CN218988820U

CN218988820U - MEMS chip packaging structure and ultrasonic sensor with same

Info

Publication number: CN218988820U
Application number: CN202222369185.6U
Authority: CN
Inventors: 慈伟杰; 储清清
Original assignee: Hefei Pilot Micro System Integration Co ltd
Current assignee: Hefei Pilot Micro System Integration Co ltd
Priority date: 2022-09-06
Filing date: 2022-09-06
Publication date: 2023-05-09
Anticipated expiration: 2032-09-06

Abstract

The utility model provides an MEMS chip packaging structure and an ultrasonic sensor with the same, comprising an MEMS chip, a packaging substrate and a patch adhesive, wherein the MEMS chip is provided with a front surface and a back surface which are opposite, the back surface is provided with a back cavity, the packaging substrate is electrically communicated with the MEMS chip, the back surface of the MEMS chip is fixedly bonded with the packaging substrate through the patch adhesive, and the back cavity of the MEMS chip is limited by the patch adhesive to form a sealing cavity. According to the utility model, the sealing cavity is additionally arranged between the MEMS chip and the packaging substrate in the ultrasonic sensor, and applies damping to the vibrating diaphragm of the MEMS chip, so that when the ultrasonic sensor stops transmitting signals, the aftershock of the vibrating diaphragm and the near-distance echo signal shielded by the tailing signal are reduced, and the blind area time of the ultrasonic sensor is reduced.

Description

MEMS chip packaging structure and ultrasonic sensor with same

Technical Field

One or more embodiments of the present disclosure relate to the field of ultrasonic sensors, and in particular, to a MEMS chip package structure and an ultrasonic sensor having the same.

Background

Ultrasonic sensors are sensors that convert ultrasonic signals into other energy signals (typically electrical signals). The ultrasonic sensor has a blind area, wherein the blind area means that when ultrasonic waves are transmitted, a transmission signal is only kept for a very short time, but after the application of the transmission signal is stopped, a certain residual vibration or tailing (due to the action of mechanical inertia) exists on the probe; in the dead zone time, the intensity of the echo signal is far smaller than that of the tail signal, so that the echo signal at a close range is shielded.

The method for inhibiting the dead zone commonly used in the prior art mainly comprises the following two steps that firstly, the dead zone inhibition is carried out on a circuit, such as an external attenuation resistor, ultrasonic wave transmitting power reduction or a time-varying gain amplifying circuit, the dead zone of a sensor is not changed greatly, the symptoms and the root cause are not treated, and the echo signal intensity is also lost when the external attenuation resistor and the ultrasonic wave transmitting power reduction are carried out; secondly, the dead zone of the sensor is restrained through encapsulation, for the piezoelectric ceramic ultrasonic ranging sensor, the dead zone of the probe is reduced, and the shell is filled with acoustic materials, for example, the encapsulation process flow of the piezoelectric ceramic ultrasonic ranging sensor comprises the steps of felt loading, silica gel loading, cover plate loading, shape sealing and the like; or a split transducer and an array are adopted, such as a common one-time ultrasonic ranging module; the method for assembling the sound absorbing material is completed manually, the processing efficiency is low, the method is not suitable for mass production, and the assembly consistency is poor; in summary, the present application provides a MEMS chip package structure and an ultrasonic sensor with the same to solve the above-mentioned problems.

Disclosure of Invention

The utility model aims to solve one of the problems in the background art, and aims to provide an MEMS chip packaging structure which applies damping to a vibrating diaphragm of an MEMS chip, reduces the influence of aftershock or tailing caused by mechanical inertia after stopping transmitting signals, prevents echo signals at a close range from being shielded, and improves the detection precision of an ultrasonic sensor during detection.

The technical scheme adopted for solving the technical problems is as follows:

the MEMS chip packaging structure in the embodiment of the utility model comprises the following components: a MEMS chip having opposing front and back sides, the back side having a back cavity; a package substrate in electrical communication with the MEMS chip; and the back of the MEMS chip is adhered and fixed with the packaging substrate through the adhesive, and the back cavity of the MEMS chip is limited by the adhesive to form a sealing cavity.

According to the MEMS chip packaging structure provided by the embodiment of the utility model, the additionally arranged sealing cavity can apply air damping to the vibrating diaphragm of the MEMS chip, so that the mechanical inertia of the vibrating diaphragm when vibration stops is reduced, the aftershock and tailing of the vibrating diaphragm are reduced, and the dead zone time is reduced.

In some embodiments, the MEMS chip is electrically connected to the package substrate by gold wires.

An ultrasonic sensor according to an embodiment of the present utility model includes: the MEMS chip packaging structure; the packaging shell is in sealing connection with the packaging substrate, the packaging shell is provided with a containing cavity, and the MEMS chip is located in the containing cavity.

In some specific embodiments, further comprising: and pouring sealant is filled in a gap between the packaging shell and the MEMS chip.

In some specific embodiments, further comprising: and the cover plate is in sealing connection with the surface, far away from the packaging substrate, of the packaging shell, and the cover plate is provided with an acoustic hole.

In some embodiments, further comprising: the waterproof dustproof film is in sealing connection with the surface, away from the packaging substrate, of the cover plate.

From the above, it can be seen that the present utility model includes the following advantages:

according to the utility model, the sealing cavity is additionally arranged between the MEMS chip and the packaging substrate in the ultrasonic sensor, and applies damping to the vibrating diaphragm of the MEMS chip, so that when the ultrasonic sensor stops transmitting signals, the aftershock of the vibrating diaphragm and the near-distance echo signal shielded by the tailing signal are reduced, and the blind area time of the ultrasonic sensor is reduced.

Drawings

For a clearer description of one or more embodiments of the present description or of the solutions of the prior art, the drawings that are necessary for the description of the embodiments or of the prior art will be briefly described, it being apparent that the drawings in the description below are only one or more embodiments of the present description, from which other drawings can be obtained, without inventive effort, for a person skilled in the art.

FIG. 1 is a schematic view of an external structure of an ultrasonic sensor according to an embodiment of the present utility model;

FIG. 2 is an exploded view of an ultrasonic sensor according to an embodiment of the present utility model;

FIG. 3 is an internal cross-sectional view of an ultrasonic sensor according to an embodiment of the present utility model;

FIG. 4 is a cross-sectional view of an ultrasonic sensor in accordance with an embodiment of the present utility model;

fig. 5 is a cross-sectional view of an ultrasonic sensor in another preferred embodiment of the present utility model.

In the reference numerals: 1. packaging a substrate; 2. a package housing; 3. pouring sealant; MEMS chip; 5. a cover plate; 6. a waterproof and dustproof film; 7. gold wires; 8. a paster adhesive; a. an acoustic aperture; b. sealing the cavity.

Detailed Description

For the purposes of promoting an understanding of the principles and advantages of the disclosure, reference will now be made in detail to the following specific examples.

The specific structure of the ultrasonic sensor in the embodiment of the present utility model is described below with reference to fig. 1 to 5.

Referring to fig. 1-4, an ultrasonic sensor according to an embodiment of the present utility model includes a MEMS chip package structure, a package housing 2, a potting adhesive 3, and a cover plate 5.

The MEMS chip packaging structure comprises an MEMS chip 4, a packaging substrate 1 and a patch adhesive 8, wherein the MEMS chip 4 is provided with a front surface and a back surface which are opposite, the back surface of the MEMS chip 4 is provided with a back cavity, the packaging substrate 1 is fixedly connected with the back surface of the MEMS chip 4, the MEMS chip 4 is electrically connected with the packaging substrate 1 through a gold wire 7, the back surface of the MEMS chip 4 is fixedly bonded with the packaging substrate 1 through the patch adhesive 8, and the back cavity of the MEMS chip 4 is defined by the patch adhesive 8 into a sealing cavity b. Alternatively, the back silicon thickness of the MEMS chip 4 is preferably 50 μm to 200 μm, and the back cavity volume of the MEMS chip 4 is reduced, so that air viscosity can better damp the diaphragm of the MEMS chip 4 when the diaphragm vibrates.

According to the MEMS chip packaging structure provided by the embodiment of the utility model, the sealing cavity b additionally arranged between the MEMS chip 4 and the packaging substrate 1 can apply air damping to the vibrating diaphragm of the MEMS chip 4, so that the mechanical inertia of the vibrating diaphragm when vibration stops is reduced, the aftershock and tailing of the vibrating diaphragm are reduced, and the dead zone time is reduced.

The packaging shell 2 is provided with a containing cavity, the packaging shell 2 is connected with the packaging substrate 1 in a sealing mode, and the MEMS chip 4 is located in the containing cavity. Optionally, the gap between the packaging shell 2 and the MEMS chip 4 is filled with the pouring sealant 3, the pouring sealant 3 connects the packaging substrate 1, the packaging shell 2 and the MEMS chip 4 into a whole, the MEMS chip 4 is reinforced, the service life of the ultrasonic sensor is prolonged, the buffering effect is achieved on adverse factors such as external impact and vibration, and the reliability of the ultrasonic sensor is improved.

The cover plate 5 is in sealing connection with the surface of the packaging shell 2, which is far away from the packaging substrate 1, and the cover plate 5 is provided with sound holes a. Alternatively, the cover plate 5 is a PCB substrate or a glass substrate or a metal substrate or a semiconductor substrate or a polymer flexible substrate. Optionally, the cover plate 5 is preferably provided with a plurality of acoustic holes a with different diameters. The sound hole a on the cover plate 5 and the MEMS chip 4 are combined into a Helmholtz resonant cavity, so that the sound pressure level of ultrasonic waves can be effectively improved, and the detection distance can be increased; the Helmholtz resonant cavity is essentially a narrow-band filter, has amplification effect on signals in a frequency band and has inhibition effect on signals out of the frequency band, and the resonant frequency of the cavity can be calculated by the following formula:

wherein f is the cavity resonance frequency; c sound velocity in air; v is the front cavity volume; s is the area of the sound outlet hole; t sound hole wall thickness; a is the radius of the sound outlet hole; λ is a correction coefficient, taking=1.3, and in the packaging process, the frequency of the helmholtz resonator can be adjusted by adjusting parameters such as the diameter, the number, and the thickness of the acoustic holes a.

In some embodiments, a waterproof and dustproof film 6 is provided on the side of the package housing 2 near the MEMS chip 4. The waterproof dustproof film 6 effectively protects external pollutants from entering the MEMS chip 4 through the sound hole a of the cover plate 5, and the reliability of the ultrasonic sensor is improved.

The present disclosure is intended to embrace all such alternatives, modifications and variances which fall within the broad scope of the appended claims. Any omissions, modifications, equivalents, improvements, and the like, which are within the spirit and principles of the one or more embodiments of the disclosure, are therefore intended to be included within the scope of the disclosure.

Claims

MEMS chip packaging structure, characterized by comprising:

-a MEMS chip (4), the MEMS chip (4) having opposite front and back sides, the back side having a back cavity;

a package substrate (1), the package substrate (1) being in electrical communication with the MEMS chip (4);

the back of the MEMS chip (4) is adhered and fixed with the packaging substrate (1) through the adhesive tape (8), and a sealing cavity (b) is defined by the adhesive tape (8) in the back cavity of the MEMS chip (4).
2. MEMS chip package according to claim 1, characterized in that the MEMS chip (4) is electrically connected to the package substrate (1) by gold wires (7).
3. An ultrasonic sensor, comprising:

the MEMS chip package structure of any of the above claims 1-2;

the packaging shell (2), the packaging shell (2) is connected with the packaging substrate (1) in a sealing mode, the packaging shell (2) is provided with a containing cavity, and the MEMS chip (4) is located in the containing cavity.
4. The ultrasonic sensor of claim 3, further comprising:

and the gap between the packaging shell (2) and the MEMS chip (4) is filled with the pouring sealant (3).
5. The ultrasonic sensor of claim 3, further comprising:

and the cover plate (5) is in sealing connection with the surface, far away from the packaging substrate (1), of the packaging shell (2), and the cover plate (5) is provided with an acoustic hole (a).
6. The ultrasonic sensor of claim 5, further comprising:

the waterproof dustproof film (6), waterproof dustproof film (6) with apron (5) keep away from the surface sealing connection of encapsulation base plate (1).