A differential pressure sensor package

Abstract

This invention relates to the field of pressure sensor packaging technology and discloses a micro differential pressure sensor packaging structure, including a PCB board. A MEMS chip is bonded to the inside of a mounting slot using conductive adhesive. Gold wires are mounted at one end of both the ASIC chip and the MEMS chip, with the other end of the gold wires mounted on the upper surface of the PCB board. Gold wires are also installed between the ASIC chip and the MEMS chip. A cover is mounted on the upper surface of the PCB board. A limiting structure is provided at the upper end of the substrate, and the MEMS chip is positioned in the middle of the limiting structure. This invention utilizes the fact that the thermal expansion coefficient of the substrate is between that of the MEMS chip and the PCB board, forming a gradient transition. This reduces interfacial stress caused by material expansion differences during temperature changes. The highly thermally conductive ceramic can quickly disperse the working heat of the MEMS chip, reducing the temperature gradient and avoiding piezoresistive bridge imbalance caused by local thermal deformation, thus preventing zero-point drift of the MEMS chip. Simultaneously, the high hardness and Young's modulus of the ceramic suppress the transmission of energy from PCB board bending or vibration, protecting the MEMS chip from external mechanical impacts.

Description

Technical Field

[0001] This utility model relates to the field of pressure sensor packaging technology, specifically a micro differential pressure sensor packaging structure. Background Technology

[0002] Pressure sensor packaging refers to the process of integrating the core sensing elements of a pressure sensor (such as MEMS chips, strain gauges, etc.) into a protective housing, while ensuring that it can work stably and reliably in the target environment. Existing pressure sensors generally adopt the COB packaging process. COB packaging is an integration technology that directly fixes the exposed chip to the printed circuit board (PCB) with adhesive or solder, and achieves electrical connection through wire bonding or flip-chip bonding. Finally, it is encapsulated and protected with materials such as epoxy resin.

[0003] In the prior art, MEMS chips for pressure sensors are generally fixed to the pads of a printed circuit board (PCB) using conductive adhesive. However, the conductive adhesive shrinks in volume during the curing process, which applies non-uniform mechanical stress to the MEMS chip. The core structure of the MEMS pressure sensor is extremely sensitive to minute stresses, which can cause the resistance of the piezoresistor to shift, thereby causing zero-point drift. Utility Model Content

[0004] The purpose of this invention is to provide a micro differential pressure sensor packaging structure that solves the problem that the conductive adhesive shrinks during the curing process, applying non-uniform mechanical stress to the MEMS chip, causing the resistance value of the MEMS chip varistor to shift, thereby causing zero-point drift.

[0005] To solve the above-mentioned technical problems, this utility model is achieved through the following technical solution:

[0006] This utility model relates to a micro differential pressure sensor packaging structure, comprising a PCB board. An ASIC chip and a substrate are bonded to the upper surface of the PCB board with conductive adhesive. A mounting groove is formed on the upper surface of the substrate. A MEMS chip is bonded to the inside of the mounting groove with conductive adhesive. Gold wires are mounted on one end of both the ASIC chip and the MEMS chip. The other end of the gold wires is mounted on the upper surface of the PCB board. A gold wire is installed between the ASIC chip and the MEMS chip. A cover is mounted on the upper surface of the PCB board. A limiting structure is provided at the upper end of the substrate, and the MEMS chip is located in the middle of the limiting structure.

[0007] Furthermore, the lower surface of the substrate has a plurality of grooves, the grooves being trapezoidal in shape, and the conductive adhesive being disposed inside the grooves.

[0008] Furthermore, the substrate is made of ceramic material.

[0009] Furthermore, the limiting structure includes a frame, a first elastic plate is provided on the lower surface of the frame, a first limiting block is provided on one side of the first elastic plate, a sliding groove is provided on the outer surface of the substrate, a limiting groove is provided on the inner surface of the sliding groove, the first elastic plate is fitted inside the sliding groove, and the first limiting block is fitted inside the limiting groove.

[0010] Furthermore, the upper surface of the frame is provided with a side plate, the outer surface of the side plate is provided with an opening, the inner surface of the opening is provided with a second elastic plate, one side of the second elastic plate is provided with a second limiting block, and the lower surface of the second limiting block abuts against the upper surface of the MEMS chip.

[0011] Furthermore, the lower surface of the frame is provided with a positioning rod, and the upper surface of the substrate is provided with a positioning hole, and the positioning rod is fitted inside the positioning hole.

[0012] Furthermore, both the second limiting block and the first limiting block have inclined surfaces on their outer surfaces.

[0013] This utility model has the following beneficial effects:

[0014] (1) This utility model uses the thermal expansion coefficient of the substrate to be between the MEMS chip and the PCB board to form a gradient transition, reduce the interface stress caused by the difference in material expansion when the temperature changes, and the high thermal conductivity ceramic can quickly disperse the working heat of the MEMS chip, reduce the temperature gradient, avoid the piezoresistive bridge imbalance caused by local thermal deformation, and avoid the zero-point drift of the MEMS chip. At the same time, the high hardness and Young's modulus of the ceramic suppress the bending or vibration energy transmission of the PCB board, and protect the MEMS chip from external mechanical impact.

[0015] (2) The present invention presses the MEMS chip downward by the second limiting block, which rigidly constrains the MEMS chip at the center of the mounting groove and counteracts vertical vibration or impact, avoids MEMS chip displacement or tilting caused by vibration or impact, prevents gold wire stretching or breakage caused by MEMS chip offset, and ensures electrical connection reliability.

[0016] Of course, any product implementing this utility model does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this utility model, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a cross-sectional view of the packaging structure of a pressure sensor in the prior art;

[0019] Figure 2 This is a schematic diagram of the overall structure of this utility model;

[0020] Figure 3 This is a cross-sectional view of the overall structure of this utility model;

[0021] Figure 4 This is a partial structural cross-sectional view of the present invention;

[0022] Figure 5 Exploded views of the substrate, MEMS chip, and limiting structure of this utility model;

[0023] Figure 6 This is a schematic diagram of the limiting structure of this utility model;

[0024] The attached diagram lists the components represented by each number as follows:

[0025] In the diagram: 1. PCB board; 2. AS IC chip; 3. Substrate; 301. Mounting slot; 302. Groove; 303. Slide groove; 304. Limiting groove; 305. Positioning hole; 4. MEMS chip; 5. Gold wire; 6. Cover; 7. Limiting structure; 701. Frame; 702. First elastic plate; 703. First limiting block; 704. Side plate; 705. Second elastic plate; 706. Second limiting block; 707. Positioning rod. Detailed Implementation

[0026] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0027] Please see Figures 1-6 As shown, this utility model is a micro differential pressure sensor packaging structure, including a PCB board 1. An ASIC chip 2 and a substrate 3 are bonded to the upper surface of the PCB board 1 with conductive adhesive. A mounting groove 301 is formed on the upper surface of the substrate 3. A MEMS chip 4 is bonded to the inside of the mounting groove 301 with conductive adhesive. A gold wire 5 is installed at one end of both the ASIC chip 2 and the MEMS chip 4. The other end of the gold wire 5 is installed on the upper surface of the PCB board 1. A gold wire 5 is installed between the ASIC chip 2 and the MEMS chip 4. A cover 6 is installed on the upper surface of the PCB board 1. A limiting structure 7 is provided at the upper end of the substrate 3. The MEMS chip 4 is located in the middle of the limiting structure 7.

[0028] Since the thermal expansion coefficient of substrate 3 is between that of MEMS chip 4 and PCB board 1, a gradient transition is formed, reducing the interface stress caused by material expansion differences when the temperature changes.

[0029] Substrate 3 is made of ceramic material;

[0030] High thermal conductivity ceramics can quickly disperse the working heat of MEMS chip 4, reduce the temperature gradient, and avoid piezoresistive bridge imbalance caused by local thermal deformation. At the same time, the high hardness and Young's modulus of ceramics suppress the transmission of bending or vibration energy of PCB board 1, and protect MEMS chip 4 from external mechanical impact.

[0031] The lower surface of the substrate 3 has several grooves 302, which are trapezoidal in shape, and conductive adhesive is disposed inside the grooves 302.

[0032] The trapezoidal design of the groove 302 can increase the anchoring area of ​​the conductive adhesive, and guide the shrinkage direction of the adhesive through the bevel structure, thereby reducing the impact of lateral stress on the substrate 3.

[0033] The limiting structure 7 includes a frame 701, a first elastic plate 702 on the lower surface of the frame 701, a first limiting block 703 on one side of the first elastic plate 702, a sliding groove 303 on the outer surface of the substrate 3, a limiting groove 304 on the inner surface of the sliding groove 303, the first elastic plate 702 being fitted inside the sliding groove 303, and the first limiting block 703 being fitted inside the limiting groove 304.

[0034] The upper surface of the frame 701 is provided with a side plate 704. The outer surface of the side plate 704 is provided with an opening. The inner surface of the opening is provided with a second elastic plate 705. A second limiting block 706 is provided on one side of the second elastic plate 705. The lower surface of the second limiting block 706 abuts against the upper surface of the MEMS chip 4.

[0035] The lower surface of the frame 701 is also provided with a positioning rod 707, and the upper surface of the substrate 3 is provided with a positioning hole 305, and the positioning rod 707 is installed inside the positioning hole 305.

[0036] Both the second limiting block 706 and the first limiting block 703 have inclined surfaces on their outer surfaces.

[0037] During encapsulation, the frame 701 of the limiting structure 7 is first pressed down, causing the first elastic plate 702 to insert into the slide groove 303. During the pressing process, the first elastic plate 702 is squeezed inward by the side wall of the slide groove 303 and elastically bends until the first limiting block 703 reaches the position of the limiting groove 304. When it returns to its original position, it is locked into the limiting groove 304 and completes self-locking. Then, conductive adhesive is applied to the mounting groove 301, and the MEMS chip 4 is placed directly above the mounting groove 301 and pushed downward, so that the inclined surface of the second limiting block 706 contacts the MEMS chip 4. The second elastic plate 705 is deformed under pressure. After the MEMS chip 4 is installed in the mounting groove 301, the second elastic plate 705 rebounds, causing the second limiting block 706 to press against the MEMS chip 4. On the outer surface, the MEMS chip 4 is rigidly constrained at the center of the mounting groove 301. Then, conductive adhesive is applied to the upper surface of the PCB board 1, and the ASIC chip 2 and the substrate 3 are placed on the conductive adhesive. The ASIC chip 2 and the substrate 3 are mounted to the PCB board 1 through the conductive adhesive. The trapezoidal design of the groove 302 on the lower surface of the substrate 3 can increase the anchoring area of ​​the conductive adhesive. The oblique structure guides the shrinkage direction of the adhesive and reduces the influence of lateral stress on the substrate 3. After the ASIC chip 2 and the substrate 3 are installed, the MEMS chip 4, the ASIC chip 2 and the PCB board 1 are electrically connected together by the gold wire 5. After the connection is completed, the cover 6 is installed on the outer surface of the PCB board 1, thus completing the packaging of the pressure sensor.

[0038] During use, the thermal expansion coefficient of the substrate 3 is between that of the MEMS chip 4 and the PCB board 1, forming a gradient transition. This reduces the interfacial stress caused by the difference in material expansion when the temperature changes. The highly thermally conductive ceramic can quickly disperse the working heat of the MEMS chip 4, reduce the temperature gradient, and avoid the piezoresistive bridge imbalance caused by local thermal deformation. At the same time, the high hardness and Young's modulus of the ceramic suppress the bending or vibration energy transmission of the PCB board 1, protecting the MEMS chip 4 from external mechanical impact. The second limiting block 706 rigidly constrains the MEMS chip 4 at the center of the mounting groove 301, and can also counteract vertical vibration or impact, preventing the MEMS chip 4 from shifting or tilting due to vibration or impact, preventing the gold wire 5 from being stretched or broken due to the offset of the MEMS chip 4, and ensuring the reliability of the electrical connection.

[0039] The preferred embodiments of this utility model disclosed above are merely illustrative of the present utility model. These preferred embodiments do not exhaustively describe all details, nor do they limit the utility model to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of this utility model, thereby enabling those skilled in the art to better understand and utilize it. This utility model is limited only by the claims and their full scope and equivalents.

Claims

1. A micro differential pressure sensor packaging structure, characterized in that: The PCB board (1) is provided with an ASIC chip (2) and a substrate (3) bonded together on the upper surface of the PCB board (1) by conductive adhesive. The upper surface of the substrate (3) is provided with a mounting groove (301), and a MEMS chip (4) is bonded together inside the mounting groove (301) by conductive adhesive. Both the ASIC chip (2) and the MEMS chip (4) have gold wires (5) installed at one end, and the other end of the gold wires (5) is installed on the upper surface of the PCB board (1). A gold wire (5) is installed between the ASIC chip (2) and the MEMS chip (4), and a cover (6) is installed on the upper surface of the PCB board (1); A limiting structure (7) is provided at the upper end of the substrate (3), and the MEMS chip (4) is disposed in the middle of the limiting structure (7).

2. The micro differential pressure sensor packaging structure according to claim 1, characterized in that: The substrate (3) has several grooves (302) on its lower surface. The grooves (302) are trapezoidal in shape, and the conductive adhesive is disposed inside the grooves (302).

3. The micro differential pressure sensor packaging structure according to claim 1, characterized in that: The substrate (3) is made of ceramic.

4. The micro differential pressure sensor packaging structure according to claim 1, characterized in that: The limiting structure (7) includes a frame (701), the lower surface of the frame (701) is provided with a first elastic plate (702), and one side of the first elastic plate (702) is provided with a first limiting block (703). The outer surface of the substrate (3) is provided with a sliding groove (303), and the inner surface of the sliding groove (303) is provided with a limiting groove (304). The first elastic plate (702) is installed inside the sliding groove (303), and the first limiting block (703) is installed inside the limiting groove (304).

5. The micro differential pressure sensor packaging structure according to claim 4, characterized in that: The upper surface of the frame (701) is provided with a side plate (704), the outer surface of the side plate (704) is provided with an opening, the inner surface of the opening is provided with a second elastic plate (705), a second limiting block (706) is provided on one side of the second elastic plate (705), and the lower surface of the second limiting block (706) abuts against the upper surface of the MEMS chip (4).

6. The micro differential pressure sensor packaging structure according to claim 5, characterized in that: The lower surface of the frame (701) is also provided with a positioning rod (707), and the upper surface of the substrate (3) is provided with a positioning hole (305). The positioning rod (707) is installed inside the positioning hole (305).

7. The micro differential pressure sensor packaging structure according to claim 5, characterized in that: Both the second limiting block (706) and the first limiting block (703) have inclined surfaces on their outer surfaces.

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