JPH0475646B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer ceramic capacitor, and more particularly to a method for manufacturing a structure that improves the reliability of connections during mounting.

Conventionally, multilayer ceramic capacitors have been mounted, for example, by soldering onto conductive lands 2 provided on the surface of a ceramic insulating substrate 1, as shown in the perspective view of FIG. 1 and the partially enlarged sectional view of FIG. It had been. The width of this conductive land 2 may be wider than the width of the external electrode 4 of the multilayer ceramic capacitor 3, but generally a predetermined distance is required between it and other adjacent components, and the mounting space is limited. Because of this problem, a land 2 having a width corresponding to the width of the external electrode 4 was provided as shown in FIG.

On the other hand, as shown in FIG. 3, which is a perspective view including a partial cross section of the multilayer ceramic capacitor 3, the internal electrodes 6 are drawn out to the side surfaces of the external electrodes 4, so that the upper and lower surfaces of the external electrodes 4 are aligned with the edge of one side of the drawn-out surface. was electrically connected across. In a rectangular parallelepiped structure, contact wear is severe at edges and corners of one side, and the mechanical strength is weaker than other parts, so as shown in a partially enlarged sectional view in FIG. There was a drawback that the electrical connection was left open at the rounded part 7, which was removed. Furthermore, even if the component is mounted as shown in Fig. 1 without being in an open state, the electrode adhesion layer at the rounded part 7 in Fig. 4 is thin, and therefore the electrical resistance becomes large, so the connection reliability was extremely low.

An object of the present invention is to provide a method for manufacturing a multilayer ceramic capacitor with high reliability of electrical connection.

According to the present invention, a method for manufacturing a multilayer ceramic capacitor is obtained, which is characterized in that the multilayer ceramic capacitor is rounded in advance before external electrodes are formed, and then the external electrodes 4 are coated and baked. In particular, according to the present invention, particles with a maximum particle size of 1.0 mm or less are made of materials included in the composition of the porcelain dielectric, or materials that do not cause chemical reactions with the porcelain dielectric at high temperatures of 500°C to 800°C, or sintered products thereof. of abrasive mixed with a buffer solution,
The method is characterized by including the step of inserting a laminated ceramic capacitor before forming external electrodes into the container and rotating and polishing the container for a predetermined period of time to round and round each edge and corner of the laminated ceramic capacitor. A method for manufacturing a multilayer ceramic capacitor is obtained.

Hereinafter, the present invention will be explained in detail with reference to FIGS. 5 to 8. 5A to 5D are perspective views showing specific examples of the external shape of the abrasive used in the practice of the present invention. The polishing effect is most excellent in the triangular prism shape shown in FIG. 1a, followed by the cubic shape in FIG. 1b, the cylindrical shape in FIG. 1c, and the spherical shape in FIG. 1d.
The laminated ceramic capacitor itself also acts as an abrasive and has the same effect as the shape shown in FIG. 1b. During the polishing process, these abrasives are also ground away, and the ground powder adheres to the laminated ceramic capacitor, degrading the capacitor's properties under the high temperature conditions of the external electrode baking process. For this reason, the material for the abrasive is the raw material that makes up the dielectric ceramic of the multilayer ceramic capacitor, a material that does not react with the ceramic dielectric at high temperatures, such as silicon oxide (SiO ₂ ), or a combination of these materials, as described below. Any suitable material may be used, such as a powder thereof or a product pressed into a predetermined shape and sintered. The size of the abrasive can be selected up to approximately 10 times the size of the laminated ceramic capacitor, but the maximum particle size should be selected for ease of separation between the capacitor and the abrasive after polishing.
Must be 1.0mm or less. In other words, the minimum shape of a multilayer ceramic capacitor is 1.0 x 1.25 x 2.0
mm, and by using an appropriate sieve, it can be easily separated from abrasives with a maximum particle size of 1.0 mm or less. Figure 6 shows the appearance of a multilayer ceramic capacitor before polishing. As an example of the polishing conditions, a high dielectric constant ceramic capacitor having a shape as shown in Fig. 6 is filled to approximately 50% of the total internal volume of a plastic cylindrical rotary pot, and then approximately 10 to 20% of the total internal volume is filled. Add an abrasive such as silicon oxide (SiO ₂ ) by volume. Next, pure water is added as a buffer solution to fill the container to 80-90% of the total internal volume, the lid is closed, and the container is rotated at a rotation speed of 30-60 rpm for 1 to 5 hours, and then taken out.

As shown in the perspective view of FIG. 7 obtained in this way,
By applying an external electrode to the rounded end of a multilayer ceramic capacitor and baking it, an electrode with a uniform thickness can be formed over the entire surface of the external electrode 4, as shown in the partial cross section of the mounted state in Figure 8. , Land 2
The reliability of the electrode connection with the electrode is significantly improved.

Here, the baking process of the external electrode is performed at a temperature of 500°C to 800°C.
Since the process is carried out at a high temperature of °C, if the fine abrasive powder adhering to the surface of the multilayer ceramic capacitor and the part penetrated from the internal electrode lead-out part causes a chemical reaction with the porcelain dielectric material, the composition of the porcelain dielectric material changes. This not only impairs the desired characteristics but also significantly reduces the reliability of the multilayer ceramic capacitor.
For this reason, the best material for the abrasive is a material powder included in the composition of the porcelain dielectric or its sintered product, and as a result of prototype evaluation, other materials can be used at high temperatures of at least 500°C to 800°C. Good properties can be obtained by selecting materials that do not chemically react with the porcelain dielectric, such as silicon oxide (SiO ₂ ), zirconium oxide (ZrO ₂ ), and alumina (Al ₂ O ₃ ). It turned out that. In addition to the above, titanium oxide, barium titanate, barium carbonate, etc. may also be used as polishing materials.

As explained above, according to the present invention, corners and edges are rounded by a relatively simple polishing process that can be mass-produced on a multilayer ceramic capacitor before external electrodes are formed, and then external electrodes are formed. A multilayer ceramic capacitor with highly reliable physical connections is achieved. The radius of curvature due to polishing is 1/5 to 1/10 of the length of the minimum side of the original rectangular parallelepiped.
By doing the above, the purpose of the present application will be achieved.

[Brief explanation of drawings]

1 and 2 are a perspective view and a partially enlarged sectional view showing an example of a conventional multilayer ceramic capacitor. FIG. 3 is a perspective view of a conventional capacitor including a partial cross section to show the state of the internal electrodes. FIG. 4 is an enlarged sectional view of the external electrode portion of a conventional capacitor.
5a to 5d show embodiments of the present invention. FIG. 3 is a perspective view showing a specific example of the shape of the abrasive material. FIG. 6 is a perspective view showing a multilayer ceramic capacitor before external electrodes are formed. FIG. 7 is a perspective view showing the appearance of FIG. 6 after polishing according to the present invention. FIG. 8 is an enlarged sectional view of a mounting section showing an embodiment of the present invention. 1... Ceramic insulating substrate, 2... Conductive land,
3... Multilayer ceramic capacitor, 4... External electrode,
5...Solder, 6...Internal electrode, 7...Rounded part.

Claims (1)

[Claims] 1. A plurality of internal electrode layers are encapsulated in a ceramic dielectric material, and 2.
A method for manufacturing a multilayer ceramic capacitor in which an external electrode is coated and baked on a prismatic multilayer ceramic body having two end faces and four side faces, the material contained in the composition constituting the ceramic dielectric or
The laminated ceramic body before external electrode formation is placed in a container in which an abrasive agent made of a material that does not cause a chemical reaction with the porcelain dielectric material or a sintered product thereof at high temperatures of 500°C to 800°C is mixed with a buffer solution. a step of rounding and rounding the edges and corners of the laminated ceramic body by rotating and polishing the container for a predetermined period of time; A method for manufacturing a multilayer ceramic capacitor, comprising the step of forming the external electrode to have a uniform thickness over the entire surface so as to commonly cover the external electrode.