JP2001160681A - Multilayer ceramic board and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer ceramic board and its manufacturing method which applies a nonshrinking process whereby steps resulting from the thickness variation of an inner conductor layer can be advantageously relaxed, and it can be made that the layer stripping hardly occurs after the pressing or baking by raising the adhesion to the inner conductor layer. SOLUTION: In manufacturing a green composite laminate 18 to be a multilayer ceramic board 11 formed by baking, such steps are executed that an inner conductor film 13 is formed on a green sheet 12 for a base, a shrink- suppressing green layer 14 is formed on the green sheet 12 for the base so as to cover the inner conductor film 13, through-holes 16 are provided, via conductors 17 are formed in the through-holes, a plurality of green sheets 12 for the base are laminated to obtain the green composite laminate 18, and it is pressed in the laminating direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer ceramic substrate to which a so-called non-shrinkage process is applied, which can substantially prevent shrinkage in a main surface direction in a firing step, and a method for manufacturing the same. It relates to a multilayer ceramic substrate obtained by the method, in particular,
The present invention relates to an improvement for solving a problem caused by the thickness of an internal conductor film provided inside a multilayer ceramic substrate.

[0002]

2. Description of the Related Art A multilayer ceramic substrate has a plurality of stacked ceramic layers. Various types of wiring conductors are provided on such a multilayer ceramic substrate.
As the wiring conductor, for example, an internal conductor film extending along a specific interface between ceramic layers inside a multilayer ceramic substrate, a via hole conductor extending so as to penetrate a specific ceramic layer, or a wiring conductor on an outer surface of the multilayer ceramic substrate There is an external conductor film to be formed.

[0003] A part of the above-described internal conductor film and via-hole conductor is sometimes used to constitute a passive component such as a capacitor element or an inductor element. Further, the external conductor film is used for mounting another chip-shaped electronic component, or used for mounting the multilayer ceramic substrate on a motherboard.

In order to increase the functionality, density and performance of such a multilayer ceramic substrate, it is effective to arrange the above-described wiring conductors in the multilayer ceramic substrate at a high density.

[0005] However, in order to obtain a multilayer ceramic substrate, a firing step must necessarily be performed. In such a firing step, shrinkage due to sintering of the ceramic occurs. It is unlikely to occur uniformly over the whole, and therefore, undesirable deformation or distortion may be caused in the wiring conductor. Deformation and distortion generated in such wiring conductors hinder the above-described high density of wiring conductors.

Therefore, in manufacturing a multilayer ceramic substrate, it has been proposed to apply a so-called non-shrinkage process which can substantially prevent shrinkage in the main surface direction of the multilayer ceramic substrate in the firing step. ing.

A method of manufacturing a multilayer ceramic substrate by a non-shrinkage process is carried out, for example, as follows.

Referring to FIG. 5, first, as shown in FIG. 5A, a base green sheet 1 containing a low-temperature sintered ceramic material is formed on a carrier film (not shown). A plurality of such base sheet green sheets 1 are prepared. Further, as the low-temperature sintered ceramic material, for example, crystallized glass or a mixture of glass and ceramic is used, and more specifically, BaO—Al ₂ O
₃ -SiO ₂ based low-temperature co-fired ceramic material is used.

Next, as shown in FIG. 5 (2), on a specific one of the base green sheets 1, a shrinkage suppressing ceramic material which does not sinter at the sintering temperature of the low-temperature sintered ceramic material described above is included. The shrinkage suppressing green layer 2 is formed. As the ceramic material for suppressing shrinkage, for example, alumina or zirconia is advantageously used.

Next, as shown in FIG. 5 (3), a green sheet 1 for a base on which a green layer 2 for suppressing shrinkage is formed.
The through hole 3 is provided so as to penetrate the specific one. The base green sheet 1 on which the shrinkage suppression green layer 2 is not formed may be provided with a through hole as necessary.

Next, as shown in FIG. 5D, a via paste 4 is formed in the through-hole 3 by applying a conductive paste.

Next, as shown in FIG. 5 (5), an internal conductor film 5 is formed on the shrinkage suppressing green layer 2 by applying a conductive paste, for example, by printing or the like. The internal conductor film 5 is connected to the via-hole conductor 4. The internal conductor film may be formed at a position not connected to the via-hole conductor 4 or may be formed on the base green sheet 1 on which the shrinkage suppressing green layer 2 is not formed.

As the above-described via-hole conductor 4 and internal conductor film 5, for example, those containing a powder made of a metal containing copper or silver are used.

Next, after the carrier film is peeled at an appropriate stage, a plurality of base green sheets 1 including the base green sheet 1 in the state shown in FIG. 5 (5) are stacked, whereby A raw composite laminate is produced. The green composite laminate is then pressed in the lamination direction.

Then, by firing the above-mentioned green composite laminate, an intended multilayer ceramic substrate is obtained.

In the above-described firing step, the low-temperature sintered ceramic material contained in the base green sheet 1 is reduced while the shrinkage in the main surface direction of the base green sheet 1 is suppressed by the shrinkage suppressing green layer 2. Sinter.
Further, in the shrinkage suppression green layer 2, a part of the material contained in the base green sheet 1 penetrates, thereby fixing the shrinkage suppression ceramic material.

In this manner, for example, the wiring conductor such as the internal conductor film 5 is prevented from being undesirably deformed or distorted by the firing step, and therefore, the wiring conductors can be arranged at a high density. become.

[0018]

As the frequency of a circuit constituted by the above-mentioned multilayer ceramic substrate increases, it is necessary to reduce the electrical resistance of wiring conductors such as via-hole conductors 4 and internal conductors 5. The thickness of the conductor film 5 is increased to about 10 to 30 μm.

However, when such internal conductor films 5 are arranged in multiple layers, a relatively large step of several tens to several hundreds μm is caused in the raw composite laminate due to the accumulation of the thickness of the internal conductor films 5. May be In the pressing step, the green composite laminate is pressed with a flat mold to have a flat appearance, but the density of the ceramic in the green composite laminate is not uniform. For this reason, in the firing step, an effect of making the ceramic density in each part of the raw composite laminate constant is generated, and therefore, undulations and irregularities may occur on the front and back surfaces of the obtained multilayer ceramic substrate.

When undulations and irregularities are generated in the multilayer ceramic substrate as described above, when a chip component such as an IC bare chip or a SAW bare chip is to be mounted on the multilayer ceramic substrate by wire bonding or solder bumping, for example, Such a problem that the chip components are easily damaged or poorly connected is encountered.

The green composite laminate is subjected to a pressing step so that the adhesiveness between the components constituting the composite laminate is increased, whereby the raw composite laminate or the fired composite laminate is fired. In the multilayer ceramic substrate, defects such as layer peeling are prevented.

However, in spite of this, the green sheet for base 1 and the internal conductor film 5 are hardly adhered,
This may cause layer peeling as described above.

As described above, the reason why the base green sheet 1 and the internal conductor film 5 are not easily bonded is related to the resin volume ratio in each of the base green sheet 1 and the internal conductor film 5. In order to make the adhesion in the pressing step easier, the resin volume ratio may be increased, but in practice, the resin volume ratio in the base green sheet 1 is about 30 to 50%. The volume ratio of the resin in the internal conductor film 5 is only about 10 to 20%. Therefore, the base green sheet 1 and the internal conductor film 5
Is poor, causing layer peeling.

From the viewpoint of reducing the amount of residual carbon after firing, the above-mentioned resin volume ratio is preferably low. However, the base green sheet 1 is usually formed by coating a slurry in which a ceramic powder, a binder, a plasticizer, and a solvent are kneaded on a carrier film having a thickness of 30 to 100 μm, and drying the slurry. Then, the carrier film is peeled off after this drying or in a later step, and only a green sheet 1 for a substrate is laminated when a green composite laminate is produced. Therefore, in order to prevent the base green sheet 1 from being damaged or broken at the time of peeling as described above, and to prevent the same from being damaged or damaged in subsequent handling, the base green sheet 1 is used. 1 is required to have a predetermined ductility or more, and therefore, the resin volume ratio is increased as described above. Usually, the resin volume ratio in the base green sheet 1 is smaller than the resin volume ratio in the internal conductor film 5.
2 to 4 times.

An object of the present invention is to provide a method of manufacturing a multilayer ceramic substrate and a multilayer ceramic substrate obtained by the manufacturing method, which can solve the problem of undulation, unevenness or delamination after firing as described above. Is to try.

[0026]

SUMMARY OF THE INVENTION In brief, the present invention solves the above-mentioned problem by changing the order of forming a shrinkage suppressing green layer and an internal conductor film on a base green sheet. I'm trying.

More specifically, the present invention relates to a green sheet for a plurality of substrates, including a low-temperature sintered ceramic material, and a low-temperature sintered ceramic material arranged in contact with a specific one of the green sheets for the substrate. The shrinkage suppressing green layer, which does not sinter at the sintering temperature, is provided by a shrinkage suppressing green layer and a conductive paste applied so as to extend in a direction along a main surface of a specific thing of the base green sheet, An internal conductor film and a via-hole conductor provided by a conductive paste applied to penetrate a specific one of the base sheet green sheet and a specific one of the shrinkage suppressing green layer and connected to the internal conductor film, Producing a green composite laminate, comprising the steps of: preparing a green composite laminate; and firing the green composite laminate. Be one directed to the law, to solve the technical problems described above, it is characterized in that it comprises the following configuration.

That is, in the above-mentioned step of preparing the green composite laminate, a step of forming an internal conductor film by applying a conductive paste on the base green sheet, and a step of covering the internal conductor film. Forming a shrinkage suppression green layer on the base green sheet, providing a through hole through the base green sheet and the shrinkage suppression green layer, and applying a conductive paste in the through hole. A step of forming a via-hole conductor, a step of stacking a plurality of base green sheets to obtain a raw composite laminate, and a step of pressing the raw composite laminate in the stacking direction. Features.

In the above-described step of forming the shrinkage suppressing green layer, if necessary, the shrinkage suppressing green layer may be formed in a via hole formed in a base green sheet to be stacked on the shrinkage suppressing green layer. It is formed so as to provide a window that exposes a part of the internal conductor film corresponding to the lower end position of the conductor, and in the step of pressing the raw composite laminate, the internal conductor film and the via-hole conductor are bonded to each other through the window May be performed.

The present invention is also directed to a multilayer ceramic substrate obtained by the above-described manufacturing method.

[0031]

1 and 2 are sectional views sequentially showing several steps included in a method for manufacturing a multilayer ceramic substrate according to an embodiment of the present invention. Fig. 2 (3)
1 shows a multilayer ceramic substrate 11 to be obtained. To manufacture such a multilayer ceramic substrate 11, the following steps are performed.

First, a ceramic slurry containing a low-temperature sintered ceramic material is prepared. As the low-temperature sintered ceramic material contained in the ceramic slurry, a material that can be sintered at a temperature of, for example, 1000 ° C. or less is used. The low-temperature sintering ceramic material is composed of, for example, crystallized glass or a mixture of glass and ceramic, and more specifically, BaO—Al ₂ O ₃ —SiO _2.
A low temperature sintered ceramic material is advantageously used.

The above-mentioned ceramic slurry is coated on a carrier film (not shown), whereby a green sheet 12 for a substrate as shown in FIG. 1A is formed and then dried. A plurality of base green sheets 12 are prepared.

Next, as shown in FIG. 1 (2), a conductive paste is applied to a specific one of the base green sheets 12 by screen printing or the like, and this is dried to form the internal conductor film 13. It is formed.

The conductive component contained in the above-mentioned conductive paste is preferably as low as possible in order to cope with an increase in the frequency of an electronic device using the multilayer ceramic substrate 11. Is preferably used. As the conductive material containing silver as a main component, for example, silver alone, an Ag-Pd alloy, an Ag-Pt alloy, or the like can be used. Further, as a conductive material containing copper as a main component, for example, metal copper,
CuO, Cu ₂ O, or the like can be used.

On the other hand, a ceramic slurry containing a shrinkage suppressing ceramic material which does not sinter at the sintering temperature of the low-temperature sintered ceramic material described above is prepared. When the above-mentioned low-temperature sintered ceramic material can be sintered at a temperature of 1000 ° C. or less, for example, a material mainly containing alumina or zirconia is advantageously used as the shrinkage suppressing ceramic material. Furthermore, MgO, TiO
₂ , a material mainly composed of BaTiO ₃ , SiC or AlN may be used as a shrinkage-suppressing ceramic material.

Next, as shown in FIG. 1C, a ceramic slurry containing the above-described shrinkage-suppressing ceramic material is applied onto the base green sheet 12 so as to cover the internal conductor film 13, and then dried. Thereby, the shrinkage suppression green layer 14 is formed. The thickness of the shrinkage suppressing green layer 14 is about 1 to 20 after drying.
It is about μm.

In forming the above-described shrinkage suppressing green layer 14, a window 15 for exposing a part of the internal conductor film 13 is formed on the shrinkage suppressing green layer 14 as necessary.
Is preferably provided. The significance of the window 15 will be apparent from the description below.

Next, as shown in FIG. 1D, through holes 16 are provided so as to penetrate the base green sheet 12 and the shrinkage suppressing green layer 14. Through hole 16
Is formed by using, for example, a mold or a laser, and has a diameter of about 75 to 200 μm.

Next, as shown in FIG. 1 (5), a conductive paste is applied in the through-hole 16 and then dried to form a via-hole conductor 17. The via-hole conductor 17 is connected to the internal conductor film 13.

As the conductive paste used to form the above-described via-hole conductor 17, the same conductive paste as that used to form the above-described internal conductive film 13 can be used.

Next, the carrier film (not shown) used for forming the base green sheet 12 is peeled off at an appropriate stage, and then, as shown in FIG. The sheets 12 are stacked, whereby a green composite laminate 18 is obtained. Note that FIG.
In (1), the green composite laminate 18 is shown in a state where a plurality of base green sheets 12 provided therein are separated from each other.

As shown in FIG. 2A, a plurality of base green sheets 12 provided in the green composite laminate 18 are not limited to those shown in FIG. It is included. These other forms can be manufactured by a method substantially similar to the method shown in FIG. 1, and these other forms are also shown in FIG. Elements corresponding to the indicated elements are denoted by the same reference numerals, and redundant description will be omitted.

In the base green sheet 12 of another form, a green sheet for forming an external conductor film 19, a green sheet for connecting via holes 17 to the external conductor film 19, and a green layer for suppressing shrinkage are formed. In some cases, the window 15 is not provided in the shrinkage suppression green layer 14.

In FIG. 2A, as can be seen by referring to both the shrinkage suppression green sheet 14 provided with the window 15 and the base green sheet 12 to be stacked thereon, A window 15 is provided corresponding to a lower end position of the via hole conductor 17 formed in the green sheet 12.

The green composite laminate 18 is then pressed in the laminating direction under heating. As a result, the raw composite laminate 18 is compressed in its thickness direction, and the lower end of the via-hole conductor 17 positioned so as to cover the window 15 digs into the window 15 as shown in FIG. Thereby, the internal conductor film 13 and the via-hole conductor 1
7 are joined to each other via the window 15.

Next, the green composite laminate 18 is fired, whereby a multilayer ceramic substrate 11 as shown in FIG. 2 (3) is obtained.

In the above-described firing step, since the shrinkage suppressing green layer 14 does not substantially shrink itself, it exerts a restraining force on the base green sheet 12 to suppress shrinkage in the main surface direction. Become. Therefore, in the green sheet 12 for the base, while the shrinkage in the main surface direction is suppressed, the low-temperature sintered ceramic material contained therein sinters and shrinks substantially only in the thickness direction. The substrate ceramic layer 20 shown in FIG.

The shrinkage suppression green layer 14 provides a shrinkage suppression ceramic layer 21. In the shrinkage suppression ceramic layer 21, the base green sheet 12 is formed.
A part of the material contained in the ceramic material penetrates, thereby fixing the shrinkage suppressing ceramic material.

According to the manufacturing method described above, since the shrinkage suppressing green layer 14 is formed so as to cover the internal conductor film 13, the binder and the binder in the ceramic slurry for forming the shrinkage suppressing green layer 14 are formed. By including a large amount of resin components such as a plasticizer,
Adhesion between the shrinkage suppression green layer 14 and the internal conductor film 13 and between the shrinkage suppression green layer 14 and the base green sheet 12 can be enhanced. Therefore, a sufficient adhesive strength can be obtained in the pressing step, and therefore, it is possible to make it difficult for the green composite laminate 18 or the fired multilayer ceramic substrate 11 to peel off.

When the internal conductor film 13 is formed on the green sheet 12 for the base, a step due to the thickness of the internal conductor film 13 is caused. When the rally is applied, the leveling in the shrinkage suppressing green layer 14 proceeds sufficiently until the ceramic slurry dries, so that the step due to the internal conductor film 13 is reduced. Therefore, the ceramic density in the green composite laminate 18 after the pressing step becomes substantially uniform, and it is possible to make the multilayer ceramic substrate 11 after firing less likely to have undulations and irregularities.

FIG. 3 is a sectional view schematically showing a multilayer ceramic substrate 31 according to another embodiment of the present invention. FIG. 3 is a diagram corresponding to FIG.
In FIG. 2, elements corresponding to the elements shown in FIG. 2 (3) are denoted by the same reference numerals, and redundant description will be omitted.

In the multilayer ceramic substrate 31 shown in FIG. 3, a plurality of base green sheets 12 to be laminated include ones in which the shrinkage suppressing green layer 14 is not formed between adjacent ones. It is characterized by:

As can be seen from the cross-sectional structure of the multilayer ceramic substrate 31 shown in FIG.
Need not be formed between all adjacent ones of the plurality of base green sheets 12, and may be arranged so as to be in contact with a specific one of the base green sheets 12. The arrangement state of the shrinkage suppressing green layer 14 may be determined in consideration of the effect of suppressing shrinkage of the base green sheet 12 and the effect of reducing the step due to the internal conductor film 13 to be obtained.

This multilayer ceramic substrate 31 can be manufactured by substantially the same manufacturing method as the multilayer ceramic substrate 11 shown in FIG.

FIG. 4 schematically shows a multilayer ceramic substrate 41 according to still another embodiment of the present invention.
It is sectional drawing corresponding to (3). In FIG. 4, FIG.
Elements corresponding to the elements shown in (3) are denoted by the same reference numerals, and redundant description will be omitted.

The multilayer ceramic substrate 41 shown in FIG. 4 is characterized in that a cavity 42 is provided. Several internal conductor films 1 are provided in the cavity 42.
3 extend and form electrode pads 43, 44 and 45 exposed in the cavity 42.

The above-mentioned electrode pads 43 and 44 serve as electrode pads for wire bonding, and the electrode pad 45 serves as an electrode pad for die bonding. Therefore, in the internal conductor film 13 that provides the electrode pads 43, 44, and 45, no shrinkage suppressing green layer is formed so as to cover the internal conductor film 13.

The multilayer ceramic substrate 41 also has
Except for the features described above, it can be manufactured by a manufacturing method substantially similar to that of the multilayer ceramic substrate 11 shown in FIG.

Although the present invention has been described with reference to some illustrated embodiments, various other modifications are possible within the scope of the present invention.

For example, the multilayer ceramic substrates 11 and 31
Alternatively, in 41, the formation state of the wiring conductor such as the internal conductor film 13, the via-hole conductor 17, and the external conductor film 19 can be variously changed.

The shrinkage suppressing green layer is formed so as to cover the outer conductor film 19 as well, and after the firing step, the shrinkage suppressing ceramic layer derived from the shrinkage suppressing green layer is removed. You may. Similarly, in the embodiment shown in FIG. 4, the electrode pads 43, 44 and 45
Each of the electrode pads 43 to 45 in the shrinkage suppressing ceramic layer derived from such a shrinkage suppressing green layer is formed after the firing step. May be removed.

The obtained multilayer ceramic substrate 11,
31 or 41, if necessary, a plating step,
A component mounting step, a sealing step, a casing step, and / or a terminal mounting step may be performed.

[0064]

As described above, according to the method for manufacturing a multilayer ceramic substrate according to the present invention, an internal conductor film is first formed on a green sheet for a substrate, and then the substrate is covered so as to cover the internal conductor film. Since the shrinkage suppression green layer is formed on the green sheet, the adhesiveness of the shrinkage suppression green layer can be increased by increasing the content ratio of the resin component in the shrinkage suppression green layer. Therefore, in the pressing step, a high adhesive strength can be obtained between the shrinkage suppressing green layer and the internal conductor film and between the shrinkage suppressing green layer and the base green sheet, and therefore, the raw composite laminate or In the multilayer ceramic substrate after firing, defects such as layer peeling can be suppressed.

Further, since the shrinkage suppressing green layer acts to alleviate the step due to the thickness of the internal conductor film, the ceramic density of the raw composite laminate can be made uniform after pressing. In addition, when fired, undulations and irregularities can be made less likely to occur in the obtained multilayer ceramic substrate. As a result, when chip components such as an IC bare chip or a SAW bare chip are mounted on a multilayer ceramic substrate, it is possible to make these chip components less likely to be damaged or damaged.
The reliability of connection by wire bonding or solder bump is improved.

In the present invention, when the shrinkage suppressing green layer is formed, the internal conductor film is formed corresponding to the lower end position of the via hole conductor formed in the base green sheet to be stacked on the shrinkage suppressing green layer. By providing a window for partially exposing, by pressing the raw composite laminate, the internal conductor film and the via-hole conductor can be joined to each other via the window. Therefore, the internal conductor film can be connected to the via hole conductor on both surfaces thereof, so that the degree of freedom of the circuit configuration realized in the multilayer ceramic substrate can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view sequentially showing several steps included in a method for manufacturing a multilayer ceramic substrate according to an embodiment of the present invention and performed before stacking green sheets 12 for a substrate.

FIG. 2 shows a process of obtaining a green composite laminate 18 by stacking the base green sheets 12 shown in FIG. 1, a process of pressing the green composite laminate 18, and a process of firing the same to obtain a multilayer ceramic substrate 11. FIG. 4 is a schematic sectional view.

FIG. 3 is a sectional view schematically showing a multilayer ceramic substrate 31 according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view schematically showing a multilayer ceramic substrate 41 according to still another embodiment of the present invention.

FIG. 5 is a green sheet 1 for a base included in a conventional method for manufacturing a multilayer ceramic substrate which is of interest to the present invention.
FIG. 4 is a schematic sectional view sequentially showing several steps performed before stacking.

[Explanation of symbols]

 11, 31, 41 Multilayer ceramic substrate 12 Green sheet for substrate 13 Internal conductor film 14 Green layer for shrinkage suppression 15 Window 16 Through hole 17 Via hole conductor 18 Raw composite laminate

Claims (3)

[Claims] 1. A plurality of green sheets for a base, comprising a low-temperature sintered ceramic material, arranged in contact with a specific one of the green sheets for a base, and fired at a sintering temperature of the low-temperature sintered ceramic material. Including a shrinkage-suppressing ceramic material that does not bond, a shrinkage-suppressing green layer, and an internal conductor film provided by a conductive paste provided so as to extend in a direction along a main surface of a specific thing of the base green sheet, A via hole conductor provided by a conductive paste applied so as to penetrate a specific thing of the base green sheet and a specific thing of the shrinkage suppressing green layer and connected to the internal conductor film, A step of preparing a raw composite laminate; and a step of baking the raw composite laminate. Forming the internal conductor film by applying the conductive paste on the substrate green sheet; and forming the shrinkage suppressing green layer on the substrate green sheet so as to cover the internal conductor film. Forming a via hole through the base green sheet and the shrinkage suppressing green layer, and forming the via hole conductor by applying the conductive paste in the through hole. Manufacturing a multilayer ceramic substrate, wherein a step of obtaining the raw composite laminate by stacking a plurality of the base green sheets and a step of pressing the raw composite laminate in the stacking direction are sequentially performed. Method. 2. In the step of forming the shrinkage suppression green layer, the shrinkage suppression green layer is formed of the via hole conductor formed on the base green sheet to be stacked on the shrinkage suppression green layer. It is formed so as to provide a window exposing a part of the internal conductor film corresponding to the lower end position, and in the step of pressing the raw composite laminate, the internal conductor film and the via-hole conductor are interposed through the window. The method for manufacturing a multilayer ceramic substrate according to claim 1, wherein the multilayer ceramic substrate is joined to each other by a step. 3. A multilayer ceramic substrate obtained by the method according to claim 1.