JP4325928B2 - BaTiO3 dielectric electrode paste and conductor paste and capacitor built-in multilayer wiring board - Google Patents

Description

The present invention relates to a BaTiO ₃ -based dielectric electrode paste and a conductor paste for forming a Cu or Ag electrode used for a BaTiO ₃ -based ceramic capacitor, a multilayer wiring board incorporating a BaTiO ₃ -based capacitor element, and the like, and the use thereof Relates to a multilayer wiring board with a built-in capacitor.

  In recent years, with the reduction in size and weight of electronic devices and the high density mounting of electronic components, there has been an increasing demand for downsizing and increasing the capacity of capacitors. In order to reduce the size and increase the capacity of the capacitor, it is necessary to make the dielectric layer thin or use a dielectric material having a high relative dielectric constant. For this reason, the dielectric material is required to have a high relative dielectric constant.

One of the dielectric materials having a high relative dielectric constant is BaTiO ₃ having a perovskite structure. Ceramic capacitors for a BaTiO ₃ as a main component is obtained by co-firing the dielectric layer and the electrode layer mainly composed of BaTiO ₃ at 1250 ° C. to 1350 ° C.. As described above, since firing at a high temperature is necessary, a low resistance conductor material such as Cu or Ag cannot be used for the electrode layer, and a high melting point metal material such as Pd, Pt, Ni or the like is used. This increases the resistance value of the capacitor.

In order to use a low resistance conductor material such as Cu or Ag, it is necessary to sinter BaTiO ₃ at a low temperature of 950 ° C. or less, and a large amount of sintering aid must be used. However, in general, the dielectric constant of the dielectric follows the logarithmic mixing rule, and the decrease in the dielectric constant due to the increase in the amount of added glass is significant.

  In addition, a structure in which a large-capacity capacitor element is built in an LTCC (Low Temperature Co-fired Ceramics) substrate on which a semiconductor chip is mounted has been proposed. By disposing the capacitor element inside the LTCC substrate closer to the semiconductor chip, the impedance of the power source that affects the semiconductor chip can be lowered, and the entire substrate can be downsized.

  As a method of forming a capacitor element inside the LTCC substrate, there is a method of forming a parallel plate capacitor by, for example, a screen printing method. Such a capacitor element built-in type LTCC substrate is formed by alternately printing electrode layers, dielectric layers and electrode layers on a ceramic green sheet, and then stacking and laminating them together with a ceramic green sheet serving as an LTCC substrate. It can produce by doing.

  Since the capacitor element used here is fired simultaneously with the LTCC substrate, it must be sintered at about 950 ° C. or less, which is the firing temperature of the LTCC substrate.

  It is also important to select a material for the electrode layer used for the capacitor element described above. That is, it is required that the interface with the dielectric layer does not peel off during firing, and that the relative dielectric constant of the dielectric layer is not lowered during simultaneous firing with the dielectric. In addition, when this electrode layer material is used for a capacitor element built-in substrate, it is possible to prevent the internal components of the LTCC substrate and the components in the dielectric material from interdiffusion to reduce the dielectric constant of the dielectric material during simultaneous firing. It is important to be a material.

However, since conductor materials such as Cu and Ag generally have a lower shrinkage temperature than BaTiO ₃ , the shrinkage temperatures of the two must be matched. For example, Patent Document 1 discloses a method of adding BaTiO ₃ powder into an electrode. In order to make the shrinkage temperatures of the two coincide, a method of adding SiO ₂ —B ₂ O ₃ glass into the electrode, a method of making BaTiO ₃ powder into fine powder, and the like have been proposed.

  Furthermore, selection of the conductor material used for the through conductor connected to the capacitor element is also important. That is, if peeling occurs between the LTCC substrate and the through conductor during firing, the sealing property within the LTCC substrate is not maintained, resulting in a significant decrease in the reliability of the LTCC substrate. Further, even when the through conductor component flows into the dielectric layer during firing, the dielectric constant of the dielectric must not be reduced.

And, in order not to cause peeling between the LTCC substrate and the through conductor, for example, SiO ₂ —B ₂ O ₃ glass, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ system in the through conductor. A method of adding glass has been proposed.
Japanese Patent Laid-Open No. 2003-68559

However, if only BaTiO ₃ is added to the electrode, the wettability between the dielectric layer and the electrode layer is low, and the interface may peel off during firing. In addition, when glass is added to the electrode, there is a problem in that the glass component in the electrode flows into the dielectric layer during firing to deteriorate the characteristics of the dielectric layer.

  Further, when the glass is simply added to the through conductor, there is a problem that the component of the through conductor flows into the dielectric layer during firing, thereby reducing the dielectric constant of the dielectric layer.

The present invention has been completed in view of the above problems, and its purpose is to eliminate the peeling of the interface between the dielectric layer and the electrode layer during firing, and to deteriorate the characteristics of the dielectric layer during firing. An object of the present invention is to provide an electrode paste for a BaTiO ₃ -based dielectric that can prevent the above.

  Another object of the present invention is to provide a conductor paste capable of maintaining the sealing property in the LTCC substrate during firing and preventing the dielectric constant of the dielectric layer from being reduced during firing.

  Another object of the present invention is to provide a multilayer wiring board with a built-in capacitor in which the interface between the dielectric layer and the electrode layer does not peel off during firing, and the characteristics of the dielectric layer do not deteriorate during firing. . It is another object of the present invention to provide a multilayer wiring board with a built-in capacitor that maintains the sealing performance in the substrate during firing and does not deteriorate the characteristics of the dielectric layer during firing.

The electrode paste for BaTiO ₃ based dielectric of the present invention contains 85 to 99.5 parts by mass of Cu or Ag powder, 0.5 to 15 parts by mass of crystallized glass for depositing barium titanate crystals, and is organic. A BaTiO ₃ dielectric electrode paste comprising a resin binder and an organic solvent, wherein the crystallized glass contains 55.1 to 59.7% by mass of BaO and 24.0 to 26.0% by mass of TiO _2. %, SiO ₂ 7.7 to 11.3 mass%, Al ₂ O ₃ 6.6 to 9.7 mass%, SrO 0.7 mass% or less, Na ₂ O 0.5 mass% or less, It contains 0.4% by mass or less of CaO.

The conductive paste of the present invention is connected to at least one of a dielectric layer made of a BaTiO ₃ based dielectric formed inside an insulating substrate, an electrode layer formed on each of upper and lower main surfaces thereof, and the electrode layer. A conductive paste for forming a through conductor in a multilayer wiring board with a built-in capacitor having a through conductor, wherein 50.0 to 95.0 parts by mass of Cu or Ag powder and a barium titanate crystal are precipitated. The crystallized glass contains 55.1 to 59.7% by mass of BaO and 24.0 of TiO ₂ while containing 5.0 to 50.0 parts by mass of a vitrified glass and an organic resin binder and an organic solvent. ˜26.0% by mass, SiO ₂ 7.7 to 11.3% by mass, Al ₂ O ₃ 6.6 to 9.7% by mass, SrO 0.7% by mass or less, and Na ₂ O 0. 5 mass% or less, Ca The is characterized in that it contains 0.4 mass% or less.

The multilayer wiring board with a built-in capacitor according to the present invention includes a dielectric layer made of a BaTiO ₃ based dielectric formed inside an insulating substrate, electrode layers respectively formed on upper and lower main surfaces thereof, and at least one of the electrode layers. The electrode layer is formed by firing the BaTiO ₃ dielectric electrode paste of the present invention.

The multilayer wiring board with a built-in capacitor according to the present invention includes a dielectric layer made of a BaTiO ₃ -based dielectric formed inside an insulating substrate, electrode layers formed respectively on the upper and lower main surfaces thereof, and at least one of the electrode layers. A through-conductor connected to one side, and the through-conductor is formed by firing the conductor paste of the present invention.

According to the electrode paste for a BaTiO ₃ dielectric of the present invention, the electrode paste includes crystallized glass that precipitates barium titanate crystals having good wettability with BaTiO _{3 as} the main component of the dielectric. Therefore, even if crystallized glass that precipitates the barium titanate crystal flows into the dielectric layer, the dielectric constant of the dielectric layer does not decrease, and the interface between the electrode layer and the dielectric layer during firing is peeled off. Can be eliminated.

Furthermore, crystallized glass, a BaO 55.1 to 59.7 wt%, the TiO ₂ from 24.0 to 26.0 wt%, a SiO ₂ from 7.7 to 11.3 wt%, _Al 2 _{O 3} of 6.6 to 9.7 wt%, 0.7 wt% or less of SrO Since it contains 0.5 mass% or less of Na ₂ O and 0.4 mass% or less of CaO, the same BaTiO ₃ crystal as the main component of the dielectric layer is precipitated during crystallization of the crystallized glass. It is possible to effectively suppress a decrease in the dielectric constant due to the inflow of the dielectric layer.

Further, according to the conductor paste of the present invention, since the conductor paste includes crystallized glass that precipitates barium titanate crystals having good wettability with BaTiO ₃ which is the main component of the dielectric layer, the dielectric paste Even if crystallized glass that precipitates the barium titanate crystal flows into the layer, the dielectric constant of the dielectric layer is not lowered, and peeling between the LTCC substrate and the through conductor during firing is eliminated. Can do.

Moreover, according to the multilayer wiring board with a built-in capacitor of the present invention, since the electrode contains the crystallized glass that precipitates barium titanate crystals having good wettability with BaTiO _{3 as} the main component of the dielectric, Sometimes, even if crystallized glass that precipitates the barium titanate crystals described above flows into the dielectric layer, the dielectric constant of the dielectric layer does not decrease, and the interface between the electrode layer and the dielectric layer during firing is peeled off. A multilayer wiring board with a built-in capacitor can be provided.

Further, according to the multilayer wiring board with a built-in capacitor according to the present invention, the through glass contains crystallized glass that precipitates barium titanate crystals having good wettability with BaTiO _{3 as} the main component of the dielectric layer. The dielectric constant of the dielectric layer does not decrease even when crystallized glass that precipitates the barium titanate crystal flows into the dielectric layer during firing, and between the LTCC substrate and the through conductor during firing. A multilayer wiring board with a built-in capacitor without peeling can be provided.

An electrode paste for a BaTiO ₃ -based dielectric (hereinafter also referred to as an electrode paste) according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an example of an embodiment of a capacitor element built-in type LTCC substrate manufactured using the electrode paste of the present invention. In FIG. 1, 1 is a dielectric layer built in an LTCC substrate, 2 is an electrode layer, and 3 is an LTCC substrate. FIG. 2 is a sectional view showing an example of an embodiment of a capacitor built-in type LTCC substrate manufactured using the electrode paste and the conductor paste of the present invention. In FIG. 2, 1 is a dielectric layer built in the LTCC substrate, 2 is an electrode layer, 3 is an LTCC substrate, and 4 is a through conductor.

In the present invention, the dielectric layer 1 is disposed inside the LTCC substrate 3 with the upper and lower surfaces sandwiched between the electrode layers 2. The through conductor 4 is connected to at least one of the electrode layers 2 and is connected to the outside of the LTCC substrate 3. The dielectric layer 1 is produced by printing and forming a dielectric layer paste composed of dielectric powder, a sintering aid, an organic resin binder, and an organic solvent, and simultaneously firing with the LTCC substrate 3. Examples of the dielectric powder include those having a perovskite structure such as SrTiO ₃ , MgTiO ₃ , and BaZrO _{3 in} addition to BaTiO ₃ .

Examples of the sintering aid include SiO ₂ —B ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —MO system (however, M Represents Ca, Sr, Mg, Ba or Zn) SiO ₂ —B ₂ O ₃ —M ³ ₂ O system (where M ³ represents Li, Na or K), SiO ₂ —B ₂ O ₃ —Al Examples thereof include ₂ O ₃ -M ³ ₂ O-based (where M ³ is the same as above), Pb-based glass, Bi-based glass and the like, or metal oxides such as CuO.

  The organic resin binder and the organic solvent used for the dielectric layer paste are not particularly limited as long as they can be co-fired with a ceramic green sheet (hereinafter also referred to as a green sheet) to be the LTCC substrate 3, For example, the same organic resin binder and organic solvent blended in the green sheet can be used.

  The electrode layer 2 is printed with an electrode paste containing 85 to 99.5 parts by mass of Cu or Ag powder, 0.5 to 15 parts by mass of crystallized glass for depositing barium titanate crystals, and an organic resin binder and an organic solvent. It is formed by forming and co-firing with a green sheet.

The composition ratio of the crystallized glass on which the barium titanate crystal is precipitated is preferably the minimum ratio with respect to the Cu or Ag powder that does not cause the interface between the dielectric layer 1 and the electrode layer 2 to peel off during firing. When the glass composition ratio of crystallized glass exceeds 15 parts by mass with respect to Cu or Ag powder, a large amount of the glass component of the electrode layer 2 flows into the dielectric layer 1 at the time of firing, and the characteristics of the dielectric layer 1 are deteriorated. There is a tendency to make it easy. On the other hand, when the glass composition ratio of the crystallized glass is less than 0.5 parts by mass, since the crystallized glass is small, the portion having good wettability with BaTiO ₃ is reduced, so that the dielectric layer 1 and the electrode layer 2 There is a tendency for the interface to peel off easily.

  When the Cu or Ag powder is used as an electrode for the LTCC substrate 3, a particle diameter of 5 μm or less is used to suppress mutual diffusion between the components of the LTCC substrate 3 and the dielectric layer 1 during simultaneous firing. It is preferable that it is fine.

The crystallized glass is one in which BaO and TiO ₂ are bonded during the crystallization to precipitate BaTiO ₃ crystals. Since BaTiO ₃ crystals are precipitated as the main phase, even if the crystallized glass flows into the dielectric layer 1 due to diffusion during firing, the characteristics of the dielectric layer 1 are not deteriorated. Further, the addition of crystallized glass to the electrode layer 2 improves the wettability between the dielectric layer 1 and the electrode layer 2, and it is possible to prevent the occurrence of peeling at the interface during firing.

Crystallized glass of the present invention has a glass composition ratio, a BaO 55.1-59.7 wt%, the TiO ₂ from 24.0 to 26.0 wt%, a SiO ₂ 7.7 to 11.3 wt%, the _Al 2 _{O 3} 6.6 to 9.7 wt% , SrO is 0.7 mass% or less, Na ₂ O is 0.5 mass% or less, CaO is 0.4 mass% or less, and the total of each component is adjusted to 100 mass%. Since TiO ₂ , SiO ₂ , Al ₂ O ₃ , SrO, Na ₂ O, and CaO are network-forming oxides, intermediate oxides, and network-modified oxides for vitrification, the minimum ratio for vitrification It is preferable that BaO is more than 59.7 wt%, TiO ₂ exceeds 26.0 mass%, SiO ₂ exceeds 7.7 wt%, when _Al 2 _{O 3} is less than 6.6 wt%, the composition tends to be difficult to vitrify . Further, BaO is less than 55.1 mass%, the TiO ₂ less than 24.0 wt%, SiO ₂ is less than 11.3 wt%, _Al 2 _{O 3} exceeds 9.7 wt%, SrO exceeds 0.7 mass%, Na ₂ O is 0.5 % And CaO exceeds 0.4% by mass, the amount of components other than BaO and TiO ₂ flowing into the dielectric layer 1 tends to increase, and the characteristics of the dielectric layer 1 tend to deteriorate.

Further, as glass for precipitating crystals with a high dielectric constant, there are glass that precipitates NaNb ₂ O ₅ in addition to the one that precipitates BaTiO ₃ , but the glass contained in the electrode paste is a crystal phase of the dielectric layer 1. Those that precipitate the same crystal phase as are preferred. That is, if the main component of the dielectric layer 1 is BaTiO ₃ , the crystallized glass that precipitates BaTiO ₃ is used. If the main component of the dielectric layer 1 is NaNb ₂ O ₅ , the crystallized glass that precipitates NaNb ₂ O ₅ is used as the electrode. It is preferably used as an additive for paste.

  The LTCC substrate 3 is formed by mixing an organic resin binder and an organic solvent into glass or a mixture of glass and ceramic powder, and firing a green sheet formed by a doctor blade method or the like.

Here, as the glass of the LTCC substrate 3, for example, _SiO 2 _-B 2 _{O 3 based, SiO 2 -B 2 O 3 -Al} 2 O 3 _{based, SiO 2 -B 2 O 3 -Al} 2 O 3 -MO -based (Wherein M represents Ca, Sr, Mg, Ba or Zn), SiO ₂ —Al ₂ O ₃ —M ¹ O—M ² O system (where M ¹ and M ² are the same or different and Ca, Sr , Mg, Ba or Zn), SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —M ¹ O—M ² O system (where M ¹ and M ² are the same as above), SiO ₂ — B ₂ O ₃ —M ³ ₂ O system (where M ³ represents Li, Na or K), SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —M ³ ₂ O system (where M ³ is the above) And Pb-based glass, Bi-based glass, and the like.

Examples of the ceramic powder include a composite oxide of Al ₂ O ₃ , SiO ₂ , ZrO ₂ and an alkaline earth metal oxide, a composite oxide of TiO ₂ and an alkaline earth metal oxide, Al ₂ O _3. And composite oxides containing at least one selected from SiO ₂ (for example, spinel, mullite, cordierite) and the like.

  As the organic resin binder to be added to and mixed with the glass powder and the ceramic powder, those conventionally used for green sheets can be used. For example, acrylic (acrylic acid, methacrylic acid or esters thereof homopolymers) Or a copolymer, specifically an acrylic ester copolymer, a methacrylic ester copolymer, an acrylic ester-methacrylic ester copolymer, etc.), a polyvinyl butyral system, a polyvinyl alcohol system, an acrylic-styrene system, Examples thereof include homopolymers or copolymers such as polypropylene carbonate and cellulose.

  As an organic solvent used in a slurry for forming a green sheet, a glass powder, a ceramic powder, and an organic resin binder are dispersed to obtain a slurry having a viscosity suitable for forming a green sheet, for example, hydrocarbons, Organic solvents such as ethers, esters, ketones, alcohols and the like can be mentioned.

  The through conductor 4 contains 50.0 to 95.0 parts by mass of Cu or Ag powder, 5.0 to 50.0 parts by mass of crystallized glass for depositing barium titanate crystals, and contains an organic resin binder and an organic solvent.

  The composition ratio of the crystallized glass on which the barium titanate crystals are precipitated is preferably the minimum ratio with respect to the Cu or Ag powder that does not cause the LTCC substrate 3 and the through conductor 4 to peel off during firing. When the glass composition ratio of the crystallized glass exceeds 50.0 parts by mass with respect to Cu or Ag powder, a large amount of the glass component of the through conductor 4 flows into the dielectric layer 1 during firing, and the dielectric constant of the dielectric layer 1 Tends to decrease. On the other hand, when the glass composition ratio of the crystallized glass is less than 5.0 parts by mass, since the crystallized glass is small, the portion with good wettability between the LTCC substrate 3 and the through conductor 4 is reduced, and the LTCC substrate 3 and There is a tendency that peeling from the through conductor 4 tends to occur.

The crystallized glass is one in which BaO and TiO ₂ are bonded during the crystallization to precipitate BaTiO ₃ crystals. Since BaTiO ₃ crystals are precipitated as the main phase, the dielectric constant of the dielectric layer 1 is less likely to decrease even if the crystallized glass flows into the dielectric layer 1 due to diffusion during firing. Further, the addition of crystallized glass to the through conductors 4 improves the wettability between the LTCC substrate 3 and the through conductors 4 and prevents the occurrence of peeling during firing.

Crystallized glass of the present invention has a glass composition ratio, a BaO 55.1-59.7 wt%, the TiO ₂ from 24.0 to 26.0 wt%, a SiO ₂ 7.7 to 11.3 wt%, the _Al 2 _{O 3} 6.6 to 9.7 wt% , SrO is 0.7 mass% or less, Na ₂ O is 0.5 mass% or less, CaO is 0.4 mass% or less, and the total of each component is adjusted to 100 mass%. Since TiO ₂ , SiO ₂ , Al ₂ O ₃ , SrO, Na ₂ O, and CaO are network-forming oxides, intermediate oxides, and network-modified oxides for vitrification, the minimum ratio for vitrification It is preferable that BaO is more than 59.7 wt%, TiO ₂ exceeds 26.0 mass%, SiO ₂ exceeds 7.7 wt%, when _Al 2 _{O 3} is less than 6.6 wt%, the composition tends to be difficult to vitrify . Further, BaO is less than 55.1 mass%, the TiO ₂ less than 24.0 wt%, SiO ₂ is less than 11.3 wt%, _Al 2 _{O 3} exceeds 9.7 wt%, SrO exceeds 0.7 mass%, Na ₂ O is 0.5 % And CaO exceeds 0.4% by mass, the amount of components other than BaO and TiO ₂ flowing into the dielectric layer 1 tends to increase, and the characteristics of the dielectric layer 1 tend to deteriorate.

  As a method of forming the dielectric layer 1 and the electrode layer 2 in the LTCC substrate 3 as described above, there is a method of forming a parallel plate capacitor by, for example, a screen printing method. Further, as a method for forming the through conductor 4 in the LTCC substrate 3, a through hole forming step by mechanical processing and a screen printing method may be combined.

  First, a layer in which electrode layer paste, dielectric layer paste, and electrode layer paste are alternately printed on a green sheet for the LTCC substrate 3 is formed. Next, through holes are formed in the LTCC substrate 3 by mechanical processing, and then the conductive paste is filled into the through holes by a screen printing method. Next, green sheets are stacked and laminated. Finally, the laminate is produced by firing at a temperature of 800 to 1000 ° C.

  Examples of the electrode paste of the present invention will be described below, but the present invention is not limited to the following examples.

In order to obtain a green sheet serving as an insulating layer of the LTCC substrate, 60% by mass of SiO ₂ —CaO—MgO glass powder as glass and 40% by mass of Al ₂ O ₃ powder as ceramic powder are mixed, and this inorganic powder 100 12 parts by mass of an acrylic resin as an organic resin binder, 6 parts by mass of a phthalic plasticizer and 30 parts by mass of toluene as a solvent were added to parts by mass, and mixed by a ball mill method to obtain a slurry. Using this slurry, a green sheet having a thickness of 200 μm was formed by a doctor blade method.

  Next, an electrode paste was applied on the green sheet by screen printing to form a capacitor element electrode pattern having a length of 100 mm × width of 100 mm × thickness of 12 μm.

  As a powder composition of the electrode layer, Cu powder and crystallized glass were mixed at a ratio shown in Table 1. For comparison, crystallized glass having other compositions were mixed at the ratios shown in Table 1. To this powder, an acrylic binder and terpineol were added and mixed with a three roll so as to have an appropriate viscosity.

  Next, the organic solvent in the printed electrode paste was dried with hot air at 80 ° C.

  Next, a dielectric layer paste was applied on the electrode paste by screen printing to form an electrode pattern of a capacitor element having a length of 22 mm × width of 22 mm × thickness of 20 μm.

As the powder of the dielectric layer of the capacitor element, a powder composed of BaTiO ₃ and a sintering aid was used. To this powder, an organic resin binder, a dispersant and an organic solvent were added and kneaded to form a paste. An acrylic binder was used as the organic resin binder, and a nonionic binder was used as the dispersant. Further, terpineol was used as the organic solvent.

  Next, the organic solvent in the printed dielectric layer paste was dried with hot air at 80 ° C.

  Next, on this dielectric layer paste, an electrode paste was applied in the same manner to form an electrode pattern of a capacitor element having a length of 20 mm × width of 20 mm × thickness of 12 μm.

  The organic solvent in the wiring conductor paste thus formed on the dielectric layer paste was dried with hot air at 80 ° C.

Finally, the green sheet on which this capacitor element (capacitor element) was formed was baked at 950 ° C. for 40 minutes in an N ₂ atmosphere to produce a capacitor element built-in type LTCC substrate.

  About the obtained LTCC board | substrate, the electric capacity of the capacitor | condenser element was measured. The capacity was measured using an impedance measuring instrument (model: 4294A precision impedance analyzer, measurement accuracy: ± 0.08%) manufactured by Agilent Technologies, Inc. under the conditions of a measurement frequency of 1 MHz and a measurement temperature of 25 ° C.

  Next, the electrode area of the capacitor element and the thickness of the dielectric layer were measured. The electrode area was measured from the top surface of the LTCC with a metal microscope (magnification is 25 times). The thickness of the dielectric layer was measured with a metal microscope (magnification is 100 times) after mirror-finishing the cross section of the LTCC substrate.

The relative dielectric constant was calculated based on the capacitance, electrode area, and dielectric thickness obtained by the measurement. In the case of a parallel plate capacitor, the relative dielectric constant of the material of the dielectric layer is C = ε ₀ · ε _r · S / d (C: capacitance of the capacitive element, ε ₀ : dielectric constant in air, ε _r : dielectric layer) The relative dielectric constant of the material, S: electrode area, d: distance between electrodes). The obtained results are shown in Table 1.

From Table 1, it was found that Sample 1 using BaO—TiO ₂ —SiO ₂ —Al ₂ O ₃ glass as the crystallized glass of the electrode paste had a high relative dielectric constant of 250 or more. On the other hand, as the electrode paste glass, Li ₂ O—B ₂ O ₃ —SiO ₂ —BaO—CaO glass, B ₂ O ₃ —ZnO—BaO—SrO glass, which does not precipitate barium titanate crystals, It was found that Samples 2 to 5 using Al ₂ O ₃ —SiO ₂ glass had a low relative dielectric constant of 200 or less.

Further, as described above claims range of a glass composition ratio, a BaO 60.7% by weight, the TiO ₂ 27.0 wt%, a SiO ₂ 6.7 wt%, vitrification of the composition is an _Al 2 _{O 3} 5.6 wt% However, devitrification occurred at the time of rapid cooling from melting of the composition, which was a process of vitrification, and it was not possible to vitrify.

In order to obtain a green sheet serving as an insulating layer, 60 parts by mass of SiO ₂ —CaO—MgO glass powder as glass and 40 parts by mass of Al ₂ O ₃ powder as ceramic powder are mixed, and 100 parts by mass of this inorganic powder is mixed. 12 parts by mass of an acrylic resin as an organic resin binder, 6 parts by mass of a phthalic acid plasticizer and 30 parts by mass of toluene as a solvent were added and mixed by a ball mill method to obtain a slurry. Using this slurry, a green sheet having a thickness of 200 μm was formed by a doctor blade method.

  Next, two sheets of a first green sheet and a second green sheet were prepared from this green sheet. The capacitor element of the present invention was formed on these green sheets. In order to examine whether the dielectric constant of the capacitor element depends on the type of the conductive paste, two capacitor elements manufactured in the same manufacturing process are formed, and through-conductors A and B are connected to the respective dielectric elements. The dielectric constants of the layers were compared. Hereinafter, a production method and an evaluation method will be described.

  First, through holes were formed in the first green sheet and the second green sheet by mechanical processing. The through hole was processed so that the cross-sectional shape was a circle having a diameter of 0.2 mm.

Next, the conductor paste B produced for comparison with the conductor paste A of the present invention was filled into the through holes formed in the first green sheet and the second green sheet. The composition ratio of the glass to be used for penetrating the conductor A, was used BaO 55.1% by weight, TiO ₂ is 24.0 wt%, SiO ₂ is 11.3 wt%, _{those Al} 2 _{O 3} comprises a 9.7 wt%. Further, as the glass used for the through conductor B, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ based glass which does not contain BaO and TiO ₂ was used.

Next, the electrode paste was applied to the dimensions shown in Table 2 by screen printing on the conductor paste formed on the second green sheet to form a capacitor element electrode pattern.

As powder contained in the electrode layer, 99.0 parts by weight of Cu, comprises 1.0 parts by weight of glass, glass composition ratio, 55.1 wt% of BaO, and TiO ₂ 24.0 wt%, a SiO ₂ 11.3 wt%, Al _A composition comprising 9.7% by mass of ₂ O ₃ was used.

  Next, an acrylic resin binder and terpineol were added to this powder, and mixed so as to have an appropriate viscosity with three rolls.

  Next, the organic solvent in the printed electrode layer paste was dried with hot air at 80 ° C.

Next, the dielectric layer paste was applied to the dimensions shown in Table 2 by screen printing on the electrode layer paste formed on the surface of the second green sheet to form a pattern to be a dielectric layer of the capacitor element. . As the dielectric powder of the dielectric layer, a powder composed of BaTiO ₃ and a sintering aid was used. To this powder, an organic resin binder, a dispersant and an organic solvent were added and kneaded to obtain a paste. An acrylic resin binder was used as the organic resin binder, and a nonionic one was used as the dispersant. Further, terpineol was used as the organic solvent.

  Next, the organic solvent in the printed dielectric layer paste was dried with hot air at 80 ° C.

  Next, on the dielectric layer paste formed on the surface of the second green sheet, the electrode layer paste was applied to the dimensions shown in Table 2 in the same manner to form a capacitor element electrode pattern.

  Next, the organic solvent in the printed electrode layer paste was dried with hot air at 80 ° C.

  Next, in order to form a surface layer pad required for applying the probe, a wiring conductor pattern was formed on the front surface of the first green sheet and the back surface of the second green sheet.

  Next, the organic solvent in the printed wiring conductor paste was dried with hot air at 80 ° C.

Next, the first green sheet and the second green sheet were superposed and vacuum pressed at a pressure of 55 kg / cm ² to obtain a ceramic green sheet laminate.

Next, the ceramic green sheet laminate on which this capacitor element was formed was fired at 900 ° C. for 40 minutes in an N ₂ atmosphere. The conditions of the atmosphere in the firing process are as follows: dielectric layer paste, electrode layer paste, conductor paste, organic resin binder contained in green sheet, organic solvent contained in green sheet, N ₂ passed through warm water at 60 ° C. It was supplied inside.

  With respect to the obtained capacitor element built-in substrate, the electric capacity of the capacitor element was measured. The capacitance was measured using an impedance measuring instrument (model: 4294A precision impedance analyzer, measurement accuracy: ± 0.08%, manufactured by Agilent Technologies) under the conditions of a measurement frequency of 1 kHz and a measurement temperature of 25 ° C.

  Next, the electrode area of the capacitor element and the thickness of the dielectric layer were measured and calculated. The area of the electrode was calculated from the length of one side of the electrode measured by a metal microscope (model: Digital HF microscope VH-8000, KEYENCE, magnification: 50 times) after mirror-finishing the cross section of the LTCC substrate. The thickness of the dielectric layer was measured with a metal microscope (model: Digital HF microscope VH-8000, KEYENCE, magnification: 50 times) after mirror-finishing the cross section of the LTCC substrate.

The relative dielectric constant was calculated based on the capacitance, electrode area, and dielectric layer thickness obtained by the measurement. In the case of a parallel plate capacitor, the relative dielectric constant of the material of the dielectric layer is C = ε ₀ · ε _r · S / d (C: capacitance of the capacitive element, ε ₀ : dielectric constant in air, ε _r : dielectric layer) The relative dielectric constant of the material, S: electrode area, d: distance between electrodes).

  The relative dielectric constant of the dielectric layer of the capacitor in the multilayer wiring boards A and B with built-in capacitors (hereinafter referred to as capacitor built-in boards A and B) containing the obtained capacitor elements with respect to the formed through conductors A and B is expressed as Table 2 shows the results calculated as values for the electrode area of the electrode pattern of the element.

According to Table 2, the relative permittivity of the capacitor element having the electrode area of 0.16 mm ² is lower than that of the other electrode areas in both the capacitor built-in substrates A and B. This is because the component of the conductor paste is a dielectric layer. It can be seen that this reflects that the capacitor element having a small electrode area is more susceptible to the inflow.

However, comparing the capacitor built-in substrates A and B having the same electrode area of 0.16 mm ² , the capacitor built-in substrate A using the conductor paste of the present invention has a higher relative dielectric constant than the conventional capacitor built-in substrate B. It can be seen that the conductor paste of the present invention has a function of suppressing a decrease in the dielectric constant of the dielectric layer. That is, it can be seen that by using the conductor paste of the present invention, a small capacitor element having an electrode area near 0.16 mm ² can be formed with a high dielectric constant.

It is sectional drawing which shows an example of embodiment of the LTCC board | substrate with a built-in capacitor | condenser element produced using the electrode paste of this invention. It is sectional drawing which shows an example of embodiment of the LTCC board | substrate with a built-in capacitor | condenser element produced using the conductor paste of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Dielectric layer 2 ... Electrode layer 3 ... LTCC board | substrate 4 ... Through-conductor

Claims (4)

BaTiO ₃ -based dielectric comprising 85 to 99.5 parts by mass of Cu or Ag powder, 0.5 to 15 parts by mass of crystallized glass for precipitating barium titanate crystals, and containing an organic resin binder and an organic solvent a-body electrode paste, the crystallized glass, the BaO from 55.1 to 59.7 wt%, the TiO ₂ from 24.0 to 26.0 wt%, a SiO ₂ 7.7-11.3 mass %, Al ₂ O ₃ 6.6 to 9.7% by mass, SrO 0.7% by mass or less, Na ₂ O 0.5% by mass or less, and CaO 0.4% by mass or less. A BaTiO ₃ -based dielectric electrode paste characterized. A capacitor comprising a dielectric layer made of a BaTiO ₃ -based dielectric formed inside an insulating substrate, electrode layers respectively formed on upper and lower main surfaces thereof, and a through conductor connected to at least one of the electrode layers A conductive paste for forming the through conductor in the built-in multilayer wiring board, comprising 50.0 to 95.0 parts by mass of Cu or Ag powder, and 5.0 to 5 of crystallized glass for depositing barium titanate crystals. 50.0 parts by mass and an organic resin binder and an organic solvent. The crystallized glass contains 55.1 to 59.7% by mass of BaO, 24.0 to 26.0% by mass of TiO ₂ , the SiO ₂ 7.7-11.3 wt%, the _Al 2 _{O 3} 6.6 to 9.7 wt%, SrO 0.7 wt% or less, Na ₂ O 0.5 wt% or less, the CaO 0.4% by mass or less Conductive paste, characterized in that there. A dielectric layer made of a BaTiO ₃ based dielectric formed inside the insulating substrate; electrode layers formed on upper and lower main surfaces thereof; and a through conductor connected to at least one of the electrode layers. A capacitor built-in multilayer wiring board, wherein the electrode layer is formed by firing the BaTiO ₃ dielectric electrode paste according to claim 1. A dielectric layer made of a BaTiO ₃ based dielectric formed inside the insulating substrate; electrode layers formed on upper and lower main surfaces thereof; and a through conductor connected to at least one of the electrode layers. And the through conductor is formed by firing the conductive paste according to claim 2.

Images