Quartz base plane differential type quartz vibrating beam accelerometer and packaging method thereof

Abstract

The invention belongs to the technical field of inertial devices, and particularly relates to a quartz base plane differential type quartz vibrating beam accelerometer and a packaging method thereof.The accelerometer comprises a shell, a circuit board, a VIA chip, a quartz substrate and a conductive contact pin, the interior of the shell is a vacuum cavity, the quartz substrate is composed of a quartz body, a rectangular step and a solder film, and the conductive contact pin is connected with the circuit board; the rectangular step is used for positioning and fixing the VIA chips, the solder film realizes welding connection of the chips, the two VIA chips output positive and negative signals through differential detection, and the circuit board provides driving signals for the chips and amplifies the output signals; the conductive pin transmits a signal and receives a control signal to regulate and control the working state of the chip. Through the vacuum cavity design, the differential detection technology, the high-precision assembly method and the reliable packaging technology, the problems that in the prior art, instability is caused by mismatching of the gluing technology and the thermal expansion coefficient, and the performance is affected by assembly errors are solved, and the measurement precision, the anti-interference capacity and the assembly stability of the accelerometer are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of inertial devices, and in particular, relates to a quartz base plane differential type quartz vibration beam accelerometer and a packaging method thereof. Background Art

[0002] The quartz beam accelerometer is a high-precision sensor that uses the piezoelectric effect and elastic properties of quartz materials to measure acceleration. With its significant advantages of direct frequency output, high precision, miniaturization, low cost and all-solid-state, it is regarded as the key development direction of the next generation of high-performance accelerometers. It can measure the acceleration of an object in a certain direction and is often used in inertial navigation systems, attitude control, motion monitoring and other fields. The high sensitivity and low drift characteristics of the quartz beam accelerometer make it a core component in high-precision inertial navigation systems (such as aviation, aerospace and submarine navigation). It can also be used for vibration monitoring and diagnosis of industrial equipment and machinery to detect abnormal conditions and prevent failures. In the aerospace field, it is used to monitor and adjust the attitude of aircraft and satellites to ensure the stability of their trajectory and position. It can also be used for health monitoring of large structures such as bridges and buildings to analyze their acceleration response under external environments such as earthquakes and wind loads.

[0003] Compared with the currently widely used quartz flexible accelerometer, the direct frequency output characteristics of the quartz vibration beam accelerometer do not require the use of an IF board (Intermediate Frequency Board, used in signal processing systems, especially in electronic instruments and communication equipment to process intermediate frequency signals), simplifying the structure and reducing costs. At the same time, its performance is excellent, with the highest accuracy reaching 0.1μg, and the accuracy of mass production can stably reach 10μg, making it have the potential to be a strategic-level accelerometer and realizing the large-scale production of navigation-level accelerometers. In addition, the quartz vibration beam accelerometer chip is made using a wet etching process, which has the advantages of low cost and mass production, and combined with modern micromachining technology, it can be further miniaturized and micro-miniaturized.

[0004] The current mainstream product structure of quartz beam accelerometers is a cylindrical barrel design, and its core components include quartz chips, TO bases (Transistor Outline Base metal packaging bases, used in the packaging structure of sensors, semiconductor devices and optoelectronic components), conductive support columns, vacuum packaging structures and circuit boards. Among them, the quartz chip is the core component of the quartz beam accelerometer. The current mainstream chip assembly method usually uses an adhesive process to fix the chip on the TO base, and then connect it to the conductive support columns through two TO bases. The main material of the TO base is metal, and the four conductive support columns use a ceramic sealing process to connect the chip and the TO base to form a component.

[0005] However, this traditional design has large performance fluctuations, poor stability, and low long-term reliability. There are few fundamental solutions to the above problems in existing literature and research. Therefore, an innovative technical solution is urgently needed to fundamentally improve the performance and reliability of quartz vibrating beam accelerometers, while reducing production costs and promoting their application in a wider range of fields. Summary of the invention

[0006] In view of the defects of the prior art, the present invention proposes a quartz base plane differential quartz vibration beam accelerometer and a packaging method thereof, which can solve the stress and process consistency problems caused by the bonding of the chip and the TO base, and realize low-stress, batch chip welding; the quartz base is used to maintain the same thermal expansion coefficient as the chip, which can improve the high and low temperature characteristics and impact resistance; and a high-precision, miniaturized plane differential structure design and assembly are realized.

[0007] On the one hand, the present invention provides a packaging method for a quartz base plane differential quartz vibration beam accelerometer, wherein the quartz base plane differential quartz vibration beam accelerometer comprises a sealing box and a tube shell that are buckled together, and a circuit board, a VIA chip, a quartz substrate and a conductive pin arranged inside the sealing box and the tube shell; the quartz substrate comprises a quartz body, a rectangular step and a solder film, wherein the rectangular steps are distributed on the quartz body at intervals for positioning and fixing the VIA chip; the solder film is plated on the rectangular steps for realizing the welding connection of the VIA chip; the packaging method comprises:

[0008] Step 1: pre-treating the rectangular step surface of the quartz substrate and plating a solder film on the rectangular step surface;

[0009] Step 2: Preliminarily place two VIA chips on the rectangular steps of the quartz substrate, and use a micromechanical adjustment tool to accurately adjust the positions of the VIA chips;

[0010] Step 3: heating the assembly formed by the quartz substrate and the VIA chip to the melting point of the solder at a set heating rate, maintaining the temperature for a certain period of time, and then slowly cooling the temperature at a set cooling rate to achieve welding of the quartz substrate and the VIA chip;

[0011] Step 4: Install the assembly formed by the welded quartz substrate and the VIA chip into the middle area of ​​the tube shell;

[0012] Step 5: Bond the circuit board to both ends of the quartz substrate respectively;

[0013] Step 6: Install the conductive pins on the tube shell, and electrically connect the circuit board to the conductive pins through the metal electrodes and the VIA chip;

[0014] Step 7: Place the sealing box cover on the tube shell for vacuum packaging. After welding, perform vacuum leakage test, mechanical property test and electromagnetic shielding test in sequence.

[0015] In a preferred implementation, further, in step 1, the process of plating the solder film includes:

[0016] The rectangular step surface of the quartz substrate is activated by plasma cleaning or chemical cleaning to remove the oxide layer and particulate impurities on the surface;

[0017] The solder film is prepared by magnetron sputtering or evaporation process: the magnetron sputtering process is used, the working gas pressure is controlled at 0.5-1.0Pa, the sputtering power is controlled at 150W-300W, and the sputtering rate is adjusted to 0.1μm / min; or the evaporation process is used, the heating temperature is controlled below the melting point of the solder alloy, and the vacuum degree is maintained at 10 -5 Torr;

[0018] During the magnetron sputtering or evaporation process, the film thickness is monitored in real time by a quartz crystal microbalance or a quartz crystal oscillator film thickness measuring instrument, the film thickness is accurately monitored, and the thickness of the solder film is accurately controlled within the range of 1μm-100μm, with a thickness deviation of ≤5%.

[0019] In a preferred implementation, further, in step 1, the solder film is composed of a metal alloy matrix, a wetting enhancer, an antioxidant, and a conductivity enhancer; the metal alloy matrix is ​​one of gold-tin alloy, indium-tin alloy, bismuth-tin alloy, silver-tin alloy, indium-bismuth-tin alloy, but not limited thereto; the wetting enhancer includes one of titanium, chromium, zirconium, nickel, and molybdenum, but not limited thereto. The antioxidant includes one of palladium, iridium, platinum, rhenium, and manganese, but not limited thereto. The conductivity enhancer includes one of silver, copper, tungsten, and zinc, but not limited thereto.

[0020] In a preferred implementation, further, in step 2, the parallelism deviation of the two VIA chips is ≤5 μm, and the positioning accuracy deviation is ≤100 μm.

[0021] In a preferred implementation, further, in step 3, the welding process of the VIA chip and the quartz substrate includes: -6 Under the condition of 2000 ℃ and 1000 ℃, a precise temperature-controlled hot plate, an infrared heating system or a laser heater is used to uniformly heat the solder film on the rectangular step surface of the quartz substrate at a heating rate of ≤5℃ / min to a temperature range within the melting point of the solder; the solder film is kept within the melting point temperature range for 5-10 minutes to ensure that the solder is completely melted and fully combined with the VIA chip and the quartz substrate to form a stable welding interface; after welding, the welding area is slowly cooled at a cooling rate of ≤5℃ / min.

[0022] In a preferred implementation, further, in step 4, the combined quartz substrate and VIA chip assembly are installed in the middle area of ​​the tube shell using low outgassing rate vacuum glue or metal solder; in step 5, the circuit board is bonded to both ends of the quartz substrate using low outgassing rate vacuum glue or metal solder.

[0023] In a preferred implementation, further, in step 6, a gold wire bonding or precision welding process is used to connect the circuit board and the VIA chip to the conductive pins through metal electrodes.

[0024] In a preferred implementation, further, in step 7, the vacuum packaging adopts any one of vacuum laser welding, eutectic welding and brazing processes.

[0025] On the other hand, the present invention further provides a quartz base plane differential quartz vibration beam accelerometer, wherein the quartz base plane differential quartz vibration beam accelerometer is manufactured by any of the packaging methods described above.

[0026] In a preferred implementation, further, the interior of the sealing box and the tube shell that are snapped together is a vacuum cavity; the two VIA chips output positive and negative signals respectively through differential detection; the circuit board is provided on one side of each VIA chip, and the circuit board includes a driving circuit and an amplifying circuit, and the driving circuit and the amplifying circuit are connected to the corresponding metal electrodes of the VIA chip; the circuit board is used to provide a driving signal for the VIA chip, and to receive and amplify the output signal of the VIA chip; the conductive pin is provided on the outer side of each circuit board, and the conductive pin is embedded in the tube shell, and the conductive pin is used to transmit the signal processed by the circuit board to an external device, and receive a control signal from the external device to regulate the working state of the VIA chip.

[0027] The beneficial effects of the present invention are:

[0028] First, the assembly method provided by the present invention ensures high-precision positioning and stable connection of the VIA chip by pre-treating the rectangular step surface of the quartz substrate and plating a solder film. At the same time, a welding process with a set heating and cooling rate is adopted to reduce internal stress and welding defects, thereby improving the mechanical stability and long-term reliability of the component. Micromechanical adjustment tools and precise electrical connection processes are used during the assembly process to ensure that the signal transmission path between the VIA chip and the circuit board and the conductive pins is stable and low-loss. The vacuum packaging process of the sealing box and the tube shell, combined with a strict testing process, further optimizes the vacuum sealing and anti-interference performance of the equipment, overcomes the defects of measurement errors, signal attenuation and poor environmental adaptability caused by insufficient assembly accuracy in the prior art, and makes the assembly process more suitable for mass production and more stable in performance.

[0029] Second, in a preferred implementation, step 1 of the present invention pre-treats the rectangular step surface of the quartz substrate by plasma cleaning or chemical cleaning, which can effectively remove surface impurities and oxide layers, and improve the adhesion and uniformity of the solder film; a solder film with a thickness of 1μm-100μm is plated by magnetron sputtering or evaporation process, which can ensure the thickness consistency and surface smoothness of the film, thereby improving the reliability and conductivity of the welding process.

[0030] Third, in the preferred implementation, the present invention improves the chip assembly accuracy by strictly controlling the parallelism deviation (≤5μm) and positioning accuracy deviation (≤100μm) of the two VIA chips in step 2, ensuring the consistency of the symmetry of the two chips during the differential detection process. Such high-precision assembly effectively reduces the signal deviation caused by installation errors, improves the sensitivity and measurement accuracy of the accelerometer, and enhances the ability to resist environmental interference. The chip and the base are both made of quartz material, and the thermal expansion coefficient and other characteristics are consistent, which effectively avoids stress and strain problems when the temperature changes.

[0031] Fourth, in a preferred implementation, step 3 of the present invention uses a precision temperature-controlled hot plate or an infrared heating system or a laser heater. By strictly controlling the heating and cooling rates to ≤5°C / min and maintaining them within the solder melting point range for 5-10 minutes, it is possible to effectively reduce thermal stress and welding defects caused by rapid temperature changes during welding, thereby improving the reliability and consistency of the welding interface.

[0032] Fifth, in the preferred implementation, the low outgassing rate vacuum adhesive of the present invention can effectively reduce the gas release in the cavity and maintain the long-term stability of the vacuum environment, while the metal solder provides excellent thermal conductivity and mechanical strength, ensuring the reliability of the components in high and low temperature cycles and vibration environments.

[0033] Sixth, in the preferred implementation, the present invention uses gold wire bonding or precision welding technology to connect the circuit board and the VIA chip to the conductive pins through metal electrodes, ensuring high stability and low loss of signal transmission, while having strong mechanical strength and long-term reliability; vacuum packaging adopts any one of vacuum laser welding, eutectic welding or brazing processes, which can be flexibly selected according to application requirements, which not only ensures the high airtightness and mechanical strength of the shell, but also effectively realizes electromagnetic shielding.

[0034] Seventh, the present invention provides a quartz base plane differential quartz vibration beam accelerometer, which effectively reduces the influence of air resistance on the vibration of the vibration beam through the design of the vacuum cavity inside the shell, improves the vibration quality factor (Q value) of the vibration beam, and thus enhances the sensitivity and accuracy of acceleration measurement. At the same time, the high-precision positioning and stable connection of the VIA chip are achieved through the rectangular steps and solder film on the quartz substrate. Combined with the differential detection technology, environmental interference such as temperature drift and common mode noise is suppressed, and the measurement accuracy and anti-interference ability are further improved. Compared with the problems of large temperature drift, weak anti-interference ability and difficult to ensure installation accuracy in the prior art, the present invention optimizes the chip structure layout and circuit design, so that the system has higher measurement stability and reliability, and has excellent batch assembly characteristics.

[0035] Eighth, in the preferred implementation, the conductive pin embedded in the tube shell design of the present invention makes the signal transmission path more stable, and at the same time ensures that the conductive performance and vacuum sealing performance are taken into account through ceramic sealing technology; the welding connection method between the sealing box and the tube shell not only improves the overall mechanical strength and airtightness of the shell, but also effectively realizes electromagnetic shielding, avoiding the influence of external electromagnetic interference on equipment performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic diagram of assembling discrete components of a quartz vibration beam accelerometer according to an embodiment of the present invention;

[0037] Figure 2 is a three-dimensional structural diagram of a quartz vibration beam accelerometer according to an embodiment of the present invention without being assembled with a sealing box;

[0038] Figure 3 is a three-dimensional structural diagram of a quartz vibration beam accelerometer assembly sealing box according to an embodiment of the present invention;

[0039] Figure 4 is a three-dimensional structural diagram of a quartz substrate according to an embodiment of the present invention;

[0040] Figure 5 The figure is a flow chart of an assembly method of a quartz vibration beam accelerometer according to an embodiment of the present invention.

[0041] Among them, 1-sealing box; 2-circuit board; 3-VIA chip; 4-quartz substrate; 4-1-quartz body; 4-2-rectangular step; 4-3-solder film; 5-tube shell; 6-conductive pin. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the technical solution of the present application, the present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0043] In the description of this application, the terms "first", "second", and "third" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance; the term "plurality" refers to two or more, unless otherwise expressly defined. Terms such as "installed", "connected", "connected", and "fixed" should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0044] In the description of the present application, it should be understood that the directions or positional relationships indicated by the terms "up", "down", "left", "right", "front", "back", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation, and therefore, should not be understood as a limitation on the present application.

[0045] In the description of this specification, the description of the terms "one embodiment / method", "some embodiments / methods", "specific embodiments / methods", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments / methods or examples in a suitable manner.

[0046] The quartz vibrating beam accelerometer is a high-precision sensor that uses the unique piezoelectric effect and elastic properties of quartz materials to directly convert acceleration into frequency signal output. However, during use, the inventors found that the quartz vibrating beam accelerometer has large performance fluctuations, poor stability, and low long-term reliability.

[0047] After a lot of experimental research, the inventor found the root of the problem. The inventor found that the performance fluctuations were mainly caused by the metal base and the adhesive process to fix the core chip components. This fixing method does not cause major problems for general chips, but for the chips in the accelerometer, it will seriously affect its performance. Under extreme temperatures and complex mechanical environments, the aging and performance inconsistency of the adhesive material can easily lead to device failure. In addition, the inventor found that due to the mismatch between the thermal expansion coefficients of the metal base and the quartz chip, thermal stress will be generated in the high and low temperature cycle environment, which will cause chip performance fluctuations or even damage.

[0048] In view of the above technical bottlenecks, the present invention proposes a quartz base plane differential quartz vibration beam accelerometer based on a large number of experimental studies. The quartz base is used to replace the metal base, and a high-precision rectangular step is designed. The stable installation of the chip is achieved through the solder film technology. This solution improves the reliability of the component and eliminates the defects caused by the adhesive process. By introducing a specially designed solder film and optimized welding conditions, the defects of the traditional process are fundamentally solved. The solder film adopts a low-melting point and high-strength metal alloy material. Its composition is precisely formulated to have good thermal conductivity and oxidation resistance. The thickness of the solder film is controlled within the range of 1μm-100μm, and is prepared by magnetron sputtering or evaporation process to ensure the uniformity of the film thickness and the strength of the bonding force. Wetting enhancers and antioxidants (such as titanium, chromium and palladium) are added to the film to improve the bonding ability with the quartz substrate, while avoiding oxidation and interface stratification during high-temperature welding. At the same time, in view of the high-temperature sensitivity of the solder film, special welding process conditions are adopted to successfully solve the potential damage of the welding high temperature to the quartz chip and substrate, and reduce the thermal stress problem of the device. In the experiment, the material ratio, thickness uniformity and heat treatment process of the solder film were optimized, and the thermal expansion coefficient mismatch problem between the chip and the base was successfully solved, which greatly improved the performance stability of the device in extreme environments. At the same time, by designing a simplified planar differential structure and adopting a symmetrical chip arrangement solution, the anti-interference ability and measurement accuracy were further improved. The optimized vacuum packaging process reduced the assembly complexity and manufacturing cost, and promoted the mass production of the device. This technical solution not only effectively overcomes the shortcomings of the existing technology, but also lays a solid foundation for the application of high-precision quartz vibration beam accelerometers in complex environments.

[0049] As the instruction manual Figure 1-4 The present invention describes a quartz base plane differential quartz vibration beam accelerometer, which includes a shell, and a circuit board 2, a VIA chip 3, a quartz substrate 4 and a conductive pin 6 arranged inside the shell.

[0050] The interior of the shell is a vacuum cavity, and its design can effectively optimize the performance of the quartz vibration beam accelerometer, specifically by reducing air resistance, improving temperature stability, and reducing the impact of environmental pollutants. The vacuum environment eliminates the air's obstruction to the vibration of the vibration beam in the VIA chip 3, reduces energy loss, and thus improves the vibration quality factor (Q value) of the vibration beam, which enables the vibration beam to maintain a higher sensitivity when subjected to external disturbances, ensuring the accuracy of acceleration measurement. The vibration frequency of the quartz vibration beam is very sensitive to temperature changes, and the presence of air will cause a heat conduction effect, which in turn affects the temperature stability of the vibration beam. The vacuum cavity isolates the influence of air, provides a more stable working environment for the vibration beam, and further improves the reliability of the measurement. The vacuum cavity effectively prevents pollutants such as moisture and dust from entering the interior of the shell, isolates moisture and particulate matter from long-term effects on the vibration beam, avoids potential damage to the performance of the VIA chip 3 and the quartz substrate 4, extends the life of internal components, and ensures the long-term stability of the equipment.

[0051] The quartz substrate 4 includes a quartz body 4-1, a rectangular step 4-2 and a solder film 4-3. The quartz body 4-1 is used to provide base support and structural stability. The rectangular steps 4-2 are spaced apart on the quartz body 4-1 and are used to accurately position and fix the VIA chip 3. The solder film 4-3 is plated on the rectangular step 4-2 to provide an efficient soldering interface for the installation of the VIA chip 3. Two VIA chips 3 are installed between the two rectangular steps 4-2 spaced apart and fixed by the solder film 4-3, achieving a stable mechanical connection and reliable signal conduction. The two VIA chips 3 are designed to perform differential detection on acceleration and output positive and negative signals respectively. The differential detection can effectively suppress the interference of environmental noise and further improve the measurement accuracy and anti-interference ability. A circuit board 2 is provided on one side of each VIA chip 3. The driving circuit and the amplifying circuit on the circuit board 2 are connected to the metal electrodes of the corresponding VIA chip 3. The driving circuit on the circuit board 2 provides the VIA chip 3 with the driving signal required for the vibration beam resonance to ensure the stable operation of the vibration beam, and receives the vibration beam frequency signal from the VIA chip 3, and performs preliminary signal amplification and processing through the amplifying circuit.

[0052] Each circuit board 2 is provided with a conductive pin 6 connected thereto on its outer side. The conductive pin 6 transmits the signal processed by the circuit board 2 to the external device, realizing the signal output of the accelerometer and the external system. The control signal of the external device is transmitted to the circuit board 2 through the conductive pin 6, thereby realizing the precise control of the working state of the vibration beam of the VIA chip 3. As a signal transfer and processing station, the circuit board 2 connects the VIA chip 3 and the conductive pin 6, forming an efficient interaction path between the internal signal and the external system, ensuring the real-time response and high-precision measurement capability of the device.

[0053] In a preferred implementation of the present application, the circuit board 2 uses miniaturized, temperature-insensitive components to reduce the impact of the external environment on performance.

[0054] VIA chip 3 is the core component of the quartz vibration beam accelerometer, which is responsible for sensing external acceleration and converting it into electrical signals. VIA chip 3 includes a vibration beam, a mass block, a flexible hinge, a vibration isolation frame, a fixed frame and a metal electrode. The vibration beam is a key component for realizing acceleration perception. When the quartz vibration beam accelerometer is subjected to external acceleration, the vibration beam will undergo a slight elastic deformation, thereby causing a change in the vibration frequency. This frequency change is proportional to the magnitude of the acceleration and provides a basis for subsequent signal processing. The mass block is used to provide inertial mass and is the direct source of the force on the vibration beam. Under the action of external acceleration, the mass block will generate an inertial force, causing the vibration beam to deform, forming a proportional relationship between acceleration and vibration beam frequency, and ensuring the physical accuracy of the sensing process. The flexible hinge connects the vibration beam and the mass block, and provides structural support and flexible deformation capability at the same time. Its design allows the vibration beam to vibrate freely under the action of inertial force while maintaining the mechanical stability of the system. The vibration isolation frame is used to isolate high-frequency vibration and mechanical shock from the external environment, avoid the influence of external interference on the vibration of the vibration beam, and ensure the purity of the signal. The fixing frame is used to provide mechanical support for the entire VIA chip, so that it can be firmly mounted on the quartz substrate, while reducing possible displacement or offset during the vibration of the vibration beam. The metal electrode is used to convert the frequency change of the vibration beam into a processable electrical signal output, providing input for subsequent signal amplification and processing for the circuit board 2.

[0055] In order to improve the measurement accuracy, the quartz vibration beam accelerometer adopts a differential detection scheme. The quartz base plane differential quartz vibration beam accelerometer uses two VIA chips 3 with the same structure and performance, one of which is used for positive acceleration signal detection and the other is used for negative acceleration signal detection. The frequency signals output by the two VIA chips 3 are the acceleration responses in the positive and negative directions respectively. By performing differential operations on the positive and negative signals, the error sources: temperature drift and common mode noise can be effectively eliminated. Since the two chips respond to temperature changes in the same way, differential operations can weaken the errors caused by temperature changes, and at the same time, the suppression effect on external common mode noise (such as mechanical vibration and electromagnetic interference) is significant. Differential detection can improve the sensitivity and accuracy of acceleration measurement and ensure the stability and reliability of the system.

[0056] Specifically, when external acceleration acts on the accelerometer, the inertial mass block (inside the VIA chip) generates a corresponding force, causing the vibration beam to deform. The deformation of the vibration beam causes its vibration frequency to change, and the metal electrode detects the change in frequency and outputs an electrical signal. The oscillation circuit of the circuit board 2 provides a driving signal for the vibration beam to ensure its resonance. The frequency signal output by the vibration beam is amplified by the signal amplification circuit of the circuit board to enhance the signal strength and reduce noise. The two VIA chips 3 perform differential detection on the acceleration, one positive and one negative output signal. The differential output can eliminate environmental errors (such as frequency drift caused by temperature changes) and improve measurement accuracy. The processed acceleration signal is transmitted to an external device through the conductive pin 6 for subsequent analysis or display.

[0057] Furthermore, differential detection uses two VIA chips with the same structural performance to detect signal changes in the same acceleration environment, and eliminates common-mode interference and errors through subtraction operations to improve measurement accuracy. Two VIA chips (set as chip A and chip B) measure acceleration at the same time, but in opposite directions (one detects positive acceleration and the other detects negative acceleration). The difference in the output signal can effectively eliminate environmental noise and system errors, such as temperature drift, mechanical vibration, etc. Differential formula:

[0058] Δf=f A -f B

[0059] Where: Δf represents the net frequency signal after differentiation, which is proportional to the external acceleration; f A Indicates the frequency signal output by chip A; f B Indicates the frequency signal output by chip B.

[0060] Two VIA chips 3 are mounted on a quartz substrate 4 and are placed symmetrically. The vibration beams of the chips are in opposite directions (for example, one is facing up and the other is facing down). Under the same acceleration, the vibration beams of the two chips are subjected to opposite forces, resulting in opposite signs of output frequency changes. Each VIA chip 3 has an independent drive circuit, but shares the same environmental conditions (temperature, pressure, etc.).

[0061] External acceleration (such as gravity acceleration or linear acceleration) acts on the entire system, and the inertial mass blocks of the two VIA chips 3 respectively feel inertial forces of the same magnitude but opposite directions. The acceleration causes the vibration beam to deform, resulting in an increase (or decrease) in the vibration beam frequency of chip A and a decrease (or increase) in the vibration beam frequency of chip B. Due to the symmetrical arrangement of the chips, the frequency changes of the two chips are the same but with opposite signs. The circuit board receives the frequency signals f of the two chips. A and f B, the net frequency change Δf is obtained by differential calculation. Differential calculation will automatically cancel out common mode noise, for example: temperature drift: temperature change has the same effect on the frequency of the two chips, which is eliminated after differential calculation. Mechanical vibration: random vibration in the non-acceleration direction has the same effect on the two chips, which is also cancelled after differential calculation. After the net frequency change Δf is processed by the circuit (such as amplification and linearization), the corresponding acceleration value is output.

[0062] In the preferred implementation of the present application, the elastic coefficient of the vibration beam of the VIA chip 3, the weight of the mass block, the stiffness of the flexible hinge and the conductive properties of the metal electrode are strictly matched to ensure that the performance of the two VIA chips 3 is consistent. The vibration isolation frame and the fixed frame are made of high-strength and low-expansion materials to isolate external interference to the greatest extent and ensure the stability of the working environment of the vibration beam. The differential signals of the two VIA chips 3 are amplified and filtered with high gain through the amplifier circuit of the circuit board 2 to further enhance the anti-noise capability.

[0063] The quartz body 4-1 is used to provide a stable installation platform for the VIA chip 3. The quartz body 4-1 adopts high-precision processing technology, and the surface has an extremely low roughness (Ra value), which ensures that the chip can fit smoothly and reduces the vibration and deviation that may occur during the installation process, thereby improving the working stability and measurement accuracy of the chip. The rectangular steps 4-2 on the quartz body 4-1 are evenly distributed and set at intervals to accurately locate the installation position of the VIA chip 3. While positioning, the rectangular steps 4-2 provide support for the VIA chip 3, and ensure that the VIA chip 3 is firmly fixed through the welding process, and is not easily affected by external forces or environmental factors and caused to move or loosen. The solder film 4-3 is evenly plated on the surface of the rectangular step by magnetron sputtering or evaporation technology to ensure that the film thickness is consistent and the bonding force is strong, meeting the high-precision installation requirements. While providing excellent electrical conductivity, the solder film 4-3 also has efficient thermal conductivity, which can quickly guide the heat generated by the VIA chip 3 when it is working, avoiding the influence of local overheating on the performance of the VIA chip 3.

[0064] In the preferred implementation of the present application, the quartz body 4-1 is made of high-purity quartz material, and its excellent mechanical strength and thermal expansion coefficient matching performance can provide stable support in extreme environments. The length of each rectangular step 4-2 is 20mm-30mm, the width is 0.5mm-2mm, and the height is 0.2mm-1mm. The processing accuracy of the rectangular step 4-2 is controlled within the micron level to ensure the accuracy of chip positioning. The thickness uniformity of the solder film 4-3 is achieved by optimizing the process of magnetron sputtering or evaporation. The solder can be indium, indium-tin alloy, tin-silver alloy or tin-silver-copper alloy, etc. The thickness of the solder film 4-3 is 1μm-100μm. At the same time, the bonding force between the solder film 4-3 and the rectangular step 4-2 is further improved by controlling the surface pretreatment of the rectangular step 4-2 (such as cleaning, plasma activation). During the welding process of VIA chip 3, precise positioning tooling and temperature-controlled welding technology are used to ensure the integrity of the solder film 4-3 and the close contact of VIA chip 3. After welding, thermal cycle test and mechanical vibration test are carried out to verify the installation reliability of VIA chip 3.

[0065] Conductive pin 6 is used to transmit the output signal of the circuit board and VIA chip to the external device. Conductive pin 6 is made of metal with excellent conductivity and oxidation resistance (such as gold-plated copper or beryllium copper) to ensure the stability and low loss of signal transmission. Conductive pin 6 is connected to the shell through a ceramic sealing process. The ceramic sealing material has excellent airtightness, which can effectively prevent gas leakage in the vacuum cavity and isolate the intrusion of external moisture or pollutants. The ceramic sealing material also has high resistivity, ensuring the insulation performance between the conductive pin 6 and the shell, avoiding leakage or interference in signal transmission.

[0066] To improve the structural stability, the sealing material and the pins are made of materials with matching thermal expansion coefficients (such as a composite structure of alumina ceramics and metal pins), and a firm bond is achieved through the metallized ceramic surface, thereby avoiding sealing failure or mechanical loosening due to temperature changes. In the preferred implementation of the present application, the ceramic sealing material is made of high-purity alumina, and the surface of the pin material is plated with gold or silver, which not only improves the conductivity but also enhances the corrosion resistance. The sealing process uses active brazing or glass-ceramic sealing technology to ensure the bonding strength and airtightness of the ceramic and metal pins. The sealing performance is tested by vacuum leakage rate to ensure the long-term stability of the vacuum cavity.

[0067] Furthermore, the housing of the quartz base plane differential quartz vibration beam accelerometer includes a sealing box 1 and a tube shell 5. The sealing box 1 is made of high-strength metal materials (such as Kovar alloy, stainless steel or copper alloy) through precision machining. The metal material has excellent mechanical strength, airtightness and conductivity, and is suitable for vacuum sealing and electromagnetic shielding requirements. The tube shell 5 includes a metal base, and a conductive pin 6 is embedded in the metal base to provide a signal input and output path. Vacuum sealing and electromagnetic shielding are achieved between the metal base and the sealing box 1 by one of the following high-reliability welding technologies:

[0068] 1. Vacuum laser welding: Welding is done in a vacuum environment using a high energy density laser beam. It has the advantages of narrow welds, small heat affected zones, and high welding strength, effectively avoiding the effects of thermal deformation on vacuum sealing performance.

[0069] 2. Eutectic welding: The metal base and the sealing box are bonded together by using welding materials to form a eutectic phase at a specific temperature. It has the advantages of high bonding strength, resistance to high and low temperature environments, and is suitable for long-term stable use.

[0070] 3. Brazing: Use solder to fill the gap between the sealing box 1 and the tube shell 5, and heat and melt the solder to achieve sealing. The process is relatively simple and suitable for medium-precision sealing requirements.

[0071] After welding is completed, the surface of the sealing box 1 and the tube shell 5 is subjected to anti-oxidation treatment (such as nickel plating or passivation) to enhance corrosion resistance and extend the service life of the equipment. The tube shell 5 and the sealing box 1 after welding can be subjected to vacuum leakage test, mechanical performance test and electromagnetic shielding test. The vacuum leakage test ensures the long-term vacuum stability of the welding seal by using a helium mass spectrometer leak detector. The mechanical performance test verifies the mechanical reliability of the welding joint by performing vibration, shock and thermal cycle tests. The electromagnetic shielding test evaluates whether the shielding performance meets the design requirements through EMI (electromagnetic interference) test.

[0072] Example 1

[0073] By comparing the structures of the cylindrical barrel-type quartz vibration beam accelerometer in the prior art and the quartz base plane differential quartz vibration beam accelerometer of the present invention, the advantages of the quartz base plane differential quartz vibration beam accelerometer of the present invention are explained.

[0074] Table 1

[0075]

[0076]

[0077] As the instruction manual Figure 5 The present invention also describes a packaging method for a quartz base plane differential quartz vibration beam accelerometer, the packaging method comprising:

[0078] Step 1: Pre-treat the rectangular step surface of the quartz substrate and plate a solder film on the rectangular step surface.

[0079] The purpose of step 1 is to enhance the bonding force between the quartz substrate surface and the solder film, ensure that the film does not fall off or warp, and improve the reliability and stability of the assembly. Provide a uniform and high-quality solder film as the basis for subsequent welding or bonding to ensure the thermal conductivity and mechanical strength of the welding part. Ensure the consistency of film thickness, reduce process deviations, and improve the quality consistency and controllability of mass production.

[0080] Specifically, the solder film is made of a metal alloy with a low melting point and high strength, and through a carefully designed formula combination, it takes into account welding performance, mechanical strength and anti-oxidation ability. The composition of the solder film includes a metal alloy matrix, a wetting enhancer, an antioxidant and a conductivity enhancer.

[0081] The metal alloy matrix is ​​the main component of the solder film, which is used to provide the basic material for molten soldering and determines the soldering temperature range and mechanical properties after soldering. The metal alloy matrix includes one of gold-tin alloy (Au80Sn20), indium-tin alloy (In50Sn50), bismuth-tin alloy (Bi58Sn42), silver-tin alloy (Ag3Sn), indium-bismuth-tin alloy (In52Bi32Sn16), but is not limited to this. Gold-tin alloy (Au80Sn20) is composed of 80% gold (Au) and 20% tin (Sn), and has excellent low melting point performance (melting point of about 280°C) and high mechanical strength, while showing excellent conductivity and corrosion resistance after soldering. Indium-tin alloy (In50Sn50) is composed of 50% indium (In) and 50% tin (Sn), with a lower melting point (about 200°C), suitable for more stringent temperature control scenarios, and has good flexibility and stability in thermal cycling environments. Bismuth-tin alloy (Bi58Sn42) is composed of 58% bismuth (Bi) and 42% tin (Sn), with a low melting point (about 138°C), suitable for ultra-low temperature welding to avoid chip overheating. The addition of bismuth (Bi) increases the mechanical strength and fatigue resistance of the welding point. Silver-tin alloy (Ag3Sn) is composed of 3% silver (Ag) and 97% tin (Sn), which can provide high conductivity and good wettability, strong high temperature resistance, and meet the precision assembly requirements of high conductivity. Indium-bismuth-tin alloy (In52Bi32Sn16) is composed of 52% indium (In), 32% bismuth (Bi) and 16% tin (Sn), with a low melting point (about 90°C), and exhibits good flexibility and reliability at ultra-low temperatures. The reinforcing effect of bismuth (Bi) improves the vibration resistance of the welding point, meeting the requirements of low temperature environments and high vibration applications. The metal alloy matrix lowers the welding temperature (90℃-300℃) and reduces the damage of high temperature to the quartz substrate and chip. Among them, the tin in the matrix metal component can enhance the heat diffusion capacity of the welding point and prevent stress caused by local overheating or rapid cooling.

[0082] The wetting enhancer includes one of titanium (Ti), chromium (Cr), zirconium (Zr), nickel (Ni), and molybdenum (Mo), but is not limited thereto. Titanium (Ti) is used as a wetting enhancer, and its content is controlled at 1% to 2%, which can improve the wettability of the solder film and the surface of the quartz substrate and promote the chemical bonding of the metal and non-metal interface. Chromium (Cr) has a similar effect to titanium, and its content is controlled at 0.5% to 1%, which can improve the bonding strength of the solder film and reduce the possibility of interface peeling. The doping amount of zirconium (Zr) is 0.1% to 0.5%, which can improve the interface wettability between the metal film and the substrate, and at the same time show good chemical stability in high-temperature welding. The doping amount of nickel (Ni) is 0.5% to 1%, which enhances the wettability of the film while improving the fatigue resistance of the welding point and providing better corrosion resistance. The doping amount of molybdenum (Mo) is 0.1% to 0.3%, which improves the wetting performance, reduces the interfacial tension during welding, and plays an important role in improving the interface bonding strength.

[0083] The antioxidant includes one of palladium (Pd), iridium (Ir), platinum (Pt), rhenium (Re), and manganese (Mn), but is not limited thereto. The doping amount of palladium (Pd) is 0.1% to 0.5%, and its stable chemical properties can effectively inhibit the oxidation of the solder surface and extend the service life of the soldering point. The doping amount of iridium (Ir) is 0.05% to 0.2%, which enhances the antioxidant ability while improving the high temperature resistance and mechanical strength of the solder film. The doping amount of platinum (Pt) is 0.1% to 0.5%, which has high antioxidant properties, extends the life of the soldering point, and can effectively inhibit the oxidation reaction on the solder surface in a high temperature environment. The doping amount of rhenium (Re) is 0.05% to 0.1%, which can provide antioxidant ability at ultra-high temperatures and enhance the durability and stability of the solder film. The doping amount of manganese (Mn) is 0.1% to 0.3%, which can improve the antioxidant property, while forming a protective film on the welding area to reduce the corrosion and aging of the welding point.

[0084] The conductivity enhancer includes one of silver (Ag), copper (Cu), tungsten (W), and zinc (Zn), but is not limited thereto. The doping amount of silver (Ag) is 1% to 3%, which improves the electrical conductivity and thermal conductivity of the solder film, while forming a fine grain structure in the welding area and enhancing the mechanical strength. The doping amount of copper (Cu) is 1% to 3%, which provides good electrical conductivity and thermal conductivity and improves the mechanical strength of the welding area. The doping amount of tungsten (W) is 0.5% to 1%, which can maintain good electrical conductivity in a high temperature environment, provide high thermal conductivity, and reduce the thermal resistance of the welding area. The doping amount of zinc (Zn) is 0.1% to 0.3%, which can improve the electrical conductivity of the film, while optimizing the thermal expansion coefficient matching of the welding point and providing a more stable signal transmission capability.

[0085] Preparation of solder film:

[0086] S1: Surface treatment before coating: The rectangular step surface of the quartz substrate is activated by plasma cleaning or chemical cleaning (such as dilute hydrofluoric acid solution) to remove the oxide layer and particulate impurities and enhance the adhesion of the solder film.

[0087] S2: Sputtering or evaporation technology: magnetron sputtering process is used, the working gas pressure is controlled at 0.5-1.0Pa, the sputtering power is controlled at 150W-300W, and the sputtering rate is adjusted to 0.1μm / min to ensure the uniformity of film deposition. For the evaporation process, the heating temperature is strictly controlled below the melting point of the solder alloy, and the vacuum degree is maintained at 10 -5 Torr.

[0088] S3: Thickness uniformity control: The film thickness is accurately monitored by a quartz crystal microbalance to ensure that the solder film thickness is uniformly distributed in the range of 1μm-100μm, with a thickness deviation of ≤5%.

[0089] Step 2: Preliminarily place two VIA chips on the rectangular steps of the quartz substrate, and use a micromechanical adjustment tool to accurately adjust the positions of the VIA chips.

[0090] The purpose of step 2 is to achieve accurate alignment of the chip on the rectangular step of the quartz substrate, ensuring that the chip spacing, parallelism and positioning accuracy meet the design requirements. It provides a reliable structural foundation for high-precision detection of differential quartz beam accelerometers and reduces performance deviations caused by assembly errors. It uses precision tools and testing equipment to optimize the chip position adjustment process, reduce the error rate of manual adjustment, and adapt to large-scale automated assembly.

[0091] Specifically, a high-precision manipulator is used to pre-align the two VIA chips at the specified position of the rectangular step, and then an optical microscope is used for preliminary position detection. After the micro-mechanical adjustment tool is used to achieve precise position adjustment, a laser interferometer is used to assist in detecting the parallelism and position deviation of the two VIA chips. The parallelism deviation control is ≤5μm, and the positioning accuracy deviation is ≤100μm. The high accuracy and stability of differential detection are ensured through planar structure design and high-precision adjustment.

[0092] Step 3: The assembly formed by the quartz substrate and the VIA chip is heated to the melting point of the solder at a set heating rate, and then slowly cooled at a set cooling rate after being kept for a certain period of time to achieve welding of the quartz substrate and the VIA chip.

[0093] The purpose of step 3 is to achieve a strong connection between the quartz substrate and the VIA chip, forming a stable electrical and mechanical joint to ensure reliability in long-term use. Precise temperature control can avoid material thermal stress caused by thermal shock or uneven heating, thereby reducing deformation and internal defects of components after welding. Provide alternatives to the bonding process, reduce dependence on solder through UV glue or optical glue, improve assembly adaptability, and adapt to different application scenarios.

[0094] Specifically, the heating equipment uses a precision temperature-controlled hot plate or an infrared heating system or a laser heater to evenly heat the device. In the welding process of step 3, in order to solve the high-temperature welding problems (such as uneven film melting, chip damage or insufficient welding strength) that may be caused by the thin thickness of the solder film (only 1μm-100μm), the following special welding processes and conditions must be used:

[0095] 1. Accurately control the temperature rise and fall rate: Due to the thin thickness of the solder film, the heating rate must be strictly controlled at ≤5℃ / min to ensure uniform heating and avoid thermal shock damage to the chip structure. The cooling rate is also maintained at ≤5℃ / min to prevent material deformation or cracks caused by thermal stress accumulation.

[0096] 2. Local heating technology: laser heating or infrared local heating technology is used. The heating equipment uses a precision temperature-controlled hot plate or infrared heating system or laser heater. Through focused high-energy density heating, only the welding area is heated to avoid thermal damage to the quartz substrate and other areas of the chip.

[0097] 3. High vacuum environment welding: During the welding process, the environmental vacuum degree must reach 10 -6 Torr to reduce oxidation and contamination and ensure the cleanliness and bonding strength of the welding interface.

[0098] 4. High-precision real-time monitoring: Use optical interferometer or infrared thermal imager to monitor the temperature distribution of the welding area and the state of the welding film in real time to ensure that the solder is evenly melted and well bonded to the quartz substrate and chip.

[0099] Optionally, the quartz substrate and VIA chip can also be bonded using a bonding process, using low-stress UV glue or deep-light glue, applied to the surface of the quartz material, and bonded using UV curing technology. Since both the quartz substrate and the VIA chip are made of quartz material, the internal stress can be reduced by homogeneous bonding, and they can adapt to high and low temperature environments. Solder can be optional or not required. After bonding is completed, the bonding quality is verified by mechanical vibration and thermal cycle experiments.

[0100] Step 4: Install the assembly formed by the welded quartz substrate and the VIA chip into the middle area of ​​the tube shell.

[0101] The purpose of step 4 is to ensure that the combined components are stably fixed in the tube shell, providing a solid and accurate position reference for subsequent assembly steps. Improve the vibration and impact resistance of the entire device to adapt to complex working environments. Through the selection of vacuum glue or metal solder, ensure the long-term vacuum performance of the components and meet the strict requirements for environmental airtightness.

[0102] Specifically, low outgassing rate vacuum glue or metal solder is used to install the combined quartz substrate 4 and VIA chip 3 components into the middle area of ​​the tube shell 5 to ensure component stability and long-term vacuum performance. Process parameters include glue curing temperature: 50℃~100℃, time controlled within 1~2 hours. Welding process: low temperature eutectic welding is adopted, and the melting point of solder is 150℃~200℃. After welding is completed, a three-coordinate measuring instrument is used to calibrate the installation position to ensure the flatness and stability of the component and the tube shell 5.

[0103] Step 5: Bond the circuit board to both ends of the quartz substrate.

[0104] The purpose of step 5 is to fix the circuit board to the quartz substrate through reliable bonding to prevent the device from failing under vibration and impact conditions. Ensure the uniformity of the adhesive layer thickness during the bonding process to avoid unstable signal transmission caused by bonding defects. While providing high-strength bonding, verify the bonding quality through testing to ensure the long-term stability of the bonding site.

[0105] Specifically, use low outgassing rate vacuum glue or metal solder to bond the circuit board to both ends of the quartz substrate, ensuring that the bonding area is evenly covered with glue to avoid gaps. The thickness of the glue layer is controlled at 0.1mm to 0.5mm. After bonding, perform preliminary curing, and then test the bonding strength through tensile and shear tests. Use a thermal infrared detection system to scan the bonding area to ensure that there are no thermal defects.

[0106] Step 6: Install the conductive pins on the tube shell, and electrically connect the circuit board to the conductive pins through the metal electrodes and the VIA chip.

[0107] The purpose of step 6 is to establish a reliable electrical connection between the circuit board and the VIA chip to ensure efficient signal transmission. Provide effective electromagnetic shielding measures to avoid signal crosstalk caused by external interference and improve the signal integrity of the device. Ensure the mechanical strength and long-term conductivity of the solder joints to meet the requirements of stable operation in complex electromagnetic environments.

[0108] Specifically, use gold wire bonding or precision welding technology to connect the circuit board and the VIA chip to the conductive pins through metal electrodes. The wiring material is selected from gold or silver wire with a diameter of 20μm-50μm to ensure conductivity and mechanical strength. The welding equipment uses an ultrasonic gold wire bonding machine, combined with a temperature control system, and the welding temperature is controlled at 150℃~200℃. During the welding process, a local shielding structure is added to avoid signal crosstalk caused by external electromagnetic interference. The wire is covered with a shielding net or conductive coating to improve electromagnetic compatibility.

[0109] Step 7: Place the sealing box cover on the tube shell for vacuum packaging. After welding, perform vacuum leakage test, mechanical property test and electromagnetic shielding test in sequence.

[0110] The purpose of step 7 is to hermetically seal the device to protect the internal components from the external environment (such as moisture, dust, etc.) and extend the service life. Enhance the mechanical strength and structural integrity of the device to adapt to the vibration and impact requirements in complex working conditions. Ensure electromagnetic shielding performance to avoid the impact of external electromagnetic interference on the performance of the device, and verify the sealing and performance stability of the device through multiple tests.

[0111] Specifically, vacuum packaging can be carried out by vacuum laser welding, eutectic welding and brazing (selected according to the requirements), and the vacuum degree of the environment is maintained at 10 -6 Torr. The laser power and welding speed of the welding process are adjusted according to the material thickness to avoid overheating and damage to components. For example, the eutectic welding temperature is set at 180℃-220℃.

[0112] Through the above assembly method, not only the assembly accuracy and reliability of the quartz base plane differential quartz vibration beam accelerometer are improved, but also the consistency and batch efficiency of the production process are optimized, providing strong support for the production of high-performance accelerometers.

[0113] Example 2

[0114] By comparing the assembly methods of the cylindrical barrel-type quartz vibration beam accelerometer of the prior art and the quartz base plane differential quartz vibration beam accelerometer of the present invention, the advantages of the assembly method of the quartz base plane differential quartz vibration beam accelerometer of the present invention are explained.

[0115] Table 2

[0116]

[0117]

[0118] As can be seen from Table 2, the present invention significantly improves assembly accuracy and consistency, especially in welding, bonding and positioning adjustment, ensuring high-quality output of mass production. Through differential detection and vacuum packaging technology, the influence of temperature drift and common mode noise is eliminated, the detection accuracy and anti-interference ability are improved, and the solder film and bonding process, as well as the vacuum packaging technology, are optimized to ensure the long-term stability and environmental adaptability of the components.

[0119] The present invention provides a quartz base plane differential quartz vibration beam accelerometer, which effectively reduces the influence of air resistance on vibration of the vibration beam through the design of the vacuum cavity inside the shell, improves the vibration quality factor (Q value) of the vibration beam, and thus enhances the sensitivity and accuracy of acceleration measurement. The rectangular step and solder film on the quartz substrate realize the high-precision positioning and stable connection of the VIA chip, and effectively suppress environmental interference such as temperature drift and common mode noise in combination with differential detection technology, thereby greatly improving the measurement accuracy and anti-interference ability. The assembly method pre-treats the surface of the rectangular step and plates the solder film, and adopts a welding process with a set heating and cooling rate to reduce internal stress and welding defects, thereby ensuring the mechanical stability and long-term reliability of the component. During the assembly process, micromechanical adjustment tools and precise electrical connection processes ensure the stability and low loss of signal transmission between the VIA chip, the circuit board and the conductive pins. The vacuum packaging process of the sealing box and the tube shell is combined with a strict testing process to optimize the vacuum sealing and anti-interference performance, overcome the problems of large temperature drift, weak anti-interference ability and insufficient assembly accuracy in the prior art, and enable the equipment to have higher measurement stability, reliability and mass production adaptability.

[0120] The above is only an embodiment of the present invention, and the common sense such as the known specific structure and characteristics in the scheme is not described in detail here. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the attached claims rather than the above description, so it is intended to include all changes within the meaning and scope of the equivalent elements of the claims. Any figure mark in the claims should not be regarded as limiting the claims involved.

Claims

1. A packaging method for a quartz base plane differential quartz vibration beam accelerometer, characterized in that: The quartz base plane differential quartz vibration beam accelerometer comprises a sealing box (1) and a tube shell (5) that are buckled together, and a circuit board (2), a VIA chip (3), a quartz substrate (4) and a conductive pin (6) arranged inside the sealing box (1) and the tube shell (5); the quartz substrate (4) comprises a quartz body (4-1), a rectangular step (4-2) and a solder film (4-3), wherein the rectangular steps (4-2) are distributed at intervals on the quartz body (4-1) and are used to position and fix the VIA chip (3); the solder film (4-3) is plated on the rectangular steps (4-2) and is used to achieve a solder connection of the VIA chip (3); the packaging method comprises: Step 1: pre-treating the rectangular step surface of the quartz substrate and plating a solder film on the rectangular step surface; Step 2: Preliminarily place two VIA chips on the rectangular steps of the quartz substrate, and use a micromechanical adjustment tool to accurately adjust the positions of the VIA chips; Step 3: heating the assembly formed by the quartz substrate and the VIA chip to the melting point of the solder at a set heating rate, maintaining the temperature for a certain period of time, and then slowly cooling the temperature at a set cooling rate to achieve welding of the quartz substrate and the VIA chip; Step 4: Install the assembly formed by the welded quartz substrate and the VIA chip into the middle area of ​​the tube shell; Step 5: Bond the circuit board to both ends of the quartz substrate respectively; Step 6: Install the conductive pins on the tube shell, and electrically connect the circuit board to the conductive pins through the metal electrodes and the VIA chip; Step 7: Place the sealing box cover on the tube shell for vacuum packaging. After welding, perform vacuum leakage test, mechanical property test and electromagnetic shielding test in sequence.

2. The packaging method according to claim 1, characterized in that: In step 1, the process of plating the solder film includes: The rectangular step surface of the quartz substrate is activated by plasma cleaning or chemical cleaning to remove the oxide layer and particulate impurities on the surface; The solder film is prepared by magnetron sputtering or evaporation process: the magnetron sputtering process is used, the working gas pressure is controlled at 0.5-1.0Pa, the sputtering power is controlled at 150W-300W, and the sputtering rate is adjusted to 0.1μm / min; or the evaporation process is used, the heating temperature is controlled below the melting point of the solder alloy, and the vacuum degree is maintained at 10 -5 Torr; During the magnetron sputtering or evaporation process, the film thickness is monitored in real time by a quartz crystal microbalance or a quartz crystal oscillator film thickness measuring instrument, the film thickness is accurately monitored, and the thickness of the solder film is accurately controlled within the range of 1μm-100μm, with a thickness deviation of ≤5%.

3. The packaging method according to claim 1, characterized in that: In step 1, the solder film is composed of a metal alloy matrix, a wetting enhancer, an antioxidant and a conductivity enhancer; the metal alloy matrix is ​​one of gold-tin alloy, indium-tin alloy, bismuth-tin alloy, silver-tin alloy, indium-bismuth-tin alloy, but not limited thereto; the wetting enhancer includes one of titanium, chromium, zirconium, nickel, and molybdenum, but not limited thereto. The antioxidant includes one of palladium, iridium, platinum, rhenium, and manganese, but not limited thereto. The conductivity enhancer includes one of silver, copper, tungsten, and zinc, but not limited thereto.

4. The packaging method according to claim 1, characterized in that: In step 2, the parallelism deviation of the two VIA chips is ≤5μm, and the positioning accuracy deviation is ≤100μm.

5. The method for assembling the quartz base plane differential type quartz vibration beam accelerometer according to claim 1, characterized in that: In step 3, the welding process of the VIA chip and the quartz substrate includes: -6 Under the condition of 2000 ℃ and 1000 ℃, a precise temperature-controlled hot plate, an infrared heating system or a laser heater is used to uniformly heat the solder film on the rectangular step surface of the quartz substrate at a heating rate of ≤5℃ / min to a temperature range within the melting point of the solder; the solder film is kept within the melting point temperature range for 5-10 minutes to ensure that the solder is completely melted and fully combined with the VIA chip and the quartz substrate to form a stable welding interface; after welding, the welding area is slowly cooled at a cooling rate of ≤5℃ / min.

6. The method for assembling the quartz base plane differential type quartz vibration beam accelerometer according to claim 1, characterized in that: In step 4, the combined quartz substrate and VIA chip assembly are mounted in the middle area of ​​the tube shell using low outgassing rate vacuum glue or metal solder; in step 5, the circuit board is bonded to both ends of the quartz substrate using low outgassing rate vacuum glue or metal solder.

7. The method for assembling the quartz base plane differential type quartz vibration beam accelerometer according to claim 1, characterized in that: In step 6, gold wire bonding or precision welding process is used to connect the circuit board and the VIA chip to the conductive pins through metal electrodes.

8. The method for assembling the quartz base plane differential type quartz vibration beam accelerometer according to claim 1, characterized in that: In step 7, the vacuum packaging adopts any one of vacuum laser welding, eutectic welding and brazing processes.

9. A quartz base plane differential quartz vibration beam accelerometer, characterized in that: The quartz base plane differential quartz vibration beam accelerometer is manufactured by the packaging method according to any one of claims 1 to 8.

10. The quartz base plane differential quartz vibration beam accelerometer according to claim 9, characterized in that: The interior of the sealing box (1) and the tube shell (5) that are buckled together is a vacuum cavity; the two VIA chips (3) are mounted on the quartz substrate (4) and respectively output positive and negative signals through differential detection; the circuit board (2) is provided on one side of each VIA chip (3), and the circuit board (2) includes a driving circuit and an amplifying circuit, and the driving circuit and the amplifying circuit are connected to the metal electrodes of the corresponding VIA chip (3); the circuit board (2) is used to provide a driving signal for the VIA chip (3) and to receive and amplify the output signal of the VIA chip (3); the conductive pin (6) is provided on the outer side of each circuit board (2), and the conductive pin (6) is embedded in the tube shell (5), and the conductive pin (6) is used to transmit the signal processed by the circuit board (2) to an external device, and receive a control signal from the external device to adjust the working state of the VIA chip (3).

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