Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2000-01-20
2001-08-28
Lam, Cathy (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C174S258000, C501S032000, C501S066000, C501S077000
Reexamination Certificate
active
06280829
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a ceramic composition for use in forming electronic components such as a chip type resistor, a thin film inductor, a thin film capacitor or a circuit board; and, more particularly, to a ceramic composition most suitable for use in forming a chip type electronic component or a circuit board on a ceramic substrate.
DESCRIPTION OF THE PRIOR ART
An alumina substrate or a glass-based insulating ceramic material having Al
2
O
3
and SiO
2
as its main components have been conventionally used as an insulating ceramic material used in manufacturing electronic components such as a chip type resistor, a thin film inductor, a thin film capacitor or a circuit board. The ceramic material is obtained by first dispersing ceramic raw materials such as SiO
2
, Al
2
O
3
, B
2
O
3
, CaO, MgO, or the like in powdery forms and a binder component in a solvent, forming the same in a sheet form, and finally sintering the same.
For example, a chip type resistor is manufactured using the following steps: First an electrode pattern using a conductive paste such as a silver paste in printed on an alumina substrate or a glass-based insulating ceramic substrate obtained via the process as described above, and then a baking is performed thereto to form electrodes between a pair of resistor layers, which are so called “embedded electrodes”. Next, a resistor paste having RuO
2
as its main component is applied to the embedded electrodes and a backing is performed to form the resistor. Further, an under glass is applied on the resistor layer, a baking being performed thereafter, and a laser trimming is performed to the resistor layer to control the resistance between the embedded electrodes. Next, an over glass is applied thereon and a baking is performed to form an overcoat layer. Next, the ceramic substrate is divided into individual chips. The individual chips are subjected to a barrel grinding. Finally, a conductive paste, e.g., sliver paste, is printed on both ends of the chip and a nickel gilt or solder gilt is performed on the conductive paste layer to form external electrodes. Through these steps, the chip resistor is obtained.
As described above, in the conventional method, the chip type electronic component such as the chip type resistor using the alumina substrate and the glass-based insulating ceramic material is obtained by dicing a sintered ceramic substrate. For this reason, burrs or cracks may form within or on the chip and the shape thereof may get distorted. Further, a dimensional accuracy of the chip may not be attained.
The chip type electronic components of a lower dimensional accuracy having burrs or cracks therein as described above are not suitable for a so-called mass loading process wherein a number of electronic components kept in a hopper or the like are subjected to a mass transfer through a pipe-shaped shoot to a predetermined destination on the circuit board to be loaded thereon. For this reason, such chip type electronic components are normally supplied in such a manner that the chip type electronic components are received on a carrier type, with each of the components being separated from one another at a same distance and a cover tape being laminated on the carrier tape. Accordingly, the chip type electronic components are loaded on the circuit board using so-called tapping loading process, wherein the chip type electronic components are taken out from the carrier tape after the cover sheet has been removed. This process is so-called tapping loading process.
In case of the tapping loading process, however, since the chip type electronic components are packed on the carrier tape at a predetermined distance therebetween, packing costs additionally incur. Further, it is cumbersome to remove the cover sheet from the carrier tape one by one and to take out individually the chip type electronic component from the carrier tape for the loading process. Furthermore, the tapping loading process are not suitable for a multi mounting method wherein a number of various kinds of electronic components are concurrently transferred to a template and then concurrently loaded on the circuit board by using suction heads.
SUMMARY OF THE INVENTION
It is, therefore, a primary object of the invention to provide a ceramic material capable of allowing a ceramic substrate made thereof to be cut by a grinding machining using a cutter, in stead of breaking means, to thereby provide chip type electronic components having an enhanced dimensional accuracy and reduced number of burrs or cracks therein, making them suitable for a mass transfer.
The above and other objects of the invention are accomplished by providing a ceramic composition obtained in such a manner that a proper amount of at least one component selected from a group of MgSiO
3
and CaSiO
3
is added to a glass-based ceramic having a properly determined composition ratio, with a sintered state thereof having at least 1500 kg/cm
2
as its anti-bending strength. By using the sintered ceramic substrate obtained from the ceramic composition, electronic components such as a chip type resistor, a thin film inductor, a thin film capacitor or a circuit board are obtained. Since the ceramic substrate constituting the electronic component as a base material has a good grindability, the electronic components can be separated into a plurality of individual chips by a grinding machining without an inadvertent break of the ceramic substrate. Further, it is possible to prevent the electronic component from being broken during a loading process.
The inventive ceramic composition for use in forming the electronic components is a ceramic composition including a glass based material including SiO
2
, Al
2
O
3
, B
2
O
3
, and at least one selected from a group of Cao and MgO; and particles dispersed in the glass based material, the particles including CaSiO
3
or MgSiO
3
as a main component, wherein a sintered state of the ceramic composition has an anti-bending strength of 1500 kg/cm
2
or higher. To be more specific, the inventive ceramic composition has less than or equal to 70 weight % of a glass based material and more than or equal to 30 weight % of the particles, the glass based material including 25-60 weight % SiO
2
, 5-25 weight % Al
2
O
3
, and 5-25 weight % B
2
O
3
, and at least 5-30 weight % of one selected from a group of MgO and CaO, and the particles including MgSiO
3
or CaSiO
3
.
MgSiO
3
or CaSiO
3
particles are, for example, filler components charged within the glass based material and are dispersed in the glass based material.
A ceramic material sintered in accordance with the present invention is obtained by a conventional forming method, wherein a green ceramic material is first formed using the ceramic composition described above and then is sintered. The anti-bending strength of the sintered ceramic material is 1500 kg/cm
2
or greater. Further, the inventive electronic component has a pattern made of a conductive material, a dielectric material, a magnetic material or a resisting material formed on the ceramic substrate of the sintered ceramic material as described above.
In the sintered ceramic material obtained from the inventive ceramic composition in forming the electronic components, at least one selected from the group of MgSiO
3
and CaSiO
3
is dispersed as a filler component. As compared with a material without MgSiO
3
or CaSiO
3
present therein, the inventive sintered ceramic material has an increased grindability, allowing the ceramic substrate to be divided into a plurality of chips. As a result, a chip type electronic component having a higher dimensional accuracy can be obtained.
Further, since boring for forming a through-hole can be performed to the ceramic substrate in a sintered state, it is possible to obtain an electronic component having the through-hole with a higher accuracy without a dimensional error which may be caused by a contraction during the sintering.
Furthermore, since the anti-bending strength of the sintered ceramic body is 1500 kg/cm
2
or gr
Amano Takashi
Kawamura Keizo
Suzuki Tetsuyuki
Lam Cathy
Rosenman & Colin, LLP.
Taiyo Yuden Co. Ltd.
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