Abstract: An object of the present invention is to provide a quartz resonator unit and a quartz oscillator having a small size and a light weight and having the capability of oscillating in the overtone mode, and also to provide a quartz element for use in the quartz resonator unit and quartz oscillator. Thus, a further object is to determine the optimum width-to-thickness ratio of the quartz element at which the quartz element having a width less than 1.5 mm and a length less than 4.7 mm does not show coupling with spurious vibrations over the entire range of operation temperature. From the experiments and evaluation performed repeatedly, it has been concluded that an AT-cut rectangular quartz element having the width-to-thickness ratio w/t in a range selected from the group consisting of 8.48 0.05, 12.18+/−0.05, 13.22+/−0.07, 14.78+/−0.07, and 15.57 0.07 is suitable as a small-sized quartz element that can oscillate at a high frequency and has excellent temperature characteristics.

Abstract: An object of the present invention is to provide a quartz resonator unit and a quartz oscillator having a small size and a light weight and having the capability of oscillating in the overtone mode, and also to provide a quartz element for use in the quartz resonator unit and quartz oscillator. Thus, a further object is to determine the optimum width-to-thickness ratio of the quartz element at which the quartz element having a width less than 1.5 mm and a length less than 4.7 mm does not show coupling with spurious vibrations over the entire range of operation temperature. From the experiments and evaluation performed repeatedly, it has been concluded that an AT-cut rectangular quartz element having the width-to-thickness ratio w/t in a range selected from the group consisting of 8.48 0.05, 12.18 ±0.05, 13.22 ±0.07, 14.78 ±0.07, and 15.57 0.07 is suitable as a small-sized quartz element that can oscillate at a high frequency and has excellent temperature characteristics.

Abstract: A method of smoothly processing a surface of crystal material, particularly a quartz crystal, to attain a good surface roughness and degree of eveness without substantial hillocks or micro-projections, without performing grinding or polishing processing. After lapping the surface of the crystal material, the lapped surface is etched with hydrofluoric acid. Finish etching is performed on the crystal material by buffer hydrofluoric acid as needed. In the manufacture of a crystal piece used in a crystal device, after the crystal wafer cut out from the rough crystal stone to the specified thickness is lapped, it is roughly etched to the desired thickness by hydrofluoric acid. Then, after ultrasonic washing by pure water, the crystal wafer is processed to the desired high quality of surface roughness, level of smoothness and thickness. The surface processing can be performed more easily, in less time, and with less labor than conventional methods, the cost is decreased, and productivity rises.