CN114739571A - Packaging device of MEMS pressure sensor - Google Patents

Abstract

The invention discloses a packaging device of an MEMS pressure sensor chip. The device comprises a glass substrate, wherein a first through hole is formed in the glass substrate, the glass substrate is fixed with the side face of the MEMS sensor pressure chip through reflow soldering, the glass substrate is fixed with a base through silver powder glass in a sintering mode, a metal pin is arranged on the base, and the first through hole and the third through hole are filled with slurry to achieve electrical connection of an electrode of the MEMS pressure sensor chip and the metal pin through sintering. According to the leadless packaging form, the sensor chip does not need to be inverted, and the leadless packaging form is particularly suitable for packaging the MEMS pressure sensor with a more complex structure; and no silicon oil is filled in the packaging structure and the protective cover is arranged, so that the reliability of the pressure sensor chip is improved, and the measurement precision and the frequency response range of the high-frequency dynamic signal of the pressure sensor are guaranteed.

Description

Packaging device of MEMS pressure sensor

Technical Field

The invention relates to the technical field of sensor packaging, in particular to a leadless packaging structure and a leadless packaging method of an MEMS pressure sensor.

Background

The common packaging mode of the MEMS pressure sensor is lead packaging, the sensor chip is connected to a test circuit through a metal lead, the metal lead is soldered to a pad of the sensor chip, and a signal of the sensor is transmitted to a pin or a circuit through the pad. In a traditional leadless packaging mode, a sensitive membrane layer is bonded with a substrate, a silicon island deviates from the substrate, and when the sensitive membrane deforms, the silicon island cannot play an overload-resistant role.

Disclosure of Invention

Aiming at the defects or shortcomings of the prior art, the invention provides a packaging device of a MEMS pressure sensor chip.

Therefore, the packaging device provided by the invention comprises a substrate and a base, wherein the base is arranged on the bottom surface of the substrate, and a silver powder glass layer is arranged between the base and the base;

the top surface of the substrate is provided with a groove, the shape of the groove is matched with the shape of the MEMS pressure sensor chip during normal assembly, the MEMS pressure sensor chip is in normal assembly, the bottom surface of the MEMS pressure sensor chip is positioned at the bottom of the groove, and the front surface of the MEMS pressure sensor chip is positioned at the top of the groove;

at least four first through holes are formed in the substrate, each first through hole penetrates through the top surface and the bottom surface of the substrate, and the at least four first through holes are distributed around the groove; the first through holes are filled with first conductive slurry;

the top surface of the substrate is also provided with a first metal layer which is electrically connected with the conductive slurry in each first through hole;

the silver powder glass layer is provided with second through holes communicated with the first through holes, welding pads are arranged between the second through holes and the corresponding first through holes, and the welding pads are electrically connected with the conductive paste in the corresponding first through holes;

third through holes communicated with the second through holes are formed in the base, and the third through holes penetrate through the top surface and the bottom surface of the base; and metal pins are arranged in the third through holes, are electrically connected with the corresponding bonding pads and penetrate out of the corresponding third through holes.

Further, second conductive slurry is filled in each third through hole.

Further, the radial dimension of the second through hole is greater than the radial dimension of the corresponding first through hole and greater than the radial dimension of the corresponding third through hole.

Further, the cross-sectional shape of recess is for falling isosceles trapezoid.

The packaging device is arranged in the shell, a cavity is reserved between the top surface of the substrate and the top surface of the shell, the through holes are located above the grooves, and the metal pins penetrate out of the shell.

Further, the housing includes an upper housing and a lower housing, and the upper housing and the lower housing are assembled by a screw.

Furthermore, a silicon cap is bonded on the front surface of the MEMS pressure sensor chip, and a cavity is formed by the silicon cap and the front surface of the MEMS pressure sensor chip.

The invention also provides an MEMS pressure sensor based on the packaging device, which comprises the packaging device, wherein an MEMS pressure sensor chip is positively arranged in the groove of the packaging device, the MEMS pressure sensor chip is connected with the side wall of the groove through a second metal layer, and the output end and the input end of a Wheatstone bridge of the MEMS pressure sensor are connected with the first metal layer through metal leads.

Furthermore, a silicon island is arranged on the bottom surface of the MEMS pressure sensor chip.

The invention also provides a packaging method of the packaging device, which comprises the following steps:

(1) fixing the MEMS pressure sensor chip 4 in the groove 5-3 through reflow soldering;

(2) adding conductive paste 5-2 into the first through hole 5-1, and then stacking the base 2 and silver powder glass 6 on the bottom surface of the glass substrate 5, wherein the silver powder glass 6 is provided with a preset through hole of the second through hole 6-1; then inserting one end of the metal pin 3 into a third through hole 2-1 and contacting with the metal pad 7;

(3) and sintering the sensor chip, the glass substrate 5, the silver powder glass 6, the base 2, the conductive paste 5-2 and the metal pins 3 together to form a sintered object.

According to the leadless packaging device adopted by the invention, the MEMS pressure sensor chip can be fixed in the groove of the substrate through a reflow soldering process, the signal on the front side of the sensor chip is connected to the metal bonding pad on the back side of the glass substrate through the substrate through hole and is finally communicated with the metal pin, the leadless signal transmission of the pressure sensor chip is realized, compared with a Through Silicon Via (TSV) technology, the leadless packaging device is more efficient and lower in cost, the problem of lead fatigue under high-frequency vibration is avoided, the signal noise caused by the lead is improved, and the reliable transmission of the high-frequency signal is ensured.

According to the leadless packaging form provided by the invention, the sensor chip does not need to be inverted, the structural design of the sensor chip is not limited, the leadless packaging form is particularly suitable for packaging an MEMS pressure sensor with the front surface of the chip needing bonding glass or the back surface of the chip having a more complex structure, and when the sensor chip is arranged on the substrate, the silicon island structure on the back surface can ensure that the sensor has overload resistance.

The packaging structure provided by the invention is free of silicone oil filling, and the protective cover with the air hole is arranged above the pressure sensor chip, so that the pressure sensor chip is further protected, and the measurement precision and the frequency response range of the pressure sensor on high-frequency dynamic signals are guaranteed.

Drawings

FIG. 1 is a schematic structural diagram of a package device according to the present invention;

FIG. 2 is a schematic view of a substrate structure;

FIG. 3 is a pressure response of an embodiment sensor;

FIG. 4 is another structural diagram of the packaging device of the present invention.

Detailed Description

Unless otherwise indicated, the terms or processes herein are understood to be implemented or carried out in a manner consistent with the understanding of those skilled in the relevant art.

The top and bottom surfaces and other directional or orientational terms used herein are consistent with the corresponding method or orientation in the drawings and it is to be understood that the specific direction or orientation in the drawings is an example of the invention and that equivalent rotation, exchange, etc. within the scope of the present disclosure by those skilled in the art are within the scope of the present invention.

The MEMS sensor pressure chip disclosed by the prior art is adopted.

The invention is based on the forward-mounted (namely the bottom of the pressure chip of the MEMS sensor is packaged in the substrate, and the front surface provided with the Wheatstone bridge is positioned at the top outwards) leadless packaging idea, so that the leadless packaging of the sensor chip can be realized in the forward-mounted form, and the forward mounting of the sensor chip can not cause any limitation on the structural design. According to the traditional leadless packaging mode based on the flip chip, the sensitive membrane layer is bonded with the substrate, the silicon island deviates from the substrate, and when the sensitive membrane deforms, the silicon island cannot play an overload-resistant role. And because the silicon island orientation is the pressure direction, the complicated chip back structure is unfavorable for designing the apron that has specific frequency channel filtering function. Therefore, the piezoresistive pressure sensor packaged by this method is weak in survivability in a severe environment such as an explosion field. Based on the leadless packaging mode provided by the invention, the pressure sensor chip can be positively arranged on the substrate, and particularly, the sensor can have at least 3 times of overload resistance by designing the silicon island. In addition, a cover cap with a filtering function can be bonded on the front surface of the chip, so that shock wave pressure signals near the resonant frequency of the sensitive diaphragm can be filtered, the sensitive diaphragm of the pressure sensor is further protected, and the environmental adaptability of the piezoresistive pressure sensor in severe environments such as an explosion field is improved.

The invention is further described in detail below with reference to the drawings and examples, which are intended to illustrate the invention and not to limit the scope of the invention.

As shown in fig. 1, the leadless packaging structure of the MEMS pressure sensor of the present invention comprises a substrate 5 and a base 2, wherein the base 2 is disposed at the bottom of the substrate 5, and the two are sintered and fixed by silver powder glass 6;

the top surface of the substrate is provided with a groove 5-3 for mounting the MEMS pressure sensor, and the shape of the groove is matched with the shape of the MEMS pressure sensor when the MEMS pressure sensor is mounted or placed, for example, the cross section of the groove is in the shape of an inverted isosceles trapezoid (namely the top edge of the isosceles trapezoid is longer than the bottom edge); at least four first through holes 5-1 are formed in the base around the groove, each first through hole penetrates through the top surface and the bottom surface of the substrate, and first conductive paste 5-2 is filled in each first through hole;

the top surface of the substrate is also provided with a first metal layer 4-1 which is electrically connected with the conductive paste 5-2 in each first through hole;

the silver powder glass layer is provided with second through holes 6-1 communicated with the first through holes, welding pads 7 are arranged between the second through holes and the corresponding first through holes, and the welding pads are electrically connected with the conductive paste in the corresponding first through holes;

third through holes 2-1 communicated with the second through holes are formed in the base, and the third through holes penetrate through the top surface and the bottom surface of the base; and metal pins 3 are arranged in the third through holes, are electrically connected with the corresponding bonding pads 7 and penetrate out of the corresponding third through holes.

In the specific scheme, the number of the metal leads, the number of the first through holes, the number of the second through holes and the number of the third through holes are determined according to the number of output ends and input ends of a Wheatstone bridge on the MEMS pressure sensor chip. A conventional wheatstone bridge generally has two input terminals and two output terminals, and accordingly, four first through holes, four second through holes, and four third through holes are formed in the package device.

When the packaging structure is adopted, an MEMS pressure sensor chip to be packaged is placed in the groove and is connected with the side wall of the groove through the second metal layer 4-2, and the output end and the input end of a Wheatstone bridge of the MEMS pressure sensor are connected with the first metal layer 4-1 through the metal lead 4-3.

The MEMS pressure sensor chip packaged by the packaging structure has the working principle that input voltage is applied to the input end of the Wheatstone bridge, and when a pressure signal acts on the sensor chip, a voltage signal which is generated at the output end of the Wheatstone bridge and is in direct proportion to the pressure is output to a detection circuit through the metal lead 4-3, the first metal layer 4-1, the conductive paste 5-2, the metal bonding pad 7 and the metal pin 3.

Taking the CYG401 pressure sensor of the kunshan double bridge as an example, after the encapsulation structure of the invention is adopted for encapsulation, the pressure response of the sensor of the above embodiment is simulated by using a solid mechanics module in COMSOL finite element software. As shown in fig. 3, when the applied pressure is 10MPa, the stress on the surface of the diaphragm is 355MPa, the rupture stress of the silicon material is not reached, and the range of the sensor can reach 10MPa when the applied pressure is 10 MPa; and for the leadless flip-chip packaged pressure sensor, when the applied pressure is 7MPa, the stress of the surface of the diaphragm is 466MPa, the rupture stress of the silicon material is exceeded, and the measuring range of the sensor is 5 MPa. Therefore, the pressure sensor packaged by the packaging method effectively improves the overload resistance and the measuring range.

The present invention may further employ the following improved or alternative features in addition to those set forth above.

In order to facilitate the operation of the packaging process, in some schemes, the third through holes are filled with second conductive paste 2-2.

In still other embodiments, the radial dimension of the second through-hole is greater than the radial dimension of the corresponding first through-hole and greater than the radial dimension of the corresponding third through-hole.

In a further scheme, the packaging structure device is arranged in a shell, a plurality of through holes 1-4 are formed in the top surface of the shell, the packaging device is arranged in the shell, a cavity is reserved between the top surface of the substrate and the top surface of the shell, meanwhile, the through holes are located above the grooves, the metal pins penetrate out of the shell, certain solid particles can be blocked in the shell, the frequency components of a pressure signal to be tested can be prevented from being lost by reasonably designing the size parameters of the air holes, no silicon oil is filled in the metal shell, and the accuracy of the pressure sensor in a high-frequency dynamic test is guaranteed. In a further scheme, the shell is formed by connecting and assembling an upper shell 1-2 and a lower shell 1-1 through threads 1-3.

The packaging method of the leadless packaging structure of the MEMS pressure sensor comprises the following steps: fixing the MEMS pressure sensor chip 4 on the inclined plane of the groove 5-3 of the glass substrate 5 through a reflow soldering process to form a whole; adding a first conductive paste 5-2 into the first through hole 5-1, and then stacking the base 2 and silver powder glass) on the bottom surface of the glass substrate 5, wherein the silver powder glass 6 is provided with a preset through hole of the second through hole 6-1; then inserting one end of the metal pin 3 into a third through hole 2-1 and contacting with the metal pad 7; and sintering the sensor chip, the glass substrate 5, the silver powder glass 6, the base 2, the conductive paste 5-2 and the metal pins 3 together to form a sintered object. Optionally, the leadless packaging structure of the MEMS pressure sensor can be assembled and finished through an annealing treatment to eliminate residual stress in materials and stress introduced by a packaging process.

Further, a sintered object may be fixed to the first metal shell 1-1; and connecting the second metal shell 1-2 with the first metal shell 1-1 through a thread structure 1-3.

For the MEMS pressure sensor chip made of the SOI silicon chip, three layers of materials of the SOI silicon chip are respectively silicon-silicon dioxide-silicon, a Wheatstone bridge composed of piezoresistors is designed on a silicon layer on the front side of the SOI silicon chip, and a sensitive membrane and a cavity are formed by carrying out deep silicon etching on a substrate silicon layer of the SOI silicon chip. When the packaging structure is adopted, the grooves 5-3 and the inclined plane fixed by the pressure sensor chip 4 in the reflow soldering mode can etch silicon through a wet etching process, the wet etching process ensures that the two surfaces have the same inclination angle, and the process is rapid and low in cost. Other main process flows for preparing the MEMS pressure sensor chip also comprise doping, photoetching, ICP etching, scribing and the like.

In the leadless packaging structure of the MEMS pressure sensor, the substrate 5 can be made of a suitable material such as glass, the substrate 2 can be made of a ceramic with a thermal conductivity coefficient similar to that of the glass substrate, such as aluminum nitride ceramic, and thermal stress generated between the substrate and the substrate due to temperature can be reduced. The silver powder glass 6 is composed of silver, glass, an organic binder, a solvent, and the like, and functions to bond the pressure sensor chip 4 to the base 2. The metal pin 3 can be made of kovar alloy, and the kovar alloy has a relatively constant low or medium expansion coefficient which is close to the expansion coefficient of the sealed material such as glass or ceramic, so that the effect of matching sealing is achieved.

In still other embodiments, as shown in FIG. 4, the front side of the MEMS pressure sensor die is bonded with a silicon cap 4-5 that forms a cavity with the front side of the MEMS pressure sensor die. In the case of a housing, the silicon cap 4-5 is located inside the housing. The design of the silicon cap can refer to the disclosure in CN 2021107989999.

Claims (10)

1. The packaging device of the MEMS pressure sensor chip is characterized by comprising a substrate (5) and a base (2), wherein the base is arranged on the bottom surface of the substrate, and a silver powder glass layer (6) is arranged between the base and the base;

the top surface of the substrate is provided with a groove (5-3), the shape of the groove is matched with the shape of the MEMS pressure sensor chip during normal assembly, the MEMS pressure sensor chip is in normal assembly, the bottom surface of the MEMS pressure sensor chip is positioned at the bottom of the groove, and the front surface of the MEMS pressure sensor chip is positioned at the top of the groove;

at least four first through holes (5-1) are arranged in the substrate, each first through hole penetrates through the top surface and the bottom surface of the substrate, and the at least four first through holes are distributed around the groove; the first through holes are filled with first conductive slurry;

the top surface of the substrate is also provided with a first metal layer (4-1), and the first metal layer is electrically connected with the conductive paste in each first through hole;

the silver powder glass layer is provided with second through holes (6-1) communicated with the first through holes, welding pads (7) are arranged between the second through holes and the corresponding first through holes, and the welding pads are electrically connected with the conductive paste in the corresponding first through holes;

third through holes (2-1) communicated with the second through holes are formed in the base, and the third through holes penetrate through the top surface and the bottom surface of the base; and metal pins (3) are arranged in the third through holes, are electrically connected with the corresponding bonding pads (7) and penetrate out of the corresponding third through holes.

2. The packaging apparatus of claim 1, wherein each third via is filled with a second conductive paste.

3. The packaging apparatus of a MEMS pressure sensor die of claim 1 wherein the radial dimension of the second via is greater than the radial dimension of the corresponding first via and greater than the radial dimension of the corresponding third via.

4. The packaging apparatus of a MEMS pressure sensor die as defined by claim 1 wherein the cross-sectional shape of the recess is an inverted isosceles trapezoid.

5. The packaging device of the MEMS pressure sensor chip as defined by claim 1 further comprising an outer casing (1), wherein the top surface of the casing has a plurality of through holes (1-4), the packaging device is mounted in the casing with a cavity between the top surface of the substrate and the top surface of the casing, the plurality of through holes are located above the grooves, and the metal pins protrude through the casing.

6. The packaging apparatus of a MEMS pressure sensor die as defined by claim 5 wherein the housing comprises an upper housing and a lower housing, and wherein the upper housing and the lower housing are assembled by threads.

7. The packaging arrangement for a MEMS pressure sensor die as defined by claim 1 wherein the front side of the MEMS pressure sensor die has bonded thereto a silicon cap (4-5) that forms a cavity with the front side of the MEMS pressure sensor die.

8. A MEMS pressure sensor, comprising a package according to any of claims 1-7, wherein a MEMS pressure sensor chip (4) is mounted in the recess of the package, the MEMS pressure sensor chip is connected to the side wall of the recess through a second metal layer (4-2), and the output and input of the wheatstone bridge of the MEMS pressure sensor are connected to the first metal layer (4-1) through metal leads (4-3).

9. The MEMS pressure sensor of claim 8, wherein a bottom surface of the MEMS pressure sensor die is provided with silicon islands.

10. A packaging method of a MEMS pressure sensor chip is characterized in that: the method comprises the following steps:

(1) fixing the MEMS pressure sensor chip 4 in the groove 5-3 through reflow soldering;

(2) adding conductive paste 5-2 into the first through hole 5-1, and then stacking the base 2 and silver powder glass 6 on the bottom surface of the glass substrate 5, wherein the silver powder glass 6 is provided with a preset through hole of the second through hole 6-1; then inserting one end of the metal pin 3 into a third through hole 2-1 and contacting with the metal pad 7;

(3) and sintering the sensor chip, the glass substrate 5, the silver powder glass 6, the base 2, the conductive paste 5-2 and the metal pins 3 together to form a sintered object.

Images