JPS6045151B2 - How to fire ceramics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for firing ceramics, and particularly to a method for firing ceramic molded bodies for electronic components.

Generally, when firing ceramics, ceramic materials molded into a predetermined shape, that is, ceramic molded bodies, are arranged in a sagger pot with zirconia powder sprinkled between them so that they do not touch each other, and then stacked in multiple tiers on a base plate. A commonly used method is to place the materials on a furnace and pass them through a tunnel-type firing furnace such as an electric furnace or a gas furnace for firing. However, with this method, the saggers and base plate are heated and cooled rapidly, making them susceptible to cracking due to thermal shock.It is therefore difficult to increase the firing rate and requires a long time, approximately one hour at the earliest. The heat loss due to the plates is large, and since the saggers are stacked in multiple tiers, the firing temperature varies between the upper, middle, and lower tiers. To prevent this, it is necessary to increase the soaking length of the baking zone. Therefore, there were problems such as the need for a large area. The present invention was made with the aim of solving the above problems, and its gist is that a ceramic material formed into a predetermined shape is placed in a rotary firing furnace together with powder of a chemically inert substance. There is a method for firing ceramics, which is characterized in that the ceramic material and powder are supplied and heated and fired while moving the ceramic material and powder from one end to the other end by rotating the firing furnace.

In a preferred embodiment, the chemically inert material powder is a material that has a high melting point and does not react with the ceramic material, such as zirconium oxide, silica, alumina, spinel, magnesia, silica nitride, silicon carbide, boron nitride, etc. metal oxide powders are used.

The ratio of ceramic molded product and powder is not particularly limited, but
In one preferred embodiment, the weight ratio is 1 x 3 (molded product: powder). Further, it is preferable to use a porous firing furnace made of mullite or alumina, which is less likely to soften or deform under hot conditions and is resistant to thermal shock.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention will now be described with reference to the accompanying drawings, which illustrate an example of the apparatus used to carry out the method. The illustrated firing furnace has a fired body supply port 1 for supplying a ceramic molded body and powder at one end, and a molded body discharge port 2 for discharging the fired ceramic molded body at the other end. It is composed of a cylindrical main body 3, a heater 4 that heats the main body 3, and a drive mechanism 5 that rotationally drives the main body 3.

The main body 3 is connected to the main body 3 via sleeves 6 provided externally near both ends thereof.
0.5 to three pairs of rollers 8 disposed on the base 7.
The roller 8 is placed at an inclination angle θ of 5 degrees and is driven by a motor 9 that rotates a roller 8 that engages with a sleeve 6 provided externally at the end on the side of the product supply port. A heat insulator 10 made of a heat insulating material is attached to the base 7, surrounding the central portion of the main body 3 and accommodating a heater 4 such as a SiC heating element, a metal heating element, or a gas burner. A helical blade 11 is provided inside the main body on the side of the supply port for the object to be fired, for advancing the ceramic molded body or the like toward the discharge port. During operation, the main body 3 rotates and is simultaneously heated by the heat source 4, and the ceramic Zug molded body and chemically inert material powder are supplied to the firing object supply port 1 by a chute 12 such as a hopper feeder, a vibration feeder, or other means.

The ceramic molded body is heated and fired while being rotated along with the powder toward the fired product discharge port 2 within the main body which rotates at a low speed. After being fired, the ceramic molded body is received in a receiver 14 through a chute 13 from the fired body discharge port 2. According to the method of the present invention as described above, since no saggers or base plates are used, heat loss can be reduced and thermal efficiency can be increased, and energy savings can be reduced to approximately 1/2 compared to the conventional method. In addition, since the ceramic molded body is heated together with the chemically inert material powder, uniform heating is possible, reducing variations in product properties, and reducing the firing time to 1/5th to 1/2 of the conventional method. It is possible to shorten the time to about 1, and at the same time, it is possible to downsize the three firing furnaces. Furthermore, unlike the conventional process of filling and taking out the saggers, it is no longer necessary, so the molding process and the firing process can be made continuous, and work efficiency can be improved. Example 14 A square plate unit for a multilayer capacitor having a length of 3 TWL and a thickness of 1 T0n was formed using a barium titanate ceramic material by a conventional method, and 120 (1) units of this unit were formed using the illustrated apparatus under the following conditions. Fired.

Inclination angle of furnace body: 1 degree Rotation speed of furnace body: 0.5 rpm Heat source: Electric heater Chemically inert material: ZrO2 Inert material supply amount: 5 m1/min Unit supply rate: 2 drums/min Firing temperature The 1290° C. unit passed through the furnace in about 4 hours and was completely fired, with no abnormalities observed in appearance and no rounded corners.

When a multilayer capacitor was manufactured by attaching electrodes to this firing unit, its capacitance was 3900 pF, and the variation was 1.5% in terms of coefficient of variation. Example 2 Square plate unit for TC type multilayer capacitor (5T0n×2
．． 5 gourds x 1 gourd) were baked in the same manner as in Example 1 under the following conditions.

Inclination angle of furnace body: 1 degree Rotation speed of furnace body: 0.5 rpm Chemically inert material: ZrO2 Inert material supply amount: 10 m1/min Unit supply rate: 2 (4) pieces/min Firing temperature: 11700C The unit is The entire amount passed through the furnace in about 3 hours and was completely fired.

Furthermore, no abnormalities such as missing corners or rounding were observed in the external appearance. When electrodes were attached to the fired unit to create a capacitor, the capacitance was 3600 pF and the variation was 1.6% when expressed as a coefficient of variation. Example 3 A disc-shaped unit for a barium titanate positive temperature coefficient thermistor (diameter 6Tm!n, thickness 5Tfrfn) was fired using the same apparatus as in Example 1 under the same conditions except that the firing temperature was 1300°C.

The entire amount passed through the unit in about 2.5 to 3 hours, but it was completely fired and turned into a semiconductor.

When I attached an electrode and measured the resistance at room temperature, it was 30Ω.
It was hot.

[Brief explanation of the drawing]

The figure is a schematic sectional view showing an example of a firing furnace used for carrying out the method of the present invention. 1 - Sintered object supply port, 2 - Sintered object discharge port, 3 - Firing furnace main body, 4 - Heater.

Claims (1)

[Claims] 1. A ceramic material formed into a predetermined shape is fed into a rotary firing furnace together with a chemically inert material powder, and by rotating the firing furnace, the ceramic material is transferred from one end to the other end. and a ceramic firing method characterized by heating and firing while moving powder. 2. The chemically inert material powder is a metal oxide powder selected from the group consisting of zirconium oxide, silica, alumina, spinel, magnesia, silicon nitride, silicon carbide, and boron nitride. Method. 3. The method according to claim 1, wherein the firing furnace body is made of mullite or alumina. 4. The method according to claim 3, wherein the firing furnace body is porous.