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In the manufacturing of typical quartz
resonators, wafers are cut from a quartz crystal bar into plates (“blanks”),
along precisely controlled directions with respect to the crystallographic
axes. The cutting is usually done with
a slurry saw. This saw consists of a
set of ~100 thin, stretched metal bands moving back and forth across multiple
quartz bars in a flood of abrasive slurry. The properties of the resonator
depend strongly on the angles of cut (see chapter 4). The angles of cut are
determined by x-ray diffraction. After shaping to required dimensions,
lapping, etching, (polishing) and cleaning, metal electrodes are applied to
the plates which are mounted into holder structures (see “Resonator
Packaging” earlier in this chapter). The plates are bonded to the mounting
clips of the holder with, e.g., a silver-filled epoxy or polyimide. The
assembly, called a crystal unit (or crystal or resonator)
is hermetically sealed.
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The above flow chart shows the major steps
in the fabrication of a resonator.
Although all the steps can affect the stability, the steps shown in
the box are usually the most important with respect to the long term stability
of the resonator. Ideally, these final
steps should be performed in an ultrahigh vacuum. Ultrahigh vacuum baking immediately before
hermetic sealing is highly desirable in order to produce low aging,
especially if the resonator is exposed to air after frequency adjustment.
(See “Aging Mechanisms” in chapter 4.)
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Quartz growing, sweeping and
etching/chemical-polishing are discussed in chapter 5.
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W.L. Bond, Crystal
Technology, John Wiley & Sons, New York, 1976.
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J. A. Kusters,
“Resonator and Device Technology," in E. A. Gerber and A. Ballato, Precision
Frequency Control, Vol. 1, pp.161-183,
Academic Press, 1985.
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