Pressure sensor and battery module

Abstract

A pressure sensor and a battery module, the pressure sensor comprises a flexible circuit board, a first protective film and a second protective film, at least one MEMS chip is electrically connected on the flexible circuit board, the first protective film is connected to the upper surface of the flexible circuit board, the second protective film is connected to the lower surface of the flexible circuit board, at least one window exposing the MEMS chip is arranged on the first protective film, and a force transmission layer covering the MEMS chip is filled in the window. The pressure sensor can effectively protect the MEMS chip, and the overall thickness of the sensor is reduced, so that the pressure sensor has the characteristics of rigid-flex combination.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a pressure sensor and battery module. Background Technology

[0002] With the implementation of new energy vehicle regulations, battery safety has become a primary concern for new energy vehicle manufacturers. Monitoring battery expansion force can effectively predict battery life and health. However, in pursuit of maximum space utilization, the space for mounting pressure sensor arrays between battery packs or cells is extremely limited. The sensor thickness needs to be controlled within 0.5mm, and the local pressure generated during battery pack charging and discharging can even reach tens of thousands of Newtons. Therefore, the array sensor also needs to have a certain degree of flexibility to adapt to deformation. Pressure sensor arrays made of organic pressure-sensitive materials are naturally thin and flexible, but the creep characteristics of organic pressure-sensitive materials lead to inherent long-term pressure drift and temperature drift. Sensors using silicon-based MEMS can effectively avoid pressure drift problems. However, MEMS themselves are fragile and require thick and rigid outer shells for protection, making effective integration into current battery packs impossible. Summary of the Invention

[0003] In view of this, the present invention provides a pressure sensor that can effectively protect MEMS chips and reduce the overall thickness of the sensor, giving it a combination of rigidity and flexibility.

[0004] A pressure sensor includes a flexible circuit board, a first protective film, and a second protective film. At least one MEMS chip is electrically connected to the flexible circuit board. The first protective film is connected to the upper surface of the flexible circuit board, and the second protective film is connected to the lower surface of the flexible circuit board. The first protective film has at least one window exposing the MEMS chip, and the window is filled with a force-conducting layer covering the MEMS chip.

[0005] Optionally, the force-conducting layer is elastic.

[0006] Optionally, the force-conducting layer is positioned away from the upper surface of the flexible circuit board and is higher than the surface of the first protective film.

[0007] Optionally, the upper surface of the force-conducting layer is a plane, and the upper surface is parallel to the surface of the first protective film.

[0008] Optionally, the vertical distance between the upper end face and the surface of the first protective film is 20μm to 100μm.

[0009] Optionally, the thickness of the first protective film is greater than the thickness of the second protective film.

[0010] Optionally, the thickness of the first protective film is 100μm to 200μm; the thickness of the second protective film is 50μm to 100μm.

[0011] Optionally, the thickness of the flexible circuit board is 50μm to 100μm.

[0012] Optionally, the thickness of the MEMS chip is 50μm to 150μm.

[0013] Optionally, the MEMS chip is fixed to the surface of the flexible circuit board by adhesive.

[0014] Optionally, the MEMS chip is connected to two first pads of the flexible circuit board via two power leads, and the MEMS chip is connected to two second pads of the flexible circuit board via two differential voltage output leads.

[0015] Optionally, the flexible circuit board includes a chip mounting area and a plug-in area that are interconnected. The MEMS chip is connected to the chip mounting area, the chip mounting area is connected between the first protective film and the second protective film, and a plug-in connector is formed at the end of the plug-in area away from the chip mounting area.

[0016] Optionally, the MEMS chip is equipped with a temperature sensor, which is connected to the flexible circuit board via a temperature output lead.

[0017] Optionally, the flexible circuit board is electrically connected to a plurality of MEMS chips arranged in a matrix, and the first protective film is provided with a plurality of windows arranged in a matrix, each MEMS chip being configured in a one-to-one correspondence with each window, and each window being provided with a force conduction layer.

[0018] This application also relates to a battery module, including a housing and a plurality of battery packs and the aforementioned pressure sensor installed in the housing, wherein at least one of the pressure sensors is provided between two adjacent battery packs, and the pressure sensor is used to detect the expansion force of the battery pack.

[0019] The pressure sensor of this invention utilizes a first protective film and a second protective film to sandwich a flexible circuit board between them. A window exposing the MEMS chip is created on the first protective film, and a force-conducting layer fills the window and protects the MEMS chip. This design effectively protects the MEMS chip while reducing the overall thickness of the sensor, giving it a rigid-flexible combination. It can be effectively integrated into battery packs and detect expansion forces in real time. The MEMS chip in this application is a piezoresistive silicon-based chip. Based on the advantages of mature silicon-based MEMS chip technology, low manufacturing cost, and high reliability, it is suitable for automotive-grade applications. Attached Figure Description

[0020] Figure 1 This is a front view structural schematic diagram of the pressure sensor of this application.

[0021] Figure 2 This is a cross-sectional structural schematic diagram of the pressure sensor of this application.

[0022] Figures 3 to 6 This is a flowchart illustrating the manufacturing process of the pressure sensor described in this application.

[0023] Figure 7 This is a front view structural schematic diagram of the pressure sensor according to the second embodiment of this application. Detailed Implementation

[0024] The following specific embodiments illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification.

[0025] In the following description, reference is made to the accompanying drawings, which illustrate several embodiments of the present application. It should be understood that other embodiments may also be used, and changes in mechanical composition, structure, electrical and operational aspects may be made without departing from the spirit and scope of the present application. The following detailed description should not be considered limiting, and the terminology used herein is for describing particular embodiments only and is not intended to limit the present application.

[0026] Although the terms first, second, etc., are used in some instances to describe various elements herein, these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

[0027] Furthermore, as used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context indicates otherwise. It should be further understood that the terms “comprising,” “including,” indicate the presence of a feature, step, operation, element, component, item, kind, and / or group, but do not exclude the presence, occurrence, or addition of one or more other features, steps, operations, elements, components, items, kinds, and / or groups. The terms “or” and “and / or” as used herein are interpreted as inclusive, or mean any one or any combination thereof. Thus, “A, B, or C” or “A, B, and / or C” means “any one of: A; B; C; A and B; A and C; B and C; A, B, and C.” Exceptions to this definition arise only when combinations of elements, functions, steps, or operations are inherently mutually exclusive in some way.

[0028] First Embodiment Figure 1 This is a front view structural diagram of the pressure sensor of this application. Figure 2 This is a cross-sectional structural schematic diagram of the pressure sensor of this application, as shown below. Figure 1 and Figure 2 As shown, the pressure sensor includes a flexible circuit board 11 (FPC), a first protective film 12, and a second protective film 13. At least one MEMS chip 14 is electrically connected to the flexible circuit board 11. The first protective film 12 is connected to the upper surface of the flexible circuit board 11, and the second protective film 13 is connected to the lower surface of the flexible circuit board 11. The first protective film 12 has at least one window 101 exposing the MEMS chip 14, and the window 101 is filled with a force-conducting layer 15 covering the MEMS chip 14. In this embodiment, the force-conducting layer 15 is used to conduct expansion force to the MEMS chip 14. The expansion force forces the MEMS chip 14 to output a deformation signal, thereby realizing the pressure detection function.

[0029] The pressure sensor of this application utilizes a first protective film 12 and a second protective film 13 to sandwich a flexible circuit board 11 between them. A window 101 is opened on the first protective film 12 to expose the MEMS chip 14, and a force-conducting layer 15 is used to fill the window 101 and protect the MEMS chip 14. This design effectively protects the MEMS chip 14 while reducing the overall thickness of the sensor, giving it a combination of rigidity and flexibility. It can be effectively integrated into the battery pack and detect expansion force in real time. The MEMS chip 14 of this application is a piezoresistive silicon-based chip. Based on the advantages of mature silicon-based MEMS chip technology, low manufacturing cost, and high reliability, it is suitable for automotive-grade applications.

[0030] Optionally, the flexible circuit board 11 may be a multilayer structure for wiring of the MEMS chip 14.

[0031] Optionally, the force-conducting layer 15 is elastic. In this embodiment, the material of the force-conducting layer 15 is one of silicone, silicone rubber, epoxy resin, and polyurethane, but is not limited thereto.

[0032] Optionally, the first protective film 12 is located on the front side of the flexible circuit board 11, used for flattening the lower surface of the device, and also serves as support and mechanical protection; the second protective film 13 is located on the back side of the flexible circuit board 11, used for flattening the upper surface of the device, and also serves as support and mechanical protection. In this embodiment, the first protective film 12 and the second protective film 13 are rigid films, and the first protective film 12 and the second protective film 13 will not deform under pressure.

[0033] Optionally, the materials of the first protective film 12 and / or the second protective film 13 may be selected from materials resistant to electrolyte corrosion such as PI, PET, and aluminum film, but are not limited thereto.

[0034] Optionally, the MEMS chip 14 is connected to the flexible circuit board 11 through interconnection processes, including gold wire bonding, RDL fan-out, 3D printing, flip-chip, etc. Among them, gold wire bonding is suitable for monitoring expansion force with stress below 2MPa, while RDL fan-out and 3D printing are preferred for monitoring expansion force above 2MPa.

[0035] Optionally, such as Figure 2 As shown, the upper surface 151 of the force transmission layer 15, which is away from the flexible circuit board 11, is higher than the surface of the first protective film 12; this design facilitates the transmission of expansion force to the MEMS chip 14.

[0036] Optionally, such as Figure 2 As shown, the upper end face 151 of the force transmission layer 15 is planar, and the upper end face 151 is parallel to the surface of the first protective film 12. This application precisely controls the height of the force transmission layer 15 and the morphology of the end face 151, which helps to improve the consistency and stability of the sensor.

[0037] Optionally, the vertical distance L1 between the upper end face 151 and the surface of the first protective film 12 is 20μm to 100μm, for example, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, or 90μm.

[0038] Optionally, the thickness of the first protective film 12 is greater than the thickness of the second protective film 13; this design can further protect the MEMS chip 14.

[0039] Optionally, the thickness L2 of the first protective film 12 is 100μm to 200μm, for example, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, or 190μm.

[0040] Optionally, the thickness L3 of the second protective film 13 is 50μm to 100μm, for example, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, or 95μm.

[0041] Optionally, the thickness L4 of the flexible circuit board 11 is 50μm to 100μm, for example, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, or 95μm.

[0042] Optionally, the thickness of the MEMS chip 14 is 50μm to 150μm, for example, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm, 110μm, 120μm, 130μm, or 140μm.

[0043] Optionally, the MEMS chip 14 is fixed to the surface of the flexible circuit board 11 by adhesive 16. In this embodiment, the adhesive 16 is made of a material with low stress modulus after curing, such as epoxy glue, DAF film, or conductive silver paste, but is not limited thereto.

[0044] Optionally, such as Figure 1 As shown, the MEMS chip 14 is connected to the two first pads of the flexible circuit board 11 through two power leads 141 (VCC and GND), and the MEMS chip 14 is connected to the two second pads of the flexible circuit board 11 through two differential voltage output leads 142 (V+ and V-).

[0045] Optionally, such as Figure 1 As shown, the flexible circuit board 11 includes a chip mounting area and a plug-in area 112 that are connected to each other. The MEMS chip 14 is connected to the chip mounting area, which is connected between the first protective film 12 and the second protective film 13. A plug-in connector 113 is formed at the end of the plug-in area away from the chip mounting area. The plug-in connector 113 is used to connect a data acquisition module.

[0046] Optionally, such as Figure 1 As shown, a temperature sensor is provided on the MEMS chip 14, and the temperature sensor is connected to the flexible circuit board 11 through a temperature output lead 143. In this embodiment, the temperature sensor is a PN junction integrated in the MEMS chip 14, and the temperature sensor is used to correct temperature drift.

[0047] Optionally, Figures 3 to 6 This is a flowchart of the manufacturing process of the pressure sensor in this application. Please refer to it. Figures 3 to 6 The steps involved in manufacturing a pressure sensor include: A MEMS chip 14 is connected to the flexible circuit board 11, and the MEMS chip 14 and the flexible circuit board 11 are electrically connected through an interconnection process. A first protective film 12 with a window 101 is attached to the upper surface of the flexible circuit board 11, and the MEMS chip 14 is exposed from the window 101. The second protective film 13 is attached to the lower surface of the flexible circuit board 11, such as... Figure 3 As shown; A layer of adhesive tape 20 is attached to the surface of the first protective film 12. The thickness of the adhesive tape 20 determines the height of the force-conducting layer 15 protruding from the first protective film 12. Since the first protective film 12 is rigid and almost incompressible, the height of the protruding force-conducting layer 15 determines the maximum range of the sensing unit. The thickness of the adhesive tape 20 is 20μm to 100μm, for example, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, or 90μm. The adhesive tape 20 can be made of flat materials such as PI or PET, but is not limited to these materials. Figure 4 As shown; After applying tape 20, inject the force-conducting layer 15 material into window 101. The potting height of this material should be slightly higher than the height of tape 20 to facilitate subsequent leveling. The force-conducting layer 15 determines the reliability and consistency of the sensor. A material with low viscoelasticity is selected to prevent creep of the device. In addition, this material needs good elasticity, compressive strength, and thermal stability. Materials such as silicone, silicone rubber, epoxy resin, and polyurethane can be selected for the force-conducting layer 15. Figure 5 As shown; After potting the force-conducting material, wait for the material to fully cure, and then perform a planarization process on the force-conducting layer 15. Since the height and surface morphology of the force-conducting layer 15 directly affect the consistency and accuracy of the sensor, this step can improve the sensor's performance. Planarization processes include mechanical polishing, chemical mechanical polishing, and plasma polishing, among which chemical mechanical polishing can achieve better surface morphology and height consistency. After polishing, remove the adhesive tape 20 to obtain the complete MEMS pressure sensor, such as... Figure 6 As shown.

[0048] Optionally, the shape of the window 101 can be circular, rectangular, etc.; the diameter of the window 101 is 2mm to 10mm, for example, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm.

[0049] Second Embodiment Figure 7 This is a front view schematic diagram of the pressure sensor according to the second embodiment of this application, as shown. Figure 7 As shown, the pressure sensor in this embodiment has a structure that is roughly the same as that in the first embodiment, except that the number of MEMS chips 14 and windows 101 are different.

[0050] Optionally, the flexible circuit board 11 is electrically connected to a plurality of MEMS chips 14 arranged in a matrix, and the first protective film 12 is provided with a plurality of windows 101 arranged in a matrix. Each MEMS chip 14 is correspondingly arranged with each window 101, and each window 101 is provided with a force conduction layer 15. In this embodiment, the plurality of MEMS chips 14 are arranged at equal intervals, but the layout can also be optimized according to the force conditions during the actual battery charging and discharging process.

[0051] In one embodiment, eight MEMS chips 14 are connected on the flexible circuit board 11, and eight windows 101 are provided on the first protective film 12; the VCC lead of the eight MEMS chips 14 is connected in parallel, the GND lead is connected in parallel, and there are two additional differential voltage output leads and temperature output leads. Therefore, a total of 26 leads need to be connected to the eight MEMS chips 14.

[0052] For arrays with a large number of MEMS chips 14 (>10), a row and column scanning layout can be used to reduce the number of leads. For example, in a 3x4 array pressure sensor, the V+ leads of all MEMS chips 14 are connected in parallel, the V- leads are connected in parallel, the VCC leads in the same row are connected in parallel, and the GND leads in the same column are connected in parallel, requiring a total of 9 leads. Adding the 12 temperature output leads, the total number of leads is 21 (which is less than the number of leads in the above-mentioned 8 MEMS chips 14 lead scheme).

[0053] Optionally, the force transmission layers 15 in each window 101 have the same height, that is, the upper surface 151 of each force transmission layer 15 is on the same horizontal plane, which is beneficial to improving the consistency and stability of the sensor.

[0054] Third Embodiment This application also relates to a battery module, including a housing and a plurality of battery packs installed in the housing and the aforementioned pressure sensor, wherein at least one pressure sensor is provided between two adjacent battery packs, and the pressure sensor is used to detect the expansion force of the battery pack.

[0055] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Furthermore, the structures or structural features involved can be arbitrarily combined and superimposed. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A pressure sensor, characterized in that, The device includes a flexible circuit board, a first protective film, and a second protective film. At least one MEMS chip is electrically connected to the flexible circuit board. The first protective film is connected to the upper surface of the flexible circuit board, and the second protective film is connected to the lower surface of the flexible circuit board. The first protective film has at least one window exposing the MEMS chip, and the window is filled with a force-conducting layer covering the MEMS chip.

2. The pressure sensor as described in claim 1, characterized in that, The force-conducting layer is elastic.

3. The pressure sensor as described in claim 1, characterized in that, The force-conducting layer is located away from the upper surface of the flexible circuit board and is higher than the surface of the first protective film; and / or, The upper surface of the force-conducting layer is a plane, and the upper surface is parallel to the surface of the first protective film.

4. The pressure sensor as described in claim 3, characterized in that, The vertical distance between the upper end face and the surface of the first protective film is 20μm to 100μm.

5. The pressure sensor as described in claim 1, characterized in that, Includes at least one of the following: The thickness of the first protective film is greater than the thickness of the second protective film; The thickness of the first protective film is 100μm to 200μm; The thickness of the second protective film is 50μm to 100μm; The thickness of the flexible circuit board is 50μm to 100μm; The thickness of the MEMS chip is 50μm to 150μm.

6. The pressure sensor as described in claim 1, characterized in that, The MEMS chip is fixed to the surface of the flexible circuit board with adhesive; and / or, The MEMS chip is connected to two first pads of the flexible circuit board via two power leads, and the MEMS chip is connected to two second pads of the flexible circuit board via two differential voltage output leads.

7. The pressure sensor as described in claim 1, characterized in that, The flexible circuit board includes a chip mounting area and a plug-in area that are connected to each other. The MEMS chip is connected to the chip mounting area, and the chip mounting area is connected between the first protective film and the second protective film. A plug-in connector is formed at the end of the plug-in area away from the chip mounting area.

8. The pressure sensor according to any one of claims 1 to 7, characterized in that, The MEMS chip is equipped with a temperature sensor, which is connected to the flexible circuit board via a temperature output lead.

9. The pressure sensor according to any one of claims 1 to 7, characterized in that, The flexible circuit board is electrically connected to a plurality of MEMS chips arranged in a matrix. The first protective film is provided with a plurality of windows arranged in a matrix. Each MEMS chip is configured in a one-to-one correspondence with each window. Each window is provided with a force conduction layer.

10. A battery module, characterized in that, The device includes a housing, a plurality of battery packs mounted in the housing, and a pressure sensor as described in any one of claims 1 to 9, wherein at least one of the pressure sensors is provided between two adjacent battery packs, and the pressure sensor is used to detect the expansion force of the battery pack.

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