KR100632393B1 - High-permittivity dielectric ceramic compositions for low-fire ceramic multilayer packages - Google Patents

Abstract

The present invention relates to a dielectric ceramic composition capable of firing at a temperature of 875 ^° C or less, in particular, the dielectric constant is in the range of 200 ~ 1000, characterized in that the dielectric loss value is less than 3%. The composition consists of a combination of 5-20 wt% Li ₂ OB ₂ O ₃ -SiO ₂ based glass frit and 80-95 wt% BaO-TiO ₂ based dielectric ceramics. The compositions developed through the present invention can be effectively applied to form part of ceramic multilayer packaging in the form of embedded capacitors.

High dielectric constant, low temperature baking, dielectric, glass frit, LTCC

Description

HIGH-PERMITTIVITY DIELECTRIC CERAMIC COMPOSITIONS FOR LOW-FIRE CERAMIC MULTILAYER PACKAGES

The present invention relates to a high-k dielectric ceramic composition, and more particularly, to a dielectric ceramic composition that can be baked at a low temperature and can be utilized as a passive component in a ceramic multilayer package.

Today, the information and telecommunications industry centering on mobile phones and PCs is showing rapid growth, and the development direction is focused on high speed, multifunction, and wireless (mobile). In order to cope with this trend, the necessity of high functionalization and integration of information and communication components is also increasing. By improving the density and complexity of thick film laminated parts, not only the size of the final product can be basically reduced, but also the price is lowered, and reliability can be improved by reducing the number of parts and solder joints. Due to the reduction in the number of mounting, there are various advantages such as the improvement of electrical characteristics through the reduction of parasitic components generated on the connection circuit.

Until now, as a method of implementing a multifunctional composite module, many techniques for implementing multilayer packaging using a ceramic material having a low dielectric loss value have been invented. However, the firing process at a high temperature of 1300 ^o C or more was required to fire most ceramic materials. Therefore, noble metals such as Pt and W have been used to form conductor lines in the ceramic packaging having a multilayered structure. These precious metals were not only high in price but also low in electrical conductivity, and thus had poor electrical characteristics.

On the other hand, Low-Temperature C-fired Ceramic (LTCC) technology implements internal electrodes such as Ag and Cu, which have excellent electrical conductivity, and passive devices such as dielectrics, magnetic materials, and resistors in a three-dimensional multilayer structure. ^It is a technology that realizes an electromagnetic functional multilayer composite module by firing simultaneously at a temperature below C. This technology can realize the integration of the board and the modularization of passive components at the same time, and is capable of coping with ultra-high frequency, which is attracting much attention and related module products are being developed.

LTCC technology has been used mainly as a three-dimensional wiring board concept using a dielectric material having a low dielectric loss value. In this case, the dielectric constant of the ceramic substrate is preferably low to minimize signal delay, and the dielectric loss value is preferably small to minimize electrical loss. (Typically, the dielectric constant is in the range of 4 to 10, and the dielectric loss value is less than 0.2%.) In addition, the firing temperature of the ceramic composition is preferably less than 900 ^o C so that the firing can be performed simultaneously with the Ag electrode. Do.

However, until recently, the necessity of adding various functions to the packaging has been raised by implementing various types of passive components inside the packaging rather than a simple wiring board in the multilayer ceramic packaging. In particular, in order to be able to implement a resonator-type filter or antenna in a multilayer ceramic packaging, a composition having a relatively high dielectric constant is required. In order to control a distributed circuit element such as a resonator type filter or an antenna to an appropriate size, the effective wavelength must be reduced. Currently, the microwave band ranges from 1 to 300 GHz, and the permittivity range is about 20 to 100 to obtain the most effective wavelength for the device in this frequency range. In addition, the value of the quality factor (Q × f) is preferably a high value of 1000 or more, and the temperature coefficient of resonant frequency is preferably ± 20 ppm / ^o C or less.

Another type of passive component that can be implemented inside the packaging is a high-capacity capacitor. In the future, it is expected that the need to further increase the directness by implementing a high-capacitance capacitor in the ceramic multilayer packaging is expected. For this purpose, a composition having a higher dielectric constant of 20 to 100 or more, which is a dielectric constant range that has been conventionally used for resonator applications, is preferable. In general, capacitors are passive components that are essential in the construction of electronic circuits in order to suppress ripple of a power supply or to couple signals. In the conventional LTCC multilayer composite module technology, it was difficult to implement a composition of dielectric constant of 100 or more, a high capacity capacitor of more than several hundred pF could not be implemented in the LTCC multilayer module, and components such as MLCC had to be added to the outside as a surface mount type.

If a dielectric composition having a dielectric constant of 100 or more can be implemented inside the LTCC, it is possible to implement a high capacity capacitor in a multilayer structure, and to realize a more integrated and highly functional module. In addition, when the firing temperature exceeds 1000 ^° C. Ag, Cu electrodes are difficult to use, so it is difficult to apply to the LTCC package, so the capacitor implemented inside the LTCC package requires a low firing temperature.

Accordingly, the present invention is to provide a high dielectric constant dielectric ceramic composition for LTCC having a dielectric constant in the range of 200 ~ 1000, while firing at less than 900 ^° C so that the Ag electrode can be used.

In order to achieve the above object, the present invention provides a high-k dielectric ceramic composition comprising 80 ~ 95wt% BaO-TiO _2- based dielectric, 5 ~ 20wt% Li ₂ OB ₂ O ₃ -SiO ₂ -based glass frit do.

The dielectric composition is (1-x) BaO- (x) CaO- (1-y) TiO _2- (y) ZrO ₂ , where x = 0.0 to 0.06 and y = 0.0 to 0.12.

The glass frit has a molar ratio of Li ₂ O in the range of 33 to 62%, B ₂ O _{3 in} the range 23 to 43%, and SiO _{2 in} the range 5 to 35%, and further 2 to 6% of CaO. And Al ₂ O ₃ in the range of 2.5-7.5%.

According to the present invention, it is possible to manufacture a dielectric material having a high dielectric constant of 200 or more and a low dielectric loss of less than 3%, which can be baked at a temperature of less than 900 ^° C., in particular 875 ^° C. or less, and the dielectric ceramic composition is It can be effectively applied to form part of low-temperature fired ceramic multilayer packaging in the form of embedded capacitors. Therefore, the present invention includes a low-temperature fired ceramic multilayer package using the high dielectric constant ceramic composition.

Hereinafter, the features of the present invention will be described in more detail with reference to specific examples.

The dielectric ceramic according to the present invention comprises the steps of: synthesizing a high dielectric constant dielectric composition, synthesizing a glass frit composition for low temperature sintering thereof, mixing two or more compositions, and low temperature sintering the mixed composition It is manufactured by.

First, the high dielectric constant dielectric composition was selected as (1-x) BaO- (x) CaO- (1-y) TiO _2- (y) ZrO ₂ based composition (x = 0.0 ~ 0.06, y = 0.0 ~ 0.12). The composition was densified only when fired at a temperature of 1350 ^o C or higher. At this time, the dielectric constant was about 1200 and the dielectric loss value was measured to be 1% or more.

The production of the dielectric, the parent material, is carried out by the following procedure. Powders were prepared using a mixed oxide method, which is a common solid state reaction. The composition of (1-x) BaO- (x) CaO- (1-y) TiO _2- (y) ZrO ₂ based composition of BaCO ₃ , TiO ₂ , CaO, ZrO ₂ commercial ceramic powder as the starting material (x = 0.0 ~ 0.06, y = 0.0 ~ 0.12), and then measure and ball mill. Ball milled mixed powder was calcined (calcining) in air for 2-3 hours in the range of 1,000 ~ 1,200 ^o C synthesized BaTiO ₃ or BaO-TiO ₂ -CaO-ZrO ₂ system.

Next, glass frit, as shown in Table 1, was synthesized for low temperature firing of the BaO-TiO ₂ based dielectric.

Table 1 Glass frit composition and characteristics

The glass frit composition was prepared through repeated preliminary experiments to prepare compositions having low glass transition temperature (T _g ) and low dielectric loss. Each raw material powder was weighed and dry mixed in the molar ratio shown in Table 1, then placed in a platinum crucible and maintained at a temperature of 1,300 ^° C. for 2 hours, and the melt was quenched in a water cooling bath. The glass thus obtained was first coarsely ground in agate oil, ethanol was pulverized secondly in a polyethylene bottle with zirconia ball as a solvent for 24 hours and then subjected to attrition milling for 5 hours. Table 1 shows the electrical properties of the glass thus prepared.

Glass frits having various types of compositional formulations prepared by the above method were mixed with BaO-TiO ₂ -based compositions and the addition range was 5-20 wt%. The prepared dielectric and glass frits were wet mixed for 24 hours in polyethylene bottles with zirconia ball as ethanol as a solvent. In order to impart moldability to the mixed powder, 2 wt% of a polyvinyl alcohol (PVA) aqueous solution was added as a binder and granulated through sieving (100 mesh), and the final composite obtained was 1,000 kg / cm 3 pressure. It was uniaxially pressed in a mold having a diameter of 10 mm to form a cylindrical shape. The specimen thus formed was heated at a heating rate of 5 ^o C / min in an electric furnace, and then sintered for 2 hours in the range of 800 to 950 ^o C, followed by furnace-cooling. The sintering characteristics and electrical characteristics of the specimens thus obtained are shown in Table 2.

[Table 2] Sintering and Electrical Properties of BaO-TiO ₂ and Glass Frit Mixing Compositions

Characteristics of Glass Frit

As shown in Table 1 above, physical and electrical characteristics of Li ₂ OB ₂ O ₃ -SiO ₂ glass were extensively investigated. As a result, Li ₂ OB ₂ O ₃ -SiO ₂ glass composition was found in G01 to G12. The dielectric loss value of less than 0.8% in the indicated composition range was found to be good electrical properties. Meanwhile, in the case of H01 to H05 having CaO and Al ₂ O ₃ added to Li ₂ OB ₂ O ₃ -SiO ₂ , the dielectric loss value was less than 0.2%, which was very low. Overall, density ranged from 2.2 to 2.5, and dielectric constants ranged from 6.3 to 8.5. The glass transition temperature (T _g ) ranged from 350 to 510 ^o C. Dielectric loss values range from 0.1 to 0.8%. In addition, the coefficient of thermal expansion (TEC) was generally measured in the range of about 100 to 170 × 10 ⁻⁷ .

Characteristics of Dielectric / Glass Frit Mixtures

Table 2 shows BaO-TiO ₂ (BaTiO ₃ ) For the composition, various kinds of glass frit were added in the range of 5 to 20 wt%, and the density and electrical characteristics of the specimens sintered at a temperature range of 850 to 950 ^° C. were shown. Overall, it exhibits excellent low temperature sintering characteristics of more than 95% relative density below 900 ^o C. Particularly in the case of S18, S19, and S36 mixture, 10 ~ 15% frit was added and the sintered density was 99% at 875 ^° C sintering temperature, indicating good densification. These compositions were examined through a scanning electron microscope (Scanning Electron Microscope) observation, it was confirmed that a compact structure without pores was obtained. Overall, the dielectric constant is shown in the range of 200 ~ 1000, and the dielectric loss value is about 1.3 ~ 3.0%.

In view of the density of 99% or more at the firing temperature of 875 ^o C or less, which is most suitable for co-firing with Ag electrodes, the dielectric constant is higher than 270 and the dielectric loss value is about 15 wt% of G11 glass frit. It shows less than 3.0%. Such compositions can be utilized as high capacity internal capacitors in LTCC thick film multilayer packages. Compared with the G series frit, the use of the H series frit exhibits a low dielectric loss value overall.

Results for Different Forms of Dielectric Compositions

In the BaO-TiO ₂ composition mainly examined in the present invention, low-temperature sintering and dielectric loss values were sufficiently low, but it was determined that the dielectric constant was 300 or less, which was rather low. Therefore, CaO and ZrO ₂ were added to improve the overall dielectric constant. That is, (1-x) BaO- (x) CaO- (1-y) TiO _2- (y) ZrO ₂ -based composition was implemented, and the composition was changed in the range of x = 0.0 ~ 0.06 and y = 0.0 ~ 0.12. . At this time, as the values of x and y increase, the overall dielectric constant is greatly improved.

As a result of changing the composition, as shown in Table 3, the low temperature sintering characteristics and the dielectric loss value were good at the composition of x = 0.04 and y = 0.08, and the dielectric constant showed very high value over 500. . Increasing the x and y values in the range further increased the dielectric constant value but increased the low temperature sintering characteristics and the dielectric loss value.

[Table 3] Sintering and Electrical Properties of BCTZ Dielectric and Glass Frit Mixing Compositions

As described above, the present invention mixes 5 to 20 wt% of Li ₂ OB ₂ O ₃ -CaO-Al ₂ O ₃ -SiO ₂ based glass frit and 80 to 95 wt% of BaO-TiO ₂ based dielectric ceramics. This provides a dielectric composition capable of firing at a temperature of 875 ^° C. or lower. Dielectric constant of the dielectric by the composition is in the range of 200 ~ 1000 and the dielectric loss value was found to be 3.0% or less. Such compositions developed through the present invention can be effectively applied to construct part of ceramic multilayer packages in the form of embedded capacitors.

Claims (6)

BaO-TiO ₂ -based dielectric 80 ~ 95wt represented by composition formula (1-x) BaO- (x) CaO- (1-y) TiO _2- (y) ZrO ₂ , x = 0.0 ~ 0.06, y = 0.0 ~ 0.12 %Wow, Consists of Li ₂ OB ₂ O ₃ -SiO ₂ -based glass frit 5 ~ 20wt% High dielectric constant dielectric ceramic composition. delete According to claim 1, wherein the glass frit has a specific ratio of Li ₂ O in the range of 33 to 62%, B ₂ O _{3 in} the range 23 to 43%, and SiO _{2 in} the range 5 to 35%. Tremor dielectric ceramic composition. 4. The high dielectric constant ceramic composition of claim 3, wherein the glass frit further comprises CaO in the range of 2-6% and Al ₂ O ₃ in the range of 2.5-7.5%. According to claim 1, wherein the glass frit is mixed with the dielectric at 10 to 20wt%, the sintering temperature of the mixed composition is 875 ^° C or less, dielectric constant is 200 ~ 750, dielectric loss is characterized in that 1 to 3% A high dielectric constant dielectric ceramic composition. A ceramic dielectric using the composition of claim 1, 3, 4, or 5.