MEMS pressure chip for isolating packaging stress

Abstract

The utility model discloses an MEMS pressure chip for isolating packaging stress, which comprises tube shells, an adhesive is fixed at the top ends of the tube shells, a silicon support is fixed at the top end of the adhesive, a gauge pressure hole is arranged between the two groups of tube shells, an upper end expansion joint is arranged at the top end in the silicon support, and a lower end expansion joint is arranged at the top end in the silicon support. A lower end expansion joint is arranged at the bottom end of the interior of the silicon support, and a chip body is installed at the top end of the silicon support. According to the utility model, the packaging stress is isolated by designing a brand new support structure on the chip, and meanwhile, the glass support is changed into monocrystalline silicon which is easier to process and consistent with the property of the chip, so that the influence of the packaging stress on the sensor is thoroughly eliminated. The thermal expansion stress release structure design is used for adapting to material expansion and shrinkage caused by temperature changes, and excessive stress and potential damage are prevented. These structures typically utilize expansion joints or other design features, allowing the material to move freely without constraint, thereby releasing stress.

Description

Technical Field

[0001] This utility model relates to the field of MEMS pressure chip technology, specifically a MEMS pressure chip for isolating packaging stress. Background Technology

[0002] Traditional piezoresistive pressure sensors have a mature and fixed structure and packaging. The back of the chip typically uses a flat glass mount, and then silicone or epoxy resin is used to bond the chip to a stainless steel base. Because the adhesive and the chip have different coefficients of thermal expansion, thermal stress mismatch when the temperature changes will cause the sensor output to drift. Furthermore, the adhesive absorbs moisture from the environment, causing localized expansion and further increasing packaging stress. Therefore, reducing or eliminating the impact of unpredictable packaging stress caused by the adhesive is a problem that needs to be solved in the packaging of piezoresistive pressure sensors. Current research and practice show that adhesives with lower Young's modulus and lower coefficients of thermal expansion can effectively reduce packaging stress, but cannot completely eliminate it. Designing stress isolation structures on the pressure chip can avoid the packaging stress caused by chip bonding. Currently, this is mainly achieved by selecting higher-performance adhesives (chip adhesives) to reduce packaging stress. However, in the field of micro-pressure measurement, the reduced packaging stress still has a significant impact on sensor performance. Therefore, we propose a MEMS pressure chip with isolated packaging stress to improve upon the above problems. Utility Model Content

[0003] The purpose of this invention is to provide a MEMS pressure chip that isolates packaging stress, so as to solve the problem mentioned in the background art of the impact of packaging stress on sensor performance.

[0004] To achieve the above objectives, this utility model provides the following technical solution: a MEMS stress chip for isolating packaging stress, comprising:

[0005] Two sets of tubing are symmetrically distributed, with a gauge pressure orifice formed between the two sets of tubing.

[0006] A silicon support is fixed to the top of the tube shell by an adhesive.

[0007] The chip body is mounted on the top of the silicon support;

[0008] The upper expansion joint is located at the top of the inside of the silicon support, and is square in shape and matches the back cavity of the chip body.

[0009] The lower expansion joint is located at the bottom of the inside of the silicon support and is distributed in a ring shape.

[0010] The upper and lower expansion joints constitute a thermal expansion stress relief structure.

[0011] As a preferred technical solution, the two sets of tubular shells are symmetrically distributed about the central axis of the silicon support.

[0012] As a preferred technical solution, the lower expansion joint is a single annular groove, and the center of the annulus is located at the geometric center of the silicon support.

[0013] As a preferred technical solution, the square outline of the upper expansion joint coincides with the projected outline of the chip body's back cavity.

[0014] As a preferred technical solution, the annular design of the lower expansion joint satisfies the following: the line connecting any point on the joint surface between the silicon support and the shell to the center of the annular circle coincides with the normal direction from that point to the annular contour.

[0015] Compared with existing technologies, the advantages of this invention are: by designing a novel support structure on the chip to isolate packaging stress, and by replacing the glass support with monocrystalline silicon, which is easier to process and has properties consistent with the chip, the influence of packaging stress on the sensor is completely eliminated. The thermal expansion stress relief structure is designed to accommodate the expansion and contraction of materials caused by temperature changes, preventing excessive stress and potential damage. These structures typically utilize expansion joints or other design features to allow materials to move freely without constraint, thereby releasing stress. Attached Figure Description

[0016] Figure 1 This is a front view structural diagram of the present utility model;

[0017] Figure 2 This is a front view cross-sectional structural diagram of the pressure gauge hole of this utility model;

[0018] Figure 3 This is a frontal cross-sectional view of the lower expansion joint of this utility model.

[0019] Figure 4 This is a front view schematic diagram of the chip structure of this utility model.

[0020] In the diagram: 1. Silicon support; 2. Tube shell; 3. Upper expansion joint; 4. Gauge pressure hole; 5. Lower expansion joint; 6. Adhesive; 7. Chip body. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. 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.

[0022] Please see Figure 1-4This utility model provides an embodiment of a MEMS pressure chip for isolating encapsulation stress, comprising a housing 2, an adhesive 6 fixed to the top of the housing 2, and a silicon support 1 fixed to the top of the adhesive 6. A pressure gauge hole 4 is provided between two sets of housings 2. An upper expansion joint 3 is provided at the top of the inside of the silicon support 1, and a lower expansion joint 5 is provided at the bottom of the inside of the silicon support 1. A chip body 7 is mounted on the top of the silicon support 1. Two sets of housings 2 are provided, and the two sets of housings 2 are symmetrically distributed about the central axis of the silicon support 1. One set of lower expansion joint 5 is provided, and the lower expansion joint 5 is located at the silicon support 1. The interior of the support 1 is arranged in a ring shape. The upper expansion joint 3 is designed as a square, which is consistent with the shape of the back cavity of the chip body 7. It serves as a thermal expansion stress release area on the side of the chip-support contact surface. A set of lower expansion joints 5 is provided, and the lower expansion joints 5 are arranged in a ring shape inside the silicon support 1. Compared with the upper expansion joint 3 groove, the lower expansion joint 5 can more efficiently reduce the encapsulation stress on the bonding surface between the chip body 7 and the casing 2. Moreover, any point on the bonding surface can point to the center and radius of the lower expansion joint 5, which can release the thermal expansion stress in any direction to the maximum extent.

[0023] Working Principle: In use, the piezoresistive chip is bonded to the silicon support 1 using silicon-silicon bonding technology to obtain a complete pressure chip. Stress relief structures are fabricated on both the chip body 7 and the silicon support 1, and on both the support and the housing 2, and the shape of the stress relief grooves is optimized. This chip can completely isolate the packaging stress caused by chip bonding, improving the micro-pressure chip's susceptibility to temperature changes and greatly enhancing the performance of the micro-pressure sensor. Since the thermal expansion coefficients of materials such as the adhesive 6, silicon, and glass are different, changes in ambient temperature will cause different materials to expand or contract to varying degrees, resulting in unexpected thermal expansion stress. Since the pressure chip measures pressure by sensing changes in stress on the chip, thermal expansion stress has a significant impact on measurement accuracy. An upper expansion joint 3 and a lower expansion joint 5 are etched into the silicon support 1. The expansion joints allow the material to move or deform under constraint, thereby releasing stress. The lower expansion joint 5 is mainly used to release the thermal stress caused by the mismatch in the coefficient of thermal expansion between the adhesive 6 and the silicone support 1, while the upper expansion joint 3 is mainly used to further isolate the thermal stress that has not been completely released.

[0024] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A MEMS stress chip for isolating packaging stress, characterized in that... ,include: Two sets of tubular shells (2) are symmetrically distributed, and a gauge pressure hole (4) is formed between the two sets of tubular shells. Silicon support (1) is fixed to the top of the tube shell (2) by adhesive (6); The chip body (7) is mounted on the top of the silicon support (1); The upper expansion joint (3) is located at the top of the inside of the silicon support (1), and is square in shape and matches the back cavity of the chip body (7); The lower expansion joint (5) is located at the bottom of the inside of the silicon support (1) and is distributed in a ring shape; The upper expansion joint (3) and the lower expansion joint (5) constitute a thermal expansion stress relief structure.

2. The MEMS stress chip for isolating packaging stress according to claim 1, characterized in that: The two sets of tubular shells (2) are symmetrically distributed about the central axis of the silicon support (1).

3. A MEMS pressure chip for isolating packaging stress according to claim 1, characterized in that: The lower expansion joint (5) is a single annular groove, and the center of the annular circle is located at the geometric center of the silicon support (1).

4. A MEMS pressure chip for isolating packaging stress according to claim 1, characterized in that: The square outline of the upper expansion joint (3) coincides with the projection outline of the back cavity of the chip body (7).

5. A MEMS stress chip for isolating packaging stress according to claim 1, characterized in that: The annular design of the lower expansion joint (5) satisfies that: any point on the joint surface between the silicon support (1) and the shell (2) has a line connecting it to the center of the annular circle that coincides with the normal direction from that point to the annular contour.

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