JP4872990B2 - Ceramic powder for green sheet, multilayer ceramic substrate, and method for producing multilayer ceramic substrate - Google Patents

Description

  The present invention relates to a ceramic powder for a green sheet and a multilayer ceramic substrate. More specifically, the present invention relates to a ceramic powder for a green sheet that gives a low-temperature fired ceramic substrate excellent in high-frequency characteristics such as microwaves and millimeter waves in the fields of information communication and automobiles, and a multilayer ceramic substrate.

  A low-temperature fired multilayer ceramic substrate has been put to practical use as a technology that supports advanced information communication. Such a low-temperature fired multilayer ceramic substrate is a multilayer substrate with built-in circuit wiring in which a circuit pattern is formed on a green sheet made of ceramic powder for a green sheet using a conductor paste, and a plurality of green sheets are laminated and fired at a low temperature. It is. Such a low-temperature fired multilayer ceramic substrate is also referred to as a co-fired substrate because a green sheet (ceramic material) and a conductor paste (conductor material) are fired simultaneously.

  As a ceramic powder for a green sheet used for producing such a low-temperature fired multilayer ceramic substrate, a mixture of a glass component and a crystalline inorganic compound (for example, alumina) is generally used. Here, low-temperature firing at about 1000 ° C. or less is possible by selecting a glass component having a softening point of 1000 ° C. or less because it is caused by rapid densification accompanying the softening of the glass component in the sintering process. Become.

In recent years, in the information communication field, the frequency band of radio waves to be used has been increased due to the increase in communication equipment and the number of channels, and the microwave and millimeter wave bands have been used. The higher the frequency of the radio wave used, the more it will change into heat in the circuit, that is, the transmission loss will increase. Therefore, users aiming to improve the performance of the product are required to reduce the transmission loss in the high frequency band. Yes. Factors that greatly affect transmission loss in such a high frequency band include the dielectric properties of the ceramic substrate and the electrical conductivity of the conductor. Among these, the dielectric characteristics of the ceramic substrate are particularly important, and the contribution rate increases as the frequency increases. For this reason, from the viewpoint of reducing transmission loss in the high frequency band, there is a need for a ceramic powder for green sheets that provides a ceramic substrate with excellent dielectric characteristics (that is, low dielectric constant ε _r and dielectric tangent tan δ).

  However, the dielectric characteristics of such a ceramic substrate have a problem that it is generally difficult to achieve compatibility with low-temperature firing. In particular, when Ag having excellent electrical conductivity is used as a conductor material, low-temperature firing at a temperature of 900 ° C. or less is required, so that it is more difficult to achieve both the above dielectric properties and low-temperature firing.

Examples of conventional ceramic powder for green sheets include, for example, 12-59.6% by weight alumina, 18-69.6% by weight borosilicate glass, 1-40% by weight anorthite crystals, There is a ceramic powder for green sheets composed of 5% by weight of celsian crystals (see, for example, Patent Document 1). Ceramic powder for such green sheets, at a low temperature sintered without selecting the firing atmosphere, and the relative dielectric constant epsilon _r is low, it is possible to provide a ceramic substrate having excellent mechanical strength.

Moreover, the composition of the aluminosilicate type | system | group glass with low dielectric constant (epsilon) _r and dielectric loss tangent tan-delta is also disclosed (for example, refer patent document 2 and nonpatent literature 1).

JP-A-6-305770 JP 11-292567 A Keizai Miyazato, 1 other, “Glass Fiber and Glass Cloth”, Journal of Japan Institute of Electronics Packaging, 2001, Vol. 4, No. 2, p. 98-101

  However, Patent Document 1 does not show the problem of transmission loss in a high frequency band (microwave or millimeter wave band), nor does it show a method for achieving both dielectric properties and low-temperature firing. In fact, the ceramic substrate obtained from the ceramic powder for green sheets disclosed in Patent Document 1 has a higher transmission loss in the high frequency band than the alumina substrate, which is a conventional material, and cannot be said to be sufficient for the high frequency band. Generally, alumina has less transmission loss in the high frequency band than borosilicate and aluminosilicate glasses, so qualitatively, the amount of alumina added in the ceramic powder for green sheets of Patent Document 1 is increased. By doing so, it seems that transmission loss in the high frequency band can be reduced to some extent. However, such a ceramic powder for green sheets may cause problems such as water absorption and insufficient strength, and therefore, a glass component with low transmission loss in a high frequency band is desired.

On the other hand, although Patent Document 2 and Non-Patent Document 1 disclose a composition of an aluminosilicate glass having a low relative dielectric constant ε _r and a dielectric loss tangent tan δ, a glass composition having this composition is used for glass fibers. However, since the softening temperature is high and the viscosity is high even after softening, it is not suitable as a component of the ceramic powder for green sheets.

  The inventors initially prepared ceramic powder for green sheets containing the glass composition of Patent Document 2 and alumina powder in various blending ratios, and pores in the low-temperature fired ceramic substrate obtained from the ceramic powder for green sheets The rate and dielectric properties in the microwave band were evaluated. Moreover, the low-temperature baking ceramic substrate was produced from the ceramic powder for green sheets of patent document 1 as a comparison object, and the same evaluation was performed. As a result, the low-temperature fired ceramic substrate obtained from the ceramic powder for green sheets using the glass powder of Patent Document 2 reflects better dielectric characteristics than the low-temperature fired ceramic substrate of Patent Document 1, and transmission loss is generally low. There were few.

  However, when the compounding ratio of the glass component is 40 to 70 vol%, the porosity of general low-temperature fired ceramic substrates including Patent Document 1 is approximately 2%, whereas the glass powder of Patent Document 2 is used. The porosity of the low-temperature fired ceramic substrate produced in this way was as large as about 20%. That is, it is considered that the low-temperature fired ceramic substrate produced from the ceramic powder for green sheets using the glass powder of Patent Document 2 has high hygroscopicity and does not satisfy the environmental resistance required for the product. As a factor for increasing the porosity of the low-temperature fired ceramic substrate, it is assumed that the glass composition of Patent Document 2 has a high viscosity after being softened. In other words, in order to become a dense ceramic, a process in which the softened glass component flows into the gaps between the alumina powders is necessary, but if the viscosity of the glass component is high, this process is completed within a practical time. It is thought that it cannot be made.

  In addition, in some ceramic powders for green sheets studied by changing the glass composition, silver diffusion occurs when multiple green sheets with circuit patterns formed using silver-based conductor paste are laminated and integrated for simultaneous firing. As a result, the softening point of the glass component in the vicinity of the conductor is lowered, the shrinkage behavior is changed, and there is a problem that warpage and wrinkles occur. Although this warp and wrinkle can be suppressed by blending an alkali metal oxide (Na2O or K2O) into the glass component, as described in Non-Patent Document 1, the warpage and wrinkles can be suppressed by blending the alkali metal oxide. Transmission loss in the high frequency band increases (that is, the dielectric characteristics decrease).

  The present invention has been made to solve the above-described problems, and can be fired at a low temperature of 900 ° C. or lower, and has excellent dielectric characteristics in a high frequency band (microwave and millimeter wave band). It is an object of the present invention to provide a ceramic powder for a green sheet and a multilayer ceramic substrate that provide a low-temperature fired ceramic substrate having low hygroscopicity and small warpage and wrinkles when fired simultaneously with a silver-based conductor paste.

Ceramic powder for a green sheet according to the present invention is a ceramic powder for a green sheet containing a glass powder and alumina powder, the glass powder is a SiO ₂ of 39 wt% or less 35% by weight or more, 9 weight and% or more 17 wt% or less of _Al 2 _{O 3,} and _B 2 _{O 3} follows 40 wt% 21 wt% or more, 10 to 20% by weight of R'O (where, R 'is, Mg, and at least one kind of) selected from the group consisting of Ca and Ba, and Li ₂ O 2 wt% or less than 0.2 wt%, 2 wt% or less 0.5% by weight or more _MO 2 ( However, M may include at least one kind of) and selected from the group consisting of Ti and Zr, is 100% by weight in whole, an average particle diameter of the alumina powder is at 1.3μm over 5μm or less Yes, the glass powder and the aluminum The weight ratio with na powder is 4: 6 to 6: 4 .

  According to the present invention, low-temperature firing at 900 ° C. or lower is possible, excellent dielectric properties in a high frequency band (microwave or millimeter wave band), low hygroscopicity, and co-firing with a silver-based conductor paste. It is possible to provide a ceramic powder for a green sheet and a multilayer ceramic substrate that give a low-temperature fired ceramic substrate with small warpage and wrinkles.

Embodiment 1 FIG.
The present inventor says that the viscosity of the glass component varies depending on its composition, and in general, the viscosity can be reduced by blending alkali metal oxide, alkaline earth metal oxide or boric acid. Several tests were conducted based on the findings and attempts were made to improve various properties. As a result, viscosity can be reduced by increasing the amount of alkaline earth metal oxide and boric acid in the glass component, and by increasing the amount of boric acid, the high frequency band (microwave It has been found that a low-temperature fired ceramic substrate having excellent dielectric properties in the band and millimeter wave band can be provided.

  Furthermore, the present inventor has limited the alkali metal oxide to Li2O, and without canceling out the dielectric characteristics in the high frequency band (microwave and millimeter wave band) improved by the blending of boric acid, It has been found that there is an effect of suppressing warpage and wrinkles.

That is, the present invention is a ceramic powder for green sheets containing glass powder and alumina powder, wherein the glass powder is 35 to 39% by weight of SiO ₂ and 9 to 17% by weight of Al ₂ O ₃ . 21-40 wt% B ₂ O ₃ , 10-20 wt% R′O (where R ′ is at least one selected from the group consisting of Mg, Ca and Ba), 0 0.2 to ₂ wt% Li ₂ O and 0.5 to 2 wt% MO ₂ (wherein M is at least one selected from the group consisting of Ti and Zr), It is a ceramic powder for a green sheet characterized by 100% by weight.

  The present invention also provides an insulating layer obtained by firing a green sheet containing the ceramic powder for green sheets at 800 to 900 ° C., and a wiring obtained by firing a conductor paste containing silver at 800 to 900 ° C. A multilayer ceramic substrate characterized in that the wiring layer provided is laminated.

  Furthermore, the present invention provides a step of obtaining a green sheet by forming a slurry containing the above-mentioned ceramic powder for green sheets into a sheet and drying, and printing a wiring on the green sheet using a conductive paste containing silver It is a method for producing a multilayer ceramic substrate including a step and a step of laminating green sheets printed with the conductor paste, pressing and integrating them, and firing at 800 to 900 ° C.

  In addition, the present glass composition does not contain alkali metals such as sodium and potassium, and a low loss can be obtained in a high frequency range, but as a feature of the present composition, crystallization of the glass may hardly occur, During sintering, the glass viscosity after softening is lowered, and undesirable phenomena such as adhesion to the firing base plate and an increase in the amount of glass penetrating into the conductor are observed. Such a phenomenon occurs depending on the firing conditions and the firing structure and does not necessarily occur. However, when it occurs, it can be suppressed by optimizing the size of fillers such as alumina contained therein. This is presumed to be due to the fact that by using a filler having a certain average particle size, the voids between the fillers become large and the amount of glass staying in the voids increases, so that the amount of glass to be exposed decreases. The upper limit of the filler size is defined by whether or not an effective mounting process is possible in practice, and the following size range is advantageous from this viewpoint. As the filler, alumina is generally used because it is excellent in characteristics and cost in a low-temperature fired multilayer substrate. However, this effect is not limited to alumina, and silicon nitride, aluminum nitride are not particularly limited. The same effect is recognized and effective in various fillers such as zirconium oxide. The effective particle size range of the filler is preferably 1.3 μm or more and 5 μm or less as an average particle size, although it varies depending on the suppression level desired for the above phenomenon. When the thickness is 1.3 μm or less, the suppressing effect is not recognized. When the thickness is 5 μm or more, the surface roughness of the base material is increased although the suppressing effect is obtained, which tends to be an obstacle in mounting. Furthermore, when high reliability of the wire bond is required, it is preferable to set the thickness to 3 μm or less because a sufficiently small surface roughness can be obtained for the mounting process.

  The ceramic powder for green sheets of Embodiment 1 in this invention contains the glass powder containing a predetermined component, and an alumina powder.

The glass powder in the present embodiment is SiO ₂ , Al ₂ O ₃ , B ₂ O 3 and R′O (where R ′ is at least one selected from the group consisting of Mg, Ca and Ba). Is), Li ₂ O, and MO ₂ (wherein M is at least one selected from the group consisting of Ti and Zr) as constituent components.

Among the glass constituents, SiO ₂ is a glass substance that vitrifies itself. However, the softening point of pure SiO ₂ far exceeds 1000 ° C., and the glass containing a large amount of SiO ₂ has a high softening point.

The content of SiO _{2 in} the present invention is 35 to 39% by weight, preferably 37 to 39% by weight. If the content of SiO ₂ is less than 35% by weight, glass cannot be stably obtained from the raw material melt, or chemically stable glass cannot be obtained. On the other hand, when the content of SiO ₂ exceeds 39% by weight, the softening point becomes high and low-temperature firing becomes difficult.

B ₂ O ₃ is also a glass material that vitrifies itself. Such _B 2 _{O 3} is, can lower the softening point by blending a glass containing SiO _2. B ₂ O ₃ forms a boron-oxygen bond in the glass skeleton. Such a bond is stronger in covalent bond than a silicon-oxygen bond and has a small electric dipole moment, so that it becomes inactive against electromagnetic waves and transmission loss can be reduced.

However, when the amount of B ₂ O ₃ increases in the glass, oxygen coordination similar to boric acid is generated, so that the glass becomes chemically unstable. Then, when the green sheet using such glass and the silver-based conductor paste are simultaneously fired, silver is remarkably diffused.

In the present invention, the content of B ₂ O ₃ is 21 to 40% by weight, preferably 22 to 28% by weight. If the content of B ₂ O ₃ is less than 21% by weight, desired dielectric properties cannot be obtained. On the other hand, if the content of B ₂ O ₃ exceeds 30% by weight, the glass becomes chemically unstable as the content increases, and the water resistance, acid resistance and alkali resistance decrease. Therefore, it is necessary to devise a process such as gold plating that is usually performed in the manufacture of high-frequency components. Specifically, it is necessary to devise such as neutralizing the plating bath or imparting a moisture-proof effect with a fluororesin or the like. However, if the content of B ₂ O ₃ exceeds 40% by weight, the chemical stability of the glass is remarkably reduced, so that a high-frequency component having desired characteristics cannot be obtained even if the above-described measures are taken.

R′O which is an alkaline earth metal oxide (where R ′ is at least one selected from the group consisting of Mg, Ca and Ba) and Li ₂ O which is an alkali metal oxide are Although it does not vitrify itself, it is a glass modifier that imparts various properties. Such R′O and Li ₂ O exist in a state in which a chemically basic alkali metal and alkaline earth metal are present in a state close to ions in a molecular-level network existing in glass, and the glass is modified to form glass. Since the skeleton is cut, the viscosity can be lowered. Further, Li 2 _O is an alkali metal oxide, it is also possible to suppress the silver diffusion.

However, in such a network, the potential of the binding energy of alkali metal and alkaline earth metal is gentle compared to the glass skeleton, so that when the amount of alkaline earth metal oxide and alkali metal oxide increases, dielectric relaxation occurs. The transmission loss increases. However, since lithium is the lightest element among alkali metals and has a short bonding distance, the natural frequency of the electric dipole moment is high and the value of the moment is small. Therefore, an increase in transmission loss can be suppressed by limiting the alkali metal to Li ₂ O.

  The content of R′O in the present invention (where R ′ is at least one selected from the group consisting of Mg, Ca and Ba) is 10 to 20% by weight, preferably 16 to 18% by weight. %. When the content of R′O is less than 10% by weight, the viscosity of the glass increases. On the other hand, if the content of R′O exceeds 20% by weight, glass cannot be stably obtained from the raw material melt, or desired dielectric properties cannot be obtained.

The content of Li ₂ O is 0.2 to 2% by weight, preferably 0.5 to 1% by weight. When the content of Li ₂ O is less than 0.2% by weight, the viscosity of the glass becomes high and silver diffusion cannot be suppressed. Moreover, when the content of Li ₂ O exceeds 2% by weight, desired dielectric properties cannot be obtained.

Al ₂ O ₃ is also a glass modifier that does not vitrify itself, but provides various properties. Such Al2O3 can improve chemical stability.

The content of Al ₂ O ₃ is 9 to 17% by weight, preferably 12 to 16% by weight. When the content of Al ₂ O ₃ is less than 12% by weight, the glass becomes chemically unstable as the content increases, and the water resistance, acid resistance and alkali resistance decrease. Therefore, it is necessary to devise a process such as gold plating that is usually performed in the manufacture of high-frequency components. Specifically, it is necessary to devise such as neutralizing the plating bath or imparting a moisture-proof effect with a fluororesin or the like. However, when the content of Al ₂ O ₃ is less than 9% by weight, the chemical stability of the glass is remarkably lowered, so that a high-frequency component having desired characteristics cannot be obtained even if the above-described measures are taken. On the other hand, if the content of Al ₂ O ₃ exceeds 17% by weight, glass cannot be stably obtained from the raw material melt.

MO ₂ (where M is at least one selected from the group consisting of Ti and Zr) is also a glass modifier that does not vitrify itself but imparts various properties. Such MO ₂ can impart desired viscosity and fluidity to the glass.

The content of MO ₂ (wherein M is at least one selected from the group consisting of Ti and Zr) in the glass is 0.5 to 2% by weight, preferably 0.5 to 1% by weight. It is. If the MO ₂ content is less than 0.5% by weight, it is difficult to obtain desired viscosity and fluidity. On the other hand, if the content of MO ₂ exceeds 2% by weight, desired dielectric properties cannot be obtained.

  Furthermore, it is also possible to mix | blend ZnO and CuO as a structural component from a viewpoint of providing much more favorable viscosity and fluidity | liquidity to glass. In this case, the content of ZnO in the glass is preferably more than 0% by weight and 10% by weight or less, more preferably 4 to 6% by weight. When the content of ZnO exceeds 10% by weight, desired dielectric properties cannot be obtained due to a decrease in the proportion of other glass components. Further, the content of CuO in the glass is preferably more than 0% by weight and 0.5% by weight or less. When the content of CuO exceeds 0.5% by weight, desired dielectric properties cannot be obtained.

  The glass in the present embodiment only needs to have the final glass composition within the above range. For example, a plurality of glasses having a glass composition outside the above range are combined to have a glass composition in the above range. It may be prepared.

  The glass powder in the present embodiment can be prepared by mixing and melting the above components and then pulverizing them according to a conventionally known method. In addition, what is necessary is just to set a melting temperature suitably according to a glass composition.

  The alumina powder in the present embodiment is not particularly limited, and a commercially available product can be used. The average particle diameters of the glass powder and the alumina powder in the present embodiment are not particularly limited, but are preferably more than 1 μm and less than 5 μm, more preferably 1.5 μm or more and 2.5 μm or less. preferable. If the average particle size is within this range, the shrinkage amount of the ceramic after firing can be reduced and the warpage of the fired product can be reduced, and an appropriate density can be given to the ceramic after firing to provide good electrical characteristics. .

  The weight ratio of the glass powder and the alumina powder in the ceramic powder for green sheets of the present embodiment is preferably in the range of 2: 3 where the ratio of the glass powder is small to 3: 2 where the ratio of the glass powder is large. Preferably it is 1: 1. If the weight ratio of the alumina powder is too large, the density of the ceramic after firing becomes low (less than 98%), and open pores remain, and the electrical characteristics may deteriorate (especially increase transmission loss) due to humidity. On the other hand, when the weight ratio of the glass powder is too large, the shrinkage amount of the ceramic after firing becomes large, and the warp of the fired product may become so large that it cannot be practically used.

  The ceramic powder for green sheets of the present embodiment can be obtained by mixing the above powders in the above proportions according to a conventionally known method. The mixing method is not particularly limited, and may be mixed using a ball mill or the like. Note that it is preferable to use a hard alumina ball or zirconia ball having high purity from the viewpoint of preventing impurities from being mixed.

  The green sheet ceramic powder thus prepared can be used to produce a multilayer ceramic substrate.

  The multilayer ceramic substrate of the present embodiment is obtained by firing an insulator layer obtained by firing a green sheet containing the ceramic powder for green sheets at 800 to 900 ° C. and a conductor paste containing silver at 800 to 900 ° C. A wiring layer provided with the obtained wiring is laminated.

  Such a multilayer ceramic substrate of the present embodiment includes a step of obtaining a green sheet by forming a slurry containing the above-mentioned ceramic powder for green sheets into a sheet and drying, and using a conductive paste containing silver, It can be manufactured by a manufacturing method including a step of printing wiring on a sheet, and a step of laminating a green sheet on which the conductor paste is printed, pressing and integrating, and baking at 800 to 900 ° C. .

  Here, the slurry containing the ceramic powder for green sheets can be prepared by adding an organic binder, a plasticizer, a dispersant and an organic solvent to the ceramic powder for green sheets of the present invention.

  The organic binder is not particularly limited, and polyvinyl butyral, acrylic resin, or the like can be used. The plasticizer is not particularly limited, and dioctyl phthalate, di-n-butyl phthalate, polyethylene glycol, and the like can be used. The dispersant is not particularly limited, and triolein or the like can be used. The organic solvent is not particularly limited, and alcohols such as toluene and ethanol can be used. The amount of the organic binder, plasticizer, dispersant, and organic solvent is not particularly limited as long as it becomes a slurry, and may be appropriately adjusted according to the type of ceramic powder for green sheets.

  The method of forming the slurry containing the ceramic powder for green sheets into a sheet is not particularly limited, and depending on the thickness of the green sheet to be produced, a doctor blade method, an extrusion method, a roll coater method, a printing method, etc. Can be used.

  The conductive paste containing silver is preferably a silver-based paste containing a conductive component mainly composed of Ag, such as Ag—Pd or Ag—Pt, from the viewpoint of conductivity, and is the most excellent Ag paste. More preferably.

  It is also possible to form a via hole in the green sheet before the step of printing the wiring on the green sheet.

  In the process of laminating green sheets on which conductor paste is printed, pressing and integrating, and firing at 800 to 900 ° C., the pressing method is not particularly limited, and hydrostatic press in warm water Can be done.

  Moreover, it is preferable to perform the heat degreasing process for the purpose of degreasing before baking at 800-900 degreeC. In the heat degreasing treatment for the purpose of such degreasing, the heat degreasing treatment temperature is preferably 300 to 500 ° C. If it is the temperature of this range, sufficient degreasing | defatting can be performed and generation | occurrence | production of a swelling, peeling, etc. can be prevented at the time of baking (baking at 800-900 degreeC) aiming at densification. Moreover, what is necessary is just to set heat degreasing process time suitably according to the magnitude | sizes of a green sheet etc., and it is preferable that it is 5 to 10 hours.

  Moreover, it is preferable that baking at 800-900 degreeC is 1-2 hours from a viewpoint of performing sufficient densification at low temperature.

  In addition, the temperature increase rate at the time of moving from the heat degreasing process for the purpose of degreasing to the baking for the purpose of densification (firing at 800 to 900 ° C.) is not particularly limited, and the size of the green sheet or the like. It may be set appropriately according to

  The multilayer ceramic substrate manufactured in this way can be fired at a low temperature of 900 ° C. or lower, has excellent dielectric properties in a high frequency band (microwave or millimeter wave band), has low hygroscopicity, and is silver-based. Warpage and wrinkles are small when fired simultaneously with the conductive paste.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated concretely, this invention is not limited to the following Example.

[Examples 1 to 12 and Comparative Examples 1 to 11]
According to the glass composition of Table 1, each glass component was mixed and melted at 1400 to 1600 ° C., and then ground using a stamp mill or a ball mill to prepare a glass powder having an average particle diameter of 2 μm.

  Next, 50 g of the glass powder and 50 g of alumina powder having an average particle diameter of 2 μm (purity 99% or more) were mixed using a ball mill to prepare a ceramic powder for green sheets, and then PVD, phthalic acid was added to the powder. An appropriate amount of di-n-butyl, triolein and ethanol was further added to prepare a slurry.

  Next, a green sheet having a thickness of about 100 μm was produced by using this slurry by a doctor blade method.

  After stacking 30 green sheets and integrating them by isostatic pressing in warm water, firing was performed at 850 ° C. for 1 hour to prepare a low-temperature fired ceramic substrate sample. This low-temperature fired ceramic substrate sample was cut using water as a coolant and processed to a diameter of about 1.3 mm and a length of about 40 mm. The dielectric properties in the microwave band of this low-temperature fired ceramic substrate sample were evaluated by a perturbation method using a TM010 resonator having a resonance frequency of about 10 GHz. Moreover, the porosity in the sample was calculated from the difference between the specific gravity of the ceramic powder for green sheets and the specific gravity of the low-temperature fired ceramic substrate sample.

  Meanwhile, a predetermined circuit was printed on the green sheet using an Ag conductor paste. Six green sheets were stacked and integrated by hydrostatic pressure pressing in warm water, and then fired at 850 ° C. for 1 hour to prepare a multilayer ceramic substrate sample. Next, the obtained multilayer ceramic substrate sample was processed into 1 inch (2.54 cm) square. In this multilayer ceramic substrate sample, it was evaluated whether or not a practical multilayer substrate without warping could be obtained. As a judgment criterion for practicality in such evaluation, it was judged that the degree of warpage was 50 μm or less per inch having practicality, and that exceeding 50 μm per inch was not practical. The results are shown in Table 2.

  As shown in Table 2, each of the multilayer ceramic substrate samples of Examples 1 to 12 has a small product of non-dielectric constant and dielectric loss tangent and excellent dielectric characteristics, and has a low porosity, and is a fired substrate. There was also practicality.

  On the other hand, the multilayer ceramic substrate samples of Comparative Examples 1, 2, 3 and 11 had a low porosity and no warpage of the fired substrate, but had a large product of non-dielectric constant and dielectric loss tangent.

  Further, the multilayer ceramic substrate samples of Comparative Examples 4 and 5 had low porosity and good dielectric properties, but warped the fired substrate.

  Moreover, although the multilayer ceramic substrate samples of Comparative Examples 6 and 8 had good dielectric properties, they had high porosity and high hygroscopicity. Therefore, it is considered that the multilayer ceramic substrate samples of Comparative Examples 6 and 8 are not suitable for use in a sealed package or a circuit board.

  Moreover, in the multilayer ceramic substrate sample of Comparative Example 7, the measurement after the firing was difficult and the measurement sample could not be obtained, so the relative permittivity and dielectric loss tangent could not be measured. From this, it is considered that the multilayer ceramic substrate sample of Comparative Example 7 is unstable with respect to moisture.

  Furthermore, although the multilayer ceramic substrate samples of Comparative Examples 9 and 10 had a low porosity, the product of the non-dielectric constant and the dielectric loss tangent was large, and the fired substrate was warped.

Embodiment 2. FIG.
The ceramic powder for green sheets used in Embodiment 2 includes the glass powder shown in Example 2 in Embodiment 1 and alumina powder. In the same manner as in the first embodiment, a laminate including 9 layers of green sheets and having a circuit pattern with an Ag conductor was formed. The produced laminate has a configuration in which all laminated layers have circuit patterns and the circuit patterns are printed on the back surface. Such a laminate was prepared using a green sheet with the average particle diameter of the alumina powder shown in Table 3 varied, fired at 850 ° C., densified, and an evaluation substrate was prepared. The setter is a general alumina porous setter. The conductor surface roughness was measured with a stylus type surface roughness meter by scanning a length of 500 μm and measuring the size between the maximum and minimum unevenness. This was done 6 points and the average value was shown. Regarding the evaluation of fusion with the setter, ◯ indicates that the fusion does not occur, △ indicates that the fusion occurs but can be easily removed, and × indicates that the fusion is strong enough that it cannot be removed without using a tool. evaluated. In the mounting process, if the maximum height difference of the unevenness is approximately 6 μm or less, the reliability is good and the process can proceed. As shown in the table, Comparative Example 12 is not preferable because fusion with the setter occurs and the surface roughness is 6 μm or more. In Comparative Example 13, since the alumina particle diameter is increased, fusion to the setter can be suppressed. However, the surface roughness considered to be due to the alumina particle size is large, which is not preferable in production. In this example, the glass composition shown in Example 2 was used, but similar effects can be obtained when other example compositions are used.

  As can be seen from the above results, the ceramic powder for green sheets of the present invention can be fired at a low temperature of 900 ° C. or lower, has excellent dielectric properties in a high frequency band (microwave or millimeter wave band), and is hygroscopic. And a low-temperature fired ceramic substrate with low warpage and wrinkles when fired simultaneously with the silver-based conductor paste. The multilayer ceramic substrate of the present invention can be fired at a low temperature of 900 ° C. or lower, has excellent dielectric properties in a high frequency band (microwave or millimeter wave band), has low hygroscopicity, and is a silver-based conductor paste. Warpage and wrinkles are small when fired simultaneously.

Claims (4)

A ceramic powder for a green sheet containing glass powder and alumina powder,
The glass powder comprises 35 wt% or more and 39 wt% or less of SiO ₂ , 9 wt% or more and 17 wt% or less of Al ₂ O ₃ , 21 wt% or more and 40 wt% or less of B ₂ O ₃ , 10 wt% % or more and 20 wt% or less of R'O (where, R 'is, Mg, Ca and at least one kind is selected from the group consisting of Ba) and, 2 wt% or less than 0.2 wt% Li ₂ O and 0.5 wt% or more 2 wt% or less of MO ₂ (where, M is at least one kind is selected from the group consisting of Ti and Zr) and a 100% by weight in all body And
The average particle diameter of the alumina powder is 1.3 μm or more and 5 μm or less ,
The weight ratio of the glass powder to the alumina powder is 4: 6 to 6: 4.
A ceramic powder for a green sheet, characterized in that 2. The ceramic powder for green sheets according to claim 1, wherein the glass powder contains at least one of ZnO exceeding 0 wt% and 10 wt% or less and CuO exceeding 0 wt% and 0.5 wt% or less. An insulating layer obtained by firing a green sheet containing the ceramic powder for green sheets according to claim 1 or 2 at 800 to 900 ° C, and a wiring obtained by firing a conductor paste containing silver at 800 to 900 ° C. A multilayer ceramic substrate characterized by being laminated with a wiring layer comprising: A step of obtaining a green sheet by forming a slurry containing the ceramic powder for green sheet according to claim 1 or 2 into a sheet and drying;
A step of printing wiring on the green sheet using a conductive paste containing silver;
A method for producing a multilayer ceramic substrate, comprising: laminating green sheets on which the conductor paste is printed, pressing and integrating the sheets, and firing at 800 to 900 ° C.