Characteristics of high frequency fundamental rectangular quartz crystal resonators

Interest in high frequency fundamental (HFF) quartz crystals is soaring in the fields of telecommunications and instrumentation. High speed communication systems require high frequency references and fundamental mode resonators have preference when either a large pulling range, a large bandwidth or a low spurious level in the spectrum are required. A manufacturing process has been developed which combines photolithographic batch technology and wet chemical local thinning on wafer. Thus, it is possible to produce HFF rectangular AT resonators with inverted mesa structure in large quantities and at reduced labor cost. A crystal was designed at 50 MHz (membrane thickness 33 micrometers) and sufficient quantities are being produced for technological characterisation and assessment. The AT-HFF resonator is very robust due to single ended rigid mounting and encapsulation in a hermetically sealed SMD ceramic package (8×3.6×1.8 mm³ ). Electrical, thermal and environmental characteristics of this type of quartz crystal are presented