Properties of 4.19 MHz miniaturized rectangular AT*-cut quartz resonators for practical use in wrist watches were investigated. The frequency spectra of resonators were obtained as a function of w/t and 1/t, where w : Width along the Z'-axis l : Length along the X-axis t : Thickness of the following three resonators:(a) Non-beveled rectangular resonator (b) Beveled rectangular resonator (c) Be veled rectangular resonator with its both side edge planes(X-Y planes) tilted. For the resonator (b), detailed frequency spectra were studied in the range of w/t=2.3 to 4.5. Temperature characteristics, coupling etc.,were investigated in the thicknes-shear mode and several unwanted modes. Thus, the trial production of resonators housed in the cases:9.0×3.7×1.8mm and 9.6×4.0×1.8mm was performed, proving their excellent temperature characteristics, great shock-resistance by l m-drop impact test, and so on. It is concluded that: (1) The secondary overtones in the width-shear mode and the width-extensional mode should be given special consideration. (2) The frequency spectra require careful investigations. (3) The inflection point of frequency-temperature curve varies with dimensions of the resonator. (4) The long-X rectangular AT-cut quartz resonator can be practically used in highly accurate quartz watch.
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