JPH118447A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board which includes a high-purity alumina sintered material layer having a high alumina content, and a metallized layer firmly coated on the sintered material layer and having a low sheet resistance. SOLUTION: In a wiring board, a metallized wiring layer 1 is coated on a surface and/or inside of an insulating substrate 2 of alumina-sintered material, containing 99 weight % or more of alumina. The metallized wiring layer 1, with respect to 100 weight % of the main components of 50-90 volume % of Mo and/or W and 10-50 volume % of alumina, contains 0-5 weight % of Nb or its compound Nb2 O5 and 0.01-10 weight % of at least one of Si, Ca, Na, Mg and their compound. A part of the metallized wiring layer 1 at least close to an interface of the substrate 2 contains 0.0005-1 weight % of Nb or its compound Nb2 O5 , and in particular, the contact interface between the metallized layer 1 and the insulating substrate 2 has a maximum roughness Rmax of 0.5 μm or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metallized wiring layer having a high adhesive strength to high-purity alumina ceramics and a low conductor resistance, and a wiring board using the same. The present invention is applied to a multilayer wiring board, a circuit board, an IC package, and the like, which are fired at the same time as the layers, and particularly to a wiring board exhibiting excellent performance in high frequency applications.

[0002]

2. Description of the Related Art Conventionally, since an alumina sintered body has excellent properties such as electrical insulation and chemical stability, electronic components such as a semiconductor element housing package for housing a semiconductor element and a circuit board having circuit wiring are provided. It is frequently used in The substrate is provided with a metallized wiring layer as a conductor for forming a circuit on the surface or inside of the alumina sintered body.

In general, as a method of metallizing an alumina-based sintered body, for example, as disclosed in JP-A-2-19678 and JP-A-3-40972, Mo-Mn A method of applying a metallized paste mainly based on and baking in a humidified hydrogen gas,
As disclosed in JP-A-63-139086, a method of directly brazing in a vacuum or an inert gas with a member composed of an alloy of an active metal such as Ti and a relatively low melting point, Japanese Patent Publication No. 60-28790. As disclosed in JP-A-63-64982 and JP-A-63-107879, on the surface of a green sheet formed by mixing a ceramic powder and an organic resin, W and Mo are mainly used by screen printing or the like. After applying the metallizing paste to be baked, the metallizing and the green sheet are appropriately laminated and then reduced in a reducing atmosphere.
A method of simultaneously sintering at 450 to 1700 ° C. (simultaneous firing method) is known. Of these, a co-firing method is generally used for manufacturing a multilayer integrated circuit board in which wiring layers are formed in multiple layers.

Alumina-based sintered bodies generally used as an insulating substrate of a wiring substrate contain alumina sintering agents such as SiO ₂ , alkaline earth oxides and rare earth element oxides in an amount of 10% by weight or more, so that alumina crystal particles are used. There is a large amount of glass component between them. When a metallized wiring layer mainly composed of a high melting point metal such as tungsten (W) or molybdenum (Mo) is formed on the surface of such an alumina sintered body by simultaneous firing, the glass component in the sintered body has a high melting point. It moves between metal particles, improves the sinterability of the metallized wiring layer, and plays a role of firmly bonding the metallized wiring layer to the insulating base.

[0005]

In recent years, due to the rapid development of integrated circuits, higher insulation resistance, lower heat dissipation, lower dielectric loss (tan δ), smoother surface of the insulating substrate, etc. have been realized. It is required to use, as an insulating substrate, a high-purity alumina-based sintered body containing 99% by weight or more of an alumina-containing material in which a sintering aid is reduced as much as possible.

However, when the amount of the sintering aid in the alumina-based sintered body is less than 10% by weight, since the absolute amount of the glass component interposed between the alumina crystals is small, the high melting point metal particles of the metallized wiring layer are not provided. Since the amount of movement of the glass component between the metallized wiring layers is reduced, and the sinterability of the metallized wiring layer is deteriorated, the metallized layer becomes porous and it is difficult to firmly adhere the metallized wiring layer to the insulating substrate. For example, Japanese Patent Application Laid-Open No. 63-64982 describes that a composition obtained by adding Al ₂ O ₃ , Ta, SiO ₂ or the like to W is applied to a high-purity alumina green sheet. Is 3 kg / mm ²
The following is insufficient for practical use.

Japanese Patent Application Laid-Open Nos. 63-201079, 2-30688 and 3-40972 disclose a method of metallizing a high-purity alumina sintered body.
On the other hand, compositions to which Al ₂ O ₃ , TiO _2, etc. are added are described, but all of these compositions are applied and baked on an alumina-based sintered body. Has not been considered at all.

Further, Japanese Patent Application Laid-Open No. 63-107879 describes that a paste obtained by adding a compound such as Ni, Ti or Zr to W and Mo is applied and simultaneously baked.
The applied alumina green sheet has a purity of about 95%, and for a sintered body having a purity of 99% or more,
Not considered at all.

Therefore, the present invention relates to an alumina (Al
High purity alumina sintered body with high content of ₂ O ₃ )
It is an object of the present invention to provide a wiring board on which a metallized metal layer having a low sheet resistance is firmly formed and adhered.

[0010]

Means for Solving the Problems The present inventors have found that W and / or Mo are present on the inside or the surface of an insulating substrate made of high alumina ceramics having an alumina content of 99% by weight or more.
After examining the structure of a wiring board having a low resistance and excellent adhesive strength in a wiring board formed by attaching a metallized wiring layer mainly composed of a metallized wiring layer, at least Nb was contained in an insulating substrate side in a specific range. In addition, the present inventors have found that the above object can be achieved by reducing the amount of Si, Ca, Na, Mg or a compound thereof to a predetermined amount and adding Nb in some cases in the metallized wiring layer. Invented the invention.

That is, the wiring board of the present invention comprises alumina
In a wiring board having a metallized wiring layer deposited and formed on the surface and / or inside of an insulating substrate made of an alumina sintered body containing at least 9% by weight, the metallized wiring layer contains Mo and / or W of 50 to 50%. With respect to 100 parts by weight of the main component consisting of 90% by volume and 10 to 50% by volume of alumina, Nb or a compound thereof is converted to 0% in terms of Nb ₂ O _5.
To 5 parts by weight and at least one of Si, Ca, Na or Mg, or a compound thereof, in an amount of 0.01 to 1 part by weight.
0 wherein a ratio of parts by weight, and the Nb or a compound thereof in the vicinity of the interface between the at least the metallized wiring layer of the insulating substrate calculated as Nb ₂ O ₅ with 0.0005 wt%
Is contained at a ratio of Also,
It is desirable that the maximum surface roughness (Rmax) of the contact interface between the metallized wiring layer and the alumina-based sintered body is 0.5 μm or more.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a wiring board according to the present invention, as shown in a schematic sectional view of FIG.
Formed on the surface and / or inside of the substrate. According to the present invention, the metallized wiring layer 1 contains 50 to 90% by volume, particularly 60 to 85% by volume, and 10 to 50% by volume, particularly 15 to 40% by volume of alumina as conductor components. % Of the main component consisting of Si, Ca, Na, M as the first subcomponent.
It is a major feature that g or at least one selected from these compounds is contained in a ratio of 0.01 to 10 parts by weight, particularly 0.01 to 7 parts by weight in terms of metal.

As shown in FIG. 1, the inclusion of the alumina particles 3 in the metallized wiring layer 1 in the above-described ratio has the effect of increasing the adhesion to the insulating substrate 2 made of an alumina-based sintered body. Therefore, the amount of alumina is 10% by volume.
When the amount is smaller, in other words, when the amount of the conductor component is more than 90% by volume, the adhesion to the insulating substrate becomes insufficient, and when the amount of alumina exceeds 50% by volume, in other words, when the amount of the conductor component is more than 50% by volume. If the number is too small, the resistance of the metallized wiring layer increases, which makes the metallized wiring layer unsuitable for forming a wiring layer on a wiring board.

As the conductor component, Mo is particularly desirable. This is because Mo has a melting point close to 800 ° C. as compared with W and is easily sintered, so that the conductor resistance is easily reduced.

The first subcomponents such as Si and Ca are as follows:
In addition to improving the sinterability of the metallized wiring layer and the sinterability of the insulating substrate, the metallized wiring layer has an effect of increasing the adhesiveness to the insulating substrate side. However, this first subcomponent is:
As it has the property of increasing the resistance of the wiring layer and increasing the transmission loss of high-frequency signals,
In particular, from the viewpoint of high frequency characteristics in high frequency applications of 1 GHz or more, it is desirable that the amount is small. Therefore, if the amount of the first subcomponent is less than 0.01 parts by weight, sufficient strength cannot be obtained in terms of sinterability of the metallized wiring layer and adhesion to the insulating substrate, and the amount exceeds 10 parts by weight. This increases the conductor resistance and increases the transmission loss of high-frequency signals in high-frequency applications.

Further, in the metallized wiring layer 1, the second
May contain Nb or a compound thereof. This Nb is composed of alumina which is one of the main components in the metallized wiring layer and W and / or Mo which are the conductor components.
Bond between the metallized wiring layer and the insulating substrate, thereby increasing the bonding strength between the metallized wiring layer and the insulating substrate. Make However, when the amount of Nb is large, warpage occurs due to a mismatch in firing shrinkage between the metallized wiring layer and the insulating substrate. From this viewpoint, it is necessary that the amount of Nb is 0 to 5 parts by weight, particularly 0.002 to 3 parts by weight, based on 100 parts by weight of the main component.

On the other hand, according to the present invention, Nb is located at least near the interface of the metallized wiring layer 1 on the insulating substrate 2.
Or 0.0005 to 1 of the compound in the total amount in terms of metal
It is important that it be contained at a ratio of 0.001 to 0.5% by weight, particularly 0.001 to 0.5% by weight. As described above, by including Nb in the vicinity of the interface with the metallized wiring layer in the above ratio, the adhesive strength of the metallized wiring layer to the alumina insulating substrate can be increased. The reason for limiting the Nb amount as described above is that if the Nb amount is less than 0.0005% by weight,
If the adhesion of the metallized wiring layer to the alumina insulating substrate is not improved and exceeds 1% by weight, Nb in the alumina insulating substrate
This is because, when the amount increases, the characteristics of the alumina insulating substrate, particularly the dielectric loss in the high frequency region, increase, and the transmission loss of the high frequency signal increases.

The insulating substrate 2 has an alumina content of 9%.
9 wt% or more, particularly 99.3 wt% or more of the alumina sintered body, and the components other than alumina of the alumina sintered body include sintering aids, raw materials, and And the like, which are mixed with the impurities. Sintering aid components include alkali metals, alkaline earth metals, rare earth metals, T
i, Zr, Si, a compound of at least one element selected from the group of Group 8 of the periodic table, particularly an oxide,
These sintering aids are contained in a proportion of 1.0% by weight or less, especially 0.7% by weight or less. The above high-purity alumina-based sintered body has a dielectric loss (tan) in a band of 1 to 10 GHz.
δ) has a value of 1 × 10 ⁻³ or less. Therefore, the wiring board of the present invention including the metallized wiring layer and the insulating substrate has a signal frequency of 1 for transmitting the wiring layer.
It is useful as a wiring board in a high frequency band of GHz to 100 GHz.

Further, according to the present invention, the maximum surface roughness (Rmax) of the interface between the insulating substrate 2 made of the alumina sintered body and the metallized wiring layer 1 is 0.5 μm or more;
In particular, it is desirable that the thickness be 1 μm or more. As shown in the sectional view of FIG. 1, the bonding between the metallized wiring layer 1 and the insulating substrate 2 of the present invention is formed by bonding the alumina particles 3 in the metallized wiring layer 1 and the alumina particles in the insulating substrate 2. This is because the metallized wiring layer 1 is firmly joined by the effect of the anchor portion 4 thus obtained. The maximum surface roughness referred to here is
As shown in FIG. 1, in the cross-sectional photograph of the interface between the metallized wiring layer 1 and the insulating substrate 2, it means the maximum width of the boundary formed by the continuous alumina component near the interface, and this maximum surface roughness is large. The more the anchor effect is significant, the higher the adhesive strength. Therefore, when the maximum surface roughness is smaller than 0.5 μm, the anchor effect is not sufficient,
High adhesive strength cannot be obtained.

It is desirable that the alumina content in the metallized layer is variously adjusted within the above-mentioned range depending on the portion where the metallized wiring layer is formed on the wiring board. For example, FIG.
Of the multilayer wiring board 5 for the internal wiring layer 6 in order to reduce the resistance of the wiring layer, especially 10 to 20% by volume. 30% by volume, adherend 8 such as solder or brazing material
The wiring layer 10 on which the metal fittings 9 and the like are attached by
0 to 50% by volume is suitably used. In the land portion 12 connected to the through hole 11, 20 to 30% by volume is particularly preferably used in terms of adhesive strength and conductor resistance.

In order to manufacture the wiring board of the present invention, at least 99% by weight of alumina and alkali metal, alkaline earth metal, rare earth metal, Ti, Zr, S
i, a doctor blade method and a rolling method using a slurry obtained by adding an organic binder and a solvent to a ceramic mixture containing 1.0% by weight or less of a compound of at least one element selected from Group 8 of the periodic table, After being formed into a sheet by, for example, Mo and / or W as a conductor component is contained in the sheet-shaped formed body by 50 to 90% by volume,
A metallizing paste in which an organic binder and a solvent are added to and mixed with a solid component mainly containing 10 to 50% by volume of alumina is printed on a wiring pattern by a screen printing method. Thereafter, if desired, a sheet-shaped molded body is laminated, and simultaneously fired in a reducing atmosphere at 1400 to 1700 ° C., whereby a wiring board having an insulating substrate and a metallized wiring layer can be manufactured.

According to the above-described wiring board of the present invention, a predetermined amount of Nb or a compound thereof is contained near the interface between the insulating substrate and the metallized wiring layer, and further, a predetermined amount of Nb is contained in the metallized wiring layer. However, under the above-mentioned firing conditions, Nb has the property of diffusing or volatilizing while producing a liquid phase by reaction with alumina.

Accordingly, Nb ₂ O ₅ is contained in the sheet-like molded body before firing in the above ratio, or the metallized paste is mainly composed of W and / or Mo and alumina as solid components. relative to 100 parts by weight of component 0 compounds such as Nb ₂ O ₅ in Nb ₂ O ₃ in terms of
After containing 5 parts by weight and applying it to the sheet-like molded body, by simultaneously baking at the above temperature, the Nb element reacts with alumina to generate a liquid phase, thereby forming a liquid phase between the metallized wiring layer and the insulating substrate. Diffusing the Nb element into the other,
Alternatively, Nb can be contained near the interface with the metallized wiring layer in the insulating substrate and further on the metallized wiring layer side by volatilizing and invading the other side once. According to the present invention, such a specific diffusion behavior of Nb is considered to be a major factor in improving the adhesion between the metallized wiring layer and the insulating substrate.

Further, in the metallized wiring layer, Si, Ca,
At least one of Na and Mg is 0.01 to 1
In order to make it contained at a ratio of 0 parts by weight, these components are added to the metallized paste, or the sintering aid component is transferred from the alumina-based sintered body to the metallized wiring layer during simultaneous firing with the insulating substrate. Can also be contained.

[0025]

EXAMPLE Alumina powder having an average particle size of 2.0 μm and a purity of 99.9% was mixed with SiO ₂ and MgO as sintering aids in a ratio of 2: 1.
An organic resin and an organic solvent were added to the mixture added at a weight ratio of 0.5% by weight and mixed by a ball mill for 24 hours to prepare a slurry. Using this, a green sheet 1 was produced by a doctor blade method.

The average particle size is 2.0 μm and the purity is 99.
Nb ₂ O ₅ was added to 9% alumina powder as a sintering aid in an amount of 0.1%.
1% by weight, SiO ₂ and MgO in a weight ratio of 2: 1 of 0.4
2% by weight of an organic resin and an organic solvent
The slurry was adjusted by mixing with a ball mill for 4 hours, and the green sheet 2 was mixed with the slurry using a doctor blade method.
Then, the prepared metallized paste was applied to the outer surface of each of the green sheets 1 and 2 by 1.5 m.
Twenty patterns of m square and 20 μm thickness were printed by the screen printing method. Next, this was simultaneously fired in a reducing atmosphere at 1600 ° C. to obtain a wiring board having a metallized metal layer formed on the surface of an alumina sintered body.

The sheet resistance, the transmission loss, and the adhesive strength of the metallized wiring layer were measured on the manufactured wiring board in accordance with the following methods. The results are shown in Tables 1 and 2.

Then, the composition of the separated metallized wiring layer was analyzed, and the components in the metallized wiring layer were analyzed. In addition, component analysis of the surface of the insulating substrate on which the metallized wiring layer was adhered was performed by ICP emission spectroscopy. Further, the obtained sample was cut, and the cross section was polished, the structure of the interface between the metallized wiring layer and the insulating substrate was observed, the denseness of the metallized wiring layer was evaluated, and the surface roughness of the interface was measured. Indicated. The measurement method was in accordance with FIG.

(Adhesive strength of metallized wiring layer) The metallized wiring layer has a length of 40.0 mm and a length of 40.0 mm.
2 One end of a metal column made of Alloy (Fe—Ni alloy) is brazed through a silver braze (Ag: 72%, Cu: 28%), and then the end opposite to the brazed portion of the metal column is vertically oriented. Then, the tensile strength when the metallized wiring layer was peeled from the alumina sintered body was examined, and the average value was calculated as the adhesive strength of the metallized metal layer, and is shown in Table 1. When a metal pillar is brazed to the metallized wiring layer, a thickness of 1.0 μm
Was formed.

(Sheet resistance of metallized wiring layer)
In the same manner as described above, a length of 3
Twenty metallized wiring layers having a thickness of 0.0 mm, a width of 3.0 mm, and a thickness of 20 μm were formed and adhered, the sheet resistance of each wiring layer was measured, and the average value was calculated as the resistance value of each metallization. Are shown in Table 1.

(Transmission loss of metallized wiring layer) In the same manner as described above, a metallized wiring layer 14 is formed on the upper surface of a 0.3 mm-thick alumina sintered body 13 as shown in FIG.
A metallized ground layer 15 was provided on the entire lower surface to form a microstrip line, and an evaluation sample for measuring transmission characteristics was obtained. At this time, so that the impedance becomes 50Ω,
The thickness and width of the metallized wiring layer on the upper surface were determined. Then, a signal of 20 GHz was input from the input terminal of the evaluation sample for transmission characteristic measurement and the transmitted signal was measured by a network analyzer, and the S21 parameter (dB) of the power ratio was calculated to evaluate the transmission loss. This S21
Is closer to 0, the transmission loss is lower and the transmission characteristics are better.

[0032]

[Table 1]

[0033]

[Table 2]

As is clear from the results shown in Table 1, in Samples No. 1, 21, 28 and 29 in which the alumina content is less than 10% by volume in the metallized wiring layer, the adhesive strength to the insulating substrate is almost all. 0, and when trying to glue the metal pillars with silver brazing after Ni plating,
The metallized wiring layer had already been peeled off. In addition, the alumina content was increased to 50% by volume as in Sample Nos. 6 and 25.
As a result, the sheet resistance increased, and the value greatly exceeded 20 mΩ / □.

Regarding the amounts of Si, Ca, Mg, and Na, the metallized wiring layer after co-firing was not added to the metallized paste when the compound containing these metals was added (samples Nos. 32 and 33). The diffusion of the sintering aid in the insulating substrate confirmed the presence of 0.01 parts by weight. However, in Sample No. 20 in which the amount of these metal components exceeded 10 parts by weight, the conductor resistance increased and the transmission loss of the high-frequency signal increased.

When the Nb compound was mixed with either the Nb compound in the metallized paste or the green sheet, Nb was detected near the interface with the metallized wiring layer of the insulating substrate in any case. In the case of sample No. 8 in which the Nb content at the interface in the insulating substrate was less than 0.0005% by weight, sufficient adhesive strength could not be obtained.
In sample No. 7 which was not blended in either, Nb
Was not detected at all, and the adhesive strength was low. Sample No. 14 in which the amount of Nb in the metallized wiring layer exceeded 5 parts by weight and the amount of Nb in the insulating substrate exceeded 1% by weight.
Showed good adhesion strength and sheet resistance, but large transmission loss and deformation of the entire wiring board.

In contrast to these comparative examples, all of the samples of the present invention could form a good metallized wiring layer having an adhesive strength of 3 kgf / mm ² or more, a sheet resistance of 15 mΩ / □ or less, and a transmission loss of 2.0 or less. . Moreover, the wiring boards of the present invention all have a surface roughness (Rmax) of 0.5 μm or more at the interface between the metallized wiring layer and the insulating substrate.
At 0 μm or more, a high adhesive strength of 5 kgf / mm ² or more was obtained.

[0038]

As described in detail above, the present invention provides a low sheet resistance, a high adhesive strength, and an excellent bonding strength to an insulating substrate made of a high-purity alumina sintered body containing 99% by weight or more of alumina. A wiring board on which a metallized wiring layer having transmission characteristics is formed can be provided. Therefore, it is preferably used as a wiring board particularly for high frequency, and is used as a cellular phone, a personal handy phone system, a circuit board for various satellite communications, a semiconductor element housing package for housing a semiconductor element, and a circuit board having a circuit wiring conductor. It can be used suitably for electronic components of the above, and the reliability of those components can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining an interface structure between a metallized wiring layer and an insulating substrate in a wiring substrate of the present invention.

FIG. 2 is a schematic sectional view for explaining an example of a wiring board of the present invention.

FIG. 3 is a schematic perspective view of an evaluation sample for measuring transmission characteristics in an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metallized wiring layer 2 Insulating substrate 3 Alumina particles 4 Anchor part 5 Wiring board 6 Internal wiring layer 7 Surface wiring layer 8 Adhering material 9 Metal fitting 10 Wiring layer 11 Through hole 12 Land part

Claims (2)

[Claims] 1. A wiring board having a metallized wiring layer formed on a surface and / or inside of an insulating substrate made of an alumina sintered body containing 99% by weight or more of alumina, wherein the metallized wiring layer is made of Mo. and a 50 to 90% by volume / or W, with respect to the main component of 100 parts by weight of the alumina from 10 to 50 vol%, and 0 to 5 parts by weight of Nb or a compound thereof calculated as Nb ₂ O _5, Si , Ca,
Na or Mg, or at least one of the compounds thereof, in an amount of 0.01 to 10 parts by weight, and Nb or its compound is Nb ₂ O at least near the interface with the metallized wiring layer of the insulating substrate. A wiring board characterized by containing 0.0005 to 1% by weight in terms of ₅ . 2. The wiring substrate according to claim 1, wherein a maximum surface roughness (Rmax) of a contact interface between said metallized wiring layer and said insulating substrate is 0.5 μm or more.