A coarse adjustment method for crystal oscillator frequency in atmospheric environment

Abstract

The present invention discloses a coarse tuning method of crystal oscillator frequency under atmospheric environment, comprising the following steps: gluing a tuning fork wafer into a base; placing a plurality of bases gluing tuning fork wafers into a fixture; installing the fixture into a coarse tuning system of the crystal oscillator frequency, photographing and positioning the frequency modulation area at the top of the tuning fork arm of the tuning fork wafer in the fixture base through a visual positioning device; detecting the frequency of the tuning fork wafer as a coarse frequency adjustment workpiece in real time to obtain an error value of the tuning fork wafer frequency; according to the error value of the tuning fork wafer frequency, using an ultrafast ultraviolet picosecond laser to remove material and perform frequency modulation on the frequency modulation area at the top of the tuning fork arm of the tuning fork wafer in the base; repeating the above two steps until the frequency of the tuning fork wafer reaches a set value. The tuning fork wafer of the present invention is gluing into the base, placed into a fixture, and using an ultrafast ultraviolet picosecond laser to remove material and perform frequency modulation on the frequency modulation area at the top of the tuning fork arm, the frequency modulation accuracy is high and the risk of thermal damage to the workpiece is small.

Description

Technical Field

[0001] The present invention relates to the technical field of crystal oscillator manufacturing, and in particular to a method for coarsely adjusting the frequency of a crystal oscillator in an atmospheric environment. Background Art

[0002] Traditional crystal oscillator frequency modulation mainly uses grinding wheels to remove materials or silver spraying to add materials. With the development of laser technology, laser frequency modulation has gradually been applied to crystal oscillator frequency modulation. However, most general laser frequency modulation is "on-chip frequency modulation", that is, Figure 1 Laser ablation is performed on the unseparated small wafer 011 on the large quartz wafer 01 shown. A mark 012 is located at each of the four corners of the large wafer 01. This on-chip frequency modulation method can only achieve coarse tuning and has the following problems:

[0003] 1) Large deviation in chip frequency modulation: The separation process after the chip frequency modulation will cause frequency deviation;

[0004] 2) Low efficiency: less than 200 wafers can be processed at a time;

[0005] 3) Risk of thermal damage: Nanosecond laser can easily cause the coating to melt.

[0006] There are many problems with traditional laser frequency modulation, such as small-sized chips are easily broken and wasted, the product transfer process between processes is complicated, and the deviation between on-chip frequency modulation and actual frequency is too large. Traditional laser frequency modulation is on-chip frequency modulation, that is, laser frequency modulation is performed when the small-sized chip has not yet been separated from the large-sized chip. After laser frequency modulation, it is still necessary to clean, break, and dispense glue to allow the small-sized chip to enter the base. Then, laser fine-tuning or ion fine-tuning will be found. A large frequency offset will be found because the coating falls off during cleaning, there is corner chipping during breaking, and the size of the left and right glue dots is different during gluing. These all lead to a large difference in the frequency when the small-sized chip is still connected to the large-sized chip and the frequency after the small-sized chip enters the base. In addition, due to size limitations of large-sized chips, there are generally only 100-200 small-sized chips on the large-sized chip, resulting in only 100-200 frequency modulations during loading and unloading at a time, which is too inefficient.

[0007] In addition, coarse tuning generates more dust particles, some of which adhere to the tuning fork arm of the crystal. During coarse tuning, the number of particles adhering to the crystal is much higher than during fine tuning. At this point, the frequency is not the exact frequency of the crystal oscillator, so the attached particles need to be blown off or cleaned before fine tuning. Because the frequency after coarse tuning is close to the exact frequency, the frequency value of fine tuning is very low, so fewer particles are generated. The PPM of coarse tuning is mostly tens of thousands of PPM, while the PPM of fine tuning is mostly tens or hundreds of PPM.

[0008] Furthermore, in crystal oscillator manufacturing, traditional fine tuning is typically performed in a vacuum environment, while coarse tuning is primarily performed in a non-vacuum (atmospheric) environment. Coarse tuning generates a large amount of dust particles that adhere to the tuning fork arm, causing the measured frequency to deviate from its true value. This excessive frequency error makes subsequent fine tuning of the crystal oscillator difficult. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a method for coarsely adjusting the crystal oscillator frequency with high frequency accuracy in a non-vacuum environment.

[0010] In order to solve the above technical problems, the technical solution adopted by the present invention is a method for coarsely adjusting the crystal oscillator frequency in an atmospheric environment, comprising the following steps:

[0011] 101) Glue the tuning fork crystal, which serves as a frequency coarse adjustment workpiece, into the base;

[0012] 102) Place the plurality of bases with the tuning fork wafers adhered thereto into a fixture;

[0013] 103) The fixture is installed in the coarse adjustment system of the crystal oscillator frequency, and the frequency tuning area at the top of the tuning fork arm of the tuning fork crystal in the fixture base is photographed and located using a visual positioning device;

[0014] 104) Real-time detection of the frequency of a tuning fork crystal used as a frequency coarse adjustment workpiece to obtain an error value of the tuning fork crystal frequency;

[0015] 105) Based on the error value of the tuning fork crystal frequency, an ultrafast ultraviolet picosecond laser is used to remove material and perform frequency modulation on the frequency modulation area at the top of the tuning fork arm of the tuning fork crystal in the base;

[0016] 106) Repeat steps 104 and 105 until the frequency of the tuning fork crystal reaches the set value.

[0017] The above-mentioned coarse tuning method comprises: the base includes a groove for carrying a tuning fork wafer; the bottom plate of the base includes two electrodes; the two electrodes on the bottom surface of the tuning fork wafer adhered to the groove of the base are electrically connected to the top of the two electrodes in the bottom plate of the base through two adhesive points of conductive glue; the clamp includes a base, a crystal oscillator carrier, a pressure plate, a frame-shaped cover and a locking mechanism; the processing area in the middle of the crystal oscillator carrier includes a plurality of base bearing holes arranged in a matrix; the bearing holes of the crystal oscillator carrier are adapted to the base; the bottom plate of the bearing holes of the crystal oscillator carrier includes two crystal oscillator frequency test holes; the base The bottom surfaces of the two electrodes are respectively exposed in the corresponding crystal oscillator frequency test holes; the frame-shaped base includes a bearing hole of the crystal oscillator carrier plate, and the bearing hole is a stepped hole that is larger at the top and smaller at the bottom. The outer contour of the crystal oscillator carrier plate is adapted to the large hole of the stepped hole, and the periphery of the bottom surface of the crystal oscillator carrier plate is located on the steps of the stepped hole; the pressing plate is arranged on the top of the large hole of the stepped hole, located above the crystal oscillator carrier plate, and the pressing plate includes through holes arranged in a matrix and corresponding to the bearing holes; the frame-shaped cover plate is pressed on the top surface of the periphery of the pressing plate; the locking mechanism includes a plurality of locking devices, which are installed on the frame of the base frame to fasten the base and the cover plate.

[0018] The above-mentioned coarse adjustment method is that the bearing hole is a rectangular hole, and the two long sides of the rectangular hole each include an avoidance groove for the base to pick up and place the chuck; the locking device includes a lock buckle and a magnet, and the frame of the base mounting locking device includes an upwardly protruding protrusion and a mounting groove of the lock buckle, and the mounting groove is arranged on the outside of the protrusion; the lock buckle includes a buckle body and two locking pins, the lower part of the buckle body is embedded in the mounting groove of the base frame and is hinged to the frame of the base, and the direction of the hinge axis of the buckle body and the base frame is the long axis direction of the base frame; the two locking pins are arranged on the upper part of the buckle body, extending outward along both sides of the buckle body, and the axial directions of the two locking pins are parallel to the long axis direction of the base frame; the outer side surface of the protrusion includes a mounting hole for the magnet, and the magnet is embedded in the mounting hole; the frame of the cover plate includes an avoidance groove corresponding to the locking device, and when the lock buckle is engaged, the protrusion and the upper part of the lock buckle body enter the avoidance groove of the cover plate frame, the inner side surface of the buckle body is in contact with the outer side surface of the protrusion, the magnet in the protrusion is attracted to the buckle body, and the two locking pins of the lock buckle are pressed on the top surface of the cover plate frame.

[0019] The coarse tuning method described above, the coarse tuning system of the crystal oscillator frequency includes a laser frequency modulation device, the visual positioning device, a frequency testing device, an XY motion platform and an industrial computer, the fixture is fixed on the XY motion platform, and is located directly above the frequency testing device; the frequency testing device includes a frequency tester and a Z-axis lifting module, and the frequency tester is fixed on the top of the Z-axis lifting module; the top of the frequency tester includes a test head, and the test head includes a plurality of probe groups arranged in a matrix, each probe group includes two probes, and the two probes of each probe group correspond to the two electrodes of a base, and are used to contact the two electrodes at the bottom of the base to test the frequency data of the tuning fork chip. The frequency data obtained by the frequency tester is transmitted to the industrial computer, and the industrial computer controls the laser frequency modulation device to emit laser to modulate the frequency of the tuning fork arm of the tuning fork chip according to the crystal oscillator frequency measured by the probe group.

[0020] In the coarse adjustment method described above, the visual positioning device includes a camera, a lens and a coaxial light source, and the laser frequency modulation device includes a laser, a galvanometer, a beam combiner and a field lens; the laser frequency modulation device is arranged above the fixture, and the ultrafast ultraviolet picosecond laser emitted by the laser is reflected by several reflectors, and the light beam expanded by a 2-8 times beam expander is the incident light of the galvanometer, and the incident light is reflected by the galvanometer and then passes through the beam combiner; the optical axis of the visual light emitted by the coaxial light source after being reflected by the beam combiner coincides with the optical axis of the laser penetrating the beam combiner, forming a combined light of the same path; the combined light is focused by the field lens to form a field lens focused light, and the field lens makes the laser and visual light paths converge at the focus to achieve spatial synchronization between the two; the camera captures a dual-channel image through the lens, which is used to capture and locate the top area of ​​the tuning fork arm, and the field lens focused light performs material removal frequency modulation on the top area of ​​the tuning fork arm.

[0021] In the above-mentioned coarse adjustment method, the visual positioning device includes a reflector, and the visual light emitted by the coaxial light source is reflected by the reflector and then reflected by the beam combiner, and coincides with the laser optical axis penetrating the beam combiner.

[0022] In the coarse adjustment method described above, the visual positioning device includes a camera, a lens and a coaxial light source. The visual positioning device composed of the camera, the lens and the coaxial light source captures and locates the top area of ​​the tuning fork arm; the laser frequency modulation device includes a laser, a galvanometer and a field lens; the laser frequency modulation device is arranged above the fixture, and the ultrafast ultraviolet picosecond laser emitted by the laser is reflected by several reflectors. The light beam expanded by a 2-8 times beam expander is the incident light of the galvanometer. The laser after the incident light is reflected by the galvanometer is focused by the field lens to form a field lens focused light. The field lens focused light performs material removal frequency modulation on the top area of ​​the tuning fork arm.

[0023] The coarse adjustment method described above, the frequency tester includes a box, a probe contact circuit board and a test circuit board and the test head, the test head is fixed on the top plate of the box, the probe on the test head is electrically connected to the probe contact circuit board, and the probe contact circuit board is communicatively connected to the test circuit board; the two probes of each probe group contact two electrodes on a base to obtain an AC voltage signal with the same frequency as the tuning fork chip frequency, the AC voltage signal with the same frequency as the tuning fork chip frequency obtained by the test head is transmitted to the test circuit board through the probe contact circuit board, the test circuit board amplifies and filters the AC voltage signal, and then uses a π network, an oscillation circuit or a phase method to accurately measure the signal frequency, and converts the measured frequency information into a digital signal; the data processed by the test circuit board is transmitted to the industrial computer in the form of a digital signal.

[0024] In the above-mentioned coarse adjustment method, the ultrafast ultraviolet picosecond laser has a laser wavelength of 355 nm, a pulse width of 10-50 ps, ​​a repetition rate of 50-200 kHz, a power of 30 W, a single pulse energy of 100-300 μJ, and a spot diameter of 5-10 μm after focusing by the field lens.

[0025] In the above-mentioned coarse adjustment method, the fixture is a multi-process fixture, which is common to the fixture for laser fine adjustment or the fixture for ion fine adjustment.

[0026] The present invention provides a coarse tuning method for the crystal oscillator frequency under atmospheric conditions. The tuning fork crystal is adhered to a base and placed in a fixture. An ultrafast ultraviolet picosecond laser is used to remove material from the frequency tuning area at the top of the tuning fork arm to achieve frequency tuning. The frequency tuning has high accuracy and low risk of thermal damage to the workpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Figure 1 It is a schematic diagram of a large-size chip in the prior art.

[0029] Figure 2 yes Figure 1 A partial enlarged view of part I in the middle.

[0030] Figure 3 It is a structural diagram of embodiment 1 of the crystal oscillator frequency coarse adjustment system of the present invention.

[0031] Figure 4 It is a structural diagram of embodiment 2 of the crystal oscillator frequency coarse adjustment system of the present invention.

[0032] Figure 5 It is a structural diagram of embodiment 3 of the crystal oscillator frequency coarse adjustment system of the present invention.

[0033] Figure 6 It is an exploded view of a frequency testing device according to an embodiment of the present invention.

[0034] Figure 7 It is a front view of a tuning fork wafer according to an embodiment of the present invention.

[0035] Figure 8 4 is a rear view of the tuning fork wafer according to an embodiment of the present invention.

[0036] Figure 9 It is a front view of the base according to an embodiment of the present invention.

[0037] Figure 10 It is a rear view of the base according to an embodiment of the present invention.

[0038] Figure 11 FIG. 4 is a perspective view of a base with a tuning fork wafer adhered thereto according to an embodiment of the present invention.

[0039] Figure 12 It is a three-dimensional diagram of the rear view of the base of an embodiment of the present invention.

[0040] Figure 13 2 is a perspective view of a clamp according to an embodiment of the present invention.

[0041] Figure 14 It is a three-dimensional diagram of the clamp after being turned over according to the embodiment of the present invention.

[0042] Figure 15 1 is an exploded view of a clamp according to an embodiment of the present invention.

[0043] Figure 16 It is a partial view of the front of the middle part of the crystal oscillator carrier plate of the clamp according to an embodiment of the present invention.

[0044] Figure 17 It is a partial view of the front of the middle part of the clamp pressure plate according to an embodiment of the present invention.

[0045] Figure 18 It is a partial view of the back side of the middle part of the crystal oscillator carrier plate of the clamp according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] The method for coarsely adjusting the crystal oscillator frequency under atmospheric conditions according to an embodiment of the present invention comprises the following steps:

[0047] 1) Adhere the tuning fork wafer 02 , which serves as a workpiece for coarse frequency adjustment, into the base 60 .

[0048] 2) Place the bases 60 with the tuning fork wafers 02 bonded thereto into the fixture 200 .

[0049] 3) The fixture 200 is installed in the coarse adjustment system of the crystal oscillator frequency, and the frequency adjustment area at the top of the tuning fork arm of the tuning fork crystal 02 in the fixture base 60 is photographed and positioned by the visual positioning device 80 .

[0050] 4) The frequency testing device 90 detects the frequency of the tuning fork crystal 02 as a frequency coarse adjustment workpiece in real time to obtain an error value of the frequency of the tuning fork crystal 02 .

[0051] 5) According to the frequency error value of the tuning fork wafer 02 , the laser frequency modulation device 70 uses an ultrafast ultraviolet picosecond laser to remove material and perform frequency modulation on the frequency modulation area at the top of the tuning fork arm of the tuning fork wafer 02 in the base 60 .

[0052] 6) Repeat steps 4 and 5 until the frequency of tuning fork chip 02 reaches the coarse adjustment setting value.

[0053] The workpiece of the method for coarsely adjusting the crystal oscillator frequency under atmospheric conditions according to the embodiment of the present invention is as follows: Figure 7 and Figure 8 The figure shows a tuning fork wafer 02 (a small-sized wafer) that has been broken and separated from a large-sized quartz wafer 01. The tuning fork wafer 02 includes two electrodes 63, and a frequency-modulation region 022 is located at the top of the tuning fork arm of the tuning fork wafer 02. The present embodiment of the present invention employs an ultrafast laser to remove material from the frequency-modulation region 022 at the top of the tuning fork arm of the tuning fork wafer 02 to increase the frequency and achieve coarse laser frequency adjustment.

[0054] The structure of the base 60 is as follows Figures 9 to 12 As shown in the figure, when coarsely adjusting the crystal oscillator frequency, the tuning fork crystal 02 of the present invention is adhered to the groove 61 of the base 60, which supports the tuning fork crystal 02, via two conductive adhesive spots 64. The base's bottom plate 62 includes two electrodes 63. The two electrodes on the bottom surface of the tuning fork crystal 02 adhered to the groove 61 of the base 60 are electrically connected to the tops of the two electrodes 63 in the bottom plate 62 of the groove 61 via the two conductive adhesive spots 64.

[0055] The structure of the fixture 200 is as follows: Figures 13 to 18As shown, it includes a frame-shaped base 10, a crystal oscillator carrier 20, a pressure plate 30, a frame-shaped cover 40, and a locking mechanism. The processing area 20A in the middle of the crystal oscillator carrier 20 includes 256 bearing holes 21 arranged in a 16×16 matrix (in another embodiment, the processing area 20A in the middle of the crystal oscillator carrier 20 includes 768 bearing holes 21 arranged in a 32×24 matrix). The bearing holes 21 are rectangular holes that adapt to the base 60. The two long sides of the rectangular hole each include an avoidance groove 42 for the base to pick up and place the chuck. Two frequency test holes 23 are provided on the bottom plate of the bearing hole 21. The bottoms of the two electrodes 63 on the bottom plate 62 of the base are exposed in the frequency test holes 23. The frame-shaped base 10 includes a receiving hole 11 for the crystal oscillator carrier 20. This hole 11 is a stepped hole that is transparent from top to bottom and larger at the top than at the bottom. The outer contour of the crystal oscillator carrier 20 matches the large hole 111 of the stepped hole, and the perimeter of the bottom surface of the crystal oscillator carrier 20 rests on the steps 112 of the stepped hole. A pressure plate 30 is positioned atop the large hole 111, above the crystal oscillator carrier 20. This pressure plate 30 also includes through-holes 31 arranged in a 16×16 matrix, corresponding to the receiving holes 21. A frame-shaped cover 40 presses against the top surface of the pressure plate 30, exposing all through-holes 31. These through-holes 31 serve as both laser processing windows and visual camera windows. The tuning fork wafer 02 in the base 60 is exposed within these through-holes 31. The locking mechanism of this embodiment includes four sets of locking devices 50, separately mounted on the four sides 14 of the base 10, securing the base 10 to the cover. The inner hole surrounded by the four frames 41 of the frame-shaped cover plate is a tapered hole that is larger at the top and smaller at the bottom.

[0056] The locking device 50 includes a lock catch 50A and a magnet 51. The base 10 includes an upwardly protruding bump 12 and a mounting groove 13 for the lock catch 50A on the frame 14 where the locking device 50 is mounted. The mounting groove 13 is arranged on the outside of the bump 12. The lock catch 50A includes a buckle body 52 and two locking pins 53. The lower portion of the buckle body 52 is embedded in the mounting groove 13 of the frame 14 and is hinged to the frame 14 via a hinge axis 54. The direction of the hinge axis 54 between the buckle body 52 and the frame is the long axis direction of the frame 14. The two locking pins 53 are arranged on the upper portion of the buckle body 52 and extend outward along both sides of the buckle body 52. ​​The axial directions of the two locking pins 53 are parallel to the long axis direction of the frame 14. The outer side surface of the bump 12 includes a mounting hole 121 for the magnet 51, and the magnet 51 is embedded in the mounting hole 121. The frame 41 of the cover 40 includes an avoidance groove 42 corresponding to the locking device 50. When the lock buckle 50A is engaged, the protrusion 12 and the upper part of the lock buckle 50A buckle body 52 enter the avoidance groove 42 of the cover frame 41, the inner side surface of the buckle body 52 is in contact with the outer side surface of the protrusion 12, the magnet 51 in the protrusion 12 is attracted to the buckle body 52, and the two lock pins 53 of the lock buckle 50A are pressed on the top surface of the cover frame 41.

[0057] The fixture 200 of the present invention can frequency-modulate 256 or 768 crystal oscillators in a single loading and unloading operation, achieving several times the efficiency of conventional laser frequency modulation. This fixture is compatible with fixtures used for laser fine tuning or ion fine tuning, simplifying the transition between processes and improving inter-process conversion efficiency. The tuning fork crystal 02 is placed into the fixture 200 via the base 60, preventing it from falling or being wasted. Furthermore, the frequency of the tuning fork crystal 02, after being glued and placed into the base, is the actual frequency. This allows for more accurate laser modulation, resulting in a more concentrated frequency for most crystal oscillators, making subsequent processes such as laser fine tuning or ion fine tuning more efficient.

[0058] In the embodiment of the present invention, the coarse adjustment process of the crystal oscillator frequency under the atmospheric environment is performed in the coarse adjustment system of the crystal oscillator frequency.

[0059] The structure of the coarse adjustment system of the crystal oscillator frequency of the present invention is as follows: Figure 3 As shown, it includes a laser frequency modulation device 70, a visual positioning device 80, a frequency testing device 90, an XY motion platform 100 and an industrial computer. The fixture 200 is fixed on the Y-axis motion mechanism of the XY motion platform 100, the Y-axis motion mechanism is installed on the X-axis motion mechanism, and the fixture 200 is located directly above the frequency testing device 90.

[0060] like Figures 3 to 6 As shown, frequency tester 90 includes a frequency tester 90A and a Z-axis lift module 91. Frequency tester 90A is fixed to the top of the Z-axis lift module. Frequency tester 90A comprises a housing 92, a probe contact circuit board 93, multiple test circuit boards 94, and a test head 95. Test head 95 includes multiple probe groups arranged in a matrix, each probe group including two probes 96. Test head 95 is fixed to a top plate 921 of housing 92. Each probe 96 on test head 95 is electrically connected to probe contact circuit board 93, which is in communication with test circuit board 94.

[0061] The two probes 96 of each probe group correspond to the two electrodes 63 on a base 60 and are used to contact the two electrodes 63 at the bottom of the base 60 to obtain an AC voltage signal with the same frequency as the tuning fork chip 02. The AC voltage signal with the same frequency as the tuning fork chip 02 obtained by the test head 95 is transmitted to the test circuit board 94 via the probe contact circuit board 93. The test circuit board 94 amplifies and filters the AC voltage signal, then accurately measures the signal frequency using a π network, an oscillation circuit, or a phase method, and converts the measured frequency information into a digital signal. The data processed by the test circuit board 94 is transmitted to the industrial computer in the form of a digital signal (such as serial communication, USB, SPI, I²C, etc.). The industrial computer controls the laser frequency modulation device 70 to emit a laser to modulate the frequency of the tuning fork arm of the tuning fork chip 02 based on the crystal oscillator frequency of the tuning fork chip 02 measured by the frequency tester 90A.

[0062] like Figure 3 As shown, the visual positioning device 80 includes a camera 81, a lens 82, and a coaxial light source 83. The laser frequency modulation device 70 includes a laser (not shown), a galvanometer 71, a beam combiner 72, and a field lens 73. The laser frequency modulation device 70 is placed directly above the fixture. The optical path of the visual positioning device 80 is arranged horizontally, while the optical path of the laser frequency modulation device 70 is arranged vertically. The optical path combination of the laser frequency modulation device 70 and the visual positioning device 80 adopts a pseudo-coaxial scheme.

[0063] The ultrafast ultraviolet picosecond laser emitted by the laser is reflected by several reflectors. The beam expanded by a 2-8 times beam expander is the incident light 71A of the galvanometer 71. The incident light 71A is reflected by the galvanometer 71 and then passes through the beam combiner 72. The optical axis of the visual light emitted by the coaxial light source 83 after being reflected by the beam combiner 72 coincides with the optical axis of the laser penetrating the beam combiner 72, forming a combined light beam of the same path. The combined light beam is focused by the field lens 73 to form the focused light of the field lens 73. The field lens 73 causes the laser and visual light paths to converge at the focal point, achieving spatial synchronization between the two. The camera 81 captures a dual-channel image through the lens 82, which is used to capture and locate the frequency modulation area 022 at the top of the tuning fork arm. The focused light of the field lens 73 modulates the frequency modulation area 022 at the top of the tuning fork arm to remove material.

[0064] The present invention uses an ultrafast ultraviolet picosecond laser to remove material from the top area of ​​the wafer tuning fork arm in the base by frequency modulation. The laser wavelength is 355nm, the pulse width is 10-50ps, the repetition rate is 50-200kHz, the power is 30W, the single pulse energy is 100-300μJ, and the spot diameter after focusing by the field lens is 5-10μm. The tuning fork arm wafer body and the coating are removed by using the ultraviolet band with a wavelength of 355nm, taking into account the light absorption characteristics of the quartz crystal and the coating materials (chromium, nickel, silver, gold). The pulse width of 10-50ps can reduce heat diffusion during the frequency modulation process.

[0065] After emitting light from the laser, the ultrafast picosecond laser is reflected by several mirrors and expanded by a 2-8x beam expander to a beam diameter of 10 mm. The expanded beam enters the galvanometer. The divergence angle before expansion is 2 mrad and the divergence angle after expansion is 0.4 mrad. After being focused by the field lens, the spot size is 5-10 μm, and the working distance of the field lens is about 150 mm.

[0066] The structure of the embodiment 2 of the coarse adjustment system of the crystal oscillator frequency of the present invention is as follows: Figure 4As shown, the only difference between Example 2 and Example 1 is that the optical path of the visual positioning device 80 is arranged vertically, and the optical path of the laser frequency modulation device 70 is also arranged vertically. The optical path combination of the laser frequency modulation device 70 and the visual positioning device 80 adopts another pseudo-coaxial solution. To this end, the visual positioning device 80 of Example 2 includes a reflector 84. The visual light emitted by the coaxial light source 83 is reflected by the reflector 84 and then reflected by the beam combiner 72, coinciding with the optical axis of the laser light that penetrated the beam combiner 72.

[0067] When using the pseudo-coaxial solution, the light reflected by the galvanometer and the visual coaxial light source pass through the beam combiner. After the visual light is reflected by the beam combiner, the optical axis is conjugated with the laser optical axis, forming the same optical path, and then focused by the field mirror to achieve real-time positioning and processing; the beam combiner allows a high transmittance of >99% for 355nm ultraviolet ultrafast laser, ensuring efficient energy transmission to the field mirror; the beam combiner allows a high reflectivity of >95% for 650nm infrared coaxial light source, and the coaxial light is reflected and overlaps with the transmitted laser spot to achieve beam combining; the coaxial light can also be reflected by several reflectors before passing through the beam combiner to match different structural layouts.

[0068] The structure of the coarse adjustment system of the crystal oscillator frequency of the present invention in embodiment 3 is as follows: Figure 5 As shown, the visual positioning device 80 includes a camera 81, a lens 82, and a coaxial light source 83. The visual positioning device 80 composed of the camera 81, the lens 82, and the coaxial light source 83 captures and locates the frequency modulation area 022 at the top of the tuning fork arm. The laser frequency modulation device 70 includes a laser, a galvanometer 71, and a field lens 73. The laser frequency modulation device 70 is arranged above the fixture. The ultrafast ultraviolet picosecond laser emitted by the laser is reflected by several reflectors. The beam expanded by a 2-8 times beam expander is the incident light of the galvanometer 71. The incident light is reflected by the galvanometer 71 and focused by the field lens 73 to form the focused light of the field lens 73. The focused light of the field lens 73 removes material from the frequency modulation area 022 at the top of the tuning fork arm.

[0069] The difference between Example 3 and Example 1 is that the optical path of the visual positioning device 80 and the optical path of the laser frequency modulation device 70 are independent of each other and no beam combining is performed, which is a paraxial solution.

[0070] When using the visual paraxial solution, the beam combiner is no longer used. The vision directly captures the crystal oscillator tuning fork arm, and the expanded light beam is reflected by the galvanometer and directly enters the field lens for focusing processing.

[0071] In the paraxial solution, coordinate transformation is required to achieve spatial alignment between the laser and the vision system and improve positioning accuracy.

[0072] 1. Establish the following three coordinate systems: laser coordinate system QU, visual coordinate system QL, and world coordinate system QW:

[0073] 1) Laser coordinate system (QU): Origin: optical center of the laser galvanometer; Z-axis: along the direction of laser propagation (focusing direction of the field lens); X-axis: perpendicular to the laser optical path plane, pointing in the direction of laser scanning; Y-axis: determined according to the right-hand rule, orthogonal to the X and Z axes.

[0074] 2) Visual coordinate system (QL): Origin: Camera optical center; Z-axis: Along the camera optical axis (conjugate with the field lens optical axis); X-axis: Horizontal to the camera image plane; Y-axis: Vertical to the camera image plane.

[0075] 3) World Coordinate System (QW): Origin: A global coordinate system defined by a calibration plate or fixed reference point; X, Y, and Z axes: Set according to the application scenario, usually the plane of the calibration plate is the XY plane, and the Z axis is perpendicular to this plane.

[0076] 2. Coordinate transformation: Coordinate transformation is a well-known prior art and will not be described in detail.

[0077] 3. Calibration:

[0078] 1) Calibration plate placement: Place a calibration plate (such as a checkerboard or dot array) in the common field of view of the laser and vision system to ensure that the calibration plate is captured by both the laser and vision system at the same time;

[0079] 2) Image acquisition and processing: Use a vision system to capture the image of the calibration plate, extract its coordinates in the vision coordinate system, use a laser system to mark or scan the calibration plate, and record the point position in the laser coordinate system;

[0080] 3) Parameter estimation: Calculate the rotation matrix and translation vector using the least squares method or other optimization algorithms. This can be combined with known geometric information of the calibration plate for constrained optimization.

[0081] After the base 60 is installed in the fixture 200, the through hole 31 on the pressure plate 30 of the fixture 200 serves as both a laser processing window and a visual photography window, which facilitates visual photography to determine the position of the tuning fork arm; the frequency tester under the fixture is lifted by the Z-axis lifting module, and the probe on the test head contacts the two electrodes at the bottom of the base to test the frequency of the chip in real time; the light spot focused by the field mirror removes material multiple times according to the frequency measured by the probe in real time until the frequency reaches the set frequency; when the fixture places 768 bases, the number of probes can be 4 (2×2), 16 (4×4), 64 (8×8) or 256 (16×16), so that the test areas do not overlap, and the size of the working range of the visual and field mirrors matches the size of the area tested by the probes.

[0082] The above embodiments of the present invention have the following beneficial effects:

[0083] 1) Universal fixtures can improve the efficiency of product transfer between processes: coarse and fine adjustment fixtures are universal, and fine adjustment can be performed directly after coarse adjustment, eliminating the cleaning process and shortening the changeover time by 80%.

[0084] 2) If a large number of products are loaded and unloaded at one time for frequency modulation, the frequency modulation efficiency can be increased by 4 times.

[0085] 3) Frequency modulation on the base, the frequency of laser modulation is more accurate: the tuning fork chip is fixed in the base by dispensing glue for coarse adjustment. This coarse adjustment method will not cause bumps to the tuning fork chip or scratches to the coating. Therefore, after the frequency modulation is completed, there will not be too much change in the frequency, and the modulated frequency accuracy is higher.

[0086] 4) The UV picosecond laser removes the material in the frequency tuning area at the top of the tuning fork arm of the tuning fork wafer, resulting in a material vaporization rate of >90% (compared to the melt sputtering of the nanosecond laser), reducing dust by more than 60%. Frequency test distortion can be avoided during coarse frequency tuning, and the coarse frequency deviation value is small, improving frequency consistency: the coarse tuning deviation can be reduced from ±2000ppm to ±500ppm.

[0087] 5) The heat diffusion depth of the UV picosecond laser is only 0.1μm (compared to 5μm for the nanosecond laser), and the coating temperature rise is less than 50°C, which fundamentally avoids oxidation of the metal coating of the tuning fork chip and reduces the risk of thermal damage.

Claims

1. A method for coarsely adjusting the crystal oscillator frequency under atmospheric conditions, characterized in that: The following steps are involved: 101) Glue the tuning fork crystal, which serves as a frequency coarse adjustment workpiece, into the base; 102) Place the plurality of bases with the tuning fork wafers adhered thereto into a fixture; 103) The fixture is installed in the coarse adjustment system of the crystal oscillator frequency, and the frequency tuning area at the top of the tuning fork arm of the tuning fork crystal in the fixture base is photographed and located using a visual positioning device; 104) Real-time detection of the frequency of a tuning fork crystal used as a frequency coarse adjustment workpiece to obtain an error value of the tuning fork crystal frequency; 105) Based on the error value of the tuning fork crystal frequency, an ultrafast ultraviolet picosecond laser is used to remove material and perform frequency modulation on the frequency modulation area at the top of the tuning fork arm of the tuning fork crystal in the base; Repeat steps 104 and 105 until the frequency of the tuning fork crystal reaches the set value; The base includes a groove for carrying a tuning fork wafer, and the bottom plate of the base includes two electrodes. The two electrodes on the bottom surface of the tuning fork wafer adhered to the groove of the base are electrically connected to the top of the two electrodes in the bottom plate of the base through two adhesive points of conductive glue; the fixture includes a base, a crystal oscillator carrier, a pressure plate, a frame-shaped cover and a locking mechanism. The processing area in the middle of the crystal oscillator carrier includes a plurality of base bearing holes arranged in a matrix. The bearing holes of the crystal oscillator carrier are adapted to the base. The bottom plate of the bearing holes of the crystal oscillator carrier includes two crystal oscillator frequency test holes. The two electrodes of the base The bottom surfaces are respectively exposed in the corresponding crystal oscillator frequency test holes; the frame-shaped base includes a bearing hole of the crystal oscillator carrier plate, and the bearing hole is a stepped hole that is larger at the top and smaller at the bottom. The outer contour of the crystal oscillator carrier plate is adapted to the large hole of the stepped hole, and the periphery of the bottom surface of the crystal oscillator carrier plate is located on the steps of the stepped hole; the pressure plate is arranged on the top of the large hole of the stepped hole, located above the crystal oscillator carrier plate, and the pressure plate includes through holes arranged in a matrix and corresponding to the bearing holes; the frame-shaped cover plate is pressed on the top surface of the periphery of the pressure plate; the locking mechanism includes a plurality of locking devices, which are installed on the frame of the base frame to fasten the base and the cover plate.

2. The coarse adjustment method according to claim 1, characterized in that: The bearing hole is a rectangular hole, and the two long sides of the rectangular hole each include an avoidance groove for the base to pick up and place the chuck; the locking device includes a lock buckle and a magnet, and the frame of the base mounting locking device includes an upwardly protruding protrusion and a mounting groove of the lock buckle, and the mounting groove is arranged on the outside of the protrusion; the lock buckle includes a buckle body and two locking pins, the lower part of the buckle body is embedded in the mounting groove of the base frame and is hinged to the frame of the base, and the direction of the hinge axis of the buckle body and the base frame is the long axis direction of the base frame; the two locking pins are arranged on the upper part of the buckle body, extending outward along both sides of the buckle body, and the axial direction of the two locking pins is parallel to the long axis direction of the base frame; the outer side surface of the protrusion includes a mounting hole for the magnet, and the magnet is embedded in the mounting hole; the frame of the cover plate includes an avoidance groove corresponding to the locking device, and when the lock buckle is buckled, the protrusion and the upper part of the lock buckle body enter the avoidance groove of the cover plate frame, the inner side surface of the buckle body is in contact with the outer side surface of the protrusion, the magnet in the protrusion is attracted to the buckle body, and the two locking pins of the lock buckle are pressed on the top surface of the cover plate frame.

3. The coarse adjustment method according to claim 1, characterized in that: The coarse adjustment system of the crystal oscillator frequency includes a laser frequency modulation device, the visual positioning device, a frequency testing device, an XY motion platform and an industrial computer. The fixture is fixed on the XY motion platform and is located directly above the frequency testing device. The frequency testing device includes a frequency tester and a Z-axis lifting module. The frequency tester is fixed on the top of the Z-axis lifting module. The top of the frequency tester includes a test head. The test head includes a plurality of probe groups arranged in a matrix. Each probe group includes two probes. The two probes of each probe group correspond to two electrodes of a base, and are used to contact the two electrodes at the bottom of the base to test the frequency data of the tuning fork chip. The frequency data obtained by the frequency tester is transmitted to the industrial computer. The upper computer software in the industrial computer controls the laser frequency modulation device to emit laser to modulate the frequency of the tuning fork arm of the tuning fork chip according to the crystal oscillator frequency measured by the probe group.

4. The coarse adjustment method according to claim 3, characterized in that: The visual positioning device includes a camera, a lens and a coaxial light source, and the laser frequency modulation device includes a laser, a galvanometer, a beam combiner and a field lens; the laser frequency modulation device is arranged above the fixture, and the ultrafast ultraviolet picosecond laser emitted by the laser is reflected by several reflectors, and the light beam expanded by a 2-8 times beam expander is the incident light of the galvanometer, and the incident light is reflected by the galvanometer and then passes through the beam combiner; the optical axis of the visual light emitted by the coaxial light source after being reflected by the beam combiner coincides with the optical axis of the laser penetrating the beam combiner, forming a combined light beam of the same path; the combined light beam is focused by the field lens to form a field lens focused light beam, and the field lens makes the laser and visual light paths converge at the focus to achieve spatial synchronization between the two; the camera captures a dual-channel image through the lens, which is used to capture and locate the top area of ​​the tuning fork arm, and the field lens focused light performs material removal frequency modulation on the top area of ​​the tuning fork arm.

5. The coarse adjustment method according to claim 4, characterized in that: The visual positioning device includes a reflector. The visual light emitted by the coaxial light source is reflected by the reflector and then reflected by the beam combiner, and coincides with the laser optical axis that penetrates the beam combiner.

6. The coarse adjustment method according to claim 3, characterized in that: The visual positioning device includes a camera, a lens and a coaxial light source. The visual positioning device composed of the camera, the lens and the coaxial light source captures and locates the top area of ​​the tuning fork arm; the laser frequency modulation device includes a laser, a galvanometer and a field lens; the laser frequency modulation device is arranged above the fixture, and the ultrafast ultraviolet picosecond laser emitted by the laser is reflected by several reflectors. The light beam expanded by the 2-8 times beam expander is the incident light of the galvanometer. The laser after the incident light is reflected by the galvanometer is focused by the field lens to form a field lens focused light. The field lens focused light performs material removal frequency modulation on the top area of ​​the tuning fork arm.

7. The coarse adjustment method according to claim 3, characterized in that: The frequency tester includes a box, a probe contact circuit board, a test circuit board and the test head. The test head is fixed on the top plate of the box. The probes on the test head are electrically connected to the probe contact circuit board, and the probe contact circuit board is communicatively connected to the test circuit board. The two probes of each probe group contact two electrodes on a base to obtain an AC voltage signal with the same frequency as the tuning fork chip. The AC voltage signal with the same frequency as the tuning fork chip obtained by the test head is transmitted to the test circuit board through the probe contact circuit board. The test circuit board amplifies and filters the AC voltage signal, and then uses a π network, an oscillation circuit or a phase method to accurately measure the signal frequency, and converts the measured frequency information into a digital signal. The data processed by the test circuit board is transmitted to the industrial computer in the form of a digital signal.

8. The coarse adjustment method according to claim 4 or 6, characterized in that: The laser wavelength of the ultrafast ultraviolet picosecond laser is 355nm, the pulse width is 10-50ps, the repetition frequency is 50-200kHz, the power is 30W, the single pulse energy is 100-300μJ, and the spot diameter after focusing by the field lens is 5-10μm.

9. The coarse adjustment method according to claim 1, characterized in that: The fixture is a multi-process fixture, which is common to laser fine-tuning fixtures or ion fine-tuning fixtures.

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