JP2003063858A - Porcelain composition which has low dielectric constant and method for manufacturing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porcelain composition which can be sintered at a low temperature, which has a low dielectric constant and small loss in the high frequency wave zone, and whose temperature dependency is small, and which has neither diffusion nor migration when Ag is used as an internal electrode, and a method for manufacturing the composition. SOLUTION: The porcelain composition which has a low dielectric constant contains, in terms of oxides in mass %, SiO2 of 26.0-38.0%, ZnO of 34.0-49.0%, Bi2 O3 of 1.0-5.7%, MgO of 1.0-6.0%, TiO2 of 3.5-15.1%, Li2 O of 2.0-6.0%, K2 O of 2.0-9.0% and B2 O3 of 0.5-3.0%. The method for manufacturing the porcelain composition comprises carrying out the wet blending with a ball mill of powder raw materials consisting of prescribed quantities of the oxides, drying and calcining at 700-900 deg.C the blended raw materials, and thereafter pulverizing and sizing the calcined materials, and then kneading on adding a binder and forming the sized materials into a predetermined shape, and printing electric conductors or the like and carrying out the lamination or the like, and finally carrying out the sintering at 800-925 deg.C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to several GHz to several tens GHz.
The present invention relates to a dielectric porcelain composition used in electronic parts and modules targeted for high frequency regions.

[0002]

2. Description of the Related Art In recent years, with the development of high-speed mass communication of information and mobile communication, in integrated circuits, not only downsizing and densification but also several GHz are used for handled signals.
Furthermore, utilization of frequencies in a band higher than that is being studied, and a material suitable for such a high frequency band is also required for a dielectric ceramic composition used for a component or a substrate. The performance required for this porcelain composition is that the relative permittivity is low in the high frequency band and that the dielectric loss tan δ is small, that is, the Q value is high.

In general, the lower the relative permittivity, the faster the signal propagation speed in the dielectric, so it is desirable that the relative permittivity ε _r be low for high frequency band applications. In terms of signal transmission, the smaller the loss, the better, and the Q value needs to be as high as possible. In addition, the function as a dielectric may be used for, for example, a filter or a resonator, but in this case, the absolute value of the temperature coefficient τ _f of the resonance frequency is as small as possible in order to operate stably with respect to temperature changes. thing,
That is, it is important that the temperature dependence is small.

The conductive material used as an internal conductor or an internal electrode on the mounting substrate is required to be thin due to miniaturization and high density. Therefore, the higher the specific resistance value is, the more loss is caused. Since it causes heat generation, it is desirable that the resistance be as low as possible. Such low resistance materials are
Although Ag, Cu, Au, or the like, all of these metals have a low melting point of around 1000 ° C.

In an integrated circuit using a porcelain composition as a substrate, a circuit pattern is printed on a green sheet by using a paste-like conductor material, and these sheets are laminated and integrally fired to form a conductive material and a porcelain composition. And are simultaneously sintered and formed. However, if the firing temperature is close to or higher than the melting point of the conductor metal, diffusion or fluidization may occur, and the conductor may become thin or disappear.

As a porcelain composition which can be fired at such a low temperature, there is so-called glass ceramics. This is a mixture of ceramic aggregate and glass.
The softening of glass enables firing at low temperatures, and various improvements have been made by combining aggregate and glass. For example, the invention disclosed in Japanese Patent Laid-Open No. 10-297960 discloses zinc orthosilicate (Zn ₂ SiO ₄ ) and cristobalite (SiO ₂ ) as an aggregate and SiO as a glass.
_2- Li ₂ O-ZnO is used, and the firing temperature is 800 to 1000 ° C.
It states that ceramics with low loss and low relative permittivity can be obtained.

However, since glass ceramics contain a large amount of glass composition, the dielectric constant is generally low, but the Q value is also low, and therefore the loss in the high frequency band is large.
In addition, since the temperature coefficient τ _{f of the} resonance frequency is large, the performance deterioration due to these becomes a problem when the frequency band becomes high. In many cases, the glass composition and the ceramic composition are separately prepared and mixed to form a green sheet, which complicates the manufacturing process.

[0008]

The object of the present invention is that low temperature sintering is possible, it is particularly suitable for using Ag for the internal electrode, the dielectric constant is low, the loss in the high frequency band is small, and the temperature dependence is high. To provide a porcelain composition having a small dielectric constant and a method for producing the same.

[0009]

The present inventors have made various studies to improve the performance of porcelain compositions used in a high frequency band of 2 GHz or higher. The target performance at that time is as follows.

Ag is used for the internal electrodes or internal conductors. Although Ag has a smaller specific resistance than Cu or Au, it has a melting point lower than these, so that conductor wear is likely to occur due to diffusion during firing. Further, Ag is apt to cause the movement of metal ions, that is, dielectric breakdown during use due to migration. The porcelain composition should have as little diffusion or migration of these Ag as possible.

From the investigation of the diffusion state, the firing temperature was 92
It was found that if the temperature is 5 ° C. or less, Ag diffusion is greatly suppressed. Therefore, as the characteristic target that the porcelain composition should have, the permittivity ε _r is 10 or less, the product of Q (reciprocal of dielectric loss tangent tan δ) and frequency f ( _expressed in GHz) is 3500 or more, and the temperature of the resonance frequency is The coefficient was set to -30 to +30 ppm / ° C, and the composition obtained with this characteristic at a firing temperature of 925 ° C or lower was examined. Here, the relative permittivity ε _r , the dielectric loss tan δ, and the temperature coefficient τ _f are measured by using the both-end short-circuited dielectric resonator method (Hacke-Coleman method).

Since the Q value has a frequency dependency and tends to decrease as the frequency increases, the fQ value (the value of the product of f and Q), which is assumed to exhibit a substantially constant value depending on the material,
We compared the superiority and inferiority of the loss. As a result of comparatively examining the performances of various porcelain compositions, the materials judged to be superior to the conventional materials are the materials having fQ of 3500 or more as described above.

The temperature dependence of the resonance frequency is measured as a temperature coefficient τ _f of the resonance frequency by the both ends short-circuit type dielectric resonator method. If this τ _f is −30 to +30 ppm / ° C., that is, if its absolute value is 30 ppm / ° C. or less, it is considered that the improvement can be made compared with the conventional material.

Glass or glass ceramics can be sintered at such a low temperature of 925 ° C. or lower. However, since the Q value is small as described above, the loss is large and the temperature dependence is large. Further, in the case of glass ceramics, a glass composition and a ceramics composition are separately prepared and mixed and fired, so that the number of steps is increased. Therefore, we decided to pursue the possibility of achieving the above target performance with a ceramic porcelain composition.

Si as a main constituent of ceramics
O ₂ and ZnO were used. These are considered to be essential components for obtaining a high frequency dielectric having a low relative permittivity and a high Q value.

With respect to these two components, various components and their contents were examined with the aim of lowering the sintering temperature, suppressing the diffusion of Ag, and ensuring the above-mentioned respective performances. As a result, Bi ₂ O ₃ , Li ₂ O, K ₂ O and B ₂
It has been found that the composite addition of 4 components of ₂ O ₃ is effective in lowering the sintering temperature without deteriorating the Q value. If each component is added alone to reduce the sintering temperature, a large amount of each component must be contained, resulting in a large decrease in Q value. However, when added in combination, Q
It was possible to reduce the sintering temperature by reducing the decrease in the value.

By additionally including TiO ₂ and MgO in a composition obtained by adding these four components to SiO ₂ and ZnO in combination, a decrease in Q value and an increase in relative permittivity can be suppressed to reduce the resonance frequency. It was possible to reduce the temperature coefficient τ _f . Inclusion of TiO ₂ reduces τ _f . However, along with this, the relative dielectric constant increases, and in addition, the Q value decreases significantly. On the other hand, it has been found that when MgO is also included, τ _f can be reduced without significantly decreasing the Q value. The addition of only MgO had no effect of reducing τ _f , but only slightly improved the Q value. TiO
Such effects can be obtained by adding together with ₂ , but the reason is not clear.

The porcelain composition thus obtained was co-fired by using Ag as an internal electrode and was investigated. As a result, Ag diffusion was not observed at firing temperatures up to 925.degree. In many cases, the inclusion of a low melting point component such as B ₂ O ₃ tends to cause Ag diffusion, but the temperature is 925 ° C.
It is considered that such diffusion is suppressed because the suppression to the following and the reduction of the amount by adding Bi ₂ O ₃ , Li ₂ O, and the like in comparison to the case of adding them alone can suppress such diffusion. Further, as a result of investigating the use of these porcelain compositions in a wet atmosphere, it was confirmed that migration did not occur.

From the above examination results, the present invention was completed by further confirming the limits at which the effects of the respective components can be effectively exhibited. The gist of the present invention is as follows. (1) Oxide composition ratio in mass% is SiO ₂ : 26.0 to 3
8.0%, ZnO: 34.0~49.0%, Bi 2 O 3: 1.0~5.7
%, MgO: 1.0 to 6.0%, TiO ₂ : 3.5 to 15.0%, L
i ₂ O: 2.0 to 6.0%, K ₂ O: 2.0 to 9.0% and B ₂ O
₃ : A low dielectric constant porcelain composition characterized by containing 0.5 to 3.0%. (2) A powder raw material of each oxide is blended in a required amount, wet-mixed in a ball mill, dried, calcined at 700 to 900 ° C., pulverized and sized, and then a binder is added and kneaded. The method for producing a low dielectric constant porcelain composition according to the above (1), which comprises printing and laminating an electric conductor and the like and then sintering at 800 to 925 ° C.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The composition range of the porcelain composition of the present invention is limited as follows. Here, the contained composition is mass% expressed in the form of oxide.

The content range of SiO ₂ is 26.0 to 38.0%. This is because if the content is less than 26.0%, the temperature coefficient τ _f of the resonance frequency is lower than −30 ppm / ° C., that is, the absolute value of the temperature coefficient exceeds 30 ppm / ° C., and the temperature dependence becomes large. On the other hand, when the content exceeds 38.0%, the Q value in the high frequency range decreases. Desirable 31.1 to 34.1%
Is the range.

ZnO is 34.0 to 49.0%. ZnO is S
iO_TwoTogether with the basic component of the porcelain composition of the present invention,
Either below 34.0% or above 49.0%
Also τ _fExceeds the range of -30 to + 30ppm / ℃,
The temperature dependence becomes large. 42.0 to 45.6% preferred
It is to be included range.

Bi ₂ O ₃ is 1.0 to 5.7% and K ₂ O is 2.0 to
9.0%, Li ₂ O 2.0-6.0%, B ₂ O ₃ 0.5-3.0%
Is contained in each. By making the composition containing these components at the same time, it is possible to sinter into a dense porcelain composition at a firing temperature of 925 ° C. or lower. When the content of each component is less than the above lower limit, the effect of lowering the sintering temperature becomes insufficient, and a dense porcelain composition cannot be obtained. However, in any case, when the content exceeds the above upper limit, the Q value decreases and the loss increases. In particular, if Bi ₂ O ₃ is too much, Ag will be diffused during firing. More preferable content ranges are 2.4 to 2.6% for Bi ₂ O ₃ and K _{2 respectively.}
O is 2.2-8.8%, Li ₂ O is 3.3-4.1%, and B ₂ O
₃ is 0.6 to 2.7%.

TiO ₂ is 3.5 to 15.0%, MgO is 1.0 to 6.
0% is also included. TiO ₂ is contained in order to reduce the temperature coefficient of resonance frequency, but it is necessary to contain TiO ₂ in an amount of 3.5% or more to obtain this effect. However, the relative permittivity increases and the Q value decreases, so the content of TiO ₂ is
Must be below 15.0%. MgO is this TiO
_It has the effect of suppressing the increase of the relative dielectric constant and the decrease of the Q value due to the inclusion of ₂ and at least 1.0% to obtain the effect.
The above is contained. However, since MgO deteriorates the sinterability, the maximum content is 6.0%. The preferred content range is T
iO ₂ is 7.2 to 8.9% and MgO is 1.9 to 2.3%.

As the components other than the above, there are various impurities mixed in the raw materials, but they are not particularly limited as long as they do not adversely affect the characteristics of the obtained ceramic composition.

The porcelain composition of the present invention is manufactured according to the usual method of firing a ceramic material. First, a required amount of each oxide powder of each component serving as a raw material is prepared and sufficiently mixed with a ball mill. Oxide powder is K
_In the case of an unstable material such as ₂ O in which the oxide itself is hygroscopic, other forms such as carbonate and hydrogen carbonate may be used. In that case, the molar amount corresponding to the amount of oxide after sintering is used. Add a quantity of powder. After mixing, calcination is carried out, and after confirming that the formation reaction of the ceramic is carried out, pulverization and sizing is performed. The calcination is preferably performed at a temperature that is not high in order to sufficiently sinter in the final firing, but if it is too low, a reaction for forming a ceramic does not occur, so it is preferable to set the temperature to 700 to 900 ° C.

A binder or the like is added to the sized powder, and the mixture is kneaded and molded, and if necessary, printing of conductive circuits, lamination, processing into a final shape, etc., and firing at 800 to 925 ° C. to obtain a porcelain composition. . If the firing temperature is less than 800 ° C, the sintering may not be sufficiently performed and the desired properties may not be obtained due to lack of denseness. Further, since the internal conductor of Ag may diffuse or migrate due to it, the firing temperature is preferably set to 925 ° C.

[0028]

[Example] [Example 1] 95% or more high-purity SiO ₂ ,
ZnO, Bi ₂ O ₃ , MgO, TiO ₂ , and K ₂ O (as KHCO ₃ ) having a purity of 90% or more and Li ₂ O (Li
₂ CO ₃ ) and the composition of the composition shown in Table 1 was used to prepare a porcelain composition.

[0029]

[Table 1]

Pure water was added to a raw material powder having a predetermined composition in a ball mill using zirconia balls, and the mixture was wet-mixed for 24 hours.
It was calcined at 0 ° C for 2 hours. After the calcination, it was confirmed by X-ray diffraction that the sintering reaction had occurred. Further, pure water was added in a ball mill made of zirconia balls and crushed for 24 hours, and after drying, a powder having a particle size of 1 to 4 μm was obtained. . A binder of a 10% PVA aqueous solution was added, and the mixture was granulated, molded into a cylindrical test piece having a diameter of 15 mm and a height of 8 mm at a pressure of 1 t / cm ² using a mold, and then fired in the atmosphere.

In this case, each sample is preliminarily tested and calcined at a temperature of 840 to 980 ° C. using a part of the test piece to find the temperature required for sufficient densification, and the temperature is regarded as the calcining temperature. All sample specimens were fired. The firing time is 2 hours in each case.

The sintered porcelain composition test piece after firing was polished at its bottom surface to be smoothed, and then the relative dielectric constant ε _r and the dielectric loss tan δ (or Q = 1 / tan) were measured by the both ends short-circuit type dielectric resonator method.
δ) was determined. Since the dielectric loss changes depending on the measured resonance frequency f, the magnitude of the loss was evaluated by the fQ value of the product of f and Q, which is assumed to be a constant value in the measured material without being influenced by the frequency. The temperature coefficient τ _f of the resonance frequency was obtained by measuring the resonance frequency in the temperature range of 25 ° C. to 85 ° C. and calculating the rate of change based on the resonance frequency f ₀ at 25 ° C. The results of these measurements are also shown in Table 2.

[0033]

[Table 2]

The Ag diffusion and migration were evaluated as follows. Approximately 10% by mass of PV of the powder amount as a binder is added to the powder after the above calcination.
A solvent consisting of xylene, toluene and butanol to which B and a small amount of a plasticizer was added was thoroughly mixed to form a slurry. Using this slurry, a tape forming machine was used to form a green sheet having a target thickness of 100 μm after firing. . Screen-print 20 μm thick Ag paste for inner layer electrodes on the green sheet, preheat to 120 ° C, press-press at 150 kgf / cm ² and then cut to the same temperature as the sample whose dielectric constant and Q value were measured. In the same manner, firing was performed for 2 hours to produce a 4225 size capacitor laminate having 9 electrode layers.

Note that the trial numbers 16, 22, 24, 29, and 36, which required a firing temperature of 940 ° C. or higher when measuring the dielectric constant and the Q value, are not suitable for using Ag electrodes. So
No capacitor laminate was prepared.

In order to investigate the presence or absence of Ag diffusion, a cross section perpendicular to the stacking direction was polished so that the internal electrodes could be observed, and SEM observation and EDS analysis of the porcelain composition portion were carried out. For migration, apply Ag paste to the electrode end surface of the capacitor laminate after firing and apply 70
After baking at 0 ° C., barrel plating of Ni / Sn was performed, PCT (Pressure Cooker Test) at 130 ° C., 90% RH, DC25V, 9 hours was performed as an external terminal, and then the insulation resistance was measured. The results are also shown in Table 2.

The diffusion of Ag is trial No. 26 containing a large amount of Bi ₂ O _3.
Other than that, none was observed. In addition, the insulation resistance after PCT was higher than 10 ⁹ Ω in all the measured samples, and it was determined that migration did not occur.

Regarding the high-frequency characteristics, as can be seen from the results in Table 2, when the content of each oxide component is within the range specified by the present invention, the initial target relative permittivity ε _r is 10 in both cases. In the following, the Qf value is 3500 or more, the temperature coefficient τ _f of the resonance frequency is −30 to +30 ppm / ° C., and the firing temperature for producing the substrate, that is, the sinterable temperature is 925 ° C. which is the applicable limit of the Ag conductor. Or less is obtained.

On the other hand, when the composition is out of the range specified in the present invention, the required characteristics are not satisfied because the required firing temperature is too high, the low fQ value and the temperature dependency are large. ing.

As described above, the porcelain composition of the present invention has a low relative permittivity, a low loss in a high frequency band, and a small temperature dependence, does not diffuse or migrate Ag used as an electrode, and has a low firing temperature. You can get its excellent characteristics with.

[0041]

The dielectric porcelain composition of the present invention has a low relative permittivity, a low loss in a high frequency band, and a small temperature dependency, and its characteristics can be obtained at a low firing temperature. Therefore, Ag having a low specific resistance can be used as an internal conductor or an electrode, and in combination with excellent high frequency performance, it can be used as a substrate for high frequency, miniaturization and high density of electronic circuits. It is suitable.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4G030 AA02 AA04 AA07 AA16 AA32                       AA35 AA37 AA43 BA12 GA08                       GA14 GA22 GA27                 5G303 AA07 AB06 AB10 AB11 AB15                       AB20 BA12 CA01 CB02 CB05                       CB14 CB16 CB17 CB30 CB35                       CB38 DA04 DA05

Claims (2)

[Claims] 1. An oxide composition ratio of mass% is SiO ₂ :
26.0~38.0%, ZnO: 34.0~49.0%, Bi 2 O 3: 1.
0~5.7%, MgO: 1.0~6.0%, TiO 2: 3.5~15.0
_{%, Li 2 O: 2.0~6.0%} , K 2 O: 2.0~9.0% and _B 2 _{O 3: 0.5~3.0%} low dielectric ceramic composition characterized by containing a. 2. A powder raw material of each oxide is blended, wet-mixed in a ball mill, dried, calcined at 700 to 900 ° C., pulverized and sized, and then a binder is added and kneaded. The method for producing a low dielectric constant porcelain composition according to claim 1, wherein the conductor is printed and laminated, and then sintered at 800 to 925 ° C.