A MEMS pressure sensor oil-filled core and packaging method thereof

Abstract

The present invention relates to the technical field of pressure sensors, and discloses an oil-filled core of a MEMS pressure sensor, including an upper cover, a base and a sensitive component; the lower end of the upper cover is sealed and connected to the base, the base and the upper cover form a sealed cavity, and the sealed cavity is filled with a detection medium; a sensitive component is provided on the base and in the sealed cavity. The MEMS pressure sensor oil-filled core and its packaging method adopt a chip composed of a silicon elastic diaphragm, a semiconductor resistor and a signal calibration module, and no signal processing circuit is required to be set externally, with less lead interconnection, simple structure, low cost, high product reliability, and easy production. The semiconductor resistor and the signal calibration module are located in different planes, and the signal calibration module is located around the silicon elastic diaphragm, so as to avoid the stress change of the silicon elastic diaphragm affecting the signal calibration module, resulting in the risk of damage to the circuit in the signal calibration module, which is conducive to ensuring accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure sensors, in particular to an oil-filled core of a MEMS pressure sensor and a packaging method thereof. Background Art

[0002] The main function of pressure sensors is to convert external pressure signals into electrical signals. They are widely used in automotive electronics, aerospace, petrochemicals, medical devices, consumer electronics and other fields.

[0003] As the core component of pressure sensor, pressure chip can be mainly divided into diffused silicon piezoresistive, capacitive, piezoelectric, resonant and other pressure sensors; among them, diffused silicon pressure sensor chip adopts advanced MEMS technology, forms pressure-sensitive pressure diaphragm through etching technology, and makes pressure-sensitive element in the pressure-sensitive pressure diaphragm area through ion implantation; in addition, MEMS pressure sensor is small in size, light in weight, low in cost, high in sensitivity, suitable for mass production, and has a wide range of application environments. Different application environments have different requirements for MEMS pressure sensor packaging methods. In order to meet the media compatibility of the sensor, oil-filled cores of pressure sensors with different packaging methods have been announced; the existing oil-filled core packaging methods are difficult to get rid of the defects of high product cost, complex manufacturing process, low precision, poor reliability, etc. Patent CN106768592A announced "an oil-filled core of pressure transmitter with signal processing function", and one of the bases announced is The high-pressure sintered seat, the base body is machined and manufactured, with low processing efficiency and high cost. The manufacturing process is not compatible with mature semiconductor packaging processes, such as automatic high-speed patch and fully automatic high-speed wire bonding. In addition, this solution sets the temperature measurement module, signal processing unit, and pressure sensing unit on the same working surface. Since the pressure sensing unit is the weakest area of ​​the sensor chip and is constantly deformed with pressure changes, the signal processing unit is also set on this surface, which will expose the microcircuit inside the chip to the risk of fatigue damage; Patent CN1056343A discloses a "medium-isolated pressure sensor packaging structure" that sets the pressure sensor packaging module inside the oil-filled cavity. Due to the hygroscopicity of the material itself and the presence of pores, the packaging module cannot ensure that there is no gas residue inside the sealed cavity. At the same time, the excessive internal silicone oil filling volume will increase the output temperature drift of the pressure sensor and reduce the sensor accuracy. In addition, the pressure chip and AS are used inside the packaging module. The IC dual-chip method increases product manufacturing costs and failure risks; Patent CN208721309U discloses "a simple oil-filled core", and the tube shell with the pressure chip is directly riveted. This process causes huge stress on the tube shell product, and the stress is transmitted to the pressure chip, thereby causing the sensor output to drift, and the consistency and accuracy are degraded. In addition, a sealing ring with a thermal expansion coefficient far exceeding that of the silicon chip is arranged inside the sealed cavity, which causes the sensor to increase the output temperature drift of the sensor under high and low temperature conditions. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the shortcomings of the prior art, the present invention provides a MEMS pressure sensor oil-filled core and a packaging method thereof, which has the advantages of high detection accuracy of the oil-filled core, and solves the problem in the prior art that a temperature measurement module, a signal processing unit and a pressure sensing unit are arranged on the same working surface. Since the pressure sensing unit is the weakest area of ​​the sensor chip and continuously deforms with changes in pressure, if the signal processing unit is also arranged on this surface, the microcircuit inside the chip will face the risk of fatigue damage, thereby reducing the accuracy of the sensor.

[0006] (II) Technical solution

[0007] In order to achieve the purpose of high detection accuracy of the above-mentioned oil-filled core, the present invention provides the following technical solutions: an oil-filled core of a MEMS pressure sensor, comprising an upper cover, a base and a sensitive component;

[0008] The lower end of the upper cover is sealed with the base, the base and the upper cover form a sealed cavity, and the sealed cavity is filled with a detection medium;

[0009] A sensitive component is disposed on the base and in the sealed cavity; the sensitive component includes a silicon elastic diaphragm and a signal calibration module located in the same plane;

[0010] The signal calibration module is located around the silicon elastic diaphragm;

[0011] A semiconductor resistor is arranged on the silicon elastic diaphragm.

[0012] Preferably, the upper surface of the base is provided with patch adhesive and positioning marks, the patch adhesive is used to bond sensitive components, and the positioning marks are distributed on the periphery of the patch adhesive.

[0013] Preferably, a back pressure sheet is provided between the patch adhesive and the sensitive component.

[0014] Preferably, a circular hole is provided at the center of the patch adhesive, and a through hole communicating with the circular hole is provided on the lower surface of the base.

[0015] Preferably, the base is further provided with a pin, the pin is provided with a lead wire electrically connected to the sensitive component, and a sintered glass is provided at the connection between the pin and the base.

[0016] Preferably, a filling hole is further provided on the base, and a steel ball is connected to the lower surface of the base and is located in the filling hole.

[0017] Preferably, a first welding ring with a conical cross-section is provided on the contact surface where the base is sealed with the lower end of the upper cover.

[0018] Preferably, the upper cover comprises a circular ring, a pressure diaphragm and an outer shell, the outer shell is provided with a second welding ring, the outer shell is connected to the circular ring through the second welding ring, the pressure diaphragm is located between the outer shell and the circular ring, and the circular ring, pressure diaphragm and outer shell are all made of the same type of metal.

[0019] Preferably, an overpressure blocking groove is provided on the upper surface of the shell, and a dielectric groove is provided on the lower surface of the shell; the dielectric groove and the overpressure blocking groove are connected.

[0020] A packaging method for an oil-filled core of a MEMS pressure sensor, the steps of the packaging method are as follows:

[0021] (a) The ring, the pressure diaphragm and the housing are coaxially assembled in sequence, and the upper cover is formed by sealing welding through a second welding ring;

[0022] (b) Bond the sensitive component to the patch adhesive of the base and position it using the positioning mark to achieve quick patching;

[0023] (c) ultrasonically heat bonding the sensitive component to the pin through the lead wire to form an electrical connection;

[0024] (d) sealingly welding the base and the upper cover by resistance welding through a first welding ring having a conical cross section;

[0025] (e) pouring liquid medium into the medium tank in the housing through the packing hole under vacuum;

[0026] (f) sealing and welding the steel ball to the packing hole on the base to form an oil-filled core;

[0027] (g) Carry out calibration test on the completed oil-filled core.

[0028] (III) Beneficial effects

[0029] Compared with the prior art, the present invention provides a MEMS pressure sensor oil-filled core and a packaging method thereof, which has the following beneficial effects:

[0030] 1. The MEMS pressure sensor oil-filled core and its packaging method adopt a chip composed of a silicon elastic diaphragm, a semiconductor resistor and a signal calibration module. There is no need to set up a signal processing circuit outside, with fewer lead interconnections, simple structure, low cost, high product reliability, and easy production. The semiconductor resistor and the signal calibration module are located in different planes, and the signal calibration module is located around the silicon elastic diaphragm, so as to avoid the stress change of the silicon elastic diaphragm affecting the signal calibration module, thereby avoiding the risk of damage to the circuits in the signal calibration module, which is conducive to ensuring accuracy.

[0031] 2. The MEMS pressure sensor oil-filled core and its packaging method, the ring, pressure diaphragm and shell are all made of the same type of metal, and all-metal packaging is used to eliminate materials with strong hygroscopicity and large thermal expansion coefficients such as PCB and plastic parts inside the sealed cavity, thereby avoiding the generation of bubbles, moisture and thermal deformation inside the sealed cavity, which would reduce product reliability and accuracy.

[0032] 3. The MEMS pressure sensor oil-filled core and its packaging method, the medium filling amount inside the sealed cavity is controlled to a minimum volume. The smaller the medium filling volume, the smaller the contraction and expansion amount caused by the CTE of the medium material under high and low temperature changes of the product, which is more conducive to improving the high and low temperature accuracy of the MEMS pressure sensor oil-filled core.

[0033] 4. The MEMS pressure sensor oil-filled core and packaging method thereof are provided with patch glue and positioning marks on the upper surface of the base. The patch glue is used to bond sensitive components. The positioning marks are distributed on the periphery of the patch glue for positioning, which facilitates high-speed automated patching. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A cross-sectional view of a first embodiment of an oil-filled core structure of a MEMS pressure sensor proposed by the present invention.

[0035] Figure 2 This is a structural diagram of the upper cover in the first embodiment of the oil-filled core of a MEMS pressure sensor proposed by the present invention.

[0036] Figure 3 This is a structural diagram of the base and sensitive components in the first embodiment of the oil-filled core of a MEMS pressure sensor proposed by the present invention.

[0037] Figure 4 This is a structural diagram of the sensitive component in the first embodiment of the oil-filled core of a MEMS pressure sensor proposed by the present invention.

[0038] Figure 5 A top view of a base in a first embodiment of an oil-filled core of a MEMS pressure sensor proposed by the present invention.

[0039] Figure 6 A cross-sectional view of a second embodiment of an oil-filled core of a MEMS pressure sensor proposed by the present invention.

[0040] Figure 7 This is a structural diagram of the sensitive component in the second embodiment of the oil-filled core of a MEMS pressure sensor proposed by the present invention.

[0041] In the figure: 10 upper cover, 20 base, 201 pin, 202 upper surface of base, 203 first welding ring, 204 filling hole, 205 sintered glass, 206 positioning mark, 301 lead, 302 patch glue, 40 sensitive component, 41 silicone elastic diaphragm, 42 signal calibration module, 43 semiconductor resistor, 44 back pressure sheet, 510 through hole, 11 ring, 12 pressure diaphragm, 13 shell, 131 overpressure blocking groove, 132 medium groove, 14 second welding ring, 15 steel ball, 16 sealing cavity, 17 detection medium. DETAILED DESCRIPTION

[0042] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Embodiment 1:

[0044] See also Figure 1-5 A MEMS pressure sensor oil-filled core comprises an upper cover 10, a base 20 and a sensitive component 40; the base 20 is provided with the sensitive component 40; the sensitive component 40 comprises a silicon elastic diaphragm 41 and a signal calibration module 42, the silicon elastic diaphragm 41 and the signal calibration module 42 are both arranged on a bare chip so that the two are located in the same horizontal plane; the signal calibration module 42 is located around the silicon elastic diaphragm 41; a semiconductor resistor 43 is arranged on the silicon elastic diaphragm 41 so that the semiconductor resistor 43 and the signal calibration module 42 are located in different planes, and the signal calibration module 42 is located around the silicon elastic diaphragm 41 The circuit of the signal calibration module 42 is damaged by the stress change of the silicon elastic diaphragm 41, which is conducive to ensuring accuracy. The principle is that the silicon elastic diaphragm 41 will produce strain when it is subjected to pressure, causing the resistance value of the semiconductor resistor 43 thereon to change differently under the action of the piezoresistive effect and the anisotropy of the material itself. The voltage signal corresponding to the pressure value is output through the Stone bridge principle. The voltage signal is amplified, high and low temperature and linear compensation are performed by the signal calibration module 42 integrated on the pressure chip, and then the voltage signal that meets the terminal use requirements is output.

[0045] The lower end of the upper cover 10 is sealed and connected to the base 20. The base 20 and the upper cover 10 form a sealed cavity 16. The sealed cavity 16 is vacuum-filled with a detection medium 17, which can be silicone oil. The sensitive component 40 is located in the sealed cavity 16 and contacts the detection medium 17. The base 20 is also provided with a filling hole 204 for filling the sealed cavity 16 with a medium. A steel ball 15 is connected to the lower surface of the base 20 and located in the filling hole 204 for sealing. A first welding ring 203 with a conical cross section is provided on the contact surface where the base 20 is sealed and connected to the lower end of the upper cover 10. During welding, a uniform and dense welding surface can be formed to ensure its sealing and structural stability.

[0046] A pin 201 is provided on the base 20, and a sintered glass 205 is provided at the connection between the pin 201 and the base 20, and the sintered glass 205 is used to insulate and seal the pin 20 and the base 20. The pin 201 and the base 20 are made of metal, preferably Kovar with a low CTE, and the surface material is gold-plated; a lead 301 electrically connected to the sensitive component 40 is provided on the pin 201, and the connection is completed by a fully automatic thermosonic bonding method. The lead 301 can be a gold wire, an aluminum wire or a copper wire, and the lead is preferably a gold wire; a patch glue 302 and a positioning mark 206 are provided on the upper surface 202 of the base 20, and the patch glue 302 is used to bond the sensitive component 40, and the positioning mark 206 is distributed on the periphery of the patch glue 302 for positioning, so as to facilitate high-speed automatic patching; a back pressure sheet 44 is also provided between the patch glue 302 and the sensitive component 40 to ensure the back pressure of the sensitive component 40;

[0047] The upper cover 10 includes a circular ring 11, a pressure diaphragm 12 and a shell 13. The shell 13 is provided with a second welding ring 14. The shell 13 is connected to the circular ring 11 through the second welding ring 14. The pressure diaphragm 12 is located between the shell 13 and the circular ring 11. The pressure diaphragm 12 is a flat diaphragm or a corrugated pressure diaphragm. The circular ring 11, the pressure diaphragm 12 and the shell 13 are all made of the same type of metal, preferably the same type of stainless steel, to eliminate thermal stress caused by CTE mismatch between materials and avoid reducing the output accuracy of the sensor.

[0048] An overpressure blocking groove 131 is provided on the upper surface 202 of the shell 13 to prevent the pressure diaphragm 12 from being damaged due to excessive deformation caused by external pressure overload; a medium groove 132 is provided on the lower surface of the shell 13, and the medium groove 132 is connected to the overpressure blocking groove 131. The groove depth of the medium groove 132 can affect the volume of the sealing cavity 16, thereby reducing the filling amount of the medium 17, keeping the medium at a minimum, and avoiding the product output drift caused by thermal expansion and contraction of the medium 17.

[0049] A packaging method for an oil-filled core of a MEMS pressure sensor, the steps of the packaging method are as follows:

[0050] (a) The ring 11, the pressure diaphragm 12 and the housing 13 are coaxially assembled in sequence, and the upper cover 10 is formed by sealing welding through the second welding ring 14;

[0051] (b) bonding the sensitive component 40 to the patch adhesive 302 of the base 20 and positioning it through the positioning mark 206 to achieve rapid patching;

[0052] (c) ultrasonically heat bonding the sensitive component 40 to the pin 201 through the lead 301 to form an electrical connection;

[0053] (d) sealingly welding the base 20 and the upper cover 10 by resistance welding through a first welding ring 203 having a conical cross section;

[0054] (e) pouring liquid medium into the medium groove 132 in the housing 13 through the filling hole 204 under vacuum;

[0055] (f) sealing and welding the steel ball 15 to the filler hole 204 on the base 20 to form an oil-filled core;

[0056] (g) Carry out calibration test on the completed oil-filled core.

[0057] Embodiment 2:

[0058] See also Figure 6-7 The difference from the first embodiment is that there is no back pressure sheet between the patch glue 302 and the sensitive component 40, and a circular hole is provided in the center of the patch glue 302, and a through hole 510 connected to the circular hole is provided on the lower surface of the base 20, so that the oil-filled core is connected to the atmospheric environment and the measurement value relative to the atmospheric pressure can be detected.

[0059] When using:

[0060] (1) External pressure acts on the pressure diaphragm 12, squeezing the medium 17 filled in the sealed cavity 16 through the pressure diaphragm 12, and then the medium 17 transmits the pressure to the sensitive component 40, thereby causing the silicon elastic diaphragm 41 on the sensitive component 40 to change. The silicon elastic diaphragm 41 will produce strain under pressure, causing the resistance value of the semiconductor resistor 43 thereon to change differently under the action of the piezoresistive effect and the anisotropy of the material itself, and outputting a voltage signal corresponding to the pressure value through the Stone bridge principle.

[0061] (2) The ring 11, the pressure diaphragm 12 and the housing 13 are all made of the same type of metal, eliminating the thermal stress caused by the CTE mismatch between the materials and avoiding the reduction of the sensor output accuracy.

[0062] The beneficial effects of the present invention are:

[0063] Compared with the prior art, the MEMS pressure sensor oil-filled core and packaging method thereof adopt a chip composed of a silicon elastic diaphragm 41, a semiconductor resistor 43 and a signal calibration module 42, and no signal processing circuit is required to be set outside. The lead wires 301 have fewer interconnections, a simple structure, low cost, and high product reliability. The semiconductor resistor 43 and the signal calibration module 42 are located in different planes, and the signal calibration module 42 is located around the silicon elastic diaphragm 41, so as to avoid the stress change of the silicon elastic diaphragm 41 affecting the signal calibration module 42, resulting in the risk of damage to the circuit in the signal calibration module 42, which is conducive to ensuring accuracy.

[0064] The ring 11, the pressure diaphragm 12 and the housing 13 are all made of the same type of metal and are fully metal packaged, so that there is no PCB, plastic parts or other materials with high hygroscopicity and thermal expansion coefficient inside the sealed cavity 16, thereby avoiding bubbles, moisture and thermal deformation inside the sealed cavity, which may reduce the reliability and accuracy of the product.

[0065] The filling amount of the medium 17 inside the sealed cavity 16 is controlled to be at a minimum volume. The smaller the filling volume of the medium 17 is, the smaller the contraction and expansion amount caused by the CTE of the dielectric material under high and low temperature changes of the product will be, which is more conducive to improving the high and low temperature accuracy of the oil-filled core of the MEMS pressure sensor; a patch glue 302 and a positioning mark 206 are provided on the upper surface 202 of the base 20, the patch glue 302 is used to bond the sensitive component 40, and the positioning mark 206 is distributed on the periphery of the patch glue 302 for positioning, which is convenient for high-speed automatic patching; the problem of arranging the temperature measurement module, model processing unit, and pressure sensing unit on the same working surface in the prior art is solved. Since the pressure sensing unit is the weakest area of ​​the sensor chip and is constantly deformed with pressure changes, the signal processing unit is also arranged on this surface, which will expose the microcircuit inside the chip to the risk of fatigue damage, thereby reducing the accuracy of the sensor.

[0066] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A MEMS pressure sensor oil-filled core, characterized in that: It comprises an upper cover (10), a base (20) and a sensitive component (40); The lower end of the upper cover (10) is sealedly connected to the base (20), the base (20) and the upper cover (10) form a sealed cavity (16), and the sealed cavity (16) is filled with a detection medium (17); A sensitive component (40) is provided on the base (20) and located in the sealed cavity (16); the sensitive component (40) comprises a silicon elastic diaphragm (41) and a signal calibration module (42) located in the same plane; The signal calibration module (42) is located around the silicon elastic diaphragm (41); A semiconductor resistor (43) is provided on the silicon elastic diaphragm (41), and the semiconductor resistor (43) and the signal calibration module (42) are located on different planes; The steps of packaging the oil-filled core are as follows: (a) the ring (11), the pressure diaphragm (12) and the housing (13) are coaxially assembled in sequence, and the upper cover (10) is formed by sealingly welding the second welding ring (14); (b) bonding the sensitive component (40) to the patch adhesive (302) of the base (20) and positioning it through the positioning mark (206) to achieve rapid patching; (c) ultrasonically thermally bonding the sensitive component (40) to the pin (201) through the lead (301) to form an electrical connection; (d) the base (20) and the upper cover (10) are sealed by resistance welding through a first welding ring (203) having a conical cross section; (e) pouring liquid medium into the medium groove (132) in the housing (13) through the filling hole (204) under a vacuum environment; (f) sealing and welding the steel ball (15) to the packing hole (204) on the base (20) to form an oil-filled core; (g) Carry out calibration test on the completed oil-filled core.

2. The oil-filled core of a MEMS pressure sensor according to claim 1, characterized in that: The upper surface (202) of the base (20) is provided with patch adhesive (302) and positioning marks (206), the patch adhesive (302) is used to bond the sensitive component (40), and the positioning marks (206) are distributed around the periphery of the patch adhesive (302).

3. The oil-filled core of a MEMS pressure sensor according to claim 2, characterized in that: A back pressure sheet (44) is also provided between the patch adhesive (302) and the sensitive component (40).

4. The oil-filled core of a MEMS pressure sensor according to claim 2, characterized in that: The patch adhesive (302) is provided with a circular hole at its center, and the lower surface of the base (20) is provided with a through hole (510) communicating with the circular hole.

5. The oil-filled core of a MEMS pressure sensor according to claim 1, characterized in that: The base (20) is also provided with a pin (201), the pin (201) is provided with a lead wire (301) electrically connected to the sensitive component (40), and a sintered glass (205) is provided at the connection between the pin (201) and the base (20).

6. The oil-filled core of a MEMS pressure sensor according to claim 1, characterized in that: A filling hole (204) is also provided on the base (20), and a steel ball (15) is connected to the lower surface of the base (20) and is located inside the filling hole (204).

7. The oil-filled core of a MEMS pressure sensor according to claim 1, characterized in that: A first welding ring (203) with a conical cross section is provided on the contact surface where the base (20) is sealed with the lower end of the upper cover (10).

8. The oil-filled core of a MEMS pressure sensor according to claim 1, characterized in that: The upper cover (10) comprises a circular ring (11), a pressure diaphragm (12) and an outer shell (13); a second welding ring (14) is provided on the outer shell (13); the outer shell (13) is connected to the circular ring (11) via the second welding ring (14); the pressure diaphragm (12) is located between the outer shell (13) and the circular ring (11); and the circular ring (11), the pressure diaphragm (12) and the outer shell (13) are all made of the same type of metal.

9. The oil-filled core of a MEMS pressure sensor according to claim 8, characterized in that: An overpressure blocking groove (131) is provided on the upper surface (202) of the shell (13), and a dielectric groove (132) is provided on the lower surface of the shell (13); the dielectric groove (132) and the overpressure blocking groove (131) are in communication.

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