JPS5858716A - Laminated ceramic condenser - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer ceramic capacitor, and in particular to a method for preventing the disappearance of internal 'g' electrodes exposed on the end faces of capacitor chips.
It is related to IF.

Generally, the internal electrodes of this type of multilayer ceramic capacitor are made of a conductive material mainly made of palladium, but recently, with the aim of reducing capacitor costs, palladium and silver have been mixed together. In addition, a conductive member is used in which the proportion of silver in the conductive member is increased to, for example, about 70% by weight.

According to this capacitor, the cost can be greatly reduced and it is preferable, but depending on the firing conditions when firing the capacitor chip, for example, if the firing is performed excessively, the internal electrodes may be exposed on the end face of the capacitor chip. There is a problem that the electrical properties of the parts are impaired.

- Such a phenomenon tends to be more pronounced as the ceramic powder constituting the dielectric layer contains more bismuth. .

Although the cause of this has not been fully elucidated, it is thought that silver among the constituent members of the internal electrodes is lost due to evaporation, diffusion, etc.

Once the internal electrodes have lost their electrical characteristics, the electrical connection with the electrode extraction layer on the end face of the capacitor chip becomes like an oven, so even though the internal electrodes are located between the ceramic layers, static The capacitance is significantly reduced, and the original function of the capacitor is expected to be improved.

For example, t+'/7' size (LXWXT) is 3.2×
22-5XL5 multilayer ceramic capacitor with a capacitance of 0.01 μF, the internal electrodes of which are formed from a conductive material containing silver and palladium, with the proportion of silver in the conductive material set to 70% by weight. In this case, excessive firing reduces the capacitance to 0°002 μF. When this capacitor was analyzed, it was found that silver disappeared from about 80% of the internal electrodes.

Therefore, if such problems can be solved without increasing the mixing ratio of palladium to conductive materials, valuable palladium can be used effectively, the original characteristics of capacitors can be obtained, and costs can be effectively reduced. It is something.

In view of these points, the present invention provides a multilayer ceramic capacitor that can sufficiently ensure electrical connectivity of the internal electrodes to the electrode extraction layer with a simple configuration and that can also effectively reduce costs. Let's discuss an example.

In the figure, 1 is a capacitor chip, which is composed of, for example, a plurality of ceramic layers 2 and internal electrodes 3 which are arranged alternately between the ceramic layers and are made of a conductive material containing silver and palladium. . The end portion 3 of the internal electrode 3 is exposed to the end surface of the capacitor chip l.
a is set to 1.2 to 2.0 times the thickness of the central portion. This can also be easily obtained by performing screen printing multiple times only on the end portion 3a of the internal electrode 3. Reference numeral 4 denotes an electrode extension layer formed on the end surface of the capacitor chip 1, and is electrically connected to each end of the internal electrode 3.

In this way, the internal electrode 3 is configured such that the end portion 3a exposed to the end surface of the capacitor chip is 1.2 to 2.0 times as thick as the central portion. Even if the firing is carried out excessively and a disappearance phenomenon occurs in the silver contained in the end portion 3a, the firing process will continue.

will not completely disappear. For this purpose, the internal electrode 3
Electrical connectivity to the electrode extraction layer 4 can be sufficiently ensured, and a decrease in capacitance can be prevented.

In addition, the internal electrode 3 is made of a conductive material containing silver and palladium, but as mentioned above, in order to ensure sufficient electrical connectivity to the electrode lead layer 4 of the end portion 3a, silver is used. The mixing ratio to the conductive member can be increased. Therefore, the cost of the capacitor can be effectively reduced.

Next, specific examples will be described. Chip size is 3
．． 2 x 2.5 x 1.5 pilgrims and capacitance is 0
．． In a 01 μF multilayer ceramic capacitor, silver,
The thickness of the end portion (within a range of 0.2 brocades from the end surface of the capacitor chip) of the internal electrode, which is made of a conductive material containing palladium and in which the proportion of silver in the conductive material is set to 70% by weight, is compared to the center portion. The electrostatic capacitance and the state of peeling between the ceramic layer and the internal electrode were measured and observed while varying the ratio by a factor of 1.0 to 3.5 times, and the results shown in the table below were obtained.

As is clear from the table above, when the thickness of the end portion (electrode extraction layer side) of the internal electrode is 1.2 times or more that of the central portion, the decrease in capacitance is small, and especially when the thickness is 1.2 times or more than the center portion, It hasn't decreased at all. On the other hand, the peeling %Ii between the ceramic layer and the end of the internal electrode becomes more pronounced as the thickness increases.
It occurs in a range exceeding 2"0 times. Therefore,
The thickness of the end portion can be used in the range of 1.2 to 20 times without any practical problem, but it is preferably in the range of 1.5 to 2.0 times.

In the present invention, the proportion of silver in the conductive member, including silver and palladium, is not limited to 70% by weight and can be increased or decreased as appropriate. Further, in the internal electrode, the width from the chip end surface of the thickened end portion can be changed as appropriate depending on the chip size, and is not limited to 0.2 m as in the embodiment.

As described above, according to the present invention, it is possible to sufficiently ensure the electrical connectivity of the internal electrodes to the electrode extraction layer with a simple configuration, and it is also possible to effectively reduce costs.

[Brief explanation of drawings]

The figure is a side sectional view showing one embodiment of the present invention. In the figure, 1 is a capacitor chip, 2 is a ceramic layer, 3 is an internal electrode, 3a is an end portion, and 4 is an electrode extension layer. 2 3 2 zuQ

Claims (1)

[Claims] Internal electrodes made of a conductive material containing silver and palladium are arranged alternately between a plurality of ceramic layers, and an electrode extension layer is formed on the exposed end surface of the internal electrode, and the electrode extension layer of the internal electrode is connected to the electrode extension layer. A multilayer ceramic capacitor characterized in that the thickness of the end portion on the n side is set to be 1.2 to 2.0 times the thickness of the central portion.