Package structure of MEMS microphone
The present invention discloses a package structure of a MEMS microphone. The package structure comprises a package substrate and a package shell, wherein the package shell is provided on the package substrate and forms a closed cavity with the package substrate. In the package structure provided by the present invention, the sound-absorbing layer is arranged on the inner wall of the Helmholtz resonant cavity. The sound-absorbing layer has a certain absorption capacity to high-frequency sound waves, but has a very low absorption to low-frequency sound waves, so it may be equivalent to a “low-pass filter”. Through the absorption of the high-frequency sound waves, a high-frequency amplitude value of sound waves can be suppressed, reducing high-frequency response of the Helmholtz resonant cavity. That is, a high-frequency cut-off frequency of the sound waves is improved, widening operation bandwidth of the MEMS microphone.
1. A package structure of a MEMS microphone, the package structure comprising: a package substrate and a package shell, the package shell being provided on the package substrate and forming a closed cavity with the package substrate, and further comprising a sound hole allowing sound to flow into the closed cavity, wherein the package shell, the package substrate and the sound hole together constitute a Helmholtz resonant cavity with a high resonant frequency, in which a MEMS chip and an ASIC chip are provided; and at least part of an inner wall of the Helmholtz resonant cavity is provided with a sound-absorbing layer configured as a low-pass filter having an absorption capacity to high-frequency sound waves but a very low absorption to low-frequency sound waves, while the thickness of the sound-absorbing layer does not excessively destroy resonance characteristics of the Helmholtz resonant cavity.
2. The package structure according to claim 1 , wherein the sound-absorbing layer is provided on the inner wall(s) of the top and/or the side of the package shell.
3. The package structure according to claim 1 , wherein the sound-absorbing layer is provided on the inner wall of the package substrate.
4. The package structure according to claim 1 , wherein the sound-absorbing layer is of a mesh structure.
5. The package structure according to claim 1 , wherein the sound-absorbing layer is provided in a coating manner.
6. The package structure according to claim 1 , wherein the sound-absorbing layer is polyimide.
7. The package structure according to claim 1 , wherein a sound-permeable layer covering the sound hole is further provided at the sound hole of the package shell.
8. The package structure according to claim 1 , wherein the sound-absorbing layer is further provided on the surface of the ASIC chip.
9. The package structure according to claim 1 , wherein the MEMS chip and the ASIC chip are provided on the package substrate; and the sound hole is provided on the package shell.
10. The package structure according to claim 1 , wherein the package shell is in the form of a flat plate, and the package structure further comprises a side wall portion for supporting the package shell on the package substrate.
11. The package structure according to claim 2 , wherein the sound-absorbing layer is of a mesh structure.
12. The package structure according to claim 2 , wherein the sound-absorbing layer is provided in a coating manner.
13. The package structure according to claim 2 , wherein the sound-absorbing layer is polyimide.
14. The package structure according to claim 2 , wherein a sound-permeable layer covering the sound hole is further provided at the sound hole of the package shell.
15. The package structure according to claim 3 , wherein the sound-absorbing layer is of a mesh structure.
16. The package structure according to claim 3 , wherein the sound-absorbing layer is provided in a coating manner.
17. The package structure according to claim 3 , wherein the sound-absorbing layer is polyimide.
18. The package structure according to claim 3 , wherein a sound-permeable layer covering the sound hole is further provided at the sound hole of the package shell.