3D Packaging Structure of MEMS Piezoelectric Sensor System and Its Heat Dissipation Method

Abstract

The present invention discloses a three-dimensional packaging structure of a MEMS piezoelectric sensor system and its heat dissipation method, which mainly consists of a cap, a surface microstructure, a copper ring, a cylindrical array, and a horizontal extension platform, a horizontal mesh structure, a ceramic substrate, a MEMS chip, a piezoelectric thin film, a micro temperature sensor, solder balls, and an ASIC chip placed inside the cap. In the present invention, the heat in the ASIC chip area is horizontally transferred to the cap through the horizontal mesh structure and the horizontal extension platform; the cylindrical array vertically welded on the horizontal extension platform conducts the heat in the ASIC chip area upward to the copper ring, and the surface microstructure welded on the copper ring increases the convective heat transfer area on the upper surface of the cap, accelerating the convective heat transfer efficiency; among them, the micro temperature sensor adhesively bonded in the annular groove of the MEMS chip above the ASIC chip area monitors the temperature of the ASIC chip area in real time.

Description

Technical Field

[0001] The present invention relates to the field of microelectromechanical technology, and particularly to a three-dimensional packaging structure of a MEMS piezoelectric sensor system and a heat dissipation method thereof. Background Art

[0002] MEMS sensors are core devices in the sensing layer of industries such as artificial intelligence, Internet of Things, robotics, driverless, and AR / VR. Using integrated circuit manufacturing and microfabrication technologies, micro-mechanics and microelectronics are functionally packaged on one or more chips to form a micro-integrated system, which usually includes a microprocessor and a micro-sensor for obtaining external information. It can sense and process various signals from the outside world such as sound, light, electricity, heat, force, and magnetism, and has the advantages of high integration, small size, and fast transmission rate.

[0003] Currently, the integration of MEMS sensing chips and ASIC microprocessor chips usually adopts a two-dimensional system-level packaging method, that is, MEMS and ASIC chips are connected by placing them side by side and wire bonding. Because of its low cost, it has become the main integration method for most MEMS devices. However, the two-dimensional packaging form occupies a large area, has long interconnection lines, and large parasitic parameters, making it difficult to conform to the development trend of high integration and miniaturization of MEMS, and severely restricting the replacement of MEMS. MEMS three-dimensional packaging can greatly reduce the packaging area through vertical stacking contact, shorten the connection length of integrated circuits, speed up the signal transmission speed, effectively reduce the parasitic effect between interconnection lines, reduce system power consumption, and greatly overcome the disadvantages of two-dimensional packaging. However, three-dimensional integration results in a higher integration density inside the system, leading to the situation where heat accumulates between chips during operation and cannot be transferred out. Continuously high heat will cause thermal stress in the package, triggering chip warping and deformation, seriously affecting the accuracy of micro-sensors and the reliability of chips. Summary of the Invention

[0004] The purpose of the present invention is to provide a three-dimensional packaging structure of a MEMS piezoelectric sensor system and a heat dissipation method thereof.

[0005] The three-dimensional packaging structure of the MEMS piezoelectric sensor system of the present invention mainly consists of a cap, a surface microstructure, a copper ring, a cylindrical array, and a horizontal extension platform, a horizontal mesh structure, a ceramic substrate, a MEMS chip, a piezoelectric thin film, a micro temperature sensor, solder balls, and an ASIC chip placed inside the cap; the ceramic substrate is provided with a central notch, and n placement grooves evenly distributed in the circumferential direction are provided on the side wall of the central notch, where n≥3; a horizontal extension platform is embedded in each placement groove; the horizontal mesh structure is welded in the central notch of the ceramic substrate and is welded to the inner ends of each horizontal extension platform; a solder ball is provided in each mesh hole of the horizontal mesh structure; the bottom of the solder ball is welded to the substrate, and the top is welded to the ASIC chip, and epoxy resin is filled around each solder ball; the ASIC chip communicates with the substrate through each solder ball; the MEMS chip is bonded to the upper surface of the ceramic substrate through a thermal conductive adhesive, and the lower surface of the MEMS chip is hermetically sealed by glass in a vacuum. A ring groove is provided on the upper surface of the MEMS chip, a piezoelectric thin film and two micro temperature sensors are provided in the ring groove, and the piezoelectric thin film covers the two micro temperature sensors; the signal line of the piezoelectric thin film passes through the silicon through hole on the MEMS chip and the glass through hole on the glass, and is connected to the buried wire in the ceramic substrate; the micro temperature sensor is located above the ASIC chip, and the signal line of the micro temperature sensor passes through the glass through hole on the glass and is connected to the buried wire in the ceramic substrate; each buried wire in the substrate is connected to the ASIC chip; the inner side wall of the cap is welded to the outer side wall of the substrate; a countersunk annular through groove is provided on the upper surface of the cap, and a transition step is formed between two groove segments with different widths of the countersunk annular through groove; the copper ring is placed on the transition step of the countersunk annular through groove and is welded to the cap; each horizontal extension platform is connected to the copper ring through a cylindrical array; the cylindrical array consists of a plurality of cylinders arranged at equal distances; the lower surface of the cylinder is welded to the horizontal extension platform, and the upper surface is welded to the lower surface of the copper ring; a surface microstructure is welded on the copper ring, and the upper surface of the surface microstructure is flush with the upper surface of the cap.

[0006] Preferably, the horizontal extension platform is in transitional fit with the placement groove.

[0007] More preferably, a step is provided at the inner end of the placement groove, and the step is 0.01-0.05 mm higher than the bottom of the placement groove.

[0008] Preferably, the surface microstructure consists of a plurality of microstructure groups arranged circumferentially along the copper ring, and each microstructure group consists of three equilateral triangle microstructure units arranged in two rows.

[0009] Preferably, the horizontal mesh structure consists of a plurality of metal strips intersecting vertically, and the sizes of the mesh holes of the horizontal mesh structure are equal.

[0010] The heat dissipation method of the three-dimensional packaging structure of the MEMS piezoelectric sensor system is as follows:

[0011] The heat in the ASIC chip area is transferred horizontally to the cap through the horizontal mesh structure and the horizontal extension platform; the cylindrical array vertically welded on the horizontal extension platform conducts the heat in the ASIC chip area upward to the copper ring, and the surface microstructure welded on the copper ring increases the convective heat transfer area on the upper surface of the cap, accelerating the convective heat transfer efficiency; among them, the micro temperature sensor adhesively bonded in the annular groove of the MEMS chip above the ASIC chip area monitors the temperature of the ASIC chip area in real time.

[0012] The beneficial effects of the present invention are as follows:

[0013] 1. The present invention buries the ASIC chip in the ceramic substrate, and uses the TSV technology to vertically stack the MEMS chip and the ASIC chip, realizing the three-dimensional integration of the MEMS chip and the ASIC chip, and utilizing the three-dimensional heat dissipation structure (surface microstructure, copper ring, horizontal mesh structure, horizontal extension platform and cylindrical array) embedded in the packaging structure space to effectively dissipate the heat of the MEMS piezoelectric sensor system.

[0014] 2. By adhesively bonding the horizontal mesh structure at the bottom of the ASIC chip, the present invention can timely evacuate the heat of the core heating area of the ASIC chip to the surrounding without affecting the electrical signal transmission, not only reducing the highest temperature of the core area, but also greatly reducing the temperature gradient inside the MEMS piezoelectric sensor system.

[0015] 3. By welding the horizontal extension platform around the horizontal mesh structure, the present invention further conducts the heat of the core area of the ASIC chip horizontally to the outer surface of the packaging structure, greatly improving the horizontal heat dissipation efficiency.

[0016] 4. On the basis of horizontal heat dissipation, by vertically welding the cylindrical array and the surface microstructure, the present invention not only realizes the heat conduction in the vertical direction, but also accelerates the air convective heat transfer efficiency on the upper surface of the MEMS piezoelectric sensor system, making full use of the three-dimensional space for heat dissipation, with good heat dissipation performance and high efficiency.

[0017] 5. All the three-dimensional heat dissipation structures of the present invention adopt copper materials with high thermal conductivity and electrical conductivity, not only having good heat dissipation performance, but also playing a good shielding role against external electromagnetic interference.

[0018] 6. By using the annular groove of the MEMS chip, the micro temperature sensor required for system temperature measurement is adhesively bonded in the annular groove, realizing the purpose of real-time monitoring of the highest temperature inside the system in a closed space and preventing chip failure caused by too high temperature. Description of the Drawings

[0019] Figure 1 is the overall structure assembly drawing of the present invention;

[0020] Figure 2 Schematic diagram of the internal structure layout of the present invention;

[0021] Figure 3 Assembly schematic diagram of the MEMS piezoelectric sensor, cylindrical array, horizontal extension platform and ceramic substrate of the present invention;

[0022] Figure 4 Spatial position schematic diagram of the horizontal network structure and solder balls in the present invention;

[0023] Figure 5 Assembly schematic diagram of the surface microstructure, copper ring, cylindrical array and horizontal extension platform in the present invention;

[0024] Figure 6 Schematic diagram of the surface microstructure in the present invention;

[0025] Figure 7 Schematic diagram of the relative positions of the horizontal network structure, horizontal extension platform and cylindrical array in the present invention. Detailed implementation manners

[0026] The present invention will be further described below with reference to the accompanying drawings.

[0027] As Figures 1 to 7As shown, the three-dimensional packaging structure of the MEMS piezoelectric sensor system mainly consists of a cap 1, a surface microstructure 2, a copper ring 3, a cylindrical array 4, and a horizontal extension platform 5, a horizontal mesh structure 6, a ceramic substrate 7, a MEMS chip 11, a piezoelectric thin film 12, a micro temperature sensor 14, solder balls 15, and an ASIC chip 17 placed inside the cap 1; the ceramic substrate 7 is provided with a central notch, and n placement grooves evenly distributed in the circumferential direction are provided on the side wall of the central notch, where n≥3; a horizontal extension platform 5 is embedded in each placement groove, and the horizontal extension platform 5 conducts heat to the cap 1; the horizontal mesh structure 6 is welded in the central notch of the ceramic substrate 7 and is welded to the inner ends of each horizontal extension platform 5; a solder ball 15 is provided in each mesh hole of the horizontal mesh structure 6; the bottom of the solder ball 15 is welded to the substrate 7, and the top is welded to the ASIC chip 17, and epoxy resin 16 is filled around each solder ball; the ASIC chip 17 communicates with the substrate 7 through each solder ball 15; the MEMS chip 11 is bonded to the upper surface of the ceramic substrate 7 through a thermal conductive adhesive 8, and the lower surface of the MEMS chip 11 is vacuum-sealed through glass 9. The upper surface of the MEMS chip 11 is provided with an annular groove, and a piezoelectric thin film 12 and two micro temperature sensors 14 are provided in the annular groove, and the piezoelectric thin film 12 covers the two micro temperature sensors 14; the MEMS chip 11 and the piezoelectric thin film 12 form a MEMS piezoelectric sensor; the signal line of the piezoelectric thin film 12 passes through the through-silicon via (TSV) 10 on the MEMS chip 11 and the through-glass via (TGV) 13 on the glass 9 and is connected to the buried wire in the ceramic substrate 7, and the buried wire in the substrate 7 is connected to the ASIC chip 17, thus realizing the communication between the MEMS piezoelectric sensor and the ASIC chip; the micro temperature sensor 14 performs real-time temperature monitoring on the high-temperature core area of the system from the ASIC chip 17, and the signal line of the micro temperature sensor 14 passes through the through-glass via on the glass 9 and is connected to the buried wire in the ceramic substrate 7, and the buried wire in the substrate 7 is connected to the ASIC chip 17; the function of the cap 1 is to seal the entire MEMS system, and the inner side wall of the cap 1 is welded to the outer side wall of the substrate 7; the upper surface of the cap 1 is provided with a countersunk annular through groove, and a transition step is formed between two groove segments with different widths of the countersunk annular through groove; the copper ring 3 is placed on the transition step of the countersunk annular through groove and is welded to the cap 1; each horizontal extension platform 5 is connected to the copper ring 3 through a cylindrical array 4; the cylindrical array 4 consists of a plurality of cylinders arranged at equal distances; the lower surface of the cylinder is welded to the horizontal extension platform 5, and the upper surface is welded to the lower surface of the copper ring 3; the surface microstructure 2 is welded on the copper ring 3, and the upper surface of the surface microstructure 2 is flush with the upper surface of the cap 1.

[0028] As a preferred embodiment, the horizontal extension platform 5 is in transitional fit with the placement groove.

[0029] More preferably, a step is provided at the inner end of the placement groove, and the step is 0.01-0.05 mm higher than the bottom of the placement groove. The side surface of the step is conducive to quickly discharging the heat of the ASIC chip 17.

[0030] As a preferred embodiment, as Figure 6 shown, the surface microstructure 2 is composed of a plurality of microstructure groups arranged circumferentially along the copper ring 3, and each microstructure group is composed of three equilateral triangle microstructure units arranged in two rows, thereby increasing the convective heat transfer area between the outer surface of the packaging structure and the air.

[0031] As a preferred embodiment, the horizontal mesh structure 6 is composed of a plurality of metal strips intersecting vertically, and the sizes of the meshes of the horizontal mesh structure 6 are equal.

[0032] The heat dissipation method of the three-dimensional packaging structure of the MEMS piezoelectric sensor system is as follows:

[0033] First, based on the principle of heat conduction, the present invention bonds the horizontal mesh structure in the ASIC chip area with the highest temperature during the operation of the MEMS piezoelectric sensor system, and welds the horizontal extension platform around the horizontal mesh structure, so that the heat is further transferred horizontally from the high-temperature ASIC chip area to the cap 1. Secondly, on the horizontal extension platform, a cylindrical array is vertically welded, so that the heat is conducted from the high-temperature ASIC chip area below to the low-temperature area above. In addition, a copper ring is welded on the upper surface of the cylindrical array, and a surface microstructure is welded on the copper ring to increase the convective heat transfer area on the upper surface of the cap and accelerate the convective heat transfer efficiency. Finally, using the annular groove of the MEMS chip, a micro temperature sensor is bonded in the high-temperature ASIC chip area to monitor the temperature of the ASIC chip area in real time. It can be seen that the three-dimensional packaging structure of the MEMS piezoelectric sensor system of the present invention can effectively dissipate heat and monitor the internal area with the highest temperature in real time.

Claims

1. The three-dimensional packaging structure of the MEMS piezoelectric sensor system includes a cap and a ceramic substrate, a MEMS chip, a piezoelectric thin film, and an ASIC chip placed inside the cap, and is characterized in that: It also includes a surface microstructure, a copper ring, a cylindrical array, as well as a horizontally extended platform, a horizontal mesh structure, a micro temperature sensor, and solder balls placed inside the cap; the ceramic substrate is provided with a central notch, and n placement grooves evenly distributed in the circumferential direction are provided on the side wall of the central notch, where n≥3; a horizontally extended platform is embedded in each placement groove; the horizontal mesh structure is welded inside the central notch of the ceramic substrate and is welded to the inner ends of each horizontally extended platform; a solder ball is provided in each mesh hole of the horizontal mesh structure; the bottom of the solder ball is welded to the substrate, and the top is welded to the ASIC chip, and epoxy resin is filled around each solder ball; the ASIC chip communicates with the substrate through each solder ball; the MEMS chip is bonded to the upper surface of the ceramic substrate through a heat-conducting adhesive, and the lower surface of the MEMS chip is sealed by glass vacuum; a ring groove is provided on the upper surface of the MEMS chip, a piezoelectric film and two micro temperature sensors are provided in the ring groove, and the piezoelectric film covers the two micro temperature sensors; the signal line of the piezoelectric film passes through the silicon through-hole on the MEMS chip and the glass through-hole on the glass, and is connected to the buried wire inside the ceramic substrate; the micro temperature sensor is located above the ASIC chip, and the signal line of the micro temperature sensor passes through the glass through-hole on the glass and is connected to the buried wire inside the ceramic substrate; each buried wire inside the substrate is connected to the ASIC chip; the inner side wall of the cap is welded to the outer side wall of the substrate; a countersunk annular through groove is provided on the upper surface of the cap, and a transition step is formed between two groove sections with different widths of the countersunk annular through groove; the copper ring is placed on the transition step of the countersunk annular through groove and is welded to the cap; each horizontally extended platform is connected to the copper ring through a cylindrical array; the cylindrical array is composed of a plurality of cylinders arranged at equal intervals; the lower surface of the cylinder is welded to the horizontally extended platform, and the upper surface is welded to the lower surface of the copper ring; a surface microstructure is welded on the copper ring, and the upper surface of the surface microstructure is flush with the upper surface of the cap.

2. The three-dimensional packaging structure of the MEMS piezoelectric sensor system according to claim 1, characterized in that: The horizontally extended platform is in transitional fit with the placement groove.

3. The three-dimensional packaging structure of the MEMS piezoelectric sensor system according to claim 2, wherein: A step is provided at the inner end of the placement groove, and the step is 0.01-0.05 mm higher than the bottom of the placement groove.

4. The three-dimensional packaging structure of the MEMS piezoelectric sensor system according to claim 1, wherein: The surface microstructure is composed of a plurality of microstructure groups arranged along the circumferential direction of the copper ring, and each microstructure group is composed of three equilateral triangle microstructure units arranged in two rows.

5. The three-dimensional packaging structure of the MEMS piezoelectric sensor system according to claim 1, characterized in that: The horizontal mesh structure is composed of a plurality of metal strips intersecting vertically, and the sizes of the mesh holes of the horizontal mesh structure are equal.

6. The heat dissipation method of the three-dimensional packaging structure of the MEMS piezoelectric sensor system according to any one of claims 1 to 5, characterized in that: The method is as follows: The heat in the ASIC chip area is horizontally transferred to the cap through the horizontal mesh structure and the horizontally extended platform; the cylindrical array vertically welded on the horizontally extended platform conducts the heat in the ASIC chip area upward to the copper ring, and the surface microstructure welded on the copper ring increases the convective heat transfer area on the upper surface of the cap and speeds up the convective heat transfer efficiency; among them, the micro temperature sensor bonded above the ASIC chip area in the ring groove of the MEMS chip monitors the temperature of the ASIC chip area in real time.

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