JP4772071B2 - Ceramic powder for green sheet and low-temperature fired multilayer ceramic substrate - Google Patents

Description

  The present invention relates to a ceramic powder for green sheets and a low-temperature fired multilayer ceramic substrate. More specifically, the present invention relates to a ceramic powder for a green sheet that provides a ceramic layer of a low-temperature fired multilayer ceramic substrate used in high-frequency modules, IC packages, and the like in the fields of information communication and automobiles, and a low-temperature fired 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 green sheets used for producing such a low-temperature fired multilayer ceramic substrate, generally a mixture of glass powder and an inorganic filler (for example, alumina) for the purpose of improving mechanical strength is used. It is done. In particular, it is possible to use a low-resistance conductor such as gold, silver, silver palladium, and copper by selecting a glass powder that softens and densifies at about 1000 ° C. or less. By using this low resistance conductor, the conductor loss due to the conductor resistance during the transmission of the high frequency signal can be reduced, so that the transmission loss of the low-temperature fired multilayer ceramic substrate can be reduced. In addition, the production cost of the low-temperature fired multilayer ceramic substrate can be reduced by selecting silver palladium having a low silver and palladium content, and copper, which are inexpensive, as the conductor.

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 greater the loss of transmission loss in the high frequency band from users aiming to improve the performance of the product, because the higher the frequency of the radio wave, the greater the transmission loss of the electrical signal in the circuit. It has been demanded. Factors that greatly affect transmission loss in such a high frequency band include dielectric characteristics of the ceramic layer and electrical conductivity of the wiring layer. Among these, the dielectric properties of the ceramic layer are particularly important, and the contribution ratio 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 layer with excellent dielectric characteristics (that is, low dielectric constant ε _r and dielectric tangent tan δ).
However, the dielectric properties of the ceramic layer have the 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 conductive material, firing at 900 ° C. or lower, if possible, at a lower temperature is required. It becomes difficult.

As a conventional ceramic powder, it consists of an inorganic filler such as 0 to 50% by weight of alumina and 50 to 100% by weight of glass, and the glass is 35 to 65% by weight of SiO ₂ and 5 to 25% by weight of Al. ₂ O ₃ , 5-35 wt% B ₂ O ₃ , 2-20 wt% CaO, 0-5 wt% BaO, 0-5 wt% MgO, 0-5 wt% SrO, 0.5 Ceramic powders consisting of ˜5 wt% ZrO ₂ , 0.5-5 wt% TiO ₂ , and 0-1 wt% alkali element (lithium, sodium, potassium) oxide are known (eg patents) Reference 1). Such ceramic powders can be densified at 850 to 1000 ° C., the dielectric constant epsilon _r is low, it is possible to give even a small ceramic layer dielectric loss.

Japanese Patent No. 3033568

When selecting a low-resistance and inexpensive silver-based conductive paste as the conductive paste, the silver is likely to diffuse into the glass portion of the green sheet during the simultaneous firing of the green sheet and the silver-based conductive paste. It is difficult to apply unless the device conductor paste is devised to suppress silver diffusion. Many green sheets are fired at a temperature of about 900 ° C., but considering the diffusion of silver, the green sheet can be densified by firing at a lower temperature, specifically about 800 ° C. Is desirable.
In recent years, there has been an increasing demand for a wiring layer having a fine wiring pattern with a line width of 50 μm or less from the viewpoint of improving the degree of integration and impedance matching. As a silver-based conductor paste for forming this fine wiring pattern, a silver-based conductor paste containing fine silver particles is used. When this silver-based conductor paste is fired at a temperature exceeding 850 ° C., the conductor Burnout may cause defects such as disconnection of the wiring pattern. Therefore, in order to prevent such defects, it is necessary to co-fire the green sheet and the silver-based conductor paste at a temperature of 850 ° C. or lower.

  As a glass that is densified by firing at a temperature of 850 ° C. or less and that provides a ceramic layer having good dielectric properties, a glass containing boron at a high concentration is conceivable. The acid resistance and alkali resistance tend to be inferior. In many cases, in a low-temperature fired multilayer ceramic substrate, after simultaneous firing, a plating film of nickel or the like is formed on the wiring layer. In this plating process, since the plating solution is generally strongly acidic or strongly alkaline, if the glass is inferior in acid resistance and alkali resistance, the ceramic layer is eroded and the adhesion of the wiring layer to the ceramic layer is reduced. The strength of the ceramic layer itself is reduced.

  Further, as a glass that gives a ceramic layer having good dielectric properties, a glass that does not contain an alkali metal element (particularly potassium or sodium) that is often contained in a low softening point glass is effective. However, when the glass does not contain an alkali metal element, it is easily affected by the diffusion of silver from the silver-based conductor paste to the glass portion of the green sheet during firing. In the glass part where silver is diffused, the softening point of the glass is remarkably lowered, the glass is raised on the wiring pattern, or shrinks between the silver diffusion part and the non-diffusion part in the green sheet during firing. Due to the large difference in behavior, many defects such as deformation of the wiring pattern, large warp of the ceramic layer, and generation of voids around the via are likely to occur.

The present invention has been made to solve the above-described problems, and provides a green sheet that can be fired at a low temperature of 750 ° C. or higher and 850 ° C. or lower, and when simultaneously fired with a silver-based conductor paste. A green layer that can form a wiring layer with a fine and good wiring pattern, has less warpage and defects, and provides a ceramic layer with excellent plating resistance and dielectric properties in the high frequency band (microwave and millimeter wave band). An object is to provide a ceramic powder for a sheet.
Another object of the present invention is to provide a low-temperature fired multilayer ceramic substrate that is less prone to warpage and defects, and has excellent plating resistance and dielectric properties in a high frequency band (microwave and millimeter wave band).

As a result of intensive studies to solve the above-mentioned problems, the present inventors have softened the glass by optimizing the contents of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , R′O and ZnO. It has been found that the temperature can be adjusted to a predetermined range, and the effect associated with a decrease in the softening point of the glass due to silver diffusion can be suppressed by blending a predetermined amount of WO ₃ .

The present invention is a ceramic powder for green sheets containing a glass powder and an inorganic filler, wherein the glass powder is expressed in terms of an oxide basis, 35 wt% to 40 wt% SiO ₂ , 9 wt%. % To 17% by weight of Al ₂ O ₃ , 21% to 40% by weight of B ₂ O ₃ , 10% to 20% by weight of R′O (where R ′ is Ca, Mg and Ba) Is an element selected from the group consisting of Ca and at least one element that necessarily contains Ca, and is 0.2 wt% or more and 2.0 wt% or less of MO ₂ (where M consists of Zr and Ti) 2 wt% or more and 10 wt% or less of ZnO 2 , and 0.2 wt% or more and 3.0 wt% or less of WO ₃ including 100 wt% in total. , Al for the C aO O ₃ weight ratio of _{(Al 2} O 3 / CaO) is Ri der 3.0 or more, and the weight ratio between the glass powder and the inorganic filler is 4: 6 or 6: wherein the 4 or less Ceramic powder for green sheets.
The present invention is also obtained by firing a ceramic layer obtained by firing a green sheet containing the above ceramic powder for a green sheet at 750 ° C. or more and 850 ° C. or less and a silver-based conductor paste at 750 ° C. or more and 850 ° C. or less. A low-temperature fired multilayer ceramic substrate comprising a wiring layer.

  According to the present invention, a green sheet that can be fired at a low temperature of 750 ° C. or higher and 850 ° C. or lower is provided, and a wiring layer having a fine and good wiring pattern can be formed when simultaneously fired with a silver-based conductor paste. Thus, it is possible to provide a ceramic powder for a green sheet that gives a ceramic layer with less warping and defects and excellent in plating resistance and dielectric properties in a high frequency band (microwave and millimeter wave band).

Embodiment 1 FIG.
The ceramic powder for green sheets of the present embodiment includes glass powder containing a predetermined component and an inorganic filler.
The glass powder in the present embodiment is SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , and R′O (where R ′ is an element selected from the group consisting of Ca, Mg, and Ba). And at least one element containing Ca), MO ₂ (wherein M is at least one element selected from the group consisting of Zr and Ti), ZnO, WO ₃ and including. _Among, SiO 2, _Al 2 _{O 3} and _B 2 _{O 3} is a component that forms the basic structure of the glass. Hereinafter, each component of the glass powder will be described in detail.

SiO ₂ is a glass substance that vitrifies itself. Since the glass containing a large amount of SiO ₂ has a high softening point, the content of SiO ₂ is not less than 35% by weight and not more than 40% by weight. When the content of SiO ₂ is less than 35% by weight, a stable glass cannot be obtained, and the strength of the glass is reduced. On the other hand, if the content of SiO ₂ exceeds 40% by weight, the softening point of the glass becomes high and firing at 850 ° C. or less becomes difficult.

B ₂ O ₃ is also a glass material that vitrifies itself. B ₂ O ₃ can lower the softening point of glass by blending with glass containing SiO ₂ . B ₂ O ₃ forms a boron-oxygen bond in the glass skeleton. This bond is stronger in covalent bond than the 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 in the glass increases, oxygen coordination similar to boric acid occurs, so that the glass becomes chemically unstable, and in particular, the acid resistance, alkali resistance, and water resistance of the glass decrease. Therefore, the content of B ₂ O ₃ needs to be 21 wt% or more and 40 wt% or less. 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 40% by weight, the water resistance, acid resistance, and alkali resistance of the glass decrease, so that the manufacturing process such as gold plating usually performed in the manufacture of high-frequency components is near neutral. Need to be done in the environment of

Al ₂ O ₃ is a glass modifier that does not vitrify itself, but imparts various properties to glass, and is a component that improves the chemical stability of glass.
The content of Al ₂ O ₃ is 9% by weight or more and 17% by weight or less. If the content of Al ₂ O ₃ is less than 9% by weight, the chemical stability of the glass is not sufficiently improved, and a manufacturing process such as gold plating usually performed on high-frequency parts is performed in a neutral environment. Need arises. 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.

Alkaline earth metal oxides are also glass modifiers that do not vitrify themselves but give the glass various properties. The alkaline earth metal oxide is represented as R′O (where R ′ is an element selected from the group consisting of Ca, Mg, and Ba, and is at least one element that necessarily contains Ca). . That is, CaO is an essential component, and MgO and BaO are optional components.
The content of R′O is 10% by weight or more and 20% by weight or less, preferably 16% by weight or more and 18% by weight or less. If it is content of this range, the water resistance of glass can be improved or the high temperature viscosity of glass can be controlled appropriately. 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.
Although it is difficult to clearly show the effects of CaO, MgO, and BaO, the content of CaO is 1% by weight to 5% by weight, the content of MgO is 1% by weight to 8% by weight, and the content of BaO When the content is 8 wt% or more and 13 wt% or less, even better characteristics can be obtained.
Further, even when the content of CaO satisfies the above range, in relation to the content of _Al 2 _{O 3,} the weight ratio of _Al 2 _{O 3} with respect to _{CaO (Al 2 O 3 / CaO} ) 3.0 Otherwise, the water resistance is lowered.

MO ₂ (wherein M is at least one element selected from the group consisting of Ti and Zr) is also a glass modifier that does not vitrify itself but imparts various properties. Specifically, ZrO ₂ can improve the water resistance of the glass, and TiO ₂ can impart desired viscosity and fluidity to the glass.
The MO ₂ content is 0.2 wt% or more and 2.0 wt% or less. When the content of MO ₂ is less than 0.2% by weight, desired water resistance, viscosity and fluidity cannot be imparted to the glass. On the other hand, when the content of MO ₂ exceeds 2.0% by weight, desired dielectric properties cannot be obtained.

ZnO is also a glass modifying substance that does not vitrify itself, but imparts various properties, and is a component that imparts good viscosity and fluidity to glass. It is conceivable to mix an alkali metal element as a component having the same effect. However, since the alkali metal element lowers the dielectric characteristics, it is necessary to blend ZnO that does not lower the dielectric characteristics.
The content of ZnO is 2% by weight or more and 10% by weight or less. If the ZnO content is less than 2% by weight, the effect of blending ZnO cannot be sufficiently obtained. On the other hand, when the content of ZnO exceeds 10% by weight, desired dielectric properties cannot be obtained.

Since the glass powder in the present embodiment does not contain an alkali metal element, it is easily affected by silver diffusing from the conductor paste during firing. In many cases, the diffusion of silver lowers the softening point of the glass in the green sheet and increases the fluidity of the glass, but this tendency is particularly noticeable in glasses that do not contain alkali metal elements. A difference occurs in the contraction behavior of the green sheet between the diffusion part and the diffusion part. That is, in the green sheet near the conductor where silver diffusion is easy, densification proceeds at a lower temperature than in the green sheet where silver diffusion is difficult to reach. WO ₃ is an effective component for alleviating such behavior, and can also suppress the occurrence of defects such as pores that are likely to occur around conductors, particularly vias.
The content of WO ₃ is 0.2% by weight or more and 3.0% by weight or less. If the content of WO ₃ is less than 0.2% by weight, the effect of blending WO ₃ cannot be sufficiently obtained. On the other hand, when the content of WO ₃ exceeds 3.0% by weight, the dielectric properties are deteriorated.

The glass powder in the present embodiment can be blended with CuO as a constituent component in order to impart even better viscosity and fluidity to the glass and to suppress coloring of the glass accompanying silver diffusion.
The content of CuO is preferably more than 0% by weight and 2% by weight or less. When the content of CuO exceeds 2% by weight, desired dielectric properties cannot be obtained.

Glass powder in this embodiment can also be formulated as a component of Li 2 _O as required.
Lithium is the lightest element among alkali metals and has a short bond distance, so that 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 with lithium among alkali metals. In particular, Li ₂ O, which is an alkali metal oxide, can also suppress silver diffusion. An alkali metal such as sodium or potassium stabilizes the properties of the glass, but it is not suitable as a component of the glass powder because it lowers the dielectric properties.

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 inorganic filler in this Embodiment is not specifically limited, What is necessary is just to select suitably according to required characteristics, such as intensity | strength and heat conductivity. For example, examples of the inorganic filler include aluminum oxide, silicon oxide, silicon nitride, boron nitride, and the like, and those that are commercially available can be used. Moreover, an inorganic filler can be used individually by 1 type or in combination of 2 or more types. Among these, it is preferable to use aluminum oxide from the viewpoint of strength, cost, and ease of use.

  The average particle diameters of the glass powder and the inorganic filler in the present embodiment are not particularly limited, but are preferably more than 1 μm and less than 3 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. .

Weight ratio of the glass powder and the inorganic filler in the green sheet ceramic powder for the present embodiment, 4: 6 or 6: 4 or less, the good Mashiku 1: 1. If the weight ratio of the inorganic filler is too large, the density of the ceramic after firing becomes low (less than 98%) and open pores remain, and the electrical characteristics are deteriorated (especially transmission loss is increased) due to strength and humidity. There is. 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 low-temperature fired multilayer ceramic substrate.

Embodiment 2. FIG.
The low-temperature fired multilayer ceramic substrate of the present embodiment includes a ceramic layer obtained by firing a green sheet containing the above-described ceramic powder for green sheets at 750 ° C. or more and 850 ° C. or less, and a silver-based conductor paste of 750 ° C. or more and 850 ° C. or less. And a wiring layer obtained by firing.
The low-temperature fired multilayer ceramic substrate is obtained by forming a slurry containing the ceramic powder for green sheets into a sheet and drying it, and forming a wiring pattern on the green sheet using a silver-based conductor paste. It can be manufactured by a manufacturing method including a printing step and a step of laminating and pressing the green sheets on which the wiring patterns are printed and then baking them at 750 ° C. or higher and 850 ° C. or lower.

Here, the slurry containing the ceramic powder for green sheets can be prepared by adding an organic binder, a plasticizer, a dispersant and a solvent to the ceramic powder for green sheets.
The organic binder is not particularly limited as long as it is a resin that can obtain sufficient mechanical strength when mixed with glass powder and an inorganic filler to form a sheet, and can be decomposed and desorbed during the heat degreasing process described below. However, those known in the art can be used. For example, polyvinyl butyral or acrylic resin can be used as the organic binder.
The plasticizer is not particularly limited, and those known in the technical field can be used. For example, as a plasticizer, dioctyl phthalate, di-n-butyl phthalate, polyethylene glycol, or the like can be used.

The dispersant is not particularly limited, and those known in the technical field can be used. For example, triolein or the like can be used as a dispersant.
The solvent is not particularly limited as long as it can dissolve an organic binder, a plasticizer, and a dispersant, and a solvent known in the art can be used. For example, alcohols such as toluene, ethanol and butanol, distilled water, etc. can be used as the solvent.
The amount of the organic binder, plasticizer, dispersant and 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.
From the viewpoint of conductivity, the silver-based conductor paste is preferably an Ag-based paste containing Ag as a main component, such as Ag—Pd or Ag—Pt, and more preferably an Ag paste having the highest conductivity. .
It is also possible to form a via hole in the green sheet before the step of printing the wiring pattern on the green sheet.

  After the green sheets on which the conductive paste is printed are laminated, pressed and integrated, and then fired at 750 ° C. or higher and 850 ° C. or lower, the pressing method is to shape the laminate so that it does not peel during firing. The method is not particularly limited as long as it can be maintained. For example, a hydrostatic press in hot water or a hot uniaxial press may be performed.

  Before firing at 750 ° C. or higher and 850 ° C. or lower, it is preferable to perform a heat degreasing treatment for degreasing. In the heat degreasing treatment for the purpose of such degreasing, the heat degreasing treatment temperature is preferably 300 ° C. or higher and 600 ° C. or lower. 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 750 degreeC or more and 850 degrees C or less) aiming at densification. Moreover, the heat degreasing treatment time may be appropriately set according to the size of the green sheet and the like, and is not particularly limited. However, in general, a sufficient degreasing effect can be obtained if it is about 2 to 10 hours. it can.

The firing at 750 ° C. or higher and 850 ° C. or lower for the purpose of densification may be performed until the strength reaches a practically sufficient level, so the conditions are not particularly limited, but generally the firing time is 10 minutes. About 1 hour.
In addition, the temperature increase rate at the time of moving from the heat degreasing process for degreasing to the baking for the purpose of densification (baking at 750 ° C. or higher and 850 ° C. or lower) is not particularly limited, What is necessary is just to set suitably according to a magnitude | size.
The low-temperature fired multilayer ceramic substrate produced in this way has less warping and defects, and is excellent in plating resistance and dielectric properties in a high frequency band (microwave and millimeter wave band).

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 15 and Comparative Examples 1 to 14]
According to the glass composition of Table 1, each glass component is mixed, melted at 1200 to 1500 ° C. for about 1 hour, and then rapidly cooled to pulverize the glass cullet obtained using a stamp mill or a ball mill. A glass powder having an average particle diameter of 2 μm was prepared.

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 for 16 hours using a ball mill to prepare a ceramic powder for green sheets. An appropriate amount of polyvinyl butyral, di-n-butyl phthalate, triolein, ethanol and butanol was further added to the green sheet ceramic powder 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.

30 green sheets were stacked and integrated by performing a hydrostatic pressure press at 300 kg / cm ² for 15 minutes in 90 ° C. warm water, and then 20 minutes at the firing temperature (densification temperature) shown in Table 2. A sample of a low-temperature fired multilayer ceramic substrate was produced by firing for ˜1 hour. This sample was cut using water as a coolant and processed into a diameter of about 1.3 mm and a length of about 40 mm. The processed samples, the perturbation method the resonant frequency used TM ₀₁₀ resonator about 10 GHz, dielectric characteristics were evaluated in the microwave band (dielectric constant and dielectric loss tangent).
In this evaluation, the dielectric loss tangent at 10 GHz of a low-temperature fired multilayer ceramic substrate produced using a glass containing an alkali metal element generally used for a low-temperature fired multilayer ceramic substrate is about 0.006 to 0.007. In view of the above, it can be said that the dielectric property is practically improved when the loss is about 0.004 or less, which is reduced by about 50%.

In addition, a sample of the low-temperature fired multilayer ceramic substrate produced in the same manner as described above by stacking 10 green sheets was processed into a length of 30 mm and a width of 15 mm. The processed sample is boiled in 500 cc of distilled water for 2 hours, then subjected to ultrasonic cleaning for 1 minute and drying at 150 ° C. for 2 hours, and the weight before and after the treatment is measured. Evaluated.
In this evaluation, if the weight change is about 0.02%, it is a general level of water resistance, and if it is 0.01% or less, it can be said that the water resistance is high.

Meanwhile, a simple circuit having vias was printed on the green sheet using an Ag conductor paste. Ten green sheets were stacked and a low-temperature fired multilayer ceramic substrate sample was produced in the same manner as described above. This sample has vias connected in the thickness direction over a plurality of layers. After cutting the via part of the obtained sample, rough polishing with SiC abrasive paper and mirror polishing with diamond paste, cross-sectional structure observation of the via and its surrounding base part is performed with a scanning electron microscope, and the periphery of the via The presence or absence of void defects in the part was observed.
In this evaluation, void defects around the vias cause problems in hermeticity, cause electrical disconnection due to via deformation, etc., and decrease the mechanical strength of the substrate. It can be said that it is preferable that there is no void defect.
Table 2 shows the results of the dielectric properties, water resistance, and void defects evaluated as described above.

As shown in Table 2, all of the samples of Examples 1 to 15 achieve densification at 750 ° C. or more and 850 ° C. or less, and are excellent in water resistance and dielectric properties, and void defects in the periphery of the via This was practically superior as a low-temperature fired multilayer ceramic substrate.
On the other hand, in the sample of the comparative example, the firing temperature for achieving densification was too high, water resistance or dielectric properties were not sufficient, or void defects occurred.
As can be seen from the above results, the ceramic powder for green sheets of the present invention gives a green sheet that can be fired at a low temperature between 750 ° C. and 850 ° C. It is possible to form a wiring layer having a good wiring pattern, to generate a ceramic layer with less warpage and defects, and excellent plating resistance and dielectric properties in a high frequency band (microwave and millimeter wave band). . Further, the low-temperature fired multilayer ceramic substrate of the present invention has less warpage and defects, and is excellent in plating resistance and dielectric properties in a high frequency band (microwave and millimeter wave band).

Claims (4)

A ceramic powder for green sheets containing glass powder and an inorganic filler,
When the glass powder is expressed on an oxide basis, it is 35 wt% or more and 40 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 an element selected from the group consisting of Ca, Mg, and Ba, and is at least one element that always contains Ca) 0.2% by weight or more and 2.0% by weight or less MO ₂ (wherein M is at least one element selected from the group consisting of Zr and Ti), 2% by weight or more and 10% by weight or less of ZnO, and containing 0.2 wt% to 3.0 wt% or less of WO _3, total becomes 100 wt%, the weight ratio of _Al 2 _{O 3} with respect to _{C aO (Al 2 O 3 /} CaO) is 3. 0 or der is, Mu and the said glass powder Weight ratio of the filler is 4: 6 or 6: ceramic powder for a green sheet, characterized in that it is 4 or less. Wherein the glass powder is characterized in that it further comprises 0 wt% excess 2.0 wt% or less of CuO, and at least one selected from the group consisting of 0 wt% excess 1 wt% or less of Li 2 _O Item 10. The ceramic powder for green sheets according to Item 1. The ceramic powder for green sheets according to claim 1 or 2 , wherein the inorganic filler is at least one selected from the group consisting of aluminum oxide, silicon oxide, silicon nitride, and boron nitride. The ceramic layer obtained by baking the green sheet containing the ceramic powder for green sheets as described in any one of Claims 1-3 at 750 degreeC or more and 850 degrees C or less, and 750 degreeC or more and 850 degrees C or less of silver-type conductor paste. A low-temperature fired multilayer ceramic substrate comprising: a wiring layer obtained by firing at a low temperature.