Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2001-12-05
2003-08-05
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S697000, C501S032000, C501S139000
Reexamination Certificate
active
06602616
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composite multilayer ceramic electronic part that is suitable for a multilayer circuit board including, for example, a microwave resonator, a filter or a multilayer capacitor, and to a method of manufacturing the same. Specifically, it relates to a composite multilayer ceramic electronic part comprising a laminate of a high dielectric-constant layer including a high dielectric-constant material with a low dielectric-constant layer including a low dielectric-constant material.
2. Description of the Related Art
Electronic equipment has become smaller in size, weight and thickness in recent years, and demands have been made to miniaturize electronic parts for use in such electronic equipment. However, conventional electronic part devices such as resonators are separately designed and constituted, and the miniaturization of these devices alone cannot sufficiently miniaturize the electronic equipment. Various multilayer ceramic substrates including electronic part devices such as capacitors or resonators inside thereof have therefore been proposed.
Such multilayer ceramic substrates must be further miniaturized and must be applied to signals of high frequency, and to this end, a variety of materials for composite multilayer substrates has been studied and proposed. Specifically, a variety of composite multilayer ceramic electronic parts including a low dielectric-constant layer and a high dielectric-constant layer have been proposed. In these ceramic electronic parts, a wiring is formed or a semiconductor device is mounted onto the low dielectric-constant layer. The high dielectric-constant layer is formed inside the low dielectric-constant layer, and comprises a material having a high dielectric constant and a low dielectric loss and thereby constitutes a capacitor or resonator. An example of these composite multilayer ceramic electronic parts is described in Japanese Unexamined Patent Application Publication No. 12-264724.
However, such composite multilayer ceramic electronic parts comprise a combination of a low dielectric-constant material and a high dielectric-constant material and thereby invite delamination in the interface between the two materials or deformation of the resulting substrates due to the difference in the shrinkage profile or in the thermal expansion coefficient between the two materials.
In high-frequency applications, Cu, Ag and other conductors which have a low electric resistance and a low melting point must be used. Accordingly, ceramic materials for use with these conductors must be fired at temperatures less than or equal to 1000° C., since the ceramics must be integrally fired with these conductors having a low melting point.
The substrate materials must have a low dielectric loss for use in a microwave region, millimeter wave region and other high frequency regions. To yield a substrate material that can be fired at temperatures less than or equal to 1000° C., it must further comprise a sintering aid such as glass in addition to a ceramic. However, sintering aids such as glass generally serve to increase the dielectric loss of the substrate material. For this reason, a substrate material, which can be fired at low temperatures of less than or equal to 1000° C. and has a low dielectric loss, cannot significantly be obtained.
SUMMARY OF THE INVENTION
Under these circumstances, an object of the present invention is to provide a composite multilayer ceramic electronic part which is resistant to delamination or deformation in the interface between different types of materials, can be fired at low temperatures and is suitable for the high-frequency applications, and a method of manufacturing the multilayer composite ceramic electronic part.
Specifically, the present invention provides, in one aspect, a composite multilayer ceramic electronic part including a high dielectric-constant layer and at least one low dielectric-constant layer laminated with each other. The high dielectric-constant layer includes a high dielectric-constant material and has a relative dielectric constant &egr;r of equal to or more than about 20, and the low dielectric-constant layer includes a low dielectric-constant material and has a relative dielectric constant &egr;r of less than or equal to about 10. In this multilayer composite ceramic electronic part, the high dielectric-constant material mainly includes a BaO—TiO
2
—ReO
3/2
dielectric and a first glass composition, where the BaO—TiO
2
—ReO
3/2
dielectric is represented by the following formula: xBaO—yTiO
2
—zReO
3/2
, where x, y and z are % by mole and satisfy the following conditions: 8≦x≦18; 52.5≦y≦65; 20≦z≦40; and x+y+z=100; and Re is a rare earth element, and the low dielectric-constant material includes a composite of a ceramic and a second glass composition.
By this configuration, the high dielectric-constant layer can constitute a capacitor or resonator using its high dielectric constant. In addition, the high dielectric-constant material yields a low dielectric loss in the high-frequency regions, specifically in the microwave region or millimeter wave region, due to crystallization of the glass composition, and thereby can constitute a capacitor or resonator having excellent high-frequency characteristics. The high dielectric-constant material can be fired at low temperatures of less than or equal to 1000° C., and a conductor mainly comprising a metal having a low relative resistance such as gold, silver or copper can be used.
The low dielectric-constant layer has a low relative dielectric constant &egr;r of less than or equal to about 10 and can thereby constitute an insulator.
By using the combination of the high dielectric-constant layer and the low dielectric-constant layer, the present invention can provide a composite multilayer ceramic electronic part including a resonator or capacitor having excellent high-frequency characteristics.
The first glass composition in the high dielectric-constant material preferably includes about 10% to 25% by weight of SiO
2
, about 10% to 40% by weight of B
2
O
3
, about 25% to 55% by weight of MgO, 0% to about 20% by weight of ZnO, 0% to about 15% by weight of Al
2
O
3
, about 0.5% to 10% by weight of Li
2
O and 0% to about 10% by weight of RO, where R is at least one of Ba, Sr and Ca.
The high dielectric-constant material preferably further includes less than or equal to about 3% by weight of CuO and about 0.1% to 10% by weight of TiO
2
based on the total weight of the high dielectric-constant material, as secondary components.
The high dielectric-constant material may include about 15% to 35% by weight of the first glass composition relative to about 65% to 85% by weight of the BaO—TiO
2
—ReO
3/2
dielectric.
Preferably, the ceramic in the low dielectric-constant material is spinel (MgAl
2
O
4
), and the second glass composition includes about 30% to 50% by mole of silicon oxides in terms of SiO
2
, 0% to about 20% by mole of boron oxides in terms of B
2
O
3
, and about 20% to 55% by mole of magnesium oxide in terms of MgO.
The second glass composition preferably further includes less than or equal to about 30% by mole of at least one of CaO, SrO and BaO based on the total amount of the second glass composition.
The second glass composition preferably includes 0% to about 15% by mole of aluminum oxides in terms of Al
2
O
3
.
The second glass composition may further include less than or equal to about 10% by weight of at least one alkali metal oxide selected from Li
2
O, K
2
O and Na
2
O, based on the total weight of the second glass composition.
The low dielectric-constant material may further include less than or equal to about 3% by weight of copper oxides in terms of CuO based on the total weight of the low dielectric-constant material.
Preferably, the ceramic in the low dielectric-constant material is MgAl
2
O
4
, the second glass composition is a borosilicate glass, and an MgAl
2
O
4
crystalline phase and at least one of an Mg
3
B
2
O
6
crysta
Chikagawa Osamu
Mori Naoya
Sugimoto Yasutaka
Blackwell-Rudasill G. A.
Dickstein Shapiro Morin & Oshinsky LLP.
Jones Deborah
Murata Manufacturing Co. Ltd
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