BVA Quartz Crystal Resonator and Oscillator Production. A Statistical Review,
Abstract:
The BVA consists of an electrodeless resonator which is decoupled from its mounting structure by four bridges. These bridges have a width of only .4 mm to get the mounting stresses away from the active centerpart as much as possible. The electrodes are plated on two more pieces, called condensors, which are made also of AT Quartz blanks with the same cutangle as the resonator blank. Since the BVA is designed an an oven quartz this is the only possibility to avoid stresses due to thermal expansion. The three parts, we call it sandwich, are rigidly hold together with clips made from stainless steel. To protect the fragile bridges against shocks the whole sandwich is mounted with springs into a rigid cage consisting of the base plate and a cover plate which are fixed to 4 columns.