JPH02248020A - Laminated ceramic capacitor - Google Patents

Abstract

PURPOSE:To reinforce the junction between an inner electrode and an outer electrode and to prevent decrease in capacitance by a method wherein a Cu-Ag alloy layer is used instead of Cu on the outer electrode of a laminated ceramic capacitor in which Ni is used as the material for the inner electrode. CONSTITUTION:A dielectric 1 and inner electrode 2 consisting of Ni is alternately laminated on a laminated ceramic capacitor, said electrode 2 is connected to every other layer to the Cu-Ag alloy layer 3 on different edge faces. On this external electrode, a second Ni metal layer 4 and a third Sn-Pb alloy layer 5 are provided against the first alloy layer 3. Solderability is improved by the alloy layer 5, and the scraping-off of solder generating when the Cu of the metal layer 3 moves into the alloy layer 5. The Cu-Ag ratio of the Cu-Ag layer 3, as the first layer, constituting the external electrode, is set at 100:1 to 100:50 in terms of parts by weight, the junction between the inner electrode and the outer electrode is reinforced, and the decrease in its capacitance can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a multilayer ceramic capacitor in which base metals are used for internal electrodes and external electrodes.

BACKGROUND OF THE INVENTION Today, the demand for multilayer ceramic capacitors is increasing to meet the demand for smaller, lighter, thinner, and smaller capacitors, and various technical issues to be improved have also been raised accordingly.

One of the items that should be improved is that the materials used for the internal electrodes, such as palladium, are expensive, so attempts are being made to replace them with cheaper materials to lower the product price. From this point of view, the use of Ni as an internal electrode material has been proposed and partially implemented. When Ni is used as the internal electrode material, a base metal such as Cu is also used as the external electrode material. This is because the commonly used Ag external electrode does not have sufficient bonding strength with the Ni internal electrode.

Problems to be Solved by the Invention However, in this configuration in which Ni is used as the internal electrode material and Cu is used as the external electrode material, the bonding between the internal electrode and the external electrode is still insufficient, and as a result, the capacitance is reduced. The reality is that it has the problem of falling through the cracks.

The present invention is intended to solve these problems, and it is an object of the present invention to provide a multilayer ceramic capacitor having a structure that allows sufficient bonding strength between internal electrodes made of Ni and external electrodes.

Means for Solving the Problem In order to solve this problem, the multilayer ceramic capacitor of the present invention has a first layer in which the external electrode is connected to the internal electrode made of Ni, and is provided on a Cu-Ag alloy layer. The second layer is a Ni metal layer, and the outermost third layer is 5n-P.
It has a structure consisting of a b alloy layer.

Function: According to this configuration, the first layer of Cu-A is heated at a predetermined baking temperature.
According to the phase diagram, in the process of baking the g-alloy layer, Cu-
Since the Ag alloy is in a molten state in a fairly wide range of ratios, it is easy to alloy, and the Cu-Ag alloy is easy to alloy with Ni, which is the internal electrode material, so the internal electrode and the external electrode (Cu-Ag alloy layer) The bond with the
There is no possibility that the capacity will run out.

Example An embodiment of the present invention will be described below.

First, Cu metal powder and Ag metal powder are blended in an amount of 1 to 45 parts by weight based on the weight part of CulOO, and a binder, a solvent, and a glass frit are added thereto and mixed.
-Ag paste was produced.

Next, apply this paste to both end faces of the element, dry it,
Baking was performed at 900°C in a neutral atmosphere. Next, Ni plating is performed thereon by an electrolytic plating method to form a Ni metal layer, and then 5n-Pb plating is performed on the Ni metal layer by an electrolytic plating method to form a 5n-Pb alloy layer,
It is a multilayer ceramic capacitor.

Here, the element body is one in which dielectric material 1 and internal electrodes 2 made of Ni are alternately laminated, as shown in FIG. 1 showing the multilayer ceramic capacitor obtained in this example. , and the internal electrodes 2 have different end faces C
It is connected to the u-Ag alloy layer 3 every other layer. Also,
4 is a Ni metal layer, and 5 is a 5n-Pb alloy layer.

Here, in the present invention, the second layer of Ni is used as the external electrode.
The reason for providing the metal layer and the third 5n-Pb alloy layer is to improve soldering properties, as in the past.
A Pb alloy layer is provided, and the second Ni metal layer is used to prevent solder erosion caused by Cu in the first Cu-Ag alloy layer migrating into the 5n-Pb alloy layer. It is provided.

Next, an experiment was conducted to evaluate the bond between the internal electrode and the external electrode. Here, a commonly used BaTiOs material is used as the dielectric 1, and the effective dielectric layer is 1.
The experiment was conducted using two layers.

The results are shown in Table 1 below. In addition, measurements were conducted on a conventional multilayer ceramic capacitor using Cu metal in the first layer of the external electrode, and on a multilayer ceramic capacitor using a Cu-Ag alloy layer (85°C, -45°C) for 20
The rate of change in capacity after 0 cycles (average value of 10 samples) was investigated. Here, of course, the experiment was performed with a second Ni metal layer and a third 5n-Pb alloy layer constituting the external electrode.

(Left below) Table 1 As shown in Table 1, when a Cu-Ag alloy layer is used as the first layer of the external electrode as in this example, there is almost no change in capacitance, and therefore the Ni internal electrode and external electrode (Cu-
It is clear that the bond between the Ag alloy layer and the Ag alloy layer is strong. However, if the amount of Ag exceeds 45 parts by weight relative to 100 parts by weight of Cu, the Cu--Ag alloy layer melts and loses its capacity.

Here, the melting point of Cu is 1083°C, and the melting point of Ag is 961°C, which is lower than that, so if baking is performed at a temperature lower than the baking temperature in the above example, Cu
Although it is theoretically possible to increase the ratio of Ag to that in the above example, on the other hand, the range (amount) of the Cu-Ag alloy in the molten state at the baking temperature decreases, and the Ni It appears that it is difficult to form an alloy with. Therefore, when looking at both the firing temperature of the dielectric (usually around 1200°C) when Ni is used as the internal electrode material and the ease of alloying with the Ni internal electrode, the firing temperature in the example above is Cu-Ag near
It seems better to bake the alloy layer, so CulO
It is considered that the ratio of Ag to O weight parts is preferably 1 to 40 weight parts.

Effects of the Invention As described above, according to the present invention, C is added to the outer electrode of a multilayer ceramic capacitor using Ni as the inner electrode material.
By using a Cu--Ag alloy layer instead of u, the bond between the internal electrode and the external electrode becomes stronger, and the effect of preventing loss of capacitance can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a multilayer ceramic capacitor according to an embodiment of the present invention. ■・・・Dielectric material, 2・・・Internal electrode, 3・
...CuAg alloy layer, 4...Ni metal layer, 5...5n-Pb alloy layer. Name of agent: Patent attorney Shigetaka Awano and one other person Figure 1 / 1-11 Guideline 2- Internal electrode 3-Q -A2 alloy 1 4-1-~l' Eclipse 7L layer 5° -S-Fb alloy layer

Claims (2)

[Claims] (1) A structure in which dielectrics and internal electrodes are alternately laminated, and external electrodes connected to the internal electrodes are provided on both end surfaces, and the external electrodes are connected to the internal electrodes made of Ni. The first layer is a Cu-Ag alloy layer, the second layer provided thereon is a Ni metal layer, and the outermost third layer is a Cu-Ag alloy layer.
A multilayer ceramic capacitor whose layers are made of Sn-Pb alloy layers. (2) The Cu-Ag ratio of the first Cu-Ag alloy layer constituting the external electrode is 100:1 to 100:
40. The multilayer ceramic capacitor according to claim 1, wherein the multilayer ceramic capacitor has a diameter of 40.