Cordierite-based sintered body, method for producing the same, and composite substrate

Patent metadata

Field	Value
Publication number	US-11198648-B2
Application number	US-201715463251-A
Country	US
Kind code	B2
Filing date	Mar 20, 2017
Priority date	Mar 23, 2016
Publication date	Dec 14, 2021
Grant date	Dec 14, 2021

Abstract

A cordierite-based sintered body according to the present invention contains cordierite as a main component and silicon nitride or silicon carbide. The cordierite-based sintered body preferably has a thermal expansion coefficient less than 2.4 ppm/° C. at 40° C. to 400° C., an open porosity of 0.5% or less, and an average grain size of 1 μm or less.

First claim

What is claimed is:

1. A composite substrate comprising, a piezoelectric substrate bonded to a cordierite-based sintered body support substrate,
wherein the cordierite-based sintered body contains cordierite as a main component and silicon nitride, the cordierite-based sintered body having:
a thermal expansion coefficient less than 2.4 ppm/° C. at 40° C. to 400° C.,
an open porosity of 0.5% or less, and
an average grain size of 0.61 μm or less,
wherein the cordierite-based sintered body has a Young's modulus of 160 GPa or more, and
wherein the cordierite-based sintered body contains silicon nitride and has a polished surface, and when the polished surface is subjected to observation of a backscattered electron image and a composition analysis with an SEM and then an area ratio of a cordierite phase to a silicon nitride phase is determined from a contrast ratio of the image and converted to a volume ratio of the sintered body, the cordierite phase is 60% to 90% by volume and the silicon nitride phase is 10% to 40% by volume;
wherein the polished surface has a center-line average roughness Ra of 1.5 nm or less; and
wherein the polished surface is a surface to which the piezoelectric substrate is bonded.

2. The composite substrate according to claim 1 , wherein the number of pores that have a maximum length of 1 μm or more and present in an area of 100 μm×100 μm of the polished surface is 10 or less.

3. The composite substrate according to claim 1 , wherein the cordierite-based sintered body has a four-point flexural strength of 220 MPa or more.

4. A method for producing a composite substrate in which a piezoelectric substrate is bonded to a cordierite-based sintered body-comprising the steps of:
(a) preparing a raw-material powder mixture by mixing 60% to 90% by volume of a cordierite powder having an average particle diameter of 0.1 to 1 μm and 10% to 40% by volume of a silicon nitride powder having an average particle diameter of 0.1 to 1 μm in a total amount of 100% by; and
(b) producing the cordierite-based sintered body by forming the raw material powder mixture into a compact having a predetermined form and subjecting the compact to hot pressing at a pressing pressure of 20 to 300 kgf/cm 2 and a firing temperature of 1350° C. to 1450° C.,
wherein the cordierite-based sintered body has a thermal expansion coefficient less than 2.4 ppm/° C. at 40° C. to 400° C.,
an open porosity of 0.5% or less, and
an average grain size of 0.61 μm or less, and
wherein the cordierite-based sintered body has a Young's modulus of 160 GPa or more,
wherein the cordierite-based sintered body contains silicon nitride and has a polished surface, and when the polished surface is subjected to observation of a backscattered electron image and a composition analysis with an SEM and then an area ratio of a cordierite phase to a silicon nitride phase is determined from a contrast ratio of the image and converted to a volume ratio of the sintered body, the cordierite phase is 60% to 90% by volume and the silicon nitride phase is 10% to 40% by volume,
wherein the polished surface has a center-line average roughness Ra of 1.5 nm or less, and
wherein the polished surface is a surface to which the piezoelectric functional substrate is bonded.

5. The composite substrate according to claim 1 , wherein the piezoelectric substrate is lithium tantalate or lithium niobate.

Assignees

• Ngk Insulators Ltd

Inventors

• Isoda Yoshinori
• Suzuki Yoshio
• Inoue Katsuhiro
• Katsuda Yuji

Classifications

• C04B2235/963

  Surface properties, e.g. surface roughness · CPC title

• C04B2235/9607

  Thermal properties, e.g. thermal expansion coefficient · CPC title

• C04B2235/5445

  submicron sized, i.e. from 0,1 to 1 micron · CPC title

• C04B2235/3873

  Silicon nitrides, e.g. silicon carbonitride, silicon oxynitride · CPC title

• C04B2235/3826

  Silicon carbides · CPC title