CN217283376U - Packaging part - Google Patents

Abstract

The application discloses a package, includes: a substrate having a first through hole; the shell is fixed on the substrate and forms a cavity with the substrate, and the shell is provided with a second through hole; the MEMS chip is positioned in the cavity and fixed on the substrate, the MEMS chip is provided with a back cavity, the first through hole is arranged corresponding to the back cavity, and the second through hole is arranged corresponding to the MEMS chip. The package can make the sound pressure level change trend of the MEMS chip near the resonant frequency become gentle without changing the low-frequency output sound pressure level, thereby improving the output sound quality of the package.

Description

Packaging part

Technical Field

The present application relates to the field of packaging technologies, and in particular, to a package with a MEMS (Micro-Electro-Mechanical System) structure.

Background

The piezoelectric MEMS loudspeaker is a small electroacoustic device using piezoelectric materials as a sound conversion element, and the principle is that the inverse piezoelectric effect is utilized, and a voltage signal is input to a vibrating diaphragm with the piezoelectric materials, so that the vibrating diaphragm vibrates, and the vibrating diaphragm and ambient air are driven to vibrate to radiate sound. Compared with the conventional moving-coil speaker, the piezoelectric MEMS speaker has the advantages of small size, low power consumption, simple process, low cost, and the like, and can be widely applied to various portable electronic devices.

In the prior art, the output sound pressure level of the piezoelectric MEMS loudspeaker changes violently near the resonant frequency, and the output sound quality of a nearby frequency band is reduced. To solve the technical problem, no effective solution has been proposed at present.

SUMMERY OF THE UTILITY MODEL

To solve the problems in the related art, the present application provides a package capable of improving sound quality near a resonance frequency of a MEMS chip.

The technical scheme of the application is realized as follows:

according to an aspect of the present application, there is provided a package including:

a substrate having a first through hole;

the shell is fixed on the substrate and forms a cavity with the substrate, and the shell is provided with a second through hole;

the MEMS chip is positioned in the cavity and fixed on the substrate, the MEMS chip is provided with a back cavity, the first through hole is arranged corresponding to the back cavity, and the second through hole is arranged corresponding to the MEMS chip.

Wherein the first through hole is positioned in the middle of the back cavity, the area of the first through hole is smaller than or equal to that of the back cavity, and the number of the first through holes comprises at least one.

Wherein the second through hole is located at a top surface or a side surface of the housing.

And the area of the second through hole is larger than or equal to that of the piezoelectric composite vibration layer of the MEMS chip.

And the area of the second through hole is smaller than that of the piezoelectric composite vibration layer of the MEMS chip.

Wherein, the MEMS chip includes:

a substrate having a cavity;

a piezoelectric composite vibration layer formed over the substrate and including a cantilever beam having a fixed end connected to the substrate and a free end suspended over the cavity;

a flexible film formed over the piezoelectric composite vibration layer and covering the cavity.

Wherein the MEMS chip comprises a piezoelectric MEMS speaker.

The package can make the sound pressure level change trend of the MEMS chip near the resonant frequency become gentle without changing the low-frequency output sound pressure level, thereby improving the output sound quality of the package.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required in the embodiments will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 illustrates an exploded view of an enclosure provided in accordance with some embodiments;

FIG. 2 illustrates a perspective view of a package provided in accordance with some embodiments;

FIG. 3 illustrates a bottom view of a package provided in accordance with some embodiments;

FIG. 4 illustrates a perspective view of a MEMS chip provided in accordance with some embodiments;

FIG. 5 illustrates an exploded view of a MEMS chip provided in accordance with some embodiments;

FIG. 6 illustrates a bottom view of a MEMS chip provided in accordance with some embodiments;

FIG. 7 shows the sound pressure level frequency response curves for the MEMS chip shown in FIG. 5 with and without a case at a particular size.

Detailed Description

The technical solutions in the embodiments of the present application will be described clearly and completely with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, and not all embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application are within the scope of protection of the present application.

Referring to fig. 1, 2 and 3, in accordance with an embodiment of the present application, a package of a MEMS chip 3 is provided, which may be used for sensors such as, but not limited to, microphones or microphones, or other actuators.

The package comprises a substrate 1 with a first through hole 4, a housing 2 and a MEMS chip 3. The housing 2 is fixed on the substrate 1 and forms a cavity with the substrate 1, and the housing 2 has a second through hole 5. The MEMS chip 3 is located in the cavity and fixed on the substrate 1, and the MEMS chip 3 has a back cavity 311, the first through hole 4 is disposed corresponding to the back cavity 311, and the second through hole 5 is disposed corresponding to the MEMS chip 3.

In some embodiments, the first through hole 4 is located at the middle of the back cavity 311, and the area of the first through hole 4 is smaller than or equal to the area of the back cavity 311, the number of the first through holes 4 includes at least one. In the embodiment shown in fig. 3, the substrate 1 has five first through holes 4. The air pressure at two sides of the substrate 1 is balanced by arranging the first through holes 4, so that the sound pressure level output of the MEMS chip 3 is ensured. In addition, the first through hole 4 also has a dust-proof function. Under the condition of the same air pressure balancing capability, the package with five first through holes 4 has better dustproof effect compared with the package with one first through hole 4. In other embodiments, the number and radius of the first vias 4 may be adjusted as needed to improve the acoustic performance of the package.

In some embodiments, the second through hole 5 is located at the top surface or at the side surface of the housing 2. The area of the second through hole 5 is larger than, equal to, or smaller than the area of the piezoelectric composite vibration layer of the MEMS chip 3. The sound quality around the resonance frequency of the MEMS chip 3 is improved by adjusting the number and porosity of the second through holes 5. In other words, without changing the sound pressure level of the low frequency, the sound pressure level response curve in the vicinity of the resonance frequency can be made gentle by providing the second through hole 5 in the housing 2, thereby improving the sound quality in the vicinity of the resonance frequency.

Referring to fig. 4, 5 and 6, the MEMS chip 3 includes a substrate 31 having a back cavity 311, a piezoelectric composite vibration layer, and a flexible film 33. The piezoelectric composite vibration layer is formed over the substrate 31 and includes a cantilever beam having a fixed end connected to the substrate 31 and a free end suspended over the back cavity 311. The flexible film 33 is formed over the piezoelectric composite vibration layer and covers the back cavity 311. In some embodiments, the MEMS chip 3 comprises a piezoelectric MEMS speaker.

In the embodiment shown in FIG. 5, the piezoelectric composite vibration layer is shown as a "bimorph" structure. Specifically, the piezoelectric composite vibration layer includes, from bottom to top, a bottom electrode 32a, a lower piezoelectric layer 32b, a middle electrode 32c, an upper piezoelectric layer 32d, an upper electrode 32e, and a mass 32 f. Wherein the flexible film 33 is covered over the upper electrode 32 e.

Fig. 7 provides sound pressure level frequency response curves of the MEMS chip 3 shown in fig. 5 packaged with the housing 2 and without the housing 2 at specific dimensions, respectively. Where the applied voltage signal was 30V, the sound pressure level was calculated at a distance of 3cm in the free field. The thickness of the substrate 1 is 0.3mm, and the diameter of the five first through holes 4 is 0.35 mm; the size of the case 2 is 3.4mm 0.85mm, and the area of the second through hole 5 is equal to the area of the piezoelectric composite vibration layer of the MEMS chip 3. The diameter of the second through-hole 5 was 0.01mm, and the porosity was 0.6. It can be seen from fig. 7 that when the MEMS chip 3 is not provided with the case 2, the sound pressure level changes more sharply around the resonance frequency, which reduces the output sound quality. When the MEMS chip 3 is packaged by the shell 2, the sound pressure level becomes more gentle near the resonant frequency, and the output tone quality is effectively improved.

In summary, the package provided by the present application makes the sound pressure level variation trend of the MEMS chip 3 near the resonant frequency gentle without changing the low frequency output sound pressure level, thereby improving the output sound quality of the package.

The present invention is not intended to be limited to the particular embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (7)

1. A package, comprising:

a substrate having a first through hole;

the shell is fixed on the substrate and forms a cavity with the substrate, and the shell is provided with a second through hole;

the MEMS chip is positioned in the cavity and fixed on the substrate, the MEMS chip is provided with a back cavity, the first through hole is arranged corresponding to the back cavity, and the second through hole is arranged corresponding to the MEMS chip.

2. The package of claim 1, wherein the first via is located at a middle of the back cavity and has a region area less than or equal to a region area of the back cavity, and the number of first vias comprises at least one.

3. The enclosure of claim 1, wherein the second via is located at a top surface or a side surface of the housing.

4. The package of claim 1, wherein the area of the second via is greater than or equal to the area of the piezoelectric composite vibration layer of the MEMS chip.

5. The package of claim 1, wherein an area of the second via is smaller than an area of a piezoelectric composite vibration layer of the MEMS chip.

6. The package of claim 1, wherein the MEMS chip comprises:

a substrate having a cavity;

a piezoelectric composite vibration layer formed over the substrate and including a cantilever beam having a fixed end connected to the substrate and a free end suspended over the cavity;

a flexible film formed over the piezoelectric composite vibration layer and covering the cavity.

7. The package of claim 1, wherein the MEMS chip comprises a piezoelectric MEMS speaker.

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