Patent ID: 8096042

Claim:
A method for manufacturing a quartz crystal unit, comprising the steps of : forming a quartz crystal tuning fork resonator capable of vibrating in a flexural mode of an inverse phase and having a quartz crystal tuning fork shape, a capacitance ratio r 1 of a fundamental mode of vibration and a capacitance ratio r 2 of a second overtone mode of vibration, the quartz crystal tuning fork shape having a dimension and a quartz crystal tuning fork base, and first and second quartz crystal tuning fork tines connected to the quartz crystal tuning fork base, each of the first and second quartz crystal tuning fork tines having opposite main surfaces and opposite side surfaces; forming at least one groove having a dimension in at least one of the opposite main surfaces of each of the first and second quartz crystal tuning fork tines so that a spaced-apart distance between the first and second quartz crystal tuning fork tines is greater than or equal to a width of the at least one groove formed in the at least one of the opposite main surfaces of each of the first and second quartz crystal tuning fork tines; determining the dimension of each of the quartz crystal tuning fork shape and the at least one groove formed in the at least one of the opposite main surfaces of each of the first and second quartz crystal tuning fork tines so that the capacitance ratio r 1 of the fundamental mode of vibration of the quartz crystal tuning fork resonator is less than the capacitance ratio r 2 of the second overtone mode of vibration thereof; providing a case having a mounting portion and a lid for covering an open end of the case; mounting the quartz crystal tuning fork resonator on the mounting portion of the case; and connecting the lid to the case to cover the open end of the case.