The Effect of Bonding on the Frequency versus. Temperature Characteristics of AT-Cut Resonators.

摘要

Although the frequency vs. temperature (f vs. t) characteristics of quartz resonators depend primarily on the angle of cut of the quartz plate with respect to the natural crystallographic axes, processing variables such as the stresses due to the mounting clips, bonding agents, and electrodes can also have important effects. For thin resonator plates, in particular, it has been found that the bonding technique employed can produce large rotations in the f vs. t characteristics. Changes in the f vs. t characteristics which correspond to shifts in apparent angle of several minutes have been observed. This paper discusses experiments which have defined the effect of bonding on the apparent angle. Nickel electrobonding was used throughout these experiments because this technique permits precise control of the bonded area, the thickness of the bonding film, and the intrinsic stress in the film. The experiments were performed on 6.4 mm (0.250 in.) diameter, 20 MHz AT-cut plates. The bonding areas were small (1 square mm) ovals placed along a blank diameter. The shift in apparent angle was measured as a function of the orientation of this diameter with respect to XX'. Downward shifts in apparent angles were observed when the bonding areas were oriented along the ZZ' direction; upward shifts were observed along the XX' direction. For a 50 micrometers (2 mils) thick bonding film, a change in bonding orientation from ZZ' to XX' produces an apparent angle shift of over 6 minutes. The shifts in apparent angle were found to be a function of the shape, area and thickness of the bonding agent, and of the orientation of the bonding area with respect to the crystallographic axes of the plate.