JPH08298365A - Ceramic board with capacitor - Google Patents

Abstract

PURPOSE: To prevent the decrease of permittivity of a dielectric which is caused by diffusion of glass component in an insulating layer composed of glass ceramic into a dielectric layer constituted of perovskite type ceramic, in a ceramic board with capacitor. CONSTITUTION: In a ceramic board 10 with capacitor, glass component contained in electrode layers 13A, B which are interposed between insulating layers 11A, B and a dielectric layer 12 and composed of Ag or the like is set to be lower than or equal to 2wt.%, preferably, lower than or equal to 1wt.%. The thickness of the electrode layers 13A, B is set to be greater than or equal to 20/μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic substrate provided with a capacitor on the surface or inside thereof, and more particularly to a ceramic substrate with a capacitor using glass ceramic as the substrate.

[0002]

2. Description of the Related Art Alumina substrates have been usually used as ceramic substrates for mounting integrated circuit chips and other electronic components. However, alumina is about 1500
Since it needs to be fired at a high temperature of ℃ or higher, the firing cost is high. Further, when forming the circuit wiring by co-firing, a high melting point metal such as W or Mo having a high specific resistance must be used, and the wiring resistance becomes higher as the wiring pattern becomes finer and the density becomes higher. However, there was a limit to high frequency driving. Therefore, as a low-temperature fired substrate on which a conductor such as Ag, Au, or Cu having low resistance can be used, a composite material (glass-ceramic) based on a mixture of ceramic powder such as alumina and glass powder, a crystallized glass system, or a non-glass system is used. Substrates have been developed that use glass ceramics as an insulating layer.

On the other hand, in order to remove noise generated by high frequency driving of an integrated circuit, a ceramic substrate having a capacitor formed inside or on its surface has been developed. As the dielectric of this capacitor, tantalum nitride (Ta: N), alumina (Al ₂ O ₃ ) or the like is used,
With a high dielectric constant, a capacitor having a perovskite crystal structure such as BaTiO ₃ , SrTiO ₃ or the like, particularly a perovskite-type ceramic containing lead such as PbTiO ₃ or Pb for the purpose of increasing the capacity or the area of a capacitor.
Materials using ZrO ₃ , Pb (Zr, Ti) O ₃ , PMN, etc. have been developed.

[0004]

However, such BaT
In a ceramic substrate with a capacitor that uses iO ₃ or the like as a dielectric, when the dielectric layer, the electrode layer, and the insulating layer made of glass ceramic are formed by simultaneous firing, an insulating material that is in contact with the electrode layers sandwiching the dielectric layer is used. Layer containing SiO ₂ , CaO, Mg contained in the glass ceramic
_{O, Al 2 O 3, B} 2 0 3 glass component or the like, to diffuse through the electrode layers varying the composition of the dielectric layer, there is a remarkable problem of lowering the dielectric constant possessed by the dielectric layer.

To solve this problem, for example, Japanese Patent Laid-Open No. 62-
In Japanese Patent No. 139394, a dielectric layer is further provided outside a dielectric layer forming a capacitor and two electrode layers sandwiching the dielectric layer, and a metal layer is provided between the dielectric layer and the insulating layer on the outside. A composite laminated ceramic component is disclosed. This is because the metal layer prevents the glass component from diffusing between the insulator layer and the outer dielectric layer. Further, in Japanese Patent Application Laid-Open No. 62-139393, the metal layer in the composite multilayer ceramic component of the above-mentioned Japanese Patent Application Laid-Open No. 62-139394 is replaced with an intermediate layer made of a mixture of a dielectric material and an insulating material. Things are disclosed.
This is because the presence of such an intermediate layer alleviates a change in the concentration of the glass component between the insulating layer and the dielectric layer and reduces the diffusion of the glass component. Furthermore, JP-A-62-17790
JP-A-62-139394 discloses that the metal body layer in the composite multilayer ceramic component disclosed in JP-A-62-139394 is a metal body layer to which a mixture of a dielectric material and an insulating material is added. This is because the metal layer similarly relaxes the change in the concentration of the glass component between the insulating layer and the dielectric layer and reduces the diffusion of the glass component.

However, in these techniques, the metal layer or the intermediate layer is interposed between the insulating layer and the dielectric layer. Therefore, at the time of firing, it is unavoidable that the glass component of the liquid phase insulating layer is diffused into the dielectric layer through the liquid phase glass component contained in the metal layer or the intermediate layer. It was Further, since the metal body layer and the intermediate body layer described above are formed by green sheet molding,
It takes time and labor to manufacture these green sheets, resulting in an increase in cost. Furthermore, when the dielectric layer is provided on the outer side, a layer that cannot be used as a capacitor or an insulator layer is interposed, which inevitably increases the thickness and requires time and effort for manufacturing.

The present invention has been made in view of the above problems, and when a capacitor is provided on a ceramic substrate containing a large amount of glass components by simultaneous firing, the diffusion of the glass components into the dielectric layer is performed by a simple method. An object of the present invention is to provide a ceramic substrate with a capacitor that has a reduced dielectric constant and a high dielectric constant.

[0008]

However, the solution is to provide a dielectric layer made of perovskite type ceramic,
An insulating layer made of glass ceramic, and Ag, Au, Pd, Pt, Cu interposed between the dielectric layer and the insulating layer.
And an electrode layer containing at least one or more of Ni as a main component, and the dielectric layer, the electrode layer, and the insulating layer are formed by co-firing. Glass component content of 2wt
% Or less, to provide a ceramic substrate with a capacitor. Here, if the content of the glass component in the electrode layer is 1 wt% or less, the diffusion of the glass component into the dielectric layer can be further reduced, which is preferable. Further, when the thickness of the electrode layer is 20 μm or more, the diffusion of the glass component into the dielectric layer can be further reduced, which is preferable.

Another solution is to provide Ag, Au, Pd between an insulator green sheet which becomes an insulator layer made of glass ceramic after firing and an unfired dielectric layer which becomes a dielectric layer after firing. , Pt, Cu, and Ni as main components, and the content of glass component is 2
A ceramic substrate with a capacitor, which is not more than wt% and which is obtained by firing an unfired ceramic laminated body with a conductive paste layer serving as an electrode layer interposed after firing. Here, the content of the glass component in the conductive paste layer is 1w.
When it is t% or less, the diffusion of the glass component into the dielectric layer can be further reduced, which is preferable. Also, when the conductive paste layer has a thickness such that the thickness of the electrode layer after firing is 20 μm or more, diffusion of the glass component into the dielectric layer can be further reduced, which is preferable.

[0010]

In the insulator layer made of glass ceramic, the amount of glass component is large. On the other hand, the dielectric layer contains less glass. Therefore, a difference in glass component concentration occurs between the insulating layer and the dielectric layer. In this state, since the glass component is in a liquid phase state during firing, the glass component tends to diffuse from the insulating layer toward the dielectric layer. By the way, in the dielectric layer, when the glass component diffuses, the glass component accumulates at the crystal grain boundaries, and the crystal composition and the crystal structure also change. That is, the characteristics of the dielectric change, and the dielectric constant decreases.

Here, the movement path of the glass component will be considered. There is an electrode layer between the insulator layer and the dielectric layer, and the glass component contained in the electrode layer also becomes a liquid phase during firing and comes into contact with the insulator layer and the dielectric layer. Therefore, it is considered that the glass component in the insulator layer diffuses into the dielectric layer via the glass component in the liquid phase electrode layer.

Therefore, an electrode layer having a small glass component content is used as an electrode layer interposed between an insulating layer and a dielectric layer to form a capacitor. Then, at the time of firing, almost no migration path in the liquid phase due to the glass component is formed in this electrode layer. Therefore, the glass component is suppressed from diffusing from the insulating layer to the dielectric layer through this moving path. The amount of the glass component contained in this electrode layer is preferably 2 wt% or less, particularly 1 wt% or less. This is because in the perovskite-type ceramic used as a dielectric, the dielectric constant sharply decreases due to the diffusion of the glass component, and therefore it is necessary to suppress the diffusion of the glass component as much as possible.

It is also effective to lengthen the movement path to suppress diffusion, and the thickness of the electrode layer is 20 after firing.
It is preferably at least μm. The thicker the thickness, the lower the electrode resistance of the capacitor, which is preferable for the characteristics of the capacitor. However, the thicker the material cost, the more the number of processes such as increasing the number of times the paste is applied increases. Therefore, an appropriate thickness may be taken in consideration of the required electrode resistance.

On the other hand, the material of the electrode layer is Ag, A
u, Pd, Pt, Cu, Ni or the like is used. The melting points of these metals are, for example, 962 ° C. for Ag and 108 for Cu.
It is low at 4 ° C and 1064 ° C in Au. Therefore, when the ceramic substrate is fired at a firing temperature close to the melting point (900 to 950 ° C.), the metal particles are thermally diffused through the contact points of each other, so that the particles are sufficiently densified without any glass component or the like. . Therefore, a small amount of glass component is added to accelerate the sintering of the electrode layer (metal particles), and even a small amount of glass component diffused from the insulating layer can be sintered. Regarding the material, particularly Ag, Cu and Ag
A silver-based alloy such as -Pd is preferable because it is relatively inexpensive and has a low resistivity.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The contents of the present invention will be described below based on embodiments with reference to the drawings. Borosilicate glass (SiO ₂ -A
l ₂ O ₃ -CaO-MgO-B ₂ O ₃ ) powder 65 wt% and alumina (Al ₂
O ₃ ) Powder 35 wt%, an organic binder and an organic solvent are appropriately added to form a slurry, which is made into a green tape by a well-known doctor blade method and punched out to obtain 35 × 35.
An insulator green sheet 1 of × 0.5 mm is formed. On the other hand, PbTiO ₃ —PbZrO ₃ -based dielectric powder is mixed with an organic binder and an organic solvent to form a slurry, which is also formed into a green tape by the doctor blade method, and punched out.
A dielectric green sheet 2 of 5 × 35 × 0.1 mm is formed. Further, A having a purity of 99.9% and an average particle diameter of 3.0 μm
g powder, glass component with a transition temperature Tg = 560 ° C. (PbO-
BaO-SiO ₂₎ was added 0-5 wt%, further acrylic binder was fabricated conductive paste mixed with plasticizers and organic solvents.

Next, as shown in FIGS. 1 and 2, a conductor paste is applied to the entire surface (30.times.30 mm) of the insulator green sheet 1A except the periphery 2.5 mm on the upper surface 1A1 in the figure and dried. The conductor paste layer 3A is formed.
Further, the dielectric green sheet 2 is provided with via hole holes of φ0.25 mm, and the via hole ink made of Ag is filled therein to form the via hole 4A1. Further, on the upper surface 2A of the sheet 2 in the drawing, the periphery 2.
Conductor paste is applied to the entire surface (30 × 30 mm) except for 5 mm and around φ1 mm near the via hole 4A1 and dried to form a conductor paste layer 3B. Furthermore, φ0.25 mm that was previously vacated in another insulator green sheet 1B.
Via holes 4A2 and 4B are filled with the via hole inks of Ag to form via holes 4A2 and 4B, and pads 5A and 5B of φ2.0 mm for measuring capacitance are connected to the upper surface 1B1 so as to be connected to these via holes. Print and form using paste.

By stacking these three green sheets, 30
The unfired ceramic compact 6 having a cross section as shown in FIG. 2 is formed by pressure bonding with a pressure of kgf / mm ² . Further, the unfired ceramic compact 6 was placed in an atmosphere of 9
Approximately 29 x 29 x 0.9 mm after firing at 30 ° C for 2 hours
A ceramic substrate with a capacitor was manufactured.

As a result, the dielectric layer 12 is provided at the center,
A capacitor C is formed by providing electrode layers 13A and 13B on the upper and lower surfaces thereof, insulating layers 11A and 11B are provided so as to sandwich the capacitor C, and an electrode is formed from the pad 15A on the upper surface 11B1 of the insulating layer 11B. A ceramic substrate 10 with a capacitor provided with a via hole 14A connected to the layer 13A and a via hole 14B connected to the electrode layer 13B from the pad 15B on the surface 11B1 was obtained. The capacitance of the capacitor C is determined by the pads 15A and 15B.
It is measured by connecting the terminal of the capacitance meter to. The measurement frequency of the electrostatic capacitance was measured at 500 kHz, which is close to the actual use frequency of the ceramic substrate.

Table 1 shows changes in the relative permittivity ε of the dielectric layer 12 calculated from the capacitance of the capacitor C when the composition of the conductor paste and the thicknesses of the electrode layers 13A and 13B are changed. Show. The PbTiO ₃ —PbZrO ₃ system dielectric used for the dielectric layer in this example is a material having a relative permittivity ε of 1660 when fired alone.

[0020] Note) 1. The relative dielectric constant when the dielectric used in this example was fired alone was 1660. 2. Among additives, Si (0Et) ₄ A, Si indicates a _{(0-C 2 H 5)} 4, and serves as a SiO ₂ after firing.

As can be seen from Table 1, when the electrode layers have the same thickness of 20 μm (Sample Nos. 3, 6, 7, and 8), the smaller the glass component of the conductor paste is, the more the relative dielectric constant of the dielectric layer is. When it is high and Ag is 100%, the relative permittivity ε shows 1290, which is the highest value. This is because, as described above, when the glass component contained in the conductor paste, that is, the electrode layer is small, the glass component diffused from the insulating layers 11A, B to the dielectric layer 12 via the electrode layers 13A, B is small. It is thought to be because of this. On the other hand, when Ag is 100%, that is, when the glass component is not contained (Sample Nos. 1 to 5), when the influence of the thickness of the electrode layer is compared, the dielectric constant of the dielectric layer increases as the thickness of the electrode layer increases. I understand.
As also described above, as the electrode layers 13A and 13B become thicker, the migration path for the glass component to diffuse from the insulating layers 11A and 11B to the dielectric layer 12 becomes longer, and as a result, to the dielectric layer 12. It is considered that the diffusion of the glass component decreased. In this case, when the thickness of the electrode layers 13A and 13B is in the range of 15 μm to 20 μm, the dielectric layer 12 is
It can be seen that the relative permittivity of is rapidly changing. Therefore,
It can be seen that the electrode layers 13A and 13B each preferably have a thickness of 20 μm or more.

In addition, the PbTiO ₃ --PbZrO ₃ system dielectric is added to glass components such as SiO ₂ , Al ₂ O ₃ , MgO and C.
When aO or the like diffuses, the glass component segregates at the crystal grain boundaries, and for example, PbTiO ₃ + SiO ₂ → PbTi ₂ O ₇ +
Pb ₄ SiO ₆ or PbZrO ₃ + SiO ₂ → Pb ₄ SiO ₆
It is considered that the reaction of + ZrO ₂ or the like occurs and the perovskite-based crystal system collapses to lower the dielectric constant. This was also confirmed by the fact that in the X-ray diffraction analysis of the dielectric layer, the lower the relative permittivity ε, the lower the peak showing the presence of PbTiO ₃ or PbZrO ₃ crystals.

Further, in sample No. 9, S which is an organic metal
The case where i (0Et) ₄ is added to the conductor paste is shown. Here, Si (0Et) ₄ means Si (0-C ₂
H ₅ ) ₄ , which becomes SiO ₂ after firing. According to Table 1, even when Si (0Et) ₄ is added by ₂ wt% (0.58 wt% in terms of SiO ₂ ), the relative permittivity is lowered. This is because the firing causes SiO ₂ to diffuse into the dielectric layer, and Si or SiO ₂ becomes PbTiO ₃ —PbZ.
It is considered that the relative dielectric constant of the dielectric layer was lowered due to the reaction with the rO ₃ system dielectric. That is, the results of this sample also prove that the decrease in the relative permittivity ε in the case of Sample Nos. 1 to 8 is due to the change in the crystal composition of the dielectric due to the diffusion of the glass component.

(Reference Example) Further, PbTiO ₃ -PbZr
Dielectric constant ε when glass component is added to O ₃ -based dielectric
By investigating the change of, the influence when the glass component diffuses is considered. PbTiO ₃ − used in the above examples
The borosilicate glass (SiO ₂ —Al ₂ O ₃ —CaO—MgO—B ₂ O ₃ ) powder used in the same manner as in the example was added to the PbZrO ₃ based dielectric powder in an amount of 0 to 7 wt%. This powder is press molded (φ11
(× 2 mm), and then baked at 930 ° C. for 2 hours. Apply Ag-epoxy paste as an electrode on the upper and lower surfaces of this fired body.
After drying, the relative permittivity ε of this fired body at 500 kHz
Was measured.

A graph of the measurement results is shown in FIG. From this graph, as the amount of glass added to the fired body increases,
It can be seen that the relative permittivity ε is lowered. This indicates that the presence of the glass component changes the crystal composition of the dielectric material, which supports the results of the above-mentioned examples. Here, when the addition amount of the glass component exceeds 2 wt%, the relative permittivity ε is remarkably lowered. Therefore, after firing the dielectric layer 1
It can be seen that the glass component existing in 2 must be suppressed to 2 wt% or less at the maximum. Then, the glass component diffuses from the electrode layers 13A and B to the dielectric layer 12 due to the difference in the glass component concentration. Therefore, if the glass component contained in the electrode layers 13A and 13B is 2 wt% or less, the dielectric Layer 1
The glass component of 2 can be suppressed to 2 wt% at the maximum.

Although the composite material glass ceramic of borosilicate glass and alumina powder is used as the insulating layer in the above-mentioned embodiment, a crystallized glass ceramic or a non-glass glass ceramic may be used. . Furthermore, a large amount of glass component (about 30 wt% or more) is used as the insulating layer.
The present invention can be applied to any ceramic material (glass ceramic material in a broad sense) contained in the above.

Further, in the above embodiment, Ag was used as the metal powder for the conductor paste to form the electrode layer, but the present invention is not limited to this, and Au, Pd, Pt, Cu and Ni may be used, or an alloy thereof may be used. It is sufficient if at least one of these metals such as Ag-Pd and Ag-Pt is the main component. These metal powders have a low temperature (900 to 1000 ° C).
This is because the electrode layer can be formed by sintering without adding a glass component or by adding a small amount of the glass component.

In the above embodiment, the dielectric layer is made of PbT.
An TiO ₃ -PbZrO ₃ system dielectric was used, but BaTiO ₃
The present invention can also be applied to the case where a dielectric material is formed by using a high dielectric constant material such as a perovskite type dielectric material such as a lead type perovskite type dielectric material. These are because the crystal composition is easily changed and the dielectric constant fluctuates / decreases due to the diffusion of the glass component.

[0029]

As apparent from the above, according to the present invention,
In order to prevent the glass component from the insulating layer from diffusing into the dielectric layer, the content of the glass component of the electrode layer interposed between the insulating layer and the dielectric layer is 2 wt% or less, particularly preferably the glass component. Should be 1 wt% or less. Alternatively,
A conductive paste having a glass component content of 2 wt% or less may be applied and fired to form an electrode layer. By such a simple method, the diffusion of the glass component from the insulating layer to the dielectric layer is suppressed, the non-dielectric constant ε of the dielectric layer is kept sufficiently high, and a capacitor having a high capacitance can be formed.

According to the present invention, a high-dielectric constant is obtained by simultaneous firing in a low-temperature fired ceramic substrate provided with an insulating layer such as glass ceramic having a low relative permittivity and wiring using a low-resistance wiring material such as Ag. Since it is possible to form a capacitor using the perovskite-based dielectric material, it is possible to increase the signal transmission speed and enhance the noise removal capability. Therefore, it is possible to form a ceramic substrate with a capacitor corresponding to a higher driving frequency.

[Brief description of drawings]

FIG. 1 is a perspective view showing a state of each sheet constituting an unfired ceramic molded body.

FIG. 2 is a cross-sectional view of an unfired ceramic compact.

FIG. 3 is a cross-sectional view of a ceramic substrate with a capacitor.

FIG. 4 is a graph showing the relationship between the amount of added glass and the relative permittivity ε of a PbTiO ₃ —PbZrO ₃ based dielectric substance to which a glass component was added and fired.

[Explanation of symbols]

 1: Insulator green sheet 2: Dielectric green sheet 3: Conductor paste layer 4: Via hole 5: Pad 6: Unfired ceramic molded body 10: Ceramic substrate with capacitor 11: Insulator layer 12: Dielectric layer 13: Electrode layer 14: Beer hole 15: Pad

Claims (6)

[Claims] 1. A dielectric layer made of a perovskite type ceramic, an insulating layer made of a glass ceramic, and a dielectric layer interposed between the dielectric layer and the insulating layer. Ag, Au, Pd, P
A ceramic substrate with a capacitor, comprising: an electrode layer containing at least one of t, Cu and Ni as a main component, and the dielectric layer, the electrode layer and the insulating layer formed by simultaneous firing. A ceramic substrate with a capacitor, wherein the glass component content of the electrode layer is 2 wt% or less. 2. The ceramic substrate with a capacitor according to claim 1, wherein the content of the glass component in the electrode layer is 1 wt% or less. 3. The ceramic substrate with a capacitor according to claim 1, wherein the electrode layer has a thickness of 20 μm or more. 4. Ag, Au, Pd, between an insulator green sheet which becomes an insulator layer made of glass ceramic after firing and an unfired dielectric layer which becomes a dielectric layer made of perovskite type ceramic after firing. A non-fired ceramic laminate containing at least one of Pt, Cu and Ni as a main component, a glass component content of 2 wt% or less, and an electrically conductive paste layer serving as an electrode layer interposed after firing is fired. A ceramic substrate with a capacitor. 5. The content of the glass component in the conductive paste layer is 1 wt% or less.
The ceramic substrate with a capacitor described in. 6. The ceramic substrate with a capacitor according to claim 3, wherein the conductive paste layer has a thickness such that the electrode layer after firing has a thickness of 20 μm or more.