JP5354320B2 - Ceramic substrate and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic substrate which has a large thermal expansion coefficient &alpha;, which has a property suitable for a high frequency substrate, which can be fired at a low temperature and which is excellent in substrate strength. <P>SOLUTION: The ceramic substrate containing Mg<SB>2</SB>SiO<SB>4</SB>as a main component and an ingredient for lowering a firing temperature has a thermal expansion coefficient &alpha; of 9.0 ppm/&deg;C or more and a ZnAl<SB>2</SB>O<SB>4</SB>content of 25 vol% or less (except zero). <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

The present invention relates to a ceramic substrate having a thermal expansion coefficient close to that of a printed wiring board, and more particularly to improvement of the bending strength of a ceramic substrate mainly composed of Mg ₂ SiO ₄ .

  For example, in the information communication field, the use frequency band tends to shift to a high frequency, and high frequency in the gigahertz (GHz) band is used in mobile communication such as satellite broadcasting, satellite communication, mobile phone and car phone. Yes.

  In the circuit board having the wiring layer used in the high frequency band as described above, a low dielectric constant board is required in order to reduce signal delay due to the capacitance between the wirings. Further, a substrate having a high Q value is required in order not to attenuate the high frequency signal. For the production of such a substrate, a low dielectric constant ceramic material (dielectric ceramic composition) is required, and development of a ceramic material having a relative dielectric constant εr of about 6 to 11 and a large Q value is desired. .

Mg ₂ SiO ₄ (forsterite) is a material with a very high Q value of Q · f = 200000 GHz or more and a very low dielectric loss, and the relative dielectric constant εr is also relatively low. It attracts attention as one of the low dielectric constant ceramic materials, and various glass ceramics containing a forsterite phase have been proposed (see Patent Document 1, Patent Document 2, etc.).

  For example, Patent Document 1 discloses a wiring substrate comprising an insulating substrate and a thin film wiring conductor layer formed on the surface thereof, and the insulating substrate has at least Si, Al, Mg as constituent elements. , Ba, rare earth elements RE and O, and at least one selected from a forsterite crystal phase and a garnite crystal phase as a crystal phase, and a Serdian crystal.

In Patent Document 2, as a crystal phase, a garnite crystal phase, a spinel crystal phase, a celsian crystal phase including an acicular crystal having an aspect ratio of 3 or more, and AlN, Si ₃ N ₄ , SiC, Al ₂ O ₃ , ZrO _{2 are used.} , low temperature co-fired ceramic sintered body containing at least one crystalline phase is disclosed selected from _{3Al 2 O 3 · 2SiO 2,} Mg 2 SiO 4.

Each of the insulating substrate described in Patent Document 1 and the ceramic sintered body described in Patent Document 2 is one in which each crystal phase is precipitated in glass by firing, and belongs to the category of so-called glass ceramics. is there.
JP-A-2005-93546 JP 2003-40668 A

  By the way, LTCC substrates that can be fired at a low temperature are widely used as inexpensive high-frequency substrates. Along with miniaturization and high integration of components, for example, devices in which bare chips, surface mount components (SMD), etc. are mounted on LTCC substrates, etc. In addition, it is also required to directly mount the LTCC substrate on a printed wiring board (PCB).

  In this case, the substrate itself is required to have further strength due to the low profile of the device and the like, and the printed wiring board and the printed wiring board There is a need for substrate materials having near thermal expansion coefficients. However, in the inventions described in the above-mentioned patent documents, the thermal expansion coefficient of the board is not taken into consideration at all, and how to design the LTCC board to realize a thermal expansion coefficient close to that of the printed wiring board. The fact is that it has hardly been examined.

  The present invention has been proposed in view of such conventional circumstances, has a thermal expansion coefficient close to that of a printed wiring board such as a glass epoxy board, has characteristics suitable for a high-frequency board, and low-temperature firing. Further, it is an object to provide a ceramic substrate having excellent substrate strength, and further to provide a manufacturing method thereof.

The present inventors have continued research for a long time in order to achieve the above-mentioned object. As a result, the following knowledge was obtained. First of all, by using Mg ₂ SiO ₄ as a dielectric material, by appropriately selecting low-temperature firing components and adjusting these compositions, a ceramic substrate having a large thermal expansion coefficient and capable of low-temperature firing can be realized. I understood it. However, in this case, insufficient strength becomes a problem. As a result of further investigations, it was found that the addition of ZnAl ₂ O ₄ was specifically effective in improving the strength.

The present invention has been completed based on these findings. That is, the ceramic substrate of the present invention is a ceramic substrate made of low-temperature fired ceramics containing Mg ₂ SiO ₄ and a low-temperature fired component as a main composition, and sintered with Mg ₂ SiO _{4. 2} SiO ₄ as a main component, ZnO, B ₂ O ₃ , CuO and RO (where R represents an alkaline earth metal) as a low-temperature calcining component, and the mass of Mg ₂ SiO ₄ is a The ratio of the mass b of ZnO to the total mass (a + b + c + d + e) where the mass of ZnO is b, the mass of B ₂ O ₃ is c, the mass of CuO is d, and the mass of RO is e, b / (a + b + c + d + e) There _{8% ~20%, B 2 O} 3 mass ratio of c c / (a + b + c + d + e) 3% to 10%, the ratio of the mass d of CuO d / (a + b + c + d + e There 2% to 8%, and the ratio e / (a + b + c + d + e) 1% to 4% of the mass e of RO, in a proportion of ZnAl ₂ O ₄ less 25% by volume (zero excluded.), Heat The expansion coefficient α is 9.0 ppm / ° C. or more, the relative dielectric constant εr is 7 ± 1, Q · f is 2000 GHz or more, and the bending strength is 100 MPa or more .

The ceramic substrate of the present invention contains Mg ₂ SiO ₄ and a low-temperature firing component as the main composition, and can be fired at a low temperature of 1000 ° C. or lower, for example. In addition, the coefficient of thermal expansion α is 9.0 ppm / ° C. or higher, which is larger than that of a normal ceramic substrate, and is close to that of a printed wiring board such as a glass epoxy board. Therefore, when mounted directly on a printed wiring board (PCB) However, the generation of stress due to the difference in thermal expansion coefficient is greatly reduced.

Furthermore, in the ceramic substrate of the present invention, the value of the coefficient of thermal expansion α is increased, and at the same time, the strength of the substrate is improved. In order to increase the value of the thermal expansion coefficient α in the ceramic substrate, for example, the ratio of Mg ₂ SiO ₄ needs to be increased. However, when the ratio of Mg ₂ SiO ₄ is increased, the substrate strength rapidly decreases. Therefore, in the ceramic substrate of the present invention, ZnAl ₂ O ₄ is added at a ratio of 25% by volume or less (zero is not included). The addition of ZnAl ₂ O ₄ is effective for improving the substrate strength, and a low-temperature fired ceramic substrate having excellent substrate strength is realized.

Moreover, in the ceramic substrate containing the Mg ₂ SiO ₄ and the low-temperature fired component, when an Ag conductor is formed on the substrate surface, a phenomenon is observed in which the conductor peripheral portion turns brown as the Ag melts. Although the quality of the ceramic substrate is greatly impaired by the occurrence of the color change, the addition of ZnAl ₂ O ₄ is also effective in preventing the color change. By adding ZnAl ₂ O ₄ , it is possible to suppress discoloration around the conductor.

  According to the present invention, a ceramic substrate having a thermal expansion coefficient close to that of a printed wiring board such as a glass epoxy board, characteristics suitable for a high-frequency board, capable of low-temperature firing, and excellent substrate strength is provided. It is possible to provide. In addition, according to the present invention, even when a conductor is formed on the substrate surface with Ag or the like, the conductor peripheral portion is not discolored, and a high-quality ceramic substrate can be provided.

  Hereinafter, embodiments of a ceramic substrate to which the present invention is applied will be described in detail.

The ceramic substrate of the present invention is a low-temperature fired ceramic substrate formed of a dielectric material containing Mg ₂ SiO ₄ (forsterite) as a main composition and a low-temperature fired component. Mg ₂ SiO ₄ has a single Q · f of 200,000 GHz or more, and a low dielectric loss material can be realized by using this as the main component. Therefore, it is conceivable that the main component is 100% Mg ₂ SiO ₄ , but it is also possible to add known additives as necessary for adjusting the dielectric constant, for example. Examples of the additive include magnesium titanate (MgTiO ₃ ) having a relative dielectric constant εr = 17 and calcium titanate (CaTiO ₃ ) having a relative dielectric constant εr = 200. In this case, since the Q value of both is lower than the Q value of forsterite, the Q value of the substrate obtained by the addition tends to decrease, and it is necessary to fully consider the addition amount.

In Mg ₂ SiO ₄ (forsterite), the stoichiometric composition is MgO: SiO ₂ = 2: 1. However, the composition is not limited to this and may be deviated from the above composition. However, if the composition deviates greatly from the stoichiometric composition, the predetermined characteristics may not be obtained. Therefore, MgO: SiO ₂ = 1.9: 1.1 to 2.1: 0.9. It is preferable.

Mg ₂ SiO ₄ (forsterite) is suitable as a constituent component of the main composition from the viewpoint of the thermal expansion coefficient α. Mg ₂ SiO ₄ (forsterite) has a large thermal expansion coefficient α, and if the ratio of Mg ₂ SiO ₄ (forsterite) in the main composition is increased, a ceramic substrate having a large thermal expansion coefficient α can be realized. . However, for example, when 100% Mg ₂ SiO ₄ is used, low-temperature firing becomes difficult and the substrate strength cannot be ensured.

Therefore, in the ceramic substrate of the present invention, the relative permittivity εr ≦ 8, Q ≧ 2000, the thermal expansion coefficient is obtained by optimizing the ratio of Mg ₂ SiO ₄ (forsterite) and using a low-temperature firing component together. A ceramic substrate capable of low-temperature firing at a temperature of α ≧ 9.0 ppm / ° C. or higher and 1000 ° C. or lower is realized. Composition and the Mg 2 _SiO 4 _{(forsterite),} the type and composition of the low-temperature co-fired component may be set in a range satisfying the properties. In particular, regarding the thermal expansion coefficient α of the ceramic substrate, by setting α ≧ 9.0 ppm / ° C. or more, the thermal expansion coefficient of the glass epoxy substrate (for example, about 9 to 14 ppm / ° C.) can be made close to the value, For example, even when the ceramic substrate of the present invention is directly mounted on a printed wiring board, it is possible to suppress the generation of stress due to a difference in thermal expansion coefficient.

As the low-temperature firing component, any material can be used as long as it is sintered at a temperature lower than that of Mg ₂ SiO ₄ (forsterite), and various oxides may be selected and used. The ratio of the low-temperature fired component is arbitrary, but the ceramic substrate of the present invention is not a glass ceramic in which the ceramic component is dispersed in the glass component, but a low-temperature fired ceramic in which Mg ₂ SiO ₄ (forsterite) is sintered. There is a need to set the ratio of the low-temperature firing component in consideration of this point.

In addition, Mg ₂ SiO _{4 as} a main component is a low dielectric loss material as described above, and the dielectric constant εr is as low as about 6 to 7, and is a material that meets the requirements for a low dielectric constant. However, if Mg ₂ SiO _{4 is used} alone, the bending strength is low, which is a serious problem in practical use. Therefore, it is preferable to improve the bending strength by selecting and adding an appropriate oxide as the low-temperature firing component.

As a result of repeated studies by the present inventors, it is effective to add ZnO, B ₂ O ₃ , CuO and RO (where R represents an alkaline earth metal) as the low-temperature firing component. Therefore, in the ceramic substrate of the present invention, it is preferable to add these four components to the main component (Mg ₂ SiO ₄ ) to obtain a main composition. The amount of each component added in the main composition has an optimum range and is preferably added within a predetermined range.

First, about ZnO, it is preferable that the addition amount shall be 8 mass%-20 mass%. That is, when the mass of Mg ₂ SiO ₄ is a, the mass of ZnO is b, the mass of B ₂ O ₃ is c, the mass of CuO is d, and the mass of RO is e, the total mass (a + b + c + d + e) It is preferable that the ratio b / (a + b + c + d + e) of the mass b of ZnO is 8% to 20%. If the amount of ZnO added [ratio of mass b of ZnO b / (a + b + c + d + e)] is less than 8% by mass, a predetermined effect cannot be obtained and the bending strength may be insufficient. Conversely, if the added amount of ZnO [ratio of mass b of ZnO to the total mass b / (a + b + c + d + e)] exceeds 20% by mass, Q decreases and it becomes difficult to achieve Q · f = 2000 GHz or more. There is a fear.

The B ₂ O _3, it is preferable that the added amount of 3 wt% to 10 wt%. That _is, the mass of B 2 _{O 3} is taken as c, be the total mass of the (a + b + c + d + e) the ratio of the mass c of _B 2 _{O 3} with respect to c / (a + b + c + d + e) 3% to 10% preferred. When the addition amount of B ₂ O ₃ [ratio c / (a + b + c + d + e) of the mass c of B ₂ O _{3 to} the total mass] is less than 3% by mass, Q is lowered and Q · f = 2000 GHz or more is achieved. Can be difficult. Conversely, if the amount of B ₂ O ₃ added [ratio c / (a + b + c + d + e) of the mass c of B ₂ O _{3 to} the total mass] exceeds 10% by mass, the substrate density cannot be obtained sufficiently and sufficient strength is obtained. Cannot be obtained.

  About CuO, it is preferable to make addition amount into 2 mass%-8 mass%. That is, when the mass of CuO is d, the ratio d / (a + b + c + d + e) of the mass d of CuO to the total mass (a + b + c + d + e) is preferably 2% to 8%. When the addition amount of CuO [ratio d / (a + b + c + d + e) of the mass d of CuO to the total mass] is less than 2% by mass, the substrate density cannot be sufficiently obtained, so the substrate firing temperature needs to be higher. is there. In this case, since simultaneous firing with the electrode becomes difficult, the use of the substrate is limited. Conversely, if the amount of CuO added [ratio d / (a + b + c + d + e) of the mass d of CuO to the total mass] exceeds 8% by mass, Q decreases and it becomes difficult to achieve Q · f = 2000 GHz or more. There is a fear.

  For RO (where R represents an alkaline earth metal), the addition amount is preferably 1% by mass to 4% by mass. That is, when the mass of RO is e, the ratio e / (a + b + c + d + e) of the mass e of RO to the total mass (a + b + c + d + e) is preferably 1% to 4%. If the amount of RO added [ratio of RO mass e to the total mass e / (a + b + c + d + e)] is less than 1% by mass, the substrate density cannot be sufficiently obtained, so the substrate firing temperature needs to be higher. is there. In this case, since simultaneous firing with the electrode becomes difficult, the use of the substrate is limited. Conversely, if the amount of RO added [ratio of RO mass e to the total mass e / (a + b + c + d + e)] exceeds 4% by mass, Q decreases and it becomes difficult to achieve Q · f = 2000 GHz or higher. There is a fear.

  In the RO, R (alkaline earth metal) may include Ca, Sr, and Ba. As the RO, one or more of these alkaline earth metal oxides may be added.

As described above, by adding the four components (ZnO, B ₂ O ₃ , CuO and RO) as low-temperature firing components to the dielectric ceramic composition mainly composed of Mg ₂ SiO ₄ (forsterite), The bending strength can be greatly improved, and the dielectric properties of Mg ₂ SiO ₄ (forsterite) can be utilized. For example, when the mass of Mg ₂ SiO ₄ is a, the mass of ZnO is b, the mass of B ₂ O ₃ is c, the mass of CuO is d, and the mass of RO is e, the ZnO with respect to the total mass (a + b + c + d + e) The ratio b / (a + b + c + d + e) of mass b is 8% to 20%, the ratio c of mass c of B ₂ O ₃ is c / (a + b + c + d + e) is 3% to 10%, and the ratio d / (a + b + c + d + e) of CuO is 2 % To 8%, RO mass e ratio e / (a + b + c + d + e) is 1% to 4%, the bending strength is 100 MPa or more, the relative permittivity εr is 7 ± 1, and Q · f is 2000 GHz. It is possible to provide the above dielectric ceramic composition.

Further, the ratio b / (a + b + c + d + e) of the mass b of ZnO to the total mass (a + b + c + d + e) is 12% to 20%, the ratio of the mass c of B ₂ O ₃ c / (a + b + c + d + e) is 3% to 9%, and CuO By setting the mass d ratio d / (a + b + c + d + e) to 4% to 8% and the RO mass e ratio e / (a + b + c + d + e) to 2% to 4%, it is possible to achieve a bending strength of 200 MPa or more. is there.

The above is the configuration of the main composition used for the ceramic substrate of the present invention. In the ceramic substrate of the present invention, ZnAl ₂ O ₄ is further contained in a proportion of 25% by volume or less (excluding zero). It is a big feature.

As described above, when Mg ₂ SiO ₄ (forsterite) is used, the substrate strength is insufficient. This lack of substrate strength can be improved to some extent by selecting a low-temperature firing component, but can be further improved by adding ZnAl ₂ O ₄ . Addition of ZnAl ₂ O ₄ is also effective for preventing discoloration around the Ag conductor. By adding ZnAl ₂ O ₄ , even when the Ag conductor is co-fired, the conductor periphery does not turn brown.

The amount of ZnAl ₂ O ₄ added is preferably 25% by volume or less (excluding zero) with respect to the main composition. If the added amount of ZnAl ₂ O ₄ exceeds 25% by volume, the bending strength may be lowered. On the other hand, if the amount of ZnAl ₂ O ₄ added is zero, the strength improving effect cannot be obtained, and the bending strength of the substrate may be insufficient. A more preferable range of the content (addition amount) of ZnAl ₂ O ₄ is 5% by volume to 20% by volume.

In order to produce the ceramic substrate of the present invention, the ZnAl ₂ O ₄ is added to the main composition and fired. Hereinafter, the manufacturing method of the ceramic substrate of this invention is demonstrated. To manufacture the ceramic substrate of the present invention, first, Mg ₂ SiO ₄ (forsterite), which is the main component of the main composition, is manufactured. Specifically, in the mixing step, MgO that is a raw material for Mg ₂ SiO ₄ (forsterite) and SiO ₂ are mixed. These raw materials may be mixed by dry mixing or wet mixing. In the case of wet mixing, for example, pure water or ethanol may be used as a mixed solvent, and mixing may be performed using a ball mill or the like. The mixing time may be, for example, about 4 hours to 24 hours.

  When the mixing is performed by wet mixing, the mixture is sufficiently dried in the drying step. In the drying step, for example, drying is performed at a temperature of 100 ° C. to 200 ° C., preferably 120 ° C. to 140 ° C. for about 12 hours to 36 hours.

The mixed and dried raw material mixture is calcined in the next calcining step. The calcination is a process of reacting MgO and SiO _{2 as} raw materials to synthesize Mg ₂ SiO ₄ (forsterite) crystals, and most of the calcination is performed by performing Mg ₂ SiO ₄ (forsterite). ) Can be obtained. Note that the calcining is performed at a temperature of 1000 ° C. to 1500 ° C., preferably 1100 ° C. to 1350 ° C. The treatment time is preferably about 1 to 24 hours.

After the calcination, the calcined product is pulverized in a pulverization step and further dried in a drying step. In the pulverization step, the calcined product is pulverized into a powder by dry pulverization or wet pulverization. When the pulverization step 4 is performed by wet pulverization, for example, pulverization may be performed using a ball mill or the like using pure water or ethanol as a mixed solvent. The mixing time may be, for example, about 4 hours to 24 hours. In the drying step 5, for example, drying is performed at a temperature of 100 ° C. to 200 ° C., preferably 120 ° C. to 140 ° C. for about 12 hours to 36 hours. This makes it possible to obtain a raw material powder of _Mg 2 SiO ₄ as a main component (forsterite).

In addition, as a raw material powder of Mg ₂ SiO ₄ (forsterite), it is also possible to use commercially available forsterite. However, in that case, instead of using commercially available forsterite as it is, for example, commercially available forsterite is wet-ground using a ball mill or the like, for example, at a temperature of 100 ° C to 200 ° C, preferably 120 ° C to 140 ° C, It is preferable to use one that has been dried for about 12 to 36 hours.

Next, a predetermined amount of raw materials (ZnO, B ₂ O ₃ , CuO and RO) of low-temperature firing components are added to the Mg ₂ SiO ₄ (forsterite) raw material powder, mixed in the mixing step, and dried in the drying step. To do. The mixing step may be carried out by dry mixing or wet mixing as in the previous mixing step. In the case of wet mixing, for example, pure water or ethanol may be used as a mixed solvent, and mixing may be performed using a ball mill or the like. The mixing time may be, for example, about 4 hours to 24 hours. The drying step may be performed under the same conditions as the previous drying step. For example, the drying is performed at a temperature of 100 ° C. to 200 ° C., preferably 120 ° C. to 140 ° C. for about 12 hours to 36 hours.

  Further, in the calcining step, the obtained raw material mixed powder is calcined. This calcining step is performed at a temperature not higher than the firing temperature, for example, 700 ° C. to 800 ° C., and the calcining time is about 1 hour to 10 hours. By performing this calcining step 8 at a temperature of about 700 ° C. to 800 ° C., forsterite can be contained in the calcined product in the form of crystals.

  Thereafter, the calcined product is pulverized in the pulverization step, and the powder pulverized in the drying step is dried. The pulverization step is performed by dry pulverization or wet pulverization. When the pulverization step is performed by wet pulverization, for example, pulverization is performed using a ball mill or the like using pure water or ethanol as a mixed solvent. The mixing time may be, for example, about 4 hours to 24 hours. In the drying step, for example, drying is performed at a temperature of 100 ° C. to 200 ° C., preferably 120 ° C. to 140 ° C. for about 12 hours to 36 hours. By performing calcining and pulverization in this way, the main component and the low-temperature firing component can be made uniform.

The dielectric ceramic composition which becomes the main composition is thus obtained. Next, ZnAl ₂ O ₄ is added, and further, an organic binder such as polyvinyl alcohol, acrylic, or ethyl cellulose is added, mixed with a ball mill or the like, and then molded into a desired shape. The molding may be performed by wet molding such as a sheet method or a printing method, or by dry molding such as press molding, and the molding method can be appropriately selected according to the shape to be molded. The amount of ZnAl ₂ O ₄ added is 25% by volume or less (excluding zero) with respect to the main composition. ZnAl ₂ O ₄ is added in the above ratio with respect to the main composition, mixed, then formed into a predetermined substrate shape and fired. The addition of ZnAl ₂ O ₄ may be performed simultaneously with the mixing of the raw material powder described above, and the same effect can be obtained thereby.

  The formed compact is fired in the firing step to obtain a sintered body. Firing is preferably performed in an atmosphere containing oxygen, such as air. Although the firing temperature can be arbitrarily set, it can be fired at a low temperature by adding the low temperature firing component, and can be fired at a temperature below the melting point of the electrode (for example, 1000 ° C. or less).

  Through the above steps, a ceramic substrate having a sufficient bending strength, a relative dielectric constant εr of 7 ± 1, Q · f of 2000 GHz or more and excellent dielectric characteristics can be obtained. The obtained ceramic substrate has a thermal expansion coefficient α of 9.0 ppm / ° C. or more, and the difference from the thermal expansion coefficient of a printed wiring board such as a glass epoxy board is small. Further, even when an Ag conductor or the like is formed on the surface of the ceramic substrate and fired simultaneously, the peripheral portion of the conductor does not change color.

  Hereinafter, specific examples to which the present invention is applied will be described based on experimental results.

Study on main composition High-purity Mg ₂ SiO ₄ , ZnO, B ₂ O ₃ , CuO, CaCO ₃ , SrCO ₃ , and BaCO ₃ were prepared as raw material powders. The average particle diameter of each raw material powder is 0.1 μm to 1.0 μm. Weighed so that the additive amount of the subcomponents (ZnO, B ₂ O ₃ , CuO, CaO, SrO, BaO) with respect to Mg ₂ SiO ₄ is as shown in Table 1, and wet-mixed for 16 hours using a ball mill. went. The obtained slurry was sufficiently dried and then calcined in the atmosphere at 700 ° C. for 2 hours to obtain a calcined body. After finely pulverizing with a ball mill until the calcined body had an average particle size of 1.0 μm, the finely pulverized powder was dried. Next, an appropriate amount of PVA (polyvinyl alcohol) is added as a binder, granulated and molded, and then fired at 950 ° C. or 975 ° C. (1300 ° C. or 1350 ° C. for Samples 1 and 2) for 4 hours, and sintered. Got the body.

  About each obtained sintered compact (sample 1-sample 17), bending strength, relative dielectric constant (epsilon) r, Q, and thermal expansion coefficient (alpha) were measured. The bending strength was measured according to Japanese Industrial Standard JIS R1601. The results are shown in Table 1.

For example, Sample 1 and Sample 2 made only of Mg ₂ SiO ₄ have a large thermal expansion coefficient α, but are difficult to sinter at low temperatures, and are fired by setting the firing temperature to 1300 ° C. or 1350 ° C. Became possible. However, even in that case, the bending strength was extremely low.

  On the other hand, Samples 3 to 17 to which a low-temperature firing component was added could be fired even at a low temperature of 950 ° C. or 975 ° C., and a certain degree of bending strength could be realized. However, in the sample 15 marked with *, the bending strength, the relative dielectric constant εr, and the value of Q did not satisfy the requirements.

From the results in Example Table 1, sample 7 was the main composition, ZnAl ₂ O ₄ was added to the finely pulverized powder of the main composition, granulated and molded, and then calcined at 960 ° C. or 950 ° C. for 4 hours, A ceramic substrate was produced. Table 2 shows the bending strength, relative dielectric constants εr, Q, and thermal expansion coefficient α of the obtained ceramic substrates (Examples 1 to 4).

As is clear from Table 2, the bending strength is greatly improved by adding ZnAl ₂ O ₄ . Further, the thermal expansion coefficient α is 9.0 ppm / ° C. or more in all the examples, and the relative dielectric constant εr and Q are also good.

Further, the addition amount of ZnAl ₂ O ₄ and 5 vol% to 30 vol%, was examined the relationship between the firing temperature and bending strength at each additive amount. The main composition was the same as Sample 7. The results are shown in FIG. When the addition amount of ZnAl ₂ O ₄ was 30% by volume, the bending strength was reduced when the firing temperature was 940 ° C.

It is a characteristic diagram showing a relationship between firing temperature and bending strength at each amount of time that the amount of ZnAl ₂ O ₄ was 5 vol% to 30 vol%.

Claims (2)

A ceramic substrate comprising a low-temperature fired ceramic in which Mg ₂ SiO ₄ and a low-temperature fired component are included as a main composition, and Mg ₂ SiO ₄ is sintered,
The main composition contains Mg ₂ SiO ₄ as a main component, and contains ZnO, B ₂ O ₃ , CuO and RO (where R represents an alkaline earth metal) as a low-temperature calcining component,
When the mass of Mg ₂ SiO ₄ is a, the mass of ZnO is b, the mass of B ₂ O ₃ is c, the mass of CuO is d, and the mass of RO is e, the amount of ZnO with respect to the total mass (a + b + c + d + e) The ratio b / (a + b + c + d + e) of mass b is 8% to 20%, the ratio c of mass c of B ₂ O ₃ is c / (a + b + c + d + e) is 3% to 10%, and the ratio d / (a + b + c + d + e) of CuO is 2 % To 8%, RO mass e ratio e / (a + b + c + d + e) is 1% to 4%,
ZnAl ₂ O ₄ is contained in a proportion of 25% by volume or less (excluding zero) ,
A ceramic substrate having a thermal expansion coefficient α of 9.0 ppm / ° C. or more, a relative dielectric constant εr of 7 ± 1, Q · f of 2000 GHz or more, and a bending strength of 100 MPa or more . _2. The ceramic substrate according to claim 1, wherein the content of ZnAl ₂ O ₄ is 5% by volume to 20% by volume.

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