JPH02141476A - Production of ceramics substrate - Google Patents

Abstract

PURPOSE:To obtain the ceramics substrate which is inexpensive and has smooth surfaces by alternately laminating and press-welding ceramics green sheets which are opposite in the warpage directions at the time of calcination in a specific form and integrally calcining the sheets. CONSTITUTION:The ceramics green sheet 10' which constitutes the ceramics substrate when calcined is formed by laminating and press-welding two sheets of the ceramics green sheets 12, 14. The sheets 12, 14 are so disposed that the film-contact surfaces of the sheets at the time of the formation of the sheets are positioned on both the outside surfaces of the ceramics substrate after calcination. The ceramics green sheets 12, 14 are laminated is such a manner that the warping direction occurring in the packing density of the ceramics particle is made to the opposite. The warping and curving stresses of the respective ceramics green sheets 12, 14 are, therefore, offset or relieved and suppressed when the sheets 12, 14 are superposed on the substrate and are press-welded by, for example, a cold isostatic pressurization method. The deformation and warpage over the entire part of the ceramic green body 10 are obviated. The stage for correcting the warpage is, therefore, not executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a ceramic substrate, and more particularly to a method for manufacturing a ceramic substrate in which a plurality of ceramic green sheets are stacked and integrally fired.

[Prior art]

Thin ceramic green sheets used for manufacturing ceramic substrates are generally manufactured by a doctor blade method or the like. In a ceramic green sheet created by such a doctor blade method or the like, the packing density of ceramic particles differs depending on the thickness direction and surface direction (width direction or length direction), which causes "warpage" during firing. This also applies to ceramic green sheets made by extrusion molding, although there are differences in degree.

Therefore, conventionally, after the ceramic green sheet has been fired, a weight is placed on the ceramic substrate, and a post-processing process is performed in which the ceramic green sheet is heated again to near the firing temperature to cause so-called "rewarping".

[Problem to be solved by the invention]

“Rewarping” in conventional ceramic substrate manufacturing methods
This process not only requires a large amount of energy equivalent to firing twice, but also has a low yield, resulting in poor productivity and difficulty in reducing product costs.

Furthermore, although ceramic can be used as the weight used in the "rewarping" process, it often reacts with the ceramic substrate, resulting in a disadvantage that the surface condition of the ceramic substrate deteriorates. Furthermore, green sheets are usually created by applying a film to the film, but in this case, although the film side of the green sheet has excellent smoothness after firing, the other side is relatively rough. In some cases, it was not suitable as a ceramic substrate for thin film formation.

Therefore, the main object of the present invention is to provide a method for manufacturing a ceramic substrate, which is inexpensive and allows a ceramic substrate having a smooth surface to be obtained.

[Means for Solving the Problems] To put it simply, the present invention is to alternately stack and press ceramic green sheets whose warp direction is opposite during firing so that the contact surface of the film becomes the outermost surface, and then integrally fire the sheets. This is a method of manufacturing a ceramic substrate.

[Effect]

Ceramic green sheets with opposite warp directions during firing are alternately laminated and pressed together so that the contact surface of the film is the outermost surface and are fired as a single unit, resulting in good surface smoothness and the warping during firing canceling out each other. suppressed.

[Effects of the Invention] According to the present invention, since the contact surface of the film is the outermost surface, the surface smoothness of the resulting ceramic substrate is good, and it can be fired without placing any weight on it, resulting in an excellent surface condition. Ceramic dry wood boards can be fired. In addition, since there is no need for re-warping, production efficiency is high and product costs can be reduced.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

〔Example〕

FIG. 1 is an exploded perspective view for explaining one embodiment of the present invention. The ceramic green body 10', which becomes a ceramic substrate when fired, is formed by laminating and pressing two ceramic green sheets 12 and 14. In this embodiment, these ceramic green sheets 12 and 14 are formed by the known F-lid blade method. A film sheet 16 is attached to the ceramic green sheets 12 and 14 as a release material to prevent the green sheets 12 and 14 from adhering to a punch or the like during crimping and to facilitate removal after crimping.
and 18 are provided. In this case, the ceramic green sheet 1214 is the film sheet 16.1
The ceramic green sheets 12 and 14 are arranged so that the film contact surfaces during molding are located on both outer surfaces of the ceramic substrate after firing.

Further, in FIG. 1, respective arrows indicate sheet forming directions of the respective ceramic green sheets 12 and 14. That is, the ceramic green sheet 12
is formed by moving the film sheet 16 in the direction shown by the arrow 12a. Similarly, ceramic green sheet 1
4 is also formed by moving the film sheet 18 in the direction shown by the arrow 14a. In this embodiment, the ceramic green sheets 12 and 14 are arranged so that their sheet forming directions are alternately orthogonal to each other.

In this way, the ceramic green body 10' in which the ceramic green sheets 12 and 14 are laminated is produced by, for example, a cold isostatic pressure method (C12 method) or the like, at a temperature of 40 to 80°C and a pressure of 300 kgf/crR or more. pressure is applied and crimped. Thereafter, as shown in FIG. 2, the ceramic green body 10' is cut into a predetermined size, and the ceramic green body 10 is integrally fired. After this firing, the film sheets 16 and 18 are preferably peeled off in advance, but they may be fired as they are.

Ceramic green sheets 12 arranged as described above
and 14, during firing, the ceramic green sheet 12 tends to curve upward, and the ceramic green sheet 14 tends to curve downward. Simply put, this is due to the difference in the packing density of ceramic particles in the upper and lower parts of the ceramic green sheets 1-12 and 14 in the thickness direction. That is, for example, in the doctor blade method, the ceramic slurry is flowed onto the moving film sheet through the gap created by the doctor blade, but the ceramic particles contained in the ceramic slurry tend to settle and therefore naturally come into contact with the film sheet. The density of the ceramic particles is higher on the side with the edge than on the opposite side. Due to such a difference in the packing density of the ceramic particles, the ceramic green sheets 12 and 14 tend to curve in respective directions during firing.

On the other hand, when looking at warpage or curvature in the surface direction during firing, warpage or curvature tends to occur in the direction perpendicular to the sheet forming direction (arrows 12a and 14a in FIG. 1). Therefore, in this embodiment, the ceramic green sheets 12 and 14 are laminated with the directionality described above.

That is, the ceramic green sheets 12 and 14 are stacked so that the directions of warpage due to the packing density of the ceramic particles are opposite to each other. Therefore, when the ceramic green sheets 12 and 14 are superimposed on the ceramic green sheets 1, pressed and fired by, for example, a cold isostatic pressure method, the warping or bending stress of the respective ceramic green sheets 12 and 14 is canceled out or alleviated. This suppresses deformation or warping of the ceramic green body 10 as a whole. Therefore, the process of "rewarping" is not performed.

The following table shows the results of a comparison between the four-layer ceramic substrate formed according to the above-described example and the four-layer ceramic substrate formed by the conventional method. In addition, in both the example and the conventional example, the purity is 99.9% or more and the average particle size is 0.4μ.
AI of m! , 20. As a sintering aid, purity 99.9
% or more, 0.5 wt% of MgO with an average particle size of 0.5 μm was added, and to this particle powder, 12 wt% of PVB (polyvinyl butyral) was added as a binder, and DO was added as a plasticizer.
6 wt% of P (dioctyl phthalate), 90 wt% of toluene-ethanol as a solvent, and 1 w of a dispersant.
t% and mixed by ball mill for 48 hours to form a ceramic slurry. After defoaming the ceramic slurry and adjusting the viscosity, a ceramic green sheet with a thickness of 0.25 mm is created by the doctor blade method.

In the example, four ceramic green sheets with opposite warping directions during firing were alternately laminated so that the film contact surface was the outermost surface, and the ceramic green sheets were heated at a temperature of 70°C for 500°C.
kgf/ct! Apply + pressure to crimp. That,
Cut into appropriate size, for example about 70 embryonic horns, and
Baking for 2 hours at a temperature of 550°C, e.g.
It forms a mm square ceramic substrate and is not "rewarped".

On the other hand, in the conventional example, the film contact surface and lamination direction are not considered (i.e., a ceramic green sheet with a thickness of one cylinder is simply molded, and then heated at 1550°C as in the example).
A ceramic substrate of 50 mm square was formed by firing at a temperature of 2 hours.

Note that these numerical values indicate average values of 100 samples.

(Margins below) In the above table, the film surface refers to the surface from which the ceramic green sheet is peeled off during production, and the dry surface refers to the opposite surface to this film surface.

As is clear from the table, in the substrate of the example, the probability that a pinhole of 10 μm or more will appear and become a defective product can be reduced from the conventional 20% to 5%. Furthermore, the difference in shrinkage rate between the vertical and horizontal directions can be reduced from 0.3% in the past to 0.1%. Furthermore, in conventional substrates, the surface roughness of the dry surface of the ceramic green sheet is 0.1 μm.
It was bad. However, in the substrate of the example, since the ceramic green sheets are laminated so that the film surfaces are on both surfaces of the substrate, the surface roughness of the substrate can be maintained at the minimum of 0.05 μm on both surfaces.

Therefore, in this manufacturing method, a ceramic substrate having a surface roughness and warpage of 0.05 μm or less can be manufactured with a yield rate of 95% or more without any "rewarping" process.

Note that a larger number of ceramic green sheets may be laminated by alternately laminating ceramic green sheets with the film surface being the outermost surface and having opposite warp directions during firing.

[Brief explanation of the drawing]

FIG. 1 is a perspective view for explaining the manufacturing process of an embodiment of the present invention. FIG. 2 is an illustrative cross-sectional view showing the ceramic green body laminated as shown in FIG. 1. In the figure, 12 and 14 are ceramic green sheets, and 16 and 18 are film sheets. Patent applicant Tsukita Seisakusho Co., Ltd. Agent Patent attorney Yama 1) Yoshito

Claims (1)

[Claims] A method for manufacturing a ceramic substrate in which ceramic green sheets with opposite warp directions during firing are laminated and pressed together alternately and fired as one unit so that the film contact surface is the outermost surface.