Novel MEMS pressure sensor without isolation diaphragm

Abstract

The invention relates to the technical field of pressure sensors, in particular to a novel MEMS pressure sensor without an isolation diaphragm, an MEMS pressure chip is bonded with a metal base through silica gel, and the outer side of the MEMS pressure chip is plated with a layer of protective film; the periphery of the metal base is connected with a metal flange, a containing groove is formed between the metal flange and the metal base, the MEMS pressure chip is located in the containing groove, the containing groove is filled with silica gel, and the silica gel covers the MEMS pressure chip; the metal flange is connected with a protective cover, the protective cover covers the containing groove, a plurality of damping holes are formed in the protective cover, and the damping holes are communicated with the containing groove. Compared with the prior art, the novel MEMS pressure sensor without the isolation diaphragm has the advantages that the protection grade and the pressure impact resistance are obviously improved, the service life of a product is greatly prolonged, and the application range of the product is greatly widened.

Description

[Technical field]

[0001] The invention relates to the technical field of pressure sensors, and in particular to a novel MEMS pressure sensor without an isolation diaphragm. [Background technology]

[0002] MEMS (micro-electromechanical system) is the integration of microcircuits and micromachines on a chip according to functional requirements. Its size is usually in the millimeter or micron level. MEMS chips are powerful and suitable for various sensors, including the widely used sensors for measuring fluid pressure. However, since the surface of MEMS chips is covered with precision circuits, they must be effectively isolated from the tested medium when used. The isolation device must not only protect the chip, but also ensure that the tested pressure can be transmitted to the MEMS chip without loss. Therefore, it must be reasonably packaged and debugged before it can be used.

[0003] There are two existing MEMS chip packaging methods:

[0004] One is the packaging method with a stainless steel isolation diaphragm. Its advantage is that the tested medium is in contact with the stainless steel, and the pressure of various corrosive gases and liquids can be directly measured. However, its disadvantages are complex structure, large size and high cost.

[0005] The other is a packaging method without an isolation diaphragm. The basic solution is to cover the MEMS chip and its associated circuits with a layer of silicone gel, so that the silicone gel can isolate the medium and transmit pressure. Its advantages are simple structure, small size and low cost. However, it also has disadvantages such as poor resistance to pressure shock, short life, poor reliability and weak medium compatibility. [Summary of the invention]

[0006] In order to overcome the above problems, the present invention proposes a novel MEMS pressure sensor without isolation diaphragm which can effectively solve the above problems.

[0007] A technical solution provided by the present invention to solve the above technical problems is: to provide a new type of MEMS pressure sensor without isolation diaphragm, including a metal base and a MEMS pressure chip, the MEMS pressure chip is bonded to the metal base by silicone, and the outer side of the MEMS pressure chip is coated with a protective film; the periphery of the metal base is connected with a metal flange, a receiving groove is formed between the metal flange and the metal base, the MEMS pressure chip is located in the receiving groove, the receiving groove is filled with silicone gel, and the silicone gel covers the MEMS pressure chip; the metal flange is connected to a protective cover, the protective cover covers the receiving groove, and a plurality of damping holes are opened on the protective cover, and the damping holes are communicated with the receiving groove.

[0008] Preferably, the thickness of the protective film is 1-10 microns.

[0009] Preferably, the plurality of damping holes are evenly distributed on the upper end surface of the protective cover.

[0010] Preferably, a metal lead pin is connected to the metal base, and a signal output end of the MEMS pressure chip is connected to one end of the metal lead pin via a gold wire.

[0011] Preferably, sintered glass is provided between the metal lead pin and the metal base.

[0012] Preferably, the metal flange is bonded to the metal base by epoxy resin glue.

[0013] Preferably, the protective cover is bonded to the metal flange by epoxy resin glue.

[0014] Preferably, the protective cover is made of a ceramic damping sheet.

[0015] Preferably, a protective film is coated on the outer side of the MEMS pressure chip, comprising the following steps:

[0016] Step S1, bonding the MEMS pressure chip to the metal base with silicone, and connecting the signal output end of the MEMS pressure chip to the metal lead pin through gold wire bonding;

[0017] Step S2, installing the metal base with the MEMS pressure chip into the coating protective cap so that the upper surface of the metal base is flush with the upper end surface of the coating protective cap;

[0018] Step S3, coating a layer of polyparaxylene protective film on the portion exposed outside the coating protective cap in a vacuum environment.

[0019] Preferably, the polyparaxylene protective film can transfer the pressure of the measured pressure medium to the MEMS pressure chip without loss.

[0020] Compared with the prior art, the protection level and pressure impact resistance of the new MEMS pressure sensor without isolation diaphragm of the present invention are significantly improved, and the product life and application range are greatly improved. Before the silicone gel protection, vacuum coating is first performed on the MEMS chip and its auxiliary circuits, which adds a reliable protective layer and can effectively resist the erosion of the medium on the MEMS chip and bonding wires; a ceramic cover is installed at the front end of the sensor, and 6 small holes distributed in a circle are opened on the cover, so that the instantaneous impact pressure from the measured fluid will not directly act on the pressure chip and bonding wires and other vulnerable components, but will be applied to the sensor from the side through the surrounding small holes after buffering, so that the silicone gel is not easily damaged and the bonding wires are not deformed or even broken by impact, which effectively improves the life and reliability of the product.

Brief Description of the Drawings

[0021] Figure 1It is a cross-sectional view of a novel MEMS pressure sensor without an isolation diaphragm according to the present invention;

[0022] Figure 2 A top view of a novel MEMS pressure sensor without an isolation diaphragm according to the present invention;

[0023] Figure 3 This is a schematic diagram of the vacuum coating installation of the novel MEMS pressure sensor without isolation diaphragm of the present invention. [Specific implementation method]

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and implementation examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] It should be noted that in the embodiments of the present invention, all directional indications (such as up, down, left, right, front, back, etc.) are limited to relative positions on the specified view, rather than absolute positions.

[0026] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0027] See also Figures 1 to 3 The novel isolation diaphragm-free MEMS pressure sensor of the present invention comprises a metal base 1 and a MEMS pressure chip 5, wherein the MEMS pressure chip 5 is bonded to the metal base 1 via a silica gel 3, and a protective film is coated on the outer side of the MEMS pressure chip 5, and the protective film covers the MEMS pressure chip 5 and its associated circuits.

[0028] The periphery of the metal base 1 is connected with a metal flange 9 , and a receiving groove is formed between the metal flange 9 and the metal base 1 . The MEMS pressure chip 5 is located in the receiving groove, and the receiving groove is filled with silicone gel 7 , and the silicone gel 7 covers the MEMS pressure chip 5 .

[0029] The metal flange 9 is connected with a protective cover 12 , the protective cover 12 covers the containing groove, and the protective cover 12 is provided with a plurality of damping holes 14 , the damping holes 14 are communicated with the containing groove.

[0030] The thickness of the protective film is 1-10 microns.

[0031] The protection cover 12 is made of a ceramic damping sheet.

[0032] The plurality of damping holes 14 are evenly distributed on the upper end surface of the protection cover 12 , and the specific number is six.

[0033] The metal base 1 is connected to a metal lead pin 2 , and the signal output end of the MEMS pressure chip 5 is connected to one end of the metal lead pin 2 via a gold wire 8 for outputting a signal.

[0034] Sintered glass 4 is provided between the metal lead pin 2 and the metal base 1 for insulation.

[0035] The metal flange 9 is bonded to the metal base 1 by epoxy resin glue 11 .

[0036] The protective cover 12 is bonded to the metal flange 9 by epoxy resin glue 11 .

[0037] The entire pressure sensor is sealed and installed with the pipeline of the tested pressure through the sealing ring 6.

[0038] The outer side of the MEMS pressure chip 5 is coated with a protective film, which includes the following steps:

[0039] Step S1, bonding the MEMS pressure chip 5 to the metal base 1 with the silica gel 3, and connecting the signal output end of the MEMS pressure chip 5 to the metal lead pin 2 through the gold wire bonding wire 8;

[0040] Step S2, installing the metal base 1 with the MEMS pressure chip 5 into a specially made coating protective cap 13, so that the upper surface of the metal base 1 is flush with the upper end surface of the coating protective cap 13;

[0041] Step S3 , coating a layer of Parylene protective film on the portion exposed outside the coating protective cap 13 in a vacuum environment.

[0042] The Parylene protective film is a highly corrosion-resistant material with a thickness of several microns, and can transmit the pressure of the measured pressure medium 10 to the MEMS pressure chip 5 without loss.

[0043] Parylene (poly-para-xylene) is a protective polymer material that can be vapor deposited under vacuum. The good penetrating power of its active molecules can form a pinhole-free, uniformly thick transparent insulating coating inside, at the bottom, and around the components, providing the components with a complete high-quality protective coating to resist the invasion of acid, alkali, salt spray, mold and various corrosive media. Because the material is elastic and the coating thickness is only a few microns, it can transmit the pressure of the measuring medium to the MEMS pressure chip without loss, just like soft and elastic silicone gel.

[0044] Compared with the prior art, the novel MEMS pressure sensor without isolation diaphragm of the present invention has the following beneficial effects:

[0045] 1. Generally, the outlet diameter of the pipeline is not large. When measuring pressure, the pressure medium 10 first directly impacts the central solid part of the protective cover 12 through the pipeline outlet, and then disperses to the surroundings and enters the sensor through the 6 damping holes 14 evenly distributed on the ceramic damping plate. This effectively reduces the direct impact on the silicone gel 7 to protect the silicone gel 7 from displacement or damage under instantaneous impact.

[0046] 2. Even if the silicone gel 7 is damaged under long-term high-frequency pressure shock, the pressure medium 10 still remains isolated from the sensor circuit due to the secondary protection of the protective film, which can greatly improve the life and reliability of the sensor.

[0047] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any modifications, equivalent substitutions and improvements made within the concept of the present invention should be included in the patent protection scope of the present invention.

Claims

1. A novel MEMS pressure sensor without isolation diaphragm, characterized in that: It includes a metal base and a MEMS pressure chip, wherein the MEMS pressure chip is bonded to the metal base through silicone, and a protective film is coated on the outer side of the MEMS pressure chip; The periphery of the metal base is connected with a metal flange, a receiving groove is formed between the metal flange and the metal base, the MEMS pressure chip is located in the receiving groove, the receiving groove is filled with silicone gel, and the silicone gel covers the MEMS pressure chip; The metal flange is connected with a protective cover, the protective cover covers the containing groove, and the protective cover is provided with a plurality of damping holes, which are communicated with the containing groove.

2. The novel MEMS pressure sensor without isolation diaphragm as claimed in claim 1, characterized in that: The thickness of the protective film is 1-10 microns.

3. The novel MEMS pressure sensor without isolation diaphragm as claimed in claim 1, characterized in that: The plurality of damping holes are evenly distributed on the upper end surface of the protection cover.

4. The novel MEMS pressure sensor without isolation diaphragm as claimed in claim 1, characterized in that: The metal base is connected with a metal lead pin, and the signal output end of the MEMS pressure chip is connected to one end of the metal lead pin through a gold wire.

5. The novel MEMS pressure sensor without isolation diaphragm as claimed in claim 4, characterized in that: Sintered glass is arranged between the metal lead pin and the metal base.

6. The novel MEMS pressure sensor without isolation diaphragm as claimed in claim 1, characterized in that: The metal flange is bonded to the metal base by epoxy resin glue.

7. The novel MEMS pressure sensor without isolation diaphragm as claimed in claim 1, characterized in that: The protective cover is bonded to the metal flange by epoxy resin glue.

8. The novel MEMS pressure sensor without isolation diaphragm as claimed in claim 7, characterized in that: The protection cover is made of a ceramic damping sheet.

9. The novel MEMS pressure sensor without isolation diaphragm as claimed in claim 1, characterized in that: The outer side of the MEMS pressure chip is coated with a protective film, comprising the following steps: Step S1, bonding the MEMS pressure chip to the metal base with silicone, and connecting the signal output end of the MEMS pressure chip to the metal lead pin through gold wire bonding; Step S2, installing the metal base with the MEMS pressure chip into the coating protective cap so that the upper surface of the metal base is flush with the upper end surface of the coating protective cap; Step S3, coating a layer of polyparaxylene protective film on the portion exposed outside the coating protective cap in a vacuum environment.

10. The novel MEMS pressure sensor without isolation diaphragm as claimed in claim 9, characterized in that: The polyparaxylene protective film can transmit the pressure of the measured pressure medium to the MEMS pressure chip without loss.

Images