JPS5833188B2 - Alumina-based porcelain composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides ceramic fired substrates such as hybrid IC
The present invention relates to ceramic substrates that require highly accurate surface smoothness, such as substrates for industrial use and substrates for thin films and thick films.

Generally, the ceramic substrate is required to have high mechanical strength and thermal conductivity, as well as excellent electrical insulation and heat resistance.

Therefore, high alumina ceramics containing alumina (AI, 03) as a main component are mainly used as substrate materials that can satisfy these characteristics.

Conventionally, this type of ceramic substrate is made by adding natural minerals such as talc, clay, and an organic binder to the main component (aluminum), thoroughly kneading it, forming it into a thin tape, and then forming it into a substrate shape. Manufactured by punching and firing.

Incidentally, since the fired substrate has irregularities of several micrometers on its surface, the fired substrate 11 may not be suitable for use as a substrate that requires a high level of smoothness.

For this reason, when the substrate after firing requires appropriate lapping or even higher precision smoothness, it is further polished to obtain the required smoothness.

An object of the present invention is to further improve the smoothness of the substrate surface after firing compared to conventional ceramic substrates.

As a substrate that is distantly related to this object, the present invention provides a novel ceramic substrate material whose main component is alumina.

That is, no explosion; the substrate material according to the invention is alumina 85
~99 weight, silica (Sin2), magnesha (
One or more types of various metal oxides such as MgO and Cab are added to make the total amount 100%, and the total fluorine content is preferably 0.3 to 5 with respect to the above total amount.
It is characterized by the addition of one or more types of fluoride to increase the weight.

The reason for limiting the amount of components in the substrate composition of the present invention is as follows.

In other words, when the content of alumina becomes 99 weight φ or more,
Since the matrix material layer interposed between the alumina grains is reduced, irregularities due to the alumina grains appear on the fired surface, resulting in poor smoothness.

In addition, the sintering temperature of porcelain is 1800° C. or higher, making it difficult to mass-produce the porcelain because the commonly used firing method cannot be used.

On the other hand, when the content of aluminum increases or decreases by 85% by weight, the smoothness of the porcelain surface is obtained, but on the other hand, the amount of matrix components other than alumina increases, resulting in a decrease in mechanical strength, heat resistance, thermal conductivity, etc. The characteristics of porcelain are lost, making it unsuitable as substrate porcelain.

The metal oxides added to the main component aluminum are added as sintering aids to promote the sintering of alumina porcelain.
It is effective in lowering the sintering temperature of porcelain.

The total content of metal oxides in porcelain is primarily determined by the alumina content, but in the present invention, 5i021Mg09
Add one or more metal oxides such as Cart Zr02t Ti021BaO in a range of 1 to 15% by weight.

In addition, the addition of fluorine, which is a feature of the present invention, is
This has the effect of accelerating the sintering of alumina-based porcelain made of metal oxides, and the higher the fluorine content, the lower the sintering temperature.

However, although there are slight differences depending on the composition of porcelain, for example, the type and amount of metal oxides used as sintering aids, the fluorine content is 0.3% of the total amount of alumina and metal oxides.
If the weight is less than that, the sintering effect will be small and the smoothness will vary greatly between the same substrate or substrates within the same manufacturing lot.

,-! On the other hand, if the weight is 5 or more, a large amount of glass is formed in the porcelain, which tends to deteriorate the mechanical strength and heat resistance.

Therefore, the preferable fluorine content is 0.3 to 5 weight, and a range of 1 to 3 weight is particularly preferable.

The main effect of fluorine addition in the present invention is that it has a remarkable viscosity reduction effect accompanying the sintering promotion effect, so there is less foaming within the porcelain and the swelling of the foam layer on the surface, the so-called blistering phenomenon. The point is that the porcelain surface becomes extremely smooth after firing.

Examples of the fluorine-containing raw material according to the present invention include calcium fluoride (CaF2), barium heptadide (BaF2),
2) Various fluorides such as magnesium fluoride (MgF2) and sodium silicofluoride (Na2SiF6) can be used.

Although the sintering temperature and porcelain properties of porcelain to which these fluorides are added differ slightly depending on the type and amount of addition, the effects on the smoothness of the porcelain surface are almost the same.

For calcium fluoride, fluorite, which is a natural mineral, can be used, but in addition to this, calcium fluoride, which is a by-product of hydrofluoric acid waste liquid treatment that is used in large quantities in the semiconductor industry, can be used.

Next, a method for manufacturing a seven-inch board according to the present invention will be explained using representative examples.

The starting raw material is the main component alumina (A 1203),
Various metal oxides such as silica (S102) and magnesia (MgO) are used as the sintering aid, and calcium fluoride (CaF2) is used as the fluoride.

For these raw material powders, it is desirable to use fine powders with an average particle size of 1 μm or less, especially for the main component, aluminum powder, so that the porcelain surface after firing will be a smooth surface with a collection of fine crystals.

In order to manufacture the substrate, first, each of the above raw material powders is weighed in a predetermined ratio, for example, 96 weight of alumina, 3.7 weight of silica, 0.3 weight of magnesha, and then 5% by weight of calcium fluoride (fluorine content: 2.4% by weight) is weighed out.

This raw material powder is placed in an alumina pot together with a solvent such as water or ethyl alcohol and a grinding ball, and is ground and mixed in a ball mill or vibration mill to a particle size of 1 μm or less, and then dried.

Next, a vehicle in which polyvinyl butyral as a binder and Flexol as a plasticizer are dissolved in a solvent such as azeodorope is added to this mixed raw material powder, and after thorough kneading, a green sheet is made, and this is shaped into a predetermined substrate shape. Punch out.

Further, this punched substrate is fired at a temperature of 1500° C. or higher in a reducing atmosphere.

The fired substrate has a water absorption rate of O and is well sintered, and the average maximum surface roughness (30 samples) is 1.3 μm, which is good smoothness, and has good mechanical strength, heat resistance, and electrical insulation properties. The characteristics required for the substrate were fully satisfied.

Below, examples according to the present invention and comparative examples using conventional methods will be shown regarding the method of manufacturing a ceramic substrate.

The main component, alumina (α-A1203
), silica (Si02
), magnesia (MgO), karja (Ca0), zirconia (Zr02), and titania (TiO□),
Calcium fluoride (CaF2) was used as a fluorine raw material and was blended into the compositions shown in substrates A1 to A11 in Table 1.

Each raw material powder was weighed to have a predetermined composition and then pulverized and mixed using a vibrating mill so that the average particle size was 1 μm or less.

6 weights of polyvinyl butyral and 40 volumes of azeodorope were added to this mixed raw material powder, and the mixture was sufficiently kneaded using a stirrer to prepare a paste.

This pasty raw material was formed into a green sheet, punched into a predetermined substrate shape using a punching machine, and then sintered in a firing furnace under the conditions shown in Table 1 to produce a ceramic substrate.

After firing, the bending strength and maximum operating temperature of the substrate were examined, and the smoothness of the substrate surface was measured using a surface roughness meter. The results are shown in Table 1.

Comparative Example The substrate composition raw materials listed in the Comparative Example column of Table 1 were milled using a vibration mill to reduce the average particle size to 1. , , m or less and mixed.

To this mixed raw material powder, 6 weight φ of polyvinyl butyral and 40 volumes of azeodrol were added, kneaded and adjusted for slip, formed into a green sheet, punched into a substrate shape, and fired in a firing furnace to produce a ceramic substrate. .

The roughness of the substrate surface after firing was examined using a surface roughness meter.

The smoothness of the fired surfaces of the ceramic substrates shown in the above Examples and Comparative Examples, that is, in an unpolished state, will be explained using an example of measuring the maximum surface roughness.

The maximum surface roughness is indicated by the maximum distance between the peaks and valleys of the surface roughness curve.

The maximum surface roughness of the fluorine-containing substrate as an example of the present invention is about 1 to 2 μm, which is very smooth, and even unpolished substrate No. 11 can be used satisfactorily as a substrate.

If even higher level of smoothness is required, the desired surface roughness can be achieved by lapping or polishing for a short time.

When the fluorine content deviates from the preferred range of the present invention,
For example, the AIO substrate with a fluorine content of 0.3 weight yield has little effect on reducing viscosity due to sintering promotion, so the effect on smoothness is slightly reduced. Although the substrate All has good smoothness on the substrate surface,
Mechanical strength and heat resistance are slightly reduced.

Thus, the practically preferable fluorine content is 0.3 to 5.
It is a weight scale.

On the other hand, the ceramic substrate of the Comparative Example, which is a conventional product, has a maximum roughness of 3 μm or more on the fired surface, and has a larger maximum roughness and inferior smoothness than the substrate of the Example of the present invention.

FIG. 1 shows the surface roughness curve of a typical ceramic substrate layer 6 in the embodiment of the present invention, and FIG. Shown in the figure.

As is clear from the figure, the fluorine-containing substrate of the present invention is superior in smoothness to the conventional substrate.

Ceramic substrates for hybrid ICs, thin films, thick films, etc. are required to have a surface roughness of 3 μm or less, and conventional substrates require a lapping process after firing. The ceramic substrate according to the invention is
The surface after firing has good smoothness, and therefore the lapping process that is conventionally performed on substrates can be omitted, which simplifies the manufacturing process and makes it possible to manufacture at low cost.

In addition to the application as a ceramic substrate, the present invention can also be used as an insulator for a spark plug, for example, because the insulator surface is smooth, reducing the adhesion of combustion substances to the insulator leg of a plug in the engine, improving stain resistance. can be expected.

It can also be applied to various precision slab parts that require smooth surfaces.

[Brief explanation of drawings]

FIG. 1 is a surface roughness curve after firing of a typical ceramic substrate according to the present invention, and FIG. 2 is a surface roughness curve after firing of a conventional ceramic substrate.

Claims (1)

[Claims] 1. One or more types of fluoride is added to the composition for a total amount of 100 or more compositions consisting of alumina 85 to 99 weight φ and one or more metal oxides t-t5 weight or more. Added alumina-based porcelain composition. 2. An alumina-based porcelain composition according to claim 1, wherein the fluorine content in the fluoride is in the range of 0.3 to 5 parts by weight based on the total amount. 3. Claim 2 states that the fluorine content is 1
An alumina-based porcelain composition characterized in that the weight is within the weight range of ~3.