# Patent

## Title
Glass ceramic composition, glass-ceramic sintered body, and monolithic ceramic electronic component

## Abstract

A glass ceramic composition is used for a multilayer ceramic substrate 2 including glass ceramic layers 3 laminated, the multilayer ceramic substrate 2 being used for a multilayer ceramic module 1. The glass ceramic composition includes a first ceramic powder mainly composed of forsterite, a second ceramic powder mainly composed of at least one component selected from CaTiO3, SrTiO3 and TiO2, and a borosilicate glass powder containing Li2O, MgO, B2O3, SiO2, ZnO and Al2O3. The glass ceramic composition contains 3 percent by weight or more of the borosilicate glass powder and further contains at least one additive selected from the group consisting of CaO, BaO and SrO.

## Background
This is a continuation-in-part of application Ser. No. 11/563,435, filed Nov. 27, 2006, which was a continuation-in-part of application Ser. No. 11/507,501, filed Aug. 22, 2006, now U.S. Pat. No. 7,368,408, which was a continuation-in-part of application Ser. No. 10/568,454 (PCT/JP2005/001463), filed Feb. 15, 2006, now U.S. Pat. No. 7,351,674.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a glass ceramic composition containing a glass component in order that the glass ceramic composition can be fired at a low temperature, a sintered glass ceramic material obtained by firing the glass ceramic composition, and a multilayer ceramic electronic component including the sintered glass ceramic material.
2. Description of the Related Art
Examples of effective methods for miniaturizing electronic apparatuses include the use of multifunction electronic components in the electronic apparatuses. Examples of multifunction electronic components include multilayer ceramic modules.
Multilayer ceramic modules include multilayer ceramic substrates. The multilayer ceramic substrates contain conductive leads for electrical connection and for constituting a passive element, such as a capacitor or an inductor. Furthermore, a variety of electronic components are mounted on multilayer ceramic substrates.
Multilayer ceramic modules are small yet have multifunctionality. Thus, the use of the multilayer ceramic modules can achieve miniaturization of electronic apparatuses.
Demand for electronic apparatuses operating at higher frequencies has been increasing as well as the miniaturization described above. In this situation, it is desirable that multilayer ceramic modules for use in a high-frequency band include multilayer ceramic substrates having satisfactory high-frequency properties. Specifically, it is desirable that insulating ceramic layers constituting multilayer structures of multilayer ceramic substrates are composed of an insulating ceramic sinter having satisfactory high-frequency properties.
Japanese Unexamined Patent Application Publication No. 2000-344571 (Patent Document 1) discloses an insulating ceramic composition suitable for a sintered insulating ceramic material capable of satisfying these requirements. Patent Document 1 discloses insulating ceramic composition with a ternary system of forsterite, calcium titanate and spinel. The insulating ceramic composition in a more preferred composition range disclosed in Patent Document 1 has a Qf of about 38,000 GHz or more and a temperature coefficient of dielectric constant of about −80 to +40 ppm·° C.−1, Qf being defined by frequency (GHz)/dielectric loss (tan δ).
When the multilayer ceramic substrate for the multilayer ceramic module is produced, a firing step is performed. In the firing step, conductive leads provided with the multilayer ceramic substrate are co-fired.
The conductive leads in the multilayer ceramic substrate must have low electrical resistance in order that the multilayer ceramic module can be used in a high-frequency region without problems. Thus, each conductive lead needs to be composed of a metal, such as copper or silver, having low resistivity.
However, the metal, such as copper or silver, has a relatively low melting point. To produce a multilayer ceramic substrate by cofiring a green substrate and a green conductive lead composed of the metal, an insulating ceramic composition for forming insulating ceramic layers constituting the multilayer ceramic substrate must be able to be fired at a low temperature, e.g., about 1,000° C. or lower.
Patent Document 1 discloses the insulating ceramic composition is fired at a firing temperature of about 1,140° C. to 1,600° C. That is, the requirement that an insulating ceramic composition can be fired at about 1,000° C. or lower is not satisfied.
Furthermore, in order to provide a multilayer ceramic substrate capable of operating at higher frequencies and to provide higher-density conductive leads, the insulating ceramic layers contained in the substrate need to have a lower dielectric constant. Patent Document 1 does not disclose the specific value of the dielectric constant of the insulating ceramic sinter obtained by firing the insulating ceramic composition disclosed therein.
International Publication No. WO2005/082806 (Patent Document 2) reports an insulating ceramic composition capable of being fired at about 1,000° C. or lower, having a low dielectric constant, and having satisfactory high-frequency properties. Specifically, Patent Document 2 reports the insulating ceramic composition capable of controlling the temperature coefficient of a resonance frequency at a low level and obtaining a higher Qf value.
Patent Document 2 discloses a glass ceramic composition containing a first ceramic powder mainly composed of forsterite; a second ceramic powder containing at least one ceramic powder selected from the group consisting of a ceramic powder mainly composed of calcium titanate, a ceramic powder mainly composed of strontium titanate and a ceramic powder mainly composed of titanium oxide; and a borosilicate glass powder, wherein the borosilicate glass powder contains about 3 to 15 percent by weight of lithium in the form of Li2O, about 30 to 50 percent by weight of magnesium in the form of MgO, about 15 to 30 percent by weight of boron in the form of B2O3, about 10 to 35 percent by weight of silicon in the form of SiO2, about 6 to 20 percent by weight of zinc in the form of ZnO, and about 0 to 15 percent by weight of aluminum in the form of Al2O3.
However, there have been advances in the reduction in the thickness of ceramic layers constituting multilayer ceramic electronic components in recent years. Furthermore, there has been an increase in signal voltage. Thus, the material constituting the ceramic layers needs to have higher electrical insulation reliability.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a glass ceramic composition having a composition capable of enhancing electrical insulation reliability in the material system of the glass ceramic composition disclosed in Patent Document 1.
It is another object of the present invention to provide a sintered insulating ceramic material obtained by firing the glass ceramic composition; and a multilayer ceramic electronic component including the sintered insulating ceramic material.
To overcome the above-described technical problems, an insulating ceramic composition according to preferred embodiments of the present invention includes a first ceramic powder mainly composed of forsterite; a second ceramic powder containing at least one ceramic powder selected from the group consisting of a ceramic powder mainly composed of calcium titanate, a ceramic powder mainly composed of strontium titanate and a ceramic powder mainly composed of titanium oxide; and a borosilicate glass powder containing about 3 to 15 percent by weight of lithium in the form of Li2O, about 20 to 50 percent by weight of magnesium in the form of MgO, about 15 to 30 percent by weight of boron in the form of B2O3, about 10 to 45 percent by weight of silicon in the form of SiO2, about 6 to 20 percent by weight of zinc in the form of ZnO, and about 0 to 15 percent by weight of aluminum in the form of Al2O3, wherein the content of the borosilicate glass powder in the glass ceramic composition is about 3 percent by weight or more, the borosilicate glass powder contains at least one additive selected from the group consisting of calcium oxide, barium oxide and strontium oxide, the lower limit of the additive content of the borosilicate glass powder is about 2 percent by weight of the total amount of calcium oxide in the form of CaO, barium oxide in the form of BaO, and strontium oxide in the form of SrO, the upper limit of the calcium oxide content of the borosilicate glass powder in the form of CaO is about 15 percent by weight, the upper limit of the barium oxide content of the borosilicate glass powder in the form of BaO is about 25 percent by weight, and the upper limit of the strontium oxide content of the borosilicate glass powder in the form of SrO is about 25 percent by weight.
In the glass ceramic composition according to preferred embodiments of the present invention, the glass ceramic composition preferably contains about 55 percent by weight or more of the first ceramic powder, about 6 to 30 percent by weight of the second ceramic powder, and about 3 to 20 percent by weight of the borosilicate glass powder.
In the glass ceramic composition according to preferred embodiments of the present invention, when the second ceramic powder contains a ceramic powder mainly composed of calcium titanate, the calcium titanate content of the glass ceramic composition in the form of CaTiO3 is preferably about 18 percent by weight or less; when the second ceramic powder contains a ceramic powder mainly composed of strontium titanate, the strontium titanate content of the glass ceramic composition in the form of SrTiO3 is preferably about 13 percent by weight or less; and when the second ceramic powder contains a ceramic powder mainly composed of titanium oxide, the titanium oxide content of the glass ceramic composition in the form of TiO2 is preferably about 0.3 to 30 percent by weight.
In the above-described preferred embodiments, when the second ceramic powder contains a ceramic powder mainly composed of calcium titanate and a ceramic powder mainly composed of titanium oxide, the calcium titanate content of the glass ceramic composition in the form of CaTiO3 is more preferably about 8 to 12 percent by weight, and the titanium oxide content of the glass ceramic composition in the form of TiO2 is more preferably about 0.3 to 3 percent by weight.
In the above-described preferred embodiments, when the second ceramic powder contains a ceramic powder mainly composed of strontium titanate and a ceramic powder mainly composed of titanium oxide, the strontium titanate content of the glass ceramic composition in the form of SrTiO3 is more preferably about 6 to 10 percent by weight, and the titanium oxide content of the glass ceramic composition in the form of TiO2 is more preferably about 0.3 to 3 percent by weight.
In the glass ceramic composition according to preferred embodiments of the present invention, the borosilicate glass powder preferably has a lithium content of about 3 to 15 percent by weight in the form of Li2O, a magnesium content of about 20 to 50 percent by weight in the form of MgO, a boron content of about 15 to 30 percent by weight in the form of B2O3, a silicon content of about 23.5 to 26.5 percent by weight in the form of SiO2, a zinc content of about 6 to 20 percent by weight in the form of ZnO, and an aluminum content of about 0 to 15 percent by weight in the form of Al2O3. In this case, the content of silicon in the borosilicate glass powder is further limited.
In the above-described preferred embodiments, the borosilicate glass powder contains about 23.5 to 26.5 percent by weight of silicon in the form of SiO2. When the lower limit of the silicon content of the borosilicate glass powder in the form of SiO2 is reduced to about 20 percent by weight, the glass ceramic composition according to preferred embodiments of the present invention preferably further contains about 1 part by weight or less of silicon in the form of SiO2 relative to 100 parts by weight of the total amount of the first ceramic powder, the second ceramic powder, and the borosilicate glass powder.
Preferably, the glass ceramic composition according to preferred embodiments of the present invention further includes a third ceramic powder mainly composed of barium zirconate. In this case, the content of the barium zirconate in the glass ceramic composition in terms of BaZrO3 is preferably about 3 to 20 percent by weight.
The present invention may also be applied to a sintered glass ceramic material prepared by forming the above-described glass ceramic composition according to preferred embodiments of the present invention into a predetermined shape and firing the resulting perform at a temperature of about 1,000° C. or lower. The sintered glass ceramic material according to preferred embodiments of the present invention includes a Mg2SiO4 crystal phase as a main phase and a Li2(Mg,Zn)SiO4 crystal phase as a subphase.
The present invention may also be applied to a multilayer ceramic electronic component including a plurality of glass ceramic layers, the glass ceramic layers being laminated; and conductive leads disposed in or on the glass ceramic layers. The multilayer ceramic electronic component includes the glass ceramic layers composed of the above-described sintered glass ceramic material according to preferred embodiments of the present invention; and the conductive leads mainly composed of copper or silver.
The glass ceramic composition according to preferred embodiments of the present invention can be fired at about 1,000° C. or lower to yield a sintered glass ceramic material having satisfactory chemical stability, relatively low dielectric constant, a high Qf value, and a stable temperature coefficient (τf) of resonance frequency.
When the multilayer ceramic electronic component is formed of the sintered glass ceramic material according to preferred embodiments of the present invention, conductive leads included in the multilayer ceramic electronic component can be mainly composed of copper or silver; hence, the multilayer ceramic electronic component can be suitably used for high-frequency applications.
Furthermore, in the glass ceramic composition according to preferred embodiments of the present invention, a borosilicate glass powder contains at least one compound selected from calcium oxide, barium oxide and strontium oxide as an additive, thereby improving the electrical insulation reliability of a sintered glass ceramic material obtained by firing the glass ceramic composition. The mechanism for improvement of insulation reliability is not exactly elucidated but is presumed as follows.
The sintered glass ceramic material according to preferred embodiments of the present invention basically includes the Mg2SiO4 crystal phase of the first ceramic powder and the Mg—Si—B—Zn—Li-based glass phase of the borosilicate glass powder. Furthermore, the sintered glass ceramic material has a microstructure in which a Li2(Mg,Zn)SiO4 crystal phase is precipitated in the Mg—Si—B—Zn—Li-based glass phase. In the case of the second ceramic powder containing TiO2, MgTiO3 and MgTi2O5 crystal phases are further precipitated. An AB2O5 type crystal phase such as the MgTi2O5 crystal phase seems to cause the degradation of the insulation reliability. Thus, when Ca, Ba and/or Sr is added to the glass phase in advance, the added element reacts with TiO2 to form an ABO3 type crystal phase, such as CaTiO3, BaTiO3 or SrTiO3 crystal phase; hence, the AB2O5 type crystal phase is not easily formed. That is, the ABO3 type crystal phase, such as CaTiO3, BaTiO3 or SrTiO3 crystal phase, is precipitated prior to the AB2O5 type crystal phase, such as MgTi2O5 crystal phase, thereby suppressing the precipitation of the AB2O5 type crystal phase, and suppressing the degradation of the insulation reliability.
Consequently, the use of a sintered glass ceramic material according to preferred embodiments of the present invention in a multilayer ceramic electronic component results in a reduction in the thickness of each glass ceramic layer contained in the multilayer ceramic electronic component.
In the glass ceramic composition according to preferred embodiments of the present invention, the content of the borosilicate glass powder can be reduced to about 20 percent by weight or less. Since the borosilicate glass powder is relatively expensive, the reduction in the content of the borosilicate glass powder is advantageous in reducing cost. Furthermore, the reduction in the content of the borosilicate glass powder facilitates control of the reaction of the second ceramic powder as an additive and the glass component, thereby resulting in easy control of the temperature coefficient (τf) of resonant frequency with the additive. Moreover, it is possible to improve the plating resistance of the sintered glass ceramic material and the mass productivity of the multilayer ceramic electronic component.
In the glass ceramic composition according to preferred embodiments of the present invention, the second ceramic powder contains a ceramic powder mainly composed of calcium titanate and a ceramic powder mainly composed of titanium oxide, wherein the calcium titanate content is about 8 to 12 percent by weight in the form of CaTiO3, and the titanium oxide content is about 0.3 to 3 percent by weight in the form of TiO2, relative to the glass ceramic composition. Thus, a sintered glass ceramic material obtained by firing the glass ceramic composition can surely provide a temperature coefficient (τf) of resonant frequency in the range of about ±10 ppm·° C.−1.
In the glass ceramic composition according to preferred embodiments of the present invention, the second ceramic powder contains a ceramic powder mainly composed of strontium titanate and a ceramic powder mainly composed of titanium oxide, wherein the strontium titanate content is about 6 to 10 percent by weight in the form of SrTiO3, and the titanium oxide content is about 0.3 to 3 percent by weight in the form of TiO2, relative to the glass ceramic composition. Thus, a sintered glass ceramic material obtained by firing the glass ceramic composition can surely provide a temperature coefficient (τf) of resonant frequency in the range of about ±10 ppm·° C.−1.
In the glass ceramic composition according to preferred embodiments of the present invention, the range of the silicon content of the borosilicate glass powder is further limited. That is, the borosilicate glass powder contains about 3 to 15 percent by weight of lithium in the form of Li2O, about 20 to 50 percent by weight of magnesium in the form of MgO, about 15 to 30 percent by weight of boron in the form of B2O3, about 23.5 to 26.5 percent by weight of silicon in the form of SiO2, about 6 to 20 percent by weight of zinc in the form of ZnO, and about 0 to 15 percent by weight of aluminum in the form of Al2O3. Thus, when the glass ceramic composition is used in an element with capacitance, a small rate of change of capacitance can be achieved before and after a load test. Consequently, when the element with capacitance is used to constitute a filter, variations in filter properties due to a variation in capacitance can be reduced.
Furthermore, the glass ceramic composition may further contain about 1 part by weight or less of silicon in the form of SiO2 relative to 100 parts by weight of the total amount of the first ceramic powder, the second ceramic powder, and the borosilicate glass powder, provided that the borosilicate glass powder has the same composition as the above-described composition except that the silicon content of the borosilicate glass powder is about 20 to 26.5 percent by weight in the form of SiO2. In this case, the same effect described above is achieved. Moreover, the lower limit of the silicon content of the borosilicate glass powder can be reduced from about 23.5 percent by weight to about 20 percent by weight, thus facilitating control of the silicon content.
In the glass ceramic composition according to preferred embodiments of the present invention, also in the case where the glass ceramic composition further includes the third ceramic powder mainly composed of barium zirconate, when the glass ceramic composition is used in an element with capacitance, a small rate of change of capacitance can be achieved before and after a load test.
In particular, when the content of barium zirconate in the form of BaZrO3 is about 3 to 20 percent by weight, a lower rate of change of capacitance can be achieved while a high Qf value and a stable temperature coefficient (τf) of resonant frequency are maintained. The effect of suppressing the rate of change of capacitance is high compared with the above-described case where the range of the silicon content of the borosilicate glass powder is limited.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of a multilayer ceramic module 1 as an example of a multilayer ceramic electronic component including a glass ceramic composition according to preferred embodiments of the present invention;
FIG. 2 is an exploded perspective view of the multilayer ceramic module 1 shown in FIG. 1;
FIG. 3 is a ternary diagram showing a molar composition ratio (x, y, z) of x(BaaCabSrc)O-y{(TiO2)1-m(ZrO2)m}-zRe2O3, which is a main component in a preferred example of a high-dielectric constant material used in the multilayer ceramic module 1 shown in FIG. 1;
FIG. 4 is a perspective view of the appearance of an LC filter 21 as another example of the multilayer ceramic electronic component including a glass ceramic composition according to preferred embodiments of the present invention;
FIG. 5 is an equivalent circuit schematic representing the LC filter 21 shown in FIG. 4; and
FIG. 6 is an exploded perspective view of a green laminate 22 as a semifinished product to be subjected to a firing step to form the LC filter 21 shown in FIG. 4.



DESCRIPTION OF THE PREFERRED EMBODIMENTS
A glass ceramic composition according to preferred embodiments of the present invention contains a first ceramic powder mainly composed of forsterite (Mg2SiO4); a second ceramic powder as an additive containing at least one ceramic powder selected from the group consisting of a ceramic powder mainly composed of calcium titanate (CaTiO3), a ceramic powder mainly composed of strontium titanate (SrTiO3), and a ceramic powder mainly composed of titanium oxide (TiO2); and a borosilicate glass powder. In particular, the borosilicate glass powder has a characteristic composition.
The borosilicate glass powder contains about 3 to 15 percent by weight of lithium in the form of Li2O, about 20 to 50 percent by weight of magnesium in the form of MgO, about 15 to 30 percent by weight of boron in the form of B2O3, about 10 to 45 percent by weight of silicon in the form of SiO2, about 6 to 20 percent by weight of zinc in the form of ZnO, and about 0 to 15 percent by weight of aluminum in the form of Al2O3. The borosilicate glass powder has a composition that can particularly precipitates a Li2(Mg,Zn)SiO4 crystal phase. Thus, a sinter obtained from the borosilicate glass powder preferably can have higher Q value and higher reliability (moisture resistance).
Lithium contained in the borosilicate glass powder serves as a constituent of Li2(Mg,Zn)SiO4 and reduces the sintering temperature of the glass ceramic composition. The reasons the lithium content of the borosilicate glass powder in the form of Li2O is limited to about 3 to 15 percent by weight are described as follows: A lithium content of less than about 3 percent by weight results in failure of densification at about 1,000° C. or lower, failure of the precipitation of the Li2(Mg,Zn)SiO4 crystal phase in a sinter and results in a reduction in Q value; and a lithium content exceeding about 15 percent by weight results in failure of precipitation of the Li2(Mg,Zn)SiO4 crystal phase in a sinter, a reduction in Q value and results in deterioration in chemical stability and insulation reliability. The lithium content in the form of Li2O is more preferably about 4 to 10 percent by weight, thereby further increasing the Q value of a sinter.
Magnesium contained in the borosilicate glass powder serves as a constituent of the Li2(Mg,Zn)SiO4 crystal phase and reduces the melting temperature during glass production. The reasons the magnesium content of the borosilicate glass powder in the form of MgO is limited to about 20 to 50 percent by weight are described as follows: A magnesium content of less than about 20 percent by weight results in failure of the precipitation of the Li2(Mg,Zn)SiO4 crystal phase in a sinter and results in a reduction in Q value; and a magnesium content exceeding about 50 percent by weight results in devitrification.
The term “devitrification” here means the partial crystallization of glass. In a specific glass composition, crystallization easily occurs during the steps from melting to rapid cooling a material powder, resulting in devitrification. The amount of crystals precipitated depends on cooling conditions and the like and thus varies thereby, in some cases, affecting the sinterability of the glass ceramic composition and dielectric properties of the sintered glass ceramic material. Furthermore, a glass ceramic material can be sintered with a reduction in the viscosity of glass immediately before crystallization. Also in this case, the partial crystallization of glass and a variation in the amount of crystals precipitated may affect the sinterability of the glass ceramic composition and dielectric properties of the sintered glass ceramic material. Significant crystallization may cause the glass ceramic composition not to sinter.
The magnesium content is more preferably about 30 to 45 percent by weight in the form of MgO, thereby further increasing the Q value of a sinter.
The reasons the boron content of the borosilicate glass powder in the form of B2O3 is limited to about 15 to 30 percent by weight is described as follows: A magnesium content of less than about 15 percent by weight results in difficulty in vitrification; and a magnesium content exceeding about 30 percent by weight results in reductions in the moisture resistance, crystallinity, and Q value of a sinter and results in deterioration in chemical stability and insulation reliability.
The phrase “difficulty in devitrification” here means that the borosilicate glass powder is not formed into an amorphous state (vitrified state) because of a low content of a network-forming oxide, such as SiO2 or B2O3. A low content of the network-forming oxide results in a mere calcine.
The boron content is more preferably about 15 to 25 percent by weight in the form of B2O3, thereby further increasing the Q value of a sinter and reducing reactivity with CaTiO3, SrTiO3, and TiO2.
Silicon contained in the borosilicate glass powder serves as a constituent of the Li2(Mg,Zn)SiO4 crystal phase. The reasons the silicon content of the borosilicate glass powder in the form of SiO2 is limited to about 10 to 45 percent by weight are described as follows: A silicon content of less than about 10 percent by weight results in low chemical stability of a sinter, thus causing devitrification in some cases; and a silicon content exceeding about 45 percent by weight results in difficulty in sintering at about 1,000° C. or lower. The silicon content in the form of SiO2 is more preferably about 15 to 30 percent by weight, thereby further increasing the Q values of a sinter.
The silicon content of the borosilicate glass powder in the form of SiO2 is still more preferably about 23.5 to 26.5 percent by weight. Thus, the absolute value of the rate of change of capacitance before and after a load test can be suppressed to about 0.5% or less when the glass ceramic composition according to preferred embodiments of the present invention is used in an element with capacitance, e.g., a capacitor. The rate of change of capacitance is represented by the following formula:

Rate of change of capacitance (%)={(C1-C0)/C0}×100

where C0 represents capacitance before the test and C1 represents capacitance after the test. The load test by which the rate of change of capacitance is found to be about 0.5% or less is an accelerated test at about 120° C., about 95% RH and about 15 V DC for 100 hours.

Even when the range of the silicon content of the borosilicate glass powder is increased to about 20 to 26.5 percent by weight, the same effect as that described above can be achieved by incorporating 1 part by weight or less of a silicon powder in the form of SiO2 relative to 100 parts by weight of the total amount of the first ceramic powder, the second ceramic powder and the borosilicate glass powder.
In the case where the absolute value of the rate of change of the capacitance of a capacitor is suppressed to about 0.5% or less, and the element with capacitance is used to form a filter, a variation in filter properties due to capacitance change can be reduced. When the absolute value of the rate of change of capacitance exceeds about 0.5%, a variation in filter properties due to capacitance change reaches an unacceptable level, which is not preferable.
In the glass ceramic composition according to preferred embodiments of the present invention, and in the case where the glass ceramic composition further includes the third ceramic powder mainly composed of barium zirconate, a small rate of change of capacitance can be achieved before and after a load test when the glass ceramic composition is used in an element with capacitance.
In particular, when the content of barium zirconate in the form of BaZrO3 is about 3 to 20 percent by weight, a lower rate of change of capacitance can be achieved while a high Qf value and a stable temperature coefficient (τf) of resonant frequency are maintained. The effect of suppressing the rate of change of capacitance is high compared with the above-described case where the range of the silicon content of the borosilicate glass powder is limited. Specifically, even when an element is subjected to a more severe load test than the above-described load test, i.e., even when the element is subjected to a load test at about 150° C., about 95% RH, and about 200 V DC for about 100 hours, the absolute value of the rate of change of capacitance before and after the load test can be suppressed to be about 0.3% or less.
Zinc contained in the borosilicate glass powder serves as a constituent of the Li2(Mg,Zn)SiO4 crystal phase and increases the Q value of a sinter. The reasons the zinc content of the borosilicate glass powder in the form of ZnO is limited to about 6 to 20 percent by weight are described as follows: When the zinc content is less than about 6 percent by weight, Li2(Mg,Zn)SiO4 is not formed in a sinter. This may reduce the Q value and deterioration of chemical stability and insulation reliability. A zinc content exceeding about 20 percent by weight results in deterioration in chemical stability and insulation reliability.
Aluminum is not contained in the borosilicate glass powder in some cases. However, an aluminum content of about 15 percent by weight or less in the form of Al2O3 results in the improvement of the chemical stability of a sinter. In compositions according to embodiments of the present invention, Al2O3 serves as a network-forming oxide and thus makes it difficult to devitrify. As described above, the term “devitrification” means crystallization during glass production. The use of partially crystallized glass causes the nonuniformity of sinterability and electrical properties. An aluminum content exceeding about 15 percent by weight in the form of Al2O3 results in difficulty in sintering at about 1,000° C. or lower. The aluminum content is more preferably about 10 percent by weight or less in the form of Al2O3.
In the glass ceramic composition according to preferred embodiments of the present invention, the content of the borosilicate glass powder is preferably about 3 to 20 percent by weight.
As described above, the reason the content of the borosilicate glass powder is preferably about 3 percent by weight or more is described as follows: a borosilicate glass powder content of less than about 3 percent by weight may cause the glass ceramic composition not to sinter at about 1,000° C. or lower. The reasons the content of the borosilicate glass powder is preferably about 20 percent by weight or less is described as follows: a borosilicate glass powder content exceeding about 20 percent by weight results in an increase in the amount of expensive glass, thus disadvantageously increasing costs. Furthermore, an increase in the amount of the borosilicate glass powder tends to relatively reduce the proportion of the above-described crystal phase, thereby possibly reducing the Q value of the resulting sinter.
In other words, a lower content of the borosilicate glass powder is preferred as long as the content of the borosilicate glass powder is about 3 percent by weight or more. A borosilicate glass powder content of about 20 percent by weight or less, i.e., about 15 percent by weight or less, is sufficient for the composition. A reduction in the content of the borosilicate glass powder facilitates control of the second ceramic powder as an additive, thereby easily adjusting temperature properties of resonant frequency with the additive.
The borosilicate glass powder contained in the glass ceramic composition according to preferred embodiments of the present invention contains at least one additive selected from the group consisting of calcium oxide, barium oxide and strontium oxide in order to improve electrical insulation reliability.
The lower limit of the additive content of the borosilicate glass powder is about 2 percent by weight of the total amount of calcium oxide in the form of CaO, barium oxide in the form of BaO and strontium oxide in the form of SrO. The upper limit of the calcium oxide content of the borosilicate glass powder in the form of CaO is about 15 percent by weight, the upper limit of the barium oxide content of the borosilicate glass powder in the form of BaO is about 25 percent by weight, and the upper limit of the strontium oxide content of the borosilicate glass powder in the form of SrO is about 25 percent by weight.
The reason the additive content is about 2 percent by weight or more is because insulation reliability is not substantially improved at an additive content of less than about 2 percent by weight. The reasons the content of calcium oxide in the form of CaO as an additive is about 15 percent by weight or less are because insulation reliability and the Q value decrease at a calcium content exceeding about 15 percent by weight. The reason the content of barium oxide in the form of BaO as an additive is about 25 percent by weight or less is because the Q value may decrease at a barium oxide content exceeding about 25 percent by weight. The reason the content of strontium oxide in the form of SrO as an additive is about 25 percent by weight or less is because the Q value may decrease at a strontium content exceeding about 25 percent by weight.
The addition of the additives, i.e., the addition of calcium oxide, barium oxide and strontium oxide in combination can further improve insulation reliability.
The glass ceramic composition according to preferred embodiments of the present invention preferably contains about 55 percent by weight or more of the first ceramic powder; and about 6 to 30 percent by weight of the second ceramic powder. Forsterite, which is a main constituent of the first ceramic powder, has a temperature coefficient (τf) of about −60 ppm/° C. CaTiO3, which is a main constituent of the second ceramic powder, has a temperature coefficient (τf) of about +800 ppm/° C. SrTiO3 has a temperature coefficient (τf) of about +1,700 ppm/° C. TiO2 has a temperature coefficient (τf) of about +450 ppm/° C. Furthermore, borosilicate glass has a negative temperature coefficient (τf). In order to achieve a temperature coefficient (τf) in the range of about ±30 ppm/° C. with these materials, the above-described composition is preferred.
Forsterite, which is a main constituent of the first ceramic powder, preferably has a molar ratio of MgO to SiO2, i.e., MgO/SiO2, of about 1.92 to 2.04 because the chemical stability of a sinter may degrade at a ratio MgO/SiO2 of less than about 1.92 or exceeding about 2.04. The first ceramic powder has a main crystal phase composed of forsterite (Mg2SiO4) with no other crystal phase. Alternatively, the first ceramic powder may further contain a small amount of at least one of a SiO2 (quartz) crystal phase, a MgO crystal phase, and a MgSiO3 (steatite) crystal phase, as other crystal phase.
In the first ceramic powder, the content of impurities other than forsterite is more preferably about 5 percent by weight or less because the Q value is reduced and chemical stability may degrade at an impurity content exceeding about 5 percent by weight. Examples of the impurities include Al2O3, B2O3, CaO, Fe2O3, MnO2, NiO, SnO2, SrO, ZnO, P2O5, TiO2, ZrO2, Li2O, Na2O and K2O.
The first ceramic powder preferably has a median particle size (D50) of about 1 μm or less because a median particle size (D50) exceeding about 1 μm may result in failure of densification at a borosilicate glass powder content of about 3 to 20 percent by weight.
The second ceramic powder as an additive serves to adjust temperature properties of resonant frequency of a sinter.
When the second ceramic powder contains a ceramic powder mainly composed of CaTiO3, the CaTiO3 content is preferably about 18 percent by weight or less because a CaTiO3 content exceeding 18 percent by weight may result in a reduction in the Q value of a sinter and results in an increase in dielectric constant to affect a transmission rate in a high-frequency band.
When the second ceramic powder contains a ceramic powder mainly composed of SrTiO3, the SrTiO3 content is preferably about 13 percent by weight or less because a SrTiO3 content exceeding 13 percent by weight may result in a reduction in the Q value of a sinter and results in an increase in dielectric constant to affect a transmission rate in a high-frequency band.
A ceramic powder mainly composed of TiO2 has the effect of increasing crystallinity. To sufficiently exert the effect, the second ceramic powder preferably contains about 0.3 percent by weight or more of the TiO2. A TiO2 content exceeding 30 percent by weight results in an increase in the dielectric constant of a sinter and affects a transmission rate in a high-frequency band. Thus, the content of the ceramic powder mainly composed of TiO2 is preferably about 30 percent by weight or less.
When the second ceramic powder contains a ceramic powder mainly composed of calcium titanate and a ceramic powder mainly composed of titanium oxide, the calcium titanate content of the glass ceramic composition in the form of CaTiO3 is preferably about 8 to 12 percent by weight, and the titanium oxide content of the glass ceramic composition in the form of TiO2 is preferably about 0.3 to 3 percent by weight.
Alternatively, the second ceramic powder may contain a ceramic powder mainly composed of strontium titanate and a ceramic powder mainly composed of titanium oxide. In this case, SrTiO3 and TiO2 serve to control temperature properties of resonant frequency. In addition, the use of SrTiO3 can achieve a low dielectric constant compared with the use of CaTiO3 or TiO2, provided that the equivalent temperature coefficient (τf) is achieved. TiO2 makes a great contribution to the promotion of crystallization of glass, i.e., TiO2 makes a great contribution to a higher Q value of a sinter and the improvement of moisture resistance.
When the second ceramic powder contains a ceramic powder mainly composed of SrTiO3 and a ceramic powder mainly composed of TiO2, the content of the SrTiO3-based ceramic powder in the glass ceramic composition is preferably about 6 to 10 percent by weight and the content of the TiO2-based ceramic powder in the glass ceramic composition is preferably about 0.3 to 3 percent by weight in order to reduce the dielectric constant of a sinter and to promote the crystallization of glass while other properties are not significantly degraded.
When the content of the SrTiO3-based ceramic powder is less than about 6 percent by weight, the temperature coefficient of resonant frequency of a sinter tends to be a large negative value. When the content of the SrTiO3-based ceramic powder exceeds about 1.0 percent by weight, the Q value of the sinter tends to decrease. Furthermore, when the content of the TiO2-based ceramic powder is less than about 0.3 percent by weight, the crystal phase tends to be difficult to precipitate. When the content of the TiO2-based ceramic powder exceeds about 3 percent by weight, the temperature coefficient of resonant frequency of a sinter tends to be a large positive value.
When the second ceramic powder contains a ceramic powder mainly composed of strontium titanate, the molar ratio of SrO to TiO2, i.e., SrO/TiO2, is preferably about 0.92 to 1.05.
At a ratio SrO/TiO2 exceeding about 1.05, unreacted SrO sometimes remains in the form of a carbonate or the like, thereby reducing the Q value and degrading moisture resistance due to reaction with a glass component, in some cases. Furthermore, a Sr2TiO4 crystal phase or the like may be precipitated. The Sr2TiO4 has a small absolute value of the temperature coefficient of dielectric constant (TCC) compared with that of SrTiO3. In the case where the Sr2TiO4 crystal phase or the like is precipitated, the amount of the second ceramic powder added is increased in order to adjust TCC of the entire system, thereby possibly reducing the Q value.
A ratio SrO/TiO2 of less than about 0.92 may result in the precipitation of SrTiO3 and TiO2. In the present invention, TiO2 may be separately added. Thus, electrical properties are controlled without problems by adjusting amounts of SrTiO3 and TiO2 added. However, the amounts of SrTiO3 and TiO2 added are adjusted in each production, thus possibly complicating control and increasing costs.
In the above-described case, the content of impurities in the ceramic powder mainly composed of strontium titanate is more preferably about 1 percent by weight or less. There are impurities contained in a starting material and impurities introduced during production steps. Examples of the impurities include Nb2O5, Fe2O3 and Na2O. When the content of a single impurity or the total content of the impurities exceeds about 1 percent by weight, the Q value may decrease.
The specific surface area of the ceramic powder mainly composed of strontium titanate is more preferably about 1.5 to 7.5 m2/g. A specific surface area of less than about 1.5 m2/g may result in difficulty in sintering. A specific surface area exceeding about 7.5 m2/g results in the enhancement of reactivity with glass, thus possibly reducing the Q value.
In the ceramic powder mainly composed of strontium titanate, the integrated intensity of an X-ray diffraction peak assigned to the SrTiO3 (222) surface is more preferably about 1,000 or more because the crystallinity of SrTiO3 is not very high at an integrated intensity of less than about 1,000, increasing reactivity with glass, thereby possibly reducing the Q value.
The above-described glass ceramic composition can be fired at about 1,000° C. or less to yield a sintered glass ceramic material. The resulting sintered glass ceramic material has a Mg2SiO4 crystal phase as a main phase and a Li2(Mg,Zn)SiO4 crystal phase as a subphase and is advantageously used to constitute a multilayer ceramic electronic component.
The glass ceramic composition according to preferred embodiments of the present invention may further contain a third ceramic powder containing at least one ceramic powder selected from a copper oxide-based ceramic powder mainly composed of copper oxide (CuO), a iron oxide-based ceramic powder mainly composed of iron oxide (Fe2O3) and a manganese oxide-based ceramic powder mainly composed of manganese oxide (MnO2) in addition to the first ceramic powder, the second ceramic powder and the borosilicate glass powder described above. In this case, the total amount of the third ceramic powder is about 2.5 parts by weight or less and contains about 0.5 parts by weight or less of the copper oxide-based ceramic powder, about 1 part by weight or less of the iron oxide-based ceramic powder and about 2 parts by weight or less of the manganese oxide-based ceramic powder, relative to 100 parts by weight of the total amount of the first ceramic powder, the second ceramic powder and the borosilicate glass powder.
The use of the glass ceramic composition further containing the third ceramic powder described above can provide a sufficiently sintered glass ceramic material even at a lower content of the borosilicate glass powder, thereby relatively increasing the content of the first ceramic powder. Thus, the sintered glass ceramic material, can surely have a Qf value of about 10,000 GHz or more and a temperature coefficient (τf) of resonant frequency in the range of about ±30 ppm·° C.−1.
FIG. 1 is a cross-sectional view of a multilayer ceramic module 1 as an example of a multilayer ceramic electronic component including a glass ceramic composition according to preferred embodiments of the present invention. FIG. 2 is an exploded perspective view of the multilayer ceramic module 1 shown in FIG. 1.
The multilayer ceramic module 1 includes a multilayer ceramic substrate 2. The multilayer ceramic substrate 2 includes a plurality of glass ceramic layers 3, the glass ceramic layers 3 being laminated; and a plurality of high-dielectric ceramic layers 4, the high-dielectric ceramic layers 4 being laminated, with the high-dielectric ceramic layers 4 being disposed between the glass ceramic layers 3.
The glass ceramic layers 3 are each composed of the sintered glass ceramic material obtained by firing the glass ceramic composition according to preferred embodiments of the present invention. For example, the glass ceramic layers 3 each have a relatively low dielectric constant of about 10 or less.
The high-dielectric ceramic layers 4 are each composed of, for example, barium titanate with glass. The high-dielectric ceramic layers 4 each have a dielectric constant of 15 or more and preferably 30 or more.
The multilayer ceramic substrate 2 includes various types of conductive leads. Typical examples of the conductive leads include inner conductive films 6 each disposed along a specific interface among the glass ceramic layers 3 and the high-dielectric ceramic layers 4; via-hole conductors 7 extending through specific layers among the glass ceramic layers 3 and the high-dielectric ceramic layers 4; and outer conductive films 8 disposed on a surface of the multilayer ceramic substrate 2.
Some of the inner conductive films 6 disposed so as to correspond to the high-dielectric ceramic layers 4 are disposed so as to provide capacitance, thereby forming capacitor elements.
The multilayer ceramic substrate 2 includes a plurality of electronic components 9 to 17 on the upper surface thereof. Among the electronic components 9 to 17 shown in the figure, for example, the electronic component 9 is a diode, electronic component 11 is a multilayer ceramic capacitor and electronic component 16 is a semiconductor IC. The electronic components 9 to 17 are electrically connected to specific films among the outer conductive films 8 disposed on the upper surface of the multilayer ceramic substrate 2. The electronic components 9 to 17 and the conductive leads disposed in the multilayer ceramic substrate 2 constitute a circuit required for the multilayer ceramic module 1.
A conductive cap 18 for shielding the electronic components 9 to 17 is fixed on the upper surface of the multilayer ceramic substrate 2. The conductive cap 18 is electrically connected to specific conductors among the via-hole conductors 7.
The multilayer ceramic module 1 is mounted on a motherboard (not shown) with specific films among the outer conductive films 8 as connection terminals disposed on the lower surface of the multilayer ceramic substrate 2.
The multilayer ceramic module 1 can be produced by a well-known multilayer ceramic co-firing technique.
That is, first, ceramic green sheets for forming the glass ceramic layers 3 are produced. Specifically, an organic vehicle containing a binder resin and a solvent is added to the glass ceramic composition, i.e., a material composition, according to preferred embodiments of the present invention to form a ceramic slurry. The ceramic slurry is formed into sheets by a doctor blade method, dried, and stamped into a predetermined shape to form ceramic green sheets. To form the conductive leads on the ceramic green sheets, a conductive paste mainly composed of copper or silver is applied thereon to form a predetermined pattern.
Ceramic green sheets for forming the high-dielectric ceramic layers 4 is produced, the ceramic green sheets including a high-dielectric ceramic composition. Specifically, one of the following compositions (1) to (4) is prepared as the high-dielectric ceramic composition:
(1) a high-dielectric ceramic composition disclosed in Japanese Unexamined Patent Application Publication No. 2001-80959, the high-dielectric ceramic composition including 100 parts by weight of a principal constituent, about 0.1 to 25 parts by weight of a first secondary constituent composed of a SiO2-based glass, and about 0.5 to 20 parts by weight of a Mn-containing second secondary constituent in the form of MnO, wherein the primary constituent is represented by the formula x(BaaCabSrc)O-y{(TiO2)1-m(ZrO2)m}-zRe2O3 (wherein x, y, and z each represent mole percent, and x+y+z=100 on a molar basis; a+b+c=1;0≦b+c<0.8; 0≦m<0.15; and Re is at least one rare earth element), and the mole fraction (x, y, z) of (BaaCabSrc)O, {(TiO2)1-m(ZrO2)m}, and Re2O3 lies within a range surrounded by point A(7, 85, 8), point B(7, 59, 34), point C(0, 59, 41), and point D(0, 85, 15) in a ternary diagram shown in FIG. 3 wherein the line AB is not included;
(2) a high-dielectric ceramic composition disclosed in Japanese Unexamined Patent Application Publication No. 2002-97072, the high-dielectric ceramic composition including a BaO—TiO2—ReO3/2-based ceramic composition represented by the formula xBaO-yTiO2-zReO3/2 (wherein x, y and z each represent mole percent and x+y+z=100; 8≦x≦1.8; 52.5≦y≦65; 20≦z≦40; and Re is at least one rare-earth element); and a glass composition containing about 10 to 25 percent by weight of SiO2, about 10 to 40 percent by weight of B2O3, about 25 to 55 percent by weight of MgO, about 0 to 20 percent by weight of ZnO, about 0 to 15 percent by weight of Al2O3, about 0.5 to 10 percent by weight of Li2O, and about 0 to 10 percent by weight of RO (wherein R represents at least one element selected from Ba, Sr and Ca);
(3) a high-dielectric ceramic composition disclosed in Japanese Unexamined Patent Application Publication No. 11-310455, the high-dielectric ceramic composition including a mixture of a BaO—TiO2—ReO3/2—BiO3-based ceramic powder (wherein Re represents a rare-earth element) and a glass powder containing about 13 to 50 percent by weight of SiO2, about 3 to 30 percent by weight of B2O3, about 40 to 80 percent by weight of an alkaline-earth metal oxide, and about 0.1 to 10 percent by weight of Li2O; and
(4) a high-dielectric ceramic composition disclosed in Japanese Unexamined Patent Application Publication No. 11-228222, the high-dielectric ceramic composition including a mixture of a BaO—TiO2—ReO3/2-based ceramic powder (wherein Re represents a rare-earth element) and a glass powder containing about 13 to 50 percent by weight of SiO2, about 3 to 30 percent by weight of B2O3, about 40 to 80 percent by weight of an alkaline-earth metal oxide, and about 0.5 to 10 percent by weight of Li2O.
The high-dielectric ceramic composition (1) preferably further contains Li2O.
Next, an organic vehicle containing a binder resin and a solvent is added to any one of the high-dielectric ceramic compositions (1) to (4) to form a ceramic slurry. The ceramic slurry is formed into sheets by a doctor blade method, dried, and stamped into a predetermined shape to form ceramic green sheets. To form the conductive leads on the ceramic green sheets, a conductive paste mainly composed of copper or silver is applied thereon to form a predetermined pattern.
A predetermined number of the resulting glass ceramic green sheets and high-dielectric ceramic green sheets are laminated in a predetermined order and pressed in the thickness direction.
The resulting green laminate is fired at a temperature of about 1,000° C. or lower, for example, about 800° C. to 1,000° C., to form the multilayer ceramic substrate 2. When each of the conductive leads is mainly composed of copper, firing is performed in a nonoxidizing atmosphere such as a nitrogen atmosphere. When each of the conductive leads is mainly composed of silver, firing is performed in an oxidizing atmosphere such as air.
The electronic components 9 to 17 are mounted on a surface of the multilayer ceramic substrate 2 by soldering or the like. The conductive cap 18 is attached to the multilayer ceramic substrate 2 to complete the multilayer ceramic module 1.
In the multilayer ceramic module 1, the glass ceramic layers 3 in the multilayer ceramic substrate 2 each contain the glass ceramic composition according to preferred embodiments of the present invention. Furthermore, each of the conductive leads 6 to 8 is mainly composed of a low-resistivity metal, such as copper or silver. Thus, it is possible to make the highly reliable multilayer ceramic module 1 having a low-dielectric glass ceramic layers 3, a satisfactory temperature properties of resonant frequency, and a high Q value and suitable for high-frequency applications. Furthermore, it is possible to make the multilayer ceramic module 1 having satisfactory insulation reliability.
FIGS. 4 to 6 are each an illustration of a LC filter 21 as another example of a multilayer ceramic electronic component including a glass ceramic composition according to preferred embodiments of the present invention. FIG. 4 is a perspective view of the appearance of the LC filter 21. FIG. 5 is an equivalent circuit schematic representing the LC filter 21. FIG. 6 is an exploded perspective view of a green laminate 22 as a semifinished product to be subjected to a firing step to form the LC filter.
As shown in FIG. 4, the LC filter 21 includes a main body 23 having a multilayer structure in which a plurality of glass ceramic layers are laminated; terminal electrodes 24 and 25 each disposed on the corresponding end on the external surface of the main body 23; and terminal electrodes 26 and 27 each disposed on the middle of the corresponding side surface.
As shown in FIG. 5, the LC filter 21 includes series-connected two inductors L1 and L2 disposed between the terminal electrodes 24 and 25; and a capacitor C disposed between the connection point of the inductors L1 and L2 and the terminal electrodes 26 and 27.
Referring to FIG. 6, the green laminate 22 is to be main body 23 after firing. The green laminate 22 includes a plurality of ceramic green sheets 28 to 40, the ceramic green sheets being laminated. The number of ceramic green sheets laminated is not limited to the number shown in the figure.
Each of the ceramic green sheets 28 to 40 is formed by adding an organic vehicle containing a binder resin and a solvent to a glass ceramic composition according to preferred embodiments of the present invention, mixing the resulting mixture to form a ceramic slurry, forming the ceramic slurry into sheets by a doctor blade method, drying the sheets, and stamping the dry sheets into a predetermined shape.
To form the inductors L1 and L2 and the capacitor C shown in FIG. 5, conductive leads are disposed on specific sheets among the ceramic green sheets 28 to 40. The conductive leads each have a structure described below.
The ceramic green sheet 30 has a coil pattern 41 partially constituting the inductor L1; a leading pattern 42 extending from one end of the coil pattern 41; and a via-hole conductor 43 disposed on the other end of the coil pattern 41.
The ceramic green sheet 31 has a coil pattern 44 partially constituting the inductor L1; and a via-hole conductor 45 disposed on one end of the via-hole conductor 44. The via-hole conductor 43 is connected to the other end of the coil pattern 44.
The ceramic green sheet 32 has a via-hole conductor 46 connected to the via-hole conductor 45.
A ceramic green sheet 33 has a capacitor pattern 47 partially constituting the capacitor C; and leading patterns 48 and 49 extending from the capacitor pattern 47. Furthermore, the ceramic green sheet 33 has a via-hole conductor 50 connected to the via-hole conductor 46.
A ceramic green sheet 34 has a capacitor pattern 51 partially constituting the capacitor C; and a via-hole conductor 52 connected to the capacitor pattern 51. The capacitor pattern 51 is connected to the via-hole conductor 50.
A ceramic green sheet 35 has a capacitor pattern 53 partially constituting the capacitor C; and leading patterns 54 and 55 extending from the capacitor pattern 53. Furthermore, the ceramic green sheet 35 has a via-hole conductor 56 connected to the via-hole conductor 52.
A ceramic green sheet 36 has a via-hole conductor 57 connected to the via-hole conductor 56.
A ceramic green sheet 37 has a coil pattern 58 partially constituting the inductor L2; and a via-hole conductor 59 disposed at one end of the coil pattern 58. The via-hole conductor 57 is connected to the other end of the coil pattern 58.
A ceramic green sheet 38 has a coil pattern 60 partially constituting the inductor L2; and leading pattern 61 extending from one end of the coil pattern 60. The via-hole conductor 59 is connected to the other end of the coil pattern 60.
A conductive paste mainly composed of copper or silver is used to form the coil patterns 41, 44, 58 and 60, the leading patterns 42, 48, 49, 54, 55 and 61, the via-hole conductors 43, 45, 46, 50, 52, 56, 57 and 59, and the capacitor patterns 47, 51 and 53 as the conductive leads. The conductive paste is applied to the sheets by screen printing.
To form the green laminate 22, the ceramic green sheets 28 to 40 are laminated in the order shown in FIG. 6 and pressed in the thickness direction.
The green laminate 22 is fired at a temperature of about 1,000° C. or lower, e.g., about 800° C. to 1,000° C., to form the main body 23 shown in FIG. 4. Firing is performed in the same way as the multilayer ceramic module 1 described above. That is, when each of the conductive leads is mainly composed of copper, firing is performed in a nonoxidizing atmosphere such as a nitrogen atmosphere. When each of the conductive leads is mainly composed of silver, firing is performed in an oxidizing atmosphere such as air.
The terminal electrodes 24 to 27 are formed on the external surface of the main body 23. For example, the terminal electrodes 24 to 27 are formed by applying and baking a conductive paste mainly composed of copper or silver or by a thin-film-forming method, such as evaporation, plating, or sputtering.
Thereby, the LC filter 21 can be produced.
As described above, each of the ceramic green sheets 28 to 40 is composed of the glass ceramic composition according to preferred embodiments of the present invention. Among the ceramic green sheets 28 to 40, the ceramic green sheets 33 and 34 that directly contribute to the formation of the capacitor C are preferably each composed of the high-dielectric ceramic composition for constituting the high-dielectric ceramic layers 4 included in the multilayer ceramic module 1 shown in FIG. 1.
The multilayer ceramic electronic component including the glass ceramic composition according to preferred embodiments of the present invention is not limited to the multilayer ceramic module 1 or the LC filter 21 shown in the figures. Examples of the component containing the glass ceramic composition according to preferred embodiments of the present invention include various multilayer ceramic substrates, such as multilayer ceramic substrates for multichip modules and multilayer ceramic substrate for hybrid integrated circuits (ICs); various combined electronic components in which electronic components are mounted on the multilayer ceramic substrates; and various multilayer chip electronic components, such as multilayer chip capacitors and multilayer chip dielectric antennae.
Experimental examples for verifying characteristics obtained by the glass ceramic composition according to preferred embodiments of the present invention and for determining the range or more preferred range of the glass ceramic composition according to preferred embodiments of the present invention will be described.
EXPERIMENTAL EXAMPLE 1
Borosilicate glass powders, having various compositions shown in Table 1, for use in a glass ceramic composition were prepared.

















TABLE 1





Type of
Li2O
MgO
BaO
CaO
SrO
B2O3
SiO2
ZnO
Al2O3



glass
(wt %)
(wt %)
(wt %)
(wt %)
(wt %)
(wt %)
(wt %)
(wt %)
(wt %)
Remarks

























G1*
2
33
3
—
2
25
27
8
—



G2
3.5
33
2
1
2
25
25.5
8
—


G3
15
23
2
—
7
20
23
10
—


G4*
16.5
25
7
—
—
20
21.5
10
—


G5*
6
18
5
—
5
26
28
8
4


G6
6
23
2
2
3
26
26
8
4


G7
5
45
4
—
—
22
18
6
—


G8*
5
52
4
—
—
18
15
6
—
Devitrified


G9*
8
34
3
1
6
14
25
7
2
Difficulty in vitrification


G10
8
34
3
2
3
16
25
7
2


G11
6
24
3
1
6
29
21
10
—


G12*
6
23
3
1
6
31
20
10
—


G13*
10
33
3
2
5
23
9
10
5
Devitrified


G14
10
38
3
—
—
23
11
10
5


G15
5
33
5
—
8
18
25
6
—


G16*
6
23
4
—
—
15
46
6
—


G17*
6
25
3
—
3
28
31
4
—


G18
6
25
3
—
5
24
31
6
—


G19
6
29
2
5
1
19
18
20
—


G20*
6
30
5
—
—
19
18
22
—


G21*
6
30
—
—
5
20
15
8
16


G22
6
27
3
1
4
20
16.5
8
14.5


G23*
5
25
27
—
—
17
19
7
—


G24
5
23
25
—
—
18
23
6
—


G25
4
33
16
—
—
17
23
7
—


G26*
6
28
1
16 
—
18
24
7
—


G27
6
35
1
10 
—
19
23
6
—


G28*
6
22
1
—
27 
16
22
6
—


G29
6
22
1
—
25 
18
20
8
—


G30
6
32
1
—
12 
19
23
7
—









In Table 1, a “type of glass” marked with an asterisk “*” represents a glass powder having a composition outside the range of the present invention.
The glass powders shown in Table 1, except for glass G8, G9, and G13 that were devitrified or difficult to vitrify, were pulverized so as to have an average particle size of about 1 to 2 μm to form borosilicate glass powders for glass ceramic compositions.
A Mg2SiO4 powder having an average particle size (median particle size D50) of about 0.8 μm was prepared as the first ceramic powder contained in a glass ceramic composition. As the second ceramic powders, a CaTiO3 powder having an average particle size of about 1.5 μm, a SrTiO3 powder having an average particle size of about 1.5 μm and a TiO2 powder having an average particle size of about 1.0 μm were prepared.
The first ceramic powder was mixed with the borosilicate glass powder and the second ceramic powder to form glass ceramic compositions corresponding to the samples shown in Table 2.











TABLE 2









Amount of
Borosilicate
Second



first ceramic
glass
ceramic powder












Sample
powder (wt %)
Type
Amount (wt %)
Type
Amount (wt %)















 1*
70.0
G1
20.0
CT
10.0


 2
70.0
G2
20.0
CT
10.0


 3
85.0
G3
3.0
CT
12.0


 4*
85.0
G4
3.0
CT
12.0


 5*
77.0
G5
15.0
ST
8.0


 6
77.0
G6
15.0
ST
8.0


 7
74.0
G7
15.0
ST
11.0


 8
75.0
G10
15.0
ST
10.0


 9
72.0
G11
15.0
ST
13.0


 10*
78.0
G12
15.0
CT
7.0


11
84.0
G14
8.0
CT
8.0


12
84.0
G15
9.0
ST
7.0


 13*
74.0
G16
18.0
CT
8.0


 14*
75.0
G17
15.0
CT
10.0


15
75.0
G18
15.0
CT
10.0


16
72.0
G19
20.0
ST
8.0


 17*
72.0
G20
20.0
ST
8.0


 18*
66.5
G21
19.0
CT
14.5


19
66.5
G22
19.0
CT
14.5


 20*
80.0
G23
10.0
ST
10.0


21
80.0
G24
10.0
ST
10.0


22
79.0
G25
10.0
CT
11.0


 23*
79.0
G26
10.0
CT
11.0


24
79.0
G27
10.0
CT
11.0


 25*
82.0
G28
10.0
ST
8.0


26
82.0
G29
10.0
ST
8.0


27
82.0
G30
10.0
ST
8.0


 28*
85.0
G15
2.0
ST
13.0


29
76.0
G15
9.0
T
15.0


30
79.0
G15
9.0
CT
12.0


31
74.0
G15
10.0
ST
6.0


32
80.0
G15
9.0
CT/T
10.0/1.0 


33
80.0
G15
9.0
ST/T
10.0/1.0 


34
83.5
G15
9.0
ST/T
6.5/1.0


35
85.0
G15
9.0
ST/T
5.0/1.0


36
80.5
G15
9.0
ST/T
7.0/5.5


37
83.4
G15
10.0
ST/T
6.5/0.1


38
80.5
G15
10.0
ST/T
6.5/3.0


39
81.0
G15
10.0
CT/T
8.0/1.0


40
77.0
G15
10.0
CT/T
12.0/1.0 


41
55.0
G15
10.0
T
35.0


42
60.0
G15
10.0
T
30.0


43
78.0
G15
8.0
ST
14.0


44
73.0
G15
9.0
CT
18.0


45
71.0
G15
9.0
CT
20.0









In Table 2, a glass ceramic composition marked with an asterisk “*” represents a glass ceramic composition outside of the range of the present invention.
In Table 2, the “amount of first ceramic powder” column shows the amount of the Mg2SiO4 powder added as the first ceramic powder.
The “type” column in the “borosilicate glass” section represents the “type of glass” shown in Table 1. The “amount” column in the “borosilicate glass” section represents the amount of the borosilicate glass powder added.
The “type” column in the “second ceramic powder” section represents at least one of the CaTiO3 (=CT) powder, the SrTiO3 (=ST) powder, and the TiO2 (=T) powder used as the second ceramic powder. The “amount” column in the “second ceramic powder” section represents the amount of the powder added.
Next, about 20 parts by weight of an acrylic resin as a binder and about 30 parts by weight of methyl ethyl ketone were added to 100 parts by weight of each glass ceramic composition for the corresponding sample shown in Table 2, and then granulation was performed. The resulting powder was formed by pressing into a substantially columnar preform. The perform was fired at a temperature of about 1,000° C. or lower to form a sintered glass ceramic material sample.
As shown in Table 3, each sample was evaluated for dielectric constant (εr), Qf value, temperature coefficient (τf) of resonant frequency and chemical stability.
The dielectric constant (εr), the Qf value, and the temperature coefficient (τf) of resonant frequency were measured by a dielectric resonator method. Dimensions of each sample were adjusted in such a manner that the measurement frequency is about 10 GHz.
With respect to chemical stability, whether or not the Qf value was significantly degraded was checked after each sample that had been evaluated for the dielectric constant (εr) and the Qf value was subjected to a pressure cooker test (PCT) at about 120° C. and about 95% RH for about 100 hours. In Table 3, a sample that was not significantly degraded had satisfactory chemical stability and is thus indicated by “Good”. A sample that was significantly degraded had unsatisfactory chemical stability and is thus indicated by “Poor”.
As shown in Table 3, insulation reliability was also evaluated. A binder and an organic solvent were added to each glass ceramic composition for the corresponding sample shown in Table 2 to form a slurry. The resulting slurry was formed into sheets by the doctor blade method. A conductive paste for forming inner electrodes was applied by printing on the sheets. The resulting sheets were laminated, pressed and fired to form a multilayer capacitor as a specimen. The resulting multilayer capacitors corresponding to the samples were subjected to an accelerated test at about 120° C., about 95% RH and about 15 V DC. After the accelerated test was performed for about 100 hours, a sample in which significant insulation degradation was not observed had satisfactory insulation reliability and indicates “Good” in Table 3. A sample in which significant insulation degradation was observed had unsatisfactory insulation reliability and indicates “Poor” in Table 3.












TABLE 3







Qf
τf
Chemical
Insulation


Sample
εr
(GHz)
(ppm · ° C.−1)
stability
reliability
















 1*
Not sintered












 2
9.5
28000
−5
Good
Good


 3
11.2
10500
5
Good
Good


 4*
9.8
8500
−15
Poor
Poor


 5*
8.9
4800
−15
Good
Good


 6
9.1
12000
−10
Good
Good


 7
10.5
39000
12
Good
Good


 8
9.5
36000
11
Good
Good


 9
18
20000
60
Good
Good


 10*
8.3
3800
20
Poor
Poor


11
9.2
26000
−10
Good
Good


12
8.9
39000
5
Good
Good








 13*
Not sintered












 14*
10.5
24000
−25
Poor
Poor


15
10.5
38500
−22
Good
Good


16
8.9
39000
−20
Good
Good


 17*
8.9
39500
−22
Poor
Poor








 18*
Not sintered












19
12.4
18000
18
Good
Good


 20*
11.0
1500
15
Good
Good


21
10.5
5500
14
Good
Good


22
9.5
20000
6
Good
Good


 23*
8.8
20000
−5
Poor
Poor


24
9.0
32000
5
Good
Good


 25*
9.8
4400
8
Good
Good


26
9.7
12000
9
Good
Good


27
9.5
38000
6
Good
Good








 28*
Not sintered












29
10.5
29000
−15
Good
Good


30
9.0
31500
4
Good
Good


31
8.8
37000
−5
Good
Good


32
11.0
48000
6
Good
Good


33
10.5
41000
10
Good
Good


34
8.9
52000
5
Good
Good


35
8.2
51000
−12
Good
Good


36
10.2
32000
15
Good
Good


37
8.5
26000
31
Good
Good


38
9.5
36000
9
Good
Good


39
8.4
41000
−9
Good
Good


40
9.8
40500
8
Good
Good


41
22
12000
50
Good
Good


42
18.0
15000
37
Good
Good


43
14.0
4500
51
Good
Good


44
16.0
11000
45
Good
Good


45
17.8
3800
48
Good
Good









In Table 3, a sample marked with an asterisk “*” is outside the range of the present invention.
The samples within the range of the present invention shown in Tables 2 and 3 each contain the borosilicate glass within the range of the present invention shown in Table 1, which is apparent from the “type” column in the “borosilicate glass” section in Table 2; the Mg2SiO4 powder as the first ceramic powder; and the second ceramic powder containing at least one ceramic powder selected from the CaTiO3 powder, the SrTiO3 powder, and the TiO2 powder. Thereby, the samples can be fired at a temperature of about 1,000° C. or lower. Furthermore, the samples each have satisfactory chemical stability, insulation reliability, a high Qf value, and a stable temperature coefficient τf.
Glass G1 shown in Table 1 contains about less than 3 percent by weight of Li2O. Thus, sample 1 containing glass G1 shown in Tables 2 and 3 was not sintered at a temperature of about 1,000° C. or lower. Glass G4 contains more than about 15 percent by weight of Li2O. Thus, sample 4 containing glass G4 had a low Qf value and degraded chemical stability and insulation reliability.
Glass G5 contains less than about 20 percent by weight of MgO. Thus, sample 5 containing glass G5 had a low Qf value. Glass G8 contains more than about 50 percent by weight of MgO. Thus, a phenomenon in which glass was partially crystallized, i.e., devitrification, occurred.
Glass G9 contains less than about 15 percent by weight of B2O3, resulting in difficulty in vitrification. Glass G12 contains more than about 30 percent by weight of B2O3. Thus, sample 10 containing glass G12 had a low Qf value and degraded chemical stability and insulation reliability.
Glass G13 contains less than about 10 percent by weight of SiO2, resulting in devitrification. Glass G16 contains more than about 45 percent by weight of SiO2. Thus, sample 13 containing glass G16 was not sintered at a temperature of about 1,000° C. or lower.
Glass G17 contains less than about 6 percent by weight of ZnO. Thus, sample 14 containing glass G17 had degraded chemical stability. Glass G20 contains more than about 20 percent by weight of ZnO. Thus, sample 17 containing glass G20 had degraded chemical stability and insulation reliability.
Glass G21 contains more than about 15 percent by weight of Al2O3. Thus, sample 18 containing glass G21 was not sintered at a temperature of about 1,000° C. or lower.
Glass G23 contains more than about 25 percent by weight of BaO. Thus, sample 20 containing glass G23 had a low Qf value.
Glass G26 contains more than about 15 percent by weight of CaO. Thus, sample 23 containing glass G26 had degraded chemical stability and insulation reliability.
Glass G28 contains more than about 25 percent by weight of SrO. Thus, sample 25 containing glass G28 had a low Qf value.
Furthermore, sample 28 was not sintered at a temperature of about 1,000° C. or lower as shown in Table 3 not because of the composition of the borosilicate glass shown in Table 1 but because of a borosilicate glass powder content of less than about 3 percent by weight as shown in Table 2.
Next, samples 12 and 29 to 45, which are with in the range of the present invention and shown in Tables 2 and 3, each containing glass G15 as the composition of the borosilicate glass shown in Table 1 are compared with respect to, in particular, the second ceramic powder.
Among samples 30, 32, 39, 40, 44 and 45 each containing CT (CaTiO3) as the second ceramic powder, sample 45 containing more than about 18 percent by weight of CT had a low Qf value and a high dielectric constant εr. Thus, the CT content is preferably about 18 percent by weight or less.
Among samples 12, 31, 33 to 38, and 43 each containing ST (SrTiO3) as the second ceramic powder, sample 43 containing more than about 13 percent by weight of ST had a low Qf value and a high dielectric constant εr. Thus, the ST content is preferably about 13 percent by weight or less.
Among samples 29 and 32 to 42 each containing T (TiO2) as the second ceramic powder, sample 41 containing more than about 30 percent by weight of T had a high dielectric constant εr. Thus, the T content is preferably about 30 percent by weight or less.
When samples each contain about 8 to 12 percent by weight of CT and about 0.3 to 3 percent by weight of T, like samples 32, 39 and 40 each containing CT (CaTiO3) and T (TiO2), each temperature coefficient (τf) of resonant frequency could be adjusted in the range of about ±10 ppm·° C.−1. Furthermore, high Qf values could be obtained.
Among samples 33 to 38 each containing ST (SrTiO3) and T (TiO2) as the second ceramic powder, each temperature coefficient (τf) of resonant frequency could be adjusted in the range of about ±10 ppm·° C.−1 in samples 33, 34, and 38 each containing about 6 to 10 percent by weight of ST and about 0.3 to 3 percent by weight of T. Furthermore, high Qf values could be obtained. In contrast, the absolute value of each temperature coefficient (τf) of resonant frequency was larger than about 10 ppm·° C.−1 in sample 35 in which the ST content was outside the range of about 6 to 10 percent by weight and in samples 36 and 37 in which the T contents are each outside the range of about 0.3 to 3 percent by weight.
EXPERIMENTAL EXAMPLE 2
As borosilicate glass powders contained in glass ceramic compositions, borosilicate glass powders having various compositions shown in Table 4 were prepared.














TABLE 4





Type









of
Li2O
MgO
BaO
SrO
B2O3
SiO2
ZnO


glass
(wt %)
(wt %)
(wt %)
(wt %)
(wt %)
(wt %)
(wt %)






















G51
4.5
29.0
—
17.0
19.0
23.5
7.0


G52
4.5
25.5
—
17.0
19.0
27.0
7.0


G53
4.5
30.0
—
17.0
19.0
23.0
6.5


G54
4.5
30.5
—
18.0
20.0
21.0
6.0


G55
4.5
30.5
—
18.0
21.0
20.0
6.0


G56
4.5
33.5
—
18.0
19.0
19.0
6.0


G57
4.5
29.5
5.5
8.0
20.0
26.5
6.0









As the first ceramic powder contained in the glass ceramic composition, a Mg2SiO4 powder was prepared as in Experimental Example 1. As the second ceramic powder, a SrTiO3 powder having an average particle size (median particle size D50) of about 1.5 μm and a TiO2 powder having an average particle size of about 1.0 μm were prepared.
Furthermore, a SiO2 powder having an average particle size of about 1.0 μm was prepared for addition to the glass ceramic compositions in specific samples.
To obtain glass ceramic compositions for samples shown in Table 5, the first ceramic powder, the borosilicate glass powder, and the second ceramic powder were mixed. The Sio2 powder was further added to the specific samples.












TABLE 5











Second





Borosilicate
ceramic
Amount of



Amount of
glass
powder
SiO2














first ceramic

Amount

Amount
(part by


Sample
powder (wt %)
Type
(wt %)
Type
(wt %)
weight)
















101
83.0
G51
10.0
ST/T
6.0/1.0
0


102
83.0
G51
10.0
ST/T
6.0/1.0
0.6


 103*
83.0
G51
10.0
ST/T
6.0/1.0
2.0


 104*
83.0
G52
10.0
ST/T
6.0/1.0
0


 105*
83.0
G52
10.0
ST/T
6.0/1.0
1.0


 106*
83.0
G52
10.0
ST/T
6.0/1.0
2.0


 107*
83.0
G53
10.0
ST/T
6.0/1.0
0


108
83.0
G53
10.0
ST/T
6.0/1.0
0.2


109
83.0
G53
10.0
ST/T
6.0/1.0
0.3


110
83.0
G53
10.0
ST/T
6.0/1.0
0.5


111
83.0
G53
10.0
ST/T
6.0/1.0
0.9


 112*
83.0
G53
10.0
ST/T
6.0/1.0
1.2


 113*
83.0
G54
10.0
ST/T
6.0/1.0
0


114
83.0
G54
10.0
ST/T
6.0/1.0
0.4


115
83.0
G54
10.0
ST/T
6.0/1.0
0.7


116
83.0
G54
10.0
ST/T
6.0/1.0
1.0


 117*
83.0
G54
10.0
ST/T
6.0/1.0
1.5


 118*
83.0
G55
10.0
ST/T
6.0/1.0
0


119
83.0
G55
10.0
ST/T
6.0/1.0
0.6


120
83.0
G55
10.0
ST/T
6.0/1.0
0.9


 121*
83.0
G55
10.0
ST/T
6.0/1.0
1.2


 122*
83.0
G56
10.0
ST/T
6.0/1.0
0


 123*
83.0
G56
10.0
ST/T
6.0/1.0
0.9


 124*
83.0
G56
10.0
ST/T
6.0/1.0
1.5


125
83.0
G57
10.0
ST/T
6.0/1.0
0


126
83.0
G57
10.0
ST/T
6.0/1.0
1.0


 127*
83.0
G57
10.0
ST/T
6.0/1.0
1.2









In Table 5, a sample marked with an asterisk “*” represents a glass ceramic composition outside the preferred range of the present invention from the standpoint of the rate of change of capacitance.
In Table 5, the “amount of first ceramic powder”, the “borosilicate glass”, and the “second ceramic powder” columns each represent the same content as in Table 2. The unit of the “amount of SiO2” is expressed as “part by weight” relative to the 100 parts by weight of the total amount of the first ceramic powder, the second ceramic powder and the borosilicate glass powder.
Columnar preforms of the glass ceramic compositions corresponding to the samples shown in Table 5 were formed as in Experimental Example 1 and fired to produce sintered glass ceramic material samples.
In each glass ceramic composition for a corresponding one of the samples, as shown in Table 6, the dielectric constant (εr), Qf value, temperature coefficient (τf) of resonant frequency, chemical stability and insulation reliability were evaluated by the same method as in Experimental Example 1. Furthermore, the rate of change of capacitance was also evaluated. Multilayer capacitors for evaluating insulation reliability were subjected to accelerated test at about 120° C. and about 15 V DC for about 100 hours, and then the rate of change of capacitance was determined using the following equation:

Rate of change of capacitance (%)={(C1−C0)/C0}×100

where C0 represents capacitance before the test and C1 represents capacitance after the test.














TABLE 6








τf


Rate of change




Qf
(ppm ·
Chemical
Insulation
of capacitance


Sample
εr
(GHz)
° C.−1)
stability
reliability
(%)





















101
8.6
50000
5
Good
Good
0.2


102
8.6
48000
3
Good
Good
0.1


 103*
8.5
38000
−2
Good
Good
0.6


 104*
8.7
48000
3
Good
Good
0.6


 105*
8.3
32000
−10
Good
Good
1.1








 106*
Satisfactory sheet was not prepared













 107*
8.8
54000
5
Good
Good
0.6


108
8.8
52000
5
Good
Good
0.4


109
8.7
48000
−5
Good
Good
0.3


110
8.6
46000
−6
Good
Good
<0.1


111
8.4
42000
−10
Good
Good
0.3


 112*
8.2
39000
−20
Good
Good
0.7


 113*
8.8
55000
5
Good
Good
0.8


114
8.6
52000
5
Good
Good
0.5


115
8.6
42000
−11
Good
Good
0.3


116
8.4
39000
−15
Good
Good
0.3


 117*
8.1
25000
−30
Good
Good
1.1


 118*
8.8
54000
6
Good
Good
1.8


119
8.4
45000
−11
Good
Good
0.2


120
8.4
43000
−15
Good
Good
0.3








 121*
Satisfactory sheet was not prepared













 122*
8.9
56000
5
Good
Good
1.8


 123*
8.5
42000
−20
Good
Good
1.5








 124*
Satisfactory sheet was not prepared













125
8.6
42000
5
Good
Good
<0.1


126
8.4
40000
−10
Good
Good
0.4


 127*
8.3
35000
−15
Good
Good
1.1









Also in Table 6, a sample marked with an asterisk “*” is outside the preferred range of the present invention.
Samples 101 to 127 shown in Table 6, except for samples 106, 121 and 124, each exhibited an excellent dielectric constant (εr), Qf value, temperature coefficient (τf) of resonant frequency, chemical stability and insulation reliability.
With respect to the rate of change of capacitance, comparisons were made among samples 101, 104, 107, 113, 118, 122 and 125, each not containing SiO2 shown in Table 5. The results demonstrated that only samples 101 and 125 exhibited a rate of change of capacitance of about 0.5% or less as shown in Table 6. This is because borosilicate glass composition G51 contained in sample 101 and borosilicate glass composition G57 contained in sample 125 each contain about 23.5 to 26.5 percent by weight of SiO2.
In contrast, borosilicate glass compositions G52, G53, G54, G55 and G56 contained in samples 104, 107, 113, 118 and 122, respectively, each contain less than about 23.5 percent by weight of SiO2 or more than about 26.5 percent by weight of SiO2 as shown in Table 4.
However, among samples 104, 107, 113, 118, and 122 each exhibiting a rate of change of capacitance of about 0.5% or more, the separate addition of about 1 part by weight of the SiO2 powder to samples 107, 113, and 118 including borosilicate glass compositions G53, G54, and G55, respectively, each containing about 20 to 26.5 percent by weight of SiO2 resulted in about 0.5% or less of the rate of change of capacitance. Specifically, sample 107 was compared with samples 108 to 111. Sample 113 was compared with samples 114 to 116. Sample 118 was compared with samples 119 and 120. The results demonstrated that the separate addition of 1 part by weight of the SiO2 powder resulted in a rate of change of capacitance of about 0.5% or less as long as the content of SiO2 in the borosilicate glass was in the range of about 20 to 26.5 percent by weight.
However, when the content of SiO2 in the borosilicate glass was in the range of about 20 to 26.5 percent by weight, the separate addition of more than about 1 part by weight of SiO2 resulted in a rate of change of capacitance of more than about 0.5%. Furthermore, an appropriate green sheet was not formed because of the slurry having increased viscosity, in some cases. Specifically, since the amount of SiO2 added was about 2.0 parts by weight in sample 103, the rate of change of capacitance was increased to about 0.6%. In sample 112, since the amount of SiO2 added was about 1.2 parts by weight, the rate of change of capacitance was increased to about 0.7%. In sample 117, since the amount of SiO2 added was about 1.5 parts by weight, the rate of change of capacitance was increased to about 1.1%. In sample 121, since the amount of SiO2 added was about 1.2 parts by weight, an appropriate green sheet was not formed. In sample 127, since the amount of SiO2 added was about 1.2 parts by weight, the rate of change of capacitance was increased to about 1.1%.
In samples 104 to 106 and 122 to 124 including glass G52 or glass G56 in which the content of SiO2 in the borosilicate glass powder was outside the range of about 20 to 26.5 percent by weight, despite the amount of the SiO2 powder separately added, the rate of change of capacitance exceeded about 0.5% or an appropriate green sheet was not formed. That is, favorable results were not obtained.
EXPERIMENTAL EXAMPLE 3
As borosilicate glass powders contained in glass ceramic compositions, glass powders described in Table 7 were prepared in addition to glass G1 to G5, G10 to G12, G14, G16 to G24, G26, G27 and G29 shown in Table 1 described above.
















TABLE 7





Type of











glass
(wt %)
(wt %)
(wt %)
(wt %)
(wt %)
(wt %)
(wt %)
(wt %)
(wt %)


 
Li2O
MgO
BaO
CaO
SrO
B2O3
SiO2
ZnO
Al2O3,


 
(  %)
(  %)
(  %)
(  %)
(  %)
(  %)
(  %)
(  %)
(  %)







G61
6
20
2
2
 3
26
29
8
4


G62
5
50
4
—
—
19
16
6
—


G63
5
20
—
—
 6
18
45
6
—


G64*
6
20
—
—
26
16
26
6
—


G65
6
30
1
—
12
19
25
7
—









In Table 7, a “type of glass” marked with an asterisk “*” represents a glass powder having a composition outside the range of the present invention.
As a first ceramic powder contained in the glass ceramic compositions, the same Mg2SiO4 powder as in Experimental Example 1 was prepared. As second ceramic powders, a SrTiO3 powder having an average particle size (median particle size, D50) of about 1.5 μm and a TiO2 powder having an average particle size of about 1.0 μm were prepared.
Furthermore, a barium zirconate (BaZrO3) powder having an average particle size of about 1.0 μm was prepared for addition to the glass ceramic compositions in specific samples.
To obtain glass ceramic compositions for samples shown in Table 8, the first ceramic powder, the borosilicate glass powder and the second ceramic powder were mixed. The BaZrO3 (indicated by “BZ” in Table 8) powder was further added to the specific samples.












TABLE 8











Second





Borosilicate
ceramic



Amount of first
glass
powder














ceramic powder

Amount

Amount
Amount of


Sample
(wt %)
Type
(wt %)
Type
(wt %)
BZ (wt %)
















 201*
63.0
G1
20.0
ST
7.0
10.0


202
63.0
G2
20.0
ST
7.0
10.0


203
81.0
G3
3.0
ST
6.0
10.0


 204*
81.0
G4
3.0
ST
6.0
10.0


 205*
67.0
G5
15.0
ST
8.0
10.0


206
67.0
G61
15.0
ST
8.0
10.0


207
63.0
G62
18.0
ST
9.0
10.0


208
65.0
G10
15.0
ST
10.0
10.0


209
69.0
G11
15.0
ST
6.0
10.0


 210*
69.0
G12
15.0
ST
6.0
10.0


211
76.0
G14
8.0
ST
6.0
10.0


212
67.0
G63
18.0
ST
5.0
10.0


 213*
67.0
G16
18.0
ST
5.0
10.0


 214*
65.0
G17
15.0
ST
10.0
10.0


215
65.0
G18
15.0
ST
10.0
10.0


216
74.0
G19
10.0
ST
6.0
10.0


 217*
74.0
G20
10.0
ST
6.0
10.0


 218*
63.0
G21
19.0
ST
8.0
10.0


219
63.0
G22
19.0
ST
8.0
10.0


 220*
75.0
G23
10.0
ST
5.0
10.0


221
75.0
G24
10.0
ST
5.0
10.0


 222*
73.0
G26
10.0
ST
7.0
10.0


223
73.0
G27
10.0
ST
7.0
10.0


 224*
74.0
G64
10.0
ST
6.0
10.0


225
74.0
G29
10.0
ST
6.0
10.0


226
79.7
G65
10.0
T
0.3
10.0


227
60.0
G65
10.0
T
20.0
10.0


228
84.0
G65
10.0
ST
6.0
0


229
82.0
G65
10.0
ST
6.0
2.0


230
81.0
G65
10.0
ST
6.0
3.0


231
74.0
G65
10.0
ST
6.0
10.0


232
66.0
G65
10.0
ST
4.0
20.0


233
73.0
G65
10.0
ST/T
6.0/1.0
10.0









In Table 8, a glass ceramic composition marked with an asterisk “*” is outside the range of the present invention.
In Table 8, the “amount of first ceramic powder”, “borosilicate glass”, and “second ceramic powder” columns each represent the same content as in Table 2.
Columnar preforms of the glass ceramic compositions corresponding to the samples shown in Table 8 were formed as in Experimental Example 1 and fired to produce sintered glass ceramic material samples.
In each glass ceramic composition for a corresponding one of the samples, as shown in Table 9, the dielectric constant (εr), Qf value, temperature coefficient (τf) of resonant frequency, chemical stability and insulation reliability were evaluated by the same method as in Experimental Example 1.













TABLE 9











Rate of





τf


change of




Qf
(ppm ·
Chemical
Insulation
capacitance


Sample
εr
(GHz)
° C.−1)
stability
reliability
(%)
















 201*
Not sintered













202
10.5
25000
5
Good
Good
0.2


203
11.7
10500
−10
Good
Good
0.25


 204*
11
8500
−15
Poor
Poor
—


 205*
8.9
4800
−10
Good
Good
0.2


206
9.1
12000
−5
Good
Good
0.25


207
10.5
32000
−10
Good
Good
0.2


208
9.2
30000
30
Good
Good
0.3


209
9.2
12000
−9
Good
Good
0.25


 210*
9.0
9000
−15
Poor
Poor
—


211
8.5
18000
−10
Good
Good
0.15


212
8.8
28000
5
Good
Good
0.1








 213*
Not sintered













 214*
10.5
9000
−5
Good
Good
0.25


215
10.5
15000
−5
Good
Good
0.2


216
8.9
39000
−20
Good
Good
0.25


 217*
9.0
39500
−22
Poor
Poor
—








 218*
Not sintered













219
9.5
11000
18
Good
Good
0.15


 220*
9.0
2000
20
Good
Good
−0.2


221
10.5
10500
25
Good
Good
−0.25


 222*
9.5
11000
30
Poor
Poor
—


223
8.8
18000
25
Good
Good
0.2


 224*
9.0
9500
9
Good
Good
0.25


225
9.8
4400
6
Good
Good
<0.1


226
9.7
65000
−50
Good
Good
<0.1


227
9.5
38000
6
Good
Good
0.3


228
8.6
49000
−10
Good
Good
0.8


229
8.2
48000
−13
Good
Good
0.4


230
8.5
41000
−11
Good
Good
0.25


231
8.9
38000
−5
Good
Good
<0.1


232
9.7
10000
45
Good
Good
−0.3


233
8.5
36000
5
Good
Good
<0.1









Also in Table 9, a sample marked with an asterisk “*” is outside the preferred range of the present invention.
The samples within the range of the present invention shown in Tables 8 and 9 each contain the borosilicate glass within the range of the present invention shown in Table 1 or 7, which is referred to the “type” column in the “borosilicate glass” section in Table 8; the Mg2SiO4 powder as the first ceramic powder; and the second ceramic powder containing at least one ceramic powder selected from the SrTiO3 powder and the TiO2 powder. Thereby, the samples can be fired at a temperature of about 1,000° C. or lower. Furthermore, the samples each have satisfactory chemical stability, insulation reliability, a high Qf value and a stable temperature coefficient τf.
Sample 201 contains glass G1 that contains less than about 3 percent by weight of Li2O shown in Table 1. Thus, as shown in Table 9, sample 201 was not sintered at a temperature of about 1,000° C. or lower. Sample 204 contains glass G4 that contains more than about 15 percent by weight of Li2O shown in Table 1. Thus, sample 204 had a low Qf value and degraded chemical stability and insulation reliability.
Sample 205 contains glass G5 that contains less than about 20 percent by weight of MgO shown in Table 1. Thus, sample 205 had a low Qf value as shown in Table 9.
Sample 210 contains glass G12 that contains more than about 30 percent by weight of B2O3 shown in Table 1. Thus, sample 210 had a low Qf value and degraded chemical stability and insulation reliability, as shown in Table 9.
Sample 213 contains glass G16 that contains more than about 45 percent by weight of SiO2 shown in Table 1. Thus, sample 213 was not sintered at about 1,000° C. or lower, as shown in Table 9.
Sample 214 contains glass G17 that contains less than about 6 percent by weight of ZnO shown in Table 1. Thus, sample 214 had a low Qf value, as shown in Table 9. Sample 217 contains glass G20 that contains more than about 20 percent by weight of ZnO shown in Table 1. Thus, the Sample 217 had degraded chemical stability and insulation reliability.
Sample 218 contains glass G21 that contains more than about 15 percent by weight of Al2O3 shown in Table 1. Thus, the Sample 218 was not sintered at about 1,000° C. or lower, as shown in Table 9.
Sample 220 contains glass G23 that contains more than about 25 percent by weight of BaO shown in Table 1. Thus, the Sample 220 had a low Qf value, as shown in Table 9.
Sample 222 contains glass G26 that contains more than about 15 percent by weight of CaO shown in Table 1. Thus, the Sample 222 had degraded chemical stability and insulation reliability, as shown in Table 9.
Sample 224 contains glass G64 that contains more than about 25 percent by weight of SrO shown in Table 7. Thus, the Sample 224 had a low Qf value, as shown in Table 9.
Effects of the presence or absence of and the content of BaZrO3 (BZ) in the glass ceramic composition of each sample on properties of the sintered glass ceramic materials will be discussed below.
Also in Experimental Example 3, as shown in Table 9, rates of change of capacitance of multilayer capacitors for evaluating insulation reliability were evaluated. However, in Experimental Example 3, only samples having good insulation reliability were evaluated for the rate of change of capacitance. In this case, capacitors were subjected to a severe accelerated test compared with the case of the evaluation of the rate of change of capacitance in Experimental Example 2. In other words, the capacitors were subjected to an accelerated test at about 150° C. and about 200 V DC for about 100 hours. The rate of change of capacitance was determined using the following equation:

Rate of change of capacitance (%)={(C1−C0)/C0}×100

where C0 represents capacitance before the test; and C1 represents capacitance after the test.

As shown in Table 9, each of BaZrO3-containing samples 202, 203, 205 to 209, 211, 212, 214 to 216, 219 to 221, and 223 to 233 advantageously had a small absolute value of the rate of change of capacitance compared with that of sample 228 not containing BaZrO3.
In particular, comparisons among samples 228 to 232 in which each of the first ceramic powders is partially replaced with BZ were made. Samples 230 to 232 each containing about 3 to 20 percent by weight of BZ each had a small absolute value of the rate of change of capacitance of about 0.3% or less, as compared with those of samples 228 and 229 containing less than about 3 percent by weight of BZ. Furthermore, samples 202, 203, 205 to 209, 211, 212, 214 to 216, 219 to 221, and 223 to 227 that contain about 3 to 20 percent by weight of BZ also had an absolute value of the rate of change of capacitance of about 0.3% or less.
EXPERIMENTAL EXAMPLE 4
In Experimental Example 4, the first ceramic powder of each of samples 118, 125 and 108 was partially replaced with about 10.0 percent by weight of BaZrO3 (indicated by “BZ” in Table 10), and used to make glass ceramic compositions of samples 251, 252, and 253, as shown in Table 10.













TABLE 10











Second






Borosilicate
ceramic
Amount



Amount of first
glass
powder
of SiO2















ceramic powder

Amount

Amount
(part by
Amount of BZ


Sample
(wt %)
Type
(wt %)
Type
(wt %)
weight)
(wt %)

















118
83.0
G55
10.0
ST/T
6.0/1.0
0
0


251
73.0
G55
10.0
ST/T
6.0/1.0
0
10.0


125
83.0
G57
10.0
ST/T
6.0/1.0
0
0


252
73.0
G57
10.0
ST/T
6.0/1.0
0
10.0


108
83.0
G53
10.0
ST/T
6.0/1.0
0.2
0


253
73.0
G53
10.0
ST/T
6.0/1.0
0.2
10.0









Table 10 also shows these compositions and those of the glass ceramic compositions of samples 118, 125 and 108 evaluated in Experimental Example 2. In Table 10, the “amount of first ceramic powder”, “borosilicate glass”, “second ceramic powder”, and “amount of BZ” columns each represent the same content as in Table 8. The “amount of SiO2” column represents the same content as in Table 5.
Columnar preforms of the glass ceramic compositions corresponding to the samples shown in Table 10 were formed as in Experimental Example 1 and fired to produce sintered glass ceramic material samples.
In each glass ceramic composition for a corresponding one of the samples, as shown in Table 11, the dielectric constant (εr), Qf value, temperature coefficient (τf) of resonant frequency, chemical stability and insulation reliability were evaluated by the same method as in Experimental Example 1.














TABLE 11











Rate of change of
Rate of change of




Qf
τf

Insulation
capacitance (1)
capacitance (2)


Sample
εr
(GHz)
(ppm · ° C.−1)
Chemical stability
reliability
(%)
(%)






















118
8.8
54000
6
Good
Good
1.8
3.2


251
8.9
41000
−5
Good
Good
<0.1
<0.1


125
8.6
42000
5
Good
Good
<0.1
0.8


252
8.8
36000
−6
Good
Good
<0.1
<0.1


108
8.8
52000
5
Good
Good
0.4
1.1


253
9.1
31000
−9
Good
Good
<0.1
<0.1









As shown in Table 11, samples 251, 252 and 253 were sintered at about 1,000° C. or lower, as in samples 118, 125 and 108, and each had satisfactory chemical stability and satisfactory insulation reliability, a high Qf value, and stable τf.
As shown in Table 11, rates of change of capacitance of multilayer capacitors for evaluating insulation reliability were also evaluated in Experimental Example 4. However, in Experimental Example 4, the rates of change of capacitance under the conditions used in Experimental Example 2 (indicated by “rate of change of capacitance (1)” in Table 11) and the rates of change of capacitance under the conditions used in Experimental Example 3 (indicated by “rate of change of capacitance (2)” in Table 11) were evaluated.
Samples 118, 125 and 108 not containing BaZrO3 each had a relatively low rate of change of capacitance (1). However, the rate of change of capacitance (2) under the more severe conditions for each of samples 118, 125 and 108 was higher than the rate of change of capacitance (1) thereof In contrast, samples 251, 252 and 253 containing BaZrO3 each had a low rate of change of capacitance (1) and a low rate of change of capacitance (2). The results demonstrate that the presence of BaZrO3 is markedly effective in suppressing a change in capacitance before and after the load test.
While preferred embodiments of the invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing the scope and spirit of the invention. The scope of the invention, therefore, is to be determined solely by the following claims.

## Claims

1. A glass ceramic composition comprising:
a first ceramic powder mainly composed of forsterite;
a second ceramic powder containing at least one ceramic powder selected from the group consisting of a ceramic powder mainly composed of calcium titanate, a ceramic powder mainly composed of strontium titanate, and a ceramic powder mainly composed of titanium oxide;
a third ceramic powder mainly composed of barium zirconate; and
about 3 percent by weight or more of a borosilicate glass powder containing about 3 to 15 percent by weight of lithium calculated as Li2O, about 20 to 50 percent by weight of magnesium calculated as MgO, about 15 to 30 percent by weight of boron calculated as B2O3, about 10 to 45 percent by weight of silicon calculated as SiO2, about 6 to 20 percent by weight of zinc calculated as ZnO, and 0 to about 15 percent by weight of aluminum calculated as Al2O3,
wherein the borosilicate glass powder contains at least about 2 percent by weight of an additive selected from the group consisting of calcium oxide, barium oxide, strontium oxide and mixtures thereof, calculated as CaO, BaO and SrO, respectively, and
wherein the upper limit of the calcium oxide content of the borosilicate glass powder is about 15 percent by weight, the upper limit of the barium oxide content of the borosilicate glass powder is about 25 percent by weight, and the upper limit of the strontium oxide content of the borosilicate glass powder is about 25 percent by weight.

2. The glass ceramic composition according to claim 1, in which the glass ceramic composition contains about 55 percent by weight or more of the first ceramic powder, about 6 to 30 percent by weight of the second ceramic powder of, about 3 to 20 percent by weight of the third ceramic powder, and about 3 to 20 percent by weight of the borosilicate glass powder.

3. The glass ceramic composition according to claim 2, wherein when the second ceramic powder contains a ceramic powder mainly composed of calcium titanate, the calcium titanate content of the glass ceramic composition calculated as CaTiO3 is about 18 percent by weight or less; when the second ceramic powder contains a ceramic powder mainly composed of strontium titanate, the strontium titanate content of the glass ceramic composition calculated as SrTiO3 is about 13 percent by weight or less; and when the second ceramic powder contains a ceramic powder mainly composed of titanium oxide, the titanium oxide content of the glass ceramic composition calculated as TiO2 is about 0.3 to 30 percent by weight.

4. The glass ceramic composition according to claim 3, wherein the second ceramic powder contains (a) a ceramic powder mainly composed of calcium titanate or a ceramic powder mainly composed of strontium titanate, and (b) a ceramic powder mainly composed of titanium oxide, wherein the calcium titanate content of the glass ceramic composition, when present, is about 8 to 12 percent by weight, the strontium titanate content of the glass ceramic composition, when present, is about 6 to 10 percent by weight, and the titanium oxide content of the glass ceramic composition is about 0.3 to 3 percent by weight.

5. The glass ceramic composition according to claim 2, wherein the borosilicate glass powder has a silicon content of about 23.5 to 26.5 percent by weight calculated as SiO2.

6. The glass ceramic composition according to claim 2, wherein the borosilicate glass powder has a silicon content of about 20 to 26.5 percent by weight calculated as SiO2, and the glass ceramic composition further comprises a positive amount up to about 1 part by weight of silicon calculated as SiO2 relative to 100 parts by weight of the total amount of the first ceramic powder, the second ceramic powder and the borosilicate glass powder.

7. The glass ceramic composition according to claim 2, wherein the borosilicate glass powder has about 30 to 45 percent by weight of magnesium content, about 15 to 25 percent by weight of boron content, about 10 to 30 percent by weight of silicon content, about 6 to 20 percent by weight of zinc content, and 0 to about 10 percent by weight of aluminum content, and wherein the borosilicate glass powder is present in an amount of up to about 20%.

8. The glass ceramic composition according to claim 2, further comprising up to 2.5 percent by weight of at least one fourth ceramic powder selected from the group consisting of up to 0.5 percent by weight of a copper oxide-based ceramic powder mainly composed of copper oxide, up to 1 percent by weight of a iron oxide-based ceramic powder mainly composed of iron oxide, and up to 2 percent by weight of a manganese oxide-based ceramic powder mainly composed of manganese oxide.

9. The glass ceramic composition according to claim 1, wherein when the second ceramic powder contains a ceramic powder mainly composed of calcium titanate, the calcium titanate content of the glass ceramic composition calculated as CaTiO3 is about 18 percent by weight or less; when the second ceramic powder contains a ceramic powder mainly composed of strontium titanate, the strontium titanate content of the glass ceramic composition calculated as SrTiO3 is about 13 percent by weight or less; and when the second ceramic powder contains a ceramic powder mainly composed of titanium oxide, the titanium oxide content of the glass ceramic composition calculated as TiO2 is about 0.3 to 30 percent by weight.

10. The glass ceramic composition according to claim 3, wherein the second ceramic powder contains (a) a ceramic powder mainly composed of calcium titanate or a ceramic powder mainly composed of strontium titanate, and (b) a ceramic powder mainly composed of titanium oxide, wherein the calcium titanate content of the glass ceramic composition, when present, is about 8 to 12 percent by weight, the strontium titanate content of the glass ceramic composition, when present, is about 6 to 10 percent by weight, and the titanium oxide content of the glass ceramic composition is about 0.3 to 3 percent by weight.

11. The glass ceramic composition according to claim 1, wherein the borosilicate glass powder has a silicon content of about 23.5 to 26.5 percent by weight calculated as SiO2.

12. The glass ceramic composition according to claim 1, wherein the borosilicate glass powder has a silicon content of about 20 to 26.5 percent by weight calculated as SiO, and the glass ceramic composition further comprises a positive amount up to about 1 part by weight of silicon calculated as SiO2 relative to 100 parts by weight of the total amount of the first ceramic powder, the second ceramic powder, the third ceramic powder and the borosilicate glass powder.

13. The glass ceramic composition according to claim 1, wherein the borosilicate glass powder has about 30 to 45 percent by weight of magnesium content, about 15 to 25 percent by weight of boron content, about 10 to 30 percent by weight of silicon content, about 6 to 20 percent by weight of zinc content, and 0 to about 10 percent by weight of aluminum content, and wherein the borosilicate glass powder is present in an amount of up to about 20%.

14. The glass ceramic composition according to claim 1, wherein the borosilicate glass powder is present in an amount of up to about 15%; the first ceramic powder has a mean particle size of about 1 μm or less; and when present, the strontium titanate has a specific surface area of about 1.5-7.5 m2/g.

15. The glass ceramic composition according to claim 1, further comprising up to 2.5 percent by weight of at least one fourth ceramic powder selected from the group consisting of up to 0.5 percent by weight of a copper oxide-based ceramic powder mainly composed of copper oxide, up to 1 percent by weight of a iron oxide-based ceramic powder mainly composed of iron oxide, and up to 2 percent by weight of a manganese oxide-based ceramic powder mainly composed of manganese oxide.

16. The glass ceramic composition according to claim 1, in which the glass ceramic composition contains about 3 to 20 percent by weight of the third ceramic powder.

17. A sintered glass ceramic material comprising a fired glass ceramic composition according to claim 1 in a predetermined shape, the sintered glass ceramic material having a Mg2SiO4 crystal phase as a main phase and a Li2(Mg,Zn)SiO4 crystal phase as a subphase.

18. The sintered glass ceramic material according to claim 17 formed by providing a glass ceramic composition according to claim 1 in a predetermined shape, and firing the formed composition at a temperature of about 1,000° C. or less.

19. A multilayer ceramic electronic component comprising the combination of
a plurality of laminated glass ceramic layers comprising the sintered glass ceramic material of claim 18; and
a plurality of conductive leads comprising copper or silver.