JPS6312375B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a ceramic multilayer capacitor,
In particular, it relates to improvements in electrode materials.

As shown in the drawing, a ceramic multilayer capacitor typically includes a plurality of internal electrodes 1, a ceramic 2 is interposed between each internal electrode 1, and the internal electrode 1 is electrically connected to any external electrode 3. It is said to be in a state of

To manufacture such a ceramic multilayer capacitor, for example, the following method is adopted.
That is, a ceramic green sheet with a thickness of 50 to 100 μm is created by printing, a doctor blade method, a spray method, etc., a paste of metal powder that will become the internal electrode 1 is printed on this ceramic green sheet, and multiple sheets of these are printed. Stacked and heat-pressed,
The integrated product was fired at 1250 to 1400°C in a natural atmosphere to produce a sintered body, and the external electrode 3 that was electrically connected to the internal electrode 1 was baked onto the end face of the sintered body.

In this case, the material of the internal electrode 1 had to satisfy the following conditions.

It must have a melting point higher than the temperature at which ceramic sinters.

Even if heated to a temperature of around 1300℃ in a natural atmosphere, it will not oxidize or react with ceramics upon contact.

Materials for the internal electrode 1 that satisfy these conditions include noble metals such as palladium, platinum, and silver-palladium, and in many ceramic multilayer capacitors to date, such noble metals have been used for the internal electrode 1. It had been.

However, although the above-mentioned noble metals have excellent properties as materials for the internal electrodes 1, they are expensive, and therefore account for as much as 20 to 50% of the cost of a ceramic multilayer capacitor, resulting in increased costs. It had become the biggest cause of this.

In order to cope with such problems, attempts have been made to use inexpensive base metals as materials for the internal electrodes 1. For example, if nickel is used as the base metal, nickel oxidizes when heated in an oxidizing atmosphere of 300° C. or higher and reacts with ceramic, making it impossible to form an electrode. In order to prevent this oxidation of nickel, the ceramic must be fired together with the internal electrode 1 in a neutral or reducing atmosphere, but in general, ceramic is strongly reduced and its specific resistance The value becomes as low as 10 to 10 ⁸ Ωcm, making it unusable as a dielectric for capacitors.

Other attempts to use a base metal as the internal electrode 1 have been made as follows. The reason why the above-mentioned attempt caused problems was that after the process of printing the metal powder paste that was to become the internal electrodes 1, the process of firing the ceramic was carried out. Therefore, if the internal electrodes 1 can be formed after firing the ceramic, the above-mentioned problems will not be encountered. Therefore, as a next attempt,
Instead of "the step of printing the metal powder paste that becomes the internal electrode 1" in the above-mentioned typical process,
A process of printing a paste of carbon powder was carried out. According to this, after the ceramic is fired, the carbon burns, leaving a gap where the internal electrode 1 is to be formed. Therefore, the internal electrode 1 has been formed by injecting molten metal such as aluminum, lead, or tin into the gap.

On the other hand, as the external electrode 3, as mentioned above,
It was formed by baking. As a material for forming the external electrodes 3, silver or silver-palladium paste is generally used and baked. Although this is a common method, since expensive noble metals are used here, as in the case of the internal electrode 1, this is a cause of an increase in the cost of the ceramic multilayer capacitor. Further, the external electrode 3 made of silver or silver-palladium has the disadvantage of being eaten away by the solder when such a ceramic multilayer capacitor is soldered to a printed circuit board or the like as a chip type component. Further, when a base metal such as nickel, lead, aluminum, or tin is used for the internal electrode 1 described above, the compatibility with the external electrode 3 made of such a noble metal is poor, resulting in a problem of poor conduction.

In order to deal with such problems regarding the external electrode 3, attempts have been made to use inexpensive copper as the material for the external electrode 3. However, the formation of the external electrode 3 using copper by baking had an important relationship with the development of glass frit constituting the copper powder paste. Lead borosilicate is a typical glass frit, but when the copper external electrode 3 is formed by baking it in a natural atmosphere, the copper is easily oxidized and becomes copper oxide, so it cannot be used for electricity. The resistance becomes high, making it unsuitable as an electrode. Therefore, one method is to bake the copper paste in a neutral or weakly reducing atmosphere, but in this case, the ceramic is reduced, the insulation resistance deteriorates, and the dielectric loss increases. This causes an inconvenience.

Therefore, the main object of the present invention is to provide a ceramic multilayer capacitor with reduced cost and improved quality.

In summary, the present invention has an internal electrode made of a base metal, and an external electrode made of at least one of copper, nickel, and aluminum.
This is a ceramic multilayer capacitor.

The invention will now be described in connection with various preferred embodiments.

Referring again to the drawings, in an embodiment of the invention:
As the material constituting the internal electrode 1, nickel,
Iron, cobalt, and also lead, aluminum, tin, etc., which have relatively low melting points, are used. These are all cheap base metals.

When using nickel, iron, cobalt, etc. listed as examples of materials for the internal electrode 1, paste of these metal powders is printed on a ceramic green sheet, and the ceramic is coated with these metals in a neutral or reducing atmosphere. The method of firing together with the paste is similar to that described in the conventional example. Here, in order to avoid the problem of ceramic reduction that has occurred in the past, a non-reducible dielectric ceramic composition is preferably used. Examples of such non-reducible dielectric ceramic compositions include the following compositions, which have already been patented by the applicant of the present application.

In the barium titanate dielectric ceramic composition represented by the composition formula {(Ba _1-x Ca _x )O} _n・(Ti _1-y Zr _y )O ₂ , m, x, and y are in the following ranges. A non-reducible dielectric ceramic composition characterized by:

1.005≦m≦1.03 0.02≦x≦0.22 0<y≦0.20 Composition formula {(Ba _1-xy Ca _x Sr _y )O} In the barium titanate dielectric ceramic composition represented by _n・TiO ₂ , m, A non-reducible dielectric ceramic composition characterized in that x and y are in the following ranges.

1.005≦m≦1.03 0.02≦x≦0.22 0.05≦y≦0.35 Composition formula {(Ba _1-xy Ca _x Sr _y )O} Barium titanate dielectric represented by _n・(Ti _1-z Zr _z )O ₂ A non-reducible dielectric ceramic composition characterized in that m, x, y, and z are in the following ranges.

1.005≦m≦1.03 0.02≦x≦0.22 0.05≦y≦0.35 0.00＜z≦0.20 When it is composed of CaZrO ₃ and MnO ₂ and is expressed as the general formula Ca _x ZrO ₃ +yMnO ₂ , x of Ca _x ZrO ₃ is and MnO ₂ for 1.00 weight of Ca _x ZrO ₃
A non-reducible dielectric ceramic composition characterized in that (=y) has the following weight ratio.

_{( Ba x Ca _ _ _ _ 1-x} ) _y ZrO ₃ x and y are in the range shown below, and (Ba _x Ca _1-x ) _y ZrO ₃
A non-reducible dielectric ceramic composition characterized in that the weight ratio of MnO ₂ (=z) to 1.00 is as shown below.

0 <x<0.20 0.85<y<1.30 0.005<z<0.08 (weight ratio) These non-reducible dielectric ceramic compositions ~
Even when fired in a neutral or reducing atmosphere, the insulation resistance does not decrease and the dielectric loss does not increase. Therefore, base metals such as nickel, iron, and cobalt can be used as internal electrodes and fired in a neutral or reducing atmosphere while preventing these base metals from being oxidized or reacting with the ceramic.

On the other hand, base metals such as lead, aluminum, and tin, which are exemplified as having a relatively low melting point, can be implanted using the implantation method already described in the prior art. The composition is not limited to the above, and ordinary dielectric ceramic compositions can be used.

As the external electrode 3 in the embodiment of this invention, copper,
Nickel or aluminum or alloys thereof are used. When copper or nickel is used, a method of baking a paste of these metal powders, a vapor deposition method, a sputtering method, an electroless plating method, a thermal spraying method, etc. can be used. In particular, glass frits with excellent properties have recently been proposed for use in baking copper. Examples are zinc borosilicate, barium borosilicate, and the like. Glass frits having these compositions have made it possible to bake copper well in a natural atmosphere. Therefore, in this case, without using a non-reducible dielectric ceramic composition as the dielectric ceramic material, a normal dielectric ceramic composition can be used to bake the copper external electrode 3 without any problem. It can be formed by It goes without saying that if the above-mentioned non-reducible dielectric ceramic composition is used as the ceramic material, the external electrode 3 can be formed by baking regardless of the composition or characteristics of the glass frit.

When using the injection method for the internal electrodes 1, since a material with a relatively low melting point is used, a method is applied in which the external electrodes 3 are provided in advance and then the metal of the internal electrodes 1 is injected.

When aluminum is used as the external electrode 3, among the above-mentioned methods for forming the copper or nickel external electrode 3, the electroless plating method cannot be applied, but other methods are equally applicable. .

As described above, according to the present invention, a ceramic multilayer capacitor is constructed using a base metal for the internal electrodes and copper, nickel, aluminum, or an alloy thereof for the external electrodes. Since metal is used, an inexpensive ceramic multilayer capacitor can be provided. Considering the current situation where electrode materials account for about half of the cost in ceramic multilayer capacitors, this cost reduction effect can be said to be extremely large. In addition, compared to the conventional case of using silver or silver-palladium as the external electrode,
The external electrode and the internal electrode will fit well, the tensile strength of the external electrode will be increased, and good conductivity can be obtained. Furthermore, unlike conventional external electrodes made of silver or silver-palladium, the phenomenon of solder erosion during soldering is less likely to occur.

[Brief explanation of the drawing]

The drawing shows a typical cross-sectional structure of a ceramic multilayer capacitor. In the figure, 1 is an internal electrode, 2 is a ceramic,
3 is an external electrode.

Claims (1)

[Claims] 1. A plurality of internal electrodes arranged in a stacked state with ceramic interposed between them to form capacitance, and a plurality of internal electrodes connected to predetermined ones of the internal electrodes for taking out the capacitance. A ceramic multilayer capacitor comprising a pair of external electrodes, wherein the internal electrodes are made of a base metal, and the external electrodes are made of at least one metal selected from the group including copper, nickel, and aluminum. , ceramic multilayer capacitor. 2. The ceramic multilayer capacitor according to claim 1, wherein the ceramic is a non-reducing ceramic. 3. The ceramic multilayer capacitor according to claim 1 or 2, wherein the external electrode is made of copper. 4. The ceramic multilayer capacitor according to claim 3, wherein the external electrode is formed by baking copper.