JPH09205035A - Multilayered ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance reliability in soldering a multilayered ceramic capacitor to a wiring board by providing a second outer electrode, composed of a mixture of copper or a copper alloy, nickel or a nickel alloy and an organic adhesive, on a first outer electrode. SOLUTION: A mixture of silver or a silver palladium alloy, glass and an organic adhesive is applied, as an outer electrode 3, onto the end face 8 of a capacitor element 7 and baked at about 800 deg.C for 30 minutes to form a first outer electrode 4. It is then coated with a mixture of silver clad copper powder having mean grain size of 10μm, silver clad nickel powder and phenol resin based adhesive and baked at about 200 deg.C for 30 minutes to form a second outer electrode 5. Finally, the second outer electrode 5 is subjected to molten solder plating to form a third electrode thus obtaining a multilayer chip ceramic capacitor.

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 multilayer ceramic capacitor.

[0002]

2. Description of the Related Art After forming a chiller into a film from ceramic fine particles, a solvent and a binder, the chiller is dried to form a green sheet. As shown in FIG. 1, a paste ink of a silver-palladium alloy and an organic binder is applied to the surface of a green sheet to form an internal electrode 2. Next, after laminating a plurality of green sheets on which the internal electrodes 2 are formed, pressure is applied by applying pressure so that the green sheets on which the internal electrodes 2 are formed are adhered to each other. Next, after cutting the green sheet after the pressure bonding into strips, 1
It is fired at about 500 ° C. to obtain a capacitor element 7.

A mixture of a silver-palladium alloy and an organic adhesive is applied to the side surface 8 of the capacitor element 7 to form a first external electrode 4. Next, after drying and curing the first external electrode 4, nickel plating is performed on the first external electrode 4 to form a second external electrode 5. Next, a method of forming a multilayer ceramic capacitor as a third external electrode 6 by forming a solder layer on the second external electrode 5 is general.

[0004]

As shown in FIG. 2, the external terminal 3 of the multilayer ceramic capacitor has a structure in which a mixture of a silver palladium alloy and an organic adhesive is applied to an end face 8 of the capacitor element 7 as shown in FIG. Some have only the electrode 4. When the multilayer ceramic capacitor having only the first external electrode 4 is mounted on a wiring board and subjected to flow soldering, the silver palladium alloy as the first external electrode 4 elutes in the molten solder, and the end face 8 of the capacitor element 7 is exposed. In some cases, solder cracking may occur and flow soldering cannot be performed.

As shown in FIG. 1, a mixture of a silver-palladium alloy and an organic adhesive is applied to the end face 8 of the capacitor element 7 to form the first external electrode 4 in order to prevent the solder cracking. Next, nickel plating is performed on the first external electrode 4 to form the second external electrode 5. Next, a solder layer is formed on the second external electrode 5 to form a three-layer structure of the third external electrode 6. The multilayer ceramic capacitor having the above three-layer structure,
When nickel plating for forming the second external electrode is performed, a plating solution remains on the capacitor element 7, and the insulation resistance is deteriorated during use of the multilayer ceramic capacitor.

A mixture of a silver-palladium alloy and an organic adhesive is applied to the end face 8 of the capacitor element 7 for the purpose of preventing the above-mentioned drawbacks to form a first external electrode 4. Next, a second external electrode 5 made of a mixture of copper or a copper alloy and an organic adhesive is formed on the first external electrode. Next, a solder layer is formed on the second external electrode 5 to form a third external electrode 6. However, the solder or solder may be generated by the copper or copper alloy of the second external electrode 5, and the organic adhesive may be exposed and the solder may not be easily wetted.

[0007]

According to the present invention, as shown in FIG. 1, an end face 8 of a capacitor element 7 is made of a mixture of silver or a silver-palladium alloy, glass and an organic adhesive. (1) forming an external electrode 4, then providing a second external electrode 5 made of a mixture of copper or a copper alloy and nickel or a nickel alloy and an organic adhesive on the first external electrode 4, By forming three layers of the third external electrode 6 which is a solder thereon, the reliability of the solderability of the multilayer ceramic capacitor to the wiring board is improved, and the reliability when the multilayer ceramic capacitor is used is very large. Improved.

[0008]

According to the capacitor of the present invention, a soldering of the external electrode 4 and a plating solution at the time of nickel plating remain on the capacitor element 7 to prevent the deterioration of the insulation of the multilayer ceramic capacitor and the like. It is manufactured.

As means therefor, a first external electrode 4 made of a mixture of silver or a silver-palladium alloy with glass and an organic adhesive and a second external electrode made of a mixture of copper or a copper alloy with nickel or a nickel alloy and an organic adhesive are used. The electrode 5 is provided, and the external electrode 3 having three layers of the third external electrode 6 which is a solder is provided on the second external electrode 5 to manufacture a highly reliable multilayer ceramic capacitor. Also,
As the second external electrode 5, a mixture of nickel or a nickel alloy and an organic adhesive may be used.

[0010]

EXAMPLE An example of the present invention will be described by taking a chip type ceramic capacitor as an example. A solvent and a binder are mixed with barium titanate-based ferroelectric ceramic fine particles to form a mixture, and bubbles in the mixture are defoamed in a vacuum to form a chiller. Next, this chiller is formed into a film having a thickness of 20 to 50 μm and dried at about 150 ° C. for 10 minutes to obtain a green sheet.

Next, as shown in FIG.
The internal electrode 2 having a thickness of 1 to 3 μm is formed on the surface of the substrate using a paste-like ink in which an organic binder is added to silver palladium. This dielectric sheet 1
0 are laminated so that the internal electrodes 2 face each other as shown in FIG. Next, the laminated dielectric sheet 10 is cut along AA 'to form a capacitor element. Next, as shown in FIG. 1, a mixture of silver or a silver-palladium alloy, glass and an organic adhesive is applied to the end face 8 of the capacitor element 7 as the external electrode 3 and baked at about 800 ° C. for 30 minutes to form the first external electrode 4 I do.

On the first external electrode 4, an average particle diameter of 10
A mixture of a silver-coated copper powder, a silver-coated nickel powder, and a phenolic resin adhesive having a thickness of μm is applied, and the first external electrode 5 is baked at about 200 ° C. for 30 minutes. Next, a molten solder plating is performed on the second external electrode 5 to form a third external electrode, thereby obtaining a chip-type multilayer ceramic capacitor. Further, the second external electrode 5 may be coated with a mixture of nickel or a nickel alloy and a phenol resin adhesive.

[0013]

The multilayer ceramic capacitor of the present invention is manufactured as described above, and has the following specific effects. Because the reliability of solderability to the wiring board has been improved,
Conventionally, the soldering defect due to solder cracking is 0.1 ~
Although it was about 1.0%, it disappeared. Since nickel plating was not used as the second external electrode 5, there was no deterioration in the insulation resistance with time due to the plating solution remaining in the capacitor element 7 during plating.

[Brief description of drawings]

FIG. 1 shows a sectional view of the present invention.

FIG. 2 shows a conventional sectional view.

FIG. 3 shows a perspective view of the invention.

FIG. 4 shows a perspective view of the invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ceramic dielectric, 2 ... Internal electrode, 3 ... External electrode, 4 ... First external electrode, 5 ... Second external electrode, 6 ... Third external electrode, 7 ... Capacitor element, 8 ... End face, 9 ...
Green sheet, 10 ... dielectric sheet.

Claims (2)

[Claims] 1. A multilayer ceramic capacitor comprising a plurality of ceramic dielectric sheets each having an internal electrode formed on a ceramic dielectric and having external electrodes attached thereto, comprising a mixture of silver or a silver-palladium alloy, glass and an organic adhesive. A first external electrode is formed, a second external electrode made of a mixture of copper or a copper alloy, nickel or a nickel alloy and an organic adhesive is provided on the first external electrode, and a solder is further formed on the second external electrode. 3. A multilayer ceramic capacitor, comprising an external electrode having three layers of a third external electrode. 2. A multilayer ceramic capacitor according to claim 1, wherein a mixture of nickel or a nickel alloy and an organic adhesive is used for the second external electrode.