JP2002037676A - Fixture for firing cermic electronics parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixture for firing a ceramic electronics parts having an improved durability by suppressing a reaction with a body to be fired. SOLUTION: A three layered structure is formed by one body forming. The structure has a base material consists of a refractory raw material of 85 wt.% silicon carbide and its both faces (inside and outside) consist of zirconia (yttoria stabilized zirconia or carcia stabilized zirconia) whose zirconia content is not less than 80 wt.%. The ratio of the thickness of the base material to both faces being 1:1 to 4:1 and the total thickness of which is not less than 5 mm and not more than 30 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0101]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jig used for firing ceramic electronic components.

[0092]

[Prior Art] Ferrite and ceramic capacitors,
When baking electronic components such as thermistors, baking jigs such as heat-shock saggers, shelves, and setters of mullite, cordierite, alumina, silicon carbide, etc. are generally used. ing. However, many ceramic electronic components such as ferrites are made of high-purity and highly reactive raw materials. If a firing jig containing a large amount of SiO2 is used, a reaction occurs with the SiO2 and the magnetic permeability decreases. The following disadvantages occur. Therefore, conventionally, a high-purity alumina setter is mounted on these thermal shock resistant firing jigs, or high-purity alumina is placed on the surface in contact with the object to be fired.
It is a method of coating hard-to-react materials such as magnesia and zirconia.
Saggers, shelves, setters, and the like having a zirconia-based coating layer in which cracking, peeling, and the like are prevented are disclosed as firing jigs. (For example, JP-A-63-217190 and JP-A-3-177383)

[0093]

However, the sagger,
When applying a coating of a hard-to-reactive substance on the surface of a shelf or a setter, apply the hard-to-reactive substance to the surface of the sagger, shelf, or setter once baked with a brush or a spray gun, and then dry and bake again. After treatment, the applied hard-to-react material must be baked on the surface of the sagger, shelf, or setter. At this time, due to the difference in the coefficient of thermal expansion between the base material of mullite, cordierite, alumina, silicon carbide, etc., and the coating layer of a non-reactive material such as high purity alumina, magnesia, zirconia, etc. As the coating proceeds, cracking and peeling of the coat tend to occur.

[0093]

SUMMARY OF THE INVENTION According to the present invention, a silicon carbide-based base material is formed by integrally molding three layers each having a zirconia (yttria-stabilized zirconia or calcia-stabilized zirconia) layer on both surfaces (front and back). This is a firing jig for firing ceramic electronic components, which has no reaction with the object to be fired and has a greatly improved durability.

[0056]

According to the present invention, there is provided a three-layer structure in which both sides (front and back) of a substrate made of 85% by weight or more of silicon carbide are made of zirconia (yttria-stabilized zirconia or calcia-stabilized zirconia) and have a zirconia content of 80% by weight or more. This is a ceramic electronic component firing jig having a structure formed by integral molding. The ratio of the thickness of the base material to the thickness of the double-sided layers (front and back layers) is from 1: 1 to 4: 1, and the total thickness is 5 mm or more.
mm or less (total thickness of front and back layers: 1 to 15 mm). When the thickness of the zirconia layer is less than this range, it is difficult for the zirconia layer to have a uniform thickness. As a result, the silicon carbide component moves to and is exposed to the zirconia-based layer, thereby contaminating the object to be fired. Conversely, if the zirconia layer is too thick, the zirconia material has a larger coefficient of thermal expansion than silicon carbide, so that the surface layer is easily peeled.

The use of silicon carbide for the base material is characterized by a higher hot strength in the temperature range in which ceramic capacitors and ferrite are fired than mullite and alumina. It can withstand the product load of the fired product and prevent the firing jig from warping even when used for a long time. In addition, the high thermal conductivity enables rapid firing, uniform firing of the product, and energy saving. The reason for using 85 wt% or more of silicon carbide for the base material is that when the silicon carbide content is less than 85 wt%, the strength of the base material is reduced, cracks and cracks are easily generated, and the product life is reduced by 20 to 50%. To do that. The reason that zirconia is used for the surface layer is
Since the reaction with the object to be fired is smaller than that of alumina or magnesia, the durability is improved and the product characteristics of the electronic component are improved. In addition, when unstable zirconia is used on both surfaces (front and back), the surface zirconia layer undergoes phase transition due to repeated use of hot, and the structural deterioration is accelerated. If the zirconia content is less than 80 wt%, the subcomponents of the zirconia layer move to the side of the object to be fired, and the product yield deteriorates.

007

EXAMPLES Examples are shown below to further clarify the features of the present invention.

Example 1 A three-layer shelf board having a silicon carbide content of a base material of 88% by weight and a zirconia (calcia stabilized) content on both sides (front and back) of 95% by weight was manufactured.
The apparent porosity of the three-layer shelf after firing is 18.5%,
The hot bending strength at a bulk specific gravity of 3.22 and 1300 ° C. was 11.5 MPa. The three-layer shelf was subjected to a pusher-type continuous ferrite firing furnace, and the shelf was stacked on a mullite base plate using a three-point support. When the base materials of the ferrite cores were arranged in a line on the shelf plate and fired, no abnormality was observed in any of the stages even after the furnace was passed 100 times. No reaction such as abnormal grain growth was observed in the ferrite core itself.

Example 2 Zirconia on Both Sides (front and back) with Silicon Carbide Content of 88% by Weight of Base Material (Yttria Stabilized)
A three-layer shelf with a content of 89% by weight was produced. The apparent porosity of the three-layer shelf after firing is 19.5%, the bulk specific gravity is 3.22, and the hot bending strength at 1300 ° C. is 10.
It was 5 MPa. The same ferrite sintering furnace and shelving as in Example 1 was performed. When the ferrite core bodies were arranged in a line on the shelf plate and fired, no abnormality was found in any of the stages even after the furnace was repeatedly passed 100 times. No reaction such as abnormal grain growth was observed in the ferrite core itself.

[0102]

COMPARATIVE EXAMPLE 1 A base material having a silicon carbide content of 80% by weight, a zirconia (yttria stabilized) content of 89% by weight on both sides (front and back) was 300 × 300 × 12 mm, and the thickness of both sides (front and back) was A 2.5 mm-thick three-layer shelf board was manufactured, and the same firing furnace and shelf assembly as in Example 1 were performed.
When the ferrite core was placed on this shelf and baked, the furnace was repeatedly passed 50 times. As a result, the initial warp was 0.11 mm to 0.33 mm diagonally, but the warp was diagonal. It increased from 1.54 mm to 2.36 mm.
No reaction such as abnormal grain growth was observed in the ferrite core itself.

[0111]

Comparative Example 2 The silicon carbide content of the substrate was 88% by weight, and the zirconia (magnesia stabilized) content on both sides (front and back) was 9
A three-layer shelf board of 3% by weight of 300 × 300 × 12 mm and a thickness of both sides (front and back) of 2.5 mm was manufactured, and the same firing furnace and shelf assembly as in Example 1 were performed.
When the ferrite core was placed on this shelf and baked, the furnace was repeatedly passed through 20 times. As a result, the rate of structural deterioration was higher than that of yttria-stabilized zirconia or calcia-stabilized zirconia. (Yttria stabilized zirconia degradation rate: 8.0% Calcia stabilized zirconia degradation rate:
8.5% Magnesia stabilized zirconia Deterioration rate: 14.
(5%) In addition, the yield of the ferrite core itself was adversely affected.

[0122]

Comparative Example 3 300 × 300 having a base material having a silicon carbide content of 88% by weight and both sides (front and back) having an alumina content of 99%.
× 12mm, both sides (front and back) thickness 2.5mm
Was manufactured, and the same sintering furnace and shelf assembly as in Example 1 were performed. When the ferrite core was placed on this shelf plate and baked, the furnace was repeatedly passed five times.
As a result of passing the furnace repeatedly 0 times, cracks entered the alumina layer on the surface, and partial peeling was observed.

[0113]

As described above, according to the present invention, a three-layer structure composed of a zirconia (yttria-stabilized zirconia or calcia-stabilized zirconia) layer on both sides (front and back) of a substrate made of silicon carbide is formed by integral molding. By molding and firing at once, there is no reaction with the object to be fired, and the durability can be greatly improved.

[0141]

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a three-layer shelf board according to a second embodiment of the present invention.

[Explanation of symbols]

1. 1. Yttria-stabilized zirconia or calcia-stabilized zirconia surface layer Silicon carbide substrate

Claims (3)

[Claims] 1. A base material is a silicon carbide refractory having a SiC content of 85 wt% or more, and both surfaces (front and back) of the base material are stabilized zirconia (a yttria-stabilized zirconia or calcia stable) having a ZrO 2 content of not less than 80 wt% and not more than 98 wt%. Zirconia), a jig for firing three-layer electronic components. 2. The silicon carbide refractory of the base material and both sides (front and back)
The electronic component firing jig according to claim 1, wherein the stabilized zirconia layer is integrally formed. 3. The thickness ratio of the base material to the double-sided layer (surface layer) is 1: 1 to 4: 1, and the total thickness is 5 mm to 30 m.
3. The jig for firing a ceramic electronic component according to claim 1, wherein the diameter is not more than m.