KR100471651B1 - Dielectric ceramic compositions for low temperature co-fired ceramic substrate and method for preparation thereof - Google Patents

Abstract

The present invention relates to a high dielectric constant MgO-CaO-TiO ₂ -based ceramic composition capable of firing at a low temperature range of about 950 ° C and a method of manufacturing the same. The composition according to the invention is suitable for use in high dielectric constant layers used inside ceramic low temperature fired multilayer substrates. The present invention includes a borosilicate glass oxide in a dielectric ceramic composition having excellent microwave dielectric properties and low-temperature firing, including an appropriate amount of boro silicate-based glass oxide and alkali metal oxide, and MgO-CaO-TiO ₂ -based calcined powder. The present invention provides a method for producing a dielectric ceramic composition having good microwave dielectric properties and low-temperature firing by adding an appropriate amount of alkali metal oxide and alkali metal oxide. The ceramic composition according to the present invention can be used in the manufacture of low-temperature fired multilayer substrates with low-cost Ag electrodes.

Description

Low temperature calcined dielectric ceramic composition and method for manufacturing the same {DIELECTRIC CERAMIC COMPOSITIONS FOR LOW TEMPERATURE CO-FIRED CERAMIC SUBSTRATE AND METHOD FOR PREPARATION THEREOF}

The present invention relates to a dielectric ceramic composition and a method of manufacturing the same. More specifically, the present invention relates to a MgO-CaO-TiO ₂ -based low temperature calcined high dielectric constant ceramic composition capable of firing in a temperature range lower than about 950 ° C. and a method of manufacturing the same.

In the current wireless communication service, the frequency band below 2 GHz is almost saturated, and since the communication service is based on multimedia such as moving pictures, it is certain that the frequency band used will be further increased to secure bandwidth. . The spread of telecommunication systems using microwaves such as personal portable communication terminals, mobile communication and satellite communication is increasing rapidly. As of 2000, the penetration rate of domestic mobile communication terminals exceeded 50% of the total population.

With the development of the mobile information and communication field, miniaturization and weight reduction of terminals and related components are emerging as an important technology element, and at the same time, high performance and low cost are also required. For smaller and lighter electronic or communication systems, it is necessary to increase the wiring density of the board and to reduce the size and weight of individual components or modules. In order to meet these demands, there is a growing interest in integration and modularization. In the concept of integration of a board, there are concepts such as PCB multilayer boards, and in terms of modularization of passive components, a multi-chip module "MCM" and the like (RR Tummala, "Ceramic and Glass-Ceramic Packing in the 1990s", J. Am. Ceram. Soc., 74 (5), 895-908 (1991)). Recently, the Low Temperature Co-fired Ceramic (LTCC) technology can realize the integration of the board and the modularization of passive components at the same time. Also relevant module products are being developed.

LTCC technology stacks ceramic thick film green sheets printed with devices and circuits, constructs vias and lateral interconnects to connect circuits in three dimensions, and then it is approximately 1000 ° C or less. Refers to an integrated ceramic module implemented by simultaneous firing at low temperature. PCB multilayer board is difficult to realize multilayer board with more than 10 layers due to the material and process problems of polymer series, and it is difficult to keep the thickness of layer below the proper thickness. There was a limit in terms of doing. However, in LTCC technology, the width of the wiring can be maintained to about 10 μm, and a product having a laminated structure of 50 layers or more has been published. The thickness between the layers is usually about 100 μm, which can be kept very thin, so that per unit area or The wiring density per unit weight can be significantly increased. Compared to thin film technology, there is no time-consuming and costly masking or physicochemical process, and the product can be manufactured by simple screen printing and firing process. have. An example of using a ceramic substrate as a multilayer and using it as a three-dimensional wiring board was a high temperature co-fired ceramic substrate (hereinafter referred to as "HTCC"). However, in this case, since the firing temperature of the ceramics exceeds 1300 ° C., the internal electrodes also use W, Mo, etc., which can withstand temperatures of 1300 ° C. or higher, resulting in poor electrical conductivity. There was a hard disadvantage. Therefore, LTCC, which can be fired at 900-1000 ° C, at which temperature of Ag and Ag / Pd internal electrodes having excellent electrical conductivity can be used, has a great advantage in terms of cost. (Thick film for Hybrid MCM And ceramic technology ", J. of KSHM-Korea, 1 (1), 61-82 (1994)).

LTCCs enable inductors, capacitors, and resistors in one module without leads, significantly reducing package size and preventing parasitic deterioration, which is very useful for high-frequency devices. Can be utilized.

The future direction of LTCC technology is expected to evolve in three phases as shown in Table 1.

At present, the development stage of domestic LTCC composition technology corresponds to the first stage, and mainly consists of low dielectric constant composition with a dielectric constant of about 5-9. In this case, it was only a concept of a simple three-dimensional high density wiring board without considering the electrical length. In other words, the LCR passive element is not embedded, and is used for the purpose of narrowing the footprint of the upper portion of the integrated circuit. In this case, unconditionally low dielectric constant is advantageous for signal transmission. However, in the case of an antenna or a filter using RF electromagnetic resonance, a distributed circuit concept using λ / 4 length is used, and thus it is necessary to appropriately control the dielectric constant of the substrate. The reason why this distributed circuit concept has not been used until now is that the current communication system is centered on personal mobile communication in the 0.8-2GHz band. It is because there is no meaning because it is several times larger than that.

However, as shown in Table 1, future communication systems are expected to develop into ultra-high frequency bands of several tens of GHz. When the frequency rises above 10 GHz, the size of λ / 4 approaches the size of the LTCC module. At frequencies above 30 GHz, the length of the wavelength drops to the millimeter range. In this case the wiring of the LTCC substrate can be treated as a distributed circuit concept, the electrical length of which is given as a function of the dielectric constant of the substrate. Therefore, in this case, a composition between 10 and 1000 with a relatively high dielectric constant is required. Low dielectric constant LTCC compositions with dielectric constants of about 6 to 9 are currently disclosed in several foreign patents (US Pat. Nos. 6,133,175, 5,714,246, 5,714,112, 5,468,695, 4,959,330, and 4,340,635). The high dielectric constant composition of 15 or more is currently little developed.

Accordingly, an object of the present invention is MgO-CaO- having a high dielectric constant capable of baking in a low temperature range of about 950 ° C so as to meet the LTCC dielectric ceramic condition that the microwave characteristics are excellent and the firing temperature should be 950 ° C or less. To provide a method for producing a TiO ₂ dielectric ceramic composition. MgO-CaO-TiO ₂ dielectric ceramic composition is a well-known composition, it is known that the firing temperature is 1350 ℃ or more, the present invention provides a method for lowering the firing temperature below 1000 ℃ by using a large amount of free oxide. .

The present invention relates to a dielectric ceramic composition and a method of manufacturing the same. More specifically, MgO-CaO-TiO ₂ -based dielectric ceramic composition capable of low-temperature firing, including boro silicate-based glass oxide and alkali metal oxide, and MgO-CaO in which MgTiO ₃ and CaTiO ₃ powders are mixed at a constant ratio. MgO-CaO-TiO ₂ -based low temperature firing intrinsically sintered at a low temperature range of 900 to 950 ° C by adding boro silicate-based glass oxides and alkali metal oxides as sintering aids to TiO ₂ -based dielectric ceramic compositions A method of making a dielectric dielectric ceramic composition is disclosed.

MgO-CaO-TiO ₂ based dielectric ceramic compositions have excellent microwave characteristics, but are known to have the disadvantage that the firing temperature is considerably high, such as 1350 ° C. As a result of repeated studies, it has been found that the firing temperature can be lowered to 950 ° C. or lower by adding a specific firing temperature lowering oxide (hereinafter referred to as “sintering aid”) to the ceramic composition.

In the MgO-CaO-TiO ₂ based dielectric ceramic composition containing the boro silicate-based glass oxide and the alkali metal oxide of the present invention, the conventional MgO-CaO-TiO ₂ based dielectric ceramic composition is fired at a temperature of 1350 ° C. or higher. Unlike what has been possible, it has the property of being calcinable even in a low temperature range of about 900 ~ 950 ℃.

In the present invention, the MgO-CaO-TiO ₂ based dielectric ceramic composition is calcined at low temperature when a certain amount of boro silicate-based oxide and alkali metal oxide are contained as a sintering aid regardless of the composition ratio between MgO, CaO and TiO ₂ . This is possible. At this time, among the MgO-CaO-TiO ₂ -based compositions, the (Mg _0.93 Ca _0.07 ) TiO ₃ -based composition is particularly excellent in microwave characteristics. When 93 mol% of MgTiO ₃ and 7 mol% of CaTiO ₃ are mixed, it is known that the dielectric constant is 20, the quality factor is 60,000, and the temperature coefficient of the resonance frequency is 0 ppm / 占 폚 (E. Nagata, J. Tanaka, M. Tsutumi, E. Bannai, "Distribution of Calcium Ion in the Crystal of MgTiO3-CaTiO3 System", Bull. Chem. Soc. Jpn., 56, 3173-3174 (1983)).

The borosilicate glass oxide used as the sintering aid is preferably a mixed oxide obtained by mixing SiO ₂ and B ₂ O ₃ in a weight ratio of 6: 4 to 7: 3, preferably 2: 1. In this case, the borosilicate glass oxide is excellent in electrical properties, but the melting point is relatively high, so in order to use as a low temperature sintering aid, it is necessary to further reduce the glass forming temperature by adding an alkali metal oxide. Therefore, in the present invention, in order to ensure good electrical properties while further lowering the firing temperature, an alkali metal oxide is added to and used in the borosilicate glass oxide. In this case, as the alkali metal oxide, Na ₂ O, MgO, Li ₂ O mixture or a mixture of Al ₂ O ₃ added thereto may be used.

As a result of investigating by varying the ratio of the components of the sintering aid, when the weight ratio SiO ₂ : B ₂ O ₃ : Na ₂ O: MgO: Li ₂ O = 32.0: 16.0: 32.2: 8.5 ~ 10.0: 9.8 ~ 11.3 The sinterability and electrical properties of the ceramic composition were found to be excellent. In particular, SiO ₂ : B ₂ O ₃ : Na ₂ O: MgO: Li ₂ O = 32.0: 16.0: 32.2: 9.0: 10.8 by weight ratio Appeared (see Table 2). However, when the sintering aid having the above composition is used, it has been shown that the hydration reactivity tends to appear. Here, the hydration reaction means a phenomenon in which the weight of the glass gradually increases due to the reaction of water and glass in the air due to the poor water resistance of the glass. In this case, when Al ₂ O ₃ is additionally added as the sintering aid component, The hydration reaction does not occur. In this case, as the amount of Al ₂ O ₃ is increased, the electrical properties of the composition are improved, and the ratio between components of the sintering aid is SiO ₂ : B ₂ O ₃ : Na ₂ O: MgO: Li ₂ O: Al ₂ O ₃ = 32.0: 16.0: 25.0: 8.5 ~ 11.5: 6.5 ~ 9.5: 6.0 ~ 12.0 The composition had excellent sintering properties and electrical properties, in particular, SiO ₂ : B ₂ O ₃ : Na ₂ O: MgO: Li ₂ O: Al ₂ O ₃ = 32.0: 16.0: 25.0: 9.5: 7.5: 10.0 was found to be most preferred (see Table 3).

The addition amount of the borosilicate glass oxide and the alkali metal oxide is preferably 5-20% based on the total weight of the dielectric ceramic composition (see Table 4). If the amount is less than 5%, the low temperature firing effect is lowered and the firing temperature is increased. If it is more than 20%, the electrical properties such as the quality factor and the dielectric constant decrease.

In addition, the manufacturing method of the MgO-CaO-TiO ₂ based dielectric ceramic composition according to the present invention,

MgTiO ₃ and CaTiO ₃ powders are weighed to a desired quantitative ratio and ball milled to obtain a dielectric calcined powder having a composition of MgO-CaO-TiO ₂ system,

Adding a boro silicate-based glass oxide and an alkali metal oxide as a sintering aid to the calcined powder, and then grinding and mixing to obtain a mixed powder,

Molding the mixed powder to obtain a molded body, and

Sintering the molded body at a temperature range of 900 ~ 950 ℃.

The mixing ratio of the MgTiO ₃ and CaTiO ₃ powder is preferably mixed so that the desired MgO-CaO-TiO ₂ system will depend on the type of composition, in particular, the amount added is 3 ~ 10 mol% range of CaTiO ₃ to MgTiO ₃ Do. This is because, in the temperature coefficient of the resonance frequency, MgTiO ₃ has a positive value and CaTiO ₃ has a negative value, so that mixing in the above range can obtain a temperature coefficient close to zero.

Typically, MgO-CaO-TiO ₂ based compositions, including (Mg _0.93 Ca _0.07 ) TiO ₃ based, which have particularly good microwave dielectric properties, require a high temperature of about 1350 ° C. for firing. However, the present invention can provide a MgO-CaO-TiO ₂ -based composition capable of low-temperature baking below 1000 ° C by adding borosilicate-based glass oxide and alkali metal oxide during the preparation of the composition.

As the borosilicate glass oxide used as the sintering aid, a mixed oxide containing SiO ₂ and B ₂ O ₃ in a weight ratio of 6: 4 to 7: 3, preferably 2: 1 is preferable. At this time, an alkali metal oxide is added to the boro silicate-based glass oxide in order to further reduce the firing temperature and ensure good electrical properties. As the alkali metal oxide, a mixture of Na ₂ O, MgO, Li ₂ O or Al ₂ O ₃ may be used.

As a result of investigating different ratios of constituents of the sintering aid, the sinterability of SiO ₂ : B ₂ O ₃ : Na ₂ O: MgO: Li ₂ O = 32.0: 16.0: 32.2: 8.5 ~ 10.0: 9.8 ~ 11.3 by weight And electrical properties were found to be excellent, in particular, SiO ₂ : B ₂ O ₃ : Na ₂ O: MgO: Li ₂ O = 32.0: 16.0: 32.2: 9.0: 10.8 by weight ratio was the most preferable (Table 2 Reference). At this time, the addition of Al ₂ O ₃ as the sintering aid component can suppress the hydration reactivity, the electrical properties of the composition is improved as the amount of Al ₂ O ₃ is increased. The ratio between components of the sintering aid is SiO ₂ : B ₂ O ₃ : Na ₂ O: MgO: Li ₂ O: Al ₂ O ₃ = 32.0: 16.0: 25.0: 8.5 ~ 11.5: 6.5 ~ 9.5: 6.0 ~ 12.0 days When sintering and electrical properties of the composition was excellent, in particular, SiO ₂ : B ₂ O ₃ : Na ₂ O: MgO: Li ₂ O: Al ₂ O ₃ = 32.0: 16.0: 25.0: 9.5: 7.5: 10.0 days The time appeared to be the most desirable (see Table 3).

The addition amount of the borosilicate glass oxide and alkali metal oxide is preferably 5-20% based on the total weight of the dielectric ceramic composition (see Table 4). If the amount is less than 5%, the low temperature firing effect is lowered and the firing temperature is increased. If it is more than 20%, the electrical properties such as the quality factor and the dielectric constant decrease.

As can be seen in the following examples, according to the production method of the present invention, sintering is possible at a low temperature of 900 ~ 950 ℃, it is possible to manufacture a ceramic composition excellent in dielectric properties.

The present invention will be described in detail by the following examples. However, the embodiments are only illustrative of the present invention, and the scope of the present invention is not limited thereto.

<Example>

As MgO, CaO and TiO ₂ raw material having a purity of 99.9% were weighed ratio amount MgTiO ₃ 111.8 g and CaTiO ₃ 9.52 g and then milling using zirconia balls with deionized water ball for 24 hours, at least 100 ℃ temperature It was dried enough. The dried powder was heated to 1100 ° C. at a heating rate of 300 ° C./h, and then calcined for 2 hours to prepare a dielectric ceramic powder having a composition of (Mg _0.93 Ca _0.07 ) TiO ₃ . 2-20% of the dielectric ceramic powder as a low-temperature sintering aid, a mixture of B ₂ O ₃ , SiO ₂ , Na ₂ O, MgO, Li ₂ O or a mixture further comprising Al ₂ O ₃ , based on the total weight of the ceramic composition The amounts were changed and added in the composition ratio as shown in Tables 2 and 3 within the range of, and each composition was ground and mixed for 24 hours.

In order to improve the moldability of the powder synthesized as described above, 2% by weight of polyvinyl alcohol (PVA) is added to the ceramic composition as a binder, granulated through sieving, and then molded to obtain a molded product. The temperature was raised from 900 ° C. to 950 ° C. at a rate of 5 ° C./min, followed by sintering for 2 hours.

The glass transition temperature Tg and the bowelasticity were measured using a dilatometer, and the dielectric constant and microwave quality factor (Q × f) values were measured by BW Hakki, PD Coleman, "A Dielectric Resonator Method of Measuring Inductive Capacitance in the Millimeter Range ", IRE Trans. Microwave Theory Tech., 8, 402-410 (1960)), the results are shown in Tables 2 and 3.

Table 2 below shows the composition and properties of the sintering aid of the present invention.

In Table 2, B ₂ O ₃ , SiO ₂ , Na ₂ O, MgO and Li ₂ O were used as sintering aids, and these were expressed as PS1 to PS9. As shown in Table 2, the weight ratio of SiO ₂ : B ₂ O ₃ in the composition of the borosilicate-based glass oxide was kept constant at 2: 1, and the ratio of Na ₂ O was also fixed at 32.2% by weight. This is because the low-temperature firing effect and electrical properties are maximized when maintaining this ratio. The amount of MgO and Li ₂ O was changed. As the amount of Li ₂ O was increased, the low temperature annealing effect was improved, but the microwave quality coefficient showed a tendency to decrease rapidly. As can be seen from Table 2, the optimum composition of the sintering aid in consideration of the microwave quality factor and low temperature plasticity is SiO ₂ : B ₂ O ₃ : Na ₂ O: MgO: Li2O = 32.0: 16.0: 32.2: 8.5 ~ 10.0: 9.8 ~ 11.3, especially, SiO ₂ : B ₂ O ₃ : Na ₂ O: MgO: Li ₂ O = 32.0: 16.0: 32.2: 9.0: 10.8 was the most preferable. In the case of using the sintering aids of PS1 to PS9 in Table 2, the hydration reactivity tends to appear, which may cause practical problems. Here, the hydration reaction means a phenomenon in which the weight of the glass gradually increases due to the reaction of water and glass in the air due to the poor water resistance of the glass. In this case, when Al ₂ O ₃ is additionally added as the sintering aid component, The hydration reaction does not occur.

Table 3 below shows the composition of the sintering aid (Altered as PSA1 to PSA7 in Table 3) to which Al ₂ O ₃ is further added, and the properties of the MgO—CaO—TiO ₂ based composition prepared accordingly.

As can be seen in Table 3, the electrical properties were improved as the amount of Al ₂ O ₃ was increased, the ratio between the components of the sintering aid is SiO ₂ : B ₂ O ₃ : Na ₂ O: MgO: Li ₂ O : Al ₂ O ₃ = 32.0: 16.0: 25.0: 8.5 ~ 11.5: 6.5 ~ 9.5: 6.0 ~ 12.0 The sinterability and electrical properties of the composition were excellent. In particular, SiO ₂ : B ₂ O ₃ : Na ₂ O : MgO: Li ₂ O: Al ₂ O ₃ = 32.0: 16.0: 25.0: 9.5: 7.5: 10.0 (PSA6) was the most preferred.

Table 4 below shows the firing behavior when fired at 950 ° C. for 2 hours.

As shown in Table 4, when the sintering aid does not contain Al ₂ O ₃ (PS8), when the sintering aid is added in an amount of 20% by weight, the hydration reaction occurs at about 10% by weight of the ceramic composition prepared. There was a problem that occurred. In order to solve this problem, as a result of further attempts to use various additives, it was found that the most effective addition of Al ₂ O ₃ . As can be seen in Table 4, when Al ₂ O ₃ is additionally added to the sintering aid, the hydration properties are significantly improved.

From Table 4, it can be seen that the best results can be obtained when 10 to 20% by weight of a sintering aid (PSA6) to which Al ₂ O ₃ is additionally added to the MgO-CaO-TiO ₂ based composition.

According to the present invention, it is possible to obtain a high-k dielectric ceramic composition for low-temperature calcined multilayer substrates having excellent plasticity and dielectric properties even at a low temperature range around 950 ° C, and through this, a high-k dielectric ceramic composition for low-temperature calcined multilayer substrates using Ag electrodes. As such, it is considered to be sufficiently available.

Claims (14)

A MgO-CaO-TiO ₂ based dielectric ceramic composition comprising a boro silicate-based glass oxide and an alkali metal oxide, 10 to 20 wt% of the mixed oxide of the borosilicate-based glass oxide and the alkali metal oxide, based on the total weight of the ceramic composition, The mixed oxide is SiO ₂ , B ₂ O ₃ , Na ₂ O, MgO and Li ₂ O is SiO ₂ : B ₂ O ₃ : Na ₂ O: MgO: Li ₂ O = 32.0: 16.0: 32.2: 8.5 ~ 10.0: 9.8 to 11.3 by weight, MgO-CaO-TiO ₂ based dielectric ceramic composition. delete delete delete The MgO-CaO-TiO ₂ based dielectric ceramic composition according to claim 1, wherein the alkali metal oxide is a mixed oxide further comprising Al ₂ O ₃ . The method of claim 5, wherein SiO ₂ , B ₂ O ₃ , Na ₂ O, MgO, Li ₂ O and Al ₂ O ₃ are used as SiO ₂ : B ₂ O ₃ : Na ₂ as the borosilicate glass oxide and the alkali metal oxide. O: MgO: Li ₂ O: Al ₂ O ₃ = 32.0: 16.0: 25.0: 8.5 to 11.5: 6.5 to 9.5: 6.0 to 12.0 MgO-CaO-TiO ₂ based dielectric ceramic composition comprising a mixed oxide mixed in a weight ratio . The MgTiO ₃ and CaTiO ₃ powder was ball milled were weighed so that the amount added is from 3 to 10 mol% of CaTiO ₃ to MgTiO _3, and then calcined to obtain a calcined dielectric powder having a composition of MgO-CaO-TiO ₂ system, In the obtained dielectric calcined powder, SiO ₂ , B ₂ O ₃ , Na ₂ O, MgO and Li ₂ O as SiO ₂ : B ₂ O ₃ : Na ₂ O: MgO: Li ₂ O = 32.0: 16.0: 32.2 : 8.5 to 10.0: A mixed oxide of borosilicate-based free oxide and alkali metal oxide mixed in a weight ratio of 9.8 to 11.3 is added in an amount of 10 to 20% by weight based on the total weight of the composition, and then pulverized and mixed to obtain a mixed powder. step, Molding the obtained mixed powder to obtain a molded body, and And sintering the molded body at a temperature in the range of 900 to 950 ° C. The method of claim 7, using a mixture such that the amount is 3 ~ 10 mol% of CaTiO ₃ range for the MgTiO ₃ and CaTiO ₃ to MgTiO ₃ powder. delete delete delete 8. The method of claim 7, wherein the alkali metal oxide is a mixed oxide further comprising Al ₂ O ₃ . 13. The method of claim 12, wherein SiO ₂ , B ₂ O ₃ , Na ₂ O, MgO, Li ₂ O, and Al ₂ O ₃ are selected from SiO ₂ : B ₂ O ₃ : Na ₂ as the borosilicate glass oxide and the alkali metal oxide. O: MgO: Li ₂ O: Al ₂ O ₃ = 32.0: 16.0: 25.0: 8.5 ~ 11.5: 6.5 ~ 9.5: 6.0 ~ 12.0 A method of using a mixed oxide mixed in a weight ratio. delete