JP2720199B2 - Ceramic substrate firing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for firing a ceramic substrate, such as a dielectric substrate for forming a capacitor, obtained by firing a ceramic green sheet.

(Prior art)

As electronic components have become smaller and more complex, there has been an increasing demand for dielectric substrates and the like for obtaining functional components by mounting various chip components.

A ceramic substrate such as a dielectric substrate is obtained by adding a binder or the like to a metal oxide powder, forming a green sheet by a method such as a doctor blade, and firing.

In order to increase the productivity of firing, it is desirable to stack the sheets in multiple stages and fire them at the same time, but in this case, the substrate is likely to warp or stick. When firing in multiple layers, firing is performed by stacking through a spreading powder. However, since traces of the spreading powder remain on the substrate, it cannot be used for firing a dense substrate.

In addition, post-processing or the like for correcting the warp is required.

〔Task〕

The present invention provides a method of firing a ceramic substrate that can be stacked and fired in multiple stages without using a litter.

In addition, it is intended to improve not only physical characteristics such as warpage but also characteristics affecting electrical characteristics such as crystallinity.

[Means for solving the problem]

The present invention solves the above-mentioned problem by performing primary firing at a low temperature and then performing main firing at a predetermined temperature using a setter having low reactivity.

That is, after stacking ceramic green sheets in multiple stages and firing at a temperature lower than a predetermined firing temperature, the ceramic substrates are alternately stacked with a less reactive setter, stacked in multiple stages, and fired at a predetermined firing temperature. It is characterized by the following.

Further, after the ceramic green sheets are stacked in multiple stages and fired at a temperature lower than a predetermined firing temperature, the ceramic substrate is fired at a temperature higher than the predetermined firing temperature with a sheet having the same composition as the ceramic substrate. The method is characterized in that the obtained setters are alternately stacked, stacked in multiple stages, and fired at a predetermined firing temperature.

[Action]

By using a setter having low reactivity, diffusion of the constituent elements during firing is prevented, and electrical characteristics can be stabilized.

Also, on the crystalline surface, the crystal grains on the surface grow uniformly,
It was confirmed that densification was achieved.

〔Example〕

 Hereinafter, examples of the present invention will be described.

As a material, SrTiO ₃ -CaTi used for capacitors
An O-shaped dielectric ceramic was used, and a ceramic green sheet for a dielectric substrate having a thickness of 0.3 to 0.5 mm was used.

First, lower than the original firing temperature of 1300-1350 ° C
It was baked at 1240 ° C. for about 2 hours. The firing was performed by stacking 20 sheets as they were. When this temperature was set to 1230 ° C., sticking occurred in the next main firing. As described above, the primary sintering temperature is a temperature at which the binder is sintered and the sintering is performed to such an extent that handling is possible, and a lower temperature than the main sintering is required.

Subsequently, as shown in FIG. 1, the primary-baked substrates 11 and the setters 12 were alternately overlapped with each other and were finally baked at 1300 ° C. As the setter 12, a flat plate having a thickness of 0.5 to 1.0 mm and made of 99% high-purity alumina having a smooth surface was used.

As a result, a dielectric substrate having a flat and smooth surface was obtained.

In addition, as a setter, a sheet having the same composition as the dielectric material is fired at 1350 ° C., which is higher than the temperature of the main firing, and a dielectric having a flat and smooth surface is similarly used by using a polished and flattened substrate. A substrate was obtained.

The warpage of the dielectric substrate obtained according to the present invention was measured as follows. Warpage per 2mm is 3 on average
According to the present invention, 3 μ and 53 μ at the maximum were 9 μ and 16 μ at the maximum (10 samples) according to the present invention.

Also, when examining the surface crystal grain size, the starting material
When a 99% pure alumina substrate setter was used, the particle size was 3-4 μm. Also,
When a setter of the same composition material was used, the particle size was 2-3 μm. For comparison, when an alumina substrate having a purity of 97% is used, the value is 3 to 10 μ, and a setter having the same composition,
Alternatively, when a high-purity alumina substrate is used, abnormal growth of the crystal is suppressed, and the crystal becomes uniform and dense. as a result,
The surface roughness of the substrate is Rmax = 1μ (Rm for 97% alumina substrate)
ax = 5μ).

In the electrical characteristics, when a 97% alumina substrate was used as a setter, ε = 270 and tan δ = 0.12%. However, when a 99% high-purity alumina setter was used, ε = 30.
0, it was confirmed that tan δ was improved to 0.05%.

〔effect〕

According to the present invention, it is possible to prevent the occurrence of warpage and sticking during firing, and furthermore, since a large number of substrates can be fired simultaneously, the productivity can be greatly improved.

Further, since diffusion to the setter can be prevented, electrical characteristics can be improved.

Furthermore, since the crystal can be densified, the crystallinity is also greatly improved.

[Brief description of the drawings]

 FIG. 1 is a front view showing an embodiment of the present invention. 11 …… Ceramic substrate 12 …… Setter

Claims (3)

(57) [Claims] 1. After laminating ceramic green sheets in multiple stages and firing at a temperature lower than a predetermined firing temperature, the ceramic substrates are alternately stacked with setters having low reactivity, laminated in multiple stages, and stacked at a predetermined firing temperature. A method for firing a ceramic substrate, comprising firing. 2. The method according to claim 1, wherein said setter is a high-purity alumina substrate. 3. A ceramic green sheet is stacked in multiple stages and fired at a temperature lower than a predetermined firing temperature, and the ceramic substrate is fired at a temperature higher than the predetermined firing temperature with a sheet having the same composition as the ceramic substrate. A ceramic substrate, which is alternately stacked with the setter obtained in this manner, stacked in multiple stages, and fired at a predetermined firing temperature.