JPH031812B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming external electrodes on the body of a multilayer electronic component such as a multilayer ceramic capacitor.

A multilayer electronic component, such as a multilayer ceramic capacitor, is manufactured by interposing internal electrodes 1 between a plurality of ceramic sheets as shown in FIG. After the construction, external electrodes 3 are formed on both ends of the main body where the internal electrodes are exposed. Conventionally, the following wet plating method has been used to form these external electrodes.

That is, after applying a conductive paste such as silver paste to both ends of the main body 2 and baking it to form the first electrode layer 4 of the external electrode 3, a nickel layer is formed on the first electrode layer 4 by electrolytic plating. A second electrode layer 5 and a third electrode layer 6 made of tin were sequentially formed, and the first, second, and third electrode layers 4, 5, and 6 constituted the external electrode 3. However, in such a so-called wet plating method, when forming the second and third electrode layers 5 and 6 as the external electrodes 3, the main body 2 is immersed in the electrolytic solution, so the electrolytic solution covers the electrodes 1. The residual ions invade the main body 2 along these lines, and their residual ions often cause various problems such as a decrease in capacitance and insulation resistance, which deteriorates the characteristics of the multilayer ceramic capacitor.

In view of the above-mentioned conventional drawbacks, the present invention employs sputtering, vacuum evaporation, or plasma spraying, which is a so-called dry plating method, to form both the second and third electrode layers of the external electrode. This prevents factors that cause deterioration of characteristics such as a decrease in resistance, stabilizes the operation of electronic components over a long period of time, and makes it possible to obtain electronic components with good heat resistance and solder adhesion to solder. .

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. A multilayer ceramic capacitor, which is an example of an electronic component manufactured by the method of the present invention, has the same structure as that obtained by the conventional method as shown in FIG. 1, and the same parts are indicated by the same reference numerals. shall be. That is, the multilayer ceramic capacitor 7 obtained by the method of the present invention has a main body 2 and external electrodes 3 formed at both ends thereof, as shown in FIG. ... are parallel to each other and alternately exposed at opposite ends of the main body 2. The external electrode 3 consists of a first electrode layer 4 directly connected to the internal electrode 1, a second electrode layer 5 of nickel, and a third electrode layer 6 of tin.

However, the external electrode 3 in the capacitor 7
A first embodiment of the method for forming the capacitor will be described based on the forming process diagrams shown in FIGS.

<First Example> A. Prepare the main body 2. This main body 2 is made by applying a paste-like electrode material containing a high melting point metal as a main component to predetermined positions on a plurality of ceramic sheets by means such as printing or coating, and then laminating and press-bonding these ceramic sheets. It is formed by firing this. As a result, the ceramic sheet becomes an integrated dielectric 8, and the paste-like electrode material is baked to become the internal electrode 1.

(b) A conductive paste containing silver, copper, nickel, or the like as a main component is applied to both ends of the main body 2 where the internal electrodes 1 are exposed.

C. Dry the paste.

D. Baking the paste in an electric furnace etc.
As a result, as shown in FIG. 3A, first electrode layers 4, 4 electrically connected to the internal electrodes 1 are formed at both ends of the main body 2, respectively.

E) The main body 2 having the first electrode layer 4 is placed in a sputtering apparatus, and a nickel layer 5' is deposited on the surface of the main body 2 by sputtering. This nickel layer 5' is formed over the entire surface of the main body 2 and the first electrode layer 4 [see FIG. 3B]. This sputtering involves applying a high voltage between an anode and an opposing nickel cathode in an activated gas atmosphere such as argon gas to generate a discharge, and nickel atoms emitted from the cathode are placed in front of the anode. This is done by attaching it to the main body 2.

F. Similarly, a tin layer 6' is deposited on the nickel layer 5' by sputtering [Fig. 3C
reference].

G. As shown in FIG.
Etching resist 9 is applied.

The etching resist 9 is hardened.

Etching is performed using a reetching agent, thereby removing unnecessary portions of the nickel layer 5' and the tin layer 6', and forming a second electrode layer of nickel that just covers only the first electrode layer 4, as shown in FIG. 3E. A third electrode layer 6 of 5 and tin is formed.

Etching resist 9 is placed on the third electrode layer 6.
remains, so remove it.

Through the above steps, a multilayer ceramic capacitor 7 as shown in FIG. 1 is obtained.

<Second Embodiment> Instead of the step (e) of forming the nickel layer 5' by sputtering in the first embodiment, and the step of forming the tin layer 6' by sputtering, vacuum evaporation, which is called a dry plating method, is used in addition to sputtering. Alternatively, the nickel layer 5' and the tin layer 6' may be sequentially formed by vacuum evaporation. The other steps are the same as in the first embodiment.

<Third Embodiment> To form the nickel layer 5' and the tin layer 6', plasma spraying, which can be counted as one of dry plating along with sputtering and vacuum evaporation, may be used. In this case as well, the steps except steps E and F are the same as in the first embodiment.

<Other Examples> Instead of removing unnecessary parts of the nickel layer 5' and tin layer 6' by applying an etching resist and etching treatment, the body surface parts where the nickel layer 5' and tin layer 6' are not required are removed in advance. The nickel layer 5' and the tin layer 6', that is, the second electrode layer 5 and the third electrode layer 6, may be formed only on the surface of the first electrode layer 4 by masking with a masking material.
Masking is performed after the first electrode layer 4 is formed. If masking is employed in this manner, the steps of applying the etching resist 9, curing, etching, and removing the etching resist 9, as in the first embodiment, become unnecessary. In this case, sputtering, vacuum evaporation,
Needless to say, any method of plasma spraying may be used.

The method of the present invention can be applied not only to laminated ceramic capacitors as in the above embodiments, but also to any laminated electronic component whose main body is made by laminating heat-resistant insulating sheets, such as laminated inductors.

As mentioned above, the present invention provides a second electrode layer of nickel and a third electrode layer of tin by sputtering called dry plating, vacuum evaporation, or plasma spraying on the first electrode layer formed on both ends of the main body. Since the main body is not immersed in liquid as in the conventional method, there is no risk of impurities entering the inside of the main body. No deterioration of characteristics such as a decrease in capacitance or a decrease in insulation resistance due to impurities occurs. Therefore, according to the present invention, it is possible to obtain an electronic component that operates stably over a long period of time, and since the electronic component has a second electrode layer made of nickel and a third electrode layer made of tin, there is no need to apply solder to the electronic component. It has sufficient heat resistance and adhesion, and can be wired and connected without any problems.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a multilayer ceramic capacitor obtained by the method of the present invention, FIG. 2 is a diagram of each step of the method of the present invention, and FIGS. 3A to 3E are sectional views of semifinished products in each of the steps. DESCRIPTION OF SYMBOLS 1... Internal electrode, 2... Main body, 3... External electrode, 4... First electrode layer, 5... Second electrode layer of nickel, 6... Third electrode layer of tin, 7... Multilayer ceramic capacitor , 9...Etching resist.

Claims (1)

[Claims] 1. External electrodes electrically connected to the internal electrodes are formed at both ends of the main body of the laminated electronic component, which is constructed by interposing internal electrodes between a plurality of heat-resistant insulating sheets and laminating the sheets together. After applying a conductive paste to required parts at both ends of the main body of the multilayer electronic component and baking it to form a first electrode layer, nickel is deposited on the first electrode layer by sputtering, vacuum evaporation, or plasma spraying. A method for forming an electrode for a laminated electronic component, comprising sequentially forming a second electrode layer and a third electrode layer made of tin.