MEMS packaging structure and packaging method

Abstract

An MEMS packaging structure disclosed by the present invention comprises a packaging tube shell and at least one group of sensor assemblies, the packaging tube shell comprises a ceramic substrate and an upper cover plate, the upper cover plate is connected to the upper surface of the ceramic substrate, and the upper cover plate and the ceramic substrate form an accommodating cavity for accommodating the sensor assemblies; the sensor assembly comprises an ASIC chip, an MEMS chip and a plurality of flexible gaskets, the ASIC chip is mounted on the ceramic substrate, the MEMS chip is located above the ASIC chip, and the flexible gaskets are connected between the ASIC chip and the MEMS chip and used for converting stress of the ASIC chip and / or the MEMS chip in the horizontal direction into deformation of the flexible gaskets in the vertical direction. The MEMS packaging structure has the advantages that the structure is simple, the stress conducted to the MEMS chip in the packaging process and the working process can be reduced, the buffering effect is good, and the precision is high. The invention further discloses a packaging method.

Description

Technical Field

[0001] The present invention relates to the field of chip technology, and in particular to a MEMS packaging structure and a packaging method. Background Art

[0002] MEMS (Micro-Electro-Mechanical System) is a micro-device or system that uses large-scale integrated circuit manufacturing technology and micro-machining technology to integrate micro-sensors, micro-actuators, micro-structures, signal processing and control circuits, power supplies, and communication interfaces on one or more chips. It is used in consumer electronics, automotive industry, aerospace, and robotics.

[0003] As the application scenarios in various fields have increasingly stringent requirements on the size and integration of equipment, the miniaturization of MEMS has become an inevitable trend and has brought many significant advantages. Miniaturized MEMS can enable aerospace equipment such as drones, precision guidance, and individual combat equipment to integrate more functional modules in a limited space, reduce the overall weight, thereby increasing the payload, and at the same time help simplify complex system wiring and improve the reliability and maintainability of equipment; in the automotive industry, smaller MEMS facilitates its flexible layout inside the vehicle, which is conducive to the compact design of automotive electronic systems, reduces production costs, and can better adapt to the demand for miniaturization of electronic components in the process of automotive intelligence and electrification.

[0004] However, in order to achieve the miniaturization goal of MEMS, the traditional discrete packaging method can no longer meet the demand. In the traditional method, the connection lines between each chip are long and complicated, occupying a lot of space, which is not conducive to the compact layout design of the equipment. And in the process of pursuing miniaturized packaging, if the packaging scheme is not designed reasonably, it will cause a series of serious problems. Usually, the thermal expansion coefficients of MEMS devices and packaging substrate materials are different. Due to the difference in thermal expansion coefficients of different materials (such as silicon-based MEMS devices and ceramic packaging substrate materials), after high-temperature reflow soldering and other process links, large stress will be generated in the cooling stage. This stress acts on the multi-axis gyroscope header die and the three-axis accelerometer header die, causing slight deformation of its structure, which in turn leads to undesirable phenomena such as the resonant frequency offset and zero bias stability of the device, greatly reducing the measurement accuracy of the sensor. In the application scenario of high-precision aerospace navigation, the accumulation of slight measurement errors may cause the aircraft to deviate from the scheduled route, resulting in catastrophic consequences.

[0005] In addition, traditional packaging processes have obvious shortcomings in terms of long-term reliability. In the actual use environment, the device will inevitably be affected by a combination of factors such as temperature fluctuations, mechanical vibrations, and humidity changes. Due to the existence of packaging stress and the limitations of the packaging structure itself, it is easy to cause failure problems such as delamination between the chip and the packaging material, and fatigue fracture of solder joints. This not only shortens the service life of the product, reduces stability, but also increases the maintenance cost and after-sales risk. For example, during the operation of an automotive autonomous driving assistance system, if the MEMS-IMU exhibits abnormal performance due to packaging failure, it may cause the vehicle's automatic control system to misjudge, posing a serious threat to the lives and safety of the driver and passengers.

[0006] Chinese patent document CN11072371 adopts a spring-type flexible connection. The MEMS carrier uses silicon etching to form a planar corrugated spring mechanism, which is stretched and suspended at both ends on the support frame. This structure is similar to a carrier suspended by springs at both ends. The MEMS chip is installed on the MEMS carrier, and the stress transmitted by the package is completely relieved through the micro-deformation of the planar corrugated elastic mechanism. The MEMS chip installed on the carrier is basically not affected by the package stress. However, this method has many defects. The stiffness of the corrugated spring structure formed by etching itself is limited. It is difficult to ensure that the planar corrugated mechanism is not damaged during the subsequent assembly of the MEMS onto the carrier. If the stiffness of the planar corrugated spring is increased, it is difficult to ensure that the stress transmitted by the package shell will not be transmitted to the MEMS carrier; due to the flexible connection of the MEMS carrier suspension mechanism, external vibrations are extremely easy to be transmitted to the MEMS bearing mechanism through the corrugated spring structure. The resonance effect between the MEMS and the carrier will overlap with the MEMS signal, causing great interference to the MEMS signal and seriously affecting the stability of the MEMS signal output. It is difficult to ensure the linear output of the MEMS signal; moreover, the inherent resonance characteristics of the spring structure will also have a hysteresis effect on the frequency response of certain types of sensors.

[0007] U.S. Patent Document US10278281B1 discloses a packaging method that uses a rigid stress isolation plate to avoid direct contact between the MEMS and the packaging case. The stress isolation plate is made in the shape of a stepped boss. The upper boss is used to carry the MEMS, and the lower step is directly connected to the packaging case. The upper boss of the stress isolation mechanism uses a plane smaller than the MEMS chip to support the MEMS chip. The purpose is to reduce the contact area between the MEMS chip and the mounting surface, so as to reduce the stress on the MEMS. The stress isolation mechanism digs out pits at the lower part of the step to reduce the contact surface between the entire isolation system and the packaging case and reduce the stress on the stress isolation mechanism from the packaging case. At the same time, a certain isolation groove is dug on the front of the lower part of the step to weaken the stress transfer between the two parts of the step. This rigid stress isolation plate reduces the stress transmitted from the outside to the MEMS chip by gradually reducing the strain of the packaging case. However, due to the fact that the area of the boss on the upper part of the step is smaller than the area of the MEMS chip in terms of structure, it is difficult to achieve absolute symmetry in the installation of the MEMS chip on the boss. Moreover, the support surface of the boss with a certain area itself will also generate strain with the change of external conditions. As a result, the stress on the MEMS chip from the boss is local, and the local stress changes the local characteristics of the MEMS chip, making it difficult for the MEMS chip to work as expected in design or causing the device to work unstably.

[0008] U.S. Patent Document US8698292B2 uses a method of preparing bumps on a glass plane to reduce the contact area between the MEMS chip and the substrate. The smaller the bumps, the smaller the stress on the MEMS chip from the bumps. However, similar to the principle in the above-mentioned patent US10278281B1, it is very difficult to achieve symmetric installation of the MEMS chip on the contact bumps on the support surface, and the possibility of the MEMS being locally affected by unbalanced stress still exists.

[0009] Chinese Patent Document CN108878376B discloses an electronic device with both low stress and high over - load resistance and its packaging method. A protective soft glue is dropped on the inner side of the bottom plate of the packaging shell and pressed to form a lower protective soft glue and a side protective soft glue; a protective soft glue is dropped on the inner surface of the packaging cover plate and pressed to form a patterned upper protective soft glue. Then, a die - attach glue dot is dropped on the lower protective soft glue, and the electronic chip is mounted into the packaging shell, ensuring that there is no direct mechanical connection between the electronic chip and the inner side surface of the packaging shell and the packaging cover plate. Then, bonding wires are bonded, and finally, the packaging cover plate is covered. This invention uses the upper protective soft glue, the lower protective soft glue, and the die - attach glue dot to buffer the external force impact in the Z - direction together, protecting the electronic chip from colliding with the packaging cover plate or the bottom plate of the packaging shell; uses the side protective soft glue to buffer the external force impact in the X and Y - axis directions, protecting the electronic chip from colliding with the side surface of the packaging shell, so that the electronic device can both resist high over - load and has relatively low packaging stress. However, in this packaging method, the thermal expansion coefficients of the soft glue and the electronic chip are quite different, which may affect the performance of the stress - sensitive electronic chip due to the stress generated by the soft glue.

[0010] Chinese Patent Document CN108751119B discloses a MEMS packaging structure and its manufacturing method. Through semiconductor processing technology, the bottom oxide layer of the SOI wafer of the bottom plate of the MEMS wafer for wafer - level packaging is formed into a bottom oxide layer pattern, exposing part of the surface of the bottom silicon layer; then, using the bottom oxide layer pattern as a mask, deep silicon etching is performed on the MEMS wafer to expose the surface of the buried oxide layer. The bottom silicon layer is etched into a stress - buffer structure, forming a scribe area, an outer frame, stress - buffer springs, a window area, a connection area, and release holes; then the MEMS wafer is immersed in HF or buffered HF solution to form a central buried oxide pattern, forming a MEMS wafer with a stress - buffer structure; finally, the wafer is diced to complete the manufacturing of the MEMS packaging structure. The stress - buffer structure of the MEMS packaging structure manufactured by this invention is connected to the bottom of the MEMS chip through the central buried oxide, achieving the purpose of reducing packaging stress. Its advantages are simple process, small chip area, high packaging yield, and low cost. However, this method requires additional semiconductor processing steps, increasing the complexity and cost of manufacturing.

[0011] The Chinese patent document CN213416273U discloses a stress isolation packaging structure for a MEMS device. A step is fabricated on the packaging bottom plate of the packaging shell, and the fixing area of the stress isolation substrate is fixed on the step. The suspended area of the stress isolation substrate is suspended above the packaging bottom plate, forming a void area between the stress isolation substrate and the packaging bottom plate. The fixing area and the suspended area are connected by a rigid substrate neck. A substrate isolation groove is fabricated between the suspended area and the fixing area, and the substrate isolation groove is outside the step and does not contact the step. The MEMS chip is fixed on the suspended area and does not directly contact the packaging shell. The mechanical stress transmitted from the packaging shell to the MEMS chip is isolated through the substrate isolation groove, and at the same time, it is ensured that the isolation system does not introduce other interfering factors that affect the performance of the MEMS chip. In this way, the performance of the MEMS chip will not deteriorate due to environmental stress. This structure solves the packaging stress problem to a certain extent, but it cannot meet the requirements of multi-chip integration and higher performance in a complex MEMS-IMU system. Summary of the Invention

[0012] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a MEMS packaging structure with a simple structure, which can reduce the stress conducted to the MEMS chip during the packaging process and the working process, has good buffering effect and high precision, and also provides a packaging method.

[0013] To solve the above technical problems, the present invention adopts the following technical solutions:

[0014] A MEMS packaging structure includes a packaging shell and at least one set of sensor components. The packaging shell includes a ceramic substrate and an upper cover plate. The upper cover plate is connected to the upper surface of the ceramic substrate and forms a receiving cavity for receiving the sensor components with the upper cover plate. The sensor components include an ASIC chip, a MEMS chip, and a plurality of flexible gaskets. The ASIC chip is mounted on the ceramic substrate, the MEMS chip is located above the ASIC chip, and the flexible gaskets are connected between the ASIC chip and the MEMS chip and are used to convert the stress of the ASIC chip and / or the MEMS chip in the horizontal direction into the deformation of the flexible gaskets in the vertical direction.

[0015] As a further improvement of the above technical solution:

[0016] The flexible gasket includes a flexible sheet, an upper boss, and a lower boss. The upper boss and the lower boss are respectively arranged above and below both ends of the flexible sheet. The upper boss is connected to the MEMS chip, and the lower boss is connected to the ASIC chip.

[0017] The upper boss and the MEMS chip form an upper contact point, the lower boss and the ASIC chip form a lower contact point, and the distance between the lower contact points of two adjacent flexible gaskets is greater than the distance between the upper contact points.

[0018] A plurality of the flexible gaskets are symmetrically arranged circumferentially around the ASIC chip and the MEMS chip.

[0019] The flexible sheet is made of silicon material, and the thickness of the flexible sheet is less than the thickness of the MEMS chip.

[0020] Four groups of the sensor assemblies are provided, and the four groups of sensor assemblies are arranged in a rectangular array. The four groups of sensor assemblies are an X-axis sensor, a Y-axis sensor, a Z-axis sensor, and a triaxial acceleration sensor respectively, and the Z-axis sensor is adjacent to the X-axis sensor and the Y-axis sensor.

[0021] An installation groove is formed on the lower surface of the ceramic substrate, a lower cover plate is covered on the installation groove, and a control component is arranged in the installation groove. The control component includes an MCU chip.

[0022] A packaging method for the above MEMS packaging structure includes the following steps:

[0023] Step S1: Mount the ASIC chip on the ceramic substrate;

[0024] Step S2: Mount the flexible gasket on the ASIC chip;

[0025] Step S3: Perform wire bonding on the ASIC chip and the ceramic substrate;

[0026] Step S4: Mount the MEMS chip on the flexible gasket;

[0027] Step S5: Perform wire bonding on the MEMS chip and the ceramic substrate;

[0028] Step S6: Connect the upper cover plate and the ceramic substrate to form a sealed accommodation cavity.

[0029] As a further improvement of the above technical solution:

[0030] In step S2, the mounting of the flexible gasket further includes the following steps:

[0031] Step S201: Install a temporary gasket on the ASIC chip to support the flexible gasket;

[0032] Step S202: Drop bonding glue on the ASIC chip and mount the flexible gasket on the ASIC chip;

[0033] Step S203: After the bonding glue is cured, remove the temporary gasket to complete the mounting of the flexible gasket.

[0034] In step S6, a parallel seam welding process is used to hermetically weld the upper cover plate and the ceramic substrate.

[0035] Compared with the prior art, the advantages of the present invention are as follows:

[0036] 1. In the MEMS packaging structure of the present invention, during the packaging process, since the coefficient of thermal expansion of the ceramic substrate is greater than that of the MEMS chip made of silicon, after high-temperature reflow soldering and other process steps are completed, a large stress will be generated during the cooling stage. The ceramic substrate and the MEMS chip mounted on the ceramic substrate will shrink horizontally. The flexible gasket absorbs the stress in the horizontal direction of the MEMS chip and converts it into the deformation of the flexible gasket in the vertical direction, driving the MEMS chip to move up and down, buffering the stress transmitted to the MEMS chip, and avoiding problems such as the resonance frequency deviation and the deterioration of zero-bias stability of the device; during the working process, when the ASIC chip and the MEMS chip are combined to form a sensor, the heat mainly comes from the ASIC chip, the temperature of the MEMS chip is higher than that of the ASIC chip, the deformation of the ASIC chip is greater than that of the MEMS chip, the flexible gasket absorbs the stress in the horizontal direction of the MEMS chip and the ASIC chip and converts it into the deformation of the flexible gasket in the vertical direction, driving the MEMS chip to move up and down, buffering the stress transmitted to the MEMS chip, and reducing the measurement error; by setting the flexible gasket to absorb and convert the stress, the structure is simple, the stress transmitted to the MEMS chip during the packaging process and the working process can be reduced, the buffering effect is good, and the precision is high.

[0037] 2. In the MEMS packaging structure of the present invention, during the packaging process, after high-temperature reflow soldering and other process steps are completed, the ceramic substrate and the MEMS chip mounted on the ceramic substrate shrink horizontally. The lower boss moves closer to the upper boss, the flexible sheet bends, causing the end of the upper boss to move upward, arching the MEMS chip supported above the flexible gasket, and causing the MEMS chip to have an upward displacement; during the working process, the deformation of the ASIC chip is greater than that of the MEMS chip, the lower boss and the upper boss move closer to or away from each other, causing the MEMS chip to have an upward or downward displacement, and the structure is simple and reliable.

[0038] 3. In the MEMS packaging structure of the present invention, the distance between the two lower contacts of two adjacent flexible gaskets is greater than the distance between the two upper contacts of two adjacent flexible gaskets, so that the MEMS chip, the flexible gasket, and the ASIC chip arranged from top to bottom form a "frustum" structure with a smaller top and a larger bottom, and the structure is more stable.

[0039] 4. In the MEMS packaging structure of the present invention, multiple flexible gaskets are symmetrically arranged, so that the flexible gaskets can absorb the stress in all directions in the horizontal direction, and the buffering effect is better; moreover, the multiple symmetrically arranged flexible gaskets support the MEMS chip and drive the MEMS chip to move up and down, more smoothly, and the attitude change of the MEMS chip during the stress buffering process is smaller.

[0040] 5. The MEMS packaging structure of the present invention uses a flexible sheet made of silicon material, which has good thermal conductivity and insulation performance. Since the MEMS chip is also made of silicon material, and the thickness of the flexible sheet is less than that of the MEMS chip, the flexible sheet is easier to bend than the MEMS chip, preventing the MEMS chip from bending and deforming, and having good reliability.

[0041] 6. The MEMS packaging structure of the present invention can achieve the orthogonality of the Z-axis sensor with the X-axis sensor and the Y-axis sensor respectively on a ceramic substrate plane through the rectangular array arrangement, with reasonable layout and smaller volume, meeting the requirements of MEMS miniaturization.

[0042] 7. The MEMS packaging structure of the present invention forms a D three-dimensional layout by installing a sensor component on the upper surface of the ceramic substrate and a control component on the lower surface, with a more compact structure, which is beneficial to the miniaturization of MEMS.

[0043] 8. The packaging method of the present invention stacks and mounts the ASIC chip, flexible gasket, and MEMS chip from bottom to top in sequence. After each layer structure is mounted, the next layer is mounted, reducing the influence on other layers during the curing and cooling after the mounting of each layer structure, and reducing the stress brought by the packaging process.

[0044] 9. In the packaging method of the present invention, since the flexible sheet and the upper and lower bosses at both ends of the flexible sheet form a cantilever beam structure, if the flexible gasket is directly mounted, the flexible sheet is prone to deformation during mounting, which is not convenient for mounting. By adding a temporary gasket to support the flexible gasket, it is convenient for the mounting of the flexible gasket. Description of the Drawings

[0045] Figure 1 It is the front view of the MEMS packaging structure of the present invention.

[0046] Figure 2 It is the top view of the MEMS packaging structure of the present invention.

[0047] Figure 3 It is the bottom view of the MEMS packaging structure of the present invention.

[0048] Figure 4 It is the front view of a single sensor component in the MEMS packaging structure of the present invention.

[0049] Figure 5 It is the top view of a single sensor component in the MEMS packaging structure of the present invention.

[0050] Figure 6 It is the front view of the flexible gasket in the MEMS packaging structure of the present invention.

[0051] Figure 7This is a top view of the flexible gasket in the MEMS packaging structure of the present invention.

[0052] Legend: 1. Packaging shell; 11. Ceramic substrate; 111. Installation groove; 12. Upper cover plate; 13. Accommodation cavity; 14. Lower cover plate; 2. Sensor assembly; 21. ASIC chip; 22. MEMS chip; 3. Flexible gasket; 31. Flexible sheet; 32. Upper boss; 321. Upper contact; 33. Lower boss; 331. Lower contact; 4. Control assembly; 41. MCU chip; 5. Temporary gasket. Detailed implementation manners

[0053] The present invention will be further described in detail below in conjunction with the accompanying drawings of the specification and specific embodiments.

[0054] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the 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 construed as a limitation of the present invention.

[0055] In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more, unless otherwise specifically defined.

[0056] In the present invention, unless otherwise clearly specified and limited, the terms "assembly", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0057] Embodiment 1:

[0058] As Figures 1 to 7As shown in the figure, the MEMS packaging structure of this embodiment includes a packaging shell 1 and at least one group of sensor components 2. The packaging shell 1 includes a ceramic substrate 11 and an upper cover plate 12. The upper cover plate 12 is connected to the upper surface of the ceramic substrate 11 and forms a receiving cavity 13 for receiving the sensor components 2 with the upper cover plate 12. The sensor components 2 include an ASIC chip 21, a MEMS chip 22, and a plurality of flexible gaskets 3. The ASIC chip 21 is mounted on the ceramic substrate 11, the MEMS chip 22 is located above the ASIC chip 21, and the flexible gasket 3 is connected between the ASIC chip 21 and the MEMS chip 22 and is used to convert the stress of the ASIC chip 21 and / or the MEMS chip 22 in the horizontal direction into the deformation of the flexible gasket 3 in the vertical direction.

[0059] In the MEMS packaging structure of this embodiment, during the packaging process, since the thermal expansion coefficient of the ceramic material of the ceramic substrate 11 is greater than that of the silicon material of the MEMS chip 22, after high-temperature reflow soldering and other process steps are completed, a large stress will be generated during the cooling stage. The ceramic substrate 11 and the MEMS chip 22 mounted on the ceramic substrate 11 will shrink in the horizontal direction. The flexible gasket 3 absorbs the stress of the MEMS chip 22 in the horizontal direction and converts it into the deformation of the flexible gasket 3 in the vertical direction, driving the MEMS chip 22 to move up and down, buffering the stress transmitted to the MEMS chip 22, and avoiding problems such as the resonance frequency deviation and the zero-bias stability deterioration of the device; during the working process, since the heat generation mainly comes from the ASIC chip 21 when the ASIC chip 21 and the MEMS chip 22 are combined to form a sensor, the temperature of the MEMS chip 22 is higher than that of the ASIC chip 21, the deformation of the ASIC chip 21 is greater than that of the MEMS chip 22, and the flexible gasket 3 absorbs the stress of the MEMS chip 22 and the ASIC chip 21 in the horizontal direction and converts it into the deformation of the flexible gasket 3 in the vertical direction, driving the MEMS chip 22 to move up and down, buffering the stress transmitted to the MEMS chip 22, and reducing the measurement error. The MEMS packaging structure of this embodiment can absorb and convert the stress by setting the flexible gasket 3, has a simple structure, can reduce the stress transmitted to the MEMS chip 22 during the packaging process and the working process, has a good buffering effect, and high precision.

[0060] Furthermore, as Figure 6 and Figure 7As shown in the figure, in this embodiment, the flexible gasket 3 includes a flexible sheet 31, an upper boss 32 and a lower boss 33. The upper boss 32 and the lower boss 33 are respectively arranged above and below both ends of the flexible sheet 31. The upper boss 32 is connected to the MEMS chip 22, and the lower boss 33 is connected to the ASIC chip 21. During the encapsulation process, after process steps such as high-temperature reflow soldering are completed, the ceramic substrate 11 and the MEMS chip 22 mounted on the ceramic substrate 11 undergo horizontal contraction. The lower boss 33 moves closer to the upper boss 32, and the flexible sheet 31 bends, causing the end of the upper boss 32 to move upward, arching the MEMS chip 22 supported above the flexible gasket 3 and causing the MEMS chip 22 to have an upward displacement. During the working process, the deformation of the ASIC chip 21 is greater than that of the MEMS chip 22. The lower boss 33 and the upper boss 32 move closer to or away from each other, causing the MEMS chip 22 to have an upward or downward displacement. The structure is simple and reliable.

[0061] Further, as Figure 5 shown in the figure, in this embodiment, the upper boss 32 and the MEMS chip 22 form an upper contact 321, and the lower boss 33 and the ASIC chip 21 form a lower contact 331. The distance between the lower contacts 331 of two adjacent flexible gaskets 3 is greater than the distance between the upper contacts 321. The distance between the two lower contacts 331 of two adjacent flexible gaskets 3 is greater than the distance between the two upper contacts 321 of two adjacent flexible gaskets 3, so that the MEMS chip 22, the flexible gasket 3, and the ASIC chip 21 arranged from top to bottom form a "frustum" structure with a smaller top and a larger bottom, and the structure is more stable.

[0062] Further, as Figure 5 shown in the figure, in this embodiment, multiple flexible gaskets 3 are symmetrically arranged in the circumferential direction of the ASIC chip 21 and the MEMS chip 22. The multiple flexible gaskets 3 are symmetrically arranged, so that the flexible gasket 3 can absorb stresses in all directions in the horizontal direction, and the buffering effect is better. Moreover, the multiple symmetrically arranged flexible gaskets 3 support the MEMS chip 22 and drive the MEMS chip 22 to move up and down more smoothly, and the attitude change of the MEMS chip during the stress buffering process is smaller. Preferably, in this embodiment, there are four flexible gaskets 3 between the ASIC chip 21 and the MEMS chip 22.

[0063] Further, in this embodiment, the flexible sheet 31 is made of silicon material, and the thickness of the flexible sheet 31 is less than that of the MEMS chip 22. The flexible sheet 31 is made of silicon material, which has good thermal conductivity and insulation properties. Since the MEMS chip 22 is also made of silicon material, and the thickness of the flexible sheet 31 is less than that of the MEMS chip 22, the flexible sheet 31 is more easily bent than the MEMS chip, preventing the MEMS chip 22 from bending and deforming, and having good reliability. Preferably, in this embodiment, the thickness of the MEMS chip 22 is 200 μm, and the thickness of the flexible sheet 31 is 100 μm - 150 μm.

[0064] Further, as Figure 2 shown, in this embodiment, there are four groups of sensor components 2, and the four groups of sensor components 2 are arranged in a rectangular array. The four groups of sensor components 2 are an X-axis sensor, a Y-axis sensor, a Z-axis sensor, and a three-axis acceleration sensor respectively, and the Z-axis sensor is adjacent to the X-axis sensor and the Y-axis sensor. Through the rectangular array arrangement, the orthogonality of the Z-axis sensor with the X-axis sensor and the Y-axis sensor can be realized on one plane of the ceramic substrate 11, with a reasonable layout and a smaller volume, meeting the requirements of MEMS miniaturization. Specifically, in this embodiment, the MEMS chip 22 corresponding to the X-axis sensor is a horizontal sensitive axis type X-axis MEMS gyro chip, the MEMS chip 22 corresponding to the Y-axis sensor is a horizontal sensitive axis type Y-axis MEMS gyro chip, the MEMS chip 22 corresponding to the Z-axis sensor is a vertical sensitive axis type Z-axis MEMS gyro chip, and the MEMS chip 22 corresponding to the three-axis acceleration sensor is a three-axis MEMS accelerometer chip.

[0065] Further, as Figure 3 shown, in this embodiment, an installation groove 111 is formed on the lower surface of the ceramic substrate 11, a lower cover plate 14 is covered on the installation groove 111, and a control component 4 including an MCU chip 41 is arranged in the installation groove 111. By installing the sensor component 2 on the upper surface of the ceramic substrate 11 and the control component 4 on the lower surface, a 3D three-dimensional layout is formed, with a more compact structure, which is beneficial to the miniaturization of MEMS. Preferably, in this embodiment, the control component 4 further includes crystal oscillators and other resistor-capacitor components.

[0066] Embodiment Two:

[0067] The encapsulation method of the MEMS encapsulation structure in Embodiment One includes the following steps:

[0068] Step S1: Mount the ASIC chip 21 on the ceramic substrate 11; specifically, first coat a piece of glue on the chip mounting area on the upper surface of the ceramic substrate 11, install the ASIC chip 21 onto the mounting glue, and after the mounting glue is cured, enter Step S2;

[0069] Step S2: Mount the flexible gasket 3 on the ASIC chip 21;

[0070] Step S3: Perform gold wire bonding between the ASIC chip 21 and the ceramic substrate 11;

[0071] Step S4: Mount the MEMS chip 22 on the flexible gasket 3; Specifically, first apply a piece of glue on the upper boss 31 of the flexible gasket 3, install the MEMS chip 22 onto the mounting glue, and then proceed to Step S5 after the mounting glue cures;

[0072] Step S5: Perform gold wire bonding between the MEMS chip 22 and the ASIC chip 21;

[0073] Step S6: Connect the upper cover plate 12 and the ceramic substrate 11 to form a sealed accommodation cavity 13.

[0074] In the packaging method of this embodiment, by stacking the ASIC chip 21, the flexible gasket 3, and the MEMS chip 22 from bottom to top for mounting in sequence, and performing the mounting of the next layer after the mounting of each layer structure is completed, the influence on other layers during the curing and cooling after the mounting of each layer structure is reduced, and the stress brought by the packaging process is reduced.

[0075] Further, as Figure 4 shown, in this embodiment, in Step S2, the mounting of the flexible gasket 3 further includes the following steps:

[0076] Step S201: Install a temporary gasket 5 on the ASIC chip 21 to support the flexible gasket 3;

[0077] Step S202: Drop mounting glue on the ASIC chip 21, and mount the flexible gasket 3 on the ASIC chip 21;

[0078] Step S203: After the mounting glue cures, remove the temporary gasket 5 to complete the mounting of the flexible gasket 3.

[0079] Since the flexible sheet 31 and the upper boss 32 and the lower boss 33 at both ends of the flexible sheet 31 form a cantilever beam structure, if the flexible gasket 3 is directly mounted, the flexible sheet 31 is prone to deformation during mounting, which is not convenient for mounting. By adding a temporary gasket 5 to support the flexible gasket 3, it is convenient for the mounting of the flexible gasket 3.

[0080] Further, in this embodiment, in Step S6, a parallel seam welding process is used to seal and weld the upper cover plate 12 and the ceramic substrate 11. The parallel seam welding process has less thermal shock to devices such as chips through local heating, which helps to protect the bonding structure of devices such as chips.

[0081] Preferably, in this embodiment, before step S1, it is necessary to install the control component 4 on the lower surface of the ceramic substrate 11. Specifically: use high-temperature conductive adhesive to mount the MCU chip 41 and resistor-capacitor devices; perform reflow soldering on the MCU chip 41 and resistor-capacitor devices mounted on the lower surface of the ceramic substrate 11; use the parallel seam welding process to seal and weld the lower cover 14 and the ceramic substrate 11; perform airtightness inspection on the lower cover 14 and the ceramic substrate 11.

[0082] Preferably, in this embodiment, after step S6, it is also necessary to perform airtightness inspection on the accommodation cavity 13; implant balls on the lower surface of the ceramic substrate 11 to serve as external pins; perform circuit trimming and forming according to the final circuit shape requirements; clean.

[0083] The above are only the preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the above-disclosed methods and technical contents, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A MEMS packaging structure, characterized in that: The invention comprises a package tube shell (1) and at least one group of sensor components (2), wherein the package tube shell (1) comprises a ceramic substrate (11) and an upper cover plate (12), wherein the upper cover plate (12) is connected to the upper surface of the ceramic substrate (11) and forms a receiving cavity (13) for receiving the sensor component (2) with the upper cover plate (12), wherein the sensor component (2) comprises an ASIC chip (21), a MEMS chip (22) and a plurality of flexible gaskets (3), wherein the ASIC chip (21) is mounted on the ceramic substrate (11), the MEMS chip (22) is located above the ASIC chip (21), and the flexible gasket (3) is connected between the ASIC chip (21) and the MEMS chip (22) and is used for converting the stress of the ASIC chip (21) and / or the MEMS chip (22) in the horizontal direction into the deformation of the flexible gasket (3) in the vertical direction.

2. The MEMS packaging structure according to claim 1, characterized in that: The flexible gasket (3) comprises a flexible sheet (31), an upper boss (32) and a lower boss (33); the upper boss (32) and the lower boss (33) are respectively arranged above and below two ends of the flexible sheet (31); the upper boss (32) is connected to the MEMS chip (22), and the lower boss (33) is connected to the ASIC chip (21).

3. The MEMS packaging structure according to claim 2, characterized in that: The upper boss (32) and the MEMS chip (22) form an upper contact (321), the lower boss (33) and the ASIC chip (21) form a lower contact (331), and the distance between the lower contacts (331) of two adjacent flexible pads (3) is greater than the distance between the upper contacts (321).

4. The MEMS packaging structure according to claim 3, characterized in that: The plurality of flexible gaskets (3) are symmetrically arranged around the ASIC chip (21) and the MEMS chip (22).

5. The MEMS packaging structure according to claim 2, characterized in that: The flexible sheet (31) is made of silicon material, and the thickness of the flexible sheet (31) is smaller than the thickness of the MEMS chip (22).

6. The MEMS packaging structure according to claim 1, characterized in that: The sensor components (2) are provided with four groups, and the four groups of sensor components (2) are arranged in a rectangular array. The four groups of sensor components (2) are respectively an X-axis sensor, a Y-axis sensor, a Z-axis sensor and a three-axis acceleration sensor, and the Z-axis sensor is adjacent to the X-axis sensor and the Y-axis sensor.

7. The MEMS packaging structure according to any one of claims 1 to 6, characterized in that: The lower surface of the ceramic substrate (11) is provided with a mounting groove (111), the mounting groove (111) is covered with a lower cover plate (14), a control component (4) is arranged in the mounting groove (111), and the control component (4) comprises an MCU chip (41).

8. A packaging method for the MEMS packaging structure according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step S1: mounting the ASIC chip (21) on the ceramic substrate (11); Step S2: mounting the flexible gasket (3) on the ASIC chip (21); Step S3: performing gold wire bonding on the ASIC chip (21) and the ceramic substrate (11); Step S4: mounting the MEMS chip (22) on the flexible gasket (3); Step S5: performing gold wire bonding on the MEMS chip (22) and the ceramic substrate (11); Step S6: connecting the upper cover plate (12) and the ceramic substrate (11) to form a sealed receiving cavity (13).

9. The packaging method according to claim 8, characterized in that: In step S2, the mounting of the flexible pad (3) further comprises the following steps: Step S201: Installing a temporary gasket (5) on the ASIC chip (21) to support the flexible gasket (3); Step S202: dripping mounting glue on the ASIC chip (21), and mounting the flexible gasket (3) on the ASIC chip (21); Step S203: After the mounting glue is cured, the temporary gasket (5) is removed to complete the mounting of the flexible gasket (3).

10. The packaging method according to claim 8, characterized in that: In step S6, a parallel sealing welding process is used to seal and weld the upper cover plate (12) and the ceramic substrate (11).

Images