JP3062279B2 - Ceramic electronic component and method of manufacturing the same - Google Patents

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 having improved external electrodes and a method of manufacturing the same.

[0002]

2. Description of the Related Art As a ceramic electronic component having external electrodes, there is a multilayer ceramic capacitor as shown in FIG.

This multilayer ceramic capacitor includes a columnar ceramic chip 21 having an internal electrode 21a, and a pair of external electrodes 22 provided at both ends of the ceramic chip 21. The internal electrodes 21a are made of nickel, are laminated in multiple layers via ceramics, and have their edges alternately exposed. The external electrode 22 has a three-layer structure, and the first layer 22a on the chip side is made of nickel,
The second layer 22b is nickel, and the third layer 22c is solder (tin-tin).
Lead alloy).

[0004] This multilayer ceramic capacitor firstly
After stacking a plurality of unfired ceramic sheets on which an electrode paste containing nickel as a main component is printed in a predetermined pattern, and cutting this into a predetermined size, a columnar unfired chip is obtained. An electrode paste containing nickel as a main component is applied to both ends of the unfired chip and fired. The unfired ceramic is fired and each electrode paste is fired to form the internal electrode 21a and the first electrode paste. Forming a layer 22a and a first layer 22a
After the components after the formation are heated in air at a temperature of 300 to 900 ° C., nickel is plated on the surface of the first layer 22a to form a second layer, and solder is formed on the surface of the second layer 22b. It is manufactured by plating to form the third layer 22c.

In the above-mentioned multilayer ceramic capacitor, the first layer 22a of the external electrode 22 is formed of the same nickel as the internal electrode 21a, so that the internal electrode 21 and the external electrode 22 are formed.
With the first layer 2 of the external electrode 22.
By applying nickel plating (second layer 22b) and solder plating (third layer 22c) to 2a, rust prevention and solder wettability are imparted. In addition, the heat treatment after the formation of the first layer 22a causes the electrical characteristics of the capacitor, for example, the capacitance and ta
The purpose is to prevent the deterioration of nδ.

[0006]

However, in the above-described multilayer ceramic capacitor, when heat is suddenly applied to the external electrode 22 at the time of soldering, internal stress acts on the nickel plating film as the second layer 22b, so that the ceramic is not applied. The chip 22 has a disadvantage of generating cracks. This problem of crack generation is not limited to a multilayer ceramic capacitor, but can also occur in a ceramic electronic component employing the same configuration as an external electrode.

In the above-mentioned manufacturing method, the external electrode 22
The first layer 22a is formed by a heat treatment after the first layer 22a is formed.
Is oxidized, so that the adhesion of nickel plating performed thereafter deteriorates, the adhesion strength decreases, and the strength of the external electrode 22 decreases significantly.

[0008] The present invention has been made in view of the above problems, this increasing the strength of the external electrodes with and has as its object can be prevented cracking during soldering
DOO is to provide a a manufacturing method thereof ceramic electronic component can.

[0009]

In order to achieve the above object, according to the present invention, there is provided a ceramic comprising a ceramic chip having an internal electrode made of a base metal or an alloy thereof, and a pair of external electrodes electrically connected to the internal electrode. In the electronic component, the external electrode is made of a base metal or an alloy thereof, and is provided with an unfired ceramic chip and an electrode page for an internal electrode.
A first layer formed by co-firing with a strike, and palladium
A second layer covering the surface of the first layer , comprising a plating film of nickel, a third layer covering the surface of the second layer , comprising a plating film of nickel or an alloy thereof , and a third layer comprising a plating film of tin or an alloy thereof , And a fourth layer that covers the surface of the second layer.

[0010] In order to achieve the above object, a second aspect is provided.
Then, an unfired ceramic chip having an electrode paste portion for an internal electrode containing a base metal or an alloy thereof as a main component is attached to an external electrode first material containing a base metal or an alloy thereof as a main component .
A step of applying an electrode paste for a layer and simultaneously firing the same with an unfired ceramic chip and an electrode paste for an internal electrode to form a first layer of an external electrode;
After formation , palladium is plated on the surface of the first layer of the external electrode
Forming a second layer of the external electrode, and the outer electrode
After two layers formed, and forming a third layer of the external electrode by plating nickel or an alloy thereof on the surface of the second layer of the external electrodes, after the third layer formation of the external electrodes, the third layer of the external electrode Forming a fourth layer of the external electrode by plating the surface with tin or an alloy thereof to produce a ceramic electronic component.

In the ceramic electronic component according to the first aspect,
Base metal or its alloy formed by paste firing
Palladium plating on the surface of the first layer of the external electrode composed of
Since the second layer made of a metal film is formed, the base metal or
Partly familiar with the alloy and palladium,
High adhesion between the first and second layers of the external electrode
I can do it. Also, a second palladium plating film
On the surface of the layer, nickel or nickel which is familiar with the second layer metal
Since a plating film of the alloy is formed, palladium and
Good compatibility with nickel or its alloys
To obtain a high degree of adhesion between the second and third layers.
Wear.

According to a second aspect of the present invention, there is provided a method of manufacturing a ceramic electronic component.
It can be formed accurately.

[0013]

FIG. 1 shows a multilayer ceramic capacitor according to the present invention. The multilayer ceramic capacitor includes a columnar ceramic chip 1 having an internal electrode 1a and a pair of external ceramic chips provided at both ends of the ceramic chip 1. And an electrode 2.

The internal electrode 1a is made of one or more of base metals such as nickel, copper, lead, zinc, iron, tin, aluminum, cobalt, and chromium, or an alloy thereof. ) And the edges thereof are alternately exposed.

The external electrode 2 has a four-layer structure, and the first layer 2a on the chip side is made of one kind selected from the same base metals as the internal electrode 1a or an alloy thereof.
It is connected to the. The second layer 2b is made of one or more alloys selected from noble metals such as gold, silver, palladium, platinum, and rhodium, and covers the first layer 2a. The third layer 2c is made of nickel or an alloy thereof, and the second layer 2b
Is covered. The fourth layer 2d is made of a plating film of tin or an alloy thereof, and covers the third layer.

Hereinafter, preferred examples of the above-mentioned multilayer ceramic capacitor will be described together with a method of manufacturing the same.

First, an electrode paste for an internal electrode containing nickel as a main component is coated on a surface of an unfired ceramic sheet having a thickness of several tens of μm made of a non-reducing ceramic composition.
Printing is performed in a predetermined pattern with a thickness of m. After printing, several tens of unprinted unfired ceramic sheets are stacked on the printing surface side of the unprinted unfired ceramic sheets and pressed together, and are pressed together with a predetermined size in the stacking direction. It is cut to obtain columnar unfired chips. The nickel layer is exposed at both end surfaces of the unfired chip.

Next, a method of immersing the electrode paste for the first layer containing nickel as a main component with a thickness of several μm to several tens μm on both end surfaces of the unfired chip over the peripheral surface. The unfired chips are fired at a temperature of about 1300 ° C. in a neutral or reducing atmosphere. By this firing, firing of the unfired ceramic and firing of each electrode paste for the internal electrode 1a and the first layer 2a are performed.

Next, a silver film to be the second layer 2b is formed on the surface of the first layer 2a by plating such as electroless plating. The thickness of the plating film formed here is 0.2 μm or more.
5 μm. Then, the component after the formation of the second layer 2b is heated at a temperature of 300 to 900 ° C. in a natural atmosphere (air).

Next, a nickel film to be the third layer 2c is formed on the surface of the second layer 2b of the heat-treated component by plating, and the solder to be the fourth layer 2d is formed on the surface of the third layer 2c. A film of (tin-lead alloy) is formed by plating.
The thickness of the plating film of both layers 2c and 2d is 0.2 μm to 5 μm.
m.

As described above, the first layer 2a of the internal electrode 1a and the external electrode 2 is made of nickel, the second layer 2b is made of silver, and the third layer 2c is made of silver.
Is nickel, and the fourth layer 2d is made of solder to manufacture a multilayer ceramic capacitor. The heat treatment after the formation of the second layer 2b is for preventing deterioration of electrical characteristics of the capacitor, for example, capacitance and tan δ. In addition, since the silver plating film to be the second layer 2b is formed on the surface of the first layer 2a before the heat treatment, the first layer 2
a of course, the second layer is not oxidized, and the third layer 2c is not oxidized.
The nickel plating film to be formed can be satisfactorily adhered to the surface of the second layer 2b.

FIG. 2 shows the results of crack inspection after soldering of the conventional product and the multilayer ceramic capacitor obtained by the above manufacturing method. In this inspection, the thickness of the silver plating film to be the second layer 2b and the thickness of the nickel plating film to be the third layer 2c were 0.2 μm, 2 μm and 5 μm, respectively.
A total of nine types of multilayer ceramic capacitors each having a thickness of μm were prepared for each of 200 pieces, and 200 pieces each having no silver plating film were prepared as conventional products. In the inspection, in order to make the same temperature state as actual soldering, each multilayer ceramic capacitor was heated to about 260 ° C with preheating of 2 minutes or more, and after maintaining the temperature for about 3 seconds, it was allowed to cool naturally. Then, the cross section of each multilayer ceramic capacitor was visually observed with an optical microscope to identify occurrence of cracks.

As can be seen from the figure, in the conventional product having no silver plating film, cracks occur when the nickel plating film is 0.2 μm, 2 μm, and 5 μm, respectively. The cracks are thicker in the nickel plating film. It was confirmed that it increased. On the other hand, in the invention product having the silver plating film as the second layer 2b, no crack was generated regardless of the thickness of the nickel plating film of the third layer 2c. Although no test results are shown, good results similar to those of the invention described above were obtained also in the case of a multilayer ceramic capacitor in which the first layer 2a of the external electrode 2 was made of copper.

FIG. 3 shows the results of inspection of the strength of the external electrodes of the conventional product and the multilayer ceramic capacitor obtained by the above-described manufacturing method. In this inspection, 10 invention multilayer ceramic capacitors having a silver plating film having a thickness of 3 μm to be the second layer 2b were prepared as invention product 1, and 10 conventional ceramic capacitors having no silver plating film were prepared. Also,
Ten multilayer ceramic capacitors similar to the invention 1 having the first layer 2a made of copper were prepared as the invention 2. In the inspection, a lead wire is soldered to the center of each external electrode of each multilayer ceramic capacitor, and when one lead wire is fixed and the other lead wire is pulled, the external electrode portion is destroyed. The strength was measured by gauge.

As can be seen from the figure, in the conventional product having no silver plating film, the average value of the tensile strength is 1.48 kgf.
On the other hand, in the invention product 1 having the silver plating film, the average value of the tensile strength was significantly improved to 4.51 kgf. Also, in the invention product 2 in which the first layer 2a of the external electrode 2 was made of copper, the average value of the tensile strength was significantly improved to 4.90 kgf.

The same effect as described above can be obtained even when a plating film of a noble metal other than silver or an alloy thereof is used as the second layer of the external electrode.

[0027]

As described in detail above, according to the ceramic electronic component of the first aspect, the first and second layers of the external electrode are provided.
High degree of adhesion between each other and between the second and third layers
And the strength of the external electrode can be greatly increased.
Even if internal stress occurs in the external electrode during
Cracks on the external electrodes
Can be stopped.

According to a second aspect of the present invention, there is provided a ceramic electronic component according to the first aspect.
Products can be manufactured accurately, and the same effects
Obtainable.

[Brief description of the drawings]

FIG. 1 is a sectional view of a multilayer ceramic capacitor according to the present invention.

FIG. 2 is a diagram showing crack inspection results after soldering.

FIG. 3 is a diagram showing an inspection result of external electrode strength.

FIG. 4 is a cross-sectional view of a conventional multilayer ceramic capacitor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ceramic chip, 1a ... Internal electrode, 2 ... External electrode, 2a ... 1st layer, 2b ... 2nd layer, 2c ... 3rd layer, 2d
... 4th layer.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masahiro Arai 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Yuden Co., Ltd. (56) References JP-A-59-16323 (JP, A) Shokai Sho-59 −44031 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01G 4/00-4/42

Claims (2)

(57) [Claims] 1. An internal electrode made of a base metal or an alloy thereof.
A ceramic chip that inherent in the ceramic electronic component and a pair of external electrodes which conduct to the internal electrodes, the external electrodes made of a base metal or an alloy thereof, green ceramic chip
Formed by simultaneous baking with electrode paste for pumps and internal electrodes
And a second layer made of a palladium plating film and covering the surface of the first layer.
Table of the second layer comprises a layer of nickel or plated film of the alloy
A third layer covering the surface of tin or a ceramic electronic component that consists plating film of an alloy covering the surface of the third layer was composed of the fourth layer, characterized in that. 2. An unfired ceramic chip having an electrode paste portion for an internal electrode containing a base metal or its alloy as a main component, and an external ceramic containing a base metal or its alloy as a main component.
A step of applying an electrode paste for the first electrode layer and simultaneously sintering this with an unfired ceramic chip and an electrode paste for the internal electrode to form a first layer of the external electrode; After forming the first layer, the surface of the first layer of the external electrode is
Forming a second layer of the external electrode by plating palladium ; and, after forming the second layer of the external electrode, plating a third layer of the external electrode by plating nickel or an alloy thereof on the surface of the second layer of the external electrode. Forming a third layer of the external electrode, and forming a fourth layer of the external electrode by plating tin or its alloy on the surface of the third layer of the external electrode after forming the third layer of the external electrode. Manufacturing method of ceramic electronic components.