Quartz crystal resonator, unit having resonator, oscillator having unit, electronic apparatus having oscillator, and method for manufacturing electronic apparatus

A quartz crystal unit comprising:

• a quartz crystal tuning fork resonator capable of vibrating in a flexural mode of an inverse phase, the quartz crystal tuning fork resonator comprising a quartz crystal tuning fork base, first and second quartz crystal tuning fork tines connected to the quartz crystal tuning fork base and each having a first main surface and a second main surface opposite the first main surface, a groove having a plurality of stepped portions formed in at least one of the first and second main surfaces of each of the first and second quartz crystal tuning fork tines, and an electrode disposed in the groove formed in at least one of the first and second main surfaces of each of the first and second quartz crystal tuning fork tines so that a merit value M1 of a fundamental mode of vibration of the quartz crystal tuning fork resonator is greater than a merit value M2 of a second overtone mode of vibration thereof, the merit values M1 and M2 being defined by the ratios Q1/r1 and Q2/r2, respectively, where Q1 and Q2 represent a quality factor of the fundamental mode of vibration and the second overtone mode of vibration, respectively, of the quartz crystal tuning fork resonator and r1 and r2 represent a capacitance ratio of the fundamental mode of vibration and the second overtone mode of vibration, respectively, of the quartz crystal tuning fork resonator;
• a case for housing the quartz crystal tuning fork resonator;
• and a lid for covering an open end of the case;
• wherein a piezoelectric constant e12 of the quartz crystal tuning fork resonator is within a range of 0.095 C/m2 to 0.19 C/m2 in the absolute value.

A quartz crystal oscillator comprising:

• a quartz crystal oscillating circuit comprised of an amplification circuit comprising a CMOS inverter and a feedback resistor, and a feedback circuit comprising a quartz crystal tuning fork resonator capable of vibrating in a flexural mode of an inverse phase, a plurality of capacitors and a drain resistor, the quartz crystal tuning fork resonator comprising a quartz crystal tuning fork base, first and second quartz crystal tuning fork tines connected to the quartz crystal tuning fork base and each having a first main surface and a second main surface opposite the first main surface, a groove having a plurality of stepped portions formed in at least one of the first and second main surfaces of each of the first and second quartz crystal tuning fork tines, and an electrode being disposed in the groove formed in at least one of the first and second main surfaces of each of the first and second quartz crystal tuning fork tines so that a merit value M1 of a fundamental mode of vibration of the quartz crystal tuning fork resonator is greater than a merit value M2 of a second overtone mode of vibration thereof, the merit values M1 and M2 being defined by the ratios Q1/r1 and Q2/r2, respectively, where Q1 and Q2 represent a quality factor of the fundamental mode of vibration and the second overtone mode of vibration, respectively, of the quartz crystal tuning fork resonator and r1 and r2 represent a capacitance ratio of the fundamental mode of vibration and the second overtone mode of vibration, respectively, of the quartz crystal tuning fork resonator;
• wherein a piezoelectric constant e12 of the quartz crystal tuning fork resonator is within a range of 0.095 C/m2 to 0.19 C/m2 in the absolute value.

In an electronic apparatus having a display portion:

• at least one quartz crystal oscillator comprising a quartz crystal oscillating circuit comprised of an amplification circuit having at least an amplifier, and a feedback circuit comprising at least a quartz crystal tuning fork resonator capable of vibrating in a flexural mode of an inverse phase, the quartz crystal tuning fork resonator comprising a quartz crystal tuning fork base, first and second quartz crystal tuning fork tines connected to the quartz crystal tuning fork base and each having a first main surface and a second main surface opposite the first main surface, a groove having a plurality of stepped portions formed in at least one of the first and second main surfaces of each of the first and second quartz crystal tuning fork tines, and an electrode disposed in the groove formed in at least one of the first and second main surfaces of each of the first and second quartz crystal tuning fork tines so that a merit value M1 of a fundamental mode of vibration of the quartz crystal tuning fork resonator is greater than a merit value M2 of a second overtone mode of vibration thereof, the merit values M1 and M2 being defined by the ratios Q1/r1 and Q2/r2, respectively, where Q1 and Q2 represent a quality factor of the fundamental mode of vibration and the second overtone mode of vibration, respectively, of the quartz crystal tuning fork resonator and r1 and r2 represent a capacitance ratio of the fundamental mode of vibration and the second overtone mode of vibration, respectively, of the quartz crystal tuning fork resonator;
• wherein a piezoelectric constant e12 of the quartz crystal tuning fork resonator is within a range of 0.095 C/m2 to 0.19 C/m2 in the absolute value.

A method for manufacturing an electronic apparatus, comprising the steps of:

• providing a display portion;
• forming at least one quartz crystal tuning fork resonator capable of vibrating in a flexural mode of an inverse phase and having a fundamental mode of vibration, a second overtone mode of vibration, a quartz crystal tuning fork base, and first and second quartz crystal tuning fork tines connected to the quartz crystal tuning fork base and each having side surfaces;
• disposing an electrode on each of two of the side surfaces of each of the first and second quartz crystal tuning fork tines so that the electrodes disposed on the side surfaces of the first quartz crystal tuning fork tine have an electrical polarity opposite to an electrical polarity of the electrodes disposed on the side surfaces of the second quartz crystal tuning fork tine;
• providing at least one quartz crystal oscillator comprising a quartz crystal oscillating circuit comprised of an amplification circuit having a CMOS inverter and a feedback resistor, and a feedback circuit having the quartz crystal tuning fork resonator;
• mounting the quartz crystal tuning fork resonator on a mounting portion of a case using a conductive adhesive or solder;
• and
• adjusting an oscillation frequency of the quartz crystal tuning fork resonator so that the quartz crystal oscillating circuit outputs an output signal of the oscillation frequency of about 32.768 kHz with a frequency deviation within a range of −100 PPM to +100 PPM;
• wherein a ratio of an absolute value of negative resistance −RL1 of the fundamental mode of vibration of the amplification circuit and a series resistance R1 of the fundamental mode of vibration of the quartz crystal tuning fork resonator is greater than a ratio of an absolute value of negative resistance −RL2 of the second overtone mode of vibration of the amplification circuit and a series resistance R2 of the second overtone mode of vibration thereof;
• wherein a merit value M1 of the fundamental mode of vibration of the quartz crystal tuning fork resonator is greater than a merit value M2 of the second overtone mode of vibration thereof, the merit values M1 and M2 being defined by the ratios Q1/r1 and Q2/r2, respectively, where Q1 and Q2 represent a quality factor of the fundamental mode of vibration and the second overtone mode of vibration, respectively, of the quartz crystal tuning fork resonator and r1 and r2 represent a capacitance ratio of the fundamental mode of vibration and the second overtone mode of vibration, respectively, of the quartz crystal tuning fork resonator;
• and
• wherein a piezoelectric constant e12 of the quartz crystal tuning fork resonator is within a range of 0.095 C/m2 to 0.19 C/m2 in the absolute value.