JPH05290619A - Conductive palladium paste - Google Patents

Abstract

PURPOSE:To provide conductive Pd paste causing less delamination, which is generated at the time of manufacturing a thin-film electrode with less quantity of Pd in forming the conductive Pd paste for high temp. baking used for ceramic electrode parts. CONSTITUTION:In forming Pb electrode paste, Pb powder 4 is combined with one of such metals each forming a stable oxide under a high temperature given during its baking as Ti, Cr, Mn and the like, so that alloy or compound powder 5 may be formed. Alternatively, Pb powder whose surface is coated with one of those metals or the mixed powder consisting of the Pd powder 4 and one of those metal powder is used to form Pb paste, so that delamination in an electrode 1 may be suppressed even in thinning the layer of the electrode 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive Pd paste for high temperature firing which is mainly used for ceramic electronic parts such as laminated ceramic capacitors.

[0002]

2. Description of the Related Art Conventionally, as a conductive paste for an internal electrode of a laminated ceramic which is fired at a high temperature in the air, a paste containing Pd powder, an organic binder, a solvent and a small amount of an organic additive has been used. In part, montmorillonite powder and ceramic powder have been added to suppress internal structural defects.

[0003]

When Pd is used as the internal electrode of the monolithic ceramic capacitor, the metal Pd is changed to palladium oxide during the sintering process, and is rapidly reduced to metal Pd at a temperature of about 820 ° C. .. When the amount of Pd is large, the reduced Pd particles combine to form a single plate electrode. However, when the amount of Pd is small, the electrode does not become a plate-shaped metal, and the electrode becomes meshed or broken, which may cause an increase in internal resistance or a decrease in capacity. Therefore, the thickness of the internal electrode is currently about 2 μm, and it has not been possible to reduce the thickness to 1 μm or less.

An object of the present invention is to solve these problems and to provide a paint for Pd electrodes, which can make the electrode film thinner.

[0005]

In order to solve the above-mentioned problems, the conductive Pd paste of the present invention is composed of Pd powder, an organic binder, a solvent, and other organic additives for electrode P.
In d paste, Pd powder in Pd paste is
It contains a metal that forms a stable oxide at high temperature, which can suppress the contraction of the Pd metal itself due to the surface energy during electrode firing. Furthermore, in the present invention, the above metal desirably contains 0.5 to 30 atomic% as a metal component in the paste. Further, the present invention is characterized in that the metal is an alloy powder or a compound powder, or a powder in which the surface of the Pd powder is coated with the metal.

The same action as this can be obtained by uniformly dispersing the metal powder in the Pd paste.

Here, the above metals are Ba, Nb, Cr and M.
n, Fe, Co, Zn, Ti, Ta, Zr, Sn, S
b, Cu, Mg, Si, Ni, Pb, Al, Cd, S
It is composed of at least one of r, Ce, Ca, and La.

[0008]

With the above-described structure, the present invention can enhance the bonding force between the electrode and the ceramic through the oxide discharged from the electrode Pd during firing of the electrode, and suppress the shrinkage of the Pd metal itself due to the surface energy. Even when the electrodes are thinned, it is possible to prevent the internal electrodes from being reticulated and broken.

The details are as follows. The problem of reticulation or breakage of the internal electrode Pd occurs because there is almost no interfacial energy effect between the metal Pd and the ceramic during the sintering process of Pd, and the influence of the surface energy of the metal Pd is greater. That is, the surface energy is generated when Pd acts to reduce the surface area and Pd tends to be close to a sphere at a high firing temperature. In order to solve this problem, it is necessary to increase the interfacial energy between the Pd electrode and the ceramic.

The conductive Pd paste of the present invention contains a metal that forms a stable oxide at a high temperature during firing.
In the process in which Pd, which has been once oxidized during firing, is further sintered after reduction, the oxide of the above-mentioned metal acts as a different phase of the metal P.
By being precipitated from the d phase, an oxide is generated at the interface between the electrode Pd and the ceramic. Since the bonding force between the oxide and the ceramic is strong and the oxide is relatively uniformly deposited at the electrode interface, it overcomes the surface energy of the Pd metal itself and prevents Pd from becoming spherical. By this action,
It is possible to make a thinner layer of Pd internal electrode as compared with the Pd internal electrode thickness currently used.

[0011]

EXAMPLES Examples of the present invention will be described in detail below.

(Example 1) Pd was formed on a green sheet 2 prepared by using a dielectric material containing barium titanate as a main component.
An internal electrode 1 was formed by a screen printing method using a paste (FIG. 1), the green sheets were laminated and then cut to produce a green chip (FIG. 2).

As the Pd paste, Pd powder 4 having a diameter of about 0.3 μm, ethyl cellulose as a binder resin,
A mixture of terpineol as a solvent at a predetermined mixing ratio, and this paste containing C having a diameter of about 0.2 to 0.3 μm.
r, Fe, Sn, Cu, Ni, TiBa alloy powder 5 as a metal component 0.1, 0.5, 3, 30, 50 atomic%
And a binder resin and a solvent were added to adjust the viscosity according to the addition amount, and the coating amount was adjusted so that the electrode 1 having a thickness of 1 μm was obtained after firing. It was printed on top of two (Fig. 3).

The green chip produced as described above was degreased at 400 ° C. and then fired at 1280 ° C. After firing, by observing the polished cross section using a microscope,
The state of the internal electrodes was examined.

The results of observing the state of the internal electrodes from one section are shown in (Table 1). Here, in the cross section being observed, electrodes having 90% or more continuous electrodes are marked with ⊚, 80% to 90% with continuous electrodes are marked with ◯, and 60 to 80% are marked with Δ.
Marks, and those with 60% or less were marked with X.

[0016]

[Table 1]

When the metal component is only Pd, the electrode has a substantially flat plate shape with a thickness of 2 μm after sintering, and defects are present in some places. However, when the paste is applied to a thickness of 1 μm, It was observed that, in the cross section after sintering, the part where Pd was not connected was nearly half, and the internal electric discharge was beginning to occur. When the metal component of the present invention is added,
Addition of 0.1 atomic% has a slight effect and tends to reduce internal electric discharge, but the continuity as an electrode was not yet sufficient. However, with the addition of 0.5 atomic%, there was a case where almost the same electrode continuity as that of Pd alone having a thickness of 2 μm was obtained. If the amount added is further increased, the bonding between the interface between the electrode and the ceramic will be good, and the internal electrical breakdown will be further reduced, but if the amount added reaches 50 atomic%,
The content rate of metal Pd decreased, and the internal electric discharge was again generated. Therefore, it is considered that about 30 atomic% is the upper limit of the added amount.

Further, Ag external electrodes were baked on these sintered chips and the capacity characteristics were examined. As a result, 0.5 atomic
%, The capacity was slightly decreased, but in almost all cases, almost the same characteristics as the additive-free 2 μm-thickness were obtained. However, when the amount added was more than that, the addition metal was other than the TiBa alloy powder and the Ti powder, and the capacity change and the temperature characteristic change occurred. Therefore, when increasing the amount of the added metal, it is necessary to adjust the type and the amount of the added metal in consideration of the fact that the additive element is supplied from the electrode to the ceramic phase.

(Example 2) 95% by weight of BaTiO ₃ powder,
Nb ₂ O ₅ powder 2% by weight, Co ₃ O ₄ powder 0.7% by weight, C
A ceramic sheet was prepared by using a ceramic powder obtained by mixing 1.3% by weight of aO powder, calcining and pulverizing the powder so as to have a firing thickness of 15 μm. The additive-free Pd paste of Example 1 was printed on the sheet so as to have a thickness of 2 μm after firing, and laminate cutting was performed to produce a green chip.

On the other hand, a ceramic sheet was prepared in the same manner with the composition obtained by removing Co ₃ O ₄ from the above composition, and an electrode paste prepared by adding 4 atomic% of Co metal to the additive-free Pd paste of Example 1 was fired thereon. Printing was performed so as to have a thickness of 1 μm, and lamination cutting was performed to produce a green chip.

Next, these green chips were fired in the same manner as in Example 1, and the state of the internal electrodes was evaluated by observing the polished cross section. In this case as well, the Pd paste containing the Co metal does not cause internal electrical breakdown even with a firing thickness of about 1 μm, and the continuity of the internal electrodes is about the same as the one with a firing thickness of 2 μm when the additive-free Pd paste is used. I was able to get it.

In this case, the amount of Co added to the electrode layer is almost the same as the amount of Co in the former dielectric layer and is supplied to the dielectric layer during firing. Therefore, the dielectric characteristics and the temperature characteristics of the capacitance of both were almost the same.

(Example 3) Cr, Mn, Sb, Si, C
Using each Pd powder containing a and 1 atomic% of Al, a paste was prepared in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. At this time, the inner electrode thickness was controlled to 1 μm after firing.

In this case, a very good state of the internal electrode, which was similar to that in the case of adding 3 atomic% of Example 1, was obtained regardless of which metal was contained.

Also, Zn, Mg, La, Zr, Nb, Pb, Sr,
The same experiment was carried out by making the samples to which Cd and Ce were added by 0.5 to 3 atomic%. In this case as well, the state of the internal electrodes was good although the capacitance characteristics changed slightly.

As described above, according to the present embodiment, the Pd paste is made to contain a metal that forms a stable oxide at a high temperature in an amount of 0.5 to 30 atomic% as a metal component by some method, whereby the internal electrode is fired. Even when the thickness was about 1 μm, it was possible to obtain a material in which internal electric discharge did not occur, and it was possible to make the internal electrode thin.

However, depending on the type and amount of the added metal,
Dielectric properties and temperature characteristics of capacitance may change, so select an additive that has almost the same dielectric composition as the additive metal when it becomes an oxide at high temperature, or an additive that has little effect on the properties. There is a need to. Further, as shown in the second embodiment, the target original characteristics can be obtained by combining the compounding ratio of the dielectric material and the metal amount ratio added to the Pd paste for internal electrodes. ..

Although the Pd paste for the internal electrode of the ceramic capacitor has been described here, Pd is formed on the ceramic surface.
Even when baking is performed, if the Pd layer is thin, Pd does not form a continuous surface but has a mesh structure. However, when the paste of the present invention is used, the same effect as in the case of the internal electrode can be obtained, and the thin film Pd electrode can be sintered.

[0029]

According to the conventional Pd paste, by adding a metal into the Pd paste, which can be changed into an oxide during the firing process and can be stably present as an oxide even in the final sintering step of the ceramic. Pd occupies most of the material cost because it is possible to reduce the thickness of internal electrodes, which was not possible.
Can be halved, and a great economic effect can be brought about. Further, the problem of the difference in the thickness shape between the portion where the electrode is present and the portion where the electrode is not present, which is a problem during the production of the high monolithic ceramic capacitor, is largely eliminated, which brings about a great effect in improving the productivity of the high monolithic ceramic capacitor and the like.

[Brief description of drawings]

FIG. 1 is a state diagram in which an electrode paste is printed on a ceramic green sheet.

FIG. 2 is a diagram showing an electrode structure of a green chip produced by stacking and cutting ceramic green sheets on which electrodes are printed.

FIG. 3 is a sectional view when a Pd paste for an electrode according to an embodiment of the present invention is applied on a ceramic green sheet.

[Explanation of symbols]

 1 Electrode 2 Ceramic Green Sheet 3 Ceramic Layer 4 Pd Particles 5 Added Metal Particles

Claims (6)

[Claims] 1. A Pd paste for electrodes, which comprises Pd powder, an organic binder, a solvent, and other organic additives, wherein the paste contains a metal that forms a stable oxide at high temperature. paste. 2. A metal that forms a stable oxide at high temperature is Ba,
Nb, Cr, Mn, Fe, Co, Zn, Ti, Ta, Z
r, Sn, Sb, Cu, Mg, Si, Ni, Pb, A
The Pd paste according to claim 1, wherein the Pd paste is a metal made of any one of l, Cd, Sr, Ce, Ca, and La, or a combination of these metals. 3. The Pd paste according to claim 1, wherein the paste contains a metal that forms a stable oxide at a high temperature in an amount of 0.5 to 30 atomic% as a metal component. 4. A metal which forms an oxide stable at high temperature is contained as an alloy or compound with Pd, or is plated or vapor-deposited on the surface of Pd powder. Pd paste. 5. The electrode is for a ceramic dielectric, and the composition of the metal forming an oxide stable at high temperature to be an oxide is substantially the same as the ceramic dielectric composition. The described Pd paste. 6. The electrode is for a ceramic dielectric, and the metal forming an oxide stable at high temperature is one or a combination of metals contained in the composition element of the ceramic dielectric. Item 2. The Pd paste according to item 1.