JP2913680B2 - Multilayer ceramic capacitors - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a multilayer ceramic capacitor.

2. Description of the Related Art A multilayer ceramic capacitor has a ceramic layer and a laminated body in which internal electrode layers, usually made of palladium or an alloy layer of silver and palladium, are alternately laminated and sintered integrally. In general, silver or an alloy of silver and palladium is provided as a terminal electrode so as to be joined to each other.

As described above, the multilayer ceramic capacitor used for an application as an electronic component must have a quality that does not impair the initial electrical performance for a long period of time. Therefore, it is necessary to completely eliminate defects in the internal structure of the multilayer ceramic capacitor. As a structural defect of this multilayer ceramic capacitor, the so-called delamination, in which the ceramic layer and the internal electrode layer are separated from each other without being in close contact with each other, is a heavy defect. Cannot be maintained.

It is conventionally known that this delamination mostly occurs in the process of sintering the above-mentioned laminate, and is more likely to occur as the number of laminates increases. Therefore, it is necessary to empirically determine the limit value of the number of layers so that delamination does not occur, and design the product below the limit value.

Problems to be Solved by the Invention However, in recent years, multilayer ceramic capacitors have been required to have more layers. That is, a multilayer ceramic capacitor having a small size and a large capacitance is desired, and in order to satisfy this requirement, a method of reducing the thickness of the ceramic dielectric layer and increasing the number of stacked layers is absolutely necessary. .

Conventionally, when the thickness of the ceramic dielectric layer is 20 μm,
At most 40 layers were the limit, but with a thickness of 10-15 μm and 60-80 layers,
It is desired to increase the capacitance four times. However, when the number of layers is increased as described above, delamination occurs as described above, and it has been difficult to realize the method.

Means for Solving the Problems The present invention is intended to reduce the occurrence of delamination in the firing step, which has been the biggest obstacle in realizing multilayering as described above, and as a ceramic layer of a multilayer ceramic, A porcelain product containing palladium in the form of PdO and 1.00 to 0.05 weight percent added to either barium titanate (BaTiO ₃ ) powder or titanium oxide (TiO ₂ ) powder By doing
The problem has been solved.

Action The porcelain composition according to the present invention is considered to improve the bonding property with the internal electrode layer, and can provide a multilayer ceramic capacitor without delamination even if the number of layers is dramatically increased. It is.

Examples Hereinafter, the present invention will be described in detail based on examples.

First, commercially available barium titanate (BaTiO ₃ ) powder or titanium oxide (TiO ₂ ) powder and palladium oxide (PdO) powder were mixed at various ratios as shown in Table 1 below and mixed by a ball mill. Thereafter, the mixed powder, a butyl acetate solution containing 8% by weight of polyvinyl butyral, and dibutyl phthalate were blended at a weight ratio of 60: 38: 2 and mixed by a ball mill. This mixed slurry is subjected to a thickness of 20 ±
The sheet was 1 μm. The sheet was printed with a palladium paste to a thickness of 3 to 7 μm by a screen printing method, and the palladium-printed sheets were stacked in various numbers, and then pressed and pressed at a pressure of 500 kg / cm ² . However, at this time, so that the thickness after pressing is 1.3 to 1.4 mm,
Sheets on which no palladium was printed were stacked on top and bottom of the stacked palladium printing sheets such that the number of sheets on the top and bottom was substantially equal. Thereafter, it was cut into a size of 2.5 mm × 1.6 mm. This laminate was heated at a temperature of 300 ° C. for 24 hours to remove a binder component such as polyvinyl butyral.
The temperature was raised at 200 ° C. per hour, and baked at 1300 ± 20 ° C. for 2 hours and sintered.

FIG. 1 shows a cross-sectional view of the sintered body thus obtained. The ceramic layer 1 and the internal electrode layer 2 shown in FIG.
FIG. 2 shows some typical modes of so-called delamination when the layers are separated from each other.

Further, in Table 1 below, all the delamination modes a, b, c, d, and e in FIG. 2 correspond to the ceramic composition of the ceramic layer 1 shown in FIG. Each cross section was observed at a magnification of 400 times with an optical microscope. When no detection was possible at all, the mark was indicated by a circle, and the case where even one was detected was also indicated by a cross, and the limit number of the number of ceramic layers n shown in FIG. Was examined.

As is clear from Table 1, when the PdO content is 0.05% by weight or more, the occurrence of delamination is remarkably suppressed.

Next, as shown in FIG. 3, the number of ceramic layers n is fixed at 15 layers,
FIG. 2 shows the result of examining the breakdown voltage value by a DC voltage by attaching an alloy electrode of indium and gallium to the end face of the sintered body of FIG. In the figure, a curve x is for a porcelain composition composed of BaTiO ₃ and PdO, and a curve y is for a porcelain composition composed of TiO ₂ and PdO.

From FIG. 3, it is recognized that when the PdO content exceeds 1% by weight, the breakdown voltage sharply decreases.

Therefore, when Table 1 and FIG. 3 are compared, it is clear that the object of the present invention is achieved when PdO is added and the content is 0.05 to 1% by weight.

Advantageous Effects of the Invention As described above, the present invention is a device in which the internal electrode layer is formed of a palladium metal layer and a ceramic layer is formed by a porcelain composition containing a small amount of PdO, which has been conventionally extremely difficult. To prevent the occurrence of delamination, which is the biggest issue in the multi-layering of multilayer ceramic capacitors, and as a result, in particular, to realize a small and large capacitance desired for multilayer ceramic capacitors. Can be.

Also, since the ceramic layer itself was formed from a porcelain composition containing a small amount of PdO, the structure was simpler than that with another anti-peeling body between this ceramic layer and the internal electrode layer. The distance between the electrodes is reduced, and the capacitance can be increased accordingly.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor illustrating an embodiment of the present invention, FIG. 2 is a view showing various delamination modes which are problems to be solved by the present invention,
FIG. 3 is a view showing the relationship between the added content of PdO and the breakdown voltage for explaining the present invention. 1 ... ceramic layer, 2 ... internal electrode layer.

Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C04B 35/00-35/49 H01B 3/00-3/14

Claims (1)

(57) [Claims] 1. A multilayer ceramic capacitor in which ceramic layers and internal electrode layers are connected alternately, wherein said ceramic layer is made of one of barium titanate (BaTiO ₃ ) powder and titanium oxide (TiO ₂ ) powder. A multi-layer ceramic capacitor formed of a porcelain product containing a palladium component in the form of PdO and adding and containing 1.00 to 0.05 weight percent, and the internal electrode layer is formed of a palladium metal layer.