VHF fundamental AT-cut resonators using flip-chip bonding

We miniaturized a very high frequency (VHF) fundamental AT-cut resonator by flip-chip bonding that joins a turned crystal chip to a ceramic package with gold bumps. The dimensions of the new resonator are 3.8 mm long /spl times/3.8 mm wide /spl times/0.9 mm high. The capacity of the resonator is a quarter of that of a conventional resonator that uses wire bonding. Moreover, we observe high stability in the 155 MHz resonator with a vibrating area of 10 /spl mu/m thickness. The new resonator is unaffected by stress and contamination due to bonding. Therefore, in the frequency vs. temperature characteristics, hysteresis errors are less than or equal to 1 ppm in the temperature cycle ranging from -40/spl deg/C to +85/spl deg/C. In the accelerated aging characteristics at an ambient temperature of +85/spl deg/C, the frequency shift is less than 1 ppm up to 6,000 hours.