Pulse output quartz flexible accelerometer servo circuit structure and assembling method

Abstract

The invention relates to the field of inertial measurement, in particular to a pulse output quartz flexible accelerometer servo circuit structure and an assembly method. One end of the capacitance-voltage conversion circuit is connected with the transconductance compensation and amplification circuit, and the other end of the capacitance-voltage conversion circuit is connected with the quartz meter head; the transconductance compensation and amplification circuit is connected with the feedback correction circuit, and the feedback correction circuit is connected with the quartz meter head to realize a closed loop; the current / frequency conversion function is added on the basis of not changing the original boundary dimension, the problems of large size and long response time of an inertial measurement system are solved, the problem of hard connection between a circuit leading-out end and a substrate is avoided by the improved shell, and the problems of signal interference and bonding pad overfusion caused by the fact that a back bonding pad is welded by adopting a flexible wire are also avoided; in addition, due to the collaborative design of the PCB substrate double-sided mounting process and local encapsulation, the reliability problems of moisture absorption, bonding pad oxidation, component corrosion, redundancy introduction and the like caused by non-airtight encapsulation of a traditional servo circuit are solved.

Description

Technical Field

[0001] The present invention relates to the field of inertial measurement, and in particular to a pulse output quartz flexible accelerometer servo circuit structure and an assembly method. Background Art

[0002] Quartz flexible accelerometers are a crucial component of medium- and high-precision inertial measurement systems. These accelerometers utilize the force balance principle to detect acceleration signals and primarily consist of a quartz meter and a servo control circuit. The servo control circuit operates on analog output, requiring a dedicated conversion module to convert the analog output to digital for subsequent computer processing. This increases the size of the measurement system, which runs counter to the trend toward miniaturization of inertial measurement systems. Furthermore, long wiring between the servo circuit and the conversion module can introduce signal interference, reduce conversion accuracy, and increase system response time.

[0003] To achieve the integrated assembly of the servo circuit and the quartz meter head, the servo circuit of a traditional analog output quartz flexible accelerometer is designed as a Φ25.4m circular module. A thick-film process is used internally to assemble chip resistors, capacitors, and integrated ICs on an alumina substrate. Wire bonding is used to form electrical interconnections, and the module is encapsulated using a semicircular ceramic cover plate and epoxy adhesive. While this assembly method enables high-density assembly of the servo circuit, it also has some disadvantages. First, the non-hermetic packaging makes the circuit susceptible to moisture absorption during storage, causing oxidation of the internal solder pads and blistering and even corrosion on the component surfaces. In severe cases, this can lead to circuit failure. Second, if excess material is accidentally introduced into the cavity formed by the ceramic cover plate and the substrate, it will randomly move during subsequent transfer and mechanical testing, causing internal short circuits or increased impedance that affects circuit function.

[0004] Finally, the quartz meter's lead terminals are manually soldered to the palladium-silver pads on the back of the servo circuit using flexible wires. Improper soldering temperature and time can cause over-melting of the pads and cracks in the ceramic substrate, reducing circuit reliability. Using flexible wires can also cause signal interference, affecting circuit dynamic parameters. Summary of the Invention

[0005] To address the challenges of existing technologies, the present invention proposes a pulse-output quartz flexible accelerometer servo circuit structure and assembly method. This circuit integrates a current / frequency conversion module to achieve digital pulse output. Using double-sided PCB substrate mounting and a partial potting process, this design mitigates the issues of moisture absorption, pad oxidation, component corrosion, and excess material found in conventional non-sealed packages. This improved structure effectively avoids signal interference and pad over-melting caused by flexible wire soldering.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a pulse output quartz flexible accelerometer servo circuit structure, characterized by comprising a differential capacitor voltage conversion circuit, a transconductance compensation and amplification circuit, a feedback correction circuit, an integral comparison circuit, and a logic control circuit; One end of the capacitance-to-voltage conversion circuit is connected to the transconductance compensation and amplification circuit, and the other end is connected to the quartz meter head; The transconductance compensation and amplification circuit is connected to the feedback correction circuit, and the feedback correction circuit is connected to the quartz meter head to realize a closed loop and output a current signal; the transconductance compensation and amplification circuit is connected to the integral comparison circuit through the debugging pad, and the other end of the integral comparison circuit is connected to the logic control circuit, and the other end of the logic control circuit is connected to the output end, and the pulse signal is output through the output end.

[0007] As a further improvement of the present invention, the output signal of the lead-out terminal includes a current output mode and a pulse output mode, and the output mode is selected according to demand.

[0008] As a further improvement of the present invention, the logic control circuit is further connected to an external positive and negative constant current source circuit, and the positive and negative constant current source circuit is connected to the integral comparison circuit.

[0009] As a further improvement of the present invention, the capacitor-voltage conversion circuit is further connected to a power supply adjustment circuit, and the power supply adjustment circuit is connected to an external power supply.

[0010] A method for assembling a pulse output quartz flexible accelerometer servo circuit structure, comprising the above-mentioned pulse output quartz flexible accelerometer servo circuit structure; The servo circuit structure is arranged in a circuit housing, which is provided with an inner cavity, a PCB substrate and a cofferdam; During assembly, the PCB substrate is placed in the inner cavity, dividing the inner cavity into an inner cavity and an outer cavity, and the inner cavity is potted through a potting port provided on the PCB substrate to form a first potting area; The cofferdam located in the external cavity is connected to the PCB substrate, and the inner space of the cofferdam is potted to form a second potting area.

[0011] As a further improvement of the present invention, the circuit housing is a Φ25.4 mm circular package, and a plurality of second lead-out terminals are evenly distributed along the edge of the circuit housing surface.

[0012] As a further improvement of the present invention, a boss is provided on the inner cavity, and the boss is adapted to the PCB substrate.

[0013] As a further improvement of the present invention, the surface of the PCB substrate is provided with interconnection through holes, which are connected to the first lead-out end of the quartz meter head.

[0014] As a further improvement of the present invention, the side of the PCB substrate close to the second lead-out end is for component assembly, and the components include plastic-encapsulated components and chip-mounted components, which are assembled using a lead-tin solder pad reflow process.

[0015] As a further improvement of the present invention, the second potting area of the PCB includes a bare chip and a thin film resistor block, which are assembled by bonding with insulating glue and interconnecting with gold wires.

[0016] Compared with the prior art, the present invention has achieved the following technical effects: Without changing the overall dimensions, this invention adds a current-to-frequency conversion function, enabling the output of digital pulse signals and eliminating the traditional reliance on external dedicated conversion modules. By reconfiguring the servo circuit module, this integrated design converts the differential capacitance signal from the quartz meter into a digital pulse signal. This not only shortens the signal transmission path, avoiding signal interference, reduced conversion accuracy, and system response delays introduced by long-distance wiring, but also compresses the entire system into a single package, meeting the miniaturization and lightweight requirements of inertial measurement systems.

[0017] The present invention adopts the collaborative design of double-sided mounting process of PCB substrate and local potting to construct a double-sealed protection structure, which completely solves the reliability problems of traditional servo circuits caused by non-airtight packaging, such as moisture absorption, pad oxidation, component corrosion and introduction of superfluous materials. Specifically, the present invention realizes high-density assembly by mounting components on both sides of the PCB substrate, combining the lead-tin pad reflow process with the bare chip bonding and gold wire bonding process, and uses internal cavity potting and cofferdam potting structure to form protection; during the assembly process, the PCB substrate is fixed in the inner cavity of the circuit housing, and the internal cavity is potted through the preset glue potting port to realize component protection and stress buffering. The external cavity is potted twice by the cofferdam structure to further block the intrusion of environmental moisture and pollutants. This double potting design not only improves the airtightness of the package, but also reduces the risk of damage to the internal circuitry from mechanical shock through the stress buffering effect of the potting material. At the same time, the interconnection through-holes designed on the PCB substrate are directly connected to the lead-out terminals of the quartz meter head, replacing the traditional soft wire soldering method and completely eliminating the problems of over-melting of the solder pad, substrate cracks, and signal crosstalk caused by improper temperature control in manual soldering. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a block diagram of the servo circuit principle of the present invention; Figure 2 A schematic diagram of the servo circuit structure and assembly of the present invention; Figure 3 This is a schematic diagram of the servo circuit assembly of the present invention.

[0019] Figure numerals: 1. first lead-out terminal; 2. cat's eye; 3. cover plate; 4. circuit housing; 5. boss; 6. second lead-out terminal; 7. assembly gap; 8. PCB substrate; 9. interconnection through hole; 10. glue filling port; 11. first potting area; 12. cofferdam; 13. second potting area. DETAILED DESCRIPTION

[0020] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be considered as illustrative in nature and not restrictive.

[0021] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0023] In the present invention, unless otherwise expressly specified or limited, terms such as "mounted," "connected," "connect," and "fixed" should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0024] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0025] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0026] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0027] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0028] The accompanying drawings illustrate various schematic diagrams of structures according to embodiments disclosed herein. These figures are not drawn to scale; for clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0029] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0030] like Figure 1As shown, the present invention provides a pulse output quartz flexible accelerometer servo circuit structure, including a differential capacitor-voltage conversion circuit, a transconductance compensation and amplification circuit, a feedback correction circuit, an integral comparison circuit and a logic control circuit; one end of the capacitor-voltage conversion circuit is connected to the transconductance compensation and amplification circuit, and the other end is connected to the quartz meter head; the transconductance compensation and amplification circuit is connected to the feedback correction circuit, and the feedback correction circuit is connected to the quartz meter head to achieve a closed loop and output a current signal; the transconductance compensation and amplification circuit is connected to the integral comparison circuit through a debugging pad, the other end of the integral comparison circuit is connected to the logic control circuit, and the other end of the logic control circuit is connected to the output end, and a pulse signal is output through the output end.

[0031] like Figure 1 As shown, in the embodiment, the differential capacitance voltage conversion circuit is connected to the quartz meter head, and is used to convert the differential capacitance signal output by the quartz meter head into a voltage signal; specifically, it is realized by a capacitance-voltage converter, which converts the capacitance change into a linear voltage change. The input end of the differential capacitance voltage conversion circuit is connected to the capacitor plate of the quartz meter head, and the output end is connected to the transconductance compensation and amplification circuit. The transconductance compensation and amplification circuit in the embodiment is used to receive the voltage signal from the differential capacitor voltage conversion circuit and convert it into a current signal. The converted signal is divided into two paths: one is transmitted to the feedback correction circuit for closed-loop control; the other is input into the integration comparison circuit as a reference signal for pulse generation.

[0032] In the embodiment, one end of the feedback correction circuit is connected to the transconductance compensation and amplification circuit, and the other end is connected to the quartz meter head to form a closed-loop feedback circuit; specifically, the pendulum position of the quartz meter head is dynamically adjusted through the PID algorithm to ensure that the accelerometer maintains high linearity within a wide bandwidth. The feedback signal is applied to the torquer coil of the quartz meter head to form a force balance closed-loop system.

[0033] In the embodiment, the integrating and comparator circuit is configured to receive the amplified current signal and compare it with a preset threshold. When the signal exceeds the threshold, the logic control circuit is triggered to generate a pulse signal. The logic control circuit in the embodiment is preferably an FPGA or ASIC chip, which has an integrated current / frequency conversion module capable of converting analog signals into digital pulse signals. The embodiment is also externally connected to a positive and negative constant current source circuit, which can provide a reference current for the integral comparison circuit and is used to separately debug the current / frequency conversion function part in the circuit; the embodiment is also provided with a debugging pad, and during the circuit structure debugging stage, the analog output and the current / frequency conversion are debugged separately, and the debugging pad is connected by gold wire bonding to achieve integrated debugging and use.

[0034] In the embodiment, the power supply adjustment circuit is connected to the differential capacitor voltage conversion circuit, which is responsible for converting the external input power supply (for example, ±15V) into the stable voltage required by each module (such as ±5V, 3.3V). The circuit preferably uses a low voltage difference regulator and a filter capacitor to reduce the interference of power supply ripple on the entire circuit.

[0035] During use, the external power supply provides a stable DC voltage after being adjusted by the power adjustment circuit. When the circuit receives the differential capacitance signal from the quartz meter head, the differential capacitance voltage conversion circuit converts it into a voltage signal, and then outputs a current signal through the conduction compensation and amplification circuit. On the one hand, the current signal is input into the torquer coil of the quartz meter head through the feedback correction circuit for closed-loop control. On the other hand, it is used as the input signal of the integral comparison circuit for integral comparison, and then output as a pulse signal through the logic control circuit. Both analog current output and digital pulse output are led out through the output terminal, and the output mode can be selected according to usage requirements.

[0036] like Figure 2 As shown, the circuit structure in the embodiment has an external dimension of Φ25.4 mm×6.5 mm, and can be matched with a standard quartz meter head to form an accelerometer. Figure 2 The left end is a quartz meter head, which is provided with a plurality of first lead terminals 1. In the embodiment, the servo circuit structure is disposed within a circuit housing 4, which is provided with a plurality of second lead terminals 6 evenly arranged along the circumference. In the embodiment, there are preferably 13 second lead terminals 6, specifically a constant current source input terminal, a frequency standard input terminal, and positive and negative channel pulse output terminals.

[0037] A cat's eye 2 is provided at the bottom of the circuit housing 4, aligned with the position of the first lead-out terminal 1. The first lead-out terminal 1 is connected to an interconnection through-hole 9 within the circuit housing 4. Electrical interconnection is achieved through manual soldering, eliminating the need for additional backside solder pads and employing flexible wires for soldering, ensuring low impedance and high reliability in signal transmission. After soldering, the circuit is encapsulated using the cat's eye 2 and a cover plate 3 of the same size, preferably sealed using a laser melting process. This arrangement leaves ample space for substrate wiring and component assembly. During use, the servo circuit structure is placed upside down on the quartz watch head and installed accordingly.

[0038] like Figure 3 As shown, the circuit housing 4 is provided with an inner cavity, which is divided into an inner cavity and an outer cavity, specifically separated by a PCB substrate 8. The PCB substrate 8 is preferably made of FR-4 material, and the thickness can be determined according to the specific usage scenario. The inner cavity of the circuit housing 4 is provided with a boss 5, and the PCB substrate 8 is bonded to the boss 5 to ensure positioning accuracy during assembly and also play a mechanical support role.

[0039] In the embodiment, the side of the PCB substrate 8 close to the second lead-out terminal 6 is for plastic-encapsulated devices and chip-type mounting devices, which are assembled using a lead-tin solder pad reflow process; the side away from the second lead-out terminal 6 is provided with a second potting area 13 and a non-potting area, and the second potting area 13 and the non-potting area are separated by a cofferdam 12. In the embodiment, the cofferdam 12 is bonded to the PCB substrate 8 by insulating glue, and an assembly gap 7 is generated during the installation of the cofferdam 12 and the circuit housing 4, which is used to achieve matching connection between the circuit and the quartz meter head; the second potting area is specifically for installing bare chips and thin-film resistor blocks. The bare chips are fixed by insulating glue, and then a gold wire bonding process is used to achieve electrical connection with the PCB substrate 8 to improve circuit reliability. The non-potting area is for chip components. The internal cavity of the circuit housing 4 is potted through the potting port on the PCB substrate 8 . In the embodiment, there are preferably two potting ports until the internal cavity is completely filled to form a first potting area 11 .

[0040] During installation, insulating glue is used to bond the PCB substrate 8 to the boss 5 inside the circuit housing 4, the interconnecting through-hole 9 is connected to the first lead-out terminal on the quartz head, and the internal cavity is potted through the glue potting port reserved on the PCB substrate 8 to achieve mechanical support; insulating glue is used to bond the PCB substrate 8 to the cofferdam, and the internal area of the cofferdam is potted to complete the entire installation process.

[0041] The double potting design of the present invention not only blocks moisture and pollutants, avoiding pad oxidation or component corrosion in the potted circuit, but also protects the internal circuit from vibration damage through stress buffering, effectively improving circuit performance and reliability.

[0042] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from all points of view, the embodiments should be regarded as illustrative and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and range of equivalents of the claims are included in the present invention. Any reference signs in the claims should not be construed as limiting the claim to which they relate.

[0043] In addition, it should be understood that although this specification describes the embodiments, not every embodiment contains only one independent technical solution. This description is for clarity only. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for the purpose of illustrating the technical concept of the present invention and cannot be used to limit the scope of protection of the present invention. Any changes made based on the technical solution in accordance with the technical concept proposed by the present invention fall within the scope of protection of the claims of the present invention.

Claims

1. A pulse output quartz flexible accelerometer servo circuit structure, characterized in that: It includes a differential capacitor voltage conversion circuit, a transconductance compensation and amplification circuit, a feedback correction circuit, an integral comparison circuit, and a logic control circuit; One end of the capacitance-to-voltage conversion circuit is connected to the transconductance compensation and amplification circuit, and the other end is connected to the quartz meter head; The transconductance compensation and amplification circuit is connected to the feedback correction circuit, and the feedback correction circuit is connected to the quartz meter head to realize a closed loop and output a current signal; the transconductance compensation and amplification circuit is connected to the integral comparison circuit through the debugging pad, and the other end of the integral comparison circuit is connected to the logic control circuit, and the other end of the logic control circuit is connected to the output end, and the pulse signal is output through the output end.

2. The pulse output quartz flexible accelerometer servo circuit structure according to claim 1, characterized in that: The output signal of the lead-out terminal includes current output mode and pulse output mode. The output mode is selected according to the needs.

3. The pulse output quartz flexible accelerometer servo circuit structure according to claim 1, characterized in that: The logic control circuit is also connected to a positive and negative constant current source circuit arranged outside, and the positive and negative constant current source circuit is connected to the integral comparison circuit.

4. The pulse output quartz flexible accelerometer servo circuit structure according to claim 1, characterized in that: The capacitor voltage conversion circuit is also connected to a power supply adjustment circuit, and the power supply adjustment circuit is connected to an external power supply.

5. A method for assembling a pulse output quartz flexible accelerometer servo circuit structure, characterized in that: It comprises a pulse output quartz flexible accelerometer servo circuit structure as claimed in any one of claims 1 to 4; The servo circuit structure is arranged in a circuit housing, which is provided with an inner cavity, a PCB substrate and a cofferdam; During assembly, the PCB substrate is placed in the inner cavity, dividing the inner cavity into an inner cavity and an outer cavity, and the inner cavity is potted through a potting port provided on the PCB substrate to form a first potting area; The cofferdam located in the external cavity is connected to the PCB substrate, and the inner space of the cofferdam is potted to form a second potting area.

6. The method for assembling a pulse output quartz flexible accelerometer servo circuit structure according to claim 5, characterized in that: The circuit housing is a Φ25.4 mm circular package, and a plurality of second lead-out terminals are evenly distributed along the edge of the circuit housing surface.

7. The method for assembling a pulse output quartz flexible accelerometer servo circuit structure according to claim 5, characterized in that: A boss is provided on the inner cavity, and the boss is adapted to the PCB substrate.

8. The method for assembling a pulse output quartz flexible accelerometer servo circuit structure according to claim 5, characterized in that: The surface of the PCB substrate is provided with interconnection through holes, which are connected to the first lead-out end of the quartz meter head.

9. The method for assembling a pulse output quartz flexible accelerometer servo circuit structure according to claim 6, characterized in that: The side of the PCB substrate close to the second lead-out end is for component assembly. The components include plastic-encapsulated components and chip-mounted components, which are assembled using a lead-tin solder pad reflow process.

10. The method for assembling a pulse output quartz flexible accelerometer servo circuit structure according to claim 5, characterized in that: The second potting area of the PCB includes a bare chip and a thin film resistor block, which are assembled by bonding with insulating adhesive and interconnecting with gold wire bonding.

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