JP2500691B2 - Low temperature sinterable low dielectric constant inorganic composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a low temperature sinterable low dielectric constant inorganic composition, and more specifically, it is mainly used for a multilayer ceramic wiring board for mounting an ultra-high speed VLSI device. The present invention relates to an inorganic composition having a low dielectric constant, which can be sintered at a low temperature of ℃ or less.

[Prior Art] Conventionally, semiconductor elements such as ICs and LSIs have been mounted on a printed circuit board such as glass epoxy or an alumina ceramic substrate. However, as semiconductor elements become highly integrated, miniaturized, and speeded up, they are mounted. The demand for high-density fine wiring, high-speed transmission, high frequency, and high heat dissipation has also increased for substrates. The conventional printed circuit board has through-hole plating,
There are problems such as workability, multi-layer adhesion, thermal deformation at high temperature,
There is a limit to high density. Therefore, it has not yet been put to practical use as a high-density mounting board, and a ceramic board has more potential.

However, since the alumina substrate also has to be sintered at a high temperature of 1500 ° C. or higher, the wiring conductor material to be co-fired is limited to refractory metals such as W and Mo having relatively high resistance. Therefore, if the transmission loss of the pulse signal is taken into consideration, there is a limit to the miniaturization of the wiring pattern.

Therefore, a low temperature sinterable multilayer ceramic substrate was developed. As the insulating material, there are a composite material system of alumina and glass, a crystallized glass system, etc., but since both are sintered at 1000 ° C. or lower, Au having a low specific resistance as a wiring conductor material,
A low melting point metal such as Ag-Pd or Cu can be used. Also, since the green sheet multi-layering method can be used,
Very advantageous for high-density fine wiring.

[Problems to be Solved by the Invention] On the other hand, for high-speed transmission, since the propagation delay time of a pulse signal is proportional to the square root of the dielectric constant of the substrate material, it is essential to reduce the dielectric constant of the substrate material. . However, not only alumina substrates (dielectric constant = about 10), but recently developed low-temperature sinterable ceramic substrates are also lower than alumina, but they have not been sufficiently low-dielectric constant and are not suitable for high speed. Still needs improvement.

For example, Japanese Patent Publication No. 61-210195 and 61-218407.
In the low temperature sinterable low dielectric constant inorganic composition shown in Japanese Patent Publication,
Cordierite, which has a low dielectric constant as a ceramic material,
Despite the use of quartz glass and quartz (α-quartz), the low permittivity is insufficient because the permittivity of glass is high.

The object of the present invention is to solve such conventional problems,
An object of the present invention is to provide an inorganic composition for an insulating layer of a high-density mounted multilayer ceramic substrate, which has a sufficiently low dielectric constant and can be fired at a low temperature of 1000 ° C or lower.

[Means for Solving the Problems] The present invention is a three-component inorganic composition consisting of a cordierite ceramic material, quartz glass, and borosilicate glass, and the borosilicate glass is expressed in terms of oxide. When followed, the main component is silicon oxide: 75-85% by weight,
Boron oxide: 15 to 20% by weight, aluminum oxide: 0.1 to 5
%, Group I element oxide: 0.1 to 5% by weight, Group II element oxide: 0.1 to 1% by weight, titanium oxide: 0 to 0.05% by weight, so that the total amount becomes 100% by weight. It is composed and when displayed as cordierite: X, quartz glass: Y, borosilicate glass: Z (weight% ratio) (X + Y +
Z = 100), the following composition points in this three-component composition diagram: (X = 0, Y = 0, Z = 100) (X = 45, Y = 0, Z = 55) (X = 0, Y = 45, Z = 55), and a low-temperature sinterable low-dielectric-constant inorganic composition characterized by being in a composition range surrounded by these three points on a line connecting the points.

The low temperature sinterable low dielectric constant inorganic composition of the present invention can be produced, for example, by the following materials and methods. That is, in the preparation of borosilicate glass, the raw materials of the respective components were weighed so as to obtain the target composition to prepare a batch, and this batch was heated at a high temperature of 1400 ° C. or higher for 2 to 4 hours to be melted and vitrified. Let The molten glass is cooled with water or poured on a thick iron plate to form flakes, and the obtained glass pieces are finely pulverized with an alumina ball mill or the like to obtain glass powder having an average particle diameter of 0.5 to 3 μm. On the other hand, cordierite and quartz glass are also pulverized into fine powder having an average particle size of 0.5 to 5 μm.

To the glass powder obtained by the above method, the cordierite or quartz glass powder is blended so as to have a target composition,
The mixture is mixed for 1 to 3 hours with a ball mill or the like to obtain a homogeneous mixed powder of borosilicate glass powder, cordierite and quartz glass powder, that is, the low temperature sinterable low dielectric constant inorganic composition of the present invention. Although the borosilicate glass powder used at this time is expressed as an oxide for clarity, it may be a system of minerals, oxides, carbonates, hydroxides or the like and may be used by a usual method.

Further, the powdery inorganic composition of the present invention obtained as described above is molded by, for example, a green sheet laminating method. That is, the vehicle is added to the powder and mixed, sufficiently kneaded using a high speed mixer or a ball mill, and uniformly dispersed to prepare a slurry, which is a green sheet having a film thickness suitable for forming an insulating layer by a slip casting method. And It should be noted that the organic vehicle such as the binder or the solvent may be a commonly used one, and the components are not limited in any way.

Next, after forming through holes for connecting the upper and lower conductors in the sheet, conductor printing is performed so as to fill the through holes with the conductor paste, and these are laminated and thermocompression bonded to have a desired multilayer structure. After removing the organic vehicle added at the time of molding, baking is performed to obtain a multilayer ceramic wiring board.

Next, each range is claimed for the composition of the borosilicate glass powder, cordierite and quartz glass powder of the low temperature sinterable low dielectric constant inorganic composition of the present invention, and the composition of the borosilicate glass powder. The reason for the limitation as described in will be described.

FIG. 1 shows a three-component composition diagram showing the component composition range of the low temperature sinterable low dielectric constant inorganic composition according to the present invention. In the figure,
(A), (b) and (c) represent each composition point, and the composition range included in the present invention is the range shown by the diagonal lines in the figure and its boundary.

In the three-component composition diagram showing the component composition range, in a region where Z (borosilicate glass weight ratio) is less than 55 and is not included in the range of the present invention, low temperature sintering at 1000 ° C. or less is difficult and dense. Since a different layer cannot be obtained, water absorption occurs and reliability decreases.

Next, the composition of the borosilicate glass powder which is one of the main components of the low temperature sinterable low dielectric constant inorganic composition according to the present invention will be described. Silicon oxide and boron oxide are both glass network formers. is there. Silicon oxide
If it exceeds 85% by weight, vitrification is difficult, and even if it is melted, the softening point of the glass is high, making it difficult to fire at low temperature. On the other hand, if it is less than 75% by weight, the softening point of the glass becomes too low, or crystallization occurs with the increase of other components, and there is a problem such as cristobalite which adversely affects the thermal expansion coefficient which is one of the important mounting board characteristics. It is likely to be deposited, or the dielectric constant, which is the most important characteristic, is increased. On the other hand, in the case of boron oxide, when it exceeds 20% by weight, the softening point of the glass is rapidly lowered, and deformation or warpage during heat treatment is likely to occur. On the other hand, if the amount is less than 15% by weight, it is necessary to lower the softening point due to the large amount of silicon oxide, but there is no effect, and the effect of suppressing crystallization of silicon oxide becomes insufficient. The other ingredients are
In order to control the solubility or stability of the glass, both are added in small amounts, but if the amount is too large, the dielectric constant and the thermal expansion coefficient will increase. Therefore, the ratio of silicon oxide to boron oxide in the borosilicate glass powder has the most important meaning in the present invention.

[Examples] Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. All percentages in the examples and comparative examples are based on weight unless otherwise specified.

Examples 1 to 26, Comparative Examples 1 to 4 Glass powders having the compositions shown in Table 1 were produced and wet-ground for 48 hours using alcohol as a dispersion medium. After sieving this, the alcohol was filtered and dried to obtain a glass powder having an average particle size of 1.9 μm and a BET specific surface area of 12 m ² / g.

Next, these glass powders and an average particle size of 2.6 μm, B
ET specific surface area were compounded in the proportions shown 5 m ² / g cordierite powder and the average particle size of 3.7 .mu.m, BET specific surface area of 6 m ² / g of silica glass powder in Table 2, respectively. As for the blending, a predetermined amount of each powder was weighed and mixed with alcohol as a dispersion medium in a ball mill for 3 hours, and then the alcohol was filtered and dried to obtain a homogeneous mixed powder.

Evaluation of the obtained inorganic composition was carried out by using a sample obtained by cutting a green laminate, which was prepared by a green sheet laminating method, and which was not printed, and which was fired after removing the organic vehicle in an electric furnace. Samples in the composition range of the present invention are 800 to 100 in air.
It was baked at a temperature of 0 ° C. for 2 hours. As an evaluation, the sintering temperature (defined as the temperature at which water absorption does not occur, that is, the temperature at which open voids disappear), the dielectric constant, the insulation resistance, and the thermal expansion coefficient were measured for each sample. The water absorption was checked by placing the sample in water and boiling it, and then measuring the difference between the weight of the sample and the dry weight. The dielectric constant was measured at 1 MHz. The electrodes were baked at 600 ° C. after applying the conductive silver paste on the upper and lower surfaces of the sample. The insulation resistance was measured at an applied voltage of 100V. The coefficient of thermal expansion was calculated from the elongation of the sample from room temperature to 250 ° C.

Table 2 shows the relationship between the mixing ratio of cordierite, quartz glass and borosilicate glass of the inorganic composition thus obtained, and the sintering temperature, dielectric constant, insulation resistance and thermal expansion coefficient.

As is clear from Table 2, in the three-component inorganic composition comprising cordierite, quartz glass and borosilicate glass, those within the component composition range of the present invention (Examples to 26) are sintered bodies. The temperature at which the water absorption does not occur and the structure becomes dense, that is, the sintering temperature is 1000 ° C or less, and the dielectric constant is 4.
It is sufficiently low at 04 to 4.83, insulation resistance is as high as 10 ¹³ Ω · cm or more, and insulation is maintained. Furthermore, since the coefficient of thermal expansion is as low as 13.7 to 45.2 × 10 ^-7 / ° C, it is clear that the precipitation of high thermal expansion crystalline cristobalite due to the crystallization of glass does not occur.

On the other hand, those outside the component composition range of the present invention (Comparative Examples 1 to 1
In 4), the sintering temperature is high, and when firing below 1000 ° C, the dielectric constant is apparently low due to the residual open voids, but the insulation resistance is low.
There is a problem in terms of reliability.

Examples 27 to 52, Comparative Examples 5 to 8 Glasses having the compositions shown in Table 3 were prepared to have an average particle size of 2.0 μm and a BET specific surface area of 11 m ² / g.

Samples were prepared and evaluated in the same manner as in Examples 1 to 26 by using these glass powders, cordierite and quartz glass powders at the compounding ratios shown in Table 4. Table 4 shows the results.

As is clear from Table 4, in the three-component inorganic composition consisting of cordierite, quartz glass and borosilicate glass, those within the component composition range of the present invention (Examples 27 to 52) were sintered. The temperature at which the body does not absorb water and becomes a dense structure, that is, the sintering temperature is 1000 ° C or less, the dielectric constant is also
3.98-4.80, which is sufficiently low, and the insulation resistance is 10 ¹³ Ω ・ cm.
Higher than the above, the insulating property is maintained. Furthermore, since the coefficient of thermal expansion is as low as 12.4 to 43.9 × 10 ^-7 / ° C, it can be seen that precipitation of highly thermally expansive crystalline cristobalite due to crystallization of glass has not occurred.

On the other hand, those having a component composition outside the range of the present invention (Comparative Examples 5
In 8), the sintering temperature is high, and when firing below 1000 ° C., the dielectric constant is apparently low due to the residual open voids, but the insulation resistance is low and there is a problem in reliability.

The composition points of the component mixture ratios used in the examples and comparative examples are shown in FIG. The numbers 1, 2, ..., 30 in the figure correspond to the compounding ratio numbers in Tables 2 and 4, respectively.

[Effects of the Invention] As described above, the low-temperature sinterable low-dielectric-constant inorganic composition of the present invention maintains the reliability of low-temperature sinterability, insulating properties, water resistance, etc., while maintaining the reliability of conventional alumina and glass. It has a lower dielectric constant than ceramics and crystallized glass. Therefore, it becomes possible to provide a multilayer ceramic wiring board for mounting an ultra-high-speed VLSI element, which can greatly contribute to an increase in mounting density and an improvement in high-speed transmission.

[Brief description of drawings]

FIG. 1 is a composition diagram showing a three-component system composition range of the present invention, and FIG.
The figure is a diagram showing the relationship between the composition range of the three-component system of the present invention and the composition points shown in Examples and Comparative Examples.

Claims (1)

(57) [Claims] 1. A three-component inorganic composition comprising a cordierite ceramic material, quartz glass, and borosilicate glass, wherein the borosilicate glass has a major component that is oxidized according to the oxide conversion notation. Silicon: 75-85% by weight,
Boron oxide: 15 to 20% by weight, aluminum oxide: 0.1 to 5
%, Group I element oxide: 0.1 to 5% by weight, Group II element oxide: 0.1 to 1% by weight, titanium oxide: 0 to 0.05% by weight, so that the total amount becomes 100% by weight. It is composed and when displayed as cordierite: X, quartz glass: Y, borosilicate glass: Z (weight% ratio) (X + Y +
Z = 100), the following composition points in this three-component composition diagram: (X = 0, Y = 0, Z = 100) (X = 45, Y = 0, Z = 55) (X = 0, Y = 45, Z = 55), and a low-temperature sinterable low-dielectric-constant inorganic composition characterized by being in a composition range surrounded by these three points on a line connecting the points.