JPS6212659A - Magnesia base ceramic sintered body for electric insulation material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnesia (MgO) ceramic sintered body as an insulating base material, and more specifically, to a magnesia (MgO) ceramic sintered body having high thermal conductivity and strength, as well as excellent hydration resistance. Mg for electrically insulating base material with
The present invention relates to an O sintered body and a method for manufacturing the same.

[Prior art] 1rIノ+-4N7.1-)shayl-v*4-1YI'
n-4G[-Jdi口'1''rhQI1.%, most of the insulating materials are Al2O3 substrates.

On the other hand, MgO base material has excellent electrical insulation properties at high temperatures, and has better high frequency properties and thermal conductivity than Al2O3 base material, so it is expected to be used as this type of integrated circuit board material. As a result, it has not been possible to obtain a material that has high water compatibility and sufficient strength, so the actual situation is that the above characteristics cannot be fully utilized and it has not been put into practical use.

For example, in the past as part of the development of MgO substrates, 2) Ig
Although several attempts and proposals have been made to impart water resistance by forming a coating layer of O.SiO2 phase, sufficient results have not been achieved.

Although it is not clear why the results of such past attempts did not result in satisfactory physical properties, it is believed that the differences in the composition, fine texture, and structure of the sintered body, as well as the differences in the manufacturing methods that lead to these differences, are the main reasons. This is probably due to this.

For example, one of the major reasons for this is that most of the conventional proposals of this kind have been made using pre-formed sheets (2M water-resistant sheets made by treating the board), as disclosed in Japanese Patent Application Laid-Open No. 58-217480.
It is also considered that the purpose was to form the g0·S io2 phase.

In other words, products made using such methods may not have sufficient water resistance, or may not have sufficient thermal conductivity.
In particular, it has not been possible to obtain a highly functional substrate that combines the various properties that make it U7 functional, such as not being fully satisfactory in terms of strength.Furthermore, as another method, JP-A No. 58-181764 has a detailed method. Although it has been proposed to mix a magnesium compound and a liquid silicon compound such as a sodium silicate solution to obtain a sintered body, it has not yet been possible to obtain a sintered body that has sufficient hydration resistance and strength.

The reason for this is not clear, but since the sintered body targeted by the patent is translucent, it may be related to the fact that the amount of liquid silicon compound must be kept to a small amount. I don't know, but before molding the mixture, it is 750~
It is conceivable that preliminary heat treatment at 1100° C. must be performed.

[Problems to be Solved by the Invention] On the other hand, the present inventors have proposed that even under such actual circumstances, the future development of IC'p & boards, for example, hybrid 1-I.
Based on the viewpoint that the characteristics of the MgO base material would be extremely effective in the development of C and laminated packages, various researches revealed that the drawbacks such as water compatibility mentioned above, which had been a major obstacle to practical application, were found. Although we have succeeded in developing sintered bodies that provide MgO substrates with improved properties, the present invention has succeeded in further improving them in terms of strength.

[Means for Solving the Problem] That is, the present invention provides a method in which the size of most of the gO crystal particles is 51L or less when viewed microscopically, and most of the 5iOz is 2M or less.
g0L1SiO2, Al2O3 is mostly MgO・
It becomes Al2O3 and mainly from the structure between the grains of MgO.
Therefore, the dielectric loss (tan δ) at 100KHz is 5X104 or less at room temperature, and the electrical insulation resistance is 10 at 300℃.
The object of the present invention is to provide a magnesia-based ceramic sintered body for electrically insulating substrates, which is characterized by having a resistance of 10 ΩlIC11 or more, as well as excellent strength and hydration resistance.

. As described above, the present invention has extremely excellent properties as an MgO sintered body for insulating substrates.
The structure of the sintered body that makes it possible to function is composed of fine MgO crystal (periclase crystal) particles and a phase mainly composed of 2MgOs SiO2 (forftyrite) (hereinafter referred to as 2Mg0LIS).
It is thought that this is essentially caused by the presence of the iO2 phase) and the MgO.Al2O:1 phase.

The ideal structure from the viewpoint of high strength and hydration resistance for the sintered body of the present invention is that all Mg
2Mg0・S i0 between O crystal grains and around each individual
It is considered that the two phases are present as small as possible, that is, as extremely thin layers, and the MgO/SiO2 phase is evenly present in 1 g of yO paste and 1 of particles 1111.
As long as these crystal phases are obtained by at least partially covering or intervening on the individual surfaces of the MgO crystal grains located inside or between the grains, and having the desired properties, it is not necessarily the case. It is not necessary to be perfect, but rather if you take into account some properties such as thermal conductivity,
On the other hand, the presence of the Mg0/Si(h phase may be small; the point is that the 2Mg0/SiO2 or MgO/Al703 phase does not sinter as a cross-sectional structure even if it is at least locally between the MgO particles, rather than around the entire circumference. It is sufficient if the particles are evenly distributed in the overall tissue. In this specification, the term "even" refers to such a structure.

Here, the sintered body of the present invention will be further explained in more detail with reference to microphotographs.

In Figure 1, 1 is MgO particle, 2 and 3 are 2Mg0
φSiO2 phase and MgO.Al2O3.

In this way, the MgO particles l are closely spaced 2
It can be seen that it is strongly sintered through the NgO.SiO2 phase 2 and the MgO.A I203 phase 3, and most of them have a grain size of 5W or more.

Incidentally, the sintered body may contain particles with a particle size of about 5 to 10μ, but the amount thereof is at most 20% or more, and is usually about 10% or more. .

Here, the 2NgO/SiO7 phase 2 covers the MgO particles (that is, exists at the grain boundaries) and the multiple MgO
Some exist across the gO particles. The thickness of this 2Mg0.SI02 phase is generally 0.5μ or less, for example, about 0.1 to 0.5μ.

In addition, in the present invention, such 2Mg0.SiO2
It is desirable that the phase is present in a volume ratio of about 3% or more, preferably about 5 to 8%.

Note that this 2MgOs SiO2 phase is produced by the reaction between MgO fine powder and the Si02 component of the organic silicate, as shown in the preferred production method described below.
Originally, it often exists as an integral part on the surface of MgO particles.

In addition, in Fig. 1, the MgO・Al2O3 phase 3 becomes MgO during firing.
It reacts with gO and exists between MgO crystal particles.
It is thought that this acts to suppress the growth of gO crystal grains and contributes to improving the strength of the sintered substrate.

Here, most of this MgO・Al2O3 crystal phase exists as 5JL or less, and preferably 1 to 3JL.
It should be about L.

In addition, in order for the sintered body of the present invention to have the desired properties, it is necessary to densely sinter high-purity MgO, and in terms of composition, the MgO purity of the MgO crystal particles is As an analytical value, it is desirable that the MgO content is 99.5% or more, particularly 99.7% or more, in terms of weight%. In this specification, the purity of these 8g0 particles is 2Mg0・SI0
Refers to the purity of the part excluding the 2 phase and llIgO・A I203 phase.

In addition, as for the composition of the sintered body as a whole, as a chemical analysis value, SiO2 is 0.5 to 5%, and SiO2 is 0.8 to 4% by weight.
%, Al2O:+Ha 0.5-20%, especially 1-1
The content of MgO, SiO2, and Al2O3 is preferably about 0%, respectively, and is 89.5% or more, particularly 98%.
．． It is desirable that it be 7% or more.

This is for the following reasons.

If S + 02; J is too small, the hydration resistance cannot be improved, and if it is too large, other properties necessary for electrically insulating substrates, such as thermal conductivity, will be impaired.
This is because if the amount of 2O3 is too small, the effect of suppressing the grain growth of NgO will be poor and it will not lead to sufficient strength improvement, while if it is too large, the thermal conductivity will be impaired.

A sintered body having such a structure composition is characterized as having the following characteristics as the present invention. Note that the values in parentheses are more desirable ranges.

Bulk density 3.4
5 or more bending strength (at room temperature, kg/mrn')
20 (28) or more thermal conductivity normal temperature
0.08 (0,10) or more (cal/cm* sec・
”0) 300℃ 0.05 (0.0G) or more Dielectric constant (room temperature, IQOKHz) 10 or less Dielectric loss (room temperature, 100KHz) IX 10= ~5
X 10-4′ insulation resistance (300℃; Ωa cm)
Hydration resistance of 10+o or more ■ 0
．． 02% Hydration resistance is 1 in the pressure cutter
Measured as the weight increase rate due to MgO becoming Mg(OH)2 in a method of holding in a 20℃, 2 atm steam atmosphere for 72 hours (the sample size was 50ss.
It is a plate-like body of 50+wm x 1mm thick, but when the thickness is such a thin plate, the size has almost no effect, so it corresponds to the increase rate per unit area.) Furthermore, the reliability as an electrically insulating board As a test method for evaluating this, a test is generally used in which the material is placed in 120°C x 2 atmospheres of water vapor for 500 hours. As a result of testing the sintered body of the present invention using this test method, there was almost no increase in weight.

A manufacturing method for producing such a sintered body of the present invention.

In particular, the preferred method of the present invention for producing the sintered body of the present invention will be explained first.

First, high purity MgO powder is prepared as the MgO component which is the main raw material.

The MgO powder used here needs to have high purity MgO crystal particles in the sintered body, so the chemical analysis value is extremely high purity in mass %, specifically 98%. As mentioned above, it is preferably prepared for a price of 83.5 dollars or less.

In this way, high-purity NgO powder is made of high-purity Mg(OH).
2, for example, by calcining at 800° C. for 2 hours.

In addition, the particle size of the powder used needs to be fine in order to form a sintered body of fine crystal particles, and specifically, the particle size of the powder used is 1.
It is a fine powder having a specific surface area of 0rn'/g or more.

Next, 2) IgO*S I, which essentially provides water resistance
As for the SiO7 component that brings about the 02 phase, the total amount of MgO and AhO= is 99.5% or more as a sintered body.
- In particular, it is desirable to set the temperature to less than 99.7 dollars, and at the same time, it is necessary to form the 2NgO・SI02 phase as a thin layer as possible on the surface of each particle of the 14g0 powder, so the organic silicate solution is It has been found desirable to use

As the organic silicate, silicate alcoholades such as ethyl silicate, methyl silicate, butyl silicate, etc. are suitable, and among them, ethyl silicate is most suitable.

Ah (h is preferably as high as possible in purity like SiO2, and specifically, it is preferable to use Al2O3 of 98 or more.

Further, as an Al2O3 source, it is preferable to use fine powder A I203, specifically the above-mentioned high purity Ab03 powder with an average particle size of 5 microns or less, especially about 1 to 3 microns, which can be fired to become fine Al2O3 powder.

In the present invention, it is also possible to use organic aluminates that can form MgO.Al2O3 by firing.

In the present invention, by mixing the A h 03 fine powder (source) with the above-mentioned desirable SiO2 source, organic silicate, and high-purity fine powder MgO, 2Mg0. It is thought that it will be possible to form a SiO2 layer coat that can generate a SiO7 phase, but when mixing, organic silicates such as ethyl silicate are usually highly hygroscopic in the air, and they themselves hydrate and precipitate SiO2. However, it is difficult to achieve the above-mentioned surface coating in the form of MgO powder, and it is effective to take precautions to prevent ethyl silicate and the like from coming into contact with air.

This can be solved by mixing MgO powder with an Al2OC source in a solvent containing an organic silicate. Suitable organic solvents include alcohols that do not hydrate with MgO; for example, ethanol is sufficient.

It is believed that by thoroughly mixing the MgO powder in a mixed solvent of ethyl silicate and ethanol in this manner, it is possible to form a 5iO2fi coating that provides preferable hydration resistance on the surface of the MgO powder.

Now, regarding the amount of organic silicate added in the present invention, in order to provide seven times better water resistance, which is a more preferred embodiment of the present invention, a certain amount or more of the 2Mg0/S+02 phase is required as described above. This is Koji where the amount of SI02 in the sintered body is more than 0.5z.

In addition, the ratio of organic silicate and organic solvent is in weight%,
Among these contents, the former is 50-10% and the latter is 50-90%.
%.

Incidentally, the sintered body of the present invention has gO・SiO in 2 due to its sintering.
The bonding state of the MgO powder surface, which is thought to result in two phases, is that Mg(OHh and (C
2H5) Si and CzHsOH react to form 0.c2o
5 It is thought that there are.

It is thought that Al2O3 is mixed with MgO and reacts during firing to form llIgO.A I203, which is present between MgO particles.

The sintered body of the present invention can then be obtained by molding the mixture in such a state before firing into a predetermined shape, usually a sheet, by a known method such as a doctor blade method or a pressing method, and firing it. The characteristic feature is the firing temperature.

In other words, according to the method of the present invention, sintering can proceed easily even when the firing temperature is extremely low, and for this purpose, in addition to incorporating AlzO:l, grain growth of MgO crystals is This is because a dense, high-strength sintered body that can withstand low-temperature sintering can be obtained.

Specifically, to obtain a dense MgO sintered body, high-temperature firing at temperatures north of 1600°C is required;
According to the present invention, a temperature of 1500°C or lower, particularly 1450°C or lower is usually sufficient, and in many cases, a sufficiently dense sintered body can be obtained even at about 1400°C.

On the other hand, in order to achieve sufficient sintering, the firing temperature is usually 1300°C or higher, preferably 1350°C or higher.

Furthermore, in the method of the present invention, when forming the mixture into a sheet shape, etc., although the mixture may be dried without any preheating treatment, the mixture is directly formed and immediately heated to a predetermined firing temperature. Can be fired.

As described above, the MgO sintered body obtained by the present invention maintains electrical properties such as sufficient strength and electrical insulation properties necessary for use as an electrically insulating MgO base material, and takes advantage of the material's characteristics of high thermal conductivity. To improve the problem of hydration resistance, which was a major weakness, without requiring special hydration treatment after obtaining the sintered body (of course, additional treatment is acceptable and effective). The invention was a success, and its industrial value is enormous, including making it possible to develop highly functional IC substrates.

The present invention will be further explained by examples.

[Example] By calcining 99.9% high purity Mg(OH)2 at 800°C for 2 hours, M with a specific surface area of 30 to 40 m''/g was produced.
gO powder was obtained.

For 100 g of this MgO powder, A h 03 powder (
Particle size 3 or less, purity 99% or more) 5g, ethylsilicon/r
ktsu JIFF ff # / ++7 C+nI+
nrrs ゛WΔ礒s 仁FPX Adjust the F compound,
Furthermore, 100 cc of a 12% polyvinyl butyral solution was added as a binder and mixed, and this mixture was molded into sheets, one at 1450°C and the other at 1440°C.
Two types of sheet-like sintered bodies having a wall thickness of 0.5+w+w were obtained by firing for a time.

The results of W4 microscopic observation and chemical analysis of the cross-sectional structure of this sintered body were as follows.

・Cross-sectional structure Extremely fine MgO (periclase) crystal grains are sintered in a densely entangled state, and 2Mg0e SiO2 phase is present in most of the spaces between the MgO crystal grains, with a total volume ratio of approximately 5
%, and a 2Mg0.SiO2 phase was also formed at some of the grain boundaries. The shape of this MgO crystal is approximately circular, and most of its sizes are 1 to 5.
The thickness of the 2Mg0φS i02 phase is approximately 0.1
It was about 0.5 #L.

Al2O3 is mostly MgO/Al2O between MgO grains:
It exists as granular crystals with a size of 1 to 3
It was the end.

-Chemical analysis values (wt%) Overall sintered body MgO 92.9% 5iTo 2.0% Al2O 35.0% The measurement results of various properties and characteristics of the sintered body were as shown in the following table. (^: Product fired at 1450℃, B is product fired at 1440℃, items without AB description are common) Bulk Density
A; 3.50. B; 3.49 bending strength (k
g/wmz) normal temperature ^; 31 B, 30 thermal conductivity (c
a I/am・5ec-”0) Room temperature 0.
11 300℃ 0. OB Dielectric constant (100KHz) Room temperature 9.3 Dielectric loss (100KHz, an δ) Room temperature A: 1.3X10-4. B:2.4
Xl0-4 Electrical insulation resistance (Ω cm ) 300°C 8 It enables the practical application of MgO as an electrical insulating material without sacrificing the material's excellent electrical properties and good thermal conductivity, making it extremely effective for improving the functionality of IC boards. Therefore, its industrial value is enormous.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional micrograph showing the crystal structure of the sintered body of the present invention. What is the scale? The scale is 3 pots. 1 is MgO particles, 2 is 2) IgO/SiO2 phase, 3 is M
gO.Al2O3 phase.

Claims (6)

[Claims] (1) Microscopically, the size of most MgO crystal particles is 5μ or less, and most of SiO_2 is 2MgO・S
In iO_2, Al_2O_3 is mostly MgO・Al_
2O_3 and consists mainly of a structure between MgO grains, and has a thermal conductivity of 0.08 cal/cm・sec at room temperature.
・Dielectric loss (tan δ) at 100 KHz above ℃
is less than 5 x 10^-^4 at room temperature, electrical insulation resistance is 300
A magnesia-based ceramic sintered body for electrically insulating base materials, characterized by having a resistance of 10^1^0 Ω·cm or more at °C and excellent strength and hydration resistance. (2) The chemical analysis value of MgO crystal particles is 39.5 in weight%
% or more of the magnesia ceramic sintered body according to claim 1. (3) The magnesia ceramic sintered body according to claim 1 or 2, which has a bulk density of 3.4 or more as a sintered body substrate. (4) The chemical analysis value as a sintered body is in weight% of SiO
_20.5-5%, Al_2O_30.5-20%, and the content of MgOS, SiO_2, and Al_2O_3 is 99.5% or more. (5) The MgO sintered body according to claim 1, which has a bending strength of 25 kg/mm^2 or more at room temperature. (6) The MgO sintered body according to claim 1, which has a dielectric constant of 10 or less at 100 kHz at room temperature.