KR20060108283A - Low-temperature firing low dielectric constant dielectric composition - Google Patents

Abstract

The present invention relates to a low-temperature fired low loss ceramic dielectric composition, and more particularly, by mixing glass frit and a specific complex oxide filler in a certain component ratio, firing is possible at a low temperature range of 950 ° C. or lower, and a dielectric constant is low, and a dielectric loss. This very low electrical loss can be minimized, so it can be effectively applied to high efficiency filter and antenna resonator. Especially, low temperature can minimize reactivity with the electrode by suppressing diffusion of silver electrode. A fired low loss ceramic dielectric composition.

Glass frit, composite oxide filler, dielectric composition

Description

Low-temperature firing low dielectric constant dielectric composition

1 is a scanning electron micrograph of a dielectric prepared by sintering at 875 ° C. using a composite oxide of ZnAl ₂ O ₄ , MgAl ₂ O ₄ , ZrSiO _4, and Mg ₂ SiO ₄ as a filler in a glass frit powder according to the present invention. It is shown.

(a) Glass frit (1): ZnAl ₂ O ₄ = 60: 40 (b) Glass frit (1): MgAl ₂ O ₄ = 60: 40

(c) Glass frit (1): ZrSiO ₄ = 60: 40 (d) Glass frit (1): Mg ₂ SiO ₄ = 85: 15

The present invention relates to a low-temperature fired low loss ceramic dielectric composition, and more particularly, by mixing glass frit and a specific complex oxide filler in a certain component ratio, firing is possible at a low temperature range of 950 ° C. or lower, and a dielectric constant is low, and a dielectric loss. This very low electric loss can be minimized, so it can be effectively applied to high efficiency filter and antenna resonator, and especially low temperature which can minimize the reactivity with the electrode by suppressing diffusion of silver (Ag) electrode. A fired low loss ceramic dielectric composition.

With the development of mobile communication and information communication systems, high frequency, small size, light weight, and high performance of electronic parts have emerged as important technology elements. For this reason, it is necessary to increase the wiring density of the board and to reduce the size and weight of individual components or modules.

Recently, by utilizing the Low Temperature Co-fired Ceramic (LTCC) technology, high-density wiring boards and various types of passive components can be integrated to produce compact, lightweight composite parts. have.

LTCC technology is a material and process for stacking ceramic thick film tapes printed with devices and circuits, connecting electrodes in three dimensions, and simultaneously firing them at a low temperature of 950 ° C or lower to obtain an integrated ceramic multilayer circuit structure. Refers to technology.

Typically, the wiring LTCC substrate is fired at a temperature of 950 ° C. or lower, and thus silver (Ag) can be used as an internal electrode, and thus, the price is lower than that of a noble metal internal electrode such as palladium (Pt) used in a conventional ceramic multilayer substrate. It has the advantage of better conductivity. In addition, by stacking various passive components such as L, C, and R in the form of a thick film tape, and connecting them through internal electrodes and via holes, ceramic thick film components, which are conventionally individualized as surface mount components (SMD), are integrated into one module. Can be implemented.

The most basic composition constituting the LTCC substrate is a wiring board having characteristics of low dielectric constant and low dielectric loss, which have different characteristics according to differences in glass and filler compositions. Usually, this is the 50 to 90 wt% of borosilicate glass-based composition and, of Al ₂ O ₃ 10 to 50% by weight, consists of a filling material (filler) of SiO ₂ or the like.

At this time, the role of glass is to soften below 700 ℃ and to form a liquid at around 850 ℃ to achieve a densification (densification) in the temperature range of 850 ~ 950 ℃, an appropriate firing temperature of LTCC, The role plays a role of increasing the mechanical strength of the fired body while maintaining the shape of the substrate in the firing process.

In more detail, the composition of the glass is mainly used borosilicate-based glass containing a small alkali oxide (alkali oxide), and has a low dielectric loss value.

For example, US Pat. No. 5,242,867 discloses a literature on compositions for LTCC wiring boards. As the glass composition, 60 to 80% of SiO ₂ and 15 to 30% of B ₂ O ₃ constitute the main composition, and 5% or less of Al ₂ O ₃ and alkali are added, and alumina or the like is used as a filler. The mixing ratio of the filler to the glass composition was about 20 to 60%. In addition, Na ₂ O, K ₂ O, Li ₂ O and the like were added as alkalis in the glass composition. The substrate produced by such a composition has a dielectric constant of 4.2 to 5.6 and a dielectric loss of about 0.1 to 0.4%.

Meanwhile, in order to realize an ultra high frequency circuit as a high density wiring board, a low dielectric constant is required for shortening a signal transmission delay time, and at the same time, it is essential to develop a composition having low loss characteristics to secure high reliability.

Among them, the dielectric loss characteristic or the signal transmission loss characteristic is very important for the implementation of the high frequency circuit. In general, when the dielectric loss is 0.10% or less, it has excellent low loss characteristics.

Dielectric losses of the LTCC substrate composition for overseas advanced wires already published are 0.15% for Dupont's 951AT, 0.20% for CT 700 from Heraeus, and A6 from Ferro Is 0.20%, and dielectric loss is in the range of 0.10 ~ 0.20%. Similar publications for low dielectric constant wiring boards include, for example, US Pat. No. 4,191,583, US Pat. No. 5,258,335, US Pat. No. 4,323,652, US Pat. No. 4,959,330, US Pat. Etc.

Accordingly, the present inventors have studied to overcome the limitations such as dielectric loss and quality factor of LTCC wiring boards conventionally used for minimizing low dielectric constant and electrical loss in order to minimize signal delay. I tried.

As a result, glass frit containing SiO ₂ , B ₂ O ₃ , Al ₂ O _3, and ZnO, and at least one composite oxide filler selected from ZnAl ₂ O ₄ , MgAl ₂ O ₄ , ZrSiO _4, and Mg ₂ SiO ₄ Firing is performed at a low temperature by using a dielectric composition contained in a certain component ratio, and the present invention has been completed by knowing that the dielectric constant, dielectric loss, and quality factor of the manufactured wiring board are significantly improved compared to the related art.

Accordingly, an object of the present invention is to provide a dielectric composition having a dielectric constant of 4 to 7 (1 MHz), a dielectric loss of 0.02 to 0.2%, and a quality factor of 500 to 5000.

The present invention relates to a dielectric composition comprising glass frit and a filler, comprising 45 to 85% by weight of glass frit containing SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ and ZnO, ZnAl ₂ O ₄ , MgAl ₂ O _The dielectric composition comprises 15 to 55% by weight of at least one composite oxide filler selected from ₄ , ZrSiO ₄ and Mg ₂ SiO ₄ .

Hereinafter, the present invention will be described in detail.

The present invention contains a specific glass frit and a composite oxide filler in a certain component ratio, firing is formed at a low temperature of 950 ° C. or lower, dielectric constant is 4 to 7 (1 MHz), dielectric loss is 0.02 to 0.2%, and quality It relates to a dielectric composition having a coefficient ranging from 500 to 5000.

Conventionally, a single compound such as Al ₂ O ₃ and SiO ₂ was used as a filler, but in the present invention, specific composite oxide fillers, for example, ZnAl ₂ O ₄ , MgAl ₂ O ₄ , ZrSiO ₄ and Mg ₂ SiO _{4 are used.} It is characterized by improving the properties of dielectric constant, dielectric loss and quality factor while being capable of low temperature firing in the range of 950 ° C. or lower, preferably 850 to 900 ° C., lower than the conventional firing temperature of 1200 ° C. or higher. The specific composite oxide filler has a low dielectric constant and a low loss characteristic, as shown in Table 1 below, and is advantageously used to improve the dielectric properties of the glass / ceramic composite due to the above properties. The dielectric constant, dielectric loss, and quality factor of the wiring board are significantly improved by more than the same as before. Looking at Table 1, it can be seen that ZnAl ₂ O ₄ and MgAl ₂ O ₄ have a dielectric loss value of 0.05% and a quality factor of about 2000 at 1 MHz. Therefore, it can be seen that the dielectric loss value of the conventional alumina is 0.30%, and the quality factor is significantly improved compared to that of 330.

Type of filling Firing temperature (℃) Bulk density (g / cm 3) Electrical Characteristics (1MHz) Permittivity (k) Dielectric loss factor (tan δ,%) Quality Factor (Q) ZnAl ₂ O ₄ 1600 4.41 7.96 0.05 2000 MgAl ₂ O ₄ 1500 3.39 7.27 0.072 1400 ZrSiO ₄ 1600 4.16 9.65 0.079 1200 MgSiO ₄ 1400 3.16 6.60 0.051 2000

Looking at the dielectric composition according to the present invention in more detail as follows.

Since the dielectric composition is generally composed of glass frit and a filler, glass frit is generally used in the art and is not particularly limited. In the present invention, SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ and ZnO are mixed and used in an appropriate ratio, and each component SiO ₂ : B ₂ O ₃ : Al ₂ O ₃ : ZnO is 47 to 70 mol%: 20 to 41 Mol%: 2-6 mol%: 1-5 mol% Ratio is formed. When the amount of SiO ₂ is less than 47% by weight, there is a problem in mechanical, chemical and physical stability. When the amount of SiO _{2 is} used in excess of 70% by weight, it is difficult to vitrify even at a high temperature of 1600 ° C or higher, and the amount of B ₂ O ₃ is 20% by weight. If it is less than%, there is a problem in vitrification, and if it exceeds 41% by weight, there is a problem in chemical and physical stability of the glass. In addition, when the amount of Al ₂ O ₃ is less than 2% by weight, it is difficult to expect improvement in chemical durability. When the amount of Al ₂ O ₃ is more than 6% by weight, there is a problem of promoting an increase in the vitrification temperature and crystallization of the glass. If it is less than% by weight, it is difficult to promote vitrification, and when it exceeds 5% by weight, there is a problem that the electrical properties of the glass are lowered. That is, it is important to maintain the relative ratio as described above with the amount of each component used selected from the condition that glass melting is well performed at a temperature of 1600 ° C. while minimizing the dielectric loss value. It measures the glass transition temperature (T _g ) and softening temperature (T _s ) and electrical properties from the inflection point measured by the dilatometer.

In addition to the above components, CaO and MgO, which are alkali rare earths, may be used in the range of 0 to 17 mol% and 0 to 3 mol%, respectively. When the CaO amount is more than 17 mol%, the devitrification phenomenon of the glass occurs, and the problem of promoting the crystallization of the glass and the deterioration of the dielectric properties occurs. When the MgO amount is more than 3 mol%, the viscosity is increased to melt the glass. Since this problem becomes difficult, it is preferable to add and use suitably within the said range.

The glass frit is generally used in the art, but is not particularly limited. In the present invention, the glass frit is manufactured by the following method. First, each raw material SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , CaO, MgO and ZnO raw material powder is weighed in a fixed ratio, ball milled, dried and ground. The pulverized product is put into a platinum crucible and melted at a temperature of 1400 to 1600 ° C. to prepare a molten liquid in a water cold bath to obtain glass. The obtained glass is first roughly ground and secondly unpulverized to prepare a glass frit powder.

Next, as the filler, at least one composite oxide selected from ZnAl ₂ O ₄ , MgAl ₂ O ₄ , ZrSiO _4, and Mg ₂ SiO ₄ having low dielectric constant, low loss, and high quality coefficient characteristics is used. The filler is used 15 to 55% by weight, if less than 15% by weight, the problem of glass is exposed on the surface of the sintered body, and if it exceeds 55% by weight there is a problem that the sintering temperature increases.

The method for preparing the composite oxide filler is generally used in the art, but is not particularly limited. In the present invention, a powder is prepared using a mixed oxide method, which is a general solid state reaction. Starting materials are ball milled by weighing MgO, Al ₂ O ₃ , ZnO, ZrO ₂ , and SiO ₂ commercially available ceramic raw powders to ZnAl ₂ O ₄ , MgAl ₂ O ₄ , ZrSiO ₄ , and Mg ₂ SiO ₄ . The ball milled mixed powder is calcined (calcining) in the air for 2 to 3 hours in the range of 1000 ~ 1200 ℃ to prepare the phase of each ZnAl ₂ O ₄ , MgAl ₂ O ₄ , ZrSiO ₄ , Mg ₂ SiO ₄ do. If the calcining temperature is less than 1000 ℃ unreacted raw material powder is present, if it exceeds 1200 ℃ it is good to maintain the above range because the problem of the growth of the particles of the synthetic phase occurs.

45 to 85 wt% of the glass frit prepared above and 15 to 55 wt% of the specific composite oxide filler are wet mixed, followed by molding to prepare a dielectric mixture. If the amount of the glass frit is less than 45% by weight, less densification is made at an appropriate temperature range of 850 to 900 ° C, and when the glass frit is more than 85% by weight, a problem of undersintering occurs at an appropriate temperature range of 850 to 900 ° C. do.

As described above, according to the present invention, by using a specific glass frit and a composite oxide filler, the dielectric constant is 4 to 7 (1 MHz), the dielectric loss is 0.02 to 0.2%, and the quality factor is 500 to 5000. As a resonator type such as a filter and an antenna, the present invention can be effectively applied to a part of ceramic multilayer packaging.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to Examples.

Example 1

MgO, Al ₂ O ₃ , ZnO, ZrO ₂ , SiO ₂ ZnAl ₂ O ₄ , MgAl ₂ O ₄ , ZrSiO ₄ , Mg ₂ SiO ₄ Weighed and ball milled to composition. At this time, the amount of each component was used as shown in Table 2 below. The ball milled mixed powder was calcined in air at 1100 ° C. for 2 hours to prepare composite oxide fillers on the respective phases of ZnAl ₂ O ₄ , MgAl ₂ O ₄ , ZrSiO ₄ , and Mg ₂ SiO ₄ . .

division MgO (g) Al ₂ O ₃ (g) ZnO (g) ZrO ₂ (g) SiO ₂ (g) ZnAl ₂ O ₄ - 56.070 43.930 - - MgAl ₂ O ₄ 28.331 71.669 - - - ZrSiO ₄ - - - 68.260 31.740 Mg ₂ SiO ₄ 57.298 - - - 42.702

Example 2

To the content shown in Table 3, each raw material SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , CaO, MgO and ZnO raw material powder was weighed in a quantitative ratio, ball milled, dried and ground. The pulverized product was put into a platinum crucible and melted at a temperature of 1600 ° C. to quench the molten liquid in a water cold bath to obtain a glass. The obtained glass was first roughly pulverized and secondly pulverized to prepare a glass frit powder.

The glass transition temperature, softening temperature and electrical characteristics of the glass frit powder obtained above were measured and shown in Table 3 below.

division Composition (mol%) Density (g / cm 3) TEC (10 ^-6 ) T _g (℃) T _s (℃) k (1 MHz) SiO ₂ B ₂ O ₃ AlO ₃ CaO MgO ZnO One 67 21 2 9 - One 2.31 3.44 719 768 4.74 2 64 20 2 13 - One 2.38 3.97 714 752 5.15 3 58 20 2 17 2 One 2.48 4.77 711 740 5.62 4 59 21 2 15 - 3 2.44 4.43 705 739 5.40 5 47 41 2 9 - One 2.23 4.71 559 625 4.64 6 52 36 2 9 - One 2.25 4.39 620 689 4.66 7 57 31 2 9 - One 2.27 4.08 686 754 4.65 8 70 22 2 - 3 3 2.23 1.05 488 513 4.10 9 70 22 2 3 - 3 2.25 2.99 637 718 4.20 10 70 22 2 One - 5 2.26 3.30 459 477 4.05 11 70 22 2 2 - 4 2.25 3.11 479 498 4.10

As shown in Table 3, the glass frit according to the present invention has a density of 2.2 to 2.5 g / cm 3, a coefficient of thermal expansion (TEC) of 1.05 to 4.77 × 10 ^-6 , and a glass transition temperature (Tg) of 500 to 700 ° C. The glass softening temperature (Ts) was found to be in the range of 480 ~ 770 ℃, the electrical properties of the measured glass specimens, it was confirmed that the dielectric constant is in the range of about 4.0 ~ 5.6, a low dielectric constant was obtained.

By selecting the type and content of the component according to the present invention, it was confirmed that the melting of the glass was performed well at about 1600 ° C. while the dielectric loss value was minimized.

Example 3

The composite oxide filler prepared in Example 1 and the glass frit prepared in Example 2 were wet mixed in a polyethylene bottle with zirconia ball as a solvent for 24 hours, respectively, in the amounts shown in Table 5 below. . In order to impart moldability to the mixed powder, 2 wt% polyvinyl alcohol (PVA) aqueous solution was added as a binder and granulated through sieving (100 mesh). A cylindrical shape was formed by uniaxial pressurization in a mold having a diameter of 10 mm at a pressure of kg / cm 3. The specimen thus formed was heated at a temperature increase rate of 5 ° C./min in an electric furnace, and then sintered at 900 ° C. for 2 hours, and then cooled by furnace.

Table 4 shows the sintering characteristics and electrical characteristics of the specimens obtained above.

division Glass frit Firing temperature (℃) Relative Density (%) Electrical Characteristics (1MHz) Kinds Usage (% by weight) Permittivity (k) Dielectric loss (tan δ,%) Quality Factor (Q) ZnAl ₂ O ₄ One 60 850 95.5 5.17 0.025 4000 875 98.8 4.94 0.023 4300 900 99.9 4.63 0.024 4200 3 50 875 99.1 6.04 0.041 2400 900 99.7 6.36 0.024 4200 4 47 825 99.9 6.34 0.015 6700 850 99.6 6.59 0.014 7100 875 99.3 6.50 0.016 6300 9 65 875 99.6 4.27 0.025 4000 900 99.9 4.70 0.022 4500 MgAl ₂ O ₄ One 60 850 96.5 5.44 0.047 2100 875 99.1 5.20 0.047 2100 900 99.7 5.11 0.049 2000 3 57 875 99.5 5.88 0.073 1400 900 99.9 6.08 0.058 1700 4 47 850 98.9 6.00 0.04 2500 875 99.7 6.22 0.04 2500 900 99.3 6.35 0.031 3200 ZrSiO ₄ One 60 850 95.2 6.60 0.1 1000 875 98.6 6.94 0.092 1100 900 99.9 7.01 0.094 1100 4 47 875 96.0 6.55 0.137 700 900 97.2 6.75 0.137 700 MgSiO ₄ One 85 875 95.2 4.09 0.123 800 900 99.9 4.39 0.122 800 3 80 900 96.8 4.29 0.180 600

As shown in Table 4, according to the present invention is formed by containing a specific composite oxide filler and glass frit as a certain component, the dielectric constant is 4.09 ~ 7.01, the dielectric loss value is about 0.022 ~ 0.1%, the quality factor is The range of 600-7100 is shown. In particular, in the case of ZnAl ₂ O ₄ composition as a whole, the dielectric loss value was measured to have very good dielectric loss characteristics of less than 0.05%. For example, when 47 wt% of A04 glass frit was added to the ZnAl ₂ O ₄ composition, a very good wiring LTCC substrate composition having a dielectric constant of 6.6 and a dielectric loss value of 0.014% (quality factor 7100) was developed at a temperature of 850 ° C. there was.

It is believed that low dielectric loss is obtained by completely eliminating the addition of alkali oxides (R ₂ O) and adding only alkaline earth oxides (RO).

The specimens show excellent low-temperature sintering properties, indicating a relative density of at least 96% below 900 ° C. As shown in the Scanning Electron Microscope of FIG. 1, it was confirmed that a dense structure without pores was obtained.

As described above, by using a specific composite oxide filler and glass frit in accordance with the present invention in a certain component ratio, low-temperature firing is possible below 950 ℃, low dielectric constant, very low dielectric loss, can minimize the electrical loss. Therefore, it is effectively applied to resonator such as filter and antenna of high efficiency. Ag) diffusion reaction of the electrode can be suppressed to minimize the reactivity with the electrode.

Claims (5)

In a dielectric composition containing glass frit and a filler, 45 to 85 wt% of glass frit containing SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ and ZnO, A dielectric composition comprising 15 to 55% by weight of at least one composite oxide filler selected from ZnAl ₂ O ₄ , MgAl ₂ O ₄ , ZrSiO ₄ and Mg ₂ SiO ₄ . The method of claim 1, wherein the SiO ₂ : B ₂ O ₃ : Al ₂ O ₃ : ZnO comprises 47 to 70 mol%: 20 to 41 mol%: 2 to 6 mol%: 1 to 5 mol% ratio. A dielectric composition characterized by. The dielectric composition according to claim 1, wherein the glass frit contains 0 to 17 mol% of CaO and 0 to 3 mol% of MgO. The dielectric composition of claim 1, wherein the acid group composition has a dielectric constant of 4 to 7 (1 MHz), a dielectric loss of 0.02 to 0.2%, and a quality factor of 500 to 5000. A low-temperature cofired ceramic (LTCC) substrate comprising the dielectric composition of any one of claims 1 to 4.

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