Piezoelectric vibration sensor structure, preparation method, packaging structure and chip

Abstract

The invention discloses a piezoelectric vibration sensor structure, a preparation method, a packaging structure and a chip, and belongs to the technical field of vibration sensors. The piezoelectric vibration sensor structure comprises a base, a supporting beam structure, a piezoelectric film and a mass block A; the mass block A is connected with the supporting beam structure, the supporting beam structure is fixed to the base, the piezoelectric film is attached to the surface of the supporting beam structure, and the piezoelectric film is connected with an electrode; the mass block A comprises a part of structure of the base, and the part of structure is used for sensing vibration acceleration; under the action of vibration acceleration, inertia force of the mass block drives the supporting beam structure to deform, stress acts on the piezoelectric film, the piezoelectric film generates charges at the electrodes to form potential, and a sensing signal is obtained through a reading circuit. The problems that a vibration sensing chip structure is low in sensitivity, large in size and the like are solved.

Description

Technical Field

[0001] The present invention relates to the field of vibration sensors, and more specifically, to a piezoelectric vibration sensor structure, a preparation method, a packaging structure and a chip. Background Art

[0002] Vibration monitoring and other applications are driving increasing demand for high-performance vibration sensors, while also placing increasing demands on size, power consumption, and cost. Microelectromechanical system (MEMS) accelerometers are primarily categorized into piezoelectric, piezoresistive, and capacitive types, depending on their operating principles. In contrast, piezoelectric vibration sensors are gaining increasing attention due to their superior radiation resistance, long-term stability, and dynamic testing characteristics. Furthermore, piezoelectric vibration sensors are passive devices that do not require an applied driving voltage. Their performance depends primarily on material properties and device structure, enabling simple sensing capabilities.

[0003] Existing vibration sensors are basically based on bulk PZT ceramics for sensitivity. They are large in size and assembled through assembly processes. They consume a lot of power and are difficult to adapt to environments with very small and compact structures, such as satellites, deep space exploration and other applications. Existing sensors based on MEMS process technology have complex structures, low sensitivity, and large responses on non-sensitive axes. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a piezoelectric vibration sensor structure, preparation method, packaging structure and chip, which solve the problems of low sensitivity and large size of the micro-vibration sensor chip structure.

[0005] The object of the present invention is achieved through the following solutions: A piezoelectric vibration sensor structure is characterized in that it includes: a base, a support beam structure, a piezoelectric film and a mass block A; the mass block A is connected to the support beam structure, the support beam structure is fixed on the base, the piezoelectric film is adhered to the surface of the support beam structure, and the piezoelectric film is connected to an electrode; the mass block A includes a portion of the base structure, which is used to sense vibration acceleration; under the action of vibration acceleration, the inertial force of the mass block A drives the support beam structure to deform, and stress acts on the piezoelectric film, the piezoelectric film generates an electric charge on the electrode to form an electric potential, and a sensing signal is obtained through a readout circuit.

[0006] Furthermore, the base includes a top silicon layer, a buried oxide layer and a bottom silicon layer from top to bottom, and a part of the bottom silicon layer is used as a part of the mass block for sensitive vibration acceleration.

[0007] Furthermore, the support beam structure includes an annular support beam structure.

[0008] Furthermore, after the annular support beam structure is excavated, a hole-carrying annular support beam structure is formed; the hole-carrying annular support beam structure is connected to the anchored structural area to support the mass block A, and the mass block A senses the vibration acceleration in the z direction.

[0009] Furthermore, when the supporting beam structure is annular, the electrodes of the piezoelectric film are designed to be divided into inner and outer circles, and the phase difference of the sensing signals corresponding to the partitioned electrodes is 180 degrees.

[0010] Furthermore, the shape of the hole includes any one of a fan shape, a square shape and a circle shape.

[0011] Furthermore, the mass block A is connected to the support beam structure, specifically including: the support beam structure is embedded in the mass block A.

[0012] Furthermore, when the support beam structure is embedded in the mass block A, the number of the support beam structures is at least three.

[0013] Furthermore, the shape of the mass block A includes a circle; the symmetry of the circular mass block is utilized to make the design of the support beam structure more flexible, and the required sensitivity and bandwidth can be freely adjusted according to the actual application scenario.

[0014] Furthermore, a mass block B is provided on the support beam structure to concentrate the stress of the beam structure. When the inertial force acts, more charges are generated and distributed on the electrodes due to the piezoelectric effect.

[0015] Furthermore, the piezoelectric vibration sensor structure is used as a unit, and an array structure is formed based on the unit.

[0016] Furthermore, when the chip center structure is used as the fixed inner anchor point, the mass block A is a side structure of the fixed inner anchor point.

[0017] Furthermore, it also includes a symmetrical structure; the anchor part and the mass block A part are bonded together to form a symmetrical structure; when the inertial force in the plane direction is applied to the symmetrical structure, the mass block A will not twist due to the symmetrical distribution of the support beam structure and the mass block A, thereby not causing deformation to the sensitive beam.

[0018] A method for preparing a piezoelectric vibration sensor structure, wherein the piezoelectric vibration sensor structure as described above is prepared based on an SOI process according to the following steps: First, make the upper electrode of the piezoelectric film; Then, a piezoelectric film is fabricated; Then, the piezoelectric film bottom electrode is made; Then, make the top silicon of the base; Finally, the base silicon is made.

[0019] Furthermore, the thickness of the piezoelectric film is designed to be in the range of 0.1 μm to 20 μm.

[0020] Furthermore, the material thickness of the top silicon layer is in the range of 1 μm to 150 μm.

[0021] Furthermore, the thickness of the bottom silicon is in the range of 300 μm to 600 μm.

[0022] A vibration sensor chip comprises the piezoelectric vibration sensor structure as described in any one of the above items.

[0023] A piezoelectric vibration sensor packaging structure, when the chip is surrounded as an anchoring area, the vibration sensor chip as described above is mounted on a base structure, and a free space is reserved in the middle of the base structure, so that the mass block has space to vibrate under vibration conditions, and at the same time limits the mass block to prevent failure during high impact; the base structure is mounted on the bottom of the packaging tube shell, and the package leads are led out to the tube shell from the chip anchoring area pads.

[0024] A piezoelectric vibration sensor packaging structure, when the middle area of ​​the chip serves as the anchoring area, the vibration sensor chip as described above is mounted on a base structure, the middle area is fixed, the base structure is provided with an air-avoiding area, and the vibration sensor chip is suspended on all sides. At this time, the packaging leads are led out from the middle anchoring area to the tube shell.

[0025] The beneficial effects of the present invention include: (1) The structural form provided by the present invention has advantages in size and can be further reduced. Due to the further reduction in size, its production cost is lower. It is particularly suitable for application environments with very compact small structures, such as satellites and deep space exploration. It achieves a simple structure while achieving higher vibration sensitivity and lower sensitivity to non-sensitive axes, making it more adaptable. In addition, the present invention proposes a highly sensitive sensitive structure design solution, which solves the problem of low sensitivity of the micro-vibration sensor chip structure. Specifically, in the embodiment, a circular mass block is used. Since the circular mass block is highly symmetrical, the structural design of the beam is more flexible, and the required sensitivity and bandwidth can be freely adjusted according to the actual application scenario. The minimum supporting beam structure can be three; the beam structure can be embedded in the mass block, shortening the size of the beam structure in the plane, reducing the chip size area, and reducing the chip cost; the array design of the sensitive structure improves the sensitivity of the device and improves the signal-to-noise ratio of the sensor; the design of the anchor point inside the chip reduces the sensitivity of the chip to packaging stress; the design of the internal anchor point, since the outer mass block is larger and heavier, under the same bandwidth, the size of the chip can be further reduced compared to the external anchor point; the design of the mass block on the beam has more concentrated stress and higher sensitivity; the use of two-piece symmetrical structure can reduce the response to vibration acceleration of non-sensitive axes.

[0026] (2) Based on the improvement of the piezoelectric sensor structure, the packaging structure was further improved. The air avoidance and position limiting of the movable structure were achieved through the air avoidance design of the base structure and the chip mounting.

[0027] (3) The present invention proposes a MEMS fabrication process based on piezoelectric film, which adopts MEMS wafer-level fabrication to meet the needs of batch fabrication and achieve low-cost and high-consistency batch fabrication. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 1 is a cross-sectional view of the structure of the piezoelectric vibration sensor of the present invention; Figure 2 Schematic diagram of deformation under out-of-plane vibration acceleration; Figure 3 Design diagram for electrode partitioning; Figure 4 Schematic diagram of the hole for the ring beam; Figure 5 It is a schematic diagram of a three-support beam structure; Figure 6 This is the electrode distribution diagram of the three-support beam structure; Figure 7 Schematic diagram of the design scheme with a mass block on the beam; (a) is a top view, (b) is a back perspective view, and (c) is a Z-direction inertial force stress simulation diagram; Figure 8 This is an example diagram of a 2*2 array structure; Figure 9a 3 is a schematic diagram of the first embodiment in which the middle portion is used as a fixed anchor point; Figure 9b 3 is a schematic diagram of the second embodiment in which the middle portion is used as a fixed anchor point; Figure 9c 3 is a schematic diagram of embodiment 3 in which the middle is used as a fixed anchor point; Figure 10 A schematic diagram of a symmetrical structure with two pieces; Figure 11 This is the process flow chart for PZT SOI preparation; Figure 12 It is a structural diagram of packaging example 1; Figure 13 This is a structural diagram of packaging example 2; In the figure, 10-piezoelectric film, 101-upper electrode of piezoelectric film, 102-lower electrode of piezoelectric film, 20-top silicon layer, 201-buried oxide layer, 202-bottom silicon, 203-partial bottom silicon, 1011-A readout electrode of sensing signal, 1012-B readout electrode of sensing signal, 1013-lower electrode of piezoelectric film of annular support beam structure, 30-mass block A, 31-support beam structure, 32-anchored structural area, 33-hole, 1011A-electrode 1, 1012 A-electrode two, 1012B-electrode three, 1011B-electrode four, 1011C-electrode five, 1012C-electrode six, 204A-mass block one, 204B-mass block two, 204C-mass block three, 2021-anchor part, 2031-mass block part, 1011-electrode A, 1012-electrode B, 40-base structure, 41-air avoidance area, 50-tube shell, 35-package leads, 2021-anchor part, 2031-mass block part. DETAILED DESCRIPTION

[0030] All features disclosed in all embodiments in this specification, or steps in all methods or processes implicitly disclosed, except for mutually exclusive features and / or steps, can be combined and / or expanded or replaced in any manner.

[0031] Generally speaking, the mechanical reception portion of a piezoelectric vibration sensor is based on the principle of inertial acceleration, while the electromechanical portion utilizes the direct piezoelectric effect of a piezoelectric crystal. When subjected to an inertial force in a specific direction or when deformed, electric charges are generated on the crystal faces or polarization planes. This conversion of mechanical energy (force, deformation) into electrical energy (charge, electric field) is known as the direct piezoelectric effect.

[0032] The inventors of the present invention believe that, in vibration measurement, since the force exerted on the piezoelectric crystal is the inertial force of the inertial mass block, the number of charges generated is proportional to the magnitude of the acceleration, so the piezoelectric sensor is essentially an acceleration sensor. Therefore, as the first aspect of the present invention, in one embodiment, a technical solution for improving the structure of a piezoelectric vibration sensor is provided. In the inventive concept, the piezoelectric effect of the piezoelectric film is utilized. Under the action of vibration acceleration, the mass block is subjected to inertial force, causing deformation of the support beam and generating stress on the piezoelectric film. Since the stress acts on the piezoelectric film, the upper and lower electrodes of the piezoelectric film generate charges to form an electric potential. The sensing signal can be obtained through the readout circuit to obtain the value of the vibration acceleration. Specifically, the cross-section of the sensor structure is as follows: Figure 1As shown, serial number 101 is the upper electrode of the piezoelectric film, serial number 10 is the piezoelectric film, the thickness of the piezoelectric film 10 is designed to be in the range of 0.1~20μm, and the material of the piezoelectric film 10 includes any one of aluminum nitride, lithium niobate, lead zirconate titanate and lithium tantalate; serial number 102 is the lower electrode of the piezoelectric film, serial number 20 is the top silicon layer, which can be designed as the top silicon layer of the SOI structure, and the thickness of its structural layer material can be between 1~150μm; serial number 201 is the buried oxide layer, which can be designed as the buried oxide layer of SOI; serial number 202 is the bottom silicon, which can be designed as the SOI bottom silicon, and its thickness range is designed to be in the range of 300~600μm. It is noted that in the concept of the present invention, a part of the bottom silicon 202 (i.e., serial number 203) is used as part of the mass block for sensitive vibration acceleration. Under the action of vibration acceleration, the inertial force of the mass block drives the support beam structure to deform, as shown in FIG. Figure 2 As shown in Figure 2, due to the stress acting on the piezoelectric film, the piezoelectric film generates charges on the upper and lower electrodes to form an electric potential.

[0033] When the supporting beam structure is annular, such as Figure 3 As shown, the following electrode partition design is made for the annular support beam structure: serial number 1011 is the readout electrode of the A sensor signal, serial number 1012 is the readout electrode of the B sensor signal, and the AB phase difference is 180 degrees. After the two groups of signals are differentiated, the common-mode interference signal can be suppressed, and the amplitude of the signal is doubled, which can improve the signal-to-noise ratio of the measurement signal. Serial number 1013 is the lower electrode of the piezoelectric film of the annular support beam structure.

[0034] In another embodiment, in order to meet the needs of some specific applications, higher sensitivity is required. Figure 4 As shown, the present invention further improves the annular support beam structure of the above embodiment by drilling a hole in the annular beam structure, with hole 33 being the hole. This drilling forms a perforated support beam structure 31. Perforated support beam structure 31 is connected to an anchoring structural region 32, supporting mass A 30, which senses z-axis vibration acceleration. Of particular note, hole 33 can be shaped like a sector, square, or circle. This improved design provides a novel sensing structure with higher sensitivity than conventional technologies, addressing the low sensitivity of micro-vibration sensor chip structures.

[0035] In another embodiment, it is also necessary to consider the sensitivity and chip size issues. Figure 5 As shown, the following design can be further performed: when the structural area 32 anchored around the chip is fixed, the middle movable area is the mass block, the support beam structure 31 is embedded in the middle mass block A 30, and the number of support beam structures 31 is reduced to a minimum, specifically 3. In this embodiment, the electrodes of the 3 support beam structures 31 are distributed as follows: Figure 6As shown, serial number 1011A corresponds to electrode 1, 1012A corresponds to electrode 2, 1012B corresponds to electrode 3, 1011B corresponds to electrode 4, 1011C corresponds to electrode 5, and 1012C corresponds to electrode 6. The above improvements can improve sensitivity while meeting chip size requirements.

[0036] In another embodiment, the sensing sensitivity of the device can be further improved to meet higher requirements of applications. Figure 7 As shown, a mass block B is further designed on the support beam structure. In this embodiment, the mass blocks B specifically include mass block 1 204A, mass block 204B, and mass block 3 204C. All of them are used to concentrate the stress of the beam. When the inertial force acts, more charge is generated and distributed on the upper and lower electrodes due to the piezoelectric effect. For example, the corresponding sensing electrodes 1011A and 1012A are distributed on both sides of the mass block 1 204A. It is important to note that this embodiment only illustrates this design method. The design scheme of this embodiment can also be applied to support structures with 4, 6, 7, 8 beams, etc., as well as annular beam structures.

[0037] In another embodiment, in order to further improve the sensing sensitivity of the device, the following is designed on the single chip: Figure 8 The array structure shown is composed of four units. It should be noted that this example is merely illustrative of the array. Arrays of varying sizes, such as 3x3 or 2x3, can be formed using this concept. Furthermore, the vibration-sensitive chip structure of the array can be other chip structures. This results in higher vibration sensitivity per unit chip area and a higher signal-to-noise ratio.

[0038] In yet another embodiment, Figure 9a 、 Figure 9b and Figure 9c As shown, to further reduce the chip area, using chip 301 as a fixed anchor and the peripheral structure 302 as a mass block can also achieve vibration acceleration sensing. The chip can be designed in either a square or circular shape. Compared to designs with external anchors, due to the larger and heavier outer mass block, the chip size can be further reduced compared to sensors of the same specifications with external anchors, given the same bandwidth (similar first-order modal frequency).

[0039] In another embodiment, in order to further reduce the response of the sensitive structure to the inertial force in the non-sensitive axis direction, the Figure 10The structure shown utilizes two bonded pieces to form a symmetrical structure, bonding the anchor portion 2021 to the mass portion 2031. This structure, when subjected to inertial forces in the in-plane direction, prevents the mass from twisting due to the symmetrical distribution of the support beam and the mass, and thus does not cause deformation to the sensitive beam. Consequently, the symmetrical structure is insensitive to other axial directions. In terms of electrode design, number 1011 is electrode A, and number 1012 is electrode B. It is important to note that this two-piece bonded symmetrical design is suitable for structures such as ring beams, multi-beams, and triple beams.

[0040] As a second aspect of the present invention, a process for preparing the above-mentioned piezoelectric sensor structure is provided, comprising the following steps: The process flow based on PZT SOI is as follows Figure 11 As shown, first, the upper electrode 101 of the piezoelectric film is patterned by photolithography using a PZT SOI with an upper electrode, then the piezoelectric film 10 is etched or corroded, and then the lower electrode 102 of the piezoelectric film is etched, followed by etching the SOI top silicon, and finally etching the bottom silicon 202 to complete the release and the preparation of the mass block 203. It is particularly noted that this embodiment only uses the PZT piezoelectric film as an example, and other piezoelectric films are similar. Figure 10 The symmetrical structure shown is manufactured by adopting a double-chip structure based on the above-mentioned single chip, and bonding the bottom silicon to the bottom silicon.

[0041] As a third aspect of the present invention, a packaging structure of the above-mentioned piezoelectric sensor structure is provided. In one embodiment of the packaging structure, as Figure 12 As shown, the chip is mounted on a base structure 40, with the surrounding area serving as an anchoring area. A reserved airspace 41 in the center of the base structure provides space for the mass to vibrate during vibrations. This also serves as a position limiter to prevent failure during high impacts. The base structure 40 is mounted on the bottom of the package 50, with package leads 35 extending from the chip anchoring pads to the bottom of the package. The base structure can be made of ceramic, silicon, metal, or other materials.

[0042] In another embodiment of the package structure, Figure 13 As shown, for applications requiring high package stress, such as environments with harsh temperature conditions, where lower package stress is desired, the central region of the vibration sensor chip serves as an anchoring area. When the vibration sensor chip is mounted on the base structure 40, the central region is fixed. Due to the airtight area 41 of the base, the vibration chip is suspended on all sides. At this time, the package leads 35 are led from the central anchoring region to the tube case 50.

[0043] As a fourth aspect of the present invention, a vibration sensor chip or any device using the chip is provided, wherein the chip includes the piezoelectric vibration sensor structure as described in any one of the above items.

[0044] The above description is merely the technical principles and preferred embodiments used in the present invention. Those skilled in the art will appreciate that the present invention is not limited to the specific embodiments described herein. It is obvious that various changes, adjustments, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the principles and concepts of the present invention, it may also include more other equivalent embodiments, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A piezoelectric vibration sensor structure, characterized in that: include: A base, a support beam structure, a piezoelectric film and a mass block A; the mass block A is connected to the support beam structure, the support beam structure is fixed on the base, the piezoelectric film is adhered to the surface of the support beam structure, and the piezoelectric film is connected to an electrode; the mass block A includes a part of the base structure, which is used to sense vibration acceleration; under the action of vibration acceleration, the inertial force of the mass block A drives the support beam structure to deform, and stress acts on the piezoelectric film, the piezoelectric film generates charges on the electrodes to form an electric potential, and a sensing signal is obtained through a readout circuit.

2. The piezoelectric vibration sensor structure according to claim 1, characterized in that: The base comprises a top silicon layer, a buried oxide layer and a bottom silicon layer from top to bottom, and a part of the bottom silicon layer is used as a part of a mass block for sensitive vibration acceleration.

3. The piezoelectric vibration sensor structure according to claim 1, characterized in that: The support beam structure includes an annular support beam structure.

4. The piezoelectric vibration sensor structure according to claim 3, characterized in that: After the annular support beam structure is subjected to the hole-digging operation, an annular support beam structure with holes is formed; the annular support beam structure with holes is connected to the anchored structural area to support the mass block A, and the mass block A senses the vibration acceleration in the z direction.

5. The piezoelectric vibration sensor structure according to claim 3, characterized in that: When the supporting beam structure is annular, the electrodes of the piezoelectric film are divided into inner and outer circles, and the phase difference of the sensing signals corresponding to the partitioned electrodes is 180 degrees.

6. The piezoelectric vibration sensor structure according to claim 4, characterized in that: The shape of the hole includes any one of a sector shape, a square shape and a circle shape.

7. The piezoelectric vibration sensor structure according to claim 1, characterized in that: The mass block A is connected to the support beam structure, which specifically includes: the support beam structure is embedded in the mass block A.

8. The piezoelectric vibration sensor structure according to claim 7, characterized in that: When the support beam structure is embedded in the mass block A, the number of the support beam structures is at least three.

9. The piezoelectric vibration sensor structure according to claim 8, characterized in that: The shape of the mass block A includes a circle; the symmetry of the circular mass block is utilized to make the design of the support beam structure more flexible, and the required sensitivity and bandwidth can be freely adjusted according to the actual application scenario.

10. The piezoelectric vibration sensor structure according to claim 1, characterized in that: The support beam structure is also provided with a mass block B for concentrating the stress of the beam structure. When the inertial force acts, more charges are generated and distributed on the electrodes due to the piezoelectric effect.

11. The piezoelectric vibration sensor structure according to claim 1, characterized in that: The piezoelectric vibration sensor structure is used as a unit, and an array structure is formed based on the unit.

12. The piezoelectric vibration sensor structure according to claim 1, characterized in that: When the chip center structure is used as the fixed inner anchor point, the mass block A is a side structure of the fixed inner anchor point.

13. The piezoelectric vibration sensor structure according to any one of claims 1, 3 and 8, characterized in that: It also includes a symmetrical structure; the anchor part and the mass block A part are bonded together to form a symmetrical structure; when the inertial force in the plane direction is applied to the symmetrical structure, the mass block A is not twisted by utilizing the symmetrical distribution of the support beam structure and the mass block A, thereby not causing deformation to the sensitive beam.

14. A method for preparing a piezoelectric vibration sensor structure, characterized in that: The piezoelectric vibration sensor structure according to claim 1 is manufactured according to the following steps based on SOI technology: First, make the upper electrode of the piezoelectric film; Then, a piezoelectric film is fabricated; Then, the piezoelectric film bottom electrode is made; Then, make the top silicon of the base; Finally, the base silicon is made.

15. The method for preparing a piezoelectric vibration sensor structure according to claim 14, wherein: The thickness of the piezoelectric film is designed to be in the range of 0.1 μm to 20 μm.

16. The method for preparing a piezoelectric vibration sensor structure according to claim 14, wherein: The material thickness of the top silicon layer is in the range of 1 μm to 150 μm.

17. The method for preparing a piezoelectric vibration sensor structure according to claim 14, wherein: The thickness of the bottom silicon is in the range of 300 μm to 600 μm.

18. A vibration sensor chip, characterized in that: The piezoelectric vibration sensor structure comprises the piezoelectric vibration sensor structure according to any one of claims 1 to 13.

19. A piezoelectric vibration sensor packaging structure, characterized in that: When the area around the chip serves as the anchoring area, the vibration sensor chip described in claim 18 is installed on the base structure, and an air-avoidance area is reserved in the middle of the base structure so that the mass block has space to vibrate under vibration conditions, and at the same time limits the mass block to prevent failure during high impact; the base structure is installed at the bottom of the package tube shell, and the package leads are led out to the tube shell from the chip anchoring area pads.

20. A piezoelectric vibration sensor packaging structure, characterized in that: When the middle area of ​​the chip serves as the anchoring area, the vibration sensor chip described in claim 18 is installed on the base structure, the middle area is fixed, the base structure is provided with an air avoidance area, and the vibration sensor chip is suspended on all sides. At this time, the package leads are led out from the middle anchoring area to the tube shell.

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