JP2009227483A - Dielectric ceramic composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric ceramic composition capable of being fired at a low temperature even when CuO is not contained and capable of improving a Q×f value. <P>SOLUTION: The dielectric ceramic composition includes a BaO-Nd<SB>2</SB>O<SB>3</SB>-TiO<SB>2</SB>based compound and 2MgO×SiO<SB>2</SB>as essential components and zinc oxide, boron oxide, alkaline earth metal oxide and a lithium compound as accessary components, wherein the content (c) of the lithium compound is 0.04 pts.mass<c<3.24 pts.mass per 100 pts.mass essential components when the lithium compound is expressed in terms of Li<SB>2</SB>O. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a dielectric ceramic composition.

  2. Description of the Related Art In recent years, mobile communication devices such as mobile phones, for which demand is increasing, use a high frequency band called a quasi-microwave of about several hundred MHz to several GHz. Therefore, devices having high-frequency characteristics (hereinafter referred to as “high-frequency devices”) are required as electronic devices such as filters, resonators, and capacitors used in mobile communication equipment. In addition, with the recent miniaturization of mobile communication devices, miniaturization of high frequency devices is also required.

In order to realize a small high-frequency device, it is required to use a material having a high relative dielectric constant at a used frequency, a small dielectric loss, and a small change in temperature characteristics of a resonance frequency as a material for the high-frequency device. As such a material, a BaO-rare earth oxide-TiO ₂ dielectric ceramic composition (hereinafter referred to as “high dielectric constant material”) has been used. When forming a high-frequency device using this high-dielectric constant material, the high-dielectric-constant material and the conductor material that becomes the electrode and wiring inside the high-frequency device are fired at the same time. It was necessary to use a material having a melting point higher than the sintering temperature and which does not melt during co-firing with a high dielectric constant material. However, since the sintering temperature of the high dielectric constant material is as high as 1300 to 1400 ° C., conventionally, expensive Pd or Pt having a high melting point has to be used for the conductor material. On the other hand, inexpensive and low-resistance Ag or an alloy containing Ag as a main component (hereinafter referred to as “Ag-based metal”) has a melting point of about 860 to 1000 ° C., and is sintered with a high dielectric constant material. Since it was lower than the temperature, it could not be used as a conductor material.

  In order to further enhance the characteristics and miniaturization of the high-frequency device using the high dielectric constant material, a high dielectric constant layer formed from the high dielectric constant material and a dielectric ceramic composition having a lower relative dielectric constant (hereinafter referred to as a dielectric ceramic composition) A multilayer device in which a low dielectric constant layer formed from a low dielectric constant material is joined has been proposed (see Patent Document 1).

The low dielectric constant material used in the multilayer device, as shown in Patent Document 2, as a main component, the ratio and having a high dielectric constant _{xBaO · yNd 2 O 3 · zTiO} 2, low dielectric constant 2MgO · Examples thereof include a dielectric ceramic composition containing both SiO ₂ (hereinafter referred to as “composite material”).

Since this composite material contains ZnO, B ₂ O ₃ , and CuO as subcomponents (sintering aids), xBaO · yNd ₂ O ₃ · zTiO ₂ and 2MgO · SiO ₂ which are different materials are included. The firing shrinkage behavior and the linear expansion coefficient are made to coincide with each other, and excessive reaction at the interface between different materials can be suppressed, and both can be fired simultaneously without defects.

The sintering temperature of the composite material is about 800 to 950 ° C., which is lower than the sintering temperature of the conventional high dielectric constant material. Therefore, the melting point is lower than that of Pd and Pt, the resistance is low, and the Ag type is inexpensive. A metal can be used as a conductor material. That is, the composite material can be co-fired with the Ag-based metal at a low temperature that can suppress melting of the Ag-based metal that is the conductor material.
JP-A-9-139320 JP 2006-124270 A

  Although CuO contained as a subcomponent in the composite material shown in Patent Document 2 has an effect of lowering the sintering temperature of the composite material, the present inventor has removed CuO from the composite material as a result of earnest research. Thus, it was found that melting of the Ag-based metal can be more reliably suppressed during the simultaneous firing of the composite material and the Ag-based metal.

  However, when CuO is not included in the composite material, the sintering temperature of the composite material itself tends to increase, and it becomes difficult to simultaneously fire the composite material and the Ag-based metal at a low temperature (a temperature lower than the melting point of the Ag-based metal). The inventor has also found that there is a tendency. It was also found that when CuO is not contained in the composite material, the dielectric loss of the composite material increases and the Q · f value (unit: GHz) tends to decrease. Q is the reciprocal of the tangent tan δ of the loss angle δ, which is the difference between the actual current and voltage phase difference in the dielectric and the ideal current and voltage phase difference of 90 degrees, and f is the resonance frequency. .

  As described above, in order to prevent the melting point of the Ag-based metal from being lowered during co-firing with the composite material, it is desired that the composite material does not contain CuO, but when the composite material does not contain CuO, As the sintering temperature of the composite material itself increases, firing of the composite material at a low temperature (a temperature lower than the melting point of the Ag-based metal) becomes difficult, and the Q · f value tends to decrease.

  Therefore, the present invention has been made in view of the above problems, and can be fired at a low temperature without containing CuO and can be improved in Q · f value. The purpose is to provide.

To achieve the above object, the dielectric ceramic composition of the present invention contains BaO—Nd ₂ O ₃ —TiO ₂ -based compound and 2MgO · SiO ₂ as main components, and zinc oxide, boron as subcomponents When an oxide, an alkaline earth metal oxide, and a lithium compound are included and the mass of the lithium compound is converted to Li ₂ O, the lithium compound content c is 0.04 with respect to 100 parts by mass of the main component. Part by mass <c <3.24 parts by mass, preferably 0.10 parts by mass ≦ c ≦ 3.00 parts by mass, more preferably 0.20 parts by mass ≦ c ≦ 1.62 parts by mass .

  According to the above composition, the melting point of the Ag-based metal can be reduced during the simultaneous firing of the dielectric ceramic composition and the Ag-based metal even if CuO that has been conventionally used as an auxiliary component is not included by including the lithium compound. The dielectric ceramic composition can be fired at a low temperature (a temperature lower than the melting point of the Ag-based metal) without lowering, and the dielectric loss can be reduced and the Q · f value can be improved.

  The dielectric ceramic composition is a raw material composition of a dielectric ceramic, and a dielectric ceramic that is a sintered body can be obtained by sintering the dielectric ceramic composition. Sintering is a phenomenon in which when a dielectric ceramic composition is heated, the dielectric ceramic composition becomes a dense object called a sintered body. In general, the density, mechanical strength, etc. of the sintered body are increased as compared with the dielectric ceramic composition before heating. The sintering temperature is the temperature of the dielectric ceramic composition when the dielectric ceramic composition is sintered. Further, firing means a heat treatment for the purpose of sintering, and the firing temperature is the temperature of the atmosphere to which the dielectric ceramic composition is exposed during the heat treatment.

  The evaluation of whether or not the dielectric ceramic composition of the present invention can be fired at a low temperature (low temperature sinterability) is performed by gradually lowering the firing temperature of the dielectric ceramic composition, and firing. It can be judged by whether or not the dielectric ceramic composition is sintered to a level at which a desired dielectric high frequency characteristic can be obtained. In addition, the dielectric characteristics of the dielectric ceramic composition of the present invention can be evaluated by the Q · f value, the change in resonance frequency due to temperature change (temperature coefficient τf of resonance frequency), and the relative dielectric constant εr. The Q · f value, the temperature coefficient τf of the resonance frequency, and the relative dielectric constant εr can be measured according to Japanese Industrial Standard “Test Method for Dielectric Properties of Fine Ceramics for Microwaves” (JISR 1627 1996)).

  ADVANTAGE OF THE INVENTION According to this invention, even if it does not contain CuO, it becomes possible to provide the dielectric ceramic composition which can be baked at low temperature and can improve Q * f value.

  Hereinafter, a preferred embodiment of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

(Dielectric porcelain composition)
The dielectric ceramic composition of the present embodiment includes, as main components, a BaO—Nd ₂ O ₃ —TiO ₂ compound and 2MgO · SiO ₂ , and zinc oxide, boron oxide, alkaline earth as subcomponents. Includes metal oxides and lithium compounds. When the mass of the lithium compound is converted to Li ₂ O, the content c of the lithium compound is 0.04 parts by mass <c <3.24 parts by mass with respect to 100 parts by mass of the main component.

<Main component>
The main component contained in the dielectric ceramic composition of the present embodiment can be expressed by a composition formula {α (xBaO · yNd ₂ O ₃ · zTiO ₂ ) + β (2MgO · SiO ₂ )}. Α in the compositional formula {α (xBaO · yNd ₂ O ₃ · zTiO ₂ ) + β (2MgO · SiO ₂ )} represents a volume ratio (volume%) of the xBaO · yNd ₂ O ₃ · zTiO ₂ component, and β is This represents the volume ratio of 2MgO.SiO ₂ components. Α and β satisfy the relationship of α + β = 100 (volume%).

2MgO · SiO ₂ contained as a part of the main component is preferably contained in the dielectric ceramic composition in the form of forsterite crystals. Whether or not a forsterite crystal is contained in the dielectric ceramic composition can be confirmed by an X-ray diffractometer (XRD).

The BaO—Nd ₂ O ₃ —TiO ₂ -based compound has a high relative dielectric constant εr, and its value is about 55 to 105. On the other hand, 2MgO.SiO ₂ (forsterite) alone has a low εr, and its value is about 6.8. In the present embodiment, the dielectric ceramic composition includes, as main components, a BaO—Nd ₂ O ₃ —TiO ₂ -based compound having a high εr and a 2MgO · SiO ₂ having a low εr as main components. Εr of an object can be lowered.

The dielectric layer formed from the dielectric ceramic composition of the present embodiment is joined to the dielectric layer formed from the conventional BaO-rare earth oxide-TiO ₂ dielectric ceramic composition (high dielectric constant material). In the case of forming a multilayer device, the multilayer device can have higher characteristics as the dielectric constant of the dielectric ceramic composition of the present embodiment is lower than that of the high dielectric constant material. For these reasons, εr of the dielectric ceramic composition of the present embodiment is preferably 50 or less, preferably 40 or less, more preferably 35 or less, and preferably 25 to 35. Particularly preferred.

BaO—Nd ₂ O ₃ —TiO ₂ -based compounds often have a positive resonance frequency temperature coefficient τf (unit: ppm / K). On the other hand, 2MgO.SiO ₂ (forsterite) alone has a negative τf, and the value is about −65 (ppm / K). In this embodiment, the dielectric ceramic composition contains, as main components, a BaO—Nd ₂ O ₃ —TiO ₂ compound having a positive τf and 2MgO · SiO ₂ having a negative τf, The positive τf and the negative τf cancel each other, so that the τf of the dielectric ceramic composition can be in the vicinity of zero. Furthermore, τf of the dielectric ceramic composition can be adjusted by increasing or decreasing the content ratio of 2MgO · SiO ₂ in the main component. The temperature coefficient τf and the Q · f value to be described later are values indicated by the sintered dielectric ceramic composition, that is, the dielectric ceramic.

  The temperature coefficient τf (unit: ppm / K) of the resonance frequency of the dielectric ceramic composition is calculated by the following formula (1).

τf = [f _T −f _ref / f _ref (T−T _ref )] × 10 ⁶ (ppm / K) (1)

Here, f _T represents the resonance frequency (kHz) at the temperature T, and f _ref represents the resonance frequency (kHz) at the reference temperature T _ref . The magnitude of the absolute value of τf means the magnitude of change in the resonance frequency of the dielectric ceramic composition with respect to temperature change. In high-frequency devices such as capacitors and dielectric filters, it is necessary to reduce the change in resonance frequency due to temperature, and therefore it is required to reduce the absolute value of τf of the dielectric ceramic composition.

  Τf of the dielectric ceramic composition of the present embodiment is preferably −40 (ppm / K) to +40 (ppm / K), and is −28 (ppm / K) to +28 (ppm / K). Is more preferable, and −20 (ppm / K) to +20 (ppm / K) is still more preferable. By setting τf within the above preferable range, when the dielectric ceramic composition is used for a dielectric resonator, the temperature change of the resonance frequency of the dielectric resonator can be reduced, and the dielectric resonator can be made high. Can be characterized.

The Q · f value (unit: GHz) of the BaO—Nd ₂ O ₃ —TiO ₂ compound is about 2000 to 8000 GHz. On the other hand, the Q · f value of 2MgO · SiO ₂ (forsterite) alone is about 200000 GHz, and the dielectric loss of 2MgO · SiO ₂ is smaller than the dielectric loss of BaO—Nd ₂ O ₃ —TiO ₂ -based compounds. . In this embodiment, the dielectric ceramic composition includes, as main components, a BaO—Nd ₂ O ₃ —TiO ₂ -based compound, and forsterite having a dielectric loss smaller than that of a BaO—Nd ₂ O ₃ —TiO ₂ -based compound. By containing, a dielectric ceramic composition having a small dielectric loss can be obtained.

  The Q · f value (unit: GHz) of the dielectric ceramic composition represents the magnitude of the dielectric loss, and is the difference between the actual current and voltage phase difference and the ideal current and voltage phase difference of 90 degrees. This is the product of the reciprocal Q (Q = 1 / tan δ) of the tangent tan δ of the loss angle δ, which is the difference, and the resonance frequency f.

  When alternating current is applied to an ideal dielectric ceramic, the current and voltage have a phase difference of 90 degrees. However, when the AC frequency is increased and the frequency becomes high, the electric polarization of the dielectric ceramic or the orientation of the polar molecules cannot follow the change of the electric field of the high frequency, or the electric flux density is changed to the electric field by conduction of electrons or ions. On the other hand, there is a phase lag (phase difference), and the actual current and voltage have a phase other than 90 degrees. A phenomenon in which part of high-frequency energy is dissipated as heat due to such a phase difference is called dielectric loss. The magnitude of the dielectric loss is represented by the above-mentioned Q · f value. The Q · f value increases as the dielectric loss decreases, and the Q · f value decreases as the dielectric loss increases. Dielectric loss means power loss of a high-frequency device, and a high-frequency device is required to have a low dielectric loss in order to achieve high performance. Therefore, a dielectric ceramic composition having a large Q · f value is required.

  The Qf value of the dielectric ceramic composition of the present embodiment is preferably 4000 GHz or more, and more preferably 4500 GHz or more.

The volume ratio α of the xBaO · yNd ₂ O ₃ · zTiO ₂ component is preferably 15 ≦ α ≦ 75, more preferably 25 ≦ α ≦ 65, and still more preferably 35 ≦ α ≦ 55. .

The volume ratio β of the 2MgO · SiO ₂ component is preferably 25 ≦ β ≦ 85, more preferably 35 ≦ β ≦ 75, and still more preferably 45 ≦ β ≦ 65.

If α exceeds 75 and β is less than 25, εr of the dielectric ceramic composition tends to increase, and it is difficult to improve the characteristics of the multilayer device bonded to the conventional high dielectric constant material. . When α exceeds 75 and β is less than 25, τf tends to increase in the positive direction, and the resonance frequency of the high-frequency device tends to fluctuate easily depending on the temperature. On the other hand, when α is less than 15 and β exceeds 85, τf of the dielectric ceramic composition tends to increase in the negative direction, and the resonance frequency of the high-frequency device tends to vary with temperature. Therefore, by setting the volume ratio α of the xBaO · yNd ₂ O ₃ · zTiO ₂ component and the volume ratio β of the 2MgO · SiO ₂ component within the above-mentioned preferable ranges, these tendencies can be suppressed.

In the composition formula of the main component {α (xBaO · yNd ₂ O ₃ · zTiO ₂ ) + β (2MgO · SiO ₂ )}, x, y and z are respectively the molar ratios of BaO, Nd ₂ O ₃ and TiO ₂ ( Mol%) and satisfies the relationship of x + y + z = 100 (mol%).

  The molar ratio x of BaO is preferably 9 ≦ x ≦ 22, more preferably 10 ≦ x ≦ 19, and still more preferably 14 ≦ x ≦ 19.

  When x is less than 9, the dielectric loss increases, the Q · f value tends to decrease, and the power loss of the high-frequency device tends to increase. On the other hand, if x exceeds 22, the sinterability at low temperature is impaired and the dielectric porcelain cannot be formed. Further, the dielectric loss increases, and the Q · f value is greatly reduced. The power loss tends to increase. Therefore, these tendencies can be suppressed by setting the molar ratio x of BaO within the above preferred range.

The molar ratio y of Nd ₂ O ₃ is preferably 9 ≦ y ≦ 29, more preferably 9 ≦ y ≦ 22, and still more preferably 12 ≦ y ≦ 17.

When y is less than 9, the dielectric loss increases, the Q · f value tends to decrease, and the power loss of the high-frequency device tends to increase. On the other hand, when y exceeds 29, the dielectric loss increases, the Q · f value tends to decrease, and τf also tends to increase in the negative direction. For this reason, the power loss of the high-frequency device increases, and the resonance frequency of the high-frequency device tends to fluctuate depending on the temperature. Therefore, these tendencies can be suppressed by setting the molar ratio y of Nd ₂ O ₃ within the above-mentioned preferable range.

The molar ratio z of TiO ₂ is preferably 61 ≦ z ≦ 74, more preferably 61.5 ≦ z ≦ 74, and still more preferably 65 ≦ z ≦ 71.

When z is less than 61, the dielectric loss increases, the Q · f value tends to decrease, and τf also tends to increase in the negative direction. Therefore, the power loss of the high-frequency device increases, and the resonance frequency of the high-frequency device tends to fluctuate depending on the temperature. On the other hand, if z exceeds 74, the low-temperature sinterability is impaired, and there is a tendency that a dielectric ceramic cannot be formed. Therefore, by setting the molar ratio z of TiO ₂ within the above preferable range, these tendencies can be suppressed.

<Subcomponent>
The dielectric ceramic composition of the present embodiment includes zinc oxide, boron oxide, alkaline earth metal oxide as subcomponents for the main components (BaO—Nd ₂ O ₃ —TiO ₂ compound and 2MgO · SiO ₂ ). And lithium compounds. The dielectric ceramic composition may further contain CuO as a subcomponent as long as it does not impair the effects of the present invention, but preferably does not contain CuO.

  Since the sintering temperature of the dielectric ceramic composition is reduced by including each of the subcomponents in the dielectric ceramic composition, the dielectric ceramic composition is at a temperature lower than the melting point of the conductor material made of Ag-based metal. Can be fired simultaneously with the Ag-based metal.

  The content of zinc oxide as a kind of subcomponent is such that the value a (unit: part by mass) when the mass of zinc oxide is converted to ZnO is 0.1 ≦ a with respect to 100 parts by mass of the main component. ≦ 12.0 is preferable, 0.5 ≦ a ≦ 9.0 is more preferable, and 1.0 ≦ a ≦ 7.0 is further more preferable.

  When a is less than 0.1, the low-temperature sintering effect (effect that enables sintering of the dielectric ceramic composition at a lower temperature) tends to be insufficient. On the other hand, when a exceeds 12.0, the dielectric loss increases and the Q · f value tends to decrease. Therefore, these tendencies can be suppressed by setting the zinc oxide content a within the above-mentioned preferred range. Specific examples of the zinc oxide include ZnO.

The content of boron oxide which is a kind of subcomponent is such that the value b (unit: part by mass) when the mass of the boron oxide is converted to B ₂ O ₃ is 0. It is preferable that 1 ≦ b ≦ 12.0, more preferably 0.5 ≦ b ≦ 9.0, and still more preferably 1.0 ≦ b ≦ 7.0.

When b is less than 0.1, the low-temperature sintering effect tends to be insufficient. On the other hand, when b exceeds 12.0, the dielectric loss increases, and the Q · f value tends to decrease. Therefore, these tendencies can be suppressed by setting the content b of the boron oxide within the above preferable range. As a specific boron oxide, B ₂ O ₃ and the like.

The content of the lithium compound as a kind of subcomponent is such that the value c (unit: part by mass) when the mass of the lithium compound is converted to Li ₂ O is 0.04 <c with respect to 100 parts by mass of the main component. <3.24, preferably 0.10 ≦ c ≦ 3.00, and more preferably 0.20 ≦ c ≦ 1.62.

When c is 0.04 or less, the low-temperature sintering effect tends to be insufficient. On the other hand, when c is 3.24 or more, the Q · f value tends to be difficult to improve. Therefore, by setting the content c of the lithium compound within the above preferable range, these tendencies can be suppressed, and even if the dielectric ceramic composition does not contain CuO, the dielectric ceramic composition is fired at a low temperature. And the Q · f value can be improved. As a specific lithium compound, Li ₂ O is preferably used because the above effect is easily obtained.

  The content of the alkaline earth metal oxide, which is a kind of subcomponent, is the value d (unit: parts by mass) when the mass of the alkaline earth metal oxide is converted to RO (R is an alkaline earth metal element). Further, it is preferable that 0.2 ≦ d ≦ 5.0, more preferably 0.5 ≦ d ≦ 3.5, and 1.0 ≦ d ≦ 3.0 with respect to 100 parts by mass of the main component. More preferably. By including the alkaline earth metal oxide in the dielectric ceramic composition, the low-temperature sintering effect of the dielectric ceramic composition becomes remarkable.

  When d is less than 0.2, the low-temperature sintering effect tends to be insufficient. On the other hand, when d exceeds 5.0, the low-temperature sintering effect becomes remarkable, but the dielectric loss increases and the Q · f value tends to decrease. Therefore, these tendencies can be suppressed by setting the content d of the alkaline earth metal oxide within the above-mentioned preferable range.

  In addition, as R which is an alkaline-earth metal, either Ba, Sr, or Ca is preferable, and these 2 types or more may be mixed and used. When Ba is used as the alkaline earth metal R, the content d of the alkaline earth metal oxide is preferably 0.5 ≦ d ≦ 3.5 in terms of BaO. When Sr is used as the alkaline earth metal R, the content d of the alkaline earth metal oxide is preferably 0.4 ≦ d ≦ 2.5 in terms of SrO. When Ca is used as the alkaline earth metal R, the content d of the alkaline earth metal oxide is preferably 0.2 ≦ d ≦ 1.5 in terms of CaO. Specific examples of the alkaline earth metal oxide RO include BaO, SrO, and CaO.

  The dielectric ceramic composition of the present embodiment preferably further contains Ag as a subcomponent in addition to the subcomponent. Thereby, the low-temperature sintering effect of the dielectric ceramic composition becomes more prominent, and a dielectric ceramic having a stable capacitance and insulation resistance value can be obtained. In addition, by containing Ag as a subcomponent in the dielectric ceramic composition, when an Ag-based metal is used for the inner conductor, diffusion of Ag from the inner conductor into the dielectric substrate can be suppressed.

  When the dielectric ceramic composition further contains Ag as a subcomponent, the Ag content e (unit: part by mass) is 0.3 ≦ e ≦ 3.0 with respect to 100 parts by mass of the main component. It is preferable that 1.0 ≦ e ≦ 2.0.

  When e is less than 0.3, the low-temperature sintering effect tends to be insufficient, and the diffusion of Ag into the dielectric substrate tends not to be sufficiently suppressed. When the diffusion of Ag into the dielectric substrate cannot be sufficiently suppressed, the content of Ag in the dielectric becomes uneven and the dielectric constant varies, or the content of Ag in the inner conductor decreases. As a result, there is a tendency that a gap is generated between the inner conductor and the dielectric substrate, or a defective conductor is generated due to the drawing of the inner conductor at a connection portion with the outside. On the other hand, when e exceeds 3.0, the low-temperature sintering effect is obtained, but the dielectric loss increases and the Q · f value tends to decrease. In addition, the amount of Ag diffused into the dielectric substrate exceeds the amount of Ag that can be accepted by the dielectric, making it easier for Se to segregate in the dielectric substrate, and reliability such as voltage load life in high frequency devices and the like. Tend to decrease. Thus, these tendencies can be suppressed by setting the content of A, which is a subcomponent, within the above-mentioned preferred range.

  In the present embodiment, since a lithium compound is contained instead of CuO that has been conventionally used as an auxiliary component, the melting point of the Ag-based metal is reduced during the simultaneous firing of the dielectric ceramic composition and the Ag-based metal. It can be further suppressed. Further, the dielectric ceramic composition of the present invention having the above composition can be fired at a low temperature (a temperature lower than the melting point of the Ag-based metal) without containing CuO, and the dielectric loss is reduced. , Q · f value can be improved.

In the present embodiment, since the main component of the dielectric ceramic composition includes a BaO—Nd ₂ O ₃ —TiO ₂ compound, the conventional BaO—rare earth oxide—TiO ₂ dielectric ceramic composition (high It is similar to the material of the dielectric constant material. Therefore, the shrinkage behavior and the linear expansion coefficient during firing of the dielectric ceramic composition of the present embodiment are equivalent to those of the high dielectric constant material. Therefore, the dielectric ceramic composition of the present embodiment and the high dielectric constant material are joined and baked to produce a multilayer device, whereby a highly characteristic multilayer device is obtained with less defects on the joint surface. be able to.

(Manufacturing method of dielectric ceramic composition)
Next, an example of a method for producing the dielectric ceramic composition of the present embodiment will be described.

Examples of raw materials for the main component and subcomponent of the dielectric ceramic composition include, for example, BaO—Nd ₂ O ₃ —TiO ₂ -based compounds, 2MgO · SiO ₂ , zinc oxide, boron oxide, lithium oxide, and alkali. An earth metal oxide or a compound that becomes these oxides by firing (heat treatment such as calcination described later) can be used. Examples of the compound that becomes the oxide by firing (heat treatment such as calcination described later) include carbonates, nitrates, oxalates, hydroxides, sulfides, organometallic compounds, and the like.

In the production of the dielectric ceramic composition, for example, barium carbonate, neodymium hydroxide, and titanium oxide, which are a part of the main component raw materials, are weighed and mixed in predetermined amounts. In this mixing, each raw material is adjusted so that the molar ratios x, y and z in the composition formula xBaO.yNd ₂ O ₃ .zTiO ₂ of the main component of the obtained dielectric ceramic composition are within the above-mentioned preferred range. Weigh.

  Mixing of barium carbonate, neodymium hydroxide, and titanium oxide can be performed by a mixing method such as dry mixing or wet mixing, and may be performed by, for example, a ball mill using a solvent such as pure water or ethanol. The mixing time may be about 4 to 24 hours.

The mixture of barium carbonate, neodymium hydroxide and titanium oxide is preferably dried at about 100 to 200 ° C., more preferably 120 to 140 ° C. for about 12 to 36 hours, followed by calcination. A BaO—Nd ₂ O ₃ —TiO ₂ compound is synthesized by this calcination. The calcination temperature is preferably 1100 to 1500 ° C, and more preferably 1100 to 1350 ° C. The calcination is preferably performed for about 1 to 24 hours.

The synthesized BaO—Nd ₂ O ₃ —TiO ₂ compound is pulverized into a powder and then dried. Thereby, a powder of a BaO—Nd ₂ O ₃ —TiO ₂ compound is obtained. The pulverization can be performed by a pulverization method such as dry pulverization or wet pulverization. For example, the pulverization can be performed by a ball mill using a solvent such as pure water or ethanol. The pulverization time may be about 4 to 24 hours. The powder may be dried at a drying temperature of preferably 100 to 200 ° C., more preferably 120 to 140 ° C. for about 12 to 36 hours.

Also, magnesium oxide and silicon oxide, which are raw materials of 2MgO.SiO ₂ (forsterite), which is the main component, are weighed in predetermined amounts and mixed. The mixing of magnesium oxide and silicon oxide can be performed by a mixing method such as dry mixing or wet mixing, for example, by a ball mill using a solvent such as pure water or ethanol. The mixing time may be about 4 to 24 hours.

The mixture of magnesium oxide and silicon oxide is preferably dried at about 100 to 200 ° C., more preferably at 120 to 140 ° C. for about 12 to 36 hours, followed by calcination. By this calcination, 2MgO.SiO ₂ (forsterite crystal) is synthesized. The calcination temperature is preferably 1100 to 1500 ° C, and preferably 1100 to 1350 ° C. The calcination is preferably performed for about 1 to 24 hours.

The synthesized forsterite crystals are pulverized into powder and then dried. Thereby, a powder of 2MgO.SiO ₂ (forsterite crystal) is obtained. The pulverization can be performed by a pulverization method such as dry pulverization or wet pulverization. For example, the pulverization can be performed by a ball mill using a solvent such as pure water or ethanol. The pulverization time may be about 4 to 24 hours. The powder may be dried at a drying temperature of preferably 100 to 200 ° C., more preferably 120 to 140 ° C. for about 12 to 36 hours.

  In addition, as mentioned above, you may use a commercially available forsterite instead of synthesizing a forsterite crystal from a magnesium containing raw material and a silicon containing raw material. That is, commercially available forsterite may be pulverized by the method described above and dried to obtain forsterite powder.

Next, the obtained BaO—Nd ₂ O ₃ —TiO ₂ -based compound powder and 2MgO · SiO ₂ (forsterite crystal) powder are blended at the volume ratio α: β described above, thereby obtaining a dielectric. The main component of the porcelain composition is obtained. In this way, when the BaO—Nd ₂ O ₃ —TiO ₂ compound and 2MgO · SiO ₂ (forsterite) are blended, the BaO—Nd ₂ O ₃ —TiO ₂ compound alone is the main component. In comparison, εr of the dielectric ceramic composition can be lowered, the temperature coefficient of the resonance frequency can be made near zero, and the dielectric loss can be reduced.

In order to increase the effect of adding 2MgO.SiO ₂ (forsterite crystal) described above, it is necessary to reduce unreacted raw material components contained in the forsterite, and therefore, a mixture of magnesium oxide and silicon oxide. When preparing the above, it is preferable to mix magnesium oxide and silicon oxide so that the number of moles of magnesium is twice that of silicon.

  Next, the powder of the main component of the obtained dielectric ceramic composition, and zinc oxide, boron oxide, lithium oxide, and alkaline earth metal carbonate, which are raw materials of subcomponents of the dielectric ceramic composition, Are weighed in predetermined amounts, and then mixed to obtain a raw material mixed powder. In addition, the weighing of each raw material of the subcomponent is performed so that the content of each subcomponent is a desired ratio (part by mass) with respect to the main component in the completed dielectric ceramic composition. Moreover, mixing can be performed by mixing methods, such as dry mixing or wet mixing, for example, can be performed with the ball mill using solvents, such as a pure water and ethanol. The mixing time may be about 4 to 24 hours.

  The raw material mixed powder is preferably dried at a drying temperature of 100 to 200 ° C., more preferably 120 to 140 ° C. for about 12 to 36 hours.

  Next, the raw material mixed powder is calcined for about 1 to 10 hours at a temperature not higher than the firing temperature (860 to 1000 ° C.) described below, for example, 700 to 800 ° C. By carrying out calcination at a temperature lower than the firing temperature in this way, it is possible to suppress the forsterite in the raw material mixed powder from melting, and the finished dielectric ceramic composition contains forsterite in the form of crystals. Can be made.

  After pulverizing the raw material mixed powder after calcination, the raw material mixed powder is dried to obtain a dielectric ceramic composition. The pulverization can be performed by a pulverization method such as dry pulverization or wet pulverization. For example, the pulverization can be performed by a ball mill using a solvent such as pure water or ethanol. The pulverization time may be about 4 to 24 hours. Drying of the raw material mixed powder after pulverization is preferably performed at a processing temperature of 100 to 200 ° C., more preferably 120 to 140 ° C. for about 12 to 36 hours.

  As described above, the main component of the dielectric ceramic composition is obtained by performing calcination and pulverization twice in total at a time before mixing each raw material and after mixing each raw material into a raw material mixed powder. And a subcomponent are uniformly mixed to obtain a dielectric ceramic composition having a uniform material.

When the dielectric ceramic composition further contains Ag as an auxiliary component, for example, a raw material containing Ag may be added to the raw material mixed powder before calcination. As a raw material containing Ag, Ag in a metal state (hereinafter referred to as “metal Ag”) or a compound that becomes metal Ag by calcination is used. Examples of the compound that becomes metal Ag by calcination include silver nitrate (AgNO ₃ ), silver oxide (Ag ₂ O), silver chloride (AgCl), and the like.

  In addition, when the dielectric ceramic composition further contains Ag as a subcomponent, after adding the metal Ag to the raw material mixed powder after calcination instead of the raw material mixed powder before calcination, Drying may be performed.

  The dielectric ceramic composition of the present embodiment described above can be used, for example, for manufacturing a multilayer device that is a kind of high-frequency device. A multilayer device is made from a multilayer ceramic substrate composed of a plurality of ceramic layers in which dielectric devices such as capacitors and inductors are integrally formed. In this multilayer ceramic substrate, a plurality of green sheets formed of dielectric ceramic compositions having different dielectric properties are prepared, and a conductor material serving as an internal electrode is arranged between the green sheets, or through holes are formed in each green sheet. After the formation, a plurality of green sheets are stacked and fired simultaneously.

  In the production of the multilayer device, after mixing the dielectric ceramic composition of the present embodiment with an organic binder such as polyvinyl alcohol, acrylic or ethyl cellulose, the resulting mixture is molded into a sheet. Get a green sheet. As a green sheet molding method, a wet molding method such as a sheet method or a printing method may be used, or dry molding such as press molding may be used.

  Next, a plurality of the obtained green sheets and other green sheets having different dielectric properties are alternately laminated in a state in which an Ag-based metal serving as an internal electrode is disposed between the green sheets. Is cut to a desired dimension to form a green chip. After subjecting the obtained green chip to a binder removal treatment, the green chip is fired to obtain a sintered body. Firing is preferably performed, for example, in an oxygen atmosphere such as in air. Moreover, it is preferable that it is below the melting point of Ag type metal used as a conductor material, specifically, it is preferable that it is 860-1000 degreeC, and it is more preferable that it is 870-940 degreeC. By forming an external electrode or the like on the obtained sintered body, a multilayer device including an internal electrode made of an Ag-based metal can be obtained.

  Thus, in an electronic device such as a multilayer device obtained using the dielectric ceramic composition of the present embodiment, the content of Cu or Zn in the internal electrode is preferably 6% by mass or less. Since such an internal electrode is difficult to melt during firing, short-circuit defects and the like can be suppressed in the obtained electronic device. In the present invention, the dielectric porcelain composition and the electronic device formed using the dielectric porcelain composition preferably do not contain Cu, but if the amount does not impair the effects of the present invention. , Cu may be contained.

  The preferred embodiments of the dielectric ceramic composition according to the present invention have been described above, but the present invention is not necessarily limited to the above-described embodiments.

  For example, the dielectric ceramic composition according to the present invention may contain other compounds within a range that allows firing at a low temperature and does not hinder the effect of improving the Q · f value. For example, a dielectric loss can be suppressed small by containing manganese oxide with respect to the main component of a dielectric ceramic composition.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

[Sample No. 1-49]
The content (parts by mass) of Li ₂ O with respect to 100 parts by mass of the main component of the dielectric ceramic composition was changed so that the values shown in Table 1 were obtained. 1 to 49 dielectric ceramic compositions were prepared. And the sample for a measurement was each produced using the obtained dielectric magnetic composition, and these fr, (epsilon) r, Q * f value, and the sintered density were measured. Sample No. For 7, 14, 21, 28, 30 to 35, 42, 49, τf was also measured. These measurement results are shown in Table 1. The dielectric magnetic composition preparation method, measurement sample preparation method, and evaluation method thereof are all the following examples, except that the conditions (Li ₂ O content, sintering temperature) shown in Table 1 were changed. Sample No. shown as 21.

(Sample No. 21)
It is represented by the composition formula {α (xBaO · yNd ₂ O ₃ · zTiO ₂ ) + β (2MgO · SiO ₂ )}, α = 55 (volume%), β = 45 (volume%), x = 18.5 (mol) %), Y = 15.4 (mol%), z = 66.1 (mol%), and 6.0 parts by mass of ZnO and 2.0 parts by mass with respect to 100 parts by mass of the main component. Part B ₂ O ₃ , 0.6 part by mass of CaO, 0.20 part by mass of Li ₂ O, and 1.0 part by mass of Ag as subcomponents. 21 dielectric ceramic compositions were prepared by the following procedure.

First, BaCO ₃ , Nd (OH) ₃ , and TiO ₂ , which are main component raw materials, are molar ratios x, y, and z in xBaO · yNd ₂ O ₃ · zTiO ₂ obtained after calcining these are the above-mentioned Each was weighed to a value.

Pure water was added to the weighed raw materials to prepare a slurry having a slurry concentration of 25% by mass. This slurry was wet mixed in a ball mill for 16 hours and then dried at 120 ° C. for 24 hours to obtain a powder. The powder was calcined in air at 1200 ° C. for 4 hours to obtain a composition formula xBaO.yNd ₂ O ₃ .zTiO ₂ (x = 18.5 (mol%), y = 15.4 (mol%)). , Z = 66.1 (mol%)), a BaO—Nd ₂ O ₃ —TiO ₂ -based compound was obtained. Pure water was added to the BaO—Nd ₂ O ₃ —TiO ₂ compound to prepare a slurry having a slurry concentration of 25 mass%. This slurry was pulverized with a ball mill for 16 hours and then dried at 120 ° C. for 24 hours to produce a BaO—Nd ₂ O ₃ TiO ₂ -based compound powder.

Next, MgO and SiO ₂ which are other raw materials of the main component were weighed so that the number of moles of magnesium atoms was twice the number of moles of silicon atoms. Pure water was added to the weighed raw materials to prepare a slurry having a slurry concentration of 25% by mass. This slurry was wet mixed in a ball mill for 16 hours and then dried at 120 ° C. for 24 hours to obtain a powder. This powder was calcined in air at 1200 ° C. for 3 hours to obtain forsterite crystals (2MgO · SiO ₂ ). Pure water was added to the forsterite crystals to prepare a slurry having a slurry concentration of 25%. The slurry was pulverized with a ball mill for 16 hours and then dried at 120 ° C. for 24 hours to produce forsterite crystal powder.

Next, with respect to the mixture obtained by mixing the obtained BaO—Nd ₂ O ₃ TiO ₂ -based compound powder and forsterite crystal powder in a volume ratio of 55:45, subcomponents of the dielectric ceramic composition After mixing ZnO, B ₂ O ₃ , CaCO ₃ , and Li ₂ O as raw materials, pure water was further added to prepare a slurry having a slurry concentration of 25 mass%. This slurry was wet mixed in a ball mill for 16 hours and then dried at 120 ° C. for 24 hours to obtain a raw material mixed powder. The obtained raw material mixed powder was calcined at 750 ° C. for 2 hours in the air to obtain a calcined powder. To the obtained calcined powder, metal Ag, which is a subcomponent of the dielectric ceramic composition, was blended. Next, pure water was added to the calcined powder containing metal Ag to prepare a slurry having a slurry concentration of 25% by mass. This slurry was wet pulverized with a ball mill for 16 hours and then dried at 120 ° C. for 24 hours. 21 dielectric ceramic composition powders were obtained. Each amount of the _BaO-Nd 2 O 3 _ZnO for a mixture of powder of powder and forsterite crystals -TiO ₂ based _{compound, B 2 O 3, CaCO 3} , Li 2 O, and metallic Ag after completion In this dielectric ceramic composition, ZnO is 6.0 parts by mass, B ₂ O ₃ is 2.0 parts by mass, CaO is 0.6 parts by mass, and Li ₂ O is 0. It adjusted so that 20 mass parts and 1.0 mass part of metal Ag might be contained, respectively.

  Sample No. A powder of 21 dielectric ceramic composition added with a polyvinyl alcohol aqueous solution as a binder and granulated is molded into a cylindrical shape having a diameter of 12 mm and a height of 6 mm, and this is fired at a firing temperature of 920 ° C. for 1 hour. Sample No. 21 dielectric ceramics were obtained. Next, the surface of the dielectric ceramic was shaved to produce a cylindrical pellet having a diameter of 10 mm and a height of 5 mm. 21 measurement samples were obtained.

Sample No. The εr, Q · f value (unit: GHz), and τf (unit: ppm / K) indicating the dielectric properties of 21 measurement samples are measured according to Japanese Industrial Standard “Test Method for Dielectric Properties of Microwave Fine Ceramics” ( JISR 1627 (1996). In addition, the sample No. The sintered body density (unit: g / cm ³ ) of 21 measurement samples was measured. These measurement results are shown in Table 1. In the measurement of εr, Q · f value, and τf, the measurement frequency was 7.5 GHz. The resonance frequency f is measured in the temperature range of −40 to 85 ° C., and τf = [f _T −f _ref / f _ref (T−T _ref )] × 10 ⁶ (ppm / K) (1) Was used to calculate τf. Moreover, T in Formula (1) was 85 _degreeC , and reference temperature _Tref was -40 degreeC. Further, fr shown in Table 1 is a resonance frequency at 20 ° C. The sintered body density is preferably as high as possible, and particularly preferably over 4.0 g / cm ³ .

Sample No. From the measurement results of 15 to 21, the dielectric ceramic composition in which the content of Li ₂ O is 0.2 parts by mass with respect to 100 parts by mass of the main component can be fired at a firing temperature of 820 to 920 ° C. It was confirmed that after firing, a Q · f value of 1942-4756 GHz was exhibited. Sample No. From the measurement results of 22 to 42, the dielectric ceramic composition in which the content of Li ₂ O as a subcomponent is 0.4 to 1.62 parts by mass with respect to 100 parts by mass of the main component is 800 to 920 ° C. It was confirmed that it can be fired at a firing temperature and exhibits a Q · f value of 2005 to 5660 GHz after firing.

On the other hand, sample No. From the measurement results of 1 to 14, the dielectric ceramic composition whose Li ₂ O content is 0.04 parts by mass or less with respect to 100 parts by mass of the main component is sintered at the firing temperatures of 800 ° C. and 820 ° C. It was confirmed that no dielectric ceramic was obtained after firing. Therefore, the sample No. whose firing temperature was 800 ° C. or 820 ° C. was used. In 1, 2, 8, and 9, the fr, εr, Q · f value, and sintered density could not be measured.

Sample No. 43-49 and sample no. 15 to 42, the Q · f when the dielectric ceramic composition having a Li ₂ O content of 3.24 parts by mass with respect to 100 parts by mass of the main component is fired at 860 to 900 ° C. The value is the same for a dielectric ceramic composition in which the content of Li ₂ O is less than 3.24 parts by mass (0.20 to 1.62 parts by mass) with respect to 100 parts by mass of the main component at 860 to 900 ° C. It was confirmed that it was smaller than Q · f value when fired and less than 4000.

[Sample No. 50]
It is represented by the composition formula {α (xBaO · yNd ₂ O ₃ · zTiO ₂ ) + β (2MgO · SiO ₂ )}, α = 55 (volume%), β = 45 (volume%), x = 18.5 (mol) %), Y = 15.4 (mol%), z = 66.1 (mol%), and 6.0 parts by mass of ZnO and 2.0 parts by mass with respect to 100 parts by mass of the main component. Part B ₂ O ₃ , 0.6 part by mass of CaO, 0 part by mass of CuO, and 1.0 part by mass of Ag as subcomponents. 50 dielectric porcelain composition was added to Sample No. It was produced by the same method as 21.

  Sample No. Thermo-mechanical analysis (TMA) was performed on the molded body of each dielectric ceramic composition of 1, 8, 15, 22, 29, 36, 43, and 50. In TMA, each sample was heated from room temperature to 1100 ° C., and the expansion coefficient (unit:% by length) of each sample at each temperature was determined. In addition, the expansion coefficient of each sample was calculated with the dimension (length) of the molded body of each dielectric ceramic composition before starting the temperature increase (at room temperature) as 100%. Moreover, the temperature increase rate of each sample was 10 degree-C / min. Further, each sample was heated while continuously supplying 200 ml / min of air to the temperature rising atmosphere of each sample. Moreover, TMA was performed in a state where a measurement load of 3.0 g was continuously applied to each sample. The results of TMA are shown in FIG. In FIG. 1, the horizontal axis (Temperature) indicates the temperature of each sample, and the vertical axis (Expansion rate) indicates the expansion rate of each sample. Further, in FIG. 1, the temperature at which the expansion coefficient starts to decrease means the temperature at which the molded body of the dielectric ceramic composition starts to sinter.

As shown in FIG. 1, it was confirmed that the sintering curve shifted to a lower temperature side as the Li ₂ O content in the dielectric ceramic composition increased. That is, it was confirmed that the dielectric ceramic composition was sintered at a lower temperature and contracted at a lower temperature as the Li ₂ O content in the dielectric ceramic composition was increased.

Further, each sample containing Li ₂ O, particularly sample No. Nos. 15, 22, 29 and 36 are sample Nos. Containing CuO. As in the case of 50, it was confirmed that sintering was performed at a low temperature.

Sample No. It is a graph which shows the result of the thermomechanical analysis (TMA) with respect to 1, 8, 15, 22, 29, 36, 43, 50.

Claims (1)

As a main component, BaO—Nd ₂ O ₃ —TiO ₂ based compound, and 2MgO · SiO ₂ are included,
As a minor component, zinc oxide, boron oxide, alkaline earth metal oxide, and lithium compound,
When the mass of the lithium compound is converted to Li ₂ O, the content c of the lithium compound is 0.04 parts by mass <c <3.24 parts by mass with respect to 100 parts by mass of the main component. A dielectric ceramic composition characterized by the above.

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