Method for manufacturing quartz crystal tuning fork resonator, quartz crystal unit having quartz crystal tuning fork resonator, and quartz crystal oscillator having quartz crystal unit

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 by etching a quartz crystal wafer to form a quartz crystal tuning fork base and a plurality of quartz crystal tuning fork tines connected to the quartz crystal tuning fork base, etching the quartz crystal wafer to form a groove having stepped portions in at least one of opposite main surfaces of each of the quartz crystal tuning fork tines, disposing a plurality of first electrodes having a first electrical polarity on the stepped portions of the grooves of respective ones of the quartz crystal tuning fork tines, and disposing a plurality of second electrodes having a second electrical polarity on side surfaces of respective ones of the quartz crystal tuning fork tines, the second electrical polarity being opposite to the first electrical polarity;
• providing a case having an interior space and an open end communicating with the interior space;
• providing a lid for covering the open end of the case;
• mounting the quartz crystal tuning fork resonator in the interior space of the case;
• and
• connecting the lid to the case to cover the open end thereof;
• wherein a width W2 of the groove formed in at least one of the opposite main surfaces of each of the quartz crystal tuning fork tines is within a range of 0.03 mm to 0.12 mm;
• and wherein a ratio W2/W is greater than 0.35 and less than 1, where W represents a width of each of the tuning fork tines;
• and
• wherein a length of the groove formed in at least one of the opposite main surfaces of each of the quartz crystal tuning fork tines is within a range of 40% to 80% of a length of each of the tuning fork tines.

A method for manufacturing a quartz crystal oscillator, comprising the steps of:

• providing a feedback circuit by forming a quartz crystal tuning fork resonator capable of vibrating in a flexural mode of an inverse phase by etching a quartz crystal wafer in a first etching process to form a quartz crystal tuning fork base and a plurality of quartz crystal tuning fork tines connected to the quartz crystal tuning fork base, etching the quartz crystal wafer in a second etching process different from the first etching process to form a groove having stepped portions in at least one of opposite main surfaces of each of the quartz crystal tuning fork tines, disposing a plurality of first electrodes having a first electrical polarity on the stepped portions of the grooves of respective ones of the quartz crystal tuning fork tines, and disposing a plurality of second electrodes having a second electrical polarity on side surfaces of respective ones of the quartz crystal tuning fork tines, the second electrical polarity being opposite to the first electrical polarity;
• mounting the quartz crystal tuning fork resonator in an interior space of a case having an open end communicating with the interior space;
• connecting a lid to the case to cover the open end thereof;
• and
• electrically connecting the quartz crystal tuning fork resonator of the feedback circuit to an amplification circuit comprised of a CMOS inverter and a feedback resistor.

A method for manufacturing a quartz crystal oscillator, comprising the steps of:

• forming a quartz crystal tuning fork resonator capable of vibrating in a flexural mode of an inverse phase by etching a quartz crystal wafer to form a quartz crystal tuning fork base and a plurality of quartz crystal tuning fork tines connected to the quartz crystal tuning fork base, etching the quartz crystal wafer to form a groove having stepped portions in at least one of opposite main surfaces of each of the quartz crystal tuning fork tines, disposing a plurality of first electrodes having a first electrical polarity on the stepped portions of the grooves of respective ones of the quartz crystal tuning fork tines, and disposing a plurality of second electrodes having a second electrical polarity on side surfaces of respective ones of the quartz crystal tuning fork tines, the second electrical polarity being opposite to the first electrical polarity;
• mounting the quartz crystal tuning fork resonator in an interior space of a case having an open end communicating with the interior space;
• connecting a lid to the case to cover the open end thereof;
• and
• electrically connecting the quartz crystal tuning fork resonator to an amplification circuit having a CMOS inverter and a feedback resistor and to capacitors and a drain resistor of a feedback circuit having the quartz crystal tuning fork resonator;
• wherein the quartz crystal tuning fork resonator has a fundamental mode of vibration and a second overtone mode of vibration;
• and
• wherein a ratio of an amplification rate α1 of the fundamental mode of vibration and an amplification rate α2 of the second overtone mode of vibration of the amplification circuit is greater than that of a feedback rate β2 of the second overtone mode of vibration and a feedback rate β1 of the fundamental mode of vibration of the feedback circuit, and a product of the amplification rate α1 and the feedback rate β1 of the fundamental mode of vibration is greater than 1.

A method for manufacturing a quartz crystal tuning fork resonator capable of vibrating in a flexural mode, comprising the steps of:

• etching a quartz crystal wafer in a first etching process to form a quartz crystal tuning fork base and a plurality of quartz crystal tuning fork tines connected to the quartz crystal tuning fork base;
• etching the quartz crystal wafer in a second etching process different from the first etching process to form a groove having stepped portions in at least one of opposite main surfaces of each of the quartz crystal tuning fork tines;
• disposing a plurality of first electrodes having a first electrical polarity on the stepped portions of the grooves of respective ones of the quartz crystal tuning fork tines;
• and
• disposing a plurality of second electrodes having a second electrical polarity on side surfaces of respective ones of the quartz crystal tuning fork tines, the second electrical polarity being opposite to the first electrical polarity.