obtain the structure shown in FIG.

Thereafter, 1,000 ceramic electronic component bodies 21 each having an external electrode formed therein are put into a cylindrical pot 20 having a capacity of 500 ml shown in FIG. 4, and further, 200 ml of water and a 3 mm diameter alumina are formed. Abrasive 2
2, and the pot 20 was rotated around the axial direction for 30 minutes at a rotation speed of 90 rpm. By this barrel polishing, the external electrode surface is polished,
The pores that existed after sintering were closed, and the glass frit that had precipitated unevenly was scraped off, and the surface of the external electrode was smoothed. Regarding the multilayer capacitor chip polished as described above (Example) and the multilayer capacitor chip not subjected to the barrel polishing (Comparative Example), Ni was electrolytically plated on the external electrode surface to a thickness of 2 μm. The Sn plating property was evaluated in the same manner as described above.

Evaluation of Sn plating property: In a Sn plating bath,
Sn plating was performed on the Ni plating film by flowing a current three times the normal current density, and the presence or absence of delamination in the plated ceramic electronic component body was detected by an ultrasonic flaw detection method. The delamination rate shown in Table 1 below indicates the rate at which delamination occurred for each of 1000 examples and comparative examples.

Further, each of the 1000 laminated capacitor chips of the embodiment and the comparative example, on which Sn was plated as described above, was allowed to stand for 1000 hours in an environment of a relative humidity of 85% and a temperature of 70 ° C. The moisture resistance load test was performed by measuring the insulation resistance between the external electrodes. The results are shown in Table 1.

[0019]

[Table 1]

As is clear from Table 1, after the external electrodes were polished under the above conditions as in the embodiment, the Ni plating film and the S
It can be seen that when the n-plated film is formed, the delamination rate can be made substantially zero, and none of the components is judged to be defective in the moisture resistance load test. That is, it is considered that pores on the surface of the external electrode are closed and unnecessary glass frit existing on the surface can be removed by the barrel polishing, so that the delamination phenomenon can be effectively prevented.

EXPERIMENTAL EXAMPLE 2 Next, an experiment was conducted in the same manner as in Experimental Example 1 except that the polishing conditions were changed to generate gloss on the surface of the plating film and occurrence of defective external electrodes after plating.

Selection of Rotation Speed of Pot Using a large number of spherical ceramic balls having a diameter of 5 mm as abrasives, the rotation speed of the pot was changed between 0 and 200 rpm, and the pot was rotated for 30 minutes. In the subsequent steps, a Ni plating film and a Sn plating film were formed in the same manner as in Experimental Example 1. The gloss of the surface of the formed plating film was measured.
Regarding the gloss, the external appearance was evaluated by visual observation, and 10 to 10 from excellent gloss to insufficient gloss.
The evaluation was divided into stages. FIG. 5 shows the results.

As is apparent from FIG. 5, the polishing material slips down the inner wall of the pot when the rotation speed is low, and together with the inner wall of the pot when the rotation speed is too high. The surface of the external electrode was not sufficiently polished, possibly due to rotation of the abrasive and the capacitor chip, and the glossiness of the final plating film surface was not sufficient. Therefore,
In order to improve the glossiness of the plating film surface by performing barrel polishing, it is preferable to perform the rotation at a rotation speed of 50 to 150 rpm.

Selection of Diameter of Abrasive Material Barrel polishing was performed by rotating the pot for 90 minutes while setting the rotation speed of the pot to 90 rpm. After barrel polishing, a plating film was formed in the same manner as in Experimental Example 1, and the gloss of the plating film surface was determined in the same manner as the selection of the rotation speed. The results are shown in Table 2 below.

[0025]

[Table 2]

As is apparent from Table 2, the diameter of the abrasive is 2
It can be seen that when the thickness is in the range of 10 to 10 mm, the glossiness of the plating film surface is good. The above barrel polishing is thought to be performed by an impact when the abrasive falls in the pot and collides with the external electrode surface of the multilayer capacitor chip. However, when the diameter of the abrasive is less than 2 mm, the weight of the abrasive decreases. Therefore, it is considered that the impact becomes too small and a sufficient polishing effect cannot be obtained. Conversely, if the diameter of the abrasive is too large, the abrasive may not be evenly distributed in the pot, or polishing variation may occur, and finally the gloss variation of the plating film between the multilayer capacitor chips was large. .

Selection of polishing time Using an abrasive made of ceramic balls having a diameter of 5 mm,
Polishing was performed at a rotation speed of 90 rpm within the time shown in Table 3 below. The subsequent steps were the same as in Experimental Example 1, and the glossiness of the plating film surface was evaluated in the same manner as described above. In addition, the shaving amount at the edge of the external electrode after polishing, that is, the thickness of the external electrode at the edge indicated by arrow A in FIG. 1 was measured.

The results are shown in Table 3 below.

[0029]

[Table 3]

As is clear from Table 3, by setting the barrel polishing time to 30 minutes or more, the glossiness of the plating film on the surface of the external electrode is improved. If the polishing time is less than 30 minutes, polishing is not sufficiently performed. The glossiness of the film surface was not sufficient.

The thickness of the external electrode at the edge portion is important for ensuring electrical connection between the end surface of the ceramic electronic component body and the external electrode portions on the side surface and the upper and lower surfaces. This is important for preventing the plating solution from entering the inside, and is also important for preventing the solder cracking resistance. However, when the barrel polishing time exceeds 90 minutes, the shaving amount of the external electrode at the edge portion exceeds 5 μm, and therefore, the thickness of the external electrode at the edge portion becomes too thin, which is inappropriate.

From the selection of the rotation speed of the pot, the selection of the diameter of the abrasive, and the selection of the barrel time during the barrel polishing, when polishing the external electrode surface of the multilayer capacitor chip, a spherical shape having a diameter of about 2 to 10 mm is used. It can be seen that it is preferable to use a ceramic material as an abrasive, set the rotation speed during barrel polishing to 50 to 150 rpm, and rotate the pot for 30 to 90 minutes.

However, the number of rotations of the pot, the diameter of the abrasive, and the barrel polishing time during the barrel polishing vary depending on the composition and dimensions of the target ceramic electronic component body and the composition and dimensions of the external electrodes. The above range may not always be preferable. That is, since the polishing conditions vary depending on the object, they cannot be uniquely determined.

Although the above embodiment has been described with reference to a multilayer capacitor, the present invention can be applied to a method of manufacturing a ceramic electronic component other than a multilayer ceramic electronic component such as a multilayer capacitor. In other words, when a plating film is formed by wet plating on the surface of an external electrode even in a ceramic electronic component having no internal electrode,
By applying the manufacturing method of the present invention, the glossiness of the plating surface on the external electrode can be increased, and a uniform plating film can be stably formed.

[0035]

According to the present invention, since the external electrode is polished prior to the formation of the plating film after the external electrode is formed, the polishing can close the pores in the external electrode baked with the conductive paste. Therefore, it is possible to prevent the plating solution from entering the ceramic electronic component body during wet plating, so that it is possible to prevent delamination between layers in the multilayer ceramic electronic component and to reliably prevent a decrease in insulation resistance and the like. It is possible to do. In particular, when an internal electrode made of a base metal such as Ni is used, oxidation or the like by a plating solution can be reliably prevented, and therefore, a highly reliable ceramic electronic component with even more excellent moisture resistance. Can be provided.

Further, since the foreign matter on the surface of the external electrode is reliably removed by the barrel polishing, plating defects such as insufficient plating can be reduced. According to the inventor of the present application, it has been confirmed that the plating failure occurrence rate can be reduced to 5 ppm or less in the method of the present invention, while the plating failure occurrence rate was conventionally about 20 ppm.

Further, by performing the above polishing,
The glossiness of the finally formed plating film surface is increased,
In addition, variations in glossiness are reduced. Therefore, a ceramic electronic component having excellent appearance quality can be provided.

Further, since the surface of the external electrode becomes smooth, the solderability is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a multilayer capacitor chip on which external electrodes are formed.

FIG. 2 is a partially cutaway enlarged sectional view showing a state where a plating film is formed on an external electrode.

FIG. 3 is a partially cutaway sectional view showing a multilayer capacitor chip when external electrodes are baked.

FIG. 4 is a perspective view for explaining barrel polishing.

FIG. 5 is a diagram showing a relationship between the number of rotations of a pot during barrel polishing and the glossiness of a plating film surface on an external electrode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ceramic electronic component body 7, 8 ... External electrode 9, 10 ... Plating film

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-192108 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01G 1/14 H01G 1/147 H01G 4 / 12 H01G 4/30

Claims (1)

(57) [Claims] A step of applying a conductive paste to the ceramic electronic component body and baking the conductive paste to form an external electrode; a step of barrel polishing the external electrode of the ceramic electronic component body; Forming at least one plating film on the external electrodes by wet plating.