JP3170431B2 - Alumina-mullite laminated structure and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated structure of an alumina sintered body and a mullite layer.
The present invention relates to a structure that is useful as an insulating material such as a multilayer substrate and an ozonizer, and particularly requires a high strength and a low dielectric constant.

[0002]

2. Description of the Related Art Conventionally, alumina-based sintered bodies have been widely used as insulating materials for circuit boards and the like because of their high insulation resistance. In addition, heat resistance, abrasion resistance, chemical resistance,
Due to its excellent mechanical properties, it is also applied to various industrial machine parts.

[0003] Alumina sintered bodies are generally made of SiO ₂ or C
It is obtained by adding a sintering aid such as alkaline earth oxides such as aO and SrO and baking it in an oxidizing atmosphere, and has a strength of about 40 to 50 kg / mm ² . . It is desired to increase the strength of the alumina sintered body, but there is a limit in improving the strength of the Al ₂ O ₃ -auxiliary system.

The coefficient of thermal expansion of the alumina sintered body is 7
８8 ppm / ° C. and a relative dielectric constant of about 9-10, but when used as an insulating material in a circuit board, particularly when applied to a board on which a semiconductor element is mounted, the coefficient of thermal expansion of the semiconductor element is Since the difference from the coefficient is large, it is desired to reduce the coefficient of thermal expansion. When a wiring layer is formed on the surface or inside of the alumina sintered body, a high relative dielectric constant increases a signal propagation delay. Therefore, it is desirable that the relative dielectric constant be small.

On the other hand, mullite (3Al ₂ O ₃ .2SiO)
₂ ) has a thermal expansion coefficient of 4 to 5 ppm / ° C., which is close to that of a semiconductor element, and has a relative dielectric constant as low as about 6 to 7; Is also suitable, but the mechanical strength is 20-30 kg / mm ²
And lower than the alumina sintered body.

Therefore, in order to utilize the low dielectric constant and low thermal expansion of mullite while utilizing the high strength of the alumina sintered body, it is conceivable to combine the alumina sintered body and the mullite sintered body. .

In Japanese Patent Publication No. 64-9266, A
There has been proposed a sintered body obtained by sintering a composition obtained by adding B ₂ O ₃ , SiO ₂ , an alkaline earth oxide, and mullite to l ₂ O ₃ and depositing mullite on the surface of the sintered body. .

[0008]

However, according to the method disclosed in Japanese Patent Publication No. 64-9266, the mullite layer can be formed only on the surface of the sintered body, and the thickness of the mullite layer is also reduced. However, there has been a problem that a mullite layer having a uniform thickness cannot be deposited depending on the firing conditions.

In general, an alumina-based sintered body to which a general-purpose SiO ₂ or alkaline earth oxide sintering aid is added has a SiO ₂ : alkaline earth oxide weight ratio of 2: 1 to 7:
When a mullite layer is formed on the surface of an alumina-based sintered body having this composition and fired, an oxide such as an alkaline earth and mullite react with each other to decompose into alumina and a liquid phase component. As the particles grow abnormally and the liquid phase is absorbed into the alumina-based sintered body, a dense mullite layer cannot be stably formed on the surface of the alumina-based sintered body. Was.

[0010]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, in an alumina-based sintering aid-based alumina-based sintered body, at least alumina and sintering aid have been used. When SiO ₂ is used and controlled to a specific composition range, even if the mullite layer is laminated, the mullite layer does not react with the auxiliary component in the sintered body, and the mullite layer can be stably present. I found it. Moreover, it has been found that a mullite composition layer is provided on the surface of an alumina-based molded body having a specific composition range, and that the alumina-based sintered body having a mullite layer laminated thereon can be obtained by simultaneously firing the layers. .

That is, according to the present invention, the sintering aid is used in an amount of 0.1 to 20.
An alumina-mullite laminated structure obtained by laminating an alumina-based sinter having a weight percentage of 10% by weight and a mullite layer containing no sintering aid or containing 10% by weight or less. and sintering aid mullite layer is a SiO ₂ of 80 to 100% by weight with respect to aid the total amount, 0
20% by weight of a metal oxide of at least one of Group 1A, 2A, 3A, 4A and Group 8 elements.

As a method of manufacturing such a laminated structure, alumina is used as a main component and a sintering aid is used in an amount of 0.1 to 20.
Production of an alumina-mullite laminate structure in which after laminating an alumina-based molded body added by weight% and a mullite forming composition to which no sintering aid is added or 10% by weight or less is added, the laminate is fired. a method, sintering aid of the alumina green body and mullite molding composition, and SiO ₂ of 80 to 100% by weight with respect to aid the total amount, 0-2
0% by weight of the periodic table 1A, 2A, 3A, 4A and 8
It is characterized by comprising at least one kind of metal oxide of the group III elements.

Hereinafter, the present invention will be described in detail. According to the present invention, the alumina-based sintered body for laminating the mullite layer is mainly composed of alumina, contains at least SiO ₂ as a sintering aid, and further has a periodic table 1A, 2A, 3A, 4A, 8
But is intended to include an oxide of at least one metal of group elements, the sintering aid composition, SiO ₂ is 1:80
00% by weight, especially 85 to 95% by weight,
A, 2A, 3A, 4A, at least one of Group 8 elements
The sintering aid having the composition of 0 to 20% by weight, particularly 5 to 15% by weight of the oxide of the kind of metal is used.
It is important that it be contained at a ratio of -20% by weight, especially 3-15% by weight.

The composition and amount of the sintering aid are as follows:
It is important to stably form the mullite layer when mullite is laminated on the alumina sintered body. In the composition of the sintering aid, if the amount of SiO ₂ is less than 80% by weight, It is easy to decompose into a liquid phase with Al ₂ O ₃ . Also, periodic table 1A, 2A, 3A, 4A, 8
When an oxide of at least one metal of the group III elements is added, even if the amount exceeds 20% by weight, the mullite is easily decomposed similarly, and a mullite layer cannot be formed stably.

The oxides of at least one metal of Group 1A, 2A, 3A, 4A and 8 elements of the Periodic Table include:
Specifically, Li, Na, K, Mg, Ca, Sr, B
a, Y, Ce, Nd, Sm, Er, Yb, Ti, and Fe oxides. Among these, CaO, MgO,
Y ₂ O ₃ is most suitable as an auxiliary.

According to the present invention, the mullite (3Al ₂ O ₃ .2SiO ₂ ) layer laminated on the alumina sintered body can exist stably.
It can be adjusted appropriately according to the purpose. In the laminated structure, the mullite layer may be laminated inside the alumina sintered body, instead of being laminated on the surface of the alumina sintered body.

In manufacturing such an alumina-mullite laminated structure, first, an alumina molded body is prepared. The molded body is, SiO ₂ is 80 to 100% by weight, in particular 85 to 95 wt%, the periodic table 1A, 2A, 3A,
4A, a sintering aid comprising at least one metal oxide of a Group 8 element having a composition of 0 to 20% by weight, especially 5 to 15% by weight, is prepared. 0.1 to 20% by weight, particularly 3 to 15% by weight is added and mixed.

Thereafter, the mixed powder is molded into an arbitrary shape by a known molding method, for example, a doctor blade method, a sheet rolling method, a mold pressing method, a cold isostatic pressing method, an extrusion molding method, or the like. An alumina molded body is produced.

Next, a mullite forming composition is prepared.
As the mullite forming composition, mullite (3Al
₂ O ₃ · ₂ SiO ₂ ) powder, or SiO ₂ powder and Al ₂ O ₃
A composition obtained by adding 1% by weight or more of mullite powder as a seed crystal to a mixture of 50 to 25:50 to 75 powder can be used. When the sintering aid is not added or when it is added, SiO ₂ which is a sintering aid component of alumina and the first group of elements 1A, 2A, 3A, 4A and 8 of the periodic table are added to the above composition. 10% by weight of at least one metal oxide
It can be added at the following ratio. Also in that case, similarly to the alumina sintered body, the amount of SiO ₂ in the sintering aid component needs to be 80 to 100% by weight.

Further, by adding an oxide of Mn, Zn or B in addition to the above-mentioned components as a sintering aid component, it is possible to perform low-temperature sintering. Also in this case, it is preferable to control the composition so that the amount of SiO ₂ in the sintering aid component is 80% by weight or more.

Then, a mullite forming composition is laminated on the above-mentioned alumina compact. As a lamination method, a mullite-forming composition is applied to the surface of the alumina-based molded body by a printing method, a dipping method, or the like, or the mullite-forming composition is used, and a doctor blade method, a sheet rolling method, a gold Mold press, cold isostatic press,
A laminate formed by molding into a predetermined shape by extrusion molding or the like is laminated and pressure-bonded to an alumina molded body, whereby a laminate of the molded body can be produced.

Next, the laminate produced as described above is fired in an oxidizing atmosphere such as air or a reducing atmosphere such as a nitrogen / hydrogen mixed atmosphere. Baking is 1250 ° C ~ 1
Simultaneous firing at 800 ° C. allows the alumina sintered body and the mullite layer to be simultaneously sintered and densified. At this time, in order to fire at 1500 ° C. or less, powder having an average particle size of submicron or a specific surface area of 1
It is preferable to use a powder of 0 m ² / g or more. Also,
When firing at 1500 ° C. to 1700 ° C., it is preferable to use a raw material having an average particle size of several microns or a specific surface area of several m ² / g. For firing at 1700 ° C. or higher, it is preferable to use a raw material having a specific surface area of several m ² / g or less while removing submicron powder as much as possible.

However, the decomposition temperature of mullite is 1810
The sintering temperature is preferably 1830 ° C., and the decomposition temperature of mullite may be accelerated at a high temperature.
700 ° C. or less is preferable.

Here, Al, Si, Periodic Table 1A, 2
At least one metal among the A, 3A, 4A, and Group 8 elements may be used in any form as long as it is a compound that becomes an oxide upon firing, such as hydroxide, carbonate, nitrate, and carbide. , Nitrides, and other compounds.

The alumina-based sintered body or the mullite layer contains, as a coloring agent, an element such as Cr which is completely dissolved in alumina, W, Mo, Re, Au, Ag, Cu, Pt.
For example, a pigment having a coloring effect by being dispersed as a metal can be added.

Next, various uses of the alumina-mullite laminated structure of the present invention will be described. FIGS. 1 and 2 show a basic structure example of an alumina-mullite laminated structure of the present invention, in which a mullite layer 2 is formed on a surface of a substrate 1 made of an alumina-based sintered body. In this case, the mullite layer may be formed on the entire outer surface of the substrate 1. The mullite layer 2 may be formed on the upper and lower surfaces of the substrate 1 as shown in FIG. 1 or may be formed inside the substrate 1 as shown in FIG. According to such a structure, since the mullite layer 2 has a lower coefficient of thermal expansion than the alumina-based sintered body, a large compressive stress is generated in the mullite layer 2 at the time of cooling after firing, and the entire laminate due to surface compressive stress is generated. Can be strengthened. In this reinforced structure, even if the thickness of the mullite layer is several μm, sufficient reinforcement occurs. However, in order to stably increase the strength, it is preferable to form a mullite layer having a thickness of 10 μm or more.

FIG. 3 shows the structure of the present invention as a multilayer wiring board,
In particular, this is a case in which it is used for a package for housing semiconductor elements. According to the semiconductor storage package of FIG. 3, the insulating substrate 3 is formed with the concave portion 5 for storing the semiconductor element 4, and the surface or the inside of the insulating substrate 3 is W, M
A wiring layer 6 such as o is formed. Also, the insulating substrate 3
Is connected to a plurality of connection pins 7 to be mounted on another external circuit board. The connection pin 7 is electrically connected to the wiring layer 6 and the semiconductor element 4.

According to the present invention, the insulating substrate 3 is formed of an alumina sintered body, but only the upper and lower insulating layers adjacent to the wiring layer 6 are formed of the mullite layer 8 and the other portions are formed of the alumina layer 9. It consists of. As described above, by sandwiching the wiring layer 6 on the insulating substrate by the mullite layer 8 having a dielectric constant lower than that of the alumina-based sintered body, the signal propagation delay in the wiring layer 6 can be reduced. Further, by forming the mullite layer 10 on the outer surface of the multilayer wiring board, the strength of the wiring board can be increased by the compressive stress of the mullite layer 10.

In order to manufacture the package for accommodating the semiconductor element, for example, a sheet-like molded body is formed from the alumina-like sheet-like molded body and the mullite-forming composition based on the above-mentioned production method, and as shown in FIG. A metal paste for forming a wiring layer such as W, Mo, and Mo-Mn, a mullite sheet-like molded body, and an alumina sheet-shaped molded body are laminated or coated so that a laminated layered body is formed. And humidified nitrogen at 1250-1800 ° C.
By co-firing in a reducing atmosphere such as a hydrogen mixed atmosphere, a semiconductor device housing package as shown in FIG. 3 is obtained.

FIG. 4 shows a case where the structure of the present invention is used for an ozonizer. FIG. 4 (a) is a plan view and FIG.
FIG. 4B is a sectional view taken along line XX in FIG. FIG.
According to this, an induction electrode layer 12, a dielectric layer 13, and a discharge electrode layer 14 are laminated on a surface of a substrate 11 made of an alumina sintered body. Further, a protective layer 15 is formed on the surface of the discharge electrode layer 14. According to such an ozonizer, ions are generated by applying a high voltage between the dielectric electrode layer 12 and the discharge electrode layer 14.

According to the present invention, in the above-mentioned ozonizer, the substrate 11 and the dielectric layer 13 are formed of an alumina sintered body, and the protective layer 15 is formed of a mullite layer. Therefore, a structure is obtained in which the alumina-based sintered body and the mullite layer are directly laminated at locations other than the portion where the discharge electrode layer 14 is formed.

As described above, since the relative dielectric constant of mullite is lower than that of alumina, the protective layer made of mullite can be formed thick, so that the discharge electrode layer 14 is strongly protected against the oxidizing action of ozone gas generated by the ozonizer. And can impart excellent durability to the ozonizer.

In order to manufacture the ozonizer shown in FIG. 4, for example, a dielectric electrode layer 1 is formed on the surface of a sheet-like molded body made of alumina.
After applying a metal paste such as W, Mo, Mo-Mn, etc. for forming No. 2, an alumina sheet-like molded body, and a metal paste such as W, Mo, Mo-Mn, etc. for forming the discharge electrode layer 14, A paste of the mullite forming composition is applied so as to completely cover the discharge electrode layer 14 to form a protective layer. Then, the laminated molded body can be manufactured by firing in a reducing atmosphere such as a humidified nitrogen / hydrogen mixed atmosphere at 1250 to 1800 ° C.

[0034]

According to the present invention, when a mullite layer is laminated on an alumina-based sintered body, the alumina-based sintered body is made of SiO ₂ of 8%.
0 to 100% by weight and Periodic Table 1A, 2A, 3A, 4
A, a sintering aid having a composition of at least one metal selected from the group 8 elements in an amount of 0 to 20% by weight is used in an amount of 0.1 to 20%;
% By weight, and the remainder is composed of an alumina-based sintered body composed of alumina, thereby suppressing the reaction between the sintering aid composed of a metal oxide and mullite, and forming a mullite layer on the surface of the alumina-based sintered body. It can be formed stably.

As a result, the alumina-mullite laminated structure of the present invention has a structure in which alumina having a thermal expansion coefficient of 7 to 8 ppm / ° C. and mullite having a thermal expansion coefficient of 4 to 5 ppm / ° C. are stably laminated. Therefore, a large compressive stress is generated in the mullite at the time of cooling after co-firing them, so that the alumina-mullite laminated structure can be strengthened by the surface compressive stress.

In a multilayer wiring board such as a package for housing a semiconductor element, a mullite layer can be formed inside a substrate made of an alumina sintered body. The relative dielectric constant of alumina is about 10, while the relative dielectric constant of mullite is 6 to 7, and the signal propagation delay is reduced by sandwiching only the wiring part of the multilayer wiring board with the mullite layer. Can be done. Thereby, the bending strength is 40 to 50.
It is possible to form a multilayer wiring board having a small propagation delay and a high strength without impairing the characteristics of the alumina sintered body of kg / mm ² . Further, by further covering this multilayer wiring board with mullite, it is possible to produce a wiring board having higher strength.

Furthermore, by covering the surface of an ozonizer prepared using the alumina-based sintered body of the present invention as a substrate and a dielectric with a mullite layer as a protective layer for a discharge electrode layer, the dielectric constant is lower than that of alumina. Thick coating becomes possible, and the protective power of the discharge electrode layer can be increased.

[0038]

【Example】

Example 1 Al ₂ O ₃ powder, SiO ₂ powder as a sintering aid component, and at least one powder of oxides of Group 1A, 2A, 3A, 4A and Group 8 of the Periodic Table are shown in Tables 1 and 2. And a known binder and a solvent, a dispersant, a plasticizer, an antifoaming agent, an antistatic agent and the like were mixed to prepare an alumina green sheet having a thickness of about 0.5 mm by a doctor blade method. A green sheet having a thickness of about 0.015 mm was prepared in the same manner for mullite powder having a composition of 3Al ₂ O ₃ .2SiO ₂ .

Then, seven alumina green sheets are laminated, and furthermore, one to three layers of mullite green sheets are laminated on the uppermost surface and the lowermost surface thereof, respectively, to form a laminate having an overall thickness of about 3.5 to 3.6 mm. Was prepared. The laminate was cut to a width of 4.82 mm and a length of about 45 mm, and these were cut in a humidified nitrogen / hydrogen mixed atmosphere at 1450 to 180 mm.
It was fired at 0 ° C. for 2 hours to obtain a sintered body having a thickness of about 3 mm, a width of about 4 mm, and a length of about 37 mm. A three-point bending test was performed using this sintered body, and the crystal phases of the mullite layer and the alumina-based sintered body were examined by X-ray diffraction. The results are shown in Tables 3 and 4.
It was shown to.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Table 3]

[0043]

[Table 4]

As is clear from the results of Tables 1 to 4, the strength of Sample No. 1 in which the amount of the sintering aid was more than 20% by weight was low. In samples No. 4 and No. 13 in which the amount of SiO ₂ in the auxiliary was less than 80% by weight of the total amount of the auxiliary, almost all of the mullite layer was decomposed into alumina, and a mullite layer was formed in the strength characteristics. No sample N
As in o.8 and 15, no strength improving effect was observed.

According to the comparison between Samples No. 7 and No. 8 and the comparison between Samples No. 15, 16, and 17, the strength is improved and the thickness of the mullite layer is increased by forming the mullite layer. It can be seen that the strength increases as the strength increases. Thus, with the product of the present invention, an alumina-mullite laminated structure having a strength of 50 kg / mm ² or more could be produced. Moreover, in the mullite layer, the mullite layer could be formed stably without sintering even after sintering.

Example 2 In the same manner as in Example 1, the composition having the composition shown in Table 5 having a thickness of 0.1 mm was used.
5mm alumina green sheet and 0.015mm thickness
A mullite green sheet was produced. Then, a W metallized paste is applied to the surface of one mullite green sheet with a thickness of 15 μm, the mullite green sheet is superimposed on the surface, and alumina green sheets are further laminated on the uppermost surface and the lowermost surface in three layers each. They were laminated to produce a laminate having a total thickness of about 3 mm. 3. the width of the laminate
82 mm, cut into a length of about 45 mm, and calcined in air at 1550-1650 ° C. for 2 hours,
A sintered body having a thickness of about 2.5 mm, a width of about 4 mm, and a length of about 37 mm was obtained. A three-point bending test was performed using this sintered body, and the crystal phases of the mullite layer and the alumina layer adjacent to the mullite layer were examined by X-ray diffraction.

[0047]

[Table 5]

As is apparent from Table 5, even in a structure in which the W metallized layer is sandwiched between the mullite layers by using a sintered body in which the composition of the alumina-based sintered body is within the range of the present invention, the mullite layer has no change at all. It stably existed, and the W metallized layer was also sintered well. On the other hand, in Samples Nos. 40 to 43 in which the amount of SiO ₂ in the alumina-based sintered body was small, the mullite layer was partially changed to alumina, and the mullite was decomposed simultaneously with the precipitation of giant acicular alumina particles. The resulting liquid phase was absorbed by the alumina sintered body and became porous.

From these results, it was found that the alumina-mullite laminated structure of the present invention can be used as a multilayer circuit board or an ozonizer having a W metallized layer as a wiring layer or an electrode layer.

[0050]

As described in detail above, the alumina of the present invention
According to the mullite laminated structure, by specifying the composition of the sintering aid component of alumina, mullite can be stably present as a laminated structure of alumina and mullite. This makes it possible to improve the mechanical strength of the laminated structure, to improve the signal propagation delay as a multilayer circuit board, and to form an oxidation protective layer on the electrode layer of the ozonizer.

[Brief description of the drawings]

FIG. 1 is a diagram showing one basic structural example of an alumina-mullite laminated structure of the present invention.

FIG. 2 is a diagram showing another basic structure example of the alumina-mullite laminated structure of the present invention.

FIG. 3 is a schematic view when the laminated structure of the present invention is used for a multilayer wiring board, particularly a package for housing a semiconductor element.

4A and 4B show a case where the laminated structure of the present invention is used for an ozonizer, wherein FIG. 4A is a plan view, and FIG. 4B is XX of FIG.
It is sectional drawing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2, 8, 10 Mullite layer 3 Insulating substrate 4 Semiconductor element 5 Depression 6 Wiring layer 7 Connection pin 9 Alumina layer 11 Substrate 12 Induction electrode layer 13 Dielectric layer 14 Discharge electrode layer 15 Protection layer

Claims (2)

(57) [Claims] An alumina obtained by laminating an alumina sintered body containing 0.1 to 20% by weight of a sintering aid and a mullite layer containing no or no more than 10% by weight of a sintering aid. -A mullite laminated structure, wherein the sintering aid in the alumina-based sintered body and the mullite layer is 8 to the total amount of the aid;
0 to 100 wt% of SiO _2, alumina, characterized in that it consists of the 1A, 2A, 3A, and at least one metal oxide of 4A and Group 8 elements of the periodic table of 0-20 wt% A mullite laminate. 2. A sintering aid containing 0.1% of alumina as a main component.
An alumina-mullite laminated structure obtained by laminating an alumina-formed body to which -20% by weight is added and a mullite-forming composition to which no sintering aid is added or to which 10% by weight or less is added, and then firing the laminate. Wherein the sintering aid for the alumina molding and the mullite molding composition is 80 to 100% by weight of SiO 2 based on the total amount of the aid.
₂ and 0 to 20% by weight of the periodic table 1A, 2A, 3A,
A method for producing an alumina-mullite laminated structure, comprising a metal oxide of at least one of Group 4A and Group 8 elements.