JPH08167776A - Alumina wiring board - Google Patents

Abstract

(57) [Summary] [Structure] The ratio of W to the total amount of Mo and W is 30.
An alumina wiring board having therein a decoupling capacitor including an alumina layer containing 5 to 30% by weight of metal powder in an amount of 5% by weight or more. [Effect] Due to changes in conditions in the manufacturing process,
Even if the thickness of the electrode layer, the thickness of each dielectric layer, the thickness of the alumina insulator layer, etc. changes, the relative permittivity of the dielectric layer can be maintained at a constant value, and a constant electrostatic It is possible to reproducibly manufacture an alumina-based wiring board having a decoupling capacitor having a capacitance. Also, even if the thickness of the electrode layer, the thickness of each dielectric layer, the thickness of the alumina insulator layer, etc. changes, the relative permittivity of the dielectric layer does not change, so the above conditions can be set freely. Therefore, the alumina-based wiring board can be easily designed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alumina wiring board, and more particularly to an alumina wiring board having a dielectric layer containing a metal powder such as W therein.

[0002]

2. Description of the Related Art In recent years, with the increase in speed and frequency of electronic equipment, the frequency of signals used in electronic parts has been increasing year by year. For this reason, there is a demand for products corresponding to the higher frequencies even in ceramic circuit boards, LSI packages, etc. used in communication devices, large computers, and the like.

As a product corresponding to such a high frequency, for example, an LSI equipped with a decoupling capacitor in order to effectively remove switching noise and the like generated in an LSI as a logic circuit having a high operating frequency. A package, a ceramics multilayer wiring board (hereinafter referred to as a ceramics multilayer wiring board including both an LSI package and a ceramics multilayer wiring board), and the like have been proposed.

Conventionally, as a method of equipping a ceramic multilayer wiring board with a decoupling capacitor, there have been a method of mounting the capacitor outside the ceramic multilayer wiring board and a method of forming the capacitor inside the ceramic multilayer wiring board.

When mounting a capacitor on the outside of a ceramic multilayer wiring board, the wiring for mounting the capacitor must be routed inside the ceramic multilayer wiring board, and the wiring must be pulled out to mount the capacitor.

In such a method of attaching a capacitor to the outside, the material of the capacitor is not limited, and one which satisfies the required characteristics is selected from the ceramic capacitors having various characteristics used so far. It has the advantage of being attached. However, in this method, there is a problem that an extra wiring must be drawn around in order to attach the external capacitor, a process therefor is required, and an extra space for attaching the external capacitor is also required. there were.

On the other hand, when manufacturing a ceramic multilayer wiring board having a capacitor inside, a green sheet formed by using ceramic powder as a raw material of the capacitor and having electrodes printed on both sides thereof is formed by alumina powder. Sandwiched inside the green sheet laminate, which is the main component,
By firing this laminated body, a ceramic capacitor was formed inside the ceramic multilayer wiring board.
With this method, since the decoupling capacitor can be formed at the same time when the alumina multilayer wiring board is manufactured, the manufacturing process can be simplified, and it is not necessary to secure an extra space outside, so the size can be reduced. It has the great advantage that

By the way, conventionally, as materials for ceramic capacitors, TiO ₂ , CaTiO ₃ , and SrTi have been used.
O _{3 and the} like are known, and in recent years, MgTiO ₃ —CaTiO ₃ and Ba (Mg, Ta,
_{X) O 3, Ba (Zn} , Nb) O 3 -Ba (Zn, T
_{a) O 3, BaO-PbO} -Nb 2 O 3 -TiO 2, B
aO-Sm ₂ O ₃ -5TiO capacitor using the ceramic-based material ₂ or the like is known.

However, in the production of the alumina multilayer wiring board, an electric circuit is formed by co-firing a conductive metal such as W or Mo with alumina powder, and in a reducing atmosphere so as not to oxidize these metals. , 1500-1
Firing was performed at a high temperature of 650 ° C. Therefore, when the above-mentioned conventionally used ceramic raw material powder green sheets are laminated and fired inside, hydrogen acts on these materials during firing in a high-temperature reducing atmosphere and the semiconductor formation reaction occurs. And reduction reactions proceed. As a result, a short circuit, alteration, etc. occur inside the capacitor, and there is a problem that it is actually difficult to form a ceramic capacitor inside the alumina multilayer wiring board.

On the other hand, it has long been known that the dielectric constant per unit volume can be improved by dispersing a metal in ceramics. By applying this method, metal powders are dispersed in ceramics. An alumina multilayer wiring board having a decoupling capacitor formed therein has also been proposed.

As an example of an alumina multilayer wiring board having such an internal capacitor formed therein, Japanese Patent Application Laid-Open No. 3-87091.
Japanese Patent Laid-Open Publication No. 2003-242242 discloses an alumina multilayer in which a dielectric layer composed of alumina as a base material and 5 to 50% by weight of at least one of Mo and W is formed inside an alumina multilayer wiring board. A wiring board is disclosed.

FIG. 1 is a cross-sectional view schematically showing the alumina multilayer wiring board described in the above publication, in which 12 is a dielectric layer.

Inside the alumina multilayer wiring board, M
Alumina layer (dielectric layer) 12 in which metal powder such as o is dispersed
Is usually formed to have a thickness of 40 to 50 μm. Internal electrode layers 13 made of W are formed on both surfaces (upper and lower surfaces) of the dielectric layer 12, and the dielectric layer 12 and the internal electrode layer 13 are formed.
And constitute the capacitor layer 14. Further, on both sides (upper and lower surfaces) of the capacitor layer 14, an insulating layer 11 made of alumina ceramics having a thickness of 0.5 to 0.6 mm is usually formed. And this dielectric layer 12
The internal electrode layers 13 formed on both sides of the
Is connected to the surface electrode 16 through. Therefore, when an electronic component such as an LSI is mounted on this alumina multilayer wiring board, the internal capacitor layer 14 functions as a decoupling capacitor, and noise or the like can be effectively removed.

Next, a method for manufacturing the alumina multilayer wiring board having the above structure will be described. First, alumina powder,
A metal oxide powder such as MoO ₃ or WO ₃ and a sintering aid are put into a ball mill or the like, kneaded and dried, and the powder solidified by the drying is crushed. Next, a binder, a solvent and the like are added to this mixed powder to prepare a slurry, which is taped by a method such as a doctor blade method and then dried again. Next, the tape obtained by the above method is cut into an appropriate length to produce a capacitor green sheet, and a high melting point metal such as W or Mo is the main component on the upper and lower surfaces of the capacitor green sheet. A conductive paste is applied or printed to form a layer for internal electrodes. Further, alumina green sheets having through holes and the like are laminated on the upper and lower sides of the capacitor green sheet via the layers for internal electrodes, and the conductive paste is poured into the through holes, dried and then baked to form an alumina multilayer wiring. Complete the manufacture of the substrate. MoO ₃ and WO ₃ existing inside the capacitor green sheet are reduced by the above-mentioned firing to become Mo and W metals. A layer to be the surface electrode layer 16 is formed on a predetermined surface of the alumina green sheet.

[0015]

However, in the above-mentioned conventional method for manufacturing a decoupling capacitor, when the green sheet laminate is fired, the electrode made of W diffuses into the dielectric layer and the diffusion layer Of various thicknesses and concentrations, such as the thickness of the W electrode layer, the thickness of the dielectric layer,
Since the thickness depends on the thickness of the alumina insulator layer, the dielectric constant of the formed dielectric layer tends to change if the conditions change.

The present invention has been made in view of the above problems, and may be caused by some fluctuations in the thickness of the W electrode layer, the thickness of the dielectric layer, the thickness of the alumina insulating layer, and the like in the inside thereof. It is an object of the present invention to provide an alumina wiring board having a built-in decoupling capacitor having a stable electrostatic capacitance value in which the dielectric constant is less likely to change.

[0017]

In order to achieve the above object, the alumina-based wiring board according to the present invention contains 5 to 30 weight% of metal powder in which the ratio of W to the total amount of Mo and W is 30 weight% or more. % Of the alumina layer (hereinafter, referred to as a dielectric layer) is included in the interior of the decoupling capacitor.

In the alumina-based wiring board according to the present invention, the dielectric layer is an alumina layer containing 5 to 30% by weight of metal powder in which the ratio of W to the total amount of Mo and W is 30% by weight or more. Does not differ from a conventional alumina wiring board having a decoupling capacitor therein, and therefore, explanations other than the dielectric layer are omitted here.

First, the material of the internal electrodes formed on both sides of the dielectric layer is preferably W in consideration of conductivity and durability. The average particle size of the W powder in the dielectric layer is 0.5.
˜3 μm is preferable, and the average particle size of Mo powder is 0.5 to 3
μm is preferred. When the ratio of W to the total amount of Mo and W is less than 30% by weight, due to changes in the thickness of the electrode layer, the thickness of each dielectric layer, the thickness of the alumina insulator layer, and the like,
Since the thickness and concentration of the metal diffusion layer formed by diffusing the metal from the electrode layer change, the relative permittivity of the dielectric layer also changes,
It becomes impossible to reproducibly form a decoupling capacitor having a certain capacitance inside the alumina wiring board. FIG. 5 is a graph showing an example thereof, in which the vertical axis represents the rate of change of the relative dielectric constant and the horizontal axis represents the ratio of W to the total amount of Mo and W. When the proportion of W with respect to the total amount of Mo and W is less than 30% by weight, the rate of change of the relative dielectric constant exceeds 3%.

If the total content of Mo and W exceeds 30% by weight, the probability of occurrence of short circuit increases. FIG. 6 shows an example thereof, in which the vertical axis represents the short-circuit rate and the horizontal axis represents the metal content. As is clear from FIG. 6, when the metal content exceeds 30 wt%, the short circuit rate sharply increases.

In the alumina-based wiring board according to the present invention, even if the thickness of the electrode layer, the thickness of each dielectric layer, and the thickness of the alumina insulating layer are changed within the range of the conditions under which they are normally formed. , The dielectric constant of the dielectric layer is maintained at a constant value.

[0022]

According to the alumina wiring board having the above structure, Mo
And a decoupling capacitor including an alumina layer containing 5 to 30% by weight of metal powder in which the ratio of W to the total amount of W is 30% by weight or more. The diffusion of the electrode layer is suppressed,
Even if the thickness of the electrode layer, the thickness of each dielectric layer, the thickness of the alumina insulator layer, etc. changes due to changes in the manufacturing process conditions, etc., the relative dielectric constant of the dielectric layer is maintained at a constant value. Is
An alumina-based wiring board having a decoupling capacitor having a constant capacitance is manufactured with good reproducibility.

Within the normal range, the relative dielectric constant of the dielectric layer changes even if the thickness of the electrode layer, the thickness of each dielectric layer, the thickness of the alumina insulating layer, or the like changes. Since it does not, the above conditions can be freely set, and the design of the alumina-based wiring board becomes easy.

[0024]

EXAMPLES AND COMPARATIVE EXAMPLES Examples of the alumina wiring board according to the present invention will be described below with reference to the drawings. Since the structure itself of the manufactured alumina wiring board is the same as that of the conventional one shown in FIG. 1, detailed description thereof will be omitted here, and the manufacturing method of the alumina wiring board will be briefly described.

First, the manufacturing process of the dielectric layer green sheet will be described.

100 parts by weight of alumina powder having an average particle size of 2 μm and a purity of 99% or more, 2 parts by weight of calcium oxide (average particle size 2 μm, a purity of 99% or more) as a sintering aid, and silicon dioxide (average) (Particle size 2 μm, Purity 99% or more)
And 2 parts by weight of magnesium oxide (average particle size: 2 μm, purity: 99% or more) were added, and an organic solvent was further added as a mixing medium to perform wet mixing. This mixed powder was added with MoO ₃ having an average particle diameter of 2 μm as a high dielectric constant imparting agent.
12 to 16 parts by weight and ₃ to 3 of WO ₃ having an average particle size of 2 μm.
7 parts by weight were added, and the mixture was pulverized and mixed in an organic solvent to prepare a slurry. Example 1 is the case where MoO ₃ is 14% by weight and WO ₃ is 5% by weight, Example 2 is the case where MoO ₃ is 12% by weight and WO ₃ is 7% by weight, and the case where only Mo0 ₃ is 19% by weight. Comparative Example 1 A case in which MoO ₃ is 16% by weight and WO ₃ is 3% by weight is referred to as Comparative Example 2.

Next, using this slurry, a green sheet was prepared by a doctor blade method, and thereafter, the alumina green sheet and a dielectric material having W electrodes formed on both surfaces thereof were formed in the same manner as in the "Prior Art". By stacking the layered green sheets and forming via holes and the like, a green sheet laminate was obtained. This laminate was baked in a nitrogen atmosphere containing hydrogen at 1600 ° C. for 3 hours to complete the production of the alumina-based multilayer wiring board. In each of the above Examples and Comparative Examples, the thickness of the electrode layer is about 10 to about 35 μm, the thickness of each dielectric layer is about 30 to about 55 μm, and the thickness of the alumina insulator layer is about 30 μm. The relative permittivity of the dielectric layer formed on the alumina wiring board was determined by changing the thickness within the range of about 200 to about 1400 μm. The results are shown in FIGS.

In order to measure the relative permittivity (ε _r ), 10 samples under the same conditions were manufactured. Regarding the measurement of the relative permittivity (ε _r ), the capacitance is measured with an impedance analyzer at a frequency of 1 kHz,
Calculate the relative permittivity (ε _r ) from the relationship between the electrode area and the thickness,
The average value of each sample was calculated.

FIG. 2 is a graph showing the relationship between the relative dielectric constant and the thickness of the electrode layer in each of the examples and comparative examples, and FIG.
4 is a graph showing the relationship between the relative dielectric constant and the thickness of the dielectric layer in each of the examples and the comparative examples, and FIG. 4 is the relationship between the relative dielectric constant and the thickness of the alumina insulating layer in each of the examples and the comparative examples. It is a graph showing.

As shown in FIGS. 2 to 4, M is contained in the dielectric layer.
When only 19% by weight of o is contained (Comparative Example 1), and when 16% by weight of Mo0 ₃ and ₃ % by weight of WO ₃ are contained in the dielectric layer (Comparative Example 2), the electrode is used. the thickness of the layer, as the thickness of each dielectric layer, and the thickness of the alumina insulator layer changes, the dielectric constant of the dielectric layer is greatly changed, MO0 ₃ is 14 wt in the dielectric layer % And WO ₃
If is contained 5 wt% (Example 1), and if _{the 3} MO0 in the dielectric layer is contained 12% by weight and WO ₃ is 7% by weight (Example 2), the electrode layer thickness The relative permittivity hardly changes even if the thickness of each dielectric layer and the thickness of the alumina insulating layer change.

As is clear from the results of the above-described Examples and Comparative Examples shown in FIGS. 2 to 4, the thickness of the electrode layer can be increased by including 30% by weight or more of W with respect to the total amount of Mo and W. The dielectric constant can be maintained at a constant value even when the manufacturing conditions such as the size are changed, and an alumina-based wiring board with a built-in decoupling capacitor having a constant capacitance can be manufactured with good reproducibility. Further, since the dielectric constant does not change depending on the thickness of the alumina insulating layer and the thickness of the dielectric layer, the design of the alumina wiring board becomes extremely easy.

The reason why the relative permittivity of the dielectric layer is constant in this way is that in the manufacturing process of the alumina wiring board,
It is considered that the diffusion of the W electrode is suppressed and the W electrode falls within a certain range.

[0033]

As described in detail above, in the multi-layered alumina wiring board according to the present invention, 5 to 3 of the metal powder in which the ratio of W to the total amount of Mo and W is 30% by weight or more is used.
Since the decoupling capacitor including the alumina layer containing 0% by weight is provided therein, the thickness of the electrode layer, the thickness of each dielectric layer, and the alumina insulator layer may change due to changes in the conditions of the manufacturing process. The dielectric constant of the dielectric layer can be maintained at a constant value even if the thickness of the dielectric layer changes, and an alumina wiring board with a decoupling capacitor with a constant capacitance can be manufactured with good reproducibility. You can

Further, the thickness of the electrode layer, the thickness of each dielectric layer,
Even if the thickness of the alumina insulator layer changes, the relative permittivity of the dielectric layer does not change, so the above conditions can be set freely and the design of the alumina wiring board can be easily performed. .

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an alumina-based multilayer wiring board having a decoupling capacitor.

FIG. 2 is a graph showing the relationship between the relative dielectric constant and the thickness of an electrode layer in each example and comparative example.

FIG. 3 is a graph showing the relationship between the relative permittivity and the thickness of a dielectric layer in each of Examples and Comparative Examples.

FIG. 4 is a graph showing the relationship between the relative dielectric constant and the thickness of the alumina insulating layer in each of Examples and Comparative Examples.

FIG. 5 is a graph showing the relationship between the ratio of W with respect to the total amount of Mo and W and the rate of change of the relative dielectric constant.

FIG. 6 is a graph showing the relationship between metal content and short-circuit rate.

[Explanation of Codes] 12 Dielectric Layer 13 Internal Electrode Layer 14 Capacitor Layer

Front page continuation (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C04B 35/111 H01L 23/12 23/14 H05K 1/03 610 D 7511-4E H01L 23/14 M

Claims (1)

[Claims] 1. A decoupling capacitor including an alumina layer containing 5 to 30% by weight of a metal powder having a W content of 30% by weight or more relative to the total amount of Mo and W therein. Alumina-based wiring board featuring.