Dual-rotating quartz crystal resonator with reduced sensitivity to acceleration

Abstract

A dual-rotation quartz crystal resonator includes a cantilevered dual-rotation resonant element having a geometrical symmetry line extending from a supported end to a free end, the geometrical symmetry line being non-perpendicular to the crystallographic z-axis of the resonant element. A method of manufacturing a crystal resonator includes: using an x-axis relative to a plate... I An in-plane rotation angle of non-zero degrees on the axis will define the x-axis of the plane. I and z I The axis is cut into one or more resonant elements by a double-rotating quartz crystal plate. The resonator is less sensitive to mechanical acceleration.

Description

Technical Field

[0001] This invention relates to frequency control products for use in various applications requiring precise and stable frequency references and / or timing signals. More specifically, this invention relates to dual-rotating quartz crystal resonators and crystal oscillator devices with reduced mechanical acceleration sensitivity. Background Technology

[0002] High-frequency stable electronic oscillators are typically composed of quartz crystal resonators. A quartz crystal resonator includes a mounted piezoelectric resonant element and a device that connects the resonator to an electronic circuit to maintain stable oscillation of the resonator.

[0003] Quartz crystal resonant elements are typically made from quartz wafers (“quartz wafers”) that are cut into quartz material (“quartz rods”) at an angle relative to the crystal axis of the material. The various properties of the resonant element depend on the cutting angle applied during the manufacture of the quartz wafer. While there are an infinite number of ways a quartz wafer can be cut relative to the crystal axes x, y, and z, certain cuts have been found to result in particularly useful properties of the resonator. Figure 1 illustrates the widely used orientations of single-rotation and double-rotation cuts. When a quartz wafer is prepared by applying a rotation about the x-axis away from the z-axis (angle θ), a single-rotation cut wafer 1 is obtained. Such a rotation defines a new axis y for the single-rotation wafer 1. I and z I And the film's x I The axis remains parallel to the crystal axis x. When a quartz wafer is manufactured by applying a double rotation (rotation about the z-axis at an angle φ relative to the x-axis and rotation about the x-axis at an angle θ relative to the z-axis), a double-rotation cutter 2 is obtained, thereby defining a new x-axis for the double-rotation cutter 2. I y I and z I Axis. x in single rotary plate 1 and double rotary plate 2 I The axes are all perpendicular to the crystal axis z (i.e., at 90°).

[0004] One example of single-rotation cutting is the commonly used AT cut, which is obtained when a quartz wafer is produced by applying a rotation about the x-axis at approximately 35° (θ) relative to the z-axis. The AT cut exhibits properties suitable for designing and manufacturing temperature-compensated crystal oscillators. The stress-compensated SC cut is an example of double-rotation cutting, which is achieved by applying a double-rotation cut (rotating about 22° (φ) relative to the x-axis about the z-axis), thereby defining the x-axis of the SC-cut wafer. I This double-rotation cut is achieved when a quartz wafer is formed by rotating the SC cut along its in-plane axis (φ≈19°, θ≈34°) about the x-axis relative to the z-axis. It can be said that the SC-cut quartz crystal resonator compensates for the mechanical stress applied along its in-plane axis. The IT cut is another example of a double-rotation cut (φ≈19°, θ≈34°), exhibiting similar performance to the SC cut.

[0005] Individual quartz crystal resonant elements are manufactured by cutting (“slicing”) quartz sheets into individual “crystal blanks”; resonant elements can be made into various shapes, among which circular and rectangular (“strip”) resonant elements are commonly used.

[0006] Various resonant element mounting and packaging techniques are known. For example, as shown in Figure 2 (prior art), a rectangular (“strip”) resonant element 6 can be asymmetrically mounted within a resonator package 1 using a cantilever mounting structure, with one or more mounting points at one end of the resonant element 6 and the second end of the resonant element being free; typically, the resonant element 6 is mounted onto a conductive pad 4 using one or two conductive adhesive dots 5, and the package is sealed using a cap 3 and a sealing ring 2.

[0007] Figure 3 (Prior Art) shows a cross-sectional view of a rectangular resonant element 6 mounted within a resonator package 1 using a cantilever mounting device. This cantilever mounting device includes two mounting adhesive points 5 located at one end of the resonant element 6, and the other end of the resonant element is free (i.e., unsupported). A line 7 of geometric symmetry of the resonant element can be defined extending from the supported end of the resonant element 6 to its free end.

[0008] Figure 4 (Prior Art) shows a cross-sectional view of a rectangular resonant element 6 mounted within a resonator package 1 using a cantilever mounting device, wherein there is only one mounting adhesive point 5 at one end of the resonant element 6, while the other end of the resonant element is free (i.e., unsupported). A line of geometric symmetry 7 can be defined for the resonant element extending from its supported end to its free end.

[0009] In the prior art, the quartz sheet is cut so that the aforementioned geometric symmetry lines align with the x-axis of the sheet. I To fabricate a single resonant element with the axis parallel (i.e., at a 0-degree angle), as described above, the x-axis of the plate... I The axis is positioned at an angle φ relative to the crystal axis x and is perpendicular to the crystal axis z.

[0010] A well-known problem associated with quartz crystal resonators and oscillator devices using them is their sensitivity to mechanical acceleration. This manifests as a change in the resonant frequency of the resonator, or a change in the frequency of the crystal oscillator's output signal caused by externally applied mechanical acceleration. In furnace-controlled crystal oscillators (OCXOs) and temperature-compensated crystal oscillators (TCXOs) used in applications with significant mechanical acceleration, the sensitivity of dual-rotating quartz crystal resonators to mechanical acceleration is often problematic.

[0011] Certain methods for reducing sensitivity to acceleration are known in the prior art, such as those disclosed in U.S. Patents 7,247,978 and 7,915,965.

[0012] The purpose of this invention is to provide a novel method for reducing the sensitivity to mechanical acceleration in a cantilevered dual-rotating crystal resonator. Summary of the Invention

[0013] On one hand, the present invention can be said to include a method for manufacturing a dual-rotation quartz crystal resonator, the dual-rotation quartz crystal resonator comprising cantilevered dual-rotation resonant elements, the method comprising the steps of: applying around y while cutting a quartz sheet into individual resonant elements. I axis and away from x I Rotation of the axis within a non-zero angle plane.

[0014] On the other hand, it can be said that the present invention includes a double-rotating quartz crystal resonator comprising a cantilevered double-rotating resonant element, wherein a geometrical line of symmetry extends from the supported end of the cantilevered resonant element to its free end, positioned at an angle other than 90° relative to the crystal axis z. In other words, in the cantilevered double-rotating resonant element of the present invention, the geometrical line of symmetry extending from the supported end of the cantilevered resonant element to its free end is not perpendicular to the crystallographic z-axis of the quartz crystal material in which the resonant element is manufactured. This non-perpendicularity is due to the aforementioned non-zero-degree in-plane rotation applied during the manufacture of the resonant element.

[0015] On the other hand, the present invention may be said to include a method for manufacturing a dual-rotation SC-cut quartz crystal resonator, the dual-rotation SC-cut quartz crystal resonator including a cantilevered resonant element, the method comprising the steps of: applying in-plane rotation (around y) within an azimuth angle range of 36° to 56° while cutting a quartz sheet into a single resonant element. I Axis, away from x I axis).

[0016] On the other hand, it can be said that the present invention includes a dual-rotational SC-cut quartz crystal resonator, which comprises a cantilevered SC-cut resonant element, wherein the geometric symmetry line extending from the supported end of the cantilevered resonant element to its free end is positioned at an angle other than 90° relative to the crystallographic axis z. In other words, in the cantilevered dual-rotational SC-cut resonant element of the present invention, the geometric symmetry line extending from the supported end of the cantilevered resonant element to its free end is not perpendicular to the crystallographic z-axis of the quartz crystal material in which the resonant element is made. This non-perpendicularity is due to the aforementioned y-axis adjustment applied during the manufacture of the resonant element. I Stay away from x I The azimuth angle of the axis is an in-plane rotation ranging from 36° to 56°.

[0017] On the other hand, it can be said that the present invention includes a quartz crystal oscillator comprising a resonator mounted on a double rotating cantilever according to the above description.

[0018] On the other hand, the present invention may be said to include an electronic device comprising a quartz crystal oscillator according to the above description.

[0019] As used in this specification, the term "comprising" means "consisting of at least part of". When interpreting each statement in this specification containing the term "comprising", features other than those using that term or beginning with that term may also exist. Related terms such as "comprise" and "comprises" will be interpreted in the same manner. Attached Figure Description

[0020] The invention is further described with reference to the accompanying drawings, in which:

[0021] Figure 1 shows the orientation of single-rotation cutting and double-rotation cutting (prior art).

[0022] Figure 2 is a schematic cross-sectional view of the structure of a cantilevered strip crystal resonator (prior art).

[0023] Figure 3 is a schematic cross-sectional view of a resonant element (prior art) mounted on a two-point cantilever.

[0024] Figure 4 is a schematic cross-sectional view of a resonant element (prior art) mounted on a single-point cantilever.

[0025] Figure 5 shows the dicing of a quartz wafer according to the prior art.

[0026] Figure 6 The wafer dicing according to the present invention is illustrated.

[0027] Figure 7 This invention illustrates the use of in-plane rotation to dicing a wafer into multiple resonant elements.

[0028] Figure 8 The graphs showing the orientation and total acceleration sensitivity of an SC cut resonator for two-point cantilever mounting relative to the in-plane rotation angle are shown.

[0029] Figure 9 The graphs showing the orientation and total acceleration sensitivity of an SC cut resonator for single-point cantilever mounting relative to the in-plane rotation angle are presented.

[0030] Figure 10A , Figure 10B , Figure 10C and Figure 10DThe graphs show the X, Y, and Z values ​​of multiple single-point cantilevered SC cut-band resonators, as well as their overall sensitivity to acceleration, which will be further discussed in subsequent experimental embodiments. Detailed Implementation

[0031] As described above, according to the present invention, a dual-rotation quartz crystal resonator element is manufactured by rotating within the wafer dicing plane.

[0032] Figure 5 and Figure 6 The concept of the present invention is illustrated. In Figure 5 (prior art), a double-rotating quartz wafer 2 is cut at angles φ and θ relative to the crystal axes x and z, respectively, to produce individual double-rotating resonant elements. For illustrative purposes, a single resonant element 6 is shown in Figure 5; in practice, multiple resonant elements are obtained from the quartz wafer. In the prior art, by cutting along a line parallel to x... I The direction of the axis and perpendicular to x I The wafer is diced along its axial direction to fabricate individual resonant elements. The resulting geometric symmetry lines of the resonant elements are related to the x-axis of the wafer. I The axis is parallel and therefore forms a 90° angle with the crystallographic z-axis (as shown by angle α). Figure 6 In this process, a double-rotational quartz wafer 2 is cut at angles φ and θ relative to the crystal axes x and z, respectively, to manufacture a single double-rotational resonant element according to the present invention. This replaces the method performed as in the prior art, which involves cutting along an axis parallel to x... I The direction and perpendicular to x I The resonant element is manufactured by dicing the wafer in the x-direction (Figure 5). The resonant element of the present invention is manufactured by dicing the wafer in the x-direction. I The process of cutting a wafer by rotating the axis in-plane at a certain non-zero angle ψ (azimuth angle). Figure 6 The resonant element 6 and its geometric symmetry line 7, produced by methods of the prior art, are also shown. Figure 6 In the middle, to illustrate in-plane rotation. The geometric symmetry line 7a of the resonant element 6a produced according to the present invention is not parallel to the x-axis of the wafer. I The axis is not perpendicular to the crystallographic z-axis, i.e., angle α ≠ 90°. It can be seen that the precise value of the angle α between the geometric symmetry line 7a of the resonant element 6a generated according to the present invention and the crystallographic z-axis is determined by the expression α = 90° - arcsin(cosθ × sinψ).

[0033] As mentioned above, such as Figure 7 As shown, several resonant elements are typically made from a single quartz crystal. The figure illustrates the quartz crystal and its x-axis. I y I and z I The axis, and the criterion (dashed) line according to the invention, which is relative to x I The axis is rotated in-plane by a non-zero angle ψ.

[0034] The sensitivity of the dual-rotational resonant element produced according to the present invention to mechanical acceleration varies with and depends on the value of the in-plane rotation (azimuth) angle ψ, and by selecting a specific value of the azimuth angle, the sensitivity to mechanical acceleration can be minimized or at least reduced. As further explained herein, the selection of a specific value of the in-plane rotation angle ψ depends on factors such as the cantilever mounting structure of the resonant element and the degree of reduction in acceleration sensitivity to be achieved.

[0035] Similar to existing resonant elements (Figures 3 and 4), the dual-rotation resonant element of the present invention can also be cantilevered and mounted on two mounting points or one mounting point at one end of the resonant element, while the other end of the resonant element is free.

[0036] like Figure 8 As shown, the sensitivity of the SC-cutting resonant element of the present invention, mounted on a dual-rotation two-point cantilever, to mechanical acceleration varies with the in-plane rotation angle. The acceleration sensitivity in each of the three mutually perpendicular directions X, Y, and Z (gamma X, gamma Y, and gamma Z), as well as the total acceleration sensitivity (gamma RMS), is plotted as a function of the in-plane rotation angle ψ. The acceleration sensitivity values ​​are measured in units of one billionth of a frequency change per billionth of acceleration (ppb / g), while the angle ψ value is measured in degrees.

[0037] like Figure 8 As shown, when an in-plane rotation of 36°≤ψ≤56° is applied to generate a resonant element from a quartz wafer cut by a double-rotation SC cut, the total acceleration sensitivity "Gamma RMS" (the root mean square value of the directional acceleration sensitivity values ​​"Gamma X", "Gamma Y", and "Gamma Z" along three mutually perpendicular directions) is approximately its minimum. This is compared to the situation without in-plane rotation (i.e.,...). Figure 8 The two-point cantilevered SC-cut resonator generated by zero rotation angle in the plane showed a total acceleration sensitivity of about 3 ppb / g. Similarly, the SC-cut resonator generated by in-plane rotation with 36°≤ψ≤56° showed a total acceleration sensitivity of less than 1 ppb / g.

[0038] like Figure 9 As shown, the sensitivity of the SC-cutting resonant element of the present invention to mechanical acceleration varies with the in-plane rotation angle, wherein the acceleration sensitivity in each of the three mutually perpendicular directions X, Y, and Z (gamma X, gamma Y, and gamma Z) and the total acceleration sensitivity (gamma RMS) are plotted as a function of the in-plane rotation angle ψ. The acceleration sensitivity value is measured in units of one billionth of a frequency change per billionth of acceleration (ppb / g), while the angle ψ value is measured in degrees.

[0039] like Figure 9As shown, when an in-plane rotation of 36°≤ψ≤56° is applied to generate a resonant element from a quartz wafer cut by a double-rotation SC cut, the total acceleration sensitivity "Gamma RMS" (the root mean square value of the directional acceleration sensitivity values ​​"Gamma X", "Gamma Y", and "Gamma Z" along three mutually perpendicular directions) is approximately its minimum. This is compared to the situation without in-plane rotation (i.e.,...). Figure 9 A single-point cantilever-mounted SC-cut resonator with zero rotation angle (in the plane) exhibits a total acceleration sensitivity of approximately 4.5 ppb / g. Similarly, a mounted SC-cut resonator with in-plane rotation of 36°≤ψ≤56° exhibits a total acceleration sensitivity of less than 2 ppb / g.

[0040] As described above, in the double-rotational resonant element of the present invention, the geometrical symmetry line is not perpendicular to the crystallographic z-axis (angle α ≠ 90°), and the precise value of the angle α between the geometrical symmetry line and the crystallographic z-axis of the resonant element produced according to the present invention is determined by the above expression. According to this expression, for a double-rotational resonant element having θ = 34° ± 20' (such as, for example, SC-cut and IT-cut resonant elements) and an in-plane rotation angle of 36° ≤ ψ ≤ 56°, the angle α will be in the range of 46° to 61°.

[0041] It should be noted that the sign of the azimuth (e.g., +46° or -46°) actually depends on the specifications used in the manufacturing process implemented at a particular manufacturer: that is, some manufacturers will consider clockwise in-plane rotation as "positive," while others may call counterclockwise in-plane rotation "positive." Figure 8 and Figure 9 As shown, in-plane rotation along only one direction will result in reduced sensitivity to acceleration. For any embodiment of the invention, it is important to choose an appropriate absolute value for the azimuth angle.

[0042] Example

[0043] Multiple single-point cantilevered SC cutters (θ = 33°45', φ = 21°56') produced strip resonators with dimensions of 5.0 mm × 3.2 mm and a nominal resonant frequency of 19.2 MHz. Their in-plane rotation (azimuth) angles ψ were 36°, 46°, and 56°. Their sensitivity to acceleration was measured in three mutually perpendicular directions X, Y, and Z. The overall sensitivity was determined based on the measurement results. The results are plotted on... Figures 10A to 10D Among them Figure 10A The magnitude values ​​of the X-axis acceleration sensitivity were plotted. Figure 10B The magnitude values ​​of the Y-axis acceleration sensitivity were plotted. Figure 10C The amplitude values ​​of the Z-axis acceleration sensitivity were plotted, and Figure 10DThe total acceleration sensitivity amplitude values ​​for each of the three in-plane rotation angles (36°, 46°, and 56°) are plotted. In these plots, each data point represents the result for a resonator at that in-plane rotation angle value, and the dashed lines plot the estimated relationship through the average of the data points at each angle. It is based on... Figures 10A to 10D The experimental data shown indicate that when manufacturing a single-point cantilevered SC-cut resonator, applying an in-plane rotation of 36° to 56° allows the total acceleration sensitivity of the resonator to be reduced to below 1 ppb / g.

[0044] Therefore, by applying a specific in-plane rotation during the wafer dicing process for manufacturing dual-rotation quartz crystal resonators, the sensitivity of cantilevered strip resonators to mechanical acceleration can be significantly reduced.

[0045] The specific value of the in-plane rotation angle used in the fabrication of dual-rotation quartz crystal resonators depends on the resonator design objectives. For example, if the design of an SC-cut single-point cantilever-mounted resonator aims to minimize the overall sensitivity to acceleration, then, as... Figure 10D As shown, an in-plane rotation angle value close to 46° should be selected for manufacturing the resonant element of the present invention. On the other hand, if the resonator is used in an application where reduced sensitivity to acceleration in the Z direction is particularly important, a smaller in-plane rotation angle will be selected for manufacturing, possibly in the range of 36° to 46° (see [reference]). Figure 10C This will result in even lower acceleration sensitivity in the X direction, although at the cost of a slight increase in the total acceleration sensitivity value.

[0046] The cantilevered dual-rotating quartz crystal resonator of this invention can be used in a variety of frequency control products, including but not limited to crystal oscillators (XOs), temperature-compensated crystal oscillators (TCXOs), and furnace-controlled crystal oscillators (OCXOs). These devices will, in turn, benefit the performance of various electronic devices and systems, including but not limited to radio communication equipment, where reducing the sensitivity of the reference frequency to mechanical acceleration is crucial.

Claims

1. A method for manufacturing a dual-rotating quartz crystal resonator with reduced mechanical acceleration sensitivity, the dual-rotating quartz crystal resonator comprising cantilevered dual-rotating resonant elements, the method comprising the following steps: With respect to the x of the slice I An in-plane rotation angle of the axis within the range of approximately 36° to approximately 56° will have an x-shape defining the sheet. I z I x in the plane I and z I The dual-rotating quartz wafer of the axis is cut into one or more resonant elements.

2. The method according to claim 1, wherein, The dual-rotating quartz crystal resonator is a stress-compensated (SC) cut quartz crystal resonator, the cantilever-mounted dual-rotating resonant element is a cantilever-mounted SC cut resonant element, and the dual-rotating quartz wafer is an SC cut quartz wafer.

3. A dual-rotational quartz crystal resonator with reduced mechanical acceleration sensitivity, comprising a cantilevered dual-rotational resonant element having a geometrical symmetry line extending from a supported end of the cantilevered resonant element to its free end, wherein the angle between the geometrical symmetry line of the resonant element and the crystallographic z-axis is in the range of about 46° to about 61°.

4. The dual-rotating quartz crystal resonator with reduced mechanical acceleration sensitivity according to claim 3, wherein, The cantilever-mounted dual rotary resonant element is a two-point cantilever-mounted dual rotary resonant element.

5. The dual-rotating quartz crystal resonator with reduced mechanical acceleration sensitivity according to claim 3, wherein, The cantilever-mounted dual rotary resonant element is a single-point cantilever-mounted dual rotary resonant element.

6. A dual-rotating quartz crystal resonator with reduced mechanical acceleration sensitivity according to any one of claims 3 to 5, exhibiting an absolute value of total acceleration sensitivity of less than 2 ppb / g.

7. A dual-rotating quartz crystal resonator with reduced mechanical acceleration sensitivity according to any one of claims 3 to 5, exhibiting an absolute value of total acceleration sensitivity of less than 1 ppb / g.

8. The dual-rotation quartz crystal resonator according to any one of claims 3 to 5, wherein, The dual-rotating quartz crystal resonator is a stress-compensated (SC) cut quartz crystal resonator, and the cantilever-mounted dual-rotating resonant element is a cantilever-mounted dual-rotating SC cut resonant element.

9. A quartz crystal oscillator comprising a resonator according to any one of claims 3 to 5.

10. An electronic device comprising the quartz crystal oscillator according to claim 9.

11. A method for manufacturing a dual-rotational resonant element, the dual-rotational resonant element being suitable for constructing a dual-rotational quartz crystal resonator with reduced mechanical acceleration sensitivity, the method comprising the following steps: With respect to the x of the slice I An in-plane rotation angle of the axis within the range of approximately 36° to approximately 56° will have an x-shape defining the sheet. I z I x in the plane I and z I The axis of the double-rotating quartz wafer is cut into one or more resonant elements.

12. The method according to claim 11, wherein, The dual-rotating quartz crystal resonator is a stress-compensated (SC) cut quartz crystal resonator, the dual-rotating resonant element is an SC cut resonant element, and the dual-rotating quartz wafer is an SC cut quartz wafer.

13. A dual-rotational resonant element suitable for constructing a dual-rotational quartz crystal resonator with reduced sensitivity to mechanical acceleration, said resonant element being adapted for cantilever mounting and having a geometrical line of symmetry, wherein, when said resonant element is cantilever mounted, the geometrical line of symmetry corresponds to an axis extending between a supported end and a free end, wherein, The angle between the geometric symmetry line of the resonant element and the crystallographic z-axis is in the range of approximately 46° to approximately 61°.

14. The dual-rotational resonant element according to claim 13, wherein, The dual-rotating quartz crystal resonator is a stress-compensated (SC) cut quartz crystal resonator, and the dual-rotating resonant element is an SC cut resonant element.

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