High-temperature-resistant and overload-resistant potting method for micro-inertial unit

Abstract

The invention provides a high-temperature-resistant and overload-resistant potting method for a micro inertial unit. The method comprises the following steps: step 1, wrapping and coating a gyroscope chip and an accelerometer chip in a circuit assembly by using organic silica gel; 2, fixing the shell on a heating table, injecting epoxy glue into the shell at a constant speed, and taking down the shell from the heating table after checking that the potting amount and the glue potting state meet the requirements; 3, the shell is fixed to a vibration meter or in a vacuum cavity, and defoaming treatment is conducted on the shell in a vibration or vacuum mode; and 4, the defoamed shell is placed in a high-temperature curing box, and the shell is taken out after the epoxy glue is completely solidified and hardened. On the premise of ensuring that the precision is not damaged, the anti-overload capacity of the micro-inertia unit is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of inertial measurement units and relates to a high temperature resistant and overload resistant potting method for a micro inertial unit. Background Art

[0002] The micro inertial measurement unit is composed of a three-axis MEMS gyroscope, a three-axis MEMS accelerometer, and a digital acquisition and processing circuit. It can sensitively sense information such as the angular velocity and acceleration of the carrier. It has the characteristics of small size, light weight, low power consumption, and strong anti-interference ability. It is widely used in navigation, guidance, and control of aerospace, drones, and tactical weapons and equipment.

[0003] As weapons and ammunition develop towards guidance, artillery shells have put forward higher requirements for the micro-inertial measurement unit's overload resistance and performance retention after firing. It needs to be able to withstand the tens of thousands of g of the firing shock load at the moment of firing to ensure that the device does not fail or degrade in performance. On the other hand, it is necessary to ensure that the zero position change and scale factor change of the micro-inertial measurement unit before and after resisting high overload are as small as possible to maximize the accuracy of the autonomous navigation system.

[0004] In the prior art, people modify the micro-inertial unit according to the needs to make it have the ability to resist overload. However, the current research focuses on improving the anti-overload ability of the micro-inertial measurement unit, ignoring the ability to maintain accuracy before and after high overload. Therefore, how to improve the anti-overload ability of the micro-inertial unit without compromising the accuracy is an urgent problem to be solved. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0006] To this end, the present invention provides a high temperature resistant and overload resistant potting method for a micro inertial unit. The present invention improves the overload resistance of the micro inertial unit while ensuring that the accuracy is not damaged.

[0007] The technical solution of the present invention is as follows:

[0008] According to one aspect, a high temperature resistant and overload resistant potting method for a micro inertial unit is provided, the method comprising:

[0009] Step 1: First, wrap and coat the gyroscope chip and accelerometer chip in the circuit assembly with organic silicone;

[0010] Step 2: Fix the shell on the heating table, then inject epoxy glue into the shell at a uniform speed, check the potting volume and the state of the glue filling to meet the requirements, and then remove the shell from the heating table;

[0011] Step 3: Fix the housing on a vibrator or in a vacuum chamber and perform degassing treatment on it by vibration or vacuum;

[0012] Step 4: Place the degassed shell in a high-temperature curing box and take it out after the epoxy glue is completely solidified and hardened.

[0013] Furthermore, the thickness of the organic silica gel is 1 mm.

[0014] According to another aspect, a high temperature resistant and overload resistant potting structure of a micro inertial unit is provided, comprising a shell, a circuit component, organic silica gel, epoxy glue and a cover plate, wherein the circuit component is arranged in the shell, and the cover plate is used to close the upper end opening of the shell, the circuit component comprises a processor, a gyroscope chip, an accelerometer chip and a circuit board, the accelerometer chip and the gyroscope chip are arranged on the upper surface of the circuit board, and the processor is arranged on the lower surface of the circuit board, and after the gyroscope chip and the accelerometer chip are fixed on the circuit board, both are wrapped and coated with organic silica gel; the epoxy glue fills all gaps between the circuit component and the shell 1.

[0015] Furthermore, the thickness of the organic silica gel is 1 mm.

[0016] Furthermore, the accelerometer chip, the gyroscope chip and the processor are all soldered to the circuit board by reflow soldering.

[0017] Furthermore, the structure also includes a plurality of external vibration dampers, which are fixedly arranged on the outer surface of the shell.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The anti-overload potting structure of a micro-inertial unit of the present invention adopts a double-stage buffering design of "inner potting material vibration absorption + external shock absorber vibration reduction", which reduces the force transmitted to the micro-inertial unit structure under overload impact and plays an anti-overload protection role;

[0020] 2. The high temperature resistant potting process of a micro inertial unit of the present invention firstly coats and wraps the MEMS inertial device with high thermal conductivity organic silica gel, effectively reducing the stress and temperature change of the sensitive components; and then potting the unit structure as a whole with high strength epoxy potting glue, ensuring that the potted product has good impact resistance and insulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 It is a schematic diagram of the internal potting structure of the micro-inertial unit provided by the present invention;

[0023] Figure 2 It is a schematic diagram of the external vibration reduction structure of the micro inertial unit provided by the present invention;

[0024] Figure 3 This is the micro-inertial unit potting process provided by the present invention;

[0025] Among them, 1 is a housing; 201 is a circuit board; 202 is a processor; 203 is a gyroscope; 204 is an accelerometer; 3 is organic silicone; 4 is epoxy glue; 5 is a cover plate; and 6 is a shock absorber. DETAILED DESCRIPTION

[0026] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0028] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0029] like Figure 3 As shown, in one embodiment of the present invention, a high temperature resistant and overload resistant potting method for a micro inertial unit is provided, the method comprising:

[0030] Step 1: First, wrap and coat the gyroscope chip and accelerometer chip in the circuit assembly with organic silicone;

[0031] Step 2: Fix the shell on the heating table, and then inject the epoxy glue into the shell at a uniform speed (such as through a syringe). After checking that the potting volume and the filling state meet the requirements, remove the shell from the heating table;

[0032] Step 3: Fix the housing on a vibrator or in a vacuum chamber and perform degassing treatment on it by vibration or vacuum;

[0033] Step 4: Place the degassed shell in a high-temperature curing box and take it out after the epoxy glue is completely solidified and hardened.

[0034] In addition, step five may be included: sealing the cover plate to the outer shell by gluing, screwing, welding, etc. to form a micro-inertial unit, and then removing the potting stress by vibration, high-temperature baking, high and low temperature impact, etc.

[0035] In this embodiment, the epoxy glue is a high-strength epoxy glue, which has better fluidity under high temperature conditions and can be potted more quickly and evenly. When there is a glue filling port, the epoxy glue is injected through the syringe at a uniform speed until the glue amount meets the requirement; when there is not enough space for the glue filling port, the bottom can be potted first, and when the glue amount is appropriate, the PCB circuit board is placed, and the glue amount can fill the entire bottom and evenly overflow from the surroundings, and then the upper part is potted until the glue amount meets the requirement.

[0036] In this embodiment, the degassing treatment is to remove the bubbles inside the glue liquid. This embodiment provides two solutions. One is to centrifuge the epoxy glue to degas before pouring the glue; the other is to degas by vibration or vacuum after pouring the glue. Among them, the epoxy glue will expand in volume after high-temperature curing, so the amount of glue poured should not exceed 80% to 90% of the internal space of the shell.

[0037] In addition, the potting stress inside the micro-inertial unit can be removed by vibration, high-temperature baking, high- and low-temperature shock, and other methods.

[0038] In this embodiment, the organic silica gel is high thermal conductivity organic silica gel, and its thickness is 1 mm.

[0039] In one embodiment of the present invention, a high temperature resistant potting process of a micro inertial unit is firstly to coat and wrap the MEMS inertial device with high thermal conductivity organic silicone rubber, so as to effectively reduce the stress and temperature change of the sensitive components; and then to pot the unit structure as a whole with high strength epoxy potting glue, so as to ensure that the potted product has good impact resistance and insulation.

[0040] According to another embodiment, Figure 1-2 As shown, a high temperature resistant and overload resistant potting structure of a micro inertial unit is provided, comprising a shell 1, a circuit component, organic silica gel 3, epoxy glue 4 and a cover plate 5, wherein the circuit component is arranged in the shell 1, and the cover plate 5 is used to seal the upper end opening of the shell 1, and the circuit component comprises a processor 202, a gyroscope chip 203, an accelerometer chip 204 and a circuit board 201, wherein the accelerometer chip 204 and the gyroscope chip 203 are arranged on the upper surface of the circuit board 201, and the processor 202 is arranged on the lower surface of the circuit board 201, and after the gyroscope chip 203 and the accelerometer chip 204 are fixed on the circuit board 201, both are wrapped and coated with organic silica gel 3; the epoxy glue fills all gaps between the circuit component and the shell 1.

[0041] In this embodiment, after the gyro chip 203 and the accelerometer chip 204 are welded, high thermal conductivity organic silicone 3 is coated around the chips. The coating thickness is about 1 mm, and it has a low elastic modulus and good thermal conductivity and insulation. It can effectively release the thermal stress caused by external mechanical stress and temperature that the gyro chip and the accelerometer chip are sensitive to.

[0042] In this embodiment, the accelerometer chip 204 , the gyroscope chip 203 and the processor 202 are all soldered to the circuit board 201 by reflow soldering.

[0043] In this embodiment, there is a gap or vacancy between the circuit assembly and the housing 1, which is filled with high-strength epoxy glue 4 to fix and protect the internal core gyro / accelerometer chip, which can prevent failure phenomena such as the internal chip falling off the PCB or the welding points of components such as capacitors breaking after a high overload impact process. Among them, the high-strength epoxy glue 4 fills the entire structure without voids, has a high elastic modulus, has good thermal conductivity, insulation and impact resistance, can absorb the force transmitted during the overload impact, and plays a protective and buffering role against the impact.

[0044] That is, the gyro and accelerometer chips are mechanical devices and are sensitive to stress. The double-layer protection of organic silicone 3 and epoxy glue 4 can reduce the high overload energy impact and play a role in stress isolation. That is, in order to solve the problem of startup temperature drift of gyro and accelerometer chips due to large temperature gradient under the conditions of small volume and high density integrated packaging, high thermal conductivity organic silicone with good thermal conductivity is used, which can effectively slow down the internal temperature distribution, reduce the temperature gradient and temperature change rate, and make the gyro and accelerometer work in a relatively stable working environment.

[0045] Preferably, the structure further comprises a plurality of external vibration dampers 6, and the vibration dampers 6 are fixedly arranged on the outer surface of the housing.

[0046] That is, the dual-stage buffer design of "internal potting material vibration absorption + external shock absorber vibration reduction" reduces the force transmitted to the micro-inertia unit structure under overload impact, and plays an anti-overload protection role. Figure 2 shown.

[0047] In addition, the structure can be obtained by using the method of the above embodiment.

[0048] In summary, the present invention first uses high thermal conductivity organic silica gel to coat and wrap the MEMS inertial device, effectively reducing the stress and temperature changes of the sensitive components; and then uses high-strength epoxy potting glue to pot the unit structure as a whole, ensuring that the potted product has good impact resistance and insulation. In addition, the present invention adopts a two-stage buffering design of "internal potting material vibration absorption + external shock absorber vibration reduction", which reduces the force transmitted to the micro-inertial unit structure under overload impact and plays an anti-overload protection role.

[0049] Features described and / or illustrated above for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with or used in place of features in other embodiments.

[0050] It should be emphasized that the term "include / comprises" when used herein refers to the presence of features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps, components or combinations thereof.

[0051] The above method of the present invention can be implemented by hardware, or by hardware combined with software. The present invention relates to such a computer-readable program, which, when executed by a logic component, enables the logic component to implement the above-mentioned device or component, or enables the logic component to implement the above-mentioned various methods or steps. The present invention also relates to a storage medium for storing the above program, such as a hard disk, a magnetic disk, an optical disk, a DVD, a flash memory, etc.

[0052] The many features and advantages of these embodiments are apparent from this detailed description, and thus the appended claims are intended to cover all such features and advantages of these embodiments that fall within their true spirit and scope. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not intended that the embodiments of the invention be limited to the exact construction and operation illustrated and described, but rather all suitable modifications and equivalents falling within the scope thereof are intended to be covered.

[0053] Parts of the present invention that are not described in detail are well known to those skilled in the art.

Claims

1. A high temperature resistant and overload resistant potting method for a micro inertial unit, characterized in that: The method comprises: Step 1: First, wrap and coat the gyroscope chip and accelerometer chip in the circuit assembly with organic silicone; Step 2: Fix the shell on the heating table, then inject epoxy glue into the shell at a uniform speed, check the potting volume and the state of the glue filling to meet the requirements, and then remove the shell from the heating table; Step 3: Fix the housing on a vibrator or in a vacuum chamber and perform degassing treatment on it by vibration or vacuum; Step 4: Place the degassed shell in a high-temperature curing box and take it out after the epoxy glue is completely solidified and hardened.

2. A high temperature resistant and overload resistant potting method for a micro inertial unit according to claim 1, characterized in that: The thickness of the silicone is 1 mm.

3. A high temperature resistant and overload resistant potting structure of a micro inertial unit, characterized in that: The device comprises a shell, a circuit assembly, organic silica gel, epoxy glue and a cover plate, wherein the circuit assembly is arranged in the shell, and the cover plate is used to close the upper end opening of the shell, the circuit assembly comprises a processor, a gyroscope chip, an accelerometer chip and a circuit board, the accelerometer chip and the gyroscope chip are arranged on the upper surface of the circuit board, and the processor is arranged on the lower surface of the circuit board. After the gyroscope chip and the accelerometer chip are fixed on the circuit board, both are wrapped and coated with organic silica gel; the epoxy glue fills all gaps between the circuit assembly and the shell 1.

4. According to claim 3, a high temperature resistant and overload resistant potting structure of a micro inertial unit is characterized in that: The thickness of the silicone is 1 mm.

5. According to claim 3, a high temperature resistant and overload resistant potting structure of a micro inertial unit is characterized in that: The accelerometer chip, the gyroscope chip and the processor are all soldered to the circuit board by reflow soldering.

6. A high temperature resistant and overload resistant potting structure of a micro inertial unit according to claims 3-5, characterized in that: The structure further comprises a plurality of external vibration absorbers, which are fixedly disposed on the outer surface of the housing.

Images