JPS59203774A - Floor powder for ceramic formed body baking - 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 The present invention relates to a bedding powder for firing ceramic molded bodies, and in particular to a bedding powder that is suitable for producing ceramic fired bodies for electronic components that have little adhesion of bedding powder during firing and have high surface smoothness. It is related to.

Conventionally, when producing a sintered body by firing ceramic molded bodies at high temperatures, in order to prevent the molded bodies from seizing together,
A heat-resistant oxide powder that is inert to the ceramic molded bodies, so-called so-called bed powder, is interposed between the ceramic molded bodies, and the ceramic bodies are stacked in multiple stages and fired. However, bedding powder adhered to the surface of the ceramic or pre-fired body after firing, which not only made it difficult to remove, but also impaired the smoothness of the surface of the ceramic or pre-fired body. In recent years, electronics and ceramics have been developed into insulating materials such as integrated circuit boards, dielectric materials such as ceramic capacitors, magnetic materials,
It is widely applied to piezoelectric materials, semiconductor materials, etc., and the demand for these materials is increasing, but as electronic devices become lighter and lighter, these ceramics and glass materials are also becoming more and more
There is an increasing demand for miniaturization, precision, and homogenization. Under these circumstances, there is a strong demand for the establishment of a method to prevent the adhesion of bedding powder to ceramic fired bodies, as this is directly linked to deterioration of product quality and reduction in productivity.

The present invention was made in view of the above-mentioned current situation, and it is possible to efficiently produce ceramic fired bodies with extremely low adhesion of bedding powder to the fired body during firing and with a high surface smoothness. The purpose is to provide the following.

In order to achieve the above object, the present inventors studied the adhesion characteristics of a large number of heat-resistant oxide powders to fired bodies when used as bedding powder. The present invention was achieved by discovering a phenomenon in which it is difficult to adhere to. That is, the bedding powder of the present invention is an oxide powder that is inert to the ceramic molded body to be fired, and is made of massive secondary crystal grains with an outer diameter of 40 to 100 μm, which are formed by aggregation of plate-shaped secondary crystals. It is characterized by being a powder.

In the present invention, the ceramic molded body to be fired includes:
In addition to widely used alumina-based or silicic acid ceramics, Mg, Ti, Ha, Sr, and Cr+Zr are used as electronic ceramics.

The target materials include oxides of metals such as Mn, and their double oxides. The oxides that are inactive to these ceramic molded bodies during high-temperature firing are mainly A/ or Zr oxides.

Particle characteristics required for a bed powder are: (1) Few particles adhere to the ceramic fired body, and the adhered particles should be easily peeled off. (2) No large bits (< dents) caused by the adhered particles remain on the surface of the fired ceramic body after the adhered particles have been peeled off.
Must be a smooth surface. (3) The main reason is that the particles of the bedding powder are not crushed and atomized during use. The bed powder of the present invention has all of these characteristics, but as described above, the particles constituting the powder are lump-like particles with an outer diameter of 40 to 1007+ m formed by aggregation of plate-shaped primary crystals. It is characterized by the fact that it is a secondary crystal grain. If the particle size is less than 40 μm, the particles tend to adhere to each other, and if the thickness of the powder layer is small, there is a drawback that the fired ceramic bodies may seize together. On the other hand, as the particle size increases, the pits on the surface of the ceramic ivy fired body that remain after the particles are peeled off become thicker when they are attached.
Impairs the surface smoothness of the fired product. Generally, it is required that the diameter of the surface pits of electro-ceramics does not exceed 100 μm, so in the present invention, from this point of view, the upper limit of the secondary crystal particle diameter is set to 100 μm. Although the secondary crystal grains may have an overall rounded granular shape as illustrated in FIG. 1, the present invention does not necessarily require such a restricted external shape, and There is no problem even if the crystal grains have large cavities and are coarsely aggregated.

The outer diameter of the particles may be measured on the particles under a microscope, but is determined by sieve analysis. The powder of the present invention is industrially classified by sieving, for example, 325 mesh (43 μm) and 170 mesh (s91
+m) are collected.

A more preferable requirement of the present invention is that 80% of the -order crystals
The average diameter is 5 to 50 μm. In the case of fine crystals in which the average medium of the plate-like crystals falls below this low limit, the adhesion to the fired body becomes strong and peeling becomes difficult. The upper limit of the -order crystal average is determined by the limit that satisfies the secondary crystal grain size, and is generally K 507+m. In the case of alumina, 80 or more primary crystals are on average 10 to 30μ
A range of m is more desirable. Further, it is also a desirable requirement that the average medium to thickness ratio of the -order crystals be in the range of 115 to 115 degrees. When this ratio becomes larger than 115,
When the peel strength of the adhered particles increases and the particles become thinner than 115°, they are easily crushed and atomized, thereby increasing the adhesion.

The powder according to the present invention as described above cannot be produced by a melting method. In the case of alumina, aggregate grains of plate-like crystals cannot be obtained using fused corundum, but are produced by firing aluminum hydroxide crystals. The shape (plate-like) and size of the obtained primary crystals of α-alumina strongly depend on the crystal shape and size of aluminum hydroxide, and are mainly determined by adjusting the precipitation conditions of aluminum hydroxide. The shape (aggregation mode of the -order crystals) and outer diameter depend on the shape and size of the -order crystals, but also vary depending on the firing conditions such as the type of mineralizing agent, the amount added, firing, temperature and time, and dynamic heating. Be determined.

The phenomenon in which the bedding powder of the present invention has difficulty adhering to ceramic fired bodies (or is easy to peel off even if it adheres) has not been fully elucidated. It is presumed that the large contact area between the particles and the ceramic molded body to be fired increases the adhesion and adhesive strength. It is presumed that this is because the contact area is significantly reduced compared to the former because it occurs at the thin tip of the plate crystal that protrudes from the outer periphery of the secondary crystal grain.

The present invention will be explained below with reference to Examples and Comparative Examples.

Example (1) Ceramic compact to be fired Bayer α-alumina powder (de-Na treated) is added with MgO powder by weight of 0.25%, and the whole is ground in an alumina bot mill to obtain a raw material powder with an average particle size of 0.657+m. was manufactured. A molding binder was added to this powder and kneaded in a conventional manner, and the resulting slurry was molded by tape casting and air-dried indoors to produce a green sheet for a ceramic substrate (ceramic molded body to be fired).

(2) Adding aluminum fluoride powder as a mineralizing agent to two types of Bayer aluminum hydroxide crystals and dynamically firing them in a rotary kiln at a maximum temperature of 1350°C.
- Eight types of alumina powder sieved using a Tyler standard sieve were tested.

The particle specifications of this powder are as shown in 41 to A8 in Table 1.

(3) Firing of ceramic molded body (1) Throat (The prepared raw sheets for ceramic substrates are stacked in 8 stages of firing sheaths and Vc, arranged in 6 rows each (48 raw sheets)), and between each sheet The powder was made to exist at a constant thickness by two methods: spreading the powder on a sieve as described in (2) above, and spraying an organic solvent slurry of the powder. Next, the molding binder was removed by heating in a firing furnace at 350'C for 1.5 hours, and then the furnace temperature was raised to 1500°C (in the atmosphere) and held for 2 hours to perform firing.

(4) Judgment of adhesion of bedding powder The 48 ceramic fired bodies obtained for each of the 8 types of bedding powder (Table 1, /161 to A8) were treated with a barrel polisher for a certain period of time, and after this treatment, the bedding powder was The percentage of the number of cylinders of the fired body to which the powder was still adhered was defined as the powder adhesion rate.

In addition, in order to determine the peeling strength of the adhered bed powder particles, a ceramic plate with a rough surface (A) made of sintered fused alumina grains with a Tyler standard sieve of 80 mesh was used.
A fired body in which the bedding powder has settled and remains (the surfaces are brought together, the rough surface (A) is fixed, and the fired body (B) is slid in parallel,
The maximum value of the tensile strength at that time was defined as the peel strength. The values shown in Table 1 are an index with the peel strength of 1 being the peel strength when fused alumina powder is used as the powder.

In order to clarify the state of the particles constituting the bed powder of the present invention, as a representative example, Table 1/F61 and Flat 5 bed powder are shown below.
Scanning electron micrographs are shown in FIGS. 1 and 2, respectively. In each figure, (a) shows the appearance of a secondary crystal particle at a magnification of x500, and (b) shows an appearance of a primary crystal particle at a magnification of x2500.

[Comparison example]

The adhesion of Oshiki powder was determined using the same method and conditions as in the above example, except that 10 kinds of alumina powders listed in Table 1/169 to A18 were used. The results are as shown in the numerical values in Table 1.

The source of the alumina tested is as follows.

169-A11; It is similar to the bed powder of the present invention in that it consists of massive secondary crystal grains formed by aggregation of fine plate-shaped α-alumina secondary crystals, but it contains secondary crystal grains of 100 μm or more. In addition, Rin 9 and Fu 10 have smaller average primary crystals.

A612-14: Powder produced by baking Bayer-precipitated aluminum hydroxide at high temperature is finely pulverized in an alumina pot mill, and consists of α single crystals and does not constitute secondary crystals as in the present invention.

zK 15-16; This is a crushed product of fused corundum.

/f617-18; Spherical alumina particles of 43 to 74 μm, A17 is a powder made of calcined α-alumina powder, and Case 18 is a powder made of spherical particles processed using a crushed product of fused corundum as raw materials.

As is clear from the values of the present invention and comparative examples shown in Table 1, the bedding powder of the present invention has significantly less adhesion to ceramic molded bodies than conventional bedding powder, and also has lower peel strength of the adhered particles. It is recognized that it is a small and excellent bed powder. Furthermore, when the lining powder of the present invention was used, the surface of the fired ceramic body after lapping was much smoother and cleaner than in the case of conventional lining powder.

As mentioned above, the bedding powder of the present invention is extremely suitable for manufacturing ceramic fired bodies for electronic components that require high surface smoothness, and has a remarkable effect of increasing the yield and improving the quality of fired bodies. .

[Brief explanation of the drawing]

FIGS. 1 and 2 are scanning electron micrographs of particles constituting the powder of the present invention, and FIG.
The figure shows the bed powder of inversion 5. In each figure, (a) is the appearance of secondary crystal particles at a magnification of ×500, and (b) is a magnification of ×2500.
This shows the appearance of primary crystal grains. Showa Light Metal Co., Ltd.

Claims (1)

[Claims] 1. Ceramic compact to be fired IC is an inert oxide powder with an outer diameter 4 formed by aggregation of plate-shaped primary crystals.
A bed powder for firing a ceramic molded body, characterized in that it consists of massive secondary crystal grains of 0 to 100 μm. 2 More than 80 plate-shaped primary crystals have an average size of 5 to 50 μm
The bedding powder for firing a ceramic molded body according to claim 1, wherein the ratio of the thickness to the average thickness is 1/~115o. 3. A patent claim characterized in that the oxide powder is substantially α-alumina and consists of massive secondary crystal grains formed by aggregation of plate-like secondary crystals with an average diameter of 10 to 30 μm. A bedding powder for firing a ceramic molded body according to Items 1 and 2 of the scope.