JPH0918149A - Multilayer ceramic board and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent migration due to permeation of moisture into the dielectric layer of a built-in capacitor and to suppress deformation of board due to firing. SOLUTION: A wiring conductor 13 and a via hole conductor 14 are formed on an insulator layer 15 for forming a capacitor 12 along with a cavity 19 for mounting an IC chip or the like. A dielectric material identical to that of the dielectric layer of capacitor 12 is printed on the outside of the capacitor 12 except the wiring conductor 13 and the via hole conductor 14 to form a dielectric layer 20 on the outside of capacitor thus making uniform the firing shrinkage of the board entirely. In order to prevent delamination, the dielectric layer 20 on the outside of capacitor is printed while being set back by 0.2mm or more from the end of insulator layer 15. Furthermore, the dielectric layer 20 on the outside of capacitor is printed while being set back by 0.2mm or more from the wiring conductor 13 and the via hole conductor 14 in order to prevent delay of high frequency signal due to high permittivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic multilayer substrate having a capacitor built therein by a printing method and a method for manufacturing the same.

[0002]

2. Description of the Related Art Recently, in the field of ceramic multilayer substrates,
In order to achieve high-density mounting and high integration, there is a capacitor in which an inner layer of a substrate is incorporated by a green sheet laminating method or a printing method. In the green sheet laminating method, for example, as shown in Japanese Patent Publication No. 5 (1999) -13367, a dielectric green sheet is sandwiched between layers forming a capacitor in a substrate, and a part of the dielectric green sheet (portion sandwiched by electrodes). ) Is used as the dielectric layer of the capacitor.

In this structure, since the dielectric layer (dielectric green sheet) is exposed on the end face of the substrate, it is required that the dielectric layer is dense (that is, moisture does not penetrate). This is because the electrodes that sandwich the dielectric layer of the capacitor are Ag,
This is because metals such as Ag-Pd and Cu are present, and migration of these metals in the presence of water may cause a short circuit in the dielectric layer. However, densification of the dielectric layer is very difficult at present, and the above-mentioned migration problem cannot be avoided.

On the other hand, when the capacitor is built in by the printing method, the dielectric layer of the capacitor can be partially printed on the inner layer of the substrate, and the dielectric layer need not be exposed at the end face of the substrate. Migration problems can be avoided.

[0005]

However, when the dielectric layer is partially formed on the inner layer of the substrate by the printing method, as shown in FIG. 4, the firing shrinkage ratio between the dielectric material and the ceramic material which is the substrate material. However, there is a drawback in that the shrinkage of the substrate becomes non-uniform due to the difference between the two, resulting in a larger substrate deformation than in the green sheet laminating method.

The present invention has been made in consideration of such circumstances, and therefore an object thereof is to avoid the problem of migration due to water permeation into the dielectric layer of the built-in capacitor and to prevent the deformation of the substrate due to firing. It is an object of the present invention to provide a ceramic multilayer substrate that can be reduced in number and a manufacturing method thereof.

[0007]

In order to achieve the above object, in the ceramic multilayer substrate according to claim 1 of the present invention, a dielectric layer constituting a capacitor is formed between insulating layers by a printing method to form the capacitor. As the insulating layer to be formed, the same dielectric material as that of the dielectric layer is applied to the outside of the capacitor except for the wiring conductors by 0.2 mm from the edge of the insulating layer.
The capacitor outer dielectric layer is formed by printing with care.

As described above, the same dielectric material as the dielectric layer is printed on the outside of the capacitor in the insulator layer forming the capacitor to form the outside-capacitor dielectric layer. A printed layer of a dielectric material is formed on almost the entire surface to make the firing shrinkage of the entire substrate uniform. Further, by printing the outer capacitor dielectric layer by 0.2 mm or more from the edge of the insulator layer, it is possible to prevent the outer capacitor dielectric layer from being exposed at the end face of the substrate, and to prevent moisture permeation to the dielectric layer. Prevent migration. In this case, if the amount of the outer capacitor dielectric layer from the edge of the insulator layer is less than 0.2 mm, the end of the insulator layer sandwiching the outer capacitor dielectric layer as shown in FIG. A phenomenon (delamination) occurs in which the edges are not joined and the gap is opened, and moisture penetrates into the dielectric layer, causing a migration problem.

By the way, according to the first aspect, by not printing the dielectric layer outside the capacitor on the wiring conductor (including the via-hole conductor), the layers above and below the capacitor forming layer can be electrically connected by the via-hole conductor. It is possible to prevent the dielectric constant of the wiring conductor portion from increasing and to avoid the problem of delay of high frequency signals.

Furthermore, when the outer capacitor dielectric layer is formed with a distance of 0.2 mm or more from the wiring conductor as in claim 2, the influence of the outer capacitor dielectric layer on the wiring conductor is further reduced, and the wiring conductor is reduced. The peripheral permittivity is further lowered, and the high frequency signal processing characteristics are further improved.

In the third aspect, the insulating layer is 1000
It is formed of a low temperature fired ceramic that is fired at a temperature of ℃ or below. This makes it possible to use a metal having a relatively low melting point and good electrical characteristics, such as Ag, Pd, Au, Pt, Cu, or an Ag-Pd alloy, as the wiring conductor or the electrode of the capacitor.

Further, in the present invention, the dielectric layer and the capacitor outer dielectric layer are formed of Pb composite perovskite. The Pb composite perovskite can be co-fired with a low temperature firing ceramic at 1000 ° C. or lower, and has a high dielectric constant, which is suitable for making a capacitor.

On the other hand, according to a fifth aspect of the present invention, a green sheet laminated body including the capacitor, the capacitor outer dielectric layer and the wiring conductor is fired, and the outside of a portion where the ceramic multilayer substrate is formed from the green sheet laminated body. A method for manufacturing a ceramic multilayer substrate according to any one of claims 1 to 4 by cutting, wherein the green sheet forming the dielectric layer of the capacitor is also formed outside the portion where the ceramic multilayer substrate is formed. The same dielectric material as the dielectric layer is printed to form the out-of-substrate dielectric layer. As a result, the firing shrinkage rate of the entire green sheet laminate is made uniform, and the deformation of the ceramic multilayer substrate to be manufactured is further reduced.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. First, the structure of the ceramic multilayer substrate 11 will be described with reference to FIG. FIG. 1 is a plan view of the layers forming the capacitors 12 in the ceramic multilayer substrate 11. On the insulator layer 15 forming the capacitor 12, the wiring conductor 1 is made of Ag-Pd conductor paste or the like.
3 is formed by screen printing, and the via-hole conductor 14 is electrically connected to the upper and lower layers.

In this embodiment, the insulator layer 15 (green sheet 22 described later) may be any low temperature fired ceramic material that can be fired at a firing temperature of 1000 ° C. or lower, for example, CaO—SiO ₂ —Al ₂ O ₃ —. B ₂ O ₃ system glass and from consisting systems Al ₂ O _3, or MgO-SiO ₂ -Al
₂ O ₃ -B ₂ O ₃ based glass and Al ₂ O ₃ based system, or PbO-SiO ₂ -B ₂ O ₃ based glass and Al ₂ O ₃ based system
More made system, SiO ₂ -B ₂ O ₃ based glass and Al ₂ O ₃
And a system made of crystallized glass. Most preferred among _{this, CaO-SiO 2 -Al 2 O} 3
-B is a low-temperature co-fired ceramic material consisting of a mixture of ₂ O ₃ based glass powder and Al ₂ O ₃ powder, the preferred composition, CaO10～55 wt%, SiO ₂ 45 to 70 wt%, Al ₂ O ₃ 0 ˜30 wt%, B ₂ O ₃ 5-20 wt% glass powder 50-65 wt%, and Al ₂ O
₃ powder 50-35% by weight.

With such a composition, only partial crystallization of anorthite or anorthite + calcium silicate occurs in the firing process, and low temperature firing at 800 to 1000 ° C. is possible in an oxidizing atmosphere (air). Not only that, the deviation of the fine pattern in the firing process can be suppressed by the above-described partial crystallization, and the fine pattern can be easily formed. In addition, even if the temperature is raised at a high speed of 30 to 50 ° C./minute during firing, the glass layer does not soften to 730 to 850 ° C. at all and maintains a porous body that does not shrink, so that cracks or carbon are generated. The binder can be easily removed without enclosing the
Furthermore, since the shrinking sintering is performed rapidly near the firing temperature of 800 to 1000 ° C., a large dense ceramic substrate can be fired in a short time.

On the other hand, as shown in FIG.
Screen-prints the electrode 16 on the insulator layer 15 (green sheet) with Ag-Pd conductor paste or the like, and then screen-prints the dielectric layer 17 with a dielectric material such as Pb composite perovskite from the above. Electrode 18
Is screen-printed. 1000 ° C
When firing below, the wiring conductor 13 and the electrodes 16, 1
As a metal forming 8, Ag-Pd, Ag, P
A metal having a relatively low melting point and good electrical characteristics, such as d, Au, Pt, or Cu, may be used. Further, as the dielectric material forming the dielectric layer 17, in addition to Pb composite perovskite,
SrTiO ₃ compound, BaTiO ₃ compound, CaT
An iO ₃ -based compound may be used, and all of these are 10
It can be co-fired with the insulator layer 15 at a temperature of 00 ° C. or lower.

In this embodiment, as shown in FIG. 1, a cavity 19 is formed at a predetermined position of the ceramic multi-layer substrate 11, and electronic parts such as an IC chip and a crystal oscillator can be mounted in the cavity 19. ing. However,
The cavity 19 may be omitted, and the capacitor 12
A RuO ₂ -based resistor may also be formed on the insulating layer 15 forming the by a printing method.

In the insulating layer 15 forming the above-mentioned capacitor 12, the wiring conductor 13 is provided outside the capacitor 12 as well.
A dielectric material identical to that of the dielectric layer 17 is printed on a portion excluding the via hole conductor 14 to form a capacitor outer dielectric layer 20 (a portion indicated by hatching in FIG. 1). The capacitor outer dielectric layer 20 is printed with a distance of 0.2 mm or more from the edge of the insulator layer 15 so that delamination does not occur. Here, the edge of the insulator layer 15 means both the outer edge of the ceramic multilayer substrate 11 and the inner edge on the side of the cavity 19, and the outer dielectric layer 20 of the capacitor is 0 from both edges. It is printed with 2 mm or more reserved.
Further, the capacitor outer dielectric layer 20 is printed with a distance of 0.2 mm or more from the wiring conductor 13 and the via-hole conductor 14 in order to prevent the delay of the high frequency signal due to the high dielectric constant.

The outer capacitor dielectric layer 20 can be screen-printed at the same time when the dielectric layer 17 of the capacitor 12 is printed, and the productivity is not reduced. In addition, the capacitor outer dielectric layer 20 corresponds to the capacitor 1
The two dielectric layers 17 may be formed continuously or separated. In either case, since both dielectric layers 17 and 20 can be printed at the same time, productivity is not reduced.

Next, the dielectric layer 20 outside the capacitor is 0.2 mm from the edge of the insulator layer 15 (hereinafter referred to as "substrate edge").
The reason why printing is made with reference to the above will be described. Since the dielectric is a porous material, as shown in FIG. 5A, when the external capacitor dielectric layer 20 is exposed at the end face of the substrate or the end face of the cavity, moisture permeates into the dielectric layers 20 and 17. Therefore, migration may occur in the electrodes 16 and 18 of the capacitor 12 and a short circuit may occur in the dielectric layer 17.

If the amount of the outer capacitor dielectric layer 20 from the substrate edge is less than 0.2 mm, the insulator layer 15 sandwiching the outer capacitor dielectric layer 20 is sandwiched as shown in FIG. 5B. Delamination occurs in which the edges are not joined and a gap is opened, and moisture penetrates into the dielectric layer 20 to cause a migration problem.

On the other hand, according to the test results of the present invention, if the amount of the outer capacitor dielectric layer 20 from the substrate end is 0.2 mm or more, as shown in FIG. Insulator layer 15 sandwiching the dielectric layer 20
The edge portions of the capacitor are in close contact with each other and completely bonded, and the entire dielectric layer 20 outside the capacitor is completely sealed by the insulating layer 15. Therefore, permeation of moisture into the capacitor outer dielectric layer 20 is prevented, and migration is prevented. Moreover,
By forming the dielectric layers 17 and 20 on substantially the entire surface of the insulating layer 15 forming the capacitor 12, the firing shrinkage rate of the entire ceramic multilayer substrate 11 is made uniform, and the ceramic multilayer substrate 11 is deformed by firing more than before. Remarkably less.

The ceramic multi-layer substrate 11 having the above structure is manufactured, for example, as follows. FIG.
It is an example of a case where a plurality of ceramic multilayer substrates 11 are manufactured from one green sheet laminated body 21, and is a plan view of a green sheet 22 forming a capacitor 12 of an inner layer of the ceramic multilayer substrate 11. Capacitor 1
The green sheet 22 forming the second dielectric layer 17 includes
The same dielectric material as the dielectric layer 17 is screen-printed on the outside of the portion where the ceramic multilayer substrate 11 is formed, and the outside-substrate dielectric layer 23 (the portion shown by the diagonal lines in FIG. 3) is formed.
The dielectric layer 23 outside the substrate is used for each ceramic multilayer substrate 11
The outer capacitor dielectric layer 20 can be screen-printed at the same time, and the productivity is not reduced.

Such green sheets 22 are laminated and co-fired at a temperature of 1000 ° C. or lower, and the outside of the portion forming the ceramic multilayer substrate 11 is cut off from the green sheet laminate 21 to obtain individual ceramic multilayer substrates 11. Divide. This cutting is performed in advance by firing the green sheet laminated body 2 before firing.
A snap line (cutting line) may be provided on the surface of No. 1 as shown by a dotted line in FIG. 3, and the firing line may be cut along the snap line after firing.

As in this embodiment, the green sheet 22 forming the dielectric layer 17 of the capacitor 12 is made of the same dielectric material as the dielectric layer 17 outside the portion where the ceramic multilayer substrate 11 is formed. If the outer dielectric layer 23 is formed by printing, the firing shrinkage of the entire green sheet laminate 21 is made uniform, and the ceramic multilayer substrate 11 to be manufactured is less deformed.

The inventors of the present invention have found that the capacitor outer dielectric layer 2
0, the ceramic multilayer substrate 11 with the dielectric layer 23 outside the substrate
Since the deformation prevention effect of No. 2 was confirmed by tests 1 and 2, the test results will be described.

[Test 1] As a low temperature fired ceramic material, a mixed powder of 60% by weight of CaO-SiO ₂ -Al ₂ O ₃ -B ₂ O ₃ based glass powder and 40% by weight of Al ₂ O ₃ powder was added with a binder, A plasticizer and a solvent are added and kneaded to prepare a slurry, and a 0.2 mm-thick green sheet is prepared by an ordinary doctor blade method. A capacitor is formed on this green sheet by a printing method. Ag-Pd conductor paste is used as the capacitor electrode, and Pb composite perovskite is used as the dielectric material.

As shown in FIG. 6 (a), the size of the green sheet of the sample used in this test 1 is 10.0 horizontal.
mm × length 7.5 mm, the size of the capacitor formed in the upper half of this green sheet is 8.5 mm wide ×
The length is 2.5 mm. The comparative example is an example in which the test sample was fired without forming the capacitor outer dielectric layer, and the example is an example in which the capacitor outer dielectric layer was formed by printing on the outside of the capacitor of the test sample and fired. Both the comparative example and the example use a sample in which four green sheets are laminated.

In the comparative example, due to the difference in firing shrinkage between the dielectric material and the green sheet, the firing shrinkage of the entire substrate becomes non-uniform, and the amount of deformation due to firing reaches 0.23 mm.

On the other hand, in the embodiment, by printing the outer capacitor dielectric layer on the outside of the capacitor, the firing shrinkage rate of the entire substrate is made uniform, and the amount of deformation due to firing is reduced to 0.03 mm. The deformation amount is significantly smaller than that of the comparative example.

[Test 2] Test 2 is a substrate deformation test in the case of manufacturing four ceramic multilayer substrates from one green sheet laminate, and the sample composition is the same as that of test 1. The comparative example is an example in which the green sheet forming the capacitor is fired without forming the dielectric layer outside the substrate, and the external deformation amount of the green sheet is as large as 1.2 mm. The outer shape is also greatly deformed.

On the other hand, in the embodiment, by printing the dielectric layer outside the substrate on the green sheet forming the capacitor, the firing shrinkage rate of the entire green sheet laminated body is made uniform, and the outer deformation amount of the green sheet due to the firing. Is 0.35 m
The amount of deformation is significantly smaller than that of the comparative example.

In the above embodiment, the ceramic multilayer substrate 11 is cut from the green sheet laminate 21 after firing. However, when the ceramic multilayer substrate 11 is cut from the green sheet laminate 21 before firing and fired. In this case, it is not necessary to form the dielectric layer 23 outside the substrate. Further, although the above embodiment is an example in which the present invention is applied to a low temperature fired ceramic substrate, it goes without saying that it may be applied to an alumina multilayer substrate.

[0035]

As is apparent from the above description, according to the ceramic multilayer substrate of the first aspect of the present invention, the insulating layer forming the capacitor is the same as the dielectric layer outside the capacitor. Dielectric material 0.2m from the edge of the insulator layer
Since the printing is performed with a distance of m or less, the dielectric layer is not exposed on the end face of the substrate, migration due to water permeation into the dielectric layer can be prevented, and the shrinkage rate of baking of the entire substrate is made uniform. As a result, deformation of the substrate due to firing can be reduced.

Further, according to the second aspect, since the capacitor outer dielectric layer is formed with a distance of 0.2 mm or more from the wiring conductor, the dielectric constant in the periphery of the wiring conductor can be lowered and the delay of the high frequency signal can be reduced. Can be prevented.

In the third aspect, the insulating layer is 1000
Since it is made of low-temperature fired ceramic that is fired at a temperature of ℃ or below, it is possible to use a metal with a relatively low melting point and good electrical characteristics as the wiring conductor and the electrode of the capacitor, and it is possible to improve high-frequency signal processing characteristics .

Further, in the present invention, since the dielectric layer and the capacitor outer dielectric layer are formed of Pb composite perovskite, it is possible to co-fire with the low temperature firing ceramic (insulator layer) at 1000 ° C. or less and it is high. The permittivity can be secured, and it can contribute to the increase of the capacitance of the capacitor.

Furthermore, in the present invention, the green sheet forming the dielectric layer of the capacitor is printed with the same dielectric material as the dielectric layer on the outside of the portion forming the ceramic multilayer substrate. The firing shrinkage rate of the entire laminate can be made uniform, and the ceramic multilayer substrate to be manufactured can be further reduced in deformation.

[Brief description of the drawings]

FIG. 1 is a plan view of a capacitor forming layer showing an embodiment of the present invention.

FIG. 2 is an exploded view showing a state before lamination of the ceramic multilayer substrate.

FIG. 3 is a plan view of a capacitor forming layer when manufacturing a plurality of ceramic multilayer substrates from one green sheet laminate.

FIG. 4 is a diagram for explaining a difference in firing shrinkage between a dielectric material and a ceramic material.

FIG. 5 is a diagram for explaining the reason why the amount of the dielectric layer outside the capacitor from the substrate edge is set to 0.2 mm or more.

FIG. 6 is a diagram for explaining the amount of external deformation of the ceramic multilayer substrates of Comparative Example and Example in Test 1.

FIG. 7 is a diagram illustrating the amount of outer shape deformation of the green sheet laminates of Comparative Example and Example in Test 2.

[Explanation of symbols]

11 ... Ceramic multilayer substrate, 12 ... Capacitor, 13 ...
Wiring conductor, 14 ... Via hole conductor, 15 ... Insulator layer, 1
6 ... Electrode, 17 ... Dielectric layer, 18 ... Electrode, 19 ... Cavity, 20 ... Capacitor outside dielectric layer, 21 ... Green sheet laminated body, 22 ... Green sheet, 23 ... Outside substrate dielectric layer.

Claims (5)

[Claims] 1. In a ceramic multi-layer substrate containing a capacitor, a dielectric layer constituting the capacitor is formed by a printing method between insulator layers, and the insulator layer forming the capacitor comprises:
The outer dielectric layer of the capacitor may be formed by printing the same dielectric material as the dielectric layer on the outside of the capacitor except the wiring conductor for 0.2 mm or more from the edge of the insulating layer. Characteristic ceramic multilayer substrate. 2. The ceramic multilayer substrate according to claim 1, wherein the capacitor outer dielectric layer is formed with a distance of 0.2 mm or more from the wiring conductor. 3. The ceramic multilayer substrate according to claim 1, wherein the insulator layer is formed of a low temperature fired ceramic fired at 1000 ° C. or lower. 4. The ceramic multilayer substrate according to claim 3, wherein the dielectric layer and the capacitor outer dielectric layer are made of Pb composite perovskite. 5. A green sheet laminated body containing the capacitor, the capacitor outer dielectric layer and the wiring conductor is fired, and the outside of the portion forming the ceramic multilayer substrate is cut off from the green sheet laminated body. 1 to 4
The method for manufacturing a ceramic multilayer substrate according to any one of 1, wherein the green sheet forming the dielectric layer of the capacitor is the same as the dielectric layer outside a portion where the ceramic multilayer substrate is formed. A method for manufacturing a ceramic multilayer substrate, comprising printing a dielectric material to form an external dielectric layer.