A very low profile, shock-resistant, surface-mountable quartz crystal unit

A very low profile, surface-mountable quartz crystal unit capable of withstanding shock levels of 100000 Gs or more has been developed. An AT-cut, 33 MHz, 3rd overtone unit has overall dimensions of .31 in (7.9 mm) diameter and 0.05 in (1.3 mm) maximum height. The unit consists of a top cover, a resonator plate, and a bottom cover. All three pieces are made of identically oriented, polished and deep-etched, swept, premium-Q quartz. A finite-element model of the three-piece sandwich, constructed using both orthotropic and general-purpose anisotropic elements, allowed the unit to be designed to the high G level. To obtain the necessary material properties, measurements were made of the breaking strength of samples of the quartz used for a range of surface treatments. Bond shear strength and bond tensile strength were measured.<
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