Dielectric ceramic, method for making the same, and monolithic ceramic capacitor

Abstract

The purpose of the present invention is to provide a dielectric ceramics, which is suitable for forming the dielectric ceramics of the dielectric ceramic layer in the laminated ceramic capacitor obtained after it is sintered in the reduction ambient. In addition, even the dielectric ceramic layer is thinned; temperature dependence of dielectric constant is not worsened and the reliability is excellent for the thinned layer. The invented dielectric ceramics is mainly composed of ABO3 (A is Ba and so on; and B is Ti and so on) and contains rare earth elements. In the aspect of the chip 21 where the ceramics composition is more than 70%, when viewing its cross-section, 5 to 70% cross-section area is occupied by the solid-melting region made of rare earth elements; and 10 to 80% periphery of the cross-section is occupied by the non-solid-melting region made of rare earth elements.

Description

technical field [0001] The present invention relates to dielectric ceramics, a method of manufacturing the same, and multilayer ceramic capacitors made of such dielectric ceramics. More particularly, the present invention relates to improvements capable of facilitating the thinning of dielectric ceramic layers in multilayer ceramic capacitors. Background technique [0002] Multilayer ceramic capacitors are generally produced by the following methods. [0003] First, a ceramic green sheet (green sheet) is prepared on the surface of which is imparted with a conductive material having a desired pattern to form internal electrodes, and which contains dielectric ceramic powder. This kind of ceramic green sheet is made of, for example, BaTiO 3 The dielectric ceramic powder as the main component is obtained, for example, by pulverizing it into a primary particle state as much as possible with a ball mill, dispersing it into a slurry, and forming the slurry into a sheet. [0004] ...

AI Technical Summary

Problems solved by technology

And in general, with BaTiO 3 As the main component of dielectric ceramics, since the Curie point is around 120°C, the temperature dependence of the dielectric body is reduced

The dielectric ceramics described in Patent Documents 5, 6 and 7 have a core of BaTiO 3 Therefore, for multilayer ceramic capacitors using such dielectric ceramics, there is a problem that the capacitance temperature characteristics deteriorate especially when the dielectric ceramics are thinned.

In addition, there is a problem of low reliability when the dielectric ceramic layer is thinned.

[0027] The dielectric ceramics having the structure described in Patent Document 8, since the structure is controlled by the calcination temperature, the electrical characteristics tend to fluctuate. Therefore, when the dielectric ceramic layer is thinned, there is a problem that the capacitance temperature characteristics and the temperature characteristics cannot be reliably guaranteed. reliability

[0028] In view of the above reasons, when the dielectric ceramic layer is thinned for the purpose of miniaturization and increase in capacity of multilayer ceramic capacitors, if the AC signal level is the same as before the thinning, it is equivalent to that in the dielectric ceramic layer. The electric field strength applied to one layer increases, so the capacitance temperature characteristic will be significantly reduced

In addition, in terms of reliability, when the dielectric ceramic layer is thinned, if the DC rated voltage is the same as before the thinning, it is equivalent to an increase in the electric field intensity applied to one of the dielectric ceramic layers, so Reliability is also significantly lower

Images