Piezoelectric substrate, piezoelectric resonating element and surface-mount piezoelectric oscillator
View Patent ↗In the case where an ultraminiature piezoelectric substrate, which has a resonating portion formed by making a concavity by etching in the surface of the piezoelectric substrate made of an anisotropic crystal material, is mass-produced by batch operation using a large-area piezoelectric substrate wafer, an annular portion surrounding each concavity is formed sufficiently thick to prevent cracking from occurring when the wafer is severed. A piezoelectric substrate 2 of an anisotropic piezoelectric crystal material has a thin resonating portion 4 and a thick annular portion 5 integrally surrounding the outer marginal edge of the resonating portion to form a concavity 3 in at least one of major surfaces of the substrate; the inner wall 5 a of the annular portion in the one crystal orientation slopes gently more than the inner wall in the other crystal orientation perpendicular to said one crystal orientation, and the piezoelectric substrate is longer in said one crystal orientation than in the other crystal orientation.
1. A piezoelectric substrate made of an anisotropic piezoelectric crystal material and comprising a thin resonating portion, and a thick annular portion integrally surrounding the outer marginal edge of said resonating portion to form concavities in both major surfaces of said piezoelectric substrate, characterized in that:
the inner wall of said annular portion defining each of said concavities gently slopes in the one crystal orientation more than in the other crystal orientation perpendicular thereto; and
the positions of those of marginal edges of the bottoms of said concavities lying in said one crystal orientation are aligned with each other.
2. The piezoelectric substrate of claim 1 , characterized in that it is made of an AT-cut crystal material.
3. A piezoelectric resonating element, characterized by the provision of excitation electrodes formed on both sides of said resonating portion in the piezoelectric substrate of claim 1 or 2 in opposed relation, lead electrodes extending from the excitation electrodes to one marginal edge of the piezoelectric substrate lengthwise thereof, and connecting pads connected to the lead electrodes, respectively.
4. A piezoelectric resonator, characterized in that the piezoelectric substrate forming the piezoelectric resonating element of claim 3 is supported at one end lengthwise thereof in a cantilever fashion in a surface-mount package.
5. A surface-mount piezoelectric oscillator, characterized by the provision of the piezoelectric resonator of claim 4 , and an oscillation circuit.