Device and method for measuring vacuum packaging leak rate of micro-electro-mechanical resonant device

Abstract

The invention provides a device and method for measuring the vacuum packaging leak rate of a micro electro mechanical resonant device, and the device comprises a resonant device which comprises a driving structure, a vibration mass block, and a vibration pickup structure; the closed-loop driving circuit is connected with the driving structure and the vibration pickup structure and used for adjusting driving voltage applied to the driving structure according to the displacement information and preset displacement target voltage; the test computer is connected with the air pressure sensor, the temperature sensor and the closed-loop drive circuit, the air pressure sensor is used for measuring the pressure value of the environment where the resonant device is located, and the temperature sensor is used for measuring the temperature value of the environment where the resonant device is located; and the test computer is used for calculating the leakage rate of the resonant device in any time period according to the driving voltage output by the closed-loop driving circuit and the environment temperature value. Through the device provided by the invention, the problems of complex structure, low measurement precision and high cost of the current leak rate measurement system are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of micro-electro-mechanical sensor, in particular to a micro-electro-mechanical resonant device vacuum packaging leak rate measuring device and method. BACKGROUND

[0002] The micro-electro-mechanical resonant device is a device with a feature size in the order of microns processed by micro-electronic technology, and is a core structural component of multiple types of sensors, such as micro-electro-mechanical gyroscopes, micro-resonant acceleration sensors, micro-resonant pressure sensors, and resonant electric field sensors, etc. The micro-electro-mechanical resonant device has the advantages of small size, low cost, and suitability for batch processing, and is widely used in various fields of civil and industrial use.

[0003] The micro-electro-mechanical resonant device is usually packaged in a hermetically sealed vacuum, that is, the device is sealed in a cavity with a certain degree of vacuum, so that the device works in a low-damping environment, has a high modal quality factor, and achieves a higher signal-to-noise ratio. After hermetically sealed vacuum packaging, the vacuum degree in the cavity will deteriorate due to internal material outgassing, packaging micro-hole leakage, and gas permeation, and even the device will fail. Therefore, it is necessary to test the leak rate of the vacuum packaging to evaluate the reliability and life of the device.

[0004] The current commonly used methods for testing leak rate mainly include helium detection method, Fourier transform infrared spectroscopy measurement method, built-in vacuum gauge method, and membrane deformation method, etc. The precision of the helium detection method depends on the precision of the helium mass spectrometer leak detector, which is generally 10 -10 Pa·m 3 / s, and is not suitable for micro-resonant devices. In addition, the helium detection method cannot accurately distinguish whether the detected helium gas is from the real leakage of the packaging or material permeation. The Fourier transform infrared spectroscopy measurement method requires that the packaging must be transparent to infrared radiation, and when there are many metal wires across the thin film or cavity in the packaging, it may interfere with infrared transmission. The built-in vacuum gauge method integrates a Pirani gauge in the device to test the internal gas pressure of the cavity, which increases the area and process complexity of the device. The membrane deformation method measures the deformation of the membrane on the surface of the cavity and the packaging gas pressure, but requires a very thin membrane layer, and the measurement precision is not accurate.

[0005] Therefore, the current measurement methods have limitations in terms of measurement precision and cost, and there is an urgent need for a simple, efficient, and accurate non-destructive leak rate measurement method. SUMMARY

[0006] In view of the above problems, one of the purposes of the present application is to provide a micro-electro-mechanical resonant device vacuum packaging leak rate measuring device to solve the problems of complex structure, low measurement precision, and high cost of the current leak rate measuring system. The second purpose of the present application is to provide a micro-electro-mechanical resonant device vacuum packaging leak rate measuring method to achieve low-cost, high-precision non-destructive testing.

[0007] To achieve one of the purposes, in the first aspect, the application provides a micro-electromechanical resonant device vacuum packaging leak rate measuring device, which adopts the technical scheme of: A micro-electromechanical resonant device vacuum packaging leak rate measuring device, the device comprises: A resonant device, comprising a driving structure, a vibrating mass block and a vibration pickup structure, the vibration pickup structure is used to obtain displacement information generated by the vibrating mass block driven by the driving structure to vibrate; A closed-loop driving circuit connected with the driving structure and the vibration pickup structure respectively, used to adjust the driving voltage applied to the driving structure according to the displacement information and a preset displacement target voltage, so as to control the resonant device to vibrate in the horizontal direction at the displacement target voltage; A test computer connected with a gas pressure sensor and a temperature sensor respectively, the gas pressure sensor is used to measure the environmental pressure value of the resonant device, and the temperature sensor is used to measure the environmental temperature value of the resonant device; The test computer is further connected with the closed-loop driving circuit, and is used to: Calibrate the matching relationship between a plurality of sample environmental pressure values collected by the gas pressure sensor and a plurality of sample driving voltages collected by the closed-loop driving circuit; Obtain the driving voltage output by the closed-loop driving circuit and the environmental temperature value at different times, and obtain the environmental pressure value corresponding to the driving voltage at each time according to the matching relationship; According to the environmental pressure value and the environmental temperature value at each time, the leak rate of the resonant device in any time period is calculated.

[0008] As one of the preferred schemes, the closed-loop driving circuit comprises: A pre-reading circuit connected with the vibration pickup structure, used to convert the displacement information into a vibration displacement voltage; An amplitude extraction unit connected with the pre-reading circuit, used to receive the vibration displacement voltage and output the amplitude of the vibration displacement voltage; A phase shifter connected with the pre-reading circuit, used to adjust the phase of the vibration displacement voltage and output a voltage signal in phase with the driving voltage; An adder connected with the amplitude extraction unit, used to receive and calculate the amplitude of the vibration displacement voltage and the displacement target voltage, and output a displacement error voltage; A controller connected with the adder, used to receive the displacement error voltage and output a driving closed-loop control voltage; A modulator connected with the phase shifter and the controller respectively, used to receive the voltage signal and the driving closed-loop control voltage, and obtain the adjusted driving voltage. The modulator is connected with the driving structure to apply the adjusted driving voltage to the driving structure.

[0009] As one of the preferred solutions, the driving structure and the vibration pickup structure include any one of a variable-area slider-film comb-type capacitor structure and a variable-gap press-film parallel-plate-type capacitor structure.

[0010] To achieve the second purpose, in a second aspect, the application provides a micro-electromechanical resonant device vacuum packaging leak rate measurement method, which adopts the technical solution of: A micro-electromechanical resonant device vacuum packaging leak rate measurement method, the method comprising: The vibration pickup structure in the resonant device obtains displacement information generated by the driving structure driving the vibration mass block to vibrate; The closed-loop driving circuit adjusts the driving voltage applied to the driving structure according to the displacement information and a preset displacement target voltage, so that the resonant device performs lateral vibration at the displacement target voltage; The test computer calibrates the matching relationship between a plurality of sample environmental pressure values collected by the gas pressure sensor and a plurality of sample driving voltages collected by the closed-loop driving circuit; The driving voltage output by the closed-loop driving circuit at different times and the environmental temperature value collected by the temperature sensor are obtained, and the environmental pressure value corresponding to the driving voltage at each time is obtained according to the matching relationship; The leak rate of the resonant device in any time period is calculated according to the environmental pressure value and the environmental temperature value at each time.

[0011] As one of the preferred solutions, the closed-loop driving circuit adjusts the driving voltage applied to the driving structure according to the displacement information and a preset displacement target voltage, which includes: The pre-reading circuit converts the displacement information into a vibration displacement voltage; The amplitude extraction unit receives the vibration displacement voltage and outputs the amplitude of the vibration displacement voltage; The phase shifter adjusts the phase of the vibration displacement voltage and outputs a voltage signal in phase with the driving voltage; The adder receives and calculates the amplitude of the vibration displacement voltage and the displacement target voltage, and outputs a displacement error voltage; The controller receives the displacement error voltage and outputs a driving closed-loop control voltage; The modulator receives the voltage signal and the driving closed-loop control voltage, and applies the adjusted driving voltage to the driving structure.

[0012] As one of the preferred solutions, the test computer calibrates the matching relationship between the plurality of sample ambient pressure values collected by the air pressure sensor and the plurality of sample drive voltages collected by the closed-loop drive circuit, comprising: Selecting a plurality of calibration air pressure values based on a specified vacuum degree range; According to the plurality of calibration air pressure values, a plurality of sample ambient pressure values collected by the air pressure sensor corresponding to the plurality of calibration air pressure values are obtained; Obtaining the sample drive voltage under each sample ambient pressure value; Fitting the plurality of sample ambient pressure values and the plurality of sample drive voltages to obtain a fitting formula of drive voltage and ambient pressure value; the fitting formula is:

[0013] Wherein, P is the ambient pressure value, the unit is Pa; f is the fitting operation of pressure under different drive voltages; V c is the drive voltage amplitude, the unit is v.

[0014] As one of the preferred solutions, the test computer calibrates the matching relationship between the plurality of sample ambient pressure values collected by the air pressure sensor and the plurality of sample drive voltages collected by the closed-loop drive circuit, comprising: Setting the total test time and the sampling interval, collecting the drive voltage output by the closed-loop drive circuit and the ambient temperature value collected by the temperature sensor at different test times within the total test time; According to the fitting formula, the ambient pressure value corresponding to the drive voltage at each test time is obtained.

[0015] As one of the preferred solutions, the test computer calibrates the matching relationship between the plurality of sample ambient pressure values collected by the air pressure sensor and the plurality of sample drive voltages collected by the closed-loop drive circuit, comprising: Establishing the change curve of the ambient pressure value at different test times within the total test time; Based on the change curve, selecting the corresponding ambient pressure value and the corresponding ambient temperature value at any two test times on the change curve, and calculating the leakage rate of the resonant device in any time period.

[0016] As one of the preferred solutions, the test computer calibrates the matching relationship between the plurality of sample ambient pressure values collected by the air pressure sensor and the plurality of sample drive voltages collected by the closed-loop drive circuit, comprising: The formula for calculating the leakage rate is:

[0017] Wherein, L is the leakage rate, the unit is Pa·m 3 / s; V is a package volume of the resonant device, in m 3 ; t1 is a first test time, in s; t2 is a second test time, in s; T1 is an ambient temperature value at the first test time, in K; T2 is an ambient temperature value at the second test time, in K; P1 is an ambient pressure value at the first test time, in Pa; P2 is an ambient pressure value at the second test time, in Pa.

[0018] As one of the preferred schemes, the test computer calibrates the matching relationship between the plurality of sample ambient pressure values collected by the gas pressure sensor and the plurality of sample driving voltages collected by the closed-loop driving circuit, and the matching relationship includes that: The unsealed resonant device and the closed-loop driving circuit are placed in a vacuum device with adjustable gas pressure. The closed-loop driving circuit outputs the driving voltage at different times, and the driving voltage includes that: The vacuum-sealed resonant device and the closed-loop driving circuit are connected.

[0019] Compared with the prior art, the present application has the following advantages: In the process of measuring the leakage rate by using the device provided by the embodiment of the present application, the test computer realizes real-time monitoring of the change of the gas pressure by the change of the driving voltage continuously output by the closed-loop driving circuit. Therefore, without additional sensors, the lossless detection is realized by using the electrical parameters of the resonator. The MEMS resonator is sensitive to the change of the Q value, and the driving voltage is sensitive to the response, so that the smallest packaging leakage can be detected. The device is suitable for leakage rate detection of various vacuum-sealed MEMS devices (gyroscopes, accelerometers, radio frequency resonators, etc.), and has high detection precision, and avoids increasing the packaging complexity and cost.

[0020] The method has the same advantages as the device described above with respect to the prior art, and will not be described here. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings needed to be used in the description of the present application. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] Figure 1 is a schematic diagram of a micro-electro-mechanical resonant device vacuum packaging leakage rate test device provided by an embodiment of the present application; Figure 2 is a schematic diagram of a micro-electro-mechanical resonant device structure provided by an embodiment of the present application; Figure 3is a micro-electromechanical resonant device closed-loop driving circuit schematic diagram provided by an embodiment of the present application; Figure 4 is a driving voltage-gas pressure calibration step flow chart in a micro-electromechanical resonant device vacuum packaging leak rate measurement method provided by an embodiment of the present application; Figure 5 is a packaging leak rate test step flow chart in a micro-electromechanical resonant device vacuum packaging leak rate measurement method provided by an embodiment of the present application.

[0023] Mark explanation: 1, resonant device; 2, driving electrode; 3, driving structure; 4, vibrating mass; 5, vibration pickup structure; 6, pickup electrode; 200, test computer; 201, first acquisition card input channel; 202, acquisition card input channel; 203, second acquisition card input channel; 300, input end of preamplifier readout circuit; 301, closed-loop driving circuit; 304, driving voltage; 401, preamplifier readout circuit; 402, vibration displacement voltage; 403, amplitude extraction unit; 404, vibration displacement voltage amplitude; 405, adder; 406, displacement target voltage; 407, voltage signal; 408, controller; 409, modulator; 410, displacement error voltage; 411, phase shifter; 412, 413, driving closed-loop control voltage. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0025] In order to facilitate the understanding of the present application, it should be noted that according to the motion form of the micro resonator structure, the gas damping suffered by the structure can be divided into sliding film motion damping and pressure film motion damping, and the modal damping is closely related to the packaging gas pressure. It is theoretically proved that the quality factor (Q value) of the micro resonator structure mode is inversely proportional to the damping, inversely proportional to the packaging gas pressure, and proportional to the number of free gas motion, as shown in formula 1. Therefore, the internal pressure of the packaging cavity can be characterized by the quality factor of the structure.

[0026] Formula 1 Wherein, p(t) is the packaging gas pressure, N(t) is the number of free gas motion, Q(t)is the quality factor (Q value) of the MEMS resonant device. Through a closed-loop control circuit, the microresonator structure can be made to vibrate with constant amplitude in one of its main operating modes, satisfying the following relationship, as shown in Equation 2.

[0027] Formula 2 in, K vf is the conversion coefficient from voltage to driving force, V c is the driving voltage amplitude, Q and k are the quality factor and stiffness of the MEMS resonant device in a certain working mode, K dv is the conversion coefficient from displacement to vibration voltage, V r is the displacement target voltage.

[0028] Since the closed-loop control circuit can meet the requirements even when the Q value changes, the driving voltage amplitude can be adjusted V c , maintain the resonator's displacement target voltage V r The following relationship can be obtained by transformation, as shown in Formula 3.

[0029] Formula 3 From Equation 3, we can see that when the microresonator is in closed-loop driving, the driving voltage amplitude is V c Inversely proportional to the Q value and the package pressure p(t) Therefore, the driving voltage amplitude can be used to represent the internal pressure of the package cavity, and thus the leakage rate change of the package can be calculated.

[0030] Based on this, firstly, referring to Figure 1 As shown, Figure 1 FIG1 is a diagram showing the overall structure of the device for measuring the leak rate of a vacuum package of a micro-electromechanical resonant device according to the present invention. Figure 1 As shown, the present invention provides a vacuum packaging leak rate measurement device for a micro-electromechanical resonant device 1, the device comprising: The resonant device 1 includes a driving structure 3, a vibration mass block 4, and a vibration pickup structure 5. The vibration pickup structure 5 is used to obtain displacement information generated by the driving structure 3 driving the vibration mass block 4 to vibrate; The closed-loop driving circuit 301 is connected to the driving structure 3 and the vibration pickup structure 5 respectively, and is used to generate a displacement target voltage 406 (such as Figure 3 V in r), the driving voltage 304 applied to the driving structure 3 is adjusted to control the resonant device 1 to vibrate in the transverse direction with a displacement target voltage 406; The test computer 200 is connected with the air pressure sensor and the temperature sensor respectively, the air pressure sensor is used for measuring the environmental pressure value where the resonant device 1 is located, and the temperature sensor is used for measuring the environmental temperature value where the resonant device 1 is located; wherein, the test computer 200 is also connected with the closed-loop driving circuit 301.

[0031] Specifically, the device comprises a micro-electro-mechanical resonant device 1, a closed-loop driving circuit 301 and a test computer 200. As shown in Figure 2 Figure 2 is a structural schematic diagram of a micro-electro-mechanical resonant device provided by the embodiment, the driving structure 3 and the vibration pickup structure 5 respectively lead out electrodes, such as the driving electrode 2 led out by the driving structure 3 and the pickup electrode 6 led out by the vibration pickup structure 5. The driving voltage 304 applied to the driving structure 3 can generate a driving force, the driving force makes the vibration mass block 4 vibrate, and the displacement change amount of the vibration mass block 4 is acquired by the vibration pickup structure 5 and output through the pickup electrode 6. In the embodiment, the driving structure 3 and the vibration pickup structure 5 can adopt a differential capacitive structure, which can be a variable-area slide-film comb-type capacitive structure or a variable-gap press-film parallel-plate capacitive structure, and can adopt an electrostatic or piezoelectric driving mode and vibration pickup mode.

[0032] The input end of the closed-loop driving circuit 301 is connected with the vibration pickup structure 5 of the micro-electro-mechanical resonant device 1, the first output end of the closed-loop driving circuit 301 is connected with the driving structure 3 of the micro-electro-mechanical resonant device 1, and the second output end of the closed-loop driving circuit 301 is connected with the input channel 202 of the acquisition card of the test computer 200.

[0033] In the embodiment, the input end of the closed-loop driving circuit 301 is connected with the resonant device 1 through the pickup electrode 6 of the vibration pickup structure 5, the closed-loop driving circuit 301 has two output ends, the first output end is connected with the driving structure 3 through the driving electrode 2, the first output end outputs the driving voltage 304 to the driving structure 3 to form a driving closed loop, and then the resonant device 1 is made to vibrate with constant amplitude at the resonant frequency under the control of the displacement target voltage 406 by the closed-loop driving circuit 301.

[0034] Specifically, even in the case of Q value change, the driving voltage amplitude Vc applied is automatically adjusted by the closed-loop control circuit to keep the displacement target voltage 406 of the resonator unchanged, and since the vibration voltage always keeps the set value, constant amplitude can be realized. The change of the driving voltage 304 can be acquired by the test computer 200.

[0035] ​The second output end of the closed-loop driving circuit 301 is connected with the input channel 202 of the acquisition card of the test computer 200, the first input channel 201 of the acquisition card of the test computer 200 is connected with the air pressure sensor, the air pressure sensor can measure the ambient pressure value of the resonant device 1, the second input channel 203 of the acquisition card of the test computer 200 is connected with the temperature sensor, and the temperature sensor can measure the ambient temperature value of the resonant device 1.

[0036] Through the test computer 200 and the air pressure sensor and the temperature sensor connected therewith, before the test starts, a plurality of ambient pressure values and the driving voltage amplitudes collected under the plurality of ambient pressure values are collected to establish a mapping relationship between the ambient pressure value and the driving voltage amplitude as a calibration reference. During the test, the data communication between the test computer 200 and the closed-loop driving circuit 301 is established, the ambient temperature value and the driving voltage amplitude are obtained in real time, and the mapping relationship obtained by the calibration before the test starts is used to obtain the leakage and the leak rate of the resonant device 1.

[0037] Specifically, after the resonant device 1, the closed-loop driving circuit 301 and the test computer 200 are assembled, and the closed-loop driving circuit 301 is vibrated at the preset displacement target voltage 406, the test computer 200 can be used for calibration and measurement of the leak rate. The test computer 200 is used for: Calibrating the matching relationship between a plurality of sample ambient pressure values collected by the air pressure sensor and a plurality of sample driving voltages collected by the closed-loop driving circuit 301; During the calibration process, a plurality of known sample ambient pressure values can be selected, and the driving voltage amplitudes are collected by the air pressure sensor and input to the test computer 200, and the mapping relationship between the sample driving voltage amplitude and the sample ambient pressure value is established, and the driving voltage-air pressure calibration is completed.

[0038] The driving voltage 304 output by the closed-loop driving circuit 301 and the ambient temperature value at different times are obtained, and the ambient pressure value corresponding to the driving voltage 304 at each time is obtained according to the matching relationship; After the calibration is completed, during the actual test process, the driving voltage 304 of the packaged resonant device 1 at each time can correspond to a sample driving voltage. The target sample driving voltage to which the current driving voltage 304 belongs is determined, the target sample driving voltage is any one of the plurality of sample driving voltages, so that the ambient pressure value matched with the target sample driving voltage is obtained. Therefore, during the test process, the air pressure sensor is no longer needed, and only the driving voltage 304 and the ambient temperature value need to be collected, and the current air pressure can be calculated in real time through the mapping relationship in the calibration process.

[0039] The leakage rate of the resonant device 1 in any time period is calculated based on the ambient pressure value and the ambient temperature value at each moment.

[0040] In summary, when using the device of the present invention and measuring leak rates, the test computer 200 monitors air pressure changes in real time through the continuous output of the closed-loop drive circuit 301, using changes in the drive voltage. This eliminates the need for additional sensors and utilizes the resonator's inherent electrical parameters for nondestructive testing. MEMS resonators are sensitive to changes in Q, and the drive voltage 304 is highly responsive, enabling detection of even the smallest package leaks. This device is suitable for leak rate testing of various vacuum-packaged MEMS devices (gyroscopes, accelerometers, RF resonators, etc.), achieving high detection accuracy while avoiding increased packaging complexity and cost.

[0041] like Figure 3 As shown, Figure 3 The schematic diagram of the closed-loop driving circuit of the micro-electromechanical resonant device of the present invention is shown. The embodiment of the present application further illustrates the closed-loop driving circuit 301. The closed-loop driving circuit 301 includes: a pre-readout circuit 401, the input end 300 of the pre-readout circuit is connected to the vibration pickup structure 5 of the resonant device 1, converts the displacement information into a vibration displacement voltage 402, and outputs the vibration displacement voltage 402; an amplitude extraction unit 403, the input end of the amplitude extraction unit 403 is connected to the output end of the pre-readout circuit 401, and outputs the voltage amplitude of the vibration displacement voltage 402; a phase shifter 411, the input end of the phase shifter 411 is connected to the output end of the pre-readout circuit 401, performs phase adjustment on the vibration displacement voltage 402, and outputs a voltage signal 407 in phase with the driving voltage 304; Adder 405, the first input terminal of adder 405 inputs displacement target voltage 406, the second input terminal of adder 405 is connected to the output terminal of amplitude extraction unit 403, and outputs displacement error voltage 410; controller 408, the input terminal of controller 408 is connected to the output terminal of adder 405, and outputs driving closed-loop control voltage 412 / 413; modulator 409, the first input terminal of modulator 409 is connected to the output of phase shifter 411, the second input terminal and the third input terminal of modulator 409 are respectively connected to the two output terminals of controller 408, and outputs driving voltage 304, and the output terminal of modulator 409 is connected to the driving structure 3 of micro-electromechanical resonant device 1.

[0042] In the embodiment, the input end 300 of the pre-reading circuit is connected with the pickup electrode 6 of the vibration pickup structure 5 of the resonant device 1, and the displacement information output by the vibration pickup structure 5 is converted into a vibration displacement voltage 402, wherein the displacement information is the displacement change amount of the vibration mass block 4 obtained by the vibration pickup structure 5; the vibration displacement voltage 402 output by the pre-reading circuit 401 is input to the amplitude extraction unit 403 through the first output end and to the phase shifter 411 through the first output end. Then, the amplitude signal of the vibration displacement voltage 402 is extracted by the amplitude extraction unit 403 to obtain a vibration displacement voltage amplitude 404, and the vibration displacement voltage amplitude 404 is input to the adder 405 to subtract the displacement target voltage 406 to obtain a displacement error voltage 410. The displacement error voltage 410 is connected to the controller 408 to obtain a driving closed-loop control voltage 412 / 413, wherein the driving closed-loop control voltage 412 and the driving closed-loop control voltage 413 are equivalent and opposite in phase. Further, the controller 408 is a PID controller, or a controller 408 with other control law.

[0043] Meanwhile, the vibration displacement voltage 402 obtains a voltage signal 407 after passing through the phase shifter 411, which is in phase and frequency with the driving voltage 304. Finally, the voltage signal 407 and the driving closed-loop control voltage 412 / 413 are input into the modulator 409 to obtain the driving voltage 304, which is connected with the driving electrode 2 of the driving structure 3 of the resonant device 1. Further, the resonant device 1 can be made to vibrate at a constant amplitude at the displacement target voltage 406 at the resonant frequency of the resonant device 1 through the closed-loop driving circuit 301.

[0044] Correspondingly, in a second aspect, the embodiment of the present application provides a micro-electro-mechanical resonant device 1 vacuum packaging leak rate measurement method, which depends on the micro-electro-mechanical resonant device 1 vacuum packaging leak rate measurement device provided by the first aspect of the present application. The method comprises the following steps: S1, the vibration pickup structure 5 in the resonant device 1 obtains displacement information generated by driving the vibration mass block 4 to vibrate by the driving structure 3; The vibration pickup structure 5 converts the actual vibration displacement of the vibration mass block 4 into displacement information, which can be obtained by capacitive detection and piezoresistive detection, etc., to provide feedback for the closed-loop control of step S2.

[0045] S2, the closed-loop driving circuit 301 adjusts the driving voltage 304 applied to the driving structure 3 according to the displacement information and the preset displacement target voltage 406, so as to control the resonant device 1 to vibrate at a constant amplitude at the displacement target voltage 406; Since the air pressure in the package cavity directly affects the energy loss (i.e. the quality factor Q value). For example, if the package leaks, the air pressure in the package cavity rises, the air damping increases, and the Q value decreases. In order to maintain a constant amplitude, the driving circuit needs to increase the driving voltage amplitude to compensate for the energy loss. When the air pressure decreases, the opposite is true. Therefore, a closed-loop control circuit is used, and the input displacement target voltage 406 makes the resonant device 1 vibrate at a constant amplitude in one of its main operating modes. In closed-loop driving mode, the driving voltage amplitude of the micro resonator is inversely proportional to the Q value, and is proportional to the internal air pressure of the package cavity.

[0046] Therefore, by monitoring the changes in the driving voltage 304 in real time, it can be indirectly determined whether the package has leaked, and the leakage rate change of the package can be further calculated, and the leakage value at a certain time can be obtained.

[0047] After the resonant device 1, the closed-loop driving circuit 301 and the test computer 200 are assembled, and the closed-loop driving circuit 301 is made to vibrate at a constant amplitude at the preset displacement target voltage 406, the leakage rate can be measured. The leakage rate measurement process includes two steps of driving voltage-air pressure calibration and package leakage rate test, both of which are performed by the test computer 200.

[0048] S3, the test computer 200 calibrates the matching relationship between the plurality of sample environment pressure values collected by the air pressure sensor and the plurality of sample driving voltages collected by the closed-loop driving circuit 301; During calibration, a plurality of known sample environment pressure values are selected and collected by the air pressure sensor into the test computer 200. The driving voltage amplitude is collected at all known air pressures, and the mapping relationship between the sample driving voltage amplitude and the sample environment pressure value is established, and the driving voltage-air pressure calibration is completed.

[0049] S4, obtaining the driving voltage 304 output by the closed-loop driving circuit 301 at different times, and the environment temperature value collected by the temperature sensor, and obtaining the environment pressure value corresponding to the driving voltage 304 at each time according to the matching relationship; After calibration, during actual testing, the driving voltage 304 of the packaged resonant device 1 at each time can correspond to a sample driving voltage. Determine the target sample driving voltage to which the current driving voltage 304 belongs, and the target sample driving voltage is any one of the plurality of sample driving voltages, so as to obtain the environment pressure value matched with the target sample driving voltage. Therefore, during testing, the air pressure sensor is no longer needed, and only the driving voltage 304 and the environment temperature value need to be collected, and the current air pressure can be calculated in real time through the mapping relationship in the calibration process.

[0050] S5, calculate the leak rate of the resonant device 1 in any time period according to the environmental pressure value and the environmental temperature value at each time.

[0051] The embodiment can use the curve of the change of the air pressure over time. On the air pressure-time curve, any two time points are manually selected every fixed time, and the corresponding air pressures at the two time points are recorded. Combined with the environmental temperature value, the leak rate of the cavity in the corresponding time period between the two time points is calculated.

[0052] In some embodiments, the starting calculation time, the sampling interval and the calculation period can be set, and the test computer 200 can collect the air pressure in the calculation period every interval time and automatically calculate the leak rate.

[0053] Further, step S2 comprises: S21, the pre-reading circuit 401 converts the displacement information into a vibration displacement voltage 402; S22, the amplitude extraction unit 403 receives the vibration displacement voltage 402 and outputs the vibration displacement voltage amplitude 404; S23, the phase shifter 411 adjusts the phase of the vibration displacement voltage 402 and outputs the voltage signal 407 in phase with the driving voltage 304; S24, the adder 405 receives and calculates the vibration displacement voltage amplitude 404 and the displacement target voltage 406, and outputs the displacement error voltage 410; S25, the controller 408 receives the displacement error voltage 410 and outputs the driving closed-loop control voltage 412 / 413; S26, the modulator 409 receives the voltage signal 407 and the driving closed-loop control voltage 412 / 413, and applies the adjusted driving voltage 304 to the driving structure 3.

[0054] Further, step S3 comprises: S27, place the unpackaged resonant device 1 and the closed-loop driving circuit 301 in a vacuum device with adjustable air pressure.

[0055] Further, step S3 comprises: S31, select a plurality of calibration air pressure values based on the specified vacuum degree range; S32, according to the plurality of calibration air pressure values, obtain a plurality of sample environmental pressure values corresponding to the plurality of calibration air pressure values collected by the air pressure sensor; S33, obtain a sample driving voltage at each sample environmental pressure value; S34, fit the plurality of sample environmental pressure values and the plurality of sample driving voltages to obtain a fitting formula of the driving voltage 304 and the environmental pressure value; the fitting formula is as formula 4: Formula 4 Wherein, P is the ambient pressure value, unit is Pa; f is the fitting operation of the pressure under different driving voltage 304; V c is the driving voltage amplitude, unit is v.

[0056] Further, the step S4 includes: S35, connecting the vacuum packaged resonant device 1 and the closed-loop driving circuit 301.

[0057] Further, the step S4 includes: S41, setting the total test time and the sampling interval, collecting the driving voltage 304 output by the closed-loop driving circuit 301 at different test times within the total test time, and the ambient temperature value collected by the temperature sensor; S42, obtaining the ambient pressure value corresponding to the driving voltage 304 at each test time according to the fitting formula.

[0058] Further, the step S5 includes: S51, establishing the change curve of the ambient pressure value at different test times within the total test time; S52, based on the change curve, selecting the ambient pressure value and the corresponding ambient temperature value at any two test times on the change curve, and calculating the leakage rate of the resonant device 1 at any time period. Wherein, the calculation formula is as formula 5: Formula 5 Wherein, L is the leakage rate, unit is Pa·m 3 / s; V is the packaging volume of the resonant device 1, unit is m 3 ; t1 is the first test time, unit is s; t2 is the second test time, unit is s; T1 is the ambient temperature value at the first test time, unit is K; T2 is the ambient temperature value at the second test time, unit is K; P1 is the ambient pressure value at the first test time, unit is Pa; P2 is the ambient pressure value at the second test time, unit is Pa.

[0059] In summary, the micro-electromechanical resonant device 1 vacuum packaging leakage rate test method and device provided by the embodiment of the present application can realize low-cost, non-destructive testing, and compared with the existing methods, the method has high test precision and good repeatability due to the use of the driving closed-loop circuit, and can realize batch high-efficiency measurement.

[0060] The following embodiment provides a specific micro-electromechanical resonant device vacuum packaging leakage rate measurement method, which includes a calibration step and a measurement step.

[0061] As Figure 4 shown, Figure 4A flow chart of a driving voltage-gas pressure calibration step in the micro-electromechanical resonator vacuum packaging leak rate measurement method of the present application is shown, and the calibration step comprises: S101, at room temperature, place the unpackaged micro-electromechanical resonator and its closed-loop driving circuit 301 in a gas pressure adjustable vacuum device; S102, input a displacement target voltage 406 in the closed-loop driving circuit 301 to make the micro-electromechanical resonator 1 vibrate at its resonant frequency, and obtain a driving closed-loop control voltage 412 / 413; S103, in the required vacuum degree range, select several gas pressure values, adjust the pressure value of the environment in which the resonator is located according to the gas pressure values, and give the environment pressure value through a gas pressure sensor; S104, collect the environment pressure value and the driving voltage amplitude by the test computer 200 until the calibration at the selected several gas pressure values is completed; S105, fit the collected series of gas pressure values with the driving voltage 304 values to obtain the driving voltage 304-gas pressure fitting formula shown in the above formula 4.

[0062] As Figure 5 shown, Figure 5 A flow chart of a packaging leak rate test step in the micro-electromechanical resonator vacuum packaging leak rate measurement method of the present application is shown, and the test step comprises: S106, connect the vacuum packaged resonator 1 with the closed-loop driving circuit 301; S107, according to the test requirements, set the total test time and the sampling interval, and collect and store the output of the driving voltage 304Vc and the temperature sensor by the test computer 200; S108, according to the driving voltage 304-gas pressure fitting formula, convert the recorded driving voltage amplitude into a gas pressure value; S109, draw a gas pressure-time curve, find a linear segment of the gas pressure-time curve, and take two points A (t1, p1, T1) and B (t2, p2, T2) on the linear segment; S210, calculate the leak rate according to the above formula 5.

[0063] It should be noted that for the method embodiment, the present application embodiment is not limited by the described action sequence, because according to the present application embodiment, certain steps can be performed in other sequences or simultaneously.

[0064] For the above method embodiment, since it is basically similar to the system embodiment, the description is relatively simple, and the relevant parts can continue to refer to the part of the system embodiment.

[0065] It should be noted that each of the embodiments of the present specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the embodiments can be mutually referred to.

[0066] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, device, or computer program product. Therefore, the embodiments of the present application can adopt a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the embodiments of the present application can adopt the form of a computer program product implemented on one or more computer usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer usable program codes.

[0067] The embodiments of the present application are described with reference to flowcharts and / or block diagrams according to the method, terminal device (system), and computer program product of the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing terminal device to produce a machine, so that the instructions executed by the computer or other programmable data processing terminal device produce a device that implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks Figure 1 The device that implements the functions specified in one block or multiple blocks.

[0068] These computer program instructions can also be stored in a computer readable storage medium that can guide the computer or other programmable data processing terminal device to work in a specific way, so that the instructions stored in the computer readable storage medium produce a product including instruction devices that implement the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks Figure 1 The device that implements the functions specified in one block or multiple blocks.

[0069] These computer program instructions can also be loaded into a computer or other programmable data processing terminal device, so that a series of operation steps are performed on the computer or other programmable terminal device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable terminal device provide a process for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks Figure 1 The device that implements the functions specified in one block or multiple blocks.

Claims

1. A device for measuring the leak rate of a micro-electromechanical resonant device vacuum package, characterized in that: The device includes: A resonant device comprising a driving structure, a vibration mass block and a vibration pickup structure, wherein the vibration pickup structure is used to obtain displacement information generated by the driving structure driving the vibration mass block to vibrate; a closed-loop driving circuit, connected to the driving structure and the vibration pickup structure, respectively, for adjusting the driving voltage applied to the driving structure according to the displacement information and a preset displacement target voltage, so as to control the resonant device to perform horizontal vibration at the displacement target voltage; A test computer is connected to a pressure sensor and a temperature sensor, respectively, wherein the pressure sensor is used to measure the pressure value of the environment in which the resonant device is located, and the temperature sensor is used to measure the temperature value of the environment in which the resonant device is located; The test computer is further connected to the closed-loop drive circuit and is used to: Calibrate the matching relationship between multiple sample ambient pressure values ​​collected by the air pressure sensor and multiple sample driving voltages collected by the closed-loop driving circuit; Obtaining the driving voltage output by the closed-loop driving circuit and the ambient temperature value at different times, and obtaining the ambient pressure value corresponding to the driving voltage at each time according to the matching relationship; The leakage rate of the resonant device in any time period is calculated based on the ambient pressure value and the ambient temperature value at each moment.

2. A micro-electromechanical resonant device vacuum packaging leak rate measurement device according to claim 1, characterized in that: The closed-loop drive circuit comprises: a front readout circuit connected to the vibration pickup structure and configured to convert the displacement information into a vibration displacement voltage; an amplitude extraction unit, connected to the pre-readout circuit, for receiving the vibration displacement voltage and outputting the vibration displacement voltage amplitude; a phase shifter connected to the pre-readout circuit, configured to adjust the phase of the vibration displacement voltage and output a voltage signal in phase with the driving voltage; an adder, connected to the amplitude extraction unit, configured to receive and calculate the vibration displacement voltage amplitude and the displacement target voltage, and output a displacement error voltage; a controller connected to the adder, configured to receive the displacement error voltage and output a driving closed-loop control voltage; a modulator, connected to the phase shifter and the controller respectively, for receiving the voltage signal and the driving closed-loop control voltage to obtain the adjusted driving voltage; The modulator is connected to the driving structure to apply the adjusted driving voltage to the driving structure.

3. The device for measuring the leak rate of a micro-electromechanical resonant device vacuum package according to claim 1, wherein: The driving structure and the vibration pickup structure include any one of a variable-area sliding film comb-tooth capacitor structure and a variable-gap squeezed film parallel plate capacitor structure.

4. A method for measuring the leak rate of a micro-electromechanical resonant device vacuum package, characterized in that the method include: The vibration pickup structure in the resonant device obtains displacement information generated by the driving structure driving the vibration mass block to vibrate; The closed-loop driving circuit adjusts the driving voltage applied to the driving structure according to the displacement information and a preset displacement target voltage, so as to control the resonant device to perform horizontal vibration at the displacement target voltage; Testing the matching relationship between a plurality of sample environmental pressure values ​​collected by the pressure sensor and a plurality of sample driving voltages collected by the closed-loop driving circuit by calibrating the pressure sensor by the computer; Obtaining the driving voltage output by the closed-loop driving circuit at different times and the ambient temperature value collected by the temperature sensor, and obtaining the ambient pressure value corresponding to the driving voltage at each time according to the matching relationship; The leakage rate of the resonant device in any time period is calculated based on the ambient pressure value and the ambient temperature value at each moment.

5. A method for measuring the vacuum packaging leak rate of a micro-electromechanical resonant device according to claim 4, characterized in that: The closed-loop driving circuit adjusts the driving voltage applied to the driving structure according to the displacement information and a preset displacement target voltage, including: The front readout circuit converts the displacement information into a vibration displacement voltage; The amplitude extraction unit receives the vibration displacement voltage and outputs the vibration displacement voltage amplitude; The phase shifter adjusts the phase of the vibration displacement voltage and outputs a voltage signal in phase with the driving voltage; The adder receives and calculates the vibration displacement voltage amplitude and the displacement target voltage, and outputs a displacement error voltage; The controller receives the displacement error voltage and outputs a driving closed-loop control voltage; The modulator receives the voltage signal and the driving closed-loop control voltage, and applies the adjusted driving voltage to the driving structure.

6. The method for measuring the vacuum packaging leak rate of a micro-electromechanical resonant device according to claim 4, wherein: The test computer calibrates the matching relationship between the multiple sample environmental pressure values ​​collected by the air pressure sensor and the multiple sample driving voltages collected by the closed-loop driving circuit, including: Based on the specified vacuum range, multiple calibration pressure values ​​are selected; According to the plurality of calibrated air pressure values, a plurality of sample environmental pressure values ​​collected by the air pressure sensor and corresponding one-to-one to the plurality of calibrated air pressure values ​​are acquired; Acquiring the sample driving voltage under each sample environmental pressure value; The multiple sample environmental pressure values ​​and the multiple sample driving voltages are fitted to obtain a fitting formula of the driving voltage and the environmental pressure value; the fitting formula is: Where P is the ambient pressure value, in Pa; f is the fitting calculation of the pressure under different driving voltages; V c is the driving voltage amplitude, in V.

7. A method for measuring the vacuum packaging leak rate of a micro-electromechanical resonant device according to claim 6, characterized in that: The step of obtaining the driving voltage output by the closed-loop driving circuit at different times and the ambient temperature value collected by the temperature sensor, and obtaining the ambient pressure value corresponding to the driving voltage at each time according to the matching relationship, includes: Setting a total test time and a sampling interval, and collecting the driving voltage output by the closed-loop driving circuit and the ambient temperature value collected by the temperature sensor at different test moments within the total test time; According to the fitting formula, the environmental pressure value corresponding to the driving voltage at each test moment is obtained.

8. The method for measuring the vacuum packaging leak rate of a micro-electromechanical resonant device according to claim 7, wherein: The calculating the leakage rate of the resonant device in any time period according to the ambient pressure value and the ambient temperature value at each moment includes: Establishing a change curve of the environmental pressure value at different test moments within the total test time; Based on the change curve, the corresponding ambient pressure values ​​and the corresponding ambient temperature values ​​at any two test moments on the change curve are selected to calculate the leakage rate of the resonant device in any time period.

9. The method for measuring the vacuum packaging leak rate of a micro-electromechanical resonant device according to claim 8, wherein: Calculating the leakage rate of the resonant device in any time period includes: The calculation formula of the leakage rate is: Where, L is the leakage rate, the unit is Pa·m 3 / s; V is the packaging volume of the resonant device, in m 3 ; t1 is the first test moment, unit is s; t2 is the second test moment, unit is s; T1 is the ambient temperature value at the first test moment, unit is K; T2 is the ambient temperature value at the second test moment, unit is K; P1 is the ambient pressure value at the first test moment, unit is Pa; P2 is the ambient pressure value at the second test moment, unit is Pa.

10. A method for measuring the vacuum packaging leak rate of a micro-electromechanical resonant device according to claim 6 or 7, characterized in that: The test computer calibrates the matching relationship between a plurality of sample ambient pressure values ​​collected by the air pressure sensor and a plurality of sample driving voltages collected by the closed-loop driving circuit, which includes: placing the unpackaged resonant device and the closed-loop driving circuit in a vacuum device with adjustable air pressure; The step of obtaining the driving voltage output by the closed-loop driving circuit at different times includes: The vacuum-packaged resonant device is connected to the closed-loop driving circuit.

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