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Precise Angular Control of Quartz-Cutting by X-Rays*
Published online by Cambridge University Press: 10 January 2013
Abstract
Methods for precise control of the cutting angles of quartz by x-ray measurements are described. The quartz must first be oriented by some other method (usually optically) before the x-ray method can be applied. The sense of direction of the cut is indicated by an arrow drawn on the outer surface of the test cut at the saw and this direction is preserved in making the x-ray measurement. The x-ray technique is an adaptation of the Bragg ionization chamber method and involves measuring the angle between the surface of the test cut or blank and an atomic reference plane parallel (or nearly parallel) to the surface. All measurements are direct, and require no computation. A Gieger-Muller tube operated in the proportional counter region is employed. Accuracy of the method is approximately ±1.5′, the measurement requires about 10-15 seconds, and is used by unskilled help. The procedures for calibrating the x-ray goniometer and measuring various types of cuts are described in detail. Methods involving precise angular adjustments of sections approximately oriented by other methods and the use of reflection intensity differences of certain planes on either side of the optic axis for detecting usable portion of electrical twins and negative and positive directions from Z are described. The methods are applicable to other fields.
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- Copyright © Cambridge University Press 1991
References
1 Parrish, William and Gordon, Samuel G., Orientation techniques for the manufacture of quartz-oscillator crystals: Am. Mineral., this issue; Cutting schemes for quartz crystals: ibid.
2 The normal precautions in the use of x-ray apparatus should be followed as prescribed in National Bureau of Standards Handbook HB 20, X-Ray protection, July 24, 1936, Supt. of Documents, Washington, D.C. The commercial apparatus is shock- and ray-proof. The on-off shutter must be closed before placing or removing the crystal from the holder. In some crystal plants, orientation of crystals mounted on jigs is attempted by x-rays. In several instances the operators get their fingers in the x-ray beam while making adjustments on the jigs. The carrying of dental films by the operator, while useful, does not indicate that the fingers are not getting in the beam.
3 Friedman Herbert; Kaiser, Herman F. and Christenson, Arthur L., Applications of Geiger-Muller counters to inspection with x-rays and gamma rays: Jour. Am. Soc. Naval Eng., 54, 177–209 (1942)Google Scholar. Forageneral discussion of G.-M. tubes see Strong, , John, , Procedures in Experimental Physics, Prentice-Hall, Inc., New York (1938)Google Scholar, Chater VII by H. V. Neher.
4 Batteries have also been used. Since very little current is drawn, they practically have shelf life.
5 Wyckoff, , Ralph, W.G., The Structure of Crystals, supplement to the 2nd ed., p26Reinhold Publishing Corp., New York (1935)Google Scholar.
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8 In some of the earlier x-measurements of quartz, while it was appreciated that this sense of direction must be preserved, instead of marking the test cut at the saw, it was stauroscoped. This introduced errors in making the corrections because the stauroscope markings were not necessarily coincident with the axes of rotation of the saw table.
9 One way of distinguishing them is to set the goniometer arm to zero for (20
3), ZZ = 49°44′. If the cut is at +2°58′ from (01
1), a reflection will be obtained at 8°33′ or at 12°59′ if cut at −2°58′ when the X-axis is vertical. For reasons mentioned above, an atomic reference plane close to the surface is required for precision measurements.
10 Where large production is required it is advisable to set up one goniometer to measure ZZ′ directly and the other XX′.
11 This method was developed by DrD'Eustachio, Dominick, “A method for determining which portion of a twinned wafer should be used”: Tech. News Bull. No. 6, Signal Corps Ground Signal Agency (1943)Google Scholar.
12 This reflection asymmetry was pointed out by Gibbs, R. E., Structure of quartz: Proc. Roy. Soc. (London), 110, 443–455 (1926)CrossRefGoogle Scholar. See also Broughton, William W., Piezoelectric apparatus: U. S. Patent Off. No. 2, 151, 736, Mar. 28, 1939 and Bond W. L. and Armstrong, E. J., op. cit.Google Scholar
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