Setter for burning

Details Setter for burning Setter for burning

2001-10-02

2004-03-16

Wilson, Gregory (Department: 1772)

Heating

Accessory means for holding, shielding or supporting work...

Openwork tray, basket, or grid structure for heat treating...

C428S116000, C264S630000

Reexamination Certificate

active

06705860

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a setter for burning, on which ceramic electronic parts are placed in a furnace when these ceramic electronic parts such as ceramic substrates and the like are burned, and particularly to a technique effective in suppressing each warp of multi-layer ceramic electronic parts burned.
In Japanese Patent Laid-open No. 2-74567, such a structure has been disclosed that since friction against a setter causes drawbacks of dispersion in the shrinkage rate and cracks and the like of a ceramic substrate in a process of burning the ceramic substrate, the ceramic substrate is floated by air during burning in order to prevent such drawbacks from be caused.
In such the structure, a microporous setter is always placed on an air intake auxiliary setter provided with air intake holes. Under this condition, the ceramic substrate is placed on the microporous setter and burned. During burning, air is supplied from the air intake holes of the air intake auxiliary setter and blows from micro-holes of the microporous setter toward a lower surface of the ceramic substrate and thereby causes the ceramic substrate to be floated.
In this structure, since the ceramic substrate is made apart from the setter during burning, the drawbacks such as shrinkage, cracks and the like of the ceramic substrate in burning are greatly suppressed, which have arisen previously.
In Japanese Patent Laid-open No. 11-79853, such a means is disclosed as to prevent contamination of burned products, which is caused by contact failure between the burned products and a setter during burning of electric material parts such as ceramic multi-layers or the like, and to prevent occurrence of inferior goods caused by adhesion between the burned products and the setter.
The above-mentioned means discloses a tape-forming method using a doctor blade method or the like so as to be able to manufacture thin setters by utilizing slurry, and the cited reference discloses a structure of the thin setter whose thickness is set to be 0.2 to 2 mm from a tape-forming point of view. The setter discloses a structure in which independent through holes are provided by a method like punching or the like of each contact surface between the burned products and the setter in order to be able to situate electric material parts such as ceramic substrates in nearly point contact manner. The setter is formed in a thin mesh shape, in which opening portions piercing a thin plate are provided.
From a point contact point of view, there is description in which one of the independent through holes has preferably an opening area set to be within a range of 0.07 to 36 mm
2
. It is also described that each opening ratio of the through holes is preferably within a range of 10 to 60% from a viewpoint of adhesive possibility between the setter and each through hole and of facility of a process of punching the through holes. Further, it is described that sintered density of the setter is set to be preferably 95% or more from a viewpoint of the strength the setter.
Japanese Patent Laid-open No. 5-270926 discloses a manufacture of lightweight setters having small thermal capacity by vesicating and hardening in a mold a mixture adding a polyurethane foam raw material to a mixture made of a ceramic powder and water, and thereafter by burning the mixture.
However, such a problem is pointed out that if ceramic electronic parts such as ceramic substrates and the like are situated on the setter having the above-mentioned structure and are burned, then characteristics of the ceramic electronic parts are deteriorated. As a means for solving the problem, from a viewpoint of replacement facility of peripheral atmospheres surrounding ceramic molds, the strength thereof and the like, it is disclosed that each ceramic mold is provided with one to ten through holes per 1 cm
2
of each placement area thereof.
Japanese Patent Laid-open No. 6-281359 discloses such a structure that a setter on which each of electric material parts such as ceramic substrates and the like are situated and burned is provided with an uneven surface placement portion for situating the electric material parts such as ceramic substrates.
Japanese Patent Laid-open No. 5-267010 discloses a structure of a pot, which is used during manufacture of voltage nonlinear resistance members primarily containing zinc oxide, composed of a pot body provided with an opening portion therein and a separate porous plate setter provided on this opening portion. Therefore, the cited reference discloses that, even in the case where a plurality of pots formed by situating the voltage nonlinear resistance members on the porous plate setter is piled up in a furnace and is burned, dispersion of a varistor characteristic greatly affected by a burning atmosphere is decreased by making the burning atmosphere per pot as uniform as possible.
SUMMARY OF THE INVENTION
As mentioned above, various structures have been proposed about a ceramic setter for putting the ceramic electronic parts in a furnace, in order to suppress the occurrence of warp or the like of the ceramic electronic parts burned to the utmost. However, at present, the warp problem of the burned ceramic electronic parts has not been sufficiently solved yet. For example, although solution of the warp problem is effectively improved by making the opening ratio increase, the strength of the setter is lowered and if heat and cool treatment is repeatedly performed in the furnace, it is easy for the setter itself to warp. This is reflected to each quality of the ceramic electronic parts resultantly.
The ceramic setter is preferably considered to be burned without having an interaction between the ceramic setter and the ceramic electronic parts situated thereon, that is, giving any affect to the ceramic electronic parts. It is preferable that the ceramic electronic parts are simply situated so that burning behavior such as shrinkage based on the characteristics proper to the ceramic electronic parts is executed.
An object of the present invention is to provide a setter for burning, which can ensure the burning behavior based on characteristics proper to ceramic electronic parts, particularly, ceramic electronic parts having a multi-layer structure such as chip condensers, high frequency module parts and the like.
The above-mentioned and other objects and novel characteristics of the present invention will be apparent from the description of this specification and the accompanied drawings.
When the present inventors develop satisfactorily ideal setters for burning, they have observed in detail each warp amount of ceramic electronic parts burned by utilizing both a conventionally used typical setter for burning and a satisfactorily ideal one. And the inventors have tried to solve problems based on observed results.
Additionally, the inventors have thought that, in a relation between the setter for burning and the ceramic electronic part situated thereon, it is necessary to determine what evaluation standards the proper setter for burning should satisfy.
According to conventional evaluation standards, it is ideal that the warp amount of the burned ceramic electronic part is zero, and the validity of a ceramic setter is determined in comparison with the magnitude of each warp amount at a zero standard. However, the inventors have thought that it is necessary to determine the warp amount by using as a standard such a state that the ceramic electronic part is burned without being affected from the setter.
This is taken up as a large problem of a warp caused after the conventional ceramic electronic part is burned, and various proposals have been made, for example, by an improvement or the like in electroconductive paste as problems of the ceramic electronic part itself.
However, even if technology capable of achieving the warp state of zero in the burned ceramic electronic part itself is developed, in the case where the warp of the ceramic electronic part burned is caused by being affected from the setter at a burning stage thereof like

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