JP2011121807A - Method for producing alumina sintered compact - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an alumina sintered compact having a small dielectric loss if the alkali metal oxide in an alumina raw material is ≤0.1 wt.%. <P>SOLUTION: The method for producing the alumina sintered compact comprises the steps of: mixing alumina raw material powder containing ≥99.4 wt.% Al<SB>2</SB>O<SB>3</SB>and ≤0.1 wt.% alkali metal oxide, a sintering aid, a binder, a plasticizer and a solvent to form slurry; compacting the slurry to form an alumina compact; and placing the alumina compact on a setter of an alumina-made refractory containing 85.0-97.5 wt.% Al<SB>2</SB>O<SB>3</SB>and 2.5-15.0 wt.% SiO<SB>2</SB>and firing the placed alumina compact. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing an alumina sintered body used for a submount of a photodiode or a laser diode, a circuit board for a transceiver, or the like.

Alumina sintered bodies used for photodiodes, laser diode submounts, transceiver circuit boards, and the like are required to have a dielectric loss (tan δ) of 1 × 10 ⁻⁴ or less. Such an alumina sintered body is manufactured by adding a sintering aid, a binder, a plasticizer, and a solvent to an alumina raw material powder, forming the green sheet by a doctor blade method, and firing it.

  If the alumina-based sintered body contains a large amount of alkali metals such as Na and K as impurities, the dielectric loss increases remarkably, so that the alkali component content in the sintered body needs to be reduced as much as possible. The cause of the large amount of alkali metal is considered to be contained in the original alumina raw material powder, and in order to avoid this, Patent Document 1 describes that the impurity content is in ppm on an element basis. An alumina ceramic composition is disclosed in which Si80 or less, Mg60 or less, Si / Mg is 1 to 5, and other metals, alkali components, etc. are one element 60 or less and the total amount 70 or less.

  As another cause of the presence of a large amount of alkali metal in the sintered body, if the setter contains a large amount of subcomponents such as an alkali component in the step of placing and firing the molded body on a setter, the subcomponent is alumina It can be considered to move to the molded body. For this reason, the high purity setter whose alumina purity is 99.9% or more was used so that the alkali component contained in the setter was reduced as much as possible.

JP-A-1-213910

In the alumina sintered body disclosed in Patent Document 1, it is necessary to reduce the amount of alkali metal oxides and impurities in the alumina raw material and to make the alumina raw material highly purified. there were. In addition, if a high-purity setter having an alumina purity of 99.9% is used, the alkali component can be prevented from moving from the setter to the ceramic molded body, but the alkali component originally contained in the alumina molded body can be reduced. There wasn't.

  The present invention has been made in view of the problems of the above-mentioned conventional method for producing an alumina sintered body, and the object thereof is to provide a dielectric if the alkali metal oxide in the alumina raw material is 0.1% by weight or less. An object of the present invention is to provide a method capable of producing an alumina sintered body with low loss.

As a result of experimenting by changing various components contained in the setter, the present inventor found that the SiO ₂ component contained in the setter has an action of absorbing the alkali component of the alumina molded body in the step of firing the alumina molded body. The invention has been completed.
That is, the method for producing an alumina sintered body of the present invention comprises an alumina raw material powder containing 99.4% by weight or more of Al ₂ O ₃ and 0.1% by weight or less of an alkali metal oxide, a sintering aid and a binder A step of mixing a plasticizer and a solvent to form a slurry;
Forming the slurry to form an alumina molded body;
Wherein placing the alumina compact, the _Al 2 _{O 3} 85.0 wt% to 97.5 wt%, on a setter made of alumina refractories containing SiO ₂ 2.5 wt% to 15.0 wt% And a method for producing an alumina sintered body, comprising a step of firing.
Here, the alumina (Al ₂ O ₃ ) content in the alumina raw material is preferably 99.4% by weight or more. When the alumina content is less than 99.4% by weight, the secondary component in the alumina raw material increases and the alkali metal oxide increases, so the setter cannot fully absorb the alkali component in the alumina molded body and the dielectric loss of the alumina sintered body Can not be lowered sufficiently.
Examples of the alkali metal oxide in the alumina raw material include Na ₂ O and K ₂ O. The content of the alkali metal oxide in the alumina raw material is preferably 0.1% by weight or less. If the amount of the alkali metal oxide exceeds 0.1% by weight, the setter cannot fully absorb the alkali component in the alumina molded body, and the dielectric loss of the alumina sintered body cannot be sufficiently reduced.
The alumina raw material may contain a small amount of impurities such as Fe ₂ O ₃ .
The setter has a SiO ₂ content ranging from 2.5 wt% to 15.0 wt%. If the SiO ₂ content is less than 2.5% by weight, the alkali component in the alumina molded body cannot be sufficiently absorbed and the dielectric loss of the alumina sintered body cannot be sufficiently reduced. When the SiO ₂ content is more than 15.0% by weight, the strength of the setter becomes weak.
The setter may contain a small amount of impurities such as Fe ₂ O ₃ and Na ₂ O.
The alumina molded body is fired at a temperature of 1620 ° C. to 1630 ° C. in an air atmosphere.

According to the present invention, since the SiO ₂ in the setter absorbs the alkali component in the alumina molded body, an alumina sintered body having a small dielectric loss can be produced.

It is an X-ray data of the alumina sintered compact which concerns on the Example of this invention, and a comparative example.

Example Sintering aid for alumina raw material containing 0.04 wt% Na ₂ O, 0.1 wt% MgO, 0.05 wt% SiO ₂ and 0.01 wt% Fe ₂ O ₃ A mixed powder, binder, plasticizer and solvent added with 0.17% by weight of MgO as an outer shell were mixed in a ball mill to prepare a slurry. The obtained slurry was formed into a film by a doctor blade method and dried to prepare a green sheet having a thickness of 400 μm. Two green sheets were laminated to form a laminate. Next, seven types of setters shown in Table 1 were prepared, and the laminate was placed on each setter, and the laminate was fired at 1625 ° C. in an air atmosphere to obtain an alumina sintered body. Tan δ of the obtained alumina sintered body was measured by a 10 GHz cavity resonance method shown in JIS R 1641, and the results shown in Table 1 were obtained.
As shown in Table 1, the tan δ of the alumina sintered body fired with the setters of Examples 1 to 5 containing 2.5% by weight or more of SiO ₂ was 1 × 10 ⁻⁴ or less, while containing SiO _2. The tan δ of the alumina sintered body fired with the setters of Comparative Examples 1 and 2 whose amount was less than 2.5% by weight was large.

Next, X-ray data of the alumina sintered bodies obtained in Example 1, Comparative Example 1 and Comparative Example 2 were measured. The results are shown in FIG. As shown in FIG. 1, the X-ray data of the alumina sintered body fired by the setter of Comparative Example 1 containing almost no SiO ₂ shows the Na compound (Na ₂ O) (MgO) ₄ (Al ₂ O ₃ ) ₁₅ The peak was out. Also, the peak of (Na ₂ O) (MgO) ₄ (Al ₂ O ₃ ) ₁₅ is slightly observed in the X-ray data of the alumina sintered body fired with the setter of Comparative Example 2 containing 1.0% by weight of SiO _2. I was out. On the other hand, the X-ray data of the alumina sintered body fired by the setter of Example 1 containing 2.5% by weight of SiO ₂ includes (Na ₂ O) (MgO) ₄ (Al ₂ O ₃ ) ₁₅ No peak appeared. From this, it is inferred that SiO ₂ in the setter absorbed the alkali component of the alumina molded body.

Claims (1)

A step of forming a slurry by mixing alumina raw material powder containing 99.4 wt% or more Al ₂ O ₃ and 0.1 wt% or less alkali metal oxide, a sintering aid, a binder, a plasticizer, and a solvent; ,
Forming the slurry to form an alumina molded body;
Wherein placing the alumina compact, the _Al 2 _{O 3} 85.0 wt% to 97.5 wt%, on a setter made of alumina refractories containing SiO ₂ 2.5 wt% to 15.0 wt% And a method of producing an alumina sintered body, comprising a step of firing.