Patent ID: 7779530

Claim:
A method for manufacturing a quartz crystal unit, comprising the steps of: disposing at least twice and in different steps at least one metal film on at least one of opposite surfaces of a quartz crystal wafer; disposing a resist on the at least one metal film disposed on the at least one of the opposite surfaces of the quartz crystal wafer; forming a quartz crystal tuning fork resonator having an overall length vibratable in a flexural mode of an inverse phase and a fundamental mode by etching the quartz crystal wafer to form a quartz crystal tuning fork base, a plurality of quartz crystal tuning fork tines connected to the quartz crystal tuning fork base, and at least one groove having a length in at least one of opposite main surfaces of at least one of the quartz crystal tuning fork tines, the quartz crystal tuning fork resonator having a second overtone mode of vibration; determining the overall length of the quartz crystal tuning fork resonator and the length of the at least one groove formed in the at least one of the opposite main surfaces of the at least one of the quartz crystal tuning fork tines so that a series resistance R 1 of the fundamental mode of vibration of the quartz crystal tuning fork resonator is less than a series resistance R 2 of the second overtone mode of vibration thereof; adjusting an oscillation frequency of the quartz crystal tuning fork resonator; 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; wherein the step of mounting the quartz crystal tuning fork resonator on the mounting portion of the case is performed before the step of adjusting an oscillation frequency of the quartz crystal tuning fork resonator.