CN114348952B

CN114348952B - MEMS pressure sensor packaging structure

Info

Publication number: CN114348952B
Application number: CN202210255118.3A
Authority: CN
Inventors: 黄晓东; 熊强; 秦明; 韩磊; 李伟华; 唐洁影; 于虹
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2022-03-16
Filing date: 2022-03-16
Publication date: 2022-05-20
Anticipated expiration: 2042-03-16
Also published as: CN114348952A

Abstract

The invention discloses an MEMS pressure sensor packaging structure, wherein a group of metal polar plates which are oppositely arranged are attached to the inner side wall of a shell, an electric field can be formed by the metal polar plates after voltage is introduced, external dirt which penetrates into a sealing cavity moves and gathers towards the metal polar plates under the action of the electric field according to a dielectric separation effect, and falls into a dirt collecting tank at the bottom end of the metal polar plates under the action of gravity, so that the problem that in the prior art, the packaging airtightness is gradually reduced along with the increase of the working time of a sensor, the external dirt is caused to enter the packaging cavity and then sink to the surface of an MEMS pressure sensor chip, and the performance of the sensor is reduced is solved. In addition, the cover-shaped corrugated diaphragm and the connection mode thereof can effectively improve the packaging air tightness of sealant assembly and reduce the prestress and thermal stress on the corrugated diaphragm; the corrugated diaphragm is made of high-toughness ceramic materials, and corrosion and damage of the corrugated diaphragm caused by severe working environments are inhibited.

Description

MEMS pressure sensor packaging structure

Technical Field

The invention relates to a sensor packaging structure, in particular to a Micro-Electro-Mechanical System (MEMS) pressure sensor packaging structure.

Background

The packaging of the sensor can isolate the MEMS sensor chip from the external severe environment, inhibit and shield the interference of the external environment, and simultaneously has the functions of electric connection, heat management, mechanical strength enhancement and the like. On the other hand, the packaging of the sensor is very easy to influence the performance of the sensor.

The packaging forms of the MEMS pressure sensor are mainly classified into plastic packaging, metal packaging, and ceramic packaging according to the material of the pressure sensor packaging case. The assembly mode of the MEMS pressure sensor packaging structure mainly comprises welding assembly and sealant assembly. For the existing MEMS pressure sensor packaging structure with the corrugated diaphragm and the silicone oil seal, although the air tightness of the welding assembly is higher than that of the sealing glue assembly, the welding assembly can bring larger prestress than that of the sealing glue assembly, the welding assembly can easily generate bubbles in a sealing cavity of the package, the welding assembly has great limitation on the material of a packaging tube shell, and the sealing glue assembly can well make up for the defects of the welding assembly. In addition, the corrugated diaphragm made of metal is easily corroded and damaged by severe working environment, and the air tightness of the corrugated diaphragm is gradually reduced along with the increase of the working time of the sensor, so that external dirt enters the sealed cavity of the package and then sinks to the surface of the MEMS pressure sensor chip, and the performance of the sensor is reduced.

Disclosure of Invention

The purpose of the invention is as follows: the MEMS pressure sensor packaging structure solves the problem that the performance of a sensor is reduced due to the fact that external dirt enters a packaging cavity and then sinks to the surface of a chip of the MEMS pressure sensor because the packaging airtightness is gradually reduced along with the increase of the working time of the sensor.

The technical scheme is as follows: an MEMS pressure sensor packaging structure comprises a corrugated diaphragm, a shell and a kovar alloy substrate; the Kovar alloy substrate is provided with a plurality of metal electrodes communicated with the outside of the bottom of the substrate; the shell is of a straight-tube structure, a group of metal polar plates which are arranged oppositely are attached to the inner side wall of the shell, the bottom ends of the metal polar plates are connected with dirt collecting grooves with upward openings, and the dirt collecting grooves connected with the metal polar plates which are arranged oppositely are arranged around the inner side wall of the shell; the MEMS pressure sensor chip is fixed on the Kovar alloy substrate, and a pin of the MEMS pressure sensor chip and the metal polar plate which is arranged oppositely are respectively connected with the corresponding metal electrode on the Kovar alloy substrate; the corrugated diaphragm and the kovar alloy substrate are respectively connected to the top end and the bottom end of the shell in a sealing mode to form a sealed cavity structure, and silicone oil is filled in the sealed cavity structure.

Furthermore, the corrugated diaphragm is of a cover-shaped structure, a circle of groove is formed in the top end of the shell, the vertical edge of the corrugated diaphragm is inserted into the groove, sealant is injected into the groove to fix the corrugated diaphragm, and the horizontal position of the corrugated diaphragm does not contact with the shell.

Further, the material of the corrugated membrane is high-toughness ceramic.

Furthermore, the shell is made of organic silicon plastics, stainless steel metal or silicon nitride ceramics.

Further, the Kovar alloy substrate is made of an iron-nickel-cobalt alloy.

Furthermore, an insulator is arranged between the metal electrode and the kovar alloy substrate.

Furthermore, an oil hole is formed in the kovar alloy substrate.

Furthermore, the sealant is organic silicon resin pouring sealant.

Further, the high-toughness ceramic is alumina ceramic.

Further, the high-toughness ceramic is zirconia ceramic.

Has the advantages that: compared with the existing packaging structure with the corrugated diaphragm and the silicone oil seal, the packaging structure has the following advantages:

1. the traditional packaging structure has no measure for solving the problem of air tightness reduction in the using process of the sensor, the structure with a self-cleaning function is added to make up the defect, and the negative influence caused by external dirt deposited on the surface of the sensor chip due to the reduction of the packaging air tightness is inhibited by utilizing a dielectric separation effect.

2. Different from the corrugated diaphragm made of metal materials in the existing packaging structure, the corrugated diaphragm made of the high-toughness ceramic material has good chemical stability, ageing resistance and fatigue resistance, so that corrosion and damage of the corrugated diaphragm caused by severe working environment are inhibited, the application occasion of the sensor is expanded, the performance of the sensor is improved, and the service life of the sensor is prolonged.

3. Different from the planar corrugated diaphragm in the existing packaging structure, the corrugated diaphragm in the invention is designed into a cover shape, so that the vertical edge of the corrugated diaphragm can be matched with the groove at the top end of the shell for sealant assembly, and the horizontal position of the corrugated diaphragm can be ensured not to be contacted with the shell after assembly. Therefore, the packaging air tightness of the sealant assembly can be effectively improved, the prestress and the thermal stress on the corrugated diaphragm are reduced, and the performance of the sensor is improved.

Drawings

FIG. 1 is a front view of a MEMS pressure sensor package structure of the present invention;

FIG. 2 is a cross-sectional view of a front view of a MEMS pressure sensor package structure of the present invention;

FIG. 3 is a top view of a cap-shaped bellows diaphragm of a MEMS pressure sensor package structure of the present invention;

FIG. 4 is a front view of a cap-shaped bellows diaphragm of a MEMS pressure sensor package structure of the present invention;

FIG. 5 is a top view of a metal plate of a MEMS pressure sensor package structure of the present invention;

FIG. 6 is a front view of a metal plate of a MEMS pressure sensor package structure of the present invention;

FIG. 7 is a right side view of a metal plate of a MEMS pressure sensor package structure of the present invention;

FIG. 8 is an overall assembly view of a MEMS pressure sensor package structure of the present invention.

Detailed Description

The invention is further explained below with reference to the drawings.

As shown in fig. 1, fig. 2 and fig. 8, a MEMS pressure sensor package structure includes a corrugated diaphragm 2, a housing 4, and a kovar alloy substrate 8. The kovar alloy substrate 8 is provided with a plurality of metal electrodes 7 communicated with the outside of the bottom of the substrate. The shell 4 is a straight cylinder structure, and the laminating has a set of metal polar plate 5 that sets up relatively on the inside wall of shell 4, and the bottom of metal polar plate 5 is connected with opening filth collecting vat 11 up, and the filth collecting vat 11 that the metal polar plate 5 that sets up relatively connected encircles the setting of the 4 inside walls of shell. The MEMS pressure sensor chip 6 is fixed on the Kovar alloy substrate 8, and the pins of the MEMS pressure sensor chip 6 and the metal polar plates 5 which are oppositely arranged are respectively connected with the corresponding metal electrodes 7 on the Kovar alloy substrate 8. The corrugated diaphragm 2 and the kovar alloy substrate 8 are respectively connected to the top end and the bottom end of the shell 4 in a sealing mode to form a sealed cavity structure, silicone oil 1 is filled in the sealed cavity structure, and an oil filling hole 10 is formed in the kovar alloy substrate 8.

Specifically, ripple diaphragm 2 is the lid column structure, and the top of shell 4 is equipped with the round recess, and ripple diaphragm 2's vertical edge inserts in the recess to sealed glue 3 of pouring into in the recess fixes ripple diaphragm 2, and reaches sealed effect, ripple diaphragm 2's level department does not take place the contact with shell 4. The shell 4 is made of organic silicon plastic, stainless steel metal material or silicon nitride ceramic material. The material of the corrugated diaphragm 2 is a ceramic material with high toughness, such as alumina ceramic and zirconia ceramic. The sealant 3 is organic silicon resin pouring sealant. The kovar alloy substrate 8 is made of iron-nickel-cobalt alloy. The metal plate 5 and the metal electrode 7 are made of aluminum, nickel-copper-zinc alloy or stainless steel. In this embodiment, the metal electrodes 7 have seven total, five of them are interconnected with the pins of the MEMS pressure sensor chip 6, and two of them are directly connected to the lower surface of the metal plate 5. An insulator 9 is arranged between the metal electrode 7 and the kovar alloy substrate 8, and plays roles of insulation and sealing.

In this embodiment, the metal polar plate 5 and the dirt collecting groove 11 at the bottom thereof are of an integrated structure, that is, the bottom edge of the metal polar plate 5 is bent inwards through two sides, and the side surface is sealed to form a sealing structure. Gaps for insulation are arranged at the ends of the two metal pole plates 5 and the dirt collecting groove 11.

For the existing MEMS pressure sensor package with the corrugated diaphragm and the silicone oil seal, the air tightness of the structure of the MEMS pressure sensor package is gradually reduced along with the increase of the working time of the sensor, so that external dirt enters a closed cavity filled with the silicone oil. The packaging structure of the invention comprises a self-cleaning function: a set of metal polar plate 5 that sets up relatively can form the electric field in the below that is close to corrugated diaphragm 2 after letting in voltage, according to the dielectric separation effect, under the effect of this electric field, the external filth of infiltration seal chamber is usually more than the dielectric constant of silicon oil because of its dielectric constant, so can take place obvious dielectric separation phenomenon and make filth move and the gathering towards metal polar plate 5, then adhere to the surface at metal polar plate 5, filth collecting vat 11 of metal polar plate 5 lower extreme is used for collecting because of the effect such as gravity from the filth that metal polar plate 5 surface sinks, the external filth that has effectively avoided getting into the airtight cavity of encapsulation sinks to MEMS pressure sensor chip surface, thereby the reduction of the sensor performance that causes.

In addition, the corrugated diaphragm is made of high-toughness ceramic materials, has good chemical stability, ageing resistance and fatigue resistance, and is favorable for inhibiting corrosion and damage of a severe working environment to the corrugated diaphragm and expanding the application occasions of the sensor by matching with the ceramic tube shell. The corrugated diaphragm 2 is designed into a cover shape, the vertical edge of the corrugated diaphragm is matched with a groove at the top end of the shell 4 for sealant assembly, and meanwhile, the corrugated diaphragm 2 is ensured to be horizontally arranged and not to contact with the shell 4 after assembly. Therefore, the packaging airtightness of the sealant assembly can be effectively improved, the prestress and the thermal stress on the corrugated diaphragm are reduced, and the performance of the sensor is improved.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. The MEMS pressure sensor packaging structure is characterized by comprising a corrugated diaphragm (2), a shell (4) and a Kovar alloy substrate (8); the Kovar alloy substrate (8) is provided with a plurality of metal electrodes (7) communicated with the outside of the bottom of the substrate; the shell (4) is of a straight-tube structure, a group of metal polar plates (5) which are arranged oppositely are attached to the inner side wall of the shell (4), the bottom ends of the metal polar plates (5) are connected with dirt collecting grooves (11) with upward openings, and the dirt collecting grooves (11) connected with the metal polar plates (5) which are arranged oppositely are arranged around the inner side wall of the shell (4); an MEMS pressure sensor chip (6) is fixed on the Kovar alloy substrate (8), and a pin of the MEMS pressure sensor chip (6) and the metal polar plate (5) which is arranged oppositely are respectively connected with a corresponding metal electrode (7) on the Kovar alloy substrate (8); the corrugated diaphragm (2) and the kovar alloy substrate (8) are respectively connected to the top end and the bottom end of the shell (4) in a sealing mode to form a sealed cavity structure, and silicone oil (1) is filled in the sealed cavity structure.

2. The MEMS pressure sensor package structure of claim 1, wherein the corrugated diaphragm (2) is a cover-shaped structure, the top end of the housing (4) is provided with a circle of groove, the vertical edge of the corrugated diaphragm (2) is inserted into the groove, and sealant (3) is injected into the groove to fix the corrugated diaphragm (2), and the horizontal position of the corrugated diaphragm (2) is not contacted with the housing (4).

3. MEMS pressure sensor package structure according to claim 1 or 2, characterized in that the material of the corrugated membrane (2) is a high-toughness ceramic.

4. The MEMS pressure sensor package structure according to claim 1 or 2, characterized in that the material of the housing (4) is silicone plastic, stainless steel metal or silicon nitride ceramic.

5. MEMS pressure sensor package structure according to claim 1 or 2, characterized in that the material of the kovar substrate (8) is a kovar.

6. The MEMS pressure sensor package structure according to claim 1 or 2, characterized in that an insulator (9) is provided between the metal electrode (7) and the kovar substrate (8).

7. The MEMS pressure sensor package structure according to claim 1 or 2, characterized in that the kovar substrate (8) is provided with oil holes (10).

8. The MEMS pressure sensor package structure of claim 2, wherein the sealant (3) is a silicone resin potting sealant.

9. The MEMS pressure sensor package structure of claim 3, wherein the high-toughness ceramic is an alumina ceramic.

10. The MEMS pressure sensor package structure of claim 3, wherein the high-toughness ceramic is a zirconia ceramic.