Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2003-01-03
2004-09-21
Mayes, Melvin C. (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S089160, C156S289000
Reexamination Certificate
active
06793751
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing a laminated ceramic electronic component, and more particularly, the present invention relates to a method for manufacturing a laminated ceramic electronic component such as a laminated ceramic capacitor, laminated inductor, and laminated LC filter.
2. Description of the Related Art
FIG. 1
is a schematic diagram showing the manufacturing process of laminated ceramic electronic components such as laminated ceramic capacitors, for example, as described in Japanese Patent Application Kokai No. H5-92406. In a manufacturing apparatus
10
described therein, a carrier film roll
12
around which a carrier film formed from a synthetic resin or the like is rolled up is first prepared. The carrier film
14
is pulled out from this carrier film roll
12
, and the surface of the carrier film
14
is coated with a ceramic slurry
18
by a coating apparatus
16
.
The carrier film
14
that is coated with the ceramic slurry
18
is sent to a drying apparatus
20
so that the ceramic slurry
18
is dried, after which the carrier film
14
is temporarily rolled up by a take-up apparatus
26
. Thus, a ceramic green sheet
22
is formed on the carrier film
14
. Next, the rolled-up carrier film is unrolled, and an internal electrode pattern constituting an internal electrode of the laminated ceramic capacitor is printed on the surface of the ceramic green sheet
22
by a printing apparatus
24
The carrier film
14
on which the internal electrode pattern is formed is dried by a drying apparatus
25
, and is then taken up in roll form again by the take-up apparatus
26
. Furthermore, instead of rolling up the carrier film
14
after the ceramic green sheet has been formed thereon, it is also be possible to continue to print an internal electrode pattern, dry the carrier film, and then roll up the film.
The rolled-up carrier film
14
is subsequently pulled out again, the ceramic green sheet
22
is cut to an appropriate size, and a plurality of the green sheets are laminated. The laminated body formed by laminating the ceramic green sheets
22
is cut into individual elements and fired, so that ceramic sintered bodies having internal electrodes are formed. Laminated ceramic capacitors are manufactured by forming external electrodes on the outer surfaces of the ceramic sintered bodies so that the external electrodes are connected to the internal electrodes.
With the recent trend toward more compact electronic devices, size reduction of laminated ceramic electronic components is required. Laminated ceramic capacitors, for example, are also becoming progressively smaller in size and larger in capacity. Accordingly, the number of layers in a ceramic sintered body is increased, and the thickness of the ceramic layers forming the ceramic sintered body is reduced. In general, however, unevenness inevitably exists on the surfaces of synthetic resin films used as carrier films to form ceramic green sheets. Because of such unevenness, recesses or pinholes may be locally produced in the thinned layers of ceramic green sheets. As a result, problems such as short-circuiting between internal electrodes and a decrease in reliability are encountered in the final product, such as a laminated ceramic capacitor. Thus, the carrier film becomes more susceptible to the effect of surface unevenness by the thinning of ceramic layers.
Therefore, it is necessary to reduce the effect of unevenness by suppressing unevenness on the carrier film surface as much as possible. Incidentally, when a film that is formed into a roll was used as the carrier film to be coated with a ceramic slurry, recesses and pinholes were locally present on the ceramic green sheet even though the surface thereof was made smooth.
As a result of diligent investigations in view of this fact, the present inventors discovered that these problems were caused by the effects of static electricity as described below. In the case of a carrier film roll, the contact area between the overlaid carrier films is increased, so that the carrier film tends to become charged with static electricity when the carrier film is pulled out, thus increasing the electrostatic charge caused by unrolling in this case. Furthermore, because the contact area between the carrier film and the ceramic green sheet is large, the carrier film is apt to be charged with static electricity when the ceramic green sheet is peeled off from the carrier film, which increases the electrostatic charge caused by peeling in this case. The amount of foreign matter mixed inside the ceramic green sheet or laminated body is increased due to the static electricity caused by such charging.
Moreover, a mold release layer or the like that is formed on the ceramic green sheet and carrier film deteriorates due to the discharge of the static electricity caused by charging, so that creases are produced in the ceramic green sheet during peeling. In particular, when the coating rate of the ceramic slurry is increased, because the pulling rate of the carrier film is also increased, the electrostatic charge caused by unrolling is increased, so that the effect of static electricity as described above is increased. As a result, problems such as short-circuiting between internal electrodes and a decrease in reliability occur in the final product such as a laminated ceramic capacitor.
Furthermore, a ceramic slurry is generally applied to the portions of the carrier film excluding both end portions thereof with respect to the direction of width. However, if the unevenness on the surface of the carrier film is reduced, the adhesion characteristics at both end portions are improved when these end portions of the carrier film in the width direction are superimposed during the take-up. Consequently, when the carrier film on which the ceramic green sheet is formed is taken up, air is introduced. If the introduced air escapes during the take-up operation of the carrier film, the roll is misaligned, which creates a problem in that the subsequent handling precision decreases significantly.
Furthermore, when thin ceramic green sheets are formed in order to achieve thinning of ceramic layers, variations in the thickness of the ceramic green sheet can be reduced by increasing the coating rate of the carrier film with the ceramic slurry. Moreover, increasing this coating rate of the ceramic slurry is an essential technique in terms of improving the productivity of laminated ceramic electronic components as well.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a method for manufacturing a laminated ceramic electronic component which makes it possible to obtain highly reliable laminated ceramic electronic components even when the coating rate of the surface of the carrier film with the ceramic slurry is increased in order to reduce the thickness of the ceramic green sheet.
According to a preferred embodiment of the present invention, a method for manufacturing a laminated ceramic electronic component includes the steps of pulling out a carrier film from a carrier film roll, coating one surface of the carrier film with a ceramic slurry at a coating rate of about 30 m/min or higher, forming a ceramic green sheet by drying the coated ceramic slurry, forming an internal electrode pattern on the ceramic green sheet, obtaining a laminated body by laminating a plurality of the ceramic green sheets on which the internal electrode patterns are formed, obtaining ceramic sintered bodies by cutting the laminated body into individual elements and firing the individual elements, and forming external electrodes on the outer surfaces of the ceramic sintered bodies, wherein the carrier film has a surface on which the ceramic slurry is coated in which the maximum height R
max
as defined in JIS B0601 is about 0.2 &mgr;m or less.
According to another preferred embodiment of the present invention, a method for manufacturing a laminated ceramic electronic
Ito Eiji
Katsuyama Takanobu
Omori Nagato
Yoneda Yasunobu
Keating & Bennett LLP
Mayes Melvin C.
Murata Manufacturing Co. Ltd.
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