CN115767948B - High-density and low-stress integration method for MEMS inertial systems - Google Patents

Abstract

The invention discloses a high-density and low-stress integration method for a MEMS inertial system. It is characterized in that the circuit board is bonded to the metal structural part through the MEMS inertial instrument ceramic tube shell; the surface of the glued metal structural part is polished by sandblasting; They are interconnected through flexible lines, which are fixed on the metal structure through adhesive; high-temperature aging, rapid temperature change, and random vibration methods are used to accelerate stress release. The present invention reduces integration stress while ensuring the degree of integration, and reduces changes in micro-electromechanical inertial instrument parameters caused by temperature changes, vibrations, and stress changes during long-term use.

Description

High-density and low-stress integration method for MEMS inertial systems

Technical field

This achievement belongs to the field of inertial technology and involves a high-density and low-stress integration method for MEMS inertial systems.

Background technique

Inertial measurement units and inertial navigation systems based on microelectromechanical inertial instruments are all microelectromechanical inertial systems. Microelectromechanical inertial systems have the advantages of small size, light weight, low power consumption, and low price. They are widely used in unmanned vehicles, drones, and robots. , guided munitions and other fields are becoming more and more widely used. At present, with the continuous improvement of the accuracy of MEMS inertial instruments and the gradual development of instrument forms towards chip-based MEMS inertial systems, more and more MEMS inertial systems use circuit board welding MEMS inertial instruments. It is integrated in the form of a chip, but the integrated stress of the circuit board is relatively large. As the external temperature changes and vibrates, the integrated stress of the circuit board changes and is eventually transferred to the MEMS inertial instrument chip, resulting in a decrease in the accuracy of the MEMS inertial instrument. Overall performance degradation.

Contents of the invention

In view of the problem that the integrated stress of the circuit board is large, resulting in a decrease in the accuracy of the micro-electromechanical inertial instrument, the purpose of the present invention is to provide a high-density and low-stress integration method for the MEMS inertial system, which can reduce the integration stress and reduce temperature changes and temperature changes while ensuring the degree of integration. Changes in MEMS inertial instrument parameters caused by vibration and stress changes during long-term use.

In order to achieve the purpose of the present invention, the high-density and low-stress integration method of the MEMS inertial system provided by the present invention adopts the following technical solutions:

The circuit board is bonded to the metal structure through the ceramic shell of the MEMS inertial instrument; the surface of the bonded metal structure is polished by sandblasting; the circuit boards are interconnected by flexible wires, and the flexible wires are fixed to the metal structure by gluing; high temperature aging, fast temperature change and random vibration methods are used to accelerate stress release.

Preferably, silicone rubber is used to fix the ceramic shell of the MEMS inertial instrument and the metal structure, and the glue thickness is controlled through a quantitative method, and the glue thickness is controlled between 100 μm and 300 μm.

Preferably, the sandblasting range is 60 mesh to 150 mesh.

Preferably, the thickness of the circuit board is controlled between 1.0mm and 1.6mm.

Preferably, the high-temperature aging stress is released, the high-temperature aging time is 24h-72h, and the aging temperature is 80°C-90°C.

Preferably, the rapid temperature change stress is released, and each rapid temperature change cycle is: high temperature 70°C to 90°C, heat preservation for 1h to 3h, cooling at -5°C/min to -10°C/min, and cooling to a low temperature of -40°C to -45℃, keep the temperature for 1h~3h, raise the temperature to the high temperature of 70℃~90℃ at 5℃/min~10℃/min; cycle this for 8~12 times to complete the rapid temperature stress release.

Preferably, the random vibration stress is released, and the vibration spectrum type is: the power spectral density in the range of 80Hz ~ 350Hz is 0.01g ² /Hz ~ 0.08g ² /Hz, and the power spectral density in the range of 20Hz ~ 80Hz is +3dB/Oct, The power spectral density in the range of 350Hz to 2000Hz is -3dB/Oct, the vibration root mean square magnitude is 6.06g, and the vibration time is 3min to 10min.

Compared with the existing technology, the beneficial effects of the present invention are as follows:

The present invention isolates installation stress by gluing and fixing the ceramic tube shell of the inertial instrument on the metal structure; reduces integrated stress changes under conditions such as temperature change and vibration, and improves parameter stability of the micro-electromechanical inertial instrument through methods such as sandblasting of the bonding structure, lightweight circuit boards, and flexible electrical interconnection and fixation; releases integrated stress through high-temperature aging, rapid temperature changes, and random vibrations, reduces parameter changes of the micro-electromechanical inertial instrument caused by integrated stress release such as gluing during long-term use, and improves the mechanical and thermal environment adaptability and long-term stability of the micro-electromechanical inertial system.

Description of drawings

The accompanying drawings are included to provide a further understanding of the embodiments of the invention, and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 shows a schematic layout diagram of a MEMS gyroscope and a MEMS accelerometer provided according to a specific embodiment of the present invention.

FIG. 2 is a schematic diagram showing a ceramic tube shell of a MEMS gyroscope and a ceramic tube shell of a MEMS accelerometer bonded to a structural member by adhesive according to a specific embodiment of the present invention.

FIG. 3 is a schematic diagram showing the sandblasting positions of the bonding surface of a structural component according to a specific embodiment of the present invention.

Figure 4 shows the MEMS gyroscope temperature change output comparison curve before and after stress release according to a specific embodiment of the present invention.

1, position, 11. Structural sandblasting position.

Detailed ways

It should be noted that, as long as there is no conflict, the embodiments and features in the embodiments of this application can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application or uses. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

As an embodiment of the present invention, a high-density and low-stress integration method for MEMS inertial systems is proposed, specifically as follows:

The MEMS inertial system integrates 3 MEMS gyroscopes and 3 MEMS accelerometers. 6 MEMS inertial instruments are welded on 3 to 6 circuit boards. The circuit boards are fixed by bonding the MEMS inertial instrument ceramic tube shell to the structure. On the components, the adhesive stress is prevented from being transmitted to the sensitive structure of the MEMS inertial instrument. Compared with the traditional printed board adhesive or screw fixation, the integrated stress transmission is greatly reduced. Silicone rubber is used to fix the ceramic shell of the MEMS inertial instrument and the metal structure. In order to avoid the collision between the inertial instrument and the structural parts during vibration if the glue is too thin, and the glue is too thick, the installation error of the inertial instrument will be large under variable temperature conditions and the orthogonality will be affected. Decrease, resulting in a decrease in system accuracy. The glue thickness is controlled through a quantitative method, and the glue thickness is controlled between 100 μm and 300 μm.

Under the condition of no sandblasting adhesive on the structure, a temperature change test was conducted after stress release. There was degumming at the adhesive position, and the MEMS gyro output jumped; in order to improve the reliability of the local bonding between the adhesive and the metal structure and reduce the stress caused by the local detachment of the adhesive. Change, the surface of the adhesive metal structure is sandblasted with 60 mesh to 150 mesh. After bonding, a temperature change test is performed after the stress is released. The MEMS gyro output jump disappears.

The circuit board and the electrical interconnection between the circuit boards will transmit stress to the MEMS inertial instrument. In order to reduce the stress transmission under conditions such as temperature changes and vibration, the thickness of the circuit board is controlled between 1.0mm and 1.6mm, and the circuit boards are interconnected through flexible wires. , the flexible wire is fixed to the metal structure through adhesive.

The integrated stress caused by integration such as gluing will be gradually released during use. In order to accelerate the stress release, a set of stress release processes are adopted. Specifically:

①High temperature aging stress release, high temperature aging time 24h~72h, aging temperature 80℃~90℃;

② Rapid temperature change stress release, each rapid temperature change cycle is: high temperature 70℃ ~ 90℃, heat preservation for 1h ~ 3h, cooling at -5℃/min ~ -10℃/min, to low temperature -40℃ ~ -45℃, Keep the temperature for 1h to 3h, then raise the temperature to a high temperature of 70℃ to 90℃ at a rate of 5℃/min to 10℃/min; cycle this for 8 to 12 times to complete the rapid temperature stress release;

③ Random vibration stress release, the vibration spectrum type is: power spectral density 0.01g ² /Hz ~ 0.08g ² /Hz in the range of 80Hz ~ 350Hz, power spectral density + 3dB/Oct in the range of 20Hz ~ 80Hz, and power spectrum density in the range of 350Hz ~ 2000Hz The power spectral density is -3dB/Oct, the vibration root mean square magnitude is 6.06g, and the vibration time is 3min~10min.

The method of the present invention will be further described below in conjunction with a microelectromechanical inertial measurement unit.

The microelectromechanical inertial measurement unit adopts an integrated integrated circuit, a concave structure, an adhesive process and a stress relief process, specifically:

The MEMS inertial measurement unit integrates 3 MEMS gyroscopes (including 5. Z-axis MEMS accelerometer 6), 6 MEMS inertial instruments are welded on 3 to 6 circuit boards. The layout of the MEMS gyroscope and MEMS accelerometer is as shown in Figure 1. The circuit board is bonded to the structural part through the MEMS inertial instrument ceramic shell. The positions 7 to 10 of the gyroscope and accelerometer bonded to the structure are shown in Figure 2. The ceramic shell of the MEMS inertial instrument and the metal structure are fixed with silicone rubber, and the thickness of the glue is controlled at 200 μm.

The surface of the adhesive metal structure is polished by sandblasting, as shown in Figure 3, and the sandblasting is 80 mesh.

The thickness of the circuit board is 1.0mm. The circuit boards are interconnected through flexible lines, and the flexible lines are fixed on the metal structure through adhesive. Through the above-mentioned low-stress integration method, the MEMS inertial measurement volume is reduced to less than ^40cm3

In order to accelerate stress relief, a stress relief process is used. Specifically:

①High temperature aging stress release, high temperature aging time 48h, aging temperature 80℃;

② Rapid temperature change stress release, each rapid temperature change cycle is: high temperature 80℃, holding for 2 hours, cooling at -5℃/min, lowering to low temperature -45℃, holding for 2h, heating at 10℃/min to high temperature of 80℃; 10 cycles of this cycle complete rapid temperature stress release;

③ Random vibration stress release, vibration spectrum type: power spectral density in the range of 80Hz ~ 350Hz is 0.04g ² /Hz, power spectrum density in the range of 20Hz ~ 80Hz is +3dB/Oct, power spectrum density in the range of 350Hz ~ 2000Hz -3dB/ Oct, the vibration root mean square magnitude is 6.06g, and the vibration time is 5min.

Through the above stress release, the temperature-variable zero-bias stability of the MEMS gyroscope is improved by more than 80%. As shown in FIG4 , a comparison of the temperature-variable output of the MEMS gyroscope before and after the stress release is shown, wherein FIG4(a) is the temperature-variable output curve of the gyroscope before the stress release, and FIG4(b) is the temperature-variable output curve of the gyroscope after the stress release.

Therefore, the present invention proposes a high-density and low-stress integration of a MEMS inertial system, which reduces the integration stress while ensuring the integration level, and reduces the micro-electromechanical inertial instrumentation caused by temperature changes, vibrations, and stress changes during long-term use. Parameter changes improve the mechanical and thermal environment adaptability and long-term stability of the MEMS inertial system.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that it can still be used Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent substitutions are made to some of the technical features; however, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (4)

1. The high-density low-stress integration method of the MEMS inertial system is characterized in that 6 MEMS inertial instruments are welded on 3 to 6 circuit boards, the circuit boards are bonded on a metal structural member through an MEMS inertial instrument ceramic shell through adhesive, and the surface of the glued metal structural member is polished through sand blasting;

   the circuit boards are interconnected through flexible wires, and the flexible wires are fixed on the metal structural member through gluing;

   the circuit boards are electrically interconnected to transfer stress to the MEMS inertial instrument, and the method adopts high-temperature aging stress release, rapid temperature change stress release and random vibration stress release and comprises the following steps:

   the high-temperature aging stress is released, the high-temperature aging time is 24-72 hours, and the aging temperature is 80-90 ℃;

   the rapid temperature change stress release is carried out, and each rapid temperature change cycle is as follows: maintaining the temperature at 70-90 ℃ for 1-3 h, cooling at-5 ℃/min to-10 ℃/min, cooling to low temperature of-40-45 ℃, maintaining the temperature for 1-3 h, and heating to 70-90 ℃ at 5 ℃/min to 10 ℃/min; the rapid temperature-changing stress release is completed by 8 to 12 cycles;

   the random vibration stress is released, and the vibration spectrum type is as follows: the power spectral density is 0.01g within the range of 80 Hz-350 Hz ² /Hz～0.08g ² The power spectral density in the range of 20 Hz-80 Hz is +3dB/Oct, the power spectral density in the range of 350 Hz-2000 Hz is-3 dB/Oct, the vibration root mean square magnitude is 6.06g, and the vibration time is 3-10 min.
2. 2. The method for integrating the high-density and low-stress of the MEMS inertial system according to claim 1, wherein the ceramic tube shell of the MEMS inertial instrument is fixed with the metal structural part by adopting silicon rubber, and the rubber thickness is controlled to be 100-300 μm by a quantitative method.
3. 3. The method of claim 1, wherein the blasting is 60-150 mesh.
4. 4. The method of claim 1, wherein the circuit board thickness is controlled between 1.0mm and 1.6mm.