MEMS speaker

This application claims the priority benefit of Taiwan application serial no. 107128366, filed on Aug. 14, 2018. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

The disclosure relates to a MEMS element, and particularly to a MEMS speaker.

Most existing speakers adopt voice coils and magnets. The main principle is to allow a current to produce a magnetic field via the coil, and the excited magnetic field and the magnet interact to produce vibration and make sound. To cope with the miniaturization trend of consumer electronic devices, such as smart phones and tablet PC, piezoelectric speakers manufactured by micro electro-mechanical processes have been developed. The piezoelectric speakers make use of piezoelectric effect to make sound. When external electric field across an actuator, the actuator deforms, thereby driving a vibration membrane to squeeze the air and produce sound.

However, the actuator needs to be fixed in the housing of the speaker. Therefore, the overall size of a piezoelectric speaker is limited by the actuator, causing the production cost of the piezoelectric speaker to be expensive and the target of further miniaturization to be not easily achievable.

The disclosure provides a micro electro-mechanical system (MEMS) speaker with an actuator disposed on an independent circuit board. Therefore, the size of the actuator is not limited by the circuit board to achieve the targets of reduction in production cost and miniaturization of the MEMS speaker.

The MEMS speaker of the disclosure includes a base, a circuit board, a spacing layer, a vibration mold, and at least one actuator. The base has a first chamber. The circuit board is disposed on the base, and has at least one support portion and a fixing portion sleeved around the at least one support portion. The at least one support portion has a first perforation, and a plurality of second perforations are formed between the at least one support portion and the fixing portion. The spacing layer is disposed on the circuit board, and a second chamber is formed between the spacing layer and the circuit board. The vibration mold is disposed on the spacing layer. The at least one actuator is disposed on the support portion of the circuit board. The at least one actuator has a shift part and a deformation part which are disposed above the first perforation of the at least one support portion. A plurality of second perforations communicate with the first chamber and the second chamber.

Based on the above, the speaker of the disclosure supports the actuator using the circuit board. Since the actuator and the circuit board are independent structures, the size of the actuator is not limited by the circuit board, thereby achieving the targets of reduction in production cost and miniaturization. In addition, the circuit board has a plurality of second perforations for adjusting the air pressure balance between the first chamber and the second chamber to avoid affecting the operation of the actuator and the vibration mold, thereby producing a speaker element with a good frequency response and a high sound production efficiency.

To make the aforementioned and other features of the disclosure more comprehensible, several embodiments accompanied with drawings are described in detail as follows.

FIG. 1A is a schematic cross-sectional view of a MEMS speaker according to an embodiment of the disclosure.

FIG. 1B is a schematic cross-sectional view of the MEMS speaker of FIG. 1A adopting a soldering method.

FIG. 1C is a schematic cross-sectional view of the MEMS speaker of FIG. 1B connected to a vibration mold of another embodiment.

FIG. 1D is a schematic cross-sectional view of a MEMS speaker configured with a plurality of shift parts according to another embodiment of the disclosure.

FIG. 2 is a schematic cross-sectional view of a MEMS speaker according to yet another embodiment of the disclosure.

FIG. 3 is a schematic cross-sectional view of a MEMS speaker according to still another embodiment of the disclosure.

FIG. 4 is a schematic cross-sectional view of a MEMS speaker according to yet another embodiment of the disclosure.

FIG. 5A is a schematic top view of a MEMS speaker according to another embodiment of the disclosure.

FIG. 5B is a schematic cross-sectional view of the actuator of FIG. 5A .

FIG. 5C is a schematic cross-sectional view of the actuator of FIG. 5B connected to a linkage block.

FIG. 6 is a schematic top view showing combination of a plurality of MEMS speakers of FIG. 5A .

FIG. 1A is a schematic cross-sectional view of a MEMS speaker according to an embodiment of the disclosure.

Please refer to FIG. 1A . A MEMS speaker 100 is adapted to be disposed in an electronic device, such as a cellular phone, a tablet PC, a desktop computer, or other electronic devices. The MEMS speaker 100 of the embodiment adopts, for example, a piezoelectric element. The operation principle is to make sound via piezoelectric effect. In short, an external electric field is applied to the MEMS speaker 100 . When electric field is applied across an actuator of the MEMS speaker 100 , the actuator is deformed, and shifted up and down, thereby driving a vibration mold to squeeze the air and make sound.

Referring to FIG. 1A , the MEMS speaker of the disclosure includes a base 110 , a circuit board 120 , a spacing layer 130 , a vibration mold 140 , and at least one actuator 150 . The base 110 adopts, for example, a package substrate material for which the processing technology in the electronic industry is mature, an electronic ceramic, or other materials with rigidity. The base 110 has a recessed first chamber C 1 , which may be used for other needed electronic elements to be placed in, for example.

The circuit board 120 is disposed on the base 110 and is located above the first chamber C 1 . The circuit board 120 has a support portion 121 and a fixing portion 122 disposed around the support portion 121 . The center of the support portion 121 has a first perforation H 1 . A plurality of second perforations H 2 are provided between the support portion 121 and the fixing portion 122 . The plurality of second perforations H 2 are disposed around the periphery of the first perforation H 1 .

In addition, the circuit board 120 of the embodiment is, for example, a printed circuit board or other materials with rigidity. The circuit board 120 includes a conductive circuit 123 disposed on an upper surface or a lower surface of the support portion 121 or the fixing portion 122 . The conductive circuit 123 is, for example, electrically connected to an external circuit to provide power needed for the operation of the MEMS speaker 100 or as a conductive path connecting external circuits.

The spacing layer 130 adopts, for example, polycrystalline silicon, silicon, and silica for which the semiconductor processing technology is mature, or other materials with rigidity. The spacing layer 130 is disposed on the circuit board 120 . The spacing layer 130 and the circuit board 120 form a second chamber C 2 , wherein the plurality of second perforations H 2 and the first perforation H 1 communicate with the first chamber C 1 and the second chamber C 2 to adjust the air pressure balance between the first chamber C 1 and the second chamber C 2 .

Furthermore, in the embodiment, the second chamber C 2 and the first chamber C 1 are, for example, a chamber space surrounded by a printed circuit board stack, a semiconductor material layer, or other materials with rigidity. Using the design of stacking a plurality of chambers, and the chamber space is expanded.

The vibration mold 140 is disposed on the spacing layer 130 and covers the second chamber C 2 . In the embodiment, the vibration mold 140 is made of, for example, polycrystalline silicon, silicon nitride, metal-alumina or aluminum alloy material, polymer, or other elastic materials.

The at least one actuator 150 (one is shown in FIG. 1A as an example) is disposed on the support portion 121 of the circuit board 120 and is located in the second chamber C 2 . The actuator 150 has a shift part 151 and a deformation part 152 which are disposed above the first perforation H 1 of the support portion 121 . In the embodiment, the deformation part 152 is disposed around the shift part 151 .

In the embodiment, the actuator 150 has a piezoelectric structure 154 formed on the deformation part 152 of the actuator 150 . The piezoelectric structure 154 includes a bottom metal layer, piezoelectric layer and top metal layer. The material of the piezoelectric layer adopts, for example, quartz, cadmium sulfide, zinc oxide or aluminum nitride and other piezoelectric monocrystalline materials, a PZT piezoelectric polycrystalline material, a piezoelectric polymer, a piezoelectric composite material, or other materials with piezoelectric properties. The disclosure is not limited to such. When the external electric field is applied across piezoelectric structure 154 of the actuator 150 , the deformation part 152 is deformed due to piezoelectric effect, thereby driving the shift part 151 to produce vibrations up and down.

In addition, the piezoelectric structure 154 further includes an electrode material layer, used to electrically connect the actuator 150 and the external circuit via the circuit board 120 .

Please refer to FIG. 1A , there is a parallel distance PD between a periphery E of the actuator 150 and an interior surface OS of the spacing layer 130 , meaning that the size of the actuator 150 is smaller than the size of the circuit board 120 . As such, the size of the actuator 150 is not limited by the circuit board 120 , and a miniaturized actuator may be produced according to needs.

Furthermore, the actuator 150 has a support structure 153 . The support structure 153 is disposed around the shift part 151 and is spaced apart from the shift part 151 . The deformation part 152 is located between the shift part 151 and the support structure 153 . The support structure 153 is used to increase the structural rigidity of the actuator 150 outside the deformation part 152 . When the MEMS speaker 100 operates, the portion of the actuator 150 disposed on the support structure 153 is fixed.

The actuator 150 of the embodiment extends toward the direction of the vibration mold 140 . The MEMS speaker 100 includes a linkage block 160 . The linkage block 160 is disposed between the vibration mold 140 and the actuator 150 . Specifically, the linkage block 160 is connected between the shift part 151 of the actuator 150 and the vibration mold 140 , so that the actuator 150 is integrated with the vibration mold 140 . When the shift part 151 of the actuator 150 shifts up and down, the vibration mold 140 is driven simultaneously.

Furthermore, the actuator 150 of the embodiment further includes at least one wire 155 ( FIG. 1A shows two wires). One end of the two wires 155 is connected to the piezoelectric structure 154 of the actuator 150 , and the other end of the two wires 155 passes through the corresponding first perforation H 1 and is connected to a surface S 1 of the circuit board 120 with respect to the actuator 150 .

Other embodiments will be exemplified below for illustration. It shall be noted that the following embodiments continue to use the element numerals and parts of disclosure in the aforementioned embodiment, wherein the same numerals are used to denote the same or similar elements, and the description of the same technical content is omitted. The aforementioned embodiment may be taken as reference for the description of the omissions, which will not be reiterated in the following embodiments.

FIG. 1B is a schematic cross-sectional view of the MEMS speaker of FIG. 1A adopting a soldering method.

Referring to FIG. 1A and FIG. 1B together, the difference between a MEMS speaker 100 A of FIG. 1B and the MEMS speaker 100 of FIG. 1A is that the electrical connection methods are different. Referring to FIG. 1B , an actuator 150 a includes at least one electrode bump 156 a ( FIG. 1B shows two electrode bumps). The two electrode bumps 156 a are disposed between a circuit board 120 a and a bottom surface BS of the actuator 150 a, and electrically connected to the piezoelectric structure 154 a to form a gap D between the actuator 150 a and the circuit board 120 a.

FIG. 1C is a schematic cross-sectional view of the MEMS speaker of FIG. 1B connected to a vibration mold of another embodiment.

Referring to FIG. 1B and FIG. 1C together, the difference between a MEMS speaker 100 B of FIG. 1C and the MEMS speaker 100 A of FIG. 1B is that the MEMS speaker 100 B has a vibration mold 140 b and does not need to be configured with a linkage block. The vibration mold 140 b has a recession part 141 b aligned with the first perforation H 1 , and the recession part 141 b extends toward the second chamber C 2 . The vibration mold 140 b is connected to a shift part 151 b of an actuator 150 b via the recession part 141 b. Therefore, the shift part 151 b of the actuator 150 b can directly drive the vibration mode 140 b without any additional linkage block.

FIG. 1D is a cross-sectional schematic view of a MEMS speaker in FIG. 1B configured with a plurality of shift parts according to another embodiment of the disclosure.

Referring to FIG. 1B and FIG. 1D together, the difference between a MEMS speaker 100 C of FIG. 1D and the MEMS speaker 100 A of FIG. 1B is that the MEMS speaker 100 C includes a shift part 151 c, a linkage block 160 c, and a deformation part 152 c. The linkage block 160 c is disposed on the shift part 151 c, the deformation part 152 c is respectively disposed at the periphery of the shift part 151 c. The shift part 151 c is connected to a vibration mold 140 c via the linkage block 160 c to drive the vibration mold 140 c simultaneously or individually. As such, when external air pressure or other factors cause the vibration frequency and the amplitude of the vibration mold 140 c to deviate, the deviation may be adjusted via the frequency and the vibrational amplitude of the shift part 151 c.

FIG. 2 is a schematic cross-sectional view of a MEMS speaker according to another embodiment of the disclosure.

Referring to FIG. 1A and FIG. 2 together. The difference between a MEMS speaker 100 D of FIG. 2 and the MEMS speaker 100 of FIG. 1A is that the setting direction of an actuator 150 d of the MEMS speaker 100 D on a circuit board 120 d is opposite to the setting direction of the actuator 150 on the circuit board 120 . A support structure 153 d of the actuator 150 d is connected to support portion 121 d of the circuit board 120 d such that a shift part 151 d extends downward toward the first perforation H 1 . Furthermore, a linkage block 160 d is disposed on a side surface SI of the shift part 151 d with respect to the support structure 153 d, thereby connecting the shift part 151 d with the vibration mold 140 d as a whole. Furthermore, one end of each of the two wires 155 d is connected to a piezoelectric structure 154 d of the actuator 150 d, and the other end of each of the two wires 155 d is connected to a surface S 2 of the circuit board 120 d facing the vibration mold 140 d.

FIG. 3 is a schematic cross-sectional view of a MEMS speaker according to another embodiment of the disclosure.

Referring to FIG. 1A and FIG. 3 together. The difference between a MEMS speaker 100 E of FIG. 3 and the MEMS speaker 100 of FIG. 1A is that an actuator 150 e of the MEMS speaker 100 E is located in the first chamber C 1 , and a support structure 153 e of the actuator 150 e is connected to a support portion 121 e of a circuit board 120 e such that a shift part 151 e extends upward toward the first perforation H 1 . Furthermore, a linkage block 160 e is disposed on a side of the shift part 151 e facing a vibration mold 140 e. The linkage block 160 e passes through the first perforation H 1 upward to connect to the vibration mold 140 e, thereby connecting the shift part 151 e and the vibration mold 140 e as a whole. In addition, one end of each of two wires 155 e is connected to a piezoelectric structure 154 e of the actuator 150 e, and the other end of each of the two wires 155 e is connected to the surface S 1 of the circuit board 120 e away from the vibration mold 140 e.

FIG. 4 is a schematic cross-sectional view of a MEMS speaker according to another embodiment of the disclosure.

Referring to FIG. 2 and FIG. 4 together. The difference between a MEMS speaker 100 F of FIG. 4 and the MEMS speaker 100 D of FIG. 2 is that an actuator 150 f of the MEMS speaker 100 F is located in the first chamber C 1 , and two electrode bumps 156 f are disposed between a circuit board 120 f and the bottom surface BS of the actuator 150 f to respectively and electrically connect to the piezoelectric structure 154 f such that a gap D is formed between the actuator 150 f and the circuit board 120 f. Furthermore, a linkage block 160 f is disposed on a side surface SI of a shift part 151 f with respect to a support structures 153 f The linkage block 160 f passes through the first perforation H 1 upward to connect to a vibration mold 140 f, thereby connecting the shift part 151 f and the vibration mold 140 f as a whole.

FIG. 5A is a schematic top view of a MEMS speaker according to another embodiment of the disclosure. FIG. 5B is a cross-sectional schematic view of the actuator of FIG. 5A . FIG. 5C is a cross-sectional schematic view of the actuator of FIG. 5B connected to a linkage block.

Referring to FIGS. 2 and 5A to 5C together. The difference between a MEMS speaker 100 G of FIG. 5A and the MEMS speaker 100 D of FIG. 2 is that an actuator 150 g of the MEMS speaker 100 G is located in the first chamber C 1 . Referring to FIGS. 5B and 5C , one end of each of the two wires 155 g is connected to a piezoelectric structure 154 g of the actuator 150 g, and the other end of each of the two wires 155 g passes through the corresponding first perforation H 1 to connect to the surface S 2 of a support portion 121 g on a circuit board 120 g facing a vibration mold 140 g. A linkage block 160 g is disposed on a side of a shift part 151 g facing the vibration mold 140 g. The linkage block 160 g passes through the first perforation H 1 upward to connect to the vibration mold 140 g, thereby connecting the shift part 151 g and the vibration mold 140 g as a whole.

FIG. 6 is a schematic top view showing combination of a plurality of MEMS speakers of FIG. 5A .

In the embodiment of FIG. 6 , the support portion 121 g on the circuit board 120 g may be designed to be multiples. The user may place a plurality of actuators 150 g on the corresponding a plurality of support portions 121 g according to actual needs, and by matching with a plurality of sets of independent conductive circuits 123 g, each MEMS speaker 100 G can make sound of a different bandwidth. A plurality of actuators 150 g are arranged in an array.

Specifically, the circuit board 120 g includes a plurality of support portions 121 g and a plurality of sets of conductive circuits 123 g. The plurality of actuators 150 g are respectively disposed on the plurality of corresponding support portions 121 g. The plurality of sets of conductive circuits are respectively disposed on the corresponding support portions 121 g, and each set of the conductive circuits 123 is electrically independent. The plurality of sets of conductive circuits 123 g are electrically connected to the plurality of corresponding actuators 150 g via a plurality of wires 115 respectively.

FIG. 6 is an array combination of four MEMS speakers 100 G. In short, by combining a plurality of MEMS speakers 100 G, the a plurality of MEMS speakers 100 G may be operated simultaneously to make sound of high power, or the actuators 150 g of various MEMS speakers 100 G respectively produce vibrations of different frequencies to achieve the effect of making sound with different bandwidths, thereby enriching the sound.

Based on the above, the speaker of the disclosure supports the actuator using the circuit board. Since the actuator and the circuit board are independent structures, the size of the actuator is not limited by the circuit board, thereby achieving the targets of reduction in production cost and miniaturization. In addition, the circuit board has a plurality of second perforations disposed around the actuator for adjusting the air pressure balance between the first chamber and the second chamber to avoid affecting the operation of the actuator and the vibration mold, so as to produce a speaker element with a good frequency response and a high sound production efficiency.

Furthermore, the circuit board is used to support the actuator, and the actuator is attached to the circuit board and is electrically connected to the circuit board via wires, wherein the wires passes through the first perforation such that the wires do not interfere with other components.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure covers modifications and variations provided that they fall within the scope of the following claims and their equivalents.