JPS6112868B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to alumina ceramics that have high electrical insulation properties, low dielectric cutoff (tan δ), and light shielding properties as semiconductor containers for electronic components.
In particular, how to achieve this light-shielding property without damaging other properties has traditionally been studied using copper, titanium, nickel, cobalt, chrome, manganese,
A method of coloring was used by adding several percent of compounds (mainly oxides) such as iron, vanadium, molybdenum, and tungsten. However, these methods generally have a negative effect on the original properties of alumina porcelain, such as lowering the insulation resistance or increasing the dielectric positive cut tan δ.
That is, the above-mentioned coloring agents generally do not contribute to color development or cause color unevenness unless they are added so as to form a stable solid melt with the ceramic matrix. The firing is generally carried out at 1,500 to 1,600°C in a humidified hydrogen or nitrogen atmosphere, but unless the amount added and the firing atmosphere are not strictly controlled, the insulation properties may be extremely deteriorated. The present invention aims to remedy these drawbacks. That is, chromium oxide forms a complete solid solution with alumina and can block light with a wavelength of 600 mμ or less (including ultraviolet rays), while at the same time it can separate molybdenum, tungsten, or their oxides (hereinafter referred to as molybdenum, etc.) into a divided state. According to the present invention, it has been found that by interposing it in this alumina/chromium oxide solid solution, complete light-shielding properties can be obtained over the entire wavelength range without impairing other electrical properties. The α-alumina/chromium oxide based reddish-purple solid solution contains 0.5 to 8 parts by weight of the chromium oxide as a solid solution per 100 parts by weight of an alumina porcelain compound consisting of 80 to 94% alumina and 6 to 10% mineralizer. It has the above-mentioned shading effect of light having a wavelength of 600 mμ or less without impairing other electrical properties. This is extremely preferable because it is the light on the low wavelength side that has a particularly strong photochemical effect on the semiconductor, but this alone does not provide a light shielding effect over the entire other wavelength range. The present invention provides that this alumina/chromium oxide solid solution has a content of not more than half of the chromium oxide without impairing other mechanical and electrical properties.
It is possible to contain Mo and W in a divided and isolated state, and furthermore, because of the relatively small amount of content,
This is based on the knowledge that a light shielding property against light in a wavelength range of 600 mμ or more can be easily obtained. The base composition of the above ceramic sintered body is alumina
For 100 parts by weight of an alumina porcelain compound consisting of 90 to 94% and the balance mineralizing agent, chromium oxide or a chromium compound that produces chromium oxide upon firing, and an amount of molybdenum metal and/or tungsten equal to or less than the chromium compound. A total of 0.5 to 8 parts by weight was added. More preferably, 0.5 to 100 parts by weight of chromium oxide is added to 100 parts by weight of the alumina porcelain compound.
5 parts by weight and 0.5 to 2 parts by weight of Mo. As shown in the comparative example below, the amount of metal Mo or W added must be equal to or less than the amount of chromium oxide added in order to satisfy all the necessary conditions such as volume resistivity, tan δ, transverse rupture strength, etc. The present invention has revealed that this is necessary. The color tone of the sintered body thus varies between reddish-purple and black based on the content of each component. Chromium oxide (Cr ₂ O ₃ ) has a hexagonal close-packed crystal structure, completely forms a solid solution with α-alumina over the entire region (forms an isomorphic substitution solid solution), and does not form a eutectic. One of the advantages of the present invention is that since it does not have the difficulty of solid solution formation as in the prior art, it can be freely increased or decreased within the above composition range depending on the use and purpose. Another advantage of the present invention is that the stable base of the alumina/chromium oxide solid solution (light-shielding property in the low wavelength range) has a relatively small amount of verticality (separation and isolation).
By dispersing and containing molybdenum or the like, light shielding properties in all other wavelength ranges can be easily produced, and at the same time, the mechanical and electrical properties are not adversely affected. Since this metal such as molybdenum is dispersed in an arc, the insulation resistance deterioration that tends to occur when metals are added does not occur according to this method. In addition, the dispersed and vertical content of molybdenum etc., although in a small amount, sufficiently contributes to blackening the color tone. The chromium oxide can be added as chromium oxide or as a compound that produces chromium oxide when heated or fired. In addition, it is preferable to add tungsten etc. in a metallic state to increase the density of the sintered body, and as for alumina, the average particle size is
Preferably, the thickness is 1.5μ or less. Further, it is preferable to use chromium oxide, tungsten, molybdenum, etc. having an average particle size equal to or smaller than that of alumina for dispersion. In this case, the average alumina grain size of the corresponding sintered body will be approximately 2 to 8 μm. In addition, as a mineralizing agent, one mainly composed of SiO ₂ , MgO, and CaO can be used, and its composition is preferably 50 to 80% by weight of SiO ₂ , 5 to 50% each of MgO and CaO, and other B It can also contain small amounts of ₂ O ₃ , BaO, etc. The present invention further provides a novel method for manufacturing a sintered body having the above structure. That is, in the above composition, one or more of chromium oxide (or a compound that produces chromium oxide upon firing), tungsten, etc. is added and mixed with alumina together with a known mineralizing agent, and a known binder is added and shaped. , 1450-1650℃ in a non-oxidizing atmosphere, preferably about
Sintering is carried out at 1500-1600°C, more preferably at about 1550°C. By this method, high quality alumina-based colored ceramics with stable color tone can be easily obtained. The invention will be more clearly understood from the examples described below. Example 1 (Experiment numbers 1 to 11) α- with alumina content of 99.8% and average particle size of 1μ
Alumina porcelain formulation consisting of 94% Al ₂ O ₃ powder and balance mineralizer with SiO ₂ :MgO:CaO ratio of 6:1:1
To 100 parts by weight, Cr ₂ O ₃ with an average particle size of 1μ, metal Mo and/or metal W with an average particle size of 0.5μ are added in parts by weight shown for each experiment number (1 to 11) in Table 1. Butyral resin was added to the raw material powder along with trichlorethylene to form a slurry, and a 1.2 mm thick slurry was manufactured using the doctor blade method.
A 2.4 mm thick sheet was obtained by stacking two sheets and pressing them together using a press, and a 60 mm diameter disk and an 8.4 mm x 36 mm rectangular plate were cut from the sheet to obtain a green sheet substrate. This was carried out at 1550 °C in a hydrogen atmosphere.
The green tape substrate was baked at ℃ for 1 hour, and the green tape substrate was sintered to prepare a rectangular plate-like sample with a thickness of 2 mm and a size of 7 mm x 30 mm. Various necessary properties were measured for these samples, and the results are also shown in Table 1. The result fulfills all the necessary properties. Control Example 1 (Experiment No. R1) As a control example, the sample was made of only 94% of the alumina and 6% of the same mineralizer as used in the example.
A sample without additives such as Cr ₂ O ₃ and Mo was pressed in the same manner as in Example 1, and thereafter sintered in the same process to obtain a reference sample. The first set of characteristics is R1.
Shown in the table. Control example 2 (experiment numbers R2 to R4) In contrast to the above example 1, more than the same amount of Cr ₂ O ₃
Samples to which Mo and/or W were added were prepared by the same process as in Example 1, and the results were also used in Example 1.
Shown in the table. As a result, deterioration was observed in all of the volume resistivity, tanδ, and transverse rupture strength.

[Table] In the present invention, it is usually not necessary to add other components to increase the light-shielding property, but for the purpose of adjusting the color tone, a very small amount of alumina and eutectic of known coloring agents are added. This does not preclude the addition of metals or metal compounds that do not form.

[Brief explanation of the drawing]

Figure 1 is a backscattered electron image (magnification: x400) showing the particle structure of the colored ceramics according to the present invention, and Figure 2 is an x-ray microanalysis photograph (magnification: ×400), and
The white dots in FIG. 2 indicate the distribution state of Mo.

Claims (1)

[Claims] 1 100 parts by weight of an alumina magnetic composition consisting of 90 to 94% alumina and the balance mineralizing agent, chromium oxide,
The alumina and the chromium oxide are made into a solid solution, and the molybdenum metal or the tungsten metal is dispersed in an arcuate manner. colored ceramics.