JPH0616470A - Ceramic substrate and its production - Google Patents

Abstract

PURPOSE:To improve deflective strength, moisture resistance and water resistance by mixing glass powder consisting of MgO, Al2O3, SiO2 B2O3 and alkaline metal oxide with Al2O3 crystal grains and calcining the mixture in a specific temp. range. CONSTITUTION:The glass powder. consisting of 10 to 30wt.% MgO, (hereafter %), 5 to 20% Al2O3, 40 to 55% SiO2, 10 to 20% B2O3 and 0 to 5% R2O (R is an alkaline metal) and having 0.1 to 10mum average grain diameters and the crystal grains consisting of the Al2O3 and having 0.1 to 10mum average grain sizes are mixed at ratios of 60 to 80% of the glass-component and 20 to 40% of the crystal-component. Respectively proper ratios of an org. binder, plasticizer and solvent are added to this mixture and the mixture is kneaded to prepare a slurry. This slurry is molded to a sheet of a prescribed thickness by a doctor blade method, etc., and the molding is calcined at 800 to 1000 deg.C after drying by heating, by which the ceramic substrate contg. the MgO-Al2O3-SiO2-B2O3-R2O glass and the 2MgO.2Al2O3.5SiO2 crystal and having a small specific dielectric constant and the excellent deflective strength, moisture resistance and water resistance is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic substrate and a method for manufacturing the same, and more particularly to a ceramic substrate often used as a multilayer wiring board for mounting electronic parts and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, ceramics have been increasingly used as a substrate material in multilayer wiring boards on which highly integrated LSIs and various electronic components are mounted, because of the demands for downsizing and reliability. Since alumina has advantages such as high strength, it occupies a large proportion in the ceramics for the substrate material. On the other hand, however, alumina has a large relative permittivity, which causes a delay in transmission signals, and has a coefficient of thermal expansion much larger than that of silicon, so that reliability cannot be ensured when components are mounted. have. Further, since alumina has a high firing temperature of about 1500 ° C. or higher, it is necessary to use W or Mo having a high melting point and a large electric resistivity for the wiring in the inner layer, and there is a problem that the electric resistance increases when the wiring is miniaturized. I also have.

In order to solve such a problem, therefore, the relative dielectric constant is made small, the coefficient of thermal expansion is made close to that of silicon, and a metal material having a low melting point such as Cu, Ag or Ag-Pd is used as the inner layer conductor. Research and development of low-temperature fired ceramics substrates that can be fired as is are underway.

Generally, a low temperature fired ceramics substrate is manufactured by mixing a glass material and a crystal material called an aggregate and firing the mixture. However, the number of combinations of glass materials and crystal materials is extremely large, and the combination of both causes a synergistic effect during firing, resulting in the characteristics of the obtained ceramic substrate (dielectric constant, thermal expansion coefficient, firing temperature,
The bending strength, etc.) changes. Therefore, it has been difficult to find the best combination and to manufacture a ceramic substrate having a stable composition and structure so that constant characteristics are always exhibited.

Against this background, the strength is improved without impairing the characteristics that the relative permittivity is low and the coefficient of thermal expansion is close to that of silicon, the speed of signal transmission is increased, and the size of mounted elements is increased. as a low-temperature fired ceramic substrate can correspond, cordierite, as shown in _{JP-a-2-225338 (2MgO · 2Al 2 O 3} · 5SiO
₂ ) Crystallized glass has come to the fore.

[0006]

However, the above-mentioned Japanese Unexamined Patent Application Publication No.
The cordierite-based crystallized glass used in JP-A-225338 has a problem that it is difficult to densify the substrate because it has a high softening temperature and a high viscosity at a high temperature.

From this point of view, it is fired so that the cordierite-based crystallized glass is deposited at a temperature of 950 ° C. or lower necessary for forming an inner layer of Ag and a temperature of 1000 ° C. or lower necessary for forming an inner layer of Cu or the like. In the case of carrying out the above, the obtained ceramic substrate has a porosity that is not sufficiently reduced, a bending strength and a moisture resistance are not sufficient, and oxidation and migration of the inner layer conductor are likely to occur and reliability is poor. There was a problem of becoming.

The present invention has been made in view of the above-mentioned problems, and it is sufficiently densified even by firing at 1000 ° C. or lower, further 950 ° C. or lower, and has a small relative dielectric constant, bending strength, moisture resistance and water resistance. It is an object of the present invention to provide a ceramic substrate excellent in the above and a manufacturing method thereof.

[0009]

In order to achieve the above object, the ceramic substrate according to the present invention is a ceramic substrate composed of glass and crystals, wherein the glass is MgO.
-Al consists _{2 O 3 -SiO 2 -B 2 O} 3 -R 2 O -based glass (R is an alkali metal), the crystal 2M
It is characterized by containing gO.2Al ₂ O ₃ .5SiO ₂ crystals (cordierite).

A method of manufacturing a ceramic substrate according to the present invention is the above-mentioned method of manufacturing a ceramic substrate, wherein M
gO, Al ₂ O ₃ , SiO ₂ , B ₂ O ₃ and R ₂ O (R
Is an alkali metal), and a glass powder consisting of Al ₂
It is characterized in that O ₃ crystal grains are mixed and fired in a temperature range of 800 ° C. or higher and lower than 1000 ° C.

[0011]

In the ceramic substrate composed of glass and crystals having the above structure, the glass is MgO--Al ₂
It is composed of O ₃ —SiO ₂ —B ₂ O ₃ —R ₂ O type glass (R is an alkali metal), the crystal contains cordierite, the softening temperature of the glass is 720 ° C. or less, and the pores are The ceramic substrate has a reduced coefficient and becomes dense, has a thermal expansion coefficient close to that of a silicon substrate, has a small relative dielectric constant, and is excellent in folding strength, moisture resistance, water resistance, and the like. In addition, since the ceramic substrate has a low softening point, it is 800 ° C or higher.
A ceramic substrate having the above characteristics can be obtained by firing at 000 ° C. or lower, and a ceramic substrate can be formed using Ag, Cu, or the like for circuit wiring.

According to the above-mentioned method for manufacturing a ceramic substrate, a glass powder made of MgO, Al ₂ O ₃ , SiO ₂ , B ₂ O ₃ and R ₂ O (R represents an alkali metal) and Al ₂ O. Mixing ₃ crystal grains, 800 ℃ or more 10
Since firing is performed in a temperature range of less than 00 ° C., cordierite is precipitated in the ceramic substrate, the porosity of the glass ceramic is reduced and the glass ceramic is densified, and the ceramic substrate having various excellent characteristics described above is manufactured.

Regarding the composition of the glass powder in the production of the ceramic substrate, MgO is 30 wt.
%, The softening temperature becomes high, the densification becomes insufficient, the relative dielectric constant becomes large, and the MgO content is 10 wt.
If it is less than%, cordierite does not precipitate and the coefficient of thermal expansion increases. When Al ₂ O ₃ exceeds 20 wt%, the softening temperature becomes high, and at a firing temperature of 1000 ° C. or less, the densification becomes insufficient and the bending strength becomes small, and Al ₂ O ₃ is 5 w.
If it is less than t%, cordierite does not precipitate and the coefficient of thermal expansion increases. SiO ₂ is high and the softening temperature exceeds 55 wt%, the bending strength is reduced becomes insufficient densification at the firing temperature of 1000 ° C. or less and SiO ₂ is 40w
If it is less than t%, the relative dielectric constant and the thermal expansion coefficient increase. B ₂ O
_{When 3} exceeds 20 wt%, the water resistance of the glass decreases, and the composition becomes non-uniform due to phase separation in the glass manufacturing process. When B ₂ O ₃ is less than 10 wt%, the softening strength increases, and 1000 If the firing temperature is below ℃, the densification will be insufficient and the bending strength will be reduced. The alkali metal is MgO,
It interacts with Al ₂ O ₃ , SiO ₂ and B ₂ O _3, and especially the synergistic effect with B ₂ O ₃ lowers the softening temperature.
If it exceeds 5 wt%, the water resistance deteriorates.

Therefore, the composition of the glass powder material is as follows:
10 to 30 wt% MgO, 5 to 20 wt% Al ₂ O ₃
%, SiO ₂ is 40 to 55 wt%, B ₂ O ₃ is 10 to 2
The range of 0 wt% and 0 to 5 wt% of alkali metal is preferable, and further, 10 to 20 wt% of MgO, 10 to 20 wt% of Al ₂ O ₃ , 40 to 55 wt% of SiO ₂ , and B ₂
O ₃ is 10 to 20 wt% and alkali metal is 1 to 5 wt%.
Is more preferable.

In the method of manufacturing a ceramic substrate, Al ₂ O ₃ is selected as the crystal of the aggregate.
Cordierite is deposited by the interaction between glass and aggregate, and good characteristics as a ceramic substrate (dielectric constant of 7.0 or less, thermal expansion coefficient of about 5.0 to 6.0, firing temperature of Less than 1000 ℃, bending strength is 20kgf / mm
² or more).

Regarding the mixing ratio of glass and crystals in the raw material, the bending strength of the obtained ceramic substrate is 20 kg.
60-80 wt% of glass to achieve f / mm ² or more
%, And crystals are preferably mixed in the range of 40 to 20 wt%.

Here, the water resistance means a property that the glass does not dissolve in water, and the moisture resistance means that the liquid permeated into the porous portion of the glass affects the inner layer conductor (oxidation or migration). Refers to the property of not giving.

[0018]

EXAMPLES Examples and comparative examples of the ceramic substrate and the manufacturing method thereof according to the present invention will be described below. MgO, A
1 ₂ O ₃ , SiO ₂ , B ₂ O ₃ and R ₂ O (R represents an alkali metal), and the average particle size is 0.1 to 10
A glass powder of μm and crystal grains of Al ₂ O _{3 having} an average particle diameter of 0.1 to 10 μm were mixed in the ratio shown in Table 1.

Next, an appropriate amount of an organic binder, a plasticizer and a solvent are added to this mixture, and the mixture is kneaded to about 10,000 cps.
It was a slurry.

Next, using the slurry, a 0.2 mm thick sheet was formed by a doctor blade method and dried at 80 ° C. for about 10 minutes. Then, this sheet is 10 ℃ / m
The temperature is raised at a rate of in and baked at about 900 ° C. for 30 minutes,
The manufacture of the sintered body of the ceramic substrate was completed.

Next, it is confirmed that cordierite crystals are deposited on the ceramic substrate manufactured by the above method.
Confirmed by line diffraction. Further, the porosity of the ceramic substrate, the relative dielectric constant at a frequency of 1 MHz, the coefficient of thermal expansion, the value of bending strength and the water resistance were measured. The porosity was measured by the Archimedes method, and the relative dielectric constant was measured by an impedance analyzer. The thermal expansion coefficient was measured as an average value from room temperature to 350 ° C. by a contact type linear expansion meter. The bending strength was measured by a three-point bending test, and the water resistance was evaluated by reducing the weight of the test piece held in boiling water for a certain period. The moisture resistance was evaluated by bringing water or steam into contact with one surface of the thin plate sample and increasing the humidity on the opposite side.

[0022]

[1 in Table 1]

[0023]

[2 in Table 1]

As is clear from Table 1, Examples 1-2
In No. 4, even if the firing temperature is 1000 ° C. or less, it can be sufficiently densified, the relative dielectric constant is small, and the bending strength,
It can be seen that it is possible to manufacture a ceramic substrate having excellent moisture resistance and water resistance.

In the temperature range in which the inner layer conductor is not melted, the higher the firing temperature of the ceramic substrate, the more dense and crystallized it is, so that a large bending strength and a small coefficient of thermal expansion can be obtained.

FIG. 1 shows the sample obtained in Example 6 as X.
It is data of X-ray diffraction intensity when line-diffracted. From FIG. 1, it was confirmed that cordierite was precipitated.
Furthermore, observation with a TEM (transmission electron microscope) revealed that cordierite was precipitated from the surface of alumina.

Comparative Example 1 is a comparative example prepared on the basis of the contents disclosed in Japanese Patent Laid-Open No. 2-225338, and is Ag.
900, which is the temperature range required for the inner layer of Cu, Cu, etc.
It can be seen that the firing strength is low because the porosity does not become sufficiently small and densification does not occur when firing at a temperature of not higher than 0 ° C. In Comparative Example 2, since the amount of MgO in the glass material is small, cordierite does not precipitate, the porosity is large, the bending strength is small, and the moisture resistance is also poor. In addition, Comparative Example 3
Then, since the glass material has a small amount of Al ₂ O ₃ , cordierite does not precipitate, the porosity is large, the bending strength is small, and the moisture resistance is poor. In Comparative Example 4, since the mixing ratio of the aggregate to the glass is small, the bending strength is small. In Comparative Example 5, since the glass material contained a large amount of K ₂ O, the substrate was deformed and the water resistance was poor. In Comparative Example 6, since the amount of B ₂ O _{3 in} the glass material is small, the porosity is large, the bending strength is small, and the moisture resistance is poor. In Comparative Example 7, since the glass material contained a large amount of B ₂ O ₃ , the substrate was deformed and the water resistance was poor. Comparative Example 8 is
It can be seen that since the mixing ratio of the aggregate to the glass is large, the porosity is large, the bending strength is small, and the moisture resistance is also poor.

[0028]

In the ceramic substrate made of glass and crystal according to the present invention as described in detail above, according to the present invention, the glass is _{MgO-Al 2 O 3 -SiO 2} -B 2 O 3 -R 2
It is made of O-based glass (R is an alkali metal), the crystal contains cordierite, the softening temperature of the glass becomes 720 ° C. or less, the porosity decreases and the density increases, and the coefficient of thermal expansion increases. Is close to a silicon substrate, has a small relative dielectric constant, and has excellent bending strength, moisture resistance, water resistance, and the like. Further, since the ceramic substrate has a low softening point, it is possible to manufacture the ceramic substrate having the above characteristics even by firing at 800 ° C. or higher and 1000 ° C. or lower, and Ag, Cu or the like having a low melting point and a low electric resistance is used for the circuit wiring. It is possible to manufacture a ceramic substrate having the same.

According to the method for producing a ceramic substrate according to the present invention, MgO, Al ₂ O ₃ , SiO ₂ , B ₂
Glass powder consisting of O ₃ and R ₂ O (R represents an alkali metal) and Al ₂ O ₃ crystal grains are mixed, and the temperature is 800 ° C.
By firing in the temperature range above 1000 ° C.,
Depositing cordierite in the ceramic substrate,
It reduces the porosity of glass ceramics to make it denser,
The coefficient of thermal expansion is close to that of a silicon substrate and the relative permittivity is small,
It is possible to manufacture a ceramic substrate having excellent bending strength, moisture resistance, water resistance and the like.

[Brief description of drawings]

FIG. 1 is X-ray diffraction intensity data when the sample obtained in Example 6 was subjected to X-ray diffraction.

Claims (2)

[Claims] 1. In a ceramic substrate composed of glass and crystals, the glass is MgO—Al ₂ O ₃ —SiO.
_{It is made of 2-} B ₂ O ₃ -R ₂ O type glass (R represents an alkali metal), and the crystal is 2MgO · 2Al ₂ O ₃ · 5.
A ceramic substrate containing SiO ₂ crystals. 2. MgO, Al ₂ O ₃ , SiO ₂ , B ₂ O
_{3. A} glass powder composed of ₃ and R ₂ O (R represents an alkali metal) and Al ₂ O ₃ crystal grains are mixed and fired in a temperature range of 800 ° C. or higher and lower than 1000 ° C. 3. A method for manufacturing the ceramic substrate described above.