阅读说明：本技术 玻璃陶瓷电介体 (Glass ceramic dielectric ) 是由 北村嘉朗 于 2019-02-27 设计创作，主要内容包括：本发明提供一种在表面形成有金属配线的情况下能够抑制玻璃成分变质的玻璃陶瓷电介体。玻璃陶瓷电介体(1)的特征在于具备：玻璃陶瓷层(2)以及在其主面形成的屏障层(3)。(The invention provides a glass ceramic dielectric which can inhibit the glass component from changing quality under the condition that metal wiring is formed on the surface. A glass ceramic dielectric (1) is characterized by comprising: a glass ceramic layer (2) and a barrier layer (3) formed on the main surface thereof.)

1. A glass ceramic dielectric characterized in that,

the glass ceramic dielectric has: a glass ceramic layer; and a barrier layer formed on a main surface of the glass ceramic layer.

2. The glass ceramic dielectric according to claim 1,

barrier layers are formed on both main surfaces of the glass ceramic layer.

3. The glass ceramic dielectric according to claim 1 or 2,

the barrier layer contains an inorganic material.

4. The glass ceramic dielectric according to any one of claims 1 to 3,

the barrier layer contains amorphous glass.

5. The glass-ceramic dielectric according to claim 4,

the amorphous glass contains 40% by mass or more of SiO₂And 15% or less of B₂O₃As a glass composition.

6. The glass-ceramic dielectric according to claim 4 or 5,

the amorphous glass contains substantially no alkali metal component.

7. The glass ceramic dielectric according to any one of claims 1 to 6,

the glass ceramic layer contains a sintered body of powder including crystalline glass powder.

8. The glass-ceramic dielectric according to claim 7,

the crystalline glass powder contains 20-65% by mass of SiO₂3-25% CaO, 7-30% MgO, 0-20% Al₂O₃And 5 to 40% of BaO, and the crystalline glass powder satisfies 1 SiO or less in terms of mass ratio₂A relationship of/BaO ≦ 4.

9. The glass ceramic dielectric according to claim 7 or 8,

the glass ceramic layer contains a sintered body of powder including 30 to 100 mass% of crystalline glass powder and 0 to 70 mass% of filler powder.

10. The glass-ceramic dielectric according to claim 9,

the filler powder contains an Al component.

11. The glass ceramic dielectric according to any one of claims 1 to 10,

the glass ceramic layer contains diopside crystals and feldspar crystals.

12. The glass ceramic dielectric according to any one of claims 1 to 11,

the glass ceramic dielectric is used as a circuit board.

13. A circuit board is characterized in that a plurality of circuit boards are arranged,

a barrier layer of a glass ceramic dielectric according to claim 12, wherein metal wiring is formed on the surface of the barrier layer.

14. A method for producing a glass ceramic dielectric according to any one of claims 4 to 12, comprising:

preparing a green sheet for a glass ceramic layer containing a crystalline glass powder and a green sheet for a barrier layer containing an amorphous glass powder;

a step of laminating the green sheets for glass ceramic layers and the green sheets for barrier layers to obtain a laminate; and the number of the first and second groups,

and a step of firing the laminate.

Technical Field

The present invention relates to a glass ceramic dielectric used for a circuit board or the like.

Background

Conventionally, glass ceramic dielectrics have been known as insulating materials for ceramic multilayer substrates on which ICs, LSIs, and the like are mounted at high density, thick film circuit elements, semiconductor packages, and the like (see, for example, patent document 1). For example, a metal wiring having a predetermined pattern is formed on the surface of a glass ceramic dielectric and used as a circuit board.

Disclosure of Invention

Technical problem to be solved by the invention

In general, metal wiring is formed by plating treatment, but the plating treatment may cause a change in the glass component contained in the glass ceramic dielectric, and may adversely affect the characteristics such as the dielectric constant and the dielectric loss.

In view of the above circumstances, an object of the present invention is to provide a glass ceramic dielectric which can be plated on the surface thereof without causing deterioration of the glass component.

Means for solving the problems

The glass ceramic dielectric of the present invention is characterized by comprising: a glass ceramic layer; and a barrier layer formed on a main surface thereof. With this arrangement, when metal wiring such as gold or silver is formed on the surface of the glass ceramic dielectric by plating, the glass component contained in the glass ceramic layer can be inhibited from being altered.

In the glass ceramic dielectric according to the present invention, it is preferable that barrier layers are formed on both main surfaces of the glass ceramic layer. With this arrangement, in the firing step in the production of the glass ceramic dielectric of the present invention, the occurrence of warpage due to the difference in thermal expansion coefficient between the glass ceramic layer and the barrier layer can be suppressed.

In the glass ceramic dielectric of the present invention, preferably, the barrier layer contains an inorganic material. With this arrangement, when the surface of the glass ceramic dielectric is subjected to plating treatment, the glass component contained in the glass ceramic layer is easily inhibited from being changed in quality.

In the glass ceramic dielectric of the present invention, the barrier layer preferably contains amorphous glass. With this arrangement, when the surface of the glass ceramic dielectric is subjected to plating treatment, the glass component contained in the glass ceramic layer is more easily inhibited from being changed in quality.

In the glass ceramic dielectric of the present invention, the amorphous glass preferably contains 40% by mass or more of SiO₂And 15% or less of B₂O₃As a glass composition. By providing such a barrier layer, a barrier layer having excellent acid resistance can be obtained, and therefore, the function as a barrier layer can be improved.

In the glass ceramic dielectric of the present invention, it is preferable that the amorphous glass contains substantially no alkali metal component. By providing such a barrier layer, a barrier layer having excellent acid resistance can be obtained, and therefore, the function as a barrier layer can be improved. The phrase "substantially not containing an alkali metal component" means that the alkali metal component is not intentionally contained as a raw material, and the incorporation of inevitable impurities is not excluded. Objectively, it means that the content of the alkali metal component is less than 0.1 mass%.

In the glass ceramic dielectric of the present invention, the glass ceramic layer preferably contains a sintered body of a powder including a crystalline glass powder. The "crystalline glass powder" refers to a glass powder in which crystals are precipitated by heat treatment. The term "heat treatment" as used herein means a heat treatment at a temperature not lower than the crystallization initiation temperature to sufficiently progress crystallization, for example, at 800 to 1000 ℃ for 20 minutes or more.

In the glass ceramic dielectric of the present invention, the crystalline glass powder preferably contains 20 to 65% by mass of SiO₂3-25% CaO, 7-30% MgO, 0-20% Al₂O₃And 5-40% of BaO as a glass composition, and SiO is satisfied at 1 ≤ by mass ratio₂A relationship of/BaO ≦ 4. The crystalline glass powder having this composition has the following properties: tong (Chinese character of 'tong')Heat treatment, feldspar crystallization and diopside crystallization (2 SiO)₂CaO — MgO) together as a main crystal. By precipitating both types of crystals, the degree of crystallinity in firing is increased, and the residual glass phase that increases the dielectric constant and dielectric loss can be reduced. Further, since the volume shrinkage of the feldspar crystal at the time of crystal precipitation is small, generation of pores accompanying crystal precipitation is suppressed. As a result, the glass ceramic dielectric can have a low dielectric constant and a low dielectric loss.

In the glass ceramic dielectric of the present invention, the glass ceramic layer preferably contains a sintered body of powder including 30 to 100 mass% of crystalline glass powder and 0 to 70 mass% of filler powder. By adding a sintered body of a powder containing a filler powder in addition to a crystalline glass powder to a glass ceramic dielectric, the characteristics of the glass ceramic dielectric such as the thermal expansion coefficient, toughness, and dielectric constant can be improved.

In the glass ceramic dielectric of the present invention, it is preferable that the filler powder contains an Al component. With this arrangement, the components of Si and Ba in the residual glass phase after the diopside crystal deposition react with the Al component in the filler powder, and the feldspar crystal is likely to be deposited.

In the glass ceramic dielectric of the present invention, the glass ceramic layer preferably contains diopside crystals and feldspar crystals. For the above reasons, when two types of crystals are contained, a glass ceramic layer having a high crystallinity and few pores can be easily obtained, and the glass ceramic dielectric can be used as a glass ceramic dielectric having a low dielectric constant and a low dielectric loss.

The glass ceramic dielectric of the present invention is suitable for use as a circuit board.

The circuit board of the present invention is characterized in that a metal wiring is formed on a surface of the barrier layer of the glass ceramic dielectric.

A method for producing a glass ceramic dielectric according to the present invention is a method for producing the above glass ceramic dielectric, comprising: preparing a green sheet for a glass ceramic layer containing a crystalline glass powder and a green sheet for a barrier layer containing an amorphous glass powder; a step of laminating the green sheets for glass ceramic layers and the green sheets for barrier layers to obtain a laminate; and a step of firing the laminate. The "amorphous glass powder" refers to a glass powder in which substantially no crystal is precipitated by heat treatment. "substantially no crystal precipitation" means that the crystallinity of the glass after heat treatment is substantially 1% or less, including the inevitable precipitation of devitrified substances.

Effects of the invention

According to the present invention, a glass ceramic dielectric can be provided which can be plated on a surface without causing deterioration of a glass component.

Drawings

FIG. 1 is a schematic cross-sectional view showing one embodiment of a glass ceramic dielectric according to the present invention.

FIG. 2 is a schematic cross-sectional view showing one embodiment of the method for producing a glass ceramic dielectric according to the present invention.

Description of the symbols

1 glass ceramic dielectric

1' laminate

2 glass ceramic layer

Green sheet for 2' glass ceramic layer

3 Barrier layer

Green sheet for 3' barrier layer

4-constraint sheet

Detailed Description

Hereinafter, embodiments of the glass ceramic dielectric according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing one embodiment of a glass ceramic dielectric according to the present invention. The glass ceramic dielectric 1 has: a glass ceramic layer 2; and a barrier layer 3 formed on the main surface 2a and the main surface 2b of the glass ceramic layer 2. The surface of the barrier layer 3 is plated to form metal wiring (not shown), thereby being used as a circuit board. If necessary, heat conduction holes and the like may be formed in the glass ceramic layer 2. The glass ceramic dielectric 1 is a plate-like member having a planar shape such as a rectangle or a circle.

By forming the barrier layer 3 on both principal surfaces of the glass ceramic layer 2, the occurrence of warpage due to a difference in thermal expansion coefficient between the glass ceramic layer 2 and the barrier layer 3 can be suppressed in the firing step in the production of the glass ceramic dielectric 1. The barrier layer 3 is not necessarily formed on both main surfaces of the glass ceramic layer 2, and the barrier layer 3 may be formed only on one main surface of the glass ceramic layer 2.

Hereinafter, each of the components will be described in detail.

(glass ceramic layer)

The glass ceramic layer includes, for example, a sintered body of a powder containing a crystalline glass powder. Examples of the crystalline glass powder include: the glass composition contains 20-65% by mass of SiO₂3-25% CaO, 7-30% MgO, 0-20% Al₂O₃5 to 40 percent of BaO, and the mass ratio of the BaO is more than or equal to 1 and less than or equal to SiO₂A relationship of/BaO ≦ 4. As described above, the glass ceramic dielectric obtained by firing the crystalline glass powder having the composition has the following properties: by the heat treatment, feldspar crystals and diopside crystals are precipitated as main crystals, and the glass ceramic dielectric can be a glass ceramic dielectric having a low dielectric constant and a low dielectric loss. Specifically, it is possible to realize a dielectric constant of 6 to 11, particularly 6 to 10, at 25 ℃ and a dielectric loss tan of 20 x 10 in a high frequency region of 0.1GHz or more^-4Hereinafter, 18X 10^-4The following, in particular 16X 10^-4The following.

The feldspar crystal is preferably a celsian crystal (BaAl)₂Si₂O₈). By crystallizing celsian, the residual glass phase after heat treatment can be effectively reduced, and a glass ceramic dielectric having low porosity and low dielectric loss can be easily obtained. In addition, anorthite crystals (CaAl) may be precipitated within a range in which dielectric loss and porosity are not increased₂Si₂O₈) And the like.

The reason why the composition of the crystalline glass powder is limited as described above will be described below. In the following description of the content of each component, "%" means "% by mass" unless otherwise specified.

SiO₂Is a network former of glass, and is a constituent component of diopside crystal and feldspar crystal. SiO 2₂The content of (b) is preferably 20 to 65%, 30 to 65%, and particularly preferably 40 to 55%. If SiO is present₂When the content of (A) is too small, vitrification becomes difficult, and when too large, low-temperature firing (for example, 1000 ℃ or lower) tends to become difficult.

CaO is a constituent of diopside crystals, and the content thereof is preferably 3 to 25%, 3 to 20%, and particularly preferably 7 to 15%. If the content of CaO is too small, diopside crystals are less likely to precipitate, and as a result, the dielectric loss of the glass ceramic dielectric tends to be high. On the other hand, if the content of CaO is too large, the fluidity of the glass is lowered, and it is difficult to obtain a dense sintered body.

MgO is also a constituent of the diopside crystal, and the content thereof is preferably 7 to 30%, 8 to 30%, 11 to 30%, and particularly preferably 12 to 20%. When the content of MgO is too small, crystals are hard to precipitate, and when too large, vitrification is difficult.

Al₂O₃Is a component for stabilizing glass, and the content thereof is preferably 0 to 20%, 0.5 to 20%, and particularly preferably 1 to 10%. If Al is present₂O₃When the content of (b) is too large, diopside crystals are difficult to precipitate, and as a result, the dielectric loss of the glass ceramic dielectric tends to be high.

BaO is a constituent of the celsian crystal, and the content thereof is preferably 5 to 40%, particularly preferably 10 to 35%. If the content of BaO is too small, the celsian crystals are difficult to precipitate. On the other hand, if the content of BaO is too large, the amount of precipitated diopside crystals tends to be small, and as a result, the dielectric loss of the glass ceramic dielectric tends to be large.

In addition, by mixing SiO₂The ratio (mass ratio) to BaO is limited to a specific range, and feldspar crystals can be effectively precipitated from the residual glass phase after firing. Specifically, it is preferable to satisfy 1. ltoreq. SiO₂The relationship of/BaO.ltoreq.4, particularly preferably 1.05. ltoreq. SiO₂The relationship of/BaO is less than or equal to 3.95. If SiO₂When the ratio to BaO is out of this range, feldspar crystals are difficult to precipitate or vitrification is difficult.

In addition, the following components can be added to the crystalline glass powder.

ZnO is a component for facilitating vitrification, and the content thereof is preferably 0 to 20%, particularly preferably 0.1 to 15%. If the content of ZnO is too large, the crystallinity tends to be weak, and the amount of precipitated diopside crystals tends to be small. As a result, the dielectric loss of the glass ceramic dielectric tends to increase.

TiO₂And ZrO₂Is a component for improving the chemical resistance (acid resistance, alkali resistance) of the glass ceramic dielectric. TiO 2₂The content of (b) is preferably 0 to 15%, particularly preferably 0.1 to 13%. If TiO₂When the content of (b) is too large, the dielectric loss of the glass ceramic dielectric tends to be too large. ZrO (ZrO)₂The content of (b) is preferably 0 to 15%, particularly preferably 0.1 to 13%. If ZrO of₂When the amount is too large, the dielectric loss of the glass ceramic dielectric tends to be too large.

In addition to the above components, in a range not impairing the characteristics such as dielectric loss of the glass ceramic dielectric, SrO and Nb may be added in an amount of 30% or less in total₂O₅、La₂O₃、Y₂O₃、P₂O₅、B₂O₃、Bi₂O₃、CuO、CeO₂、MnO、Sb₂O₃SnO, etc.

In addition, Li₂O、Na₂O、K₂The alkali metal component such as O tends to cut the glass network and increase the dielectric loss. In addition, the insulating properties of the glass ceramic dielectric tend to be lowered. Therefore, the total amount of alkali metal oxides is preferably 5% or less, particularly preferably 1% or less, and most preferably substantially not contained (specifically, less than 0.1%).

Average particle diameter D of crystalline glass powder₅₀Preferably 10 μm or less, and particularly preferably 5 μm or less. If the average particle diameter D of the crystalline glass powder is₅₀If the size is too large, pores are likely to be generated in the glass ceramic dielectric. On the other hand, the average particle diameter D of the crystalline glass powder₅₀The lower limit of (b) is not particularly limited, but is preferably 0.1 μm or more, and particularly preferably 1 μm or more, from the viewpoint of ease of handling and processing cost. In the present specification, the particle size of the powder is a value measured by a laser diffraction scattering method.

For the purpose of improving the characteristics such as the thermal expansion coefficient, toughness, and dielectric constant, a filler powder may be mixed with a crystalline glass powder and sintered to obtain a glass ceramic layer. Examples of the filler powder include ceramic powders such as alumina powder, cordierite powder, mullite powder, quartz powder, zircon powder, titania powder, and zirconia powder, and quartz glass powder, and these can be used alone or in combination of 2 or more.

By using ceramic powder containing an Al component as filler powder, Si and Ba components in the residual glass phase after diopside crystallization react with the Al component in the ceramic powder, and feldspar crystals are likely to precipitate. Examples of the ceramic powder containing an Al component include alumina powder, cordierite powder, mullite powder, celsian, canadian, barium aluminate, aluminum titanate, spinel, calcium aluminate, magnesium aluminate, and aluminum nitride.

In addition, the crystallinity can be improved by mixing a small amount (for example, about 0.1 to 1 mass%) of diopside or celsian crystals as crystal nuclei.

The mixing ratio of the crystalline glass powder and the filler powder is preferably 30 to 100 mass% of the crystalline glass powder and 0 to 70 mass% of the filler powder, more preferably 40 to 90 mass% of the crystalline glass powder and 10 to 60 mass% of the filler powder, still more preferably 45 to 80 mass% of the crystalline glass powder and 20 to 55 mass% of the filler powder, and particularly preferably 50 to 70 mass% of the crystalline glass powder and 30 to 50 mass% of the filler powder. When the content of the filler powder is too large, densification of the glass ceramic dielectric tends to be difficult.

Average particle diameter D of filler powder₅₀Preferably 0.01 to 100 μm, 0.1 to 50 μm, 0.5 to 20 μm, and particularly preferably 1 to 10 μm. If the mean particle diameter D of the filler powder₅₀If the amount is too small, the glass powder is dissolved in the crystalline glass powder, and it is difficult to obtain an effect of improving the characteristics such as the thermal expansion coefficient, toughness, dielectric constant, and chemical resistance. On the other hand, if the average particle diameter D of the filler powder₅₀If the amount is too large, the flow of the crystalline glass powder during firing is inhibited, and pores are likely to be generated in the glass ceramic dielectric. By making the particle diameters of the crystalline glass powder and the filler powder close to each other, the dispersibility when mixing the two is excellent, and a homogeneous glass ceramic dielectric can be easily obtained. Further, since the sinterability is improved, a dense glass ceramic dielectric can be easily obtained.

By heat-treating the crystalline glass powder or the mixture of the crystalline glass powder and the filler powder at a temperature not lower than the crystallization starting temperature of the crystalline glass powder, a glass ceramic layer in which diopside crystals and feldspar crystals are precipitated as main crystals can be obtained.

The content of diopside crystals in the glass ceramic layer is preferably 35% by mass or more, and particularly preferably 40% by mass or more. If the content of the diopside crystal is too small, the dielectric loss tends to be large. On the other hand, if the content of the diopside crystal is too large, pores in the glass ceramic layer increase, so the upper limit is preferably 80 mass% or less, and particularly preferably 70 mass% or less.

The content of the feldspar crystals in the glass ceramic layer is preferably 20 to 65 mass%, 25 to 60 mass%, and particularly preferably 30 to 55 mass%. When the content of the feldspar crystal is too small, the porosity in the glass ceramic layer becomes large, and as a result, the dielectric loss tends to become large. On the other hand, if the content of feldspar crystals is too large, the dielectric loss tends to be large and the mechanical strength tends to be low because diopside crystals are relatively small.

In the glass ceramic layer, the residual glass phase is preferably 0.5% by mass or more, and particularly preferably 1% by mass or more. If the residual glass phase is too small, pores are likely to be generated in the glass ceramic layer. Further, when the content of the residual glass phase is too large, diopside crystals and feldspar crystals tend to be relatively small, and the dielectric loss tends to be large, so the upper limit is preferably 20 mass% or less, and particularly preferably 10 mass% or less.

The porosity of the glass ceramic layer is preferably 3 vol% or less, and particularly preferably 2 vol% or less. When the porosity is increased, disconnection of wiring tends to occur or dielectric loss tends to be increased when a glass ceramic dielectric is used as a circuit board.

In order to obtain a desired mechanical strength, the thickness of the glass ceramic layer is preferably adjusted to be within a range of 200 to 2000 μm and 300 to 1500 μm, and more preferably 500 to 1000 μm.

(Barrier layer)

The barrier layer preferably contains an inorganic material, and particularly preferably contains amorphous glass. With this arrangement, when the surface of the glass ceramic dielectric is subjected to plating treatment, the glass component contained in the glass ceramic layer is easily inhibited from being changed in quality.

The barrier layer (amorphous glass layer) containing amorphous glass contains, for example, a sintered body of amorphous glass powder. The amorphous glass (amorphous glass powder) preferably contains 40% by mass or more of SiO as a glass composition₂15% or less of B₂O₃. The reason why the glass composition is limited in this manner will be described below. In the following description of the content of each component, "%" means "% by mass" unless otherwise specified.

SiO₂Is a component forming a glass network. SiO 2₂The content of (b) is preferably 40% or more, 42% or more, 45% or more, and particularly preferably 47% or more. If SiO₂If the content of (b) is too small, the acid resistance is poor, and when metal wiring is formed on the surface of the glass ceramic dielectric, the amorphous glass layer is difficult to function as a barrier layer. In addition, if SiO₂When the content of (b) is too large, the sinterability is poor, and it is difficult to obtain a dense amorphous glass layer, and the function as a barrier layer tends to be deteriorated. Thus, SiO₂The content of (b) is preferably 85% or less, 80% or less, 70% or less, and particularly preferably 60% or less.

B₂O₃The glass powder is a component that significantly improves the meltability by lowering the melting temperature, and has the effect of improving the flowability of the glass powder during sintering for forming an amorphous glass layer. However, if the content is too large, the acid resistance is poor, and the function as a barrier layer of the amorphous glass layer tends to be lowered. Thus, B₂O₃The content of (b) is preferably 15% or less, 12% or less, 10% or less, and particularly preferably 8% or less. In order to obtain the above-mentioned effects of improving meltability and fluidity, B₂O₃The content of (b) is preferably 1% or more, 2% or more, and particularly preferably 3% or more.

The amorphous glass layer may contain the following components in addition to the above components.

Al₂O₃Is a component for improving the acid resistance of the amorphous glass layer. Al (Al)₂O₃The content of (b) is preferably 0 to 25%, 0.1 to 20%, 1 to 15%, and particularly preferably 2 to 10%. If Al is present₂O₃When the content of (b) is too large, the meltability tends to be lowered.

MgO, CaO, SrO and BaO are components that lower the melting temperature to improve the meltability and lower the softening point. The total amount of these components is preferably 0 to 45%, 0.1 to 45%, and particularly preferably 1 to 40%. If the total amount of these components is too large, the acid resistance tends to decrease. The content of each component of MgO, CaO, SrO and BaO is preferably 0 to 35%, 0.1 to 33%, and particularly preferably 1 to 30%. If the content of these components is too large, the acid resistance tends to be lowered.

ZnO is a component for improving the meltability by lowering the melting temperature. The content of ZnO is preferably 0 to 10%, 0.1 to 7%, and particularly preferably 1 to 5%. When the content of ZnO is too large, acid resistance tends to decrease.

In addition to the above components, various components may be contained within a range not impairing the effects of the present invention. For example, the content of each of the components can be 15% or less, or one after the otherThe content of P is 10% or less, particularly 5% or less, and the total amount is 30% or less₂O₅、La₂O₃、Ta₂O₅、TeO₂、TiO₂、Nb₂O₅、Gd₂O₃，Y₂O₃、CeO₂、Sb₂O₃、SnO₂、Bi₂O₃、As₂O₃And ZrO₂And the like.

In order to significantly reduce the acid resistance of the amorphous glass layer, it is preferable that the amorphous glass layer does not substantially contain an alkali metal component (Li)₂O、Na₂O、K₂O, etc.).

The softening point of the glass constituting the amorphous glass layer is preferably 700 to 1000 ℃, and particularly preferably 750 to 900 ℃. When the softening point is too low, the coating material flows excessively during firing, and it is difficult to obtain a barrier layer having a uniform thickness. As a result, the function as a barrier layer is likely to be reduced. On the other hand, if the softening point is too high, it is difficult to obtain a dense barrier layer, and the function as a barrier layer may be reduced.

In order to sufficiently exhibit the function, the thickness of the barrier layer is preferably 30 μm or more and 50 μm or more, and particularly preferably 80 μm or more. When the thickness of the barrier layer is too large, the dielectric constant and the dielectric loss of the entire glass ceramic dielectric become large, and therefore, it is preferably 300 μm or less, 200 μm or less, and particularly preferably 150 μm or less.

(method for producing glass ceramic dielectric)

FIG. 2 is a schematic cross-sectional view showing one embodiment of the method for producing a glass ceramic dielectric according to the present invention.

First, a green sheet 2 'for a glass ceramic layer containing a crystalline glass powder and a green sheet 3' for a barrier layer (amorphous glass layer) containing an amorphous glass powder are prepared and prepared by a known green sheet method. Specifically, each green sheet is obtained by adding a vehicle including a resin binder, an organic solvent, and the like to crystalline glass powder and amorphous glass powder as raw materials, kneading the mixture to prepare a glass paste, and sheet-molding the obtained glass paste on a substrate such as a PET (polyethylene terephthalate) film by a doctor blade. The thickness of the green sheet may be appropriately selected depending on the intended thicknesses of the glass ceramic layer 2 and the barrier layer 3, and is usually about 100 to 250 μm, and further about 120 to 200 μm. Each green sheet may be machined as necessary to provide through holes for forming conductors and electrodes.

Next, the obtained green sheet 2 'for glass ceramic layer and the green sheet 3' for barrier layer were laminated to obtain a laminate. Here, it is preferable that each green sheet is thermocompression bonded by thermocompression to improve the adhesiveness of each layer. In fig. 2 (a), 3 glass ceramic layer green sheets 2 ' are stacked, and one barrier layer green sheet 3 ' is stacked on each of both surfaces to produce a laminate 1 '. The number of laminated glass ceramic layer green sheets 2' may be appropriately selected depending on the thickness of the target glass ceramic layer 2, and is usually 2 to 10 sheets, and further 3 to 7 sheets. The number of the barrier layer green sheets 3' to be stacked may be 1, but 2 or more sheets may be stacked.

Next, the laminate 1' is fired in a state of being sandwiched between the pair of constraining sheets 4 ((b) of fig. 2). Thus, the glass-ceramic-layer green sheet 2 'and the barrier-layer green sheet 3' become the glass ceramic layer 2 and the barrier layer (amorphous glass layer) 3, respectively. Then, a glass ceramic dielectric 1 in which the barrier layers 3 were formed on both main surfaces of the glass ceramic layer 2 was obtained (fig. 2 (c)).

The constraining sheet 4 serves to suppress shrinkage in the plane direction of the laminate 1' during firing. As the constraining sheet 4, for example, a green sheet containing ceramic powder such as alumina powder can be used. When the restraint sheet 4 is removed after firing, the ceramic powder contained in the restraint sheet 4 may adhere to the surface of the barrier layer 3, but the ceramic powder hardly affects the characteristics such as the dielectric loss of the glass ceramic dielectric 1, and therefore, the removal by polishing or the like is not necessarily required.

The firing temperature is preferably a temperature at which the crystalline glass powder contained in the green sheet 2' for a glass ceramic layer is sufficiently crystallized. Specifically, the firing temperature is preferably not less than the crystallization temperature of the crystalline glass powder, more preferably not less than (crystallization starting temperature of the crystalline glass powder +50 ℃), and particularly preferably not less than (crystallization starting temperature of the crystalline glass powder +100 ℃) (firing condition a). By providing such a configuration, the glass ceramic dielectric 1 satisfying desired characteristics such as dielectric loss can be obtained.

From another viewpoint, the firing temperature is preferably a temperature at which the amorphous glass powder contained in the barrier layer green sheet 3' is sufficiently softened and fluidized to be sintered. Specifically, the firing temperature is preferably not less than the softening point of the amorphous glass powder, more preferably not less than (the softening point of the amorphous glass powder +50 ℃), and particularly preferably not less than (the softening point of the amorphous glass powder +100 ℃) (firing condition B). By providing such a configuration, the glass ceramic dielectric 1 in which the barrier layer 3 having desired characteristics is formed can be obtained.

The firing temperature preferably satisfies both firing conditions a and B described above. This makes it possible to obtain a glass ceramic dielectric 1 having desired characteristics. The firing temperature is preferably 800 to 1000 ℃, 800 to 950 ℃, and particularly preferably 850 to 900 ℃.

The surface of the barrier layer 3 in the obtained glass ceramic dielectric 1 is subjected to plating treatment to form metal wiring (not shown), thereby obtaining a circuit board.