JPH08288173A - Ceramic electronic component - Google Patents

Abstract

PURPOSE: To improve solderability of an external electrode by grinding a surface of a Cu sintering external electrode including glass formed on an end surface of a ceramic element. CONSTITUTION: A plurality of internal electrodes 2 are so arranged as to be overlapped in the interior of a ceramic element 1 via a dielectric layer 3 made of ceramics and led out alternately on both end surfaces of the ceramic element 1, and external electrodes 4 made of Cu electrically connected with the internal electrodes 2 are formed on both end surfaces of the ceramic element 1. This external electrode 4 is a Cu sintering electrode including glass, and further, the surface is ground. Accordingly, as glass leaked onto the surface of the external electrode 4 is removed, the electrode has an excellent soldering property. Thus, a plating film by wet type electrolytic plating is not required on the external electrode, and a fear that plating liquid leaks into the ceramic element is removed, so that ceramic electronic components excellent in reliability can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic electronic component, and more particularly to a ceramic electronic component formed with a Cu baking electrode as an external electrode.

[0002]

2. Description of the Related Art For example, a monolithic ceramic capacitor, which is a ceramic electronic component, is
Dielectric layer 30 in which a plurality of internal electrodes 20 are made of ceramic
Ceramic element 10 having a structure in which it is arranged so as to overlap with each other and is alternately drawn out to both end faces.
And an external electrode 40 formed by applying and baking a conductive paste for forming an external electrode on both end surfaces thereof.

By the way, in such a ceramic electronic component, a conductive paste containing noble metal Ag powder or Ag / Pd alloy powder and glass frit is usually used as the external electrode 40 formed by coating and baking. Because
The ratio of the external electrode material cost to the manufacturing cost of the ceramic electronic component is high, which causes a cost increase. Therefore, in order to reduce the cost of the external electrode material, the external electrode 40 is made to be a base metal. For example, an approach is to use Cu having good conductivity and being resistant to solder erosion by the external electrode 40. The Cu external electrodes 40 are formed on the both end surfaces of the ceramic element 10 by Cu.
It is formed by applying and baking a conductive paste containing powder and glass frit.

However, since the volume of Cu powder becomes smaller as it is sintered, the glass becomes external electrode 40 after sintering.
The surface of the external electrode is covered with the glass film. If soldering is performed in this state, there is a problem that the solder wettability of the external electrode is poor and a soldering defect is likely to occur.

Therefore, the baked Cu external electrode 4 is used.
In order to improve the solderability of 0, as shown in FIG.
Sn or Sn with good solderability on the external electrode 40
The / Pb alloy was wet electrolytic plated to form the plating film 50. Note that Ni plating is usually performed before the Sn or Sn / Pb alloy plating is performed.

[0006]

However, the above-mentioned ceramic electronic component (multilayer ceramic capacitor) in which the plating film 50 is formed on the Cu external electrode 40 by wet electrolytic plating is used as a plating solution during plating. Penetrates into the ceramic element 10 through the Cu external electrode 40,
The adhesion strength between the dielectric layer 30 forming the ceramic element 10 and the internal electrode 20 is deteriorated. When such a ceramic electronic component is soldered to a printed circuit board,
A crack may occur between the dielectric layer 30 and the internal electrode 20 due to the thermal shock, and if such a crack is generated, there is a problem that electrical characteristics such as capacitance drop and insulation resistance deterioration are deteriorated. Further, in the ceramic electronic component having the Cu external electrode 40 as described above, the number of steps for forming the plating film 50 by wet electrolytic plating is increased, resulting in an increase in cost.

Therefore, according to the present invention, in order to solve the above-mentioned problem, it is not necessary to plate the external electrode 40 with Cu.
Providing a highly reliable ceramic electronic component in which the cost is not increased due to the formation of the plating film 50 by forming the baking electrode and the crack does not occur between the dielectric layer 30 and the internal electrode 20 due to the thermal shock. The purpose is to do.

[0008]

The present invention is a ceramic electronic component having an external electrode on an end face of a ceramic element, wherein the external electrode is composed only of a baked electrode of Cu containing glass, the surface of which is polished. It is a ceramic electronic component characterized by

[0009]

According to the present invention, the surface of the external electrode is baked by baking Cu containing glass formed on the end face of the ceramic element to remove the glass film covering the surface of the external electrode.
The solderability of the external electrode can be improved. Therefore, it is not necessary to perform conventional wet electrolytic plating on the external electrodes to improve solderability.

[0010]

EXAMPLES Hereinafter, the present invention will be clarified from the description of examples.

FIG. 1 is a sectional view of a monolithic ceramic capacitor which is a ceramic electronic component according to an embodiment of the present invention. As shown in FIG. 1, a plurality of internal electrodes 2 are arranged inside a ceramic element 1 so as to overlap with each other with a dielectric layer 3 made of ceramic interposed therebetween, and are alternately drawn out to both end surfaces of the ceramic element 1. External electrodes 4 made of Cu and electrically connected to the internal electrodes 2 on both end faces of the ceramic element 1.
Are formed. The external electrode 4 is C containing glass.
u is a baking electrode, and its surface is polished,
The glass exuding on the surface of the external electrode 4 is removed, so that the electrode has good solderability. Therefore, the conventional wet electrolytic plating for improving solderability is not applied on the external electrode 4.

The method of forming the external electrodes of the ceramic electronic component (multilayer ceramic capacitor) of the present invention will be described in more detail below.

First, a conductive paste containing Cu powder for forming an external electrode and glass frit is applied to both end faces of the ceramic element 1 and baked to form an external electrode 4. in this case,
As shown in the cross-sectional view of the laminated ceramic capacitor in which the Cu-baked external electrode 4 of FIG. 2 is formed, the surface of the external electrode 4 is covered with the glass film 5. That is, when the Cu powder is sintered, the volume of the Cu powder becomes small and the external electrode 4 becomes dense, so that the glass film 5 is formed as a result of the glass being extruded onto the surface of the external electrode 4. It is what is done. The conductive paste may be applied by any method such as a dipping method and a printing method. The external electrode 4 of Cu is baked at a predetermined baking temperature and in a neutral or weak reducing atmosphere so that the external electrode 4 is not oxidized.

Next, the ceramic element 1 having the external electrodes 4 formed thereon, an abrasive, and a medium such as water or an organic solvent are put into a pot, and the pot is placed on a rotary table, and at a predetermined rotation speed. It is rotated and barrel-polished to remove the glass 5 covering the surface of the external electrode 4. After that, the ceramic element 1 whose surface of the external electrode 4 is polished is taken out from the pot to obtain a ceramic electronic component. The polishing is not limited to the barrel polishing method and may be another polishing method such as a sandblast method.

By the above-mentioned external electrode forming method, a ceramic electronic component having a Cu-baked external electrode 4 having good solderability, in which the glass film 5 covering the surface of the external electrode 4 is removed, as shown in FIG. can get. Therefore, the step of forming a plating film by wet electrolytic plating on the external electrode 4 for improving solderability can be eliminated.

Next, in order to confirm the effect of the ceramic electronic component of the present invention, L dimension 2.0 mm, W dimension 1.25 mm, T
The ceramic electronic component of the embodiment of the present invention shown in FIG. 1 having a size of 0.8 mm and the ceramic electronic component of the conventional example shown in FIG. 3 (two layers of Ni and Sn plating films on a Cu baking electrode) And the heat resistance to solder heat resistance are shown below. The same ceramic element and conductive paste as those used in the examples of the present invention were used for producing the conventional ceramic electronic component.

These tests were carried out by placing a ceramic electronic component on a printed circuit board and immersing it in a solder bath at 260 ° C. for 5 seconds. After the test, the state of soldering of the ceramic electronic component to the printed board was visually inspected, and whether cracks were formed between the dielectric layer 3 and the internal electrode 2 was inspected using an ultrasonic flaw detector. Prior to the test, the ceramic electronic components were
It was immersed in a flux solution of ethanol containing 100%. As a result, it was confirmed that in all 100 of the present invention, no defective soldering of the external electrodes 4 occurred and no cracks were formed. On the other hand, in the conventional ceramic electronic component, it was confirmed that 8 out of 100 cracked parts. Therefore, it can be seen that the electronic components obtained according to the examples of the present invention have good solderability and excellent heat resistance.

[0018]

As described above, the ceramic electronic component of the present invention has the baked external electrode 4 of Cu having a good solderability. Therefore, it is not necessary to form a plating film on the external electrode 4 by wet electrolytic plating. Therefore, infiltration of the plating solution into the ceramic element 1 is eliminated, a crack is not generated between the dielectric layer 3 and the internal electrode 2 due to a thermal shock, and a highly reliable ceramic electronic component having no deterioration in electrical characteristics is provided. Can be realized. Further, it is possible to eliminate the step of forming a plated film by wet electrolytic plating, and it is possible to prevent an increase in cost due to the formation of the plated film. Since the external electrode 4 of the ceramic electronic component of the present invention is an electrode made of Cu, solder erosion is less likely to occur as compared with the conventional electrode made of Ag.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a monolithic ceramic capacitor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a monolithic ceramic capacitor for explaining a process of forming the monolithic ceramic capacitor of FIG.

FIG. 3 is a sectional view of a conventional monolithic ceramic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ceramic element 2 ... Internal electrode 3 ... Dielectric layer 4 ... External electrode 5 ... Glass film

Claims (1)

[Claims] 1. A ceramic electronic component having an external electrode on an end face of a ceramic element, wherein the external electrode comprises only a baking electrode of Cu containing glass, and the surface is polished. Electronic components.