Ngk Insulators, Inc.

Toshinao Nakahara

Yuji Hori

Tomoyoshi Tai

Akira Hamajima

A composite substrateincludes a piezoelectric substrateand a support layerbonded to the piezoelectric substrate. The support layeris made of a material having no crystalline anisotropy in a bonded surface thereof and has a smaller thickness than the piezoelectric substrate. The piezoelectric substrateand the support layerare bonded together with an adhesive layertherebetween. The composite substratehas a total thickness of 180 &#x3bc;m or less. The base thickness ratio Tr=t2/(t1+t2) is 0.1 to 0.4, where t1 is the thickness of the piezoelectric substrate, and t2 is the thickness of the support layer. The thickness t1 is 100 &#x3bc;m or less. The thickness t2 is 50 &#x3bc;m or less.

Composite substrate, piezoelectric device, and method for manufacturing composite substrate

In a composite substrate, a back surface of a piezoelectric substrate and a front surface of a support substrate are bonded to each other with an adhesive layer. The adhesive layer includes a swelling portion at an outer peripheral area thereof, and the piezoelectric substrate is bonded to the support substrate in an area excluding the swelling portion. Accordingly, air bubbles do not easily enter between the swelling portion of the adhesive layer and the piezoelectric substrate, and separations caused by the air bubbles can be prevented. As a result, the support substrate and the piezoelectric substrate can be reliably bonded to each other with the adhesive layer including the swelling portion in the outer peripheral area thereof.

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Kasugai, Japan

Toshinao Nakahara