Plastic and nonmetallic article shaping or treating: processes – Outside of mold sintering or vitrifying of shaped inorganic... – Shaping or treating of multilayered – impregnated – or...
Reexamination Certificate
2000-03-22
2001-05-08
Fiorilla, Christopher A. (Department: 1731)
Plastic and nonmetallic article shaping or treating: processes
Outside of mold sintering or vitrifying of shaped inorganic...
Shaping or treating of multilayered, impregnated, or...
C264S643000, C264S667000
Reexamination Certificate
active
06228318
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a manufacturing method of a ceramics component having a microstructure used in various fields of industry, for example, a manufacturing method of a ceramics component having a microstructure such as a composite piezoelectric material.
2. Description of the Background Art
FIG. 1
is a perspective view showing a structure of a composite piezoelectric material
21
as an example of a ceramics component having a microstructure.
Referring to
FIG. 1
, composite piezoelectric material
21
has a structure in which piezoelectric ceramics columns
22
are formed in a resin
23
.
The conventional manufacturing of a composite piezoelectric material of such a structure includes the method of employing mechanical working such as cutting and abrasion, the process by laser abrasion as well as the method of using a mold with a microscopic pattern formed in the resin as disclosed in U.S. Pat. No. 5,676,906.
FIGS. 2-8
are sectional views showing an example of a manufacturing method of a ceramics component with a forest of microscopic columns, disclosed in U.S. Pat. No. 5,676,906.
Referring to
FIG. 2
, deep X-ray lithography is effected by directing synchrotron radiation (SR)
40
onto a conductive substrate
1
coated with a resist
2
that has sensitivity to X-ray through a mask
3
for X-ray lithography.
As X-ray lithography mask
3
, a mask of a relatively thick absorber can be used formed of, for example, silicon nitride having a thickness of 2 &mgr;m as a support film
31
and tungsten having a thickness of 5 &mgr;m as an absorber pattern
32
. Alternatively, nickel mesh having a thickness of at least 30 &mgr;m can be used.
Referring to
FIG. 3
, a resist structure
4
is produced by a development process.
Referring to
FIG. 4
, nickel plating is applied on resist structure
4
to produce a nickel mold
5
. Then, resist structure
4
is removed.
Referring to
FIG. 5
, resin molding is effected using the produced nickel mold
5
to form a resin mold
6
. This resin mold
6
can be configured to have, for example, a hole of 25 &mgr;m square and 300 &mgr;m in depth arranged in a two dimensional manner at the pitch of 50 &mgr;m.
Referring to
FIG. 6
, a ceramics slurry
17
is poured into resin mold
6
and then dried.
Referring to
FIG. 7
, resin mold
6
is removed by plasma
50
.
Referring to
FIG. 8
, the binder is removed and baking is effected to obtain a ceramics structure
9
with many columns.
According to the conventional art disclosed in the above U.S. Pat. No. 5,676,906, there is a possibility of the microstructure collapsing due to the insufficient strength during removal of the resin mold if the solvent ratio of the used ceramics slurry is high. The structure subjected to the baking process becomes porous with the possibility of inducing problems from the standpoint of property and strength.
Furthermore, according to the conventional art, there was a case where warping occurs during baking since the shape differs between the top face and the bottom face of the ceramics component depending upon the absence/presence of a resin mold. It was extremely difficult to suppress such warping. Therefore, it was not easy to fabricate a ceramics component of a large area by the conventional method.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above problems, and provide a method of manufacturing a ceramics component of a microstructure without collapse, and also of a large area suppressed in generation of warping.
According to an aspect of the present invention, a manufacturing method of a ceramics component having a microstructure is provided. This manufacturing method includes the steps of filling a resin mold with ceramics paste, apply press-forming with ceramics powder placed on the ceramics paste, and baking after the resin mold is removed.
According to the present invention, paste (the state of the raw material of ceramics used in extrusion) is placed on a resin mold. Powder (the state of the raw material used in press-forming) is provided therearound, and press-forming is applied. Since the paste has a solvent ratio lower than that of a slurry, collapse of the ceramics microstructure and problems of the property and strength are solved. Paste is inferior than slurry from the standpoint of fluidity due to the low solvent ratio. However pressure can be applied by virtue of providing powder, whereby injection into a microscopic hole is possible.
According to the present invention, generation of warping can be suppressed. By virtue of the double layer structure of paste and powder, the warping caused by difference in the shape between the top face and the bottom face can be canceled by controlling each shrinkage rate of the two layers. More specifically, generation of warping can be suppressed by optimizing the injection pressure or paste composition, increasing the shrinkage rate of the powder portion by mixing excessively large particles into the powder portion, and the like.
According to the present invention, a ceramics microstructure can be fabricated without collapse. Also, suppression of warping allows manufacturing of a ceramics component of a large area.
Preferably, microscopic particles obtained by pulverizing a baked structure of a ceramics material of a type identical to that of the ceramics component is mixed into the ceramics powder.
By setting the type of the ceramics powder identical to that of the ceramics component, change in the property of the component can be prevented even if ceramics powder is mixed into the ceramics component during the manufacturing process.
Further preferably, the microscopic particle obtained by pulverizing the ceramics material baked structure of a type identical to that of the ceramics component is mixed 0-30 wt % in the ceramics powder.
If the amount of microscopic particles mixed becomes greater than 30 wt %, sufficient press-forming cannot be achieved. The handling thereafter will become difficult to induce the possibility of a problem during the manufacturing process.
Also preferably, the amount of binder included in the ceramics paste is 3-30 vol % with respect to the entire ceramics paste, and the amount of solvent is 40-45 vol % with respect to the entire ceramics paste.
If the amount of binder is less than 3 vol %, there may be difficulty in maintaining the microstructure when the resin mold is removed. If the amount of binder is greater than 30 vol %, there may be difficulty in maintaining the microstructure after removing the binder.
Furthermore, if the amount of solvent is less than 40 vol %, the paste will become too hard to be introduced into the resin mold. If the amount of solvent is greater than 45 vol %, it will be difficult to maintain the microstructure after removing the binder.
Preferably, the pressure is to be adjusted to 250-3200 kgf/cm
2
in the press-forming step.
Further preferably, the pressure is to be adjusted to 250-3000 kgf/cm
2
in the press-forming step.
If this pressure is lower than 250 kgf/cm
2
, sufficient press-forming cannot be achieved to cause a problem during the manufacturing process. If the pressure becomes 3200 kgf/cm
2
or greater, the difference in density between the particles of the ceramics paste and the base becomes so large that warping or peeling will occur.
As to ceramics paste of a viscosity that facilitates the blending process and injection into a resin mold, the pressure range of 250-3000 kgf/cm
2
is preferable for press-forming
Preferably, the ceramics powder placed on the paste is adjusted to have a thickness of 1-5 mm after the press-forming step.
It is extremely difficult to set the thickness of the ceramics powder smaller than 1 mm by the current processing technique. If the thickness is set greater than 5 mm, the pressure applied in the press-forming step in the upward direction and the downward direction will be effected only at the surface and not conveyed to the interior. This will induce the problem of the generation of a crack or the like.
Preferably, the
Hirata Yoshihiro
Nakamae Kazuo
Fiorilla Christopher A.
McDermott & Will & Emery
Sumitomo Electric Industries Ltd.
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