CN114348952B - A MEMS pressure sensor package structure - Google Patents

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

A MEMS pressure sensor package structure

technical field

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

Background technique

The package of the sensor can isolate the MEMS sensor chip from the external harsh environment, suppress and shield the interference of the external environment, and also have the functions of electrical connection, thermal management and enhanced mechanical strength. On the other hand, the packaging of the sensor can easily affect the performance of the sensor.

According to the material of the pressure sensor package, the packaging forms of MEMS pressure sensors are mainly divided into plastic packaging, metal packaging and ceramic packaging. The assembly methods of the MEMS pressure sensor package structure mainly include welding assembly and sealant assembly. For the existing MEMS pressure sensor package structure with corrugated diaphragm and silicone oil seal, although the airtightness of the welding assembly is higher than that of the sealant assembly, the welding assembly will bring more air-tightness than the sealant assembly. With greater pre-stress, the welding assembly is also prone to generate air bubbles in the sealing cavity of the package, and the welding assembly has great restrictions on the packaging material, and the sealant assembly can well compensate for the above shortcomings of the welding assembly. In addition, the corrugated diaphragm made of metal is prone to corrosion and damage in harsh working environments, and its air tightness will gradually decrease with the increase of the working time of the sensor, causing external dirt to enter the sealed cavity of the package and sink to the MEMS pressure. sensor chip surface, resulting in reduced sensor performance.

SUMMARY OF THE INVENTION

Purpose of the invention: In view of the above prior art, a MEMS pressure sensor packaging structure is proposed, which solves the problem that the air tightness of the package gradually decreases with the increase of the working time of the sensor, causing external dirt to enter the packaging cavity and sink to the surface of the MEMS pressure sensor chip. As a result, the sensor performance is degraded.

Technical solution: a MEMS pressure sensor package structure, comprising a corrugated diaphragm, a casing, and a Kovar alloy substrate; the Kovar alloy substrate is provided with a number of metal electrodes connected to the bottom of the substrate; the casing is a straight cylinder structure, A set of oppositely arranged metal electrode plates are attached to the inner side wall of the casing, the bottom end of the metal electrode plates is connected with a dirt collection tank with an upward opening, and the dirts connected to the oppositely arranged metal electrode plates are connected. The collection tank is arranged around the inner side wall of the casing; the MEMS pressure sensor chip is fixed on the Kovar alloy substrate, and the pins of the MEMS pressure sensor chip and the oppositely arranged metal plates are respectively connected to the Kovar alloy substrate The corrugated diaphragm and the Kovar alloy substrate are sealed and connected to the top and bottom ends of the casing, respectively, to form a sealed cavity structure, and the sealed cavity structure is filled with silicone oil.

Further, the corrugated diaphragm is a cover-like structure, the top of the casing is provided with a groove, the vertical edge of the corrugated diaphragm is inserted into the groove, and the sealant is injected into the groove. To fix the corrugated diaphragm, the level of the corrugated diaphragm is not in contact with the housing.

Further, the material of the corrugated diaphragm is high-toughness ceramics.

Further, the material of the casing is organic silicon plastic, stainless steel metal or silicon nitride ceramics.

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

Further, an insulator is provided between the metal electrode and the Kovar substrate.

Further, the Kovar alloy substrate is provided with oil injection holes.

Further, the sealant adopts silicone resin potting glue.

Further, the high toughness ceramics are alumina ceramics.

Further, the high toughness ceramics are zirconia ceramics.

Beneficial effects: Compared with the existing package structure with corrugated diaphragm and silicone oil seal, the present invention has the following advantages:

1. The existing packaging structure has no measures to deal with the problem of air tightness decline during the use of the sensor. The present invention adds a structure with a self-cleaning function to make up for this deficiency, and uses the dielectric separation effect to suppress the air tightness of the package. Negative effects of contamination deposited on the sensor chip surface.

2. Different from the corrugated diaphragm made of metal material in the existing packaging structure, the corrugated diaphragm in the present invention is made of high-toughness ceramic material, which has good chemical stability, aging resistance and fatigue resistance, which not only helps to suppress The corrosion and damage of the corrugated diaphragm in the harsh working environment also helps to expand the application of the sensor and improve the performance and service life of the sensor.

3. Different from the flat corrugated diaphragm in the existing packaging structure, the corrugated diaphragm in the present invention is designed into a cover shape, which not only enables the vertical edge of the corrugated diaphragm to fit into the groove at the top of the casing for sealant assembly, but also allows for sealing. It can ensure that the level of the corrugated diaphragm is not in contact with the housing after assembly. This can effectively improve the air tightness of the sealant assembly, reduce the prestress and thermal stress on the corrugated diaphragm, and improve the performance of the sensor.

Description of drawings

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

2 is a cross-sectional view corresponding to a front view of a MEMS pressure sensor packaging structure of the present invention;

3 is a top view of a lid-shaped corrugated diaphragm of a MEMS pressure sensor packaging structure of the present invention;

4 is a front view of a lid-shaped corrugated diaphragm of a MEMS pressure sensor packaging structure of the present invention;

5 is a top view of a metal electrode plate of a MEMS pressure sensor packaging structure of the present invention;

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

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

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

Detailed ways

The present invention will be further explained below in conjunction with the accompanying 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 number of metal electrodes 7 connected to the bottom of the substrate. The outer casing 4 is a straight cylinder structure, and a group of oppositely arranged metal pole plates 5 are attached to the inner side wall of the outer casing 4. The bottom end of the metal pole plate 5 is connected with a dirt collection tank 11 with an upward opening, and the oppositely arranged metal pole plates are connected. The connected dirt collection tank 11 is arranged around the inner side wall of the housing 4 . 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 oppositely disposed metal electrode plates 5 are respectively connected to the corresponding metal electrodes 7 on the Kovar alloy substrate 8 . The corrugated diaphragm 2 and the Kovar alloy substrate 8 are sealed and connected to the top and bottom ends of the casing 4 respectively to form a sealed cavity structure. The sealed cavity structure is filled with silicone oil 1 , and the Kovar alloy substrate 8 is provided with an oil injection hole 10 .

Specifically, the corrugated diaphragm 2 is a cover-like structure, the top of the casing 4 is provided with a ring of grooves, the vertical edge of the corrugated diaphragm 2 is inserted into the groove, and the sealant 3 is injected into the groove to fix the corrugated diaphragm 2 , and to achieve the sealing effect, the level of the corrugated diaphragm 2 is not in contact with the casing 4 . The housing 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 uses a silicone resin potting compound. The material of the Kovar substrate 8 is an iron-nickel-cobalt alloy. The material of the metal electrode plate 5 and the metal electrode 7 is generally selected from aluminum, nickel-copper-zinc alloy or stainless steel. In this embodiment, there are a total of seven metal electrodes 7 , five of which are interconnected with the pins of the MEMS pressure sensor chip 6 , and two are directly connected to the lower surface of the metal electrode plate 5 . An insulator 9 is provided between the metal electrode 7 and the Kovar alloy substrate 8, which plays the role of insulation and sealing.

In this embodiment, the metal electrode plate 5 and the dirt collection tank 11 at the bottom are integrally formed, that is, the bottom edge of the metal electrode plate 5 is bent inward through both sides, and the sides are edge-sealed to form a structure. The two metal electrode plates 5 and the ends of the dirt collecting tank 11 are provided with gaps for insulation.

For the existing MEMS pressure sensor package with corrugated diaphragm and silicone oil seal, the airtightness of the structure will gradually decrease with the increase of the working time of the sensor, resulting in the entry of external dirt into the closed cavity filled with silicone oil. The packaging structure of the present invention includes a self-cleaning function: a set of oppositely arranged metal plates 5 will form an electric field near the corrugated diaphragm 2 after a voltage is applied. According to the dielectric separation effect, under the action of the electric field, Because the dielectric constant of the external dirt that penetrates into the sealed cavity is usually much larger than that of the silicone oil, an obvious dielectric separation phenomenon will occur, causing the dirt to move and gather toward the metal electrode plate 5, and then adhere to the metal electrode plate. 5, the dirt collection tank 11 at the lower end of the metal electrode plate 5 is used to collect the dirt that sinks from the surface of the metal electrode plate 5 due to gravity and other effects, effectively preventing the external dirt entering the sealed cavity of the package from sinking to the MEMS. pressure on the surface of the sensor chip, resulting in a decrease in sensor performance.

In addition, the corrugated diaphragm in the present invention is made of high-toughness ceramic material, which has good chemical stability, aging resistance and fatigue resistance, which not only helps to inhibit the corrosion and damage of the corrugated diaphragm in harsh working environments, but also Helps to expand the application of the sensor with the use of the ceramic case. The corrugated diaphragm 2 is designed into a cover shape, so that its vertical edge fits with the groove at the top of the casing 4 for sealant assembly, while ensuring that the horizontal position of the corrugated diaphragm 2 does not contact the casing 4 after assembly. This can effectively improve the air tightness of the sealant assembly, reduce the prestress and thermal stress on the corrugated diaphragm, and improve the performance of the sensor.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention.

Claims (10)

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.

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