Oventone-mode limits on at-cut fundamental crystal resonator, through twice plating method

This paper introduces a method to limit overtone-mode on AT-Cut fundamental mode crystal resonator. According to the energy trapping theory, twice plating method is employed to increase the mass of the main electrode. The key design parameters are the diameter and thickness of the mass loading, which are determined so that the maximum ratio of the equivalent resistance at the overtone mode to that at the fundamental mode may be achieved. Experimental results in 4MHz AT-Cut fundamental mode resonator show that the equivalent resistance of the fundamental mode is less than 30ohm while the third-order overtone mode achieved a resistance of more than 150ohm.